WorldWideScience

Sample records for bulk glassy alloys

  1. Cast bulk glassy alloys:fabrication,alloy development and properties

    Institute of Scientific and Technical Information of China (English)

    Qingsheng Zhang; Chunling Qin; Akihisa Inoue

    2010-01-01

    Metallic glasses represent an interesting group of materials as they possess outstanding physical, chemical and mechanical properties compared to their crystalline counterparts. Currently, with well designed compositions it is possible to cast liquid alloys into the glassy state at low critical cooling rates from 100 K·s-1 to 1 K·s-1 and in large critical sample sizes up to several centimeters, which significantly enhances the promise for possible applications as advanced engineering materials. This paper reviews the development of(ZrCu)-based bulk metallic glasses with large sizes by copper mold casting and their unique properties. Additionally, the ex-situ and in-situ second phases reinforced BMG composites with large plasticity are also presented.

  2. Soft-ferromagnetic bulk glassy alloys with large magnetostriction and high glass-forming ability

    Directory of Open Access Journals (Sweden)

    Jiawei Li

    2011-12-01

    Full Text Available The effect of Dy addition on the glass-forming ability (GFA, magnetostriction as well as soft-magnetic properties and fracture strength in FeDyBSiNb glassy alloys was investigated. In addition to the increase of supercooled liquid region from 55 to 100 K, the addition of Dy is effective in approaching alloy to an eutectic point and increasing the saturation magnetostrction (λs. Accordingly, bulk glassy alloy (BGA rods with diameters up to 4 mm were produced, which exhibit a large λs as high as 65×10-6. Besides, the BGA system exhibits superhigh fracture strength of 4000 MPa, combined with good soft-magnetic properties.

  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. 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.

  5. 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.

  6. Formation and investigation of the structure and mechanical properties of bulk metallic glassy composite (Ti-Zr)-(Cu-Ni-Co) alloys with the addition of Boron

    Energy Technology Data Exchange (ETDEWEB)

    Zadorozhnyy, V.Yu., E-mail: vuz@wpi-aimr.tohoku.ac.jp [WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan); Inoue, A.; Louzguine-Luzgin, D.V. [WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan)

    2012-12-15

    (Ti-Zr)-(Cu-Ni-Co) bulk metallic alloys containing 1000 mass ppm of boron were investigated in the present work. Taking compositional formula (Ti-Zr){sub 49.5+x}(Cu-Ni){sub 49.5-x}Co{sub 1} as a basis, we increased the content of Ti and Zr elements and decreased the content of Cu and Ni with the purpose of production of crystal-glassy composites. Such a kind of approach may allow combination of high strength of glassy alloys and good plasticity of crystalline alloys in these composite materials. According to this approach a large number of the alloys of different composition and different diameters were prepared and investigated. Some of the prepared bulk glassy-crystal composite samples showes rather good properties: the compressive strength of 1800-2500 MPa and compressive plasticity up to 13.5%.

  7. Fabrication of bulk glassy Zr41Ti14Ni8Cu12.5Be22.5Fe2 alloy by water quenching

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A glassy Zr41Ti14Ni8Cu12.5Be22.5Fe2 rod with a diameter of 9 mm was successfully produced by water quenching.The effects of iron addition on thermal stability and hardness of Zr41Ti14Ni8Cu12.5Be22.5Fe2 bulk amorphous alloy were investigated by XR D,DSC and microhardness test.It is found that the full annealing would enhance the strength of the alloy significantly.The cause of the increase in hardness was analyzed and the formation mechanisms of the bulk amorphous alloy are discussed.

  8. 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

  9. Effect of repeated melting of the mother ingot on the thermal stability of a Zr60Al15Ni25 bulk glassy alloy

    Institute of Scientific and Technical Information of China (English)

    YAN Zhijie; LI Jinfu; WANG Honghua; HE Shunrong; ZhOU Yaohe

    2003-01-01

    The effect of repeated melting of the mother ingot on the thermal stability of a Zr60Al15Ni25 glassy alloy was investigated by differential scanning calorimetry (DSC). Experimental results indicate that after the repeated melting of the ingots at 1300 and 1580 K, the glass transition temperature Ts increases from 686.4 to 690.7 and 696.8 K and the onset temperature of crystallization Tx from 757.9 to 758.6 and 763.4 K, respectively, indicating that the thermal stability becomes higher after the repeated arc melting of the mother ingot and that it is more effective at higher temperature. Within the framework of structure heredity, the origin of the improvement of the thermal stability of Zr60Al15Ni2s bulk glassy alloy is discussed.

  10. 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.

  11. 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

  12. Ultrahigh performance of Ti-based glassy alloy tube sensor for Coriolis mass flowmeter

    Institute of Scientific and Technical Information of China (English)

    MA Chao-li; A. INOUE; ZHANG Tao

    2006-01-01

    Bulk metallic glasses (BMGs) have potential applications for both structural and functional components owing to their good mechanical properties. With the aim of demonstrating great engineering value of BMGs, a direct melt-forming technique based on suction casting for the production of glassy alloy tubes was developed. The fabrication, structure, geometry, properties and sensor performance of the tubes were examined. The results show that the Coriolis mass flowmeters using the Ti-based glassy alloy sensor tube exhibit excellent measurement sensitivity, viz. 28.5 times higher than that of the conventional flowmeter manufactured using stainless steel (SUS316) tube.

  13. 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.)

  14. Effect of niobium on glass-formation ability and soft magnetic properties of Gd-doping glassy alloys

    Institute of Scientific and Technical Information of China (English)

    LIU Xuan; DING Yanhong; ZHAO Shuisheng; LONG Yi; YE Rongchang; CHANG Yongqin

    2008-01-01

    The effect of niobium on glass-formation ability and soft magnetic properties were studied in Fe-Gd-B glassy alloys. The glassy alloys exhibited high glass-formation ability when the dement of Nb was added. Bulk glassy rod (Fe0.87Co0.13)68.5Gd3.5Nb3B25 with a diameter up to 3 mm was produced by eopper mold casting. The size of the atom might play an important role in increasing glass-formation ability. The coercive force of glassy (Fe0.87Co0.13)71.5-xGd3.5NbxB25 (x=1.2, 1.5, 2, 2.5, 3, 4)alloys decreased after the addition of niobium element and was in the range of 1.5-2.9 A/m. The permeability spectrum of (Fe0.87Co0.13)7.3Gd3.5Nb1.5B25glassy ribbon showed that the relaxation fiequency (f0) was 6.1 MHz.

  15. Thermal stability and mechanical properties of Gd-Co-Al bulk glass alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The glass forming ability of Gd-Co-Al ternary alloy systems with a composition ranging from 50% to 70% (molar fraction)for Gd and from 5% to 40% (molar fraction) for Al were investigated by copper mold casting and Gd60Co25Al15 bulk glass alloy cylinders with the maximum diameter of 5 mm were obtained. The reduced glass transformation temperature (Tg/Tm) and the distance of supercooling region △Tx are 0.616 and 45 K, respectively for this Gd-Co-Al alloy. The compressive fracture strength (σf) and elastic modulus (E) of Gd-Co-Al glassy alloys are 1 170-1 380 MPa and 59-70 GPa, respectively. The Gd-Al-Co bulk glassy alloys with high glass forming ability and good mechanical properties are promising for the future development as a new type function materials.

  16. 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.

  17. Production, Properties and Applications of Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Tao Zhang; Akihisa Inoue

    2000-01-01

    A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.

  18. Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

    Institute of Scientific and Technical Information of China (English)

    ZHUO Long-Chao; PANG Shu-Jie; WANG Hui; ZHANG Tao

    2009-01-01

    Based on a new approach for designing glassy alloy compositions,bulk Al-based alloys with good glass-forming ability (GFA) are synthesized.The cast Al86Si0.5Ni4.06Co2.94 Y6Sc0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod.The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 Gpa and maximum strength of 1.27 Gpa as well as an obvious plastic strain of about 2.4% during compressive deformation.This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Ideal solution behaviour of glassy Cu–Ti, Zr, Hf alloys and properties of amorphous copper

    Energy Technology Data Exchange (ETDEWEB)

    Ristić, R. [Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, HR-3100 Osijek (Croatia); Cooper, J.R. [Department of Physics, Cavendish Laboratory, J.J. Thomson Avenue, CB3 0HE Cambridge (United Kingdom); Zadro, K.; Pajić, D. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia); Ivkov, J. [Institute of Physics, Bijenička cesta 46, HR-10002 Zagreb (Croatia); Babić, E. [Department of Physics, Faculty of Science, Bijenička cesta 32, HR-10002 Zagreb (Croatia)

    2015-02-05

    Highlights: • Ideal solution behaviour (ISB) is established in all Cu–Ti, Zr, Hf glassy alloys. • ISB enables reliable estimates for various properties of amorphous Cu. • ISB also impacts glass forming ability in these and probably other similar alloys. - Abstract: A comprehensive study of selected properties of amorphous (a) Cu–TE alloys (TE = Ti, Zr and Hf) has been performed. Data for average atomic volumes of a-Cu–Hf, Ti alloys combined with literature data show that ideal solution behaviour (Vegard’s law) extends over the whole glass forming range (GFR) in all a-Cu–TE alloys. This enables one to obtain an insight into some properties and probable atomic arrangements for both, a-TEs (Ristić et al., 2010) and a-Cu by extrapolation of the data for alloys. Indeed the atomic volumes and other properties studied for all a-Cu–TE alloys extrapolate to the same values for a-Cu. Depending on the property, these values are either close to those of crystalline (c) Cu, or are close to those for liquid (L) Cu. In particular, the electronic transport properties of a-Cu seem close to those of L-Cu, whereas the static properties, such as the density of states, and Young’s modulus, converge to those of c-Cu. The possible impact of these results on our understanding of a-Cu–TE alloys, including glass forming ability, is discussed.

  6. 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.

  7. Rotating speed effect on electronic transport behaviors of Ni-Nb-Zr-H glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fukuhara, Mikio, E-mail: fukuhara@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer The electronic transport behaviors of (Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 100-y}H{sub y} (0 {<=} y {<=} 15) glassy alloys, which produced by rotating (or quenching) speeds of 3000 and 10,000 rpm, have been studied as a function of hydrogen content. Black-Right-Pointing-Pointer The resistivity for (Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 97.8}H{sub 2.2} alloy, produced by rotating speed of 10,000 rpm, displayed 0.1 n{Omega} cm, which is 0.01% of silver (1.62 {mu}{Omega} cm) at room temperature, between 40 and 252 K. Black-Right-Pointing-Pointer Supercooling of the molten alloy induces a superior ballistic conductor and a room-temperature Coulomb oscillation. - Abstract: The electronic transport behaviors of (Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 100-y}H{sub y} (0 {<=} y {<=} 15) glassy alloys, produced by rotating (or quenching) speeds of 3000 and 10,000 rpm, have been studied as a function of hydrogen content. These alloys show semiconducting, superior ballistic transport, superconducting and electric current-induced Coulomb oscillation, as hydrogen content increases. The resistivity for (Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 97.8}H{sub 2.2} alloy, produced by rotating speed of 10,000 rpm, displayed 0.1 n{Omega} cm, which is 0.01% of silver (1.62 {mu}{Omega} cm) at room temperature, between 40 and 252 K. The Coulomb oscillation of the 10,000 rpm-(Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 95.2}H{sub 4.8} alloy is about 4-fold larger than that of the 3000 rpm-(Ni{sub 0.39}Nb{sub 0.25}Zr{sub 0.35}){sub 91.1}H{sub 8.9} alloy. Supercooling of the molten alloy induces a superior ballistic conductor and a room-temperature Coulomb oscillation at lower and higher hydrogen contents, respectively.

  8. 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.

  9. Glass-forming ability analysis of selected Fe-based bulk amorphous alloys

    Directory of Open Access Journals (Sweden)

    R. Nowosielski

    2010-09-01

    Full Text Available Purpose: The paper mainly aims to present the structure and thermal stability of selected Fe-based bulk metallic glasses: Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4.Design/methodology/approach: The investigated samples were cast in form of the rods by the pressure die casting method. The structure analysis of the studied materials in as-cast state was carried out using XRD and TEM methods. The thermal stability associated with glass transition temperature (Tg, onset (Tx and peak (Tp crystallization temperature was examined by differential scanning calorimetry (DSC. Several parameters have been used to determine the glass-forming ability of studied alloys. The parameters of GFA included reduced glass transition temperature (Trg, supercooled liquid region (ΔTx, the stability (S and (Kgl parameter.Findings: The XRD and TEM investigations revealed that the studied as-cast metallic glasses were fully amorphous. Changes of the onset and peak crystallization temperature and the glass transition temperature as a function of glassy samples thickness were stated. The good glass-forming ability (GFA enabled casting of the Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4 glassy rods.Practical implications: The obtained examination results confirm the utility of applied investigation methods in the thermal stability analysis of examined bulk amorphous alloys. It is evident that parameters Trg, ΔTx, Kgl, S could be used to determine glass-forming ability of studied bulk metallic glasses.Originality/value: The success of fabrication of studied Fe-based bulk metallic glasses in form of rods with diameter up to 3 mm is important for the future progress in research of this group of materials.

  10. 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)

  11. Minor alloying behavior in bulk metallic glasses and high-entropy alloys

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk metallic glass in the compos-ites,and improve the mechanical properties. Minor Y addition can destabilize the crystalline phases by inducing lattice distortion as a result to improve the glass-forming ability,and the lattice distortion energy is closely related to the effi-ciency of space filling of the competing crystalline phases. A long-period ordered structure can precipitate in the Mg-based bulk metallic glass by yttrium alloying. For the high-entropy alloys,solid solution can be formed by alloying,and its me-chanical properties can be comparable to most of the bulk metallic glasses.

  12. Dielectric relaxation and AC conductivity studies of Se90Cd10−xInx glassy alloys

    Directory of Open Access Journals (Sweden)

    Nitesh Shukla

    2016-06-01

    Full Text Available Chalcogenide glassy alloys of Se90Cd10−xInx (x = 2, 4, 6, 8 are synthesized by melt quench technique. The prepared glassy alloys have been characterized by techniques such as differential scanning calorimetry (DSC, scanning electron microscopy (SEM and energy dispersive X-ray (EDAX. Dielectric properties of Se90Cd10−xInx (x = 2, 4, 6, 8 chalcogenide glassy system have been studied using impedance spectroscopic technique in the frequency range 42 Hz to 5 MHz at room temperature. It is found that the dielectric constants ɛ′, dielectric loss factor ɛ″ and loss angle Tan δ depend on frequency. ɛ′, ɛ″ and loss angle Tan δ are found to be decreasing with the In content in Se90Cd10−xInx glassy system. AC conductivity of the prepared sample has also been studied. It is found that AC conductivity increases with frequency where as it has decreasing trend with increasing In content in Se–Cd matrix. The semicircles observed in the Cole–Cole plots indicate a single relaxation process.

  13. 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.

  14. 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).

  15. 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.

  16. 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

  17. 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.

  18. Bulk amorphous metallic alloys: Synthesis by fluxing techniques and properties

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi; Shen, Tongde; Schwarz, R.B.

    1997-05-01

    Bulk amorphous alloys having dimensions of at least 1 cm diameter have been prepared in the Pd-Ni-P, Pd-Cu-P, Pd-Cu-Ni-P, and Pd-Ni-Fe-P systems using a fluxing and water quenching technique. The compositions for bulk glass formation have been determined in these systems. For these bulk metallic glasses, the difference between the crystallization temperature T{sub x}, and the glass transition temperature T{sub g}, {Delta}T = T{sub x} - T{sub g}, ranges from 60 to 1 10 K. These large values of {Delta}T open the possibility for the fabrication of amorphous near net-shape components using techniques such as injection molding. The thermal, elastic, and magnetic properties of these alloys have been studied, and we have found that bulk amorphous Pd{sub 40}Ni{sub 22.5}Fe{sub 17.5}P{sub 20} has spin glass behavior for temperatures below 30 K. 65 refs., 14 figs., 3 tabs.

  19. 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.

  20. 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.

  1. Temperature dependence of electrical and thermal properties of Te{sub 82.2}Ge{sub 13.22}Si{sub 4.58} glassy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hegab, N.A.; Fadel, M.; Afifi, M.A.; Shawer, M.F. [Physics Department, Faculty of Education, Ain Shams University, Cairo (Egypt)

    2000-09-21

    Thin film and bulk samples were prepared from synthesized amorphous Te{sub 82.2}Ge{sub 13.22}Si{sub 4.58} chalcogenide glassy alloy by the thermal evaporation technique. X-ray analysis shows that both synthesized material and thin film forms have an amorphous nature. The electrical and thermal conductivities for the bulk sample were studied as a function of temperature in a range below T{sub g} (T{sub g}=423 K). The obtained results for electrical conductivity are explained in accordance with the Mott and Davis model. The switching effects in amorphous films were also investigated. The switching phenomenon for this composition was of memory type. The mean value of the threshold voltage V-bar{sub th} was found to increase linearly with increasing film thickness (98.9-250.1 nm), while it decreased exponentially with increasing temperature (below T{sub g}). The results obtained are explained in accordance with the electrothermal model for the switching process. (author)

  2. Microstructural development at weld interface between Zr-based glassy alloy and stainless steel by resistance microwelding

    Science.gov (United States)

    Fukumoto, S.; Minami, M.; Soeda, A.; Matsushima, M.; Takahashi, M.; Yokoyama, Y.; Fujimoto, K.

    2012-08-01

    Zr-based bulk metallic glasses are expected to be welded to conventional structural alloys. Dissimilar welding of metallic glasses to stainless steel was carried out by resistance microwelding. The metallurgical analysis of the weld interface revealed the welding mechanism. A thin reaction layer was formed between the two liquid materials. The melting of stainless steel should be limited to obtain sound joints.

  3. Influence of Small Cr Addition on Thermal Stability and Magnetic Properties of Fe-Co-Zr-Nb-B Glassy Alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Fe62Co8-xCrxZr6Nb4B2o (x=0-4 at. Pct) metallic glasses show high thermal stability with a maximum supercooled liquid region of about 84.8 K. The addition of 2 at. pet Cr causes the extension of the supercooled liquid region remarkably, leading to the enhancement of thermal stability and glass-forming ability. The crystallization of the Fe-based glassy alloys takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as a-Fe, Fe2Zr and ZrB2- The long-range atomic rearrangements required for the precipitation of the multiple crystalline phases seem to play an important role in the appearance of the large supercooled liquid region through the retardation of the crystallization reactions. The Fe-based alloys exhibit soft ferromagnetic properties. The saturation magnetization decreases with increasing Cr content while the saturated magnetostriction increases as a function of Cr content. There is no distinct change in the saturation magnetization and coercive force with annealing temperature below the crystallization temperature. The devitrification gives rise to a considerable enhancement in both σs and Hc.

  4. Glassy Dynamics

    DEFF Research Database (Denmark)

    Jensen, Henrik J.; Sibani, Paolo

    2007-01-01

    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......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...... scales makes it impossible for a structural glass at low temperature to reach thermodynamic equilibrium . However, over short time scales the properties of glasses may appear to be time independent as in thermal equilibrium. Only when several orders of magnitude of time scales are covered is one able...

  5. Electroanalysis using macro-, micro-, and nanochemical architectures on electrode surfaces. Bulk surface modification of glassy carbon microspheres with gold nanoparticles and their electrical wiring using carbon nanotubes.

    Science.gov (United States)

    Dai, Xuan; Wildgoose, Gregory G; Salter, Chris; Crossley, Alison; Compton, Richard G

    2006-09-01

    Gold nanoparticles (approximately 30-60 nm in diameter) were deposited onto the surface of glassy carbon microspheres (10-20 microm) through electroless plating to produce bulk (i.e., gram) quantities of nanoparticle surface-modified microspheres. The gold nanoparticle-modified powder was then characterized by means of scanning electron microscopy and cyclic voltammetry. The voltammetric response of a macroelectrode consisting of a film of gold nanoparticle-modified glassy carbon microspheres, bound together and "wired-up" using multiwalled carbon nanotubes (MWCNTs), was investigated. We demonstrate that by intelligently exploiting both nano- and microchemical architectures and wiring up the electroactive centers using MWCNTs in this way, we can obtain macroelectrode voltammetric behavior while only using approximately 1% by mass of the expensive gold material that would be required to construct the equivalent gold film macrodisk electrode. The potential utility of electrodes constructed using chemical architectures such as this was demonstrated by applying them to the analytical determination of arsenic(III) concentration. An optimized limit of detection of 2.5 ppb was obtained.

  6. 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.

  7. 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.

  8. Electrical conduction mechanism in Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9 multi-component glassy alloys

    Directory of Open Access Journals (Sweden)

    Indra Sen Ram

    2015-08-01

    Full Text Available Electrical conductivity of Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9 glassy systems was studied employing impedance spectroscopic technique in the frequency range 100 Hz to 1 MHz and in the temperature range 308-388 K. The DC conductivity (σdc at each temperature was evaluated from the low frequency plateau region for all the samples under investigation. The bulk conductivity for each sample was also evaluated from Nyquist impedance plots. The semicircle shape of Nyquist plot exhibit dipolar nature of samples. The activation energy for glassy, amorphous and crystalline region from the Arrhenius plot of the DC conductivity and bulk conductivity was evaluated. From the results it is found that activation energy varied from 0.091 to 0.194 eV in glassy, 0.686 to 0.002 eV in amorphous and 0.215 to 0.503 eV in crystalline region. The activation energy (ΔE from DC conductivity and bulk conductivity found to be close in corresponding regions. The pre-exponential factor was also calculated for all three regions.

  9. 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...

  10. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    Science.gov (United States)

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation.

  11. Oxidation behaviour of bulk W-Cr-Ti alloys prepared by mechanical alloying and HIPing

    Energy Technology Data Exchange (ETDEWEB)

    García-Rosales, C., E-mail: cgrosales@ceit.es [CEIT and Tecnun (University of Navarra), E-20018 San Sebastian (Spain); López-Ruiz, P.; Alvarez-Martín, S.; Calvo, A.; Ordás, N. [CEIT and Tecnun (University of Navarra), E-20018 San Sebastian (Spain); Koch, F.; Brinkmann, J. [Max-Planck-Institut für Plasmaphysik (IPP), EURATOM Association, D-85748 Garching (Germany)

    2014-10-15

    Self-passivating tungsten based alloys are expected to provide a major safety advantage compared to pure tungsten when used as first wall armour of future fusion reactors, due to the formation of a protective oxide scale, preventing the formation of volatile and radioactive WO{sub 3} in case of a loss of coolant accident with simultaneous air ingress. In this work results of isothermal oxidations tests at 800 and 1000 °C on bulk alloy WCr12Ti2.5 performed by thermogravimetric analysis (TGA) and by exposure to flowing air in a furnace are presented. In both cases a thin, dense Cr{sub 2}O{sub 3} layer is found at the outer surface, below which a Cr{sub 2}WO{sub 6} scale and Ti{sub 2}CrO{sub 5} layers alternating with WO{sub 3} are formed. The Cr{sub 2}O{sub 3}, Cr{sub 2}WO{sub 6} and Ti{sub 2}CrO{sub 5} scales act as protective barriers against fast inward O{sup 2−} diffusion. The oxidation kinetics seems to be linear for the furnace exposure tests while for the TGA tests at 800 °C the kinetics is first parabolic, transforming into linear after an initial phase. The linear oxidation rates are 2–3 orders of magnitude lower than for pure W.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lollobrigida, V. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F. [Istituto Nazionale di Ricerca Metrologica (INRIM), I-10135 Torino (Italy); Borgatti, F. [CNR, Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), I-40129 Bologna (Italy); Torelli, P.; Panaccione, G. [CNR, Istituto Officina dei Materiali (IOM), Lab. TASC, I-34149 Trieste (Italy); Tortora, L. [Laboratorio di Analisi di Superficie, Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Ingegneria Meccanica, Università Tor Vergata, I-00133 Rome (Italy); Stefani, G.; Offi, F. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy)

    2014-05-28

    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.

  13. 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.

  14. Compositional ordering and stability in nanostructured, bulk thermoelectric alloys.

    Energy Technology Data Exchange (ETDEWEB)

    Hekmaty, Michelle A.; Faleev, S.; Medlin, Douglas L.; Leonard, F.; Lensch-Falk, J.; Sharma, Peter Anand; Sugar, J. D.

    2009-09-01

    Thermoelectric materials have many applications in the conversion of thermal energy to electrical power and in solid-state cooling. One route to improving thermoelectric energy conversion efficiency in bulk material is to embed nanoscale inclusions. This report summarize key results from a recently completed LDRD project exploring the science underpinning the formation and stability of nanostructures in bulk thermoelectric and the quantitative relationships between such structures and thermoelectric properties.

  15. High Field Conduction in Thin Films of a-(Ge.20{Se0}.80)1-x{Pb}x Glassy Alloys

    OpenAIRE

    KUMAR, Rachna SINGH and Santosh

    2008-01-01

    The present paper reports d.c. conductivity measurements at high electric fields in vacuum evaporated amorphous thin films of (Ge.20Se0.80)1-xPbx (where x = 0, 0.02, 0.04, 0.06 and 0.10) glassy alloys. Current-Voltage (I-V) Characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behavior is observed. However, at high electric fields (E \\sim 104 V/cm), non-ohmic behavior is observed. An analysis of the experimental data confirms the...

