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Sample records for intermetallic compound formation

  1. Formation of Intermetallic Compounds During Explosive Welding

    NASA Astrophysics Data System (ADS)

    Greenberg, Bella A.; Ivanov, Mikhail A.; Pushkin, Mark S.; Inozemtsev, Alexei V.; Patselov, Alexander M.; Tankeyev, Anatoliy P.; Kuzmin, Sergey V.; Lysak, Vladimir I.

    2016-11-01

    Transition states between traditional, i.e., plain and wavy, shapes of the interface during explosive welding were studied. A sequence of the transition states was found for the studied copper-titanium and copper-tantalum joints. Some transition states are common for the joints under study, while others are only typical of the copper-titanium joints, due to sufficiently high solubility of original elements. A transition state has been found, during which cusps, even though they are solid phase, look like splashes on the water. The key role of these splashes is that they evidence the lower boundary of the `weldability window.' The study found certain self-organization processes of the cusps that cause them to turn into a quasi-wavy shape of the interface, and then, as the welding mode is intensified, into a wavy shape. The role of intermetallic compounds was analyzed, due to which a wave only consists of cusps in case mutual solubility of original metals is sufficiently high.

  2. Formation of Intermetallic Compounds During Explosive Welding

    NASA Astrophysics Data System (ADS)

    Greenberg, Bella A.; Ivanov, Mikhail A.; Pushkin, Mark S.; Inozemtsev, Alexei V.; Patselov, Alexander M.; Tankeyev, Anatoliy P.; Kuzmin, Sergey V.; Lysak, Vladimir I.

    2016-08-01

    Transition states between traditional, i.e., plain and wavy, shapes of the interface during explosive welding were studied. A sequence of the transition states was found for the studied copper-titanium and copper-tantalum joints. Some transition states are common for the joints under study, while others are only typical of the copper-titanium joints, due to sufficiently high solubility of original elements. A transition state has been found, during which cusps, even though they are solid phase, look like splashes on the water. The key role of these splashes is that they evidence the lower boundary of the `weldability window.' The study found certain self-organization processes of the cusps that cause them to turn into a quasi-wavy shape of the interface, and then, as the welding mode is intensified, into a wavy shape. The role of intermetallic compounds was analyzed, due to which a wave only consists of cusps in case mutual solubility of original metals is sufficiently high.

  3. Intermetallic compound formation at Cu-Al wire bond interface

    SciTech Connect

    Bae, In-Tae; Young Jung, Dae; Chen, William T.; Du Yong

    2012-12-15

    Intermetallic compound (IMC) formation and evolution at Cu-Al wire bond interface were studied using focused ion beam /scanning electron microscopy, transmission electron microscopy (TEM)/energy dispersive x-ray spectroscopy (EDS), nano beam electron diffraction (NBED) and structure factor (SF) calculation. It was found that discrete IMC patches were formed at the Cu/Al interface in as-packaged state and they grew toward Al pad after high temperature storage (HTS) environment at 150 Degree-Sign C. TEM/EDS and NBED results combined with SF calculation revealed the evidence of metastable {theta} Prime -CuAl{sub 2} IMC phase (tetragonal, space group: I4m2, a = 0.404 nm, c= 0.580 nm) formed at Cu/Al interfaces in both of the as-packaged and the post-HTS samples. Two feasible mechanisms for the formation of the metastable {theta} Prime -CuAl{sub 2} phase are discussed based on (1) non-equilibrium cooling of wire bond that is attributed to highly short bonding process time and (2) the epitaxial relationships between Cu and {theta} Prime -CuAl{sub 2}, which can minimize lattice mismatch for {theta} Prime -CuAl{sub 2} to grow on Cu.

  4. Formation of intermetallic compound coating on magnesium AZ91 cast alloy

    NASA Astrophysics Data System (ADS)

    Zhu, Tianping; Gao, Wei

    2009-08-01

    This study describes an intermetallic compound coating formed on AZ91 Mg cast alloy. The Al sputtered on AZ91 cast alloy reacted with substrate during a short period of heat treatment at 435°C, resulting in the formation of a continuous intermetallic compound layer. The short period treatment has the advantage of minimizing the negative effect on the microstructure of substrate and the mechanical properties, comparing with the reported diffusion coatings. DSC measurement and examination on the cross-section of Al sputtered samples show that local melting occurred along the Al/substrate interface at the temperature range between 430~435°C. The formation mechanism of intermetallic compound coating is proposed in terms of the local melting at Al/substrate interface. The salt water immersion test showed significant improvement in corrosion resistance of the intermetallic compound coated AZ91 cast alloy compared with the as-cast alloys.

  5. Evaluation of Gibbs free energies of formation of Ce-Cd intermetallic compounds using electrochemical techniques

    NASA Astrophysics Data System (ADS)

    Shibata, Hiroki; Hayashi, Hirokazu; Akabori, Mitsuo; Arai, Yasuo; Kurata, Masaki

    2014-08-01

    Gibbs free energies of formation of six Ce-Cd intermetallic compounds, CeCd, CeCd2, CeCd3, CeCd58/13, CeCd6 and CeCd11, were evaluated systematically using electrochemical techniques in the temperature range of 673-923 K in the LiCl-KCl-CeCl3-CdCl2 molten salt bath. The linear dependence of the Gibbs free energies of formation on temperature yields to the enthalpies and entropies of formation of these intermetallic compounds. By extrapolating the Gibbs free energy of Ce-Cd intermetallic compounds to the Cd distillation temperature, it was clear that the Gibbs free energy of Ce-Cd intermetallic compounds decreases gradually from CeCd6 to CeCd2 and attains minimum value at CeCd2. This suggests on the Cd distillation from the U-Pu-Ce-Cd alloy that the dissolution of U or Pu into CeCd2 should be mostly taken into consideration.

  6. Effects of filling material and laser power on the formation of intermetallic compounds during laser-assisted friction stir butt welding of steel and aluminum alloys

    NASA Astrophysics Data System (ADS)

    Fei, Xinjiang; Jin, Xiangzhong; Peng, Nanxiang; Ye, Ying; Wu, Sigen; Dai, Houfu

    2016-11-01

    In this paper, two kinds of materials, Ni and Zn, are selected as filling material during laser-assisted friction stir butt welding of Q235 steel and 6061-T6 aluminum alloy, and their influences on the formation of intermetallic compounds on the steel/aluminum interface of the joints were first studied. SEM was used to analyze the profile of the intermetallic compound layer and the fractography of tensile fracture surfaces. In addition, EDS was applied to investigate the types of the intermetallic compounds. The results indicate that a thin iron-abundant intermetallic compound layer forms and ductile fracture mode occurs when Ni is added, but a thick aluminum-abundant intermetallic compound layer generates and brittle fracture mode occurs when Zn is added. So the tensile strength of the welds with Ni as filling material is greater than that with Zn as filling material. Besides, the effect of laser power on the formation of intermetallic compound layer when Ni is added was investigated. The preheated temperature field produced by laser beam in the cross section of workpiece was calculated, and the tensile strength of the joints at different laser powers was tested. Results show that only when suitable laser power is adopted, can suitable preheating temperature of the steel reach, then can thin intermetallic compound layer form and high tensile strength of the joints reach. Either excessive or insufficient laser power will reduce the tensile strength of the joints.

  7. Confinement Effects on Evolution of Intermetallic Compounds During Metallurgical Joint Formation

    NASA Astrophysics Data System (ADS)

    Park, M. S.; Gibbons, S. L.; Arróyave, R.

    2014-07-01

    In this work, we compare the microstructural evolution of Sn/Cu/Sn and Cu/Sn/Cu `sandwich' configurations under metallurgical bonding conditions. These simulations are relevant in explaining experimental observations that suggest that the resulting dominant intermetallic compound in Cu-Sn systems depends on the relative supply of Cu and Sn. Through the analysis of morphological evolution and growth rate, it is shown that the Cu6Sn5 layer becomes dominant in the Sn/Cu/Sn structure, while the Cu/Sn/Cu structure is dominated by Cu3Sn after extended reaction periods.

  8. Intermetallic Compound Formation Mechanisms for Cu-Sn Solid-Liquid Interdiffusion Bonding

    NASA Astrophysics Data System (ADS)

    Liu, H.; Wang, K.; Aasmundtveit, K. E.; Hoivik, N.

    2012-09-01

    Cu-Sn solid-liquid interdiffusion (SLID) bonding is an evolving technique for wafer-level packaging which features robust, fine pitch and high temperature tolerance. The mechanisms of Cu-Sn SLID bonding for wafer-level bonding and three-dimensional (3-D) packaging applications have been studied by analyzing the microstructure evolution of Cu-Sn intermetallic compounds (IMCs) at elevated temperature up to 400°C. The bonding time required to achieve a single IMC phase (Cu3Sn) in the final interconnects was estimated according to the parabolic growth law with consideration of defect-induced deviation. The effect of predominantly Cu metal grain size on the Cu-Sn interdiffusion rate is discussed. The temperature versus time profile (ramp rate) is critical to control the morphology of scallops in the IMC. A low temperature ramp rate before reaching the bonding temperature is believed to be favorable in a SLID wafer-level bonding process.

  9. Some statistics on intermetallic compounds.

    PubMed

    Dshemuchadse, Julia; Steurer, Walter

    2015-02-01

    It is still largely unknown why intermetallic phases show such a large variety of crystal structures, with unit cell sizes varying between 1 and more than 20 000 atoms. The goal of our study was, therefore, to get a general overview of the symmetries, unit cell sizes, stoichiometries, most frequent structure types, and their stability fields based on the Mendeleev numbers as ordering parameters. A total of 20829 structures crystallizing in 2166 structure types have been studied for this purpose. Thereby, the focus was on a subset of 6441 binary intermetallic compounds, which crystallize in 943 structure types.

  10. Enthalpies of formation of Cd–Pr intermetallic compounds and thermodynamic assessment of the Cd–Pr system

    PubMed Central

    Reichmann, Thomas L.; Richter, Klaus W.; Delsante, Simona; Borzone, Gabriella; Ipser, Herbert

    2014-01-01

    In the present study standard enthalpies of formation were measured by reaction and solution calorimetry at stoichiometric compositions of Cd2Pr, Cd3Pr, Cd58Pr13 and Cd6Pr. The corresponding values were determined to be −46.0, −38.8, −35.2 and −24.7 kJ/mol(at), respectively. These data together with thermodynamic data and phase diagram information from literature served as input data for a CALPHAD-type optimization of the Cd–Pr phase diagram. The complete composition range could be described precisely with the present models, both with respect to phase equilibria as well as to thermodynamic input data. The thermodynamic parameters of all intermetallic compounds were modelled following Neumann–Kopp rule. Temperature dependent contributions to the individual Gibbs energies were used for all compounds. Extended solid solubilities are well described for the low- and high-temperature modifications of Pr and also for the intermetallic compound CdPr. A quite good agreement with all viable data available from literature was found and is presented. PMID:25540475

  11. On the formation of Al{sub 3}Ni{sub 2} intermetallic compound by aluminothermic reduction of nickel oxide

    SciTech Connect

    Parsa, M.R.; Soltanieh, M.

    2011-07-15

    Simultaneous reduction of NiO and formation of Al{sub 3}Ni{sub 2} intermetallic compound at 880, 940 and 1000 deg. C were investigated by means of the thermal reduction method. The optimal Ni contents for the starting samples were determined at different times and temperatures through the compositional analysis. The microstructure of the metallic quenched samples was observed by scanning electron microscope. Moreover, the X-ray diffraction analysis and energy disperse spectrometry were applied to characterize the formation of the phases. The results showed that the metallic samples consisted of Al{sub 3}Ni{sub 2}, Al{sub 3}Ni and Al phases and that there was no trace of Ni, NiO and Al{sub 2}O{sub 3}. It was found that after 10 min at the applied temperatures, the reaction completed. For the longer time, the dispersed Al{sub 3}Ni{sub 2} nuclei were grown and its continuous network formed. By increasing the temperature, the thickness of the Al{sub 3}Ni precipitation around Al{sub 3}Ni{sub 2} phase is enhanced in the samples with the same Ni content. A model was proposed for these reactions. - Research Highlights: {yields} Simultaneous reduction of NiO, and Al{sub 3}Ni{sub 2} intermetallics formation at temperatures lower than Ni melting point. {yields} Presently a mechanism for such a process. {yields} Parametric study of microstructure and formed phases.

  12. Formation of Intermetallic Compounds Between Liquid Sn and Various CuNi x Metallizations

    NASA Astrophysics Data System (ADS)

    Vuorinen, V.; Yu, H.; Laurila, T.; Kivilahti, J. K.

    2008-06-01

    Interfacial reactions between liquid Sn and various Cu-Ni alloy metallizations as well as the subsequent phase transformations during the cooling were investigated with an emphasis on the microstructures of the reaction zones. It was found that the extent of the microstructurally complex reaction layer (during reflow at 240°C) does not depend linearly on the Ni content of the alloy metallization. On the contrary, when Cu is alloyed with Ni, the rate of thickness change of the total reaction layer first increases and reaches a maximum at a composition of about 10 at.% Ni. The reaction layer is composed of a relatively uniform continuous (Cu,Ni)6Sn5 reaction layer (a uniphase layer) next to the NiCu metallizations and is followed by the two-phase solidification structures between the single-phase layer and Sn matrix. The thickness of the two-phase layer, where the intermetallic tubes and fibers have grown from the continuous interfacial (Cu,Ni)6Sn5 layer, varies with the Ni-to-Cu ratio of the alloy metallization. In order to explain the formation mechanism of the reaction layers and their observed kinetics, the phase equilibria in the Sn-rich side of the SnCuNi system at 240°C were evaluated thermodynamically utilizing the available data, and the results of the Sn/Cu x Ni1- x diffusion couple experiments. With the help of the assessed data, one can also evaluate the minimum Cu content of Sn-(Ag)-Cu solder, at which (Ni,Cu)3Sn4 transforms into (Cu,Ni)6Sn5, as a function of temperature and the composition of the liquid solders.

  13. Influence of Ti and La Additions on the Formation of Intermetallic Compounds in the Al-Zn-Si Bath

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Gu, Qin-Fen; Li, Qian; Lu, Hu-Sheng

    2016-09-01

    The effect of Ti and La additions on the formation of intermetallic compounds (IMCs) in the galvalume (55Al-Zn-1.6Si wt pct) bath was investigated experimentally and further studied with first-principles calculation. The studied baths contain: 1 wt pct Fe, with Ti content ranging from 0.05 to 0.15 wt pct and La content ranging from 0.05 to 0.30 wt pct. Combination of the experimental results with the thermodynamic analysis shows that the solubility of Fe in the alloy bath decreases with an increase of Ti content, which results in the formation of mass dross. Compared with the Ti-containing alloy, La promotes the formation of τ 5 phase (Fe2Al8Si). When both Ti and La are added, Fe4Al13, τ 5, τ 6 (β-Al4.5FeSi), TiAl3, and Ti2Al20La phases were observed. Since these IMCs would consume more Si in the bath, the decrease of Si content with Ti and La additions is more significant than that of the bath without these additions. Furthermore, the formation mechanism of Ti/TiAl3/Ti2La20La core-shell structure in the coating bath is proposed. This study has implications for strategic design of industry hot-dip production with exceptional mechanical properties of Al alloy coating.

  14. Ultrarapid formation of homogeneous Cu6Sn5 and Cu3Sn intermetallic compound joints at room temperature using ultrasonic waves.

    PubMed

    Li, Zhuolin; Li, Mingyu; Xiao, Yong; Wang, Chunqing

    2014-05-01

    Homogeneous intermetallic compound joints are demanded by the semiconductor industry because of their high melting point. In the present work, ultrasonic vibration was applied to Cu/Sn foil/Cu interconnection system at room temperature to form homogeneous Cu6Sn5 and Cu3Sn joints. Compared with other studies based on transient-liquid-phase soldering, the processing time of our method was dramatically reduced from several hours to several seconds. This ultrarapid intermetallic phase formation process resulted from accelerated interdiffusion kinetics, which can be attributed to the sonochemical effects of acoustic cavitation at the interface between the liquid Sn and the solid Cu during the ultrasonic bonding process.

  15. Polarity effect of electromigration on kinetics of intermetallic compound formation in Pb-free solder V-groove samples

    NASA Astrophysics Data System (ADS)

    Gan, H.; Tu, K. N.

    2005-03-01

    Intermetallic compound (IMC) formation is critical for the reliability of microelectronic interconnections, especially for flip chip solder joints. In this article, we investigate the polarity effect of electromigration on kinetics of IMC formation at the anode and the cathode in solder V-groove samples. We use V-groove solder line samples, with width of 100 μm and length of 500-700 μm, to study interfacial IMC growth between Cu electrodes and Sn-3.8Ag-0.7Cu (in wt %) solder under different current density and temperature settings. The current densities are in the range of 103 to 104A/cm2 and the temperature settings are 120, 150, and 180 °C. While the same types of IMCs, Cu6Sn5 and Cu3Sn, form at the solder/Cu interfaces independent of the passage of electric current, the growth of the IMC layer has been enhanced by electric current at the anode and inhibited at the cathode, in comparison with the no-current case. We present a kinetic model, based on the Cu mass transport in the sample, to explain the growth rate of IMC at the anode and cathode. The growth of IMC at the anode follows a parabolic growth rule, and we propose that the back stress induced in the IMC plays a significant role. The model is in good agreement with our experimental data. We then discuss the influence of both chemical force and electrical force, and their combined effect on the IMC growth with electric current.

  16. New twisted intermetallic compound superconductor: A concept

    NASA Technical Reports Server (NTRS)

    Coles, W. D.; Brown, G. V.; Laurence, J. C.

    1972-01-01

    Method for processing Nb3Sn and other intermetallic compound superconductors produces a twisted, stabilized wire or tube which can be used to wind electromagnetics, armatures, rotors, and field windings for motors and generators as well as other magnetic devices.

  17. First-principles studies of Ni-Ta intermetallic compounds

    SciTech Connect

    Zhou Yi; Wen Bin; Ma Yunqing; Melnik, Roderick; Liu Xingjun

    2012-03-15

    The structural properties, heats of formation, elastic properties, and electronic structures of Ni-Ta intermetallic compounds are investigated in detail based on density functional theory. Our results indicate that all Ni-Ta intermetallic compounds calculated here are mechanically stable except for P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2}. Furthermore, we found that Pmmn-Ni{sub 3}Ta is the ground state stable phase of Ni{sub 3}Ta polymorphs. The polycrystalline elastic modulus has been deduced by using the Voigt-Reuss-Hill approximation. All Ni-Ta intermetallic compounds in our study, except for NiTa, are ductile materials by corresponding G/K values and poisson's ratio. The calculated heats of formation demonstrated that Ni{sub 2}Ta are thermodynamically unstable. Our results also indicated that all Ni-Ta intermetallic compounds analyzed here are conductors. The density of state demonstrated the structure stability increases with the Ta concentration. - Graphical abstract: Mechanical properties and formation heats of Ni-Ta intermetallic compounds are discussed in detail in this paper. Highlights: Black-Right-Pointing-Pointer Ni-Ta intermetallic compounds are investigated by first principle calculations. Black-Right-Pointing-Pointer P21/m-Ni{sub 3}Ta and hc-NiTa{sub 2} are mechanically unstable phases. Black-Right-Pointing-Pointer Pmmn-Ni{sub 3}Ta is ground stable phase of Ni{sub 3}Ta polymorphs. Black-Right-Pointing-Pointer All Ni-Ta intermetallic compounds are conducting materials.

  18. The polarity effect of electromigration on intermetallic compound formation and back stress in v-groove solder lines

    NASA Astrophysics Data System (ADS)

    Ou, Shengquan

    2005-07-01

    The trend of the miniaturization of VLSI and electronic packaging toward higher input/output density, smaller feature size and greater performance makes electromigration a serious reliability concern in flip chip technology. As an integral part of the joint, intermetallic compound (IMC) formation is very important to achieve good joint strength. However, the effect of electromigration on the IMC formation is a subject in which still very little is known. We utilize solder v-groove samples etched on (001) Si wafer with 100 mum opening to study the polarity effect of electromigration on IMC formation in solder joints. We focus on the interaction between chemical and electrical forces, and the influence of interface morphology on the IMC dissolution. The current densities used are from 103 to 104 A/cm2 and the temperature settings are in the range of 120°C to 180°C. We have found in both 95.5Sn3.8Ag0.7Cu/Cu and 96.5Sn3.5Ag systems the growth of the IMC has been enhanced by electric current at the anode and inhibited at the cathode. For Ni-Sn compound, kinetic analysis using the motion of the two interfaces gives the general formula of the growth rate as dXdt=aX + b. We have introduced the concept of mean-field theory and the classic model of Zener's precipitation growth into the discussion of the Cu-Sn compound growth under electromigration. A parabolic dependence of the IMC growth on time at the anode is derived as x 2 ≅ (Cm-Ce)2 (Cs-Ce)2 Dt. The interaction between chemical and electrical forces brings a dynamic equilibrium in IMC dissolution at the cathode. This has been proved theoretically and experimentally. A new critical product has been derived from this dynamic equilibrium, which can provide us a critical IMC thickness before voids formation at a given current density. Our study shows the dissolution rate of Cu with current density 5x103 A/cm2 at 150°C is about 0.076 mum/hr. We also notice that the interface morphology plays an important role in the IMC

  19. Crystal structure analysis of intermetallic compounds

    NASA Technical Reports Server (NTRS)

    Conner, R. A., Jr.; Downey, J. W.; Dwight, A. E.

    1968-01-01

    Study concerns crystal structures and lattice parameters for a number of new intermetallic compounds. Crystal structure data have been collected on equiatomic compounds, formed between an element of the Sc, Ti, V, or Cr group and an element of the Co or Ni group. The data, obtained by conventional methods, are presented in an easily usable tabular form.

  20. Chemical effect on diffusion in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Ting

    With the trend of big data and the Internet of things, we live in a world full of personal electronic devices and small electronic devices. In order to make the devices more powerful, advanced electronic packaging such as wafer level packaging or 3D IC packaging play an important role. Furthermore, ?-bumps, which connect silicon dies together with dimension less than 10 ?m, are crucial parts in advanced packaging. Owing to the dimension of ?-bumps, they transform into intermetallic compound from tin based solder after the liquid state bonding process. Moreover, many new reliability issues will occur in electronic packaging when the bonding materials change; in this case, we no longer have tin based solder joint, instead, we have intermetallic compound ?-bumps. Most of the potential reliability issues in intermetallic compounds are caused by the chemical reactions driven by atomic diffusion in the material; thus, to know the diffusivities of atoms inside a material is significant and can help us to further analyze the reliability issues. However, we are lacking these kinds of data in intermetallic compound because there are some problems if used traditional Darken's analysis. Therefore, we considered Wagner diffusivity in our system to solve the problems and applied the concept of chemical effect on diffusion by taking the advantage that large amount of energy will release when compounds formed. Moreover, by inventing the holes markers made by Focus ion beam (FIB), we can conduct the diffusion experiment and obtain the tracer diffusivities of atoms inside the intermetallic compound. We applied the technique on Ni3Sn4 and Cu3Sn, which are two of the most common materials in electronic packaging, and the tracer diffusivities are measured under several different temperatures; moreover, microstructure of the intermetallic compounds are investigated to ensure the diffusion environment. Additionally, the detail diffusion mechanism was also discussed in aspect of diffusion

  1. More statistics on intermetallic compounds - ternary phases.

    PubMed

    Dshemuchadse, Julia; Steurer, Walter

    2015-05-01

    How many different intermetallic compounds are known so far, and in how many different structure types do they crystallize? What are their chemical compositions, the most abundant ones and the rarest ones? These are some of the questions we are trying to find answers for in our statistical analysis of the structures of the 20,829 intermetallic phases included in the database Pearson's Crystal Data, with the goal of gaining insight into some of their ordering principles. In the present paper, we focus on the subset of 13,026 ternary intermetallics, which crystallize in 1391 different structure types; remarkably, 667 of them have just one representative. What makes these 667 structures so unique that they are not adopted by any other of the known intermetallic compounds? Notably, ternary compounds are known in only 5109 of the 85,320 theoretically possible ternary intermetallic systems so far. In order to get an overview of their chemical compositions we use structure maps with Mendeleev numbers as ordering parameters.

  2. Oxygen stabilized zirconium vanadium intermetallic compound

    DOEpatents

    Mendelsohn, Marshall H.; Gruen, Dieter M.

    1982-01-01

    An oxygen stabilized intermetallic compound having the formula Zr.sub.x OV.sub.y where x=0.7 to 2.0 and y=0.18 to 0.33. The compound is capable of reversibly sorbing hydrogen at temperatures from -196.degree. C. to 450.degree. C. at pressures down to 10.sup.-6 Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO.sub.2.

  3. Surface structures of In-Pd intermetallic compounds. I. Experimental study of In thin films on Pd(111) and alloy formation

    SciTech Connect

    McGuirk, G. M.; Ledieu, J.; Gaudry, É.; Weerd, M.-C. de; Fournée, V.

    2014-08-28

    A combination of experimental methods was used to study the structure of In thin films deposited on the Pd(111) surface and the alloying behavior. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy results indicate that surface alloying takes place at room temperature. Below 2 monolayer equivalents (MLEs), the LEED patterns show the formation of three rotational domains of InPd(110) of poor structural quality on top of the Pd(111) substrate. Both core-levels and valence band XPS spectra show that the surface alloy does not yet exhibit the electronic structure characteristic of the 1:1 intermetallic compound under these conditions. Annealing the 1 MLE thin film up to 690 K yields to a transition from a multilayer InPd near-surface intermetallic phase to a monolayer-like surface alloy exhibiting a well ordered (√(3)×√(3)) R30{sup ∘} superstructure and an estimated composition close to In{sub 2}Pd{sub 3}. Annealing above 690 K leads to further In depletion and a (1 × 1) pattern is recovered. The (√(3)×√(3)) R30{sup ∘} superstructure is not observed for thicker films. Successive annealing of the 2 MLE thin film leads the progressive disappearance of the InPd diffraction spots till a sharp (1 × 1) pattern is recovered above 690 K. In the high coverage regime (from 4 to 35 MLE), the formation of three rotational domains of a bcc-In{sub 7}Pd{sub 3} compound with (110) orientation is observed. This In-rich phase probably grows on top of interfacial InPd(110) domains and is metastable. It transforms into a pure InPd(110) near-surface intermetallic phase in a temperature range between 500 and 600 K depending on the initial coverage. At this stage, the surface alloy exhibits core-level chemical shifts and valence band (VB) spectra identical to those of the 1:1 InPd intermetallic compound and resembling Cu-like density of states. Annealing at higher temperatures yields to a decrease of the In

  4. Surface structures of In-Pd intermetallic compounds. I. Experimental study of In thin films on Pd(111) and alloy formation

    NASA Astrophysics Data System (ADS)

    McGuirk, G. M.; Ledieu, J.; Gaudry, É.; de Weerd, M.-C.; Fournée, V.

    2014-08-01

    A combination of experimental methods was used to study the structure of In thin films deposited on the Pd(111) surface and the alloying behavior. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy results indicate that surface alloying takes place at room temperature. Below 2 monolayer equivalents (MLEs), the LEED patterns show the formation of three rotational domains of InPd(110) of poor structural quality on top of the Pd(111) substrate. Both core-levels and valence band XPS spectra show that the surface alloy does not yet exhibit the electronic structure characteristic of the 1:1 intermetallic compound under these conditions. Annealing the 1 MLE thin film up to 690 K yields to a transition from a multilayer InPd near-surface intermetallic phase to a monolayer-like surface alloy exhibiting a well ordered (√{3}× &sqrt{3}); {R30}° superstructure and an estimated composition close to In2Pd3. Annealing above 690 K leads to further In depletion and a (1 × 1) pattern is recovered. The (√{3}× √{3}) {R30}° superstructure is not observed for thicker films. Successive annealing of the 2 MLE thin film leads the progressive disappearance of the InPd diffraction spots till a sharp (1 × 1) pattern is recovered above 690 K. In the high coverage regime (from 4 to 35 MLE), the formation of three rotational domains of a bcc-In7Pd3 compound with (110) orientation is observed. This In-rich phase probably grows on top of interfacial InPd(110) domains and is metastable. It transforms into a pure InPd(110) near-surface intermetallic phase in a temperature range between 500 and 600 K depending on the initial coverage. At this stage, the surface alloy exhibits core-level chemical shifts and valence band (VB) spectra identical to those of the 1:1 InPd intermetallic compound and resembling Cu-like density of states. Annealing at higher temperatures yields to a decrease of the In concentration in the near

  5. Influence of nanoparticle addition on the formation and growth of intermetallic compounds (IMCs) in Cu/Sn-Ag-Cu/Cu solder joint during different thermal conditions

    NASA Astrophysics Data System (ADS)

    Tan, Ai Ting; Tan, Ai Wen; Yusof, Farazila

    2015-06-01

    Nanocomposite lead-free solders are gaining prominence as replacements for conventional lead-free solders such as Sn-Ag-Cu solder in the electronic packaging industry. They are fabricated by adding nanoparticles such as metallic and ceramic particles into conventional lead-free solder. It is reported that the addition of such nanoparticles could strengthen the solder matrix, refine the intermetallic compounds (IMCs) formed and suppress the growth of IMCs when the joint is subjected to different thermal conditions such as thermal aging and thermal cycling. In this paper, we first review the fundamental studies on the formation and growth of IMCs in lead-free solder joints. Subsequently, we discuss the effect of the addition of nanoparticles on IMC formation and their growth under several thermal conditions. Finally, an outlook on the future growth of research in the fabrication of nanocomposite solder is provided.

  6. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  7. SYNTHESIS AND CHARACTERIZATION OF NEW INTERMETALLIC COMPOUNDS

    SciTech Connect

    Professor Monica Sorescu

    2003-05-07

    This six-month work is focused mainly on the properties of novel magnetic intermetallics. In the first project, we synthesized several 2:17 intermetallic compounds, namely Nd{sub 2}Fe{sub 15}Si{sub 2}, Nd{sub 2}Fe{sub 15}Al{sub 2}2, Nd{sub 2}Fe{sub 15}SiAl and Nd{sub 2}Fe{sub 15}SiMn, as well as several 1:12 intermetallic compounds, such as NdFe{sub 10}Si{sub 2}, NdFe{sub 10}Al{sub 2}, NdFe{sub 10}SiAl and NdFe{sub 10}MnAl. In the second project, seven compositions of Nd{sub x}Fe{sub 100-x-y}B{sub y} ribbons were prepared by a melt spinning method with Nd and B content increasing from 7.3 and 3.6 to 11 and 6, respectively. The alloys were annealed under optimized conditions to obtain a composite material consisting of the hard magnetic Nd{sub 2}Fe{sub 14}B and soft magnetic {alpha}-Fe phases, typical of a spring magnet structure. In the third project, intermetallic compounds of the type Zr{sub 1}Cr{sub 1}Fe{sub 1}T{sub 0.8} with T=Al, Co and Fe were subjected to hydrogenation. In the fourth project, we performed three crucial experiments. In the first experiment, we subjected a mixture of Fe{sub 3}O{sub 4} and Fe(80-20 wt%) to mechanochemical activation by high-energy ball milling, for time periods ranging from 0.5 to 14 hours. In the second experiment, we ball-milled Fe{sub 3}O{sub 4}:Co{sup 2+} (x=0.1) for time intervals between 2.5 and 17.5 hours. Finally, we exposed a mixture of Fe{sub 3}O{sub 4} and Co(80-20 wt%) to mechanochemical activation for time periods ranging from 0.5 to 10 hours. In all cases, the structural and magnetic properties of the systems involved were elucidated by X-ray diffraction (XRD), Moessbauer spectroscopy and hysteresis loop measurements. The four projects resulted in four papers, which are currently being considered for publication in Intermetallics, IEEE Transactions on Magnetics, Journal of Materials Science Letters and Journal of Materials Science. The contributions reveal for the first time in literature the effect of

  8. Magnetic phase transitions in layered intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Mushnikov, N. V.; Gerasimov, E. G.; Rosenfeld, E. V.; Terent'ev, P. B.; Gaviko, V. S.

    2012-10-01

    Magnetic, magnetoelastic, and magnetotransport properties have been studied for the RMn2Si2 and RMn6Sn6 (R is a rare earth metal) intermetallic compounds with natural layered structure. The compounds exhibit wide variety of magnetic structures and magnetic phase transitions. Substitution of different R atoms allows us to modify the interatomic distances and interlayer exchange interactions thus providing the transition from antiferromagnetic to ferromagnetic state. Near the boundary of this transition the magnetic structures are very sensitive to the external field, temperature and pressure. The field-induced transitions are accompanied by considerable change in the sample size and resistivity. It has been shown that various magnetic structures and magnetic phase transitions observed in the layered compounds arise as a result of competition of the Mn-Mn and Mn-R exchange interactions.

  9. Roles of Titanium-Intermetallic Compound Layer

    NASA Astrophysics Data System (ADS)

    Lee, Chii-Chang

    Four different configurations have been tested: Al-Cu, Ti/Al-Cu, Al-Cu/Ti, and Ti/Al-Cu/Ti to evaluate the possible contributions of Ti-intermetallic compound layer(s) to enhancement of the lifetime to failure. Basically, the proposed mechanisms can be classified into two groups: shunting effect and effects limited to changes in Al-Cu conducting layer(s). A resistance monitoring technique was adopted to supplement lifetime measurement to separate these two effects. By correlating the first resistance jump (spike) to the happening of a complete open across Al-Cu layer, it was found that the shunting effect contributes to enhancement of the lifetime by 4 times in Ti/Al-Cu, 2 times in Al-Cu/Ti, and 2 times in Ti/Al-Cu/Ti. A Ti underlayer was found to contribute mainly the shunting effect. However, from drift velocity measurements and failure mode analysis, it is possible to deduce that a Ti overlayer contributes not only the shunting effect but also another effect that acts to diminish the grain boundary mass transport rate by a factor of about 76. It is believed that the latter effect is a consequence of the high compressive yield stength conferred by the Ti-intermetallic compound overlayer to the Al-Cu layer. Finally, an important non-destructive technique, based on the characteristic x-rays generated by energetic electrons, to characterize the mass divergences in multilayer interconnects, was developed in this research, called SMEISIS, representing Simultaneous Multiple Elements Intensity Scanning of Interconnecting Stripes. This technique was proved to be capable of revealing detail about the shapes, nature, and location of mass divergence that cannot be revealed by thermal wave image technique and that requires time consuming multiple sectioning in TEM and SEM methods.

  10. Formation of NiAl Intermetallic Compound by Cold Spraying of Ball-Milled Ni/Al Alloy Powder Through Postannealing Treatment

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Li, Chang-Jiu; Wang, Xiu-Ru; Ren, Zhi-Liang; Li, Cheng-Xin; Yang, Guan-Jun

    2008-12-01

    Ni/Al alloy powders were synthesized by ball milling of nickel-aluminum powder mixture with a Ni/Al atomic ratio of 1:1. Ni/Al alloy coating was deposited by cold spraying using N2 as accelerating gas. NiAl intermetallic compound was evolved in situ through postspray annealing treatment of cold-sprayed Ni/Al alloy coating. The effect of annealing temperature on the phase transformation behavior from Ni/Al mechanical alloy to intermetallics was investigated. The microstructure of the mechanically alloying Ni/Al powder and NiAl coatings was characterized by scanning electron microscopy and x-ray diffraction analysis. The results show that a dense Ni/Al alloy coating can be successfully deposited by cold spraying using the mechanically alloyed powder as feedstocks. The as-sprayed alloy coating exhibited a laminated microstructure retained from the mechanically alloying powder. The annealing of the subsequent Ni/Al alloy coating at a temperature higher than 850 °C leads to complete transformation from Ni/Al alloy to NiAl intermetallic compound.

  11. X (X: Al, Mo, Ti, Pt, Si, Nb, V, and Zr) intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Chen, Qiang; Huang, Zhiwei; Zhao, Zude; Hu, Chuankai

    2014-09-01

    In the present study, the ground-state properties of Ni3X intermetallic compounds were analyzed by means of the first-principles pseudo-potential method using the Cambridge serial total energy package code. The calculated lattice parameters of Ni3X intermetallic compounds are in good agreement with the experimental and other theoretical data. The single-crystal elastic constants were calculated; the hardness, ductile, and plasticity of materials were analyzed. The calculated enthalpies of formation showed that all of intermetallic compounds were thermodynamically stable; Debye temperature and heat capacity are calculated and discussed. Moreover, the chemical bonding in these intermetallic compounds was interpreted by calculating the density of states, electron density difference distribution, and Mulliken analysis; magnetism properties were briefly analyzed.

  12. Surfaces of complex intermetallic compounds: insights from density functional calculations.

    PubMed

    Hafner, Jürgen; Krajčí, Marian

    2014-11-18

    CONSPECTUS: Complex intermetallic compounds are a class of ordered alloys consisting of quasicrystals and other ordered compounds with large unit cells; many of them are approximant phases to quasicrystals. Quasicrystals are the limiting case where the unit cell becomes infinitely large; approximants are series of periodic structures converging to the quasicrystal. While the unique properties of quasicrystals have inspired many investigations of their surfaces, relatively little attention has been devoted to the surface properties of the approximants. In general, complex intermetallic compounds display rather irregular, often strongly corrugated surfaces, making the determination of their atomic structure a very complex and challenging task. During recent years, scanning tunneling microscopy (STM) has been used to study the surfaces of several complex intermetallic compounds. If atomic resolution can be achieved, STM permits visualization of the local atomistic surface structure. However, the interpretation of the STM images is often ambiguous and sometimes even impossible without a realistic model of the structure of the surface and the distribution of the electronic density above the surface. Here we demonstrate that ab initio density functional theory (DFT) can be used to determine the energetics and the geometric and electronic structures of the stable surfaces of complex intermetallic compounds. Calculations for surfaces with different chemical compositions can be performed in the grand canonical ensemble. Simulated cleavage experiments permit us to determine the formation of the cleavage planes requiring the lowest energy. The investigation of the adsorption of molecular species permits a comparison with temperature-programmed thermal desorption experiments. Calculated surface electronic densities of state can be compared with the results of photoelectron spectroscopy. Simulations of detailed STM images can be directly confronted with the experimental results

  13. FORMATION OF INTERMETALLIC COMPOUND DISPERSIONS

    DOEpatents

    Bryner, J.S.

    1959-12-01

    BS>A method is presented for preparing dispersions containing thorium bismuthide in equiaxed form and having an average particle size of about 30 microns. Thorium particles having one dimension not greater than 0.015 in. are immersed in liquid bismuth at a temperature between 500 and 600 deg C, the quantity of thorium being in excess of its solubility in the bismuth.

  14. Valence of neptunium in intermetallic compounds

    SciTech Connect

    Spitsyn, V.I.; Ionova, G.V.

    1987-07-01

    The authors use Moessbauer spectroscopy and quantum chemical calculations to determine the valence and electronic structure of neptunium in its intermetallic forms with a variety of alloys. The isomeric shifts are measured on Np 237 nuclei. Quantum electronic properties and population density estimates are calculated within the framework of the Hartree-Fock-Slater method.

  15. Enhancement on wettability and intermetallic compound formation with an addition of Al on Sn-0.7Cu lead-free solder fabricated via powder metallurgy method

    NASA Astrophysics Data System (ADS)

    Adli, Nisrin; Razak, Nurul Razliana Abdul; Saud, Norainiza

    2016-07-01

    Due to the toxicity of lead (Pb), the exploration of another possibility for lead-free solder is necessary. Nowadays, SnCu alloys are being established as one of the lead-free solder alternatives. In this study, Sn-0.7Cu lead-free solder with an addition of 1wt% and 5wt% Al were investigated by using powder metallurgy method. The effect of Al addition on the wettability and intermetallic compound thickness (IMC) of Sn-0.7Cu-Al lead-free solder were appraised. Results showed that Al having a high potential to enhance Sn-0.7Cu lead-free solder due to its good wetting and reduction of IMC thickness. The contact angle and IMC of the Sn-0.7Cu-Al lead-free solder were decreased by 14.32% and 40% as the Al content increased from 1 wt% to 5 wt%.

  16. ESCA studies of methanation catalysts derived from intermetallic compounds

    SciTech Connect

    Chin, R.L.; Elattar, A.; Wallace, W.E.; Hercules, D.M.

    1980-10-30

    Studies of methanation catalysts derived from intermetallic compounds provided evidence that the high activity previously reported for ThNi/sub 5/ for the methanation reaction was due to a surface enrichment of the catalyst with nickel during reduction in hydrogen at 300/sup 0/C or during the reaction of carbon monoxide with hydrogen. The less active thorium oxide/nickel catalyst prepared by a conventional impregnation method had a much lower surface concentration of metallic nickel. The deactivation of the ThCo/sub 5/ intermetallic compound by deposition of graphitic carbon was also confirmed.

  17. Unique intermetallic compounds prepared by shock wave synthesis

    NASA Technical Reports Server (NTRS)

    Otto, G.; Reece, O. Y.; Roy, U.

    1971-01-01

    Technique compresses fine ground metallic powder mixture beyond crystal fusion point. Absence of vapor pressure voids and elimination of incongruous effects permit application of technique to large scale fabrication of intermetallic compounds with specific characteristics, e.g., semiconduction, superconduction, or magnetic properties.

  18. Explosive reaction pressing of intermetallic compounds from stoichiometric powder mixtures

    SciTech Connect

    Kochsiek, D.; Pruemmer, R.; Brunold, A.

    1995-09-01

    Intermetallic NiAl, TiAl, and TiAl{sub 3} were synthesized by shock compression experiments from stoichiometric powder mixtures of nickel and aluminium as well as of titanium and aluminium. Good consolidation and complete intermetallic reaction were achieved by the direct method of explosive compaction. For each powder mixture, a certain individual threshold pressure has to be exceeded in order to initiate intermetallic reaction. The reacting compounds melted completely with subsequent rapid solidification during the passage of the shock wave. The new material shows high hardness. Pores are formed by gaseous reaction products in the NiAl and TiAl{sub 3} compacts. The TiAl structure is fully-dense and dendritic.

  19. Oxygen-stabilized zirconium-vanadium intermetallic compound

    DOEpatents

    Mendelsohn, M.H.; Gruen, D.M.

    1981-10-06

    An oxygen stabilized intermetallic compound having the formula Zr/sub x/OV/sub y/ where x = 0.7 to 2.0 and y = 0.18 to 0.33 is described. The compound is capable of reversibly sorbing hydrogen at temperatures from - 196/sup 0/C to 450/sup 0/C at pressures down to 10/sup -6/ Torr. The compound is also capable of selectively sorbing hydrogen from gaseous mixtures in the presence of CO and CO/sub 2/.

  20. Quantum criticality in selected uranium intermetallic and organometallic compounds

    NASA Astrophysics Data System (ADS)

    Nasreen, Farzana

    My thesis presents the studies of the bulk properties of materials that exhibit unusual low-temperature properties due to the proximity of a quantum-critical point (QCP), for which long-range magnetic order can be suppressed to 0 K as a consequence of quantum fluctuations. A material can be tuned to the QCP by variation of a non-thermal control parameter such as hydrostatic pressure, magnetic field and chemical pressure/doping. Most of my experimental studies were performed at extreme conditions, such as high magnetic fields, low temperatures and/or high pressures. Two classes of materials were studied, namely uranium intermetallics and organometallics. The investigations on uranium intermetallics were done on compounds close to the edge of magnetism, i.e. the UCu4+xAl 8-x, UCuxAl5-x and UFe1-xNixAl compounds. Several of those compounds exhibit deviations from traditional Fermi-liquid theory and show non-Fermi liquid (NFL) scaling at low temperatures. Field-induced magnetic transitions were studied for some selected uranium compounds (UNiAl, UNiGa, UNiGe and UIrGe) as well. Furthermore, a study of organometallic quantum magnet (DTN: NiCl2-4SC(NH 2)2), which exhibits field-induced quantum criticality, is presented. In DTN, the magnetic-field induced polarization shows magneto-electric couplings between the antiferromagnetic Ni spins and the soft organic lattice.

  1. Point Defects Quenched in Nickel Aluminide and Related Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Fan, Jiawen

    Point defects in the highly ordered B2 compounds NiAl, CoAl and FeAl were studied using the perturbed gammagamma angular correlations (PAC) technique. Quadrupole interactions detected at dilute ^{111}In probes on Al sites in NiAl and CoAl were identified with complexes containing one or two vacancies in the first atomic shell. Measurements on rapidly quenched NiAl and CoAl exhibited increases in site fractions of vacancy-probe complexes caused by formation of thermal defects. Site fractions were analyzed using the law of mass action to obtain absolute vacancy concentrations. PAC is shown to be a powerful new technique for the quantitative study of equilibrium defects in solids. For NiAl, the vacancy concentration quenched-in from a given temperature was found to be independent of composition over the range 50.4 -53.5 at.% Ni, identifying the Schottky defect (vacancy pair) as the dominant equilibrium defect, and ruling out the so-called triple defect. Formation energies and entropies of Schottky pairs were determined to be 2.66(8) and 3.48(12) eV, and 12(1) and 17(2) k_{rm B}, respectively, for NiAl and CoAl. The entropies suggest huge vacancy concentrations, 13%, at the melting temperatures of NiAl and CoAl. Migration energies of Ni and Co vacancies were found to be 1.8(2) and 2.5(2) eV, respectively. FeAl exhibited complex behavior. A low-temperature regime was detected in NiAl and CoAl within which vacancies are mobile but do not anneal out, so that the vacancy concentration remains constant. In NiAl, this "bottleneck" regime extends from 350 to 700 ^circC. Vacancies were found to be bound to the In probes with an energy very close to 0.20 eV in NiAl and CoAl. An explanation of the bottleneck is proposed in terms of saturation of all lattice sinks. This annealing bottleneck should exist in a wide range of intermetallic compounds when there is a sufficiently high vacancy concentration.

  2. The Shock Hugoniot of the Intermetallic Compound Ni3Al

    SciTech Connect

    Knapp, I.; Millett, J. C. F.; Meziere, Y. J. E.; Gray, G. T. III; Bourne, N. K.

    2006-07-28

    The behaviour of the intermetallic compound, Ni3Al under shock loading conditions has been measured. The Hugoniot Elastic Limit occurs at ca. 530 MPa, which converts to a 1-D yield stress of 273 MPa, in agreement with quasi-static data. In contrast, the ductility at shock-induced strain-rates appears much reduced when compared to lower strain-rates. The Hugoniot in terms of shock velocity and particle velocity suggests that Ni3Al is more compressible than pure nickel. This is in agreement with the greater stiffnesses in nickel, measured using ultrasonic techniques.

  3. Synthesis gas reactions over catalysts formed by oxidation of thorium-containing intermetallic compounds

    SciTech Connect

    Imamura, H.; Wallace, W.E.

    1980-09-01

    Intermetallic compounds containing 1:1, 1:2, 1:5, and 7:3 thorium-nickel ratios were prepared, powdered, and treated with oxygen at room temperature or 350/sup 0/C. The resulting catalysts contained mainly thorium dioxide and metallic nickel, and the nickel dispersions, as measured by CO adsorption, were 1.1-6.0%. The catalysts were active for the reaction of 3:1 hydrogen/carbon monoxide in proportion to the amount of oxygen uptake during pretreatment, and were highly selective for methane formation. Turnover numbers of up to 10.6 were obtained at 205/sup 0/C. The methanation reaction over 3.9 and 25Vertical Bar3< nickel on thoria support prepared by the conventional impregnation method gave similar conversions at 490/sup 0/-510/sup 0/C as the oxidized intermetallic compounds did at approx. 200/sup 0/C.

  4. Structural and Electronic Investigations of Complex Intermetallic Compounds

    SciTech Connect

    Ko, Hyunjin

    2008-01-01

    In solid state chemistry, numerous investigations have been attempted to address the relationships between chemical structure and physical properties. Such questions include: (1) How can we understand the driving forces of the atomic arrangements in complex solids that exhibit interesting chemical and physical properties? (2) How do different elements distribute themselves in a solid-state structure? (3) Can we develop a chemical understanding to predict the effects of valence electron concentration on the structures and magnetic ordering of systems by both experimental and theoretical means? Although these issues are relevant to various compound classes, intermetallic compounds are especially interesting and well suited for a joint experimental and theoretical effort. For intermetallic compounds, the questions listed above are difficult to answer since many of the constituent atoms simply do not crystallize in the same manner as in their separate, elemental structures. Also, theoretical studies suggest that the energy differences between various structural alternatives are small. For example, Al and Ga both belong in the same group on the Periodic Table of Elements and share many similar chemical properties. Al crystallizes in the fcc lattice with 4 atoms per unit cell and Ga crystallizes in an orthorhombic unit cell lattice with 8 atoms per unit cell, which are both fairly simple structures (Figure 1). However, when combined with Mn, which itself has a very complex cubic crystal structure with 58 atoms per unit cell, the resulting intermetallic compounds crystallize in a completely different fashion. At the 1:1 stoichiometry, MnAl forms a very simple tetragonal lattice with two atoms per primitive unit cell, while MnGa crystallizes in a complicated rhombohedral unit cell with 26 atoms within the primitive unit cell. The mechanisms influencing the arrangements of atoms in numerous crystal structures have been studied theoretically by calculating electronic

  5. Development of New Cryocooler Regenerator Materials-Ductile Intermetallic Compounds

    SciTech Connect

    K.A. Gschneidner; A.O. Pecharsky; V.K. Pecharsky

    2004-09-30

    The volumetric heat capacities of a number of binary and ternary Er- and Tm-based intermetallic compounds, which exhibited substantial ductilities, were measured from {approx}3 to {approx}350 K. They have the RM stoichiometry (where R = Er or Tm, and M is a main group or transition metal) and crystallize in the CsCl-type structure. The heat capacities of the Tm-based compounds are in general larger than the corresponding Er-based materials. Many of them have heat capacities which are significantly larger than those of the low temperature (<15 K) prototype cryocooler regenerator materials HoCu{sub 2}, Er{sub 3}Ni and ErNi. Utilization of the new materials as regenerators in the various cryocoolers should improve the performance of these refrigeration units for cooling below 15 K.

  6. Intermetallic Phase Formation in Explosively Welded Al/Cu Bimetals

    NASA Astrophysics Data System (ADS)

    Amani, H.; Soltanieh, M.

    2016-08-01

    Diffusion couples of aluminum and copper were fabricated by explosive welding process. The interface evolution caused by annealing at different temperatures and time durations was investigated by means of optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and x-ray diffraction. Annealing in the temperature range of 573 K to 773 K (300 °C to 500 °C) up to 408 hours showed that four types of intermetallic layers have been formed at the interface, namely Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Moreover, it was observed that iron trace in aluminum caused the formation of Fe-bearing intermetallics in Al, which is near the interface of the Al-Cu intermetallic layers. Finally, the activation energies for the growth of Al2Cu, AlCu + Al3Cu4, Al4Cu9, and the total intermetallic layer were calculated to be about 83.3, 112.8, 121.6, and 109.4 kJ/mol, respectively. Considering common welding methods ( i.e., explosive welding, cold rolling, and friction welding), although there is a great difference in welding mechanism, it is found that the total activation energy is approximately the same.

  7. CO2 laser welding of titanium aluminide intermetallic compound

    NASA Astrophysics Data System (ADS)

    Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

    2000-02-01

    Titanium aluminide intermetallic compound is studied to find out good welding conditions using CO2 laser irradiation. In the experiment, we used the casting titanium aluminide containing iron, vanadium and boron with a thickness of 2 mm. We carried out bead-on-plate laser welding at various initial temperatures of specimens varied from room temperature to 873 [K] in inert gas environment filled with argon. We measured fused depth, bead width and Vickers hardness. As a result of experiments, welding speeds that allow full bead-on- plate welding to be possible were strongly by dependent on the initial temperature, 3000 [mm/min], initial temperature 873 [K], 2600 [mm/mm], initial temperature 673 [K], and 2000 [mm/min] with 300 [K]. Transverse crack-free welding was achieved, when initial temperature was at 873 [K].

  8. Effects of elastic anisotropy on mechanical behavior of intermetallic compounds

    SciTech Connect

    Yoo, M.H.

    1991-01-01

    Fundamental aspects of the deformation and fracture behavior of ordered intermetallic compounds are examined within the framework of linear anisotropic elasticity theory of dislocations and cracks. The orientation dependence and the tension/compression asymmetry of yield stress are explained in terms of the anisotropic coupling effect of non-glide stresses to the glide strain. The anomalous yield behavior is related to the disparity (edge/screw) of dislocation mobility and the critical stress required for the dislocation multiplication mechanism of Frank-Read type. The slip-twin conjugate relationship, extensive faulting, and pseudo-twinning (martensitic transformation) at a crack tip can be enhanced also by the anisotropic coupling effect, which may lead to transformation toughening of shear type.

  9. Micromechanisms of intergranular brittle ftacture in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Vitek, V.

    1991-06-01

    Grain boundaries in intermetallic compounds such as Ni3A1 are inherently brittle. The reason is usually sought in grain boundary cohesion but in metals even brittle fracture is accompanied by some local plasticity and thus not only cohesion but also dislocation mobility in the boundary region need to be studied. We first discuss here the role of an irreversible shear deformation at the crack tip during microcrack propagation assuming that these two processes are concomitant. It is shown that a pre-existing crack cannot propagate in a brittle manner once the dislocation emission occurs. However, if a microcrack nucleates during loading it can propagate concurrently with the development of the irreversible shear deformation at the crack tip. The latter is then the major energy dissipating process. In the second part of this paper we present results of atomistic studies of grain boundaries in Ni3A1 and CU3Au which suggest that substantial structural differences exist between strongly and weakly ordered L12 alloys. We discuss then the consequence of these differences for intergranular brittleness in the framework of the above model for microcrack propagation. On this basis we propose an explanation for the intrinsic intergranular brittleness in some L12 alloys and relate it directly to the strength of ordering. Les joints de grains dans les composés intermétalliques de type Ni3AI sont de nature fragile. L'origine de cette fragilité est habituellement dans la cohésion des joints de grains. Dans les métaux, cependant, même la rupture fragile est accompagnée d'une certaine déformation plastique locale, de telle sorte que non seulement la cohésion mais aussi la mobilité des dislocations près des joints doit être étudiée. Nous discutons d'abord le rôle d'une déformation en cisaillement irréversible en tête de fissure pendant la propagation de cette fissure, en supposant que les deux processus sont concomitants. Nous montrons qu'une fissure préexistante ne

  10. Griffiths phase behaviour in a frustrated antiferromagnetic intermetallic compound

    PubMed Central

    Ghosh, Krishanu; Mazumdar, Chandan; Ranganathan, R.; Mukherjee, S.

    2015-01-01

    The rare coexistence of a Griffiths phase (GP) and a geometrically frustrated antiferromagnetism in the non-stoichiometric intermetallic compound GdFe0.17Sn2 (the paramagnetic Weiss temperature θp ~ −59 K) is reported in this work. The compound forms in the Cmcm space group with large structural anisotropy (b/c ~ 4). Interestingly, all the atoms in the unit cell possess the same point group symmetry (Wycoff position 4c), which is rather rare. The frustration parameter, f = |θp|/TN has been established as 3.6, with the Néel temperature TN and Griffiths temperature TG being 16.5 and 32 K, respectively. The TG has been determined from the heat capacity measurement and also from the magnetocaloric effect (MCE). It is also shown that substantial difference in GP region may exist between zero field and field cooled measurements - a fact hitherto not emphasized so far. PMID:26515256

  11. Magnetic and crystallographic structures in UTX intermetallic compounds

    SciTech Connect

    Robinson, R.A.; Lawson, A.C.; Sechovsky, V.; Havela, L.; Kergadallan, Y.; Nakotte, H.; de Boer, F.R.

    1993-08-01

    Uranium, along with other actinides and lanthanides, forms a large group of ternary intermetallic compounds of stoichiometry UTX (T = transition metal, X = p-electron metal). These compounds are formed in several structure types and the occurrence and stability of particular structures with respect to the transition metal content suggests reasonable systematics. The authors have also investigated the magnetic structures of selected UTX compounds and it is revealing to relate the crystallographic and magnetic structures, because of the relationship between the magnetic symmetry and that of the U-atom environment produced by the 5f-ligand hybridization, and the consequent anisotropic exchange. Those of ZrNiAl structure type are collinear, with moments along the hexagonal c-axis. In the orthorhombic NiSiTi structure type, the moments are confined to the b- c plane (perpendicular to the uranium chains) and the structures are often incommensurate. In the hexagonal CaIn{sub 2} (or GaGeLi) structure type, the magnetic structures form in an orthorhombic cell, and at least in the disordered centric group, again the moments lie perpendicular to the nearest-neighbor uranium spacing. This work presents a phenomenology of trends in UTX ternary compounds. It is shown that there is an apparent strong hybridization parallel to nearest neighbor U-U directions, with ferromagnetic coupling in the same directions. There may be a systematic relationship between the hybridization anisotropy and the magnetic anisotropy, in which the quantization axes are the same and the moments point along directions of relatively weak hybridization.

  12. Recent advances in nanocrystalline intermetallic tin compounds for the negative electrode of lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Alcántara, Ricardo; Nwokeke, Uche G.; Nacimiento, Francisco; Lavela, Pedro; Tirado, José L.

    2011-06-01

    Intermetallic compounds of tin and first-row transition metals have been considered as potential anode materials for Li-ion batteries that could improve the performance of pure tin. Particularly, the solids dispersed at the nano scale provide interesting behavior. Thus CoSn, FeSn2 and CoSn3 nanocrystalline samples have been obtained at low temperatures. As compared with micrometric particles of CoSn, significantly higher reversible capacities are found for nanocrystalline CoSn. For nanocrystalline CoSn3 maximum reversible capacities of 690 mAh g-1 were observed in lithium test cells. Nanocrystalline products in the series CoSn2-FeSn2 could be prepared by chemical reduction in polyol solvents using a "one-pot" method. Superparamagnetic nanocrystalline FeSn2 delivers reversible capacities of ca. 600 mAhg-1 by the formation of LixSn phases and superparamagnetic iron nanoparticles. A comparison between the properties of nano- FeSn2 and micro-FeSn2 shows a significantly better electrochemical behavior and electrode stability for the nanocrystalline material. For Fe1-xCoxSn2 solid solutions with x= 0.25, 0.3, 0.5, 0.6 and 0.8, particle diameters of about 20 nm and different morphologies were obtained. The substitution of iron by cobalt induces a contraction of the unit cell volume and the hyperfine parameters of the 57Fe Mössbauer spectra reveal a superparamagnetic behavior. The intermediate compositions exhibit better electrochemical performance than the limit compositions CoSn2 and FeSn2. To improve the performance of CoSnx intermetallics, composites in which the nanocrystalline intermetallic material is embedded in an amorphous layer based on the polyacrylonitrile (PAN) polymer were used. The PAN shell contributes to stabilize the intermetallic phases upon electrochemical cycling.

  13. Hydrogen occupancy in the RNi{sub 4}Mg (R=Y, La, Ce, and Nd) intermetallic compounds and hydrides

    SciTech Connect

    Hahn-Herrera, Otto; Orgaz, Emilio; Aburto, Andrea

    2009-10-15

    We have investigated the effect of hydrogen on the electronic strtucture of the RNi{sub 4}Mg (R=Y, La, Ce, Pr, and Nd) intermetallics. By means of a two-step approach, the projected plane-wave and linearized plane-waves methods, we studied the hydrogen-insertion energetics on the intermetallic matrix and the H-vacancy formation in the hydride compound. We found that particular interstitial sites in the intermetallics are suitable to allocate hydrogen and form a solid solution. The effect of these interstitials on the electronic structure is discussed. In the other hand, the hydrogen-occupied sites in the hydride are found to be energetically equivalent.

  14. Application of random walk concept to the cyclic diffusion mechanisms for self-diffusion in intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Tiwari, G. P.; Mehrotra, R. S.; Iijima, Y.

    2014-02-01

    Huntington-Elcock-McCombie (HEM) mechanism involving six consecutive and correlated jumps, a triple-defect mechanism (TDM) involving three correlated jumps and an anti-structure bridge (ASB) mechanism invoking the migration of an anti-structure atom are the three mechanisms currently in vogue to explain the self- and solute diffusion in intermetallic compounds. Among them, HEM and TDM are cyclic in nature. The HEM and TDM constitute the theme of the present article. The concept of random walk is applied to them and appropriate expressions for the diffusion coefficient are derived. These equations are then employed to estimate activation energies for self-diffusion via HEM and TDM processes and compared with the available experimental data on activation energy for self-diffusion in intermetallic compounds. The resulting activation energies do not favour HEM and TDM for the self-diffusion in intermetallic compounds. A comparison of the sum of experimentally determined activation energies for vacancy formation and migration with the activation energies for self-diffusion determined from radioactive tracer method favours the conventional monovacancy-mediated process for self-diffusion in intermetallic compounds.

  15. High hardness in the biocompatible intermetallic compound β-Ti3Au

    PubMed Central

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K.; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M.; Morosan, E.

    2016-01-01

    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

  16. High hardness in the biocompatible intermetallic compound β-Ti3Au.

    PubMed

    Svanidze, Eteri; Besara, Tiglet; Ozaydin, M Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M; Morosan, E

    2016-07-01

    The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

  17. Preparation of a Ti-Ni intermetallic compound by using a drop shaft

    SciTech Connect

    Suzuki, Y.; Shimokawa, K.; Ueda, Y.; Nagao, J.

    1996-10-01

    A Ti-Ni intermetallic compound could be formed rapidly from Ti and Ni powder compact with SHS process. Microgravity experiments using a drop shaft are carried out. This report shows the effect of microgravity or high gravity on formability of an intermetallic compound. It is concluded that the specimen forms a porous and nearly amorphous alloy by rapid cooling under microgravity, but with rapid cooling under high gravity after microgravity, the specimen forms a uniform and dense structure with better crystallinity.

  18. Surface integrity on grinding of gamma titanium aluminide intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Murtagian, Gregorio Roberto

    Gamma-TiAl is an ordered intermetallic compound characterized by high strength to density ratio, good oxidation resistance, and good creep properties at elevated temperatures. However, it is intrinsically brittle at room temperature. This thesis investigates the potential for the use of grinding to process TiAl into useful shapes. Grinding is far from completely understood, and many aspects of the individual mechanical interactions of the abrasive grit with the material and their effect on surface integrity are unknown. The development of new synthetic diamond superabrasives in which shape and size can be controlled raises the question of the influence of those variables on the surface integrity. The goal of this work is to better understand the fundamentals of the abrasive grit/material interaction in grinding operations. Experimental, analytical, and numerical work was done to characterize and predict the resultant deformation and surface integrity on ground lamellar gamma-TiAl. Grinding tests were carried out, by analyzing the effects of grit size and shape, workpiece speed, wheel depth of cut, and wear on the subsurface plastic deformation depth (PDD). A practical method to assess the PDD is introduced based on the measurement of the lateral material flow by 3D non-contact surface profilometry. This method combines the quantitative capabilities of the microhardness measurement with the sensitivity of Nomarski microscopy. The scope and limitations of this technique are analyzed. Mechanical properties were obtained by quasi-static and split Hopkinson bar compression tests. Residual stress plots were obtained by x-ray, and surface roughness and cracking were evaluated. The abrasive grit/material interaction was accounted by modeling the force per abrasive grit for different grinding conditions, and studying its correlation to the PDD. Numerical models of this interaction were used to analyze boundary conditions, and abrasive size effects on the PDD. An explicit 2D

  19. Gravity segregation of complex intermetallic compounds in liquid aluminum-silicon alloys

    SciTech Connect

    Shabestari, S.G.; Gruzleski, J.E.

    1995-04-01

    Primary crystals of intermetallics that are rich in iron, manganese, and chromium form at temperatures above the liquidus, and because their density is higher than that of liquid aluminum, they cause gravity segregation in the melt. Segregation may occur either in the mold at slow cooling rates or in the bulk liquid in furnaces or ladles. The kinetics of settling of these intermetallic compounds in a melt of Al-12.5 pct Si having 1.2 pct Fe, 0.3 pct Mn, and 0.1 pct Cr has been studied. Sedimentation was investigated at 630 C for settling times of 30, 90, and 180 minutes in an electric resistance furnace. The effect of settling time and height of melt on the volume percent, number, and size of intermetallic compounds was studied by image analysis. The volume percent of intermetallics increases with distance from the melt surface. Both the number of particles and the average size increase during sedimentation. The rate of settling varies with position in the melt due to depletion of intermetallics near the surface and an increase near the bottom. The settling velocities obtained experimentally were compared with terminal velocities calculated by Stokes` law. Good agreement was generally found. The settling speed of intermetallics reaches the terminal velocity at very short times and very close to the liquid surface. Stokes` law is therefore applicable to virtually all locations within the melt.

  20. X-Ray Diffraction of Intermetallic Compounds: A Physical Chemistry Laboratory Experiment

    ERIC Educational Resources Information Center

    Varberg, Thomas D.; Skakuj, Kacper

    2015-01-01

    Here we describe an experiment for the undergraduate physical chemistry laboratory in which students synthesize the intermetallic compounds AlNi and AlNi3 and study them by X-ray diffractometry. The compounds are synthesized in a simple one-step reaction occurring in the solid state. Powder X-ray diffractograms are recorded for the two compounds…

  1. Charge transfer on the metallic atom-pair bond, and the crystal structures adopted by intermetallic compounds.

    PubMed

    Rajasekharan, T; Seshubai, V

    2012-01-01

    It has been argued in our recent papers that the heat of formation of intermetallic compounds is mostly concentrated in the nearest neighbor unlike atom-pair bonds, and that the positive term in Miedema's equation is associated with charge transfer on the bond to maintain electroneutrality. In this paper, taking examples of some well populated crystal-structure types such as MgCu(2), AsNa(3), AuCu(3), MoSi(2) and SiCr(3) types, the effect of such charge transfer on the crystal structures adopted by intermetallic compounds is examined. It is shown that the correlation between the observed size changes of atoms on alloying and their electronegativity differences is supportive of the idea of charge transfer between atoms. It is argued that the electronegativity and valence differences need to be of the required magnitude and direction to alter, through charge transfer, the elemental radius ratios R(A)/R(B) to the internal radius ratios r(A)/r(B) allowed by the structure types. Since the size change of atoms on alloying is highly correlated to how different R(A)/R(B) is from the ideal radius ratio for a structure type, the lattice parameters of intermetallic compounds can be predicted with excellent accuracy knowing R(A)/R(B). A practical application of the approach developed in our recent papers to superalloy design is presented. PMID:22186292

  2. Microstructural evolution and intermetallic formation in Al-8wt% Si-0.8wt% Fe alloy due to grain refiner and modifier additions

    NASA Astrophysics Data System (ADS)

    Hassani, Amir; Ranjbar, Khalil; Sami, Sattar

    2012-08-01

    An alloy of Al-8wt% Si-0.8wt% Fe was cast in a metallic die, and its microstructural changes due to Ti-B refiner and Sr modifier additions were studied. Apart from usual refinement and modification of the microstructure, some mutual influences of the additives took place, and no mutual poisoning effects by these additives, in combined form, were observed. It was noticed that the dimensions of the iron-rich intermetallics were influenced by the additives causing them to become larger. The needle-shaped intermetallics that were obtained from refiner addition became thicker and longer when adding the modifier. It was also found that α-Al and eutectic silicon phases preferentially nucleate on different types of intermetallic compounds. The more iron content of the intermetallic compounds and the more changes in their dimensions occurred. Formation of the shrinkage porosities was also observed.

  3. Resonant ultrasound spectroscopy: Elastic properties of some intermetallic compounds

    SciTech Connect

    Chu, F.; Thoma, D.J.; He, Y.; Maloy, S.A.; Mitchell, T.E.

    1996-09-01

    A novel nondestructive evaluation method, resonant ultrasound spectroscopy (RUS), is reviewed with an emphasis upon defining the elastic properties of intermetallic phases. The applications and advantages of RUS as compared to other conventional elastic constant measurement methods are explained. RUS has been employed to measure the elastic properties of single crystal and/or polycrystalline intermetallics, such as Laves phases (C15 HfV{sub 2} and NbCr{sub 2}), Nb-modified titanium aluminides, and transition metal disilicides (C11{sub b} MoSi{sub 2}, C40 NbSi{sub 2} and TaSi{sub 2}). For Laves phases, the elastic properties of HfV{sub 2}-based C15 phases show various anomalies and those of C15 NbCr{sub 2} do not. For Nb-modified titanium aluminides, the elastic properties of O-phase alloys are investigated as a function of alloying content. For transition metal disilicides, single crystal elastic constants of MoSi{sub 2}, NbSi{sub 2}, and TaSi{sub 2} are obtained and compared. Based on the experimentally determined elastic properties, the characteristics of interatomic bonding in these materials are examined and the possible impact of the elastic properties on mechanical behavior is discussed.

  4. Hydrides of intermetallic compounds and alloys: their properties and application in atomic technology

    SciTech Connect

    Perevezentsev, A. N.; Andreev, B. M.; Kapyshev, V. K.; Rivkis, L. A.; Malek, M. P.; Bystritskii, V. M.; Stolupin, V. A.

    1988-11-01

    The Soviet and foreign literature is reviewed and an attempt is made to systematize the large amount of information on the fundamental properties of most of the well-known hydride-forming intermetallic compounds and their practical use for the extraction, cleaning, and storage of hydrogen and the separation of its isotopes.

  5. Modeling of Intermetallic Compounds Growth Between Dissimilar Metals

    NASA Astrophysics Data System (ADS)

    Wang, Li; Wang, Yin; Prangnell, Philip; Robson, Joseph

    2015-09-01

    A model has been developed to predict growth kinetics of the intermetallic phases (IMCs) formed in a reactive diffusion couple between two metals for the case where multiple IMC phases are observed. The model explicitly accounts for the effect of grain boundary diffusion through the IMC layer, and can thus be used to explore the effect of IMC grain size on the thickening of the reaction layer. The model has been applied to the industrially important case of aluminum to magnesium alloy diffusion couples in which several different IMC phases are possible. It is demonstrated that there is a transition from grain boundary-dominated diffusion to lattice-dominated diffusion at a critical grain size, which is different for each IMC phase. The varying contribution of grain boundary diffusion to the overall thickening kinetics with changing grain size helps explain the large scatter in thickening kinetics reported for diffusion couples produced under different conditions.

  6. Catalyst and semiconductor studies involving oxidized rare earth intermetallic compounds. [Visible radiation

    SciTech Connect

    Shamsi, A.

    1981-01-01

    The intermetallic compounds (LaNi/sub 5/, CeNi/sub 5/, Ce/sub 2/Ni/sub 17/, TbNi/sub 5/, ZrNi/sub 5/, LaCo/sub 5/ ThCo/sub 5/ and CeCo/sub 5/) were oxidized with nitric oxide (NO), synthesis gas (SG) and oxygen (O/sub 2/). Most of these intermetallic compounds react readily with the oxidizers and were transformed into a mixture of transition metal and rare earth oxide for ThO/sub 2/) during the oxidation processes. Samples were also prepared by a freeze-drying method. The catalytic activity of these materials for synthesis gas conversion was measured with a single pass microreactor operating at 1 atm total pressure, and the major products were CH/sub 4/, CO/sub 2/, C/sub 2/H/sub 4/, C/sub 2/H/sub 6/ and H/sub 2/O. The product distribution indicated that the formation of methane is favored for most of the catalysts. CeCo/sub 5/ and LaCo/sub 5/ oxidized with O/sub 2/ were found to have higher olefin to paraffin ratio than the other catalysts. Carbon deposition occurs on the oxidized Co compound and ZrNi/sub 5/ during the catalytic reaction. The preparation of polycrystalline rare earth iron oxide electrodes by heating the rare earth (R) iron compounds (RFe/sub 2/, RFe/sub 3/, R/sub 2/Fe/sub 17/ and R/sub 6/Fe/sub 23/) in air in the flame of a Fisher burner is reported. Iron oxide and titanium oxide are also prepared by heating Fe and Ti metal in air for comparison. The current-voltage (I-V) properties of these materials are measured in aqueous solution of 1 M NaOH. The flatband potentials (V/sub fb/) are determined with respect to a fixed potential (SCE) extrapolating to zero current in I-V curves. Photoelectrolysis of water occurs at these electrodes, resulting in the evolution of oxygen (O/sub 2/) from the RFeO/sub x/ electrodes and hydrogen from the Pt electrode. Most of these electrodes are found to be stable under experimental conditions and anodic photocurrents are generated by light energy greater than the band gap energy (E/sub g/).

