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Sample records for bulk glassy alloys

  1. Ferromagnetic bulk glassy alloys

    International Nuclear Information System (INIS)

    This paper deals with the review on the formation, thermal stability and magnetic properties of the Fe-based bulk glassy alloys in as-cast bulk and melt-spun ribbon forms. A large supercooled liquid region over 50 K before crystallization was obtained in Fe-(Al, Ga)-(P, C, B, Si), Fe-(Cr, Mo, Nb)-(Al, Ga)-(P, C, B) and (Fe, Co, Ni)-Zr-M-B (M=Ti, Hf, V, Nb, Ta, Cr, Mo and W) systems and bulk glassy alloys were produced in a thickness range below 2 mm for the Fe-(Al, Ga)-(P, C, B, Si) system and 6 mm for the Fe-Co-(Zr, Nb, Ta)-(Mo, W)-B system by copper-mold casting. The ring-shaped glassy Fe-(Al, Ga)-(P, C, B, Si) alloys exhibit much better soft magnetic properties as compared with the ring-shaped alloy made from the melt-spun ribbon because of the formation of the unique domain structure. The good combination of high glass-forming ability and good soft magnetic properties indicates the possibility of future development as a new bulk glassy magnetic material

  2. Bulk glassy Ni(Co-)Nb-Ti-Zr alloys with high corrosion resistance and high strength

    International Nuclear Information System (INIS)

    Bulk glassy Ni60-xCoxNb20Ti10Zr10 (x=0-20 at.%) alloys with a large supercooled liquid region of more than 40 K were formed by copper-mold casting. The alloys with 5 and 10 at.% cobalt possess the highest glass-forming ability in the present alloy system and their critical diameter for glass formation is 1.5 mm. The bulk glassy alloys with different cobalt contents exhibit nearly the same corrosion behavior in HCl solutions. Their corrosion rates are less than 10-3 mm per year in 1 N and 6 N HCl solutions. The bulk glassy alloys are spontaneously passivated with low passive current densities of around 10-1 A m-2 in 1 N and 6 N HCl solutions. XPS analysis revealed the formation of a niobium-enriched passive film on the alloys by air-exposure or immersion in the acids, which could be responsible for the high corrosion resistance of the glassy Ni-based alloys. The Vickers hardness, Young's modulus, compressive fracture strength and compressive fracture elongation of the 1.5 mm diameter bulk glassy alloys are 860, 160 GPa, 3050 MPa and 2% respectively. The facture surface exhibits a vein-like morphology

  3. Mechanical properties of Fe-Ni-Cr-Si-B bulk glassy alloy

    International Nuclear Information System (INIS)

    The mechanical properties and crystallization behavior of new Fe-Ni-Cr-Si-B-based bulk glassy alloys were investigated. The suitability of the continuous roll casting method for the production of bulk metallic glass (BMG) sheets in such alloy systems was also examined. BMG samples (Fe-Ni-Cr-Si-B, Fe-Ni-Zr-Cr-Si-B, Fe-Ni-Zr-Cr-W-Si-B) in amorphous strip, cylindrical, and sheet forms were prepared through melt spinning, copper mold casting, and twin roll strip casting, respectively. Fe-Ni-Cr-Si-B alloy exhibited compressive strength of up to 2.93 GPa and plastic strain of about 1.51%. On the other hand, the Fe-Ni-Zr-Cr-Si-B, composite-type bulk sample with diameter of 2.0 mm showed remarkable compressive plastic strain of about 4.03%. The addition of zirconium was found to enhance the homogeneous precipitation of nanocrystalline less than 7 nm and to develop a hybrid-composite microstructure with increasing sample thickness. Twin roll strip casting was successfully applied to the fabrication of sheets in Fe-Ni-Cr-Si-B-based BMGs. The combined characteristics of high mechanical properties and ease of microstructure control proved to be promising in terms of the future progress of structural bulk amorphous alloys

  4. Glass formation, corrosion behavior and mechanical properties of bulk glassy Cu-Hf-Ti-Nb alloys

    International Nuclear Information System (INIS)

    Bulk glassy (Cu0.6Hf0.25Ti0.15)100-xNb x (x = 0-8 at.%) alloys with maximum diameters of 2.5-4 mm were produced by copper-mold casting. The corrosion rates in 1 N HCl and 3 mass% NaCl solutions significantly decrease with an increase in Nb content. The 6 at.% Nb alloy shows distinct spontaneous passive region in the HCl solution. The alloys with a larger amount of Nb are spontaneously passivated with lower passive current densities and higher pitting corrosion potentials in the NaCl solution. X-ray photoelectron spectroscopy analysis revealed that the formation of Hf-, Nb- and Ti-enriched surface film on the alloys could be responsible for the high corrosion resistance of the Cu-Hf-Ti-Nb alloys in HCl and NaCl solutions. Young's modulus, compressive fracture strength and compressive plastic strain are 130 GPa, 2405 MPa and 2.8%, respectively, for the 4 at.% Nb alloy, 126 GPa, 2305 MPa and 2.1%, respectively, for the 8 at.% Nb alloy

  5. Co-based soft magnetic bulk glassy alloys optimized for glass-forming ability and plasticity

    Indian Academy of Sciences (India)

    LI LI; HUAIJUN SUN; YUNZHANG FANG; JIANLONG ZHENG

    2016-06-01

    Co-based bulk glassy alloys (BGAs) have become more and more important because of their nearly zero magnetostriction and high giant magneto-impedance effect. Here, we report the improvement of glass-formingability (GFA), soft-magnetic properties and plasticity by a small addition of Mo atoms in CoFeBSiNbMo BGAs.(Co$_{0.6}$Fe$_{0.4}$)$_{69}$B$_{20.8}$Si$_{5.2}$Nb$_{5−x}$Mo$_{x}$ ferromagnetic BGA cylindrical glassy rods were fabricated successfully with adiameter of 5 mm by conventional copper mould casting method. It reveals that the substitution of a small amount of Mo for Nb makes the composition to approach a eutectic point and effectively enhances the GFA of alloy. Inaddition to high GFA and superhigh strength, the compressive test shows that the Mo addition can improve the plasticity for the obtained BGAs. The combination of high GFA, excellent soft-magnetic properties and good plasticitydemonstrated in our alloys is promising for the future applications as functional materials.

  6. Synthesis of ferromagnetic Fe-based bulk glassy alloys in the Fe-Si-B-P-C system

    International Nuclear Information System (INIS)

    Multi-component Fe76P5(BxSiyCz)19 glassy alloys were fount to exhibit a distinct glass transition, followed by a supercooled liquid region before crystallization in a rather wide composition range. The largest value of the supercooled liquid region defined by the difference between the glass transition temperature (Tg) and crystallization temperature (Tx), ΔTx (=Tx - Tg) was 54 K for Fe76P5(Si0.3B0.5C0.2)19. Furthermore, the crystallization of the glassy alloy occurs through a single exothermic reaction, which means simultaneous precipitation of several kinds of crystallites leading to higher glassy forming ability (GFA) due to the necessity of the atomic rearrangement on a long range scale. By copper mold casting, bulk glassy alloy rods with diameters up to 3 mm were produced. The representative Fe76P5(B0.5Si0.3C0.2)19 alloy exhibits rather high saturation magnetization of 1.44 T with good soft-magnetic properties, i.e., low coercive force of 1.2 A/m, and high effective permeability of 17,600 at 1 kHz under a field of 1 A/m. The bulk glassy alloy also possesses superhigh fracture strength of 3700 MPa and Young's modulus of 185 GPa. This new ferromagnetic bulk glassy alloy simultaneously exhibiting high GFA, rather high saturation magnetization, excellent soft-magnetic properties and superhigh fracture strength is promising for future applications as not only functional but also structural material

  7. Study of local structure in hyper-eutectic Zr-Cu-Al bulk glassy alloys by positron annihilation techniques

    Science.gov (United States)

    Ishiyama, T.; Ishii, K.; Yokoyama, Y.; Konno, T. J.; Iwase, A.; Hori, F.

    2016-01-01

    The Zr-Cu-Al bulk glassy (BG) alloy, which has amorphous structure, possesses various properties such as high strength and toughness with compositional dependence. In the present study, density, positron annihilation lifetime and coincidence Doppler Broadening measurement have been performed for various compositional hyper-eutectic Zr-Cu-Al BG alloys. The density of hyper-eutectic Zr-Cu-Al BG alloys increases with decreasing of Zr fraction. In contrast, positron lifetime for all compositional alloys is almost constant about 165 psec. In addition, the CDB ratio profile is almost the same for hyper-eutectic alloys. This unchanging trend of CDB ratio profile is quite different from that of hypo-eutectic BG alloys. These results reveal that different internal structure exists in hyper and hypo-eutectic BG alloys.

  8. Unusual glass-forming ability of new Zr-Cu-based bulk glassy alloys containing an immiscible element pair

    International Nuclear Information System (INIS)

    We herein report the unusual glass-forming ability (GFA) of a new series of quinary Zr48Cu36-xNixAg8Al8 (048Cu36Ag8Al8 alloy. By cooper mold casting, an as-cast glassy rod with a diameter of 30 mm can be easily obtained for the representative alloy Zr48Cu32Ni4Ag8Al8. The possible reasons for the excellent GFA of the new quinary alloys with an immiscible element pair are discussed based on the atomic size distribution, chemical compatibility among the components and atomic structure of glassy alloys. (author)

  9. Enhanced glass-forming ability of FeCoBSiNb bulk glassy alloys prepared using commercial raw materials through the optimization of Nb content

    International Nuclear Information System (INIS)

    We optimized the alloy compositions by modifying the Nb content in [(Fe0.5Co0.5)0.75B0.20Si0.05]100-xNbx(x=3.6-4.4) alloy system. As a result, it was found that the Nb content of 4.3 at. % was effective for approaching alloy to a eutectic point. By copper mold casting, [(Fe0.5Co0.5)0.75B0.20Si0.05]95.7Nb4.3 bulk glassy alloy rods with diameters up to 4 mm were successfully synthesized even using commercial raw materials. These glassy alloys exhibit a rather high saturation magnetization of 0.77 T and low coercive force of 2.5 A/m.

  10. Effect of Cr addition on the glass-forming ability, magnetic properties, and corrosion resistance in FeMoGaPCBSi bulk glassy alloys

    International Nuclear Information System (INIS)

    The effect of Cr addition on the glass-forming ability (GFA), the magnetic properties, and corrosion resistance in Fe-Mo-Ga-P-C-B-Si glassy alloys was investigated. In addition to a slight increase of supercooled liquid region from 50 to 55 K, the substitution of a small amount of Fe with Cr was found to be effective for approaching alloy to a eutectic point, resulting in an increase in GFA. By copper mold casting, bulk glassy alloy rods with diameters up to 3 mm were produced. These glassy alloys exhibit a rather high saturation magnetization of 0.84-1.11 T with good soft-magnetic properties, i.e., low coercive force of 2.3-2.9 A/m, and high effective permeability of 13 360-15 960 at 1 kHz under a field of 1 A/m. The passive current density of the glassy alloy rod in 3 mass % NaCl solution decreased significantly from 1x102 to 3x10-1 A/m2 with an increase in Cr content, indicating that the addition of Cr is effective in enhancing the corrosion resistance

  11. Glass formation ability, structure and magnetocaloric effect of a heavy rare-earth bulk metallic glassy Gd55Co20Fe5Al20 alloy

    International Nuclear Information System (INIS)

    The glass formation ability, the structure and the magnetocaloric effect of the bulk metallic glassy Gd55Co20Fe5Al20 alloy were investigated. Bulk metallic glassy (BMGs) alloys were prepared by a copper-mold casting method. The glass forming ability and their structure were studied by using X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The XRD analysis revealed that the as-cast cylinder of Gd55Co20Fe5Al20 alloy showed fully amorphous structure in 2 mm diameter. The DSC revealed that the bulk cylinder of the Gd55Co20Fe5Al20 alloy showed a distinct glass transition temperature and a relatively wide supercooled liquid region before crystallization. SQUID investigated the magnetic properties and the entropy changes. The Curie temperature of Gd55Co20Fe5Al20 BMGs alloy was about 130 K, but the maximum magnetic entropy changes(-ΔSM) showed at about 125 K, a little lower than the Curie temperature 130 K. The reason could probably be due to the presence of a little amount of nanocrystalline particles between amorphous phases. The BMG alloy has the characteristic of second-order transition (SOT) on Arrott plots. The results showed that the amorphous sample had a relatively improved magnetocaloric effect, indicating that the amorphous alloy could be considered as a candidate for magnetic refrigeration applications in the temperature interval range of 100-200 K

  12. New bulk glassy alloys in Cu-Zr-Ag ternary system prepared by casting and milling

    International Nuclear Information System (INIS)

    The thermal stability, crystallization behaviour and glass forming ability of Cu-Zr-Ag system have been investigated on the basis of a ternary phase diagram. We altered the concentration of the alloys from the Cu58Zr42 to the concentration of the deep eutectic point of the Cu-Zr-Ag ternary system and we calculated the glass forming ability parameters. This paper summarises the results of the procedure during which Cu-Zr-Ag amorphous alloys with different Ag content (0-25%) were prepared by casting and ball-milling. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mold. The supercooled liquid region (ΔTx) exceeded 75K. Following the characterization of the cast alloys, master alloys of identical composition were milled in a Fritsch Pulverisette 2 ball-mill. The powders, milled for various periods of time were analysed by XRD in order to define the amorphous fraction.

  13. Structure and density of Fe36Co36B19.2Si4.8Nb4 bulk glassy alloy

    Directory of Open Access Journals (Sweden)

    A. Januszka

    2012-06-01

    Full Text Available Purpose: The work presents density measurements of bulk metallic glasses in as-cast state. Additionally casting method and structure characterization was displayed.Design/methodology/approach: The studies were performed on Fe36Co36B19.2Si4.8Nb4 metallic glasses in form of rods with diameter 2 and 3 mm. Samples were fabricated using copper mould casting method. The master alloy characteristic temperatures (Tm – melting point and Tl – liquidus temperature were determinate by differential thermal analysis (DTA. The structure was characterized by X-ray (XRD method and scanning electron microscope (SEM. The densities of metallic glassy rods have been measured by using the Archimedes principle.Findings: The XRD and SEM investigations revealed that the studied samples in form of rods were amorphous. Broad diffraction “halo” was observed for every testing piece. Fracture observation confirmed glassy state of samples. Archimedes principle allows calculating density of tested sample.Practical implications: The FeCo-based bulk metallic glasses have attracted great interest for a variety application fields for example electric applications, precision machinery materials or structural materials. Metallic glasses exhibit higher density than their crystalline counterparts and could be apply as a satisfactory structural material.Originality/value: The obtained results confirm the utility of applied investigation methods in the thermal and structure analysis of examined amorphous alloys. Density of metallic glasses is important properties which influence on specific application these materials. This materials offer attractive qualities, combining some of the desirable properties of conventional crystalline metals and the formability of conventional oxide glasses.

  14. Irradiation effect of swift heavy ion for Zr{sub 50}Cu{sub 40}Al{sub 10} bulk glassy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Onodera, Naoto; Ishii, Akito; Ishii, Kouji; Iwase, Akihiro [Department of Materials Science, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Yokoyama, Yoshihiko [Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai 980-8577 (Japan); Saitoh, Yuichi [Japan Atomic Energy Agency (JAEA), Takasaki Advanced Radiation Research Institute, 1233, Watanuki-machi, Takasaki, Gunma 370-1292 (Japan); Ishikawa, Norito [Japan Atomic Energy Agency (JAEA), Tokai Research and Development Center, Naka-ku, Ibaraki 319-1195 (Japan); Yabuuchi, Atsushi [Research Organization for the 21st Century, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Hori, Fuminobu, E-mail: horif@mtr.osakafu-u.ac.jp [Department of Materials Science, Osaka Prefecture University, 1-1, Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan)

    2013-11-01

    It has been reported that heavy ion irradiation causes softening in some cases of Zr-based bulk metallic glass alloys. However, the fundamental mechanisms of such softening have not been clarified yet. In this study, Zr{sub 50}Cu{sub 40}Al{sub 10} bulk glassy alloys were irradiated with heavy ions of 10 MeV I at room temperature. The maximum fluence was 3 × 10{sup 14} ions/cm{sup 2}. The positron annihilation measurements have performed before and after irradiation to investigate changes in free volume. We discuss the relationship between the energy loss and local open volume change after 10 MeV I irradiation compared with those obtained for 200 MeV Xe and 5 MeV Al. The energy loss analysis in ion irradiation for the positron lifetime has revealed that the decreasing trend of positron lifetime is well expressed as a function of total electronic energy deposition rather than total elastic energy deposition. It means that the positron lifetime change by the irradiation has a relationship with the inelastic collisions with electrons during heavy ion irradiation.

  15. Small atom diffusion in the glassy and supercooled liquid states of bulk amorphous ZrTiCuNiBe alloys

    International Nuclear Information System (INIS)

    New bulk metallic ZrTiCuNiBe glass forming alloys exhibit an excellent stability over a large supercooled liquid region and offer the opportunity to investigate atomic transport in the supercooled liquid state. We present measurements of atomic diffusion of beryllium in Zr41.2Ti13.8Cu12.5Ni10Be22.5 and Zr46.7Ti8.3Cu7.5Ni10Be27.5 in the temperature range between 530 K and 710 K. Below the glass transition temperature, Tg∼625 K, the data suggest a single atomic jump diffusion behavior of Be with a migration enthalpy of about 1 eV/atom in both alloys. Below Tg, Be diffusivity in Zr46.7Ti8.3Cu7.5Ni10Be27.5 is by one order of magnitude higher than in Zr41.2Ti13.8Cu12.5Ni10Be27.5 which can be explained by a larger fraction of free volume in this alloy. Above the glass transition the temperature dependence of Be diffusivity increases in both alloys, leading to apparent activation energies of 4.5 eV/atom in Zr41.2Ti13.8Cu12.5Ni10Be22.5 and 1.9 eV/atom in Zr46.7Ti8.3Cu7.5Ni10Be27.5. By taking into account the change in configurational entropy due to the glass transition, we explain the mechanism for diffusion of Be in the supercooled liquid states of the ZrTiNiCuBe alloys by single atomic jumps in a continously changing configuration of neighboring atoms. The corresponding migration enthalpies are the same as in the solid states, and the larger activation energies above Tg are mimiced by the increase of configurational entropy with temperature which is smaller in Zr46.7Ti8.3Cu7.5Ni10Be27.5 than in Zr41.2Ti13.8Cu12.5Ni10Be22.5. A comparison of Be diffusivity and viscosity of Zr46.7Ti8.3Cu7.5Ni10Be27.5 above Tg reveals a breakdown of the Stokes-Einstein relation, indicating cooperative processes in the supercooled liquid state. (orig.)

  16. Large bulk soft magnetic [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 glassy alloy prepared by B2O3 flux melting and water quenching

    International Nuclear Information System (INIS)

    The large bulk soft magnetic glassy [(Fe0.5Co0.5)0.75B0.20Si0.05]96Nb4 alloy specimens with the diameters up to 7.7 mm have been prepared by water quenching the melt immersed in the molten flux of B2O3. The maximum diameter of the obtained specimens is approximately 1.5 times as large as the previous result for copper mold casting. The bulk specimen with 7.7 mm in diameter exhibits the saturation magnetization of 1.13 T, the coercivity lower than 20 A/m at room temperature, and the Curie temperature of 732 K. This bulk specimen is the thickest of any soft magnetic glassy alloys formed until now

  17. Iron - based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2010-07-01

    Full Text Available Purpose: The paper presents a structure characterization, thermal and soft magnetic properties analysis of Fe-based bulk amorphous materials in as-cast state and after crystallization process. In addition, the paper gives some brief review about achieving, formation and structure of bulk metallic glasses as a special group of amorphous materials.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4 metallic glass in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties contained initial and maximum magnetic permeability, coercive force and magnetic after-effects measurements were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations revealed that the studied as-cast bulk metallic glasses in form of ribbons and rods were amorphous. Two stage crystallization process was observed for studied bulk amorphous alloy. The differences of crystallization temperature between ribbons and rods with chosen thickness are probably caused by different amorphous structures as a result of the different cooling rates in casting process. The SEM images showed that studied fractures could be classified as mixed fractures with indicated two zones contained “river” and “smooth” areas. The changing of chosen soft magnetic properties (μr, Bs, Hc obtained for samples with different thickness is a result of the non-homogenous amorphous structure of tested metallic glasses. The annealing process in temperature range from 373 to 773 K causes structural relaxation of tested amorphous materials, which leads to changes in their physical properties. The qualitative

  18. Synthesis and properties of Cu-Zr-Ag-Al glassy alloys with high glass-forming ability

    International Nuclear Information System (INIS)

    New Cu-Zr-based glassy alloys with an unusual glass-forming ability (GFA) were synthesized in the Cu-Zr-Ag-Al system, based on a ternary Cu45Zr45Ag10 alloy. The quaternary alloys exhibit large supercooled liquid region of 75-108 K and high-reduced glass transition temperature of 0.581-0.610. The best GFA was obtained for Cu36Zr48Ag8Al8 alloy, from which bulk glassy samples of up to 25 mm diameter were successfully fabricated by an injection mold casting method. The bulk glassy alloys exhibit high-compressive fracture strength of 1836-1981 MPa with plastic strain of 0.1-1.0% and excellent corrosion resistance in 1N H2SO4 solution

  19. Effects of boron content on the glass-forming ability and mechanical properties of Co–B–Ta glassy alloys

    International Nuclear Information System (INIS)

    Highlights: • Glassy rods with diameters up to 3 mm were formed in Co92−xBxTa8 (x = 30−37.5) system. • The plasticity of Co–B–Ta glassy alloys increases with increasing B content. • The plastic strains of above 2.0% were observed in these glassy alloys. • These Co–B–Ta glassy alloys exhibit ultrahigh strength of above 5000 MPa. • The relationships of elastic constants with mechanical properties were studied. - Abstract: The effects of boron content on the glass-forming ability, mechanical and elastic properties in Co92−xBxTa8 (at.%, x = 30, 32.5, 35, and 37.5) bulk glassy alloys were investigated. Among these alloys studied, the Co59.5B32.5Ta8 alloy exhibits the highest glass-forming ability, which could form a glassy rod at least 3 mm in diameter by the copper mold casting method. It is found that the plasticity of those glassy alloys increases with decreasing boron content. The plastic strains for the Co59.5B32.5Ta8 and Co62B30Ta8 BMGs are up to ∼2.1% and ∼2.5%, respectively. The decrease of shear modulus with decreasing boron content results in the increase of Poisson’s ratio, which is responsible for the improved plasticity. In addition, the strength of the ductile glassy alloys remains very high at above 5000 MPa, although enhancing plasticity is accompanied by the loss of some strength. The present results show that Co–B–Ta bulk metallic glass with good glass-forming ability and significant plasticity as well as ultrahigh strength can be synthesized by adjusting alloy composition

  20. Formation and corrosion behavior of glassy Ni-Nb-Ti-Zr-Co(-Cu) alloys

    International Nuclear Information System (INIS)

    Bulk glassy Ni55Nb20Ti10Zr8Co7 alloy with a critical diameter of 2 mm was synthesized by copper-mold casting and the glass transition temperature, crystallization temperature and supercooled liquid region are 858 K, 911 K and 52 K, respectively. High corrosion resistance in 1N HCl and H2SO4 solutions was recognized for the glassy alloys Ni55Nb20Ti10Zr8Co7 together with Ni53Nb20Ti10Zr8Co6Cu3 which possesses higher glass-forming ability. They are spontaneously passivated with low passive current densities of the order of 10-2 A/m2 and their corrosion rate was less than 10-3 mm/year in the solutions. A small amount addition of Cu (3 at.%) in the Ni-Nb-Ti-Zr-Co glassy alloy system has little effect on corrosion behavior and surface film composition. Niobium-rich passive films form on the glassy Ni-Nb-Ti-Zr-Co(-Cu) alloys, which could be responsible for the high corrosion resistance

  1. Ultrasonic properties of Cu45Zr(45-x)HfxAg10 glassy alloys

    International Nuclear Information System (INIS)

    Using ultrasonics, the acoustic characteristics of Cu45Zr(45-x)HfxAg10 (x=0-25) glassy alloys were examined in terms of complex elasticity. The values of bulk modulus (K), Lame parameter (λ), Young's (E) and shear (G) moduli of Cu45Zr(45-x)HfxAg10 glassy alloys are found to have a unique order for metallic materials, except for polymers. The large Poisson ratio (∝0.421) and the lower G /K ratio (∝0.167) at 25 at% Hf indicate rubbery characteristics that readily undergo uniaxial volume-preserving deformation but resist three-dimensional nonvolume-preserving deformation. The complex dynamic viscosity shows that visco-elasticity of the glassy alloys is dominated by shear motion. The large peaks in K and λ, and small ones in E and G at 5 at% Hf, and one large peak in the shear attenuation coefficient at 2.5 at% Hf, may indicate atomic morphological change by electron-transverse phonon coupling. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Bulk amorphous Mg-based alloys

    DEFF Research Database (Denmark)

    Pryds, Nini

    The present paper describes the preparation and properties of bulk amorphous quarternary Mg-based alloys and the influence of additional elements on the ability of the alloy to form bulk amorphous. The main goal is to find a Mg-based alloy system which shows both high strength to weight ratio and a...... low glass transition temperature. The alloys were prepared by using a relatively simple technique, i.e. rapid cooling of the melt in a copper wedge mould. The essential structural changes that are achieved by going from the amorphous to the crystalline state through the supercooled liquid state are...... discussed in this paper. On the basis of these measurements phase diagrams of the different systems were constructed. Finally, it is demonstrated that when pressing the bulk amorphous alloy onto a metallic dies at temperatures within the supercooled liquid region, the alloy faithfully replicates the surface...

  3. On the origin of bulk glass forming ability in Cu-Hf, Zr alloys

    Science.gov (United States)

    Ristić, Ramir; Zadro, Krešo; Pajić, Damir; Figueroa, Ignacio A.; Babić, Emil

    2016-04-01

    Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed-matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30–70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free-energy considerations and provides a simple way to select the compositions with high GFA.

  4. Thermal stability and magnetic properties of Fe-Co-B-Si-Nb glassy alloys

    International Nuclear Information System (INIS)

    The fully glassy rods of [(FexCo1-x)0.75Si0.05B0.25]94Nb6 alloys (x=0.4, 0.5 and 0.6) in diameters up to 2 mm were produced by copper mold casting. The effect of Fe substitution in these glassy alloys on thermal stability and melting behavior were studied by differential scanning calorimetry. Phase evolution of the glassy alloys during heating crystallization process was evaluated using X-rays diffraction. The first crystallization stage results in the precipitation of metastable (Fe,Co)23B6 crystalline phase in the glassy alloys. The behaviour of the glassy alloys in DC applied field was investigated by means of vibrating sample magnetometer. The investigated samples are soft magnetic. Further, the influence of crystallization on the saturation magnetization (Ms), coercivity (Hc) and Curie temperature (Tc) were evaluated, which indicated that (Fe,Co)23B6 phase can improve the Ms and Tc, while also increase the Hc.

  5. Cu-based bulk amorphous alloy with larger glass-forming ability and supercooled liquid region

    Energy Technology Data Exchange (ETDEWEB)

    Fu, H.M. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); School of Engineering, University of Queensland, St. Lucia, Qld 4072 (Australia)], E-mail: waterdrophmfu@hotmail.com; Zhang, H.F. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, H. [Faculty of Engineering and Surveying, University of Southern Queensland, Toowoomba, Qld 4350 (Australia); Hu, Z.Q. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2008-06-30

    The glassy rod with a maximum sample thickness of 11 mm and larger supercooled liquid region of 108 K was successfully fabricated when substituting Cu with minor amount of Ag in the Cu-Zr-Al-Gd alloy system. The value of {gamma} reaches a maximum of 0.418 for the Cu{sub 45.5}Zr{sub 45}Al{sub 7}Gd{sub 2}Ag{sub 0.5} bulk metallic glass (BMG) alloy. The high glass-forming ability (GFA) and larger supercooled liquid region are discussed from atomic size, negative mixing heat among constituent elements and thermodynamics.

  6. Superconducting State Parameters of Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    Aditya M. Vora

    2012-12-01

    Full Text Available Well recognized empty core (EMC pseudopotential of Ashcroft is used to investigate the superconducting state parameters viz; electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature TC, isotope effect exponent α and effective interaction strength NOV of some (Ni33Zr671 – xVx (x = 0, 0.05, 0.1, 0.15 bulk amorphous alloys. We have incorporated five different types of local field correction functions, proposed by Hartree (H, Taylor (T, Ichimaru-Utsumi (IU, Farid et al. (F and Sarkar et al. (S to show the effect of exchange and correlation on the aforesaid properties. Very strong influence of the various exchange and correlation functions is concluded from the present study. The TC obtained from Sarkar et al. (S local field correction function are found an excellent agreement with available theoretical data. Quadratic TC equation has been proposed, which provide successfully the TC values of bulk amorphous alloys under consideration. Also, the present results are found in qualitative agreement with other such earlier reported data, which confirms the superconducting phase in the s bulk amorphous alloys.

  7. Role of Ge incorporation in the physical and dielectric properties of Se$_{75}$Te$_{25}$ and Se$_{85}$Te$_{15}$ glassy alloys

    Indian Academy of Sciences (India)

    SHARMA J; KUMAR S

    2016-05-01

    The effect of Ge additive on the physical and dielectric properties of Se$_{75}$Te$_{25}$ and Se$_{85}$Te$_{15}$ glassy alloys has been investigated. It is inferred that on adding Ge, the physical propertiesi.e., average coordination number, average number of constraints and average heat of atomization increase but lone pair electrons, fraction of floppy modes, electronegativity, degree of crosslinking and deviation of stoichiometry (R) decrease. The effect of Ge doping on the dielectric propertiesof the bulk Se$_{75}$Te$_{25}$ and Se$_{85}$Te$_{15}$ glassy alloys has also been studied in the temperature range 300–350 K for different frequencies (1 kHz–5 MHz). It is found that, with doping, the dielectric constant $\\epsilon'$ and dielectric loss $\\epsilon "$ increase with increase in temperature and decrease with increase in frequency. The role of the third element Ge, as an impurity in the two pure binary Se$_{75}$Te$_{25}$ and Se$_{85}$Te$_{15}$ glassy alloys has been discussed in terms of the nature of covalent bonding and electronegativity difference between the elements used in making the aforesaid glassy systems.

  8. Composition dependent of dielectric properties in Se100-xSnx glassy alloys

    International Nuclear Information System (INIS)

    Research highlights: → The study of dielectric relaxation in some amorphous material is expected to reveal structural information which, in effect, can be useful for the understanding of the conduction mechanism as well. → In this paper, the temperature and frequency dependence of the dielectric constants and the dielectric losses in Se100-xSnx glassy systems in the frequency range (1 kHz-5 MHz) and temperature range (300 K-350 K) have been measured which are found to be highly dependent on frequency and temperature. → The change of the dielectric parameters with Sn in a-Se could be explained on the basis of the electro-negativity difference and the nature of covalent character of bonds between the constituent elements used in making the above glassy alloys. - Abstract: In this paper we report the composition dependence of dielectric properties in Se100-xSnx (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constant (ε') and the dielectric loss (ε'') in the above glassy systems, in the frequency range (1 kHz to 5 MHz) and temperature range (300-350 K) have been measured. It has been found that ε' and ε'' both are frequency and temperature dependent and are also found to increase with increasing concentration of Sn in pure amorphous Se. The role of Sn, as an impurity in the pure a-Se glassy alloy, has also been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have also been correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  9. Study of electrical properties of glassy Se100–Te alloys

    Indian Academy of Sciences (India)

    N Mehta; A Dwivedi; R Arora; S Kumar; A Kumar

    2005-10-01

    Temperature and frequency dependence of a.c. conductivity have been studied in glassy Se100–Te ( = 10, 20 and 30) over different range of temperatures and frequencies. An agreement between experimental and theoretical results suggests that the a.c. conductivity behaviour of selenium–tellurium system (Se100–Te) can be successfully explained by correlated barrier hopping (CBH) model. The density of defect states has been determined using this model for all the glassy alloys. The results show that bipolaron hopping dominates over single-polaron hopping in this glassy system. This is explained in terms of lower values of the maximum barrier height for single-polaron hopping. The values of density of charged defect states increase with increase in Te concentration. This is in agreement with our previous results obtained from SCLC measurements.

  10. Dielectric relaxation in glassy Se75In25−Pb alloys

    Indian Academy of Sciences (India)

    J Sharma; S Kumar

    2010-03-01

    In this paper we report the effect of Pb incorporation in the dielectric properties of a-Se75In25 glassy alloy. The temperature and frequency dependence of the dielectric constants and the dielectric losses in glassy Se75In25−Pb ( = 0, 5, 10 and 15) alloys in the frequency range (1 kHz–5 MHz) and temperature range (300–340 K) have been measured. A detailed analysis shows that the dielectric losses are dipolar in nature and can be understood in terms of hopping of charge carriers over a potential barrier as suggested by Elliott for the case of chalcogenide glasses. It has been found that both dielectric constant and the dielectric loss are highly dependent on frequency and temperature and also found to increase with increasing concentration of Pb in binary a-Se 75 In 25 glassy system. The results have been interpreted in terms of increase in the density of defect states by the incorporation of Pb as a metallic additive in the aforesaid glassy system.

  11. Glassy metallic plastics

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper reports a class of bulk metallic glass including Ce-, LaCe-, CaLi-, Yb-, and Sr-based metallic glasses, which are regarded as glassy metallic plastics because they combine some unique properties of both plastics and metallic alloys. These glassy metallic plastics have very low glass transition temperature (Tg~25oC to 150oC) and low Young’s modulus (~20 GPa to 35 GPa). Similar to glassy plastics, these metallic plastics show excellent plastic-like deformability on macro-, micro- and even nano-scale in their supercooled liquid range and can be processed, such as elongated, compressed, bent, and imprinted at low temperatures, in hot water for instance. Under ambient conditions, they display such metallic properties as high thermal and electric conductivities and excellent mechanical properties and other unique properties. The metallic plastics have potential applications and are also a model system for studying issues in glass physics.

  12. Bulk eutectic Cu–Ag alloys with abundant twin boundaries

    International Nuclear Information System (INIS)

    Abundant growth twin boundaries are found and characterized in two bulk eutectic Cu–Ag alloys that can be obtained conveniently. The statistical electron backscattering diffraction results show that both hetero-twin and cube-on-cube orientation relationships coexist in the eutectic Cu–Ag alloy. The tensile strength of the eutectic alloy increases with a decrease in the layer thickness of the Cu/Ag phase. This study provides a potential way to produce bulk eutectic Cu–Ag alloy with abundant twin boundaries that offers a combination of high strength and high ductility.

  13. Microstructure and properties of glassy NdCoAl alloys with Ga and Nb additions

    International Nuclear Information System (INIS)

    The glass forming ability and structure upon fast cooling were investigated for Nd60Co30Al10 with Ga and Nb additions. The investigated alloys contained 1, 3 and 5 at. % of Ga or Nb. From every composition different samples were produced. The melt spinning apparatus was used to make glassy ribbons 4 mm wide and 0.03 mm thick and by copper mould casting rods with diameters of 1 and 2 mm were cast. The structure of the samples was investigated by means of Xray diffraction and electronic microscopy and the thermal stability by differential scanning calorimetry (DSC). In order to rule out the effect of composition and cooling conditions, the microstructure and thermal behaviour of master alloys with and without Ga and Nb additions were also checked. The paper will discuss the microstructure formation for different samples, as a function of two parameters: the composition and the cooling rate

  14. Microstructure evolution and mechanical properties of Nb-alloyed Cu-based bulk metallic glasses and composites

    International Nuclear Information System (INIS)

    Highlights: • The microstructures of as-cast BMGs undergo a composite-amorphous evolution. • The 15.1% of plasticity and the 2205 MPa of fracture strength are achieved. • The dispersed crystals in glassy matrix enhance the plasticity of BMG. - Abstract: This paper reports the microstructure evolution of Cu50.2 Zr40.8Ti9−xNbx (x = 0.5, 1.0, and 2.0 at.%) bulk metallic glass and bulk metallic glass composites accompanied with the addition of Nb and the corresponding mechanical properties. The X-ray diffraction and characterization of microstructures demonstrate that the microstructures of as-cast alloys undergo a composite-amorphous evolution. DSC analysis indicates that the glass-forming ability of as-cast alloys increases with addition of Nb. The microstructure evolution can be contributed to the combination of the stabilization of Nb on precipitated crystalline phases and cooling time. 1.0 at.% Nb-alloyed sample has the best plasticity (15.1%) and the highest fracture strength (2205 MPa) among three as-cast alloys. This work suggests that the uniformly dispersed tiny crystalline phases in glassy matrix can enhance the plasticity of bulk metallic glasses

  15. Electrocatalytic oxidation of methanol on Ni and NiCu alloy modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Danaee, I.; Jafarian, M.; Forouzandeh, F.; Mahjani, M.G. [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran); Gobal, F. [Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran (Iran)

    2008-08-15

    Nickel and nickel-copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) prepared by galvanostatic deposition were examined for their redox process and electrocatalytic activities towards the oxidation of methanol in alkaline solutions. The methods of cyclic voltammetery (CV) and chronoamperometry (CA) were employed. The cyclic voltammogram of NiCu alloy demonstrates the formation of {beta}/{beta} crystallographic forms of the nickel oxyhydroxide under prolonged repetitive potential cycling in alkaline solution. In CV studies, in the presence of methanol NiCu alloy modified electrode shows a significantly higher response for methanol oxidation. The peak current of the oxidation of nickel hydroxide increase is followed by a decrease in the corresponding cathodic current in presence of methanol. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of methanol was found to be 2 x 10{sup -6} cm{sup 2} s{sup -1} in agreement with the values obtained from CV measurements. (author)

  16. Composition dependence of dielectric properties in Se{sub 100-x}Cu{sub x} glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, J.; Shrotriya, D.; Kumar, S., E-mail: dr-santosh-kr@yahoo.com [Department of Physics, Christ Church College, Kanpur-208001 (India)

    2015-06-24

    In this paper we report the composition dependent of dielectric properties in Se{sub 100-x}Cu{sub x} (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K–350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  17. Read/write characteristics of a new type of bit-patterned-media using nano-patterned glassy alloy

    International Nuclear Information System (INIS)

    The paper reports a feasibility study of new type bit-patterned-media using a nano-patterned glassy alloy template for ultra-high density hard disk applications. The prototype bit-patterned-media was prepared using a nano-hole array pattern fabricated on a Pd-based glassy alloy thin film and a Co/Pd multilayered film filled in the nano-holes. The prepared prototype bit-patterned-media had a smooth surface and isolated Co/Pd multilayer magnetic dots, where the average dot diameter, the average dot pitch and the average dot height were 30, 60 and 19 nm, respectively. MFM (magnetic force microscope) observation revealed that each dot was magnetized in a perpendicular direction and the magnetization could reverse when an opposite magnetic field was applied. Static read/write tester measurements showed that repeated writing and reading on isolated magnetic dots were possible in combination with conventional magnetic heads and high-accuracy positioning technologies. The present study indicates that the new type of bit-patterned-media composed of nano-hole arrays fabricated on glassy alloy film template and Co/Pd multilayer magnetic dots are promising for applications to next generation ultra-high density hard disk drives. - Highlights: ► Prototype BPM using a nano-hole array pattern of imprinted Pd-based glassy alloy thin film and Co/Pd multilayered film was set. ► The prototype BPM has smooth surface and isolated Co/Pd multilayer magnetic dots with an average dot diameter of 30 nm. ► Dots acted as perpendicular magnetic dot and were able to read, erase and write in a row by a usual perpendicular magnetic head.

  18. Chemical vapor deposition synthesis of carbon nanospheres over Fe-based glassy alloy particles

    International Nuclear Information System (INIS)

    Highlights: • A mass of carbon nanospheres have been synthesized. • The Fe76Si9B10P5 particles were employed as both the catalyst and support. • Carbon nanospheres with amorphous walls have uniform size distribution (50–150 nm). - Abstract: A mass of carbon nanospheres (CNSs) have been synthesized by chemical vapor deposition of C2H2 directly over Fe-based glassy alloy particles (Fe76Si9B10P5) without the addition of an external catalyst. The morphology and microstructure as well as the growth mechanism of the CNSs have been investigated by using scanning and transmission electron microscopy. The results showed that the obtained products consist of hollow CNSs and CNSs with Fe nanoparticles encapsulated. The CNSs with amorphous walls have high purity (>95%) and uniform size distribution (50–150 nm). The possible formation and growth mechanism of the CNSs were discussed on the basis of the investigation on their initial growth stages

  19. Effect of some metallic additives (Ag, Cd, and Zn) on the crystallization kinetics of glassy Se70Te30 alloy

    International Nuclear Information System (INIS)

    Highlights: → The addition of Ag, Cd, and Zn at lower concentration (2 at%) in binary Se70Te30 alloy significantly affects its thermally activated non-isothermal crystallization. → We have found that the maximum change in different kinetic parameters is observed for Ag additive. → The peak crystallization temperature depends on the mean atomic weight of the alloy. → The activation energy of crystallization in ternary alloys is increased with the increase in average heat of atomization. - Abstract: The present work reports the effect of some additives (Ag, Cd, and Zn) on the crystallization kinetics of glassy Se70Te30 alloy in terms of kinetic parameters of crystallization. Differential scanning calorimetry (DSC) technique is used for this purpose in non-isothermal mode. Various kinetic parameters (crystallization temperature Tc, activation energy of crystallization Ec, rate constant K, and order parameter n) are calculated using the non-isothermal methods.

  20. Effect of Sb incorporation on the dark conductivity and photoconductivity of Se75In25 glassy alloy thin films

    International Nuclear Information System (INIS)

    In the present paper current-voltage (I-V) characteristics have been studied at various temperatures in vacuum evaporated thin films of Se75In25-xSbx (where x=0, 5, 10 and 15) glassy alloys. Ohmic behavior is observed at low electric fields, while at high electric fields (E∼104 V/cm) current becomes superohmic. An analysis of the experimental data confirms that due to large currents dielectric breakdown occurs at high voltages which may prohibit the SCLC mechanism in Se75In25 sample. Such type of behavior is not observed when the third element Sb as an impurity is incorporated in the Se75In25 binary glassy alloy. In case of samples with 5-15 at% of Sb, the experimental data are found to fit well with the theory of space charge limited conduction (SCLC). Density of defect states (DOS) near Fermi-level is determined for these samples by applying the theory of an SCLC. Temperature and intensity dependence of the photoconductivity in the aforesaid glassy systems has been also examined. The variation in DOS could be correlated with the photoconductivity results obtained. The observed discontinuity at 10 at% of an Sb could be correlated with the coordination number and chemically ordered network model (CONM).

  1. Synthesis and characterization of a bulk amorphous alloy

    International Nuclear Information System (INIS)

    The production and characterization of bulk metallic glasses have been an area of intense focus in materials research for many years because of their superior mechanical properties over their crystalline counterparts. A bulk metallic glass Zr/sub 55/Cu/sub 30/Al/sub 10/Ni/sub 5/ has been synthesized by copper mold casting and characterized by differential scanning calorimetry and x-ray diffraction. Crystallization behavior of the alloy is discussed. Composite of amorphous glass was produced by adding SiC and hardness and tensile strength have been measured. (author)

  2. Bulk undercooling, nucleation, and macrosegregation of Pb-Sn alloys

    Science.gov (United States)

    Degroh, H. C., III; Laxmanan, V.

    1988-01-01

    Preliminary ground-based studies on the undercooling behavior of large samples (23 g) of lead-tin alloys are presented. Evidence of gravity-related segregation effects is found, and a possible area for future microgravity experimentation is thus identified. Detailed descriptions of the experimental procedure used to achieve bulk undercoolings of between 0.5 and 34 K, depending on composition, are given. The bulk undercoolings obtained in this study are comparable with those found in small droplets. The large size of the present samples enabled the observation of sedimentation and other macrosegregation processes.

  3. Effect of radiation on bulk swelling of plutonium alloys

    International Nuclear Information System (INIS)

    Several studies show that plutonium alloys present bulk swelling. More precisely, length (as measured by dilatometry) and lattice parameter (as measured by X-ray diffraction) increase with time and seems to reach saturation after a few months for the microscopic scale. This bulk swelling can be correlated to self-induced radiation due to the decay of the different plutonium isotopes (238Pu, 239Pu, 241Pu and 242Pu) which also induce helium that tends to forms clusters, then bubbles. Many experimental and theoretical results have already been published on this topic. The goal of this paper is to review some of the results and to propose a strategy for both experiments and modelling to try to answer some of the remaining questions regarding swelling and more generally self-irradiation defects in plutonium alloys

  4. Oxygen Behavior in Bulk Amorphous Zr-base Alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Bulk Zr55Al10Ni5Cu30 metallic glass plates with a dimension of 85 mm×35mm×4 mm and a complicated plate werefabricated by injecting casting method using spongy zirconium and industrial purity aluminum, nickel and copper asraw materials. It was shown that the holding time of liquid metals at elevated temperatures had a great influence onthe oxygen content of the plates due to the contamination resulting from the atmosphere. Increasing holding timeresulted in the increase of oxygen content in the injected alloy. The glass transition temperatures of the bulk metallicglass plates are higher than that reported in the literature and crystallization temperature is lower for the one withhigher oxygen content at the same heating rate. The extension of the undercooled liquid region △Tx reaching about87 K is 3 K higher than that previously reported and 26 K higher than that with oxygen content of 0.076 wt pct forthe one with oxygen content as high as 0.065 wt pct. Therefore the oxygen content of the alloy has a significantinfluence on the glass forming ability and thermal stability of bulk metal glass. It is suggested that direct correlationbetween high glass forming ability and large △Tx is only valid for a well-defined Iow oxygen concentration or has tobe reconsidered by incorporating oxygen as an additional alloying element.

  5. Bulk metallic glassy surface native oxide: Its atomic structure, growth rate and electrical properties

    International Nuclear Information System (INIS)

    Formation of a native oxide layer on the surface of bulk metallic glasses (BMGs) influences significantly the nanoscale tribological properties and mechanical behavior of the BMGs used in nanodevices. However, our knowledge of the native oxidation process on the BMG surface and structure of the corresponding oxides remains limited because the oxide layer is very thin. Here we conducted a combined state-of-the-art experimental technique study of the atomic structure, oxidations states and electrical conductivity of the native surface oxides on a Cu−Zr−Al BMG formed at ambient conditions by aberration-corrected scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (AFM). This allowed shedding light on the atomic structure, metal oxidation state, growth behavior and nanoscale electrical properties of the surface oxide. The conductive AFM measurements reveal that the electrical conductivity of the native oxide layer transits from the initially metallic to a nonlinear one after some air exposure, and finally changes to insulative state. These findings represent a significant step forward in the knowledge of surface oxides and open up the possibility of fabricating nanoscale electrical devices based on BMGs with controllable conductivity

  6. 'Age-hardened alloy' based on bulk polycrystalline oxide ceramic

    Science.gov (United States)

    Gurnani, Luv; Singh, Mahesh Kumar; Bhargava, Parag; Mukhopadhyay, Amartya

    2015-05-01

    We report here for the first time the development of 'age-hardened/toughened' ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a 'near-ideal' microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe2O4) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO-MgFe2O4 alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.

  7. A comparative study of the density of defect states in bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$

    Indian Academy of Sciences (India)

    KUMAR ANJANI; DWIVEDI PRABHAT K; SHUKLA R K; KUMAR A

    2016-05-01

    The present paper reports the comparative study of density of defect states (DOS) between bulk samples and thin films of glassy Se$_{90}$Sb$_{10}$. These glasses have been prepared by the quenching technique. Thin films of these glasses have been prepared by vacuum evaporation technique. Space-charge-limited conduction (SCLC) has been measured at different temperatures.The density of localized states near Fermi level is calculated by fitting the data to the theory of SCLC for the case of uniform distribution of localized states for bulk as well as for thin films. A comparison has been made between the density of states calculated in these two cases.

  8. Space-charge-limited conduction in Se90Sb4Ag6 glassy alloy: observation of Meyer–Neldel rule

    Indian Academy of Sciences (India)

    Anjani Kumar; A Kumar

    2015-02-01

    The present paper reports the measurements of space-charge-limited conduction (SCLC) in glassy Se90Sb4Ag6 alloy. For this purpose, – characteristics have been taken at certain fixed temperatures. The results indicate that super-ohmic behaviour is observed at high electric fields. The results fit well with the theory of SCLC for the uniform distribution of traps. From the temperature dependence of conductivity, activation energy is obtained at different electric fields, which is found to be field dependent. Pre-exponential factor is found to depend on the activation energy and obeys Meyer–Neldel rule.

  9. Glassy Dynamics

    DEFF Research Database (Denmark)

    Jensen, Henrik J.; Sibani, Paolo

    2007-01-01

    The term glassy dynamics is often used to refer to the extremely slow relaxation observed in several types of many component systems. The time span needed to reach a steady, time independent, state will typically be far beyond experimentally accessible time scales. When melted alloys are cooled...... down they typically do not enter a crystalline ordered state. Instead the atoms retain the amorphous arrangement characteristic of the liquid high temperature phase while the mobility of the molecules decreases very many orders of magnitude. This colossal change in the characteristic dynamical time...

  10. Microstructure and corrosion resistance of Ti-Zr-Cu-Pd-Sn glassy and nanocrystalline alloys

    International Nuclear Information System (INIS)

    The microstructure and corrosion behavior of the Ti47.5Zr15Cu30Pd7.5Sn5 as-spun ribbons and as-cast rod have been investigated using HREM and potentiodynamic polarization study in simulated body fluids. The results of HREM reveal that, with decreasing cooling rate, the size and volume of nano-particles dispersed in glassy matrix increase for the Ti47.5Zr15Cu30Pd7.5Sn5 as-prepared samples. The as-spun ribbons with small size nano-particle show high corrosion resistance in PBS(-) and Hanks' solution, may be due to the formation of CuZr phase, resulting in the enrichment of Ti and Pd in the glassy matrix, which is helpful to form protective passive film. Comparatively, poor corrosion resistance is observed for the as-cast rod sample with larger nano-particles in both solutions. (author)

  11. Formation and crystallization of bulk Pd82Si18 amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    蒲建; 王敬丰; 肖建中; 崔昆

    2003-01-01

    Bulk amorphous Pd82Si18 alloy with the largest diameter of 8 mm was prepared by water quenching the molten alloy with flux medium in a quartz tube. The calculation result indicates that the bulk Pd82Si18 amorphous alloys have a low critical cooling rate (Rc) of 4.589 K/s or less. The experimental results show that purifying melt may improve glass forming ability(GFA) of undercooled melt, while liquid phase separation (LPS) of undercooled melt will decrease its GFA. There are some differences in crystallization experiments between bulk metallic glass and amorphous ribbons of Pd82Si18 alloys. These include the numbers of exothermic peak, glass transition temperature Tg, crystallization temperature Tx, region of undercooling liquid (ΔT=Tx-Tg) respectively. The links of cooling rates of melt and crystallization of Pd82Si18 amorphous alloys are explored.

  12. Synthesis and Characterization of Bulk Metallic Glasses, Composites and Hybrid Porous Structures by Powder Metallurgy of Metallic Glassy Powders

    OpenAIRE

    Kim, Jin Young

    2015-01-01

    Metallic glasses exhibit many attractive attributes such as outstanding mechanical, magnetic, and chemical properties. Due to the absence of crystal defects, metallic glasses display remarkable mechanical properties including higher specific strength than crystalline alloys, high hardness and larger fracture resistance than ceramics. The technological breakthrough of metallic glasses, however, has been greatly hindered by the limited plastic strain to failure. Thus, several strategies ha...

  13. Correlation between liquid structure and glass forming ability in glassy Ag-based binary alloys

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The atomic structures of liquid Ag-based binary alloys have been investigated in the solidification process by means of X-ray diffraction. The results of liquid structure show that there is a break point in the mean nearest neighbor distance r1 and the coordination number Nmin for glass-forming liquid, while the correlation radius rc and the coordination number Nmin display a monotone variational trend above the break point. It means glass-forming liquids have a steady changing in structure above liquidus and more inhomogeneous state at liquidus. We conclude that there is a strong correlation between liquid structure and glass forming ability in Ag-based binary alloys.

  14. Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

    International Nuclear Information System (INIS)

    We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

  15. Ceramic filters for bulk inoculation of nickel alloy castings

    OpenAIRE

    F. Binczyk; J. Śleziona; P. Gradoń

    2011-01-01

    The work includes the results of research on production technology of ceramic filters which, besides the traditional filtering function, playalso the role of an inoculant modifying the macrostructure of cast nickel alloys. To play this additional role, filters should demonstratesufficient compression strength and ensure proper flow rate of liquid alloy. The role of an inoculant is played by cobalt aluminateintroduced to the composition of external coating in an amount from 5 to 10 wt.% . The ...

  16. Role of Alloying Additions in Glass Formation and Properties of Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Na Chen

    2010-12-01

    Full Text Available Alloying addition, as a means of improving mechanical properties and saving on costs of materials, has been applied to a broad range of uses and products in the metallurgical fields. In the field of bulk metallic glasses (BMGs, alloying additions have also proven to play effective and important roles in promoting glass formation, enhancing thermal stability and improving plasticity of the materials. Here, we review the work on the role of alloying additions in glass formation and performance improvement of BMGs, with focus on our recent results of alloying additions in Pd-based BMGs.

  17. Effect of Viscosity on the Microformability of Bulk Amorphous Alloy in Supercooled Liquid Region

    International Nuclear Information System (INIS)

    Previously published results have shown that viscosity greatly influences on the deformation behavior of the bulk amorphous alloy in supercooled liquid region during microforming process. And viscosity is proved to be a component of the evaluation index which indicating microformability. Based on the fluid flow theory and assumptions, bulk amorphous alloy can be regarded as the viscous materials with a certain viscosity. It is helpful to understand how the viscosity plays an important role in viscous materials with various viscosities by numerical simulation on the process. Analysis is carried out by linear state equation in FEM with other three materials, water, lubricant oil and polymer melt, whose viscosities are different obviously. The depths of the materials flow into the U-shaped groove during the microimprinting process are compared in this paper. The result shows that the deformation is quite different when surface tension effect is not considered in the case. With the lowest viscosity, water can reach the bottom of micro groove in a very short time. Lubricant oil and polymer melt slower than it. Moreover bulk amorphous alloys in supercooled liquid state just flow into the groove slightly. Among the alloys of different systems including Pd-, Mg- and Zr-based alloy, Pd-based alloy ranks largest in the depth. Mg-based alloy is the second. And Zr-based alloy is the third. Further more the rank order of the viscosities of the alloys is Pd-, Mg- and Zr-based. It agrees well with the results of calculation. Therefore viscosity plays an important role in the microforming of the bulk amorphous alloy in the supercooled liquid state.

  18. Determination of Anthracene on Ag-Au Alloy Nanoparticles/Overoxidized-Polypyrrole Composite Modified Glassy Carbon Electrodes

    Directory of Open Access Journals (Sweden)

    Emmanuel I. Iwuoha

    2010-10-01

    Full Text Available A novel electrochemical sensor for the detection of anthracene was prepared by modifying a glassy carbon electrode (GCE with over-oxidized polypyrrole (PPyox and Ag-Au (1:3 bimetallic nanoparticles (Ag-AuNPs. The composite electrode (PPyox/Ag-AuNPs/GCE was prepared by potentiodynamic polymerization of pyrrole on GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were chemically prepared by the reduction of AgNO3 and HAuCl4 using C6H5O7Na3 as the reducing agent as well as the capping agent and then immobilized on the surface of the PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique which confirmed the homogeneous formation of the bimetallic alloy nanoparticles. Transmission electron microscopy showed that the synthesized bimetallic nanoparticles were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3 exhibited a higher electrocatalytic effect compared to that observed when GCE was modified with each constituent of the composite (i.e., PPyox, Ag-AuNPs and bare GCE. A linear relationship between anodic current and anthracene concentration was attained over the range of 3.0 × 10−6 to 3.56 × 10−4 M with a detection limit of 1.69 × 10−7 M. The proposed method was simple, less time consuming and showed a high sensitivity.

  19. Phase formation characteristics and magnetic properties of bulk Ni2MnGe Heusler alloy

    International Nuclear Information System (INIS)

    Highlights: • Annealing temperature and alloy composition drastically alter the obtained phases. • Annealing at 900 and 950 °C facilitates the formation of L21 Heusler phase. • Bulk Ni2MnGe shows simple ferromagnetic ordering with a Curie temperature of 300 K. • Ni2MnGe alloy does not undergo a martensitic phase transition. - Abstract: We have systemically studied the effects of annealing temperature and alloy composition on the structural and magnetic properties of bulk Ni2MnGe and Ni2.1Mn0.9Ge Heusler alloys. We have observed that both annealing temperature and the alloy composition drastically alter the phases found in the samples due to the presence of competing ternary phases. Annealing at 900 and 950 °C for both alloy compositions facilitate the formation of L21 Heusler phase. Nevertheless, formation of Ni5Mn4Ge3 and Ni16Mn6Ge7 phases cannot be prevented for Ni2MnGe and Ni2.1Mn0.9Ge alloys, respectively. In order to estimate the magnetic contribution of the Ni5Mn4Ge3 impurity phase to that of the parent Ni2MnGe, we have also synthesized pure Ni5Mn4Ge3 alloy. Antiferromagnetic nature of Ni5Mn4Ge3 with low magnetization response allows us to reveal the magnetic response of the stoichiometric bulk Ni2MnGe. Bulk Ni2MnGe shows simple ferromagnetic behavior with a Curie temperature of 300 K, in agreement with the previous results on thin films. Despite the divergence of magnetization curves between field cooled (FC) and field heated (FH) modes, stoichiometric Ni2MnGe alloy does not undergo a martensitic phase transition based on our variable temperature X-ray diffraction experiments

  20. Microstructural characterization of Mg-based bulk metallic glass and nanocomposite

    International Nuclear Information System (INIS)

    New magnesium-based bulk metallic glasses Mg60Cu30Y10 have been prepared by pressure casting. Glassy alloys were successfully annealed to become nanocomposite containing 200 nm crystallites in an amorphous matrix. The microstructure of bulk glassy alloy and nanocomposite obtained during heat treatment was examined by X-ray diffraction and scanning and high-resolution electron microscopy. Metallic glass has been also studied to explain the structural characteristics by the reverse Monte Carlo (RMC) modeling based on the diffraction data. The HRTEM images allow to indicate some medium-range order (MRO) regions about 2–3 nm in size and formation of local atomic clusters. The RMC modeling results confirmed some kinds of short range order (SRO) structures. It was found that the structure of bulk metallic glass formed by the pressure casting is homogeneous. The composite material contained very small particles in the amorphous matrix. Homogeneous glassy alloy had better corrosion resistance than a composite containing nanocrystalline particles in a glassy matrix. - Highlights: • RMC modeling demonstrates some kinds of SRO structures in Mg-based BMGs. • HRTEM indicated MRO regions about 2–3 nm and SRO regions about 0.5 nm in size. • Mg-based glassy alloys were successfully annealed to become nanocomposite material. • Crystalline particles have spherical morphology with an average diameter of 200 nm. • Glassy alloy had higher corrosion resistance than a nanocomposite sample

  1. Crystalline Precipitate in a Bulk Glass Forming Zr-Based Alloy and Its Effect on Mechanical Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Cylindrical and sheet samples of bulk metallic glass with a nominal composition of Zr52.5Ni14.6Al10Cu17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigated by tensile and compressive tests at room temperature. Oxygen contents and the sample sizes (or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating the alloy melt up to 200 K above its melting temperature can effectively prevent the formation of the crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylinders and thickness up to 1 mm for sheets even the oxygen content is as higher as 0.08 wt pct.With increasing the sample sizes, the crystalline precipitates increase in volume fraction and size. The formation of the precipitates experienced two stages, i.e., initially nucleation and isotropic growth, and then anisotropic growth, finally forming faceted morphologies. Fully glassy Zr52.5Ni14.6Al10Cu17.9Ti5 alloy exhibits excellent tensile and compressive properties at room temperature. The presence of crystalline precipitates significantly decreases the tensile and compressive properties. With increasing the crystalline precipitates, the area of vein patterns on the fracture surface decreases, but the fracture steps increase, and the fracture mode changes from ductile to brittle resulting from the larger stress concentration caused by the larger sizes and faceted shapes of the crystalline precipitates.

