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Sample records for oxide dispersion strengthening

  1. Ion implantations of oxide dispersion strengthened steels

    NASA Astrophysics Data System (ADS)

    Sojak, S.; Simeg Veternikova, J.; Slugen, V.; Petriska, M.; Stacho, M.

    2015-12-01

    This paper is focused on a study of radiation damage and thermal stability of high chromium oxide dispersion strengthened steel MA 956 (20% Cr), which belongs to the most perspective structural materials for the newest generation of nuclear reactors - Generation IV. The radiation damage was simulated by the implantation of hydrogen ions up to the depth of about 5 μm, which was performed at a linear accelerator owned by Slovak University of Technology. The ODS steel MA 956 was available for study in as-received state after different thermal treatments as well as in ions implanted state. Energy of the hydrogen ions chosen for the implantation was 800 keV and the implantation fluence of 6.24 × 1017 ions/cm2. The investigated specimens were measured by non-destructive technique Positron Annihilation Lifetime Spectroscopy in order to study the defect behavior after different thermal treatments in the as-received state and after the hydrogen ions implantation. Although, different resistance to defect production was observed in individual specimens of MA 956 during the irradiation, all implanted specimens contain larger defects than the ones in as-received state.

  2. Joining of Oxide Dispersion Strengthened Steels for Advanced Reactors

    NASA Astrophysics Data System (ADS)

    Baker, B. W.; Brewer, L. N.

    2014-12-01

    The design, manufacture, and experimental analysis of structural materials capable of operation in the high temperatures, corrosive environments, and radiation damage spectra of future reactor designs remain one of the key pacing items for advanced reactor designs. The most promising candidate structural materials are vanadium-based refractory alloys, silicon carbide composites and oxide dispersion strengthened steels. Of these, oxide dispersion strengthened steels are a likely near-term candidate to meet required demands. This paper reviews different variants of oxide dispersion strengthened steels and discusses their capability with regard to high-temperature strength, corrosion resistance, and radiation damage resistance. Additionally, joining of oxide dispersion strengthened steels, which has been cited as a limiting factor preventing their use, is addressed and reviewed. Specifically, friction stir welding of these steels is reviewed as a promising joining method for oxide dispersion strengthened steels.

  3. OXIDE DISPERSION-STRENGTHENED HEAT EXCHANGER TUBING

    SciTech Connect

    Harper, Mark A.

    2001-11-06

    Oxide dispersion strengthened (ODS) alloys (e.g. the INCOLOY{reg_sign} MA956 alloy) are known for their excellent high temperature properties and are prime candidate materials for the construction of very high temperature heat exchangers that will be used in Vision 21 power plants. The main limitation of these materials is their poor weldability. Commercially available ODS tubing also tends to exhibit relatively poor circumferential creep strength due to current processing practices resulting in a fine grain size in the transverse direction. Thus far, these two characteristics of the ODS tubing have restricted its use to mostly non-pressure containing applications. The objectives of this program are to develop: (a) an MA956 tube with sufficient circumferential creep strength for long term use as heat exchanger tubing for very high temperatures; (b) a welding technique(s) for producing adequate joints between an MA956 tube and an MA956 tube, and an MA956 tube and an INCONEL 601 tube; (c) the bending strain limits, below which recrystallization will not occur in a MA956 tube during normal operation; and (d) the high temperature corrosion limits for the MA956 alloy with respect to working-fluid side and fireside environments. Also, this program seeks to generate data for use by heat exchanger designers and the ASME Boiler and Pressure Vessel Code, and perform an analysis of the mechanical property, tube bending, and corrosion data in order to determine the implications on the design of a very high temperature heat exchanger (T>1093 C/2000 F). After one year, work is currently being conducted on increasing the circumferential strength of a MA956 tube, developing joining techniques for this material, determining the tube bending strain limits, and establishing the high temperature corrosion parameters for the MA956 alloy in environments expected to be present in Vision 21 power plants. Work in these areas will is continuing into the next fiscal year, with success

  4. Oxide-dispersion strengthening of porous powder metalurgy parts

    DOEpatents

    Judkins, Roddie R.

    2002-01-01

    Oxide dispersion strengthening of porous metal articles includes the incorporation of dispersoids of metallic oxides in elemental metal powder particles. Porous metal articles, such as filters, are fabricated using conventional techniques (extrusion, casting, isostatic pressing, etc.) of forming followed by sintering and heat treatments that induce recrystallization and grain growth within powder grains and across the sintered grain contact points. The result is so-called "oxide dispersion strengthening" which imparts, especially, large increases in creep (deformation under constant load) strength to the metal articles.

  5. Development oxide dispersion strengthened ferritic steels for fusion

    SciTech Connect

    Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S.

    1997-04-01

    Uniaxial tension creep response is reported for an oxide dispersion strengthened (ODS) steel, Fe-13.5Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) manufactured using the mechanical alloying process. Acceptable creep response is obtained at 900{degrees}C.

  6. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Hotzler, R. K.; Glasgow, T. K.

    1980-01-01

    Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

  7. Oxide dispersion strengthening of nickel electrodeposits for microsystem applications.

    SciTech Connect

    Janek, Richard P.; Kotula, Paul Gabriel; Buchheit, Thomas Edward; Michael, R. P.; Goods, Steven Howard

    2003-11-01

    Oxide dispersion strengthened nickel (ODS-Ni) electrodeposits were fabricated to net shape in a nickel sulfamate bath using the LIGA process. A 20 g/l charge of 10 nm Al{sub 2}O{sub 3} powder was suspended in the bath during electrodeposition to produce specimens containing an approximately 0.001-0.02 volume fraction dispersion of the alumina particulate. Mechanical properties are compared to baseline specimens fabricated using an identical sulfamate bath chemistry without the Al{sub 2}O{sub 3} powder charge. Results reveal that the as-deposited ODS-Ni exhibited significantly higher yield strength and ultimate tensile strength than the baseline material. This increase in as-deposited strength is attributed to Orowan strengthening. The ODS-Ni also showed improved retention of room temperature strength after annealing over a range of temperatures up to 600 C. Microscopy revealed that this resistance to anneal softening was due to an inhibition of grain growth in the presence of the oxide dispersion. Nanoindentation measurements revealed that the properties of the dispersion strengthened deposit were uniform through its thickness, even in narrow, high aspect ratio structures. At elevated temperatures, the strength of the ODS-Ni was approximately three times greater than that of the baseline material although with a significant reduction in hot ductility.

  8. Microstructural change on electron irradiated oxide dispersion strengthened ferritic steels

    NASA Astrophysics Data System (ADS)

    Kinoshita, H.; Akasaka, N.; Takahashi, H.; Shibahara, I.; Onose, S.

    1992-09-01

    Oxide dispersion strengthened (ODS) ferritic steels were irradiated in a high voltage electron microscope (HVEM) to study their response to irradiation. Fe-13Cr with 0.25 wt% Y2O3 as dispersed particles and containing additions of either 0.45% Nb, 0.45% V and 0.67% Zr were irradiated at 673 and 723 K up to 15 dpa. The Y2O3 particles in all specimens were stable under these irradiation conditions. During irradiation, two types of dislocations were formed but observable voids were not formed. Furthermore, plate-like and granular-like precipitates formed in both the irradiated and nonirradiated regions.

  9. Fracture toughness of oxide-dispersion strengthened copper

    SciTech Connect

    Alexander, D.J.

    1996-10-01

    The fracture toughness of an oxide-dispersion strengthened copper alloy AL-15 has been examined at room temperature and 250{degrees}C, in air and in vacuum (< 10{sup {minus}6} torr). Increasing test temperature causes a significant decrease in the fracture toughness of this material, in either air or vacuum environments. In addition, specimens oriented in the T-L orientation (crack growth parallel to the extrusion direction) show significantly lower toughness than those in the L-T orientation (crack growth perpendicular to the extrusion direction).

  10. Advanced oxide dispersion strengthened sheet alloys for improved combustor durability

    NASA Technical Reports Server (NTRS)

    Henricks, R. J.

    1981-01-01

    Burner design modifications that will take advantage of the improved creep and cyclic oxidation resistance of oxide dispersion strengthened (ODS) alloys while accommodating the reduced fatigue properties of these materials were evaluated based on preliminary analysis and life predictions, on construction and repair feasibility, and on maintenance and direct operating costs. Two designs - the film cooled, segmented louver and the transpiration cooled, segmented twin Wall - were selected for low cycle fatigue (LCF) component testing. Detailed thermal and structural analysis of these designs established the strain range and temprature at critical locations resulting in predicted lives of 10,000 cycles for MA 956 alloy. The ODs alloys, MA 956 and HDA 8077, demonstrated a 167 C (300 F) temperature advantage over Hastelloy X alloy in creep strength and oxidation resistance. The MA 956 alloy was selected for mechanical property and component test evaluations. The MA 956 alloy was superior to Hastelloy X in LCF component testing of the film cooled, segmented louver design.

  11. Diffusion bonding of the oxide dispersion strengthened steel PM2000

    NASA Astrophysics Data System (ADS)

    Sittel, Wiebke; Basuki, Widodo W.; Aktaa, Jarir

    2013-11-01

    Ferritic oxide dispersion strengthened (ODS) steels are well suited as structural materials, e.g. for claddings in fission reactors and for plasma facing components in fusion power plants due to their high mechanical and oxidation stability at high temperatures and their high irradiation resistance. PM2000 is an iron based ODS ferritic steel with homogeneously distributed nanometric yttria particles. Melting joining techniques are not suitable for such ODS materials because of the precipitation and agglomeration of the oxide particles and hence the loss of their strengthening effect. Solid state diffusion bonding is thus chosen to join PM2000 and is investigated in this work with a focus on oxide particles. The diffusion bonding process is aided by the computational modeling, including the influence of the ODS particles. For modeling the microstructure stability and the creep behavior of PM2000 at various, diffusion bonding relevant temperatures (50-80% Tm) are investigated. Particle distribution (TEM), strength (tensile test) and toughness (Charpy impact test) obtained at temperatures relevant for bonding serve as input for the prediction of optimal diffusion bonding parameters. The optimally bonded specimens show comparable strength and toughness relative to the base material.

  12. Longitudinal shear behavior of several oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1978-01-01

    Two commercial oxide dispersion strengthened (ODS) alloys, MA-753 and MA-754, and three experimental ODS alloys, MA-757E, MA-755E, and MA-6000E, were tested in shear at 760 C. Comparisons were made with other turbine blade and vane alloys. All of the ODS alloys exhibited less shear strength than directionally solidified Mar-M 200 = Hf or then conventionally cast B-1900. The strongest ODS alloy tested, MA-755E, was comparable in both shear and tensile strength to the lamellar directionally solidified eutectic alloy gamma/gamma prime - delta. Substantial improvements in shear resistance were found for all alloys tested when the geometry of the specimen was changed from one generating a transverse tensile stress in the shear area to one generating a transverse compressive stress. Finally, 760 C shear strength as a fraction of tensile strength was found to increase linearly with the log of the transverse tensile ductility.

  13. Development of oxide dispersion strengthened ferritic steels for fusion

    SciTech Connect

    Mukhopadhyay, D.K.; Froes, F.H.; Gelles, D.S.

    1998-03-01

    An oxide dispersion strengthened (ODS) ferritic steel with high temperature strength has been developed in line with low activation criteria for application in fusion power systems. The composition Fe-13.5Cr-2W-0.5Ti-0.25Y{sub 2}O{sup 3} was chosen to provide a minimum chromium content to insure fully delta-ferrite stability. High temperature strength has been demonstrated by measuring creep response of the ODS alloy in uniaxial tension at 650 and 900 C in an inert atmosphere chamber. Results of tests at 900 C demonstrate that this alloy has creep properties similar to other alloys of similar design and can be considered for use in high temperature fusion power system designs. The alloy selection process, materials production, microstructural evaluation and creep testing are described.

  14. Oxide Dispersion Strengthened Iron Aluminide by CVD Coated Powders

    SciTech Connect

    Asit Biswas Andrew J. Sherman

    2006-09-25

    This I &I Category2 program developed chemical vapor deposition (CVD) of iron, aluminum and aluminum oxide coated iron powders and the availability of high temperature oxidation, corrosion and erosion resistant coating for future power generation equipment and can be used for retrofitting existing fossil-fired power plant equipment. This coating will provide enhanced life and performance of Coal-Fired Boilers components such as fire side corrosion on the outer diameter (OD) of the water wall and superheater tubing as well as on the inner diameter (ID) and OD of larger diameter headers. The program also developed a manufacturing route for readily available thermal spray powders for iron aluminide coating and fabrication of net shape component by powder metallurgy route using this CVD coated powders. This coating can also be applid on jet engine compressor blade and housing, industrial heat treating furnace fixtures, magnetic electronic parts, heating element, piping and tubing for fossil energy application and automotive application, chemical processing equipment , heat exchanger, and structural member of aircraft. The program also resulted in developing a new fabrication route of thermal spray coating and oxide dispersion strengthened (ODS) iron aluminide composites enabling more precise control over material microstructures.

  15. Selective laser sintering of MA956 oxide dispersion strengthened steel

    NASA Astrophysics Data System (ADS)

    Hunt, Ryan M.; Kramer, Kevin J.; El-Dasher, Bassem

    2015-09-01

    Oxide Dispersion Strengthened (ODS) steels' qualities of radiation damage resistance and high strength at high temperature make them promising nuclear structural materials. However, the dispersed yttria that gives ODS steel its beneficial qualities are generally compromised during joining processes, making fabrication difficult and expensive. The selective laser sintering process offers a potential path through this barrier by which net-shape parts can feasibly be built via additive manufacturing without fully melting the structure. Rastering a 400 W laser over a 110 μm MA956 ODS steel powder bed, we additively built parts with varying build conditions. Although density was achieved to within 97% of the wrought MA956, ultimate tensile strengths achieved only 65% of the wrought strength. Spectroscopy analysis points to the agglomeration of the yttria nano-particles as a possible explanation for the loss in strength. Further study might benefit from exploration of other parameters such as thinner powder build layers which would require less energy input to achieve sintering while minimizing time above the melting temperature.

  16. Creep degradation in oxide-dispersion-strengthened alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    Oxide dispersion strengthened Ni-base alloys in wrought bar form are studied for creep degradation effects similar to those found in thin gage sheet. The bar products evaluated included ODS-Ni, ODS-NiCr, and three types of advanced ODS-NiCrAl alloys. Tensile test specimens were exposed to creep at various stress levels at 1365 K and then tensile tested at room temperature. Low residual tensile properties, change in fracture mode, the appearance of dispersoid-free bands, grain boundary cavitation, and internal oxidation in the microstructure were interpreted as creep degradation effects. This work showed that many ODS alloys are subject to creep damage. Degradation of tensile properties occurred after very small amounts of creep strain, ductility being the most sensitive property. All the ODS alloys which were creep damaged possessed a large grain size. Creep damage appears to have been due to diffusional creep which produced dispersoid-free bands around boundaries acting as vacancy sources. Low angle and possibly twin boundaries acted as vacancy sources.

  17. Oxide dispersion strengthened steel irradiation with helium ions

    NASA Astrophysics Data System (ADS)

    Pouchon, M. A.; Chen, J.; Döbeli, M.; Hoffelner, W.

    2006-06-01

    Oxide dispersion strengthened (ODS) ferritic steels are investigated as possible structural material for the future generation of high temperature gas cooled nuclear reactors. ODS-steels are considered to replace other high temperature materials for tubing or structural parts. The oxide particles serve for interfacial pinning of moving dislocations. Therefore, the creep resistance is improved. In case of the usage of these materials in reactors, the behavior under irradiation must be further clarified. In this paper the effects induced by 4He2+ implantation into a ferritic ODS steel are investigated. The fluence ranges from 1016 to 1017 cm-2 and the energy from 1 to 2 MeV. The induced swelling is investigated for implantations at room temperature and 470 K. It is derived from the irradiation induced surface displacement, which is measured with an atomic force microscope (AFM). With a displacement damage of 0.6 dpa, a volume increase of 0.65% is observed at room temperature and 0.33% at 470 K. A cross-sectional cut is performed by focused ion beam and investigated by transmission electron microcopy (TEM). The defect density observed on the TEM micrographs agrees well with the computational simulation (TRIM) of the damage profile.

  18. Strengthening of metallic alloys with nanometer-size oxide dispersions

    DOEpatents

    Flinn, J.E.; Kelly, T.F.

    1999-06-01

    Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains. 20 figs.

  19. Strengthening of metallic alloys with nanometer-size oxide dispersions

    DOEpatents

    Flinn, John E.; Kelly, Thomas F.

    1999-01-01

    Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains.

  20. Dispersion strengthened copper

    DOEpatents

    Sheinberg, H.; Meek, T.T.; Blake, R.D.

    1990-01-09

    A composition of matter is described which is comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide. A method for making this composition of matter is also described. This invention relates to the art of powder metallurgy and, more particularly, it relates to dispersion strengthened metals.

  1. Low cost fabrication development for oxide dispersion strengthened alloy vanes

    NASA Technical Reports Server (NTRS)

    Perkins, R. J.; Bailey, P. G.

    1978-01-01

    Viable processes were developed for secondary working of oxide dispersion strengthened (ODS) alloys to near-net shapes (NNS) for aircraft turbine vanes. These processes were shown capable of producing required microstructure and properties for vane applications. Material cost savings of 40 to 50% are projected for the NNS process over the current procedures which involve machining from rectangular bar. Additional machining cost savings are projected. Of three secondary working processes evaluated, directional forging and plate bending were determined to be viable NNS processes for ODS vanes. Directional forging was deemed most applicable to high pressure turbine (HPT) vanes with their large thickness variations while plate bending was determined to be most cost effective for low pressure turbine (LPT) vanes because of their limited thickness variations. Since the F101 LPT vane was selected for study in this program, development of plate bending was carried through to establishment of a preliminary process. Preparation of ODS alloy plate for bending was found to be a straight forward process using currently available bar stock, providing that the capability for reheating between roll passes is available. Advanced ODS-NiCrAl and ODS-FeCrAl alloys were utilized on this program. Workability of all alloys was adequate for directional forging and plate bending, but only the ODS-FeCrAl had adequate workability for shaped preform extrustion.

  2. Development of Oxide Dispersion Strengthened MCrAlY Coatings

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Schläfer, T.; Richardt, K.; Brühl, M.

    2008-12-01

    MCrAlY materials are widely used as bond coats for thermal barrier coatings on turbine blades. The aim of this work is to improve mechanical properties and wear resistance of thermal sprayed NiCoCrAlY-coatings by strengthening the coating with hard phase particles. In order to retain the effect of the dispersion reinforcement at high temperatures, the use of temperature-stable oxide hard phases such as ZrO2-Y2O3 is necessary. To realize this new material structure, the high-energy ball-milling process is applied and analyzed. The mixture ratio between NiCoCrAlY and ZrO2-Y2O3 was varied between 5 and 10 wt.% ZrO2-Y2O3. The influences of the milling time of the high-energy ball-milling process on the distribution of the hard phases in the metal matrix were analyzed. After spraying with a HVOF system the mechanical properties of the coatings are measured and compared with conventional NiCoCrAlY coatings.

  3. Radiation-sustained nanocluster metastability in oxide dispersion strengthened materials

    NASA Astrophysics Data System (ADS)

    Ribis, J.; Bordas, E.; Trocellier, P.; Serruys, Y.; de Carlan, Y.; Legris, A.

    2015-12-01

    ODS materials constitute a new promising class of structural materials for advanced fission and fusion energy application. These Fe-Cr based ferritic steels contain ultra-high density of dispersion-strengthening nanoclusters conferring excellent mechanical properties to the alloy. Hence, guarantee the nanocluster stability under irradiation remain a critical issue. Nanoclusters are non-equilibrium multicomponent compounds (YTiCrO) forming through a complex nucleation pathway during the elaboration process. In this paper, it is proposed to observe the response of these nanoclusters when the system is placed far from equilibrium by means of ion beam. The results indicate that the Y, Ti, O and Cr atoms self-organized so that nanoclusters coarsened but maintain their non-equilibrium chemical composition. It is discussed that the radiation-sustained nanocluster metastability emerges from cooperative effects: radiation-induced Ostwald ripening, permanent creation of vacancies in the clusters, and fast Cr diffusion mediated by interstitials.

  4. Evaluation of Oxide Dispersion Strengthened (ODS) molybdenum alloys

    SciTech Connect

    Bianco, R.; Buckman, R.W. Jr.

    1995-12-31

    A series of fourteen (14) novel high-strength molybdenum alloy compositions containing a dispersion of very fine (< 1 {mu}m diameter) oxide particles were consolidated using two proprietary powder metallurgy techniques. The developmental compositions were evaluated to determine the microstructural stability and mechanical properties from cryogenic (-148{degrees}F) to elevated temperatures (4000{degrees}F) for material in the as-swaged (>98% cold work) condition and for as-swaged material in the heat treated condition. Extremely fine oxide particle sizes (<1000 {Angstrom}) were observed by Transmission Electron Microscopy (TEM) for a number of the experimental compositions in the as-swaged condition. A one hour recrystallization temperature as high as 3990{degrees}F was measured and a ductile-to-brittle transition temperature as low as {approximately}58{degrees}F for material in the recrystallized condition was determined. The preliminary results support the alloy design concept feasibility.

  5. Oxide-dispersion-strengthened turbine blades, volume 1

    NASA Technical Reports Server (NTRS)

    Millan, P. P., Jr.; Mays, J. C.

    1986-01-01

    The objective of Project 4 was to develop a high-temperature, uncooled gas turbine blade using MA6000 alloy. The program objectives were achieved. Production scale up of the MA6000 alloy was achieved with a fair degree of tolerance to nonoptimum processing. The blade manufacturing process was also optimized. The mechanical, environmental, and physical property evaluations of MA6000 were conducted. The ultimate tensile strength, to about 704 C (130 F), is higher than DS MAR-M 247 but with a corresponding lower tensile elongation. Also, above 982 C (180 F) MA6000 tensile strength does not decrease as rapidly as MAR-M 247 because the ODS mechanism still remains active. Based on oxidation resistance and diffusional stability considerations, NiCrAlY coatings are recommended. CoCrAly coating should be applied on top of a thin NiCrAlY coating. Vibration tests, whirlpit tests, and a high-rotor-rig test were conducted to ensure successful completion of the engine test of the MA6000 TFE731 high pressure turbine blades. The results of these tests were acceptable. In production quantities, the cost of the Project 4 MA6000 blade is estimated to be about twice that of a cast DS MAR-M 247 blade.

  6. Oxide-dispersion-strengthened turbine blades. Volume 2

    NASA Technical Reports Server (NTRS)

    Millan, P. P., Jr.; Mays, J. C.; Humbert, D. R.

    1987-01-01

    The overall objective of Project 4 was to develop and test a high-temperature, uncooled gas turbine blade using MA6000 alloy. Production scale up of the MA6000 alloy was achieved with a fair degree of tolerance to non-optimum processing. The blade manufacturing process was also optimized. The mechanical, environmental, and physical property evaluations of MA6000 were conducted. The ultimate tensile strength, to about 704 C (1300 F), is higher than DS MAR-M 247 but with a corresponding lower tensile elongation. Also, above 982 C (1800 F) MA6000 tensile strength does not decrease as rapidly as MAR-M 247 because the ODS mechanism still remains active. Based on oxidation resistance and diffusional stability considerations, NiCrAlY coatings are recommended. CoCrAlY coating should be applied on top of a thin NiCrAlY coating if hot corrosion is expected. Vibration, whirlpit, and high-rotor-rig tests were conducted to ensure successful completion of the engine test of the MA6000 TFE731 high pressure turbine blades. Test results were acceptable. In production quantities, the cost of the Project 4 MA6000 blade is estimated to be twice that of a cast DS MAR-M 247 blade.

  7. Method of producing an oxide dispersion strengthened coating and micro-channels

    DOEpatents

    Kang, Bruce S; Chyu, Minking K; Alvin, Mary Anne; Gleeson, Brian M

    2013-12-17

    The disclosure provides a method for the production of composite particles utilizing a mechano chemical bonding process following by high energy ball milling on a powder mixture comprised of coating particles, first host particles, and second host particles. The composite particles formed have a grain size of less than one micron with grains generally characterized by a uniformly dispersed coating material and a mix of first material and second material intermetallics. The method disclosed is particularly useful for the fabrication of oxide dispersion strengthened coatings, for example using a powder mixture comprised of Y.sub.2O.sub.3, Cr, Ni, and Al. This particular powder mixture may be subjected to the MCB process for a period generally less than one hour following by high energy ball milling for a period as short as 2 hours. After application by cold spraying, the composite particles may be heat treated to generate an oxide-dispersion strengthened coating.

  8. Processing and characterization of a hipped oxide dispersion strengthened austenitic steel

    NASA Astrophysics Data System (ADS)

    Zhou, Zhangjian; Yang, Shuo; Chen, Wanhua; Liao, Lu; Xu, Yingli

    2012-09-01

    An oxide dispersion strengthened (ODS) austenitic steel with a nominal chemical composition of Fe-18Cr-8Ni-1Mo-0.5Ti-0.35Y2O3 (in wt.%) was prepared by mechanical alloying (MA) combined with hot isostatic pressing (HIP). The morphology of MA powders was observed by SEM. The microstructure of the HIPed ODS austenitic steels and chemical composition of the oxide particles were examined by TEM combined with an energy dispersive spectrometry. The oxide dispersion particles with sizes less than 20 nm were determined to be complex Y-Ti-Si-O oxides. The tensile test showed that the fabricated ODS austenitic steel had very high strength and good ductility. The ultimate tensile strength was around 1000 MPa with a total elongation of 33.5% at room temperature, while at temperature of 700 °C, the ultimate tensile strength still reached around 500 MPa.

  9. Oxide dispersion strengthened ferritic steels: a basic research joint program in France

    NASA Astrophysics Data System (ADS)

    Boutard, J.-L.; Badjeck, V.; Barguet, L.; Barouh, C.; Bhattacharya, A.; Colignon, Y.; Hatzoglou, C.; Loyer-Prost, M.; Rouffié, A. L.; Sallez, N.; Salmon-Legagneur, H.; Schuler, T.

    2014-12-01

    AREVA, CEA, CNRS, EDF and Mécachrome are funding a joint program of basic research on Oxide Dispersion Strengthened Steels (ODISSEE), in support to the development of oxide dispersion strengthened 9-14% Cr ferritic-martensitic steels for the fuel element cladding of future Sodium-cooled fast neutron reactors. The selected objectives and the results obtained so far will be presented concerning (i) physical-chemical characterisation of the nano-clusters as a function of ball-milling process, metallurgical conditions and irradiation, (ii) meso-scale understanding of failure mechanisms under dynamic loading and creep, and, (iii) kinetic modelling of nano-clusters nucleation and α/α‧ unmixing.

  10. Preliminary study of oxide-dispersion-strengthened B-1900 prepared by mechanical alloys

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.; Quatinetz, M.

    1975-01-01

    An experimental oxide dispersion strengthened (ODS) alloy based on the B-1900 composition was produced by the mechanical alloying process. Without optimization of the processing for the alloy or the alloy for the processing, recrystallization of the extruded product to large elongated grains was achieved. Materials having grain length-width ratios of 3 and 5.5 were tested in tension and stress-rupture. The ODS B-1900 exhibited tensile strength similar to that of cast B-1900. Its stress-rupture life was lower than that of cast B-1900 at 760 C. At 1095 C the ODS B-1900 with the higher grain length-width ratio (5.5) had stress-rupture life superior to that of cast B-1900. It was concluded that, with optimization, oxide dispersion strengthening of B-1900 and other complex cast nickel-base alloys has potential for improving high temperature properties over those of the cast alloy counterparts.

  11. Study of structural inhomogeneity of commercial oxide-dispersion-strengthened steels

    NASA Astrophysics Data System (ADS)

    Veternikova, J.; Degmova, J.; Skraba, M.; Petriska, M.; Sojak, S.; Slugen, V.

    2014-04-01

    Oxide-dispersion-strengthened steels, candidate materials for construction of new generation of nuclear reactors, can have inhomogeneous structure and anisotropic mechanical properties due to their fabrication, especially by process of mechanical alloying. This paper examines two similar commercial oxide-dispersion-strengthened steels MA 956 and PM 2000 in two different orientations of samples in order to study inhomogeneity of defect presence using positron annihilation techniques. Positron data showed small or negligible differences between samples of individual steels (up to 4 % for average lifetime). Moreover, structural divergence between two orientations (transversal cut and longitudinal cut) of the same steel was also not apparent. However, higher presence of defects and also bigger defects were found for both orientations of MA 956 samples. The structure of PM 2000 probably contains fewer defects with smaller size, though their occurrence in surface and subsurface layers up to 1.6 μm (from Doppler broadening spectroscopy) seem to be less homogeneous than in MA 956.

  12. Radiation Stability of Nanoclusters in Nano-structured Oxide Dispersion Strengthened (ODS) Steels

    SciTech Connect

    Certain, Alicia G.; Kuchibhatla, Satyanarayana V N T; Shutthanandan, V.; Hoelzer, D. T.; Allen, T. R.

    2013-03-01

    Nanostructured oxide dispersion strengthened (ODS) steels are considered candidates for nuclear fission and fusion applications at high temperature and dose. The complex oxide nanoclusters in these alloys provide high-temperature strength and are expected to afford better radiation resistance. Proton, heavy ion, and neutron irradiations have been performed to evaluate cluster stability in 14YWT and 9CrODS steel under a range of irradiation conditions. Energy-filtered transmission electron microscopy and atom probe tomography were used in this work to analyze the evolution of the oxide population.

  13. Irradiation effects in oxide dispersion strengthened (ODS) Ni-base alloys for Gen. IV nuclear reactors

    NASA Astrophysics Data System (ADS)

    Oono, Naoko; Ukai, Shigeharu; Kondo, Sosuke; Hashitomi, Okinobu; Kimura, Akihiko

    2015-10-01

    Oxide particle dispersion strengthened (ODS) Ni-base alloys are irradiated by using simulation technique (Fe/He dual-ion irradiation) to investigate the reliability to Gen. IV high-temperature reactors. The fine oxide particles with less than 10 nm in average size and approximately 8.0 × 1022 m-3 in number density remained after 101 dpa irradiation. The tiny helium bubbles were inside grains, not at grain-boundaries; it is advantageous effect of oxide particles which trap the helium atoms at the particle-matrix interface. Ni-base ODS alloys demonstrated their great ability to overcome He embrittlement.

  14. Creep and tensile properties of several oxide dispersion strengthened nickel base alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    The creep properties at 1365 K of several oxide dispersion strengthened (ODS) alloys were studied, where the creep exposures involved low strains, on the order of 1% or less, after nominally 100 hours of testing. It was found that ODS alloys possess threshold stresses for creep. Creep in polycrystalline ODS alloys is an inhomogeneous process. The threshold stresses in large grain size ODS Ni-20Cr and Ni-16Cr-4/5Al type alloys are dependent on the grain aspect ratio.

  15. Quantification of oxide particle composition in model oxide dispersion strengthened steel alloys.

    PubMed

    London, A J; Lozano-Perez, S; Moody, M P; Amirthapandian, S; Panigrahi, B K; Sundar, C S; Grovenor, C R M

    2015-12-01

    Oxide dispersion strengthened ferritic steels (ODS) are being considered for structural components of future designs of fission and fusion reactors because of their impressive high-temperature mechanical properties and resistance to radiation damage, both of which arise from the nanoscale oxide particles they contain. Because of the critical importance of these nanoscale phases, significant research activity has been dedicated to analysing their precise size, shape and composition (Odette et al., Annu. Rev. Mater. Res. 38 (2008) 471-503 [1]; Miller et al., Mater. Sci. Technol. 29(10) (2013) 1174-1178 [2]). As part of a project to develop new fuel cladding alloys in India, model ODS alloys have been produced with the compositions, Fe-0.3Y2O3, Fe-0.2Ti-0.3Y2O3 and Fe-14Cr-0.2Ti-0.3Y2O3. The oxide particles in these three model alloys have been studied by APT in their as-received state and following ion irradiation (as a proxy for neutron irradiation) at various temperatures. In order to adequately quantify the composition of the oxide clusters, several difficulties must be managed, including issues relating to the chemical identification (ranging and variable peak-overlaps); trajectory aberrations and chemical structure; and particle sizing. This paper presents how these issues can be addressed by the application of bespoke data analysis tools and correlative microscopy. A discussion follows concerning the achievable precision in these measurements, with reference to the fundamental limiting factors.

  16. Microstructure and Mechanical Properties of Ultrafine-Grained Austenitic Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Mao, Xiaodong; Kang, Suk Hoon; Kim, Tae Kyu; Kim, Seul Cham; Oh, Kyu Hwan; Jang, Jinsung

    2016-11-01

    316L stainless steel based austenitic oxide dispersion strengthened (AODS) steel was fabricated by mechanical alloying (MA) and hot isostatic pressing (HIP). The AODS sample exhibited an ultrafine-grained (UFG) structure with a bimodal grain size distribution (large grains of about 1200 nm and fine grains of about 260 nm). Two groups of oxide particles were observed; fine Y2Ti2O7 of about 7.7 nm and coarse Cr2O3 particles of about 200 nm in diameter. Tensile tests of the hot-rolled AODS steel samples showed yield strength of up to 890 MPa at room temperature, which is nearly four times higher than that of conventional 316L stainless steel. Micro-indentation and hardness tests indicated even higher yield strength of up to 1200 MPa, which shows a good agreement with the calculated value by combining of the grain refinement strengthening by the Hall-Petch relation and the dispersion strengthening by the Orowan mechanism. The lower strength from tensile tests should be attributed to the formation of micro-cracks at the interfaces between coarse Cr2O3 particles and the matrix. Coarse Cr2O3 particles were also frequently observed inside the fracture surface dimples of the creep ruptured sample at 923 K (650 °C) and 140 MPa. It is thus suggested that the yield strength and elongation could be further improved by controlling the coarse Cr2O3 particles.

  17. Microstructure and Mechanical Properties of Ultrafine-Grained Austenitic Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Mao, Xiaodong; Kang, Suk Hoon; Kim, Tae Kyu; Kim, Seul Cham; Oh, Kyu Hwan; Jang, Jinsung

    2016-06-01

    316L stainless steel based austenitic oxide dispersion strengthened (AODS) steel was fabricated by mechanical alloying (MA) and hot isostatic pressing (HIP). The AODS sample exhibited an ultrafine-grained (UFG) structure with a bimodal grain size distribution (large grains of about 1200 nm and fine grains of about 260 nm). Two groups of oxide particles were observed; fine Y2Ti2O7 of about 7.7 nm and coarse Cr2O3 particles of about 200 nm in diameter. Tensile tests of the hot-rolled AODS steel samples showed yield strength of up to 890 MPa at room temperature, which is nearly four times higher than that of conventional 316L stainless steel. Micro-indentation and hardness tests indicated even higher yield strength of up to 1200 MPa, which shows a good agreement with the calculated value by combining of the grain refinement strengthening by the Hall-Petch relation and the dispersion strengthening by the Orowan mechanism. The lower strength from tensile tests should be attributed to the formation of micro-cracks at the interfaces between coarse Cr2O3 particles and the matrix. Coarse Cr2O3 particles were also frequently observed inside the fracture surface dimples of the creep ruptured sample at 923 K (650 °C) and 140 MPa. It is thus suggested that the yield strength and elongation could be further improved by controlling the coarse Cr2O3 particles.

  18. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1990-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  19. Dispersion strengthened copper

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1989-01-01

    A composition of matter comprised of copper and particles which are dispersed throughout the copper, where the particles are comprised of copper oxide and copper having a coating of copper oxide, and a method for making this composition of matter.

  20. THE STRUCTURE AND INTERDIFFUSIONAL DEGRADATION OF ALUMINIDE COATINGS ON OXIDE DISPERSION STRENGTHENED ALLOYS

    SciTech Connect

    Boone, D. H.; Crane, D. A.; Whittle, D. P.

    1981-04-01

    A study of the effects of oxide dispersion strengthened {ODS) superalloy composition and coating processing on the structure and diffusional stability of aluminide coatings was undertaken. Increasing substrate aluminum content results in the formation of a more typical nickel base superalloy aluminide coating structure that is more resistant to spallation during high temperature isothermal exposure. The coating application process also affected coating stability, a low aluminum, outward diffusion type resulting in greater apparent stability. A SEM deep etching and fractography examination technique was used in an attempt to establish the location and kinetics of void formation. Alurninide protective lifetimes are still found to be far short of the alloys rnechnital property capabilities.

  1. Several braze filler metals for joining an oxide-dispersion-strengthened nickel-chromium-aluminum alloy

    NASA Technical Reports Server (NTRS)

    Gyorgak, C. A.

    1975-01-01

    An evaluation was made of five braze filler metals for joining an aluminum-containing oxide dispersion-strengthened (ODS) alloy, TD-NiCrAl. All five braze filler metals evaluated are considered suitable for joining TD-NiCrAl in terms of wettability and flow. Also, the braze alloys appear to be tolerant of slight variations in brazing procedures since joints prepared by three sources using three of the braze filler metals exhibited similar brazing characteristics and essentially equivalent 1100 C stress-rupture properties in a brazed butt-joint configuration. Recommendations are provided for brazing the aluminum-containing ODS alloys.

  2. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  3. High resolution neutron diffraction crystallographic investigation of Oxide Dispersion Strengthened steels of interest for fusion technology

    NASA Astrophysics Data System (ADS)

    Coppola, R.; Rodriguez-Carvajal, J.; Wang, M.; Zhang, G.; Zhou, Z.

    2014-12-01

    High resolution neutron diffraction measurements have been carried out to characterize the crystallographic phases present in different Oxide Dispersion Strengthened (ODS) steels of interest for fusion technology. The different lattice structures, Im3m for the ferritic ODS and Fm3m for the austenitic ODS, are resolved showing line anisotropy effects possibly correlated with differences in dislocation densities and texture. Many contributions from minority phases are detected well above the background noise; none of the expected crystallographic phases, such as M23C6 and including Y2O3, fits them, but the TiN phase is identified in accordance with results of other microstructural techniques.

  4. Creep and stress rupture of oxide dispersion strengthened mechanically alloyed Inconel alloy MA 754

    NASA Technical Reports Server (NTRS)

    Howson, T. E.; Tien, J. K.; Stulga, J. E.

    1980-01-01

    The creep and stress rupture behavior of the mechanically alloyed oxide dispersion strengthened nickel-base alloy MA 754 was studied at 760, 982 and 1093 C. Tensile specimens with a fine, highly elongated grain structure, oriented parallel and perpendicular to the longitudinal grain direction were tested at various stresses in air under constant load. It was found that the apparent stress dependence was large, with power law exponents ranging from 19 to 33 over the temperature range studied. The creep activation energy, after correction for the temperature dependence of the elastic modulus, was close to but slightly larger than the activation energy for self diffusion. Rupture was intergranular and the rupture ductility as measured by percentage elongation was generally low, with values ranging from 0.5 to 16 pct. The creep properties are rationalized by describing the creep rates in terms of an effective stress which is the applied stress minus a resisting stress consistent with the alloy microstructure. Values of the resisting stress obtained through a curve fitting procedure are found to be close to the values of the particle by-pass stress for this oxide dispersion strengthened alloy, as calculated from the measured oxide particle distribution.

  5. The elastic modulus correction term in creep activation energies Applied to oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

    Malu, M.; Tien, J. K.

    1975-01-01

    The effect of elastic modulus and the temperature dependence of elastic modulus on creep activation energies for an oxide dispersion strengthened nickel-base superalloy are investigated. This superalloy is commercially known as Inconel Alloy MA 753, strengthened both by gamma-prime precipitates and by yttria particles. It is shown that at intermediate temperatures, say below 1500 F, where elastic modulus is weakly dependent on temperature, the modulus correction term to creep activation energy is small. Accordingly, modulus corrections are insignificant for the superalloy considered, which shows high apparent creep activation energies at this temperature. On the contrary, at very high temperatures, the elastic modulus correction term can be significant, thus reducing the creep activation energy to that of vacancy self-diffusion. In order to obtain high-temperature creep resistance, a high-value elastic modulus with a weak dependence on temperature is required.

  6. Void swelling of an oxide dispersion strengthened ferritic alloy in a high voltage electron microscope

    NASA Astrophysics Data System (ADS)

    Snykers, M.

    1980-03-01

    An oxide dispersion strengthened ferritic alloy with nominal composition Fe-13Cr-3.5Ti-1.5Mo-2TiO 2 and a cast alloy with a composition close to that of the matrix of the oxide dispersion strengthened alloy are irradiated in a high voltage electron microscope in the temperature range 380-550°C. The alloys are doped with 0-30 ppm helium. For alloys containing 10 ppm He a peak swelling temperature at 450°C is found. A maximum swelling of 1.1% is found at an irradiation dose of 20 dpa. In the absence of He no swelling is found in the temperature range 430-470°C. The swelling rate is highest at the onset of swelling. The results obtained here are quite similar to those for some ferritic steels such as FV607, EM 12 and HT9, except for the influence of He and for the dose dependence.

  7. Alloying design of oxide dispersion strengthened ferritic steel for long life FBRs core materials

    NASA Astrophysics Data System (ADS)

    Ukai, S.; Harada, M.; Okada, H.; Inoue, M.; Nomura, S.; Shikakura, S.; Asabe, K.; Nishida, T.; Fujiwara, M.

    1993-09-01

    Oxide dispersion strengthened (ODS) ferritic steels with excellent swelling resistance and superior high temperature strength are prospective cladding materials for advanced fast breeder reactors. The addition of Ti in 13Cr-3W ODS ferritic steels improved the high temperature strength remarkably by the formation of uniformly distributed ultra-fine oxide particles. ODS ferritic steels have a bamboo-like grain structure and a strong deformation texture. The decrease of creep rupture strength in the bi-axial direction compared to the uni-axial direction is attributed mainly to this unique bamboo grain structure. Nearly equivalent creep rupture strength for both bi-axial and uni-axial direction was successfully attained by introducing the α to γ transformation in ODS martensitic steel.

  8. Structure and mechanical properties of Fe-Ni-Zr oxide-dispersion-strengthened (ODS) alloys

    NASA Astrophysics Data System (ADS)

    Darling, K. A.; Kapoor, M.; Kotan, H.; Hornbuckle, B. C.; Walck, S. D.; Thompson, G. B.; Tschopp, M. A.; Kecskes, L. J.

    2015-12-01

    A series of bulk nanostructured Fe-Ni-Zr oxide-dispersion-strengthened (ODS) alloys were synthesized using high energy mechanical alloying and consolidated using high temperature equal channel angular extrusion. The resultant microstructures are composed of nano/ultrafine or micrometer-sized grains with larger intermetallic precipitates and small Zr oxide clusters (<10 nm diameter, measured and confirmed by atom probe tomography). The ODS alloys possess elevated compression properties, e.g., 1.2 and 2.4 GPa compressive yield stress at room temperature for samples consolidated at 700 °C and 1000 °C, respectively. This work highlights the relationship between processing, microstructure, and properties for this class of ferritic ODS alloys.

  9. Development of oxide dispersion strengthened turbine blade alloy by mechanical alloying

    NASA Technical Reports Server (NTRS)

    Merrick, H. F.; Curwick, L. R. R.; Kim, Y. G.

    1977-01-01

    There were three nickel-base alloys containing up to 18 wt. % of refractory metal examined initially for oxide dispersion strengthening. To provide greater processing freedom, however, a leaner alloy was finally selected. This base alloy, alloy D, contained 0.05C/15Cr / 2Mo/4W/2Ta/4.5Al/2.Ti/015Zr/0.01-B/Bal. Ni. Following alloy selection, the effect of extrusion, heat treatment, and oxide volume fraction and size on microstructure and properties were examined. The optimum structure was achieved in zone annealed alloy D which contained 2.5 vol. % of 35 mm Y2O3 and which was extruded 16:1 at 1038 C.

  10. Advanced characterizations of austenitic oxide dispersion-strengthened (ODS) steels for high-temperature reactor applications

    NASA Astrophysics Data System (ADS)

    Miao, Yinbin

    Future advanced nuclear systems involve higher operation temperatures, intenser neutron flux, and more aggressive coolants, calling for structural materials with excellent performances in multiple aspects. Embedded with densely and dispersedly distributed oxide nanoparticles that are capable of not only pinning dislocations but also trapping radiation-induced defects, oxide dispersion-strengthened (ODS) steels provide excellence in mechanical strength, creep resistance, and radiation tolerance. In order to develop ODS steels with qualifications required by advanced nuclear applications, it is important to understand the fundamental mechanisms of the enhancement of ODS steels in mechanical properties. In this dissertation, a series of austenitic ODS stainless steels were investigated by coordinated state-of-the-art techniques. A series of different precipitate phases, including multiple Y-Ti-O, Y-Al-O, and Y-Ti-Hf-O complex oxides, were observed to form during mechanical alloying. Small precipitates are likely to have coherent or cubic-on-cubic orientation relationships with the matrix, allowing the dislocation to shear through. The Orowan looping mechanism is the dominant particle-dislocation interaction mode as the temperature is low, whereas the shearing mechanism and the Hirsch mechanism are also observed. Interactions between the particles and the dislocations result in the load-partitioning phenomenon. Smaller particles were found to have the stronger loading-partitioning effect. More importantly, the load-partitioning of large size particles are marginal at elevated temperatures, while the small size particles remain sustaining higher load, explaining the excellent high temperature mechanical performance of ODS steels.

  11. High resolution Transmission Electron Microscopy characterization of a milled oxide dispersion strengthened steel powder

    NASA Astrophysics Data System (ADS)

    Loyer-Prost, M.; Merot, J.-S.; Ribis, J.; Le Bouar, Y.; Chaffron, L.; Legendre, F.

    2016-10-01

    Oxide Dispersion Strengthened (ODS) steels are promising materials for generation IV fuel claddings as their dense nano-oxide dispersion provides good creep and irradiation resistance. Even if they have been studied for years, the formation mechanism of these nano-oxides is still unclear. Here we report for the first time a High Resolution Transmission Electron Microscopy and Energy Filtered Transmission Electron Microscopy characterization of an ODS milled powder. It provides clear evidence of the presence of small crystalline nanoclusters (NCs) enriched in titanium directly after milling. Small NCs (<5 nm) have a crystalline structure and seem partly coherent with the matrix. They have an interplanar spacing close to the (011) bcc iron structure. They coexist with larger crystalline spherical precipitates of 15-20 nm in size. Their crystalline structure may be metastable as they are not consistent with any Y-Ti-O or Ti-O structure. Such detailed observations in the as-milled grain powder confirm a mechanism of Y, Ti, O dissolution in the ferritic matrix followed by a NC precipitation during the mechanical alloying process of ODS materials.

  12. Processing-Microstructure Relationships in Friction Stir Welding of MA956 Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Baker, Bradford W.; Menon, E. Sarath K.; McNelley, Terry R.; Brewer, Luke N.; El-Dasher, Bassem; Farmer, Joseph C.; Torres, Sharon G.; Mahoney, Murray W.; Sanderson, Samuel

    2014-12-01

    A comprehensive set of processing-microstructure relationships is presented for friction stir welded oxide dispersion strengthened MA956 steel. Eight rotational speed/traverse speed combinations were used to produce friction stir welds on MA956 plates using a polycrystalline cubic boron nitride tool. Weld conditions with high thermal input produced defect-free, full-penetration welds. Electron backscatter diffraction results showed a significant increase in grain size, a persistent body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone sensitive to weld parameters. Micro-indentation showed an asymmetric reduction in hardness across a transverse section of the weld. This gradient in hardness was greatly increased with higher heat inputs. The decrease in hardness after welding correlates directly with the increase in grain size and may be explained with a Hall-Petch type relationship.

  13. Effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion strengthened steel

    NASA Astrophysics Data System (ADS)

    Gwon, Jin-Han; Kim, Jeoung-Han; Lee, Kee-Ahn

    2015-04-01

    The effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion-strengthened (ODS) steel were examined. Cryomilling was newly tried on this ODS steel to control oxides, grains, and dislocation microstructures. Fe-14Cr-3W-0.4Ti (wt.%) alloy powder and 0.3 wt.%Y2O3 powder were mixed and were mechanically alloyed (MA) through ball milling at each of room temperature (RT) and -150 °C and then hot isostatic pressing (HIP), hot rolling, and annealing processes were implemented to manufacture two types of ODS ferritic steel, K1 (RT) and K4 (-150 °C). Oxide particles were shown to be finer and more uniformly distributed in K4 (5-10 nm size distribution) than in K1 (average size 30 nm). The two alloys were subjected to high temperature compression (RT ∼ 900 °C) tests. K4 represented higher yield strength under all temperature conditions. However, K4 showed rapid strength decreases at high temperatures exceeding 700 °C and showed similar levels of strengths to K1 at 900 °C. This is considered attributable to the fact that although cryomilling increased the number density of oxide particles, it simultaneously reduced grain sizes too much, so that grain boundary weakening at high temperatures could not be sufficiently prevented.

  14. Microstructure and Mechanical Property of 12Cr Oxide Dispersion Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Xu, Haijian; Lu, Zheng; Jia, Chunyan; Gao, Hao; Liu, Chunming

    2016-03-01

    Nanostructured oxide dispersion strengthened (ODS) steels with nominal compositions (wt%): Fe-12Cr-2W-0.3Ti-0.3Y2O3 were produced by mechanical alloying and hot isostatic pressing. The microstructure was characterized by means of electron microscopy (EBSD, TEM and HRTEM) and the hardness and the tensile properties at different temperatures were measured. The results showed that the ultimate tensile strength of the fabricated 12Cr-ODS steel reached nearly 1,100 MPa at room temperature and maintained around 340 MPa at 700°C. Nano-oxide particles with size ranging from several nm to 30 nm and the number density was 3.6 × 1020/m3 were observed by TEM. Following heat treatment, including normalizing at 1,100°C for 1 h and tempering at 750°C for 2 h, the average grain size was a little decreased. The number of nano-oxide particles increased and the number density was 8.9 × 1020/m3. Specimens showed much higher ductility and there was a slight increase of ultimate tensile strength and Vickers hardness at the same time.

  15. Alternative Fabrication Routes toward Oxide-Dispersion-Strengthened Steels and Model Alloys

    NASA Astrophysics Data System (ADS)

    Bergner, Frank; Hilger, Isabell; Virta, Jouko; Lagerbom, Juha; Gerbeth, Gunter; Connolly, Sarah; Hong, Zuliang; Grant, Patrick S.; Weissgärber, Thomas

    2016-07-01

    The standard powder metallurgy (PM) route for the fabrication of oxide-dispersion-strengthened (ODS) steels involves gas atomization to produce a prealloyed powder, mechanical alloying (MA) with fine oxide powders, consolidation, and finally thermal/thermomechanical treatment (TMT). It is well established that ODS steels with superior property combinations, for example, creep and tensile strength, can be produced by this PM/MA route. However, the fabrication process is complex and expensive, and the fitness for scaling up to the industrial scale is limited. At the laboratory scale, production of small amounts of well-controlled model systems continues to be desirable for specific purposes, such as modeling-oriented experiments. Thus, from the laboratory to industrial application, there is growing interest in complementary or alternative fabrication routes for ODS steels and related model systems, which offer a different balance of cost, convenience, properties, and scalability. This article reviews the state of the art in ODS alloy fabrication and identifies promising new routes toward ODS steels. The PM/AM route for the fabrication of ODS steels is also described, as it is the current default process. Hybrid routes that comprise aspects of both the PM route and more radical liquid metal (LM) routes are suggested to be promising approaches for larger volumes and higher throughput of fabricated material. Although similar uniformity and refinement of the critical nanometer-sized oxide particles has not yet been demonstrated, ongoing innovations in the LM route are described, along with recent encouraging preliminary results for both extrinsic nano-oxide additions and intrinsic nano-oxide formation in variants of the LM route. Finally, physicochemical methods such as ion beam synthesis are shown to offer interesting perspectives for the fabrication of model systems. As well as literature sources, examples of progress in the authors' groups are also highlighted.

  16. Alternative Fabrication Routes toward Oxide-Dispersion-Strengthened Steels and Model Alloys

    NASA Astrophysics Data System (ADS)

    Bergner, Frank; Hilger, Isabell; Virta, Jouko; Lagerbom, Juha; Gerbeth, Gunter; Connolly, Sarah; Hong, Zuliang; Grant, Patrick S.; Weissgärber, Thomas

    2016-11-01

    The standard powder metallurgy (PM) route for the fabrication of oxide-dispersion-strengthened (ODS) steels involves gas atomization to produce a prealloyed powder, mechanical alloying (MA) with fine oxide powders, consolidation, and finally thermal/thermomechanical treatment (TMT). It is well established that ODS steels with superior property combinations, for example, creep and tensile strength, can be produced by this PM/MA route. However, the fabrication process is complex and expensive, and the fitness for scaling up to the industrial scale is limited. At the laboratory scale, production of small amounts of well-controlled model systems continues to be desirable for specific purposes, such as modeling-oriented experiments. Thus, from the laboratory to industrial application, there is growing interest in complementary or alternative fabrication routes for ODS steels and related model systems, which offer a different balance of cost, convenience, properties, and scalability. This article reviews the state of the art in ODS alloy fabrication and identifies promising new routes toward ODS steels. The PM/AM route for the fabrication of ODS steels is also described, as it is the current default process. Hybrid routes that comprise aspects of both the PM route and more radical liquid metal (LM) routes are suggested to be promising approaches for larger volumes and higher throughput of fabricated material. Although similar uniformity and refinement of the critical nanometer-sized oxide particles has not yet been demonstrated, ongoing innovations in the LM route are described, along with recent encouraging preliminary results for both extrinsic nano-oxide additions and intrinsic nano-oxide formation in variants of the LM route. Finally, physicochemical methods such as ion beam synthesis are shown to offer interesting perspectives for the fabrication of model systems. As well as literature sources, examples of progress in the authors' groups are also highlighted.

  17. Microstructural evolution and some mechanical properties of nanosized yttrium oxide dispersion strengthened 13Cr steel

    NASA Astrophysics Data System (ADS)

    Tich Nguyen, Van; Phuong Doan, Dinh; BaoTrung Tran, Tran; Duong Luong, Van; Nguyen, Van An; Phan, Anh Tu

    2010-09-01

    Oxide dispersion strengthened (ODS) steels, manufactured by a mechanical alloying method, during the past few years, appear to be promising candidates for structural applications in nuclear power plants. The purpose of this work is to elaborate the manufacturing processes of ODS 13Cr steel with the addition of 1.0 wt% yttrium oxide through the powder metallurgy route using the high energy ball mill. Microstructural analysis by scanning electron microscopy (SEM), x-ray diffraction (XRD) and hardness testing have been used to optimize the technological parameters of milling, hot isostatic pressing and heat-treatment processes. The steel hardness increases with decreasing particle size of 13Cr ODS steel. The best hardness was obtained from more than 70 h of milling in the two tanks planetary ball mill or 30 h of milling in the one tank planetary ball mill and hot isostatic pressing at 1150 °C . The particle size of the steel is less than 100 nm, and the density and hardness are about 7.3 g cm-3 and 490 HB, respectively. Report submitted to the 5th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN, Hanoi, 9-12 November 2010.

  18. Characterization of microstructural and mechanical properties of a reduced activation ferritic oxide dispersion strengthened steel

    NASA Astrophysics Data System (ADS)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.

    2011-09-01

    For specific blanket and divertor applications in future fusion power reactors a replacement of presently considered Reduced Activation Ferritic Martensitic (RAFM) steels as structural material by suitable oxide dispersion strengthened (ODS) ferritic martensitic steels would allow a substantial increase of the operating temperature from ˜823 K to about 923 K. Temperatures above 973 K in the He cooled modular divertor concept necessitate the use of Reduced Activation Ferritic (RAF)-ODS-steels, which are not limited by a phase transition. The development concentrates on the ferritic ODS-steel Fe-13Cr-1W-0.3Ti-0.3Y 2O 3. The microstructures of a mechanically alloyed powder particle are observed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ageing experiments for 1000 h and 3000 h at 1123.5 K and 1223.5 K of compacted Fe-13Cr-1W-0.3Ti-0.3Y 2O 3 were executed. The impact especially on the oxide particles in terms of segregation and decomposition effects were monitored by electron energy loss spectroscopy (EELS). Long term vacuum creep experiments have been performed with rolled Fe-13Cr-1W-0.3Ti-0.3Y 2O 3 at 923.5 K and 1023.5 K, which will be compared to reference alloys.

  19. High gas velocity oxidation and hot corrosion testing of oxide dispersion-strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.; Lowell, C. E.

    1975-01-01

    Several oxide dispersion strengthened (ODS) nickel-base alloys were tested in high velocity gases for cyclic oxidation resistance at temperatures to 1200 C and times to 500 hours and for hot corrosion resistance at 900 C for 200 hours. Nickel-chromium-aluminum ODS alloys were found to have superior resistance to oxidation and hot corrosion when compared to bare and coated nickel-chromium ODS alloys. The best of the alloys tested had compositions of nickel - 15.5 to 16 weight percent chromium with aluminum weight percents between 4.5 and 5.0. All of the nickel-chromium-aluminum ODS materials experienced small weight losses (less than 16 mg/sq cm).

  20. Friction consolidation of oxide dispersion strengthened INCOLOY RTM alloy MA956 powder

    NASA Astrophysics Data System (ADS)

    Catalini, David

    INCOLOYRTM MA956 is a ferritic ODS alloy. It has very good oxidation resistance by virtue of its large chromium and aluminum concentrations and high mechanical strength and creep resistance at elevated temperatures thanks to oxide dispersion strengthening. The conventional processing route utilized to obtain this alloy involves two main multistep stages. The first (or front end) stage of the process consists of a dry, high-energy milling process which mixes very fine Y2O3 particles with elemental alloy powders by Mechanical Alloying (MA) in an attritor. The second (or back end) stage of the process consists of consolidating the mechanically alloyed powder by hot extrusion in vacuum-sealed cans at about 1000°C, or by degassing followed by hot isostatic pressing (HIP). The precipitation of a fine dispersion of yttrium-aluminum-rich oxides (Y-Al-O) during the consolidation is at the origin of the high temperature mechanical strength of this alloy. Three different thermodynamically stable oxides are known to exist for the binary Y2O3:Al 2O3 system: Y4Al2O9, YAlO 3 and Y3Al5O12. All three of them have been observed in this type of alloys when processed by the route described above. Their size ranges from just a few up to hundreds of nm. In this work, the applicability of Friction Consolidation to this ODS alloy was investigated in order to tackle the downsides of the conventional processing route (multisteps and extremely high raw material final cost). For this study, mechanically alloyed INCOLOYRTM MA956 powder was consolidated through Friction Consolidation under three different sets of processing conditions. As a result, three small compacts of low porosity have been achieved with a refined equiaxed ferritic grain structure smaller than 10 microns and the desired oxide dispersion. Two types of mixed Y-Al oxides were observed by different complementary techniques, Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD

  1. Friction stir welding and processing of oxide dispersion strengthened (ODS) alloys

    SciTech Connect

    Ren, Weiju

    2014-11-11

    A method of welding including forming a filler material of a first oxide dispersoid metal, the first oxide dispersoid material having first strengthening particles that compensate for decreases in weld strength of friction stir welded oxide dispersoid metals; positioning the filler material between a first metal structure and a second metal structure each being comprised of at least a second oxide dispersoid metal; and friction welding the filler material, the first metal structure and the second metal structure to provide a weld.

  2. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; Stubbins, James F.

    2015-01-26

    We report comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y2O3, fluorite Y2O3–HfO2 solid solution and pyrochlore (or fluorite) Y2(Ti,Hf)2 - xO7 - x. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Moreover, two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. Our results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation.

  3. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    DOE PAGES

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; et al

    2015-01-26

    We report comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y2O3, fluorite Y2O3–HfO2 solid solution and pyrochlore (or fluorite) Y2(Ti,Hf)2 - xO7 - x. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Moreover, two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and themore » steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. Our results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation.« less

  4. Microstructural development in high volume fraction gamma prime Ni-base oxide-dispersion-strengthened superalloys

    NASA Astrophysics Data System (ADS)

    Kang, S. K.; Benn, R. C.

    1985-07-01

    The mechanical alloying process has successfully combined oxide-dispersion-strengthening with conventional gamma prime precipitation hardening for advanced gas turbine materials. INCONEL* alloy MA 6000, a mechanically alloyed Ni-base superalloy, has the highest temperature capability among commercially available superalloys. Further improvement of the intermediate temperature strength has been pursued by both increasing the gamma prime content up to 80 vol pct and controlling the additions of refractory metals. The microstructural development of these new experimental alloys is reported in this paper, especially for an alloy, nominally identified as Alloy 51, having the composition Ni-9.3 pct Cr-8.5 pct Al-6.6 pct W-3.4 pct Mo-0.15 pct Zr-0.01 pct B-l.l pct Y2O3 (wt pct). Both the primary and the secondary recrystallized microstructures of the alloy were characterized in terms of gamma grain structure, gamma prime precipitate morphology, orientation relationships, dispersoids, carbide/nitride particles, and chemical composition of intermetallic phases. The microstructural stability of the alloy under stress rupture conditions was also investigated in terms of coarsening/coalescence of gamma prime precipitates. Correlation of the microstructural information with the high temperature properties of the alloy is also briefly discussed.

  5. Creep lifetime prediction of oxide-dispersion-strengthened nickel-base superalloys: A micromechanically based approach

    NASA Astrophysics Data System (ADS)

    Heilmaier, M.; Reppich, B.

    1996-12-01

    The high-temperature creep behavior of the oxide-dispersion-strengthened (ODS) nickel-base superalloys MA 754 and MA 6000 has been investigated at temperatures up to 1273 K and lifetimes of approximately 4000 hours using monotonic creep tests at constant true stress σ, as well as true constant extension rate tests (CERTs) atdot \\varepsilon . The derivation of creep rupture-lifetime diagrams is usually performed with conventional engineering parametric methods, according to Sherby and Dorn or Larson and Miller. In contrast, an alternative method is presented that is based on a more microstructural approach. In order to describe creep, the effective stress model takes into account the hardening contribution σ p caused by the presence of second-phase particles, as well as the classical Taylor back-stress σ p caused by dislocations. The modeled strain rate-stress dependence can be transferred directly into creep-rupture stress-lifetime diagrams using a modified Monkman-Grant (MG) relationship, which adequately describes the interrelation betweendot \\varepsilon representing dislocation motion, and lifetime t f representing creep failure. The comparison with measured creep-rupture data proves the validity of the proposed micromechanical concept.

  6. Fracture toughness and fatigue crack growth of oxide dispersion strengthened copper

    SciTech Connect

    Alexander, D.J.; Gieseke, B.G.

    1996-04-01

    The fracture toughness and fatigue crack growth behavior of copper dispersion strengthened with aluminum oxide (0.15 wt % Al) was examined. In the unirradiated condition, the fracture toughness was about 45 kJ/m{sup 2} (73 MPa{radical}m) at room temperature, but decreased significantly to only 3 Kj/m{sup 2} (20 MPa{radical}m), at 250{degrees}C. After irradiation at approximately 250{degrees}C to about 2.5 displacements per atom (dpa), the toughness was very low, about 1 kJ/m{sup 2} (48 MOa{radical}m), and at 250{degrees}C the toughness was very low, about 1kJ/m{sup 2} (12 mPa{radical}m). The fatigue crack growth rate of unirradiated material at room temperature is similiar to other candidate structural alloys such as V-4Cr-4Ti and 316L stainless steel. The fracture properties of this material at higher temperatures and in controlled environments need further investigation, in both irradiated and unirradiated conditions.

  7. The interfacial orientation relationship of oxide nanoparticles in a hafnium-containing oxide dispersion-strengthened austenitic stainless steel

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Cui, Bai; Chen, Wei-Ying; Miller, Michael K.; Powers, Kathy A.; McCreary, Virginia; Gross, David; Almer, Jonathan; Robertson, Ian M.; Stubbins, James F.

    2015-03-15

    This work reports comprehensive investigations on the orientation relationship of the oxide nanoparticles in a hafnium-containing austenitic oxide dispersion-strengthened 316 stainless steel. The phases of the oxide nanoparticles were determined by a combination of scanning transmission electron microscopy–electron dispersive X-ray spectroscopy, atom probe tomography and synchrotron X-ray diffraction to be complex Y–Ti–Hf–O compounds with similar crystal structures, including bixbyite Y{sub 2}O{sub 3}, fluorite Y{sub 2}O{sub 3}–HfO{sub 2} solid solution and pyrochlore (or fluorite) Y{sub 2}(Ti,Hf){sub 2−x}O{sub 7−x}. High resolution transmission electron microscopy was used to characterize the particle–matrix interfaces. Two different coherency relationships along with one axis-parallel relation between the oxide nanoparticles and the steel matrix were found. The size of the nanoparticles significantly influences the orientation relationship. The results provide insight into the relationship of these nanoparticles with the matrix, which has implications for interpreting material properties as well as responses to radiation. - Highlights: • The oxide nanoparticles in a hafnium-containing austenitic ODS were characterized. • The nanoparticles are Y–Hf–Ti–O enriched phases according to APT and STEM–EDS. • Two coherency and an axis-parallel orientation relationships were found by HR-TEM. • Particle size has a prominent effect on the orientation relationship (OR). • Formation mechanism of the oxide nanoparticles was discussed based on the ORs.