  16. Boundary Engineering for the Thermoelectric Performance of Bulk Alloys Based on Bismuth Telluride.

    Science.gov (United States)

    Mun, Hyeona; Choi, Soon-Mok; Lee, Kyu Hyoung; Kim, Sung Wng

    2015-07-20

    Thermoelectrics, which transports heat for refrigeration or converts heat into electricity directly, is a key technology for renewable energy harvesting and solid-state refrigeration. Despite its importance, the widespread use of thermoelectric devices is constrained because of the low efficiency of thermoelectric bulk alloys. However, boundary engineering has been demonstrated as one of the most effective ways to enhance the thermoelectric performance of conventional thermoelectric materials such as Bi2 Te3 , PbTe, and SiGe alloys because their thermal and electronic transport properties can be manipulated separately by this approach. We review our recent progress on the enhancement of the thermoelectric figure of merit through boundary engineering together with the processing technologies for boundary engineering developed most recently using Bi2 Te3 -based bulk alloys. A brief discussion of the principles and current status of boundary-engineered bulk alloys for the enhancement of the thermoelectric figure of merit is presented. We focus mainly on (1) the reduction of the thermal conductivity by grain boundary engineering and (2) the reduction of thermal conductivity without deterioration of the electrical conductivity by phase boundary engineering. We also discuss the next potential approach using two boundary engineering strategies for a breakthrough in the area of bulk thermoelectric alloys.

  17. 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.

  18. 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)

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. 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.

  4. 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.)

  5. 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.

  6. 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.

  7. Combustion Synthesis of Large Bulk Nanostructured Ni65Al21Cr14 Alloy

    Directory of Open Access Journals (Sweden)

    Jiqiang Ma

    2011-01-01

    Full Text Available A large bulk nanostructured Ni65Al21Cr14 alloy with dimensions of Φ 100 mm × 6 mm was produced by combustion synthesis technique followed with rapid solidification. The Ni65Al21Cr14 alloy was composed of γ′-Ni3Al/γ-Ni(Al, Cr eutectic matrix and γ-Ni(Al, Cr dendrite. The eutectic matrix consisted of 80–150 nm cuboidal γ′-Ni3Al and 2–5 nm γ-Ni(Al, Cr boundary. The dentrite was comprised of high-density growth twins with about 3–20 nm in width. The nanostructured Ni65Al21Cr14 alloy exhibited simultaneously high fracture strength of 2200 MPa and good ductility of 26% in compression test.

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

    OpenAIRE

    Philippe, Matthieu; Fagnard, Jean-François; Kirsch, Sébastien; Xu, Zhihan; Dennis, Anthony; Shi, Yunhua; Cardwell, David A.; Vanderheyden, Benoît; Vanderbemden, Philippe

    2014-01-01

    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 surfa...

  9. Glassy composition for hermetic seals

    Science.gov (United States)

    Wilder, Jr., James A.

    1980-01-01

    The invention relates to a glassy composition adaptable for sealing to aluminum-based alloys to form a hermetically-sealed insulator body. The composition may either be employed as a glass or, after devitrifying heat treatment, as a glass-ceramic.

  10. Brittle metallic glass deforms plastically at room temperature in glassy multilayers

    Science.gov (United States)

    Sharma, Parmanand; Yubuta, Kunio; Kimura, Hisamichi; Inoue, Akihisa

    2009-07-01

    Bulk metallic glasses are emerging as a new class of materials that can have applications ranging from structural materials to materials for future nanotechnology. However, catastrophic mechanical failure is a serious issue hindering the use of these materials in engineering applications. Here we introduce an approach to understanding and solving the problem of brittleness of metallic glasses. We have shown that even a very brittle metallic glass (La based) can be forced to deform plastically at room temperature if it is made in the form of multilayers involving other metallic glasses, i.e., a two-phase glass. The mechanically soft glassy layer (La based) having a lower critical shear stress acts as a nucleation or an initiation site for shear bands and the mechanically hard glassy layer (Zr based) acts as an obstacle to the propagation of shear bands. This process results in the multiplication of shear bands. Since the shear bands are associated with a local rise in temperature, a large number of shear bands can raise the overall temperature of the soft layer and eventually can drive it to the supercooled liquid state, where deformation of metallic glass is very large and homogeneous. The results reported here not only clarify the mechanism of large plastic deformation in two-phase glassy alloys but also suggest the possibility of a different kind of two-phase bulk glassy alloys exhibiting large plastic deformation at room temperature.

  11. Nanowear of a Zr Based Bulk Metallic Glass/Nanocrystalline Alloy

    Institute of Scientific and Technical Information of China (English)

    LIANGSong; HEJian-ying; CHUWu-yang; LIJin-xu; SUNDong-bai; QIAOLi-jie

    2004-01-01

    The hardness, elastic modulus, nano-scratch resistance and wear depth for a bulk metallic glass of Zr57NbsCu15.4 Ni12.6Al10 and its partial crystallization alloys have been measured by using nanoindentation method. The results showed that partial crystallization did not influence the reduced elastic modulus but increased the hardness, and then increased the scratch coefficient. The scratch coefficient increased linearly with increasing the hardness H but decreases when H>6.2GPa. Partial crystallization decreased evidently the wear depth, and when the load was large the wear depth decreased with increasing the hardness.

  12. 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.

  13. 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.

  14. Evolution of structure and local magnetic fields during crystallization of HITPERM glassy alloys studied by in situ diffraction and nuclear forward scattering of synchrotron radiation.

    Science.gov (United States)

    Miglierini, Marcel; Pavlovič, Márius; Procházka, Vít; Hatala, Tomáš; Schumacher, Gerhard; Rüffer, Rudolf

    2015-11-14

    Evolution of structure and local magnetic fields in (Fe(1-x)Co(x))76Mo8Cu1B15 (HITPERM) metallic glass ribbons with various amounts of Co (x = 0, 0.25, 0.5) were studied in situ using diffraction and nuclear forward scattering of synchrotron radiation. It was found that crystallization of all three glasses proceeds in two stages. In the first stage, bcc (Fe,Co) nanocrystals are formed, while in the second stage additional crystalline phases evolve. For all three glasses, the crystallization temperatures at the wheel side were found to be lower than at the air side of the ribbon. The crystallization temperatures were found to decrease with increasing Co content. The lattice parameters of the bcc nanocrystals decrease up to about 550 °C and then increase pointing to squeezing Mo atoms out of the nanograins or to interface effects between the nanocrystals and the glassy matrix. Nuclear forward scattering enabled separate evaluation of the contributions that stem from structurally different regions within the investigated samples including the newly formed nanocrystals and the residual amorphous matrix. Even minor Co content (x = 0.25) has a substantial effect not only upon the magnetic behaviour of the alloy but also upon its structure. Making use of hyperfine magnetic fields, it was possible to unveil structurally diverse positions of Fe atoms that reside in a nanocrystalline lattice with different numbers of Co nearest neighbours.

  15. Complete Composition Tunability of Cu(Ni)-Ti-Zr Alloys for Bulk Metallic Glass Formation

    Institute of Scientific and Technical Information of China (English)

    Ze-xiu Zhang; Chun-li Dai; Jian Xu

    2009-01-01

    In the Cu-Zr-Ti ternary system, a new composition zone of bulk metallic glasses (BMGs) formation was discovered, locating at the 55-57 at. Pct Cu, 30-31 at. Pct Ti and 13-14 at. Pct Zr, and near Cu-Ti binary subsystem rather than the Cu-Zr binary. For these alloys, BMG rods of 2 mm in diameter can be fabricated by using copper mould casting. It is expected that these BMG-forming alloys correlate with (L→CuTi+Cu2TiZr+Cu61Zr14) eutectic reaction that the undercooled melt undergoes during solidification. Adopting "3D pinpointing ap-proach", compositional dependence of glass-forming ability (GFA) in Cu(Ni)-Ti-Zr pseudo ternary system was revisited. Optimized BMG-forming composition is located at Cu50.4Ni5.6Ti31Zr13, with a critical diameter of 6 mm for complete BMG formation. Its GFA is significantly superior to Vit 101 (Cu47Ni8Ti34Zr11) previously developed by Caltech group. The effect that the GFA of the ternary base alloy was improved by substitution of Ni for Cu is attributed to a role of retarding the crystallization of Cu51Zr14 intermetallics.

  16. 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)

  17. Kinetic Characteristic of Hydrogenation Zr-Ti-Cu-Ni-Be Bulk Amorphous Alloys

    Institute of Scientific and Technical Information of China (English)

    Delin PENG; Jun SHEN; Jianfei SUN; Yuyong CHEN

    2004-01-01

    The relationship between the hydrogen content and the microhardness and the charging period, the effect of hydrogen on the activation energy, the kinetics of glass transition and crystallization of Zr-Ti-Cu-Ni-Be bulk amorphous alloy were studied by differential scanning calorimetry (DSC) and the Kissinger equation. It shows that both of the hydrogen content and the microhardness are related to the charging period, and that the glass transition and crystallization behavior are associated with the heating rate, and possess the kinetic effect. Hydrogen increases the glass transition temperature and the crystallization temperature, decreasing the enthalpies in the different stages of crystallization.Hydrogen increases the activation energies of the glass transition and the crystallization and changes the kinetic effect. The dependent extent between the glass transition, the crystallization and heating rate decreases after hydrogen charging.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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...

  5. 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

  6. Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics.

    Science.gov (United States)

    Nguyen, Duc; Zhu, Zhi-Guang; Pringle, Brian; Lyding, Joseph; Wang, Wei-Hua; Gruebele, Martin

    2016-06-22

    Glassy metallic alloys are richly tunable model systems for surface glassy dynamics. Here we study the correlation between atomic mobility, and the hopping rate of surface regions (clusters) that rearrange collectively on a minute to hour time scale. Increasing the proportion of low-mobility copper atoms in La-Ni-Al-Cu alloys reduces the cluster hopping rate, thus establishing a microscopic connection between atomic mobility and dynamics of collective rearrangements at a glass surface made from freshly exposed bulk glass. One composition, La60Ni15Al15Cu10, has a surface resistant to re-crystallization after three heating cycles. When thermally cycled, surface clusters grow in size from about 5 glass-forming units to about 8 glass-forming units, evidence of surface aging without crystal formation, although its bulk clearly forms larger crystalline domains. Such kinetically stable glass surfaces may be of use in applications where glassy coatings stable against heating are needed.

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

    Science.gov (United States)

    Philippe, M. P.; Fagnard, J.-F.; Kirsch, S.; Xu, Z.; Dennis, A. R.; Shi, Y.-H.; Cardwell, D. A.; Vanderheyden, B.; Vanderbemden, P.

    2014-07-01

    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 superconductor alone below this saturation level, and especially when the applied field is removed. The results of the study show further that the beneficial effects on the trapped field are enhanced when the ferromagnet covers the entire surface of the superconductor for different ferromagnetic components of various shapes and fixed volume.

  8. 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)

  9. Preparation of Plate Fe60Co8Zr10Mo5W2B15 Bulk Amorphous Alloy and Its Fracture Toughness

    Institute of Scientific and Technical Information of China (English)

    XIAO Huaxing; CHEN Guang

    2005-01-01

    With processes of arc melting, inductive melting and copper mold suction casting, a plate Fe-based bulk amorphous alloy Fe60Co8Zr10Mo5W2B15 with a thickness of 1mm was prepared. The surfaces and fractures of the cast bulk amorphous alloy were agleam and with typical metallic luster. The glass transition temperature(Tg), supercooled liquid region(△Tx)and reduced glass transition temperature(T rg)of the prepared Fe-based amorphous alloy are 884 K,63 K, and 0.611 respectively. The fracture toughness of the cast bulk amorphous alloy is at the level of 1.6 MPa·m1/2.

  10. 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.

  11. 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.

  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. 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%.

  15. 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.

  16. 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...

  17. Is Cu60Ti10Zr30 a bulk glass-forming alloy?

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saida, J.; Kato, H.;

    2003-01-01

    and high-resolution transmission electron microscopy. Surprisingly, we found that the alloy in both geometries contains cubic nanometer-sized crystals of about 5-7 nm in diameter with a lattice parameter of 0.45 nm for ribbons and 7-15 nm in diameter with a lattice parameter of 0.42 nm for rods...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Investigation of microstructure of bulk Ni 2MnGa alloy by means of electron backscatter diffraction analysis

    Science.gov (United States)

    Koblischka-Veneva, A.; Gachot, C.; Leibenguth, P.; Mücklich, F.

    2007-09-01

    The microstructure of bulk samples of the shape memory alloy Ni 2MnGa is evaluated by means of electron backscatter diffraction (EBSD). The crystallographic orientation of individual grains can be determined with a high spatial resolution using an automated recording of Kikuchi patterns. The obtained data are presented in form of image quality (IQ) and orientation maps, pole figures and orientation distribution functions. Local EBSD maps and pole figures reveal details about the orientation of the twin structure. The twin structure is clearly resolved within the EBSD mappings; the matrix is oriented in [1 0 0] direction and there is a 90° misorientation to the neighboring twin. Furthermore, pole figures obtained by EBSD are compared to those determined by means of X-ray texture analysis. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis.

  5. 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.

  6. 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.

  7. 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.

  8. 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...

  9. 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)

  10. Study on Surface and Bulk Properties of Ce-5 % Lanthanum Alloy

    Institute of Scientific and Technical Information of China (English)

    Luo Lizhu; Wang Xiaolin; Fu Xiaoguo; Zhang Yanzhi; Zhao Zhengping; Liu Chunrong

    2004-01-01

    The surface and bulk properties of Ce-5% La were studied with X-ray photoelectron spectroscopy (XPS)and X-ray diffraction (XRD), respectively.The XRD analysis shows that cerium in bulk is in γ-phase, and its lattice parameter is 0.516 nm.And we also find Ce2O3 in the bulk from the XRD figure but no existence of metal lanthanum because of its small quantity.The XPS analysis shows that there are always oxides existing in the surface.The O1s peak always exists at the binding energy of 530.3 eV, which may be attributed to Ce2O3 and La2O3, but no evidence was found for the existence of CeO2.It is concluded that there is a thick layer of Ce2O3 on the sample surface.And the Ce3d peak show multi-split in the figure, in which there are two peaks in each region, 3d5/2 and 3d3/2, and the binding energy of these peaks are 882.86, 887.70 eV for 3d5/2, and 901.44, 905.93 eV for 3d3/2.The special phenomena can be attributed to the changes of 4f electronic configuration, and the cerium in the sample exhibits properties similar to Ce2O3.But the influence of the addition of lanthanum to cerium is not visible, and further investigations are expected.

  11. 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.

  12. 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.

  13. 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

  14. Glassy Carbon Coating Deposited on Hybrid Structure of Composite Materials

    Directory of Open Access Journals (Sweden)

    Posmyk A.

    2016-06-01

    Full Text Available This paper presents a method of production metal matrix composites with aluminum oxide foam covered by glassy carbon layer used as reinforcement. The glassy carbon coating was formed for decreasing of friction coefficient and reducing the wear. In first step of technology liquid glassy carbon precursor is on ceramic foam deposited, subsequently cured and carbonated at elevated temperature. In this way ceramic foam is covered with glassy carbon coating with thickness of 2-8 μm. It provides desirable amount of glassy carbon in the structure of the material. In the next step, porous spheres with carbon coating are infiltrated by liquid matrix of Al-Cu-Mg alloy. Thereby, equable distribution of glassy carbon in composite volume is achieved. Moreover, typical problems for composites reinforced by particles like sedimentation, agglomeration and clustering of particles are avoided. Tribological characteristics during friction in air versus cast iron as a counterpart were made. Produced composites with glassy carbon layer are characterised by friction coefficient between 0.08-0.20, thus meeting the typical conditions for solid lubricants.

  15. Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

    Institute of Scientific and Technical Information of China (English)

    YI; Seonghoon

    2010-01-01

    Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

  16. 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.

  17. 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.

  18. 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

    gap at the crystal-mould interface during crystallisation. The maximum amorphous layer thickness decreases from similar to3 mm to zero when the Al content increases in the range from 0 to about y = 10%. The evolution of the microstructure of the initially amorphous phase was examined by x...... 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...... measurements to be 60-150 K/s, in agreement with estimates from the literature. The Vickers hardness (Hv) of the amorphous material for y = 2% is higher (similar to 360 kg/mm(2)) than for y = 0 (similar to 290 kg/mm(2)). On crystallisation the hardness of the latter material increases to the 400 kg/mm(2) level...

  19. 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.

  20. 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

  1. 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.

  2. Glass Formability and Soft Magnetic Properties of Bulk Y-Fe-B-Ti Metals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Ti effects on the glass forming ability and the magnetic properties of Y-Fe-B-Ti bulk metallic glasses have been investigated. Substituting 2 and 4 at% Ti for Fe or B in Y6Fe70B22 alloys decrease the saturation magnetization (σs) and deteriorate the glass forming ability, respectively. However, substitution of 2 at% Ti for Y in Y6Fe72B22 alloy induces larger supercooled region of 72.7℃, which not only makes the bulk glassy rod as large as 3mm in diameter, but also results in the superior soft magnetic properties of σ5=126emu/g,coercivity ( Hc ) = 0.2 Oe and Curie temperature (Tc) = 268℃. Among all Y-Fe-B-Ti bulk amorphous rods, Y4Fe72B22Ti2 displays the best glass forming ability and also the proper soft magnetic properties.

  3. 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)

  4. 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...

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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.

  14. 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 ...

  15. 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

  16. 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.

  17. Bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} alloys fabricated by consolidation of mechanically alloyed amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Bo; Wang, Xinfu; Li, Xianyu; Wang, Dan; Qin, Yong; Han, Fusheng, E-mail: fshan@issp.ac.cn

    2014-02-15

    Highlights: • Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5 at%) amorphous powders were synthesized by MA. • Bulk Al{sub 75}V{sub 12.5}Fe{sub 12.5} amorphous alloy is obtained by means of hydraulic pressing. • The Vickers microhardness of bulk sample is in the range of 821-927 HV. -- Abstract: Hydraulic press was used to produce bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5) (at.%) alloy by consolidation of mechanically alloyed amorphous powder. The as-milled powders and bulk alloy were examined by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The glass-forming ability was evaluated in accordance with the milling time. The results show that the glass-forming ability of the mechanical-alloyed Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} powders decreases with the increase of x. The onset crystallization temperatures (T{sub x}{sup onset}) of the three powders are 749 K, 771 K and 712 K, respectively. The results also indicate that the quality of consolidation is very good and the product’s Vickers microhardness is relatively high (821–927 HV)

  18. 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

  19. 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.

  20. Formation,thermal stability and mechanical properties of Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Ti42.5Zr7.5Cu40Ni5Sn5 bulk metallic glass with a critical diameter of 4 mm was fabri-cated by the conventional copper mould casting method. The supercooled liquid region ΔTx,reduced glass transition temperature Trg,γ parameter,and δparameter of the alloy were measured to be 63.9 K,0.561,0.393,and 1.400,respectively,im-plying that the alloy has an excellent glass-forming ability. The bulk metallic glass exhibits high compressive fracture strength of 2162 MPa with distinct plastic strain of 0.9%. The fracture surface consists mainly of vein-like patterns,typical of bulk glassy alloys.

  1. 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.

  2. 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.

  3. 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

  4. 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  

  5. 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.

  6. 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.

  7. 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).

  8. 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.

  9. An interatomic potential for studying CuZr bulk metallic glasses

    DEFF Research Database (Denmark)

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

    2007-01-01

    -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......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...

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. Kinetic analysis of the non-isothermal crystallization process, magnetic and mechanical properties of FeCoBSiNb and FeCoBSiNbCu bulk metallic glasses

    Science.gov (United States)

    Ramasamy, Parthiban; Stoica, Mihai; Taghvaei, A. H.; Prashanth, K. G.; Ravi Kumar, Eckert, Jürgen

    2016-02-01

    The crystallization kinetics of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 and {[(Fe0.5Co0.5)0.75B0.2Si0.05]0.96Nb0.04}99.5Cu0.5 bulk metallic glasses were evaluated using differential scanning calorimetry under non-isothermal condition. The fully glassy rods with diameters up to 2 mm were obtained by copper mold injection casting. Both glasses show good thermal stability, but the addition of only 0.5% Cu completely changes the crystallization behavior. The average activation energy required for crystallization decreases from 645 kJ/mol to 425 kJ/mol after Cu addition. Upon heating, the Cu-free alloy forms only the metastable Fe23B6 phase. In contrast, two well-separated exothermic events are observed for the Cu-added bulk glassy samples. First, the (Fe,Co) phase nucleates and then (Fe,Co)2B and/or (Fe,Co)3B crystallize from the remaining glassy matrix. The Cu-added alloy exhibits a lower coercivity and a higher magnetic saturation than the base alloy, both in as-cast as well as in annealed condition. Besides, the Cu-added glassy sample with 2 mm diameter exhibits a maximum compressive fracture strength of 3913 MPa together with a plastic strain of 0.6%, which is highest plastic strain ever reported for 2 mm diameter ferromagnetic bulk metallic glass sample. Although Cu addition improves the magnetic and mechanical properties of the glass, it affects the glass-forming ability of the base alloy.

  15. Sn and Nb modified ultrafine Ti-based bulk alloys with high-strength and enhanced ductility

    Energy Technology Data Exchange (ETDEWEB)

    Cao, G. H. [Department of Materials Engineering, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Schneider, R.; Gerthsen, D. [Laboratorium fuer Elektronenmikroskopie, Karlsruher Institut fuer Technologie, D-76128 Karlsruhe (Germany); Chulist, R.; Schaarschuch, R.; Oertel, C.-G.; Skrotzki, W. [Institut fuer Strukturphysik, Technische Universitaet Dresden, D-01062 Dresden (Germany)

    2013-02-11

    Sn and Nb modified ultrafine eutectic Ti-Fe alloys with high strength and plasticity prepared by cold crucible levitation melting were tested in compression at room temperature. (Ti{sub 70.5}Fe{sub 29.5}){sub 93.15}Sn{sub 3.85}Nb{sub 3} alloy exhibited an ultimate compressive strength of 2.36 GPa at 15% plastic strain. Electron microscopy revealed that lamellar structures in Ti{sub 70.5}Fe{sub 29.5} alloy could be tailored by the addition of Sn and Nb to obtain a globular structure. The microstructural refinement, morphology of phase constituents, and their relationships to the mechanical properties are discussed.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. Crystallization in Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass under pressure

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Zhou, T.J.; Rasmussen, Helge Kildahl;

    2000-01-01

    The effect of pressure on the crystallization behavior of the bulk metallic glass-forming Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy with a wide supercooled liquid region has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction measurements using synchrotron radiation......)], reporting a decrease of the crystallization temperature under pressure in a pressure range of 0-6 GPa for the bulk glass Zr41Ti14Cu12.5Ni9Be22.5C1 alloy. Compressibility with a volume reduction of approximately 22% at room temperature does not induce crystallization in the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk...... glass alloy. This indicates that the densification effect induced by pressure in the pressure range investigated plays a minor role in the crystallization behavior of this bulk glass alloy. The different crystallization behavior of the carbon-free and the carbon-containing glassy alloys has been...

  1. Carbon dioxide foaming of glassy polymers

    NARCIS (Netherlands)

    Wessling, M.; Borneman, Z.; Boomgaard, van den Th.; Smolders, C.A.

    1994-01-01

    The mechanism of foaming a glassy polymer using sorbed carbon dioxide is studied in detail. A glassy polymer supersaturated with nitrogen forms a microcellular foam, if the polymer is quickly heated above its glass transition temperature. A glassy polymer supersaturated with CO2 forms this foam-like

  2. 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.

  3. 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

  4. Glass Formation in Ni-Zr-(Al Alloy Systems

    Directory of Open Access Journals (Sweden)

    Lanping Huang

    2013-01-01

    Full Text Available Structural and thermal properties of binary Ni100-xZrx (30alloys obtained by melt spinning and copper mold casting methods were investigated. The fully amorphous samples in a bulk form cannot be obtained in the binary Ni-Zr alloys over a wide composition range, though they have Tg/Tl and γ values close to or even higher than those of the binary Cu-Zr bulk metallic glasses (BMGs. The low thermal stability of the supercooled liquid against crystallization and the formation of the equilibrium crystalline phases with a high growth rate are responsible for their low glass-forming abilities (GFAs. Relatively low thermal conductivities of Ni-based alloys are also considered to be another factor to limit their GFAs. The GFA of the binary Ni65.5Zr34.5 alloy alloyed with 4% or 5% Al was enhanced, and a fully glassy rod with a diameter of 0.5 mm was formed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Louzguine-Luzgin, D.V., E-mail: dml@wpi-aimr.tohoku.ac.jp [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Bazlov, A.I. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); National University of Science and Technology “MISiS”, Moscow 119049 (Russian Federation); Ketov, S.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, A. [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); School of Materials Science and Engineering, Tianjin University, 300072 (China); Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia)

    2015-07-15

    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-Fe{sub 36}Cr{sub 12}Mo{sub 10} phase. • Reduced liquidus temperature of Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 6}B{sub 15}RE{sub 2} alloys.

  6. 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..

  7. Use of portable X-ray fluorescence instrument for bulk alloy analysis on low corroded indoor bronzes

    Energy Technology Data Exchange (ETDEWEB)

    Šatović, D., E-mail: dsatovic@alu.hr [Department of Conservation and Restoration, Academy of Fine Arts, Ilica 85, 10000 Zagreb (Croatia); Desnica, V. [Department of Conservation and Restoration, Academy of Fine Arts, Ilica 85, 10000 Zagreb (Croatia); Fazinić, S. [Laboratory for Ion Beam Interactions, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb (Croatia)

    2013-11-01

    One of the most often used non-destructive methods for elemental analysis when performing field measurements on bronze sculptures is X-ray fluorescence (XRF) analysis based on portable instrumentation. However, when performing routine in-situ XRF analysis on corroded objects obtained results are sometimes considerably influenced by the corrosion surface products. In this work the suitability of portable XRF for bulk analysis of low corroded bronzes, which were initially precisely characterized using sophisticated and reliable laboratory methods, was investigated and some improvements in measuring technique and data processing were given. Artificially corroded bronze samples were analyzed by a portable XRF instrument using the same methodology and procedures as when performing in-situ analysis on real objects. The samples were first investigated using sophisticated complementary laboratory techniques: Scanning Electron Microscopy, Proton-Induced X-ray Emission Spectroscopy and Rutherford Backscattering Spectrometry, in order to gain precise information on the formation of the corrosion product layers and in-depth elemental profile of corrosion layers for different aging parameters. It has been shown that for corrosion layers of up to ca. 25 μm a portable XRF can yield very accurate quantification results. - Highlights: • XRF quantification is very accurate for bronze corrosion layers of up to ca. 25 μm. • Corrosion layer formation on bronze described in two phases. • Corrosion layers precisely characterized using PIXE, RBS and SEM. • Corrosion approximated as CuO for layer thickness calculations via X-ray attenuations • Increasingly lighter corrosion matrix may cause SnLα radiation intensity inversion.