  2. Effects of B2 precipitate size on transformation-induced plasticity of Cu–Zr–Al glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kuo, C.N. [Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC (China); Huang, J.C., E-mail: jacobc@mail.nsysu.edu.tw [Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC (China); Li, J.B.; Jang, J.S.C. [Institute of Materials Science and Engineering, Department of Mechanical Engineering, National Central University, Chung-Li, Taiwan, ROC (China); Lin, C.H. [Department of Mechanical and Electromechanical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC (China); Nieh, T.G. [Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, ROC (China); Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 (United States)

    2014-03-25

    Highlights: • This paper addresses the effects of the CuZr B2 size and distribution on plasticity. • There is a critical size to induce the martensitic/twinning transformation. • An analytic model based on melt flow dynamics is settled. -- Abstract: To demonstrate the effect of processing on the microstructure and subsequent mechanical property of bulk metallic glasses, we prepared two alloys, Cu{sub 47.5}Zr{sub 47.5}Al{sub 5} and Cu{sub 47.5}Zr{sub 48}Al{sub 4}Co{sub 0.5}, using two different designs of suction mold – one with a sharp inlet and one with a blunt inlet. The two alloys have been demonstrated previously to be ductile via phase transformation of the B2 phase and twin formation during plastic deformation. Microstructures of the as-cast as well plastically deformed samples, in particular, the size and distribution of the B2 phase, were examined using X-ray diffraction, scanning and transmission electron microscopy. Compressive tests were conducted on samples cast by different molds and their properties were found to closely correlate with the B2 morphology. Fluid dynamics during suction casting was also analyzed. Effects of Vena contracta, flow velocity, and Reynolds number were discussed and compared favorably with experimental observations.

  3. Ceramic filters for bulk inoculation of nickel alloy castings

    Directory of Open Access Journals (Sweden)

    F. Binczyk

    2011-07-01

    Full Text Available The work includes the results of research on production technology of ceramic filters which, besides the traditional filtering function, playalso the role of an inoculant modifying the macrostructure of cast nickel alloys. To play this additional role, filters should demonstratesufficient compression strength and ensure proper flow rate of liquid alloy. The role of an inoculant is played by cobalt aluminateintroduced to the composition of external coating in an amount from 5 to 10 wt.% . The required compression strength (over 1MPa isprovided by the supporting layers, deposited on the preform, which is a polyurethane foam. Based on a two-level fractional experiment24-1, the significance of an impact of various technological parameters (independent variables on selected functional parameters of theready filters was determined. Important effect of the number of the supporting layers and sintering temperature of filters after evaporationof polyurethane foam was stated.

  4. Fabrication of Fe-based bulk metallic glasses with plastic deformation and nanocrystalline alloys with Bs of 1.9 tesla by using structural heterogeneity

    International Nuclear Information System (INIS)

    An Fe-Metalloids-based Fe76Si9B10P5 (at%) bulk metallic glass (BMG) exhibits unusual combination of high saturation magnetic flux density (Bs) of 1.51 T due to high Fe content as well as high glass-forming ability leading to a glassy rod with a diameter of 2.5 mm despite not-containing any glass-forming metal elements. A small amount of Cu-added (Fe76Si9.4B8.4P6)99.9Cu0.1 BMG exhibits a yielding strength of 3.25 GPa and a large plastic deformation of about 4% in compression. The unusual deformation behavior with distinguishable highly dense multiple shear bands on the fracture surface could be due to the existence of a large number of α-Fe like clusters, less than 10 nm in diameter, embedded in a glassy matrix. The melt-spun Fe83.3-84.3Si4B8P3-4Cu0.7 alloys also have heterogeneous amorphous structures including a large amount of α-Fe clusters, 2-3 nm in diameter, due to the unusual effect of the simultaneous addition of the proper amounts of P and Cu. The hetero-amorphous alloys exhibit higher Bs of about 1.67 T than the representative amorphous and the nanocrystalline alloys, and the low coercivity (Hc) of 5-10 A/m. A homogeneous nanocrystalline structure composed of small α-Fe grains with a size of about 10 nm can be realized by crystallizing the hetero-amorphous alloys. The nanocrystalline alloys show extremely high Bs of 1.88-1.94 T almost comparable to the commercial Fe-3.5mass%Si crystalline soft magnetic alloys, and low Hc of 7-10 A/m due to the simultaneous realization of the homogeneous nanocrystalline structure and small magnetostriction of 2-3 x 10-6. In addition, these alloys have a great advantage of lower material cost for engineering and industry, and thus should make a contribution to energy saving, and conservation of earth resources and environment. (author)

  5. Enhanced ion irradiation resistance of bulk nanocrystalline TiNi alloy

    Energy Technology Data Exchange (ETDEWEB)

    Kilmametov, A.R. [Institute for Nanotechnology, Forschungszentrum Karlsruhe GmbH, Postfach 3640, 76021 Karlsruhe, Buchig (Germany); Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marx Street, 450000 Ufa (Russian Federation)], E-mail: ascar2@yandex.ru; Gunderov, D.V.; Valiev, R.Z. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marx Street, 450000 Ufa (Russian Federation); Balogh, A.G. [Institute for Materials Science, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany); Hahn, H. [Institute for Nanotechnology, Forschungszentrum Karlsruhe GmbH, Postfach 3640, 76021 Karlsruhe, Buchig (Germany); Joint Research Laboratory Nanomaterials, Technische Universitaet Darmstadt, Petersenstr. 23, 64287 Darmstadt (Germany)

    2008-11-15

    Bulk ordered nanocrystalline Ti{sub 49.4}Ni{sub 50.6} alloys with a grain size of 23-31 nm were prepared using severe plastic deformation. Nanocrystalline and coarse-grained alloys were subjected to 1.5 MeV Ar{sup +} ion irradiation at room temperature. At the same damage dose the nanocrystalline alloy retained the long-range order while the coarse-grained counterpart was amorphized. In contrast to former irradiation studies, fully dense nanocrystalline materials are used in the present study for the first time.

  6. Crystallization Kinetics of Fe76.5- x C6.0Si3.3B5.5P8.7Cu x ( x = 0, 0.5, and 1 at. pct) Bulk Amorphous Alloy

    Science.gov (United States)

    Jung, Hyo Yun; Stoica, Mihai; Yi, Seonghoon; Kim, Do Hyang; Eckert, Jürgen

    2015-06-01

    The influence of Cu on crystallization kinetics of Fe76.5- x C6.0Si3.3B5.5P8.7Cu x ( x = 0, 0.5, and 1 at. pct) bulk amorphous alloys was investigated by isothermal and isochronal differential scanning calorimetry combined with X-ray diffraction. The thermal analysis revealed that the crystallization of the amorphous matrix proceeds through at least two exothermic events. The Cu-free glassy alloy forms by primary crystallization the metastable Fe23C6 phase, while upon 0.5 at. pct Cu addition the primary crystallized phase is α-Fe. The activation energy for crystallization, calculated using both Kissinger and Ozawa methods, decreases from about 500 kJ/mol to about 330 kJ/mol. Further increase of Cu addition to 1 at. pct promotes the concomitant crystallization of several phases, as α-Fe, FeB, Fe3C, and Fe2P. In order to understand the crystallization behavior of the alloys as a function of Cu content, the Avrami exponent n, evaluated from the Johnson-Mehl-Avrami equation, was in details analyzed. The current study reveals that the minor Cu addition plays a crucial role at the initial stage of the crystallization. Among the studied alloys, the glassy samples with 0.5 at. pct Cu addition have the optimum compositional condition for the single α-Fe formation with a high nucleation rate.

  7. Survey of BGFA Criteria for the Cu-Based Bulk Amorphous Alloys

    Directory of Open Access Journals (Sweden)

    D. Janovszky

    2011-01-01

    Full Text Available To verify the effect of composition on the bulk glass forming ability (BGFA of Cu-based alloys, properties have been collected from the literature (~100 papers, more than 200 alloys. Surveying the BGFA criteria published so far, it has been found that the atomic mismatch condition of Egami-Waseda is fulfilled for all the Cu-based BGFAs, the value being above 0,3. The Zhang Bangwei criterion could be applied for the binary Cu-based alloys. The Miracle and Senkov criteria do not necessarily apply for Cu based bulk amorphous alloys. The critical thickness versus =/(+ plot of Lu and Liu extrapolates to =0.36, somewhat higher than the 0.33 value found in other BGFA alloys. The Park and Kim parameter correlates rather poorly with the critical thickness for Cu based alloys. The Cheney and Vecchino parameter is a good indicator to find the best glass former if it is possible to calculate the exact liquids projection. In 2009 Xiu-lin and Pan defined a new parameter which correlates a bit better with the critical thickness. Based on this survey it is still very difficult to find one parameter in order to characterize the real GFA without an unrealized mechanism of crystallization.

  8. Mechanical behavior of a bulk nanostructured iron alloy

    Science.gov (United States)

    Carsley, J. E.; Fisher, A.; Milligan, W. W.; Aifantis, E. C.

    1998-09-01

    Bulk, fully dense materials were prepared from Fe-10Cu with grain diameters between 45 nm and 1.7 µm. The materials were prepared by ball milling of powders in a glove box, followed by hot isostatic pressing (hipping) or powder forging. Larger grain sizes were obtained by thermal treatment of the consolidated powders. The bulk materials were relatively clean, with oxygen levels below 1500 wpm and other contaminants less than 0.1 at. pct. The mechanical behavior of these materials was unique. At temperatures from 77 to 470 K, the first and only mechanism of plastic deformation was intense shear banding, which was accompanied by a perfectly plastic stress-strain response (absence of strain hardening). There was a large tension-compression asymmetry in the strength, and the shear bands did not occur on the plane of maximum shear stress or the plane of zero extension. This behavior, while unusual for metals, has been observed in amorphous polymers and metallic glasses. On the other hand, the fine-grained Fe-10Cu materials behaved like coarse-grained iron in some respects, particularly by obeying the Hall-Petch equation with constants reasonably close to those of pure iron and by exhibiting low-temperature mechanical behavior which was very similar to that of steels. Transmission electron microscopy (TEM) studies found highly elongated grains within shear bands, indicating that shear banding occurred by a dislocation-based mechanism, at least at grain sizes above 100 nm. Similarities and differences between the fine-grained Fe-10Cu and metals, polymers, metallic glasses, radiation-damaged metals, and quench-damaged metals are discussed.

  9. Unified picture of spin-dependent transport in GMR multilayered structures and bulk ferromagnetic alloys

    Science.gov (United States)

    Schroeder, P. A.; Holody, P.; Loloee, R.; Vouille, C.; Barthelemy, A.; Fert, A.; Hsu, S. Y.

    1998-01-01

    We have observed a positive (inverse) CPP-MR in magnetic multilayers of the forms: (a) ( XY/Cu/Co/Cu) n with XY being the alloys FeCr, FeV, NiCr, CoCr, and (b) (Z/Cr/NiFe/Cr) n with Z = Fe and Co. For (a) the inverted results arise primarily from spin-dependent scattering in the bulk of the alloy, and are linked consistently to: (1) their magnetization; (2) band-structure calculations and (3) resistivity of bulk alloys. For (b) samples, the inverse MRs arise primarily from the scattering at the Fe/Cr and Co/Cr interfaces. Inverse MR for X/Y interfaces and XY alloys (eg. Fe/Cr and FeCr) arises from the similarity of the matching problem of X and Y d levels at interfaces and in alloys. For all XY the CIP-MR was negative, confirming that CIP-MR is strongly influenced by channeling effect and current inhomogenieties.

  10. Core level shifts in Cu-Pd alloys as a function of bulk composition and structure

    Science.gov (United States)

    Boes, Jacob R.; Kondratyuk, Peter; Yin, Chunrong; Miller, James B.; Gellman, Andrew J.; Kitchin, John R.

    2015-10-01

    CuPd alloys are important materials in hydrogen purification, where they are used as dense Pd-based separation membranes. Cu is added to impart sulfur tolerance and improved mechanical properties. At intermediate compositions and T < 873 K, a BCC alloy (B2) phase occurs, which has superior separation characteristics to those of the FCC phases that form at high Cu and high Pd compositions. Identifying the composition and temperature window where the B2 phase forms is a critical need to enable the design of improved alloys. A composition spread alloy film of Cu and Pd was synthesized. The film was characterized by electron back scatter diffraction and X-ray photoelectron spectroscopy, providing the core level shifts as a function of bulk composition and bulk structure. An anomalous deviation in the Cu core level shift was observed in the composition range 0.33 < xPd < 0.55 over which the B2 phase occurs. Density functional theory calculations were used to simulate core level shifts in the FCC and B2 alloy structures. They suggest that the anomalous deviation in core level shift is due to formation of the ordered B2 phase in this composition range.

  11. Bulk and surface contributions to enhanced solar-cell performance induced by aluminium alloying

    Energy Technology Data Exchange (ETDEWEB)

    Loelgen, P.; Bisschop, F.J. (FOM-Instituut voor Atoom- en Molecuulfysica, Amsterdam (Netherlands)); Sinke, W.C.; Steeman, R.A. (Netherlands Energy Research Foundation (ECN), Petten (Netherlands)); Verhoef, L.A.; Michiels, P.P.; Van Zolingen, R.J.C. (R S Renewable Energy Systems, Amsterdam (Netherlands))

    1991-11-01

    Use was made of the Light Beam Induced Current Decay technique to study Al-alloying effects in semi-crystalline Si solar cells. With this technique one is able to separate the minority-carrier diffusion length in the Si bulk and the effective back-surface recombination velocity. An increase in diffusion length of about 30% was measured, as well as a reduction of the effective back-surface recombination velocity to {<=} 10{sup 3} cm/s after Al-alloying. We investigated the effects of various processing conditions on both recombination mechanisms. Consequences for low-cost Si solar cell design are discussed. 8 figs., 1 tab., 9 refs.

  12. EFFECT OF THE TEMPERATURE ON THE FRICTION AND WEAR PROPERTIES OF BULK AMORPHOUS ALLOY

    OpenAIRE

    DAWIT ZENEBE SEGU; PYUNG HWANG; SEOCK-SAM KIM

    2014-01-01

    The present paper report the results of an experimental investigation of the temperature effect on the sliding friction and wear properties of the bulk metallic glass (BMG). To improve the friction and wear properties of the BMG, the disk specimens were developed in the alloy system of Fe67.6C7.1Si3.3B5.5P8.7Cr2.3Mo2.6Al2Co1.0 using hot metal and industrial ferro-alloys. The friction and wear test was performed using flat-on-flat contact configuration of unidirectional tribometer and Si3N4 ce...

  13. Effect of impurity (Sb and Ag) incorporation on the a.c. conductivity and dielectric properties of a-Se70Te30 glassy alloy

    International Nuclear Information System (INIS)

    The effect of additives (Sb and Ag) on a.c. conductivity and dielectric properties of Se70Te30 glassy alloy at temperature range 300-350 K and frequency range 1 kHz-5 MHz has been studied. Experimental results indicate that a.c. conductivity and dielectric parameters depend on temperature, frequency and the impurity incorporated in Se-Te glassy system. The a.c. conductivity in the aforesaid frequency range is found to obey the ωs law. A strong dependence of a.c. conductivity and exponent s in the entire temperature and frequency range contradicts quantum-mechanical tunneling (QMT) model and can be interpreted in terms of the correlated barrier hopping (CBH) model. The temperature and frequency dependence of the dielectric parameters are also studied and it is found that the results agrees by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in chalcogenide glasses. The change in the dielectric parameters with the opposite influence of the replacement of Te by Sb on the one hand, and by Ag, on the other hand is being correlated by the nature of covalent character of the studied composition and with the change in density of defect states.

  14. Coupling between bulk ordering and surface segregation: from alloy surfaces to surface alloys

    International Nuclear Information System (INIS)

    -The knowledge of the alloy surfaces is of prime interest to understand their catalytic properties. On the one hand, the determination of the stability of the surface alloys depends very strongly on the behaviours of the AcB1-c alloy surfaces. On the other hand, the knowledge of the kinetics of the formation-dissolution of surface alloys can allow to understand the equilibrium segregation isotherm. We have then studied the relation between the equilibrium surface segregation in an alloy AcB1-c and the kinetics of dissolution of a few metallic layers of A/B and the inverse deposit. We have used an energetic model derived from the electronic structure (T.I.B.M.) allowing us to study the surface segregation both in the disordered state and in the ordered one. The kinetics of dissolution were studied using the kinetic version of this model (K.T.I.B.M.) consistent with the equilibrium model. To illustrate our study, we have chosen the Cu-Pd system, a model for the formation of surface alloys and for which a great number of studies, both experimental and theoretical, are in progress. We then have shown for the (111) surface of this system that the surface alloys obtained during the dissolution are related to the alloy surfaces observed for the equilibrium segregation. The Cu-Pd system is characteristic of systems which have a weak segregation energy. Then, we have performed an equivalent study for a system with a strong segregation energy. Our choice was directly put on the Pt-Sn system. The surface behaviour, both in equilibrium and during the kinetics of dissolution, is very different from the Cu-Pd case. In particular, we have found pure 2-D surface alloys. Finally, a quenched molecular dynamics study has allowed us to determine the relative stability of various possible surface superstructures. (author)

  15. Comparison of surface and bulk crystallization of the amorphous Fe70Co10B20 alloy

    International Nuclear Information System (INIS)

    The effects of surface and bulk crystallization of the amorphous Fe70Co10B22 alloy are investigated by the aid of optical microscopy, scanning electron microscopy, and Moessbauer spectroscopy after annealings detecting γ-radiation and conversion electrons. The chemical composition of the amorphous matrix and of crystalline particles are determined by energy and wave dispersive analyses of X-rays. Measurements show that eutectic particles of crystallizing phases are observed in the bulk. Besides the non-uniformly distributed eutectic crystallites, an appreciable amount of α-Fe-Co phase is present at the surface of the sample

  16. Kinetics Study of (Se80Te20100–xCdx Glassy Alloy by Differential Thermal Analysis Using Non-Isothermal Technique

    Directory of Open Access Journals (Sweden)

    Mainika

    2011-01-01

    Full Text Available The kinetics of crystallization in (Se80Te20100 – xCdx (x = 0, 2, 4 and 6 alloys at different heating rates have been studied by Differential Thermal Analysis in non-isothermal condition. A comparison of various quantitative methods to assess the level of stability of the glassy material in the above mentioned system is presented. All these methods are based on the characteristics temperature obtained by heating of the samples, such as glass transition temperature (Tg, temperature of crystallization (Tc, and the melting temperature (Tm. From the dependence of glass transition temperature on heating rate, the activation energy (Eg has been calculated on the basis of the Kissinger and Moynihan models.

  17. Formation and crystallization kinetics of Nd-Fe-B-based bulk amorphous alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qiong; Ge, Hongliang; Zhang, Pengyue; Li, Dongyun; Wang, Zisheng [China Jiliang University, Magnetism Key Laboratory of Zhejiang Province, Hangzhou (China)

    2014-06-15

    In order to improve the glass-forming ability (GFA) of Nd-Fe-B ternary alloys to obtain fully amorphous bulk Nd-Fe-B-based alloy, the effects of Mo and Y doping on GFA of the alloys were investigated. It was found that the substitution of Mo for Fe and Y for Nd enhanced the GFA of the Nd-Y-Fe-Mo-B alloys. It was also revealed that the GFA of the samples was optimized by 4 at.% Mo doping and increased with theYcontent. The fully amorphous structures were all formed in the Nd{sub 6-x}Y{sub x}Fe{sub 68}Mo{sub 4}B{sub 22} (x =1-5) alloy rods with 1.5 mm-diameter. After subsequent crystallization, the devitrified Nd{sub 3}Y{sub 3}Fe{sub 68}Mo{sub 4}B{sub 22} alloy rod exhibited a uniform distribution of grains with a coercivity of 364.1 kA/m. The crystallization behavior of Nd{sub 3}Y{sub 3}Fe{sub 68}Mo{sub 4}B{sub 22} BMG was investigated in isothermal situation. The Avrami exponent n determined by JAM plot is lower than 2.5, implying that the crystallization is mainly governed by a growth of particles with decreasing nucleation rate. (orig.)

  18. Tensile and compression properties of Zr-based bulk amorphous alloy at different temperatures

    Institute of Scientific and Technical Information of China (English)

    WANG; Xu; LOU; Decheng; GAO; Zhanjun; LIU; Lei; LIANG; Hong

    2005-01-01

    Mechanical properties of the Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy at different temperatures were investigated. The compression test was carried out on a Gleebe-3200 machine at 345 and 375℃, respectively, in the supercooled liquid region. It is shown that decreasing the compressive rate and increasing temperature have a similar influence trend on the compressive behavior of the bulk amorphous alloy. Room and low temperature tensile strengths were tested on the Instron materials testing system. At low temperature, the tensile strength decreased with decreasing of the testing temperature.Hardness measurement indicated that below the glass transition temperature, the hardness decreased with increasing of the annealing temperature and duration time. It,however, increased when the annealing treatment was performed above the glass transition temperature.

  19. Crystallization kinetics of bulk Cu_(58.1)Zr_(35.9)Al)6 alloy

    Institute of Scientific and Technical Information of China (English)

    WANG Shao-xu; ZHU Chun-lei; QUAN Shi-guang; LI Yan-hui; WANG Ying-min; WANG Qing; DONG Chuang

    2009-01-01

    The crystallization kinetics of the bulk amorphous Cu_(58.1)Zr_(35.9)Al_6 alloy was examined by differential scanning calorimetry under continuous heating and isothermal annealing.During continuous heating,the activation energy of crystallization was determined to be 383 kJ/mol by Kissinger method.However,on the isothermal annealing,the activation energy was determined to be 459.2 kJ/mol by the Arrhenius method,which was much larger than that obtained from the Kissinger method.The different temperatures at which crystallization occurs are responsible for the discrepancy in the activation energy.The average Avrami exponent of about 3.5 implies that the crystallization process of the bulk amorphous Cu_(58.1)Zr_(35.9)Al_6 alloy is diffusion-controlled with a nucleation rate decreasing with time.

  20. New nickel-based bulk metallic glasses with extremely high nickel content

    International Nuclear Information System (INIS)

    The effect of boron addition on glass formation in the Ni70Pd10P20 alloy was investigated. The composition containing 4 at% boron showed an improved glass-forming ability. A glassy Ni70Pd10P16B4 alloy rod with a diameter of 2.5 mm was prepared by a copper mold casting technique. This is the first time that a Ni-based bulk metallic glass with such an extremely high Ni content of 70 at% has been produced. The obtained glassy Ni70Pd10P16B4 alloy exhibited rather good mechanical properties and corrosion resistance.

  1. Critically designing today’s melt processed bulk magnesium alloys using boron rich nanoparticles

    International Nuclear Information System (INIS)

    Highlights: • B4C nanoparticles increased the tensile ductility of Mg–Al alloy to about 25%. • SiB6 nanoparticles increased the tensile ductility of Mg–Zn alloy to about 23%. • ZrB2 nanoparticles increased the tensile strength of Mg–RE alloy to above 400 MPa. • Hypothetically, 5–10% cold working could significantly increase tensile strength. • Hypothetically, 5–10% cold working could maintain tensile ductility above 10%. - Abstract: In this work, boron rich nanoparticles (B4C, SiB6 and ZrB2) were added to bulk melt processed Mg–Al, Mg–Zn and Mg–RE (Rare Earth) series contemporary magnesium alloys, respectively. The most obvious positive effect when adding B4C nanoparticles to the Mg–Al alloy was the significant increase in tensile ductility (to about 25%). Here, there was no significant change in grain size or crystallographic texture due to nanoparticle addition. However, it was observed that stacking faults formed more easily in the magnesium matrix due to nanoparticle addition. Also, it was observed that coarser nanoparticles broke down high strain zones (HSZs) during tensile deformation. The addition of SiB6 to Mg–Zn alloy also resulted in similar significant increase in tensile ductility (to about 23%). Tensile deformation induced alignment of more rounded and spherical nanoparticles was observed. Stacking faults forming more easily in the alloy matrix was also observed. However, the formation of nanograins (nanoscale recrystallization) during room temperature tensile deformation was observed in this system. This implied that nanograin rotation during deformation was also responsible for the observed enhanced tensile ductility. When ZrB2 was added to Mg–RE alloy, the tensile strength was significantly enhanced (yield strength >400 MPa) after thermal ageing. Here, the ZrB2 nanoparticles induced the formation of thermal ageing resistant long period stacking/ordered (LPSO) nanograins and nanolayers in the Mg–RE alloy matrix

  2. Thermal and elastic properties of Cu–Zr–Be bulk metallic glass forming alloys

    OpenAIRE

    Duan, Gang; Lind, Mary Laura; De Blauwe, Katrien; Wiest, Aaron; Johnson, William L.

    2007-01-01

    The compositional dependence of thermal and elastic properties of Cu–Zr–Be ternary bulk metallic glass forming alloys was systematically studied. There exists a linear relationship between the glass transition temperature Tg and the total Zr concentration. G decreases linearly with increasing Zr concentration as well. The results also show that Tg, shear modulus G, and Poisson's ratio nu are very sensitive to changes in compositions. Low Tg, low G, and relatively high nu can be achieved with ...

  3. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.; Pedersen, Allan Schrøder; Hattel, J.; Linderoth, Søren

    2000-01-01

    Bulk amorphous (Mg(1-gamma)Al(gamma))(60)CU(30)Y(10) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper wedge mould. The temperature vs, time was recorded during the cooling and solidification process of the melt and compared with a spacial and......-ray diffraction (XRD) and differential scanning calorimetry (DSC) for different alloy compositions and annealing temperatures. On annealing into the supercooled liquid state (441 K), specimens with no Al content remain basically amorphous while nanoparticles are formed and remain stable also at higher...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  4. The mechanism of PEO process on Al-Si alloys with the bulk primary silicon

    International Nuclear Information System (INIS)

    This study focuses on mechanism of ceramic coating on Al-Si alloys with bulk primary Si using plasma electrolytic oxidation (PEO) technology. Al-Si alloys with 27-32%Si in weight were used as substrates. The morphologies, composition and microstructure of PEO coatings were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray system (EDX). Results showed that the PEO process had four different stages. The effect of bulk Si is greatly on the morphology and composition of coatings at first three stages. Anodic oxide films formed on Al and Si phases, respectively. When the voltage exceeded 40 V, glow appeared and concentrated on the localized zone of interface of Al and Si phase. Al-Si-O compounds formed and covered on the dendrite Si phase surface, and the coating on bulk Si, which was silicon oxide, was rougher than that on other phase. If the treatment time was long enough, the coatings with uniform surface morphologies and elements distribution will be obtained but the microstructure of inner layer is looser due to the bulk Si.

  5. Inducing anisotropy in bulk Nd–Fe–Co–Al–B nanocrystalline alloys by quenching in magnetic field

    International Nuclear Information System (INIS)

    We have observed magnetic anisotropy in bulk Nd55−xCoxFe30Al10B5 (x=10, 15 and 20) alloys prepared by copper mold suction casting method with a presence of external magnetic field (quenching field) μ0H=0.25 T. By changing direction of the measuring field from perpendicular to parallel one in comparison with that of the quenching field, coercive force of the alloys slightly decreases while remanent magnetization and squareness of hysteresis loop increase more clearly. It is also found that the higher Co-concentration in the alloys the larger magnetic anisotropy is induced. The structure analyses manifest nanocrystalline particles embedded in residual amorphous matrix of the alloys. The size of the particles is in range of 10–30 nm and their crystalline phases consist of Nd2(Fe,Co)14B, Nd3Co, Nd3Al, NdAl2 and Nd. - Highlights: ► Inducing anisotropy in bulk nanocrystalline alloys by quenching in magnetic field. ► Magnitude of the induced anisotropy is enhanced by Co-concentration. ► Nd2(Fe,Co)14B stick-like nanograins is main factor for anisotropy of the alloys. ► Bulk Nd–Co–Fe–Al–B nanocrystalline alloys fabricated by rapid solidification. ► High coercivities up to 1.6 T achieved in bulk Nd–Co–Fe–Al–B nanocrystalline alloys.

  6. Correlation between Structures of Bulk Amorphous Zr-Ti-Ni-Cu-Be Alloy in Different States

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The structures of the bulk amorphous Zr41Ti14Cu12.5Ni10.0Be22.5 alloy have been analyzed in solid, supercooled liquid and liquid with X-ray diffraction. The first coordination sphere radii and the first coordination numbers are 0.312 nm, 11.2 in solid state, 0.301 nm, 10.932 in supercooled liquid region and 0.305 nm, 11.296 in liquid state. The structures are the same in different states. But it shows some tendency to crystallizing that the first coordination sphere radius and the first coordination number drop in supercooled liquid region.

  7. Kinetics of glass transition and crystallization in multicomponent bulk amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Differential scanning calorimeter (DSC) is used to investigate apparent activation energy of glass transition and crystallization of Zr-based bulk amorphous alloys by Kissinger equation under non-isothermal condition. It is shown that the glass transition behavior as well as crystallization reaction depends on the heating rate and has a characteristic of kinetic effects. After being isothermally annealed near glass transition temperature, the apparent activation energy of glass transition increases and the apparent activation energy of crystallization reaction decreases. However, the kinetic effects are independent of the pre-annealing.

  8. Fitting of accurate interatomic pair potentials for bulk metallic alloys using unrelaxed LDA energies

    International Nuclear Information System (INIS)

    We present a general and simple method for obtaining accurate, local density approximation (LDA-) quality interatomic potentials for a large class of bulk metallic alloys. The method is based on our analysis of atomic relaxation, which reveals that the energy released in the relaxation process can be approximated by calculating the epitaxially constrained energies of the constituents A and B. Therefore, the pair potential is fitted to the LDA-calculated epitaxial energies of the constituents (to capture the relaxation energies), and to the unrelaxed energies of ordered AnBm compounds (to capture the fixed-lattice open-quotes chemicalclose quotes energy). The usefulness of our approach is demonstrated by carrying out this procedure for the Cu1-xAux alloy system. The resulting pair potential reproduces the relaxed LDA formation energies of ordered compounds rather accurately, even though we used only unrelaxed energies as input. We also predict phonon spectra of the elements and ordered compounds in very good agreement with the LDA results. From the calculations for ∼10000 atom supercells representing the random alloy, we obtain the bond lengths and relaxation energies of the random phase that are not accessible to direct LDA calculations. We predict that, while in Cu-rich alloys the Cu-Cu bond is shorter than the Cu-Au bond, at higher Au compositions this order is switched. Furthermore, we find that Au-rich Cu1-xAux alloys have ground states that correspond to (001) superlattices of n monolayers of fcc Au stacked on m monolayers of the L10 CuAu-I structure. The potential developed in this work is available at the site http://www.sst.nrel.gov/data/download.html for interested users. copyright 1999 The American Physical Society

  9. High strength bulk Fe-Co alloys produced by powder metallurgy

    International Nuclear Information System (INIS)

    Fe-Co alloys are extensively used in lamination form, but there are certain power generation applications that require Fe-Co rotors in bulk form. Experiencing only a dc magnetic field, these rotors can be as large as 0.5 m in diameter, depending on the size of the generator. The forging of such large pieces of Fe-Co has proven to be difficult. The present study investigates powder metallurgy processing of a gas atomized FeCoNbV alloy through hot isostatic pressing (HIP) for manufacturing large size rotors with improved mechanical strength. Gas atomized FeCoNbV alloy powders with and without ball milling were hot isostatic pressed at temperatures between 675 and 850 deg. C at a fixed pressure of 193 MPa for up to 6 h. Ball milling prior to HIP improved the yield strength. A further improvement in yield strength and in ductility was obtained after a disordering heat treatment at 730 deg. C followed by a rapid quench to room temperature. The optimum HIP and annealing conditions resulted in samples with yield strengths of 870 MPa. The compacts exhibited average coercivity values of 6.4 Oe and maximum permeability values of 1100

  10. Fabrication of Nb3Al superconducting bulks by mechanical alloying method

    Science.gov (United States)

    Qi, Ming; Pan, Xi Feng; Zhang, Ping Xiang; Cui, Li Jun; Li, Cheng Shan; Yan, Guo; Chen, Yong Liang; Zhao, Yong

    2014-06-01

    Since it can directly prepare the Nb-Al supersaturated solid solution, mechanical alloying is thought as a promising method to make high-performance Nb3Al superconductors at a low temperature annealing condition, without the complicated rapid heating, quenching and transformation (RHQT) process. In this paper, we investigate the effects of milling time, the content of Al and annealing temperature on phase formation and superconducting properties of mechanical alloying Nb3Al bulks in detail. The study results show that Nb-Al supersaturated solid solution could be obtained by high energy ball milling, as long as the Nb-Al blended powder is ball milled for 1 h, even the amorphous phase appears with the ball milling time prolonging to 10 h, the Nb-Al intermetalics do not come out either. Amorphous phase is hardly beneficial to synthesizing the Nb3Al phase, instead, it will make the products impurity. By optimizing the milling time, elements composition and annealing temperature , pure Nb3Al phase is obtained and the highest onset superconducting transition temperature (Tc-onset) reaches 15.8 K and the critical current density (Jc) 106 A/cm2 at 8 K without outer field. This paper also discusses the main reasons that affect the superconducting properties of mechanical alloying Nb3Al superconductor.

  11. A glassy carbon electrode modified with nanoporous PdFe alloy for highly sensitive continuous determination of nitrite

    International Nuclear Information System (INIS)

    Nanoporous palladium-iron alloy (np-PdFe) was fabricated by dealloying. It possesses a three-dimensional nanospongy architecture with a typical dimension of ∼ 5 nm and displays a high catalytic activity towards oxidation of nitrite in phosphate buffer of pH 7.0 at a working voltage of 1.2 V (vs. the reversible hydrogen electrode). Compared to np-Pd and a commercial Pd/C catalyst, the np-PdFe alloy exhibits superior detection capability such as a wide linear range (that extends from 0.5 to 25.5 mM), fast amperometric response (within 2 s), and a low detection limit (0.8 μM). Long-term tests demonstrate that the np-PdFe alloy has improved reproducibility and durability, with almost no activity loss upon continuous nitrite detection for two weeks. The method was applied to determine nitrite in sausage and the results are in good agreement with those of the Griess method. (author)

  12. Microstructure evolution upon devitrification and crystallization studies of Ti-Hf-Zr-Cu-Ni-Sn-Si glassy alloy

    International Nuclear Information System (INIS)

    The phase components and microstructure of as-cast Ti41.5Cu37.5Ni7.5Zr2.5Sn5Hf5Si1 glass forming alloy was investigated by differential scanning calorimetry (DSC), scanning electron microscopy and in-situ neutron diffraction studies. For diameters above 3 mm the samples present small crystals identified as the Ti5Sn3Cu and cubic Ti(CuNi) phases. Crystallization studies in the DSC furnace and in-situ neutron diffraction reveal that the cubic titanium phase is TiNi(Cu) with the Pm-3m space group and not the β-Ti phase. The evolution of phases above Tγ show that the TiNi phase is metastable and decomposes at Tx=727 K to form the γ-TiCu phase. The Ti5Sn3Cu phase does not evolve in this temperature range. At room temperature by compression measurements, the alloy with 2 mm diameter shows a high failure limit of 2120 MPa with 2,1% of plasticity.

  13. Mechanical behaviour of nanocomposites derived from zirconium based bulk amorphous alloys

    International Nuclear Information System (INIS)

    The effects on mechanical properties of partial crystallization of a zirconium based bulk amorphous alloy (Vit1) are investigated. Nanocomposites are produced by appropriate heat treatments at temperatures higher than the glass transition temperature. Mechanical properties at room temperature are investigated by compression tests and hardness measurements including nanoindentation. The variation of the fracture stress with the degree of crystallinity is related to the nature, the size and the dispersion of the crystals in the amorphous phase. The variations of microstructure are estimated thanks to differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. A significant connexion between crystals induces a decrease of the fracture stress whereas hardness continuously increases with crystallinity. From nanoindentation tests, Young's modulus and apparent yield stresses were roughly estimated and it is concluded that crystallization tends to increase the yield stress. Nevertheless, AFM observations of the imprints after indentation suggest that the mechanism of deformation can vary significantly with crystallization

  14. Non-equilibrium transformation path for bulk undercooled hypereutectic Fe-B alloy

    Energy Technology Data Exchange (ETDEWEB)

    Yang, W. [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Liu, F., E-mail: liufeng@nwpu.edu.c [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Wang, H.F.; Chen, Z.; Yang, G.C.; Zhou, Y.H. [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China)

    2010-02-18

    Assuming phenomenological thermal flow balance and solute conservation, the non-equilibrium transformation path has been studied for recalescence of bulk undercooled hypereutectic Fe-B alloy. Taking advantage of the defined stoichiometry for primarily formed intermetallic Fe{sub 2}B, a convenient and accurate tracking of the average liquid concentration during recalescence can be performed. Applying thermodynamic calculations for liquid/solid Gibbs energy difference, the predictions of the post-recalescence temperature T{sub R} and the as-formed solid fraction in recalescence are shown to be in good agreement with the experimental results. On this basis, a transformation path accompanied by the evolution of temperature and concentration in the residual liquid has been constructed. This clearly shows a transition from non-equilibrium to near-equilibrium process upon recalescence.

  15. Synthesis of bulk nanostructured aluminum alloy component through vacuum plasma spray technique

    Energy Technology Data Exchange (ETDEWEB)

    Laha, T. [Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, EC 3464, Miami, FL 33174 (United States); Agarwal, A. [Mechanical and Materials Engineering, Florida International University, 10555 West Flagler Street, EC 3464, Miami, FL 33174 (United States)]. E-mail: agarwala@fiu.edu; McKechnie, T. [Plasma Processes Inc., Huntsville, AL 35811 (United States); Rea, K. [Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States); Seal, S. [Mechanical, Materials and Aerospace Engineering, University of Central Florida, Orlando, FL 32816 (United States)

    2005-12-15

    The benefits of large-size engineering components with nanocrystalline structure (providing improved strength) are yet to be realized due to processing difficulties and associated grain growth problems. In this work, a free-standing bulk nanocrystalline structure of hypereutectic aluminum alloy (Al-21wt.%Si) has been fabricated through the vacuum plasma spray (VPS) forming technique using micron-size powder feedstock. Optical microscopy, scanning electron microscopy and transmission electron microscopy have been used to investigate the evolution of multi-scale microstructure as the result of rapid solidification in VPS forming process. The characterization implies the presence of nanosized eutectic Al-Si grains (25-100 nm) with uniformly distributed ultrafine primary silicon particles of submicron size. The effect of microstructural evolution on mechanical properties has been studied by tensile testing and microhardness measurement. A considerable improvement in ultimate tensile strength and hardness of the sprayed deposit has been observed in comparison with conventionally cast hypereutectic Al-17wt.%Si alloys.

  16. Plastic deformability and precipitation of nanocrystallites during compression for a Cu-Zr-Ti-Sn bulk metallic glass

    International Nuclear Information System (INIS)

    (Cu0.5Zr0.425Ti0.075)99Sn1 bulk metallic glass with a glass transition temperature of 683 K and a supercooled liquid region of 47 K was synthesized by copper mold casting. The bulk glassy alloy exhibits high strength of 1810 MPa and superior plasticity in uniaxial compression at ambient temperature. High resolution transmission electron microscopy for the bulk glassy sample subject to a plastic strain of 3% shows the formation of nanocrystallites in the glassy matrix. The plastic deformability of the (Cu0.5Zr0.425Ti0.075)99Sn1 bulk metallic glass is attributed to the in situ precipitation of nanocrystallites during the compression

  17. Influence of Si on glass forming ability and properties of the bulk amorphous alloy Mg60Cu30Y10

    International Nuclear Information System (INIS)

    Research highlights: → The partial substitution of Cu by the right amount of Si increases the glass forming ability of the bulk amorphous alloy Mg60Cu30Y10. → The serrations size of Mg60Cu30-xY10Six is dependent on the content of Si. → The creep displacement of Mg60Cu30-xY10Six alloys decrease with increasing Si content. → The elastic modulus and nano-hardness of Mg60Cu30-xY10Six are dependent on the Si content. - Abstract: We studied the influence of partially replacing Cu by Si in the bulk amorphous alloy Mg30Cu30Y10. Glass forming ability (GFA), examined using X-ray diffraction and a differential scanning calorimeter, was increased at 1% Si, but decreased for larger Si concentrations. Nano-indentation measured nano-hardness, elastic modulus and load-displacement curves. The elastic modulus and nano-hardness increased with increasing Si content to a maximum at 2.5%. The load-displacement curves during nano-indentation revealed displacement serrations. These increased with decreasing loading rates, decreased with increasing Si content. The load-displacement curves also indicated that these bulk amorphous alloys exhibited primary creep at room temperature just like other high strength alloys. The creep displacement decreased with increasing Si content.

  18. Reconstructed PtFe Alloy Nanoparticles with Bulk-Surface Differential Structure for Methanol Oxidation

    International Nuclear Information System (INIS)

    The high cost of the catalyst material is a large obstacle for the commercialization of Direct Methanol Fuel Cells. In present work, the non-noble metal Fe was added to the conventional Pt/C catalyst in order to lowering the catalyst cost without sacrificing the catalytic performance. A chemically dealloying procedure was adopted to leach out the surface iron atoms and thereby increasing the stability of the catalyst. Through these procedures, the PtFe bulk-surface differential nano-catalyst was obtained. The shift in diffraction angles according to XRD spectra confirms the formation of the alloy structure between Pt and Fe. TEM results indicate that the chemically dealloyed PtFe/C nanoparticles are uniformly-dispersed with optimized average size. The PtFe bulk-surface differential structure is inferred from XPS as no surface Fe atoms are detected in spite of the change in Pt electronic structure. The existence of Fe atoms inside the nanoparticles is further confirmed by the ICP characterization. Electrochemical characterizations show that the catalytic activity is increased to 2.8 times, compared to the Pt/C catalyst, which can be ascribed to the electronic effect of Fe. A further evidence for the electronic effect comes from the CO stripping spectroscopy, in which the onset potential for CO oxidation shifts dramatically toward the negative potential side compared with Pt/C. Owing to the bulk-surface differential structure, the chemically dealloyed PtFe/C catalysts exhibits nearly the same stability compared to that of the Pt/C catalyst

  19. Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wenfei; YAO Kefu; ZHAO Zhankui

    2004-01-01

    Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid ΔT=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.

  20. Effects of Nb and Si on densities of valence electrons in bulk and defects of Fe3Al alloys

    Institute of Scientific and Technical Information of China (English)

    邓文; 钟夏平; 黄宇阳; 熊良钺; 王淑荷; 郭建亭; 龙期威

    1999-01-01

    Positron lifetime measurements have been performed in binary Fe3Al and Fe3Al doping with Nb or Si alloys. The densities of valence electrons of the bulk and microdefects in all tested samples have been calculated by using the positron lifetime parameters. Density of valence electron is low in the bulk of Fe3Al alloy. It indicates that, the 3d electrons in a Fe atom have strong-localized properties and tend to form covalent bonds with Al atoms, and the bonding nature in Fe3Al is a mixture of metallic and covalent bonds. The density of valence electron is very low in the defects of Fe3Al grain boundary, which makes the bonding cohesion in grain boundary quite weak. The addition of Si to Fe3Al gives rise to the decrease of the densities of valence electrons in the bulk and the grain boundary thus the metallic bonding cohesion. This makes the alloy more brittle. The addition of Nb to Fe3Al results in the decrease of the ordering energy of the alloy and increases the density of valence electron and th

  1. Preparation of a bulk Fe83B17 soft magnetic alloy by undercooling and copper-mold casting methods

    International Nuclear Information System (INIS)

    Bulk Fe83B17 eutectic alloy rods with diameters up to 3 mm were prepared by undercooling solidification combined with Cu-mold casting. The results showed that the rapid solidification led to an increase in the nucleation rate, an inhibition of the grain growth and a competition between a stable Fe2B phase and a metastable Fe3B phase. Then, pure nano-lamellar eutectic microstructures and the metastable Fe3B phase were successfully obtained in as-solidified alloys, which resulted in improved soft magnetic properties. - Highlights: • Pure nano-lamellar eutectic structure was directly formed in the bulk Fe-B alloys. • The metastable Fe3B phase was directly formed in the bulk Fe-B alloys. • Undercooling solidification combined with Cu-mold casting was applied. • The information on bcc Fe, Fe2B and Fe3B-magnetism relationship was provided. • Nano-lamellar eutectic structures enhance the soft magnetic properties

  2. Numerical simulation of the bulk forming processes for 1345 aluminum alloy billets

    Directory of Open Access Journals (Sweden)

    Fakhreddine. KHEROUF

    2015-08-01

    Full Text Available This paper presents an improved numerical simulation of bulk metal forming processes. It takes into the account the advanced formalism of large displacements and large deformations. Also, the interface workpiece formalism in considered. Metallographic studies are conducted to determine the evolution of the micro hardness as a function of annealing time and that to characterize accurately the plastic range of aluminum alloy for a range of plasticity 120%. The obtained results of metallographic studies are used to simulate a hot upsetting under the friction law of the plastic wave. Several simulations of forging operations of an axisymmetric billet by a rigid axisymmetric conical tool are performed with ABAQUS/standard computer code and that for preheated billets from 20 °C to 500 °C. The numerical study of the evolution of the normal stress at the interface has shown that the latter is independent of the tool roughness for a temperature close to 500 °C. The numerical study also allowed us to define the three areas of forging whatever cold; warm and hot forging. The effects of friction coefficient on the metal flow and contact pressure are numerically explored.

  3. Influence of Kinetic and Thermodynamic Factors on the Glass-Forming Ability of Zirconium-Based Bulk Amorphous Alloys

    OpenAIRE

    Mukherjee, S.; Schroers, J.; Johnson, W. L.; Rhim, W. K.

    2005-01-01

    The time-temperature-transformation curves for three zirconium-based bulk amorphous alloys are measured to identify the primary factors influencing their glass-forming ability. The melt viscosity is found to have the most pronounced influence on the glass-forming ability compared to other thermodynamic factors. Surprisingly, it is found that the better glass former has a lower crystal-melt interfacial tension. This contradictory finding is explained by the icosahedral short-range order of the...

  4. Effects of configurational changes on electrical resistivity during glass-liquid transition of two bulk metal-alloy glasses

    International Nuclear Information System (INIS)

    Consequences of increase in structural fluctuations on heating Pd40Ni10Cu30P20 and Zr46.75Ti8.25Cu7.5Ni10Be27.5 through their glass to liquid transition range were investigated by measuring the electrical resistivity, ρ, an electron scattering property. The temperature coefficient of resistivity (TCR = (1/ρ) dρ/dT) of the liquid and glassy states is negative. The plots of their ρ against T in the Tg (glass to liquid transition) range show a gradual change in the slope similar to the change observed generally for the plots of the density, elastic modulus, and refractive index. As fluctuations in the melt structure involve fewer configurations on cooling, ρ increases. In the energy landscape description, the melt's structure explores fewer minima with decrease in T, vibrational frequencies increase, and electron scattering and ρ increase. Plots of (−dρ/dT) against T resemble the plot of the specific heat of other glasses and show a sub-Tg feature and a rapid rise at T near Tg. Analysis shows that the magnitude of negative TCR is dominated by change in the phonon characteristics, and configurational fluctuations make it more negative. The TCR of the liquid and glassy states seems qualitatively consistent with the variation in the structure factor in Ziman's model for pure liquid metals as extended by Nagel to metal alloys and used to explain the negative TCR of a two-component metal glass

  5. Design of ductile bulk metallic glasses by adding ''soft'' atoms

    International Nuclear Information System (INIS)

    We propose a strategy for the design of ductile bulk metallic glasses (BMGs) through minor substitution using relatively large atoms, which make the bonding nature become more metallic and with it less shear resistant. Such a locally modified structure results in topological heterogeneity, which appears to be crucial for achieving enhanced plasticity. This strategy is verified for Ti-Zr-Cu-Pd glassy alloys, in which Cu was replaced by In, and seems to be extendable to other BMG systems. The atomic-scale heterogeneity in BMGs is somewhat analog to defects in crystalline alloys and helps to improve the overall plasticity of BMGs.

  6. Bulk deformation of Ti-6.8Mo-4.5Fe-1.5Al (Timetal LCB) alloy

    International Nuclear Information System (INIS)

    Recently, a low-cost near-β titanium alloy (Timetal LCB Ti-6.8Mo-4.5Fe-1.5Al wt%) containing iron and molybdenum has been developed. This alloy is cold formable in the β microstructure and can be aged to high strengths by precipitating the α phase. Due to its combination of cold formability and high strength, the alloy is a potential replacement for steel components in the automotive industry. The current study was undertaken to evaluate the cold bulk forming characteristics of Timetal LCB for use in lightweight automotive applications. Room-temperature compression tests conducted over a strain-rate range of 0.01 to 5/s indicate that the bulk cold compression of the alloy is affected by two factors: the microstructure and the length-to-diameter aspect ratio of the specimen. In the aged condition, when the microstructure has α-phase particles distributed along flow lines the β-phase matrix, the alloy has the propensity for shear failure when deformed in compression in a direction parallel to the flow lines. In the solution-heat-treated condition, the microstructure consists of β grains with athermal ω phase. In this condition, the alloy can be cold compressed to 75% reduction in height using specimens with aspect ratio of 1.125, but fails by shear for a larger aspect ratio of 1.5. Plastic deformation of the material occurs initially by single slip in most grains, but changes to multiple slip at true plastic strains larger than about 0.15. At a slow strain rate, the deformation is uniform, and the material work hardens continuously

  7. Nonenzymatic sensing of glucose at neutral pH values and low working potential using a glassy carbon electrode modified with platinum-iron alloy nanoparticles on a carbon support

    International Nuclear Information System (INIS)

    Alloy nanoparticles of the type PtxFe (where x is 1, 2 or 3) were synthesized by coreduction with sodium borohydride in the presence of carbon acting as a chemical support. The resulting nanocomposites were characterized by scanning electron microscopy and X-ray diffraction. The nanocomposite was placed on a glassy carbon electrode, and electrochemical measurements indicated an excellent catalytic activity for the oxidation of glucose even a near-neutral pH values and at a working voltage as low as 50 mV (vs. SCE). Under optimized conditions, the sensor responds to glucose in the 10.0 μM to 18.9 mM concentration range and with a 3.0 μM detection limit (at an S/N ratio of 3). Interferences by ascorbic acid, uric acid, fructose, acetamidophenol and chloride ions are negligible. (author)

  8. Cyclic Fatigue Fracture of Zr55Al10Ni5Cu30 Bulk Amorphous Alloy with Quenched-in Crystallites

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The effects of quenched-in crystallites on the fracture of bulk amorphous alloys under cyclic loading condition wereinvestigated in this paper. For the fully amorphous alloy and specimen with fine crystallites the fatigue crack initiationoccurred on the surface. For the specimen with larger crystallites the crack originated from a big broken crystallitenear the surface. The average striation spacing on amorphous area is much larger than that on the crystallite.Crack initiation occurred at the crystallites is due to that the brittle crystallites broke easily under cyclic deformationcondition. The fine crystallites seemed to be protruded from the amorphous matrix and some bulges appeared onthe surface of specimen with fine crystallites under cyclic loading.

  9. Cooperative strings and glassy interfaces.

    Science.gov (United States)

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-01

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer. PMID:26100908

  10. Microstructure and mechanical properties of bulk nanocrystalline Al-Fe alloy processed by mechanical alloying and spark plasma sintering

    International Nuclear Information System (INIS)

    Nanocrystalline Al-5 at.% Fe alloy powders produced by mechanical alloying were consolidated by spark plasma sintering. The sintered sample showed high strength >1000 MPa with a large plastic strain of 15% at room temperature and 500 MPa at 350 deg. C. Microstructure characterizations by transmission electron microscopy and atom probe tomography revealed that the sintered samples are composed of α-Al and Al6Fe nanocrystalline regions with 90 nm in diameter and a minor fraction of Al13Fe4 phase and coarsened 0.5-1 μm α-Al grains. This bimodally grained feature is attributed to the relatively large plastic strain for the strength level of 1000 MPa at room temperature.

  11. Magnetic characterisation of large grain, bulk Y–Ba–Cu–O superconductor–soft ferromagnetic alloy hybrid structures

    International Nuclear Information System (INIS)

    Highlights: • Large grain, bulk YBaCuO superconductor (SC) combined with ferromagnetic elements. • The flux lines curve outwards through the ferromagnet in the remanent state. • The trapped field in the SC is enhanced by the presence of the ferromagnet. • The effects of the SC and the ferromagnet add when the ferromagnet is saturated. - Abstract: Large grain, bulk Y–Ba–Cu–O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell’s algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the

  12. Magnetic characterisation of large grain, bulk Y–Ba–Cu–O superconductor–soft ferromagnetic alloy hybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Philippe, M.P., E-mail: M.Philippe@ulg.ac.be [SUPRATECS and Department of Electrical Engineering and Computer Science (B28), University of Liège, 4000 Liège (Belgium); Fagnard, J.-F.; Kirsch, S. [SUPRATECS and Department of Electrical Engineering and Computer Science (B28), University of Liège, 4000 Liège (Belgium); Xu, Z.; Dennis, A.R.; Shi, Y.-H.; Cardwell, D.A. [Bulk Superconductivity Group, Engineering Department, University of Cambridge, Cambridge CB2 1PZ (United Kingdom); Vanderheyden, B.; Vanderbemden, P. [SUPRATECS and Department of Electrical Engineering and Computer Science (B28), University of Liège, 4000 Liège (Belgium)

    2014-07-15

    Highlights: • Large grain, bulk YBaCuO superconductor (SC) combined with ferromagnetic elements. • The flux lines curve outwards through the ferromagnet in the remanent state. • The trapped field in the SC is enhanced by the presence of the ferromagnet. • The effects of the SC and the ferromagnet add when the ferromagnet is saturated. - Abstract: Large grain, bulk Y–Ba–Cu–O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell’s algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the

  13. High thermal shock resistance of the hot rolled and swaged bulk W-ZrC alloys

    Science.gov (United States)

    Xie, Z. M.; Liu, R.; Miao, S.; Yang, X. D.; Zhang, T.; Fang, Q. F.; Wang, X. P.; Liu, C. S.; Lian, Y. Y.; Liu, X.; Luo, G. N.

    2016-02-01

    The thermal shock (single shot) resistance and mechanical properties of the W-0.5wt% ZrC (WZC) alloys manufactured by ordinary sintering followed by swaging or rolling process were investigated. No cracks or surface melting were detected on the surface of the rolled WZC alloy plates after thermal shock at a power density of 0.66 GW/m2 for 5 ms, while primary intergranular cracks appear on the surface of the swaged WZC samples after thermal shock at a power density of 0.44 GW/m2 for 5 ms. Three point bending tests indicate that the rolled WZC alloy has a flexural strength of ˜2.4 GPa and a total strain of 1.8% at room temperature, which are 100% and 260% higher than those of the swaged WZC, respectively. The fracture energy density of the rolled WZC alloy is 3.23 × 107 J/m3, about 10 times higher than that of the swaged WZC (2.9 × 106 J/m3). The high thermal shock resistance of the rolled WZC alloys can be ascribed to their extraordinary ductility and plasticity.

  14. Effects of superimposed hydrostatic pressure on flow and fracture of a Zr-Ti-Ni-Cu-Be bulk amorphous alloy

    International Nuclear Information System (INIS)

    Recent successes in producing bulk amorphous alloys have renewed interest in this class of materials. Although amorphous metallic alloys have been shown to exhibit strengths in excess of 2.0 GPa, most of the earlier studies on such materials were conducted on tape or ribbon specimens due to the high cooling rates required to achieve the amorphous structure. The primary purpose of this investigation was to determine the effects of superimposed hydrostatic pressure on the flow and fracture behavior of a Zr-Ti-Ni-Cu-Be bulk metallic glass utilizing procedures successfully utilized on a range of structural materials, as reviewed recently. In general, few studies of this type have been conducted on metallic glasses, although thin ribbons (i.e., 300 microm thick) of a Pd-Cu-Si amorphous material tested with superimposed pressure have been reported previously. In particular, the effects of superimposed hydrostatic pressure over levels ranging from 50 MPa to 575 MPa on the flow/fracture behavior of cylindrical tensile specimens were compared to the flow and fracture behavior of identical materials tested in uniaxial tension and compression. It is shown that changes in stress triaxiality, defined as σm/bar σ, over the range of -0.33 to 0.33 produced a negligible effect on the fracture stress and fracture strain, while the orientation of the macroscopic fracture plane with respect to the loading axis was significantly affected by changes in σm/bar σ

  15. Mechanical alloying of Fe-Si and milling of α- and β-FeSi2 bulk phases

    International Nuclear Information System (INIS)

    Research highlights: Mechanical alloying of Fe-Si and milling of α- and β-FeSi2 bulk phases deals with the formation of various Fe-Si phases applying milling technique. Systematic studies were performed on the relative intensities on the different structures depending on the milling periods. - Abstract: Iron disilicide synthesis by mechanical alloying was performed. ε-FeSi, α-Fe1-xSi2, amorphous FeSi2 were formed with relative intensities depending on the milling period. β-FeSi2 phase was formed after annealing the gridded powder at the temperature where this phase is stable. Moessbauer spectroscopy and X-ray diffraction methods were applied to determine the different phases formed. The morphology of the resulting particles was observed by high resolution scanning electron microscopy. The effect of the milling on bulk iron-silicide samples was and studied chemical effects of the ball milling on Fe-Si2 systems have been studied.

  16. Mechanical alloying of Fe-Si and milling of {alpha}- and {beta}-FeSi{sub 2} bulk phases

    Energy Technology Data Exchange (ETDEWEB)

    Dezsi, I., E-mail: dezsi@kfki.rmki.h [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, 114 P.O. Box 49 (Hungary); Fetzer, Cs. [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, 114 P.O. Box 49 (Hungary); Bujdoso, L. [MTA Research Institute for Solid State Physics and Optics, H-1525 Budapest, 114 P.O. Box 49 (Hungary); Broetz, J.; Balogh, A.G. [Institute of Materials Science, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2010-10-15

    Research highlights: Mechanical alloying of Fe-Si and milling of {alpha}- and {beta}-FeSi{sub 2} bulk phases deals with the formation of various Fe-Si phases applying milling technique. Systematic studies were performed on the relative intensities on the different structures depending on the milling periods. - Abstract: Iron disilicide synthesis by mechanical alloying was performed. {epsilon}-FeSi, {alpha}-Fe{sub 1-x}Si{sub 2}, amorphous FeSi{sub 2} were formed with relative intensities depending on the milling period. {beta}-FeSi{sub 2} phase was formed after annealing the gridded powder at the temperature where this phase is stable. Moessbauer spectroscopy and X-ray diffraction methods were applied to determine the different phases formed. The morphology of the resulting particles was observed by high resolution scanning electron microscopy. The effect of the milling on bulk iron-silicide samples was and studied chemical effects of the ball milling on Fe-Si{sub 2} systems have been studied.

