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Sample records for metallic glass composite

  1. Metallic glass composition

    DOEpatents

    Kroeger, Donald M.; Koch, Carl C.

    1986-01-01

    A metallic glass alloy that is either iron-based or nickel-based or based on a mixture of iron and nickel, containing lesser amounts of elements selected from the group boron, silicon carbon and phosphorous to which is added an amount of a ductility enhancing element selected from the group cerium, lanthanum, praseodymium and neodymium sufficient to increase ductility of the metallic glass upon annealing.

  2. From powders to bulk metallic glass composites.

    PubMed

    Krämer, Lisa; Champion, Yannick; Pippan, Reinhard

    2017-07-27

    One way to adjust the properties of materials is by changing its microstructure. This concept is not easily applicable on bulk metallic glasses (BMGs), because they do not consist of grains or different phases and so their microstructure is very homogeneous. One obvious way to integrate inhomogeneities is to produce bulk metallic glass composites (BMGCs). Here we show how to generate BMGCs via high-pressure torsion (HPT) starting from powders (amorphous Zr-MG and crystalline Cu). Using this approach, the composition can be varied and by changing the applied shear strains, the refinement of the microstructure is adjustable. This process permits to produce amorphous/crystalline composites where the scale of the phases can be varied from the micro- to the nanometer regime. Even mixing of the two phases and the generation of new metallic glasses can be achieved. The refinement of microstructure increases the hardness and a hardness higher than the initial BMG can be obtained.

  3. Metallic glass nanostructures of tunable shape and composition

    PubMed Central

    Liu, Yanhui; Liu, Jingbei; Sohn, Sungwoo; Li, Yanglin; Cha, Judy J.; Schroers, Jan

    2015-01-01

    Metals of hybrid nano-/microstructures are of broad technological and fundamental interests. Manipulation of shape and composition on the nanoscale, however, is challenging, especially for multicomponent alloys such as metallic glasses. Although top–down approaches have demonstrated nanomoulding, they are limited to very few alloy systems. Here we report a facile method to synthesize metallic glass nanoarchitectures that can be applied to a broad range of glass-forming alloys. This strategy, using multitarget carousel oblique angle deposition, offers the opportunity to achieve control over size, shape and composition of complex alloys at the nanoscale. As a consequence, nanostructures of programmable three-dimensional shapes and tunable compositions are realized on wafer scale for metallic glasses including the marginal glass formers. Realizing nanostructures in a wide compositional range allows chemistry optimization for technological usage of metallic glass nanostructures, and also enables the fundamental study on size, composition and fabrication dependences of metallic glass properties. PMID:25901951

  4. Metallic glass nanostructures of tunable shape and composition.

    PubMed

    Liu, Yanhui; Liu, Jingbei; Sohn, Sungwoo; Li, Yanglin; Cha, Judy J; Schroers, Jan

    2015-04-22

    Metals of hybrid nano-/microstructures are of broad technological and fundamental interests. Manipulation of shape and composition on the nanoscale, however, is challenging, especially for multicomponent alloys such as metallic glasses. Although top-down approaches have demonstrated nanomoulding, they are limited to very few alloy systems. Here we report a facile method to synthesize metallic glass nanoarchitectures that can be applied to a broad range of glass-forming alloys. This strategy, using multitarget carousel oblique angle deposition, offers the opportunity to achieve control over size, shape and composition of complex alloys at the nanoscale. As a consequence, nanostructures of programmable three-dimensional shapes and tunable compositions are realized on wafer scale for metallic glasses including the marginal glass formers. Realizing nanostructures in a wide compositional range allows chemistry optimization for technological usage of metallic glass nanostructures, and also enables the fundamental study on size, composition and fabrication dependences of metallic glass properties.

  5. Economic manufacturing of bulk metallic glass compositions by microalloying

    DOEpatents

    Liu, Chain T.

    2003-05-13

    A method of making a bulk metallic glass composition includes the steps of:a. providing a starting material suitable for making a bulk metallic glass composition, for example, BAM-11; b. adding at least one impurity-mitigating dopant, for example, Pb, Si, B, Sn, P, to the starting material to form a doped starting material; and c. converting the doped starting material to a bulk metallic glass composition so that the impurity-mitigating dopant reacts with impurities in the starting material to neutralize deleterious effects of the impurities on the formation of the bulk metallic glass composition.

  6. Metallic glass-strengthened thermoplastic elastomer composites

    NASA Astrophysics Data System (ADS)

    Liu, Xue; Liu, Hao; Wang, Dong; Wang, Enpeng; Liu, Wenjian; Yao, Kefu; Chen, Na

    2017-06-01

    Thermoplastic elastomers (TPEs) and metallic glasses (MGs), both lack of long-range ordering structure, have different physical and mechanical properties. To combine unique viscoelasticity of elastomers and excellent wear resistance of MGs, we propose to introduce a Pd40Ni40Si4P16 MG into a commercial styrene-butadiene-styrene (SBS) TPE to form MG/TPE composites. Serving as a hard and strong second phase dispersed in the SBS matrix, the micrometer-sized MG particles can effectively improve the wear resistance of the matrix due to a strengthening effect. In particular, the MG/TPE composite with an addition of 60 wt% MG shows significantly enhanced wear resistance up to about three times that of the SBS matrix. The present results provide a new way to enhance the wear resistance of the widely used TPEs, which may generate immense economic value by extending their service life.

  7. Composition Effect on Intrinsic Plasticity or Brittleness in Metallic Glasses

    PubMed Central

    Zhao, Yuan-Yun; Inoue, Akihisa; Chang, Chuntao; Liu, Jian; Shen, Baolong; Wang, Xinmin; Li, Run-Wei

    2014-01-01

    The high plasticity of metallic glasses is highly desirable for a wide range of novel engineering applications. However, the physical origin of the ductile/brittle behaviour of metallic glasses with various compositions and thermal histories has not been fully clarified. Here we have found that metallic glasses with compositions at or near intermetallic compounds, in contrast to the ones at or near eutectics, are extremely ductile and also insensitive to annealing-induced embrittlement. We have also proposed a close correlation between the element distribution features and the plasticity of metallic glasses by tracing the evolutions of the element distribution rearrangement and the corresponding potential energy change within the sliding shear band. These novel results provide useful and universal guidelines to search for new ductile metallic glasses at or near the intermetallic compound compositions in a number of glass-forming alloy systems. PMID:25043428

  8. Structure and constitution of glass and steel compound in glass-metal composite

    SciTech Connect

    Lyubimova, Olga N.; Morkovin, Andrey V.; Dryuk, Sergey A.; Nikiforov, Pavel A.

    2014-11-14

    The research using methods of optical and scanning electronic microscopy was conducted and it discovered common factors on structures and diffusing zone forming after welding glass C49-1 and steel Ct3sp in technological process of creating new glass-metal composite. Different technological modes of steel surface preliminary oxidation welded with and without glass were investigated. The time of welding was varied from minimum encountering time to the time of stabilizing width of diffusion zone.

  9. Methods of making metallic glass foil laminate composites

    DOEpatents

    Vianco, Paul T.; Fisher, Robert W.; Hosking, Floyd M.; Zanner, Frank J.

    1996-01-01

    A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone.

  10. Methods of making metallic glass foil laminate composites

    DOEpatents

    Vianco, P.T.; Fisher, R.W.; Hosking, F.M.; Zanner, F.J.

    1996-08-20

    A process for the fabrication of a rapidly solidified foil laminate composite. An amorphous metallic glass foil is flux treated and coated with solder. Before solidification of the solder the foil is collected on a take-up spool which forms the composite into a solid annular configuration. The resulting composite exhibits high strength, resiliency and favorable magnetic and electrical properties associated with amorphous materials. The composite also exhibits bonding strength between the foil layers which significantly exceeds the bulk strength of the solder alone. 6 figs.

  11. Electrical conductivity of a bulk metallic glass composite

    NASA Astrophysics Data System (ADS)

    Wang, K.; Fujita, T.; Chen, M. W.; Nieh, T. G.; Okada, H.; Koyama, K.; Zhang, W.; Inoue, A.

    2007-10-01

    The authors report the electrical conductivity of a bulk metallic glass (BMG) based composite fabricated by warm extrusion of a mixture of gas-atomized glassy powders and ductile α-brass powders. The conductivity of the BMG composite can be well modeled by the percolation theory and the critical percolation threshold volume of the high-conductive brass phase was estimated to be about 10%. It was found that the short irregular brass fibers can dramatically reduce the resistivity of the BMG, leading to an improved material with both high strength and good conductivity for functional applications.

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

    PubMed

    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.

  13. Plastic stability of metallic glass composites under tension

    NASA Astrophysics Data System (ADS)

    Wu, F. F.; Li, S. T.; Zhang, G. A.; Wu, X. F.; Lin, P.

    2013-10-01

    The plastic stability of metallic glass composites (MGCs) under tension was investigated. There exists a critical normalized strain-hardening rate determining the plastic stability of MGCs: if the normalized strain-hardening rate is smaller than the critical normalized strain-hardening rate, the plastic instability occurs, thus, leading to localized plastic strain in MGCs; otherwise the plastic stability is in charge of the plastic deformation of the MGCs, so the strain localization or necking is effectively suppressed, which results in homogeneous elongation in MGCs.

  14. Design of Bulk Metallic Glasses and Glass Matrix Composites Near Intermetallic Composition by the Principle of Competitive Growth

    NASA Astrophysics Data System (ADS)

    Ma, G. Z.; Chen, D.

    2016-11-01

    A Cu49Zr51 intermetallic is used as a base for synthesizing metallic glasses and composites with glass matrixes [(Cu49Zr51)100 - x Al x , where x = 0, 2, 4, 6, 8, 10 and 12 at.%]. The introduction of aluminum raises the microhardness and the ultimate compressive strength. In addition, the suppression of formation of crystalline phase upon the introduction of 8 at.% Al provides a glass-like structure in alloy (Cu49Zr51)92Al8. The formation of the glass-like structure is discussed within the concept of competitive nucleation of different intermetallics.

  15. Microwave Absorbing Properties of Metallic Glass/Polymer Composites

    DTIC Science & Technology

    2011-09-01

    of strategic importance for stealth technology. This work examined high magnetic permeability cobalt -based metallic glasses dispersed in epoxy...of strategic importance for stealth technology. This work examined high magnetic permeability cobalt -based metallic glasses dispersed in epoxy...present day. Lossy materials such as carbonyl iron and ferrites have been used in stealth technology as well as other electromagnetic shielding

  16. Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit.

    PubMed

    Wu, Fu-Fa; Chan, K C; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang

    2014-06-16

    Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19' phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties.

  17. Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit

    PubMed Central

    Wu, Fu-Fa; Chan, K. C.; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang

    2014-01-01

    Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties. PMID:24931632

  18. Metallic glass composition. [That does not embrittle upon annealing

    DOEpatents

    Kroeger, D.M.; Koch, C.C.

    1984-09-14

    This patent pertains to a metallic glass alloy that is either iron-based or nickel-based or based on a mixture of iron and nickel, containing lesser amounts of elements selected from the group boron, silicon, carbon and phosphorous to which is added an amount of a ductility-enhancing element selected from the group cerium, lanthanum, praseodymium and neodymium sufficient to increase ductility of the metallic glass upon annealing.

  19. Dynamic mechanical properties of a Ti-based metallic glass matrix composite

    SciTech Connect

    Li, Jinshan Cui, Jing; Bai, Jie; Kou, Hongchao; Wang, Jun; Qiao, Jichao

    2015-04-21

    Dynamic mechanical behavior of a Ti{sub 50}Zr{sub 20}Nb{sub 12}Cu{sub 5}Be{sub 13} bulk metallic glass composite was investigated using mechanical spectroscopy in both temperature and frequency domains. Storage modulus G′ and loss modulus G″ are determined by temperature, and three distinct regions corresponding to different states in the bulk metallic glass composite are characterized. Physical parameters, such as atomic mobility and correlation factor χ, are introduced to analyze dynamic mechanical behavior of the bulk metallic glass composite in the framework of quasi-point defects (QPD) model. The experimental results are in good agreement with the prediction of QPD model.

  20. Bulk metallic glasses and their composites: Composition optimization, thermal stability, and microstructural tunability

    NASA Astrophysics Data System (ADS)

    Khalifa, Hesham Ezzat

    A design protocol utilizing common elements for bulk metallic glass formation has been employed to develop novel, low cost Fe-, and Ti- based bulk metallic glasses. A critical obstacle that was successfully overcome in this work is the omission of beryllium in these alloys. Beryllium is of vital importance in many bulk metallic glass forming systems, but it is expensive and poses considerable health risks. Bulk metallic glasses in these novel Fe-, and Ti-based systems exhibit extremely high mechanical strength and excellent thermal stability. Devitrification and cooling rate experiments were used to identify crystalline phase formation and assess activation energy for crystallization, as well as to explore and develop ductile BMG composites. To better control microstructure in these BMG composites, a novel processing technique, called semi-solid forging was developed, wherein the alloy melt is heated to above the melt temperature of the glass, but below the melt temperature of the ductile crystalline phase. Such an approach permits the maintenance of a glassy, or nanocrystalline matrix phase, while simultaneously coarsening and homogenizing the ductile, secondary phase. This processing approach leads to enhanced ductility in the alloys, which, to this point, has not been observed using conventional casting methods. The combination of novel, low-cost, alloy compositions with semi-solid forging has been successfully utilized to develop new high strength structural materials with enhanced ductility and toughness. Microstrutural and mechanical properties of these novel, toughened, BMG composites are presented. A comprehensive analysis of the relationship between deformation mechanisms and microstructure reveals that enhanced ductility is predicated on matching fundamental mechanical and microstructural length scales in a Ti-Ni-Si-Mo BMG composite. Under optimized microstructural conditions, a maximum compressive strength exceeding 2400 MPa with ˜ 30% total strain to

  1. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-04-12

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  2. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  3. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  4. Plasmonic glasses: optical properties of amorphous metal-dielectric composites.

    PubMed

    Antosiewicz, Tomasz J; Apell, S Peter

    2014-01-27

    Plasmonic glasses composed of metallic inclusions in a host dielectric medium are investigated for their optical properties. Such structures characterized by short-range order can be easily fabricated using bottom-up, self-organization methods and may be utilized in a number of applications, thus, quantification of their properties is important. We show, using T-Matrix calculations of 1D, 2D, and 3D plasmonic glasses, that their plasmon resonance position oscillates as a function of the particle spacing yielding blue- and redshifts up to 0.3 eV in the visible range with respect to the single particle surface plasmon. Their properties are discussed in light of an analytical model of an average particle's polarizability that originates from a coupled dipole methodology.

  5. Compositional landscape for glass formation in metal alloys.

    PubMed

    Na, Jong Hyun; Demetriou, Marios D; Floyd, Michael; Hoff, Andrew; Garrett, Glenn R; Johnson, William L

    2014-06-24

    A high-resolution compositional map of glass-forming ability (GFA) in the Ni-Cr-Nb-P-B system is experimentally determined along various compositional planes. GFA is shown to be a piecewise continuous function formed by intersecting compositional subsurfaces, each associated with a nucleation pathway for a specific crystalline phase. Within each subsurface, GFA varies exponentially with composition, wheres exponential cusps in GFA are observed when crossing from one crystallization pathway to another. The overall GFA is shown to peak at multiple exponential hypercusps that are interconnected by ridges. At these compositions, quenching from the high-temperature melt yields glassy rods with diameters exceeding 1 cm, whereas for compositions far from these cusps the critical rod diameter drops precipitously and levels off to 1 to 2 mm. The compositional landscape of GFA is shown to arise primarily from an interplay between the thermodynamics and kinetics of crystal nucleation, or more precisely, from a competition between driving force for crystallization and liquid fragility.