  7. Possibility of Mg- and Ca-based intermetallic compounds as new biodegradable implant materials.

    PubMed

    Hagihara, Koji; Fujii, Kenta; Matsugaki, Aira; Nakano, Takayoshi

    2013-10-01

    Mg- or Ca-based intermetallic compounds of Mg2Ca, Mg2Si, Ca2Si and CaMgSi are investigated as possible new candidates for biodegradable implant materials, attempting to improve the degradation behavior compared to Mg and Ca alloys. The reactivity of Ca can be indeed reduced by the formation of compounds with Mg and Si, but its reactivity is still high for applications as an implant material. In contrast, Mg2Si shows a higher corrosion resistance than conventional Mg alloys while retaining biodegradability. In cytotoxicity tests under the severe condition conducted in this study, both pure Mg and Mg2Si showed relatively high cytotoxicity on preosteoblast MC3T3-E1. However, the cell viability cultured in the Mg2Si extract medium was confirmed to be better than that in a pure Mg extract medium in all the conditions investigated with the exception of the 10% extract medium, because of the lower corrosion rate of Mg2Si. The cytotoxicity derived from the Si ion was not significantly detected in the Mg2Si extract medium in the concentration level of ~70 mg/l measured in the present study. For aiming the practical application of Mg2Si as an implant material, however, its brittle nature must be improved.

  8. On the site preferences of ternary additions to triple defect B2 intermetallic compounds

    SciTech Connect

    Pike, L.M.; Chen, S.L.; Chang, Y.A.

    1995-12-31

    Knowledge of the site preference of ternary solute additions is essential to developing an understanding of how these solutes affect the properties of B2 intermetallic compounds. A quasichemical model will be presented which is able to predict the site preferences of dilute solute additions to triple defect B2 compounds. The only parameters required are enthalpies of formation at the stoichiometric composition. General equations are developed which can be used to determine site occupations and defect concentrations for dilute as well as non-dilute solute additions. These equations use atom pair bond enthalpies as the parameters. It is found that the site preferences of dilute additions are not always in agreement with predictions based on the solubility lobes in ternary Gibbs isotherms, Predictions for dilute additions to NiAl and FeAl are compared to experimental results found in the literature. Satisfactory correlation is found between the model and the experimental results. In addition, the predictions from the model on vacancy concentrations in Fe doped NiAl are compared to recent experimental results by the authors.

  9. Synthesis, Characterization and Properties of Nanoparticles of Intermetallic Compounds

    SciTech Connect

    DiSalvo, Francis J.

    2015-03-12

    The research program from 2010 to the end of the grant focused on understanding the factors important to the synthesis of single phase intermetallic nano-particles (NPs), their size, crystalline order, surface properties and electrochemical activity. The synthetic method developed is a co-reduction of mixtures of single metal precursors by strong, soluble reducing agents in a non-protic solvent, tetrahydrofuran (THF). With some exceptions, the particles obtained by room temperature reduction are random alloys that need to be annealed at modest temperatures (200 to 600 °C) in order to develop an ordered structure. To avoid significant particle size growth and agglomeration, the particles must be protected by surface coatings. We developed a novel method of coating the metal nanoparticles with KCl, a by-product of the reduction reaction if the proper reducing agents are employed. In that case, a composite product containing individual metal nanoparticles in a KCl matrix is obtained. The composite can be heated to at least 600 °C without significant agglomeration or growth in particle size. Washing the annealed product in the presence of catalyst supports in ethylene glycol removes the KCl and deposits the particles on the support. Six publications present the method and its application to producing and studying new catalyst/support combinations for fuel cell applications. Three publications concern the use of related methods to explore new lithium-sulfur battery concepts.

  10. TiNiSn: A gateway to the (1,1,1) intermetallic compounds

    SciTech Connect

    Cook, B.A.; Harringa, J.L.; Tan, Z.S.; Jesser, W.A.

    1996-06-01

    Recent awareness of the transport properties of Skutterudite pnictides has stimulated an interest in numerous other intermetallic compounds having a gap in the density of states at the Fermi level including the MNiSn compounds where M = (Ti, Zr, Hf). These intermetallic half-Heusler compounds are characterized by high Seebeck coefficients ({minus}150 to {minus}300 {micro}V/deg.) and reasonable carrier mobilities (30 to 50 cm{sup 2}/V-s) at room temperature which make them attractive candidates for intermediate temperature thermoelectric applications. Samples of TiNiSn were prepared by arc melting and homogenized by heat treatment. The temperature dependence of the electrical resistivity, Seebeck coefficient, and thermal diffusivity of these samples was characterized between 22 C and 900 C. The electrical resistivity and thermopower both decrease with temperature although the resistivity decreases at a faster rate. Electrical power factors in excess of 25 {micro}W/cm-C{sup 2} were observed in nearly single phase alloys within a 300 to 600 C temperature range. A brief survey of other selected ternary intermetallic compounds is also presented.

  11. Oxidation behavior of plasma sintered beryllium-titanium intermetallic compounds as an advanced neutron multiplier

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Hwan; Nakamichi, Masaru

    2013-07-01

    Beryllium intermetallic compounds (beryllides) such as Be12Ti are very promising candidates for advanced neutron multiplier materials in a demonstration fusion power reactor (DEMO). However, beryllides are too brittle to be fabricated either into pebble-type or rod-type shapes via conventional methods (i.e. arc melting and hot isostatic pressing). We have proposed a plasma sintering technique as a new method for beryllide fabrication, and our studies on the properties of plasma sintered beryllides are ongoing. In the present work, the oxidation properties of plasma sintered beryllides were investigated at 1273 K for 24 h in a dry air atmosphere to evaluate the high temperature properties of this material. Thermal gravimetry measurements indicate that specimens with larger fractions of Be12Ti phase corresponding to samples that have been sintered for longer time periods, exhibit superior oxidation properties. Our evaluation of the oxidation behavior of each phase in our beryllide samples is as follows: Be12Ti and Be17Ti2 both have good oxidation resistance, owing to the formation of dense and protective scales, while the Be and Be2Ti phases are mainly responsible for thermal-gravimetry (TG) weight gains, which is indicative of severe oxidation. We attribute the degradation in oxidation resistance specifically to Be2Ti that transforms into TiO2, and also find this phase to be the cause of deterioration in the mechanical properties of samples, owing to cracks near Be2Ti phase conglomerates.

  12. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

    PubMed Central

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-01-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

  13. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound

    NASA Astrophysics Data System (ADS)

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-08-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys.

  14. Increasing strength and conductivity of Cu alloy through abnormal plastic deformation of an intermetallic compound.

    PubMed

    Han, Seung Zeon; Lim, Sung Hwan; Kim, Sangshik; Lee, Jehyun; Goto, Masahiro; Kim, Hyung Giun; Han, Byungchan; Kim, Kwang Ho

    2016-01-01

    The precipitation strengthening of Cu alloys inevitably accompanies lowering of their electric conductivity and ductility. We produced bulk Cu alloys arrayed with nanofibers of stiff intermetallic compound through a precipitation mechanism using conventional casting and heat treatment processes. We then successfully elongated these arrays of nanofibers in the bulk Cu alloys to 400% of original length without breakage at room temperature using conventional rolling process. By inducing such an one-directional array of nanofibers of intermetallic compound from the uniform distribution of fine precipitates in the bulk Cu alloys, the trade-off between strength and conductivity and between strength and ductility could be significantly reduced. We observed a simultaneous increase in electrical conductivity by 1.3 times and also tensile strength by 1.3 times in this Cu alloy bulk compared to the conventional Cu alloys. PMID:27488621

  15. Electronic and high pressure elastic properties of RECd and REHg (RE=Sc, La and Yb) intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Devi, Hansa; Pagare, Gitanjali; Chouhan, Sunil S.; Sanyal, Sankar P.

    2015-01-01

    Structural, electronic, elastic and mechanical properties of Cd and Hg based rare earth intermetallics (RECd and REHg; RE=Sc, La and Yb) have been investigated using the full-potential linearized augmented plane-wave (FP-LAPW) method within the density-functional theory (DFT). The ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B‧) have been obtained using optimization method and are found in good agreement with the available experimental results. The calculated enthalpy of formation shows that LaHg has the strongest alloying ability and structural stability. The electronic band structures and density of states reveal the metallic character of these compounds. The structural stability mechanism is also explained through the electronic structures of these compounds. The chemical bonding between rare earth atoms and Cd, Hg is interpreted by the charge density plots along (1 1 0) direction. The elastic constants are predicted from which all the related mechanical properties like Poisson's ratio (σ), Young's modulus (E), shear modulus (GH) and anisotropy factor (A) are calculated. The ductility/brittleness of these intermetallics is predicted. Chen's method has been used to predict the Vicker's hardness of RECd and REHg compounds. The pressure variation of the elastic constants is also reported in their B2 phase.

  16. Radiation-induced crystalline-to-amorphous transition in intermetallic compounds of the Cu-Ti alloy system

    SciTech Connect

    Lam, N.Q.; Okamoto, P.R.; Devanathan, R. ); Sabochick, M.J. . Computer Applications Div.)

    1992-02-01

    Recent progress in molecular-dynamics studies of radiation-induced crystalline-to-amorphous transition in the ordered intermetallic compounds of the Cu-Ti system is discussed. The effect of irradiation was simulated by the generation of Frenkel pairs,which resulted in both the formation of stable point defects and chemical disorder upon defect recombination. The thermodynamic, structural and mechanical responses of the compounds during irradiation were determined by monitoring changes in the system potential energy, volume expansion, pair correlation function, diffraction patterns, and elastic constants. It was found that the intermetallics Cu{sub 4}Ti{sub 3}, CuTi, and CuTi{sub 2} could be rendered amorphous by the creation of Frenkel pairs, but Cu{sub 4}Ti could not, consistent with experimental observations during electron irradiation. However, the simulations showed that Cu{sub 4}Ti did become amorphous when clusters of Frenkel pairs were introduced, indicating that this compound may be susceptible to amorphization by heavy-ion bombardment. A generalization of the Lindemann criterion was used to develop a thermodynamic description of solid-state amorphization as a disorder- induced melting process.

  17. Hydride Properties and IRON-57 Mossbauer Effect Studies in TITANIUM(COPPER(1-Y)IRON(Y)) Intermetallic Compounds.

    NASA Astrophysics Data System (ADS)

    Zakaria, Ahmad

    1987-12-01

    The hydrogen absorption properties of the Ti(Cu _{rm 1-y}Fe _{rm y}) (0 <=q y <=q 1) intermetallic compound were systematically investigated. X-ray diffraction data indicated that the intermetallic compound adopted the gammaTiCu structure for 0 <=q y <=q.1 and crystallized in the TiFe structure for.5 <=q y <=q 1. A mixture of these two phases was observed for 0.1 < y <.5. The lattice parameters for the pure intermetallic compounds and hydrided samples were measured. The heat of hydride formation, DeltaH, as a function of Fe content was determined from pressure-composition isotherms and the Van't Hoff relation. In the composition range 0 <=q y <=q.1 the value of DeltaH varied from -74.3 kJ (mole H_{2 })^{-1} to -59.1 kJ (mole H_{2})^{ -1}. For.5 <=q y <=q 1 it went from -49.5 kJ (mole H_{2})^{-1} to -27.3 kJ (mole H_ {2})^{-1}. We have found that DeltaH values derived from a model proposed by Shilov et al. for calculating DeltaH of the multicomponent hydrides were in good agreement with the experimental data by about 3%. Other properties of the hydride such as hydrogen storage capacity and hysteresis effect were also found to be y dependent. Systematic ^{57}Fe Mossbauer effect studies were also carried out in the intermetallic compound and hydride systems with the emphasis on the isomer shift measurements. The total s-electron densities at the Fe nucleus (|psi_{ rm s}({rm o})|^ {2}) increases when the Fe content y decreases in the pure intermetallic compounds. | psi_{rm s}({rm o })|^{2} decreases with the introduction of the hydrogen. In the hydride system |psi_{rm s}({rm o})|^{2 } was found to be y independent. Interpretation of the data was based on the changes in | psi_{rm s}({rm o })|^{2} due to expansion and contraction of the host lattice and the electronic structure differences. The decrease in | psi_{rm s}({rm o })|^{2} due to the hydrogenation in the TiCu-like hydride (0 <=q y <=q.1) could be accounted for by the volume effect only. For TiFe-like hydride

  18. Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element

    SciTech Connect

    Yang, S. C.; Ho, C. E.; Chang, C. W.; Kao, C. R.

    2007-04-15

    Massive spalling of intermetallic compounds has been reported in the literature for several solder/substrate systems, including SnAgCu soldered on Ni substrate, SnZn on Cu, high-Pb PbSn on Cu, and high-Pb PbSn on Ni. In this work, a unified thermodynamic argument is proposed to explain this rather unusual phenomenon. According to this argument, two necessary conditions must be met. The number one condition is that at least one of the reactive constituents of the solder must be present in a limited amount, and the second condition is that the soldering reaction has to be very sensitive to its concentration. With the growth of intermetallic, more and more atoms of this constituent are extracted out of the solder and incorporated into the intermetallic. As the concentration of this constituent decreases, the original intermetallic at the interface becomes a nonequilibrium phase, and the spalling of the original intermetallic occurs.

  19. Low temperature properties of some Er-rich intermetallic compounds

    SciTech Connect

    K.A. Gshneidner,jr; A.O. Pecharsky; L.Hale; V.K. Pecharsky

    2004-09-30

    The low temperature volumetric heat capacity ({approx}3.5 to 350 K) and magnetic susceptibility ({approx}4 to 320 K) of Er{sub 3}Rh, Er{sub 3}Ir, Er{sub 3}Pt, Er{sub 2}Al, and Er{sub 2}Sn have been measured. All of the compounds order antiferromagnetically (or ferrimagnetically), and most exhibit more than one magnetic ordering transition. The volumetric heat capacities in general are smaller than those of the prototype magnetic regenerator materials, except for Er{sub 3}Ir in the 12 to 14 K temperature range.

  20. Long-Term Behavior of the Tritides Formed by Nickel-Based Intermetallic Compounds

    SciTech Connect

    Bowman, Jr., R. C.; Steinmeyer, R. H.; Matson, L. K.; Attalla, A.; Craft, B. D.

    1985-04-01

    Some properties of the tritide phases formed by the intermetallic compounds Mg2Ni, ZrNi, and LaNi5 have been studied. Whereas ZrNiT3 will retain its stoichiometry indefinitely when sufficient gaseous tritium is available, the stoichiometries of Mg2NiT4 and LaNi5T6.9 decrease with time. Although all three intermetallic tritides can retain large quantities of the helium-3 tritium decay daughter product in the solid phase, irreversible release of helium begins after several hundred days for ZrNiTx and Mg2NiTx. However, LaNi5Tx retains all of the helium generated in the solid for at least 2400 days. NMR measurements for ZrNiTx and Mg2NiTx imply that helium is retained in microscopic bubbles as previously observed in several binary metal tritides.

  1. Degradation behavior of Ca-Mg-Zn intermetallic compounds for use as biodegradable implant materials.

    PubMed

    Hagihara, Koji; Shakudo, Shuhei; Fujii, Kenta; Nakano, Takayoshi

    2014-11-01

    With the goal of developing new biodegradable implant materials, we have investigated the degradation behavior of (Ca, Mg)-based intermetallic compounds. The degradation behavior of the compounds within the Ca-Mg-Zn system was roughly classified into four groups, and their behaviors were strongly influenced by the compositions of the compounds. For example, the Ca3MgxZn(15-x) compound exhibited a large solubility region with varying the Mg/Zn ratio, and the Ca3Mg12Zn3 phase alloy with the lowest Zn content was rapidly broken apart within 6h of immersion. Alternatively, the Ca3Mg4.6Zn10.4 phase alloy with the highest Zn content retained the bulk shape even after 250 h of immersion. These varying degradation behaviors were ascribed to the difference in the formability of Zn oxide as a protective layer against corrosion on the specimen surfaces, depending on the Zn content. The gained results suggest that there is a feasibility on developing new biodegradable materials based on intermetallic compounds in which the degradation rate can be controlled by their compositions.

  2. The atomic structure of low-index surfaces of the intermetallic compound InPd.

    PubMed

    McGuirk, G M; Ledieu, J; Gaudry, É; de Weerd, M-C; Hahne, M; Gille, P; Ivarsson, D C A; Armbrüster, M; Ardini, J; Held, G; Maccherozzi, F; Bayer, A; Lowe, M; Pussi, K; Diehl, R D; Fournée, V

    2015-08-21

    The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ∼580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ∼660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (≥750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and "global" measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature. PMID:26298146

  3. The atomic structure of low-index surfaces of the intermetallic compound InPd

    NASA Astrophysics Data System (ADS)

    McGuirk, G. M.; Ledieu, J.; Gaudry, É.; de Weerd, M.-C.; Hahne, M.; Gille, P.; Ivarsson, D. C. A.; Armbrüster, M.; Ardini, J.; Held, G.; Maccherozzi, F.; Bayer, A.; Lowe, M.; Pussi, K.; Diehl, R. D.; Fournée, V.

    2015-08-01

    The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ˜580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ˜660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (≥750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and "global" measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature.

  4. The atomic structure of low-index surfaces of the intermetallic compound InPd

    SciTech Connect

    McGuirk, G. M.; Ledieu, J.; Gaudry, É.; Weerd, M.-C.; Fournée, V. de; Hahne, M.; Gille, P.; Ivarsson, D. C. A.; Armbrüster, M.; Ardini, J.; Held, G.; Maccherozzi, F.; Bayer, A.; Lowe, M.; Pussi, K.; Diehl, R. D.

    2015-08-21

    The intermetallic compound InPd (CsCl type of crystal structure with a broad compositional range) is considered as a candidate catalyst for the steam reforming of methanol. Single crystals of this phase have been grown to study the structure of its three low-index surfaces under ultra-high vacuum conditions, using low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy (STM). During surface preparation, preferential sputtering leads to a depletion of In within the top few layers for all three surfaces. The near-surface regions remain slightly Pd-rich until annealing to ∼580 K. A transition occurs between 580 and 660 K where In segregates towards the surface and the near-surface regions become slightly In-rich above ∼660 K. This transition is accompanied by a sharpening of LEED patterns and formation of flat step-terrace morphology, as observed by STM. Several superstructures have been identified for the different surfaces associated with this process. Annealing to higher temperatures (≥750 K) leads to faceting via thermal etching as shown for the (110) surface, with a bulk In composition close to the In-rich limit of the existence domain of the cubic phase. The Pd-rich InPd(111) is found to be consistent with a Pd-terminated bulk truncation model as shown by dynamical LEED analysis while, after annealing at higher temperature, the In-rich InPd(111) is consistent with an In-terminated bulk truncation, in agreement with density functional theory (DFT) calculations of the relative surface energies. More complex surface structures are observed for the (100) surface. Additionally, individual grains of a polycrystalline sample are characterized by micro-spot XPS and LEED as well as low-energy electron microscopy. Results from both individual grains and “global” measurements are interpreted based on comparison to our single crystals findings, DFT calculations and previous literature.

  5. Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge

    NASA Astrophysics Data System (ADS)

    Nagasawa, Shinobu; Koishi, Tetsuya; Tokoi, Yoshinori; Suzuki, Tsuneo; Nakayama, Tadachika; Suematsu, Hisayuki; Niihara, Koichi

    2014-02-01

    The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N2 ambient gas with varying number of turns of the wire (Nt), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (Kp) was calculated. It increased with an increase in Nt to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in Kp, the Ni composition ratio of the prepared particles (CNi) became closer to that of the wire (= 51.2 mol %). Furthermore, the collection rate (Rc) increased and the median particle diameter (d50) decreased. In particular, the change in d50 due to the change in Nt was not predicted by the relationship of d50 and Dth in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which Nt is 0.4 turns/mm, K is 3.4, and P is 100 kPa, where relatively high value of Kp was obtained. From these results, Kp was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.

  6. Brittle intermetallic compound makes ultrastrong low-density steel with large ductility.

    PubMed

    Kim, Sang-Heon; Kim, Hansoo; Kim, Nack J

    2015-02-01

    Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

  7. Development of Cu alloy anode and separator coated with Al-Ni intermetallic compound

    SciTech Connect

    Toyokura, K.; Hoshino, K.; Yamamoto, M.

    1996-12-31

    Anode made of Cu alloy and separator coated with Al-Ni intermetallic compound have been developed for VCFC. Anode of Ni alloy is usually used. However, the alternative of cost lower than Ni alloy anode should be needed, because Ni is expensive. Cu is attractive as an anode material for VCFC because it is inexpensive and electrochemically noble. However, the creep resistance of Cu is not sufficient, compared with Ni alloy. In this study, strengthening due to oxide-dispersed microstructure has been developed in Cu-Ni-Al alloy with the two-step sintering process. A wet-seal technique has been widely applied for gas-sealing and supporting of electrolyte in MCFC. Since the wet-seal area is exposed to a severe corrosive environment, corrosion resistance of material for wet sealing is related with the cell performance. Al-Ni plating with post-heat treating for stainless steel has been investigated. Stainless steel substrate was plated with Al after being coated with Ni, then heat-treated at 750 {degrees}C for 1 hour in Ar gas atmosphere. Due to the treatment, Al-Ni intermetallic compound ( mainly Al3Ni2 ) layer is formed on stainless steel surface. The long-term immersion test was carried out till 14,500 hours in 62 mol% Li{sub 2}CO{sub 3}-38 mol% K{sub 2}CO{sub 3} at 650 {degrees}C under air-30%CO{sub 2} atmosphere, for the purpose of evaluating the corrosion resistance and thermal stability of Al-Ni intermetallic compound layer in actual generating with VCFC.

  8. Magnetostriction and magnetism of rare earth intermetallic compounds: First principle study

    NASA Astrophysics Data System (ADS)

    Gavrilenko, V. I.; Wu, R. Q.

    2001-06-01

    Magnetism and magnetostriction of rare earth intermetallic compounds, GdCo2, GdFe2, NdCo2, SmCo2, and ErCo2, have been studied by using the first principles full-potential linearized augmented plane-wave method with the generalized gradient approximation. The calculated magnetostriction coefficients agree well with experiment. The itinerant electrons of transition metal elements are found to play a significant role in magnetoelastic coupling. The strong anisotropy of magnetostriction in GdCo2 is explained. Contributions due to spatial anisotropic charge distribution of the incomplete 4f shells are calculated and discussed.

  9. Properties Evaluation and Studying Production Mechanism of Nanocrystalline NiAl Intermetallic Compound by Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Khajesarvi, Ali; Akbari, Golamhossein

    2016-04-01

    Ni50Al50 intermetallic compound was synthesized by mechanical alloying (MA) of elemental mixtures of Ni and Al powders in a planetary ball mill. After 16 hours of milling and obtaining crystallites with a critical size, the initial NiAl compound was formed along with the combustive reaction after opening the vial lid. In the time interval of 16 to 128 hours, the reaction from combustive state reached the explosive state. Finally, after 128 hours of milling, the initial powders were wholly transformed into NiAl before completion of the milling time. Structural changes of powder particles during MA were studied by X-ray diffractometry and scanning electron microscopy. The crystallite size measurements revealed that the grain size of the NiAl phase decreased from 155 to 26 nm with increasing MA time from 8 to 128 hours. Microhardness for nanocrystalline Ni50Al50 intermetallic compound produced after 128 hours of milling was measured as about 350 Hv.

  10. Intermetallic Formation at Interface of Al/Cu Clad Fabricated by Hydrostatic Extrusion and Its Properties.

    PubMed

    Lee, Jongbeom; Jeong, Haguk

    2015-11-01

    Al/Cu clad composed of Al core and Cu sheath has been produced by hydrostatic extrusion at 523 K, at an extrusion rate of 27. The prepared specimen was post-annealed at temperatures of 673 K and 773 K for various time durations, and the effect of annealing conditions have been analyzed. The hardness at the interface between Al and Cu matrix of the Al/Cu bimetal clad increases because of annealing. Results indicate that the hardness is more sensitive to annealing temperature than the annealing time. Three kinds of intermetallic compounds (IMC), namely, CuAl, Cu3Al2, and CuAl2, are formed at the Al-Cu interface, upon annealing at 673 K. On the other hand, four kinds of IMCs, namely, Cu4Al3, CuAl, Cu3Al2, CuAl2, are formed at the annealing temperature of 773 K. The growth of each IMC follows the parabolic law as a function of annealing times at certain annealing temperature. The growth rate of each IMC is limited to its interdiffusion rate constant. The IMC Cu4Al3 appears upon annealing at 773 K, and not during annealing at 673 K, because of the higher value of activation energy associated with its formation, when compared to other IMCs. PMID:26726557

  11. Characterization of second-phase plates in a Gd5Ge3 intermetallic compound

    SciTech Connect

    Cao, Qing; Chumbley, Leonard S.

    2013-05-16

    Rare-earth compounds based on the stoichiometry R5(SixGe1-x)4 (R = rare-earth elements) exhibit many unusual features, including possessing R5(SixGe1-x)3 thin plates which always precipitate from the matrix despite efforts to suppress their formation. In an effort to better understand the unique relationship between these two intermetallic alloy systems, the bulk microstructure of the compound Gd5Ge3 was examined using scanning (SEM) and transmission electron microscopy (TEM) and optical microscopy. Surprisingly, SEM examination revealed a series of thin plates present in the Gd5Ge3 matrix similar to what is seen in Gd5Ge4. TEM observation revealed that a role reversal had occurred, with the thin plates possessing the orthorhombic structure and composition of Gd5Ge4. The orientation relationship between Gd5Ge4 thin plates and the Gd5Ge3 matrix was determined to be Graphic the same relationship reported for Gd5Ge3 plates precipitating from a Gd5Ge4 matrix. However, by exchanging the respective roles of the phases as regards matrix vs. precipitate, the total number of precipitation variants seen can be increased from two to six. The persistence with which these two intermetallic systems co-exist is truly unique. However, understanding exactly the kinetic and thermodynamic conditions that lead to their unique relationship is hampered by the high formation temperatures at which the observed reaction occurs.

  12. Intermetallic nanoparticles

    SciTech Connect

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules

    2015-07-14

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  13. Intermetallic nanoparticles

    SciTech Connect

    Singh, Dileep; Yusufoglu, Yusuf; Timofeeva, Elena; Routbort, Jules L.

    2015-11-20

    A process for preparing intermetallic nanoparticles of two or more metals is provided. In particular, the process includes the steps: a) dispersing nanoparticles of a first metal in a solvent to prepare a first metal solution, b) forming a reaction mixture with the first metal solution and a reducing agent, c) heating the reaction mixture to a reaction temperature; and d) adding a second metal solution containing a salt of a second metal to the reaction mixture. During this process, intermetallic nanoparticles, which contain a compound with the first and second metals are formed. The intermetallic nanoparticles with uniform size and a narrow size distribution is also provided. An electrochemical device such as a battery with the intermetallic nanoparticles is also provided.

  14. Surface structures of In-Pd intermetallic compounds. II. A theoretical study

    SciTech Connect

    Gaudry, É.; McGuirk, G. M.; Ledieu, J.; Fournée, V.

    2014-08-28

    The (110) surface of the InPd intermetallic compound and the In–Pd surface alloy properties are investigated in the framework of the density functional theory, within the projector augmented plane-wave method. Surface segregation is calculated to be energetically unfavorable at stoichiometric InPd(110) surfaces, while indium antisites are shown to segregate to the surface in off-stoichiometric InPd(110) systems. Concerning surface alloys obtained by burying In-doped Pd layers in Pd(111), we demonstrated that the most stable ones are those presenting atomic indium concentrations below 50 at. % (11 at. %, 25 at. %, 33 at. %). According to our calculations, the In-doped Pd layers with concentration above or equal to 50% lead to In-doped Pd multilayers, each presenting an atomic indium concentration below 50 at. %. Alloying and segregation effects in InPd intermetallic compound and In–Pd surface alloys clearly agree with the larger bonding strength of In–Pd (−0.44 eV) compared to In–In (−0.29 eV) and Pd–Pd (−0.31 eV)

  15. First principles calculations of the optical and plasmonic response of Au alloys and intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Keast, V. J.; Barnett, R. L.; Cortie, M. B.

    2014-07-01

    Pure Au is widely used in plasmonic applications even though its use is compromised by significant losses due to damping. There are some elements that are less lossy than Au (e.g. Ag or Al) but they will normally oxidize or corrode under ambient conditions. Here we examine whether alloying Au with a second element would be beneficial for plasmonic applications. In order to evaluate potential alternatives to pure Au, the density of states (DOS), dielectric function and plasmon quality factor have been calculated for alloys and compounds of Au with Al, Cd, Mg, Pd, Pt, Sn, Ti, Zn and Zr. Substitutional alloying of Au with Al, Cd, Mg and Zn was found to slightly improve the plasmonic response. Of the large number of intermetallic compounds studied, only AuAl2, Au3Cd, AuMg, AuCd and AuZn were found to be suitable for plasmonic applications.

  16. A review on the synthesis, crystal growth, structure and physical properties of rare earth based quaternary intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Mumbaraddi, Dundappa; Sarkar, Sumanta; Peter, Sebastian C.

    2016-04-01

    This review highlights the synthesis and crystal growth of quaternary intermetallic compounds based on rare earth metals. In the first part of this review, we highlight briefly about intermetallics and their versatile properties in comparison to the constituent elements. In the next part, we have discussed about various synthesis techniques with more focus on the metal flux technique towards the well shaped crystal growth of novel compounds. In the subsequent parts, several disordered quaternary compounds have been reviewed and then outlined most known ordered quaternary compounds with their complex structure. A special attention has been given to the ordered compounds with structural description and relation to the parent binary and ternary compounds. The importance of electronic and structural feature is highlighted as the key roles in designing these materials for emerging applications.

  17. Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

    SciTech Connect

    Jongik Park

    2004-12-19

    EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} are two members of the RT{sub 2}X{sub 2} (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr{sub 2}Si{sub 2} structure are known for their wide variety of magnetic properties, Extensive studies of the RT{sub 2}X{sub 2} series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-earth nickel germanides RNi{sub 2}Ge{sub 2} were recently studied in more detail [4]. The purpose of this dissertation is to investigate the electronic structure (both valence band and shallow core levels) of single crystals of EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} and to check the assumptions that the f electrons are non-interacting and, consequently, the rigid-band model for these crystals would work [11], using synchrotron radiation because, to the best of our knowledge, no photoemission measurements on those have been reported. Photoemission spectroscopy has been widely used to study the detailed electronic structure of metals and alloys, and especially angle-resolved photoemission spectroscopy (ARPES) has proven to be a powerful technique for investigating Fermi surfaces (FSs) of single-crystal compounds.

  18. Effect of Intermetallic Compound Phases on the Mechanical Properties of the Dissimilar Al/Cu Friction Stir Welded Joints

    NASA Astrophysics Data System (ADS)

    Khodir, S. A.; Ahmed, M. M. Z.; Ahmed, Essam; Mohamed, Shaymaa M. R.; Abdel-Aleem, H.

    2016-09-01

    Types and distribution of intermetallic compound phases and their effects on the mechanical properties of dissimilar Al/Cu friction stir welded joints were investigated. Three different rotation speeds of 1000, 1200 and 1400 rpm were used with two welding speeds of 20 and 50 mm/min. The results show that the microstructures inside the stir zone were greatly affected by the rotation speed. Complex layered structures that containing intermetallic compound phases such as CuAl2, Al4Cu9 were formed in the stir zone. Their amount found to be increased with increasing rotation speed. However, the increasing of the rotation speed slightly lowered the hardness of the stir zone. Many sharp hardness peaks in the stir zones were found as a result of the intermetallic compounds formed, and the highest peaks of 420 Hv were observed at a rotation speed of 1400 rpm. The joints ultimate tensile strength reached a maximum value of 105 MPa at the rotation speed of 1200 rpm and travel speed of 20 mm/min with the joint efficiency ranged between 88 and 96% of the aluminum base metal. At the travel speed of 50 mm/min, the maximum value of the ultimate tensile strength was 96 MPa at rotation speed of 1400 rpm with the joint efficiency ranged between 79 and 90%. The fracture surfaces of tensile test specimens showed no evidence for the effect of the brittle intermetallic compounds in the stir zones on the tensile strength of the joints.

  19. Microstructural Evolution of Intermetallic Compounds in TCNCP Cu Pillar Solder Joints

    NASA Astrophysics Data System (ADS)

    Liang, Chien-Lung; Lin, Kwang-Lung; Peng-Wei, Jr.

    2016-01-01

    This study investigated the microstructure, especially intermetallic compounds (IMCs), formed between a Cu pillar and Cu trace joined by thermal compression bonding with nonconductive paste (NCP). Continuous, uniform layers of Cu3Sn formed on the surface of both the Cu pillar and Cu trace. However, the growth of Cu6Sn5 was suppressed, forming nonuniformly on the Cu trace due to NCP filler entrapment at the Cu-solder interface that hindered Sn diffusion flux. Multireflow induced rapid growth of IMCs within the Cu pillar solder joint. The combination of multireflow and thermal cycle testing gave rise to asymmetric growth of IMCs between the chip side and substrate side as a result of stress migration induced by thermal cycling.

  20. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, Iver E.; Lograsso, Barbara K.; Ellis, Timothy W.

    1994-01-01

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material.

  1. Gas atomization synthesis of refractory or intermetallic compounds and supersaturated solid solutions

    DOEpatents

    Anderson, I.E.; Lograsso, B.K.; Ellis, T.W.

    1994-11-29

    A metallic melt is atomized using a high pressure atomizing gas wherein the temperature of the melt and the composition of the atomizing gas are selected such that the gas and melt react in the atomization spray zone to form a refractory or intermetallic compound in the as-atomized powder particles. A metallic melt is also atomized using a high pressure atomizing gas mixture gas wherein the temperature of the melt and the ratio of a reactive gas to a carrier gas are selected to form powder particles comprising a supersaturated solid solution of the atomic species of the reactive gas in the particles. The powder particles are then heat treated to precipitate dispersoids in-situ therein to form a dispersion strengthened material. 9 figures.

  2. Whisker formation in Sn and Pb-Sn coatings: Role of intermetallic growth, stress evolution, and plastic deformation processes

    SciTech Connect

    Chason, E.; Jadhav, N.; Kumar, K. S.; Chan, W. L.; Reinbold, L.

    2008-04-28

    We have simultaneously measured the evolution of intermetallic volume, stress, and whisker density in Sn and Pb-Sn alloy layers on Cu to study the fundamental mechanisms controlling whisker formation. For pure Sn, the stress becomes increasingly compressive and then saturates, corresponding to a plastically deformed region spreading away from the growing intermetallic particles. Whisker nucleation begins after the stress saturates. Pb-Sn layers have similar intermetallic growth kinetics but the resulting stress and whisker density are much less. Measurements after sputtering demonstrate the important role of the surface oxide in inhibiting stress relaxation.

  3. Multiconfigurational nature of 5f orbitals in uranium and plutonium and their intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Booth, Corwin

    2013-03-01

    The structural, electronic, and magnetic properties of U and Pu elements and intermetallics remain poorly understood despite decades of effort, and currently represent an important scientific frontier toward understanding matter. The last decade has seen great progress both due to the discovery of superconductivity in PuCoGa5 and advances in theory that finally can explain fundamental ground state properties in elemental plutonium, such as the phonon dispersion curve, the non-magnetic ground state, and the volume difference between the α and δ phases. A new feature of the recent calculations is the presence not only of intermediate valence of the Pu 5f electrons, but of multiconfigurational ground states, where the different properties of the α and δ phases are primarily governed by the different relative weights of the 5f4, 5f5, and 5f6 electronic configurations. The usual method for measuring multiconfigurational states in the lanthanides is to measure the lanthanide LIII-edge x-ray absorption near-edge structure (XANES), a method that is severely limited for the actinides because the spectroscopic features are not well enough separated. Advances in resonant x-ray emission spectroscopy (RXES) have now allowed for spectra with sufficient resolution to resolve individual resonances associated with the various actinide valence states. Utilizing a new spectrometer at the Stanford Synchrotron Radiation Lightsource (SSRL), RXES data have been collected that show, for the first time, spectroscopic signatures of each of these configurations and their relative changes in various uranium and plutonium intermetallic compounds. In combination with conventional XANES spectra on related compounds, these data indicate such states may be ubiquitous in uranium and plutonium intermetallics, providing a new framework toward understanding properties ranging from heavy fermion behavior, superconductivity, and intermediate valence to mechanical and fundamental bonding behavior in

  4. Fundamental study about CO2 laser welding of titanium aluminide intermetallic compound

    NASA Astrophysics Data System (ADS)

    Kuwahara, Gaku; Yamaguchi, Shigeru; Nanri, Kenzo; Ootani, Masanori; Tetsuka, Masato; Seto, Sachio; Arai, Mikiya; Fujioka, Tomoo

    2000-11-01

    Titanium aluminide intermetallic compound is attracting attentions as heat-resistant and high-specific strength material in the next generation, especially, it is promising material in the field of aerospace components. Conventional machining process including welding, however, can be hardly applied due to its very low ductility. The objective of this study, as a first stage, is to find out paying attention to crack and hardness the fundamental good conditions of the bead-on-plate welding of TiAl intermetallic compound using CO2 laser irradiation. In the experiment, we used the casting gamma titanium aluminide contained iron, vanadium and boron with a thickness of 2mm. We carried out bead-on-plate laser welding in the titanium aluminide material in inert gas environment filled with argon. We measured fused depth, Vickers hardness, transverse crack numbers and so on as major parameters of welding speed from 1000 to 4600 mm/min and initial temperature of specimen from R.T. to 873 K with a beam spot size of 0.5 mm and an output power of 1.5 kW. In addition, the specimens were analyzed by Electron Probe X-ray Micro Analyzer, Energy Dispersive X-ray Spectroscopy and X-ray Diffractometry. As a result of experiments, transverse crack-free welding was achieved, when initial temperature was at 873 K. In every condition, the value of Vickers hardness of fused zone increased compared with base. We think the reason of it is an increase of (alpha) 2(Ti3Al) phase, which is caused by rapid cooling, taking in Oxygen, fine structure and so on.

  5. Effects of Bonding Wires and Epoxy Molding Compound on Gold and Copper Ball Bonds Intermetallic Growth Kinetics in Electronic Packaging

    NASA Astrophysics Data System (ADS)

    Gan, C. L.; Classe, F. C.; Chan, B. L.; Hashim, U.

    2014-04-01

    This paper discusses the influence of bonding wires and epoxy mold compounds (EMC) on intermetallic compound (IMC) diffusion kinetics and apparent activation energies ( E aa) of CuAl and AuAl IMCs in a fineline ball grid array package. The objective of this study is to study the CuAl and AuAl IMC growth rates with different epoxy mold compounds and to determine the apparent activation energies of different combination of package bills of materials. IMC thickness measurement has been carried out to estimate the coefficient of diffusion ( D o) and E aa various aging conditions of different EMCs and bonding wires. Apparent activation energies ( E aa) of both wire types were investigated after high temperature storage life tests (HTSL) for both molding compounds. Au bonds were identified to have faster IMC formation, compared to slower IMC growth of Cu. The E aa obtained for CuAl IMC diffusion kinetics are 1.08 and 1.04 eV with EMC A and EMC B, respectively. For AuAl IMC diffusion kinetics, the E aa obtained are 1.04 and 0.98 eV, respectively, on EMC A and EMC B. These values are close to previous HTSL studies conducted on Au and Cu ball bonds and are in agreement to the theory of HTSL performance of Au and Cu bonding wires.Overall, EMC B shows slightly lower apparent activation energy ( E aa) valueas in CuAl and AuAl IMCs. This proves that the different types of epoxy mold compounds have some influence on IMC growth rates.

  6. Observation of superconductivity in the intermetallic compound β-IrSn4.

    PubMed

    Tran, Vinh Hung; Bukowski, Zbigniew; Wiśniewski, Piotr; Tran, Lan Maria; Zaleski, Andrzej J

    2013-04-17

    Low-temperature dc-magnetization, ac electrical resistivity and specific heat measurements were performed on single crystals of the intermetallic compound β-IrSn4. The compound crystallizes in the tetragonal MoSn4-type structure (space group I41/acd) and exhibits superconductivity below Tc = 0.9 ± 0.05 K. Further, the magnitude of the ratios ΔCp/(γnkBTc) = 1.29, 2Δ/(kBTc) = 3.55 and of the electron-phonon coupling λ[overline](e-ph) = 0.5 imply that superconductivity in β-IrSn4 can be ascribed to a s-wave weak coupling regime. We determined crucial thermodynamic characteristics of the superconducting state. It turned out that depending on the assumption of either a spherical or non-spherical Fermi surface, the superconductivity can be ascribed to either a type-I and type-II/1 or type-II in clean limit, respectively. However, the behavior of the upper critical field and the anisotropic crystalline structure of the studied compound provide strong support to the type-II superconductivity. In the normal state the resistivity exhibits a prominent quadratic temperature dependence, which together with a large Kadowaki-Woods ratio and with the enhanced effective mass indicate that the electrons in β-IrSn4 are strongly correlated.

  7. Atomic disorder induced by mechanical milling in the intermetallic compound CoAl

    NASA Astrophysics Data System (ADS)

    Di, L. M.; Bakker, H.; de Boer, F. R.

    1992-10-01

    The stoichiometric intermetallic compound CoAl with the CsCl-structure was subjected to ball milling. Structural changes during ball milling were studied by measurements of the magnetization and the lattice parameter. The behaviour of Coal upon milling turns out to be quite similar to that of CoGa. The increase of the magnetization and the decrease of the lattice parameter with the milling time show that, similar to CoGa, triple-defect disorder is generated by ball milling. By comparing the measured magnetization to the magnetization of Co xAl 100- x compounds with excess Co, the concentration of defects is derived for milled samples. In order to interpret our results, the existing experimental data of lattice parameters, X-ray densities calculated from the lattice parameters and macroscopic densities for Co xAl 100- x compounds were analyzed according to Edelin's equations. The defect volumes for vacancies and anti-site atoms obtained by fitting these experimental data have reasonable values. By means of the defect concentrations obtained from our magnetization measurements and the defect volumes by fitting the experimental data, the change of the lattice parameter was calculated by means of Edelin's equation. The agreement between the calculated lattice parameter and the measured lattice parameter is quite satisfactory.

  8. Growth of a Au-Ni-Sn intermetallic compound on the solder-substrate interface after aging

    SciTech Connect

    Minor, Andrew M.; Morris, J.W., Jr.

    1999-12-16

    Au/Ni metallization has become increasingly common in microelectronic packaging when Cu pads are joined with Pb-Sn solder. The outermost Au layer serves to protect the pad from corrosion and oxidation and the Ni layer provides a diffusion barrier to inhibit detrimental growth of Cu-Sn intermetallics. As a result of reflowing eutectic Pb-Sn on top of Au/Ni metallization, the as-solidified joints have AuSn{sub 4} precipitates distributed throughout the bulk of the solder joint, and Ni{sub 3}Sn{sub 4} intermetallics at the interface. Recent work has shown that the Au-Sn redeposits onto the interface during aging, compromising the strength of the joint. The present work shows that the redeposited intermetallic layer is a ternary compound with stoichiometry Au{sub 0.5}Ni{sub 0.5}Sn{sub 4}. The growth of this intermetallic layer was investigated, and results show that the ternary compound is observed to grow after as little as 3 hours at 150 C and after 3 weeks at 150 C has grown to a thickness of 10 {micro}m. Additionally, methods for inhibiting the growth of the ternary layer were investigated and it was determined that multiple reflows, both with and without additional aging can substantially limit the thickness of the ternary layer.

  9. Elastic and Thermodynamic Properties of Complex Mg-Al Intermetallic Compounds via Orbital-Free Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Zhuang, Houlong; Chen, Mohan; Carter, Emily A.

    2016-06-01

    Magnesium-aluminum (Mg-Al) alloys are important metal alloys with a wide range of engineering applications. We investigate the elastic and thermodynamic properties of Mg, Al, and four stoichiometric Mg-Al compounds including Mg17Al12 , Mg13Al14 , and Mg23Al30 , and MgAl2 with orbital-free density-functional theory (OFDFT). We first calculate the lattice constants, zero-temperature formation energy, and independent elastic constants of these six materials and compare the results to those computed via Kohn-Sham DFT (KSDFT) benchmarks. We obtain excellent agreement between these two methods. Our calculated elastic constants of hexagonal close-packed Mg and face-centered-cubic Al are also consistent with available experimental data. We next compute their phonon spectra using the force constants extracted from the very fast OFDFT calculations, because such calculations are computationally challenging using KSDFT. This is especially the case for the Mg23Al30 compound, whose 3 ×3 ×3 supercell consists of 1431 atoms. We finally employ the quasiharmonic approximation to investigate temperature-dependent thermodynamic properties, including formation energies, heat capacities, and thermal expansion of the four Mg-Al intermetallic compounds. The calculated heat capacity and thermal expansion of both Mg and Al agree well with experimental data. We additionally find that Mg13Al14 and MgAl2 are both unstable, consistent with their absence from the equilibrium Mg-Al phase diagram. Our work demonstrates that OFDFT is an efficient and accurate quantum-mechanical computational tool for predicting elastic and thermodynamic properties of complicated Mg-Al alloys and also should be applicable to many other engineering alloys.

  10. In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

    SciTech Connect

    Qu, Lin; Zhao, Ning; Ma, Haitao Zhao, Huijing; Huang, Mingliang

    2014-05-28

    Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu{sub 6}Sn{sub 5} IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end after solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu{sub 6}Sn{sub 5} IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics.

  11. Growth kinetics of Al–Fe intermetallic compounds during annealing treatment of friction stir lap welds

    SciTech Connect

    Movahedi, M.; Kokabi, A.H.; Seyed Reihani, S.M.; Najafi, H.; Farzadfar, S.A.; Cheng, W.J.; Wang, C.J.

    2014-04-01

    In this study, we explored the growth kinetics of the Al–Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 °C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state. The results showed that the growth kinetics of the IM layer was not governed by a parabolic diffusion law. Presence of the IM compounds as well as high stored energy near the joint interface of the as-welded sample was recognized to be the origin of the observed deviation from the parabolic diffusion law. - Highlights: • This work provided a new insight into growth kinetics of Al–Fe IM thickness. • The growth kinetics of IM layer was not governed by a parabolic diffusion law. • IM near the joint interface was the origin of deviation from the parabolic law. • High stored energy at joint interface was origin of deviation from parabolic law.

  12. Discovery and characterization of magnetism in sigma-phase intermetallic Fe-Re compounds

    SciTech Connect

    Cieślak, J. Dubiel, S. M.; Tobola, J.; Reissner, M.

    2014-11-14

    Systematic experimental studies (vibrating sample magnetometry) supported by theoretical calculations (electronic structure by spin self-consistent Korringa-Kohn-Rostoker Green's function method) were performed on a series of intermetallic sigma-phase Fe{sub 100−x}Re{sub x} (x = 43–53) compounds. All investigated samples exhibit magnetism with an ordering temperature ranging between ∼65 K for x = 43 and ∼23 K for x = 53. The magnetism was revealed to be itinerant and identified as a spin-glass (SG) possibly having a re-entrant character. The SG was found to be heterogeneous, viz., two regimes could be distinguished as far as irreversibility in temperature dependence of magnetization is concerned: (1) of a weak irreversibility and (2) of a strong one. According to the theoretical calculations, the main contribution to the magnetism comes from Fe atoms occupying all five sub lattices, while Re atoms have rather small magnetic moments. However, the calculated average magnetic moments highly (ferromagnetic ordering model) or moderately (antiparallel ordering model) overestimate the experimental data.

  13. Interaction Between the Growth and Dissolution of Intermetallic Compounds in the Interfacial Reaction Between Solid Iron and Liquid Aluminum

    NASA Astrophysics Data System (ADS)

    Chen, Shuhai; Yang, Dongdong; Zhang, Mingxin; Huang, Jihua; Zhao, Xingke

    2016-10-01

    The interfacial reaction between solid steel and liquid aluminum has been widely investigated in past decades; however, some issues, such as the solid/liquid interfacial structure, formation mechanisms of FeAl3 and Fe2Al5, and interaction between the growth and dissolution of intermetallic compounds, are still not fully understood. In this study, a hot-dipping method is designed to investigate the interfacial reaction in the temperature range between 973 K and 1273 K (700 °C 1000 °C) for 10 to 60 seconds. The intensification of the dissolution leads to the transformation of FeAl3/liquid aluminum into Fe2Al5/liquid aluminum in the solid/liquid structure with increasing reaction temperature. The formation of FeAl3 adhered to the interface depends not only on the reaction mechanism but also on precipitation at relatively low temperatures. In contrast, precipitation is the only formation mechanism for FeAl3 at relatively high temperatures. Austenitizing results in the complete transformation of the tongue-like Fe2Al5/Fe interface to a flat shape. The growth of Fe2Al5 with respect to the maximum thickness is governed by the interfacial reaction process, whereas the growth of Fe2Al5 with respect to the average thickness is governed by the diffusion process in the range of 973 K to 1173 K (700 °C to 900 °C) for 10 to 60 seconds. The dissolution of the parent metal is due to the natural dissolution of FeAl3 at low temperatures and Fe2Al5 at high temperatures.

  14. Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements

    SciTech Connect

    Kumar, P; Kashyap, A; Balamurugan, B; Shield, JE; Sellmyer, DJ; Skomski, R

    2014-01-27

    First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands.

  15. Permanent magnetism of intermetallic compounds between light and heavy transition-metal elements.

    PubMed

    Kumar, P; Kashyap, A; Balamurugan, B; Shield, J E; Sellmyer, D J; Skomski, R

    2014-02-12

    First-principle calculations are used to investigate the intrinsic magnetic properties of intermetallic alloys of the type XMn, where X is a 4d or 5d element and M is Fe or Co. Emphasis is on the hexagonal C14 Laves-phase 1:2 and 1:5 alloys, the latter crystallizing in the CaCu5 structure. These series are of interest in permanent magnetism from fundamental and practical viewpoints, respectively. In the former, the unit cells form a prototypical motif where a heavy atom with high spin-orbit coupling and magnetocrystalline anisotropy is surrounded by many somewhat smaller M atoms with high magnetization, and the latter are Laves-phase derivatives of renewed interest in permanent magnetism. Our DFT calculations predict magnetic moments, magnetizations and anisotropies, as well as formation energies. The results are analyzed across the 4d and 5d series, especially with respect to hybridization effects between 3d and 4d/5d bands.

  16. The intermetallic formation and growth kinetics at the interface of near eutectic tin-silver-copper solder alloys and gold/nickel metallization

    NASA Astrophysics Data System (ADS)

    Gao, Mao

    The formation of a one micron thick layer of an intermetallic compound between a solder alloy and a metallic substrate generally constitutes a good solder joint in an electronic device. However, if the compound grows too thick, and/or if multiple intermetallic compounds form, poor solder joint reliability may result. Thus significant interest has been focused on intermetallic compound phase selection and growth kinetics at such solder/metal interfaces. The present study focuses on one such specific problem, the formation and growth of intermetallic compounds at near eutectic Sn-Ag-Cu solder alloy/Ni interfaces. Sn-3.0Ag-0.5Cu solder was reflowed on Au/Ni substrates, resulting in the initial formation and growth of (CuNi)6Sn 5 at Sn-3.0Ag-0.5Cu /Ni interfaces. (NiCu)3Sn4 formed between the (CuNi)6Sn5 and the Ni substrate when the concentration of Cu in the liquid SnAgCu solder decreased to a critical value which depended upon temperature: 0.37, 0.31 and 0.3(wt.%) at reflow temperatures of 260°C, 245°C and 230°C respectively. The growth rate of (CuNi)6Sn5 was found to be consistent with extrapolations of a diffusion limited growth model formulated for lower temperature, solid state diffusion couples. The long range diffusion of Cu did not limit growth rates. The spalling of (CuNiAu)6Sn5 from (NiCu)3 Sn4 surfaces during reflow was also examined. When the Cu concentration in the solder decreased to approximately 0.28wt.%, the (Cu,Ni,Au) 6Sn5 was observed to spall. Compressive stress in (CuNiAu) 6Sn5 and weak adhesion between (CuNiAu)6Sn 5 and (NiCu)3Sn4 was found to cause this effect.

  17. Magnetic properties of the intermetallic compounds PrNiSn and NdNiSn

    NASA Astrophysics Data System (ADS)

    Beirne, Eamonn Daniel

    Inelastic neutron scattering has been used to determine the crystalline electric field (CEF) excitations in the intermetallic compound PrNiSn. Polycrystalline samples of PiNiSn are found to have 7 excitations up to 30 meV, with strong low-lying modes at 2.0, 3.5, and 5.1 meV. The site symmetry of Pr3+ in this system is such that the degeneracy of the 9 levels in the J = 4 ground state multiplet is removed completely by the crystal field. From fitting this data, it is clear that the ground state is a singlet that couples to each of the other 8 excited states. The wavefunctions of the levels are determined and a level scheme proposed for this material. Inelastic scattering results are also presented for a single crystal of PrNiSn. The dispersion of the low-lying E = 3.5 meV CEF excitation is documented, showing 4 distinct modes corresponding to the 4 Pr ions in the unit cell. Susceptibility and magnetisation results for PrNiSn and NdNiSn are presented. From these measurements it is clear that the PrNiSn does not order magnetically down to 2K, whereas NdNiSn has an antifenomagnetic transition at TN = 3.1K. Resistivity measurements on PrNiSn also show no evidence of a magnetic transition, but there are gradient changes at around 4.5K and 12K. This corresponds to a local maximum at 12K and local minimum at 4.5K along the b-axis in this compound. Measurements on single crystals of these compounds show strong anisotropy in both cases, attributed to CEF effects. From the proposed CEF level scheme, the bulk properties such as the susceptibility can be modelled. Neutron powder diffraction measurements on both PrNiSn and NdNiSn confirm that there is no magnetic transition down to 1.6K in PrNiSn, and TN is confirmed for NdNiSn. Structural Rietveld fitting confirms the room temperature orthorhombic structure in both systems down to low temperature, but the magnetic structure of NdNiSn can not be determined. This is due to the magnetic peaks below TN doubling up, indicating a

  18. Effects of Inert Nanoparticles of High-Melting-Point Compositions on Grain Structure and Strength of Ni3Al Intermetallic Compounds

    NASA Astrophysics Data System (ADS)

    Ovcharenko, V. E.; Boyangin, E. N.; Chudinov, V. A.

    2016-08-01

    The paper represents experimental findings both in the area of effects of nanoparticles of inert high-melting-point TiN compounds on a Ni3Al intermetallic grain structure creation in the conditions of high temperature synthesis under pressure, and in the area of impact of grain structure modification on intermetallic compounds' strength factor temperature dependence. It was demonstrated that appending a stoichiometric composition of nanosized particles of high-melting-point inert chemical compounds (TiN) initiates a manyfold loss of average size of grain of Ni3Al intermetallic compounds, synthesized under pressure, as well as a sufficient intermetallic compounds' strength rise within a wide range of temperatures (up to 1 000 degree C). Electron-microscopic evaluations of a synthesized intermetallic structure with TiN nanoparticles, showed that, during the process of intermetallic polycrystalline structure creation from high temperature synthesis products melts, TiN nanoparticles are mainly spread throughout the boundaries and joints of grain structure, acting as stoppers of grain boundaries migration.

  19. Dissolution and Interfacial Reactions of (Cu,Ni)6Sn5 Intermetallic Compound in Molten Sn-Cu-Ni Solders

    NASA Astrophysics Data System (ADS)

    Wang, Chao-hong; Lai, Wei-han; Chen, Sinn-wen

    2014-01-01

    (Cu,Ni)6Sn5 is an important intermetallic compound (IMC) in lead-free Sn-Ag-Cu solder joints on Ni substrate. The formation, growth, and microstructural evolution of (Cu,Ni)6Sn5 are closely correlated with the concentrations of Cu and Ni in the solder. This study reports the interfacial behaviors of (Cu,Ni)6Sn5 IMC (Sn-31 at.%Cu-24 at.%Ni) with various Sn-Cu, Sn-Ni, and Sn-Cu-Ni solders at 250°C. The (Cu,Ni)6Sn5 substrate remained intact for Sn-0.7 wt.%Cu solder. When the Cu concentration was decreased to 0.3 wt.%, (Cu,Ni)6Sn5 significantly dissolved into the molten solder. Moreover, (Cu,Ni)6Sn5 dissolution and (Ni,Cu)3Sn4 formation occurred simultaneously for the Sn-0.1 wt.%Ni solder. In Sn-0.5 wt.%Cu-0.2 wt.%Ni solder, many tiny (Cu,Ni)6Sn5 particulates were formed and dispersed in the solder matrix, while in Sn-0.3 wt.%Cu-0.2 wt.%Ni a lot of (Ni,Cu)3Sn4 grains were produced. Based on the local equilibrium hypothesis, these results are further discussed based on the liquid-(Cu, Ni)6Sn5-(Ni,Cu)3Sn4 tie-triangle, and the liquid apex is suggested to be very close to Sn-0.4 wt.%Cu-0.2 wt.%Ni.

  20. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    PubMed

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase.

  1. Investigations of Zr-Ni intermetallic compounds by perturbed angular correlations

    NASA Astrophysics Data System (ADS)

    Dey, C. C.

    2013-09-01

    The hyperfine interactions experienced by 181Ta in ZrNi5 and Zr2Ni7 intermetallic compounds have been investigated by the perturbed angular correlation (PAC) technique. In ZrNi5, a strong electric quadrupole interaction (∼40%) with ωQ=72.0(1) Mrad/s, η=0.25(1), δ=0 at room temperature has been found due to the presence of Zr2Ni7 contaminating phase produced during sample preparation in the arc furnace. A weak quadrupole interaction of Zr2Ni7 (∼5%) with ωQ=65(1) Mrad/s, η=0.24(6), δ=0 has also been observed. The cubic component of ZrNi5 also has been observed (∼40% at room temperature) in this sample along with associated defect (15%). It is found that at 873 K, the cubic fraction increases to ∼54% at the cost of its defect fraction. No magnetic interaction in ZrNi5 has been observed which supports the earlier PAC results but rules out the result of strong magnetic ordering found from magnetization measurement. In Zr2Ni7, two regular fractions corresponding to two different crystallographic sites of Zr have been clearly identified with the parameters ωQ(1)=70.9(1) Mrad/s, η(1)=0.28(1), δ=1.3(3)% and ωQ(2)=64(1) Mrad/s, η(2)=0.34(8), δ=0 while contradictory results were reported from previous measurements.

  2. Role of defect coordination environment on point defects formation energies in Ni-Al intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Tennessen, Emrys; Rondinelli, James

    We present a relationship among the point defect formation energies and the bond strengths, lengths, and local coordination environment for Ni-Al intermetallic alloys based on density functional calculations, including Ni3Al, Ni5Al3, NiAl,Ni3Al4, Ni2Al3 and NiAl3. We find the energetic stability of vacancy and anti-site defects for the entire family can be attributed primarily to changes in interactions among first nearest neighbors, owing to spatially localized charge density reconstructions in the vicinity of the defect site. We also compare our interpretation of the local coordination environment with a DFT-based cluster expansion and discuss the performance of each approach in predicting defect stability in the Ni-Al system.

  3. Effect of Y2O3 and TiC Reinforcement Particles on Intermetallic Formation and Hardness of Al6061 Composites via Mechanical Alloying and Sintering

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Liang; Lin, Chen-Han

    2015-08-01

    Al6061-based composites reinforced with 2 wt pctY2O3 and 2 wt pctTiC particles produced by mechanical alloying were investigated. The reinforced particles play important roles in the microstructural development and in determining the properties of the alloys. High-energy ball milling can facilitate a solid-state reaction between reinforced particles and the Al matrix, and the reaction kinetics of atomic diffusion can be accelerated enormously by subsequent sintering processing. As a result, complex intermetallic compounds and oxide particles can be formed in the alloy. In this study, the effect of reinforcement on phase formation and mechanical properties of Al6061-based composites has been examined. The results suggest that nano-Y2O3 particles can act as nucleation sites to facilitate formation of Al-Si-Y-O-based oxide particles. The addition of TiC particles can effectively refine the grain structure and encourage formation of iron-rich intermetallic compounds. Nanoindentation was used to understand the local variations in mechanical properties of the Al6061-based composites.

  4. Processing, compositional range, and mechanical behavior of the Mo(5)Si(3)C intermetallic compound

    NASA Astrophysics Data System (ADS)

    Ross, Eli Nickerson

    The intermetallic compound Mo5Si3C was studied in order to examine optimal processing methods, elevated temperature mechanical behavior, and the influence of crystal symmetry on the potential for improved room temperature ductility/toughness in ternary silicides. During the course of the investigation, samples were produced using nonconsumable arc melting and vacuum hot pressing of either blended or mechanically alloyed powders. The most significant challenge to the production of single-phase Mo5 Si3C was the significantly narrower range of homogeneity for the ternary compound than originally reported. The primary reason for this discrepancy is thought to be the use of x-ray diffraction (XRD) as the sole means of phase identification in the original study, whereas the current work augmented XRD with other microstructural analysis techniques. Further complicating the processing of Mo5Si3C was the occurrence of composition shifts during powder processing. These shifts in stoichiometry were correlated to observed microstructural features and likely the result of thermodynamically favored reactions between silica present in the starting powders and carbon. Because of these complications, materials for mechanical testing typically contained between one and 6 volume percent of phases other than Mo5Si3C, with samples having the nominal composition Mo4.8Si3C0.87 closest to single phase. An average microhardness value of 13.2 GPa was recorded for the ternary phase at room temperature, and an indentation fracture toughness of approximately 2.5 MPa·m1/2 was determined. In the temperature range 1000 to 1300°C, materials tested in compression displayed properties that were highly strain rate and grain size dependent, indicating the influence of boundary-controlled deformation mechanisms. The behavior of samples tested in four-point bending at 1200°C showed similar behavior, with larger grain size materials failing after limited deformation while finer grain size materials

  5. Effects of metallic nanoparticle doped flux on the interfacial intermetallic compounds between lead-free solder ball and copper substrate

    SciTech Connect

    Sujan, G.K. Haseeb, A.S.M.A. Afifi, A.B.M.

    2014-11-15

    Lead free solders currently in use are prone to develop thick interfacial intermetallic compound layers with rough morphology which are detrimental to the long term solder joint reliability. A novel method has been developed to control the morphology and growth of intermetallic compound layers between lead-free Sn–3.0Ag–0.5Cu solder ball and copper substrate by doping a water soluble flux with metallic nanoparticles. Four types of metallic nanoparticles (nickel, cobalt, molybdenum and titanium) were used to investigate their effects on the wetting behavior and interfacial microstructural evaluations after reflow. Nanoparticles were dispersed manually with a water soluble flux and the resulting nanoparticle doped flux was placed on copper substrate. Lead-free Sn–3.0Ag–0.5Cu solder balls of diameter 0.45 mm were placed on top of the flux and were reflowed at a peak temperature of 240 °C for 45 s. Angle of contact, wetting area and interfacial microstructure were studied by optical microscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was observed that the angle of contact increased and wetting area decreased with the addition of cobalt, molybdenum and titanium nanoparticles to flux. On the other hand, wettability improved with the addition of nickel nanoparticles. Cross-sectional micrographs revealed that both nickel and cobalt nanoparticle doping transformed the morphology of Cu{sub 6}Sn{sub 5} from a typical scallop type to a planer one and reduced the intermetallic compound thickness under optimum condition. These effects were suggested to be related to in-situ interfacial alloying at the interface during reflow. The minimum amount of nanoparticles required to produce the planer morphology was found to be 0.1 wt.% for both nickel and cobalt. Molybdenum and titanium nanoparticles neither appear to undergo alloying during reflow nor have any influence at the solder/substrate interfacial reaction. Thus, doping

  6. Behavior of alloys of the PtPd intermetallic compound with Hf and Zr in the electrosynthesis of peroxo salts

    SciTech Connect

    Toroptseva, N.T.; Vaseva, A.Yu.

    1988-08-10

    The objective of this study was to investigate the behavior of anodes made of alloys of the PtPd intermetallic compound with Hf and Zr in the synthesis of potassium peroxodicarbonates and peroxoborates. The investigations were based on polarization measurements in different regimes on stationary and rotating electrodes, the determination of the current yield of active oxygen in galvano- and potentiostatic syntheses, and the study of the kinetics of catalytic decomposition of peroxide solutions in the presence of the electrode in the range 289-308 K.

  7. Structure and mechanical properties of cement and intermetallic compounds via ab-initio simulations

    NASA Astrophysics Data System (ADS)

    Dharmawardhana, Chamila Chathuranga

    structural material such as cement. However, it is far too early to be applicable for cement. Thus, this study used intermetallic compounds as a test case to develop new AIMD methods. In light of this objective, a direct method to calculate high temperature mechanical properties was devised for Mo5Si3 (T1 phase) and Mo5B2Si 3 (T2 phase). It was found that thermal expansion anisotropy (TEA) of T1 phase is captured by this simulation. It was also found an AIMD method to reduce TEA of Mo5Si3 (T1 phase) by strategic alloying. With further research these methods may be transferrable to cement and may allow optimizing the performance of hydraulic cements.

  8. Stability of molybdenum nanoparticles in Sn-3.8Ag-0.7Cu solder during multiple reflow and their influence on interfacial intermetallic compounds

    SciTech Connect

    Haseeb, A.S.M.A. Arafat, M.M. Johan, Mohd Rafie

    2012-02-15

    This work investigates the effects of molybdenum nanoparticles on the growth of interfacial intermetallic compound between Sn-3.8Ag-0.7Cu solder and copper substrate during multiple reflow. Molybdenum nanoparticles were mixed with Sn-3.8Ag-0.7Cu solder paste by manual mixing. Solder samples were reflowed on a copper substrate in a 250 Degree-Sign C reflow oven up to six times. The molybdenum content of the bulk solder was determined by inductive coupled plasma-optical emission spectrometry. It is found that upon the addition of molybdenum nanoparticles to Sn-3.8Ag-0.7Cu solder, the interfacial intermetallic compound thickness and scallop diameter decreases under all reflow conditions. Molybdenum nanoparticles do not appear to dissolve or react with the solder. They tend to adsorb preferentially at the interface between solder and the intermetallic compound scallops. It is suggested that molybdenum nanoparticles impart their influence on the interfacial intermetallic compound as discrete particles. The intact, discrete nanoparticles, by absorbing preferentially at the interface, hinder the diffusion flux of the substrate and thereby suppress the intermetallic compound growth. - Highlights: Black-Right-Pointing-Pointer Mo nanoparticles do not dissolve or react with the SAC solder during reflow. Black-Right-Pointing-Pointer Addition of Mo nanoparticles results smaller IMC thickness and scallop diameter. Black-Right-Pointing-Pointer Mo nanoparticles influence the interfacial IMC through discrete particle effect.

  9. Review of magnetic properties and magnetocaloric effect in the intermetallic compounds of rare earth with low boiling point metals

    NASA Astrophysics Data System (ADS)

    Ling-Wei, Li

    2016-03-01

    The magnetocaloric effect (MCE) in many rare earth (RE) based intermetallic compounds has been extensively investigated during the last two decades, not only due to their potential applications for magnetic refrigeration but also for better understanding of the fundamental problems of the materials. This paper reviews our recent progress on studying the magnetic properties and MCE in some binary or ternary intermetallic compounds of RE with low boiling point metal(s) (Zn, Mg, and Cd). Some of them exhibit promising MCE properties, which make them attractive for low temperature magnetic refrigeration. Characteristics of the magnetic transition, origin of large MCE, as well as the potential application of these compounds are thoroughly discussed. Additionally, a brief review of the magnetic and magnetocaloric properties in the quaternary rare earth nickel boroncarbides RENi2B2C superconductors is also presented. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374081 and 11004044), the Fundamental Research Funds for the Central Universities, China (Grant Nos. N150905001, L1509006, and N140901001), the Japan Society for the Promotion of Science Postdoctoral Fellowships for Foreign Researchers (Grant No. P10060), and the Alexander von Humboldt (AvH) Foundation (Research stipend to L. Li).

  10. Exploring phase stability, electronic and mechanical properties of Ce-Pb intermetallic compounds using first-principles calculations

    NASA Astrophysics Data System (ADS)

    Tao, Xiaoma; Wang, Ziru; Lan, Chunxiang; Xu, Guanglong; Ouyang, Yifang; Du, Yong

    2016-05-01

    The phase stability, electronic and mechanical properties of Ce-Pb intermetallics have been investigated by using first-principles calculations. Five stable and four metastable phases of Ce-Pb intermetallics were verified. Among them, CePb2 has been confirmed as HfGa2-type structure. For Ce5Pb3, the high pressure phase transformation from D8m to D88 with trivalent Ce has been predicted to occur at P=1.2 GPa and a high temperature phase transformation has been predicted from D8m to D88 with tetravalent Ce at 531.5 K. The calculated lattice constants of the five stable phases are in good agreement with experimental values. The electronic density of states, charge density and electron localization function of Ce3Pb have been calculated, which indicated that the Ce and Pb show ionic behavior. The polycrystalline bulk modulus, shear modulus, Young's modulus, and Poisson's ratio are also estimated from the calculated single crystalline elastic constants. All of the calculated elastic constants satisfy mechanical stability criteria. The microhardness and mechanical anisotropy are predicted. The anisotropic nature of the Ce-Pb intermetallic compounds are demonstrated by the three-dimensional orientation dependent surfaces of Young's moduli and linear compressibility are also demonstrated. The longitudinal, transverse and average sound velocities and the Debye temperatures are also obtained in this work. The Ce3Pb has the largest Debye temperature of 192.6 K, which means the Ce3Pb has a highest melting point and high thermal conductivity than other compounds.

  11. Formation of intermetallics at the interface of explosively welded Ni-Al multilayered composites during annealing

    NASA Astrophysics Data System (ADS)

    Ogneva, T. S.; Lazurenko, D. V.; Bataev, I. A.; Mali, V. I.; Esikov, M. A.; Bataev, A. A.

    2016-04-01

    The Ni-Al multilayer composite was fabricated using explosive welding. The zones of mixing of Ni and Al are observed at the composite interfaces after the welding. The composition of these zones is inhomogeneous. Continuous homogeneous intermetallic layers are formed at the interface after heat treatment at 620 °C during 5 h These intermetallic layers consist of NiAl3 and Ni2Al3 phases. The presence of mixed zones significantly accelerates the growth rate of intermetallic phases at the initial stages of heating.

  12. The role of zinc on the chemistry of complex intermetallic compounds

    SciTech Connect

    Xie, Weiwei

    2014-01-01

    Combining experiments and electronic structure theory provides the framework to design and discover new families of complex intermetallic phases and to understand factors that stabilize both new and known phases. Using solid state synthesis and multiple structural determinations, ferromagnetic β-Mn type Co8+xZn12–x was analyzed for their crystal and electronic structures.