  8. ENABLING THE PRACTICAL APPLICATION OF OXIDE DISPERSION-STRENGTHENED FERRITIC STEELS

    SciTech Connect

    Wright, Ian G; Pint, Bruce A; Dyadko, Dr. Eugene G.; Bornstein, Norman S.; Tatlock, Gordon J

    2007-01-01

    Effort has continued to evaluate joints made in oxide dispersion-strengthened (ODS) FeCrAl by (i) pulsed plasma-assisted diffusion (PPAD) bonding, and (ii) transient liquid phase (TLP) bonding. Creep tests of PPAD-bonded butt joints in air at 1000 C, using small, shoulder-loaded, dog bone-shaped specimens and an incrementally-loaded test technique, indicated that failure occurred at loads of up to 82% of that required to fail the parent alloy in the same test. For high creep-strength ferritic steels joined by conventional welding methods, strength reduction factors of 50-80% are considered to be acceptable. The failures apparently did not initiate along the joints; the observed mode of failure of the joined specimens was the same as observed for monolithic specimens of this alloy, by crack-initiated transgranular brittle fracture, followed by ductile overload failure. The progress of TLP bonding has been slower, with the major effort focused on understanding the behavior of the transient liquid phase and its interaction with the alloy microstructure during the various stages of bonding. Creep testing using the same procedures also has been used to evaluate changes resulting from torsional deformation of ODS-FeCrAl tubes in an attempt to modify their microstructures and increase their hoop strength. Interpretation of the results so far has not shown a clear trend, largely due to difficulties in measuring the effective angle of twist in the specimen gauge lengths. Other issues that have been addressed are the refinement of an approach for prediction of the oxidation-limited service lifetime of alumina scale-forming ODS alloys, and alternative routes for ODS alloy powder processing. Analysis of alloy specimens oxidized to failure (in some cases involving exposures for many thousands of hours) over a range of temperatures has provided an improved basis for calculating the values of parameters required in the lifing model (minimum Al content for protective behavior

  9. The influence of gamma prime on the recrystallization of an oxide dispersion strengthened superalloy - MA 6000E

    NASA Technical Reports Server (NTRS)

    Hotzler, R. K.; Glasgow, T. K.

    1982-01-01

    The requirement of large, recrystallized, highly elongated grains is of primary importance to the development of suitable high temperature properties in oxide dispersion strengthened-superalloys. In the present study the recrystallization behavior of MA 6000E, a recently developed Y2O3 strengthened superalloy produced by mechanical alloying, was examined using transmission and replication microscopy. Gradient and isothermal annealing treatments were applied to extruded and hot rolled products. It was found that conversion from a very fine (0.2 micron) grain structure to a coarse (approximately 10 mm) grain structure is controlled by the dissolution of the gamma prime phase, while grain shape was controlled primarily by the thermal gradient. The fine uniform oxide dispersion appeared to have only a secondary influence in determining the grain shape as columnar grains could be grown transverse to the working direction by appropriate application of the thermal gradient.

  10. Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

    SciTech Connect

    Rieken, Joel

    2011-12-13

    Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

  11. Manufacture and engine test of advanced oxide dispersion strengthened alloy turbine vanes. [for space shuttle thermal protection

    NASA Technical Reports Server (NTRS)

    Bailey, P. G.

    1977-01-01

    Oxide-Dispersion-strengthened (ODS) Ni-Cr-Al alloy systems were exploited for turbine engine vanes which would be used for the space shuttle thermal protection system. Available commercial and developmental advanced ODS alloys were evaluated, and three were selected based on established vane property goals and manufacturing criteria. The selected alloys were evaluated in an engine test. Candidate alloys were screened by strength, thermal fatigue resistance, oxidation and sulfidation resistance. The Ni-16Cr (3 to 5)Al-ThO2 system was identified as having attractive high temperature oxidation resistance. Subsequent work also indicated exceptional sulfidation resistance for these alloys.

  12. History of Resistance Welding Oxide Dispersion Strengthened Cladding and other High Temperature Materials at Center for Advanced Energy Studies

    SciTech Connect

    Larry Zirker; Nathan Jerred; Dr. Indrajit Charit; James Cole

    2012-03-01

    Research proposal 08-1079, 'A Comparative Study of Welded ODS Cladding Materials for AFCI/GNEP,' was funded in 2008 under an Advanced Fuel Cycle Initiative (AFCI) Research and Development Funding Opportunity, number DE-PS07-08ID14906. Th proposal sought to conduct research on joining oxide dispersion strengthen (ODS) tubing material to a solid end plug. This document summarizes the scientific and technical progress achieved during the project, which ran from 2008 to 2011.

  13. Mechanically Alloyed-Oxide Dispersion Strengthened Steels for Use in Space Nuclear Power Systems

    NASA Astrophysics Data System (ADS)

    El-Genk, Mohamed S.; Tournier, Jean-Michel

    2004-02-01

    The mechanical and thermo-physical properties of Mechanically Alloyed (MA)-Oxide Dispersion Strengthened (ODS) steels are reviewed and their potential for use in space nuclear reactor power systems is examined. The three MA-ODS alloys examined are Inconel MA-ODS754 (77.55Ni, 20Cr, 1Fe, 0.5Ti, 0.3Al, 0.05C, and 0.6Y2O3), Incoloy MA-ODS956 (74.45Fe, 20Cr, 4.5Al, 0.5Ti, 0.05C, 0.5Y2O3), and Incoloy MA-ODS957 (84.55Fe, 14Cr, 0.3Mo, 0.9Ti, 0.25Y2O3). The major advantages of these alloys are: (a) their strength at high temperatures (>1000 K) is relatively higher and decreases slower with temperature than niobium (Nb) and molybdenum (Mo) refractory alloys; (b) they are relatively lightweight and less expensive; (c) they have been shown to experience low swelling and embrittlement with exposure to high-energy neutrons (> 0.1 MeV) up to a fluence of 1023 n/cm2; and (d) their high resistance to oxidation and nitration at high temperatures, which simplifies handling and assembly. These MS-ODS alloys are also lighter and much stronger than 316-stainless steel and super-alloys such as Inconel 601, Haynes 25, and Hastalloy-X at moderately high temperatures (688-1000 K). The little data available on the compatibility of the MA-ODS alloys with alkali liquid metals up to 1100 K are encouraging, however, additional tests at typical operation temperatures (1000-1400 K) in liquid metal cooled and alkali metal heat pipe-cooled space nuclear reactors are needed. The anisotropy of the MA-ODS alloys when cold worked, and in particularly when rolled into tubes, should not hinder their use in space nuclear power systems, in which the operation pressure is either near atmospheric or as high as 2 MPa.

  14. Mechanically Alloyed-Oxide Dispersion Strengthened Steels for Use in Space Nuclear Power Systems

    SciTech Connect

    El-Genk, Mohamed S.; Tournier, Jean-Michel

    2004-02-04

    The mechanical and thermo-physical properties of Mechanically Alloyed (MA)-Oxide Dispersion Strengthened (ODS) steels are reviewed and their potential for use in space nuclear reactor power systems is examined. The three MA-ODS alloys examined are Inconel MA-ODS754 (77.55Ni, 20Cr, 1Fe, 0.5Ti, 0.3Al, 0.05C, and 0.6Y2O3), Incoloy MA-ODS956 (74.45Fe, 20Cr, 4.5Al, 0.5Ti, 0.05C, 0.5Y2O3), and Incoloy MA-ODS957 (84.55Fe, 14Cr, 0.3Mo, 0.9Ti, 0.25Y2O3). The major advantages of these alloys are: (a) their strength at high temperatures (>1000 K) is relatively higher and decreases slower with temperature than niobium (Nb) and molybdenum (Mo) refractory alloys; (b) they are relatively lightweight and less expensive; (c) they have been shown to experience low swelling and embrittlement with exposure to high-energy neutrons (> 0.1 MeV) up to a fluence of 1023 n/cm2; and (d) their high resistance to oxidation and nitration at high temperatures, which simplifies handling and assembly. These MS-ODS alloys are also lighter and much stronger than 316-stainless steel and super-alloys such as Inconel 601, Haynes 25, and Hastalloy-X at moderately high temperatures (688-1000 K). The little data available on the compatibility of the MA-ODS alloys with alkali liquid metals up to 1100 K are encouraging, however, additional tests at typical operation temperatures (1000-1400 K) in liquid metal cooled and alkali metal heat pipe-cooled space nuclear reactors are needed. The anisotropy of the MA-ODS alloys when cold worked, and in particularly when rolled into tubes, should not hinder their use in space nuclear power systems, in which the operation pressure is either near atmospheric or as high as 2 MPa.

  15. Final Technical Report - High-Performance, Oxide-Dispersion-Strengthened Tubes for Production of Ethylene adn Other Industrial Chemicals

    SciTech Connect

    McKimpson, Marvin G.

    2006-04-06

    This project was undertaken by Michigan Technological University and Special Metals Corporation to develop creep-resistant, coking-resistant oxide-dispersion-strengthened (ODS) tubes for use in industrial-scale ethylene pyrolysis and steam methane reforming operations. Ethylene pyrolysis tubes are exposed to some of the most severe service conditions for metallic materials found anywhere in the chemical process industries, including elevated temperatures, oxidizing atmospheres and high carbon potentials. During service, hard deposits of carbon (coke) build up on the inner wall of the tube, reducing heat transfer and restricting the flow of the hydrocarbon feedstocks. About every 20 to 60 days, the reactor must be taken off-line and decoked by burning out the accumulated carbon. This decoking costs on the order of $9 million per year per ethylene plant, accelerates tube degradation, and requires that tubes be replaced about every 5 years. The technology developed under this program seeks to reduce the energy and economic cost of coking by creating novel bimetallic tubes offering a combination of improved coking resistance, creep resistance and fabricability not available in current single-alloy tubes. The inner core of this tube consists of Incoloy(R) MA956, a commercial ferritic Fe-Cr-Al alloy offering a 50% reduction in coke buildup combined with improved carburization resistance. The outer sheath consists of a new material - oxide dispersion strengthened (ODS) Alloy 803(R) developed under the program. This new alloy retains the good fireside environmental resistance of Alloy 803, a commercial wrought alloy currently used for ethylene production, and provides an austenitic casing to alleviate the inherently-limited fabricability of the ferritic Incoloy(R) MA956 core. To provide mechanical compatibility between the two alloys and maximize creep resistance of the bimetallic tube, both the inner Incoloy(R) MA956 and the outer ODS Alloy 803 are oxide dispersion

  16. Innovative Powder Processing of Oxide Dispersion Strengthened ODS Ferritic Stainless Steels

    SciTech Connect

    Rieken, Joel; Anderson, Iver; Kramer, Matthew

    2011-04-01

    An innovative gas atomization reaction synthesis technique was employed as a viable method to dramatically lower the processing cost for precursor oxide dispersion forming ferritic stainless steel powders (i.e., Fe-Cr-(Hf,Ti)-Y). During this rapid solidification process the atomized powders were enveloped by a nano-metric Cr-enriched metastable oxide film. Elevated temperature heat treatment was used to dissociate this metastable oxide phase through oxygen exchange reactions with Y-(Hf,Ti) enriched intermetallic compound precipitates. These solid state reactions resulted in the formation of highly stable nano-metric mixed oxide dispersoids (i.e., Y-Ti-O or Y-Hf-O) throughout the alloy microstructure. Subsequent high temperature (1200 C) heat treatments were used to elucidate the thermal stability of each nano-metric oxide dispersoid phase. Transmission electron microscopy coupled with X-ray diffraction was used to evaluate phase evolution within the alloy microstructure.

  17. Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation

    SciTech Connect

    Catalini, David; Kaoumi, Djamel; Reynolds, Anthony; Grant, Glenn J.

    2015-07-09

    INCOLOY® MA956 is a ferritic Oxide Dispersion Strengthened (ODS) alloy. Three different oxides, Y4Al2O9, YAlO3 and Y3Al5O12, have been observed in this alloy. The oxide particle sizes range from just a few up to hundreds of nm and these particles are responsible of the high temperature mechanical strength of this alloy. Mechanically alloyed MA956 powder was consolidated via Friction Consolidation using three different processing conditions. As a result, three small compacts of low porosity were produced. The compacts exhibited a refined equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion.YAlO3 and Y3Al5O12 were identified in the compacts by Scanning Electron Microscopy (SEM), Electron Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of Y3Al5O12 precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS showing an aluminum enrichment trend as precipitates grow in size.

  18. Effects of aluminum additions to gas atomized reaction synthesis produced oxide dispersion strengthened alloys

    NASA Astrophysics Data System (ADS)

    Spicher, Alexander Lee

    The production of an aluminum containing ferritic oxide dispersion strengthened (ODS) alloy was investigated. The production method used in this study was gas atomization reaction synthesis (GARS). GARS was chosen over the previously commercial method of mechanical alloying (MA) process due to complications from this process. The alloy compositions was determined from three main components; corrosion resistance, dispersoid formation, and additional elements. A combination of Cr and Al were necessary in order to create a protective oxide in the steam atmosphere that the boiler tubing in the next generation of coal-fired power plants would be exposed to. Hf and Y were chosen as dispersoid forming elements due to their increased thermal stability and potential to avoid decreased strength caused by additions of Al to traditional ODS materials. W was used as an additive due to benefits as a strengthener as well as its benefits for creep rupture time. The final composition chosen for the alloy was Fe-16Cr-12Al-0.9W-0.25Hf-0.2Y at%. The aforementioned alloy, GA-1-198, was created through gas atomization with atomization gas of Ar-300ppm O2. The actual composition created was found to be Fe-15Cr-12.3Al-0.9W-0.24Hf-0.19Y at%. An additional alloy that was nominally the same without the inclusion of aluminum was created as a comparison for the effects on mechanical and corrosion properties. The actual composition of the comparison alloy, GA-1-204, was Fe-16Cr-0Al-0.9W-0.25Hf-0.24Y at%. An investigation on the processing parameters for these alloys was conducted on the GA-1-198 alloy. In order to predict the necessary amount of time for heat treatment, a diffusion study was used to find the diffusion rate of oxygen in cast alloys with similar composition. The diffusion rate was found to be similar to that of other GARS compositions that have been created without the inclusion of aluminum. The effect of heat treatment time was investigated with temperatures of 950°C, 1000

  19. Oxide Dispersion Strengthened Fe(sub 3)Al-Based Alloy Tubes: Application Specific Development for the Power Generation Industry

    SciTech Connect

    Kad, B.K.

    1999-07-01

    A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe3Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100C in the power generation industry. A particular 'in service application' anomaly of Fe3Al-based alloys is that the environmental resistance is maintained up to 1200C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism.

  20. Dispersoid Distribution and Microstructure in Fe-Cr-Al Ferritic Oxide Dispersion-Strengthened Alloy Prepared by Friction Consolidation

    NASA Astrophysics Data System (ADS)

    Catalini, David; Kaoumi, Djamel; Reynolds, Anthony P.; Grant, Glenn J.

    2015-10-01

    INCOLOY® MA956 is a ferritic oxide dispersion-strengthened alloy manufactured by mechanical alloying followed by hot extrusion in vacuum-sealed cans or by degassing and hot isostatic pressing. This could be followed by a tailored heat treatment sequence in order to obtain a desired microstructure and to allow the oxide dispersion to precipitate. Three different oxides, responsible for the high-temperature mechanical strength, have been observed in this alloy: Y4Al2O9, YAlO3, and Y3Al5O12. Their sizes range from just a few to hundreds of nanometers. In this work, mechanically alloyed MA956 powder was consolidated via friction consolidation, a single-step and potentially cheaper processing alternative. Three fully dense compacts were produced. The compacts exhibited a refined, equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion. YAlO3 and Y3Al5O12 were identified by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction. The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of Y3Al5O12 precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS, showing an aluminum enrichment trend as precipitates grew in size.

  1. High-temperature deformation mechanisms and constitutive equations for the oxide dispersion-strengthened superalloy MA 956

    NASA Astrophysics Data System (ADS)

    Haghi, M.; Anand, L.

    1990-01-01

    An experimental study of the constitutive response of the oxide dispersion-strengthened (ODS) superalloy MA 956, which consists of an Fe-Cr-Al matrix dispersion strengthened with yttria, has been performed. Single-crystal specimens of MA 956 having remarkably simple initial microstructures have been tested in compression in the temperature range of 900 °C to 1200 °C and in the axial strain-rate range of 1.8 x 10-4 s-1 to 10-2 s-1. The deformation response of the material has been examined by performing constant true strain-rate tests, strain-rate jump tests, and stress relaxation tests. The orientation dependence of the stress-strain response of the single crystals has been compensated for by determining the operative slip systems and resolving the stresses and strains accordingly. These experiments, together with electron-microscopic observations of deformed and quenched specimens, allow a number of conclusions to be drawn about the physics of particle strengthening in this simple ODS alloy at high temperatures. Further, drawing on this physical understanding, a set of phenomenological internal variable constitutive equations which model the high-temperature deformation behavior of this alloy is also developed. These equations reasonably well model not only the temperature and strain-rate sensitivity of the flow stress but also the strain-hardening behavior of the material.

  2. Microstructure, strengthening mechanisms and hot deformation behavior of an oxide-dispersion strengthened UFG Al6063 alloy

    SciTech Connect

    Asgharzadeh, H.; Kim, H.S.; Simchi, A.

    2013-01-15

    An ultrafine-grained Al6063/Al{sub 2}O{sub 3} (0.8 vol.%, 25 nm) nanocomposite was prepared via powder metallurgy route through reactive mechanical alloying and hot powder extrusion. Scanning electron microcopy, transmission electron microscopy, and back scattered electron diffraction analysis showed that the grain structure of the nanocomposite is trimodal and composed of nano-size grains (< 0.1 {mu}m), ultrafine grains (0.1-1 {mu}m), and micron-size grains (> 1 {mu}m) with random orientations. Evaluation of the mechanical properties of the nanocomposite based on the strengthening-mechanism models revealed that the yield strength of the ultrafine-grained nanocomposite is mainly controlled by the high-angle grain boundaries rather than nanometric alumina particles. Hot deformation behavior of the material at different temperatures and strain rates was studied by compression test and compared to coarse-grained Al6063 alloy. The activation energy of the hot deformation process for the nanocomposite was determined to be 291 kJ mol{sup -1}, which is about 64% higher than that of the coarse-grained alloy. Detailed microstructural analysis revealed that dynamic recrystallization is responsible for the observed deformation softening in the ultrafine-grained nanocomposite. - Highlights: Black-Right-Pointing-Pointer The strengthening mechanisms of Al6063/Al{sub 2}O{sub 3} nanocomposite were evaluated. Black-Right-Pointing-Pointer Hot deformation behavior of the nanocomposite was studied. Black-Right-Pointing-Pointer The hot deformation activation energy was determined using consecutive models. Black-Right-Pointing-Pointer The restoration mechanisms and microstructural changes are presented.

  3. Effect of prior creep at 1365 K on the room temperature tensile properties of several oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    An experimental study was conducted to determine whether oxide dispersion-strengthened (ODS) Ni-base alloys in wrought bar form are subject to creep degradation effects similar to those found in thin-gage sheet. The bar products evaluated included ODS-Ni, ODS-NiCr, and advanced ODS-NiCrAl types; the alloys included microstructures ranging from an essentially perfect single crystal to a structure consisting of very small elongated grains. Tensile test specimens were exposed to creep at various stress levels at 1365 K and then tensile tested at room temperature. Low residual tensile properties, change in fracture mode, appearance of dispersoid free bands, grain boundary cavitation, and/or internal oxidation are interpreted as creep degradation effects. The amount of degradation depends on creep strain, and degradation appears to be due to diffusional creep which produces dispersoid free bands around grain boundaries acting as vacancy sources.

  4. Elevated Temperature Compressive Strength Properties of Oxide Dispersion Strengthened NiAl After Cryo-milling and Roasting in Nitrogen

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Grahle, Peter; Arzt, Eduard; Hebsur, Mohan

    1998-01-01

    In an effort to superimpose two different elevated temperature strengthening mechanisms in NiAl, several lots of oxide dispersion strengthened (ODS) NiAl powder have been cryo-milled in liquid nitrogen to introduce AlN particles at the grain boundaries. As an alternative to cryo-milling, one lot of ODS NiAl was roasted in nitrogen to produce AlN. Both techniques resulted in hot extruded AlN-strengthened, ODS NiAl alloys which were stronger than the base ODS NiAl between 1200 and 1400 K. However, neither the cryo-milled nor the N2-roasted ODS NiAl alloys were as strong as cryo-milled binary NiAl containing like amounts of AlN. The reason(s) for the relative weakness of cryo-milled ODS NiAl is not certain; however the lack of superior strength in N2-roasted ODS NiAl is probably due to its relatively large AlN particles.

  5. Effect of simulated Earth reentry exposure on mechanical properties of several oxide dispersion strengthened and superalloy sheet materials

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    The effects of simulated multiple reentry into the earth's atmosphere on the mechanical properties of several high temperature metallic sheet materials were evaluated. The materials included five tin-gage (nominally 0.025- or 0.037-cm) oxide dispersion strengthened (ODS) alloys and two thin-gage (nominally 0.037-cm) superalloys. Multiple reentry conditions were simulated through cyclic Plasma Arc Tunnel (PAT) exposure. PAT exposure generally consisted of 100 cycles of 600 second duration at 1255, 1366, or 1477 K in a Mach 4.6 airstream with an impact pressure of nominally 800 N/m2. PAT exposure generally produced a uniform oxide scale, oxide pits or intergranular oxidation, Kirkendall porosity, and alloy depletion zones except for the aluminum-containing ODS alloys. Only a uniform oxide scale was formed on the aluminum-containing ODS alloys. PAT exposure did not significantly affect the mechanical properties of the thin-gage (nominally 0.025- or 0.037-cm) alloys evaluated. Thus it appears that the microstructural changes produced by Plasma Arc Tunnel exposure has little influence on mechanical properties.

  6. Fabrication technological development of the oxide dispersion strengthened alloy MA957 for fast reactor applications

    SciTech Connect

    ML Hamilton; DS Gelles; RJ Lobsinger; GD Johnson; WF Brown; MM Paxton; RJ Puigh; CR Eiholzer; C Martinez; MA Blotter

    2000-03-27

    A significant amount of effort has been devoted to determining the properties and understanding the behavior of the alloy MA957 to define its potential usefulness as a cladding material, in the fast breeder reactor program. The numerous characterization and fabrication studies that were conducted are documented in this report. The alloy is a ferritic stainless steel developed by International Nickel Company specifically for structural reactor applications. It is strengthened by a very fine, uniformly distributed yttria dispersoid. Its fabrication involves a mechanical alloying process and subsequent extrusion, which ultimately results in a highly elongated grain structure. While the presence of the dispersoid produces a material with excellent strength, the body centered cubic structure inherent to the material coupled with the high aspect ratio that results from processing operations produces some difficulties with ductility. The alloy is very sensitive to variations in a number of processing parameters, and if the high strength is once lost during fabrication, it cannot be recovered. The microstructural evolution of the alloy under irradiation falls into two regimes. Below about 550 C, dislocation development, {alpha}{prime} precipitation and void evolution in the matrix are observed, while above about 550 C damage appears to be restricted to cavity formation within oxide particles. The thermal expansion of the alloy is very similar to that of HT9 up to the temperature where HT9 undergoes a phase transition to austenitic. Pulse magnetic welding of end caps onto MA957 tubing can be accomplished in a manner similar to that in which it is performed on HT9, although the welding parameters appear to be very sensitive to variations in the tubing that result from small changes in fabrication conditions. The tensile and stress rupture behavior of the alloy are acceptable in the unirradiated condition, being comparable to HT9 below about 700 C and exceeding those of HT9

  7. Summary of Prior Work on Joining of Oxide Dispersion-Strengthened Alloys

    SciTech Connect

    Wright, Ian G; Tatlock, Gordon J; Badairy, H.; Chen, C-L.

    2009-08-01

    There is a range of joining techniques available for use with ODS alloys, but care should be exercised in matching the technique to the final duty requirements of the joint. The goal for joining ODS alloys is a joint with no local disruption of the distribution of the oxide dispersion, and no significant change in the size and orientation of the alloy microstructure. Not surprisingly, the fusion welding processes typically employed with wrought alloys produce the least satisfactory results with ODS alloys, but some versions, such as fusion spot welding, and the laser and electron-beam welding technologies, have demonstrated potential for producing sound joints. Welds made using solid-state spot welding reportedly have exhibited parent metal properties. Thus, it is possible to employ processes that result in significant disruption of the alloy microstructure, as long as the processing parameters are adjustment to minimize the extent of or influence of the changes in the alloy microstructure. Selection among these joining approaches largely depends on the particular application and component configuration, and an understanding of the relationships among processing, alloy microstructure, and final properties is key. Recent developments have resulted in friction welding evolving to be a prime method for joining ODS sheet products, and variants of brazing/diffusion bonding have shown excellent promise for use with tubes and pipes. The techniques that come closest to the goal defined above involve solid-state diffusion bonding and, in particular, it has been found that secondary recrystallization of joints made by pulsed plasma-assisted diffusion can produce the desired, continuous, large alloy grain structure through the joint. Such joints have exhibited creep rupture failure at >82% of the load needed to fail the monolithic parent alloy at 1000 C.

  8. Elevated temperature compressive steady state deformation and failure in the oxide dispersion strengthened alloy MA 6000E

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1984-01-01

    The compressive flow strength-strain rate behavior of the oxide-dispersion-strengthened alloy MA 6000E has been studied in the temperature range 1144-1366 K, with strain rates ranging from 2.1 x 10 to the -5th to 2.1 x 10 to the -7th per s. It is found that the inherent strength of the alloy is essentially the same in all test directions and that the low strength observed in tensile tests results from the inability of grain boundaries to support high tensile stresses. The failure of MA 6000E under high-temperature, slow plastic flow conditions is shown to be the result of concentrated slip. Slow plastic deformation in MA 6000E can be described by a threshold stress model of creep where threshold stresses are calculated from relatively fast testing procedures and the effective stress exponent for creep is assumed to be 3.5.

  9. Stability of nanoclusters in 14YWT oxide dispersion strengthened steel under heavy ion-irradiation by atom probe tomography

    SciTech Connect

    Jianchao He; Farong Wan; Kumar Sridharan; Todd R. Allen; A. Certain; V. Shutthanandan; Y.Q. Wu

    2014-12-01

    14YWT oxide dispersion strengthened (ODS) ferritic steel was irradiated with of 5 MeV Ni2+ ions, at 300 C, 450 C, and 600 C to a damage level of 100 dpa. The stability of Ti–Y–O nanoclusters was investigated by applying atom probe tomography (APT) in voltage mode, of the samples before and after irradiations. The average size and number density of the nanoclusters was determined using the maximum separation method. These techniques allowed for the imaging of nanoclusters to sizes well below the resolution limit of conventional transmission electron microscopy techniques. The most significant changes were observed for samples irradiated at 300 C where the size (average Guinier radius) and number density of nanoclusters were observed to decrease from 1.1 nm to 0.8 nm and 12 1023 to 3.6 1023, respectively. In this study, the nanoclusters are more stable at higher temperature.

  10. Characterization of Residual Stress as a Function of Friction Stir Welding Parameters in Oxide Dispersion Strengthened (ODS) Steel MA956

    SciTech Connect

    Brewer, Luke N.; Bennett, Martin S.; Baker, B. W.; Payzant, E. Andrew; Kolbus, Lindsay M.

    2015-09-08

    This article characterizes the residual stresses generated by friction stir welding of oxide dispersion strengthened steel MA956 over a series of welding conditions. A plate of MA956 steel was friction stir welded at three conditions: 500 rpm/25 millimeters per minute (mmpm), 400 rpm/50 mmpm and 400 rpm/100 mmpm. The residual stresses across these welds were measured using both x-ray and neutron diffraction techniques. Longitudinal residual stresses up to eighty percent of the yield strength were observed for the 400 rpm/100 mmpm condition. Increasing the traverse rate while holding the rotational speed fixed increased the residual stress levels in the stir zone and at the stir zone-thermomechanically affected zone interface. The stress profiles displayed the characteristic M shape, and the asymmetry between advancing and retreating stress peaks was limited, occurring mainly on the root side of the weld. The large magnitude of the stresses was maintained throughout the thickness of the plates.

  11. End Closure Joining of Ferritic-Martensitic and Oxide-Dispersion Strengthened Steel Cladding Tubes by Magnetic Pulse Welding

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Gu; Park, Jin-Ju; Lee, Min-Ku; Rhee, Chang-Kyu; Kim, Tae-Kyu; Spirin, Alexey; Krutikov, Vasiliy; Paranin, Sergey

    2015-07-01

    The magnetic pulse welding (MPW) technique was employed for the end closure joining of fuel pin cladding tubes made of ferritic-martensitic (FM) steel and oxide-dispersion strengthened (ODS) steel. The technique is a solid-state impact joining process based on the electromagnetic force, similar to explosive welding. For a given set of optimal process parameters, e.g., the end-plug geometry, the rigid metallurgical bonding between the tube and end plug was obtained by high-velocity impact collision accompanied with surface jetting. The joint region showed a typical wavy morphology with a narrow grain boundary-like bonding interface. There was no evidence of even local melting, and only the limited grain refinement was observed in the vicinity of the bonding interface without destructing the original reinforcement microstructure of the FM-ODS steel, i.e., a fine grain structure with oxide dispersion. No leaks were detected during helium leakage test, and moreover, the rupture occurred in the cladding tube section without leaving any joint damage during internal pressure burst test. All of the results proved the integrity and durability of the MPWed joints and signified the great potential of this method of end closure joining for advanced fast reactor fuel pin fabrication.

  12. Recrystallization Process in Fe-Cr-Al Oxide Dispersion-Strengthened Alloy: Microstructural Evolution and Recrystallization Mechanism

    NASA Astrophysics Data System (ADS)

    Pimentel, G.; Chao, J.; Capdevila, C.

    2014-05-01

    Mechanically alloyed iron-base oxide dispersion-strengthened (ODS) alloys are the class of advanced materials for application in heat exchangers tubing in which creep and oxidation resistance are paramount. The yttria dispersion in such alloys improves the high-temperature creep and stress rupture life. The strength is further enhanced by the development of a coarse-grained microstructure during recrystallization. Factors controlling the evolution of this desirable microstructure are explored in this work, focusing specifically on PM 2000. The results presented in terms of orientation imaging, transmission electron microscopy, and scanning electron microscopy indicate that the recrystallization process consists of two different stages. Before the coarse grain takes place, the alloy undergoes an extended recovery process followed by abnormal grain growth. The initial microstructure consisted of subgrains (submicrometer sizes) with a strong <110>∥RD fiber texture ( α fiber), which are transformed into coarse grains (mm sizes) with orientations <112>∥RD. The aim of this study is to describe the mechanisms involved in the intermediate stages of recrystallization process from the submicrometer grain size to the abnormal grain size.

  13. Nanocavity formation and hardness increase by dual ion beam irradiation of oxide dispersion strengthened FeCrAl alloy

    NASA Astrophysics Data System (ADS)

    Kögler, R.; Anwand, W.; Richter, A.; Butterling, M.; Ou, Xin; Wagner, A.; Chen, C.-L.

    2012-08-01

    Open volume defects generated by ion implantation into oxide dispersion strengthened (ODS) alloy and the related hardness were investigated by positron annihilation spectroscopy and nanoindentation measurements, respectively. Synchronized dual beam implantation of Fe and He ions was performed at room temperature and at moderately enhanced temperature of 300 °C. For room temperature implantation a significant hardness increase after irradiation is observed which is more distinctive in heat treated than in as-received ODS alloy. There is also a difference between the simultaneous and sequential implantation mode as the hardening effect for the simultaneously implanted ODS alloy is stronger than for sequential implantation. The comparison of hardness profiles and of the corresponding open volume profiles shows a qualitative agreement between the open volume defects generated on the nanoscopic scale and the macroscopic hardness characteristics. Open volume defects are drastically reduced for performing the simultaneous dual beam irradiation at 300 °C which is a more realistic temperature under application aspects. Few remaining defects are clusters of 3-4 vacancies in connection with Y oxide nanoparticles. These defects completely disappear in a shallow layer at the surface. The results are in agreement with hardness measurements showing little hardness increase after irradiation at 300 °C. Suitable characteristics of ODS alloy for nuclear applications and the close correlation between He-related open volume defects and the hardness characteristics are verified.

  14. Effect of alloying with titanium on the microstructure of an oxide dispersion strengthened 13.5% Cr steel

    NASA Astrophysics Data System (ADS)

    Rogozhkin, S. V.; Bogachev, A. A.; Kirillov, D. I.; Nikitin, A. A.; Orlov, N. N.; Aleev, A. A.; Zaluzhnyi, A. G.; Kozodaev, M. A.

    2014-12-01

    Microstructure and phase composition of a high-chromium oxide dispersion strengthened (ODS) steel Fe-13.5% Cr-2% W-0.3% Y2O3 without a titanium additive, as well as alloyed with 0.2, 0.3, and 0.4 wt %Ti, has been studied using transmission electron microscopy. A comparison of the nanoscale state of the steels under investigation with that of an ODS Eurofer steel alloyed with 0.2 wt % V has been carried out. In all of the states found, a high number density of nanosized oxide inclusions has been observed. Upon an increase of the titanium concentration in the steel Fe-13.5% Cr-2% W-0.3% Y2O3 to 0.3 wt %, the average size of the particles decreases, while their number density grows. In this steel, single nanosized (0.1-0.7 μm) grains or their agglomerates have been found, as well as coarse (6-8 μm) grains.

  15. Void formation and microstructural development in oxide dispersion strengthened ferritic steels during electron-irradiation

    NASA Astrophysics Data System (ADS)

    Saito, J.; Suda, T.; Yamashita, S.; Ohnuki, S.; Takahashi, H.; Akasaka, N.; Nishida, M.; Ukai, S.

    1998-10-01

    ODS ferritic steels (13Cr-0.5Ti-0.2Y 2O 3) were prepared by the mechanical alloying method followed by the hot extrusion and several heat treatments including recrystallization. ODS steels with different heat treatment and a ferritic/martensitic (F/M) steel for the reference were irradiated to 12 dpa at 670-770 K in HVEM. After recrystallization, the dislocation density decreased with increasing grain size, however, the oxide particles did not show any obvious change in the size and the number density. During the electron-irradiation the microstructure was relatively stable, i.e. oxide particles showed good stability and the dislocation density remained almost constant. A limited void formation was observed in the specimens, and the suppressive effect due to dislocations with high number density was confirmed. From these results, the behavior of microstructure and the limited void formation in ODS steels have been discussed.

  16. Evaluation of liquid metal embrittlement susceptibility of oxide dispersion strengthened steel MA956

    NASA Astrophysics Data System (ADS)

    Baker, B. W.; Brewer, L. N.

    2014-10-01

    This research examined the susceptibility of MA956 to liquid metal embrittlement using two experimental approaches. In both approaches, historical data on traditional steels was used to determine likely conditions to promote liquid metal embrittlement in lead and lead-bismuth eutectic environments. U-bend specimens of MA956 were found to be immune to liquid metal embrittlement after prolonged exposure to liquid lead. Similarly, slow strain rate testing of MA956 showed immunity to liquid metal embrittlement for both lead and lead-bismuth at temperatures of 328 °C and 150 °C respectively corresponding to the melting temperature of each embrittler individually. These results suggest that the same passive protective oxide layers that limit general corrosion and oxidation also prevent liquid metal embrittlement.

  17. Mechanism for radiation damage resistance in yttrium oxide dispersion strengthened steels

    NASA Astrophysics Data System (ADS)

    Brodrick, J.; Hepburn, D. J.; Ackland, G. J.

    2014-02-01

    ODS steels based on yttrium oxide have been suggested as potential fusion reactor wall materials due to their observed radiation resistance properties. Presumably this radiation resistance can be related to the interaction of the particle with vacancies, self-interstitial atoms (SIAs) and other radiation damage debris. Density functional theory has been used to investigate this at the atomic scale. Four distinct interfaces, some based on HRTEM observations, between iron and yttrium oxide were investigated. It is been shown that the Y2O3-Fe interface acts as a strong trap with long-range attraction for both interstitial and vacancy defects, allowing recombination without altering the interface structure. The catalytic elimination of defects without change to the microstructure explains the improved behaviour of ODS steels with respect to radiation creep and swelling.

  18. Optimization of an oxide dispersion strengthened Ni-Cr-Al alloy for gas turbine engine vanes

    NASA Technical Reports Server (NTRS)

    Klarstrom, D. L.; Grierson, R.

    1975-01-01

    The investigation was carried out to determine the optimum alloy within the Ni-16Cr-Al-Y2O3 system for use as a vane material in advanced aircraft gas turbine engines. Six alloys containing nominally 4%, 5% and 6% Al with Y2O3 levels of 0.8% and 1.2% were prepared by mechanical attrition. Six small-scale, rectangular extrusions were produced from each powder lot for property evaluation. The approximate temperatures for incipient melting were found to be 1658 K (2525 F), 1644 K (2500 F) and 1630 K (2475 F) for the 4%, 5% and 6% aluminum levels, respectively. With the exception of longitudinal crystallographic texture, the eight extrusions selected for extensive evaluation either exceeded or were close to mechanical property goals. Major differences between the alloys became apparent during dynamic oxidation testing, and in particular during the 1366 K (2000 F)/500 hour Mach 1 tests carried out by NASA-Lewis. An aluminum level of 4.75% was subsequently judged to be optimum based on considerations of dynamic oxidation resistance, susceptibility to thermal fatigue cracking and melting point.

  19. Effect of Process Parameters on Microstructure and Hardness of Oxide Dispersion Strengthened 18Cr Ferritic Steel

    NASA Astrophysics Data System (ADS)

    Nagini, M.; Vijay, R.; Rajulapati, Koteswararao V.; Rao, K. Bhanu Sankara; Ramakrishna, M.; Reddy, A. V.; Sundararajan, G.

    2016-08-01

    Pre-alloyed ferritic 18Cr steel (Fe-18Cr-2.3W-0.3Ti) powder was milled with and without nano-yttria in high-energy ball mill for varying times until steady-state is reached. The milled powders were consolidated by upset forging followed by hot extrusion. Microstructural changes were examined at all stages of processing (milling, upset forging, and extrusion). In milled powders, crystallite size decreases and hardness increases with increasing milling time reaching a steady-state beyond 5 hours. The size of Y2O3 particles in powders decreases with milling time and under steady-state milling conditions; the particles either dissolve in matrix or form atomic clusters. Upset forged sample consists of unrecrystallized grain structure with few pockets of fine recrystallized grains and dispersoids of 2 to 4 nm. In extruded and annealed rods, the particles are of cuboidal Y2Ti2O7 at all sizes and their size decreased from 15 nm to 5 nm along with significant increase in number density. The oxide particles in ODS6 are of cuboidal Y2Ti2O7 with diamond cubic crystal structure ( Fd bar{3} m) having a lattice parameter of 10.1 Å and are semicoherent with the matrix. The hardness values of extruded and annealed samples predicted by linear summation model compare well with measured values.

  20. Nano-cluster stability following neutron irradiation in MA957 oxide dispersion strengthened material

    NASA Astrophysics Data System (ADS)

    Ribis, J.; Lozano-Perez, S.

    2014-01-01

    ODS steels are promising materials for Sodium cooled Fast Reactors since their fine distribution of nano-clusters confers excellent mechanical properties. However, the nano-feature stability needs to be assessed under neutron irradiation. Before irradiation, the characterizations show that nano-particles are finely distributed within the ferritic matrix and are identified to have a pyrochlore type structure. After irradiation of the MA957 alloy in the Phenix French reactor at 412 °C up to 50 dpa and 430 °C up to 75 dpa, transmission electron microscopy characterization reveals a very slight density fall but no distinguishable difference in nano-features size before and after irradiation. In addition, after both irradiations, the nano-oxides are still (Y, Ti, O) compounds with orientation relationship with the matrix. A multislice simulation of high resolution images suggests that nano-particles still have a fcc pyrochlore type structure after irradiation. A possible change of lattice parameter seems to be highlighted, possibly due to disordering by cascade effect.

  1. Creep and tensile properties of several oxide-dispersion-strengthened nickel-base alloys at 1365 K

    NASA Technical Reports Server (NTRS)

    Wittenberger, J. D.

    1977-01-01

    The tensile properties at room temperature and at 1365 K and the tensile creep properties at low strain rates at 1365 K were measured for several oxide-dispersion-strengthened (ODS) alloys. The alloys examined included ODS Ni, ODS Ni-20Cr, and ODS Ni-16Cr-Al. Metallography of creep tested, large grain size ODS alloys indicated that creep of these alloys is an inhomogeneous process. All alloys appear to possess a threshold stress for creep. This threshold stress is believed to be associated with diffusional creep in the large grain size ODS alloys and normal dislocation motion in perfect single crystal (without transverse low angle boundaries) ODS alloys. Threshold stresses for large grain size ODS Ni-20Cr and Ni-16Cr-Al type alloys are dependent on the grain aspect ratio. Because of the deleterious effect of prior creep on room temperature mechanical properties of large grain size ODS alloys, it is speculated that the threshold stress may be the design limiting creep strength property.

  2. Stability Of Nanoclusters In 14YWT Oxide Dispersion Strengthened Steel Under Heavy Ion-irradiation By Atom Probe Tomography

    SciTech Connect

    He, Jianchao; Wan, F.; Sridharan, Kumar; Allen, Todd R.; Certain, Alicia G.; Shutthanandan, V.; Wu, Yaqiao

    2014-12-01

    14YWT oxide dispersion strengthened (ODS) ferritic steel was irradiated with of 5 MeV Ni2+ ions, at 300 °C, 450 °C, and 600 °C to a damage level of 100 dpa. The stability of Ti–Y–O nanoclusters was investigated by applying atom probe tomography (APT) in voltage mode, of the samples before and after irradiations. The average size and number density of the nanoclusters was determined using the maximum separation method. These techniques allowed for the imaging of nanoclusters to sizes well below the resolution limit of conventional transmission electron microscopy techniques. The most significant changes were observed for samples irradiated at 300 °C where the size (average Guinier radius) and number density of nanoclusters were observed to decrease from 1.1 nm to 0.8 nm and 12 × 1023 to 3.6 × 1023, respectively. In this study, the nanoclusters are more stable at higher temperature.

  3. Characterization of Residual Stress as a Function of Friction Stir Welding Parameters in Oxide Dispersion Strengthened (ODS) Steel MA956

    DOE PAGES

    Brewer, Luke N.; Bennett, Martin S.; Baker, B. W.; Payzant, E. Andrew; Kolbus, Lindsay M.

    2015-09-08

    This article characterizes the residual stresses generated by friction stir welding of oxide dispersion strengthened steel MA956 over a series of welding conditions. A plate of MA956 steel was friction stir welded at three conditions: 500 rpm/25 millimeters per minute (mmpm), 400 rpm/50 mmpm and 400 rpm/100 mmpm. The residual stresses across these welds were measured using both x-ray and neutron diffraction techniques. Longitudinal residual stresses up to eighty percent of the yield strength were observed for the 400 rpm/100 mmpm condition. Increasing the traverse rate while holding the rotational speed fixed increased the residual stress levels in the stirmore » zone and at the stir zone-thermomechanically affected zone interface. The stress profiles displayed the characteristic M shape, and the asymmetry between advancing and retreating stress peaks was limited, occurring mainly on the root side of the weld. The large magnitude of the stresses was maintained throughout the thickness of the plates.« less

  4. Epitaxial Fe/Y2O3 interfaces as a model system for oxide-dispersion-strengthened ferritic alloys

    SciTech Connect

    Kaspar, Tiffany C.; Bowden, Mark E.; Wang, Chong M.; Shutthanandan, V.; Overman, Nicole R.; Van Ginhoven, Renee M.; Wirth, Brian D.; Kurtz, Richard J.

    2015-02-01

    The fundamental mechanisms underlying the superior radiation tolerance properties of oxide-dispersion-strengthened ferritic steels and nanostructured ferritic alloys are poorly understood. Thin film heterostructures of Fe/Y2O3 can serve as a model system for fundamental studies of radiation damage. Epitaxial thin films of Y2O3 were deposited by pulsed laser deposition on 8% Y:ZrO2 (YSZ) substrates with (100), (110), and (111) orientation. Metallic Fe was subsequently deposited by molecular beam epitaxy. Characterization by x-ray diffraction and Rutherford backscattering spectrometry in the channeling geometry revealed a degree of epitaxial or axiotaxial ntation for Fe(211) deposited on Y2O3(110)/YSZ(110). In contrast, Fe on Y2O3(111)/YSZ(111) was fully polycrystalline, and Fe on Y2O3(100)/YSZ(100) exhibited out-of-plane texture in the [110] direction with little or no preferential in-plane orientation. Scanning transmission electron microscopy imaging of Fe(211)/Y2O3(110)/YSZ(110) revealed a strongly islanded morphology for the Fe film, with no epitaxial grains visible in the cross-sectional sample. Well-ordered Fe grains with no orientation to the underlying Y2O3 were observed. Well-ordered crystallites of Fe with both epitaxial and non-epitaxial orientations on Y2O3 are a promising model system for fundamental studies of radiation damage phenomena. This is illustrated with preliminary results of He bubble formation following implantation with a helium ion microscope. He bubble formation is shown to preferentially occur at the Fe/Y2O3 interface.

  5. Stability of several oxide dispersion strengthened alloys and a directionally solidified gamma/gamma prime-alpha eutectic alloy in a thermal gradient

    NASA Technical Reports Server (NTRS)

    Staniek, G.; Whittenberger, J. D.

    1980-01-01

    Thermal gradient testing of three oxide dispersion strengthened alloys (two Ni-base alloys, MA 754 and MA 6000 E, and the Fe-base MA 956) and the directionally solidified eutectic alloy, gamma/gamma prime-alpha, have been conducted. Experiments were carried out with maximum temperatures up to 1200 C and thermal gradients on the order of 100 C/mm. The oxide dispersion strengthened alloys were difficult to test because the thermal stresses promoted crack nucleation and growth; thus the ability of these alloys to maintain a thermal gradient may be limited. The stability of individual fibers in gamma/gamma prime-alpha was excellent; however, microstructural changes were observed in the vicinity of grain boundaries. Similar structures were also observed in isothermally annealed material; therefore thermal gradients do not affect the microstructure of gamma/gamma prime-alpha in any significant manner.

  6. Oxide-Dispersion-Strengthened Fe3Al-Based Alloy Tubes: Application-Specific Development for the Power Generation Industry

    SciTech Connect

    Kad, BK

    2001-07-20

    A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe{sub 3}Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100 C in the power generation industry. A particular ''in service application'' anomaly of Fe{sub 3}Al-based alloys is that the environmental resistance is maintained up to 1200 C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism. Thus, the challenges of this program are manifold: (1) to produce thin walled ODS-Fe{sub 3}Al tubes, employing powder extrusion methodologies, with (2) adequate increased strength for service at operating temperatures, and (3) to mitigate creep failures by enhancing the as-processed grain size in ODS-Fe{sub 3}Al tubes. Our research progress till date has resulted in the successful batch production of typically 8 Ft. lengths of 1-3/8 inch diameter, 1/8 inch wall thickness, ODS-Fe{sub 3}Al tubes via a proprietary single step extrusion consolidation process. The process parameters for such consolidation methodologies have been prescribed and evaluated as being routinely reproducible. Such processing parameters (i.e., extrusion ratios, temperature, can design etc.) were particularly guided by the need to effect post-extrusion recrystallization and grain growth at a sufficiently low temperature, while still meeting the creep requirement at service temperatures. Static recrystallization studies show that elongated grains (with their long axis parallel to the extrusion axis), typically 200-2000 {micro}m in diameter, and several millimeters long can be obtained routinely, at 1200 C. The growth kinetics are affected by the interstitial impurity content in the powder batches. For example complete recrystallization, across the tube wall thickness, is observed for clean

  7. Cyclic oxidation of coated Oxide Dispersion Strengthened (ODS) alloys in high velocity gas streams at 1100 deg C

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.

    1978-01-01

    Several overlay coatings on ODS NiCrAl's were tested in Mach 1 and Mach 0.3 burner rigs to examine oxidation and thermal fatigue performance. The coatings were applied by various methods. Based on weight change, macroscopic, and metallographic observations in Mach 1 tests Nascoat 70 on TD-NiCrAl exhibited the best oxidation resistance. In Mach 0.3 tests PWA 267 and ATD-1, about equally, were the best coatings on YD-NiCrAl (Nascoat 70 was not tested in Mach 0.3 rigs).

  8. High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi2Sr2CaCu2O8+x round wire

    NASA Astrophysics Data System (ADS)

    Kajbafvala, Amir; Nachtrab, William; Kumar, Raj; Hunte, Frank; Wong, Terence; Schwartz, Justin

    2013-12-01

    High strength dispersion strengthened (DS) Ag/Al alloys with various Al content are studied as candidates for sheathing Bi2Sr2CaCu2O8+x (Bi2212) wire. The Ag/Al alloys are fabricated by powder metallurgy and internally oxidized in pure oxygen. The time and temperature of the internal oxidation heat treatment is varied to maximize the strength after undergoing the Bi2212 partial melt process (PMP). Vickers micro-hardness number (HVN), room temperature tensile behavior, optical and scanning electron microscopy, ion channeling contrast imaging using a focused ion beam and electrical resistivity measurements are used to characterize the alloys. An Ag/0.2wt%Mg (Ag/Mg) alloy is used for comparison. Results show that internal oxidation at 650-700  ° C for 4 h produces the highest HVN for the DS Ag/Al alloy; when oxidized at 675 ° C for 4 h the HVN, yield strength and tensile strength of the DS Ag/Al are 50% higher than the corresponding values of Ag/Mg. Microstructural observations show that Al2O3 precipitates play the main role in strengthening the DS Ag/Al alloy. The alloy retains its fine grain structure and strength after PMP heat treatment.

  9. Microstructure of oxide dispersion strengthened Eurofer and iron-chromium alloys investigated by means of small-angle neutron scattering and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Heintze, C.; Bergner, F.; Ulbricht, A.; Hernández-Mayoral, M.; Keiderling, U.; Lindau, R.; Weissgärber, T.

    2011-09-01

    Oxide dispersion strengthening of ferritic/martensitic chromium steels is a promising route for the extension of the range of operation temperatures for nuclear applications. The investigation of dedicated model alloys is an important means in order to separate individual effects contributing to the mechanical behaviour under irradiation and to improve mechanistic understanding. A powder metallurgy route based on spark plasma sintering was applied to fabricate oxide dispersion strengthened (ODS) Fe9Cr model materials. These materials along with Eurofer97 and ODS-Eurofer were investigated by means of small-angle neutron scattering (SANS) and TEM. For Fe9Cr-0.6 wt.%Y 2O 3, TEM results indicate a peak radius of the size distribution of Y 2O 3 particles of 4.2 nm with radii ranging up to 15 nm, and a volume fraction of 0.7%, whereas SANS indicates a peak radius of 3.8 nm and a volume fraction of 0.6%. It was found that the non-ODS Fe9Cr and Eurofer97 are suitable reference materials for ODS-Fe9Cr and ODS-Eurofer, respectively, and that the ODS-Fe9Cr variants are suitable model materials for the separated investigation of irradiation-Y 2O 3 particle interaction effects.

  10. MATE (Materials for Advanced Turbine Engines) Program, Project 3. Volume 2: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner

    NASA Technical Reports Server (NTRS)

    Bose, S.; Sheffler, K. D.

    1988-01-01

    The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Two yttria (Y2O3) dispersion strengthened alloys were evaluated; Incoloy MA956 and Haynes Development Alloy (HDA) 8077 (NiCrAl base). Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. MA956 was selected as the final alloy based on manufacturing reproducibility for evaluation as a burner liner. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components and using a louvered configuration was designed and constructed. The louvered configuration was chosen because of field experience and compatibility with the bill of material PW2037 design. The simulated flight cycle for the ground based engine tests consisted of 4.5 min idle, 1.5 min takeoff and intermediate conditions in a PW2037 engine with average uncorrected combustor exit temperature of 1527 C. Post test evaluation consisting of visual observations and fluorescent penetrant inspections was conducted after 500 cycles of testing. No loss of integrity in the burner liner was shown.

  11. MATE (Materials for Advanced Turbine Engines) Program, Project 3. Volume 2: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner. Final report

    SciTech Connect

    Bose, S.; Sheffler, K.D.

    1988-02-01

    The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Two yttria (Y2O3) dispersion strengthened alloys were evaluated; Incoloy MA956 and Haynes Development Alloy (HDA) 8077 (NiCrAl base). Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. MA956 was selected as the final alloy based on manufacturing reproducibility for evaluation as a burner liner. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components and using a louvered configuration was designed and constructed. The louvered configuration was chosen because of field experience and compatibility with the bill of material PW2037 design. The simulated flight cycle for the ground based engine tests consisted of 4.5 min idle, 1.5 min takeoff and intermediate conditions in a PW2037 engine with average uncorrected combustor exit temperature of 1527 C. Post test evaluation consisting of visual observations and fluorescent penetrant inspections was conducted after 500 cycles of testing. No loss of integrity in the burner liner was shown.

  12. Small angle neutron scattering analyses and high temperature mechanical properties of nano-structured oxide dispersion strengthened steels produced via cryomilling

    SciTech Connect

    Kim, Jeoung Han; Byun, Thak Sang; Shin, Eunjoo; Seol, Jae-Bok; Young, Sung; Reddy, N. S.

    2015-08-17

    Three oxide dispersion-strengthened (ODS) steels are produced in order to investigate the effect of the mechanical alloying (MA) temperature on the microstructural evolution and high temperature mechanical properties. The microstructural evolution with different MA conditions is examined using small angle neutron scattering. As the MA temperature decreases, the density of the nanoclusters below 10 nm increases and their mean diameter decreases. A low temperature during MA leads to a high strength in the compression tests performed at 500 *C; however, this effect disappears in testing at 900 *C. The milling process at *70 *C exhibits excellent high fracture toughness, which is better than the benchmark material 14YWT-SM10. However, the *150 *C milling process results in significantly worse fracture toughness properties. The reasons for this strong temperature dependency are discussed.

  13. Fabrication of 13Cr-2Mo Ferritic/Martensitic Oxide-Dispersion-Strengthened Steel Components by Mechanical Alloying and Spark-Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Bogachev, I.; Grigoryev, E.; Khasanov, O. L.; Olevsky, E.

    2014-06-01

    The outcomes of the mechanical alloying of 13Cr-2Mo ferritic/martensitic steel and yttria (oxide-dispersion-strengthened steel) powders in a ball mill are reported in terms of the powder particle size and morphology evolution. The optimal ball mill rotation speed and the milling time are discussed. The densification kinetics of the mechanically alloyed powder during the process of spark-plasma sintering is analyzed. An optimal set of the compaction processing parameters, including the maximum temperature, the dwell time, and the heating rate, is determined. The specifics of the densification are discussed in terms of the impact of major spark-plasma sintering parameters as well as the possible phase transformations occurring during compaction processing.

  14. Tensile and creep properties of the experimental oxide dispersion strengthened iron-base sheet alloy MA-956E at 1365 K

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1978-01-01

    A study of the 1365 K tensile properties, creep characteristics and residual room temperature properties after creep testing of the experimental oxide dispersion strengthened iron-base alloy MA-956E (Fe-20Cr-4.5Al-0.5Ti-0.5Y2O3) was conducted. The 1365 K tensile properties, particularly ductility, are strongly dependent on strain rate. It appears that MA-956E does not easily undergo slow plastic deformation. Rather than deform under creep loading conditions, the alloy apparently fails by a crack nucleation and growth mechanism. Fortunately, there appears to be a threshold stress below which crack nucleation and/or growth does not occur.

  15. Materials for Advanced Turbine Engines (MATE): Project 3: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner, volume 1

    NASA Technical Reports Server (NTRS)

    Henricks, R. J.; Sheffler, K. D.

    1984-01-01

    The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Incoloy MA 956 (FeCrAl base) and Haynes Developmental Alloy (HDA) 8077 (NiCrAl base) were evaluated. Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. Both alloys demonstrated a +167C (300 F) advantage of creep and oxidation resistance with no improvement in thermal fatigue capability compared to a current generation combustor alloy (Hastelloy X). MA956 alloy was selected for further demonstration because it exhibited better manufacturing reproducibility than HDA8077. Additional property tests were conducted on MA956. To accommodate the limited thermal fatigue capability of ODS alloys, two segmented, mechanically attached, low strain ODS combustor design concepts having predicted fatigue lives or = 10,000 engine cycles were identified. One of these was a relatively conventional louvered geometry, while the other involved a transpiration cooled configuration. A series of 10,000 cycle combustor rig tests on subscale MA956 and Hastelloy X combustor components showed no cracking, thereby confirming the beneficial effect of the segmented design on thermal fatigue capability. These tests also confirmed the superior oxidation and thermal distortion resistance of the ODS alloy. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components was designed and constructed.

  16. Microstructure and Mechanical Properties of Oxide-Dispersion Strengthened Al6063 Alloy with Ultra-Fine Grain Structure

    NASA Astrophysics Data System (ADS)

    Asgharzadeh, H.; Simchi, A.; Kim, H. S.

    2011-03-01

    The microstructure and mechanical properties of the ultra-fine grained (UFG) Al6063 alloy reinforced with nanometric aluminum oxide nanoparticles (25 nm) were investigated and compared with the coarse-grained (CG) Al6063 alloy (~2 μm). The UFG materials were prepared by mechanical alloying (MA) under high-purity Ar and Ar-5 vol pct O2 atmospheres followed by hot powder extrusion (HPE). The CG alloy was produced by HPE of the gas-atomized Al6063 powder without applying MA. Electron backscatter diffraction under scanning electron microscopy together with transmission electron microscopy studies revealed that the microstructure of the milled powders after HPE consisted of ultra-fine grains (>100 nm) surrounded by nanostructured grains (<100 nm), revealing the formation of a bimodal grain structure. The grain size distribution was in the range of 20 to 850 nm with an average of 360 and 300 nm for Ar and Ar-5 pct O2 atmospheres, respectively. The amount of oxide particles formed by reactive mechanical alloying under the Ar/O2 atmosphere was ~0.8 vol pct, whereas the particles were almost uniformly distributed throughout the aluminum matrix. The UFG materials exhibited significant improvement in the hardness and yield strength with an absence of strain hardening behavior compared with CG material. The fracture surfaces showed a ductile fracture mode for both CG and UFG Al6063, in which the dimple size was related to the grain structure. A mixture of ductile-brittle fracture mode was observed for the UFG alloy containing 0.8 vol pct Al2O3 particles. The tensile behavior was described based on the formation of nonequilibrium grain boundaries with high internal stress and dislocation-based models.

  17. Irradiation creep of dispersion strengthened copper alloy

    SciTech Connect

    Pokrovsky, A.S.; Barabash, V.R.; Fabritsiev, S.A.

    1997-04-01

    Dispersion strengthened copper alloys are under consideration as reference materials for the ITER plasma facing components. Irradiation creep is one of the parameters which must be assessed because of its importance for the lifetime prediction of these components. In this study the irradiation creep of a dispersion strengthened copper (DS) alloy has been investigated. The alloy selected for evaluation, MAGT-0.2, which contains 0.2 wt.% Al{sub 2}O{sub 3}, is very similar to the GlidCop{trademark} alloy referred to as Al20. Irradiation creep was investigated using HE pressurized tubes. The tubes were machined from rod stock, then stainless steel caps were brazed onto the end of each tube. The creep specimens were pressurized by use of ultra-pure He and the stainless steel caps subsequently sealed by laser welding. These specimens were irradiated in reactor water in the core position of the SM-2 reactors to a fluence level of 4.5-7.1 x 10{sup 21} n/cm{sup 2} (E>0.1 MeV), which corresponds to {approx}3-5 dpa. The irradiation temperature ranged from 60-90{degrees}C, which yielded calculated hoop stresses from 39-117 MPa. A mechanical micrometer system was used to measure the outer diameter of the specimens before and after irradiation, with an accuracy of {+-}0.001 mm. The irradiation creep was calculated based on the change in the diameter. Comparison of pre- and post-irradiation diameter measurements indicates that irradiation induced creep is indeed observed in this alloy at low temperatures, with a creep rate as high as {approx}2 x 10{sup {minus}9}s{sup {minus}1}. These results are compared with available data for irradiation creep for stainless steels, pure copper, and for thermal creep of copper alloys.

  18. Brazing copper to dispersion-strengthened copper

    SciTech Connect

    Ryding, D.G.; Allen, D.; Lee, R.

    1996-08-01

    The Advanced Photon Source (APS) is a state-of-the-art synchrotron light source that will produce intense x-ray beams, which will allow the study of smaller samples and faster reactions and processes at a greater level of detail that has been possible to date. The beam is produced by using third-generation insertion devices in a 7 GeV electron/positron storage ring that is 1100 meters in circumference. The heat load from these intense high power devices is very high and certain components must sustain total heat loads of 3 to 15 kW and heat fluxes of 30 W/mm{sup 2}. Because the beams will cycle on and off many times, thermal shock and fatigue will be a problem. High heat flux impinging on a small area causes a large thermal gradient that results in high stress. GlidCop{reg_sign}, a dispersion strengthened copper, is the desired material because of its high thermal conductivity and superior mechanical properties as compared to copper and its alloys. GlidCop is not amenable to joining by fusion welding, and brazing requires diligence because of high diffusivity. Brazing procedures were developed using optical and scanning electron microscopy.

  19. Process for the synthesis of nanophase dispersion-strengthened aluminum alloy

    DOEpatents

    Barbour, John C.; Knapp, James Arthur; Follstaedt, David Martin; Myers, Samuel Maxwell

    1998-12-15

    A process for fabricating dispersion-strengthened ceramic-metal composites is claimed. The process comprises in-situ interaction and chemical reaction of a metal in gaseous form with a ceramic producer in plasma form. Such composites can be fabricated with macroscopic dimensions. Special emphasis is placed on fabrication of dispersion-strengthened aluminum oxide-aluminum composites, which can exhibit flow stresses more characteristic of high strength steel.

  20. Cryogenic properties of dispersion strengthened copper for high magnetic fields

    NASA Astrophysics Data System (ADS)

    Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

    2014-01-01

    Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

  1. Cryogenic properties of dispersion strengthened copper for high magnetic fields

    SciTech Connect

    Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

    2014-01-27

    Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

  2. Enriched aluminide coatings for dispersion strengthened nickel materials

    NASA Technical Reports Server (NTRS)

    Levinstein, M. A.

    1973-01-01

    Improved aluminide/barrier coating combinations for dispersion strengthened nickel materials were investigated. The barrier materials involved alloys with refractory metal content to limit interdiffusion between the coating and the substrate, thereby minimizing void formation. Improved aluminide coatings involved the dispersion of aluminum-rich compounds. Coatings were tested in argon at 1533 K (2300 F) for 100 hours and in cyclic oxidation at 1422 K (2100 F). Two coatings on TDNiCr completed 300 hours of oxidation testing, none on TDNi. Selected coating combinations were evaluated in Mach 1 burner rig testing using JP-4 fuel and air at 1422 K (2100 F) and 1477 K (2200 F) for 350 and 100 hours, respectively. Static oxidation in 1-hour cycles was conducted at 1533 K (2300 F) for 100 hours. For comparison purposes a physical vapor deposition (PVD) NiCrAlY coating was tested concurrently. Only the NiCrA1Y coating survived the 1477 K (2200 F)/100-hour burner rig test and 275 hours of the 350-hour 1422 K (2100 F) test. Elevated temperature exposure reduced room temperature tensile properties but had little effect on elevated temperature properties.

  3. Solid electrolytes strengthened by metal dispersions

    DOEpatents

    Lauf, Robert J.; Morgan, Chester S.

    1983-01-01

    An improvement in solid electrolytes of advanced secondary batteries of the sodium-sulfur, sodium-halogen, and like combinations is achieved by providing said battery with a cermet electrolyte containing a metal dispersion ranging from 0.1 to 10.0 vol. % of a substantially nonreactive metal selected from the group consisting essentially of Pt, Cr, Fe, Co, Ni, Nb, their alloys, and their physical mixtures in the elemental or uncombined state, the remainder of said cermet being an ion-conductive ceramic material.

  4. Solid electrolytes strengthened by metal dispersions

    DOEpatents

    Lauf, R.J.; Morgan, C.S.

    1981-10-05

    An improvement in solid electrolytes of advanced secondary batteries of the sodium-sulfur, sodium-halogen, and like combinations is achieved by providing said battery with a cermet electrolyte containing a metal dispersion ranging from 0.1 to 10.0 vol. % of a substantially nonreactive metal selected from the group consisting essentially of Pt, Cr, Fe, Co, Ni, Nb, their alloys, and their physical mixtures in the elemental or uncombined state, the remainder of said cermet being an ion-conductive ceramic material.

  5. Alloyed coatings for dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Wermuth, F. R.; Stetson, A. R.

    1971-01-01

    Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

  6. Processing and microstructure characterisation of oxide dispersion strengthened Fe-14Cr-0.4Ti-0.25Y2O3 ferritic steels fabricated by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Zhang, Hongtao; Huang, Yina; Ning, Huanpo; Williams, Ceri A.; London, Andrew J.; Dawson, Karl; Hong, Zuliang; Gorley, Michael J.; Grovenor, Chris R. M.; Tatlock, Gordon J.; Roberts, Steve G.; Reece, Michael J.; Yan, Haixue; Grant, Patrick S.

    2015-09-01

    Ferritic steels strengthened with Ti-Y-O nanoclusters are leading candidates for fission and fusion reactor components. A Fe-14Cr-0.4Ti + 0.25Y2O3 (14YT) alloy was fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). The densification of the 14YT alloys significantly improved with an increase in the sintering temperature. Scanning electron microscopy and electron backscatter diffraction revealed that 14YT SPS-sintered at 1150 °C under 50 MPa for 5 min had a high density (99.6%), a random grain orientation and a bimodal grain size distribution (<500 nm and 1-20 μm). Synchrotron X-ray diffraction patterns showed bcc ferrite, Y2Ti2O7, FeO, and chromium carbides, while transmission electron microscopy and atom probe tomography showed uniformly dispersed Y2Ti2O7 nanoclusters of <5 nm diameter and number density of 1.04 × 1023 m-3. Due to the very much shorter consolidation times and lower pressures used in SPS compared with the more usual hot isostatic pressing routes, SPS is shown to be a cost-effective technique for oxide dispersion strengthened (ODS) alloy manufacturing with microstructural features consistent with the best-performing ODS alloys.