  6. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    SciTech Connect

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-07

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 {mu}{Omega} cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  7. Soft magnetic composites manufactured by warm co-extrusion of bulk metallic glass and steel powders

    NASA Astrophysics Data System (ADS)

    Johnson, Francis; Raber, Thomas R.; Zabala, Robert J.; Buresh, Steve J.; Tanico, Brian

    2013-05-01

    Soft magnetic composites of Fe-based bulk metallic glass and low-alloy steel have been manufactured by warm co-extrusion of precursor powders at temperatures within the supercooled liquid region of the glass. Composites were manufactured with amorphous volume fractions of 75%, 67%, and 100%. Full consolidation of the constituent powders was observed with the bulk metallic glass remaining substantially amorphous. The composite electrical resistivity was observed to be anisotropic with a resistivity of 79 μΩ cm measured transverse to the extrusion axis in a sample with 75% amorphous volume fraction. A 0-3 connectivity pattern with the low-resistivity steel phase embedded in a 3-dimensionally connected high-resistivity bulk metallic glass phase was observed with scanning electron microscopy. This confirms that the flow characteristics of the bulk metallic glass and the steel powders were comparable during extrusion at these temperatures. The saturation magnetization of 1.3 T was consistent with the volume weighted average of the saturation magnetization of the two phases. A relatively high quasistatic coercivity of 8 Oe was measured and is likely due to slight crystallization of the bulk metallic glass as well as domain wall pinning at prior particle boundaries. Careful control of the thermal environment during the extrusion process is required to minimize glass crystallization and achieve the desired balance of magnetic and electrical properties.

  8. Computation assisted design of favored composition for ternary Mg-Cu-Y metallic glass formation.

    PubMed

    Wang, Q; Li, J H; Liu, B X

    2015-06-14

    With the aid of ab initio calculations, a realistic interatomic potential was constructed for the Mg-Cu-Y ternary system under the proposed formalism of smoothed and long-range second-moment approximation of tight-binding. Taking the potential as the starting base, an atomistic computation/simulation route was developed for designing favored and optimized compositions for Mg-Cu-Y metallic glass formation. Simulations revealed that the physical origin of metallic glass formation is the collapse of crystalline lattice when solute concentration exceeds a critical value, thus leading to predict a hexagonal region in the Mg-Cu-Y composition triangle, within which metallic glass formation is energetically favored. It is proposed that the hexagonal region can be defined as the intrinsic glass formation region, or quantitative glass formation ability of the system. Inside the hexagonal region, the driving force for formation of each specific glassy alloy was further calculated and correlated with its forming ability in practice. Calculations pinpointed the optimized stoichiometry in the Mg-Cu-Y system to be Mg64Cu16Y20, at which the formation driving force reaches its maximum, suggesting that metallic glasses designed to have compositions around Mg64Cu16Y20 are most stable or easiest to obtain. The predictions derived directly from the atomistic simulations are supported by experimental observations reported so far in the literature. Furthermore, Honeycutt-Anderson analysis indicated that pentagonal bipyramids (although not aggregating to form icosahedra) dominate in the local structure of the Mg-Cu-Y metallic glasses. A microscopic picture of the medium-range packing can then be described as an extended network of the pentagonal bipyramids, entangled with the fourfold and sixfold disclination lines, jointly fulfilling the space of the metallic glasses.

  9. Research of structure, mechanical and operation properties of glass-metal composites

    NASA Astrophysics Data System (ADS)

    Lyubimova, O. N.; Lyubimov, E. V.; Solonenko, E. P.; Morkovin, A. V.; Dryuk, S. A.

    2016-11-01

    The technological bases for the creation of the new structural material—glass-metal composite—are explored in this paper. Properties of the new material: structure and properties of the contact zone of glass and steel, tensile strength under static and dynamic loading, corrosion resistance and abrasion resistance under abrasive wear in the corrosive environment are theoretically and experimentally studied. The limit of thermal stability for experimental composite specimens equals 440°C. Corrosion tests show that the corrosion acceleration is the same for all composite specimens and does not depend on the solution concentration and the initial specimen weight. Steel specimens show significant changes in geometrical characteristics in comparison with composite specimens. Its prospect and ability to compete with steel is proved. The practical application is proposed for glass-metal composite rods.

  10. Low beryllium content Zr-based bulk metallic glass composite with plasticity and work hardenability

    SciTech Connect

    Zheng, Q. E-mail: dujuan@nimte.ac.cn; Du, J. E-mail: dujuan@nimte.ac.cn

    2014-01-28

    A modified Zr-based bulk metallic glass matrix composite Zr{sub 47.67}Cu{sub 40}Ti{sub 3.66}Ni{sub 2.66}Be{sub 6} has been produced by increasing the contents of elements of Zr and Cu with higher Poisson ratio and reducing the contents of Ti, Ni, and Be elements with lower Poisson ratio based on famous metallic glass former Vitreloy 1. A compressive yielding strength of 1804 MPa, fracture strength of 1938 MPa and 3.5% plastic strain was obtained for obtained metallic glass composite. Also, work-hardening behavior was observed during compressive experiment which was ascribed to the interaction of the in situ precipitated CuZr phase and shear bands.

  11. Fracture Morphology and Local Deformation Characteristics in the Metallic Glass Matrix Composite Under Tension

    NASA Astrophysics Data System (ADS)

    Wang, Y. S.; Sun, X. H.; Hao, G. J.; Guo, Z. X.; Zhang, Y.; Lin, J. P.; Sui, M. L.; Qiao, J. W.

    2017-04-01

    Fracture and deformation characteristics of the Ti-based metallic glass matrix composite have been studied by the tensile test and the in situ TEM tension test. Typically, the composite exhibits the high strength and considerable plasticity. Microscopically, it was found that shear deformation zone formed at the crack tip in glass phase, which can bring about quick propagation of shear bands. However, the plastic deformation zone nearby the crack tip in dendrites will postpone or retard the crack extension by dislocations. The attributions of micro-deformations to mechanical properties of composites were discussed.

  12. Fibre-matrix bond strength studies of glass, ceramic, and metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grande, D. H.; Mandell, J. F.; Hong, K. C. C.

    1988-01-01

    An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.

  13. Fibre-matrix bond strength studies of glass, ceramic, and metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grande, D. H.; Mandell, J. F.; Hong, K. C. C.

    1988-01-01

    An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.

  14. Three-dimensional imaging of shear bands in bulk metallic glass composites.

    PubMed

    Hunter, A H; Araullo-Peters, V; Gibbons, M; Restrepo, O D; Niezgoda, S R; Windl, W; Flores, K M; Hofmann, D C; Marquis, E A

    2016-12-01

    The mechanism of the increase in ductility in bulk metallic glass matrix composites over monolithic bulk metallic glasses is to date little understood, primarily because the interplay between dislocations in the crystalline phase and shear bands in the glass could neither be imaged nor modelled in a validated way. To overcome this roadblock, we show that shear bands can be imaged in three dimensions by atom probe tomography from density variations in the reconstructed atomic density, which density-functional theory suggests being a local-work function effect. Imaging of near-interface shear bands in Ti48 Zr20 V12 Cu5 Be15 bulk metallic glass matrix composite permits measurement of their composition, thickness, branching and interactions with the dendrite interface. These results confirm that shear bands here nucleate from stress concentrations in the glass due to intense, localized plastic deformation in the dendrites rather than intrinsic structural inhomogeneities. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  15. Optical properties of dy doped lead and bismuth borate glasses - effect of glass composition, metal and semiconducting nanoparticles

    NASA Astrophysics Data System (ADS)

    Ooi, Hio Giap

    The optical properties of Dy3+ ions in lead borate and bismuth borate glasses are studied as a function of glass composition with PbO content (29.5 to 69.5mol%) and Bi2O3 content (29.5 to 59.5 mol%). We also studied the effect of metal and semiconducting nanoparticles on the absorption and fluorescence emission of Dy3+ ions in both lead and bismuth borate glasses. The absorption coefficient at each wavelength is obtained from the optical absorption spectrum of a glass sample, and the number density of rare-earth (RE) ions is calculated from the measurement of the glass density. These two parameters are then used to calculate the oscillator strength of each transition using Judd-Ofelt theory. Using the oscillator strength for each transition, we obtained the intensity parameters which represent changes in the symmetry of the ligand field at the Dy 3+ site (due to structural group changes and changes in Dy-O covalency). Radiative transition probabilities, the radiative lifetime of the excited states and the branching ratios are then obtained from these intensity parameters. The fluorescence spectra, obtained using 355 nm and 458 nm laser excitation, are analyzed by determining the area ratio of yellow/blue (Y/B) peaks and the wavelength of the hypersensitive transition (HST). The compositional dependence and effect of nanoparticles on the stimulated emission cross-section (sigmap), are then evaluated using radiative transition probability, the refractive index of the host glass, effective fluorescence linewidth, and the position of the band. In all of the glass systems, it was found that the optical properties are strongly influenced by structural changes arising from compositional variation and size of nanoparticles. Dy 3+ transitions exhibit large sigmap suggesting the possible utilization of these materials in laser applications.

  16. Atomistic Design of Favored Compositions for Synthesizing the Al-Ni-Y Metallic Glasses

    PubMed Central

    Wang, Q.; Li, J. H.; Liu, J. B.; Liu, B. X.

    2015-01-01

    For a ternary alloy system promising for obtaining the so-called bulk metallic glasses (BMGs), the first priority issue is to predict the favored compositions, which could then serve as guidance for the appropriate alloy design. Taking the Al-Ni-Y system as an example, here we show an atomistic approach, which is developed based on a recently constructed and proven realistic interatomic potential of the system. Applying the Al-Ni-Y potential, series simulations not only clarify the glass formation mechanism, but also predict in the composition triangle, a hexagonal region, in which a disordered state, i.e., the glassy phase, is favored energetically. The predicted region is defined as glass formation region (GFR) for the ternary alloy system. Moreover, the approach is able to calculate an amorphization driving force (ADF) for each possible glassy alloy located within the GFR. The calculations predict an optimized sub-region nearby a stoichiometry of Al80Ni5Y15, implying that the Al-Ni-Y metallic glasses designed in the sub-region could be the most stable. Interestingly, the atomistic predictions are supported by experimental results observed in the Al-Ni-Y system. In addition, structural origin underlying the stability of the Al-Ni-Y metallic glasses is also discussed in terms of a hybrid packing mode in the medium-range scale. PMID:26592568

  17. Bulk metallic glass matrix composites: Processing, microstructure, and application as a kinetic energy penetrator

    NASA Astrophysics Data System (ADS)

    Dandliker, Richard B.

    The development of alloys with high glass forming ability allows fabrication of bulk samples of amorphous metal. This capability makes these materials available for applications which require significant material thickness in all three dimensions. Superior mechanical properties and advantages in processing make metallic glass a choice candidate as a matrix material for composites. This study reports techniques for making composites by melt-infiltration casting using the alloy Zrsb{41.2}Tisb{13.8}Cusb{12.5}Nisb{10.0}Besb{22.5} (VitreloyspTM 1) as a matrix material. Composite rods 5 cm in length and 7 mm in diameter were made and found to have a nearly fully amorphous matrix; there was less than 3 volume percent crystallized matrix material. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed samples were made with uniaxially aligned tungsten and carbon steel continuous wire reinforcement; the majority of the analysis presented is of these samples. The measured porosity was typically less than 3%. The results also indicate necessary guidelines for developing processing techniques for large scale production, new reinforcement materials, and other metallic glass compositions. Analysis of the microstructure of the tungsten wire and steel wire reinforced composites was performed by x-ray diffraction, scanning electron microscopy, scanning Auger microscopy, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The most common phase in the crystallized matrix is most likely a Laves phase with the approximate formula Besb{12}Zrsb3TiNiCu. In tungsten-reinforced composites, a crystalline reaction layer 240 nm thick of tungsten nanocrystals in an amorphous matrix formed. In the steel reinforced composites, the reaction layer was primarily composed of a mixed metal carbide, mainly ZrC. One promising application of the metallic glass matrix composite is as a kinetic

  18. Bulk Metallic Glasses and Composites for Optical and Compliant Mechanisms

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C.; Agnes, Gregory S.

    2013-01-01

    Mechanisms are used widely in engineering applications due to their ability to translate force and movement. They are found in kinematic pairs, gears, cams, linkages, and in flexure mechanisms (also known as compliant mechanisms). Mechanisms and flexures are used widely in spacecraft design, especially in the area of optics, where precise positioning of telescope mirrors requires elastic flexing of elements. A compliant mechanism is generally defined as a flexible mechanism that uses an elastic body deformation to cause a displacement (such as positing a mirror). The mechanisms are usually constructed as a single monolithic piece of material, and contain thin struts to allow for large elastic bending with low input force. This creates the largest problem with developing precise mechanisms; they must be fabricated from a single piece of metal, but are required to have strict accuracy on their dimensions. They are generally required to have high strength, elasticity, and low coefficient of thermal expansion.

  19. Composition mediated serration dynamics in Zr-based bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Qiao, J. W.; Tian, H.; Sun, B. A.; Wang, B. C.; Xu, B. S.; Chen, M. W.

    2015-11-01

    The composition mediated serration dynamics in Zr-based bulk metallic glasses (BMGs) is investigated by statistics analyses of the elastic-energy density, and free volumes during shear-banding are beneficial to understand serrated-flow behavior. The amplitude and elastic-energy density display a gradually increasing and then decreasing trend with increasing the content of Zr. It is based on the free-volume theory describing the atomic-level structure of ternary Zr-Cu-Al BMGs. The good agreement between the molecular dynamics simulation and experimental results provides evidence for the variation of free volumes as the elementary mechanism of composition mediated serration dynamics.

  20. Composition mediated serration dynamics in Zr-based bulk metallic glasses

    SciTech Connect

    Wang, Z.; Qiao, J. W. E-mail: mwchen@wpi-aimr.tohoku.ac.jp; Wang, B. C.; Xu, B. S.; Tian, H.; Sun, B. A.; Chen, M. W. E-mail: mwchen@wpi-aimr.tohoku.ac.jp

    2015-11-16

    The composition mediated serration dynamics in Zr-based bulk metallic glasses (BMGs) is investigated by statistics analyses of the elastic-energy density, and free volumes during shear-banding are beneficial to understand serrated-flow behavior. The amplitude and elastic-energy density display a gradually increasing and then decreasing trend with increasing the content of Zr. It is based on the free-volume theory describing the atomic-level structure of ternary Zr-Cu-Al BMGs. The good agreement between the molecular dynamics simulation and experimental results provides evidence for the variation of free volumes as the elementary mechanism of composition mediated serration dynamics.

  1. Microyielding of core-shell crystal dendrites in a bulk-metallic-glass matrix composite

    SciTech Connect

    Huang, E. -Wen; Qiao, Junwei; Winiarski, Bartlomiej; Lee, Wen -Jay; Scheel, Mario; Chuang, Chih -Pin; Liaw, Peter K.; Lo, Yu -Chieh; Zhang, Yong; Di Michiel, Marco

    2014-03-18

    In-situ synchrotron x-ray experiments have been used to follow the evolution of the diffraction peaks for crystalline dendrites embedded in a bulk metallic glass matrix subjected to a compressive loading-unloading cycle. We observe irreversible diffraction-peak splitting even though the load does not go beyond half of the bulk yield strength. The chemical analysis coupled with the transmission electron microscopy mapping suggests that the observed peak splitting originates from the chemical heterogeneity between the core (major peak) and the stiffer shell (minor peak) of the dendrites. A molecular dynamics model has been developed to compare the hkl-dependent microyielding of the bulk metallic-glass matrix composite. As a result, the complementary diffraction measurements and the simulation results suggest that the interfaces between the amorphous matrix and the (211) crystalline planes relax under prolonged load that causes a delay in the reload curve which ultimately catches up with the original path.

  2. Polyamorphism in metalic glass.

    SciTech Connect

    Sheng, H. W.; Liu, H. Z.; Cheng, Y. Q.; Wen, J.; Lee, P.L.; Luo, W.K.; Shastri, S.D.; Ma, E.; X-Ray Science Division; Johns Hopkins Univ.; Chinese Academy of Sciences

    2007-03-01

    A metal, or an alloy, can often exist in more than one crystal structure. The face-centered-cubic and body-centered-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral) coordination environments. Here, we report an in situ X-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce{sub 55}Al{sub 45} metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modeling of the effects of f-electron delocalization. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties due to different bonding and structural characteristics.