  17. Characteristics of bulk liquid undercooling and crystallization behaviors of jet electrodeposition Ni–W–P alloy

    Indian Academy of Sciences (India)

    J K Yu; Y H Wang; G Z Xing; Q Qiao; B Liu; Z J Chu; C L Li; F You

    2015-02-01

    The undercooling of Ni–W– P ternary alloy coating melt was investigated by in situ differential scanning calorimeter (DSC) with the flux processing technique. The results showed that the highest undercooling of Ni–W–P ternary alloy with 359 K was obtained as the thermal treatment temperature of themelt being 1679 K and the cooling rate being 50 K min-1. When cooling rate is fixed, the change of undercooling depends on the melt processing temperature, and the undercooling will increase rapidly at the first stage. The effects of thermal treatment temperature and cooling rates on the undercooling were discussed.

  18. Surface and bulk characterization of molten In and In-Sn alloys

    OpenAIRE

    Ricci E; Novakovic R.; Montanari R.; Giuranno D.; Gauzzi F.; Varone A.

    2011-01-01

    In this work a double contribution to the characterization of molten In and In-Sn alloys considered as main components of an important class of lead free solder materials is shown: the study of the influence of oxygen on the capillary phenomena and the XRD investigation of the structure of liquid in a range of temperatures around that of liquidus. The surface tension behaviour of In-Sn binary alloys at different compositions, in terms of effective oxygen pressure, were compared with the...

  19. Deformation of Zr41 Ti14 CU12.5 Ni10 Be22.5 bulk amorphous alloy under isobaric pressure in super-cooled liquid region

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ke-qin; LU Qi-zhu

    2005-01-01

    The curve of crystallization transition during continuous heating for the Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloy was measured by means of dilatation(Fully automatic transformation recording/measuring instrument) and X-ray diffraction(XRD) method. The deformation behavior of the alloy at various heating rates in the supercooled liquid region was studied. The results show that the glass transition temperature of the alloy increases slightly and the supercooled liquid region(SLR) increases significantly with increasing heating rate. The deformation amount under isobaric pressure of 1 N for the alloy in the SLR increases with increasing heating rate. As the heating rate of the alloy increases from 5 to 100 ℃/min, the amount of deformation of the alloy increases from 8.3% to 45%.

  20. Fabrication of ternary Ca-Mg-Zn bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2013-02-01

    Full Text Available Purpose: The paper describes the preparation, structure and thermal properties of ternary Ca-Mg-Zn bulk metallic glass in form of as-cast rods.Design/methodology/approach: The investigations on the ternary Ca-Mg-Zn glassy rods were conducted by using X-ray diffraction (XRD, scanning electron microscopy (SEM which energy dispersive X-ray analysis (EDS.Findings: The X-ray diffraction investigations have revealed that the studied as-cast rod was amorphous. The fractures of studied alloy could be classified as mixed fracture with indicated “river” and “smooth” fractures. Both type of the fracture surfaces consist of weakly formed “river” and “shell” patterns and “smooth” regions. The “river” patterns are characteristic for metallic glassy alloys.Practical implications: The studied Ca-based bulk metallic glasses is a relatively new group of material. Ca-based bulk metallic glasses are applied for many applications in different elements. Ca-based bulk metallic glasses have many unique properties such as low density (~2.0 g/cm3, low Youn g’s modulus ( ~20 to 30 GPa. The elastic modulus of Ca-b ased BMGs is comparable to that of hum an bone s, and Ca, Mg, and Zn are biocompatible. These features make the Ca-Mg-Zn–based alloys attractive for use in biomedical applications.Originality/value: Fabrication of amorphous alloy in the form of rod ternary Ca-Mg-Zn alloy by pressure die casting method.

  1. Is Cu60Ti10Zr30 a bulk glass-forming alloy?

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saida, J.; Kato, H.; Ohsuna, T.; Inoue, A.

    2003-01-01

    The microstructures of Cu60Ti10Zr30 alloys fabricated by using two different methods, (rods of 2.5 mm in diameter prepared by a copper-mold casting method, and ribbons of about 0.03 mm in thickness prepared by the melt-spinning method), have been investigated by transmission electron microscopy a...

  2. Surface and bulk characterization of molten In and In-Sn alloys

    Directory of Open Access Journals (Sweden)

    Ricci E.

    2011-05-01

    Full Text Available In this work a double contribution to the characterization of molten In and In-Sn alloys considered as main components of an important class of lead free solder materials is shown: the study of the influence of oxygen on the capillary phenomena and the XRD investigation of the structure of liquid in a range of temperatures around that of liquidus. The surface tension behaviour of In-Sn binary alloys at different compositions, in terms of effective oxygen pressure, were compared with the data of pure In and the theoretical predictions, revealing that the lower oxidizability of indium was shown to control indium–tin alloys with a tin content up to about 80 at% , due to the presence of the most volatile oxide In2O. From the XRD spectra the radial distribution functions (RDF have been determined for each alloys. Experiments of High Temperature X-ray diffraction (HT-XRD showed that atomic clustering forms in the melt immediately before the appearing of the first solid. The structure of clusters is correlated to that of solid.

  3. Flow and Fracture of Bulk Metallic Glass Alloys and their Composites

    Energy Technology Data Exchange (ETDEWEB)

    Flores, K M; Suh, D; Howell, R; Asoka-Kumar, P; Dauskardt, R H

    2001-06-20

    The fracture and plastic deformation mechanisms of a Zr-Ti-Ni-Cu-Be bulk metallic glass and a composite utilizing a crystalline reinforcement phase are reviewed. The relationship between stress state, free volume and shear band formation are discussed. Positron annihilation techniques were used to confirm the predicted increase in free volume after plastic straining. Strain localization and failure were examined for a wide range of stress states. Finally, methods for toughening metallic glasses are considered. Significant increases in toughness are demonstrated for a composite bulk metallic glass containing a ductile second phase which stabilizes shear band formation and distributes plastic deformation.

  4. Magnetism and half-metallicity in bulk Ti{sub 2}CoSn Heusler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadian, F., E-mail: farzad.ahmadian@gmail.com

    2013-11-05

    Highlights: •The Ti{sub 2}CoSn Heusler alloy has HM nature at the equilibrium volume. •The minority spin and spin-flip gaps are equal to 0.87 eV and 0.47 eV, respectively. •The M{sub tot} of Ti{sub 2}CoSn was obtained 3μ{sub B} which is in agreement with Slater–Pauling rule. •The Ti{sub 2}CoSn Heusler alloy maintains the HM nature between 5.68 and 7.02 Å. •The InSb and CdTe are suitable substrates for growing the Ti{sub 2}CoSn Heusler alloy. -- Abstract: Electronic structure calculations based on density functional (DFT) theory within the generalized gradient approximation (GGA) for the Ti{sub 2}CoSn Heusler compound have been performed using the self-consistent full-potential linearized augmented plane wave (FPLAPW) method. The Ti{sub 2}CoSn Heusler alloy was predicted to be a complete half-metal. The total magnetic moment of Ti{sub 2}CoSn was obtained 3μ{sub B} per formula unit for the equilibrium lattice parameter which is in agreement with Slater–Pauling rule M{sub tot} = Z{sub tot}−18. The minority spin and spin-flip gaps were calculated equal to 0.87 eV and 0.47 eV, respectively. The spin–orbit interaction has a negligible contribution to the half-metallic and magnetic properties of Ti{sub 2}CoSb alloy. In addition, the band structure and density of states (DOSs) were studied and the origin of minority band gap was also discussed. The Ti{sub 2}CoSn Heusler alloy maintains the half-metallic characteristic for lattice constants between 5.68 and 7.02 Å leading to be an interesting material in the field of spintronics.

  5. Formation and magnetic properties of the L10 phase in bulk, powder and hot compacted Mn–Ga alloys

    International Nuclear Information System (INIS)

    The formation and stability of the L10 phase in Mn–Ga binary alloys with compositions in the range 50–75 at% Mn (in steps of 5 at%) has been studied. Of these, single-phase L10 structure was successfully produced in the 55, 60 and 65 at% Mn alloys by annealing the high temperature phases, which had been retained to room temperature following arc melting. Further annealing and thermal analysis were used to determine the phase transformation temperatures in the alloys and the results were used to guide further processing. The saturation magnetisation, Ms, and the anisotropy field, Ha, were determined in applied fields up to 14 T. For Mn55Ga45, µ0Ms=0.807 T and µ0Ha=4.4 T were observed. Mechanically milled Mn55Ga45 powder had coercivity of µ0Hc=0.393 T, which was a twentyfold increase compared to the bulk material but the magnetisation was reduced (cf. powder: µ0M5 T=0.576 T, bulk: µ0M5 T=0.780 T). Annealing the powder at 400 °C led to recovery of the magnetisation but reduced the coercivity, which was still 10 times as high as the bulk value. A degree of texture of 0.45 was achieved by magnetic alignment of the powder particles, leading to a remanence of 0.526 T. Furthermore, isotropic hot compacts of powders were produced with packing density from 83% to 99%, in which the improved coercivity of the powders was partially retained. - Highlights: • Single phase L10 structure achieved in compounds with 55 to 65 at% Mn. • Saturation polarisation of 0.81 T measured in the L10 phase in Mn55Ga45. • Milled Mn–Ga L10 powder showed greatly increased coercivity. • L10 hot compacts could be produced with a packing density of 83–99%. • A partial magnetic field alignment of the powder particles was achieved

  6. Theoretical investigation of the electronic structures and magnetic properties of the bulk and surface (001) of the quaternary Heusler alloy NiCoMnGa

    Energy Technology Data Exchange (ETDEWEB)

    Al-zyadi, Jabbar M. Khalaf, E-mail: Jabbar_alzyadi@yahoo.com [Department of Physics, College of Education, University of Basrah, Basrah 6100 (Iraq); Gao, G.Y. [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, Kai-Lun [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of sciences, Shenyang 110015 (China)

    2015-03-15

    In this paper, we study the electronic structures, magnetic properties, and half-metallicity of the bulk and (001) surface of Heusler alloy NiCoMnGa. Our first-principles calculations exhibit that, within the generalized gradient approximation (GGA) of the electronic exchange–correlation functional, the quaternary Heusler alloy NiCoMnGa is a half-metallic ferromagnet at the equilibrium lattice constant of 5.795 Ǻ with a total spin magnetic moment of 5 μ{sub B} per formula unit. The calculated total atomic magnetic moment follows the Slater–Pauling rule. At the same equilibrium lattice constant, the half-metallicity confirmed in the bulk NiCoMnGa, is destroyed at both MnGa- and NiCo-terminated (001) surfaces and subsurfaces. Based on the magnetic property calculations, the magnetic moments of Co, Mn, and Ga atoms at the NiCo- and MnGa-terminated surfaces increase with respect to the corresponding bulk values while the atomic magnetic moment of Ni at the NiCo-terminated surface decreases. - Highlights: • The bulk NiCoMnGa quaternary-Heusler alloy is found to be a half-metallic ferromagnet. • Surface studies show that the half-metallicity of bulk NiCoMnGa is destroyed. • The magnetic moments are increased (decreased) at the (001) surface. • The quaternary-Heusler alloy follows a Slater–Pauling behavior.

  7. Bulk and porous metastable beta Ti-Nb-Zr(Ta) alloys for biomedical applications

    International Nuclear Information System (INIS)

    In this work, metastable beta Ti-Nb-Zr(Ta) ingots were manufactured by vacuum arc melting. The ingots thus obtained were divided into two batches: the first subjected to cold rolling (CR) from 30 to 85% of thickness reduction and subsequent annealing in the 450 to 900 deg. C temperature region, and the second atomized to produce 100 μm size powders. This powder was used to manufacture open-cell porous material. Regardless of the CR intensity, Ti-(18...20)Nb-(5...6)Zr (at.%) samples subjected to 600 deg. C (1 h) annealing showed a significant material softening due to the stress-induced martensitic transformation. The Young's modulus of these alloys varied between 45 and 55 GPa, and the yield stress, between 300 and 500 MPa. The obtained Young's moduli, which are comparable to 55-66 GPa of concurrent beta-titanium alloys and 45-50 GPa of superelastic Ti-Ni alloys, come close to those of cortical bones. Compression testing of the porous material as a function of porosity (from ∼ 45 to 66%) and interconnected cell size (d50 from 300 to 760 μm) showed the following properties: Young's modulus from 7.5 to 3.7 GPa, which comes close to that of trabecular bones, and ultimate compression strength, of from 225 to 70 MPa.

  8. Structure and soft magnetic properties of Fe72B20Si4Nb4 bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2009-01-01

    Full Text Available Purpose: The paper presents a microstructure characterization, thermal stability and soft magnetic properties analysis of Fe-based bulk amorphous materials.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4 glassy alloy in form of ribbons and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations have revealed that the studied as-cast bulk metallic glasses were amorphous. Broad diffraction halo can be seen for all tested samples, indicating the formation of a glassy phase with the diameters up to 2 mm. The fracture surface of rod samples appears to consist of small fracture zones, which leads to breaking of the samples into parts. A two stage crystallization process was observed for studied amorphous alloy. The changes of crystallization temperatures and magnetic properties as a function of glassy samples thickness were stated.Practical implications: The studied Fe-based alloy system has good glass-forming ability and thermal stability for casting bulk metallic glasses, which exhibit good soft magnetic properties, useful for many electric and magnetic applications.Originality/value: The obtained examination results confirm the utility of applied investigation methods in the microstructure, thermal and soft magnetic properties analysis of examined bulk amorphous alloys.

  9. Half-metallicity of bulk and (1 1 1) surface for full-Heusler alloy Co2VAl: A density functional study

    International Nuclear Information System (INIS)

    Highlights: •The bulk and (1 1 1) surface half-metallicity of Heusler alloy Co2VAl are investated. •The half-metallic ferromagnetism with a ground state is confirmed in bulk Co2VAl. •The bulk HM property is preserved at two surfaces but lost at other two surfaces. •The present work would be helpful for the applications of spintronic devices. -- Abstract: Motivated by the recent experimental synthesis of the bulk and thin films for full-Heusler alloy Co2VAl, we investigate the structural, electronic and magnetic properties of the bulk Co2VAl and its (1 1 1) surfaces based on the density functional theory. The half-metallic ferromagnetism with the magnetic moment of 2.00 μB per formula unit is confirmed in the bulk Co2VAl with L21 structure. For the four possible (1 1 1) surfaces, it is shown from the present DOS that the bulk half-metallicity is preserved at V- and Al-terminated surfaces but destroyed by some surface states at Co–V- and Co–Al-terminated surfaces. We also find that the atomic magnetic moments at the (1 1 1) surfaces are greatly different from the bulk values due to the effect of symmetry breaking at the surface. Moreover, the structure relaxation indicates that Al- and V-terminated surfaces are more favorable to the applications of spintronic devices

  10. Thermal stability of Zr55Al10Ni5Cu30 bulk amorphous alloy during continuous heating and isothermal annealing

    Institute of Scientific and Technical Information of China (English)

    高玉来; 沈军; 孙剑飞; 王刚; 邢大伟; 周彼德

    2003-01-01

    The crystallization behavior of Zr55Al10Ni5Cu30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order exponential decay relation between the characteristic temperatures and the heating rates during continuous heating process. The activation energy for glass transition Eg and that for crystallization Ep and Ex during continuous heating were evaluated by Kissinger plots. In addition, there is a second order exponential decay relation between the annealing temperature and the corresponding crystallization time during isothermal annealing. The isothermal activation energy obtained by Arrhenius equation increases as crystallization proceeds, indicating the sufficient stability of the residual amorphous structure after initial crystallization.

  11. Magnetization behavior and magnetocaloric effect in bulk amorphous Fe60Co5Zr8Mo5W2B20 alloy

    International Nuclear Information System (INIS)

    Microstructure by X-ray diffraction and Mössbauer spectroscopy, and isothermal magnetic entropy changes in the bulk amorphous Fe60Co5Zr8Mo5W2B20 alloy in the as-quenched state and after annealing at 720 K for 15 min are studied. The as-cast and heat treated alloy is paramagnetic at room temperature. The quadrupole splitting distribution is unimodal after annealing indicating the more homogenous structure in comparison with that for the as-cast alloy. Curie temperature slightly increases after annealing from 265±2 K in the as-quenched state to 272±2 K and the alloy exhibits the second order magnetic phase transition. The maximum of isothermal magnetic entropy changes appears at the Curie points and is equal to 0.30 and 0.42 J/(kg·K) for the alloy in the as-quenched state and after annealing, respectively. In the paramagnetic region the material behaves as a Curie–Weiss paramagnet. - Highlights: ► Bulk amorphous Fe60Co5Zr8Mo5W2B20 alloy is paramagnetic at room temperature. ► Curie temperature slightly increases after annealing at 720 K for 15 min. ► Alloy exhibits the second order magnetic phase transition. ► Maximum magnetic entropy changes increases after annealing. ► In the paramagnetic region the material is a Curie–Weiss paramagnet.

  12. An interatomic potential for studying CuZr bulk metallic glasses

    DEFF Research Database (Denmark)

    Paduraru, Anca; Kenoufi, Abdel; Bailey, Nicholas;

    2007-01-01

    The mechanical properties of BMGs are remarkably different from the ones of ordinary metallic alloys due to the atomic level disorder in the glassy state. Unlike crystalline materials plastic deformation in metallic glasses cannot be caused by lattice defects but takes place through atomic......-scale deformation events and may furthermore involve localization through formation of shear bands. In this paper, an Effective Medium Theory (EMT) potential optimized for modeling the mechanical and thermodynamic properties of CuZr bulk metallic glass is studied. The late transition metals crystallizing in close......-packed structures, and their alloys, while still allowing simulations with millions of atoms is discussed....

  13. Microstructures and mechanical properties of bulk nanocrystalline Fe–Al–C alloys made by mechanically alloying with subsequent spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Yoritoshi Minamino, Yuichiro Koizumi, Nobuhiro Tsuji, Naoko Hirohata, Kiyoshi Mizuuchi and Yoshihira Ohkanda

    2004-01-01

    Full Text Available The microstructure and superior mechanical properties of bulk nanocrystalline Fe–Al–C alloys made by mechanically alloying (MA with subsequent spark plasma sintering (SPS were investigated. Three kinds of nanocrystalline Fe–24 at% Al–X at%C (X=1,2,4 alloy powder were produced by MA from iron and aluminum powder with addition of methanol, and were subsequently consolidated at 1073–1273 K under 64 MPa by SPS. These compacts have the relative densities of 99.97% (1 at%C to 99.5% (4 at%C. The structure of compacts with 1at%C is composed of grains of Fe3Al of 1.5 μm in diameter and nano κ-carbides (Fe3AlC0.5 precipitates, while those of compacts with 2 and 4 at%C are composed of nanocrystalline Fe3Al of about 80 nm in diameter, nano κ-carbides and small amount of large α-grains of about 1 μm in diameter. These structures maintain the nanostructure even at 973 K, that is, they have the good thermal stability. The mechanical properties of these compacts were measured by compression tests at room temperature (RT to 973 K in vacuum. The compacts with 1 and 2 at%C of this work perform the superior mechanical properties (e.g. yield strength of 2150 MPa and rupture strain of 0.14 for compact with 2 at%C at R.T. when compared with the ordinary Fe3Al casting (e.g. the yield strength of 380 MPa and rupture strain of 0.12.

  14. Effect of ZnCdTe-Alloyed Nanocrystals on Polymer–Fullerene Bulk Heterojunction Solar Cells

    OpenAIRE

    Wang Yan; Hou Yanbing; Tang Aiwei; Feng Zhihui; Feng Bin; Li Yan; Teng Feng

    2009-01-01

    Abstract The photovoltaic properties of solar cell based on the blends of poly[2-methoxy-5-(2-ethylhexoxy-1,4-phenylenevinylene) (MEH-PPV), fullerene (C60), and ZnCdTe-alloyed nanocrystals were investigated. Comparing the spectral response of photocurrent of the MEH-PPV:C60(+ZnCdTe) nanocomposite device with that of the devices based on MEH-PPV:C60and pristine MEH-PPV, one can find that the nanocomposite device exhibits an enhanced photocurrent. In comparing the composite devices with differe...

  15. Preparation and Properties of Mg-Cu-Y-Al bulk Amorphous Alloys

    DEFF Research Database (Denmark)

    Pryds, Nini; Eldrup, Morten Mostgaard; Ohnuma, M.;

    2000-01-01

    temporal numerical simulation of that process. It is concluded that good thermal contact is maintained between the amorphous part of the solidified sample and the mould, while a rather poor contact develops between the crystalline part of the sample and the mould, probably due to the appearance of a narrow...... temperatures in specimens containing a few percent Al. The alloy with no Al crystallises apparently without the formation of nanoparticles. The critical cooling rate for the formation of an amorphous Mg(60)CU(30)Y(10) specimen was determined experimentally by a combination of DSC data and temperature vs, time...

  16. Nanoscopic transformations and GMR in bulk non-equilibrium Cu-Co alloys

    International Nuclear Information System (INIS)

    We have investigated ribbons of the alloy series Cu1-xCox (x=0.05, 0.10, 0.15, and 0.20) using transmission electron microscopy and magnetotransport measurements to correlate nanostructural transformations to its giant magnetoresistance (GMR) behavior. Instead of dealing with a simple granular system, as it is commonly assumed, we show that spinodal decomposition in the form of lamellar phases is in fact the common feature observed in these materials, and that GMR is seen whenever this decomposition is observed. The formation of these nanoscopic lamellae as metastable segregated phases can be understood via a Cahn-Hilliard analysis

  17. Effect of ball milling time on nanocrystalline powders and bulk ultrafine-grained Mg-3Al-Zn alloy

    Directory of Open Access Journals (Sweden)

    Feng Jie

    2015-01-01

    Full Text Available Bulk ultrafine-grained Mg-3Al-Zn alloy has been made of elemental powders by mechanical milling, vacuum hot pressing and warm extrusion sequentially. As the only variable, ball milling time was 20 h, 40 h, 60 h and 80 h, respectively. Microstructural studies and mechanical strength were characterized by SEM, XRD, TEM and tensile tests. At 60 h, the particle size of the milled powders decreased to 10 μm. With extension of time, the grain sizes of nanocrystalline powders were 41, 39.5, 38.5 and 38 nm. Under the same hot pressing and extrusion conditions, the grain sizes of extruded materials were 600, 565, 555 and 550 nm, respectively. The results of tensile tests showed that increasing milling time under 60 h improved the strength of the extruded alloys, however, reduced the ductility due to lower relative density and more defects. This also indicated that better ductility with high strength should be obtained if densification process was further improved. Meanwhile, the high ultimate strength of 419 MPa results from oxide dispersion strengthening and dislocation strengthening besides grain refinement strengthening.

  18. The Magnetization Reversal Processes Of Bulk (Nd, Y-(Fe, Co-B Alloy In The As-Quenched State

    Directory of Open Access Journals (Sweden)

    Dośpiał M.

    2015-09-01

    Full Text Available The magnetization reversal processes of bulk Fe64Co5Nd6Y6B19 alloy in the as-quenched state have been investigated. From the analysis of the initial magnetization curve and differential susceptibility versus an internal magnetic field it was deduced, that the main mechanism of magnetization reversal process is the pinning of domain walls at the grain’s boundaries of the Nd2Fe14B phase. Basing on the dependence of the reversible magnetization component as a function of magnetic field it was found that reversible rotation of a magnetic moment vector and motion of domain walls in multi-domain grains result in high initial values of the reversible component. The presence of at least two maxima on differential susceptibility of irreversible magnetization component in function of magnetic field imply existence of few pinning sites of domain walls in Fe64Co5Nd6Y6B19 alloy. The dominant interactions between particles have been determined on the basis of the Wohlfarth dependence. Such a behavior of Wohlfarth’s plot implies that the dominant interaction between grains becomes short range exchange interactions.

  19. The effect of synthesis parameters on transport properties of nanostructured bulk thermoelectric p-type silicon germanium alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zamanipour, Zahra; Shi, Xinghua; Dehkordi, Arash M.; Krasinski, Jerzy S.; Vashaee, Daryoosh [Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, OK 74106 (United States)

    2012-10-15

    Nanostructured silicon germanium thermoelectric materials prepared by mechanical alloying and sintering method have recently shown large enhancement in figure-of-merit, ZT. The fabrication of these structures often involves many parameters whose understanding and precise control is required to attain large ZT. In order to find the optimum parameters for further enhancing the ZT of this material, we have grown and studied both experimentally and theoretically different nanostructured p-type SiGe alloys. The effect of various parameters of milling process and sintering conditions on the thermoelectric properties of the grown samples were studied. The electrical and thermal properties were calculated using Boltzmann transport equation and were compared with the data of nanostructured and crystalline SiGe. It was found that the thermal conductivity not only depends on the average crystallite size in the bulk material, but also it is a strong function of alloying, porosity, and doping concentration. The Seebeck coefficient showed weak dependency on average crystallite size. The electrical conductivity changed strongly with synthesis parameters. Therefore, depending on the synthesis parameters the figure-of-merit reduced or increased by {proportional_to}60% compared with that of the crystalline SiGe. The model calculation showed that the lattice part of thermal conductivity in the nanostructured sample makes {proportional_to}80% of the total thermal conductivity. In addition, the model calculation showed that while the room temperature hole mean free path (MFP) in the nanostructured sample is dominated by the crystallite boundary scattering, at high temperature the MFP is dominated by acoustic phonon scattering. Therefore, the thermal conductivity can be further reduced by smaller crystallite size without significantly affecting the electrical conductivity in order to further enhance ZT. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Molecular dynamics study of the ternary Cu50Ti25Zr25 bulk glass forming alloy

    Directory of Open Access Journals (Sweden)

    Celtek M.

    2011-05-01

    Full Text Available The structure and thermodynamic properties of a ternary Cu50Ti25Zr25 metallic glass forming alloy in solid-liquid to glass phases were studied using molecular dynamics (MD method based on tight-binding (TB potentials. An atomic description of the melting, glass formation and crystallization process has been analyzed using different heating and cooling rates. The computed Glass Forming Ability (GFA parameters are in good agreement with experimental data. The structure analysis of the Cu50Ti25Zr25 based on molecular dynamics simulation will be also presented and compared with available MD results. We have also discussed the crystallization transition with two different interatomic potentials used in this work

  1. Non-monotonic influence of a magnetic field on the electrochemical behavior of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions

    Institute of Scientific and Technical Information of China (English)

    Hong-di Zhang; Xiao-yu Li; Jing Pang; Li-juan Yin; Hai-jian Ma; Ying-jie Li; Yan Liu; Wei-min Wang

    2014-01-01

    The corrosion behavior and microstructure of Fe78Si9B13 glassy alloy in NaOH and NaCl solutions under a 0.02-T magnetic field were investigated through electrochemical testing and scanning electron microscopy (SEM). The current-density prepeak (PP) in the anodic polarization curves in low-concentration NaOH solutions (classified as type I) tends to disappear when the NaOH concentration is increased to 0.4 mol/L and the magnetic field is applied. Under the magnetic field, the height of the second current-density peak is increased in low-concentration NaOH solutions (type I) but decreased in high-concentration NaOH solutions (type II). The non-monotonic effect of the magnetic field was similarly observed in the case of polarization curves of samples measured in NaCl solutions. Ring-like corroded patterns and round pits are easily formed under the magnetic field in NaOH and NaCl solutions. These experimental results were discussed in terms of the magnetohydrodynamic (MHD) effect.

  2. Prominent Fe-based bulk amorphous steel alloy with large supercooled liquid region and superior corrosion resistance

    International Nuclear Information System (INIS)

    Graphical abstract: SEM images of the surface profile on the blade edge-tip for (a) commercial blade and (b) Fe-B9 BAS blade. SEM images of blade edge-tip for (c) as-received commercial blade, (d) commercial blade after cutting test of 25 cm length, (e) as-prepared Fe-B9 BAS blade, and (f) Fe-B9 BAS blade after cutting test of 25 cm length. -- Highlights: • An Fe-based BAS with high GFA and large supercooled region has been successfully produced. • Fe-B9 BAS exhibits higher corrosion resistance than 304 SS and 316 SS in Hank’s solution. • Fe-B9 BAS blade exhibits much higher sharpness than the commercial one. • Fe-B9 BAS blade presents much better durability than the commercial one on cutting test. -- Abstract: A prominent Fe-base bulk amorphous steel (BAS) alloy which presents high glass forming ability (GFA), good corrosion resistance, superior mechanical properties and relative lower cost. The Fe41Cr15Co7Mo14C21−xBxY2 (x = 5–10) BAS rods with a diameter of 2–6 mm, can be fabricated by the suction casting method. The highest GFA value can be obtained by adjusting the ratio of boron/carbon, reaching to the value of γ = 0.4 and γm = 0.69 for the alloy composition of Fe41Ce15Co7Mo14C12B9Y2. Meanwhile, this alloy also presents very large supercooled liquid region up to 81 K, favourable to be fabricated into micro-surgery tools by thermoplastic forming. In addition, the Fe-base BAS alloy exhibits extremely high hardness around 1200 Hv. The anodic polarization measurement of the Fe-based BAS exhibits a higher corrosion resistance than 304 SS and 316 SS in the Hank’s balanced salt solution. The sharpness test results reveal that the Fe-based BAS blade exhibits much higher sharpness because of its lower surface roughness and higher hardness. Moreover, the Fe-base BAS blade presents much better durability on cutting testing, it can remain relatively sharper edge-tip with a low blade sharpness index (BSI) value of 0.38 (in comparison with the BSI value

  3. Crystalline Behavior and Magnetic Properties of Nd60Fe30-xAl10Cox(x=0,5,10) Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    徐晖; 谭晓华; 董远达

    2003-01-01

    Crystalline behavior and magnetic properties of Nd60Fe30-xAl10Cox (x=0,5,10) bulk amorphous alloys were investigated by differential scanning calorimeter (DSC), X-ray diffraction (XRD) and the vibrating sample magnetometer (VSM). Neither glass transition nor supercooled liquid region before crystallization was observed for the as-cast Nd60Fe30-xAl10Cox (x=0,5,10) bulk amorphous alloys. The glass forming ability can be improved significantly by the addition of Co. The as-cast Nd60Fe30-xAl10Cox (x=0,5,10) alloys show hard magnetic behavior. With the addition of Co content, intrinsic coercivity (iHc) increases while the saturation magnetization(σs) and remanence (σr) decrease. The Curie temperature for the as-cast Nd60Fe30-xAl10Cox alloys increases from 451 K for x=0 to 468 K for x=10. Some precipitation of crystalline phases does not affect the hard magnetic properties of Nd60Fe30-xAl10Cox (x=0,5,10) alloys, while the hard magnetic behavior disappears quickly after the alloys being completely crystallized.

  4. Structure and magnetic properties of Fe36Co36B19Si5Nb4 bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2008-10-01

    Full Text Available Purpose: The work presents a microstructure characterization, thermal stability and soft magnetic properties analysis of Fe-based bulk metallic glasses.Design/methodology/approach: The studies were performed on bulk amorphous ribbons and rods. The amorphous structure of tested materials was examined by X-ray diffraction (XRD and transmission electron microscopy (TEM methods. The thermal properties associated with crystallization temperature of the glassy samples were measured using differential thermal analysis (DTA and differential scanning calorimetry (DSC. The magnetic properties were determined by the Maxwell-Wien bridge and VSM methods.Findings: The X-ray diffraction and transmission electron microscopy investigations have revealed that the studied as-cast bulk metallic glasses were amorphous. Based from the XRD analysis and TEM investigations of the Fe36Co36B19Si5Nb4 rod samples, it was believed that the tested alloy can be fabricated into a bulk glassy rod with the diameter of up to 4 mm. A two stage crystallization process was observed for studied bulk amorphous alloy. The changes of Curie temperatures, crystallization temperatures and magnetic properties as a function of glassy ribbons thickness (time of solidification were stated. The investigated magnetic properties allow to classify the studied metallic glasses as soft magnetic materials.Practical implications: The studied bulk metallic glasses are suitable materials for many electrical application in different elements of magnetic circuits and for manufacturing of sensors and precise current transformers.Originality/value: The obtained examination results confirm the utility of applied investigation methods in the microstructure, thermal and soft magnetic properties analysis of examined bulk amorphous alloys.

  5. Influence of germanium nano-inclusions on the thermoelectric power factor of bulk bismuth telluride alloy

    Energy Technology Data Exchange (ETDEWEB)

    Satyala, Nikhil; Zamanipour, Zahra; Norouzzadeh, Payam; Krasinski, Jerzy S.; Vashaee, Daryoosh, E-mail: daryoosh.vashaee@okstate.edu [School of Electrical and Computer Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, Oklahoma 74106 (United States); Tahmasbi Rad, Armin [School of Material Science and Engineering, Helmerich Advanced Technology Research Center, Oklahoma State University, Tulsa, Oklahoma 74106 (United States); Tayebi, Lobat, E-mail: daryoosh.vashaee@okstate.edu [School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078 (United States)

    2014-05-28

    Nanocomposite thermoelectric compound of bismuth telluride (Bi{sub 2}Te{sub 3}) with 5 at. % germanium nano-inclusions was prepared via mechanically alloying and sintering techniques. The influence of Ge nano-inclusions and long duration annealing on the thermoelectric properties of nanostructured Bi{sub 2}Te{sub 3} were investigated. It was found that annealing has significant effect on the carrier concentration, Seebeck coefficient, and the power factor of the thermoelectric compound. The systematic heat treatment also reduced the density of donor type defects thereby decreasing the electron concentration. While the as-pressed nanocomposite materials showed n-type properties, it was observed that with the increase of annealing time, the nanocomposite gradually transformed to an abundantly hole-dominated (p-type) sample. The long duration annealing (∼500 h) resulted in a significantly enhanced electrical conductivity pertaining to the augmentation in the density and the structural properties of the sample. Therefore, a simultaneous enhancement in both electrical and Seebeck coefficient characteristics resulted in a remarkable increase in the thermoelectric power factor.

  6. Effect of ZnCdTe-Alloyed Nanocrystals on Polymer–Fullerene Bulk Heterojunction Solar Cells

    Directory of Open Access Journals (Sweden)

    Wang Yan

    2009-01-01

    Full Text Available Abstract The photovoltaic properties of solar cell based on the blends of poly[2-methoxy-5-(2-ethylhexoxy-1,4-phenylenevinylene (MEH-PPV, fullerene (C60, and ZnCdTe-alloyed nanocrystals were investigated. Comparing the spectral response of photocurrent of the MEH-PPV:C60(+ZnCdTe nanocomposite device with that of the devices based on MEH-PPV:C60and pristine MEH-PPV, one can find that the nanocomposite device exhibits an enhanced photocurrent. In comparing the composite devices with different ZnCdTe:[MEH-PPV + C60] weight ratios of 10 wt% (D1–1, 20 wt% (D1–2, 40 wt% (D1–3, and 70 wt% (D1–4, it was found that the device D1–3exhibits the best performance. The power conversion efficiency (η is improved doubly compared with that of the MEH-PPV:C60device.

  7. Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Akihisa Inoue

    2011-04-01

    Full Text Available This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs. In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni and Cu–Zr–Ag–Al–(Nb bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

  8. Preparation of a bulk Fe{sub 83}B{sub 17} soft magnetic alloy by undercooling and copper-mold casting methods

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Changlin, E-mail: ycl@nwpu.edu.cn; Sheng, Gang; Chen, Guiyun; Liu, Feng

    2013-11-15

    Bulk Fe{sub 83}B{sub 17} eutectic alloy rods with diameters up to 3 mm were prepared by undercooling solidification combined with Cu-mold casting. The results showed that the rapid solidification led to an increase in the nucleation rate, an inhibition of the grain growth and a competition between a stable Fe{sub 2}B phase and a metastable Fe{sub 3}B phase. Then, pure nano-lamellar eutectic microstructures and the metastable Fe{sub 3}B phase were successfully obtained in as-solidified alloys, which resulted in improved soft magnetic properties. - Highlights: • Pure nano-lamellar eutectic structure was directly formed in the bulk Fe-B alloys. • The metastable Fe{sub 3}B phase was directly formed in the bulk Fe-B alloys. • Undercooling solidification combined with Cu-mold casting was applied. • The information on bcc Fe, Fe{sub 2}B and Fe{sub 3}B-magnetism relationship was provided. • Nano-lamellar eutectic structures enhance the soft magnetic properties.

  9. Development and structural characterization of exchange-spring-like nanomagnets in (Fe,Co)-Pt bulk nanocrystalline alloys

    Science.gov (United States)

    Crisan, O.; Crisan, A. D.; Mercioniu, I.; Nicula, R.; Vasiliu, F.

    2016-03-01

    FePt-based alloys are currently under scrutiny for their possible use as materials for perpendicular magnetic recording. Another possible application is in the field of permanent magnets without rare-earths, magnets that may operate at higher temperatures than the classic Nd-Fe-B magnets. Within this study, FeCoPt alloys prepared by rapid solidification from the melt are structurally and magnetically characterized. In the as-cast FeCoPt ribbons, a three-phase structure comprising well-ordered CoFePt and CoPt L10 phases embedded in a disordered fcc FePt matrix was evidenced by XRD, HREM and SAED. Extended transmission electron microscopy analysis demonstrates the incipient formation of ordered L10 phases. X-ray diffraction was used to characterize the phase structure and to obtain the structural parameters of interest for L10 ordering. In the as-cast state, the co-existence of hard magnetic CoFePt and CoPt L10 tetragonal phases with the soft fcc FePt phase is obtained within a refined microstructure made of alternatively disposed grains (grain sizes from 1 to 7 nm). Following a thermal treatment of 1 h at 670 °C, the soft magnetic fcc matrix phase transforms to tetragonal L10 phases (disorder-order transition). The resulting CoPt and CoFePt L10 phases have grains of around 5-20 nm in size. In the as-cast state, magnetic measurements show a quite large remanence (0.75 T), close to the value of the parent L10 FePt phase. Coercive fields of about 200 kA/m at 5 K were obtained, comparable with those reported for some FePt-based bulk alloys. Upon annealing both remanence and coercivity are increased and values of up to 254 kA/m at 300 K are obtained. The polycrystalline structure of the annealed FeCoPt samples, as well as the formation of multiple c-axis domains in different CoPt and CoFePt regions (which leads to a reduction of the magneto-crystalline anisotropy) may account for the observed coercive fields that are lower than in the case of very thin FeCoPt films. A

  10. Magnetic properties and half-metallic in bulk and (001) surface of Ti2MnAl Heusler alloy with Hg2CuTi-type structure

    International Nuclear Information System (INIS)

    Using the first-principles projector augmented wave potential within the generalized gradient approximation, we investigate the magnetic and electronic properties in the bulk and (001) surface of the Heusler alloy Ti2MnAl with Hg2CuTi-type. For the bulk, our calculations indicate that the Heusler alloy Ti2MnAl exhibits antiferromagnetic half-metallicity at the equilibrium lattice constant. Owing to the surface effects, the half-metallicity which can be observed in bulk is destroyed in five terminations. The high spin polarization only maintains in TiMn-termination. Through further studies on the atomic magnetic moments, we find that the moment of surface Ti1 is enhanced obviously, as well as the absolute value of surface Mn atomic moment. - Highlights: • The bulk Ti2MnAl alloy exhibits antiferromagnetic half-metallicity. • The half-metallicity is destroyed in five terminations. • The high spin polarization only maintains in TiMn-termination

  11. Atomic-scale simulation study of some bulk and interfacial properties of iron aluminium ordered alloys

    International Nuclear Information System (INIS)

    A semi-empirical potential was designed for B2 and DO3 iron aluminides and used to study point defects and grain boundaries in these compounds. At low temperature, departure from B2 stoichiometry is accommodated with antisite defects; when T increases, iron vacancies appear and defects have a trend to form clusters, the structure of which is very sensitive to this departure. Our calculations, relying on T = 0 K formation energies, predict the nature of major defects, but lead to underestimated quantitative results, which may point out the essential role of atomic vibrations. In the stoichiometric B2 compound, the diffusion of both species is induced by four-jump cycles involving iron vacancies. Although the agreement between our calculated activation energies and other experiments is good, the calculated diffusion coefficients are below the experimental ones. Here again, this discrepancy may be put down to the overlooking of phonon contributions. The second application concerns the atomic structures of the [001] (310) symmetric tilt grain boundary in the B2 and DO3 compounds. At low temperature, in the stoichiometric B2 compound, we obtain an iron-rich single stable structure (pseudo-symmetric), whose structure is strongly influenced by the bulk composition (with intergranular segregation of the major element). In the stoichiometric DO3 compound, many energetically equivalent structures exist, all being systematically aluminium-rich. The study of the B2 grain boundary structure at high temperature shows a phase transition favouring a symmetric structure. Its high excess energy at low temperature emphasizes the influence of atomic vibrations in the interfacial properties of B2 Fe-Al compounds. (author)

  12. Structures of bulk amorphous Zr41Ti14Ni10Cu12.5Be22.5 alloy in amorphous, crystalline, supercooled liquid and liquid states

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The amorphous and crystal structures of Zr41Ti14Ni10Cu12.5Be22.5 alloy have been analyzed with X-ray diffractometer. The structures of bulk amorphous Zr41Ti14Ni10Cu12.5B22.5 alloy in solid, supercooled liquid and liquid states are almost of the same structure. The RDFs (Radius Distribution Function), the first coordination number, the first coordination radius, the correlation radius and atom number of the cluster were calculated for bulk amorphous Zr41Ti14Ni10Cu12.5B22.5 alloy in different states. The first coordination sphere radii and the first coordination numbers are 0.312nm, 11.2 in solid state, 0.301nm, 10.932 in supercooled liquid region and 0.305nm, 11.296 in liquid state. The crystal structure of Zr41Ti14Ni10Cu12.5B22.5 alloy is consisted of several intermetallic compounds which are CuZr2, Be2Zr, etc. The reason of formation glass for this alloy is that there is a larger resistance for atoms to rearrange and form intermetallic compounds in a long range order.

  13. Crystallization behavior and consolidation of ball milled Zr60Ti5Ag5Cu12.5Ni10Al7.5 glassy powders

    International Nuclear Information System (INIS)

    Devitrification and consolidation of Zr60Ti5Ag5Cu12.5Ni10Al7.5 glassy powders produced by ball milling of intermetallic compounds have been investigated. The crystallization behavior is characterized by the formation of a nanoscale quasicrystalline phase along with a minor amount of tetragonal Zr2Cu phase during the first stage of the crystallization process. In the second crystallization event the metastable QC transform into the tetragonal Zr2Cu phase. The viscous flow of the supercooled liquid was studied by parallel plate rheometry, showing a distinct viscosity drop related to the glass transition, corroborating the results from DSC measurements. Consolidation of the glassy powders was performed by uniaxial hot pressing. The consolidation parameters were properly selected in order to obtain partially crystallized bulk samples with a composite microstructure characterized by the contemporary presence of glassy, quasicrystalline and tetragonal Zr2Cu phases. Hardness measurements reveal a Vickers hardness of 4.61 GPa and an estimated yield strength of 1.53 GPa. These results show that powder metallurgy methods are suitable for the production of Zr-based alloys characterized by a composite microstructure consisting of glassy, quasicrystalline and crystalline phases with mechanical properties similar to materials prepared by other techniques

  14. Near-forward Raman scattering by bulk and surface phonon-polaritons in the model percolation-type ZnBeSe alloy

    OpenAIRE

    Hussein, Rami Hajj; Pagès, Olivier; Firszt, Franciszek; Paszkowicz, Wojtek; Maillard, Alain

    2013-01-01

    We study the bulk and surface phonon-polaritons of the Zn0.67Be0.33Se zincblende alloy by near-forward Raman scattering. The short (Be-Se) bond exhibits a distinct percolation doublet in the conventional backscattering Raman spectra, corresponding to a three-mode behavior in total [1(Zn-Se),2(Be-Se)] for Zn0.67Be0.33Se. This offers an opportunity to achieve a refined understanding of the phonon-polariton modes of a zincblende alloy beyond the current two-mode approximation, corresponding to a...

  15. Molecular level assessment of thermal transport and thermoelectricity in materials: From bulk alloys to nanostructures

    Science.gov (United States)

    Kinaci, Alper

    The ability to manipulate material response to dynamical processes depends on the extent of understanding of transport properties and their variation with chemical and structural features in materials. In this perspective, current work focuses on the thermal and electronic transport behavior of technologically important bulk and nanomaterials. Strontium titanate is a potential thermoelectric material due to its large Seebeck coefficient. Here, first principles electronic band structure and Boltzmann transport calculations are employed in studying the thermoelectric properties of this material in doped and deformed states. The calculations verified that excessive carrier concentrations are needed for this material to be used in thermoelectric applications. Carbon- and boron nitride-based nanomaterials also offer new opportunities in many applications from thermoelectrics to fast heat removers. For these materials, molecular dynamics calculations are used to evaluate lattice thermal transport. To do this, first, an energy moment term is reformulated for periodic boundary conditions and tested to calculate thermal conductivity from Einstein relation in various systems. The influences of the structural details (size, dimensionality) and defects (vacancies, Stone-Wales defects, edge roughness, isotopic disorder) on the thermal conductivity of C and BN nanostructures are explored. It is observed that single vacancies scatter phonons stronger than other type of defects due to unsatisfied bonds in their structure. In pristine states, BN nanostructures have 4-6 times lower thermal conductivity compared to C counterparts. The reason of this observation is investigated on the basis of phonon group velocities, life times and heat capacities. The calculations show that both phonon group velocities and life times are smaller in BN systems. Quantum corrections are also discussed for these classical simulations. The chemical and structural diversity that could be attained by

  16. A Combinatorial Approach to the Investigation of Metal Systems that Form Both Bulk Metallic Glasses and High Entropy Alloys

    Science.gov (United States)

    Welk, Brian A.; Gibson, Mark A.; Fraser, Hamish L.

    2016-03-01

    In this work, compositionally graded specimens were deposited using the laser engineered net-shaping (LENS™) additive manufacturing technique to study the glass-forming ability of two bulk metallic glass (BMG) and high entropy alloy (HEA) composite systems. The first graded specimen varied from Zr57Ti5Al10Cu20Ni8 (BMG) to CoCrFeNiCu0.5 (HEA) and the second graded specimen varied from TiZrCuNb (BMG) to (TiZrCuNb)65Ni35 (HEA). After deposition, laser surface melting experiments were performed parallel to the gradient to remelt and rapidly solidify the specimen. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to determine the morphology and composition variations in the as-deposited and laser surface melted phases. Selected area diffraction of the melt pool regions confirmed an almost fully amorphous region in the first gradient and an amorphous matrix/crystalline dendrite composite structure in the second gradient.

  17. Bulk Shear-Wave Transduction Experiments Using Magnetostrictive Transducers with a Thin Fe-Co Alloy Patch

    International Nuclear Information System (INIS)

    Recently, the results of many studies have clarified the successful performance of magnetostrictive transducers in which a ferromagnetic patch is used for the transduction of guided shear waves; this is because a thin ferromagnetic patch with strong magnetostriction is very useful for generating and detecting shear wave. This investigation deals with bulk shear wave transduction by means of magnetostriction; on the other hand, the existing studies have been focused on guided shear waves. A modular transducer was developed: this transducer comprised a coil, magnets, and a thin ferromagnetic patch that was made of Fe-Co alloy. Some experiments were conducted to verify the performance of the developed transducer. Radiation directivity pattern of the developed transducer was obtained, and a test to detect the damage on a side drill hole of a steel block specimen was carried out. From the results of these tests, the good performance of the transducer for nondestructive testing was verified on the basis of the signal-to-noise ratio and narrow beam directivity

  18. Bulk synthesis by spray forming of Al–Cu–Fe and Al–Cu–Fe–Sn alloys containing a quasicrystalline phase

    International Nuclear Information System (INIS)

    Highlights: • 40 kg Bulk material spray formed based on Al–Cu–Fe and Al–Cu–Fe + Sn. • Deposited Al–Cu–Fe alloy showed single phase bulk quasicrystals(QC). • DSC, XRD and microscopic analyses were done to ascertain the QC nature. • Sn does not help in single phase quasicrystal formation in the deposit. • The possible structural evolution mechanisms have been discussed in detail. - Abstract: In this study, Al–Cu–Fe alloys without and with the addition of Sn and containing a quasicrystalline phase were spray deposited. The spray-deposited bulk materials were characterized in terms of microstructure and hardness. The results showed that the Al62.5Cu25Fe12.5 alloy contains the icosahedral quasicrystalline phase (i-phase) along with the minor λ-Al13Fe4 phase, whereas the Al62.5Cu25Fe12.5 + Sn alloy contains five phases: the major i-phase and the crystalline phases of Sn, θ-Al2Cu, λ-Al13Fe4 and β-AlFe(Cu) phases. These results have been corroborated by X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM) and differential scanning calorimetry (DSC). The hardness value of the Al–Cu–Fe alloy reached 10.5 GPa at 50 g load and then decreased steadily with increase in the applied load, while that for Al–Cu–Fe–Sn alloy it was originally somewhat lower, then decreased dramatically with slight increase in the applied load but stayed constant with further load increase. The hardness indentations in Al–Cu–Fe alloy introduced cracking in the material, whereas in the case of Al–Cu–Fe–Sn alloy the Sn-rich areas inhibited the crack growth. The present study provides an insight into the mechanism of phase and microstructural evolutions during spray forming of the studied alloys. Furthermore, the role of Sn in terms of microstructure and properties is highlighted

  19. Relation between calculated Lennard-Jones potential and thermal stability of Cu-based bulk metallic glasses

    International Nuclear Information System (INIS)

    Two metallic bulk glasses, Cu60Zr30Ti10 and Cu47Ti33Zr11Ni8Si1, with a diameter of 3 mm were prepared by copper mold casting method. Dilatometric measurement was carried out on the two glassy alloys to obtain information about the average nearest-neighbour distance r0 and the effective depth of pair potential V0. By assuming a Lennard-Jones potential, r0 and V0 were calculated to be 0.28 nm and 0.16 eV for Cu60Zr30Ti10 and 0.27 nm and 0.13 eV for Cu47Ti33Zr11Ni8Si1, respectively. It was found that the glassy alloy Cu60Zr30Ti10 was more stable than Cu47Ti33Zr11Ni8Si1 against heating from both experiment and calculation

  20. Effects of the Cooling Rate on the Plasticity of Pd40.5Ni40.5P19 Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    LI Yang; QIU Sheng-Bao; SHAO Yang; YAO Ke-Fu

    2011-01-01

    We prepare Pd40.5Ni40.5P19 glassy samples with purified ingots by copper mold casting at a high cooling rate and by water quenching at a low cooling rate.Both of them exhibit different supercooled liquid regions and multiple glass transition characteristics in their differential scanning calorimetric curves.The plasticity of the glassy sample prepared by copper mold casting is about 5% while that prepared by water quenching is almost zero (0.2%),indicating that cooling rate has influenced the plasticity of glassy alloys.By using high resolution TEM image analysis,it is revealed that there exist characteristic regions with different contrasts in the full glassy samples.The characteristic size is about 20-40nm for the glassy sample prepared by water quenching and 2-4nm for the one prepared by copper mold casting.The large difference in the plasticity of the glassy samples prepared by different cooling rates is believed to be related to the difference in the size of the characteristic nanoscale structures.The results indicate that adjusting cooling rate in preparation of glassy samples could modify the thermal and mechanical properties of the glassy alloys.Bulk metallic glass (BMG) is a kind of new structural and functional material developed in recent years.Because of many excellent demonstrated properties such as high strength,corrosion resistance,elastic deformability and magnetic properties,BMGs have become a hot research topic in the materials field.A large number of BMG alloy systems have been developed and some breakthroughs have been achieved in their mechanical and functional properties.[1-5] The first reported bulk metallic glass with a critical size over one centimeter is the Pd40Ni40P20 glassy alloy,which nowadays can be obtained to be as large as 25mm in diameter.[6] Although Pd40Ni40P20 glassy alloy shows a large glass forming ability,it is very brittle with barely global plasticity.Recently,it was found that the bulk glassy alloy system containing

  1. A new TiCuHfSi bulk metallic glass with potential for biomedical applications

    International Nuclear Information System (INIS)

    Highlights: • A TiCuHfSi bulk metallic glass was designed based on binary deep eutectics. • The designed alloy exhibits excellent glass forming ability. • The alloy possesses excellent mechanical properties and corrosion resistance. • The BMG is promising in medical applications. - Abstract: A new Ti41.3Cu43.7Hf13.9Si1.1 bulk metallic glass (BMG), free of Ni, Al and Be elements, was designed using the proper mixing of binary deep eutectics. The alloy exhibited excellent glass forming ability (GFA) and could be cast into single glassy rod up to 3 mm in diameter by copper mould casting method. The appropriate atomic-size mismatch, the large negative heat of mixing among constituent elements, and the possible formation of glassy HfSiO4 facilitated its superior GFA. The BMG also showed good mechanical properties with fracture strength of 1685 MPa and Young’s modulus of 95 GPa as well as better corrosion resistance in both NaCl and Hank’s solutions, compared with pure Ti and Ti–6Al–4V alloy. The above results demonstrated that the developed BMG is promising in biomedical applications

  2. Low temperature diffusion process using rare earth-Cu eutectic alloys for hot-deformed Nd-Fe-B bulk magnets

    Energy Technology Data Exchange (ETDEWEB)

    Akiya, T., E-mail: akiya.takahiro@nims.go.jp; Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Liu, J.; Hono, K. [Elements Strategy Initiative Center for Magnetic Materials, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Hioki, K.; Hattori, A. [Daido Steel Co., LTD, Nagoya 457-8545 (Japan)

    2014-05-07

    The low temperature grain boundary diffusion process using RE{sub 70}Cu{sub 30} (RE = Pr, Nd) eutectic alloy powders was applied to sintered and hot-deformed Nd-Fe-B bulk magnets. Although only marginal coercivity increase was observed in sintered magnets, a substantial enhancement in coercivity was observed when the process was applied to hot-deformed anisotropic bulk magnets. Using Pr{sub 70}Cu{sub 30} eutectic alloy as a diffusion source, the coercivity was enhanced from 1.65 T to 2.56 T. The hot-deformed sample expanded along c-axis direction only after the diffusion process as RE rich intergranular layers parallel to the broad surface of the Nd{sub 2}Fe{sub 14}B are thickened in the c-axis direction.

  3. Low temperature diffusion process using rare earth-Cu eutectic alloys for hot-deformed Nd-Fe-B bulk magnets

    International Nuclear Information System (INIS)

    The low temperature grain boundary diffusion process using RE70Cu30 (RE = Pr, Nd) eutectic alloy powders was applied to sintered and hot-deformed Nd-Fe-B bulk magnets. Although only marginal coercivity increase was observed in sintered magnets, a substantial enhancement in coercivity was observed when the process was applied to hot-deformed anisotropic bulk magnets. Using Pr70Cu30 eutectic alloy as a diffusion source, the coercivity was enhanced from 1.65 T to 2.56 T. The hot-deformed sample expanded along c-axis direction only after the diffusion process as RE rich intergranular layers parallel to the broad surface of the Nd2Fe14B are thickened in the c-axis direction

  4. Study of dynamic properties for NaK binary liquid alloy using first principle and theoretical predictions of isothermal bulk modulus using elastic constants

    International Nuclear Information System (INIS)

    Study of atomic motions in the binary liquid alloys have been studied in terms of dynamical variables like velocity auto correlation, power spectrum and mean square displacement. Elastic constants and isothermal bulk modulus have been calculated to see the effeectiveness of ab-initio pseudopotentials which has been used in this paper. This appraoch is free from the fitting parameters and results obtained using this appraoch have been found very close to the average values

  5. Study of dynamic properties for NaK binary liquid alloy using first principle and theoretical predictions of isothermal bulk modulus using elastic constants

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Anil, E-mail: anil-t2001@yahoo.com; Kashyap, Rajinder [Department of Physics, Govt. P. G. College Solan-173212, Himachal Pradesh (India); Sharma, Nalini; Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University Shimla-171005, Himachal Pradesh (India)

    2014-04-24

    Study of atomic motions in the binary liquid alloys have been studied in terms of dynamical variables like velocity auto correlation, power spectrum and mean square displacement. Elastic constants and isothermal bulk modulus have been calculated to see the effeectiveness of ab-initio pseudopotentials which has been used in this paper. This appraoch is free from the fitting parameters and results obtained using this appraoch have been found very close to the average values.

  6. Stability of metastable phase and soft magnetic properties of bulk Fe-B nano-eutectic alloy prepared by undercooling solidification combined with CU-mold chilling

    Science.gov (United States)

    Yang, Changlin; Zhang, Jun; Huang, Huili; Song, Qijiao; Liu, Feng

    2015-11-01

    Bulk Fe83B17 nano-eutectic alloys were prepared by undercooling solidification combined with Cu-mold chilling method. Stable phase Fe2B and metastable phase Fe3B were found to coexist in the as-solidified microstructure. The soft magnetic properties were improved significantly by the nano-lamellar eutectic and the metastable phase and, were increased further by annealing at 1173 K for 1.5 h after which the metastable phase was decomposed completely.

  7. Noncontact measurement of high-temperature surface tension and viscosity of bulk metallic glass-forming alloys using the drop oscillation technique

    OpenAIRE

    Mukherjee, S.; Johnson, W. L.; Rhim, W. K.

    2005-01-01

    High-temperature surface tension and viscosities for five bulk metallic glass-forming alloys with widely different glass-forming abilities are measured. The measurements are carried out in a high-vacuum electrostatic levitator using the drop oscillation technique. The surface tension follows proportional mathematical addition of pure components' surface tension except when some of the constituent elements have much lower surface tension. In such cases, there is surface segregation of the low ...

  8. Liquid -to-glass transition in bulk glass-forming Cu55-xZr45Agx alloys using molecular dynamic simulations

    Directory of Open Access Journals (Sweden)

    Celtek M.

    2011-05-01

    Full Text Available We report results from molecular dynamics (MD studies concerning the microscopic structure of the ternary, bulk metallic glass-forming Cu55-x Zr45Agx (x=0,10,20 alloys using tight-binding potentials. Understanding of the nature of Glass Forming Ability (GFA of studied alloys, GFA parameters, glass transition temperature (T-g, melting temperature (T-m, reduced glass transition temperature (T-g/T-m, the supercooled liquid region and other parameters were simulated and compared with experiments. The computed pair distribution functions reproduce well experimental x-ray data of Inoue and co-workers. Structure analysis of the Cu-Zr-Ag alloy based on MD simulation will be also presented

  9. Thermomagnetic transitions and coercivity mechanism in bulk composite Nd{sub 60}Fe{sub 30}Al{sub 10} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Zempoalteca, R. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico); Betancourt, I. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico)], E-mail: israelb@correo.unam.mx; Valenzuela, R. [Departamento de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Mexico D.F. 04510 (Mexico)

    2009-10-15

    The thermomagnetic behaviour (within the temperature range 553-300 K) for the bulk composite Nd{sub 60}Fe{sub 30}Al{sub 10} alloy is described in terms of a transition from paramagnetic to superferromagnetic state at T=553 K, followed by a ferromagnetic ordering for T<473 K. For the superferromagnetic regime, the alloy thermomagnetic response was associated to a homogeneous distribution of magnetic clusters with mean magnetic moment and size of 1072 {mu}{sub B} and 2.5 nm, respectively. For T<473 K, a pinning model of domain walls described properly the alloy coercivity dependence with temperature, from which the domain wall width and the magnetic anisotropy constant were estimated as being of {approx}8 nm and {approx}10{sup 5} J/m{sup 3}, typical values of hard magnetic phases. Results are supported by microstructural and magnetic domain observations.

