Science.gov

Sample records for oxide dispersion strengthening

  1. Oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    MA6000E alloy is strengthened at high temperatures by dispersion of yttrium oxide. Strength properties are about twice those of conventional nickel base alloys. Good thermal fatigue, intermediate temperature strength, and good oxidation resistance give alloy unique combination of benefits. Application in aircraft gas turbine is improved.

  2. Oxide dispersion strengthened superalloy

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    MA6000E alloy is strengthened at high temperatures by dispersion of yttrium oxide. Strength properties are about twice those of conventional nickel base alloys. Good thermal fatigue, intermediate temperature strength, and good oxidation resistance give alloy unique combination of benefits. Application in aircraft gas turbine is improved.

  3. 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.

  4. 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

  5. Forging Oxide-Dispersion-Strengthened Superalloys

    NASA Technical Reports Server (NTRS)

    Harf, F. H.; Glasgow, T. K.; Moracz, D. J.; Austin, C. M.

    1986-01-01

    Cladding of mild steel prevents surface cracking when alloy contacts die. Continual need for improvements in properties of alloys capable of withstanding elevated temperatures. Accomplished by using oxide-dispersion-strengthed superalloys such as Inconel Alloy MA 6000. Elevated tensile properties of forged alloy equal those of hot-rolled MA 6000 bar. Stress-rupture properties somewhat lower than those of bar stock but, at 1,100 degrees C, exceed those of strongest commercial single crystal, directionally solidified and conventionally cast superalloys.

  6. 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.

  7. 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.

  8. 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.

  9. Mechanical properties of oxide dispersion strengthened (ODS) molybdenum alloys

    SciTech Connect

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

    1998-03-01

    Oxide dispersion strengthened molybdenum, Mo-ODS, developed by a proprietary powder metallurgy process, exhibits a creep rupture life at 0.65T{sub m} (1,600 C) of three to five orders of magnitude greater than unalloyed molybdenum, while maintaining ductile fracture behavior at temperatures significantly below room temperature. In comparison, the creep rupture life of the Mo-50Re solid solution strengthened alloy at 1,600 C is only an order of magnitude greater than unalloyed molybdenum. The results of microstructural characterization and thermal stability and mechanical property testing are discussed.

  10. 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.

  11. Fabrication of oxide dispersion strengthened ferritic clad fuel pins

    SciTech Connect

    Zirker, L.R. ); Bottcher, J.H. ); Shikakura, S. ); Tsai, C.L. . Dept. of Welding Engineering); Hamilton, M.L. )

    1991-01-01

    A resistance butt welding procedure was developed and qualified for joining ferritic fuel pin cladding to end caps. The cladding are INCO MA957 and PNC ODS lots 63DSA and 1DK1, ferritic stainless steels strengthened by oxide dispersion, while the end caps are HT9 a martensitic stainless steel. With adequate parameter control the weld is formed without a residual melt phase and its strength approaches that of the cladding. This welding process required a new design for fuel pin end cap and weld joint. Summaries of the development, characterization, and fabrication processes are given for these fuel pins. 13 refs., 6 figs., 1 tab.

  12. 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).

  13. 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.

  14. Development of oxide dispersion strengthened ferritic steels for fusion

    NASA Astrophysics Data System (ADS)

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

    1998-10-01

    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 2O 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°C 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.

  15. 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.

  16. Oxide dispersion strengthened nickel produced by nonreactive milling

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1976-01-01

    It is shown that oxide dispersion strengthened alloys can be produced by a postulated nonreactive milling mechanism whereby the dispersoid is trapped at the interface between welding metal powder particles. This interparticle welding is possible because, without a suitable and sufficiently vigorous chemical reaction between the metal powder particles and the milling fluid, no protective, weld-preventing reaction coating is formed on these particles. Using water as the nonreactive milling fluid, Ni - 1.8-vol % thoria and Ni - 1.8-vol % yttria alloys with 1093 C tensile strengths ranging from 122.3 to 141.5 MN/sq m (17,900 to 20,500 psi) were produced by nonreactive milling.

  17. 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.

  18. 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.

  19. 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.

  20. Comparative thermal fatigue resistance of several oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Bizon, P. T.

    1981-01-01

    The thermal fatigue resistance of several oxide dispersion strengthened (ODS) alloys has been evaluated through cyclic exposure in fluidized beds. The ODS nickel-base alloy MA 754 and ODS iron-base alloy MA 956 as well as four experimental ODS Ni-16Cr-4.5Al base alloys with and without Ta additions were examined. Both bare and coated alloys were subjected to up to 6000 cycles where each cycle consisted of a 3 minute immersion in a fluidized bed at 1130 C followed by a 3 minute immersion in a bed at 357 C. Testing revealed that the thermal fatigue resistance of the ODS nickel-base alloys was excellent and about equal to that of directionally solidified superalloys. However, the thermal fatigue resistance of MA 956 was found to be poor. Metallographic examination of tested specimens revealed that, in general, the post-test microstructures can be rationalized on the basis of previous diffusion, mechanical property, and oxidation studies.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Relaxation path of metastable nanoclusters in oxide dispersion strengthened materials

    NASA Astrophysics Data System (ADS)

    Ribis, J.; Thual, M. A.; Guilbert, T.; de Carlan, Y.; Legris, A.

    2017-02-01

    ODS steels are a promising class of structural materials for sodium cooled fast reactor application. The ultra-high density of the strengthening nanoclusters dispersed within the ferritic matrix is responsible of the excellent creep properties of the alloy. Fine characterization of the nanoclusters has been conducted on a Fe-14Cr-0.3Ti-0.3Y2O3 ODS material using High Resolution and Energy Filtered Transmission Electron Microscopy. The nanoclusters exhibit a cubic symmetry possibly identified as f.c.c and display a non-equilibrium YTiCrO chemical composition thought to be stabilized by a vacancy supersaturation. These nanoclusters undergo relaxation towards the Y2Ti2O7-like state as they grow. A Cr shell is observed around the relaxed nano-oxides, this size-dependent shell may form after the release of Cr by the particles. The relaxation energy barrier appears to be higher for the smaller particles probably owing to a volume/surface ratio effect in reason to the full coherency of the nanoclusters.

  6. 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.

  7. Transient liquid phase bonding of ferritic oxide dispersion strengthened alloys

    NASA Astrophysics Data System (ADS)

    Krishnardula, Venu Gopal

    2006-04-01

    Oxide dispersion strengthened (ODS) alloys possess excellent properties including resistance to oxidation, corrosion, creep and thermal fatigue. In addition, ferritic ODS alloys exhibit resistance to void swelling and are of particular interest to the nuclear industry. The present study involves the joining of fuel cans to end caps that will be utilized in the nuclear industry. Mechanically alloyed (MA) ODS alloys possess coarse columnar grain structure strengthened with nanosize yttria dispersoids. In that past, fusion welding techniques resulted in microstructural disruption leading to poor joints. This work investigated joining of two ferritic MA ODS alloys, MA956 and PM2000, using; (a) Transient liquid phase (TLP) bonding and (b) Solid-state diffusion bonding. TLP bonds were prepared with MA956 and PM2000 in the unrecrystallized and recrystallized conditions using electron beam physical vapor deposited (EBPVD) boron thin films as interlayers. The use of thin interlayers reduced the amount of substrate dissolution and minimized the bondline microstructural disruption. Different bond orientations were also investigated. Successful bonds with better microstructural continuity were obtained when substrates were joined in the unrecrystallized condition followed by post bond recrystallization heat treatment with the substrate faying surface aligned along the working (extrusion or rolling) direction than when substrates were aligned perpendicular to the working direction. This was attributed to the number of yttria stringers cut by the bondline, which is less when the substrate faying surface is lying parallel to the working direction than when the substrate faying surface is lying perpendicular to the working direction. Solid-state diffusion bonding was conducted using MA956 and PM2000 in the unrecrystallized and recrystallized conditions. Bonding occurred only when an unrecrystallized substrate was involved. Bonding occurred at unusually low stresses. This may be

  8. 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.

  9. Oxidation and hot corrosion of coated and bare oxide dispersion strengthened superalloy MA-755E

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.; Santoro, G. J.

    1981-01-01

    Cyclic hot corrosion and oxidation of an experimental oxide dispersion strengthened (ODS) superalloy MA-755E were conducted in a hot gas stream at Mach 0.3. The response of the ODS alloy, bare or with protective coatings, was similar to that of a conventional cast alloy, IN-792, in hot corrosion at 900 C. However, during oxidation at 1100 and 1150 C the ODS alloy differed from the cast alloy by developing a greater amount of subsurface porosity. Compared with a diffused aluminide coating, an electron beam vapor deposited NiCrAlY coating offered superior oxidation protection and decreased porosity formation. In additional testing, the tendency to form porosity was associated with the large grains of recrystallized powder metallurgy alloys but was independent of the presence of an oxide dispersion.

  10. Development of porosity in an oxide dispersion strengthened ferritic alloy containing nanoscale oxide particles

    SciTech Connect

    Schneibel, Joachim H; Liu, Chain T; Hoelzer, David T; Mills, Michael J.; Sarosi, P. M.; Hayashi, Taisuke; Wendt, Ullrich; Heyse, Hartmut

    2007-01-01

    The development of porosity at 1000 C in an oxide dispersion strengthened ferritic alloy containing ultra-fine oxide particles with diameters on the order of a few nm is investigated. A comparison with an alloy fabricated by internal oxidation demonstrates that the porosity formation is associated with mechanical alloying with Y2O3 in argon. The pores grow in spite of a sub-micron grain size suggesting that the grain boundaries are not effective paths for removing entrapped gas from the pores.

  11. 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.

  12. The influence of deformation, annealing and recrystallisation on oxide nanofeatures in oxide dispersion strengthened steel

    NASA Astrophysics Data System (ADS)

    Dawson, Karl; Tatlock, Gordon J.

    2017-04-01

    This work demonstrates that Y-Ti oxide nanofeatures, observed in as-extruded oxide dispersion strengthened steel, are structurally modified by cold forging. A 950 °C heat treatment promoted restructuring of the deformed particles and partial recrystallisation of the cold forged alloy. Transmission electron microscopy revealed that cuboid shaped nanofeatures were deformed during forging, which resulted in high number densities of lens shaped yttrium-titanium oxide particles. Annealing the forged alloy promoted partial recrystallisation of the ferritic matrix. Particle morphology reverted from lens shaped, as witnessed in the deformed material, to cuboid shaped oxide nanofeatures, identical to those observed in as-extruded material. Precipitation distributions evaluated in both recrystallised and recovering grains were indistinguishable from those first measured in the as-extruded alloy. TEM images revealed a widespread orientation relationship between the oxide precipitates and the recrystallised grains; registration with the ferrite lattice was omnipresent in both recovering and recrystallised grains.

  13. When do oxide precipitates form during consolidation of oxide dispersion strengthened steels?

    NASA Astrophysics Data System (ADS)

    Deschamps, A.; De Geuser, F.; Malaplate, J.; Sornin, D.

    2016-12-01

    The processing of oxide dispersion strengthened (ODS) steels involves ball milling, where the oxide forming species are driven in solid solution. Precipitation of the nanometre-scale oxides occurs during subsequent annealing and consolidation. This paper reports in-situ Small-Angle X-ray Scattering measurements of the formation of these precipitates during heating of cold-compressed as-milled powders. Clusters are already initially present, and precipitation starts at 300 °C. The maximum precipitate density is achieved at 600 °C, followed by very slow coarsening at higher temperature. These results open the way to understand the coupled evolution of precipitation and crystalline defects during heating and consolidation of ODS steels.

  14. Stability of Y-Ti-O nanoparticles during laser deposition of oxide dispersion strengthened steel powder

    NASA Astrophysics Data System (ADS)

    Euh, Kwangjun; Arkhurst, Barton; Kim, Il Hyun; Kim, Hyun-Gil; Kim, Jeoung Han

    2017-09-01

    This study investigated the feasibility of a direct energy deposition process for fabrication of oxide dispersion strengthened steel cladding. The effect of the laser working power and scan speed on the microstructural stability of oxide nanoparticles in the deposition layer was examined. Y-Ti-O type oxide nanoparticles with a mean diameter of 45 nm were successfully dispersed by the laser deposition process. The laser working power significantly affected nanoparticle size and number density. A high laser power with a low scan speed seriously induced particle coarsening and agglomeration. Compared with bulk oxide dispersion strengthened steel, the hardness of the laser deposition layer was much lower because of a relatively coarse particle and grain size. Formation mechanism of nanoparticles during laser deposition was discussed.

  15. Characterisation of nanosized oxides in ODM401 oxide dispersion strengthened steel

    NASA Astrophysics Data System (ADS)

    Dawson, Karl; Tatlock, Gordon J.

    2014-01-01

    Changes to the microstructure of oxide dispersion strengthened (ODS) alloy ODM401 in response to high temperature heat treatments have been observed. Extensive analysis of thin foil and extraction replica specimens has been performed using transmission electron microscopy (TEM), convergent beam electron diffraction (CBED) and energy dispersive X-ray spectroscopy (EDS). A distribution of 2 nm (mean diameter) particles, with a number density of 2 × 1023 m-3, was observed in the extruded material. Following a heat treatment of 1 h at 1300 °C the number density of the dispersoids was diminished and their mean diameter increased to an average size of 5 nm. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and chemically sensitive, high resolution, phase contrast, transmission electron microscopy has been used to positively identify nanometer scale pyrochlore oxides. Identification and a complete characterisation of the A2B2O7 structures, including the lattice positions of trivalent (A) and tetravalent (B) species is presented. The composition of the oxide particles was shown to be complex and the role of cations other than yttrium and titanium, in particular aluminium, must be considered in future analysis of the oxide phases and their nucleation and growth behaviour. The majority of the cube shaped oxide particles displayed one of two orientation relationships (OR) with the ferritic matrix. Cube on cube and the Baker and Nutting, cube edge on cube, relationships were identified.

  16. Growth of oxide particles in FeCrAl- oxide dispersion strengthened steels at high temperature

    NASA Astrophysics Data System (ADS)

    Oono, N. H.; Ukai, S.; Hayashi, S.; Ohtsuka, S.; Kaito, T.; Kimura, A.; Torimaru, T.; Sakamoto, K.

    2017-09-01

    The growth of oxide particles in FeCrAl- oxide dispersion strengthened steel (ODSS) considering an accident condition of the light-water reactor at above 1500 K was studied by using a high-temperature annealing. Oxide particles grew from 9 nm to more than 50 nm as maximum at 1623 K for 27 h, with decreasing their number density in two orders of magnitude. Most of the oxide particles in 15Cr-7Al were identified as YAM or YAP, while the oxide particles in 15Cr-7Al-0.4Zr were identified trigonal Y4Zr3O12. Zr addition to 15Cr-7Al ODSS accelerated the growth of the oxide particles, which is quite contrary to the effect of Zr addition during sintering as suggested in the literature. The kinetics of coarsening was characterized by an equation of Ostwald ripening. The diffusion activation energies obtained in the present materials were quite larger than the conventional diffusion activation energy of Y in alpha-iron. Gibbs free energy of oxides should be considered to discuss the coarsening.

  17. Oxide dispersion strengthening of alloys. (Latest citations from the EI Compendex plus database). Published Search

    SciTech Connect

    Not Available

    1993-08-01

    The bibliography contains citations concerning oxide dispersion strengthening and hardening of alloys. The citations include methods of alloy preparation, and mechanical and physical properties. The high temperature characteristics of such dispersion hardening allows use of the alloys in gas turbines as turbine blades and combustor components, and boilers, as refractories and combustors. Oxide dispersion hardening is applied to noble metals, steels, aluminum, superalloys, and powder metallurgy for many nonferrous alloys. (Contains a minimum of 166 citations and includes a subject term index and title list.)

  18. Development of Advanced Oxide Dispersion Strengthened Tungsten Heavy Alloy for Penetrator Application

    DTIC Science & Technology

    2005-09-30

    preparation, sintering, cyclic heat-treatment, swaging , and annealing processes, on microstructures and static/dynamic mechanical properties of ODS tungsten ... tungsten / tungsten contiguity. The swaging and annealing processes of ODS tungsten heavy alloy increase the tensile strength with decreasing the...Final Report for 2nd Year Contract of AOARD 034032 Development of Advanced Oxide Dispersion Strengthened Tungsten Heavy Alloy for

  19. Thermal fatigue and oxidation data of oxide dispersion-strengthened alloys

    NASA Technical Reports Server (NTRS)

    Hofer, K. E.; Hill, V. L.; Humphreys, V. E.

    1980-01-01

    Thermal fatigue and oxidation data were obtained 24 specimens representing 9 discrete oxide dispersion-strengthened alloy compositions or fabricating techniques. Double edge wedge specimens, both bare metal and coated for each systems, were cycled between fluidized beds maintained at 1130 C with a three minute immersion in each bed. The systems included alloys identified as 262 in hardness of HRC 38; 264 in hardness of HRC 38, 40 and 43; 265 HRC 39, 266 of HRC 37 and 40; 754; and 956. Specimens in the bare condition of 265 HRC 39 and 266 HRC 37 survived 6000 cycles without cracking on the small radius of the double edge wedge specimen. A coated specimen of 262 HRC 38, 266 HRC 37 and 266 HRC40 also survived 6000 cycles without cracking. A duplicate coated specimen of 262 HRC 38 alloy survived 5250 cycles before cracks appeared. All the alloys showed little weight change compared compared to alloys tested in prior programs.

  20. Particles control in selective laser melting in-situ oxide dispersion strengthened method

    NASA Astrophysics Data System (ADS)

    Zhou, Xin; An, Zhibin; Shen, Zhijian; Liu, Wei; Yao, Chenguang

    2017-01-01

    Stainless steel selective laser melting (SLM) can be considered as a new possible approach for in-situ formation of oxide dispersion strengthened (ODS) steels because of the dispersion of amorphous oxide nano-particles due to the trace amounts of laser chamber oxygen and in-situ internal oxidation of reactive elements. In this paper it is demonstrated that the particle sizes and distributions can be adjusted by choosing different chamber oxygen level through controlling the quantity of initial reactive cores and the available reactive solutes of each core.

  1. An oxide dispersion strengthened alloy for gas turbine blades

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1979-01-01

    The strength of the newly developed alloy MA-6000E is derived from a nickel alloy base, an elongated grain structure, naturally occurring precipitates of gamma prime, and an artificial distribution of extremely fine, stable oxide particles. Its composition is Ni-15Cr-2Mo-2Ta-4W-4.5Al-2.5Ti-0.15Zr 0.05C-0.01B-1.1Y2O3. It exhibits the strength of a conventional nickel-base alloy at 1400 F but is quite superior at 2000 F. Its shear strength is relatively low, necessitating consideration of special joining procedures. Its high cycle, low cycle, and thermal fatigue properties are excellent. The relationship between alloy microstructure and properties is discussed.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Irradiation performance of oxide dispersion strengthened copper alloys to 150 dpa at 415{degree}C

    SciTech Connect

    Edwards, D.J.; Kumar, A.S.; Anderson, K.R.; Stubbins, J.F.; Garner, F.A.; Hamilton, M.L.

    1991-11-01

    Results have been obtained on the post-irradiation properties of various oxide dispersion strengthened copper alloys irradiated from 34 to 150 dpa at 415{degrees}C in the Fast Flux Test Facility. The GlidCop alloys strengthened by Al{sub 2}O{sub 3} continue to outperform other alloys with respect to swelling resistance, and retention of both electrical conductivity and yield strength. Several castable ODS alloys and a Cr{sub 2}O{sub 3}-strengthened alloy show increasingly poor resistance to radiation, especially in their swelling behavior. A HfO{sub 2}-strengthened alloy retains most of its strength and its electrical conductivity reaches a constant level after 50 dpa, but it exhibits a higher residual radioactivity.

  7. Irradiation performance of oxide dispersion strengthened copper alloys to 150 dpa at 415 degree C

    SciTech Connect

    Edwards, D.J.; Kumar, A.S. ); Anderson, K.R.; Stubbins, J.F. ); Garner, F.A.; Hamilton, M.L. )

    1991-11-01

    Results have been obtained on the post-irradiation properties of various oxide dispersion strengthened copper alloys irradiated from 34 to 150 dpa at 415{degrees}C in the Fast Flux Test Facility. The GlidCop alloys strengthened by Al{sub 2}O{sub 3} continue to outperform other alloys with respect to swelling resistance, and retention of both electrical conductivity and yield strength. Several castable ODS alloys and a Cr{sub 2}O{sub 3}-strengthened alloy show increasingly poor resistance to radiation, especially in their swelling behavior. A HfO{sub 2}-strengthened alloy retains most of its strength and its electrical conductivity reaches a constant level after 50 dpa, but it exhibits a higher residual radioactivity.

  8. An oxide dispersion strengthened Ni-W-Al alloy with superior high temperature strength

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1976-01-01

    Oxide dispersion strengthened alloys based on the WAZ-20 nickel-base alloy were prepared by the mechanical alloying process described by Benjamin (1973), and evaluated. The results of microstructural examinations and mechanical property determinations are discussed. It is shown that WAZ-20, a high gamma-prime fraction alloy having a high gamma-prime solvus temperature, can be effectively dispersion strengthened. The strengths obtained were outstanding, especially at 1150 and 1205 C. The strength is attributed to a combination of highly alloyed matrix, elongated grain structure, and hard phase dispersion. Tensile ductility can be improved by post-recrystallization heat treatment. The new alloy shows some potential for low stress post-extrusion forming.

  9. Oxide Particle Growth During Friction Stir Welding of Fine Grain MA956 Oxide Dispersion-Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Baker, Brad W.; Knipling, Keith E.; Brewer, Luke N.

    2017-03-01

    Friction stir welding of an aluminum-containing oxide dispersion-strengthened steel causes significant oxide particle growth visible at both the nano- and microscales. Quantitative stereology of scanning electron images, small-angle X-ray scattering, energy-dispersive X-ray spectroscopy, and atom-probe tomography is used to quantify the degree of particle coarsening as a function of welding parameters. Results show the dispersed oxides are significantly coarsened in the stir zone due to a proposed combination of agglomeration, Ostwald ripening, and phase transformation within the Al2O3-Y2O3 system. This oxide particle coarsening effectively removes all strengthening contribution of the original oxide particles, as confirmed by uniaxial tensile tests and microhardness measurements.

  10. Oxide Particle Growth During Friction Stir Welding of Fine Grain MA956 Oxide Dispersion-Strengthened Steel

    NASA Astrophysics Data System (ADS)

    Baker, Brad W.; Knipling, Keith E.; Brewer, Luke N.

    2017-01-01

    Friction stir welding of an aluminum-containing oxide dispersion-strengthened steel causes significant oxide particle growth visible at both the nano- and microscales. Quantitative stereology of scanning electron images, small-angle X-ray scattering, energy-dispersive X-ray spectroscopy, and atom-probe tomography is used to quantify the degree of particle coarsening as a function of welding parameters. Results show the dispersed oxides are significantly coarsened in the stir zone due to a proposed combination of agglomeration, Ostwald ripening, and phase transformation within the Al2O3-Y2O3 system. This oxide particle coarsening effectively removes all strengthening contribution of the original oxide particles, as confirmed by uniaxial tensile tests and microhardness measurements.

  11. 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.

  12. 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.

  13. Corrosion behavior of oxide dispersion strengthened ferritic steels in supercritical water

    NASA Astrophysics Data System (ADS)

    Gao, Wenhua; Guo, Xianglong; Shen, Zhao; Zhang, Lefu

    2017-04-01

    The corrosion resistance of three different Cr content oxide dispersion strengthened (ODS) ferritic steels in supercritical water (SCW) and their passive films formed on the surface have been investigated. The results show that the dissolved oxygen (DO) and chemical composition have significant influence on the corrosion behavior of the ODS ferritic steels. In 2000 ppb DO SCW at 650 °C, the 14Cr-4Al ODS steel forms a tri-layer oxide film and the surface morphologies have experienced four structures. For the tri-layer oxide film, the middle layer is mainly Fe-Cr spinel and the Al is gradually enriched in the inner layer.

  14. 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.

  15. 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.

  16. Mechanosynthesis of A Ferritic ODS (Oxide Dispersion Strengthened) Steel Containing 14% Chromium and Its Characterization

    NASA Astrophysics Data System (ADS)

    Rivai, A. K.; Dimyati, A.; Adi, W. A.

    2017-05-01

    One of the advanced materials for application at high temperatures which is aggressively developed in the world is ODS (Oxide Dispersion strengthened) steel. ODS ferritic steels are one of the candidate materials for future nuclear reactors in the world (Generation IV reactors) because it is able to be used in the reactor above 600 °C. ODS ferritic steels have also been developed for the interconnect material of SOFC (Solid Oxide Fuel Cell) which will be exposed to about 800 °C of temperature. The steel is strengthened by dispersing homogeneously of oxide particles (ceramic) in nano-meter sized in the matrix of the steel. Synthesis of a ferritic ODS steel by dispersion of nano-particles of yttrium oxide (yttria: Y2O3) as the dispersion particles, and containing high-chromium i.e. 14% has been conducted. Synthesis of the ODS steels was done mechanically (mechanosynthesis) using HEM (High Energy ball Milling) technique for 40 and 100 hours. The resulted samples were characterized using SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscope), and XRD (X-ray diffraction) to analyze the microstructure characteristics. The results showed that the crystal grains of the sample with 100 hours milling time was much smaller than the sample with 40 hours milling time, and some amount of alloy was formed during the milling process even for 40 hours milling time. Furthermore, the structure analysis revealed that some amount of iron atom substituted by a slight amount of chromium atom as a solid solution. The quantitative analysis showed that the phase mostly consisted of FeCr solid-solution with the structure was BCC (body-centered cubic).

  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

    2016-11-01

    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.

  18. Transmission electron microscopy of oxide dispersion strengthened (ODS) molybdenum: effects of irradiation on material microstructure

    SciTech Connect

    Baranwal, R. and Burke, M.G.

    2003-03-03

    Oxide dispersion strengthened (ODS) molybdenum has been characterized using transmission electron microscopy (TEM) to determine the effects of irradiation on material microstructure. This work describes the results-to-date from TEM characterization of unirradiated and irradiated ODS molybdenum. The general microstructure of the unirradiated material consists of fine molybdenum grains (< 5 {micro}m average grain size) with numerous low angle boundaries and isolated dislocation networks. 'Ribbon'-like lanthanum oxides are aligned along the working direction of the product form and are frequently associated with grain boundaries, serving to inhibit grain boundary and dislocation movement. In addition to the 'ribbons', discrete lanthanum oxide particles have also been detected. After irradiation, the material is characterized by the presence of nonuniformly distributed large ({approx} 20 to 100 nm in diameter), multi-faceted voids, while the molybdenum grain size and oxide morphology appear to be unaffected by irradiation.

  19. 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.

  20. 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.

  1. 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.

  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. 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.

  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. Load-Partitioning in an Oxide Dispersion-Strengthened 310 Steel at Elevated Temperatures

    SciTech Connect

    Miao, Yinbin; Mo, Kun; Zhou, Zhangjian; Liu, Xiang; Lan, Kuan-Che; Zhang, Guangming; Park, Jun-Sang; Almer, Jonathan; Stubbins, James F.

    2016-12-05

    Here the high temperature tensile performance of an oxide dispersion-strengthened (ODS) 310 steel is reported upon. The microstructure of the steel was examined through both transmission electron microscopy (TEM) and synchrotron scattering. In situ synchrotron tensile investigation was performed at a variety of temperatures, from room temperature up to 800°C. Pyrochlore structure yttrium titanate and sodium chloride structure titanium nitride phases were identified in the steel along with an austenite matrix and marginal residual α’-martensite. The inclusion phases strengthen the steel by taking extra load through particle-dislocation interaction during plastic deformation or dislocation creep procedures. As temperature rises, the load partitioning effect of conventional precipitate phases starts to diminish, whereas those ultra-fine oxygen-enriched nanoparticles continue to bear a considerable amount of extra load. Introduction of oxygen-enriched nanoparticles in austenitic steel proves to improve the high temperature performance, making austenitic ODS steels promising for advanced nuclear applications.

  7. Oxide dispersion strengthening of alloys. (Latest citations from the Metals Abstracts/Alloys Index database). Published Search

    SciTech Connect

    Not Available

    1993-09-01

    The bibliography contains citations concerning oxide dispersion strengthening and hardening of alloys. The citations include methods of alloy preparation, and mechanical and physical properties. The high temperature characteristics of such dispersion hardening allows use of the alloys in gas turbines as turbine blades and combustor components, and in boilers, as refractories and combustors. Applications of oxide dispersion hardening include noble metals, steels, aluminum, superalloys, and powder metallurgy for many nonferrous alloys. (Contains 250 citations and includes a subject term index and title list.)

  8. Nuclear Applications of Oxide Dispersion Strengthened and Nano-Featured Alloys: An Introduction

    NASA Astrophysics Data System (ADS)

    Rebak, Raul B.

    2014-12-01

    The Nuclear Materials Committee of TMS is sponsoring the current topic in JOM, which is dedicated to a newer generation of materials called oxide dispersion strengthened (ODS) alloys and nano-featured alloys (NFA). These newer materials are fabricated by using powder stock materials and processing them through high energy attrition followed by either extrusion or forging. The presence of nano-sized oxides throughout the matrix makes the recrystallized alloy have grains that are smaller than 1 µm diameter. The nano-features in the matrix of ODS or NFA materials make them highly resistant to degradation by irradiation such as void swelling. There are four papers dedicated to ODS and NFA materials, including fabrication, joining and testing.

  9. 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.

  10. 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.

  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. Creep of oxide dispersion strengthened materials (with special reference to TD nichrome)

    NASA Technical Reports Server (NTRS)

    Lin, J.; Sherby, O. D.

    1978-01-01

    It was shown that the creep behavior of oxide dispersion strengthened (ODS) alloys is controlled principally by the creep properties of the matrix of the alloy devoid of particles. Thus, diffusion controlled slip process determine the rate controlling step in such materials. The role of the particles is to stabilize a fine substructure which is invariant with the creep stress over a wide range of stress. This characteristic leads to negligible strain hardening during creep and suggests that creep relations developed for pure metals and many solid solution alloys at constant structure should be used to describe the creep of ODS alloys. A second characteristics of the ODS alloys is that a stress may exist below which creep will not occur (threshold stress).

  14. Effects of mechanical force on grain structures of friction stir welded oxide dispersion strengthened ferritic steel

    NASA Astrophysics Data System (ADS)

    Han, Wentuo; Kimura, Akihiko; Tsuda, Naoto; Serizawa, Hisashi; Chen, Dongsheng; Je, Hwanil; Fujii, Hidetoshi; Ha, Yoosung; Morisada, Yoshiaki; Noto, Hiroyuki

    2014-12-01

    The weldability of oxide dispersion strengthened (ODS) ferritic steels is a critical obstructive in the development and use of these steels. Friction stir welding has been considered to be a promising way to solve this problem. The main purpose of this work was to reveal the effects of mechanical force on grain structures of friction stir welded ODS ferritic steel. The grain appearances and the misorientation angles of grain boundaries in different welded zones were investigated by the electron backscatter diffraction (EBSD). Results showed that the mechanical force imposed by the stir tool can activate and promote the recrystallization characterized by the transformation of boundaries from LABs to HABs, and contribute to the grain refinement. The type of recrystallization in the stir zone can be classified as the continuous dynamic recrystallization (CDRX).

  15. Study of Residual Stress and Vacancy Defects in Oxide Dispersion Strengthened Steels

    NASA Astrophysics Data System (ADS)

    Slugeň, V.; Veterníková, J.; Kilpeläinen, S.; Tuomisto, F.

    This study was focused on commercial oxide-dispersion strengthened (ODS) steels -MA 956 (20%Cr), ODM 751 (16%Cr) and ODS Eurofer (9%Cr), developed for fuel cladding of GEN IV reactors. The ODS steels are described in order to comparison their microstructure features. Vacancy defects were observed by Doppler Broadening Spectroscopy (DBS) and Positron Annihilation Lifetime Spectroscopy (PALS). Residual stress proportional to all kinds of defects was investigated by Magnetic Barkhausen Noise (MBN) measurement. The positron techniques demonstrated the highest defect concentration for ODS Eurofer followed by MA 956. The lowest defect density belongs to ODM 751; although these defects are the largest (three or four vacancy clusters). MA 956 and ODS Eurofer have di-vacancies in predominance. MBN results are in a good accordance with positron techniques. The highest residual stress is for ODS Eurofer, followed by MA 956. Finally, the lowest residual stress proportional to hardness is found for ODM 751.

  16. Positron study of alpha particles effect on oxide-dispersion-strengthened steels

    NASA Astrophysics Data System (ADS)

    Veternikova, J.; Slugen, V.; Stancek, S.; Degmova, J.; Sabelova, V.; Sojak, S.; Petriska, M.; Hinca, R.

    2013-06-01

    Microstructure of oxide-dispersion-strengthened steels with different chromium content - MA 956 (20% Cr), ODM 751 (16% Cr) and MA 957 (14% Cr) were studied by positron annihilation lifetime spectroscopy. Samples were measured before and after helium ion implantation (He2+); therefore microstructure changes and radiation resistance to alpha particles of these steels were observed. Defect accumulation due to the radiation treatment was proven in all investigated materials. After ion implantation, mean lifetimes increased of about ~ 10 ps, which indicates significant change in microstructure. According to calculations of a defect volume from defect concentration and pre-dominant size of defects, ODM 751 is the most resistant steel in comparison to other investigated materials.

  17. Stability of nanoclusters in an oxide dispersion strengthened alloy under neutron irradiation

    DOE PAGES

    Liu, Xiang; Miao, Yinbin; Wu, Yaqiao; ...

    2017-06-01

    In this paper, we report atom probe tomography results of the nanoclusters in a neutron-irradiated oxide dispersion strengthened alloy. Following irradiation to 5 dpa at target temperatures of 300 °C and 450 °C, fewer large nanoclusters were found and the residual nanoclusters tend to reach an equilibrium Guinier radius of 1.8 nm. With increasing dose, evident decrease in peak oxygen and titanium (but not yttrium) concentrations in the nanoclusters was observed, which was explained by atomic weight, solubility, diffusivity, and chemical bonding arguments. Finally, the chemical modifications indicate the equilibrium size is indeed a balance of two competing processes: radiationmore » enhanced diffusion and collisional dissolution.« less

  18. Processing and structure of a Nitrogen Alloyed Oxide Dispersion Strengthened Austenitic Stainless Steel by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Xu, Yingli; Zhou, Zhangjian

    2013-03-01

    Pure metallic powders of Fe, Cr, Ni, W, Ti and nano-Y2O3 powders were mechanical alloyed by high energy mechanical milling under N2 atmosphere to develop a nitrogen contained oxide dispersion strengthened austenitic steel powders. The compositions of the mixed powders are Fe-18Cr-8Ni-2W-1Ti-0.35Y2O3. The effects of milling time on nitrogen absorption were investigated. The nitrogen contents in the as-milled powders reached 0.31 wt% after milling for 60 hours and nearly 0.8 wt% after milling for 150 hours. The as-milled powders were then annealed under vacuum at 1173K and 1373 K to promote the formation of the resultant equilibrium phases. Fully austenitic structure was achieved after annealing at 1173K.

  19. Texture evolution in Oxide Dispersion Strengthened (ODS) steel tubes during pilgering process

    NASA Astrophysics Data System (ADS)

    Vakhitova, E.; Sornin, D.; Barcelo, F.; François, M.

    2017-10-01

    Oxide Dispersion Strengthened (ODS) steels are foreseen as fuel cladding material in the coming generation of Sodium Fast Reactors (SFR). Cladding tubes are manufactured by hot extrusion and subsequent cold forming steps. In this study, a 9 wt% Cr ODS steel exhibiting α-γ phase transformation at high temperature is cold formed under industrial conditions with a large section reduction in two pilgering steps. The influence of pilgering process parameters and intermediate heat treatment on the microstructure evolution is studied experimentally using Electron Backscattering Diffraction (EBSD) and X-ray Diffraction (XRD) methods. Pilgered samples show elongated grains and a high texture formation with a preferential orientation along the rolling direction. During the heat treatment, grain morphology is recovered from elongated grains to almost equiaxed ones, while the well-known α-fiber texture presents an unexpected increase in intensity. The remarkable temperature stability of this fiber is attributed to a crystallographic structure memory effect during phase transformations.