  3. An improved tensile deformation model for in-situ dendrite/metallic glass matrix composites

    PubMed Central

    Sun, X. H.; Qiao, J. W.; Jiao, Z. M.; Wang, Z. H.; Yang, H. J.; Xu, B. S.

    2015-01-01

    With regard to previous tensile deformation models simulating the tensile behavior of in-situ dendrite-reinforced metallic glass matrix composites (MGMCs) [Qiao et al., Acta Mater. 59 (2011) 4126; Sci. Rep. 3 (2013) 2816], some parameters, such as yielding strength of the dendrites and glass matrix, and the strain-hardening exponent of the dendrites, are estimated based on literatures. Here, Ti48Zr18V12Cu5Be17 MGMCs are investigated in order to improve the tensile deformation model and reveal the tensile deformation mechanisms. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis for the first time, and those of the glass matrix and composites are obtained by tension. Besides, the tensile behavior of the MGMCs is divided into four stages: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (work-hardening), and (4) plastic-plastic (softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. Thus, the improved model can be applied to clarify and predict the tensile behavior of the MGMCs. PMID:26354724

  4. An improved tensile deformation model for in-situ dendrite/metallic glass matrix composites

    NASA Astrophysics Data System (ADS)

    Sun, X. H.; Qiao, J. W.; Jiao, Z. M.; Wang, Z. H.; Yang, H. J.; Xu, B. S.

    2015-09-01

    With regard to previous tensile deformation models simulating the tensile behavior of in-situ dendrite-reinforced metallic glass matrix composites (MGMCs) [Qiao et al., Acta Mater. 59 (2011) 4126; Sci. Rep. 3 (2013) 2816], some parameters, such as yielding strength of the dendrites and glass matrix, and the strain-hardening exponent of the dendrites, are estimated based on literatures. Here, Ti48Zr18V12Cu5Be17 MGMCs are investigated in order to improve the tensile deformation model and reveal the tensile deformation mechanisms. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis for the first time, and those of the glass matrix and composites are obtained by tension. Besides, the tensile behavior of the MGMCs is divided into four stages: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (work-hardening), and (4) plastic-plastic (softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. Thus, the improved model can be applied to clarify and predict the tensile behavior of the MGMCs.

  5. An improved tensile deformation model for in-situ dendrite/metallic glass matrix composites.

    PubMed

    Sun, X H; Qiao, J W; Jiao, Z M; Wang, Z H; Yang, H J; Xu, B S

    2015-09-10

    With regard to previous tensile deformation models simulating the tensile behavior of in-situ dendrite-reinforced metallic glass matrix composites (MGMCs) [Qiao et al., Acta Mater. 59 (2011) 4126; Sci. Rep. 3 (2013) 2816], some parameters, such as yielding strength of the dendrites and glass matrix, and the strain-hardening exponent of the dendrites, are estimated based on literatures. Here, Ti48Zr18V12Cu5Be17 MGMCs are investigated in order to improve the tensile deformation model and reveal the tensile deformation mechanisms. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis for the first time, and those of the glass matrix and composites are obtained by tension. Besides, the tensile behavior of the MGMCs is divided into four stages: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (work-hardening), and (4) plastic-plastic (softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. Thus, the improved model can be applied to clarify and predict the tensile behavior of the MGMCs.

  6. Effect of chemical composition on the shock response of Zr-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Brown, A. D.; Wang, F.; Laws, K. J.; Eakins, D.; Chapman, D. J.; Hazell, P. J.; Ferry, M.; Escobedo, J. P.

    2015-06-01

    Plate impact experiments were conducted on Zr-based bulk metallic glasses (BMG) with nominal compositions of Zr55Cu30Ni5Al30 and Zr46Cu38Ag8Al38. Velocity interferometry was used to measure the free surface velocity (FSV) histories. These measurements allowed calculation of the Hugoniot elastic limits and onset stresses of fracture (i.e. spall strength) for each alloy. The soft recovered specimens were fully characterized by means of optical and electron microscopy, x-ray diffraction and differential scanning calorimetry. The characterization results aided to assess the effect of chemical composition on the microstructural evolution, i.e. phase changes or crystallization, within the BMGs during shock loading. These changes were then correlated to the differences in strength and ductility on the nominally brittle amorphous BMGs. The most significant results from this study will be presented. State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology.

  7. Plasticity-improved Zr-Cu-Al bulk metallic glass matrix composites containing martensite phase

    SciTech Connect

    Sun, Y.F.; Wei, B.C.; Wang, Y.R.; Li, W.H.; Cheung, T.L.; Shek, C.H.

    2005-08-01

    Zr{sub 48.5}Cu{sub 46.5}Al{sub 5} bulk metallic glass matrix composites with diameters of 3 and 4 mm were produced through water-cooled copper mold casting. Micrometer-sized bcc based B2 structured CuZr phase containing martensite plate, together with some densely distributed nanocrystalline Zr{sub 2}Cu and plate-like Cu{sub 10}Zr{sub 7} compound, was found embedded in a glassy matrix. The microstructure formation strongly depends on the composition and cooling rate. Room temperature compression tests reveal significant strain hardening and plastic strains of 7.7% and 6.4% before failure are obtained for the 3-mm- and 4-mm-diam samples, respectively. The formation of the martensite phase is proposed to contribute to the strain hardening and plastic deformation of the materials.

  8. Plasticity-improved Zr-Cu-Al bulk metallic glass matrix composites containing martensite phase

    NASA Astrophysics Data System (ADS)

    Sun, Y. F.; Wei, B. C.; Wang, Y. R.; Li, W. H.; Cheung, T. L.; Shek, C. H.

    2005-08-01

    Zr48.5Cu46.5Al5 bulk metallic glass matrix composites with diameters of 3 and 4mm were produced through water-cooled copper mold casting. Micrometer-sized bcc based B2 structured CuZr phase containing martensite plate, together with some densely distributed nanocrystalline Zr2Cu and plate-like Cu10Zr7 compound, was found embedded in a glassy matrix. The microstructure formation strongly depends on the composition and cooling rate. Room temperature compression tests reveal significant strain hardening and plastic strains of 7.7% and 6.4% before failure are obtained for the 3-mm- and 4-mm-diam samples, respectively. The formation of the martensite phase is proposed to contribute to the strain hardening and plastic deformation of the materials.

  9. Twinning-induced plasticity (TWIP) and work hardening in Ti-based metallic glass matrix composites.

    PubMed

    Fan, J; Qiao, J W; Wang, Z H; Rao, W; Kang, G Z

    2017-05-12

    The present study demonstrates that Ti-based metallic glass matrix composites (MGMCs) with a normal composition of Ti43Zr32Ni6Ta5Be14 containing ductile dendrites dispersed in the glass matrix has been developed, and deformation mechanisms about the tensile property have been investigated by focusing on twinning-induced plasticity (TWIP) effect. The Ti-based MGMC has excellent tensile properties and pronounced tensile work-hardening capacity, with a yield strength of 1100 MPa and homogeneous elongation of 4%. The distinguished strain hardening is ascribed to the formation of deformation twinning within the dendrites. Twinning generated in the dendrites works as an obstacle for the rapid propagation of shear bands, and then, the localized necking is avoided, which ensures the ductility of such kinds of composites. Besides, a finite-element model (FEM) has been established to explain the TWIP effect which brings out a work-hardening behavior in the present MGMC instead of a localized strain concentration. According to the plasticity theory of traditional crystal materials and some new alloys, TWIP effect is mainly controlled by stacking fault energy (SFE), which has been analyzed intensively in the present MGMC.

  10. Microyielding of core-shell crystal dendrites in a bulk-metallic-glass matrix composite

    DOE PAGES

    Huang, E. -Wen; Qiao, Junwei; Winiarski, Bartlomiej; ...

    2014-03-18

    In-situ synchrotron x-ray experiments have been used to follow the evolution of the diffraction peaks for crystalline dendrites embedded in a bulk metallic glass matrix subjected to a compressive loading-unloading cycle. We observe irreversible diffraction-peak splitting even though the load does not go beyond half of the bulk yield strength. The chemical analysis coupled with the transmission electron microscopy mapping suggests that the observed peak splitting originates from the chemical heterogeneity between the core (major peak) and the stiffer shell (minor peak) of the dendrites. A molecular dynamics model has been developed to compare the hkl-dependent microyielding of the bulkmore » metallic-glass matrix composite. As a result, the complementary diffraction measurements and the simulation results suggest that the interfaces between the amorphous matrix and the (211) crystalline planes relax under prolonged load that causes a delay in the reload curve which ultimately catches up with the original path.« less

  11. Insights from the Lattice-Strain Evolution on Deformation Mechanisms in Metallic-Glass-Matrix Composites

    SciTech Connect

    Jia, Haoling; Zheng, Lili; Li, Weidong; Li, Nan; Qiao, Junwei; Wang, Gongyao; Ren, Yang; Liaw, Peter K.; Gao, Yanfei

    2015-02-18

    In this paper, in situ high-energy synchrotron X-ray diffraction experiments and micromechanics-based finite element simulations have been conducted to examine the lattice-strain evolution in metallic-glass-matrix composites (MGMCs) with dendritic crystalline phases dispersed in the metallic-glass matrix. Significant plastic deformation can be observed prior to failure from the macroscopic stress–strain curves in these MGMCs. The entire lattice-strain evolution curves can be divided into elastic–elastic (denoting deformation behavior of matrix and inclusion, respectively), elastic–plastic, and plastic–plastic stages. Characteristics of these three stages are governed by the constitutive laws of the two phases (modeled by free-volume theory and crystal plasticity) and geometric information (crystalline phase morphology and distribution). The load-partitioning mechanisms have been revealed among various crystalline orientations and between the two phases, as determined by slip strain fields in crystalline phase and by strain localizations in matrix. Finally, implications on ductility enhancement of MGMCs are also discussed.

  12. Insights from the Lattice-Strain Evolution on Deformation Mechanisms in Metallic-Glass-Matrix Composites

    DOE PAGES

    Jia, Haoling; Zheng, Lili; Li, Weidong; ...

    2015-02-18

    In this paper, in situ high-energy synchrotron X-ray diffraction experiments and micromechanics-based finite element simulations have been conducted to examine the lattice-strain evolution in metallic-glass-matrix composites (MGMCs) with dendritic crystalline phases dispersed in the metallic-glass matrix. Significant plastic deformation can be observed prior to failure from the macroscopic stress–strain curves in these MGMCs. The entire lattice-strain evolution curves can be divided into elastic–elastic (denoting deformation behavior of matrix and inclusion, respectively), elastic–plastic, and plastic–plastic stages. Characteristics of these three stages are governed by the constitutive laws of the two phases (modeled by free-volume theory and crystal plasticity) and geometric informationmore » (crystalline phase morphology and distribution). The load-partitioning mechanisms have been revealed among various crystalline orientations and between the two phases, as determined by slip strain fields in crystalline phase and by strain localizations in matrix. Finally, implications on ductility enhancement of MGMCs are also discussed.« less

  13. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    NASA Astrophysics Data System (ADS)

    Maaroufi, A.; Oabi, O.; Lucas, B.

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO-55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator - semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10-1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10-8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson-Cole model, and an account of the interpretation of results is given.

  14. Experimental Investigation of Low-Velocity Repeated Impacts on Glass Fiber Metal Composites

    NASA Astrophysics Data System (ADS)

    Rajkumar, G. R.; Krishna, M.; Narasimha Murthy, H. N.; Sharma, S. C.; Vishnu Mahesh, K. R.

    2012-07-01

    The aim of this study was to experimentally investigate the effect of repeated low-velocity impacts on tensile strength of fiber metal laminates (FMLs) using instrumented drop weight impact tester. FMLs were fabricated layer by layer intercalating three layers of aluminum 6061 and two layers of glass fiber-reinforced epoxy. The FMLs were subjected to repeated low-velocity impacts (<10 m/s) at the same location on the FML. The degradation of mechanical property due to impact(s) was studied using Zwick UTM at distances of 0, 20, 40, and 60 mm from the impact point. Results indicate that ultimate tensile strength, failure strain, and ductility of all specimens initially decrease, and then remain constant with increase in number of impacts. A closer examination of impacted FML by scanning electron microscope indicates that thinning and shear fracture in aluminum layers, as well as delamination, and fiber failure in composites plies were present.

  15. Dynamic Deformation Behaviors of an In Situ Ti-Based Metallic Glass Matrix Composite

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Zhang, T. W.; Yang, H. J.; Qiao, J. W.

    2016-11-01

    Quasi-static and dynamic deformation behaviors, fracture characteristics, and microstructural evolution of an in situ dendrite-reinforced metallic glass matrix composite: Ti50Zr20V10Cu5Be15 within a wide range of strain rates are investigated. Compared with the quasi-static compression, the yielding stress increases, but the macroscopic plasticity significantly decreases upon dynamic compression. The effects of the strain rate on strain hardening upon quasi-static loading and flow stress upon dynamic loading are evaluated, respectively. The Zerilli-Armstrong (Z-A) model based on dendrite-dominated mechanism is employed to further uncover the dependence of the yielding stress on the strain rate.

  16. Atomic interaction mechanism for designing the interface of W/Zr-based bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Li, Z. K.; Fu, H. M.; Sha, P. F.; Zhu, Z. W.; Wang, A. M.; Li, H.; Zhang, H. W.; Zhang, H. F.; Hu, Z. Q.

    2015-03-01

    The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on the W substrate surface. Sessile drop experiment proves the prediction and corresponding in-situ coating appears at the interface. Besides, the atomic interaction mechanism was proven to be effective in many other systems by the sessile drop technique. Considering the interfacial morphology, Nb was added into the alloy to fabricate W/Zr-based BMGCs. As expected, the Nb addition effectively suppressed the W-Zr reaction and damage to W fibers. Both the compressive and tensile properties are improved obviously.

  17. Atomic interaction mechanism for designing the interface of W/Zr-based bulk metallic glass composites.

    PubMed

    Li, Z K; Fu, H M; Sha, P F; Zhu, Z W; Wang, A M; Li, H; Zhang, H W; Zhang, H F; Hu, Z Q

    2015-03-11

    The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on the W substrate surface. Sessile drop experiment proves the prediction and corresponding in-situ coating appears at the interface. Besides, the atomic interaction mechanism was proven to be effective in many other systems by the sessile drop technique. Considering the interfacial morphology, Nb was added into the alloy to fabricate W/Zr-based BMGCs. As expected, the Nb addition effectively suppressed the W-Zr reaction and damage to W fibers. Both the compressive and tensile properties are improved obviously.

  18. Revealing homogeneous plastic deformation in dendrite-reinforced Ti-based metallic glass composites under tension

    NASA Astrophysics Data System (ADS)

    Wu, F. F.; Wei, J. S.; Chan, K. C.; Chen, S. H.; Zhao, R. D.; Zhang, G. A.; Wu, X. F.

    2017-02-01

    The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation. In addition, dendrite-reinforce MGCs are verified as being intrinsically ductile, and can be used as good coatings for improving the surface properties of pure titanium or titanium alloys. These findings are helpful in designing, producing, and using MGCs with improved performance properties.

  19. Revealing homogeneous plastic deformation in dendrite-reinforced Ti-based metallic glass composites under tension

    PubMed Central

    Wu, F. F.; Wei, J. S.; Chan, K. C.; Chen, S. H.; Zhao, R. D.; Zhang, G. A.; Wu, X. F.