  13. Estimation of the composition of intermetallic compounds in LiCl-KCl molten salt by cyclic voltammetry.

    PubMed

    Liu, Ya L; Liu, Kui; Yuan, Li Y; Chai, Zhi F; Shi, Wei Q

    2016-08-15

    In this work, the compositions of Ce-Al, Er-Al and La-Bi intermetallic compounds were estimated by the cyclic voltammetry (CV) technique. At first, CV measurements were carried out at different reverse potentials to study the co-reduction processes of Ce-Al, Er-Al and La-Bi systems. The CV curves obtained were then re-plotted with the current as a function of time, and the coulomb number of each peak was calculated. By comparing the coulomb number of the related peaks, the compositions of the Ce-Al, Er-Al and La-Bi intermetallic compounds formed in the co-reduction process could be estimated. The results showed that Al11Ce3, Al3Ce, Al2Ce and AlCe could be formed by the co-reduction of Ce(iii) and Al(iii). For the co-reduction of Er(iii) and Al(iii), Al3Er2, Al2Er and AlEr were formed. In a La(iii) and Bi(iii) co-existing system in LiCl-KCl melts, LaBi2, LaBi and Li3Bi were the major products as a result of co-reduction.

  14. Chemistry of intermetallic hydrides

    SciTech Connect

    Reilly, J.J.

    1991-01-01

    Certain intermetallic hydrides are safe, convenient and inexpensive hydrogen storage compounds. A particular advantage of such compounds is the ease with which their properties can be modified by small changes in alloy composition or preparation. This quality can be exploited to optimize their storage properties for particular applications, e.g. as intermetallic hydride electrodes in batteries. We will be concerned herein with the more important aspects of the thermodynamic and structural principles which regulate the behavior of intermetallic hydrogen systems and then illustrate their application using the archetype hydrides of LaNi5, FeTi and Mg alloys. The practical utility of these classes of materials will be briefly noted.

  15. Phase transitions as a function of material constants and temperature in intermetallic compounds of the terfenol-D type

    NASA Astrophysics Data System (ADS)

    Fridman, Yu. A.; Klevets, F. N.; Voĭtenko, A. P.

    2010-07-01

    A model of magnetic and magnetoelastic properties of intermetallic compounds has been considered with the inclusion of the influence of the “giant” magnetoelastic coupling and the biquadratic exchange interaction. The phase transitions as a function of material constants and temperature have been investigated in the framework of the proposed model. It has been demonstrated that the ferromagnetic and quadrupole phases can be formed in the system under consideration. In this case, the phase transition between these phases is a first-order transition and occurs through the intermediate, i.e., quadrupole-ferromagnetic, state. The dependences of the phase transition temperature on the Heisenberg and biquadratic exchange interaction constants have been obtained for compounds of the terfenol-D type.

  16. Magnetotransport and magnetothermal properties of the ternary intermetallic compound TbFe2Al10

    NASA Astrophysics Data System (ADS)

    Khandelwal, Ashish; Chattopadhyay, M. K.; Roy, S. B.

    2016-09-01

    We have studied the temperature and field dependences of electrical resistivity and heat capacity of TbFe2Al10, and have also complimented the above studies with low field magnetization measurements. In zero magnetic field, TbFe2Al10 exhibits paramagnetic (PM) to ferrimagnetic (Ferri-I) and Ferri-I to antiferromagnetic (AFM) phase transitions below 17.6 and 10 K respectively. We have found that the electrical resistivity of TbFe2Al10 exhibits a sharp rise across the PM to Ferri-I phase transition in this compound. Our analysis indicates that this sharp rise of electrical resistivity is related to the formation of new zone boundaries (across the PM to Ferri-I phase transition) that reduce the area of the Fermi surface. We have found that TbFe2Al10 exhibits large magnetoresistance (MR) below 100 K. Overall, the MR behaviour of TbFe2Al10 below 17.6 K in different magnetic fields reveals strong competition between AFM and ferromagnetic (FM) correlations, which seems to be quite intrinsic to the magnetic structure of the compound. Our analysis indicates that the large MR and magnetocaloric effect persisting deep inside the PM regime of TbFe2Al10 is mainly related to the presence of FM spin fluctuations and the formation of a Griffiths like (GL) phase consisting of FM clusters within the PM regime. The formation of the GL phase may be mediated by the static crystal defects in the midst of the competing inter and intra layer magnetic interactions.

  17. FP-LAPW based investigation of structural, electronic and mechanical properties of CePb3 intermetallic compound

    NASA Astrophysics Data System (ADS)

    Pagare, Gitanjali; Abraham, Jisha Annie; Jain, Ekta; Sanyal, Sankar P.

    2015-08-01

    A theoretical study of structural, electronic, elastic and mechanical properties of CePb3 intermetallic compound has been investigated systematically using first principles density functional theory. The calculations are carried out within the three different forms of generalized gradient approximation (GGA) and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B') are calculated and obtained lattice parameter of this compound shows well agreement with the experimental results. We have calculated three independent second order elastic constants (C11, C12 and C44), which has not been calculated and measured yet. From energy dispersion curves, it is found that the studied compound is metallic in nature. Ductility of this compound is analyzed using Pugh's criteria and Cauchy's pressure (C11-C12). The mechanical properties such as Young's modulus, shear modulus, anisotropic ratio, Poison's ratio have been calculated for the first time using the Voigt-Reuss-Hill (VRH) averaging scheme. The average sound velocities (vm), density (ρ) and Debye temperature (θD) of this compound are also estimated from the elastic constants.

  18. FP-LAPW based investigation of structural, electronic and mechanical properties of CePb{sub 3} intermetallic compound

    SciTech Connect

    Pagare, Gitanjali Jain, Ekta; Abraham, Jisha Annie; Sanyal, Sankar P.

    2015-08-28

    A theoretical study of structural, electronic, elastic and mechanical properties of CePb{sub 3} intermetallic compound has been investigated systematically using first principles density functional theory. The calculations are carried out within the three different forms of generalized gradient approximation (GGA) and LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a{sub 0}), bulk modulus (B) and its pressure derivative (B′) are calculated and obtained lattice parameter of this compound shows well agreement with the experimental results. We have calculated three independent second order elastic constants (C{sub 11}, C{sub 12} and C{sub 44}), which has not been calculated and measured yet. From energy dispersion curves, it is found that the studied compound is metallic in nature. Ductility of this compound is analyzed using Pugh’s criteria and Cauchy's pressure (C{sub 11}-C{sub 12}). The mechanical properties such as Young's modulus, shear modulus, anisotropic ratio, Poison's ratio have been calculated for the first time using the Voigt–Reuss–Hill (VRH) averaging scheme. The average sound velocities (v{sub m}), density (ρ) and Debye temperature (θ{sub D}) of this compound are also estimated from the elastic constants.

  19. The sequence of intermetallic formation and solidification pathway of an Al–13Mg–7Si–2Cu in-situ composite

    SciTech Connect

    Farahany, Saeed; Nordin, Nur Azmah; Ourdjini, Ali; Abu Bakar, TutyAsma; Hamzah, Esah; Idris, Mohd Hasbullah; Hekmat-Ardakan, Alireza

    2014-12-15

    The phase transformation sequence and solidification behaviour of an Al–13Mg–7Si–2Cu in-situ composite was examined using a combination of computer-aided cooling curve thermal analysis and interrupted quenching techniques. Five different phases were identified by analysing the derivative cooling curves, the X-ray diffraction profile, optical and scanning electron microscopy images and the corresponding energy dispersive spectroscopy. It has been found that the solidification of this alloy begins with primary Mg{sub 2}Si precipitation and continues with the formation of eutectic Al–Mg{sub 2}Si, followed by Al{sub 5}FeSi and simultaneous precipitation of Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 2}Cu complex intermetallic phases. The formation of the last three intermetallic compounds changes the solidification behaviour of these composites remarkably due to their complex eutectic formation reactions. The solidification of the alloy, calculated using the Factsage thermochemical analysis software, has demonstrated a good agreement with the experiments in terms of compound prediction, their weight fractions and reaction temperatures. - Highlights: • Solidification path of a commercial Al-13Mg-7Si-2Cu composite was characterized. • Five different phases were identified and then confirmed with EDS and XRD results. • Mg{sub 2}Si, Al-Mg{sub 2}Si,Al{sub 5}FeSi (β),Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) and Al{sub 2}Cu(θ) precipitated respectively. • Solidification was predicted using the Factsage thermochemical analysis software.

  20. Formation of Intermetallic Ni-Al Coatings by Mechanical Alloying with Different Intensities

    NASA Astrophysics Data System (ADS)

    Zadorozhnyy, V. Yu.; Kaloshkin, S. D.; Churyukanova, M. N.; Borisova, Yu. V.

    2013-04-01

    Intermetallic Ni-Al coatings on the Ni substrate were prepared by the mechanical alloying (MA) method in mechanical activators of vibratory and planetary type. It was found that coatings that were fabricated in a high-energy (planetary) activator in comparison with those fabricated in a low-energy (vibratory) activator are more homogeneous, have higher density, and experience better adhesion to the substrate. It was shown that different intermetallic phases (NiAl, NiAl3, and Ni2Al3) can form directly during the MA treatment in the planetary activator.

  1. Evolution of the Intermetallic Compounds in Ni/Sn-2.5Ag/Ni Microbumps for Three-Dimensional Integrated Circuits

    NASA Astrophysics Data System (ADS)

    Hsu, H. H.; Huang, Y. T.; Huang, S. Y.; Chang, T. C.; Wu, Albert T.

    2015-10-01

    Ni/Sn-2.5Ag/Ni samples were used to simulate the microbumps in three-dimensional (3D) packaging. The annealed test was adopted to observe the microstructure of intermetallic compound formation at 100°C, 125°C, and 150°C up to 1000 h. In the Ni/Sn-2.5Ag/Ni, predominant phases of layer-type Ni3Sn4 and Ag3Sn particles could be seen under the thermal treatment. The formation of Ni3Sn4 followed a parabolic rate law at each aging temperature. Due to the limited solder volume, the remaining solder of the microbump was completely exhausted after long-time annealing at 150°C. The activation energy for Ni3Sn4 formation in the Ni/Sn-2.5Ag/Ni microbump was 171.8 kJ/mol. Furthermore, the consumption of the Ni under bump metallization (UBM) was estimated based on the mass balance of Ni atoms during the interfacial reaction.

  2. The evolution of γ-Mg17Al12 intermetallic compound during accumulative back extrusion and subsequent ageing treatment

    NASA Astrophysics Data System (ADS)

    Maghsoudi, M. H.; Zarei-Hanzaki, A.; Abedi, H. R.; Shamsolhodaei, A.

    2015-11-01

    Accumulative back extrusion (ABE) processing, as a novel severe plastic deformation (SPD) method, has been recently justified to be capable of modifying the microstructural characteristics of alloys. In line to its ongoing researches, the present work has been planned to study the evolution of γ-Mg17Al12 intermetallic phase during ABE and subsequent ageing treatment in a high Al-bearing Mg-Al-Zn alloy. The behaviour of γ intermetallic has been systematically examined as following points of view: (i) strain-temperature-dependent morphology changes, (ii) strain-induced dissolution, and (iii) re-ageing behaviour as a function of time and temperature. Aiming to analyse the morphology of eutectic γ compound with respect to the strain and temperature, 2D projections of effective diameter, shape factor and globularity have been made in strain/temperature graphs. The processing conditions (strain and temperature) corresponding to the desired and undesired morphologies are introduced and microstructurally explained through underlying plasticity mechanisms, i.e., 'necking-thinning-particle separation' and 'brittle fragmentation.' The former mechanism is suggested to be in relation with partial strain-induced dissolution of eutectic γ phase, leading to generation of a supersaturated solid solution. This has resulted to the observation of 'off-stoichiometry' phenomena in Mg17Al12 phase and has been justified through dislocation-assisted deformation mechanism at elevated temperature. Surprisingly, a unique re-ageing behaviour has been found for the obtained solid solutions, where a modified kinetics and morphology of γ phase precipitation were characterized. The altered precipitation behaviour is attributed to the specific defect structure achieved by SPD acting as fast diffusion channel for Al solutes.

  3. The role of fluid flow and intermetallic phases in the formation of the primary Al-phase in AlSi alloys

    NASA Astrophysics Data System (ADS)

    Mikołajczak, P.; Ratke, L.

    2012-01-01

    In secondary AlSi alloys, the presence of small amounts of Fe causes the formation of intermetallic phases, which have a negative effect on mechanical and physical properties of castings. To understand the effect of fluid flow on the microstructure and intermetallic phases, Al-5/7/9 wt pet Si 0.2/0.5/1.0 wt pet Fe alloys have been directionally solidified under defined thermal (gradient 3 K/mm, solidification velocity 0.04 mm/s) and fluid flow (rotating magnetic field 6 mT) conditions. The primary α-Al phase and intermetallic phases were studied using light microscopy and SEM with EDX. The influence of fluid flow and intermetallic phases (β-Al5FeSi) on microstructure was characterized by changes of primary and secondary dendrite arm spacing and specific surface area of the dendrites. We observe a pronounced effect of flow on the length of the intermetallic precipitates, a macro-segregation Fe and Si and even small amounts of iron and thus intermetallics reduce possible effects of flow on microstructural parameters.

  4. Perpendicular Growth Characteristics of Cu-Sn Intermetallic Compounds at the Surface of 99Sn-1Cu/Cu Solder Interconnects

    NASA Astrophysics Data System (ADS)

    Chen, Zhiwen; Liu, Changqing; Wu, Yiping; An, Bing

    2015-12-01

    The growth of intermetallic compounds (IMCs) on the free surface of 99Sn-1Cu solder joints perpendicular to the interdiffusion direction has been investigated in this work. The specimens were specifically designed and polished to reveal a flat free surface at the solder/Cu interface for investigation. After aging at 175°C for progressively increased durations, the height of the perpendicular IMCs was examined and found to follow a parabolic law with aging duration that could be expressed as y = 0.11√ t, where t is the aging duration in hours and y is the height of the perpendicular IMCs in μm. For comparison, the planar growth of IMCs along the interdiffusion direction was also investigated in 99Sn-1Cu/Cu solder joints. After prolonged aging at 175°C, the thickness of the planar interfacial IMC layers also increased parabolically with aging duration and could be expressed as h_{{IMC}} = 0.27√ t + 4.6, where h is the thickness in μm and t is the time in hours. It was found that both the planar and perpendicular growth of the IMCs were diffusion-controlled processes, but the perpendicular growth of the IMCs was much slower than their planar growth due to the longer diffusion distance. It is proposed that Cu3Sn forms prior to the formation of Cu6Sn5 in the perpendicular IMCs, being the reverse order compared with the planar IMC growth.

  5. Synthesis, crystal structure, and magnetic properties of novel intermetallic compounds R2Co2SiC (R = Pr, Nd).

    PubMed

    Zhou, Sixuan; Mishra, Trinath; Wang, Man; Shatruk, Michael; Cao, Huibo; Latturner, Susan E

    2014-06-16

    The intermetallic compounds R2Co2SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a new stuffed variant of the W2CoB2 structure type in orthorhombic space group Immm with unit cell parameters a = 3.978(4) Å, b = 6.094(5) Å, c = 8.903(8) Å (Z = 2; R1 = 0.0302) for Nd2Co2SiC. Silicon, cobalt, and carbon atoms form two-dimensional flat sheets, which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements indicate that the rare earth cations in both analogues order ferromagnetically at low temperature (TC ≈ 12 K for Nd2Co2SiC and TC ≈ 20 K for Pr2Co2SiC). Single-crystal neutron diffraction data for Nd2Co2SiC indicate that Nd moments initially align ferromagnetically along the c axis around ∼12 K, but below 11 K, they tilt slightly away from the c axis, in the ac plane. Electronic structure calculations confirm the lack of spin polarization for Co 3d moments. PMID:24898034

  6. Micromagnetic analysis of the hardening mechanisms of nanocrystalline MnBi and nanopatterned FePt intermetallic compounds.

    PubMed

    Kronmüller, H; Yang, J B; Goll, D

    2014-02-12

    The uniaxial intermetallic compounds of L10-FePt and the low temperature NiAs structure of MnBi are suitable alloys for application as high-density recording materials or as high-coercivity permanent magnets. Single domain particles of these materials are characterized by coercive fields above 1 T over a large temperature range. In particular MnBi shows a coercive field of 2 T at 450 K. Its extraordinary magnetic properties in the temperature range up to 600 K are due to an increase of the magnetocrystalline anisotropy constant from 1.2 MJ m(-3) at 300 K to 2.4 MJ m(-3) at 450 K. In spite of the large coercivities obtained for both type of materials their experimental values deviate considerably from the theoretical values Hc = 2K1/Js valid for a homogeneous rotation process in spherical particles. As is well known these discrepancies are due to the deteriorating effects of the microstructure. For an analysis of the coercive fields the Stoner-Wohlfarth theory has to be expanded with respect to higher anisotropy constants and to microstructural effects such as misaligned grains and grain surfaces with reduced anisotropy constants. It is shown that the temperature dependence and the angular dependence of Hc for FePt as well as MnBi can be quantitatively interpreted by taking into account the above mentioned intrinsic and microstructural effects. PMID:24469256

  7. The magnetic behavior of the intermetallic compound NdMn2Ge2 studied by magnetization and hyperfine interactions measurements

    NASA Astrophysics Data System (ADS)

    Bosch-Santos, B.; Carbonari, A. W.; Cabrera-Pasca, G. A.; Saxena, R. N.; Freitas, R. S.

    2015-05-01

    The magnetic behavior of the intermetallic compound NdMn2Ge2 was investigated by bulk magnetization measurements and measurements of hyperfine interactions using perturbed γ-γ angular correlation (PAC) spectroscopy. Magnetization measurements indicate the presence of four magnetic transitions associated with the Mn and Nd magnetic sublattices. At high temperatures, magnetic measurements show a change in the slope of the magnetization due to an antiferromagnetic transition around TN ˜ 425 K and a well defined ferromagnetic transition at TC ˜ 320 K. Moreover, at ˜210 K a peak is observed in the magnetization curve, which is assigned to the reorientation of the Mn spin, and at ˜25 K an increase in the magnetic moment is also observed, which is ascribed to the ordering of Nd ions. PAC measurements using 140La(140Ce) and 111In(111Cd) probe nuclei allowed the determination of the temperature dependence of the magnetic hyperfine field (Bhf) at Nd and Mn sites, respectively. PAC results with 111Cd probe nuclei at Mn sites show that the dependence of Bhf with temperature follows the expected behavior for the host magnetization associated with the magnetic ordering of Mn ions. From these results, the antiferromagnetic transition followed by a ferromagnetic ordering is clearly observed. PAC results with 140Ce probe nuclei at Nd sites, however, showed a strong deviation from the Brillouin function, which is attributed to the Ce 4f-electron contribution to Bhf.

  8. Synthesis, crystal structure, and magnetic properties of novel intermetallic compounds R2Co2SiC (R = Pr, Nd).

    PubMed

    Zhou, Sixuan; Mishra, Trinath; Wang, Man; Shatruk, Michael; Cao, Huibo; Latturner, Susan E

    2014-06-16

    The intermetallic compounds R2Co2SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a new stuffed variant of the W2CoB2 structure type in orthorhombic space group Immm with unit cell parameters a = 3.978(4) Å, b = 6.094(5) Å, c = 8.903(8) Å (Z = 2; R1 = 0.0302) for Nd2Co2SiC. Silicon, cobalt, and carbon atoms form two-dimensional flat sheets, which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements indicate that the rare earth cations in both analogues order ferromagnetically at low temperature (TC ≈ 12 K for Nd2Co2SiC and TC ≈ 20 K for Pr2Co2SiC). Single-crystal neutron diffraction data for Nd2Co2SiC indicate that Nd moments initially align ferromagnetically along the c axis around ∼12 K, but below 11 K, they tilt slightly away from the c axis, in the ac plane. Electronic structure calculations confirm the lack of spin polarization for Co 3d moments.

  9. Metamagnetism-enhanced magnetocaloric effect in the rare earth intermetallic compound Ho5Ge4

    NASA Astrophysics Data System (ADS)

    Nirmala, R.; Morozkin, A. V.; Rajivgandhi, R.; Nigam, A. K.; Quezado, S.; Malik, S. K.

    2016-11-01

    Magnetic and magnetocaloric properties of polycrystalline Ho5Ge4 (orthorhombic, Sm5Ge4-type, Space group Pnma, No. 62, oP36) compound have been studied. This compound orders antiferromagnetically at ~24 K (TN). From the magnetization vs field isotherms obtained close to the magnetic transition temperature, magnetocaloric effect (MCE) has been estimated. The isothermal magnetic entropy change (ΔSM) reaches a maximum value of ~-27 J/kg-K at ~30 K for a field change of 140 kOe. A metamagnetic transition is observed in the field dependent magnetization data at temperatures below 20 K, for critical fields above 20 kOe, giving rise to a ferromagnetic order and hence a large MCE. The magnetic moment value at 2.5 K is ~8μB/Ho3+ in 90 kOe field.

  10. Formation of intermetallic phases in AlSi7Fe1 alloy processed under microgravity and forced fluid flow conditions and their influence on the permeability

    NASA Astrophysics Data System (ADS)

    Steinbach, S.; Ratke, L.; Zimmermann, G.; Budenkova, O.

    2016-03-01

    Ternary Al-6.5wt.%Si-0.93wt.%Fe alloy samples were directionally solidified on-board of the International Space Station ISS in the ESA payload Materials Science Laboratory (MSL) equipped with Low Gradient Furnace (LGF) under both purely diffusive and stimulated convective conditions induced by a rotating magnetic field. Using different analysis techniques the shape and distribution of the intermetallic phase β-Al5SiFe in the dendritic microstructure was investigated, to study the influence of solidification velocity and fluid flow on the size and spatial arrangement of intermetallics. Deep etching as well as 3-dimensional computer tomography measurements characterized the size and the shape of β-Al5SiFe platelets: Diffusive growth results in a rather homogeneous distribution of intermetallic phases, whereas forced flow promotes an increase in the amount and the size of β-Al5SiFe platelets in the centre region of the samples. The β-Al5SiFe intermetallics can form not only simple platelets, but also be curved, branched, crossed, interacting with dendrites and porosity located. This leads to formation of large and complex groups of Fe-rich intermetallics, which reduce the melt flow between dendrites leading to lower permeability of the mushy zone and might significantly decrease feeding ability in castings.

  11. Polar intermetallic compounds of the silicon and arsenic family elements and their ternary hydrides and fluorides

    SciTech Connect

    Leon-Escamilla, E.A.

    1996-10-17

    An investigation has been made on the effects of hydrogen and fluoride in the solid state chemistry of alkaline-earth and divalent rare-earth metal pnictide (Pn) and tetrelide (Tt) phases A{sub 5}(Pn,Tt,){sub 3}Z{sub x}, where A = Ca, Sr, Ba, Sm, Eu, Yb; Pn = As, Sb, Bi; Tt = Si, Ge, Sn, Pb and Z = H, F. Several trivalent rare-earth-metal pnictides, RE{sub 5}Pn{sub 3} (RE = Y, La, Gd, Tb, Dy, Ho, Er, Tm) and alkaline-earth-metal trielides, A{sub 5}Tr{sub 3}Z{sub x} (Tr = Ga, In, Tl) have been included in an effort to complete observed structural trends. Two main experimental techniques were followed throughout this work, (a) reactions in absence of hydrogen or under continuous high vacuum, and (b) reactions with binary metal hydrides, AH{sub x}, in closed containers. The results demonstrate that all the phases reported with the {beta}-Yb{sub 5}Sb{sub 3}-type structure in the A{sub 5}Pn{sub 3} systems are hydrogen-stabilized compounds. Reactions in absence of hydrogen lead to compounds with the Mn{sub 5}Si{sub 3}-type structure. The structure type {beta}-Yb{sub 5}Sb{sub 3} (= Ca{sub 5}SB{sub 3}F) was found to be characteristic of ternary systems and inaccurately associated with phases that form in the Y{sub 5}Bi{sub 3}-type. A new series of isomorphous Zintl compounds with the Ca{sub 16}Sb{sub 11}-type structure were prepared and studied as well. All the alkaline-earth-metal tetrelides, A{sub 5}Tt{sub 3}, that crystallize in the Cr{sub 5}B{sub 3}-type structure can be interstitially derivatized by hydrogen or fluoride. Binary and ternary compounds were characterized by Guinier powder patterns, single crystal X-ray and powder neutron diffraction techniques. In an effort to establish property-structure relationships, electrical resistivity and magnetic measurements were performed on selected systems, and the results were explained in terms of the Zintl concepts, aided by extended Hueckel band calculations.

  12. Focused ion beam induced microstructural alterations: texture development, grain growth, and intermetallic formation.

    PubMed

    Michael, Joseph R

    2011-06-01

    Copper, gold, and tungsten thin films have been exposed to 30 kV Ga+ ion irradiation, and the resulting microstructural modifications are studied as a function of ion dose. The observed microstructural changes include texture development with respect to the easy channeling direction in the target, and in the case of Cu, an additional intermetallic phase is produced. Texture development in these target materials is a function of the starting materials grain size, and these changes are not observed in large grained materials. The accepted models of differential damage driven grain growth are not supported by the results of this study. The implications of this study to the use of focused ion beam tools for sample preparation are discussed. PMID:21466753

  13. Focused ion beam induced microstructural alterations: texture development, grain growth, and intermetallic formation.

    PubMed

    Michael, Joseph R

    2011-06-01

    Copper, gold, and tungsten thin films have been exposed to 30 kV Ga+ ion irradiation, and the resulting microstructural modifications are studied as a function of ion dose. The observed microstructural changes include texture development with respect to the easy channeling direction in the target, and in the case of Cu, an additional intermetallic phase is produced. Texture development in these target materials is a function of the starting materials grain size, and these changes are not observed in large grained materials. The accepted models of differential damage driven grain growth are not supported by the results of this study. The implications of this study to the use of focused ion beam tools for sample preparation are discussed.

  14. Crystallographic features of the structure of a martensite packet of the NiMn intermetallic compound

    NASA Astrophysics Data System (ADS)

    Khlebnikova, Yu. V.; Egorova, L. Yu.; Rodionov, D. P.; Belosludtseva, E. S.; Kazantsev, V. A.

    2016-06-01

    Optical microscopy, scanning electron microscopy, and X-ray diffraction are used to show that a pseudosingle crystal forms upon cooling of an alloy Ni49Mn51 single crystal below the temperature of the β→θ (bcc → fct) transformation. At room temperature, this pseudosingle crystal has the structure of tetragonal L10 martensite with parameters a = 0.3732 nm and c = 0.3537 nm and a tetragonality c/ a = 0.94775. The temperatures of the forward and reverse B2 → L10 transformations are determined. The crystallographic features of martensite packet formation are analyzed. As shown by EBSD, neighboring martensite packets always have three kinds of tetragonal martensite plates, which are in a twin position and have different tetragonality axis directions. Repeated heating and quenching of the pseudosingle crystal result in recrystallization with the formation of coarse grains. The packet structure of the tetragonal martensite is retained in this case, and the sizes of the packets formed within a grain decrease by a factor of 2-3 as compared to the initial pseudosingle crystal.

  15. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  16. Study of the feasibility of producing Al-Ni intermetallic compounds by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Mohammed, Kahtan S.; Naeem, Haider T.; Iskak, Siti Nadira

    2016-08-01

    Mechanical alloying (MA) was employed to synthesize Al-Zn-Mg-Cu alloys of high weight percentage of the nickel component from the elemental powders of constituents via high-energy ball milling. The mixed powders underwent 15 h of milling time at 350 rpm speed and 10: 1 balls/powder weight ratio. The samples were cold-compacted and sintered thereafter. The sintered compacts underwent homogenization treatments at various temperatures conditions and were aged at 120°C for 24 h (T6). The milled powders and heat-treated Al alloy products were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The crystallite sizes and microstrains of the alloyed powder were estimated via measuring the broadening of XRD peaks using the Williamson-Hall equation. The results have revealed that optimum MA time of 15 h has led to the formation of Al-based solid solutions of Zn, Mg, Cu, and Ni. The outcomes showed that the Vickers hardness of the sintered Al-Zn-Mg-Cu compacts of Ni alloys was enhanced following aging at T6 tempering treatments. Higher compression strength of Al-alloys with the addition of 15% nickel was obtained next to the aging treatment.

  17. The effect of intermetallic compound morphology on Cu diffusion in Sn-Ag and Sn-Pb solder bump on the Ni/Cu Under-bump metallization

    NASA Astrophysics Data System (ADS)

    Jang, Guh-Yaw; Duh, Jenq-Gong

    2005-01-01

    The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1-x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles, only the (Ni1-x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1-y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content in the solder near the solder/IMC interface played an important role in the formation of the (Cu1-y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed. The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer (EPMA). During reflow, the atomic flux of Cu was on the order of 1016-1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems.

  18. Crystal structure and chemical bonding of novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}

    SciTech Connect

    Jung, Yaho; Nam, Gnu; Jeon, Jieun; Kim, Youngjo; You, Tae-Soo

    2012-12-15

    A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} has been synthesized using the high-temperature reaction method and characterized by both powder and single-crystal X-ray diffractions. The title compound crystallized in the orthorhombic crystal system (space group Immm, Z=2, Pearson symbol oI78) with fifteen crystallographically unique atomic positions in the asymmetric unit, and the lattice parameters are refined as a=4.5244(4) A, b=6.9932(6) A, and c=53.043(5) A. The complex crystal structure of the title compound can be described as a 2:1 intergrowth of two closely related compounds: La{sub 2}Li{sub 2}Ge{sub 3} (Ce{sub 2}Li{sub 2}Ge{sub 3}-type) and La{sub 3}Li{sub 4}Ge{sub 4} (Zr{sub 3}Cu{sub 4}Si{sub 4}-type) acting like 'building-blocks' along the c-axis. Six La sites are categorized into three distinct types based on the local coordination environment showing the coordination numbers of 12-14. Three unique Li sites are placed in the centers of local tetrahedra formed by four Ge atoms which eventually construct Ge{sub 2} dimers or 1-dimensional cis-/trans-Ge chains. Theoretical investigations using the tight-binding linear muffin-tin orbital (LMTO) method provide rationales for an improved structural stability and for unique local coordination geometries established by anionic elements including [LiGe{sub 4}] tetrahedra, cis-/trans-Ge chain and Ge{sub 2} dimers. - Graphical abstract: Reported is a novel ternary Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16}. The complex crystal structure can be viewed as a simple combination of two closely related known compounds acting as 'building-blocks', La{sub 2}Li{sub 2}G{sub 3} and La{sub 3}Li{sub 4}Ge{sub 4}, in a 2:1 stoichiometric ratio. Highlights: Black-Right-Pointing-Pointer A novel Li-containing polar intermetallic compound La{sub 11}Li{sub 12}Ge{sub 16} was synthesized. Black-Right-Pointing-Pointer The complex crystal structure was easily explained as

  19. Effect of trace elements vanadium and nickel on iron intermetallic phases formation and distribution in DC cast 5xxx series aluminum ingots

    NASA Astrophysics Data System (ADS)

    Li, Gaofeng

    AA5657 alloy is one of the important members of 5xxx-series alloys. It has application in many fields as packing, electricity, architectural, and printing. These applications require high quality surface finishing, and the alloy ingots require homogeneous microstructure. In the industry of DC (direct-chill) casting of 1xxx and 5xxx-series aluminium ingots, there exist different cooling rates from the casting surface to the ingot center. Thus, different Fe intermetallic phases such as AlmFe, Al6Fe, alpha-AlFeSi and Al3Fe can form preferentially in different positions of the ingot. The Fe intermetallic phase transition in DC casting ingot may cause microstructure inhomogeneities, which in turn cause the so called fir-tree zones (FTZs) in the ingots as well as streaks and bands on the Al sheets. Nowadays, with the increase of impurity in aluminium smelting raw materials (coke, alumina, etc.), the levels of trace elements present in the primary metal is gradually increasing. The impact of this increase on the aluminium transformation process and the final products is uncertain. Thus, there is a clear need to better understand these impacts, which will allow identifying ways to mitigate the negative impacts. The study presented in this thesis was performed on AA5657 alloys to study the effect of trace elements V and Ni on Fe intermetallic phases formation and distribution. A slice of AA1050 alloy ingot with visible FTZs was also studied to characterize the Fe intermetallic phases transition across the FTZs. A DC simulator was built in the lab, which can reproduce the solidification conditions in the sub-surface regions of industry ingots. The methods for the characterization of Fe intermetallic particles were developed in this research. AlmFe, Al6Fe, alpha-AlFeSi and alpha-Al3Fe intermetallic phases were successfully identified by using Deep-etching method, EDS and EBSD technique in combination. Quantitative analysis of the Fe intermetallic particles was carried out by

  20. Synthesis of Xenon and Iron/Nickel Intermetallic Compounds Under the Thermodynamic Conditions of the Earth's Core.

    NASA Astrophysics Data System (ADS)

    Stavrou, E.; Zaug, J. M.; Crowhurst, J.; Lobanov, S.; Goncharov, A. F.; Prakapenka, V.; Prescher, C.; Yao, Y.; Liu, H.; Dai, Z.; Oleynik, I.; Steele, B.; Cong, K. N.

    2015-12-01

    The lower Xe abundance in Earth's atmosphere, in comparison to other noble gases like Ar and Kr, is one of the most challenging open questions in geosciences [1]. The origin of the so-called "missing Xe paradox" is usually attributed to the inclusion of Xe in the interior of Earth[2]. Although Xe is known to form compounds (e.g. with hydrogen, oxygen), none of them can be related with Earth's interior. Indeed, only a very low amount of Xe can be incorporated in silica at <1 GPa and 500K [3]. On the other hand, experimental attempts have failed to trace possible formation of Fe-Xe compounds up to 155 GPa and bellow 2500K [4]. A very recent theoretical study, suggests that Xe-Ni and Xe-Fe compounds can form at thermodynamic conditions representative of Earth's outer core [5]. Here we explored the possible formation of stable compounds in the Xe-Fe/Ni system at thermodynamic conditions representative of Earth's outer core starting from the following mixtures: a) Xe-Fe, b) Xe-Ni and c) Xe and an Fe/Ni alloy representative of Earth's core (ca 6% Ni). Using in situ synchrotron X-ray diffraction and Raman spectroscopy we report the formation of: a) a XeNi3 compound, in the form of a CrNi3-type FCC solid solution, above 150 GPa and 1500K, b) a Xe(Fe/Ni)3 compound, tentatively characterized as an orthorhombic NbPd3-type solid solution, above 190 GPa and 2000K and c) a still not completely characterized XeFexcompound above 180 GPa and 2000K. This work provides a plausible explanation of the "missing Xe paradox", and underscores the importance of understanding the novel rules of high-pressure chemistry for an improved understanding of the structure and chemistry of the Earth's core. [1] E. Anders, E. and T. Owen, Science 198, 453 (1977). [2] Caldwell, W. A. et al.,Science 277, 930 (1997). [3] C. Sanloup et al.,Science 310, 1174(2005). [4] D. Nishio-Hamane et al.,Geophys. Res. Lett. 37, L04302 (2010). [5] L. Zhu et al., Nature chemistry 6, 664 (2014).

  1. Effects of Fe Fe bond length change in NaZn13-type intermetallic compounds on magnetic properties and magnetic entropy change

    NASA Astrophysics Data System (ADS)

    Wang, Guang-Jun; Hu, Feng-Xia; Wang, Fang; Shen, Bao-Gen

    2004-04-01

    In this paper the effects of Fe-Fe bond length change on magnetic properties and magnetic entropy change have been investigated on LaFe12.4-xSixCo0.6 and LaFe12.3-xAlxCo0.7 intermetallic compounds. According to the analyses of Fe-Fe bond length change, the variation of Curie temperature and the unusual magnetic phase transition which results in the large magnetic entropy change were explained. The effects of the substitution of Co and Si for Fe on magnetic entropy change and field-induced itinerant-electron metamagnetic transition in LaFe12.4-xSixCo0.6 compounds were also studied and the considerable magnetic entropy change has been achieved.

  2. Random-anisotropy ferromagnetic state in the C u5G d0.54C a0.42 intermetallic compound

    NASA Astrophysics Data System (ADS)

    Krnel, M.; Vrtnik, S.; Koželj, P.; Kocjan, A.; Jagličić, Z.; Boulet, P.; de Weerd, M. C.; Dubois, J. M.; Dolinšek, J.

    2016-03-01

    By applying the alloy design concept that stable intermetallic phases between two immiscible elements can be formed by adding a third element that forms stable compounds with both elements, we have synthesized the first known stable intermetallic compound of Cu, Gd, and Ca, where copper acts as the mediating element between the immiscible Gd and Ca. A compound with the composition C u84G d9C a7 (equivalent to C u5G d0.54C a0.42 ) was synthesized by the Czochralski technique in the form of a large single crystal of high structural perfection, and the structural model was determined by x-ray diffraction (XRD). The compound crystallizes in the hexagonal system, space group P 6 /mmm, and the crystal structure is isotypic to the C u5.44T b0.78 . The unit cell contains inherent disorder due to partial occupation of the Cu3 site and the substitutional disorder at the Gd/Ca mixed site located at the vertices of the hexagonal unit cell, where Gd and Ca randomly substitute each other. The random substitution of magnetic Gd by nonmagnetic Ca atoms makes the magnetic Gd lattice disordered, which leads to interesting magnetic ordering at low temperatures that occurs below TC=24 K in zero and low external magnetic fields. By performing a large set of complementary experiments along two perpendicular crystallographic directions (the [001] hexagonal-axis direction and the [100] hexagonal-plane direction), we show that the zero-field collective magnetic state can be described as a random-anisotropy ferromagnetic state, where random magnetic anisotropies originate from the magnetic dipole interactions between the Gd moments in the magnetically disordered lattice. The random-anisotropy ferromagnetic state in the C u84G d9C a7 is characterized by randomness and frustration of magnetic interactions, which are the two ingredients that allow classifying this state into the generic class of spin glasses. Our paper opens the possibility to search for new ternary intermetallic phases in the

  3. Magnetic structure of R2CoGa8 (R = Gd, Tb, and Dy): Structural tuning of magnetic properties in layered Ga-based intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Mardegan, J. R. L.; Adriano, C.; Vescovi, R. F. C.; Faria, G. A.; Pagliuso, P. G.; Giles, C.

    2014-03-01

    In this work we have determined the magnetic structure of R2CoGa8 (R = Gd, Tb, and Dy) intermetallic compounds using x-ray resonant magnetic scattering in order to study the evolution of the anisotropic magnetic properties along the series for R = Gd-Tm. The three compounds have a commensurate antiferromagnetic spin structure with a magnetic propagation vector τ⃗= (1/2,1/2,1/2) and a Néel temperature of approximately 20, 28.5, and 15.2 K for R = Gd, Tb, and Dy, respectively. The critical exponent β obtained from the temperature dependence of the magnetic peaks suggest a three-dimensional universality class for the three compounds. Comparing the simulated and integrated intensities we conclude that the magnetic moment direction is in the ab plane for the Gd2CoGa8 compound and parallel to the c axis for the Tb2CoGa8 and Dy2CoGa8 compounds. The evolution of the magnetic properties of the R2CoGa8 series for R = Gd-Tm is discussed taking into account the indirect Ruderman-Kittel-Kasuya-Yoshida interaction and crystalline-electric field effects. The comparison between the reported magnetic properties of the Ga-based compounds with those for the In-based isostructural family reveals differences in their exchange couplings that contribute to the understanding of the role of the f-electron magnetism in these classes of materials.

  4. Comparison of Sn-Ag-Cu Solder Alloy Intermetallic Compound Growth Under Different Thermal Excursions for Fine-Pitch Flip-Chip Assemblies

    NASA Astrophysics Data System (ADS)

    Tian, Ye; Liu, Xi; Chow, Justin; Wu, Yi Ping; Sitaraman, Suresh K.

    2013-08-01

    The intermetallic compound (IMC) evolution in Cu pad/Sn-Ag-Cu solder interface and Sn-Ag-Cu solder/Ni pad interface was investigated using thermal shock experiments with 100- μm-pitch flip-chip assemblies. The experiments show that low standoff height of solder joints and high thermomechanical stress play a great role in the interfacial IMC microstructure evolution under thermal shock, and strong cross-reaction of pad metallurgies is evident in the intermetallic growth. Furthermore, by comparing the IMC growth during thermal aging and thermal shock, it was found that thermal shock accelerates IMC growth and that kinetic models based on thermal aging experiments underpredict IMC growth in thermal shock experiments. Therefore, new diffusion kinetic parameters were determined for the growth of (Cu,Ni)6Sn5 using thermal shock experiments, and the Cu diffusion coefficient through the IMC layer was calculated to be 0.2028 μm2/h under thermal shock. Finite-element models also show that the solder stresses are higher under thermal shock, which could explain why the IMC growth is faster and greater under thermal shock cycling as opposed to thermal aging.

  5. Reactive spreading: Adsorption, ridging and compound formation

    SciTech Connect

    Saiz, E.; Cannon, R.M.; Tomsia, A.P.

    2000-09-11

    Reactive spreading, in which a chemically active element is added to promote wetting of noble metals on nonmetallic materials, is evaluated. Theories for the energetics and kinetics of the necessary steps involved in spreading are outlined and compared to the steps in compound formation that typically accompany reactive wetting. These include: fluid flow, active metal adsorption, including nonequilibrium effects, and triple line ridging. All of these can be faster than compound nucleation under certain conditions. Analysis and assessment of recently reported experiments on metal/ceramic systems lead to a focus on those conditions under which spreading proceeds ahead of the actual formation of a new phase at the interface. This scenario may be more typical than believed, and perhaps the most effective situation leading to enhanced spreading. A rationale for the pervasive variability and hysteresis observed during high temperature wetting also emerges.

  6. Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

    NASA Astrophysics Data System (ADS)

    Naghibolashrafi, N.; Keshavarz, S.; Hegde, Vinay I.; Gupta, A.; Butler, W. H.; Romero, J.; Munira, K.; LeClair, P.; Mazumdar, D.; Ma, J.; Ghosh, A. W.; Wolverton, C.

    2016-03-01

    Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. Fe2TiSb , expected to be a full Heusler compound crystallizing in the L 21 structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition Fe1.5TiSb with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into Fe1.5TiSb grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant Fe1.5TiSb phase appears to crystallize in a defective L 21 -like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the L 21 structure was performed. Using the cluster expansion, we computationally scanned >103 configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group R 3 m , with composition Fe1.5TiSb , i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of L 21 phase Fe2TiSb and C 1b phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the R 3 m structure is the ground state.

  7. Calculation of alloying effect on formation enthalpy of TiCu intermetallics from first-principles calculations for designing Ti-Cu-system metallic glasses

    NASA Astrophysics Data System (ADS)

    Shirasawa, Naoya; Takigawa, Yorinobu; Uesugi, Tokuteru; Higashi, Kenji

    2016-01-01

    The effect of alloying on the formation enthalpy of TiCu intermetallics was investigated via first-principles calculations to propose a new design method for Ti-Cu-system metallic glasses. The calculation results showed good agreement with the reported experimental results that Ni, Pd, Sn and Zr improve this system's glass-forming ability. According to the calculation results, a Ti-Zr-Cu-Ga system was designed as a potential new bulk Ti-based metallic glass, and a bulk sample with a 2-mm diameter was fabricated.

  8. Investigations of intermetallic alloy hydriding mechanisms. Annual progress report, May 1 1979-April 30, 1980

    SciTech Connect

    Livesay, B.R.; Larsen, J.W.

    1980-05-01

    Investigations are being conducted on mechanisms involved with the hydrogen-metal interactions which control the absorption and desorption processes in intermetallic compounds. The status of the following investigations is reported: modeling of hydride formation; microbalance investigations; microstructure investigations; flexure experiments; resistivity experiments; and nuclear backscattering measurements. These investigations concern fundamental hydrogen interaction mechanisms involved in storage alloys.

  9. Ba{sub 5}Ti{sub 12}Sb{sub 19+x}, a polar intermetallic compound with a stuffed gamma-brass structure

    SciTech Connect

    Bie Haiying; Mar, Arthur

    2009-11-15

    The polar intermetallic compound Ba{sub 5}Ti{sub 12}Sb{sub 19+x} (x<=0.2) has been synthesized by reaction of the elements. Single-crystal X-ray diffraction analysis revealed that it adopts a new structure type (Ba{sub 5}Ti{sub 12}Sb{sub 19.102(6)}, space group P43-barm, Z=2, a=12.4223(11) A, V=1916.9(3) A{sup 3}). The set of Ba and Sb sites corresponds to the structure of Cu{sub 9}Al{sub 4}, a gamma-brass type with a primitive cell. A complex three-dimensional framework of Ti atoms, in the form of linked planar Ti{sub 9} clusters, is stuffed within the gamma-brass-type Ba-Sb substructure. Notwithstanding its relationship to the gamma-brass structure, the compound does not appear to conform to the Hume-Rothery electron concentration rules. Band structure calculations on an idealized Ba{sub 5}Ti{sub 12}Sb{sub 19} model suggest that the availability of bonding states above the Fermi level is responsible for the partial occupation, but only to a limited degree, of an additional Sb site within the structure. Magnetic measurements indicated Pauli paramagnetic behaviour. - A gamma-brass substructure built up of Ba-Sb clusters is stuffed with planar Ti{sub 9} clusters.

  10. SrZn2Sn2 and Ca2Zn3Sn6 — two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    NASA Astrophysics Data System (ADS)

    Stegmaier, Saskia; Fässler, Thomas F.

    2012-08-01

    SrZn2Sn2 and Ca2Zn3Sn6, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn2Sn2 comprises (anti-)PbO-like {ZnSn4/4} and {SnZn4/4} layers. Ca2Zn3Sn6 shows similar {ZnSn4/4} layers and {Sn4Zn} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn2Sn2 adopts the SrPd2Bi2 structure type, and Ca2Zn3Sn6 is isotypic to the R2Zn3Ge6 compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn2Sn2 and Ca2Zn3Sn6 are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {Sn4Zn} layers of Ca2Zn3Sn6.

  11. Hyperfine field at Mn in the intermetallic compound LaMnSi2 measured by PAC using 111Cd nuclear probe

    NASA Astrophysics Data System (ADS)

    Domienikan, C.; Bosch-Santos, B.; Cabrera Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

    2015-04-01

    Magnetic hyperfine field at Mn site has been measured in the orthorhombic intermetallic compound LaMnSi2 with PAC spectroscopy using radioactive 111In- 111Cd nuclear probe. Samples of LaMnSi2 were prepared by melting pure metallic components in stoichiometric proportion in an arc furnace under argon atmosphere. The samples were sealed in a quartz tube under helium atmosphere, annealed at 1000 °C for 60 h and quenched in water. Samples were analyzed with X-ray diffraction method. 111In was introduced in the samples by thermal diffusion at 1000 °C for 60 h. PAC measurements were carried out with a six BaF2 detector spectrometer at several temperatures between 50 K and 410 K. Results show well defined quadrupole and magnetic interactions at all temperatures. The magnetic hyperfine field (Bhf) measured at 50 K is 7.1(1) T. The temperature dependence of Bhf follows the normal Brillouin-like behavior expected for a simple ferromagnetic ordering. The ferromagnetic transition temperature (Tc) was determined to be 401(1) K.

  12. Effect of microstructure and texture on the magnetic and magnetocaloric properties of the melt-spun rare earth intermetallic compound DyNi

    NASA Astrophysics Data System (ADS)

    Rajivgandhi, R.; Chelvane, J. Arout; Nigam, A. K.; Park, Je-Geun; Malik, S. K.; Nirmala, R.

    2016-11-01

    Magnetization measurements have been carried out on the melt-spun ribbon sample of the rare earth intermetallic compound DyNi (Orthorhombic, FeB-type, Space group Pnma) and its magnetic and magnetocaloric properties are compared with those of the arc-melted analog. The arc-melted DyNi orders ferromagnetically at around 61 K (TC) whereas the melt-spun DyNi orders ferromagnetically at about 47 K. The maximum isothermal magnetic entropy change, ∆Smmax , near TC of the arc-melted and the melt-spun DyNi is found to be -32.7 J/kg K and -22.4 J/kg K, respectively, for a field change of 140 kOe. For low magnetic field changes of ~20 kOe, the relative cooling power (RCP) is ~660 J/kg for the arc melted DyNi and ~460 J/kg for the melt-spun ribbon. The reduction in TC and magnetocaloric effect may be attributed to the microstructure-induced anisotropy developed during the melt-spinning process.

  13. Asymmetrical Precipitation of Ag3Sn Intermetallic Compounds Induced by Thermomigration of Ag in Pb-Free Microbumps During Solid-State Aging

    NASA Astrophysics Data System (ADS)

    Su, Yu-Ping; Wu, Chun-Sen; Ouyang, Fan-Yi

    2016-01-01

    Three-dimensional integrated circuit technology has become a major trend in electronics packaging in the microelectronics industry. To effectively remove heat from stacked integrated circuitry, a temperature gradient must be established across the chips. Furthermore, because of the trend toward higher device current density, Joule heating is more serious and temperature gradients across soldered joints are expected to increase. In this study we used heat-sink and heat-source devices to establish a temperature gradient across SnAg microbumps to investigate the thermomigration behavior of Ag in SnAg solder. Compared with isothermal conditions, small Ag3Sn particles near the hot end were dissolved and redistributed toward the cold end under a temperature gradient. The results indicated that temperature gradient-induced movement of Ag atoms occurred from the hot side toward the cold side, and asymmetrical precipitation of Ag3Sn resulted. The mechanism of growth of the intermetallic compound (IMC) Ag3Sn, caused by thermomigration of Ag, is discussed. The rate of growth Ag3Sn IMC at the cold side was found to increase linearly with solid-aging time under a temperature gradient. To understand the force driving Ag diffusion under the temperature gradient, the molar heat of transport ( Q*) of Ag in Sn was calculated as +13.34 kJ/mole.

  14. Growth Behavior of Intermetallic Compounds in Cu/Sn3.0Ag0.5Cu Solder Joints with Different Rates of Cooling

    NASA Astrophysics Data System (ADS)

    Yang, Linmei; Zhang, Z. F.

    2015-01-01

    The growth behavior of intermetallic compounds (IMC) in Cu/Sn3.0Ag0.5Cu solder joints, including the interfacial Cu6Sn5 layer and Ag3Sn, and Cu6Sn5 in the solder, were investigated when different cooling methods—quenched water, cooling in air, and cooling in a furnace after reflow—were used. For the solder joint quenched in water, no obvious Cu6Sn5 or Ag3Sn was detected in the solder, and the thickness of interfacial Cu6Sn5 layer was slightly thinner than that of the joint cooled in air. On the basis of results from scanning electron microscopy and energy-dispersive spectrometry, a mechanism is proposed for growth of IMC in Sn3.0Ag0.5Cu solder during solidification. The rate of cooling has a substantial effect on the morphology and size of Ag3Sn, which evolved into large plate-like shapes when the joint was cooled slowly in a furnace. However, the morphology of Ag3Sn was branch-like or particle-like when the joint was cooled in air. This is attributed to re-growth of Ag3Sn grains via substantial atomic diffusion during the high-temperature stage of furnace cooling.

  15. Huge positive hyperfine fields for Sn impurity atoms on R sites of R T intermetallic compounds (R=rare-earth, T=Fe, Co)

    NASA Astrophysics Data System (ADS)

    Krylov, V. I.; Delyagin, N. N.

    2006-10-01

    The magnetic hyperfine field Bhf of the 119Sn impurity atom on the R site of the RFe 2 (R=Sm, Tb, Tm), TbCo 2, RCo 5 (R=Dy, Ho, Er), GdCo 3 and Gd 2Co 7 intermetallic compounds has been investigated by Mössbauer spectroscopy technique. At 5 K, very large hyperfine fields equal to 46-56 T were observed. The B values are several times larger than commonly observed for Sn in 3d-based magnetic hosts. The hyperfine fields are positive (that is parallel to the 3d magnetic moments direction). The results can be interpreted qualitatively in terms of the theory proposed for the impurity atoms in homogeneous ferromagnetic hosts [J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 8 (1981) 573; J. Kanamori, H. Katayama-Yoshida, K. Terakura, Hyperfine Interact. 9 (1981) 363; M. Akai, H. Akai, J. Kanamori, J. Phys. Soc. Jpn. 54 (1985) 4246; S. Blügel, H. Akai, R. Zeller, P.H. Dederichs, Phys. Rev. B 35 (1987) 3271], when it is considered that the splitting between bonding and antibonding hybrid states is strongly dependent on the interatomic distance. As the distance between the probe atom and neighboring magnetic atoms increases, the population of the antibonding states grows and, as a consequence, the corresponding positive contribution to the B increases sharply. For Sn atom the positive contribution to the B dominates when the interatomic distance exceeds 0.28-0.29 nm.

  16. Structure Defect Property Relationships in Binary Intermetallics

    NASA Astrophysics Data System (ADS)

    Medasani, Bharat; Ding, Hong; Chen, Wei; Persson, Kristin; Canning, Andrew; Haranczyk, Maciej; Asta, Mark

    2015-03-01

    Ordered intermetallics are light weight materials with technologically useful high temperature properties such as creep resistance. Knowledge of constitutional and thermal defects is required to understand these properties. Vacancies and antisites are the dominant defects in the intermetallics and their concentrations and formation enthalpies could be computed by using first principles density functional theory and thermodynamic formalisms such as dilute solution method. Previously many properties of the intermetallics such as melting temperatures and formation enthalpies were statistically analyzed for large number of intermetallics using structure maps and data mining approaches. We undertook a similar exercise to establish the dependence of the defect properties in binary intermetallics on the underlying structural and chemical composition. For more than 200 binary intermetallics comprising of AB, AB2 and AB3 structures, we computed the concentrations and formation enthalpies of vacancies and antisites in a small range of stoichiometries deviating from ideal stoichiometry. The calculated defect properties were datamined to gain predictive capabilities of defect properties as well as to classify the intermetallics for their suitability in high-T applications. Supported by the US DOE under Contract No. DEAC02-05CH11231 under the Materials Project Center grant (Award No. EDCBEE).

  17. Magnetocaloric effects in RTX intermetallic compounds (R = Gd-Tm, T = Fe-Cu and Pd, X = Al and Si)

    NASA Astrophysics Data System (ADS)

    Zhang, Hu; Shen, Bao-Gen

    2015-12-01

    The magnetocaloric effect (MCE) of RTSi and RT Al systems with R = Gd-Tm, T = Fe-Cu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RTX compounds exhibit various crystal structures and magnetic properties, which then result in different MCE. Large MCE has been observed not only in the typical ferromagnetic materials but also in the antiferromagnetic materials. The magnetic properties have been studied in detail to discuss the physical mechanism of large MCE in RTX compounds. Particularly, some RTX compounds such as ErFeSi, HoCuSi, HoCuAl exhibit large reversible MCE under low magnetic field change, which suggests that these compounds could be promising materials for magnetic refrigeration in a low temperature range. Project supported by the National Natural Science Foundation of China (Grant Nos. 51371026, 11274357, and 51327806) and the Fundamental Research Funds for the Central Universities (Grant Nos. FRF-TP-14-011A2 and FRF-TP-15-002A3).

  18. Low-Temperature Synthesis Routes to Intermetallic Superconductors

    SciTech Connect

    Schaak, Raymond E

    2008-01-08

    Over the past few years, our group has gained expertise at developing low-temperature solution-based synthetic pathways to complex nanoscale solids, with particular emphasis on nanocrystalline intermetallic compounds. Our synthetic capabilities are providing tools to reproducibly generate intermetallic nanostructures with simultaneous control over crystal structure, composition, and morphology. This DOE-funded project aims to expand these capabilities to intermetallic superconductors. This could represent an important addition to the tools that are available for the synthesis and processing of intermetallic superconductors, which traditionally utilize high-temperature, high-pressure, thin film, or gas-phase vacuum deposition methods. Our current knowledge of intermetallic superconductors suggests that significant enhancements could result from the inherent benefits of low-temperature solution synthesis, e.g. metastable phase formation, control over nanoscale morphology to facilitate size-dependent property studies, robust and inexpensive processability, low-temperature annealing and consolidation, and impurity incorporation (for doping, stoichiometry control, flux pinning, and improving the critical fields). Our focus is on understanding the superconducting properties as a function of synthetic route, crystal structure, crystallite size, and morphology, and developing the synthetic tools necessary to accomplish this. This research program can currently be divided into two classes of superconducting materials: intermetallics (transition metal/post transition metal) and metal carbides/borides. Both involve the development and exploitation of low-temperature synthesis routes followed by detailed characterization of structures and properties, with the goal of understanding how the synthetic pathways influence key superconducting properties of selected target materials. Because of the low-temperature methods used to synthesize them and the nanocrystalline morphologies

  19. The analysis of the magnetic properties in the intermetallic YxGd1-xNi3 compounds

    NASA Astrophysics Data System (ADS)

    Bajorek, Anna; Chrobak, Artur; Chełkowska, Grażyna; Kwiecień-Grudziecka, Marzena

    2012-12-01

    In the paper an influence of Gd/Y substitution on the magnetic properties and exchange interactions of the YxGd1-xNi3 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0) polycrystalline compounds have been studied. The partial replacement of Gd by Y atoms is reflected in decreasing of the Curie temperature (TC) as well as decreasing of effective the magnetic moment (μeff). It has been shown that such a behaviour strongly depends on the magnetic interactions. Exchange coupling parameters of R-R (ARR), T-T (ATT) and R-T (ART) have been evaluated from M(T) magnetization curves (2-300 K, 2 T) based on the mean field theory (MFT) calculation. The magnetocaloric effect (MCE) has been estimated from the family of magnetic isotherms. The magnetic entropy indicates relatively small change with the Gd/Y substitution. The value of ΔSm(T,H) is higher for Gd-rich compounds and, respectively, decreases with Gd/Y substitution.

  20. Comments on the thermoelectric power of intermetallic rare-earth compounds with well localized 4f shells

    NASA Astrophysics Data System (ADS)

    Szukiel, A. E.

    2016-05-01

    The anomalous temperature variation of the thermoelectric power in the metallic rare-earth compounds with well-localized 4f shells is sometimes interpreted as resulting from the conduction electrons scattering in the Born approximation on the acoustic phonons and on the localized spins in the s-f exchange interaction. Such an interpretation relies on the results of some theoretical works where the sign reversal and the maxima of the thermoelectric power were obtained within these simple models. In the present paper we prove that neither the electron-phonon scattering nor the magnetic s-f scattering in the Born approximation (nor both of them) do lead to the effects mentioned above.

  1. Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under temperature gradient

    PubMed Central

    Zhao, N.; Zhong, Y.; Huang, M.L.; Ma, H.T.; Dong, W.

    2015-01-01

    The growth behavior of intermetallic compounds (IMCs) at the liquid-solid interfaces in Cu/Sn/Cu interconnects during reflow at 250 °C and 280 °C on a hot plate was investigated. Being different from the symmetrical growth during isothermal aging, the interfacial IMCs showed clearly asymmetrical growth during reflow, i.e., the growth of Cu6Sn5 IMC at the cold end was significantly enhanced while that of Cu3Sn IMC was hindered especially at the hot end. It was found that the temperature gradient had caused the mass migration of Cu atoms from the hot end toward the cold end, resulting in sufficient Cu atomic flux for interfacial reaction at the cold end while inadequate Cu atomic flux at the hot end. The growth mechanism was considered as reaction/thermomigration-controlled at the cold end and grain boundary diffusion/thermomigration-controlled at the hot end. A growth model was established to explain the growth kinetics of the Cu6Sn5 IMC at both cold and hot ends. The molar heat of transport of Cu atoms in molten Sn was calculated as + 11.12 kJ/mol at 250 °C and + 14.65 kJ/mol at 280 °C. The corresponding driving force of thermomigration in molten Sn was estimated as 4.82 × 10−19 N and 6.80 × 10−19 N. PMID:26311323

  2. The effect of intermetallic compound evolution on the fracture behavior of Au stud bumps joined with Sn-3.5Ag solder

    NASA Astrophysics Data System (ADS)

    Lee, Young-Kyu; Ko, Yong-Ho; Kim, Jun-Ki; Lee, Chang-Woo; Yoo, Sehoon

    2013-01-01

    The microstructure and joint properties of Au stud bumps joined with Sn-3.5Ag solder were investigated as functions of flip chip bonding temperature and aging time. Au stud bumps were bonded on solder-onpad (SOP) at bonding temperature of 260°C and 300°C for 10 s, respectively. Aging treatment was carried out at 150°C for 100 h, 300 h, and 500 h, respectively. After flip chip bonding, intermetallic compounds (IMCs) of AuSn, AuSn2, and AuSn4 were formed at the interface between the Au stud bump and Sn-3.5Ag solder. At a bonding temperature of 300°C, AuSn2 IMC clusters, which were surrounded by AuSn4 IMCs, were observed in the Sn-3.5Ag solder bump. After flip chip bonding, bonding strength was approximately 220.5mN/bump. As aging time increased, the bonding strength decreased. After 100 h of aging treatment, the bonding strength of the joint bonded at 300°C was lower than that bonded at 260°C due to the fast growth rate of the AuSn2 IMCs. The main failure modes were interface fractures between the AuSn2 IMCs and AuSn4 IMCs, fractures through the AuSn2 IMCs and pad lift. Initial joint microstructures after flip chip bonding strongly affected the bonding strengths of aged samples.

  3. The magnetic behavior of the intermetallic compound NdMn{sub 2}Ge{sub 2} studied by magnetization and hyperfine interactions measurements

    SciTech Connect

    Bosch-Santos, B. Carbonari, A. W.; Cabrera-Pasca, G. A.; Saxena, R. N.; Freitas, R. S.

    2015-05-07

    The magnetic behavior of the intermetallic compound NdMn{sub 2}Ge{sub 2} was investigated by bulk magnetization measurements and measurements of hyperfine interactions using perturbed γ–γ angular correlation (PAC) spectroscopy. Magnetization measurements indicate the presence of four magnetic transitions associated with the Mn and Nd magnetic sublattices. At high temperatures, magnetic measurements show a change in the slope of the magnetization due to an antiferromagnetic transition around T{sub N} ∼ 425 K and a well defined ferromagnetic transition at T{sub C} ∼ 320 K. Moreover, at ∼210 K a peak is observed in the magnetization curve, which is assigned to the reorientation of the Mn spin, and at ∼25 K an increase in the magnetic moment is also observed, which is ascribed to the ordering of Nd ions. PAC measurements using {sup 140}La({sup 140}Ce) and {sup 111}In({sup 111}Cd) probe nuclei allowed the determination of the temperature dependence of the magnetic hyperfine field (B{sub hf}) at Nd and Mn sites, respectively. PAC results with {sup 111}Cd probe nuclei at Mn sites show that the dependence of B{sub hf} with temperature follows the expected behavior for the host magnetization associated with the magnetic ordering of Mn ions. From these results, the antiferromagnetic transition followed by a ferromagnetic ordering is clearly observed. PAC results with {sup 140}Ce probe nuclei at Nd sites, however, showed a strong deviation from the Brillouin function, which is attributed to the Ce 4f-electron contribution to B{sub hf}.

  4. Controlling Interfacial Reactions and Intermetallic Compound Growth at the Interface of a Lead-free Solder Joint with Layer-by-Layer Transferred Graphene.

    PubMed

    Ko, Yong-Ho; Lee, Jong-Dae; Yoon, Taeshik; Lee, Chang-Woo; Kim, Taek-Soo

    2016-03-01

    The immoderate growth of intermetallic compounds (IMCs) formed at the interface of a solder metal and the substrate during soldering can degrade the mechanical properties and reliability of a solder joint in electronic packaging. Therefore, it is critical to control IMC growth at the solder joints between the solder and the substrate. In this study, we investigated the control of interfacial reactions and IMC growth by the layer-by-layer transfer of graphene during the reflow process at the interface between Sn-3.0Ag-0.5Cu (in wt %) lead-free solder and Cu. As the number of graphene layers transferred onto the surface of the Cu substrate increased, the thickness of the total IMC (Cu6Sn5 and Cu3Sn) layer decreased. After 10 repetitions of the reflow process for 50 s above 217 °C, the melting temperature of Sn-3.0Ag-0.5Cu, with a peak temperature of 250 °C, the increase in thickness of the total IMC layer at the interface with multiple layers of graphene was decreased by more than 20% compared to that at the interface of bare Cu without graphene. Furthermore, the average diameter of the Cu6Sn5 scallops at the interface with multiple layers of graphene was smaller than that at the interface without graphene. Despite 10 repetitions of the reflow process, the growth of Cu3Sn at the interface with multiple layers of graphene was suppressed by more than 20% compared with that at the interface without graphene. The multiple layers of graphene at the interface between the solder metal and the Cu substrate hindered the diffusion of Cu atoms from the Cu substrate and suppressed the reactions between Cu and Sn in the solder. Thus, the multiple layers of graphene transferred at the interface between dissimilar metals can control the interfacial reaction and IMC growth occurring at the joining interface. PMID:26856638

  5. Effects of post-reflow cooling rate and thermal aging on growth behavior of interfacial intermetallic compound between SAC305 solder and Cu substrate

    NASA Astrophysics Data System (ADS)

    Hu, Xiaowu; Xu, Tao; Jiang, Xiongxin; Li, Yulong; Liu, Yi; Min, Zhixian

    2016-04-01

    The interfacial reactions between Cu and Sn3Ag0.5Cu (SAC305) solder reflowed under various cooling rates were investigated. It is found that the cooling rate is an important parameter in solder reflow process because it influences not only microstructure of solder alloy but also the morphology and growth of intermetallic compounds (IMCs) formed between solder and Cu substrate. The experimental results indicate that only scallop-like Cu6Sn5 IMC layer is observed between solder and Cu substrate in case of water cooling and air cooling, while bilayer composed of scallop-like Cu6Sn5 and thin layer-like Cu3Sn is detected under furnace cooling due to sufficient reaction time to form Cu3Sn between Cu6Sn5 IMC and Cu substrate which resulted from slow cooling rate. Samples with different reflow cooling rates were further thermal-aged at 423 K. And it is found that the thickness of IMC increases linearly with square root of aging time. The growth constants of interfacial IMC layer during aging were obtained and compared for different cooling rates, indicating that the IMC layer thickness increased faster in samples under low cooling rate than in the high cooling rate under the same aging condition. The long prismatic grains were formed on the existing interfacial Cu6Sn5 grains to extrude deeply into solder matrix with lower cooling rate and long-term aging, and the Cu6Sn5 grains coarsened linearly with cubic root of aging time.

  6. Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under temperature gradient

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Zhong, Y.; Huang, M. L.; Ma, H. T.; Dong, W.

    2015-08-01

    The growth behavior of intermetallic compounds (IMCs) at the liquid-solid interfaces in Cu/Sn/Cu interconnects during reflow at 250 °C and 280 °C on a hot plate was investigated. Being different from the symmetrical growth during isothermal aging, the interfacial IMCs showed clearly asymmetrical growth during reflow, i.e., the growth of Cu6Sn5 IMC at the cold end was significantly enhanced while that of Cu3Sn IMC was hindered especially at the hot end. It was found that the temperature gradient had caused the mass migration of Cu atoms from the hot end toward the cold end, resulting in sufficient Cu atomic flux for interfacial reaction at the cold end while inadequate Cu atomic flux at the hot end. The growth mechanism was considered as reaction/thermomigration-controlled at the cold end and grain boundary diffusion/thermomigration-controlled at the hot end. A growth model was established to explain the growth kinetics of the Cu6Sn5 IMC at both cold and hot ends. The molar heat of transport of Cu atoms in molten Sn was calculated as + 11.12 kJ/mol at 250 °C and + 14.65 kJ/mol at 280 °C. The corresponding driving force of thermomigration in molten Sn was estimated as 4.82 × 10-19 N and 6.80 × 10-19 N.

  7. Effect of Cross-Interaction between Ni and Cu on Growth Kinetics of Intermetallic Compounds in Ni/Sn/Cu Diffusion Couples during Aging

    NASA Astrophysics Data System (ADS)

    Hong, K. K.; Ryu, J. B.; Park, C. Y.; Huh, J. Y.

    2008-01-01

    The solid-state, cross-interaction between the Ni layer on the component side and the Cu pad on the printed circuit board (PCB) side in ball grid array (BGA) solder joints was investigated by employing Ni(15 μm)/Sn(65 μm)/Cu ternary diffusion couples. The ternary diffusion couples were prepared by sequentially electroplating Sn and Ni on a Cu foil and were aged isothermally at 150, 180, and 200°C. The growth of the intermetallic compound (IMC) layer on the Ni side was coupled with that on the Cu side by the mass flux across the Sn layer that was caused by the difference in the Ni content between the (Cu1- x Ni x )6Sn5 layer on the Ni side and the (Cu1- y Ni y )6Sn5 layer on the Cu side. As the consequence of the coupling, the growth rate of the (Cu1- x Ni x )6 Sn5 layer on the Ni side was rapidly accelerated by decreasing Sn layer thickness and increasing aging temperature. Owing to the cross-interaction with the top Ni layer, the growth rate of the (Cu1- y Ni y )6Sn5 layer on the Cu side was accelerated at 150°C and 180°C but was retarded at 200°C, while the growth rate of the Cu3Sn layer was always retarded. The growth kinetic model proposed in an attempt to interpret the experimental results was able to reproduce qualitatively all of the important experimental observations pertaining to the growth of the IMC layers in the Ni/Sn/Cu diffusion couple.

  8. Ab initio study of the structural, elastic, thermodynamic, electronic and vibration properties of TbMg intermetallic compound

    NASA Astrophysics Data System (ADS)

    Mogulkoc, Y.; Ciftci, Y. O.; Kabak, M.; Colakoglu, K.

    2014-07-01

    The structural, elastic, thermodynamic, electronic and vibrational properties of CsCl-type TbMg have been studied by performing ab initio calculations based on density functional theory using the Vienna Ab initio Simulation Package (VASP). The exchange correlation potential within the generalized-gradient approximation (GGA) of projector augmented wave (PAW) method is used. The calculated structural parameters, such as the lattice constant, bulk modulus, its pressure derivative, formation energy and second-order elastic constants are presented in this paper. The obtained results are compared with related experimental and theoretical studies. The electronic band calculations, total density of states (DOS), partial DOS and charge density are also presented. Formation enthalpy and Cauchy pressure are determined. In order to obtain more information the elastic properties such as Zener anisotropy factor, Poisson’s ratio, Young modulus, isotropic shear modulus, Debye temperature and melting point have been carried out. The elastic constants are calculated in zero and different pressure ranges (0-50 GPa) with bulk modulus. We have performed the thermodynamic properties of TbMg by using quasi-harmonic Debye model. The temperature and pressure variation of the volume, bulk modulus, and thermal expansion coefficient have been predicted over a pressure range of 0-25 GPa for of TbMg. Pressure dependence of the anisotropy factors, Young’s modulus, Poisson’s ratios, bulk modulus and axis compressibility of TbMg are presented along different directions and planes. Finally, the phonon dispersion curves are presented for TbMg.

  9. Volatile compound formation during argan kernel roasting.

    PubMed

    El Monfalouti, Hanae; Charrouf, Zoubida; Giordano, Manuela; Guillaume, Dominique; Kartah, Badreddine; Harhar, Hicham; Gharby, Saïd; Denhez, Clément; Zeppa, Giuseppe

    2013-01-01

    Virgin edible argan oil is prepared by cold-pressing argan kernels previously roasted at 110 degrees C for up to 25 minutes. The concentration of 40 volatile compounds in virgin edible argan oil was determined as a function of argan kernel roasting time. Most of the volatile compounds begin to be formed after 15 to 25 minutes of roasting. This suggests that a strictly controlled roasting time should allow the modulation of argan oil taste and thus satisfy different types of consumers. This could be of major importance considering the present booming use of edible argan oil.