  7. 1300 K compressive properties of several dispersion strengthened NiAl materials

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Gaydosh, D. J.; Kumar, K. S.

    1990-01-01

    To examine the potential of rapid solidification technology (RST) as a means to fabricate dispersion-strengthened aluminides, cylindrical compression samples were machined from the gauge section of their tensile specimens and tested in air at 1300 K. While microscopy indicates that RST can produce fine dispersions of TiB2, TiC and HfC in a NiAl matrix, the mechanical property data reveal that only HfC successfully strengthens the intermetallic matrix. The high stress exponents (above 10) and/or independence of strain rate on stress for NiAl-HfC materials suggest elevated temperature mechanical behavior similar to that found in oxide dispersion-strengthened alloys. Furthermore, an apparent example of departure side pinning has been observed, and as such, it is indicative of a threshold stress for creep.

  8. Corrosion of oxide dispersion strengthened iron-chromium steels and tantalum in fluoride salt coolant: An in situ compatibility study for fusion and fusion-fission hybrid reactor concepts

    NASA Astrophysics Data System (ADS)

    El-Dasher, Bassem; Farmer, Joseph; Ferreira, James; de Caro, Magdalena Serrano; Rubenchik, Alexander; Kimura, Akihiko

    2011-12-01

    Primary candidate classes of materials for future nuclear power plants, whether they be fission, fusion or hybrids, include oxide dispersion strengthened (ODS) ferritic steels which rely on a dispersion of nano-oxide particles in the matrix for both mechanical strength and swelling resistance, or tantalum alloys which have an inherent neutron-induced swelling resistance and high temperature strength. For high temperature operation, eutectic molten lithium containing fluoride salts are attractive because of their breeding capability as well as their relatively high thermal capacity, which allow for a higher average operating temperature that increases power production. In this paper we test the compatibility of Flinak (LiF-NaF-KF) salts on ODS steels, comparing the performance of current generation ODS steels developed at Kyoto University with the commercial alloy MA956. Pure tantalum was also tested for comparative purposes. In situ data was obtained for temperatures ranging from 600 to 900 °C using a custom-built high temperature electrochemical impedance spectroscopy cell. Results for ODS steels show that steel/coolant interfacial resistance increases from 600 to 800 °C due to an aluminum enriched layer forming at the surface, however an increase in temperature to 900 °C causes this layer to break up and aggressive attack to occur. Performance of current generation ODS steels surpassed that of the MA956 ODS steel, with an in situ impedance behavior similar or better than that of pure tantalum.

  9. High temperature dispersion strengthening of NiAl

    NASA Technical Reports Server (NTRS)

    Sherman, M.; Vedula, K.

    1986-01-01

    A potential high temperature strengthening mechanism for alloys based on the intermetallic compound NiAl was investigated. This study forms part of an overall program at NASA Lewis Research Center for exploring the potential of alloys based on NiAl for high temperature applications. An alloy containing 2.26 at% Nb and produced by hot extrusion of blended powders was examined in detail using optical and electron microscopy. Interdiffusion between the blended Nb and NiAl powders results in the formation of intermediate phases. A fine dispersion of precipitates of a hexagonal, ordered NiAlNb phases in a matrix of NiAl can be produced and this results in strengthening of the alloy by interfering with dislocation motion at high temperature. These precipitates are, however, found to coarsen during the high temperature (1300 K) deformation at slow strain rates and this may impose some limitatioins on the use of this strengthening mechanism.

  10. New insights into the chemical structure of Y2Ti2O7-δ nanoparticles in oxide dispersion-strengthened steels designed for sodium fast reactors by electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Badjeck, V.; Walls, M. G.; Chaffron, L.; Malaplate, J.; March, K.

    2015-01-01

    In this paper we study by high resolution scanning transmission electron microscopy coupled with electron energy-loss spectroscopy (STEM-EELS) an oxide dispersion-strengthened (ODS) steel with the nominal composition Fe-14Cr-1W-0.3TiH2-0.3Y2O3 (wt.%) designed to withstand the extreme conditions met in Gen. IV nuclear reactors. After denoising via principal component analysis (PCA) the data are analyzed using independent component analysis (ICA) which is useful in the investigation of the physical properties and chemical structure of the material by separating the individual spectral responses. The Y-Ti-O nanoparticles are found to be homogeneously distributed in the ferritic matrix, sized from 1 to 20 nm and match a non-stoichiometric pyrochlore-Y2Ti2O7-δ structure for sizes greater than 5 nm. We show that they adopt a (Y-Ti-O)-Cr core-shell structure and that Cr also segregates at the matrix grain boundaries, which may slightly modify the corrosion properties of the steel. Using Ti-L2,3 and O-K fine structure (ELNES) the Ti oxidation state is shown to vary from the center of the nanoparticles to their periphery, from Ti4+ in distorted Oh symmetry to a valency often lower than 3+. The sensitivity of the Ti "white lines" ELNES to local symmetry distortions is also shown to be useful when investigating the strain induced in the nanoparticles by the surrounding matrix. The Cr-shell and the variation of the Ti valence state highlight a complex nanoparticle-matrix interface.

  11. Bi2Sr2CaCu2O8 + x round wires with Ag/Al oxide dispersion strengthened sheaths: microstructure-properties relationships, enhanced mechanical behavior and reduced Cu depletion

    NASA Astrophysics Data System (ADS)

    Kajbafvala, Amir; Nachtrab, William; Wong, Terence; Schwartz, Justin

    2014-09-01

    Ag/Al alloys with various Al content (0.50 wt%, 0.75 wt%, 1.00 wt%, and 1.25 wt%) are made by powder metallurgy and used as the outer sheath material for Bi2Sr2CaCu2O8 + x (Bi2212)/Ag/AgAl multifilamentary round wires (RW). Bi2212/Ag/AgAl RW microstructural, mechanical and electrical properties are studied in various conditions, including as-drawn, after internal oxidation, and after partial melt processing (PMP). The results are compared with the behavior of a Bi2212/Ag/Ag0.20Mg wire of the same geometry. The grains in as-drawn Ag/Al alloys are found to be ˜25% smaller than those in the corresponding Ag/0.20 wt%Mg, but after PMP, the Ag/Al and Ag/0.20 wt%Mg grain sizes are comparable. Tensile tests show that Bi2212/Ag/AgAl green wires have yield strength (YS) of ˜115 MPa, nearly 65% higher than that of Bi2212/Ag/Ag0.20Mg. After PMP, the Bi2212/Ag/AgAl YS is about 35% greater than that of Bi2212/Ag/Ag0.20Mg. Furthermore, Bi2212/Ag/AgAl wires exhibit higher ultimate tensile strength and modulus and twice the elongation-to-failure. Atomic resolution high-angle annular dark-field scanning transmission electron microscopy, high resolution transmission electron microscopy and energy dispersive spectroscopy demonstrate the formation of nanosize MgO and Al2O3 precipitates via internal oxidation. Large spherical MgO precipitates are observed on the Ag grain boundaries of Ag/0.20 wt%Mg alloy, whereas the Al2O3 precipitates are distributed homogenously in the dispersion-strengthened (DS) Ag/Al alloy. Furthermore, it is found that less Cu diffused from the Bi2212 filaments in the Bi2212/Ag/Ag0.75Al wire during PMP than from the filaments in the Bi2212/Ag/Ag0.20Mg wire. These results show that DS Ag/Al alloy is a strong candidate for improved Bi2212 wire.

  12. Creep-strengthening of steel at high temperatures using nano-sized carbonitride dispersions.

    PubMed

    Taneike, Masaki; Abe, Fujio; Sawada, Kota

    2003-07-17

    Creep is a time-dependent mechanism of plastic deformation, which takes place in a range of materials under low stress-that is, under stresses lower than the yield stress. Metals and alloys can be designed to withstand creep at high temperatures, usually by a process called dispersion strengthening, in which fine particles are evenly distributed throughout the matrix. For example, high-temperature creep-resistant ferritic steels achieve optimal creep strength (at 923 K) through the dispersion of yttrium oxide nanoparticles. However, the oxide particles are introduced by complicated mechanical alloying techniques and, as a result, the production of large-scale industrial components is economically unfeasible. Here we report the production of a 9 per cent Cr martensitic steel dispersed with nanometre-scale carbonitride particles using conventional processing techniques. At 923 K, our dispersion-strengthened material exhibits a time-to-rupture that is increased by two orders of magnitude relative to the current strongest creep-resistant steels. This improvement in creep resistance is attributed to a mechanism of boundary pinning by the thermally stable carbonitride precipitates. The material also demonstrates enough fracture toughness. Our results should lead to improved grades of creep-resistant steels and to the economical manufacture of large-scale steel components for high-temperature applications. PMID:12867976

  13. Compatability of dispersion-strengthened platinum with resistojet propellants

    NASA Technical Reports Server (NTRS)

    Whalen, Margaret V.; Nathal, Michael V.

    1987-01-01

    Resistojets for the Space Station require long life and multipropellant capability. The choice of available materials to meet these requirements is limited. Dispersion-strengthened platinum was selected. Past results indicated that it should be suffieiently inert in candidate propellant environments and should be capable of operating at moderate temperatures for extended periods. A series of propellant compatibility tests was done with platinum strengthened with either yttria or zirconia. Data presented included the results of 1000-hr tests in CO2, H2, ammonia (NH3), N2, steam, hydrazine (N2H4), and methane (CH4); and 2000-hr tests in H2 and NH3. The platinum samples were tested at 1400 C in CO2, H2, NH3, N2, steam, and N2H4; at 500 C in CH4; and at 800 C in N2H4. The mass-loss results indicated material life, exptrapolated from experimental mass-loss data, in excess of 100 000 hr in all environments except steam and N2H4, where it was greater than or =45000 hr. Generally, on the basis of mass loss, there were no compatibility concerns in any of the environments considered. Optical and scanning electron microscopy were used to determine the effect of propellants on the material surface and to evaluate material stability.

  14. Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

    DOE PAGES

    Maloy, Stuart A.; Saleh, Tarik A.; Anderoglu, Osman; Romero, Tobias J.; Odette, G. Robert; Yamamoto, Takuya; Li, S.; Cole, James I.; Fielding, Randall

    2015-08-06

    Tensile test results at 25 and 300 °C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295 °C in the Advanced Test Reactor (ATR), are reported. The engineering stress–strain curves are analyzed to provide true stress–strain constitutive σ(ε) laws for all of these alloys. In the irradiated condition, the σ(ε) fall into categories of: strain softening, nearly perfectly plastic and strain hardening. Increases in yield stress (Δσy) and reductions in uniform strain ductility (eu) are observed, where as the latter can be understood in terms ofmore » the alloy's σ(ε) behavior. Increases in the average σ(ε) in the range of 0–10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are analyzed to establish relations between Δσy and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress (σyu). The latter shows that higher σyu correlates with lower Δσy. In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher eu than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. As a result, notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.« less

  15. Oxide strengthened molybdenum-rhenium alloy

    DOEpatents

    Bianco, Robert; Buckman, Jr., R. William

    2000-01-01

    Provided is a method of making an ODS molybdenum-rhenium alloy which includes the steps of: (a) forming a slurry containing molybdenum oxide and a metal salt dispersed in an aqueous medium, the metal salt being selected from nitrates or acetates of lanthanum, cerium or thorium; (b) heating the slurry in the presence of hydrogen to form a molybdenum powder comprising molybdenum and an oxide of the metal salt; (c) mixing rhenium powder with the molybdenum powder to form a molybdenum-rhenium powder; (d) pressing the molybdenum-rhenium powder to form a molybdenum-rhenium compact; (e) sintering the molybdenum-rhenium compact in hydrogen or under a vacuum to form a molybdenum-rhenium ingot; and (f) compacting the molybdenum-rhenium ingot to reduce the cross-sectional area of the molybdenum-rhenium ingot and form a molybdenum-rhenium alloy containing said metal oxide. The present invention also provides an ODS molybdenum-rhenium alloy made by the method. A preferred Mo--Re-ODS alloy contains 7-14 weight % rhenium and 2-4 volume % lanthanum oxide.

  16. Creep and fracture of dispersion-strengthened materials

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    1991-01-01

    The creep and fracture of dispersion strengthened materials is reviewed. A compilation of creep data on several alloys showed that the reported values of the stress exponent for creep varied between 3.5 and 100. The activation energy for creep exceeded that for lattice self diffusion in the matrix in the case of some materials and a threshold stress behavior was generally reported in these instances. The threshold stress is shown to be dependent on the interparticle spacing and it is significantly affected by the initial microstructure. The effect of particle size and the nature of the dispersoid on the threshold stress is not well understood at the present time. In general, most studies indicate that the microstructure after creep is similar to that before testing and very few dislocations are usually observed. It is shown that the stress acting on a dispersoid due to a rapidly moving dislocation can exceed the particle yield strength of the G sub p/1000, where G sub p is the shear modulus of the dispersoid. The case when the particle deforms is examined and it is suggested that the dislocation creep threshold stress of the alloy is equal to the yield strength of the dispersoid under these conditions. These results indicate that the possibility that the dispersoid creep threshold stress is determined by either the particle yield strength or the stress required to detach a dislocation from the dispersoid matrix interface. The conditions under which the threshold stress is influenced by one or the other mechanism are discussed and it is shown that the particle yield strength is important until the extent of dislocation core relaxation at the dispersoid matrix interface exceeds about 25 pct. depending on the nature of the particle matrix combination. Finally, the effect of grain boundaries and grain morphology on the creep and fracture behavior of dispersoid strengthened alloys is examined.

  17. Oxide strengthened molybdenum-rhenium alloy

    SciTech Connect

    Bianco, Robert; Buckman, William R. Jr.

    1998-12-01

    Provided is a method of making an ODS molybdenum-rhenium alloy which includes the steps of: (1) forming a slurry containing molybdenum oxide and a metal salt dispersed in an aqueous medium, the metal salt being selected from nitrates or acetates of lanthanum, cerium or thorium; (2) heating the slurry in the presence of hydrogen to form a molybdenum powder comprising molybdenum and an oxide of the metal salt; (3) mixing rhenium powder with the molybdenum powder to form a molybdenum-rhenium powder; (4) pressing the molybdenum-rhenium powder to form a molybdenum-rhenium compact; (5) sintering the molybdenum-rhenium compact in hydrogen or under a vacuum to form a molybdenum-rhenium ingot; and (6) compacting the molybdenum-rhenium ingot to reduce the cross-sectional area of the molybdenum-rhenium ingot and form a molybdenum-rhenium alloy containing said metal oxide. The present invention also provides an ODS molybdenum-rhenium alloy made by the method.

  18. Dispersion and precipitation strengthened nanocrystalline and ultra fine grained copper.

    PubMed

    Stobrawa, J P; Rdzawski, Z M; Głuchowski, W J

    2012-12-01

    Dispersion and precipitation strengthened copper alloys is a group of functional and structural materials used where combination of high electrical conductivity with high strength is required. A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to those with ultra fine grain size of a copper matrix. This study was aimed to investigate mechanical properties, electrical conductivity and microstructure in Cu-yttria microcomposite produced by powder metallurgy methods and in CuCr0.6 alloy strips processed by continuous repetitive corrugation and straightening (CRCS). The changes of mechanical properties (HV, ultimate tensile strength, 0.2 yield strength) electrical conductivity as well as microstructure evolution versus true strain were investigated. The microstructure was investigated using optical and electron microscopy (HRTEM and SEM). Possibility of quenching elimination during processing has been also analysed. The Cu-yttria microcomposite produced by powder metallurgy methods and CRCS process of a CuCr0.6 alloys strips effectively reduced the grain size, demonstrating the powder metallurgy and CRCS as a promising new methods for producing nano and ultra fine grained copper matrix.

  19. Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

    SciTech Connect

    Maloy, Stuart A.; Saleh, Tarik A.; Anderoglu, Osman; Romero, Tobias J.; Odette, G. Robert; Yamamoto, Takuya; Li, S.; Cole, James I.; Fielding, Randall

    2015-08-06

    Tensile test results at 25 and 300 °C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295 °C in the Advanced Test Reactor (ATR), are reported. The engineering stress–strain curves are analyzed to provide true stress–strain constitutive σ(ε) laws for all of these alloys. In the irradiated condition, the σ(ε) fall into categories of: strain softening, nearly perfectly plastic and strain hardening. Increases in yield stress (Δσy) and reductions in uniform strain ductility (eu) are observed, where as the latter can be understood in terms of the alloy's σ(ε) behavior. Increases in the average σ(ε) in the range of 0–10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are analyzed to establish relations between Δσy and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress (σyu). The latter shows that higher σyu correlates with lower Δσy. In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher eu than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. As a result, notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.

  20. Oxidation-induced contraction and strengthening of boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.; Wagner, T. C.

    1981-01-01

    An investigation was conducted to measure and understand the physical and mechanical effects that occur in boron fibers during and after thermal treatment in a controlled oxygen argon gaseous mixture. Of principal concern was the optimization of this treatment as a secondary processing method for significantly improving fiber tensile strength. Strengthening was accomplished by an oxidation induced axial contraction of the fiber and a resulting axial compression of strength limiting flaws within the fiber's tungsten boride core. Various physical observations were used to develop mechanistic models for oxidation, contraction, and flow formation. Processing guidelines are discussed for possibly exceeding the 5.5 GN/sq m strength limit and also for achieving fiber strengthening during application of boron containing diffusion barrier coatings.

  1. Irradiation effect of nano-bubble dispersion strengthened (N-BDS) alloy

    NASA Astrophysics Data System (ADS)

    Oono, Naoko; Kawano, Ryohei; Shi, Shi; Ukai, Shigeharu; Hayashi, Shigenari; Kondo, Sosuke; Hashitomi, Okinobu; Kimura, Akihiko

    2013-11-01

    Nano-bubble dispersion strengthened (N-BDS) Fe was made from Fe and polymethylmethacrylate (PMMA) powder and irradiated by 6.4 MeV Fe3+ ions to investigate the cavity strengthening and the bubble to void evolution. The bubbles accelerated the irradiation-induced cavity growth. The hardness of the N-BDS Fe was 500 MPa higher than that of unalloyed Fe and the hardness increased by irradiation, while that of unalloyed Fe did not increase. Cavity is probably the origin of the irradiation hardening of N-BDS Fe.

  2. Creep resistant, precipitation-dispersion-strengthened, martensitic stainless steel and method thereof

    DOEpatents

    Buck, Robert F.

    1994-01-01

    An iron-based, corrosion-resistant, precipitation strengthened, martensitic steel essentially free of delta ferrite for use at high temperatures has a nominal composition of 0.05-0.1 C, 8-12 Cr, 1-5 Co, 0.5-2.0 Ni, 0.41-1.0 Mo, 0.1-0.5 Ti, and the balance iron. This steel is different from other corrosion-resistant martensitic steels because its microstructure consists of a uniform dispersion of fine particles, which are very closely spaced, and which do not coarsen at high temperatures. Thus at high temperatures this steel combines the excellent creep strength of dispersion-strengthened steels, with the ease of fabricability afforded by precipitation hardenable steels.

  3. Creep resistant, precipitation-dispersion-strengthened, martensitic stainless steel and method thereof

    DOEpatents

    Buck, R.F.

    1994-05-10

    An iron-based, corrosion-resistant, precipitation strengthened, martensitic steel essentially free of delta ferrite for use at high temperatures has a nominal composition of 0.05--0.1 C, 8--12 Cr, 1--5 Co, 0.5--2.0 Ni, 0.41--1.0 Mo, 0.1--0.5 Ti, and the balance iron. This steel is different from other corrosion-resistant martensitic steels because its microstructure consists of a uniform dispersion of fine particles, which are very closely spaced, and which do not coarsen at high temperatures. Thus at high temperatures this steel combines the excellent creep strength of dispersion-strengthened steels, with the ease of fabricability afforded by precipitation hardenable steels. 2 figures.

  4. Grinding as an approach to the production of high-strength, dispersion-strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Orth, N. W.; Quatinetz, M.; Weeton, J. W.

    1970-01-01

    Mechanical process produces dispersion-strengthened metal alloys. Power surface contamination during milling is removed by a cleaning method that involves heating thin shapes or partially-compacted milled powder blends in hydrogen to carefully controlled temperature schedules.

  5. Development of dispersion strengthened nickel-chromium alloy (Ni-Cr-Th-O2) sheet for space shuttle vehicles, part 1

    NASA Technical Reports Server (NTRS)

    Klingler, L. J.; Weinberger, W. R.; Bailey, P. G.; Baranow, S.

    1971-01-01

    A dispersion-strengthened alloy, TD nickel chromium (TDNiCr) is being developed for use on the thermal protection system of the space shuttle at temperatures up to 1204 C(2200 F). Manufacturing processes were developed for the fabrication of sheet and foil to specifications. The addition of aluminum to the basic TDNiCr composition provides outstanding oxidation resistance up to 1260 C(2300 F); aluminum levels of 2 to 4% are considered optimum for space shuttle application.

  6. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  7. The role of grain size and shape in strengthening of dispersion hardened nickel alloys.

    NASA Technical Reports Server (NTRS)

    Wilcox, B. A.; Clauer, A. H.

    1972-01-01

    Thermomechanical processing was used to develop various microstructures in Ni, Ni-2ThO2, Ni-20Cr, Ni-20Cr-2ThO2, Ni-20Cr-10W and Ni-20Cr-10W-2ThO2, and the influence of microstructure on room temperature and elevated temperature strength was investigated. The yield strength at 25 C increased with substructure refinement according to the Hall-Petch relation. It was found that substructure refinement was a much more potent means of strengthening at room temperature than was dispersion hardening. At elevated temperature (1093 C), the most important microstructural feature affecting strength of dispersion hardened nickel alloys was the grain aspect ratio, i.e. grain length, L, divided by grain width,l. The yield strength and creep strength increased linearly with increasing L/l.

  8. Strengthened currents override the effect of warming on lobster larval dispersal and survival.

    PubMed

    Cetina-Heredia, Paulina; Roughan, Moninya; van Sebille, Erik; Feng, Ming; Coleman, Melinda A

    2015-12-01

    Human-induced climate change is projected to increase ocean temperature and modify circulation patterns, with potential widespread implications for the transport and survival of planktonic larvae of marine organisms. Circulation affects the dispersal of larvae, whereas temperature impacts larval development and survival. However, the combined effect of changes in circulation and temperature on larval dispersal and survival has rarely been studied in a future climate scenario. Such understanding is crucial to predict future species distributions, anticipate ecosystem shifts and design effective management strategies. We simulate contemporary (1990s) and future (2060s) dispersal of lobster larvae using an eddy-resolving ocean model in south-eastern Australia, a region of rapid ocean warming. Here we show that the effects of changes in circulation and temperature can counter each other: ocean warming favours the survival of lobster larvae, whereas a strengthened western boundary current diminishes the supply of larvae to the coast by restricting cross-current larval dispersal. Furthermore, we find that changes in circulation have a stronger effect on connectivity patterns of lobster larvae along south-eastern Australia than ocean warming in the future climate so that the supply of larvae to the coast reduces by ~4% and the settlement peak shifts poleward by ~270 km in the model simulation. Thus, ocean circulation may be one of the dominant factors contributing to climate-induced changes of species ranges.

  9. Strengthened currents override the effect of warming on lobster larval dispersal and survival.

    PubMed

    Cetina-Heredia, Paulina; Roughan, Moninya; van Sebille, Erik; Feng, Ming; Coleman, Melinda A

    2015-12-01

    Human-induced climate change is projected to increase ocean temperature and modify circulation patterns, with potential widespread implications for the transport and survival of planktonic larvae of marine organisms. Circulation affects the dispersal of larvae, whereas temperature impacts larval development and survival. However, the combined effect of changes in circulation and temperature on larval dispersal and survival has rarely been studied in a future climate scenario. Such understanding is crucial to predict future species distributions, anticipate ecosystem shifts and design effective management strategies. We simulate contemporary (1990s) and future (2060s) dispersal of lobster larvae using an eddy-resolving ocean model in south-eastern Australia, a region of rapid ocean warming. Here we show that the effects of changes in circulation and temperature can counter each other: ocean warming favours the survival of lobster larvae, whereas a strengthened western boundary current diminishes the supply of larvae to the coast by restricting cross-current larval dispersal. Furthermore, we find that changes in circulation have a stronger effect on connectivity patterns of lobster larvae along south-eastern Australia than ocean warming in the future climate so that the supply of larvae to the coast reduces by ~4% and the settlement peak shifts poleward by ~270 km in the model simulation. Thus, ocean circulation may be one of the dominant factors contributing to climate-induced changes of species ranges. PMID:26268457

  10. Development of oxide dispersion strengthened ferritic steels for fusion

    SciTech Connect

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.; Gelles, D.S.

    1996-04-01

    Seven ODS steels, Fe(5-13.5)Cr-2W-0.5Ti-0.25 Y{sub 2}O{sub 3} (in weight percent) were manufactured using the mechanical alloying process. Only the composition Fe-13.5Cr3W-0.5Ti-0.25Y{sub 2}O{sub 3} showed no austenite formation at any temperature using differential thermal analysis and hence was selected as an experimental alloy for the present investigation. Milled powders were consolidated by hot isostatic pressing and hot swaging. Electron microscopy studies indicated high material homogeneity. The hardness of the as-swaged specimen was 65 R{sub c}. Annealing of the as-swaged material at 800, 900, 1000, 1100, and 1200{degrees}C showed a minor decrease in the hardness.

  11. The microstructure and properties of rapidly solidified, dispersion-strengthened NiAl

    NASA Technical Reports Server (NTRS)

    Jha, S. C.; Ray, R.

    1990-01-01

    An advanced rapid solidification technology for processing reactive and refractory alloys, utilized to produce large quantities of melt-spun filaments of NiAl, is presented. The melt-spun filaments are pulverized to fine particle sizes, and subsequently consolidated by hot extrusion or hot isostatic pressing. Rapid solidification process gives rise to very fine-grained microstructures. However, exposure to elevated temperature during hot consolidation leads to grain growth. Alloying agents such as borides, carbides, and tungsten can pin the grain boundaries and retard the grain growth. Various alloy compositions are investigated. The eventual goal is to utilize the hot-extruded and forged stock to grow single-crystal NiAl blades for advanced gas-turbine engine applications. Single-crystal NiAl, containing a uniform dispersion of carbide strengthening precipitates, is expected to lead to highly creep-resistant turbine blades, and is of considerable interest to the aerospace propulsion industry.

  12. Fabrication and characterization of Y2O3 dispersion strengthened copper alloys

    NASA Astrophysics Data System (ADS)

    Carro, G.; Muñoz, A.; Monge, M. A.; Savoini, B.; Pareja, R.; Ballesteros, C.; Adeva, P.

    2014-12-01

    Three copper base materials were fabricated following different routes: cast Cu-1 wt.%Y (C-Cu1Y) produced by vacuum induction melting, and Cu-1 wt.%Y (PM-Cu1Y) and Cu-1 wt.%Y2O3 (PM-Cu1Y2O3) both processed by a powder metallurgy route and sintering by hot isostatic pressing. PM-Cu1Y alloy was prepared by cryomilling and PM-Cu1Y2O3 by conventional milling at room temperature. The materials were characterized by X-ray diffraction, optical and electron microscopy and microhardness measurements. C-Cu1Y presents a characteristic eutectic microstructure while PM-Cu1Y2O3 exhibits a composite like microstructure. Electron microscopy analyses of as-HIP PM-Cu1Y revealed irregular decoration of yttrium-rich oxides at the grain boundaries and an inhomogeneous dispersion of polygonal shaped yttrium-rich oxides dispersed in the Cu matrix. Tensile tests performed on PM-Cu-1Y on the temperature range of 293-773 K have showed a decrease of the yield strength at temperatures higher than 473 K, and monotonically decrease of the ultimate tensile strength and maximum plastic strain on increasing temperature.

  13. The influence of hot working on the subsequent recrystallization of a dispersion strengthened superalloy-MA 6000

    NASA Astrophysics Data System (ADS)

    Singer, R. F.; Gessinger, G. H.

    1982-08-01

    An experimental charge of the oxide dispersion and γ' precipitation strengthened superalloy MA 6000 was hot worked in the as-extruded, fine grained condition. The recrystallization during post-deformation annealing was followed by optical and electron microscopy. Coarse grain formation occurs by secondary rather than primary recrystallization (abnormal or discontinuous grain growth) as indicated by the driving forces involved, the inhibition of normal grain growth, the well-defined coarsening temperature, and the dependence of secondary grain size on temperature. Straining at high temperatures and low strain rates produces material which cannot be subsequently recrystallized. The reason is the loss of driving force during straining due to normal grain growth. The influence of deformation rate and deformation temperature can be properly accounted for by using the diffusion compensated strain rate for description of deformation conditions. Normal grain growth is accelerated by straining. It is suggested that this is caused by an acceleration of the rate controlling processes, namely, particle dragging or particle coarsening.

  14. Evidence for core–shell nanoclusters in oxygen dispersion strengthened steels measured using X-ray absorption spectroscopy

    SciTech Connect

    Liu, S.; Odette, G. R.; Segre, C. U.

    2014-02-01

    Nanostructured ferritic alloys (NFA) dispersion strengthened by an ultra high density of Y–Ti–O enriched nano-features (NF) exhibit superior creep strength and the potential for high resistance to radiation damage. However, the detailed character of the NF, that precipitate from solid solution during hot consolidation of metallic powders mechanically alloyed with Y₂O₃, are not well understood. In order to clarify the nature of the NF, X-ray absorption spectroscopy (XAS) technique, including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were used to characterize the local structure of the Ti and Y atoms in both NFA powders and consolidated alloys. The powders were characterized in the as-received, as-milled and after annealing milled powders at 850, 1000 and 1150 °C. The consolidated alloys included powders hot isostatic pressed (HIPed) at 1150 °C and commercial vendor alloys, MA957 and J12YWT. The NFA XAS data were compared various Ti and Y-oxide standards. The XANES and EXAFS spectra for the annealed and HIPed powders are similar and show high temperature heat treatments shift the Y and Ti to more oxidized states that are consistent with combinations of Y₂Ti₂O₇ and, especially, TiO. However, the MA957 and J12YWT and annealed–consolidated powder data differ. The commercial vendor alloys results more closely resemble the as-milled powder data and all show that a significant fraction of substitutional Ti remains dissolved in the (BCC) ferrite matrix.

  15. Dispersion strengthening of precipitation hardened Al-Cu-Mg alloys prepared by rapid solidification and mechanical alloying

    NASA Technical Reports Server (NTRS)

    Gilman, P. S.; Sankaran, K. K.

    1988-01-01

    Several Al-4Cu-1Mg-1.5Fe-0.75Ce alloys have been processed from either rapidly solidified or mechanically alloyed powder using various vacuum degassing parameters and consolidation techniques. Strengthening by the fine subgrains, grains, and the dispersoids individually or in combination is more effective when the alloys contain shearable precipitates; consequently, the strength of the alloys is higher in the naturally aged rather than the artificially aged condition. The strengths of the mechanically alloyed variants are greater than those produced from prealloyed powder. Properties and microstructural features of these dispersion strengthened alloys are discussed in regards to their processing histories.

  16. The oxidation behavior of Co-15 wt % Cr alloy containing dispersed oxides formed by internal oxidation

    SciTech Connect

    Hou, P.Y.; Shui, Z.R.; Stringer, J.

    1991-12-01

    Internal oxidation pretreatments of Co-15wt%Cr and Co-15wt%Cr-1wt%Ti were carried out using a Rhines pack in quartz, in mullite and in alumina. A dispersion of titanium oxide particles formed in the Ti-containing alloy as a result of the internal oxidation. However, silicon also diffused into all treated specimens when the pretreatments were carried out in quartz or in mullite. The effect of various pretreatments on the subsequent oxidation of these alloys was studied at 1000{degree}C, and compared with that of Co-15wt%Cr-1wt%Si alloy. The main purpose of this study was to determine the relative effectiveness of the dispersed oxide particles and the contaminated silicon on the selective oxidation of chromium. It was found that the oxidation behavior of both treated alloys were strongly affected by the degree of silicon contamination. Selective oxidation of chromium to form a nearly continuous protective Cr{sub 2}O{sub 3} scale was achieved with greater than 0.4wt% silicon. The presence of dispersed particles reduced initial oxidation rate, but was ineffective in promoting Cr{sub 2}O{sub 3} scale formation.

  17. The nano-particle dispersion strengthening of V-4Cr-4Ti alloys for high temperature application in fusion reactors

    NASA Astrophysics Data System (ADS)

    Zheng, Pengfei; Chen, Jiming; Xu, Zengyu; Duan, Xuru

    2013-10-01

    V-4Cr-4Ti was identified as an attractive structural material for Li blanket in fusion reactors. However, both high temperature and irradiation induced degradation are great challenges for this material. It was thought that the nano-particles with high thermal stability can efficiently strengthen the alloy at elevated temperatures, and accommodate the irradiation induced defects at the boundaries. This study is a starting work aiming at improving the creep resistance and reducing the irradiation induced degradation for V-4Cr-4Ti alloy. Currently, we focus on the preparation of some comparative nano-particle dispersion strengthened V-4Cr-4Ti alloys. A mechanical alloying (MA) route is used to fabricate yttrium and carbides added V-4Cr-4Ti alloys. Nano-scale yttria, carbides and other possible particles have a combined dispersion-strengthening effect on the matrices of these MA-fabricated V-4Cr-4Ti alloys. High-temperature annealing is carried out to stabilize the optimized nano-particles. Mechanical properties are tested. Microstructures of the MA-fabricated V-4Cr-4Ti alloys with yttrium and carbide additions are characterized. Based on these results, the thermal stability of different nano-particle agents are classified. ITER related China domestic project 2011GB108007.

  18. Comparison of the Oxidation Rates of Some New Copper Alloys

    NASA Technical Reports Server (NTRS)

    Ogbuji, Linus U. J. Thomas; Humphrey, Donald L.

    2002-01-01

    Copper alloys were studied for oxidation resistance and mechanisms between 550 and 700 C, in reduced-oxygen environments expected in rocket engines, and their oxidation behaviors compared to that of pure copper. They included two dispersion-strengthened alloys (precipitation-strengthened and oxide-dispersion strengthened, respectively) and one solution-strengthened alloy. In all cases the main reaction was oxidation of Cu into Cu2O and CuO. The dispersion-strengthened alloys were superior to both Cu and the solution-strengthened alloy in oxidation resistance. However, factors retarding oxidation rates seemed to be different for the two dispersion-strengthened alloys.

  19. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1975-01-01

    The sintered aluminum powder (SAP) technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of a nickel alloy containing, by weight, 17% Cr, 5% Al, and 0.2% Y. The SAP-NiCrAl alloy (without the ytterbium removed by oxdation) was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. Annealing treatments were applied after working to determine the recrystallization response. The NiCrAlY alloy, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl alloy exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl alloy as has been reported for other oxide dispersion strengthened alloys. In contrast, the unoxidized NiCrAlY alloy exhibited only primary recrystallization.

  20. Well-dispersed chitosan/graphene oxide nanocomposites.

    PubMed

    Yang, Xiaoming; Tu, Yingfeng; Li, Liang; Shang, Songmin; Tao, Xiao-Ming

    2010-06-01

    Nanocomposites of chitosan and graphene oxide are prepared by simple self-assembly of both components in aqueous media. It is observed that graphene oxide is dispersed on a molecular scale in the chitosan matrix and some interactions occur between chitosan matrix and graphene oxide sheets. These are responsible for efficient load transfer between the nanofiller graphene and chitosan matrix. Compared with the pure chitosan, the tensile strength, and Young's modulus of the graphene-based materials are significantly improved by about 122 and 64%, respectively, with incorporation of 1 wt % graphene oxide. At the same time, the elongation at the break point increases remarkably. The experimental results indicate that graphene oxide sheets prefer to disperse well within the nanocomposites.

  1. Duetting--a mechanism to strengthen pair bonds in a dispersed pair-living primate (Lepilemur edwardsi)?

    PubMed

    Méndez-Cárdenas, Maria G; Zimmermann, Elke

    2009-08-01

    Duetting is defined as an interactively organized pair display in which one pair partner coordinates its vocalizations in time with those of the other. It is widespread among tropical birds and cohesive pair-living primates, in which it is suggested to strengthen pair bonds. We know very little about the presence and function of duetting in dispersed pair-living mammals. We studied duetting behavior in a solitary foraging, but pair-sleeping, primate, the Milne Edwards' sportive lemur, in a dry deciduous forest of north-western Madagascar. We radio-tracked six pairs throughout 1 year and recorded their sleeping sites and associations, home-range use, and vocal and behavioral interactions. Three different periods were covered (mating, pregnancy, and offspring care). Sleeping partners form long-term pair bonds, indicated by an almost exclusive pair-specific usage of sleeping sites and home-ranges across periods. We explored three functional hypothesis of duetting: mate reunion, pair reunion, and joint-territorial defense. Pairs regularly engaged in duet calling. Duetting increased significantly during the offspring care period. Duetting occurred significantly more often at feeding sites than at sleeping sites. Pair partners synchronized behavioral activities after duetting. The activity most often synchronized was locomotion. Pair partners played an equal role in duetting with no difference between sexes in starting or terminating duetting. Altogether, our results provide support for the hypothesis that in dispersed pair-living primates, duetting evolved as a mechanism to coordinate activities between pair partners dispersed in space, to strengthen pair bonds, and, perhaps, to limit infanticide and nutritional stress in lactating females.

  2. The Mechanisms of Dispersion Strengthening and Fracture in Al-based XD (TM) Alloys

    NASA Technical Reports Server (NTRS)

    Aiken, R. M., Jr.

    1990-01-01

    The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength, and the fracture toughness of metal matrix composites of both pure aluminum and Al(4 percent)Cu(1.5 percent)Mg with 0 to 15 vol percent TiB2 were examined. Higher TiB2 volume fractions increased the tensile yield strength both at room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. The fracture toughness of the Al(4 percent)Cu(1.5 percent)Mg alloys decreased rapidly with TiB2 additions of 0 to 5 vol percent and more slowly with TiB2 additions of 5 to 15 vol percent. Fracture toughness appears to be independent of TiB2 particle size. The isothermal-aging response of the precipitation strengthened Al(4 percent)Cu(1.5 percent)Mg alloys was not altered by the presence of TiB2.

  3. Deposition and Oxidation of Oxide-Dispersed CoNiCrAlY Bondcoats

    NASA Astrophysics Data System (ADS)

    Okada, Mitsutoshi; Vassen, Robert; Karger, Matthias; Sebold, Doris; Mack, Daniel; Jarligo, Maria Ophelia; Bozza, Francesco

    2014-01-01

    CoNiCrAlY powder and nano-size alumina powder were milled by a high-energy-attrition ball-mill, and an oxide-dispersed powder was produced with a mixed structure of metal and alumina in each particle. The oxide-dispersed bond coat powder was deposited by HVOF. Pores, however, were observed in the coating since the alumina was deposited without sufficient melting. Isothermal oxidation tests were carried out for the bond coat specimens at a temperature of 1373 K up to 1000 h in air. As a result, oxidation proceeded inside the coating, since oxygen penetrated through pores formed in the dispersed alumina. However, the authors find that another deposition using higher power levels led to a bond coat without pores. A commercially available oxide-dispersed CoNiCrAlY powder was also deposited by HVOF and VPS, and isothermal oxidation tests were performed. The analysis clarifies that the HVOF bond coat exhibited the thinnest thermally grown oxide than those of the VPS bond coat and conventional metallic bond coat. Furnace cycling tests were conducted using the specimens with an additional ceramic thermal-barrier coating. The specimen with the bond coat sprayed by VPS using commercial oxide-dispersed powder showed almost same number of cycles to delamination compared with the specimen with the conventional metal bond coat.

  4. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    NASA Astrophysics Data System (ADS)

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-01

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900°C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W2C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  5. The dispersion and aggregation of graphene oxide in aqueous media

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Niu, Yang; Zhou, Jihan; Wen, Hao; Zhang, Zhenyu; Luo, Da; Gao, Dongliang; Yang, Juan; Liang, Dehai; Li, Yan

    2016-07-01

    Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions.Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the

  6. The effect of various oxide dispersions on the oxidation resistance of Fe{sub 3}Al

    SciTech Connect

    Pint, B.A.; Alexander, K.B.; Tortorelli, P.F.

    1996-10-01

    Oxide-dispersed Fe-28at.%Al-2%Cr alloys were produced by a powder metallurgy technique followed by hot extrusion. Yttria and ceria were added to the base alloy to assess the effect of these dopants on the oxidation behavior. The amount of dopant was varied from 0.05-0.5 at.% Y in a series of Y{sub 2}O{sub 3}-dispersed alloys. isothermal and cyclic oxidation testing was conducted at temperatures from 800{degrees} to 1300{degrees}C. A CeO{sub 2} addition was detrimental to the oxidation behavior. The Y{sub 2}O{sub 3} improved the {alpha}-Al{sub 2}O{sub 3} scale adhesion relative to an undoped alloy, but was not as effective as similar additions to an oxide-dispersed FeCrAl alloy.

  7. Structure of graphene oxide dispersed with ZnO nanoparticles

    SciTech Connect

    Yadav, Rishikesh Pandey, Devendra K.; Khare, P. S.

    2014-10-15

    Graphene has been proposed as a promising two-dimensional nanomaterial with outstanding electronic, optical, thermal and mechanical properties for many applications. In present work a process of dispersion of graphene oxide with ZnO nanoparticles in ethanol solution with different pH values, have been studied. Samples have been characterized by XRD, SEM, PL, UV-visible spectroscopy and particles size measurement. The results analysis indicates overall improved emission spectrum. It has been observed that the average diameter of RGO (Reduced Graphene Oxide) decreases in presence of ZnO nanoparticles from 3.8μm to 0.41μm.

  8. The dispersion and aggregation of graphene oxide in aqueous media.

    PubMed

    Wang, Meng; Niu, Yang; Zhou, Jihan; Wen, Hao; Zhang, Zhenyu; Luo, Da; Gao, Dongliang; Yang, Juan; Liang, Dehai; Li, Yan

    2016-08-14

    Graphene oxide (GO), as a typical two-dimensional material, possesses a range of oxygen-containing groups and shows surfactant and/or polyelectrolyte-like characteristics. Herein, GO sheets with narrow size distribution were prepared by an ultracentrifugation-based process and the aggregation behaviour of GO in pure water and an electrolyte aqueous solution were studied using laser light scattering (LLS). When adding common electrolytes, such as NaCl and MgCl2, into the GO dispersions, aggregation occurs and irreversible coagulation eventually occurs too. However, the GO dispersion can still remain stable when adding excess AlCl3. The zeta potential of the GO dispersion changes from negative to positive after the addition of access AlCl3, indicating that electrostatic repulsion is still responsible for the dispersion of GO, which is in good agreement with the LLS results. This finding on the dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions. PMID:27432559

  9. Effectively Exerting the Reinforcement of Dopamine Reduced Graphene Oxide on Epoxy-Based Composites via Strengthened Interfacial Bonding.

    PubMed

    Li, Wenbin; Shang, Tinghua; Yang, Wengang; Yang, Huichuan; Lin, Song; Jia, Xiaolong; Cai, Qing; Yang, Xiaoping

    2016-05-25

    The effects of dopamine reduced graphene oxide (pDop-rGO) on the curing activity and mechanical properties of epoxy-based composites were evaluated. Taking advantage of self-polymerization of mussel-inspired dopamine, pDop-rGO was prepared through simultaneous functionalization and reduction of graphene oxide (GO) via polydopamine coating. Benefiting from the universal binding ability of polydopamine, good dispersion of pDop-rGO in epoxy matrix was able to be achieved as the content of pDop-rGO being below 0.2 wt %. Curing kinetics of epoxy composites with pDop-rGO were systematically studied by nonisothermal differential scanning calorimetry (DSC). Compared to the systems of neat epoxy or epoxy composites containing GO, epoxy composites loaded with pDop-rGO showed lower activation energy (Eα) over the range of cure (α). It revealed that the amino-bearing pDop-rGO was able to react with epoxy matrix and enhance the curing reactions as an amine-type curing agent. The nature of the interactions at GO-epoxy interface was further evaluated by Raman spectroscopy, confirming the occurrence of chemical bonding. The strengthened interfacial adhesion between pDop-rGO and epoxy matrix thus enhanced the effective stress transfer in the composites. Accordingly, the tensile and flexural properties of EP/pDop-rGO composites were enhanced due to both the well dispersion and strong interfacial bonding of pDop-rGO in epoxy matrix.

  10. Subcritical crack growth behavior of dispersion oxide ceramics.

    PubMed

    Kirsten, Armin; Begand, Sabine; Oberbach, Thomas; Telle, Rainer; Fischer, Horst

    2010-10-01

    Zirconia (Y-TZP) is used as material for components of implants and prostheses because of its high short-term strength. The mechanical long-term reliability, however, is limited for Y-TZP because of hydrothermal aging effects and a pronounced tendency for subcritical crack growth. The hypothesis of this study was that a substantial amount of alumina in a zirconia matrix can help to significantly suppress subcritical crack growth and thereby improve the mechanical long-term reliability. The Weibull parameters as well as the parameters of the subcritical crack growth were determined for Alumina, Y-TZP, and two dispersion ceramics, that is Alumina Toughened Zirconia (ATZ, 20% alumina/80% Y-TZP), and Zirconia Toughened Alumina (ZTA, 75% alumina/25% Y-TZP). The long-term failure probability as a function of service time was predicted for the four ceramics. The parameter n of the subcritical crack growth was approx. 80% higher for ATZ compared to Y-TZP. In consequence, the estimated lifetime revealed a significant better mechanical long-term reliability for ATZ. It can be concluded that tailored dispersion oxide ceramics can address the aging problem of monolithic zirconia. This makes ATZ very interesting for components of joint replacement as well as for dental prostheses and implants.

  11. Colloidal polyaniline dispersions: antibacterial activity, cytotoxicity and neutrophil oxidative burst.

    PubMed

    Kucekova, Zdenka; Humpolicek, Petr; Kasparkova, Vera; Perecko, Tomas; Lehocký, Marián; Hauerlandová, Iva; Sáha, Petr; Stejskal, Jaroslav

    2014-04-01

    Polyaniline colloids rank among promising application forms of this conducting polymer. Cytotoxicity, antibacterial activity, and neutrophil oxidative burst tests were performed on cells treated with colloidal polyaniline dispersions. The antibacterial effect of colloidal polyaniline against gram-positive and gram-negative bacteria was most pronounced for Bacillus cereus and Escherichia coli, with a minimum inhibitory concentration of 3,500 μg mL(-1). The data recorded on human keratinocyte (HaCaT) and a mouse embryonic fibroblast (NIH/3T3) cell lines using an MTT assay and flow cytometry indicated a concentration-dependent cytotoxicity of colloid, with the absence of cytotoxic effect at around 150 μg mL(-1). The neutrophil oxidative burst test then showed that colloidal polyaniline, in concentrations <150 μg mL(-1), was not able to stimulate the production of reactive oxygen species in neutrophils and whole human blood. However, it worked efficiently as a scavenger of those already formed.

  12. Fabrication Technological Development of the Oxide Dispersion Strengthened Alloy MA957 for Fast Reactor Applications

    SciTech Connect

    Hamilton, Margaret L.; Gelles, David S.; Lobsinger, Ralph J.; Johnson, Gerald D.; Brown, W. F.; Paxton, Michael M.; Puigh, Raymond J.; Eiholzer, Cheryl R.; Martinez, C.; Blotter, M. A.

    2000-02-28

    A significant amount of effort has been devoted to determining the properties and understanding the behavior of the alloy MA957 to define its potential usefulness as a cladding material in the fast breeder reactor program. The numerous characterization and fabrication studies that were conducted are documented in this report.

  13. Processing of two iron-chromium oxide dispersion strengthened steels by mechanical alloying

    SciTech Connect

    McKimpson, M.G.; Niemi, A.N. ); Gelles, D.S. )

    1989-04-01

    Two low activation ferritic ODS alloys have been manufactured, using mechanical alloying procedures, into extruded bar. The alloy compositions in weight percent are: Fe-14Cr-1.0Ti-0.5W-0.25Y{sub 2}O{sub 3} and Fe-9Cr-2.0W-0.3V-0.08C-0.25Y{sub 2}O{sub 3}. Dispersoid phase instability is indicated in the 9Cr carbon- containing alloy, but the 14Cr alloy appears to offer a novel material which may be suitable for first wall applications and warrants further study. 2 refs., 5 figs., 4 tabs.

  14. The development and evaluation of a cobalt base oxidation resistant dispersion strengthened alloy

    NASA Technical Reports Server (NTRS)

    Irani, K. K.

    1971-01-01

    The Co-18Cr-20Ni-4 Vol % ThO2 powders were prepared by a flash drying selective reduction process starting with an aqueous solution of metal salts and colloidal thoria. Powders were consolidated and extruded into rods with a minimum density of 99% of theoretical. Swaging and annealing studies were conducted to determine the conditions that would lead to a product with high stress-rupture strength. The best process yielded a stress-rupture life of 7.2 hours at 10 KSI (69 MN sq m and 2000 F (1094 C). The alloy recrystallized to a duplex (coarse-fine) structure and thus did not exhibit the desired strength of 3000 hours at 15 KSI (103.5MN/sq m and 2000 F (1094 C).

  15. Characterization of an oxide dispersion strengthened superalloy, MA-6000E, for turbine blade applications. [turbine blade

    NASA Technical Reports Server (NTRS)

    Kim, Y. G.; Merrick, H. F.

    1979-01-01

    Alloy MA 6000E was developed by the mechanical alloying process for turbine blade applications. The nominal composition of the experimental alloy is Ni-15CR-2Mo-4W-4.5Al- 2.5Ti-2Ta- .15Zr-.05C-.01B-1.1Y2O3. The 1000 hour rupture strength in the longitudinal direction is about 145 MPa at 1093 C and about 483 MPa at 760 C. The alloy displays normal three-stage creep behavior. Typically the creep elongation is 3.5% at 760 C and 2% at 1093 C. The alloy is notch ductile (K sub 1 = 3.5). The rupture properties of the alloy are not significantly degraded by thermal cycling or prior stress isothermal exposure. The alloy also has excellent longitudinal high and low cycle fatigue resistance. Limited testing indicates that MA 6000E posesses good off-axis mechanical properties. The transverse tensile elongation at 760 C is about 3%. The 100 hour transverse rupture strength is 331 MPa at 760 C and about 55 MPa at 1093 C.

  16. Dispersal

    USGS Publications Warehouse

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  17. Effect of solvents on the electro-optical switching of graphene oxide dispersions

    NASA Astrophysics Data System (ADS)

    Ahmad, Rana Tariq Mehmood; Hong, Seung-Ho; Shen, Tian-Zi; Masud, Aurangzeb Rashid; Song, Jang-Kun

    2016-06-01

    The electrical manipulation of graphene oxide (GO) alignment in aqueous dispersions is a useful technique with various applications. In particular, the electrical switching of GO particles can be used to devise optical birefringent liquid crystal displays. However, the electric switching of aqueous GO dispersions with a high ionic concentration requires driving voltages with high frequencies (˜10 kHz), which is a challenging limitation. We demonstrate that stable electro-optical switching can be achieved at low frequencies (100 Hz) using GO dispersions in organic solvents instead of water. The hydrodynamic flow of the solvent and the electrophoretic drift of the GO particles are hindered in the GO dispersions in organic solvents with lower dielectric constants. Moreover, the electro-optical performance of these GO dispersions is similar to the aqueous GO dispersions, despite the lower magnitude of the ionization ratio for the GO particle functional groups. These results are crucial for developing a liquid crystal display device using GO dispersions.

  18. Development of dispersion strengthened nickel-chromium alloy (Ni-Cr-ThO2) sheet for space shuttle vehicles, part 2

    NASA Technical Reports Server (NTRS)

    Klingler, L. J.; Weinberger, W. R.; Bailey, P. G.; Baranow, S.

    1972-01-01

    Two dispersion strengthened nickel base alloy systems were developed for use at temperatures up to 1204 C(2200 F); TD nickel chromium (TDNiCr) and TD nickel chromium aluminum (TDNiCrA1). They are considered candidate materials for use on the thermal protection systems of the space shuttle and for long term use in aircraft gas turbine engine applications. Improved manufacturing processes were developed for the fabrication of TDNiCr sheet and foil to specifications. Sheet rolling process studies and extrusion studies were made on two aluminum containing alloys: Ni-16%Cr-3.5%A1-2%ThO2 and Ni-16%Cr-5.0%A12%ThO2. Over 1600 kg.(3500 lb.) of plate, sheet, foil, bar and extrusion products were supplied to NASA Centers for technology studies.

  19. Superplastic forming and diffusion bonding of rapidly solidified, dispersion strengthened aluminum alloys for elevated temperature structural applications

    NASA Technical Reports Server (NTRS)

    Ting, E. Y.; Kennedy, J. R.

    1989-01-01

    Rapidly solidified alloys, based upon the Al-Fe-V-Si system and designed for elevated temperature applications, were evaluated for superplasticity and diffusion bonding behavior. Alloys with 8, 16, 27, and 36 volume percent silicide dispersoids were produced; dispersoid condition was varied by rolling at 300, 400, and 500 C (572, 752, and 932 F). Superplastic behavior was evaluated at strain rates from 1 x 10(exp -6)/s to 8.5/s at elevated temperatures. The results indicate that there was a significant increase in elongation at higher strain rates and at temperatures above 600 C (1112 F). However, the exposure of the alloys to temperatures greater than 600 C (1112 F) resulted in the coarsening of the strengthening dispersoid and the degradation of mechanical properties. Diffusion bonding was possible using low gas pressure at temperatures greater than 600 C (1112 F) which also resulted in degraded properties. The bonding of Al-Fe-V-Si alloys to 7475 aluminum alloy was performed at 516 C (960 F) without significant degradation in microstructure. Bond strengths equal to 90 percent that of the base metal shear strength were achieved. The mechanical properties and microstructural characteristics of the alloys were investigated.

  20. The mechanisms of dispersion strengthening and fracture in Al-based XD(tm) alloys, part 1

    NASA Technical Reports Server (NTRS)

    Aikin, R. M., Jr.

    1990-01-01

    The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength; the fracture toughness; and the fatigue crack growth rate of metal matrix composites of Al-4(pct)Cu-1.5(pct)Mg with TiB2 were examined. The influence of reinforcement volume fraction was also examined for pure aluminum with TiB2. Higher TiB2 volume fractions increased the tensile yield strength at both room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. Interparticle spacing appears to be the factor that controls the strength of these alloys, with the exact nature of the dependence relying on the nature of dislocation slip in the matrix (planar vs. diffuse). The isothermal aging response of the precipitation strengthened Al-4(pct)Cu-1.5(pct)Mg alloys was not accelerated by the presence of TiB2. Cold work prior to artificial aging created additional geometrically necessary dislocations which serve as heterogeneous nucleation sites leading to accelerated aging, a finer precipitate size, and an increase in the strength of the alloy.

  1. Formation of metallic and metal hydrous oxide dispersions

    NASA Technical Reports Server (NTRS)

    Matijevic, E.; Sapieszko, R. S.

    1979-01-01

    The formation, via hydrothermally induced precipitation from homogeneous solution, of a variety of well-defined dispersions of metallic and hydrous metal in the conditions under which the particles are produced (e.g., pH and composition of the growth medium, aging temperature, rate of heating, or degree of agitation) can be readily discerned by following changes in the mass, composition, and morphology of the final solid phase. The generation of colloidal dispersions in the absence of gravity convection or sedimentation effects may result in the appearance of morphological modifications not previously observed in terrestrially formed hydrosols.

  2. Oxidations of alkenes and lignin model compounds in aqueous dispersions

    SciTech Connect

    Zhu, Weiming.

    1991-01-01

    The objective was to develop methods to oxidize water-immiscible alkenes and lignin model compounds with polymer colloid supported transition metal catalysts. The oxidations of organic compounds were carried out in aqueous phase with several water-soluble oxidants and dioxygen. Cationic polymer latexes were prepared by the emulsion copolymerization of vinylbenzyl chloride, divinylbenzene, and vinyl octadecyl ether, or styrene, or n-decyl methacrylate, and the subsequent quaternization of copolymers with trimethylamine. The latex particles were 44 nm to 71 nm in diameter. The latex bound Mn porphyrin catalysts were formed with MnTSPP [TSPP = meso-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrin], which catalyzed the oxidation of cyclohexene, cycloocetene, allylbenzene, and 1-octene by sodium hypochlorite (NaOCl) and potassium peroxymonosulfate (KHSO[sub 5]). The latex bound porphyrin catalysts showed higher activity than MnTSPP in solution. Oxidations of 3,4-dimethoxybenzyl alcohol (DMBA), 4-hydroxy-3-methoxytoluene (HMT), and 3,4-dimethoxytoluene (DMT) were performed with either dioxygen or hydrogen peroxide and CoPcTS (PcTS = tetrasulfonatophthalocyanine), FePcTS, CuPcTS, NiPcTS, FeTCPP [TCPP = meso-tetrakis(4-carboxyphenyl)porphyrin], and MnTSPP. CoPcTS catalyzed the autoxidation of DMBA and HMT at 70-85[degrees]C and pH [ge] 8. All catalysts were active for the oxidation of DMBA, HMT, and DMT with H[sub 2]O[sub 2]. Aqueous solutions of KHSO[sub 5] oxidized water-immiscible alkenes at room temperature in the absence of organic solvent. The acidic pH [le] 1.7 solutions of commercial 2KHSO[sub 5][center dot]K[sub 2]SO[sub 4] in water produced diols from all reactive alkenes except cyclooctene. Adjustment of initial pH to [ge]6.7 with NaHCO[sub 3] enabled selective epoxidations.

  3. Formation of zinc oxide films using submicron zinc particle dispersions

    SciTech Connect

    Rajachidambaram, Meena Suhanya; Varga, Tamas; Kovarik, Libor; Sanghavi, Rahul P.; Shutthanandan, V.; Thevuthasan, Suntharampillai; Han, Seungyeol; Chang, Chih-hung; Herman, Gregory S.

    2012-07-27

    The thermal oxidation of submicron metallic Zn particles was studied as a method to form nanostructured ZnO films. The particles used for this work were characterized by electron microscopy, x-ray diffraction and thermal analysis to evaluate the Zn-ZnO core shell structure, surface morphology, and oxidation characteristics. Significant nanostructural changes were observed for films annealed to 400 °C or higher, where nanoflakes, nanoribbons, nanoneedles and nanorods were formed as a result of stress induced fractures arising in the ZnO outer shell due to differential thermal expansion between the metallic Zn core and the ZnO shell. Mass transport occurs through these defects due to the high vapor pressure for metallic Zn at temperatures above 230 °C, whereupon the Zn vapor rapidly oxidizes in air to form the ZnO nanostructures. The Zn particles were also incorporated into zinc indium oxide precursor solutions to form thin film transistor test structures to evaluate the potential of forming nanostructured field effect sensors using simple solution processing.

  4. Dispersion engineering of high-Q silicon microresonators via thermal oxidation

    SciTech Connect

    Jiang, Wei C.; Zhang, Jidong; Usechak, Nicholas G.; Lin, Qiang

    2014-07-21

    We propose and demonstrate a convenient and sensitive technique for precise engineering of group-velocity dispersion in high-Q silicon microresonators. By accurately controlling the surface-oxidation thickness of silicon microdisk resonators, we are able to precisely manage the zero-dispersion wavelength, while simultaneously further improving the high optical quality of our devices, with the optical Q close to a million. The demonstrated dispersion management allows us to achieve parametric generation with precisely engineerable emission wavelengths, which shows great potential for application in integrated silicon nonlinear and quantum photonics.

  5. Synthesis of micro-dispersed zirconium oxide for glass manufacturing

    NASA Astrophysics Data System (ADS)

    Goncharuk, V.; Starodubtsev, P.; Maslennikova, I.

    2016-01-01

    A rather simple and original method for processing of zirconium-containing raw material form Algoma deposit (Khabarovsk region, Russia) was suggested, which comprised fluorination of the initial sample with a diluted HF solution followed by the thermal treatment of fluorination products and pyrohydrolysis of zirconium tetrafluoride. Water vapors obtained by hydrogen and oxygen burning in a hydrogen torch as well as by simple evaporation were used for pyrohydrolysis. The feed rate of the water and its temperature were regulated. The temperature of water vapors reached 800-1200 °C. Zirconium dioxide with a purity of 99.97% or more and a dispersity of 0.1 gm or less was synthesized.

  6. Oxidation of depleted uranium penetrators and aerosol dispersal at high temperatures

    SciTech Connect

    Elder, J.C.; Tinkle, M.C.

    1980-12-01

    Aerosols dispersed from depleted uranium penetrators exposed to air and air-CO/sub 2/ mixtures at temperatures ranging from 500 to 1000/sup 0/C for 2- or 4-h periods were characterized. These experiments indicated dispersal of low concentrations of aerosols in the respirable size range (typically <10/sup -3/% of penetrator mass at 223 cm/s (5 mph) windspeed). Oxidation was maximum at 700/sup 0/C in air and 800/sup 0/C in 50% air-50% CO/sub 2/, indicating some self-protection developed at higher temperatures. No evidence of self-sustained burning was observed, although complete oxidation can be expected in fires significantly exceeding 4 h, the longest exposure of this series. An outdoor burning experiment using 10 batches of pine wood and paper packing material as fuel caused the highest oxidation rate, probably accelerated by disruption of the oxide layer accompanying broad temperature fluctuation as each fuel batch was added.

  7. Binary Synergy Strengthening and Toughening of Bio-Inspired Nacre-like Graphene Oxide/Sodium Alginate Composite Paper.

    PubMed

    Chen, Ke; Shi, Bin; Yue, Yonghai; Qi, Juanjuan; Guo, Lin

    2015-08-25

    A crucial requirement for most engineering materials is the excellent balance of strength and toughness. By mimicking the hybrid hierarchical structure in nacre, a kind of nacre-like paper based on binary hybrid graphene oxide (GO)/sodium alginate (SA) building blocks has been successfully fabricated. Systematic evaluation for the mechanical property in different (dry/wet) environment/after thermal annealing shows a perfect combination of high strength and toughness. Both of the parameters are nearly many-times higher than those of similar materials because of the synergistic strengthening/toughening enhancement from the binary GO/SA hybrids. The successful fabrication route offers an excellent approach to design advanced strong integrated nacre-like composite materials, which can be applied in tissue engineering, protection, aerospace, and permeable membranes for separation and delivery. PMID:26167700

  8. Facile preparation of highly-dispersed cobalt-silicon mixed oxide nanosphere and its catalytic application in cyclohexane selective oxidation

    PubMed Central

    2011-01-01

    Highly dispersed cobalt-silicon mixed oxide [Co-SiO2] nanosphere was successfully prepared with a modified reverse-phase microemulsion method. This material was characterized in detail by X-ray diffraction, transmission electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance spectra, X-ray absorption spectroscopy near-edge structure, and N2 adsorption-desorption measurements. High valence state cobalt could be easily obtained without calcination, which is fascinating for the catalytic application for its strong oxidation ability. In the selective oxidation of cyclohexane, Co-SiO2 acted as an efficient catalyst, and good activity could be obtained under mild conditions. PMID:22067075

  9. Minimizing Oxidation and Stable Nanoscale Dispersion Improves the Biocompatibility of Graphene in the Lung

    PubMed Central

    Duch, Matthew C.; Scott Budinger, G. R.; Liang, Yu Teng; Soberanes, Saul; Urich, Daniela; Chiarella, Sergio E.; Campochiaro, Laura A; Gonzalez, Angel; Chandel, Navdeep S.; Hersam, Mark C.; Mutlu, Gökhan M.

    2011-01-01

    To facilitate the proposed use of graphene and its derivative graphene oxide (GO) in widespread applications, we explored strategies that improve the biocompatibility of graphene nanomaterials in the lung. In particular, solutions of aggregated graphene, Pluronic dispersed graphene, and GO were administered directly into the lungs of mice. The introduction of GO resulted in severe and persistent lung injury. Furthermore, in cells, GO increased the rate of mitochondrial respiration and the generation of reactive oxygen species, activating inflammatory and apoptotic pathways. In contrast, this toxicity was significantly reduced in the case of pristine graphene after liquid phase exfoliation, and was further minimized when the unoxidized graphene was well-dispersed with the block copolymer Pluronic. Our results demonstrate that the covalent oxidation of graphene is a major contributor to its pulmonary toxicity and suggest that dispersion of pristine graphene in Pluronic provides a pathway for the safe handling and potential biomedical application of two-dimensional carbon nanomaterials. PMID:22023654

  10. Well-Dispersed and Size-Controlled Supported Metal Oxide Nanoparticles Derived from MOF Composites and Further Application in Catalysis.

    PubMed

    Liu, Hong; Zhang, Suoying; Liu, Yayuan; Yang, Zhuhong; Feng, Xin; Lu, Xiaohua; Huo, Fengwei

    2015-07-01

    Supported metal oxide nanoparticles are important in heterogeneous catalysis; however, the ability to tailor their size, structure, and dispersion remains a challenge. A strategy to achieve well-dispersed and size-controlled supported metal oxides through the manageable growth of a metal organic framework (Cu-BTC) on TiO2 followed by pyrolysis is described.