  8. 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...

  9. Copper nanowall array grown on bulk Fe-Co-Ni alloy substrate at room temperature as lithium-ion battery current collector

    Energy Technology Data Exchange (ETDEWEB)

    Hu Yingying, E-mail: yyhu@phy.ccnu.edu.cn; Liu Jinping; Ding Ruimin; Wang Kai; Jiang Jian; Ji Xiaoxu; Li Yuanyuan; Huang Xintang, E-mail: xthuang@phy.ccnu.edu.c

    2010-09-30

    Large-scale copper nanowall array on the bulk Fe-Co-Ni alloy substrate has been prepared in aqueous solution at room temperature via an electroless deposition method. The thickness of the nanowalls is about 15 nm. A possible growth mechanism of the nanowalls was proposed. The effects of reaction temperature, reaction time and the amount of critical agent (Fe{sup 3+}) on the morphology and crystalline phase of the nanowalls were investigated. Furthermore, the electrochemical performance of Sn film supported on the as-prepared copper nanowalls current collector is enhanced in comparison with that on the commercial copper foil when used as anode for Li-ion batteries with the operating voltage window of 0.01-2.0 V (vs. Li). After 20 cycles, the discharge capacity of Sn-Cu nanowalls anode still remained 365.9 mAh g{sup -1}, that is, 40% retention of the reversible capacity, while the initial charge capacity of Sn film cast on commercial Cu foil was 590 mAh g{sup -1}, dropping rapidly to 260 mAh g{sup -1} only after 10 cycles.

  10. 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...

  11. First-principles study on magnetism and half-metallicity in bulk and various (001) surfaces of Heusler alloy Zr2VSn with Hg2CuTi-type structure

    Science.gov (United States)

    Deng, Zun-Yi; Zhang, Jian-Min

    2016-07-01

    Structural, electronic and magnetic properties in the bulk and five different (001) surfaces (ZrV-, ZrSn-, VV-, ZrZr- and SnSn-terminations) of Zr2 VSn Heusler alloy with Hg2 CuTi -type structure are studied by using first-principles calculations based on density-functional theory. The bulk Zr2 VSn Heusler alloy is ferrimagnetic half-metallicity with equilibrium lattice constant 6.815 Å and total magnetic moment -1.000 μB / f.u . , following the Slater-Pauling rule μt =Zt - 18 . The atoms on different surface layers exhibit different displacements, electronic and magnetic properties. All five (001) surfaces lose the half-metallicity and are not usable in spintronics devices.

  12. 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.

  13. 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).

  14. 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

  15. 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.

  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. Structure and Properties of Mg-Cu-(Y,Ca Bulk Metallic Glasses / Struktura I Własności Masywnych Szkieł Metalicznych Mg-Cu-(Y,Ca

    Directory of Open Access Journals (Sweden)

    Babilas R.

    2015-12-01

    Full Text Available The work presents preparation methods, structure characterization and mechanical properties analysis of Mg-based bulk metallic glasses in as-cast state and after crystallization process. The studies were performed on Mg60Cu30Y10 and Mg37Cu36Ca27 glassy alloys in the form of plates and rods. The X-ray diffraction investigations revealed that the tested samples with different thicknesses and shapes were amorphous. The characteristics of the fractured surfaces showed mixed fractures with the “river” and “mirror” patterns, which are characteristic for the glassy materials and some “smooth” areas. The samples of Mg37Cu36Ca27 alloy presented a two-stage crystallization process, but addition of Y caused a single stage crystallization behavior. Qualitative phase analysis from the X-ray data of examined alloys annealed at 473 K enabled the identification of Mg, Mg2Cu, Cu2Mg and CaCu crystalline phases. The changes of compressive strength as a function of annealing temperature for studied rods were stated. The best mechanical properties including microhardness and compressive strength were obtained for the alloy with the addition of Y in as-cast state.

  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. 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.

  5. 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.

  6. 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

  7. 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...

  8. 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

  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. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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

  17. Effect of Nb in (La0.5Ce0.5)64-xAl16Ni5Cu15Nbx (x=0-5) bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guo-qing; LIU Jin-fang; ZENG Qiao-shi; WANG Li-na; LIU Jin-qiang; JIANG Jian-zhong

    2006-01-01

    The effect of Nb in (La0.5Ce0.5)64-xAl16Ni5Cu15Nbx (x=0-5, mole fraction) bulk metallic glasses was investigated by X-ray diffractometry, differential scanning calorimetry, and scanning electron microscopy. Fully amorphous rods up to 5 mm in diameter were obtained using copper mold. Their lower glass transition temperatures are of about 401-407 K and wide supercooled liquid regions are up to 75 K. The oxidation resistance of the LaCe-based glassy alloys can be largely enhanced by adding tiny Nb, which makes the developed LaCe-based bulk metallic glasses more attractive for potential industrial applications.

  18. Mechanical alloying of Cu/Al plates and preparation of bulk amorphous/nanocrystalline composite by thermoplastic deformation%搅拌摩擦法制备Cu-Al非晶/纳米晶复合材料

    Institute of Scientific and Technical Information of China (English)

    徐红霞; 段辉平; 宋洪海

    2013-01-01

    利用搅拌摩擦技术,使叠放在一起的Cu、Al板材发生强烈的热塑性变形.对搅拌区产物的显微结构分析表明:Cu、Al板材被搅拌破碎并充分混合在一起,Cu、Al元素发生扩散并实现合金化;在搅拌区中有许多尺寸> 1μm的非晶相和非晶/纳米晶复合相,非晶相的基体中含有平均尺寸约为5nm的纳米晶.热塑性变形技术不仅可用于块体金属材料的机械合金化,也可用于制备块体非晶/纳米晶复合材料.%Strong thermoplastic deformation of overlapped Cu and Al plates had been realized by stir friction processing. Transmission electron microscopy investigation on the microstructure of the stirred zone demonstrate that the Cu and Al plates are torn into shreds and well-mixed in the stirred zone. The inter-diffusion between Cu and Al shreds happens, resulting in the mechanical alloying of Cu/Al plates. There are many amorphous phases with size of more than 1 micron and amorphous/nanocrystalline composite phases in the deformation zone. The average size of the nanocrystallines surrounded by amorphous phases, is about 5 nanometers. Experimental results strongly suggest that the thermoplastic deformation technique can not only be used to do mechanical alloying for bulk metallic materials but also to fabricate bulk amorphous/crystalline materials.

  19. 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.

  20. 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

  1. Effects of gravity on the mi-crostructure of Zr41Ti14-Cu12.5Ni10Be22.5 bulk glass forming alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The ZrTiCuNiBe alloy is melt and solidified by Bridgman unidirectional solidification on two gravity field orientations (the gravity field orientation is parallel and opposite to solidification direction). Effects of gravity on morphology and microstructure are investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD). When gravity field orientation is parallel to solidification direction, less needle-like primary phase is embedded in a matrix eutectic; when gravity field orientation is opposite to solidification direction, a large amount of coarser needle-like primary phases were observed.

  2. 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

  3. 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...

  4. 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.

  5. 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

  6. Fabrication of arrayed glassy carbon field emitters

    Energy Technology Data Exchange (ETDEWEB)

    Sohda, Y.; Tanenbaum, D.M.; Turner, S.W.; Craighead, H.G. [School of Engineering and Applied Physics, Cornell University, Ithaca, New York 14853 (United States)

    1997-03-01

    Glassy carbon has desirable properties for electron field emission such as surface inertness, electrical conductivity, and thermal stability. In addition, a uniform thick substrate with a polished surface is easily obtainable. This enables one to apply large scale integrated circuit processing for fabricating arrayed tips. By using oxygen reactive ion etching, cusps over 3.5 {mu}m in height and 2.5 {mu}m in base diameter are fabricated with a tip radius of under 10 nm. The process is assisted by the formation of a layer of etch products which protects the newly forming tip from bending and over etching. The field emission current up to 50 {mu}A from the glassy carbon tips is obtained by applying high voltage to a mesh anode. The current which passed through the mesh anode is collected at another electrode and measured. The Fowler{endash}Nordheim plot suggests the existence of nm scale structure on the tip. This favorable result indicates glassy carbon substrate is a good substrate for field emitter arrays. {copyright} {ital 1997 American Vacuum Society.}

  7. 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%

  8. 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%.

  9. 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.

  10. 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.)

  11. 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.

  12. 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.

  13. Soft magnetic properties and thermal stability of bulk Fe{sub 83}B{sub 17} alloy prepared by undercooling and Cu-mold casting methods

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Changlin, E-mail: ycl@nwpu.edu.cn; Zhang, Jun; Huang, Huili; Sheng, Gang; Liu, Feng

    2015-06-15

    The thermal stability and soft magnetic properties of bulk Fe{sub 83}B{sub 17} rods with nano-lamellar eutectic structures and metastable Fe{sub 3}B 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 Fe{sub 3}B 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 Fe{sub 3}B phase was obtained. • The soft magnetic properties of the sample remain stability by annealing. • Nano-lamellar eutectic structures enhance the soft magnetic properties.

  14. 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.

  15. 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)

  16. 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.

  17. 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.

  18. 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%.

  19. 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

  20. The dependence of nano-contact magnetoresistance on the bulk scattering spin asymmetry in CoFe alloys with oxidation impurities

    Science.gov (United States)

    Shiokawa, Yohei; Jung, JinWon; Otsuka, Takahiko; Sahashi, Masashi

    2015-08-01

    Nano-contact magnetoresistance (NCMR) spin-valves (SVs) using an AlOx nano-oxide-layer (NOL) have numerous nanocontacts in the thin AlOx oxide layer. The NCMR theoretically depends on the bulk scattering spin asymmetry ( β) of the ferromagnetic material in the nanocontacts. To determine the relationship between NCMR and β, we investigated the dependence of NCMR on the composition of the ferromagnetic material Co1-xFex. The samples were annealed at 270 °C and 380 °C to enhance the MR ratio. For both annealing temperatures, the magnetorsistance ratio in the low-resistance area product region at less than 1 Ω μm2 was maximized for Co0.5Fe0.5. To evaluate β exactly, we fabricated current-perpendicular-to-plane giant magnetoresistance SVs with Co1-xFex/Cu/Co1-xFex layers and used Valet and Fert's theory to solve the diffusion equation of the spin accumulation for a ferromagnetic layer/non-ferromagnetic layer of five layers with a finite diffusion length. The evaluated β for Co1-xFex was also maximized for Co0.5Fe0.5. Additionally, to determine the difference between the experimental MR ratio of NCMR SVs and the theoretical MR ratio, we fabricated Co0.5Fe0.5 with oxygen impurities and estimated the decrease in β with increasing oxygen impurity concentration. Our Co0.5Fe0.5 nano-contacts fabricated using ion-assisted oxidation may contain oxygen impurities, and the oxygen impurities might cause a decrease in β and the MR ratio.

  1. Atomic structure of Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} bulk metallic glass alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hui, X. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)], E-mail: huixd01@hotmail.com; Fang, H.Z.; Chen, G.L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Shang, S.L.; Wang, Y. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Qin, J.Y. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University - Southern Campus, Jinan 250061 (China); Liu, Z.K. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

    2009-01-15

    Ab initio molecular dynamics (AIMD) calculations were performed on the atomic configuration of Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} bulk metallic glass. The local structures were characterized in terms of structure factors (SF), pair correlation functions (PCF), coordinate numbers, bond pairs and Voronoi polyhedra. The glass transition temperature, generalized PCF and SF predicated by AIMD are in good agreement with the experimental data. Icosahedral short-range orders (ISRO) are found to be the most dominant, in view of the presence of the majority of bond pairs with 1551, 1541 and 1431, and Voronoi polyhedra with <0,3,6,1>, <0,2,8,1>, <0,0,12,0> and <0,2,8,4>. Icosahedral medium range orders (IMROs) are formed from icosahedra via the linkage of vertex-, edge-, face- and intercross-shared atoms. The glass structure on the nanometer scale is accumulated by polyhedra through an efficient packing mode. It is suggested that the extraordinary glass-forming ability of this alloy is essentially attributable to the formation of ISRO and IMRO, and the dense packing of atoms.

  2. Large enhancement of bulk spin polarization by suppressing CoMn anti-sites in Co2Mn(Ge0.75Ga0.25) Heusler alloy thin film

    Science.gov (United States)

    Li, S.; Takahashi, Y. K.; Sakuraba, Y.; Tsuji, N.; Tajiri, H.; Miura, Y.; Chen, J.; Furubayashi, T.; Hono, K.

    2016-03-01

    We have investigated the structure and magneto-transport properties of Co2Mn(Ge0.75Ga0.25) (CMGG) Heusler alloy thin films with near-stoichiometric and Mn-rich compositions in order to understand the effect of Co-Mn anti-sites on bulk spin polarization. Anomalous x-ray diffraction measurements using synchrotron radiated x-rays confirmed that CoMn anti-sites easily form in the near-stoichiometric CMGG compound at annealing temperature higher than 400 °C, while it can be suppressed in Mn-rich CMGG films. Accordingly, large enhancement in negative anisotropic magnetoresistance of CMGG films and giant magnetoresistance (GMR) in current-perpendicular-to-plane (CPP) pseudo spin valves were observed in the Mn-rich composition. A large resistance-area product change (ΔRA) of 12.8 mΩ μm2 was demonstrated in the CPP-GMR pseudo spin valves using the Mn-rich CMGG layers after annealing at 600 °C. It is almost twice of the maximum output observed in the CPP-GMR pseudo spin valves using the near-stoichiometric CMGG. These indicate that the spin polarization of CMGG is enhanced in the Mn-rich composition through suppressing the formation of CoMn-antisites in CMGG films, being consistent with first-principle calculation results.

  3. 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

  4. 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

  5. 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.

  6. Enhanced mechanical properties due to structural changes induced by devitrification in Fe-Co-B-Si-Nb bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Fornell, J., E-mail: Jordina.Fornell@campus.uab.ca [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Gonzalez, S. [WPI-Advaced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan); Rossinyol, E. [Servei de Microscopia, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Surinach, S.; Baro, M.D. [Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Louzguine-Luzgin, D.V. [WPI-Advaced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan); Perepezko, J.H. [Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706 (United States); Sort, J. [Institucio Catalana de Recerca i Estudis Avancats and Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain); Inoue, A. [WPI-Advaced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577 (Japan)

    2010-11-15

    Fe{sub 36}Co{sub 36}B{sub 19.2}Si{sub 4.8}Nb{sub 4} bulk glassy rods were synthesized by copper mould casting. The effects of annealing treatments on the microstructure, elastic and mechanical properties of this alloy are investigated. Annealing below the glass transition temperature induces the formation of atomic clusters with pseudo-tenfold symmetry with a close relationship to the Fe{sub 23}B{sub 6} phase. Annealing at sufficiently high temperatures promotes the formation of stable Fe{sub 2}B and FeB phases and Fe(Co) solid solution. The as-cast alloy exhibits ultra-high hardness (H > 14 GPa), high reduced Young's modulus (E{sub r} > 200 GPa) and good wear resistance. These properties are further enhanced after thermal treatments (H > 18 GPa and E{sub r} > 260 GPa are achieved in the fully crystallized sample). The mechanical hardening is accompanied with an increase of the elastic recovery and a decrease of the Poisson's ratio. The different microstructural mechanisms responsible for these annealing-induced changes in mechanical and elastic properties are discussed.

  7. 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

  8. Glassy dynamics of driven elastic manifolds

    Energy Technology Data Exchange (ETDEWEB)

    Vinokur, V.M.

    1996-12-31

    We study the low-temperature dynamics of an elastic manifold driven through a random medium. For driving forces well below the zero- temperature depinning force, the manifold advances via thermally activated hops over the energy barriers separating favorable metastable states. We develop a scaling theory of the thermally activated dynamics (creep) and find a nonlinear glassy response for the driven manifold, {upsilon}{approximately}exp(-const{times}F{sup - {mu}}). We consider an exactly solvable 1-D model for random driven dynamics which exhibits a creep-like velocity-force characteristic. We discuss a microscopic mechanism for the creep motion and show that the distribution of waiting times for the hopping processes scales as a power law. This power-law distribution naturally yields an exponential response for the creep of the manifold.

  9. 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.

  10. 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.)

  11. 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.

  12. 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.

  13. Shock-wave studies of anomalous compressibility of glassy carbon

    Science.gov (United States)

    Molodets, A. M.; Golyshev, A. A.; Savinykh, A. S.; Kim, V. V.

    2016-02-01

    The physico-mechanical properties of amorphous glassy carbon are investigated under shock compression up to 10 GPa. Experiments are carried out on the continuous recording of the mass velocity of compression pulses propagating in glassy carbon samples with initial densities of 1.502(5) g/cm3 and 1.55(2) g/cm3. It is shown that, in both cases, a compression wave in glassy carbon contains a leading precursor with amplitude of 0.135(5) GPa. It is established that, in the range of pressures up to 2 GPa, a shock discontinuity in glassy carbon is transformed into a broadened compression wave, and shock waves are formed in the release wave, which generally means the anomalous compressibility of the material in both the compression and release waves. It is shown that, at pressure higher than 3 GPa, anomalous behavior turns into normal behavior, accompanied by the formation of a shock compression wave. In the investigated area of pressure, possible structural changes in glassy carbon under shock compression have a reversible character. A physico-mechanical model of glassy carbon is proposed that involves the equation of state and a constitutive relation for Poisson's ratio and allows the numerical simulation of physico-mechanical and thermophysical properties of glassy carbon of different densities in the region of its anomalous compressibility.

  14. High temperature annealing studies of strontium ion implanted glassy carbon

    Science.gov (United States)

    Odutemowo, O. S.; Malherbe, J. B.; Prinsloo, L.; Langa, D. F.; Wendler, E.

    2016-03-01

    Glassy carbon samples were implanted with 200 keV strontium ions to a fluence of 2 × 1016 ions/cm2 at room temperature. Analysis with Raman spectroscopy showed that ion bombardment amorphises the glassy carbon structure. Partial recovery of the glassy carbon structure was achieved after the implanted sample was vacuum annealed at 900 °C for 1 h. Annealing the strontium ion bombarded sample at 2000 °C for 5 h resulted in recovery of the glassy carbon substrate with the intensity of the D peak becoming lower than that of the pristine glassy carbon. Rutherford backscattering spectroscopy (RBS) showed that the implanted strontium diffused towards the surface of the glassy carbon after annealing the sample at 900 °C. This diffusion was also accompanied by loss of the implanted strontium. Comparison between the as-implanted and 900 °C depth profiles showed that less than 30% of the strontium was retained in the glassy carbon after heat treatment at 900 °C. The RBS profile after annealing at 2000 °C indicated that no strontium ions were retained after heat treatment at this temperature.

  15. 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...

  16. 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 ...

  17. 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)

  18. 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.

  19. Enthalpy and Mechanical Relaxation of Glassy Gelatin Films

    OpenAIRE

    Badii, F; IA Farhat

    2005-01-01

    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 mechan...

  20. 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, ...

  1. 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

  2. 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

  3. 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.

  4. Treatment of early glassy cell carcinoma of uterine cervix

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ok Bae; Kim, Jin Hee; Choi, Tae Jin [Keimyung University School of Medicine, Daegu (Korea, Republic of)

    2006-06-15

    The purpose of this study was to investigate the clinical findings, treatment, and outcome of patients with glassy cell carcinoma of cervix. We reviewed all cases of glassy cell carcinoma of the uterine cervix confirmed and treated at the Dongsan Medical Center, Keimyung University, between January 1993 and December 2005. There were 7 cases with histopathologically confirmed gassy cell carcinoma. A tumor was diagnosed as glassy cell carcinoma if over 50% of the tumor cell type displayed glassy cell features. Six patients with stage IB had radical hysterectomy and bilateral pelvic node dissection, and 2 of them received adjuvant external pelvic irradiation with concurrent chemotherapy. Remaining one patient with stage IIA had curative concurrent chemoradiotherapy with external pelvic irradiation and brachytherapy. There were 7 patients diagnosed as glassy cell carcinoma among the 3,745 (0.2%) patients of carcinoma of uterine cervix. The mean age of 7 patients was 44 years with range of 35 to 53 years of age. The most frequent symptom was vaginal bleeding (86%). By the punch biopsy undertaken before treatment of 7 cases, 2 only cases could diagnose as glassy cell carcinoma of uterine cervix, but remaining of them confirmed by surgical pathological examination. The mean follow up duration was 73 months with range of 13 to 150 months. All 7 patients were alive without disease after treatment. Glassy cell carcinoma of the uterine cervix is a distinct clinicopathologic entity that demonstrates an aggressive biologic behavior. However for early-stage disease, we may have more favorable clinical outcome with radical surgery followed by chemoradiotherapy.

  5. 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

  6. The potential for bulk undercooling as an industrial process

    Science.gov (United States)

    Laxmanan, V.

    1984-01-01

    The main focus is on solidification occurring in highly supercooled melts. Solidification rates in such melts are extremely high, an attractive feature from a commercial standpoint. Thus, the reported growth velocities for pure Ni and Co dendrites at a supercooling of 175 K are in excess of 180 km/hr. Rapidly quenched crystalline alloys produced by various atomization processes (e.g., centrifugal atomization or inert gas atomization) or melt spinning are examples of solidification processes, currently being intensively explored commercially, wherein extremely high solidification rates are achieved. Estimated dendrite tip growth rates are about 2 km/hr in a binary Al-4.5 wt % alloy, with a heat transfer coefficient of 6.4x10 sub 5 w/sq cm K or 15 cal/cu cm sK. In the limit, when the solidification rate exceeds a critical value, a glassy microstructure is obtained even in highly alloyed melts, which under normal conditions would solidity to form one or more crystalline phases. Glassy metals, also called metallic glasses, are candidate materials for distribution transformers because of their very low energy losses and are also being used in brazing and soldering applications.

  7. 超高强钴基块体非晶合金的组成设计%Alloy Design of Ultrahigh Strength Co-Based Bulk M etallic Glasses

    Institute of Scientific and Technical Information of China (English)

    王菊; 李然; 张涛

    2014-01-01

    Bulk metallic glasses ( BMGs) are a kind of disorder metal materials with high strength, high hardness and large elastic limit.The development of these materials is one of the most attractive topics for advanced metal materials . How to improve the strength of materials is an eternal topic for material scientists .In this paper, we summarized alloy compositions, thermal stability and mechanical properties of typical Co-based BMGs as the best candidates to design ultra-high strength BMGs due to their excellent mechanical properties .Possible relationships between the mechanical properties and other physical parameters, like elastic moduli, hardness and characteristic temperature in various kinds of BMG sys-tems are investigated.The Young’ s modulus, the Vickers hardness or the glass transition temperature shows a linear de-pendence on the fracture strength.According to the above results, the design method of element constitution for the ultra-strong Co-based BMGs was presented.The metalloid element(s) with the characteristics of strong covalent bond and the transition metal element( s) with high elastic moduli and high melting temperature should be adopted to be great beneficial for the development of ultrahigh strength Co-based BMGs.%块体非晶合金是一类具有高强度、高硬度和大弹性极限的无序金属材料,其优异的力学性能是目前先进金属材料领域研究热点之一,如何提高材料的强度是材料研究领域永恒的主题。系统地总结了已知具有超高强度的一类块体非晶合金材料---钴基块体非晶合金的成分、热学稳定性及力学性能;同时研究了不同非晶合金的断裂强度与其弹性常数、硬度和特征温度的关联。研究结果表明:在非晶合金体系中杨氏模量、维氏硬度、玻璃转变温度与断裂强度之间都存在较好的线性变化关系。基于以上结果,本课题组提出了超高强钴基块体非晶合金的组成设计

  8. Magnetic properties of the suction-cast bulk amorphous alloy: (Fe{sub 0.61}Co{sub 0.10}Zr{sub 0.025}Hf{sub 0.025}Ti{sub 0.02}W{sub 0.02}B{sub 0.20}){sub 96}Y{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Błoch, K., E-mail: bloch@wip.pcz.pl

    2015-09-15

    This paper presents the results of studies into the structural and magnetic properties of the bulk amorphous alloy: (Fe{sub 0.61}Co{sub 0.10}Zr{sub 0.025}Hf{sub 0.025}Ti{sub 0.02}W{sub 0.02}B{sub 0.20}){sub 96}Y{sub 4}, fabricated in the form of rods of length: 20 mm, and diameters: 1 mm and 2 mm. The samples were produced using the suction-casting method. The amorphicity of the investigated alloy, in the as-quenched state, was verified using X-ray diffractometry and Mössbauer spectroscopy. Studies of the magnetic susceptibility disaccommodation and the approach to magnetic saturation facilitated the conclusion that the investigated alloy, obtained in the form of rods of 2 mm diameter, can be characterized by a higher packing density of atoms; this was further confirmed by the results of Mössbauer spectroscopy. - Highlights: • Samples were obtained using using the suction-casting method. • The samples were manufactured in the shape of rods of diameters 1 mm and 2 mm. • The amorphous structure was confirmed using XRD and Mössbauer spectroscopy. • Magnetic properties were analyzed in terms of contents of structural defects. • Time stability of magnetic properties was studied by disaccommodation phenomenon.