  10. Fe-based bulk metallic glasses prepared by centrifugal casting method

    Directory of Open Access Journals (Sweden)

    R. Babilas

    2011-10-01

    Full Text Available Purpose: The work presents a casting method, structure characterization and analysis of chosen properties of Fe-based bulk metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe72B20Si4Nb4, Fe36Co36B19Si5Nb4, Fe43Co14Ni14B20Si5Nb4 metallic glasses in form of rings. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The crystallization behaviour of the studied alloys was examined by differential thermal analysis (DTA. The soft magnetic property examinations of tested materials contained initial magnetic permeability and measurements of magnetic permeability relaxation.Findings: The XRD and TEM investigations revealed that the studied as-cast bulk glassy samples in forms of ring were amorphous for all tested alloys. The SEM images showed that fractures of studied rings indicated two structurally different zones, which contained “river” patterns and “smooth” areas. The samples of studied alloys presented two stage crystallization process, which was observed for all tested rings with different thickness. The changes of crystallization temperatures versus the thickness of the glassy samples were stated. The magnetic permeability relaxation, which is directly proportional to the microvoids concentration in amorphous structure decreased with increase of sample thickness. These results could be assumed as the change of amorphous structure in function of thickness.Practical implications: The centrifugal casting method is very simple, useful and effective method to produce bulk amorphous materials in the form of rings or tubes.Originality/value: The preparation of bulk metallic glasses in the form of rings for three different Fe-based alloy systems is very important for the future progress in research and practical applications of iron-based bulk amorphous materials.

  11. Investigation of the structure and properties of Fe-Co-B-Si-Nb bulk amorphous alloy obtained by pressure die casting method

    Directory of Open Access Journals (Sweden)

    W. Pilarczyk

    2012-12-01

    Full Text Available Purpose: The main aim of this paper is investigation of the microstructure and thermal properties of selected Fe-Co-B-Si-Nb bulk amorphous alloy.Design/methodology/approach: The studies were performed on Fe-Co-B-Si-Nb alloy in form of rods with diameter of ø=1.5 and ø=2 mm. Master alloy ingot with compositions of Fe37.44Co34.56B19.2Si4.8Nb4 was prepared by induction melting of pure Fe, Co, B, Si and Nb elements in argon atmosphere. The structure analysis of the studied materials in as-cast state was carried out using X-ray diffraction (XRD. The thermal properties: glass transition temperature (Tg, onset crystallization temperature (Tx and peak crystallization temperature (Tp of the as-cast alloys were examined by differential scanning calorimetry (DSC method. The microscopic observation of the fracture morphology of studied amorphous materials in rods form with different diameter was carried out by means of scanning electron microscope (SEM, within different magnification.Findings: The Fe-based bulk metallic glasses in form of rod were successfully produced by die pressure casting method. The investigation revealed that the studied rods are amorphous. These materials exhibit good glassforming ability. These tested rods with diameter of 1.5 and 2 mm exhibit similar characteristic temperatures (Tg, Tx, Tp. The exothermic peaks describing crystallization process of studied bulk metallic glasses are observed Morphology of cross section rods is changing having contact with copper mould during casting from smooth fracture inside rod to fine narrow dense veins pattern near to rod surface. These rods have smooth surface and metallic luster. The presented fractures are characteristic for metallic glasses.Practical implications: The success of production of studied Fe-based bulk metallic glasses is important for future practical application of those materials as elements of magnetic circuits, sensors and precise current transformers

  12. Thermal properties of Fe-based bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2012-12-01

    Full Text Available Purpose: The aim of paper is presentation of results bulk metallic glasses thermal properties such as temperatures typical for glassy transition and thermal conductivity. Design/methodology/approach: Investigations were realized for Fe36Co36B19.2Si4.8Nb4 samples with dimension 3 mm in diameter. Bulk test pieces were fabricated by copper mold casting method. Thermal analysis of master alloy (DTA and samples in as-cast state (DSC was realized. For amorphous structure confirmation the X-ray diffraction phase analysis (XRD was realized. Additionally scanning electron microscopy (SEM micrographs were performed in order to structure analysis. Thermal conductivity was determined by prototype measuring station.Findings: The XRD and SEM analysis confirmed amorphous structure of samples. Broad diffraction “halo” was observed for every testing piece. Fracture morphology is smooth with many “veins” on the surface, which are characteristic for glassy state. DTA analysis confirmed eutectic chemical composition of master alloy. Thermal conductivity measurements proved that both samples have comparable thermal conductivity.Practical implications: The FeCo-based bulk metallic glasses have attracted great interest for a variety application fields for example precision machinery materials, electric applications, structural materials, sporting goods, medical devices. Thermal conductivity is useful and important property for example computer simulation of temperature distribution and glass forming ability calculation.Originality/value: The obtained results confirm the utility of applied investigation methods in the thermal and structure analysis of examined amorphous alloys. Thermal conductivity was determined using the prototype measuring station, which is original issue of the paper. In future, the measuring station will be expanded for samples with different dimensions.

  13. First-principles-aided design of a new Ni-base superalloy: Influence of transition metal alloying elements on grain boundary and bulk cohesion

    International Nuclear Information System (INIS)

    A new approach to the design of Ni-base polycrystalline superalloys is proposed. In this approach, we assume that the creep–rupture characteristics of a superalloy are mostly determined by the strength of interatomic bonding at grain boundaries (GBs) and in the bulk of γ matrix. The ideal work of separation, Wsep, of a GB is used as a fundamental thermodynamic quantity that controls the mechanical strength of an interface, whereas the partial cohesive energy, χ, of an alloy component serves to characterize its contribution into the strength of the bulk. Using the Σ5 (2 1 0)[1 0 0] symmetric tilt GB as a representative high-angle GB in Ni, we calculate Wsep,χ, and GB segregation energies, Eseg, for the complete set of 4d and 5d transition metal impurities, to which we add B (a typical microalloying addition), S and Bi (notoriously known as harmful impurities in Ni-base superalloys). The purpose of the analysis is to identify the elements that demonstrate a high tendency to segregate to GBs, have positive (preferably high) partial cohesive energies in the bulk, and have positive impact on Wsep of GBs. We refer to these elements as low-alloying additions. Our study reveals Zr, Hf, Nb, Ta and B as the most promising low-alloying additions. Our next step is to introduce the elements found in the first step into a new powder metallurgy (P/M) Ni-base superalloy. The results of the subsequent testing confirm that the newly created P/M superalloy indeed demonstrates superior mechanical properties at high temperatures compared to the existing Russian P/M alloy EP741NP

  14. Evolution of thermoelectric performance for (Bi,Sb)2Te3 alloys from cutting waste powders to bulks with high figure of merit

    Science.gov (United States)

    Fan, Xi‧an; Cai, Xin zhi; Han, Xue wu; Zhang, Cheng cheng; Rong, Zhen zhou; Yang, Fan; Li, Guang qiang

    2016-01-01

    Bi2Te3 based cutting waste powders from cutting wafers were firstly selected as raw materials to prepare p-type Bi2Te3 based thermoelectric (TE) materials. Through washing, reducing, composition correction, smelting and resistance pressing sintering (RPS) process, p-type (Bi,Sb)2Te3 alloy bulks with different nominal stoichiometries were successfully obtained. The evolution of microstructure and TE performance for (Bi,Sb)2Te3 alloys were investigated in detail. All evidences confirmed that most of contaminants from line cutting process such as cutting fluid and oxides of Bi, Sb or Te could be removed by washing, reducing and smelting process used in this work. The carrier content and corresponding TE properties could be adjusted effectively by appropriate composition correction treatment. At lastly, a bulk with a nominal stoichiometry of Bi0.44Sb1.56Te3 was obtained and its' dimensionless figure of merit (ZT) was about 1.16 at 90 °C. The ZT values of Bi0.36Sb1.64Te3 and Bi0.4Sb1.6Te3 alloy bulks could also reach 0.98 and 1.08, respectively. Different from the conventional recycling technology such as hydrometallurgy extraction methods, the separation and extraction of beneficial elements such as Bi, Sb and Te did not need to be performed and the Bi2Te3 based bulks with high TE properties could be directly obtained from the cutting waste powders. In addition, the recycling technology introduced here was green and more suitable for practical industrial application. It can improve material utilization and lower raw material costs of manufacturers.

  15. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts

    Directory of Open Access Journals (Sweden)

    Rodiansono Rodiansono

    2015-07-01

    Full Text Available A bulk structure of inexpensive intermetallic nickel-tin (Ni-Sn alloys catalysts demonstrated highly selective in the hydrogenation of levulinic acid in water into g-valerolactone. The intermetallic Ni-Sn catalysts were synthesized via a very simple thermochemical method from non-organometallic precursor at low temperature followed by hydrogen treatment at 673 K for 90 min. The molar ratio of nickel salt and tin salt was varied to obtain the corresponding Ni/Sn ratio of 4.0, 3.0, 2.0, 1.5, and 0.75. The formation of Ni-Sn alloy species was mainly depended on the composition and temperature of H2 treatment. Intermetallics Ni-Sn that contain Ni3Sn, Ni3Sn2, and Ni3Sn4 alloy phases are known to be effective heterogeneous catalysts for levulinic acid hydrogenation giving very excellence g-valerolactone yield of >99% at 433 K, initial H2 pressure of 4.0 MPa within 6 h. The effective hydrogenation was obtained in H2O without the formation of by-product. Intermetallic Ni-Sn(1.5 that contains Ni3Sn2 alloy species demonstrated very stable and reusable catalyst without any significant loss of its selectivity. © 2015 BCREC UNDIP. All rights reserved. Received: 26th February 2015; Revised: 16th April 2015; Accepted: 22nd April 2015  How to Cite: Rodiansono, R., Astuti, M.D., Ghofur, A., Sembiring, K.C. (2015. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (2: 192-200. (doi:10.9767/bcrec.10.2.8284.192-200Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.2.8284.192-200  

  16. Cast bulk Zr57Ti5Al10Cu20Ni8 amorphous alloy with tendency of phase separation

    International Nuclear Information System (INIS)

    Zr-Ti-Al-Cu-Ni alloys show excellent glass forming ability (GFA). Amorphous cylindrical samples of diameter from 8 to 20 mm were produced by casting the Zr57Cu20Al10Ni8Ti5 alloy melt into a copper mould. The Zr57Cu20Al10Ni8Ti5 amorphous alloy shows some particular crystallization characteristics: measurements by differential scanning calorimetry (DSC) reveal three exothermic peaks in the DSC traces at continuous heating. The third peak of the highest peak temperature shifts towards lower temperature with the decrease of the cooling rates at which the amorphous alloys were formed, while the first two peaks remain unchanged. Isothermal annealing near the glass transition temperature causes the third peak shifting towards a definitive temperature and then it becomes quite stable during further annealing. The shift of the third peak is attributed to the tendency of phase separation of the alloy. (orig.)

  17. In-plane/out-of-plane disorder influence on the magnetic anisotropy of Fe1-yMnyPt-L10 bulk alloy

    Science.gov (United States)

    Cuadrado, R.; Liu, Kai; Klemmer, Timothy J.; Chantrell, R. W.

    2016-03-01

    The random substitution of a non-magnetic species instead of Fe atoms in FePt-L10 bulk alloy will permit to tune the magnetic anisotropy energy of this material. We have performed by means of first principles calculations a study of Fe1-yMnyPt-L10 (y = 0.0, 0.08, 0.12, 0.17, 0.22, and 0.25) bulk alloy for a fixed Pt concentration when the Mn species have ferro-/antiferromagnetic (FM,AFM) alignment at the same(different) atomic plane(s). This substitution will promote several in-plane lattice values for a fixed amount of Mn. Charge hybridization will change compared to the FePt-L10 bulk due to this lattice variation leading to a site resolved magnetic moment modification. We demonstrate that this translates into a total magnetic anisotropy reduction for the AFM phase and an enhancement for the FM alignment. Several geometric configurations were taken into account for a fixed Mn concentration because of different possible Mn positions in the simulation cell.

  18. Effect of Si addition on glass-forming ability and mechanical properties of Cu-Zr-Al bulk metallic glass

    International Nuclear Information System (INIS)

    Research highlights: The Cu50Zr43Al7 alloy has a surprising GFA, and the glassy rods with diameter of 10 mm have been produced in this research. It has not been reported that the Cu-based glassy rods (Cu ≥ 50 at.%) to be produced with the critical diameter greater than 10 mm. The novelty of this research is that the glass formation has been improved and the critical diameter increased to 12 mm for the alloy having x = 1 with the addition of Si. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. - Abstract: The effect of Si addition on the glass-forming ability (GFA) and mechanical properties of (Cu50Zr43Al7)100-xSix (x = 0, 0.5, 1, 1.5 and 2 at.%) alloys were investigated. The GFA of Cu50Zr43Al7 alloy is improved by addition of a small amount of Si, and the critical diameter for glass formation increases from 10 mm for the alloy with x = 0-12 mm for the alloy with x = 1 when prepared using copper mold casting. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. In the uniaxial compression, the bulk glassy alloys exhibit a limited plastic strain of less than 1%, but the compressive fracture strength and Young's modulus were obtained in high values of 1969-2129 MPa and 101-144 GPa, respectively. Fracture surface and shear bands of samples were studied by using scanning electron microscopy (SEM).

  19. Effect of Minor Alloying on Crystallization Behavior and Thermal Properties of Zr64.5Ni15.5Al11.5Cu8.5 Bulk Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    Muhammad Iqbal; Javed Iqbal Akhter; Haifeng Zhang; Zhuangqi Hu

    2011-01-01

    Minor alloying plays an important role in the synthesis and improvement of thermal stability of bulk metallic glasses (BMGs). The present study was conducted to investigate the effect of minor additions of Y, Ti and Nb on the crystallization behavior and the thermal properties of Zr64.5Ni15.5Al11.5Cu8.5 alloy. Thermal parameters and the activation energies for crystallization were calculated for four (Zr0.645Ni0.155Al0.115-Cu0.085)100-xMx (M=Y, Ti and Nb, while x=0, 2 at.%) alloys. The present alloys have wide supercooled liquid region of ≥87K. Maximum activation energy was found to be greater than 300 k J/mol for the base alloy. Four crystalline phases were identified in the samples annealed at 823 K for 20 min. Reduced glass transition temperature (Trg) and other thermal parameters such as γ, δ and /β were improved by Y and Ti addition. Nb addition resists crystallization below annealing temperature 713 K, however, its effect on thermal properties is not very promising.

  20. Study of oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 by thermogravimetric analyser

    Indian Academy of Sciences (India)

    A Dhawan; K Raetzke; F Faupel; S K Sharma

    2001-06-01

    The oxidation behaviour of Zr-based bulk amorphous alloy Zr65Cu17.5Ni10Al7.5 has been studied in air environment at various temperatures in the temperature range 591–684 K using a thermogravimetric analyser (TGA). The oxidation kinetics of the alloy in the amorphous phase obeys the parabolic rate law for oxidation in the temperature range 591–664 K. The values of the activation energy and pre-factor as calculated from the Arrhenius temperature dependence of the rate constants have been found to be 1.80 eV and 2.12 × 109 g cm–2.sec–1/2, respectively.

  1. Magnetic anisotropy of Fe1−yXyPt-L10 [X = Cr, Mn, Co, Ni, Cu] bulk alloys

    International Nuclear Information System (INIS)

    We demonstrate by means of fully relativistic first principles calculations that, by substitution of Fe by Cr, Mn, Co, Ni, or Cu in FePt-L10 bulk alloys, with fixed Pt content, it is possible to tune the magnetocrystalline anisotropy energy by adjusting the content of the non-magnetic species in the material. The changes in the geometry due to the inclusion of each element induces different values of the tetragonality and hence changes in the magnetic anisotropy and in the net magnetic moment. The site resolved magnetic moments of Fe increase with the X content while those of Pt and X are simultaneously reduced. The calculations are in good quantitative agreement with experimental data and demonstrate that models with fixed band structure but varying numbers of electrons per unit cell are insufficient to describe the experimental data for doped FePt-L10 alloys.

  2. Effects of femtosecond laser ablation on the surface morphology and microstructure of a bulk TiCuPdZr glass alloy

    Institute of Scientific and Technical Information of China (English)

    WANG Hongshui; LIANG Chunyong; CHEN Xueguang; WANG Lei; YANG Yang; YANG Jianjun; ZHU Shengli; LI Changyi

    2009-01-01

    The effects of femtosecond laser ablation on the surface characteristics and microstructure of a bulk TiCuPdZr glass alloy were investigated. The heat influence zone of femtosecond laser ablated with a laser energy of 100 μJ exhibits a ripple-like feather, while a porous structure appears on the surface of the specimen ablated by a 200 μJ femtosecond laser. The contents of Ti, Zr, and Pd on the ablated surface decrease and that of Cu increases with increasing laser energy. The crystallization process occurs on the glass alloy specimens during femtosecond laser ablation, and the crystallinity of a 100 μJ femtosecond laser-ablated specimen is greater than that of a 200 μJ femtosecond laser-ablated one.

  3. Nano-scratch behavior of a bulk Zr-10Al-5Ti-17.9Cu-14.6Ni amorphous alloy

    International Nuclear Information System (INIS)

    The tribological behavior of a Zr-10Al-5Ti-17.9Cu-14.6Ni (at.%) bulk amorphous alloy, in both the as-cast and annealed states, was investigated using nano-scratch tests, including ramping load scratch and multiple sliding wear techniques. The crystallization sequence of the alloy was also characterized. Mechanical properties, such as Young's modulus, hardness, friction coefficient, and tribological wear were measured. These properties were found to vary with microstructure. In general, an increase in annealing temperature results in an increase in hardness, which in turn produces a decrease in friction coefficient but an increase in wear resistance. Samples having a structure consisting of supercooled liquid matrix with dispersed nanocrystalline particles exhibit the best wear performance. (c) 2000 Materials Research Society

  4. Semisolid Microstructural Evolution during Partial Remelting of a Bulk Alloy Prepared by Cold Pressing of the Ti-Al-2024Al Powder Mixture

    Directory of Open Access Journals (Sweden)

    Yahong Qin

    2016-03-01

    Full Text Available A new method, powder thixoforming, has been proposed to fabricate an in situ Al3Tip/2024Al composite. During partial remelting, the microstructural evolution of the bulk alloy prepared by cold pressing of the Ti, Al, 2024Al powder mixture was investigated, and the formation mechanism of the Al3Ti particles produced by the reaction between the Ti powder and the Al alloy melt is also discussed in detail. The results indicate that the microstructural evolution of the 2024 alloy matrix can be divided into three stages: a rapid coarsening of the powder grains; a formation of primary α-Al particles surrounded with a continuous liquid film; and a slight coarsening of the primary α-Al particles. Simultaneously, a reaction layer of Al3Ti can be formed on the Ti powder surface when the bulk is heated for 10 min at 640 °C The thickness (X of the reaction layer increases with the time according to the parabolic law of \\(X = -0.43t^{2} + 4.21t + 0.17\\. The stress generated in the reaction layer due to the volume dilatation can be calculated by using the equationσ \\(\\sigma_{Al_{3}Ti} = -\\frac{ E_{Al_{3}Ti} }{6(1-v{Al_{3}Ti}} \\frac{ t^{3}_{Al_{3}Ti} }{t_{Ti}} \\left(\\frac{1}{R} - \\frac{1}{R_{0}} \\right \\. Comparing the obtained data with the results of the drip experiment, the reaction rate for the Ti powder and Al powder mixture is greater than that for the Ti plate and Al alloy mixture, respectively.

  5. Catalytic Hydrogenation of Levulinic Acid in Water into g-Valerolactone over Bulk Structure of Inexpensive Intermetallic Ni-Sn Alloy Catalysts

    OpenAIRE

    Rodiansono Rodiansono; Maria Dewi Astuti; Abdul Ghofur; Kiky C. Sembiring

    2015-01-01

    A bulk structure of inexpensive intermetallic nickel-tin (Ni-Sn) alloys catalysts demonstrated highly selective in the hydrogenation of levulinic acid in water into g-valerolactone. The intermetallic Ni-Sn catalysts were synthesized via a very simple thermochemical method from non-organometallic precursor at low temperature followed by hydrogen treatment at 673 K for 90 min. The molar ratio of nickel salt and tin salt was varied to obtain the corresponding Ni/Sn ratio of 4.0, 3.0, 2.0, 1.5, a...

  6. Effects of gravity field onglass forming ability in ZrTiCuNiBe alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The solidification and glass forming ability of Zr41Ti14Cu12.5Ni10Be22.5 bulk glassy forming alloy is investigated by Bridgman unidirectional solidification at different growth velocities under different gravity field orientations. Large differences in glass formation, undercooling and crystallization morphology on different solidification conditions have been found and discussed from the point of view of gravity induced convection. The results are useful for understanding the nucleation and growth in the melt and glass formation mechanism in the alloy.

  7. A new Ti-Zr-Hf-Cu-Ni-Si-Sn bulk amorphous alloy with high glass-forming ability

    International Nuclear Information System (INIS)

    The effect of Sn substitution for Cu on the glass-forming ability was investigated in Ti41.5Zr2.5Hf5Cu42.5-xNi7.5Si1Sn x (x = 0, 1, 3, 5, 7) alloys by using differential scanning calorimetry (DSC) and X-ray diffractometry. The alloy containing 5% Sn shows the highest glass-forming ability (GFA) among the Ti-Zr-Hf-Cu-Ni-Si-Sn system. Fully amorphous rod sample with diameters up to 6 mm could be successfully fabricated by the copper mold casting Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy. The activation energies for glass transition and crystallization for Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 amorphous alloy are both larger than those values for the Sn-free alloy. The enhancement in GFA and thermal stability after the partial replacement of Cu by Sn may be contributed to the strong atomic bonding nature between Ti and Sn and the increasing of atomic packing density. The amorphous Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 alloy also possesses superior mechanical properties

  8. Structural Order in Glassy Water

    OpenAIRE

    Giovambattista, Nicolas; Debenedetti, Pablo G.; Sciortino, Francesco; Stanley, H. Eugene

    2005-01-01

    We investigate structural order in glassy water by performing classical molecular dynamics simulations using the extended simple point charge (SPC/E) model of water. We perform isochoric cooling simulations across the glass transition temperature at different cooling rates and densities. We quantify structural order by orientational and translational order metrics. Upon cooling the liquid into the glassy state, both the orientational order parameter $Q$ and translational order parameter $\\tau...

  9. Tunable magnetism and half-metallicity in bulk and (1 0 0) surface of quaternary Co2MnGe1-xGax Heusler alloy

    International Nuclear Information System (INIS)

    The structural, magnetic and half-metallic properties of the bulk and (1 0 0) surface of quaternary Heusler alloy Co2MnGe1-xGax are investigated from the first-principles calculations. For the bulk, the lattice constant and total magnetic moment follow the Vegard law and Slater-Pauling rule well, respectively. Except for Co2MnGa, the Co2MnGe1-xGax series are half-metallic. Because the Fermi level of Co2MnGe0.5Ga0.5 is just located at the middle of the minority-spin gap, we predict that it bears the most robust half-metallicity as against remnant doped alloys. As for the Co2MnGe1-xGax(1 0 0) surface, the analyses on relaxed atomic positions and surface energies reveal that Co-Ge and Co-Ga bonding are more favourable than Co-Mn bonding and the terminations involving surface Mn atoms are more stable than CoCo terminations. By comparing with the bulk values, the surface Co and Mn magnetic moments are enhanced obviously. The calculated PDOS of all accessible 'ideal' surfaces show that the half-metallicity observed in bulk has been destroyed by the surface states, which is a possible reason why the tunnel magnetoresistence steeply drops as temperature increases. However, in the pure atomic terminations the surface properties can be slightly adjusted by the Ga-doped concentrations in bulk through the dipolar interaction. As a result, in the MnMn termination of Co2MnGe0.5Ga0.5(1 0 0) the spin polarization of 1 0 0% is detected, indicating that in the pure Mn atomic termination the half-metallicity of the (1 0 0) surface can remain if the corresponding bulk presents excellent half-metallic stability. Thus we predict that this thin film will present a higher potential for applications in ferromagnetic electrodes.

  10. Bulk undercooling

    Science.gov (United States)

    Kattamis, T. Z.

    1984-01-01

    Bulk undercooling methods and procedures will first be reviewed. Measurement of various parameters which are necessary to understand the solidification mechanism during and after recalescence will be discussed. During recalescence of levitated, glass-encased large droplets (5 to 8 mm diam) high speed temperature sensing devices coupled with a rapid response oscilloscope are now being used at MIT to measure local thermal behavior in hypoeutectic and eutectic binary Ni-Sn alloys. Dendrite tip velocities were measured by various investigators using thermal sensors or high speed cinematography. The confirmation of the validity of solidification models of bulk-undercooled melts is made difficult by the fineness of the final microstructure, the ultra-rapid evolution of the solidifying system which makes measurements very awkward, and the continuous modification of the microstructure which formed during recalescence because of precipitation, remelting and rapid coarsening.

  11. Surface passivation and interface properties of bulk GaAs and epitaxial-GaAs/Ge using atomic layer deposited TiAlO alloy dielectric.

    Science.gov (United States)

    Dalapati, G K; Chia, C K; Tan, C C; Tan, H R; Chiam, S Y; Dong, J R; Das, A; Chattopadhyay, S; Mahata, C; Maiti, C K; Chi, D Z

    2013-02-01

    High quality surface passivation on bulk-GaAs substrates and epitaxial-GaAs/Ge (epi-GaAs) layers were achieved by using atomic layer deposited (ALD) titanium aluminum oxide (TiAlO) alloy dielectric. The TiAlO alloy dielectric suppresses the formation of defective native oxide on GaAs layers. X-ray photoelectron spectroscopy (XPS) analysis shows interfacial arsenic oxide (As(x)O(y)) and elemental arsenic (As) were completely removed from the GaAs surface. Energy dispersive X-ray diffraction (EDX) analysis and secondary ion mass spectroscopy (SIMS) analysis showed that TiAlO dielectric is an effective barrier layer for reducing the out-diffusion of elemental atoms, enhancing the electrical properties of bulk-GaAs based metal-oxide-semiconductor (MOS) devices. Moreover, ALD TiAlO alloy dielectric on epi-GaAs with AlGaAs buffer layer realized smooth interface between epi-GaAs layers and TiAlO dielectric, yielding a high quality surface passivation on epi-GaAs layers, much sought-after for high-speed transistor applications on a silicon platform. Presence of a thin AlGaAs buffer layer between epi-GaAs and Ge substrates improved interface quality and gate dielectric quality through the reduction of interfacial layer formation (Ga(x)O(y)) and suppression of elemental out-diffusion (Ga and As). The AlGaAs buffer layer and TiAlO dielectric play a key role to suppress the roughening, interfacial layer formation, and impurity diffusion into the dielectric, which in turn largely enhances the electrical property of the epi-GaAs MOS devices. PMID:23331503

  12. Approaching theoretical strength in glassy carbon nanolattices

    Science.gov (United States)

    Bauer, J.; Schroer, A.; Schwaiger, R.; Kraft, O.

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm-3 are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.

  13. New Ti-based Ti–Cu–Zr–Fe–Sn–Si–Ag bulk metallic glass for biomedical applications

    International Nuclear Information System (INIS)

    Highlights: • Novel Ti47Cu38Zr7.5Fe2.5Sn2Si1Ag2 (at.%) bulk metallic glass (BMG) with a critical diameter of 7 mm was discovered. • The present BMG is the largest Ni- and Be-free Ti-based BMG containing low content of noble metal reported to date. • The glassy alloy possesses high specific strength, low Young’s modulus, and good corrosion resistance and bio-compatibility. • Combination of high glass-forming ability and good mechano- and bio-compatibility for the Ti-based BMG demonstrates the potential for use in biomedical applications. - Abstract: A novel Ni-free Ti47Cu38Zr7.5Fe2.5Sn2Si1Ag2 (at.%) bulk metallic glass (BMG) with superior glass-forming ability, good mechanical properties and excellent biocompatibility was discovered. The Ti-based BMG with a diameter of 7 mm can be prepared by copper mold casting and the supercooled liquid region was 52 K. Compressive strength, specific strength, Young’s modulus and microhardness of the Ti-based BMG were about 2.08 GPa, 3.2 × 105 N m/kg, 100 GPa and 588 Hv, respectively. Electrochemical measurements indicated that the Ti-based glassy alloy possesses higher corrosion resistance than Ti–6Al–4V alloy in a simulated body fluid environment. Attachment, spreading out and proliferation of MC3T3-E1 cells on the Ti-based BMG surface demonstrated the excellent biocompatibility. Mechanisms of the formation and properties for the Ti-based glassy alloy are also discussed. The combination of high glass-forming ability, excellent mechanical properties, high corrosion resistance and good biocompatibility demonstrates the potential of the Ni-free Ti-based BMG for use in biomedical applications

  14. Intergranular glassy films: An overview

    Energy Technology Data Exchange (ETDEWEB)

    Subramaniam, Anandh [Indian Institute of Technology, New Delhi 110016 (India)]. E-mail: anandh333@rediffmail.com; Koch, Christoph T. [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, 70569 Stuttgart (Germany); Cannon, Rowland M. [Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 (United States); Ruehle, Manfred [Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, 70569 Stuttgart (Germany)

    2006-04-25

    In certain ceramics like Si{sub 3}N{sub 4}, SiC, SrTiO{sub 3}, Al{sub 2}O{sub 3}, etc., the grain boundary (GB) region can have an amorphous film of about 1-2 nm thickness. These intergranular glassy films (IGFs) are characterized by a nearly constant thickness which is basically independent of the orientation of the bounding grains, but is dependent on the composition of the ceramic. The IGF is resistant to crystallization and is thought to represent an equilibrium configuration. The presence of the IGF, along with its structure, plays an important role in determining the properties of the ceramic as a whole. Important amongst these properties, keeping in mind the system based specificities, are fracture, creep, oxidation and electrical behaviour. Depending on the system, various synthetic routes like liquid phase sintering, solid-state activated sintering, crystallization of glass surrounding the crystal, etc., have led to the formation of IGFs. Equilibrium thickness amorphous films on surfaces have also been synthesized which are considered to be the surface analogue of IGFs. Important advances in the microscopy techniques have provided invaluable insights into the structure of IGFs, along with its interface with the bounding crystals. These techniques include: high-resolution microscopy, Fresnel contrast imaging, diffuse dark field imaging, diffraction analysis, electron holography, high-angle annular dark field imaging, energy-dispersive X-ray analysis and electron energy loss spectroscopy. It is now being progressively realized that the composition and structure within the IGF is graded, i.e., it has a diffuse interface with the bounding crystals and that the amorphous material in the IGF is different from the bulk glass forming in that system. The order induced by the bounding crystals on the IGF is seen as a contributing factor to the gradation. In spite of the achievements, a lot of open questions remain regarding the formation of IGFs, its behaviour with

  15. Intergranular glassy films: An overview

    International Nuclear Information System (INIS)

    In certain ceramics like Si3N4, SiC, SrTiO3, Al2O3, etc., the grain boundary (GB) region can have an amorphous film of about 1-2 nm thickness. These intergranular glassy films (IGFs) are characterized by a nearly constant thickness which is basically independent of the orientation of the bounding grains, but is dependent on the composition of the ceramic. The IGF is resistant to crystallization and is thought to represent an equilibrium configuration. The presence of the IGF, along with its structure, plays an important role in determining the properties of the ceramic as a whole. Important amongst these properties, keeping in mind the system based specificities, are fracture, creep, oxidation and electrical behaviour. Depending on the system, various synthetic routes like liquid phase sintering, solid-state activated sintering, crystallization of glass surrounding the crystal, etc., have led to the formation of IGFs. Equilibrium thickness amorphous films on surfaces have also been synthesized which are considered to be the surface analogue of IGFs. Important advances in the microscopy techniques have provided invaluable insights into the structure of IGFs, along with its interface with the bounding crystals. These techniques include: high-resolution microscopy, Fresnel contrast imaging, diffuse dark field imaging, diffraction analysis, electron holography, high-angle annular dark field imaging, energy-dispersive X-ray analysis and electron energy loss spectroscopy. It is now being progressively realized that the composition and structure within the IGF is graded, i.e., it has a diffuse interface with the bounding crystals and that the amorphous material in the IGF is different from the bulk glass forming in that system. The order induced by the bounding crystals on the IGF is seen as a contributing factor to the gradation. In spite of the achievements, a lot of open questions remain regarding the formation of IGFs, its behaviour with temperature, its dependence on

  16. Microstructure, tensile properties and fatigue behaviour of bulk nanoquasicrystalline Al alloy Al93Fe3Cr2Ti2

    Czech Academy of Sciences Publication Activity Database

    Chlupová, Alice; Chlup, Zdeněk; Kruml, Tomáš; Kuběna, Ivo; Roupcová, Pavla

    Ostrava : Tanger Ltd, 2011, Paper no. 1338. ISBN 978-80-87294-23-9. [NANOCON 2011. International Conference /3./. Brno (CZ), 21.09.2011-23.09.2011] R&D Projects: GA ČR(CZ) GAP204/11/1453 Institutional research plan: CEZ:AV0Z20410507 Keywords : Al alloy * nanostructured materials * quasicrystals * fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics

  17. Electrum, the Gold-Silver Alloy, from the Bulk Scale to the Nanoscale: Synthesis, Properties, and Segregation Rules.

    Science.gov (United States)

    Guisbiers, Grégory; Mendoza-Cruz, Rubén; Bazán-Díaz, Lourdes; Velázquez-Salazar, J Jesús; Mendoza-Perez, Rafael; Robledo-Torres, José Antonio; Rodriguez-Lopez, José-Luis; Montejano-Carrizales, Juan Martín; Whetten, Robert L; José-Yacamán, Miguel

    2016-01-26

    The alloy Au-Ag system is an important noble bimetallic phase, both historically (as "Electrum") and now especially in nanotechnology, as it is applied in catalysis and nanomedicine. To comprehend the structural characteristics and the thermodynamic stability of this alloy, a knowledge of its phase diagram is required that considers explicitly its size and shape (morphology) dependence. However, as the experimental determination remains quite challenging at the nanoscale, theoretical guidance can provide significant advantages. Using a regular solution model within a nanothermodynamic approach to evaluate the size effect on all the parameters (melting temperature, melting enthalpy, and interaction parameters in both phases), the nanophase diagram is predicted. Besides an overall shift downward, there is a "tilting" effect on the solidus-liquidus curves for some particular shapes exposing the (100) and (110) facets (cube, rhombic dodecahedron, and cuboctahedron). The segregation calculation reveals the preferential presence of silver at the surface for all the polyhedral shapes considered, in excellent agreement with the latest transmission electron microscopy observations and energy dispersive spectroscopy analysis. By reviewing the nature of the surface segregated element of different bimetallic nanoalloys, two surface segregation rules, based on the melting temperatures and surface energies, are deduced. Finally, the optical properties of Au-Ag nanoparticles, calculated within the discrete dipole approximation, show the control that can be achieved in the tuning of the local surface plasmon resonance, depending of the alloy content, the chemical ordering, the morphology, the size of the nanoparticle, and the nature of the surrounding environment. PMID:26605557

  18. A coupling of rapid crystallization and plastic consolidation as a method for mass scale production of bulk submicrocrystalline aluminum alloys

    Energy Technology Data Exchange (ETDEWEB)

    Dybiec, Henryk [Department of Structure and Mechanics of Solids US and T AGH, al. Mickiewicza 30, 30 059 Krakow (Poland)

    2010-05-15

    Rapid crystallization is a well-known method for production of ultrafine-grained metallic materials using the overcooling effect. Unfortunately, this method provides material in dispersed form with very limited dimensions of individual particles, which must be consolidated to bulk form for engineering use. To prevent destabilization of ultrafine-grain structure of polycrystalline particles the consolidation process should to be quick enough and must be conducted at reasonably low temperatures. Such reasons suggest the process of plastic consolidation. In this process plastic deformation of individual particles develops new surfaces in status nascendi, which is able to create strong bonds between collectively deformed particles of dispersed materials and converts the powder to the bulk form. The plastic consolidation by isothermal extrusion is the agglomeration process of plastically deformable particles without involving diffusion effects. Bulk materials with no measurable porosity are the product of this process, in which the character of interaction among individual particles of powder shows similar character to interaction at grain boundaries in polycrystalline metals. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  19. Microstructure and hard magnetic properties in bulk rods of Nd60Fe30Al10 glass forming alloys

    International Nuclear Information System (INIS)

    The Nd60Fe30Al10 alloy exhibits a large glass forming ability which allows to obtain relatively thick cast rods containing large volume fractions of amorphous phases. In this work the microstructure and the hard magnetic properties of as-cast rods are characterized. The alloy is processed by suction casting into a chilled copper mould to obtain cylinders 5 mm diameter and 50 mm length. This diameter is selected because it is an upper limit for this processing route, beyond which the hard properties largely deteriorate. A room temperature coercivity of 0.34 T is obtained. The sample microstructure is heterogeneous, with very different size scales near the surface and along the central zone. However, in both regions a large fraction of an amorphous ferromagnetic phase is observed; it is found that paramagnetic nanocrystalline phases - mainly Nd or Nd-rich particles, embedded in the amorphous matrix - are somewhat coarser in the central zone. These larger nanocrystals, less efficient to pin domain walls, are proposed to be responsible for the lower coercive fields observed, as compared with those found in cylinders 1-3 mm diameter where no inhomogeneities are found. This conclusion is supported by microstructure, calorimetric and magnetic observations.

  20. Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

    Institute of Scientific and Technical Information of China (English)

    Jianfei SUN; Jun SHEN; Zhenye ZHU; Gang WANG; Dawei XING; Yulai GAO; Bide ZHOU

    2004-01-01

    The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr52.5Ti5Al10- Ni14.6Cu17.9)(100-x)/100Snx ·(x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equation proposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease first as the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Sn larger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by a decrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr52.5Ti5Al10Ni14.6Cu17.9 and (Zr5 2.5Ti5 Al10 Ni14.6 Cu 17.9)0.97Sn3 was evaluated by Kissinger equation. It is noted that the Sn addition increases the activation energies for glass transition and crystallization, implying that the higher thermal stability can be obtained by appropriate addition of Sn.

  1. Thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses

    International Nuclear Information System (INIS)

    The effects of adding small amount of aluminum to the binary Cu50Zr50 bulk metallic glass (BMG) on the thermal and mechanical properties were investigated. The Al addition was limited to 3 ≤ x ≤ 10 at.% in order to form fully amorphous bulk samples. Glassy rods of 3 mm diameter of these alloys were prepared by copper mold suction casting. The (Cu50Zr50)100-xAl x BMGs (x = 0 and 3 ≤ x ≤ 10 at.%) were characterized with differential scanning calorimetry (DSC), X-ray diffraction (XRD), Vickers microhardness test and nanoindentation, respectively. The glass transition temperatures, crystallization temperatures and super-cooled liquid regions of the specimens increased with increasing Al content. The microhardness of the specimens also increases with increasing Al content. Room temperature nanoindentation was carried out on the cross-section of the rods. The results showed that the nanohardness and creep displacement were dependent on the Al content

  2. Crystal growth limitation as a critical factor for formation of Fe-based bulk metallic glasses

    International Nuclear Information System (INIS)

    In the present work we study the formation mechanism and crystallization behavior of Fe-based bulk metallic glasses influenced by the addition of rare-earth elements. Samples are characterized by conventional X-ray diffractometry, optical microscopy, and high-resolution field-emission-gun scanning and transmission electron microscopy. In the rare-earth-containing alloys, bulk metallic glasses are formed with populations of quenched-in nuclei. Consequently, crystallization on isothermal annealing occurs without any incubation period. This behavior, not typical of bulk metallic glasses in general, implies that in the rare-earth-containing alloys glass formation is possible only because of restricted crystal growth: both on cooling from the molten and on heating from the glassy state, growth of the primary χ-Fe36Cr12Mo10 crystals is too slow to be significant on a reasonable timescale. The low growth rate is connected with large inhomogeneous strain in the growing nanoparticles, while nucleation of eutectic colonies is hampered by slow diffusion of a rare-earth alloying element

  3. Glassy carbon based supercapacitor stacks

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M.; Braun, A.; Koetz, R.; Haas, O. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    Considerable effort is being made to develop electrochemical double layer capacitors (EDLC) that store relatively large quantities of electrical energy and possess at the same time a high power density. Our previous work has shown that glassy carbon is suitable as a material for capacitor electrodes concerning low resistance and high capacity requirements. We present the development of bipolar electrochemical glassy carbon capacitor stacks of up to 3 V. Bipolar stacks are an efficient way to meet the high voltage and high power density requirements for traction applications. Impedance and cyclic voltammogram measurements are reported here and show the frequency response of a 1, 2, and 3 V stack. (author) 3 figs., 1 ref..

  4. Crystallization behavior of Fe- and Co-based bulk metallic glasses and their glass-forming ability

    International Nuclear Information System (INIS)

    In the present work we study and compare the crystallization behavior of Fe- and Co-based good bulk glass formers with an exceptionally high glass-forming ability leading to the critical thickness of cast samples reaching 1 cm. For Fe-based alloys we also investigate the effect of opposite C/B content ratio on the glass-forming ability and the crystallization behavior. The structure and phase composition of the glassy samples were examined by conventional X-ray diffractometry and transmission electron microscopy while thermal stability and phase transformations were studied by differential scanning calorimetry. The reasons for high glass-forming ability are discussed. The glass-forming ability of the studied alloys depends on both factors: the type of crystallization reaction and characteristic temperatures. - Highlights: • Crystallization of Fe-based and Co-based bulk glass-forming alloys. • The reasons for enhanced glass-forming ability of these alloys are discussed. • Low growth rate of χ-Fe36Cr12Mo10 phase. • Reduced liquidus temperature of Fe48Cr15Mo14C6B15RE2 alloys

  5. Gd-Dy-Al-Co bulk metallic glasses with large magnetic entropy change and refrigeration capacity

    International Nuclear Information System (INIS)

    Novel Gd56-xDyxAl24Co20 (x = 0, 14, 17) bulk metallic glasses (BMGs) were prepared by copper mold casting. They exhibit magnetic entropy changes (ΔSM) comparable to that of Gd53Al24Co20Zr3 BMG and crystalline Gd. Moreover, these glassy alloys have broad entropy change peaks, resulting in the refrigeration capacities of 751.4 J kg-1, 702.8 J kg-1, and 682.3 J kg-1 for Gd56Al24Co20, Gd42Dy14Al24Co20, and Gd39Dy17Al24Co20 at 5 Tesla. The large magnetocaloric effect makes these BMGs attractive candidates as magnetic refrigerant in temperature range of 50-140 K. It is also found that the Curie temperature of this kind of metallic glass linearly declines with the increase of Dy. The ΔSM of metallic glasses reaches maximum at certain content of Dy. These findings are expected to provide a meaningful guidance for the composition design of rare earth based glassy alloys for refrigeration application.

  6. Effect neutron irradiation on glassy carbon

    International Nuclear Information System (INIS)

    Consideration is being given to change of mass (m), volume (v), specific electric resistance (ρ), coefficient of linear thermal expansion (α), dynamic elasticity modulus (E), bending strength (σ) of glassy carbon materials under neutron irradiation. It is shown that neutron irradiation of glassy carbon leads to its shrinkage, accompanied by material disordering. Shrinkage and disordering of glassy carbon decrease with growth both of temperature of material treatment and irradiation temperature

  7. Self-consistent linear-muffin-tin-orbitals coherent-potential technique for bulk and surface calculations: Cu-Ni, Ag-Pd, and Au-Pt random alloys

    OpenAIRE

    Abrikosov, I. A.; Skriver, Hans Lomholt

    1993-01-01

    We present an efficient technique for calculating surface properties of random alloys based on the coherent-potential approximation within a tight-binding linear-muffin-tin-orbitals basis. The technique has been applied in the calculation of bulk thermodynamic properties as well as (001) surface energies and work functions for three fcc-based alloys (Cu-Ni, Ag-Pd, and Au-Pt) over the complete concentration range. The calculated mixing enthalpies for the Ag-Pd and Au-Pt systems agrees with exp...

  8. Self-consistent linear-muffin-tin-orbitals coherent-potential technique for bulk and surface calculations: Cu-Ni, Ag-Pd, and Au-Pt random alloys

    DEFF Research Database (Denmark)

    Abrikosov, I. A.; Skriver, Hans Lomholt

    1993-01-01

    We present an efficient technique for calculating surface properties of random alloys based on the coherent-potential approximation within a tight-binding linear-muffin-tin-orbitals basis. The technique has been applied in the calculation of bulk thermodynamic properties as well as (001) surface...... energies and work functions for three fcc-based alloys (Cu-Ni, Ag-Pd, and Au-Pt) over the complete concentration range. The calculated mixing enthalpies for the Ag-Pd and Au-Pt systems agrees with experimental values, and the calculated concentration dependence of the lattice parameters agrees with...

  9. Impedance aspect of charge storage at graphite and glassy carbon electrodes in potassium hexacyanoferrate (II) redox active electrolyte

    OpenAIRE

    Katja Magdić; Višnja Horvat-Radošević; Krešimir Kvastek

    2016-01-01

    Different types of charge storage mechanisms at unmodified graphite vs. glassy carbon electrodes in acid sulphate supporting solution containing potassium hexacyanoferrate (II) redox active electrolyte, have been revealed by electrochemical impedance spectroscopy and supported by cyclic voltammetry experiments. Reversible charge transfer of Fe(CN)63-/4- redox reaction detected by assessment of CVs of glassy carbon electrode, is in impedance spectra indicated by presence of bulk diffusion impe...

  10. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    Science.gov (United States)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  11. Relook on fitting of viscosity with undercooling of glassy liquids

    Indian Academy of Sciences (India)

    C Chattopadhyay; S Sangal; K Mondal

    2014-02-01

    The present approach is on the modification of viscosity fitting of undercooled liquid as a function of undercooling. The method consists of finding analytical solution of three arbitrary constants of the Vogel–Fulcher–Tamman (VFT) equation by choosing three viscosity data at three critical temperatures for an undercooled liquid. Three critical temperatures are liquidus temperature (l), crystallization onset temperature (x) and glass transition temperature (g). The experimental viscosity data at or very near to these three critical temperatures (depending on the availability in literature) have been utilized to achieve the analytical solution. The analytical solution of VFT equation is further examined by selecting the experimental data points away from the critical temperatures in order to check their (l, x and g) significance towards the solution. Total absolute error (TAE) and total squared error (TSE) values obtained from the present method with respect to the experimental viscosity data in the temperature range between l and g are very much comparable and in most of the cases lower than that of existing `best-fit' cited in the literature for a number of glassy alloys. Moreover, this method interestingly enables us to find the fragility parameters for a number of glassy alloys and convincingly explain their true glass forming abilities (GFA).

  12. Glass formation, magnetic properties and magnetocaloric effect of ternary Ho–Al–Co bulk metallic glass

    International Nuclear Information System (INIS)

    A ternary Ho–Al–Co system with high glass-forming ability (GFA) was developed and fully glassy rods with diameters up to 1 cm can be produced for the best glass former of Ho55Al27.5Co17.5 alloy. The thermal stability and low-temperature magnetic properties of the Ho55Al27.5Co17.5 bulk metallic glass (BMG) were studied. The magnetic transition temperature of this alloy is ∼14 K as determined by the thermomagnetic measurement. Two indicators, i.e. isothermal magnetic entropy change (ΔSM) and the relative cooling power (RCP), were adopted to evaluate the magnetocaloric effect (MCE) of the alloy under a low magnetic field up to 2 T, which can be generated by permanent magnets. The values of |ΔSM| and RCP are 7.98 J kg−1 K−1 and 191.5 J kg−1, respectively. The Ho55Al27.5Co17.5 BMG with good MCE and high GFA provides an attractive candidate for magnetic refrigeration applications, like hydrogen liquefaction and storage. - Highlights: ► A ternary Ho–Al–Co BMG system with high glass-forming ability was developed. ► Fully glassy rods of Ho55Al27.5Co17.5 alloy were produced up to 1 cm in diameter. ► The thermal stability and magnetic properties of the BMG were evaluated. ► The BMG exhibits good magnetocaloric effect under a low magnetic field up to 2 T.

  13. Structural order in glassy water.

    Science.gov (United States)

    Giovambattista, Nicolas; Debenedetti, Pablo G; Sciortino, Francesco; Stanley, H Eugene

    2005-06-01

    We investigate structural order in glassy water by performing classical molecular dynamics simulations using the extended simple point charge (SPC/E) model of water. We perform isochoric cooling simulations across the glass transition temperature at different cooling rates and densities. We quantify structural order by orientational and translational order metrics. Upon cooling the liquid into the glassy state, both the orientational order parameter Q and translational order parameter tau increase. At T=0 K, the glasses fall on a line in the Q-tau plane or order map. The position of this line depends only on density and coincides with the location in the order map of the inherent structures (IS) sampled upon cooling. We evaluate the energy of the IS, eIS(T), and find that both order parameters for the IS are proportional to eIS. We also study the structural order during the transformation of low-density amorphous ice (LDA) to high-density amorphous ice (HDA) upon isothermal compression and are able to identify distinct regions in the order map corresponding to these glasses. Comparison of the order parameters for LDA and HDA with those obtained upon isochoric cooling indicates major structural differences between glasses obtained by cooling and glasses obtained by compression. These structural differences are only weakly reflected in the pair correlation function. We also characterize the evolution of structural order upon isobaric annealing, leading at high pressure to very-high density amorphous ice (VHDA). PMID:16089741

  14. Ending Aging in Super Glassy Polymer Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Lau, CH; Nguyen, PT; Hill, MR; Thornton, AW; Konstas, K; Doherty, CM; Mulder, RJ; Bourgeois, L; Liu, ACY; Sprouster, DJ; Sullivan, JP; Bastow, TJ; Hill, AJ; Gin, DL; Noble, RD

    2014-04-16

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N-2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

  15. Ending aging in super glassy polymer membranes.

    Science.gov (United States)

    Lau, Cher Hon; Nguyen, Phuc Tien; Hill, Matthew R; Thornton, Aaron W; Konstas, Kristina; Doherty, Cara M; Mulder, Roger J; Bourgeois, Laure; Liu, Amelia C Y; Sprouster, David J; Sullivan, James P; Bastow, Timothy J; Hill, Anita J; Gin, Douglas L; Noble, Richard D

    2014-05-19

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations. PMID:24740816

  16. Dynamics and Geometry of Icosahedral Order in Liquid and Glassy Phases of Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Masato Shimono

    2015-07-01

    Full Text Available The geometrical properties of the icosahedral ordered structure formed in liquid and glassy phases of metallic glasses are investigated by using molecular dynamics simulations. We investigate the Zr-Cu alloy system as well as a simple model for binary alloys, in which we can change the atomic size ratio between alloying components. In both cases, we found the same nature of icosahedral order in liquid and glassy phases. The icosahedral clusters are observed in liquid phases as well as in glassy phases. As the temperature approaches to the glass transition point Tg, the density of the clusters rapidly grows and the icosahedral clusters begin to connect to each other and form a medium-range network structure. By investigating the geometry of connection between clusters in the icosahedral network, we found that the dominant connecting pattern is the one sharing seven atoms which forms a pentagonal bicap with five-fold symmetry. From a geometrical point of view, we can understand the mechanism of the formation and growth of the icosahedral order by using the Regge calculus, which is originally employed to formulate a theory of gravity. The Regge calculus tells us that the distortion energy of the pentagonal bicap could be decreased by introducing an atomic size difference between alloying elements and that the icosahedral network would be stabilized by a considerably large atomic size difference.

  17. Influence of nickel on structure and hardness of Fe-Co bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-01-01

    Full Text Available Purpose: In the present paper, influence of Ni addition on structure and hardness Fe-based bulk metallic glass were investigated.Design/methodology/approach: The studies were performed on Fe36+xCo36-x-yNiyB19.2Si4.8Nb4 ( x= 0;1, y=0;10;15 glassy alloy in a form of rods with diameter up to 5 mm. The tests, carried out to obtain amorphous metallic glasses, were realized with the use pressure die casting method. The system includes a copper mould, high frequency power supply, quartz nozzle and a source of inert gas as argon. The following experimental techniques were used for the test of structure: X-ray diffraction (XRD phase analysis and scanning electron microscopy (SEM. Microhardness was examined by Vickers diamond testing machine.Findings: The X-ray diffraction revealed that all samples with thickness 2 mm were amorphous. The structural studies revealed that amorphous structure depended on thickness and nickel contents in a preliminary alloy.Research limitations/implications: The relationship between structure and microhardness can be useful for practical application of these alloys.Practical implications: The Fe-based bulk metallic glasses attracted great interest for a variety of application fields, for example structural materials, electric applications, precision machinery materials. These amorphous alloys exhibit high strength, a high elastic strain limit, high fracture toughness, and other useful mechanical properties which are attractive to many engineering applications.Originality/value: The originality of this paper are studies of changes of structure and hardness of Fe36+xCo36-x-yNiyB19.2Si4.8Nb4 ( x= 0;1, y=0;10;15 mainly depending on Ni addition in this alloy

  18. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

    Science.gov (United States)

    Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

  19. The effect of matrix fracture toughness on the plastic deformation of the metallic glassy composite

    International Nuclear Information System (INIS)

    Highlights: • The effect of the glassy matrix fracture toughness on the plasticity of composites was studied. • The larger plastic strain was obtained in the glassy matrix with higher toughness. • The formation of shear bands and micro-crack reduced the energy of crack for development. - Abstract: In the present study, two kinds of bulk metallic glasses (Zr55Cu30Al10Ni5 and Cu46Zr42Al7Y5) with high strength and no plastic strain were adopted as matrixes. Both of them were reinforced by ductile crystalline TiNb with the same volume fraction and particle size. The compression results showed that the plastic strain of TiNb/Zr55Cu30Al10Ni5 composite was higher 292% than that of TiNb/Cu46Zr42Al7Y5 composite. It should be related to the fracture toughness of the glassy matrix. For the glassy matrix with high toughness, the formation of shear bands and micro-crack at the front of the crack reduced the energy of main crack development. It resulted in a large plastic strain. On the other hand, for the brittle metallic glassy matrix, crack developed quickly through the cross section so that no more shear bands was formed. It resulted in the failure of the sample with smaller plastic strain

  20. Microfabrication with femtosecond laser processing : (A) laser ablation of ferrous alloys, (B) direct-write embedded optical waveguides and integrated optics in bulk glasses.

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Junpeng; McDaniel, Karen Lynn; Palmer, Jeremy Andrew; Yang, Pin; Griffith, Michelle Lynn; Vawter, Gregory Allen; Harris, Marc F.; Tallant, David Robert; Luk, Ting Shan; Burns, George Robert

    2004-11-01

    At Sandia National Laboratories, miniaturization dominates future hardware designs, and technologies that address the manufacture of micro-scale to nano-scale features are in demand. Currently, Sandia is developing technologies such as photolithography/etching (e.g. silicon MEMS), LIGA, micro-electro-discharge machining (micro-EDM), and focused ion beam (FIB) machining to fulfill some of the component design requirements. Some processes are more encompassing than others, but each process has its niche, where all performance characteristics cannot be met by one technology. For example, micro-EDM creates highly accurate micro-scale features but the choice of materials is limited to conductive materials. With silicon-based MEMS technology, highly accurate nano-scale integrated devices are fabricated but the mechanical performance may not meet the requirements. Femtosecond laser processing has the potential to fulfill a broad range of design demands, both in terms of feature resolution and material choices, thereby improving fabrication of micro-components. One of the unique features of femtosecond lasers is the ability to ablate nearly all materials with little heat transfer, and therefore melting or damage, to the surrounding material, resulting in highly accurate micro-scale features. Another unique aspect to femtosecond radiation is the ability to create localized structural changes thought nonlinear absorption processes. By scanning the focal point within transparent material, we can create three-dimensional waveguides for biological sensors and optical components. In this report, we utilized the special characteristics of femtosecond laser processing for microfabrication. Special emphasis was placed on the laser-material interactions to gain a science-based understanding of the process and to determine the process parameter space for laser processing of metals and glasses. Two areas were investigated, including laser ablation of ferrous alloys and direct

  1. New Ti-based Ti–Cu–Zr–Fe–Sn–Si–Ag bulk metallic glass for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Shujie; Liu, Ying; Li, Haifei; Sun, Lulu [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Zhang, Tao, E-mail: zhangtao@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-03-15

    Highlights: • Novel Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with a critical diameter of 7 mm was discovered. • The present BMG is the largest Ni- and Be-free Ti-based BMG containing low content of noble metal reported to date. • The glassy alloy possesses high specific strength, low Young’s modulus, and good corrosion resistance and bio-compatibility. • Combination of high glass-forming ability and good mechano- and bio-compatibility for the Ti-based BMG demonstrates the potential for use in biomedical applications. - Abstract: A novel Ni-free Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with superior glass-forming ability, good mechanical properties and excellent biocompatibility was discovered. The Ti-based BMG with a diameter of 7 mm can be prepared by copper mold casting and the supercooled liquid region was 52 K. Compressive strength, specific strength, Young’s modulus and microhardness of the Ti-based BMG were about 2.08 GPa, 3.2 × 10{sup 5} N m/kg, 100 GPa and 588 Hv, respectively. Electrochemical measurements indicated that the Ti-based glassy alloy possesses higher corrosion resistance than Ti–6Al–4V alloy in a simulated body fluid environment. Attachment, spreading out and proliferation of MC3T3-E1 cells on the Ti-based BMG surface demonstrated the excellent biocompatibility. Mechanisms of the formation and properties for the Ti-based glassy alloy are also discussed. The combination of high glass-forming ability, excellent mechanical properties, high corrosion resistance and good biocompatibility demonstrates the potential of the Ni-free Ti-based BMG for use in biomedical applications.

  2. Molecular mobility in glassy dispersions

    Science.gov (United States)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  3. Simulation study of mechanical properties of bulk metallic glass systems: martensitic inclusions and twinned precipitates

    Science.gov (United States)

    Zaheri, A.; Abdeljawad, F.; Haataja, M.

    2014-12-01

    Monolithic bulk metallic glasses (BMGs) exhibit a unique combination of mechanical properties, such as high strength and large elasticity limits, but the lack of ductility is considered the main Achilles' heel of BMG systems. To increase the competitiveness of BMGs vis-à-vis conventional structural materials, the problem of catastrophic failure via intense plastic strain localization (‘shear banding’) has to be addressed. Recent experimental observations suggest that the addition of structural heterogeneities, in the form of crystalline particles, to BMG systems hinders the catastrophic propagation of shear bands and leads to enhanced ductility. These structural heterogeneities can be introduced by either forming BMG composites, where second-phase crystalline particles accommodate applied loads via martensitic transformation mechanisms, or developing glassy alloys that precipitate crystalline particles under deformation, a process by which further deformation can be sustained by twinning mechanisms in the crystalline phase. In this work, we present a non-linear continuum model capable of capturing the structural heterogeneity in the glassy phase and accounting for intrinsic work hardening via martensitic transformations in second-phase reinforcements in BMG composites and deformation twinning in precipitated crystalline particles. Simulation results reveal that in addition to intrinsic work hardening in the crystalline phase, particle size greatly affects the overall mechanical behavior of these BMG systems. The precipitation of crystalline particles in monolithic BMGs yields two-phase microstructures that promote more homogeneous deformation, delay the propagation of incipient shear bands, and ultimately result in improved ductility characteristics.

  4. Simulation study of mechanical properties of bulk metallic glass systems: martensitic inclusions and twinned precipitates

    International Nuclear Information System (INIS)

    Monolithic bulk metallic glasses (BMGs) exhibit a unique combination of mechanical properties, such as high strength and large elasticity limits, but the lack of ductility is considered the main Achilles' heel of BMG systems. To increase the competitiveness of BMGs vis-à-vis conventional structural materials, the problem of catastrophic failure via intense plastic strain localization (‘shear banding’) has to be addressed. Recent experimental observations suggest that the addition of structural heterogeneities, in the form of crystalline particles, to BMG systems hinders the catastrophic propagation of shear bands and leads to enhanced ductility. These structural heterogeneities can be introduced by either forming BMG composites, where second-phase crystalline particles accommodate applied loads via martensitic transformation mechanisms, or developing glassy alloys that precipitate crystalline particles under deformation, a process by which further deformation can be sustained by twinning mechanisms in the crystalline phase. In this work, we present a non-linear continuum model capable of capturing the structural heterogeneity in the glassy phase and accounting for intrinsic work hardening via martensitic transformations in second-phase reinforcements in BMG composites and deformation twinning in precipitated crystalline particles. Simulation results reveal that in addition to intrinsic work hardening in the crystalline phase, particle size greatly affects the overall mechanical behavior of these BMG systems. The precipitation of crystalline particles in monolithic BMGs yields two-phase microstructures that promote more homogeneous deformation, delay the propagation of incipient shear bands, and ultimately result in improved ductility characteristics. (paper)

  5. Pd-Si binary bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    YAO KeFu; CHEN Na

    2008-01-01

    Pd80+xSi20-x (x=0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature Tg, the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover, the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability, which can be greatly improved by fluxing treatment.