  10. Preparation and properties of the Ni-Al/Fe-Al intermetallics composite coating produced by plasma cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Min; Liu, Bang-Wu; Sun, Dong-Bai

    2011-12-01

    A novel approach to produce an intermetallic composite coating was put forward. The microstructure, microhardness, and dry-sliding wear behavior of the composite coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) analysis, microhardness test, and ball-on-disc wear experiment. XRD results indicate that some new phases FeAl, Fe0.23Ni0.77Al, and Ni3Al exit in the composite coating with the Al2O3 addition. SEM results show that the coating is bonded with carbon steel metallurgically and exhibits typical rapid directional solidification structures. The Cr7C3 carbide and intermetallic compounds co-reinforced composite coating has a high average hardness and exhibits an excellent wear resistance under dry-sliding wear test compared with the Cr7C3 carbide-reinforced composite coating. The formation mechanism of the intermetallic compounds was also investigated.

  11. Formation of Stoichiometric CsFn Compounds

    NASA Astrophysics Data System (ADS)

    Zhu, Qiang; Oganov, Artem R.; Zeng, Qingfeng

    2015-01-01

    Alkali halides MX, have been viewed as typical ionic compounds, characterized by 1:1 ratio necessary for charge balance between M+ and X-. It was proposed that group I elements like Cs can be oxidized further under high pressure. Here we perform a comprehensive study for the CsF-F system at pressures up to 100 GPa, and find extremely versatile chemistry. A series of CsFn (n >= 1) compounds are predicted to be stable already at ambient pressure. Under pressure, 5p electrons of Cs atoms become active, with growing tendency to form Cs (III) and (V) valence states at fluorine-rich conditions. Although Cs (II) and (IV) are not energetically favoured, the interplay between two mechanisms (polyfluoride anions and polyvalent Cs cations) allows CsF2 and CsF4 compounds to be stable under pressure. The estimated defluorination temperatures of CsFn (n = 2,3,5) compounds at atmospheric pressure (218°C, 150°C, -15°C, respectively), are attractive for fluorine storage applications.

  12. Reaction synthesis of intermetallics

    SciTech Connect

    Deevi, S.C.; Sikka, V.K.

    1994-12-31

    Exothermicity associated with the synthesis of aluminides was utilized to obtain nickel, iron, and cobalt aluminides. Combustion synthesis, extrusion, and hot pressing were utilized to obtain intermetallics and their composites. Extrusion conditions, reduction ratios, and hot-pressing conditions of the intermetallics and their composites are discussed.

  13. Contrasts in Structural and Bonding Representations among Polar Intermetallic Compounds. Strongly Differentiated Hamilton Populations for Three Related Condensed Cluster Halides of the Rare-Earth Elements

    SciTech Connect

    Gupta, Shalabh; Meyer, Gerd; Corbett, John D.

    2010-10-01

    The crystal and electronic structures of three related R{sub 3}TnX{sub 3} phases (R = rare-earth metal, Tn = transition metal, X = Cl, I) containing extended mixed-metal chains are compared and contrasted: (1) Pr{sub 3}RuI{sub 3} (P2{sub 1}/m), (2) Gd{sub 3}MnI{sub 3} (P2{sub 1}/m), and (3) Pr{sub 3}RuCl{sub 3} (Pnma). The structures all feature double chains built of pairs of condensed R{sub 6}(Tn) octahedral chains encased by halogen atoms. Pr{sub 3}RuI{sub 3} (1) lacks significant Ru-Ru bonding, evidently because of packing restrictions imposed by the large closed-shell size of iodine. However, the vertex Pr2 atoms on the chain exhibit a marked electronic differentiation. These are strongly bound to the central Ru (and to four I), but very little to four neighboring Pr in the cluster according to bond populations, in contrast to Pr2-Pr 'bond' distances that are very comparable to those elsewhere. In Gd{sub 3}MnI{sub 3} (2), the smaller metal atoms allow substantial distortions and Mn-Mn bonding. Pr{sub 3}RuCl{sub 3} (3), in contrast to the iodide (1), can be described in terms of a more tightly bound superstructure of (2) in which both substantial Ru-Ru bonding and an increased number of Pr-Cl contacts in very similar mixed-metal chains are favored by the smaller closed-shell contacts of chlorine. Local Spin Density Approximation (LSDA) Linearized Muffin-Tin Orbital (LMTO)-ASA calculations and Crystal Orbital Hamilton Population (COHP) analyses show that the customary structural descriptions in terms of condensed, Tn-stuffed, R-R bonded polyhedral frameworks are poor representations of the bonding in all. Hamilton bond populations (-ICOHP) for the polar mixed-metal R-Tn and the somewhat smaller R-X interactions account for 75-90% of the total populations in each of these phases, together with smaller contributions and variations for R-R and Tn-Tn interactions. The strength of such R-Tn contributions in polar intermetallics was first established or anticipated by

  14. Formation of flavour compounds in the Maillard reaction.

    PubMed

    van Boekel, M A J S

    2006-01-01

    This paper discusses the importance of the Maillard reaction for food quality and focuses on flavour compound formation. The most important classes of Maillard flavour compounds are indicated and it is shown where they are formed in the Maillard reaction. Some emphasis is given on the kinetics of formation of flavour compounds. It is concluded that the essential elements for predicting the formation of flavour compounds in the Maillard reaction are now established but much more work needs to be done on specific effects such as the amino acid type, the pH, water content and interactions in the food matrix. It is also concluded that most work is done on free amino acids but hardly anything on peptides and proteins, which could generate peptide- or protein-specific flavour compounds. PMID:16386869

  15. Theoretical screening of intermetallic ThMn12-type phases for new hard-magnetic compounds with low rare earth content.

    PubMed

    Körner, Wolfgang; Krugel, Georg; Elsässer, Christian

    2016-01-01

    We report on theoretical investigations of intermetallic phases derived from the ThMn12-type crystal structure. Our computational high-throughput screening (HTS) approach is extended to an estimation of the anisotropy constant K1, the anisotropy field Ha and the energy product (BH)max. The calculation of K1 is fast since it is based on the crystal field parameters and avoids expensive total-energy calculations with many k-points. Thus the HTS approach allows a very efficient search for hard-magnetic materials for which the magnetization M and the coercive field Hc connected to Ha represent the key quantities. Besides for NdFe12N which has the highest magnetization we report HTS results for several intermetallic phases based on Cerium which are interesting as alternative hard-magnetic phases because Cerium is a less ressource-critical element than Neodymium. PMID:27098547

  16. Theoretical screening of intermetallic ThMn12-type phases for new hard-magnetic compounds with low rare earth content

    PubMed Central

    Körner, Wolfgang; Krugel, Georg; Elsässer, Christian

    2016-01-01

    We report on theoretical investigations of intermetallic phases derived from the ThMn12-type crystal structure. Our computational high-throughput screening (HTS) approach is extended to an estimation of the anisotropy constant K1, the anisotropy field Ha and the energy product (BH)max. The calculation of K1 is fast since it is based on the crystal field parameters and avoids expensive total-energy calculations with many k-points. Thus the HTS approach allows a very efficient search for hard-magnetic materials for which the magnetization M and the coercive field Hc connected to Ha represent the key quantities. Besides for NdFe12N which has the highest magnetization we report HTS results for several intermetallic phases based on Cerium which are interesting as alternative hard-magnetic phases because Cerium is a less ressource-critical element than Neodymium. PMID:27098547

  17. Reactions of intermetallic clusters

    NASA Astrophysics Data System (ADS)

    Farley, R. W.; Castleman, A. W., Jr.

    1990-02-01

    Reaction of bismuth-alkali clusters with closed-shell HX acids provides insight into the structures, formation, and stabilities of these intermetallic species. HC1 and HI are observed to quantitatively strip BixNay and BixKy, respectively, of their alkali component, leaving bare bismuth clusters as the only bismuth-containing species detected. Product bismuth clusters exhibit the same distribution observed when pure bismuth is evaporated in the source. Though evaporated simultaneously from the same crucible, this suggests alkali atoms condense onto existing bismuth clusters and have negligible effect on their formation and consequent distribution. The indistinguishibility of reacted and pure bismuth cluster distributions further argues against the simple replacement of alkali atoms with hydrogen in these reactions. This is considered further evidence that the alkali atoms are external to the stable bismuth Zintl anionic structures. Reactivities of BixNay clusters with HC1 are estimated to lie between 3×10-13 for Bi4Na, to greater than 4×10-11 for clusters possessing large numbers of alkali atoms. Bare bismuth clusters are observed in separate experiments to react significantly more slowly with rates of 1-9×10-14 and exhibit little variation of reactivity with size. The bismuth clusters may thus be considered a relatively inert substrate upon which the alkali overlayer reacts.

  18. Local magnetic moment formation at 119Sn Mössbauer impurity in RCo2 (R=Gd,Tb,Dy,Ho,Er) Laves phase compounds

    NASA Astrophysics Data System (ADS)

    de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

    2008-04-01

    In this work, we theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a Mösbauer Sn119 impurity diluted at the R site (R=Gd,Tb,Dy,Ho,Er) of the cubic Laves phase intermetallic compounds RCo2. One considers that the magnetic hyperfine fields have two contributions, (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24, 1601 (1963)] model, and (ii) the contribution from the induced magnetic moments arising from the Co neighboring sites. Our calculated self-consistent total magnetic hyperfine fields are in a good agreement with recent experimental data.

  19. Evidence of ferromagnetism in vanadium substituted layered intermetallic compounds RE (Co1-xVx) 2 Si2 (RE=Pr and Nd; 0 ≤ x ≤ 0.35)

    NASA Astrophysics Data System (ADS)

    Chowdhury, R. Roy; Dhara, S.; Bandyopadhyay, B.

    2016-03-01

    In intermetallic compounds RECo2Si2 (RE=Pr and Nd), cobalt has been partially substituted by vanadium to obtain RE(Co1-xVx)2Si2 (0 ≤ x ≤ 0.35). The parent compounds are antiferromagnetic below about 30 K due to the ordering of localized magnetic moments that are present only on rare-earth ions, cobalt being non-magnetic in the parent compounds. The present study demonstrates that in these compounds where 3 d and 4 f ions occupy different layers in the crystal structure, V substitution and subsequent lattice expansion results in the occurrence of inequivalent magnetic ions and complex interactions that lead to multiple magnetic transitions. At temperatures around 40-50 K, the temperature dependence of magnetization indicates a ferrimagnetic transition which is accompanied by a rapid decrease in the temperature dependence of resistivity. Below temperatures ∼30 K, the samples begin to show ferromagnetic-like behavior with the appearance of a coercive field and saturation in the magnetization at magnetic fields above ∼2 T. These two magnetic transitions are indicated also by prominent λ-like peaks in specific heat measurements. At around 10 K, a sharp drop in the resistivity indicates another magnetic transition which is followed by a rapid increase in coercive field with decrease in temperature. In a magnetic field of 9 T, the latter transition shifts to a lower temperature and that leads to a positive magnetoresistance. The onset of ferromagnetism at ∼30 K is accompanied with an exchange bias field which is observed for the first time in layered intermetallic compounds. The exchange bias field increases rapidly below the transition at ∼10 K and reaches ∼16% of coercive field at 2 K.

  20. Some natural compounds enhance N epsilon-(carboxymethyl)lysine formation.

    PubMed

    Fujiwara, Yukio; Kiyota, Naoko; Motomura, Keita; Mera, Katsumi; Takeya, Motohiro; Ikeda, Tsuyoshi; Nagai, Ryoji

    2008-04-01

    Since pyridoxamine, which traps intermediates in the Maillard reaction and lipid peroxidation reaction, significantly inhibits the development of retinopathy and neuropathy in the streptozotocin-induced diabetic rat, treatment with advanced glycation end product inhibitors and antioxidants may be a potential strategy for the prevention of clinical diabetic complications. However, the paradoxical effect of green tea has been reported; although plasma hydroperoxide levels were ameliorated, the level of N epsilon-(carboxyethyl)lysine (CML) in tendon and plasma was increased by the oral administration of green tea to diabetic rats. In the present study, we measured the effect of natural compounds on CML formation by enzyme-linked immunosorbent assay. A significant amount of CML was observed when bovine serum albumin was incubated with ribose for 7 days. Under the same conditions, natural compounds, such as desgalactotigonin, showed inhibitory effects, whereas quercetin and acteoside enhanced CML formation, indicating that natural compounds contain both inhibitors and enhancers for CML formation. PMID:18079486

  1. Chemistry and Properties of Complex Intermetallics from Metallic Fluxes

    SciTech Connect

    Kanatzidis, Mercouri G.

    2015-03-28

    This project investigated the reaction chemistry and synthesis of new intermetallic materials with complex compositions and structures using metallic fluxes as solvents. It was found that the metallic fluxes offer several key advantages in facilitating the formation and crystal growth of new materials. The fluxes mostly explored were liquid aluminum, gallium and indium. The main purpose of this project was to exploit the potential of metallic fluxes as high temperature solvent for materials discovery in the broad class of intermetallics. This work opened new paths to compound formation. We discovered many new Si (or Ge)-based compounds with novel structures, bonding and physicochemical properties. We created new insights about the reaction chemistry that is responsible for stabilizing the new materials. We also studied the structural and compositional relationships to understand their properties. We investigated the use of Group-13 metals Al, Ga and In as solvents and have generated a wide variety of new results including several new ternary and quaternary materials with fascinating structures and properties as well as new insights as to how these systems are stabilized in the fluxes. The project focused on reactions of metals from the rare earth element family in combination with transition metals with Si and Ge. For example molten gallium has serves both as a reactive and non-reactive solvent in the preparation and crystallization of intermetallics in the system RE/M/Ga/Ge(Si). Molten indium behaves similarly in that it too is an excellent reaction medium, but it gives compounds that are different from those obtained from gallium. Some of the new phase identified in the aluminide class are complex phases and may be present in many advanced Al-matrix alloys. Such phases play a key role in determining (either beneficially or detrimentally) the mechanical properties of advanced Al-matrix alloys. This project enhanced our basic knowledge of the solid state chemistry

  2. The μ3 model of acids and bases: extending the Lewis theory to intermetallics.

    PubMed

    Stacey, Timothy E; Fredrickson, Daniel C

    2012-04-01

    A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system.

  3. Process and apparatus for formation of photovoltaic compounds

    DOEpatents

    Hall, Robert B.; Rocheleau, Richard E.

    1985-01-01

    The invention relates to a process and apparatus for formation and deposition of thin films on a substrate, in a vacuum, by evaporation of the elements to form a Zn.sub.x Cd.sub.1-x S compound having a preselected fixed ratio of cadmium to zinc, characterized by the evaporation of cadmium and zinc at a rate the ratio of which is proportional to the stoichiometric ratio of those elements in the intended compound and evaporation of sulfur at a rate at least twice the combined rates of cadmium and zinc, and at least twice that required by the stoichiometry of the intended compound.

  4. The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

    SciTech Connect

    Priyotomo, Gadang Nuraini, Lutviasari; Kaneno, Yasuyuki

    2015-12-29

    The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observed on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.

  5. The effect of pH on the corrosion behavior of intermetallic compounds Ni3(Si,Ti) and Ni3(Si,Ti) + 2Mo in sodium chloride solutions

    NASA Astrophysics Data System (ADS)

    Priyotomo, Gadang; Nuraini, Lutviasari; Kaneno, Yasuyuki

    2015-12-01

    The corrosion behavior of the intermetallic compounds, Ni3(Si,Ti) (L12: single phase) and Ni3(Si,Ti) + 2Mo (L12 and (L12 + Niss) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m3 NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni3(Si,Ti) for the immersion test at lower pH, while the pitting attack was observed on this compound for this test at neutral solution. Furthermore, Ni3(Si,Ti)+2Mo had the preferential dissolution of L12 compared to (L12 + Niss) mixture region at lower pH, while pitting attack occurred in (L12 + Niss) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni3(Si,Ti)+2Mo is lower than that of Ni3(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.

  6. Anti-mackay polyicosahedral clusters in La-Ni-Mg ternary compounds: synthesis and crystal structure of the La(43)Ni(17)Mg(5) new intermetallic phase.

    PubMed

    Solokha, Pavlo; De Negri, Serena; Pavlyuk, Volodymyr; Saccone, Adriana

    2009-12-21

    The crystal structure of the complex La(43)Ni(17)Mg(5) ternary phase was solved and refined from X-ray single crystal diffraction data. It is characterized by a very large unit cell and represents a new structure type: La(43)Ni(17)Mg(5) - orthorhombic, Cmcm, oS260, a = 10.1895(3), b = 17.6044(14), c = 42.170(3) A, Z = 4, wR1 = 0.0598, wR2 = 0.0897, 4157 F(2) values, 176 variables. The crystal structures of the La-rich La-Ni-Mg intermetallic phases La(4)NiMg, La(23)Ni(7)Mg(4), and La(43)Ni(17)Mg(5) have been comparatively analyzed. The constitutive fragments of these structures are binary polyicosahedral core-shell clusters of Mg(4)La(22) and Mg(5)La(24) compositions together with binary polytetrahedral clusters of nickel and lanthanum atoms. The structures of the Mg-La clusters are described in detail as a unique feature of the analyzed intermetallic phases; the dodecahedral Voronoi polyhedra are proposed as a useful tool to characterize polyicosahedral clusters. The arrangements of the building units in the studied phases show some regularities; particularly the i(4)3, i(5)3 and L-i(4) units, made up of polyicosahedral clusters and analogous to the Kreiner i(3) and L units, are proposed as structural blocks.

  7. A reliability study on tin based lead free micro joint including intermetallic and void evolution

    NASA Astrophysics Data System (ADS)

    Feyissa, Frezer Assefa

    In microelectronics soldering to Cu pad lead to formation of two intermetallic structures in the solder -pad interface. The growth of these layers is accompanied by microscopic voids that usually cause reliability concern in the industry. Therefore it is important to understand factors that contribute for the growth of IMC using various combination of reflow time, Sn thickness and aging temperature. Systematic study was conducted on Cu-Sn system to investigate the formation and growth of intermetallic compound (IMC) as well as voiding evolution for different solder thicknesses. The growth of the Cu6Sn5 IMC layer was found to be increasing as the Sn thicknesses increase after reflow while the Cu3Sn layer were decreasing under same conditions. Also after reflow and aging more voiding were shown to occur in the thin solder than thicker one.

  8. Formation and evolution of intermetallic nanoparticles and vacancy defects under irradiation in Fesbnd Nisbnd Al ageing alloy characterized by resistivity measurements and positron annihilation

    NASA Astrophysics Data System (ADS)

    Druzhkov, A. P.; Danilov, S. E.; Perminov, D. A.; Arbuzov, V. L.

    2016-08-01

    In this paper, we study the effects of intermetallic nanoparticles like Ni3Al on the evolution of vacancy defects in the fcc Fesbnd Nisbnd Al alloy under electron irradiation using positron annihilation spectroscopy. Electrical resistivity measurements have been used as a testing method for characterizing the evolution in the underlying precipitate microstructure due to heat treatment and irradiation. It was shown that the nanosized (∼4.5 nm) intermetallic precipitates homogeneously distributed in the alloy matrix caused a several-fold decrease in the accumulation of vacancies as compared to their accumulation in the pre-quenched alloy. This effect was enhanced with the irradiation temperature. The irradiation-induced growth of intermetallic nanoparticles was also observed in the pre-quenched Fesbnd Nisbnd Al alloy under irradiation at 573 K. Thus, resistivity measurement and positron confinement in ultrafine intermetallic particles, which we revealed earlier, provided the control over the evolution of coherent precipitates, along with vacancy defects, during irradiation and annealing.

  9. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  10. Heats of Formation and Bond Energies in Group III Compounds

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Allendorf, Mark D.; Melius, Carl F.; Arnold, James O. (Technical Monitor)

    1999-01-01

    We present heats of formation and bond energies for Group-III compounds obtained from calculations of molecular ground-state I electronic energies. Data for compounds of the form MXn are presented, where M = B, Al, Ga, and In, X = He H, Cl, and CH3, and n = 1-3. Energies for the B, Al, and Ga compounds are obtained from G2 predictions, while those for the In compounds are obtained from CCSD(T)/CBS calculations; these are the most accurate calculations for indium-containing compounds published to date. In most cases, the calculated thermochemistry is in good agreement with published values derived from experiments for those species that have well-established heats of formation. Bond energies obtained from the heats of formation follow the expected trend (Cl much greater than CH3 approx. H). However, the CH3M-(CH3)2 bond energies obtained for trimethylgallium and trimethylindium are considerably stronger (greater than 15 kcal/mol) than currently accepted values.

  11. Kinetics of the Formation of Intercalation Compounds in Crystalline Graphite

    NASA Technical Reports Server (NTRS)

    Sharma, P. K.; Hickey, G. S.

    1995-01-01

    Crystalline graphite has a structure that can be best described as an ordered stack of flat aromatic layers. It is known to form intercalation compounds with bromine and nitric acid. Their formation was studied using thermal measurements and analytical techniques. Samples of graphite treated with either bromine or nitric acid were prepared by contacting these reagents with powdered graphite.

  12. SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} - two new Ae-Zn-Sn polar intermetallic compounds (Ae: alkaline earth metal)

    SciTech Connect

    Stegmaier, Saskia; Faessler, Thomas F.

    2012-08-15

    SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}, two closely related new polar intermetallic compounds, were obtained by high temperature reactions of the elements. Their crystal structures were determined with single crystal XRD methods, and their electronic structures were analyzed by means of DFT calculations. The Zn-Sn structure part of SrZn{sub 2}Sn{sub 2} comprises (anti-)PbO-like {l_brace}ZnSn{sub 4/4}{r_brace} and {l_brace}SnZn{sub 4/4}{r_brace} layers. Ca{sub 2}Zn{sub 3}Sn{sub 6} shows similar {l_brace}ZnSn{sub 4/4}{r_brace} layers and {l_brace}Sn{sub 4}Zn{r_brace} slabs constructed of a covalently bonded Sn scaffold capped by Zn atoms. For both phases, the two types of layers are alternatingly stacked and interconnected via Zn-Sn bonds. SrZn{sub 2}Sn{sub 2} adopts the SrPd{sub 2}Bi{sub 2} structure type, and Ca{sub 2}Zn{sub 3}Sn{sub 6} is isotypic to the R{sub 2}Zn{sub 3}Ge{sub 6} compounds (R=La, Ce, Pr, Nd). Band structure calculations indicate that both SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6} are metallic. Analyses of the chemical bonding with the electron localization function (ELF) show lone pair like basins at Sn atoms and Zn-Sn bonding interactions between the layers for both title phases, and covalent Sn-Sn bonding within the {l_brace}Sn{sub 4}Zn{r_brace} layers of Ca{sub 2}Zn{sub 3}Sn{sub 6}. - Graphical abstract: Crystal structures of the new Ae-Zn-Sn polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Highlights: Black-Right-Pointing-Pointer New polar intermetallic phases SrZn{sub 2}Sn{sub 2} and Ca{sub 2}Zn{sub 3}Sn{sub 6}. Black-Right-Pointing-Pointer Obtained by high temperature reactions of the elements. Black-Right-Pointing-Pointer Single crystal XRD structure determination and DFT electronic structure calculations. Black-Right-Pointing-Pointer Closely related crystal and electronic structures. Black-Right-Pointing-Pointer Metallic conductivity coexisting with lone pairs and covalent bonding

  13. Thermal barrier coating system with intermetallic overlay bond coat

    SciTech Connect

    Duderstadt, E.C.; Nagaraj, B A.

    1993-08-24

    A superalloy article is described having a thermal barrier coating system thereon, comprising: a substrate made of a material selected from the group consisting of a nickel-based superalloy and a cobalt-based superalloy; and a thermal barrier coating system on the substrate, the thermal barrier coating system including an intermetallic bond coat overlying the substrate, the bond coat being selected from the group consisting of a nickel aluminide and a platinum aluminide intermetallic compound, a thermally grown aluminum oxide layer overlying the intermetallic bond coat, and a ceramic topcoat overlying the aluminum oxide layer.

  14. Vacancy formation and extraction energies in semiconductor compounds and alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.

    1990-01-01

    A model for calculating the extraction energies and vacancy-formation energies in diamond-cubic and zinc-blende semiconductors is developed on the basis of Harrison's (1980, 1983) tight-binding theory. The extraction energies provide a reference from which other final states of the removed atoms can be calculated. The results of calculations show that, in a given compound, the calculated extraction energies are larger for the anion than for the cation, with the difference between the cation and the anion being larger in the II-VI than in the III-V compounds. This is in agreement with experimental results.

  15. A Compound Inhibits Biofilm Formation of Staphylococcus aureus from Streptomyces.

    PubMed

    Suzuki, Naomoto; Ohtaguro, Norihiro; Yoshida, Yasuaki; Hirai, Motoshi; Matsuo, Hirotaka; Yamada, Yoichi; Imamura, Nobutaka; Tsuchiya, Tomofusa

    2015-01-01

    Biofilm is one virulence factor of bacteria. It contributes not only to bacterial adherence to many kinds of infection-establishing surfaces, but also to bacterial resistance against antimicrobial agents and antiseptic agents. Thus, inhibitors of bacterial biofilm formation should be useful in the prevention of infections. We found that a culture of Streptomyces sp. strain MC11024 showed inhibitory activity on biofilm formation by Staphylococcus aureus and isolated streptorubin B as an inhibitor of this formation in S. aureus. The biofilm formation of methicillin resistant S. aureus (MRSA) N315 was reduced to less than 30% at 1 µg/mL of streptorubin B, and at this concentration cell growth was not affected. Our study suggests that streptorubin B has the potential to be a leading compound of anti-infectious agents of S. aureus.

  16. Model for compound formation during ion-beam mixing

    SciTech Connect

    Desimoni, J.; Traverse, A. )

    1993-11-01

    We propose an ion-beam-mixing model that accounts for compound formation at a boundary between two materials during ion irradiation. It is based on Fick's law together with a chemical driving force in order to simulate the chemical reaction at the boundary. The behavior of the squared thickness of the mixed layer, [ital X][sup 2], with the irradiation fluence, [Phi], has been found in several mixing experiments to be either quadratic ([ital X][sup 2][alpha][Phi][sup 2]) or linear ([ital X][sup 2][alpha][Phi]), a result which is qualitatively reproduced. Depending on the fluence range, compound formation or diffusion is the limiting process of mixing kinetics. A criterion is established in terms of the ratio of the diffusion coefficient [ital D] due to irradiation to the chemical reaction rate squared which allows us to predict quadratic or linear behavior. When diffusion is the limiting process, [ital D] is enhanced by a factor which accounts for the formation of a compound in the mixed layer. Good agreement is found between the calculated mixing rates and the data taken from mixing experiments in metal/Si bilayers.

  17. High-temperature structural intermetallics

    SciTech Connect

    Yamaguchi, M.; Inui, H.; Ito, K.

    2000-01-01

    In the last one and a half decades, a great deal of fundamental and developmental research has been made on high-temperature structural intermetallics aiming at the implementation of these intermetallics in aerospace, automotive and land-based applications. These intermetallics include aluminides formed with either titanium, nickel or iron and silicides formed with transition metals. Of these high-temperature intermetallics, TiAl-based alloys with great potential in both aerospace and automotive applications have been attracting particular attention. Recently TiAl turbocharger wheels have finally started being used for turbochargers for commercial passenger cars of a special type. The current status of the research and development of these high-temperature intermetallics is summarized and a perspective on what directions future research and development of high-temperature intermetallics should take is provided.

  18. Molecular mechanisms of compounds affecting bacterial biofilm formation and dispersal.

    PubMed

    Landini, Paolo; Antoniani, Davide; Burgess, J Grant; Nijland, Reindert

    2010-04-01

    Bacteria can switch between planktonic forms (single cells) and biofilms, i.e., bacterial communities growing on solid surfaces and embedded in a matrix of extracellular polymeric substance. Biofilm formation by pathogenic bacteria often results in lower susceptibility to antibiotic treatments and in the development of chronic infections; thus, biofilm formation can be considered an important virulence factor. In recent years, much attention has been directed towards understanding the biology of biofilms and towards searching for inhibitors of biofilm development and of biofilm-related cellular processes. In this report, we review selected examples of target-based screening for anti-biofilm agents: We focus on inhibitors of quorum sensing, possibly the most characterized target for molecules with anti-biofilm activity, and on compounds interfering with the metabolism of the signal molecule cyclic di-GMP metabolism and on inhibitors of DNA and nucleotide biosynthesis, which represent a novel and promising class of biofilm inhibitors. Finally, we discuss the activation of biofilm dispersal as a novel mode of action for anti-biofilm compounds. PMID:20165945

  19. Progress in donor assisted coal liquefaction: Hydroaromatic compound formation

    SciTech Connect

    Kottenstette, R.J.; Stephens, H.P.

    1993-12-31

    The role of hydrogen donor compounds in coal liquefaction has been extensively investigated since the mid 1960`s using model compounds and process derived hydrogen donor solvents. Our recent research and that of other investigators have shown that two model compounds in particular have great efficacy in solvating low rank coals. 1,2,3,10b tetrahydrofluoranthene (H{sub 4}Fl) and 1,2,3,6,7,8 hexahydropyrene (H{sub 6}Py) have been used to dissolve Wyodak coal to > 95% soluble material as measured by tetrahydrofuran (THF). Although these hydrogen donors are very effective, they may not be found in any significant concentrations in actual liquefaction process recycle solvents. Therefore, studies with process derived recycle materials are necessary to understand donor solvent chemistry. The objective of this paper is to present results of solvent hydrogenation experiments using heavy distillate solvents produced during testing at the Wilsonville Advanced Coal Liquefaction Test Facility. We evaluated the impact of hydrogenation conditions upon hydrogen donor formation in process derived distillates and compared these process derived solvents with the highly effective H{sub 4}Fl and H{sub 6}Py donors in coal liquefaction tests. This paper presents data on reaction conditions used for distillate hydrotreating and subsequent coal liquefaction, with an aim toward understanding the relationship between reaction conditions and donor solvent quality in recycle distillates.

  20. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1992-12-31

    This paper briefly summarizes recent advances in intermetallic research and development. Ordered intermetallics based on aluminides and silicides possess attractive properties for structural applications at elevated temperatures in hostile environments; however, brittle fracture and poor fracture resistance limit their use as engineering materials in many cases. In recent years, considerable efforts have been devoted to the study of the brittle fracture behavior of intermetallic alloys; as a result, both intrinsic and extrinsic factors governing brittle fracture have been identified. Recent advances in first-principles calculations and atomistic simulations further help us in understanding atomic bonding, dislocation configuration, and alloying effects in intermetallics. The basic understanding has led to the development of nickel, iron, and titanium aluminide alloys with improved mechanical and metallurgical properties for structural use. Industrial interest in ductile intermetallic alloys is high, and several examples of industrial involvement are mentioned.

  1. Recent advances in ordered intermetallics

    SciTech Connect

    Liu, C.T.

    1994-12-31

    Ordered intermetallic alloys based on aluminides and silicides offer many advantages for structural use at high temperatures in hostile environments. Attractive properties include excellent oxidation and corrosion resistance, light weight, and superior strength at high temperatures. The major concern for structural use of intermetallics was their low ductility and poor fracture resistance at ambient temperatures. For the past 10 years, considerable effort was devoted to R&D of ordered intermetallic alloys, and progress has been made on understanding intrinsic and extrinsic factors controlling brittle fracture in intermetallic alloys based on aluminides and silicides. Parallel effort on alloy design has led to the development of a number of ductile and strong intermetallic alloys based on Ni{sub 3}Al, NiAl, Fe{sub 3}Al, FeAl, Ti{sub 3}Al, and TiAl systems for structural applications.

  2. Formation of xenon-nitrogen compounds at high pressure

    PubMed Central

    Howie, Ross T.; Turnbull, Robin; Binns, Jack; Frost, Mungo; Dalladay-Simpson, Philip; Gregoryanz, Eugene

    2016-01-01

    Molecular nitrogen exhibits one of the strongest known interatomic bonds, while xenon possesses a closed-shell electronic structure: a direct consequence of which renders both chemically unreactive. Through a series of optical spectroscopy and x-ray diffraction experiments, we demonstrate the formation of a novel van der Waals compound formed from binary Xe-N2 mixtures at pressures as low as 5 GPa. At 300 K and 5 GPa Xe(N2)2-I is synthesised, and if further compressed, undergoes a transition to a tetragonal Xe(N2)2-II phase at 14 GPa; this phase appears to be unexpectedly stable at least up to 180 GPa even after heating to above 2000 K. Raman spectroscopy measurements indicate a distinct weakening of the intramolecular bond of the nitrogen molecule above 60 GPa, while transmission measurements in the visible and mid-infrared regime suggest the metallisation of the compound at ~100 GPa. PMID:27748357

  3. The phenomenon of formation of prebiological compounds in volcanic processes.

    PubMed

    Markhinin, E K; Podkletnov, N E

    1977-10-01

    Organic matter has been found in the juvenile ash of seven volcanoes in Kamchatka, the Kurile Islands and Indonesia. Its amount in one eruption is of the order of 1 00 000 tons. This matter constitutes a multicomponent mixture (more than 150 components) of, mainly, high boiling (b.p. over 250 degrees C) organic compounds of a complex structure. These are represented by hydrocarbons of saturated and aromatic nature, and, among them, polycyclic hydrocarbons, amino acids, amino sugars and other heteroatomic molecules, also containing N, O, S and C1. The formation of the above mentioned organic compounds is associated with volcanic processes--with abiogenous synthesis taking place in ash-gas clouds and, possibly, in the entrails of the Earth (hydrocarbons and their heteroatomic derivatives have also been found in volcanic bombs). On the strength of these facts, volcanic phenomena are regarded as the process which serves as the starting point of the chemical evolution from the inanimate to the animate matter.

  4. Formation of xenon-nitrogen compounds at high pressure

    NASA Astrophysics Data System (ADS)

    Howie, Ross T.; Turnbull, Robin; Binns, Jack; Frost, Mungo; Dalladay-Simpson, Philip; Gregoryanz, Eugene

    2016-10-01

    Molecular nitrogen exhibits one of the strongest known interatomic bonds, while xenon possesses a closed-shell electronic structure: a direct consequence of which renders both chemically unreactive. Through a series of optical spectroscopy and x-ray diffraction experiments, we demonstrate the formation of a novel van der Waals compound formed from binary Xe-N2 mixtures at pressures as low as 5 GPa. At 300 K and 5 GPa Xe(N2)2-I is synthesised, and if further compressed, undergoes a transition to a tetragonal Xe(N2)2-II phase at 14 GPa this phase appears to be unexpectedly stable at least up to 180 GPa even after heating to above 2000 K. Raman spectroscopy measurements indicate a distinct weakening of the intramolecular bond of the nitrogen molecule above 60 GPa, while transmission measurements in the visible and mid-infrared regime suggest the metallisation of the compound at ~100 GPa.

  5. Magnetocaloric effect of RM2 (R = rare earth, M = Ni, Al) intermetallic compounds made by centrifugal atomization process for magnetic refrigerator

    NASA Astrophysics Data System (ADS)

    Matsumoto, K.; Asamato, K.; Nishimura, Y.; Zhu, Y.; Abe, S.; Numazawa, T.

    2012-12-01

    RM2 (R = rare earth, M = Al, Ni and Co) compounds have large entropy change and magnetic transition temperatures can be controlled by change of R and/or M so that are suitable to a magnetic refrigerator for hydrogen liquefaction under development. In order to improve refrigerator performance, spherical powdered HoAl2, DyAl2, and GdNi2 compounds with submillimeter diameter were synthesized by centrifugal atomization process. By measuring the magnetization and heat capacity, we obtained entropy change by magnetic fields and entropy as functions of temperature and magnetic field, which are essential for analysing the magnetic refrigeration cycle. All samples showed sharp magnetic transitions and had good potentials for use in magnetic refrigeration.

  6. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Structural Feature and Solute Trapping of Rapidly Grown Ni3Sn Intermetallic Compound

    NASA Astrophysics Data System (ADS)

    Qin, Hai-Yan; Wang, Wei-Li; Wei, Bing-Bo

    2009-11-01

    The rapid dendritic growth of primary Ni3Sn phase in undercooled Ni-30.9%Sn-5%Ge alloy is investigated by using the glass fluxing technique. The dendritic growth velocity of Ni3Sn compound is measured as a function of undercooling, and a velocity of 2.47 m/s is achieved at the maximum undercooling of 251 K (0.17TL). The addition of the Ge element reduces its growth velocity as compared with the binary Ni75Sn25 alloy. During rapid solidification, the Ni3Sn compound behaves like a normal solid solution and it displays a morphological transition of “coarse dendrite-equiaxed grain-vermicular structure" with the increase of undercooling. Significant solute trapping of Ge atoms occurs in the whole undercooling range.

  7. Compound eye formation in the termite Incisitermes minor (Isoptera: Kalotermitidae).

    PubMed

    Rose, Taylor C; Ediger, Emily F; Lehman-Schletewitz, Joy; McClane, Nathan W; Schweigert, Kristen C; Alzweideh, Saif; Wadsworth, Lauren; Husseneder, Claudia; Morris, Joshua W; Ziesmann, Jurgen

    2015-07-01

    The postembryonic development and caste differentiation patterns of lower termites have been described multiple times in a variety of different species. However, most of these studies focused on gross ontogeny, without carefully describing the maturation of any particular organ or organ system. The few studies that have attempted to correlate caste development and organ differentiation have produced somewhat inconsistent results, especially in the area of eye formation. Therefore, in order to help further elucidate the relationship between eye formation and postembryonic differentiation in lower termites, we studied eye development in the termite, Incisitermes minor (Hagen). Eye formation in I. minor began in the earliest larvae, with only an eye primordium. However, in all later larval stages, characteristic eye structures were observed and were shown to progressively differentiate through larval and nymphal stages. Curiously, pigmentation began with three to eight groups of cells in early larvae and the number of these pigmented groups increased along the developmental time course. Ultimately, a uniformly pigmented eye area was formed by the early nymphal stage. The overall eye area also gradually increased along with normal caste development, but the characteristic lenses seen in a prototypical insect compound eye did not completely form until after the final nymphal stage. Electrophysiological measurements provided clear evidence that eyes were indeed functional at all stages of development where pigment was present. Based upon this data, the eye development pattern in I. minor appeared to follow a divergent pathway from holometabolous insects and an intermediate pathway between typical hemimetabolous eye development and the heterochronic shift observed in other termite species.

  8. Magnetic properties of the intermetallic compounds MM prime X(M=Cr,Mn, M prime =Ru,Rh,Pd, and X=P,As)

    SciTech Connect

    Kanomata, T.; Kawashima, T.; Utsugi, H.; Goto, T. ); Hasegawa, H. ); Kaneko, T. )

    1991-04-15

    Magnetization, magnetic susceptibility, and crystal structure are investigated on the ternary chromium arsenides CrM{prime}As (M{prime}=Ru,Rh,Pd) and ternary manganese phosphides and arsenides MnM{prime}P(M{prime}=Rh,Pd) and MnM{prime}As(M{prime}=Ru,Pd). MnRhP, MnRuAs, and MnPdAs are ferromagnets with a Curie temperature of {ital T}{sub {ital c}}=401, 496, and 210 K, respectively. CrRhAs is an antiferromagnet with a Neel temperature of {ital T}{sub {ital N}}=165 K. MnPdP and CrPdAs show spin-glass-like freezing. A magnetic order-order transition is observed for CrRuAs. Susceptibility {chi} versus temperature curves are well expressed by a formula {chi} =C{prime}/({ital T} {minus} {theta}{sup {prime}}{sub {ital P}}){sup {gamma}} for all present compounds. The values of {gamma} are about 3/2 for manganese compounds and CrPdAs, and about 1/2 for CrRuAs and CrRhAs.

  9. Crystal structure and magnetic properties of new Fe3Co3 X 2 (X  =  Ti, Nb) intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Nguyen, Manh Cuong; Balasubramanian, Balamurugan; Das, Bhaskar; Sellmyer, David J.; Zeng, Zhi; Ho, Kai-Ming; Wang, Cai-Zhuang

    2016-05-01

    The structure and magnetic properties of new magnetic Fe3Co3 X 2 (X  =  Ti, Nb) compounds are studied by genetic algorithm, first-principles density functional theory (DFT) calculations, and experiments. The atomic structure of a hexagonal structure with P-6m2 symmetry is determined. The simulated x-ray diffraction (XRD) spectra of the P-6m2 structures agree well with experimental XRD data for both Fe3Co3Ti2 and Fe3Co3Nb2. The magnetic properties of these structures as well as the effect of the disorder of Fe and Co on their magnetic properties are also investigated. The magnetocrystalline anisotropy energy is found to be very sensitive to the occupancy disorder between Fe and Co.

  10. New icosahedral nanoclusters in crystal structures of intermetallic compounds: Topological types of 50-atom deltahedra D50 in samson phases β-Mg2Al3 and ɛ-Mg23Al30

    NASA Astrophysics Data System (ADS)

    Blatov, V. A.; Ilyushin, G. D.

    2012-12-01

    A database of intermetallic compounds has been compiled using the TOPOS program package. This database includes 514 topological types, containing 12- and 13-atom icosahedral i clusters. An isolated group of 1649 i clusters is described by 14 point groups and their maximum symmetry D 3 d (bar 3 m) and T h ( m bar 3) is established, respectively, in 47 and 25 types of crystal structures. A structural analysis of the outer quasispherical shells showed that local 63-atom i configurations 1@12@50, which contain 50 atoms in the second layer, are implemented in 8 out of 19 cases. Examples of new topologically different types of 50-atom D50 deltahedra in the Samson phases ɛ-Mg23Al30 and β-Mg2Al3 are presented. Four topologically different sites with coordination numbers of 5, 6, 6, or 7 are established in the ɛ shell and seven sites with coordination numbers of 5, 5, 6, 6, 6, 6, or 7 are found in the β shell. The inner i clusters for the β-Mg2Al3 structure (with the symmetry bar 3 m) and the ɛ-Mg23Al30 structure (with the symmetry bar 3) have a similar chemical composition, i.e., Mg7Al6 and Mg6Al7, and their 50-atom shells are chemically identical to 18Mg + 32Al. The configurations found supplement the series of known two-layer icosahedral Bergman and Mackay clusters in the form of deltahedra with 32- and 42-atom shells.

  11. Compound chondrule formation via collision of supercooled droplets

    NASA Astrophysics Data System (ADS)

    Arakawa, Sota; Nakamoto, Taishi

    2016-09-01

    We present a novel model showing that compound chondrules are formed by collisions of supercooled droplets. This model reproduces two prominent observed features of compound chondrules: the nonporphyritic texture and the size ratio between two components.

  12. Synthesis, structure, and bonding in K12Au21Sn4. A polar intermetallic compound with dense Au20 and open AuSn4 layers

    SciTech Connect

    Li, Bin; Kim, Sung-Jin; Miller, Gordon J.; and Corbett, John D.

    2009-10-29

    The new phase K{sub 12}Au{sub 21}Sn{sub 4} has been synthesized by direct reaction of the elements at elevated temperatures. Single crystal X-ray diffraction established its orthorhombic structure, space group Pmmn (No. 59), a = 12.162(2); b = 18.058(4); c = 8.657(2) {angstrom}, V = 1901.3(7) {angstrom}{sup 3}, and Z = 2. The structure consists of infinite puckered sheets of vertex-sharing gold tetrahedra (Au{sub 20}) that are tied together by thin layers of alternating four-bonded-Sn and -Au atoms (AuSn{sub 4}). Remarkably, the dense but electron-poorer blocks of Au tetrahedra coexist with more open and saturated Au-Sn layers, which are fragments of a zinc blende type structure that maximize tetrahedral heteroatomic bonding outside of the network of gold tetrahedra. LMTO band structure calculations reveal metallic properties and a pseudogap at 256 valence electrons per formula unit, only three electrons fewer than in the title compound and at a point at which strong Au-Sn bonding is optimized. Additionally, the tight coordination of the Au framework atoms by K plays an important bonding role: each Au tetrahedra has 10 K neighbors and each K atom has 8-12 Au contacts. The appreciably different role of the p element Sn in this structure from that in the triel members in K{sub 3}Au{sub 5}In and Rb{sub 2}Au{sub 3}Tl appears to arise from its higher electron count which leads to better p-bonding (valence electron concentrations = 1.32 versus 1.22).

  13. Intermetallic Layers in Soldered Joints

    1998-12-10

    ILAG solves the one-dimensional partial differential equations describing the multiphase, multicomponent, solid-state diffusion-controlled growth of intermetallic layers in soldered joints. This software provides an analysis capability for materials researchers to examine intermetallic growth mechanisms in a wide variety of defense and commercial applications involving both traditional and advanced materials. ILAG calculates the interface positions of the layers, as well as the spatial distribution of constituent mass fractions, and outputs the results at user-prescribed simulation times.

  14. First-principles investigation of the structural stability and electronic properties of Pd doped monoclinic Cu6Sn5 intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Shao, Wei-Quan; Lu, Wen-Cai; Chen, Sha-Ou

    2014-12-01

    Tri-layer Au/Pd/Ni(P) films have been widely used as surface finish over the Cu pads in high-end packaging applications. It was found that a thin (Cu,Pd)6Sn5 IMC layer was beneficial in effective reducing inter-diffusion between a Cu substrate and a solder, and therefore the growth of the IMC layer and the EM (electromigration) processes. In this study, the structural properties and phase stability of monoclinic Cu6Sn5-based structures with Pd substitutions were studied by using the first-principles method. The (Cu,Pd)6Sn5 structure with the 4e site substituted by Pd has the lowest heat of formation and is the most stable among (Cu,Pd)6Sn5 structures. Hybridization of Pd-d and Sn-p states is a dominant factor for stability improvement. Moreover, Pd atoms concentration corresponding to the most stable structure of (Cu,Pd)6Sn5 was found to be 1.69 %, which is consistent with the experimental results.

  15. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    SciTech Connect

    Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-15

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi{sub 2-x}Sn (MnCu{sub 2}Al-type), Ti{sub 2}Ni{sub 2}Sn (U{sub 2}Pt{sub 2}Sn-type), and Ti{sub 5}NiSn{sub 3} (Hf{sub 5}CuSn{sub 3}-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi{sub 2}Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti{sub 0.8}NiSb (MgAgAs-type), Ti{sub 5}Ni{sub 0.45}Sb{sub 2.55} (W{sub 5}Si{sub 3}-type), and Ti{sub 5}NiSb{sub 3} (Hf{sub 5}CuSn{sub 3}-type). The solubility of Ni in Ti{sub 0.8}NiSb decreases number of vacancies in Ti site up to Ti{sub 0.91}Ni{sub 1.1}Sb composition. - Graphical abstract: Isothermal section of the Ti-Ni-Sn phase diagram and DOS distribution in hypothetical TiNi{sub 1+x}Sn solid solution. Highlights: Black-Right-Pointing-Pointer Ti-Ni-Sn phase diagram was constructed at 1073 K. Black-Right-Pointing-Pointer Four ternary compounds are formed: TiNiSn, TiNi{sub 2-x}Sn, Ti{sub 2}Ni{sub 2}Sn, and Ti{sub 5}NiSn{sub 3}. Black-Right-Pointing-Pointer Three ternary compounds exist in Ti-Ni-Sb system at 873 K. Black-Right-Pointing-Pointer The TiNi{sub 2}Sb compound is absent.

  16. What Plurals and Compounds Reveal about Constraints in Word Formation

    ERIC Educational Resources Information Center

    Jaensch, Carol; Heyer, Vera; Gordon, Peter; Clahsen, Harald

    2014-01-01

    Morphological systems are constrained in how they interact with each other. One case that has been widely studied in the psycholinguistic literature is the avoidance of plurals inside compounds (e.g. *"rats eater" vs. "rat eater") in English and other languages, the so-called "plurals-in-compounds effect." Several…

  17. Efficiency of heating methods for polymer fibers with formation of adhesion compounds

    SciTech Connect

    Markova, L.V.; Markov, E.M.; Pinchuk, I.S.

    1995-12-01

    Efficiency of contact and contactless methods of heating of a fiber polymer material upon formation of adhesion compounds between its layers is analyzed. The advisability of contact heating in the preliminary stage and contactless heating in the final stage of formation of compounds is shown.

  18. Multi-component intermetallic electrodes for lithium batteries

    DOEpatents

    Thackeray, Michael M; Trahey, Lynn; Vaughey, John T

    2015-03-10

    Multi-component intermetallic negative electrodes prepared by electrochemical deposition for non-aqueous lithium cells and batteries are disclosed. More specifically, the invention relates to composite intermetallic electrodes comprising two or more compounds containing metallic or metaloid elements, at least one element of which can react with lithium to form binary, ternary, quaternary or higher order compounds, these compounds being in combination with one or more other metals that are essentially inactive toward lithium and act predominantly, but not necessarily exclusively, to the electronic conductivity of, and as current collection agent for, the electrode. The invention relates more specifically to negative electrode materials that provide an operating potential between 0.05 and 2.0 V vs. metallic lithium.

  19. Fundamentals of mechanical behavior in structural intermetallics: A synthesis of atomistic and continuum modeling

    SciTech Connect

    Yoo, M.H.; Fu, C.L.

    1993-08-01

    After a brief account of the recent advances in computational research on mechanical behavior of structural intermetallics, currently unresolved problems and critical issues are addressed and the knowledge base for potential answers to these problems is discussed. As large-scale problems (e.g., dislocation core structures, grain boundaries, and crack tips) are treated by atomistic simulations, future development of relevant interatomic potentials should be made consistent with the results of first-principles calculations. The bulk and defect properties calculated for intermetallic compounds, both known and as yet untested, can furnish insights to alloy designers in search of new high-temperature structural intermetallics.

  20. Third Intermetallic Matrix Composites Symposium, volume 350

    SciTech Connect

    Graves, J.A.; Bowman, R.R.; Lewandowski, J.J.

    1994-04-01

    Partial contents include: issues in potential IMC application for aerospace structures; powder metallurgy processing of intermetallic matrix composites; microstructure and properties of intermetallic matrix composites produced by reaction synthesis; combustion synthesis of niobium aluminide matrix composites; ambient temperature synthesis of bulk intermetallics; wear behavior of SHS intermetallic matrix composites; fracture characteristics of metal-intermetallic laminates produced by SHS reactions; and vapor phase synthesis of Ti aluminides and the interfacial bonding effect on the mechanical property of micro-composites reinforced by pyrolized SiC fibers.

  1. Possibility of diacetyl and related compounds as the 4-carbon compound necessary for the formation of riboflavin in Ashbya gossypii.

    PubMed

    Nakajima, K; Mitsuda, H

    1984-01-01

    The effects of various compounds (0.5%) involved in the butanediol and the glycolytic pathways on riboflavin formation in whole cells of Ashbya gossypii at rest were examined. The addition of acetate, glycerol and diacetyl inhibited riboflavin formation, while the addition of acetoin had no effect on it, and the addition of ethanol, 2,3-butanediol, pyruvic acid and glucose accelerated it. The relation of diacetyl and acetoin to riboflavin formation during resting cell incubation in the presence of 0.5% ethanol and various concentrations of 2,3-butanediol was examined. The results quantitatively revealed a precursor-product relation between riboflavin formation and the formation of diacetyl and acetoin. The results obtained provide evidence that a high flavinogenic agent, ethanol, was converted to acetaldehyde, pyruvic acid, acetoin and diacetyl in this order, that a week flavinogenic agent, 2,3-butanediol, was transferred to diacetyl through acetoin, and that the diacetyl produced can be utilized as the 4-carbon compound for riboflavin formation in the flavinogenic mold, Ashbya gossypii. It remains obscure whether diacetyl is enzymatically involved in riboflavin formation. PMID:6534171

  2. Calculation of Formation and Decay of Heavy Compound Nuclei

    NASA Astrophysics Data System (ADS)

    Cherepanov, E. A.

    2001-04-01

    The report describes a method for calculating fusion and decay probabilities in reactions leading to the production of transfermium elements. The competition between quasi-fission and fussion is described on the basis of the Dinuclear System Concept (DNSC). The both competition between fusion and quasi-fission and statistical decay of heavy highly fissionable excited compound nuclei is described in an approach based on the Monte-Carlo method.

  3. Formation of bioorganic compounds in aqueous solution induced by plasma.

    PubMed

    Harada, K; Takasaki, M; Naraoka, H; Nomoto, S

    1984-01-01

    When plasma jet of Ar-arc plasma was blown into an aqueous solution containing organic compounds, oxidation reactions were induced in the solution. The plasma-induced reaction was a powerful oxidation which could convert a methyl to a carboxyl group and cleave a carbon-carbon bond without using any oxidizing reagent. This reaction could be regarded as a model for the solar plasma-induced reaction in the primitive hydrosphere.

  4. Investigating secondary aerosol formation from agricultural amines and reduced sulfur compounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gas phase amines and reduced sulfur compounds are often co-emitted from agricultural processes. Amines have been recently recognized as potentially major sources of agricultural aerosol formation, while the reduced sulfur compounds are largely ignored. There is a severe lack of knowledge and under...

  5. The oil body formation and breakup in the compound vortex

    NASA Astrophysics Data System (ADS)

    Chaplina, T. O.; Stepanova, E. V.

    2012-04-01

    The flows in the Ocean and Atmosphere combine different types of motion: streams, jets, wakes, vortices and waves. When flows transport solid bodies or immiscible admixtures picturesque flow patterns are revealed and indicated the type of flow. Different spiral patterns visualize vortex flow structure. In experiments is studied the transport of finite volumes of immiscible admixture introduced on the free surface of water drawn into the vortex motion in the vertical cylindrical container. The basic medium was tap water, preliminary degasified to make the visualization less difficult. The fixed volume of immiscible admixture (castor or sunflower oil) is introduced on the quiescent free surface of water inside the cylindrical container. The generation of compound vortex in the cylindrical container started after all the disturbances caused by deposition of the oil volume are damped. In compound vortex the flow oil patch with smooth boundary placed onto free surface is transformed into a set of spiral arms and separate drops contacting with the central oil volume. The droplets are separated from the central spot and slowly travel towards the container sidewall. With time, the spot is transformed into pronounced spiral arms. The most part of oil under the influence of vortex flow is gathered into the central volume contacting with the free surface. This volume is called "the oil body". On the lower frequencies of disk rotation and respectively slow flow gyration the oil body has smooth boundaries with water and air. The growth of disk rotation frequency leads to more pronounced deformation of the contact surface between liquid and air, the boundary of the oil body and water then is covered by small pimples. At the further increase of disk rotation frequency the oil body comes to the breakup, the water-oil boundary become irregular and on the lowest part of the oil body the analog of foam appears (the water-oil emulsion). The work is supported by Ministry of Education

  6. Lignin peroxidase compound III. Mechanism of formation and decomposition

    SciTech Connect

    Wariishi, Hiroyuki; Gold, M.H. )

    1990-02-05

    Lignin peroxidase compound III (LiPIII) was prepared via three procedures: (a) ferrous LiP + O{sub 2} (LiPIIIa), (b) ferric LiP + O{sub 2}{sup {bar {sm bullet}}} (LiPIIIb), and (c) LiP compound II + excess H{sub 2}O{sub 2} followed by treatment with catalase (LiPIIIc). LiPIIIa, b, and c each have a Soret maximum at {approximately}414 nm and visible bands at 543 and 578 nm. LiPIIIa, b, and c each slowly reverted to native ferric LiP, releasing stoichiometric amounts of O{sub 2}{sup {bar {sm bullet}}} in the process. The LiPIII reversion reactions obeyed first-order kinetics with rate constants of {approximately}1.0 {times} 10{sup {minus}3} s{sup {minus}1}. In the presence of excess peroxide, at pH 3.0, native LiP, LiPII, and LiPIIIa, b, and c are all converted to a unique oxidized species (LiPIII*) with a spectrum displaying visible bands at 543 and 578 nm, but with a Soret maximum at 419 nm, red-shifted 5 nm from that of LiPIII. LiPIII* is bleached and inactivated in the presence of excess H{sub 2}O{sub 2} via a biphasic process. The fast first phase of this bleaching reaction obeys second-order kinetics, with a rate constant of 1.7 {times} 10{sup 1} M{sup {minus}1} s{sup {minus}1}. Addition of veratryl alcohol to LiPIII* results in its rapid reversion to the native enzyme, via an apparent one-step reaction that obeys second-order kinetics, with a rate constant of 3.5 {times} 10{sup 1} M{sup {minus}1} s{sup {minus}1}. Stoichiometric amounts of O{sub 2}{sup {bar {sm bullet}}} are released during this reaction. When this reaction was run under conditions that prevented further reactions, HPLC analysis of the products demonstrated that veratryl alcohol was not oxidized. These results suggest that the binding of veratryl alcohol to LiPIII* displaces O{sub 2}{sup {bar {sm bullet}}}, thus returning the enzyme to its native state. In contrast, the addition of veratryl alcohol to LiPIII did not affect the rate of spontaneous reversion of LiPIII to the native enzyme.

  7. A Thermodynamic Approach to Predict Formation Enthalpies of Ternary Systems Based on Miedema's Model

    NASA Astrophysics Data System (ADS)

    Mousavi, Mahbubeh Sadat; Abbasi, Roozbeh; Kashani-Bozorg, Seyed Farshid

    2016-07-01

    A novel modification to the thermodynamic semi-empirical Miedema's model has been made in order to provide more precise estimations of formation enthalpy in ternary alloys. The original Miedema's model was modified for ternary systems based on surface concentration function revisions. The results predicted by the present model were found to be in excellent agreement with the available experimental data of over 150 ternary intermetallic compounds. The novel proposed model is capable of predicting formation enthalpies of ternary intermetallics with small discrepancies of ≤20 kJ/mol as well as providing reliable enthalpy variations.

  8. alpha-Dicarbonyl compounds--key intermediates for the formation of carbohydrate-based melanoidins.

    PubMed

    Kroh, Lothar W; Fiedler, Thorsten; Wagner, Janine

    2008-04-01

    The Maillard reaction of carbohydrates and amino acids is the chemical basis for flavor and color formation in many processed foods. Dicarbonyl compounds, such as 1-, 3-deoxyosones and 1,4-dideoxyosones, as well as short-chain dicarbonyls, such as methylgyoxal or glyoxal, are key compounds of the Maillard browning reaction. The alpha-dicarbonyls are also starting materials for polymerization reactions which lead to formation of carbohydrate-based melanoidins. With regard to the dicarbonyl compound, different possible chemical structures of melanoidins will be discussed. The analysis by size-exclusion chromatography revealed that those colored compounds differ in their molecular size and are directly associated with reactions having specific alpha-dicarbonyl compounds. PMID:18448818

  9. Local magnetic moment formation at 119Sn Mössbauer impurity in RFe2 ( R=rare-earth metals) Laves phases compounds

    NASA Astrophysics Data System (ADS)

    de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

    2010-05-01

    The purpose of the present work is to theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a non-magnetic s-p Mössbauer 119Sn impurity diluted on R sites ( R=rare-earth metals) of the cubic Laves phases intermetallic compounds RFe2. One considers that the magnetic hyperfine field has two contributions (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24 (1963) 1601] model and (ii) the contribution from the induced magnetic moments arising from the Fe neighboring sites. We have in this case a two-center Blandin-Campbell-like [Phys. Rev. Lett. 31 (1973) 51; J. Magn. Magn. Mater. 1 (1975) 1] problem, where a magnetic 3d-element located at a distance from the 119Sn impurity gives an extra magnetization to a polarized electron gas which is strongly charge perturbed at the 119Sn impurity site. We also include in the model, the nearest-neighbor perturbation due to the translational invariance breaking introduced by the impurity. Our self-consistent total magnetic hyperfine field calculations are in a very good agreement with recent experimental data.

  10. Oxidation of high-temperature intermetallics; Proceedings of the Workshop, Cleveland, OH, Sept. 22, 23, 1988

    NASA Technical Reports Server (NTRS)

    Grobstein, Toni (Editor); Doychak, Joseph (Editor)

    1989-01-01

    The present conference on the high-temperature oxidation behavior of aerospace structures-applicable intermetallic compounds discusses the influence of reactive-element additions on the oxidation of Ni3Al base alloys, the effect of Ni3Al oxidation below 850 C on fracture behavior, the oxidation of FeAl + Hf, Zr, and B, the synergistic effect of Al and Si on the oxidation resistance of Fe alloys, and pack cementation coatings of Cr-Al on Fe, Ni, and Co alloys. Also discussed are the formation of alumina on Nb- and Ti-base alloys, the oxidation behavior of titanium aluminide alloys, silicide coatings for refractory metals, the oxidation of chromium disilicide, and the oxidation behavior of nickel beryllides.

  11. Intermetallic-Based High-Temperature Materials

    SciTech Connect

    Sikka, V.K.

    1999-04-25

    The intermetallic-based alloys for high-temperature applications are introduced. General characteristics of intermetallics are followed by identification of nickel and iron aluminides as the most practical alloys for commercial applications. An overview of the alloy compositions, melting processes, and mechanical properties for nickel and iron aluminizes are presented. The current applications and commercial producers of nickel and iron aluminizes are given. A brief description of the future prospects of intermetallic-based alloys is also given.

  12. An intermetallic forming steel under radiation for nuclear applications

    NASA Astrophysics Data System (ADS)

    Hofer, C.; Stergar, E.; Maloy, S. A.; Wang, Y. Q.; Hosemann, P.

    2015-03-01

    In this work we investigated the formation and stability of intermetallics formed in a maraging steel PH 13-8 Mo under proton radiation up to 2 dpa utilizing nanoindentation, microcompression testing and atom probe tomography. A comprehensive discussion analyzing the findings utilizing rate theory is introduced, comparing the aging process to radiation induced diffusion. New findings of radiation induced segregation of undersize solute atoms (Si) towards the precipitates are considered.

  13. Compound-Nucleus Formation Following Direct Interactions to Highly-Excited Final States

    SciTech Connect

    Dietrich, F S

    2008-02-05

    When direct reactions populate highly excited, unbound configurations in the residual nucleus, the nucleus may further evolve into a compound nucleus. Alternatively, the residual system may decay by emitting particles into the continuum. Understanding the relative weights of these two processes as a function of the angular momentum and parity deposited in the nucleus is important for the surrogate-reaction technique. A particularly interesting case is compound-nucleus formation via the (d, p) reaction, which may be a useful tool for forming compound nuclei off the valley of stability in inverse-kinematics experiments. We present here a study of the compound formation probability for a closely-related direct reaction, direct-semidirect radiative neutron capture.

  14. Method for making devices having intermetallic structures and intermetallic devices made thereby

    DOEpatents

    Paul, Brian Kevin; Wilson, Richard Dean; Alman, David Eli

    2004-01-06

    A method and system for making a monolithic intermetallic structure are presented. The structure is made from lamina blanks which comprise multiple layers of metals which are patternable, or intermetallic lamina blanks that are patternable. Lamina blanks are patterned, stacked and registered, and processed to form a monolithic intermetallic structure. The advantages of a patterned monolithic intermetallic structure include physical characteristics such as melting temperature, thermal conductivity, and corrosion resistance. Applications are broad, and include among others, use as a microreactor, heat recycling device, and apparatus for producing superheated steam. Monolithic intermetallic structures may contain one or more catalysts within the internal features.

  15. The recruitment of knowledge regarding plurality and compound formation during language comprehension.

    PubMed

    Fiorentino, Robert; Bost, Jamie; Abel, Alyson D; Zuccarelli, Jordan

    2012-01-01

    Compound formation has been a major focus of research and debate in mental lexicon research. In particular, it has been widely observed that compounds with a regular plural non-head are dispreferred, and a long line of research has examined the nature of this constraint, including which morphological, semantic or phonological properties of the non-head underlie this dispreference. While it is typically assumed that this constraint in fact leads to the barring of a compound analysis to a noun-noun string which would otherwise violate the constraint, its implementation during sentence comprehension has not been thoroughly examined. Using self-paced reading, we demonstrate that knowledge of pluralization and compound formation is immediately utilized in the assignment of structure to noun-noun strings, and that the dispreference for regular plural non-heads in fact leads the parser away from the compound analysis in favor of a more complex grammatical alternative. These results provide new evidence for the online deployment of knowledge regarding pluralization and its interaction with compound formation, and inform our understanding of how morphological information is deployed during, and impacts real-time sentence comprehension. PMID:25083167

  16. Formation of degradation compounds from lignocellulosic biomass in the biorefinery: sugar reaction mechanisms.

    PubMed

    Rasmussen, Helena; Sørensen, Hanne R; Meyer, Anne S

    2014-02-19

    The degradation compounds formed during pretreatment when lignocellulosic biomass is processed to ethanol or other biorefinery products include furans, phenolics, organic acids, as well as mono- and oligomeric pentoses and hexoses. Depending on the reaction conditions glucose can be converted to 5-(hydroxymethyl)-2-furaldehyde (HMF) and/or levulinic acid, formic acid and different phenolics at elevated temperatures. Correspondingly, xylose can follow different reaction mechanisms resulting in the formation of furan-2-carbaldehyde (furfural) and/or various C-1 and C-4 compounds. At least four routes for the formation of HMF from glucose and three routes for furfural formation from xylose are possible. In addition, new findings show that biomass monosaccharides themselves can react further to form pseudo-lignin and humins as well as a wide array of other compounds when exposed to high temperatures. Hence, several aldehydes and ketones and many different organic acids and aromatic compounds may be generated during hydrothermal treatment of lignocellulosic biomass. The reaction mechanisms are of interest because the very same compounds that are possible inhibitors for biomass processing enzymes and microorganisms may be valuable biobased chemicals. Hence a new potential for industrial scale synthesis of chemicals has emerged. A better understanding of the reaction mechanisms and the impact of the reaction conditions on the product formation is thus a prerequisite for designing better biomass processing strategies and forms an important basis for the development of new biorefinery products from lignocellulosic biomass as well. PMID:24412507

  17. Suppressors made from intermetallic materials

    SciTech Connect

    Klett, James W; Muth, Thomas R; Cler, Dan L

    2014-11-04

    Disclosed are several examples of apparatuses for suppressing the blast and flash produced as a projectile is expelled by gases from a firearm. In some examples, gases are diverted away from the central chamber to an expansion chamber by baffles. The gases are absorbed by the expansion chamber and desorbed slowly, thus decreasing pressure and increasing residence time of the gases. In other examples, the gases impinge against a plurality of rods before expanding through passages between the rods to decrease the pressure and increase the residence time of the gases. These and other exemplary suppressors are made from an intermetallic material composition for enhanced strength and oxidation resistance at high operational temperatures.

  18. Current activated tip sintering of Ni-Ti intermetallics

    NASA Astrophysics Data System (ADS)

    Sharma, Nitin

    This thesis investigated the current activated tip-sintering of reactive mixtures of nickel and titanium to form Ni-Ti intermetallics. The effect of elemental powder composition, heating profile and micro-jet inert gas pressures on the developed macro- and microstructure was investigated. The heating profile brought upon by selective electric current application was found to have a significant effect on whether the reaction is a volumetric combustion or a self-propagating high temperature one. The best results in terms of homogeneity and Ni-Ti intermetallics yield, were obtained for an inert gas pressure of 4 psi under for the nickel rich composition. In addition, surprising results at the higher inert gas pressures show the formation of hollow products, which can give rise future exploration of this technique for combustion synthesizing hollow products of different shapes.

  19. Bacterial ethane formation from reduced, ethylated sulfur compounds in anoxic sediments

    USGS Publications Warehouse

    Oremland, R.S.; Whiticar, Michael J.; Strohmaier, F.E.; Kiene, R.P.

    1988-01-01

    Trace levels of ethane were produced biologically in anoxic sediment slurries from five chemically different aquatic environments. Gases from these locations displayed biogenic characteristics, having 12C-enriched values of ??13CH4 (-62 to -86%.), ??13C2H6 (-35 to -55%.) and high ratios (720 to 140,000) of CH4 [C2H6 + C3H8]. Endogenous production of ethane by slurries was inhibited by autoclaving or by addition of the inhibitor of methanogenic bacteria, 2-bromoethanesulfonic acid (BES). Ethane formation was stimulated markedly by ethanethiol (ESH), and, to a lesser extent, by diethylsulfide (DES). Formation of methane and ethane in ESH- or DES-amended slurries was blocked by BES. Experiments showed that ethionine (or an analogous compound) could be a precursor of ESH. Ethylamine or ethanol additions to slurries caused only a minor stimulation of ethane formation. Similarly, propanethiol additions resulted in only a minor enhancement of propane formation. Cell suspensions of a methyltrophic methanogen produced traces of ethane when incubated in the presence of DES, although the organism did not grow on this compound. These results indicate that methanogenic bacteria produce ethane from the traces of ethylated sulfur compounds present in recent sediments. Preliminary estimates of stable carbon isotope fractionation associated with sediment methane formation from dimethylsulfide was about 40%., while ethane formation from DES and ESH was only 4. 6 and 6.5%., respectively. ?? 1988.

  20. Forming metal-intermetallic or metal-ceramic composites by self-propagating high-temperature reactions

    DOEpatents

    Rawers, James C.; Alman, David E.; Petty, Jr., Arthur V.

    1996-01-01

    Industrial applications of composites often require that the final product have a complex shape. In this invention intermetallic or ceramic phases are formed from sheets of unreacted elemental metals. The process described in this invention allows the final product shape be formed prior to the formation of the composite. This saves energy and allows formation of shaped articles of metal-intermetallic composites composed of brittle materials that cannot be deformed without breaking.

  1. A Connectionist Model of Stimulus Class Formation with a Yes/No Procedure and Compound Stimuli

    ERIC Educational Resources Information Center

    Tovar, Angel E.; Chavez, Alvaro Torres

    2012-01-01

    We analyzed stimulus class formation in a human study and in a connectionist model (CM) with a yes/no procedure, using compound stimuli. In the human study, the participants were six female undergraduate students; the CM was a feed-forward back-propagation network. Two 3-member stimulus classes were trained with a similar procedure in both the…

  2. Deduction of compound nucleus formation probability from the fragment angular distributions in heavy-ion reactions

    NASA Astrophysics Data System (ADS)

    Yadav, C.; Thomas, R. G.; Mohanty, A. K.; Kapoor, S. S.

    2015-07-01

    The presence of various fissionlike reactions in heavy-ion induced reactions is a major hurdle in the path to laboratory synthesis of heavy and super-heavy nuclei. It is known that the cross section of forming a heavy evaporation residue in fusion reactions depends on the three factors—the capture cross section, probability of compound nucleus formation PCN, and the survival probability of the compound nucleus against fission. As the probability of compound nucleus formation, PCN is difficult to theoretically estimate because of its complex dependence on several parameters; attempts have been made in the past to deduce it from the fission fragment anisotropy data. In the present work, the fragment anisotropy data for a number of heavy-ion reactions are analyzed and it is found that deduction of PCN from the anisotropy data also requires the knowledge of the ratio of relaxation time of the K degree of freedom to pre-equilibrium fission time.