  20. The role of dispersoids in maintaining the corrosion resistance of mechanically alloyed oxide dispersion strengthened alloys

    SciTech Connect

    Cama, H.; Hughes, T.A.

    1995-05-15

    Amongst the various commercial mechanically alloyed (MA) oxide dispersion strengthened (ODS) alloys available, ferritic alloys are most suitable for use at temperatures exceeding 1,100 C, since {gamma}{prime} particle dissolution results in the loss of strength of nickel based MA ODS alloys. In commercial MA ODS alloys, yttria particles are commonly added in the starting powers, and it is well known that they are not retained in the final product because they react with aluminum and oxygen present in the system during thermomechanical processing and form mixed (Y,Al) oxide particles. In this paper the role of (Y,Al) oxide particles in maintaining the overall aluminum concentration in the matrix necessary to repair the outer oxide scale is discussed. It is well known that during exposure in air, aluminum is lost from the bulk of MA ODS alloys to the growth of a surface alumina film. The extent of aluminum lost is dependent on the section thickness and can significantly affect the volume fraction of the aluminum rich dispersoids. Coarsening of the dispersoids at temperatures up to 1,200 C in the thick MA 956 bar occurs without significant aluminum loss, while their volume fraction increases continuously. However, coarsening of the dispersoids in the thinner ODM 751 tube at 1,200 and 1,300 C is accompanied by dissolution of the dispersoid particles in order to maintain the aluminum concentration in the matrix.

  1. Chemical Synthesis and Oxide Dispersion Properties of Strengthened Tungsten via Spark Plasma Sintering.

    PubMed

    Ding, Xiao-Yu; Luo, Lai-Ma; Chen, Hong-Yu; Zhu, Xiao-Yong; Zan, Xiang; Cheng, Ji-Gui; Wu, Yu-Cheng

    2016-10-28

    Highly uniform oxide dispersion-strengthened materials W-1 wt % Nd₂O₃ and W-1 wt % CeO₂ were successfully fabricated via a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering at 1700 °C to suppress grain growth. The samples were characterized by performing field emission scanning electron microscopy and transmission electron microscopy analyses, Vickers microhardness measurements, thermal conductivity, and tensile testing. The oxide particles were dispersed at the tungsten grain boundaries and within the grains. The thermal conductivity of the samples at room temperature exceeded 140 W/m·K. The tensile tests indicated that W-1 wt % CeO₂ exhibited a ductile-brittle transition temperature between 500 °C and 550 °C, which was a lower range than that for W-1 wt % Nd₂O₃. Surface topography and Vickers microhardness analyses were conducted before and after irradiations with 50 eV He ions at a fluence of 1 × 10(22) m(-2) for 1 h in the large-powder material irradiation experiment system. The grain boundaries of the irradiated area became more evident than that of the unirradiated area for both samples. Irradiation hardening was recognized for the W-1 wt % Nd₂O₃ and W-1 wt % CeO₂ samples.

  2. Chemical Synthesis and Oxide Dispersion Properties of Strengthened Tungsten via Spark Plasma Sintering

    PubMed Central

    Ding, Xiao-Yu; Luo, Lai-Ma; Chen, Hong-Yu; Zhu, Xiao-Yong; Zan, Xiang; Cheng, Ji-Gui; Wu, Yu-Cheng

    2016-01-01

    Highly uniform oxide dispersion-strengthened materials W–1 wt % Nd2O3 and W–1 wt % CeO2 were successfully fabricated via a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering at 1700 °C to suppress grain growth. The samples were characterized by performing field emission scanning electron microscopy and transmission electron microscopy analyses, Vickers microhardness measurements, thermal conductivity, and tensile testing. The oxide particles were dispersed at the tungsten grain boundaries and within the grains. The thermal conductivity of the samples at room temperature exceeded 140 W/m·K. The tensile tests indicated that W–1 wt % CeO2 exhibited a ductile–brittle transition temperature between 500 °C and 550 °C, which was a lower range than that for W–1 wt % Nd2O3. Surface topography and Vickers microhardness analyses were conducted before and after irradiations with 50 eV He ions at a fluence of 1 × 1022 m−2 for 1 h in the large-powder material irradiation experiment system. The grain boundaries of the irradiated area became more evident than that of the unirradiated area for both samples. Irradiation hardening was recognized for the W–1 wt % Nd2O3 and W–1 wt % CeO2 samples. PMID:28773999

  3. Evaluation of oxide dispersion strengthened (ODS) molybdenum and molybdenum-rhenium Alloys

    SciTech Connect

    Mueller, A.J.; Bianco, R.; Buckman, R.W. Jr.

    1999-10-22

    Oxide dispersion strengthened (ODS) molybdenum alloys being developed for high temperature applications possess excellent high temperature strength and creep resistance. In addition they exhibit a ductile-to-brittle transition temperature (DBIT) in the worked and stress-relieved condition under longitudinal tensile load well below room temperature. However, in the recrystallized condition, the DBTT maybe near or above room temperature, depending on the volume fraction of oxide dispersion and the amount of prior work. Dilute rhenium additions (7 and 14 wt.%) to ODS molybdenum were evaluated to determine their effect on low temperature ductility. The addition of 7 wt.% rhenium to the ODS molybdenum did not significantly enhance the mechanical properties. However, the addition of 14 wt.% rhenium to the ODS molybdenum resulted in a DBTT well below room temperature in both the stress-relieved and recrystallized condition. Additionally, the tensile strength of ODS Mo-14Re is greater than the base ODS molybdenum at 1,000 to 1,250 C.

  4. Quantifying the composition of yttrium and oxygen rich nanoparticles in oxide dispersion strengthened steels.

    PubMed

    Williams, C A; Smith, G D W; Marquis, E A

    2013-02-01

    Atom probe tomography (APT) is used to investigate the composition of oxygen rich nanoparticles within a ferritic matrix in Fe-14Cr-2W-0.1Ti oxide-dispersion-strengthened (ODS) steel. This study investigates whether artifacts associated with APT analysis are the cause of a sub-stoichiometric oxide composition measurement. Bulk Y₂O₃ is analyzed by APT, thus demonstrating the ability of the technique to measure near-stoichiometric composition measurements in insulating oxides. Through analysis of the sequence of ion hits on the detector during APT data acquisition, it is shown that a proportion of yttrium hits are spatially correlated but oxygen hits are not. Y-O based nanoparticles in a ferritic matrix are analyzed by APT using voltage pulsing and a laser pulsing with a range of laser energies from 0.3-0.8 nJ. When the material is analyzed using a high effective evaporation field, this influences the effect of trajectory aberrations, and the apparent size of the nanoparticles is reduced. Some reduction in Y:O ratio is observed, caused by high instances of multiple-ion evaporation events. From a detailed comparison between the results of APT analysis of the bulk Y₂O₃ the nanoparticles in the ODS material are concluded to have an approximate Y:O ratio of 1:1.

  5. Creep behavior of oxide dispersion strengthened 8Cr-2WVTa and 8Cr-1W steels

    NASA Astrophysics Data System (ADS)

    Shinozuka, K.; Tamura, M.; Esaka, H.; Shiba, K.; Nakamura, K.

    2009-01-01

    Microstructures and creep behavior of two martensitic oxide dispersion strengthened (ODS) steels 8%Cr-2%W-0.2%V-0.1%Ta (J1) and 8%Cr-1%W (J2) with finely dispersed Y 2Ti 2O 7 have been investigated. Creep tests have been carried out at 670, 700 and 730 °C. Creep strength of J1 is stronger than that of any other ODS martensitic steels and the hoop strength of the ferritic ODS steel cladding. At the beginning of creep test, shrinkage was frequently observed for J1. This is one of the reasons for high creep strength of J1. The δ-ferrite, which is untransformed to austenite at hot isostatic press and hot rolling temperatures, was elongated along the rolling direction, and volume fraction of δ-ferrite in J1 is larger than J2. Although the elongated δ-ferrite affects the anisotropy of creep behavior, the extent of anisotropy in J1 is not so large as that of the ferritic ODS steel.

  6. Microscopy of Alloy Formation on Arc Plasma Sintered Oxide Dispersion Strengthen (ODS) Steel

    NASA Astrophysics Data System (ADS)

    Bandriyana, B.; Sujatno, A.; Salam, R.; Dimyati, A.; Untoro, P.

    2017-07-01

    The oxide dispersed strengthened (ODS) alloys steel developed as structure material for nuclear power plants (NPP) has good resistant against creep due to their unique microstructure. Microscopy investigation on the microstructure formation during alloying process especially at the early stages was carried out to study the correlation between structure and property of ODS alloys. This was possible thanks to the arc plasma sintering (APS) device which can simulate the time dependent alloying processes. The ODS sample with composition of 88 wt.% Fe and 12 wt.% Cr powder dispersed with 1 wt.% ZrO2 nano powder was mixed in a high energy milling, isostatic compressed to form sample coins and then alloyed in APS. The Scanning Electron Microscope (SEM) with X-ray Diffraction Spectroscopy (EDX) line scan and mapping was used to characterize the microstructure and elemental composition distribution of the samples. The alloying process with unification of each Fe and Cr phase continued by the alloying formation of Fe-Cr by inter-diffusion of both Fe and Cr and followed by the improvement of the mechanical properties of hardness.

  7. 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.

  8. 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).

  9. 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.

  10. 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.

  11. 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; ...

    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

  12. 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.

  13. Influence of nanovoids on α-α' phase separation in FeCrAl oxide dispersion strengthened alloy

    SciTech Connect

    Capdevila, Carlos; Aranda, M. M.; Rememnteria, R.; Dominquez-Reyes, R.; Uriones-Garrote, E.; Miller, Michael K.

    2015-08-10

    The presence of nanovoids in the vicinity of oxide particles in FeCrAl oxide dispersion strengthened (ODS) alloy has been identified. These nanovoids are inherent to the manufacturing route and remain quite resistant during heat treatments. Positron annihilation spectroscopy (PAS) experiments demonstrate that these nanovoids trap Cr inside thereby reducing the Cr-content in the matrix. In conclusion, this might lead to a delay in the α–α' phase separation process as observed by atom probe tomography (APT).

  14. Development of Oxide Dispersion Strengthened (ODS) Ferritic Steel Through Powder Forging

    NASA Astrophysics Data System (ADS)

    Kumar, Deepak; Prakash, Ujjwal; Dabhade, Vikram V.; Laha, K.; Sakthivel, T.

    2017-02-01

    Oxide dispersion strengthened (ODS) ferritic steels are candidates for cladding tubes in fast breeder nuclear reactors. In this study, an 18%Cr ODS ferritic steel was prepared through powder forging route. Elemental powders with a nominal composition of Fe-18Cr-2 W-0.2Ti (composition in wt.%) with 0 and 0.35% yttria were prepared by mechanical alloying in a Simoloyer attritor under argon atmosphere. The alloyed powders were heated in a mild steel can to 1473 K under flowing hydrogen atmosphere. The can was then hot forged. Steps of sealing, degassing and evacuation are eliminated by using powder forging. Heating ODS powder in hydrogen atmosphere ensures good bonding between alloy powders. A dense ODS alloy with an attractive combination of strength and ductility was obtained after re-forging. On testing at 973 K, a loss in ductility was observed in yttria-containing alloy. The strength and ductility increased with increase in strain rate at 973 K. Reasons for this are discussed. The ODS alloy exhibited a recrystallized microstructure which is difficult to achieve by extrusion. No prior particle boundaries were observed after forging. The forged compacts exhibited isotropic mechanical properties. It is suggested that powder forging may offer several advantages over the traditional extrusion/HIP routes for fabrication of ODS alloys.

  15. Development of Oxide Dispersion Strengthened (ODS) Ferritic Steel Through Powder Forging

    NASA Astrophysics Data System (ADS)

    Kumar, Deepak; Prakash, Ujjwal; Dabhade, Vikram V.; Laha, K.; Sakthivel, T.

    2017-04-01

    Oxide dispersion strengthened (ODS) ferritic steels are candidates for cladding tubes in fast breeder nuclear reactors. In this study, an 18%Cr ODS ferritic steel was prepared through powder forging route. Elemental powders with a nominal composition of Fe-18Cr-2 W-0.2Ti (composition in wt.%) with 0 and 0.35% yttria were prepared by mechanical alloying in a Simoloyer attritor under argon atmosphere. The alloyed powders were heated in a mild steel can to 1473 K under flowing hydrogen atmosphere. The can was then hot forged. Steps of sealing, degassing and evacuation are eliminated by using powder forging. Heating ODS powder in hydrogen atmosphere ensures good bonding between alloy powders. A dense ODS alloy with an attractive combination of strength and ductility was obtained after re-forging. On testing at 973 K, a loss in ductility was observed in yttria-containing alloy. The strength and ductility increased with increase in strain rate at 973 K. Reasons for this are discussed. The ODS alloy exhibited a recrystallized microstructure which is difficult to achieve by extrusion. No prior particle boundaries were observed after forging. The forged compacts exhibited isotropic mechanical properties. It is suggested that powder forging may offer several advantages over the traditional extrusion/HIP routes for fabrication of ODS alloys.

  16. 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.

  17. TEM in situ micropillar compression tests of ion irradiated oxide dispersion strengthened alloy

    NASA Astrophysics Data System (ADS)

    Yano, K. H.; Swenson, M. J.; Wu, Y.; Wharry, J. P.

    2017-01-01

    The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near-surface irradiation damage layers just a few micrometers thick. In situ transmission electron microscopic (TEM) mechanical testing is one such promising method. In this work, microcompression pillars are fabricated from a Fe2+ ion irradiated bulk specimen of a model Fe-9%Cr oxide dispersion strengthened (ODS) alloy. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated microstructure. Measured elastic modulus values, once adjusted for the amount of deformation and deflection in the base material, are also within the expected range. A pillar size effect is only observed in samples with minimum dimension ≤100 nm due to the low inter-obstacle spacing in the as received and irradiated material. TEM in situ micropillar compression tests hold great promise for quantitatively determining mechanical properties of shallow ion-irradiated layers.

  18. 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.

  19. Enhancement of Physical and Mechanical Properties of Oxide Dispersion-Strengthened Tungsten Heavy Alloys

    NASA Astrophysics Data System (ADS)

    Daoush, Walid Mohamed Rashad; Elsayed, Ayman Hamada Abdelhady; Kady, Omayma Abdel Gawad El; Sayed, Mohamed Abdallah; Dawood, Osama Monier

    2016-05-01

    Oxide dispersion-strengthened (ODS) tungsten heavy alloys are well known for their excellent mechanical properties which make them useful for a wide range of high-temperature applications. In this investigation, microstructural, magnetic, and mechanical properties of W-5 wt pct Ni alloys reinforced with 2 wt pct Y2O3, ZrO2 or TiO2 particles were investigated. Cold-pressed samples were sintered under vacuum at 1773 K (1500 °C) for 1 hour. The results show that, among three kinds of oxides, Y2O3 is the most efficient oxide to consolidate W powder by sintering. W-Ni-Y2O3 alloys form relatively uniform interconnected structure and also show higher density and compressive strength than those of W-Ni-ZrO2 and W-Ni-TiO2. On the other hand, W-Ni-TiO2 and W-Ni-ZrO2 alloys have non-homogeneous microstructure due to the formation of Ni globules in some areas in the matrix and almost nickel-free zones in other areas causing the appearance of pores. The Vickers hardness values for W-Ni-TiO2 alloys are slightly higher than those of W-Ni-ZrO2 and Ni-W-Y2O3 due to the smaller particle size of TiO2 than the other oxides. At room temperature, the investigated alloys have very weak magnetic properties. This is due to the combination of the ferromagnetic nickel metal binder with the non-magnetic tungsten forming the weak magnetic W-Ni solid solution. Moreover, the measured (mass) magnetizations had small values of the power of 10-3 emu/g. Additionally, the values of coercivity ( H C) and remanence ( M r) for the W-Ni-TiO2 alloy were higher than that of the W-Ni-Y2O3 and W-Ni-ZrO2 alloys due to the particle size effect of TiO2 nanoparticles.

  20. 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

  1. Creep and residual mechanical properties of cast superalloys and oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1981-01-01

    Tensile, stress-rupture, creep, and residual tensile properties after creep testing were determined for two typical cast superalloys and four advanced oxide dispersion strengthened (ODS) alloys. The superalloys examined included the nickel-base alloy B-1900 and the cobalt-base alloy MAR-M509. The nickel-base ODS MA-757 (Ni-16CR-4Al-0.6Y2O3 and the iron-base ODS alloy MA-956 (Fe-20Cr-5Al-0.8Y2O3) were extensively studied, while limited testing was conducted on the ODS nickel-base alloys STCA (Ni-16Cr-4.5Al-2Y2O3) with a without Ta and YD-NiCrAl (Ni-16Cr-5Al-2Y2O3). Elevated temperature testing was conducted from 114 to 1477 K except for STCA and YD-NiCrAl alloys, which were only tested at 1366 K. The residual tensile properties of B-1900 and MAR-M509 are not reduced by prior creep testing (strains at least up to 1 percent), while the room temperature tensile properties of ODS nickel-base alloys can be reduced by small amounts of prior creep strain (less than 0.5 percent). The iron-base ODS alloy MA-956 does not appear to be susceptible to creep degradation at least up to strains of about 0.25 percent. However, MA-956 exhibits unusual creep behavior which apparently involves crack nucleation and growth.

  2. 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.

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Rieken, Joel Rodney

    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 different

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. Microstructural characterization of oxide dispersion strengthened (ODS) Fe-12Cr-0.5Y2O3 alloy

    NASA Astrophysics Data System (ADS)

    Shamsudin, Farha Mizana; Radiman, Shahidan; Abdullah, Yusof; Hamid, Nasri A.

    2016-11-01

    Oxide dispersion strengthened (ODS) ferritic alloy containing 12wt% Cr and 0.5wt% Y2O3 was prepared by mechanical alloying (MA) method and then compacted into bulk shape. Field emission scanning electron microscopy (FESEM) was performed to characterize the microstructure of milled alloy powder. The fragments and nanoclusters of Y2O3 were observed in this alloy powder. FESEM-EDS mapping on the milled alloy powder reveal the uniformity of the element distribution achieved by the alloy. The Y element is finely dispersed into the alloy matrix and the O element is observed indicating the presence of oxides throughout the alloy sample. The compacted alloy was then heat treated at 1050°C and analyzed by field emission scanning electron microscope (FESEM). The formations of nano-scale Y2O3 were observed after the heat treatment process of alloy indicating the dispersion and incorporation of Y2O3 nanoparticles into the alloy matrix.

  11. Fabrication of Oxide Dispersion Strengthened Bond Coats with Low Al2O3 Content

    NASA Astrophysics Data System (ADS)

    Bergholz, Jan; Pint, Bruce A.; Unocic, Kinga A.; Vaßen, Robert

    2017-06-01

    Nanoscale oxide dispersions have long been used to increase the oxidation and wear resistance of alloys used as bond coatings in thermal barrier coatings. Their manufacturing via mechanical alloying is often accompanied by difficulties regarding their particle size, homogeneous distribution of the oxide dispersions inside the powder, involving considerable costs, due to cold welding of the powder during milling. A significant improvement in this process can be achieved by the use of process control agent (PCA) to achieve the critical balance between cold welding and fracturing, thereby enhancing the process efficiency. In this investigation, the influence of the organic additive stearic acid on the manufacturing process of Al2O3-doped CoNiCrAlY powder was investigated. Powders were fabricated via mechanical alloying at different milling times and PCA concentrations. The results showed a decrease in particle size, without hindering the homogeneous incorporation of the oxide dispersions. Two powders manufactured with 0.5 and 1.0 wt.% PCA were deposited by high velocity oxygen fuel (HVOF) spraying. Results showed that a higher content of elongated particles in the powder with the higher PCA content led to increased surface roughness, porosity and decreased coating thickness, with areas without embedded oxide particles.

  12. Fatigue properties of MA 6000E, a gamma-prime strengthened ODS alloy. [Oxide Dispersion Strengthened Ni-base alloy for gas turbine blade applications

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    MA 6000E is a corrosion resistant, gamma-prime strengthened ODS alloy under development for advanced turbine blade applications. The high temperature, 1093 C, rupture strength is superior to conventional nickel-base alloys. This paper addresses the fatigue behavior of the alloy. Excellent properties are exhibited in low and high cycle fatigue and also thermal fatigue. This is attributed to a unique combination of microstructural features, i.e., a fine distribution of dispersed oxides and other nonmetallics, and the highly elongated grain structure which advantageously modify the deformation characteristics and crack initiation and propagation modes from that characteristic of conventional gamma-prime hardened superalloys.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. Development of an oxide-dispersion-strengthened steel by introducing oxygen carrier compound into the melt aided by a general thermodynamic model

    PubMed Central

    Moghadasi, Mohammad Amin; Nili-Ahmadabadi, Mahmoud; Forghani, Farsad; Kim, Hyoung Seop

    2016-01-01

    In general, melting process is not a common method for the production of oxide dispersion strengthened (ODS) alloys due to agglomeration and coarsening of oxide particles. However, vacuum casting process has recently been employed as a promising process to produce micro-scale oxide dispersed alloys. In this paper, we report the process and characterization of in situ formation and uniform dispersion of nano-scale Y-Ti oxide particles in Fe-10Ni-7Mn (wt.%) alloy. The processing route involves a solid-liquid reaction between the added TiO2 as an oxygen carrier and dissolved yttrium in liquid metal leading to an optimal microstructure with nano-sized dispersed oxide particles. The developed thermodynamic model shows the independence of the final phase constituents from experimental conditions such as melting temperature or vacuum system pressure which offers a general pathway for the manufacture of oxide dispersion strengthened materials. PMID:27941814

  18. Development of an oxide-dispersion-strengthened steel by introducing oxygen carrier compound into the melt aided by a general thermodynamic model

    NASA Astrophysics Data System (ADS)

    Moghadasi, Mohammad Amin; Nili-Ahmadabadi, Mahmoud; Forghani, Farsad; Kim, Hyoung Seop

    2016-12-01

    In general, melting process is not a common method for the production of oxide dispersion strengthened (ODS) alloys due to agglomeration and coarsening of oxide particles. However, vacuum casting process has recently been employed as a promising process to produce micro-scale oxide dispersed alloys. In this paper, we report the process and characterization of in situ formation and uniform dispersion of nano-scale Y-Ti oxide particles in Fe-10Ni-7Mn (wt.%) alloy. The processing route involves a solid-liquid reaction between the added TiO2 as an oxygen carrier and dissolved yttrium in liquid metal leading to an optimal microstructure with nano-sized dispersed oxide particles. The developed thermodynamic model shows the independence of the final phase constituents from experimental conditions such as melting temperature or vacuum system pressure which offers a general pathway for the manufacture of oxide dispersion strengthened materials.

  19. Mechanical and Raman spectroscopic studies of multi-ion-beam irradiated 12,18Cr-oxide dispersion strengthened steels

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwen; Qian, Xin; Wang, Xu; Liu, Shiyi; Wang, Cheng; Li, Ting; Zhao, Ziqiang; Lu, Daogang

    2013-02-01

    12,18Cr-oxide dispersion strengthened (ODS) steels were irradiated at room temperature by single beam (2.2 MeV He+ or 3.0 MeV H+ or 21.0 MeV Si4+), dual-ion-beam (2.2 MeV He+ and 3.0 MeV H+) and triple-ion-beam (21.0 MeV Si4+, 2.2 MeV He+ and 3.0 MeV H+). Five combination of H, He, He+H, Si, Si+He+H irradiation were used. The mechanical properties of 12,18Cr-ODS steels exhibited that triple-ion-beam irradiation could strengthen irradiation swelling and hardening effect. Carbon segregation and several new carbon peaks appeared in the Raman spectrum of irradiated 12Cr-ODS steel. A clear correlation was established between the carbon distribution and the damage distribution.

  20. 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.

  1. 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.

  2. Atom probe tomographic analysis of high dose oxide-dispersion strengthened steel (alloy MA957) at selected irradiation conditions

    NASA Astrophysics Data System (ADS)

    Bailey, Nathan Alexander

    In an effort to understand the effect of high dose neutron irradiation on fast reactor cladding candidate materials, oxide-dispersion strengthened (ODS) alloy MA957 was irradiated to doses exceeding 100 displacements per atom (dpa) at various irradiation temperatures. The finely distributed Y-Ti-O particles, which provide MA957 its attractive properties, were examined by atom probe tomography (APT). Significant increases in oxide cluster number density and reductions in oxide cluster size were observed in specimens irradiated at 412 °C and below. A substantial hardness increase, measured by nanoindentation, was also observed at these low irradiation temperatures. It was found that the increase in oxide cluster number density, reduction in oxide cluster size, and associated increase in hardness is due to the inhibition of reformation processes of the Y-Ti-O particles following ballistic dissolution by incident radiation. Redistribution of oxide particle material along the grain boundaries is also observed at the low irradiation temperatures. The intermetallic phase alpha' was observed in the low temperature samples. This observation of this phase provides additional experimental evidence for the location of the phase boundary for this low temperature precipitate. The conclusion of this work is that MA957 is microstructurally stable under neutron irradiation at and above 495 °C.

  3. Mechanical response and deformation mechanisms of ferritic oxide dispersion strengthened steel structures produced by selective laser melting

    SciTech Connect

    Boegelein, Thomas; Dryepondt, Sebastien N.; Pandey, Amit; Dawson, Karl; Tatlock, Gordon J.

    2015-01-28

    Oxide dispersion strengthened (ODS) ferritic steels typically contain a fine dispersion of nanoscopic Y(Al, Ti) oxides, leading to an improvement in mechanical and physical properties. For a rapid prototyping technique, selective laser melting (SLM), was successfully applied to consolidate as-mechanically alloyed ODS-PM2000 (Fe 19Cr 5.5Al 0.5Ti 0.5Y2O3; all wt.%) powder to fabricate solid and thin-walled builds of different thickness. Our work is intended to act as a first study to investigate the tensile response of such configurations at room temperature, using miniaturized test specimens along and perpendicular to the growth direction. The 0.2% offset yield strength of as-grown wall builds was inferior to conventional PM2000 alloy (recrystallized), but could be significantly increased by conducting post-build heat treatments. Young s modulus and yield strength showed anisotropy and were enhanced when testing perpendicular to the build growth direction. Electron backscatter diffraction revealed a strong [001] fibre texture along the growth direction, which explains the anisotropic behaviour. In addition, studies on the morphology of the individual fracture surfaces, the grain structure of the cross-section near this region and the size distribution of ODS particles in such builds were conducted. A fine dispersion of precipitates was retained in all SLM builds, and findings suggest that a certain amount of Y is probably still in atomic solution in the as-grown condition and forms new small nanoscopic dispersoids during annealing, which lead to enhanced strengthening.

  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. 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.

  7. Long-term microstructural stability of oxide-dispersion strengthened Eurofer steel annealed at 800 °C

    NASA Astrophysics Data System (ADS)

    Zilnyk, K. D.; Sandim, H. R. Z.; Bolmaro, R. E.; Lindau, R.; Möslang, A.; Kostka, A.; Raabe, D.

    2014-05-01

    Oxide-dispersion strengthened ferritic martensitic steels such as ODS-Eurofer grade are good candidates for structural applications in future fusion power reactors. Long-term annealing treatments in vacuum were carried out in cold-rolled samples (80% reduction in thickness) from 1 h up to 4320 h (6 months) at 800 °C, i.e. the maximum temperature in the ferritic phase field, to follow its softening behavior. The microstructural stability of this steel was mapped using several characterization techniques including scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, Vickers microhardness testing, X-ray diffraction texture measurements, low-temperature electrical resistivity, and magnetic coercive field measurements. ODS-Eurofer steel displays good microstructural stability. Discontinuous recrystallization occurs at the early stages of annealing resulting in a low volume fraction of recrystallized grains. Extended recovery is the predominant softening mechanism at this temperature for longer times.

  8. 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.

  9. 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

  10. 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.

  11. Characterisation of a complex thin walled structure fabricated by selective laser melting using a ferritic oxide dispersion strengthened steel

    SciTech Connect

    Boegelein, Thomas Louvis, Eleftherios; Dawson, Karl; Tatlock, Gordon J.; Jones, Andy R.

    2016-02-15

    Oxide dispersion strengthened (ODS) alloys exhibit superior mechanical and physical properties due to the presence of nanoscopic Y(Al, Ti) oxide precipitates, but their manufacturing process is complex. The present study is aimed at further investigation of the application of an alternative, Additive Manufacturing (AM) technique, Selective Laser Melting (SLM), to the production of consolidated ODS alloy components. Mechanically alloyed PM2000 (ODS-FeCrAl) powders have been consolidated and a fine dispersion of Y-containing precipitates were observed in an as built thin-walled component, but these particles were typically poly-crystalline and contained a variety of elements including O, Al, Ti, Cr and Fe. Application of post-build heat treatments resulted in the modification of particle structures and compositions; in the annealed condition most precipitates were transformed to single crystal yttrium aluminium oxides. During the annealing treatment, precipitate distributions homogenised and localised variations in number density were diminished. The resulting volume fractions of those precipitates were 25–40% lower than have been reported in conventionally processed PM2000, which was attributed to Y-rich slag-like surface features and inclusions formed during SLM. - Highlights: • A wall structure was grown from ODS steel powder using selective laser melting. • A fine dispersion of nano-precipitates was apparent in as-build material. • Precipitates were multi-phased containing several elements, e.g. O, Ti, Al, Fe, Cr, Y. • Post-build annealing changed those into typically single-crystalline Y–Al–O. • The anneal also reduced and stabilised the volume fraction of precipitates to ~ 0.006.

  12. 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.

  13. Texture analysis of oxide dispersion strengthened (ODS) Fe alloys by X-ray and neutron diffraction

    NASA Astrophysics Data System (ADS)

    Béchade, J. L.; Mathon, M. H.; Branger, V.; Réglé, H.; Alamo, A.

    2002-07-01

    The ferritic ODS alloys studied were obtained by mechanical alloying. This strengthening method is very attractive, in particular for nuclear applications. In order to ensure the alloy a good compromise between mechanical resistance and ductility at high temperatures, it is necessary to control the microstructure and in particular the evolution during the recrystallization. First, a preliminary study, performed by X ray diffraction and optical microscopy, shows several grain growth mechanisms ; in particular, the “abnormal” grain growth mechanism which conducts to a large grain size [1], [2]. After annealing (3600s at 1470^{circ}C), the 30% cold-worked (swaging) alloys exhibit an heterogeneous microstructure with a large grains size ( 200 to 500 μm) in the heart and near the surface of the material when the intermediate zone is inhabited by small grains ( 1 μm). Fora higher cold-work level (60%), large size grains are only present in the periphery of the material. On account of the large grain size and strong heterogeneity of the microstructure, texture analysis using laboratory x-ray beam in not well adapted and so we have decided to use neutron beam. The neutron diffraction texture analysis has been performed at the Laboratoire Léon Brillouin on the 6T1 diffractometer on 2 different rods of the alloy (corresponding to the reduction ratios of 30% and 60%). Specific samples have been machined to characterise separately the zones with a different microstructure. After deformation, the alloys exhibit a typical α-fibre texture \\{ hkl \\} <1l0> whatever the area of the sample and the reduction ratio. After recrystallization, a very inhomogeneous texture is evidenced through the thickness of the sample, in particular for the rod deformed with a reduction ratio of 30% : in the heart and in the periphery of the rod, a “single-crystal” type texture is observed; the a fibre remains for the intermediate diameter of the rod. For the rod cold rolled with a

  14. Dispersion-strengthened copper-niobium composites

    SciTech Connect

    Troxell, J.

    1995-06-01

    GlidCop dispersion-strengthened copper is a family of engineered alloys which combine high strength, high thermal and electrical conductivities, and outstanding resistance to softening following exposure to elevated temperatures. A proprietary process based on GlidCop dispersion-strengthened copper technology improves mechanical properties through the addition of niobium. Two grades have been developed: Al-60 + NB1000 and Al-15 + NB1000. Each composite contains 10% niobium by weight, in the form of uniformly dispersed particles. The technology produces a uniform distribution of niobium in the internally oxidized, dispersion-strengthened copper powder. This powder can be consolidated in the same manner as conventional GlidCop Powder to produce a variety of mill shapes. The addition of 10% niobium to the Al-60 matrix increases strength and hardness with only minimal reduction in electrical conductivity. The room-temperature properties of Al-60 + NB1000 following exposure to 980 C (1,800 F), are compared with the properties of some commonly used RWMA welding materials which have also been exposed to elevated temperatures. While Al-60 + NB1000 has outstanding as-extruded mechanical properties, the cold workability of this material is limited. A cold-workable composite using the lower aluminum oxide Al-15 + NB1000 indicate that the properties of the as-extruded bar are improved by cold work, specifically drawing.

  15. Influence of Texture on Impact Toughness of Ferritic Fe-20Cr-5Al Oxide Dispersion Strengthened Steel.

    PubMed

    Sánchez-Gutiérrez, Javier; Chao, Jesus; Vivas, Javier; Galvez, Francisco; Capdevila, Carlos

    2017-07-03

    Fe-based oxide dispersion strengthened (ODS) steels are oriented to applications where high operating temperatures and good corrosion resistance is paramount. However, their use is compromised by their fracture toughness, which is lower than other competing ferritic-martenstic steels. In addition, the route required in manufacturing these alloys generates texture in the material, which induces a strong anisotropy in properties. The V-notched Charpy tests carried out on these alloys, to evaluate their impact toughness, reveal that delaminations do not follow the path that would be expected. There are many hypotheses about what triggers these delaminations, but the most accepted is that the joint action of particles in the grain boundaries, texture induced in the manufacturing process, and the actual microstructure of these alloys are responsible. In this paper we focused on the actual role of crystallographic texture on impact toughness in these materials. A finite elements simulation is carried out to solely analyze the role of texture and eliminate other factors, such as grain boundaries and the dispersed particles. The work allows us to conclude that crystallographic texture plays an important role in the distribution of stresses in the Charpy specimens. The observed delaminations might be explained on the basis that the crack in the grain, causing the delamination, is directly related to the shear stresses τ12 on both sides of the grain boundary, while the main crack propagation is a consequence of the normal stress to the crack.

  16. Influence of Texture on Impact Toughness of Ferritic Fe-20Cr-5Al Oxide Dispersion Strengthened Steel

    PubMed Central

    Sánchez-Gutiérrez, Javier; Chao, Jesus; Vivas, Javier; Galvez, Francisco; Capdevila, Carlos

    2017-01-01

    Fe-based oxide dispersion strengthened (ODS) steels are oriented to applications where high operating temperatures and good corrosion resistance is paramount. However, their use is compromised by their fracture toughness, which is lower than other competing ferritic-martenstic steels. In addition, the route required in manufacturing these alloys generates texture in the material, which induces a strong anisotropy in properties. The V-notched Charpy tests carried out on these alloys, to evaluate their impact toughness, reveal that delaminations do not follow the path that would be expected. There are many hypotheses about what triggers these delaminations, but the most accepted is that the joint action of particles in the grain boundaries, texture induced in the manufacturing process, and the actual microstructure of these alloys are responsible. In this paper we focused on the actual role of crystallographic texture on impact toughness in these materials. A finite elements simulation is carried out to solely analyze the role of texture and eliminate other factors, such as grain boundaries and the dispersed particles. The work allows us to conclude that crystallographic texture plays an important role in the distribution of stresses in the Charpy specimens. The observed delaminations might be explained on the basis that the crack in the grain, causing the delamination, is directly related to the shear stresses τ12 on both sides of the grain boundary, while the main crack propagation is a consequence of the normal stress to the crack. PMID:28773104

  17. Low Cost Process for Manufacture of Oxide Dispersion Strengthened (ODS) Turbine Nozzle Components.

    DTIC Science & Technology

    1979-12-01

    SWTTPROCESS FORJIANUFACTURE OF9OXIDE)ISPERSIONSTRENGTHENED (ODS) O0 TURBINE !IJOZZLE COMPONENTS, -- , General Electric Company Aircraft Engine Group...machining processes for low pressure turbine (LPT) vanes , high pressure turbine (HPT) vanes , and HPT band segments for the F101 engine . The primary intent...for aircraft turbine nozzle components. These processes were shown capable of maintaining required microstructures and properties for the vane and

  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. 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.