    2017-01-01

    The tensile plastic deformation of dendrite-reinforced Ti-based metallic glass composites (MGCs) was investigated. It was found that there is a critical normalized strain-hardening rate (NSHR) that determines the plastic stability of MGCs: if the NSHR is larger than the critical value, the plastic deformation of the MGCs will be stable, i.e. the necking and strain localization can be effectively suppressed, resulting in homogeneous plastic elongation. In addition, dendrite-reinforce MGCs are verified as being intrinsically ductile, and can be used as good coatings for improving the surface properties of pure titanium or titanium alloys. These findings are helpful in designing, producing, and using MGCs with improved performance properties. PMID:28195216

  20. Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites

    PubMed Central

    Khanolkar, Gauri R.; Rauls, Michael B.; Kelly, James P.; Graeve, Olivia A.; Hodge, Andrea M.; Eliasson, Veronica

    2016-01-01

    The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding. PMID:26932846

  1. Phase formation and mechanical properties of Cu-Zr-Ti bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Kim, Byoung Jin; Yun, Young Su; Kim, Won Tae; Kim, Do Hyang

    2016-11-01

    The effect of the type of the crystalline phase and its volume fraction on the mechanical property of Cu50Zr50-xTix alloys (x = 0-10) bulk metallic glass composites has been investigated in this study. Up to 6 at% of Ti, B19' phase particles distributed in the glassy matrix, while at 8 and 10% of Ti, B2 phase particles are retained in the glass matrix due to suppression of the eutectoid transformation of B2 phase and by avoidance of martensitic transformation of B2 into B19'. The volume fraction of crystalline phase is strongly dependent on the cooling rate. The larger volume fraction of the crystalline phases results in the lower yield stress, the higher plastic strain, and the more pronounced work hardening behavior. At the crystalline volume fraction below 30%, the variation of the yield strength can be described by the rule of mixture model (ROM), while at the crystalline volume fraction higher than 50% by the load-bearing model (LBM). At the crystal fractions between 30 and 50%, there is a yield strength drop and a transition from the ROM to the LBM. This transition is due to the formation of the crystalline structural framework at higher crystal fraction.

  2. Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

    SciTech Connect

    R, Lisha; P, Geetha; B, Aravind P.; Anantharaman, M. R.; T, Hysen; Ojha, S.; Avasthi, D. K.; Ramanujan, R. V.

    2015-06-24

    The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

  3. Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

    NASA Astrophysics Data System (ADS)

    R, Lisha; T, Hysen; P, Geetha; B, Aravind P.; Ojha, S.; Avasthi, D. K.; Ramanujan, R. V.; Anantharaman, M. R.

    2015-06-01

    The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

  4. Local melting to design strong and plastically deformable bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Qin, Yue-Sheng; Han, Xiao-Liang; Song, Kai-Kai; Tian, Yu-Hao; Peng, Chuan-Xiao; Wang, Li; Sun, Bao-An; Wang, Gang; Kaban, Ivan; Eckert, Jürgen

    2017-02-01

    Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties.

  5. A finite-deformation constitutive model for bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Marandi, Kianoosh; Shim, V. P. W.

    2014-05-01

    The focus of this study is the development of an elastic-viscoplastic, three-dimensional, finite-deformation constitutive model to describe the large deformation behavior of bulk metallic glass (BMG) composite. A macroscopic theoretical formulation is proposed based on thermodynamic considerations to describe the response at ambient temperature and pressure, as well as at different strain rates. A constitutive equation is derived using the principle of thermodynamics and the augmenting of free energy. This is done by assuming that deformation within the constituent phases of the composite is affine; kinetic equations defining plastic shear and evolution of free volume concentration are then derived. The constitutive model is subsequently implemented in a finite-element program (Abaqus/Explicit) via a user-defined material subroutine. Numerical predictions are compared with experimental results from tests on La-based in situ BMG composite (La-Al-Cu-Ni) specimens cast in-house; this demonstrates that the model is able to describe the material behavior observed.

  6. Local melting to design strong and plastically deformable bulk metallic glass composites

    PubMed Central

    Qin, Yue-Sheng; Han, Xiao-Liang; Song, Kai-Kai; Tian, Yu-Hao; Peng, Chuan-Xiao; Wang, Li; Sun, Bao-An; Wang, Gang; Kaban, Ivan; Eckert, Jürgen

    2017-01-01

    Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties. PMID:28211890

  7. Quinary metallic glass alloys

    DOEpatents

    Lin, X.; Johnson, W.L.

    1998-04-07

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  8. Quinary metallic glass alloys

    DOEpatents

    Lin, Xianghong; Johnson, William L.

    1998-01-01

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  9. Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C.; Roberts, Scott; Kozachkov, Henry; Demetriou, Marios D.; Schramm, Joseph P.; Johnson, William L.

    2012-01-01

    Bulk metallic glasses (BMGs), a class of amorphous metals defined as having a thickness greater than 1 mm, are being broadly investigated by NASA for use in spacecraft hardware. Their unique properties, attained from their non-crystalline structure, motivate several game-changing aerospace applications. BMGs have low melting temperatures so they can be cheaply and repeatedly cast into complex net shapes, such as mirrors or electronic casings. They are extremely strong and wear-resistant, which motivates their use in gears and bearings. Amorphous metal coatings are hard, corrosion-resistant, and have high reflectivity. BMG composites, reinforced with soft second phases, can be fabricated into energy-absorbing cellular panels for orbital debris shielding. One limitation of BMG materials is their inability to be welded, bonded, brazed, or fastened in a convenient method to form larger structures. Cellular structures (which can be classified as trusses, foams, honeycombs, egg boxes, etc.) are useful for many NASA, commercial, and military aerospace applications, including low-density paneling and shields. Although conventional cellular structures exhibit high specific strength, their porous structures make them challenging to fabricate. In particular, metal cellular structures are extremely difficult to fabricate due to their high processing temperatures. Aluminum honeycomb sandwich panels, for example, are used widely as spacecraft shields due to their low density and ease of fabrication, but suffer from low strength. A desirable metal cellular structure is one with high strength, combined with low density and simple fabrication. The thermoplastic joining process described here allows for the fabrication of monolithic BMG truss-like structures that are 90% porous and have no heat-affected zone, weld, bond, or braze. This is accomplished by welding the nodes of stacked BMG composite panels using a localized capacitor discharge, forming a single monolithic structure

  10. A Tensile Deformation Model for In-situ Dendrite/Metallic Glass Matrix Composites

    PubMed Central

    Qiao, J. W.; Zhang, T.; Yang, F. Q.; Liaw, P. K.; Pauly, S.; Xu, B. S.

    2013-01-01

    In-situ dendrite/metallic glass matrix composites (MGMCs) with a composition of Ti46Zr20V12Cu5Be17 exhibit ultimate tensile strength of 1510 MPa and fracture strain of about 7.6%. A tensile deformation model is established, based on the five-stage classification: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (yield platform), (4) plastic-plastic (work hardening), and (5) plastic-plastic (softening) stages, analogous to the tensile behavior of common carbon steels. The constitutive relations strongly elucidate the tensile deformation mechanism. In parallel, the simulation results by a finite-element method (FEM) are in good agreement with the experimental findings and theoretical calculations. The present study gives a mathematical model to clarify the work-hardening behavior of dendrites and softening of the amorphous matrix. Furthermore, the model can be employed to simulate the tensile behavior of in-situ dendrite/MGMCs. PMID:24085187

  11. Effects of chemical composition on the shock response of Zr-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Escobedo, J. P.; Chapman, D. J.; Laws, K. J.; Brown, A. D.; Wang, F.; Eakins, D.; Hazell, P. J.; Ferry, M.

    2017-01-01

    The effect chemical composition on the shock response of two bulk metallic glass (BMG) alloys with slightly different elemental compositions (Zr55Cu10Ni5Al30 and Zr46Cu38Ag8Al8) has been investigated. Plate-impact experiments were conducted at a peak compressive stress of ˜10GPa, above the expected elastic limit of these alloys (˜7GPa). Velocity interferometry was used to measure the particle (up) and free surface velocity (FSV) histories. These measurements allowed calculation of the Hugoniot elastic limits and onset stresses of fracture (i.e. spall strength) for each alloy. The soft recovered specimens were characterized by means of optical and electron microscopy. It was found that the Zr55Cu10Ni5Al30 exhibited a higher HEL and spall strength and a smooth fracture surface morphology consisting of dimple-like features. Conversely, the lower spall strength of the Zr46Cu38Ag8Al38 alloy seems to correlate with rougher fracture surface that shows cup-cone features associated with a predominantly brittle dynamic fracture.

  12. Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives From Bulk Metallic Glasses and Composites

    NASA Technical Reports Server (NTRS)

    Hoffman, Douglas C.; Potter, Benjamin

    2013-01-01

    Quality knives are typically fabricated from high-strength steel alloys. Depending on the application, there are different requirements for mechanical and physical properties that cause problems for steel alloys. For example, diver's knives are generally used in salt water, which causes rust in steel knives. Titanium diver's knives are a popular alternative due to their salt water corrosion resistance, but are too soft to maintain a sharp cutting edge. Steel knives are also magnetic, which is undesirable for military applications where the knives are used as a tactical tool for diffusing magnetic mines. Steel is also significantly denser than titanium (8 g/cu cm vs. 4.5 g/cu cm), which results in heavier knives for the same size. Steel is hard and wear-resistant, compared with titanium, and can keep a sharp edge during service. A major drawback of both steel and titanium knives is that they must be ground or machined into the final knife shape from a billet. Since most knives have a mirrored surface and a complex shape, manufacturing them is complex. It would be more desirable if the knife could be cast into a net or near-net shape in a single step. The solution to the deficiencies of titanium, steel, and ceramic knives is to fabricate them using bulk metallic glasses (or composites). These alloys can be cast into net or near-net shaped knives with a combination of properties that exceed both titanium and steel. A commercially viable BMG (bulk metallic glass) or composite knife is one that exhibits one or all of the following properties: It is based on titanium, has a self-sharpening edge, can retain an edge during service, is hard, is non-magnetic, is corrosion-resistant against a variety of corrosive environments, is tough (to allow for prying), can be cast into a net-shape with a mirror finish and a complex shape, has excellent wear resistance, and is low-density. These properties can be achieved in BMG and composites through alloy chemistry and processing. For

  13. Metal Halide Optical Glasses.

    DTIC Science & Technology

    1988-01-01

    HEAVY METAL FLUORIDE GLASSES C. T. Moynihan, R. Mossadegh and S. N. Crichton Materials Engineering Department, Rensselaer Polytechnic Institute Troy...and Tesar, A. A., J. Am. Ceram. Soc., 67, p. C-164 (1984). 11. Crichton , S. N., Mossadegh, R., Schroeder, J., and Moynihan, C. T., unpublished data. 12...FLUORIDE GLASSES C. T. Moynihan, S. M. Opalka, R. Mossadegh, S. N. Crichton and A. J. Bruce Center for Glass Science and Technology Materials Engineering

  14. Atomistic modeling to investigate the favored composition for metallic glass formation in the Ca-Mg-Ni ternary system.

    PubMed

    Zhao, S; Li, J H; An, S M; Li, S N; Liu, B X

    2017-05-17

    A realistic interatomic potential was first constructed for the Ca-Mg-Ni system and then applied to Monte Carlo simulations to predict the favored composition for metallic glass formation in the ternary system. The simulations not only predict a hexagonal composition region, within which the Ca-Mg-Ni metallic glass formation is energetically favored, but also pinpoint an optimized sub-region within which the amorphization driving force, i.e. the energy difference between the solid solution and disordered phase, is larger than that outside. The simulations further reveal that the physical origin of glass formation is the solid solution collapsing when the solute atom exceeds the critical solid solubility. Further structural analysis indicates that the pentagonal bi-pyramids dominate in the optimized sub-region. The large atomic size difference between Ca, Mg and Ni extends the short-range landscape and facilitates the development of a hybridized packing model in the medium-range, and eventually enhancing the glass formation in the system. The predictions are well supported by the experimental observations reported so far, and could be of help for designing the ternary glass formation.

  15. Towards an understanding of tensile deformation in Ti-based bulk metallic glass matrix composites with BCC dendrites

    NASA Astrophysics Data System (ADS)

    Kolodziejska, Joanna A.; Kozachkov, Henry; Kranjc, Kelly; Hunter, Allen; Marquis, Emmanuelle; Johnson, William L.; Flores, Katharine M.; Hofmann, Douglas C.

    2016-03-01

    The microstructure and tension ductility of a series of Ti-based bulk metallic glass matrix composite (BMGMC) is investigated by changing content of the β stabilizing element vanadium while holding the volume fraction of dendritic phase constant. The ability to change only one variable in these novel composites has previously been difficult, leading to uninvestigated areas regarding how composition affects properties. It is shown that the tension ductility can range from near zero percent to over ten percent simply by changing the amount of vanadium in the dendritic phase. This approach may prove useful for the future development of these alloys, which have largely been developed experimentally using trial and error.

  16. Development of tough, low-density titanium-based bulk metallic glass matrix composites with tensile ductility

    PubMed Central

    Hofmann, Douglas C.; Suh, Jin-Yoo; Wiest, Aaron; Lind, Mary-Laura; Demetriou, Marios D.; Johnson, William L.

    2008-01-01

    The mechanical properties of bulk metallic glasses (BMGs) and their composites have been under intense investigation for many years, owing to their unique combination of high strength and elastic limit. However, because of their highly localized deformation mechanism, BMGs are typically considered to be brittle materials and are not suitable for structural applications. Recently, highly-toughened BMG composites have been created in a Zr–Ti-based system with mechanical properties comparable with high-performance crystalline alloys. In this work, we present a series of low-density, Ti-based BMG composites with combinations of high strength, tensile ductility, and excellent fracture toughness. PMID:19074287

  17. Controlling the length scale and distribution of the ductile phase in metallic glass composites through friction stir processing

    PubMed Central

    Arora, Harpreet Singh; Mridha, Sanghita; Grewal, Harpreet Singh; Singh, Harpreet; Hofmann, Douglas C; Mukherjee, Sundeep

    2014-01-01

    We demonstrate the refinement and uniform distribution of the crystalline dendritic phase by friction stir processing (FSP) of titanium based in situ ductile-phase reinforced metallic glass composite. The average size of the dendrites was reduced by almost a factor of five (from 24 μm to 5 μm) for the highest tool rotational speed of 900 rpm. The large inter-connected dendrites become more fragmented with increased circularity after processing. The changes in thermal characteristics were measured by differential scanning calorimetry. The reduction in crystallization enthalpy after processing suggests partial devitrification due to the high strain plastic deformation. FSP resulted in increased hardness and modulus for both the amorphous matrix and the crystalline phase. This is explained by interaction of shear bands in amorphous matrix with the strain-hardened dendritic phase. Our approach offers a new strategy for microstructural design in metallic glass composites. PMID:27877687

  18. Microstructural Control via Copious Nucleation Manipulated by In Situ Formed Nucleants: Large-Sized and Ductile Metallic Glass Composites.

    PubMed

    Song, Wenli; Wu, Yuan; Wang, Hui; Liu, Xiongjun; Chen, Houwen; Guo, Zhenxi; Lu, Zhaoping

    2016-10-01

    A novel strategy to control the precipitation behavior of the austenitic phase, and to obtain large-sized, transformation-induced, plasticity-reinforced bulk metallic glass matrix composites, with good tensile properties, is proposed. By inducing heterogeneous nucleation of the transformable reinforcement via potent nucleants formed in situ, the characteristics of the austenitic phase are well manipulated. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Triad ''Metal - Enamel - Glass''

    NASA Astrophysics Data System (ADS)

    Mukhina, T.; Petrova, S.; Toporova, V.; Fedyaeva, T.

    2014-10-01

    This article shows how to change the color of metal and glass. Both these materials are self-sufficient, but sometimes used together. For example, enameling. In this case, the adhesion between metal substrate and stekloobraznae enamel layer, which was conducted on a stretching and a bend, was tested.

  20. Plasticity in Ni59Zr20Ti16Si2Sn3 metallic glass matrix composites containing brass fibers synthesized by warm extrusion of powders

    NASA Astrophysics Data System (ADS)

    Bae, D. H.; Lee, M. H.; Kim, D. H.; Sordelet, D. J.

    2003-09-01

    Deformation behavior of centimeter-scale Ni-based metallic glass matrix composites reinforced by brass fibers, synthesized by warm extrusion of gas atomized powders, has been investigated under the uniaxial compression condition at room temperature. Throughout the extrusion process, all blended spherical powders are elongated along the extrusion direction. The brass fibers are well distributed in the metallic glass matrix for the metallic glass matrix composites containing the brass up to 0.4 in volume fraction and no pores are visible. With increasing the brass content, elastic modulus and strength decrease due to the softness of the brass, but enhanced macroscopic plasticity is observed due to the formation of multiple shear bands, initiated from the interface between brass fiber and metallic glass matrix, as well as their confinement between the brass fibers. These behaviors are not observed in the sample synthesized by warm extrusion of only metallic glass powders.