  3. Monitoring the apple polyphenol oxidase-modulated adduct formation of phenolic and amino compounds.

    PubMed

    Reinkensmeier, Annika; Steinbrenner, Katrin; Homann, Thomas; Bußler, Sara; Rohn, Sascha; Rawel, Hashadrai M

    2016-03-01

    Minimally processed fruit products such as smoothies are increasingly coming into demand. However, they are often combined with dairy ingredients. In this combination, phenolic compounds, polyphenoloxidases, and amino compounds could interact. In this work, a model approach is presented where apple serves as a source for a high polyphenoloxidase activity for modulating the reactions. The polyphenoloxidase activity ranged from 128 to 333nakt/mL in different apple varieties. From these, 'Braeburn' was found to provide the highest enzymatic activity. The formation and stability of resulting chromogenic conjugates was investigated. The results show that such adducts are not stable and possible degradation mechanisms leading to follow-up products formed are proposed. Finally, apple extracts were used to modify proteins and their functional properties characterized. There were retaining antioxidant properties inherent to phenolic compounds after adduct formation. Consequently, such interactions may also be utilized to improve the textural quality of food products.

  4. Monitoring the apple polyphenol oxidase-modulated adduct formation of phenolic and amino compounds.

    PubMed

    Reinkensmeier, Annika; Steinbrenner, Katrin; Homann, Thomas; Bußler, Sara; Rohn, Sascha; Rawel, Hashadrai M

    2016-03-01

    Minimally processed fruit products such as smoothies are increasingly coming into demand. However, they are often combined with dairy ingredients. In this combination, phenolic compounds, polyphenoloxidases, and amino compounds could interact. In this work, a model approach is presented where apple serves as a source for a high polyphenoloxidase activity for modulating the reactions. The polyphenoloxidase activity ranged from 128 to 333nakt/mL in different apple varieties. From these, 'Braeburn' was found to provide the highest enzymatic activity. The formation and stability of resulting chromogenic conjugates was investigated. The results show that such adducts are not stable and possible degradation mechanisms leading to follow-up products formed are proposed. Finally, apple extracts were used to modify proteins and their functional properties characterized. There were retaining antioxidant properties inherent to phenolic compounds after adduct formation. Consequently, such interactions may also be utilized to improve the textural quality of food products. PMID:26471529

  5. Rare-Earth Transition-Metal Intermetallics: Structure-bonding-Property Relationships

    SciTech Connect

    Han, Mi-Kyung

    2006-01-01

    Our explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding-property relationships. Our work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe13-xSix system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn13-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides RE2-xFe4Si14-y and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb3Zn3.6Al7.4: Partially ordered structure of Tb3.6Zn13-xAl7.4 compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn39(CrxAl1-x

  6. Rare-earth transition-metal intermetallics: Structure-bonding-property relationships

    SciTech Connect

    Han, M. K.

    2006-01-01

    The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe13-xSix system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re2-xFe4Si14-y and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb3Zn3.6Al7.4: Partially ordered structure of Tb3Zn3.6Al7.4 compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn39(CrxAl1-x)81

  7. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  8. In depth study of molybdenum silicon compound formation at buried interfaces

    NASA Astrophysics Data System (ADS)

    Zoethout, Erwin; Louis, Eric; Bijkerk, Fred

    2016-09-01

    Angle resolved x-ray photoelectron spectroscopy (ARXPS) has been employed to determine non-destructively the in-depth interface formation during thin film growth. Buried interfaces underneath the nanometer thick layers are probed by identifying the chemical shift of compound materials in photoelectron spectroscopy and using the angular response to quantify the compound amounts from the measured intensities. The thin interfaces in molybdenum-silicon multilayers grown at ambient temperature are investigated. This system is an example of an almost perfect 1D-system, where the interface region is only a small part of the individual layer thicknesses of 3 to 5 nm. Despite the low growth temperature, both the interfaces of this multilayer show layer thickness dependent interface formation. While the silicon-on-molybdenum interface shows a limited interface thickness of 0.4 nm of Mo5Si3, the molybdenum-on-silicon interface shows a more complex evolution. For this interface, the composition of the first 2.0 nm of deposited layer thickness is best described as a molybdenum-silicon compound layer with a molybdenum rich top and a MoSi2 bottom layer. After 2.5 nm of the deposited layer thickness, the molybdenum rich compound at the top has transformed into polycrystalline molybdenum on top of 1.8 nm MoSi2 at the interface. The formation of the 1.8 nm MoSi2 precedes the formation of polycrystalline molybdenum on top. Angle resolved x-ray photoelectron spectroscopy (ARXPS) is shown to be a good tool to study the interface phenomena beneath the nanometer thick top layers. In the case of Mo/Si multilayer mirrors, this ARXPS study shows that the compound formation at the interface accounts for the majority of the extreme ultraviolet reflectance loss.

  9. Precipitation of organic arsenic compounds and their degradation products during struvite formation.

    PubMed

    Lin, Jin-Biao; Yuan, Shoujun; Wang, Wei; Hu, Zhen-Hu; Yu, Han-Qing

    2016-11-01

    Roxarsone (ROX) and arsanilic acid (ASA) have been extensively used as organoarsenic animal feed additives. Organic arsenic compounds and their degradation products, arsenate (As(V)) and arsenite (As(III)), exist in the effluent from anaerobic reactors treating animal manure contaminated by ROX or ASA with ammonium (NH4(+)-N) and phosphate (PO4(3-)-P) together. Therefore, arsenic species in the effluent might be involved in the struvite formation process. In this study, the involvement of organic arsenic compounds and their degradation products As(V) and As(III) in the struvite crystallization was investigated. The results demonstrated that arsenic compounds did not substantially affect the PO4(3-)-P recovery, but confirmed the precipitation of arsenic during struvite formation. The precipitation of arsenic compounds in struvite was considerably affected by a solution pH from 9.0 to 11.0. With an increase in pH, the content of ASA and ROX in the precipitation decreased, but the contents of As(III) and As(V) increased. In addition, the arsenic content of As(V) in the struvite was higher than that of As(III), ASA and ROX. The results indicated that the struvite could be contaminated when the solution contains arsenic species, but that could be minimized by controlling the solution pH and maintaining anaerobic conditions during struvite formation. PMID:27262276

  10. Metabolic Impact of Redox Cofactor Perturbations on the Formation of Aroma Compounds in Saccharomyces cerevisiae.

    PubMed

    Bloem, Audrey; Sanchez, Isabelle; Dequin, Sylvie; Camarasa, Carole

    2015-10-16

    Redox homeostasis is a fundamental requirement for the maintenance of metabolism, energy generation, and growth in Saccharomyces cerevisiae. The redox cofactors NADH and NADPH are among the most highly connected metabolites in metabolic networks. Changes in their concentrations may induce widespread changes in metabolism. Redox imbalances were achieved with a dedicated biological tool overexpressing native NADH-dependent or engineered NADPH-dependent 2,3-butanediol dehydrogenase, in the presence of acetoin. We report that targeted perturbation of the balance of cofactors (NAD(+)/NADH or, to a lesser extent, NADP(+)/NADPH) significantly affected the production of volatile compounds. In most cases, variations in the redox state of yeasts modified the formation of all compounds from the same biochemical pathway (isobutanol, isoamyl alcohol, and their derivatives) or chemical class (ethyl esters), irrespective of the cofactors. These coordinated responses were found to be closely linked to the impact of redox status on the availability of intermediates of central carbon metabolism. This was the case for α-keto acids and acetyl coenzyme A (acetyl-CoA), which are precursors for the synthesis of many volatile compounds. We also demonstrated that changes in the availability of NADH selectively affected the synthesis of some volatile molecules (e.g., methionol, phenylethanol, and propanoic acid), reflecting the specific cofactor requirements of the dehydrogenases involved in their formation. Our findings indicate that both the availability of precursors from central carbon metabolism and the accessibility of reduced cofactors contribute to cell redox status modulation of volatile compound formation.

  11. Environmental Effects in Advanced Intermetallics

    SciTech Connect

    Liu, C.T.

    1998-11-24

    This paper provides a comprehensive review of environmental embrittlement in iron and nickel aluminizes. The embrittlement involves the interaction of these intermetallics with moisture in air and generation of atomic hydrogen, resulting in hydrogen-induced embrittlement at ambient temperatures. Environmental embrittlement promotes brittle grain-boundary fracture in Ni{sub 3}Al alloys but brittle cleavage fracture in Fe{sub 3}Al-FeAl alloys. The embrittlement strongly depends on strain rate, with tensile-ductility increase with increasing strain rate. It has been demonstrated that environmental embrittlement can be alleviated by alloying additions, surface modifications, and control of grain size and shape. Boron tends to segregate strongly to grain boundaries and is most effective in suppressing environmental embrittlement in Ni{sub 3}Al alloys. The mechanistic understanding of alloy effects and environmental embrittlement has led to the development of nickel and iron aluminide alloys with improved properties for structural use at elevated temperatures in hostile environments.

  12. Method of making sintered ductile intermetallic-bonded ceramic composites

    DOEpatents

    Plucknett, Kevin; Tiegs, Terry N.; Becher, Paul F.

    1999-01-01

    A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite.

  13. Method of making sintered ductile intermetallic-bonded ceramic composites

    DOEpatents

    Plucknett, K.; Tiegs, T.N.; Becher, P.F.

    1999-05-18

    A method of making an intermetallic-bonded ceramic composite involves combining a particulate brittle intermetallic precursor with a particulate reactant metal and a particulate ceramic to form a mixture and heating the mixture in a non-oxidizing atmosphere at a sufficient temperature and for a sufficient time to react the brittle intermetallic precursor and the reactant metal to form a ductile intermetallic and sinter the mixture to form a ductile intermetallic-bonded ceramic composite. 2 figs.

  14. Catalytic asymmetric carbon-carbon bond formation via allylic alkylations with organolithium compounds

    NASA Astrophysics Data System (ADS)

    Pérez, Manuel; Fañanás-Mastral, Martín; Bos, Pieter H.; Rudolph, Alena; Harutyunyan, Syuzanna R.; Feringa, Ben L.

    2011-05-01

    Carbon-carbon bond formation is the basis for the biogenesis of nature's essential molecules. Consequently, it lies at the heart of the chemical sciences. Chiral catalysts have been developed for asymmetric C-C bond formation to yield single enantiomers from several organometallic reagents. Remarkably, for extremely reactive organolithium compounds, which are among the most broadly used reagents in chemical synthesis, a general catalytic methodology for enantioselective C-C formation has proven elusive, until now. Here, we report a copper-based chiral catalytic system that allows carbon-carbon bond formation via allylic alkylation with alkyllithium reagents, with extremely high enantioselectivities and able to tolerate several functional groups. We have found that both the solvent used and the structure of the active chiral catalyst are the most critical factors in achieving successful asymmetric catalysis with alkyllithium reagents. The active form of the chiral catalyst has been identified through spectroscopic studies as a diphosphine copper monoalkyl species.

  15. Environmental embrittlement in ordered intermetallic alloys

    SciTech Connect

    Liu, C.T.; Stoloff, N.S.

    1992-12-31

    Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

  16. Stereoselective Synthesis of Tetrahydroindolizines through the Catalytic Formation of Pyridinium Ylides from Diazo Compounds.

    PubMed

    Day, Jonathan; McKeever-Abbas, Ben; Dowden, James

    2016-05-01

    Commercially available iron(III) and copper(I) complexes catalyzed multicomponent cycloaddition reactions between diazo compounds, pyridines, and electrophilic alkenes to give alkaloid-inspired tetrahydroindolizidines in high yield with high diastereoselectivity. Hitherto, the catalytic formation of versatile pyridinium ylides from metal carbenes has been poorly developed; the broad utility demonstrated herein sets the stage for the invention of further multicomponent reactions in future. PMID:27059910

  17. Formation of dioxin-like compounds from the pyrolysis of some halogenated flame retardants

    SciTech Connect

    Alsabbagh, A.M.

    1990-01-01

    Polybrominated dibenzo-p-dioxins and polybrominated dibenzofurans as well as polyhalogenated phenazines have been shown to form from the pyrolysis of some flame retardants. In addition, chlorine-bromine exchange was shown to occur in the formation of halogenated dibenzo-p-dioxins and halogenated phenazines when both chlorine and bromine sources are present in the pyrolysis mixture. There was no chlorine-hydrogen exchange observed in the formation of chloro-bromo-dibenzo-dioxins, chloro-bromo-dibenzofurans and chloro-bromophenazines. At high temperatures, the amino-group of the halogenated anilines may be replaced by oxygen and yield halogenated dibenzo-pdioxins and halogenated dibenzofurans, in addition to the halogenated phenazines. The complete substitution of bromine with chlorine was demonstrated to occur, which is probably why chlorinated dibenzo-p-dioxins and chlorinated dibenzofurans are more widely spread than the brominated analogs, since chlorinated compounds are used in much larger quantities than the brominated compounds. The addition of antimony (III) oxide to the flame-retardant formulations showed initial increase in the formation of the halogenated dibenzo-p-dioxins and the halogenated phenazines. The mass spectra of bromo-phenazines, chloro-phenazines and chloro-bromo-phenazines have been presented. The similarity in the structure of the halogenated phenazines and the halogenated dibenzo-p-dioxins may be of interest to be used in the search of compounds with breast cancer therapeutic use, although the toxicity of the halogenated phenazines should be thoroughly investigated.

  18. Intermetallic NaAu2 as a heterogeneous catalyst for low-temperature CO oxidation.

    PubMed

    Xiao, Chaoxian; Wang, Lin-Lin; Maligal-Ganesh, Raghu V; Smetana, Volodymyr; Walen, Holly; Thiel, Patricia A; Miller, Gordon J; Johnson, Duane D; Huang, Wenyu

    2013-07-01

    The enhanced stability and modified electronic structure of intermetallic compounds provide discovery of superior catalysts for chemical conversions with high activity, selectivity, and stability. We find that the intermetallic NaAu2 is an active catalyst for CO oxidation at low temperatures. From density functional theory calculations, a reaction mechanism is suggested to explain the observed low reaction barrier of CO oxidation by NaAu2, in which a CO molecule reacts directly with an adsorbed O2 to form an OOCO* intermediate. The presence of surface Na increases the binding energy of O2 and decreases the energy barrier of the transition states.

  19. Nitrogen dioxide formation in the gliding arc discharge-assisted decomposition of volatile organic compounds.

    PubMed

    Bo, Zheng; Yan, Jianhua; Li, Xiaodong; Chi, Yong; Cen, Kefa

    2009-07-30

    To apply gliding arc discharge (GAD) plasma processing to volatile organic compounds (VOCs) emission control, the formation of NO(2) as an undesired byproduct needs to be addressed. Comparative results of effluent temperature and product concentrations between experiment and thermodynamic equilibrium calculation show that the NO(2) formation in dry air GAD is totally out of thermodynamic equilibrium. Meanwhile, obvious NO (A(2)Sigma+)) and N(2)(+) (B(2)Sigma(u)(+)) are detected as the major reactive species in the dry air GAD plasma region. These results suggest that the thermal (or Zeldovich) NO(x) formation mechanism is not significant in GAD system, while the energy level and the density of electrons in the plasma region will severely influence the NO(2) formation. The presence of 500 ppm VOCs in the feed gases shows a limiting influence on the NO(2) formation, which is in the order of aromatic hydrocarbon (C(6)H(6) and C(7)H(8))>straight-chain hydrocarbon (C(4)H(10) and C(6)H(14))>halogenated hydrocarbon (CCl(4)). The influences of VOCs chemical structure, supply voltage, feed gas humidity, and reactor geometry on NO(2) formation are investigated, and the results correspond to above mechanism analysis. Based on the above, the possible pathways of the inhibition of NO(2) formation in GAD-assisted VOCs decomposition process are discussed.

  20. Source Contribution of Volatile Organic Compounds to Ozone Formation in Southeast Texas

    NASA Astrophysics Data System (ADS)

    Ying, Q.

    2009-12-01

    The Houston-Galveston-Brazoria (HGB) and Beaumont-Port Arthur (BPA) areas in the southeast Texas are respectively in severe and moderate non-attainment status for the National Ambient Air Quality Standards for ozone (O3). In order to design effective emission control strategies to improve ozone air quality, it is necessary to understand the contribution of volatile organic compounds (VOCs) from different sources to O3 formation. In this study, a source-oriented SAPRC-99 gas phase photochemical mechanism was developed and incorporated into the Community Multiscale Air Quality (CMAQ) model to determine the contribution of volatile organic compounds (VOCs) from different sources to the predicted net ozone formation rate in southeast Texas during the Texas Air Quality Study (TexAQS) from 16 August - 6 September 2000. Contribution from eight different sources: biogenic, diesel engines, highway gasoline vehicles, off-highway gasoline engines, solvent utilization, petroleum industry, other industries and wildfire were resolved. This is the first time that the regional source contribution of VOCs to O3 formation has been quantified using a three-dimensional source oriented modeling approach in southeast Texas. Regional source contribution analysis indicates that the VOCs emitted from petrochemical industries are responsible to a large amount of O3 formation in the HGB and BPA area. The peak O3 formation rate due to petroleum industry and other industries combined is ~8 ppb hr(-1) in early afternoon hours, which rivals the O3 formation rate due to biogenic sources (~ 9 ppb hr(-1)). Gasoline vehicles also contribute significantly to the ozone formation, with a maximum contribution of ~3.5 ppb hr(-1). The spatial coverage of vehicle sources is larger that of industrial sources. Solvent utilization contributes ~1.2 ppb hr(-1) and has similar spatial coverage as gasoline vehicle sources. VOC emissions from reciprocating engines powered by natural gas are the most significant

  1. Wear Behavior and Mechanism of Fe-Al Intermetallic Coating Prepared by Hot-Dip Aluminizing and Diffusion

    NASA Astrophysics Data System (ADS)

    Zhang, Q. Y.; Zhou, Y.; Liu, J. Q.; Chen, K. M.; Mo, J. G.; Cui, X. H.; Wang, S. Q.

    2016-05-01

    A Fe-Al intermetallic compound coating was prepared on AISI H13 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests of the Fe-Al intermetallic coating were performed at 298 K to 873 K (25 °C to 600 °C). The wear behavior of the Fe-Al intermetallic coating was noticed to vary markedly with the temperature and load. At 298 K (25 °C), the wear rate rapidly increased with an increase of the load. As the temperature was elevated, the wear rate dramatically decreased except for the cases under 300 N at 473 K and 673 K (200 °C and 400 °C). The Fe-Al intermetallic coating possessed an excellent elevated-temperature wear performance, especially at 673 K to 873 K (400 °C to 600 °C), but worse room-temperature one, which were noticed to be attributed to the existence and inexistence of thin tribo-oxide layers, respectively. Such a thin tribo-oxide layer was considered to provide a protection for the intermetallic compound. When the tribo-oxide layer did not form at room temperature or the formed one was massively delaminated above the critical load at elevated temperatures, Fe-Al intermetallic coating possessed poor wear resistance.

  2. Exo-Melt{trademark} process for intermetallic powders

    SciTech Connect

    Sikka, V.K.; Deevi, S.C.

    1996-06-01

    The methods of powder production for intermetallics are reviewed. An innovative method known as Exo-Melt{trademark} is described for producing molten aluminides for gas- and water-atomization processes that require a molten metal stream. The Exo-Melt{trademark} process is based on the effective utilization of the heats of formation of aluminides from their constituent elements. The Exo-Melt{trademark} process principles are discussed along with a description of a furnace-loading sequence that uses the principles for practical applications. The benefits of the Exo-Melt{trademark} process are compared with the problems associated with the conventional melting process.

  3. Metabolic Impact of Redox Cofactor Perturbations on the Formation of Aroma Compounds in Saccharomyces cerevisiae

    PubMed Central

    Sanchez, Isabelle; Dequin, Sylvie; Camarasa, Carole

    2015-01-01

    Redox homeostasis is a fundamental requirement for the maintenance of metabolism, energy generation, and growth in Saccharomyces cerevisiae. The redox cofactors NADH and NADPH are among the most highly connected metabolites in metabolic networks. Changes in their concentrations may induce widespread changes in metabolism. Redox imbalances were achieved with a dedicated biological tool overexpressing native NADH-dependent or engineered NADPH-dependent 2,3-butanediol dehydrogenase, in the presence of acetoin. We report that targeted perturbation of the balance of cofactors (NAD+/NADH or, to a lesser extent, NADP+/NADPH) significantly affected the production of volatile compounds. In most cases, variations in the redox state of yeasts modified the formation of all compounds from the same biochemical pathway (isobutanol, isoamyl alcohol, and their derivatives) or chemical class (ethyl esters), irrespective of the cofactors. These coordinated responses were found to be closely linked to the impact of redox status on the availability of intermediates of central carbon metabolism. This was the case for α-keto acids and acetyl coenzyme A (acetyl-CoA), which are precursors for the synthesis of many volatile compounds. We also demonstrated that changes in the availability of NADH selectively affected the synthesis of some volatile molecules (e.g., methionol, phenylethanol, and propanoic acid), reflecting the specific cofactor requirements of the dehydrogenases involved in their formation. Our findings indicate that both the availability of precursors from central carbon metabolism and the accessibility of reduced cofactors contribute to cell redox status modulation of volatile compound formation. PMID:26475113

  4. Abiotic formation of hydrocarbons and oxygenated compounds during thermal decomposition of iron oxalate

    NASA Technical Reports Server (NTRS)

    McCollom, T. M.; Simoneit, B. R.

    1999-01-01

    The formation of organic compounds during the decomposition of iron oxalate dihydrate (IOD) was investigated as a possible analog for abiotic organic synthesis in geological systems. After heating at 330 degrees C for 2-4 days, IOD decomposed to a mixture of the minerals siderite and magnetite plus gas and non-volatile organic compounds. The organic products included an extremely large variety of compounds, making identification of individual reaction products difficult. However, the non-volatile products were dominated by several homologous series of alkylated cyclic compounds mostly containing a single aromatic ring, including alkylphenols, alkylbenzenes, alkyltetrahydronaphthols, and alkyltetrahydronaphthalenes. Traces of n-alkanols, n-alkanoic acids, n-alkanones, and n-alkanes were also identified. Carbon in the gas phase was predominantly CO2 (+CO?), with lesser amounts of light hydrocarbons to > C6 including all possible branched and normal isomers of the alkanes and alkenes. The organic products were apparently the result of two concurrent reaction processes: (1) condensation of the two-carbon units present in the initial oxalate moiety, and (2) Fischer-Tropsch-type synthesis from CO2 or CO generated during the experiment. Compounds produced by the former process may not be characteristic of synthesis from the single-carbon precursors which predominate in geologic systems, suggesting iron oxalate decomposition may not provide a particularly suitable analog for investigation of abiotic organic synthesis. When water was included in the reaction vessels, CO2 and traces of methane and light hydrocarbon gases were the only carbon products observed (other than siderite), suggesting that the presence of water allowed the system to proceed rapidly towards equilibrium and precluded the formation of metastable organic intermediates.

  5. Dislocation sources in ordered intermetallics

    SciTech Connect

    Yoo, M.H.; Appel, F.; Wagner, R.; Mecking, H.

    1996-09-01

    An overview on the current understanding of dislocation sources and multiplication mechanisms is made for ordered intermetallic alloys of the L1{sub 2}, B2, and D0{sub 19} structures. In L1{sub 2} alloys, a large disparity of edge/screw segments in their relative mobility reduces the efficiency of a Frank-Read Type multiplication mechanism. In Fe-40%Al of the B2 structure, a variety of dislocation sources are available for <111> slip, including ones resulting from condensation of thermal vacancies. In NiAl with the relatively high APB energy, <100> dislocations may result from the dislocation decomposition reactions, the prismatic punching out from inclusion particles, and/or steps and coated layers of the surface. Internal interfaces often provide sites for dislocation multiplication, e.g., grain boundaries, sub-boundaries in Ni{sub 3}Ga, NiAl and Ti{sub 3}Al, and antiphase domain boundaries in Ti{sub 3}Al. As for the crack tip as a dislocation source, extended SISFs trailed by super-Shockley partials emanating form the cracks in Ni{sub 3}Al and Co{sub 3}Ti are discussed in view of a possible toughening mechanism.

  6. Advanced ordered intermetallic alloy deployment

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Easton, D.S.

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  7. Formation and emission of volatile polonium compound by microbial activity and polonium methylation with methylcobalamin.

    PubMed

    Momoshima, N; Song, L X; Osaki, S; Maeda, Y

    2001-07-15

    We observed biologically mediated emission of Po from culture solution inoculated sea sediment extract and incubated under natural light/dark cycle condition or dark condition the emitted Po compound would be lipophilic because of effective collection in organic solvent. Sterilization of the culture medium with antibiotics or CuSO4 completely suppressed growth of microorganisms and resulted in no emission of Po, indicating biological activity of microorganisms is responsible for formation and emission of volatile Po compound. Po emission also occurred when seawater was used as a culture medium. Our finding indicates a possibility of biotic source for atmospheric Po in the environment, which has been believed to be originated from abiotic sources. We compared emission behavior of Po and S in the culture experiments, the elements belong to XVI group in the Periodical Table, and consider that their emission mechanisms involved would be different though the emission of both elements is supported by biological activity of microorganisms. One of the chemical forms of S emitted was confirmed to be dimethyl sulfide (DMS) but that of Po is not known. Methylation experiments of Po with methylcobalamin demonstrated a formation and emission of volatile Po compound. The methylation of Po with methylcobalamin might be related to the observed Po emission in the culture experiments.

  8. Ammoxidation of Lignocellulosic Materials: Formation of Nonheterocyclic Nitrogenous Compounds from Monosaccharides

    PubMed Central

    2013-01-01

    Ammoxidized technical lignins are valuable soil-improving materials that share many similarities with native terrestrial humic substances. In contrast to lignins, the chemical fate of carbohydrates as typical minor constituents of technical lignins during the ammoxidation processes has not been thoroughly investigated. Recently, we reported the formation of N-heterocyclic, ecotoxic compounds (OECD test 201) from both monosaccharides (d-glucose, d-xylose) and polysaccharides (cellulose, xylan) under ammoxidation conditions and showed that monosaccharides are a source more critical than polysaccharides in this respect. GC/MS-derivatization analysis of the crude product mixtures revealed that ammoxidation of carbohydrates which resembles the conditions encountered in nonenzymatical browning of foodstuff affords also a multitude of nonheterocyclic nitrogenous compounds such as aminosugars, glycosylamines, ammonium salts of aldonic, deoxyaldonic, oxalic and carbaminic acids, urea, acetamide, α-hydroxyamides, and even minor amounts of α-amino acids. d-Glucose and d-xylose afforded largely similar product patterns which differed from each other only for those products that were formed under preservation of the chain integrity and stereoconfiguration of the respective monosaccharide. The kinetics and reaction pathways involved in the formation of the different classes of nitrogenous compounds under ammoxidation conditions are discussed. PMID:23967905

  9. Formation of highly oxidized multifunctional compounds: Autoxidation of peroxy radicals formed in the oxidation of alkenes

    NASA Astrophysics Data System (ADS)

    Mentel, Thomas; Ehn, Mikael; Thornton, Joel; Kleist, Einhard; Pullinen, Iida; Springer, Monika; Wahner, Andreas; Wildt, Jürgen

    2015-04-01

    Recent studies show that peroxy radicals are key intermediates in particle formation. Permutation reactions involving highly oxidized peroxy radicals form stable products with extremely low volatility (ELVOC). We suggest that ELVOC are the postulated organic compounds that explain growth of small particles (Ehn et al., Nature, 2014). To elucidate the pathways of ELVOC formation, experiments were performed in the Juelich Plant Atmosphere Chamber. We applied High Resolution Nitrate-Chemical Ionization Mass Spectrometry for detection of ELVOC including highly oxidized peroxy radicals. ELVOC were produced by ozonolysis of a-pinene and other cyclic alkenes (Rissanen et al., JACS, 2014, Mentel et al., ACPD, 2015), as well as by reactions of the target compounds with OH. ELVOC with C10 skeletons carry a large number of oxygens, still containing 14 or 16 H-atoms. ELVOC-dimers with twice the number of C-atoms of the reactant were also observed. The formation of ELVOC can be explained by fast intramolecular H-shifts in combination with classical peroxy radical termination reactions, leading to ketones, alcohols, and hydroperoxides (including peroxy acids). The subsequent H-shifts enable the formation of an increasing number of hydroperoxide groups under reproduction of a peroxy radical (containing now two more oxygens). Addition of NOX to the system increases the concentrations of nitrates at the expense of the corresponding peroxy radicals, confirming their identification as peroxy radicals. Furthermore, the concentrations of ELVOC dimers decrease strongly with increasing NOX suggesting that they are indeed formed by peroxy-peroxy permutation reactions. ELVOC are involved in new particle formation, and can explain the major fraction of the early growth observed in field studies. ELVOC dimers are very likely key in new particle formation as their formation is strongly suppressed with increasing NOX in accordance with the observed NOX dependence of new particle formation (Ehn

  10. Effect of different cooking methods on lipid oxidation and formation of volatile compounds in foal meat.

    PubMed

    Domínguez, Rubén; Gómez, María; Fonseca, Sonia; Lorenzo, José M

    2014-06-01

    The influence of four different cooking methods (roasting, grilling, microwaving and frying) on cooking loss, lipid oxidation and volatile profile of foal meat was studied. Cooking loss were significantly (P<0.001) affected by thermal treatment, being higher (32.5%) after microwaving and lower after grilling (22.5%) and frying (23.8%). As expected, all the cooking methods increased TBARs content, since high temperature during cooking causes increased oxidation in foal steaks, this increase was significantly (P<0.001) higher when foal steaks were microwaved or roasted. The four different cooking methods led to increased total volatile compounds (between 366.7 and 633.1AU×10(6)/g dry matter) compared to raw steaks (216.4AU×10(6)/g dry matter). The roasted steaks showed the highest volatile content, indicating that increased cooking temperature increases the formation of volatile compounds. Aldehydes were the most abundant compounds in cooked samples, with amounts of 217.2, 364.5, 283.5 and 409.1AU×10(6)/g dry matter in grilled, microwaved, fried and roasted samples, respectively, whereas esters were the most abundant compounds in raw samples, with mean amounts of 98.8AU×10(6)/g dry matter.

  11. Pressure-induced bonding and compound formation in xenon-hydrogen solids

    SciTech Connect

    Somayazulu, Maddury; Dera, Przemyslaw; Goncharov, Alexander F; Gramsch, Stephen A; Liermann, Peter; Yang, Wenge; Liu, Zhenxian; Mao, Ho-kwang; Hemley, Russell J

    2010-11-03

    Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe-H{sub 2} binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe-Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa.

  12. [Chlorination byproducts formation potentials of typical nitrogenous organic compounds in water].

    PubMed

    Xu, Qian; Xu, Bin; Qin, Cao; Xia, Sheng-Ji; Gao, Nai-Yun; Tian, Fu-Xiang; Li, Da-Peng

    2011-07-01

    Twelve typical nitrogenous organic compounds including herbicides, pesticides, amino acids, industrial products etc in polluted raw water were selected to investigate formation of typical carbonaceous and nitrogenous DBPs during chlorination and chloramination. To indentify the formation mechanism of carbonaceous and nitrogenous disinfection byproducts from nitrogenous chemicals, chlorination and chloroamination of urea herbicides, triazine herbicides, amino acid, and other compounds were investigated. As a result, the potential precursors for different DBPs were defined as well. It has been identified that widely used urea herbicides could produce as many as 9 specific DBPs. The chlorotoluron shows highest reactivity and yields chloroform (CF), monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), 1,1-dichloro-acetone (1,1-DCP), 1,1,1-trichloro-acetone (1,1,1-TCP), chloropicrin (NTCM), dichloro-acetonitrile (DCAN), dimethylnitrosamine (NDMA). The results indicated that aldicarb and dinoseb are important precursors of CF, DCAA, MCAA, NTCM as well. High concentrations of CF and DCAA were found during L-tryptophan chlorination. Furthermore, DBPs formation pathways and mechanisms were suggested during chlorination and chloramination of chlorotoluron, ametryn, dinoseb L-tryptophan.

  13. Preparation and hydrogen storage properties of Mg2Ni intermetallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Shao, Huaiyu; Xu, Hairuo; Wang, Yuntao; Li, Xingguo

    2004-03-01

    In this work we investigated the hydrogen storage properties of stoichiometric Mg2Ni intermetallic nanoparticles produced from Mg and Ni nanoparticles. The mean size of the Mg2Ni particles is about 30-50 nm and the lattice constants of the Mg2Ni compound are a = 5.22 Å, c = 13.29 Å. The Mg2Ni compound showed excellent hydrogen storage properties without activation. It can absorb 2.77, 2.93 and 3.03 wt% hydrogen at 523, 573 and 623 K respectively. After one simple activation process, the obtained Mg2Ni absorbed 1.74, 2.07, 2.31 and 2.82 wt% hydrogen at 293, 348, 426 and 493 K respectively. The absorption and desorption plateau hydrogen pressures are about 2.5 and 0.8 bar at 523 K, 5.9 and 3.4 bar at 573 K and 12.7 and 9.7 bar at 623 K. The resulting van't Hoff equation is log(P/bar) = -3464/T+6.541 and the formation enthalpy (DgrH) and entropy (DgrS) for the Mg2NiH4 are -66.32 kJ/mol H2 and -125.3 J K-1/mol H2.

  14. Compound-specific sulfur isotope analysis of thiadiamondoids of oils from the Smackover Formation, USA

    USGS Publications Warehouse

    Zvi Gvirtzman,; Ward Said-Ahmad,; Ellis, Geoffrey S.; Ronald J. Hill,; J. Michael Moldowan,; Zhibin Wei,; Alon Amrani,

    2015-01-01

    Thiadiamondoids (TDs) are diamond-like compounds with a sulfide bond located within the cage structure. These compounds were suggested as a molecular proxy for the occurrence and extent of thermochemical sulfate reduction (TSR). Compound-specific sulfur-isotope analysis of TDs may create a multi-parameter system, based on molecular and δ34S values that may be sensitive over a wider range of TSR and thermal maturation stages. In this study, we analyzed a suite of 12 Upper Jurassic oil and condensate samples generated from source rocks in the Smackover Formation to perform a systematic study of the sulfur isotope distribution in thiadiamondoids (one and two cages). For comparison we measured the δ34S composition of benzothiophenes (BTs) and dibenzothiophenes (DBTs). We also conducted pyrolysis experiments with petroleum and model compounds to have an insight into the formation mechanisms of TDs. The δ34S of the TDs varied significantly (ca 30‰) between the different oils depending on the degree of TSR alteration. The results showed that within the same oil, the one-cage TDs were relatively uniform, with 34S enriched values similar to those of the coexisting BTs. The two-cage TDs had more variable δ34S values that range from the δ34S values of BTs to those of the DBTs, but with general 34S depletion relative to one cage TDs. Hydrous pyrolysis experiments (360 °C, 40 h) with either CaSO4 or elemental S (equivalent S molar concentrations) and adamantane as a model compound demonstrate the formation of one cage TDs in relatively low yields (<0.2%). Higher concentrations of TDs were observed in the elemental sulfur experiments, most likely because of the higher rates of reaction with adamantane under these experimental conditions. These results show that the formation of TDs is not exclusive to TSR reactions, and that they can also form by reaction with reduced S species apart from sulfate reduction, though at low yields. Oxygenated compounds, most notably 2

  15. Compound-specific sulfur isotope analysis of thiadiamondoids of oils from the Smackover Formation, USA

    NASA Astrophysics Data System (ADS)

    Gvirtzman, Zvi; Said-Ahmad, Ward; Ellis, Geoffrey S.; Hill, Ronald J.; Moldowan, J. Michael; Wei, Zhibin; Amrani, Alon

    2015-10-01

    Thiadiamondoids (TDs) are diamond-like compounds with a sulfide bond located within the cage structure. These compounds were suggested as a molecular proxy for the occurrence and extent of thermochemical sulfate reduction (TSR). Compound-specific sulfur-isotope analysis of TDs may create a multi-parameter system, based on molecular and δ34S values that may be sensitive over a wider range of TSR and thermal maturation stages. In this study, we analyzed a suite of 12 Upper Jurassic oil and condensate samples generated from source rocks in the Smackover Formation to perform a systematic study of the sulfur isotope distribution in thiadiamondoids (one and two cages). For comparison we measured the δ34S composition of benzothiophenes (BTs) and dibenzothiophenes (DBTs). We also conducted pyrolysis experiments with petroleum and model compounds to have an insight into the formation mechanisms of TDs. The δ34S of the TDs varied significantly (ca 30‰) between the different oils depending on the degree of TSR alteration. The results showed that within the same oil, the one-cage TDs were relatively uniform, with 34S enriched values similar to those of the coexisting BTs. The two-cage TDs had more variable δ34S values that range from the δ34S values of BTs to those of the DBTs, but with general 34S depletion relative to one cage TDs. Hydrous pyrolysis experiments (360 °C, 40 h) with either CaSO4 or elemental S (equivalent S molar concentrations) and adamantane as a model compound demonstrate the formation of one cage TDs in relatively low yields (<0.2%). Higher concentrations of TDs were observed in the elemental sulfur experiments, most likely because of the higher rates of reaction with adamantane under these experimental conditions. These results show that the formation of TDs is not exclusive to TSR reactions, and that they can also form by reaction with reduced S species apart from sulfate reduction, though at low yields. Oxygenated compounds, most notably 2

  16. Salt lakes of Western Australia - Natural abiotic formation of volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Krause, T.; Studenroth, S.; Mulder, I.; Tubbesing, C.; Kotte, K.; Ofner, J.; Junkermann, W.; Schöler, H. F.

    2012-04-01

    Western Australia is a semi-/arid region that is heavily influenced by global climate change and agricultural land use. The area is known for its many ephemeral saline and hypersaline lakes with a wide range of hydrogeochemical parameters that have gradually changed over the last fifty years. Historically, the region was covered by eucalyptus trees and shrubs, but was cleared mainly within 10 years after WWII to make room for wheat and live stock. After the clearance of the deep rooted native plants the groundwater started to rise, bringing increased amounts of dissolved salts and minerals to the surface and discharging them into streams and lakes. Thus most of Western Australia is influenced by secondary salinisation (soil salting) [1]. Another problem is that the discharged minerals affect the pH of ground and surface water, which ranges from acidic to slightly basic. During the 2011 campaign surface water was measured with a pH between 2.5 and 7.1. Another phenomenon in Western Australia is the decrease of rainfall over the last decades assumed to be linked to the secondary salinisation. The rising saline and mineral rich groundwater increases the biotical and abiotical activity of the salt lakes. Halogenated and non-halogenated volatile organic compounds emitted from those lakes undergo fast oxidation and chemical reactions to form small particles modifying cloud microphysics and thus suppressing rain events [2]. Our objective is to gain a better understanding of this extreme environment with its hypersaline acidic lakes with regard to the potential abiotic formation of volatile organic compounds and its impact on the local climate. In spring 2011 fifty-three sediment samples from ten salt lakes in the Lake King region where taken, freeze-dried and ground. In order to simulate the abiotic formation of volatile organic compounds the soil samples were resuspended with water in gas-tight headspace vials. The headspace was measured using a purge and trap GC

  17. Defect formation and carrier doping in epitaxial films of the infinite layer compound

    SciTech Connect

    Feenstra, R.; Pennycook, S.J.; Chisholm, M.F.

    1996-02-01

    The correlation between defect formation and carrier doping in epitaxial films of the infinite layer compound SrCuO{sub 2} has been studied via molecular beam epitaxy controlled layer-by-layer growth experiments, chemically resolved scanning transmission electron microscopy, scanning tunneling microscopy, x-ray diffraction, electrical transport measurements, and post-growth oxidation-reduction annealing. Based on the complementary information provided by these experiments, it is concluded that the carrier doping is dominated by the formation of an electron-doped, Sr and O deficient matrix under mildly oxidizing growth conditions. Hole-doping is induced by extended defects containing excess Sr atoms and may lead to superconductivity after high-temperature oxidation.

  18. Target-seeking antifibrotic compound enhances wound healing and suppresses scar formation in mice.

    PubMed

    Järvinen, Tero A H; Ruoslahti, Erkki

    2010-12-14

    Permanent scars form upon healing of tissue injuries such as those caused by ischemia (myocardial infarction, stroke), trauma, surgery, and inflammation. Current options in reducing scar formation are limited to local intervention. We have designed a systemically administered, target-seeking biotherapeutic for scar prevention. It consists of a vascular targeting peptide that specifically recognizes angiogenic blood vessels and extravasates into sites of injury, fused with a therapeutic molecule, decorin. Decorin prevents tissue fibrosis and promotes tissue regeneration by inhibiting TGF-β activity and by other regulatory activities. The decorin-targeting peptide fusion protein had substantially increased neutralizing activity against TGF-β1 in vitro compared with untargeted decorin. In vivo, the fusion protein selectively accumulated in wounds, and promoted wound healing and suppressed scar formation at doses where nontargeted decorin was inactive. These results show that selective targeting yields a tissue-healing and scar-reducing compound with enhanced specificity and potency. This approach may help make reducing scar formation by systemic drug delivery a feasible option for surgery and for the treatment of pathological processes in which scar formation is a problem. PMID:21106754

  19. A comparative first-principles study on electronic structures and mechanical properties of ternary intermetallic compounds Al8Cr4Y and Al8Cu4Y: Pressure and tension effects

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Pang, Mingjun; Tan, Yong; Zhan, Yongzhong

    2016-11-01

    An investigation into the bulk properties, elastic properties and Debye temperature under pressure, and deformation mode under tension of Al8Cu4Y and Al8Cr4Y compounds was investigated by using first principles calculations based on density functional theory. The calculated lattice constants for the ternary compounds (Al8Cu4Y and Al8Cr4Y) are in good agreement with the experimental data. It can be seen from interatomic distances that the bonding between Al1 atom and Cr, Y, and Al2 atoms in Al8Cr4Y are stronger than Al8Cu4Y. The results of cohesive energy show that Al8Cr4Y should be easier to be formed and much stronger chemical bonds than Al8Cu4Y. The bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν can be obtained by using the Voigt-Reuss-Hill averaging scheme. From the results of elastic properties, Al8Cr4Y has the stronger mechanical behavior than Al8Cu4Y. Our calculations also show that pressure has a greater effect on mechanical behavior for both compounds. The ideal tensile strength are obtained by stress-strain relationships under [001](001) uniaxial tensile deformation, which are 15.4 and 23.4 GPa for Al8Cu4Y and Al8Cr4Y, respectively. The total and partial density of states and electron charge density under uniaxial tensile deformations for Al8Cu4Y and Al8Cr4Y compounds are also calculated and discussed in this work.

  20. The synthesis and formation process of a new cubic conductive Cu7O(8-y)(NO3) compound

    NASA Astrophysics Data System (ADS)

    Yazawa, Ichiro; Sugise, Ryoji; Terada, Norio; Jo, Masatoshi; Oka, Kunihiko

    1990-08-01

    The synthesis and formation process of a new cubic conductive Cu7O(8-y)(NO3) compound was studied. This material was formed as an intermediate compound in the decomposition process of copper nitrate by a firing process in oxygen flowing gas. It has a CuO2 plane in its lattice structure and is a parent material of the new metallic copper oxide compounds.

  1. Compound nucleus formation probability PCN defined within the dynamical cluster-decay model

    NASA Astrophysics Data System (ADS)

    Chopra, Sahila; Kaur, Arshdeep; Gupta, Raj K.

    2015-01-01

    With in the dynamical cluster-decay model (DCM), the compound nucleus fusion/ formation probability PCN is defined for the first time, and its variation with CN excitation energy E* and fissility parameter χ is studied. In DCM, the (total) fusion cross section σfusion is sum of the compound nucleus (CN) and noncompound nucleus (nCN) decay processes, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of the evaporation residues (ER) and fusion-fission (ff), including the intermediate mass fragments (IMFs), each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process where P0=1 and P is calculated for the entrance channel nuclei. The calculations are presented for six different target-projectile combinations of CN mass A~100 to superheavy, at various different center-of-mass energies with effects of deformations and orientations of nuclei included in it. Interesting results are that the PCN=1 for complete fusion, but PCN <1 or ≪1 due to the nCN conribution, depending strongly on both E* and χ.

  2. Organic nitrate aerosol formation via NO3 + biogenic volatile organic compounds in the southeastern United States

    NASA Astrophysics Data System (ADS)

    Ayres, B. R.; Allen, H. M.; Draper, D. C.; Brown, S. S.; Wild, R. J.; Jimenez, J. L.; Day, D. A.; Campuzano-Jost, P.; Hu, W.; de Gouw, J.; Koss, A.; Cohen, R. C.; Duffey, K. C.; Romer, P.; Baumann, K.; Edgerton, E.; Takahama, S.; Thornton, J. A.; Lee, B. H.; Lopez-Hilfiker, F. D.; Mohr, C.; Wennberg, P. O.; Nguyen, T. B.; Teng, A.; Goldstein, A. H.; Olson, K.; Fry, J. L.

    2015-12-01

    Gas- and aerosol-phase measurements of oxidants, biogenic volatile organic compounds (BVOCs) and organic nitrates made during the Southern Oxidant and Aerosol Study (SOAS campaign, Summer 2013) in central Alabama show that a nitrate radical (NO3) reaction with monoterpenes leads to significant secondary aerosol formation. Cumulative losses of NO3 to terpenes are correlated with increase in gas- and aerosol-organic nitrate concentrations made during the campaign. Correlation of NO3 radical consumption to organic nitrate aerosol formation as measured by aerosol mass spectrometry and thermal dissociation laser-induced fluorescence suggests a molar yield of aerosol-phase monoterpene nitrates of 23-44 %. Compounds observed via chemical ionization mass spectrometry (CIMS) are correlated to predicted nitrate loss to BVOCs and show C10H17NO5, likely a hydroperoxy nitrate, is a major nitrate-oxidized terpene product being incorporated into aerosols. The comparable isoprene product C5H9NO5 was observed to contribute less than 1 % of the total organic nitrate in the aerosol phase and correlations show that it is principally a gas-phase product from nitrate oxidation of isoprene. Organic nitrates comprise between 30 and 45 % of the NOy budget during SOAS. Inorganic nitrates were also monitored and showed that during incidents of increased coarse-mode mineral dust, HNO3 uptake produced nitrate aerosol mass loading at a rate comparable to that of organic nitrate produced via NO3 + BVOCs.

  3. Systematic assessment of scaffold hopping versus activity cliff formation across bioactive compound classes following a molecular hierarchy.

    PubMed

    Stumpfe, Dagmar; Dimova, Dilyana; Bajorath, Jürgen

    2015-07-01

    Scaffold hopping and activity cliff formation define opposite ends of the activity landscape feature spectrum. To rationalize these events at the level of scaffolds, active compounds involved in scaffold hopping were required to contain topologically distinct scaffolds but have only limited differences in potency, whereas compounds involved in activity cliffs were required to share the same scaffold but have large differences in potency. A systematic search was carried out for compounds involved in scaffold hopping and/or activity cliff formation. Results obtained for compound data sets covering more than 300 human targets revealed clear trends. If scaffolds represented multiple but fewer than 10 active compounds, nearly 90% of all scaffolds were exclusively involved in hopping events. With increasing compound coverage, the fraction of scaffolds involved in both scaffold hopping and activity cliff formation significantly increased to more than 50%. However, ∼40% of the scaffolds representing large numbers of active compounds continued to be exclusively involved in scaffold hopping. More than 200 scaffolds with broad target coverage were identified that consistently represented potent compounds and yielded an abundance of scaffold hops in the low-nanomolar range. These and other subsets of scaffolds we characterized are of prime interest for structure-activity relationship (SAR) exploration and compound design. Therefore, the complete scaffold classification generated in the course of our analysis is made freely available.

  4. Spark plasma sintering of titanium aluminide intermetallics and its composites

    NASA Astrophysics Data System (ADS)

    Aldoshan, Abdelhakim Ahmed

    Titanium aluminide intermetallics are a distinct class of engineering materials having unique properties over conventional titanium alloys. gamma-TiAl compound possesses competitive physical and mechanical properties at elevated temperature applications compared to Ni-based superalloys. gamma-TiAl composite materials exhibit high melting point, low density, high strength and excellent corrosion resistance. Spark plasma sintering (SPS) is one of the powder metallurgy techniques where powder mixture undergoes simultaneous application of uniaxial pressure and pulsed direct current. Unlike other sintering techniques such as hot iso-static pressing and hot pressing, SPS compacts the materials in shorter time (< 10 min) with a lower temperature and leads to highly dense products. Reactive synthesis of titanium aluminide intermetallics is carried out using SPS. Reactive sintering takes place between liquid aluminum and solid titanium. In this work, reactive sintering through SPS was used to fabricate fully densified gamma-TiAl and titanium aluminide composites starting from elemental powders at different sintering temperatures. It was observed that sintering temperature played significant role in the densification of titanium aluminide composites. gamma-TiAl was the predominate phase at different temperatures. The effect of increasing sintering temperature on microhardness, microstructure, yield strength and wear behavior of titanium aluminide was studied. Addition of graphene nanoplatelets to titanium aluminide matrix resulted in change in microhardness. In Ti-Al-graphene composites, a noticeable decrease in coefficient of friction was observed due to the influence of self-lubrication caused by graphene.

  5. Incremental Reactivity Effects of Anthropogenic and Biogenic Volatile Organic Compounds on Secondary Organic Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Kacarab, M.; Li, L.; Carter, W. P. L.; Cocker, D. R., III

    2015-12-01

    Two surrogate reactive organic gas (ROG) mixtures were developed to create a controlled reactivity environment simulating different urban atmospheres with varying levels of anthropogenic (e.g. Los Angeles reactivity) and biogenic (e.g. Atlanta reactivity) influences. Traditional chamber experiments focus on the oxidation of one or two volatile organic compound (VOC) precursors, allowing the reactivity of the system to be dictated by those compounds. Surrogate ROG mixtures control the overall reactivity of the system, allowing for the incremental aerosol formation from an added VOC to be observed. The surrogate ROG mixtures were developed based on that used to determine maximum incremental reactivity (MIR) scales for O3 formation from VOC precursors in a Los Angeles smog environment. Environmental chamber experiments were designed to highlight the incremental aerosol formation in the simulated environment due to the addition of an added anthropogenic (aromatic) or biogenic (terpene) VOC. All experiments were conducted in the UC Riverside/CE-CERT dual 90m3 environmental chambers. It was found that the aerosol precursors behaved differently under the two altered reactivity conditions, with more incremental aerosol being formed in the anthropogenic ROG system than in the biogenic ROG system. Further, the biogenic reactivity condition inhibited the oxidation of added anthropogenic aerosol precursors, such as m-xylene. Data will be presented on aerosol properties (density, volatility, hygroscopicity) and bulk chemical composition in the gas and particle phases (from a SYFT Technologies selected ion flow tube mass spectrometer, SIFT-MS, and Aerodyne high resolution time of flight aerosol mass spectrometer, HR-ToF-AMS, respectively) comparing the two controlled reactivity systems and single precursor VOC/NOx studies. Incremental aerosol yield data at different controlled reactivities provide a novel and valuable insight in the attempt to extrapolate environmental chamber

  6. Cloud processing of organic compounds: Secondary organic aerosol and nitrosamine formation

    NASA Astrophysics Data System (ADS)

    Hutchings, James W., III

    Cloud processing of atmospheric organic compounds has been investigated through field studies, laboratory experiments, and numerical modeling. Observational cloud chemistry studies were performed in northern Arizona and fog studies in central Pennsylvania. At both locations, the cloud and fogs showed low acidity due to neutralization by soil dust components (Arizona) and ammonia (Pennsylvania). The field observations showed substantial concentrations (20-5500 ng•L -1) of volatile organic compounds (VOC) in the cloud droplets. The potential generation of secondary organic aerosol mass through the processing of these anthropogenic VOCs was investigated through laboratory and modeling studies. Under simulated atmospheric conditions, in idealized solutions, benzene, toluene, ethylbenzene, and xylene (BTEX) degraded quickly in the aqueous phase with half lives of approximately three hours. The degradation process yielded less volatile products which would contribute to new aerosol mass upon cloud evaporation. However, when realistic cloud solutions containing natural organic matter were used in the experiments, the reaction kinetics decreased with increasing organic carbon content, resulting in half lives of approximately 7 hours. The secondary organic aerosol (SUA) mass formation potential of cloud processing of BTEX was evaluated. SOA mass formation by cloud processing of BTEX, while strongly dependent on the atmospheric conditions, could contribute up to 9% of the ambient atmospheric aerosol mass, although typically ˜1% appears realistic. Field observations also showed the occurrence of N-nitrosodimethylamine (NDMA), a potent carcinogen, in fogs and clouds (100-340 ng•L -1). Laboratory studies were conducted to investigate the formation of NDMA from nitrous acid and dimethylamine in the homogeneous aqueous phase within cloud droplets. While NDMA was produced in the cloud droplets, the low yields (<1%) observed could not explain observational concentrations

  7. Effect of ajoene, the major antiplatelet compound from garlic, on platelet thrombus formation.

    PubMed

    Apitz-Castro, R; Badimon, J J; Badimon, L

    1992-10-15

    Ajoene, (E,Z)-4,5,9-trithiadodeca-1,6,11-triene 9-oxide, is a potent antiplatelet compound isolated from alcoholic extracts of garlic (Allium sativum). Ajoene reversibly inhibits in vitro platelet aggregation as well as release reaction induced by all known agonists. We used a well characterized cylindrical perfusion chamber to study the effect of ajoene on platelet deposition onto physiological substrates such as pig aortic subendothelium and tunica media as a model of mildly and severely damaged vessel wall respectively. Experiments were performed under flow conditions of high and low shear rate that mimic laminar blood flow in small and medium size arteries (1690 sec-1 and 212 sec-1). Our results indicate that ajoene prevents thrombus formation both at low and high shear rate in citrated whole blood. The inhibitory effect of ajoene on platelet-thrombus formation seems to be dependent on its inhibition of fibrinogen binding, since significantly higher concentrations of ajoene are needed to affect von Willebrand factor binding to GPIIb/IIIa receptors. Further, ajoene does not impair Ristocetin-induced platelet agglutination, mediated by GPIb. Our results suggest that ajoene may be useful for the acute prevention of thrombus formation induced by vascular damage.

  8. In-situ neutron diffraction analysis of deformation behavior of ductile rare-earth intermetallic yttrium-copper

    NASA Astrophysics Data System (ADS)

    Williams, Scott H.

    Intermetallic compounds exhibit favorable properties for numerous diverse engineering applications. Many intermetallic compounds possess high strength and high stiffness at elevated temperature, excellent corrosion resistance, and low density, making them potentially useful in a wide range of applications. However, several drawbacks, limited ductility in particular, have prevented these compounds from achieving wide-spread application. In order to make full use of potential of intermetallic compounds, these limitations must be better understood and overcome. In the search for improved ductility in intermetallics, recent findings from an Ames Laboratory research group have uncovered an entire family of compounds possessing the B2 structure which exhibit room temperature tensile ductility. These materials do not require third-element additions, off-stoichiometric chemistry, disordering, or elaborate environmental testing conditions to enhance ductility. Previous studies have investigated various structural and physical properties of this family of compounds, yet the mechanisms for ductility remain uncertain. Low temperature phase transformations are known to occur in several of these compounds. Suggestions for possible mechanisms have included stress-induced phase transformation, as well as the deformation accommodated through crystallographic twinning. In-situ neutron diffraction allows for observations of structural changes and the relationship to macroscopic physical properties. Using this investigation technique, experiments have been conducted to examine rare-earth intermetallic YCu for evidence of phase transformation, twinning, or indications of other deformation behavior. Results give insight into the crystal structure of the compound, indicating a high degree of crystal lattice coherency, and resulting dynamical diffraction behavior not commonly observed in engineering materials.

  9. Surfaces of Intermetallics: Quasicrystals and Beyond

    SciTech Connect

    Yuen, Chad

    2012-01-01

    The goal of this work is to characterize surfaces of intermetallics, including quasicrystals. In this work, surface characterization is primarily focused on composition and structure using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) performed under ultrahigh vacuum (UHV) conditions.

  10. Synthesis and Modeling of Hollow Intermetallic Ni-Zn Nanoparticles Formed by the Kirkendall Effect

    SciTech Connect

    Jana, Subhra; Chang, Ji Woong; Rioux, Robert M.

    2013-10-09

    Intermetallic Ni–Zn nanoparticles (NPs) were synthesized via the chemical conversion of nickel NPs using a zerovalent organometallic zinc precursor. After the injection of a diethylzinc solution, Ni NPs progressively transformed from a solid to a hollow Ni–Zn intermetallic structure with time. During the transformation of Ni NPs to intermetallic structures, they retained their overall spherical morphology. The growth mechanism for the solid-to-hollow nanoparticle transformation is ascribed to the nanoscale Kirkendall effect due to unequal diffusion rates of Ni and Zn. We develop a diffusion model for nonreactive, homogeneous, diffusion-controlled intermetallic hollow NP formation including moving boundaries at the interfaces of void–solid and solid–bulk solutions. Apparent diffusion coefficients for both metals and vacancy were evaluated from modeling the time-dependent growth of the void. The apparent diffusion coefficients obtained in this system compared favorably with results from measurement at grain boundaries in bulk Ni–Zn. This study represents the first combined experimental modeling of the formation of hollow nanostructures by the nanoscale Kirkendall effect.

  11. Wet chemical synthesis of intermetallic Pt3Zn nanocrystals via weak reduction reaction together with UPD process and their excellent electrocatalytic performances

    NASA Astrophysics Data System (ADS)

    Chen, Qiaoli; Zhang, Jiawei; Jia, Yanyan; Jiang, Zhiyuan; Xie, Zhaoxiong; Zheng, Lansun

    2014-05-01

    Platinum based alloy nanocrystals are promising catalysts for a variety of important practical process. However, it remains a great challenge to synthesize platinum-based intermetallic compound nanocrystals with well-defined surface structures. In this communication, taking the synthesis of concave cubic intermetallic Pt3Zn nanocrystals with {hk0} facets as an example, we proposed a new synthesis strategy for intermetallic compounds by reduction of noble metal precursors via a slow reduction process and reduction of transition metal ions via an underpotential deposition (UPD) process in wet chemical synthesis. The as-prepared intermetallic Pt3Zn nanocrystals exhibited superior CO poisoning tolerance and high electro-catalytic activity in both methanol and formic acid oxidation reactions in comparison with solid solution Pt3Zn nanocrystals and Pt/C.Platinum based alloy nanocrystals are promising catalysts for a variety of important practical process. However, it remains a great challenge to synthesize platinum-based intermetallic compound nanocrystals with well-defined surface structures. In this communication, taking the synthesis of concave cubic intermetallic Pt3Zn nanocrystals with {hk0} facets as an example, we proposed a new synthesis strategy for intermetallic compounds by reduction of noble metal precursors via a slow reduction process and reduction of transition metal ions via an underpotential deposition (UPD) process in wet chemical synthesis. The as-prepared intermetallic Pt3Zn nanocrystals exhibited superior CO poisoning tolerance and high electro-catalytic activity in both methanol and formic acid oxidation reactions in comparison with solid solution Pt3Zn nanocrystals and Pt/C. Electronic supplementary information (ESI) available: Additional characterization data. See DOI: 10.1039/c4nr00313f

  12. Amines compounds as inhibitors of PCDD/Fs de novo formation on sintering process fly ash.

    PubMed

    Xhrouet, Céline; Nadin, Caroline; De Pauw, Edwin

    2002-06-15

    The polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are highly toxic compounds produced by some natural processes and different human activities. Waste incineration as well as steel and iron industries, in particular, the sintering process, are among the principal sources of these pollutants. In this paper, two inhibitors, triethanolamine (TEA) and monoethanolamine (MEA) are tested relating to their abilityto prevent the de novo formation of PCDD/Fs on sinter plant fly ash. The amounts of both PCDDs and PCDFs, formed by thermal treatment of the fly ash, decrease when inhibitors are added. The best results, up to 90% reduction of the PCDD/ Fs formation, are obtained when MEA is mixed with the fly ash at the highest concentration tested (2 wt %). The addition of inhibitors modifies the PCDFs/PCDDs ratios and, under some experimental conditions, the PCDD/Fs homologue distributions, suggesting that more than one pathway for the de novo formation of PCDD/Fs exist. On the other hand, no modification in the PCDD/Fs isomer distributions is observed as a result of the addition of inhibitors, in accordance with the possible thermodynamic control of these distributions. The temperature tested, 325 and 400 degrees C, does not affect the inhibition activity; however, longer reaction times (4 h instead of 2 h) give better percentages of PCDD/Fs reduction. The results suggest that the two inhibitors and especially MEA can reduce the PCDD/Fs formation on sinter plant fly ash under various conditions of temperature and reaction time, making them suitable for use in the real process. Tests performed in parallel at a real sinter plant are in good agreement with the laboratory experiments and confirm that the use of inhibitors is an appropriate technique for the prevention of PCDD/Fs emissions from sintering processes.

  13. Induction of contact drematitis in guinea pigs by quaternary ammonium compounds: the mechanisms of antigen formation

    SciTech Connect

    Schallreuter, K.R.; Schulz, K.H.; Wood, J.M.

    1986-12-01

    Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites to the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable ion-pairs are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface.

  14. Identification of volatile organic compounds in suburban Bangkok, Thailand and their potential for ozone formation

    NASA Astrophysics Data System (ADS)

    Suthawaree, Jeeranut; Tajima, Yosuke; Khunchornyakong, Alisa; Kato, Shungo; Sharp, Alice; Kajii, Yoshizumi

    2012-02-01

    Measurement of Volatile Organic Compound (VOC) was carried out in suburban Bangkok during July 2-8, 2008. Analysis was performed using GC-FID and GC-MS. High mixing ratios of VOCs detected during the morning and evening are most likely due to vehicular emissions. Averaged VOC mixing ratios revealed distinct difference between mixing ratios of weekdays and weekend, which the latter were found to be lower. The most abundance species were propane and toluene. Ratios of benzene over toluene suggested that additional toluene mixing ratios was owing to industrial emission, which was particularly larger during weekdays. Comparison between C2Cl4 and CH3Cl mixing ratios obtained for suburban Tokyo reveal a relatively lower influence of biomass burning than suburban Bangkok. Elucidating by Ozone Formation Potential, toluene was found to contribute the most to O3 production followed by ethylene, m-,p-xylene, and propylene.

  15. Sucuk and pastırma: microbiological changes and formation of volatile compounds.

    PubMed

    Kaban, Güzin

    2013-12-01

    There is an increasing interest in traditional foods in Turkey like other countries. Sucuk, dry-fermented sausage, and pastırma, a type of dry-cured meat product, are traditional Turkish meat products that are widely consumed. Sucuk is air-dried and neither smoked nor ripened by mold. In spite of increasing use of starter culture in production of sucuk in the industry, traditionally produced sucuk is generally preferred by the consumers because of its sensory characteristics. Pastırma is traditionally processed under natural conditions where air temperature and relative humidity depend on climate and weather conditions. Pastırma differs from other raw cured meat products made from whole pieces of meat in terms of manufacturing process, ingredients, microbial properties and flavor. In this study, microbiological changes and formation of volatile compounds in sucuk and pastırma were reviewed. PMID:23608196

  16. Formation, structure, and properties of "welded" h-BN/graphene compounds

    NASA Astrophysics Data System (ADS)

    Chernozatonskii, L. A.; Demin, V. A.; Artyukh, A. A.

    2016-07-01

    Structures of h-BN/graphene with holes where atoms at the edges are bonded to each other by sp 2 hybridized C-B and C-N bonds and form continuous junctions from layer to layer with topological defects inside holes have been considered. Their formation, as well as the moiré-type stable atomic structure of such compounds (with different rotation angles of graphene with respect to the hexagonal boron nitride monolayer) with closed hexagonal holes in the AA centers of packing of the moiré superlattice, has been studied. The stability, as well as the electronic and mechanical properties, of such bilayer BN/graphene nanomeshes has been analyzed within electron density functional theory. It has been shown that they have semiconducting properties. Their electronic band structures and mechanical characteristics differ from the respective properties of separate monolayer nanomeshes with the same geometry and arrangement of holes.

  17. Formation, characterization and computational studies of mono- and dinuclear rhenium(I) chromone compounds

    NASA Astrophysics Data System (ADS)

    Ebinumoliseh, Ifeoma; Booysen, Irvin Noel; Akerman, Matthew Piers; Xulu, Bheki

    2016-11-01

    Herein, we report the formation and characterization of a novel dinuclear rhenium(I) compound, fac-(Re(CO)3Br)2(μ-chret) (1) [chret = N, N'-bis(2-amino-3-imino)methylenechromone-1,2-ethane] and a mononuclear metal complex, fac-[Re(CO)3(bzch)Br] (2) [bzch = 2-benzimidazole-4H-chromen-4-one]. The metal complexes were characterized by 1H NMR-, IR-, UV-Vis, melting point and conductivity measurements. The solid-state structures for 1 and 2 were confirmed via single crystal X-ray analysis. X-ray studies of 2 revealed the transformation of the chb diimine into the bzch chelator (in 2). The simulated IR spectra for the respective metal complexes provided insight in the interpretation of their corresponding experimental spectra.

  18. Formation of Heavy Compound Nuclei, Their Survival and Correlation with Longtime-Scale Fission

    SciTech Connect

    Karamian, S. A.; Yakushev, A.-B.

    2007-05-22

    Fusion of two massive nuclei with formation of super-heavy compound nucleus (CN) is driven by the potential energy gradient, as follows from the analysis of nuclear reaction cross-sections. The conservative energy of the system is deduced in simple approximation using regularized nuclear mass and interaction barrier values. Different reaction for the synthesis of Zc (110-118) nuclei are compared and the favourable conditions are found for fusion of the stable (W-Pt) isotopes with radioactive fission fragment projectiles, like 94Kr or 100Sr. Thus, the cold fusion method can be extended for a synthesis of elements with Z > 113. Survival of the evaporation residue is defined by the neutron-to-fission probability ratio and by the successful emission of gammas at final step of the reaction. Numerical estimates are presented. Fixation of evaporation residue products must correlate with longtime-scale fission and available experimental results are discussed.

  19. Quaternary borocarbides: New class of intermetallic superconductors

    NASA Technical Reports Server (NTRS)

    Nagarajan, R.; Gupta, L. C.; Dhar, S. K.; Mazumdar, Chandan; Hossain, Zakir; Godart, C.; Levy-Clement, C.; Padalia, B. D.; Vijayaraghavan, R.

    1995-01-01

    Our recent discovery of superconductivity (SC) in the four-element multiphase Y-Ni-B-C system at an elevated temperature (TC approximately 12 K) has opened up great possibilities of identifying new superconducting materials and generating new physics. Superconductivity with Tc (greater than 20 K) higher than that known so far in bulk intermetallics has been observed in multiphase Y-Pd-B-C and Th-Pd-B-C systems and a family of single phase materials RENi2B2C (RE= Y, rare earth) have been found. Our investigations show YNi2B2C to be a strong coupling hard type-II SC. HC2(T) exhibits an unconventional temperature dependence. Specific heat and magnetization studies reveal coexistence of SC and magnetism in RNi2B2C (R = Ho, Er, Tm) with magnetic ordering temperatures (Tc approximately 8 K, 10.5 K, 11 K and Tm approximately 5 K, approximately 7K, approximately 4 K respectively) that are remarkably higher than those in known magnetic superconductors . Mu-SR studies suggest the possibility of Ni atoms carrying a moment in TmNi2B2C. Resistivity results suggests a double re-entrant transition (SC-normal-SC) in HoNi2B2C. RENi2B2C (RE = Ce, Nd, Gd) do not show SC down to 4.2 K. The Nd- and Gd-compounds order magnetically at approximately 4.5 K and approximately 19.5 K, respectively. Two SC transitions are observed in Y-Pd-B-C (Tc approximately 22 K, approximately 10 K) and in Th-Pd-B-C (Tc approximately 20 K, approximately 14 K) systems, which indicate that there are at least two structures which support SC in these borocarbides. In our multiphase ThNi2B2C we observe SC at approximately 6 K. No SC was seen in multiphase UNi2B2C, UPd2B2C, UOs2Ge2C and UPd5B3C(0.35) down to 4.2 K. Tc in YNi2B2C is depressed by substitutions (Gd, Th and U at Y-sites and Fe, Co at Ni-sites).

  20. Volatile organic compound emissions from green waste composting: Characterization and ozone formation

    NASA Astrophysics Data System (ADS)

    Kumar, Anuj; Alaimo, Christopher P.; Horowitz, Robert; Mitloehner, Frank M.; Kleeman, Michael J.; Green, Peter G.

    2011-04-01

    Composting of green waste separated from the disposed solid waste stream reduces biodegradable inputs into landfills, and contributes valuable soil amendments to agriculture. Agencies in regions with severe air quality challenges, such as California's San Joaquin Valley (SJV), have raised concerns about gases emitted during the composting process, which are suspected to contribute to persistent high levels of ground-level ozone formation. The goal of the current study is to thoroughly characterize volatile organic compound (VOC) emissions from green waste compost piles of different ages (fresh tipped piles, 3-6 day old windrows, and 2-3 week old windrows). Multiple sampling and analytical approaches were applied to ensure the detection of most gaseous organic components emitted. More than 100 VOCs were detected and quantified in this study, including aliphatic alkanes, alkenes, aromatic hydrocarbons, biogenic organics, aldehydes, ketones, alcohols, furans, acids, esters, ether, halogenated hydrocarbons and dimethyl disulfide (DMDS). Alcohols were found to be the dominating VOC in the emissions from a compost pile regardless of age, with fluxes ranging from 2.6 to 13.0 mg m -2 min -1 with the highest emissions coming from the younger composting windrows (3-6 days). Average VOC emissions other than alcohols were determined to be 2.3 mg m -2 min -1 from younger windows, which was roughly two times higher than either the fresh tipping pile (1.2 mg m -2 min -1) or the older windrows (1.4 mg m -2 min -1). It was also observed that the older windrows emit a slightly larger proportion of more reactive compounds. Approximately 90% of the total VOCs were found to have maximum incremental reactivity of less than 2. Net ozone formation potential of the emissions was also assessed.

  1. The Formation of Organic Compounds of Astrobiological Interest by the Irradiation Processing of Astrophysical Ices

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.

    2015-01-01

    Many environments in space contain very low temperature mixed molecular ices that are exposed to ionizing radiation in the form of cosmic rays and high-energy photons. While traditional chemistry would not be expected to occur at the temperatures typical of these ices (T < 50 K), ionizing radiation can break bonds in the original molecules in the ices to form highly reactive ions and radicals. These ions and radicals are subsequently free to react despite the low temperatures of the original ices. Laboratory experiments, many of them carried out at the Astrochemistry Laboratory at NASA-Ames, show that the irradiation of ices made of even simple molecules like H2O, CO, CO2, CH4, NH3, etc. can result in the robust formation of large numbers of far more complex organic compounds. Many of these new products are of direct interest to astrobiology. For example, the irradiation of mixed molecular ices has been shown to produce amino acids, amphiphiles, quinones, sugars, heterocyclic compounds, and nucleobases, all molecular building blocks used by terrestrial life. Insofar as the presence of these materials plays a role in the origin of life on planets, this has profound implications for the potential abundance of life in the universe since these experiments simulate universal conditions that are expected to be found wherever new stars and planets form.