  9. 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.

  10. 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

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

    DEFF Research Database (Denmark)

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

    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...

  12. 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

  13. 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.

  14. Segment Orientation and Optical Birefringence of Amorphous Polymers Under Tensile Deformation: Novel Computational Method applied to Different Glassy Polycarbonates

    Science.gov (United States)

    Natarajan, Upendra; Sulatha, M. S.

    2005-03-01

    Orientation dependent optical properties of Bisphenol A polycarbonate and two aliphatic substituted polycarbonates in glassy phase have been studied by atomistic modeling using molecular mechanics simulations under tensile deformation. Probability distributions and orientation functions show that phenylene rings and carbonate groups vectors along the main chain orient towards stretching direction following deformation. Interchain packing of rings and carbonates become ordered with strain. Efficient computational approach for calculation of optical birefringence of amorphous polymers is presented and applied to the polycarbonates in detail. Polarizability anisotropy of the polymer segments and chain as a function of deformation is calculated by combining information on the conformations and group polarizabilities, and used to estimate birefringence during deformation. Simulated and experimental values for segment orientation and bulk birefringence are in very good agreement. Effect of the optical properties of atomic groups on bulk birefringence is brought forth for the first time by molecular simulation for polymers other than polyethylene.

  15. 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.

  16. 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

    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...

  17. 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

  18. 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.

  19. 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.

  20. Understanding soft glassy materials using an energy landscape approach.

    Science.gov (United States)

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

    2016-09-01

    Many seemingly different soft materials-such as soap foams, mayonnaise, toothpaste and living cells-display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids. PMID:27322823

  1. 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.

  2. 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)

  3. 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.

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. Structure and Optical Properties of Polycrystalline InxSb30 – xSe70 (0 ≤ x ≤ 25 Chalcogenide Alloys

    Directory of Open Access Journals (Sweden)

    Shaveta Sharma

    2016-06-01

    Full Text Available The spectroscopic studies of various physical properties of glassy and polycrystalline chalcogenide alloys are important due to their importance as active materials in various solid state devices. The composition dependence of these properties are explained on the basis of coordination number, but the splitting of this effect from the nature of additive is imperative for furthering the understanding of these systems. In the present work, the structural and spectroscopic investigations of melt quenched bulk In-Sb-Se chalcogenide alloys have been studied by XRD, RAMAN and optical spectroscopic techniques. The XRD study reveals the polycrystalline nature of the samples. The composition was analysed using the energy dispersive X-ray spectroscopy technique. The XRD study reveals the crystallization of Sb2Se3 and β-In2Se3 phases while the increase in the intensity for β-In2Se3 phase has been observed with the increase in indium content. The RAMAN spectra also reveal the formation of chalcogenide based Sb and In structural units. The diffused reflectance spectrum was used to calculate the optical absorption in 800-1500 nm spectral region and used to study the composition dependence of the optical gap in these samples. The results have been discussed in conjunction with the heterogeneous phases; density of defect states; electronegativity and average mean bond energy for these polycrystalline alloys.

  12. Structural and Mechanical Characterization of Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Jürgen Eckert

    2011-12-01

    Full Text Available Thermal stability, structure and mechanical properties of the multi-component Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 bulk metallic glass have been studied in detail. The glassy material displays good thermal stability against crystallization and a fairly large supercooled liquid region of 52 K. During heating, the alloy transforms into a metastable icosahedral quasicrystalline phase in the first stage of crystallization. At high temperatures, the quasicrystalline phase undergoes a transformation to form tetragonal and cubic NiZr2-type phases. Room-temperature compression tests of the as-cast sample show good mechanical properties, namely, high compressive strength of about 1,630 MPa and fracture strain of 3.3%. This is combined with a density of 6.32 g/cm3 and values of Poisson’s ratio and Young’s modulus of 0.377 and 77 GPa, respectively. The mechanical properties of the glass can be further improved by cold rolling. The compressive strength rises to 1,780 MPa and the fracture strain increases to 8.3% for the material cold-rolled to a diameter reduction of 10%.

  13. Large area bulk superconductors

    Science.gov (United States)

    Miller, Dean J.; Field, Michael B.

    2002-01-01

    A bulk superconductor having a thickness of not less than about 100 microns is carried by a polycrystalline textured substrate having misorientation angles at the surface thereof not greater than about 15.degree.; the bulk superconductor may have a thickness of not less than about 100 microns and a surface area of not less than about 50 cm.sup.2. The textured substrate may have a thickness not less than about 10 microns and misorientation angles at the surface thereof not greater than about 15.degree.. Also disclosed is a process of manufacturing the bulk superconductor and the polycrystalline biaxially textured substrate material.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. 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

  19. 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.

  20. 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...

  1. 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.

    2015-11-01

    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 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.

  2. Dynamics of caged ions in glassy ionic conductors.

    Science.gov (United States)

    Habasaki, J; Ngai, K L; Hiwatari, Y

    2004-05-01

    At sufficiently high frequency and low temperature, the dielectric responses of glassy, crystalline, and molten ionic conductors all invariably exhibit nearly constant loss. This ubiquitous characteristic occurs in the short-time regime when the ions are still caged, indicating that it could be a determining factor of the mobility of the ions in conduction at longer times. An improved understanding of its origin should benefit the research of ion conducting materials for portable energy source as well as the resolution of the fundamental problem of the dynamics of ions. We perform molecular dynamics simulations of glassy lithium metasilicate (Li2SiO3) and find that the length scales of the caged Li+ ions motions are distributed according to a Levy distribution that has a long tail. These results suggest that the nearly constant loss originates from "dynamic anharmonicity" experienced by the moving but caged Li+ ions and provided by the surrounding matrix atoms executing correlated movements. The results pave the way for rigorous treatments of caged ion dynamics by nonlinear Hamiltonian dynamics.

  3. 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

  4. 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

  5. Deformation in Thin Glassy Polymer Films from Surface towards Interior

    Science.gov (United States)

    Chowdhury, Mithun; de Silva, Johann P.; Cross, Graham L. W.

    Polymer thin glassy films occupy an important place in last two decades of condensed matter research, concerning its surprising surface mobility and spatially dependent structural relaxation. However, ranges of cleverly designed indirect measurements on confined polymer glassy films already probed its mechanical properties; it is still a challenging task to directly probe such small confined volume through conventional mechanical testing. We have designed confined layer compression testing with a precisely designed and aligned flat probe during nanoindentation, which was further accompanied with atomic force microscopy. Due to natural confinement from the surrounding material, we show that a state of `uniaxial strain' is created beneath the probe under small axial strains. By this methodology we are able to directly probe uniaxial flows under both anelastic and plastic conditions while doing controlled creep studies at different positions in the film starting from surface towards interior. Depending on the extent of deformation, we found ranges of effects, such as densification, anelastic yield, and plastic yield. Enhanced creep rate upon deformation supports the idea of `deformation induced mobility'. Work performed at Trinity College Dublin.

  6. 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...

  7. Multiscale simulations of PS-SiO2 nanocomposites: from melt to glassy state.

    Science.gov (United States)

    Mathioudakis, I G; Vogiatzis, G G; Tzoumanekas, C; Theodorou, D N

    2016-09-28

    The interaction energetics, molecular packing, entanglement network properties, segmental dynamics, and elastic constants of atactic polystyrene-amorphous silica nanocomposites in the molten and the glassy state are studied via molecular simulations using two interconnected levels of representation: (a) a coarse-grained one, wherein each polystyrene repeat unit is mapped onto a single "superatom" and the silica nanoparticle is viewed as a solid sphere. Equilibration at all length scales at this level is achieved via connectivity-altering Monte Carlo simulations. (b) A united-atom (UA) level, wherein the polymer chains are represented in terms of a united-atom forcefield and the silica nanoparticle is represented in terms of a simplified, fully atomistic model. Initial configurations for UA molecular dynamics (MD) simulations are obtained by reverse mapping well-equilibrated coarse-grained configurations. By analysing microcanonical UA MD trajectories, the polymer density profile is studied and the polymer is found to exhibit layering in the vicinity of the nanoparticle surface. An estimate of the enthalpy of mixing between polymer and nanoparticles, derived from the UA simulations, compares favourably against available experimental values. The dynamical behaviour of polystyrene (in neat and filled melt systems) is characterized in terms of bond orientation and dihedral angle time autocorrelation functions. At low concentration in the molten polymer matrix, silica nanoparticles are found to cause a slight deceleration of the segmental dynamics close to their surface compared to the bulk polymer. Well-equilibrated coarse-grained long-chain configurations are reduced to entanglement networks via topological analysis with the CReTA algorithm, yielding a slightly lower density of entanglements in the filled than in the neat systems. UA melt configurations are glassified by MD cooling. The elastic moduli of the resulting glassy nanocomposites are computed through an

  8. 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)

  9. 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.

  10. 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

  11. Preparation of fine-grained bulk materials in the Fe-Co system by shock compression

    CERN Document Server

    Mashimo, T; Huang, X S; Murata, H; Sakakibara, M

    2002-01-01

    Fine-grained bulk alloys with no crack in the 70:30 mol% Fe-Co system were prepared by means of shock compression of water-atomized powder and mechanical alloying (MA) treated ones. The grain size of the water-atomized bulk body was smaller (<=50 mu m) than that of the molten bulk body (about 100 mu m). The grain size decreased greatly with the MA treatment time, and ones for 21 h were estimated to be about 15 nm from the x-ray diffraction patterns. The coercivity value of the water-atomized bulk body was much larger than that of the molten bulk body. The coercivity value of the MA-treated bulk body increased with the MA treatment time, and then decreased, despite the very small grain size, probably due to the effect of ferromagnetic exchange interaction.

  12. 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).

  13. Cell division and death inhibit glassy behaviour of confluent tissues

    CERN Document Server

    Matoz-Fernandez, D A; Sknepnek, Rastko; Barrat, J L; Henkes, S

    2016-01-01

    We investigate the effects of cell division and apopotosis on collective dynamics in two-dimensional epithelial tissues. Our model includes three key ingredients observed across many epithelia, namely cell-cell adhesion, cell death and a cell division process that depends on the surrounding environment. We show a rich non-equilibrium phase diagram depending on the ratio of cell death to cell division and on the adhesion strength. For large apopotosis rates, cells die out and the tissue disintegrates. As the death rate decreases, however, we show, consecutively, the existence of a gas-like phase, a gel-like phase, and a dense confluent (tissue) phase. Most striking is the observation that the tissue is self-melting through its own internal activity, ruling out the existence of any glassy phase.

  14. 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.;

    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....

  15. 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)

  16. 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

  17. Electroanalysis of trimethoprim on metalloporphyrin incorporated glassy carbon electrode.

    Science.gov (United States)

    Rajith, Leena; Kumar, Krishnapillai Girish

    2010-09-01

    Trimethoprim (TMP) is a bacteriostatic antibiotic mainly used in the prophylaxis and treatment of urinary tract infections. It belongs to the class of chemotherapeutic agents known as dihydrofolate reductase inhibitors. Its use is associated with idiosyncratic reactions, including liver toxicity and agranulocytosis. In order to determine TMP electrochemically, a metalloporphyrin modified glassy carbon electrode was prepared by coating [5,10,15,20- tetrakis(4-methoxyphenyl) porphyrinato]Mn (III)chloride (TMOPPMn(III)Cl) solution on the surface of the electrode. The electrochemical behaviour of TMP in Phosphate buffer solution (PBS) on TMOPPMn(III)Cl modified glassy carbon electrode (TMOPPMn(III)Cl/GCE) was explored using differential pulse voltammetry (DPV). The voltammograms showed enhanced oxidation response at the TMOPPMn (III)Cl/GCE with respect to the bare GCE for TMP, attributable to the electrocatalytic activity of TMOPPMn(III)Cl. Electrochemical parameters of the oxidation of TMP on the modified electrode were analyzed. The electro-oxidation of TMP was found to be irreversible, pH dependent and adsorption controlled on the modified electrode. It is found that the oxidation peak current is proportional to the concentration of TMP over the range 6 × 10⁻⁸ - 1 × 10⁻⁶ M with a very low detection limit of 3 × 10⁻⁹ M at 2 min open circuit accumulation. The repeatability expressed as relative standard deviation (RSD) for n = 9 was 3.2% and the operational stability was found to be 20 days. Another striking feature is that equimolar concentration of sulfamethoxazole did not interfere in the determination of TMP. Applicability to assay the drug in urine and tablet samples has also been studied.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. Fabrication of Ti-based composites based on bulk amorphous alloys by spark plasma sintering and crystallization of amorphous phase%放电等离子烧结-非晶晶化法合成钛基块状非晶复合材料

    Institute of Scientific and Technical Information of China (English)

    李元元; 杨超; 李小强; 陈友

    2011-01-01

    In order to circumvent low plasticity of bulk amorphous alloys (BAAs), a material forming method by coupling spark plasma sintering with crystallization of amorphous phase, fabricating composites based on BAAs (CBBAAs) with excellent mechanical property was reviewed systematically. By appropriate annealing of sintered BAAs prepared from spark plasma sintering in the supercooled liquid region of a mechanically alloyed amorphous powder, crystallized ductile β-Ti phase with controllable grain size, phase morphology and distribution can precipitate from the amorphous phase, and therefore, CBBAAs with a matrix of amorphous phase or crystallized β-Ti phase were obtained. The effect of different additions or substitute elements on the particle size, thermal property and microstructure of TiNbCuNiAl amorphous powder, and the influence of different sintering parameters on the microstructure and mechanical property of fabricated CBBAAs were investigated. The theoretical bases of fabricating crystallized phase-containing CBBAAs, and nucleation and growth mechanism of crystalline phase during the crystallization process were elucidated. The facture mechanism of fabricated CBBAAs under stress was explained based on a proposed "Developed hard-soft model". The results provide a promising method for fabricating large-sized crystallized phase-containing bulk composites with excellent mechanical property by powder metallurgy.%鉴于块状非晶合金(BAAs)的低塑性特征,回顾了利用放电等离子烧结-非晶晶化法制备高性能块状材料的成形技术,即先机械合金化制备钛基多组元非晶合金粉末,然后利用放电等离子烧结在粉末的过冷液相区固结非晶粉末,再利用非晶晶化法使烧结的非晶块体在随后的烧结和热处理过程中晶化析出-Ti延性相,控制延性相的形貌、尺度和分布,合成以非晶相或β-Ti晶化相为基体的钛基块状非晶复合材料(CBBAAs),研究不同添加或替换组元对TiNb

  7. 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.

  8. 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)

  9. Surface composition of ordered alloys: An off-stoichiometric effect

    DEFF Research Database (Denmark)

    Ruban, Andrei

    2002-01-01

    I predict the existence of an off-stoichiometric effect in ordered alloys in the form of a distinct transition in the surface segregation behavior of alloy components near the bulk stoichiometric composition. It is caused by the discontinuity in the effective chemical potential at the stoichiomet...... at the stoichiometric composition. The effect is predicted to occur at the (111) surface of ordered Ni3Al and Pt3Fe alloys....

  10. 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...

  11. 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.

  12. Bulk Metallic Glasses for Implantable Medical Devices and Surgical Tools.

    Science.gov (United States)

    Meagher, Philip; O'Cearbhaill, Eoin D; Byrne, James H; Browne, David J

    2016-07-01

    With increasing knowledge of the materials science of bulk metallic glasses (BMGs) and improvements in their properties and processing, they have started to become candidate materials for biomedical devices. A dichotomy in the types of medical applications has also emerged, in which some families of BMGs are being developed for permanent devices whilst another family - of Mg-based alloys - is showing promise in bioabsorbable implants. The current status of these metallurgical and technological developments is summarized.

  13. 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

  14. 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

  15. Activation of glassy carbon electrodes by photocatalytic pretreatment

    Energy Technology Data Exchange (ETDEWEB)

    Dumanli, Onur [Department of Chemistry, Faculty of Science and Art, Ondokuz Mayis University, Kurupelit, 55139 Samsun (Turkey); Onar, A. Nur [Department of Chemistry, Faculty of Science and Art, Ondokuz Mayis University, Kurupelit, 55139 Samsun (Turkey)], E-mail: nonar@omu.edu.tr

    2009-11-01

    This paper describes a simple and rapid photocatalytic pretreatment procedure that removes contaminants from glassy carbon (GC) surfaces. The effectiveness of TiO{sub 2} mediated photocatalytic pretreatment procedure was compared to commonly used alumina polishing procedure. Cyclic voltammetric and chronocoulometric measurements were carried out to assess the changes in electrode reactivity by using four redox systems. Electrochemical measurements obtained on photocatalytically treated GC electrodes showed a more active surface relative to polished GC. In cyclic voltammograms of epinephrine, Fe(CN){sub 6}{sup 3-/4-} and ferrocene redox systems, higher oxidation and reduction currents were observed. The heterogeneous electron transfer rate constants (k{sup o}) were calculated for Fe(CN){sub 6}{sup 3-/4-} and ferrocene which were greater for photocatalytic pretreatment. Chronocoulometry was performed in order to find the amount of adsorbed methylene blue onto the electrode and was calculated as 0.34 pmol cm{sup -2} for photocatalytically pretreated GC. The proposed photocatalytic GC electrode cleansing and activating pretreatment procedure was more effective than classical alumina polishing.

  16. Glassy cell carcinoma of the cervix: a literature review.

    Science.gov (United States)

    Zolciak-Siwinska, A; Jonska-Gmyrek, J

    2014-08-01

    Glassy cell carcinoma (GCC) is a histologically aggressive subtype of cervical cancer with rapid growth and early metastases. The prognosis for patients with GCC is poor. This article reviews the literature pertinent to the epidemiology, cytology, pathology, immunohistochemistry, treatment and prognosis of GCC. MEDLINE (PubMed) was searched for all articles or abstracts on patients diagnosed with GCC published (in English) since the original definition by Glucksmann and Cherry, Cancer 1956;9:971. Accurate diagnosis of GCC enables implementation of the correct treatment strategy. Early-stage GCC should be treated with hysterectomy and pelvic lymph node dissection, with adjuvant radiochemotherapy if at least one intermediate or high risk factor for cervical cancer is present. Advanced GCC should be treated with neoadjuvant radiochemotherapy or chemotherapy with the aim of making the disease operable. There is a need for retrospective evaluation of GCC treatment from several centres to explore knowledge about this rare entity. Future studies should explore the role of targeted therapies and the most efficient chemotherapy regimen for the management of GCC.

  17. 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.

  18. The chromium site in doped glassy lithium tetraborate

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, T.D. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Echeverria, E.; Beniwal, Sumit [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States); Adamiv, V.T.; Burak, Ya. V.; Enders, Axel [Institute of Physical Optics, 23 Dragomanov Street, Lviv 79005 (Ukraine); Petrosky, J.C.; McClory, J.W. [Department of Engineering Physics, Air Force Institute of Technology, 2950 Hobson Way, Wright Patterson Air Force Base, OH 45433 (United States); Dowben, P.A., E-mail: pdowben1@unl.edu [Department of Physics and Astronomy, 855 North 16th Street, Theodore Jorgensen Hall, University of Nebraska-Lincoln, Lincoln, NE 68588-0299 (United States)

    2014-10-15

    Using extended X-ray absorption fine structure (EXAFS) spectroscopy, we find that Cr substitutes primarily in the Li{sup +} site as a dopant in lithium tetraborate Li{sub 2}B{sub 4}O{sub 7} glasses, in this case 98.4Li{sub 2}B{sub 4}O{sub 7}–1.6Cr{sub 2}O{sub 3} or nominally Li{sub 1.98}Cr{sub 0.025}B{sub 4}O{sub 7}. This strong preference for a single site is nonetheless accompanied by site distortions and some site disorder, helping explain the optical properties of chromium doped Li{sub 2}B{sub 4}O{sub 7} glasses. The resulting O coordination shell has a contraction of the Cr–O bond lengths as compared to the Li–O bond lengths. There is also an increase in the O coordination number. - Graphical abstract: Lithium tetraborate: labeled are the B1 and B2 sites, where the latter correspond to BO{sub 3} and BO{sub 4} structures respectively. - Highlights: • Adoption of the Li + site for chromium dopants in lithium tetraborate identified. • Increased oxygen coordination for glass over the crystalline lithium tetraborate. • Distortions about the doping chromium characterized. • Local bond order is preserved in spite of the glassy nature.

  19. 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.

  20. Fe-based bulk metallic glasses used for magnetic shielding

    Science.gov (United States)

    Şerban, Va; Codrean, C.; Uţu, D.; Ercuţa, A.

    2009-01-01

    The casting in complex shapes (tubullar) and the main magnetic properties of bulk metallic glasses (BMG) alloys from the ferromagnetic Fe-Cr-Ni-Ga-P-Si-C system, with a small adittion of Ni (3%) were studied. Samples as rods and sockets having the thickness up to 1 mm were obtained from master alloys by melt injection by low cooling rates into a Cu mold and annealed in order to ensure adequate magnetic requirements. The structure was examined by X-ray diffraction (XRD) and the basic magnetic properties (coercivity, magnetic remanence, initial susceptibility, etc.) were determined by conventional low frequency induction method. The experimental investigations on producing of BMG ferromagnetic alloys with 3% Ni show the possibility to obtain magnetic shields of complex shape with satisfactory magnetic properties. The presence of Ni does not affect the glass forming ability, but reduce the shielding capacity.

  1. 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

  2. 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 ...

  3. 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.

  4. Diffusion or bulk flow

    DEFF Research Database (Denmark)

    Schulz, Alexander

    2015-01-01

    the concentration gradient or bulk flow along a pressure gradient. The driving force seems to depend on the mode of phloem loading. In a majority of plant species phloem loading is a thermodynamically active process, involving the activity of membrane transporters in the sieve-element companion cell complex. Since...... assimilate movement includes an apoplasmic step, this mode is called apoplasmic loading. Well established is also the polymer-trap loading mode, where the phloem-transport sugars are raffinose-family oligomers in herbaceous plants. Also this mode depends on the investment of energy, here for sugar......Assimilates synthesized in the mesophyll of mature leaves move along the pre-phloem transport pathway to the bundle sheath of the minor veins from which they are loaded into the phloem. The present review discusses the most probable driving force(s) for the pre-phloem pathway, diffusion down...

  5. Bulk-Fill Resin Composites

    DEFF Research Database (Denmark)

    Benetti, Ana Raquel; Havndrup-Pedersen, Cæcilie; Honoré, Daniel;

    2015-01-01

    the 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-viscosity bulk...

  6. 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 ...

  7. Glassy aerosols with a range of compositions nucleate ice heterogeneously at cirrus temperatures

    Directory of Open Access Journals (Sweden)

    S. Dobbie

    2012-04-01

    Full Text Available Atmospheric secondary organic aerosol (SOA is likely to exist in an ultra viscous or glassy state, particularly at low temperatures and humidities. It has also been shown that glassy aqueous citric acid aerosol is able to nucleate ice heterogeneously under conditions relevant to cirrus in the tropical tropopause layer (TTL. In this study we test if glassy aerosols with a range of chemical compositions heterogeneously nucleate ice under cirrus conditions. Three single component aqueous solution aerosols (raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA and levoglucosan and one multi component aqueous solution aerosol (raffinose mixed with five dicarboxylic acids and ammonium sulphate were studied in both the liquid and glassy states at a large cloud simulation chamber. The investigated organic compounds have similar functionality to oxidised organic material found in atmospheric aerosol and have estimated temperature/humidity induced glass transition thresholds that fall within the range predicted for atmospheric SOA. All the aerosols tested were found to nucleate ice heterogeneously in the deposition mode at temperatures relevant to the TTL (<200 K. Raffinose and HMMA, which form glasses at higher temperatures, nucleated ice heterogeneously at temperatures as high as 214.6 and 218.5 K respectively. We present the calculated ice active surface site density, ns, of the aerosols tested here and also of glassy citric acid aerosol as a function of relative humidity with respect to ice (RHi. We also propose a parameterisation which can be used to estimate heterogeneous ice nucleation by glassy aerosol for use in cirrus cloud models up to ~220 K. Finally, we show that heterogeneous nucleation by glassy aerosol may compete with ice nucleation on mineral dust particles in mid-latitudes cirrus.

  8. Glassy aerosols with a range of compositions nucleate ice heterogeneously at cirrus temperatures

    Directory of Open Access Journals (Sweden)

    T. W. Wilson

    2012-09-01

    Full Text Available Atmospheric secondary organic aerosol (SOA is likely to exist in a semi-solid or glassy state, particularly at low temperatures and humidities. Previously, it has been shown that glassy aqueous citric acid aerosol is able to nucleate ice heterogeneously under conditions relevant to cirrus in the tropical tropopause layer (TTL. In this study we test if glassy aerosol distributions with a range of chemical compositions heterogeneously nucleate ice under cirrus conditions. Three single component aqueous solution aerosols (raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA and levoglucosan and one multi component aqueous solution aerosol (raffinose mixed with five dicarboxylic acids and ammonium sulphate were studied in both the liquid and glassy states at a large cloud simulation chamber. The investigated organic compounds have similar functionality to oxidised organic material found in atmospheric aerosol and have estimated temperature/humidity induced glass transition thresholds that fall within the range predicted for atmospheric SOA. A small fraction of aerosol particles of all compositions were found to nucleate ice heterogeneously in the deposition mode at temperatures relevant to the TTL (<200 K. Raffinose and HMMA, which form glasses at higher temperatures, nucleated ice heterogeneously at temperatures as high as 214.6 and 218.5 K respectively. We present the calculated ice active surface site density, ns, of the aerosols tested here and also of glassy citric acid aerosol as a function of relative humidity with respect to ice (RHi. We also propose a parameterisation which can be used to estimate heterogeneous ice nucleation by glassy aerosol for use in cirrus cloud models up to ~220 K. Finally, we show that heterogeneous nucleation by glassy aerosol may compete with ice nucleation on mineral dust particles in mid-latitudes cirrus.