  20. 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.

  1. 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.; ...

    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

  2. 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.

  3. 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.

  4. TEM and HRTEM study of oxide particles in an Al-alloyed high-Cr oxide dispersion strengthened ferritic steel with Hf addition

    NASA Astrophysics Data System (ADS)

    Dou, Peng; Kimura, Akihiko; Kasada, Ryuta; Okuda, Takanari; Inoue, Masaki; Ukai, Shigeharu; Ohnuki, Somei; Fujisawa, Toshiharu; Abe, Fujio; Jiang, Shan; Yang, Zhigang

    2017-03-01

    The nanoparticles in an Al-alloyed high-Cr oxide dispersion strengthened (ODS) ferritic steel with Hf addition, i.e., SOC-16 (Fe-15Cr-2W-0.1Ti-4Al-0.62Hf-0.35Y2O3), have been examined by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Relative to an Al-alloyed high-Cr ODS ferritic steel without Hf addition, i.e., SOC-9 (Fe-15.5Cr-2W-0.1Ti-4Al-0.35Y2O3), the dispersion morphology and coherency of the oxide nanoparticles in SOC-16 were significantly improved. Almost all the small nanoparticles (diameter <10 nm) in SOC-16 were found to be consistent with cubic Y2Hf2O7 oxides with the anion-deficient fluorite structure and coherent with the bcc steel matrix. The larger particles (diameter >10 nm) were also mainly identified as cubic Y2Hf2O7 oxides with the anion-deficient fluorite structure. The results presented here are compared with those of SOC-9 with a brief discussion of the underlying mechanisms of the unusual thermal and irradiation stabilities of the oxides as well as the superior strength, excellent irradiation tolerance and extraordinary corrosion resistance of SOC-16.

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

    NASA Astrophysics Data System (ADS)

    Kaspar, T. C.; Bowden, M. E.; Wang, C. M.; Shutthanandan, V.; Overman, N. R.; van Ginhoven, R. M.; Wirth, B. D.; Kurtz, R. 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 (1 0 0), (1 1 0), and (1 1 1) 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 orientation for Fe(2 1 1) deposited on Y2O3(1 1 0)/YSZ(1 1 0). In contrast, Fe on Y2O3(1 1 1)/YSZ(1 1 1) was fully polycrystalline, and Fe on Y2O3(1 0 0)/YSZ(1 0 0) exhibited out-of-plane texture in the [1 1 0] direction with little or no preferential in-plane orientation. Scanning transmission electron microscopy imaging of Fe(2 1 1)/Y2O3(1 1 0)/YSZ(1 10) 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.

  6. 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.

  7. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  8. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  9. 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

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

    SciTech Connect

    Kad, B.K.

    2002-02-08

    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% 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

  11. High-Temperature Tensile Properties of Nano-Oxide Dispersion Strengthened Ferritic Steels Produced by Mechanical Alloying and Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Boulnat, Xavier; Fabregue, Damien; Perez, Michel; Mathon, Marie-Hélène; de Carlan, Yann

    2013-06-01

    Oxide-dispersion strengthened (ODS) ferritic steels were produced by mechanical alloying and subsequent spark plasma sintering. Very fast heating rates were used to minimize porosity when controlling grain size and precipitation of dispersoids within a compacted material. Sintering cycles performed at 1373 K (1100 °C) induced heterogeneous, but fine grain size distribution and high density of nano-oxides. Yield strengths at room temperature and at 923 K (650 °C) are 975 MPa and 298 MPa, respectively. Furthermore, high-temperature ductility is much increased: total strain of 28 pct at 923 K (650 °C).

  12. 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).

  13. Thermogravity system designed for use in dispersion strengthening studies

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1972-01-01

    A thermogravimetry system designed to study the reduction of oxides in metal and alloy powders to be used in dispersion strengthened materials is described. The apparatus was devised for use at high temperatures with controlled atmospheres. Experimental weight change and moisture evolution results for the thermal decomposition of calcium oxalate monohydrate in dry helium, and experimental weight change results for the reduction of nickel oxide in dry hydrogen and hydrogen containing 15,000 PPM water vapor are presented. The system is currently being successfully applied to the evaluation of the reduction characteristics and the removal of impurities from metals and alloys to be used for dispersion strengthening.

  14. Thermogravimetry system designed for use in dispersion strengthening studies.

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1972-01-01

    A thermogravimetry system, designed to study the reduction of oxides in metal and alloy powders to be used in dispersion strengthened materials, is described. The apparatus was devised for use at high temperatures with controlled atmospheres. Experimental weight change and moisture evolution results for the thermal decomposition of calcium oxalate monohydrate in dry helium, and experimental weight change results for the reduction of nickel oxide in dry hydrogen and hydrogen containing 15,000 p.p.m. water vapor are presented. The system is currently being successfully applied to the evaluation of the reduction characteristics and the removal of impurities from metals and alloys to be used for dispersion strengthening.

  15. The corrosion product of Cs-Te corrosive compound with 11Cr-Ferritic/Martensitic Steel and 9Cr-Oxide Dispersion Strengthened steel

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Tanigaki, T.; Fujimura, R.; Fukumoto, K.; Uno, M.

    2015-05-01

    Cs-Te corrosion tests were performed to FBR fuel cladding candidate materials listed below: 11Cr-Ferritic/Martensitic Steel (F/M steel) and 9Cr Oxide Dispersion Strengthened steel (ODS steel). The corrosion products of Cs-Te corrosive compound Cs2Te3 with F/M steel or ODS steel were picked up from the specimens after the corrosion test by focus ion beam method (FIB) and the corrosion products were specified based on element analysis and crystal analysis by transmit electron microscopy (TEM) with electron dispersion X-ray spectrum (EDS). The result of analysis allowed us to presume Cs-Te corrosion reactions in the Fe-Cr based fuel cladding material. The presumable reactions are 4Te + 3/23 Cr23C6 →Cr3Te4 + 18/23 C and 4Te + 3Cr →Cr3Te4 .

  16. 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.

  17. Creep deformation of dispersion-strengthened copper

    SciTech Connect

    Broyles, S.E.; Anderson, K.R.; Groza, J.R.; Gibeling, J.C.

    1996-05-01

    The creep behavior of an internally oxidized, Al{sub 2}O{sub 3} dispersion-strengthened copper alloy, GlidCop Al-15, has been investigated in the temperature range of 745 to 994 K. The results exhibit a high apparent stress exponent (10 to 21) and a high apparent activation energy for creep (253.3 kJ/mole). To describe the creep behavior of this alloy, the Roesler-Arzt model for attractive particle/dislocation interaction is applied. The results are in good agreement with the model when account is taken of the effects of the fine elongated grains and heavily dislocated structures revealed through transmission electron microscopy. The analysis demonstrates that the dislocation/particle interaction is of moderate strength in this alloy, consistent with the observation that the particle/matrix interface is partially coherent. In addition, the analysis reveals that the choice of mechanism and corresponding activation energy for vacancy diffusion has only a small effect on the calculated model parameters. It is argued that the weak dependence of subgrain size on stress demonstrates that creep deformation is particle controlled, rather than subgrain size controlled. In addition, the poorly developed subgrain structure and high dislocation densities are attributed to the presence of the fine oxide particles. Finally, the dependence of rupture time on stress is shown to be consistent with a description of creep fracture based on diffusive cavity growth with continuous nucleation.

  18. Microstructural comparison of effects of hafnium and titanium additions in spark-plasma-sintered Fe-based oxide-dispersion strengthened alloys

    NASA Astrophysics Data System (ADS)

    Huang, Yina; Zhang, Hongtao; Auger, Maria A.; Hong, Zuliang; Ning, Huanpo; Gorley, Michael J.; Grant, Patrick S.; Reece, Michael J.; Yan, Haixue; Roberts, Steve G.

    2017-04-01

    Two oxide dispersion strengthened alloys: 14Cr-0.25Y2O3-0.22Hf (wt.%) and Fe-14Cr-0.25Y2O3-0.4Ti (wt.%) were fabricated by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS). Electron backscatter diffraction showed grain sizes in the range 0.5-15 μm in both alloys. Transmission electron microscopy and scanning transmission electron microscopy showed a homogeneous distribution of nano-oxides precipitated during SPS. Using high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and atom probe tomography, several different oxide phases were found in both alloys, but the majority of dispersoids were Y-Hf-O type in Fe-14Cr-0.25Y2O3-0.22Hf and Y-Ti-O type in Fe-14Cr-0.25Y2O3-0.4Ti. There were a variety of orientation relationships between the different dispersoids and the ferritic matrix. Both alloys had dispersoid densities of ∼1023/m3, with average diameters of 4.3 nm and 3.5 nm in the 0.22Hf and 0.4Ti containing alloys, respectively. Per atom added, Hf (0.07 at.%) is suggested to be more potent than Ti (0.46 at.%) in refining the nano-oxides.

  19. 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.

  20. Enhanced Radiation-tolerant Oxide Dispersion Strengthened Steel and its Microstructure Evolution under Helium-implantation and Heavy-ion Irradiation

    NASA Astrophysics Data System (ADS)

    Lu, Chenyang; Lu, Zheng; Wang, Xu; Xie, Rui; Li, Zhengyuan; Higgins, Michael; Liu, Chunming; Gao, Fei; Wang, Lumin

    2017-01-01

    The world eagerly needs cleanly-generated electricity in the future. Fusion reactor is one of the most ideal energy resources to defeat the environmental degradation caused by the consumption of traditional fossil energy. To meet the design requirements of fusion reactor, the development of the structural materials which can sustain the elevated temperature, high helium concentration and extreme radiation environments is the biggest challenge for the entire material society. Oxide dispersion strengthened steel is one of the most popular candidate materials for the first wall/blanket applications in fusion reactor. In this paper, we evaluate the radiation tolerance of a 9Cr ODS steel developed in China. Compared with Ferritic/Martensitic steel, this ODS steel demonstrated a significantly higher swelling resistance under ion irradiation at 460 °C to 188 displacements per atom. The role of oxides and grain boundaries on void swelling has been explored. The results indicated that the distribution of higher density and finer size of nano oxides will lead a better swelling resistance for ODS alloy. The original pyrochlore-structured Y2Ti2O7 particles dissolved gradually while fine Y-Ti-O nano clusters reprecipitated in the matrix during irradiation. The enhanced radiation tolerance is attributed to the reduced oxide size and the increased oxide density.

  1. Enhanced Radiation-tolerant Oxide Dispersion Strengthened Steel and its Microstructure Evolution under Helium-implantation and Heavy-ion Irradiation

    PubMed Central

    Lu, Chenyang; Lu, Zheng; Wang, Xu; Xie, Rui; Li, Zhengyuan; Higgins, Michael; Liu, Chunming; Gao, Fei; Wang, Lumin

    2017-01-01

    The world eagerly needs cleanly-generated electricity in the future. Fusion reactor is one of the most ideal energy resources to defeat the environmental degradation caused by the consumption of traditional fossil energy. To meet the design requirements of fusion reactor, the development of the structural materials which can sustain the elevated temperature, high helium concentration and extreme radiation environments is the biggest challenge for the entire material society. Oxide dispersion strengthened steel is one of the most popular candidate materials for the first wall/blanket applications in fusion reactor. In this paper, we evaluate the radiation tolerance of a 9Cr ODS steel developed in China. Compared with Ferritic/Martensitic steel, this ODS steel demonstrated a significantly higher swelling resistance under ion irradiation at 460 °C to 188 displacements per atom. The role of oxides and grain boundaries on void swelling has been explored. The results indicated that the distribution of higher density and finer size of nano oxides will lead a better swelling resistance for ODS alloy. The original pyrochlore-structured Y2Ti2O7 particles dissolved gradually while fine Y-Ti-O nano clusters reprecipitated in the matrix during irradiation. The enhanced radiation tolerance is attributed to the reduced oxide size and the increased oxide density. PMID:28079191

  2. Enhanced Radiation-tolerant Oxide Dispersion Strengthened Steel and its Microstructure Evolution under Helium-implantation and Heavy-ion Irradiation.

    PubMed

    Lu, Chenyang; Lu, Zheng; Wang, Xu; Xie, Rui; Li, Zhengyuan; Higgins, Michael; Liu, Chunming; Gao, Fei; Wang, Lumin

    2017-01-12

    The world eagerly needs cleanly-generated electricity in the future. Fusion reactor is one of the most ideal energy resources to defeat the environmental degradation caused by the consumption of traditional fossil energy. To meet the design requirements of fusion reactor, the development of the structural materials which can sustain the elevated temperature, high helium concentration and extreme radiation environments is the biggest challenge for the entire material society. Oxide dispersion strengthened steel is one of the most popular candidate materials for the first wall/blanket applications in fusion reactor. In this paper, we evaluate the radiation tolerance of a 9Cr ODS steel developed in China. Compared with Ferritic/Martensitic steel, this ODS steel demonstrated a significantly higher swelling resistance under ion irradiation at 460 °C to 188 displacements per atom. The role of oxides and grain boundaries on void swelling has been explored. The results indicated that the distribution of higher density and finer size of nano oxides will lead a better swelling resistance for ODS alloy. The original pyrochlore-structured Y2Ti2O7 particles dissolved gradually while fine Y-Ti-O nano clusters reprecipitated in the matrix during irradiation. The enhanced radiation tolerance is attributed to the reduced oxide size and the increased oxide density.

  3. 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.

  4. Effects of heavy-ion irradiation on the grain boundary chemistry of an oxide-dispersion strengthened Fe-12 wt.% Cr alloy

    NASA Astrophysics Data System (ADS)

    Marquis, Emmanuelle A.; Lozano-Perez, Sergio; Castro, Vanessa de

    2011-10-01

    Understanding the behaviour of oxide-dispersion strengthened (ODS) ferritic martensitic steels under irradiation is of prime importance in the design of future fusion reactors. Although changes in grain boundary chemistry during irradiation can significantly affect fracture strength, little is known on the behaviour of grain boundaries in ODS steels. Here, the effect of heavy-ion implantation at 500 °C on grain boundary chemistry in a model ODS Fe-12 wt.% Cr alloy was investigated using atom-probe tomography (APT) and analytical scanning-transmission electron microscopy ((S)TEM) techniques. While chromium and carbon segregation at grain boundaries is found in annealed alloys before irradiation, the three-dimensional APT reconstructions and TEM observations after irradiation reveal a complex distribution of Cr segregation and depletion at grain boundaries of varying character.

  5. 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.

  6. 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.

  7. Epitaxial Fe Thin Films on {100} Y2Ti2O7: Model Interfaces for Nano-Oxide Dispersion Strengthened Steels

    NASA Astrophysics Data System (ADS)

    Stan, T.; Wu, Y.; Wells, P. B.; Zhou, H. D.; Odette, G. R.

    2017-08-01

    Nanostructured Ferritic Alloys, a variant of oxide dispersion strengthened steels, contain a high density of ≈2.5 nm Y-Ti-O nano-oxides (NOs) that provide remarkable irradiation tolerance, enhance recombination of vacancies and self-interstitial irradiation defects, and trap He in fine-scale bubbles at their interfaces. To complement studies of embedded NOs, mesoscopic-scale metal-oxide interfaces were fabricated by electron beam deposition of Fe films on {100} Y2Ti2O7 (YTO) bulk single-crystal substrates. We report, for the first time, the dominant epitaxial orientation relationship (OR) for the polycrystalline Fe film: {110}Fe{100}YTO and 〈111〉Fe〈110〉YTO. Further, one large grain region had an OR that is also found in embedded NOs: {100}Fe{100}YTO and 〈100〉Fe〈110〉YTO. HRTEM studies show clean, semicoherent interfaces with misfit dislocation spacings of 0.7 and 1.4 nm, respectively. These observations are important for the development of first principles models of metal-oxide interfaces, and the bilayers themselves will be used to observe the He partitioning between the Fe, YTO, and the corresponding interface.

  8. Influence of nano-Al2O3-reinforced oxide-dispersion-strengthened Cu on the mechanical and tribological properties of Cu-based composites

    NASA Astrophysics Data System (ADS)

    Zhao, Xiang; Guo, Lei-chen; Zhang, Long; Jia, Ting-ting; Chen, Cun-guang; Hao, Jun-jie; Shao, Hui-ping; Guo, Zhi-meng; Luo, Ji; Sun, Jun-bin

    2016-12-01

    The mechanical and tribological properties of Cu-based powder metallurgy (P/M) friction composites containing 10wt%-50wt% oxide-dispersion-strengthened (ODS) Cu reinforced with nano-Al2O3 were investigated. Additionally, the friction and wear behaviors as well as the wear mechanism of the Cu-based composites were characterized by scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS) elemental mapping. The results indicated that the Cu-based friction composite containing 30wt% ODS Cu exhibited the highest hardness and shear strength. The average and instantaneous friction coefficient curves of this sample, when operated in a high-speed train at a speed of 300 km/h, were similar to those of a commercial disc brake pad produced by Knorr-Bremse AG (Germany). Additionally, the lowest linear wear loss of the obtained samples was (0.008 ± 0.001) mm per time per face, which is much lower than that of the Knorr-Bremse pad ((0.01 ± 0.001) mm). The excellent performance of the developed pad is a consequence of the formation of a dense oxide composite layer and its close combination with the pad body.

  9. Braze joints of dispersion strengthened copper

    NASA Astrophysics Data System (ADS)

    Chen, Shaofeng; Bao, Tingshan; Chin, Bryan A.

    1996-10-01

    Prior attempts to join alumina dispersion strengthened alloys (GlidCop) to itself, stainless steel (SS) and other materials have been less than successful. Typically these joints show low strength and poor ductility due to the segregation of alumina particles at the braze interface. This paper presents the results of a study undertaken to develop low activation brazing alloys, fluxes and processes for vacuum, argon and air environments to join alumina dispersion strengthened copper alloys to 304 SS. Vacuum and argon experiments were conducted using a Gleeble resistance heated system. Air brazing experiments were conducted in a resistance heated furnace with active fluxes. A reactive braze alloy composition has been developed which eliminates the segregation of Al 2O 3 particles at the braze interface and produces joints with excellent strength and ductility. Wetting and mechanical properties of the braze alloys were measured. Tensile properties, microstructure, microhardness and measurements of the compositional segregation across the braze joint are discussed.

  10. DISPERSION STRENGTHENED NICKEL-BASE ALLOYS.

    DTIC Science & Technology

    The swaged cone of extruded Nichrome-thoria alloys prepared by the thermal decomposition of thorium nitrate onto alloy powder indicated descreased... swaging of these dispersion-strengthened Nichrome alloys was dependent on the presence of a mild steel jacket on the alloy rod as a result of the canned...extrusion practice. Efforts to cold swage the alloy materials without this jacket were unsuccessful. (Author)

  11. 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.

  12. Advanced gas atomization production of oxide dispersion strengthened (ODS) Ni-base superalloys through process and solidification control

    NASA Astrophysics Data System (ADS)

    Meyer, John Louis Lamb

    A novel gas atomization reaction synthesis (GARS) method was utilized to produce precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE)-containing intermetallic. Although Al is necessary for industrial superalloy production, the Ni-Cr base alloy system was selected as a simplified system more amenable to characterization. This was done in an effort to better study the effects of processing parameters. Consolidation and heat-treatment were performed to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nanometric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiment that found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloys, but the Hf-containing system exhibited five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was easier to characterize, and make observations on the effects of processing parameters, the Ti-containing system was used for experimental atomization trials. An internal oxidation model was used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed to investigate the effects of gas atomization pressure and reactive-gas concentration on the particle size distribution (PSD). Also, the effect on the rapidly solidified microstructure (as a function of powder size

  13. Brazing of dispersion-strengthened aluminum

    SciTech Connect

    Bjoerneklett, B.; Grong, O.; Anisdahl, L.; Hellum, E.; Sande, V.

    1996-03-01

    In recent years, the use of rapid solidification powder metallurgy has made it possible to develop a new family of aluminum alloys exhibiting unique properties. One of these materials, dispersion-strengthened (DS) aluminum, is currently being produced for commercial purposes at Raufoss Technology AS, Norway. Dispersion-strengthened aluminum derives its high strength from nanoscale AlN particles embedded in an aluminum matrix. DS Al is expected to be well suited as construction material for high-temperature applications where weight reductions are of particular concern. The present investigation has focused on the wetting behavior of DS aluminum under conditions applicable to brazing. The results from the Sessile drop experiments show that a eutectic Al-Si brazing alloy will completely wet the base metal both under high-vacuum conditions and in controlled argon atmospheres, provided that the partial pressure of oxygen is sufficiently low. The main problem appears to be the stability of the matrix grain structure. In general, the process of grain erosion and coarsening can be controlled by restricting the supply of the brazing alloy so that only a small metal volume is exposed to erosion. In addition, there is a great potential for reducing the thermodynamic driving force of the erosion reaction by proper adjustments of the brazing alloy composition and/or the brazing temperature. Sill, grain boundary liquidation may be a problem which, in turn, may require additions of surface active elements to the filler metal to control the wetting behavior.

  14. Time-dependent edge-notch sensitivity of oxide and gamma prime dispersion strengthened sheet materials at 1000 to 1800 F (538 - 982 C)

    NASA Technical Reports Server (NTRS)

    Wilson, D. J.

    1972-01-01

    Research was carried out to determine whether an oxide dispersion hardened alloy, TD-Ni, Cr, and low volume fraction gamma prime strengthened nickel-base alloy, Modified Waspaloy, were susceptible to time-dependent edge-notch sensitivity. The results were evaluated in terms of the mechanical characteristics of the alloys and the dislocation motion mechanisms operative. As far as could be determined, the results of the investigation were consistent with the following important concepts developed for Waspaloy and Inconel 718: (1) Time-dependent edge-notch sensitivity occurs when notched specimens are loaded below the approximate 0.2 percent smooth specimen offset yield strength and when data from smooth specimens indicate that small amounts of creep consume large rupture life fractions. (2) When precipitate particles are sheared by dislocations, the deformation is localized and time-dependent notch sensitivity occurs. When dislocations by-pass precipitate particles the deformation is homogeneous. Under these conditions, no time-dependent notch sensitivity has been observed.

  15. 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.

  16. 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.

  17. Fabrication of oxide dispersion strengthened bond coats with low Al2O3 content [Fabrication of ODS bond coats with low Al2O3 content

    DOE PAGES

    Bergholz, Jan; Pint, Bruce A.; Unocic, Kinga A.; ...

    2017-03-23

    Here, nanoscale oxide dispersions have long been used to increase the oxidation and wear resistance of alloys used as bond coatings in thermal barrier coatings. Their manufacturing via mechanical alloying is often accompanied by difficulties regarding their particle size, homogeneous distribution of the oxide dispersions inside the powder, involving considerable costs, due to cold welding of the powder during milling. A significant improvement in this process can be achieved by the use of process control agent (PCA) to achieve the critical balance between cold welding and fracturing, thereby enhancing the process efficiency. In this investigation, the influence of the organicmore » additive stearic acid on the manufacturing process of Al2O3-doped CoNiCrAlY powder was investigated. Powders were fabricated via mechanical alloying at different milling times and PCA concentrations. The results showed a decrease in particle size, without hindering the homogeneous incorporation of the oxide dispersions. Two powders manufactured with 0.5 and 1.0 wt.% PCA were deposited by high velocity oxygen fuel (HVOF) spraying. Results showed that a higher content of elongated particles in the powder with the higher PCA content led to increased surface roughness, porosity and decreased coating thickness, with areas without embedded oxide particles.« less

  18. 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.

  19. 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.

  20. 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.

  1. Solid state welding of dispersion-strengthened nickel alloys

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.

    1971-01-01

    Two-step solid state welding cycle applied to carefully prepared surfaces of an unrecrystallized alloy prevents loss of parent-metal strength at weld joint of dispersion-strengthened, nickel-chromium alloy.

  2. Characteristics of alumina particles in dispersion-strengthened copper alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-hui; Li, Xiao-xian

    2014-11-01

    Two types of alumina dispersion-strengthened copper (ADSC) alloys were fabricated by a novel in-situ reactive synthesis (IRS) and a traditional internal oxidation (IO) process. The features of alumina dispersoids in these ADSC alloys were investigated by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. It is found that nano-sized γ-Al2O3 particles of approximately 10 nm in diameter are homogeneously distributed in the IRS-ADSC composites. Meanwhile, larger-sized, mixed crystal structure alumina with rod-shaped morphology is embedded in the IO-ADSC alloy. The IRS-ADSC composites can obtain better mechanical and physical properties than the IO-ADSC composites; the tensile strength of the IRS-ADSC alloy can reach 570 MPa at room temperature, its electrical conductivity is 85% IACS, and the Rockwell hardness can reach 86 HRB.

  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. Dispersion Strengthening of High Temperature Niobium Alloys

    DTIC Science & Technology

    1989-07-31

    completely plastic and stainless steel system which allows for the rapid and automatic jet thinning of Nb alloys using hydrofluoric acid. A solution...by its effect on the DBTT as shown in Fig. 7 (Ref. 18). For the DBTT to be well below ambient, an arbitrary temperature of-130"C (-2000F) may be chosen...effect of increasing the DBTT and that oxygen tied up as oxides will not be detrimental. Thus the actual allowable oxygen concentration in the

  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. Microstructure of rapidly solidified Al 2O 3 dispersion strengthened type 316 stainless steel

    NASA Astrophysics Data System (ADS)

    Megusar, J.; Arnberg, L.; Vander Sande, J. B.; Grant, N. J.

    An aluminum oxide dispersion strengthened 316 stainless steel was developed by surface oxidation. Surface oxidation was chosen as a preferred method in order to minimize formation of less stable chromium oxides. Ultra low C+N 316 stainless steel was alloyed with 1 wt% A1, rapidly solidified to produce fine powders and attrited to approximately 0.5 pm thick flakes to provide for surface oxidation. Oxide particles in the extruded material were identified mostly as A1 oxides, In the preirradiated condition, oxide dispersion retarded crystallization and grain growth and had an effect on room temperature tensile properties. These structural modifications are expected to have an effect on the swelling resistance, structure stability and high temperature strength of austenitic stainless steels (Path A 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. 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.

  9. Low-cycle fatigue of dispersion-strengthened copper

    SciTech Connect

    Robles, J. ); Anderson, K.R.; Groza, J.R.; Gibeling, J.C. )

    1994-10-01

    The cyclic deformation behavior of a dispersion-strengthened copper alloy, GlidCop Al-15, has been studied at plastic strain amplitudes in the range 0.1 pct [<=] [Delta][var epsilon][sub p]/2 [<=] 0.8 pct. Compared to pure polycrystalline copper, the dispersion-strengthened material exhibits a relatively stable cyclic response as a consequence of the dislocation substructures inherited from prior processing and stabilized by the Al[sub 2]O[sub 3] particles. These dislocation structures remain largely unaltered during the course of deformation; hence, they do not reveal any of the features classically associated with copper tested in fatigue. At low amplitudes, the fatigue lifetimes of the dispersion-strengthened copper and the base alloy are similar; however, the former is more susceptible to cracking at stress concentrations because of its substantially greater strength. This similarity in fatigue life-times is a consequence of the dispersal of both deformation and damage accumulation by the fine grain size and dislocation/particle interactions in the GlidCop alloy. The operation of these mechanisms is reflected in the fine surface slip markings and rough fracture surface features for this material.

  10. 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.

  11. The response of dispersion-strengthened copper alloys to high fluence neutron irradiation at 415 degree C

    SciTech Connect

    Edwards, D.J.; Newkirk, J.W. ); Garner, F.A.; Hamilton, M.L. ); Nadkarny, A.; Samal, P. )

    1992-06-01

    Various oxide-dispersion-strengthened copper alloys have been irradiated to 150 dpa at 415{degree}C in the Fast Flux Test Facility (FFTF). The Al{sub 2}0{sub 3} - strengthened GlidCop{trademark} alloys, followed closely by a HfO{sub 2} - strengthened alloy, displayed the best swelling resistance, electrical conductivity, and tensile properties. The conductivity of the HfO{sub 2} - strengthened alloy reached a plateau at the higher levels of irradiation, instead of exhibiting the steady decrease in conductivity observed in the other alloys. A high initial oxygen content resulted in significantly higher swelling for a series of castable oxide-dispersion-strengthened alloys, while a Cr{sub 2}0{sub 3} - strengthened alloy showed poor resistance to radiation.

  12. The response of dispersion-strengthened copper alloys to high fluence neutron irradiation at 415{degree}C

    SciTech Connect

    Edwards, D.J.; Newkirk, J.W.; Garner, F.A.; Hamilton, M.L.; Nadkarny, A.; Samal, P.

    1992-06-01

    Various oxide-dispersion-strengthened copper alloys have been irradiated to 150 dpa at 415{degree}C in the Fast Flux Test Facility (FFTF). The Al{sub 2}0{sub 3} - strengthened GlidCop{trademark} alloys, followed closely by a HfO{sub 2} - strengthened alloy, displayed the best swelling resistance, electrical conductivity, and tensile properties. The conductivity of the HfO{sub 2} - strengthened alloy reached a plateau at the higher levels of irradiation, instead of exhibiting the steady decrease in conductivity observed in the other alloys. A high initial oxygen content resulted in significantly higher swelling for a series of castable oxide-dispersion-strengthened alloys, while a Cr{sub 2}0{sub 3} - strengthened alloy showed poor resistance to radiation.

  13. Effect of TMP variables upon structure and properties in ODS alloy HDA 8077 sheet. [ThermoMechanical Processing of Oxide Dispersion Strengthened nickel alloy

    NASA Technical Reports Server (NTRS)

    Rothman, M. F.; Tawancy, H. M.

    1980-01-01

    The effects of oxide content level and variations in thermomechanical processing upon the final structure and properties of HDA 8077 sheet have been systematically examined. It was found that creep strength and formability are substantially influenced by both oxide content and TMP schedule. Variations in creep properties obtained appear to correlate with observed microstructures.

  14. THE USE OF DISPERSION STRENGTHENED COPPER IN ACCELERATOR DESIGNS

    SciTech Connect

    R. VALDIVIEZ; D. SCHRAGE; ET AL

    2000-10-01

    Dispersion strengthened copper, known by the trade name GLIDCOP{reg_sign}, has found various applications in accelerator designs. Glidcop has material properties similar to OFE copper, such as thermal and electrical conductivity. Unlike OFE, however, Glidcop has yield and ultimate strengths equivalent to those of mild-carbon steel, making it a good structural material. This paper covers some accelerator components fabricated with Glidcop, material properties measured from room to brazing temperatures, and a furnace-brazing process that has produced good, consistent results with Glidcop.

  15. 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.

  16. Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1972-01-01

    Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

  17. 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.

  18. 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

    NASA Astrophysics Data System (ADS)

    Maloy, S. A.; Saleh, T. A.; Anderoglu, O.; Romero, T. J.; Odette, G. R.; Yamamoto, T.; Li, S.; Cole, J. I.; Fielding, R.

    2016-01-01

    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(ɛ) laws for all of these alloys. In the irradiated condition, the σ(ɛ) 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 the latter can be understood in terms of the alloy's σ(ɛ) behavior. Increases in the average σ(ɛ) in the range of 0-10% strain are smaller than the corresponding Δσy, and vary more from alloy to alloy. The data are also 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. Notably lower interstitial solute contents correlate with improved ductility and homogenous deformation in broadly similar steels.

  19. In-Situ Fracture Studies and Modeling of the Toughening Mechanism Present in Wrought Low-Carbon Arc-Cast Molybdenum, Titanium-Zirconium-Molybdenum, and Oxide-Dispersion-Strengthened Molybdenum Flat Products

    NASA Astrophysics Data System (ADS)

    Cockeram, B. V.; Chan, K. S.

    2008-09-01

    In-situ testing, ultrasonic C-scans, and metallography were used to show that a crack-divider delamination form of thin-sheet toughening occurs in wrought low-carbon arc-cast (LCAC) unalloyed molybdenum, oxide-dispersion-strengthened (ODS) molybdenum, and a wrought molybdenum alloy with 0.5 pct Ti and 0.1 pct Zr additions by weight (TZM), at temperatures greater than or equal to the ductile-to-brittle transition temperature (DBTT). Cracking along boundaries relieves mechanical constraints and frees ligaments that may plastically stretch to produce toughening. Anisotropy in fracture toughness with lower values in the short-transverse (ST) direction is shown to produce the crack-divider delaminations at the crack tip in the longitudinal (LT) and transverse (TL) orientations. The delamination zone increases with increasing stress-intensity factors to sizes significantly larger than the plastic zone; this leads to large increases in fracture toughness by the thin-sheet-toughening mechanism. Fracture in ODS Mo alloys proceeds mainly along grain boundaries to produce small ligaments that exhibit ductility for both LT and TL orientations, resulting in a lower DBTT and higher toughness values at lower temperatures than those observed in LCAC molybdenum and TZM. A combination of grain-boundary fracture and cleavage is prevalent in LCAC molybdenum and TZM. The predominant tendency for microcracking along grain boundaries to leave fine, ductile ligaments in ODS molybdenum can be attributed to a fine-grained microstructure with a ≈1- to 2- μm thickness of sheetlike grains. The presence of mixed grain-boundary fracture and cleavage in LCAC molybdenum and TZM can be attributed to a microstructure with a larger thickness of sheetlike grains (4 to 15 μm).

  20. 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; ...

    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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Structural Analysis of Dispersion Strengthened Al-Al4C3 Material by XRD Method

    NASA Astrophysics Data System (ADS)

    Varchola, Marián; Saksl, Karel; Durišin, Juraj; Besterci, Michal

    2011-04-01

    Dispersion strengthened materials belong into the group of composite materials, which are made mainly by powder metallurgy. Their structure has a polycrystalline matrix, in which dispersion particles are incorporated, mainly oxide, carbide and nitride type. The Al-C systems belong among modern materials designed for work at elevated temperature. This work focused on a study of the microstructure in containing 4 vol.% Al4C3. The microstructure was analyzed X-ray diffraction line profile analysis. It is a powerful and convenient method to probe the microstructural characteristics of composites materials. In this paper the development of texture and size of crystallites in composite material dependence on annealing time and temperature was examined. Texture of the experimental materials was analyzed by means texture coefficient (TC). TC for the (220) plane in Al4C3 composite indicate the presence of markedly deformed texture. Size of crystallites depends on annealing temperatures and times.

  6. Oxidation-Strengthened High-Temperature Rivets

    NASA Technical Reports Server (NTRS)

    Mclemore, R. L.

    1982-01-01

    Shear strength of titanium-niobium rivets improves with oxidation. Ti-Nb rivets developed for fastening parts of Space Shuttle thrustors may be suitable also for other high-temperature applications in oxidizing environments--for example, in burner cans of commercial jet engines and boilers and retorts for coal gasification systems.

  7. Contribution to Kinetics of Superplastic Deformation of Dispersion Strengthened Al-Al4C3 System

    NASA Astrophysics Data System (ADS)

    Besterci, Michal; Varchola, Marián; Kováč, Ladislav; Velgosová, Oksana

    2012-02-01

    The influence of temperature at constant strain rate has been evaluated with respect to superplastic behavior of dispersion strengthened Al-Al4C3 composite with 4 vol.% of Al4C3 phase. The dispersion strengthened Al-Al4C3 was prepared by powder metallurgy. Material can be characterized by grain size around 1 μm and dispersed particle Al4C3 size around 50 nm. This material showed superplastic behavior for strain rate 10-3 s-1 by test temperature 573 K. The mechanism of superplastic deformation was also investigated. For the presented material with low content of disperse particle slip on grain boundaries is typical. The final fracture is transcrystalline with dimples with their mean size 1.25 μm. The dimples are initialized by Al4C3 particles in size from 40 to 50 nm.