  2. Brown carbon formation by aqueous-phase carbonyl compound reactions with amines and ammonium sulfate.

    PubMed

    Powelson, Michelle H; Espelien, Brenna M; Hawkins, Lelia N; Galloway, Melissa M; De Haan, David O

    2014-01-21

    Reactions between small water-soluble carbonyl compounds, ammonium sulfate (AS), and/or amines were evaluated for their ability to form light-absorbing species in aqueous aerosol. Aerosol chemistry was simulated with bulk phase reactions at pH 4, 275 K, initial concentrations of 0.05 to 0.25 M, and UV-vis and fluorescence spectroscopy monitoring. Glycolaldehyde-glycine mixtures produced the most intense absorbance. In carbonyl compound reactions with AS, methylamine, or AS/glycine mixtures, product absorbance followed the order methylglyoxal > glyoxal > glycolaldehyde > hydroxyacetone. Absorbance extended into the visible, with a wavelength dependence fit by absorption Ångstrom coefficients (Å(abs)) of 2 to 11, overlapping the Å(abs) range of atmospheric, water-soluble brown carbon. Many reaction products absorbing between 300 and 400 nm were strongly fluorescent. On a per mole basis, amines are much more effective than AS at producing brown carbon. In addition, methylglyoxal and glyoxal produced more light-absorbing products in reactions with a 5:1 AS-glycine mixture than with AS or glycine alone, illustrating the importance of both organic and inorganic nitrogen in brown carbon formation. Through comparison to biomass burning aerosol, we place an upper limit on the contribution of these aqueous carbonyl-AS-amine reactions of ≤ 10% of global light absorption by brown carbon. PMID:24351110

  3. Harnessing redox activity for the formation of uranium tris(imido) compounds

    NASA Astrophysics Data System (ADS)

    Anderson, Nickolas H.; Odoh, Samuel O.; Yao, Yiyi; Williams, Ursula J.; Schaefer, Brian A.; Kiernicki, John J.; Lewis, Andrew J.; Goshert, Mitchell D.; Fanwick, Phillip E.; Schelter, Eric J.; Walensky, Justin R.; Gagliardi, Laura; Bart, Suzanne C.

    2014-10-01

    Classically, late transition-metal organometallic compounds promote multielectron processes solely through the change in oxidation state of the metal centre. In contrast, uranium typically undergoes single-electron chemistry. However, using redox-active ligands can engage multielectron reactivity at this metal in analogy to transition metals. Here we show that a redox-flexible pyridine(diimine) ligand can stabilize a series of highly reduced uranium coordination complexes by storing one, two or three electrons in the ligand. These species reduce organoazides easily to form uranium-nitrogen multiple bonds with the release of dinitrogen. The extent of ligand reduction dictates the formation of uranium mono-, bis- and tris(imido) products. Spectroscopic and structural characterization of these compounds supports the idea that electrons are stored in the ligand framework and used in subsequent reactivity. Computational analyses of the uranium imido products probed their molecular and electronic structures, which facilitated a comparison between the bonding in the tris(imido) structure and its tris(oxo) analogue.

  4. Elastic anisotropy, vibrational, and thermodynamic properties of U{sub 2}Ti intermetallic compound with AlB{sub 2}-type structure under high pressure up to 100 GPa

    SciTech Connect

    Yang, Jinwen; Gao, Tao; Liu, Benqiong; Sun, Guangai; Chen, Bo

    2015-03-28

    Structural, elastic anisotropy, dynamical, and thermodynamic properties of U{sub 2}Ti have been studied by employing density functional theory and density functional perturbative theory. The optimized lattice parameters a, c, unit volume V, bulk modulus B, and bond lengths d{sub U-U}, d{sub U-Ti} of U{sub 2}Ti are in favorable agreement with the available experimental data and other theoretical values. The elastic constants under pressure were obtained using “energy-strain” method. The polycrystalline modulus, Poisson's ratio, brittle/ductile characteristics, Debye temperature and the integration of elastic wave velocities over different directions, and hardness under pressure are also evaluated successfully. The anisotropy of the directional bulk modulus and the Young's modulus is systematically predicted for the first time. It turns out that U{sub 2}Ti should be stabilized mechanically up to 100 GPa, this compound just possesses slightly elastic anisotropy at zero pressure; however, the anisotropy becomes more and more significant with the increasing pressure. In particular, the phonon dispersion curves and phonon density of state under pressure are reported for the first time. The Raman and infrared-active phonon modes at Γ point are further assigned. Our results indicate that U{sub 2}Ti is also stable dynamically up to 100 GPa. Additionally, within the calculated phonon density of states, the thermodynamic properties are predicted.

  5. Dissolution of iron intermetallics in Al-Si alloys through nonequilibrium heat treatment

    SciTech Connect

    Anantha Narayanan, L. |; Samuel, F.H.; Gruzleski, J.E.

    1995-08-01

    Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-1Fe alloys is found to be between 515 C and 520 C.

  6. Process for synthesizing compounds from elemental powders and product

    DOEpatents

    Rabin, Barry H.; Wright, Richard N.

    1993-01-01

    A process for synthesizing intermetallic compounds from elemental powders. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe.sub.3 Al and FeAl.

  7. Iron-binding compounds impair Pseudomonas aeruginosa biofilm formation, especially under anaerobic conditions.

    PubMed

    O'May, Che Y; Sanderson, Kevin; Roddam, Louise F; Kirov, Sylvia M; Reid, David W

    2009-06-01

    The success of Pseudomonas aeruginosa in cystic fibrosis (CF) and other chronic infections is largely attributed to its ability to grow in antibiotic-resistant biofilm communities. This study investigated the effects of limiting iron levels as a strategy for preventing/disrupting P. aeruginosa biofilms. A range of synthetic and naturally occurring iron-chelating agents were examined. Biofilm development by P. aeruginosa strain PAO1 and CF sputum isolates from chronically infected individuals was significantly decreased by iron removal under aerobic atmospheres. CF strains formed poor biofilms under anaerobic conditions. Strain PAO1 was also tested under anaerobic conditions. Biofilm formation by this model strain was almost totally prevented by several of the chelators tested. The ability of synthetic chelators to impair biofilm formation could be reversed by iron addition to cultures, providing evidence that these effective chelating compounds functioned by directly reducing availability of iron to P. aeruginosa. In contrast, the biological chelator lactoferrin demonstrated enhanced anti-biofilm effects as iron supplementation increased. Hence biofilm inhibition by lactoferrin appeared to occur through more complex mechanisms to those of the synthetic chelators. Overall, our results demonstrate the importance of iron availability to biofilms and that iron chelators have potential as adjunct therapies for preventing biofilm development, especially under low oxygen conditions such as encountered in the chronically infected CF lung. PMID:19429753

  8. Analysis of diarylmethylamine compounds using electrospray mass spectrometry: formation mechanisms of radical ions and dehydro cations.

    PubMed

    Cai, Tian; Xu, Xiao-Ying; Wu, Zhi-Jun

    2015-12-01

    A series of diarylmethylamine compounds were analyzed using electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF-MS). [M](+)˙ and [M - H](+) were both observed, but showed different abundances. A possible mechanism for the formation of [M](+)˙ and [M - H](+) was proposed to explicate the rule for the ratio change of I([M](+)˙)/I([M-H](+)). The [M](+)˙ has two structures, which can interconvert into each other in the gas phase. The substituted groups on the benzene rings play a crucial role in the transfer between the two structures. Electron withdrawing groups can prevent the formation of carbocations, thus nitro-containing diarylmethylamines remained mainly as structure I and were detected as [M](+)˙. On the contrary, electron donating groups help to stabilize carbocations. This makes structure I transfer to structure II, and structure II prefers to further generate [M - H](+) by loss of an H radical. Nuclear magnetic resonance and D-labelled MS experiments indicate that the 1-C-H bond has strong activity.

  9. Ab initio molecular dynamics study of H2 formation inside POSS compounds.

    PubMed

    Kudo, Takako; Taketsugu, Tetsuya; Gordon, Mark S

    2011-04-01

    The mechanism and dynamics of the formation of a hydrogen molecule by incorporating two hydrogen atoms in a stepwise manner into the cavity of some POSS (polyhedral oligomeric silsesquioxanes) compounds has been investigated by ab initio molecular orbital and ab initio molecular dynamics (AIMD) methods. The host molecules in the present reactions are two types of POSS, T(8) ([HSiO(1.5)](8)) and T(12)(D(2d)) ([HSiO(1.5)](12)). AIMD simulations were performed at the CASSCF level of theory, in which two electrons and two orbitals of the colliding hydrogen atoms are included in the active space. The trajectories were started by inserting the second hydrogen atom into the hydrogen atom-encapsulated-POSS (H + H@T(n) → H(2)@T(n); n = 8 and 12). In many cases, the gradual formation of a hydrogen molecule has been observed after frequent collisions of two hydrogen atoms within the cages. The effect of the introduction of an argon atom in T(12) is discussed as well.

  10. [Chemical Loss of Volatile Organic Compounds and Its Impact on the Formation of Ozone in Shanghai].

    PubMed

    Wang, Hong-li

    2015-09-01

    The spatial characterization of ozone (O3) and its precursors was studied based on the field measurements in urban and rural areas of Shanghai during the summer of 2014. The chemical loss of volatile organic compounds (VOCs) was estimated by the parameterization method. The mixing ratio of VOCs was 20 x 10(-9) in urban area and 17 x 10(-9) in the west rural area during the measurements. The average values of the maximum incremental reactivity were comparable in urban and rural areas, namely 5. 0 mol.mol-1 (O3/VOCs). By contrast, the chemical loss of VOCs was 8. 3 x 10(-9) in west rural area, which was two times as that in urban area. The more chemical loss of VOCs was probably one of the important reasons leading to the higher O3 concentration in west rural area. The regional transport might be important reason of the variation of O3 in the eastern coastal rural area. The chemical loss of VOCs showed good agreement with the local formation of O3 in both urban and rural areas, suggesting a similar efficiency of O3 formation from the chemical loss of VOCs. Among the chemical loss, aromatics and alkenes are the dominant VOC species of the atmospheric chemistry which accounts for more than 90% . The diurnal profile of VOC chemical loss matched well with the production of O3 with one-hour postponement.

  11. Kinetics and mechanisms of formation of earthy and musty odor compounds: Chloroanisoles during water chlorination.

    PubMed

    Zhang, Kejia; Zhou, Xinyan; Zhang, Tuqiao; Mao, Minmin; Li, Lei; Liao, Wenchao

    2016-11-01

    Chloroanisoles are often reported as off-flavor compounds which produce an earthy and musty flavors and odors in drinking water. To improve understanding and ultimately minimize the formation of 2,4-dichloroanisole (2,4-DCA), 2,6-dichloroanisole (2,6-DCA) and 2,4,6-trichloroanisole (2,4,6-TCA), which have low odor threshold concentrations (OTC: 0.03-4 ng L(-1)), a kinetic database for the chlorination of anisole was established by kinetic measurements. The results showed that HOCl reacted with anisole in acidic solution, with the hydrogen ion as an important catalyst. Quantification of product distribution of the produced chloroanisoles demonstrated that a chlorine attack in the para-position was favored over the ortho-position. A kinetic model was formulated, which permitted investigation of the relative importance of the chlorine dose and other water quality parameters including the concentrations of anisole and several metal ions, as well as temperature, on the product distribution of chloroanisoles. In general, high chlorine doses led to low concentrations of intermediates. The presence of ions such as Fe(3+) and Al(3+) facilitated the formation of chloroanisoles, but Zn(2+) and Mn(2+) did not. The kinetic model can be applied to optimize water chlorination and minimize earthy and musty odors. PMID:27561731

  12. Modelling the contribution of biogenic volatile organic compounds to new particle formation in the Jülich plant atmosphere chamber

    NASA Astrophysics Data System (ADS)

    Roldin, P.; Liao, L.; Mogensen, D.; Dal Maso, M.; Rusanen, A.; Kerminen, V.-M.; Mentel, T. F.; Wildt, J.; Kleist, E.; Kiendler-Scharr, A.; Tillmann, R.; Ehn, M.; Kulmala, M.; Boy, M.

    2015-09-01

    We used the Aerosol Dynamics gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM) to simulate the contribution of BVOC plant emissions to the observed new particle formation during photooxidation experiments performed in the Jülich Plant-Atmosphere Chamber and to evaluate how well smog chamber experiments can mimic the atmospheric conditions during new particle formation events. ADCHAM couples the detailed gas-phase chemistry from Master Chemical Mechanism with a novel aerosol dynamics and particle phase chemistry module. Our model simulations reveal that the observed particle growth may have either been controlled by the formation rate of semi- and low-volatility organic compounds in the gas phase or by acid catalysed heterogeneous reactions between semi-volatility organic compounds in the particle surface layer (e.g. peroxyhemiacetal dimer formation). The contribution of extremely low-volatility organic gas-phase compounds to the particle formation and growth was suppressed because of their rapid and irreversible wall losses, which decreased their contribution to the nano-CN formation and growth compared to the atmospheric situation. The best agreement between the modelled and measured total particle number concentration (R2 > 0.95) was achieved if the nano-CN was formed by kinetic nucleation involving both sulphuric acid and organic compounds formed from OH oxidation of BVOCs.

  13. A study on the formation of solid state nanoscale materials using polyhedral borane compounds

    NASA Astrophysics Data System (ADS)

    Romero, Jennifer V.

    The formation of boron containing materials using a variety of methods was explored. The pyrolysis of a metal boride precursor solution can be accomplished using a one-source method by combining TiCl4, B10H 14 and CH3CN in one reaction vessel and pyrolyzing it at temperatures above 900 °C. Amorphous dark blue colored films were obtained after the pyrolysis reactions. Well-defined spherical shaped grains or particles were observed by SEM. The amorphous films generated contained titanium, however, the determination of the boron content of the films was inconclusive. This one pot method making metal boride thin films has the advantage of being able to dictate the stoichiometry of the reactants. Another part of this work represents the first report of both the use of metal boride materials and the use of a titanium-based compound for the formation of nanotubes. This method provides a facile method for generating well-formed boron-containing carbon nanotubes in a "one-pot" process through an efficient aerosol process. The formation of metal boride corrosion resistant layers was also explored. It was shown that metallic substrates can be effectively boronized using paste mixtures containing boron carbide and borax. The formation of a Fe4B 2 iron boride phase was achieved, however, this iron boride phase does not give enough corrosion protection. The formation of a corrosion resistant metal boride coating with strong adhesion was accomplished by boronization of a thermal sprayed nickel layer on the surface of steel. Surfactants were explored as possible nanoreactors in which metal boride nanoparticles could be formed to use as nanotube growth catalyst via room temperature reaction. Different surfactants were used, but none of them successfully generated very well dispersed metal boride nanoparticles. Nanoparticles with varying shapes and sizes were generated which were highly amorphous. The carboxylic acid derivative of closo-C2B 10 cages was explored as a ligand in the

  14. Formation of nitrate and ammonium ions in titanium dioxide mediated photocatalytic degradation of organic compounds containing nitrogen atoms

    SciTech Connect

    Low, G.K.-C.; McEvoy, S.R.; Matthews, R.W. )

    1991-03-01

    The photocatalytic oxidation of a related series of primary, secondary, and tertiary amines and other nitrogen- and sulfur-containing organic compounds over a UV-illuminated film of TiO{sub 2} has been studied. The compounds were as follows: n-pentylamine, piperidine, pyridine, phenylalanine, desipramine, thioridazine, penicillamine, isosorbide dinitrate, 4-nitrocatechol, 2,4-dinitrophenol, cyclophosphamide, 5-fluorouracil, atrazine, ethylenediaminetetracetic acid, and tetrabutylammonium phosphate. Both ammonium and nitrate ions were formed. The relative concentration of the two ions depended on the nature of the nitrogen in a compound, but was also influenced by the illumination time and concentration of the solute. It was found that for n-pentylamine, piperidine and pyridine, the rate of formation of ammonium ions was n-pentylamine {much gt} pyridine > piperidine. The order of rates of nitrate formation was pyridine = piperidine {much gt} pentylamine. For n-pentylamine the rate of formation of ammonium ions was {approximately}100 times that of nitrate.

  15. Insight into structural, mechanical, electronic and thermodynamic properties of intermetallic phases in Zr-Sn system from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Zhan, Yongzhong; Wu, Junyan; Wei, Xuanchen

    2015-11-01

    The structural, phase stabilities, mechanical, electronic and thermodynamic properties of intermetallic phases in Zr-Sn system are investigated by using first-principles method. The equilibrium lattice constants, enthalpy of formation (ΔHform) and elastic constants are obtained and compared with available experimental and theoretical data. The configuration of Zr4Sn is measured with reasonable precision. The ΔHform of five hypothetical structures are obtained in order to find possible metastable phase for Zr-Sn system. The mechanical properties, including bulk modulus, shear modulus, Young's modulus and Poisson's ratio, are calculated by Voigt-Reuss-Hill approximation and the Zr5Sn4 and Zr5Sn3 show excellent mechanical properties. The electronic density of states for Zr5Sn4, Zr5Sn3 and cP8-Zr3Sn are calculated to further investigate the stability of intermetallic compounds. Through the quasi-harmonic Debye model, the Debye temperature, heat capacity and thermal expansion coefficient under temperature of 0-300 K and pressure of 0-50 GPa for Zr5Sn3 and Zr5Sn4 are deeply investigated.

  16. A kinetic model for the formation of hierarchical nanostructures during the evaporation of phase-forming compound solutions

    NASA Astrophysics Data System (ADS)

    Melikhov, I. V.; Alekseeva, O. V.; Rudin, V. N.; Kozlovskaya, E. D.; Noskov, A. V.

    2016-03-01

    A kinetic model for the precipitation of a dispersed compound from solutions is formulated, based on a description of the evolution in the function of its particle distribution according to its states during precipitation. A boundary problem about the precipitation of a compound during the evaporation of a solvent from a solution under conditions in which the rate of aggregate formation is high is considered. The solution to this boundary problem can be used to describe the formation of a film of polystyrene during the evaporation of its solution in toluene and o-xylene deposited onto a substrate.

  17. Compton Profile Study of Intermetallic Ti{sub 3}Al

    SciTech Connect

    Vyas, V.; Sharma, G.; Mishra, M. C.; Sharma, B. K.; Joshi, K. B.

    2011-10-20

    The Compton scattering measurement on intermetallic alloy Ti{sub 3}Al is reported in this work. The measurement is made using 59.54 keV gamma-rays from Am{sup 241} source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

  18. New candidates for the Pt8Ti structures in intermetallics

    NASA Astrophysics Data System (ADS)

    Gilmartin, Erin; Corbitt, Jacqueline; Hart, Gus

    2008-03-01

    The only known intermetallic structure with an 8:1 stoichiometry is that of Pt8Ti. Because of its uniqueness, this structure has been studied in Pt, Pd, and Ni rich systems. However, these metals have only been paired with a handful of other elements. Are there more elements that when alloyed with Pt, Pd, or Ni order with the Pt8Ti structure? We explored 40 different Pd- and Pt-based binary systems. We calculated their formation enthalpies for the Pt8Ti structure, compared the value to the tie line between pure Pd/Pt and experimentally-observed ground states. We find that there are other (beyond those experimentally observed) possible alloys with this structure. These new Pt/Pd-rich alloys could fin application in the jewelry and catalysis industries.

  19. Formation of environmentally persistent free radicals from the heterogeneous reaction of ozone and polycyclic aromatic compounds.

    PubMed

    Borrowman, Cuyler K; Zhou, Shouming; Burrow, Timothy E; Abbatt, Jonathan P D

    2016-01-01

    In the 1980s long-lived radical species were identified in cigarette tar. Since then, environmentally persistent free radicals (EPFRs) have been observed in ambient particulate matter, and have been generated in particulate matter generated from internal combustion engines. For the first time, we measure in situ the formation and decay of EPFRs through the heterogeneous reaction of ozone and several polycyclic aromatic compounds (PAC). Solid anthracene (ANT), pyrene (PY), benzo[a]pyrene (BAP), benzo[ghi]perylene (BGHIP), 1,4-naphthoquinone (1,4NQ), and 9,10-anthraquinone (AQ) were reacted with gas-phase ozone in a flow system placed in the active cavity of an electron paramagnetic resonance (EPR) spectrometer, and the formation of radicals was measured on the timescale of tens of minutes at ambient levels of ozone down to 30 ppb. For most substrates the net radical production is initially rapid, slows at intermediate times, and is followed by a slow decay. For oxidized solid BAP, radical signal persists for many days in the absence of ozone. To evaluate the effect of substrate phase, the solid PAHs were also dissolved in squalane, an organic oil inert to ozone, which yielded a much higher maximum radical concentration and faster radical decay when exposed to ozone. With higher mobility, reactants were apparently able to more easily diffuse and react with each other, yielding the higher radical concentrations. The EPR spectra exhibit three radicals types, two of which have been assigned to semiquinone species and one to a PAH-derived, carbon-centered radical. Although our system uses levels of PAC not typically found in the environment it is worth noting that the amounts of radical formed, on the order of 10(18) radicals per g, are comparable to those observed in ambient particulate matter.

  20. Formation of environmentally persistent free radicals from the heterogeneous reaction of ozone and polycyclic aromatic compounds.

    PubMed

    Borrowman, Cuyler K; Zhou, Shouming; Burrow, Timothy E; Abbatt, Jonathan P D

    2016-01-01

    In the 1980s long-lived radical species were identified in cigarette tar. Since then, environmentally persistent free radicals (EPFRs) have been observed in ambient particulate matter, and have been generated in particulate matter generated from internal combustion engines. For the first time, we measure in situ the formation and decay of EPFRs through the heterogeneous reaction of ozone and several polycyclic aromatic compounds (PAC). Solid anthracene (ANT), pyrene (PY), benzo[a]pyrene (BAP), benzo[ghi]perylene (BGHIP), 1,4-naphthoquinone (1,4NQ), and 9,10-anthraquinone (AQ) were reacted with gas-phase ozone in a flow system placed in the active cavity of an electron paramagnetic resonance (EPR) spectrometer, and the formation of radicals was measured on the timescale of tens of minutes at ambient levels of ozone down to 30 ppb. For most substrates the net radical production is initially rapid, slows at intermediate times, and is followed by a slow decay. For oxidized solid BAP, radical signal persists for many days in the absence of ozone. To evaluate the effect of substrate phase, the solid PAHs were also dissolved in squalane, an organic oil inert to ozone, which yielded a much higher maximum radical concentration and faster radical decay when exposed to ozone. With higher mobility, reactants were apparently able to more easily diffuse and react with each other, yielding the higher radical concentrations. The EPR spectra exhibit three radicals types, two of which have been assigned to semiquinone species and one to a PAH-derived, carbon-centered radical. Although our system uses levels of PAC not typically found in the environment it is worth noting that the amounts of radical formed, on the order of 10(18) radicals per g, are comparable to those observed in ambient particulate matter. PMID:26603953

  1. Oral administration of the broad-spectrum antibiofilm compound toremifene inhibits Candida albicans and Staphylococcus aureus biofilm formation in vivo.

    PubMed

    De Cremer, Kaat; Delattin, Nicolas; De Brucker, Katrijn; Peeters, Annelies; Kucharíková, Soña; Gerits, Evelien; Verstraeten, Natalie; Michiels, Jan; Van Dijck, Patrick; Cammue, Bruno P A; Thevissen, Karin

    2014-12-01

    We here report on the in vitro activity of toremifene to inhibit biofilm formation of different fungal and bacterial pathogens, including Candida albicans, Candida glabrata, Candida dubliniensis, Candida krusei, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. We validated the in vivo efficacy of orally administered toremifene against C. albicans and S. aureus biofilm formation in a rat subcutaneous catheter model. Combined, our results demonstrate the potential of toremifene as a broad-spectrum oral antibiofilm compound. PMID:25288093

  2. Brushing up on the history of intermetallics in dentistry

    NASA Astrophysics Data System (ADS)

    Waterstrat, Richard M.

    1990-03-01

    Employing a silver-tin-mercury intermetallic to repair cavities may seem a little unusual, but intermetallics are quite common in dentistry, ranging from gold crowns to braces. Although the human mouth can be unfriendly territory for a brittle intermetallic alloy, dental amalgam has been around since 659 A.D., and its technology has been developed to the point where a filling can be expected to last 30 years or more.

  3. Characterization of Atmospheric Volatile Organic Compounds in the North Dakota Bakken Formation

    NASA Astrophysics Data System (ADS)

    Sive, B. C.; Zhou, Y.; Day, D.; Desyaterik, Y.; Evanoski-Cole, A. R.; Gebhart, K.; Hecobian, A.; Li, Y.; Malm, W. C.; Prenni, A. J.; Schichtel, B. A.; Schurman, M. I.; Sullivan, A.; Vimont, J.; Collett, J. L., Jr.

    2014-12-01

    A field campaign was conducted from 23 November 2013 through 28 March 2014 in the Bakken formation of North Dakota to investigate the impacts of rapidly increasing oil and gas production operations on air quality throughout the region. Whole air samples were collected at three different sites during the study period for volatile organic compound (VOC) measurements. The main sampling location was the north unit of Theodore Roosevelt National Park (THRO), where one daytime and one nighttime sample were collected each day throughout the campaign period. Daytime samples were also collected every second day at the Fort Union Trading Post National Historic Site (FOUS) and once a week at the Medicine Lake National Wildlife Refuge, MT. A signature of elevated nonmethane hydrocarbon (NMHC) mixing ratios was observed throughout the campaign at all three sites; THRO and FOUS had the highest levels as they are located in high well density areas. Moreover, the C2-C5 alkane mixing ratios were approximately an order of magnitude greater than regional background levels. Light alkane mixing ratios at THRO, the most impacted site, were similar to those at urban sites influenced by petrochemical industry emissions, with ethane and propane reaching maximums of 95 ppbv and 164 ppbv, respectively. The i-pentane to n-pentane ratio for all sites was ~0.75, clearly demonstrating the widespread impact from oil and gas production emissions throughout the region. Alkanes dominated the hydroxyl radical reactivity, and their overall influence on regional air quality will be explored.

  4. Photochemical formation of hydroxyl radical in red-soil-polluted seawater - effects of dissolved organic compounds

    NASA Astrophysics Data System (ADS)

    Uehara, M.; Arakaki, T.

    2006-12-01

    Development of pineapple farmlands and construction of recreational facilities caused runoff of red soil into the coastal ocean (locally termed as red soil pollution) in the north of Okinawa Island, Japan. Red soil is acidic and contains a few percent of iron oxide. We were interested in the formation of hydroxyl radical (·OH), the most potent oxidant in the environment, from the photo-Fenton reaction (reaction between Fe(II) and HOOH) in red-soil-polluted seawater. Various artificial seawater solutions were prepared by adding red soil, HOOH, and/or humic acid to clean seawater, and were used for photochemical experiments. Commercially available humic acid was used to represent natural organic compounds. All the solutions were filtered through 0.45 micron filter before conducting photochemical experiments. Comparisons among the solutions indicated that dissolved chemicals from the red-soil only slightly increased the OH radical photoformation. Photoformation rates of OH radicals of the HOOH + red soil solutions were similar to the calculated rates from direct photolysis of HOOH. Furthermore, addition of humic acid to the HOOH + red soil solutions did not significantly enhance the photo-Fenton reaction, suggesting that Fe(II), even if it had been formed, did not react with HOOH to form OH radicals at detectable level in seawater.

  5. An Analysis of Intermetallic Bonding between a Ring Carrier and an Aluminum Piston Alloy

    NASA Astrophysics Data System (ADS)

    Manasijević, Srećko; Dolić, Natalija; Zovko Brodarac, Zdenka; Djurdjević, Mile; Radiša, Radomir

    2014-09-01

    This paper presents the results of an analysis of the formation of an intermetallic bond between a ring carrier and an aluminum piston alloy. The ring carrier is made of austenitic cast iron (Ni-Resist) to increase the wear resistance of the first ring groove and is applied in highly loaded diesel engines. The most important thing is that the Ni-Resist (ferrous) must be bonded with a non-ferrous piston material during the casting of the piston. A metallographic investigation using an optical microscope in combination with the SEM/EDS analysis of the quality of the intermetallic bonding layer was done. The test results show that if the proper conditions are met, then the preparation of the ring carrier can be made successfully, as can the formation of the metal connection between the two materials of different qualities.

  6. A magnetization study of RCo 12B 6 intermetallics

    NASA Astrophysics Data System (ADS)

    Mittag, M.; Rosenberg, M.; Buschow, K. H. J.

    1989-11-01

    The magnetic properties of polycrystalline intermetallics RCo 12B 6 with R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm have been studied in the temperature range 3-300 K and in fields up to 2 T. All compounds order magnetically between Tc=134.3 K for CeCo 12B 6 and Tc=162 K for GdCo 12B 6. YCo 12B 6 has an average Co moment of 0.42μ B. Since the Co moment is constant for all samples the R moments can be easily obtained and they are in good agreement with free R 3+ ion values. Ce is quadripositive in CeCo 12B 6 and therefore nonmagnetic. All light rare-earth compounds are ferromagnetic, while all heavy rare-earth compounds are ferrimagnetic with compensation points between Tcomp=11.6 K ( TmCo12B6) and Tcomp=82.8 K ( TbCo12B6). In the paramagnetic state an effective magnetic moment of 1.94μ B per Co atom has been found. The mean-field approximation yields a 3d-3d exchange integral of {J CoCo}/{k B}=110 K . The 3d-4f exchange integral is much smaller and equal to about {J RCo}/{k B}=6 K .

  7. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  8. Study of the formation of carbonyl compounds in edible oils and fats by 1H-NMR and FTIR

    NASA Astrophysics Data System (ADS)

    Moya Moreno, M. C. M.; Mendoza Olivares, D.; Amézquita López, F. J.; Peris Martínez, V.; Bosch Reig, F.

    1999-05-01

    Oils and fats start decomposing from the moment they are isolated from their natural environment. Heating accelerates oxidative rancidity and frying at high temperatures produces thermal degradation with the formation of decomposition products, such as aldehydes, ketones, free acids and hydroxilic compounds that in high levels can be harmful to human health. The decomposition products formed up to 300°C were determined by means of 1H-NMR spectroscopy and an FTIR spectroscopic method was developed for the quantification of carbonyl compounds generated during heating. The results show that there is a formation of carbonyl compounds starting at 150°C and when the sample was heated at 300°C for 40 min, the following contents (expressed as butyraldehyde mass fraction) were found: olive oil 10.5%, sunflower oil 11.3%, corn oil 3.0%, seeds oil (sunflower, safflower and canola seed) 6.6% and lard 3.5%.

  9. Trace elements and the mechanical properties of intermetallic compounds

    SciTech Connect

    Lin, Hui; Pope, D.P.; George, E.P.

    1995-02-01

    In this paper the brittleness of grain boundaries in Ni{sub 3}Al is discussed with special emphasis on the effects of B. The effects of alloy stoichiometry, environment (hydrogen), grain boundary character and B levels are described and interpreted in terms of current theories. It is shown that the grain boundaries in Ni{sub 3}Al are intrinsically weaker than the bulk (the weakness is not an impurity effect), the weakness is exacerbated by atmospheric moisture, and that B in the boundaries both increases the intrinsic strength of the boundaries and reduces the deleterious effects of atmospheric moisture. Only low angle boundaries and twin boundaries are intrinsically strong in Ni{sub 3}Al, even in the absence of B.

  10. Addressing Machining Issues for the Intermetallic Compound 60-NITINOL

    NASA Technical Reports Server (NTRS)

    Stanford, Malcolm K.; Wozniak, Walter A.; McCue, Terry R.

    2012-01-01

    60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

  11. Effects of Molybdate, Tungstate, and Selenium Compounds on Formate Dehydrogenase and Other Enzyme Systems in Escherichia coli1

    PubMed Central

    Enoch, Harry G.; Lester, Robert L.

    1972-01-01

    The role of selenium and molybdenum in the metabolism of Escherichia coli was explored by growing cells in a simple salts medium and examining the metabolic consequences of altering the concentration of molybdenum and selenium compounds in the medium. The addition of tungstate increased the molybdate deficiency of this medium, as reflected by lowered levels of enzyme systems previously recognized to require compounds of molybdenum and selenium for their formation [formate-dependent oxygen reduction, formate dehydrogenase (FDH) (EC 1.2.2.1), and nitrate reductase (EC 1.9.6.1)]. The requirement for selenium and molybdenum appears to be unique to the enzymes of formate and nitrate metabolism since molybdate- and selenite-deficient medium had no effect on the level of several dehydrogenase and oxidase systems, for which the electron donors were reduced nicotinamide adenine dinucleotide, succinate, d- or l-lactate, and glycerol. In addition, no effect was observed on the growth rate or cell yield with any carbon source tested (glucose, glycerol, dl-lactate, acetate, succinate, and l-malate) when the medium was deficient in molybdenum and selenium. dl-Selenocystine was about as effective as selenite in stimulating the formation of formate dehydrogenase, whereas dl-selenomethionine was only 1% as effective. In aerobic cells, an amount of FDH was formed such that 3,200 or 3,800 moles of formate were oxidized per min per mole of added selenium (added as dl-selenocystine or selenite, respectively). PMID:4555402

  12. Quorum sensing signalling and biofilm formation of brewery-derived bacteria, and inhibition of signalling by natural compounds.

    PubMed

    Priha, O; Virkajärvi, V; Juvonen, R; Puupponen-Pimiä, R; Nohynek, L; Alakurtti, S; Pirttimaa, M; Storgårds, E

    2014-11-01

    Bacteria use quorum sensing signalling in various functions, e.g. while forming biofilms, and inhibition of this signalling could be one way to control biofilm formation. The aim of this study was to evaluate the production of signalling molecules and its correlation with the biofilm formation capability of bacteria isolated from brewery filling process. A further aim was to study berry extracts and wood-derived terpenes for their possible quorum sensing inhibitory effects. Out of the twenty bacteria studied, five produced short-chain and five long-chain AHL (acyl homoserine lactone) signalling molecules when tested with the Chromobacterium violaceum CV026 reporter bacterium. Production of AI-2 (autoinducer-2) signalling molecules was detected from nine strains with the Vibrio harveyi BB170 bioassay. Over half of the strains produced biofilm in the microtitre plate assay, but the production of AHL and AI-2 signalling molecules and biofilm formation capability did not directly correlate with each other. Out of the 13 berry extracts and wood-derived terpenes screened, four compounds decreased AHL signalling without effect on growth. These were betulin, raspberry extract and two cloudberry extracts. The effect of these compounds on biofilm formation of the selected six bacterial strains varied. The phenolic extract of freeze-dried cloudberry fruit caused a statistically significant reduction of biofilm formation of Obesumbacterium proteus strain. Further experiments should aim at identifying the active compounds and revealing whether quorum sensing inhibition causes structural changes in the biofilms formed. PMID:24944110

  13. Efficacy of zinc compounds in controlling Fusarium head blight and deoxynivalenol formation in wheat (Triticum aestivum L.).

    PubMed

    Savi, Geovana D; Piacentini, Karim C; de Souza, Stephany Ramos; Costa, Maíra E B; Santos, Cristina M R; Scussel, Vildes M

    2015-07-16

    The efficiency of zinc compounds (zinc sulfate, ZnSO4 and zinc oxide, ZnO in regular and nanosize, respectively) on wheat plants was evaluated against growth of Fusarium graminearum and DON formation. In addition, any possible effects on the grain microstructures were observed by scanning electron microscopy (SEM), and the remaining residue of Zn on wheat plants was analyzed. The plants were inoculated with F. graminearum and treated with Zn compounds (100mM) onto spikelets at the anthesis stage. When wheat plants reached maturation, grains were harvested and evaluated for Fusarium (number of colonies, CFU/g), DON formation, and SEM observation, followed by determination of possible remaining Zn residue. The groups treated with ZnSO4 and ZnO-NP showed a reduction in number of CFU of F. graminearum when compared to the control. Similarly for DON formation, i.e. the toxin was reduced to non-detected levels in the treated group. ZnO-NP efficiently reduced F. graminearum and DON formation in the grains at low concentration. Zn remained within the international recommended level for consumption and the treatment did not cause any damage to wheat grains. New strategies of control using Zn compounds in addition to conventional treatments could increase the efficiency against FBH and DON formation.

  14. High-Performance Pd3Pb Intermetallic Catalyst for Electrochemical Oxygen Reduction.

    PubMed

    Cui, Zhiming; Chen, Hao; Zhao, Mengtian; DiSalvo, Francis J

    2016-04-13

    Extensive efforts to develop highly active and strongly durable electrocatalyst for oxygen reduction are motivated by a need for metal-air batteries and fuel cells. Here, we report a very promising catalyst prototype of structurally ordered Pd-based alloys, Pd3Pb intermetallic compound. Such structurally ordered Pd3Pb/C exhibits a significant increase in mass activity. More importantly, compared to the conventional Pt/C catalysts, ordered Pd3Pb/C is highly durable and exhibits a much longer cycle life and higher cell efficiency in Zn-air batteries. Interestingly, ordered Pd3Pb/C possesses very high methanol tolerance during electrochemical oxygen reduction, which make it an excellent methanol-tolerant cathode catalyst for alkaline polymer electrolyte membrane fuel cells. This study provides a promising route to optimize the synthesis of ordered Pd-based intermetallic catalysts for fuel cells and metal-air batteries.

  15. High-Performance Pd3Pb Intermetallic Catalyst for Electrochemical Oxygen Reduction.

    PubMed

    Cui, Zhiming; Chen, Hao; Zhao, Mengtian; DiSalvo, Francis J

    2016-04-13

    Extensive efforts to develop highly active and strongly durable electrocatalyst for oxygen reduction are motivated by a need for metal-air batteries and fuel cells. Here, we report a very promising catalyst prototype of structurally ordered Pd-based alloys, Pd3Pb intermetallic compound. Such structurally ordered Pd3Pb/C exhibits a significant increase in mass activity. More importantly, compared to the conventional Pt/C catalysts, ordered Pd3Pb/C is highly durable and exhibits a much longer cycle life and higher cell efficiency in Zn-air batteries. Interestingly, ordered Pd3Pb/C possesses very high methanol tolerance during electrochemical oxygen reduction, which make it an excellent methanol-tolerant cathode catalyst for alkaline polymer electrolyte membrane fuel cells. This study provides a promising route to optimize the synthesis of ordered Pd-based intermetallic catalysts for fuel cells and metal-air batteries. PMID:26848634

  16. Energetic Properties of Rocket Propellants Evaluated through the Computational Determination of Heats of Formation of Nitrogen-Rich Compounds.

    PubMed

    Forquet, Valérian; Miró Sabaté, Carles; Chermette, Henry; Jacob, Guy; Labarthe, Émilie; Delalu, Henri; Darwich, Chaza

    2016-03-01

    The use of ab initio and DFT methods to calculate the enthalpies of formation of solid ionic compounds is described. The results obtained from the calculations are then compared with those from experimental measurements on nitrogen-rich salts of the 2,2-dimethyltriazanium cation (DMTZ) synthesized in our laboratory and on other nitrogen-rich ionic compounds. The importance of calculating accurate volumes and lattice enthalpies for the determination of heats of formation is also discussed. Furthermore, the crystal structure and hydrogen-bonding networks of the nitroformate salt of the DMTZ cation is described in detail. Lastly, the theoretical heats of formation were used to calculate the specific impulses (Isp ) of the salts of the DMTZ cation in view of a prospective application in propellant formulations.

  17. Prompt HO2 formation following the reaction of OH with aromatic compounds under atmospheric conditions.

    PubMed

    Nehr, Sascha; Bohn, Birger; Wahner, Andreas

    2012-06-21

    The secondary formation of HO(2) radicals following OH + aromatic hydrocarbon reactions in synthetic air under normal pressure and temperature was investigated in the absence of NO after pulsed production of OH radicals. OH and HO(x) (=OH + HO(2)) decay curves were recorded using laser-induced fluorescence after gas-expansion. The prompt HO(2) yields (HO(2) formed without preceding NO reactions) were determined by comparison to results obtained with CO as a reference compound. This approach was recently introduced and applied to the OH + benzene reaction and was extended here for a number of monocyclic aromatic hydrocarbons. The measured HO(2) formation yields are as follows: toluene, 0.42 ± 0.11; ethylbenzene, 0.53 ± 0.10; o-xylene, 0.41 ± 0.08; m-xylene, 0.27 ± 0.06; p-xylene, 0.40 ± 0.09; 1,2,3-trimethylbenzene, 0.31 ± 0.06; 1,2,4-trimethylbenzene, 0.37 ± 0.09; 1,3,5-trimethylbenzene, 0.29 ± 0.08; hexamethylbenzene, 0.32 ± 0.08; phenol, 0.89 ± 0.29; o-cresol, 0.87 ± 0.29; 2,5-dimethylphenol, 0.72 ± 0.12; 2,4,6-trimethylphenol, 0.45 ± 0.13. For the alkylbenzenes HO(2) is the proposed coproduct of phenols, epoxides, and possibly oxepins formed in secondary reactions with O(2). In most product studies the only quantified coproducts were phenols whereas only a few studies reported yields of epoxides. Oxepins have not been observed so far. Together with the yields of phenols from other studies, the HO(2) yields determined in this work set an upper limit to the combined yields of epoxides and oxepins that was found to be significant (≤0.3) for all investigated alkylbenzenes except m-xylene. For the hydroxybenzenes the currently proposed HO(2) coproducts are dihydroxybenzenes. For phenol and o-cresol the determined HO(2) yields are matching the previously reported dihydroxybenzene yields, indicating that these are the only HO(2) forming reaction channels. For 2,5-dimethylphenol and 2,4,6-trimethylphenol no complementary product studies are available.

  18. High-pressure processing decelerates lipolysis and formation of volatile compounds in ovine milk blue-veined cheese.

    PubMed

    Calzada, J; Del Olmo, A; Picon, A; Gaya, P; Nuñez, M

    2013-01-01

    Enzyme-rich cheeses are prone to over-ripening during refrigerated storage. Blue-veined cheeses fall within this category because of the profuse growth of Penicillium roqueforti in their interior, which results in the production of highly active proteinases, lipases, and other enzymes responsible for the formation of a great number of flavor compounds. To control the excessive formation of free fatty acids (FFA) and volatile compounds, blue-veined cheeses were submitted to high-pressure processing (HPP) at 400 or 600 MPa on d 21, 42, or 63 after manufacture. Cheeses were ripened for 30d at 10°C and 93% relative humidity, followed by 60 d at 5°C, and then held at 3°C until d 360. High-pressure processing influenced the concentrations of acetic acid and short-chain, medium-chain, and long-chain FFA. The effect was dependent on treatment conditions (pressure level and cheese age at the time of treatment). The lowest concentrations of acetic acid and FFA were recorded for cheeses treated at 600 MPa on d 21; these cheeses showed the lowest esterase activity values. Acetic acid and all FFA groups increased during ripening and refrigerated storage. The 102 volatile compounds detected in cheese belonged to 10 chemical groups (5 aldehydes, 12 ketones, 17 alcohols, 12 acids, 35 esters, 9 hydrocarbons, 5 aromatic compounds, 3 nitrogen compounds, 3 terpenes, and 1 sulfur compound). High-pressure processing influenced the levels of 97 individual compounds, whereas 68 individual compounds varied during refrigerated storage. Total concentrations of all groups of volatile compounds were influenced by HPP, but only ketones, acids, esters, and sulfur compounds varied during refrigerated storage. The lowest total concentrations for most groups of volatile compounds were recorded for the cheese pressurized at 600 MPa on d 21. A principal component analysis combining total concentrations of groups of FFA and volatile compounds discriminated cheeses by age and by the pressure level

  19. Deformation-Induced Amorphization of Copper-Titanium Intermetallics

    NASA Astrophysics Data System (ADS)

    Askenazy, Philip Douglas

    Two methods of inducing amorphization in Cu-Ti intermetallic compounds by mechanical means have been investigated. Ingots of compositions Cu_{35}Ti _{65} and Cu_ {33.3}Ti_{66.7} were rapidly quenched into ribbons. The microstructure consisted largely of microcrystals in an amorphous matrix, which were either quenched in or grown by annealing. The ribbons were cold-rolled, which reduced their effective thickness by a factor of about 8. The status of the intermetallic compound CuTi_2 was monitored by x-ray diffraction and transmission electron microscopy (TEM). The crystals were found to amorphize as rolling progressed. This behavior was not reproduced in polycrystalline samples that had no amorphous matrix present initially. The presence of the amorphous phase is thus necessary for amorphization of the crystal: it eliminates the need to nucleate the new glass, and it prevents the ribbon from disintegrating at high deformation stages. It may also change the deformation mechanism that occurs in the crystals, retarding the onset of amorphization. Diffuse scattering in close-packed directions is similar to that seen in electron irradiation experiments. It is postulated that the chemical disorder present in antiphase boundaries caused by deformation raises the free energy of the crystal higher than that of the amorphous phase. Ingots of the same compound were worn against each other in a custom-built wear apparatus. The design eliminates iron contamination of the wear sample and requires relatively small quantities of material. Alteration of the surface structure was monitored by plane-view and cross -sectional TEM. Larger subsurface crystals exhibit diffuse scattering, similar to that found in the rolled samples. A wide range of grain sizes was observed, due to the inhomogeneous nature of the wear process. An unusual phase was observed at the surface, consisting of a nanometer-scale mixture of aligned nanocrystalline regions and disordered areas. Some amorphous phase is

  20. Compound-Specific Isotopic Analysis of Meteoritic Amino Acids as a Tool for Evaluating Potential Formation Pathways

    NASA Technical Reports Server (NTRS)

    Elsila, Jamie E.; Burton, Aaron S.; Callahan, Michael C.; Charnley, Steven B.; Glavin, Daniel P.; Dworkin, Jason P.

    2012-01-01

    Measurements of stable hydrogen, carbon, and nitrogen isotopic ratios (delta D, delta C-13, delta N-15) of organic compounds can reveal information about their origin and formation pathways. Several formation mechanisms and environments have been postulated for the amino acids detected in carbonaceous chondrites. As each proposed mechanism utilizes different precursor molecules, the isotopic signatures of the resulting amino acids may point towards the most likely of these proposed pathways. The technique of gas chromatography coupled with mass spectrometry and isotope ratio mass spectrometry provides compound-specific structural and isotopic information from a single splitless injection, enhancing the amount of information gained from small amounts of precious samples such as carbonaceous chondrites. We have applied this technique to measure the compound-specific C, N, and H isotopic ratios of amino acids from seven CM and CR carbonaceous chondrites. We are using these measurements to evaluate predictions of expected isotopic enrichments from potential formation pathways and environments, leading to a better understanding of the origin of these compounds.

  1. Formation of a compound flux rope by the merging of two filament channels, the associated dynamics, and its stability

    SciTech Connect

    Joshi, Navin Chandra; Inoue, Satoshi; Magara, Tetsuya E-mail: njoshi98@gmail.com

    2014-11-01

    We present observations of compound flux rope formation, which occurred on 2014 January 1, via merging of two nearby filament channels, the associated dynamics, and its stability using multiwavelength data. We also discuss the dynamics of cool and hot plasma moving along the newly formed compound flux rope. The merging started after the interaction between the southern leg of the northward filament and the northern leg of the southward filament at ≈01:21 UT and continued until a compound flux rope formed at ≈01:33 UT. During the merging, the cool filament plasma heated up and started to move along both sides of the compound flux rope, i.e., toward the north (≈265 km s{sup –1}) and south (≈118 km s{sup –1}) from the point of merging. After traveling a distance of ≈150 Mm toward the north, the plasma cooled down and started to return back to the south (≈14 km s{sup –1}) after ≈02:00 UT. The observations provide a clear example of compound flux rope formation via merging of two different flux ropes and the occurrence of a flare through tether cutting reconnection. However, the compound flux rope remained stable in the corona and had a confined eruption. The coronal magnetic field decay index measurements revealed that both the filaments and the compound flux rope axis lie within the stability domain (decay index <1.5), which may be the possible cause for their stability. The present study also deals with the relationship between the filament's chirality (sinistral) and the helicity (positive) of the surrounding flux rope.

  2. Intermetallics Characterization of Lead-Free Solder Joints under Isothermal Aging

    NASA Astrophysics Data System (ADS)

    Choubey, Anupam; Yu, Hao; Osterman, Michael; Pecht, Michael; Yun, Fu; Yonghong, Li; Ming, Xu

    2008-08-01

    Solder interconnect reliability is influenced by environmentally imposed loads, solder material properties, and the intermetallics formed within the solder and the metal surfaces to which the solder is bonded. Several lead-free metallurgies are being used for component terminal plating, board pad plating, and solder materials. These metallurgies react together and form intermetallic compounds (IMCs) that affect the metallurgical bond strength and the reliability of solder joint connections. This study evaluates the composition and extent of intermetallic growth in solder joints of ball grid array components for several printed circuit board pad finishes and solder materials. Intermetallic growth during solid state aging at 100°C and 125°C up to 1000 h for two solder alloys, Sn-3.5Ag and Sn-3.0Ag-0.5Cu, was investigated. For Sn-3.5Ag solder, the electroless nickel immersion gold (ENIG) pad finish was found to result in the lowest IMC thickness compared to immersion tin (ImSn), immersion silver (ImAg), and organic solderability preservative (OSP). Due to the brittle nature of the IMC, a lower IMC thickness is generally preferred for optimal solder joint reliability. A lower IMC thickness may make ENIG a desirable finish for long-life applications. Activation energies of IMC growth in solid-state aging were found to be 0.54 ± 0.1 eV for ENIG, 0.91 ± 0.12 eV for ImSn, and 1.03 ± 0.1 eV for ImAg. Cu3Sn and Cu6Sn5 IMCs were found between the solder and the copper pad on boards with the ImSn and ImAg pad finishes. Ternary (Cu,Ni)6Sn5 intermetallics were found for the ENIG pad finish on the board side. On the component side, a ternary IMC layer composed of Ni-Cu-Sn was found. Along with intermetallics, microvoids were observed at the interface between the copper pad and solder, which presents some concern if devices are subject to shock and vibration loading.

  3. Image encryption schemes for joint photographic experts group and graphics interchange format formats based on three-dimensional baker with compound chaotic sequence generator

    NASA Astrophysics Data System (ADS)

    Ji, Shiyu; Tong, Xiaojun; Zhang, Miao

    2013-01-01

    We propose several methods to transplant the compound chaotic image encryption scheme with permutation based on three-dimensional (3-D) baker onto image formats such as the joint photographic experts group (JPEG) and graphics interchange format (GIF). The new methods avert the discrete cosine transform and quantization, which result in floating point precision loss, and succeed to encrypt and decrypt JPEG images lossless. The ciphered JPEG images generated by our solution own much better randomness than most other existing schemes. Our proposed method for GIF keeps the property of animation successfully. The security test results indicate the proposed methods have high security, and the speed of our algorithm is faster than classical solutions. Since JPEG and GIF image formats are popular contemporarily, we show that the prospect of chaotic image encryption is promising.

  4. Nonstoichiometry of Al-Zr intermetallic phases

    SciTech Connect

    Radmilovic, V.; Thomas, G.

    1994-06-01

    Nonstoichiometry of metastable cubic {beta}{prime} and equilibrium tetragonal {beta} Al-Zr intermetallic phases of the nominal composition Al{sub 3}Zr in Al-rich alloys has been extensively studied. It is proposed that the ``dark contrast`` of {beta}{prime} core in {beta}{prime}/{sigma}{prime} complex precipitates, in Al-Li-Zr based alloys, is caused by incorporation of Al and Li atoms into the {beta}{prime} phase on Zr sublattice sites, forming nonstoichiometric Al-Zr intermetallic phases, rather than by Li partitioning only. {beta}{prime} particles contain very small amounts of Zr, approximately 5 at.%, much less than the stoichiometric 25 at.% in the Al{sub 3}Zr metastable phase. These particles are, according to simulation of high resolution images, of the Al{sub 3}(Al{sub 0.4}Li{sub 0.4}Zr{sub 0.2}) type. Nonstoichiometric particles of average composition Al{sub 4}Zr and Al{sub 6}Zr are observed also in the binary Al-Zr alloy, even after annealing for several hours at 600{degree}C.

  5. Formation of aromatic compounds from carbohydrates. X reaction of xylose, glucose, and glucuronic acid in acidic solution at 300C

    SciTech Connect

    Theander, O.; Nelson, D.A.; Hallen, R.T.

    1987-04-01

    For several years our respective groups have investigated the formation of aromatic compounds from carbohydrates in aqueous solution at various pH-values under reflux or hydrothermolytic conditions. For instance, previous papers in this series concerned the degradation of hexoses, pentoses, erythrose, dihydroxyacetone, and hexuronic acids to phenolic and enolic components. Of particular interest were the isolation and identification of catechols, an acetophenone, and chromones from pentoses and hexuronic acids at pH 4.5. The formation of these compounds, as well as reductic acid, was found to be more pronounced than that of 2-furaldehyde under acidic conditions. The aromatic precursors of 3 and 4 were also isolated from these reaction mixtures. This is in contrast to the high yields of 2 obtained from pentoses and hexuronic acids at very low pH.

  6. Formation of green-blue compounds in Brassica rapa root by high pressure processing and subsequent storage.

    PubMed

    Ueno, Shigeaki; Hayashi, Mayumi; Shigematsu, Toru; Fujii, Tomoyuki

    2009-04-23

    The effect of high pressure treatment on biochemical changes during storage was investigated using Brassica rapa root. High pressure treated samples with 400 and 600 MPa formed unique green-blue color during 7-d storage at 4 degrees C. The mechanism of green-blue compound formation would be based on biochemical pathway for a unique green-blue pigment synthesis, containing O2-dependent steps and possibly enzymatic reactions.

  7. Inhibition of Biofilm Formation, Quorum Sensing and Infection in Pseudomonas aeruginosa by Natural Products-Inspired Organosulfur Compounds

    PubMed Central

    Cady, Nathaniel C.; McKean, Kurt A.; Behnke, Jason; Kubec, Roman; Mosier, Aaron P.; Kasper, Stephen H.; Burz, David S.; Musah, Rabi A.

    2012-01-01

    Using a microplate-based screening assay, the effects on Pseudomonas aeruginosa PAO1 biofilm formation of several S-substituted cysteine sulfoxides and their corresponding disulfide derivatives were evaluated. From our library of compounds, S-phenyl-L-cysteine sulfoxide and its breakdown product, diphenyl disulfide, significantly reduced the amount of biofilm formation by P. aeruginosa at levels equivalent to the active concentration of 4-nitropyridine-N-oxide (NPO) (1 mM). Unlike NPO, which is an established inhibitor of bacterial biofilms, our active compounds did not reduce planktonic cell growth and only affected biofilm formation. When used in a Drosophila-based infection model, both S-phenyl-L-cysteine sulfoxide and diphenyl disulfide significantly reduced the P. aeruginosa recovered 18 h post infection (relative to the control), and were non-lethal to the fly hosts. The possibility that the observed biofilm inhibitory effects were related to quorum sensing inhibition (QSI) was investigated using Escherichia coli-based reporters expressing P. aeruginosa lasR or rhIR response proteins, as well as an endogenous P. aeruginosa reporter from the lasI/lasR QS system. Inhibition of quorum sensing by S-phenyl-L-cysteine sulfoxide was observed in all of the reporter systems tested, whereas diphenyl disulfide did not exhibit QSI in either of the E. coli reporters, and showed very limited inhibition in the P. aeruginosa reporter. Since both compounds inhibit biofilm formation but do not show similar QSI activity, it is concluded that they may be functioning by different pathways. The hypothesis that biofilm inhibition by the two active compounds discovered in this work occurs through QSI is discussed. PMID:22715388

  8. Synthesis and densification of Ni{sub 3}(Si, Ti) intermetallics by hot isostatic pressing

    SciTech Connect

    Van Dyck, S.; Delaey, L.; Froyen, L.; Buekenhout, L.

    1996-12-31

    The production of complex parts from Ni{sub 3}(Si, Ti) intermetallic materials by reactive powder metallurgy offers significant advantages over more conventional processing techniques. The main problem associated with reactive powder metallurgy is controlling the exothermic reaction accompanying the synthesis of the intermetallic compound. The uncontrolled release of heat during the conversion of the reactants into nickel silicide leads to unacceptable deformation and melting of the part. The thermal evolution of a part during reactive synthesis of the intermetallic phase is described based on kinetic and heat transfer equations, giving the temperature and phase change as a function of the applied temperature cycle and the mass and size of the part under consideration. From this model, methods for controlling the exothermic reaction during synthesis are derived. When preparing nickel silicides by reactive powder metallurgy, the application of external pressure is required to eliminate porosity and to obtain good mechanical properties. The properties of materials produced by hot isostatic pressing, with different methods of reaction control, are compared to materials prepared from prealloyed powders. It is shown that by reactive HIP, materials can be obtained with a fracture strength exceeding 2,000 MPa.

  9. Insights into the Formation and Evolution of Individual Compounds in the Particulate Phase during Aromatic Photo-Oxidation.

    PubMed

    Pereira, Kelly L; Hamilton, Jacqueline F; Rickard, Andrew R; Bloss, William J; Alam, Mohammed S; Camredon, Marie; Ward, Martyn W; Wyche, Kevin P; Muñoz, Amalia; Vera, Teresa; Vázquez, Mónica; Borrás, Esther; Ródenas, Milagros

    2015-11-17

    Secondary organic aerosol (SOA) is well-known to have adverse effects on air quality and human health. However, the dynamic mechanisms occurring during SOA formation and evolution are poorly understood. The time-resolved SOA composition formed during the photo-oxidation of three aromatic compounds, methyl chavicol, toluene and 4-methyl catechol, were investigated at the European Photoreactor. SOA was collected using a particle into liquid sampler and analyzed offline using state-of-the-art mass spectrometry to produce temporal profiles of individual photo-oxidation products. In the photo-oxidation of methyl chavicol, 70 individual compounds were characterized and three distinctive temporal profile shapes were observed. The calculated mass fraction (Ci,aer/COA) of the individual SOA compounds showed either a linear trend (increasing/decreasing) or exponential decay with time. Substituted nitrophenols showed an exponential decay, with the nitro-group on the aromatic ring found to control the formation and loss of these species in the aerosol phase. Nitrophenols from both methyl chavicol and toluene photo-oxidation experiments showed a strong relationship with the NO2/NO (ppbv/ppbv) ratio and were observed during initial SOA growth. The location of the nitrophenol aromatic substitutions was found to be critically important, with the nitrophenol in the photo-oxidation of 4-methyl catechol not partitioning into the aerosol phase until irradiation had stopped; highlighting the importance of studying SOA formation and evolution at a molecular level.

  10. Zintl and intermetallic phases grown from calcium/lithium flux

    NASA Astrophysics Data System (ADS)

    Blankenship, Trevor

    Metal flux synthes is a useful alternative method to high temperature solid state synthesis; it allows easy diffusion of reactants at lower temperatures, and presents favorable conditions for crystal growth. A mixed flux of calcium and lithium in a 1:1 ratio was explored in this work; this mixture melts at 300°C and is an excellent solvent for main group elements and CaH 2. Reactions of p-block elements in a 1:1 Ca/Li flux have produced several new intermetallic and Zintl phases. Electronegative elements from groups 14 and 15 are reduced to anions in this flux, yielding charge-balanced products. More electropositive metals from group 13 are not fully reduced; the resulting products are complex intermetallics. The reactions of tin or lead and carbon in Ca/Li flux produced the analogous phases Ca11Tt3C8 (Tt = Sn, Pb) in the monoclinic C21/c space group (a = 13.2117(8) A, b =10.7029(7) A, c = 14.2493(9) A, beta = 105.650(1)° for the Sn analog). These compounds are carbide Zintl phases that includes the rare combination of C3 4- and C22- units as well as Sn4- or Pb4- anions. Ca/Li flux reactions of CaH2 and arsenic have produced the Zintl phases LiCa3As 2H in orthorhombic Pnma (a = 11.4064(7), b = 4.2702(3), c = 11.8762(8) A), and Ca 13As6C0.46N1.155H6.045in tetragonal P4/mbm (a = 15.7493(15), c = 9.1062(9) A). The complex stoichiometry of the latter phase was caused by incorporation of light element contaminants and was studied by neutron diffraction, showing mixing of anionic sites to achieve charge balance. Ca/Li flux reactions with group 13 metals have resulted in several new intermetallic phases. Reactions of indium and CaH2 in the Ca/Li flux (with or without boron) formed Ca53In13B4-x H23+x(2.4 < x < 4.0) in cubic space group Im-3 (a = 16.3608(6) A) which features metallic indium atoms and ionic hydride sites. The electronic properties of this "subhydride" were confirmed by 1H and 115In NMR spectroscopy. Attempts to replace boron with carbon yielded Ca12InC13-x

  11. Ozone formation potentials of organic compounds from different emission sources in the South Coast Air Basin of California

    NASA Astrophysics Data System (ADS)

    Chen, Jianjun; Luo, Dongmin

    2012-08-01

    Different organic compounds exhibit different propensities for ozone formation. Two approaches were used to study the ozone formation potentials or source reactivities of different anthropogenic organic compounds emission categories in California's South Coast Air Basin (SoCAB). The first approach was based on the combination of total organic gases (TOG) emission speciation profiles and the maximum incremental reactivity (MIR) scale of organic species. The second approach quantified ozone impacts from different emission sources by performing 3-dimensional air quality model sensitivity analysis involving increased TOG emissions from particular sources. The source reactivities derived from these two approaches agree reasonably well for 58 anthropogenic organic compounds emission categories in the SoCAB. Both approaches identify TOG emissions from mobile sources as having the highest reactivity. Source reactivities from both approaches were also combined with TOG emissions from each source category to produce a 2005 reactivity-based anthropogenic TOG emission inventory for the SoCAB. The top five reactivity-based anthropogenic TOG emission sources in the SoCAB during 2005 were: light-duty passenger cars, off-road equipment, consumer products, light-duty trucks category 2 (i.e., 3751-5750 lb), and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that livestock waste and composting emission categories were two of the five largest mass-based anthropogenic TOG emission sources. The reactivity-based TOG emission inventory is an important addition to the mass-based TOG emission inventory because it represents the ozone formation potentials from emission sources and can be used to assist in determining targeted sources for developing organic compounds reduction policies.

  12. Influence of Dopant on Growth of Intermetallic Layers in Sn-Ag-Cu Solder Joints

    NASA Astrophysics Data System (ADS)

    Li, G. Y.; Bi, X. D.; Chen, Q.; Shi, X. Q.

    2011-02-01

    The interfacial interaction between Cu substrates and Sn-3.5Ag-0.7Cu- xSb ( x = 0, 0.2, 0.5, 0.8, 1.0, 1.5, and 2.0) solder alloys has been investigated under different isothermal aging temperatures of 100°C, 150°C, and 190°C. Scanning electron microscopy (SEM) was used to measure the thickness of the intermetallic compound (IMC) layer and observe the microstructural evolution of the solder joints. The IMC phases were identified by energy-dispersive x-ray spectroscopy (EDX) and x-ray diffractometry (XRD). The growth of both the Cu6Sn5 and Cu3Sn IMC layers at the interface between the Cu substrate and the solder fits a power-law relationship with the exponent ranging from 0.42 to 0.83, which suggests that the IMC growth is primarily controlled by diffusion but may also be influenced by interface reactions. The activation energies and interdiffusion coefficients of the IMC formation of seven solder alloys were determined. The addition of Sb has a strong influence on the growth of the Cu6Sn5 layer, but very little influence on the formation of the Cu3Sn IMC phase. The thickness of the Cu3Sn layer rapidly increases with aging time and temperature, whereas the thickness of the Cu6Sn5 layer increases slowly. This is probably due to the formation of Cu3Sn at the interface between two IMC phases, which occurs with consumption of Cu6Sn5. Adding antimony to Sn-3.5Ag-0.7Cu solder can evidently increase the activation energy of Cu6Sn5 IMC formation, reduce the atomic diffusion rate, and thus inhibit excessive growth of Cu6Sn5 IMCs. This study suggests that grain boundary pinning is one of the most important mechanisms for inhibiting the growth of Cu6Sn5 IMCs in such solder joints when Sb is added.

  13. Titanium aluminide intermetallic alloys with improved wear resistance

    DOEpatents

    Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

    2014-07-08

    The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

  14. Evolution of Intermetallic Phases in Soldering of the Die Casting of Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Song, Jie; Wang, Xiaoming; DenOuden, Tony; Han, Qingyou

    2016-06-01

    Most die failures are resulted from chemical reactions of dies and molten aluminum in the die casting of aluminum. The formation of intermetallic phases between a steel die and molten aluminum is investigated by stationary immersion tests and compared to a real die casting process. Three intermetallic phases are identified in the stationary immersion tests: a composite layer and two compact layers. The composite layer is a mixture of α bcc, Al, and Si phases. The α bcc phase changes in morphology from rod-like to spherical shape, while the growth rate of the layer changes from parabolic to linear pattern with immersion time. The first compact layer forms rapidly after immersion and maintains a relatively constant thickness. The second compact layer forms after 4 hours of immersion and exhibits parabolic growth with immersion time. In comparison, only a composite layer and the first compact layer are observed in a real die casting process. The fresh molten aluminum of high growth rate washes away the second intermetallic layer easily.

  15. Prediction of Host-Guest Na-Fe Intermetallics at High Pressures.

    PubMed

    Zhou, Yuanyuan; Wang, Hui; Zhu, Chunye; Liu, Hanyu; Tse, John S; Ma, Yanming

    2016-07-18

    High pressure can fundamentally alter the electronic structure of elemental metals, leading to the unexpected formation of intermetallics with unusual structural features. In the present study, the phase stabilities and structural changes of Na-Fe intermetallics under pressure were studied using unbiased structure searching methods, combined with density functional theory calculations. Two intermetallics with stoichiometries Na3Fe and Na4Fe are found to be thermodynamically stable at pressures above 120 and 155 GPa, respectively. An interesting structural feature is that both have form a host-guest-like structure with Na sublattices constructed from small and large polygons similar to the host framework of the self-hosting incommensurate phases observed in Group I and II elements. Apart from the one-dimensional (1D) Fe chains running through the large channels, more interestingly, electrides are found to localize in the small channels between the layers. Electron topological analysis shows secondary bonding interactions between the Fe atoms and the interstitial electrides help to stabilize these structures. PMID:27341197

  16. Regulation of formation of volatile compounds of tea (Camellia sinensis) leaves by single light wavelength.

    PubMed

    Fu, Xiumin; Chen, Yiyong; Mei, Xin; Katsuno, Tsuyoshi; Kobayashi, Eiji; Dong, Fang; Watanabe, Naoharu; Yang, Ziyin

    2015-11-16

    Regulation of plant growth and development by light wavelength has been extensively studied. Less attention has been paid to effect of light wavelength on formation of plant metabolites. The objective of this study was to investigate whether formation of volatiles in preharvest and postharvest tea (Camellia sinensis) leaves can be regulated by light wavelength. In the present study, in contrast to the natural light or dark treatment, blue light (470 nm) and red light (660 nm) significantly increased most endogenous volatiles including volatile fatty acid derivatives (VFADs), volatile phenylpropanoids/benzenoids (VPBs), and volatile terpenes (VTs) in the preharvest tea leaves. Furthermore, blue and red lights significantly up-regulated the expression levels of 9/13-lipoxygenases involved in VFADs formation, phenylalanine ammonialyase involved in VPBs formation, and terpene synthases involved in VTs formation. Single light wavelength had less remarkable influences on formation of volatiles in the postharvest leaves compared with the preharvest leaves. These results suggest that blue and red lights can be promising technology for remodeling the aroma of preharvest tea leaves. Furthermore, our study provided evidence that light wavelength can activate the expression of key genes involved in formation of plant volatiles for the first time.

  17. Regulation of formation of volatile compounds of tea (Camellia sinensis) leaves by single light wavelength

    PubMed Central

    Fu, Xiumin; Chen, Yiyong; Mei, Xin; Katsuno, Tsuyoshi; Kobayashi, Eiji; Dong, Fang; Watanabe, Naoharu; Yang, Ziyin

    2015-01-01

    Regulation of plant growth and development by light wavelength has been extensively studied. Less attention has been paid to effect of light wavelength on formation of plant metabolites. The objective of this study was to investigate whether formation of volatiles in preharvest and postharvest tea (Camellia sinensis) leaves can be regulated by light wavelength. In the present study, in contrast to the natural light or dark treatment, blue light (470 nm) and red light (660 nm) significantly increased most endogenous volatiles including volatile fatty acid derivatives (VFADs), volatile phenylpropanoids/benzenoids (VPBs), and volatile terpenes (VTs) in the preharvest tea leaves. Furthermore, blue and red lights significantly up-regulated the expression levels of 9/13-lipoxygenases involved in VFADs formation, phenylalanine ammonialyase involved in VPBs formation, and terpene synthases involved in VTs formation. Single light wavelength had less remarkable influences on formation of volatiles in the postharvest leaves compared with the preharvest leaves. These results suggest that blue and red lights can be promising technology for remodeling the aroma of preharvest tea leaves. Furthermore, our study provided evidence that light wavelength can activate the expression of key genes involved in formation of plant volatiles for the first time. PMID:26567525

  18. A ship-in-a-bottle strategy to synthesize encapsulated intermetallic nanoparticle catalysts: Exemplified for furfural hydrogenation

    DOE PAGESBeta

    Maligal-Ganesh, Raghu V.; Xiao, Chaoxian; Goh, Tian Wei; Wang, Lin -Lin; Gustafson, Jeffrey; Pei, Yuchen; Qi, Zhiyuan; Johnson, Duane D.; Zhang, Shiran; Tao, Franklin; et al

    2016-01-28

    In this paper, intermetallic compounds are garnering increasing attention as efficient catalysts for improved selectivity in chemical processes. Here, using a ship-in-a-bottle strategy, we synthesize single-phase platinum-based intermetallic nanoparticles (NPs) protected by a mesoporous silica (mSiO2) shell by heterogeneous reduction and nucleation of Sn, Pb, or Zn in mSiO2-encapsulated Pt NPs. For selective hydrogenation of furfural to furfuryl alcohol, a dramatic increase in activity and selectivity is observed when intermetallic NPs catalysts are used in comparison to Pt@mSiO2. Among the intermetallic NPs, PtSn@mSiO2 exhibits the best performance, requiring only one-tenth of the quantity of Pt used in Pt@mSiO2 for similarmore » activity and near 100% selectivity to furfuryl alcohol. A high-temperature oxidation–reduction treatment easily reverses any carbon deposition-induced catalyst deactivation. X-ray photoelectron spectroscopy shows the importance of surface composition to the activity, whereas density functional theory calculations reveal that the enhanced selectivity on PtSn compared to Pt is due to the different furfural adsorption configurations on the two surfaces.« less

  19. Thermomechanical processing of plasma sprayed intermetallic sheets

    DOEpatents

    Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

    2001-01-01

    A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

  20. In situ XPS study of methanol reforming on PdGa near-surface intermetallic phases

    PubMed Central

    Rameshan, Christoph; Stadlmayr, Werner; Penner, Simon; Lorenz, Harald; Mayr, Lukas; Hävecker, Michael; Blume, Raoul; Rocha, Tulio; Teschner, Detre; Knop-Gericke, Axel; Schlögl, Robert; Zemlyanov, Dmitry; Memmel, Norbert; Klötzer, Bernhard

    2012-01-01

    In situ X-ray photoelectron spectroscopy and low-energy ion scattering were used to study the preparation, (thermo)chemical and catalytic properties of 1:1 PdGa intermetallic near-surface phases. Deposition of several multilayers of Ga metal and subsequent annealing to 503–523 K led to the formation of a multi-layered 1:1 PdGa near-surface state without desorption of excess Ga to the gas phase. In general, the composition of the PdGa model system is much more variable than that of its PdZn counterpart, which results in gradual changes of the near-surface composition with increasing annealing or reaction temperature. In contrast to near-surface PdZn, in methanol steam reforming, no temperature region with pronounced CO2 selectivity was observed, which is due to the inability of purely intermetallic PdGa to efficiently activate water. This allows to pinpoint the water-activating role of the intermetallic/support interface and/or of the oxide support in the related supported PdxGa/Ga2O3 systems, which exhibit high CO2 selectivity in a broad temperature range. In contrast, corresponding experiments starting on the purely bimetallic model surface in oxidative methanol reforming yielded high CO2 selectivity already at low temperatures (∼460 K), which is due to efficient O2 activation on PdGa. In situ detected partial and reversible oxidative Ga segregation on intermetallic PdGa is associated with total oxidation of intermediate C1 oxygenates to CO2. PMID:22875996

  1. Formation of Polycyclic Aromatic Hydrocarbons and Nitrogen Containing Polycyclic Aromatic Compounds in Titan's Atmosphere, the Interstellar Medium and Combustion

    NASA Astrophysics Data System (ADS)

    Landera, Alexander

    2013-12-01

    Several different mechanisms leading to the formation of (substituted) naphthalene and azanaphthalenes were examined using theoretical quantum chemical calculations. As a result, a series of novel synthetic routes to Polycyclic Aromatic Hydrocarbons (PAHs) and Nitrogen Containing Polycyclic Aromatic Compounds (N-PACs) have been proposed. On Earth, these aromatic compounds originate from incomplete combustion and are released into our environment, where they are known to be major pollutants, often with carcinogenic properties. In the atmosphere of a Saturn's moon Titan, these PAH and N-PACs are believed to play a critical role in organic haze formation, as well as acting as chemical precursors to biologically relevant molecules. The theoretical calculations were performed by employing the ab initio G3(MP2,CC)/B3LYP/6-311G** method to effectively probe the Potential Energy Surfaces (PES) relevant to the PAH and N-PAC formation. Following the construction of the PES, Rice-Ramsperger-Kassel-Markus (RRKM) theory was used to evaluate all unimolecular rate constants as a function of collision energy under single-collision conditions. Branching ratios were then evaluated by solving phenomenological rate expressions for the various product concentrations. The most viable pathways to PAH and N-PAC formation were found to be those where the initial attack by the ethynyl (C2H) or cyano (CN) radical toward a unsaturated hydrocarbon molecule led to the formation of an intermediate which could not effectively lose a hydrogen atom. It is not until ring cyclization has occurred, that hydrogen elimination leads to a closed shell product. By quenching the possibility of the initial hydrogen atom elimination, one of the most competitive processes preventing the PAH or N-PAC formation was avoided, and the PAH or N-PAC formation was allowed to proceed. It is concluded that these considerations should be taken into account when attempting to explore any other potential routes towards

  2. HIGHLY SENSITIVE ASSAY FOR ANTICHOLINESTERASE COMPOUNDS USING 96 WELL PLATE FORMAT

    EPA Science Inventory

    One of the approaches for reducing uncertainties in the assessment of human exposure is to better characterize concentrations of hazardous compounds that may be present in our immediate environment. A significant limitation to this approach, however, is that sampling and labora...