  11. Magnetic Properties of Core/Shell Structured Iron/Iron-oxide Nanoparticles Dispersed in Polymer Matrix

    NASA Astrophysics Data System (ADS)

    Nemati Porshokouh, Zohreh; Khurshid, Hafsa; Phan, Manh-Huong; Srikanth, Hariharan

    2014-03-01

    Iron-based nanoparticles (NPs) show interesting magnetic properties for a wide range of applications; however rapid oxidation of iron limits its practical use. Protecting iron with a thin layer of iron-oxide is a possible way to prevent oxidation, forming core/shell (CS) iron/iron-oxide. Due to the different diffusivity rates of the two materials, a gap appears between the core and shell after a period of time (Kirkendall effect), degrading the magnetic properties of the sample. We minimize the Kirkendall effect while retaining good magnetic properties of ~12.5 nm CS iron/iron-oxide NPs by dispersing them into a polymer matrix. Magnetic measurements reveal that after a period of 3 months the blocking temperature (TB) of as-made CS NPs decreases from 107 K to 90 K. The change in TB marks the formation of a gap between the core and shell, which is also evident from HRTEM studies. By contrast, NPs dispersed in RP show no change in TB over the same time period. We repeated experiments with ~10.5 nm CS NPs and the results are consistent. Our study shows the importance of dispersing CS NPs in polymers to preserve desirable magnetic properties for practical applications, ranging from RF sensors and microwave devices to bioengineering.

  12. Highly Dispersible and Stable Anionic Boron Cluster-Graphene Oxide Nanohybrids.

    PubMed

    Cabrera-González, Justo; Cabana, Laura; Ballesteros, Belén; Tobias, Gerard; Núñez, Rosario

    2016-04-01

    An efficient process to produce boron cluster-graphene oxide nanohybrids that are highly dispersible in water and organic solvents is established for the first time. Dispersions of these nanohybrid materials in water were extraordinarily stable after one month. Characterization of hybrids after grafting of appropriate cobaltabisdicarbollide and closo-dodecaborate derivatives onto the surface of graphene oxide (GO) was done by FT-IR, XPS, and UV/Vis. Thermogravimetric analysis (TGA) clearly shows a higher thermal stability for the modified-GO nanohybrids compared to the parent GO. Of particular note, elemental mapping by energy-filtered transmission electron microscopy (EFTEM) reveals that a uniform decoration of the graphene oxide surface with the boron clusters is achieved under the reported conditions. Therefore, the resulting nanohybrid systems show exceptional physico-chemical and thermal properties, paving the way for an enhanced processability and further expanding the range of application for graphene-based materials.

  13. Use of Nanofibers to Strengthen Hydrogels of Silica, Other Oxides, and Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Capadona, Lynn A.; Hurwitz, Frances; Vivod, Stephanie L.; Lake, Max

    2010-01-01

    Research has shown that including up to 5 percent w/w carbon nanofibers in a silica backbone of polymer crosslinked aerogels improves its strength, tripling compressive modulus and increasing tensile stress-at-break five-fold with no increase in density or decrease in porosity. In addition, the initial silica hydrogels, which are produced as a first step in manufacturing the aerogels, can be quite fragile and difficult to handle before cross-linking. The addition of the carbon nanofiber also improves the strength of the initial hydrogels before cross-linking, improving the manufacturing process. This can also be extended to other oxide aerogels, such as alumina or aluminosilicates, and other nanofiber types, such as silicon carbide.

  14. Studies in treatment of disperse dye waste: Membrane-wet oxidation process

    SciTech Connect

    Dhale, A.D.; Mahajani, V.V.

    2000-07-01

    An integrated process, membrane-wet oxidation (MEMWO) has been demonstrated to treat the disperse dye bath waste. The dye bath waste stream containing azo class disperse dye CL 79, was studied to demonstrate the process. A nanofiltration membrane (MPT 30) showed > 99% color and 97% chemical oxygen demand (COD) rejection of dye compound. The concentrate was then treated by wet oxidation (WO) process. WO of dye was studied in the range of 160--225 C and oxygen partial pressure 0.69--1.38 MPa. A homogeneous copper sulfate was found to be a suitable catalyst to effectively destroy the dye as well as the real waste. While non catalytic WO of dye achieved 75% reduction in COD during 120 min with 99% color destruction, the catalytic WO showed about 90% reduction in COD. The performance of WO of actual waste stream was comparable with that of pure dye molecule.

  15. Zirconium doped nano-dispersed oxides of Fe, Al and Zn for destruction of warfare agents

    SciTech Connect

    Stengl, Vaclav; Houskova, Vendula; Bakardjieva, Snejana; Murafa, Nataliya; Marikova, Monika; Oplustil, Frantisek; Nemec, Tomas

    2010-11-15

    Zirconium doped nano dispersive oxides of Fe, Al and Zn were prepared by a homogeneous hydrolysis of the respective sulfate salts with urea in aqueous solutions. Synthesized metal oxide hydroxides were characterized using Brunauer-Emmett-Teller (BET) surface area and Barrett-Joiner-Halenda porosity (BJH), X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). These oxides were taken for an experimental evaluation of their reactivity with sulfur mustard (HD or bis(2-chloroethyl)sulfide), soman (GD or (3,3'-Dimethylbutan-2-yl)-methylphosphonofluoridate) and VX agent (S-[2-(diisopropylamino)ethyl]-O-ethyl-methylphosphonothionate). The presence of Zr{sup 4+} dopant can increase both the surface area and the surface hydroxylation of the resulting doped oxides, decreases their crystallites' sizes thereby it may contribute in enabling the substrate adsorption at the oxide surface thus it can accelerate the rate of degradation of warfare agents. Addition of Zr{sup 4+} converts the product of the reaction of ferric sulphate with urea from ferrihydrite to goethite. We found out that doped oxo-hydroxides Zr-FeO(OH) - being prepared by a homogeneous hydrolysis of ferric and zirconium oxo-sulfates mixture in aqueous solutions - exhibit a comparatively higher degradation activity towards chemical warfare agents (CWAs). Degradation of soman or VX agent on Zr-doped FeO(OH) containing ca. 8.3 wt.% of zirconium proceeded to completion within 30 min.

  16. Iron oxide nanoparticle-mediated hyperthermia stimulates dispersal in bacterial biofilms and enhances antibiotic efficacy

    PubMed Central

    Nguyen, Thuy-Khanh; Duong, Hien T. T.; Selvanayagam, Ramona; Boyer, Cyrille; Barraud, Nicolas

    2015-01-01

    The dispersal phase that completes the biofilm lifecycle is of particular interest for its potential to remove recalcitrant, antimicrobial tolerant biofilm infections. Here we found that temperature is a cue for biofilm dispersal and a rise by 5 °C or more can induce the detachment of Pseudomonas aeruginosa biofilms. Temperature upshifts were found to decrease biofilm biomass and increase the number of viable freely suspended cells. The dispersal response appeared to involve the secondary messenger cyclic di-GMP, which is central to a genetic network governing motile to sessile transitions in bacteria. Furthermore, we used poly((oligo(ethylene glycol) methyl ether acrylate)-block-poly(monoacryloxy ethyl phosphate)-stabilized iron oxide nanoparticles (POEGA-b-PMAEP@IONPs) to induce local hyperthermia in established biofilms upon exposure to a magnetic field. POEGA-b-PMAEP@IONPs were non-toxic to bacteria and when heated induced the detachment of biofilm cells. Finally, combined treatments of POEGA-b-PMAEP@IONPs and the antibiotic gentamicin reduced by 2-log the number of colony-forming units in both biofilm and planktonic phases after 20 min, which represent a 3.2- and 4.1-fold increase in the efficacy against planktonic and biofilm cells, respectively, compared to gentamicin alone. The use of iron oxide nanoparticles to disperse biofilms may find broad applications across a range of clinical and industrial settings. PMID:26681339

  17. Structure-dependent interatomic dispersion coefficients in oxides with maximally localized Wannier functions

    NASA Astrophysics Data System (ADS)

    Sukhomlinov, Sergey V.; Smirnov, Konstantin S.

    2012-11-01

    The interatomic C6 dispersion coefficients in crystalline and amorphous SiO2 and ZrO2 structures were obtained with the approach proposed by Silvestrelli (2008 Phys. Rev. Lett. 100 053002) and based on the use of maximally localized Wannier functions (MLWFs) for partitioning the electron density. Localization of Wannier functions close to the nuclei in oxide systems makes it possible to assign the MLWFs to the atoms in an unambiguous way and then to compute the C6 coefficients in an atom pairwise manner. A modification of the method is suggested in which the MLWFs are condensed to effective orbitals centred on the atoms and parameters of these effective orbitals are used for computing the interatomic dispersion coefficients. The obtained values of the dispersion coefficients were found to vary not only from one oxide to another, but also between different modifications of the same compound. The oxygen-oxygen coefficient {C}_{6}^{{OO}} reveals the largest variation and its value in ZrO2 structures is twice as large as that in SiO2 ones. Atomic characteristics obtained in the frame of the effective orbital method, such as the self-atom dispersion coefficient, and the oxide ion polarizability were found to correlate with the metal-oxygen bond length and the oxygen coordination number in the systems. This behaviour is attributed to the confinement of electrons by the electrostatic potential. The values of the coefficient and of the polarizability were related to charges of the oxygen atoms. In all studied systems the oxygen atoms having larger absolute values of charge were found to be less polarizable because of a stronger confinement effect. The obtained results can be used in the development of polarizable force fields for the atomistic modelling of oxide materials.

  18. Surface plasmon dispersion analysis in the metal-oxide-metal tunnel diode

    NASA Technical Reports Server (NTRS)

    Donohue, J. F.; Wang, E. Y.

    1987-01-01

    A detailed model of surface plasmon dispersion in the metal-oxide-metal tunnel diode is presented in order to clarify the spectral emission from this diode. The model predicts the location of the spectral peaks and the emission between the peaks by considering the effects of retardation on the surface plasmon. A nonradiative mode is found to play a major role in the transition from the visible to UV peaks in the diode spectra.

  19. Structure-dependent interatomic dispersion coefficients in oxides with maximally localized Wannier functions.

    PubMed

    Sukhomlinov, Sergey V; Smirnov, Konstantin S

    2012-11-28

    The interatomic C(6) dispersion coefficients in crystalline and amorphous SiO(2) and ZrO(2) structures were obtained with the approach proposed by Silvestrelli (2008 Phys. Rev. Lett. 100 053002) and based on the use of maximally localized Wannier functions (MLWFs) for partitioning the electron density. Localization of Wannier functions close to the nuclei in oxide systems makes it possible to assign the MLWFs to the atoms in an unambiguous way and then to compute the C(6) coefficients in an atom pairwise manner. A modification of the method is suggested in which the MLWFs are condensed to effective orbitals centred on the atoms and parameters of these effective orbitals are used for computing the interatomic dispersion coefficients. The obtained values of the dispersion coefficients were found to vary not only from one oxide to another, but also between different modifications of the same compound. The oxygen-oxygen coefficient C6(OO) reveals the largest variation and its value in ZrO(2) structures is twice as large as that in SiO(2) ones. Atomic characteristics obtained in the frame of the effective orbital method, such as the self-atom dispersion coefficient, and the oxide ion polarizability were found to correlate with the metal-oxygen bond length and the oxygen coordination number in the systems. This behaviour is attributed to the confinement of electrons by the electrostatic potential. The values of the coefficient and of the polarizability were related to charges of the oxygen atoms. In all studied systems the oxygen atoms having larger absolute values of charge were found to be less polarizable because of a stronger confinement effect. The obtained results can be used in the development of polarizable force fields for the atomistic modelling of oxide materials.

  20. Covalent modification of graphite oxide with acetic anhydride to enhance dispersibility in organic solvents

    NASA Astrophysics Data System (ADS)

    Li, Jingjing; Yang, Anwei; Zhang, Chen; Zhang, Lei; Sun, Feifei; Ma, Ning

    2016-05-01

    Graphite oxide (GO) was modified by acetic anhydride via a catalyzed ring-opening reaction of the attached epoxy groups at very mild condition. The dispersion of the modified GO is thus largely imporved in many organic solvents and the highest GO concentration reaches 2.0mg/mL in alkyl(aryl) chlorides, ethers, alcohols and cyclohexane, which is amongst the highest value for GO in organics.

  1. Thermally induced all-optical inverter and dynamic hysteresis loops in graphene oxide dispersions.

    PubMed

    Melle, Sonia; Calderón, Oscar G; Egatz-Gómez, Ana; Cabrera-Granado, E; Carreño, F; Antón, M A

    2015-11-01

    We experimentally study the temporal dynamics of amplitude-modulated laser beams propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. Nonlinear refraction induced in the sample by thermal effects leads to both phase reversing of the transmitted signals and dynamic hysteresis in the input-output power curves. A theoretical model including beam propagation and thermal lensing dynamics reproduces the experimental findings. PMID:26560566

  2. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    PubMed Central

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  3. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    NASA Astrophysics Data System (ADS)

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-08-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB.

  4. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide.

    PubMed

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 (o)C) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB. PMID:27555475

  5. Highly dispersed green silicate and oxide pigments precipitated from model systems of postgalvanic waste.

    PubMed

    Klapiszewska, Beata; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

    2003-10-15

    A procedure was worked out to obtain highly dispersed green silicate and oxide pigments precipitated from postgalvanic waste. The highly dispersed chromium(III) silicates and oxides were produced from the waste, originating from chromium plating, by reduction of Cr(VI) to Cr(III) employing various reducing agents. All the reductions were conducted in an acidic medium. Solutions of Cr(III), obtained in reducing processes, were employed to precipitate silicate pigments (using sodium metasilicate solution and containing mainly chromium(III) silicates) and oxide pigments (using sodium hydroxide and containing chromium(III) oxides). The precipitated silicates and oxides were subjected to a comprehensive physicochemical analysis (estimating bulk density, capacities to absorb water, dibutyl phthalate, paraffin oil, particle size distribution, and morphology of particle surface). Precipitation process (its parameters) and heating of the reactive mixture exerts a significant effect on the principal physicochemical properties of the pigments. The heating significantly affects first of all color shade of the obtained silicate and oxide pigments as well as their dispersion. Coprecipitated chromium(III) and iron(III) silicates exhibit a brownish color and a reasonably uniform character. Apart from primary agglomerates (in the range of 414-717 nm), they contain small amounts of secondary agglomerates (in the range of 4154-6445 nm). Best physicochemical parameters have been demonstrated by chromium pigments which have been precipitated from chromium solutions reduced using hydrogen peroxide. Chromium(III) oxides deserve particular distinction since their structure includes primary particles, primary agglomerates but is completely free of secondary agglomerates. The pigments manifest a brightly green color and a low capacity to absorb water (100 cm3 x 100 g(-1)). Application of hydrophobicity-inducing agents in the course of precipitation has corrected physicochemical parameters

  6. Dispersal of human and plant pathogens biofilms via nitric oxide donors at 4 °C.

    PubMed

    Marvasi, Massimiliano; Durie, Ian A; Henríquez, Tania; Satkute, Aiste; Matuszewska, Marta; Prado, Raphael Carvalho

    2016-12-01

    Recent studies suggest that nitric oxide donors capable of manipulating nitric oxide-mediated signaling in bacteria could induce dispersal of biofilms. Encased in extracellular polymeric substances, human and plant pathogens within biofilms are significantly more resistant to sanitizers. This is particularly a problem in refrigerated environments where food is processed. In an exercise aimed to study the potential of nitric oxide donors as biofilm dispersal in refrigerated conditions, we compared the ability of different nitric oxide donors (SNAP, NO-aspirin and Noc-5) to dislodge biofilms formed by foodborne, human and plant pathogens treated at 4 °C. The donors SNAP and Noc-5 were efficient in dispersing biofilms formed by Salmonella enterica, pathogenic Escherichia coli and Listeria innocua. The biomasses were decreased up to 30 % when compared with the untreated controls. When the plant pathogens Pectobacterium sp. and Xanthomonas sp. were tested the dispersion was mainly limited to Pectobacterium carotovorum biofilms, decreasing up to 15 % after exposure to molsidomine. Finally, the association of selected nitric oxide donors with sanitizers (DiQuat, H2O2, peracetic acid and PhenoTek II) was effective in dispersing biofilms. The best dispersal was achieved by pre-treating P. carotovorum with molsidomine and then peracetic acid. The synergistic effect was estimated up to ~35 % in dispersal when compared with peracetic acid alone. The association of nitric oxide donors with sanitizers could provide a foundation for an improved sanitization procedure for cleaning refrigerate environments.

  7. Dispersal of human and plant pathogens biofilms via nitric oxide donors at 4 °C.

    PubMed

    Marvasi, Massimiliano; Durie, Ian A; Henríquez, Tania; Satkute, Aiste; Matuszewska, Marta; Prado, Raphael Carvalho

    2016-12-01

    Recent studies suggest that nitric oxide donors capable of manipulating nitric oxide-mediated signaling in bacteria could induce dispersal of biofilms. Encased in extracellular polymeric substances, human and plant pathogens within biofilms are significantly more resistant to sanitizers. This is particularly a problem in refrigerated environments where food is processed. In an exercise aimed to study the potential of nitric oxide donors as biofilm dispersal in refrigerated conditions, we compared the ability of different nitric oxide donors (SNAP, NO-aspirin and Noc-5) to dislodge biofilms formed by foodborne, human and plant pathogens treated at 4 °C. The donors SNAP and Noc-5 were efficient in dispersing biofilms formed by Salmonella enterica, pathogenic Escherichia coli and Listeria innocua. The biomasses were decreased up to 30 % when compared with the untreated controls. When the plant pathogens Pectobacterium sp. and Xanthomonas sp. were tested the dispersion was mainly limited to Pectobacterium carotovorum biofilms, decreasing up to 15 % after exposure to molsidomine. Finally, the association of selected nitric oxide donors with sanitizers (DiQuat, H2O2, peracetic acid and PhenoTek II) was effective in dispersing biofilms. The best dispersal was achieved by pre-treating P. carotovorum with molsidomine and then peracetic acid. The synergistic effect was estimated up to ~35 % in dispersal when compared with peracetic acid alone. The association of nitric oxide donors with sanitizers could provide a foundation for an improved sanitization procedure for cleaning refrigerate environments. PMID:27457245

  8. Possibilities of practical usage of dispersed aluminim oxidation by liquid water

    NASA Astrophysics Data System (ADS)

    Larichev, M. N.; Laricheva, O. O.; Shaitura, N. S.; Shkolnikov, E. I.

    2012-12-01

    The goal of this work is to show the possibility of practical usage of the environmentally pure oxidation process of preliminarily dispersed aluminum (aluminum powders of the ASD or PAD grade according to TU (Technical Specifications) 48-5-226-87, which are serially produced in industry) with liquid water in order to obtain gaseous hydrogen in volumes sufficient to provide the operation of energizers based on airhydrogen fuel cells (AHFC) for portable and stationary devices (up to 3 kW). It is shown that the synthesis of aluminum oxides-hydroxides with the specified phase and chemical compositions as well as the particle shape and size can be provided simultaneously with producing commercial hydrogen. The practical usage of hydrogen, which is formed in the oxidation reaction of metallic aluminum with liquid water at pressures close to atmospheric (particularly, to service AHFCs), requires reaction intensification to increase the oxidation rate of aluminum. In this work, we considered the aspects of practical implementation of thermal, ultrasonic, and chemical activation as well as their combinations for this purpose. As the chemical activator of oxidation, we used the additives of calcium oxide (<5% of the mass of oxidized aluminum). Application of each activation method affects the phase and chemical compositions as well as the structure of formed aluminum hydroxides, which provides the possibility of their reproducible production. Thus, simultaneously with the production of commercial hydrogen, solid oxidation products satisfying the needs of industry in aluminum oxides and having the specified composition, purity, and particle shape and size can be synthesized. The acquired experimental results and elements of the design of specially developed industrial apparatuses, which were used when performing this work, can be applied when designing the model of the hydrogen generator—the prototype of the hydrogen generator for portable and stationary devices or devices

  9. Characterization and dispersibility of improved thermally stable amide functionalized graphene oxide

    SciTech Connect

    Rani, Sumita; Kumar, Mukesh; Kumar, Rajiv; Kumar, Dinesh; Sharma, Sumit; Singh, Gulshan

    2014-12-15

    Graphical abstract: Improved thermal stability and surface study of amide functionalized graphene oxide. - Highlights: • Amide functionalized graphene oxides (AGOs) were synthesized from aniline, 2-aminothiazole and 2-aminopyrimidine. • Achieved enhancement in thermal stability of AGOs as compare to GO. • AGOs are found to be highly dispersible in water, DMSO and DMF. • Dispersibility is stable for more than two and half months. - Abstract: Amidation of graphene oxide (GO) with aniline, 2-aminothiazole and 2-aminopyrimidine results in the synthesis of amide functionalized graphene oxides (AGOs). Scanning electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), UV–vis and Raman spectroscopy were used to investigate the properties of AGOs. It was found that, contrary to GO, AGOs are soluble in water, dimethyl sulfoxide, dimethylformamide and can be stabilized for months. TGA of AGOs shows the major weight loss above 670 °C as compared to GO in which significant weight loss occurs near 200 °C. Thus AGOs show strong improvement in thermal properties.

  10. Synthesis, Characterization, and Catalytic Function of Novel Highly Dispersed Tungsten Oxide Catalysts on Mesoporous Silica

    SciTech Connect

    Herrera, Jose E.; Kwak, Ja Hun; Hu, Jian Zhi; Wang, Yong; Peden, Charles HF; Macht, Josef; Iglesia, Enrique

    2006-04-01

    The physical and chemical properties of tungsten oxide supported on SBA-15 mesoporous silica prepared by a controlled grafting process through atomic layer deposition (ALD) were studied using complementary characterization methods. X-ray diffraction, optical absorption and transmission electron microscopy showed that tungsten oxide species are highly dispersed on SBA-15 surfaces, even at 30 wt.% WOx contents (surface density: 1.33 WOx/nm2). ALD methods led to samples with much better thermal stability than those prepared via impregnation. Dehydration reactions of 2-butanol and methanol dehydration were used as probe reactions. Differences in reaction rates between the samples prepared by ALD and conventional impregnation reflect the sintering resistance of catalysts prepared by ALD. Notably, temperature programmed oxidation of spent catalysts showed that carbon formation was not responsible for the different dehydration rates in samples prepared by ALD and impregnation..

  11. Single-step synthesis of graphene quantum dots by femtosecond laser ablation of graphene oxide dispersions.

    PubMed

    Russo, Paola; Liang, Robert; Jabari, Elahe; Marzbanrad, Ehsan; Toyserkani, Ehsan; Zhou, Y Norman

    2016-04-28

    In the last few years, graphene quantum dots (GQDs) have attracted the attention of many research groups for their outstanding properties, which include low toxicity, chemical stability and photoluminescence. One of the challenges of GQD synthesis is finding a single-step, cheap and sustainable approach for synthesizing these promising nanomaterials. In this study, we demonstrate that femtosecond laser ablation of graphene oxide (GO) dispersions could be employed as a facile and environmentally friendly synthesis method for GQDs. With the proper control of laser ablation parameters, such as ablation time and laser power, it is possible to produce GQDs with average sizes of 2-5 nm, emitting a blue luminescence at 410 nm. We tested the feasibility of the synthesized GQDs as materials for electronic devices by aerosol-jet printing of an ink that is a mixture of water dispersion of laser synthesized GQDs and silver nanoparticle dispersion, which resulted in lower resistivity of the final printed patterns. Preliminary results showed that femtosecond laser synthesized GQDs can be mixed with silver nanoparticle dispersion to fabricate a hybrid material, which can be employed in printing electronic devices by either printing patterns that are more conductive and/or reducing costs of the ink by decreasing the concentration of silver nanoparticles (AgNPs) in the ink. PMID:27071944

  12. Effect of Acid Oxidation on the Dispersion Property of Multiwalled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Goh, P. S.; Ismail, A. F.; Aziz, M.

    2009-06-01

    A means of dispersion of multiwalled carbon nanotube (MWCNT) via mixed acid (HNO3 and H2SO4) oxidation with different treatment durations was investigated through the solubility study of the treated carbon nanotubes in some common solvents. Fourier transformed infrared (FTIR) characterization of the reaction products revealed that the surface of MWCNTs was successfully functionalized with surface acidic groups. The acid-base titration demonstrated that the amount of surface acidic groups increased in parallel with the refluxing duration. The acid modified MWCNTs were found to be well dispersed in polar solvents, such as ethanol and water due to the presence of the hydrophilic acid functional groups on the surface of raw MWCNTs. Such chemical modification of carbon nanotube properties will pave the way towards the realistic applications in the nanotechnology world.

  13. Ductility Enhancement of Molybdenum Phase by Nano-sizedd Oxide Dispersions

    SciTech Connect

    Bruce Kang

    2008-07-31

    The present research is focused on ductility enhancement of molybdenum (Mo) alloys by adding nano-sized oxide particles to the alloy system. The research approach includes: (1) determination of microscopic mechanisms responsible for the macroscopic ductility enhancement effects through atomistic modeling of the metal-ceramic interface; (2) subsequent computer simulation-aided optimization of composition and nanoparticle size of the dispersion for improved performance; (3) synthesis and characterization of nanoparticle dispersion following the guidance from atomistic computational modeling analyses (e.g., by processing a small sample of Mo alloy for evaluation); and (4) experimental testing of the mechanical properties to determine optimal ductility enhancement.Through atomistic modeling and electronic structure analysis using full-potential linearized muffin-tin orbital (FP-LMTO) techniques, research to date has been performed on a number of selected chromium (Cr) systems containing nitrogen (N) and/or magnesium oxide (MgO) impurities. The emphasis has been on determining the properties of the valence electrons and the characteristics of the chemical bonds they formed. It was found that the brittle/ductile behavior of this transitional metal system is controlled by the relative population of valence charges: bonds formed by s valence electrons yield metallic, ductile behavior, whereas bonds formed by d valence electrons lead to covalent, brittle behavior. The presence of valence bands from impurities also affects the metal bonding, thereby explaining the detrimental and beneficial effects induced by the inclusion of N impurities and MgO dispersions. These understandings are useful for optimizing ductility enhancement effects on the dispersion materials.

  14. The influence of fabrication procedure on the void swelling of an oxide dispersion strengthened ferritic alloy in a HVEM

    NASA Astrophysics Data System (ADS)

    Snykers, M.; Biermans, F.; Cornelis, J.

    The influence of changes in the fabrication procedure of ferritic alloys with compositions Fe-13Cr-Ti-Mo-TiO 2 on the swelling behaviour are investigated. The fabrication procedures are: casting, powder metallurgy 3- milling in air and powder metallurgy 3- milling in argon. No difference is found for the results obtained for the materials fabricated by casting and by powder metallurgy 3- milling in air. Slightly different results are obtained for the material fabricated by powder metallurgy 3- milling in argon. This material contains argon in solution in the matrix, which causes a small shift of the peak swelling temperature and of the peak swelling helium concentration for tests carried out at 450°C. The overall swelling of this material is the lowest due to the small grain size and to the high density of inclusions.

  15. Precipitation-Redispersion of Cerium Oxide Nanoparticles with Poly(acrylic acid): Toward Stable Dispersions

    SciTech Connect

    Sehgal,A.; Lalatonne, Y.; Berret, J.; Morvan, M.

    2005-01-01

    We exploit a precipitation-redispersion mechanism for complexation of short chain polyelectrolytes with cerium oxide nanoparticles to extend their stability ranges. As synthesized, cerium oxide sols at pH 1.4 consist of monodisperse cationic nanocrystalline particles having a hydrodynamic diameter of 10 nm and a molecular weight of 400 000 g mol{sup -1}. We show that short chain uncharged poly(acrylic acid) at low pH when added to a cerium oxide sols leads to macroscopic precipitation. As the pH is increased, the solution spontaneously redisperses into a clear solution of single particles with an anionic poly(acrylic acid) corona. The structure and dynamics of cerium oxide nanosols and their hybrid polymer-inorganic complexes in solution are investigated by static and dynamic light scattering, X-ray scattering, and chemical analysis. Quantitative analysis of the redispersed sol gives rise to an estimate of 40-50 polymer chains per particle for stable suspension. This amount represents 20% of the mass of the polymer-nanoparticle complexes. This complexation adds utility to the otherwise unstable cerium oxide dispersions by extending the range of stability of the sols in terms of pH, ionic strength, and concentration.

  16. Viscosity of copper oxide nanoparticles dispersed in ethylene glycol and water mixture

    SciTech Connect

    Namburu, Praveen K.; Kulkarni, Devdatta P.; Das, Debendra K.; Misra, Debasmita

    2007-11-15

    Nanofluids are new kinds of fluids engineered by dispersing nanoparticles in base fluids. This paper presents an experimental investigation of rheological properties of copper oxide nanoparticles suspended in 60:40 (by weight) ethylene glycol and water mixture. Nanofluids of particle volume percentage ranging from 0% to 6.12% were tested. The experiments were carried over temperatures ranging from -35 C to 50 C to demonstrate their applicability in cold regions. For the particle volume concentrations tested, nanofluids exhibited Newtonian behavior. An experimental correlation was developed based on the data, which relates viscosity with particle volume percent and the nanofluid temperature. (author)

  17. A One-Step, Solvothermal Reduction Method for Producing Reduced Graphene Oxide Dispersions in Organic Solvents

    PubMed Central

    Dubin, Sergey; Gilje, Scott; Wang, Kan; Tung, Vincent C.; Cha, Kitty; Hall, Anthony S.; Farrar, Jabari; Varshneya, Rupal; Yang, Yang; Kaner, Richard B.

    2014-01-01

    Refluxing graphene oxide (GO) in N-methyl-2-pyrrolidinone (NMP) results in deoxygenation and reduction to yield a stable colloidal dispersion. The solvothermal reduction is accompanied by a color change from light brown to black. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images of the product confirm the presence of single sheets of the solvothermally reduced graphene oxide (SRGO). X-ray photoelectron spectroscopy (XPS) of SRGO indicates a significant increase in intensity of the C=C bond character, while the oxygen content decreases markedly after the reduction is complete. X-ray diffraction analysis of SRGO shows a single broad peak at 26.24° 2θ (3.4 Å), confirming the presence of graphitic stacking of reduced sheets. SRGO sheets are redispersible in a variety of organic solvents, which may hold promise as an acceptor material for bulk heterojunction photovoltaic cells, or electromagnetic interference shielding applications. PMID:20586422

  18. Low-temperature carbon monoxide oxidation catalysed by regenerable atomically dispersed palladium on alumina

    SciTech Connect

    Peterson, Eric J.; DelaRiva, Andrew T.; Lin, Sen; Johnson, Ryan S.; Guo, Hua; Miller, Jeffrey T.; Kwak, Ja Hun; Peden, Charles H.F.; Kiefer, Boris; Allard, Lawrence F.; Ribeiro, Fabio H.; Datye, Abhaya K.

    2014-09-15

    Catalysis by single isolated atoms of precious metals has attracted much recent interest since it promises the ultimate economy in atom efficiency. Previous reports have been confined to reducible oxide supports such as FeOx, TiO₂ or CeO₂. Here we show that isolated Pd atoms can be stabilized on industrially relevant gamma-alumina supports. At low Pd loadings (≤0.5 wt%) these catalysts contain exclusively atomically dispersed Pd species. The addition of lanthanum-oxide to the alumina, long known for its ability to improve alumina stability, is found to also help in the stabilization of isolated Pd atoms. Aberration-corrected scanning transmission electron microscopy (AC-STEM) confirms the presence of intermingled Pd and La on the gamma-alumina surface. Operando X-ray absorption spectroscopy, performed on Pd/La-alumina and Pd/gamma-alumina (0.5 wt% Pd) demonstrates the presence of catalytically active atomically dispersed ionic Pd in the Pd/La-doped gamma-alumina system. CO oxidation reactivity measurements show onset of catalytic activity at 40 °C, indicating that the ionic Pd species are not poisoned by CO. The reaction order in CO and O₂ is positive, suggesting a reaction mechanism that is different from that on metallic Pd. The catalyst activity is lost if the Pd species are reduced to their metallic form, but the activity can be regenerated by oxidation at 700 °C in air. The high-temperature stability of these ionic Pd species on commercial alumina supports makes this catalyst system of potential interest for low-temperature exhaust treatment catalysts.

  19. The electrocatalytic oxidation of methanol at finely dispersed platinum nanoparticles in polypyrrole films

    SciTech Connect

    Hepel, M.

    1998-01-01

    A new method of the formation of composite polypyrrole films containing a highly dispersed three-dimensional array of platinum catalyst particles is presented. PtCl{sub 4}{sup 2{minus}} anions were trapped inside the polypyrrole matrix during the electropolymerization of pyrrole. In the next step followed by solution exchange, PtCl{sub 4}{sup 2{minus}} anions were reduced to Pt{sup 0} particles with an average size of 10 nm. Metallic particles were incorporated in electrically conducting polypyrrole films in order to achieve multielectron-transfer processes in a three-dimensional matrix. These films were characterized using the electrochemical quartz crystal microbalance technique. The use of this technique allowed evaluation of the Pt{sup 0} loading inside the polymer film. The electropolymerization process was controlled by measuring frequency changes of piezoelectrodes. The presence of Pt{sup 0} particles in composite polypyrrole films and their uniform distribution were confirmed by energy-dispersive x-ray spectroscopy and x-ray diffraction. The size of the Pt{sup 0} particles was evaluated from transmission electron microscopy experiments. The electrocatalytic effect toward the methanol oxidation was observed. Larger surface area and higher catalytic activity were found for electrodes with dispersed Pt{sup 0} nanoparticles in the polymer evaluation of matrix than electrodes with electrodeposited Pt{sup 0} on the surface of the conductive polymer.

  20. Photochromic Properties of Tungsten Oxide/Methylcellulose Composite Film Containing Dispersing Agents.

    PubMed

    Yamazaki, Suzuko; Ishida, Hiroki; Shimizu, Dai; Adachi, Kenta

    2015-12-01

    Tungsten oxide-based photochromic films which changed reversibly in air between colorless- transparent in the dark and dark blue under UV irradiation were prepared by using methylcellulose as a film matrix and polyols such as ethylene glycol (EG), propylene glycol (PG), and glycerin (Gly) as dispersing agents. Influence of the dispersing agents and water in the films on the photochromic behavior was systematically studied. Under UV irradiation, absorption bands around 640 and 980 nm increased and the coloring rate was the following order: Gly > EG > PG. An increase in the amounts of dispersing agents or water accelerated the coloring rate. By increasing the water content of the film, a new absorption peak appeared at ca. 775 nm and the Raman spectra indicated a shift of W-O-W stretching vibration to lower wavenumber which was due to the formation of hydrogen bonding. All absorption spectra were fit by three Lorentz functions, whose bands were ascribed to various packing of WO6 octahedra. After the light was turned off, the formation of W(5+) was stopped and bleaching occurred by the reaction with O2 in air to recover its original transparent state. We anticipate that the biodegradable photochromic films developed in this study can be applied in recyclable display medium and especially in detachable films for glass windows whose light transmission properties are changed by sunlight, i.e., for usage as an alternative of smart windows without applying voltage. PMID:26552031

  1. Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata.

    PubMed

    Booth, Andy; Størseth, Trond; Altin, Dag; Fornara, Andrea; Ahniyaz, Anwar; Jungnickel, Harald; Laux, Peter; Luch, Andreas; Sørensen, Lisbet

    2015-02-01

    An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO₂) nanoparticles (PAA-CeO₂) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO₂ did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO₂ concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO₂ aggregation or zeta potential. The ecotoxicity of the PAA-CeO₂ dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO₂ EC₅₀ values for growth inhibition (GI; 0.024 mg/L) were 2-3 orders of magnitude lower than pristine CeO₂ EC₅₀ values reported in the literature. The concentration of dissolved cerium (Ce(3+)/Ce(4+)) in PAA-CeO₂ exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096-0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO₂ exposure. In contrast to pristine CeO₂ nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO₂ nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO₂ leads to an increase in toxicity compared to

  2. The azo dye Disperse Red 13 and its oxidation and reduction products showed mutagenic potential.

    PubMed

    Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; de Oliveira, Danielle Palma

    2015-10-01

    Common water pollutants, azo dyes and their degradation products have frequently shown toxicity, including carcinogenic and mutagenic effects, and can induce serious damage in aquatic organisms and humans. In the present study, the mutagenic potential of the azo dye Disperse Red 13 (DR13) was first evaluated using the Micronucleus Assay in human lymphocytes. Subsequently, in order to mimic hepatic biotransformation, controlled potential electrolysis was carried out with a DR13 solution using a Potentiostat/Galvanostat. In addition, a DR13 solution was oxidized using S9 (homogenate of rat liver cells). DR13 oxidation and the reduction products were identified using HPLC-DAD and GC/MS, and their mutagenic potential investigated by way of a Salmonella/microsome assay using TA98 and YG1041 strains, with no S9. The original azo dye DR13 induced chromosomal damage in human lymphocytes, and the respective oxidation and reduction products also showed mutagenic activity, as detected by the Salmonella/microsome assay. Furthermore sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, 2-chloro-4-nitro-benzamine, 4-nitro-benzamine and 2-(ethylphenylamine)-ethanol were identified as products of the DR13 reduction/oxidation reactions. Thus it was concluded that the contamination of water effluents with DR13 is a health risk not only due to the dye itself, but also due to the possibility of drinking contaminated water, considering the harmful compounds that can be produced after hepatic biotransformation. PMID:26247324

  3. The azo dye Disperse Red 13 and its oxidation and reduction products showed mutagenic potential.

    PubMed

    Chequer, Farah Maria Drumond; Lizier, Thiago Mescoloto; de Felício, Rafael; Zanoni, Maria Valnice Boldrin; Debonsi, Hosana Maria; Lopes, Norberto Peporine; de Oliveira, Danielle Palma

    2015-10-01

    Common water pollutants, azo dyes and their degradation products have frequently shown toxicity, including carcinogenic and mutagenic effects, and can induce serious damage in aquatic organisms and humans. In the present study, the mutagenic potential of the azo dye Disperse Red 13 (DR13) was first evaluated using the Micronucleus Assay in human lymphocytes. Subsequently, in order to mimic hepatic biotransformation, controlled potential electrolysis was carried out with a DR13 solution using a Potentiostat/Galvanostat. In addition, a DR13 solution was oxidized using S9 (homogenate of rat liver cells). DR13 oxidation and the reduction products were identified using HPLC-DAD and GC/MS, and their mutagenic potential investigated by way of a Salmonella/microsome assay using TA98 and YG1041 strains, with no S9. The original azo dye DR13 induced chromosomal damage in human lymphocytes, and the respective oxidation and reduction products also showed mutagenic activity, as detected by the Salmonella/microsome assay. Furthermore sulfate 2-[(4-aminophenyl)ethylamino]-ethanol monohydrate, 2-chloro-4-nitro-benzamine, 4-nitro-benzamine and 2-(ethylphenylamine)-ethanol were identified as products of the DR13 reduction/oxidation reactions. Thus it was concluded that the contamination of water effluents with DR13 is a health risk not only due to the dye itself, but also due to the possibility of drinking contaminated water, considering the harmful compounds that can be produced after hepatic biotransformation.

  4. Controllable Edge Oxidation and Bubbling Exfoliation Enable the Fabrication of High Quality Water Dispersible Graphene

    PubMed Central

    Tian, Suyun; Sun, Jing; Yang, Siwei; He, Peng; Wang, Gang; Di, Zengfeng; Ding, Guqiao; Xie, Xiaoming; Jiang, Mianheng

    2016-01-01

    Despite significant progresses made on mass production of chemically exfoliated graphene, the quality, cost and environmental friendliness remain major challenges for its market penetration. Here, we present a fast and green exfoliation strategy for large scale production of high quality water dispersible few layer graphene through a controllable edge oxidation and localized gas bubbling process. Mild edge oxidation guarantees that the pristine sp2 lattice is largely intact and the edges are functionalized with hydrophilic groups, giving rise to high conductivity and good water dispersibility at the same time. The aqueous concentration can be as high as 5.0 mg mL−1, which is an order of magnitude higher than previously reports. The water soluble graphene can be directly spray-coated on various substrates, and the back-gated field effect transistor give hole and electron mobility of ~496 and ~676 cm2 V−1 s−1, respectively. These results achieved are expected to expedite various applications of graphene. PMID:27666869

  5. Controllable Edge Oxidation and Bubbling Exfoliation Enable the Fabrication of High Quality Water Dispersible Graphene

    NASA Astrophysics Data System (ADS)

    Tian, Suyun; Sun, Jing; Yang, Siwei; He, Peng; Wang, Gang; di, Zengfeng; Ding, Guqiao; Xie, Xiaoming; Jiang, Mianheng

    2016-09-01

    Despite significant progresses made on mass production of chemically exfoliated graphene, the quality, cost and environmental friendliness remain major challenges for its market penetration. Here, we present a fast and green exfoliation strategy for large scale production of high quality water dispersible few layer graphene through a controllable edge oxidation and localized gas bubbling process. Mild edge oxidation guarantees that the pristine sp2 lattice is largely intact and the edges are functionalized with hydrophilic groups, giving rise to high conductivity and good water dispersibility at the same time. The aqueous concentration can be as high as 5.0 mg mL‑1, which is an order of magnitude higher than previously reports. The water soluble graphene can be directly spray-coated on various substrates, and the back-gated field effect transistor give hole and electron mobility of ~496 and ~676 cm2 V‑1 s‑1, respectively. These results achieved are expected to expedite various applications of graphene.

  6. Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

    NASA Astrophysics Data System (ADS)

    Szenti, Imre; Bugyi, László; Kónya, Zoltán

    2015-11-01

    The behavior of rhodium layers deposited on oxidized, 0.15-20.0 ML thick Mo films formed on a nearly stoichiometric TiO2(110) single crystal was characterized by AES, TPD and work function (WF) measurements. The oxidation of 0.15-2.7 ML thick Mo deposits was performed via the redox reaction with the titania support at 1000 K. Molybdenum oxide supports of MoO3 and MoO2 surface composition were formed by the oxidation of 20 ML thick Mo multilayers by O2 at 650 K and 1000 K, respectively. Rh grows in a layer-by-layer fashion on a mixed titanium-molybdenum oxide produced in the reaction between titania and 0.15 ML Mo, corresponding to a considerably enhanced dispersion of rhodium as compared with that on the clean TiO2(110). The surface reactivity of Rh layers supported by molybdenum oxides as a function of pre-annealing temperature was followed by carbon monoxide adsorption-desorption cycles. The CO uptake of a 0.4 ML thick Rh film formed on the MoO3 support was strongly suppressed at 300 K, indicating the encapsulation of rhodium with MoOX species of low surface free energy. The CO adsorption capability of rhodium particles supported by both MoO3 and MoO2 layers was eliminated due to pre-annealing at 600 K, related to the extended decoration of metal particles by MoOX moiety. The encapsulation of the rhodium films proceeded above 600 K on both supports, and annealing to 1000 K resulted in nearly equal WF values, indicating the formation of MoOX overlayers of similar surface composition close to MoO2. AES depth profiles revealed that the 0.4 ML thick Rh deposits covered by MoOX at 1000 K preserved their island structure.

  7. Single-step synthesis of graphene quantum dots by femtosecond laser ablation of graphene oxide dispersions

    NASA Astrophysics Data System (ADS)

    Russo, Paola; Liang, Robert; Jabari, Elahe; Marzbanrad, Ehsan; Toyserkani, Ehsan; Zhou, Y. Norman

    2016-04-01

    In the last few years, graphene quantum dots (GQDs) have attracted the attention of many research groups for their outstanding properties, which include low toxicity, chemical stability and photoluminescence. One of the challenges of GQD synthesis is finding a single-step, cheap and sustainable approach for synthesizing these promising nanomaterials. In this study, we demonstrate that femtosecond laser ablation of graphene oxide (GO) dispersions could be employed as a facile and environmentally friendly synthesis method for GQDs. With the proper control of laser ablation parameters, such as ablation time and laser power, it is possible to produce GQDs with average sizes of 2-5 nm, emitting a blue luminescence at 410 nm. We tested the feasibility of the synthesized GQDs as materials for electronic devices by aerosol-jet printing of an ink that is a mixture of water dispersion of laser synthesized GQDs and silver nanoparticle dispersion, which resulted in lower resistivity of the final printed patterns. Preliminary results showed that femtosecond laser synthesized GQDs can be mixed with silver nanoparticle dispersion to fabricate a hybrid material, which can be employed in printing electronic devices by either printing patterns that are more conductive and/or reducing costs of the ink by decreasing the concentration of silver nanoparticles (AgNPs) in the ink.In the last few years, graphene quantum dots (GQDs) have attracted the attention of many research groups for their outstanding properties, which include low toxicity, chemical stability and photoluminescence. One of the challenges of GQD synthesis is finding a single-step, cheap and sustainable approach for synthesizing these promising nanomaterials. In this study, we demonstrate that femtosecond laser ablation of graphene oxide (GO) dispersions could be employed as a facile and environmentally friendly synthesis method for GQDs. With the proper control of laser ablation parameters, such as ablation time and

  8. Effects of metal oxide nanoparticles on the stability of dispersions of weakly charged colloids.

    PubMed

    Herman, David; Walz, John Y

    2015-05-01

    The stability behavior of dispersions of weakly charged silica colloids was studied in the presence of highly charged metal oxide nanoparticles. Experiments were performed using 5 nm zirconia as well as 10 nm alumina nanoparticles (both positively charged), which were added to 0.1 vol % suspensions of 1.0 μm silica microparticles at the silica IEP. Both types of nanoparticles provided effective stabilization of the silica; i.e., the silica suspensions were stabilized for longer than the observation period (greater than 12 h). Stability was observed at zirconia concentrations as low as 10(-4) vol % and at an alumina concentration of 10(-2) vol %. The nanoparticles adsorbed onto the microparticle surfaces (confirmed via SEM imaging), which increased the zeta-potential of the silica. Force profile measurements performed with colloidal probe atomic force microscopy showed that the adsorption was effectively irreversible.

  9. Nonlinear photoluminescence imaging of isotropic and liquid crystalline dispersions of graphene oxide.

    PubMed

    Senyuk, Bohdan; Behabtu, Natnael; Pacheco, Benjamin G; Lee, Taewoo; Ceriotti, Gabriel; Tour, James M; Pasquali, Matteo; Smalyukh, Ivan I

    2012-09-25

    We report a visible-range nonlinear photoluminescence (PL) from graphene oxide (GO) flakes excited by near-infrared femtosecond laser light. PL intensity has nonlinear dependence on the laser power, implying a multiphoton excitation process, and also strongly depends on a linear polarization orientation of excitation light, being at maximum when it is parallel to flakes. We show that PL can be used for a fully three-dimensional label-free imaging of isotropic, nematic, and lamellar liquid crystalline dispersions of GO flakes in water. This nonlinear PL is of interest for applications in direct label-free imaging of composite materials and study of orientational ordering in mesomorphic phases formed by these flakes, as well as in biomedical and sensing applications utilizing GO.

  10. Highly bendable bilayer-type photo-actuators comprising of reduced graphene oxide dispersed in hydrogels

    PubMed Central

    Kim, Dowan; Lee, Heon Sang; Yoon, Jinhwan

    2016-01-01

    To avoid the problem of reduced graphene oxide (rGO) restacking in aqueous solution, the preparation of light-responsive poly(N-isopropylacrylamide) incorporating rGO (PNIPAm/rGO) was achieved by the chemical reduction of GO dispersed in the hydrogel matrix. Due to the enhanced photothermal efficiency of the rGO, the prepared PNIPAm/rGO underwent large volume reductions in response to irradiation by visible light of modest intensity. With respect to potential applications, bilayer-type photo-actuators comprising a PNIPAm/rGO active layer and poly(acrylamide) passive layer were fabricated; these achieved a full bending motion upon visible-light exposure. Adjusting the swelling ratio of each layer in the initial state yielded bidirectional photo-actuators that showed the active motion of turning inside out. Furthermore, we demonstrated that the fabricated actuation system would exhibit controlled bending motion in response to solar radiation. PMID:26865239

  11. Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles.

    PubMed

    Bixner, Oliver; Lassenberger, Andrea; Baurecht, Dieter; Reimhult, Erik

    2015-08-25

    High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core-shell architectures. PMID:26226071

  12. Effects of metal oxide nanoparticles on the stability of dispersions of weakly charged colloids.

    PubMed

    Herman, David; Walz, John Y

    2015-05-01

    The stability behavior of dispersions of weakly charged silica colloids was studied in the presence of highly charged metal oxide nanoparticles. Experiments were performed using 5 nm zirconia as well as 10 nm alumina nanoparticles (both positively charged), which were added to 0.1 vol % suspensions of 1.0 μm silica microparticles at the silica IEP. Both types of nanoparticles provided effective stabilization of the silica; i.e., the silica suspensions were stabilized for longer than the observation period (greater than 12 h). Stability was observed at zirconia concentrations as low as 10(-4) vol % and at an alumina concentration of 10(-2) vol %. The nanoparticles adsorbed onto the microparticle surfaces (confirmed via SEM imaging), which increased the zeta-potential of the silica. Force profile measurements performed with colloidal probe atomic force microscopy showed that the adsorption was effectively irreversible. PMID:25860256

  13. Complete Exchange of the Hydrophobic Dispersant Shell on Monodisperse Superparamagnetic Iron Oxide Nanoparticles

    PubMed Central

    2015-01-01

    High-temperature synthesized monodisperse superparamagnetic iron oxide nanoparticles are obtained with a strongly bound ligand shell of oleic acid and its decomposition products. Most applications require a stable presentation of a defined surface chemistry; therefore, the native shell has to be completely exchanged for dispersants with irreversible affinity to the nanoparticle surface. We evaluate by attenuated total reflectance−Fourier transform infrared spectroscopy (ATR−FTIR) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) the limitations of commonly used approaches. A mechanism and multiple exchange scheme that attains the goal of complete and irreversible ligand replacement on monodisperse nanoparticles of various sizes is presented. The obtained hydrophobic nanoparticles are ideally suited for magnetically controlled drug delivery and membrane applications and for the investigation of fundamental interfacial properties of ultrasmall core–shell architectures. PMID:26226071

  14. Structure and optical properties of noble metal and oxide nanoparticles dispersed in various polysaccharide biopolymers

    NASA Astrophysics Data System (ADS)

    Djoković, V.; Božanic, D. K.; Vodnik, V. V.; Krsmanović, R. M.; Trandafilovic, L. V.; Dimitrijević-Branković, S.

    2011-10-01

    We present the results on the structure and the optical properties of noble metal (Ag, Au) and oxide (ZnO) nanoparticles synthesized by various methods in different polysaccharide matrices such as chitosan, glycogen, alginate and starch. The structure of the obtained nanoparticles was studied in detail with microscopic techniques (TEM, SEM), while the XPS spectroscopy was used to investigate the effects at the nanoparticle-biomolecule interfaces. The antimicrobial activity of the nanocomposite films with Ag nanoparticles was tested against the Staphylococcus aureus, Escherichia coli and Candida albicans pathogens. In addition, we will present the results on the structure and optical properties of the tryptophan amino acid functionalized silver nanoparticles dispersed in water soluble polymer matrices.

  15. High methanol oxidation activity of well-dispersed pt nanoparticles on carbon nanotubes using nitrogen doping.

    PubMed

    Fang, Wei-Chuan

    2009-10-09

    Pt nanoparticles (NPs) with the average size of 3.14 nm well dispersed on N-doped carbon nanotubes (CNTs) without any pretreatment have been demonstrated. Structural properties show the characteristic N bonding within CNTs, which provide the good support for uniform distribution of Pt NPs. In electrochemical characteristics, N-doped CNTs covered with Pt NPs show superior current density due to the fact that the so-called N incorporation could give rise to the formation of preferential sites within CNTs accompanied by the low interfacial energy for immobilizing Pt NPs. Therefore, the substantially enhanced methanol oxidation activity performed by N-incorporation technique is highly promising in energy-generation applications.

  16. Highly bendable bilayer-type photo-actuators comprising of reduced graphene oxide dispersed in hydrogels

    NASA Astrophysics Data System (ADS)

    Kim, Dowan; Lee, Heon Sang; Yoon, Jinhwan

    2016-02-01

    To avoid the problem of reduced graphene oxide (rGO) restacking in aqueous solution, the preparation of light-responsive poly(N-isopropylacrylamide) incorporating rGO (PNIPAm/rGO) was achieved by the chemical reduction of GO dispersed in the hydrogel matrix. Due to the enhanced photothermal efficiency of the rGO, the prepared PNIPAm/rGO underwent large volume reductions in response to irradiation by visible light of modest intensity. With respect to potential applications, bilayer-type photo-actuators comprising a PNIPAm/rGO active layer and poly(acrylamide) passive layer were fabricated; these achieved a full bending motion upon visible-light exposure. Adjusting the swelling ratio of each layer in the initial state yielded bidirectional photo-actuators that showed the active motion of turning inside out. Furthermore, we demonstrated that the fabricated actuation system would exhibit controlled bending motion in response to solar radiation.

  17. Oil lubricant tribological behaviour improvement through dispersion of few layer graphene oxide.

    PubMed

    Sarno, Maria; Senatore, Adolfo; Cirillo, Claudia; Petrone, Vincenzo; Ciambelli, Paolo

    2014-07-01

    Few layer graphene oxide (GO) nanosheets were prepared by a very fast modified Hummers method and widely characterized. Avoiding further chemical reactions, trying to take advantage of the easy exfoliation of GO favoring the formation of a tribofilm, and using a methodology well known to the lubricant industry, they were added to a mineral oil by the help of a dispersant. The tribological behaviour of GO in mineral oil was investigated under a wide spectrum of conditions, from boundary and mixed lubrication to elastohydrodynamic regimes. A ball on disc setup tribometer has been used to verify the friction reduction due to nanosheets dispersed in mineral oil. Their good friction and anti-wear properties may possibly be attributed to the small and extremely thin laminated structure, which offer lower shear stress and prevent interaction between metal interfaces. Furthermore, the results clearly prove that graphene platelets in oil easily form a protective film to prevent the direct contact between steel surfaces and, thereby, improving the frictional behaviour of the base oil. This evidence is also related to the frictional coefficient trend in boundary regime.

  18. Alternating magnetic field energy absorption in the dispersion of iron oxide nanoparticles in a viscous medium

    NASA Astrophysics Data System (ADS)

    Smolkova, Ilona S.; Kazantseva, Natalia E.; Babayan, Vladimir; Smolka, Petr; Parmar, Harshida; Vilcakova, Jarmila; Schneeweiss, Oldrich; Pizurova, Nadezda

    2015-01-01

    Magnetic iron oxide nanoparticles were obtained by a coprecipitation method in a controlled growth process leading to the formation of uniform highly crystalline nanoparticles with average size of 13 nm, which corresponds to the superparamagnetic state. Nanoparticles obtained are a mixture of single-phase nanoparticles of magnetite and maghemite as well as nanoparticles of non-stoichiometric magnetite. The subsequent annealing of nanoparticles at 300 °C in air during 6 h leads to the full transformation to maghemite. It results in reduced value of the saturation magnetization (from 56 emu g-1 to 48 emu g-1) but does not affect the heating ability of nanoparticles. A 2-7 wt% dispersion of as-prepared and annealed nanoparticles in glycerol provides high heating rate in alternating magnetic fields allowed for application in magnetic hyperthermia; however the value of specific loss power does not exceed 30 W g-1. This feature of heat output is explained by the combined effect of magnetic interparticle interactions and the properties of the carrier medium. Nanoparticles coalesce during the synthesis and form aggregates showing ferromagnetic-like behavior with magnetization hysteresis, distinct sextets on Mössbauer spectrum, blocking temperature well about room temperature, which accounts for the higher energy barrier for magnetization reversal. At the same time, low specific heat capacity of glycerol intensifies heat transfer in the magnetic dispersion. However, high viscosity of glycerol limits the specific loss power value, since predominantly the Neel relaxation accounts for the absorption of AC magnetic field energy.

  19. Spontaneous phase separation during self-assembly in bi-dispersed spherical iron oxide nanoparticle monolayers

    SciTech Connect

    Stanley, Jacob; Boucheron, Leandra; Shpyrko, Oleg E-mail: oshpyrko@physics.ucsd.edu; Lin, Binhua E-mail: oshpyrko@physics.ucsd.edu; Meron, Mati

    2015-04-20

    Recent developments in the synthesis of iron oxide nanoparticles have resulted in the ability to fabricate roughly spherical particles with extremely high size uniformity (low polydispersity). These particles can form self-assembled monolayer films at an air-water interface. When the polydispersity of the particles is low, these monolayers can be well-ordered over a length scale dozens of times the particle size. The van der Waals force between the particles is what drives this self-assembly. Through the use of Grazing Incidence X-Ray Diffraction we demonstrate that, when these films are formed at the liquid surface from bi-dispersed solutions containing 10 and 20 nm spherical particles suspended in chloroform, the particles phase separate into well-ordered patches during the self-assembly process. Furthermore, the domain sizes of these phase separated regions are at most 2–3 times smaller than that of a film comprising only mono-dispersed particles and their degree of disorder is comparable. This is shown for multiple solutions with differing ratios of 10 and 20 nm particles.

  20. [Removal of arsenic from dispersed drinking water by iron oxide-coated sand].

    PubMed

    Yuan, T; Luo, Q

    2001-05-01

    The iron oxide-coated sand(IOCS) was developed by treating normal river sand with molysite and investigated by batch, column tests and autoptic experiment to evaluate it's ability of eliminating arsenic from dispersed drinking water. The results showed that IOCS was relatively stable and can be seen iron oxide distributedly patched the surface of sand by scan electron microscope. IOCS needn't any activation pretreatment. It reached the maximum adsorption within 30-60 min. The removal percentage of arsenate was decreased but the one of arsenite had little change when the pH varied from 5 to 9. And the arsenic adsorption matched the Langmuir isotherm. In 5 circles of runs, it treated 408-426 (arsenite) beds and 390-412(arsenate) beds volume of water with 75 g(50 ml) IOCS respectively when the influent arsenic concentration was 1.0 mg.L-1. And the arsenic percentage recovery was above 94% when regenerating the IOCS by 0.2 mol.L-1 NaOH. The home simulation unit contained IOCS 3.0 kg produced 209 L and 198 L, 196 L and 185 L of water when the influent arsenate or arsenite concentration was 1.0 mg.L-1, and 200 L arsenic free water with the influent arsenic 0.202-1.733 mg.L-1 during the field experimental period. The water quality was not affected by the adsorbent. With low-cost and simple operation, the IOCS should be a promising novel medium for arsenic removal in dispersed drinking water.

  1. The oxidation and corrosion of ODS alloys

    NASA Technical Reports Server (NTRS)

    Lowell, Carl E.; Barrett, Charles A.

    1990-01-01

    The oxidation and hot corrosion of high temperature oxide dispersion strengthened (ODS) alloys are reviewed. The environmental resistance of such alloys are classified by oxide growth rate, oxide volatility, oxide spalling, and hot corrosion limitations. Also discussed are environmentally resistant coatings for ODS materials. It is concluded that ODS NiCrAl and FeCrAl alloys are highly oxidation and corrosion resistant and can probably be used uncoated.

  2. Dispersion-precipitation synthesis of nanosized magnetic iron oxide for efficient removal of arsenite in water.

    PubMed

    Cheng, Wei; Xu, Jing; Wang, Yajie; Wu, Feng; Xu, Xiuyan; Li, Jinjun

    2015-05-01

    Nanosized magnetic iron oxide was facilely synthesized by a dispersion-precipitation method, which involved acetone-promoted precipitation of colloidal hydrous iron oxide nanoparticles and subsequent calcination of the precipitate at 250°C. Characterization by X-ray diffraction, transmission electron microscopy, Raman spectroscopy, nitrogen sorption, and vibrating-sample magnetometry revealed that the material was a composite of α-Fe2O3 and γ-Fe2O3 with primary particle size of 15-25 nm and specific surface area of 121 m(2)/g, as well as superparamagnetic property. The material was used as adsorbent for the removal of arsenite in water. Batch experiments showed that the adsorption isotherms at pH 3.0-11.0 fit the Langmuir equation and the adsorption obeys pseudo-second-order kinetics. Its maximum sorption capability for arsenite is 46.5 mg/g at pH 7.0. Coexisting nitrate, carbonate, sulfate, chloride, and fluoride have no significant effect on the removal efficiency of arsenite, while phosphate and silicate reduce the removal efficiency to some extent. The As(III) removal mechanism is chemisorption through forming inner-sphere surface complexes. The efficiency of arsenic removal is still maintained after five cycles of regeneration-reuse. PMID:25612934

  3. Purified graphene oxide dispersions lack in vitro cytotoxicity and in vivo pathogenicity.

    PubMed

    Ali-Boucetta, Hanene; Bitounis, Dimitrios; Raveendran-Nair, Rahul; Servant, Ania; Van den Bossche, Jeroen; Kostarelos, Kostas

    2013-03-01

    Prompted by the excitement from the description of single layer graphene, increased attention for potential applications in the biomedical field has been recently placed on graphene oxide (GO). Determination of the opportunities and limitations that GO offers in biomedicine are particularly prone to inaccuracies due to wide variability in the preparation methodologies of GO material in different laboratories, that results in significant variation in the purity of the material and the yield of the oxidation reactions, primarily the Hummers method used. Herein, the fabrication of highly pure, colloidally stable, and evenly dispersed GO in physiologically-relevant aqueous buffers in comparison to conventional GO is investigated. The purified GO material is thoroughly characterized by a battery of techniques, and is shown to consist of single layer GO sheets of lateral dimensions below 500 nm. The cytotoxic impact of the GO in vitro and its inflammation profile in vivo is investigated. The purified GO prepared and characterized here does not induce significant cytotoxic responses in vitro, or inflammation and granuloma formation in vivo following intraperitoneal injection. This is one of the initial steps towards determination of the safety risks associated with GO material that may be interacting with living tissue.

  4. The Use of Binary Polymeric Networks in Stabilizing Polyethylene Oxide Solid Dispersions.

    PubMed

    Jones, David S; Tian, Yiwei; Li, Shu; Yu, Tao; Abu-Diak, Osama A; Andrews, Gavin P

    2016-10-01

    The objective of this study was to determine if a high Tg polymer (Eudragit(®) S100) could be used to stabilize amorphous domains of polyethylene oxide (PEO) and hence improve the stability of binary polymer systems containing celecoxib (CX). We propose a novel method of stabilizing the amorphous PEO solid dispersion through inclusion of a miscible, high Tg polymer, namely, that can form strong inter-polymer interactions. The effects of inter-polymer interactions and miscibility between PEO and Eudragit S100 are considered. Polymer blends were first manufactured via hot-melt extrusion at different PEO/S100 ratios (70/30, 50/50, and 30/70 wt/wt). Differential scanning calorimetry and dynamic mechanical thermal analysis data suggested a good miscibility between PEO and S100 polymer blends, particularly at the 50/50 ratio. To further evaluate the system, CX/PEO/S100 ternary mixtures were extruded. Immediately after hot-melt extrusion, a single Tg that increased with increasing S100 content (anti-plasticization) was observed in all ternary systems. The absence of powder X-ray diffractometry crystalline Bragg's peaks also suggested amorphization of CX. Upon storage (40°C/75% relative humidity), the formulation containing PEO/S100 at a ratio of 50:50 was shown to be most stable. Fourier transform infrared studies confirmed the presence of hydrogen bonding between Eudragit S100 and PEO suggesting this was the principle reason for stabilization of the amorphous CX/PEO solid dispersion system.

  5. Preparation of highly water-dispersible titanium-silicon binary oxide materials by sol-gel method.

    PubMed

    Kaneko, Yoshiro

    2011-03-01

    The preparation of highly water-dispersible titanium-silicon binary oxide materials was performed by the following two-stage sol-gel reactions. First, the mixture of titanium tetraisopropoxide and 3-aminopropyltrimethoxysilane was stirred in a mixed solvent of isopropyl alcohol and 0.5 mol/L methanolic hydrochloric acid at room temperature, followed by heating in an open system until the solvent was evaporated. Then, the aqueous solution obtained by adding water to the resulting product was heated in the open system until the water was completely reevaporated. The resulting product was dispersed well in water, and its aqueous dispersion was highly transparent and cut off UV light, confirmed by UV-Vis measurements. The solid product obtained by lyophilization of its aqueous dispersion was redispersed in water. The average particle size of the product was assessed to be < 10 nm by dynamic light scattering (DLS) in water and transmission electron microscopy (TEM) measurements, indicating that the product was a water-dispersible spherical nanoparticle. It was assumed that the water-dispersible property of the product probably originated from the TiO2/SiO1.5(CH2)3NH3 x Cl core/shell structure. In addition, highly transparent films can be prepared from the aqueous dispersion of the product, and these films also cut off the UV light, evaluated by UV-Vis measurements.

  6. Nitrogen-doped and simultaneously reduced graphene oxide with superior dispersion as electrocatalysts for oxygen reduction reaction

    SciTech Connect

    Lee, Cheol-Ho; Yun, Jin-Mun; Lee, Sungho; Jo, Seong Mu; Yoo, Sung Jong; Cho, Eun Ae; Khil, Myung-Seob; Joh, Han-Ik

    2014-11-15

    Nitrogen doped graphene oxide (Nr-GO) with properties suitable for electrocatalysts is easily synthesized using phenylhydrazine as a reductant at relatively low temperature. The reducing agent removes various oxygen functional groups bonded to graphene oxide and simultaneously dope the nitrogen atoms bonded with phenyl group all over the basal planes and edge sites of the graphene. The Nr-GO exhibits remarkable electrocatalytic activities for oxygen reduction reaction compared to the commercial carbon black and graphene oxide due to the electronic modification of the graphene structure. In addition, Nr-GO shows excellent dispersibility in various solvent due to the dopant molecules.