  8. Elevated Temperature Properties of a Dispersion Strengthened Al(Fe, V, Si) Alloy

    DTIC Science & Technology

    1991-12-01

    ASTM STP 890, M. E. Fine and E. A. Starke, Jr., Eds., American Society for Testing and Materials, pp. 211-236, 1986. 3. Raybould , D., "Forming of...and Materials Society, pp 181-197, 1988. 6. Skinner, D. J., Rye, D., Raybould , D., and Brown, A. M., "Dispersion Strengthened Al-Fe-V-Si Alloys

  9. 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.

  10. Dispersion Strengthening.

    DTIC Science & Technology

    1987-07-27

    doctoral thesis of J. Moyer. b. Quench Rate Effects: Rapid quench rate experiments (10 3 to 105 °C/min.) were performed to study the effect of carbon ... segregation in the austenite, autotempering and room temperature aging on the overall strength of several ferrous martensites. Concurrently, the

  11. On Roesler and Arzt's new model of creep in dispersion strengthened alloys

    SciTech Connect

    Orlova, A.; Cadek, J. )

    1992-08-01

    The model of creep in dispersion (noncoherent particle) strengthened alloys assuming thermally activated detachment of dislocations from particles to be the rate controlling process, recently presented by Roesler and Arzt (1990), is correlated with some available creep and structure data for aluminum alloys strengthened by Al4C3 and Al2O3 particles. It is shown that though the model requires applied stress dependent apparent activation energy of creep, the stress dependence of creep rate can be satisfactorily accounted for even when this activation energy is stress independent, admitting a strong stress dependence of the preexponential structure factor, i.e., of the mobile dislocation density. On the other hand, the model is not able to account for the temperature dependence of creep rate if it is significantly stronger than that of the coefficient of lattice diffusion, as is usually the case with alloys strengthened by noncoherent particles in which the attractive dislocation/particle interaction can be expected. 14 refs.

  12. 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.

  13. 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.

  14. Processing of Novel Nanoparticle Dispersion Strengthened Ceramics for Improved Mechanical Performance

    DTIC Science & Technology

    1993-12-14

    A2751 1 965 Eeto liii Optics MRC Materials Education M CLiaison Program Mchanical Polymers Behavior SECOND ANNUAL REPORT PROCESSING OF NOVEL...NANOPARTICLE DISPERSION STRENGTHENE D CERAMICS FOR IMPROVED MECHANICAL PE RFORMANCE Professors 11. M . Chan, (P.1.), M . P. Harmer (Co-P.I.), ___ and...Institute ONR Grant No.: N00014-92-J-1635 Mod. P00002 EPRI Contract: RP2426-54 Amend. 1 Re ,ort Period: 15 December 1992 - 14 December 1993 M ateral R

  15. Mechanical properties of dispersion strengthened copper: A comparison of braze cycle annealed and coarse grain microstructures

    SciTech Connect

    Stephens, J.J.; Bourcier, R.J.; Vigil, F.J.; Schmale, D.T.

    1988-09-01

    The tensile properties of a commercial oxide dispersion strengthened copper alloy (Glidcop A1-15, Low Oxygen Grade) have been studied at both room temperature and elevated temperatures in various microstructural conditions. The alloy has been examined in various fine grained conditions with highly elongated grains and substantial amount of cold work, as well as a coarse grained condition obtained using secondary recrystallization. The fine grained specimen conditions included the as-extruded condition, a thermal cycle of 5 minutes at 980/degree/C, appropriate for a simulated Ti-Cu-Ni braze cycle, and an extended Ti-Cu-Ni braze thermal cycle of 15 minutes at 980/degree/C. The coarse grained condition was obtained by a long term anneal, i.e., 100 hrs at 1040/degree/C. The results for room temperature tests indicated that the two braze thermal cycles had only a small effect on both yield and tensile strength, but did realize small increases in ductility, compared to the as-extruded condition. However, the coarse-grained condition exhibited significant decreases in both yield and tensile strength, along with a large increase in ductility. Both optical metallography and scanning electron microscopy were used in order to understand the changes observed in strain to fracture and fracture mode at the various temperatures. The room temperature fracture surfaces all exhibited classic ductile rupture with dimpled fracture surfaces. The fracture surfaces at higher temperatures and slower strain rates exhibited an increased tendency to fracture with some grain boundary void formation. 25 refs., 25 figs., 6 tabs.

  16. Fabrication of Ta2O5 Dispersion-Strengthened Mo-Si-B Alloy by Powder Metallurgical Method

    NASA Astrophysics Data System (ADS)

    Byun, Jong Min; Choi, Won June; Bang, Su-Ryong; Park, Chun Woong; Do Kim, Young

    2017-01-01

    In this study, we investigate the effect of oxide dispersion strengthening on mechanical properties by dispersion of nano-sized Ta2O5 particles in Mo-Si-B alloy. A Mo-Si-B core-shell powder consisting of two intermetallic compounds of Mo5SiB2 and Mo3Si as the core and nano-sized Mo solid solution surrounding intermetallic compounds was fabricated by chemical vapor transport. And Mo-Si-B core-shell powder with uniformly dispersed nano-sized Ta2O5 particles on the surface of a Mo solid solution shell was produced by a wet blending process with TaCl5 solution and heat treatment. Then, pressureless sintering was performed at 1400°C for 3 h under a H2 atmosphere. The hardness and fracture toughness of the Ta2O5-dispersed Mo-Si-B alloy were measured using Vickers hardness and 3-point bending tests, respectively. The Vickers hardness and fracture toughness of the fabricated Mo-Si-B-Ta2O5 alloy were more improved than that of the Mo-Si-B alloy fabricated using core-shell powder with no addition of Ta2O5 particles (Mo-Si-B alloy: 353 Hv, 13.5 MPa·√m, Mo-Si-B-Ta2O5 alloy: 509 Hv, 15.1 MPa·√m).

  17. 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.

  18. 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.

  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 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.

  20. The role of grain size and shape in the 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 microsstructures in Ni, Ni-2ThO2, Ni-20Cr, Ni-20CR-2ThO2, Ni-20Cr-10W-and Ni-20Cr-10W-2ThO2. The yield strength at 25 C increased with substructure refinement according to the Hall-Petch relation, and substructure refinement was a much more potent means of strengthening than was dispersion hardening. At elevated temperature (1093 C), the most important microstructural feature affecting strength was the grain aspect ratio (grain length, L, divided by grain width, 1. The yield strength and creep strength increased linearly with increasing L/1.

  1. The effect of high temperature braze thermal cycles on mechanical properties of a dispersion strengthened copper alloy

    SciTech Connect

    Stephens, J.J.; Schmale, D.T.

    1987-08-01

    Room temperature (RT) and elevated temperature (200 to 400/sup 0/C) mechanical properties were determined on thin tubes of low oxygen grade Glidcop Al-15 (CDA alloy 15715) (99.7% Cu) in both the as-cold worked condition and subsequent to high temperature braze thermal cycles. For the RT tests, three different braze thermal cycles were employed: (1) 5 min at 870/sup 0/C cycle, (2) 30 min at 870/sup 0/C cycle, (3) 5 min at 980/sup 0/C cycle. Results of RT tests showed that ultimate tensile strength declined from 486 MPa to approx.425 MPa in the thermally cycled condition. Typical tensile ductilities at RT increased from 8% to approx.18%. The effect of the braze thermal cycle is to apparently induce a modest amount of recovery (without recrystallization) in the dispersion strengthened matrix. These results are consistent with long term annealing studies conducted on solid rectangular bar pieces of Glidcop Al-15. In the elevated temperature (200 to 400/sup 0/C) tensile property tests, the effect of the braze cycle on ultimate tensile strength is most pronounced at 200/sup 0/C, but becomes negligible by 400/sup 0/C. The dependence of ultimate tensile strength on imposed strain rate and temperature can be adequately characterized by a phenomenological creep equation appropriate for the power-law breakdown regime. Analysis of the low temperature creep data for Thoria dispersed nickel of Wilcox and Clauer is included to demonstrate that the phenomenological equation used has general applicability for the case of oxide dispersion strengthened metals at homologous temperatures <0.5T/sub M/.

  2. 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.

  3. Development of oxide dispersion strengthened ferritic steels for fusion reactors

    SciTech Connect

    Mukhopadhay, D.K.; Suryanarayana, C.; Froes, F.H.; Hebeisen, J.; Gelles, D.S.

    1996-12-31

    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-13.5Cr-2W-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 C, 900 C, 1,000 C, 1,100 C and 1,200 C showed a minor decrease in the hardness.

  4. Evaluation of Oxide Dispersion Strengthened (ODS) Molybdenum Alloys

    DTIC Science & Technology

    1997-01-01

    containing 4 parts concentrated sulfuric acid and 1 part distilled water using a Type 304 stainless steel cathode and a direct current accelerating...Ductile-to-Brittle Transition Temperature ( DBTT ): The following mechanical properties were measured from the ODS molybdenum alloy rods: (a) 0.2...and to determine the DBTT . Elevated Temperature Tensile Tests: Elevated temperature tensile specimens of each as- swaged alloy were equilibrated

  5. 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.

  6. Strengthening effect of reduced graphene oxide in steel clad copper rod

    NASA Astrophysics Data System (ADS)

    Gao, Haitao; Liu, Xianghua; Ai, Zhengrong; Zhang, Shilong; Liu, Lizhong

    2016-11-01

    Reduced graphene oxide has been extensively used as reinforcing agent owing to their high mechanical properties. In this work, an attempt is made to synthesize steel clad copper rod reinforced with reduced graphene oxide (RGO) by the combination of powder-in-tube and intermediate annealing (IA). Experiments show that the Fe/RGO/Cu composites manifest better mechanical properties than Fe/Cu composites. In the process of groove rolling, RGO acts as effective binder, which can greatly improve the adhesive strength of copper scrap and two metals. Moreover, the strengthening effect of RGO is tightly related to its dispersion state. The RGO diffuses much more uniformly on the metallic substrate under the IA temperature of 1100 °C than 800 °C, which can be characterized by less deformation twins appearing at the interface of core copper and the formation of Fe-RGO-Cu transition belt at the bonding interface. In this case, the peak hardness, tensile strength and shear strength of Fe/RGO/Cu composites are 52 HV, 125 and 41 MPa higher than those of the Fe/Cu composites, respectively. The difference of strengthening effect and mechanisms of RGO under 800 and 1100 °C of IA are systematically discussed by referring to experimental results.

  7. Microstructures and properties of Al2O3 dispersion-strengthened copper alloys prepared through different methods

    NASA Astrophysics Data System (ADS)

    Yan, Zhi-qiao; Chen, Feng; Ye, Fu-xing; Zhang, Dong-ping; Cai, Yi-xiang

    2016-12-01

    Al2O3 dispersion copper alloy powder was prepared by internal oxidation, and three consolidation methods—high-velocity compaction (HVC), hot pressing (HP), and hot extrusion (HE)—were used to prepare Al2O3 dispersion-strengthened copper (Cu-Al2O3) alloys. The microstructures and properties of these alloys were investigated and compared. The results show that the alloys prepared by the HP and HE methods exhibited the coarsest and finest grain sizes, respectively. The alloy prepared by the HVC method exhibited the lowest relative density (98.3% vs. 99.5% for HP and 100% for HE), which resulted in the lowest electrical conductivity (81% IACS vs. 86% IACS for HP and 87% IACS for HE). However, this alloy also exhibited the highest hardness (77 HRB vs. 69 HRB for HP and 70 HRB for HE), the highest compressive strength (443 MPa vs. 386 MPa for HP and 378 MPa for HE), and the best hardness retention among the investigated alloys. The results illustrate that the alloy prepared by the HVC method exhibits high softening temperature and good mechanical properties at high temperatures, which imply long service life when used as spot-welding electrodes.

  8. Evaluation of dispersion strengthened nickel-base alloy heat shields for space shuttle application

    NASA Technical Reports Server (NTRS)

    Johnson, R., Jr.; Killpatrick, D. H.

    1976-01-01

    The results obtained in a program to evaluate dispersion-strengthened nickel-base alloys for use in a metallic radiative thermal protection system operating at surface temperatures to 1477 K for the space shuttle were presented. Vehicle environments having critical effects on the thermal protection system are defined; TD Ni-20Cr characteristics of material used in the current study are compared with previous results; cyclic load, temperature, and pressure effects on sheet material residual strength are investigated; the effects of braze reinforcement in improving the efficiency of spotwelded joints are evaluated; parametric studies of metallic radiative thermal protection systems are reported; and the design, instrumentation, and testing of full scale subsize heat shield panels in two configurations are described. Initial tests of full scale subsize panels included simulated meteoroid impact tests, simulated entry flight aerodynamic heating, programmed differential pressure loads and temperatures simulating mission conditions, and acoustic tests simulating sound levels experienced during boost flight.

  9. Mechanical property changes and microstructures of dispersion-strengthened copper alloys after neutron irradiation at 411, 414, and 529 degree C

    SciTech Connect

    Anderson, K.R.; Stubbins, J.F. ); Garner, F.A.; Hamilton, M.L. )

    1990-06-01

    Dispersion strengthened copper alloys have shown promise for certain high heat flux applications in both near term and long term fusion devices. This study examines mechanical properties changes and microstructural evolution in several oxide dispersion strengthened alloys which were subjected to high levels of irradiation-induced displacement damage. Irradiations were carried out in FFTF to 34 and 50 dpa at 411--414{degree}C and 32 dpa at 529{degree}C. The alloys include several oxide dispersion-strengthened alloys based on the Cu-Al system, as well as ones based on the Cu-Cr and Cu-Hf systems. Of this group, certain of the Cu-Al alloys, those produced by an internal oxidation technique to contain alumina weight fractions of 0.15 to 0.25% outperformed the other alloys in all respects. These alloys, designated CuAl15, CuAl20, and CuAl25, were found to be resistant to void swelling up to 50 dpa at 414{degree}C, and to retain their superior mechanical and physical properties after extended irradiation. The major factor which controls the stability during irradiation was found to be the dispersoid volume fraction and distribution. The other alloys examined were less resistant to radiation-induced properties changes for a variety of reasons. Some of these include dispersoid redistribution by ballistic resolution, effects of retained dissolved oxygen, and non-uniformity of dispersion distribution. The effect of laser welding was also examined. This joining technique was found to be unacceptable since it destroys the dispersoid distribution and thereby the resistance of the alloys to radiation-induced damage.

  10. Annealing behavior of alumina dispersion-strengthened copper strips rolled under different conditions

    NASA Astrophysics Data System (ADS)

    Kim, S.-H.; Lee, D. N.

    2002-06-01

    A study has been made of annealing behavior of a boron-added alumina dispersion-strengthened copper (ADSC) strip, Glidcop Al-25, and specimens fabricated by rolling of the strip by 25 to 28 pct under various conditions. All the specimens, including the starting strip, had similar microstructures consisting of microbands aligned parallel to the rolling direction. The textures of the specimens were characterized by β fiber, which runs from the copper orientation {112}<111> over the S orientation {123}<634> to the brass orientation {110}<112> in the Euler orientation space, with the intensities in the S and the brass components being higher than the copper component and with the S components having higher intensities than the brass component in the surface layers. When annealed at 1123 K for 1 hour, the center region of the starting strip and cold-rolled specimens underwent recrystallization, with recrystallization texture being approximated by {112}<312>, whereas the specimens rolled at 813 K did not undergo recrystallization through the thickness. These results have been discussed based on detailed microstructures and microtextures.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. The role of process history, phase morphology and interface strength upon the mechanical properties of dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Ansell, G. S.

    1972-01-01

    An analytical rationale for the sensitivity-insensitivity of dispersion-strengthened systems to process history is provided. In particular, the research was focussed upon the influence of the particle-matrix interface bond in TD-Nickel and TD-Nichrome, and the manner in which the differences in both elastic constants and thermal expansion coefficients between these phases stress this interface when these alloys are subjected to mechanical and thermal loads upon the mechanical properties of these alloys.

  14. Structure-property relationships in oxide-dispersed iron-beryllia alloys

    NASA Technical Reports Server (NTRS)

    Wolf, S.; Grant, N. J.

    1977-01-01

    Two BeO dispersed iron alloys containing about 2.5 and 5.5 v/o dispersoid were produced by attritting, internally oxidizing, and extruding dilute, prealloyed Fe-Be powders. As-extruded alloys were given various thermomechanical treatments involving room temperature swaging and annealing above and below the allotropic transformation temperature. The elevated temperature rupture strengths were measured and correlated with changes in structure; strengthening trends were examined in the light of proposed models for such strengthening. The results obtained showed that the elevated temperature strength was determined by the oxide interparticle spacing (IPS) in recrystallized material and IPS as well as prior deformation in swaged specimens. In fact, a parametric correlation was found between rupture strength values in the longitudinal direction with prestrain during swaging. The overall pattern in strength and microstructural observations were more consistent with a strength-stored energy (substructure) dependence than a strength-grain shape (grain aspect ratio) relation.

  15. Structure-property relationships in oxide-dispersed iron-beryllia alloys

    NASA Technical Reports Server (NTRS)

    Wolf, S.; Grant, N. J.

    1977-01-01

    Two BeO dispersed iron alloys containing about 2.5 and 5.5 v/o dispersoid were produced by attritting, internally oxidizing, and extruding dilute, prealloyed Fe-Be powders. As-extruded alloys were given various thermomechanical treatments involving room temperature swaging and annealing above and below the allotropic transformation temperature. The elevated temperature rupture strengths were measured and correlated with changes in structure; strengthening trends were examined in the light of proposed models for such strengthening. The results obtained showed that the elevated temperature strength was determined by the oxide interparticle spacing (IPS) in recrystallized material and IPS as well as prior deformation in swaged specimens. In fact, a parametric correlation was found between rupture strength values in the longitudinal direction with prestrain during swaging. The overall pattern in strength and microstructural observations were more consistent with a strength-stored energy (substructure) dependence than a strength-grain shape (grain aspect ratio) relation.

  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. 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.

  18. 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.

  19. High temperature Oxidation of ODS alloy with zirconia dispersions synthesized using Arc Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Bandriyana; Sujatno, A.; Salam, R.; Sugeng, B.; Dimyati, A.

    2017-02-01

    Microstructure formation and oxidation behaviour of the Oxide Dispersion Strengthened (ODS) steels for application as structure material in Nuclear Power Plant was investigated. A mixture composed of Fe and 12 wt. % Cr powder with addition of 0.5 and 1 wt.% ZrO2 particles was milled and isostatic pressed to form a sample coin. The coin was then consolidated in the Arc Plasma Sintering (APS) for 4 minutes. The samples were subjected to the high temperature oxidation test in the Magnetic Suspension Balance (MSB). The oxidation test was carried out at 700°C for 6 hours to evaluate the oxide growth in the early stage of it formation by extraction the mass gain curve. The Scanning Electron Microscope (SEM) imaging and X-ray Diffraction Spectroscopy (EDX) elemental mapping were performed to study the microstructure change and compositional distribution. SEM and EDX observation revealed the time dependent development of the Fe-Cr-phases during consolidation. The oxidation rate behaviour of the samples followed the parabolic rate characteristic for inward oxidation process driven by oxygen inward diffusion through the oxide scale with the maximum weight gain around of 60 g/m2. The oxidation resistance was strongly affected by the formation of the oxide protective layer on the surface. In so far, addition of zirconia particles has played no significant role to the oxidation behaviour.

  20. Strengthening Mechanisms, Creep and Fatigue Processes in Dispersion Hardened Niobium Alloy

    DTIC Science & Technology

    1992-04-01

    of dispersoids provides an attractive alternative to other strengthening methods such as solid solution stengthening , which is not effective at the...not enough, i.e. necking starts early, to establish a steady state region. As mentioned earlier in this section the shape of the creep curves cannot

  1. Improved Mechanical and Tribological Properties of Metal-Matrix Composites Dispersion-Strengthened by Nanoparticles 

    PubMed Central

    Levashov, Evgenii; Kurbatkina, Victoria; Alexandr, Zaytsev

    2009-01-01

    Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix composites (MMCs) and alloys reinforced with nanoparticles is a promising way to resolve this problem. In this work, we have investigated the effect of nano-sized WC, ZrO2, Al2O3, and Si3N4 additives on the properties of sintered dispersion-strengthened Co- and Fe-based MMCs. The results show an increase in the hardness (up to 10 HRB), bending strength (up to 50%), wear resistance (by a factor of 2–10) and a decrease in the friction coefficient (up to 4-fold) of the dispersion-strengthened materials. The use of designed alloys as a binder of cutting diamond tools gave a 4-fold increment in the service life, without reduction in their cutting speed.

  2. Non-dispersive infrared nitrous oxide detector

    SciTech Connect

    Lessure, H.; Simizu, S.; Denes, L.

    1996-12-31

    Governmental guidelines are being established for monitoring the anesthetic gas nitrous oxide (N{sub 2}O) in hospitals, dentistry and veterinary practice to guard against deleterious effects on personnel in the workplace. Yet traditional equipment for monitoring N{sub 2}O was too expensive for continuous monitoring at low concentrations. Thus, there has been a pressing need to develop low-cost high-sensitivity instruments that could be used to continuously monitor nitrous oxide in the relevant working environments. A nitrous oxide detector has been developed which is capable of detecting concentrations as low as a few ppm nitrous oxide in the presence of large changing backgrounds of 0-1,500 ppm carbon dioxide and water vapor in the range of 30-70% RH at normal room temperatures. The detector utilizes three channels to measure the IR absorption due to the N{sub 2}O relative to the CO{sub 2} background and a reference channel. The prototype devices have an LCD readout for continuous display of the readings. Additional features include an analog output for remote data acquisition and audiovisual alerts for two threshold levels. Data will be presented to show the sensitivity and performance of the detector and discuss some of the issues related to bringing it from research to its current state as a pre-production prototype.

  3. 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.

  4. Development and characterization of joining techniques for dispersion-strengthened alumina

    SciTech Connect

    Lugscheider, E.; Broich, U.; Buerger, W.

    1997-09-01

    The suitability of active brazing technology for joining TiC-strengthened alumina (ATC) to itself and to stainless steel is evaluated. The main emphasis is put on the investigation of the microstructural and mechanical properties of the active brazed joints. Furthermore, the electrical properties are investigated by determining the specific electrical resistance of active brazed Al{sub 2}O{sub 3}/TiC joints. For fabrication of the joints two process technologies are applied: vacuum furnace brazing and induction brazing under shielding gas. Four-point bend tests revealed that some of the vacuum-brazed ATC joints reach bending strengths comparable to those of bulk ATC. The induction brazing process is shown to be applicable when ATC has to be joined to metals, as in stainless steel for example. However, mechanically tough ATC-steel joints can only be fabricated when using very ductile filler metals, which are able to compensate thermally induced stresses by plastic deformation.

  5. Elastic?plastic FEM analysis on low cycle fatigue behavior for alumina dispersion-strengthened copper/stainless steel joint

    NASA Astrophysics Data System (ADS)

    Nishi, H.

    2004-08-01

    Since the first wall and divertor components of fusion power plants are subjected to severe stresses caused by thermal expansion and electromagnetic forces, it is important to evaluate the fatigue strength of joints. In this study, elastic-plastic finite element analysis was performed for low cycle fatigue behavior of stainless steel/alumina dispersion-strengthened copper (DS Cu) joint in order to investigate the fatigue life and the fracture behavior of the joint. The results showed that a strain concentration occurred at the interface during low cycle fatigue, but as the strain range increased the strain concentration shifted away from the interface and into the DS Cu. The fatigue life and fracture location were evaluated taking into account of the strain concentration. Predictions of the fatigue life and fracture location were consistent with those measured by the low cycle fatigue test.

  6. Vibronic dispersion in the copper oxide superconductors

    NASA Astrophysics Data System (ADS)

    Goodenough, J. B.; Zhou, J.-S.

    1994-02-01

    Attempts to describe the normal-state electronic behavior of the copper oxide superconductors have been unable to reconcile the following observations: (i) a well-defined Fermi surface with a locus predicted by band theory, but having charge carriers of a sign predicted for a Mott-Hubbard splitting of the band; (ii) a change in sign of the carriers to that predicted by band theory, but without a significant change in the locus of the Fermi surface, on overdoping beyond the narrow superconductive compositional range; (iii) a remarkable stability of the narrow range of superconductive charge-carrier concentrations in the CuO2 sheets even in the presence of charge transfer from nonsuperconductive intergrowth layers; (iv) a dramatic sensitivity of the Néel temperature of the parent compound to oxidation of the CuO2 sheets, but the persistence of antiferromagnetic spin fluctuations into the superconductive compositions; and (v) unusual transport properties that cannot be treated within the Migdal approximation and are insensitive to high magnetic fields. To address this impasse, we propose a phenomenological polaron model based on the observation that the system must accommodate to the coexistence of ``ionic'' and ``covalent'' Cu-O bonding having different equilibrium Cu-O bond lengths. We designate this entity a correlation polaron. Covalent Cu-O bonding with molecular-orbital formation occurs within the polaron, which moves in a background of ionic Cu-O bonding. Vibronic coupling at the ``avoided crossover'' from ionic to covalent bonding allows diffusional motion of uncoupled polarons without any motional enthalpy in the mobility. At temperatures T>Tl>~300 K the polarons are uncoupled and move randomly; in the narrow superconductive compositional range they condense below Tl to form a distinguishable thermodynamic phase consisting of extended vibronic states. In this ``polaron liquid,'' a distinction between bonding and antibonding states within the polarons opens a

  7. 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.

  8. 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.

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

    SciTech Connect

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-06

    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 Degree-Sign C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W{sub 2}C 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Low cycle fatigue strength of diffusion bonded joints of alumina dispersion-strengthened copper to stainless steel

    NASA Astrophysics Data System (ADS)

    Nishi, H.; Araki, T.

    2000-12-01

    It is proposed that the first wall and divertor components of ITER employ alumina dispersion-strengthened copper (DS Cu) joined to austenitic stainless steel. In this work, low cycle fatigue tests were performed on a direct diffusion bonded joint, a diffusion bonded joint with a Au interlayer, stainless steel and DS Cu in order to investigate their fatigue strength and fracture behavior. For the direct diffusion bonded joint, the fatigue strength in the small strain range was considerably lower than that of the DS Cu, while in the large strain range the fatigue strength was similar to that of the DS Cu. The low cycle fatigue strength of the Au interlayer joint increased compared with the direct diffusion bonded joint, and was the same as that of the DS Cu. The strain distribution in joint specimens was not uniform, because the deformation stress was different between the 316 stainless steel and the DS Cu. The fracture locations for the joint specimens varied depending on their strain distribution.

  15. Fabricating high performance tungsten alloys through zirconium micro-alloying and nano-sized yttria dispersion strengthening

    NASA Astrophysics Data System (ADS)

    Liu, R.; Xie, Z. M.; Hao, T.; Zhou, Y.; Wang, X. P.; Fang, Q. F.; Liu, C. S.

    2014-08-01

    Pure W, W-0.2wt%Zr (WZ), and W-0.2wt%Zr-1.0wt%Y2O3 (WZY) with a relative density of above 97% were fabricated by spark-plasma-sintering method. The tensile tests indicated that the WZ and WZY alloys exhibited a DBTT between 400 and 500 °C, about 200 °C lower than pure W. The ultimate tensile strength of WZY alloy at 700 °C is 534 MPa, which is 81% and 58% higher than those of WZ alloy (295 MPa) and pure W (337 MPa), respectively. The grain size of WZY alloy is about 3.2 μm, smaller than that of WZ alloy and pure W. Besides, at room temperature the fracture strength and hardness of the WZY alloy is higher than that of pure W. The improved mechanical property of the WZY alloy was suggested to be originated from the enhanced grain boundaries cohesion by Zr micro-alloying and nano-sized yttria dispersion strengthening.

  16. Microstructure and Mechanical Properties of Nano-Size Zirconium Carbide Dispersion Strengthened Tungsten Alloys Fabricated by Spark Plasma Sintering Method

    NASA Astrophysics Data System (ADS)

    Xie, Zhuoming; Liu, Rui; Fang, Qianfeng; Zhang, Tao; Jiang, Yan; Wang, Xianping; Liu, Changsong

    2015-12-01

    W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature, higher tensile strength at high temperature, and a lower ductile to brittle transition temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C-600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening. supported by the Innovation Program of Chinese Academy of Sciences (No. KJCX2-YW-N35), the National Magnetic Confinement Fusion Science Program of China (No. 2011GB108004), National Natural Science Foundation of China (Nos. 51301164, 11075177, 11274305), and Anhui Provincial Natural Science Foundation of China (No. 1408085QE77)

  17. Nitrogen Impurity Gettering in Oxide Dispersion Ductilized Chromium

    SciTech Connect

    Brady, Michael P; Anderson, Ian M; Weaver, Mark; Meyer III, Harry M; Walker, Larry R; Miller, Michael K; Larson, David James; Wright, Ian G; Sikka, Vinod K; Rar, Andrei; Pharr, George Mathews; Keiser, James R; Walls, Claudia Alexandra

    2003-01-01

    Work by Scruggs in the 1960s demonstrated that tensile ductility could be achieved at room temperature in powder metallurgically-produced Cr alloyed with MgO. During consolidation, much of the MgO converted to the MgCr{sub 2}O{sub 4} spinel phase, which was hypothesized to getter nitrogen from the Cr, rendering it ductile. We have duplicated this effect, achieving room temperature tensile elongations of 4% for hot-pressed Cr-6MgO-(0-1)Ti (wt.%) and 10% for hot-pressed and extruded Cr-6MgO-0.75Ti. Direct incorporation of nitrogen into the MgCr{sub 2}O{sub 4} phase was not detected; however, impurities, particularly nitrogen and sulfur, were observed to segregate to and/or precipitate at interfaces between the MgO/MgCr{sub 2}O{sub 4} phases and the Cr matrix. Exploratory studies of other non-spinel forming oxide dispersions (La{sub 2}O{sub 3}, TiO{sub 2} and Y{sub 2}O{sub 3}) showed a similar pattern of impurity segregation/precipitation, suggesting that there is nothing unique about spinel dispersions in Cr with regards to impurities. However, none of these other dispersions resulted in similar levels of tensile elongation.

  18. Nanosecond Laser-Assisted Nitrogen Doping of Graphene Oxide Dispersions.

    PubMed

    Kepić, Dejan; Sandoval, Stefania; Pino, Ángel Pérez Del; György, Enikö; Cabana, Laura; Ballesteros, Belén; Tobias, Gerard

    2017-02-09

    N-doped reduced graphene oxide (RGO) has been prepared in bulk form by laser irradiation of graphene oxide (GO) dispersed in an aqueous solution of ammonia. A pulsed Nd:YAG laser with emission wavelengths in the infrared (IR) 1064 nm, visible (Vis) 532 nm, and ultraviolet (UV) 266 nm spectral regions was employed for the preparation of the N-doped RGO samples. Regardless of the laser energy employed, the resulting material presents a higher fraction of pyrrolic nitrogen compared to nitrogen atoms in pyridinic and graphitic coordination. Noticeably, whereas increasing the laser fluence of UV and Vis wavelengths results in an increase in the total amount of nitrogen, up to 4.9 at. % (UV wavelength at 60 mJ cm(-2) fluence), the opposite trend is observed when the GO is irradiated in ammonia solution through IR processing. The proposed laser-based methodology allows the bulk synthesis of N-doped reduced graphene oxide in a simple, fast, and cost efficient manner.

  19. 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.

  20. 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).

  1. Solid state welding processes for an oxide dispersion strengthened nickel-chromium-aluminum alloy

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1975-01-01

    Solid-state welding processes were evaluated for joining TD-NiCrAl (Ni-16Cr-4Al-2ThO2) alloy sheet. Both hot-press and resistance spot welding techniques were successfully applied in terms of achieving grain growth across the bond line. Less success was achieved with a resistance seam welding process. In stress-rupture shear and tensile shear tests of lap joints at 1100 C, most failures occurred in the parent material, which indicates that the weld quality was good and that the welds were not a plane of weakness. The overall weld quality was not as good as previously attained with TD-NiCr, probably because the presence of alumina at the faying surfaces and the developmental TD-NiCrAl sheet, which was not of the quality of the TD-NiCr sheet in terms of surface flatness and dimensional control.

  2. Processing, Microstructure, and Material Property Relationships Following Friction Stir Welding of Oxide Dispersion Strengthened Steels

    DTIC Science & Technology

    2013-09-01

    and (b) SolidWorks image to scale of the same geometry overlaid with a machinable new geometry with an increased radius of curvature and narrower...144 Figure 4.10 (a) Cutaway SolidWorks model showing bolt restraint and seating restraint and (b) photograph of a tensile specimen...Figure 4.1c), and (c) cutaway SolidWorks model of the lead containment apparatus. ......................................................205 Figure

  3. 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.

  4. Progress in the utilization of an oxide-dispersion-strengthened alloy for small engine turbine blades

    NASA Technical Reports Server (NTRS)

    Beatty, T. G.; Millan, P. P.

    1984-01-01

    The conventional means of improving gas turbine engine performance typically involves increasing the turbine inlet temperature; however, at these higher operational temperatures the high pressure turbine blades require air-cooling to maintain durability. Air-cooling imposes design, material, and economic constraints not only on the turbine blades but also on engine performance. The use of uncooled turbine blades at increased operating temperatures can offer significantly improved performance in small gas turbine engines. A program to demonstrate uncooled MA6000 high pressure turbine blades in a GTEC TFE731 turbofan engine is being conducted. The project goals include demonstration of the advantages of using uncooled MA6000 turbine blades as compared with cast directionally solidified MAR-M 247 blades.

  5. Corrigendum to ;TEM in situ micropillar compression tests of ion irradiated oxide dispersion strengthened alloy;

    NASA Astrophysics Data System (ADS)

    Yano, K. H.; Swenson, M. J.; Wu, Y.; Wharry, J. P.

    2017-07-01

    An error was discovered by the authors in Fig. 4c of the original article. The degree of rotation is incorrectly identified as ±45°. It should be ±1.5°. This value is correctly noted in the text of the original article. A modified Fig. 4 is provided for clarity. Readers should note that this error does not alter the results or conclusions of the original article. Rather, we provide this corrigendum to eliminate a potential point of confusion for any researcher attempting to replicate our focused ion beam milling procedures for compression pillars.

  6. 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.

  7. 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.

  8. Dispersion and oxidative stability of O/W emulsions and oxidation of microencapsulated oil.

    PubMed

    Miyagawa, Yayoi; Adachi, Shuji

    2017-04-01

    Oil-in-water (O/W) emulsions are among the dispersion systems commonly used in food, and these emulsions are in thermodynamically unstable or metastable states. In this paper, various methods for preparing O/W emulsions are outlined. Since the commodity value of food is impaired by the destabilization of O/W emulsions, experimental and theoretical approaches to assess the stability of O/W emulsions are overviewed, and factors affecting the dispersion stability of emulsions are discussed based on the DLVO theory and the concept of the stability factor. The oxidation of lipids in O/W emulsions is unhealthy and gives rise to unpleasant odors. Factors affecting the autoxidation of lipids are discussed, and theoretical models are used to demonstrate that a reduction of the oil droplet size suppresses or retards autoxidation. Microencapsulated lipids or oils exhibit distinct features in the oxidation process. Models that explain these features are described. It is demonstrated that a reduction in the oil droplet size is also effective for suppressing or retarding the oxidation of microencapsulated oils.

  9. Stable zinc oxide nanoparticle dispersions in ionic liquids

    NASA Astrophysics Data System (ADS)

    Wittmar, Alexandra; Gautam, Devendraprakash; Schilling, Carolin; Dörfler, Udo; Mayer-Zaika, Wolfgang; Winterer, Markus; Ulbricht, Mathias

    2014-05-01

    The influence of the hydrophilicity and length of the cation alkyl chain in imidazolium-based ionic liquids on the dispersability of ZnO nanoparticles by ultrasound treatment was studied by dynamic light scattering and advanced rheology. ZnO nanopowder synthesized by chemical vapor synthesis was used in parallel with one commercially available material. Before preparation of the dispersion, the nanoparticles characteristics were determined by transmission electron microscopy, X-ray diffraction, nitrogen adsorption with BET analysis, and FT-IR spectroscopy. Hydrophilic ionic liquids dispersed all studied nanopowders better and in the series of hydrophilic ionic liquids, an improvement of the dispersion quality with increasing length of the alkyl chain of the cation was observed. Especially, for ionic liquids with short alkyl chain, additional factors like nanoparticle concentration in the dispersion and the period of the ultrasonic treatment had significant influence on the dispersion quality. Additionally, nanopowder characteristics (crystallite shape and size as well as the agglomeration level) influenced the dispersion quality. The results indicate that the studied ionic liquids are promising candidates for absorber media at the end of the gas phase synthesis reactor allowing the direct preparation of non-agglomerated nanoparticle dispersions without supplementary addition of dispersants and stabilizers.