  9. Production and Characterization of Brass-matrix Composites Reinforced with Ni59Zr20Ti16Si2Sn3 Glassy Particles

    Directory of Open Access Journals (Sweden)

    Bum Sung Kim

    2012-05-01

    Full Text Available Brass-matrix composites reinforced with 40 and 60 vol.% of Ni59Zr20Ti16Si2Sn3 glassy particles were produced by powder metallurgy. The crystallization behavior and the temperature dependence of the viscosity of the glass reinforcement were studied in detail to select the proper sintering parameters in order to avoid crystallization of the glassy phase during consolidation. The brass-glass powder mixtures were prepared through manual blending as well as by ball milling to analyze the effect of the matrix ligament size on the mechanical properties of the composites. The powder mixtures were then consolidated into highly-dense bulk specimens at temperatures within the supercooled liquid region by hot pressing followed by hot extrusion. The preparation of the powder mixtures has a strong influence on the mechanical behavior of the composites. The strength increases from 500 MPa for pure brass to 740 and 925 MPa for the blended composites with 40 and 60vol.% of glass reinforcement, while the strength increases to 1,240 and 1,640 MPa for the corresponding composites produced by ball milling. Modeling of the mechanical properties indicates that this behavior is related to the reduced matrix ligament size characterizing the milled composites.

  10. Glass Formation Ability and Kinetics of the Gd55Al20Ni25 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    JO Chol-Lyong; XIA Lei; DING Ding; DONG Yuan-Da

    2006-01-01

    @@ We report a new bulk glass-forming alloy Gd55Al20Ni25. The bulk sample of the alloy is prepared in the shape of rods in diameter 2mm by suction casting. The rod exhibits typical amorphous characteristics in the xray diffraction pattern, paramagnetic property at 300K, distinct glass transition and multi-step crystallization behaviour in differential scanning calorimetry traces. The glass formation ability of the alloy is investigated by using the reduced glass transition temperature Tγg and the parameter γ. Kinetics of glass transition and primary crystallization is also studied. The fragility parameter m obtained from the Vogel-Fulcher-Tammann dependence of glass transition temperature Tg on ln φ (φ is the heating rate) classifies the bulk metallic glasses into the intermediate category according to Angells classification.

  11. 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...

  12. 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)

  13. 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)

  14. 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.

  15. 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.

  16. 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...

  17. ( 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.

  18. 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

  19. 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

  20. Effect of entanglements on mechanical properties of glassy polymers

    Science.gov (United States)

    Hoy, Robert Scott

    Glass forming polymers are of great industrial importance and scientific interest because of their unique mechanical properties, which arise from the connectivity and random-walk-like structure of the constituent chains. In this thesis I study the relation of entanglements to the mechanical properties of model polymer glasses and brushes using molecular dynamics simulations. We perform extensive studies of glassy strain hardening, which stabilizes polymers against strain localization and fracture. Fundamental inconsistencies in existing entropic models of strain hardening imply that our understanding of its microscopic origins is far from complete. The dependence of stress on strain and entanglement density is consistent with experiment and entropic models. However, many of the assumptions of these models are totally inconsistent with our simulation results. The dependence on temperature, rate and interaction strength can be understood as reflecting changes in the plastic flow stress rather than a network entropy. A substantial energetic contribution to the stress rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. The deformation of the entanglement network is not affine to the macroscopic stretch. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain. The entropic back stress responsible for shape recovery arises from chain orientation rather than entanglement. We also present some other results unrelated to strain hardening. We analyze the entanglement of polymer brushes embedded in long-chain melts and in implicit good and theta solvents. The melt-embedded brushes are more self-entangled than those in the solvents. The degree of self-entanglement of the brushes in the solvents follows a simple

  1. A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals.

    Science.gov (United States)

    Lamura, G; Shiroka, T; Bonfà, P; Sanna, S; Bernardini, F; De Renzi, R; Viennois, R; Giannini, E; Piriou, A; Emery, N; Cimberle, M R; Putti, M

    2013-04-17

    The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment 'freezes' at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.

  2. 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

  3. Atomistic modelling and prediction of glass forming ability in bulk metallic glasses

    Science.gov (United States)

    Sedighi, Sina

    Atomistic modeling (via molecular dynamics with EAM interaction potentials) was conducted for the detailed investigation of kinetics, thermodynamics, structure, and bonding in Ni-Al and Cu-Zr metallic glasses. This work correlates GFA with the nature of atomic-level bonding and vibrational properties, with results potentially extensible to the Transition Metal -- Transition Metal and Transition Metal -- Metalloid alloy classes in general. As a first step in the development of a liquid-only GFA tuning approach, an automated tool has also been created for the broad compositional sampling of liquid and glassy phase properties in multicomponent (binary, ternary, quaternary) alloy systems. Its application to the Cu-Zr alloy system shows promising results, including the successful identification of the two highest GFA compositions, Cu50Zr50 and Cu64Zr 36. Combined, the findings of this work highlight the critical importance of incorporating more complex alloy-specific information regarding the nature of bonding and ordering at the atomic level into such an approach.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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...

  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. Self-organization and the physics of glassy networks

    Science.gov (United States)

    Boolchand, P.; Lucovsky, G.; Phillips, J. C.; Thorpe, M. F.

    Network glasses are the physical prototype for many self-organized systems, ranging from proteins to computer science. Conventional theories of gases, liquids and crystals do not account for the strongly material-selective character of the glass-forming tendency, the phase diagrams of glasses or their optimizable properties. A new topological theory, only 25 years old, has succeeded where conventional theories have failed. It shows that (probably all slowly quenched) glasses, including network glasses, are the result of the combined effects of a few simple mechanisms. These glass-forming mechanisms are topological in nature and have already been identified for several important glasses, including chalcogenide alloys, silicates (window glass and computer chips) and proteins.

  11. Thermoplastic Micro-Forming of Bulk Metallic Glasses: A Review

    Science.gov (United States)

    Li, Ning; Chen, Wen; Liu, Lin

    2016-04-01

    Bulk metallic glasses are a fascinating class of metallic alloys with an isotropic amorphous structure that is rapidly quenched from liquid melts. The absence of a crystalline micro-structure endows them with a portfolio of properties such as high strength, high elasticity, and excellent corrosion resistance. Whereas the limited plasticity and hence poor workability at ambient temperature impede the structural application of bulk metallic glasses, the unique superplasticity within the supercooled liquid region opens an alternative window of so-called thermoplastic forming, which allows precise and versatile net-shaping of complex geometries on length scales ranging from nanometers to centimeters that were previously unachievable with conventional crystalline metal processing. Thermoplastic forming not only breaks through the bottleneck of the manufacture of bulk metallic glasses at ambient temperature but also offers an alluring prospect in micro-engineering applications. This paper comprehensively reviews some pivotal aspects of bulk metallic glasses during thermoplastic micro-forming, including an in-depth understanding of the crystallization kinetics of bulk metallic glasses and the thermoplastic processing time window, the thermoplastic forming map that clarifies the relationship between the flow characteristics and the formability, the interfacial friction in micro-forming and novel forming methods to improve the formability, and the potential applications of the hot-embossed micro-patterns/components.

  12. 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.

  13. 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.)

  14. 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.)

  15. 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.

  16. Research activities of biomedical magnesium alloys in China

    Science.gov (United States)

    Zheng, Yufeng; Gu, Xuenan

    2011-04-01

    The potential application of Mg alloys as bioabsorable/biodegradable implants have attracted much recent attention in China. Advances in the design and biocompatibility evaluation of bio-Mg alloys in China are reviewed in this paper. Bio-Mg alloys have been developed by alloying with the trace elements existing in human body, such as Mg-Ca, Mg-Zn and Mg-Si based systems. Additionally, novel structured Mg alloys such as porous, composited, nanocrystalline and bulk metallic glass alloys were tried. To control the biocorrosion rate of bio-Mg implant to match the self-healing/regeneration rate of the surrounding tissue in vivo, surface modification layers were coated with physical and chemical methods.

  17. 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

  18. 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.

  19. Modification of glassy carbon surfaces by atmospheric pressure cold plasma torch

    DEFF Research Database (Denmark)

    Mortensen, Henrik Junge; Kusano, Yukihiro; Leipold, Frank;

    2006-01-01

    The effect of plasma treatment on glassy carbon (GC) surfaces was studied with adhesion improvement in mind. A newly constructed remote plasma source was used to treat GC plates. Pure He and a dilute NH3/He mixture were used as feed gases. Optical emission spectroscopy was performed for plasma to...

  20. Glassy-winged sharpshooter oviposition effects on foliar grapevine and red-tipped photinia terpenoid levels

    Science.gov (United States)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important vector of Xylella fastidiosa, the bacterium that causes Pierce's disease of grapevine and is a threat to grape production throughout the United States. Female GWSS deposit egg masses be...

  1. Glassy-winged sharpshooter oviposition effects on photinia volatile chemistry with implications on egg parasitoid effectiveness

    Science.gov (United States)

    An effective way to limit incidence of Pierce’s disease of grapevine is to reduce populations of glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), which transmit the causal bacterium, Xylella fastidiosa. One strategy is to utilize egg parasitoids such as ...

  2. Glassy-winged sharpshooter can use a mechanical mechanism to inoculate Xylella fastidiosa into grapevines

    Science.gov (United States)

    Xylem-feeding leafhoppers such as the glassy-winged sharpshooter, Homalodisca vitripennis (Cicadellidae: Cicadellinae), are thought to inoculate the bacterium Xylella fastidiosa (Xf) from colonies bound to cuticle of the sharpshooter’s functional foregut (precibarium and cibarium). The mechanism of ...

  3. 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.

  4. 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

  5. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Directory of Open Access Journals (Sweden)

    R. Wagner

    2012-09-01

    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 aerosol particles that have re

  6. 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

  7. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    Science.gov (United States)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    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 aerosol particles that have re-vitrified in contact

  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. 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

  11. Modeling selective intergranular oxidation of binary alloys

    Science.gov (United States)

    Xu, Zhijie; Li, Dongsheng; Schreiber, Daniel K.; Rosso, Kevin M.; Bruemmer, Stephen M.

    2015-01-01

    Intergranular attack of alloys under hydrothermal conditions is a complex problem that depends on metal and oxygen transport kinetics via solid-state and channel-like pathways to an advancing oxidation front. Experiments reveal very different rates of intergranular attack and minor element depletion distances ahead of the oxidation front for nickel-based binary alloys depending on the minor element. For example, a significant Cr depletion up to 9 μm ahead of grain boundary crack tips was documented for Ni-5Cr binary alloy, in contrast to relatively moderate Al depletion for Ni-5Al (˜100 s of nm). We present a mathematical kinetics model that adapts Wagner's model for thick film growth to intergranular attack of binary alloys. The transport coefficients of elements O, Ni, Cr, and Al in bulk alloys and along grain boundaries were estimated from the literature. For planar surface oxidation, a critical concentration of the minor element can be determined from the model where the oxide of minor element becomes dominant over the major element. This generic model for simple grain boundary oxidation can predict oxidation penetration velocities and minor element depletion distances ahead of the advancing front that are comparable to experimental data. The significant distance of depletion of Cr in Ni-5Cr in contrast to the localized Al depletion in Ni-5Al can be explained by the model due to the combination of the relatively faster diffusion of Cr along the grain boundary and slower diffusion in bulk grains, relative to Al.

  12. 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)

  13. 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.

  14. Designing new biocompatible glass-forming Ti75-x Zr10 Nbx Si15 (x = 0, 15) alloys: corrosion, passivity, and apatite formation.

    Science.gov (United States)

    Abdi, Somayeh; Oswald, Steffen; Gostin, Petre Flaviu; Helth, Arne; Sort, Jordi; Baró, Maria Dolors; Calin, Mariana; Schultz, Ludwig; Eckert, Jürgen; Gebert, Annett

    2016-01-01

    Glass-forming Ti-based alloys are considered as potential new materials for implant applications. Ti75 Zr10 Si15 and Ti60 Zr10 Nb15 Si15 alloys (free of cytotoxic elements) can be produced as melt-spun ribbons with glassy matrix and embedded single β-type nanocrystals. The corrosion and passivation behavior of these alloys in their homogenized melt-spun states have been investigated in Ringer solution at 37°C in comparison to their cast multiphase crystalline counterparts and to cp-Ti and β-type Ti-40Nb. All tested materials showed very low corrosion rates as expressed in corrosion current densities icorr  corrosion properties, the Nb-containing nearly single-phase glassy alloy can compete with the β-type Ti-40Nb alloy. SBF tests confirmed the ability for formation of hydroxyapatite on the melt-spun alloy surfaces. All these properties recommend the new glass-forming alloys for application as wear- and corrosion-resistant coating materials for implants.

  15. 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.

  16. New Developments of Ti-Based Alloys for Biomedical Applications

    Directory of Open Access Journals (Sweden)

    Yuhua Li

    2014-03-01

    Full Text Available Ti-based alloys are finding ever-increasing applications in biomaterials due to their excellent mechanical, physical and biological performance. Nowdays, low modulus β-type Ti-based alloys are still being developed. Meanwhile, porous Ti-based alloys are being developed as an alternative orthopedic implant material, as they can provide good biological fixation through bone tissue ingrowth into the porous network. This paper focuses on recent developments of biomedical Ti-based alloys. It can be divided into four main sections. The first section focuses on the fundamental requirements titanium biomaterial should fulfill and its market and application prospects. This section is followed by discussing basic phases, alloying elements and mechanical properties of low modulus β-type Ti-based alloys. Thermal treatment, grain size, texture and properties in Ti-based alloys and their limitations are dicussed in the third section. Finally, the fourth section reviews the influence of microstructural configurations on mechanical properties of porous Ti-based alloys and all known methods for fabricating porous Ti-based alloys. This section also reviews prospects and challenges of porous Ti-based alloys, emphasizing their current status, future opportunities and obstacles for expanded applications. Overall, efforts have been made to reveal the latest scenario of bulk and porous Ti-based materials for biomedical applications.

  17. 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.

  18. 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...

  19. 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.

  20. Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

    International Nuclear Information System (INIS)

    The knowledge of surface composition and atomic arrangement is prerequisite for understanding of catalytic properties of an alloy catalyst. Gaining such knowledge is rather difficult, especially for those possessing surface segregation. Pd–Cu alloy is used in many fields and possesses surface segregation. In this paper kinetic Monte Carlo method is used to explore the surface composition and structure and to examine the effects of bulk composition and temperature on the surface segregation of Pd–Cu alloys. It is shown that the segregation basically completes within 900 s at 500 K. Below 900 K and within 20 min the enriched surface Cu atoms mainly come from the top five layers. For the first time we demonstrate that there exists a “bulk-inside flocking” or clustering phenomenon (the same component element congregates in bulk) in Pd–Cu alloys. Our results indicate that for alloys with higher Cu content there are small Pd ensembles like monomers, dimers and trimers with contiguous subsurface Pd atoms. - Highlights: • Kinetic Monte Carlo was first used to study surface segregation of Pd–Cu alloys. • Bulk-inside flocking (the same component element congregates in bulk) was observed. • Small Pd ensembles with contiguous subsurface Pd exist on surfaces of Cu-rich alloys

  1. Kinetic Monte Carlo simulation of surface segregation in Pd–Cu alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Feng [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); He, Xiang [Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008 (China); Chen, Zhao-Xu, E-mail: zxchen@nju.edu.cn [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); Huang, Yu-Gai [Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University (China); JiangSu Second Normal University, Nanjing (China)

    2015-11-05

    The knowledge of surface composition and atomic arrangement is prerequisite for understanding of catalytic properties of an alloy catalyst. Gaining such knowledge is rather difficult, especially for those possessing surface segregation. Pd–Cu alloy is used in many fields and possesses surface segregation. In this paper kinetic Monte Carlo method is used to explore the surface composition and structure and to examine the effects of bulk composition and temperature on the surface segregation of Pd–Cu alloys. It is shown that the segregation basically completes within 900 s at 500 K. Below 900 K and within 20 min the enriched surface Cu atoms mainly come from the top five layers. For the first time we demonstrate that there exists a “bulk-inside flocking” or clustering phenomenon (the same component element congregates in bulk) in Pd–Cu alloys. Our results indicate that for alloys with higher Cu content there are small Pd ensembles like monomers, dimers and trimers with contiguous subsurface Pd atoms. - Highlights: • Kinetic Monte Carlo was first used to study surface segregation of Pd–Cu alloys. • Bulk-inside flocking (the same component element congregates in bulk) was observed. • Small Pd ensembles with contiguous subsurface Pd exist on surfaces of Cu-rich alloys.

  2. 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.

  3. Glassy cell carcinoma of the uterine cervix a rare histology. Report of three cases with a review of the literature

    Directory of Open Access Journals (Sweden)

    Deshpande Archana

    2004-01-01

    Full Text Available Glassy cell carcinoma is a poorly differentiated variant of adenosquamous carcinoma of the cervix associated with an aggressive course and a poor prognosis. We present three cases of glassy cell carcinoma of the cervix. Patients presented with a cervical growth which was biopsied. Histology the tumours showed nests of cells with a granular or clear cytoplasm, displaying marked pleomorphism and mitoses. Stroma showed an eosinophilic infiltrate. Two tumours showed a pure glassy cell pattern and one showed glandular differentiation with intracellular and extracellular mucin. Patients were treated with a combination of surgery, radiotherapy and chemotherapy but showed a poor response. Two patients died of the disease of pelvic or distant metastases within two years of diagnosis and one was lost to follow up. Although glassy cell carcinoma runs an aggressive clinical course, an early diagnosis may help in a more effective management and offer a better prognosis.

  4. 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...

  5. 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.

  6. H2-splitting on Pt/Ru alloys supported on sputtered HOPG

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria; Dahl, Søren; Chorkendorff, Ib

    2011-01-01

    that alloying Pt with Ru improves significantly the resistance toward CO poisoning with respect to pure Pt, and the resistance increases with an increasing amount of Ru in the bulk alloys. The faster hydrogen exchange rate with respect to the pure metals and the higher CO tolerance of the alloys are attributed......, and it is attributed to geometrical ensemble effects. © 2011 American Chemical Society....

  7. ENVIRONMENTAL FRIENDLY ANODIZING ON AZ91D MAGNESIUM ALLOYS AND COATING CHARACTERISTICS

    Institute of Scientific and Technical Information of China (English)

    A. Saijo; M. Hino; M. Hiramatsu; T. Kanadani

    2005-01-01

    An environmental friendly anodizing treatment (Anomag) from a phosphate-based solution without heavy metals on AZ91D magnesium alloy was studied. The characteristics of the coatings,such as structure, composition and corrosion resistance were investigated. The effects of this anodizing treatment on the mechanical properties were examined. X-ray diffraction (XRD) analysis revealed that the structure of the coatings is amorphous or glassy. In salt spray tests coatings with an average thickness of 10μm had an anticorrosive performance of over 1000 hours. Fatigue tests revealed that anodizing onto AZ91D magnesium alloy does not affect the fatigue strength. These results demonstrate the utility of this anodizing treatment on magnesium alloy for application as a structural material, such as in the automotive field.

  8. Ta,Nb和Mo对Ti50Ni20Cu25Sn5非晶合金玻璃形成能力的影响%Effects of Ta, Nb and Mo Additions on Glass-forming Ability of Ti50Ni20Cu25Sn5 Amorphous Alloy

    Institute of Scientific and Technical Information of China (English)

    杨冠军; 张涛; 井上明久

    2003-01-01

    利用旋转铜辊急冷法和铜模铸造法制备非晶合金薄带或圆棒,并采用X衍射仪(XRD)、差示扫描量热仪(DSC)和差示热分析仪(DTA)研究了Ta,Nb和Mo对Ti50Ni20Cu25Sn5非晶合金玻璃形成能力(GFA)的影响.结果表明,Ta的添加提高了Ti50Ni20Cu25Sn5合金的GFA,Mo的添加降低了该合金的GFA,Nb的添加则对该合金的GFA没有明显的影响;含Ta合金具有超过60 K的宽过冷液态区(△Tx),且其约化玻璃转变温度因子(Tg/Tm)大于含Nb合金和含Mo合金;采用常规铜模铸造法制备出了直径为1mm的(Ti0.5Ni0.2Cu0.25Sn0.05)98Ta2和(Ti0.5Ni0.2Cu0.25Sn0.05)96Ta4块状非晶圆棒;(Ti0.5Ni0.2Cu0.25Sn0.05)98Ta2块状非晶圆棒的Tg,△Tx和Tg/Tm分别为678 K,84 K和0.60,而(Ti0.5Ni0.2Cu0.25Sn0.05)96Ta4块状非晶圆棒的Tg,△Tx和Tg/Tm分别为680 K,70 K和0.60.%Effects of Ta, Nb and Mo additions on the glass-forming ability (GFA) of the Ti5oNi20Cu25Sn5 alloy were studied by melt-spinning and copper mold casting methods. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and differential thermal analysis (DTA) . The results show that the GFA is improved by Ta additions and decreased by Mo additions. No obvious improvement is observed in Nb-added alloys. The Ta-added alloys exhibit a wide supercooled liquid region exceeding 60 K before crystallization. The reduced glass transition temperature (Tg/Tm) of the Ta-added alloys is higher than those of the Nb- and Mo-added alloys. Cylindrical rods of 1 mm in diameter containing fully glassy phase were successfully synthesized for(Ti0.5Ni0. 2Cu0. 25Sn0.05) 98Ta2 and (Ti0. 5Ni0. 2Cu0. 28Sn0. 08) 96Ta4 by conventional copper mold casting. The Tg, △ Tx and Tg/Tm of the bulk glassy rod are 678 K, 84 K and 0. 60 for (Ti0. 5Ni0.2Cu0.25Sn0. 05) 98Ta2 alloy, and are 680 K, 70 K and 0.60 for(Ti0. 5Ni0.2Cu0. 25Sn0. 05 )96Ta4 alloy respectively.

  9. 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.

  10. Age-dependent modes of extensional necking instability in soft glassy materials.

    Science.gov (United States)

    Hoyle, David M; Fielding, Suzanne M

    2015-04-17

    We study the instability to necking of an initially cylindrical filament of soft glassy material subject to extensional stretching. By numerical simulation of the soft glassy rheology model and a simplified fluidity model, and by analytical predictions within a highly generic toy description, we show that the mode of instability is set by the age of the sample relative to the inverse of the applied extensional strain rate. Young samples neck gradually via a liquidlike mode, the onset of which is determined by both the elastic loading and plastic relaxation terms in the stress constitutive equation. Older samples fail at smaller draw ratios via a more rapid mode, the onset of which is determined only by the solidlike elastic loading terms (though plastic effects arise later, once appreciable necking develops). We show this solidlike mode to be the counterpart, for elastoplastic materials, of the Considère mode of necking in strain-rate-independent solids. PMID:25933343

  11. 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)

  12. Relaxation of enthalpy fluctuations during sub-T(g) annealing of glassy selenium.

    Science.gov (United States)

    Gulbiten, Ozgur; Mauro, John C; Lucas, Pierre

    2013-06-28

    The relaxation behavior of glass is influenced by the presence of dynamical heterogeneities, which lead to an intrinsically non-monotonic decay of fluctuations in density and enthalpy during isothermal annealing. This is apparently a universal feature of fragile glass forming systems associated with localized spatial variations in relaxation time. Here we present direct experimental observation of the nonmonotonic evolution of enthalpy fluctuations in glassy selenium annealed near room temperature. The nonmonotonic change in the distribution of enthalpy fluctuations measured by heat capacity spectroscopy offers direct evidence for the presence of dynamical heterogeneity in this glass. An enthalpy landscape model of selenium is then used to simulate annealing under identical conditions. The simulation results closely follow the evolution of enthalpy fluctuations observed experimentally. The close match between model and experiment demonstrate that enthalpy and density fluctuations are sources of dynamical heterogeneities in glassy materials.

  13. Glassy states and super-relaxation in populations of coupled phase oscillators.

    Science.gov (United States)

    Iatsenko, D; McClintock, P V E; Stefanovska, A

    2014-01-01

    Large networks of coupled oscillators appear in many branches of science, so that the kinds of phenomena they exhibit are not only of intrinsic interest but also of very wide importance. In 1975, Kuramoto proposed an analytically tractable model to describe these systems, which has since been successfully applied in many contexts and remains a subject of intensive research. Some related problems, however, remain unclarified for decades, such as the existence and properties of the oscillator glass state. Here we present a detailed analysis of a very general form of the Kuramoto model. In particular, we find the conditions when it can exhibit glassy behaviour, which represents a kind of synchronous disorder in the present case. Furthermore, we discover a new and intriguing phenomenon that we refer to as super-relaxation where the oscillators feel no interaction at all while relaxing to incoherence. Our findings offer the possibility of creating glassy states and observing super-relaxation in real systems.