  1. Developing photorefractive glass composites

    NASA Astrophysics Data System (ADS)

    Duignan, Jason P.; Taylor, Lesley L.; Cook, Gary

    2002-01-01

    The production of a transparent photorefractive glass composite would offer a useful alternative to bulk crystal materials. We aim to produce such a material by incorporating single domain photorefractive Fe:LiNbO3 particles into a refractive index matched glass host. This glass host is also required to be chemically compatible with the photorefractive material. This compatibility will ensure that the Fe:LiNbO3 particles added to the host glass will remain in the intended crystalline phase and not simply dissolve in the glass. Due to the high refractive index of the Fe:LiNbO3 (no equals 2.35 532 nm), producing a chemically compatible and refractive index matched glass host is technically challenging. By examining common Tellurite, Bismuthate, and Gallate glasses as a starting point and then developing new and hybrid glasses, we have succeeded in producing a chemically compatible glass host and also a refractive index matched glass host. We have produced preliminary glass composite samples which contain a large amount of Fe:LiNbO3. We are currently able to retain nearly 90% of the incorporated Fe:LiNbO3 in the correct crystalline phase, a substantial improvement over previous work conducted in this area in recent years. In this paper we present our progress and findings in this area.

  2. Compositional origin of unusual β-relaxation properties in La-Ni-Al metallic glasses

    SciTech Connect

    Zhu, Z. G.; Li, Y. Z.; Wang, Z.; Gao, X. Q.; Wen, P.; Bai, H. Y.; Wang, W. H.; Ngai, K. L.

    2014-08-28

    The β-relaxation of metallic glasses (MGs) bears nontrivial connections to their microscopic and macroscopic properties. In an effort to elucidate the mechanism of the β-relaxation, we studied by dynamical mechanical measurements the change of its properties on varying the composition of La{sub 60}Ni{sub 15}Al{sub 25} in various ways. The properties of the β-relaxation turn out to be very sensitive to the composition. It is found that the isochronal loss peak temperature of β-relaxation, T{sub β,peak}, is effectively determined by the total (La + Ni) content. When Cu is added into the alloy to replace either La, Ni, or Al, the T{sub β,peak} increases with decrease of the (La + Ni) content. The trend is in accordance with data of binary and ternary MGs formed from La, Ni, Al, and Cu. Binary La-Ni MGs have pronounced β-relaxation loss peaks, well separated from the α-relaxation. In contrast, the β-relaxation is not resolved in La-Al and La-Cu MGs, showing up as an excess wing. For the ternary La-Ni-Al MGs, increase of La or Ni content is crucial to lower the T{sub β,peak}. Keeping the Al content fixed, increase of La content lowers the T{sub β,peak} further, indicating the more important role La plays in lowering T{sub β,peak} than Ni. The observed effects on changing the composition of La{sub 60}Ni{sub 15}Al{sub 25} lead to the conclusion that the properties of the β-relaxation are mainly determined by the interaction between the largest solvent element, La, and the smallest element, Ni. From our data, it is further deduced that La and Ni have high mobility in the MGs, and this explains why the β-relaxation in this La-based MGs is prominent and well resolved from the α-relaxation as opposed to Pd- and Zr-based MGs where the solvent and largest atoms, Pd and Zr, are the least mobile.

  3. Compositional origin of unusual β-relaxation properties in La-Ni-Al metallic glasses.

    PubMed

    Zhu, Z G; Li, Y Z; Wang, Z; Gao, X Q; Wen, P; Bai, H Y; Ngai, K L; Wang, W H

    2014-08-28

    The β-relaxation of metallic glasses (MGs) bears nontrivial connections to their microscopic and macroscopic properties. In an effort to elucidate the mechanism of the β-relaxation, we studied by dynamical mechanical measurements the change of its properties on varying the composition of La60Ni15Al25 in various ways. The properties of the β-relaxation turn out to be very sensitive to the composition. It is found that the isochronal loss peak temperature of β-relaxation, Tβ,peak, is effectively determined by the total (La + Ni) content. When Cu is added into the alloy to replace either La, Ni, or Al, the Tβ,peak increases with decrease of the (La + Ni) content. The trend is in accordance with data of binary and ternary MGs formed from La, Ni, Al, and Cu. Binary La-Ni MGs have pronounced β-relaxation loss peaks, well separated from the α-relaxation. In contrast, the β-relaxation is not resolved in La-Al and La-Cu MGs, showing up as an excess wing. For the ternary La-Ni-Al MGs, increase of La or Ni content is crucial to lower the Tβ,peak. Keeping the Al content fixed, increase of La content lowers the Tβ,peak further, indicating the more important role La plays in lowering Tβ,peak than Ni. The observed effects on changing the composition of La60Ni15Al25 lead to the conclusion that the properties of the β-relaxation are mainly determined by the interaction between the largest solvent element, La, and the smallest element, Ni. From our data, it is further deduced that La and Ni have high mobility in the MGs, and this explains why the β-relaxation in this La-based MGs is prominent and well resolved from the α-relaxation as opposed to Pd- and Zr-based MGs where the solvent and largest atoms, Pd and Zr, are the least mobile.

  4. Coating thickness control in continuously fabricating metallic glass-coated composite wires

    NASA Astrophysics Data System (ADS)

    Zhang, Bao-yu; Chen, Xiao-hua; Lu, Zhao-ping; Hui, Xi-dong

    2013-05-01

    A continuous production process was developed for coating bulk metallic glasses on the metallic wire surface. The effects of processing parameters, including the drawing velocity and coating temperature, on the coating thickness were investigated. It is found that the coating thickness increases with the increase in drawing velocity but decreases with the increase in coating temperature. A fluid mechanical model was developed to quantify the coating thickness under various processing conditions. By using this theoretical model, the coating thickness was calculated, and the calculated values are in good agreement with the experimental data.

  5. Direct Observation on the Evolution of Shear Banding and Buckling in Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glass Composite

    NASA Astrophysics Data System (ADS)

    Chen, J. H.; Chen, Y.; Jiang, M. Q.; Chen, X. W.; Fu, H. M.; Zhang, H. F.; Dai, L. H.

    2014-11-01

    The evolution of micro-damage and deformation of each phase in the composite plays a pivotal role in the clarification of deformation mechanism of composite. However, limited model and mechanical experiments were conducted to reveal the evolution of the deformation of the two phases in the tungsten fiber reinforced Zr-based bulk metallic glass composite. In this study, quasi-static compressive tests were performed on this composite. For the first time, the evolution of micro-damage and deformation of the two phases in this composite, i.e., shear banding of the metallic glass matrix and buckling deformation of the tungsten fiber, were investigated systematically by controlling the loading process at different degrees of deformation. It is found that under uniaxial compression, buckling of the tungsten fiber occurs first, while the metallic glass matrix deforms homogeneously. Upon further loading, shear bands initiate from the fiber/matrix interface and propagate in the metallic glass matrix. Finally, the composite fractures in a mixed mode, with splitting in the tungsten fiber, along with shear fracture in the metallic glass matrix. Through the analysis on the stress state in the composite and resistance to shear banding of the two phases during compressive deformation, the possible deformation mechanism of the composite is unveiled. The deformation map of the composite, which covers from elastic deformation to final fracture, is obtained as well.

  6. Multi-scale Characterisation of the 3D Microstructure of a Thermally-Shocked Bulk Metallic Glass Matrix Composite

    PubMed Central

    Zhang, Wei; Bodey, Andrew J.; Sui, Tan; Kockelmann, Winfried; Rau, Christoph; Korsunsky, Alexander M.; Mi, Jiawei

    2016-01-01

    Bulk metallic glass matrix composites (BMGMCs) are a new class of metal alloys which have significantly increased ductility and impact toughness, resulting from the ductile crystalline phases distributed uniformly within the amorphous matrix. However, the 3D structures and their morphologies of such composite at nano and micrometre scale have never been reported before. We have used high density electric currents to thermally shock a Zr-Ti based BMGMC to different temperatures, and used X-ray microtomography, FIB-SEM nanotomography and neutron diffraction to reveal the morphologies, compositions, volume fractions and thermal stabilities of the nano and microstructures. Understanding of these is essential for optimizing the design of BMGMCs and developing viable manufacturing methods. PMID:26725519

  7. Multi-scale Characterisation of the 3D Microstructure of a Thermally-Shocked Bulk Metallic Glass Matrix Composite

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Bodey, Andrew J.; Sui, Tan; Kockelmann, Winfried; Rau, Christoph; Korsunsky, Alexander M.; Mi, Jiawei

    2016-01-01

    Bulk metallic glass matrix composites (BMGMCs) are a new class of metal alloys which have significantly increased ductility and impact toughness, resulting from the ductile crystalline phases distributed uniformly within the amorphous matrix. However, the 3D structures and their morphologies of such composite at nano and micrometre scale have never been reported before. We have used high density electric currents to thermally shock a Zr-Ti based BMGMC to different temperatures, and used X-ray microtomography, FIB-SEM nanotomography and neutron diffraction to reveal the morphologies, compositions, volume fractions and thermal stabilities of the nano and microstructures. Understanding of these is essential for optimizing the design of BMGMCs and developing viable manufacturing methods.

  8. Multi-scale Characterisation of the 3D Microstructure of a Thermally-Shocked Bulk Metallic Glass Matrix Composite.

    PubMed

    Zhang, Wei; Bodey, Andrew J; Sui, Tan; Kockelmann, Winfried; Rau, Christoph; Korsunsky, Alexander M; Mi, Jiawei

    2016-01-04

    Bulk metallic glass matrix composites (BMGMCs) are a new class of metal alloys which have significantly increased ductility and impact toughness, resulting from the ductile crystalline phases distributed uniformly within the amorphous matrix. However, the 3D structures and their morphologies of such composite at nano and micrometre scale have never been reported before. We have used high density electric currents to thermally shock a Zr-Ti based BMGMC to different temperatures, and used X-ray microtomography, FIB-SEM nanotomography and neutron diffraction to reveal the morphologies, compositions, volume fractions and thermal stabilities of the nano and microstructures. Understanding of these is essential for optimizing the design of BMGMCs and developing viable manufacturing methods.

  9. Effect of strain rates on deformation behaviors of an in situ Ti-based metallic glass matrix composite

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Chu, M. Y.; Wang, Y. S.; Yang, H. J.; Qiao, J. W.

    2016-06-01

    Quasi-static and dynamic deformation behaviors of an in situ dendrite-reinforced metallic glass matrix composite: Ti56Zr18V10Cu4Be12 were investigated. Upon quasi-static compression, the composite exhibits distinguished work hardening, accompanied by the ultimate strength of 1290 MPa and the plasticity of 20 %. The improved plasticity is attributed to the multiplication of shear bands within the glass matrix and pileups of dislocations within the dendrites. Upon dynamic compression, the stable plastic flow prevails and the yielding stress increases with the strain rate. The macroscopic plasticity decreases considerably, since the shear bands cannot be effectively hindered by dendrites with deteriorated toughness. The dendrite-dominated mechanism results in the positive strain-rate sensitivity, and the Cowper-Symonds model is employed to depict the strain-rate dependency of yielding strength.

  10. Metallic Glass Cooling

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A sample of advanced metallic glass alloy cools down during an experiment with the TEMPUS furnace on STS-94, July 7, 1997, MET:5/23:35 (approximate). The sequence shows the sample glowing, then fading to black as scientists began the process of preserving the liquid state, but lowering the temperature below the normal solidification temperature of the alloy. This process is known as undercooling. (10 second clip covering approximately 50 seconds.) TEMPUS (stands for Tiegelfreies Elektromagnetisches Prozessiere unter Schwerelosigkeit (containerless electromagnetic processing under weightlessness). It was developed by the German Space Agency (DARA) for flight aboard Spacelab. The DARA project scientist was Igon Egry. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). DARA and NASA are exploring the possibility of flying an advanced version of TEMPUS on the International Space Station. (354KB JPEG, 2700 x 2038 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300189.html.

  11. Thermal rejuvenation in metallic glasses

    PubMed Central

    Saida, Junji; Yamada, Rui; Wakeda, Masato; Ogata, Shigenobu

    2017-01-01

    Abstract Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery annealing) was investigated experimentally and theoretically for various alloy compositions. An increase in the potential energy, a decrease in the density, and a change in the local structure as well as mechanical softening were observed after thermal rejuvenation. Two parameters, one related to the annealing temperature, T a/T g, and the other related to the cooling rate during the recovery annealing process, V c/V i, were proposed to evaluate the rejuvenation phenomena. A rejuvenation map was constructed using these two parameters. Since the thermal history of metallic glasses is reset above 1.2T g, accompanied by a change in the local structure, it is essential that the condition of T a/T g ≥ 1.2 is satisfied during annealing. The glassy structure transforms into a more disordered state with the decomposition of icosahedral short-range order within this temperature range. Therefore, a new glassy structure (rejuvenation) depending on the subsequent quenching rate is generated. Partial rejuvenation also occurs in a Zr55Al10Ni5Cu30 bulk metallic glass when annealing is performed at a low temperature (T a/T g ~ 1.07) followed by rapid cooling. This behavior probably originates from disordering in the weakly bonded (loosely packed) region. This study provides a novel approach to improving the mechanical properties of metallic glasses by controlling their glassy structure. PMID:28458739

  12. The corrosion behavior of in-situ Zr-based metallic glass matrix composites in different corrosive media

    NASA Astrophysics Data System (ADS)

    Tian, H. F.; Qiao, J. W.; Yang, H. J.; Wang, Y. S.; Liaw, P. K.; Lan, A. D.

    2016-02-01

    The corrosion behavior of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 metallic glass matrix composites (MGMCs) in different corrosive media, including 1 M NaCl, 1 M HCl, 0.5 M H2SO4, and 1 M NaOH solutions, was studied. The electrochemical characteristics of the composites were investigated by potentiodynamic-polarization measurements. The results show that the corrosion resistance in NaOH solution is the poorest in terms of the corrosion potential (Ecorr) and corrosion current density (icorr). For comparison, the chemical immersion tests were conducted. The corroded surface morphologies after electrochemical and immersion measurements both show that the amorphous matrix and crystalline dendrites exhibit different corrosion behaviors. The possible interpretation of the observed morphology evolution was proposed. The effect of a very base metallic element of beryllium on the corrosion dynamic process has been emphasized.

  13. Plasmonically enhanced Faraday effect in metal and ferrite nanoparticles composite precipitated inside glass.

    PubMed

    Nakashima, Seisuke; Sugioka, Koji; Tanaka, Katsuhisa; Shimizu, Masahiro; Shimotsuma, Yasuhiko; Miura, Kiyotaka; Midorikawa, Katsumi; Mukai, Kohki

    2012-12-17

    Using femtosecond laser irradiation and subsequent annealing, nanocomposite structures composed of spinel-type ferrimagnetic nanoparticles (NPs) and plasmonic metallic NPs have been formed space-selectively within glass doped with both α-Fe(2)O(3) and Al. The Faraday rotation spectra exhibit a distinct negative peak at around 400 nm, suggesting that the ferrimagnetic Faraday response is enhanced by the localized surface plasmon resonance (LSPR) due to metallic Al NPs. At the interfaces in the nanocomposites, the ferrimagnetism of magnetite NPs is directly coupled with the plasmon in the Al NPs. The control of the resonance wavelength of the magneto-optical peaks, namely, the size of plasmonic NPs has been demonstrated by changing the irradiation or annealing conditions.

  14. Composition-dependent stability of the medium-range order responsible for metallic glass formation

    DOE PAGES

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; ...