  7. Ductility Enhancement of Molybdenum Phase by Nano-sized Oxide Dispersions

    SciTech Connect

    Kang, Bruce

    2008-07-18

    The objective of this research is to understand and to remedy the impurity effects for room-temperature ductility enhancement of molybdenum (Mo) based alloys by the inclusion of nano-sized metal oxide dispersions. This research combines theoretical, computational, and experimental efforts. The results will help to formulate systematic strategies in searching for better composed Mo-based alloys with optimal mechanical properties. For this project, majority of the research effort was directed to atomistic modeling to identify the mechanisms responsible for the oxygen embrittling and ductility enhancement based on fundamental electronic structure analysis. Through first principles molecular dynamics simulations, it was found that the embrittling impurity species were attracted to the metal oxide interface, consistent with previous experiments. Further investigation on the electronic structures reveals that the presence of embrittling species degrades the quality of the metallic chemical bonds in the hosting matrix in a number of ways, the latter providing the source of ductility. For example, the spatial flexibility of the bonds is reduced, and localization of the impurity states occurs to pin the dislocation flow. Rice’s criterion has been invoked to explain the connections of electronic structure and mechanical properties. It was also found that when impurity species become attracted to the metal oxide interface, some of the detrimental effects are alleviated, thus explaining the observed ductility enhancement effects. These understandings help to develop predictive capabilities to facilitate the design and optimization of Mo and other high temperature alloys (e.g. ODS alloys) for fossil energy materials applications. Based on the theoretical and computational studies, the experimental work includes the preparation of Mo powders mixed with candidate nano-sized metal oxides, which were then vacuum hot-pressed to make the Mo alloys. Several powder mixing methods

  8. Shape- and size-selective electrochemical synthesis of dispersed silver(I) oxide colloids.

    PubMed

    Murray, B J; Li, Q; Newberg, J T; Menke, E J; Hemminger, J C; Penner, R M

    2005-11-01

    Silver(I) oxide (Ag2O) micro- and nanoparticles were electrochemically synthesized by anodizing a sacrificial silver wire in a basic aqueous sulfate solution. Ag2O particles were released from the silver electrode surface during synthesis producing a visible sol "stream". The composition of these particles was established using selected area electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. The shape of Ag2O crystallites could be adjusted using the potential of the silver wire generator electrode. The generation of a dispersed Ag2O sol and the observed shape selectivity are both explained by a two-step mechanism involving the anodic dissolution of silver metal, Ag0 --> Ag+(aq) + 1e-, followed by the precipitation of Ag2O particles, 2Ag+ + 2OH- --> Ag2O(s) + H2O. Within 100 mV of the voltage threshold for particle growth, cubic particles with a depression in each face ("hopper crystals") were produced. The application of more positive voltages resulted in the generation of 8-fold symmetric "flower"-shaped particles formed as a consequence of fast growth in the <111> crystallographic direction. The diameter of flower particles was adjustable from 250 nm to 1.8 microm using the growth duration at constant potential.

  9. Π Band Dispersion along Conjugated Organic Nanowires Synthesized on a Metal Oxide Semiconductor

    PubMed Central

    2016-01-01

    Surface-confined dehalogenation reactions are versatile bottom-up approaches for the synthesis of carbon-based nanostructures with predefined chemical properties. However, for devices generally requiring low-conductivity substrates, potential applications are so far severely hampered by the necessity of a metallic surface to catalyze the reactions. In this work we report the synthesis of ordered arrays of poly(p-phenylene) chains on the surface of semiconducting TiO2(110) via a dehalogenative homocoupling of 4,4″-dibromoterphenyl precursors. The supramolecular phase is clearly distinguished from the polymeric one using low-energy electron diffraction and scanning tunneling microscopy as the substrate temperature used for deposition is varied. X-ray photoelectron spectroscopy of C 1s and Br 3d core levels traces the temperature of the onset of dehalogenation to around 475 K. Moreover, angle-resolved photoemission spectroscopy and tight-binding calculations identify a highly dispersive band characteristic of a substantial overlap between the precursor’s π states along the polymer, considered as the fingerprint of a successful polymerization. Thus, these results establish the first spectroscopic evidence that atomically precise carbon-based nanostructures can readily be synthesized on top of a transition-metal oxide surface, opening the prospect for the bottom-up production of novel molecule–semiconductor devices. PMID:27115554

  10. Dispersion and interaction of graphene oxide in amorphous and semi-crystalline nano-composites: a PALS study

    NASA Astrophysics Data System (ADS)

    Maurer, Frans H. J.; Arza, Carlos R.

    2015-06-01

    The influence of dispersion and interaction of Graphene Oxide (GO) in semicrystalline Polyhydroxy butyrate (PHB) and glassy amorphous Poly(tBP-oda) is explored by Positron Annihilation Lifetime Spectroscopy (PALS). The ortho-Positronium lifetimes which represent the main free volume hole size of both polymers are mainly affected by the large differences in internal stresses built up by the shrinkage of the polymers during their preparation, restricted by the platelet structure of GO. The ortho-Positronium intensities, which represent the ortho-Positronium formation probabilities, suggest a strong dependency of on the dispersion of the nano-particles and their aspect ratio.

  11. Dispersion medium modulates oxidative stress response of human lung epithelial cells upon exposure to carbon nanomaterial samples

    SciTech Connect

    Herzog, Eva Byrne, Hugh J.; Davoren, Maria; Casey, Alan; Duschl, Albert; Oostingh, Gertie Janneke

    2009-05-01

    Due to their large specific surface area, the potential of nanoparticles to be highly reactive and to induce oxidative stress is particularly high. In addition, some types of nanoparticles contain transition metals as trace impurities which are known to generate reactive oxygen species (ROS) in biological systems. This study investigates the potential of two types of single-walled carbon nanotube samples, nanoparticulate carbon black and crocidolite asbestos to induce ROS in lung epithelial cells in vitro. Carbon nanotube and carbon black samples were used as produced, without further purification or processing, in order to best mimic occupational exposure by inhalation of airborne dust particles derived from carbon nanomaterial production. Intracellular ROS were measured following short-term exposure of primary bronchial epithelial cells (NHBE) and A549 alveolar epithelial carcinoma cells using the redox sensitive probe carboxydichlorofluorescin (carboxy-DCFDA). The oxidative potential of agglomerated nanomaterial samples was compared following dispersion in cell culture medium with and without foetal calf serum (FCS) supplement. In addition, samples were dispersed in dipalmitoylphosphatidylcholine (DPPC), the major component of lung surfactant. It could be illustrated that in vitro exposure of lung epithelial cells to carbon nanomaterial samples results only in moderate or low oxidative stress under the exposure conditions employed. However, cell responses are strongly dependent on the vehicle used for dispersion. Whereas the presence of DPPC increased intracellular ROS formation, FCS seemed to protect the cells from oxidative insult.

  12. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    NASA Astrophysics Data System (ADS)

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-03-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL‑1, with a detection limit of 0.1 ng·mL‑1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples.

  13. Novel Signal-Amplified Fenitrothion Electrochemical Assay, Based on Glassy Carbon Electrode Modified with Dispersed Graphene Oxide

    PubMed Central

    Wang, Limin; Dong, Jinbo; Wang, Yulong; Cheng, Qi; Yang, Mingming; Cai, Jia; Liu, Fengquan

    2016-01-01

    A novel signal-amplified electrochemical assay for the determination of fenitrothion was developed, based on the redox behaviour of organophosphorus pesticides on a glassy carbon working electrode. The electrode was modified using graphene oxide dispersion. The electrochemical response of fenitrothion at the modified electrode was investigated using cyclic voltammetry, current-time curves, and square-wave voltammetry. Experimental parameters, namely the accumulation conditions, pH value, and volume of dispersed material, were optimised. Under the optimum conditions, a good linear relationship was obtained between the oxidation peak current and the fenitrothion concentration. The linear range was 1–400 ng·mL−1, with a detection limit of 0.1 ng·mL−1 (signal-to-nose ratio = 3). The high sensitivity of the sensor was demonstrated by determining fenitrothion in pakchoi samples. PMID:27003798

  14. Dispersion and surface functionalization of oxide nanoparticles for transparent photocatalytic and UV-protecting coatings and sunscreens

    NASA Astrophysics Data System (ADS)

    Faure, Bertrand; Salazar-Alvarez, German; Ahniyaz, Anwar; Villaluenga, Irune; Berriozabal, Gemma; De Miguel, Yolanda R.; Bergström, Lennart

    2013-04-01

    This review describes recent efforts on the synthesis, dispersion and surface functionalization of the three dominating oxide nanoparticles used for photocatalytic, UV-blocking and sunscreen applications: titania, zinc oxide, and ceria. The gas phase and liquid phase synthesis is described briefly and examples are given of how weakly aggregated photocatalytic or UV-absorbing oxide nanoparticles with different composition, morphology and size can be generated. The principles of deagglomeration are reviewed and the specific challenges for nanoparticles highlighted. The stabilization of oxide nanoparticles in both aqueous and non-aqueous media requires a good understanding of the magnitude of the interparticle forces and the surface chemistry of the materials. Quantitative estimates of the Hamaker constants in various media and measurements of the isoelectric points for the different oxide nanoparticles are presented together with an overview of different additives used to prepare stable dispersions. The structural and chemical requirements and the various routes to produce transparent photocatalytic and nanoparticle-based UV-protecting coatings, and UV-blocking sunscreens are described and discussed.

  15. A reduced graphene oxide nanofiltration membrane intercalated by well-dispersed carbon nanotubes for drinking water purification.

    PubMed

    Chen, Xianfu; Qiu, Minghui; Ding, Hao; Fu, Kaiyun; Fan, Yiqun

    2016-03-14

    In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for drinking water purification to retain the nanoparticles, dyes, proteins, organophosphates, sugars, and particularly humic acid. Experimentally, it is shown that the rGO-CNT hybrid NF membranes have high retention efficiency, good permeability and good anti-fouling properties. The retention was above 97.3% even for methyl orange (327 Da); for other objects, the retention was above 99%. The membrane's permeability was found to be as high as 20-30 L m(-2) h(-1) bar(-1). Based on these results, we can conclude that (i) the use of BCPs as a surfactant can enhance steric repulsion and thus disperse CNTs effectively; (ii) placing well-dispersed 1D CNTs within 2D graphene sheets allows an uniform network to form, which can provide many mass transfer channels through the continuous 3D nanostructure, resulting in the high permeability and separation performance of the rGO-CNT hybrid NF membranes.

  16. Effect of Mo Dispersion Size and Water Vapor on Oxidation of Two-Phase Directionally Solidified NiAl-9Mo In-Situ Composites

    SciTech Connect

    Brady, Michael P; Bei, Hongbin; Meisner, Roberta Ann; Lance, Michael J; Tortorelli, Peter F

    2014-01-01

    Oxidation of two-phase NiAl-9Mo eutectics with 3 different growth rates/2nd phase Mo dispersion sizes were investigated at 900 C in air and air with 10% water vapor. Good oxidation resistance via alumina formation was observed in dry air, with Mo volatilization loss minimized by fine submicron Mo dispersions. However, extensive Mo volatilization and in-place internal oxidation of prior Mo phase regions was observed in wet air oxidation. Ramifications of this phenomenon for the development of multi-phase high-temperature alloys are discussed

  17. Matrix solid-phase dispersion with chitosan-zinc oxide nanoparticles combined with flotation-assisted dispersive liquid-liquid microextraction for the determination of 13 n-alkanes in soil samples.

    PubMed

    Khajeh, Mostafa; Yan, Hongyuan; Arefnejad, Esmat; Bohlooli, Mousa

    2014-11-01

    In this study, chitosan-zinc oxide nanoparticles were used as a sorbent of miniaturized matrix solid-phase dispersion combined with flotation-assisted dispersive liquid-liquid microextraction for the simultaneous determination of 13 n-alkanes such as C8 H18 and C20 H42 in soil samples. The solid samples were directly blended with the chitosan nanoparticles in the solid-phase dispersion method. The eluent of solid-phase dispersion was applied as the dispersive solvent for the following flotation-assisted dispersive liquid-liquid microextraction for further purification and enrichment of the target compounds prior to gas chromatography with flame ionization detection. Under the optimum conditions, good linearity with correlation coefficients in the range 0.9991 < r(2) < 0.9995 and low detection limits between 0.08 to 2.5 ng/g were achieved. The presented procedure combined the advantages of chitosan-zinc oxide nanoparticles, solid-phase dispersion and flotation-assisted dispersive liquid-liquid microextraction, and could be applied for the determination of n-alkanes in complicated soil samples with acceptable recoveries.

  18. Platinum nanocatalysts loaded on graphene oxide-dispersed carbon nanotubes with greatly enhanced peroxidase-like catalysis and electrocatalysis activities

    NASA Astrophysics Data System (ADS)

    Wang, Hua; Li, Shuai; Si, Yanmei; Zhang, Ning; Sun, Zongzhao; Wu, Hong; Lin, Yuehe

    2014-06-01

    A powerful enzymatic mimetic has been fabricated by employing graphene oxide (GO) nanocolloids to disperse conductive carbon supports of hydrophobic carbon nanotubes (CNTs) before and after the loading of Pt nanocatalysts. The resulting GOCNT-Pt nanocomposites could present improved aqueous dispersion stability and Pt spatial distribution. Unexpectedly, they could show greatly enhanced peroxidase-like catalysis and electrocatalysis activities in water, as evidenced in the colorimetric and electrochemical investigations in comparison to some inorganic nanocatalysts commonly used. Moreover, it is found that the new enzyme mimetics could exhibit peroxidase-like catalysis activity comparable to natural enzymes; yet, they might circumvent some of their inherent problems in terms of catalysis efficiency, electron transfer, environmental stability, and cost effectiveness. Also, sandwiched electrochemical immunoassays have been successfully conducted using GOCNT-Pt as enzymatic tags. Such a fabrication avenue of noble metal nanocatalysts loaded on well-dispersed conductive carbon supports should be tailored for the design of different enzyme mimics promising the extensive catalysis applications in environmental, medical, industrial, and particularly aqueous biosensing fields.A powerful enzymatic mimetic has been fabricated by employing graphene oxide (GO) nanocolloids to disperse conductive carbon supports of hydrophobic carbon nanotubes (CNTs) before and after the loading of Pt nanocatalysts. The resulting GOCNT-Pt nanocomposites could present improved aqueous dispersion stability and Pt spatial distribution. Unexpectedly, they could show greatly enhanced peroxidase-like catalysis and electrocatalysis activities in water, as evidenced in the colorimetric and electrochemical investigations in comparison to some inorganic nanocatalysts commonly used. Moreover, it is found that the new enzyme mimetics could exhibit peroxidase-like catalysis activity comparable to natural

  19. In situ spectroscopic investigation of molecular structures of highly dispersed vanadium oxide on silica under various conditions

    SciTech Connect

    Gao, X.; Wachs, I.R.; Bare, S.R.; Weckhuysen, B.M.

    1998-12-24

    The molecularly dispersed V{sub 2}O{sub 5}/SiO{sub 2} supported oxides were prepared by the incipient wetness impregnation of 2-propanol solutions of V-isopropoxide. The experimental maximum dispersion of surface vanadium oxide species on SiO{sub 2} was achieved at {approximately}12 wt% v{sub 2}O{sub 5} ({approximately}2.6 V atoms/nm{sup 2}). The surface structures of the molecularly dispersed V{sub 2}O{sub 5}/SiO{sub 2} samples under various conditions were extensively investigated by in situ Raman, UV-vis-NIR DRS and XANES spectroscopies. The combined characterization techniques revealed that in the dehydrated state only isolated VO{sub 4} species are present on the silica surface up to monolayer coverage. Interestingly, the three-member siloxane rings on the silica surface appear to be the most favorable sites for anchoring the isolated, three-legged (SiO){sub 3} V{double_bond}O species. Hydration dramatically changes the molecular structure of the surface vanadium oxide species. The specific structure of the hydrated surface vanadium oxide species is dependent on the degree of hydration. The molecular structure of the fully hydrated vanadium oxide species closely resembles V{sub 2}O{sub 5}{center_dot}nH{sub 2}O gels, rather than V{sub 2}O{sub 5} crystallites. The fully hydrated surface vanadium oxide species are proposed to be chain and/or two-dimensional polymers with highly distorted square-pyramidal VO{sub 5} connected by V-OH-V bridges, which are stabilized on the silica surface by the sixth neighbor of Si-OH hydroxyls via Si-OH{hor_ellipsis}V hydrogen bonds. In analogy to the hydration process, alcoholysis occurs during methanol chemisorption, and similar molecular structures are proposed to interpret the interaction between methanol molecules and the surface vanadium oxide species on silica.

  20. Synchronous Improvement of Dispersibility and Electrical Property of Antimony Doped Tin Oxide Nanoparticles Processed by Polyvinyl Alcohol

    NASA Astrophysics Data System (ADS)

    Liu, Shimin; Wen, Bin; Jiang, Weiwei; Liu, Chaoqian; Ding, Wanyu; Wang, Nan; Chai, Weiping

    2015-08-01

    Antimony doped tin oxide (ATO) nanoparticles were prepared by wet chemical coprecipitation method with different contents of polyvinyl alcohol (PVA) dispersant. The prepared ATO nanoparticles have been characterized by means of XRD, SEM, HRTEM, SAED, EDS, bulk density and electrical resistivity measurement. Results indicated that the approach functionalized by PVA dispersant enables a synchronous improvement of two important properties namely the dispersibility and electrical conductivity due to the mechanism of avoiding the formation of agglomeration of nanoparticles, which could be regarded as primary factors for the enhanced electron transfer of powders: The surface area over which are crucial for the interfacial arrangement and electron charge scattering/transfer processes. The bulk density and electrical resistivity decreased to a minimum of 0.90 g/cm3 and 1.44 Ωṡcm at PVA dispersant content of 5%, and increased rapidly at higher PVA contents. The prepared ATO nanoparticles can serve as a kind of effective conductive filler in insulating species such as plastics, textile and rubber.

  1. Synthesis of water-dispersible zinc oxide quantum dots with antibacterial activity and low cytotoxicity for cell labeling

    NASA Astrophysics Data System (ADS)

    Hsu, Shan-hui; Lin, Ying Yi; Huang, Sherry; Lem, Kwok Wai; Huong Nguyen, Dinh; Lee, Dai Soo

    2013-11-01

    Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

  2. Synthesis of water-dispersible zinc oxide quantum dots with antibacterial activity and low cytotoxicity for cell labeling.

    PubMed

    Hsu, Shan-hui; Lin, Ying Yi; Huang, Sherry; Lem, Kwok Wai; Nguyen, Dinh Huong; Lee, Dai Soo

    2013-11-29

    Typical photoluminescent semiconductor nanoparticles, called quantum dots (QDs), have potential applications in biological labeling. When used to label stem cells, QDs may impair the differentiation capacity of the stem cells. In this study, we synthesized zinc oxide (ZnO) QDs in methanol with an average size of ∼2 nm. We then employed two different types of polyethylene glycol (PEG) molecules (SH-PEG-NH2 and NH2-PEG-NH2) to conjugate ZnO QDs and made them water-dispersible. Fourier transform infrared spectroscopy spectra indicated the attachment of PEG molecules on ZnO QDs. No obvious size alteration was observed for ZnO QDs after PEG conjugation. The water-dispersible ZnO QDs still retained the antibacterial activity and fluorescence intensity. The cytotoxicity evaluation revealed that ZnO QDs at higher concentrations decreased cell viability but were generally safe at 30 ppm or below. Cell lines of hepatocytes (HepG2), osteoblasts (MC3T3-E1) and mesenchymal stem cells (MSCs) were successfully labeled by the water-dispersible ZnO QDs at 30 ppm. The ZnO QD-labeled MSCs maintained their stemness and differentiation capacity. Therefore, we conclude that the water-dispersible ZnO QDs developed in this study have antibacterial activity, low cytotoxicity, and proper labeling efficiency, and can be used to label a variety of cells including stem cells.

  3. Microbial oxidation of dispersed graphite by nitrifying bacteria 2011.2

    NASA Astrophysics Data System (ADS)

    Zhu, Chunlin; Hao, Qingli; Huang, Yang; Yang, Jiazhi; Sun, Dongping

    2013-09-01

    A facile and green microbial method to produce graphite oxide nanosheets and nanoparticles is described. The obtained graphite oxide nanosheets have few layers with 0.7-1.5 nm height and 50-300 nm size. The carbon nanoparticles possess the size of 20-60 nm and the height of 2-4 nm.A facile and green microbial method to produce graphite oxide nanosheets and nanoparticles is described. The obtained graphite oxide nanosheets have few layers with 0.7-1.5 nm height and 50-300 nm size. The carbon nanoparticles possess the size of 20-60 nm and the height of 2-4 nm. Electronic supplementary information (ESI) available: Experimental section, characterization details and the mechanism of the oxidation process. Microscopic photographs of graphite during the microbial oxidation and the proposed mechanism of microbial oxidation of graphite. See DOI: 10.1039/c3nr02069j

  4. Removal of aluminum(III)-based turbidity in water using hydrous titanium oxide dispersed in ion-exchange resins

    SciTech Connect

    Venkataramani, B.; Karweer, S.B.; Iyer, R.K.; Phatak, G.M.; Iyer, R.M.

    1988-04-01

    An adsorber consisting of hydrous titanium oxide (HTiO) dispersed in a Dowex-type ion-exchange resin matrix (designated RT resins) has been developed which is capable of removing Al(III)-based colloidal dispersions in the neutral pH condition. The effect of resin crosslinking, particle size, HTiO loading, turbidity level, and flow rate on the turbidity removal efficiency of RT resins has been studied. It is demonstrated that a train of columns comprising RT resin, H/sup +/, and OH/sup -/ form of resins could be used for large-scale purification operations at high flow rates. These columns, apart from removing turbidity and associated radioactivity, can effectively remove dissolved uranium present in ppb levels when used for water purification in nuclear reactors.

  5. Enhancement of hole injection using ozone treated Ag nanodots dispersed on indium tin oxide anode for organic light emitting diodes

    SciTech Connect

    Moon, Jong-Min; Bae, Jung-Hyeok; Jeong, Jin-A; Jeong, Soon-Wook; Park, No-Jin; Kim, Han-Ki; Kang, Jae-Wook; Kim, Jang-Joo; Yi, Min-Su

    2007-04-16

    The authors report the enhancement of hole injection using an indium tin oxide (ITO) anode covered with ultraviolet (UV) ozone-treated Ag nanodots for fac tris (2-phenylpyridine) iridium Ir(ppy){sub 3}-doped phosphorescent organic light-emitting diodes (OLEDs). X-ray photoelectron spectroscopy and UV-visible spectrometer analysis exhibit that UV-ozone treatment of the Ag nanodots dispersed on the ITO anode leads to formation of Ag{sub 2}O nanodots with high work function and high transparency. Phosphorescent OLEDs fabricated on the Ag{sub 2}O nanodot-dispersed ITO anode showed a lower turn-on voltage and higher luminescence than those of OLEDs prepared with a commercial ITO anode. It was thought that, as Ag nanodots changed to Ag{sub 2}O nanodots by UV-ozone treatment, the decrease of the energy barrier height led to the enhancement of hole injection in the phosphorescent OLEDs.

  6. Optimization of particle size for high birefringence and fast switching time in electro-optical switching of graphene oxide dispersions.

    PubMed

    Ahmad, R T M; Hong, Seung-Ho; Shen, Tian-Zi; Song, Jang-Kun

    2015-02-23

    In order to use graphene oxide (GO) dispersions for electro-optical applications, both a high GO concentration and a high electrical sensitivity are essential; however, these have not been achieved to date. Here, we report that by optimizing the mean size of GO particles to approximately 0.5 μm, one can obtain a high GO concentration of up to 2 wt% and high electrical sensitivity simultaneously. By reducing the mean GO-particle size, the interparticle interaction and the rotational viscosity can be significantly reduced, and a high-concentration isotropic phase can be obtained. As a result, the maximum birefringence increases and the dynamic response becomes faster. However, further decrease of the mean size below 0.1 μm causes a decrease in the anisotropy of electrical polarizability, resulting in the reduction of the electrical sensitivity of GO dispersions. PMID:25836480

  7. A reduced graphene oxide nanofiltration membrane intercalated by well-dispersed carbon nanotubes for drinking water purification

    NASA Astrophysics Data System (ADS)

    Chen, Xianfu; Qiu, Minghui; Ding, Hao; Fu, Kaiyun; Fan, Yiqun

    2016-03-01

    In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for drinking water purification to retain the nanoparticles, dyes, proteins, organophosphates, sugars, and particularly humic acid. Experimentally, it is shown that the rGO-CNT hybrid NF membranes have high retention efficiency, good permeability and good anti-fouling properties. The retention was above 97.3% even for methyl orange (327 Da); for other objects, the retention was above 99%. The membrane's permeability was found to be as high as 20-30 L m-2 h-1 bar-1. Based on these results, we can conclude that (i) the use of BCPs as a surfactant can enhance steric repulsion and thus disperse CNTs effectively; (ii) placing well-dispersed 1D CNTs within 2D graphene sheets allows an uniform network to form, which can provide many mass transfer channels through the continuous 3D nanostructure, resulting in the high permeability and separation performance of the rGO-CNT hybrid NF membranes.In this study, we report a promising rGO-CNT hybrid nanofiltration (NF) membrane that was fabricated by loading reduced graphene oxide that was intercalated with carbon nanotubes (rGO-CNTs) onto an anodic aluminum oxide (AAO) microfiltration membrane via a facile vacuum-assisted filtration process. To create this NF membrane, the CNTs were first dispersed using block copolymers (BCPs); the effects of the types and contents of BCPs used on the dispersion of CNTs have been investigated. The as-prepared rGO-CNT hybrid NF membranes were then used for

  8. Pseudosolid, shear-thinning gel formation in binary dispersions of metal oxide nanoparticles at low volume fractions.

    PubMed

    Weston, J S; Venkataramani, D; Aichele, C P; Grady, B P; Harwell, J; Resasco, D

    2014-12-16

    Hydroxyl groups on the surface of metal oxide nanoparticles (nps) can be protonated or deprotonated depending on solution pH, changing both the magnitude and sign of the nps' surface charge. Binary mixtures of fumed metal oxide nps, dispersed in water at a solution pH where one species is positively charged and the other is negatively charged, form pseudosolid gels at volume fractions as low as 1.5 vol %. This work maps out regions of gel formation for binary mixtures of silica and alumina nps, silica and titania nps, and alumina and titania nps. The microscopic structure of these gels is investigated using transmission electron microscopy (TEM), small-angle x-ray scattering (SAXS), acoustic spectroscopy, and light microscopy.

  9. Platinum nanocatalysts loaded on graphene oxide-dispersed carbon nanotubes with greatly enhanced peroxidase-like catalysis and electrocatalysis activities.

    PubMed

    Wang, Hua; Li, Shuai; Si, Yanmei; Zhang, Ning; Sun, Zongzhao; Wu, Hong; Lin, Yuehe

    2014-07-21

    A powerful enzymatic mimetic has been fabricated by employing graphene oxide (GO) nanocolloids to disperse conductive carbon supports of hydrophobic carbon nanotubes (CNTs) before and after the loading of Pt nanocatalysts. The resulting GOCNT-Pt nanocomposites could present improved aqueous dispersion stability and Pt spatial distribution. Unexpectedly, they could show greatly enhanced peroxidase-like catalysis and electrocatalysis activities in water, as evidenced in the colorimetric and electrochemical investigations in comparison to some inorganic nanocatalysts commonly used. Moreover, it is found that the new enzyme mimetics could exhibit peroxidase-like catalysis activity comparable to natural enzymes; yet, they might circumvent some of their inherent problems in terms of catalysis efficiency, electron transfer, environmental stability, and cost effectiveness. Also, sandwiched electrochemical immunoassays have been successfully conducted using GOCNT-Pt as enzymatic tags. Such a fabrication avenue of noble metal nanocatalysts loaded on well-dispersed conductive carbon supports should be tailored for the design of different enzyme mimics promising the extensive catalysis applications in environmental, medical, industrial, and particularly aqueous biosensing fields.

  10. A study of the dispersity of iron oxide and iron oxide-noble metal (Me = Pd, Pt) supported systems

    NASA Astrophysics Data System (ADS)

    Cherkezova-Zheleva, Z. P.; Shopska, M. G.; Krstić, J. B.; Jovanović, D. M.; Mitov, I. G.; Kadinov, G. B.

    2007-09-01

    Samples of one-(Fe) and two-component (Fe-Pd and Fe-Pt) catalysts were prepared by incipient wetness impregnation of four different supports: TiO2 (anatase), γ-Al2O3, activated carbon, and diatomite. The chosen synthesis conditions resulted in the formation of nanosized supported phases—iron oxide (in the one-component samples), or iron oxide-noble metal (in the two-component ones). Different agglomeration degrees of these phases were obtained as a result of thermal treatment. Ultradisperse size of the supported phase was maintained in some samples, while a process of partial agglomeration occurred in others, giving rise to nearly bidisperse (ultra-and highdisperse) supported particles. The different texture of the used supports and their chemical composition are the reasons for the different stability of the nanosized supported phases. The samples were tested as heterogeneous catalysts in total benzene oxidation reaction.

  11. Small-sized and highly dispersed Pt nanoparticles loading on graphite nanoplatelets as an effective catalyst for methanol oxidation.

    PubMed

    Zhang, Genlei; Yang, Zhenzhen; Huang, Chengde; Zhang, Wen; Wang, Yuxin

    2015-06-14

    A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the highest electrocatalytic activity and the best stability toward the methanol oxidation reaction. Moreover, the Pt/I-IL (10)/GNP catalyst markedly outperforms the commercial Pt/C from Johnson Matthey in terms of both methanol oxidation activity and stability, revealed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy.

  12. Enhancement of ethanol oxidation at Pt and PtRu nanoparticles dispersed over hybrid zirconia-rhodium supports

    NASA Astrophysics Data System (ADS)

    Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.

    2014-12-01

    A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.

  13. Preparation of water-dispersible porous g-C3N4 with improved photocatalytic activity by chemical oxidation.

    PubMed

    Li, Hui-Jun; Sun, Bo-Wen; Sui, Li; Qian, Dong-Jin; Chen, Meng

    2015-02-01

    Hydrophilic treatment of bulk graphene-like carbon nitride (g-C3N4) for future applications has aroused extensive interest, due to its enhanced specific surface area and unusual electronic properties. Herein, water-dispersible g-C3N4 with a porous structure can be obtained by chemical oxidation of bulk g-C3N4 with K2Cr2O7-H2SO4. Acid oxidation results in the production of hydroxyl and carboxyl groups on its basal plane and the formation of a porous structure of g-C3N4 at the same time. The porous g-C3N4 appears as networks with tens of micrometers in width and possesses a high specific surface area of 235.2 m(2) g(-1). The final concentration of porous g-C3N4 can be up to 3 mg mL(-1). Compared with bulk g-C3N4, the as-obtained porous g-C3N4 exhibits excellent water dispersion stability and shows great superiority in photoinduced charge carrier separation and transfer. The photocatalytic activities of porous g-C3N4 towards degradation of organic pollutants are much higher than those of the bulk due to the larger band gap (by 0.2 eV) and specific surface areas.

  14. Small-sized and highly dispersed Pt nanoparticles loading on graphite nanoplatelets as an effective catalyst for methanol oxidation.

    PubMed

    Zhang, Genlei; Yang, Zhenzhen; Huang, Chengde; Zhang, Wen; Wang, Yuxin

    2015-06-14

    A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the highest electrocatalytic activity and the best stability toward the methanol oxidation reaction. Moreover, the Pt/I-IL (10)/GNP catalyst markedly outperforms the commercial Pt/C from Johnson Matthey in terms of both methanol oxidation activity and stability, revealed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. PMID:25986338

  15. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Deadmore, D. L.

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  16. Dispersion fraction enhances cellular growth of carbon nanotube and aluminum oxide reinforced ultrahigh molecular weight polyethylene biocomposites.

    PubMed

    Patel, Anup Kumar; Balani, Kantesh

    2015-01-01

    Ultrahigh molecular weight polyethylene (UHMWPE) is widely used as bone-replacement material for articulating surfaces due to its excellent wear resistance and low coefficient of friction. But, the wear debris, generated during abrasion between mating surfaces, leads to aseptic loosening of implants. Thus, various reinforcing agents are generally utilized, which may alter the surface and biological properties of UHMWPE. In the current work, the cellular response of compression molded UHMWPE upon reinforcement of bioactive multiwalled carbon nanotubes (MWCNTs) and bioinert aluminum oxide (Al2O3) is investigated. The phase retention and stability were observed using X-ray diffraction, Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The reinforcement of MWCNTs and Al2O3 has shown to alter the wettability (from contact angle of ~88°±2° to ~118°±4°) and surface energy (from ~23.20 to ~17.75 mN/m) of composites with respect to UHMWPE, without eliciting any adverse effect on cytocompatibility for the L929 mouse fibroblast cell line. Interestingly, the cellular growth of the L929 mouse fibroblast cell line is observed to be dominated by the dispersion fraction of surface free energy (SFE). After 48 h of incubation period, a decrease in metabolic activity of MWCNT-Al2O3 reinforced composites is attributed to apatite formation that reduces the dispersion fraction of surface energy. The mineralized apatite during incubation was confirmed and quantified by energy dispersive spectroscopy and X-ray diffraction respectively. Thus, the dispersion fraction of surface free energy can be engineered to play an important role in achieving enhanced metabolic activity of the MWCNT-Al2O3 reinforced UHMWPE biopolymer composites.

  17. A generalized method toward high dispersion of transition metals in large pore mesoporous metal oxide/silica hybrids.

    PubMed

    Bérubé, François; Khadraoui, Abdelkarim; Florek, Justyna; Kaliaguine, Serge; Kleitz, Freddy

    2015-07-01

    A series of transition metal acetylacetonates and acetates were used as precursors to generate high loadings of metal sites finely dispersed on SBA-15 silica. To achieve this, grafting of chelated transition metal precursors was performed directly to the surface of the as-synthesized SBA-15/P123 composite material. The thus-obtained metal/SBA-15 materials were studied by a variety of methods, e.g., elemental analysis, Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance UV-visible spectroscopy (DR-UV-vis), X-ray photoelectron spectroscopy (XPS) and N2 physisorption measurements at -196 °C. From the results, the proposed functionalization method was found to be a highly tunable and reproducible strategy to disperse transition metal oxides in mesoporous silica materials. The results from elemental analysis of the modified materials confirmed that the amount of grafted species is a function of the initial concentration of precursor in the solution used for grafting. The chelated complexes were found to strongly interact with the silanol groups of the silica material, resulting in a ligand-exchange process, as corroborated by FTIR. However, different metal precursors showed distinct reactivity towards the surface of mesoporous silica, owing to differences in the stability of the complexes under the conditions used for grafting. DR-UV-vis and XPS analyses suggest that when the stability of a given precursor decreases, the grafting procedure can lead to the formation of small clusters of the metal oxide on the silica surface. XRD and SEM also show that grafting of lower stability complexes, such as Mn(acac)3, Cu(acetate)2 and VO(acac)2, on the silica surface can result in the formation of large crystals on the external surface of the SBA-15 particles. Nevertheless, it was established by XPS analysis that only a small percentage of the grafted species leads to the formation of bulk

  18. Oxidation-Reduction Resistance of Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

    2003-01-01

    Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

  19. Effect of silica capping on the oxidation of Fe3O4 nanoparticles in dispersion revealed by x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Warland, A.; Antoniak, C.; Darbandi, M.; Weis, C.; Landers, J.; Keune, W.; Wende, H.

    2012-06-01

    Fe3O4 nanoparticles have been investigated as they are biocompatible and their surface can be functionalized. We synthesized iron oxide nanoparticles using a water-in-oil microemulsion method. Bare and silica-coated iron oxide nanoparticles of a core size of 6 nm dispersed in ethanol have been investigated by means of x-ray absorption spectroscopy (XAS). Due to a dedicated experimental setup the particles can be measured directly in dispersion. XAS allows us to disentangle the contributions of the Fe2+ and Fe3+ ions and therefore to estimate the amount of Fe3O4 in the particles. In case of the silica coated particles a high amount of magnetite was obtained. In contrast, the bare nanoparticles showed indications of a further oxidation into γ-Fe2O3 even in dispersion.

  20. A New Class of Highly Dispersed VOx Catalysts on Mesoporous Silica: Synthesis, Characterization, and Catalytic Activity in the Partial Oxidation of Ethanol

    SciTech Connect

    Kwak, Ja Hun; Herrera, Jose E.; Hu, Jian Zhi; Wang, Yong; Peden, Charles HF

    2006-01-26

    The morphology of vanadium oxide supported on a titania-modified mesoporous silica (MCM-41), obtained by means of a careful grafting process through atomic layer deposition, was studied using a variety of characterization techniques. The XRD together with TEM, 51V-NMR, Raman, FTIR and DRS-UV-Vis results showed that the vanadia species are extremely well dispersed onto the surface of the mesoporous support; the dispersion being stable upon thermal treatments up to 400 °C. Studies of the catalytic activity of these materials were performed using the partial oxidation of ethanol as a probe reaction. The results indicate an intrinsic relationship between dispersion, the presence of a TiO2-VOx phase, and catalytic activity for oxidation and dehydration.

  1. [Analysis of the mechanism of intensification of fermentation process using yeast cells in a suspension of high-dispersed oxides].

    PubMed

    Bagatskaya, A N; Mazurenko, R V; Makhno, S N; Gorbik, P P

    2014-01-01

    The differential microcalorimetry was used to explore an influence of particles of silicon dioxide, and also other high-dispersed oxides (0.05% of masses.) in water suspension of yeast cells on intensification of the process of their fermentation in endogenous metabolic conditions. It was shown that intensification of the processes of the vital activity of yeast microorganisms was observed in the specified interval of the concentration of silicon dioxide hydrosol particles. Mechanisms of interaction between SiO2 particles and a surface of a cellular organism, as well as interaction between SiO2 particles and one of metabolism products--carbon dioxide were studied. It was found out, that Al2O3, TiO2 hydrosols also had a stimulating effect, but it is lower compared to that of SiO2.

  2. Effect of temperature on rheological properties of copper oxide nanoparticles dispersed in propylene glycol and water mixture.

    PubMed

    Kulkarni, Devdatta P; Das, Debendra K; Patil, Shirish L

    2007-07-01

    This paper reports on experimental investigation of the rheological behavior of copper oxide nanoparticles dispersed in a 60:40 propylene glycol and water mixture. Nanofluids of a particle volume concentration from 0 to 6% have been tested in this study. The experiments were conducted over a temperature range of -35 degrees C to 50 degrees C to establish their behavior for use as a heat transfer fluid in cold climates. The experiments reveal that this nanofluid in the range of particle volume percentage tested exhibits a Newtonian behavior. A new exponential correlation has been developed from the experimental data, which expresses the viscosity as a function of particle volume percent and the temperature of the nanofluid. The slope of relative viscosity curve was found to be higher at lower temperatures.

  3. Aloe barbadensis Miller mediated green synthesis of mono-disperse copper oxide nanoparticles: Optical properties

    NASA Astrophysics Data System (ADS)

    Gunalan, Sangeetha; Sivaraj, Rajeshwari; Venckatesh, Rajendran

    2012-11-01

    In this paper, we report on the synthesis of nanostructured copper oxide particles by both chemical and biological method. A facile and efficient synthesis of copper oxide nanoparticles was carried out with controlled surface properties via green chemistry approach. The CuO nanoparticles synthesized are monodisperse and versatile and were characterized with the help of UV-Vis, PL, FT-IR, XRD, SEM, and TEM techniques. The particles are crystalline in nature and average sizes were between 15 and 30 nm. The morphology of the nanoparticles can be controlled by tuning the amount of Aloe vera extract. This new eco-friendly approach of synthesis is a novel, cheap, and convenient technique suitable for large scale commercial production and health related applications of CuO nanoparticles.

  4. Aqueous dispersions of oxide nanoparticles as a treatment for pyoinflammatory diseases with chronic component

    NASA Astrophysics Data System (ADS)

    Rutberg, Ph; Kolikov, V.; Moshkin, A.; Snetov, V.; Stogov, A.; Khalilov, M.

    2011-04-01

    Promising direction of surgery related to the treatment of acute purulent wounds with chronic component could be utilization of aqueous dispersions of nanostructures (ADN) produced by pulsed electric discharge in water. The investigation is addressed to finding out the opportunity of usage of an ADN for treatment of purulent wounds with a chronic component and comparison of its efficiency with the widespread antiseptics. For realization of investigation was used ADN, which has maximal share of "small" nanostructures (<100 nm) with the greatest surface electric charge. High activity of reparative processes is established at use of ADN and subsequent moderate changes of the further healing. The attributes of cellular atypia and preternatural representations about inflammatory reactions are not revealed at local use of ADN.

  5. Suppression of grain growth in nanocrystalline Bi{sub 2}Te{sub 3} through oxide particle dispersions

    SciTech Connect

    Humphry-Baker, Samuel A.; Schuh, Christopher A.

    2014-11-07

    The strategy of suppressing grain growth by dispersing nanoscale particles that pin the grain boundaries is demonstrated in a nanocrystalline thermoelectric compound. Yttria nanoparticles that were incorporated by mechanical alloying enabled nanocrystalline (i.e., d < 100 nm) Bi{sub 2}Te{sub 3} to be retained up to a homologous temperature of 0.94 T{sub m} for durations over which the grain size of the unreinforced compound grew to several microns. The nanostructure appeared to saturate at a grain size that depended on volume fraction (f) according to an f {sup −1/3} relationship, in accordance with theoretical models in the limit of high volume fractions of particles. Interestingly, at low temperatures, the particles stimulate enhanced grain growth over the unreinforced compound, due to particle-stimulated nucleation of recrystallization. To help prevent this effect, in-situ composites formed by internal oxidation of yttrium are compared with those made ex-situ by incorporation of yttria nanoparticles, with the result that the in-situ dispersion eliminates recrystallization at low temperatures and therefore improves nanostructure stabilization. These developments offer a pathway to thermally stabilized bulk nanocrystalline thermoelectrics processed via a powder route.

  6. Tensile and fracture toughness properties of the nanostructured oxide dispersion strengthened ferritic alloy 13Cr-1W-0.3Ti-0.3Y 2O 3

    NASA Astrophysics Data System (ADS)

    Eiselt, Ch. Ch.; Klimenkov, M.; Lindau, R.; Möslang, A.; Odette, G. R.; Yamamoto, T.; Gragg, D.

    2011-10-01

    The realization of fusion power as an attractive energy source requires advanced structural materials that can cope with ultra-severe thermo-mechanical loads and high neutron fluxes experienced by fusion power plant components, such as the first wall, divertor and blanket structures. Towards this end, two variants of a 13Cr-1W-0.3Ti-0.3Y 2O 3 reduced activation ferritic (RAF-) ODS steel were produced by ball milling phase blended Fe-13Cr-1W, 0.3Y 20 3 and 0.3Ti powders in both argon and hydrogen atmospheres. The milled powders were consolidated by hot isostatic pressing (HIP). The as-HIPed alloys were then hot rolled into 6 mm plates. Microstructural, tensile and fracture toughness characterization of the hot rolled alloys are summarized here and compared to results previously reported for the as-HIPed condition.

  7. Highly dispersible and stable copper terephthalate metal-organic framework-graphene oxide nanocomposite for an electrochemical sensing application.

    PubMed

    Wang, Xia; Wang, Qingxiang; Wang, Qinghua; Gao, Feng; Gao, Fei; Yang, Yizhen; Guo, Hongxu

    2014-07-23

    A highly dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) = copper terephthalate metal-organic framework, GO = graphene oxide) was prepared through a simple ultrasonication method. The morphology and structure of the obtained composite were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). On the basis of the characterization results, the binding mechanism of the Cu(tpa) and GO was speculated to be the cooperative interaction of π-π stacking, hydrogen bonding, and Cu-O coordination. The electrochemical sensing property of Cu(tpa)-GO composite was investigated through casting the composite on a glassy carbon electrode (GCE), followed by an electro-reduction treatment to transfer the GO in the composite to the highly conductive reduced form (electrochemically reduced graphene, EGR). The results demonstrated that the electrochemical signals and peak profiles of the two drugs of acetaminophen (ACOP) and dopamine (DA) were significantly improved by the modified material, owing to the synergistic effect from high conductivity of EGR and unique electron mediating action of Cu(tpa). Under the optimum conditions, the oxidation peak currents of ACOP and DA were linearly correlated to their concentrations in the ranges of 1-100 and 1-50 μM, respectively. The detection limits for ACOP and DA were estimated to be as low as 0.36 and 0.21 μM, respectively. PMID:25000168

  8. Highly dispersible and stable copper terephthalate metal-organic framework-graphene oxide nanocomposite for an electrochemical sensing application.

    PubMed

    Wang, Xia; Wang, Qingxiang; Wang, Qinghua; Gao, Feng; Gao, Fei; Yang, Yizhen; Guo, Hongxu

    2014-07-23

    A highly dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) = copper terephthalate metal-organic framework, GO = graphene oxide) was prepared through a simple ultrasonication method. The morphology and structure of the obtained composite were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). On the basis of the characterization results, the binding mechanism of the Cu(tpa) and GO was speculated to be the cooperative interaction of π-π stacking, hydrogen bonding, and Cu-O coordination. The electrochemical sensing property of Cu(tpa)-GO composite was investigated through casting the composite on a glassy carbon electrode (GCE), followed by an electro-reduction treatment to transfer the GO in the composite to the highly conductive reduced form (electrochemically reduced graphene, EGR). The results demonstrated that the electrochemical signals and peak profiles of the two drugs of acetaminophen (ACOP) and dopamine (DA) were significantly improved by the modified material, owing to the synergistic effect from high conductivity of EGR and unique electron mediating action of Cu(tpa). Under the optimum conditions, the oxidation peak currents of ACOP and DA were linearly correlated to their concentrations in the ranges of 1-100 and 1-50 μM, respectively. The detection limits for ACOP and DA were estimated to be as low as 0.36 and 0.21 μM, respectively.

  9. Oxidized carbon nitrides: water-dispersible, atomically thin carbon nitride-based nanodots and their performances as bioimaging probes.

    PubMed

    Oh, Junghoon; Yoo, Ran Ji; Kim, Seung Yeon; Lee, Yong Jin; Kim, Dong Wook; Park, Sungjin

    2015-04-13

    Three-dimensional (3D) carbon nitride (C3 N4 )-based materials show excellent performance in a wide range of applications because of their suitable band structures. To realize the great promise of two-dimensional (2D) allotropes of various 3D materials, it is highly important to develop routes for the production of 2D C3 N4 materials, which are one-atom thick, in order to understand their intrinsic properties and identify their possible applications. In this work, water-dispersible, atomically thin, and small carbon nitride nanodots were produced using the chemical oxidation of graphitic C3 N4 . Various analyses, including X-ray diffraction, X-ray photoelectron, Fourier-transform infrared spectroscopy, and combustion-based elemental analysis, and thermogravimetric analysis, confirmed the production of 3D oxidized C3 N4 materials. The 2D C3 N4 nanodots were successfully exfoliated as individual single layers; their lateral dimension was several tens of nanometers. They showed strong photoluminescence in the visible region as well as excellent performances as cell-imaging probes in an in vitro study using confocal fluorescence microscopy.

  10. Uniform dispersion of graphene oxide in aluminum powder by direct electrostatic adsorption for fabrication of graphene/aluminum composites

    NASA Astrophysics Data System (ADS)

    Li, Zan; Fan, Genlian; Tan, Zhanqiu; Guo, Qiang; Xiong, Dingbang; Su, Yishi; Li, Zhiqiang; Zhang, Di

    2014-08-01

    The excellent properties of graphene promote it as an ideal reinforcement in composites. However, dispersing graphene homogenously into metals is a key challenge that limits the development of high-performance graphene-reinforced metal matrix composites. Here, via simple electrostatic interaction between graphene oxide (GO) and Al flakes, uniform distribution of reduced graphene oxide (RGO) in an Al matrix is achieved. The adsorption process of GO on Al flakes is efficient, as it can be completed in minutes and proceeds spontaneously without any chemical agents. GO can be partially reduced by the electron interchange during the adsorption process and could be thoroughly reduced after subsequent thermal annealing. A densified RGO/Al composite can be obtained by hot pressing the RGO/Al composite powders. By employing the preceding fabrication process, a composite reinforced with only 0.3 wt.% of RGO shows an 18 and 17% increase in elastic modulus and hardness, respectively, over unreinforced Al, demonstrating RGO is a better reinforcement than most other reinforcements.

  11. Effects of cation compositions on the electronic properties and optical dispersion of indium zinc tin oxide thin films by electron spectroscopy

    SciTech Connect

    Denny, Yus Rama; Seo, Soonjoo; Lee, Kangil; Oh, Suhk Kun; Kang, Hee Jae; Heo, Sung; Chung, Jae Gwan; Lee, Jae Cheol; Tougaard, Sven

    2015-02-15

    Highlights: • REELS analysis can provide optical dispersion and electronic properties of oxide materials. • The band gap varied with In/Zn/Sn compositions and increased after annealing. • The optical properties were examined using REELS in conjunction with the Tougaard–Yubero model. • The dispersion parameters were determined by a single-oscillator Wemple–DiDomenico model. • The Zn and Sn contents play a crucial role in determining the single-oscillator constant and dispersion energy of IZTO thin films. - Abstract: The electronic properties and optical dispersion of indium zinc tin oxide (IZTO) films with different cation compositions were investigated by reflection electron energy loss spectroscopy (REELS). The REELS spectra of IZTO films revealed that the band gap varied with different Sn/Zn ratios and In content. The optical properties were examined with REELS data using Tougaard–Yubero model and the results were compared with the envelope of the transmission spectra obtained using a UV-spectrometer. The dispersion behavior of the refractive index from REELS results was studied in terms of the single-oscillator Wemple–DiDomenico model. The results showed that the different compositions of In/Zn/Sn caused a change in the dispersion parameters of IZTO thin films in contrast to the static values of refractive indices and dielectric constant which remained the same. Our work demonstrated that REELS is an efficient tool to study the optical properties of a material by obtaining the optical parameters.

  12. Stability of dispersions of colloidal hematite/yttrium oxide core-shell particles.

    PubMed

    Plaza, R C; Quirantes, A; Delgado, A V

    2002-08-01

    The colloidal stability of suspensions of hematite/yttria core/shell particles is investigated in this work and compared with that of the pure hematite cores. The different electrical surface characteristics of yttrium and iron oxides, as well as the diameters of both types of spherical particles, dominate the overall process of particle aggregation. The aggregation kinetics of the suspensions was followed by measuring their optical absorbance as a function of time. By previously calculating the extinction cross section of particle doublets, it was demonstrated that for both core and core/shell particles the turbidity of the suspensions should increase on aggregation. Such an increase was in fact found in the systems in spite of the ever-present tendency of the particles to settle under gravity. The authors used the initial slope of the turbidity increment time plots as a measure of the ease of aggregation between particles. Thus, they found that the essential role played by pH on the charge generation on the two oxides and the shift of one pH unit between the isoelectric points of hematite and yttria manifest in two features: (i) the stability decreases on approaching the isoelectric point from either the acid or basic side and (ii) the maximum instability is found for hematite at pH 7 and for hematite/yttria at pH 8, that is, close to the isoelectric points of alpha-Fe(2)O(3) and Y(2)O(3), respectively. The role of added electrolyte is simply to yield the suspensions of either type more unstable. Using the surface free energy of the particles, the authors could estimate their Hamaker constants in water. From these and their zeta potentials, the DLVO theory of stability was used to quantitatively explain their results.

  13. Synthesis of tin and tin oxide nanoparticles of low size dispersity for application in gas sensing.

    PubMed

    Nayral, C; Viala, E; Fau, P; Senocq, F; Jumas, J C; Maisonnat, A; Chaudret, B

    2000-11-17

    Nanocomposite core-shell particles that consist of a Sn0 core surrounded by a thin layer of tin oxides have been prepared by thermolysis of [(Sn(NMe2)2)2] in anisole that contains small, controlled amounts of water. The particles were characterized by means of electronic microscopies (TEM, HRTEM, SEM), X-ray diffraction (XRD) studies, photoelectron spectroscopy (XPS), and Mossbauer spectroscopy. The TEM micrographs show spherical nanoparticles, the size and size distribution of which depends on the initial experimental conditions of temperature, time, water concentration, and tin precursor concentration. Nanoparticles of 19 nm median size and displaying a narrow size distribution have been obtained with excellent yield in the optimized conditions. HRTEM, XPS, XRD and Mossbauer studies indicate the composite nature of the particles that consist of a well-crystallized tin beta core of approximately equals 11 nm covered with a layer of approximately equals 4 nm of amorphous tin dioxide and which also contain quadratic tin monoxide crystallites. The thermal oxidation of this nanocomposite yields well-crystallized nanoparticles of SnO2* without coalescence or size change. XRD patterns show that the powder consists of a mixture of two phases: the tetragonal cassiterite phase, which is the most abundant, and an orthorhombic phase. In agreement with the small SnO2 particle size, the relative intensity of the adsorbed dioxygen peak observed on the XPS spectrum is remarkable, when compared with that observed in the case of larger SnO2 particles. This is consistent with electrical conductivity measurements, which demonstrate that this material is highly sensitive to the presence of a reducing gas such as carbon monoxide. PMID:11151840

  14. Intercalation of aggregation-free and well-dispersed gold nanoparticles into the walls of mesoporous silica as a robust "green" catalyst for n-alkane oxidation.

    PubMed

    Chen, Lifang; Hu, Juncheng; Richards, Ryan

    2009-01-28

    Aggregate-free and well-dispersed gold nanoparticles were intercalated into the walls of mesoporous silica forming a nanoreactor demonstrating high catalytic activity for "green" alkane oxidation. The material is robust and can be recycled. The method may be developed to intercalate other metal or alloy nanoparticles into the walls of mesoporous silica.

  15. Sensitive determination of Amaranth in drinks by highly dispersed CNT in graphene oxide "water" with the aid of small amounts of ionic liquid.

    PubMed

    Wang, Meiling; Sun, Yinlu; Yang, Xiongbo; Zhao, Jianwei

    2015-07-15

    Graphene oxide (GO) is a pH-dependent amphiphile. In this paper, it was found that carbon nanotubes (CNTs) can be highly dispersed in graphene oxide "water" with the aid of prototype ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). The introduction of [BMIM][PF6] not only can minimize the defects of poor electrical conductivity of GO, but also can improve the dispersibility of CNT in water. Hence, a new composite of CNT/GO-[BMIM][PF6] with high dispersibility and strong conductivity was presented for the first time and employed in the sensitive determination of Amaranth in soft drinks. The detection limit achieved (0.1 nM) is much lower than the guideline values in soft drinks. The ease of preparation, low background current, high sensitivity and stability can create novel avenues and applications for fabricating robust sensors for determination of other azo dyes in foods.

  16. Nanoscale strengthening mechanisms in metallic thin film systems

    NASA Astrophysics Data System (ADS)

    Schoeppner, Rachel Lynn

    Nano-scale strengthening mechanisms for thin films were investigated for systems governed by two different strengthening techniques: nano-laminate strengthening and oxide dispersion strengthening. Films were tested under elevated temperature conditions to investigate changes in deformation mechanisms at different operating temperatures, and the structural stability. Both systems exhibit remarkable stability after annealing and thus long-term reliability. Nano-scale metallic multilayers with smaller layer thicknesses show a greater relative resistance to decreasing strength at higher temperature testing conditions than those with larger layer thicknesses. This is seen in both Cu/Ni/Nb multilayers as well as a similar tri-component bi-layer system (Cu-Ni/Nb), which removed the coherent interface from the film. Both nanoindentation and micro-pillar compression tests investigated the strain-hardening ability of these two systems to determine what role the coherent interface plays in this mechanism. Tri-layer films showed a higher strain-hardening ability as the layer thickness decreased and a higher strain-hardening exponent than the bi-layer system: verifying the presence of a coherent interface increases the strain-hardening ability of these multilayer systems. Both systems exhibited hardening of the room temperature strength after annealing, suggesting a change in microstructure has occurred, unlike that seen in other multilayer systems. Oxide dispersion strengthened Au films showed a marked increase in hardness and wear resistance with the addition of ZnO particles. The threshold for stress-induced grain-refinement as opposed to grain growth is seen at concentrations of at least 0.5 vol%. These systems exhibited stable microstructures during thermal cycling in films containing at least 1.0%ZnO. Nanoindentation experiments show the drop in hardness following annealing is almost completely attributed to the resulting grain growth. Four-point probe resistivity

  17. Core-shell tin oxide, indium oxide, and indium tin oxide nanoparticles on silicon with tunable dispersion: electrochemical and structural characteristics as a hybrid Li-ion battery anode.

    PubMed

    Osiak, Michal J; Armstrong, Eileen; Kennedy, Tadhg; Torres, Clivia M Sotomayor; Ryan, Kevin M; O'Dwyer, Colm

    2013-08-28

    Tin oxide (SnO2) is considered a very promising material as a high capacity Li-ion battery anode. Its adoption depends on a solid understanding of factors that affect electrochemical behavior and performance such as size and composition. We demonstrate here, that defined dispersions and structures can improve our understanding of Li-ion battery anode material architecture on alloying and co-intercalation processes of Lithium with Sn from SnO2 on Si. Two different types of well-defined hierarchical Sn@SnO2 core-shell nanoparticle (NP) dispersions were prepared by molecular beam epitaxy (MBE) on silicon, composed of either amorphous or polycrystalline SnO2 shells. In2O3 and Sn doped In2O3 (ITO) NP dispersions are also demonstrated from MBE NP growth. Lithium alloying with the reduced form of the NPs and co-insertion into the silicon substrate showed reversible charge storage. Through correlation of electrochemical and structural characteristics of the anodes, we detail the link between the composition, areal and volumetric densities, and the effect of electrochemical alloying of Lithium with Sn@SnO2 and related NPs on their structure and, importantly, their dispersion on the electrode. The dispersion also dictates the degree of co-insertion into the Si current collector, which can act as a buffer. The compositional and structural engineering of SnO2 and related materials using highly defined MBE growth as model system allows a detailed examination of the influence of material dispersion or nanoarchitecture on the electrochemical performance of active electrodes and materials.

  18. Tunable optical limiting optofluidic device filled with graphene oxide dispersion in ethanol.

    PubMed

    Fang, Chaolong; Dai, Bo; Hong, Ruijin; Tao, Chunxian; Wang, Qi; Wang, Xu; Zhang, Dawei; Zhuang, Songlin

    2015-01-01

    An optofluidic device with tunable optical limiting property is proposed and demonstrated. The optofluidic device is designed for adjusting the concentration of graphene oxide (GO) in the ethanol solution and fabricated by photolithography technique. By controlling the flow rate ratio of the injection, the concentration of GO can be precisely adjusted so that the optical nonlinearity can be changed. The nonlinear optical properties and dynamic excitation relaxation of the GO/ethanol solution are investigated by using Z-scan and pump-probe measurements in the femtosecond regime within the 1.5 μm telecom band. The GO/ethanol solution presents ultrafast recovery time. Besides, the optical limiting property is in proportion to the concentration of the solution. Thus, the threshold power and the saturated power of the optical limiting property can be simply and efficiently manipulated by controlling the flow rate ratio of the injection. Furthermore, the amplitude regeneration is demonstrated by employing the proposed optofluidic device. The signal quality of intensity-impaired femtosecond pulse is significantly improved. The optofluidic device is compact and has long interaction length of optical field and nonlinear material. Heat can be dissipated in the solution and nonlinear material is isolated from other optical components, efficiently avoiding thermal damage and mechanical damage. PMID:26477662

  19. Solid dispersion of acetaminophen and poly(ethylene oxide) prepared by hot-melt mixing.

    PubMed

    Yang, Min; Wang, Peng; Huang, Chien-Yueh; Ku, M Sherry; Liu, Huiju; Gogos, Costas

    2010-08-16

    In this study, a model drug, acetaminophen (APAP), was melt mixed with poly(ethylene oxide) (PEO) using a Brabender mixer. APAP was found to recrystallize upon cooling to room temperature for all the drug loadings investigated. Higher drug loading leads to faster recrystallization rate. However, the morphology of the recrystallized drug crystals is identical in samples with different drug loadings and does not change with the storage time. To adjust the drug's dissolution rate, nanoclay Cloisite 15A and 30B were added into the binary mixture. The presence of either of the nanoclay dramatically accelerates the drug's recrystallization rate and slows down the drug's releasing rate. The drop of the releasing rate is mainly due to the decrease of wettability, as supported by the contact angle data. Data analysis of the dissolution results suggests that the addition of nanoclays changes the drug's release mechanism from erosion dominant to diffusion dominant. This study suggests that nanoclays may be utilized to tailor the drug's releasing rate and to improve the dosage form's stability by dramatically shortening the lengthy recrystallization process. PMID:20435110

  20. Tunable optical limiting optofluidic device filled with graphene oxide dispersion in ethanol

    PubMed Central

    Fang, Chaolong; Dai, Bo; Hong, Ruijin; Tao, Chunxian; Wang, Qi; Wang, Xu; Zhang, Dawei; Zhuang, Songlin

    2015-01-01

    An optofluidic device with tunable optical limiting property is proposed and demonstrated. The optofluidic device is designed for adjusting the concentration of graphene oxide (GO) in the ethanol solution and fabricated by photolithography technique. By controlling the flow rate ratio of the injection, the concentration of GO can be precisely adjusted so that the optical nonlinearity can be changed. The nonlinear optical properties and dynamic excitation relaxation of the GO/ethanol solution are investigated by using Z-scan and pump-probe measurements in the femtosecond regime within the 1.5 μm telecom band. The GO/ethanol solution presents ultrafast recovery time. Besides, the optical limiting property is in proportion to the concentration of the solution. Thus, the threshold power and the saturated power of the optical limiting property can be simply and efficiently manipulated by controlling the flow rate ratio of the injection. Furthermore, the amplitude regeneration is demonstrated by employing the proposed optofluidic device. The signal quality of intensity-impaired femtosecond pulse is significantly improved. The optofluidic device is compact and has long interaction length of optical field and nonlinear material. Heat can be dissipated in the solution and nonlinear material is isolated from other optical components, efficiently avoiding thermal damage and mechanical damage. PMID:26477662

  1. Solid dispersion of acetaminophen and poly(ethylene oxide) prepared by hot-melt mixing.

    PubMed

    Yang, Min; Wang, Peng; Huang, Chien-Yueh; Ku, M Sherry; Liu, Huiju; Gogos, Costas

    2010-08-16

    In this study, a model drug, acetaminophen (APAP), was melt mixed with poly(ethylene oxide) (PEO) using a Brabender mixer. APAP was found to recrystallize upon cooling to room temperature for all the drug loadings investigated. Higher drug loading leads to faster recrystallization rate. However, the morphology of the recrystallized drug crystals is identical in samples with different drug loadings and does not change with the storage time. To adjust the drug's dissolution rate, nanoclay Cloisite 15A and 30B were added into the binary mixture. The presence of either of the nanoclay dramatically accelerates the drug's recrystallization rate and slows down the drug's releasing rate. The drop of the releasing rate is mainly due to the decrease of wettability, as supported by the contact angle data. Data analysis of the dissolution results suggests that the addition of nanoclays changes the drug's release mechanism from erosion dominant to diffusion dominant. This study suggests that nanoclays may be utilized to tailor the drug's releasing rate and to improve the dosage form's stability by dramatically shortening the lengthy recrystallization process.

  2. Aqueously dispersed silver nanoparticle-decorated boron nitride nanosheets for reusable, thermal oxidation-resistant surface enhanced Raman spectroscopy (SERS) devices.

    PubMed

    Lin, Yi; Bunker, Christopher E; Fernando, K A Shiral; Connell, John W

    2012-02-01

    The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because ofthe unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures. PMID:22280102

  3. Aqueously Dispersed Silver Nanoparticle-Decorated Boron Nitride Nanosheets for Reusable, Thermal Oxidation-Resistant Surface Enhanced Raman Spectroscopy (SERS) Devices

    NASA Technical Reports Server (NTRS)

    Lin, Yi; Bunker, Christopher E.; Fernandos, K. A. Shiral; Connell, John W.

    2012-01-01

    The impurity-free aqueous dispersions of boron nitride nanosheets (BNNS) allowed the facile preparation of silver (Ag) nanoparticle-decorated BNNS by chemical reduction of an Ag salt with hydrazine in the presence of BNNS. The resultant Ag-BNNS nanohybrids remained dispersed in water, allowing convenient subsequent solution processing. By using substrate transfer techniques, Ag-BNNS nanohybrid thin film coatings on quartz substrates were prepared and evaluated as reusable surface enhanced Raman spectroscopy (SERS) sensors that were robust against repeated solvent washing. In addition, because of the unique thermal oxidation-resistant properties of the BNNS, the sensor devices may be readily recycled by short-duration high temperature air oxidation to remove residual analyte molecules in repeated runs. The limiting factor associated with the thermal oxidation recycling process was the Ostwald ripening effect of Ag nanostructures.