  14. Characterization of superconducting magnesium-diboride films on glassy carbon and sapphire substrates

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, E.; Zavala, E. P. [Instituto de Fisica, UNAM, Apartado Postal 20-364, 01000 Mexico D. F. (Mexico); Rocha, M. F. [Escuela Superior de Ingenieria Mecanica y Electrica, IPN, Mexico D. F. (Mexico); Jergel, M.; Falcony, C. [Departamento de Fisica, CINVESTAV-IPN, Apartado postal 14-740, 07000 Mexico D. F. (Mexico)

    2008-02-15

    IBA methods were applied to measure elemental depth profiles of precursors and superconducting MgB{sub 2} thin films deposited on glassy carbon (Good Fellows) and sapphire (Al{sub 2}O{sub 3}) substrates. For each type of substrates we obtained a pair of samples i.e. one amorphous precursor and one superconducting film which were then characterized. A 3{sup H}e{sup +} beam was used to bombard both, precursors and superconducting films in order to obtain the samples elemental composition profiles. The zero resistance T{sub co} and the middle of transition T{sub cm} values were 26.0 K and 29.7 K for the MgB{sub 2} film deposited on glassy carbon substrate. In the case of sapphire substrate the T{sub co} and T{sub cm} values were 25.0 K and 27.9 K, respectively. (Author)

  15. 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.

  16. 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...

  17. 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

  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. Metal alloy identifier

    Science.gov (United States)

    Riley, William D.; Brown, Jr., Robert D.

    1987-01-01

    To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

  20. 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 ...

  1. Solute induced relaxation in glassy polymers: Experimental measurements and nonequilibrium thermodynamic model

    Energy Technology Data Exchange (ETDEWEB)

    Minelli, Matteo; Doghieri, Ferruccio [Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali (DICAM), Centro Interdipartimentale per la Ricerca Industriale - Meccanica Avanzata e Materiali (CIRI-MAM), Alma Mater Studiorum - Università di Bologna, via Terracini 28 - (Italy)

    2014-05-15

    Data for kinetics of mass uptake from vapor sorption experiments in thin glassy polymer samples are here interpreted in terms of relaxation times for volume dilation. To this result, both models from non-equilibrium thermodynamics and from mechanics of volume relaxation contribute. Different kind of sorption experiments have been considered in order to facilitate the direct comparison between kinetics of solute induced volume dilation and corresponding data from process driven by pressure or temperature jumps.

  2. 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

  3. 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.

  4. 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...

  5. 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.

  6. 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...

  7. 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.

  8. 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...

  9. 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)

  10. 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)

  11. 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...

  12. Diffusion slowdown in the nanostructured liquid Ga-Sn alloy

    Energy Technology Data Exchange (ETDEWEB)

    Podorozhkin, Dmitri Y.; Charnaya, Elena V. [Institute of Physics, St. Petersburg State University, St. Petersburg (Russian Federation); Lee, Min Kai [Department of Physics, National Cheng Kung University, Tainan (China); NSC Instrument Center at NCKU, Tainan (China); Chang, Lieh-Jeng [Department of Physics, National Cheng Kung University, Tainan (China); Haase, Juergen; Michel, Dieter [Faculty of Physics and Geophysics, Leipzig University (Germany); Kumzerov, Yurii A.; Fokin, Alexsandr V. [A.F. Ioffe Physico-Technical Institute, RAS, St. Petersburg (Russian Federation)

    2015-04-01

    The diffusion of gallium in liquid Ga-Sn alloy embedded into different porous silica matrices was studied by NMR. Spin relaxation was measured for two gallium isotopes, {sup 71}Ga and {sup 69}Ga, at two magnetic fields. Pronounced rise of quadrupole contribution to relaxation was observed for the nanostructured alloy which increased with decreasing the pore size. The correlation time of atomic mobility was evaluated and found to be much larger than in the relevant bulk melt which evidenced a pronounced diffusion slowdown in the Ga-Sn alloy under nanoconfinement. It is shown that the diffusion was slower by a factor of 30 for the alloy within 7 nm pores. The spectral densities of electric field gradients at zero frequency were found to double for the finest pores. The Knight shift was found to decrease but slightly for the nanostructured alloy. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Nanocrystalline Ni-Co Alloy Synthesis by High Speed Electrodeposition

    Directory of Open Access Journals (Sweden)

    Jamaliah Idris

    2013-01-01

    Full Text Available 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 parameters, such as cathodic current density and temperature at constant pH, on electrodeposition and microstructure of Ni-Co alloys were examined. A homogeneous surface morphology was obtained at all current densities of the plated samples, and it was evident that the current density and temperature affect the coating thickness of Ni-Co alloy coatings.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes.

    Science.gov (United States)

    Ghanem, Mohamed A; Compton, Richard G; Coles, Barry A; Canals, Antonio; Marken, Frank

    2005-10-01

    The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.

  3. An approach to predict free surface fracture in bulk forming

    Science.gov (United States)

    Ragab, A. R.

    2006-04-01

    This work presents a unified approach to predict surface strains at failure in bulk forming processes. The approach does not deal with a specific process but rather with prescribed strain and stress paths. The material to be processed is assumed to possess an initial void volume fraction that grows and colaesces with straining, ending by fracture. The predictions are based on a formulation for voided solids according to the Gurson-Tvergaard yield function adapted to include orthotropic anisotropy. The incident of fracture is characterized by shear band formation within the ligaments of the matrix material among spheroidal voids as described by McClintock. The results are represented by a straight line plot of tensile limit strain versus the compressive strain for different loading paths. These limit curves are shown to be dependent on the initial void fraction, hardening, and anisotropy of the matrix matrial. Alloys with lower initial void fractions as well as those of higher hardening show better workability. The model is applied to predict bulk formability curves for steels AISI 1040 and 1045, Aluminum AI 7075-T6, and copper, based on the proper selection of micromechanical parameters for these alloys. The validity of the model is ensured through fairly favorable comparison with experimentally determined limit curves. The current failure conditions are suitable to predict the experimental dual slope fracture line that may exist for some alloys such as cold-drawn steel AISI 1045 and aluminum 2024-T6 by considering two mechanisms of failure: internal necking in the ligament material between voids, followed by transition to shear band formation.

  4. Elastic properties of Pd40Cu30Ni10P20 bulk glass in supercooled liquid region

    DEFF Research Database (Denmark)

    Nishiyama, N.; Inoue, A.; Jiang, Jianzhong

    2001-01-01

    In situ ultrasonic measurements for the Pd40Cu30Ni10P20 bulk glass in three states: Glassy solid, supercooled liquid, and crystalline, have been performed. It is found that velocities of both longitudinal and transverse waves and elastic moduli (shear modulus, bulk modulus, Young's modulus......, and Lame parameter), together with Debye temperature, gradually decrease with increasing temperature through the glass transition temperature as the Poisson's ratio increases. The behavior of the velocity of transverse wave vs. temperature in the supercooled liquid region could be explained by viscosity...... flow, rather than the two different crystallization processes in the region, suggested in the literature. No decomposition was detected at a temperature only 5 K below the crystallization temperature....

  5. Crystallization of a Ti-based Bulk Metallic Glass Induced by Electropulsing Treatment

    Institute of Scientific and Technical Information of China (English)

    Yong-jiang HUANG; Xiang CHENG; Hong-bo FAN; Shi-song GUAN; Zhi-liang NING; Jian-fei SUN

    2016-01-01

    The effect of electropulsing treatment (EPT)on the microstructure of a Ti-based bulk metallic glass (BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG.When the maximum current density is no more than 2 720 A/mm2 ,the samples retains amorphous nature,whereas,beyond that,crystalline phases precipitate from the glassy matrix.During EPT,the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720 A/mm2 is higher than the crystallization temperature of the BMG,leading to the crystallization event.

  6. Effect of metal impregnation in the field cool magnetization of bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Kita, M. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)]. E-mail: kita@istec.or.jp; Nariki, S. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Sakai, N. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan); Hirabayashi, I. [Superconductivity Research Laboratory, ISTEC, 1-10-13 Shinonome, Koto-ku, Tokyo 135-0062 (Japan)

    2006-10-01

    Gd-Ba-Cu-O bulk superconductors have significant potential for various applications due to the high critical current density and the highly trapped magnetic fields. Recently we have developed a large sized bulk superconductor using Gd210, which is discovered in the microgravity experiment. We investigated the mechanical properties and the cryostability of the Gd-Ba-Cu-O bulk superconductor to determine how to improve toughness and heat conduction of the large sized bulk superconductor. We introduced a stainless ring around the circumference of the bulk to increase the fracture strength of the bulk. Also, we introduced Al wires inserted in the hole along the c-axis of the bulk, and then the sample was subjected to the impregnation by using Bi-Sn-Cd alloy. We measured the trapped magnetic fields and the repulsive forces of the samples. The trapped magnetic field distributions were 1.13-1.36 T. The repulsive forces at 1 mm gap between the sample bulk and the permanent magnet with the surface magnetic induction of 0.37 T were about 70 N at 77 K. We have also measured the temperature dependence of the trapped magnetic field, and confirmed the effect of metal impregnation.

  7. Coulombic Fluids Bulk and Interfaces

    CERN Document Server

    Freyland, Werner

    2011-01-01

    Ionic liquids have attracted considerable interest in recent years. In this book the bulk and interfacial physico-chemical characteristics of various fluid systems dominated by Coulomb interactions are treated which includes molten salts, ionic liquids as well as metal-molten salt mixtures and expanded fluid metals. Of particular interest is the comparison of the different systems. Topics in the bulk phase concern the microscopic structure, the phase behaviour and critical phenomena, and the metal-nonmetal transition. Interfacial phenomena include wetting transitions, electrowetting, surface freezing, and the electrified ionic liquid/ electrode interface. With regard to the latter 2D and 3D electrochemical phase formation of metals and semi-conductors on the nanometer scale is described for a number of selected examples. The basic concepts and various experimental methods are introduced making the book suitable for both graduate students and researchers interested in Coulombic fluids.

  8. Synergetic effects in CO adsorption on Cu-Pd(111) alloys

    DEFF Research Database (Denmark)

    Lopez, Nuria; Nørskov, Jens Kehlet

    2001-01-01

    We present density functional calculations for the interaction of CO on different Cu-Pd(111) bulk and surface alloys. The modification of the adsorption properties with respect to hose of the adsorption on pure Cu(111) and Pd(111) is described in terms of changes in the adsorption sites...... and the change of the electronic structure occurring upon alloying. The presence of cooperative, synergetic. effects is found to be important specially for Cu-rich bulk alloys. In this case. a larger adsorption energy is found for the inactive component than for the pure inactive system. This activation induces...

  9. Alloyed steel

    International Nuclear Information System (INIS)

    The composition and properties are listed of alloyed steel for use in the manufacture of steam generators, collectors, spacers, emergency tanks, and other components of nuclear power plants. The steel consists of 0.08 to 0.11% w.w. C, 0.6 to 1.4% w.w. Mn, 0.35 to 0.6% w.w. Mo, 0.02 to 0.07% w.w. Al, 0.17 to 0.37% w.w. Si, 1.7 to 2.7% w.w. Ni, 0.03 to 0.07% w.w. V, 0.005 to 0.012% w.w. N, and the rest is Fe. The said steel showed a sufficiently low transition temperature between brittle and tough structures, a greater depth of hardenability, and better weldability than similar steels. (B.S.)

  10. Bulk Superconductors in Mobile Application

    Science.gov (United States)

    Werfel, F. N.; Delor, U. Floegel-; Rothfeld, R.; Riedel, T.; Wippich, D.; Goebel, B.; Schirrmeister, P.

    We investigate and review concepts of multi - seeded REBCO bulk superconductors in mobile application. ATZ's compact HTS bulk magnets can trap routinely 1 T@77 K. Except of magnetization, flux creep and hysteresis, industrial - like properties as compactness, power density, and robustness are of major device interest if mobility and light-weight construction is in focus. For mobile application in levitated trains or demonstrator magnets we examine the performance of on-board cryogenics either by LN2 or cryo-cooler application. The mechanical, electric and thermodynamical requirements of compact vacuum cryostats for Maglev train operation were studied systematically. More than 30 units are manufactured and tested. The attractive load to weight ratio is more than 10 and favours group module device constructions up to 5 t load on permanent magnet (PM) track. A transportable and compact YBCO bulk magnet cooled with in-situ 4 Watt Stirling cryo-cooler for 50 - 80 K operation is investigated. Low cooling power and effective HTS cold mass drives the system construction to a minimum - thermal loss and light-weight design.

  11. Structural characterizations and thermal analyses of Se{sub 70}Te{sub 30} chalcogenide glassy alloy

    Energy Technology Data Exchange (ETDEWEB)

    Abd-Elrahman, M.I., E-mail: mostafaia11@yahoo.com [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Khafagy, Rasha M. [Materials Science Laboratory, Physics Department, Girls College for Arts, Science, and Education, Ain Shams University, Cairo (Egypt); Zaki, Shiamaa A.; Hafiz, M.M. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt)

    2014-01-10

    Highlights: • Thermal annealing results in amorphous-crystalline change in Se{sub 70}Te{sub 30}. • The average crystallite size increases when the temperature annealing increases. • The kinetics study includes the estimation of the crystallization parameters. - Abstract: The structural characterizations of Se{sub 70}Te{sub 30} chalcogenide glass for the as-prepared and thermal annealed samples are identified using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The isothermal thermal annealing process results in a transformation from the amorphous to the crystalline state. The average crystallite size increases from 8.67 to 11.24 nm when the temperature annealing increases from 95 to 118 °C. The thermal analyses of Se{sub 70}Te{sub 30} glass are investigated using a differential thermal analyzer (DTA) at five different heating rates under non-isothermal conditions. The activation energy of the glass forming (E{sub g}) as a parameter for the glass transition is estimated by employing different approaches proposed for thermal analyses. The study of crystallization kinetics includes the estimation of the activation energy of crystallization (E{sub c}), frequency factor (K{sub o}) and Avrami exponent (n)

  12. Influence of Cr on the nanoclusters formation and superferromagnetic behavior of Fe-Cr-Nb-B glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chiriac, H.; Whitmore, L.; Grigoras, M.; Ababei, G.; Stoian, G.; Lupu, N., E-mail: nicole@phys-iasi.ro [National Institute of Research and Development for Technical Physics, 700050 Iasi (Romania)

    2015-05-07

    High resolution imaging and electron diffraction confirm that in the as-quenched state the structure of Fe{sub 79.7−x}Cr{sub x}Nb{sub 0.3}B{sub 20} (x = 11–13 at. %) melt-spun ribbons is completely amorphous, independent of the Cr content. Energy-dispersive X-ray spectroscopy mapping emphasizes clearly the presence of Fe and Cr clusters varying from approximately 1 to 2–3 nm in size with the increase of Cr content from 11 to 13 at. %. The Fe and Cr atoms segregate the atomic scale to form nanometer sized clusters, influencing strongly the macroscopic magnetic behavior. The Curie temperature of the system, T{sub C}{sup system}, confirmed by the magnetic susceptibility versus temperature measurements, gives the strength of the magnetic interactions between clusters. The inter-cluster interactions are much stronger for lower contents of Cr, the microstructure is less uniform, and T{sub C}{sup system} increases from 290 K for 13 at. % Cr to 330 K for 11.5 at. % Cr. The whole system transforms to a ferromagnetic state through interactions between the clusters. Zero-field cooling and field cooling curves confirm the cluster behavior with a blocking temperature, T{sub b}, of about 250 K. Above T{sub b}, the ribbons behave as a superferromagnetic system, whilst below the blocking temperature a classical ferromagnetic behavior is observed.

  13. Fabrication and evaluation of nickel cobalt alloy electrocatalysts for alkaline water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Hoon [School of Integrative Engineering, Chung-Ang University, Heukseokno 84, Dongjak-gu, Seoul 156-756 (Korea, Republic of); Ahn, Sang Hyun; Choi, Insoo [Fuel Cell Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Pyo, Sung Gyu [School of Integrative Engineering, Chung-Ang University, Heukseokno 84, Dongjak-gu, Seoul 156-756 (Korea, Republic of); Kim, Hyoung-Juhn; Jang, Jong Hyun [Fuel Cell Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791 (Korea, Republic of); Kim, Soo-Kil, E-mail: sookilkim@cau.ac.kr [School of Integrative Engineering, Chung-Ang University, Heukseokno 84, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

    2014-07-01

    As a catalyst for the hydrogen evolution reaction (HER) in alkaline water splitting, NiCo alloys of various compositions were prepared through electrodeposition onto Cu substrates. The composition of each alloy catalyst was varied by controlling the molar ratio of Co{sup 2+} ions in the electrolyte. With an increase in the Co content, the morphologies of the NiCo alloys were progressively changed from a round to polygonal shape. The NiCo alloys all exhibited a Ni rich surface, as confirmed by the bulk-to-surface compositional ratio and degree of alloying. The catalytic activities of the NiCo alloys toward the HER of water splitting were electrochemically tested in a KOH electrolyte, and the specific activities were characterized by considering the electrochemical surface areas of Ni and Co. The effect of alloying was demonstrated to be a significant enhancement of HER activity, resulting from a change in the electronic structures of Ni and Co.

  14. Novel pre-alloyed powder processing of modified alnico 8: Correlation of microstructure and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, I. E., E-mail: andersoni@ameslab.gov; Kassen, A. G.; White, E. M. H.; Zhou, L.; Tang, W.; Palasyuk, A.; Dennis, K. W.; McCallum, R. W.; Kramer, M. J. [Ames Laboratory (USDOE), Iowa State University, Ames, Iowa 50011 (United States)

    2015-05-07

    Progress is reviewed on development of an improved near-final bulk magnet fabrication process for alnico 8, as a non-rare earth permanent magnet with promise for sufficient energy density and coercivity for electric drive motors. This study showed that alnico bulk magnets in near-final shape can be made by simple compression molding from spherical high purity gas atomized pre-alloyed powder. Dwell time at peak sintering temperature (1250 °C) greatly affected grain size of the resulting magnet alloys. This microstructure transformation was demonstrated to be useful for gaining partially aligned magnetic properties and boosting energy product. While a route to increased coercivity was not identified by these experiments, manufacturability of bulk alnico magnet alloys in near-final shapes was demonstrated, permitting further processing and alloy modification experiments that can target higher coercivity and better control of grain anisotropy during grain growth.

  15. Non-isothermal crystallization kinetics and glass-forming ability of Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} bulk metallic glass investigated by differential scanning calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Pan; Zhao, Shaofan; Yao, Kefu [Tsinghua University, School of Materials Science and Engineering, Beijing (China); Wang, Xin [Hebei University of Technology, School of Materials Science and Engineering, Tianjin (China)

    2015-07-15

    The non-isothermal crystallization kinetics and glass-forming ability of Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} 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, Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} 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 Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} glassy alloy has also been determined using Barandiaran-Colmenero's method. (orig.)

  16. Mechanical alloying in immiscible alloy systems

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In recent years, mechanical alloying (MA) of immiscible alloy systems characterized by positive heat of mixing has been extensively investigated. The present article reviews the latest progress in MA of immiscible alloy systems including the mechanisms of non-equilibrium phase transformation and metastable phase formation of the MA-driven supersaturated solid solutions, amorphous phases and nanophase composites as well as their mechanical and physical properties related to those metastable phases.

  17. Fatigue behaviour and crack growth rate of cryorolled Al 7075 alloy

    International Nuclear Information System (INIS)

    Highlights: → High cycle fatigue of cryorolled Al 7075 alloy has been investigated. → Cryorolled Al alloy showed significant enhancement in fatigue strength. → FCGR resistance of the ufg Al alloy is higher at higher values of applied stress. - Abstract: The effects of cryorolling (CR) on high cycle fatigue (HCF) and fatigue crack growth rate behaviour of Al 7075 alloy have been investigated in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic (liquid nitrogen) temperature and its tensile strength, fatigue life, and fatigue crack growth mechanism were studied by using tensile testing, constant amplitude stress controlled fatigue testing, and fatigue crack growth rate testing using load shedding (decreasing ΔK) technique. The microstructural characterization of the alloy was carried out by using Field emission scanning electron microscopy (FESEM). The cryorolled Al alloy after 70% thickness reduction exhibits ultrafine grain (ufg) structure as observed from its FESEM micrographs. The cryorolled Al 7075 alloys showed improved mechanical properties (Y.S, U.T.S, Impact energy and Fracture toughness are 430 Mpa, 530 Mpa, 21 J, 24 Mpa m1/2 for 40CR alloy) as compared to the bulk 7075 Al alloy. It is due to suppression of dynamic recovery and accumulation of higher dislocations density in the cryorolled Al alloys. The cryorolled Al alloy investigated under HCF regime of intermediate to low plastic strain amplitudes has shown the significant enhancement in fatigue strength as compared to the coarse grained (CG) bulk alloy due to effective grain refinement. Fatigue crack growth (FCGR) resistance of the ufg Al alloy has been found be higher, especially at higher values of applied stress intensity factor ΔK The reasons behind such crack growth retardation is due to diffused crack branching mechanism, interaction between a propagating crack and the increased amount of grain boundaries (GB), and steps developed

  18. SeZnSb alloy and its nano tubes, graphene composites properties

    OpenAIRE

    Abhay Kumar Singh

    2013-01-01

    Composite can alter the individual element physical property, could be useful to define the specific use of the material. Therefore, work demonstrates the synthesis of a new composition Se96-Zn2-Sb2 and its composites with 0.05% multi-walled carbon nano tubes and 0.05% bilayer graphene, in the glassy form. The diffused amorphous structure of the multi walled carbon nano tubes and bilayer gaphene in the Se96-Zn2-Sb2 alloy have been analyzed by using the Raman, X-ray photoluminescence spectrosc...

  19. Dynamic Plastic Deformation (DPD): A Novel Technique for Synthesizing Bulk Nanostructured Metals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    While some superior properties of nanostructured materials (with structural scales below 100 nm) have attracted numerous interests of material scientists, technique development for synthesizing nanostructured metals and alloys in 3-dimensional (3D) bulk forms is still challenging despite of extensive investigations over decades.Here we report a novel synthesis technique for bulk nanostructured metals based on plastic deformation at high Zener-Hollomon parameters (high strain rates or low temperatures), i.e., dynamic plastic deformation (DPD).The basic concept behind this approach will be addressed together with a few examples to demonstrate the capability and characteristics of this method. Perspectives and future developments of this technique will be highlighted.

  20. Preparation and Mechanical Behavior of Mg-Based Bulk Metallic Glasses and their Matrix Composite

    Institute of Scientific and Technical Information of China (English)

    SI Yi; Zhao Jianguo; WU Fufa; WU Xiaofeng

    2012-01-01

    Mg87-xCuxDy13(x=22,27,32) bulk metallic glasses (BGMs) with a diameter of 6-8 mm and insitu Mg phase reinforced Mg7oCu17Dy13 BMG matrix composite with a diameter of 3 mm have been prepared by copper mould casting.The glass forming ability (GFA) of Mg-Cu-Dy alloys have been investigated by differential scanning calorimetry (DSC) and X-Ray diffraction (XRD) and trie mechanical properties have been measured.Results show that Mgs7-xCuxDy13(x=22,27,32) alloys in the Mg-Cu-Dy alloy system exhibit excellent GFA,and Mg60Cu27Dy13 alloy has the largest GFA among these alloys.And In-situ Mg phase reinforced Mg70Cu17Dy13 BMG matrix composite exhibits some work hardening and a high fracture compressive strength of 702.38 MPa and some plastic strain of 0.81%.The improvement of the mechanical properties is attributed to the fact that the Mg phase distributed in the amorphous matrix of the alloy has some effective load bearing and plastic deformation ability to restrict the expanding of shear bands and cracks and produce its own plastic deformation.

  1. Submicron particles of Co, Ni and Co–Ni alloys

    Indian Academy of Sciences (India)

    P Saravanan; T A Jose; P John Thomas; G U Kulkarni

    2001-10-01

    Magnetic sub-micron sized particles (with diameters in the range 100–600 nm) of Co, Ni and Co–Ni alloys, protected with polyvinylpyrrolidone have been prepared in gram quantities using the polyol process. Experiments carried out with different metal precursors and starting compositions have yielded reliable routes to produce particles of the desired diameters in the 100–600 nm range. The particles were characterized with X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, thermogravimetric analysis and magnetic measurements. The particles are found to be stable under ambient conditions indefinitely. The coercivity values of the Co and Ni particles are ∼ 50% higher compared to the corresponding bulk values. The alloy particles follow a trend similar to the bulk alloys.

  2. Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A Zr-based bulk metallic glass (BMG) with a composition of (Zr75Cu25)78.5Ta4Ni10Al7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr75Cu25)74.5Ta8Ni10Al7.5 have been prepared by copper-mold casting. The compres-sive deformation behavior of the BMG and BMGC was investigated in the super-cooled region at different temperatures and various strain rates ranging from 8×10-4s-1 to 8×10-2s-1. It was found that both the strain rate and test temperature signifi-cantly affect the deformation behavior of the two alloys. The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism for the two kinds of alloys was discussed in terms of the transition state theory.

  3. Design of multi materials combining crystalline and amorphous metallic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Volland, A.; Ragani, J.; Liu, Y.; Gravier, S.; Suery, M. [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France); Blandin, J.J., E-mail: jean-jacques.blandin@simap.grenoble-inp.fr [Grenoble University/CNRS, SIMAP Laboratory, Grenoble INP/UJF, 38402 Saint-Martin d' Heres (France)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Elaboration of multi materials associating metallic glasses and conventional crystalline alloys by co-deformation performed at temperatures close to the glass transition temperature of the metallic glasses. Black-Right-Pointing-Pointer Elaboration of filamentary metal matrix composites with a core in metallic glass by co extrusion. Black-Right-Pointing-Pointer Sandwich structures produced by co-pressing. Black-Right-Pointing-Pointer Detection of atomic diffusion from the glass to the crystalline alloys during the processes. Black-Right-Pointing-Pointer Good interfaces between the metallic glasses and the crystalline alloys, as confirmed by mechanical characterisation. - Abstract: Multi materials, associating zirconium based bulk metallic glasses and crystalline metallic alloys like magnesium alloys or copper are elaborated by co-deformation processing performed in the supercooled liquid regions (SLR) of the bulk metallic glasses. Two processes are investigated: co-extrusion and co-pressing. In the first case, filamentary composites with various designs can be produced whereas in the second case sandwich structures are obtained. The experimental window (temperature, time) in which processing can be carried out is directly related to the crystallisation resistance of the glass which requires getting information about the crystallisation conditions in the selected metallic glasses. Thermoforming windows are identified for the studied BMGs by thermal analysis and compression tests in their SLR. The mechanical properties of the produced multi materials are investigated thanks to specifically developed mechanical devices and the interfaces between the amorphous and the crystalline alloys are characterised.