    2014-09-18

    The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. Furthermore, we focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. These results show that a Bergman-type motifmore » with crystallization-resisting icosahedral symmetry is energetically most favorable in the composition range 0.63 < xCu < 0.68, and is the underlying motif for one of the three optimal glass-forming ranges observed experimentally for this binary system (Li et al., 2008). This work establishes an energy-based methodology to evaluate specific medium-range structural motifs which compete with stable crystalline nuclei in deeply undercooled liquids.« less

  15. Composition-dependent stability of the medium-range order responsible for metallic glass formation

    SciTech Connect

    Zhang, Feng; Ji, Min; Fang, Xiao-Wei; Sun, Yang; Wang, Cai-Zhuang; Mendelev, Mikhail I.; Kramer, M. J.; Napolitano, Ralph E.; Ho, Kai-Ming

    2014-09-18

    The competition between the characteristic medium-range order corresponding to amorphous alloys and that in ordered crystalline phases is central to phase selection and morphology evolution under various processing conditions. We examine the stability of a model glass system, Cu–Zr, by comparing the energetics of various medium-range structural motifs over a wide range of compositions using first-principles calculations. Furthermore, we focus specifically on motifs that represent possible building blocks for competing glassy and crystalline phases, and we employ a genetic algorithm to efficiently identify the energetically favored decorations of each motif for specific compositions. These results show that a Bergman-type motif with crystallization-resisting icosahedral symmetry is energetically most favorable in the composition range 0.63 < xCu < 0.68, and is the underlying motif for one of the three optimal glass-forming ranges observed experimentally for this binary system (Li et al., 2008). This work establishes an energy-based methodology to evaluate specific medium-range structural motifs which compete with stable crystalline nuclei in deeply undercooled liquids.

  16. Tensile deformation mechanisms of an in-situ Ti-based metallic glass matrix composite at cryogenic temperature.

    PubMed

    Bai, J; Li, J S; Qiao, J W; Wang, J; Feng, R; Kou, H C; Liaw, P K

    2016-08-31

    Remarkable tensile ductility was first obtained in an in-situ Ti-based bulk metallic glass (BMG) composite at cryogenic temperature (77 K). The novel cryogenic tensile plasticity is related to the effective accommodation of ductile body-centered cubic dendrites at 77 K, characteristic of the prevailing slip bands and dislocations, as well as lattice disorder, which can effectively hinder the propagation of critical shear bands. The greatly increased yield strength of dendrites contributes to the high yield strength of composite at 77 K. A trend of stronger softening is observed at low temperature, and a criterion is proposed to understand the softening behavior. The current research could also provide a guidance to the promising cryogenic application of these new advanced BMG composites.

  17. Tensile deformation mechanisms of an in-situ Ti-based metallic glass matrix composite at cryogenic temperature

    SciTech Connect

    Bai, J.; Li, J. S.; Qiao, J. W.; Wang, J.; Feng, R.; Kou, H. C.; Liaw, P. K.

    2016-08-31

    Remarkable tensile ductility was first obtained in an in-situ Ti-based bulk metallic glass (BMG) composite at cryogenic temperature (77 K). The novel cryogenic tensile plasticity is related to the effective accommodation of ductile body-centered cubic dendrites at 77 K, characteristic of the prevailing slip bands and dislocations, as well as lattice disorder, which can effectively hinder the propagation of critical shear bands. The greatly increased yield strength of dendrites contributes to the high yield strength of composite at 77 K. A trend of stronger softening is observed at low temperature, and a criterion is proposed to understand the softening behavior. In conclusion, the current research could also provide a guidance to the promising cryogenic application of these new advanced BMG composites.

  18. Tensile deformation mechanisms of an in-situ Ti-based metallic glass matrix composite at cryogenic temperature

    DOE PAGES

    Bai, J.; Li, J. S.; Qiao, J. W.; ...

    2016-08-31

    Remarkable tensile ductility was first obtained in an in-situ Ti-based bulk metallic glass (BMG) composite at cryogenic temperature (77 K). The novel cryogenic tensile plasticity is related to the effective accommodation of ductile body-centered cubic dendrites at 77 K, characteristic of the prevailing slip bands and dislocations, as well as lattice disorder, which can effectively hinder the propagation of critical shear bands. The greatly increased yield strength of dendrites contributes to the high yield strength of composite at 77 K. A trend of stronger softening is observed at low temperature, and a criterion is proposed to understand the softening behavior.more » In conclusion, the current research could also provide a guidance to the promising cryogenic application of these new advanced BMG composites.« less

  19. Towards an understanding of tensile deformation in Ti-based bulk metallic glass matrix composites with BCC dendrites

    PubMed Central

    Kolodziejska, Joanna A; Kozachkov, Henry; Kranjc, Kelly; Hunter, Allen; Marquis, Emmanuelle; Johnson, William L; Flores, Katharine M; Hofmann, Douglas C

    2016-01-01

    The microstructure and tension ductility of a series of Ti-based bulk metallic glass matrix composite (BMGMC) is investigated by changing content of the β stabilizing element vanadium while holding the volume fraction of dendritic phase constant. The ability to change only one variable in these novel composites has previously been difficult, leading to uninvestigated areas regarding how composition affects properties. It is shown that the tension ductility can range from near zero percent to over ten percent simply by changing the amount of vanadium in the dendritic phase. This approach may prove useful for the future development of these alloys, which have largely been developed experimentally using trial and error. PMID:26932509

  20. Tensile deformation mechanisms of an in-situ Ti-based metallic glass matrix composite at cryogenic temperature

    PubMed Central

    Bai, J.; Li, J. S.; Qiao, J. W.; Wang, J.; Feng, R.; Kou, H. C.; Liaw, P. K.

    2016-01-01

    Remarkable tensile ductility was first obtained in an in-situ Ti-based bulk metallic glass (BMG) composite at cryogenic temperature (77 K). The novel cryogenic tensile plasticity is related to the effective accommodation of ductile body-centered cubic dendrites at 77 K, characteristic of the prevailing slip bands and dislocations, as well as lattice disorder, which can effectively hinder the propagation of critical shear bands. The greatly increased yield strength of dendrites contributes to the high yield strength of composite at 77 K. A trend of stronger softening is observed at low temperature, and a criterion is proposed to understand the softening behavior. The current research could also provide a guidance to the promising cryogenic application of these new advanced BMG composites. PMID:27576728

  1. Tensile deformation mechanisms of an in-situ Ti-based metallic glass matrix composite at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Bai, J.; Li, J. S.; Qiao, J. W.; Wang, J.; Feng, R.; Kou, H. C.; Liaw, P. K.

    2016-08-01

    Remarkable tensile ductility was first obtained in an in-situ Ti-based bulk metallic glass (BMG) composite at cryogenic temperature (77 K). The novel cryogenic tensile plasticity is related to the effective accommodation of ductile body-centered cubic dendrites at 77 K, characteristic of the prevailing slip bands and dislocations, as well as lattice disorder, which can effectively hinder the propagation of critical shear bands. The greatly increased yield strength of dendrites contributes to the high yield strength of composite at 77 K. A trend of stronger softening is observed at low temperature, and a criterion is proposed to understand the softening behavior. The current research could also provide a guidance to the promising cryogenic application of these new advanced BMG composites.

  2. Metallic Glass Nano-composite Thin Films for High-performance Functional Applications

    NASA Astrophysics Data System (ADS)

    Das, Santanu; Arora, Harpreet Singh; Mukherjee, Sundeep

    2017-07-01

    Metallic glass nanocomposite thin films were synthesized for an immiscible Ag-Cu alloy system by magnetron sputtering. The structure of the films was unique, consisting of homogeneously dispersed nanocrystallites in an amorphous matrix. The size and volume fraction of the nanocrystallites increased with increasing film thickness resulting in increased elastic modulus and hardness. The high electrical conductivity of the nanocomposite films was examined by a valence-band study, which showed that exchange interaction between Ag and Cu in the nanocomposite structure resulted in enhanced charge carrier concentration. The inverse correlation between electrical conductivity and film thickness was explained by surface and interface scattering of electrons with increasing volume fraction of nanocrystallites. The small temperature dependence of conductivity was attributed to the distorted Fermi surface of the nanocomposite films resulting in a greater contribution from structure scattering, which is temperature-independent.

  3. Alloying Behavior and Properties of Al-Based Composites Reinforced with Al85Fe15 Metallic Glass Particles Fabricated by Mechanical Alloying and Hot Pressing Consolidation

    NASA Astrophysics Data System (ADS)

    Zhang, Lanxiang; Yang, LiKun; Leng, Jinfeng; Wang, Tongyang; Wang, Yan

    2017-04-01

    In this study, Al85Fe15 metallic glass particles with high onset crystallization temperature (1209 K) were synthesized by a mechanical alloying method. High-quality 6061Al-based composites reinforced with Al85Fe15 metallic glass particles were fabricated by a vacuum hot-pressing sintering technique. The glass particles with flake-like shape are distributed uniformly in the Al matrix. The bulk composites possess high relative density, excellent hardness and strength. The microhardness values of the Al-based bulk composites with the additions of 20 vol.% and 30 vol.% Al85Fe15 particles are 204 MPa and 248 MPa, respectively, which are much higher than that of 6061Al (61 MPa). The compressive yield strength of the 30 vol.% glass-reinforced composite is 478 MPa, which is enhanced by 273% compared with 6061Al. The amorphous characteristic and homogeneous dispersion of glass particles account for the excellent mechanical properties of the Al-based composites. In addition, the corrosion behavior of Al-based composites in a seawater solution has been investigated by electrochemical polarization measurements. Compared to 6061Al, the 30 vol.% glass-reinforced composite shows the lower corrosion/passive current density and larger passive region, indicating the greatly enhanced corrosion resistance.

  4. Alloying Behavior and Properties of Al-Based Composites Reinforced with Al85Fe15 Metallic Glass Particles Fabricated by Mechanical Alloying and Hot Pressing Consolidation

    NASA Astrophysics Data System (ADS)

    Zhang, Lanxiang; Yang, LiKun; Leng, Jinfeng; Wang, Tongyang; Wang, Yan

    2017-01-01

    In this study, Al85Fe15 metallic glass particles with high onset crystallization temperature (1209 K) were synthesized by a mechanical alloying method. High-quality 6061Al-based composites reinforced with Al85Fe15 metallic glass particles were fabricated by a vacuum hot-pressing sintering technique. The glass particles with flake-like shape are distributed uniformly in the Al matrix. The bulk composites possess high relative density, excellent hardness and strength. The microhardness values of the Al-based bulk composites with the additions of 20 vol.% and 30 vol.% Al85Fe15 particles are 204 MPa and 248 MPa, respectively, which are much higher than that of 6061Al (61 MPa). The compressive yield strength of the 30 vol.% glass-reinforced composite is 478 MPa, which is enhanced by 273% compared with 6061Al. The amorphous characteristic and homogeneous dispersion of glass particles account for the excellent mechanical properties of the Al-based composites. In addition, the corrosion behavior of Al-based composites in a seawater solution has been investigated by electrochemical polarization measurements. Compared to 6061Al, the 30 vol.% glass-reinforced composite shows the lower corrosion/passive current density and larger passive region, indicating the greatly enhanced corrosion resistance.

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

    PubMed

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

    2016-01-12

    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.

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

    PubMed Central

    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

  7. Metastable metallic hydrogen glass

    SciTech Connect

    Nellis, W J

    2001-02-06

    The quest for metallic hydrogen has been going on for over one hundred years. Before hydrogen was first condensed into a liquid in 1898, it was commonly thought that condensed hydrogen would be a metal, like the monatomic alkali metals below hydrogen in the first column of the Periodic Table. Instead, condensed hydrogen turned out to be transparent, like the diatomic insulating halogens in the seventh column of the Periodic Table. Wigner and Huntington predicted in 1935 that solid hydrogen at 0 K would undergo a first-order phase transition from a diatomic to a monatomic crystallographically ordered solid at {approx}25 GPa. This first-order transition would be accompanied by an insulator-metal transition. Though searched for extensively, a first-order transition from an ordered diatomic insulator to a monatomic metal is yet to be observed at pressures up to 120 and 340 GPa using x-ray diffraction and visual inspection, respectively. On the other hand, hydrogen reaches the minimum electrical conductivity of a metal at 140 GPa, 0.6 g/cm{sup 3}, and 3000 K. These conditions were achieved using a shock wave reverberating between two stiff sapphire anvils. The shock wave was generated with a two-stage light-gas gun. This temperature exceeds the calculated melting temperature at 140 GPa by a factor of {approx}2, indicating that this metal is in the disordered fluid phase. The disorder permits hydrogen to become metallic via a Mott transition in the liquid at a much smaller pressure than in the solid, which has an electronic bandgap to the highest pressures reached to date. Thus, by using the finite temperature achieved with shock compression to achieve a disordered melt, metallic hydrogen can be achieved at a much lower pressure in a fluid than in a solid. It is not known how, nor even whether, metallic hydrogen can be quenched from a fluid at high pressures to a disordered solid metallic glass at ambient pressure and temperature. Because metallization occurs by simply

  8. Effect of geometrical constraint condition on the formation of nanoscale twins in the Ni-based metallic glass composite

    SciTech Connect

    Lee, M H; Kim, B S; Kim, D H; Ott, R T; Sansoz, F; Eckert, J

    2014-04-25

    We investigated the effect of geometrically constrained stress-strain conditions on the formation of nanotwins in alpha-brass phase reinforced Ni59Zr20Ti16Si2Sn3 metallic glass (MG) matrix deformed under macroscopic uniaxial compression. The specific geometrically constrained conditions in the samples lead to a deviation from a simple uniaxial state to a multi-axial stress state, for which nanocrystallization in the MG matrix together with nanoscale twinning of the brass reinforcement is observed in localized regions during plastic flow. The nanocrystals in the MG matrix and the appearance of the twinned structure in the reinforcements indicate that the strain energy is highly confined and the local stress reaches a very high level upon yielding. Both the effective distribution of reinforcements on the strain enhancement of composite and the effects of the complicated stress states on the development of nanotwins in the second-phase brass particles are discussed.

  9. Designing tensile ductility in metallic glasses

    PubMed Central

    Sarac, Baran; Schroers, Jan

    2013-01-01

    Effectiveness of a second phase in metallic glass heterostructures to improve mechanical properties varies widely. Unfortunately, methods to fabricate such heterostructures like foams and composites do not allow controlled variation of structural features. Here we report a novel strategy, which allows us to vary heterostructural features independently, thereby enabling a systematic and quantitative study. Our approach reveals the optimal microstructural architecture for metallic glass heterostructures to achieve tensile ductility. Critical design aspect is a soft second phase, which is most effective when spacing between the second phase assumes the critical crack length of the metallic glass. This spacing should coincide with the second phase’s size, and beyond, the specific second phase morphology of the heterostructure is crucial. These toughening strategies are only effective in samples that are large compared with the spacing of the second phase. The identified design aspects provide guidance in designing tensile ductility into metallic glasses. PMID:23863967

  10. Designing tensile ductility in metallic glasses

    NASA Astrophysics Data System (ADS)

    Sarac, Baran; Schroers, Jan

    2013-07-01

    Effectiveness of a second phase in metallic glass heterostructures to improve mechanical properties varies widely. Unfortunately, methods to fabricate such heterostructures like foams and composites do not allow controlled variation of structural features. Here we report a novel strategy, which allows us to vary heterostructural features independently, thereby enabling a systematic and quantitative study. Our approach reveals the optimal microstructural architecture for metallic glass heterostructures to achieve tensile ductility. Critical design aspect is a soft second phase, which is most effective when spacing between the second phase assumes the critical crack length of the metallic glass. This spacing should coincide with the second phase’s size, and beyond, the specific second phase morphology of the heterostructure is crucial. These toughening strategies are only effective in samples that are large compared with the spacing of the second phase. The identified design aspects provide guidance in designing tensile ductility into metallic glasses.

  11. Iodine confinement into metal-organic frameworks (MOFs)-low temperature sintering glasses to form novel glass composite material (GCM) alternative waste forms.