  6. Pd-Si binary bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content,the glass transition temperature Tg,the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover,the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability,which can be greatly improved by fluxing treatment.

  7. Approaching theoretical strength in glassy carbon nanolattices.

    Science.gov (United States)

    Bauer, J; Schroer, A; Schwaiger, R; Kraft, O

    2016-04-01

    The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced--achieved by an 80% shrinkage of the polymer during pyrolysis--and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm(-3) are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio. PMID:26828314

  8. Electro-oxidation of some non-steroidal anti-inflammatory drugs on an alumina nanoparticle-modified glassy carbon electrode

    OpenAIRE

    TABESHNIA, Mahla; HELI, Hossein; Jabbari, Ali

    2010-01-01

    The electro-oxidation of mefenamic acid, diclofenac, and indomethacin on glassy carbon and alumina nanoparticle-modified glassy carbon electrodes in a phosphate buffer solution at physiological pH was studied. The techniques of cyclic voltammetry, chronoamperometry, impedance spectroscopy, and steady state polarization measurements were applied. The drugs were irreversibly oxidized on bath electrodes via an anodic peak and the process was controlled by diffusion in the bulk of soluti...

  9. Kinetics of dioxygen reduction on gold and glassy carbon electrodes in neutral media

    OpenAIRE

    Gotti, Guillaume; Fajerwerg, Katia; Evrard, David; Gros, Pierre

    2013-01-01

    The electrochemical reduction of dioxygen (O₂) has been studied on bulk gold (Au) and glassy carbon (GC) electrodes in aqueous neutral solution close to blood ionic composition. The mechanism was found to involve two successive bielectronic steps with hydrogen peroxide (H₂O₂) as the reaction intermediate whatever the electrode material used. On Au, O₂ and H₂O₂ were reduced at close potentials. The determination of the kinetic parameters of O₂ electroreduction was thus achieved after removing ...

  10. Temperature stability of gamma-ray-induced effects in glassy arsenic trisulfide

    International Nuclear Information System (INIS)

    The author studied the effect of low-temperature annealing (up to the softening point) on the energy dependences of the optical absorption coefficient α in the region of Urbach's edge (α 2 cm-1) and the microhardness H of glassy arsenic trisulfide irradiated with gamma rays from a CO60 source (absorbed dosages of 106-107 Gy). Bulk samples of As2S3, obtained by direct synthesis in evacuated ampuls consisting of especially pure components, were used

  11. Glassy slags for minimum additive waste stabilization

    International Nuclear Information System (INIS)

    Glassy slag waste forms are being developed to complement glass waste forms in implementing Minimum Additive Waste Stabilization (MAWS) for supporting DOE's environmental restoration efforts. The glassy slag waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. The MAWS approach was adopted by blending multiple waste streams to achieve up to 100% waste loadings. The crystalline phases, such as spinels, are very durable and contain hazardous and radioactive elements in their lattice structures. These crystalline phases may account for up to 80% of the total volume of slags having over 80% metal loading. The structural bond strength model was used to quantify the correlation between glassy slag composition and chemical durability so that optimized slag compositions were obtained with limited crucible melting and testing. Slag compositions developed through crucible melts were also successfully generated in a pilot-scale Retech plasma centrifugal furnace at Ukiah, California. Utilization of glassy slag waste forms allows the MAWS approach to be applied to a much wider range of waste streams than glass waste forms. The initial work at ANL has indicated that glassy slags are good final waste forms because of (1) their high chemical durability; (2) their ability to incorporate large amounts of metal oxides; (3) their ability to incorporate waste streams having low contents of flux components; (4) their less stringent requirements on processing parameters, compared to glass waste forms; and (5) their low requirements for purchased additives, which means greater waste volume reduction and treatment cost savings

  12. Effect of Surface Modifications of Ti40Zr10Cu38Pd12 Bulk Metallic Glass and Ti-6Al-4V Alloy on Human Osteoblasts In Vitro Biocompatibility

    Science.gov (United States)

    Blanquer, Andreu; Hynowska, Anna; Nogués, Carme; Ibáñez, Elena; Sort, Jordi; Baró, Maria Dolors; Özkale, Berna; Pané, Salvador; Pellicer, Eva

    2016-01-01

    The use of biocompatible materials, including bulk metallic glasses (BMGs), for tissue regeneration and transplantation is increasing. The good mechanical and corrosion properties of Ti40Zr10Cu38Pd12 BMG and its previously described biocompatibility makes it a potential candidate for medical applications. However, it is known that surface properties like topography might play an important role in regulating cell adhesion, proliferation and differentiation. Thus, in the present study, Ti40Zr10Cu38Pd12 BMG and Ti6-Al-4V alloy were surface-modified electrochemically (nanomesh) or physically (microscratched) to investigate the effect of material topography on human osteoblasts cells (Saos-2) adhesion, proliferation and differentiation. For comparative purposes, the effect of mirror-like polished surfaces was also studied. Electrochemical treatments led to a highly interconnected hierarchical porous structure rich in oxides, which have been described to improve corrosion resistance, whereas microscratched surfaces showed a groove pattern with parallel trenches. Cell viability was higher than 96% for the three topographies tested and for both alloy compositions. In all cases, cells were able to adhere, proliferate and differentiate on the alloys, hence indicating that surface topography plays a minor role on these processes, although a clear cell orientation was observed on microscratched surfaces. Overall, our results provide further evidence that Ti40Zr10Cu38Pd12 BMG is an excellent candidate, in the present two topographies, for bone repair purposes. PMID:27243628

  13. Glassy behavior in magnetic fine particles

    CERN Document Server

    Muro, M G D; Labarta, A

    2000-01-01

    A detailed study of the static and dynamic magnetic properties of nanocrystalline barium hexaferrite powder was done. Particles of about 10 nm diameter exhibit the main features attributed to glassy behavior. Different results make evident the presence of strong interactions in the studied system. This glassy state is mostly attributed to the frustration induced by magnetic interactions between randomly distributed particles, although the surface spins contribution cannot be discarded. The effective energy barrier distribution obtained from the analysis of the time dependence of the thermoremanence in terms of the T ln (t/tau sub 0) scaling shows a maximum located at energies higher than the mean anisotropy energy barrier. When doing the relaxation experiments after field cooling at increasing fields, the obtained effective energy distribution progressively resembles the anisotropy energy distribution. Therefore, we demonstrate how the glassy state can be erased by applying a magnetic field.

  14. Synthesis and Characterization of Glassy Carbon Nanowires

    Directory of Open Access Journals (Sweden)

    C. M. Lentz

    2011-01-01

    Full Text Available The advent of carbon-based micro- and nanoelectromechanical systems has revived the interest in glassy carbon, whose properties are relatively unknown at lower dimensions. In this paper, electrical conductivity of individual glassy carbon nanowires was measured as a function of microstructure (controlled by heat treatment temperature and ambient temperature. The semiconducting nanowires with average diameter of 150 nm were synthesized from polyfurfuryl alcohol precursors and characterized using transmission electron and Raman microscopy. DC electrical measurements made at 90 K to 450 K show very strong dependence of temperature, following mixed modes of activation energy and hopping-based conduction.

  15. Active cage model of glassy dynamics.

    Science.gov (United States)

    Fodor, Étienne; Hayakawa, Hisao; Visco, Paolo; van Wijland, Frédéric

    2016-07-01

    We build up a phenomenological picture in terms of the effective dynamics of a tracer confined in a cage experiencing random hops to capture some characteristics of glassy systems. This minimal description exhibits scale invariance properties for the small-displacement distribution that echo experimental observations. We predict the existence of exponential tails as a crossover between two Gaussian regimes. Moreover, we demonstrate that the onset of glassy behavior is controlled only by two dimensionless numbers: the number of hops occurring during the relaxation of the particle within a local cage and the ratio of the hopping length to the cage size. PMID:27575182

  16. Gold based bulk metallic glass

    OpenAIRE

    Schroers, Jan; Lohwongwatana, Boonrat; Johnson, William L.; Peker, Atakan

    2005-01-01

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5 mm in the best glassformer. Au49Ag5.5Pd2.3Cu26.9Si16.3 has a liquidus temperature of 644 K, a glass transition temperature of 401 K, and a supercooled liquid region of 58 K. The Vickers hardness of the alloys in this system...

  17. Gold based bulk metallic glass

    Science.gov (United States)

    Schroers, Jan; Lohwongwatana, Boonrat; Johnson, William L.; Peker, Atakan

    2005-08-01

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5mm in the best glassformer. Au49Ag5.5Pd2.3Cu26.9Si16.3 has a liquidus temperature of 644K, a glass transition temperature of 401K, and a supercooled liquid region of 58K. The Vickers hardness of the alloys in this system is ˜350Hv, twice that of conventional 18-karat crystalline gold alloys. This combination of properties makes the alloys attractive for many applications including electronic, medical, dental, surface coating, and jewelry.

  18. Gold based bulk metallic glass

    International Nuclear Information System (INIS)

    Gold-based bulk metallic glass alloys based on Au-Cu-Si are introduced. The alloys exhibit a gold content comparable to 18-karat gold. They show very low liquidus temperature, large supercooled liquid region, and good processibility. The maximum casting thickness exceeds 5 mm in the best glassformer. Au49Ag5.5Pd2.3Cu26.9Si16.3 has a liquidus temperature of 644 K, a glass transition temperature of 401 K, and a supercooled liquid region of 58 K. The Vickers hardness of the alloys in this system is ∼350 Hv, twice that of conventional 18-karat crystalline gold alloys. This combination of properties makes the alloys attractive for many applications including electronic, medical, dental, surface coating, and jewelry

  19. Infiltration of Glassy Bodies with Zirconia Nanoparticles

    International Nuclear Information System (INIS)

    Zirconia nanoparticles (10-50 nm) were infiltrated into commercial glasses to modify their mechanical properties. The process developed allows a homogeneous distribution of the nanoparticles within the glassy matrix. Differential thermal analysis, thermo-gravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy and energy dispersive spectroscopy mapping analysis where utilized to characterize the resulting composites

  20. Bulk metallic glass tube casting

    International Nuclear Information System (INIS)

    Research highlights: → Tubular specimens of Zr55Cu30Al10Ni5 cast in custom arc-melting furnace. → Tilt casting supplemented by suction casting. → Bulk metallic glass formed only with optimized processing parameters. → Fully amorphous tubes with 1.8 mm wall thickness and 25 mm diameter. - Abstract: Tubular bulk metallic glass specimens were produced, using a custom-built combined arc-melting tilt-casting furnace. Zr55Cu30Al10Ni5 tubes with outer diameter of 25 mm and 0.8-3 mm wall thicknesses were cast, with both tilt and suction casting to ensure mold filling. Tilt casting was found to fill one side of the tube mold first, with the rest of the tube circumference filled subsequently by suction casting. Optimized casting parameters were required to fully fill the mold and ensure glass formation. Too small melt mass and too low arc power filled the mold only partially. However, too large melt mass and higher arc power which lead to the best mold filling also lead to partial crystallization. Variations in processing parameters were explored, until a glassy ring with 1.8 mm thickness was produced. Different sections of the as-cast ring were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and instrumented indentation to ensure amorphous microstructure. Atomic force microscopy (AFM) was used to compare the surface qualities of the first- and last-filled sections. These measurements confirmed the glassy structure of the cast ring, and that, the tilt cast tube section consistently showed better surface quality than the suction cast section. Optimized casting parameters are required to fully realize the potential of directly manufacturing complex shapes out of high-purity bulk metallic glasses by tilt casting.

  1. Structure, thermal and magnetic properties of Fe43Co14Ni14B20Si5Nb4 bulk metallic glass

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-02-01

    Full Text Available Purpose: The paper presents structure characteristics, thermal stability and soft magnetic properties analysis of Fe-based bulk metallic glass in as-cast state and after crystallization process.Design/methodology/approach: The studies were performed on Fe43Co14Ni14B20Si5Nb4 metallic glass in a form of plates and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal stability of the glassy samples was measured using differential scanning calorimetry (DSC. The soft magnetic properties examination of tested material contained initial magnetic permeability and magnetic permeability relaxation measurements.Findings: The XRD and TEM investigations revealed that the studied as-cast plates and rods were amorphous. Broad diffraction halo could be observed for all tested samples, indicating the formation of a glassy phase with the diameters up to 3 mm for rods. The fracture surface of rod samples appears to consist of two different zones which might correspond with different amorphous structures of studied materials. The thermal stability parameters of rod with diameter of 3 mm, such as glass transition temperature, onset crystallization temperature and supercooled liquid area were measured by DSC to be 797 K, 854 K, 57 K, respectively. The heat treatment process of rod samples involved in crystallization of α-Fe phase and formation of iron borides at temperature above 873 K.Practical implications: The appropriate increase of annealing temperature significantly improved soft magnetic properties of examined alloy by increasing the initial magnetic permeability and decreasing the magnetic permeability relaxation.Originality/value: The success of fabrication of studied Fe-based bulk metallic glass in a form of plates and rods is important for the future progress in research and practical application of those glassy materials.

  2. Short range ordering and microstructure property relationship in amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Shariq, A.

    2006-07-01

    A novel algorithm, ''Next Neighbourhood Evaluation (NNE)'', is enunciated during the course of this work, to elucidate the next neighbourhood atomic vicinity from the data, analysed using tomographic atom probe (TAP) that allows specifying atom positions and chemical identities of the next neighbouring atoms for multicomponent amorphous materials in real space. The NNE of the Pd{sub 55}Cu{sub 23}P{sub 22} bulk amorphous alloy reveals that the Pd atoms have the highest probability to be the next neighbours to each other. Moreover, P-P correlation corroborates earlier investigations with scattering techniques that P is not a direct next neighbour to another P atom. Analogous investigations on the Fe{sub 40}Ni{sub 40}B{sub 20} metallic glass ribbons, in the as quenched state and for a state heat treated at 350 C for 1 hour insinuate a pronounced elemental inhomogeneity for the annealed state, though, it also depicts glimpse of a slight inhomogeneity for B distribution even for the as quenched sample. Moreover, a comprehensive microstructural investigation has been carried out on the Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy system. TEM and TAP investigations evince that the as cast bulk samples constitutes a composite structure of an amorphous phase and crystalline phase(s). The crystallization is essentially triggered at the mould walls due to heterogeneous nucleation. The three dimensional atomic reconstruction maps of the volume analysed by TAP reveal a complex stereological interconnected network of two phases. The phase that is rich in Zr and Al concentration is depleted in Co concentration while the phase that is rich in Co concentration is depleted both in Zr and Al. Zr{sub 53}Co{sub 23.5}Al{sub 23.5} glassy splat samples exhibit a single exothermic crystallization peak contrary to the as cast bulk sample with a different T{sub g} temperature. A single homogeneous amorphous phase revealed by TEM investigations depicts that the faster cooling

  3. Titanium and zirconium based wrought alloys and bulk metallic glasses for fluoride ion containing 11.5 M HNO3 medium

    International Nuclear Information System (INIS)

    Aqueous reprocessing of plutonium-rich mixed oxide fuels require fluoride as a catalyst in boiling nitric acid for an effective dissolution of the spent fuel. The corrosion behavior of the candidate dissolver materials zircaloy-4 (Zr-4) and commercial pure titanium (CP-Ti grade 2) in boiling 11.5 M HNO3 + 0.05 M NaF has been established. High corrosion rates were obtained for Zr- 4 and CP-Ti in nitric acid containing fluoride ions. Complexing the fluoride ions either with Al(NO3)3 or ZrO(NO3)2 aided in decreasing the corrosion rates of Zr-4 and CP-Ti. High corrosion resistance is claimed as one of the principal property of the amorphous alloy when compared to the crystalline alloy. Thus Ni60Nb40 and Ni60Nb30Ta10 amorphous ribbons were prepared and exposed in boiling 11.5 M HNO3 and 11.5 M HNO3 + 0.05 M NaF. In nitric acid these alloys did not show any sign of corrosion attack. XPS analysis confirmed that the passivity was due to the formation passive films of thickness ≈3 nm enriched with Nb2O5 and of ≈1.5 nm enriched with both Nb2O5 and Ta2O5 on the respective surfaces of the ribbons. In boiling 11.5 M HNO3 + 0.05 M NaF, severe corrosion attack was observed on Ni60Nb40 ribbon, due to the instability of the oxide/metal interface. The Ni60Nb30Ta10 amorphous ribbon exhibited corrosion resistance of at least an order of magnitude higher than that for Ni60Nb40 ribbon

  4. Bulk amorphous (Fe, Co, Ni)70(Zr, Nb, M)10B20 (M=Ti, Ta or Mo) soft magnetic alloys

    International Nuclear Information System (INIS)

    The substitution of 1.5 at% Zr by Ti, Ta or Mo in the basic Fe56Co7Ni7Zr7.5Nb2.5B20 alloy has the effect of increasing the glass-forming ability, as well as increasing the Ms from 1.01 to 1.07 T, of the ρRT from 1.51 to 2.08 μ Ω m and decreasing the Hc from 9.5 to 6.1 A/m

  5. Plastic flow modeling in glassy polymers

    Energy Technology Data Exchange (ETDEWEB)

    Clements, Brad [Los Alamos National Laboratory

    2010-12-13

    Glassy amorphous and semi-crystalline polymers exhibit strong rate, temperature, and pressure dependent polymeric yield. As a rule of thumb, in uniaxial compression experiments the yield stress increases with the loading rate and applied pressure, and decreases as the temperature increases. Moreover, by varying the loading state itself complex yield behavior can be observed. One example that illustrates this complexity is that most polymers in their glassy regimes (i.e., when the temperature is below their characteristic glass transition temperature) exhibit very pronounced yield in their uniaxial stress stress-strain response but very nebulous yield in their uniaxial strain response. In uniaxial compression, a prototypical glassy-polymer stress-strain curve has a stress plateau, often followed by softening, and upon further straining, a hardening response. Uniaxial compression experiments of this type are typically done from rates of 10{sup -5} s{sup -1} up to about 1 s{sup -1}. At still higher rates, say at several thousands per second as determined from Split Hopkinson Pressure Bar experiments, the yield can again be measured and is consistent with the above rule of thumb. One might expect that that these two sets of experiments should allow for a successful extrapolation to yet higher rates. A standard means to probe high rates (on the order of 105-107 S-I) is to use a uniaxial strain plate impact experiment. It is well known that in plate impact experiments on metals that the yield stress is manifested in a well-defined Hugoniot Elastic Limit (HEL). In contrast however, when plate impact experiments are done on glassy polymers, the HEL is arguably not observed, let alone observed at the stress estimated by extrapolating from the lower strain rate experiments. One might argue that polymer yield is still active but somehow masked by the experiment. After reviewing relevant experiments, we attempt to address this issue. We begin by first presenting our recently

  6. Short- and medium-range order in (Zr70Cu20Ni10)90-xTaxAl10 bulk amorphous alloys

    International Nuclear Information System (INIS)

    We have used x-ray scattering to examine short-range and medium-range order in (Zr70Cu20Ni10)90-xTaxAl10 amorphous alloys. Analysis of the radial distribution functions (RDF's) shows that the addition of 4 at. % Ta enhances the average short-range topological order, as the nearest-neighbor peak in the RDF becomes more sharply defined. The enhanced order due to the Ta addition persists beyond the first few atomic shells, however, out to distances of at least 15 A. From resonant x-ray scattering near the Zr K absorption edge, we are able to extract differential radial distribution functions (DRDF's) which show the atomic environment around Zr atoms only. The DRDF's show that Ta has little effect on the nearest neighbors of Zr atoms, but does significantly enhance the medium-range order (over distances of 5-15 A from an average Zr atom). To explain these observations, we propose that topologically ordered atomic clusters are a significant feature of the structure of Zr-based amorphous alloys and that the influence of Ta is to enhance the order associated with packing of these clusters

  7. Ubiquitous "glassy" relaxation in catalytic reaction networks

    OpenAIRE

    Awazu, Akinori; Kaneko, Kunihiko

    2009-01-01

    Study of reversible catalytic reaction networks is important not only as an issue for chemical thermodynamics but also for protocells. From extensive numerical simulations and theoretical analysis, slow relaxation dynamics to sustain nonequlibrium states are commonly observed. These dynamics show two types of salient behaviors that are reminiscent of glassy behavior: slow relaxation along with the logarithmic time dependence of the correlation function and the emergence of plateaus in the rel...

  8. Vapor Condensed and Supercooled Glassy Nanoclusters.

    Science.gov (United States)

    Qi, Weikai; Bowles, Richard K

    2016-03-22

    We use molecular simulation to study the structural and dynamic properties of glassy nanoclusters formed both through the direct condensation of the vapor below the glass transition temperature, without the presence of a substrate, and via the slow supercooling of unsupported liquid nanodroplets. An analysis of local structure using Voronoi polyhedra shows that the energetic stability of the clusters is characterized by a large, increasing fraction of bicapped square antiprism motifs. We also show that nanoclusters with similar inherent structure energies are structurally similar, independent of their history, which suggests the supercooled clusters access the same low energy regions of the potential energy landscape as the vapor condensed clusters despite their different methods of formation. By measuring the intermediate scattering function at different radii from the cluster center, we find that the relaxation dynamics of the clusters are inhomogeneous, with the core becoming glassy above the glass transition temperature while the surface remains mobile at low temperatures. This helps the clusters sample the highly stable, low energy structures on the potential energy surface. Our work suggests the nanocluster systems are structurally more stable than the ultrastable glassy thin films, formed through vapor deposition onto a cold substrate, but the nanoclusters do not exhibit the superheating effects characteristic of the ultrastable glass states. PMID:26866858

  9. Wafer-level microstructuring of glassy carbon

    Science.gov (United States)

    Hans, Loïc. E.; Prater, Karin; Kilchoer, Cédric; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-03-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. One application is glass molding that allows to realize high resolution diffractive optical elements on large areas and at affordable price appropriate for mass production. We study glassy carbon microstructuring for future precision compression molding of low and high glass-transition temperature. For applications in optics the uniformity, surface roughness, edge definition and lateral resolution are very important parameters for a stamp and the final product. We study different methods of microstructuring of glassy carbon by etching and milling. Reactive ion etching with different protection layers such as photoresists, aluminium and titanium hard masks have been performed and will be compare with Ion beam etching. We comment on the quality of the structure definition and give process details as well as drawbacks for the different methods. In our fabrications we were able to realize optically flat diffractive structures with slope angles of 80° at typical feature sizes of 5 micron and 700 nm depth qualified for high precision glass molding.

  10. Formation and physical properties of Fe-based bulk metallic glasses with Ni addition

    Directory of Open Access Journals (Sweden)

    S. Lesz

    2008-11-01

    Full Text Available Purpose: The main aim of the paper was investigations of formation and changes of physical properties (magnetic properties and microhardness of Fe based bulk metallic glasses (BMGs with Ni addition.Design/methodology/approach: The following experimental techniques were used: transmission electron microscopy (TEM, scanning electron microscopy (SEM and X-ray diffraction (XRD phase analysis method to test the structure, electrical resistivity in situ measurements (four-point probe, measurements of magnetic properties, microhardness of investigated ribbons was determined by Vickers method.Findings: The structural studies revealed an amorphous structure for the ribbons with thicknesses up to 0.27 mm, regardless of their thickness.Research limitations/implications: More investigations for example Mössbauer spectrometry have to be conducted on different thickness of ribbons in order to confirm conclusions contained in the work.Practical implications: According to the results presented in the present paper the examined Fe-based bulk glassy alloys with Ni addition as a soft ferromagnetic material may be utilized in construction of magnetic cores such as choke coils, common mode and noise filter and is of great technological interest.Originality/value: The originality of the paper are examinations of changes of structure and physical properties on cross section and on surface of ribbons.

  11. High strength and ductile bulk Ti-Ni-Cu-Nb alloy with submicron-size structure units obtained by arc-melting

    International Nuclear Information System (INIS)

    The structure of an arc-melted ingot of the Ti50Ni20Cu20Nb10 alloy of about 30 mm diameter and 10 mm height was studied by X-ray diffractometry, transmission electron microscopy (TEM). Mechanical properties were tested by an Instron-type testing machine. The ingot sample has a disperse submicron-size complex eutectic structure (including ternary eutectic) consisting of a quaternary β-(Ti, Nb, Ni, Cu) solid solution, a monoclinic TiNi-type (Ti, Nb)(Ni, Cu) phase and a (Ti, Nb)2(Cu, Ni) phase which is a solution of Nb (replacing Ti) and Ni (replacing Cu) in the tetragonal Ti2Cu phase. The sample exhibits high mechanical properties and does not require additional mold injection casting procedure to obtain fine microstructure

  12. Quasi-static and dynamic compressive deformation of a bulk nanolayered Ag–Cu eutectic alloy: Macroscopic response and dominant deformation mechanisms

    International Nuclear Information System (INIS)

    Nanostructured multilayered material systems offer an attractive method of increasing material strength. This work examines the response of a bulk eutectic silver–copper material (Ag60Cu40, subscripts indicating atomic percent) which has a hierarchical structure of alternating Ag and Cu layers with thicknesses down to 50 nm. The hierarchical structure consists of two primary arrangements of layers, eutectic colonies of parallel layers, most commonly found at the material interior, and “grains” consisting of alternating Ag and Cu layers which emanate from a central region in a radial pattern, most commonly found at the material exterior surface. We show that the hierarchical structure causes a significant increase in the measured strength response when comparing the Ag60Cu40 response to that of the constituent materials in their bulk nanograined or micrograined form. The deformation mechanisms of this material are studied under compressive loading over the quasi-static and dynamic regime (10−3–103 s−1) with strain between 5% and 50%

  13. Quasi-static and dynamic compressive deformation of a bulk nanolayered Ag–Cu eutectic alloy: Macroscopic response and dominant deformation mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Kingstedt, O.T., E-mail: kingste1@illinois.edu [Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 306 Talbot Laboratory, MC-236, 104 South Wright Street, Urbana, IL 61801 (United States); Eftink, B. [Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, 201 Materials Science and Engineering Building, 1304 West Green Street, Urbana, IL 61801 (United States); Lambros, J. [Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 306 Talbot Laboratory, MC-236, 104 South Wright Street, Urbana, IL 61801 (United States); Robertson, I.M. [Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, 201 Materials Science and Engineering Building, 1304 West Green Street, Urbana, IL 61801 (United States)

    2014-02-10

    Nanostructured multilayered material systems offer an attractive method of increasing material strength. This work examines the response of a bulk eutectic silver–copper material (Ag{sub 60}Cu{sub 40}, subscripts indicating atomic percent) which has a hierarchical structure of alternating Ag and Cu layers with thicknesses down to 50 nm. The hierarchical structure consists of two primary arrangements of layers, eutectic colonies of parallel layers, most commonly found at the material interior, and “grains” consisting of alternating Ag and Cu layers which emanate from a central region in a radial pattern, most commonly found at the material exterior surface. We show that the hierarchical structure causes a significant increase in the measured strength response when comparing the Ag{sub 60}Cu{sub 40} response to that of the constituent materials in their bulk nanograined or micrograined form. The deformation mechanisms of this material are studied under compressive loading over the quasi-static and dynamic regime (10{sup −3}–10{sup 3} s{sup −1}) with strain between 5% and 50%.

  14. Enhancement of glass-forming ability and mechanical behavior of zirconium–lanthanide two-phase bulk metallic glasses

    International Nuclear Information System (INIS)

    Highlights: • This work provides a new concept for design of two-phase BMGs. • The formation of two-glass structure in two-liquid systems is analyzed. • A strategy for improving GFA of two-phase metallic glasses is proposed. • A family of two-phase metallic glasses in bulk form is developed. • The mechanical behavior of two-phase BMGs is studied for the first time. - Abstract: Development of the two-phase bulk metallic glasses (BMGs) is essentially retarded due to difficulties in finding of phase-separated (immiscible) alloys with high glass-forming ability (GFA) of coexistent phases. Referring to the concept of solute partitioning and minimization of free energy, in this work we present an idea that a metallic liquid system containing two liquids with individual self-assembled eutectic composition may yield two-phase BMGs upon casting. The formation of the two-glass structure is discussed and a strategy of partial substitution of chemically similar elements for overcoming the drawback of low GFA is proposed. A family of two-phase zirconium–lanthanide based metallic glasses in bulk form is developed. The mechanical behavior of the two-phase BMGs with different ratio of zirconium-rich to lanthanide-rich glassy phase is studied for the first time. This work provides a new concept for fabrication of two-phase BMGs and reveals the role of constituent phases in determining the mechanical properties of the whole glass

  15. Microstructural characteristics of an AZ91 matrix-glassy carbon particle composite

    Energy Technology Data Exchange (ETDEWEB)

    Olszowka-Myalska, Anita; Myalski, Jerzy; Botor-Probierz, Agnieszka [Faculty of Materials Sciences and Metallurgy, Silesian University of Technology (Poland)

    2010-07-15

    This paper presents the results of a microstructural investigation of a new type of ultralight glassy carbon particles (C{sub p})-AZ91 magnesium alloy matrix composite manufactured by the powder metallurgy method. Glassy C{sub p} with unmodified surfaces and surfaces modified with SiO{sub 2} amorphous nanocoating were used in the experiment. The composite microstructure, with an emphasis given on the interface, was characterized by scanning electron microscope (SEM), TEM, and HRTEM microscopy. Uniform distribution of the particles in the matrix and their good bonding with the metal matrix were observed. A continuous very thin MgO oxide layer containing needle-like Al{sub 2}MgO{sub 4} phase was detected at the glassy carbon-AZ91 interface. An increase of aluminum concentration at the interface as a result of Mg and Al diffusion into the SiO{sub 2} nanolayer was observed in the case of particles modified with SiO{sub 2}. Crystalline phases containing carbon were not detected at the interface. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  16. Self-organized intermittent plastic flow in bulk metallic glasses

    International Nuclear Information System (INIS)

    Under stress, bulk metallic glasses irreversibly deform through shear banding processes that manifest as serrated flow behavior. These serration events exhibit a shock-and-aftershock, earthquake-like behavior. Statistical analysis shows that the shear avalanches can self-organize to a critical state (SOC). In analogy to the smooth macroscopic-scale crystalline plasticity that arises from the spatio-temporal averages of disruptive earthquake-like events at the nanometer scale, shear avalanches in glassy metals are another model system that can be used to study SOC behavior. With our understanding of SOC behavior, we further demonstrate how to enhance the plasticity of glassy (brittle) materials. It is expected that the findings can be extended to other glassy or brittle materials.

  17. Microstructure evolution in Nd:YAG laser-welded (Zr53Cu30Ni9Al8)Si0.5 bulk metallic glass alloy

    International Nuclear Information System (INIS)

    To generate a rapid welding thermal cycle for a (Zr53Cu30Ni9Al8)Si0.5 bulk metallic glass (BMG) weld, the Nd:YAG pulse laser welding process with pre-selected welding variables is used in this study. The microstructure development and crystallization behavior in the weld fusion zone (WFZ) and the heat-affected zone (HAZ) are investigated by scanning electron microscopy (SEM), micro-area X-ray diffractometry (XRD) and transmission electron microscopy (TEM). From the results, it is observed that the HAZ is liable to crystallize, although no crystallization occurs within the WFZ. The spherical type crystalline phases (with a particle size of 20-200 nm) observed in the HAZ, which are rich in Zr, Cu and Ni, result in a change of chemical composition in this region. Furthermore, if the particle size in the crystallized area is greater than 50 nm, cracks may form.

  18. Controlling Bulk Cu6Sn5 Nucleation in Sn0.7Cu/Cu Joints with Al Micro-alloying

    Science.gov (United States)

    Xian, J. W.; Belyakov, S. A.; Gourlay, C. M.

    2016-01-01

    We show that dilute Al additions can control the size of primary Cu6Sn5 rods in Sn-0.7Cu/Cu ball grid array joints. In Sn-0.7Cu-0.05Al/Cu joints, the number of primary Cu6Sn5 per mm2 is ˜7 times higher and the mean three-dimensional length of rods is ˜4 times smaller than in Al-free Sn-0.7Cu/Cu joints, while the area fraction of primary Cu6Sn5 is similar. It is shown that epitaxial nucleation of primary Cu6Sn5 occurs on δ-Cu33Al17 or γ 1-Cu9Al4 particles, which are stable in the Sn-0.7Cu-0.05Al melt during holding at 250°C. The observed facet relationships agree well with previously determined orientation relationships between δ-Cu33Al17 and Cu6Sn5 in hypereutectic Sn-Cu-Al alloys and result in a good lattice match with <˜2.5% lattice mismatch on two different interfacial planes.

  19. Soft magnetic properties and thermal stability of bulk Fe83B17 alloy prepared by undercooling and Cu-mold casting methods

    International Nuclear Information System (INIS)

    The thermal stability and soft magnetic properties of bulk Fe83B17 rods with nano-lamellar eutectic structures and metastable Fe3B phases were investigated by annealing at 973–1273 K for 1.5 h. Samples with a diameter of 3 mm were prepared by undercooling solidification combined with Cu-mold casting. The decomposition of Fe3B and the transformation of nano-lamellar eutectic structures were finished after annealing at 1173 K for 1.5 h. Increasing annealing temperature showed that the soft magnetic properties of the sample were kept relatively stable. The saturation magnetization and retentivity were decreased only slightly, while the coercivity was decreased significantly. - Highlights: • Thermal stability of the nano-lamellar eutectic structure was obtained. • Thermal stability of the metastable Fe3B phase was obtained. • The soft magnetic properties of the sample remain stability by annealing. • Nano-lamellar eutectic structures enhance the soft magnetic properties

  20. Temperature stability of gamma-ray-induced effects in glassy arsenic trisulfide

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O.I.

    1987-07-01

    The author studied the effect of low-temperature annealing (up to the softening point) on the energy dependences of the optical absorption coefficient ..cap alpha.. in the region of Urbach's edge (..cap alpha.. < 10/sup 2/ cm/sup -1/) and the microhardness H of glassy arsenic trisulfide irradiated with gamma rays from a CO/sup 60/ source (absorbed dosages of 10/sup 6/-10/sup 7/ Gy). Bulk samples of As/sub 2/S/sub 3/, obtained by direct synthesis in evacuated ampuls consisting of especially pure components, were used.

  1. Study of lithium glassy solid electrolyte/electrode interface by impedance analysis

    Indian Academy of Sciences (India)

    A Karthikeyan; P Vinatier; A Levasseur

    2000-06-01

    Cells of lithium ion conducting glassy electrolyte Li2SO4–Li2O–B2O3 with different combinations of electrodes (stainless steel blocking electrode, lithium non-blocking electrode and TiS2 electrode) have been prepared. The a.c. impedance measurements of the cells have been studied at elevated temperature as a function of time. The circuit elements such as bulk resistance, double layer capacitance and charge transfer resistance have been inferred and their time dependence studied. The results show that the electrolyte and the interface are chemically very stable with the different types of electrodes studied here.

  2. Spatially heterogeneous ages in glassy dynamics

    International Nuclear Information System (INIS)

    We construct a framework for the study of fluctuations in the nonequilibrium relaxation of glassy systems with and without quenched disorder. We study two types of two-time local correlators with the aim of characterizing the heterogeneous evolution in these systems: in one case we average the local correlators over histories of the thermal noise, in the other case we simply coarse-grain the local correlators obtained for a given noise realization. We explain why the noise-averaged correlators describe the fingerprint of quenched disorder when it exists, while the coarse-grained correlators are linked to noise-induced mesoscopic fluctuations. We predict constraints on the distribution of the fluctuations of the coarse-grained quantities. In particular, we show that locally defined correlations and responses are connected by a generalized local out-of-equilibrium fluctuation-dissipation relation. We argue that large size heterogeneities in the age of the system survive in the long-time limit. A symmetry of the underlying theory, namely invariance under reparametrizations of the time coordinates, underlies these results. We establish a connection between the probabilities of spatial distributions of local coarse-grained quantities and the theory of dynamic random manifolds. We define, and discuss the behavior of, a two-time dependent correlation length from the spatial decay of the fluctuations in the two-time local functions. We characterize the fluctuations in the system in terms of their fractal properties. For concreteness, we present numerical tests performed on disordered spin models in finite and infinite dimensions. Finally, we explain how these ideas can be applied to the analysis of the dynamics of other glassy systems that can be either spin models without disorder or atomic and molecular glassy systems. (author)

  3. Voltammetric Response of Epinephrine at Carbon Nanotube Modified Glassy Carbon Electrode and Activated Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    WANG Juan; TANG Ping; ZHAO Fa-qiong; ZENG Bai-zhao

    2005-01-01

    The electrochemical behavior of epinephrine at activated glassy carbon electrode and carbon nanotube-coated glassy carbon electrode was studied. Epinephrine could exhibit an anodic peak at about 0.2 V (vs. SCE) at bare glassy carbon electrode, but it was very small.However, when the electrode was activated at certain potential (i. e. 1.9V) or modified with carbon nanotube, the peak became more sensitive,resulting from the increase in electrode area in addition to the electrostatic attraction. Under the selected conditions, the anodic peak current was linear to epinephrine concentration in the range of 3.3 × 10-7-1.1 × 10-5mol/L at activated glassy carbon electrode and in the range of 1.0 × 10-6-5.0 × 10-5 mol/L at carbon nanotube-coated electrode. The correlation coefficients were 0. 998 and 0. 997, respectively. The determination limit was 1.0 × 10-7 mol/L. The two electrodes have been successfully applied for the determination of epinephrine in adrenaline hydrochloride injection with recovery of 95%-104%.

  4. Water sorption and diffusion in glassy polymers

    Science.gov (United States)

    Davis, Eric Mikel

    Water sorption and diffusion in glassy polymers is important in many fields, including drug delivery, desalination, energy storage and delivery, and packaging. Accurately measuring and understanding the underlying transport mechanisms of water in these glassy polymers is often complex due to both the nonequilibrium state of the polymer and the self-associating nature of water (e.g., hydrogen bonding). In this work, water sorption and diffusion in a number of glassy polymers were measured using gravimetric and spectroscopic techniques, including quartz spring microbalance, quartz crystal microbalance, and in situ time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian diffusion was observed in all polymers studied, indicated by an initial stage of water uptake, followed by a second stage of continuous, gradual uptake of water at later experimental times. These phenomena were attributed to diffusion driven by a concentration gradient, as well as diffusion driven by slow polymer relaxation resulting in additional water ingress over time. In order to gain additional insight into these phenomena, which are a product of nonequilibrium state of the polymers, diffusion-relaxation models were developed and employed to determine the time scales for both diffusion and polymer relaxation, where the ratio of these values (Deborah number) confirmed the observed non-Fickian water diffusion. In addition, the solubility of water in these polymers was predicted using two nonequilibrium thermodynamic models: the nonequilibrium lattice fluid (NELF) model and the nonequilibrium statistical associating fluid theory (NE-SAFT), where excellent agreement between the NE-SAFT predictions and experimental data was obtained over the entire water vapor activity range explored. Furthermore, the states of water were analyzed using the Zimm-Lundberg clustering theory, as well as in situ FTIR-ATR spectroscopy, where the latter technique provides a

  5. Coextrusion forming characteristics of novel Cu alloy/bulk metallic glass composite%新型铜合金/非晶复合材料的挤压成形特性

    Institute of Scientific and Technical Information of China (English)

    刘勇; 张丽; 郭洪民; 杨湘杰

    2011-01-01

    A novel Cu alloy/bulk metallic glass (BMG) composite was fabricated through the coextrusion process, based on the excellent thermoplastic forming characteristics of BMG in the supercooled liquid region (SLR). The Cu-based amorphous Cu40Zr44Ag8Al8 and pure Cu alloy were selected as components. The Cu alloy/BMG composite bar was easily fabricated at extrusion temperature of 703 K and extrusion speed of 0.4 mm/min. The morphology and structure of the core BMG before and after the coextrusion with Cu were characterized by optical microscopy (OM), X-ray diffractometry (XRD), differential scanning calorimetry(DSC) and microhardness(HV). The results indicate that the core BMG can reach the approximately uniform distribution of the dimension after suffering the shortly inhomogeneous distribution of the dimension in the initial stages of coextrusion. Combining the analysis of XRD, DSC and micro hardness (HV), it can be concluded that the crystallization of core BMG does not occur after the coextrusion with Cu at 703 K.%基于大块非晶在过冷液相区间具有较好的热塑性成形特点,选择铜基非晶Cu40Zr44Ag8Al8和铜合金,通过挤压成形工艺,制备出一种新型的铜合金/非晶复合材料;在703 K和挤压速度为0.4 mm/min下对该复合材料进行挤压,获得铜合金、非晶复合材料棒材.通过光学金相(OM)、X射线衍射(XRD)、示差扫描量热分析(DSC)和维氏硬度测试(HV)对挤压变形前、后芯部非晶进行形貌观察和结构分析.结果表明:芯部非晶在挤压前期呈不均匀分布,而后分布非常均匀;结合XRD、DSC和硬度的结果分析,在703 K下挤压后,芯部非晶没有发生晶化.

  6. Terbium induced glassy magnetism in La,Ca-based cobaltites

    International Nuclear Information System (INIS)

    The La0.8–xTbxCa0.2CoO3 cobaltites of orthoperovskite Pbnm structure were investigated by the X-ray and neutron diffraction, specific heat, and magnetization measurements. The terbium doping has two important effects, it increases the size disorder on perovskite A-sites and influences the magnetic properties due to large Ising-type moments (∼8.9 Bohr magnetons per Tb). The compounds show a bulk magnetic moment below TC = 82 K, 53 K, and 30 K for x = 0.1, 0.2, and 0.3, respectively. The neutron diffraction evidences a long-range ferromagnetic arrangement of cobalt moments, combined below ∼20 K with ordering of terbium moments in a canted arrangement. A homogeneous magnetic phase is proved for the x = 0.1 sample, while x = 0.2 and 0.3 are in an intrinsically non-homogeneous magnetic state with long-range ordering only comprising 55% and 30% of the sample volumes. The ac susceptibility experiments prove a glassy character of the terbium doped samples and provide arguments for the short-range ordering above TC and wide distribution of relaxation times

  7. Mo-Si alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Heatherly, L.; Wright, J.L. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  8. Effects of the Cooling Rate on the Plasticity of Pd40.5Ni40.5P19 Bulk Metallic Glasses

    International Nuclear Information System (INIS)

    We prepare Pd40.5Ni40.5P19 glassy samples with purified ingots by copper mold casting at a high cooling rate and by water quenching at a low cooling rate. Both of them exhibit different supercooled liquid regions and multiple glass transition characteristics in their differential scanning calorimetric curves. The plasticity of the glassy sample prepared by copper mold casting is about 5% while that prepared by water quenching is almost zero (0.2%), indicating that cooling rate has influenced the plasticity of glassy alloys. By using high resolution TEM image analysis, it is revealed that there exist characteristic regions with different contrasts in the full glassy samples. The characteristic size is about 20–40 nm for the glassy sample prepared by water quenching and 2–4 nm for the one prepared by copper mold casting. The large difference in the plasticity of the glassy samples prepared by different cooling rates is believed to be related to the difference in the size of the characteristic nanoscale structures. The results indicate that adjusting cooling rate in preparation of glassy samples could modify the thermal and mechanical properties of the glassy alloys. (condensed matter: structure, mechanical and thermal properties)

  9. Structure of glassy GeO2

    International Nuclear Information System (INIS)

    The full set of partial structure factors for glassy germania, or GeO2, were accurately measured by using the method of isotopic substitution in neutron diffraction in order to elucidate the nature of the pair correlations for this archetypal strong glass former. The results show that the basic tetrahedral Ge(O1/2)4 building blocks share corners with a mean inter-tetrahedral Ge-O-circumflex-Ge bond angle of 132(2)0. The topological and chemical ordering in the resultant network displays two characteristic length scales at distances greater than the nearest neighbour. One of these describes the intermediate range order, and manifests itself by the appearance of a first sharp diffraction peak in the measured diffraction patterns at a scattering vector kFSDP∼1.53 A-1, while the other describes so-called extended range order, and is associated with the principal peak at kPP = 2.66(1) A-1. We find that there is an interplay between the relative importance of the ordering on these length scales for tetrahedral network forming glasses that is dominated by the extended range ordering with increasing glass fragility. The measured partial structure factors for glassy GeO2 are used to reproduce the total structure factor measured by using high energy x-ray diffraction and the experimental results are also compared to those obtained by using classical and first principles molecular dynamics simulations

  10. Devitrification of the glassy state in suspensions of charged platelets

    NARCIS (Netherlands)

    Mourad, M.C.D.; Verhoeff, A.A.; Belov, D.V.; Petukhov, A.V.; Lekkerkerker, H.N.W.

    2009-01-01

    Colloidal suspensions of charged gibbsite platelets at salt concentrations of 10−2 M and below and with a sufficiently high particle concentration form a kinetically arrested, glassy state. We study the evolution of the glassy state in suspensions of three different gibbsite systems. Despite differe

  11. Thermal Expansion Characteristics and Thermal Conductivity of FeCo-based Bulk Amorphous Alloys%铁钴基块体非晶合金的热膨胀特性和热导率

    Institute of Scientific and Technical Information of China (English)

    陈庆军; 王健; 沈军; 周贤良; 华小珍; 董应虎

    2016-01-01

    采用真空非自耗电弧炉制备出Fe24+xCo24-xCr15Mo14C15B6Y2(x=0,2,4,6,8,at%)块体非晶合金,利用热膨胀测试仪和激光闪射热导率测试仪测量合金的热膨胀系数和热导率并与差示扫描量热曲线和高温XRD图谱进行对比,研究不同Co含量块体非晶合金的线性热膨胀行为随温度的变化规律和Co元素含量、不同组织对铁钻基块体合金热导率的影响.结果表明,随着Co含量减小,不同Co含量铁钴基非晶合金均出现规律相似的两次晶化过程,并且二次晶化起始温度依次提高.当x=0时,在875℃附近热膨胀系数出现第3个极大值点;25℃时Fe24+xCo24-xCr15Mo14C15B6Y2 (x=0,2,4,6,8)铁钴基非晶合金热导率在7.12~7.35 W/(m·K)范围内,在700℃温度退火处理的Fe24+xCo24-xCr15Mo14C15B6Y2 (x=0,2,4,6,8)铁钴基非晶合金的热导率值为7.5~9.46 W/(m·K),然而920℃退火处理后,热导率变化比较显著并出现先升高后下降的趋势.%Fe24+xCo24-xCr15Mo14C15B6Y2(x=0,2,4,6,8,at%) bulk amorphous alloys were prepared by a non-consumable arc-melting furnace.The thermal expansion coefficient and thermal conductivity of the amorphous alloy were tested by thermal expansion test instrument and laser indeed thermal conductivity tester,respectively,and the results were compared with the differential scanning calorimetry (DSC) curves and XRD patterns.Linear thermal expansion behavior with the temperature change of FeCo-based amorphous alloys with different Co contents and the effect of different Co element contents and different organizations on thermal conductivity of FeCo-base amorphous alloy were investigated.The results show that with the decrease of Co content,FeCo-base amorphous alloys have two crystallization processes,and the initial and the secondary crystallization temperature increase in turn.Thermal expansion coefficient of Fe24Co24Cr15Mo14C15B6Y2 has the third maximum point around 875 ℃.At 25 ℃,thermal conductivity of the Fe

  12. Bulk metallic glasses: A new class of engineering materials

    Indian Academy of Sciences (India)

    Joysurya Basu; S Ranganathan

    2003-06-01

    Bulk glass-forming alloys have emerged over the past fifteen years with attractive properties and technological promise. A number of alloy systems based on lanthanum, magnesium, zirconium, palladium, iron, cobalt and nickel have been discovered. Glass-forming ability depends on various factors like enthalpy of mixing, atomic size and multicomponent alloying. A number of processes is available to synthesise bulk metallic glasses. The crystallisation behaviour and mechanical properties of these alloys pose interesting scientific questions. Upon crystallisation many of these glasses transform to bulk nanocrystals and nanoquasicrystals. A detailed study of the structure and the crystallisation behaviour of glasses has enabled the elucidation of the possible atomic configuration in liquid alloys. Their crystallisation behaviour can be exploited to synthesise novel nanocomposite microstructures and their mechanical properties can be enhanced. A broad overview of the present status of the science and technology of bulk metallic glasses and their potential technological uses is presented.

  13. Developing and Characterizing Bulk Metallic Glasses for Extreme Applications

    Science.gov (United States)

    Roberts, Scott Nolan

    Metallic glasses have typically been treated as a "one size fits all" type of material. Every alloy is considered to have high strength, high hardness, large elastic limits, corrosion resistance, etc. However, similar to traditional crystalline materials, properties are strongly dependent upon the constituent elements, how it was processed, and the conditions under which it will be used. An important distinction which can be made is between metallic glasses and their composites. Charpy impact toughness measurements are performed to determine the effect processing and microstructure have on bulk metallic glass matrix composites (BMGMCs). Samples are suction cast, machined from commercial plates, and semi-solidly forged (SSF). The SSF specimens have been found to have the highest impact toughness due to the coarsening of the dendrites, which occurs during the semi-solid processing stages. Ductile to brittle transition (DTBT) temperatures are measured for a BMGMC. While at room temperature the BMGMC is highly toughened compared to a fully glassy alloy, it undergoes a DTBT by 250 K. At this point, its impact toughness mirrors that of the constituent glassy matrix. In the following chapter, BMGMCs are shown to have the capability of being capacitively welded to form single, monolithic structures. Shear measurements are performed across welded samples, and, at sufficient weld energies, are found to retain the strength of the parent alloy. Cross-sections are inspected via SEM and no visible crystallization of the matrix occurs. Next, metallic glasses and BMGMCs are formed into sheets and eggbox structures are tested in hypervelocity impacts. Metallic glasses are ideal candidates for protection against micrometeorite orbital debris due to their high hardness and relatively low density. A flat single layer, flat BMG is compared to a BMGMC eggbox and the latter creates a more diffuse projectile cloud after penetration. A three tiered eggbox structure is also tested by firing

  14. Nano-scale solute partitioning in devitrified bulk metallic glass

    International Nuclear Information System (INIS)

    Devitrification of bulk metallic glass leads to a novel microstructure, with high-density nanoscale crystalline precipitates evenly distributed in a glassy matrix. Significant chemical segregation is revealed at unprecedented detail by atom-probe tomography. This level of detail is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mystery for over a decade

  15. The microstructure and mechanical properties of Ni78Ag2P20 alloy

    Directory of Open Access Journals (Sweden)

    S. Kąc

    2007-11-01

    Full Text Available Purpose: The aim of the work was to investigate the influence of silver as a modifying constituent on structure formation in Ni-P based glass forming matrix and to characterize mechanical properties of the alloys.Design/methodology/approach: Nickel-silver-phosphorus Ni78Ag2P20 alloy was produced using arc melting in argon protective atmosphere from commercial powders. The alloy was melt spun. The microstructure of the arc melted droplet is investigated in scanning electron microscope with EDS and micro-hardness tester and the melt spun ribbon is investigated using light microscope and transmission electron microscope. Then the mechanical properties are evaluated with use of micro-hardness measurements.Findings: A strong tendency for demixing of Ni-P-rich and Ag-rich liquids is observed leading to formation of the primary structure consisting of slightly hypo-eutectic Ni-P-rich regions and Ag rich regions. The melt spinning process produced the amorphous Ni-P and Ag-rich crystalline structure. The alloys hardness and elasticity modulus were characterized. The melt spun ribbons are slightly softer than the crystalline Ni-P regions. In case of the melt spun ribbons, a softening influence of silver was observed giving the lower hardness for Ni78Ag2P20 than Ni80P20. The alloy constituents in a bulk crystalline state present the higher values of elasticity modulus when compared to the melt spun ribbons.Research limitations/implications: It has been shown that the criterion of a high positive values of mixing enthalpies can be applied to design the materials that should separate before the solidification to form a hard glassy matrix / soft crystalline composite. The amorphization of the crystalline Ni-P-based alloys can lead to formation of more flexible materials with a lower elasticity modulus and lower hardness.Practical implications: The main limits for application of the glassy alloys are the high prices of the materials used for alloying and the

  16. Simulations of Soft Glassy Matter with Ripening

    Science.gov (United States)

    Hwang, Hyun Joo; Riggleman, Robert; Crocker, John

    2015-03-01

    Soft glassy matter (SGM) such as foams, emulsions, and colloids, exhibit interesting rheological properties that have long defied explanation. In particular, the shear modulus of these materials displays weak power law frequency dependence. To understand the origin of this property in more depth, we have built a three-dimensional, modified Bubble Dynamics model. The bubbles interact with a purely repulsive harmonic potential and ripen according to diffusion-based governing equations. An energy minimizer is implemented to quasi-statically relax topological rearrangements in the system as ripening proceeds. Preliminary results show that the model displays expected intermittent particle rearrangements and a weakly frequency-dependent shear modulus behaving like a power law fluid. We find that the anomalous relaxation properties and avalanche-like nature of the rearrangements can be related to different measures of the systems potential energy landscape.

  17. How Glassy States Affect Brown Carbon Production?

    Science.gov (United States)

    Liu, P.; Li, Y.; Wang, Y.; Bateman, A. P.; Zhang, Y.; Gong, Z.; Gilles, M. K.; Martin, S. T.

    2015-12-01

    Secondary organic material (SOM) can become light-absorbing (i.e. brown carbon) via multiphase reactions with nitrogen-containing species such as ammonia and amines. The physical states of SOM, however, potentially slow the diffusion of reactant molecules in organic matrix under conditions that semisolids or solids prevail, thus inhibiting the browning reaction pathways. In this study, the physical states and the in-particle diffusivity were investigated by measuring the evaporation kinetics of both water and organics from aromatic-derived SOMs using a quartz-crystal-microbalance (QCM). The results indicate that the SOMs derived from aromatic precursors toluene and m-xylene became solid (glassy) and the in particle diffusion was significantly impeded for sufficiently low relative humidity ( urban atmospheres that ultimately influence the climate and tropospheric photochemistry.

  18. Ubiquitous ``glassy'' relaxation in catalytic reaction networks

    Science.gov (United States)

    Awazu, Akinori; Kaneko, Kunihiko

    2009-10-01

    Study of reversible catalytic reaction networks is important not only as an issue for chemical thermodynamics but also for protocells. From extensive numerical simulations and theoretical analysis, slow relaxation dynamics to sustain nonequlibrium states are commonly observed. These dynamics show two types of salient behaviors that are reminiscent of glassy behavior: slow relaxation along with the logarithmic time dependence of the correlation function and the emergence of plateaus in the relaxation-time course. The former behavior is explained by the eigenvalue distribution of a Jacobian matrix around the equilibrium state that depends on the distribution of kinetic coefficients of reactions. The latter behavior is associated with kinetic constraints rather than metastable states and is due to the absence of catalysts for chemicals in excess and the negative correlation between two chemical species. Examples are given and generality is discussed with relevance to bottleneck-type dynamics in biochemical reactions as well.

  19. Chemical isomeric effects on propanol glassy structures

    CERN Document Server

    Cuello, G J; Bermejo, F J; Cabrillo, C

    2002-01-01

    We have studied the structure of both propanol isomers in their glassy and crystalline states by neutron diffraction. The glass-transition temperatures of 1- and 2-propanol are about 98 and 115 K, respectively and, surprisingly, even larger differences are observed for the melting temperatures of the stable crystals, which are 148 and 185 K, respectively. Their supercooled liquid phases show rather different relaxation spectra, 1-propanol manifesting strong deviations from Debye behavior, whereas 2-propanol shows a far weaker effect. We discuss the spectra obtained for the static structure factor and the static pair correlation function D(r). There is a noticeable difference in the position of the first sharp diffraction peak, which clearly indicates a density change, well correlated with the period of the intermolecular oscillations shown by D(r). (orig.)

  20. Nitrogen-doping effect on glass formation and primary phase selection in Cu-Zr-Al alloys

    International Nuclear Information System (INIS)

    Research highlights: → Optimal nitrogen doping enhances the glass-forming ability of Cu49Zr44Al7 alloy. → Trace N controls the type of primary precipitate phase during solidification. → The study provides new candidates for the alloying of BMGs in improving GFA. → The study provides effective way in designing BMG composites with selective phase. - Abstract: Effects of nitrogen doping on the glass formation and primary precipitate phase in a ternary Cu-Zr-Al alloy were investigated. An optimized doping level of nitrogen (∼1000 appm) can improve the glass-forming ability of Cu49Zr44Al7 alloy. The type of primary phases from ZrCu (B2) to an unknown Zr- and Al-rich crystalline phase with chemical atomic composition of around Cu38Zr49Al13 in the bulk glassy matrix is controllable by the micro-adjustment of N concentration, which can be utilized as an effective way to design BMG-based composites with selective second phase particles.

  1. Indentation creep behaviors of Mg61Cu28Gd11 and (Mg61Cu28Gd11)99.5Sb0.5 bulk metallic glasses at room temperature

    Institute of Scientific and Technical Information of China (English)

    SUN Yingdi; LI Ziquan; LIU Jinsong; CONG Mengqi; QIN Jingya

    2011-01-01

    The room temperature creep behaviors of Mg61Cu28Gd11 and (Mg61Cu28Gd11i)99.5Sb0.5 bulk metallic glasses (BMGs) were revealed by means of nanoindentation technique. The creep mechanism was explored by characterization of creep rate sensitivity, creep compliance and retardation spectra. The results showed that the experimental creep curves could be well described by a generalized Kelvin model. The low creep rate sensitivity of both Mg-based BMGs indicated that their room temperature creep was dominated by localized shear flow. In addition, the (Mg61Cu28Gd11)99.5Sb0.5 glassy alloy exhibited lower creep rate sensitivity, creep compliance and milder retardation peak, indicating its higher creep-resistance and less relaxed state. Furthermore, the creep retardation spectrum consisted of two relatively separated peaks with the well defined characteristic relaxation times.

  2. Carbon Alloys-Multi-functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Yasuda, Eiichi [MSL, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)], E-mail: yasuda.e.aa.@m.titech.ac.jp; Enami, Takashi; Hoteida, Nobuyuki [MSL, Tokyo Institute of Technology, Yokohama 226-8503 (Japan); Lanticse-Diaz, L.J. [University of the Philippines (Philippines); Tanabe, Yasuhiro [Nagoya University (Japan); Akatsu, Takashi [MSL, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)

    2008-02-25

    Last decade after our proposal of the 'Carbon Alloys' concept, many different kinds of Carbon Alloys, such as carbon nanotubes, carbon nanofibers, graphene sheet with magnetism, semi-conducting BCN compounds, graphite intercalation compounds, exfoliated carbon fiber, etc. have been found and developed. To extend the concept further, it is important to make it into intelligent materials by incorporating multiple functions. One example of the multi-functionalization is the development of homo-atomic Carbon Alloys from glassy carbon (GC) that exhibits high electrical conductivity and low gas permeability after treatment at critical conditions. Glassy carbon underwent metamorphosis to graphite spheres at HIP condition, and improved resistance to oxidation after alloying with Ta. The other one is shape utilization of the nano-sized carbon by understanding the effect of its large surfaces or interfaces in nanotechnology treatment. Recently carbon nanofiber was produced by polymer blend technology (PB) which was proposed by Prof. A. Oya during the Carbon Alloy project and progressed into intelligent carbon nanofiber (CNF) materials. CNF is combined into the polymer composites which is a candidate material for the bipolar separator in fuel cell. The superior properties, i.e., high electrical conductivity, high modulus, high strength, etc., of the CNF is being utilized in the preparation of this polymer composite.