  4. Alloy Fabrication Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — At NETL’s Alloy Fabrication Facility in Albany, OR, researchers conduct DOE research projects to produce new alloys suited to a variety of applications, from gas...

  5. Micro-morphological changes prior to adhesive bonding: high-alumina and glassy-matrix ceramics

    Directory of Open Access Journals (Sweden)

    Marco Cícero Bottino

    2008-06-01

    Full Text Available The aim of this study was to qualitatively demonstrate surface micro-morphological changes after the employment of different surface conditioning methods on high-alumina and glassy-matrix dental ceramics. Three disc-shaped high-alumina specimens (In-Ceram Alumina, INC and 4 glassy-matrix ceramic specimens (Vitadur Alpha, V (diameter: 5 mm and height: 5 mm were manufactured. INC specimens were submitted to 3 different surface conditioning methods: INC1 - Polishing with silicon carbide papers (SiC; INC2 - Chairside air-borne particle abrasion (50 µm Al2O3; INC3 - Chairside silica coating (CoJet; 30 µm SiOx. Vitadur Alpha (V specimens were subjected to 4 different surface conditioning methods: V1 - Polishing with SiC papers; V2 - HF acid etching; V3 - Chairside air-borne particle abrasion (50 µm Al2O3; V4 - Chairside silica coating (30 µm SiOx. Following completion of the surface conditioning methods, the specimens were analyzed using SEM. After polishing with SiC, the surfaces of V specimens remained relatively smooth while those of INC exhibited topographic irregularities. Chairside air-abrasion with either aluminum oxide or silica particles produced retentive patterns on both INC and V specimens, with smoother patterns observed after silica coating. V specimens etched with HF presented a highly porous surface. Chairside tribochemical silica coating resulted in smoother surfaces with particles embedded on the surface even after air-blasting. Surface conditioning using air-borne particle abrasion with either 50 µm alumina or 30 µm silica particles exhibited qualitatively comparable rough surfaces for both INC and V. HF acid gel created the most micro-retentive surface for the glassy-matrix ceramic tested.

  6. Characterization of hydrogen interactions with the surface of alpha-2 titanium aluminide alloys

    Science.gov (United States)

    Shanabarger, Mickey R.

    1990-01-01

    The interaction of hydrogen at the surface of alpha-2 titanium aluminide alloys with Nb additions has been investigated with Auger electron spectroscopy (AES) and reflected electron energy loss (REELS) spectroscopy. The hydrogen was either adsorbed onto the alloy surface from the gas phase or it was pre-charged into the alloy forming an alpha-2 hydride. No effect of either adsorbed or absorbed hydrogen was observed in the Auger spectra. A shift in the bulk plasmon loss energy (observed with REELS) was measured for both conditions. The potential significance of these results in relation to hydrogen interactions in this alloy is discussed.

  7. Electroanalysis of thiocyanate using a novel glassy carbon electrode modified by aryl radicals and cobalt tetracarboxyphthalocyanine

    Energy Technology Data Exchange (ETDEWEB)

    Matemadombo, Fungisai; Nyokong, Tebello [Rhodes University, Grahamstown (South Africa). Department of Chemistry; Westbroek, Philippe [Ghent University, Ghent (Belgium). Department of Textiles

    2007-12-01

    Electrochemical grafting of 4-nitrobenzenediazonium tetrafluoroborate onto a glassy carbon electrode (GCE) results in the formation of a nitrophenyl radical, which reacts with the surface to form a covalent bond (grafting) and results in a nitrophenyl modified electrode. The nitro group is electrochemically reduced to a NH{sub 2} group. Cobalt tetracarboxyphthalocyanine (CoTCPc) complex is then attached to the NH{sub 2} group using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as coupling agents. The new CoTCPc modified electrode was characterized using cyclic voltammetry and then employed for the catalytic oxidation of thiocyanate. (author)

  8. Electrooxidation of carbo/thiocarbohydrazide and their hydrazone derivatives at a glassy carbon electrode

    Indian Academy of Sciences (India)

    G P Mamatha; B S Sherigara; K M Mahadevan

    2007-05-01

    Electrochemical oxidation of thio/carbohydrazide and their hydrazone derivatives Benzaldehyde thiocarbohydrazone [BTCH] diacetylene thiocarbohydrazone [DATCH] have been studied in Britton Robinson buffer in aqueous and nonaqueous media at a glassy carbon electrode. The effects of pH, sweep rate, concentration, temperature and surfactants have been studied. The complex bis (carbo/thiocabohydrazide) Zn(II) chloride was also subjected to voltammetric analysis in order to understand the reactivity both in free and metal bound states. The reaction conditions were optimized for the determination of above compounds in micrograms quantities by differential pulse voltammetry, analytical utility of this investigation is also highlighted.

  9. Cytochrome C Dynamics at Gold and Glassy Carbon Surfaces Monitored by in Situ Scanning Tunnel Microscopy

    DEFF Research Database (Denmark)

    Andersen, Jens Enevold Thaulov; Møller, Per; Pedersen, Marianne Vind;

    1995-01-01

    composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve in time, and structures resembling individual cyt c molecules can be distinguished in the space between the 50 nm structures. Cyt c aggregates also form at glassy carbon but have a different, unbroken character...... where cyt c both sticks well to the surface and exhibits notable mobility. The observations suggest that characteristic surface specific, internally mobile protein aggregates are formed at both surfaces and that in situ molecular resolution of the STM pictures may have been achieved....

  10. Polymorphic ethyl alcohol as a model system for the quantitative study of glassy behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, H.E.; Schober, H.; Gonzalez, M.A. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Bermejo, F.J.; Fayos, R.; Dawidowski, J. [Consejo Superior de Investigaciones Cientificas, Madrid (Spain); Ramos, M.A.; Vieira, S. [Universidad Autonoma de Madrid (Spain)

    1997-04-01

    The nearly universal transport and dynamical properties of amorphous materials or glasses are investigated. Reasonably successful phenomenological models have been developed to account for these properties as well as the behaviour near the glass-transition, but quantitative microscopic models have had limited success. One hindrance to these investigations has been the lack of a material which exhibits glass-like properties in more than one phase at a given temperature. This report presents results of neutron-scattering experiments for one such material ordinary ethyl alcohol, which promises to be a model system for future investigations of glassy behaviour. (author). 8 refs.

  11. Fine kinetics of natural physical ageing in glassy As{sub 10}Se{sub 90}

    Energy Technology Data Exchange (ETDEWEB)

    Balitska, V. [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Lviv State University of Vital Activity Safety, 35, Kleparivska Str., Lviv 79007 (Ukraine); Golovchak, R. [Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN 37044 (United States); Kozdras, A. [Faculty of Physics of Opole Technical University, 75, Ozimska Str., Opole 45370 (Poland); Shpotyuk, O., E-mail: shpotyuk@novas.lviv.ua [Institute of Materials, Scientific Research Company “Carat”, 202 Stryjska Str., 79031 Lviv (Ukraine); Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa 42201 (Poland)

    2014-02-01

    Sigmoid behavior of natural physical ageing in glassy As{sub 10}Se{sub 90} 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.

  12. Simple Model for the Deformation-Induced Relaxation of Glassy Polymers

    Science.gov (United States)

    Fielding, S. M.; Larson, R. G.; Cates, M. E.

    2012-01-01

    Glassy polymers show “strain hardening”: at constant extensional load, their flow first accelerates, then arrests. Recent experiments have found this to be accompanied by a striking and unexplained dip in the segmental relaxation time. Here we explain such behavior by combining a minimal model of flow-induced liquefaction of a glass with a description of the stress carried by strained polymers, creating a nonfactorable interplay between aging and strain-induced rejuvenation. Under constant load, liquefaction of segmental motion permits strong flow that creates polymer-borne stress. This slows the deformation enough for the segmental modes to revitrify, causing strain hardening.

  13. Optical properties of chalcogenide glassy semiconductor Se95Te5 doped by samarium

    International Nuclear Information System (INIS)

    The optical width of forbidden band, refraction index and extinction index are defined by investigation of optical transmission spectrum of chalcogenide glassy semiconductor Se95Te5 doped by samarium Eo is oscillator energy connected with energy gap and Ed is dispersion energy characterizing the interband transition force are defined within the framework of one-oscillator model. The influence of samarium impurity on optical and dispersion parameters can be connected with peculiarity of impurity atom distribution, changes of chemical band and coordination number

  14. Direct Electrochemistry of Catalase on Single Wall Carbon Nanotubes Modified Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    Qiang ZHAO; Lun Hui GUAN; Zhen Nan GU; Qian Kun ZHUANG

    2005-01-01

    Direct electrochemistry of catalase (Ct) has been studied on single wall carbon nanotubes (SWNTs) modified glassy carbon (GC) electrode. A pair of well-defined nearly reversible redox peaks is given at --0.48 V (vs. SCE) in 0.1 mol/L phosphate solution (pH 7.0).The peak current in cyclic voltammogram is proportional to the scan rate. The peak potential of catalase is shifted to more negative value when the pH increases. Catalase can adsorb on the SWNTs modified electrode.

  15. Electrochemical behavior of paclitaxel and its determination at glassy carbon electrode

    OpenAIRE

    Jayant I. Gowda; Sharanappa T. Nandibewoor

    2014-01-01

    The electrochemical behavior of paclitaxel drug was studied at a glassy carbon electrode in phosphate buffer solutions using cyclic and differential-pulse voltammetric techniques. The oxidation process was shown to be irreversible over the pH range (3.0–10.4) and was diffusion controlled. Effects of anodic peak potential (Ep), anodic peak current (Ipa), scan rate, pH, heterogeneous rate constant (k0), etc have been discussed. A possible electro-oxidation mechanism was proposed. An analytical ...

  16. State transformations and ice nucleation in glassy or (semi-solid amorphous organic aerosol

    Directory of Open Access Journals (Sweden)

    K. J. Baustian

    2012-10-01

    Full Text Available Glassy or amorphous (semi-solid organic aerosol particles have the potential to serve as surfaces for heterogeneous ice nucleation in cirrus clouds. Raman spectroscopy and optical microscopy have been used in conjunction with a cold stage to examine water uptake and ice nucleation on individual aqueous organic glass particles at atmospherically relevant temperatures (200–273 K. Three organic compounds considered proxies for atmospheric secondary organic aerosol (SOA were used in this investigation: sucrose, citric acid and glucose. Internally mixed particles consisting of each organic species and ammonium sulfate were also investigated.

    Results from water uptake experiments were used to construct glass transition curves and state diagrams for each organic and corresponding mixture. A unique glass transition point on each state diagram, Tg', was used to quantify and compare results from this study to previous works. Values of Tg' determined for aqueous sucrose, glucose and citric acid glasses were 236 K, 230 K and 220 K, respectively. Values of Tg' for internally mixed organic/sulfate particles were always significantly lower; 210 K, 207 K and 215 K for sucrose/sulfate, glucose/sulfate and citric acid/sulfate, respectively.

    All investigated organic species were observed to serve as heterogeneous ice nuclei at tropospheric temperatures. Heterogeneous ice nucleation on pure organic particles occurred at Sice=1.1–1.4 for temperatures between 235 K and 200 K. Particles consisting of 1:1 organic-sulfate mixtures remained liquid over a greater range of conditions but were in some cases also observed to depositionally nucleate ice at temperatures below 202 K (Sice=1.25–1.38.

    Glass transition curves constructed from experimental data were incorporated into the Community Aerosol Radiation Model for Atmospheres (CARMA along with the

  17. Determination of Trace Thiocyanate by a Chitosan-Modified Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A chitosan-modified glassy carbon electrode(CMGCE) was employed for the determination of thiocyanate. The measurement was carried out by means of anodic stripping voltammetry. The effects of several experimental parameters, such as pH, the amount of modifier, deposition potential and deposition time were studied for analytical application, respectively. A liner response was obtained in the concentration range of 3.5×10-8-9.3×10-7 g/mL of SCN-. The detection limit was found to be 1.9×10-8 g/mL. The method was satisfactorily used to detect SCN- in saliva.

  18. A Novel Amperometric Nitric Oxide Sensor Based on Polythionine /Nation Modified Glassy Carbon Electrode

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel amperometric sensor for the determination of nitric oxide was developed by coating polythionine / nafion on a glassy carbon electrode. This sensor exhibited a great enhancement to the oxidation of nitric oxide. The oxidation peak currents were linear to the concentration of nitric oxide over the wide range from 3.6×10-7 to 6.8×10-5 mol. L-1, and the detection limit was 7.2×10-8 mol. L-1. Experimental results showed that this nitric oxide sensor possessed excellent selectivity and longer stability. NO releasing from rat kidney was monitored by this sensor.

  19. Design of Thermo Mechanicaln Processing and Transformation Behaviour of Bulk Si-Mn Trip Steel

    OpenAIRE

    J. Zrnik; Mamuzić, I.; Lukaš, P.; Muransky, O.; Jenčuš, P.; Novy, Z.

    2006-01-01

    In the last decade, a lot of effort has been paid to optimising the thermomechanical processing of TRIP steels that stands for transformation induced plasticity. The precise characterization of the resulting multiphase microstructure of low alloyed TRIP steels is of great importance for the interpretation and optimisation of their mechanical properties. The results obtained in situ neutron diffraction laboratory experiment concerning the austenite to ferrite transformation in Si-Mn bulk TRIP ...

  20. PLUTONIUM-THORIUM ALLOYS

    Science.gov (United States)

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  1. Effects of macroscopic bulk defects on the damping behaviors of materials

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A large number of macroscopic pores or graphite particulates wereintroduced into commercially pure Al and ZA27 alloy by infiltration proces s to comparatively study the influence of macroscopic defects on the damping beh aviors of the materials. The mean diameter of the bulk defects is (1.0±0.5) mm, and the volume fractions of pores and graphite particulates are in the range of 50%—75% and 19%—94%, separately. It is shown that addition of a number of por es or graphite particulates can significantly improve the damping of commerciall y pure Al, due to the comprehensive effects of the macroscopic and microscopic d efects. However, the pores have little effect on the damping capacity of high da mping ZA27 alloy, and graphite particulates make the high temperature internal f riction peak decrease. It is considered that graphite particulates may repress t he intrinsic damping mechanism of ZA27 alloy.

  2. Glass Stability and Kinetic Analysis of Iron-Metalloid Bulk Metallic Glass

    Science.gov (United States)

    Santhaweesuk, Charuayporn

    Multicomponent Fe-based bulk metallic glasses (BMGs) with a combination of excellent properties such as good soft magnetic properties, high strength, high hardness, and high corrosion resistance have attracted increasing attention both from a basic science research standpoint and due to their industrial application potential. However, many of the elemental additions which lead to the easiest glass formation are expensive. The identification of alloys composed of abundant and inexpensive elements that still retain excellent properties would promote applications for engineering and industry. In short, the development of the Fe-based BMG without any glass-forming metal elements and with high glass forming ability is desired. This study shows that the thermal stability of the Fe-based alloys can be improved beyond a simple rule of mixtures prediction by utilizing a well-balance multi-metalloid approach. The kinetics aspect of glass-forming ability is studied experimentally for Fe-B-Si-P alloys. The systematic variation in alloy composition gives access to differences in phase selection and the final dimensions of glass formation. Two alloys, representing the best glass-forming composition and the poorest glass-forming composition, were studied in terms of their stability to crystallization, solidification microstructure evolution and thermal history. The utility of the wedge-casting technique is developed to examine bulk glass-forming alloys by combining multiple temperature profiles of the quenching melt with a measurement-based kinetic analysis of the phase selection competition and critical cooling rate conditions. Based upon direct thermal measurement, microstructural analysis and kinetic modeling, it was found that both representative alloys show a board spectrum of solidification microstructures which include a critical cooling rate range. The kinetic competition in the formation of certain phases can enhance or detract from the final dimension of bulk glass

  3. ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

    Directory of Open Access Journals (Sweden)

    A. Benchettara

    2014-12-01

    Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

  4. ELECTROCHEMICAL DETERMINATION OF ETHANOL, 2- PROPANOL AND 1-BUTANOL ON GLASSY CARBON ELECTRODE MODIFIED WITH NICKEL OXIDE FILM

    Directory of Open Access Journals (Sweden)

    A. Benchettara

    2015-07-01

    Full Text Available In this work, we present the modification of a glassy carbon electrode with nickel oxide film which is performed in two successive steps. In the first one, the electrochemical deposition of metallic nickel on the glassy carbon electrode (GCE is achieved in 0.1M boric acid; in the second step, the metallic deposit is anodically oxidized in 0.1M NaOH. These two operations were carried out in a three electrode cell with a filiform platinum auxiliary electrode, a SCE as potential reference and a working microelectrode of modified glassy carbon with nickel oxides. This electrode is characterized by several electrochemical techniques and is used for the catalytic determination of ethanol, 2-propanol and 1-butanol in 0.1 M NaOH. The proposed chemical mechanism shows that NiO2 acts as a mediator.

  5. Fatigue and corrosion of a Pd-based bulk metallic glass in various environments

    International Nuclear Information System (INIS)

    Bulk metallic glasses (BMGs) possess attractive properties for biomedical applications, including high strength, hardness and corrosion resistance, and low elastic modulus. In this study, we conduct rotating beam fatigue tests on Pd43Ni10Cu27P20 bulk metallic glass in air and Eagle's medium (EM) and measure the corrosive resistance of the alloy by submersion in acidic and basic electrolytes. Fatigue results are compared to those of commonly used biometals in EM. Rotating beam fatigue tests conducted in air and in Eagle's medium show no deterioration in fatigue properties in this potentially corrosive environment out to 107 cycles. A specimen size effect is revealed when comparing fatigue results to those of a similar alloy of larger minimum dimensions. Corrosion tests show that the alloy is not affected by highly basic (NaOH) or saline (NaCl) solutions, nor in EM, and is affected by chlorinated acidic solutions (HCl) to a lesser extent than other commonly used biometals. Corrosion in HCl initiates with selective leaching of late transition metals, followed by dissolution of Pd. - Highlights: • Fatigue limit of 600 MPa with no deterioration when exposed to Eagle's medium. • Fatigue shows sample size effect. • Pd-based BMG is unaffected by saline or strong basic solutions. • Pd-based BMG is substantially more resistant to chlorinated acids than CoCrMo, 316 L Stainless, or Ti6Al4V alloys. • Corrosion shows selective leaching of late transition metals, followed by Pd and P

  6. Handling of bulk solids theory and practice

    CERN Document Server

    Shamlou, P A

    1990-01-01

    Handling of Bulk Solids provides a comprehensive discussion of the field of solids flow and handling in the process industries. Presentation of the subject follows classical lines of separate discussions for each topic, so each chapter is self-contained and can be read on its own. Topics discussed include bulk solids flow and handling properties; pressure profiles in bulk solids storage vessels; the design of storage silos for reliable discharge of bulk materials; gravity flow of particulate materials from storage vessels; pneumatic transportation of bulk solids; and the hazards of solid-mater

  7. Phase diagrams for surface alloys

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Stoltze, Per;

    1997-01-01

    We discuss surface alloy phases and their stability based on surface phase diagrams constructed from the surface energy as a function of the surface composition. We show that in the simplest cases of pseudomorphic overlayers there are four generic classes of systems, characterized by the sign...... of the heat of segregation from the bulk and the sign of the excess interactions between the atoms in the surface (the surface mixing energy). We also consider the more complicated cases a with ordered surface phases, nonpseudomorphic overlayers, second layer segregation, and multilayers. The discussion...... is based on density-functional calculations using the coherent-potential approximation and on effective-medium theory. We give self-consistent density-functional results for the segregation energy and surface mixing energy for all combinations of the transition and noble metals. Finally we discuss...

  8. Stability of Bulk Metallic Glass Structure. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D. B.

    2003-06-01

    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

  9. Effect of palladium on sulfide tarnishing of noble metal alloys.

    Science.gov (United States)

    Suoninen, E; Herø, H; Minni, E

    1985-10-01

    Electron spectroscopic studies of Au-Ag-Cu alloys of the type used for dental castings show that small additions (less than or equal to 3 wt%) of palladium reduce essentially the thickness of the sulfide layer formed on surfaces of samples treated in aqueous Na2S solutions. Relative to silver, palladium does not enrich in the sulfide, but statistically significant enrichment is found immediately below the sulfide layer. This enrichment probably takes place during the exposure of the substrate surface to atmosphere before the sulfiding treatment. The mechanism of the impeding effect of palladium on sulfiding is assumed to be a decrease in diffusion from the bulk alloy to the surface due to the enriched layer. The effect cannot be explained by changes in the electronic structure of the alloy due to palladium alloying.

  10. Laser treatment of aluminum copper alloys: A mechanical enhancement

    International Nuclear Information System (INIS)

    Aluminum-copper alloys are commonly used as structural components for the car and aircraft industry. They combine low density, high strength, high fracture toughness and good machinability. Moreover, the strength and wear-resistance of the surface of alloys are improved by a high power laser beam. In this way the molten surface will be self-quenched by conduction of heat into the bulk. This technique ensures solidification velocities of 0.01--1 m/s. These high solidification velocities have a significant influence on the size and distribution of the morphology. This work concentrates on Al-Cu alloys, in which the Cu content ranges between 0--40 wt.%, and is aimed at describing the mechanical and microstructural properties of these alloys upon variation of the laser scan velocity in the range of 0.0125 to 0.125 m/s

  11. Nonhysteretic superelasticity of shape memory alloys at the nanoscale.

    Science.gov (United States)

    Zhang, Zhen; Ding, Xiangdong; Sun, Jun; Suzuki, Tetsuro; Lookman, Turab; Otsuka, Kazuhiro; Ren, Xiaobing

    2013-10-01

    We perform molecular dynamics simulations to show that shape memory alloy nanoparticles below the critical size not only demonstrate superelasticity but also exhibit features such as absence of hysteresis, continuous nonlinear elastic distortion, and high blocking force. Atomic level investigations show that this nonhysteretic superelasticity results from a continuous transformation from the parent phase to martensite under external stress. This aspect of shape memory alloys is attributed to a surface effect; i.e., the surface locally retards the formation of martensite and then induces a critical-end-point-like behavior when the system is below the critical size. Our work potentially broadens the application of shape memory alloys to the nanoscale. It also suggests a method to achieve nonhysteretic superelasticity in conventional bulk shape memory alloys.

  12. Elastic properties of Pu metal and Pu-Ga alloys

    Energy Technology Data Exchange (ETDEWEB)

    Soderlind, P; Landa, A; Klepeis, J E; Suzuki, Y; Migliori, A

    2010-01-05

    We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga ({delta}) alloys together with ab initio equilibrium equation-of-state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from {alpha} {yields} {beta} {yields} {gamma} plutonium, thus suggesting increasing f-electron correlation (localization). For the {delta}-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants, suggest a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.

  13. Elastic properties of Pu metal and Pu-Ga alloys

    Science.gov (United States)

    Söderlind, Per; Landa, Alex; Klepeis, J. E.; Suzuki, Y.; Migliori, A.

    2010-06-01

    We present elastic properties, theoretical and experimental, of Pu metal and Pu-Ga (δ) alloys together with ab initio equilibrium equation of state for these systems. For the theoretical treatment we employ density-functional theory in conjunction with spin-orbit coupling and orbital polarization for the metal and coherent-potential approximation for the alloys. Pu and Pu-Ga alloys are also investigated experimentally using resonant ultrasound spectroscopy. We show that orbital correlations become more important proceeding from α→β→γ plutonium, thus suggesting increasing f -electron correlation and a corresponding softening of the elastic moduli. For the δ-Pu-Ga alloys we find a softening with larger Ga content, i.e., atomic volume, bulk modulus, and elastic constants imply a weakened chemical bonding with addition of Ga. Our measurements confirm qualitatively the theory but uncertainties remain when comparing the model with experiments.

  14. High strength alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  15. High strength alloys

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  16. New fermions in the bulk

    CERN Document Server

    de Brito, K P S

    2016-01-01

    Spinor fields on 5-dimensional Lorentzian manifolds are classified, according to the geometric Fierz identities that involve their bilinear covariants. Based upon this classification that generalises the celebrated 4-dimensional Lounesto classification of spinor fields, new non-trivial classes of 5-dimensional spinor fields are, hence, found, with important potential applications regarding bulk fermions and their subsequent localisation on brane-worlds. In addition, quaternionic bilinear covariants are used to derive the quaternionic spin density, through the truncated exterior bundle. In order to accomplish a realisation of these new spinors, a Killing vector field is constructed on the horizon of 5-dimensional Kerr black holes. This Killing vector field is shown to reach the time-like Killing vector field at the spatial infinity, through a current 1-form density, constructed with the derived new spinor fields. The current density is, moreover, expressed as the f\\"unfbein components, assuming a condensed for...