  10. Environment-friendly route for stable aqueous dispersion of reduced graphene oxide for heat transfer application.

    PubMed

    Ota, Jyotiranjan; Hait, S K; Ramakumar, S S V; Basu, B; Malhotra, R K

    2013-08-01

    A simultaneous functionalization and reduction route to prepare stable dispersion of reduced graphene oxide from graphene oxide has been described. Diethanol amine has been introduced for the first time as an environment friendly reducing agent in a simple reflux reaction. Diethanol amine acts as a reducing agent and helps to enhance the stability of dispersion, making hydrogen bonding by virtue of two functional groups. The prepared dispersion of 0.025 mg/mL concentration is stable for months together and has a zeta potential value -45 V at room temperature. UV-Vis study shows peak at 264 nm that is signatory for reduced graphene oxide. TEM images confirm spread thin sheets of graphene of few hundred nanometer lateral dimension. Thermal diffusivity studies suggest nearly 60% enhancement for the dispersion in comparison to base fluid, water. This suggests graphene dispersion is promising for heat transfer applications.

  11. 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.

  12. Crossover from disordered to core-shell structures of nano-oxide Y2O3 dispersed particles in Fe

    NASA Astrophysics Data System (ADS)

    Higgins, M. P.; Lu, C. Y.; Lu, Z.; Shao, L.; Wang, L. M.; Gao, F.

    2016-07-01

    Molecular dynamic simulations of Y2O3 in bcc Fe and transmission electron microscopy (TEM) observations were used to understand the structure of Y2O3 nano-clusters in an oxide dispersion strengthened steel matrix. The study showed that Y2O3 nano-clusters below 2 nm were completely disordered. Y2O3 nano-clusters above 2 nm, however, form a core-shell structure, with a shell thickness of 0.5-0.7 nm that is independent of nano-cluster size. Y2O3 nano-clusters were surrounded by off-lattice Fe atoms, further increasing the stability of these nano-clusters. TEM was used to corroborate our simulation results and showed a crossover from a disordered nano-cluster to a core-shell structure.

  13. 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.

  14. Optimization of HIP bonding conditions for ITER shielding blanket/first wall made from austenitic stainless steel and dispersion strengthened copper alloy

    NASA Astrophysics Data System (ADS)

    Sato, S.; Hatano, T.; Kuroda, T.; Furuya, K.; Hara, S.; Enoeda, M.; Takatsu, H.

    1998-10-01

    Optimum bonding conditions were studied on the Hot Isostatic Pressing (HIP) bonded joints of type 316L austenitic stainless steel and Dispersion Strengthened Copper alloy (DSCu) for application to the ITER shielding blanket / first wall. HIP bonded joints were fabricated at temperatures in a 980-1050°C range, and a series of mechanical tests and metallurgical observations were conducted on the joints. Also, bondability of two grades of DSCu (Glidcop Al-25 ® and Al-15 ®) with SS316L was examined in terms of mechanical properties of the HIP bonded joints. From those studies it was concluded that the HIP temperature of 1050°C was an optimal condition for obtaining higher ductility, impact values and fatigue strength. Also, SS316L/Al-15 joints showed better results in terms of ductility and impact values compared with SS316L/Al-25 joints.

  15. Modifying γ-Al2O3 surface with Y2Sn2O7 pyrochlore: on monolayer dispersion behaviour of composite oxides.

    PubMed

    Xu, Xianglan; Liu, Fang; Tian, Jinshu; Peng, Honggen; Liu, Wenming; Fang, Xiuzhong; Zhang, Ning; Wang, Xiang

    2017-03-21

    To investigate the dispersion behaviours of composite oxides onto the supports, and to achieve better supports for Pd for CO oxidation, a series of Y2Sn2O7/Al2O3 composite oxides with different Y2Sn2O7 loadings were prepared via deposition-precipitation method. Using XRD and XPS extrapolation methods, it is revealed that similar to single component metal oxides, composite oxides can also disperse spantaneously onto the support surfaces to form a monlayer with a certain capacity. The monolayer dispersion capacity/threshhold for Y2Sn2O7 on γ-Al2O3 surface is 0.109 mmol*100 m-2 γ-Al2O3, equalling to 7.2% Y2Sn2O7 weight loading. It is deserved to mention here that this is the first work to demonstrate the monolayer dispersion phenomenon of a composite oxide on a support. After the combination of Y2Sn2O7 with γ-Al2O3, active oxygen species can be introduced onto the catalyst surfaces. Therefore, the interaction between Pd and the supports can be strengthened, thus improving the Pd dispersion in comparison with the individual Y2Sn2O7 support and inducing synergistic effect between Pd and the composite supports, which is beneficial to the activity of the catalysts. By tuning the γ-Al2O3 surface with different amount of pyrochlore Y2Sn2O7 compound, the CO oxidation activity on the 1%Pd/Y2Sn2O7/Al2O3 has been improved. These findings may put new insights for people to design and prepare competitve supported noble metal catalysts with less amount of noble metals.

  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. 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.

  18. 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.

  19. Transient thermal effect, nonlinear refraction and nonlinear absorption properties of graphene oxide sheets in dispersion.

    PubMed

    Zhang, Xiao-Liang; Liu, Zhi-Bo; Li, Xiao-Chun; Ma, Qiang; Chen, Xu-Dong; Tian, Jian-Guo; Xu, Yan-Fei; Chen, Yong-Sheng

    2013-03-25

    The nonlinear refraction (NLR) properties of graphene oxide (GO) in N, N-Dimethylformamide (DMF) was studied in nanosecond, picosecond and femtosecond time regimes by Z-scan technique. Results show that the dispersion of GO in DMF exhibits negative NLR properties in nanosecond time regime, which is mainly attributed to transient thermal effect in the dispersion. The dispersion also exhibits negative NLR in picosecond and femtosecond time regimes, which are arising from sp(2)- hybridized carbon domains and sp(3)- hybridized matrix in GO sheets. To illustrate the relations between NLR and nonlinear absorption (NLA), NLA properties of the dispersion were also studied in nanosecond, picosecond and femtosecond time regimes.

  20. 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.

  1. A review of the irradiation evolution of dispersed oxide nanoparticles in the b.c.c. Fe-Cr system: Current understanding and future directions

    NASA Astrophysics Data System (ADS)

    Wharry, Janelle P.; Swenson, Matthew J.; Yano, Kayla H.

    2017-04-01

    Thus far, a number of studies have investigated the irradiation evolution of oxide nanoparticles in b.c.c. Fe-Cr based oxide dispersion strengthened (ODS) alloys. But given the inconsistent experimental conditions, results have been widely variable and inconclusive. Crystal structure and chemistry changes differ from experiment to experiment, and the total nanoparticle volume fraction has been observed to both increase and decrease. Furthermore, there has not yet been a comprehensive review of the archival literature. In this paper, we summarize the existing studies on nanoparticle irradiation evolution. We note significant observations with respect to oxide nanoparticle crystallinity, composition, size, and number density. We discuss four possible contributing mechanisms for nanoparticle evolution: ballistic dissolution, Ostwald ripening, irradiation-enhanced diffusion, and homogeneous nucleation. Finally, we propose future directions to achieve a more comprehensive understanding of irradiation effects on oxide nanoparticles in ODS alloys.

  2. Mechanochemical reactions and strengthening in epoxy-cast aluminum iron-oxide mixtures

    NASA Astrophysics Data System (ADS)

    Ferranti, Louis, Jr.

    2007-12-01

    Epoxy-cast Al+Fe2O3 thermite composites are an example of a structural energetic material that can simultaneously release chemical energy while providing structural strength. The structural/mechanical response and chemical reaction behavior are closely interlinked through characteristics of deformation and intermixing of reactants. In this work, the structural and energetic response of composites made from stoichiometric mixtures of nano- and micro-scale aluminum and hematite (Fe2O3) powders dispersed in 47 to 78 vol.% epoxy was investigated by characterizing the mechanical behavior under high-strain rate and shock loading conditions. The main focus of the work was to understand the influence of microstructure on mechanical behavior in epoxy-cast Al+Fe2O3 materials when exposed to high stress, large strain, and high rate loading conditions. The material's Hugoniot at pressures up to approximately 20 GPa for an Al+Fe2O3+78 vol.% epoxy composite and up to approximately 8 GPa for Al+Fe2O3+60 vol.% epoxy composite has been determined. The results reveal an inert pressure-relative volume (P-V) and shock-particle velocity (US-UP) response in the range of the shock-conditions explored, with the Al+Fe2O3+60 vol.% epoxy composite showing a greater shock stiffness. The addition of solid particle inclusions alters the Hugoniot response as compared to pure epoxy behavior. This is attributed to possible induced bulk damage that changes the composite's response as impact stress increases. While the 78 vol.% epoxy composition shows a transition from "undamaged" to "damaged" behavior that approaches pure epoxy response, the 60 vol.% epoxy composition exhibits a gradual toughening behavior. Impact experiments have also been conducted for characterizing the high-strain rate deformation and fracture response obtained from instrumented reverse Taylor tests using high-speed camera and velocity interferometry. The results show that these composite materials exhibit viscoelastic

  3. Development of dispersion-strengthened Ni-Cr-ThOz alloys for the space shuttle thermal protection system

    NASA Technical Reports Server (NTRS)

    Blankenship, C. P.; Saunders, N. T.

    1972-01-01

    Manufacturing processes were developed for TD-NiCr providing small sheet (45 x 90 cm), and larger sheet (60 x 150 cm) and foil. The alternate alloy, DS-NiCr, was produced by pack-chromizing Ni-ThO2 sheet. Formability criteria are being established for basic sheet forming processes, which are brake forming, corrugation forming, joggling, dimpling, and beading. Resistance spot welding (fusion and solid state), resistance seam welding, solid state diffusion welding, and brazing are included in the joining programs. Major emphasis is centered on an Al-modified Ni-Cr-ThO2 alloy development. These alloys, containing 3 to 5% Al, form the protective Al2O3 scale. This enhances oxidation resistance under reentry conditions. Both TD-NiCrAl and DS-NiCrAl alloys are included. A tentative composition of Ni-16Cr-3.5Al-2ThO2 was selected based on oxidation resistance and fabricability.

  4. Dispersibility of reduced alkylamine-functionalized graphene oxides in organic solvents.

    PubMed

    Jang, Jinhee; Pham, Viet Hung; Hur, Seung Hyun; Chung, Jin Suk

    2014-06-15

    The alkylamine functionalization of graphene oxide is well known as an efficient approach to prepare reduced functionalized graphene oxide (RFGO) that is highly dispersible in organic solvents. Herein, we systematically investigated the effects of long-chain alkylamine functionalization of graphene oxide on the organic solvent dispersibility and electrical conductivity of RFGO. Three kinds of alkylamines, octylamine, dodecylamine and hexadecylamine, were chosen as functionalization agents. The alkylamine functionalization of graphene oxide was characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis and X-ray diffraction. RFGO using octylamine exhibited the best electrical conductivity of greater than 180 S/m. All of the RFGOs had excellent dispersibility, up to 3.0 mg/mL, in organic solvents, with Hansen solubility parameters in the range of 6.3<(δ(p)+δ(h))<13.7.

  5. In situ polymerization of highly dispersed polypyrrole on reduced graphite oxide for dopamine detection.

    PubMed

    Qian, Tao; Yu, Chenfei; Wu, Shishan; Shen, Jian

    2013-12-15

    A composite consisting of reduced graphite oxide and highly dispersed polypyrrole nanospheres was synthesized by a straightforward technique, by in situ chemical oxidative polymerization. The novel polypyrrole nanospheres can prevent the aggregation of reduced graphite oxide sheets by electrostatic repulsive interaction, and enhance their electrochemical properties in the nano-molar measurement of dopamine in biological systems with a linear range of 1-8000 nM and a detection limit as low as 0.3 nM.

  6. Determination of dispersion parameters for oxidizing air and the oxidation rate of calcium sulfites in a pilot desulfurization plant

    SciTech Connect

    Burenkov, D.K.; Derevich, I.V.; Rzaev, A.I.

    1995-10-01

    In the effort to remove sulfur oxides from waste gases, the widest use is gained by desulfurization plants based on wet collection of sulfur dioxide in empty absorbers in which a limestone-gypsum suspension is sprayed, with gypsum being produced as a commodity product. Dispersion of oxidizing air in a model liquid and the oxidation rate of calcium sulfites in a suspension contained in the sump of a pilot desulfurization plant absorber are studied experimentally. Flow velocities, bubble trajectories, and oxidation rates were determined and are presented.

  7. 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.

  8. Dispersing carbon-based nanomaterials in aqueous phase by graphene oxides.

    PubMed

    Li, Yilun; Yang, Juan; Zhao, Qinghua; Li, Yan

    2013-11-05

    Graphene oxides (GO) can be considered as polyelectrolytes with surfactant-like characteristics. On one hand, due to the electrical repulsion between the negatively charged ionized edges, GO exhibits great water solubility; on the other hand, its hydrophobic central plane retains the potential of strong π-π interaction with other conjugated sp(2) network structures. Therefore, it is expected that GO can serve as an excellent dispersing agent for dispersion of various carbon-based nanomaterials in aqueous phase. Here we report a systematic study of dispersing various carbon-based nanomaterials, including SWNTs, C60, and graphene, by aqueous GO. The GO-dispersed all-carbon nanocomposites are characterized using various spectroscopic methods and electron microscopies, and their stabilities are tested. Compared to other dispersing agents, the GO concentration is much lower than the concentrations of other dispersing agents used when similar contents of carbon-based nanomaterials are dispersed. Involving only simple ultrasonication and centrifugation processes, GO dispersion thus offers an easy manipulation for large-scale solution-dispersed all-carbon nanocomposites.

  9. Continuous supercritical hydrothermal synthesis of iron oxide nanoparticle dispersions and their characterization

    NASA Astrophysics Data System (ADS)

    Daschner de Tercero, M.; Röder, C.; Fehrenbacher, U.; Teipel, U.; Türk, M.

    2014-04-01

    Electrostatically stabilized iron oxide nanoparticle dispersions were synthesized using a continuous hydrothermal process at 673 K and 30 MPa. The average size of the primary particles was in the range 5-30 nm. The influence of the flow conditions as well as the composition of the starting material on the dispersion properties was investigated. A new Raman spectroscopic measurement setup was used for the characterization of the structure of the nanoparticles in dispersed form. The use of differential centrifugal sedimentation for the determination of the size distribution of the dispersed particles proved to be convenient and powerful to determine the influence of the investigated parameters on the dispersion properties. For certain compositions of the starting material and flow conditions using a conventional T-union, narrow size distributions concerning both primary particles and agglomerates could be obtained.

  10. Oxidative treatment, dispersion effect, and simulation of multi-walled carbon nanotubes in aqueous solution

    NASA Astrophysics Data System (ADS)

    Song, Kai; Guo, Li-Quan; Chen, Hui

    2017-01-01

    In the present work, the multi-walled carbon nanotubes (MWCNTs) were modified by the treatment with concentrated nitric and sulfuric acid mixture (3: 1 vol/vol). The obtained material was characterized by X-ray diffraction (XRD). The effect of two surfactants, methylcellulose (MC) and cetyltrimethylammonium bromide (CTAB) on dispersing of MWCNTs in aqueous solution was monitored by UV-Vis spectroscopy and transmission electron microscopy (TEM). Also, the dispersing effect of the surfactants was simulated by three-dimensional Monte Carlo method. The results showed that the oxidative treatment leads to purification of the neat MWCNTs, and directly improved their dispersing. The mixture containing both MC and CTAB surfactants has better dispersing effect than individual surfactants. The optimum concentration ratio of MC, CTAB, and MWCNTs was 2: 3: 1. In the simulation model, MWCNTs were dispersed randomly. The simulation results may be helpful for the further research on mechanical and electrical properties of composites reinforced with MWCNTs.

  11. Morphology of Iron-Oxide Nanoparticle-Dispersed Glass Composites

    NASA Astrophysics Data System (ADS)

    Taketomi, Susamu

    2004-10-01

    We obtained dispersed-nanocrystal/glass composites by impregnating amorphous yttrium iron garnet (YIG) nanoparticles (produced by an alkoxide method) into the 49 nm diameter pores in the spongelike structure of porous silica glass (controlled pore glass or CPG) followed by heat treatment at 1000°C for 0.1 h. We observed the surface and cross section of the sample by field emission scanning electron microscopy (FE-SEM). The backscattered electron image (BSEI) of the sample surface clearly showed the nanoparticles while the secondary electron image (SEI) showed them obscurely. A similar observation of the sample cross section revealed that the CPG fused together ˜2 μm in depth from the surface while its inner core preserved the spongelike network structure. The particles were independently dispersed with sizes ranging from 20 nm to 40 nm in this fused shell with an average particle density of approximately 100 μm-2. No particles were found in the inner core. Even in the fused shell, no particles were found in those areas in which the spongelike structure was preserved. It is concluded that the particles act as seeds for triggering the fusion of the spongelike glass.

  12. Dispersion characteristics of various metal oxide secondary nanoparticles in culture medium for in vitro toxicology assessment.

    PubMed

    Kato, Haruhisa; Fujita, Katsuhide; Horie, Masanori; Suzuki, Mie; Nakamura, Ayako; Endoh, Shigehisa; Yoshida, Yasukazu; Iwahashi, Hitoshi; Takahashi, Kayori; Kinugasa, Shinichi

    2010-04-01

    The aim of this study is to characterize the dispersion characteristics of various metal oxide nanoparticles and secondary nanoparticle formation in culture medium. Many studies have already investigated the in vitro toxicities of various metal oxide nanoparticles; however, there have been few discussions about the particle transport mode to cells during a period of toxicity assessment. The particle transport mode would strongly affect the amount of uptake by cells; therefore, estimation of the transport mode for various metal oxide particles is important. Fourteen different metal oxide nanoparticle dispersions in a culture medium were examined. The sizes of the secondary nanoparticles were observed to be larger than 100 nm by dynamic light scattering (DLS). According to Stokes law and the Stokes-Einstein assumption, pure metal oxide particles with such sizes should gravitationally settle faster than diffusion processes; however, the secondary metal oxide particles examined in this study exhibited unexpectedly slower gravitational settling rates. The slow gravitational settling kinetics of particles was estimated to be caused by the inclusion of protein into the secondary nanoparticles, which resulted in lower densities than the pure metal oxide particles. The ratios of metal oxide to protein in secondary particles could be affected by the protein adsorption ability of the corresponding metal oxide primary particles. To the best of our knowledge, it was clarified for the first time that stably dispersed secondary metal oxide nanoparticles with slow gravitational settling kinetics are induced by secondary nanoparticles consisting of small amounts of metal oxide particles and large amounts of protein, which results in lower particle densities than the pure metal oxide particles. The estimation of particle dynamics in culture medium using this method would be significant to recognize the inherent toxicity of nanoparticles.

  13. 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.

  14. 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.

  15. 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.

  16. Thermal stability and mechanical properties of HfC dispersion strengthened W alloys as plasma-facing components in fusion devices

    NASA Astrophysics Data System (ADS)

    Wang, Y. K.; Miao, S.; Xie, Z. M.; Liu, R.; Zhang, T.; Fang, Q. F.; Hao, T.; Wang, X. P.; Liu, C. S.; Liu, X.; Cai, L. H.

    2017-08-01

    HfC dispersion strengthened tungsten alloys were prepared by the spark plasma sintering (SPS) and an ordinary sintering followed by swaging, respectively. The HfC content is optimized as 0.5 wt% through spark plasma sintering (SPS) processing. The thermal stability, thermal conductivity and mechanical properties of swaged W-0.5 wt%HfC (WHC05) alloys were systematically investigated. Grain of swaged WHC05 has an obvious round bar shaped morphology with an average diameter of 24.5 μm and an average length of 187 μm, respectively, which keeps stability with increasing annealing temperature up to 1400 °C. The ductile-brittle transition temperature of swaged WHC05 is about 250 °C, much lower than that of SPSed WHC05 samples (∼500 °C). The ultimate tensile strength of swaged WHC05 alloys annealed at 1200 °C has no significant drops in a wide tested temperature range from 300 °C to 800 °C. The thermal conductivity of swaged WHC05 annealed at 1200 °C is up to 174 W/m·K at room temperature and always larger than 137 W/m·K from RT to 500 °C, which is much higher than that of the unannealed one and just the same with ITER grade W.

  17. Selective Aerobic Oxidation of Alcohols over Atomically-Dispersed Non-Precious Metal Catalysts

    SciTech Connect

    Xie, Jiahan; Yin, Kehua; Serov, Alexey; Artyushkova, Kateryna; Pham, Hien N.; Sang, Xiahan; Unocic, Raymond R.; Atanassov, Plamen; Datye, Abhaya K.; Davis, Robert J.

    2016-12-15

    Catalytic oxidation of alcohols often requires the presence of expensive transition metals. We show that earth-abundant Fe atoms dispersed throughout a nitrogen-containing carbon matrix catalyze the oxidation of benzyl alcohol and 5-hydroxymethylfurfural by O2 in the aqueous phase. Furthermore, the activity of the catalyst can be regenerated by a mild treatment in H2. An observed kinetic isotope effect indicates that β-H elimination from the alcohol is the kinetically relevant step in the mechanism, which can be accelerated by substituting Fe with Cu. Dispersed Cr, Co, and Ni also convert alcohols, demonstrating the general utility of metal–nitrogen–carbon materials for alcohol oxidation catalysis. Oxidation of aliphatic alcohols is substantially slower than that of aromatic alcohols, but adding 2,2,6,6-tetramethyl-1-piperidinyloxy as a co-catalyst with Fe can significantly improve the reaction rate.

  18. 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.

  19. 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

  20. Conversion of nitrogen oxides on commercial photocatalytic dispersion paints

    NASA Astrophysics Data System (ADS)

    Laufs, S.; Burgeth, G.; Duttlinger, W.; Kurtenbach, R.; Maban, M.; Thomas, C.; Wiesen, P.; Kleffmann, J.

    2010-06-01

    In the present study, photocatalytic reactions of nitrogen oxides (NO x = NO + NO 2) were studied on commercial TiO 2 doped facade paints in a flow tube photoreactor under simulated atmospheric conditions. Fast photocatalytic conversion of NO and NO 2 was observed only for the photocatalytic paints and not for non-catalytic reference paints. Nitrous acid (HONO) was formed in the dark on all paints studied, however, it efficiently decomposes under irradiation only on the photocatalytic samples. Thus, it is concluded that photocatalytic paint surfaces do not represent a daytime source of HONO, in contrast to other recent studies on pure TiO 2 surfaces. As main final product, the formation of adsorbed nitric acid/nitrate anion (HNO 3/NO 3-) was observed with near to unity yield. In addition, traces of H 2O 2 were observed in the gas phase only in the presence of O 2. Formation of the greenhouse gas nitrous oxide (N 2O) could be excluded. The uptake kinetics of NO, NO 2 and HONO was very fast under atmospheric conditions (e.g. γ(NO + TiO 2) > 10 -5). Thus, the uptake on urban surfaces (painted houses, etc.) will be limited by transport. For a hypothetically painted street canyon, an average reduction of nitrogen oxide levels of ca. 5% is estimated. Since the harmful HNO 3/NO 3- is formed on the surface of the photoactive paints, whereas it is formed in the gas phase in the atmosphere, the use of photocatalytic paints may also help to reduce acid deposition, e.g. on plants, or nitric acid related health issues.

  1. Oral Rg1 supplementation strengthens antioxidant defense system against exercise-induced oxidative stress in rat skeletal muscles

    PubMed Central

    2012-01-01

    Background Previous studies reported divergent results on nutraceutical actions and free radical scavenging capability of ginseng extracts. Variations in ginsenoside profile of ginseng due to different soil and cultivating season may contribute to the inconsistency. To circumvent this drawback, we assessed the effect of major ginsenoside-Rg1 (Rg1) on skeletal muscle antioxidant defense system against exhaustive exercise-induced oxidative stress. Methods Forty weight-matched rats were evenly divided into control (N = 20) and Rg1 (N = 20) groups. Rg1 was orally administered at the dose of 0.1 mg/kg bodyweight per day for 10-week. After this long-term Rg1 administration, ten rats from each group performed an exhaustive swimming, and remaining rats considered as non-exercise control. Tibialis anterior (TA) muscles were surgically collected immediately after exercise along with non-exercise rats. Results Exhaustive exercise significantly (p<0.05) increased the lipid peroxidation of control group, as evidenced by elevated malondialdehyde (MDA) levels. The increased oxidative stress after exercise was also confirmed by decreased reduced glutathione to oxidized glutathione ratio (GSH/GSSG ratio) in control rats. However, these changes were completely eliminated in Rg1 group. Catalase (CAT) and glutathione peroxidase (GPx) activities were significantly (p<0.05) increased by Rg1 in non-exercise rats, while no significant change after exercise. Nevertheless, glutathione reductase (GR) and glutathione S-transferase (GST) activities were significantly increased after exercise in Rg1 group. Conclusions This study provide compelling evidences that Rg1 supplementation can strengthen antioxidant defense system in skeletal muscle and completely attenuate the membrane lipid peroxidation induced by exhaustive exercise. Our findings suggest that Rg1 can use as a nutraceutical supplement to buffer the exhaustive exercise-induced oxidative stress. PMID:22607394

  2. 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

  3. 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.

  4. Selective Aerobic Oxidation of Alcohols over Atomically-Dispersed Non-Precious Metal Catalysts

    DOE PAGES

    Xie, Jiahan; Yin, Kehua; Serov, Alexey; ...

    2016-12-15

    Catalytic oxidation of alcohols often requires the presence of expensive transition metals. We show that earth-abundant Fe atoms dispersed throughout a nitrogen-containing carbon matrix catalyze the oxidation of benzyl alcohol and 5-hydroxymethylfurfural by O2 in the aqueous phase. Furthermore, the activity of the catalyst can be regenerated by a mild treatment in H2. An observed kinetic isotope effect indicates that β-H elimination from the alcohol is the kinetically relevant step in the mechanism, which can be accelerated by substituting Fe with Cu. Dispersed Cr, Co, and Ni also convert alcohols, demonstrating the general utility of metal–nitrogen–carbon materials for alcohol oxidationmore » catalysis. Oxidation of aliphatic alcohols is substantially slower than that of aromatic alcohols, but adding 2,2,6,6-tetramethyl-1-piperidinyloxy as a co-catalyst with Fe can significantly improve the reaction rate.« less

  5. Platinum particles dispersed poly(diphenylamine) modified electrode for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Santhosh, P.; Gopalan, A.; Vasudevan, T.; Lee, Kwang-Pill

    2006-09-01

    A modified potentiostatic method, termed the 'pulse pontentiostatic method' (PPSM) was used to get nano fibrillar poly(diphenylamine) (PDPA) film on Indium tin oxide (ITO) coated glass electrode and also for making modified electrode with platinum particles dispersed in PDPA. Platinum clusters were electrodispersed under constant potential on PDPA films to obtain catalytic electrodes for methanol oxidation. Energy dispersive analysis of X-rays (EDAX) results showed that the Pt microparticles are deposited into PDPA film. Scanning electron micrograph, SEM images show that the deposition results spherical catalytic particles. X-ray photoelectron spectroscopy (XPS) results inform that the net electronic charge on carbon atom and also the imine/amine ratio was not affected by Pt loadings. The modification of electrode surface by nano fibular PDPA improves the electrocatalytic activity for methanol oxidation.

  6. Synthesis and Properties of Highly Dispersed Ionic Silica–Poly(ethylene oxide) Nanohybrids

    PubMed Central

    2013-01-01

    We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent. PMID:23351113

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Resonance Raman scattering from Cd1-xZnxS nanoparticles dispersed in oxide glass

    NASA Astrophysics Data System (ADS)

    Arora, Akhilesh K.; Rajalakshmi, M.

    2000-11-01

    Resonance Raman scattering from 1 and 2 LO phonons is investigated from Cd1-xZnxS nanoparticles dispersed in oxide glass before and after annealing. The resonance profiles are found to exhibit asymmetry which is attributed to the interference effects arising from a nonresonant contribution to the polarizability. The energies of the resonances are found to be consistent with the direct interband transition energies estimated from the reported optical data.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. Electro-deposition of oxide-dispersed nickel composites and the behavior of their mechanical properties

    NASA Astrophysics Data System (ADS)

    Kim, Myong Jin; Kim, Joung Soo; Kim, Dong Jin; Kim, Hong Pyo

    2009-10-01

    Oxide-dispersed nickel composites were produced by electro-deposition of nickel with various types of oxide nano-powders in a sulfamate bath. The effect of the oxide concentration in the bath on the mechanical properties of the electro-deposited composites was studied. The current efficiency of the electro-deposition process was analyzed for different types of oxide nano-powders and for in terms of the amounts embedded in the nickel (Ni) matrix. To evaluate the mechanical strength and the thermal stability, micro-hardness, tensile strength and elongation were measured at room temperature for composites that were heat-treated in a temperature range of 298 K to 1123 K. The results of the experiments showed that a higher oxide powder concentration in the bath led to a greater amount of the oxide particle co-deposited in the nickel matrix. This resulted in higher micro-hardness and improved high-temperature thermal stability. However, an inhomogeneous distribution of the co-deposited oxide powders in the composites was observed to weaken the thermal stability of their tensile strength and elongation.

  18. 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

  19. 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.

  20. Furoxan Nitric Oxide Donors Disperse Pseudomonas aeruginosa Biofilms, Accelerate Growth, and Repress Pyoverdine Production.

    PubMed

    Poh, Wee Han; Barraud, Nicolas; Guglielmo, Stefano; Lazzarato, Loretta; Rolando, Barbara; Fruttero, Roberta; Rice, Scott A

    2017-08-18

    The use of nitric oxide (NO) as a signal for biofilm dispersal has been shown to increase the susceptibility of many biofilms to antibiotics, promoting their eradication. The delivery of NO to biofilms can be achieved by using NO donors with different kinetics and properties of NO release that can influence their efficacy as biofilm control agents. In this study, the kinetics of three furoxan derivatives were evaluated. The effects of these NO donors, which have an advantageous pharmacological profile of slower onset with an extended duration of action, on Pseudomonas aeruginosa growth, biofilm development, and dispersal were also characterized. Compound LL4254, which showed a fast rate of NO release, induced biofilm dispersal at approximately 200 μM. While LL4212 and LL4216 have a slower rate of NO release, both compounds could induce biofilm dispersal, under the same treatment conditions, when used at higher concentrations. In addition, LL4212 and LL4216 were found to promote P. aeruginosa growth in iron-limited minimal medium, leading to a faster rate of biofilm formation and glucose utilization, and ultimately resulted in early dispersal of biofilm cells through carbon starvation. High concentrations of LL4216 also repressed production of the siderophore pyoverdine by more than 50-fold, via both NOx-dependent and NOx-independent mechanisms. The effects on growth and pyoverdine levels exerted by the furoxans appeared to be mediated by NO-independent mechanisms, suggesting functional activities of furoxans in addition to their release of NO and nitrite. Overall, this study reveals that secondary effects of furoxans are important considerations for their use as NO-releasing dispersal agents and that these compounds could be potentially redesigned as pyoverdine inhibitors.

  1. A Method for Converting Aqueous Demetallization Products into Dispersed Metal Oxide Nanocatalysts in Heavy Oil

    NASA Astrophysics Data System (ADS)

    Abdrabo, Amr Abdelrazek Elgeuoshy Meghawry

    Metallic heteroatoms deactivate expensive catalyst and, thus, should be removed at early stages during crude oil processing. Electro and biological demetallization are examples of two emerging techniques which remove the metallic heteroatoms; mainly nickel and vanadium, into ions or ionic complexes ultimately residing in the aqueous phase of a two phase water/oil system. This work investigates the conversion of the aqueous metallic species into metal oxide nanoparticles, which are effective upgrading catalysts, dispersed in the oil phase. The conversion step commenced in-situ within a water-in-oil emulsion structure, and the resultant nanoparticles remain very well dispersed in the heavy oil phase. The product nanoparticles were characterized, after successful collection from the oil phase, using X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-Ray spectroscopy (EDX). Despite the complexity of the heavy oil system, results confirmed the in-situ formation of NiO and V2O5 nanoparticles with mean sizes of 20 and 15 nm, respectively. Some aggregates have, nevertheless, formed, due to the relatively high temperature requirement of the method. Investigating the catalytic role of the as-prepared nanoparticles was limited to the NiO nanoparticles, since only low concentrations of V 2O5 could be prepared. An attempt to increase the concentration of dispersed V2O5 by using precursors with higher solubility in water was not successful. A semi-batch reactor setup was employed to investigate the catalytic hydrocracking of heavy oil in the presence of dispersed NiO nanoparticles. On the other hand, batch reactor arrangement was employed to study the thermalcracking of heavy oil in the presence of dispersed NiO nanoparticles.

  2. The rheology of oxide dispersions and the role of concentrated electrolyte solutions

    SciTech Connect

    Biggs, Simon; Tindley, Amy

    2007-07-01

    Stability control of particulate dispersions is critical to a wide range of industrial processes. In the UK nuclear industry, significant volumes of waste materials arising from the corrosion products of Magnox fuel rods currently require treatment and storage. The majority of this waste is present as aqueous dispersions of oxide particulates. Treatment of these dispersions will require a variety of unit operations including mobilisation, transport and solid- liquid separation. Typically these processes must operate across a narrow optimal range of pH and the dispersions are, almost without exception, found in complex electrolyte conditions of high overall concentration. Knowledge of the behaviour of oxides in various electrolyte conditions and over a large pH range is essential for the efficient design and control of any waste processing approach. The transport properties of particle dispersions are characterised by the rheological properties. It is well known that particle dispersion rheology is strongly influenced by particle-particle interaction forces, and that particle-particle interactions are strongly influenced by adsorbed ions on the particle surfaces. Here we correlate measurements of the shear yield stress and the particle zeta potentials to provide insight as to the role of ions in moderating particle interactions. The zeta potential of model TiO{sub 2} suspensions were determined (Colloidal Dynamics Zeta Probe) over a range of pH for a series of alkali metal halides and quaternary ammonium halides at a range of solution concentrations (0.001 M - 1 M). The results show some surprising co-ion effects at high electrolyte concentrations (>0.5 M) and indicate that even ions generally considered to be indifferent induce a shift in iso-electric point (i.e.p.) which is inferred as being due to specific adsorption of ions. The shear yield stress values of concentrated titania dispersions were measured using a Bohlin C-VOR stress controlled rheometer. The shear

  3. Effects of oil dispersant on ozone oxidation of phenanthrene and pyrene in marine water.

    PubMed

    Gong, Yanyan; Zhao, Dongye

    2017-04-01

    This work investigated effects of a popular oil dispersant (Corexit EC9500A) on oxidation of phenanthrene and pyrene (two model polycyclic aromatic hydrocarbons) in Gulf coast seawater under simulated atmospheric ozone. The degradation data followed a two-stage pseudo-first order kinetics, a slower initial reaction rate followed by a much faster rate in longer time. The ozonation rate for pyrene was faster than that for phenanthrene. The presence of 18 and 180 mg/L of the dispersant inhibited the first-order degradation rate by 32-80% for phenanthrene, and 51-85% for pyrene. In the presence of 18 mg/L of the dispersant, the pyrene degradation rate increased with increasing ozone concentration, but decreased with increasing solution pH and temperature, while remained independent of ionic strength. For the first time, the results indicate that atmospheric ozone may play a significant role in the weathering of dispersed persistent oil components in natural and engineered systems.