  3. Degradation and formation of polycyclic aromatic compounds during bioslurry treatment of an aged gasworks soil.

    PubMed

    Lundstedt, Staffan; Haglund, Peter; Oberg, Lars

    2003-07-01

    The goals of this study were to investigate the relative degradation rates of polycyclic aromatic compounds (PACs) in contaminated soil, and to assess whether persistent oxidation products are formed during their degradation. Samples were taken on five occasions during a pilot-scale bioslurry treatment of soil from a former gasworks site. More than 100 PACs were identified in the soil, including unsubstituted polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs), heterocyclic PACs, and oxygenated PAHs (oxy-PAHs), such as ketones, quinones, and coumarins. During the treatment, the low molecular weight PAHs and heterocyclics were degraded faster than the high molecular weight compounds. The unsubstituted PAHs also appear to have degraded more quickly than the corresponding alkyl-PAHs and nitrogen-containing heterocyclics. No new oxidation products that were not present in the untreated soil were identified after the soil treatment. However, oxy-PAHs that were present in the untreated soil were generally degraded more slowly than the parent compounds, suggesting that they were formed during the treatment or that they are more persistent. Two oxidation products, 1-acenaphthenone and 4-oxapyrene-5-one, were found at significantly higher concentrations at the end of the study. Because oxy-PAHs can be acutely toxic, mutagenic, or carcinogenic, we suggest that this group of compounds should also be monitored during the treatment of PAH-contaminated soil. PMID:12836964

  4. Geometrical Formation of Compound Starch Grains in Rice Implements Voronoi Diagram.

    PubMed

    Matsushima, Ryo; Maekawa, Masahiko; Sakamoto, Wataru

    2015-11-01

    Starch forms transparent grains, called starch grains (SGs), in amyloplasts. One of the major morphological SG forms in Poaceae, called a compound SG, is formed by assemblies of small starch granules in an amyloplast. Starch granules assemble as a well-ordered structure; however, the mechanism that regulates this organization has not been identified. In this study, we examined how starch granules grow and converge into the final SG morphology. First, we found that the number of starch granules in an amyloplast is almost constant from the early developmental stage until endosperm maturity. Next, we quantitatively evaluated the geometrical similarities between starch granules and a Voronoi diagram, which is a mathematical tessellation of space based on the distance to a specific set of points in the space. The in silico growth simulation showed that the geometrical patterns of compound SGs resembling a Voronoi diagram is determined by physical interactions among the free-growing starch granules and the amyloplast envelope membrane. The geometrical similarity between compound SGs and a Voronoi diagram is likely a result of maximum loading and storage of starch in the amyloplast. The simulation described in this study provides a greater understanding of how compound SGs are formed and also has the potential to explain morphological variations of SGs.

  5. Ionic Strength-Induced Formation of Smectite Quasicrystals Enhances Nitroaromatic Compound Sorption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The influence of ionic strength on nitroaromatic compound sorption from water by K+- and Ca2+-saturated smectite (SWy-2) was examined. The results indicated that sorption of 1,3-dinitrobenzene by K-SWy-2 increased up to 2.2 times as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorp...

  6. ISOTOPIC (14C) AND CHEMICAL COMPOSITION OF ATMOSPHERIC VOLATILE ORGANIC COMPOUND FRACTIONS - PRECURSORS TO OZONE FORMATION

    EPA Science Inventory

    Atmospheric volatile organic compounds (VOCs) are an important factor in the production of ozone near ground level [3]. Many hydrocarbons originate from auto exhaust. However, a number of VOCs, e.g., isoprene, are known to be natural in origin. To develop reliable models for un...

  7. Formation and Ecotoxicity of N-Heterocyclic Compounds on Ammoxidation of Mono- and Polysaccharides

    PubMed Central

    2013-01-01

    Ammoxidation of technical lignins under mild conditions is a suitable approach to artificial humic substances. However, carbohydrates as common minor constituents of technical lignins have been demonstrated to be a potential source of N-heterocyclic ecotoxic compounds. Ethyl acetate extracts of ammoxidation mixtures of the monosaccharides glucose and xylose exhibited considerable growth inhibiting activity in the OECD 201 test, with 4-methyl-1H-imidazole, 4-(hydroxymethyl)-1H-imidazole, and 3-hydroxypyridine being the most active compounds. The amount of N-heterocyclic compounds formed at moderate ammoxidation conditions (70 °C, 0.2 MPa O2, 3 h) was significantly lower for the polysaccharides cellulose and xylan (16–30 μg/g of educt) compared to glucose (15.4 mg). Ammoxidation at higher temperature is not recommendable for carbohydrate-rich materials as much higher amounts of N-heterocyclic compounds were formed from both monosaccharides (100 °C: 122.4–160.5 mg/g of educt) and polysaccharides (140 °C: 5.52–16.03 mg/g of educt). PMID:23967874

  8. Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

    PubMed

    Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

    2015-12-18

    The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates.

  9. Peculiarities in the formation of complex organic compounds in a nitrogen-methane atmosphere during hypervelocity impacts

    NASA Astrophysics Data System (ADS)

    Zaitsev, M. A.; Gerasimov, M. V.; Safonova, E. N.; Vasiljeva, A. S.

    2016-03-01

    Results of the experiments on model impact vaporization of peridotite, a mineral analogue of stony asteroids, in a nitrogen-methane atmosphere are presented. Nd-glass laser (γ = 1.06 µm) was used for simulation. Pulse energy was ~600-700 J, pulse duration ~10-3 s, vaporization tempereature ~4000-5000 K. The gaseous medium (96% vol. of N2 and 4% vol. of CH4, P = 1 atm) was a possible analogue of early atmospheres of terrestrial planets and corresponded to the present-day atmosphere composition of Titan, a satellite of Saturn. By means of pyrolytic gas chromatography/mass spectrometry, it is shown that solid condensates obtained in laser experiments contain relatively complex lowand high-molecular weight (kerogen-like) organic compounds. The main products of condensate pyrolysis were benzene and alkyl benzenes (including long-chain ones), unbranched aliphatic hydrocarbons, and various nitrogen-containing compounds (aliphatic and aromatic nitriles and pyrrol). It is shown that the nitrogen-methane atmosphere favors the formation of complex organic compounds upon hypervelocity impacts with the participation of stony bodies even with a small methane content in it. In this process, falling bodies may not contain carbon, hydrogen, and other chemical elements necessary for the formation of the organic matter. In such conditions, a noticeable contribution to the impact-induced synthesis of complex organic substances is probably made by heterogeneous catalytic reactions, in particular, Fischer-Tropsch type reactions.

  10. Low resistance Cu3Ge compounds formation by the low temperature treatment of Cu/Ge system in atomic hydrogen

    NASA Astrophysics Data System (ADS)

    Kazimirov, A. I.; Erofeev, E. V.; Fedin, I. V.; Kagadei, V. A.; Yurjev, Y. N.

    2016-06-01

    The research deals with the regularities for Cu3Ge compound formation under the low temperature treatment of a double-layer Cu/Ge system deposited on i-GaAs substrate in atomic hydrogen flow. The treatment of a Cu/Ge/i-GaAs system with layer thicknesses, respectively, of 122 and 78 nm, in atomic hydrogen with a flow rate of 1015 at.cm-2s-1 for a duration of 2.5-10 min at room temperature, leads to an interdiffusion of Cu and Ge and formation of a polycrystalline film containing stoichiometric phase Cu3Ge. The film consists of vertically oriented grains of dimensions 100-150 nm and has a minimum specific resistance of 4.5 μΩ cm. Variation in the treatment duration of Cu/Ge/i-GaAs samples in atomic hydrogen affects Cu and Ge distribution profiles, the phase composition of films formed, and the specific resistance of the latter. As observed, Cu3Ge compound synthesis at room temperature demonstrates the stimulative effects characteristic of atomic hydrogen treatment for both Cu and Ge diffusion and for the chemical reaction of Cu3Ge compound generation. Activation of these processes can be conditioned by the energy released during recombination of hydrogen atoms adsorbed on the surface of a Cu/Ge/i-GaAs sample.

  11. High-temperature- and high-pressure-induced formation of the Laves-phase compound XeS2

    NASA Astrophysics Data System (ADS)

    Yan, Xiaozhen; Chen, Yangmei; Xiang, Shikai; Kuang, Xiaoyu; Bi, Yan; Chen, Haiyan

    2016-06-01

    We explore the reactivity of xenon with sulfur under high pressure, using unbiased structure searching techniques combined with first-principles calculations, which identify a stable XeS2 compound crystallized in a Laves phase with hypercoordinated (16-fold) Xe at 191 GPa and 0 K. Taking the thermal effects into account, we find that increasing the temperature could further stabilize it. The formation of XeS2 is a consequence of pressure-induced charge transfer from Xe to S atoms and the delocalization of Xe 5 p and S 3 p electrons. Meanwhile, the stabilization into a Laves phase of XeS2 is the result of delocalized chemical bonding and the need for optimum structure packing. The present discussion of the formation mechanism in XeS2 is general, and conclusions can be used to understand the formation of other Laves-phase compounds and the Xe chemistry that allows closed-shell Xe to participate in chemical reactions.

  12. UV-based advanced oxidation processes for the treatment of odour compounds: efficiency and by-product formation.

    PubMed

    Zoschke, Kristin; Dietrich, Norman; Börnick, Hilmar; Worch, Eckhard

    2012-10-15

    The occurrence of the taste and odour compounds geosmin and 2-methyl isoborneol (2-MIB) affects the organoleptic quality of raw waters from drinking water reservoirs worldwide. UV-based oxidation processes for the removal of these substances are an alternative to adsorption and biological processes, since they additionally provide disinfection of the raw water. We could show that the concentration of geosmin and 2-MIB could be reduced by VUV irradiation and the combination of UV irradiation with ozone and hydrogen peroxide in pure water and water from a drinking water reservoir. The figure of merit EE/O is an appropriate tool to compare the AOPs and showed that VUV and UV/O(3) yielded the lowest treatment costs for the odour compounds in pure and raw water, respectively. Additionally, VUV irradiation with addition of ozone, generated by the VUV lamp, was evaluated. The generation of ozone and the irradiation were performed in a single reactor system using the same low-pressure mercury lamp, thereby reducing the energy consumption of the treatment process. The formation of the undesired by-products nitrite and bromate was investigated. The combination of VUV irradiation with ozone produced by a VUV lamp avoided the formation of relevant concentrations of the by-products. The internal generation of ozone is capable to produce ozone concentrations sufficient to reduce EE/O below 1 kWh m(-3) and without the risk of the formation of nitrite or bromate above the maximum contaminant level.

  13. Formation of volatile compounds during heating of spice paprika (Capsicum annuum) powder.

    PubMed

    Cremer, D R; Eichner, K

    2000-06-01

    Spice paprika (red pepper; Capsicum annuum) is the most cultivated spice worldwide and is used mainly for its color and pungency. However, current research is also focusing on the flavor as an important parameter. This paper deals with the kinetics of the formation of those volatiles that indicate a decrease in spice paprika quality due to Maillard reaction, hydrolytic reactions, and oxidative degradation reactions of lipids such as fatty acids and carotenoids. Spice paprika volatiles were quantitatively analyzed by means of headspace gas chromatography (HS-GC) and solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS). The kinetics of their formation were investigated, and the respective activation energies determined. Strecker aldehyde, acetone, and methanol formation followed a pseudo-zero-order reaction kinetic, and formation of dimethyl sulfide (DMS) was characterized by a first-order kinetic. The activation energies determined were between 86.3 and 101.8 for the Strecker aldehydes acetaldehyde (AA), 2-methylpropanal (2-MP), 3-methylbutanal (3-MB), and 2-methylbutanal (2-MB), 130.7 for acetone, 114.2 for methanol, and 109.7 kJ/mol for DMS. The amounts of Strecker aldehydes formed were correlated to the concentrations of the corresponding free amino acids present in the samples. The formation of hexanal and 6-methyl-5-hepten-2-one in Capsicum annuum during processing was confirmed, and the formation of beta-ionone was probably described for the first time. During heating, the concentration of hexanal increased rapidly. The formation of 6-methyl-5-hepten-2-one confirms that Capsicum annuum fruits contain lycopene.

  14. Change in haloacetic acid formation potential during UV and UV/H2O2 treatment of model organic compounds.

    PubMed

    Sakai, Hiroshi; Autin, Olivier; Parsons, Simon

    2013-07-01

    Haloacetic acids (HAAs) are disinfection by-products produced by the chlorination of organic matter, including amino acids. Advanced oxidation processes are expected to be effective for the destruction of HAA precursors; however, recent studies have reported the possible failure of these processes to reduce HAA formation potential. This study examined HAA formation potential during the course of UV or UV/H2O2 treatment of three organic compounds: leucine, serine, and resorcinol. HAA formation potential decreased in the treatment of resorcinol, while the potential increased slightly in the treatment of serine and greatly increased for leucine. The chemical structure required for HAA formation was assumed to be produced during the course of UV/H2O2 treatment of leucine and serine. Also, H abstraction from the δ carbon was assumed to result from the initial degradation of leucine by the hydroxyl radical during the UV/H2O2 treatment. The hydroxyl radical may have further reacted with leucine moiety to shorten its carbon chain. This would have produced a chemical structure capable of forming HAA, thus increasing HAA formation potential.

  15. Change in haloacetic acid formation potential during UV and UV/H2O2 treatment of model organic compounds.

    PubMed

    Sakai, Hiroshi; Autin, Olivier; Parsons, Simon

    2013-07-01

    Haloacetic acids (HAAs) are disinfection by-products produced by the chlorination of organic matter, including amino acids. Advanced oxidation processes are expected to be effective for the destruction of HAA precursors; however, recent studies have reported the possible failure of these processes to reduce HAA formation potential. This study examined HAA formation potential during the course of UV or UV/H2O2 treatment of three organic compounds: leucine, serine, and resorcinol. HAA formation potential decreased in the treatment of resorcinol, while the potential increased slightly in the treatment of serine and greatly increased for leucine. The chemical structure required for HAA formation was assumed to be produced during the course of UV/H2O2 treatment of leucine and serine. Also, H abstraction from the δ carbon was assumed to result from the initial degradation of leucine by the hydroxyl radical during the UV/H2O2 treatment. The hydroxyl radical may have further reacted with leucine moiety to shorten its carbon chain. This would have produced a chemical structure capable of forming HAA, thus increasing HAA formation potential. PMID:23415308

  16. On the formation of molecules and solid-state compounds from the AGB to the PN phases

    NASA Astrophysics Data System (ADS)

    García-Hernández, D. A.; Manchado, A.

    2016-07-01

    During the asymptoyic giant branch (AGB) phase, different elements are dredge- up to the stellar surface depending on progenitor mass and metallicity. When the mass loss increases at the end of the AGB, a circumstellar dust shell is formed, where different (C-rich or O-rich) molecules and solid-state compounds are formed. These are further processed in the transition phase between AGB stars and planetary nebulae (PNe) to create more complex organic molecules and inorganic solid-state compounds (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors in C-rich environments and oxides and crystalline silicates in O-rich ones). We present an observational review of the different molecules and solid-state materials that are formed from the AGB to the PN phases. We focus on the formation routes of complex fullerene (and fullerene-based) molecules as well as on the level of dust processing depending on metallicity.

  17. Nitrogen-heterocyclic compounds in meteorites - Significance and mechanisms of formation

    NASA Astrophysics Data System (ADS)

    Stoks, P. G.; Schwartz, A. W.

    1981-04-01

    Samples of the Murchison, Murray, and Orgueil carbonaceous meteorites were analyzed for nitrogen-heterocyclic compounds using gas chromatography, cation and anion exclusion liquid chromatography, and mass spectrometry. The H2O and HCOOH extracts, as well as the 3M-HCl hydrolyzate of the Allende sample were taken through all stages of analysis. Concentrations ranging from 114-655 ppb of the purines adenine, guanine, hypoxanthine, and xanthine were found to be present in acid extracts. All four biologically significant purines, as well as the pyrimidine uracil have been identified in meteorites. It was concluded that the suite of N-heterocyclic compounds identified in meteorites do not permit a clear distinction between mechanisms of synthesis such as the Fischer-Tropsch type, and other candidates.

  18. Formation of an activated N-nitroso compound in nitrite-treated fava beans (Vicia faba).

    PubMed

    Piacek-Llanes, B G; Tannenbaum, S R

    1982-01-01

    Fava beans are prominent in the diet of the Colombian population at high gastric cancer risk. Upon nitrite treatment under simulated gastric conditions, a potent mutagen was formed as detected by a forward mutation assay using Salmonella typhimurium TM677 without microsomal activation. The promutagen was partially purified by preparative t.l.c. and normal phase h.p.l.c. of the acetone-soluble portion of a dried aqueous extract. The nitrosated promutagen fully accounted for the mutagenicity observed with whole fava beans. One gram of fresh fava beans yielded approximately 0.35 nmol of mutagen. Mutagenicity data indicated that this mutagen was more potent than N-methyl-N'-nitro-N-nitrosoguanidine. The characteristics of the mutagen were typical of an activated N-nitroso compound, that is a compound in which the N-nitroso moiety is attached to an activating group, such as a carbonyl group. Irradiation of the mutagen yielded a Griess positive reaction. By reverse-phase h.p.l.c. photohydrolysis, a single peak could be ascribed to the mutagen. Its stability varied as a function of pH, being most unstable under alkaline conditions. Cysteine and phosphate concentration had no effect on its rate of decomposition, thereby strongly suggesting that the mutagen is an N-nitrosourea. The results obtained in this study support the hypothesis of carcinogenesis via the intragastric production of activated N-nitroso compounds. PMID:7151253

  19. Secondary brown carbon - Formation of light-absorbing compounds in atmospheric particulates from selected dicarbonyls and amines

    NASA Astrophysics Data System (ADS)

    Kampf, Christopher; Filippi, Alexander; Hoffmann, Thorsten

    2015-04-01

    One of the main open questions regarding organic compounds in atmospheric chemistry today is related to the formation of optically-active compounds and the occurrence of so called brown carbon (Andreae and Gelencsér, 2006). While organic compounds in ambient fine particles for decades have been assumed to not absorb solar radiation, thus resulting in a net cooling effect on climate (IPCC, 2007), it is now generally accepted that a continuum of light-absorbing carbonaceous species is present in fine aerosols (Pöschl, 2003). In this study, light-absorbing compounds from reactions between dicarbonyl compounds, i.e., glyoxal, methylglyoxal, acetylacetone, 2,3-butanedione, 2,5-hexanedione, and glutaraldehyde, and amine species, i.e., ammonia and glycine, were investigated at atmospherically relevant concentrations in bulk solution experiments mimicking atmospheric particulates. Product analyses were performed using UV/Vis spectrophotometry and (ultra) high performance liquid chromatography coupled to diode array detection and ion trap mass spectrometry (HPLC-DAD-ESI-MS/MS), as well as ultra-high resolution (Orbitrap) mass spectrometry (UHPLC-ESI-HRMS/MS). We demonstrate that light-absorbing compounds are formed from a variety of atmospherically relevant dicarbonyls via particle phase reactions with amine nucleophiles. Single dicarbonyl and mixed dicarbonyl experiments were performed and products were analyzed. The reaction products are suggested to be cyclic nitrogen containing compounds such as imidazoles or dihydropyridines as well as open chain compounds resulting from aldol condensation reactions. Further, the reactive turnover was found to be higher at increasing pH values. The aforementioned processes may be of higher relevance in regions with high aerosol pH, e.g., resulting from high ammonia emissions as for example in northern India (Clarisse et al., 2009). References Andreae, M.O., and Gelencsér, A. (2006): Black carbon or brown carbon? The nature of light

  20. Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

    1998-01-01

    We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.

  1. Results on powder injection molding of Ni{sub 3}Al and application to other intermetallic compositions

    SciTech Connect

    Cooper, R.M.

    1992-12-31

    Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni{sub 3}Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

  2. Results on powder injection molding of Ni[sub 3]Al and application to other intermetallic compositions

    SciTech Connect

    Cooper, R.M.

    1992-01-01

    Net forming processes are under development to allow affordable production of intermetallic components. Powder injection molding (PIM) mav be employed for the production of complex-shaped intermetallic geometries. Proper choice of powder parameters and processing conditions can lead to the formation of fullv dense structures through pressure-less sintering. In this study, Ni[sub 3]Al with 0.04 wt.-% boron has been successfully injection molded and sintered to full density. A yield strength of 340 MPa, ultimate tensile strength (UTS) of 591 MPa, and 8% elongation were attained for injection molded and sintered tensile bars. Powder characteristics and sintering behavior are given for the nickel aluminide employed in this study to highlight the powder attributes needed for injection molding. Molding parameters, debinding and sintering schedules, along, with mechanical properties are presented to indicate the viability of PIM for intermetallics. This approach based on the understanding of key powder characteristics and use of the reactive synthesis powder process mav be extended to the successful injection molding of other intermetallic systems.

  3. Use of HμREL Human Coculture System for Prediction of Intrinsic Clearance and Metabolite Formation for Slowly Metabolized Compounds.

    PubMed

    Hultman, Ia; Vedin, Charlotta; Abrahamsson, Anna; Winiwarter, Susanne; Darnell, Malin

    2016-08-01

    Design of slowly metabolized compounds is an important goal in many drug discovery projects. Standard hepatocyte suspension intrinsic clearance (CLint) methods can only provide reliable CLint values above 2.5 μL/min/million cells. A method that permits extended incubation time with maintained performance and metabolic activity of the in vitro system is warranted to allow in vivo clearance predictions and metabolite identification of slowly metabolized drugs. The aim of this study was to evaluate the static HμREL coculture of human hepatocytes with stromal cells to be set up in-house as a standard method for in vivo clearance prediction and metabolite identification of slowly metabolized drugs. Fourteen low CLint compounds were incubated for 3 days, and seven intermediate to high CLint compounds and a cocktail of cytochrome P450 (P450) marker substrates were incubated for 3 h. In vivo clearance was predicted for 20 compounds applying the regression line approach, and HμREL coculture predicted the human intrinsic clearance for 45% of the drugs within 2-fold and 70% of the drugs within 3-fold of the clinical values. CLint values as low as 0.3 μL/min/million hepatocytes were robustly produced, giving 8-fold improved sensitivity of robust low CLint determination, over the cutoff in hepatocyte suspension CLint methods. The CLint values of intermediate to high CLint compounds were at similar levels both in HμREL coculture and in freshly thawed hepatocytes. In the HμREL coculture formation rates for five P450-isoform marker reactions, paracetamol (CYP1A2), 1-OH-bupropion (CYP2B6), 4-OH-diclofenac (CYP2C9), and 1-OH-midazolam (3A4) were within the range of literature values for freshly thawed hepatocytes, whereas 1-OH-bufuralol (CYP2D6) formation rate was lower. Further, both phase I and phase II metabolites were detected and an increased number of metabolites were observed in the HμREL coculture compared to hepatocyte suspension. In conclusion, HμREL coculture can

  4. HIGHLY SENSITIVE ASSAY FOR ANTICHOLINESTERASE COMPOUNDS USING 96 WELL PLATE FORMAT

    EPA Science Inventory

    The rapid and sensitive detection of organophosphate insecticides using a 96 well plate format is reported. Several features of this assay make it attractive for development as a laboratory-based or field screening assay. Acetylcholinesterase (AChE) was stabilized in a gelati...

  5. Formation of Toxic Iodinated Disinfection By-Products from Compounds Used in Medical Imaging

    EPA Science Inventory

    Iodinated X-ray contrast media (ICM) were investigated as a source of iodine in the formation of iodo-trihalomethane (iodo-THM) and iodo-acid disinfection byproducts (DBPs), both of which are highly genotoxic and/or cytotoxic in mammalian cells. ICM are widely used at medical cen...

  6. Synthesis of superheavy elements and dinuclear-system concept of compound-nucleus formation

    SciTech Connect

    Antonenko, N.V.; Adamian, G.G.; Cherepanov, E.A.

    1996-12-31

    Dinuclear system concept is applied to the analysis of reactions used for the synthesis of elements with Z = 110, 112, 114, and 116. The inner fusion barriers obtained for these reactions are in good agreement with the experimental estimations resulted from the excitation energies of compound nuclei. A model is suggested for the calculation of the competition between complete fusion and quasifission in reactions with heavy nuclei. The fusion rate through the inner fusion barrier in mass asymmetry is found by using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation. The influence of dissipative effects on the dynamics of nuclear fusion is considered.

  7. Photoassisted carbon dioxide reduction and formation of twoand three-carbon compounds. [prebiological photosynthesis

    NASA Technical Reports Server (NTRS)

    Halmann, M.; Aurian-Blajeni, B.; Bloch, S.

    1981-01-01

    The photoassisted reduction of aqueous carbon dioxide in the presence of naturally occurring minerals is investigated as a possible abiotic precursor of photosynthesis. Aqueous carbon dioxide saturated suspensions or surfaces of the minerals nontronite, bentonite, anatase, wolframite, molybdenite, minium, cinnabar and hematite were irradiated with high-pressure mercury lamps or sunlight. Chemical analyses reveal the production of formic acid, formaldehyde, methanol and methane, and the two and three-carbon compounds glyoxal (CHOCHO) and malonaldehyde (CH2(CHO)2). It is suggested that such photosynthetic reactions with visible light in the presence of semiconducting minerals may provide models for prebiological carbon and nitrogen fixation in both oxidized and reduced atmospheres.

  8. Formation of halogenated organic byproducts during medium-pressure UV and chlorine coexposure of model compounds, NOM and bromide.

    PubMed

    Zhao, Quan; Shang, Chii; Zhang, Xiangru; Ding, Guoyu; Yang, Xin

    2011-12-01

    When chlorine is applied before or during UV disinfection of bromide-containing water, interactions between chlorine, bromide and UV light are inevitable. Formation of halogenated organic byproducts was studied during medium-pressure UV (MPUV) and chlorine coexposure of phenol, nitrobenzene and benzoic acid and maleic acid, chosen to represent electron-donating aromatics, electron-withdrawing aromatics, and aliphatic structures in natural organic matter (NOM), respectively. All were evaluated in the presence and absence of bromide. MPUV and chlorine coexposure of phenol produced less total organic halogen (TOX, a collective parameter for halogenated organic byproducts) than chlorination in the dark, and more haloacetic acids instead of halophenols. Increases in TOX were found in the coexposure of nitrobenzene and benzoic acid, but maleic acid was rather inert during coexposure. The presence of bromide increased the formation of brominated TOX but did not significantly affect total TOX formation, in spite of the fact that it reduced hydroxyl radical levels. MPUV and chlorine coexposure of NOM gave a higher differential UV absorbance of NOM and a larger shift to lower molecular weight compounds than chlorination in the dark. However, TOX formation with NOM remained similar to that observed from dark chlorination.

  9. Carbazole-based emitting compounds: Synthesis, photophysical properties and formation of nanoparticles

    NASA Astrophysics Data System (ADS)

    Adhikari, Ravi M.

    Carbazole is a heterocyclic tricyclic aromatic organic compound consisting of two six-membered benzene rings fused on either side of a five-membered nitrogen-containing ring. A large number of carbazole derivatives have been designed and synthesized and organic electronic devices based on these derivatives such as organic light emitting diodes (OLEDs), have been investigated. Ever since Tang and VanSlyke constructed electroluminescent (EL) devices using organic materials as emitters, development of efficient and stable EL materials has taken good momentum. Carbazole derivatives are widely used as materials for EL and hole-transporting layers of OLEDs which use their high charge mobility. The optical and electrical properties of carbazoles are affected by substitution on the 2-, 3-, 6-, 7- and 9H-positions. Many carbazole derivatives have sufficiently high triplet energy to make them an efficient host where they can serve as red, green, or blue triplet emitters. Highly fluorescent and stable carbazole-based compounds were synthesized and characterized. Substitution of carbazoles at 3- and 6-position by tert-butyl group enhanced the solubility. They showed high extinction coefficients of absorption (Amax ≈ 328-353 nm) and quantum yields of fluorescence (lambdamax ≈ 386-437 nm; phiF ≈ 0.72-0.89; tauF ≈ 2.09-3.91 ns) in dichloromethane. The quantum yields of fluorescence of these compounds in the solid state were also high (lambdamax ≈ 385-422 nm; phiF ≈ 0.40-0.85). Simple synthetic procedures were developed to prepare other stable carbazoles. These compounds emit blue, green, and orange-red light. The red-shifted emission in the solid state which can be as much as 120nm relative to that in solution is highly dependent on the nature and positions of the substituents. The presence of a carbaldehyde or malononitrile on the carbazole moiety quenches fluorescence severely in solution and in the solid state. However, the effect is not the same for the

  10. Formation of biomineral iron oxides compounds in a Fe hyperaccumulator plant: Imperata cylindrica (L.) P. Beauv.

    PubMed

    Fuente, V; Rufo, L; Juárez, B H; Menéndez, N; García-Hernández, M; Salas-Colera, E; Espinosa, A

    2016-01-01

    We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica.

  11. Different formats of imprinted polymers for determining organotin compounds in environmental samples.

    PubMed

    Gallego-Gallegos, Mercedes; Muñoz-Olivas, Riansares; Cámara, Carmen

    2009-02-01

    Organotin compounds and their degradation products enter the environment mainly as a result of their use as biocides and antifouling paints. Analysis of these compounds in environmental samples has to be very sensitive and selective so that their concentrations corresponding to the low environmental target values can also be detected. Generally, analysis of a complex matrix leads to high interferences during the different process steps; clean-up procedures are recommended to overcome this problem. For the past many years, solid phase extraction by employing imprinted materials has been extensively used for many organic substances that are used for pre-concentration and clean-up purposes with excellent results. Here, we present three different imprinted polymers prepared via bulk, precipitation, and emulsion polymerization methods that use similar compositions. The synthesized polymer particles were characterized morphologically by employing scanning electron microscopy and Brunauer-Emmett-Teller analysis. Binding properties were calculated using the Langmuir-Freundlich isotherm. Depending on the properties of the materials, different analytical applications for complex matrices are proposed. These applications are mainly used on tributyltin and its degradation products for environmental analysis.

  12. Formation of biomineral iron oxides compounds in a Fe hyperaccumulator plant: Imperata cylindrica (L.) P. Beauv.

    PubMed

    Fuente, V; Rufo, L; Juárez, B H; Menéndez, N; García-Hernández, M; Salas-Colera, E; Espinosa, A

    2016-01-01

    We report a detailed work of composition and location of naturally formed iron biominerals in plant cells tissues grown in iron rich environments as Imperata cylindrica. This perennial grass grows on the Tinto River banks (Iberian Pyritic Belt) in an extreme acidic ecosystem (pH∼2.3) with high concentration of dissolved iron, sulphate and heavy metals. Iron biominerals were found at the cellular level in tissues of root, stem and leaf both in collected and laboratory-cultivated plants. Iron accumulated in this plant as a mix of iron compounds (mainly as jarosite, ferrihydrite, hematite and spinel phases) was characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Mössbauer spectroscopy (MS), magnetometry (SQUID), electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX; TEM-EDX; HRSTEM). A low fraction of phosphorous was detected in this iron hyperaccumulator plant. Root and rhizomes tissues present a high proportion of ferromagnetic iron oxide compounds. Iron oxides-rich zones are localized in electron dense intra and inter-cellular aggregates that appear as dark deposits covering the inner membrane and organelles of the cell. This study aims to contribute to a better understanding of the mechanisms of accumulation, transport, distribution of iron in Imperata cylindrica. PMID:26592710

  13. Determination of ideal-gas enthalpies of formation for key compounds: The 1988 project results

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Nguyen, A.; Hossenlopp, I.A.; Smith, N.K.

    1990-07-01

    The results of a study aimed at improvement of group contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weakness where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase and vapor-pressure measurements. Ideal-gas enthalpies of formation are reported for 3-methylbuta-1,2-diene; 2,5-dimethylhexa-2,4-diene; acetaldoxime; N,N-diethylhydroxylamine; 1-methylpyrrolidin-2-one; and phenanthrene. Solid and liquid-phase enthalpies of formation at 298.15 K are determined for benzamide. Ring corrections, group terms, and next-nearest-neighbor interaction terms useful in the application of group contribution correlations are derived. 54 refs., 2 figs., 21 tabs.

  14. Ozonolysis of a series of biogenic organic volatile compounds and secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    Bernard, François; Quilgars, Alain; Cazaunau, Mathieu; Grosselin, Benoît.; Daele, Véronique; Mellouki, Abdelwahid; Winterhalter, Richard; Moortgat, Geert K.

    2010-05-01

    Secondary organic aerosols are formed via nucleation of atmospheric organic vapours on pre-existing particles observed in various rural environments where the organic fraction represents the major part of the observed nano-particle (Kavouras and Stephanou, 2002; Kulmala et al., 2004a). However, nucleation of organic vapors appears to be unlikely thermodynamically in relevant atmospheric conditions (Kulmala et al., 2004b). In this work, a systematic study has been conducted to investigate the aerosol formation through the ozonolysis of a series of monotepenes using a newly developed aerosol flow reactor and the ICARE indoor simulation chamber. The nucleation thresholds have been determined for SOA formed through the reaction of ozone with a-Pinene, sabinene, myrcene and limonene in absence of any observable existing particles. The measurements were performed using the flow reactor combined to a particle counter (CPC 3022). Number concentrations of SOA have been measured for different concentration of consumed monoterpenes. The data obtained allow us to estimate the nucleation threshold for a range of 0.2 - 45 ppb of consumed monoterpenes. The nucleation threshold values obtained here (≤ 1 ppb of the consumed monoterpenes) have been found to be lower than the previously reported ones (Berndt et al., 2003; Bonn and Moortgat, 2003; Koch et al., 2000; Lee and Kamens, 2005). The ICARE simulation chamber has been used to study the mechanism of the reaction of ozone with various acyclic terpenes (myrcene, ocimene, linalool and a-farnesene) and to derive the SOA mass formation yield. The time-concentration profiles of reactants and products in gas-phase were obtained using in-situ Fourier Transform Infrared Spectroscopy. In addition, the number and mass concentrations of SOA have been monitored with a Scanning Mobility Particle Sizer. The chemical composition of the SOA formed has been tentatively characterised using Liquid Chromatography - Mass Spectrometry. The results

  15. Model compound study of the pathways for aromatic hydrocarbon formation in soot.

    SciTech Connect

    Tomczyk, N. A.; Hunt, J. E.; Winans, R. E.; Solum, M. S.; Pugmire, R. J.; Fletcher, T. H.

    2002-04-29

    To explore the mechanisms for formation of aromatic hydrocarbons as precursors to soot, a model system using combustion of biphenyl in a fuel rich flame is studied. The soots acquired at three different temperatures are solvent extracted and the extract characterized by both GCMS and high resolution mass spectrometry. A description of the NMR results for the whole soots has been published (1). The production of most products could be rationalized from the coupling of biphenyls and subsequent aromatic species and the addition of acetylenes to existing aromatic molecules. Early work by Badger on pyrolysis of hydrocarbons is used in developing these schemes (2). The reaction schemes to produce larger aromatic hydrocarbons will be discussed. Richter and Howard have discussed in detail potential reaction mechanisms in the formation of aromatics as precursors to soot (3).

  16. Determination of ideal-gas enthalpies of formation for key compounds: The 1988 project results

    NASA Astrophysics Data System (ADS)

    Steele, W. V.; Chirico, R. D.; Nguyen, A.; Hossenlopp, I. A.; Smith, N. K.

    1990-07-01

    The results of a study aimed at improvement of group contribution methodology for estimation of thermodynamic properties of organic substances are reported. Specific weakness where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase and vapor pressure measurements. Ideal-gas enthalpies of formation are reported for 3-methylbuta 1,2-diene; 2,5-dimethylhexa 2,4-diene; acetaldoxime; N,N-diethyl hydroxylamine; 1-methylpyrrolidin-2-one; and phenanthrene. Solid and liquid phase enthalpies of formation at 298.15 K are determined for benzamide. Ring corrections, group terms, and next-nearest-neighbor interaction terms useful in the application of group contribution correlations are derived.

  17. Antioxidant Compounds in Traditional Indian Pickles May Prevent the Process-Induced Formation of Benzene.

    PubMed

    Kharat, Mahesh M; Adiani, Vanshika; Variyar, Prasad; Sharma, Arun; Singhal, Rekha S

    2016-01-01

    Pickles in the Indian market contain ascorbic acid from the raw material used and benzoate as an added preservative that are involved in the formation of benzene in soft drinks. In this work, 24 market pickle samples were surveyed for benzene content, as well as its precursors and other constituents that influence its formation. The analysis showed that pickle samples were high in acid content (low pH) and showed significant amount of ascorbic acid, minerals (Cu and Fe), and benzoic acid present in them. Also, most samples exhibited high antioxidant activity that might be attributed to the ingredients used, such as fruits and spices. The solid-phase microextraction headspace gas chromatography-mass spectrometry method was developed in-house for benzene analysis. Eleven of 24 samples had benzene, with the highest concentration of 4.36 ± 0.82 μg of benzene per kg of pickle for a lime pickle that was also reported to have highest benzoic acid and considerably less hydroxyl radical ((•)OH) scavenging activity. However, benzene levels for all 11 samples were considerably below the World Health Organization regulatory limit of 10 μg/kg for benzene in mineral water. Studies on model systems revealed that the high antioxidant activity of Indian pickles may have had a strong inhibitory effect on benzene formation.

  18. Antioxidant Compounds in Traditional Indian Pickles May Prevent the Process-Induced Formation of Benzene.

    PubMed

    Kharat, Mahesh M; Adiani, Vanshika; Variyar, Prasad; Sharma, Arun; Singhal, Rekha S

    2016-01-01

    Pickles in the Indian market contain ascorbic acid from the raw material used and benzoate as an added preservative that are involved in the formation of benzene in soft drinks. In this work, 24 market pickle samples were surveyed for benzene content, as well as its precursors and other constituents that influence its formation. The analysis showed that pickle samples were high in acid content (low pH) and showed significant amount of ascorbic acid, minerals (Cu and Fe), and benzoic acid present in them. Also, most samples exhibited high antioxidant activity that might be attributed to the ingredients used, such as fruits and spices. The solid-phase microextraction headspace gas chromatography-mass spectrometry method was developed in-house for benzene analysis. Eleven of 24 samples had benzene, with the highest concentration of 4.36 ± 0.82 μg of benzene per kg of pickle for a lime pickle that was also reported to have highest benzoic acid and considerably less hydroxyl radical ((•)OH) scavenging activity. However, benzene levels for all 11 samples were considerably below the World Health Organization regulatory limit of 10 μg/kg for benzene in mineral water. Studies on model systems revealed that the high antioxidant activity of Indian pickles may have had a strong inhibitory effect on benzene formation. PMID:26735038

  19. Organic aerosol formation from biogenic compounds over the Ponderosa pine forest in Colorado

    NASA Astrophysics Data System (ADS)

    Roux, Alma Hodzic; Lee-Taylor, Julia; Cui, Yuyan; Madronich, Sasha

    2013-05-01

    The secondary organic aerosol (SOA) formation and regional growth from biogenic precursors is of particular interest given their abundance in the atmosphere, and has been investigated during the Rocky Mountain Biogenic Aerosol field Study in 2011 in the pine forest canopy (dominated by terpene emissions) using both WRF/Chem 4km simulations and the GECKO-A explicit chemistry box-model runs. We have quantified the relative contribution of different biogenic precursors to SOA levels that were measured by the aerosol mass spectrometer at the site, and investigated the relative contribution of OH, O3 and NO3 chemistry to the formed SOA mass during day-and nighttime. Although, the local production and mass concentrations of submicron organic aerosols at the site seem relatively modest ˜1-2 ug/m3, we show that the optically active regional mass is increased as the SOA formation continues for several days in the background forest air. We investigate whether the simplified SOA parameterizations used in 3D models can capture this growth. In addition, preliminary comparisons of the number concentrations and the composition of ultrafine particles (8 - 30nm) from WRF/Chem simulations and TD-CIMS measurements are also discussed, and the contribution of organic aerosols to CCN formation is quantified.

  20. Entrance-channel mass-asymmetry dependence of compound nucleus formation time in light heavy-ion reactions

    SciTech Connect

    Szanto de Toledo, A.; Carlson, B.V.; Beck, C.

    1996-12-01

    The entrance-channel mass-asymmetry dependence of the compound nucleus formation time in light heavy-ion reactions has been investigated within the framework of semiclassical dissipative collision models. The model calculations have been applied successfully to the formation of the {sup 38}Ar compound nucleus as populated via the {sup 9}Be+{sup 29}Si, {sup 11}B+{sup 27}Al, {sup 12}C+{sup 26}Mg, and {sup 19}F+{sup 19}F entrance channels. The shape evolution of several other light composite systems appears to be consistent with the so-called {open_quote}{open_quote}Fusion Inhibition Factor{close_quote}{close_quote} which has been observed experimentally. As found previously in more massive systems for the fusion-evaporation process, the entrance-channel mass-asymmetry degree of freedom appears to determine the competition between the different mechanisms as well as the time scales involved. {copyright} {ital 1996 The American Physical Society.}

  1. Compositions, Formation Mechanism, and Neuroprotective Effect of Compound Precipitation from the Traditional Chinese Prescription Huang-Lian-Jie-Du-Tang.

    PubMed

    Zhang, Chenze; Zhao, Rui; Yan, Wenqiang; Wang, Hui; Jia, Menglu; Zhu, Nailiang; Zhu, Yindi; Zhang, Yuzhong; Wang, Penglong; Lei, Haimin

    2016-01-01

    Compounds in the form of precipitation (CFP) are universally formed during the decocting of Chinese prescriptions, such as Huang-Lian-Jie-Du-Tang (HLJDT). The formation rate of HLJDT CFP even reached 2.63% ± 0.20%. The identification by liquid chromatography mass spectrometry (LC-MS(n)) proved that the main chemical substances of HLJDT CFP are baicalin and berberine, which is coincident with the theory that the CFP might derive from interaction between acidic and basic compounds. To investigate the formation mechanism of HLJDT CFP, baicalin and berberine were selected to synthesize a simulated precipitation and then the baicalin-berberine complex was obtained. Results indicated that the melting point of the complex interposed between baicalin and berberine, and the UV absorption, was different from the mother material. In addition, ¹H-NMR integral and high-resolution mass spectroscopy (HR-MS) can validate that the binding ratio was 1:1. Compared with baicalin, the chemical shifts of H and C on glucuronide had undergone significant changes by ¹H-, (13)C-NMR, which proved that electron transfer occurred between the carboxylic proton and the lone pair of electrons on the N atom. Both HLJDT CFP and the baicalin-berberine complex showed protective effects against cobalt chloride-induced neurotoxicity in differentiated PC12 cells. It is a novel idea, studying the material foundation of CFP in Chinese prescriptions. PMID:27548137

  2. Formation pathways and opioid activity data for 3-hydroxypyridinium compounds derived from glucuronic acid and opioid peptides by Maillard processes.

    PubMed

    Horvat, Stefica; Roscić, Maja; Lemieux, Carole; Nguyen, Thi M-D; Schiller, Peter W

    2007-07-01

    The kinetics of formation and identity of the reaction products of the glucuronic acid with three representative opioid peptides were investigated in vitro. Peptides were conjugated with glucuronic acid either in solution or under dry-heating conditions. From the incubations performed in solution N-(1-deoxy-D-fructofuranos-1-yluronic acid)-peptide derivatives (Amadori compounds) were isolated, whereas from the dry-heated reactions products containing the 3-hydroxypyridinium moiety at the N-terminal of the peptide chain were obtained. Experiments performed under mild dry-heating conditions (40 degrees C) in model systems based on Leu-enkephalin and glucuronic acid, and in environment of either 40% or 75% relative humidity, revealed that the higher level of humidity promoted a process that enhanced 3-hydroxypyridinium compound generation. The mechanism of 3-hydroxypyridinium formation is discussed. In comparison with their respective parent peptides, the N-(1-deoxy-D-fructofuranosyl-uronic acid) derivatives of the opioid peptides showed three- to 11-fold lower mu- and delta-receptor-binding affinities and agonist potencies in the functional assays, likely as a consequence of the steric bulk introduced at the N-terminal amino group. The further decrease in opioid activity observed with the 3-hydroxypyridinium-containing peptides may be due to the lower pK(a) of the 3-hydroxypyridinium moiety and to delocalization of the positive charge in the pyridinium ring system. PMID:17630992

  3. Impacts of competitive inhibition, parent compound formation and partitioning behavior on the removal of antibiotics in municipal wastewater treatment.

    PubMed

    Plósz, Benedek G Y; Leknes, Henriette; Thomas, Kevin V

    2010-01-15

    We present a process model that predicts the removal of the antibiotic micropollutants, sulfamethoxazole (SMX), tetracycline (TCY), and ciprofloxacin (CIP), in an activated sludge treatment system. A novel method was developed to solve the inverse problem of inferring process rate, sorption, and correction factor parameter values from batch experimental results obtained under aerobic and anoxic conditions. Instead of spiking the batch reactors with reference substances, measurements were made using the xenobiotic organic micropollutant content of preclarified municipal sewage. Parent compound formation and removal were observed, and the model developed using the simulation software West showed limited efficiency to describe the selected micropollutants profiles, when growth substrate removal occurs. The model structure was optimized by accounting for competitive inhibition by readily biodegradable substrates on the cometabolic micropollutant biotransformation processes. Our results suggest that, under anoxic conditions, hydrophobicity-independent mechanisms can significantly impact solid-liquid partitioning that our model takes into account by using the sorption coefficient as a lumped parameter. Forward dynamic simulations were carried out to evaluate the developed model and to confirm it for SMX using data obtained in a full-scale treatment plant. Evaluation of measured and simulation results suggest that, robust model prediction can be achieved by approximating the influent load of chemicals biodegrading via a given parent compound, e.g., human conjugates, as an antibiotic mass that is proportional to the parent compound load. PMID:20000564

  4. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis.

    PubMed

    Holm, Nils G; Neubeck, Anna

    2009-10-22

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur.

  5. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis.

    PubMed

    Holm, Nils G; Neubeck, Anna

    2009-01-01

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur. PMID:19849830

  6. Reduction of nitrogen compounds in oceanic basement and its implications for HCN formation and abiotic organic synthesis

    PubMed Central

    2009-01-01

    Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native Fe and Ni and are adsorbed on authigenic layer silicates and zeolites. The native metals as well as the molecular hydrogen reducing CO2 to CO/CH4 and NO3-/NO2- to NH3/NH4+ are a result of serpentinization of mafic rocks. Oceanic plates are conveyor belts of reduced carbon and nitrogen compounds from the off-axis hydrothermal environments to the subduction zones, where compaction, dehydration, desiccation and diagenetic reactions affect the organic precursors. CO/CH4 and NH3/NH4+ in fluids distilled out of layer silicates and zeolites in the subducting plate at an early stage of subduction will react upon heating and form HCN, which is then available for further organic reactions to, for instance, carbohydrates, nucleosides or even nucleotides, under alkaline conditions in hydrated mantle rocks of the overriding plate. Convergent margins in the initial phase of subduction must, therefore, be considered the most potent sites for prebiotic reactions on Earth. This means that origin of life processes are, perhaps, only possible on planets where some kind of plate tectonics occur. PMID:19849830

  7. Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.-H.; Cho, W.D.

    1996-11-01

    Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  8. SOA Formation form the NO3 radicals Chemistry of Isoprene, Monoterpenes, Sesquiterpenes, Biogenic Oxygenated Compounds, and Aromatics

    NASA Astrophysics Data System (ADS)

    Kleindienst, T. E.; Jaoui, M.; Docherty, K.; Corse, E.; Offenberg, J. H.; Lewandowski, M.

    2011-12-01

    Volatile organic compounds (VOCs) are oxidized in the atmosphere primarily by hydroxyl radicals (OH) during daylight hours but also by nitrate radicals (NO3) during overnight, photochemically inactive periods. While reactions with OH have received considerable attention with regard to gas-phase reaction products and secondary organic aerosol (SOA) formation, less is known about the mechanisms and products resulting from nighttime NO3 reactions despite their potential for SOA formation. To date, there have been limited studies on the chemical characteristics of aerosol reaction products formed from VOCs oxidation with NO3, and few SOA reaction products have been identified. Nighttime reactions have nevertheless been incorporated into some air quality models despite the limited information available and substantial uncertainties which still exist. The National Exposure Research Laboratory of the U.S. Environmental Protection Agency recently undertook an integrated laboratory research effort to better understand the contribution of NO3 reactions to nighttime SOA formation. Isoprene, methacrolein, a-pinene, b-pinene, d-limonene, b-caryophyllene, farnesene, a-humulene, 2-methyl-3-buten-2-ol, toluene, m-xylene, and naphthalene were reacted with NO3 under a wide range of conditions in a series of separate photochemical reaction chamber experiments. These hydrocarbons are thought to contribute to ambient SOA formation. NO3 was formed through thermal decomposition of N2O5. The yield, physical characteristics, and composition of SOA formed in each experiment was analyzed by a suite of instruments including a scanning mobility particle sizer, a Sunset Labs semi continuous EC-OC monitor, a volatility differential mobility analyzer, a direct insertion probe-mass spectrometer, a high resolution time-of-flight aerosol mass spectrometer, and a gas-chromatography-mass spectrometer. To understand the relative contributions of nighttime versus daytime VOCs reactions, a similar

  9. Reactions of SIV species with organic compounds: formation mechanisms of organo-sulfur derivatives in atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Passananti, Monica; Shang, Jing; Dupart, Yoan; Perrier, Sébastien; George, Christian

    2015-04-01

    Secondary organic aerosol (SOA) have an important impact on climate, air quality and human health. However the chemical reactions involved in their formation and growth are not fully understood or well-constrained in climate models. It is well known that inorganic sulfur (mainly in oxidation states (+IV) and (+VI)) plays a key role in aerosol formation, for instance sulfuric acid is known to be a good nucleating gas. In addition, acid-catalyzed heterogeneous reactions of organic compounds has shown to produce new particles, with a clear enhancement in the presence of ozone (Iinuma 2013). Organosulfates have been detected in tropospheric particles and aqueous phases, which suggests they are products of secondary organic aerosol formation process (Tolocka 2012). Originally, the production of organosulfates was explained by the esterification reaction of alcohols, but this reaction in atmosphere is kinetically negligible. Other formation pathways have been suggested such as hydrolysis of peroxides and reaction of organic matter with sulfite and sulfate radical anions (SO3-, SO4-) (Nozière 2010), but it remains unclear if these can completely explain atmospheric organo-sulfur aerosol loading. To better understand the formation of organo-sulfur compounds, we started to investigate the reactivity of SIV species (SO2 and SO32-) with respect to specific functional groups (organic acids and double bonds) on atmospherically relevant carboxylic acids and alkenes. The experiments were carried out in the homogeneous aqueous phase and at the solid-gas interface. A custom built coated-wall flow tube reactor was developed to control relativity humidity, SO2 concentration, temperature and gas flow rate. Homogeneous and heterogeneous reaction kinetics were measured and resulting products were identified using liquid chromatography coupled with an orbitrap mass spectrometer (LC-HR-MS). The experiments were performed with and without the presence of ozone in order to evaluate any

  10. Comets and the formation of biochemical compounds on the primitive Earth--a review.

    PubMed

    Oró, J; Mills, T; Lazcano, A

    1992-01-01

    Thirty years ago it was suggested that comets impacting on the primitive Earth may have represented a significant source of terrestrial volatiles, including some important precursors for prebiotic synthesis (Oró, 1961, Nature 190: 389). This possibility is strongly supported not only by models of the collisional history of the early Earth, but also by astronomical evidence that suggests that frequent collisions of comet-like bodies from the circumstellar disk around the star beta Pictoris are taking place. Although a significant fraction of the complex organic compounds that appear to be present in cometary nuclei were probably destroyed during impact, it is argued that cometary collisions with the primitive Earth represented an important source of both free-energy and volatiles, and may have created transient, gaseous environments in which prebiotic synthesis may have taken place.

  11. SCB ignition of pyrotechnics, thermites and intermetallics

    SciTech Connect

    Bickes, R.W. Jr.; Grubelich, M.C.

    1996-09-01

    We investigated ignition of pyrotechnics, metal-fuel/metal-oxide compositions (thermites), and exothermic alloy compositions (intermetallics) using a semiconductor bridge (SCB). It was shown that these materials could be ignited at low energy levels with an appropriately designed SCB, proper loading density, and good thermal isolation. Materials tested included Al/CuO, B/BaCrO{sub 4}, TiH{sub 1.65}/KClO{sub 4}, Ti/KClO{sub 4}, Zr/BaCrO{sub 4}, Zr/CuO, Zr/Fe{sub 2}O{sub 3}, Zr/KClO{sub 4}, and 100-mesh Al/Pd. Firing set was a capacitor discharge unit with charge capacitors ranging from 3 to 20,000 {mu}F at charge voltages 5-50 V. Devices functioned a few miliseconds after onset of current pulse at input energies as low as 3 mJ. We also report on a thermite torch design.

  12. High temperature intermetallic binders for HVOF carbides

    SciTech Connect

    Shaw, K.G.; Gruninger, M.F.; Jarosinski, W.J.

    1994-12-31

    Gas turbines technology has a long history of employing the desirable high temperature physical attributes of ceramic-metallic (cermet) materials. The most commonly used coatings incorporate combinations of WC-Co and Cr{sub 3}C{sub 2}-NiCr, which have also been successfully utilized in other non-turbine coating applications. Increased turbine operating temperatures and other high temperature service conditions have made apparent the attractive notion of increasing the temperature capability and corrosion resistance of these coatings. In this study the intermetallic binder NiAl has been used to replace the cobalt and NiCr constituents of conventional WC and Cr{sub 3}C{sub 2} cermet powders. The composite carbide thermal spray powders were fabricated for use in the HVOF coating process. The structure of HVOF deposited NiAl-carbide coatings are compared directly to the more familiar WC-Co and Cr{sub 3}C{sub 2}-NiCr coatings using X-ray diffraction, back-scattered electron imaging (BEI) and electron dispersive spectroscopy (EDS). Hardness variations with temperature are reported and compared between the NiAl and Co/NiCr binders.

  13. Thermal stress effects in intermetallic matrix composites

    NASA Technical Reports Server (NTRS)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-01-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  14. Ground state searches in fcc intermetallics

    SciTech Connect

    Wolverton, C.; de Fontaine, D. ); Ceder, G. ); Dreysse, H. . Lab. de Physique du Solide)

    1991-12-01

    A cluster expansion is used to predict the fcc ground states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. The intermetallic structures are not assumed, but derived regorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearized-muffin-tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.

  15. Thermal stress effects in intermetallic matrix composites

    NASA Astrophysics Data System (ADS)

    Wright, P. K.; Sensmeier, M. D.; Kupperman, D. S.; Wadley, H. N. G.

    1993-09-01

    Intermetallic matrix composites develop residual stresses from the large thermal expansion mismatch (delta-alpha) between the fibers and matrix. This work was undertaken to: establish improved techniques to measure these thermal stresses in IMC's; determine residual stresses in a variety of IMC systems by experiments and modeling; and, determine the effect of residual stresses on selected mechanical properties of an IMC. X ray diffraction (XRD), neutron diffraction (ND), synchrotron XRD (SXRD), and ultrasonics (US) techniques for measuring thermal stresses in IMC were examined and ND was selected as the most promising technique. ND was demonstrated on a variety of IMC systems encompassing Ti- and Ni-base matrices, SiC, W, and Al2O3 fibers, and different fiber fractions (Vf). Experimental results on these systems agreed with predictions of a concentric cylinder model. In SiC/Ti-base systems, little yielding was found and stresses were controlled primarily by delta-alpha and Vf. In Ni-base matrix systems, yield strength of the matrix and Vf controlled stress levels. The longitudinal residual stresses in SCS-6/Ti-24Al-llNb composite were modified by thermomechanical processing. Increasing residual stress decreased ultimate tensile strength in agreement with model predictions. Fiber pushout strength showed an unexpected inverse correlation with residual stress. In-plane shear yield strength showed no dependence on residual stress. Higher levels of residual tension led to higher fatigue crack growth rates, as suggested by matrix mean stress effects.

  16. Role of two alternate water networks in Compound I formation in P450eryF.

    PubMed

    Sen, Kakali; Thiel, Walter

    2014-03-20

    The P450eryF enzyme (CYP107A1) hydroxylates 6-deoxyerythronolide B to erythronolide B during erythromycin synthesis by Saccharopolyspora erythraea. In many P450 enzymes, a conserved "acid-alcohol pair" is believed to participate in the proton shuttling pathway for O2 activation that generates the reactive oxidant (Compound I, Cpd I). In CYP107A1, the alcohol-containing amino acid is replaced with alanine. The crystal structure of DEB bound to CYP107A1 indicates that one of the substrate hydroxyl groups (5-OH) may facilitate proton transfer during O2 activation. We applied molecular dynamics (MD) and hybrid quantum mechanics/molecular mechanics (QM/MM) techniques to investigate substrate-mediated O2 activation in CYP107A1. In the QM/MM calculations, the QM region was treated by density functional theory, and the MM region was represented by the CHARMM force field. The MD simulations suggest the existence of two water networks around the active site, the one found in the crystal structure involving E360 and an alternative one involving E244. According to the QM/MM calculations, the first proton transfer that converts the peroxo to the hydroperoxo intermediate (Compound 0, Cpd 0) proceeds via the E244 water network with direct involvement of the 5-OH group of the substrate. For the second proton transfer from Cpd 0 to Cpd I, the computed barriers for the rate-limiting homolytic O-O cleavage are similar for the E360 and E244 pathways, and hence both glutamate residues may serve as proton source in this step.

  17. The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine.

    PubMed

    Orola, Liana; Veidis, Mikelis V; Sarcevica, Inese; Actins, Andris; Belyakov, Sergey; Platonenko, Aleksandrs

    2012-08-01

    The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified.

  18. Investigation of formation of nitrogen compounds in coal combustion. Final report

    SciTech Connect

    Blair, D.W.; Crane, I.D.; Wendt, J.O.L.

    1983-10-01

    This is the final report on DOE contract number DE-AC21-80MC14061. It concerns the formation of nitrogen oxide from fuel-bound nitrogen during coal combustion. The work reported was divided into three tasks. They addressed problems of time-resolving pyrolysis rates of coal under simulated combustion conditions, the combustion of the tar that results from such pyrolysis, and theoretical modeling of the pyrolysis process. In all of these tasks, special attention was devoted to the fate of coal nitrogen. The first two tasks were performed by Exxon Research and Engineering Company. 49 references.

  19. The effect of pH on polymorph formation of the pharmaceutically active compound tianeptine.

    PubMed

    Orola, Liana; Veidis, Mikelis V; Sarcevica, Inese; Actins, Andris; Belyakov, Sergey; Platonenko, Aleksandrs

    2012-08-01

    The anti-depressant pharmaceutical tianeptine has been investigated to determine the dynamics of polymorph formation under various pH conditions. By varying the pH two crystalline polymorphs were isolated. The molecular and crystal structures have been determined to identify the two polymorphs. One polymorph is an amino carboxylic acid and the other polymorph is a zwitterion. In the solid state the tianeptine moieties are bonded through hydrogen bonds. The zwitterion was found to be less stable and transformed to the acid form. During this investigation an amorphous form was identified. PMID:22569228

  20. Heats of formation of phosphorus compounds determined by current methods of computational quantum chemistry

    NASA Astrophysics Data System (ADS)

    Haworth, Naomi L.; Bacskay, George B.

    2002-12-01

    The heats of formation of a range of phosphorus containing molecules (P2, P4, PH, PH2, PH3, P2H2, P2H4, PO, PO2, PO3, P2O, P2O2, HPO, HPOH, H2POH, H3PO, HOPO, and HOPO2) have been determined by high level quantum chemical calculations. The equilibrium geometries and vibrational frequencies were computed via density functional theory, utilizing the B3LYP/6-31G(2df,p) functional and basis set. Atomization energies were obtained by the application of ab initio coupled cluster theory with single and double excitations from (spin)-restricted Hartree-Fock reference states with perturbative correction for triples [CCSD(T)], in conjunction with cc-pVnZ basis sets (n=T, Q, 5) which include an extra d function on the phosphorus atoms and diffuse functions on the oxygens, as recommended by Bauschlicher [J. Phys. Chem. A 103, 11126 (1999)]. The valence correlated atomization energies were extrapolated to the complete basis limit and corrected for core-valence (CV) correlation and scalar relativistic effects, as well as for basis set superposition errors (BSSE) in the CV terms. This methodology is effectively the same as the one adopted by Bauschlicher in his study of PO, PO2, PO3, HPO, HOPO, and HOPO2. Consequently, for these molecules the results of this work closely match Bauschlicher's computed values. The theoretical heats of formation, whose accuracy is estimated as ranging from ±1.0 to ±2.5 kcal mol-1, are consistent with the available experimental data. The current set of theoretical data represent a convenient benchmark, against which the results of other computational procedures, such as G3, G3X, and G3X2, can be compared. Despite the fact that G3X2 [which is an approximation to the quadratic CI procedure QCISD(T,Full)/G3Xlarge] is a formally higher level theory than G3X, the heats of formation obtained by these two methods are found to be of comparable accuracy. Both reproduce the benchmark heats of formation on the average to within ±2 kcal mol-1 and, for these

  1. The natural chlorine cycle - Formation of the carcinogenic and greenhouse gas compound chloroform in drinking water reservoirs.

    PubMed

    Forczek, Sándor T; Pavlík, Milan; Holík, Josef; Rederer, Luděk; Ferenčík, Martin

    2016-08-01

    Chlorine cycle in natural ecosystems involves formation of low and high molecular weight organic compounds of living organisms, soil organic matter and atmospherically deposited chloride. Chloroform (CHCl3) and adsorbable organohalogens (AOX) are part of the chlorine cycle. We attempted to characterize the dynamical changes in the levels of total organic carbon (TOC), AOX, chlorine and CHCl3 in a drinking water reservoir and in its tributaries, mainly at its spring, and attempt to relate the presence of AOX and CHCl3 with meteorological, chemical or biological factors. Water temperature and pH influence the formation and accumulation of CHCl3 and affect the conditions for biological processes, which are demonstrated by the correlation between CHCl3 and ΣAOX/Cl(-) ratio, and also by CHCl3/ΣAOX, CHCl3/AOXLMW, CHCl3/ΣTOC, CHCl3/TOCLMW and CHCl3/Cl(-) ratios in different microecosystems (e.g. old spruce forest, stagnant acidic water, humid and warm conditions with high biological activity). These processes start with the biotransformation of AOX from TOC, continue via degradation of AOX to smaller molecules and further chlorination, and finish with the formation of small chlorinated molecules, and their subsequent volatilization and mineralization. The determined concentrations of chloroform result from a dynamic equilibrium between its formation and degradation in the water; in the Hamry water reservoir, this results in a total amount of 0.1-0.7 kg chloroform and 5.2-15.4 t chloride. The formation of chloroform is affected by Cl(-) concentration, by concentrations and ratios of biogenic substrates (TOC and AOX), and by the ratios of the substrates and the product (feedback control by chloroform itself).

  2. The natural chlorine cycle - Formation of the carcinogenic and greenhouse gas compound chloroform in drinking water reservoirs.

    PubMed

    Forczek, Sándor T; Pavlík, Milan; Holík, Josef; Rederer, Luděk; Ferenčík, Martin

    2016-08-01

    Chlorine cycle in natural ecosystems involves formation of low and high molecular weight organic compounds of living organisms, soil organic matter and atmospherically deposited chloride. Chloroform (CHCl3) and adsorbable organohalogens (AOX) are part of the chlorine cycle. We attempted to characterize the dynamical changes in the levels of total organic carbon (TOC), AOX, chlorine and CHCl3 in a drinking water reservoir and in its tributaries, mainly at its spring, and attempt to relate the presence of AOX and CHCl3 with meteorological, chemical or biological factors. Water temperature and pH influence the formation and accumulation of CHCl3 and affect the conditions for biological processes, which are demonstrated by the correlation between CHCl3 and ΣAOX/Cl(-) ratio, and also by CHCl3/ΣAOX, CHCl3/AOXLMW, CHCl3/ΣTOC, CHCl3/TOCLMW and CHCl3/Cl(-) ratios in different microecosystems (e.g. old spruce forest, stagnant acidic water, humid and warm conditions with high biological activity). These processes start with the biotransformation of AOX from TOC, continue via degradation of AOX to smaller molecules and further chlorination, and finish with the formation of small chlorinated molecules, and their subsequent volatilization and mineralization. The determined concentrations of chloroform result from a dynamic equilibrium between its formation and degradation in the water; in the Hamry water reservoir, this results in a total amount of 0.1-0.7 kg chloroform and 5.2-15.4 t chloride. The formation of chloroform is affected by Cl(-) concentration, by concentrations and ratios of biogenic substrates (TOC and AOX), and by the ratios of the substrates and the product (feedback control by chloroform itself). PMID:27231877

  3. Effects of sulfhydryl compounds, carbohydrates, organic acids, and sodium sulfite on the formation of lysinoalanine in preserved egg.

    PubMed

    Luo, Xu-Ying; Tu, Yong-Gang; Zhao, Yan; Li, Jian-Ke; Wang, Jun-Jie

    2014-08-01

    To identify inhibitors for lysinoalanine formation in preserved egg, sulfhydryl compounds (glutathione, L-cysteine), carbohydrates (sucrose, D-glucose, maltose), organic acids (L-ascorbic acid, citric acid, DL-malic acid, lactic acid), and sodium sulfite were individually added at different concentrations to a pickling solution to prepare preserved eggs. Lysinoalanine formation as an index of these 10 substances was determined. Results indicate that glutathione, D-glucose, maltose, L-ascorbic acid, citric acid, lactic acid, and sodium sulfite all effectively diminished lysinoalanine formation in preserved egg albumen and yolk. When 40 and 80 mmol/L of sodium sulfite, citric acid, L-ascorbic acid, and D-glucose were individually added into the pickling solution, the inhibition rates of lysinoalanine in the produced preserved egg albumen and yolk were higher. However, the attempt of minimizing lysinoalanine formation was combined with the premise of ensuring preserved eggs quality. Moreover, the addition of 40 and 80 mmol/L of sodium sulfite, 40 and 80 mmol/L of D-glucose, 40 mmol/L of citric acid, and 40 mmol/L of L-ascorbic acid was optimal to produce preserved eggs. The corresponding inhibition rates of lysinoalanine in the albumen were approximately 76.3% to 76.5%, 67.6% to 67.8%, 74.6%, and 74.6%, and the corresponding inhibition rates of lysinoalanine in the yolk were about 68.7% to 69.7%, 50.6% to 51.8%, 70.4%, and 57.8%. It was concluded that sodium sulfite, D-glucose, L-ascorbic, and citric acid at suitable concentrations can be used to control the formation of lysinoalanine during preserved egg processing.

  4. Effects of sulfhydryl compounds, carbohydrates, organic acids, and sodium sulfite on the formation of lysinoalanine in preserved egg.

    PubMed

    Luo, Xu-Ying; Tu, Yong-Gang; Zhao, Yan; Li, Jian-Ke; Wang, Jun-Jie

    2014-08-01

    To identify inhibitors for lysinoalanine formation in preserved egg, sulfhydryl compounds (glutathione, L-cysteine), carbohydrates (sucrose, D-glucose, maltose), organic acids (L-ascorbic acid, citric acid, DL-malic acid, lactic acid), and sodium sulfite were individually added at different concentrations to a pickling solution to prepare preserved eggs. Lysinoalanine formation as an index of these 10 substances was determined. Results indicate that glutathione, D-glucose, maltose, L-ascorbic acid, citric acid, lactic acid, and sodium sulfite all effectively diminished lysinoalanine formation in preserved egg albumen and yolk. When 40 and 80 mmol/L of sodium sulfite, citric acid, L-ascorbic acid, and D-glucose were individually added into the pickling solution, the inhibition rates of lysinoalanine in the produced preserved egg albumen and yolk were higher. However, the attempt of minimizing lysinoalanine formation was combined with the premise of ensuring preserved eggs quality. Moreover, the addition of 40 and 80 mmol/L of sodium sulfite, 40 and 80 mmol/L of D-glucose, 40 mmol/L of citric acid, and 40 mmol/L of L-ascorbic acid was optimal to produce preserved eggs. The corresponding inhibition rates of lysinoalanine in the albumen were approximately 76.3% to 76.5%, 67.6% to 67.8%, 74.6%, and 74.6%, and the corresponding inhibition rates of lysinoalanine in the yolk were about 68.7% to 69.7%, 50.6% to 51.8%, 70.4%, and 57.8%. It was concluded that sodium sulfite, D-glucose, L-ascorbic, and citric acid at suitable concentrations can be used to control the formation of lysinoalanine during preserved egg processing. PMID:25047093

  5. New insights into the formation of volatile compounds in mainstream cigarette smoke

    PubMed Central

    Feng, S.; van Heemst, J.; McAdam, K. G.