    SciTech Connect

    Nenoff, Tina Maria; Garino, Terry J.; Sava, Dorina Florentina

    2010-11-01

    The safe handling of reprocessed fuel addresses several scientific goals, especially when considering the capture and long-term storage of volatile radionuclides that are necessary during this process. Despite not being a major component of the off-gas, radioiodine (I{sub 2}) is particularly challenging, because it is a highly mobile gas and {sup 129}I is a long-lived radionuclide (1.57 x 10{sup 7} years). Therefore, its capture and sequestration is of great interest on a societal level. Herein, we explore novel routes toward the effective capture and storage of iodine. In particular, we report on the novel use of a new class of porous solid-state functional materials (metal-organic frameworks, MOFs), as high-capacity adsorbents of molecular iodine. We further describe the formation of novel glass-composite material (GCM) waste forms from the mixing and sintering of the I{sub 2}-containing MOFs with Bi-Zn-O low-temperature sintering glasses and silver metal flakes. Our findings indicate that, upon sintering, a uniform monolith is formed, with no evidence of iodine loss; iodine is sequestered during the heating process by the in situ formation of AgI. Detailed materials characterization analysis is presented for the GCMs. This includes powder X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), thermal analysis (thermogravimetric analysis (TGA)), and chemical durability tests including aqueous leach studies (product consistency test (PCT)), with X-ray fluorescence (XRF) and inductively coupled plasma-mass spectrometry (ICP-MS) of the PCT leachate.

  12. Survival of Composite Resin Restorations of severely Decayed Primary Anterior Teeth retained by Glass Fiber Posts or Reversed-orientated Metal Posts.

    PubMed

    Vafaei, Ali; Ranjkesh, Bahram; Lovschall, Henrik; Erfanparast, Leila; Jafarabadi, Mohammad A; Oskouei, Sina Ghertasi; Isidor, Flemming

    2016-01-01

    The aim of this study was to compare the survival of composite resin restorations retained by glass fiber posts or reversed-orientated (upside-down) metal posts in severely decayed primary anterior teeth after 6, 12, and 18 months. A total of forty-four 3- to 5-year-old children with bilateral severely decayed primary maxillary canines were included. Patients were treated under general anesthesia. After pulpectomy, an intracanal post was seated in the primary maxillary canine on each side: either a glass fiber post or a metallic post in reversed orientation and teeth restored with light-cured composite. Survival rate of each technique was evaluated at predetermined follow-ups and data were analyzed with McNemar's test (α = 0.05). The difference in survival of restorations retained by two types of posts was not statistically significant in clinical and radiographical evaluations after 6, 12, and 18 months. The survival rate of reversed-orientated metal and glass fiber posts after 18 months was 81.1 and 67.6% respectively (p = 0.14). Reversed-orientated metal post did not show lower clinical survival compared with glass fiber posts in 18-month follow-up. Hence, reversed-orientated metal post can be considered as a potential method to obtain retention for composite restorations in severely decayed primary anterior teeth. How to cite this article: Vafaei A, Ranjkesh B, L0vschall H, Erfanparast L, Jafarabadi MA, Oskouei SG, Isidor F. Survival of Composite Resin Restorations of severely Decayed Primary Anterior Teeth retained by Glass Fiber Posts or Reversed-orientated Metal Posts. Int J Clin Pediatr Dent 2016;9(2):109-113.

  13. Survival of Composite Resin Restorations of severely Decayed Primary Anterior Teeth retained by Glass Fiber Posts or Reversed-orientated Metal Posts

    PubMed Central

    Ranjkesh, Bahram; Lovschall, Henrik; Erfanparast, Leila; Jafarabadi, Mohammad A; Oskouei, Sina Ghertasi; Isidor, Flemming

    2016-01-01

    ABSTRACT Aim: The aim of this study was to compare the survival of composite resin restorations retained by glass fiber posts or reversed-orientated (upside-down) metal posts in severely decayed primary anterior teeth after 6, 12, and 18 months. Materials and methods: A total of forty-four 3- to 5-year-old children with bilateral severely decayed primary maxillary canines were included. Patients were treated under general anesthesia. After pulpectomy, an intracanal post was seated in the primary maxillary canine on each side: either a glass fiber post or a metallic post in reversed orientation and teeth restored with light-cured composite. Survival rate of each technique was evaluated at predetermined follow-ups and data were analyzed with McNemar’s test (α = 0.05). Results: The difference in survival of restorations retained by two types of posts was not statistically significant in clinical and radiographical evaluations after 6, 12, and 18 months. The survival rate of reversed-orientated metal and glass fiber posts after 18 months was 81.1 and 67.6% respectively (p = 0.14). Conclusion: Reversed-orientated metal post did not show lower clinical survival compared with glass fiber posts in 18-month follow-up. Hence, reversed-orientated metal post can be considered as a potential method to obtain retention for composite restorations in severely decayed primary anterior teeth. How to cite this article: Vafaei A, Ranjkesh B, L0vschall H, Erfanparast L, Jafarabadi MA, Oskouei SG, Isidor F. Survival of Composite Resin Restorations of severely Decayed Primary Anterior Teeth retained by Glass Fiber Posts or Reversed-orientated Metal Posts. Int J Clin Pediatr Dent 2016;9(2):109-113. PMID:27365929

  14. Tuning the Mechanical and Antimicrobial Performance of a Cu-Based Metallic Glass Composite through Cooling Rate Control and Annealing.

    PubMed

    Villapún, Victor M; Esat, F; Bull, S; Dover, L G; González, S

    2017-05-06

    The influence of cooling rate on the wear and antimicrobial performance of a Cu52Z41Al₇ (at. %) bulk metallic glass (BMG) composite was studied and the results compared to those of the annealed sample (850 °C for 48 h) and to pure copper. The aim of this basic research is to explore the potential use of the material in preventing the spread of infections. The cooling rate is controlled by changing the mould diameter (2 mm and 3 mm) upon suction casting and controlling the mould temperature (chiller on and off). For the highest cooling rate conditions CuZr is formed but CuZr₂ starts to crystallise as the cooling rate decreases, resulting in an increase in the wear resistance and brittleness, as measured by scratch tests. A decrease in the cooling rate also increases the antimicrobial performance, as shown by different methodologies (European, American and Japanese standards). Annealing leads to the formation of new intermetallic phases (Cu10Zr₇ and Cu₂ZrAl) resulting in maximum scratch hardness and antimicrobial performance. However, the annealed sample corrodes during the antimicrobial tests (within 1 h of contact with broth). The antibacterial activity of copper was proved to be higher than that of any of the other materials tested but it exhibits very poor wear properties. Cu-rich BMG composites with optimised microstructure would be preferable for some applications where the durability requirements are higher than the antimicrobial needs.

  15. Effects of chemical composition and test conditions on the dynamic tensile response of Zr-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, F.; Laws, K. J.; Trujillo, C. P.; Brown, A. D.; Cerreta, E. K.; Hazell, P. J.; Quadir, M. Z.; Ferry, M.; Escobedo, J. P.

    2015-06-01

    The effects of impact velocity and temperature on the dynamic mechanical behavior of two bulk metallic glasses (BMG) with slightly different elemental compositions (Zr55Cu30Ni5Al30 and Zr46Cu38Ag8Al38) have been investigated. Bullet-shaped samples were accelerated by a gas gun to speeds in the 400 ~ 600m/s range and tested at room temperature and 250 °C. The specimens impacted a steel extrusion die which subjected them to high strains at high strain-rates. The extruded samples were subsequently soft recovered by using low density foams. The deformed specimens were examined by optical and electron microscopy, x-ray diffraction and hardness measurements. The characterization results aided to assess the effect of chemical composition on the microstructural evolution, i.e. phase changes or crystallization, which might influence the ductility on the nominally brittle amorphous BMGs. The most significant results from this study will be presented. School of Engineering and Information Technology, UNSW Canberra.

  16. Relaxation Pathways in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Gallino, Isabella; Busch, Ralf

    2017-09-01

    At temperatures below the glass transition temperature, physical properties of metallic glasses, such as density, viscosity, electrical resistivity or enthalpy, slowly evolve with time. This is the process of physical aging that occurs among all types of glasses and leads to structural changes at the microscopic level. Even though the relaxation pathways are ruled by thermodynamics as the glass attempts to re-attain thermodynamic equilibrium, they are steered by sluggish kinetics at the microscopic level. Understanding the structural and dynamic pathways of the relaxing glassy state is still one of the grand challenges in materials physics. We review some of the recent experimental advances made in understanding the nature of the relaxation phenomenon in metallic glasses and its implications to the macroscopic and microscopic properties changes of the relaxing glass.

  17. Thermoplastic Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C. (Inventor); Roberts, Scott N. (Inventor); Kozachkov, Henry (Inventor); Demetriou, Marios D. (Inventor); Schramm, Joseph P. (Inventor); Johnson, William L. (Inventor)

    2015-01-01

    Systems and methods for joining BMG Composites are disclosed. Specifically, the joining of BMG Composites is implemented so as to preserve the amorphicity of their matrix phase and the microstructure of their particulate phase. Implementation of the joining method with respect to the construction of modular cellular structures that comprise BMG Composites is also discussed.

  18. Origin of embrittlement in metallic glasses

    PubMed Central

    Garrett, Glenn R.; Demetriou, Marios D.; Launey, Maximilien E.; Johnson, William L.

    2016-01-01

    Owing to their glassy nature, metallic glasses demonstrate a toughness that is extremely sensitive to the frozen-in configurational state. This sensitivity gives rise to “annealing embrittlement,” which is often severe and in many respects limits the technological advancement of these materials. Here, equilibrium configurations (i.e., “inherent states”) of a metallic glass are established around the glass transition, and the configurational properties along with the plane-strain fracture toughness are evaluated to associate the intrinsic glass toughness with the inherent state properties and identify the fundamental origin of embrittlement. The established correlations reveal a one-to-one correspondence between toughness and shear modulus continuous over a broad range of inherent states, suggesting that annealing embrittlement is controlled almost solely by an increasing resistance to shear flow. This annealing embrittlement sensitivity is shown to vary substantially between metallic glass compositions, and appears to correlate well with the fragility of the metallic glass. PMID:27573817

  19. Designing novel bulk metallic glass composites with a high aluminum content

    PubMed Central

    Chen, Z. P.; Gao, J. E.; Wu, Y.; Wang, H.; Liu, X. J.; Lu, Z. P.

    2013-01-01

    The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades. In this paper, we reported formation of a series of BMG matrix composites which contain a high Al content up to 55 at.%. These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting. Our results indicate that proper additions of transition element Fe which have a positive heat of mixing with the main constituents La and Ce can appreciably improve the formability of the BMG matrix composites by suppressing the precipitation of Al(La,Ce) phase resulted from occurrence of the phase separation. However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys. PMID:24284800

  20. Designing novel bulk metallic glass composites with a high aluminum content.

    PubMed

    Chen, Z P; Gao, J E; Wu, Y; Wang, H; Liu, X J; Lu, Z P

    2013-11-27

    The long-standing challenge for forming Al-based BMGs and their matrix composites with a critical size larger than 1 mm have not been answered over the past three decades. In this paper, we reported formation of a series of BMG matrix composites which contain a high Al content up to 55 at.%. These composites can be cast at extraordinarily low cooling rates, compatible with maximum rod diameters of over a centimetre in copper mold casting. Our results indicate that proper additions of transition element Fe which have a positive heat of mixing with the main constituents La and Ce can appreciably improve the formability of the BMG matrix composites by suppressing the precipitation of Al(La,Ce) phase resulted from occurrence of the phase separation. However, the optimum content of Fe addition is strongly dependant on the total amount of the Al content in the Al-(CoCu)-(La,Ce) alloys.

  1. Intermediate Temperature Brittleness in Metallic Glasses.

    PubMed

    Wang, Chao; Cao, Qing Ping; Wang, Xiao Dong; Zhang, Dong Xian; Ramamurty, Upadrasta; Narayan, Ramasubramanian Lakshmi; Jiang, Jian-Zhong

    2017-04-01

    All metallic glasses (MGs), irrespective of their compositions, become brittle in the intermediate temperature range of 0.6-0.7 Tg However, most materials are expected to carry higher strains during deformation with increasing temperature. This behavior of MGs is explained by describing the competition between shear banding and diffusive relaxation processes, and is reminiscent of the "intermediate temperature ductility minimum" observed in polycrystalline metals. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Shock Processing and High Strain Rate Properties of Bulk Metallic Glasses and Their Composites

    DTIC Science & Technology

    2008-09-26

    of 6th Int. Conf. on Tungsten, Refractory & Hard metals, February 7-8, 2006, Co -Chairmen: Aminesh Bose and Robert J. Dowding, MPIF, Princeton, NJ...Summer School on Multiscale Modeling in Materials Science and Engineering, Eifel Mountains, Germany, July 23-28, 2007 (poster). M. Martin, T. Sekine, T

  3. Deformation behavior of metallic glass composites reinforced with shape memory nanowires studied via molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Şopu, D.; Stoica, M.; Eckert, J.

    2015-05-01

    Molecular dynamics simulations indicate that the deformation behavior and mechanism of Cu64Zr36 composite structures reinforced with B2 CuZr nanowires are strongly influenced by the martensitic phase transformation and distribution of these crystalline precipitates. When nanowires are distributed in the glassy matrix along the deformation direction, a two-steps stress-induced martensitic phase transformation is observed. Since the martensitic transformation is driven by the elastic energy release, the strain localization behavior in the glassy matrix is strongly affected. Therefore, the composite materials reinforced with a crystalline phase, which shows stress-induced martensitic transformation, represent a route for controlling the properties of glassy materials.

  4. DEVELOPMENT OF GLASS COMPOSITIONS TO IMMOBILIZE ALKALI, ALKALINE EARTH, LANTHANIDE AND TRANSITION METAL FISSION PRODUCTS FROM NUCLEAR FUEL REPROCESSING

    SciTech Connect

    Marra, J.; Billings, A.

    2009-06-24

    The Advanced Fuel Cycle Initiative (AFCI) waste management strategy revolves around specific treatment of individual or groups of separated waste streams. A goal for the separations processes is to efficiently manage the waste to be dispositioned as high level radioactive waste. The Advanced Fuel Cycle Initiative (AFCI) baseline technology for immobilization of the lanthanide (Ln) and transition metal fission product (TM) wastes is vitrification into a borosilicate glass. A current interest is to evaluate the feasibility of vitrifying combined waste streams to most cost effectively immobilize the wastes resulting from aqueous fuel reprocessing. Studies showed that high waste loadings are achievable for the Ln only (Option 1) stream. Waste loadings in excess of 60 wt % (on a calcined oxide basis) were demonstrated via a lanthanide borosilicate (LaBS) glass. The resulting glasses had excellent relative durability as determined by the Product Consistency Test (PCT). For a combined Ln and TM waste stream glass (Option 2), noble metal solubility was found to limit waste loading. However, the measured PCT normalized elemental releases for this glass were at least an order of magnitude below that of Environmental Assessment (EA) glass. Current efforts to evaluate the feasibility of vitrifying combined Ln, TM, alkali (Cs is the primary radionuclide of concern) and alkaline earth (Sr is the primary radionuclide of concern) wastes (Option 3) have shown that these approaches are feasible. However, waste loading limitations with respect to heat load (Cs/Sr loading), molybdenum solubility and/or noble metal solubility will likely be realized and must be considered in determining the cost effectiveness of these approaches.

  5. Elastic heterogeneity in metallic glasses.

    SciTech Connect

    Dmowski, , W.; Iwashita, T.; Chuang, C.-P.; Almer, J. D; Egami, T.; X-Ray Science Division; Univ. of Tennessee; ORNL

    2010-01-01

    When a stress is applied on a metallic glass it deforms following Hook's law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about 3/4 in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

  6. Processing of bulk metallic glass.

    PubMed

    Schroers, Jan

    2010-04-12

    Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)-based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass-transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF-based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made.

  7. Elastic Heterogeneity in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Dmowski, W.; Iwashita, T.; Chuang, C.-P.; Almer, J.; Egami, T.

    2010-11-01

    When a stress is applied on a metallic glass it deforms following Hook’s law. Therefore it may appear obvious that a metallic glass deforms elastically. Using x-ray diffraction and anisotropic pair-density function analysis we show that only about (3)/(4) in volume fraction of metallic glasses deforms elastically, whereas the rest of the volume is anelastic and in the experimental time scale deform without resistance. We suggest that this anelastic portion represents residual liquidity in the glassy state. Many theories, such as the free-volume theory, assume the density of defects in the glassy state to be of the order of 1%, but this result shows that it is as much as a quarter.