  4. Catalytic Conversion of Short-Chain Alcohols on Atomically Dispersed Au and Pd Supported on Nanoscale Metal Oxides

    NASA Astrophysics Data System (ADS)

    Wang, Chongyang

    With the development of technologies for cellulosic biomass conversion to fuels and chemicals, bio-alcohols are among the main alternative feedstocks to fossil fuels. The research pursued in my thesis was the investigation of gold and palladium as catalysts for the application of short aliphatic alcohols to hydrogen generation and value-added chemicals production. Specifically, selective methanol steam reforming and non-oxidative ethanol dehydrogenation to hydrogen and acetaldehyde were investigated in this thesis work. A major aim of the thesis was to develop atomically efficient catalysts with tuned surface chemistry for the desired reactions, using suitable synthesis methods. Methanol steam reforming (SRM) for hydrogen production has recently been investigated on gold catalysts to overcome the drawbacks of copper catalysts (deactivation, pyrophoricity). Previous work at Tufts University has shown that both CeO2 and ZnO are suitable supports for gold. In this thesis, nanoscale composite oxides ZnZrOx were prepared by a carbon hard-template method, which resulted in homogeneous distribution of Zn species in the matrix of ZrO2. Tunable surface chemistry of ZnZrO x was demonstrated by varying the Zn/Zr ratio to suppress the strong Lewis acidity of ZrO2, which leads to undesired production of CO through methanol decomposition. With atomic dispersion of gold, Au/ZnZrO x catalyzes the SRM reaction exclusively via the methanol self-coupling pathway up to 375°C. The activity of Au/ZnZrOx catalysts was compared to Au/TiO2, which is another catalyst system demonstrating atomic dispersion of gold. Similarity in the apparent activation energy of SRM on all the supported gold catalysts studied in this thesis and in the literature further confirms the same single-site Au-Ox-MO centers as active sites for SRM with indirect effects of the supports exploited. With this fundamental understanding of gold-catalyzed C1 alcohol reforming, the Au/ZnZrOx catalyst was evaluated for the

  5. Graphene oxide-based microspheres for the dispersive solid-phase extraction of non-steroidal estrogens from water samples.

    PubMed

    Wen, Yingying; Niu, Zongliang; Ma, Yanling; Ma, Jiping; Chen, Lingxin

    2014-11-14

    A modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method based on the dispersive solid-phase extraction (dSPE) combined with high performance liquid chromatography (HPLC) was developed for the determination of non-steroidal estrogens in water samples. In this study, graphene oxide-based silica microspheres (SiO2@GO) were used as dSPE material for the preconcentration of analytes. HPLC was used for the separation and detection. This was the first time that the synthesized SiO2@GO microspheres were used as stationary phases for the off-line preconcentration of the non-steroidal estrogens in dSPE. dSPE parameters, such as sample pH, volume and type of eluent were optimized. Application of the developed method to analyze spiked lake, reservoir and tap water samples resulted in good recoveries values ranging from 70 to 106% with relative standard deviation values lower than 7.0% in all cases. Limits of detection were in the range of 0.2-6.1 μg/L. The combined data obtained in this study recommended that the proposed method is very fast, simple, repeatable and accurate for the detection of non-steroidal estrogens. Furthermore, the SiO2@GO microspheres application could potentially be expanded to extract and pre-concentrate other compounds in various matrices.

  6. NIR-Vis-UV Light-Responsive Actuator Films of Polymer-Dispersed Liquid Crystal/Graphene Oxide Nanocomposites.

    PubMed

    Cheng, Zhangxiang; Wang, Tianjie; Li, Xiao; Zhang, Yihe; Yu, Haifeng

    2015-12-16

    To take full advantage of sunlight for photomechanical materials, NIR-vis-UV light-responsive actuator films of polymer-dispersed liquid crystal (PDLC)/graphene oxide (GO) nanocomposites were fabricated. The strategy is based on phase transition of LCs from nematic to isotropic phase induced by combination of photochemical and photothermal processes in the PDLC/GO nanocomposites. Upon mechanical stretching of the film, both topological shape change and mesogenic alignment occurred in the separated LC domains, enabling the film to respond to NIR-vis-UV light. The homodispersed GO flakes act as photoabsorbent and nanoscale heat source to transfer NIR or VIS light into thermal energy, heating the film and photothermally inducing phase transition of LC microdomains. By utilizing photochemical phase transition of LCs upon UV-light irradiation, one azobenzene dye was incorporated into the LC domains, endowing the nanocomposite films with UV-responsive property. Moreover, the light-responsive behaviors can be well-controlled by adjusting the elongation ratio upon mechanical treatment. The NIR-vis-UV light-responsive PDLC/GO nanocomposite films exhibit excellent properties of easy fabrication, low-cost, and good film-forming and mechanical features, promising their numerous applications in the field of soft actuators and optomechanical systems driven directly by sunlight.

  7. Facile synthesis of well-dispersed Bi2S3 nanoparticles on reduced graphene oxide and enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, Yajie; Tian, Guohui; Mao, Guijie; Li, Rong; Xiao, Yuting; Han, Taoran

    2016-08-01

    Here we present a facile method for the synthesis of highly dispersed Bi2S3 nanoparticles (Bi2S3 NPs) with an average diameter of ca. 25 ± 3 nm on the surface of reduced graphene oxide (RGO) via a poly(sodium-p-styrenesul-fonate) (PSS) asisted hydrothermal process. Such synthetic strategy can avoid excess aggregates of Bi2S3 nanoparticles, meanwhile from effective interfacial contact between Bi2S3 nanoparticles and RGO nanosheets, and inhibit the recombination of photogenerated charges. The enhanced charge transfer properties were proved by photoluminescence (PL) measurement. The obtained Bi2S3 NPs/RGO composites showed more significant visible light photoactivity for the degradation of 2,4-dichlorophenol and Rhodamine B than that pure Bi2S3 and the control sample prepared in the absence of PSS. The enhanced photocatalytic performance could be attributed to the synergistic effect of efficient separation of photogenerated electron-hole pairs, increased catalytic active sites and visible light utilization.

  8. Role of carbon nanotube dispersion in fracture toughening of plasma sprayed aluminum oxide-carbon nanotube nanocomposite coating

    NASA Astrophysics Data System (ADS)

    Balani, Kantesh

    Aluminum oxide (Al2O3, or alumina) is a conventional ceramic known for applications such as wear resistant coatings, thermal liners, heaters, crucibles, dielectric systems, etc. However applications of Al 2O3 are limited owing to its inherent brittleness. Due to its excellent mechanical properties and bending strength, carbon nanotubes (CNT) is an ideal reinforcement for Al2O3 matrix to improve its fracture toughness. The role of CNT dispersion in the fracture toughening of the plasma sprayed Al2O3-CNT nanocomposite coating is discussed in the current work. Pretreatment of powder feedstock is required for dispersing CNTs in the matrix. Four coatings namely spray dried Al2O 3 (A-SD), Al2O3 blended with 4wt.% CNT (A4C-B), composite spray dried Al2O3-4wt.% CNT (A4C-SD) and composite spray dried A1203-8wt.% CNT (A8C-SD), are synthesized by plasma spraying. Owing to extreme temperatures and velocities involved in the plasma spraying of ceramics, retention of CNTs in the resulting coatings necessitates optimizing plasma processing parameters using an inflight particle diagnostic sensor. A bimodal microstructure was obtained in the matrix that consists of fully melted and resolidified structure and solid state sintered structure. CNTs are retained both in the fully melted region and solid-state sintered regions of processed coatings. Fracture toughness of A-SD, A4C-B, A4C-SD and A8C-SD coatings was 3.22, 3.86, 4.60 and 5.04 MPa m1/2 respectively. This affirms the improvement of fracture toughness from 20% (in A4C-B coating) to 43% (in A4C-SD coating) when compared to the A-SD coating because of the CNT dispersion. Fracture toughness improvement from 43% (in A4C-SD) to 57% (in A8C-SD) coating is evinced because of the CNT content. Reinforcement by CNTs is described by its bridging, anchoring, hook formation, impact alignment, fusion with splat, and mesh formation. The Al2O3/CNT interface is critical in assisting the stress transfer and utilizing excellent mechanical

  9. A simple way to synthesize well-dispersed Gd{sub 2}O{sub 3} nanoparticles onto reduced graphene oxide sheets

    SciTech Connect

    Yang, Shengsheng; Gao, Hui; Wang, Yunfei; Xin, Shuangyu; He, Yongming; Wang, Yanzhao; Zeng, Wei

    2013-01-15

    Graphical abstract: Display Omitted Highlights: ► A simple approach to obtain Gd{sub 2}O{sub 3} nanoparticles onto RGO sheets. ► Gd{sub 2}O{sub 3} nanoparticles could be bonded with RGO by the residual C-OH or COOH groups. ► The as-prepared Gd{sub 2}O{sub 3} nanoparticles are well-dispersed and in the size of 10–50 nm. -- Abstract: High quality and dispersible rare-earth oxides (RE{sub 2}O{sub 3}) nanocrystals have drawn great attention because of their potential applications in the optical, electrical and biological fields. Here, we demonstrated a simple approach for the production of gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticles onto the surface of reduced graphene oxide (RGO) sheets by the chemical and the subsequent thermal reduction reactions. The residual oxygen functionalities derived from the reduction of graphene oxide (GO) played an important role to complex Gd{sub 2}O{sub 3} nanoparticles with RGO sheets. And the as-synthesized Gd{sub 2}O{sub 3} nanoparticles are uniform and well-dispersed with their particle size in the range of 10–50 nm. The approach would open up a new window for simple and effective synthesis of high quality RE{sub 2}O{sub 3} in nano scale.

  10. An effective non-covalent grafting approach to functionalize individually dispersed reduced graphene oxide sheets with high grafting density, solubility and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Bi, Shu-Guang; Ye, Yun-Sheng; Xue, Yang; Xie, Xiao-Lin; Mai, Yiu-Wing

    2015-02-01

    Polymer-functionalized reduced graphene oxide (polymer-FG), produced as individually dispersed graphene sheets, offers new possibilities for the production of nanomaterials that are useful for a broad range of potential applications. Although non-covalent functionalization has produced graphene with good dispersibility and a relatively complete conjugated network, there are few reports related to the effective functionalization of reduced graphene oxide (RGO) using a simple, general method. Herein, we report a facile and effective approach for the preparation of polymer-FG from a non-covalently functionalized pyrene-terminal polymer in benzoyl alcohol (BnOH). This aromatic alcohol (BnOH) was used as the liquid medium for the dispersion of graphene oxide (GO) with a pyrene-terminal polymer, and as an effective reductant; this makes the synthesis procedure convenient and the production of polymer-FG easily scalable because the conversion of GO to RGO and the non-covalent functionalization proceed simultaneously. The resulting polymer-FG sheets show organo-dispersibility, high electrical conductivity and good processability, and have a similar grafting density comparable to covalently made materials, thus making them promising candidates for applications such as electrochemical devices, nanomaterials and polymer nanocomposites. Hence, this work provides a general methodology for preparing individually dispersed graphene sheets with desirable properties.Polymer-functionalized reduced graphene oxide (polymer-FG), produced as individually dispersed graphene sheets, offers new possibilities for the production of nanomaterials that are useful for a broad range of potential applications. Although non-covalent functionalization has produced graphene with good dispersibility and a relatively complete conjugated network, there are few reports related to the effective functionalization of reduced graphene oxide (RGO) using a simple, general method. Herein, we report a facile

  11. Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoO(x)/γ-Al2O3 catalysts calcined in N2.

    PubMed

    Zhang, Lingling; Dong, Lihui; Yu, Wujiang; Liu, Lianjun; Deng, Yu; Liu, Bin; Wan, Haiqin; Gao, Fei; Sun, Keqin; Dong, Lin

    2011-03-15

    The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoO(x)/γ-Al(2)O(3) catalysts calcined in N(2). XRD, Raman, XPS, FTIR, and UV-vis DRS results suggested that CoO/γ-Al(2)O(3) was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al(2)O(3) below its dispersion capacity of 1.50 mmol/(100 m(2) γ-Al(2)O(3)), whereas Co(3)O(4)/γ-Al(2)O(3) was obtained from cobalt nitrate precursors and Co(3)O(4) preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100m(2) γ-Al(2)O(3)). Compared with Co(3)O(4)/γ-Al(2)O(3), CoO/γ-Al(2)O(3) catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H(2)-TPR, O(2)-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al(2)O(3) catalysts.

  12. Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoO(x)/γ-Al2O3 catalysts calcined in N2.

    PubMed

    Zhang, Lingling; Dong, Lihui; Yu, Wujiang; Liu, Lianjun; Deng, Yu; Liu, Bin; Wan, Haiqin; Gao, Fei; Sun, Keqin; Dong, Lin

    2011-03-15

    The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoO(x)/γ-Al(2)O(3) catalysts calcined in N(2). XRD, Raman, XPS, FTIR, and UV-vis DRS results suggested that CoO/γ-Al(2)O(3) was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al(2)O(3) below its dispersion capacity of 1.50 mmol/(100 m(2) γ-Al(2)O(3)), whereas Co(3)O(4)/γ-Al(2)O(3) was obtained from cobalt nitrate precursors and Co(3)O(4) preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100m(2) γ-Al(2)O(3)). Compared with Co(3)O(4)/γ-Al(2)O(3), CoO/γ-Al(2)O(3) catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H(2)-TPR, O(2)-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al(2)O(3) catalysts. PMID:21216407

  13. Intermetallic strengthened alumina-forming austenitic steels for energy applications

    NASA Astrophysics Data System (ADS)

    Hu, Bin

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, materials required are strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and Ni3Al precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe 2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. This research starts with microstructural and microchemical analyses of these intermetallic strengthened alumina-forming austenitic steels in a scanning electron microscope. The microchemistry of precipitates, as determined by energy-dispersive x-ray spectroscopy and transmission electron microscope, is also studied. Different thermo-mechanical treatments were carried out to these stainless steels in an attempt to further improve their mechanical properties. The microstructural and microchemical analyses were again performed after the thermo-mechanical processing. Synchrotron X-ray diffraction was used to measure the lattice parameters of these steels after different thermo-mechanical treatments. Tensile tests at both room and elevated temperatures were performed to study mechanical behaviors of this novel alloy system; the deformation mechanisms were studied by strain rate jump tests at elevated temperatures. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these alumina-forming austenitic steels after creep tests. Experiments were carried out to study the effects of boron and carbon additions in the aged alumina-forming austenitic steels.

  14. Relationship between nitric oxide- and calcium-dependent signal transduction pathways in growth hormone release from dispersed goldfish pituitary cells.

    PubMed

    Chang, John P; Sawisky, Grant R; Davis, Philip J; Pemberton, Joshua G; Rieger, Aja M; Barreda, Daniel R

    2014-09-15

    Nitric oxide (NO) and Ca(2+) are two of the many intracellular signal transduction pathways mediating the control of growth hormone (GH) secretion from somatotropes by neuroendocrine factors. We have previously shown that the NO donor sodium nitroprusside (SNP) elicits Ca(2+) signals in identified goldfish somatotropes. In this study, we examined the relationships between NO- and Ca(2+)-dependent signal transduction mechanisms in GH secretion from primary cultures of dispersed goldfish pituitary cells. Morphologically identified goldfish somatotropes stained positively for an NO-sensitive dye indicating they may be a source of NO production. In 2h static incubation experiments, GH release responses to the NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) were attenuated by CoCl2, nifedipine, verapamil, TMB-8, BHQ, and KN62. In column perifusion experiments, the ability of SNP to induce GH release was impaired in the presence of TMB-8, BHQ, caffeine, and thapsigargin, but not ryanodine. Caffeine-elicited GH secretion was not affected by the NO scavenger PTIO. These results suggest that NO-stimulated GH release is dependent on extracellular Ca(2+) availability and voltage-sensitive Ca(2+) channels, as well as intracellular Ca(2+) store(s) that possess BHQ- and/or thapsigargin-inhibited sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPases, as well as TMB-8- and/or caffeine-sensitive, but not ryanodine-sensitive, Ca(2+)-release channels. Calmodulin kinase-II also likely participates in NO-elicited GH secretion but caffeine-induced GH release is not upstream of NO production. These findings provide insights into how NO actions many integrate with Ca(2+)-dependent signalling mechanisms in goldfish somatotropes and how such interactions may participate in the GH-releasing actions of regulators that utilize both NO- and Ca(2+)-dependent transduction pathways. PMID:25038498

  15. Relationship between nitric oxide- and calcium-dependent signal transduction pathways in growth hormone release from dispersed goldfish pituitary cells.

    PubMed

    Chang, John P; Sawisky, Grant R; Davis, Philip J; Pemberton, Joshua G; Rieger, Aja M; Barreda, Daniel R

    2014-09-15

    Nitric oxide (NO) and Ca(2+) are two of the many intracellular signal transduction pathways mediating the control of growth hormone (GH) secretion from somatotropes by neuroendocrine factors. We have previously shown that the NO donor sodium nitroprusside (SNP) elicits Ca(2+) signals in identified goldfish somatotropes. In this study, we examined the relationships between NO- and Ca(2+)-dependent signal transduction mechanisms in GH secretion from primary cultures of dispersed goldfish pituitary cells. Morphologically identified goldfish somatotropes stained positively for an NO-sensitive dye indicating they may be a source of NO production. In 2h static incubation experiments, GH release responses to the NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) were attenuated by CoCl2, nifedipine, verapamil, TMB-8, BHQ, and KN62. In column perifusion experiments, the ability of SNP to induce GH release was impaired in the presence of TMB-8, BHQ, caffeine, and thapsigargin, but not ryanodine. Caffeine-elicited GH secretion was not affected by the NO scavenger PTIO. These results suggest that NO-stimulated GH release is dependent on extracellular Ca(2+) availability and voltage-sensitive Ca(2+) channels, as well as intracellular Ca(2+) store(s) that possess BHQ- and/or thapsigargin-inhibited sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPases, as well as TMB-8- and/or caffeine-sensitive, but not ryanodine-sensitive, Ca(2+)-release channels. Calmodulin kinase-II also likely participates in NO-elicited GH secretion but caffeine-induced GH release is not upstream of NO production. These findings provide insights into how NO actions many integrate with Ca(2+)-dependent signalling mechanisms in goldfish somatotropes and how such interactions may participate in the GH-releasing actions of regulators that utilize both NO- and Ca(2+)-dependent transduction pathways.

  16. Area integrated emission of biogenic nitric oxide by Lagrangian dispersion modeling (LASAT): Milan oasis, Taklimakan desert (Xinjiang, PR China)

    NASA Astrophysics Data System (ADS)

    Badawy, M.; Wu, Z.; Behrendt, T.; Fechner, A. D.; Meixner, F. X.; Andreae, M. O.; Mamtimin, B.

    2012-04-01

    Today's knowledge of soil biogenic NO emission rates from arid and hyper-arid land is based on a total of about 20 experimental studies. Nevertheless, biogenic NO emissions even from non-managed arid and hyper-arid soils are significant and may range between 1-10 ng m-2 s-1 (in terms of nitrogen, if conditions for soil NO production are favourable (optimum soil moisture, high soil temperatures). Irrigated and fertilized oases, ranging about 3000 km long around the great Central Asian Taklimakan desert form the backbone of the agricultural output (80% of the Chinese cotton production) of the Xinjiang Uygur Autonomous Region (NW-China). Recent and future development of farmland and intensification of agriculture will definitely impact the regional soil NO emission and consequently the budget of nitrogen oxides and ozone. Up to today, only a few studies have preliminarily addressed soil biogenic NO emissions from the Taklimakan desert. In our contribution, we will focus on the quantification of the area integrated NO emission from the Milan oasis located on the most southern fringe of the Takalimkan desert (39.26° N, 88.91° E). At a first step, the 3D distribution of ambient NO concentration is calculated using a state-of-the-art commercially available dispersion model (LASAT 3.2, Lagrange Simulation of Aerosol-Transport). Performing the dispersion simulation, transport and turbulent diffusion are simulated for a group of representative "simulation particles" by means of a stochastic process (Lagrange simulation). Surface sources (individual cotton fields, Jujube orchards) are known: their geographical location as well as their areal extent, their stage of vegetation growth as well as irrigation and fertilization events and amounts, soil temperatures and soil water contents. This information is used to up-scale our results of field specific potential net NO emission, which has been parameterized in terms of soil temperature, soil water content, and soil nutrient

  17. High temperature mechanical properties of a zirconium-modified, precipitation- strengthened nickel, 30 percent copper alloy

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1974-01-01

    A precipitation-strengthened Monel-type alloy has been developed through minor alloying additions of zirconium to a base Ni-30Cu alloy. The results of this exploratory study indicate that thermomechanical processing of a solution-treated Ni-30Cu-0.2Zr alloy produced a dispersion of precipitates. The precipitates have been tentatively identified as a Ni5Zr compound. A comparison of the mechanical properties, as determined by testing in air, of the zirconium-modified alloy to those of a Ni-30Cu alloy reveals that the precipitation-strengthened alloy has improved tensile properties to 1200 K and improved stress-rupture properties to 1100 K. The oxidation characteristics of the modified alloy appeared to be equivalent to those of the base Ni-30Cu alloy.

  18. An exploratory study of a zirconium-modified, precipitation-strengthened nickel-30 copper alloy

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1974-01-01

    A precipitation-strengthened alloy has been produced through minor additions of zirconium to a base Ni-30Cu alloy. The results of this exploratory study indicate that thermomechanical processing of a solution-treated Ni-30Cu-0.2Zr alloy produced a dispersion of precipitates. The precipitates have been tentatively identified as a Ni5Zr compound. Comparison of the mechanical properties, as determined by testing in air, of the Zr-modified alloy to those of a Ni-30Cu alloy reveals that the precipitation-strengthened alloy has improved tensile properties to 1200 K and improved stress-rupture properties to 1100 K. The oxidation characteristics of the modified alloy appeared to be equivalent to those of the base Ni-30Cu alloy.

  19. Recyclable enzyme mimic of cubic Fe3O4 nanoparticles loaded on graphene oxide-dispersed carbon nanotubes with enhanced peroxidase-like catalysis and electrocatalysis

    SciTech Connect

    Wang, Hua; Li, Shuai; Si, Yanmei; Sun, Zhongzhao; Li, Shuying; Lin, Yuehe

    2014-01-01

    Fe3O4 nanoparticles as nanocatalysts may present peroxidase-like catalysis activities and high electrocatalysis if loaded on conductive carbon nanotube (CNT) supports; however, their catalysis performances in an aqueous system might still be challenged by the poor aqueous dispersion of hydrophobic carbon supports and/or low stability of loaded iron catalysts. In this work, amphiphilic graphene oxide nanosheets were employed as “surfactant” to disperse CNTs to create stable graphene oxide-dispersed CNT (GCNT) supports in water for covalently loading cubic Fe3O4 nanoparticles with improved distribution and binding efficiency. Compared with original Fe3O4 nanos and CNT-loaded Fe3O4 nanocomplex, the prepared GCNT–Fe3O4 nanocomposite could achieve higher aqueous stability and, especially, much stronger peroxidase-like catalysis and electrocatalysis to H2O2, presumably resulting from the synergetic effects of two conductive carbon supports and cubic Fe3O4 nanocatalysts effectively loaded. Colorimetric and direct electrochemical detections of H2O2 and glucose using the GCNT–Fe3O4 nanocomposite were conducted with high detection sensitivities, demonstrating the feasibility of practical sensing applications. Such a magnetically recyclable “enzyme mimic” may circumvent some disadvantages of natural protein enzymes and common inorganic catalysts, featuring the multi-functions of high peroxidase-like catalysis, strong electrocatalysis, magnetic separation/recyclability, environmental stability, and direct H2O2 electrochemistry.

  20. Temperature dependence of frequency dispersion in III–V metal-oxide-semiconductor C-V and the capture/emission process of border traps

    SciTech Connect

    Vais, Abhitosh Martens, Koen; DeMeyer, Kristin; Lin, Han-Chung; Ivanov, Tsvetan; Collaert, Nadine; Thean, Aaron; Dou, Chunmeng; Xie, Qi; Maes, Jan; Tang, Fu; Givens, Michael; Raskin, Jean-Pierre

    2015-08-03

    This paper presents a detailed investigation of the temperature dependence of frequency dispersion observed in capacitance-voltage (C-V) measurements of III-V metal-oxide-semiconductor (MOS) devices. The dispersion in the accumulation region of the capacitance data is found to change from 4%–9% (per decade frequency) to ∼0% when the temperature is reduced from 300 K to 4 K in a wide range of MOS capacitors with different gate dielectrics and III-V substrates. We show that such significant temperature dependence of C-V frequency dispersion cannot be due to the temperature dependence of channel electrostatics, i.e., carrier density and surface potential. We also show that the temperature dependence of frequency dispersion, and hence, the capture/emission process of border traps can be modeled by a combination of tunneling and a “temperature-activated” process described by a non-radiative multi-phonon model, instead of a widely believed single-step elastic tunneling process.

  1. 1-Butyl-3-aminopropyl imidazolium-functionalized graphene oxide as a nanoadsorbent for the simultaneous extraction of steroids and β-blockers via dispersive solid-phase microextraction.

    PubMed

    Serrano, Maria; Chatzimitakos, Theodoros; Gallego, Mercedes; Stalikas, Constantine D

    2016-03-01

    In this study, we describe the synthesis of graphene oxide functionalized with the ionic liquid 1-butyl-3-aminopropyl imidazolium chloride and its use as an adsorbent for the dispersive solid-phase microextraction (micro SPE) of four anabolic steroids and six β-blockers from aqueous samples of environmental importance, prior to their HPLC-diode array detector analysis. As the ionic liquid is covalently attached to graphene oxide sheets, it is made possible for it to participate in the dispersive micro SPE procedure. The limits of detection and limits of quantification of the proposed method were found to be in the range of 7-23ng/L and between 20 and 70ng/L, respectively. The linearity was satisfactory, with the determination coefficients to range from 0.9940 to 0.9998 while the within- and between-day relative standard deviation of the method ranged between 3.1 and 7.6% and from 4.0 to 8.5%, respectively. In order to test the applicability of the proposed method in real-life samples, the effluent from a municipal wastewater treatment plant as well as natural water samples from two rivers and a lake were collected and analyzed. After the analysis of samples, the effluent from municipal wastewater treatment plant was fortified with the analytes, at concentrations equal to 2 and 10 times the LOQs. Recoveries were calculated after subtracting the native (no-spike) concentrations of analytes, when needed. All the recoveries were in the range of 87-98%. A comparison study attests to the superiority of the developed nanomaterial over graphene oxide and graphene for the dispersive micro SPE of steroids and β-blockers.

  2. 1-Butyl-3-aminopropyl imidazolium-functionalized graphene oxide as a nanoadsorbent for the simultaneous extraction of steroids and β-blockers via dispersive solid-phase microextraction.

    PubMed

    Serrano, Maria; Chatzimitakos, Theodoros; Gallego, Mercedes; Stalikas, Constantine D

    2016-03-01

    In this study, we describe the synthesis of graphene oxide functionalized with the ionic liquid 1-butyl-3-aminopropyl imidazolium chloride and its use as an adsorbent for the dispersive solid-phase microextraction (micro SPE) of four anabolic steroids and six β-blockers from aqueous samples of environmental importance, prior to their HPLC-diode array detector analysis. As the ionic liquid is covalently attached to graphene oxide sheets, it is made possible for it to participate in the dispersive micro SPE procedure. The limits of detection and limits of quantification of the proposed method were found to be in the range of 7-23ng/L and between 20 and 70ng/L, respectively. The linearity was satisfactory, with the determination coefficients to range from 0.9940 to 0.9998 while the within- and between-day relative standard deviation of the method ranged between 3.1 and 7.6% and from 4.0 to 8.5%, respectively. In order to test the applicability of the proposed method in real-life samples, the effluent from a municipal wastewater treatment plant as well as natural water samples from two rivers and a lake were collected and analyzed. After the analysis of samples, the effluent from municipal wastewater treatment plant was fortified with the analytes, at concentrations equal to 2 and 10 times the LOQs. Recoveries were calculated after subtracting the native (no-spike) concentrations of analytes, when needed. All the recoveries were in the range of 87-98%. A comparison study attests to the superiority of the developed nanomaterial over graphene oxide and graphene for the dispersive micro SPE of steroids and β-blockers. PMID:26858116

  3. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry for quick detection of sulfur-oxidizing bacteria in environmental water samples

    NASA Astrophysics Data System (ADS)

    Sun, Chengjun; Jiang, Fenghua; Gao, Wei; Li, Xiaoyun; Yu, Yanzhen; Yin, Xiaofei; Wang, Yong; Ding, Haibing

    2016-03-01

    Detection of sulfur-oxidizing bacteria has largely been dependent on targeted gene sequencing technology or traditional cell cultivation, which usually takes from days to months to carry out. This clearly does not meet the requirements of analysis for time-sensitive samples and/or complicated environmental samples. Since energy-dispersive X-ray spectrometry (EDS) can be used to simultaneously detect multiple elements in a sample, including sulfur, with minimal sample treatment, this technology was applied to detect sulfur-oxidizing bacteria using their high sulfur content within the cell. This article describes the application of scanning electron microscopy imaging coupled with EDS mapping for quick detection of sulfur oxidizers in contaminated environmental water samples, with minimal sample handling. Scanning electron microscopy imaging revealed the existence of dense granules within the bacterial cells, while EDS identified large amounts of sulfur within them. EDS mapping localized the sulfur to these granules. Subsequent 16S rRNA gene sequencing showed that the bacteria detected in our samples belonged to the genus Chromatium, which are sulfur oxidizers. Thus, EDS mapping made it possible to identify sulfur oxidizers in environmental samples based on localized sulfur within their cells, within a short time (within 24 h of sampling). This technique has wide ranging applications for detection of sulfur bacteria in environmental water samples.

  4. Strengthening Resilience in Families

    ERIC Educational Resources Information Center

    Guild, Diane; Espiner, Deborah

    2014-01-01

    Rolling with Resilience (RwR) provides a springboard for developing strategies that build strengths and supports to foster developmental assets in children and youth (Benson, Scales, & Roehlkepartain, 2011). In Circle of Courage terms, resilience is strengthened by opportunities for Belonging, Mastery, Independence, and Generosity (Brendtro,…

  5. as the Strengthening Precipitates

    NASA Astrophysics Data System (ADS)

    Lu, Qi; Xu, Wei; van der Zwaag, Sybrand

    2014-12-01

    Generally, Laves phase and M23C6 are regarded as undesirable phases in creep-resistant steels due to their very high-coarsening rates and the resulting depletion of beneficial alloying elements from the matrix. In this study, a computational alloy design approach is presented to develop martensitic steels strengthened by Laves phase and/or M23C6, for which the coarsening rates are tailored such that they are at least one order of magnitude lower than those in existing alloys. Their volume fractions are optimized by tuning the chemical composition in parallel. The composition domain covering 10 alloying elements at realistic levels is searched by a genetic algorithm to explore the full potential of simultaneous maximization of the volume fraction and minimization of the precipitates coarsening rate. The calculations show that Co and W can drastically reduce the coarsening rate of Laves and M23C6 and yield high-volume fractions of precipitates. Mo on the other hand was shown to have a minimal effect on coarsening. The strengthening effects of Laves phase and M23C6 in the newly designed alloys are compared to existing counterparts, showing substantially higher precipitation-strengthening contributions especially after a long service time. New alloys were designed in which both Laves phase and M23C6 precipitates act as strengthening precipitates. Successfully combining MX and M23C6 was found to be impossible.

  6. Investigation of the oxidation behavior of dispersion stabilized alloys when exposed to a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.

    1974-01-01

    The oxidation behavior of TD-NiCr and TD-NiCrAlY alloys have been studied at 2000 and 2200 F in static and high speed flowing air environments. The TD-NiCrAlY alloys preoxidized to produce an Al2O3 scale on the surface showed good oxidation resistance in both types of environments. The TD-NiCr alloy which had a Cr2O3 oxide scale after preoxidation was found to oxidize more than an order of magnitude faster under the dynamic test conditions than at comparable static test conditions. Although Cr2O3 normally provides good oxidation protection, it was rapidly lost due to formation of volatile CrO3 when exposed to the high speed air stream. The preferred oxide arrangement for the dynamic test consisted of an external layer of NiO with a porous mushroom type morphology, an intermediate duplex layer of NiO and Cr2O3, and a continuous inner layer of Cr2O3 in contact with the alloy substrate. An oxidation model has been developed to explain the observed microstructure and overall oxidation behavior of all alloys.

  7. Rapid synthesis of water-dispersible superparamagnetic iron oxide nanoparticles by a microwave-assisted route for safe labeling of endothelial progenitor cells.

    PubMed

    Carenza, Elisa; Barceló, Verónica; Morancho, Anna; Montaner, Joan; Rosell, Anna; Roig, Anna

    2014-08-01

    We synthesize highly crystalline citrate-coated iron oxide superparamagnetic nanoparticles that are stable and readily dispersible in water by an extremely fast microwave-assisted route and investigate the uptake of magnetic nanoparticles by endothelial cells. Nanoparticles form large aggregates when added to complete endothelial cell medium. The size of the aggregates was controlled by adjusting the ionic strength of the medium. The internalization of nanoparticles into endothelial cells was then investigated by transmission electron microscopy, magnetometry and chemical analysis, together with cell viability assays. Interestingly, a sevenfold more efficient uptake was found for systems with larger nanoparticle aggregates, which also showed significantly higher magnetic resonance imaging effectiveness without compromising cell viability and functionality. We are thus presenting an example of a straightforward microwave synthesis of citrate-coated iron oxide nanoparticles for safe endothelial progenitor cell labeling and good magnetic resonance cell imaging with potential application for magnetic cell guidance and in vivo cell tracking.

  8. Preparation of Highly Dispersed Reduced Graphene Oxide Decorated with Chitosan Oligosaccharide as Electrode Material for Enhancing the Direct Electron Transfer of Escherichia coli.

    PubMed

    Luo, Zhimin; Yang, Dongliang; Qi, Guangqin; Yuwen, Lihui; Zhang, Yuqian; Weng, Lixing; Wang, Lianhui; Huang, Wei

    2015-04-29

    Water-dispersed reduced graphene oxide/chitosan oligosaccharide (RGO-CTSO) was prepared by chemical reduction of graphene oxide and synchronous functionalization with biocompatible chitosan oligosaccharide (CTSO). ζ potential measurement indicated that RGO-CTSO was highly stable in the acidic aqueous solution. RGO-CTSO was used to modify glassy carbon electrode (GCE) as the growth template of Escherichia coli (E. coli). The enhanced direct electron transfer of E. coli on the RGO-CTSO-modified GCE was studied by cyclic voltammetry. Compared with GCE or RGO-modified GCE, RGO-CTSO-modified GCE was more suitable for the adhesion growth of E. coli to improve direct electron transfer. The biocompatibility and versatility of RGO-CTSO made it promising for use as an anode material in microbial fuel cells.

  9. The effects of oxide evolution on mechanical properties in proton- and neutron-irradiated Fe-9%Cr ODS steel

    NASA Astrophysics Data System (ADS)

    Swenson, M. J.; Dolph, C. K.; Wharry, J. P.

    2016-10-01

    The objective of this study is to evaluate the effect of irradiation on the strengthening mechanisms of a model Fe-9%Cr oxide dispersion strengthened steel. The alloy was irradiated with protons or neutrons to a dose of 3 displacements per atoms at 500 °C. Nanoindentation was used to measure strengthening due to irradiation, with neutron irradiation causing a greater increase in yield strength than proton irradiation. The irradiated microstructures were characterized using transmission electron microscopy and atom probe tomography (APT). Cluster analysis reveals solute migration from the Y-Ti-O-rich nanoclusters to the surrounding matrix after both irradiations, though the effect is more pronounced in the neutron-irradiated specimen. Because the dissolved oxygen atoms occupy interstitial sites in the iron matrix, they contribute significantly to solid solution strengthening. The dispersed barrier hardening model relates microstructure evolution to the change in yield strength, but is only accurate if solid solution contributions to strengthening are considered simultaneously.

  10. The role of the substrate on the dispersion in accumulation in III-V compound semiconductor based metal-oxide-semiconductor gate stacks

    SciTech Connect

    Krylov, Igor; Ritter, Dan; Eizenberg, Moshe

    2015-09-07

    Dispersion in accumulation is a widely observed phenomenon in metal-oxide-semiconductor gate stacks based on III-V compound semiconductors. The physical origin of this phenomenon is attributed to border traps located in the dielectric material adjacent to the semiconductor. Here, we study the role of the semiconductor substrate on the electrical quality of the first layers at atomic layer deposited (ALD) dielectrics. For this purpose, either Al{sub 2}O{sub 3} or HfO{sub 2} dielectrics with variable thicknesses were deposited simultaneously on two technology important semiconductors—InGaAs and InP. Significantly larger dispersion was observed in InP based gate stacks compared to those based on InGaAs. The observed difference is attributed to a higher border trap density in dielectrics deposited on InP compared to those deposited on InGaAs. We therefore conclude that the substrate plays an important role in the determination of the electrical quality of the first dielectric monolayers deposited by ALD. An additional observation is that larger dispersion was obtained in HfO{sub 2} based capacitors compared to Al{sub 2}O{sub 3} based capacitors, deposited on the same semiconductor. This phenomenon is attributed to the lower conduction band offset rather than to a higher border trap density.

  11. Understanding the performance of melt-extruded poly(ethylene oxide)-bicalutamide solid dispersions: characterisation of microstructural properties using thermal, spectroscopic and drug release methods.

    PubMed

    Abu-Diak, Osama A; Jones, David S; Andrews, Gavin P

    2012-01-01

    In this article, we have prepared hot-melt-extruded solid dispersions of bicalutamide (BL) using poly(ethylene oxide) (PEO) as a matrix platform. Prior to preparation, miscibility of PEO and BL was assessed using differential scanning calorimetry (DSC). The onset of BL melting was significantly depressed in the presence of PEO, and using Flory-Huggins (FH) theory, we identified a negative value of -3.4, confirming miscibility. Additionally, using FH lattice theory, we estimated the Gibbs free energy of mixing which was shown to be negative, passing through a minimum at a polymer fraction of 0.55. Using these data, solid dispersions at drug-to-polymer ratios of 1:10, 2:10 and 3:10 were prepared via hot-melt extrusion. Using a combination of DSC, powder X-ray diffractometry and scanning electron microscopy, amorphous dispersions of BL were confirmed at the lower two drug loadings. At the 3:10 BL to PEO ratio, crystalline BL was detected. The percent crystallinity of PEO was reduced by approximately 10% in all formulations following extrusion. The increased amorphous content within PEO following extrusion accommodated amorphous BL at drug to polymer loadings up to 2:10; however, the increased amorphous domains with PEO following extrusion were not sufficient to fully accommodate BL at drug-to-polymer ratios of 3:10.

  12. Facile preparation of well-dispersed CeO2-ZnO composite hollow microspheres with enhanced catalytic activity for CO oxidation.

    PubMed

    Xie, Qingshui; Zhao, Yue; Guo, Huizhang; Lu, Aolin; Zhang, Xiangxin; Wang, Laisen; Chen, Ming-Shu; Peng, Dong-Liang

    2014-01-01

    In this article, well-dispersed CeO2-ZnO composite hollow microspheres have been fabricated through a simple chemical reaction followed by annealing treatment. Amorphous zinc-cerium citrate hollow microspheres were first synthesized by dispersing zinc citrate hollow microspheres into cerium nitrate solution and then aging at room temperature for 1 h. By calcining the as-produced zinc-cerium citrate hollow microspheres at 500 °C for 2 h, CeO2-ZnO composite hollow microspheres with homogeneous composition distribution could be harvested for the first time. The resulting CeO2-ZnO composite hollow microspheres exhibit enhanced activity for CO oxidation compared with CeO2 and ZnO, which is due to well-dispersed small CeO2 particles on the surface of ZnO hollow microspheres and strong interaction between CeO2 and ZnO. Moreover, when Au nanoparticles are deposited on the surface of the CeO2-ZnO composite hollow microspheres, the full CO conversion temperature of the as-produced 1.0 wt % Au-CeO2-ZnO composites reduces from 300 to 60 °C in comparison with CeO2-ZnO composites. The significantly improved catalytic activity may be ascribed to the strong synergistic interplay between Au nanoparticles and CeO2-ZnO composites.

  13. Platinum-TM (TM = Fe, Co) alloy nanoparticles dispersed nitrogen doped (reduced graphene oxide-multiwalled carbon nanotube) hybrid structure cathode electrocatalysts for high performance PEMFC applications.

    PubMed

    Vinayan, B P; Ramaprabhu, S

    2013-06-01

    The efforts to push proton exchange membrane fuel cells (PEMFC) for commercial applications are being undertaken globally. In PEMFC, the sluggish kinetics of oxygen reduction reactions (ORR) at the cathode can be improved by the alloying of platinum with 3d-transition metals (TM = Fe, Co, etc.) and with nitrogen doping, and in the present work we have combined both of these aspects. We describe a facile method for the synthesis of a nitrogen doped (reduced graphene oxide (rGO)-multiwalled carbon nanotubes (MWNTs)) hybrid structure (N-(G-MWNTs)) by the uniform coating of a nitrogen containing polymer over the surface of the hybrid structure (positively surface charged rGO-negatively surface charged MWNTs) followed by the pyrolysis of these (rGO-MWNTs) hybrid structure-polymer composites. The N-(G-MWNTs) hybrid structure is used as a catalyst support for the dispersion of platinum (Pt), platinum-iron (Pt3Fe) and platinum-cobalt (Pt3Co) alloy nanoparticles. The PEMFC performances of Pt-TM alloy nanoparticle dispersed N-(G-MWNTs) hybrid structure electrocatalysts are 5.0 times higher than that of commercial Pt-C electrocatalysts along with very good stability under acidic environment conditions. This work demonstrates a considerable improvement in performance compared to existing cathode electrocatalysts being used in PEMFC and can be extended to the synthesis of metal, metal oxides or metal alloy nanoparticle decorated nitrogen doped carbon nanostructures for various electrochemical energy applications.

  14. Comparative study of iron oxide nanoparticles as-prepared and dispersed in Copaiba oil using Mössbauer spectroscopy with low and high velocity resolution.

    PubMed

    Oshtrakh, M I; Šepelák, V; Rodriguez, A F R; Semionkin, V A; Ushakov, M V; Santos, J G; Silveira, L B; Marmolejo, E M; De Souza Parise, M; Morais, P C

    2013-01-01

    Iron oxide nanoparticles, probably magnetite, as-prepared and dispersed in Copaiba oil were studied by Mössbauer spectroscopy using two different spectrometers: with a low velocity resolution (512 channels) for measurements at 295 and 21K and with a high velocity resolution (4096 channels) for measurements at 295 and 90K. The fitting of all measured spectra demonstrated that usual models applied to fit Mössbauer spectra of magnetite and maghemite particles were not suitable. Therefore, the recorded spectra were fitted using a large number of spectral components on the basis of better quality of the fit and linearity of differential spectra. The number of components obtained for the better fit appeared to be different for spectra measured with a low and a high velocity resolution. However, these results demonstrated differences of Mössbauer parameters for iron oxide nanoparticles as-prepared and dispersed in Copaiba oil at applied temperatures. The effect of Copaiba oil molecules on Mössbauer parameters may be a result of the interactions of polar molecules such as kaurinic acid with nanoparticles' surface.

  15. Comparative study of iron oxide nanoparticles as-prepared and dispersed in Copaiba oil using Mössbauer spectroscopy with low and high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Šepelák, V.; Rodriguez, A. F. R.; Semionkin, V. A.; Ushakov, M. V.; Santos, J. G.; Silveira, L. B.; Marmolejo, E. M.; Parise, M. De Souza; Morais, P. C.

    Iron oxide nanoparticles, probably magnetite, as-prepared and dispersed in Copaiba oil were studied by Mössbauer spectroscopy using two different spectrometers: with a low velocity resolution (512 channels) for measurements at 295 and 21 K and with a high velocity resolution (4096 channels) for measurements at 295 and 90 K. The fitting of all measured spectra demonstrated that usual models applied to fit Mössbauer spectra of magnetite and maghemite particles were not suitable. Therefore, the recorded spectra were fitted using a large number of spectral components on the basis of better quality of the fit and linearity of differential spectra. The number of components obtained for the better fit appeared to be different for spectra measured with a low and a high velocity resolution. However, these results demonstrated differences of Mössbauer parameters for iron oxide nanoparticles as-prepared and dispersed in Copaiba oil at applied temperatures. The effect of Copaiba oil molecules on Mössbauer parameters may be a result of the interactions of polar molecules such as kaurinic acid with nanoparticles' surface.

  16. Comparative study of iron oxide nanoparticles as-prepared and dispersed in Copaiba oil using Mössbauer spectroscopy with low and high velocity resolution.

    PubMed

    Oshtrakh, M I; Šepelák, V; Rodriguez, A F R; Semionkin, V A; Ushakov, M V; Santos, J G; Silveira, L B; Marmolejo, E M; De Souza Parise, M; Morais, P C

    2013-01-01

    Iron oxide nanoparticles, probably magnetite, as-prepared and dispersed in Copaiba oil were studied by Mössbauer spectroscopy using two different spectrometers: with a low velocity resolution (512 channels) for measurements at 295 and 21K and with a high velocity resolution (4096 channels) for measurements at 295 and 90K. The fitting of all measured spectra demonstrated that usual models applied to fit Mössbauer spectra of magnetite and maghemite particles were not suitable. Therefore, the recorded spectra were fitted using a large number of spectral components on the basis of better quality of the fit and linearity of differential spectra. The number of components obtained for the better fit appeared to be different for spectra measured with a low and a high velocity resolution. However, these results demonstrated differences of Mössbauer parameters for iron oxide nanoparticles as-prepared and dispersed in Copaiba oil at applied temperatures. The effect of Copaiba oil molecules on Mössbauer parameters may be a result of the interactions of polar molecules such as kaurinic acid with nanoparticles' surface. PMID:22465304

  17. Facile synthesis of water-dispersible Cu2O nanocrystal-reduced graphene oxide hybrid as a promising cancer therapeutic agent

    NASA Astrophysics Data System (ADS)

    Hou, Chengyi; Quan, Haocheng; Duan, Yourong; Zhang, Qinghong; Wang, Hongzhi; Li, Yaogang

    2013-01-01

    We report a Cu2O nanocrystal-reduced graphene oxide hybrid that is dispersible in water and has anticancer activity under both visible and near-infrared light irradiation. In contrast to the highly efficient killing of both normal and cancer cells initiated by the photothermal effect, the photocatalytic effect of this material results in the selective killing of cancer cells under visible light irradiation. These results have implications for safe and widely applicable cancer therapy agents.We report a Cu2O nanocrystal-reduced graphene oxide hybrid that is dispersible in water and has anticancer activity under both visible and near-infrared light irradiation. In contrast to the highly efficient killing of both normal and cancer cells initiated by the photothermal effect, the photocatalytic effect of this material results in the selective killing of cancer cells under visible light irradiation. These results have implications for safe and widely applicable cancer therapy agents. Electronic supplementary information (ESI) available: Characterization of the over-reduced products and the photocatalytic activity of the CRGO. See DOI: 10.1039/c2nr32938g

  18. Platinum-TM (TM = Fe, Co) alloy nanoparticles dispersed nitrogen doped (reduced graphene oxide-multiwalled carbon nanotube) hybrid structure cathode electrocatalysts for high performance PEMFC applications.

    PubMed

    Vinayan, B P; Ramaprabhu, S

    2013-06-01

    The efforts to push proton exchange membrane fuel cells (PEMFC) for commercial applications are being undertaken globally. In PEMFC, the sluggish kinetics of oxygen reduction reactions (ORR) at the cathode can be improved by the alloying of platinum with 3d-transition metals (TM = Fe, Co, etc.) and with nitrogen doping, and in the present work we have combined both of these aspects. We describe a facile method for the synthesis of a nitrogen doped (reduced graphene oxide (rGO)-multiwalled carbon nanotubes (MWNTs)) hybrid structure (N-(G-MWNTs)) by the uniform coating of a nitrogen containing polymer over the surface of the hybrid structure (positively surface charged rGO-negatively surface charged MWNTs) followed by the pyrolysis of these (rGO-MWNTs) hybrid structure-polymer composites. The N-(G-MWNTs) hybrid structure is used as a catalyst support for the dispersion of platinum (Pt), platinum-iron (Pt3Fe) and platinum-cobalt (Pt3Co) alloy nanoparticles. The PEMFC performances of Pt-TM alloy nanoparticle dispersed N-(G-MWNTs) hybrid structure electrocatalysts are 5.0 times higher than that of commercial Pt-C electrocatalysts along with very good stability under acidic environment conditions. This work demonstrates a considerable improvement in performance compared to existing cathode electrocatalysts being used in PEMFC and can be extended to the synthesis of metal, metal oxides or metal alloy nanoparticle decorated nitrogen doped carbon nanostructures for various electrochemical energy applications. PMID:23644681

  19. Well-dispersed Pt cubes on porous Cu foam: high-performance catalysts for the electrochemical oxidation of glucose in neutral media.

    PubMed

    Niu, Xiangheng; Lan, Minbo; Zhao, Hongli; Chen, Chen

    2013-07-15

    The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well-dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen-printed carbon electrode (SPCE) substrate through initially synthesizing the three-dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt-based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at -0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8% loss of electrocatalytic activity after 100 repetitive measurements.

  20. Strengthening family systems.

    PubMed

    Starn, J

    1993-01-01

    The childbearing year is a psychosocial transition that involves changes in roles and status for each member of the family. This change is perhaps most significant in the transition that occurs with the birth of the first child. Thus, childbirth education can be looked upon as an opportunity to strengthen family systems through anticipatory guidance and skill building that family members may use throughout the life cycle.

  1. Dispersible carbon nanotubes.

    PubMed

    Soulié-Ziakovic, Corinne; Nicolaÿ, Renaud; Prevoteau, Alexandre; Leibler, Ludwik

    2014-01-27

    A method is proposed to produce nanoparticles dispersible and recyclable in any class of solvents, and the concept is illustrated with the carbon nanotubes. Classically, dispersions of CNTs can be achieved through steric stabilization induced by adsorbed or grafted polymer chains. Yet, the surface modification of CNTs surfaces is irreversible, and the chemical nature of the polymer chains imposes the range of solvents in which CNTs can be dispersed. To address this limitation, supramolecular bonds can be used to attach and to detach polymer chains from the surface of CNTs. The reversibility of supramolecular bonds offers an easy way to recycle CNTs as well as the possibility to disperse the same functional CNTs in any type of solvent, by simply adapting the chemical nature of the stabilizing chains to the dispersing medium. The concept of supramolecular functionalization can be applied to other particles, for example, silica or metal oxides, as well as to dispersing in polymer melts, films or coatings.

  2. FUNDAMENTAL STUDIES OF THE DURABILITY OF MATERIALS FOR INTERCONNECTS IN SOLID OXIDE FUEL CELLS

    SciTech Connect

    Hammer, J.; Laney, S.; Jackson, W.; Pettit, F.; Meier, J.; Dhanaraj, N.; Beuth, J.

    2005-01-28

    This task involves theoretical analysis of possible alternative metallic interconnect schemes including: Ni and dispersion-strengthened Ni, low CTE alloys based on Fe-Ni (Invar), coatings to suppress evaporation, and incorporation of high conductivity paths. The most promising systems are being evaluated experimentally with regard to durability and oxide conductivity.

  3. Molecularly imprinted polymer on a SiO2 -coated graphene oxide surface for the fast and selective dispersive solid-phase extraction of Carbamazepine from biological samples.

    PubMed

    Khalilian, Faezeh; Ahmadian, Setareh

    2016-04-01

    A surface carbamazepine-imprinted polymer was grafted and synthesized on the SiO2 /graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using the sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2 /graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and porogen, respectively. Nonimprinted polymer was also prepared for comparison. The properties of the molecularly imprinted polymer were characterized using field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The surface molecularly imprinted polymer was utilized as an adsorbent of dispersive solid-phase extraction for separation and preconcentration of carbamazepine. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the nonimprinted polymer was examined in absence and presence of competitive drugs. The carbamazepine calibration curve showed linearity in the ranges 0.5-500 μg/L. The limits of detection and quantification under the optimized conditions were 0.1 and 0.3 μg/L, respectively. The within-day and between-day relative standard deviations (n = 3) were 3.6 and 4.3%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 85%. PMID:26899307

  4. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-01-01

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  5. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-04-06

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  6. Manganese oxides and associated minerals as constituents of dispersed mineralization of metasomatic rocks in the Dukat ore field

    NASA Astrophysics Data System (ADS)

    Filimonova, L. G.; Sivtsov, A. V.; Trubkin, N. V.

    2010-08-01

    Lithiophorite and coronadite—varieties of vernadite and todorokite—make up finely dispersed colloform mixtures along with minor grains and nanoparticles of aluminosilicates and ore minerals in metasomatic rocks of the Dukat ore field, which were formed in local areas of fluid and hydrothermal-solution discharge at the upper level of the ore-forming system. Fe-vernadite associates with feroxyhyte, magnetite, apatite, K-feldspar, native silver, and acanthite in greisenized granitoids and with epidote, cerianite, plattnerite, and Fe-chlorite in quartz-garnet-chlorite propylites. Todorokite with high Pb, Tl, and Sn contents associates with epidote, albite, bitumen, and native silver in quartz-epidote-chlorite propylites. Al-vernadite, coronadite, and lithiophorite associate with opal, kaolinite, Fe-chlorite, zincite, uraninite, native silver, and acanthite in argillisites. These data allowed us to estimate the conditions of manganese accumulation in the epithermal ore-forming system and deposition conditions of Mn-rich, finely dispersed mineral mixtures in mineralized zones hosted in metasomatic rocks of the ore field.

  7. Iron oxide functionalized graphene nano-composite for dispersive solid phase extraction of chemical warfare agents from aqueous samples.

    PubMed

    Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Tak, Vijay; Goud, D Raghavender; Dubey, D K; Pardasani, Deepak

    2015-05-15

    Present study deals with the preparation and evaluation of graphene based magnetic nano-composite for dispersive solid phase extraction of Chemical Weapons Convention (CWC) relevant chemicals from aqueous samples. Nano-composite, Fe3O4@SiO2-G was synthesized by covalently bonding silica coated Fe3O4 onto the graphene sheets. Nerve agents (NA), Sulfur mustard (SM) and their non-toxic environmental markers were the target analytes. Extraction parameters like amount of sorbent, extraction time and desorption conditions were optimized. Dispersion of 20 milligram of sorbent in 200mL of water sample for 20min. followed by methanol/chloroform extraction produced average to good recoveries (27-94%) of targeted analytes. Recoveries of real agents exhibited great dependency upon sample pH and ionic strength. Sarin produced maximum recovery under mild acidic conditions (56% at pH 5) while VX demanded alkaline media (83% at pH 9). Salts presence in the aqueous samples was found to be advantageous, raising the recoveries to as high as 94% for SM. Excellent limits of detection (LOD) for sulphur mustard and VX (0.11ngmL(-1) and 0.19ngmL(-1) respectively) proved the utility of the developed method for the off-site analysis of CWC relevant chemicals.

  8. Iron oxide functionalized graphene nano-composite for dispersive solid phase extraction of chemical warfare agents from aqueous samples.

    PubMed

    Chinthakindi, Sridhar; Purohit, Ajay; Singh, Varoon; Tak, Vijay; Goud, D Raghavender; Dubey, D K; Pardasani, Deepak

    2015-05-15

    Present study deals with the preparation and evaluation of graphene based magnetic nano-composite for dispersive solid phase extraction of Chemical Weapons Convention (CWC) relevant chemicals from aqueous samples. Nano-composite, Fe3O4@SiO2-G was synthesized by covalently bonding silica coated Fe3O4 onto the graphene sheets. Nerve agents (NA), Sulfur mustard (SM) and their non-toxic environmental markers were the target analytes. Extraction parameters like amount of sorbent, extraction time and desorption conditions were optimized. Dispersion of 20 milligram of sorbent in 200mL of water sample for 20min. followed by methanol/chloroform extraction produced average to good recoveries (27-94%) of targeted analytes. Recoveries of real agents exhibited great dependency upon sample pH and ionic strength. Sarin produced maximum recovery under mild acidic conditions (56% at pH 5) while VX demanded alkaline media (83% at pH 9). Salts presence in the aqueous samples was found to be advantageous, raising the recoveries to as high as 94% for SM. Excellent limits of detection (LOD) for sulphur mustard and VX (0.11ngmL(-1) and 0.19ngmL(-1) respectively) proved the utility of the developed method for the off-site analysis of CWC relevant chemicals. PMID:25828545

  9. Platinum-TM (TM = Fe, Co) alloy nanoparticles dispersed nitrogen doped (reduced graphene oxide-multiwalled carbon nanotube) hybrid structure cathode electrocatalysts for high performance PEMFC applications

    NASA Astrophysics Data System (ADS)

    Vinayan, B. P.; Ramaprabhu, S.

    2013-05-01

    The efforts to push proton exchange membrane fuel cells (PEMFC) for commercial applications are being undertaken globally. In PEMFC, the sluggish kinetics of oxygen reduction reactions (ORR) at the cathode can be improved by the alloying of platinum with 3d-transition metals (TM = Fe, Co, etc.) and with nitrogen doping, and in the present work we have combined both of these aspects. We describe a facile method for the synthesis of a nitrogen doped (reduced graphene oxide (rGO)-multiwalled carbon nanotubes (MWNTs)) hybrid structure (N-(G-MWNTs)) by the uniform coating of a nitrogen containing polymer over the surface of the hybrid structure (positively surface charged rGO-negatively surface charged MWNTs) followed by the pyrolysis of these (rGO-MWNTs) hybrid structure-polymer composites. The N-(G-MWNTs) hybrid structure is used as a catalyst support for the dispersion of platinum (Pt), platinum-iron (Pt3Fe) and platinum-cobalt (Pt3Co) alloy nanoparticles. The PEMFC performances of Pt-TM alloy nanoparticle dispersed N-(G-MWNTs) hybrid structure electrocatalysts are 5.0 times higher than that of commercial Pt-C electrocatalysts along with very good stability under acidic environment conditions. This work demonstrates a considerable improvement in performance compared to existing cathode electrocatalysts being used in PEMFC and can be extended to the synthesis of metal, metal oxides or metal alloy nanoparticle decorated nitrogen doped carbon nanostructures for various electrochemical energy applications.The efforts to push proton exchange membrane fuel cells (PEMFC) for commercial applications are being undertaken globally. In PEMFC, the sluggish kinetics of oxygen reduction reactions (ORR) at the cathode can be improved by the alloying of platinum with 3d-transition metals (TM = Fe, Co, etc.) and with nitrogen doping, and in the present work we have combined both of these aspects. We describe a facile method for the synthesis of a nitrogen doped (reduced graphene

  10. Solid polymer electrolyte composite membrane comprising a porous support and a solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide

    DOEpatents

    Liu, Han; Mittelsteadt, Cortney K; Norman, Timothy J; Griffith, Arthur E; LaConti, Anthony B

    2015-02-24

    A solid polymer electrolyte composite membrane and method of manufacturing the same. According to one embodiment, the composite membrane comprises a thin, rigid, dimensionally-stable, non-electrically-conducting support, the support having a plurality of cylindrical, straight-through pores extending perpendicularly between opposing top and bottom surfaces of the support. The pores are unevenly distributed, with some or no pores located along the periphery and more pores located centrally. The pores are completely filled with a solid polymer electrolyte, the solid polymer electrolyte including a dispersed reduced noble metal or noble metal oxide. The solid polymer electrolyte may also be deposited over the top and/or bottom surfaces of the support.

  11. In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Kaige; Li, Gongke; Hu, Yuling

    2015-10-01

    The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn2+ linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn2+ linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real

  12. Preparation and characterization of porous granular ceramic containing dispersed aluminum and iron oxides as adsorbents for fluoride removal from aqueous solution.

    PubMed

    Chen, Nan; Zhang, Zhenya; Feng, Chuanping; Zhu, Dirui; Yang, Yingnan; Sugiura, Norio

    2011-02-15

    Porous granular ceramic adsorbents containing dispersed aluminum and iron oxides were synthesized by impregnating with salt solutions followed by precipitation at 600°C. In the present work detailed studies were carried out to investigate the effect of contact time, adsorbent dose, initial solution pH and co-existing anions. Characterization studies on the adsorbent by SEM, XRD, EDS, and BET analysis were carried out to clarify the adsorption mechanism. The adsorbents were sphere in shape, 2-3mm in particle size, highly porous and showed specific surface area of 50.69 sq m/g. The fluoride adsorption capacity of prepared adsorbent was 1.79 mg/g, and the maximum fluoride removal was obtained at pH 6. Both the Langmuir and Freundlich isotherm models were found to represent the measured adsorption data well. The experimental data were well explained with pseudo-second-order kinetic model. Results from this study demonstrated potential utility of Al/Fe dispersed in porous granular ceramics that could be developed into a viable technology for fluoride removal from aqueous solution.

  13. Synthesis of well-dispersed magnetic CoFe2O4 nanoparticles in cellulose aerogels via a facile oxidative co-precipitation method.

    PubMed

    Wan, Caichao; Li, Jian

    2015-12-10

    With the increasing emphasis on green chemistry, it is becoming more important to develop environmentally friendly matrix materials for the synthesis of nanocomposites. Cellulose aerogels with hierarchical micro/nano-scale three-dimensional network beneficial to control and guide the growth of nanoparticles, are suitable as a class of ideal green nanoparticles hosts to fabricate multifunctional nanocomposites. Herein, a facile oxidative co-precipitation method was carried out to disperse CoFe2O4 nanoparticles in the cellulose aerogels matrixes, and the cellulose aerogels were prepared from the native wheat straw based on a green NaOH/polyethylene glycol solution. The mean diameter of the well-dispersed CoFe2O4 nanoparticles in the hybrid aerogels is 98.5 nm. Besides, the hybrid aerogels exhibit strong magnetic responsiveness, which could be flexibly actuated by a small magnet. And this feature also makes this class of magnetic aerogels possibly useful as recyclable adsorbents and some magnetic devices. Meanwhile, the mild green preparation method could also be extended to fabricate other miscellaneous cellulose-based nanocomposites.

  14. Controlled formation of reactive Fe particles dispersed in a carbon matrix active for the oxidation of aqueous contaminants with H₂O₂.

    PubMed

    Tristão, Juliana Cristina; de Mendonça, Fernanda Gomes; Lago, Rochel Montero; Ardisson, José Domingos

    2015-01-01

    In this work, reactive iron nanoparticles dispersed in a carbon matrix were produced by the controlled thermal decomposition of Fe(3+) ions in sucrose. During the sucrose decomposition, the Fe(3+) ions are reduced to form iron nanometric cores dispersed in a porous carbonaceous matrix. The materials were prepared with iron contents of 1, 4, and 8 wt.% and heated at 400, 600, and 800 °C. Analyses by X-ray diffraction, Mössbauer spectroscopy, magnetization measurements, Raman spectroscopy, termogravimetric analyses, BET surface area, scanning, and transmission electron microscopy showed that at 400 °C, the materials are composed essentially of Fe3O4 particles, while treatments at higher temperatures, i.e., 600 and 800 °C, produced phases such as Fe(0) and Fe3C. The composites were tested for the oxidation of methylene blue with H2O2 by a Fenton-type reaction and also H2O2 decomposition, showing better performance for the material containing 8 % of iron heated at 400 and 600 °C. These results are discussed in terms of Fe(2+) surface species in the Fe3O4 nanoparticles active for the Fenton reaction. PMID:24519746

  15. Stable dispersions of polymer-coated graphitic nanoplatelets

    NASA Technical Reports Server (NTRS)

    Stankovich, Sasha (Inventor); Nguyen, Sonbinh T. (Inventor); Ruoff, Rodney S. (Inventor)

    2011-01-01

    A method of making a dispersion of reduced graphite oxide nanoplatelets involves providing a dispersion of graphite oxide nanoplatelets and reducing the graphite oxide nanoplatelets in the dispersion in the presence of a reducing agent and a polymer. The reduced graphite oxide nanoplatelets are reduced to an extent to provide a higher C/O ratio than graphite oxide. A stable dispersion having polymer-treated reduced graphite oxide nanoplatelets dispersed in a dispersing medium, such as water or organic liquid is provided. The polymer-treated, reduced graphite oxide nanoplatelets can be distributed in a polymer matrix to provide a composite material.

  16. Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications

    SciTech Connect

    Stubbins, James; Heuser, Brent; Robertson, Ian; Sehitoglu, Huseyin; Sofronis, Petros; Gewirth, Andrew

    2015-04-22

    This “Blue Sky” project was directed at exploring the opportunities that would be gained by developing Oxide Dispersion Strengthened (ODS) alloys based on the Fe-Cr-Ni austenitic alloy system. A great deal of research effort has been directed toward ferritic and ferritic/martensitic ODS alloys which has resulted in reasonable advances in alloy properties. Similar gains should be possible with austenitic alloy which would also take advantage of other superior properties of that alloy system. The research effort was aimed at the developing an in-depth understanding of the microstructural-level strengthening effects of ODS particles in austentic alloys. This was accomplished on a variety of alloy compositions with the main focus on 304SS and 316SS compositions. A further goal was to develop an understanding other the role of ODS particles on crack propagation and creep performance. Since these later two properties require bulk alloy material which was not available, this work was carried out on promising austentic alloy systems which could later be enhanced with ODS strengthening. The research relied on a large variety of micro-analytical techniques, many of which were available through various scientific user facilities. Access to these facilities throughout the course of this work was instrumental in gathering complimentary data from various analysis techniques to form a well-rounded picture of the processes which control austenitic ODS alloy performance. Micromechanical testing of the austenitic ODS alloys confirmed their highly superior mechanical properties at elevated temperature from the enhanced strengthening effects. The study analyzed the microstructural mechanisms that provide this enhanced high temperature performance. The findings confirm that the smallest size ODS particles provide the most potent strengthening component. Larger particles and other thermally- driven precipitate structures were less effective contributors and, in some cases, limited

  17. Strengthening by intermetallic nanoprecipitation in Fe–Cr–Al–Ti alloy

    DOE PAGES

    Capdevila, C.; Aranda, M. M.; Rementeria, R.; Chao, J.; Urones-Garrote, E.; Aldazabal, J.; Miller, Michael K.