    2010-01-01

    A sampling system has been set up to monitor a group of volatile smoke analytes (nitric oxide, acetaldehyde, acetone, benzene, toluene, 1,3 butadiene, isoprene and carbon dioxide) from mainstream cigarette smoke on a puff-resolved basis. The system was able to record gas evolution profiles during puffing and interpuff periods without interruption (e.g. taking clearing puffs). Gas phase smoke analytes were sampled as close to the mouth end of the cigarette filter as possible in order to minimise any dead volume effect. The results revealed that, for some volatile species, a significant fraction (e.g. up to 30% for benzene) in the cigarette mainstream smoke had been generated during the preceding smoulder period. These species were trapped or absorbed within the cigarette rod and then subsequently eluted during the puff. The identification of the two sources of the mainstream smoke, a smouldering source and a puffing source, has not been reported before. The observation contributes to the fundamental knowledge of the cigarette smoke formation and may have implications on wider smoke chemistry and associated effects. Figure A cross-sectional schematic of a burning cigarette, illustrating the main chemical and physical processes involved in the smoke formation PMID:20101495

  6. Determination of ideal-gas enthalpies of formation for key compounds: The 1989 project results

    NASA Astrophysics Data System (ADS)

    Steele, W. V.; Chirico, R. D.; Nguyen, A.; Hossenlopp, I. A.; Smith, N. K.

    1991-10-01

    The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic and organosilicon substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor pressure measurements, and differential scanning calorimetric (dsc) heat capacity measurements. Ideal gas enthalpies of formation of (+ or -) butan-2-ol, tetradecan-1-ol, hexan-1,6-diol, methacrylamide, benzoyl formic acid, naphthalene 2,6-dicarboxylic acid dimethyl ester, and tetraethylsilane are reported. A crystalline-phase enthalpy of formation at 298.15 K was determined for naphthalene-2,6-dicarboxylic acid, which decomposed at 695 K before melting. The combustion calorimetry of tetraethylsilane used the proven fluorine-additivity methodology. Critical temperature and critical density were determined for tetraethylsilane with differential scanning calorimeter and the critical pressure was derived. Group additivity parameters useful in the application of group contribution correlations are derived.

  7. Determination of ideal-gas enthalpies of formation for key compounds:

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Nguyen, A.; Hossenlopp, I.A.; Smith, N.K.

    1991-10-01

    The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic and organosilicon substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (d.s.c.) heat-capacity measurements. Ideal-gas enthalpies of formation of ({plus minus})-butan-2-ol, tetradecan-1-ol, hexan-1,6-diol, methacrylamide, benzoyl formic acid, naphthalene-2,6-dicarboxylic acid dimethyl ester, and tetraethylsilane are reported. A crystalline-phase enthalpy of formation at 298.15 K was determined for naphthalene-2,6-dicarboxylic acid, which decomposed at 695 K before melting. The combustion calorimetry of tetraethylsilane used the proven fluorine-additivity methodology. Critical temperature and critical density were determined for tetraethylsilane with differential scanning calorimeter and the critical pressure was derived. Group-additivity parameters useful in the application of group- contribution correlations are derived. 112 refs., 13 figs., 19 tabs.

  8. Modulation of volatile organic compound formation in the Mycodiesel-producing endophyte Hypoxylon sp. CI-4.

    PubMed

    Ul-Hassan, Syed Riyaz; Strobel, Gary A; Booth, Eric; Knighton, Berk; Floerchinger, Cody; Sears, Joe

    2012-02-01

    An endophytic Hypoxylon sp. (strain CI-4) producing a wide spectrum of volatile organic compounds (VOCs), including 1,8-cineole, 1-methyl-1,4-cyclohexadiene and cyclohexane, 1,2,4-tris(methylene), was selected as a candidate for the modulation of VOC production. This was done in order to learn if the production of these and other VOCs can be affected by using agents that may modulate the epigenetics of the fungus. Many of the VOCs made by this organism are of interest because of their high energy densities and thus the potential they might have as Mycodiesel fuels. Strain CI-4 was exposed to the epigenetic modulators suberoylanilide hydroxamic acid (SAHA, a histone deacetylase) and 5-azacytidine (AZA, a DNA methyltransferase inhibitor). After these treatments the organism displayed striking cultural changes, including variations in pigmentation, growth rates and odour, in addition to significant differences in the bioactivities of the VOCs. The resulting variants were designated CI4-B, CI4-AZA and CI4-SAHA. GC/MS analyses of the VOCs produced by the variants showed considerable variation, with the emergence of several compounds not previously observed in the wild-type, particularly an array of tentatively identified terpenes such as α-thujene, sabinene, γ-terpinene, α-terpinolene and β-selinene, in addition to several primary and secondary alkanes, alkenes, organic acids and derivatives of benzene. Proton transfer reaction mass spectroscopic analyses showed a marked increase in the ratio of ethanol (mass 47) to the total mass of all other ionizable VOCs, from ~0.6 in the untreated strain CI-4 to ~0.8 in CI-4 grown in the presence of AZA. Strain CI4-B was created by exposure of the fungus to 100 µM SAHA; upon removal of the epigenetic modulator from the culture medium, it did not revert to the wild-type phenotype. Results of this study have implications for understanding why there may be a wide range of VOCs found in various isolates of this fungus in nature.

  9. Formation of toxic iodinated disinfection by-products from compounds used in medical imaging.

    PubMed

    Duirk, Stephen E; Lindell, Cristal; Cornelison, Christopher C; Kormos, Jennifer; Ternes, Thomas A; Attene-Ramos, Matias; Osiol, Jennifer; Wagner, Elizabeth D; Plewa, Michael J; Richardson, Susan D

    2011-08-15

    Iodinated X-ray contrast media (ICM) were investigated as a source of iodine in the formation of iodo-trihalomethane (iodo-THM) and iodo-acid disinfection byproducts (DBPs), both of which are highly genotoxic and/or cytotoxic in mammalian cells. ICM are widely used at medical centers to enable imaging of soft tissues (e.g., organs, veins, blood vessels) and are designed to be inert substances, with 95% eliminated in urine and feces unmetabolized within 24 h. ICM are not well removed in wastewater treatment plants, such that they have been found at elevated concentrations in rivers and streams (up to 100 μg/L). Naturally occurring iodide in source waters is believed to be a primary source of iodine in the formation of iodo-DBPs, but a previous 23-city iodo-DBP occurrence study also revealed appreciable levels of iodo-DBPs in some drinking waters that had very low or no detectable iodide in their source waters. When 10 of the original 23 cities' source waters were resampled, four ICM were found--iopamidol, iopromide, iohexol, and diatrizoate--with iopamidol most frequently detected, in 6 of the 10 plants sampled, with concentrations up to 2700 ng/L. Subsequent controlled laboratory reactions of iopamidol with aqueous chlorine and monochloramine in the absence of natural organic matter (NOM) produced only trace levels of iodo-DBPs; however, when reacted in real source waters (containing NOM), chlorine and monochloramine produced significant levels of iodo-THMs and iodo-acids, up to 212 nM for dichloroiodomethane and 3.0 nM for iodoacetic acid, respectively, for chlorination. The pH behavior was different for chlorine and monochloramine, such that iodo-DBP concentrations maximized at higher pH (8.5) for chlorine, but at lower pH (6.5) for monochloramine. Extracts from chloraminated source waters with and without iopamidol, as well as from chlorinated source waters with iopamidol, were the most cytotoxic samples in mammalian cells. Source waters with iopamidol but no

  10. The influence of roasting procedure on the formation of mutagenic compounds in coffee.

    PubMed

    Albertini, S; Friederich, U; Schlatter, C; Würgler, F E

    1985-06-01

    Mutagenic products can be formed during the processing of food and especially as a result of heat treatment. Direct acting mutagenic activity was found in extracts of instant coffee and roasted coffee beans using Salmonella typhimurium TA100 in vitro. The mutagenic activities of the four pure coffee varieties examined (Coffea arabica Santos, Coffea arabica Columbia, Coffee robusta Indonesia, Coffee robusta Camerun) were within the same range. Twenty milligrams per plate freeze-dried powder prepared from aqueous roast coffee extracts induced between six and ten times the number of revertants found in the negative controls. Green coffee beans had no mutagenic activity. Mutagenicity increased with roasting time up to 4 min in the Probat drum roaster and then remained constant (i.e. no further increase after 8 min, the time normally used to roast coffee). The genotoxic compounds were quickly formed at temperatures below 220 degrees C (in normally roasted coffee the beans must reach a temperature of 220 degrees C). Mutagenic activity was independent of the roasting procedure (Jetzon procedure v. Probat drum roaster). PMID:3891559

  11. Formation of Nanoscale Composites of Compound Semiconductors Driven by Charge Transfer.

    PubMed

    Gao, Weiwei; Dos Reis, Roberto; Schelhas, Laura T; Pool, Vanessa L; Toney, Michael F; Yu, Kin Man; Walukiewicz, Wladek

    2016-08-10

    Composites are a class of materials that are formed by mixing two or more components. These materials often have new functional properties compared to their constituent materials. Traditionally composites are formed by self-assembly due to structural dissimilarities or by engineering different layers or structures in the material. Here we report the synthesis of a uniform and stoichiometric composite of CdO and SnTe with a novel nanocomposite structure stabilized by the dissimilarity of the electronic band structure of the constituent materials. The composite has interesting electronic properties which range from highly n-type in CdO to semi-insulating in the intermediate composition range to highly p-type in SnTe. This can be explained by the overlap of the conduction and valence band of the constituent compounds. Ultimately, our work identifies a new class of composite semiconductors in which nanoscale self-organization is driven and stabilized by charge transfer between constituent materials. PMID:27459505

  12. Role of Fe compounds in light aggregate formation from a reservoir sediment.

    PubMed

    Wei, Y-L; Lin, Y-Y

    2009-11-15

    A one-step thermal process at 1050 degrees C and 1150 degrees C including bloating and sintering reactions produced lightweight aggregates (LWAs) with an apparent particle density of 2.08 and 1.18gcm(-3), respectively, from pellets made of the sediment of a local reservoir. The roles of Fe compounds occurred in the sediment in bloating mechanism were determined with X-ray absorption spectroscopy (XAS) technique. About 59at% of the total Fe is in forms of Fe(2+) in the raw sediment; whereas most Fe was oxidized to Fe(3+) in all LWAs, except in core part of the LWA produced at 1150 degrees C. The bloating reactions occurred in the core of the 1150 degrees C LWA is suggested to be mainly associated with the decomposition of FeSO(4) into FeO with a concomitant release of SO(2), SO(3), and O(2); the valence state of Fe was not changed. The generally accepted mechanism - the chemical reduction of Fe(2)O(3) component to FeO with a release of O(2) is responsible for the bloating phenomenon - is not observed in present study. PMID:19541415

  13. Neutrophil myeloperoxidase and its substrates: formation of specific markers and reactive compounds during inflammation

    PubMed Central

    Kato, Yoji

    2016-01-01

    Myeloperoxidase is an inflammatory enzyme that generates reactive hypochlorous acid in the presence of hydrogen peroxide and chloride ion. However, this enzyme also uses bromide ion or thiocyanate as a substrate to form hypobromous or hypothiocyanous acid, respectively. These species play important roles in host defense against the invasion of microorganisms. In contrast, these enzyme products modify biomolecules in hosts during excess inflammation, indicating that the action of myeloperoxidase is both beneficial and harmful. Myeloperoxidase uses other endogenous compounds, such as serotonin, urate, and l-tyrosine, as substrates. This broad-range specificity may have some biological implications. Target molecules of this enzyme and its products vary, including low-molecular weight thiols, proteins, nucleic acids, and lipids. The modified products represent biomarkers of myeloperoxidase action. Moderate inhibition of this enzyme might be critical for the prevention/modulation of excess, uncontrolled inflammatory events. Some phytochemicals inhibit myeloperoxidase, which might explain the reductive effect caused by the intake of vegetables and fruits on cardiovascular diseases. PMID:27013775

  14. Formation of Nanoscale Composites of Compound Semiconductors Driven by Charge Transfer.

    PubMed

    Gao, Weiwei; Dos Reis, Roberto; Schelhas, Laura T; Pool, Vanessa L; Toney, Michael F; Yu, Kin Man; Walukiewicz, Wladek

    2016-08-10

    Composites are a class of materials that are formed by mixing two or more components. These materials often have new functional properties compared to their constituent materials. Traditionally composites are formed by self-assembly due to structural dissimilarities or by engineering different layers or structures in the material. Here we report the synthesis of a uniform and stoichiometric composite of CdO and SnTe with a novel nanocomposite structure stabilized by the dissimilarity of the electronic band structure of the constituent materials. The composite has interesting electronic properties which range from highly n-type in CdO to semi-insulating in the intermediate composition range to highly p-type in SnTe. This can be explained by the overlap of the conduction and valence band of the constituent compounds. Ultimately, our work identifies a new class of composite semiconductors in which nanoscale self-organization is driven and stabilized by charge transfer between constituent materials.

  15. Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides.

    PubMed

    Zhang, Qingnan; Hu, Shu-Xian; Qu, Hui; Su, Jing; Wang, Guanjun; Lu, Jun-Bo; Chen, Mohua; Zhou, Mingfei; Li, Jun

    2016-06-01

    The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment.

  16. Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides.

    PubMed

    Zhang, Qingnan; Hu, Shu-Xian; Qu, Hui; Su, Jing; Wang, Guanjun; Lu, Jun-Bo; Chen, Mohua; Zhou, Mingfei; Li, Jun

    2016-06-01

    The chemistry of lanthanides (Ln=La-Lu) is dominated by the low-valent +3 or +2 oxidation state because of the chemical inertness of the valence 4f electrons. The highest known oxidation state of the whole lanthanide series is +4 for Ce, Pr, Nd, Tb, and Dy. We report the formation of the lanthanide oxide species PrO4 and PrO2 (+) complexes in the gas phase and in a solid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr(V) oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in a suitable coordination environment. PMID:27100273

  17. Formation of nanostructured Group IIA metal activated sensors: The transformation of Group IIA metal compound sites

    NASA Astrophysics Data System (ADS)

    Tune, Travis C.; Baker, Caitlin; Hardy, Neil; Lin, Arthur; Widing, Timothy J.; Gole, James L.

    2015-05-01

    Trends in the Group IIA metal oxides and hydroxides of magnesium, calcium, and barium are unique in the periodic table. In this study we find that they display novel trends as decorating nanostructures for extrinsic semiconductor interfaces. The Group IIA metal ions are strong Lewis acids. We form these M2+ ions in aqueous solution and bring these solutions in contact with a porous silicon interface to form interfaces for conductometric measurements. Observed responses are consistent with the formation of MgO whereas the heavier elements display behaviors which suggest the effect of their more basic nature. Mg(OH)2, when formed, represents a weak base whereas the heavier metal hydroxides of Ca, Sr, and Ba are strong bases. However, the hydroxides tend to give up hydrogen and act as Brönsted acids. For the latter elements, the reversible interaction response of nanostructures deposited to the porous silicon (PS) interface is modified, as the formation of more basic sites appears to compete with M2+ Lewis acidity and hydroxide Brönsted acidity. Mg2+ forms an interface whose response to the analytes NH3 and NO is consistent with MgO and well explained by the recently developing Inverse Hard/Soft Acid/Base model. The behavior of the Ca2+ and Ba2+ decorated interfaces as they interact with the hard base NH3 follows a reversal of the model, indicating a decrease in acidic character as the observed conductometric response suggests the interaction with hydroxyl groups. A change from oxide-like to hydroxide-like constituents is supported by XPS studies. The changes in conductometric response is easily monitored in contrast to changes associated with the Group IIA oxides and hydroxides observed in XPS, EDAX, IR, and NMR measurements.

  18. A first-principles study on structural stability and mechanical properties of polar intermetallic phases CaZn2 and SrZn2

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Cheng; Liu, Yong; Li, De-Jiang; Li, Ke; Jin, Hua-Lan; Xu, Ying-Xuan; Xu, Chun-Shui; Zeng, Xiao-Qin

    2014-12-01

    Structural stability and electronic properties of polar intermetallic CaZn2 and SrZn2 in both CeCu2-type and MgZn2-type structures have been investigated using first-principles method. The calculated equilibrium lattice parameters agree closely with the available experimental and other theoretical results. In terms of formation enthalpy, it is discovered that the present compounds with CeCu2-type structure are energetically more stable than that with MgZn2-type. They are all mechanically stable according to the criteria of elastic stability. In particular, we have investigated the pressure effect on the compressive behaviour and structural stability of each compound. Subsequently, the bulk modulus, shear modulus, Young's modulus, theoretical hardness, Poisson's ratio and Debye temperature in the ground state can be estimated using Voigt-Reuss-Hill homogenization method. Mechanical anisotropy is characterized by the anisotropic factors and direction-dependent Young's modulus. Finally, the electronic structures are determined to reveal the bonding characteristics of considered phases.

  19. Volatile and intermediate-volatility organic compounds in sub-urban Paris: variability, origin and importance for SOA formation

    NASA Astrophysics Data System (ADS)

    Ait-Helal, W.; Borbon, A.; Sauvage, S.; de Gouw, J. A.; Colomb, A.; Gros, V.; Freutel, F.; Crippa, M.; Afif, C.; Baltensperger, U.; Beekmann, M.; Doussin, J.-F.; Durand-Jolibois, R.; Fronval, I.; Grand, N.; Leonardis, T.; Lopez, M.; Michoud, V.; Miet, K.; Perrier, S.; Prévôt, A. S. H.; Schneider, J.; Siour, G.; Zapf, P.; Locoge, N.

    2014-02-01

    Measurements of gaseous and particulate organic carbon were performed during the MEGAPOLI experiments, in July 2009 and January-February 2010, at the SIRTA observatory in sub-urban Paris. Measurements of primary and secondary volatile organic compounds (VOCs), of both anthropogenic and biogenic origins, including for the first time C12-C16 n-alkanes of intermediate volatility (IVOCs), suspected to be efficient precursors of secondary organic aerosol (SOA). The time series of gaseous carbon are generally consistent with times series of particulate organic carbon at regional scales and are clearly affected by meteorology and air mass origin. Concentration levels of anthropogenic VOCs in urban and sub-urban Paris were surprisingly low (2-963 ppt) compared to other megacities worldwide and to rural continental sites. Urban enhancement ratios of anthropogenic VOC pairs agree well between the urban and sub-urban Paris sites, showing the regional extent of anthropogenic sources of similar composition. Contrary to other primary anthropogenic VOCs (aromatics and alkanes), IVOCs showed lower concentrations in winter (< 5 ppt) compared to summer (13-27 ppt) in agreement with a gas-particle partitioning in favor of their transfer to the particle phase in winter. Higher concentrations of most oxygenated VOCs in winter (18-5984 ppt) suggest their dominant primary anthropogenic origin. The respective role of primary anthropogenic gaseous compounds in regional SOA formation was investigated by estimating the SOA mass concentration expected from the anthropogenic VOCs and IVOCs (I / VOCs) measured at SIRTA. From an approach based on emissions inferred from the I / VOC concentrations times the SOA formation yields', the so-called integrated approach conducted in this study, 46% of the SOA measured at SIRTA is explained by our measured concentrations of I / VOC, with 10% explained by only C12-C16 IVOCs. From results of an alternative time-resolved approach, the explained variability

  20. Formation of alpha-dicarbonyl compounds in beer during storage of Pilsner.

    PubMed

    Bravo, Adriana; Herrera, Julio C; Scherer, Erika; Ju-Nam, Yon; Rübsam, Heinrich; Madrid, Jorge; Zufall, Carsten; Rangel-Aldao, Rafael

    2008-06-11

    With the aim of determining the formation of alpha-dicarbonyl intermediates during beer aging on the shelf, alpha-dicarbonyls were identified and quantified after derivatization with 1,2-diaminobenze to generate quinoxalines. The sensory effects of alpha-dicarbonyls were evaluated by the quantification of key Strecker aldehydes and by GC-olfactometry (GCO)analysis of beer headspace using solid phase microextraction. Four alpha-dicarbonyls, reported here for the first time, were detected in fresh and aged beers, three were derived from the 2,3-enolization pathway of mono- and disaccharides, and the fourth was derived from the epimerization of 3-deoxy-2-hexosulose. Ten alpha-dicarbonyls were quantified during beer processing and during different periods of beer aging at 28 degrees C. The aging periods were from 15 to 105 days. During beer aging, 1-deoxydiuloses were produced and degraded, while 1,4-dideoxydiuloses were produced at the highest rates. The GCO analysis indicated that forced beer aging increased the amounts of furaneol, trans-2-nonenal, and phenylacetaldehyde. The blockage of alpha-dicarbonyls inhibited the accumulation of sensory-active aldehydes in the beer headspace.

  1. Impact of molecular weight on the formation of electrosprayed chitosan microcapsules as delivery vehicles for bioactive compounds.

    PubMed

    Gómez-Mascaraque, Laura G; Sanchez, Gloria; López-Rubio, Amparo

    2016-10-01

    The molecular weight of chitosan is one of its most determinant characteristics, which affects its processability and its performance as a biomaterial. However, information about the effect of this parameter on the formation of electrosprayed chitosan microcapsules is scarce. In this work, the impact of chitosan molecular weight on its electrosprayability was studied and correlated with its effect on the viscosity, surface tension and electrical conductivity of solutions. A Discriminant Function Analysis revealed that the morphology of the electrosprayed chitosan materials could be correctly predicted using these three parameters for almost 85% of the samples. The suitability of using electrosprayed chitosan capsules as carriers for bioactive agents was also assessed by loading them with a model active compound, (-)-epigallocatechin gallate (EGCG). This encapsulation, with an estimated efficiency of around 80% in terms of preserved antioxidant activity, showed the potential to prolong the antiviral activity of EGCG against murine norovirus via gradual bioactive release combined with its protection against degradation in simulated physiological conditions.

  2. Compounds of tin(IV) - catalysts of amide formation. Effect of temperature and nature of leaving group

    SciTech Connect

    Oleinik, N.M.; Garkusha-Bozhko, I.P.; Usanova, I.V.

    1988-09-20

    The effect of substitution of the ester oxygen atom by sulfur in p-nitrophenyl acetate on its aminolysis rate with benzylamine in beneze at 25/degree/C in the presence of dibutyltin dibenzoate as catalyst was studied. Such substitution leads to a decrease in the catalytic activity by approximately a half, and this is explained by the smaller capacity of the sulfur atom for the formation of hydrogen bonds. The effect of temperature on the rate of the reaction of N-benzyl-oxycarbonylglycine p-nitrophenyl ester with glycine tert-butyl ester in benzene in the presence of dibutyltin dibenzoate was also investigated in the range of 10-50/degree/C. The Arrhenius equation is not fulfilled in this case. The obtained facts demonstrate the multistage character of the catalytic reaction and do not contradict the authors previously proposed bifunctional mechanism of catalysis by tin(IV) compounds.

  3. Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics

    PubMed Central

    Booth, C.H.; Jiang, Yu; Wang, D.L.; Mitchell, J.N.; Tobash, P.H.; Bauer, E.D.; Wall, M.A.; Allen, P.G.; Sokaras, D.; Nordlund, D.; Weng, T.-C.; Torrez, M.A.; Sarrao, J.L.

    2012-01-01

    Uranium and plutonium’s 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (e.g., the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) and X-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework toward understanding the strongly-correlated behavior of actinide materials. PMID:22706643

  4. Volatile organic compounds measured in summer in Beijing and their role in ground-level ozone formation

    NASA Astrophysics Data System (ADS)

    Shao, Min; Lu, Sihua; Liu, Ying; Xie, Xin; Chang, Chichung; Huang, Shan; Chen, Zhongmin

    2009-01-01

    Beijing has long suffered from serious ground-level ozone pollution, and volatile organic compounds (VOCs) play a key role in ozone formation. To understand the chemical speciation of VOCs in Beijing, nonmethane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs) were measured in summer in Beijing and nearby provinces (VOCs in this work means NMHCs+OVOCs). A variation of VOC mixing ratios and chemical speciation from 2004 to 2006 was observed at an urban site in Beijing. The typical VOC species, e.g., propane, propene, and toluene, had comparable or lower mixing ratios than levels found in other cities that previously hosted the Olympic Games, while the mixing ratios for isoprene were higher. The chemical compositions of VOCs within Beijing were heavily influenced by vehicular emissions and differed from those obtained in Tianjin and Hebei Province. OVOCs were an important component, accounting for 54% and 37% in the VOC mixing ratio in 2005 and 2006, respectively, and about 40% of the OH loss rates. The main reactive VOC compounds were aldehydes and alkenes. By using isoprene chemistry and the ratio of ethylbenzene to mp-xylene, the initial mixing ratios of VOCs were estimated. The VOCs had similar variation patterns to ambient ozone and peroxyacetyl nitrate (PAN) concentrations. The correlation between daily maximum ozone concentrations and initial VOCs revealed that ozone formation was sensitive to VOCs for both urban (Peking University, PKU) and rural (Yufa) sites. A reduction in NOx would lead to a decrease in ozone at Yufa, but would cause increased ozone at the PKU site.

  5. Formation of nitrogen- and sulfur-containing light-absorbing compounds accelerated by evaporation of water from secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Nguyen, Tran B.; Lee, Paula B.; Updyke, Katelyn M.; Bones, David L.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey A.

    2012-01-01

    Aqueous extracts of secondary organic aerosols (SOA) generated from the ozonolysis of d-limonene were subjected to dissolution, evaporation, and re-dissolution in the presence and absence of ammonium sulfate (AS). Evaporation with AS at pH 4-9 produced chromophores that were stable with respect to hydrolysis and had a distinctive absorption band at 500 nm. Evaporation accelerated the rate of chromophore formation by at least three orders of magnitude compared to the reaction in aqueous solution, which produced similar compounds. Absorption spectroscopy and high-resolution nanospray desorption electrospray ionization (nano-DESI) mass spectrometry experiments suggested that the molar fraction of the chromophores was small (<2%), and that they contained nitrogen atoms. Although the colored products represented only a small fraction of SOA, their large extinction coefficients (>105 L mol-1 cm-1 at 500 nm) increased the effective mass absorption coefficient of the residual organics in excess of 103 cm2 g-1 - a dramatic effect on the optical properties from minor constituents. Evaporation of SOA extracts in the absence of AS resulted in the production of colored compounds only when the SOA extract was acidified to pH ˜ 2 with sulfuric acid. These chromophores were produced by acid-catalyzed aldol condensation, followed by a conversion into organosulfates. The presence of organosulfates was confirmed by high resolution mass spectrometry experiments. Results of this study suggest that evaporation of cloud or fog droplets containing dissolved organics leads to significant modification of the molecular composition and serves as a potentially important source of light-absorbing compounds.

  6. Formation of Nitrogen- and Sulfur-Containing Light-Absorbing Compounds Accelerated by Evaporation of Water from Secondary Organic Aerosols

    SciTech Connect

    Nguyen, Tran B.; Lee, Paula B.; Updyke, Katelyn M.; Bones, David L.; Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey

    2012-01-14

    Aqueous extracts of secondary organic aerosols (SOA) generated from the ozonolysis of dlimonene were subjected to dissolution, evaporation, and re-dissolution in the presence and absence of ammonium sulfate (AS). Evaporation with AS at pH 4-9 produced chromophores that were stable with respect to hydrolysis and had a distinctive absorption band at 500 nm. Evaporation accelerated the rate of chromophore formation by at least three orders of magnitude compared to the reaction in aqueous solution, which produced similar compounds. Absorption spectroscopy and high-resolution nanospray desorption electrospray ionization (nano-DESI) mass spectrometry experiments suggested that the molar fraction of the chromophores was small (< 2%), and that they contained nitrogen atoms. Although the colored products represented only a small fraction of SOA, their large extinction coefficients (>10{sup 5} L mol{sup -1} cm{sup -1} at 500 nm) increased the effective mass absorption coefficient of the residual organics in excess of 10{sup 3} cm{sup 2} g{sup -1} - a dramatic effect on the optical properties from minor constituents. Evaporation of SOA extracts in the absence of AS resulted in the production of colored compounds only when the SOA extract was acidified to pH {approx} 2 with sulfuric acid. These chromophores were produced by acid-catalyzed aldol condensation, followed by a conversion into organosulfates. The presence of organosulfates was confirmed by high resolution mass spectrometry experiments. Results of this study suggest that evaporation of cloud or fog droplets containing dissolved organics leads to significant modification of the molecular composition and serves as a potentially important source of light-absorbing compounds.

  7. Predicting density functional theory total energies and enthalpies of formation of metal-nonmetal compounds by linear regression

    NASA Astrophysics Data System (ADS)

    Deml, Ann M.; O'Hayre, Ryan; Wolverton, Chris; Stevanović, Vladan

    2016-02-01

    The availability of quantitatively accurate total energies (Etot) of atoms, molecules, and solids, enabled by the development of density functional theory (DFT), has transformed solid state physics, quantum chemistry, and materials science by allowing direct calculations of measureable quantities, such as enthalpies of formation (Δ Hf ). Still, the ability to compute Etot and Δ Hf values does not, necessarily, provide insights into the physical mechanisms behind their magnitudes or chemical trends. Here, we examine a large set of calculated Etot and Δ Hf values obtained from the DFT+U -based fitted elemental-phase reference energies (FERE) approach [V. Stevanović, S. Lany, X. Zhang, and A. Zunger, Phys. Rev. B 85, 115104 (2012), 10.1103/PhysRevB.85.115104] to probe relationships between the Etot/Δ Hf of metal-nonmetal compounds in their ground-state crystal structures and properties describing the compound compositions and their elemental constituents. From a stepwise linear regression, we develop a linear model for Etot, and consequently Δ Hf , that reproduces calculated FERE values with a mean absolute error of ˜80 meV/atom. The most significant contributions to the model include calculated total energies of the constituent elements in their reference phases (e.g., metallic iron or gas phase O2), atomic ionization energies and electron affinities, Pauling electronegativity differences, and atomic electric polarizabilities. These contributions are discussed in the context of their connection to the underlying physics. We also demonstrate that our Etot/Δ Hf model can be directly extended to predict the Etot and Δ Hf of compounds outside the set used to develop the model.

  8. Volatile organic compounds speciation and their influence on ozone formation potential in an industrialized urban area in Brazil.

    PubMed

    Galvão, Elson Silva; Santos, Jane Meri; Reis Junior, Neyval Costa; Stuetz, Richard Michael

    2016-09-01

    Speciation and the influence on the ozone formation potential (OFP) from volatile organic compounds (VOCs) have been studied between February June 2013 in Vitória, ES, Brazil. Passive samplers were installed at three air-quality monitoring stations and a total of 96 samplings were collected. A total of 78 VOCs were characterized by gas chromatograph-mass spectrometer. The predominant group was organic acids, followed by alcohols and substituted aromatics and 14 precursor species were quantified. An analysis correlating concentrations with wind direction was conducted to identify possible sources. The OFP was calculated applying the scale of maximum incremental reactivity proposed by Carter.[ 23 ] Ozone precursors with the greatest OFP such as undecane, toluene, ethylbenzene and m, p-xylene compounds were the most abundant with means of 0.855, 0.365, 0.259 and 0.289 µg m(-3), respectively. The benzene, toluene, ethylbenzene and xylene (BTEX) group was found below the limits considered harmful to the health of the population living in Vitória. The OFP calculated for the precursors group was 22.55 µg m(-3) for the rainy season and 32.11 µg m(-3) for the dry season. The VOC/NOx ratio in Vitória is approximately 1.71, indicating that the region has a VOC-limiting condition for the production of ozone. PMID:26776458

  9. Formation of combustible hydrocarbons and H2 during photocatalytic decomposition of various organic compounds under aerated and deaerated conditions.

    PubMed

    Mozia, Sylwia; Kułagowska, Aleksandra; Morawski, Antoni W

    2014-01-01

    A possibility of photocatalytic production of useful aliphatic hydrocarbons and H2 from various organic compounds, including acetic acid, methanol, ethanol and glucose, over Fe-modified TiO2 is discussed. In particular, the influence of the reaction atmosphere (N2, air) was investigated. Different gases were identified in the headspace volume of the reactor depending on the substrate. In general, the evolution of the gases was more effective in air compared to a N2 atmosphere. In the presence of air, the gaseous phase contained CO2, CH4 and H2, regardless of the substrate used. Moreover, formation of C2H6 and C3H8 in the case of acetic acid and C2H6 in the case of ethanol was observed. In case of acetic acid and methanol an increase in H2 evolution under aerated conditions was observed. It was concluded that the photocatalytic decomposition of organic compounds with simultaneous generation of combustible hydrocarbons and hydrogen could be a promising method of "green energy" production.

  10. Volatile organic compounds speciation and their influence on ozone formation potential in an industrialized urban area in Brazil.

    PubMed

    Galvão, Elson Silva; Santos, Jane Meri; Reis Junior, Neyval Costa; Stuetz, Richard Michael

    2016-09-01

    Speciation and the influence on the ozone formation potential (OFP) from volatile organic compounds (VOCs) have been studied between February June 2013 in Vitória, ES, Brazil. Passive samplers were installed at three air-quality monitoring stations and a total of 96 samplings were collected. A total of 78 VOCs were characterized by gas chromatograph-mass spectrometer. The predominant group was organic acids, followed by alcohols and substituted aromatics and 14 precursor species were quantified. An analysis correlating concentrations with wind direction was conducted to identify possible sources. The OFP was calculated applying the scale of maximum incremental reactivity proposed by Carter.[ 23 ] Ozone precursors with the greatest OFP such as undecane, toluene, ethylbenzene and m, p-xylene compounds were the most abundant with means of 0.855, 0.365, 0.259 and 0.289 µg m(-3), respectively. The benzene, toluene, ethylbenzene and xylene (BTEX) group was found below the limits considered harmful to the health of the population living in Vitória. The OFP calculated for the precursors group was 22.55 µg m(-3) for the rainy season and 32.11 µg m(-3) for the dry season. The VOC/NOx ratio in Vitória is approximately 1.71, indicating that the region has a VOC-limiting condition for the production of ozone.

  11. Formation of volatile compounds in kefir made of goat and sheep milk with high polyunsaturated fatty acid content.

    PubMed

    Cais-Sokolińska, D; Wójtowski, J; Pikul, J; Danków, R; Majcher, M; Teichert, J; Bagnicka, E

    2015-10-01

    This article explored the formation of volatile compounds during the production of kefir from goat and sheep milks with high polyunsaturated fatty acids (PUFA) as a result of feeding animals forage supplemented with maize dried distillers grains with solubles (DDGS). The increased PUFA content of the goat and sheep milks resulted in significant changes to the fermentation process. In particular, apart from an increase in the time taken to ferment sheep milk, fermentation yielded less 2,3-butanedione. The highest quantities of this compound were assayed in kefir produced from goat milk with an increased content of PUFA. An increase of PUFA significantly elevated ethanal synthesis during lactose-alcohol fermentation of sheep milk. Neither the origin of milk (sheep or goat) nor the level of PUFA had any statistical effect on the amount of ethanal assayed during the fermentation of milk and within the finished product. The proportion of l(+)-lactic acid was higher in kefirs produced using goat milk compared with sheep milk and did not depend on the content of PUFA in milk fat. The content of PUFA had a significant effect on the aroma profile of the resulting kefirs. An increase in PUFA content resulted in the loss of whey aroma in goat milk kefirs and the animal odor in sheep milk kefirs, and a creamy aroma became more prevalent in kefirs made from sheep milk. PMID:26277315

  12. Formation of volatile compounds in kefir made of goat and sheep milk with high polyunsaturated fatty acid content.

    PubMed

    Cais-Sokolińska, D; Wójtowski, J; Pikul, J; Danków, R; Majcher, M; Teichert, J; Bagnicka, E

    2015-10-01

    This article explored the formation of volatile compounds during the production of kefir from goat and sheep milks with high polyunsaturated fatty acids (PUFA) as a result of feeding animals forage supplemented with maize dried distillers grains with solubles (DDGS). The increased PUFA content of the goat and sheep milks resulted in significant changes to the fermentation process. In particular, apart from an increase in the time taken to ferment sheep milk, fermentation yielded less 2,3-butanedione. The highest quantities of this compound were assayed in kefir produced from goat milk with an increased content of PUFA. An increase of PUFA significantly elevated ethanal synthesis during lactose-alcohol fermentation of sheep milk. Neither the origin of milk (sheep or goat) nor the level of PUFA had any statistical effect on the amount of ethanal assayed during the fermentation of milk and within the finished product. The proportion of l(+)-lactic acid was higher in kefirs produced using goat milk compared with sheep milk and did not depend on the content of PUFA in milk fat. The content of PUFA had a significant effect on the aroma profile of the resulting kefirs. An increase in PUFA content resulted in the loss of whey aroma in goat milk kefirs and the animal odor in sheep milk kefirs, and a creamy aroma became more prevalent in kefirs made from sheep milk.

  13. Intermetallic alloy welding wires and method for fabricating the same

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1996-01-01

    Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

  14. Intermetallic alloy welding wires and method for fabricating the same

    DOEpatents

    Santella, M.L.; Sikka, V.K.

    1996-06-11

    Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

  15. Thermodynamic properties and phase equilibria of selected Heusler compounds

    NASA Astrophysics Data System (ADS)

    Yin, Ming

    Heusler compounds are ternary intermetallics with many promising properties such as spin polarization and magnetic shape memory effect. A better understanding of their thermodynamic properties facilitates future design and development. Therefore, standard enthalpies of formation and heat capacities from room temperature to 1500 K of selected Heusler compounds X2YZ (X = Co, Fe, Ni, Pd, Rh, Ru; Y = Co, Cu, Fe, Hf, Mn, Ni, Ti, V, Zr; Z = Al, Ga, In, Si, Ge, Sn) and half-Heusler compounds XYSn (X = Au, Co, Fe, Ir, Ni, Pd, Pt, Rh; Y = Hf, Mn, Ti, Zr) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation were compared with those predicted from ab initio calculations and the extended semi-empirical Miedema's model. Trends in standard enthalpy of formation with respect to the periodic classification of elements were discussed. The effect of a fourth element (Co, Cu, Fe, Pd; Ti, V; Al, Ga, In, Si, Ge) on the standard enthalpy of formation of Ni2MnSn was also investigated. Lattice parameters of the compounds with an L21 structure were determined using X-ray powder diffraction analysis. Differential scanning calorimetry was used to determine melting points and phase transformation temperatures. Phase relationships were investigated using scanning electron microscopy with an energy dispersive spectrometer. The isothermal section of the Fe-Sn-Ti ternary system at 873 K was established using equilibrated alloys. Three ternary compounds including the Heusler compound Fe2SnTi were observed. A new ternary compound Fe5Sn9Ti 6 was reported and the crystal structure of FeSnTi2 was determined for the first time.

  16. Multi-year evaluation of ambient volatile organic compounds: temporal variation, ozone formation, meteorological parameters, and sources.

    PubMed

    Kim, Ku H; Chun, Ho-Hwan; Jo, Wan K

    2015-02-01

    The multi-year characteristics of ambient volatile organic compounds (VOCs) and their source contribution in a selected metropolitan (Seoul) and rural (Seokmolee) areas in Korea were investigated to provide the framework for development and implementation of ambient VOC control strategies. For Seoul, none of the three VOC groups exhibited any significant trend in their ambient concentrations, whereas for Seokmolee, they all showed a generally decreasing trend between 2005 and 2008 and an increasing trend after 2008. Two paraffinic (ethane and propane) and two olefin (ethylene and propylene) hydrocarbons displayed higher concentrations during the cold season than warm season, while the other target VOCs did not exhibit any significant trends. Ethylene and toluene were the first and second largest contributors to ozone formation, respectively, whereas several other VOCs displayed photochemical ozone formation potential values less than 0.01 ppb. For both areas, there was a significant negative correlation between ambient temperature and the selected VOC group concentrations. In contrast, a significant positive correlation was observed between relative humidity and the three VOC group concentrations, while no significant correlation was observed between wind speed and VOC group concentrations. For Seoul, the combination of vehicle exhaust and gasoline/solvent evaporation was the greatest source of VOCs, followed by liquid natural gas (LNG) and liquid petroleum gas (LPG). However, combination of LNG and LPG was the greatest source of VOCs at Seokmolee, followed by the combination of vehicle exhaust and gasoline evaporation, and then biogenic sources. PMID:25632908

  17. Formation of Low Volatility Organic Compounds and Secondary Organic Aerosol from Isoprene Hydroxyhydroperoxide Low-NO Oxidation.

    PubMed

    Krechmer, Jordan E; Coggon, Matthew M; Massoli, Paola; Nguyen, Tran B; Crounse, John D; Hu, Weiwei; Day, Douglas A; Tyndall, Geoffrey S; Henze, Daven K; Rivera-Rios, Jean C; Nowak, John B; Kimmel, Joel R; Mauldin, Roy L; Stark, Harald; Jayne, John T; Sipilä, Mikko; Junninen, Heikki; Clair, Jason M St; Zhang, Xuan; Feiner, Philip A; Zhang, Li; Miller, David O; Brune, William H; Keutsch, Frank N; Wennberg, Paul O; Seinfeld, John H; Worsnop, Douglas R; Jimenez, Jose L; Canagaratna, Manjula R

    2015-09-01

    Gas-phase low volatility organic compounds (LVOC), produced from oxidation of isoprene 4-hydroxy-3-hydroperoxide (4,3-ISOPOOH) under low-NO conditions, were observed during the FIXCIT chamber study. Decreases in LVOC directly correspond to appearance and growth in secondary organic aerosol (SOA) of consistent elemental composition, indicating that LVOC condense (at OA below 1 μg m(-3)). This represents the first simultaneous measurement of condensing low volatility species from isoprene oxidation in both the gas and particle phases. The SOA formation in this study is separate from previously described isoprene epoxydiol (IEPOX) uptake. Assigning all condensing LVOC signals to 4,3-ISOPOOH oxidation in the chamber study implies a wall-loss corrected non-IEPOX SOA mass yield of ∼4%. By contrast to monoterpene oxidation, in which extremely low volatility VOC (ELVOC) constitute the organic aerosol, in the isoprene system LVOC with saturation concentrations from 10(-2) to 10 μg m(-3) are the main constituents. These LVOC may be important for the growth of nanoparticles in environments with low OA concentrations. LVOC observed in the chamber were also observed in the atmosphere during SOAS-2013 in the Southeastern United States, with the expected diurnal cycle. This previously uncharacterized aerosol formation pathway could account for ∼5.0 Tg yr(-1) of SOA production, or 3.3% of global SOA. PMID:26207427

  18. Formation of Low Volatility Organic Compounds and Secondary Organic Aerosol from Isoprene Hydroxyhydroperoxide Low-NO Oxidation.

    PubMed

    Krechmer, Jordan E; Coggon, Matthew M; Massoli, Paola; Nguyen, Tran B; Crounse, John D; Hu, Weiwei; Day, Douglas A; Tyndall, Geoffrey S; Henze, Daven K; Rivera-Rios, Jean C; Nowak, John B; Kimmel, Joel R; Mauldin, Roy L; Stark, Harald; Jayne, John T; Sipilä, Mikko; Junninen, Heikki; Clair, Jason M St; Zhang, Xuan; Feiner, Philip A; Zhang, Li; Miller, David O; Brune, William H; Keutsch, Frank N; Wennberg, Paul O; Seinfeld, John H; Worsnop, Douglas R; Jimenez, Jose L; Canagaratna, Manjula R

    2015-09-01

    Gas-phase low volatility organic compounds (LVOC), produced from oxidation of isoprene 4-hydroxy-3-hydroperoxide (4,3-ISOPOOH) under low-NO conditions, were observed during the FIXCIT chamber study. Decreases in LVOC directly correspond to appearance and growth in secondary organic aerosol (SOA) of consistent elemental composition, indicating that LVOC condense (at OA below 1 μg m(-3)). This represents the first simultaneous measurement of condensing low volatility species from isoprene oxidation in both the gas and particle phases. The SOA formation in this study is separate from previously described isoprene epoxydiol (IEPOX) uptake. Assigning all condensing LVOC signals to 4,3-ISOPOOH oxidation in the chamber study implies a wall-loss corrected non-IEPOX SOA mass yield of ∼4%. By contrast to monoterpene oxidation, in which extremely low volatility VOC (ELVOC) constitute the organic aerosol, in the isoprene system LVOC with saturation concentrations from 10(-2) to 10 μg m(-3) are the main constituents. These LVOC may be important for the growth of nanoparticles in environments with low OA concentrations. LVOC observed in the chamber were also observed in the atmosphere during SOAS-2013 in the Southeastern United States, with the expected diurnal cycle. This previously uncharacterized aerosol formation pathway could account for ∼5.0 Tg yr(-1) of SOA production, or 3.3% of global SOA.

  19. Up-and-coming IMCs. [Intermetallic-Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bowman, Randy; Noebe, Ronald

    1989-01-01

    While the good oxidation and environmental resistance, high melting points, and comparatively low densities of such ordered intermetallics as Ti3Al, NiAl, FeAl, and NbAl3 render them good candidates for advanced aerospace structures, their poor toughness at low temperatures and low strength at elevated temperatures have prompted the development of fiber-reinforced intermetallic-matrix composites (IMCs) with more balanced characteristics. Fabrication methods for continuous-fiber IMCs under development include the P/M 'powder cloth' method, the foil/fiber method, and thermal spraying. The ultimate success of IMCs depends on fibers truly compatible with the matrix materials.

  20. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered). PMID:14577885

  1. Submicron Magnetite Grains and Carbon Compounds in Martian Meteorite ALH84001: Inorganic, Abiotic Formation by Shock and Thermal Metamorphism

    NASA Astrophysics Data System (ADS)

    Treiman, Allan H.

    2003-06-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe3O4, reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  2. Emissions of biogenic volatile organic compounds and subsequent formation of secondary organic aerosols in a Larix kaempferi forest

    NASA Astrophysics Data System (ADS)

    Mochizuki, T.; Miyazaki, Y.; Ono, K.; Wada, R.; Takahashi, Y.; Saigusa, N.; Kawamura, K.; Tani, A.

    2015-04-01

    We conducted simultaneous measurements of concentrations and above-canopy fluxes of isoprene and α-pinene, along with their oxidation products in aerosols in a Larix kaempferi (Japanese larch) forest in summer 2012. Vertical profiles of isoprene showed the maximum concentration near the forest floor with a peak around noon, whereas oxidation products of isoprene, i.e., methacrolein (MACR) and methyl vinyl ketone (MVK), showed higher concentrations near the canopy level of the forest. The vertical profile suggests large emissions of isoprene near the forest floor, likely due to Dryopteris crassirhizoma (a fern species), and the subsequent reaction within the canopy. The concentrations of α-pinene also showed highest values near the forest floor with maximums in the early morning and late afternoon. The vertical profiles of α-pinene suggest its large emissions from soil and litter in addition to emissions from L. kaempferi leaves at the forest site. Isoprene and its oxidation products in aerosols exhibited similar diurnal variations within the forest canopy, providing evidence for secondary organic aerosol (SOA) formation via oxidation of isoprene most likely emitted from the forest floor. Although high abundance of α-pinene was observed in the morning, its oxidation products in aerosols showed peaks in daytime, due to a time lag between the emission and atmospheric reactions of α-pinene to form SOA. Positive matrix factorization (PMF) analysis indicated that anthropogenic influence is the most important factor contributing to the elevated concentrations of molecular oxidation products of isoprene- (> 64%) and α-pinene-derived SOA (> 57%). The combination of the measured fluxes and vertical profiles of biogenic volatile organic compounds (BVOCs) suggests that the inflow of anthropogenic precursors/aerosols likely enhanced the formation of both isoprene- and α-pinene-SOA within the forest canopy even when the BVOC flux was relatively low. This study highlights

  3. Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

    PubMed

    Treiman, Allan H

    2003-01-01

    Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive hypothesis is offered here. The carbonate globules were deposited from hydrothermal water, without biological mediation. Thereafter, ALH84001 was affected by an impact shock event, which raised its temperature nearly instantaneously to 500-700K, and induced iron-rich carbonate in the globules to decompose to magnetite and other minerals. The rapidity of the temperature increase caused magnetite grains to nucleate in abundance; hence individual crystals were very small. Nucleation and growth of magnetite crystals were fastest along edges and faces of the precursor carbonate grains, forcing the magnetite grains to be platy or elongated, including the "truncated hexa-octahedra" shape. ALH84001 had formed at some depth within Mars where the lithostatic pressure was significantly above that of Mars' surface. Also, because the rock was at depth, the impact heat dissipated slowly. During this interval, magnetite crystals approached chemical equilibria with surrounding minerals and gas. Their composition, nearly pure Fe(3)O(4), reflects those of equilibria; elements that substitute into magnetite are either absent from iron-rich carbonate (e.g., Ti, Al, Cr), or partitioned into other minerals during magnetite formation (Mg, Mn). Many microstructural imperfections in the magnetite grains would have annealed out as the rock cooled. In this post-shock thermal regime, carbon-bearing gas from the decomposition of iron carbonates reacted with water in the rock (or from its surroundings) to produce organic matter via Fischer-Tropschlike reactions. Formation of such organic compounds like polycyclic aromatic hydrocarbons would have been catalyzed by the magnetite (formation of graphite, the thermochemically stable phase, would be kinetically hindered).

  4. Ozone Formation Potentials from Different Anthropogenic Emission Sources of Volatile Organic Compounds in California's South Coast Air Basin

    NASA Astrophysics Data System (ADS)

    Chen, J.; Luo, D.; Croes, B.

    2010-12-01

    Different volatile organic compounds (VOC) exhibit different propensities for ozone formation. Two approaches were used to study the relative ozone formation potentials (source reactivities) of different anthropogenic VOC emission source categories in California’s South Coast Air Basin (SoCAB). The first approach combined emission speciation profiles for total organic gases (TOG) with maximum incremental reactivity (MIR) scales for VOC species. The second approach quantified ozone impacts from different sources by performing 3-dimensional air quality model sensitivity analyses involving increased TOG emissions from particular sources. The source reactivities for 58 VOC emission categories in SoCAB derived from these two approaches agree reasonably well (R2 = ~0.9). Both approaches revealed the two emissions source types with the highest TOG reactivity were mobile sources and managed forest burning. Also, a reactivity-based TOG emission inventory for SoCAB in 2005 was produced by combining the source reactivities from both approaches with TOG emissions from anthropogenic source categories. The top five reactivity-based source categories are: light-duty passenger cars, off-road equipments, consumer products, light-duty trucks, and recreational boats. This is in contrast to the mass-based TOG emission inventory, which indicates that farming operations (mainly from animal waste) was one of the five largest mass-based anthropogenic TOG emission sources. Compared to the mass-based TOG emission inventory, the reactivity-based TOG emission inventory more appropriately represents the ozone formation potentials from emission sources, and highlights those sources that should be targeted for future regulations.

  5. Dissolution of Cu/Mg Bearing Intermetallics in Al-Si Foundry Alloys

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2016-08-01

    Evolutions of the Cu/Mg bearing intermetallics were thoroughly investigated in four Al-Si hypoeutectic alloys containing various Cu (1 and 1.6 wt pct) and Mg (0.4 and 0.8 wt pct) contents. The area fractions of Cu/Mg bearing phases before and after solution heat treatment (SHT) were quantified to evaluate the solubility/stability of the phases. Two Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π-Al8FeMg3Si6) which appear as gray color under optical microscope were discriminated by the developed etchant. Moreover, the concentrations of the elements (Cu, Mg, and Si) in α-Al were analyzed. The results illustrated that in the alloys containing ~0.4 pct Mg, Q-Al5Cu2Mg8Si6 phase was dissolved after 6 hours of SHT at 778 K (505 °C); but containing in the alloys ~0.8 pct Mg, it was insoluble/ partially soluble. Furthermore, after SHT at 778 K (505 °C), Mg2Si was partially substituted by Q-phase. Applying a two-step SHT [6 hours@778 K (505 °C) + 8 hours@798 K (525 °C)] in the alloys containing ~0.4 pct Mg helped to further dissolve the remaining Mg bearing intermetallics and further modified the microstructure, but in the alloys containing ~0.8 pct Mg, it caused partial melting of Q-phase. Thermodynamic calculations were carried out to assess the phase formation in equilibrium and in non-equilibrium conditions. There was an excellent agreement between the experimental results and the predicted results.

  6. Dissolution of Cu/Mg Bearing Intermetallics in Al-Si Foundry Alloys

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2016-10-01

    Evolutions of the Cu/Mg bearing intermetallics were thoroughly investigated in four Al-Si hypoeutectic alloys containing various Cu (1 and 1.6 wt pct) and Mg (0.4 and 0.8 wt pct) contents. The area fractions of Cu/Mg bearing phases before and after solution heat treatment (SHT) were quantified to evaluate the solubility/stability of the phases. Two Mg-bearing intermetallics (Q-Al5Cu2Mg8Si6, π-Al8FeMg3Si6) which appear as gray color under optical microscope were discriminated by the developed etchant. Moreover, the concentrations of the elements (Cu, Mg, and Si) in α-Al were analyzed. The results illustrated that in the alloys containing ~0.4 pct Mg, Q-Al5Cu2Mg8Si6 phase was dissolved after 6 hours of SHT at 778 K (505 °C); but containing in the alloys ~0.8 pct Mg, it was insoluble/ partially soluble. Furthermore, after SHT at 778 K (505 °C), Mg2Si was partially substituted by Q-phase. Applying a two-step SHT [6 hours@778 K (505 °C) + 8 hours@798 K (525 °C)] in the alloys containing ~0.4 pct Mg helped to further dissolve the remaining Mg bearing intermetallics and further modified the microstructure, but in the alloys containing ~0.8 pct Mg, it caused partial melting of Q-phase. Thermodynamic calculations were carried out to assess the phase formation in equilibrium and in non-equilibrium conditions. There was an excellent agreement between the experimental results and the predicted results.

  7. Observations of a dynamical-to-kinematic diffraction transition in plastically deformed polycrystalline intermetallic YCu

    SciTech Connect

    Williams, Scott H.; Brown, Donald W.; Clausen, Bjorn; Russell, Alan; Gschneidner Jr., Karl A.

    2014-03-01

    Unlike most intermetallic compounds, polycrystalline YCu, a B2 (CsCl-type) intermetallic, is ductile at room temperature. The mechanisms for this behavior are not fully understood. In situ neutron diffraction was used to investigate whether a stress-induced phase transformation or twinning contribute to the ductility; however, neither mechanism was found to be active in YCu. Surprisingly, this study revealed that the intensities of the diffraction peaks increased after plastic deformation. It is thought that annealing the samples created nearly perfect crystallinity, and subsequent deformation reduced this high degree of lattice coherency, resulting in a modified mosaic structure that decreased or eliminated the extinction effect. Analysis of changes in diffraction peak intensity showed a region of primary plasticity that exhibits significant changes in diffraction behavior. Fully annealed samples initially contain diffracting volumes large enough to follow the dynamical theory of diffraction. When loaded beyond the yield point, dislocation motion disrupts the lattice perfection, and the diffracting volume is reduced to the point that diffraction follows the kinematic theory of diffraction. Since the sample preparation and deformation mechanisms present in this study are common in numerous material systems, this dynamical to kinematic diffraction transition should also be considered in other diffraction experiments. These measurements also suggest the possibility of a new method of investigating structural characteristics. (C) 2014 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

  8. Process for synthesizing compounds from elemental powders and product

    DOEpatents

    Rabin, B.H.; Wright, R.N.

    1993-12-14

    A process for synthesizing intermetallic compounds from elemental powders is described. The elemental powders are initially combined in a ratio which approximates the stoichiometric composition of the intermetallic compound. The mixed powders are then formed into a compact which is heat treated at a controlled rate of heating such that an exothermic reaction between the elements is initiated. The heat treatment may be performed under controlled conditions ranging from a vacuum (pressureless sintering) to compression (hot pressing) to produce a desired densification of the intermetallic compound. In a preferred form of the invention, elemental powders of Fe and Al are combined to form aluminide compounds of Fe[sub 3] Al and FeAl. 25 figures.

  9. Compound nucleus formation probability PCN determined within the dynamical cluster-decay model for various "hot" fusion reactions

    NASA Astrophysics Data System (ADS)

    Kaur, Arshdeep; Chopra, Sahila; Gupta, Raj K.

    2014-08-01

    The compound nucleus (CN) fusion/formation probability PCN is defined and its detailed variations with the CN excitation energy E*, center-of-mass energy Ec .m., fissility parameter χ, CN mass number ACN, and Coulomb interaction parameter Z1Z2 are studied for the first time within the dynamical cluster-decay model (DCM). The model is a nonstatistical description of the decay of a CN to all possible processes. The (total) fusion cross section σfusion is the sum of the CN and noncompound nucleus (nCN) decay cross sections, each calculated as the dynamical fragmentation process. The CN cross section σCN is constituted of evaporation residues and fusion-fission, including intermediate-mass fragments, each calculated for all contributing decay fragments (A1, A2) in terms of their formation and barrier penetration probabilities P0 and P. The nCN cross section σnCN is determined as the quasi-fission (qf) process, where P0=1 and P is calculated for the entrance-channel nuclei. The DCM, with effects of deformations and orientations of nuclei included in it, is used to study the PCN for about a dozen "hot" fusion reactions forming a CN of mass number A ˜100 to superheavy nuclei and for various different nuclear interaction potentials. Interesting results are that PCN=1 for complete fusion, but PCN<1 or PCN≪1 due to the nCN contribution, depending strongly on different parameters of the entrance-channel reaction but found to be independent of the nuclear interaction potentials used.

  10. Isoprene Epoxydiols as Precursors to Secondary Organic Aerosol Formation: Acid-Catalyzed Reactive Uptake Studies with Authentic Compounds

    PubMed Central

    Lin, Ying-Hsuan; Zhang, Zhenfa; Docherty, Kenneth S.; Zhang, Haofei; Budisulistiorini, Sri Hapsari; Rubitschun, Caitlin L.; Shaw, Stephanie L.; Knipping, Eladio M.; Edgerton, Eric S.; Kleindienst, Tadeusz E.; Gold, Avram; Surratt, Jason D.

    2011-01-01

    Isoprene epoxydiols (IEPOX), formed from the photooxidation of isoprene under low-NOx conditions, have recently been proposed as precursors of secondary organic aerosol (SOA) on the basis of mass spectrometric evidence. In the present study, IEPOX isomers were synthesized in high purity (> 99%) to investigate their potential to form SOA via reactive uptake in a series of controlled dark chamber studies followed by reaction product analyses. IEPOX-derived SOA was substantially observed only in the presence of acidic aerosols, with conservative lower-bound yields of 4.7–6.4% for β-IEPOX and 3.4–5.5% for δ-IEPOX, providing direct evidence for IEPOX isomers as precursors to isoprene SOA. These chamber studies demonstrate that IEPOX uptake explains the formation of known isoprene SOA tracers found in ambient aerosols, including 2-methyltetrols, C5-alkene triols, dimers, and IEPOX-derived organosulfates. Additionally, we show reactive uptake on the acidified sulfate aerosols supports a previously unreported acid-catalyzed intramolecular rearrangement of IEPOX to cis- and trans-3-methyltetrahydrofuran-3,4-diols (3-MeTHF-3,4-diols) in the particle phase. Analysis of these novel tracer compounds by aerosol mass spectrometry (AMS) suggests that they contribute to a unique factor resolved from positive matrix factorization (PMF) of AMS organic aerosol spectra collected from low-NOx, isoprene-dominated regions influenced by the presence of acidic aerosols. PMID:22103348

  11. Source profiles and ozone formation potentials of volatile organic compounds in three traffic tunnels in Kaohsiung, Taiwan.

    PubMed

    Chen, K S; Lai, C H; Ho, Y T

    2003-01-01

    Twenty-five volatile organic compounds (VOCs) up to C10 were measured using Carbotrap multibed thermal adsorption tubes during the morning and afternoon rush hours on four different days in all three traffic tunnels in Kaohsiung, Taiwan. A gas chromatograph (GC) equipped with a flame-ionization detector (FID) was then used to analyze the VOCs. The analytical results show that VOC concentrations increase with traffic flow rate, and emission profiles in the three tunnels are mostly in the range C2-C6. In addition to the traffic conditions and vehicle type, the pattern of emissions in each tunnel was also influenced by other factors, such as vehicle age, nearby pollution sources, and the spatial or temporal variation of VOCs in the urban atmosphere. The ozone formation potential (OFP) in each tunnel was assessed based on the maximum incremental reactivities of the organic species, demonstrating that OFP increases with traffic flow rate. Vehicle distribution influences the contributions of organic group to OFP in a tunnel. Meanwhile, when ranked in descending order of contribution to OFP in all tunnels, the organic groups followed the sequence olefins, aromatics, and paraffins.

  12. Impact of molecular weight on the formation of electrosprayed chitosan microcapsules as delivery vehicles for bioactive compounds.

    PubMed

    Gómez-Mascaraque, Laura G; Sanchez, Gloria; López-Rubio, Amparo

    2016-10-01

    The molecular weight of chitosan is one of its most determinant characteristics, which affects its processability and its performance as a biomaterial. However, information about the effect of this parameter on the formation of electrosprayed chitosan microcapsules is scarce. In this work, the impact of chitosan molecular weight on its electrosprayability was studied and correlated with its effect on the viscosity, surface tension and electrical conductivity of solutions. A Discriminant Function Analysis revealed that the morphology of the electrosprayed chitosan materials could be correctly predicted using these three parameters for almost 85% of the samples. The suitability of using electrosprayed chitosan capsules as carriers for bioactive agents was also assessed by loading them with a model active compound, (-)-epigallocatechin gallate (EGCG). This encapsulation, with an estimated efficiency of around 80% in terms of preserved antioxidant activity, showed the potential to prolong the antiviral activity of EGCG against murine norovirus via gradual bioactive release combined with its protection against degradation in simulated physiological conditions. PMID:27312621

  13. Emissions of biogenic volatile organic compounds and subsequent formation of secondary organic aerosols in a Larix kaempferi forest

    NASA Astrophysics Data System (ADS)

    Mochizuki, T.; Miyazaki, Y.; Ono, K.; Wada, R.; Takahashi, Y.; Saigusa, N.; Kawamura, K.; Tani, A.

    2015-10-01

    We conducted simultaneous measurements of concentrations and above-canopy fluxes of isoprene and α-pinene, along with their oxidation products in aerosols in a Larix kaempferi (Japanese larch) forest in summer 2012. Vertical profiles of isoprene showed the maximum concentration near the forest floor with a peak around noon, whereas oxidation products of isoprene, i.e., methacrolein (MACR) and methyl vinyl ketone (MVK), showed higher concentrations near the canopy level of the forest. The vertical profile suggests large emissions of isoprene near the forest floor, likely due to Dryopteris crassirhizoma (a fern species), and the subsequent reaction within the canopy. The concentrations of α-pinene also showed highest values near the forest floor, with maximums in the early morning and late afternoon. The vertical profiles of α-pinene suggest its large emissions from soil and litter in addition to emissions from L. kaempferi leaves at the forest site. Isoprene and its oxidation products in aerosols exhibited similar diurnal variations within the forest canopy, providing evidence of secondary organic aerosol (SOA) formation via oxidation of isoprene most likely emitted from the forest floor. Although high abundance of α-pinene was observed in the morning, its oxidation products in aerosols showed peaks in daytime, due to a time lag between the emission and atmospheric reactions of α-pinene to form SOA. Positive matrix factorization (PMF) analysis indicated that anthropogenic influence is the most important factor contributing to the elevated concentrations of molecular oxidation products of isoprene- (> 64 %) and α-pinene-derived SOA (> 57 %). The combination of the measured fluxes and vertical profiles of biogenic volatile organic compounds (BVOCs) suggests that the inflow of anthropogenic precursors/aerosols likely enhanced the formation of both isoprene SOA and α-pinene SOA within the forest canopy even when the BVOC flux was relatively low. This study

  14. SDAS, Si and Cu Content, and the Size of Intermetallics in Al-Si-Cu-Mg-Fe Alloys

    NASA Astrophysics Data System (ADS)

    Sivarupan, Tharmalingam; Taylor, John Andrew; Cáceres, Carlos Horacio

    2015-05-01

    Plates of Al-(a)Si-(b)Cu-Mg-(c)Fe alloys with varying content of (mass pct) Si ( a = 3, 4.5, 7.5, 9, 10, or 11), Cu ( b = 0, 1, or 4), and Fe ( c = 0.2, 0.5 or 0.8) were cast in sand molds with a heavy chill at one end to ensure quasi-directional solidification over a wide range of Secondary Dendrite Arm Spacing (SDAS). Statistical analysis on the size of the β-Al5FeSi, α-Al8Fe2Si, or Al2Cu intermetallics on Backscattered Electron images showed that a high Si content reduced the size of the β platelets in alloys with up to 0.5 Fe content regardless of the SDAS, whereas at small SDAS the refining effect extended up to 0.8 Fe, and involved α-phase intermetallics which replaced the beta platelets at those concentrations. At low Si contents, a high Cu level appeared to have similar refining effects as increased Si, through the formation of α-phase particles in the post-eutectic stage which agglomerated with the Al2Cu intermetallics. A high content of Si appears to make the overall refining process less critical in terms of SDAS/cooling rate.

  15. Structure of high-molecular carbonaceous compound in carbonaceous chondrites and formation of IR-spectroscopically similar compounds in the laboratory.

    PubMed

    Murae, T

    1997-01-01

    Main components of carbonaceous matter in carbonaceous chondrites are high molecular organic matter. Examinations of the compounds using pyrolysis GC/MS and FT-IR indicated the structural resemblance of major part of the molecule for all of the compounds from different types of carbonaceous chondrites (8 Antarctic and 2 none-Antarctic meteorites). A carbonaceous matter derived from graphite on a shock experiment using a rail gun (1g projectile at 7 km/s) showed similar IR spectrum to those of the meteoritic high-molecular organic matter. C-60 fullerene also gave a similar compound (with minor differences in IR spectra) on a shock experiment under the same conditions. A shock experiment using coronene also examined. PMID:11541332

  16. Structure of high-molecular carbonaceous compound in carbonaceous chondrites and formation of IR-spectroscopically similar compounds in the laboratory

    NASA Astrophysics Data System (ADS)

    Murae, T.

    1997-05-01

    Main components of carbonaceous matter in carbonaceous chondrites are high molecular organic matter. Examinations of the compounds using pyrolysis GC/MS and FT-IR indicated the structural resemblance of major part of the molecule for all of the compounds from different types of carbonaceous chondrites (8 Antarctic and 2 none-Antarctic meteorites). A carbonaceous matter derived from graphite on a shock experiment using a rail gun (1g projectile at 7 km/s) showed similar IR spectrum to those of the meteoritic high-molecular organic matter. C-60 fulleren also gave a similar compound (with minor differences in IR spectra) on a shock experiment under the same conditions. A shock experiment using coronene also examined.

  17. Micro and nano-texturization of intermetallic oxide alloys by a single anodization step: preparation of artificial self-cleaning surfaces.

    PubMed

    Feil, Adriano F; Weibel, Daniel E; Corsetti, Rodrigo R; Pierozan, Matheus D; Michels, Alexandre F; Horowitz, Flavio; Amaral, Lívio; Teixeira, Sérgio R

    2011-10-01

    Micro- and nanostructures of Ti-γCu (γ = 0, 30, 50, 70, and 100 wt %) intermetallic alloys were produced through a single anodization step. It was found that the original alloy composition influences the final oxide morphology obtained after anodization which presented formation of a microstructure with nanotubes, nanoparticles or nanopillars on the surface. Pure Ti and Cu oxide metals and their alloys presented hydrophilic or superhydrophilic properties immediately after anodization. When the anodized pure metal and/or Ti-γCu surfaces were functionalized with trimethoxypropylsilane (TPMSi), by dipping and coating with a thin perfluorinated layer, the treated substrates became in all cases superhydrophobic (water contact angles in the range of 152-166°), showing excellent self-cleaning properties with hysteresis below 3°. These results can be explained by a combination of nanomicro morphologies with low surface energy compounds in the topmost monolayers. The decrease in hysteresis was associated with a higher M-OH bond concentration on the anodized surfaces, which allowed for more complete TMPSi coating coverage. This study also indicates that easy and effective fabrication of superhydrophobic surfaces in pure metals and alloys is possible without involving traditional multistep processes. PMID:21919435

  18. Advances in processing of NiAl intermetallic alloys and composites for high temperature aerospace applications

    NASA Astrophysics Data System (ADS)

    Bochenek, Kamil; Basista, Michal

    2015-11-01

    Over the last few decades intermetallic compounds such as NiAl have been considered as potential high temperature structural materials for aerospace industry. A large number of investigations have been reported describing complex fabrication routes, introducing various reinforcing/alloying elements along with theoretical analyses. These research works were mainly focused on the overcoming of main disadvantage of nickel aluminides that still restricts their application range, i.e. brittleness at room temperature. In this paper we present an overview of research on NiAl processing and indicate methods that are promising in solving the low fracture toughness issue at room temperature. Other material properties relevant for high temperature applications are also addressed. The analysis is primarily done from the perspective of NiAl application in aero engines in temperature regimes from room up to the operating temperature (over 1150 °C) of turbine blades.

  19. Pressure tuning of competing magnetic interactions in intermetallic CeFe2

    SciTech Connect

    Wang, Jiyang; Feng, Yejun; Jaramillo, R.; van Wezel, Jasper; Canfield, Paul C.; Rosenbaum, T.F.

    2012-07-20

    We use high-pressure magnetic x-ray diffraction and numerical simulation to determine the low-temperature magnetic phase diagram of stoichiometric CeFe2. Near 1.5 GPa we find a transition from ferromagnetism to antiferromagnetism, accompanied by a rhombohedral distortion of the cubic Laves crystal lattice. By comparing pressure and chemical substitution we find that the phase transition is controlled by a shift of magnetic frustration from the Ce-Ce to the Fe-Fe sublattice. Notably the dominant Ce-Fe magnetic interaction, which sets the temperature scale for the onset of long-range order, remains satisfied throughout the phase diagram but does not determine the magnetic ground state. Our results illustrate the complexity of a system with multiple competing magnetic energy scales and lead to a general model for magnetism in cubic Laves phase intermetallic compounds.

  20. The role of organic compounds in cloud formation: Relative importance of entrainment, co-condensation and particle-phase properties

    NASA Astrophysics Data System (ADS)

    Lowe, Samuel; Partridge, Daniel; Topping, David; Riipinen, Ilona

    2016-04-01

    The organic fraction of atmospheric aerosols is widely acknowledged to affect the cloud nucleating potential of aerosols. Cloud droplet formation through activation of non-volatile CCN is considered to be relatively well understood, however, there are fewer systematic studies on the activation of aerosols containing semi-volatile organic compounds that co-condense alongside water vapour, thus enhancing CCN activity. Although the significance of co-condensation of organic vapours for cloud droplet number concentration predictions has recently been identified, it remains uncertain how this process may interact with atmospheric dynamics. In addition to co-condensation of existing in-cloud material, additional semi-volatile mass can be entrained from the surrounding environment. Reduced cloud droplet number concentrations are expected as the parcel is diluted with clean air; however, additional soluble mass in the particle phase promotes droplet activation. The extent of increased droplet activation due to co-condensation relies also on the physiochemical properties of the organic compounds, as seen in several other phase partitioning sensitivity studies. In this work we study the simultaneous impact of entrainment and co-condensation, the relative importance of these two processes at different atmospheric conditions, their interactions with each other, and the particle-phase chemistry in terms of cloud microphysical properties and their parametric sensitivities. To assess the importance of the entrainment of semi-volatile materials as compared with their co-condensation and chemical properties, a pseudo-adiabatic cloud parcel model with a detailed description of bin microphysics is employed. We have added the co-condensation process to the model such that it is coupled with the parametric entrainment representation. The effects of entrainment and co-condensation are benchmarked independently and simultaneously against a control simulation. Furthermore, we probe the