  4. 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.

  5. Fabricating Water Dispersible Superparamagnetic Iron Oxide Nanoparticles for Biomedical Applications through Ligand Exchange and Direct Conjugation

    PubMed Central

    Lam, Tina; Avti, Pramod K.; Pouliot, Philippe; Maafi, Foued; Tardif, Jean-Claude; Rhéaume, Éric; Lesage, Frédéric; Kakkar, Ashok

    2016-01-01

    Stable superparamagnetic iron oxide nanoparticles (SPIONs), which can be easily dispersed in an aqueous medium and exhibit high magnetic relaxivities, are ideal candidates for biomedical applications including contrast agents for magnetic resonance imaging. We describe a versatile methodology to render water dispersibility to SPIONs using tetraethylene glycol (TEG)-based phosphonate ligands, which are easily introduced onto SPIONs by either a ligand exchange process of surface-anchored oleic-acid (OA) molecules or via direct conjugation. Both protocols confer good colloidal stability to SPIONs at different NaCl concentrations. A detailed characterization of functionalized SPIONs suggests that the ligand exchange method leads to nanoparticles with better magnetic properties but higher toxicity and cell death, than the direct conjugation methodology.

  6. Manipulation of structural color reflection in graphene oxide dispersions using electric fields.

    PubMed

    Hong, Seung-Ho; Shen, Tian-Zi; Song, Jang-Kun

    2015-07-27

    Aqueous graphene oxide (GO) dispersions with a photonic crystal structure are carefully prepared to produce structural color reflection. We fabricate a simple reflective GO cell with a unique electrode design and demonstrate that the resulting structural color reflection is electrically erasable and rewritable. GO concentration and the direction of the electric field are vital factors in the development of the device. The resulting device works well, although it exhibits a rather slow response time; in particular, the spontaneous recovery time from dark to bright color reflection requires tens of minutes. Through the application of a horizontal electric field parallel to the substrate, the recovery time can be improved, resulting in a recovery period of 3 min. Although many unsolved issues remain, the findings in GO dispersion may provide a new possibility for color filter-less bi-stable color displays with low power consumption.

  7. Colloidal processing of chemically prepared zinc oxide varistors. Part 1, milling and dispersion of powder.

    SciTech Connect

    Lockwood, Steven John; Cesarano, Joseph, III; Voigt, James A.; Bell, Nelson Simmons; Dimos, Duane Brian

    2003-07-01

    Chemically prepared zinc oxide powders are fabricated for the production of high aspect ratio varistor components. Colloidal processing was performed to reduce agglomerates to primary particles, form a high solids loadingslurry, and prevent dopant migration. The milled and dispersed powder exhibited a viscoelastic to elastic behavioral transition at a volume loading of 43-46%. The origin of this transition was studied using acoustic spectroscopy, zeta potential measurements, and oscillatory rheology. The phenomenon occurs due to a volume fraction solids dependent reduction in the zeta potential of the solid phase. It is postulated to result from divalent ion binding within the polyelectrolyte dispersant chain and was mitigated using a polyethylene glycol plasticizing additive. This allowed for increased solids loading in the slurry and a green body fabrication study to be presented in our companion paper.

  8. 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.

  9. 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)

  10. Oxidation and dispersion of HT in the environment: the August 1986 field experiment at Chalk River.

    PubMed

    Brown, R M; Ogram, G L; Spencer, F S

    1990-02-01

    The short-range environmental dispersion and oxidation of a release of tritiated hydrogen (HT) to the atmosphere has been studied in a field experiment. Emphasis was placed on the processes leading to the appearance of tritiated water (HTO) vapor in the atmosphere because HTO is much more radiotoxic than HT. The following conclusions were reached: No evidence was found for the rapid conversion of HT to HTO in the atmosphere; HTO observed in air, during and after the release, arose mainly from HT oxidation in the soil followed by emission of HTO; HT deposition velocities to soil ranged from 0.041 cm s-1 to 0.13 cm s-1, consistent with previous chamber measurements; the rate of HTO loss from soil, averaged over 21 d, was less than 1% h-1; and HTO concentrations in vegetation water initially increased with time after the release, then by 48 h decreased exponentially at a rate similar to soils.

  11. Atomic-scale chemical quantification of oxide interfaces using energy-dispersive X-ray spectroscopy

    SciTech Connect

    Lu, Ping; Van Benthem, Mark; Xiong, Jie; Jia, Quanxi

    2013-04-29

    Atomic-scale quantification of chemical composition across oxide interfaces is important for understanding physical properties of epitaxial oxide nanostructures. Energy-dispersive X-ray spectroscopy (EDS) in an aberration-corrected scanning transmission electron microscope was used to quantify chemical composition across the interface of ferromagnetic La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and antiferromagnetic BiFeO{sub 3} quantum structure. This research demonstrates that chemical composition at atomic columns can be quantified by Gaussian peak-fitting of EDS compositional profiles across the interface. Cation diffusion was observed at both A- and B-sublattice sites; and asymmetric chemical profiles exist across the interface, consistent with the previous studies.

  12. 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

  13. A one-step, solvothermal reduction method for producing reduced graphene oxide dispersions in organic solvents.

    PubMed

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

    2010-07-27

    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 degrees 2theta (3.4 A), 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.

  14. 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.

  15. Synthesis of nickel nanoparticles supported on metal oxides using electroless plating: controlling the dispersion and size of nickel nanoparticles.

    PubMed

    Wu, Zhijie; Ge, Shaohui; Zhang, Minghui; Li, Wei; Tao, Keyi

    2009-02-15

    Nickel nanoparticles supported on metal oxides were prepared by a modified electroless nickel-plating method. The process and mechanism of electroless plating were studied by changing the active metal (Ag) loading, acidity, and surface area of metal oxides and were characterized by UV-vis spectroscopy, transmission electron microscopy, scanning electron microscopy, and H(2) chemisorption. The results showed that the dispersion of nickel nanoparticles was dependent on the interface reaction between the metal oxide and the plating solution or the active metal and the plating solution. The Ag loading and acidity of the metal oxide mainly affected the interface reaction to change the dispersion of nickel nanoparticles. The use of ultrasonic waves and microwaves and the change of solvents from water to ethylene glycol in the electroless plating could affect the dispersion and size of nickel nanoparticles.

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

    PubMed

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

    2015-12-02

    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.

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. Tailoring the chemical composition and dispersion behavior of fluorinated graphene oxide via CF4 plasma

    NASA Astrophysics Data System (ADS)

    Zhou, Baoming; Qian, Xiaoming; Li, Mingming; Ma, Jilan; Liu, Liangsen; Hu, Chuansheng; Xu, Zhiwei; Jiao, Xiaoning

    2015-03-01

    Grafting fluorine onto graphene oxide (GO) by CF4 plasma treatment was investigated in this study. An easy, low-cost, and effective synthesis of the high-dispersive fluorinated GO (FGO) with tunable atomic ratio of F/O ( R F/O) has been realized and the R F/O can be readily manipulated just by adjusting the reaction time. The influence of plasma treatment time on the microstructure, morphology, and dispersion of graphene nanosheets was systematically analyzed. X-ray photoelectron spectroscopy analysis confirmed that fluorine has been grafted onto graphene, and the R F/O was gradually increased to 3.54 for the FGO treated for 20 min. Morphology investigation indicated that etching on the edge of GO occurred during the fluorination. The dispersion performance of FGO in water reduced continuously, which in N, N-dimethylacetamide (DMAc) increased firstly and then decreased with the increase in plasma time. The zeta potentials of FGO in DMAc reached the lowest at -28.6 mV when GO was treated for 10 min. The dispersion of FGO in water should be attributed to the decrease of C-O group, while there was a same variation trend of FGO zeta potential in DMAc as the value of C-F content, regardless of R F/O, CF2 group content and CF3 group content. The GO film was super-hydrophilic and the film of FGO treated for 20 min was found to be neither hydrophilic nor hydrophobic.

  3. 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.

  4. 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

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

    PubMed

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

    2016-02-11

    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.

  6. 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.

  7. Water dispersible superparamagnetic Cobalt iron oxide nanoparticles for magnetic fluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Salunkhe, Ashwini B.; Khot, Vishwajeet M.; Ruso, Juan M.; Patil, S. I.

    2016-12-01

    Superparamagnetic nanoparticles of Cobalt iron oxide (CoFe2O4) are synthesized chemically, and dispersed in an aqueous suspension for hyperthermia therapy application. Different parameters such as magnetic field intensity, particle concentration which regulates the competence of CoFe2O4 nanoparticle as a heating agents in hyperthermia are investigated. Specific absorption rate (SAR) decreases with increase in the particle concentration and increases with increase in applied magnetic field intensity. Highest value of SAR is found to be 91.84 W g-1 for 5 mg. mL-1 concentration. Oleic acid conjugated polyethylene glycol (OA-PEG) coated CoFe2O4 nanoparticles have shown superior cyto-compatibility over uncoated nanoparticles to L929 mice fibroblast cell lines for concentrations below 2 mg. mL-1. Present work provides the underpinning for the use of CoFe2O4 nanoparticles as a potential heating mediator for magnetic fluid hyperthermia.

  8. Graphene oxides dispersing and hosting graphene sheets for unique nanocomposite materials.

    PubMed

    Tian, Leilei; Anilkumar, Parambath; Cao, Li; Kong, Chang Yi; Meziani, Mohammed J; Qian, Haijun; Veca, L Monica; Thorne, Tim J; Tackett, Kenneth N; Edwards, Travis; Sun, Ya-Ping

    2011-04-26

    Graphene oxides (GOs), beyond their widely reported use as precursors for single-layer graphene sheets, are in fact excellent materials themselves (polymers in two-dimension, polyelectrolyte-like, aqueous solubility and biocompatibility, etc.). In this reported work we used aqueous GOs to effectively disperse few-layer graphene sheets (GNs) in suspension for facile wet-processing into nanocomposites of GNs embedded in GOs (as the polymeric matrix). The resulting lightweight and plastic-like nanocomposite materials remained mechanically flexible even at high loadings of GNs, and they were found to be highly efficient in thermal transport, with the experimentally determined thermal diffusivity competitive to those typically observed only in well-known thermally conductive metals such as aluminum and copper. As demonstrated, GOs apparently represent a unique class of two-dimensional polymeric materials for potentially "all-carbon" nanocomposites, among others, which may find technological applications independent of those widely proclaimed for graphene sheets.

  9. Magnetic Investigations of Titanium Doped Gamma Iron Oxides Dispersed in Polymers

    NASA Astrophysics Data System (ADS)

    Chipara, Mircea; Morjan, Ioan; Zaleski, Jeffrey

    2005-03-01

    Titanium doped gamma iron oxide nanoparticles were prepared by laser pyrolisis. X-Ray studies indicated the presence of γ Fe2O3 and β FeO(OH). Small amounts of γ titanium maghemite were observed. The average particle size is 5 nm (Transmission Electron Microscopy). Magnetic nanoparticles were dispersed by sonicating a solution of styrene-isoprene-styrene blockcopolymer. The solvent was evaporated by heating at 75 ^0C for 24 hours. The as obtained films were studied by SQUID and ferromagnetic resonance (FMR). The temperature dependence of the magnetization and of hysteresis loops in the temperature range 4 K -- 300 K is reported. The temperature dependence of FMR line parameters in then range 100 K to 450 K is reported. A weak matrix effect within the glass transition range of the polymeric matrix has been observed.

  10. AMPK activation promotes lipid droplet dispersion on detyrosinated microtubules to increase mitochondrial fatty acid oxidation

    PubMed Central

    Herms, Albert; Bosch, Marta; Reddy, Babu J.N.; Schieber, Nicole L.; Fajardo, Alba; Rupérez, Celia; Fernández-Vidal, Andrea; Ferguson, Charles; Rentero, Carles; Tebar, Francesc; Enrich, Carlos; Parton, Robert G.; Gross, Steven P.; Pol, Albert

    2015-01-01

    Lipid droplets (LDs) are intracellular organelles that provide fatty acids (FAs) to cellular processes including synthesis of membranes and production of metabolic energy. While known to move bidirectionally along microtubules (MTs), the role of LD motion and whether it facilitates interaction with other organelles are unclear. Here we show that during nutrient starvation, LDs and mitochondria relocate on detyrosinated MT from the cell centre to adopt a dispersed distribution. In the cell periphery, LD–mitochondria interactions increase and LDs efficiently supply FAs for mitochondrial beta-oxidation. This cellular adaptation requires the activation of the energy sensor AMPK, which in response to starvation simultaneously increases LD motion, reorganizes the network of detyrosinated MTs and activates mitochondria. In conclusion, we describe the existence of a specialized cellular network connecting the cellular energetic status and MT dynamics to coordinate the functioning of LDs and mitochondria during nutrient scarcity. PMID:26013497

  11. 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.

  12. Suppression of grain growth in nanocrystalline Bi2Te3 through oxide particle dispersions

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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) Bi2Te3 to be retained up to a homologous temperature of 0.94 Tm 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 -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.

  13. Results of recent reactor-material tests on dispersal of oxide fuel from a disrupted core

    SciTech Connect

    Spencer, B.W.; Wilson, R.J.; Vetter, D.L.; Erickson, E.G.; Dewey, G.

    1985-01-01

    The results of experimental investigations and related analyses are reported addressing the dispersal of molten oxide fuel from a disrupted core via various available pathways for the CRBR system. These investigations included the GAPFLOW tests in which pressure-driven and gravity drainage tests were performed using dispersal pathways mocking up the intersubassembly gaps, the CAMEL C6 and C7 tests in which molten fuel entered sodium-filled control assembly ducts under prototypic thermal-hydraulic conditions, and the Lower Internals Drainage (LID) tests in which molten fuel drained downward through simulated below-core structure (orifice plate stacks) as the bottom of control assembly ducts. The results of SHOTGUN tests addressing basic freezing of molten UO/sub 2/ and UO/sub 2//metal mixtures flowing through circular tubes are also reported. Test results have invariably shown the existance of stable UO/sub 2/ crusts on the inside surfaces of the flow paths. Appreciable removal of fuel was indicated prior to freezing-induced immobilization. Application of heat transfer models based upon the presence of stable, insulating fuel crusts tends to overpredict the removal process.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Stanley, Jacob; Boucheron, Leandra; Lin, Binhua; Meron, Mati; Shpyrko, Oleg

    2015-04-01

    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.

  17. [Preparation of budesonide-poly (ethylene oxide) solid dispersions using supercritical carbon dioxide and in vitro evaluation].

    PubMed

    Liu, Hui; Pan, Wei-san; Zhou, Li-li; Zhang, Zhi-hong

    2007-02-01

    An application of supercritical fluids technology for processing of budesonide-poly (ethylene oxide) solid dispersions was presented. The correlations of the operation parameters in the preparation process were studied. Solid dispersions of budesonide in poly (ethylene oxide) were prepared using a static method for supercritical carbon dioxide and characterized by powder X-ray diffractometry, differential scanning calorimetry, intrinsic dissolution, and in vitro dissolution. It was found that the optimum condition of solid dispersions formation was as follows: temperature, 40 degrees C ; pressure, 20 MPa; the ratio of budesonide and poly (ethylene oxide) , 1: 10. Drug existed in amorphous state in hydrophilic poly (ethylene oxide) carriers and intrinsic solubility and dissolution rates were significantly enhanced. The mechanism of the enhanced dissolution may be attributed to the amorphous character of the budesonide, improvement of the wettability of the hydrophobic budesonide, together with the formation of hydrogen bond of budesonide and hydrophilic poly (ethylene oxide). The supercritical fluids process can be used as an alternative method for preparation of solid dispersions.

  18. Effects of nickel-oxide nanoparticle pre-exposure dispersion status on bioactivity in the mouse lung.

    PubMed

    Sager, Tina; Wolfarth, Michael; Keane, Michael; Porter, Dale; Castranova, Vincent; Holian, Andrij

    2016-01-01

    Nanotechnology is emerging as one of the world's most promising new technologies. From a toxicology perspective, nanoparticles possess two features that promote their bioactivity. The first involves physical-chemical characteristics of the nanoparticle, which include the surface area of the nanoparticle. The second feature is the ability of the nanoparticle to traverse cell membranes. These two important nanoparticle characteristics are greatly influenced by placing nanoparticles in liquid medium prior to animal exposure. Nanoparticles tend to agglomerate and clump in suspension, making it difficult to reproducibly deliver them for in vivo or in vitro experiments, possibly affecting experimental variability. Thus, we hypothesize that nanoparticle dispersion status will correlate with the in vivo bioactivity/toxicity of the particle. To test our hypothesis, nano-sized nickel oxide was suspended in four different dispersion media (phosphate-buffered saline (PBS), dispersion medium (DM), a combination of dipalmitoyl-phosphatidyl choline (DPPC) and albumin in concentrations that mimic diluted alveolar lining fluid), Survanta®, or pluronic (Pluronic F-68). Well-dispersed and poorly dispersed suspensions were generated in each media by varying sonication time on ice utilizing a Branson Sonifer 450 (25W continuous output, 20 min or 5 min, respectively). Mice (male, C57BL/6J, 7-weeks-old) were given 0-80 µg/mouse of nano-sized nickel oxide in the different states of dispersion via pharyngeal aspiration. At 1 and 7 d post-exposure, mice underwent whole lung lavage to assess pulmonary inflammation and injury as a function of dispersion status, dose and time. The results show that pre-exposure dispersion status correlates with pulmonary inflammation and injury. These results indicate that a greater degree of pre-exposure dispersion increases pulmonary inflammation and cytotoxicity, as well as decreases in the integrity of the blood-gas barrier in the lung.

  19. 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. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Environmentally friendly synthesis of p-doped reduced graphene oxide with high dispersion stability by using red table wine.

    PubMed

    Kim, Suk-Joon; Lee, Jang Mi; Kumer, Roy Arup; Park, Sung Young; Kim, Sang Chun; In, Insik

    2015-05-01

    Reduced graphene oxide (rGO) with high dispersion stability and p-type semiconducting property was synthesized by using environmentally friendly mussel-inspired chemistry with red table wine. (+)-Catechin and tannic acid, polyphenolic model compounds present in wine, were selected and successfully utilized for the synthesis of soluble polycatechol-functionalized rGO.

  1. Surface plasmon strengthened nonlinearity in indium-tin-oxide coated Cu-doped potassium sodium barium strontium niobate crystals

    NASA Astrophysics Data System (ADS)

    Zhao, Hua; Li, Liang; Hu, Guangwei; Zhang, Jingwen

    2015-08-01

    Employing fast response, Cu-doped (K0.5Na0.5)0.2(Sr0.75 Ba0.25)0.9Nb2O6 (KNSBN) crystals in modifying ITO coating to support visible surface plasmon polaritons (SPPs) to strengthen nonlinearity in KNSBN, we found: (1) a 2 dimensional diffraction pattern was observed with only two writing beams; (2) The reflectivity on the very first surface was changed 2.3%, equivalent to 0.023 refractive index change; (3) 3.0% energy transferring to the reflection on the first surface was measured, resulting unambiguously from energy transferring in subwavelength scale. All these results are consist with our theoretical consideration based on phase grating mediation SPP excitation, which is promising in designing photonic devices.

  2. 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.

  3. 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.

  4. 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

  5. Nuclear waste treatment - Studying the mixed ion type effects and concentration on the behaviour of oxide dispersions

    SciTech Connect

    Omokanye, Qanitalillahi; Biggs, Simon

    2007-07-01

    In order to gain good control over a particulate dispersion it is necessary to accurately characterise the strength of inter-particle forces that may be operating. Such control is not routinely used, as yet, in the nuclear industry despite the possible benefits. We are investigating the impact of mixed electrolyte systems, for example NaCl and Na{sub 2}SO{sub 4}, on the stability of oxide simulant particle dispersions. The electro-acoustic zeta potentials and shear yield stresses for concentrated dispersions have been measured across a range of pH conditions and electrolyte concentrations (0.001 M - 1.0 M). This paper summarizes initial data from these studies showing how the shear yield stress of concentrated aqueous oxide particle dispersions, can be adjusted through regulation of pH and the addition of background electrolytes (salt). The yield stress as a function of pH for these dispersions in mixed electrolytes showed a direct correlation with corresponding measurements of the zeta potential. Changes in the background electrolyte concentration or type were seen to cause a shift in the position of the isoelectric point (iep). Measurements of the shear yield stress showed a maximum at the iep corresponding to the position of maximum instability in the suspension. The consequences of these data for the efficient treatment of solid-liquid systems will be discussed. (authors)

  6. Processable conductive graphene/polyethylene nanocomposites: Effects of graphene dispersion and polyethylene blending with oxidized polyethylene on rheology and microstructure

    SciTech Connect

    Iqbal, Muhammad Z.; Abdala, Ahmed A.; Mittal, Vikas; Seifert, Sӧnke; Herring, Andrew M.; Liberatore, Matthew W.

    2016-08-01

    Poor dispersion of graphene in non-polar polymer matrices creates composites with limited applications. A method to improve the dispersion of graphene in polyethylene (PE) via blending PE with oxidized PE (OPE) is examined. Graphene was produced by simultaneous thermal exfoliation and reduction of graphite oxide. Nanocomposites of graphene with PE as well as graphene with PE/OPE-blends were prepared by solvent blending. Improved dispersion of graphene in PE/OPE blends substantially decreases percolation from both rheological (0.3 vol%) and electrical (0.13 vol%) measurements compared to neat PE nanocomposites (1 and 0.29 vol%), respectively. A universal Brownian dispersion of graphene in polymers was concluded similar to that of nanotubes, following the Doi-Edwards theory. Micromechanical models, such as Mori-Tanaka and Halpin-Tsai models, modeled the mechanical properties of the nanocomposites. The nanocomposites microstructure, studied by small angle x-ray scattering, confirmed better dispersion of graphene at lower loadings and the formation of surface fractals in the blend/graphene nanocomposites; whereas only mass fractals were observed in neat PE/graphene nanocomposites.

  7. Decomposition of polychlorinated biphenyls in soil with a dispersion mixture of metallic calcium and calcium oxide.

    PubMed

    Mitoma, Yoshiharu; Mallampati, Srinivasa Reddy; Miyata, Hideaki; Kakeda, Mitsunori

    2013-02-01

    This study describes the decomposition of polychlorinated biphenyls (PCBs) in soil with dispersion mixtures of metallic calcium (Ca) and calcium oxide (CaO) at different temperatures. In these experiments, naturally moisturized and contaminated soil (1.0 g [31 ppm PCBs]), CaO (dried 2.0 wt%), and metallic Ca (0.01 g [0.25 mmol]) were introduced into a stainless steel pressure reactor under 0.1 MPa N(2) gas. The mixtures were stirred magnetically and heated at 260, 280, and 300 °C, respectively. Soil treatment with metallic Ca and CaO under various temperature conditions is extremely effective for degrading existing PCBs. Decomposition resulted from dechlorination (DC). Initial moisture in soil acted as a hydrogen source during stirring. Soil moisture can be beneficial for hydrodechlorination in the presence of metallic Ca and CaO. Furthermore, metallic Ca and CaO can greatly increase the number of collisions and mutual refinement. Treatment at 260, 280, and 300 °C combined with metallic Ca and CaO is effective for the decomposition (approximately 95 % DC) of PCBs in soil under natural moisture conditions.

  8. 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

  9. Stable aqueous dispersion of superparamagnetic iron oxide nanoparticles protected by charged chitosan derivatives

    NASA Astrophysics Data System (ADS)

    Szpak, Agnieszka; Kania, Gabriela; Skórka, Tomasz; Tokarz, Waldemar; Zapotoczny, Szczepan; Nowakowska, Maria

    2013-01-01

    This article presents the synthesis and characterization of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) coated with ultrathin layer of anionic derivative of chitosan. The water-based fabrication involved a two-step procedure. In the first step, the nanoparticles were obtained by co-precipitation of ferrous and ferric aqueous salt solutions with ammonia in the presence of cationic derivative of chitosan. In the second step, such prepared materials were subjected to adsorption of oppositely charged chitosan derivative which resulted in the preparation of negatively charged SPIONs. They were found to develop highly stable dispersion in water. The core size of the nanocoated SPIONs, determined using transmission electron microscopy, was measured to be slightly above 10 nm. The coated nanoparticles form aggregates with majority of them having hydrodynamic diameter below 100 nm, as measured by dynamic light scattering. Their composition and properties were studied using FTIR and thermogravimetric analyses. They exhibit magnetic properties typical for superparamagnetic material with a high saturation magnetization value of 123 ± 12 emu g-1 Fe. Very high value of the measured r 2 relaxivity, 369 ± 3 mM-1 s-1, is conducive for the potential application of the obtained SPIONs as promising contrast agents in magnetic resonance imaging.

  10. Graphite oxide-dispersed CdTe quantum dots nanocomposite for flexible display luminescent membranes.

    PubMed

    Liu, Cui; Du, Lei; Lin, Yongjun; Liang, Jiyuan; Liu, Jun'an; Cao, Yuan-Cheng

    2017-03-08

    A quantum dot (QD) dispersant material was prepared using graphite oxide (GO). Luminescent films were prepared using polyvinyl alcohol as the polymer matrix. First, water-soluble CdTe QDs were prepared by wet chemistry and GO was synthesized using a modified Hummers method. X-Ray diffraction tests showed that the GO reflection peak [001] was 11.9°, which indicates that the d-spacing is 0.7431 nm; atomic force microscopy showed a GO thickness of 200 nm. Fourier transform infrared spectra showed vibrations at 1624 cm(-1) for the carbonyl groups, and 3260 cm(-1) for the GO samples; the -C-O vibration was at 1320 cm(-1) and -COOH, -OH vibrations were at 950 cm(-1) . Fluorescent tests showed that pH had an impact on the QD colloidal stability. GO was neutralized before use as the host media for the GO/QDs nanocomposite. The results proved that the resultant nanocomposite is promising for use in brightness enhancement films in flexible displays.

  11. 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.

  12. 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.

  13. Crossover from disordered to core-shell structures of nano-oxide Y{sub 2}O{sub 3} dispersed particles in Fe

    SciTech Connect

    Higgins, M. P.; Wang, L. M.; Gao, F.; Lu, C. Y.; Lu, Z.; Shao, L.

    2016-07-18

    Molecular dynamic simulations of Y{sub 2}O{sub 3} in bcc Fe and transmission electron microscopy (TEM) observations were used to understand the structure of Y{sub 2}O{sub 3} nano-clusters in an oxide dispersion strengthened steel matrix. The study showed that Y{sub 2}O{sub 3} nano-clusters below 2 nm were completely disordered. Y{sub 2}O{sub 3} nano-clusters above 2 nm, however, form a core-shell structure, with a shell thickness of 0.5–0.7 nm that is independent of nano-cluster size. Y{sub 2}O{sub 3} nano-clusters were surrounded by off-lattice Fe atoms, further increasing the stability of these nano-clusters. TEM was used to corroborate our simulation results and showed a crossover from a disordered nano-cluster to a core-shell structure.

  14. 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

  15. Redox equilibria of iron oxides in aqueous-based magnetite dispersions: effect of pH and redox potential.

    PubMed

    Pang, Suh Cem; Chin, Suk Fun; Anderson, Marc A

    2007-07-01

    The effect of pH and redox potential on the redox equilibria of iron oxides in aqueous-based magnetite dispersions was investigated. The ionic activities of each dissolved iron species in equilibrium with magnetite nanoparticles were determined and contoured within the Eh-pH framework of a composite stability diagram. Both standard redox potentials and equilibrium constants for all major iron oxide redox equilibria in magnetite dispersions were found to differ from values reported for noncolloidal systems. The "triple point" position of redox equilibrium among Fe(II) ions, magnetite, and hematite shifted to a higher standard redox potential and an equilibrium constant which was several orders of magnitude higher. The predominant area of magnetite stability was enlarged to cover a wider range of both pH and redox potentials as compared to that of a noncolloidal magnetite system.

  16. Electrocatalytic oxidation of formaldehyde on platinum well-dispersed into single-wall carbon nanotube/polyaniline composite film

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Zhu, Zan-Zan; Shi, Jin; Li, Hu-Lin

    2007-09-01

    Single-walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dissolved SWNTs. The composite films were dispersed Pt by electrodeposition technique. The presence of SWNTs and platinum in the composite film was confirmed by XRD analysis and scanning electron microscopy (SEM). Four-point probe investigation and electrochemical impedance spectroscopy (EIS) revealed that the well arrangement of PANI coated SWNTs in these films enhanced electric conductivity and facilitated the charge-transfer of the composite films. Cyclic voltammogram (CV) and chronoamperogram showed that Pt-modified SWNT/PANI composite film performs higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formaldehyde oxidation. The results imply that the SWNT/PANI composite film as a promising support material improves the electrocatalytic activity for formaldehyde oxidation greatly.

  17. 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.

  18. Investigation of Dispersion, Stability, and Tribological Performance of Oil-Based Aluminum Oxide Nanofluids

    DTIC Science & Technology

    2012-01-01

    protecting. The role of each mechanism depends on the lubricating conditions and the type of nanoparticle. 2.4.1 Metal Oxide Nanoparticles...Hernandez Battez et al., [24] explored three different metal oxide nanoparticles in a tribological study. Copper oxide , zinc oxide , and zirconium...maximum friction reduction exceeding 20% occurred at the lowest particle loading for both zinc oxide and zirconium oxide . The maximum wear reduction

  19. 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.

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

    PubMed Central

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

    2013-01-01

    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. PMID:27877568

  1. Reduction of greenhouse gases emissions during anoxic wastewater treatment by strengthening nitrite-dependent anaerobic methane oxidation process.

    PubMed

    Ma, Ru; Hu, Zhen; Zhang, Jian; Ma, Hao; Jiang, Liping; Ru, Dongyun

    2017-03-20

    Nitrite-dependent anaerobic methane oxidation (n-damo) is a recently discovered process performed by NC10 phylum, which plays an important role in greenhouse gases (GHG) reduction. In this study, co-existence of n-damo bacteria and methanogens was successfully achieved by using upflow anaerobic sludge blanket (UASB) reactor. Reactor with inorganic carbon source (CO2/H2) showed the highest abundance of n-damo bacteria and the highest n-damo potential activity, resulted in its highest nitrogen removal rate. Significant reduction in GHG was obtained after introduction of n-damo process, especially for N2O. Furthermore, GHG emissions decreased with the increase of n-damo bacteria abundance. Community structure analysis found carbon source could influence the diversity of n-damo bacteria indirectly. And phylogenetic analysis showed that all the obtained sequences were assigned to group B, mainly due to in situ production and consumption of CH4.

  2. Dispersive micro solid-phase extraction of triazines from waters using oxidized single-walled carbon nanohorns as sorbent.

    PubMed

    Jiménez-Soto, Juan Manuel; Cárdenas, Soledad; Valcárcel, Miguel

    2012-07-06

    This article evaluates the usefulness of dispersed single-walled carbon nanohorns as sorbent for the isolation and preconcentration of triazines from waters. For this purpose, the carbon nanoparticles were oxidized to increase their solubility in aqueous media in order to obtain a stable dispersion that can be used as extractant of the selected pollutants. Then, 1 mL of the dispersion containing the oxidized single-walled carbon nanohorns at a concentration of 0.2 g/L was added to 10 mL of sample and stirred for 2 min using a vortex. Then, the whole volume was passed through a disposable 0.45 μm Nylon filter which retained the nanoparticles enriched with the triazines. Further elution with methanol permitted the gas chromatographic analysis of the analytes and subsequent identification and quantification by mass spectrometry working under the selected ion monitoring mode (SIM). The limits of detection (LODs) were in low nanogram per liter level, which allowed the detection of the selected triazines at the concentration stated by legislation. The precision of the method, calculated as relative standard deviation, was acceptable in all instances. Finally, the recovery study carried out in different water samples provided average values between 87% and 94%. The results obtained revealed the applicability of oxidized single-walled carbon nanohorns for the proposed analytical problem.

  3. Influence of nanometric oxide dispersion on creep resistance of ODS FeAl prepared from prealloyed powders

    SciTech Connect

    Wolski, K.; Thevenot, F.; Le Coze, J.

    1996-03-01

    Intermetallic Fe-40at% Al is characterized by excellent oxidation and corrosion resistance at high temperatures, low cost of raw materials, relatively low density (6.0 g/cm{sup 3}) and significant ductility at room temperature. The ductility depends on composition, boron addition, environmental effect and in optimized conditions of processing was measured to be at least 6%. One of the limitations of this material is its insufficient creep strength at about 700 C, the temperature for potential applications instead of stainless steels or standard superalloys. This paper is focused on the rheological properties of FeAl prepared by attrition coupled with in situ formation of the dispersion and subsequent sintering. Critical steps of processing, leading to the formation of the nanosized ceramic dispersion are also addressed, however a detailed description of the type of oxides formed is presented elsewhere. This paper describes a part of a larger study aimed at the improvement of the creep strength of FeAl by dispersion of oxides.

  4. Equivalent distributed capacitance model of oxide traps on frequency dispersion of C-V curve for MOS capacitors

    NASA Astrophysics Data System (ADS)

    Lu, Han-Han; Xu, Jing-Ping; Liu, Lu; Lai, Pui-To; Tang, Wing-Man

    2016-11-01

    An equivalent distributed capacitance model is established by considering only the gate oxide-trap capacitance to explain the frequency dispersion in the C-V curve of MOS capacitors measured for a frequency range from 1 kHz to 1 MHz. The proposed model is based on the Fermi-Dirac statistics and the charging/discharging effects of the oxide traps induced by a small ac signal. The validity of the proposed model is confirmed by the good agreement between the simulated results and experimental data. Simulations indicate that the capacitance dispersion of an MOS capacitor under accumulation and near flatband is mainly caused by traps adjacent to the oxide/semiconductor interface, with negligible effects from the traps far from the interface, and the relevant distance from the interface at which the traps can still contribute to the gate capacitance is also discussed. In addition, by excluding the negligible effect of oxide-trap conductance, the model avoids the use of imaginary numbers and complex calculations, and thus is simple and intuitive. Project supported by the National Natural Science Foundation of China (Grant Nos. 61176100 and 61274112), the University Development Fund of the University of Hong Kong, China (Grant No. 00600009), and the Hong Kong Polytechnic University, China (Grant No. 1-ZVB1).

  5. 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

  6. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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

  8. 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.

  9. Fabrication of water-dispersible single-walled carbon nanotube powder using N-methylmorpholine N-oxide.

    PubMed

    Choi, Hyejun; Woo, Jong Seok; Han, Joong Tark; Park, Soo-Young

    2017-09-13

    Dispersion of nanocarbon materials in liquid media is one of prerequisites for practical applications via solution processing such as spraying, printing, spinning, etc. Here we report that water-dispersible single-walled carbon nanotubes (SWCNTs) were prepared through successive treatments with chlorosulfuric acid (CSA)/H2O2 and N-methylmorpholine N-oxide (NMO) monohydrate. The powder of the CSA/H2O2- and NMO-treated SWCNTs (N-SWCNTs) could be readily redispersed in water in concentrations as high as 1 g L-1 without requiring a dispersant. The mechanism responsible for the high dispersity of the N-SWCNT powder in polar solvents, including water, was elucidated based on the high polarity of the NMO molecule. In order to highlight the wide applicability of the N-SWCNTs, they were used successfully to prepare conducting thin films by spray-coating plastic substrates with an aqueous hybrid solution containing the N-SWCNTs and Ag nanowires (NWs). In addition, a flexible, large-area thin-film heater was prepared based on the N-SWCNT/AgNW hybrid film with a transmittance of 93% and sheet resistance of 30 Ω sq-1. © 2017 IOP Publishing Ltd.

  10. 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.

  11. 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

  12. Nitric oxide signaling in Pseudomonas aeruginosa biofilms mediates phosphodiesterase activity, decreased cyclic di-GMP levels, and enhanced dispersal.