    2016-02-05

    In this paper, the strengthening mechanism observed during ageing at temperatures of 435 and 475 °C in the oxide dispersion strengthened (ODS) Fe–Cr–Al–Ti system has been investigated. Atom probe tomography (APT) and high-resolution transmission electron microscopy (HRTEM) analyses determined that the alloy undergoes simultaneous precipitation of Cr-rich (α' phase) and nanoscale precipitation of TiAl-rich intermetallic particles (β' phase). APT indicated that the composition of the intermetallic β' phase is Fe2AlTi0.6Cr0.4, and the evolving composition of α' phase with ageing time was also determined. The results obtained from HRTEM analyses allow us to confirm that the β' precipitates exhibit a cubicmore » structure and hence their crystallography is related to the Heusler-type Fe2AlTi (L21) structure. Finally, the strengthening could be explained on the basis of two hardening effects that occur simultaneously: the first is due to the α-α' phase separation through the modulus effect, and the second mechanism is due to the interaction of nanoscale β' particles with dislocations.« less

  18. Investigation on different oxides as candidates for nano-sized ODS particles in reduced-activation ferritic (RAF) steels

    NASA Astrophysics Data System (ADS)

    Hoffmann, Jan; Rieth, Michael; Lindau, Rainer; Klimenkov, Michael; Möslang, Anton; Sandim, Hugo Ricardo Zschommler

    2013-11-01

    Future generation reactor concepts are based on materials that can stand higher temperatures and higher neutron doses in corrosive environments. Oxide dispersion strengthened steels with chromium contents ranging from 9 to 14 wt.% - produced by mechanical alloying - are typical candidate materials for future structural materials in fission and fusion power plants.

  19. Adsorptive removal of trace sulfonamide antibiotics by water-dispersible magnetic reduced graphene oxide-ferrite hybrids from wastewater.

    PubMed

    Wu, Jianrong; Zhao, Hongyan; Chen, Rong; Pham-Huy, Chuong; Hui, Xuanhong; He, Hua

    2016-09-01

    A one-pot solvothermal synthesis method was developed to prepare reduced graphene oxide (RGO) supported ferrite hybrids using graphite oxide and metal ions (Fe(3+)) as starting materials. The as-prepared composites were characterized by transmission electron microscopy(TEM), Fourier transform infrared spectrophotometer (FT-IR), X-ray powder diffraction pattern(XRD) and vibrating sample magnetometer (VSM). It was shown that Fe3O4 nanoparticles with a uniform size of ∼35nm were anchored on RGO nanosheets. Importantly, the obtained nanocomposites are effective adsorbents for the determination of three sulfonamides in wastewater. Several parameters affecting the extraction efficiency were optimized, including amount of adsorbent, extraction time, pH and desorption conditions. Compared with other adsorbents, the as-prepared RGO-Fe3O4 showed the better extraction efficiencies for the SAS due to the large surface area of RGO. A linear range from 1 to 200ng/mL was obtained with a high correlation coefficient (R(2)>0.9987), and the limits of detection for three SAs ranged from 0.43 to 0.57ng/mL. This method was successfully applied to the analysis of SAs in environmental wastewater samples, the recoveries in different sample matrices were in the range from 89.1 and 101.7% with relative standard deviations less than 8.6%. It is believed that such composites will find wide applications in the water pretreatment area.

  20. Adsorptive removal of trace sulfonamide antibiotics by water-dispersible magnetic reduced graphene oxide-ferrite hybrids from wastewater.

    PubMed

    Wu, Jianrong; Zhao, Hongyan; Chen, Rong; Pham-Huy, Chuong; Hui, Xuanhong; He, Hua

    2016-09-01

    A one-pot solvothermal synthesis method was developed to prepare reduced graphene oxide (RGO) supported ferrite hybrids using graphite oxide and metal ions (Fe(3+)) as starting materials. The as-prepared composites were characterized by transmission electron microscopy(TEM), Fourier transform infrared spectrophotometer (FT-IR), X-ray powder diffraction pattern(XRD) and vibrating sample magnetometer (VSM). It was shown that Fe3O4 nanoparticles with a uniform size of ∼35nm were anchored on RGO nanosheets. Importantly, the obtained nanocomposites are effective adsorbents for the determination of three sulfonamides in wastewater. Several parameters affecting the extraction efficiency were optimized, including amount of adsorbent, extraction time, pH and desorption conditions. Compared with other adsorbents, the as-prepared RGO-Fe3O4 showed the better extraction efficiencies for the SAS due to the large surface area of RGO. A linear range from 1 to 200ng/mL was obtained with a high correlation coefficient (R(2)>0.9987), and the limits of detection for three SAs ranged from 0.43 to 0.57ng/mL. This method was successfully applied to the analysis of SAs in environmental wastewater samples, the recoveries in different sample matrices were in the range from 89.1 and 101.7% with relative standard deviations less than 8.6%. It is believed that such composites will find wide applications in the water pretreatment area. PMID:27428453

  1. Origin of the large dispersion of magnetic properties in nanostructured oxides: Fe(x)O/Fe3O4 nanoparticles as a case study.

    PubMed

    Estrader, Marta; López-Ortega, Alberto; Golosovsky, Igor V; Estradé, Sònia; Roca, Alejandro G; Salazar-Alvarez, German; López-Conesa, Lluís; Tobia, Dina; Winkler, Elin; Ardisson, José D; Macedo, Waldemar A A; Morphis, Andreas; Vasilakaki, Marianna; Trohidou, Kalliopi N; Gukasov, Arsen; Mirebeau, Isabelle; Makarova, O L; Zysler, Roberto D; Peiró, Francesca; Baró, Maria Dolors; Bergström, Lennart; Nogués, Josep

    2015-02-21

    The intimate relationship between stoichiometry and physicochemical properties in transition-metal oxides makes them appealing as tunable materials. These features become exacerbated when dealing with nanostructures. However, due to the complexity of nanoscale materials, establishing a distinct relationship between structure-morphology and functionalities is often complicated. In this regard, in the FexO/Fe3O4 system a largely unexplained broad dispersion of magnetic properties has been observed. Here we show, thanks to a comprehensive multi-technique approach, a clear correlation between the magneto-structural properties in large (45 nm) and small (9 nm) FexO/Fe3O4 core/shell nanoparticles that can explain the spread of magnetic behaviors. The results reveal that while the FexO core in the large nanoparticles is antiferromagnetic and has bulk-like stoichiometry and unit-cell parameters, the FexO core in the small particles is highly non-stoichiometric and strained, displaying no significant antiferromagnetism. These results highlight the importance of ample characterization to fully understand the properties of nanostructured metal oxides.

  2. In situ loading of well-dispersed silver nanoparticles on nanocrystalline magnesium oxide for real-time monitoring of catalytic reactions by surface enhanced Raman spectroscopy.

    PubMed

    Zhang, Kaige; Li, Gongke; Hu, Yuling

    2015-10-28

    The surface-enhanced Raman spectroscopy (SERS) technique is of great importance for insight into the transient reaction intermediates and mechanistic pathways involved in heterogeneously catalyzed chemical reactions under actual reaction conditions, especially in water. Herein, we demonstrate a facile method for in situ synthesis of nanocrystalline magnesium oxide-Ag(0) (nano MgO-Ag(0)) hybrid nanomaterials with dispersed Ag nanoparticles (Ag NPs) on the surface of nanocrystalline magnesium oxide (nano MgO) via Sn(2+) linkage and reduction. As a benefit from the synergy effect of nano MgO and Ag NPs, the nano MgO-Ag(0) exhibited both excellent SERS and catalytic activities for the reduction of 4-nitrothiophenol in the presence of NaBH4. The nano MgO-Ag(0) was used for real-time monitoring of the catalytic reaction process of 4-nitrothiophenol to 4-aminothiophenol in an aqueous medium by observing the SERS signals of the reactant, intermediate and final products. The intrinsic reaction kinetics and reaction mechanism of this reaction were also investigated. This SERS-based synergy technique provides a novel approach for quantitative in situ monitoring of catalytic chemical reaction processes.

  3. Quantitation of Oxidative Stress Gene Expression in Human Cell Lines Treated with Water-Dispersible MnO Nanoparticles.

    PubMed

    Choi, Jong Seob; Choi, Jong Young; Na, Hyon Bin; Seo, Tae Seok

    2015-06-01

    The objective of this study was to assess cytotoxicity of engineered MnO nanoparticles by quantifying the reactive oxygen species (ROS) related genes (glutathione S-transferase (GST) and catalase) using real time-polymerase chain reaction (RT-PCR) and molecular beacon (MB) technologies. Monodisperse MnO nanoparticles of 14 nm in size were synthesized by the encapsulation of polyethyleneglycol (PEG)-phospholipid shell around the MnO core to endow high water-dispersibility and biocompatibility. In vitro cytotoxicity was evaluated at different concentrations (10, 50 and 100 μg/ml) and incubation times (12, 24 and 48 h) with human cancer cell lines (glioblastoma, lung adenocarcinoma and neuroblastoma cells). Both genetic and cellular cytotoxic screening methods produced consistent results, showing that GST and catalase ROS gene expression was maximized in 24 h incubation at 100 μg/ml concentration of MnO nanoparticles for each cell line. However, the cytotoxicity effect of the PEG-phospholipid coated MnO nanoparticle was not significant compared with control experiments, demonstrating its high potential in the applications of nanomedicines for a diagnostic and therapeutic tool.

  4. Introducing a highly dispersed reduced graphene oxide nano-biohybrid employing chitosan/hydroxyethyl cellulose for controlled drug delivery.

    PubMed

    Mianehrow, Hanieh; Afshari, Ronak; Mazinani, Saeedeh; Sharif, Farhad; Abdouss, Majid

    2016-07-25

    In this research, an attempt was made to stabilize reduced graphene oxide (rGO) in all pH ranges, incorporating both chitosan (CS) and hydroxyethyl cellulose (HEC) to make a proper drug carrier with suitable stability and drug release behaviour. The stability of rGO-CS-HEC nanohybrid was assessed using field emission scanning electron microscopy (FE-SEM), ultraviolet-visible spectroscopy (UV-Vis) and Zeta potential measurements. Results depicted that the novel synthesized nanohybrid was stable in all pH ranges, due to the utilization of HEC, while without incorporation of this material, the rGO-CS nanohybrid aggregated at neutral and alkaline media, due to the ionic nature of chitosan. In addition, drug loading and release behaviour of folic acid (FA), as a model drug, was investigated to assess the role of chitosan on the release behaviour of FA from the rGO-CS-HEC nanohybrid in comparison with rGO-HEC and rGO-CS nanohybrids. It was proved that the resultant nanohybrid could release nearly 27% more FA than the rGO-HEC nanohybrid and only 9% lower than the rGO-CS nanohybrid during 120h. Moreover, the biocompatibility of the resultant nanohybrid was also checked to introduce the novel rGO-CS-HEC nanohybrid as a suitable candidate for drug delivery application. PMID:27286635

  5. Electrophoretic deposition of multi-walled carbon nanotubes on porous anodic aluminum oxide using ionic liquid as a dispersing agent

    NASA Astrophysics Data System (ADS)

    Hekmat, F.; Sohrabi, B.; Rahmanifar, M. S.; Jalali, A.

    2015-06-01

    Multi-wall carbon nanotubes (MW-CNTs) have been arranged in nanochannels of anodic aluminum oxide template (AAO) by electrophoretic deposition (EPD) to make a vertically-aligned carbon nanotube (VA-CNT) based electrode. Well ordered AAO templates were prepared by a two-step anodizing process by applying a constant voltage of 45 V in oxalic acid solution. The stabilized CNTs in a water-soluble room temperature ionic liquid (1-methyl-3-octadecylimidazolium bromide), were deposited in the pores of AAO templates which were conductive by deposition of Ni nanoparticles in the bottom of pores. In order to obtain ideal results, different EPD parameters, such as concentration of MWCNTs and ionic liquid on stability of MWCNT suspensions, deposition time and voltage which are applied in EPD process and also optimal conditions for anodizing of template were investigated. The capacitive performance of prepared electrodes was analyzed by measuring the specific capacitance from cyclic voltammograms and the charge-discharge curves. A maximum value of 50 Fg-1 at the scan rate of 20 mV s-1was achieved for the specific capacitance.

  6. Iron oxide functionalized graphene oxide as an efficient sorbent for dispersive micro-solid phase extraction of sulfadiazine followed by spectrophotometric and mode-mismatched thermal lens spectrometric determination.

    PubMed

    Kazemi, Elahe; Dadfarnia, Shayessteh; Haji Shabani, Ali Mohammad; Abbasi, Amir; Rashidian Vaziri, Mohammad Reza; Behjat, Abbas

    2016-01-15

    A simple and rapid dispersive micro-solid phase extraction (DMSPE) combined with mode-mismatched thermal lens spectrometry as well as fiber optic linear array spectrophotometry was developed for the separation, extraction and determination of sulfadiazine. Graphene oxide was synthesized using the modified Hummers method and functionalized with iron oxide nanoparticles by means of a simple one step chemical coprecipitation method. The synthesized iron oxide functionalized graphene oxide was utilized as an efficient sorbent in DMSPE of sulfadiazine. The retained analyte was eluted by using 180µL of a 6:4 mixture of methanol/acetic acid solution and was spectrophotometrically determined based on the formation of an azo dye through coupling with thenoyltrifluoroacetone. Under the optimized conditions, with the application of spectrophotometry technique and with a sample volume of 100mL, the method exhibited a linear dynamic range of 3-80µg L(-1) with a detection limit of 0.82µg L(-1), an enrichment factor of 200 as well as the relative standard deviations of 2.6% and 4.3% (n=6) at 150µg L(-1) level of sulfadiazine for intra- and inter-day analyses, respectively. Whereas, through the application of the thermal lens spectrometry and a sample volume of 10mL, the method exhibited a linear dynamic range of 1-800µg L(-1) with a detection limit of 0.34µg L(-1) and the relative standard deviations of 3.1% and 5.4% (n=6) at 150µg L(-1) level of sulfadiazine for intra- and inter-day analyses, respectively. The method was successfully applied to the determination of sulfadiazine in milk, honey and water samples.

  7. Effects of chromium and aluminum on mechanical and oxidation properties of iron-nickel-base superalloys based on CG-27

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1985-01-01

    The effects of chromium and aluminum on the mechanical and oxidation properties of a series of gamma-prime-strengthened alloys based on CG-27 were studied. Gamma-prime dispersion and solid-solution strengthening were the principal modes of alloy strengthening. The oxidation attack parameter K sub a decreased with increasing Cr and Al contents for each alloy group based on Al content. As a group, alloys with 3 wt % Al had the lowest attack parameters. Therefore, 3 wt % is the optimum level of Al for parabolic oxidation behavior. Spalling, due to diffusion-induced grain growth, was controlled by the overall Cr and Al levels. The alloy with 4 wt % Cr and 3 wt % Al had stress-rupture properties superior to those of the base alloy, CG-27, and maintained parabolic oxidation behavior while the Cr content was reduced by two-thirds of its value in cast CG-27.

  8. DISPERSION HARDENING OF URANIUM METAL

    DOEpatents

    Arbiter, W.

    1963-01-15

    A method of hardening U metal involves the forming of a fine dispersion of UO/sub 2/. This method consists of first hydriding the U to form a finely divided powder and then exposing the powder to a very dilute O gas in an inert atmosphere under such pressure and temperature conditions as to cause a thin oxide film to coat each particle of the U hydride, The oxide skin prevents agglomeration of the particles as the remaining H is removed, thus preserving the small particle size. The oxide skin coatings remain as an oxide dispersion. The resulting product may be workhardened to improve its physical characteristics. (AEC)

  9. A new diffusion-inhibited oxidation-resistant coating for superalloys

    NASA Technical Reports Server (NTRS)

    Gedwill, M. A.; Glasgow, T. K.; Levine, S. R.

    1981-01-01

    A concept for enhanced protection of superalloys consists of adding an oxidation- and diffusion-resistant cermet layer between the superalloy and the outer oxidation-resistant metallic alloy coating. Such a duplex coating was compared with a physical-vapor-deposited (PVD) NiCrAlY coating in cyclic oxidation at 1150 C. The substrate alloy was MA 754 - an oxide-dispersion-strengthened superalloy that is difficult to coat. The duplex coating, applied by plasma spraying, outperformed the PVD coating on the basis of weight change and both macroscopic and metallographic observations.

  10. Ocular dispersion

    NASA Astrophysics Data System (ADS)

    Hammer, Daniel X.; Noojin, Gary D.; Thomas, Robert J.; Stolarski, David J.; Rockwell, Benjamin A.; Welch, Ashley J.

    1999-06-01

    Spectrally resolved white-light interferometry (SRWLI) was used to measure the wavelength dependence of refractive index (i.e., dispersion) for various ocular components. The accuracy of the technique was assessed by measurement of fused silica and water, the refractive indices of which have been measured at several different wavelengths. The dispersion of bovine and rabbit aqueous and vitreous humor was measured from 400 to 1100 nm. Also, the dispersion was measured from 400 to 700 nm for aqueous and vitreous humor extracted from goat and rhesus monkey eyes. For the humors, the dispersion did not deviate significantly from water. In an additional experiment, the dispersion of aqueous and vitreous humor that had aged up to a month was compared to freshly harvested material. No difference was found between the fresh and aged media. An unsuccessful attempt was also made to use the technique for dispersion measurement of bovine cornea and lens. Future refinement may allow measurement of the dispersion of cornea and lens across the entire visible and near-infrared wavelength band. The principles of white- light interferometry including image analysis, measurement accuracy, and limitations of the technique, are discussed. In addition, alternate techniques and previous measurements of ocular dispersion are reviewed.

  11. A micro-alloyed ferritic steel strengthened by nanoscale precipitates

    SciTech Connect

    Shen, Yongfeng; Wang, Chong M.; Sun, Xin

    2011-10-25

    A ferritic steel with finely dispersive precipitates was investigated to reveal the fundamental strengthening mechanisms. The steel has a yield strength of 760 MPa, approximately three times higher than that of conventional Ti-bearing high strength hot-rolled sheet steels, and its ultimate tensile strength reaches 850 MPa with an elongation-to-failure value of 18%. Using energy dispersive X-ray spectroscopy (EDXS) and transmission electron microscope (TEM), fine carbides TiC with an average diameter of 10 nm were observed in the ferrite matrix of the 0.08%Ti steel, and some cubic M23C6 precipitates were also observed at the grain boundaries and the interior of the grains. The finely dispersive TiC precipitates in the matrix provide matrix strengthening. The estimated magnitude of precipitation strengthening is around 458 MPa, depending on the average size of the nanoscale precipitates. Dislocation densities increased from 3.42×1013 m-2 to 1.69 × 1014 m-2, respectively, with increasing tensile strain from 5.5% to 22%. The measured work-hardening behavior can be related to the observed dislocation accumulations resulting from the dispersive nano-scale precipitates.

  12. Matrix solid-phase dispersion and solid-phase microextraction applied to study the distribution of fenbutatin oxide in grapes and white wine.

    PubMed

    Montes, R; Canosa, P; Lamas, J Pablo; Piñeiro, A; Orriols, I; Cela, R; Rodríguez, I

    2009-12-01

    The fate of the acaricide fenbutatin oxide (FBTO) during the elaboration of white wine is evaluated. Matrix solid-phase dispersion (MSPD) and solid-phase microextraction (SPME) were used as sample preparation techniques applied to the semi-solid and the liquid matrices involved in this research, respectively. Selective determination of FBTO was achieved by gas chromatography with atomic emission detection (GC-AED). GC coupled to mass spectrometry was also used to establish the identity of FBTO by-products detected in must and wine samples. MSPD extractions were accomplished using C18 as dispersant and co-sorbent. Sugars and other polar interferences were first removed with water and water/acetone mixtures, then FBTO was recovered with 8 mL of acetone. When used in combination with GC-AED, the MSPD method provided limits of quantification (LOQs) in the low nanogram per gram range, recoveries around 90% and relative standard deviations below 13% for extractions performed in different days. Performance of SPME for must and wine was mainly controlled by the extraction temperature, time and fibre coating. Under final conditions, FBTO was extracted in the headspace mode for 45 min at 100 degrees C, using a 100 microm poly(dimethylsiloxane)-coated fibre. The achieved LOQs remained around or below 0.1 ng mL(-1), depending on the type of sample, and the inter-day precision ranged from 10% to 13%. FBTO residues in grapes stayed mostly on the skin of the fruit. Although FBTO was not removed during must and white wine elaboration, it remained associated with suspended particles existing in must and lees, settled after must fermentation, with a negligible risk of being transferred to commercialised wine. On the other hand, two by-products of FBTO (bis and mono (2-methyl-2-phenylpropyl) tin) were identified, for first time, in must and final white wines obtained from FBTO treated grapes. Found values for the first species ranged from 0.03 to 0.9 ng mL(-1). PMID:19806346

  13. Layer-by-layer films and colloidal dispersions of graphene oxide nanosheets for efficient control of the fluorescence and aggregation properties of the cationic dye acridine orange

    NASA Astrophysics Data System (ADS)

    Hansda, Chaitali; Chakraborty, Utsav; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Pabitra Kumar

    2016-03-01

    Chemically derived graphene oxide (GO) nanosheets have received great deal of interest for technological application such as optoelectronic and biosensors. Aqueous dispersions of GO become an efficient template to induce the association of cationic dye namely Acridine Orange (AO). Interactions of AO with colloidal GO was governed by both electrostatic and π-π stacking cooperative interactions. The type of dye aggregations was found to depend on the concentration of GO in the mixed ensemble. Spectroscopic calculations revealed the formation of both H and J-type dimers, but H-type aggregations were predominant. Preparation of layer-by-layer (LbL) electrostatic self-assembled films of AO and GO onto poly (allylamine hydrochloride) (PAH) coated quartz substrate is also reported in this article. UV-Vis absorption, steady state and time resolve fluorescence and Raman spectroscopic techniques have been employed to explore the detail photophysical properties of pure AO, AO/GO mixed solution and AO/GO LbL films. Scanning electron microscopy was also used for visual evidence of the synthesized nanodimensional GO sheets. The fluorescence quenching of AO in the presence of GO in aqueous solution was due to the interfacial photoinduced electron transfer (PET) from photoexcited AO to GO i.e. GO acts as an efficient quenching agent for the fluorescence emission of AO. The quenching is found to be static in nature. Raman spectroscopic results also confirmed the interaction of AO with GO and the electron transfer. The formation of AO/GO complex via very fast excited state electron transfer mechanism may be proposed as to prepare GO-based fluorescence sensor for biomolecular detection without direct labeling the biomolecules by fluorescent probe.

  14. Facile synthesis of highly stable and well-dispersed mesoporous ZrO(2)/carbon composites with high performance in oxidative dehydrogenation of ethylbenzene.

    PubMed

    Li, Qiang; Xu, Jie; Wu, Zhangxiong; Feng, Dan; Yang, Jianping; Wei, Jing; Wu, Qingling; Tu, Bo; Cao, Yong; Zhao, Dongyuan

    2010-09-28

    Highly ordered mesoporous ZrO(2)/carbon (FDU-15) composites have been synthesized via a facile evaporation induced triconstituent co-assembly (EISA) approach by using Pluronic F127 as a template and zirconium oxychloride octahydrate and resol as Zr and carbon sources. The synthesized mesoporous composites exhibit a highly ordered two-dimensional (2-D) hexagonal mesostructure with relatively high specific surface areas (up to 947 m(2) g(-1)), pore sizes around 3.8 nm and high pore volumes (up to 0.71 cm(3) g(-1)). The results clearly show that the crystalline zirconia nanoparticles (ca. 1.9-3.9 nm) are well-dispersed in amorphous matrices of the ordered mesoporous carbon FDU-15 materials, which construct the nanocomposites. The ordered mesostructures of the obtained ZrO(2)/FDU-15 composites can be well-retained even at the high pyrolysis temperature (up to 900 degrees C), suggesting a high thermal stability. The zirconia content of the ZrO(2)/FDU-15 composites can be tunable in a wide range (up to 47%). Moreover, the resultant mesoporous ZrO(2)/FDU-15 composites exhibit high catalytic activity in oxidative dehydrogenation (ODH) of ethylbenzene (EB) to styrene (ST), with high ethylbenzene conversion (59.6%) and styrene selectivity (90.4%), which is mainly attributed to the synergistic catalytic effect between the oxygen-containing groups located on the carbon pore walls and weakly basic sites of the nanocrystalline ZrO(2). Furthermore, the high specific surface areas and opening pore channels are also responsible for their high catalytic activity. Therefore, it is a very promising catalyst material in styrene production on an industrial scale.

  15. Selective dispersive micro solid-phase extraction using oxidized multiwalled carbon nanotubes modified with 1,10-phenanthroline for preconcentration of lead ions.

    PubMed

    Feist, Barbara

    2016-10-15

    A dispersive micro solid phase extraction (DMSPE) method for the selective preconcentration of trace lead ions on oxidized multiwalled carbon nanotubes (ox-MWCNTs) with complexing reagent 1,10-phenanthroline is presented. Flame and electrothermal atomic absorption spectrometry (F-AAS, ET-AAS) were used for detection. The influence of several parameters such as pH, amount of sorbent and 1,10-phenanthroline, stirring time, concentration and volume of eluent, sample flow rate and sample volume was examined using batch procedures. Moreover, effects of inorganic matrix on recovery of the determined elements were studied. The experiment shows that foreign ions did not influence on recovery of the determined element. The method characterized by high selectivity toward Pb(II) ions. Lead ions can be quantitatively retained at pH 7 from sample volume up to 400mL and then eluent completely with 2mL of 0.5molL(-1)HNO3. The detection limits of Pb was 0.26μgL(-1) for F-AAS and 6.4ngL(-1) for ET-AAS. The recovery of the method for the determined lead was better than 97% with relative standard deviation lower than 3.0%. The preconcentration factor was 200 for F-AAS and 100 for ET-AAS. The maximum adsorption capacity of the adsorbent was found to be about 350mgg(-1). The method was applied for determination of Pb in fish samples with good results. Accuracy of the method was verified using certified reference material DOLT-3 and ERM-BB186. PMID:27173531

  16. Fast throughput determination of 21 allergenic disperse dyes from river water using reusable three-dimensional interconnected magnetic chemically modified graphene oxide followed by liquid chromatography-tandem quadrupole mass spectrometry.

    PubMed

    Zhao, Yong-Gang; Li, Xiao-Ping; Yao, Shan-Shan; Zhan, Ping-Ping; Liu, Jun-Chao; Xu, Chang-Ping; Lu, Yi-Yu; Chen, Xiao-Hong; Jin, Mi-Cong

    2016-01-29

    We report the template-free fabrication of three-dimensional hierarchical nanostructures, i.e., three-dimensional interconnected magnetic chemically modified graphene oxide (3D-Mag-CMGO), through a simple and low-cost self-assembly process using one-pot reaction based on solvothermal method. The excellent properties of the 3D-Mag-CMGO are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), FTIR, elementary analyzer (EA) and X-ray photoelectron spectroscopy (XPS). The easiness-to-handle of the magnetic dispersive solid phase extraction (Mag-dSPE) procedure is developed for preconcentration of 21 allergenic disperse dyes from river water. The obtained results show the higher extraction capacity of 3D-Mag-CMGO with recoveries between 80.0-112.0%. Furthermore, an ultra-fast liquid chromatography-tandem quadrupole mass spectrometry (UFLC-MS/MS) method for determination of 21 allergenic disperse dyes in river at sub-ppt levels has been developed with pretreatment of the samples by Mag-dSPE. The limits of quantification (LOQs) for the allergenic disperse dyes are between 0.57-34.05ng/L. Validation results on linearity, specificity, trueness and precision, as well as on application to the analysis of 21 allergenic disperse dyes in fifty real samples demonstrate the applicability to environment monitoring analysis. PMID:26777090

  17. Graphene-and-Copper Artificial Nacre Fabricated by a Preform Impregnation Process: Bioinspired Strategy for Strengthening-Toughening of Metal Matrix Composite.

    PubMed

    Xiong, Ding-Bang; Cao, Mu; Guo, Qiang; Tan, Zhanqiu; Fan, Genlian; Li, Zhiqiang; Zhang, Di

    2015-07-28

    Metals can be strengthened by adding hard reinforcements, but such strategy usually compromises ductility and toughness. Natural nacre consists of hard and soft phases organized in a regular "brick-and-mortar" structure and exhibits a superior combination of mechanical strength and toughness, which is an attractive model for strengthening and toughening artificial composites, but such bioinspired metal matrix composite has yet to be made. Here we prepared nacre-like reduced graphene oxide (RGrO) reinforced Cu matrix composite based on a preform impregnation process, by which two-dimensional RGrO was used as "brick" and inserted into "□-and-mortar" ordered porous Cu preform (the symbol "□" means the absence of "brick"), followed by compacting. This process realized uniform dispersion and alignment of RGrO in Cu matrix simultaneously. The RGrO-and-Cu artificial nacres exhibited simultaneous enhancement on yield strength and ductility as well as increased modulus, attributed to RGrO strengthening, effective crack deflection and a possible combined failure mode of RGrO. The artificial nacres also showed significantly higher strengthening efficiency than other conventional Cu matrix composites, which might be related to the alignment of RGrO. PMID:26083407

  18. Dispersion Modeling.

    ERIC Educational Resources Information Center

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  19. Solute strengthening at high temperatures

    NASA Astrophysics Data System (ADS)

    Leyson, G. P. M.; Curtin, W. A.

    2016-08-01

    The high temperature behavior of solute strengthening has previously been treated approximately using various scaling arguments, resulting in logarithmic and power-law scalings for the stress-dependent energy barrier Δ E(τ ) versus stress τ. Here, a parameter-free solute strengthening model is extended to high temperatures/low stresses without any a priori assumptions on the functional form of Δ E(τ ) . The new model predicts that the well-established low-temperature, with energy barrier Δ {{E}\\text{b}} and zero temperature flow stress {τy0} , transitions to a near-logarithmic form for stresses in the regime 0.2<τ /{τy0}≤slant 0.5 and then transitions to a power-law form at even lower stresses τ /{τy0}<0.03 . Δ {{E}\\text{b}} and {τy0} remains as the reference energy and stress scales over the entire range of stresses. The model is applied to literature data on solution strengthening in Cu alloys and captures the experimental results quantitatively and qualitatively. Most importantly, the model accurately captures the transition in strength from the low-temperature to intermediate-temperature and the associated transition for the activation volume. Overall, the present analysis unifies the different qualitative models in the literature and, when coupled with the previous parameter-free solute strengthening model, provides a single predictive model for solute strengthening as a function of composition, temperature, and strain rate over the full range of practical utility.

  20. Effects of Pt dispersion on electronic and oxide ionic conductivity in Pr1.90Ni0.71Cu0.24Ga0.05O4.

    PubMed

    Ishihara, T; Hyodo, J; Schraknepper, H; Tominaga, K; Ida, S

    2016-04-28

    The effects of dispersing Pt particles in bulk Pr1.90Ni0.71Cu0.21Ga0.05O(4+δ) (PNCG) on the electrical conductivity and oxygen permeability of the material were studied. The different thermal expansion coefficients of PNCG and Pt generated a mechanical compressive strain in the PNCG. This may cause the electrical conductivity to decrease in samples containing Pt. In contrast, the oxide ion conductivity estimated from the oxygen permeability increased upon dispersion of Pt. These variations appear to be related to the electron hole and interstitial oxygen concentrations. Moreover, the present study suggests that the mechanical strain induces a chemical strain via the introduction of oxygen defects as well as changes in cation valences. PMID:27049143

  1. Fog dispersion

    NASA Technical Reports Server (NTRS)

    Frost, W.; Christensen, L. S.; Collins, F. G.; Camp, D. W.

    1980-01-01

    A study of economically viable techniques for dispersing warm fog at commercial airports is presented. Five fog dispersion techniques are examined: evaporation suppression, downwash, mixing, seeding with hygroscopic material, thermal techniques, and charged particle techniques. Thermal techniques, although effective, were found to be too expensive for routine airport operations, and detrimental to the environment. Seeding or helicopter downwash are practical for small-scale or temporary fog clearing, but are probably not useful for airport operations on a routine basis. Considerable disagreement exists on the capability of charged particle techniques, which stems from the fact that different assumptions and parameter values are used in the analytical models. Recommendations resulting from the review of this technique are listed, and include: experimental measurements of the parameters in question; a study to ascertain possible safety hazards, such as increased electrical activity or fuel ignition during refueling operations which could render charged particle techniques impractical; and a study of a single charged particle generator.

  2. A comparison between monitoring and dispersion modeling approaches to assess the impact of aviation on concentrations of black carbon and nitrogen oxides at Los Angeles International Airport.

    PubMed

    Penn, Stefani L; Arunachalam, Saravanan; Tripodis, Yorghos; Heiger-Bernays, Wendy; Levy, Jonathan I

    2015-09-15

    Aircraft activity and airport operations can increase combustion-related air pollutant concentrations, but it is difficult to distinguish aviation emissions from traffic and other local sources. Emission inventories are uncertain and dispersion models may not capture aircraft plume complexity; ambient monitoring data require detailed statistical analyses to extract aviation signals. The goal of this study is to compare two modeling approaches including monitoring-based regression models and the EDMS/AERMOD dispersion model, informing improvements and allowing quantitation of aviation impacts on air quality through multi-pollutant sensitivity and multi-monitor fate/transport analyses. Aggregate concentration comparisons are similar, though diurnal patterns show potential weaknesses in near-field dispersion, treatment of overnight conditions, and emission inventory accuracy. PMID:25956147

  3. A comparison between monitoring and dispersion modeling approaches to assess the impact of aviation on concentrations of black carbon and nitrogen oxides at Los Angeles International Airport.

    PubMed

    Penn, Stefani L; Arunachalam, Saravanan; Tripodis, Yorghos; Heiger-Bernays, Wendy; Levy, Jonathan I

    2015-09-15

    Aircraft activity and airport operations can increase combustion-related air pollutant concentrations, but it is difficult to distinguish aviation emissions from traffic and other local sources. Emission inventories are uncertain and dispersion models may not capture aircraft plume complexity; ambient monitoring data require detailed statistical analyses to extract aviation signals. The goal of this study is to compare two modeling approaches including monitoring-based regression models and the EDMS/AERMOD dispersion model, informing improvements and allowing quantitation of aviation impacts on air quality through multi-pollutant sensitivity and multi-monitor fate/transport analyses. Aggregate concentration comparisons are similar, though diurnal patterns show potential weaknesses in near-field dispersion, treatment of overnight conditions, and emission inventory accuracy.

  4. 27 CFR 24.153 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Strengthening bonds. In any instance where the penal sum of the bond on file becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum or give a... limiting the amount of either bond to less than its full penal sum. Strengthening bonds will show...

  5. 27 CFR 26.69 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Liquors and Articles in Puerto Rico Bonds § 26.69 Strengthening bonds. In all cases where the penal sum of... surety to attain a sufficient penal sum, or give a new bond to cover the entire liability. Strengthening... penal sum. Strengthening bonds shall show the current date of execution and the effective date....

  6. 27 CFR 19.246 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Strengthening bonds. In all cases when the penal sum of any bond becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum, or give a new... amount of any bond to less than its full penal sum. Strengthening bonds shall show the current date...

  7. Glass strengthening and patterning methods

    DOEpatents

    Harper, David C; Wereszczak, Andrew A; Duty, Chad E

    2015-01-27

    High intensity plasma-arc heat sources, such as a plasma-arc lamp, are used to irradiate glass, glass ceramics and/or ceramic materials to strengthen the glass. The same high intensity plasma-arc heat source may also be used to form a permanent pattern on the glass surface--the pattern being raised above the glass surface and integral with the glass (formed of the same material) by use of, for example, a screen-printed ink composition having been irradiated by the heat source.

  8. Burnishing Techniques Strengthen Hip Implants

    NASA Technical Reports Server (NTRS)

    2010-01-01

    In the late 1990s, Lambda Research Inc., of Cincinnati, Ohio, received Small Business Innovation Research (SBIR) awards from Glenn Research Center to demonstrate low plasticity burnishing (LPB) on metal engine components. By producing a thermally stable deep layer of compressive residual stress, LPB significantly strengthened turbine alloys. After Lambda patented the process, the Federal Aviation Administration accepted LPB for repair and alteration of commercial aircraft components, the U.S. Department of Energy found LPB suitable for treating nuclear waste containers at Yucca Mountain. Data from the U.S. Food and Drug Administration confirmed LPB to completely eliminate the occurrence of fretting fatigue failures in modular hip implants.

  9. Microstructure and Mechanism of Strengthening of Microalloyed Pipeline Steel: Ultra-Fast Cooling (UFC) Versus Laminar Cooling (LC)

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Wang, X.; Hu, W.; Kang, J.; Yuan, G.; Di, H.; Misra, R. D. K.

    2016-06-01

    A novel thermo-mechanical controlled processing (TMCP) schedule involving ultra-fast cooling (UFC) technique was used to process X70 (420 MPa) microalloyed pipeline steel with high strength-high toughness combination. A relative comparison is made between microstructure and mechanical properties between conventionally processed (CP) and ultra-fast cooled (UFC) pipeline steels, together with differences in strengthening mechanisms with respect to both types of processes. UFC-processed steel exhibited best combination of strength and good toughness compared to the CP process. The microstructure of CP pipeline steel mainly consisted of acicular ferrite (AF), bainitic ferrite (BF), and dispersed secondary martensite/austenite (M/A) constituent and a small fraction of fine quasi-polygonal ferrite. In contrast, the microstructure of UFC-processed pipeline steel was predominantly composed of finer AF, BF, and dispersed M/A constituent. The primary strengthening mechanisms in UFC pipeline steel were grain size strengthening and dislocation strengthening with strength increment of ~277 and ~151 MPa, respectively. However, the strengthening contribution in CP steel was related to grain size strengthening, dislocation strengthening, and precipitation strengthening, and the corresponding strength increments were ~212, ~149 and ~86 MPa, respectively. The decrease in strength induced by reducing Nb and Cr in UFC pipeline steel was compensated by enhancing the contribution of grain size strengthening in the UFC process. In conclusion, cooling schedule of UFC combined with LC is a promising method for processing low-cost pipeline steels.

  10. Niobium oxide dispersed on a carbon-ceramic matrix, SiO2/C/Nb2O5, used as an electrochemical ascorbic acid sensor.

    PubMed

    Arenas, Leliz T; Villis, Paulo C M; Arguello, Jacqueline; Landers, Richard; Benvenutti, Edilson V; Gushikem, Yoshitaka

    2010-11-15

    A film of niobium oxide was immobilized on a SiO(2)/C carbon-ceramic matrix (specific surface area 270 m(2)g(-1)) and characterized by N(2) adsorption-desorption isotherms, scanning electron microscopy, X-ray photoelectron spectroscopy and atomic force microscopy. This new carbon-ceramic material, SiO(2)/C/Nb(2)O(5), was used for construction of electrodes, and it shows ability to improve the electron-transfer between the electrode surface and ascorbic acid. The electrocatalytic oxidation of ascorbic acid was made by differential pulse and cyclic voltammetry techniques, making it potentially useful for developing a new ascorbic acid sensor.

  11. Colloidal Dispersions

    NASA Astrophysics Data System (ADS)

    Russel, W. B.; Saville, D. A.; Schowalter, W. R.

    1992-03-01

    The book covers the physical side of colloid science from the individual forces acting between submicron particles suspended in a liquid through the resulting equilibrium and dynamic properties. The relevant forces include Brownian motion, electrostatic repulsion, dispersion attraction, both attraction and repulsion due to soluble polymer, and viscous forces due to relative motion between the particles and the liquid. The balance among Brownian motion and the interparticle forces decides the questions of stability and phase behavior. Imposition of external fields produces complex effects, i.e. electrokinetic phenomena (electric field), sedimentation (gravitational field), diffusion (concentration/chemical potential gradient), and non-Newtonian rheology (shear field). The treatment aims to impart a sound, quantitative understanding based on fundamental theory and experiments with well-characterized model systems. This broad grasp of the fundamentals lends insight and helps to develop the intuitive sense needed to isolate essential features of technological problems and design critical experiments. Some exposure to fluid mechanics, statistical mechanics, and electricity and magnetism is assumed, but each subject is reintroduced in a self-contained manner.

  12. An evaluation of an overlay coated ODS superalloy in high temperature oxidation and burner rig environments

    SciTech Connect

    Ganesan, P.; Smith, G.D. )

    1989-01-01

    Inconel alloy MA 6000 is a precipitation hardenable, oxide dispersion strengthened nickel base superalloy produced by mechanical alloying. The alloy was developed as an airfoil section material for advanced gas turbines. The desire for maximum service life prompted a study to evaluate the coatability of alloy MA 6000 and its performance in the coated condition. This paper presents preliminary results of this study and compares the oxidation and burner-rig test results of coated alloy MA 6000, with and without the interlayer, with the performance of uncoated alloy MA 6000.

  13. Oxidation of methanol on perovskite-type La 2- xSr xNiO 4 (0 ≤ x ≤ 1) film electrodes modified by dispersed nickel in 1 M KOH

    NASA Astrophysics Data System (ADS)

    Singh, R. N.; Singh, A.; Mishra, D.; Anindita; Chartier, P.

    Finely-dispersed nickel particles are electrodeposited on high surface-area perovskite-type La 2- xSr xNiO 4 (0 ≤ x ≤ 1) electrodes for possible use in a direct methanol fuel cell (DMFC). The study is conducted by cyclic voltammetry, chronoamperometry, impedance spectroscopy and anodic Tafel polarization techniques. The results show that the apparent electrocatalytic activities of the modified oxide electrodes are much higher than those of unmodified electrodes under similar experimental conditions; the observed activity is the greatest with the modified La 1.5Sr 0.5NiO 4 electrode. At 0.550 V (vs. Hg|HgO) in 1 M KOH + 1 M CH 3OH at 25 °C, the latter electrode delivers a current density of over 200 mA cm -2, whereas other electrodes of the series produce relatively low values (65-117 mA cm -2). To our knowledge, such high methanol oxidation current densities have not been reported on any other non-platinum electrode in alkaline solution. Further, the modified electrodes are not poisoned by methanol oxidation intermediates/products.

  14. Selective separation and determination of the synthetic colorants in beverages by magnetic solid-phase dispersion extraction based on a Fe3 O4 /reduced graphene oxide nanocomposite followed by high-performance liquid chromatography with diode array detection.

    PubMed

    Wang, Xi; Chen, Ning; Han, Qing; Yang, Zaiyue; Wu, Jinhua; Xue, Cheng; Hong, Junli; Zhou, Xuemin; Jiang, Huijun

    2015-06-01

    A facile adsorbent, a nanocomposite of Fe3 O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong π-π interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 μg/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3 O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment. PMID:25864558

  15. Selective separation and determination of the synthetic colorants in beverages by magnetic solid-phase dispersion extraction based on a Fe3 O4 /reduced graphene oxide nanocomposite followed by high-performance liquid chromatography with diode array detection.

    PubMed

    Wang, Xi; Chen, Ning; Han, Qing; Yang, Zaiyue; Wu, Jinhua; Xue, Cheng; Hong, Junli; Zhou, Xuemin; Jiang, Huijun

    2015-06-01

    A facile adsorbent, a nanocomposite of Fe3 O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong π-π interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 μg/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3 O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment.

  16. Quantitation of oxidative stress gene expression in MCF-7 human cell lines treated with water-dispersible CuO nanoparticles.

    PubMed

    Kumaran, Rangarajulu Senthil; Choi, Yong-Keun; Kim, Hyung Joo; Kim, Kwang Jin

    2014-06-01

    The objective of this study was to assess the cytotoxicity of water-dispersible CuO nanoparticles by quantifying the reactive oxygen species (ROS)-related genes (glutathione S-transferase (GST) and catalase) using real-time polymerase chain reaction (RT-PCR). Monodisperse CuO nanoparticles of 14 nm in size were used. Cytotoxicity of CuO nanoparticles was evaluated under in vitro condition at different concentrations (10, 50, and 100 μg/ml) and incubation times (12, 24, and 48 h) with human cancer cell lines (breast cancer epithelial cells). The genetic level cytotoxic screening produced consistent results showing that GST and catalase ROS gene expression was maximized in 24 h incubation at 100 μg/ml concentration of CuO nanoparticles. However, the cytotoxicity of water-dispersible CuO nanoparticle was not significant compared with control experiments, demonstrating its high potential in the application of nanomedicines for a diagnostic and therapeutic tool.

  17. Revised Orowan Strengthening: Effective Interparticle Spacing and Strain Field Considerations

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Lopez, Hugo; Kongshaug, Daniel; Schultz, Ben; Rohatgi, Pradeep

    2012-06-01

    The increase in yield strength resulting from a dispersed unshearable secondary phase is important in precipitation-hardenable alloys and is considered one of the primary strengthening mechanisms of metal matrix nanocomposites. The Orowan strengthening equation, which is used to predict increases in yield stress, consists of two parameters: the interparticle mean free path for dislocation motion and the matrix distortion parameter. Upon comparison with experimental and simulated data over a large range of particles sizes, it is shown that descriptions of the interparticle mean free path used by various researchers all differ and fail to accurately predict the experimental data. An alternative description is proposed that describes interparticle spacing for a random particle distribution rather than applying the regular particle arrangements of the current formulations. Second, an alternate description of the matrix distortion parameter, which is less arbitrary than the current descriptions, is also proposed. Taken together, a revised Orowan strengthening equation results and more accurately describes the increase in yield strength for real materials that possess random particle arrangements.

  18. Fracture toughness for copper oxide superconductors

    DOEpatents

    Goretta, Kenneth C.; Kullberg, Marc L.

    1993-01-01

    An oxide-based strengthening and toughening agent, such as tetragonal Zro.sub.2 particles, has been added to copper oxide superconductors, such as superconducting YBa.sub.2 Cu.sub.3 O.sub.x (123) to improve its fracture toughness (K.sub.IC). A sol-gel coating which is non-reactive with the superconductor, such as Y.sub.2 BaCuO.sub.5 (211) on the ZrO.sub.2 particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO.sub.2 coated with 211 yielded a 123 composite with a K.sub.IC of 4.5 MPa(m).sup.0.5.

  19. Fracture toughness for copper oxide superconductors

    DOEpatents

    Goretta, K.C.; Kullberg, M.L.

    1993-04-13

    An oxide-based strengthening and toughening agent, such as tetragonal ZrO[sub 2] particles, has been added to copper oxide superconductors, such as superconducting YBa[sub 2]Cu[sub 3]O[sub x] (123) to improve its fracture toughness (K[sub IC]). A sol-gel coating which is non-reactive with the superconductor, such as Y[sub 2]BaCuO[sub 5] (211) on the ZrO[sub 2] particles minimized the deleterious reactions between the superconductor and the toughening agent dispersed therethrough. Addition of 20 mole percent ZrO[sub 2] coated with 211 yielded a 123 composite with a K[sub IC] of 4.5 MPa(m)[sup 0.5].

  20. Concepts for the Development of Nanoscale Stable Precipitation-Strengthened Steels Manufactured by Conventional Methods

    NASA Astrophysics Data System (ADS)

    Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.; Anderoglu, O.; Fine, M. E.; Chung, Y.-W.; Speer, J. G.; Findley, K. O.; Dogan, Ö. N.; Jablonski, P. D.; Maloy, S. A.; Hackenberg, R. E.; Clarke, A. J.; Clarke, K. D.

    2014-12-01

    The development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modified alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.

  1. Small fatigue crack propagation in Y2O3 strengthened steels

    NASA Astrophysics Data System (ADS)

    Hutař, P.; Kuběna, I.; Ševčík, M.; Šmíd, M.; Kruml, T.; Náhlík, L.

    2014-09-01

    This paper is focused on two type of Y2O3 strengthened steels (Fe-14Cr ODS and ODS-EUROFER). Small fatigue crack propagation was experimentally measured using special small cylindrical specimens (diameter 2 and 2.6 mm) with shallow notch grinded in the gauge length. In the middle of this notch, a pre-crack of length of 50 μm was fabricated using a focused ion beam technique. Fatigue crack growth rate was measured for different applied total strain amplitudes and described using plastic part of the J-integral. Obtained results were compared with published data of EUROFER 97. The effect of the oxide dispersion on small fatigue crack propagation was found rather insignificant. Ferritic Fe-14Cr ODS steel shows more brittle behaviour, i.e. for the same cyclic plasticity, characterised by the plastic part of the J-integral, the small cracks grow faster. A new methodology for residual lifetime prediction of structures containing physically small cracks, based on plastic part of the J-integral, is presented.

  2. Concepts for the development of nanoscale stable precipitation-strengthened steels manufactured by conventional methods

    SciTech Connect

    Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.; Anderoglu, O.; Fine, M. E.; Chung, Y. -W.; Speer, J. G.; Findley, K. O.; Dogan, O. N.; Jablonski, P. D.; Maloy, S. A.; Hackenberg, R. E.; Clarke, A. J.; Clarke, K. D.

    2014-11-11

    In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modified alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.

  3. Concepts for the development of nanoscale stable precipitation-strengthened steels manufactured by conventional methods

    DOE PAGES

    Yablinsky, C. A.; Tippey, K. E.; Vaynman, S.; Anderoglu, O.; Fine, M. E.; Chung, Y. -W.; Speer, J. G.; Findley, K. O.; Dogan, O. N.; Jablonski, P. D.; et al

    2014-11-11

    In this study, the development of oxide dispersion strengthened ferrous alloys has shown that microstructures designed for excellent irradiation resistance and thermal stability ideally contain stable nanoscale precipitates and dislocation sinks. Based upon this understanding, the microstructures of conventionally manufactured ferritic and ferritic-martensitic steels can be designed to include controlled volume fractions of fine, stable precipitates and dislocation sinks via specific alloying and processing paths. The concepts proposed here are categorized as advanced high-Cr ferritic-martensitic (AHCr-FM) and novel tailored precipitate ferritic (TPF) steels, which have the potential to improve the in-reactor performance of conventionally manufactured alloys. AHCr-FM steels have modifiedmore » alloy content relative to current reactor materials (such as alloy NF616/P92) to maximize desirable precipitates and control phase stability. TPF steels are designed to incorporate nickel aluminides, in addition to microalloy carbides, in a ferritic matrix to produce fine precipitate arrays with good thermal stability. Both alloying concepts may also benefit from thermomechanical processing to establish dislocation sinks and modify phase transformation behaviors. Alloying and processing paths toward designed microstructures are discussed for both AHCr-FM and TPF material classes.« less

  4. Adsorption studies of Cd(II) onto Al 2O 3/Nb 2O 5 mixed oxide dispersed on silica matrix and its on-line preconcentration and determination by flame atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mendonça Costa, Lucimara; Ribeiro, Emerson Schwingel; Segatelli, Mariana Gava; do Nascimento, Danielle Raphael; de Oliveira, Fernanda Midori; Tarley, César Ricardo Teixeira

    2011-05-01

    The present study describes the adsorption characteristic of Cd(II) onto Nb 2O 5/Al 2O 3 mixed oxide dispersed on silica matrix. The characterization of the adsorbent has been carried out by infrared spectroscopy (IR), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), energy dispersive X-ray fluorescence analysis (EDXRF) and specific surface area ( SBET). From batch experiments, adsorption kinetic of Cd(II) was described by a pseudo-second-order kinetic model. The Langmuir linear isotherm fitted to the experimental adsorption isotherm very well, and the maximum adsorption capacity was found to be 17.88 mg g -1. Using the effective material, a method for Cd(II) preconcentration at trace level was developed. The method was based on on-line adsorption of Cd(II) onto SiO 2/Al 2O 3/Nb 2O 5 at pH 8.64, in which the quantitative desorption occurs with 1.0 mol L -1 hydrochloric acid towards FAAS detector. The experimental parameters related to the system were studied by means of multivariate analysis, using 2 4 full factorial design and Doehlert matrix. The effect of SO 42-, Cu 2+, Zn 2+ and Ni 2+ foreign ions showed no interference at 1:100 analyte:interferent proportion. Under the most favorable experimental conditions, the preconcentration system provided a preconcentration factor of 18.4 times, consumption index of 1.08 mL, sample throughput of 14 h -1, concentration efficiency of 4.35 min -1, linear range from 5.0 up to 35.0 μg L -1 and limits of detection and quantification of 0.19 and 0.65 μg L -1 respectively. The feasibility of the proposed method for Cd(II) determination was assessed by analysis of water samples, cigarette sample and certified reference materials TORT-2 (Lobster hepatopancreas) and DOLT-4 (Dogfish liver).

  5. High-performance electrode for medium-temperature solid oxide fuel cells. Control of microstructure of ceria-based anodes with highly dispersed ruthenium electrocatalysts

    SciTech Connect

    Uchida, Hiroyuki; Osuga, Takashi; Watanabe, Masahiro

    1999-05-01

    In order to enhance gas-diffusion rates in a mixed-conducting samaria-doped ceria (SDC) anode, micrometer-sized pores were prepared by sintering a SDC paste containing fine polymer beads (d = 1.2 {micro}m) coated on an yttria-stabilized zirconia electrolyte. SDC anodes prepared under different conditions were examined to determine their pore-size distribution, pore volume, ohmic resistance, polarization behavior, and morphological structure. Both the anodic overpotential and the ohmic resistance of SDC anodes were lowered appreciably by controlling their microstructures. The performance of a SDC anode with optimized microstructure was enhanced further with highly dispersed Ru catalysts at 3 wt % loading, especially at low operating temperatures at about 800 C. The current density on a Ru-SDC anode at an overpotential of 0.1 V was 0.5 A/cm{sup 2} at 800 C.

  6. Oxidation resistance in LBE and air and tensile properties of ODS ferritic steels containing Al/Zr elements

    NASA Astrophysics Data System (ADS)

    Gao, R.; Xia, L. L.; Zhang, T.; Wang, X. P.; Fang, Q. F.; Liu, C. S.

    2014-12-01

    The effects of Al and Zr addition on improvement of oxidation resistance in lead-bismuth eutectic (LBE) and in air as well as the tensile properties were investigated for the oxide dispersion strengthened (ODS) steels. The 16Cr-4Al-0.8Zr-ODS steel samples were fabricated by a sol-gel method combining with spark plasma sintering technique. The tests in LBE at 600 °C for 1000 h indicate the good oxidation resistance comparing with the specimens without Zr/Al elements. The samples also exhibit superior oxidation resistance in air due to formation of dense and continuous aluminum oxide film. Minor Zr addition prevents the Al element induced coarsening of the oxide particles in ODS steels and significantly improves the ultimate tensile stress and total elongation of the samples.

  7. In situ loading of well-dispersed gold nanoparticles on two-dimensional graphene oxide/SiO2 composite nanosheets and their catalytic properties.

    PubMed

    Zhu, Chengzhou; Han, Lei; Hu, Peng; Dong, Shaojun

    2012-03-01

    We demonstrated a simple, in situ reduction route to the synthesis of two-dimensional graphene oxide/SiO(2) (GSCN) hybrid nanostructures consisting of Au nanoparticles (Au NPs) supported on the both sides of GSCN. The as-prepared GSCN/Au NPs hybrid nanomaterials exhibited good catalytic activity for the reduction of 4-nitrophenol. This approach provided a useful platform based on GO hybrid nanomaterials for the fabrication of GSCN/Au NPs hybrid nanomaterials, which could be very useful in catalytic applications.

  8. 27 CFR 28.66 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... bonds. In all cases where the penal sum of any bond becomes insufficient, the principal shall either give a strengthening bond with the same surety to attain a sufficient penal sum, or give a new bond to... of any bond to less than its full penal sum. Strengthening bonds shall show the current date...

  9. 27 CFR 17.107 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Strengthening bonds. 17.107 Section 17.107 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... and in effect becomes insufficient, the principal may give a strengthening bond in a sufficient...

  10. Novel percolation phenomena and mechanism of strengthening elastomers by nanofillers.

    PubMed

    Wang, Zhenhua; Liu, Jun; Wu, Sizhu; Wang, Wenchuan; Zhang, Liqun

    2010-03-28

    Nano-strengthening by employing nanoparticles is necessary for high-efficiency strengthening of elastomers, which has already been validated by numerous researches and industrial applications, but the underlying mechanism is still an open challenge. In this work, we mainly focus our attention on studying the variation of the tensile strength of nanofilled elastomers by gradually increasing the filler content, within a low loading range. Interestingly, the percolation phenomenon is observed in the relationship between the tensile strength and the filler loading, which shares some similarities with the percolation phenomenon occurring in rubber toughened plastics. That is, as the loading of nanofillers (carbon black, zinc oxide) increases, the tensile strength of rubber nanocomposites (SBR, EPDM) increases slowly at first, then increases abruptly and finally levels off. Meanwhile, the bigger the particle size, the higher the filler content at the percolation point, and the lower the corresponding tensile strength of rubber nanocomposites. The concept of a critical particle-particle distance (CPD) is proposed to explain the observed percolation phenomenon. It is suggested that rubber strengthening through nanoparticles is attributed to the formation of stretched straight polymer chains between neighbor particles, induced by the slippage of adsorbed polymer chains on the filler surface during tension. Meanwhile, the factors to govern this CPD and the critical minimum particle size (CMPS) figured out in this work are both discussed and analyzed in detail. Within the framework of this percolation phenomenon, this paper also clearly answers two important and intriguing issues: (1) why is it necessary and essential to strengthen elastomers through nanofillers; (2) why does it need enough loading of nanofillers to effectively strengthen elastomers. Moreover, on the basis of the percolation phenomenon, we give out some guidance for reinforcement design of rubbery materials

  11. Strengthening mechanisms of tungsten powder reinforced uranium

    SciTech Connect

    Krawizcki, M.A.

    1990-04-01

    Tungsten powder reinforced uranium composites exhibit a three-fold increase in yield strength due to precipitation hardening. The tungsten-rich interphase precipitates form at the moving beta to alpha phase boundary during slow cooling. Further increases in yield strength, attained with increasing tungsten content, are due to composite strengthening. The composite strengthening is verified by increasing elastic modulus with increasing tungsten content. Age hardening behavior is observed, with strengthening occurring at aging temperatures low, in the alpha phase. Temperatures higher in alpha give initial strengthening followed by rapid overaging. Beta phase aging temperatures result in a very soft structure with interphase precipitates observable optically. Wrought material exhibits significant strain hardening as well as composite strengthening due to elongation of the tungsten particles. 36 refs., 36 figs., 10 tabs.

  12. A model cerium oxide matrix composite reinforced with a homogeneous dispersion of silver particulate - prepared using the glycine-nitrate process

    SciTech Connect

    Weil, K. Scott; Hardy, John S.

    2005-01-31

    Recently a new method of ceramic brazing has been developed. Based on a two-phase liquid composed of silver and copper oxide, brazing is conducted directly in air without the need of an inert cover gas or the use of surface reactive fluxes. Because the braze displays excellent wetting characteristics on a number ceramic surfaces, including alumina, various perovskites, zirconia, and ceria, we were interested in investigating whether a metal-reinforced ceramic matrix composite (CMC) could be developed with this material. In the present study, two sets of homogeneously mixed silver/copper oxide/ceria powders were synthesized using a combustion synthesis technique. The powders were compacted and heat treated in air above the liquidus temperature for the chosen Ag-CuO composition. Metallographic analysis indicates that the resulting composite microstructures are extremely uniform with respect to both the size of the metallic reinforcement as well as its spatial distribution within the ceramic matrix. The size, morphology, and spacing of the metal particulate in the densified composite appears to be dependent on the original size and the structure of the starting combustion synthesized powders.

  13. In-syringe dispersive solid-phase extraction using dissolvable layered double oxide hollow spheres as sorbent followed by high-performance liquid chromatography for determination of 11 phenols in river water.

    PubMed

    Tang, Sheng; Lin, Xuan Hao; Li, Sam Fong Yau; Lee, Hian Kee

    2014-12-19

    Layered double oxide hollow spheres (LDO-HSs) were synthesized and employed as a dissolvable sorbent in dispersive solid-phase extraction (DSPE) to extract eleven United States Environmental Protection Agency's priority phenols from aqueous samples. With their higher specific surface area, LDO-HSs showed much higher extraction efficiency than normal layered double hydroxides and layered double oxides. The entire extraction process was accomplished in a syringe. After DSPE, the sorbent with the analytes was isolated conveniently by directly expelling the spent sample solution out of the syringe. The analyte-enriched sorbent was then subsequently dissolved by withdrawing an acidic solution into the syringe. The final extract was analyzed by high-performance liquid chromatography with ultraviolet detection. The results showed that this method provided low limits of detection for the phenols (0.005-0.153 μg/L), good linearity (r(2)≥ 0.9956) and relative standard deviations of ≤ 6.7%. The optimized method was applied to water samples from 3 rivers. This simple extraction procedure was demonstrated to be a fast, efficient and convenient DSPE approach.

  14. Bonds that strengthen under force

    NASA Astrophysics Data System (ADS)

    Vogel, Viola

    2006-03-01

    While the adhesive strength of most receptor-ligand interactions is exponentially reduced if strained, some receptor-ligand complexes exist that strengthen under force which is the hallmark of catch bonds. Although the existence of catch bonds was theoretically predicted, the first experimental demonstrations of their existence were given only recently, i.e. for the bacterial adhesin FimH that is located at the tip of type I fimbriae of E. coli and for p-selectin. In a major collaborative effort, we studied the structural origin by which the FimH-mannose bond is switched by force to a high binding state. Mutational studies were thereby combined with steered molecular dynamic simulations to decipher how force might affect protein conformation. Force-activation of FimH leads to a complex `stick-and-roll' bacterial adhesion behavior in which E. coli preferentially rolls over mannosylated surfaces at low shear but increasingly sticks firmly as the shear is increased. Interesting similarities are further seen if comparing the structural mechanisms by which liganded FimH and liganded integrins are switched to a high binding state. This comparison was made possible by docking fibronectin's 10^th type III module (fnIII10) to αVβ3 integrin. αVβ3 can switch from the ``closed'' αVβ3 integrin headpiece to the ``open'' conformation by opening the hinge angle between the βA domain and the hybrid domain of the β-integrin. The ``open'' state has been implicated by many experimental laboratories to correspond to the activated state of integrins. W. E. Thomas, E. Trintchina, M. Forero, V. Vogel, E. Sokurenko, Bacterial adhesion to target cells enhanced by shear-force, Cell, 109 (2002) 913. W. E. Thomas, L. M. Nilsson, M. Forero, E. V. Sokurenko, V. Vogel, Shear-dependent `stick-and-roll' adhesion of type 1 fimbriated Escherichia coli, Molecular Microbiology 53 (2004) 1545. W. Thomas, M. Forero, O. Yakovenko, L. Nilsson, P. Vicini, E. Sokurenko, V. Vogel, Catch Bond Model

  15. HIV communication capacity strengthening: a critical review.

    PubMed

    Lettenmaier, Cheryl; Kraft, Joan Marie; Raisanen, Keris; Serlemitsos, Elizabeth

    2014-08-15

    HIV communication is most effective and sustainable when it is designed and implemented locally and tailored to the local context. This requires capacity strengthening at national, subnational, and community levels. Through a review of the published and selected "grey" literature, we examine HIV communication capacity strengthening: definitions, measurements, implementation, and effects. We found limited documentation of HIV communication capacity needs or systematic approaches to address them. Most HIV communication capacity strengthening to date has focused on building individual competencies to design and manage social and behavior change communication programs through training courses, often coupled with networking opportunities for participants, post-training mentoring, and technical assistance. A few of these efforts have been evaluated through pre- and post-training tests and qualitative interviews with participants and have shown potential for improvement in individual skills and knowledge. Health communication capacity assessment tools that measure individual and organizational competencies exist, but they have most often been used to identify capacity building needs, not for evaluating capacity strengthening efforts. A new definition of capacity strengthening, grown out of recent efforts to improve effectiveness of international health and development programs, focuses on improving organizational and societal systems that support performance and individual competencies. We propose a holistic model for HIV communication capacity strengthening and call for rigorous documentation and evaluation to determine and scale-up optimal capacity building interventions for strengthening social and behavior change communication for HIV prevention, care, and treatment in developing countries. PMID:25007200

  16. Strengthening Concurrent Enrollment through NACEP Accreditation

    ERIC Educational Resources Information Center

    Scheffel, Kent; McLemore, Yvette; Lowe, Adam

    2015-01-01

    This chapter describes how implementing the National Alliance of Concurrent Enrollment Partnerships' 17 accreditation standards strengthens a concurrent enrollment program, enhances secondary-postsecondary relations, and benefits students, their families, and secondary and postsecondary institutions.

  17. Strengthening mechanisms of tungsten powder reinforced uranium

    SciTech Connect

    Lewis, M.A.K.; Hill, M.A.; Rollett, A.D.; Dunn, P.S.; Mortensen, A.; Massachusetts Inst. of Tech., Cambridge, MA )

    1989-01-01

    Tungsten powder reinforced uranium exhibits a three-fold increase in yield strength due to precipitation hardening. The tungsten-rich interphase precipitates form at moving phase boundaries during slow cooling. Further increases in yield strength, attained with increasing tungsten content, are due to composite strengthening; this is verified by increasing elastic modulus with increasing tungsten content. Age hardening behavior is observed, with strengthening occurring at aging temperatures low in the alpha phase. Aging higher in alpha gives initial strengthening followed by rapid overaging. Beta phase aging results in a very soft structure with precipitates visible optically. Wrought material exhibits significant strain hardening as well as composite strengthening due to elongation of the tungsten particles. 7 refs., 15 figs., 4 tabs.

  18. Sleep On It: How Snoozing Strengthens Memories

    MedlinePlus

    ... please review our exit disclaimer . Subscribe Sleep On It How Snoozing Strengthens Memories When you learn something new, the best way to remember it is to sleep on it. That’s because sleeping ...