  17. Ordered bulk degradation via autophagy

    DEFF Research Database (Denmark)

    Dengjel, Jörn; Kristensen, Anders Riis; Andersen, Jens S

    2008-01-01

    During amino acid starvation, cells undergo macroautophagy which is regarded as an unspecific bulk degradation process. Lately, more and more organelle-specific autophagy subtypes such as reticulophagy, mitophagy and ribophagy have been described and it could be shown, depending on the experimental...... setup, that autophagy specifically can remove certain subcellular components. We used an unbiased quantitative proteomics approach relying on stable isotope labeling by amino acids in cell culture (SILAC) to study global protein dynamics during amino acid starvation-induced autophagy. Looking...... at proteasomal and lysosomal degradation ample cross-talk between the two degradation pathways became evident. Degradation via autophagy appeared to be ordered and regulated at the protein complex/organelle level. This raises several important questions such as: can macroautophagy itself be specific and what...

  18. Microwave disinfestation of bulk timber.

    Science.gov (United States)

    Plaza, Pedro Jose; Zona, Angela Tatiana; Sanchís, Raul; Balbastre, Juan Vicente; Martínez, Antonio; Muñoz, Eva Maria; Gordillo, Javier; de los Reyes, Elías

    2007-01-01

    In this paper a complete microwave system for bulk timber disinfestation is developed and tested. A commercial FEM simulator has been used to design the applicator, looking for structures providing uniform field distributions, which is a factor of capital relevance for a successful treatment. Special attention has also been given to the reduction of electromagnetic energy leakage. A dual polarized cylindrical applicator with a corrugated flange has been designed. The applicator has also been numerically tested emulating some real-life operating conditions. A prototype has been built using two low-cost magnetrons of 900 W and high power coaxial cables and it has been tested inside a shielded semianechoic chamber. The tests have been carried out in three stages: validation of the applicator design, determination of the lethal dosage as a function of the insect position and the maximum wood temperature allowed and statement of safe operation procedures. PMID:18351001

  19. Isotopic signatures by bulk analyses

    International Nuclear Information System (INIS)

    Los Alamos National Laboratory has developed a series of measurement techniques for identification of nuclear signatures by analyzing bulk samples. Two specific applications for isotopic fingerprinting to identify the origin of anthropogenic radioactivity in bulk samples are presented. The first example is the analyses of environmental samples collected in the US Arctic to determine the impact of dumping of radionuclides in this polar region. Analyses of sediment and biota samples indicate that for the areas sampled the anthropogenic radionuclide content of sediments was predominantly the result of the deposition of global fallout. The anthropogenic radionuclide concentrations in fish, birds and mammals were very low. It can be surmised that marine food chains are presently not significantly affected. The second example is isotopic fingerprinting of water and sediment samples from the Rocky Flats Facility (RFP). The largest source of anthropogenic radioactivity presently affecting surface-waters at RFP is the sediments that are currently residing in the holding ponds. One gram of sediment from a holding pond contains approximately 50 times more plutonium than 1 liter of water from the pond. Essentially 100% of the uranium in Ponds A-1 and A-2 originated as depleted uranium. The largest source of radioactivity in the terminal Ponds A-4, B-5 and C-2 was naturally occurring uranium and its decay product radium. The uranium concentrations in the waters collected from the terminal ponds contained 0.05% or less of the interim standard calculated derived concentration guide for uranium in waters available to the public. All of the radioactivity observed in soil, sediment and water samples collected at RFP was naturally occurring, the result of processes at RFP or the result of global fallout. No extraneous anthropogenic alpha, beta or gamma activities were detected. The plutonium concentrations in Pond C-2 appear to vary seasonally

  20. Separating the ferromagnetic and glassy behavior within the metal-organic magnet Ni (TCNQ) 2

    Science.gov (United States)

    Berlie, Adam; Terry, Ian; Szablewski, Marek; Giblin, Sean R.

    2015-11-01

    An in-depth study of the metal-organic magnet Ni (TCNQ) 2 was conducted where the deuterated form was synthesised both to attempt to alter the magnetic properties of the material and to be advantageous in techniques such as neutron scattering and muon spectroscopy. Deuteration saw a 3 K increase in TC with magnetization and heat capacity measurements demonstrating a spin wave contribution at low temperatures confirming the 3D nature of the ferromagnetic state shown by Ni (TCNQ-D4)2 . AC susceptibility results suggest there is a glassy component associated with the magnetically ordered state, though muon spectroscopy measurements did not support the presence of a spin glass state. Instead muon spectroscopy at zero magnetic field indicated the presence of two magnetic transitions, one at 20 K and another below 6 K; the latter is likely due to the system entering a quasistatic regime, similar to what one might expect of a superspin or cluster glass. Neutron diffraction measurements further supported this by revealing very weak magnetic Bragg peaks suggesting that the magnetism may have a short coherence length and be confined to small grains or clusters. The separation of the ferromagnetic and glassy magnetic components of the material's properties suggest that this system may show promise as a metal-organic magnet which is easily modified to change its magnetic properties, providing larger grain sizes can be synthesized.

  1. Mediatorless solar energy conversion by covalently bonded thylakoid monolayer on the glassy carbon electrode.

    Science.gov (United States)

    Lee, Jinhwan; Im, Jaekyun; Kim, Sunghyun

    2016-04-01

    Light reactions of photosynthesis that take place in thylakoid membranes found in plants or cyanobacteria are among the most effective ways of utilizing light. Unlike most researches that use photosystem I or photosystem II as conversion units for converting light to electricity, we have developed a simple method in which the thylakoid monolayer was covalently immobilized on the glassy carbon electrode surface. The activity of isolated thylakoid membrane was confirmed by measuring evolving oxygen under illumination. Glassy carbon surfaces were first modified with partial or full monolayers of carboxyphenyl groups by reductive C-C coupling using 4-aminobenzoic acid and aniline and then thylakoid membrane was bioconjugated through the peptide bond between amine residues of thylakoid and carboxyl groups on the surface. Surface properties of modified surfaces were characterized by cyclic voltammetry, contact angle measurements, and electrochemical impedance spectroscopy. Photocurrent of 230 nA cm(-2) was observed when the thylakoid monolayer was formed on the mixed monolayer of 4-carboxylpheny and benzene at applied potential of 0.4V vs. Ag/AgCl. A small photocurrent resulted when the 4-carboxyphenyl full monolayer was used. This work shows the possibility of solar energy conversion by directly employing the whole thylakoid membrane through simple surface modification.

  2. Structural characterization and aging of glassy pharmaceuticals made using acoustic levitation.

    Science.gov (United States)

    Benmore, Chris J; Weber, J K R; Tailor, Amit N; Cherry, Brian R; Yarger, Jeffery L; Mou, Qiushi; Weber, Warner; Neuefeind, Joerg; Byrn, Stephen R

    2013-04-01

    Here, we report the structural characterization of several amorphous drugs made using the method of quenching molten droplets suspended in an acoustic levitator. (13) C NMR, X-ray, and neutron diffraction results are discussed for glassy cinnarizine, carbamazepine, miconazole nitrate, probucol, and clotrimazole. The (13) C NMR results did not find any change in chemical bonding induced by the amorphization process. High-energy X-ray diffraction results were used to characterize the ratio of crystalline to amorphous material present in the glasses over a period of 8 months. All the glasses were stable for at least 6 months except carbamazepine, which has a strong tendency to crystallize within a few months. Neutron and X-ray pair distribution function analyses were applied to the glassy materials, and the results were compared with their crystalline counterparts. The two diffraction techniques yielded similar results in most cases and identified distinct intramolecular and intermolecular correlations. The intramolecular scattering was calculated based on the crystal structure and fit to the measured X-ray structure factor. The resulting intermolecular pair distribution functions revealed broad-nearest and next-nearest neighbor molecule-molecule correlations. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1290-1300, 2013. PMID:23381910

  3. A neutron-X-ray, NMR and calorimetric study of glassy Probucol synthesized using containerless techniques

    Science.gov (United States)

    Weber, J. K. R.; Benmore, C. J.; Tailor, A. N.; Tumber, S. K.; Neuefeind, J.; Cherry, B.; Yarger, J. L.; Mou, Q.; Weber, W.; Byrn, S. R.

    2013-10-01

    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.

  4. A critical study of the emergence of glass and glassy metals as “green” materials

    International Nuclear Information System (INIS)

    Highlights: • We provide a study on the capabilities of glass/glassy metals as green materials. • A well materials selection provides certain strategic and competitive advantages. • Points of view on the actually and future influence of these materials are done. • Glasses are materials that are fully recyclable, with a life cycle perfectly closed. • Glassy metals are considered to be among the emerging materials of the future. - Abstract: In 2008, The National Academy of Engineering (NAE – Washington, DC) identified the glass family (glasses, glass ceramics and glass composites) as central to many of the great engineering achievements of the twentieth century: the development of solid state lasers and optical glass fibers, biomaterials, glasses for imaging technologies, and glass films in microelectronic devices. The work reported in this paper discusses the importance of glass and metallic glasses as environmental friendly materials and also provide some points of view about the future influence of these materials for the related fields of industrial engineering and industrial ecology. The environmental capabilities of metallic glasses (MGs), which are considered to be among the important materials of the future, have not been sufficiently investigated. However, some aspects have yet to be done: the biocompatibility of most MGs, obtaining valuable MGs from waste materials, using MGs in green energy applications (solar cells and hydrogen production), using MGs in catalyst systems, as well as the possibility for using MGs in systems for retention and purification of dangerous pollutants and in the nuclear industry

  5. Effect of chemical substituents on the structure of glassy diphenyl polycarbonates.

    Science.gov (United States)

    Sulatha, M S; Natarajan, Upendra

    2011-02-24

    Polycarbonates offer a wide variety of physical property behavior that is difficult to predict due to complexities at the molecular scale. Here, the physical structure of amorphous glassy polycarbonates having aliphatic and cycloaliphatic chemical groups is explored through atomistic simulations. The influence of chemical structure on solubility parameter, torsion distributions, radial distribution function, scattering structure factor, orientation distributions of phenylene rings and carbonate groups, and free volume distributions, leading to interchain packing effects, are shown. The effect of the cyclohexyl ring at the isopropylidene carbon as compared to the effect of the methyl groups positioned on the phenylene rings results in a larger reduction in the solubility parameter (δ). The interchain distance estimated for polycarbonates in this work is in the range of 5-5.8 Å. The o-methyl groups on the phenylene rings, as compared to a cyclohexyl ring, lead to higher interchain distances. The highest interchain distance is observed with a trimethylcyclohexylidene group at the isopropylidene carbon. Atomistic simulations reveal two different types of packing arrangement of nearest-neighbor chains in the glassy state, one type of which agrees with the NMR experimental data. The fundamental insights provided here can be utilized for design of chemical structures for tailored macroscopic properties.

  6. Novel electroanalysis of hydroxyurea at glassy carbon and gold electrode surfaces

    Directory of Open Access Journals (Sweden)

    Keerti M. Naik

    2014-09-01

    Full Text Available A simple and a novel electroanalysis of hydroxyurea (HU drug at glassy carbon and gold electrode was investigated for the first time using cyclic, linear sweep and differential pulse voltammetric techniques. The oxidation of HU was irreversible and exhibited a diffusion controlled process on both electrodes. The oxidation mechanism was proposed. The dependence of the current on pH, the concentration, nature of buffer, and scan rate was investigated to optimize the experimental conditions for the determination of HU. It was found that the optimum buffer pH was 7.0, a physiological pH. In the range of 0.01 to 1.0 mM, the current measured by differential pulse voltammetry showed a linear relationship with HU concentration with limit of detection of 0.46 µM for glassy carbon electrode and 0.92 µM for gold electrode. In addition, reproducibility, precision and accuracy of the method were checked as well. The developed method was successfully applied to HU determination in pharmaceutical formulation and human biological fluids. The method finds its applications in quality control laboratories and pharmacokinetics.

  7. Mechanistic study of carvacrol processing and stabilization as glassy solid solution and microcapsule.

    Science.gov (United States)

    Tackenberg, Markus W; Geisthövel, Carola; Marmann, Andreas; Schuchmann, Heike P; Kleinebudde, Peter; Thommes, Markus

    2015-01-30

    Essential oils and other liquid active pharmaceutical ingredients (APIs) are frequently microencapsulated to improve shelf life, handling, and for tailoring release. A glassy solid solution (GSS), a single-phase system, where the excipient is plasticized by the API, could be an alternative formulation system. Thus this study focuses on the investigation of two formulation strategies using carvacrol as a model compound, namely a microcapsule (MC) and a glassy solid solution (GSS). Applying the solubility parameter approach, polyvinylpyrrolidone (PVP) was chosen as a suitable matrix material for a GSS system, whereas maltodextrin and sucrose served as excipients for a microcapsule (MC) system. Differential scanning calorimetry (DSC) measurements of the excipients' glass transition temperatures and the melting point of carvacrol verified plasticizing properties of carvacrol on PVP. Batch mixing processes, as preliminary experiments for future extrusion processes, were performed to prepare GSSs and MCs with various amounts of carvacrol, followed by crushing and sieving. Maximally 4.5% carvacrol was encapsulated in the carbohydrate material, whereas up to 16.3% were stabilized as GSS, which is an outstanding amount. However, grinding of the samples led to a loss of up to 30% of carvacrol.

  8. Incoherent chimera and glassy states in coupled oscillators with frustrated interactions

    Science.gov (United States)

    Choe, Chol-Ung; Ri, Ji-Song; Kim, Ryong-Son

    2016-09-01

    We suggest a site disorder model that describes the population of identical oscillators with quenched random interactions for both the coupling strength and coupling phase. We obtain the reduced equations for the suborder parameters, on the basis of Ott-Antonsen ansatz theory, and present a complete bifurcation analysis of the reduced system. New effects include the appearance of the incoherent chimera and glassy state, both of which are caused by heterogeneity of the coupling phases. In the incoherent chimera state, the system displays an exotic symmetry-breaking behavior in spite of the apparent structural symmetry where the oscillators for both of the two subpopulations are in a frustrated state, while the phase distribution for each subpopulation approaches a steady state that differs from each other. When the incoherent chimera undergoes Hopf bifurcation, the system displays a breathing incoherent chimera. The glassy state that occurs on a surface of three-dimensional parameter space exhibits a continuum of metastable states with zero value of the global order parameter. Explicit formulas are derived for the system's Hopf, saddle-node, and transcritical bifurcation curves, as well as the codimension-2 crossing points, including the Takens-Bogdanov point.

  9. Electrochemical study of functionalization on the surface of a chitin/platinum-modified glassy carbon paste electrode.

    Science.gov (United States)

    Sugawara, Kazuharu; Yugami, Asako; Terui, Norifumi; Kuramitz, Hideki

    2009-11-01

    To functionalize chitin surfaces using proteins, we developed a glucose oxidase (GOD)-chitin/platinum-modified glassy carbon paste electrode (GCPE) as a model. In a weakly acidic solution, negatively charged GOD were immobilized by the protonated acetylamide groups on chitin. When the electrode was immersed in a solution containing GOD, the enzyme was readily immobilized due to the electrostatic interaction. In addition, measurements were performed using electrodes made with powders of different sizes because sensor performance depends on the particle sizes of glassy carbon powder. PMID:19907096

  10. Creep Resistant Zinc Alloy

    Energy Technology Data Exchange (ETDEWEB)

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  11. Biocompatibility of dental alloys

    Energy Technology Data Exchange (ETDEWEB)

    Braemer, W. [Heraeus Kulzer GmbH and Co. KG, Hanau (Germany)

    2001-10-01

    Modern dental alloys have been used for 50 years to produce prosthetic dental restorations. Generally, the crowns and frames of a prosthesis are prepared in dental alloys, and then veneered by feldspar ceramics or composites. In use, the alloys are exposed to the corrosive influence of saliva and bacteria. Metallic dental materials can be classified as precious and non-precious alloys. Precious alloys consist of gold, platinum, and small amounts of non-precious components such as copper, tin, or zinc. The non-precious alloys are based on either nickel or cobalt, alloyed with chrome, molybdenum, manganese, etc. Titanium is used as Grade 2 quality for dental purposes. As well as the dental casting alloys, high purity electroplated gold (99.8 wt.-%) is used in dental technology. This review discusses the corrosion behavior of metallic dental materials with saliva in ''in vitro'' tests and the influence of alloy components on bacteria (Lactobacillus casei and Streptococcus mutans). The test results show that alloys with high gold content, cobalt-based alloys, titanium, and electroplated gold are suitable for use as dental materials. (orig.)

  12. Mechanochemical investigation of a glassy epoxy-amine thermoset subjected to fatigue

    Science.gov (United States)

    Foster, Stephen Finley

    Covalent bonds in organic molecules can be produced, altered, and broken through various sources of energy and processes. These include photochemical, thermochemical, chemical, and mechanochemical processes. Polymeric materials derive their physical properties from the time scale of motion, summation of intermolecular forces, and number of chain entanglements and crosslinks. Glassy thermoset polymers experience mechanical fatigue during dynamic stress loading and properties diminish with inevitable material failure at stress levels below the ultimate tensile strength (UTS). Damage modeling has been successful in predicting the number of cycles required to induce failure in a specimen due to stress. However, it does not directly provide an explanation of the origin of fatigue in polymers. It is hypothesized herein that mechanical failure at stress levels below the ultimate strength property is due to the accumulation of mechanically induced homolytic chain scission events throughout the glassy thermoset network. The goal of this research will be to quantify homolytic chain scission events with fatigue cycles with the ultimate goal of correlating mechanical property loss with degradation of covalent network structure. To accomplish this goal, stable free nitroxyl radicals were incorporated into an epoxy-amine matrix to detect homolytic chain scission resulting from fatigue. Chapter II discusses a successful synthesis and characterization of the nitroxyl radical molecule, a product of 4-hydroxy-2,2,5,5-tetramethylpiperdin-1-yl-oxyl (TEMPO) and isophorone diisocyanate designated as BT-IPDI. In Chapter III, the epoxy-amine reaction was determined to be unaffected by incorporation of up to 5 wt% of BT-IPDI. Although 50% UTS fatigue studies produced property degradation and fatigue failure as shown in Chapter IV, analysis of BT-IPDI through EPR did not detect homolytic chain scission. Chapter V reveals that mechano-radicals were produced from cryo-grinding the glassy

  13. Development of a new β Ti alloy with low modulus and favorable plasticity for implant material.

    Science.gov (United States)

    Liang, S X; Feng, X J; Yin, L X; Liu, X Y; Ma, M Z; Liu, R P

    2016-04-01

    One of the most important development directions of the Ti and its alloys is the applications in medical field. Development of new Ti alloys with low elastic modulus and/or favorable biocompatibility plays an important role for promoting its application in medical field. In this work, a new β Ti alloy (Ti-31Nb-6Zr-5Mo, wt.%) was designed for implant material using d-electron alloy design method. Microstructure and tensile properties of the designed alloy after hot rolling (HR) and solution followed by aging treatments (SA) were investigated. Results show that the designed alloy is composed of single β phase. However, microstructural analysis shows that the β phase in the designed alloy separates into Nb-rich and Nb-poor phase regions. The Nb-rich regions in HR specimen are typical elongated fiber texture, but are equiaxed particles with several micrometers in SA specimen. Tensile results show that the designed alloy has low Young's modulus of 44 GPa for HR specimen and 48 GPa for SA specimen which are very close to the extreme of Young's modulus of bulk titanium alloys. At the same time, the designed alloy has favorable plasticity in term of elongation of 26.7% for HR specimen and 20.6% for SA specimen, and appropriate tensile strength over 700 MPa. In short, the designed alloy has low elastic modulus close to that of bone and favorable plasticity and strength which can be a potential candidate for hard tissue replacements. PMID:26838858

  14. Materials Properties Database for Selection of High-Temperature Alloys and Concepts of Alloy Design for SOFC Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Z Gary; Paxton, Dean M.; Weil, K. Scott; Stevenson, Jeffry W.; Singh, Prabhakar

    2002-11-24

    To serve as an interconnect / gas separator in an SOFC stack, an alloy should demonstrate the ability to provide (i) bulk and surface stability against oxidation and corrosion during prolonged exposure to the fuel cell environment, (ii) thermal expansion compatibility with the other stack components, (iii) chemical compatibility with adjacent stack components, (iv) high electrical conductivity of the surface reaction products, (v) mechanical reliability and durability at cell exposure conditions, (vii) good manufacturability, processability and fabricability, and (viii) cost effectiveness. As the first step of this approach, a composition and property database was compiled for high temperature alloys in order to assist in determining which alloys offer the most promise for SOFC interconnect applications in terms of oxidation and corrosion resistance. The high temperature alloys of interest included Ni-, Fe-, Co-base superal

  15. Towards the Better: Intrinsic Property Amelioration in Bulk Metallic Glasses

    Science.gov (United States)

    Sarac, Baran; Zhang, Long; Kosiba, Konrad; Pauly, Simon; Stoica, Mihai; Eckert, Jürgen

    2016-06-01

    Tailoring the intrinsic length-scale effects in bulk metallic glasses (BMGs) via post-heat treatment necessitates a systematic analyzing strategy. Although various achievements were made in the past years to structurally enhance the properties of different BMG alloys, the influence of short-term sub-glass transition annealing on the relaxation kinetics is still not fully covered. Here, we aim for unraveling the connection between the physical, (thermo)mechanical and structural changes as a function of selected pre-annealing temperatures and time scales with an in-house developed Cu46Zr44Al8Hf2 based BMG alloy. The controlled formation of nanocrystals below 50 nm with homogenous distribution inside the matrix phase via thermal treatment increase the material’s resistance to strain softening by almost an order of magnitude. The present work determines the design aspects of metallic glasses with enhanced mechanical properties via nanostructural modifications, while postulating a counter-argument to the intrinsic property degradation accounted for long-term annealing.

  16. Rapidly solidified surface melts of Ni-B-Si-Cr brazing alloy

    Science.gov (United States)

    Tucker, T. R.; Ayers, J. D.

    1981-10-01

    Sintered powder layers of a Ni-based brazing alloy were consolidated by scanned electron beam radiation to produce a continuous fused coating. The surface of this coating was then remelted by laser and electron beams under differing conditions, resulting in a variety of resolidification structures. Alloy BNi2 was chosen for these studies because it exhibits substantial hardening on grain refinement and because it can be prepared in the glassy state relatively easily. Surface microhardness for BNi2 reaches a maximum of about 1200 DPH at a cooling rate approaching 105 K/s. For higher quench rates, hardness decreases and ductility increases. As the cooling rate approaches 107 k/s, overlapping beam scans produce an extended amorphous surface. A solidification rate higher than that needed to produce an amorphous structure in a single melt pass is necessary to avoid surface cracking or crystallization when overlapping melt passes are employed.

  17. Development of a novel high-entropy alloy with eminent efficiency of degrading azo dye solutions

    Science.gov (United States)

    Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P.

    2016-09-01

    In addition to its scientific importance, the degradation of azo dyes is of practical significance from the perspective of environmental protection. Although encouraging progress has been made on developing degradation approaches and materials, it is still challenging to fully resolve this long-standing problem. Herein, we report that high entropy alloys, which have been emerging as a new class of metallic materials in the last decade, have excellent performance in degradation of azo dyes. In particular, the newly developed AlCoCrTiZn high-entropy alloy synthesized by mechanical alloying exhibits a prominent efficiency in degradation of the azo dye (Direct Blue 6: DB6), as high as that of the best metallic glass reported so far. The newly developed AlCoCrTiZn HEA powder has low activation energy barrier, i.e., 30 kJ/mol, for the degrading reaction and thus make the occurrence of reaction easier as compared with other materials such as the glassy Fe-based powders. The excellent capability of our high-entropy alloys in degrading azo dye is attributed to their unique atomic structure with severe lattice distortion, chemical composition effect, residual stress and high specific surface area. Our findings have important implications in developing novel high-entropy alloys for functional applications as catalyst materials.

  18. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  19. Hypervelocity impact on Zr51Ti5Ni10Cu25Al9 bulk metallic glass

    International Nuclear Information System (INIS)

    Highlights: → Hypervelocity impact experiments were performed on a bulk metallic glass. → Morphology of the bullet hole presents three different regions. → The post-impact samples keep glassy structure. → Mechanical properties of the post-impact samples were studied by nanoindentation. → Mechanical properties of the post-impact samples were discussed by free-volume model. - Abstract: In this study, the hypervelocity impact experiments were performed on Zr51Ti5Ni10Cu25Al9 bulk metallic glass using a two-stage light gas gun. The morphologies of the bullet holes exhibit three different regions: melting area, vein-pattern area, and radiating core feature area, suggesting that various regions experience different stress states during the hypervelocity impact. For the post-impact samples, the nano-hardness increases and plastic deformability decreases both with the increase in the distance from the bullet hole and with the decrease in the impact velocity, which is discussed by means of spherical stress wave theory and free-volume model.

  20. Laser ignition of bulk 1018 carbon steel in pure oxygen

    Science.gov (United States)

    Nguyen, K.; Branch, M. C.

    1986-01-01

    Experiments were undertaken to study the ignition characteristics of bulk 1018 carbon steel in a pure oxygen environment. Cylindrical 1018 carbon steel specimens 5 mm in diameter and 5 mm high were ignited by a focused CW CO2 laser beam in a cool, static, pure oxygen environment at oxygen pressures ranging from 0.103 to 6.895 MPa. A two-color pyrometer was designed and used to measure the ignition temperatures of the specimens. The temperature history of a spot approximately 0.5 mm in diameter located at the center of the specimen top surface was recorded with a maximum time resolution of 25 microsec, and with an accuracy of a few percent. Ignition temperature of bulk 1018 carbon steel was identified from the temperature history curve with the aid of the light intensity curve. Results show that 1018 carbon steel specimens ignite at temperatures between 1388 and 1450 K, which are below the melting range of the alloy (1662-1685 K). The ignition temperature of 1018 carbon steel is mildly dependent on oxygen pressure over the range of oxygen pressure investigated in this study.