    PubMed

    Barraud, Nicolas; Schleheck, David; Klebensberger, Janosch; Webb, Jeremy S; Hassett, Daniel J; Rice, Scott A; Kjelleberg, Staffan

    2009-12-01

    Bacteria in biofilms often undergo active dispersal events and revert to a free-swimming, planktonic state to complete the biofilm life cycle. The signaling molecule nitric oxide (NO) was previously found to trigger biofilm dispersal in the opportunistic pathogen Pseudomonas aeruginosa at low, nontoxic concentrations (N. Barraud, D. J. Hassett, S. H. Hwang, S. A. Rice, S. Kjelleberg, and J. S. Webb, J. Bacteriol. 188:7344-7353, 2006). NO was further shown to increase cell motility and susceptibility to antimicrobials. Recently, numerous studies revealed that increased degradation of the secondary messenger cyclic di-GMP (c-di-GMP) by specific phosphodiesterases (PDEs) triggers a planktonic mode of growth in eubacteria. In this study, the potential link between NO and c-di-GMP signaling was investigated by performing (i) PDE inhibitor studies, (ii) enzymatic assays to measure PDE activity, and (iii) direct quantification of intracellular c-di-GMP levels. The results suggest a role for c-di-GMP signaling in triggering the biofilm dispersal event induced by NO, as dispersal requires PDE activity and addition of NO stimulates PDE and induces the concomitant decrease in intracellular c-di-GMP levels in P. aeruginosa. Furthermore, gene expression studies indicated global responses to low, nontoxic levels of NO in P. aeruginosa biofilms, including upregulation of genes involved in motility and energy metabolism and downregulation of adhesins and virulence factors. Finally, site-directed mutagenesis of candidate genes and physiological characterization of the corresponding mutant strains uncovered that the chemotaxis transducer BdlA is involved in the biofilm dispersal response induced by NO.

  13. Synthesis and purification of oxide nanoparticle dispersions by modified emulsion precipitation.

    PubMed

    Shi, Jingyu; Verweij, Henk

    2005-06-07

    ZrO2 and Fe2O3 precursor nanoparticles are synthesized, well-dispersed in decane, via a modified emulsion precipitation (MEP) method. This method starts with preparing two thermostable water-in-oil (w/o) emulsions with nonylphenol tetra(ethylene glycol) ether (Arkopal-40) as the main surfactant, didodecyldimethylammonium bromide (DiDAB) as the cosurfactant, decane as the continuous oil phase, and either a metal salt solution or a hexamethylenetetramine (HMTA) precipitation agent solution as the dispersed water phase. After mixing of the two emulsions, individual precursor particles are formed by precipitation in the confinement of the aqueous solution droplets. Excess water is removed by azeotropic distillation, and steric stabilization of the particles in the remaining oil medium is achieved with poly(octadecyl methacrylate) (PODMA), initially present dissolved in the oil phase. A purification process is conducted to remove the precipitation reaction byproduct and excess surfactants from the nanoparticle dispersions. Transmission electron microscopy (TEM) characterization shows that the ZrO2 and Fe2O3 precursor nanoparticles are both non-agglomerated, spherical, and have a narrow particle size distribution, centered at 4 nm in diameter. The precipitation from the dispersion of byproduct NH4Cl after water removal, and insoluble surfactant DiDAB after dilution with pure decane, is confirmed by X-ray diffraction (XRD). NMR results show that most of the oil-soluble surfactant Arkopal-40 can be removed from the dispersion by a 3x repeated dead-end pressure filtration process. It is shown that, after purification, the nanoparticle dispersions can be used for the preparation of homogeneous nanostructured coatings. The purification procedure as discussed provides guidelines for up-scaling the process and reuse of emulsifiers.

  14. 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.

  15. Microbial oxidation of dispersed graphite by nitrifying bacteria 2011.2.

    PubMed

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

    2013-10-07

    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.

  16. 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.

  17. 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.

  18. Highly dispersible edge-selectively oxidized graphene with improved electrical performance.

    PubMed

    Park, Jisoo; Kim, Yern Seung; Sung, Sae Jin; Kim, Taehoon; Park, Chong Rae

    2017-01-26

    We prepared liquid phase exfoliated edge-selectively oxidized graphene (LPEOG) with a high concentration in water (∼14.7 mg ml(-1)) and a high ratio of a single layer (70%). The edge of graphite was selectively oxidized by step II oxidation of the modified Hummers method, and we subsequently exfoliated the edge-selectively oxidized graphite (EOG) into LPEOG. The edge selective oxidation of the LPEOG was confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), zeta-potentiometry, Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The highly concentrated LPEOG ink can be used in solution processing such as simple drawing or spin casting. Reduced LPEOG showed a higher conductivity (120 000 S m(-1)) than that of reduced graphene oxide (68 800 S m(-1)) despite the small lateral size. A transparent conducting film prepared from the LPEOG ink showed a lower surface resistance (∼2.97 kΩ sq(-1)) at a higher transmittance (>83.0 %T) compared to those of the graphene oxide based film. These results indicate that preservation of π-conjugation of the basal plane of graphene is critical for electrical performance of graphene. Our method facilitates solution processing of graphene for a wide range of applications.

  19. Highly Dispersed Polyoxometalate-Doped Porous Co3 O4 Water Oxidation Photocatalysts Derived from POM@MOF Crystalline Materials.

    PubMed

    Lan, Qing; Zhang, Zhi-Ming; Qin, Chao; Wang, Xin-Long; Li, Yang-Guang; Tan, Hua-Qiao; Wang, En-Bo

    2016-10-17

    Rational design of earth-abundant photocatalysts is an important issue for solar energy conversion and storage. Polyoxometalate (POM)@Co3 O4 composites doped with highly dispersive molecular metal-oxo clusters, synthesized by loading a single Keggin-type POM cluster into each confined space of a metal-organic framework (MOF), exhibit significantly improved photocatalytic activity in water oxidation compared to the pure MOF-derived nanostructure. The systematic synthesis of these composite nanocrystals allows the conditions to be tuned, and their respective water oxidation catalytic performance can be efficiently adjusted by varying the thermal treatment temperature and the feeding amount of the POM. This work not only provides a modular and tunable synthetic strategy for preparing molecular cluster@TM oxide (TM=transition metal) nanostructures, but also showcases a universal strategy that is applicable to design and construct multifunctional nanoporous metal oxide composite materials. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effect of Dielectric Titanium, Yttrium, and Silicon Oxide Nanoparticles on Electro-Optical Characteristics of Polymer-Dispersed Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Zhdanov, K. R.; Romanenko, A. I.; Zharkova, G. M.

    2016-01-01

    Electro-optical characteristics of composite polymer-dispersed liquid crystals doped (implanted) with inorganic SiO2, TiO2, and Y2O3 nanoparticles in strong electric fields are studied. The composites were obtained by the method of phase separation of liquid crystals (5CB) and polymer (polyvinyl acetate). It is revealed that implantation of up to 1 wt.% of nanoparticles does not noticeably affect the morphology of the composites. The implanted particles change the mismatch between the refractive indices of the polymer and the liquid crystal, and the strong particle aggregation increases the light scattering that can improve the electrooptical contrast of the composites. Changes of the dielectric permittivity with the field are correlated with the light transmittance. It is found that the yttrium and silicon oxides decrease and the titanium oxides increase the Fredericks threshold field. The titanium oxides and to a greater extent the silicon oxides decrease the dependence of the light transmittance on the changes in the dielectric permittivity.

  1. Dispersion-precipitation synthesis of highly active nanosized Co3O4 for catalytic oxidation of carbon monoxide and propane

    NASA Astrophysics Data System (ADS)

    Zhang, Weidong; Wu, Feng; Li, Jinjun; You, Zhixiong

    2017-07-01

    Nanosized Co3O4 catalyst was prepared through a dispersion-precipitation method involving a reaction between wet cobalt hydroxide and acetic acid, which forms a colloidal dispersion, and subsequent dilution, which destabilizes and precipitates the colloidal particles. The catalyst had a particle size of 5-15 nm and a specific surface area of 82 m2/g. Compared with the analogue prepared by conventional alkali-induced precipitation method, the nanosized catalyst was more reducible and contained a larger amount of active surface oxygen species, as revealed by experiments using temperature-programmed reduction in hydrogen and temperature-programmed desorption of oxygen. The oxygen species could contribute to the observed higher activity in the catalytic oxidation of carbon monoxide and propane. In addition, a kinetics study revealed that the apparent activation energies for carbon monoxide and propane oxidation over the catalyst were 34.0 and 49.5 kJ/mol, respectively, much lower than those over the analogue (54.7 and 71.1 kJ/mol, respectively). Furthermore, a long-term test (76 h) showed that the nanosized catalyst is highly stable.

  2. Peptide Cross-linkers: Immobilization of Platinum Nanoparticles Highly Dispersed on Graphene Oxide Nanosheets with Enhanced Photocatalytic Activities.

    PubMed

    Mizutaru, Tsukasa; Marzun, Galina; Kohsakowski, Sebastian; Barcikowski, Stephan; Hong, Dachao; Kotani, Hiroaki; Kojima, Takahiko; Kondo, Takahiro; Nakamura, Junji; Yamamoto, Yohei

    2017-03-22

    For exerting potential catalytic and photocatalytic activities of metal nanoparticles (MNPs), immobilization of MNPs on a support medium in highly dispersed state is desired. In this Research Article, we demonstrated that surfactant-free platinum nanoparticles (PtNPs) were efficiently immobilized on graphene oxide (GO) nanosheets in a highly dispersed state by utilizing oligopeptide β-sheets as a cross-linker. The fluorenyl-substituted peptides were designed to form β-sheets, where metal-binding thiol groups and protonated and positively charged amino groups are integrated on the opposite sides of the surface of a β-sheet, which efficiently bridge PtNPs and GO nanosheet. In comparison to PtNP/GO composite without the peptide linker, the PtNP/peptide/GO ternary complex exhibited excellent photocatalytic dye degradation activity via electron transfer from GO to PtNP and simultaneous hole transfer from oxidized GO to the dye. Furthermore, the ternary complex showed photoinduced hydrogen evolution upon visible light irradiation using a hole scavenger. This research provides a new methodology for the development of photocatalytic materials by a bottom-up strategy on the basis of self-assembling features of biomolecules.

  3. Highly dispersed Pd nanoparticles on chemically modified graphene with aminophenyl groups for formic acid oxidation

    NASA Astrophysics Data System (ADS)

    Yang, Su-Dong; Shen, Cheng-Min; Tong, Hao; He, Wei; Zhang, Xiao-Gang; Gao, Hong-Jun

    2011-11-01

    A novel electrode material based on chemically modified graphene (CMG) with aminophenyl groups is covalently functionalized by a nucleophilic ring-opening reaction between the epoxy groups of graphene oxide and the aminophenyl groups of p-phenylenediamine. Palladium nanoparticles with an average diameter of 4.2 nm are deposited on the CMG by a liquid-phase borohydride reduction. The electrocatalytic activity and stability of the Pd/CMG composite towards formic acid oxidation are found to be higher than those of reduced graphene oxide and commercial carbon materials such as Vulcan XC-72 supported Pd electrocatalysts.

  4. Improvement of particle size of indium tin oxide nanoparticles by in-situ dispersion method for solution based transparent heater

    NASA Astrophysics Data System (ADS)

    Hong, Sung-Jei; Cha, Seung-Jae; Lee, Jae-Yong; Kim, Young-Sung

    2017-01-01

    In this study, particles size of indium tin oxide nanoparticles (ITO-NPs) was improved by in-situ dispersion method. Polyvinylpyrrolidone (PVP) was used as dispersing agent, and reduced precipitates heat-treated at 400 °C. Brunauer, Emmett & Teller (BET) specific surface area (SSA) analysis and X-ray diffractometer (XRD) observations found that their particle size was improved by using the in-situ dispersion. In addition, we found that the particle size of the crystalline ITO-NPs was changed with the concentration of the PVP as well as the heat-treatment temperature. When 2 wt% PVP was applied, the highest BET SSA of the ITO-NPs, 114.7 m2/g, was obtained after heat-treatment at 400 °C. In fact, the lowest sized, less than 7 nm, ITO-NPs was observed with high resolution transmission electron microscope (HRTEM). The ITO-NPs were well dispersed in the solvent to formulate a 20 wt% ITO-NPs solution. ITO-NPs coated layer on 3 × 3 cm2 quartz substrate showed sheet resistance of 319 Ω/□ and optical transmittance of 89.5% after heat-treatment at 900 °C. Heat was well generated at the ITO-NPs coated layer with supplied voltage. Also, temperature of above 150 °C was obtained from the transparent heater, and 89 °C was obtained with low power, 0.21 W/cm2, that is superior to commercial heaters. [Figure not available: see fulltext.

  5. Optimized permeation and antifouling of PVDF hybrid ultrafiltration membranes: synergistic effect of dispersion and migration for fluorinated graphene oxide

    NASA Astrophysics Data System (ADS)

    Li, Mingming; Shi, Jie; Chen, Cheng; Li, Nan; Xu, Zhiwei; Li, Jing; Lv, Hanming; Qian, Xiaoming; Jiao, Xiaoning

    2017-03-01

    Nanoparticles may have suffered from low modification efficiency in hybrid membranes due to embedding and aggregating in polymer matrix. In order to analyze the modification mechanisms of nanoparticle migration and dispersion on the properties of hybrid membranes, we designed different F/ O ratios ( R F/ O ) of fluorinated graphene oxide (FGO, diameter = 1.5 17.5 μm) by carbon tetrafluoride (CF4) plasma treatment GO for 3, 5, 10, 15, and 20 min and successfully prepared novel PVDF hybrid membranes containing FGO via the phase inversion method. After a prolonged plasma treatment, the R F/ O of FGO was enhanced sharply, indicating an increasing compatibility of FGO with the matrix, especially FGO-20 (GO treated for 20 min). FGO contents in the top layer, sublayer, and the whole of membranes were probed by X-ray photoelectron spectroscopy, energy-dispersive spectrometer, and indirect computation, respectively. In the top layer of membranes, FGO contents declined from 13.14 wt% (PVDF/GO) to 4.00 wt% (PVDF/FGO-10) and 1.96 wt% (PVDF/FGO-20) due to the reduced migration ability of FGO. It is worth mentioning that PVDF/FGO-10 membranes exhibited an excellent water flux and flux recovery rate (up to 406.90 L m-2 h-1 and 88.9%), which were improved by 67.3% and 14.6% and 52.5% and 24.0% compared with those of PVDF/GO and PVDF/FGO-20 membranes, respectively, although the dispersion and migration ability of FGO-10 was maintained at a moderate level. It indicated that the migration and dispersion of FGO in membranes could result in dynamic equilibrium, which played a key role in making the best use of nanomaterials to optimize membrane performance.

  6. 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.

  7. 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

  8. Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties.

    PubMed

    Lartigue, Lenaic; Innocenti, Claudia; Kalaivani, Thangavel; Awwad, Azzam; Sanchez Duque, Maria del Mar; Guari, Yannick; Larionova, Joulia; Guérin, Christian; Montero, Jean-Louis Georges; Barragan-Montero, Véronique; Arosio, Paolo; Lascialfari, Alessandro; Gatteschi, Dante; Sangregorio, Claudio

    2011-07-13

    Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.

  9. 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.

  10. Dispersing molecular cobalt in graphitic carbon nitride frameworks for photocatalytic water oxidation.

    PubMed

    Zhang, Guigang; Huang, Caijin; Wang, Xinchen

    2015-03-01

    The development of water oxidation catalysts (WOCs) to cooperate with light-energy transducers for solar energy conversion by water splitting and CO2 fixation is a demanding challenge. The key measure is to develop efficient and sustainable WOCs that can support a sustainable photocatalyst to reduce over-potentials and thus to enhance reaction rate of water oxidation reaction. Cobalt has been indentified as active component of WOCs for photo/electrochemical water oxidation, and its performance relies strongly on the contact and adhesion of the cobalt species with photoactive substrates. Here, cobalt is homogeneously engineered into the framework of pristine graphitic carbon nitride (g-C3 N4 ) via chemical interaction, establishing surface junctions on the polymeric photocatalyst for the water oxidation reaction. This modification promotes the surface kinetics of oxygen evolution reaction by the g-C3 N4 -based photocatalytic system made of inexpensive substances, and further optimizations in the optical and textural structure of Co-g-C3 N4 is envisaged by considering ample choice of modification schemes for carbon nitride materials.

  11. Highly Dispersed Ultrafine Pt Nanoparticles on Reduced Graphene Oxide Nanosheets: In Situ Sacrificial Template Synthesis and Superior Electrocatalytic Performance for Methanol Oxidation.

    PubMed

    Wu, Shouliang; Liu, Jun; Tian, Zhenfei; Cai, Yunyu; Ye, Yixing; Yuan, Qinglin; Liang, Changhao

    2015-10-21

    We report a simple and environmentally friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (±0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.

  12. Effect of particle size and dispersion status on cytotoxicity and genotoxicity of zinc oxide in human bronchial epithelial cells.

    PubMed

    Roszak, Joanna; Catalán, Julia; Järventaus, Hilkka; Lindberg, Hanna K; Suhonen, Satu; Vippola, Minnamari; Stępnik, Maciej; Norppa, Hannu

    2016-07-01

    Data available on the genotoxicity of zinc oxide (ZnO) nanoparticles (NPs) are controversial. Here, we examined the effects of particle size and dispersion status on the cytotoxicity and genotoxicity of nanosized and fine ZnO, in the presence and absence of bovine serum albumin (BSA; 0.06%) in human bronchial epithelial BEAS-2B cells. Dynamic light scattering analysis showed the most homogenous dispersions in water alone for nanosized ZnO and in water with BSA for fine ZnO. After a 48-h treatment, both types of ZnO were cytotoxic within a similar, narrow dose range (1.5-3.0μg/cm(2)) and induced micronuclei at a near toxic dose range (1.25-1.75μg/cm(2)), both with and without BSA. In the comet assay, nanosized ZnO (1.25-1.5μg/cm(2)), in the absence of BSA, caused a statistically significant increase in DNA damage after 3-h and 6-h treatments, while fine ZnO did not. Our findings may be explained by better uptake or faster intracellular dissolution of nanosized ZnO without BSA during short treatments (3-6h; the comet assay), with less differences between the two ZnO forms after longer treatments (>48h; the in vitro micronucleus test). As ZnO is genotoxic within a narrow dose range partly overlapping with cytotoxic doses, small experimental differences e.g. in the dispersion of ZnO particles may have a substantial effect on the genotoxicity of the nominal doses added to the cell culture.

  13. [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.

  14. 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.

  15. Preparation of highly dispersed Pt-SnOx nanoparticles supported on multi-walled carbon nanotubes for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Hu, Chuangang; Cao, Yanxia; Yang, Lin; Bai, Zhengyu; Guo, Yuming; Wang, Kui; Xu, Pengle; zhou, Jianguo

    2011-07-01

    To maximize the utilization of catalysts and thereby reduce the high price, a new strategy was developed to prepare highly dispersed Pt-SnOx nanoparticles supported on 8-Hydroxyquinoline (HQ) functionalized multi-walled carbon nanotubes (MWCNTs). HQ functionalized MWCNTs (HQ-MWCNTs) provide an ideal support for improving the utilization of platinum-based catalysts, and the introduction of SnOx to the catalyst prevents the CO poisoning effectively. The as-prepared catalysts are characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. It is found that the HQ functionalization process preserves the integrity and electronic structure of MWCNTs, and the resulting Pt-SnOx particles are well dispersed on the HQ-MWCNTs with an average diameter of ca. 2.2 nm. Based on the electrochemical properties characterized by cyclic voltammetry and chronoamperometry, the Pt-SnOx/HQ-MWCNTs catalyst displays better electrocatalytic activity and stability for the methanol oxidation. It is worth mentioning that the forward peak current density of Pt-SnOx/HQ-MWCNTs catalyst is ca. 1.9 times of that of JM commercial 20% Pt/C catalyst, which makes it the preferable catalyst for direct methanol fuel cells.

  16. An ambient aqueous synthesis for highly dispersed and active Pd/C catalyst for formic acid electro-oxidation

    NASA Astrophysics Data System (ADS)

    Cheng, Niancai; Lv, Haifeng; Wang, Wei; Mu, Shichun; Pan, Mu; Marken, Frank

    An experimentally simple process is reported in aqueous solution and under ambient conditions to prepare highly dispersed and active Pd/C catalyst without the use of a stabilizing agent. The [Pd(NH 3) 4] 2+ ion is synthesized with gentle heating in aqueous ammonia solution without formation of Pd(OH) x complex intermediates. The adsorbed [Pd(NH 3) 4] 2+ on the surface of carbon (Vulcan XC-72) is reduced in situ to Pd nanoparticles by NaBH 4. The Pd/C catalyst obtained is characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that highly dispersed Pd/C catalyst with 20 wt.% Pd content and with an average Pd nanoparticle diameter of 4.3-4.7 nm could be obtained. The electrochemical measurements show that the Pd/C catalyst without stabilizer has a higher electro-oxidation activity for formic acid compared to that of a Pd/C catalyst prepared in a traditional high temperature polyol process in ethylene glycol.

  17. 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.

  18. 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.

  19. Highly selective adsorption of lead ions by water-dispersible magnetic chitosan/graphene oxide composites.

    PubMed

    Fan, Lulu; Luo, Chuannan; Sun, Min; Li, Xiangjun; Qiu, Huamin

    2013-03-01

    Magnetic chitosan/graphene oxide (MCGO) materials were fabricated through a facile and fast process and their application as excellent adsorbents for metal ions was also demonstrated. The characteristics results of FTIR, SEM, TEM, VSM and XRD showed that MCGO was successfully prepared. The SEM and TEM revealed that magnetic chitosan had been assembled on the surface of graphene oxide layers with a high density. The XRD and VSM indicated the MCGO had enough magnetic response to meet the need of magnetic separation. The magnetic chitosan grafted with graphene oxide sheets showed an increased surface area. The MCGO was used as sorbents for the removal of Pb(II) ions from large volumes of aqueous solutions. The effects of pH, contact time, and concentration on Pb(II) ions sorption were investigated. The results indicated that Pb(II) ions sorption on MCGO was strongly dependent on pH. The abundant functional groups on the surfaces of MCGO played an important role on Pb(II) sorption. Equilibrium studies showed that the data of Pb(II) adsorption followed the Langmuir model. The maximum adsorption capacity for Pb(II) was estimated to be 76.94 mg/g. The MCGO was stable and easily recovered. Copyright © 2012 Elsevier B.V. All rights reserved.

  20. 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.

  1. Selective removal of phosphate from wastewater using hydrated metal oxides dispersed within anionic exchange media.

    PubMed

    Acelas, Nancy Y; Martin, Benjamin D; López, Diana; Jefferson, Bruce

    2015-01-01

    Hydrated ferric oxide (HFeO), hydrated zirconium oxide (HZrO) and hydrated copper oxide (HCuO) were immobilized within a microporous anion exchange resin (IRA-400), forming hybrid media for enhanced phosphate removal from aqueous systems. Empirical data from batch kinetic trials fitted the pseudo second order mechanism for chemical adsorption and each media was rate limited by intraparticle diffusion overall. These models were also used to predict the adsorption rate constants and the equilibrium adsorption capacities, which ranged from 26.51 to 30.44 mgP g(-1), and from 24.15 to 27.90 mgP g(-1) of media for the calculated and experimental capacities, respectively. The phosphate adsorption behavior by the hybrid materials fit both the Langmuir and Freundlich adsorption isotherms (R(2)>0.94), and the maximum adsorption capacities were 111.1 mgP g(-1) for HFeO, 91.74 mgP g(-1) for HZrO and 74.07 mgP g(-1) for HCuO. The effect of competing ions such as sulfate reduced these capacities to 18.52 mgP g(-1) for HFeO and 18.97 mgP g(-1) for HZrO. Despite this decrease, HFeO was capable of reducing the phosphate in a real wastewater matrix by 83%, and the HZrO media was able to reduce it by 86%, suggesting that such hybrid media have the potential for application at full scale.

  2. 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

  3. Amperometric glucose biosensor based on glucose oxidase dispersed in multiwalled carbon nanotubes/graphene oxide hybrid biocomposite.

    PubMed

    Palanisamy, Selvakumar; Cheemalapati, Srikanth; Chen, Shen-Ming

    2014-01-01

    An amperometric glucose biosensor based on enhanced and fast direct electron transfer (DET) of glucose oxidase (GOx) at enzyme dispersed multiwalled carbon nanotubes/graphene oxide (MWCNT/GO) hybrid biocomposite was developed. The fabricated hybrid biocomposite was characterized by transmission electron microscopy (TEM), Raman and infrared spectroscopy (IR). The TEM image of hybrid biocomposite reveals that a thin layer of GOx was covered on the surface of MWCNT/GO hybrid composite. IR results validate that the hybrid biocomposite was formed through the electrostatic interactions between GOx and MWCNT/GO hybrid composite. Further, MWCNT/GO hybrid composite has also been characterized by TEM and UV-visible spectroscopy. A pair of well-defined redox peak was observed for GOx immobilized at the hybrid biocomposite electrode than that immobilized at the MWCNT modified electrode. The electron transfer rate constant (Ks) of GOx at the hybrid biocomposite was calculated to be 11.22s(-1). The higher Ks value revealed that fast DET of GOx occurred at the electrode surface. Moreover, fabricated biosensor showed a good sensitivity towards glucose oxidation over a linear range 0.05-23.2mM. The limit of detection (LOD) was estimated to be 28μM. The good features of the proposed biosensor could be used for the accurate detection of glucose in the biological samples. © 2013.

  4. Phonon dispersion of Cu oxides from ab initio DFPT+U+J calculations

    NASA Astrophysics Data System (ADS)

    Cococcioni, M.; Himmetoglu, B.; Floris, A.

    2012-12-01

    After almost three decades from its discovery high Tc superconductivity is still waiting for a comprehensive explanation. Ab initio computer simulations can play a very important role in clarifying the physics of high Tc superconductors. One particular aspect, still under investigation, is the role played by the electron-phonon coupling in the onset of superconductivity at finite doping. To explore the effects of this coupling on the behavior of these materials is a formidable task as it requires the ability to efficiently compute phonons and to precisely capture the effects of electronic correlation (the parent materials of high Tc superconductors are, in general, correlated oxides). In this work we present the latest extension of density functional perturbation theory (DFPT - used to compute the vibrational properties of materials) to the corrected DFT+U+J functional we recently introduced to study the effects of electronic correlation on Cu oxides. The phonon frequencies and modes of CaCuO2, a prototype of high Tc parent materials, are computed and discussed in comparison with available experiments and calculations based on "standard" DFT approximations. This new numerical tool will be very important to investigate the role of electron-phonon couplings on the structural and transport properties of many transition-metal minerals for which electronic localization and magnetism play a very important role.

  5. 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.

  6. 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.

  7. Highly-dispersed Ta-oxide catalysts prepared by electrodeposition in a non-aqueous plating bath for polymer electrolyte fuel cell cathodes.

    PubMed

    Seo, Jeongsuk; Cha, Dongkyu; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2012-09-18

    The Ta-oxide cathode catalysts were prepared by electrodeposition in a non-aqueous solution. These catalysts showed excellent catalytic activity and have an onset potential of 0.92 V(RHE) for the oxygen reduction reaction (ORR). The highly-dispersed Ta species at the nanometer scale on the carbon black was an important contributor to the high activity.

  8. Dispersed three-pulse infrared photon echoes of nitrous oxide in water and octanol.

    PubMed

    Shattuck, J T; Schneck, J R; Chieffo, L R; Erramilli, S; Ziegler, L D

    2013-12-12

    Dispersed IR three-pulse photon echoes due to the antisymmetric (ν3) stretch mode of N2O dissolved in H2O and 1-octanol at room temperature are reported and analyzed. The experimentally determined transition frequency-frequency correlation function (FFCF) in these two solvents is explained in terms of inertial solvent contributions, hydrogen bond network fluctuations, and, for octanol, the motions of the alkyl chains. The H2O hydrogen bond fluctuations result in 1.5 ps FFCF decay, in agreement with relaxation rates determined from photon echo based measurements of other aqueous solutions including salt solutions. In octanol, hydrogen bond fluctuations decay on a slower time scale of 3.3 ps and alkyl chain motions result in an inhomogeneous broadening contribution to the ν3 absorption spectrum that decays on a 35 ps time scale. Rotational reorientation of N2O is nearly 3 times faster in octanol as compared to water. Although the vibrational ν3 N2O absorption line shapes in water and octanol are similar, the line widths result from different coherence loss mechanisms. A hot band contribution in the N2O in octanol solution is found to have a significant effect on the echo spectrum due to its correspondingly stronger transition moment than that of the fundamental transition. The dephasing dynamics of the N2O ν3 stretch mode is of interest as a probe in ultrafast studies of complex or nanoconfined systems with both hydrophobic and hydrophilic regions such as phospholipids, nucleic acids, and proteins. These results demonstrate the value of the N2O molecule to act as a reporter of equilibrium fluctuations in such complex systems particularly due to its solubility characteristics and long vibrational lifetime.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Comparison of magnesium status using X-ray dispersion analysis following magnesium oxide and magnesium citrate treatment of healthy subjects.

    PubMed

    Shechter, Michael; Saad, Tomer; Shechter, Alon; Koren-Morag, Nira; Silver, Burton B; Matetzky, Shlomi

    2012-03-01

    The magnesium content in food consumed in the Western world is steadily decreasing. Hypomagnesemia is associated with increased incidence of diabetes mellitus, metabolic syndrome, all-cause and coronary artery disease mortality. We investigated the impact of supplemental oral magnesium citrate versus magnesium oxide on intracellular magnesium levels ([Mg2+]i) and platelet function in healthy subjects with no apparent heart disease. In a randomized, prospective, double-blind, crossover study, 41 (20 women) healthy volunteers [mean age 53±8 (range 31-75) years] received either magnesium oxide monohydrate tablets (520 mg/day of elemental magnesium) or magnesium citrate tablets (295.8 mg/day of elemental magnesium) for one month (phase 1), followed by a four-week wash-out period, and then crossover treatment for one month (phase 2). [Mg2+]i was assessed from sublingual cells through x-ray dispersion (normal values 37.9±4.0 mEq/L), serum magnesium levels, platelet aggregation, and quality-of-life questionnaires were assessed before and after each phase. Oral magnesium oxide, rather than magnesium citrate, significantly increased [Mg2+]i (34.4±3 versus 36.3±2 mEq/L, p<0.001 and 34.7±2 versus 35.4±2 mEq/L, p=0.097; respectively), reduced total cholesterol (201±37 versus 186±27 mg/dL, p=0.016 and 187±28 versus 187±25 mg/dL, p=0.978; respectively) and low-density lipoprotein (LDL) cholesterol (128±22 versus 120±25 mg/dL, p=0.042 and 120±23 versus 121±22 mg/dL, p=0.622; respectively). Noteworthy is that both treatments significantly reduced epinephrine-induced platelet aggregation (78.9±16% versus 71.7±23%, p=0.013 and 81.3±15% versus 73.3±23%, p=0.036; respectively). Thus, oral magnesium oxide treatment significantly improved [Mg2+]i, total and LDL cholesterol compared with magnesium citrate, while both treatments similarly inhibited platelet aggregation in healthy subjects with no apparent heart disease.

  15. 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

  16. Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

    NASA Astrophysics Data System (ADS)

    Morimoto, Yasuo; Izumi, Hiroto; Yoshiura, Yukiko; Tomonaga, Taisuke; Oyabu, Takako; Myojo, Toshihiko; Kawai, Kazuaki; Yatera, Kazuhiro; Shimada, Manabu; Kubo, Masaru; Yamamoto, Kazuhiro; Kitajima, Shinichi; Kuroda, Etsushi; Kawaguchi, Kenji; Sasaki, Takeshi

    2015-11-01

    We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO2) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO2 nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO2 nanoparticles (2, 10 mg/m3, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO2 nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO2 nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO2 nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO2 nanoparticles have a pulmonary toxicity that can lead to irreversible lesions.

  17. 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.

  18. Effect of particle size on gamma radiation shielding property of gadolinium oxide dispersed epoxy resin matrix composite

    NASA Astrophysics Data System (ADS)

    Li, Ran; Gu, Yizhuo; Wang, Yidong; Yang, Zhongjia; Li, Min; Zhang, Zuoguang

    2017-03-01

    Epoxy resin matrix composites filled with dispersed micro and nano gadolinium oxide (Gd2O3) particles of different contents were fabricated in this study. The γ radiation shielding and mechanical properties of these micro and nano composites were evaluated by measuring mass attenuation coefficients at photon energies from 31 keV to 356 keV and flexural performances. Adding Gd2O3 obviously increases mass attenuation coefficients of composites, and the enhancement is stronger at low photon energy because of dominating photoelectric effect and k-edge of element gadolinium. Effect of Gd2O3 particle size on shielding property of composite was also discussed. The results show that nano-Gd2O3 composites have better ability to shield X and γ ray than micro-Gd2O3 composites, and an enhanced effect of ~28% is obtained with Gd2O3 content of around 5 wt.% at 59.5 keV. The reason is attributed to higher probability of interaction between γ-ray and nano particles. Especially, this effect is prominent in low particle concentration. For flexural property, nano-Gd2O3/epoxy composite show equivalent flexural strength and up to15% higher flexural modulus compared with micro-Gd2O3/epoxy composite. Based on these experimental results, nano-Gd2O3 reinforced epoxy composite is believed to be a promising novel radiation shielding material.

  19. Enhanced molecular level dispersion and interface bonding at low loading of modified graphene oxide to fabricate super nylon 12 composites.

    PubMed

    Roy, Sunanda; Tang, Xiuzhi; Das, Tanya; Zhang, Liying; Li, Yongmei; Ting, Sun; Hu, Xiao; Yue, C Y

    2015-02-11

    Development of advanced graphene based polymer composites is still confronted with severe challenges due to its poor dispersion caused by restacking, weak interface bonding, and incompatibility with polymer matrices which suppress exertion of the actual potential of graphene sheets in composites. Here, we have demonstrated an efficient chemical modification process with polyethylenimine (PEI) to functionalize graphene oxide which can overcome the above-mentioned drawbacks and also can remarkably increase the overall strength of the nylon 12 composites even at very low graphene loading. Chemical modification was analyzed by various surface characterizations including X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Addition of only 0.25 and 0.35 wt % modified GO showed 37% and 54% improvement in tensile strength and 65% and 74% in Young's modulus, respectively, compared with that of the neat polymer. The dynamic mechanical analysis showed ∼39% and 63% increment in storage modulus of the nanocomposites. Moreover, the nanocomposites exhibited significantly high thermal stability (∼15 °C increment by only 0.35 wt %) as compared to neat polymer. Furthermore, the composites rendered outstanding resistance against various chemicals.

  20. 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.

  1. 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.

  2. One-pot ionic liquid-assisted synthesis of highly dispersed PtPd nanoparticles/reduced graphene oxide composites for nonenzymatic glucose detection.

    PubMed

    Li, Mian; Bo, Xiangjie; Zhang, Yufan; Han, Ce; Guo, Liping

    2014-06-15

    A series of highly dispersed bimetallic PtPd alloy nanoparticles (NPs) anchored on reduced graphene oxide (RGO) have been synthesized with the assistance of ionic liquid (IL: [VEIM]BF4). Different ratios of (PtCl6)(2-) and (PdCl4)(2-) ions were firstly attached to IL functionalized graphene oxide (GO) sheets in ethylene glycol (EG), and then the encased metal ions and graphene oxide sheets were reduced simultaneously by EG with the assistance of microwave. The characterization results of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and X-ray diffraction (XRD) demonstrate that PtPd alloy NPs with small particle sizes are uniformly dispersed on RGO. Electrochemical measurements reveal that PtPd-IL-RGO modified electrode can directly catalyze glucose oxidation and display enhanced current response compared with PtPd-RGO (such as: a response time within 3s, a linear range from 0.1 to 22 mM at 0 V, good reproducibility, considerable stability, and excellent anti-interference to electroactive molecules and Cl(-)). The superior catalytic activity and selectivity make PtPd-IL-RGO nanomaterials very promising for applications in direct detection of glucose.