  19. Effect of Y2O3 content on the oxidation behavior of Fe-Cr-Al-based ODS alloys

    NASA Astrophysics Data System (ADS)

    Ul-Hamid, Anwar

    2003-02-01

    A study was conducted to investigate the cyclic oxidation behavior of two oxide dispersion strengthened (ODS) Fe-Cr-Al based alloys containing 0.17 wt.% and 0.7 wt.% Y2O3. The alloys were oxidized in air for 100 h at 1200°C based on a 24 h cycle period. X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM) were used to characterize the structure, morphology, and composition of the oxide scales. Both alloys formed highly adherent and continuous layers of α-Al2O3 exhibiting a morphology indicative of inward scale growth. The role of Y2O3 was to promote adherence by segregating to the grain boundaries within the oxide. Concurrently, Y2O3 generated micro-porosity resulting in a scale of comparatively higher thickness in the alloy with 0.7 wt.% Y2O3.

  20. Role of Y-Al Oxides During Extended Recovery Process of a Ferritic ODS Alloy

    NASA Astrophysics Data System (ADS)

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, M. K.

    2015-08-01

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process, mainly located at the grain boundaries. Finally, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.

  1. Role of Y-Al oxides during extended recovery process of a ferritic ODS alloy

    DOE PAGES

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, Michael K.

    2015-08-04

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process,more » mainly located at the grain boundaries. Lastly, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.« less

  2. Role of Y-Al oxides during extended recovery process of a ferritic ODS alloy

    SciTech Connect

    Capdevila, C.; Pimentel, G.; Aranda, M. M.; Rementeria, R.; Dawson, K.; Urones-Garrote, E.; Tatlock, G. J.; Miller, Michael K.

    2015-08-04

    The microstructural stability of Y-Al oxides during the recrystallization of Fe-Cr-Al oxide dispersion strengthened alloy is studied in this work. The goal is to determine the specific distribution pattern of oxides depending where they are located: in the matrix or at the grain boundaries. It was concluded that those located at the grain boundaries yielded a faster coarsening than the ones in the matrix, although no significant differences in composition and/or crystal structure were observed. However, the recrystallization heat treatment leads to the dissolution of the Y2O3 and its combination with Al to form the YAlO3 perovskite oxide particles process, mainly located at the grain boundaries. Lastly, atom probe tomography analysis revealed a significant Ti build-up at the grain boundaries that might affect subsequent migration during recrystallization.

  3. Strengthening of oxidation resistant materials for gas turbine applications

    NASA Technical Reports Server (NTRS)

    Platts, D. R.; Kirchner, H. P.; Gruver, R. M.

    1972-01-01

    Compressive surface layers were formed on hot-pressed silicon carbide and nitride. The objective of these treatments was to improve the impact resistance of these materials at 1590 K (2400 F). Quenching was used to form compressive surface layers on silicon carbide. The presence of the compressive stresses was demonstrated by slotted rod tests. Compressive stresses were retained at elevated temperatures. Improvements in impact resistance at 1590 K (2400 F) and flexural strength at room temperature were achieved using cylindrical rods 3.3 mm (0.13 in.) in diameter. Carburizing treatments were used to form the surface layers on silicon nitride. In a few cases using rectangular bars improvements in impact resistance at 1590 K (2400 F) were observed.

  4. METHOD OF INCREASING THE DISPERSIBILITY OF SLURRY PARTICLES

    DOEpatents

    McBride, J.P.

    1959-12-15

    A method is described for increasing the dispersibility of metallic oxide particles, particularly thorium oxide, in slurries. Organo-silicon compounds, such as organosilicon halides and silicate esters, are deposited on the surface of the oxide particles. A firing step conducted at temperatures of 600 to 1200 deg C removes the organic groups leaving a surface coating of silica, which provides the desired increase in particle dispersibility.

  5. SMED - Sulphur MEditerranean Dispersion

    NASA Astrophysics Data System (ADS)

    Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

    2016-04-01

    Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model

  6. Effects of the molecular level dispersion of graphene oxide on the free volume characteristics of poly(vinyl alcohol) and its impact on the thermal and mechanical properties of their nanocomposites.

    PubMed

    Sharma, S K; Prakash, J; Pujari, P K

    2015-11-21

    Poly(vinyl alcohol), PVA, reinforced with carbon nanofillers has shown drastic variations in thermal as well as mechanical properties. In order to establish structure-property correlations, these variations have been correlated with modifications in the hydrogen bonding structure as well as the crystallinity of the PVA matrix without paying much attention to molecular packing in the amorphous region of this semicrystalline polymer. In order to investigate the molecular packing in PVA-graphene oxide (GO) nanocomposites, free volume characterization of PVA-GO nanocomposites has been carried out using ortho-positronium (o-Ps) probe. The variations in free volume size, density and size distribution have been determined through o-Ps lifetime and the corresponding intensity as well as its lifetime distribution. The variation in hydrogen bonding and its effect on crystallinity has been determined by Fourier Transform Infra Red (FTIR) and X-ray diffraction (XRD) measurements. The variation in the thermal (glass transition temperature) and mechanical (Young's modulus, tensile strength and percentage strain at break) properties of the nanocomposites is explained in view of the free volume structure and crystallinity of the PVA matrix which are severely modified due to the molecular-level dispersion of GO sheets in the PVA matrix. PMID:26465337

  7. Oil Phase Evaporation Induced Self-Assembly of Hydrophobic Nanoparticles into Spherical Clusters with Controlled Surface Chemistry in an Oil-in-Water Dispersion and Comparison of Behaviors of Individual and Clustered Iron Oxide Nanoparticles

    PubMed Central

    Qiu, Penghe; Jensen, Christina; Charity, Njoku; Towner, Rheal; Mao, Chuanbin

    2010-01-01

    We report a general method for preparing nanoparticle clusters (NPCs) in an oil-in-water emulsion system mediated by cetyl trimethylammonium bromide (CTAB) where previously, only individual nanoparticles were obtained. NPCs of magnetic, metallic and semiconductor nanoparticles have been prepared to demonstrate the generality of the method. The NPCs were spherical and composed of densely packed individual nanoparticles. The number density of nanoparticles in the oil phase was found to be critical for the formation, morphology and yield of NPCs. The method developed here is scalable and can produce NPCs in nearly 100% yield at a concentration of 5 mg/ml in water which is approximately 5 times higher than the highest value reported in literature. The surface chemistry of NPCs can also be controlled by replacing CTAB with polymers containing different functional groups via a similar procedure. The reproducible production of NPCs with well defined shapes has allowed us to compare the properties of individual and clustered iron oxide nanoparticles including magnetization, magnetic moments and contrast enhancement in magnetic resonance imaging (MRI). We found that due to their collective properties, NPCs are more responsive to an external magnetic field and can potentially serve as better contrast enhancement agents than individually dispersed magnetic NPs in MRI. PMID:21117657

  8. Extending of flat normal dispersion profile in all-solid soft glass nonlinear photonic crystal fibres

    NASA Astrophysics Data System (ADS)

    Siwicki, Bartłomiej; Kasztelanic, Rafał; Klimczak, Mariusz; Cimek, Jarosław; Pysz, Dariusz; Stępień, Ryszard; Buczyński, Ryszard

    2016-06-01

    The bandwidth of coherent supercontinuum generated in optical fibres is strongly determined by the all-normal dispersion characteristic of the fibre. We investigate all-normal dispersion limitations in all-solid oxide-based soft glass photonic crystal fibres with various relative inclusion sizes and lattice constants. The influence of material dispersion on fibre dispersion characteristics for a selected pair of glasses is also examined. A relation between the material dispersion of the glasses and the fibre dispersion has been described. We determined the parameters which limit the maximum range of flattened all-normal dispersion profile achievable for the considered pair of heavy-metal-oxide soft glasses.

  9. Lectures on Dispersion Theory

    DOE R&D Accomplishments Database

    Salam, A.

    1956-04-01

    Lectures with mathematical analysis are given on Dispersion Theory and Causality and Dispersion Relations for Pion-nucleon Scattering. The appendix includes the S-matrix in terms of Heisenberg Operators. (F. S.)

  10. Dispersion y dinamica poblacional

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  11. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C.; Carleton, R.L.; George, E.P.

    1998-11-01

    The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

  12. Does Environmental Knowledge Inhibit Hominin Dispersal?

    PubMed

    Wren, Colin D; Costopoulos, Andre

    2015-07-01

    We investigated the relationship between the dispersal potential of a hominin population, its local-scale foraging strategies, and the characteristics of the resource environment using an agent-based modeling approach. In previous work we demonstrated that natural selection can favor a relatively low capacity for assessing and predicting the quality of the resource environment, especially when the distribution of resources is highly clustered. That work also suggested that the more knowledge foraging populations had about their environment, the less likely they were to abandon the landscape they know and disperse into novel territory. The present study gives agents new individual and social strategies for learning about their environment. For both individual and social learning, natural selection favors decreased levels of environmental knowledge, particularly in low-heterogeneity environments. Social acquisition of detailed environmental knowledge results in crowding of agents, which reduces available reproductive space and relative fitness. Agents with less environmental knowledge move away from resource clusters and into areas with more space available for reproduction. These results suggest that, rather than being a requirement for successful dispersal, environmental knowledge strengthens the ties to particular locations and significantly reduces the dispersal potential as a result. The evolved level of environmental knowledge in a population depends on the characteristics of the resource environment and affects the dispersal capacity of the population. PMID:26932570

  13. Dispersants displace hot oiling

    SciTech Connect

    Wash, R.

    1984-02-01

    Laboratory experiments and field testing of dispersants in producing wells have resulted in development of 2 inexpensive paraffin dispersant packages with a broad application range, potential for significant savings over hot oiling, and that can be applied effectively by both continuous and batch treating techniques. The 2 dispersants are soluble in the carrier solvent (one soluble in oil, one in water); are able to readily disperse the wax during a hot flask test conducted in a laboratory; and leave the producing interval water wet. Field data on the 2 dispersants are tabulated, demonstrating their efficacy.

  14. Theory of dispersive microlenses

    NASA Technical Reports Server (NTRS)

    Herman, B.; Gal, George

    1993-01-01

    A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

  15. New concept of critical infrastructure strengthening

    NASA Astrophysics Data System (ADS)

    Gazizov, Talgat R.; Orlov, Pavel E.; Zabolotsky, Alexander M.; Kuksenko, Sergey P.

    2016-06-01

    Strengthening of critical infrastructure is considered. Modal reservation of electronics is proposed as a new concept of the strengthening. The concept combines a widely used cold backup and a recently proposed modal filtration. It makes electronics reliable as well as protected against electromagnetic interference, especially the ultra-wide band pulses. New printed circuit board structure is suggested for implementation of the proposed concept. Results of simulation in time and frequency domains are presented for the suggested structures. Considerable attenuation of dangerous excitations shows that the new concept and structure are promising.

  16. Selective solid-phase extraction and analysis of trace-level Cr(III), Fe(III), Pb(II), and Mn(II) Ions in wastewater using diethylenetriamine-functionalized carbon nanotubes dispersed in graphene oxide colloids.

    PubMed

    Zhu, Xiangbing; Cui, Yuemei; Chang, Xijun; Wang, Hua

    2016-01-01

    Multi-walled carbon nanotubes (MCNTs) were dispersed in graphene oxide (GO) colloids to be further functionalized with diethylenetriamine (DETA), resulting in GO-MCNTs-DETA nanocomposites for the solid-phase extraction and analysis of Cr(III), Fe(III), Pb(II), and Mn(II) ions at the trace levels in wastewater. Inductively coupled plasma optical emission spectrometry (ICP-OES) indicates that this new solid-phase sorbent could facilitate the maximum static adsorption capacities of 5.4, 13.8, 6.6 and 9.5 mg g(-1) for Cr(III), Fe(III), Pb(II), and Mn(II) ions, respectively, showing the adsorption capacity up to 95% within about 30 min. Moreover, the detection limits of the GO-MCNTs-DETA-based analysis method were found to be 0.16, 0.50, 0.24 and 0.38 ng mL(-1) for Cr(III), Fe(III), Pb(II), and Mn(II) ions, respectively, with the relative standard deviation of lower than 3.0% (n=5). Importantly, common coexisting ions showed no significant interference on the separation and pre-concentration of these heavy metal ions at pH 4.0. Subsequently, the GO-MCNTs-DETA sorbent was successfully employed for the separation and analysis of trace-level Cr(III), Fe(III), Pb(II), and Mn(II) ions in wastewater samples yielding 75-folds concentration factors. PMID:26695275

  17. Graphene oxide-based dispersive micro-solid phase extraction for separation and preconcentration of nicotine from biological and environmental water samples followed by gas chromatography-flame ionization detection.

    PubMed

    Mahpishanian, Shokouh; Sereshti, Hassan

    2014-12-01

    Graphene oxide (GO) has showed great potential to use as an adsorbent in sample preparation procedures. In this research, GO was used as an effective adsorbent in a simple GO-based dispersive micro-solid phase extraction (GO-D-µ-SPE) method for isolation and preconcentration of nicotine prior to gas chromatography-flame ionization detection (GC-FID). The prepared GO was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric analysis/differential thermal analysis (TGA/DTA), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques. Various experimental parameters affecting the extraction recovery, including the amount of GO, extraction time, pH of the sample solution, salt concentration, and desorption conditions were investigated and optimized. Under the optimized conditions, a linear response was obtained in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. The limit of detection (LOD) of the method at a signal to noise ratio of 3 was 1.5 ng mL(-1). The linearity was in the concentration range of 5-2000 ng mL(-1) with a determination coefficient of 0.9987. Intraday and inter-day precisions were obtained equal to 2.7% and 5.2%, respectively. The method was successfully applied to the nicotine analysis in biological and water samples with the recoveries in the range of 88.7-109.7%. PMID:25159381

  18. Didactic/Experiential Program for Memory Strengthening.

    ERIC Educational Resources Information Center

    Chenoweth, Barbara; And Others

    This paper describes a program for memory strengthening for older adults which combines lectures by experts with small group discussions. The importance of peer counselor involvement, particularly in focusing on the concerns of older people and the most effective ways to address these concerns is emphasized. Program objectives, session topics, and…

  19. Strengthening Language Experiences for Children through Fingerplays.

    ERIC Educational Resources Information Center

    Baker, Betty Ruth

    Fingerplays--brief stories that rhyme and can be dramatized by using the fingers--are an old activity for children that can be traced in Indian lore to a time before Columbus. Today, fingerplays delight and fascinate young children and provide a variety of learning opportunities. Fingerplays can provide a source for strengthening language…

  20. Strengthening 4-H Program Communication through Technology

    ERIC Educational Resources Information Center

    Robideau, Kari; Santl, Karyn

    2011-01-01

    Advances in technology are transforming how youth and parents interact with programs. The Strengthening 4-H Communication through Technology project was implemented in eight county 4-H programs in Northwest Minnesota. This article outlines the intentional process used to effectively implement technology in program planning. The project includes:…

  1. Eccentric Strengthening for Chronic Lateral Epicondylosis

    PubMed Central

    Wen, Dennis Y.; Schultz, Brian J.; Schaal, Bob; Graham, Scott T.; Kim, Byung Sung

    2011-01-01

    Background: Effective treatments for chronic lateral epicondylosis have not been studied adequately. Eccentric overload exercises have been used with success for other chronic tendinopathy, mainly Achilles and patellar. Hypothesis/Purpose: To compare a wrist extensor eccentric strengthening exercise program with a wrist extensor stretching/modality program for the treatment of chronic lateral epicondylosis. The authors hypothesized that the eccentric strengthening program would produce more favorable results than a stretching/modality program. Study Design: Prospective randomized controlled trial. Methods: Twenty-eight adults with lateral epicondylosis of greater than 4 weeks’ duration were randomized to an eccentric strengthening group or a stretching group. Exercises were taught by a physical therapist, and participants performed most of the exercises on their own at home. Pain scores with visual analog scale from 0 to 100 were obtained at baseline and then at 4, 8, 12, 16, and 20 weeks after the start of the exercise program. Results: Both groups improved their pain scores from baseline to the 4-week time point, followed by nonsignificant further decreases in pain scores thereafter. No statistically significant differences were found between the eccentric strengthening group and stretching groups at any follow-up time point. Conclusions: Despite previous reports documenting favorable results with eccentric exercises for other tendinopathy, the authors were unable to show any statistical advantage to eccentric exercises for lateral epicondylosis during these periods compared with local modalities and stretching exercises. PMID:23016049

  2. Strengthening 4-H by Analyzing Enrollment Data

    ERIC Educational Resources Information Center

    Hamilton, Stephen F.; Northern, Angela; Neff, Robert

    2014-01-01

    The study reported here used data from the ACCESS 4-H Enrollment System to gain insight into strengthening New York State's 4-H programming. Member enrollment lists from 2009 to 2012 were analyzed using Microsoft Excel to determine trends and dropout rates. The descriptive data indicate declining 4-H enrollment in recent years and peak…

  3. Optimization of polymeric dispersant concentration for the dispersion-stability of magnetite nanoparticles in water solution.

    PubMed

    Song, Geun-Dong; Kim, Mun-Hwan; Maeng, Wan-Young

    2014-12-01

    Fouling of various Fe oxide particulates on heat transfer tubes in the coolant of the secondary system of a nuclear power plant has been known to reduce the heat transfer performance and degrade the integrity of system components. Thus, in order to mitigate such a fouling problem, an addition of polymeric dispersant has been proposed to remove the oxide partculates. In this paper, experimental studies was conducted for evaluating the effect of polymeric dispersants (PAA: Polyacrylic acid, PMA: Polymethacrylic acid, PAAMA: Polymaleic acid-co-acrylic acid) on the dispersion stability of magnetite nanoparticles (MNPs, Fe3O4) for the reduction of fouling and corrosion of carbon steel by the settling test, the transmittance, zeta-potential, and particle size measurements, and the electrochemical corrosion tests. It was observed that the critical concentration for maximizing the dispersionstability of MNPs was in the range of concentration ratio (dispersant/MNPs) of 0.1 to 0.01 and the dispersion-stability of MNPs was not improved when the dispersant concentration is above this critical value. This non-linearity above a critical dispersant concentration may be explained by the agglomerations between MNPs. While there is no significant increase of corrosion rate with an addition of up to 10 ppm PAA, the addition of 100 ppm PAA increases the growth rate of oxide layer rapidly and deteriorates the formation of protective oxide on carbon steel. It is thus reasonably stated that the optimization of polymeric dispersants variables and its impacts on the corrosion of structural materials is necessary for the best application at plants. PMID:25971094

  4. Costs of dispersal.

    PubMed

    Bonte, Dries; Van Dyck, Hans; Bullock, James M; Coulon, Aurélie; Delgado, Maria; Gibbs, Melanie; Lehouck, Valerie; Matthysen, Erik; Mustin, Karin; Saastamoinen, Marjo; Schtickzelle, Nicolas; Stevens, Virginie M; Vandewoestijne, Sofie; Baguette, Michel; Barton, Kamil; Benton, Tim G; Chaput-Bardy, Audrey; Clobert, Jean; Dytham, Calvin; Hovestadt, Thomas; Meier, Christoph M; Palmer, Steve C F; Turlure, Camille; Travis, Justin M J

    2012-05-01

    Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro-organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade-offs, they give rise to covariation between dispersal and other life-history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life-history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models. PMID:21929715

  5. Intragenomic Conflict over Dispersal.

    PubMed

    Farrell, Elizabeth J; Úbeda, Francisco; Gardner, Andy

    2015-09-01

    Intragenomic conflict may arise when social partners are more related through one parent than the other-for example, owing to individuals or gametes of one sex dispersing further prior to fertilization. In particular, genes originating from the former parent are favored to promote selflessness, and those originating from the latter parent are favored to promote selfishness. While the impact of patterns of dispersal on the evolution of intragenomic conflict has received recent attention, the consequences of intragenomic conflict for the evolution of dispersal remain to be explored. We suggest that if the evolution of dispersal is driven at least in part by kin selection, differential relatedness of social partners via their mothers versus their fathers may lead to an intragenomic conflict, with maternal-origin genes and paternal-origin genes favoring different rates of dispersal. As an illustration, we extend a classic model of the evolution of dispersal to explore how intragenomic conflict may arise between an individual's maternal-origin and paternal-origin genes over whether that individual should disperse in order to ease kin competition. Our analysis reveals extensive potential for intragenomic conflict over dispersal and predicts that genes underpinning dispersal phenotypes may exhibit parent-of-origin-specific expression, which may facilitate their discovery. PMID:26655360

  6. Valence holes observed in nanodiamonds dispersed in water.

    PubMed

    Petit, Tristan; Pflüger, Mika; Tolksdorf, Daniel; Xiao, Jie; Aziz, Emad F

    2015-02-21

    Colloidal dispersion is essential for most nanodiamond applications, but its influence on nanodiamond electronic properties remains unknown. Here we have probed the electronic structure of oxidized detonation nanodiamonds dispersed in water by using soft X-ray absorption and emission spectroscopies at the carbon and oxygen K edges. Upon dispersion in water, the π* transitions from sp(2)-hybridized carbon disappear, and holes in the valence band are observed.

  7. Technology of Strengthening Steel Details by Surfacing Composite Coatings

    NASA Astrophysics Data System (ADS)

    Burov, V. G.; Bataev, A. A.; Rakhimyanov, Kh M.; Mul, D. O.

    2016-04-01

    The article considers the problem of forming wear resistant meal ceramic coatings on steel surfaces using the results of our own investigations and the analysis of achievements made in the country and abroad. Increasing the wear resistance of surface layers of steel details is achieved by surfacing composite coatings with carbides or borides of metals as disperse particles in the strengthening phase. The use of surfacing on wearing machine details and mechanisms has a history of more than 100 years. But still engineering investigations in this field are being conducted up to now. The use of heating sources which provide a high density of power allows ensuring temperature and time conditions of surfacing under which composites with peculiar service and functional properties are formed. High concentration of energy in the zone of melt, which is created from powder mixtures and the hardened surface layer, allows producing the transition zone between the main material and surfaced coating. Surfacing by the electron beam directed from vacuum to the atmosphere is of considerable technological advantages. They give the possibility of strengthening surface layers of large-sized details by surfacing powder mixtures without their preliminary compacting. A modified layer of the main metal with ceramic particles distributed in it is created as a result of heating surfaced powders and the detail surface layer by the electron beam. Technology of surfacing allows using powders of refractory metals and graphite in the composition of powder mixtures. They interact with one another and form the particles of the hardening phase of the composition coating. The chemical composition of the main and surfaced materials is considered to be the main factor which determines the character of metallurgical processes in local zones of melt as well as the structure and properties of surfaced composition.

  8. 27 CFR 25.94 - Strengthening bonds.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) Requirement. When the penal sum of the brewer's bond (calculated as provided in § 25.93) in effect is not... strengthening bond in sufficient penal sum if the surety is the same as on the bond in effect. If the surety is... bond may not in any way release a former bond or limit a bond to less than the full penal sum. (c)...

  9. Strengthening an affiliation without a merger.

    PubMed

    Hegwer, Laura Ramos

    2015-04-01

    Froedtert Health and the Medical College of Wisconsin have created a shared governance structure with joint committees focused on value, IT, marketing, strategic planning, and other areas. A new funds-flow model shifts a percentage of the health system's bottom line to the medical college to support physician recruitment,joint initiatives, academic programs, and a strategic reserve. The strengthened affiliation has enhanced the ability of the organizations to engage in accountable care and population health initiatives, among other benefits.

  10. Strengthening an affiliation without a merger.

    PubMed

    Hegwer, Laura Ramos

    2015-04-01

    Froedtert Health and the Medical College of Wisconsin have created a shared governance structure with joint committees focused on value, IT, marketing, strategic planning, and other areas. A new funds-flow model shifts a percentage of the health system's bottom line to the medical college to support physician recruitment,joint initiatives, academic programs, and a strategic reserve. The strengthened affiliation has enhanced the ability of the organizations to engage in accountable care and population health initiatives, among other benefits. PMID:26665524

  11. Understanding backward design to strengthen curricular models.

    PubMed

    Emory, Jan

    2014-01-01

    Nurse educators have responded to the call for transformation in education. Challenges remain in planning curricular implementation to facilitate understanding of essential content for student success on licensure examinations and in professional practice. The conceptual framework Backward Design (BD) can support and guide curriculum decisions. Using BD principles in conjunction with educational models can strengthen and improve curricula. This article defines and describes the BD process, and identifies reported benefits for nursing education. PMID:24743175

  12. Development of dispersion-strengthened XD (trademark) Cu alloys for high heat-flux applications

    NASA Technical Reports Server (NTRS)

    Kumar, K. Sharvan

    1993-01-01

    In a previous effort sponsored by NASA LeRC, the XD(trademark) process was used to produce ZrB2 particulate reinforcements in Cu and the resulting extruded material was microstructurally characterized and evaluated in tension over a range of temperatures. A problem that was encountered in that study was microstructural inhomogeneity resulting from the frequent presence of 'ZrB2 agglomerates' that were several microns in size. The presence of these agglomerates was attributed to improper mixing of powders in the green compact used in the XD process for elemental boron powder segregation. In this program, several milling parameters were examined in an effort to optimize this processing step; two levels of ZrB2 reinforcements were considered (7 vol. percent and 15 vol. percent). Microstructures of the reacted powder mass were examined to verify the absence of these agglomerates. Larger bathes of powder were then mixed, reacted, machined to size, canned, and extruded. The microstructure and tensile properties of these extrusions were examined, and the measured properties were correlated with the observed microstructure. Large unreacted or partially reacted Zr particles were present. These particles affected the mechanical properties deleteriously, and their presence is attributed to insufficient heat of reaction during XD synthesis. Alternate processing routes are recommended.

  13. Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

    NASA Technical Reports Server (NTRS)

    Johnson, R., Jr.; Killpatrick, D. H.

    1973-01-01

    The work reported constitutes the first phase of a two-phase program. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr material characteristics are reviewed and compared with TD Ni-20Cr produced in previous development efforts; cyclic load, temperature, and pressure effects on TD Ni-20Cr sheet material are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded, diffusion-bonded, or seam-welded joints are evaluated through tests of simple lap-shear joint samples; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full-scale subsize heat shield panels are described. Tests of full-scale subsize panels included simulated meteoroid impact tests; simulated entry flight aerodynamic heating in an arc-heated plasma stream; programmed differential pressure loads and temperatures simulating mission conditions; and acoustic tests simulating sound levels experienced by heat shields during about boost flight. Test results are described, and the performances of two heat shield designs are compared and evaluated.

  14. Aqueous dispersions of magnetite nanoparticles complexed with copolyether dispersants: experiments and theory.

    PubMed

    Zhang, Qian; Thompson, M Shane; Carmichael-Baranauskas, Anita Y; Caba, Beth L; Zalich, Michael A; Lin, Yin-Nian; Mefford, O Thompson; Davis, Richey M; Riffle, Judy S

    2007-06-19

    Magnetite (Fe3O4) nanoparticles have been synthesized and complexed with carboxylate-functional block copolymers, and then aqueous dispersions of the complexes were investigated as functions of their chemical and morphological structures. The block copolymer dispersants had either poly(ethylene oxide), poly(ethylene oxide-co-propylene oxide), or poly(ethylene oxide-b-propylene oxide) outer blocks, and all of them had a polyurethane center block that contained pendent carboxylate groups. The complexes were formed through interactions of the carboxylates with the surfaces of the magnetite nanoparticles. The magnetite cores of the magnetite-copolymer complexes were near 10 nm in diameter, and the particles were superparamagnetic. Complexes with mass ratios of polymer to magnetite varying from 50:50 to 85:15 were studied. One of our objectives is to design complexes that form stable dispersions of discrete particles in water, yet that can be actuated (moved together) upon exposure to a uniform magnetic field. DLVO calculations that accounted for magnetic attractive interparticle forces, as well as van der Waals, steric, and electrostatic forces are presented. Compositions were identified wherein a shallow, attractive interparticle potential minimum appears once the magnetic term is applied. This suggests that it may be possible to tune the structures of superparamagnetic nanoparticle shells to allow discrete dispersions without a field, yet weak flocculation could be induced upon exposure to a field.

  15. Strengthening health systems by health sector reforms

    PubMed Central

    Senkubuge, Flavia; Modisenyane, Moeketsi; Bishaw, Tewabech

    2014-01-01

    Background The rising burden of disease and weak health systems are being compounded by the persistent economic downturn, re-emerging diseases, and violent conflicts. There is a growing recognition that the global health agenda needs to shift from an emphasis on disease-specific approaches to strengthening of health systems, including dealing with social, environmental, and economic determinants through multisectoral responses. Methods A review and analysis of data on strengthening health sector reform and health systems was conducted. Attention was paid to the goal of health and interactions between health sector reforms and the functions of health systems. Further, we explored how these interactions contribute toward delivery of health services, equity, financial protection, and improved health. Findings Health sector reforms cannot be developed from a single global or regional policy formula. Any reform will depend on the country's history, values and culture, and the population's expectations. Some of the emerging ingredients that need to be explored are infusion of a health systems agenda; development of a comprehensive policy package for health sector reforms; improving alignment of planning and coordination; use of reliable data; engaging ‘street level’ policy implementers; strengthening governance and leadership; and allowing a holistic and developmental approach to reforms. Conclusions The process of reform needs a fundamental rather than merely an incremental and evolutionary change. Without radical structural and systemic changes, existing governance structures and management systems will continue to fail to address the existing health problems. PMID:24560261

  16. Seed dispersal in fens

    USGS Publications Warehouse

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  17. Dispersal of forest insects

    NASA Technical Reports Server (NTRS)

    Mcmanus, M. L.

    1979-01-01

    Dispersal flights of selected species of forest insects which are associated with periodic outbreaks of pests that occur over large contiguous forested areas are discussed. Gypsy moths, spruce budworms, and forest tent caterpillars were studied for their massive migrations in forested areas. Results indicate that large dispersals into forested areas are due to the females, except in the case of the gypsy moth.

  18. Visualizing Dispersion Interactions

    ERIC Educational Resources Information Center

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  19. Spores Disperse, Too!

    ERIC Educational Resources Information Center

    Schumann, Donna N.

    1981-01-01

    Suggests the use of spores and spore-producing structures to show adaptations facilitating spore dispersal and dispersal to favorable environments. Describes several activities using horsetails, ferns, and mosses. Lists five safety factors related to use of mold spores in the classroom. (DS)

  20. Dispersal from Microbial Biofilms.

    PubMed

    Barraud, Nicolas; Kjelleberg, Staffan; Rice, Scott A

    2015-12-01

    One common feature of biofilm development is the active dispersal of cells from the mature biofilm, which completes the biofilm life cycle and allows for the subsequent colonization of new habitats. Dispersal is likely to be critical for species survival and appears to be a precisely regulated process that involves a complex network of genes and signal transduction systems. Sophisticated molecular mechanisms control the transition of sessile biofilm cells into dispersal cells and their coordinated detachment and release in the bulk liquid. Dispersal cells appear to be specialized and exhibit a unique phenotype different from biofilm or planktonic bacteria. Further, the dispersal population is characterized by a high level of heterogeneity, reminiscent of, but distinct from, that in the biofilm, which could potentially allow for improved colonization under various environmental conditions. Here we review recent advances in characterizing the molecular mechanisms that regulate biofilm dispersal events and the impact of dispersal in a broader ecological context. Several strategies that exploit the mechanisms controlling biofilm dispersal to develop as applications for biofilm control are also presented. PMID:27337281

  1. A Column Dispersion Experiment.

    ERIC Educational Resources Information Center

    Corapcioglu, M. Y.; Koroglu, F.

    1982-01-01

    Crushed glass and a Rhodamine B solution are used in a one-dimensional optically scanned column experiment to study the dispersion phenomenon in porous media. Results indicate that the described model gave satisfactory results and that the dispersion process in this experiment is basically convective. (DC)

  2. Evolution of dispersal distance.

    PubMed

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  3. Mechanical behavior of polymer-grafted iron oxide nano particles under large shear deformation

    NASA Astrophysics Data System (ADS)

    Jiao, Yang; Senses, Erkan; Akcora, Pinar; Stevens Institute of Technology Team

    2014-03-01

    Grafting particles with polymers is an effective strategy to control the dispersion and assembly of fillers that will enhance the structural and mechanical stability of polymer nanocomposites (PNCs). Viscoelastic properties of polymer-grafted nanoparticles (NPs) dispersed in homopolymer melts at nonlinear regimes are particularly important as nonlinearities are sensitive to any microstructural change. Her, we report on the nonlinear mechanical behavior of poly(styrene) (PS)-grafted iron oxide NPs in PS homopolymers to reveal the importance of brush-matrix interface and dynamic entanglement under large shear deformations. With oscillatory shear flow, wetting is enabled and long-range ordering of particles is achieved in the system where free chains are longer than the grafted one. We show that large oscillatory deformations can strengthen the interfaces that result in the enhanced mechanical properties. These shear-induced ordered particles can perform as reinforced polymer networks for energy absorbing application. We acknowledge financial support by NSF-CAREER-DMR (#1048865).

  4. Catalytic process for formaldehyde oxidation

    NASA Technical Reports Server (NTRS)

    Kielin, Erik J. (Inventor); Brown, Kenneth G. (Inventor); D'Ambrosia, Christine M. (Inventor)

    1996-01-01

    Disclosed is a process for oxidizing formaldehyde to carbon dioxide and water without the addition of energy. A mixture of formaldehyde and an oxidizing agent (e.g., ambient air containing formaldehyde) is exposed to a catalyst which includes a noble metal dispersed on a metal oxide which possesses more than one oxidation state. Especially good results are obtained when the noble metal is platinum, and the metal oxide which possesses more than one oxidation state is tin oxide. A promoter (i.e., a small amount of an oxide of a transition series metal) may be used in association with the tin oxide to provide very beneficial results.

  5. Dispersal and metapopulation stability.

    PubMed

    Wang, Shaopeng; Haegeman, Bart; Loreau, Michel

    2015-01-01

    Metapopulation dynamics are jointly regulated by local and spatial factors. These factors may affect the dynamics of local populations and of the entire metapopulation differently. Previous studies have shown that dispersal can stabilize local populations; however, as dispersal also tends to increase spatial synchrony, its net effect on metapopulation stability has been controversial. Here we present a simple metapopulation model to study how dispersal, in interaction with other spatial and local processes, affects the temporal variability of metapopulations in a stochastic environment. Our results show that in homogeneous metapopulations, the local stabilizing and spatial synchronizing effects of dispersal cancel each other out, such that dispersal has no effect on metapopulation variability. This result is robust to moderate heterogeneities in local and spatial parameters. When local and spatial dynamics exhibit high heterogeneities, however, dispersal can either stabilize or destabilize metapopulation dynamics through various mechanisms. Our findings have important theoretical and practical implications. We show that dispersal functions as a form of spatial intraspecific mutualism in metapopulation dynamics and that its effect on metapopulation stability is opposite to that of interspecific competition on local community stability. Our results also suggest that conservation corridors should be designed with appreciation of spatial heterogeneities in population dynamics in order to maximize metapopulation stability. PMID:26557427

  6. Dispersion in isotachophoresis

    NASA Astrophysics Data System (ADS)

    Bercovici, Moran; Santiago, Juan G.

    2008-11-01

    Isotachophoresis (ITP) is a widely used separation and preconcentration technique, which has been utilized in numerous applications including drug discovery, toxin detection, and food analysis. In ITP, analytes are segregated and focused between relatively high mobility leading ions and relatively low mobility trailing ions. These electromigration dynamics couple with advective processes associated with non-uniform electroosmotic flow (EOF). The latter generates internal pressure gradients leading to strong dispersive fluxes. This dispersion is nearly ubiquitous and currently limits the sensitivity and resolution of typical ITP assays. Despite this, there has been little work studying these coupled mechanisms. We performed an analytical and experimental study of dispersion dynamics in ITP. To achieve controlled pressure gradients, we suppressed EOF and applied an external pressure head to balance electromigration. Under these conditions, we show that radial electromigration (as opposed to radial diffusion as in Taylor dispersion) balances axial electromigration. To validate the analysis, we monitored the shape of a focusing fluorescent zone as a function of applied electric field. These experiments show that ITP dispersion may result in analyte widths an order of magnitude larger than predicted by the typical non-dispersive theory. Our goal is to develop a simplified dispersion model to capture this phenomenon, and to implement it in a numerical solver for general ITP problems.

  7. Characterization of a Fe/Y{sub 2}O{sub 3} metal/oxide interface using neutron and x-ray scattering

    SciTech Connect

    Watkins, E. B.; Majewski, J. E-mail: jarek@lanl.gov; Kashinath, A.; Wang, P.; Baldwin, J. K.; Demkowicz, M. J. E-mail: jarek@lanl.gov

    2014-07-28

    The structure of metal/oxide interfaces is important to the radiation resistance of oxide dispersion-strengthened steels. We find evidence of gradual variations in stoichiometry and magnetization across a Fe/Y{sub 2}O{sub 3} metal/oxide heterophase interface using neutron and x-ray reflectometry. These findings suggest that the Fe/Y{sub 2}O{sub 3} interface is a transitional zone approximately ∼64 Å-thick containing mixtures or compounds of Fe, Y, and O. Our results illustrate the complex chemical and magnetic nature of Fe/oxide interfaces and demonstrate the utility of combined neutron and x-ray techniques as tools for characterizing them.

  8. Dispersive hydrodynamics: Preface

    NASA Astrophysics Data System (ADS)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  9. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  10. Fickian dispersion is anomalous

    NASA Astrophysics Data System (ADS)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  11. Fickian dispersion is anomalous

    SciTech Connect

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  12. Fickian dispersion is anomalous

    DOE PAGES

    Cushman, John H.; O’Malley, Dan

    2015-06-22

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion wemore » illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Finally, power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.« less

  13. Carboxymethylated glucomannan as paper strengthening agent.

    PubMed

    Wang, Meng; He, Weitao; Wang, Shun; Song, Xianliang

    2015-07-10

    Strength additives play an important role in allowing the papermaking industry to achieve its objectives. In this study, a new kind of paper strengthening agent based on glucomannan was developed by treating it with sodium chloroacetate under alkaline conditions, and the effects on paper properties were evaluated. Results indicated that carboxymethylated glucomannan could significantly improve the paper properties. Compared to the untreated paper, the density, burst index, tensile index, and folding endurance were increased by 15.2%, 22.8%, 34.6%, 179.0%, respectively, when 0.9% carboxymethylated glucomannan was used. Polyamide-epichlorohydrin (PAE) was used to improve the wet strength of the paper. When 0.6% PAE and 0.6% carboxymethylated glucomannan were used, the burst index, dry tensile index, wet tensile index of paper were increased by 14.1%, 25%, 34.3%, respectively, as compared to that of the control, while the folding endurance decreased slightly. In addition, dry tensile index and wet tensile index were increased with increasing the carboxymethylation time of glucomannan. The results demonstrated that PAE and carboxymethylated glucomannan displayed a synergistic effect. SEM analysis illustrated that paper strengthening agent could increase the combination of fibers in paper.

  14. Strengthening the Canadian alcohol advertising regulatory system.

    PubMed

    Heung, Carly M; Rempel, Benjamin; Krank, Marvin

    2012-05-24

    Research evidence points to harmful effects from alcohol advertising among children and youth. In particular, exposure to alcohol advertising has been associated with adolescents drinking both earlier and heavier. Although current federal and provincial guidelines have addressed advertising practices to prevent underage drinking, practice has not been supported by existing policy. While protective measures such as social marketing campaigns have the potential for counteracting the effects from alcohol advertising, the effectiveness of such measures can be easily drowned out with increasing advertising activities from the alcohol industry, especially without effective regulation. Research reviewed by the European Focus on Alcohol Safe Environment (FASE) Project has identified a set of key elements that are necessary to make alcohol advertising policy measures effective at protecting children and youth from the harmful effects of alcohol marketing. Using these key elements as an evaluation framework, there are critical components in the Canadian alcohol advertising regulatory system that clearly require strengthening. To protect impressionable children and youth against the harmful effects of alcohol advertising, 13 recommendations to strengthen current alcohol advertising regulations in Canada are provided for Canadian policy-makers, advertising standard agencies, and public health groups.

  15. Strengthening the Canadian alcohol advertising regulatory system.

    PubMed

    Heung, Carly M; Rempel, Benjamin; Krank, Marvin

    2012-01-01

    Research evidence points to harmful effects from alcohol advertising among children and youth. In particular, exposure to alcohol advertising has been associated with adolescents drinking both earlier and heavier. Although current federal and provincial guidelines have addressed advertising practices to prevent underage drinking, practice has not been supported by existing policy. While protective measures such as social marketing campaigns have the potential for counteracting the effects from alcohol advertising, the effectiveness of such measures can be easily drowned out with increasing advertising activities from the alcohol industry, especially without effective regulation. Research reviewed by the European Focus on Alcohol Safe Environment (FASE) Project has identified a set of key elements that are necessary to make alcohol advertising policy measures effective at protecting children and youth from the harmful effects of alcohol marketing. Using these key elements as an evaluation framework, there are critical components in the Canadian alcohol advertising regulatory system that clearly require strengthening. To protect impressionable children and youth against the harmful effects of alcohol advertising, 13 recommendations to strengthen current alcohol advertising regulations in Canada are provided for Canadian policy-makers, advertising standard agencies, and public health groups. PMID:23618638

  16. Strengthening the foundations of proliferation assessment tools.

    SciTech Connect

    Rexroth, Paul E.; Saltiel, David H.; Rochau, Gary Eugene; Cleary, Virginia D.; Ng, Selena; Greneche, Dominique; Giannangeli, Don; Charlton, William S.; Ford, David

    2007-09-01

    Robust and reliable quantitative proliferation assessment tools have the potential to contribute significantly to a strengthened nonproliferation regime and to the future deployment of nuclear fuel cycle technologies. Efforts to quantify proliferation resistance have thus far met with limited success due to the inherent subjectivity of the problem and interdependencies between attributes that lead to proliferation resistance. We suggest that these limitations flow substantially from weaknesses in the foundations of existing methodologies--the initial data inputs. In most existing methodologies, little consideration has been given to the utilization of varying types of inputs--particularly the mixing of subjective and objective data--or to identifying, understanding, and untangling relationships and dependencies between inputs. To address these concerns, a model set of inputs is suggested that could potentially be employed in multiple approaches. We present an input classification scheme and the initial results of testing for relationships between these inputs. We will discuss how classifying and testing the relationship between these inputs can help strengthen tools to assess the proliferation risk of nuclear fuel cycle processes, systems, and facilities.

  17. Writing Strengthens Orthography and Alphabetic-Coding Strengthens Phonology in Learning to Read Chinese

    ERIC Educational Resources Information Center

    Guan, Connie Qun; Liu, Ying; Chan, Derek Ho Leung; Ye, Feifei; Perfetti, Charles A.

    2011-01-01

    Learning to write words may strengthen orthographic representations and thus support word-specific recognition processes. This hypothesis applies especially to Chinese because its writing system encourages character-specific recognition that depends on accurate representation of orthographic form. We report 2 studies that test this hypothesis in…

  18. When is dispersal for dispersal? Unifying marine and terrestrial perspectives.

    PubMed

    Burgess, Scott C; Baskett, Marissa L; Grosberg, Richard K; Morgan, Steven G; Strathmann, Richard R

    2016-08-01

    Recent syntheses on the evolutionary causes of dispersal have focused on dispersal as a direct adaptation, but many traits that influence dispersal have other functions, raising the question: when is dispersal 'for' dispersal? We review and critically evaluate the ecological causes of selection on traits that give rise to dispersal in marine and terrestrial organisms. In the sea, passive dispersal is relatively easy and specific morphological, behavioural, and physiological adaptations for dispersal are rare. Instead, there may often be selection to limit dispersal. On land, dispersal is relatively difficult without specific adaptations, which are relatively common. Although selection for dispersal is expected in both systems and traits leading to dispersal are often linked to fitness, systems may differ in the extent to which dispersal in nature arises from direct selection for dispersal or as a by-product of selection on traits with other functions. Our analysis highlights incompleteness of theories that assume a simple and direct relationship between dispersal and fitness, not just insofar as they ignore a vast array of taxa in the marine realm, but also because they may be missing critically important effects of traits influencing dispersal in all realms. PMID:26118564

  19. Plant Volatile Analogues Strengthen Attractiveness to Insect

    PubMed Central

    Sun, Yufeng; Yu, Hao; Zhou, Jing-Jiang; Pickett, John A.; Wu, Kongming

    2014-01-01

    Green leaf bug Apolygus lucorum (Meyer-Dür) is one of the major pests in agriculture. Management of A. lucorum was largely achieved by using pesticides. However, the increasing population of A. lucorum since growing Bt cotton widely and the increased awareness of ecoenvironment and agricultural product safety makes their population-control very challenging. Therefore this study was conducted to explore a novel ecological approach, synthetic plant volatile analogues, to manage the pest. Here, plant volatile analogues were first designed and synthesized by combining the bioactive components of β-ionone and benzaldehyde. The stabilities of β-ionone, benzaldehyde and analogue 3 g were tested. The electroantennogram (EAG) responses of A. lucorum adult antennae to the analogues were recorded. And the behavior assay and filed experiment were also conducted. In this study, thirteen analogues were acquired. The analogue 3 g was demonstrated to be more stable than β-ionone and benzaldehyde in the environment. Many of the analogues elicited EAG responses, and the EAG response values to 3 g remained unchanged during seven-day period. 3 g was also demonstrated to be attractive to A. lucorum adults in the laboratory behavior experiment and in the field. Its attractiveness persisted longer than β-ionone and benzaldehyde. This indicated that 3 g can strengthen attractiveness to insect and has potential as an attractant. Our results suggest that synthetic plant volatile analogues can strengthen attractiveness to insect. This is the first published study about synthetic plant volatile analogues that have the potential to be used in pest control. Our results will support a new ecological approach to pest control and it will be helpful to ecoenvironment and agricultural product safety. PMID:24911460

  20. Cauchy's dispersion equation reconsidered : dispersion in silicate glasses.

    SciTech Connect

    Smith, D. Y.; Inokuti, M.; Karstens, W.; Physics; Univ. of Vermont; St. Michael's College

    2002-01-01

    We formulate a novel method of characterizing optically transparent substances using dispersion theory. The refractive index is given by a generalized Cauchy dispersion equation with coefficients that are moments of the uv and ir absorptions. Mean dispersion, Abbe number, and partial dispersion are combinations of these moments. The empirical relation between index and dispersion for families of glasses appears as a consequence of Beer's law applied to the uv spectra.

  1. Drilling mud dispersants

    SciTech Connect

    Gleason, P. A.; Brase, I. E.

    1985-05-21

    Dispersants useful in aqueous drilling mud formulations employed in the drilling of subterranean wells where high temperature and high pressure environments are encountered are disclosed. The dispersants, when used in amounts of about 0.1 to 25 ppb provide muds containing colloidal material suspended in an aqueous medium with improved high temperature and high pressure stability. The dispersants are water soluble sulfonated vinyl toluene-maleic anhydride copolymers which have a molar ratio of vinyl toluene to maleic anhydride of about 1:1 to less than about 2:1, a molecular weight of 1,000 to 25,000 and at least about 0.7 sulfonic acid groups per vinyl toluene unit.

  2. Uranium Dispersion & Dosimetry Model.

    SciTech Connect

    MICHAEL,; MOMENI, H.

    2002-03-22

    The Uranium Dispersion and Dosimetry (UDAD) program provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility such as a uranium mine or mill. Only transport through the air is considered. Exposure results from inhalation, external irradiation from airborne and ground-deposited activity, and ingestion of foodstuffs. Individual dose commitments, population dose commitments, and environmental dose commitments are computed. The program was developed for application to uranium mining and milling; however, it may be applied to dispersion of any other pollutant.

  3. Ensemble Atmospheric Dispersion Modeling

    SciTech Connect

    Addis, R.P.

    2002-06-24

    Prognostic atmospheric dispersion models are used to generate consequence assessments, which assist decision-makers in the event of a release from a nuclear facility. Differences in the forecast wind fields generated by various meteorological agencies, differences in the transport and diffusion models, as well as differences in the way these models treat the release source term, result in differences in the resulting plumes. Even dispersion models using the same wind fields may produce substantially different plumes. This talk will address how ensemble techniques may be used to enable atmospheric modelers to provide decision-makers with a more realistic understanding of how both the atmosphere and the models behave.

  4. Uranium Dispersion & Dosimetry Model.

    2002-03-22

    The Uranium Dispersion and Dosimetry (UDAD) program provides estimates of potential radiation exposure to individuals and to the general population in the vicinity of a uranium processing facility such as a uranium mine or mill. Only transport through the air is considered. Exposure results from inhalation, external irradiation from airborne and ground-deposited activity, and ingestion of foodstuffs. Individual dose commitments, population dose commitments, and environmental dose commitments are computed. The program was developed for applicationmore » to uranium mining and milling; however, it may be applied to dispersion of any other pollutant.« less

  5. MAMA Dispersion Solutions

    NASA Astrophysics Data System (ADS)

    Lennon, Daniel

    2009-07-01

    Wavelength dispersion solutions will be determined on a yearly basis as part of a long-term monitoring program. Deep engineering wavecals for each MAMA grating will be obtained at common cenwaves. Intermediate settings will also be taken to check the reliability of derived dispersion solutions. Final selection was determined on basis of past monitoring and C17 requirements. The internal wavelength calibrations will be taken using the LINE line lamp. Extra-deep wavecals are included for some echelle modes and first order modes to ensure detection of weak lines.

  6. MULTI-PHASE HIGH TEMPERATURE ALLOYS: EXPLORATION OF LAVES-STRENGTHENED STEELS

    SciTech Connect

    Yamamoto, Yukinori; Brady, Michael P; Lu, Zhao Ping; Liu, Chain T

    2007-01-01

    Exploratory effort was initiated for the development of Fe-base alloys strengthened by intermetallic Laves phase combined with MC (M: metals) carbide for improved elevated-temperature strength in fossil energy system components such as super-heater tubes and industrial gas turbines. Work in FY 2006 was focused on strengthening of Fe-Cr-Ni base austenitic stainless alloys by Fe2Nb Laves-phase precipitates with/without MC carbides, in combination with the improvement of oxidation resistance via Al-modification to promote alumina scale formation. A series of Fe-Cr-Ni-Nb base austenitic alloys with additions of Mo, Al, Si, C, B, etc. were cast and thermomechanically processed, and then tensile creep-rupture tested at the conditions of 750-850oC/70-170 MPa. The Al-modified alloys strengthened by Laves + MC show superior creep strength to that of conventional type 347 stainless steels, and their creep life-limit reaches up to 500 h at 750 oC/100 MPa. These alloys also show an excellent oxidation resistance from 650-800oC in air and air + 10% water vapor environments due to formation of a protective Al2O3 scale. Microstructural analysis of alloys strengthened by only Laves phase revealed that the Laves phase was effective to pin dislocations when the particle size is less than 0.5 m, but the resultant creep rupture lives were relatively short. The Al-modification was also applied to an advanced carbide-strengthened austenitic stainless steel, and it yielded creep resistance comparable to state-of-the-art austenitic alloys such as NF709, together with protective alumina scale formation. Modification of this alloy composition for its creep strength and oxidation resistance will be pursued in FY2007. Preliminary results suggest that the developed alloys with Al-modification combined with MC carbide strengthening are promising as a new class of high-temperature austenitic stainless steels.

  7. Warm fog dispersal

    NASA Technical Reports Server (NTRS)

    Frost, W.

    1983-01-01

    The charged particle generator was further tested after some design modification. The generator performance was measured with additional instrumentation and found to confirm previous measurements. Plans for a field testing were than developed. The overall status of the program and the field test plans were presented to a group of atmospheric scientists and electrostatic experts at the NASA/MSFC sponsored USRA Workshop on Electrostatic Fog Dispersal at NCAR, Boulder, Colorado discussed in previous sections. The recommendations from this workshop are being evaluated as to whether NASA should proceed with the field test or whether further theoretical research on the phenomenon of electrostatic fog dispersal and additional development of the charged particle generator should be carried out. Information obtained from the USRA Workshop clearly identified three physical mechanisms that could possibly influence the fog dispersal process, which heretofore have not been considered, and which may provide additional insight to the direction of further fog dispersal work. These mechanisms are: the effect of corona discharge on the electric field strength at the surface, the influx of fog into the cleared volume by turbulent diffusion, and the increase in supersaturation as liquid water is removed, activating haze particles, and thus generating more fog. Plans are being formulated to investigate these mechanisms.

  8. Acoustic dispersive prism

    PubMed Central

    Esfahlani, Hussein; Karkar, Sami; Lissek, Herve; Mosig, Juan R.

    2016-01-01

    The optical dispersive prism is a well-studied element, which allows separating white light into its constituent spectral colors, and stands in nature as water droplets. In analogy to this definition, the acoustic dispersive prism should be an acoustic device with capability of splitting a broadband acoustic wave into its constituent Fourier components. However, due to the acoustical nature of materials as well as the design and fabrication difficulties, there is neither any natural acoustic counterpart of the optical prism, nor any artificial design reported so far exhibiting an equivalent acoustic behaviour. Here, based on exotic properties of the acoustic transmission-line metamaterials and exploiting unique physical behaviour of acoustic leaky-wave radiation, we report the first acoustic dispersive prism, effective within the audible frequency range 800 Hz–1300 Hz. The dispersive nature, and consequently the frequency-dependent refractive index of the metamaterial are exploited to split the sound waves towards different and frequency-dependent directions. Meanwhile, the leaky-wave nature of the structure facilitates the sound wave radiation into the ambient medium. PMID:26739504

  9. Microstructural refinement and strengthening of Cu-4 Cr-2 Nb alloy by mechanical milling

    SciTech Connect

    Anderson, K.R.; Groza, J.R.; Ulmer, D.G.

    1997-07-15

    Lately, a variety of dispersion strengthened (DS) copper alloys that provide a good combination of thermal/electrical conductivity and mechanical strength have been developed. Strengthening is usually achieved by the introduction of a ceramic, refractory metal or intermetallic secondary phase. Cu-Cr-Nb is one such DS alloy in which strengthening is provided by Cr{sub 2}Nb intermetallic particles. Mechanical milling of as-atomized Cu-4 Cr-2 Nb alloy powders substantially increases the mechanical strength (hardness) of the starting material. This is achieved through a drastic grain size, as well as large precipitate size refinement. A more uniform precipitate distribution is also attained. Whether milling is performed with steel or WC vial and balls the hardness saturates at approximately 100 HRB after about 4 hr milling. However, this benefit of MM was offset by an equally severe decrease in electrical conductivity. This decrease is attributed to impurities/contamination from the milling media introduced into the milled powder, primarily, Fe and C, or, WC and Co.

  10. Research capacity strengthening in the South.

    PubMed

    Nchinda, Thomas C

    2002-06-01

    Active promotion of evidence-based decision-making at all levels of the health field is a necessary step in the direction of improving the health of the population. Recent studies have shown that the burden of disease in developing countries is high particularly the burden of infectious, communicable and non-communicable diseases and health problems of mothers and children. There is presently, a mismatch between this increased disease and health burden and the technical and human capacity of developing countries to use existing knowledge and to generate new knowledge to combat these diseases and health problems. It is therefore necessary to assist developing countries to build indigenous research capability so they can undertake studies in their own national settings the results of which will lead to the development of appropriate control strategies in their countries. Building indigenous research capacity will enable developing country scientists to translate results of studies carried out elsewhere into their individual national settings. Eventually results of such studies will increase the global knowledge base about the particular health problems and contribute to finding appropriate solutions to them. The research will, finally, increase knowledge-based decision-making by their health leadership of the country. This paper has set out to describe some experiences in capacity strengthening over the last few decades and to propose from these, mechanisms for building these capacities in a sustainable manner. This paper has described the steps in capability strengthening with special emphasis on identification of trainees, their training and deployment on return. The paper has described mechanisms of research sustainability including creation of suitable career structures, remuneration of researchers and the importance of building up suitable infrastructure for research to meet increasing demands and competence. The place of partnerships South-South, South

  11. Octave spanning wedge dispersive mirrors with low dispersion oscillations.

    PubMed

    Habel, Florian; Shirvanyan, Vage; Trubetskov, Michael; Burger, Christian; Sommer, Annkatrin; Kling, Matthias F; Schultze, Martin; Pervak, Vladimir

    2016-05-01

    A novel concept for octave spanning dispersive mirrors with low spectral dispersion oscillations is presented. The key element of the so-called wedge dispersive mirror is a slightly wedged layer which is coated on a specially optimized dispersive multilayer stack by a common sputter coating process. The group delay dispersion (GDD) of a pulse reflected on a wedge dispersive mirror is nearly free of oscillations. Fabricated mirrors with negative GDD demonstrate the compression of a pulse down to 3.8 fs as good as double angled mirrors optimized for the same bandwidth.

  12. Fatigue test of RC beams strengthened with prestressed CFLs

    NASA Astrophysics Data System (ADS)

    Guo, Xinyan; Huang, Peiyan; Liu, Guangwan; Xie, Jianhe

    2008-11-01

    Applying prestress to fiber reinforced polymer (FRP) can be used more efficiently since a greater portion energy of its tensile capacity is engaged. Based on carbon fiber laminate (CFL), fatigue tests are made to find out the fatigue behavior of reinforced concrete (RC) beams strengthened with prestressed CFL. The interfacial debonding is a main failure mode for RC beams strengthened with prestressed CFLs under the cyclic loading. Furthermore, it has been found that the stress value of CFLs decide whether the additional prestressing has a negative or positive effect on the fatigue behavior of the strengthened beam, and the excessive prestressing would reduce the fatigue life of the strengthened beam.

  13. Structural improvement of strengthened deck panels with externally bonded plates

    SciTech Connect

    Sim, Jongsung; Oh, Hongseob . E-mail: opera69@chollian.net

    2005-07-01

    Concrete bridge decks require eventual replacement and rehabilitation due to decreasing load-carrying capacity. This paper compares different strengthening design procedures that improve the usability and structural performance of bridge decks. The failure characteristics of bridge decks strengthened with various materials such as carbon fiber sheet, glass fiber sheet, steel plate, and grid CFRP and GFRP are analyzed, and the theoretical load-carrying capacities are evaluated using traditional beam and yield line theory, and punching shear analysis. The strengthening materials increase the punching shear strength of the deck and change the failure mode of the strengthened panel.

  14. Evaluating the performance of skewed prestressed concrete bridge after strengthening

    NASA Astrophysics Data System (ADS)

    Naser, Ali Fadhil; Zonglin, Wang

    2013-06-01

    The objectives of this paper are to explain the application of repairing and strengthening methods on the damaged members of the bridge structure, to analyze the static and dynamic structural response under static and dynamic loads after strengthening, and to evaluate the structural performance after application of strengthening method. The repairing and strengthening methods which are used in this study include treatment of the cracks, thickening the web of box girder along the bridge length and adding internal pre-stressing tendons in the thickening web, and construct reinforced concrete cross beams (diaphragms) between two box girders. The results of theoretical analysis of static and dynamic structural responses after strengthening show that the tensile stresses are decreased and become less than the allowable limit values in the codes. The values of vertical deflection are decreased after strengthening. The values of natural frequencies after strengthening are increased, indicating that the strengthening method is effective to reduce the vibration of the bridge structure. Therefore, the strengthening methods are effective to improve the bearing capacity and elastic working state of the bridge structure and to increase the service life of the bridge structure.

  15. Modifying Silicates for Better Dispersion in Nanocomposites

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi

    2005-01-01

    , the co-ion exchange strengthens the polymer/silicate interface and ensures irreversible separation of the silicate layers. One way in which it does this is to essentially tether one amine of each diamine molecule to a silicate surface, leaving the second amine free for reaction with monomers during the synthesis of a polymer. In addition, the incorporation of alkyl ammonium ions into the galleries at low concentration helps to keep low the melt viscosity of the oligomer formed during synthesis of the polymer and associated processing - a consideration that is particularly important in the case of a highly cross-linked, thermosetting polymer. Because of the chemical bonding between the surface-modifying amines and the monomers, even when the alkyl ammonium ions become degraded at high processing temperature, the silicate layers do not aggregate and, hence, nanometer-level dispersion is maintained.

  16. Health-system strengthening and tuberculosis control.

    PubMed

    Atun, Rifat; Weil, Diana E C; Eang, Mao Tan; Mwakyusa, David

    2010-06-19

    Weak health systems are hindering global efforts for tuberculosis care and control, but little evidence is available on effective interventions to address system bottlenecks. This report examines published evidence, programme reviews, and case studies to identify innovations in system design and tuberculosis control to resolve these bottlenecks. We outline system bottlenecks in relation to governance, financing, supply chain management, human resources, health-information systems, and service delivery; and adverse effects from rapid introduction of suboptimum system designs. This report also documents innovative solutions for disease control and system design. Solutions pursued in individual countries are specific to the nature of the tuberculosis epidemic, the underlying national health system, and the contributors engaged: no one size fits all. Findings from countries, including Bangladesh, Cambodia, India, Tanzania, Thailand, and Vietnam, suggest that advances in disease control and system strengthening are complementary. Tuberculosis care and control are essential elements of health systems, and simultaneous efforts to innovate systems and disease response are mutually reinforcing. Highly varied and context-specific responses to tuberculosis show that solutions need to be documented and compared to develop evidence-based policies and practice. PMID:20488514

  17. Nanotwinned fcc metals: Strengthening versus softening mechanisms

    NASA Astrophysics Data System (ADS)

    Stukowski, A.; Albe, K.; Farkas, D.

    2010-12-01

    The strengthening effect of twins in nanocrystalline metals has been reported both in experiment and simulation. While twins are mostly considered as effective barriers to dislocation slip transfer, they can also provide nucleation sites for dislocations or migrate during the deformation process, thereby contributing to plasticity. By comparing twinned and nontwinned samples, we study the effect of twins on the deformation behavior of nanocrystalline Cu and Pd using atomistic simulations. While Cu shows hardening due to the presence of twins, Pd shows the opposite effect. A quantitative dislocation analysis method is applied, which allows to analyze dislocation interactions with twin planes and grain boundaries and to measure dislocation, stacking fault, and twin-boundary densities as functions of strain. A statistical analysis of the occurring dislocation types provides direct evidence for the role of twin boundaries as effective sources for twinning dislocations, which are the reason for the observed softening in some fcc materials. In addition, we discuss how the orientation of the loading direction with respect to the twin planes affects the response of nanotwinned Cu and Pd.

  18. Strengthening bioterrorism prevention: global biological materials management.

    PubMed

    Salerno, Reynolds M; Hickok, Lauren T

    2007-06-01

    The anthrax attacks of 2001 demonstrated that bioterrorism poses a significant threat to U.S. national security. This threat is increasing as a result of the rapid expansion in scale and technical capabilities of the global biotechnology industry, which is broadening the availability of materials, technologies, and expertise needed to produce a biological weapon and is lowering the barriers to biological weapons terrorism and proliferation. At the same time, there has been a rise of sophisticated yet loosely networked transnational terrorist groups that have shown an interest in bioterrorism. The United States must confront this convergence. Although the U.S. government pursues many different biodefense programs to bolster its ability to detect and respond to a bioterrorist attack, these efforts must be augmented with preventive measures to meet today's international challenges. U.S. Homeland Security Presidential Directive 10 of April 2004 defines "Prevention and Protection" as one of the four essential pillars of the U.S. response to the bioterrorist threat. However, while bioscience and policy experts have proposed a variety of preventive initiatives, the creation of such programs has been slow and limited. Global biological materials management, which would focus on identifying and protecting those biological materials at the greatest risk of being used maliciously, is one potential solution. Such an approach would augment current U.S. biodefense efforts, provide the international community an effective means of mitigating the global threat of bioterrorism, and strengthen the international community's battle against emerging infectious disease.

  19. Micropolar crystal plasticity simulation of particle strengthening

    NASA Astrophysics Data System (ADS)

    Mayeur, J. R.; McDowell, D. L.

    2015-09-01

    The yield and work hardening behavior of a small-scale initial-boundary value problem involving dislocation plasticity in an idealized particle strengthened system is investigated using micropolar single crystal plasticity and is compared with results for the same problem from dislocation dynamics simulations. A micropolar single crystal is a work-conjugate higher-order continuum that treats the lattice rotations as generalized displacements, and supports couple stresses that are work-conjugate to the lattice torsion-curvature, leading to a non-symmetric Cauchy stress. The resolved skew-symmetric component of the Cauchy stress tensor results in slip system level kinematic hardening during heterogeneous deformation that depends on gradients of lattice torsion-curvature. The scale-dependent mechanical response of the micropolar single crystal is dictated both by energetic (higher-order elastic constants) and dissipative (plastic torsion-curvature) intrinsic material length scales. We show that the micropolar model captures essential details of the average stress-strain behavior predicted by discrete dislocation dynamics and of the cumulative slip and dislocation density fields predicted by statistical dislocation dynamics.

  20. Strengthening blood programs in developing countries.

    PubMed

    McCullough, Terri Konstenius; McCullough, Jeffrey

    2013-12-01

    The lack of an adequate and safe blood supply is a major limitation to health care in the developing world. It is estimated that about 80% of the worlds' population has access to only 20% of the world's blood supply. When experts from the developed world attempt to provide assistance to blood programs in the developing world, this must be done with respect for the situation and the people who often work under difficult conditions. Important factors in the potential to strengthen blood availability and safety are government support, a national blood policy, the nature and leadership of the blood organization, transfusion medicine expertise, and hospital relations. A key first step is to carry out a needs assessment of the policies, governmental support, organizations, public attitudes about blood donation, and personnel and operations involved in providing the current blood supply. The important facets of the assessment are: the tool itself, the manner in which the assessment is conducted, and the presentation of the results. The assessment should provide recommendations for infrastructure, operations, standard procedures, testing strategies, training programs, types of donors and donor recruitment, budgeting, quality systems, and hospital relations. A sound assessment provides the groundwork and strategy for moving forward. Technical assistance from developed world experts to colleagues in the developing world can be extremely valuable in improving blood availability, safety, and the quality of blood services in the developing world.