  3. A sorption and dilation investigation of amorphous glassy polymers and physical aging

    Science.gov (United States)

    Punsalan, David Troy

    The goal of this work was to investigate the effect of physical aging on penetrant sorption and dilation in glassy polymers. At the present time, this topic is fundamental in nature but may be relevant to previously observed declines in the productivity of polymeric gas separation membranes. Though physical aging is well known to occur in glassy polymers, it is often neglected in most contexts. However, since gas sorption and diffusion occurs on a molecular scale, reduction of unrelaxed volume due of physical aging may have a large impact on the macroscopically observed manifestations of these phenomena. In addition to experimental investigations of the effect of physical aging on the polymer-penetrant environment, various models of sorption and dilation are studied. Of the numerous models available in the literature, the theory of dual mode sorption, Sanchez-Lacombe lattice fluid equation of state and site-distribution model have previously demonstrated notable success and are applied to three polymers of varying chain flexibility: MatrimidRTM, Ultem RTM and LexanRTM (Tg = 313, 215 and 150°C respectively). Since the lattice fluid equation of state is intend for use on equilibrium media, only partial descriptions of solubility are expected. A variation of the Sanchez-Lacombe equation of state which takes into account the non-equilibrium nature of the glassy state, suitably called the Non-Equilibrium Lattice Fluid model, is also considered. In this work, the sorption and dilation data were used to study the presence of unrelaxed volume in glassy polymer materials and how it is affected by physical aging. A variety of other characterizational techniques were explored as well. Substantial changes in the sorption, dilation and CO2 partial molar volume due to physical aging were observed for bulk films of Matrimid RTM and LexanRTM, but not for Ultem RTM. Gas solubility was found to be lower in thin (ℓ = 0.1mum) MatrimidRTM films than in thick films (ℓ = 25.4mum

  4. Atmospheric pressure plasma treatment of glassy carbon for adhesion improvement

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Mortensen, Henrik Junge; Stenum, Bjarne;

    2007-01-01

    density increased with the plasma treatments. Adhesion test of the treated glassy carbon covered with cured epoxy showed cohesive failure, indicating strong bonding after the treatments. This is in contrast to the adhesion tests of untreated samples where the epoxy readily peeled off the glassy carbon.......Glassy carbon plates were treated with an atmospheric pressure dielectric barrier discharge (DBD). He gas, gas mixtures of He and reactive gases such as O2, CO2 and NH3, Ar gas and Ar/NH3 gas mixture were used as treatment gases. The oxygen and nitrogen contents on the surface as well as defect...

  5. Strain-induced softening of glassy and crystalline polymers

    International Nuclear Information System (INIS)

    The data on strain-induced softening of glassy and crystalline polymers accompanied by development of the capability of high reversible strains in the samples are analyzed. It is shown that in the first strain cycle, the test sample demonstrates properties typical of glassy or crystalline state, whereas repeated stretching induces transition into a rubber-like high-elasticity state in which the polymer is capable of high reversible strains. It is noted that this transition represents a physical basis of strain-induced softening of glassy and crystalline polymers. The bibliography includes 114 references

  6. Electrochemical and microstructural characterization of platinum supported on glassy carbon

    OpenAIRE

    Terzić Sanja; Jovanović Vladislava M.; Tripković Dušan; Kowal Andrzej; Stoch Jerzy

    2007-01-01

    The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE) for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE) for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment o...

  7. Change of glassy carbon structure and characteristics under neutron irradiation

    International Nuclear Information System (INIS)

    Results of the investigation into samples of glassy carbon SU-1300, SU-2000 after irradiation in the BOR-60 reactor at 360 - 400 Deg C are presented. It is established that the effect of significant radiation compression of the glassy carbon under irradiation retains till neutron fluence 3.6 x 1026 m-2 (E > 0.18 MeV). It is shown that radiation shrinkage is produced by shrinkage of graphite-like beds and decrease of molecular porosity. Increasing temperature of glassy carbon preparation from 1300 to 2000 Deg C tends to decrease of graphitization of the material under irradiation

  8. Glass-ceramic coated Mg-Ca alloys for biomedical implant applications.

    Science.gov (United States)

    Rau, J V; Antoniac, I; Fosca, M; De Bonis, A; Blajan, A I; Cotrut, C; Graziani, V; Curcio, M; Cricenti, A; Niculescu, M; Ortenzi, M; Teghil, R

    2016-07-01

    Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid. PMID:27127065

  9. Impedance aspect of charge storage at graphite and glassy carbon electrodes in potassium hexacyanoferrate (II redox active electrolyte

    Directory of Open Access Journals (Sweden)

    Katja Magdić

    2016-04-01

    Full Text Available Different types of charge storage mechanisms at unmodified graphite vs. glassy carbon electrodes in acid sulphate supporting solution containing potassium hexacyanoferrate (II redox active electrolyte, have been revealed by electrochemical impedance spectroscopy and supported by cyclic voltammetry experiments. Reversible charge transfer of Fe(CN63-/4- redox reaction detected by assessment of CVs of glassy carbon electrode, is in impedance spectra indicated by presence of bulk diffusion impedance and constant double-layer/pseudocapacitive electrode impedance compared to that measured in the pure supporting electrolyte. Some surface retention of redox species detected by assessment of CVs of graphite electrode is in impedance spectra indicated by diffusion impedance coupled in this case by diminishing of double-layer/pseudo­capacitive impedance compared to that measured in the pure supporting electrolyte. This phenomenon is ascribed to contribution of additional pseudocapacitive impedance generated by redox reaction of species confined at the electrode surface.

  10. A structural approach to relaxation in glassy liquids

    Science.gov (United States)

    Schoenholz, S. S.; Cubuk, E. D.; Sussman, D. M.; Kaxiras, E.; Liu, A. J.

    2016-05-01

    In contrast with crystallization, there is no noticeable structural change at the glass transition. Characteristic features of glassy dynamics that appear below an onset temperature, T0 (refs ,,), are qualitatively captured by mean field theory, which assumes uniform local structure. Studies of more realistic systems have found only weak correlations between structure and dynamics. This raises the question: is structure important to glassy dynamics in three dimensions? We answer this question affirmatively, using machine learning to identify a new field, `softness' which characterizes local structure and is strongly correlated with dynamics. We find that the onset of glassy dynamics at T0 corresponds to the onset of correlations between softness (that is, structure) and dynamics. Moreover, we construct a simple model of relaxation that agrees well with our simulation results, showing that a theory of the evolution of softness in time would constitute a theory of glassy dynamics.

  11. Metagenomics of Glassy-Winged Sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae)

    Science.gov (United States)

    A Metagenomics approach was used to identify unknown organisms which live in association with the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicadellidae). Metagenomics combines molecular biology and genetics to identify, and characterize genetic material from unique biological ...

  12. Ductile mode electrochemical oxidation assisted micromachining for glassy carbon

    International Nuclear Information System (INIS)

    Recently, a new mechanical machining process using electrochemical oxidation was reported. Electrochemical oxidation assisted micromachining was applied to the machining of glassy carbon. The material removal process of the electrochemical oxidation assisted micromachining consists of repeated cycles of oxidation followed by removal of the oxide layer. In this paper, we experimentally investigate and compare the critical chip thickness for ductile mode cutting in mechanical machining and electrochemical oxidation assisted micromachining of glassy carbon. The theoretical critical chip thickness is calculated for mechanical machining of glassy carbon and experimentally verified. The effect of electrochemical oxidation on the critical chip thickness for ductile mode micromachining is also studied for glassy carbon. It is found that the critical chip thickness is increased for the electrochemical oxidation assisted micromachining. (paper)

  13. Glassy dislocation dynamics in 2D colloidal dimer crystals.

    Science.gov (United States)

    Gerbode, Sharon J; Agarwal, Umang; Ong, Desmond C; Liddell, Chekesha M; Escobedo, Fernando; Cohen, Itai

    2010-08-13

    Although glassy relaxation is typically associated with disorder, here we report on a new type of glassy dynamics relating to dislocations within 2D crystals of colloidal dimers. Previous studies have demonstrated that dislocation motion in dimer crystals is restricted by certain particle orientations. Here, we drag an optically trapped particle through such dimer crystals, creating dislocations. We find a two-stage relaxation response where initially dislocations glide until encountering particles that cage their motion. Subsequent relaxation occurs logarithmically slowly through a second process where dislocations hop between caged configurations. Finally, in simulations of sheared dimer crystals, the dislocation mean squared displacement displays a caging plateau typical of glassy dynamics. Together, these results reveal a novel glassy system within a colloidal crystal. PMID:20868079

  14. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    OpenAIRE

    Wei Zheng; Remko van den Hurk; Yong Cao; Rongbing Du; Xuejun Sun; Yiyu Wang; McDermott, Mark T.; Stephane Evoy

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, ...

  15. Autonomic Self-Repairing Glassy Materials

    International Nuclear Information System (INIS)

    A new process that enables glassy materials to self-repair from mechanical damage is presented in this paper. Contrary to intrinsic self-healing, which involves overheating to enable crack healing by glass softening, this process is based on an extrinsic effect produced by vanadium boride (VB) particles dispersed within the glass matrix. Self-repair is obtained through the oxidation of VB particles, and thus without the need to increase the operating temperature. The VB healing agent is selected for its capacity to oxidize at a lower temperature than the softening point of the glass. Thermogravimetric analyses indeed show that VB oxidation is rapid and occurs below the glass transition temperature. Solid-state nuclear magnetic resonance spectroscopy indicates that VB is oxidized into V2O5 and B2O3, which enable the local formation of glass. The autonomic self-healing effect is demonstrated by an in situ experiment visualized using an environmental scanning electron microscope. It is shown that a crack could be healed by the VB oxidation products. (authors)

  16. SYNTHESIS OF Na-Y NANOZEOLITE ON GLASSY CARBON BY SEEDING METHOD

    Directory of Open Access Journals (Sweden)

    Hany Tovina

    2011-04-01

    Full Text Available Nanozeolite synthesis was carried out through seeding method, in which the seed was Y zeolite (member of faujasite,FAU, family using tetraethyl orto silicate (TEOS as silica source, and aluminium isopropoxide Al[(CH32CHO]3 asaluminum source, and tetramethylammoniumhydroxide (TMAOH as template, under hydrothermal condition. Theseeds then were grown on glassy carbon (GC sheet, that prior being used was modified, using layer by layer (LbLtechnique, with three layers of polyelectrolytes: Poly(diallyldimethylammoniumchloride, PDDA; Poly-4-sodiumstyrenesulfonate,PSS; and PDDA again. The seeded GC sheet then was immersed into colloidal suspension with molarcomposition as follow: 14Na2O: Al2O3: 10SiO2: 798H2O: 3Na2SO4 and the pH of the suspension was kept at 9,0 beforewas treated hydrothermally for 20 hours at 100 oC. The variation on number of seed layers on GC (1, 2 and 3 layers,observed by SEM, showed that homogenous structure and crystal size was obtained with 1 layer of seeds applied on thesurface of glassy carbon. When more layers of seeds applied, the agregation and intergrowth of zeolite crystals in thethin film of zeolite became more visible. XRD pattern of the as-prepared thin film zeolite indicates that the zeolite hasnanoparticle structure. Furthermore, the pattern of glassy carbon predominated the XRD pattern and covered the patternof Y-zeolite. On the other hand, XRD of as prepared bulk Y-zeolite shows structure of FAU framework

  17. Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing

    Science.gov (United States)

    Yoda, Shinichi

    1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8

  18. Steady-state tensile viscous flow forming of bulk metallic glass

    International Nuclear Information System (INIS)

    Highlights: ► A simple setup is demonstrated for tensile viscous flow forming of bulk metallic glass to large aspect ratio. ► The flow stress of the part of the material to be deformed is lowered thermally, by local induction heating. ► Applying the mechanical load to the less-softened ends, via attached wires, is straight forward. ► An asymmetric configuration allows to form rods into wire by a steady-state process. ► For this asymmetric configuration, preparing the preform and attaching the wires requires no machining. - Abstract: Tensile viscous flow is explored as a forming method for metallic glasses in their supercooled liquid temperature region. Bulk amorphous preforms with nominal alloy composition Zr55Cu30Al10Ni5 were produced by arc melting and tilt- and suction casting into a copper mould. A simple loading rig, in which the preform is suspended from a wire, combined with selective heating of the section to be deformed, avoids the need for complicated loading grips. Different strategies are evaluated to attach the sample to the rig and to selectively heat the central part of the specimen. Finite element models were compared with experiments to verify the design of the induction heating coil and optimize process parameters. Differential scanning calorimetry and X-ray diffraction measurements show that the material is glassy before and after deformation. The rapid decrease of flow stress with increasing temperature means that the process can be controlled thermally at constant load instead of mechanically at constant temperature. An asymmetric configuration, where the selective heating zone is moved relative to the specimen during the deformation, allows to form rods into wire by a steady-state process. The effect of deformation on induction heating under constant tension was found to be inherently self-stabilizing, reducing the need for precise process control.

  19. Cooling Rate Dependent Ellipsometry Measurements to Determine the Dynamics of Thin Glassy Films.

    Science.gov (United States)

    Glor, Ethan C; Fakhraai, Zahra

    2016-01-01

    This report aims to fully describe the experimental technique of using ellipsometry for cooling rate dependent Tg (CR-Tg) experiments. These measurements are simple high-throughput characterization experiments, which can determine the glass transition temperature (Tg), average dynamics, fragility and the expansion coefficient of the super-cooled liquid and glassy states for a variety of glassy materials. This technique allows for these parameters to be measured in a single experiment, while other methods must combine a variety of different techniques to investigate all of these properties. Measurements of dynamics close to Tg are particularly challenging. The advantage of cooling rate dependent Tg measurements over other methods which directly probe bulk and surface relaxation dynamics is that they are relatively quick and simple experiments, which do not utilize fluorophores or other complicated experimental techniques. Furthermore, this technique probes the average dynamics of technologically relevant thin films in temperature and relaxation time (τα) regimes relevant to the glass transition (τα > 100 sec). The limitation to using ellipsometry for cooling rate dependent Tg experiments is that it cannot probe relaxation times relevant to measurements of viscosity (τα film remains throughout the experiment. PMID:26863256

  20. Pareto-optimal alloys

    DEFF Research Database (Denmark)

    Bligaard, Thomas; Johannesson, Gisli Holmar; Ruban, Andrei; Skriver, Hans Lomholt; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    2003-01-01

    cost. In this letter we present a database consisting of the lattice parameters, bulk moduli, and heats of formation for over 64 000 ordered metallic alloys, which has been established by direct first-principles density-functional-theory calculations. Furthermore, we use a concept from economic theory......, the Pareto-optimal set, to determine optimal alloy solutions for the compromise between low compressibility, high stability, and cost....

  1. Containerless solidification of Zr41Ti14Cu12.5Ni10Be22.5 glass-forming alloy in drop tube

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Droplets of Zr41Ti14Cu12.5Ni10Be22.5 glass form-ing alloys with different sizes are solidified in a drop tubecontainerless processing. Glass transition behavior, crystal-lization kinetics, and the phase evolution during annealing of the Zr41Ti14Cu12.5Ni10Be22.5 glassy spheres are investigated. The experimental results indicate that the apparent activation energy of the glass transition (Eg = 435.5 kJ/mol), and the activation energy of the main crystallization reaction (Ep1 = 249.6 kJ/mol) are obviously different from those of bulk glass samples prepared by water quenched (Eg = 559.1 kJ/mol and Ep1 =192.5 kJ/mol). The difference is discussed in the view point of the atomic configuration of the liquid state of the metallic glass and nucleation mechanism.

  2. Confinement for More Space: A Larger Free Volume and Enhanced Glassy Dynamics of 2-Ethyl-1-hexanol in Nanopores.

    Science.gov (United States)

    Kipnusu, Wycliffe K; Elsayed, Mohamed; Kossack, Wilhelm; Pawlus, Sebastian; Adrjanowicz, Karolina; Tress, Martin; Mapesa, Emmanuel U; Krause-Rehberg, Reinhard; Kaminski, Kamil; Kremer, Friedrich

    2015-09-17

    Broadband dielectric spectroscopy and positron annihilation lifetime spectroscopy are employed to study the molecular dynamics and effective free volume of 2-ethyl-1-hexanol (2E1H) in the bulk state and when confined in unidirectional nanopores with average diameters of 4, 6, and 8 nm. Enhanced α-relaxations with decreasing pore diameters closer to the calorimetric glass-transition temperature (T(g)) correlate with the increase in the effective free volume. This indicates that the glassy dynamics of 2D constrained 2E1H is mainly controlled by density variation. PMID:26722745

  3. Cheap and easy modification of glassy carbon electrode for voltammetric determination of dopamine in the presence of ascorbic acid

    Directory of Open Access Journals (Sweden)

    A Naseri

    2011-10-01

    Full Text Available Background and the purpose of the study: Different methods have been proposed to modify glassy carbon electrode in order to determine dopamine (DA, as one of the most important neurotransmitters in central nervous systems of mammalian. These methods are time comsuming and in some cases expensive. In this work, a very simple and cheap pretreatment method is developed for the bare glassy carbon electrode (GCE to determine DA in the presence of Ascorbic acid (AA.   Methods: Cyclic voltammetry as an electrochemical activation procedure was used for activation of glassy carbon electrode in order to separate diffrential pulse peaks of DA and AA. The effect of different parameters such as pH for supporting electrolyte, range of potential and the number of cycles were investigated. Finally, differential pulse voltammetry was used to determine DA in the presence of AA. Results: On the activated electrode under optimum condition, anodic peak of AA shifted to negative potentials and peak current decreased, but the peak current of DA increased. The peak current was linearly proportional to the bulk concentration of DA in the range of 6.5×10-7- 1.8×10-5 mol l-1. The limit of detection was 6.2×10-7 mol l-1. Conclusion: A simple and cheap method was developed for the activation of glassy carbon electrode. It was possible to determine DA in the presence of AA on the treated electrode. The proposed method was used to determine DA in pharmacutical samples.      

  4. Solubility of gases and liquids in glassy polymers.

    Science.gov (United States)

    De Angelis, Maria Grazia; Sarti, Giulio C

    2011-01-01

    This review discusses a macroscopic thermodynamic procedure to calculate the solubility of gases, vapors, and liquids in glassy polymers that is based on the general procedure provided by the nonequilibrium thermodynamics for glassy polymers (NET-GP) method. Several examples are presented using various nonequilibrium (NE) models including lattice fluid (NELF), statistical associating fluid theory (NE-SAFT), and perturbed hard sphere chain (NE-PHSC). Particular applications illustrate the calculation of infinite-dilution solubility coefficients in different glassy polymers and the prediction of solubility isotherms for different gases and vapors in pure polymers as well as in polymer blends. The determination of model parameters is discussed, and the predictive abilities of the models are illustrated. Attention is also given to the solubility of gas mixtures and solubility isotherms in nanocomposite mixed matrices. The fractional free volume determined from solubility data can be used to correlate solute diffusivities in mixed matrices. PMID:22432612

  5. Synthesis and Characterization of Glassy Carbon Nano wires

    International Nuclear Information System (INIS)

    The advent of carbon-based micro- and nano electromechanical systems has revived the interest in glassy carbon, whose properties are relatively unknown at lower dimensions. In this paper, electrical conductivity of individual glassy carbon nano wires was measured as a function of microstructure (controlled by heat treatment temperature) and ambient temperature. The semiconducting nano wires with average diameter of 150 nm were synthesized from poly furfuryl alcohol precursors and characterized using transmission electron and Raman microscopy. DC electrical measurements made at 90 K to 450 K show very strong dependence of temperature, following mixed modes of activation energy and hopping-based conduction.

  6. Effect of neutron irradiation on properties of glassy carbon

    International Nuclear Information System (INIS)

    The gas-impermeable chemically inert glassy carbon is considered as the material for manufacturing convective tubes. Its resistance to the neutron irradiation is determined. It is shown, that low crystal structure ordering in combination with the low thermal expansion coefficient conditioned its radiation shrinkage within the range of 140-750 deg C. The glassy hydrogen samples irradiation leads to: increase in the materials density; decrease in the specific electric resistance (increase in the thermal conductivity); insignificant increase in the dynamic modulus elasticity. The radiation effects decrease with the material treatment temperature increase

  7. Changes in properties of glassy carbon as a result of radiation action

    International Nuclear Information System (INIS)

    The authors studied the changes in the physical properties of glassy carbon under the influence of neutron irradiation at various temperatures. The radiation effects on glassy carbon were compared with those of reactor graphite

  8. Glassy dynamics in condensed isolated polymer chains.

    Science.gov (United States)

    Tress, Martin; Mapesa, Emmanuel U; Kossack, Wilhelm; Kipnusu, Wycliffe K; Reiche, Manfred; Kremer, Friedrich

    2013-09-20

    In the course of miniaturization down to the nanometer scale, much remains unknown concerning how and to what extent the properties of materials are changed. To learn more about the dynamics of condensed isolated polymer chains, we used broadband dielectric spectroscopy and a capacitor with nanostructured electrodes separated by 35 nanometers. We measured the dynamic glass transition of poly(2-vinylpyridine) and found it to be bulk-like; only segments closer than 0.5 nanometer to the substrate were weakly slowed. Our approach paves the way for numerous experiments on the dynamics of isolated molecules. PMID:24052303

  9. New Class of Plastic Bulk Metallic Glass

    International Nuclear Information System (INIS)

    An intrinsic plastic Cu45Zr46Al7Ti2 bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs

  10. Crystallization of Mg-based bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    CHEN Gang; M. FERRY

    2006-01-01

    Mg-based bulk metallic glass fabricated by conventional copper mould method was aged at different temperatures. X-ray diffractometry(XRD), scanning electron microscopy(SEM), atomic force microscopy(AFM) and focused ion beam(FIB) miller were employed to examine specimens obtained under different conditions. The crystallization of Mg-based bulk metallic glass depends upon both the aging temperature and the aging time. As temperature increases or the holding time increases, the microstructure of the aged specimen varies from glassy one to crystalline one plus glassy phase and then to absolutely multiphase crystalline one. From the FIB images, it is clear that Mg-based bulk metallic glass could not only crystallize completely but also display dendrite-like growth style. From the AFM images, there are not only significant variations of microstructures but also surface morphology of specimens obtained under different conditions. It is proposed that the surface morphology varies as the treating temperature increases. The Vickers hardness of different specimens increases as the fraction of crystalline phase (s) increases.

  11. Formation of cerium-based bulk metallic glasses

    International Nuclear Information System (INIS)

    We report the formation and composition range of Ce-based bulk metallic glasses. Ternary Ce-Al-Cu(Co,Ni) glassy rods of 1-3 mm in diameter can be easily formed in a wide composition range by a conventional copper mold cast method. Substituting Ce with low-cost Ce-rich misch metal (MM), MM-Al-Cu bulk glasses with a similar high glass-forming ability (GFA) can be obtained. With minor addition of extra elements such as Fe, Co, Ni, Nb, Zn and Si, the critical diameter of the full glassy rods of the Ce-Al-Cu matrix can be markedly enhanced from 2 mm to at least 3-10 mm. It is found that the often-cited empirical criteria for bulk metallic glass formation cannot interpret the formation and the addition effect on GFA of the metallic glasses. The striking effect and mechanism of microalloying on the GFA of the metallic glasses are studied. These materials with extremely low glass transition temperatures (341-439 K, even below the boiling temperature of water) and excellent deformability at low temperatures could have potential applications

  12. Atmospheric pressure plasma treatment of glassy carbon for adhesion improvement

    DEFF Research Database (Denmark)

    Kusano, Yukihiro; Mortensen, Henrik Junge; Stenum, Bjarne; Goutianos, Stergios; Mitra, Susanta; Ghanbari-Siahkali, Afshin; Kingshott, Peter; Sørensen, Bent F.; Bindslev, Henrik

    2007-01-01

    Glassy carbon plates were treated with an atmospheric pressure dielectric barrier discharge (DBD). He gas, gas mixtures of He and reactive gases such as O2, CO2 and NH3, Ar gas and Ar/NH3 gas mixture were used as treatment gases. The oxygen and nitrogen contents on the surface as well as defect...

  13. Microscopic model of the glass transition and the glassy state

    International Nuclear Information System (INIS)

    A microscopic model of the glass transition and the glassy state is presented. It is exactly solvable, and offers a unified view of the equilibrium and non-equilibrium aspects of the glass transition. It also provides a statistical-mechanical justification of the irreversible thermodynamic models of the glass transition proposed earlier. (author)

  14. An Approach to Glassy Systems with Direct-Interaction Approximation

    Science.gov (United States)

    Takeshi, O.; Goto, S.; Matsumoto, T.; Nakahara, A.; Otsuki, M.

    The direct-interaction approximation, which is a self-consistent closure theory for calculating the correlation function of the velocity Fourier coefficients of turbulence, is applied to the nonlinear Langevin equation for glassy systems. We discuss the resultant closure equations in relation to the mode-coupling theory and the fluctuation-dissipation theorem.

  15. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    Science.gov (United States)

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  16. Shear banding and yield stress in soft glassy materials

    NARCIS (Netherlands)

    P.C.F. Møller; S. Rodts; M.A.J. Michels; D. Bonn

    2008-01-01

    Shear localization is a generic feature of flows in yield stress fluids and soft glassy materials but is incompletely understood. In the classical picture of yield stress fluids, shear banding happens because of a stress heterogeneity. Using recent developments in magnetic resonance imaging velocime

  17. Glassy carbon supercapacitor: 100,000 cycles demonstrated

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M.; Braun, A.; Schnyder, B.; Koetz, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    A 5 V glassy carbon capacitor stack was built consisting of four bipolar and two end-plate electrodes. More than 100,000 charging/discharging cycles were applied to test the stability of the double-layer capacitor. Low and high frequency resistances were measured as a function of the number of cycles. (author) 2 figs., 1 ref.

  18. Electrochemical and microstructural characterization of platinum supported on glassy carbon

    Directory of Open Access Journals (Sweden)

    Terzić Sanja

    2007-01-01

    Full Text Available The effect of the electrochemical oxidation of glassy carbon on the deposition of platinum particles and the electrocatalytic activity of platinum supported on oxidized glassy carbon were studied for methanol oxidation in H2SO4 solution. Platinum was potentiostatically deposited from H2SO4 + 6mM H2PtCl6 solution. Glassy carbon was anodically polarized in 1 M NaOH at 1.41 V (SCE for 35 and 95 s and in 0.5 M H2SO4 at 2V (SCE for 35; 95 s and 2.25 V for 35 and 95 s. Electrochemical treatment of the GC support leads to a better distribution of platinum on the substrate and has remarkable effect on the activity. The activity of the Pt/GCox electrode for methanol oxidation is larger than that of polycrystalline Pt and by more than one order of magnitude larger than that of a Pt/GC electrode. This increase in activity indicates the pronounced role of the organic residues of the GC support on the properties of Pt particles deposited on glassy carbon.

  19. Correction for Compton scattering in glassy-carbon diffraction patterns

    International Nuclear Information System (INIS)

    In a preliminary investigation reported here, it has been found that the use of Co-Ni balanced filters not only provide better monochromatization of CuKα, but is quite suitable for determining the incoherent (Compton) scattering in two Glassy-Carbon (GC) samples

  20. Glass formation in mechanical milled Ni-Ti-Zr-Sn pre-alloy powders

    International Nuclear Information System (INIS)

    Glass formation by mechanical milling was achieved in a multicomponent Ni-based alloy system. It was found that the milling time required for forming a fully glassy phase decreased with the increase in Zr content. The enhanced atomic size mismatch of constituents was responsible for the increase of glass forming ability of these alloys. The transformation from crystalline to glassy phase might be due to the destabilization of crystalline phase, induced by a combination of factors involving refinement of grain size, high pressure exerted to powders during repeated collision, and elastic mismatch energy.

  1. Advanced tensile testing methods for bulk superconductors at cryogenic temperatures

    International Nuclear Information System (INIS)

    Tensile tests of bulk high Tc superconductors at room temperature have been generally performed by gluing the bulk specimens to Al-alloy rods. Because of the difference in the coefficient of thermal expansion, thermal stresses were induced at cryogenic temperatures especially near the interface between the specimen and the rods. In this study, tensile testing methods with minimized effect of the thermal stress were tried by using specimens cut from Dy-Ba-Cu-O superconductors. These were: (1) The rod material of Al-alloy was replaced with Ti-alloy, which has the coefficient close to the bulk. (2) The interlayer made of the identical bulk superconductor was inserted between the specimen and the Ti-alloy rod. The nominal tensile strength at the liquid nitrogen temperature (LNT) of the specimen glued to the Ti-alloy rods was significantly higher than that glued to the Al-alloy rods. The application of the interlayers increased the strength significantly. The FEM analysis showed that the thermal tensile stress component in the direction of loading axis within the specimen at LNT is markedly reduced by the method (1) and substantially eliminated in the method (2)

  2. Particle size dependent isothermal crystallization kinetics in a Se–Te glassy system

    Energy Technology Data Exchange (ETDEWEB)

    Svoboda, Roman, E-mail: roman.svoboda@upce.cz; Málek, Jiří

    2015-06-20

    Highlights: • Influence of particle size on isothermal crystallization of Se–Te glasses was studied by DSC. • Nature of the crystallization complexity was revealed by deconvolution procedure. • Overlapping competing surface and bulk nucleation-growth mechanisms were identified. • Presence of the A and B types of spherulitic crystallites was confirmed by DSC. • Increasing tellurium content leads to an increase of the apparent activation energy. - Abstract: Differential scanning calorimetry (DSC) was used to study the crystallization behaviour in a selenium–tellurium (Se–Te) glassy system under isothermal conditions. The particle-size-dependent isothermal crystallization kinetics were described in terms of the Johnson–Mehl–Avrami (JMA) nucleation-growth model. The complexity of the crystallization process was found to be represented by overlapping competing surface and bulk nucleation-growth mechanisms. Based on the deconvolution in terms of the JMA model, the particular crystal growth processes were identified, and the interpretation of their physical origins was performed. Presence of the A and B types of spherulitic crystallites was confirmed; the temperature range of the transition in-between these two spherulitic forms was determined to be similar as for pure selenium. Increasing tellurium content was found to cause an increase of the apparent activation energy of the overall crystallization process as well as a gradual increase of the dominance of the CNT (classical nucleation theory)-based volume-located crystal growth over the surface crystallization, which originates from mechanically induced heterogeneities.

  3. Electrochemical stability of citrate-capped gold nanoparticles electrostatically assembled on amine-modified glassy carbon

    International Nuclear Information System (INIS)

    The stability of citrate-capped gold nanoparticles assembled on covalently attached ethylenediamine films on glassy carbon was probed using cyclic voltammetry and scanning electron microscopy. The accessible potential windows in 0.01 M HClO4 and phosphate buffer (pH 7.4) were found to be very similar to those for re-constructed polycrystalline bulk gold. At the nanoparticle electrodes, gold is dissolved at high positive potentials and re-deposited at lower potentials resulting in the formation of fewer, larger particles. The electrografted amine layer does not limit the stability range and citrate-capping groups do not stabilise the nanoparticles to oxidation. In addition to the structural stability of the nanoparticle electrodes, preliminary investigations of the stability of their activity for voltammetric analyses were also undertaken. Repeated voltammetric reduction of H2O2 at the nanoparticle electrodes showed excellent reproducibility indicating that the nanoparticle surface maintained a constant activity for the redox process. In contrast, a re-constructed polycrystalline bulk gold electrode did not exhibit a stable response under the same conditions.

  4. Electrodeposited NiCu Alloy Catalysts for Glucose Oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Jieun; Park, Hansoo; Kim, Sookil [Chung-Ang Univ., Seoul (Korea, Republic of); Ahn, Sang Hyun; Jang, Jong Hyun [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2014-07-15

    NiCu alloys have been suggested as potential candidates for catalysts in glucose oxidation. In this study, NiCu alloys with different compositions were prepared on a glassy carbon substrate by changing the electrodeposition potential to examine the effect of Ni/Cu ratios in alloys on catalytic activity toward glucose oxidation. Cyclic voltammetry and chronoamperometry showed that NiCu alloys had higher catalytic activity than pure Ni and Cu catalysts. Especially, Ni{sub 59}Cu{sub 41} had superior catalytic activity, which was about twice that of Ni at a given oxidation potential. X-ray analyses showed that the oxidation state of Ni in NiCu alloys was increased with the content of Cu by lattice expansion. Ni components in alloys with higher oxidation state were more effective in the oxidation of glucose.

  5. Electrodeposited NiCu Alloy Catalysts for Glucose Oxidation

    International Nuclear Information System (INIS)

    NiCu alloys have been suggested as potential candidates for catalysts in glucose oxidation. In this study, NiCu alloys with different compositions were prepared on a glassy carbon substrate by changing the electrodeposition potential to examine the effect of Ni/Cu ratios in alloys on catalytic activity toward glucose oxidation. Cyclic voltammetry and chronoamperometry showed that NiCu alloys had higher catalytic activity than pure Ni and Cu catalysts. Especially, Ni59Cu41 had superior catalytic activity, which was about twice that of Ni at a given oxidation potential. X-ray analyses showed that the oxidation state of Ni in NiCu alloys was increased with the content of Cu by lattice expansion. Ni components in alloys with higher oxidation state were more effective in the oxidation of glucose

  6. 2H NMR studies of supercooled and glassy aspirin

    Science.gov (United States)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  7. Loss of halogens from crystallized and glassy silicic volcanic rocks

    Science.gov (United States)

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  8. Photo-triggered wrinkling of glassy nematic films

    International Nuclear Information System (INIS)

    A linear analysis is performed to explore the stability of an azobenzene-containing glassy nematic film on a soft elastic foundation under uniform illumination by UV light. It is found that the film can buckle to form wrinkles when the light intensity and the geometric and material parameters of the system are properly chosen. The results may help in the fabrication of photo-triggered wrinkled surfaces which are particularly attractive for applications where remote addressing is desired. (paper)

  9. Enhanced Thermal Transport through Soft Glassy Nano-disc Paste

    OpenAIRE

    Bhandari, Susheel S.; Muralidhar, K; Joshi, Yogesh M

    2013-01-01

    We study diffusion of heat in an aqueous suspension of disc shaped nanoparticles of Laponite, which has finite elasticity and paste-like consistency, by using the Mach-Zehnder interferometer. We estimate the thermal diffusivity of the suspension by comparing the experimentally obtained temperature distribution to that with analytical solution. We observe that despite highly constrained Brownian diffusivity of particles owing to its soft glassy nature, suspensions at very small concentrations ...

  10. Solubility, diffusivity and permeability of gases in glassy polymers

    OpenAIRE

    Gemeda, Aweke Elias

    2015-01-01

    Gas separation membranes of high CO2 permeability and selectivity have great potential in both natural gas sweetening and carbon dioxide capture. Many modified PIM membranes results permselectivity above Robinson upper bound. The big problem that should be solved for these polymers to be commercialized is their aging through time. In high glassy polymeric membrane such as PIM-1 and its modifications, solubility selectivity has more contribution towards permselectivity than diffusivity sel...

  11. Surface characterization of silver and palladium modified glassy carbon

    Indian Academy of Sciences (India)

    Aleksandra A Perić-Grujić; Olivera M Nešković; Miomir V Veljković; Zoran V Laušević; Mila D Laušević

    2007-12-01

    In this work, the influence of silver and palladium on the surface of undoped, boron doped and phosphorus doped glassy carbon has been studied. The silver and palladium concentrations in solution, after metal deposition, were measured by atomic absorption spectrophotometer. The morphology of metal coatings was characterized by scanning electron microscopy. In order to investigate the nature and thermal stability of surface oxygen groups, temperature-programmed desorption method combined with mass spectrometric analyses, was performed. The results obtained have shown that silver and palladium spontaneously deposit from their salt solutions at the surface of glassy carbon samples. Silver deposits have dendrite structure, whilst palladium forms separate clusters. The highest amount of both silver and palladium deposits at the surface of sample containing the highest quantity of surface oxide complexes. It has been concluded that carboxyl groups and structure defects are responsible for metal reduction. Calculated desorption energies have shown that the surface modification by metal deposition leads to the formation of more stable surface of undoped and doped glassy carbon samples.

  12. Exploration for facultative endosymbionts of glassy-wingedsharpshooter (Hemiptera: Cicadellidae)

    Energy Technology Data Exchange (ETDEWEB)

    Montllor-Curley, C.; Brodie, E.L.; Lechner, M.G.; Purcell, A.H.

    2006-07-01

    Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae),glassy-winged sharpshooter, was collected in California and severalstates in the southeastern United States in 2002 and 2003 and analyzedfor endosymbiotic bacteria. Hemolymph, eggs, and bacteriomes wereexamined for the presence of bacteria by polymerase chain reaction. Asubset of hemolymph and egg samples had their 16S rRNA gene ampliconscloned and sequenced or analyzed by restriction digest patterns ofsamples compared with known bacterial DNA. Baumannia cicadellinicola, oneof the primary symbionts of glassy-winged sharpshooter, was found in themajority of hemolymph samples, although it has been considered until nowto reside primarily inside the specialized host bacteriocytes. Wolbachiasp., a common secondary symbiont in many insect taxa investigated todate, was the second most frequently detected bacterium in hemolymphsamples. In addition, we detected bacteria that were most closely related(by 16S rRNA gene sequence) to Pseudomonas, Stenotrophomonas, andAcinetobacter in hemolymph samples of one and/or two glassy-wingedsharpshooters, but their origin is uncertain.

  13. Quasi-equilibrium in glassy dynamics: a liquid theory approach

    International Nuclear Information System (INIS)

    We introduce a quasi-equilibrium formalism in the theory of liquids in order to obtain a set of coarse grained dynamical equations for the description of long time glassy relaxation. Our scheme allows to use typical approximations devised for equilibrium to study glassy dynamics. After introducing dynamical Ornstein–Zernike relations, we focus on the hypernetted chain (HNC) approximation and a recent closure scheme developed by Szamel. In both cases we get dynamical equations that have the structure of the mode-coupling theory (MCT) equations in the long time regime. The HNC approach, that was so far used to get equilibrium quantities is thus generalized to a fully consistent scheme where long-time dynamic quantities can also be computed. In the context of this approximation we get an asymptotic description of both equilibrium glassy dynamics at high temperature and of aging dynamics at low temperature. The Szamel approximation on the other hand is shown to lead to the canonical MCT equations obtained by Götze for equilibrium dynamics. We clarify the way phase space is sampled according to MCT during dynamical relaxation. (fast track communication)

  14. Non-Equilibrium Water-Glassy Polymer Dynamics

    Science.gov (United States)

    Davis, Eric; Minelli, Matteo; Baschetti, Marco; Sarti, Giulio; Elabd, Yossef

    2012-02-01

    For many applications (e.g., medical implants, packaging), an accurate assessment and fundamental understanding of the dynamics of water-glassy polymer interactions is of great interest. In this study, sorption and diffusion of pure water in several glassy polymers films, such as poly(styrene) (PS), poly(methyl methacrylate) (PMMA), poly(lactide) (PLA), were measured over a wide range of vapor activities and temperatures using several experimental techniques, including quartz spring microbalance (QSM), quartz crystal microbalance (QCM), and time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. Non-Fickian behavior (diffusion-relaxation phenomena) was observed by all three techniques, while FTIR-ATR spectroscopy also provides information about the distribution of the states of water and water transport mechanisms on a molecular-level. Specifically, the states of water are significantly different in PS compared to PMMA and PLA. Additionally, a purely predictive non-equilibrium lattice fluid (NELF) model was applied to predict the sorption isotherms of water in these glassy polymers.

  15. Molecular mechanisms of deformation and failure in glassy materials

    Science.gov (United States)

    Rottler, Joerg

    2004-03-01

    Understanding the molecular origins of macroscopic mechanical properties is a fundamental scientific challenge. Fracture of both amorphous and crystalline materials involves many length scales reaching from the continuum to atomic level processes near a crack tip. Using molecular simulations of simple models for amorphous glassy materials, we first study elastoplastic deformation and discuss the nature of the shear yield stress and its dependence on loading conditions, strain rate and temperature. We then focus on the deformation of glassy polymeric systems into crazes at large strains. In the craze, polymers ( 0.5 nm diameter) are bundled into an intricate network of 10 nm diameter fibrils that extends 10 micrometers on either side of a mm crack tip. Analysis of local geometry and stresses provide insight into the real-space nature of the entanglements that control craze formation as well as melt dynamics. Crazes are also shown to share many features with jammed systems such as granular media and foams, but are unique in jamming under a tensile load. This allows explanations for the exponential force distribution in jammed systems to be tested. The force distribution strongly influences the ultimate breakdown of the craze fibrils either through disentanglement or chain scission. We conclude by quantifying the contribution of crazing to the unusually large fracture energy of glassy polymers.

  16. Retardation of Bulk Water Dynamics by Disaccharide Osmolytes

    CERN Document Server

    Shukla, Nimesh; Chen, Lee; Chergui, Majed; Othon, Christina M

    2016-01-01

    The bioprotective nature of disaccharides is hypothesized to derive from the modification of the hydrogen bonding network of water which protects biomolecules through lowered water activity at the protein interface. Using ultrafast fluorescence spectroscopy we measured the relaxation of bulk water dynamics around the induced dipole moment of two fluorescent probes (Lucifer Yellow Ethylenediamine and Tryptophan). Our results indicate a reduction in bulk water reorganization rate of approximately of 30%. We observe this retardation in the low concentration regime measured at 0.1M and 0.25 M, far below the onset of glassy dynamics. This reduction in water activity could be significant in crowded biological systems, contributing to global change in protein energy landscape, resulting in a significant enhancement of protein stability under environmental stress. We observed similar dynamic reduction for two disaccharide osmolytes, sucrose and trehalose, with trehalose being the more effective dynamic reducer.

  17. Investigation of glassy state molecular motions in thermoset polymers

    Science.gov (United States)

    Tu, Jianwei

    This dissertation presents the investigation of the glassy state molecular motions in isomeric thermoset epoxies by means of solid-state deuterium (2H) NMR spectroscopy technique. The network structure of crosslinked epoxies was altered through monomer isomerism; specifically, diglycidyl ether of bisphenol A (DGEBA) was cured with isomeric amine curatives, i.e., the meta-substituted diaminodiphenylsulfone (33DDS) and para-substituted diaminodiphenylsulfone (44DDS). The use of structural isomerism provided a path way for altering macroscopic material properties while maintaining identical chemical composition within the crosslinked networks. The effects of structural isomerism on the glassy state molecular motions were studied using solid-state 2H NMR spectroscopy, which offers unrivaled power to monitor site-specific molecular motions. Three distinctive molecular groups on each isomeric network, i.e., the phenylene rings in the bisphenol A structure (BPA), the phenylene rings in the diaminodiphenylsulfone structure (DDS), and the hydroxypropoyl ether group (HPE) have been selectively deuterated for a comprehensive study of the structure-dynamics- property relationships in thermoset epoxies. Quadrupolar echo experiments and line shape simulations were employed as the main research approach to gain both qualitative and quantitative motional information of the epoxy networks in the glassy state. Quantitative information on the geometry and rate of the molecular motions allows the elucidation of the relationship between molecular motions and macro physical properties and the role of these motions in the mechanical relaxation. Specifically, it is revealed that both the BPA and HPE moieties in the isomeric networks have almost identical behaviors in the deep glassy state, which indicates that the molecular motions in the glassy state are localized, and the correlation length of the motions does not exceed the length of the DGEBA repeat unit. BPA ring motions contribute

  18. Effect of Co on the microstructure, magnetic properties and thermal stability of bulk Fe{sub 73-x}Co{sub x}Nb{sub 5}Y{sub 3}B{sub 19} (where x = 0 or 10) amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nabialek, Marcin G., E-mail: nmarcell@wp.pl [Institute of Physics, Czestochowa University of Technology, 19 Armii Krajowej Av., 42-200 Czestochowa (Poland); Szota, Michal [Institute of Materials Engineering, Czestochowa University of Technology, 19 Armii Krajowej Av., 42-200 Czestochowa (Poland); Dospial, Marcin J. [Institute of Physics, Czestochowa University of Technology, 19 Armii Krajowej Av., 42-200 Czestochowa (Poland)

    2012-06-15

    Highlights: Black-Right-Pointing-Pointer The paper presents the results of structure, thermal stability and magnetic properties of Fe{sub 73-x}Co{sub x}Nb{sub 5}Y{sub 3}B{sub 19} (where x = 0 or 10) bulk amorphous alloys in the as-cast state in the form of plates with a thickness of 0.5 mm and an area of 100 mm{sup 2}. Black-Right-Pointing-Pointer Results of this study indicate that despite the negative effect of exchange of Fe onto Co, what results in decrease of the saturation of magnetization, Curie temperature and thermal stability, it is clear that such a slight deterioration of these parameters is compensated with a significant reduction of the coercivity field values. Black-Right-Pointing-Pointer What testify that amorphous alloys with the addition of Co can be successfully used as magnetic cores in modern medium power transformers. - Abstract: The paper presents the results of structure, thermal stability and magnetic properties of bulk Fe{sub 73-x}Co{sub x}Nb{sub 5}Y{sub 3}B{sub 19} (where x = 0 or 10) amorphous alloys in the as-cast state, in the form of 0.5 mm thick plates with an area of 100 mm{sup 2}. The amorphous structure of the investigated alloys was confirmed by studies of Moessbauer effect and X-ray diffractometry. On the basis of measurements performed using a vibrating sample magnetometer (VSM), it was found that substituting 10% of Fe with Co in Fe{sub 73-x}Co{sub x}Nb{sub 5}Y{sub 3}B{sub 19} alloy, had only a small effect on the value of saturation magnetization ({mu}{sub 0}M{sub S}), and was of the same importance in terms of the values of the coercivity field (H{sub C}) and the Curie temperature (T{sub C}). The magnetization for both samples increases in high magnetic fields due to rotation of magnetic moments near the structural defects called quasidislocalised dipoles, near the area known as the approach to ferromagnetic saturation. For field values with a linear relationship ({mu}{sub 0}H){sup -1} of the reduced saturation magnetization

  19. Dynamics of nanoscale ripple relaxation on alloy surfaces.

    Science.gov (United States)

    Ramasubramaniam, Ashwin; Shenoy, Vivek B

    2008-02-01

    As an alloy surface evolves under capillary forces, differing mobilities of the individual components can lead to kinetic alloy decomposition at the surface. In this paper, we address the relaxation of nanoscale sinusoidal ripples on alloy surfaces by considering the effects of both surface and bulk diffusion. In the absence of bulk diffusion, we derive exact analytical expressions for relaxation rates and identify two natural time scales that govern the relaxation dynamics. Bulk diffusion is shown to reduce kinetic surface segregation and enhance relaxation rates, owing to intermixing near the surface. Our results provide a quantitative framework for the interpretation of relaxation experiments on alloy surfaces. PMID:18352033

  20. Blue-light activated rapid polymerization for defect-free bulk Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC) crosslinked networks.

    Science.gov (United States)

    Shete, Abhishek U; El-Zaatari, Bassil M; French, Jonathan M; Kloxin, Christopher J

    2016-08-18

    A visible-light (470 nm wavelength) sensitive Type II photoinitiator system is developed for bulk Cu(i)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions in crosslinked networks. The accelerated photopolymerization eliminates UV-mediated azide decomposition allowing for the formation of defect-free glassy networks which exhibit a narrow glass transition temperature. PMID:27499057

  1. Enthalpy and Mechanical Relaxation of Glassy Gelatin Films

    Directory of Open Access Journals (Sweden)

    F Badii

    2005-10-01

    Full Text Available Glassy materials are not thermodynamically stable and during storage below the glass transition temperature (Tg, they are subjected to the time dependent changes towards the equilibrium. These changes are known as physical ageing, which is the basic feature of glassy materials below Tg. During ageing process, physical properties such as enthalpy and volume decrease and these changes are accompanied by important changes in mechanical properties such as change to modulus, compliance and mechanical relaxation, which are of great technological importance. The aim of this study is to investigate the occurrence of the mechanical relaxation in the glassy gelatin and compare it to the enthalpy relaxation phenomenon and try to correlate the rate of mechanical relaxation to the rate of enthalpy relaxation, which is the more reliable and frequent way for studying physical ageing. The extent of enthalpy relaxation of gelatin films with different water contents of 8%, 12 and 17%, measured by differential scanning calorimetry (DSC, was found to increase with increasing the ageing time. The mechanical behaviour of the gelatin films was measured, using dynamic mechanical thermal analysis (DMTA. The mechanical behaviour of gelatin showed time and frequency-dependent changes. Storage modulus increased during isothermal ageing and gelatin became harder and stiffer at higher frequency than that at low frequency. In order to assess the rate of mechanical relaxation, the classical time-ageing time superposition was applied to the results. The rate and extent of mechanical ageing were increased at higher water contents. A good agreement was found between the rate of the enthalpy relaxation and the changes to the mechanical properties at different water contents, suggesting that DSC measurements of enthalpy relaxation, which can be more easily implemented, can be used as indicator of mechanical changes.

  2. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    International Nuclear Information System (INIS)

    Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models

  3. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Shpotyuk, O. [Scientific Research Company “Carat” (Ukraine); Kozyukhin, S. A., E-mail: sergkoz@igic.ras.ru [Russian Academy of Sciences, Kurnakov Institute of General and Inorganic Chemistry (Russian Federation); Shpotyuk, M. [Scientific Research Company “Carat” (Ukraine); Ingram, A. [Opole Technical University (Poland); Szatanik, R. [Opole University (Poland)

    2015-03-15

    Using As{sub 2}S{sub 3} and AsS{sub 2} glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

  4. Ion implantation inhibits cell attachment to glassy polymeric carbon

    International Nuclear Information System (INIS)

    Implantation of MeV gold, oxygen, carbon ions into GPC alters the surface topography of GPC and enhances the already strong tendency for cells to attach to GPC. We have shown that implantation of silver ions near the surface strongly inhibits cell growth on GPC. Both enhanced adhesion of and inhibition of cell growth are desirable improvements on cardiac implants that have long been successfully fabricated from biocompatible glassy polymeric carbon (GPC). In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that ion beam assisted deposition (IBAD) of silver, as well as silver ion bombardment, can favorably influence the surface of GPC for biomedical applications

  5. Voltammetric determination of europium (III) at glassy carbon electrode

    International Nuclear Information System (INIS)

    The present studies are aimed to look into the suitability of solid electrodes for voltammetric determination of europium. The voltammetric results at glassy carbon electrode are compared with those at hanging mercury drop electrode. Electrode process at GCE is quasi reversible and going towards irreversibility at higher scan rates. The transfer coefficient (α.na) and diffusion coefficient (D) and rate constant of heterogenous charge transfer (Ks). Linear sweep voltammetric technique was found to be suitable for trace level determination of europium in aqueous matrices. (author)

  6. Bulk ordering and surface segregation in Ni50Pt50

    DEFF Research Database (Denmark)

    Pourovskii, L.P.; Ruban, Andrei; Abrikosov, I.A.;

    2001-01-01

    in the bulk compare well with experimental data. The surface-alloy compositions for the (111) and (110) facets above the ordering transition temperature are also found to be in a good agreement with experiments. It is demonstrated that the segregation profile at the (110) surface of NiPt is mainly caused...

  7. Nickel hydroxide nanocrystals-modified glassy carbon electrodes for sensitive L-histidine detection

    International Nuclear Information System (INIS)

    Highlights: •Hourglass-like Ni(OH)2 was prepared via a simple and facile route in solution. •The sensor has a detection limit of 80 nM. •The sensor shows much better catalytic performance compared with bulk material. •The sensor shows a great potential for practicable applications. -- Abstract: Hourglass-like nickel hydroxide nanostructure was synthesized via a simple and facile route in solution. The as-prepared nickel hydroxide nanocrystals were characterized by X-ray diffraction (XRD), scanning electronmicroscope (SEM) and transmission electron microscopy (TEM) for the morphology study. The TEM experimental data indicate that the growth of hourglass-like nanocrystal is along the c axis of β-Ni(OH)2. The composites had a good electron transferring and biocompatibility. The L-histidine biosensor was fabricated by drop casting the Ni(OH)2/ethanol solution (2.5 g L−1) on the surface of the glassy carbon electrode (GCE). The prepared biosensor shows better catalytic performance compared with bulk material or other similar materials, with the detection limit of 80 nM and the linear range from 0.1 μM to 0.5 mM (R2 = 0.993) in a 0.1 M NaOH solution. The effects of electroactive interferents at the test conditions can be negligible which showed an excellent selectivity of the biosensor. The proposed method was also successfully applied for the determination of L-histidine in human blood serum sample. High sensitivity, excellent selectivity and ease of preparation make this sensor promising for the applications in the development of detecting some other amino acids and proteins

  8. A Study of the effect of gamma radiation on some alloy materials for use as dosimetry systems and its applications

    International Nuclear Information System (INIS)

    Alloys are metallic materials consisting of two or more elements combined in such a way that they cannot be readily separated by physical means. More than 90% of metals used are in the form of alloys. Alloys can be divided into two types: ferrous and non- ferrous. In metallurgy, a nonferrous metal is any metal that is not ferrous, including alloys, that does not contain iron in appreciable amounts. Groups of inorganic glassy materials which always contain one or more of the chalcogen elements S, Se or Te, in conjunction with more electropositive elements as As, Sb and Bi, are recognized as chalcogenide glasses but Ferroalloy refers to various alloys of iron with a high proportion of one or more other elements, for example ferrotitanium alloy. Chalcogenide glasses are generally less robust, more weakly bonded materials than oxide glasses. Glasses were prepared from Ge, Se, As and Te elements with purity 99.999%.These glasses are reactive at high temperature with oxygen. Therefore, synthesis was accomplished in evacuated clean silica tubes. The tubes were washed by distilled water, and then dried in a furnace whose temperature was about 100 degree C. The weighted materials were introduced into the cleaned silica tubes and then evacuated to about 10-4 torr and sealed. The sealed tubes were placed inside the furnace and the temperature of the furnace was raised gradually up to 900 degree C within 1 hour and kept constant for 10 hours. Moreover, shaking of the constituent materials inside the tube in the furnace was necessary for realizing the homogeneity of the composition. After synthesis, the tube was quenched into ice water. The glassy ingots could be obtained by drastic quenching. Then materials were removed from the tubes and kept in dry atmosphere. Thin films of the selected compositions were prepared by thermal evaporation technique under vacuum 10-4 torr with constant thickness 100 nm. Ferrotitanium alloy is prepared by the reduction of rutile and ilmenite ores

  9. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses.

    Science.gov (United States)

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc metals and most alloys are typically poor glass-formers with large Rc > 10(10) K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness. PMID:26567672

  10. Structural and spectroscopic studies of a commercial glassy carbon

    International Nuclear Information System (INIS)

    Highlights: • Structural and spectroscopic probes show that glassy carbon is very like amorphous carbon. • No evidence for fullerene-like material being present to a significant extent. • A small quantity of water is trapped in the network and may account for batch-to-batch variation in properties. - Abstract: Glassy carbon is a form of carbon made by heating a phenolic resin to high temperature in an inert atmosphere. It has been suggested that it is composed of fullerene-like structures. The aim of the present work was to characterize the material using both structural (neutron diffraction and transmission electron microscopy) and spectroscopic (inelastic neutron scattering, Raman and X-ray photoelectron spectroscopies) methods. We find no evidence to support the suggestion of fullerene-like material being present to a significant extent, rather the model that emerges from all of the techniques is that the material is very like amorphous carbon, consisting of regions of small graphite-like basic structural units of partly stacked but mismatched structure with the edges terminated by hydrogen or hydroxyls. We do find evidence for the presence of a small quantity of water trapped in the network and suggest that this may account for batch-to-batch variation in properties that may occur

  11. Modeling VOC Sorption and Transport in Glassy Polymeric Membranes

    Science.gov (United States)

    De Angelis, Maria Grazia; Olivieri, Luca; Sarti, G. C.

    2010-06-01

    In this work we evaluated the sorption, diffusion and permeation of a series of volatile organic compounds (VOCs) (acetone, n-butane, n-pentane, n-hexane, ethanol, methanol, chloroform and toluene) into glassy polymers of increasing fractional free volume (FFV): Polycarbonate (PC), Amorphous Teflon AF1600 and AF2400, poly-trimethylsilyl norbornene (PTMSN) and poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Based on some experimental data of sorption and diffusion, and on theoretical and empirical models for the solubility and diffusion coefficients, the permeability for vapor/N2 mixtures was evaluated. These parameters are useful for the membrane separation processes and for other applications such as chemical sensors. The ideal separation factors of glassy polymeric membranes versus mixtures of VOCs and N2 were estimated at various pressures and compositions and at 25° C. The selectivity vs. permeability maps for the mixtures considered were plotted, showing that some of these materials show potentially the same selective ability of rubbery polymeric films. In particular it is shown that, the higher the FFV, the better the vapor/gas selectivity.

  12. Structural and spectroscopic studies of a commercial glassy carbon

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Stewart F., E-mail: stewart.parker@stfc.ac.uk [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Imberti, Silvia; Callear, Samantha K. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Albers, Peter W. [AQura GmbH, AQ-EM, Rodenbacher Chaussee 4, D-63457 Hanau (Germany)

    2013-12-12

    Highlights: • Structural and spectroscopic probes show that glassy carbon is very like amorphous carbon. • No evidence for fullerene-like material being present to a significant extent. • A small quantity of water is trapped in the network and may account for batch-to-batch variation in properties. - Abstract: Glassy carbon is a form of carbon made by heating a phenolic resin to high temperature in an inert atmosphere. It has been suggested that it is composed of fullerene-like structures. The aim of the present work was to characterize the material using both structural (neutron diffraction and transmission electron microscopy) and spectroscopic (inelastic neutron scattering, Raman and X-ray photoelectron spectroscopies) methods. We find no evidence to support the suggestion of fullerene-like material being present to a significant extent, rather the model that emerges from all of the techniques is that the material is very like amorphous carbon, consisting of regions of small graphite-like basic structural units of partly stacked but mismatched structure with the edges terminated by hydrogen or hydroxyls. We do find evidence for the presence of a small quantity of water trapped in the network and suggest that this may account for batch-to-batch variation in properties that may occur.

  13. Complex networks and glassy dynamics: walks in the energy landscape

    International Nuclear Information System (INIS)

    We present a simple mathematical framework for the description of the dynamics of glassy systems in terms of a random walk in a complex energy landscape pictured as a network of minima. We show how to use the tools developed for the study of dynamical processes on complex networks, in order to go beyond mean-field models that consider that all minima are connected to each other. We consider several possibilities for the rates of transitions between minima, and show that in all cases the existence of a glassy phase depends on a delicate interplay between the network's topology and the relationship between the energy and degree of a minimum. Interestingly, the network's degree correlations and the details of the transition rates do not play any role in the existence (or in the value) of the transition temperature, but have an impact only on more involved properties. For Glauber or Metropolis rates in particular, we find that the low temperature phase can be further divided into two regions with different scaling properties of the average trapping time. Overall, our results rationalize and link the empirical findings concerning correlations between the energies of the minima and their degrees, and should stimulate further investigations on this issue

  14. Use of glassy carbon as a working electrode in controlled potential coulometry.

    Science.gov (United States)

    Plock, C E; Vasquez, J

    1969-11-01

    Glassy carbon has been used as the working electrode in controlled potential coulometry. The results of coulometric investigations of chromium, copper, iron, uranium and neptunium are compared with results obtained with platinum or mercury working electrodes. The accuracy of results with the glassy carbon electrode compares favourably with the results obtainable with the other electrodes, but the precision is poorer. PMID:18960665

  15. Evaluation of grapevine as a host for the glassy-winged sharpshooter

    Science.gov (United States)

    Grapevine was evaluated as a feeding and oviposition host for the glassy-winged sharpshooter. Two sets of experiments were conducted. The first set compared performance and preference of glassy-winged sharpshooter females for grapevine (cv. Chardonnay) versus cowpea (Vigna unguiculata cultivar black...