  3. The impact of four ethylene oxide-propylene oxide block copolymers on the surface tension of dispersions of soils and minerals in water

    NASA Astrophysics Data System (ADS)

    Hagenhoff, Kerstin; Dong, Jingfeng; Chowdhry, Babur; Torres, Luis; Leharne, Stephen

    A comprehensive series of aqueous solutions of four ethylene oxide-propylene oxide-ethylene oxide block copolymers (EPE) of varying concentrations have been prepared. The EPE molecules are amphiphilic with the P blocks providing the hydrophobic segment of the molecules and the E blocks providing the hydrophilic parts. The surface tension of these solutions has been measured and compared with the surface tension of dispersions of soils (a clay soil and a sandy soil) and minerals (quartz-silica sand, bentonite and kaolinite) in the same aqueous solutions. It is observed that all the block copolymers reduce the surface tension of water; the extent to which it is reduced is determined by the surface activity of the EPE block copolymer, which in turn is related to the balance between the sizes of the P and E blocks. It is further observed that the in the presence of soil the surface tension increases as a result of block copolymer adsorption to the soil/water interface. The extent of adsorption appears to be related to the texture of the soil - the clay soil used in this investigation adsorbs more block copolymer than the sandy soil. In the presence of the mineral phases the surface tension reductions are variable. With bentonite the EPE block copolymers are completely adsorbed at low EPE concentrations as shown by surface tension values that are the same as those measured for pure water. Adsorption to kaolinite is limited and once the adsorption sites have been filled the surface tension of the aqueous phase is approaches the surface tension of the same solution without the presence of bentonite. On the other hand the silica sand is a poor adsorbent. Adsorption to the mineral phases is also dependent upon the relative hydrophobicity of the block copolymer. The more hydrophobic (as inferred by the critical micelle concentration) the copolymer the less readily it is adsorbed by the mineral phases. Thus relatively hydrophobic EPE block copolymers produce a relatively

  4. 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.

  5. 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

  6. Comparison of n-type and p-type GaAs oxide growth and its effects on frequency dispersion characteristics

    SciTech Connect

    Hinkle, C. L.; Sonnet, A. M.; Milojevic, M.; Aguirre-Tostado, F. S.; Kim, H. C.; Kim, J.; Wallace, R. M.; Vogel, E. M.

    2008-09-15

    The electrical characteristics of n- and p-type gallium arsenide (GaAs) capacitors show a striking difference in the ''accumulation'' capacitance frequency dispersion. This difference has been attributed by some to a variation in the oxide growth, possibly due to photoelectrochemical properties of the two substrates. We show that the oxide growth on n- and p-type GaAs substrates is identical when exposed to identical environmental and chemical conditions while still maintaining the diverse electrical characteristics. The difference in electron and hole trap time constants is suggested as the source of the disparity of the frequency dispersion for n-type versus p-type GaAs devices.

  7. Raspberrylike SiO2@reduced graphene oxide@AgNP composite microspheres with high aqueous dispersity and excellent catalytic activity.

    PubMed

    Xiao, Wei; Zhang, Yanhua; Liu, Bitao

    2015-03-25

    The hybridizations of functional microspheres with graphene or graphene oxide (GO) sheets often suffer from severe agglomeration behaviors, leading to poor water dispersity of the resultant composite materials. Here, we first demonstrate that the sonication-assisted self-assembly of tiny GO sheets (whose lateral size less than 200 nm) on microspheric substrates like cationic polyelectrolyte-modified SiO2 microspheres could effectively overcome such a common drawback. On the basis of this facile strategy, we further developed reduced graphene oxide/silver nanoparticle composite film wrapped SiO2 microspheres, which not only possessed unique raspberrylike structure and high aqueous dispersity but also exhibited exceptional catalytic activity toward the reduction of 4-nitrophenol.

  8. Measuring antioxidant efficiency of wort, malt, and hops against the 2,2'-azobis(2-amidinopropane) dihydrochloride-induced oxidation of an aqueous dispersion of linoleic acid.

    PubMed

    Liégeois, C; Lermusieau, G; Collin, S

    2000-04-01

    This paper presents a simple, convenient method for determining the efficiency of antioxidants in aqueous systems. Production of conjugated diene hydroperoxide by oxidation of linoleic acid in an aqueous dispersion is monitored at 234 nm. 2, 2'-Azobis(2-amidinopropane) dihydrochloride is used as a free radical initiator. Among 12 antioxidants tested, phenolic compounds proved to be the most efficient, both kinetically and in terms of the inhibition time (T(inh)). Applied to wort, malt, and hops, the method confirmed a significant antioxidant activity in such products, especially hops. This assay can be used to follow oxidative changes throughout the brewing process and to understand the contribution of each raw material.

  9. 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. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Controlled release from solid dispersion composed of poly(ethylene oxide)-Carbopol interpolymer complex with various cross-linking degrees of Carbopol.

    PubMed

    Ozeki, T; Yuasa, H; Kanaya, Y

    2000-02-03

    Solid dispersion composed of the poly(ethylene oxide) (PEO)-Carbopol((R)) (CP) interpolymer complex containing phenacetin (PHE) was prepared by using six grades of CP having various cross-linking degrees. We attempted to control the medicine release from the PEO-CP solid dispersion by varying the CP grade. The powder X-ray diffraction pattern and differential scanning calorimetry curves suggested that PHE existed in the amorphous state, and PEO in the crystalline state disappeared in the solid dispersions. The release profile of PHE varied depending on the CP grade. A small release rate was observed at CP910 and CP971P that are cross-linked at low and middle degrees, respectively. The Fourier transform-infrared (FT-IR) spectra showed that the amount of the PEO-CP complex formed by hydrogen bonding changed depending on the CP grade. With the cross-linked CP, a good correlation was observed between the hydrogen bonding percent and the percent released of the PHE after 60 min (D(60 min)), indicating that PHE release was controlled by the amount of PEO-CP complex formation in the solid dispersion. These results show that it is feasible to control the medicine release from PEO-CP solid dispersion by varying the CP grade.

  11. Theme: Strengthening Programs.

    ERIC Educational Resources Information Center

    Russell, Earl B.; And Others

    1993-01-01

    Program improvement is the theme of eight articles in this issue. Articles discuss collaborative relationships, strengthening programs, outcomes-based education and tech prep, improving adult education, futures studies, program evaluation, and supervised agricultural experience. (JOW)

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Enhanced thermoelectric figure-of-merit in Bi-Sb-Te nanocomposites with homogenously dispersed oxide ceramic ZrO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Madavali, B.; Kim, H. S.; Lee, K. H.; Hong, S. J.

    2017-06-01

    In this research, p-type BiSbTe/ZrO2 nanocomposite powders were fabricated by high-energy ball milling. Different weight percentages of ZrO2 (2, 4, and 6 wt. %) nanoparticles were incorporated into the bulk (BiSbTe) matrix by consolidation of as-synthesized nanocomposites (NCs) powder by spark plasma sintering at 673 K. The phase and existence of ZrO2 nano-inclusions was confirmed by X-ray diffraction and transmission electron microscopy-selected area electron diffraction analysis. The Seebeck coefficient of the BiSbTe/ZrO2 NCs was significantly improved (˜36% for 4 wt. % added NCs) by a decrease in the carrier concentration and energy filtering effect, whereas the thermal conductivity was much reduced via strong scattering of carriers/phonons. The peak thermoelectric figure-of-merit (1.34 ± 0.06) was obtained for BiSbTe into which 2 wt. % ZrO2 was dispersed, which was approximately 20% greater than that of the undispersed sample. The hardness of the nanocomposites was significantly improved (˜27%) due to grain-boundary hardening and a dispersion strengthening mechanism.

  17. 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.

  18. Influence of High Shear Dispersion on the Production of Cellulose Nanofibers by Ultrasound-Assisted TEMPO-Oxidation of Kraft Pulp

    PubMed Central

    Loranger, Eric; Piché, André-Olivier; Daneault, Claude

    2012-01-01

    Cellulose nanofibers can be produced using a combination of TEMPO, sodium bromide (NaBr) and sodium hypochlorite, and mechanical dispersion. Recently, this process has been the subject of intensive investigation. However, studies on the aspects of mechanical treatment of this process remain marginal. The main objective of this study is to evaluate the high shear dispersion parameters (e.g., consistency, stator-rotor gap, recirculation rate and pH) and determine their influences on nanocellulose production using ultrasound-assisted TEMPO-oxidation of Kraft pulp. All nanofiber gels produced in this study exhibited rheological behaviors known as shear thinning. From all the dispersion parameters, the following conditions were identified as optimal: 0.042 mm stator-rotor gap, 200 mL/min recycle rate, dispersion pH of 7 and a feed consistency of 2%. High quality cellulose gel could be produced under these conditions. This finding is surely of great interest for the pulp and paper industry.

  19. On the behavior of reduced graphene oxide based electrodes coated with dispersed platinum by alternate current methods in the electrochemical degradation of reactive dyes.

    PubMed

    Del Río, A I; García, C; Molina, J; Fernández, J; Bonastre, J; Cases, F

    2017-09-01

    The electrochemical behavior of different carbon-based electrodes with and without nanoparticles of platinum electrochemically dispersed on their surface has been studied. Among others, reduced graphene oxide based electrodes was used to determine the best conditions for the decolorization/degradation of the reactive dye C.I. Reactive Orange 4 in sulfuric medium. Firstly, the electrochemical behavior was evaluated by cyclic voltammetry. Secondly, different electrolyses were performed using two cell configurations: cell with anodic and cathodic compartments separated (divided configuration) and without any separation (undivided configuration). The best results were obtained when reduced graphene oxide based anodes were used. The degree of decolorization was monitored by spectroscopic methods and high performance liquid chromatography. It was found that all of them followed pseudo-first order kinetics. When reduced graphene oxide-based electrodes coated with dispersed platinum by alternate current methods electrodes were used, the lowest energy consumption and the higher decolorization kinetics rate were obtained. Scanning Electronic Microscopy was used to observe the morphological surface differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Aggregation of zinc oxide nanoparticles: from non-aqueous dispersions to composites used as photoactive layers in hybrid solar cells.

    PubMed

    Rhodes, R; Horie, M; Chen, H; Wang, Z; Turner, M L; Saunders, B R

    2010-04-15

    Hybrid solar cells are third-generation solar cells that are colloidal in nature. The composites used as photoactive layers within hybrid solar cells comprise conjugated polymers and inorganic semiconductor nanoparticles (e.g., nanocrystals and nanorods). The composites are usually prepared by spin casting non-aqueous dispersions consisting of polymer, nanoparticles and a co-solvent blend. The factors governing colloidal stability of the dispersions used for composite preparation have not been reported in detail. Here, the factors governing the stability of non-aqueous ZnO nanocrystal and nanorod dispersions as well as the relationship between dispersion stability and the extents of nanoparticle aggregation within model composites are studied. The polymers used are poly[[(2-methyl-4-methoxyphenyl)imino]-9,9-di-(2'-ethylhexyl)-fluorene-2,7-diyl] (PTAA) and poly[2,6-(4,4-bis-(2-ethyhexyl)-4H-cyclopenta [2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzo thiadiazole)] (PCPDTBT). FTIR in conjunction with thermogravimetric analysis data showed that up to 30% of the surfaces for the as-prepared ZnO nanocrystals and nanorods were occupied by acetate ligands. 1-Propylamine was found to form covalent coordinate bonds with ZnO and this contributes the ability of this co-solvent to promote enhanced ZnO dispersion stability. The morphologies of the composites were investigated using optical microscopy, AFM and TEM. A strong link was found between colloidal stability of the parent ZnO dispersions, extent of nanoparticle aggregation within the composites and pK(a) for the conjugate acid of the co-solvent. Electrostatic interactions did not control ZnO dispersion stability or composite morphology. Extensive nanometer-scale nanoparticle aggregation was evident within the composites. This was attributed to incompatibility between the polymer and (ligand covered) ZnO nanoparticles. Strategies for reducing uncontrolled nanoparticle aggregation are suggested.

  1. 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.

  2. 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,…

  3. 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,…

  4. Strengthening America's Families.

    ERIC Educational Resources Information Center

    Alvarado, Rose; Kumpfer, Karol

    2000-01-01

    Improving parenting practices and the family environment is the most effective, enduring strategy for combating juvenile delinquency. Describes the Office of Juvenile Justice and Delinquency Prevention's Strengthening America's Families Initiative. Highlights several family-focused prevention programs identified as exemplary, explaining how they…

  5. Synthesis of nanostructured iron oxides dispersed in carbon materials and in situ XRD study of the changes caused by thermal treatment

    NASA Astrophysics Data System (ADS)

    Gonçalves, Gustavo R.; Schettino, Miguel A.; Morigaki, Milton K.; Nunes, Evaristo; Cunha, Alfredo G.; Emmerich, Francisco G.; Passamani, Edson C.; Baggio-Saitovitch, Elisa; Freitas, Jair C. C.

    2015-07-01

    Carbon-based magnetic nanocomposites are of large interest for applications in catalysis, magnetic separation, water cleaning, and magnetic resonance imaging, among others. This work describes the synthesis of nanocomposites consisting of iron oxides dispersed into a char (obtained from the carbonization at 700 °C of a lignocellulosic precursor) and the study of the thermal transformations occurring in these materials as a consequence of heat treatments. The materials were prepared by impregnation of the char with iron nitrate in the presence of ammonium hydroxide in aqueous suspension. X-ray diffraction experiments performed using synchrotron radiation and Mössbauer spectroscopy showed that the as-prepared material was composed of amorphous Fe3+ oxides. Scanning electron microscopy images combined with energy-dispersive X-ray spectrometry indicated a homogeneous dispersion of iron oxides and of silica particles (naturally present in the lignocellulosic precursor) throughout the char. X-ray diffractograms recorded in situ during the heat treatment of the as-prepared material showed the presence of small hematite crystallites (average size 22 nm) starting from ca. 300 °C. Further heating caused a progressive growth of the hematite crystallites up to ca. 500 °C, when the conversion to magnetite (Fe3O4) started to take place. At higher temperatures, wüstite (Fe1-xO) was detected as an intermediate phase and austenitic iron (γ-Fe) became the dominant phase at temperatures from 900 °C. A steep weight loss was observed in the TG curve accompanying this last reduction stage; upon cooling, γ-Fe was converted into α-Fe (ferrite), which was the dominant phase at room temperature in this heat-treated sample.

  6. 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

    2016-03-04

    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.

  7. Pt3Ti nanoparticles: fine dispersion on SiO2 supports, enhanced catalytic CO oxidation, and chemical stability at elevated temperatures.

    PubMed

    Saravanan, Govindachetty; Abe, Hideki; Xu, Ya; Sekido, Nobuaki; Hirata, Hirohito; Matsumoto, Shin-ichi; Yoshikawa, Hideki; Yamabe-Mitarai, Yoko

    2010-07-06

    A platinum-based intermetallic phase with an early d-metal, Pt(3)Ti, has been synthesized in the form of nanoparticles (NPs) dispersed on silica (SiO(2)) supports. The organometallic Pt and Ti precursors, Pt(1,5-cyclooctadiene)Cl(2) and TiCl(4)(tetrahydrofuran)(2), were mixed with SiO(2) and reduced by sodium naphthalide in tetrahydrofuran. Stoichiometric Pt(3)Ti NPs with an average particle size of 2.5 nm were formed on SiO(2) (particle size: 20-200 nm) with an atomically disordered FCC-type structure (Fm3m; a = 0.39 nm). A high dispersivity of Pt(3)Ti NPs was achieved by adding excessive amounts of SiO(2) relative to the Pt precursor. A 50-fold excess of SiO(2) resulted in finely dispersed, SiO(2)-supported Pt(3)Ti NPs that contained 0.5 wt % Pt. The SiO(2)-supported Pt(3)Ti NPs showed a lower onset temperature of catalysis by 75 degrees C toward the oxidation reaction of CO than did SiO(2)-supported pure Pt NPs with the same particle size and Pt fraction, 0.5 wt %. The SiO(2)-supported Pt(3)Ti NPs also showed higher CO conversion than SiO(2)-supported pure Pt NPs even containing a 2-fold higher weight fraction of Pt. The SiO(2)-supported Pt(3)Ti NPs retained their stoichiometric composition after catalytic oxidation of CO at elevated temperatures, 325 degrees C. Pt(3)Ti NPs show promise as a catalytic center of purification catalysts for automobile exhaust due to their high catalytic activity toward CO oxidation with a low content of precious metals.

  8. 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

    2017-01-01

    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.

  9. Examination of aqueous oxidized cellulose dispersions as a potential drug carrier. II. In vitro and in vivo evaluation of phenylpropanolamine release from microparticles and pellets.

    PubMed

    Zhu, Lihua; Kumar, Vijay; Banker, Gilbert S

    2004-08-06

    The purpose of this research is to investigate the release of phenylpropanolamine from oxidized cellulose-phenylpropanolamine (OC-PPA) complexes prepared using aqueous OC dispersions (degree of neutralization, DN, 0-0.44) and phenylpropanolamine-hydrochloride (PPA.HCl) (concentration, 0.5 M or 1.4 M) in vitro and in vivo. The results showed a faster drug release from the OC-PPA complex made using the OC dispersion with a DN value of 0.22 than from those prepared using dispersions with DN values of 0.29 to 0.44. No significant difference existed between the release profiles of OC-PPA microparticles made using OC dispersions with DN values of 0.29 to 0.44. OC-PPA complexes that contained smaller size particles or higher drug levels, or that were processed by freeze drying released PPA faster. Compared with microparticles, the pellets of OC-PPA complexes released PPA more slowly initially. An increase in pH or ionic strength of the dissolution medium increased the release of PPA, which is attributable to increased polymer hydration and solubilization at higher pH and ionic strength conditions. The OC-PPA pellets implanted subcutaneously in rats released 100% of their PPA in 9 to 12 hours. A good correlation was found between the in vivo and in vitro release data. Tissue pathology results showed no significant inflammatory tissue reactions. In conclusion, the partially ionized aqueous OC dispersions have the potential to be used as an implantable biodegradable carrier for amine drugs.

  10. Interactions and dispersion stability of aluminum oxide colloidal particles in electroless nickel solutions in the presence of comb polyelectrolytes.

    PubMed

    de Hazan, Yoram; Reuter, Torben; Werner, Dennis; Clasen, Rolf; Graule, Thomas

    2008-07-15

    The effect of comb polyelectrolytes on the dispersion stability of colloidal alumina particles in DI water and commercial electroless nickel (EN) solutions was investigated. Adsorption of polyelectrolytes and major EN components onto colloidal alumina was assessed by TGA, chemical analysis, and zeta potential measurements. Zeta potential measurements were made during titrations of comb-polyelectrolyte-stabilized dispersions with EN solutions to full ionic strength for the first time. The compilation of titration curves made with varying amounts of comb polyelectrolytes provides high resolution and novel insight into the particle/surfactant/EN systems. Continuous decrease in particle/EN components surface interactions with the increase in comb polyelectrolyte coverage is observed. Laser diffraction measurements reveal steric stabilization of nano- and submicronmeter alumina dispersions in both DI water and EN solutions with >7 wt% and >2 wt% comb polyelectrolyte, respectively.

  11. Four-wave mixing based widely tunable wavelength conversion using 1-m dispersion-shifted bismuth-oxide photonic crystal fiber.

    PubMed

    Chow, K K; Kikuchi, K; Nagashima, T; Hasegawa, T; Ohara, S; Sugimoto, N

    2007-11-12

    We demonstrate widely tunable wavelength conversion based on four-wave mixing using a dispersion-shifted bismuth-oxide photonic crystal fiber (Bi-PCF). A 1-meter-long Bi-PCF is used as the nonlinear medium for wavelength conversion of a 10 Gb/s non-return-to-zero (NRZ) signal. A 3- dB working range of the converted signal over 35 nm is obtained with around 1-dB power penalty in the bit-error-rate measurements.

  12. 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.

  13. Strengthening of Ceramic-based Artificial Nacre via Synergistic Interactions of 1D Vanadium Pentoxide and 2D Graphene Oxide Building Blocks

    NASA Astrophysics Data System (ADS)

    Knöller, Andrea; Lampa, Christian P.; Cube, Felix Von; Zeng, Tingying Helen; Bell, David C.; Dresselhaus, Mildred S.; Burghard, Zaklina; Bill, Joachim

    2017-01-01

    Nature has evolved hierarchical structures of hybrid materials with excellent mechanical properties. Inspired by nacre’s architecture, a ternary nanostructured composite has been developed, wherein stacked lamellas of 1D vanadium pentoxide nanofibres, intercalated with water molecules, are complemented by 2D graphene oxide (GO) nanosheets. The components self-assemble at low temperature into hierarchically arranged, highly flexible ceramic-based papers. The papers’ mechanical properties are found to be strongly influenced by the amount of the integrated GO phase. Nanoindentation tests reveal an out-of-plane decrease in Young’s modulus with increasing GO content. Furthermore, nanotensile tests reveal that the ceramic-based papers with 0.5 wt% GO show superior in-plane mechanical performance, compared to papers with higher GO contents as well as to pristine V2O5 and GO papers. Remarkably, the performance is preserved even after stretching the composite material for 100 nanotensile test cycles. The good mechanical stability and unique combination of stiffness and flexibility enable this material to memorize its micro- and macroscopic shape after repeated mechanical deformations. These findings provide useful guidelines for the development of bioinspired, multifunctional systems whose hierarchical structure imparts tailored mechanical properties and cycling stability, which is essential for applications such as actuators or flexible electrodes for advanced energy storage.

  14. Strengthening of Ceramic-based Artificial Nacre via Synergistic Interactions of 1D Vanadium Pentoxide and 2D Graphene Oxide Building Blocks

    PubMed Central

    Knöller, Andrea; Lampa, Christian P.; Cube, Felix von; Zeng, Tingying Helen; Bell, David C.; Dresselhaus, Mildred S.; Burghard, Zaklina; Bill, Joachim

    2017-01-01

    Nature has evolved hierarchical structures of hybrid materials with excellent mechanical properties. Inspired by nacre’s architecture, a ternary nanostructured composite has been developed, wherein stacked lamellas of 1D vanadium pentoxide nanofibres, intercalated with water molecules, are complemented by 2D graphene oxide (GO) nanosheets. The components self-assemble at low temperature into hierarchically arranged, highly flexible ceramic-based papers. The papers’ mechanical properties are found to be strongly influenced by the amount of the integrated GO phase. Nanoindentation tests reveal an out-of-plane decrease in Young’s modulus with increasing GO content. Furthermore, nanotensile tests reveal that the ceramic-based papers with 0.5 wt% GO show superior in-plane mechanical performance, compared to papers with higher GO contents as well as to pristine V2O5 and GO papers. Remarkably, the performance is preserved even after stretching the composite material for 100 nanotensile test cycles. The good mechanical stability and unique combination of stiffness and flexibility enable this material to memorize its micro- and macroscopic shape after repeated mechanical deformations. These findings provide useful guidelines for the development of bioinspired, multifunctional systems whose hierarchical structure imparts tailored mechanical properties and cycling stability, which is essential for applications such as actuators or flexible electrodes for advanced energy storage. PMID:28102338

  15. Well-dispersed NiO nanoparticles supported on nitrogen-doped carbon nanotube for methanol electrocatalytic oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Wang, Pengcheng; Zhou, Yingke; Hu, Min; Chen, Jian

    2017-01-01

    Nitrogen-doped carbon nanotube supporting NiO nanoparticles were synthesized by a chemical precipitation process coupled with subsequent calcination. The morphology and structure of the composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the electrochemical performance was evaluated using cyclic voltammetry and chronoamperometric technique. The effects of nitrogen doping, calcination temperature and content of NiO nanoparticles on the electrocatalytic activity toward methanol oxidation were systematically studied. The results show that the uniformly dispersed ultrafine NiO nanoparticles supported on nitrogen-doped carbon nanotube are obtained after calcination at 400 °C. The optimized composite catalysts present high electrocatalytic activity, fast charge-transfer process, excellent accessibility and stability for methanol oxidation reaction, which are promising for application in the alkaline direct methanol fuel cells.

  16. 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.

  17. 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.

  18. Three-dimensional patterning of solid microstructures through laser reduction of colloidal graphene oxide in liquid-crystalline dispersions.

    PubMed

    Senyuk, Bohdan; Behabtu, Natnael; Martinez, Angel; Lee, Taewoo; Tsentalovich, Dmitri E; Ceriotti, Gabriel; Tour, James M; Pasquali, Matteo; Smalyukh, Ivan I

    2015-05-21

    Graphene materials and structures have become an essential part of modern electronics and photovoltaics. However, despite many production methods, applications of graphene-based structures are hindered by high costs, lack of scalability and limitations in spatial patterning. Here we fabricate three-dimensional functional solid microstructures of reduced graphene oxide in a lyotropic nematic liquid crystal of graphene oxide flakes using a pulsed near-infrared laser. This reliable, scalable approach is mask-free, does not require special chemical reduction agents, and can be implemented at ambient conditions starting from aqueous graphene oxide flakes. Orientational ordering of graphene oxide flakes in self-assembled liquid-crystalline phases enables laser patterning of complex, three-dimensional reduced graphene oxide structures and colloidal particles, such as trefoil knots, with 'frozen' orientational order of flakes. These structures and particles are mechanically rigid and range from hundreds of nanometres to millimetres in size, as needed for applications in colloids, electronics, photonics and display technology.

  19. 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

    2014-01-08

    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.

  20. 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.

  1. 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.

  2. 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

    2013-06-07

    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.

  3. Aniline as a dispersing and stabilizing agent for reduced graphene oxide and its subsequent decoration with Ag nanoparticles for enzymeless hydrogen peroxide detection.

    PubMed

    Liu, Sen; Wang, Lei; Tian, Jingqi; Luo, Yonglan; Zhang, Xinxin; Sun, Xuping

    2011-11-15

    An aqueous dispersion of reduced graphene oxide (rGO) has been successfully prepared via chemical reduction of graphene oxide (GO) by hydrazine hydrate in the presence of aniline for the first time. The noncovalent functionalization of rGO by aniline leads to a rGO dispersion that can be very stable for several months without the observation of any floating or precipitated particles. Several analytical techniques including Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to characterize the resulting rGO. Taking advantages of the fact reducing ability of aniline toward AgNO(3), we further demonstrated the subsequent decoration of rGO with Ag nanoparticles (AgNPs) by in situ chemical reduction of silver salts. It was found that such AgNP/rGO nanocomposites exhibit good catalytic activity toward the reduction of hydrogen peroxide (H(2)O(2)), leading to an enzymeless sensor with a fast amperometric response time of less than 2s. The linear detection range is estimated to be from 100 μM to 80 mM (r=0.9991), and the detection limit is estimated to be 7.1 μM at a signal-to-noise ratio of 3.

  4. Self-recovery of Pd nanoparticles that were dispersed over La(Sr)Fe(Mn)O3 for intelligent oxide anodes of solid-oxide fuel cells.

    PubMed

    Shin, Tae Ho; Okamoto, Yohei; Ida, Shintaro; Ishihara, Tatsumi

    2012-09-10

    Self-recovery is one of the most-desirable properties for functional materials. Recently, oxide anodes have attracted significant attention as alternative anode materials for solid-oxide fuel cells (SOFCs) that can overcome reoxidation, deactivation, and coke-deposition. However, the electrical conductivity and surface activity of the most-widely used oxide anodes remain unsatisfactory. Herein, we report the synthesis of an "intelligent oxide anode" that exhibits self-recovery from power-density degradation in the redox cycle by using a Pd-doped La(Sr)Fe-(Mn)O(3) cell as an oxide anode for the SOFCs. We investigated the anodic performance and oxidation-tolerance of the cell by using Pd-doped perovskite as an anode and fairly high maximum power densities of 0.5 and 0.1 W cm(-2) were achieved at 1073 and 873 K, respectively, despite using a 0.3 mm-thick electrolyte. Long-term stability was also examined and the power density was recovered upon exposure of the anode to air. This recovery of the power density can be explained by the formation of Pd nanoparticles, which were self-recovered through reoxidation and reduction. In addition, the self-recovery of the anode by oxidation was confirmed by XRD and SEM and this process was effective for improving the durability of SOFC systems when they were exposed to severe operating conditions.

  5. Atomically dispersed Co atoms on MoS2 monolayer: A promising high-activity catalyst for CO oxidation

    NASA Astrophysics Data System (ADS)

    Liu, Shangguo; Huang, Shiping

    2017-12-01

    We systematic investigated the CO oxidation reaction over a single Co atom supported by MoS2 monolayer (Co/MoS2) on the basis of density functional theory calculations and ab initio molecular dynamics simulations. The binding energy of a single Co atom onto MoS2 monolayer is up to 2.80 eV, making the diffusion and aggregation of supported Co atom difficult. For CO oxidation reaction, both Eley-Rideal and Langmuir-Hinshelwood mechanisms are considered. The energy barriers of CO oxidation through the Langmuir-Hinshelwood mechanism for the rate-limiting step of formation the peroxide-like O-C-O-O intermediate is only 0.57 eV. The relatively high CO oxidation activity of Co/MoS2 may be attributed to the strong electronic resonance among the 3d orbital of the Co atoms and the antibonding 2π* orbitals of adsorbed CO and O2. We proposal that the MoS2 monolayer can serve as a defect-free two dimensional single atom catalysts substrate for CO oxidation reaction. It provides not only a large surface ratio, but also a uniform distribution anchoring points for fixing metal atoms as activation sites. We hope that this work contributes to design more effective nonprecious-metal single-atom catalysts for CO oxidation and widen the applications of monolayer MoS2 materials.

  6. Process for strengthening silicon based ceramics

    SciTech Connect

    Kim, Hyoun-Ee; Moorhead, A.J.

    1991-03-07

    A process for strengthening silicon based ceramic monolithic materials and composite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400{degrees}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.

  7. 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.

  8. 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.

  9. Electric conductance of dispersions of metal oxides in solutions of weak acids in mixed dioxane-water solvents.

    PubMed

    Kosmulski, Marek; Mączka, Edward

    2012-08-15

    The electric conductance of solutions of sulfuric, oxalic, benzoic, and salicylic acid (up to 0.02 M) in dioxane-water mixed solvents (90% and 93% dioxane by mass) has been studied in the presence and absence of TiO(2) and Al(2)O(3) (0.5-5% by mass). TiO(2) and Al(2)O(3) enhanced the conductance of solutions of organic acids in aqueous dioxane. The conductance is interpreted in terms of adsorption of acid in molecular form, dissolution of ceramic oxides in form of anionic complexes, and leaching of acidic impurities from ceramic oxides.

  10. 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%.

  11. 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

  12. Impact of tween 20 hydroperoxides and iron on the oxidation of methyl linoleate and salmon oil dispersions.

    PubMed

    Nuchi, C D; McClements, D J; Decker, E A

    2001-10-01

    To determine the role of surfactant hydroperoxides on the oxidative stability of fatty acids, the oxidation of methyl linoleate micelles and salmon oil-in-water emulsions was measured as a function of varying Tween 20 hydroperoxide concentrations. Increasing Tween 20 hydroperoxide concentrations from 3.5 to 14.7 micromol hydroperoxide/g Tween 20 decreased the lag phase of headspace hexanal formation but did not increase the total amount of hexanal formed in methyl linoleate/Tween 20 micelles. In the micelle system, Fe(2+) decreased the lag phase of hexanal formation but increased total hexanal concentrations only in micelles with the highest Tween 20 hydroperoxide concentrations (14.7 micromol hydroperoxide/g surfactant). Increasing Tween 20 surfactant hydroperoxide concentrations also increased the oxidation of salmon oil-in-water emulsions as determined by lipid hydroperoxides and headspace propanal. In both the micelle and emulsion systems, the prooxidant effect of Fe(2+) decreased with increasing Tween 20 hydroperoxide concentrations. These data show that surfactant hydroperoxides such as those in Tween 20 could decrease the oxidative stability of lipids in food emulsions.

  13. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. 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.

  15. Green synthesis of core-shell gold-palladium@palladium nanocrystals dispersed on graphene with enhanced catalytic activity toward oxygen reduction and methanol oxidation in alkaline media

    NASA Astrophysics Data System (ADS)

    Zheng, Jie-Ning; Li, Shan-Shan; Ma, Xiaohong; Chen, Fang-Yi; Wang, Ai-Jun; Chen, Jian-Rong; Feng, Jiu-Ju

    2014-09-01

    Well-defined core-shell gold-palladium@palladium nanocrystals (AuPd@Pd) are facilely prepared by a simple and green wet-chemical method at 25 °C. A Good's buffer, 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid (HEPES), is used as a reducing agent and a shape-directing agent, while there is no template, seed, organic solvent, or surfactant involved. The AuPd@Pd nanocrystals are uniformly dispersed on graphene nanosheets by ultrasonication, resulting in the formation of graphene supported AuPd@Pd (G-AuPd@Pd). The as-prepared nanocomposites exhibit the improved catalytic activity, good tolerance, and better stability for oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) in alkaline media, compared with the G-Pd and commercial Pd black catalysts. The as-developed method may provide a promising pathway for large-scale fabrication of AuPd-based catalysts.

  16. How the dispersion of magnesium oxide nanoparticles effects on the viscosity of water-ethylene glycol mixture: Experimental evaluation and correlation development

    NASA Astrophysics Data System (ADS)

    Afrand, Masoud; Abedini, Ehsan; Teimouri, Hamid

    2017-03-01

    In this paper, the effect of dispersion of magnesium oxide nanoparticles on viscosity of a mixture of water and ethylene glycol (50-50% vol.) was examined experimentally. Experiments were performed for various nanofluid samples at different temperatures and shear rates. Measurements revealed that the nanofluid samples with volume fractions of less than 1.5% had Newtonian behavior, while the sample with volume fraction of 3% showed non-Newtonian behavior. Results showed that the viscosity of nanofluids enhanced with increasing nanoparticles volume fraction and decreasing temperature. Results of sensitivity analysis revealed that the viscosity sensitivity of nanofluid samples to temperature at higher volume fractions is more than that of at lower volume fractions. Finally, because of the inability of the existing model to predict the viscosity of MgO/EG-water nanofluid, an experimental correlation has been proposed for predicting the viscosity of the nanofluid.

  17. Binding of alkenes and ionic liquids to B-H-functionalized boron nanoparticles: creation of particles with controlled dispersibility and minimal surface oxidation.

    PubMed

    Perez, Jesus Paulo L; Yu, Jiang; Sheppard, Anna J; Chambreau, Steven D; Vaghjiani, Ghanshyam L; Anderson, Scott L

    2015-05-13

    The interaction of B-H-functionalized boron nanoparticles with alkenes and nitrogen-rich ionic liquids (ILs) is investigated by a combination of X-ray photoelectron spectroscopy, FTIR spectroscopy, dynamic light scattering, thermogravimetric analysis, and helium ion microscopy. Surface B-H bonds are shown to react with terminal alkenes to produce alkyl-functionalized boron particles. The interaction of nitrogen-rich ILs with the particles appears, instead, to be dominated by boron-nitrogen bonding, even for an ILs with terminal alkene functionality. This chemistry provides a convenient approach to producing and capping boron nanoparticles with a protective organic layer, which is shown to protect the particles from oxidation during air exposure. By controlling the capping group, particles with high dispersibility in nonpolar or polar liquids can be produced. For the particles capped with ILs, the effect of particle loading on hypergolic ignition of the ILs is reported.

  18. 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.

  19. Strengthening regional safeguards

    SciTech Connect

    Palhares, L.; Almeida, G.; Mafra, O.

    1996-08-01

    Nuclear cooperation between Argentina and Brazil has been growing since the early 1980`s and as it grew, so did cooperation with the US Department of Energy (DOE). The Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC) was formed in December 1991 to operate the Common System of Accounting and Control of Nuclear Materials (SCCC). In April 1994, ABACC and the DOE signed an Agreement of Cooperation in nuclear material safeguards. This cooperation has included training safeguards inspectors, exchanging nuclear material measurement and containment and surveillance technology, characterizing reference materials, and studying enrichment plant safeguards. The goal of the collaboration is to exchange technology, evaluate new technology in Latin American nuclear facilities, and strengthen regional safeguards. This paper describes the history of the cooperation, its recent activities, and future projects. The cooperation is strongly supported by all three governments: the Republics of Argentina and Brazil and the United States.

  20. 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.