  16. Heterogeneous nucleation of ice particles on glassy aerosols modifies TTL cirrus

    Science.gov (United States)

    Wilson, T. W.; Murray, B. J.; Dobbie, S.; Al-Jumur, S. M.; Cui, Z.; Wagner, R.; Moehler, O.; Schnaiter, M.; Benz, S.; Niemand, M.; Saathoff, H.; Skrotzki, J.; Ebert, V.; Wagner, S.; Karcher, B.

    2010-12-01

    Experiments at the AIDA chamber, Karlsruhe Institute of Technology, have shown that glassy aqueous citric acid aerosol can nucleate ice at temperatures relevant to the tropical tropopause layer (TTL)(1). Modelling suggests this new route to the formation of TTL cirrus can provide an explanation for the very low ice particle number density observed in cirrus clouds in this region and may lead to high in-cloud supersaturations(1). Nucleation of ice on glassy aerosol is consistent with the absence of traditional ice nuclei in sampled TTL cirrus residue(2). In addition, we will present new data from experiments performed in July 2010 at the AIDA chamber using glassy aerosols composed of other atmospherically relevant compounds (levoglucosan, raffinose) and an internal mixture of five dicarboxylic acids and ammonium sulphate (raffinose/M5AS)(3). All four systems tested nucleate ice when in a glassy state. This indicates that heterogeneous ice nucleation is a general property of glassy aerosols and that natural aerosols which are composed of similar molecules will also nucleate ice if glassy. Glassy aqueous levoglucosan and raffinose/M5AS aerosol nucleated ice at temperatures similar to those found for glassy aqueous citric acid aerosol (<202 K). Whereas raffinose, which forms a glass at much higher temperatures, nucleated ice heterogeneously at up to ~220 K. This activity at higher temperatures suggests that ice nucleation by glassy aerosol may also play a role in the formation of warmer ice clouds. (1)B. J. Murray et al., Heterogeneous nucleation of ice particles on glassy aerosols under cirrus conditions, Nature Geosci, 2010, 3, 233-237. (2)K. D. Froyd et al., Aerosols that form subvisible cirrus at the tropical tropopause, Atmos. Chem. Phys., 2010, 10, 209-218. (3)B. Zobrist et al., Do atmospheric aerosols form glasses?, Atmos. Chem. Phys., 2008, 8, 5221-5244.

  17. Bulk chemicals from biomass

    NARCIS (Netherlands)

    Haveren, van J.; Scott, E.L.; Sanders, J.P.M.

    2008-01-01

    Given the current robust forces driving sustainable production, and available biomass conversion technologies, biomass-based routes are expected to make a significant impact on the production of bulk chemicals within 10 years, and a huge impact within 20-30 years. In the Port of Rotterdam there is a

  18. Heat transport in bulk/nanoporous/bulk silicon devices

    Energy Technology Data Exchange (ETDEWEB)

    Criado-Sancho, M. [Departamento de Ciencias y Técnicas Físicoquimicas, Facultad de Ciencias, UNED, Senda del Rey 9, 20040 Madrid (Spain); Jou, D., E-mail: David.Jou@uab.cat [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Institut d' Estudis Catalans, Carme 47, 08001 Barcelona, Catalonia (Spain)

    2013-02-04

    We study heat transport in bulk/nanoporous/bulk silicon devices; we show that, despite bulk/nanoporous devices may act as thermal rectifiers, the non-linear aspects of their joint thermal conductance are not strong enough to lead to a negative differential thermal resistance, necessary to allow bulk/nanoporous/bulk Si devices to act as thermal transistors. Furthermore, we explicitly study the effective thermal conductivity of the mentioned devices for several temperatures, geometries, porosities, and pore size.

  19. Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading

    OpenAIRE

    Vásquez, V Z C; Özcan, M.; Kimpara, E T

    2009-01-01

    OBJECTIVES: This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy. METHODS: Metallic frameworks (diameter: 5 mm, thickness: 4 mm) (N=96, n=12 per group) were cast in cpTi and gold alloy, airborne particle abraded with 150 microm aluminum oxide. Low-fusing glassy matrix ceramics and a conventional feld...

  20. Mechanically driven phase separation and corresponding microhardness change in Cu60Zr20Ti20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhou, Y.H.; Jiang, Jianzhong

    2005-01-01

    Rolling deformation of bulk Cu60Zr20Ti20 metallic glass has been performed at cryogenic temperature. The specimens exhibit excellent ductility, and are rolled up to 97% reduction in thickness without fracture. Crystallization is suppressed during the deformation, however, phase separation is...... observed in the glassy matrix when the thickness reduction exceeds 89%. Once the phase separation occurs, the microhardness of the specimen increases drastically, indicating the existence of work hardening by severe plastic deformation of the metallic glass....

  1. Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon

    CERN Document Server

    Garion, Cédric

    2014-01-01

    Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator [1] [2]. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in gl...

  2. Manufacturing of glassy thin shell for adaptive optics: results achieved

    Science.gov (United States)

    Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

    2012-07-01

    Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

  3. Structural relaxation in a glassy liquid crystal: MBBA

    International Nuclear Information System (INIS)

    Combined neutron and Raman scattering measurements were performed to analyze the solid polymorphic modifications of a typical nematic liquid crystal substance, MBBA. A glassy solid phase, classified as oriented molecular glass (OMG) may be produced by fast cooling from the nematic phase. A sequence of irreversible phase transitions was observed on reheating OMG. Four different solid modifications were found: two structurally relaxed amorphous 'mesophases' and two crystalline ones. A distinct modification can be found by slow crystallization from the nematic phase and it can be transformed reversibly into an other crystal structure by further cooling. The role of medium range order in the non-crystalline phases and the structural relaxation of the OMG state were analyzed. (author)

  4. Iodine based nuclear waste immobilization in phosphate glassy matrix

    International Nuclear Information System (INIS)

    The incorporation of iodine in an inorganic matrix is a challenging issue due to its volatility while processed at high temperature. Since one application could be the conditioning of iodine 129, a long-lived radioactive isotope issued from nuclear spent fuel reprocessing, this phenomenon should be strictly controlled. The development of a conditioning matrix could also require chemical durability properties so that to make the final material suitable for a potential long term disposal. Two ways of conditioning, both allowing iodine incorporation at atomic scale -first step for efficient immobilization-, are related in the literature: Ceramic matrix belonging to the lead-vanado-phosphate system and glassy matrices of borosilicate or phosphate systems. In the present study, we present and characterize low melting points glasses of the AgI-Ag2O-P2O5 system, whose potentialities for the atomic incorporation of iodine inactive isotope have already been investigated in the past but with other specifications. The synthesized glasses showed efficient iodine incorporation rate (lesser iodine volatilization than other glassy systems). Nevertheless, the low thermal stability of this material, due to a low glass transition temperature, did not allowed us to carry out durability tests in dynamic conditions at 100 deg C , which would be useful for further compositional benchmarking. Further compositional optimizations have been performed by the use of additives so that to increase both the Tg, and the chemical durability. The effects of phosphate network reticulating additives as well as the mechanisms of iodine atomic incorporation have monitored by NMR spectroscopy. (author)

  5. Gamma ray attenuation in a developed borate glassy system

    International Nuclear Information System (INIS)

    Measurements and calculations of gamma ray attenuation coefficients in glass barriers of xBaO–5ZnO–5MgO–14Na2O–-1Li2O–(75−x)B2O3, previously prepared by the melt-quenching technique [1], were performed for γ-ray of energies 121.8, 244.7, 344.14, 661.66, 778.7, 974, 1086.7, 1173.24, 1332.5, and 1407.9 keV; which emitted from 152Eu, 137Cs, and 60Co radioactive gamma ray sources. The transmitted γ-rays were detected by 3″×3″ and 5″×5″ NaI (Tl) scintillation γ-ray spectrometers, and a highly calibrated survey meter. The mass attenuation coefficients of γ-rays (σ(E)) were deduced from the attenuation curves, while the WinXCom computer program (version 3.1) was used to calculate the mass attenuation coefficients of γ-rays for such energies at different barium concentrations of a glassy system. A good agreement between both experimental and theoretical results was achieved as well as results obtained by other workers in similar field. - Highlights: • Design new glass system can be used as nuclear radiation shielding material. • Three different systems were used to measure γ-ray attenuation coefficients. • The γ-ray attenuation coefficients in this glass system were measured for 10 γ-energy lines. • Good agreement between experimental, theoretical, and results by other workers have been achieved. • Improvement of σ and HVL by increasing BaO concentration up to 50% in our glassy system

  6. Bulk materials handling review

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2007-02-15

    The paper provides details of some of the most important coal handling projects and technologies worldwide. It describes development by Aubema Crushing Technology GmbH, Bedeschi, Cimbria Moduflex, DBT, Dynamic Air Conveying Systems, E & F Services, InBulk Technologies, Nord-Sen Metal Industries Ltd., Pebco Inc, Primasonics International Ltd., R.J.S. Silo Clean (International) Ltd., Takraf GmbH, and The ACT Group. 17 photos.

  7. Effect of Yttrium Addition on Glass Forming Ability of ZrCuAlSi Alloy

    International Nuclear Information System (INIS)

    The effect of yttrium addition on glass formation of a ZrCuAlSi alloy is investigated. The maximum diameter 8mm of the glassy rods for (Zr46.3Cu43.3Al8.9Si1.5)100−xYx alloy with x = 2.5 is obtained by copper mould casting. Apparent enhancement of the glass formation ability is found with addition of yttrium, mainly due to the purification of the alloy melt and the suppression of formation of the primary phases by yttrium. (condensed matter: structure, mechanical and thermal properties)

  8. Au nanoparticles and graphene quantum dots co-modified glassy carbon electrode for catechol sensing

    Science.gov (United States)

    Zhao, Xuan; He, Dawei; Wang, Yongsheng; Hu, Yin; Fu, Chen

    2016-03-01

    In this letter, the gold nanoparticles and graphene quantum dots were applied to the modification of glassy carbon electrode for the detection of catechol. The synergist cooperation between gold nanoparticles and graphene quantum dots can increase specific surface area and enhance electronic and catalytic properties of glassy carbon electrode. The detection limit of catechol is 0.869 μmol/L, demonstrating the superior detection efficiency of the gold nanoparticles and graphene quantum dots co-modified glassy carbon electrode as a new sensing platform.

  9. Preparation of Platinum Implanted Glassy Carbon Electrode and Electro-oxidation of Formic Acid and Formaldehyde

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The glassy carbon substrates were bombarded with 5×1017 ions/cm2 of platinum.The surface composition of implanted electrode and concentration-depth profiles of various elements were measured by AES.The chemical state of Pt in glassy carbon electrode implanted with platinum (Pt/GC) was detected by X-ray Photoelectron Spectroscopy (XPS).The electro-oxidation of HCOOH and HCHO have been investigated on Pt/GC and smooth Pt electrodes.The results show that the platinum implanted into glassy carbon is much more active than the smooth platinum metal for electro-oxidation of HCOOH and HCHO.

  10. Design of experiment (DOE) study of biodegradable magnesium alloy synthesized by mechanical alloying using fractional factorial design

    Science.gov (United States)

    Salleh, Emee Marina; Ramakrishnan, Sivakumar; Hussain, Zuhailawati

    2014-06-01

    The biodegradable nature of magnesium (Mg) makes it a most highlighted and attractive to be used as implant materials. However, rapid corrosion rate of Mg alloys especially in electrolytic aqueous environment limits its performance. In this study, Mg alloy was mechanically milled by incorporating manganese (Mn) as alloying element. An attempt was made to study both effect of mechanical alloying and subsequent consolidation processes on the bulk properties of Mg-Mn alloys. 2k-2 factorial design was employed to determine the significant factors in producing Mg alloy which has properties closes to that of human bones. The design considered six factors (i.e. milling time, milling speed, weight percentage of Mn, compaction pressure, sintering temperature and sintering time). Density and hardness were chosen as the responses for assessing the most significant parameters that affected the bulk properties of Mg-Mn alloys. The experimental variables were evaluated using ANOVA and regression model. The main parameter investigated was compaction pressure.

  11. Corrosion behaviour of FePt-based bulk magnets in artificial saliva solution

    International Nuclear Information System (INIS)

    Bulk hard magnetic FePt-based alloys are proposed as new materials for dental applications. In this study the corrosion behaviour of bulk Fe50Pt50, Fe35Pt35P30 and Fe53Pt44C3 magnets prepared by spark plasma sintering of mechanically milled powders is evaluated in artificial saliva solution at 37 oC in dependence on their exposure time and in comparison to that of other relevant dental alloys by means of electrochemical polarisation measurements and scanning electron microscopy. The alloys exhibit in this environment a platinum-like behaviour and thus, they are highly stable also during long-term exposure. Enhanced corrosion activity does not occur when coupling these alloys with commercial dental alloys of Fe- and CoCr-based. A particular low-corroding state is attained in combination with the dental spring steel Fe-18Cr-18Mn-2Mo-1N

  12. Bulk forming of industrial micro components in conventional metals and bulk metallic glasses

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Paldan, Nikolas Aulin; Eriksen, Rasmus Solmer; Gastaldi, T.; Wert, John A.; Eldrup, Morten Mostgaard

    2007-01-01

    glasses will at elevated temperatures behave like a highly viscous liquid, which can easily form even complicated geometries in 1 step. The strengths and limitations of forming the 2 materials are analyzed for a micro 3D component in a silver alloy and an Mg-Cu-Y BMG. ©2007 American Institute of Physics......For production of micro components in large numbers, forging is an interesting and challenging process. The conventional metals like silver, steel and aluminum often require multi-step processes, but high productivity and increased strength justify the investment. As an alternative, bulk metallic...

  13. Sub-nanoscale nanoimprint fabrication of atomically stepped glassy substrates of silicate glass and acryl polymer

    Science.gov (United States)

    Yoshimoto, Mamoru

    2015-11-01

    In the nanoimprint process, the resolution limit of patterning has attracted much attention from both scientific and industrial aspects. In this article, we briefly review the main achievements of our research group on sub-nanoscale nanoimprint fabrication of atomically patterned glassy substrates of oxide glass and polymer. By applying the sapphire (α-Al2O3 single crystal) wafers with self-organized nanopatterns of atomic steps as thermal nanoimprinting molds, we successfully transferred their nanoscale patterns onto the surfaces of glassy substrates such as soda-lime silicate glasses and poly(methyl methacrylate) polymers. The surfaces of nanoimprinted glassy materials exhibited regularly arrayed atomic stairs with 0.2-0.3 nm step height, which were in good agreement with the sub-nanopatterns of sapphire molds. These atomically stepped morphologies on the glassy substrates were found to be stable for about 1 year.

  14. Determination of Volatility and Element Fractionation in Glassy Fallout Debris by SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Todd L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tenner, Travis Jay [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bonamici, Chloe Elizabeth [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kinman, William Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Pollington, Anthony Douglas [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Steiner, Robert Ernest [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-10

    The purpose of this report is to characterize glassy fallout debris using the Trinity Test and then characterize the U-isotopes of U3O8 reference materials that contain weaponized debris.

  15. Design of $Cu_{8}Zr_{5}$-based bulk metallic glasses

    OpenAIRE

    Yang, L.; Xia, J H; Wang, Q; Dong, C; Chen, L. Y.; Ou, X; Liu, J. F.; Jiang, J. Z.; Klementiev, K.; Saksl, K.; Franz, H.; Schneider, J. R.; L. Gerward

    2006-01-01

    Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by ...

  16. Compressive fracture characteristics of Zr-based bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The compressive fracture characteristics of Zr-based bulk metallic glass under uniaxial compression tests are studied.The zigzag rheological behavior is observed in the compression stress-strain curves of amorphous alloys.At room temperature the uniaxial compression fracture takes place along the plane which is at a 45-degree angle to the direction of the compressive stress.The microstructure of a typical fracture pattern is the vein network.A unique,finger-like vein pattern is found to exist at the fracture surface of Zr-based bulk metallic glass.

  17. Wormholes in Bulk Viscous Cosmology

    OpenAIRE

    Jamil, Mubasher

    2008-01-01

    We investigate the effects of the accretion of phantom energy with non-zero bulk viscosity onto a Morris-Thorne wormhole. We have found that if the bulk viscosity is large then the mass of wormhole increases rapidly as compared to small or zero bulk viscosity.

  18. Equilibrium Distribution of the Inherent States and their Dynamics in Glassy Systems and Granular Media

    OpenAIRE

    Fierro, Annalisa; Nicodemi, Mario; Coniglio, Antonio

    2001-01-01

    The present paper proposes a Statistical Mechanics approach to the inherent states of glassy systems and granular materials, following the original ideas developed by Edwards for granular materials. Two lattice models, a diluted Spin Glass and a system of hard-spheres under gravity, introduced in the context of glassy systems and granular materials, are evolved using a ``tap dynamics'' analogous to that of experiments on granular materials. The asymptotic macrostates, reached by the system, a...

  19. Positron annihilation study of graphite, glassy carbon and C60/C70 fullerene

    International Nuclear Information System (INIS)

    ACAR (Angular Correlation of Annihilation Radiation) and positron lifetime measurements have been made on, HOPG (Highly Oriented Pyrolytic Graphite), isotropic fine-grained graphite, glassy carbons and C60/C70 powder. HOPG showed marked bimodality along the c-axis and anisotropy in ACAR momentum distribution, which stem from characteristic annihilation between 'interlayer' positrons and π-electrons in graphite. ACAR curves of the isotropic graphite and glassy carbons are even narrower than that of HOPG perpendicular to the c-axis. Positron lifetime of 420 and 390 - 480 psec, much longer than that of 221 psec in HOPG, were observed for the isotropic graphite and glassy carbons respectively, which are due to positron trapping in structural voids in them. Positron lifetime and ACAR width (FWHM) can be well correlated to void sizes (1.7 to 5.0 nm) of glassy carbons which have been determined by small angle neutron (SAN) scattering measurements. ACAR curves and positron lifetime of C60/C70 powder agree well with those of glassy carbons. This shows that positron wave functions extend, as in the voids of glassy carbons, much wider than open spaces of the octahedral interstices of the face-centered cubic (FCC) structure of C60 crystal and strongly suggests positron trapping in the 'soccer ball' vacancy. Possible positron states in the carbon materials are discussed with a simple model of void volume-trapping. Preliminary results on neutron irradiation damage in HOPG are also presented. (author)

  20. Preparation, structure and properties of Fe-based bulk metallic glasses

    OpenAIRE

    R. Nowosielski; R. Babilas

    2010-01-01

    Purpose: The work presents preparation methods, structure characterization and chosen properties analysis of Fe-based bulk metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe43Co14Ni14B20Si5Nb4 metallic glass in form of rings, plates and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The thermal properties of the glassy sa...

  1. Dielectric studies of molecular motions in glassy and liquid nicotine

    Science.gov (United States)

    Kaminski, K.; Paluch, M.; Ziolo, J.; Ngai, K. L.

    2006-06-01

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10-2-109 Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural α-relaxation and its precursor, the Johari-Goldstein β-relaxation. The α-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric α-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein β-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural α-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

  2. Glassy Dynamics versus Thermodynamics: The Case of 2-Adamantanone.

    Science.gov (United States)

    Szewczyk, D; Jeżowski, A; Vdovichenko, G A; Krivchikov, A I; Bermejo, F J; Tamarit, J Ll; Pardo, L C; Taylor, J W

    2015-07-01

    The heat capacity and thermal conductivity of the monoclinic and the fully ordered orthorhombic phases of 2-adamantanone (C10H14O) have been measured for temperatures between 2 and 150 K. The heat capacities for both phases are shown to be strikingly close regardless of the site disorder present in the monoclinic crystal which arises from the occupancy of three nonequivalent sites for the oxygen atom. The heat capacity curves are also well accounted for by an evaluation carried out within the harmonic approximation in terms of the g(ω) vibrational frequency distributions measured by means of inelastic neutron scattering. Such spectral functions show however a significant excess of low frequency modes for the crystal showing statistical disorder. In contrast, large differences are found for the thermal conductivity which contrary to what could be expected, shows the substitutionally disordered crystal to exhibit better heat transport properties than the fully ordered orthorhombic phase. Such an anomalous behavior is understood from examination of the crystalline structure of the orthorhombic phase which leads to very strong scattering of heat-carrying phonons due to grain boundary effects able to yield a largely reduced value of the conductivity as well as to a plateau-like feature at intermediate temperatures which contrasts with a bell-shaped maximum shown by data pertaining the disordered crystal. The relevance of the present findings within the context of glassy dynamics of the orientational glass state is finally discussed. PMID:26073682

  3. Quantitative measurements of phase transitions in nano- and glassy materials

    Energy Technology Data Exchange (ETDEWEB)

    Parise, J B [Geosciences, Stony Brook University, Stony Brook NY 11794-2100 (United States); Ehm, L [Mineral Physics, Stony Brook University, Stony Brook NY 11794-2100 (United States); Benmore, C J [X-ray Science Division, Argonne National Laboratory, Argonne IL 60439 (United States); Antao, S M [Department of Geosciences, University of Calgary 2500 University Dr. NW Calgary, Alberta, T2N 1N4 (Canada); Michel, F M, E-mail: John.Parise@Stonybrook.ed [Molecular and Environmental Interface Science, Stanford Linear Accelerator Center, 575 Sand Hill Road, MS 99 Menlo Park, CA 94025 (United States)

    2010-03-01

    Novel approaches to the collection and treatment of total x-ray scattering using high energy (> 65 keV) x-ray beams and area detectors allow in situ studies of unprecedented precision to be performed on nano-crystalline (n) and glassy materials at extremes of pressure (p) and temperature (T). Gradual structural transitions in glasses, liquids and nano-materials occurring via continuous changes in density, or involving phases related by pseudo symmetry are inherently difficult to identify due to their disordered nature. In such cases supplementary physical measurements along with modeling of the pair distribution function (PDF) provide powerful constraints on the possible models for the transition. Examples include transitions from n-FeS with a mackinawite-like structure to high p forms with structures related to NiAs structure-type. The distinction between the various high p models - MnP-type, troilite, FeS-III related or mixtures of these phases - is subtle; great care needs to be exercised in refining structure models to fit the observed data. Acoustic techniques are particularly valuable in identifying high p phase transitions in glasses, since measured changes in compressional velocities relate to density changes in the glass while shear waves provide an insight into network rigidity.

  4. Gamma ray attenuation in a developed borate glassy system

    Science.gov (United States)

    Saeed, Aly; El shazly, R. M.; Elbashar, Y. H.; Abou El-azm, A. M.; El-Okr, M. M.; Comsan, M. N. H.; Osman, A. M.; Abdal-monem, A. M.; El-Sersy, A. R.

    2014-09-01

    Measurements and calculations of gamma ray attenuation coefficients in glass barriers of xBaO-5ZnO-5MgO-14Na2O--1Li2O-(75-x)B2O3, previously prepared by the melt-quenching technique [1], were performed for γ-ray of energies 121.8, 244.7, 344.14, 661.66, 778.7, 974, 1086.7, 1173.24, 1332.5, and 1407.9 keV; which emitted from 152Eu, 137Cs, and 60Co radioactive gamma ray sources. The transmitted γ-rays were detected by 3″×3″ and 5″×5″ NaI (Tl) scintillation γ-ray spectrometers, and a highly calibrated survey meter. The mass attenuation coefficients of γ-rays (σ(E) were deduced from the attenuation curves, while the WinXCom computer program (version 3.1) was used to calculate the mass attenuation coefficients of γ-rays for such energies at different barium concentrations of a glassy system. A good agreement between both experimental and theoretical results was achieved as well as results obtained by other workers in similar field.

  5. Iron-based bulk metallic glasses - Optimization of casting

    Czech Academy of Sciences Publication Activity Database

    Stloukal, Ivo; Král, Lubomír; Čermák, Jiří

    Ostrava: Tanger s. r. o, 2009, s. 481-487. ISBN 978-80-87294-04-8. [METAL 2009. Mezinárodní konference metalurgie a materiálů /18./. Hradec nad Moravicí (CZ), 19.05.2009-21.05.2009] R&D Projects: GA ČR GA106/08/1241 Institutional research plan: CEZ:AV0Z20410507 Keywords : bulk metallic glasses * iron-based alloy * casting optimization Subject RIV: BJ - Thermodynamics

  6. Fabrication of bulk metallic glasses by centrifugal casting method

    OpenAIRE

    R. Nowosielski; R. Babilas

    2007-01-01

    Purpose: The aim of the present work is characterization of the centrifugal casting method, apparatus andproduced amorphous materials, which are also known as bulk metallic glassesDesign/methodology/approach: The studied centrifugal casting system consists of two main parts: castingapparatus and injection system of molten alloy. The described centrifugal casting method was presented bypreparing a casting apparatus “CentriCast – 5”. The apparatus includes a cylindrical copper mold, which isrot...

  7. Creating bulk nanocrystalline metal.

    Energy Technology Data Exchange (ETDEWEB)

    Fredenburg, D. Anthony (Georgia Institute of Technology, Atlanta, GA); Saldana, Christopher J. (Purdue University, West Lafayette, IN); Gill, David D.; Hall, Aaron Christopher; Roemer, Timothy John (Ktech Corporation, Albuquerque, NM); Vogler, Tracy John; Yang, Pin

    2008-10-01

    Nanocrystalline and nanostructured materials offer unique microstructure-dependent properties that are superior to coarse-grained materials. These materials have been shown to have very high hardness, strength, and wear resistance. However, most current methods of producing nanostructured materials in weapons-relevant materials create powdered metal that must be consolidated into bulk form to be useful. Conventional consolidation methods are not appropriate due to the need to maintain the nanocrystalline structure. This research investigated new ways of creating nanocrystalline material, new methods of consolidating nanocrystalline material, and an analysis of these different methods of creation and consolidation to evaluate their applicability to mesoscale weapons applications where part features are often under 100 {micro}m wide and the material's microstructure must be very small to give homogeneous properties across the feature.

  8. Explosive bulk charge

    Science.gov (United States)

    Miller, Jacob Lee

    2015-04-21

    An explosive bulk charge, including: a first contact surface configured to be selectively disposed substantially adjacent to a structure or material; a second end surface configured to selectively receive a detonator; and a curvilinear side surface joining the first contact surface and the second end surface. The first contact surface, the second end surface, and the curvilinear side surface form a bi-truncated hemispherical structure. The first contact surface, the second end surface, and the curvilinear side surface are formed from an explosive material. Optionally, the first contact surface and the second end surface each have a substantially circular shape. Optionally, the first contact surface and the second end surface consist of planar structures that are aligned substantially parallel or slightly tilted with respect to one another. The curvilinear side surface has one of a smooth curved geometry, an elliptical geometry, and a parabolic geometry.

  9. The Incredible Bulk

    CERN Document Server

    Fukushima, Keita; Kumar, Jason; Sandick, Pearl; Yamamoto, Takahiro

    2014-01-01

    Recent experimental results from the LHC have placed strong constraints on the masses of colored superpartners. The MSSM parameter space is also constrained by the measurement of the Higgs boson mass, and the requirement that the relic density of lightest neutralinos be consistent with observations. Although large regions of the MSSM parameter space can be excluded by these combined bounds, leptophilic versions of the MSSM can survive these constraints. In this paper we consider a scenario in which the requirements of minimal flavor violation, vanishing $CP$-violation, and mass universality are relaxed, specifically focusing on scenarios with light sleptons. We find a large region of parameter space, analogous to the original bulk region, for which the lightest neutralino is a thermal relic with an abundance consistent with that of dark matter. We find that these leptophilic models are constrained by measurements of the magnetic and electric dipole moments of the electron and muon, and that these models have ...

  10. Bulk muscles, loose cables.

    Science.gov (United States)

    Liyanage, Chamari R D G; Kodali, Venkata

    2014-01-01

    The accessibility and usage of body building supplements is on the rise with stronger internet marketing strategies by the industry. The dangers posed by the ingredients in them are underestimated. A healthy young man came to the emergency room with palpitations and feeling unwell. Initial history and clinical examination were non-contributory to find the cause. ECG showed atrial fibrillation. A detailed history for any over the counter or herbal medicine use confirmed that he was taking supplements to bulk muscle. One of the components in these supplements is yohimbine; the onset of symptoms coincided with the ingestion of this product and the patient is symptom free after stopping it. This report highlights the dangers to the public of consuming over the counter products with unknown ingredients and the consequential detrimental impact on health. PMID:25326558

  11. Layered Structures in Deformed Metals and Alloys

    DEFF Research Database (Denmark)

    Hansen, Niels; Zhang, Xiaodan; Huang, Xiaoxu

    2014-01-01

    Layered structures characterize metals and alloys deformed to high strain. The morphology is typical lamellar or fibrous and the interlamellar spacing can span several length scales down to the nanometer dimension. The layered structures can be observed in bulk or in surface regions, which is shown......-structure relationships. Finally, the results will be discussed based on universal principles for the evolution of microstructure and properties during plastic deformation of metals and alloys from low to high strain....

  12. Fabrication of bulk metallic glasses by centrifugal casting method

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2007-01-01

    Full Text Available Purpose: The aim of the present work is characterization of the centrifugal casting method, apparatus andproduced amorphous materials, which are also known as bulk metallic glassesDesign/methodology/approach: The studied centrifugal casting system consists of two main parts: castingapparatus and injection system of molten alloy. The described centrifugal casting method was presented bypreparing a casting apparatus “CentriCast – 5”. The apparatus includes a cylindrical copper mold, which isrotated by a motor. The transmission allows to changing the speed of rotating mold.Findings: Bulk metallic glasses are a novel class of engineering materials, which exhibit excelent mechanical,thermal, magnetic and corrosion properties. Centrifugal casting is a useful method to produce bulk amorphousmaterials in form of rings, tubes or cylindrical parts. Presented centrifugal casting method and casting apparatushas been prepared to fabricate the samples of bulk metallic glass in form of rings with an outer diameter of 25mm and controlled thicknesses by changing the weight of the molten alloy.Research limitations/implications: Studied centrifugal casting method and casting apparatus has beenprepared to fabricate the samples of bulk metallic glass. For future research a characterization of microstructureand properties of prepared material will be performed.Practical implications: The centrifugal casting is a useful process to produce bulk amorphous materials in formof rings, tubes or graded amorphous matrix composites. It seems to be a very simple method, which allows toobtain BMG materials.Originality/value: The centrifugal casting method allows to produce bulk amorphous rings with thicknessabove 1-mm.

  13. Corrosion behavior of bulk metallic glasses in different aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The corrosion behavior of as-cast fully amorphous, structural relaxed amorphous and crystallized Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glasses (BMGs) in NaCl, HCl and NaOH solutions was investigated by electrochemical polarization and immersion methods. X-ray photoelectron spectroscopy measurements was used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The corrosion resistance of the Fe65.5Cr4Mo4Ga4P12C5B5.5 BMG was better than its structural relaxation/crystallization counterparts and common alloys (such as stainless steel, carbonized steel, and steel) in the selected aqueous solutions. The high corrosion resistance of this alloy in corrosive solutions leads to the formation of Fe-, Cr- and Mo-enriched protective thin surface films.

  14. Design of Cu8Zr5-based bulk metallic glasses

    DEFF Research Database (Denmark)

    Yang, L.; Xia, J.H.; Wang, Q.; Dong, C.; Chen, L.Y.; Ou, X.; Liu, J.F.; Jiang, J.Z.; Klementiev, K.; Saksl, K.; Franz, H.; Schneider, J.R.; Gerward, Leif

    2006-01-01

    Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary syste.......382)(100-x)Nb-x, where x=1.5 and 2.5 at. %, and (Cu0.618Zr0.382)(98)Sn-2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.......Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary system......, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu-Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0...

  15. Stability of bulk metallic glass structure

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D.B.

    2003-06-18

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

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

    Science.gov (United States)

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

    2016-08-01

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

  17. Evaluation of interface characterization and adhesion of glass ceramics to commercially pure titanium and gold alloy after thermal- and mechanical-loading

    NARCIS (Netherlands)

    Ccahuana Vasqueza, Vanessa Zulema; Ozcan, Mutlu; Kimpara, Estevao Tomomitsu

    2009-01-01

    Objectives. This study evaluated the effect of thermal- and mechanical-cycling on the shear bond strength of three low-fusing glassy matrix dental ceramics to commercial pure titanium (cpTi) when compared to conventional feldspathic ceramic fused to gold alloy. Methods. Metallic frameworks (diameter

  18. Rapid Determination of Uranium in Water Samples by Adsorptive Cathodic Stripping Voltammetry Using a Tin-Bismuth Alloy Electrode

    International Nuclear Information System (INIS)

    In this work, the tin-bismuth alloy electrode (SnBiE) was used for U(VI) concentration determination for the first time. Compared to the conventional solid electrode (glassy carbon electrode and bismuth bulk electrode), the SnBiE possesses a higher hydrogen overpotential, which indicates that the tin-bismuth alloy can considerably extend the application of potentially available electrode detection systems. Combining with electrochemical behavior analysis and spectrometric measurements as well as theoretical calculation methods, the geometric structures of uranium-cupferron (N-nitrosophenylhydroxylamine) complexes have been revealed and a more detailed electrode mechanism has been proposed. The electroanalysis results show that the optimal sensitivity could be obtained by using diphenylguanidine as the auxiliary reagent. The calibration plot for U(VI) quantification was linear from 0.5 nM to 30 nM with a correlation coefficient of 0.999. In the meanwhile, a detection limit of 0.24 nM was obtained in connection with an accumulation time of 30 s, which is comparable with that of mercury analogues. The practical applications of SnBiE have been tentatively performed for the determination of UO22+ in real water samples and the results were well consistent with those by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). A very simple, convenient and cheap approach was established for the determination of UO22+ in natural water samples containing surfactants without the otherwise necessity of sample pretreatment, which drastically reduce the analysis time

  19. First-principles study on the effect of alloying elements on the elastic deformation response in β-titanium alloys

    International Nuclear Information System (INIS)

    Theoretical deformation response of hypothetical β-titanium alloys was investigated using first-principles calculation technique under periodic boundary conditions. Simulation was carried out on hypothetical 54-atom supercell of Ti–X (X = Cr, Mn, Fe, Zr, Nb, Mo, Al, and Sn) binary alloys. The results showed that the strength of Ti increases by alloying, except for Cr. The most effective alloying elements are Nb, Zr, and Mo in the current simulation. The mechanism of bond breaking was revealed by studying the local structure around the alloying element atom with respect to volume change. Moreover, the effect of alloying elements on bulk modulus and admissible strain was investigated. It was found that Zr, Nb, and Mo have a significant effect to enhance the admissible strain of Ti without change in bulk modulus

  20. First-principles study on the effect of alloying elements on the elastic deformation response in β-titanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gouda, Mohammed K., E-mail: mohamed.kamal@ejust.edu.eg; Gepreel, Mohamed A. H. [Materials Science and Engineering Department, Egypt-Japan University of Science and Technology, Borg El Arab, Alexandria 21934 (Egypt); Nakamura, Koichi [Materials Science and Engineering Department, Egypt-Japan University of Science and Technology, Borg El Arab, Alexandria 21934 (Egypt); Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Kyoto 615-8540 (Japan)

    2015-06-07

    Theoretical deformation response of hypothetical β-titanium alloys was investigated using first-principles calculation technique under periodic boundary conditions. Simulation was carried out on hypothetical 54-atom supercell of Ti–X (X = Cr, Mn, Fe, Zr, Nb, Mo, Al, and Sn) binary alloys. The results showed that the strength of Ti increases by alloying, except for Cr. The most effective alloying elements are Nb, Zr, and Mo in the current simulation. The mechanism of bond breaking was revealed by studying the local structure around the alloying element atom with respect to volume change. Moreover, the effect of alloying elements on bulk modulus and admissible strain was investigated. It was found that Zr, Nb, and Mo have a significant effect to enhance the admissible strain of Ti without change in bulk modulus.

  1. Nanocrystalline Ni-Co Alloy Synthesis by High Speed Electrodeposition

    OpenAIRE

    Jamaliah Idris; Chukwuekezie Christian; Eyu Gaius

    2013-01-01

    Electrodeposition of nanocrystals is economically and technologically viable production path for the synthesis of pure metals and alloys both in coatings and bulk form. The study presents nanocrystalline Ni-Co alloy synthesis by high speed electrodeposition. Nanocrystalline Ni-Co alloys coatings were prepared by direct current (DC) and deposited directly on steel and aluminum substrates without any pretreatment, using high speed electrodeposition method. The influence of the electrolysis par...

  2. High temperature oxidation of bulk RuAl alloy

    OpenAIRE

    Bellina, Paul J.

    2006-01-01

    In thermal barrier coatings (TBCs), thermal insulation is provided by an outer Y2O3 partially-stabilized zirconia (YSZ) layer. Beneath this layer a chemical barrier is needed to protect the underlying superalloy from the thermal oxidation, because the porous YSZ is permeable to oxygen. Chemical protection is provided by a thin ?-Al2O3 layer between the metal and thermal barrier. This layer grows during oxidation and hence is known as the thermally grown oxide (TGO). Since the superalloys are ...

  3. Inflation from bulk viscosity

    CERN Document Server

    Bamba, Kazuharu

    2015-01-01

    We explore the perfect fluid description of the inflationary universe. In particular, we investigate a fluid model with the bulk-viscosity term. We find that the three observables of inflationary cosmology: the spectral index of the curvature perturbations, the tensor-to-scalar ratio of the density perturbations, and the running of the spectral index, can be consistent with the recent Planck results. We also reconstruct the explicit equation of state (EoS) of the viscous fluid from the spectral index of the curvature perturbations compatible with the Planck analysis. In the reconstructed models of the viscous fluid, the tensor-to-scalar ratio of the density perturbations can satisfy the constraints obtained from the Planck satellite. The running of the spectral index can explain the Planck data. In addition, it is demonstrated that in the reconstructed models of the viscous fluid, the graceful exit from inflation can be realized. Furthermore, we show that the singular inflation can occur in the viscous fluid ...

  4. Bulk-Fill Resin Composites

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel;

    2015-01-01

    restorative procedure. The aim of this study, therefore, was to compare the depth of cure, polymerization contraction, and gap formation in bulk-fill resin composites with those of a conventional resin composite. To achieve this, the depth of cure was assessed in accordance with the International Organization...... for Standardization 4049 standard, and the polymerization contraction was determined using the bonded-disc method. The gap formation was measured at the dentin margin of Class II cavities. Five bulk-fill resin composites were investigated: two high-viscosity (Tetric EvoCeram Bulk Fill, SonicFill) and...... three low-viscosity (x-tra base, Venus Bulk Fill, SDR) materials. Compared with the conventional resin composite, the high-viscosity bulk-fill materials exhibited only a small increase (but significant for Tetric EvoCeram Bulk Fill) in depth of cure and polymerization contraction, whereas the low...

  5. Room-temperature dynamic quasi-elastic mechanical behavior of a Zr-Cu-Fe-Al bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Zadorozhnyy, V.Yu.; Zadorozhnyy, M.Yu.; Shuryumov, A.Yu.; Golovin, I.S. [National University of Science and Technology ' ' MISiS' ' , 119049, Moscow (Russian Federation); Ketov, S.V.; Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577 (Japan)

    2016-02-15

    The paper represents storage modulus and internal friction modulation upon cyclic loading of Zr{sub 61}Cu{sub 27}Fe{sub 2}Al{sub 10} bulk metallic glassy samples within quasi-reversible deformation regime. The structure of the samples was studied by X-ray diffraction and transmission electron microscopy including high-resolution imaging and selected-area electron diffraction. It is found that kinetically frozen anelastic deformation accumulates on mechanical cycling at room temperature and causes an increase in the storage modulus and even nanocrystallization of a metallic glassy phase after a certain number of cycles. The study has shown that even a minor cyclic deformation in an elastic region can lead to the changes the atomic structure and in turn affect the elastic modulus. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Sorption of water by bidisperse mixtures of carbohydrates in glassy and rubbery states.

    Science.gov (United States)

    Ubbink, Job; Giardiello, Maria-Isabelle; Limbach, Hans-Jörg

    2007-09-01

    Water sorption by bidisperse carbohydrate mixtures consisting of varying ratios of a narrow-molecular-weight distribution maltopolymer and the disaccharide maltose is investigated to establish a quantitative relation between the composition of the carbohydrate system and the water sorption isotherm. The sorption of water is approached from two limiting cases: the glassy state at low water content and the dilute aqueous carbohydrate solution. In the glassy state, the water content at a given water activity decreases with increasing maltose content of the matrix, whereas in the rubbery state it increases with increasing maltose content. The water sorption behavior in the glassy state is quantified using a variety of models, including the often-utilized but physically poorly founded Guggenheim-Anderson-de Boer model, several variants of the free-volume theory of sorption by glassy polymers, and a two-state sorption model introduced in the present paper. It is demonstrated that both the free-volume models and the two-state sorption model, which all encompass the Flory-Huggins theory for the rubbery-state sorption but which differ in their modeling of the glassy-state sorption, provide a physically consistent foundation for the analysis of water sorption by the carbohydrate matrixes. PMID:17691841

  7. Formation of oxygen complexes in controlled atmosphere at surface of doped glassy carbon

    Indian Academy of Sciences (India)

    Aleksandra A Perić-Grujić; Tatjana M Vasiljević; Olivera M Nešković; Miomir V Veljković; Zoran V Laušević; Mila D Laušević

    2006-10-01

    The effects of boron and phosphorus incorporation in phenolic resin precursor to the oxidation resistance of glassy carbon have been studied. In order to reveal the nature and composition of the oxygen complexes formed at the surface of doped glassy carbon, under controlled atmosphere, the surface of the samples was cleaned under vacuum up to 1273 K. Specific functional groups, subsequently formed under dry CO2 or O2 atmosphere on the surface of boron-doped and phosphorus-doped glassy carbon samples, were examined using the temperature-programmed desorption method combined with mass spectrometric analysis. Characterization of surface properties of undoped and doped samples has shown that in the presence of either boron or phosphorus heteroatoms, a lower amount of oxygen complexes formed after CO2 exposure, while, typically, higher amount of oxygen complexes formed after O2 exposure. It has been concluded that the surface of undoped glassy carbon has a greater affinity towards CO2, while in the presence of either boron or phosphorus heteroatoms, the glassy carbon surface affinity becomes greater towards O2, under experimental conditions.

  8. Electrical Resistance Alloys and Low-Expansion Alloys

    DEFF Research Database (Denmark)

    Kjer, Torben

    1996-01-01

    The article gives an overview of electrical resistance alloys and alloys with low thermal expansion. The electrical resistance alloys comprise resistance alloys, heating alloys and thermostat alloys. The low expansion alloys comprise alloys with very low expansion coefficients, alloys with very low...... thermoelastic coefficients and age hardenable low expansion alloys....

  9. Preparation and characterization of Zr-based bulk metallic glasses in form of plate

    International Nuclear Information System (INIS)

    Highlights: • Zr-based BMGs in form of plate was successful produced by die pressure casting method. • Many techniques have been used to characterize the structure of Zr55Cu30Ni5Al10 alloy. • The calculated GFA parameters show that the alloy exhibits satisfactory GFA. • The studies reveal that tested as-cast Zr-based alloy is in amorphous state. - Abstract: Zr-based bulk metallic glasses present an interesting combination of physical, chemical and mechanical properties. During the last decade, intensive progress has been made and a number of applications have been suggested for these materials. In order to successfully apply these materials, it is necessary to accurately characterize their structure, thermal stability and other properties accurately. The aim of the presented work is the manufacturing, examination of the structure of selected Zr-based bulk metallic alloys and confirmation of an amorphous structure using X-ray analysis, microscopic observation and thermal analysis. In this work, the Zr-based bulk metallic glasses in form of plate was successful produced by die pressure casting method. Designed scientific station for casting zirconium based amorphous alloys in the form of plates and rods with selected dimensions is in our university a comprehensive method for achieving amorphous materials which enables us to maintain repeatability of as-cast samples with the amorphous structure and the assumed dimensions range. The diffraction pattern and exothermic reaction as well as the fracture surface morphology reveal that studied as-cast Zr-based alloy is in amorphous state. The calculated GFA parameters show that the alloy exhibits satisfactory glass-forming ability in form of studied plate. These obtained values can suggest that studied alloys are suitable materials for further planned practical application at welding process. The success of Zr-based bulk metallic glasses production in form of plate with obtained sizes is important for future progress

  10. Interactions between high temperature deformation and crystallization in zirconium based bulk metallic glasses

    OpenAIRE

    Gravier, Sébastien; Blandin, Jean-Jacques; Donnadieu, Patricia

    2008-01-01

    Abstract High temperature deformation of a ZrTiCuNiBe bulk metallic glass (BMG) is investigated by compression tests in the supercooled liquid region. When temperature is decreased or strain rate is increased, the amorphous alloy exhibits the usual Newtonian ? non Newtonian behavior transition. Owing to appropriate heat treatments, partially crystallized alloys are produced, the associated microstructures are characterized and the volume fractions of crystal are measured. The inter...

  11. Two Glass Transitions Associated to Different Dynamic Disorders in the Nematic Glassy State of a Non-Symmetric Liquid Crystal Dimer Dopped with g-Alumina Nanoparticles

    Directory of Open Access Journals (Sweden)

    Sergio Diez-Berart

    2015-06-01

    Full Text Available In the present work, the nematic glassy state of the non-symmetric LC dimer α-(4-cyanobiphenyl-4′-yloxy-ω-(1-pyrenimine-benzylidene-4′-oxy undecane is studied by means of calorimetric and dielectric measurements. The most striking result of the work is the presence of two different glass transition temperatures: one due to the freezing of the flip-flop motions of the bulkier unit of the dimer and the other, at a lower temperature, related to the freezing of the flip-flop and precessional motions of the cyanobiphenyl unit. This result shows the fact that glass transition is the consequence of the freezing of one or more coupled dynamic disorders and not of the disordered phase itself. In order to avoid crystallization when the bulk sample is cooled down, the LC dimer has been confined via the dispersion of γ-alumina nanoparticles, in several concentrations.

  12. Electrodeposited gold nanoparticles on glassy carbon: Correlation between nanoparticles characteristics and oxygen reduction kinetics in neutral media

    International Nuclear Information System (INIS)

    Gold nanoparticles (AuNPs) were deposited onto glassy carbon (GC) by constant potential electrolysis (CPE) using various sets of potential and duration from −0.3 to 0.7 V/SHE and 10 to 1800 s, respectively. The physico-chemical characteristics of the as-obtained deposits were investigated by cyclic voltammetry (CV) in H2SO4, field emission gun scanning electron microscopy (FEG-SEM), and Pb underpotential deposition (UPD). Their performances toward the oxygen reduction reaction (ORR) in a NaCl–NaHCO3 (0.15 M/0.028 M, pH 7.4) neutral solution were examined and correlated to AuNPs size and density. The best results were obtained using the deposits which exhibited a high density (555 ± 49 μm−2) of relatively small AuNPs (25 ± 12 nm). The Koutecky–Levich treatment was systematically applied to all the deposits in order to determine the number of electrons n exchanged for the ORR in the potential range from 0.1 to −1.0 V/SHE. The values of the cathodic transfer coefficients βn were also extracted and compared to the values reported for unmodified GC and bulk Au. A map of the βn values as a function of AuNPs electrodeposition potential and duration was also provided

  13. Joining of bulk metallic glass to brass by thick-walled cylinder explosion

    International Nuclear Information System (INIS)

    This paper reports the development of a thick-walled cylinder explosion technique to weld a typical Zr-based bulk metallic glass (Vitreloy 1 (Vit 1)) to a commercial Cu-based crystalline alloy (brass). It is shown that a strong metallurgical bonding between the Vit 1 and the brass is achieved, which is due to significant atomic diffusion across the welding interface and shock wave propagation in the weldment. The dissimilar joining of the noncrystalline to crystalline alloy extends the application of bulk metallic glasses as structural and functional materials

  14. ( Cu50Zr42Al8)96Y4块状非晶的变温晶化行为%Effects of Temperature on Crystallization Behavior of Bulk( Cu50Zr42Al8 ) 96Y4Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    屠鹏; 寇生中

    2011-01-01

    研究(Cu50Zr42Al8)96 Y4大块非晶合金在连续升温过程中的晶化行为.结果表明,随升温速度的加快,玻璃转变温度Tg、晶化起始温度Tx、晶化峰值温度Tp都向高温区移动,过冷温度区△Tx扩大到了72.5K.运用Kissinger法分别计算出玻璃转变激活能Eg为512.34kJ/mol、晶化起始激活能Ex为372.44 kJ/mol、晶化峰的激活能Ep1和Ep1为404.52kJ/mol、404.75kJ/mol.运用FWO法计算出了晶化阶段激活能Ex,发现当晶化量小于50%时,随晶化量的增大,阶段激活能变化不大;当晶化量大于50%时,随晶化量的增大,阶段激活能呈逐渐减小的趋势.%Crystallization behavior of bulk ( Cu50 Zr42 Al8 ) 96 Y4 amorphous alloy during continuous temperature increment was described. With increasing of the temperature , The results indicate that the glass transformation temperature ( Tg ) , crystallization initial temperature ( Tz) and crystallization peak temperature ( Tp ) tend to high temperature zone , and under-cooled temperature zone △TX is enlarged to 72.5 K. The glass transformation activation energy Eg, crystallization initial activation energy Ex and crystallization peak activation energy Ep are calculated by theKissinger formula which is 512. 34 kj/mol, 372.44 kJ/mol, 404. 52 kJ/mol and 404. 75 kJ/mol respectively. In addition, crystallization phase activation energy Ex is calculated by the FWO equation. The research found that there is no notable change in the crystallization phase activation energy is increased with the increasing of crystallization degree when crystallization degree is lower than 50% ; on the contrary, when crystallization degree is higher than 50% , the crystallization phase activation energy is decreased with the increasing of crystallization degree.

  15. Temporal disconnectivity of the energy landscape in glassy systems

    Science.gov (United States)

    Lempesis, Nikolaos; Boulougouris, Georgios C.; Theodorou, Doros N.

    2013-03-01

    An alternative graphical representation of the potential energy landscape (PEL) has been developed and applied to a binary Lennard-Jones glassy system, providing insight into the unique topology of the system's potential energy hypersurface. With the help of this representation one is able to monitor the different explored basins of the PEL, as well as how - and mainly when - subsets of basins communicate with each other via transitions in such a way that details of the prior temporal history have been erased, i.e., local equilibration between the basins in each subset has been achieved. In this way, apart from detailed information about the structure of the PEL, the system's temporal evolution on the PEL is described. In order to gather all necessary information about the identities of two or more basins that are connected with each other, we consider two different approaches. The first one is based on consideration of the time needed for two basins to mutually equilibrate their populations according to the transition rate between them, in the absence of any effect induced by the rest of the landscape. The second approach is based on an analytical solution of the master equation that explicitly takes into account the entire explored landscape. It is shown that both approaches lead to the same result concerning the topology of the PEL and dynamical evolution on it. Moreover, a "temporal disconnectivity graph" is introduced to represent a lumped system stemming from the initial one. The lumped system is obtained via a specially designed algorithm [N. Lempesis, D. G. Tsalikis, G. C. Boulougouris, and D. N. Theodorou, J. Chem. Phys. 135, 204507 (2011), 10.1063/1.3663207]. The temporal disconnectivity graph provides useful information about both the lumped and the initial systems, including the definition of "metabasins" as collections of basins that communicate with each other via transitions that are fast relative to the observation time. Finally, the two examined

  16. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    International Nuclear Information System (INIS)

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz

  17. Immobilization of DNA at Glassy Ccarbon Electrodes: A Critical Study of Adsorbed Layer

    Directory of Open Access Journals (Sweden)

    G. A. Rivas

    2005-11-01

    Full Text Available In this work we present a critical study of the nucleic acid layer immobilized atglassy carbon electrodes. Different studies were performed in order to assess the nature of theinteraction between DNA and the electrode surface. The adsorption and electrooxidation of DNAdemonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. TheDNA layer immobilized at a freshly polished glassy carbon electrode was very stable even afterapplying highly negative potentials. The electron transfer of potassium ferricyanide, catechol anddopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlledpotential conditions and thick (obtained by casting the glassy carbon surface with highly concentratedDNA solutions DNA layers was slower than that at the bare glassy carbon electrode, although thiseffect was dependent on the thickness of the layer and was not charge selective. Raman experimentsshowed an important decrease of the vibrational modes assigned to the nucleobases residues,suggesting a strong interaction of these residues with the electrode surface. The hybridization ofoligo(dG21 and oligo(dC21 was evaluated from the guanine oxidation signal and the reduction of theredox indicator Co(phen33+ . In both cases the chronopotentiometric response indicated that thecompromise of the bases in the interaction of DNA with the electrode surface is too strong, preventingfurther hybridization. In summary, glassy carbon is a useful electrode material to detect DNA in adirect and very sensitive way, but not to be used for the preparation of biorecognition layers by directadsorption of the probe sequence on the electrode surface for detecting the hybridization event.

  18. Spectroscopic ellipsometric and Raman spectroscopic investigations of pulsed laser treated glassy carbon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Csontos, J., E-mail: jcsontos@titan.physx.u-szeged.hu [University of Szeged, Department of Optics and Quantum Electronics, Dóm tér 9, H-6720 Szeged (Hungary); Pápa, Z.; Gárdián, A. [University of Szeged, Department of Optics and Quantum Electronics, Dóm tér 9, H-6720 Szeged (Hungary); Füle, M. [University of Szeged, Department of Experimental Physics, Dóm tér 9, H-6720 Szeged (Hungary); Budai, J. [University of Szeged, Department of Optics and Quantum Electronics, Dóm tér 9, H-6720 Szeged (Hungary); Toth, Z. [University of Szeged, Department of Optics and Quantum Electronics, Dóm tér 9, H-6720 Szeged (Hungary); University of Szeged, Department of Oral Biology and Experimental Dental Research, Tisza Lajos krt. 64, H-6720 Szeged (Hungary)

    2015-05-01

    Highlights: • Laser treatment modifies the top layer of glassy carbon as shown by ellipsometry. • Raman signal is composed from signals of the layer and the glassy carbon substrate. • Using volumetric fluence allows to compare the effects of different lasers. • Melting effects of glassy carbon was observed in case of Nd:YAG laser treatment. - Abstract: In this study spectroscopic ellipsometry (SE) and Raman spectroscopy are applied to study structural modification of glassy carbon, due to high intensity laser ablation. Two KrF lasers with different pulse durations (480 fs and 18 ns), an ArF (20 ns), and a frequency doubled Nd:YAG laser (8 ns) were applied to irradiate the surface of glassy carbon targets. The main characteristics of the different laser treatments are compared by introducing the volumetric fluence which takes into account the different absorption values at different wavelengths. SE showed the appearance of a modified layer on the ablated surfaces. In the case of the ns lasers the thickness of this layer was in the range of 10–60 nm, while in the case of fs laser it was less than 20 nm. In all cases the average refractive index (n) of the modified layers slightly decreased compared to the refractive index of glassy carbon. Increase in extinction coefficient (k) was observed in the cases of ArF and fs KrF laser treatment, while the k values decreased significantly in the cases of nanosecond pulse duration KrF and Nd:YAG laser treatments. In the Raman spectra of the ablated areas the characteristic D and G peaks were widened due to appearance of an amorphous phase. Both Raman spectroscopy and SE indicate that the irradiated areas show carbon nanoparticle formation in all cases.

  19. Surface heat treatment of zirconium alloy

    International Nuclear Information System (INIS)

    A body composed of a zirconium alloy is afforded enhanced corrosion resistance to a high pressure and high temperature steam environment by an integral surface region of β-quenched zirconium formed in situ by laser beam scanning and afforded good mechanical and structural properties by a bulk region whose metallurgical structure is selected to optimize these mechanical properties. (author)

  20. Analysis of trace-elemental geochemical characteristics of glassy meteorites from Hainan island by INAA

    International Nuclear Information System (INIS)

    The concentrations of more than 20 elements in the glassy meteorites from Hainan Island of China have been measured by INAA. Precision and accuracy of the INAA method have been evaluated by using USGS and Chinese standard reference materials (GSR), indicating that relative standard deviations for most element are less than 5%. A comparative study on the REE patterns and other trace elements shows that the geochemical characteristics of the glassy meteorites from Hainan Island are close to those of the Chinese continental sediment and the North America shale, implying that their parent rock is younger sediment

  1. Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

    Science.gov (United States)

    Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

    2008-11-01

    The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

  2. Mechanical Testing of Iron based Bulk Metallic Glasses and Their Suitability for Force Sensors

    Directory of Open Access Journals (Sweden)

    Erenc-Sędziak T.

    2013-01-01

    Full Text Available Thermal, mechanical and magnetic properties of (Fe-Co-(Zr/Si-Nb-B alloys in the form of rapidly quenched rods of 1.2 mm in diameter were studied. The as-cast alloys with Zr were crystalline, and the alloys with Si were amorphous. Microhardness measured at 50 g load is from 500 to 2000 HV (the less cobalt, the higher, and the compressive strength reaches nearly 4000 MPa for Si doped alloys and 2000 MPa for Zr doped ones. This substantial difference may be attributed to partial crystallinity of the latter alloys. The magnetic hysteresis loops of fully amorphous rods measured under compression, exhibited a clear dependence of permeability vs. stress, proving that iron-based bulk metallic glasses may be promising materials for magnetoelastic force sensors.

  3. Mining the bulk positron lifetime

    Energy Technology Data Exchange (ETDEWEB)

    Aourag, H.; Guittom, A. [Centre de Recherche Nucleaire d' Alger (CRNA), Alger Gare - Algiers (Algeria)

    2009-02-15

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Mining the bulk positron lifetime

    International Nuclear Information System (INIS)

    We introduce a new approach to investigate the bulk positron lifetimes of new systems based on data-mining techniques. Through data mining of bulk positron lifetimes, we demonstrate the ability to predict the positron lifetimes of new semiconductors on the basis of available semiconductor data already studied. Informatics techniques have been applied to bulk positron lifetimes for different tetrahedrally bounded semiconductors in order to discover computational design rules. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Advances in bulk port development

    Energy Technology Data Exchange (ETDEWEB)

    Soros, P. (Soros Associates Consulting Engineers, New York, NY (USA))

    1991-03-01

    The article features several recently developed bulk ports which illustrate aspects of new technology or concepts in maritime transport. Low handling capacity bulk terminals at Ponta da Madeira, Brazil and Kooragang Island, Australia and the low-cost bulk port at Port of Corpus Christi, Texas are described. Operations at the ports of Pecket and Tocopilla in Chile, which had special technical problems, are mentioned. Coal terminals at Port Kembla, Australia and St. Johns River in Florid Jacksonville, Florida are featured as examples of terminals which had to be designed to meet high environmental standards. 13 refs., 2 figs., 14 photos.

  6. Bulk Nuclear Properties from Reactions

    OpenAIRE

    Danielewicz, P.

    2002-01-01

    Extraction of bulk nuclear properties by comparing reaction observables to results from semiclassical transport-model simulations is discussed. Specific properties include the nuclear viscosity, incompressibility and constraints on the nuclear pressure at supranormal densities.

  7. Bulk charges in eleven dimensions

    CERN Document Server

    Hawking, Stephen William

    1998-01-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge preserving between 1/16 and 1/4 of the supersymmetries. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singlely charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped a...

  8. Non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 bulk metallic glass investigated by differential scanning calorimetry

    Science.gov (United States)

    Gong, Pan; Zhao, Shaofan; Wang, Xin; Yao, Kefu

    2015-07-01

    The non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 glassy alloy were investigated by differential scanning calorimetry. The activation energies corresponding to the characteristic temperatures have been calculated by Kissinger and Ozawa equations. Based on Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall models, it has been found that the local activation energy is higher at the beginning of the crystallization process for the first exothermic peak. The local Avrami exponent indicates that the first-step crystallization is mainly a high-dimensional nucleation and growth with an increasing nucleation rate. According to the calculated fragility index, Ti41Zr25Be28Fe6 alloy can be classified as "strong glass former." The studied alloy also possesses a critical size up to centimeter order, and the high glass-forming ability is probably related to the relatively low Gibbs energy difference between the liquid and crystalline states. The critical cooling rate of Ti41Zr25Be28Fe6 glassy alloy has also been determined using Barandiaran-Colmenero's method.

  9. Scattering effects and high-spatial-frequency nanostructures on ultrafast laser irradiated surfaces of zirconium metallic alloys with nano-scaled topographies.

    Science.gov (United States)

    Li, Chen; Cheng, Guanghua; Sedao, Xxx; Zhang, Wei; Zhang, Hao; Faure, Nicolas; Jamon, Damien; Colombier, Jean-Philippe; Stoian, Razvan

    2016-05-30

    The origin of high-spatial-frequency laser-induced periodic surface structures (HSFL) driven by incident ultrafast laser fields, with their ability to achieve structure resolutions below λ/2, is often obscured by the overlap with regular ripples patterns at quasi-wavelength periodicities. We experimentally demonstrate here employing defined surface topographies that these structures are intrinsically related to surface roughness in the nano-scale domain. Using Zr-based bulk metallic glass (Zr-BMG) and its crystalline alloy (Zr-CA) counterpart formed by thermal annealing from its glassy precursor, we prepared surfaces showing either smooth appearances on thermoplastic BMG or high-density nano-protuberances from randomly distributed embedded nano-crystallites with average sizes below 200 nm on the recrystallized alloy. Upon ultrashort pulse irradiation employing linearly polarized 50 fs, 800 nm laser pulses, the surfaces show a range of nanoscale organized features. The change of topology was then followed under multiple pulse irradiation at fluences around and below the single pulse threshold. While the former material (Zr-BMG) shows a specific high quality arrangement of standard ripples around the laser wavelength, the latter (Zr-CA) demonstrates strong predisposition to form high spatial frequency rippled structures (HSFL). We discuss electromagnetic scenarios assisting their formation based on near-field interaction between particles and field-enhancement leading to structure linear growth. Finite-difference-time-domain simulations outline individual and collective effects of nanoparticles on electromagnetic energy modulation and the feedback processes in the formation of HSFL structures with correlation to regular ripples (LSFL). PMID:27410083

  10. Formulation of thermodynamics for the glassy state: Configurational energy as a modest source of energy

    NARCIS (Netherlands)

    2001-01-01

    Glass is an under-cooled liquid that very slowly relaxes towards the equilibrium crystalline state. Its energy balance is ill understood, since it is widely believed that the glassy state cannot be described thermodynamically. However, the classical paradoxes involving the Ehrenfest relations and Pr

  11. Physical ageing in the above-bandgap photoexposured glassy arsenic selenides

    Energy Technology Data Exchange (ETDEWEB)

    Kozdras, A [Faculty of Physics of Opole University of Technology, 75, Ozimska str., Opole, PL-45370 (Poland); Golovchak, R [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine); Shpotyuk, O [Lviv Scientific Research Institute of Materials of SRC ' Carat' , 202, Stryjska str., Lviv, UA-79031 (Ukraine)

    2007-08-15

    Physical ageing induced by above-bandgap light illumination is studied in glassy As-Se using differential scanning calorimetry. It is shown that measurable effect like to known short-term physical ageing is observed only in Se-rich glasses. The kinetics of this effect is compared with that caused by natural storage in a dark.

  12. Optical and mechanical behaviors of glassy silicone networks derived from linear siloxane precursors

    Science.gov (United States)

    Jang, Heejun; Seo, Wooram; Kim, Hyungsun; Lee, Yoonjoo; Kim, Younghee

    2016-01-01

    Silicon-based inorganic polymers are promising materials as matrix materials for glass fiber composites because of their good process ability, transparency, and thermal property. In this study, for utilization as a matrix precursor for a glass-fiber-reinforced composite, glassy silicone networks were prepared via hydrosilylation of linear/pendant Si-H polysiloxanes and the C=C bonds of viny-lterminated linear/cyclic polysiloxanes. 13C nuclear magnetic resonance spectroscopy was used to determine the structure of the cross-linked states, and a thermal analysis was performed. To assess the mechanical properties of the glassy silicone networks, we performed nanoindentation and 4-point bending tests. Cross-linked networks derived from siloxane polymers are thermally and optically more stable at high temperatures. Different cross-linking agents led to final networks with different properties due to differences in the molecular weights and structures. After stepped postcuring, the Young's modulus and the hardness of the glassy silicone networks increased; however, the brittleness also increased. The characteristics of the cross-linking agent played an important role in the functional glassy silicone networks.

  13. The Glassy-Winged Sharpshooter Vector of Xylella fastidiosa Harbors a Phytoreovirus

    Science.gov (United States)

    The glassy-winged sharpshooter (GWSS) vector of Xylella fastidiosa harbors a phytoreovirus species designated as Homalodisca vitripennis reovirus (HoVRV). Double-shelled isometric virus particles purified from GWSS adults resembled those observed in thin sections of GWSS salivary glands by transmis...

  14. Photocatalytic activity in monodisperse In2O3 nanocrystals incorporated into transparent silica glassy matrix

    International Nuclear Information System (INIS)

    Highlights: • The silica glassy matrix doped with In2O3 NCs was prepared. • The microstructure and photocatalytic activity of the samples were investigated. • The influence of doping concentrations on the size of the In2O3 NCs was studied. • The photodegradation efficiency was improved by doping In2O3 NCs. - Abstract: A general and facile chemical synthesis approach has been established for the successful doping of monodisperse semiconducting In2O3 nanocrystals inside a porous transparent silica glassy matrix. The preparation of silica glassy matrix loaded with specific In2O3 precursors is performed by using the sol–gel method. Then, the samples are sintered by using atmosphere control methods to generate the In2O3 nanocrystals growth inside the deep volume of the silica matrix. The resulting In2O3 nanocrystals are characterized by X-ray powder diffraction, energy dispersive X-ray spectrum and transmission electron microscopy. Photocatalytic activity of the as-prepared products is also measured, and the result shows that the photodegradation efficiency of silica glassy matrix has been significantly improved by doping In2O3 nanocrystals

  15. The Cooling History of Layered Glassy Impactites (Tagamites): Influence Upon Preservation of Impact Diamonds

    Science.gov (United States)

    Valter, A. A.; Dobraynskii, Yu. P.

    2002-03-01

    The cooling down dynamics was calculated for the rock mass of essentially glassy tagamites from the Boltysh Astrobleme on the Ukrainian Shield and for the body of diamond-bearing tagamites of the Popigai Astrobleme in the north of West Siberia.

  16. Abundance and consumption rate of glassy-winged sharpshooter (Hemiptera: Cicadellidae) on peaches and plums

    Science.gov (United States)

    Homalodisca vitripennis, also known as the glassy-winged sharpshooter, is a primary vector of phony peach and plum leaf scald diseases caused by Xylella fastidiosa Wells et al. Two of the following scions, (Prunus persica L. Batch cvs. Flordaking and June Gold and Prunus salicina L. cvs. Methley an...

  17. Kinetic undercooling in solidification of a hypereutectic Al-Si alloy; Effect of solidifying within a ceramic preform composite

    OpenAIRE

    Sundarrajan, A.; Mortensen, A.; Kattamis, T. Z.; Flemings, M. C.

    1997-01-01

    Dendrite tip temperature measurements are reported for the hypereutectic alloy Al-30% Si, directionally solidified as a bulk (non-composite) alloy, and also as the matrix of a fibrous metal matrix composite. Over the range of tip velocities studied (10-1000 mu m s) the primary Si tip undercooling in the directionally solidified bulk alloy increases slightly with increasing tip velocity, and indicates, by its large value, the presence of significant kinetic undercooling. This is in contrast wi...

  18. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Directory of Open Access Journals (Sweden)

    B. J. Murray

    2012-04-01

    Full Text Available The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA, levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosols that have re-vitrified in

  19. Concentration and electrode material dependence of the voltammetric response of iodide on platinum, glassy carbon and boron-doped diamond in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide

    International Nuclear Information System (INIS)

    The electro-oxidation of iodide has been investigated as a function of concentration using steady-state microelectrode voltammetry, transient cyclic voltammetry and linear-sweep semi-integral voltammetry on platinum, glassy carbon and boron-doped diamond electrodes in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. Two oxidation processes are observed on all of the investigated electrode materials, with the first being assigned to the oxidation of iodide to triiodide (confirmed by UV/visible spectroscopy) and the second being attributed to the oxidation of triiodide to iodine. Iodide oxidation is kinetically more facile on platinum compared to glassy carbon or boron-doped diamond. At elevated bulk iodide concentrations, the nucleation and growth of sparingly soluble electrogenerated iodine at the electrode surface was observed and imaged in situ using optical microscopy. The diffusion coefficient of iodide was determined to be 2.59 (±0.04) × 10−7 cm2 s−1 and independent of the bulk concentration of iodide. The steady-state iodide oxidation current measured at a platinum microelectrode was found to be a linear function of iodide concentration, as expected if there are no contributions from non-Stokesian mass-transport processes (electron hopping and/or Grotthuss-type exchange) under the investigated conditions

  20. Aerodynamic levitator for large-sized glassy material production.

    Science.gov (United States)

    Yoda, Shinichi; Cho, Won-Seung; Imai, Ryoji

    2015-09-01

    Containerless aerodynamic levitation processing is a unique technology for the fabrication of bulk non-crystalline materials. Using conventional aerodynamic levitation, a high reflective index (RI) material (BaTi2O5 and LaO3/2-TiO2-ZrO2 system) was developed with a RI greater than approximately 2.2, which is similar to that of diamond. However, the glass size was small, approximately 3 mm in diameter. Therefore, it is essential to produce large sized materials for future optical materials applications, such as camera lenses. In this study, a new aerodynamic levitator was designed to produce non-crystalline materials with diameters larger than 6 mm. The concept of this new levitator was to set up a reduced pressure at the top of the molten samples without generating turbulent flow. A numerical simulation was also performed to verify the concept. PMID:26429456

  1. Friction Stir Welding of Zr_(55)Al_(10)Ni_5Cu_(30) Bulk Metallic Glass to Crystalline Aluminum

    Institute of Scientific and Technical Information of China (English)

    Zuoxiang Qin; Cuihong Li; Haifeng Zhang; Zhongguang Wang; Zhuangqi Hu; Zhiqiang Liu

    2009-01-01

    The Zr_(55)Al_(10)Ni_5Cu_(30) bulk metallic glass plate were successfully welded to crystalline aluminum plates by using a friction stir welding (FSW) method. The welded zone was examined. No defects, cracks or pores were observed and no other crystalline phases except for aluminum were found in the welded joint. The strength of the joint is higher than that of aluminum. The glassy phase in the stir zone keeps the amorphous state, showing a successful welding. The storage modulus softens over the glass transition. And the weldability was discussed according to this phenomena.

  2. TEM of nanostructured metals and alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karnthaler, H.P.; Waitz, T.; Rentenberger, C.; Mingler, B

    2004-12-15

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni{sub 3}Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands.

  3. TEM of nanostructured metals and alloys

    International Nuclear Information System (INIS)

    Nanostructuring has been used to improve the mechanical properties of bulk metals and alloys. Transmission electron microscopy (TEM) including atomic resolution is therefore appropriate to study these nanostructures; four examples are given as follows. (1) The early stages of precipitation at RT were investigated in an Al-Mg-Si alloy. By high resolution TEM it is shown that the precipitates lie on (0 0 1) planes having an ordered structure. (2) In Co alloys the fronts of martensitic phase transformations were analysed showing that the transformation strains are very small thus causing no surface relief. (3) Re-ordering and recrystallization were studied by in situ TEM of an Ni3Al alloy being nanocrystalline after severe plastic deformation. (4) In NiTi severe plastic deformation is leading to the formation of amorphous shear bands. From the TEM analysis it is concluded that the amorphization is caused by plastic shear instability starting in the shear bands

  4. Solid solution lithium alloy cermet anodes

    Science.gov (United States)

    Richardson, Thomas J.

    2013-07-09

    A metal-ceramic composite ("cermet") has been produced by a chemical reaction between a lithium compound and another metal. The cermet has advantageous physical properties, high surface area relative to lithium metal or its alloys, and is easily formed into a desired shape. An example is the formation of a lithium-magnesium nitride cermet by reaction of lithium nitride with magnesium. The reaction results in magnesium nitride grains coated with a layer of lithium. The nitride is inert when used in a battery. It supports the metal in a high surface area form, while stabilizing the electrode with respect to dendrite formation. By using an excess of magnesium metal in the reaction process, a cermet of magnesium nitride is produced, coated with a lithium-magnesium alloy of any desired composition. This alloy inhibits dendrite formation by causing lithium deposited on its surface to diffuse under a chemical potential into the bulk of the alloy.

  5. The correlation between swelling and radiation-induced segregation in iron-chromium-nickel alloys

    International Nuclear Information System (INIS)

    The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is estimated using diffusivities derived from grain boundary segregation measurements in irradiated iron-chromium-nickel alloys. The resistance to void swelling in iron- and nickel-base alloys correlates with the segregation and both are functions of bulk alloy composition. Alloys that display the greatest amount of nickel enrichment and chromium depletion are found to be most resistant to void swelling, as predicted. Additionally, swelling is shown to be greater in alloys in which the RIS profiles are slow to develop

  6. A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

    Science.gov (United States)

    Vomero, Maria; van Niekerk, Pieter; Nguyen, Vivian; Gong, Nick; Hirabayashi, Mieko; Cinopri, Alessio; Logan, Kyle; Moghadasi, Ali; Varma, Priya; Kassegne, Sam

    2016-02-01

    We present a novel technology for transferring glassy carbon microstructures, originally fabricated on a silicon wafer through a high-temperature process, to a polymeric flexible substrate such as polyimide. This new transfer technique addresses a major barrier in Carbon-MEMS technology whose widespread use so has been hampered by the high-temperature pyrolysis process (⩾900 °C), which limits selection of substrates. In the new approach presented, patterning and pyrolysis of polymer precursor on silicon substrate is carried out first, followed by coating with a polymer layer that forms a hydrogen bond with glassy carbon and then releasing the ensuing glassy carbon structure; hence, transferring it to a flexible substrate. This enables the fabrication of a unique set of glassy carbon microstructures critical in applications that demand substrates that conform to the shape of the stimulated/actuated or sensed surface. Our findings based on Fourier transform infared spectroscopy on the complete electrode set demonstrate—for the first time—that carbonyl groups on polyimide substrate form a strong hydrogen bond with hydroxyl groups on glassy carbon resulting in carboxylic acid dimers (peaks at 2660 and 2585 cm-1). This strong bond is further confirmed by a tensile test that demonstrated an almost perfect bond between these materials that behave as an ideal composite material. Further, mechanical characterization shows that ultimate strain for such a structure is as high as 15% with yield stress of ~20 MPa. We propose that this novel technology not only offers a compelling case for the widespread use of carbon-MEMS, but also helps move the field in new and exciting directions.

  7. A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

    International Nuclear Information System (INIS)

    We present a novel technology for transferring glassy carbon microstructures, originally fabricated on a silicon wafer through a high-temperature process, to a polymeric flexible substrate such as polyimide. This new transfer technique addresses a major barrier in Carbon-MEMS technology whose widespread use so has been hampered by the high-temperature pyrolysis process (⩾900 °C), which limits selection of substrates. In the new approach presented, patterning and pyrolysis of polymer precursor on silicon substrate is carried out first, followed by coating with a polymer layer that forms a hydrogen bond with glassy carbon and then releasing the ensuing glassy carbon structure; hence, transferring it to a flexible substrate. This enables the fabrication of a unique set of glassy carbon microstructures critical in applications that demand substrates that conform to the shape of the stimulated/actuated or sensed surface. Our findings based on Fourier transform infared spectroscopy on the complete electrode set demonstrate—for the first time—that carbonyl groups on polyimide substrate form a strong hydrogen bond with hydroxyl groups on glassy carbon resulting in carboxylic acid dimers (peaks at 2660 and 2585 cm−1). This strong bond is further confirmed by a tensile test that demonstrated an almost perfect bond between these materials that behave as an ideal composite material. Further, mechanical characterization shows that ultimate strain for such a structure is as high as 15% with yield stress of ∼20 MPa. We propose that this novel technology not only offers a compelling case for the widespread use of carbon-MEMS, but also helps move the field in new and exciting directions. (paper)

  8. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    International Nuclear Information System (INIS)

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10−2 K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 1010 K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness

  9. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Shattuck, Mark D. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics and Benjamin Levich Institute, The City College of the City University of New York, New York, New York 10031 (United States); O’Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate R{sub c}, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. R{sub c} (or the corresponding critical casting thickness d{sub c}) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small R{sub c} < 10{sup −2} K/s, pure metals and most alloys are typically poor glass-formers with large R{sub c} > 10{sup 10} K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with R{sub c} approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for

  10. Preparation, structure and properties of Fe-based bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-06-01

    Full Text Available Purpose: The work presents preparation methods, structure characterization and chosen properties analysis of Fe-based bulk metallic glasses in as-cast state.Design/methodology/approach: The studies were performed on Fe43Co14Ni14B20Si5Nb4 metallic glass in form of rings, plates and rods. The amorphous structure of tested samples was examined by X-ray diffraction (XRD, transmission electron microscopy (TEM and scanning electron microscopy (SEM methods. The thermal properties of the glassy samples was measured using differential scanning calorimetry (DSC. The soft magnetic properties examination of tested material contained coercive force, initial magnetic permeability and magnetic permeability relaxation measurements. Findings: The XRD and TEM investigations revealed that the studied as-cast samples were amorphous. Broad diffraction halo is typical for metallic amorphous structures that have a large degree of short-range order. The characteristics of the fractured surfaces showed different zones, which might correspond with different amorphous structures of studied materials. The temperature interval of the supercooled liquid region (ΔTx defined by the difference between Tg and Tx, is as large as 56 K for the rod with diameter of 3 mm. Differences in coercivity and magnetic permeability between samples with different thickness might be resulted by some difference of amorphous structure.Practical implications: The centrifugal casting method and the pressure die casting method are useful to produce bulk amorphous materials in form of rings, plats and rods.Originality/value: The preparation of studied Fe-based bulk metallic glass in form of rings, plates and rods is important for the future progress in research and practical application of that glassy materials.

  11. Looking for a bulk point

    CERN Document Server

    Maldacena, Juan; Zhiboedov, Alexander

    2015-01-01

    We consider Lorentzian correlators of local operators. In perturbation theory, singularities occur when we can draw a position-space Landau diagram with null lines. In theories with gravity duals, we can also draw Landau diagrams in the bulk. We argue that certain singularities can arise only from bulk diagrams, not from boundary diagrams. As has been previously observed, these singularities are a clear diagnostic of bulk locality. We analyze some properties of these perturbative singularities and discuss their relation to the OPE and the dimensions of double-trace operators. In the exact nonperturbative theory, we expect no singularity at these locations. We prove this statement in 1+1 dimensions by CFT methods.

  12. Gamma probe dry bulk densities

    International Nuclear Information System (INIS)

    The gamma density probe is a useful instrument for measuring water content in small volumes of soil. Essentially, the gamma probe measures the density of the soil and water between a source and a detector. To transpose the gamma densities into water content, the dry bulk density of the soil is needed. A nondestructive method for estimating dry bulk densities for use with the gamma probe is proposed. The procedure is based on the assumption that water content values in a field dry condition were more stable than the dry bulk density values and could be transferred from one point to another. The procedure was successfully used on three areas in Reynolds Creek Experimental Watershed in southwest Idaho. (U.S.)

  13. Bulk Viscosity of Interacting Hadrons

    OpenAIRE

    Wiranata, A.; M. Prakash

    2009-01-01

    We show that first approximations to the bulk viscosity $\\eta_v$ are expressible in terms of factors that depend on the sound speed $v_s$, the enthalpy, and the interaction (elastic and inelastic) cross section. The explicit dependence of $\\eta_v$ on the factor $(\\frac 13 - v_s^2)$ is demonstrated in the Chapman-Enskog approximation as well as the variational and relaxation time approaches. The interesting feature of bulk viscosity is that the dominant contributions at a given temperature ari...

  14. Bulk Viscosity of Interacting Hadrons

    CERN Document Server

    Wiranata, A

    2009-01-01

    We show that first approximations to the bulk viscosity $\\eta_v$ are expressible in terms of factors that depend on the sound speed $v_s$, the enthalpy, and the interaction (elastic and inelastic) cross section. The explicit dependence of $\\eta_v$ on the factor $(\\frac 13 - v_s^2)$ is demonstrated in the Chapman-Enskog approximation as well as the variational and relaxation time approaches. The interesting feature of bulk viscosity is that the dominant contributions at a given temperature arise from particles which are neither extremely nonrelativistic nor extremely relativistic. Numerical results for a model binary mixture are reported.

  15. Wear behaviour of Zr-based in situ bulk metallic glass matrix composites

    Indian Academy of Sciences (India)

    X F WU; G A ZHANG; F F WU

    2016-06-01

    Zr-based bulk metallic glass (BMG) and its in situ BMG matrix composites with diameter of 3 mm were fabricated by conventional Cu-mould casting method and the dry sliding wear behaviour of the BMG and composites was investigated. Compared to the pure BMG, the composites exhibited a markedly improved wear resistance from 10 to 48% due to the existence of various volume fractions of the ductile $\\beta$-Zr dendritic phase embedded in the glassy matrix. The composites showed lower friction coefficient and wear rate than the pure BMG. Meanwhile, the surface wearing of the composite with a proper amount of $\\beta$-Zr dendrites was less severe compared to that of the pure BMG. The worn surface of the composite was covered with mild grooves and some fine wear debris, which exhibited the characteristic of a mild abrasive wear. The improvement of the wear resistance of the composite with the proper amount of $\\beta$-Zr crystalline phase is attributed to the fact that the $\\beta$-Zr crystalline phase distributed in the amorphous matrix has some effective load bearing, plastic deformation and work hardening ability to decrease strain accumulation and the release of strain energy in the glassy matrix, restrict the expanding of shear bands and cracks, and occur plastic deformation homogeneously.

  16. Bulk charges in eleven dimensions

    Science.gov (United States)

    Hawking, S. W.; Taylor-Robinson, M. M.

    1998-07-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge. Solutions involving anomaly terms preserve between 1/16 and 1/4 of the supersymmetries but Chern-Simons fluxes generally break all of the remaining supersymmetry. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singly charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped around a space with non-zero first Pontryagin class picks up an electric charge proportional to the Pontryagin number.

  17. Bulk viscosity and deflationary universes

    CERN Document Server

    Lima, J A S; Waga, I

    2007-01-01

    We analyze the conditions that make possible the description of entropy generation in the new inflationary model by means of a nearequilibrium process. We show that there are situations in which the bulk viscosity cannot describe particle production during the coherent field oscillations phase.

  18. Longitudinal bulk acoustic mass sensor

    DEFF Research Database (Denmark)

    Hales, Jan Harry; Teva, Jordi; Boisen, Anja;

    2009-01-01

    A polycrystalline silicon longitudinal bulk acoustic cantilever is fabricated and operated in air at 51 MHz. A mass sensitivity of 100 Hz/fg (1 fg=10(-15) g) is obtained from the preliminary experiments where a minute mass is deposited on the device by means of focused ion beam. The total noise i...

  19. Vanadium alloys: development strategy

    International Nuclear Information System (INIS)

    A strategy for the development of vanadium alloys for use in radiation environments is outlined. An attractive reference alloy (V-15Cr-5Ti) has been identified. The critical issues in developing vanadium base alloys are summarized

  20. Static mechanical properties for Ca48Mg27Cu25 bulk metallic glass by ultrasonic velocity measurement

    International Nuclear Information System (INIS)

    The static mechanical properties of a Ca48Mg27Cu25 bulk metallic glass were investigated using a technique of ultrasonic measurement and compressive test. The Young's modulus (E), Poisson's ratio (v), shear modulus (G) and bulk modulus (B) for the Ca48Mg27Cu25 alloy at room temperature are significantly smaller than those for Zr- and Pd- based bulk metallic glasses. The values of E, v, G and B for the Ca48Mg27Cu25 alloy are 29.8GPa, 0.230, 12.1GPa and 18.4GPa, respectively. The results of compression test for the Ca48Mg27Cu25 alloy have been also described.

  1. Host plant effects on development and reproduction of the glassy-winged sharpshooter, Homalodisca vitripennis (Homoptera: Cicadellidae)

    Science.gov (United States)

    Development, survivorship, longevity, reproduction and life table parameters of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar), were examined in the laboratory using three host plants, sunflower (Helianthus annuus L.), Chrysanthemum morifolium L. and euonymus (Euonymus japonica Thu...

  2. Polymerisationseigenschaften von Bulk-Fill Kompositen

    OpenAIRE

    Maier, Eva

    2015-01-01

    Hintergrund und Ziele: Untersuchung der Polymerisationseigenschaften von Bulk-Fill Kompositen bzgl. Konversionsrate (degree of conversion = DC), Vickers-Härte (HV), Polymerisationsschrumpfungsstress (PSS) und Polymerisationsvolumenschrumpfung (PVS) im Vergleich zu konventionellen Kompositen. Material und Methode: Untersucht wurden die Bulk-Fill Komposite Filtek Bulk Fill Flowable (FBF, 3M ESPE, Seefeld), Surefil Smart Dentin Replacement (SDR, Dentsply, Konstanz), Tetric EvoCeram Bulk Fill...

  3. On the deposition mechanisms and the formation of glassy Cu-Zr thin films

    Science.gov (United States)

    Almyras, G. A.; Matenoglou, G. M.; Komninou, Ph.; Kosmidis, C.; Patsalas, P.; Evangelakis, G. A.

    2010-04-01

    We report on molecular dynamics (MD) simulations and physical vapor deposition experimental results concerning the development of glassy and nanocrystalline Cu-Zr thin films. MD has revealed that when Cu and Zr are deposited sequentially, a thin film overlayer is formed that consists of nanocrystalline a-Zr and t-Zr2Cu, while if Cu and Zr are simultaneously deposited, amorphous CuZr thin film emerges, due to the formation of icosahedral-like clusters that impede nucleation. Thin films grown by pulsed laser deposition and magnetron sputtering techniques were analyzed by x-ray diffraction and high-resolution transmission electron microscopy and yielded unequivocal evidence that validates our MD predictions. These findings may indicate an alternative pathway for the growth of metallic nanocomposites or glassy films.

  4. The unusual morphology, structure, and magnetic property evolution of glassy carbon upon high pressure treatment

    Energy Technology Data Exchange (ETDEWEB)

    Jin, C.Q.; Wang, X.; Liu, Z.X.; Zhang, Y.L.; Li, F.Y.; Yu, R.C. [Chinese Academy of Sciences, Beijing (China). Inst. of Physics. Beijing High Pressure Research Center

    2003-12-01

    Glassy carbon (GC) has been high-pressure high-temperature treated. An interesting morphology evolution from the pristine sample to the high pressure products was observed. It is found that GC can be graphitized under pressure at a temperature much lower than that at ambient condition. Furthermore the in-situ structure and electrical measurements of GC and graphitized glassy carbon (GGC) under high temperature and high pressure have been investigated up to 30 GPa. We particularly emphasize the unusual magnetic properties of GC treated under high pressures and high temperatures. A paramagnetic to ferromagnetic-like, and then to superconducting (a diamagnetic signal with hysteresis magnetic response) -like behavior, which can be observed at temperatures as high as 80 K, appears as a successive evolution from the initial GC to GGC in accordance with three regions distinguished by the graphitization temperature. This interesting evolution of magnetic properties probably evokes the new understanding of carbon element. (author)

  5. Connection between NMR and electrical conductivity in glassy chalcogenide fast ionic conductors

    International Nuclear Information System (INIS)

    The work documented in this thesis follows the traditional order. In this chapter a general discussion of ionic conduction and of glassy materials are followed by a brief outline of the experimental techniques for the investigation of fast ionic conduction in glassy materials, including NMR and impedance spectroscopy techniques. A summary of the previous and present studies is presented in the last section of this introductory chapter. The details of the background theory and models are found in the Chapter II, followed by the description of the experimental details in Chapter III. Chapter IV of the thesis describes the experimental results and the analysis of the experimental observations followed by the conclusions in chapter V

  6. Encapsulation of the alpha-tocopherol in a glassy food model matrix

    Directory of Open Access Journals (Sweden)

    Melina Campagnaro Farias

    2007-03-01

    Full Text Available alpha-tocopherol was encapsulated in a glassy food model based on solution of maltodextrin (DE 20 and gelatin, through the use of quick freeze and freeze-drying procedures. The ratio of the maltodextrin, alpha-tocopherol and gelatin was 3:2:1 respectively. The morphology of the glassy food model was observed by scanning electron microscopy, whose analyses showed a slightly smooth surface and a rather fragile and porous structure due to cavities formed by ice crystals during freezing, and the absence of crystalline structure. It was observed by x ray diffraction that the material is an amorphous state. The samples stored in a specific plastic vessel isolated from gas and light held its amorphous state with no variations that concern to morphology and keeping 100% of the encapsulated alpha-tocopherol up to 90 days at 25 and 35 °C.

  7. Direct visualization of photoinduced glassy dynamics on the amorphous silicon carbide surface by STM movies

    Science.gov (United States)

    Nguyen, Duc; Nienhaus, Lea; Haasch, Richard T.; Lyding, Joseph; Gruebele, Martin

    2015-03-01

    Glassy dynamics can be controlled by light irradiation. Sub- and above-bandgap irradiation cause numerous phenomena in glasses including photorelaxation, photoexpansion, photodarkening and pohtoinduced fluidity. We used scanning tunneling microscopy to study surface glassy dynamics of amorphous silicon carbide irradiated with above- bandgap 532 nm light. Surface clusters of ~ 4-5 glass forming unit in diameter hop mostly in a two-state fashion, both without and with irradiation. Upon irradiation, the average surface hopping activity increases by a factor of 3. A very long (~1 day) movie of individual clusters with varying laser power density provides direct evidence for photoinduced enhanced hopping on the glass surfaces. We propose two mechanisms: heating and electronic for the photoenhanced surface dynamics.

  8. Connection between NMR and electrical conductivity in glassy chalcogenide fast ionic conductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K.H.

    1995-11-01

    The work documented in this thesis follows the traditional order. In this chapter a general discussion of ionic conduction and of glassy materials are followed by a brief outline of the experimental techniques for the investigation of fast ionic conduction in glassy materials, including NMR and impedance spectroscopy techniques. A summary of the previous and present studies is presented in the last section of this introductory chapter. The details of the background theory and models are found in the Chapter II, followed by the description of the experimental details in Chapter III. Chapter IV of the thesis describes the experimental results and the analysis of the experimental observations followed by the conclusions in chapter V.

  9. Fixation of Simulated Highly Radioactive Wastes in Glassy Solids

    International Nuclear Information System (INIS)

    Current laboratory development work at ORNL aims at incorporating high-activity-level wastes in high-density insoluble glasses, containing all radioactive constituents in the solid. Experiments with simulated TBP-25 (aluminium, HNOs), Purex and Darex (stainless steel, HNOs) wastes have indicated the technical feasibility of such a process. Dense, microcrystalline solids may be as acceptable as true glasses; their greater thermal conductivity compensates somewhat for the increase in surface area over that of true glasses. Phosphate and borophosphate glasses were prepared from all three types of waste in thelaboratory.Caesium volatility was limited to the — 0.1% due to physical entrainment, and ruthenium volatility was lowered to -0.5% by addition of phosphite or hypophosphite. Other additives included PbO, Ca(OH)2, NaOH, and MgO. Bulk densities varied from 2.36 to 2.90 g/cm3 for TBP-25 and from 2.63 to 2.80 g/cm3 for Purex waste. Corresponding volume reductions from the concentrated waste solutions were 7.2 -9.3 and 5.7 - 8.3; initial softening points varied from 875 to 100°C and from 830 to 975°C respectively. Darex tests are still preliminary. Semi-continuous operation on a semi-engineering scale produced a true glass from TBP-25 waste and a microcrystalline solid from Purex. The thermal conductivity of the glass varied from 1.05 BTU/hr-ft-F° at 320° F to 1.6 at 1050°F, about 10 times higher than that of the calcine without additives. Ruthenium volatility was held to <10% by phosphite addition. Stainless steel is a satisfactory material for construction of the calcination-fixation container. Essentially all the internal corrosion takes place during the relatively short (2-6 hr) period in which the last of the acid and water are expelled at the maximum temperature. Melt production increased the corrosion of 304L stainless steel from 5 to 42 mil/month for a 24-hr evaporation-fixation cycle on TBP-25 waste and from 8 to 140 mil/ month on Purex waste. Operation

  10. Formation and Compression Behavior of Two-Phase Bulk Metallic Glasses with a Minor Addition of Aluminum

    Institute of Scientific and Technical Information of China (English)

    ZONG Hai-Tao; MA Ming-Zhen; ZHANG Xin-Yu; QI Li; LI Gong; JING Qin; LIU Ri-Ping

    2011-01-01

    A remarkable enhancement in room-temperature compressive deformability is realized by the minor-addition of 1.5 at. % Al in ZrTi-based bulk metallic glass.Two amorphous phases are observed by transmission electron microscopy in the Al-containing alloys and this explains the improvement of compression deformability. The studies suggest that phase separation might occur in glass forming alloys with a negative enthalpy of mixing.

  11. Investigation of intergranular glassy films in polycrystalline ceramics using Transmission Electron Microscopy

    OpenAIRE

    Bhattacharyya, Somnath

    2006-01-01

    The presence of intergranulaur glassy films (IGFs) in ceramics such as Si3N4 and SiC strongly influences their material properties, including fracture toughness and creep resistance. The aim of this PhD work is to apply a variety of conventional as well as newly developed transmission electron microscopy (TEM) techniques in the detailed characterization of these films. Fresnel fringes hidden in high-resolution micrographs can be used to objectively demarcate the glass-crystal interface and...

  12. Study of 2-Nitrofluorene Interaction with DNA at a Glassy Carbon Electrode

    Czech Academy of Sciences Publication Activity Database

    Skalová, Štěpánka; Stávková, K.; Vyskočil, V.; Barek, J.

    Ústí nad Labem: Best servis, 2016 - (Navrátil, T.; Fojta, M.; Schwarzová, K.), s. 196-200 ISBN 978-80-905221-4-5. [Moderní elektrochemické metody /36./. Jetřichovice (CZ), 23.05.2016-27.05.2016] R&D Projects: GA ČR GBP206/12/G151 Institutional support: RVO:61388955 Keywords : DNA biosensor * glassy carbon electrode * voltammetry Subject RIV: CG - Electrochemistry

  13. Fine kinetics of natural physical ageing in glassy As10Se90

    International Nuclear Information System (INIS)

    Sigmoid behavior of natural physical ageing in glassy As10Se90 reveals multi-step-wise growing kinetics of enthalpy losses. Phenomenological description of this kinetics can be adequately developed in terms of first-order relaxation processes, tending atomic structure from initial towards more thermodynamically equilibrium state. This kinetics is shown to obey characteristic stretched exponential behavior originated from a number of growing steps, attributed to the interconnected processes of chalcogen chain alignment and cooperative shrinkage of glass network

  14. Optical-spectroscopic signature of radiation-induced instability in glassy arsenic sulphides

    OpenAIRE

    Shpotyuk, Ya.; Polovynko, I.

    2012-01-01

    Optical changes caused by 60Co g-irradiation are studied in glassy-like As2S3. The observed long-wave shift in the range of fundamental optical absorption edge accompanied by increase in transmittance is explained as a manifestation of complicated nature of radiation-induced structural transformations associated with coordination topological defects and additional shrinkage input from natural physical ageing.

  15. Layer-by-layer Assembly of Noble Metal Nanoparticles on Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    CHEN Da; ZHENG Long-Zhen

    2008-01-01

    Silver,gold,platinum and palladium nanoparticles were initially prepared in the AOT[sodium bis(2-ethylhexyl)-sulfosuccinate]micelle and characterized by ultraviolet-visible spectroscopy,transmission electron macroscopy,X-ray diffraction,Fourier transform-infrared spectroscopy,and zeta potential analysis.The negatively charged Pt nanoparticles were self-assembled on a glassy carbon electrode by a layer-by-layer method and the modified electrode electrocatalytic reactivity toward methanol oxidation was studied.

  16. Electrochemical behaviour of platinum at polymer-modified glassy carbon electrodes

    Indian Academy of Sciences (India)

    Carmem L P S Zanta; C A Martínez-Huitle

    2007-07-01

    In this paper, the preparations and voltammetric characteristics of chitosan-modified glassy carbon (Ct-MGC) and platinum electrodes are studied. Ct-MGC can be used for pre-concentration and quantification of trace amounts of platinum in solution. At low pH medium, the complex of Pt with protonated group -NH3+ in the chitosan molecule has been confirmed by FT-IR spectra studies.

  17. A search for disordered (glassy) phase in solid 3He deformed in situ

    OpenAIRE

    Lisunov, A. A.; Maidanov, V. A.; Rubanskiy, V. Yu.; Rubets, S. P.; Rudavskii, E. Ya.; Rybalko, A. S.; Tikhii, V. A.

    2010-01-01

    A disordered (glassy) state has been searched in solid 3He deformed in the course of experiment employing precise measurements of pressure. The analysis of the temperature dependence of the crystal pressure measured at a constant volume shows that the main contribution to the pressure is made by the phonon subsystem, the influence of the disordered phase being very weak. Annealing of the deformed crystal does not affect this state. The results obtained differ greatly from the corresponding da...

  18. Fast dynamics of substituted polyacetylenes in glassy states and its relation to gas permeability

    International Nuclear Information System (INIS)

    We studied local dynamics of three substituted polyacetylenes in glassy states using a quasielastic neutron scattering technique in an energy range from -2 to 10 meV and found a clear correlation between the local mobility and the gas permeability in these polymers. On the basis of the Q dependence of the relaxation rate we will discuss possible motions related to the gas permeability. (author)

  19. From frustration to glassiness via quantum fluctuations and random tiling with exotic entropy

    OpenAIRE

    Klich, I.; Lee, S.-H.; Iida, K.

    2013-01-01

    When magnetic moments (spins) are regularly arranged in a geometry of a triangular motif, the spins may not satisfy simultaneously their interactions with their neighbors. This phenomenon, called frustration, leads to numerous energetically equivalent magnetic states (ground states), which results in exotic states such as spin liquid and spin ice. Here we report an alternative situation: a system that, classically, is to be a liquid in the clean limit freezes into a glassy state induced by qu...

  20. Structural and dynamical features of multiple metastable glassy states in a colloidal system with competing interactions

    OpenAIRE

    Klix, Christian L.; Royall, C. Patrick; Tanaka, Hajime

    2010-01-01

    Systems in which a short-ranged attraction and long-ranged repulsion compete are intrinsically frustrated, leading their structure and dynamics to be dominated either by mesoscopic order or by metastable disorder. Here we report the latter case in a colloidal system with long-ranged electrostatic repulsions and short-ranged depletion attractions. We find a variety of states exhibiting slow non-diffusive dynamics: a gel, a glassy state of clusters, and a state reminiscent of a Wigner glass. Va...

  1. The influence of deformation and chemical composition on elementary free volumes in glassy polymers

    International Nuclear Information System (INIS)

    A relation between positronium annihilation characteristics and concentration of elementary free volumes is considered for the case of positronium formation before its localization. We estimated the diffusion coefficient of nonlocalized positronium (∼ 10-4 cm2/s0. The positron annihilation lifetime studies of unaxial compression and annealing of some glassy polymers revealed variations of the shape of elementary free volumes size-distributions. (author)

  2. Improved stability of redox enzyme layers on glassy carbon electrodes via covalent grafting

    Energy Technology Data Exchange (ETDEWEB)

    Pellissier, Marie; Barriere, Frederic [Universite de Rennes 1, CNRS UMR no. 6226, Sciences Chimiques de Rennes, Equipe MaCSE (France); Downard, Alison J. [MacDiarmid Institute for Advanced Materials and Nanotechnology, Department of Chemistry, University of Canterbury, Christchurch (New Zealand); Leech, Donal [School of Chemistry, National University of Ireland, Galway (Ireland)

    2008-06-15

    One of the challenges in the field of enzymatic biofuel cells is to significantly improve their current limited lifetime. In the present work, we report the covalent immobilization of enzyme layers on glassy carbon electrodes, functionalized via electrochemical reduction of in situ generated aryldiazonium salts bearing carboxylic acid groups. We present the performance and the stability over time of the modified electrodes. For glucose oxidase - modified electrodes, stable catalytic activity is observed for a minimum of 6 weeks. (author)

  3. Cooperative heterogeneous facilitation: multiple glassy states and glass-glass transition

    OpenAIRE

    Sellitto, Mauro

    2012-01-01

    The formal structure of glass singularities in the mode-coupling theory (MCT) of supercooled liquids dynamics is closely related to that appearing in the analysis of heterogeneous bootstrap percolation on Bethe lattices, random graphs and complex networks. Starting from this observation one can build up microscopic on lattice realizations of schematic MCT based on cooperative facilitated spin mixtures. I discuss a microscopic implementation of the F13 schematic model including multiple glassy...

  4. Complex Nonlinear Deformation of Nanometer Intergranular Glassy Films in βSi3N4

    OpenAIRE

    Chen, Jun; Ouyang, Lizhi; Rulis, Paul; Misra, Anil; Ching, W. Y.

    2005-01-01

    The mechanical properties of a model of Y-doped intergranular glassy film in silicon nitride ceramics are studied by large-scale ab initio modeling. By linking directly to its electronic structure, it is shown that this microstructure has a complex nonlinear deformation under stress and Y doping significantly enhances the mechanical properties. The calculation of the electrostatic potential across the film supports the space charge model in ceramic microstructures.

  5. Complex nonlinear deformation of nanometer intergranular glassy films in beta-Si3N4.

    Science.gov (United States)

    Chen, Jun; Ouyang, Lizhi; Rulis, Paul; Misra, Anil; Ching, W Y

    2005-12-16

    The mechanical properties of a model of Y-doped intergranular glassy film in silicon nitride ceramics are studied by large-scale ab initio modeling. By linking directly to its electronic structure, it is shown that this microstructure has a complex nonlinear deformation under stress and Y doping significantly enhances the mechanical properties. The calculation of the electrostatic potential across the film supports the space charge model in ceramic microstructures. PMID:16384476

  6. Glucose Biosensor Based on a Glassy Carbon Electrode Modified with Polythionine and Multiwalled Carbon Nanotubes

    OpenAIRE

    Wenwei Tang; Lei Li; Lujun Wu; Jiemin Gong; Xinping Zeng

    2014-01-01

    A novel glucose biosensor was fabricated. The first layer of the biosensor was polythionine, which was formed by the electrochemical polymerisation of the thionine monomer on a glassy carbon electrode. The remaining layers were coated with chitosan-MWCNTs, GOx, and the chitosan-PTFE film in sequence. The MWCNTs embedded in FAD were like "conductive wires" connecting FAD with electrode, reduced the distance between them and were propitious to fast direct electron transfer. Combining with good ...

  7. Potentiometric application of boron- and phosphorus-doped glassy carbon electrodes

    Directory of Open Access Journals (Sweden)

    ZORAN V. LAUSEVIC

    2001-03-01

    Full Text Available Acomparative study was carried out of the potentiometric application of boronand phosphorus-doped and undoped glassy carbon samples prepared at the same heat treatment temperature (HTT 1000°C. The electrochemical activities of the obtained electrode materials were investigated on the example of argentometric titrations. It was found that the electrochemical behaviour of the doped glassy carbon samples are very similar to a Sigri (undoped glassy carbon sample (HTT 2400°C. The experiments showed that the potentiometric response depends on the polarization mode, the nature of the sample, the pretreatment of the electrode surface, and the nature of the supporting electrolyte. The amounts of iodide, bromide, and of chloridewere determined to be 1.27 mg, 0.80 mg and 0.54 mg, respectively, with a maximum relative standard deviation of less than 1.1%. The obtained results are in good agreement with the results of comparative potentiometric titrations using a silver indicator electrode. The titrationmethod was applied to the indirect determination of pyridoxine hydrochloride, i.e., vitamin B6.

  8. Hydrogen Isotopes of Glassy and Phyllosilicate Spherules in Al Rais (CR) and Orgueil (CI) Chondrites

    Institute of Scientific and Technical Information of China (English)

    GUAN Yunbin; Michael E. ZOLENSKY

    2004-01-01

    The hydroxyl in phyllosilicate minerals is the most common occurrence of water in primitive meteorites.Direct hydrogen isotopic analysis of this water component using an ion microprobe has been made in some glassy or phyllosilicate spherules from the Al Rais (CR) and Orgueil (CI) chondrites. The spherules from Al Rais show large deuterium excesses (δD = +200 - +800) relative to terrestrial standards, whereas deuterium-enrichments in the spherules from Orgueil are much smaller (δD = +40 - +130‰). The phyllosilicate spherules are products of aqueous alteration of glassy precursors. In A1 Rais the phyllosilicate spherules have relatively higher δD values than the glassy ones, indicating that water introduced during aqueous alteration was deuterium-enriched. The deuterium-enrichments in the phyllosilicate spherules from Orgueil could result from isotopic exchange under thermodynamic conditions within the solar nebula. The much larger δD excesses of the Al Rais spherules, however, cannot be attributed to the similar process;instead, an interstellar origin needs to be invoked.

  9. Direct electron transfer from glucose oxidase immobilized on a nano-porous glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of); Tabrizi, Mahmoud Amouzadeh [Department of Chemistry, Institute for Advanced Studies in Basic Sciences, P.O. Box 45195-1159, Gava Zang, Zanjan (Iran, Islamic Republic of)

    2011-11-30

    Highlights: > A direct electron transfer reaction of glucose oxidase was observed on the surface of a nano-porous glassy carbon electrode. > A pair of well-defined and reversible redox peaks was observed at the formal potential of approximately -0.439 V. > The apparent electron transfer rate constant was measured to be 5.27 s{sup -1}. > A mechanism for the observed direct electron transfer reaction was proposed, which consists of a two-electron and a two-proton transfer. - Abstract: A pair of well-defined and reversible redox peaks was observed for the direct electron transfer (DET) reaction of an immobilized glucose oxidase (GOx) on the surface of a nano-porous glassy carbon electrode at the formal potential (E{sup o}') of -0.439 V versus Ag/AgCl/saturated KCl. The electron transfer rate constant (k{sub s}) was calculated to be 5.27 s{sup -1}. The dependence of E{sup o}' on pH indicated that the direct electron transfer of the GOx was a two-electron transfer process, coupled with two-proton transfer. The results clearly demonstrate that the nano-porous glassy carbon electrode is a cost-effective and ready-to-use scaffold for the fabrication of a glucose biosensor.

  10. A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

    Energy Technology Data Exchange (ETDEWEB)

    Weber, J.K.R., E-mail: rweber@anl.gov [Materials Development, Inc., Arlington Heights, IL 60004 (United States); Argonne National Laboratory, Argonne, IL 60439 (United States); Benmore, C.J. [Argonne National Laboratory, Argonne, IL 60439 (United States); Department of Physics, Arizona State University, AZ 85287 (United States); Tailor, A.N.; Tumber, S.K. [Materials Development, Inc., Arlington Heights, IL 60004 (United States); Neuefeind, J. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Cherry, B. [Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Yarger, J.L. [Department of Physics, Arizona State University, AZ 85287 (United States); Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Mou, Q. [Magnetic Resonance Research Center, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Weber, W. [Department of Physics, Arizona State University, AZ 85287 (United States); Department of Chemistry and Biochemistry, Arizona State University, AZ 85287 (United States); Byrn, S.R. [Department of Industrial and Physical Pharmacy, Purdue University, IN 47907 (United States)

    2013-10-16

    Highlights: • Acoustic levitation was used to make phase-pure glassy forms of pharmaceutical compounds. • Neutrons, X-rays and NMR were used to characterize the glasses. • The glass comprised of slightly distorted molecules packed in a random network. • Potential for new drug synthesis routes is discussed. - Abstract: Acoustic levitation was used to trap 1–3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses.

  11. Voltammetric determination of adenosine and guanosine using fullerene-C(60)-modified glassy carbon electrode.

    Science.gov (United States)

    Goyal, Rajendra N; Gupta, Vinod K; Oyama, Munetaka; Bachheti, Neeta

    2007-02-28

    A fullerene-C(60)-modified glassy carbon electrode (GCE) is used for the simultaneous determination of adenosine and guanosine by differential pulse voltammetry. Compared to a bare glassy carbon electrode, the modified electrode exhibits an apparent shift of the oxidation potentials in the cathodic direction and a marked enhancement in the voltammetric peak current response for both the biomolecules. Linear calibration curves are obtained over the concentration range 0.5muM-1.0mM in 0.1M phosphate buffer solution at pH 7.2 with a detection limit of 3.02x10(-7)M and 1.45x10(-7)M for individual determination of adenosine and guanosine, respectively. The interference studies showed that the fullerene-C(60)-modified glassy carbon electrode exhibited excellent selectivity in the presence of hypoxanthine, xanthine, uric acid and ascorbic acid. The proposed procedure was successfully applied to detect adenosine and guanosine in human blood plasma and urine, without any preliminary pre-treatment. PMID:19071420

  12. Gold nanoparticles directly modified glassy carbon electrode for non-enzymatic detection of glucose

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Gang; Shu, Honghui; Ji, Kai [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); Oyama, Munetaka [Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8520 (Japan); Liu, Xiong [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China); He, Yunbin, E-mail: ybhe@hubu.edu.cn [Ministry-of-Education Key Laboratory for the Green Preparation and Application of Functional Materials, Faculty of Materials Science and Engineering, Hubei University, No. 368 Youyi Avenue, Wuchang, Wuhan 430062 (China)

    2014-01-01

    This work describes controllable preparation of gold nanoparticles on glassy carbon electrodes by using the seed mediated growth method, which contains two steps, namely, nanoseeds attachment and nanocrystals growth. The size and the dispersion of gold nanoparticles grown on glassy carbon electrodes could be easily tuned through the growth time based on results of field-emission scanning electron microscopy. Excellent electrochemical catalytic characteristics for glucose oxidation were observed for the gold nanoparticles modified glassy carbon electrodes (AuNPs/GC), resulting from the extended active surface area provided by the dense gold nanoparticles attached. It exhibited a wide linear range from 0.1 mM to 25 mM with the sensitivity of 87.5 μA cm{sup −2} mM{sup −1} and low detection limit down to 0.05 mM for the sensing of glucose. The common interfering species such as chloride ion, ascorbic acid, uric acid and 4-acetamidophenol were verified having no interference effect on the detection of glucose. It is demonstrated that the seed mediated method is one of the facile approaches for fabricating Au nanoparticles modified substrates, which could work as one kind of promising electrode materials for the glucose nonenzymatic sensing.

  13. Microscopic theory of the glassy dynamics of passive and active network materials.

    Science.gov (United States)

    Wang, Shenshen; Wolynes, Peter G

    2013-03-28

    Signatures of glassy dynamics have been identified experimentally for a rich variety of materials in which molecular networks provide rigidity. Here we present a theoretical framework to study the glassy behavior of both passive and active network materials. We construct a general microscopic network model that incorporates nonlinear elasticity of individual filaments and steric constraints due to crowding. Based on constructive analogies between structural glass forming liquids and random field Ising magnets implemented using a heterogeneous self-consistent phonon method, our scheme provides a microscopic approach to determine the mismatch surface tension and the configurational entropy, which compete in determining the barrier for structural rearrangements within the random first order transition theory of escape from a local energy minimum. The influence of crosslinking on the fragility of inorganic network glass formers is recapitulated by the model. For active network materials, the mapping, which correlates the glassy characteristics to the network architecture and properties of nonequilibrium motor processes, is shown to capture several key experimental observations on the cytoskeleton of living cells: Highly connected tense networks behave as strong glass formers; intense motor action promotes reconfiguration. The fact that our model assuming a negative motor susceptibility predicts the latter suggests that on average the motorized processes in living cells do resist the imposed mechanical load. Our calculations also identify a spinodal point where simultaneously the mismatch penalty vanishes and the mechanical stability of amorphous packing disappears. PMID:23556772

  14. Electrochemical pre anodization of glassy carbon electrode and application to determine chloramphenicol

    International Nuclear Information System (INIS)

    This paper suggested a method to enhance the performance of carbon electrodes for the determination of chloramphenicol (CAP). The sensitivity and the reproducibility of the carbon electrodes could be enhanced easily by electrochemical pretreatment. Some kinds of carbon material were studied including glassy carbon, graphite carbon and pyrolytic carbon. Numerous kinds of supporting electrolyte have been tried. For glassy carbon electrode, the acidic solution, H2SO4 5 mM, resulted in best performance at pretreated voltage of +2.1V (vs. Ag/ AgCl) in duration of 250 second. However, for graphite and pyrolytic carbon electrodes, the phosphate buffer solution pH 6.0 gave the best performance at +1.7V (vs. Ag/ AgCl) in duration of 20 seconds. The detection limit could be at very low concentration of CAP: 0.8 ng/ ml for glassy carbon electrode, 3.5 ng/ ml for graphite carbon electrode. The method was successful applied to aqua-agriculture water sample and milk sample with simple extraction as well as direct ointment sample analysis. (author)

  15. Electrochemically modified sulfisoxazole nanofilm on glassy carbon for determination of cadmium(II) in water samples

    International Nuclear Information System (INIS)

    Highlights: • Sulfisoxazole was grafted onto glassy carbon electrode. • The electrode was characterized by spectroscopic and electrochemical methods. • It has been used for the determination of Cd(II) ions in real samples in very low concentrations. -- Abstract: Sulfisoxazole (SO) was grafted to glassy carbon electrode (GCE) via the electrochemical oxidation of SO in acetonitrile solution containing 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB). The prepared electrode was characterized by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), reflection–absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS). The ellipsometric thickness of SO nanofilm at the glassy carbon surface was obtained as 14.48 ± 0.11 nm. The stability of the SO modified GCE was studied. The SO modified GCE was also utilized for the determination of Cd(II) ions in water samples in the presence of Pb(II) and Fe(II) by adsorptive stripping voltammetry. The linearity range and the detection limit of Cd(II) ions were 1.0 × 10−10 to 5.0 × 10−8 M and 3.3 × 10−11 M (S/N = 3), respectively

  16. Graphene oxide-mediated electrochemistry of glucose oxidase on glassy carbon electrodes.

    Science.gov (United States)

    Castrignanò, Silvia; Valetti, Francesca; Gilardi, Gianfranco; Sadeghi, Sheila J

    2016-01-01

    Glucose oxidase (GOD) was immobilized on glassy carbon electrodes in the presence of graphene oxide (GO) as a model system for the interaction between GO and biological molecules. Lyotropic properties of didodecyldimethylammonium bromide (DDAB) were used to stabilize the enzymatic layer on the electrode surface resulting in a markedly improved electrochemical response of the immobilized GOD. Transmission electron microscopy images of the GO with DDAB confirmed the distribution of the GO in a two-dimensional manner as a foil-like material. Although it is known that glassy carbon surfaces are not ideal for hydrogen peroxide detection, successful chronoamperometric titrations of the GOD in the presence of GO with β-d-glucose were performed on glassy carbon electrodes, whereas no current response was detected upon β-d-glucose addition in the absence of GO. The GOD-DDAB-GO system displayed a high turnover efficiency and substrate affinity as a glucose biosensor. The simplicity and ease of the electrode preparation procedure of this GO/DDAB system make it a good candidate for immobilizing other biomolecules for fabrication of amperometric biosensors. PMID:25939764

  17. Micro and nano indentation studies on Zr60Cu10Al15Ni15 bulk metallic glass

    International Nuclear Information System (INIS)

    Highlights: • Highest hardness is observed in the fully crystalline regions. • Large atomic misfit between intermetallic phases provides additional hardening. • A unique case of ISE is observed in both glassy as well as crystalline regions. - Abstract: Partially vitrified Zr60Cu10Al15Ni15 bulk metallic glass has been synthesized using water cooled copper mold drop casting technique. Kinetically favorable microstructures having different morphologies are observed throughout the volume of the bulk metallic glass sample. X-ray diffraction studies indicate formation of hard intermetallic compounds such as Zr3Al2 and Zr2Ni in certain regions along with amorphous structures. Microindentation studies carried out in different regions of the sample reveal microstructure dependent deformation behavior. Highest hardness is observed in the fully crystallized regions compared to pure glassy regions in the same sample. Further nanoindentation in the same sample is used to understand dynamic mechanical properties of microstructures in different regions. The pile-up morphologies around the indent and differences in load–displacement curves provide vital information on deformation behavior of sample in different microstructure sensitive regions

  18. Bulk Combinatorial Synthesis and High Throughput Characterization for Rapid Assessment of Magnetic Materials: Application of Laser Engineered Net Shaping (LENS™)

    Science.gov (United States)

    Geng, J.; Nlebedim, I. C.; Besser, M. F.; Simsek, E.; Ott, R. T.

    2016-07-01

    A bulk combinatorial approach for synthesizing alloy libraries using laser engineered net shaping (LENS™; i.e., 3D printing) was utilized to rapidly assess material systems for magnetic applications. The LENS™ system feeds powders in different ratios into a melt pool created by a laser to synthesize samples with bulk (millimeters) dimensions. By analyzing these libraries with autosampler differential scanning calorimeter/thermal gravimetric analysis and vibrating sample magnetometry, we are able to rapidly characterize the thermodynamic and magnetic properties of the libraries. The Fe-Co binary alloy was used as a model system and the results were compared with data in the literature.

  19. Bulk Combinatorial Synthesis and High Throughput Characterization for Rapid Assessment of Magnetic Materials: Application of Laser Engineered Net Shaping (LENS™)

    Science.gov (United States)

    Geng, J.; Nlebedim, I. C.; Besser, M. F.; Simsek, E.; Ott, R. T.

    2016-04-01

    A bulk combinatorial approach for synthesizing alloy libraries using laser engineered net shaping (LENS™; i.e., 3D printing) was utilized to rapidly assess material systems for magnetic applications. The LENS™ system feeds powders in different ratios into a melt pool created by a laser to synthesize samples with bulk (millimeters) dimensions. By analyzing these libraries with autosampler differential scanning calorimeter/thermal gravimetric analysis and vibrating sample magnetometry, we are able to rapidly characterize the thermodynamic and magnetic properties of the libraries. The Fe-Co binary alloy was used as a model system and the results were compared with data in the literature.

  20. Plasticity-improved Zr-Cu-Al bulk metallic glass matrix composites containing martensite phase

    International Nuclear Information System (INIS)

    Zr48.5Cu46.5Al5 bulk metallic glass matrix composites with diameters of 3 and 4 mm were produced through water-cooled copper mold casting. Micrometer-sized bcc based B2 structured CuZr phase containing martensite plate, together with some densely distributed nanocrystalline Zr2Cu and plate-like Cu10Zr7 compound, was found embedded in a glassy matrix. The microstructure formation strongly depends on the composition and cooling rate. Room temperature compression tests reveal significant strain hardening and plastic strains of 7.7% and 6.4% before failure are obtained for the 3-mm- and 4-mm-diam samples, respectively. The formation of the martensite phase is proposed to contribute to the strain hardening and plastic deformation of the materials