  8. A High Strain-Rate Investigation of a Zr-Based Bulk Metallic Glass and an HTPB Polymer Composite

    DTIC Science & Technology

    2011-03-01

    or 4.0 mm diameter. The long cylindrical bars were then metallographically polished to a mirror finish first using SiC grit paper (1200 grit and 2400...systems (such as with tungsten in LM-1), but the arrangement may also decrease the amount of energy (such as with silicon carbide in aluminum). In...metallic glass. Scripta Materialia 41, 937-943. 29. Sarva S., Nemat-Nasser S. (2001) Dynamic compressive strength of silicon carbide under uniaxial

  9. Glass electrolyte composition

    DOEpatents

    Kucera, G.H.; Roche, M.F.

    1985-01-08

    An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na/sub 2/O, ZrO/sub 2/, Al/sub 2/O/sub 3/ and SiO/sub 2/ in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2 x 10/sup -3/ (ohm-cm)/sup -1/ at 300/sup 0/C and a glass transition temperature in excess of 500/sup 0/C.

  10. Glass electrolyte composition

    DOEpatents

    Kucera, Gene H.; Roche, Michael F.

    1985-01-01

    An ionically conductive glass is disclosed for use as electrolyte in a high temperature electrochemical cell, particularly a cell with sodium anode and sulfur cathode. The glass includes the constituents Na.sub.2 O, ZrO.sub.2, Al.sub.2 O.sub.3 and SiO.sub.2 in selected proportions to be a single phase solid solution substantially free of crystalline regions and undissolved constituents. Other advantageous properties are an ionic conductivity in excess of 2.times.10.sup.-3 (ohm-cm).sup.-1 at 300.degree. C. and a glass transition temperature in excess of 500.degree. C.

  11. DEVELOPMENT OF A POROUS METALLIC COMPOSITE MATERIAL

    DTIC Science & Technology

    POROUS METALS, ALUMINUM COMPOUNDS, BONDING, CLAY, COATINGS, COMPOSITE MATERIALS, COPPER, DEPOSITS, ELECTROCHEMISTRY, ELECTROPLATING, EXPANDED...PLASTICS, GLASS, GRAPHITE, METALS, NICKEL, OXIDES, PAINTS, PLASTICS, PLATING, POLYMERS, POROUS MATERIALS, SILVER, SPHERES, STYRENES, UREIDES, VACUUM APPARATUS, VAPOR PLATING.

  12. Compositional threshold for Nuclear Waste Glass Durability

    SciTech Connect

    Kruger, Albert A.; Farooqi, Rahmatullah; Hrma, Pavel R.

    2013-04-24

    Within the composition space of glasses, a distinct threshold appears to exist that separates "good" glasses, i.e., those which are sufficiently durable, from "bad" glasses of a low durability. The objective of our research is to clarify the origin of this threshold by exploring the relationship between glass composition, glass structure and chemical durability around the threshold region.

  13. Criticality in Bulk Metallic Glass Constituent Elements

    NASA Astrophysics Data System (ADS)

    Mota, Rodrigo Miguel Ojeda; Graedel, T. E.; Pekarskaya, Evgenia; Schroers, Jan

    2017-07-01

    Bulk metallic glasses (BMGs), which readily form amorphous phases during solidification, are increasingly being used in first applications of watch components, electronic casings, and sporting goods. The compositions of BMGs typically include four to six elements. Various political and geological factors have recently led to supply disruptions for several metals, including some present in BMG compositions. In this work, we assess the "criticality" of 22 technologically interesting BMG compositions, compare the results with those for three common engineering alloy groups, and derive recommendations for BMG composition choices from a criticality perspective. The criticality of BMGs is found to be generally much higher compared with those for the established engineering alloys. Therefore, criticality concerns should also be considered in the choice between existing and developing novel BMGs.

  14. Graphite fiber reinforced glass matrix composites for aerospace applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.; Dicus, D. L.

    1979-01-01

    The graphite fiber reinforced glass matrix composite system is described. Although this composite is not yet a mature material, it possesses low density, attractive mechanical properties at elevated temperatures, and good environmental stability. Properties are reported for a borosilicate glass matrix unidirectionally reinforced with 60 volume percent HMS graphite fiber. The flexural strength and fatigue characteristics at room and elevated temperature, resistance to thermal cycling and continuous high temperature oxidation, and thermal expansion characteristics of the composite are reported. The properties of this new composite are compared to those of advanced resin and metal matrix composites showing that graphite fiber reinforced glass matrix composites are attractive for aerospace applications.

  15. Graphite fiber reinforced glass matrix composites for aerospace applications

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.; Dicus, D. L.

    1979-01-01

    The graphite fiber reinforced glass matrix composite system is described. Although this composite is not yet a mature material, it possesses low density, attractive mechanical properties at elevated temperatures, and good environmental stability. Properties are reported for a borosilicate glass matrix unidirectionally reinforced with 60 volume percent HMS graphite fiber. The flexural strength and fatigue characteristics at room and elevated temperature, resistance to thermal cycling and continuous high temperature oxidation, and thermal expansion characteristics of the composite are reported. The properties of this new composite are compared to those of advanced resin and metal matrix composites showing that graphite fiber reinforced glass matrix composites are attractive for aerospace applications.

  16. Magnetic antenna using metallic glass

    NASA Technical Reports Server (NTRS)

    Desch, Michael D. (Inventor); Farrell, William M. (Inventor); Houser, Jeffrey G. (Inventor)

    1996-01-01

    A lightweight search-coil antenna or sensor assembly for detecting magnetic fields and including a multi-turn electromagnetic induction coil wound on a spool type coil form through which is inserted an elongated coil loading member comprised of metallic glass material wrapped around a dielectric rod. The dielectric rod consists of a plastic or a wooden dowel having a length which is relatively larger than its thickness so as to provide a large length-to-diameter ratio. A tri-axial configuration includes a housing in which is located three substantially identical mutually orthogonal electromagnetic induction coil assemblies of the type described above wherein each of the assemblies include an electromagnetic coil wound on a dielectric spool with an elongated metallic glass coil loading member projecting therethrough.

  17. The dynamic compressive behavior of beryllium bearing bulk metallic glasses

    SciTech Connect

    Bruck, H.A.; Rosakis, A.J.; Johnson, W.L.

    1996-02-01

    In 1993, a new beryllium bearing bulk metallic glass with the nominal composition of Zr{sub 41.25}Ti{sub 13.75}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} was discovered at Caltech. This metallic glass can be cast as cylindrical rods as large as 16 mm in diameter, which permitted specimens to be fabricated with geometries suitable for dynamic testing. For the first time, the dynamic compressive yield behavior of a metallic glass was characterized at strain rates of 10{sup 2} to 10{sup 4}/s by using the split Hopkinson pressure bar. A high-speed infrared thermal detector was also used to determine if adiabatic heating occurred during dynamic deformation of the metallic glass. From these tests it appears that the yield stress of the metallic glass is insensitive to strain rate and no adiabatic heating occurs before yielding. {copyright} {ital 1996 Materials Research Society.}

  18. Production of glass or glass-ceramic to metal seals with the application of pressure

    DOEpatents

    Kelly, Michael D.; Kramer, Daniel P.

    1987-11-10

    In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

  19. Production of glass or glass-ceramic to metal seals with the application of pressure

    DOEpatents

    Kelly, M.D.; Kramer, D.P.

    1985-01-04

    In a process for preparing a glass or glass-ceramic to metal seal comprising contacting the glass with the metal and heat-treating the glass and metal under conditions whereby the glass to metal seal is effected and, optionally, the glass is converted to a glass-ceramic, an improvement comprises carrying out the heat-treating step using hot isostatic pressing.

  20. Composite metal membrane

    DOEpatents

    Peachey, N.M.; Dye, R.C.; Snow, R.C.; Birdsell, S.A.

    1998-04-14

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  1. Composite metal membrane

    DOEpatents

    Peachey, Nathaniel M.; Dye, Robert C.; Snow, Ronny C.; Birdsell, Stephan A.

    1998-01-01

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  2. Metallic glass nanostructures: fabrication, properties, and applications.

    PubMed

    Liu, Lianci; Hasan, Molla; Kumar, Golden

    2014-02-21

    Remarkable progress has been made in fabrication and characterization of metal nanostructures because of their crucial role in energy conversion, nanophotonics, nanoelectronics, and biodiagnostics. Less emphasis has been placed on the synthesis of nanostructures from metallic alloys, which are better suited than elemental metals for certain applications such as fuel-cell catalysts. The main challenges in fabrication of alloy nanostructures are controlling their chemical stoichiometry, crystal structures, and shapes because of anisotropic nucleation and growth rates. These limitations can be overcome by using metallic glasses (amorphous metal alloys) which are isotropic and provide additional control handles through their tunable compositions and degree of crystallinity. Here, we review the recent developments in fabrication and characterization of metallic glass (MG) nanostructures. The focus is on sub-micron structures synthesized by unconventional thermoplastic techniques. A concept of self-assembly is introduced for fashioning functional structures using MG nanostructures as building blocks. The article concludes with a brief discussion about unique properties and prospective applications of MG nanostructures.

  3. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Thompson, E. R.

    1980-01-01

    High levels of mechanical performance in tension, flexure, fatigue, and creep loading situations of graphite fiber reinforced glass matrix composites are discussed. At test temperatures of up to 813 K it was found that the major limiting factor was the oxidative instability of the reinforcing graphite fibers. Particular points to note include the following: (1) a wide variety of graphite fibers were found to be comparable with the glass matrix composite fabrication process; (2) choice of fiber, to a large extent, controlled resultant composite performance; (3) composite fatigue performance was found to be excellent at both 300 K and 703 K; (4) composite creep and stress rupture at temperatures of up to 813 K was limited by the oxidative stability of the fiber; (5) exceptionally low values of composite thermal expansion coefficient were attributable to the dimensional stability of both matrix and fiber; and (6) component fabricability was demonstrated through the hot pressing of hot sections and brazing using glass and metal joining phases.

  4. METAL COMPOSITIONS

    DOEpatents

    Seybolt, A.U.

    1959-02-01

    Alloys of uranium which are strong, hard, and machinable are presented, These alloys of uranium contain bctween 0.1 to 5.0% by weight of at least one noble metal such as rhodium, palladium, and gold. The alloys may be heat treated to obtain a product with iniproved tensile and compression strengths,

  5. Effect of Nb on the corrosion behavior of continuous bulk metallic glass-coated steel wire composites

    NASA Astrophysics Data System (ADS)

    Chen, Xiao-hua; Zhang, Bao-yu; Hui, Xi-dong

    2013-06-01

    (Zr41.2Ti13.8Cu12.5Ni10Be22.5)100- x Nb x (at%, x=0 and 8) bulk metallic glasses (BMGs) were coated on the surface of Q195 steel wires by a continuous coating process. The potentiodynamic polarization tests of these BMGs were conducted in 3.5wt% NaCl aqueous solution. It is found that the addition of 8at% Nb into Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy results in the improvement of corrosion resistance with the pitting potential of -52 mV, the open circuit potential of -446 mV, and the corrosion current density of 9.86×10-6 mA/cm2. This may be attributed to that Nb is beneficial to passivate and stabilize Zr and Ti.

  6. Structural Aspects of Metallic Glasses

    SciTech Connect

    Miracle, Daniel; Egami, Takeshi; Flores, Katharine M; Kelton, Kenneth

    2007-01-01

    A recent structural model reconciles apparently conflicting features of randomness, short-range order, and medium-range order that coexist in metallic glasses. In this efficient cluster packing model, short-range order can be described by efficiently packed solute-centered clusters, producing more than a dozen established atomic clusters, including icosahedra. The observed preference for icosahedral short-range order in metallic glasses is consistent with the theme of efficient atomic packing and is further favored by solvent-centered clusters. Driven by solute-solute avoidance, medium-range order results from the organization in space of overlapping, percolating (via connected pathways), quasi-equivalent clusters. Cubic-like and icosahedral-like organization of these clusters are consistent with measured medium-range order. New techniques such as fluctuation electron microscopy now provide more detailed experimental studies of medium-range order for comparison with model predictions. Microscopic free volume in the efficient cluster packing model is able to represent experimental and computational results, showing free volume complexes ranging from subatomic to atomic-level sizes. Free volume connects static structural models to dynamic processes such as diffusion and deformation. New approaches dealing with 'free' and 'anti-free' microscopic volume and coordinated atomic motion show promise for modeling the complex dynamics of structural relaxations such as the glass transition. Future work unifying static and dynamic structural views is suggested.

  7. Database for waste glass composition and properties

    SciTech Connect

    Peters, R.D.; Chapman, C.C.; Mendel, J.E.; Williams, C.G.

    1993-09-01

    A database of waste glass composition and properties, called PNL Waste Glass Database, has been developed. The source of data is published literature and files from projects funded by the US Department of Energy. The glass data have been organized into categories and corresponding data files have been prepared. These categories are glass chemical composition, thermal properties, leaching data, waste composition, glass radionuclide composition and crystallinity data. The data files are compatible with commercial database software. Glass compositions are linked to properties across the various files using a unique glass code. Programs have been written in database software language to permit searches and retrievals of data. The database provides easy access to the vast quantities of glass compositions and properties that have been studied. It will be a tool for researchers and others investigating vitrification and glass waste forms.

  8. Ductility and work hardening in nano-sized metallic glasses

    SciTech Connect

    Chen, D. Z.; Gu, X. W.; An, Q.; Goddard, W. A.; Greer, J. R.

    2015-02-09

    In-situ nano-tensile experiments on 70 nm-diameter free-standing electroplated NiP metallic glass nanostructures reveal tensile true strains of ∼18%, an amount comparable to compositionally identical 100 nm-diameter focused ion beam samples and ∼3 times greater than 100 nm-diameter electroplated samples. Simultaneous in-situ observations and stress-strain data during post-elastic deformation reveal necking and work hardening, features uncharacteristic for metallic glasses. The evolution of free volume within molecular dynamics-simulated samples suggests a free surface-mediated relaxation mechanism in nano-sized metallic glasses.

  9. Fractal atomic-level percolation in metallic glasses.

    PubMed

    Chen, David Z; Shi, Crystal Y; An, Qi; Zeng, Qiaoshi; Mao, Wendy L; Goddard, William A; Greer, Julia R

    2015-09-18

    Metallic glasses are metallic alloys that exhibit exotic material properties. They may have fractal structures at the atomic level, but a physical mechanism for their organization without ordering has not been identified. We demonstrated a crossover between fractal short-range (<2 atomic diameters) and homogeneous long-range structures using in situ x-ray diffraction, tomography, and molecular dynamics simulations. A specific class of fractal, the percolation cluster, explains the structural details for several metallic-glass compositions. We postulate that atoms percolate in the liquid phase and that the percolating cluster becomes rigid at the glass transition temperature.

  10. Chemical segregation in metallic glass nanowires

    SciTech Connect

    Zhang, Qi; Li, Mo; Li, Qi-Kai

    2014-11-21

    Nanowires made of metallic glass have been actively pursued recently due to the superb and unique properties over those of the crystalline materials. The amorphous nanowires are synthesized either at high temperature or via mechanical disruption using focused ion beam. These processes have potential to cause significant changes in structure and chemical concentration, as well as formation of defect or imperfection, but little is known to date about the possibilities and mechanisms. Here, we report chemical segregation to surfaces and its mechanisms in metallic glass nanowires made of binary Cu and Zr elements from molecular dynamics simulation. Strong concentration deviation are found in the nanowires under the conditions similar to these in experiment via focused ion beam processing, hot imprinting, and casting by rapid cooling from liquid state. Our analysis indicates that non-uniform internal stress distribution is a major cause for the chemical segregation, especially at low temperatures. Extension is discussed for this observation to multicomponent metallic glass nanowires as well as the potential applications and side effects of the composition modulation. The finding also points to the possibility of the mechanical-chemical process that may occur in different settings such as fracture, cavitation, and foams where strong internal stress is present in small length scales.

  11. Amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1984-01-01

    An improved amorphous metal composite and process of making the composite. The amorphous metal composite comprises amorphous metal (e.g. iron) and a low molecular weight thermosetting polymer binder. The process comprises placing an amorphous metal in particulate form and a thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  12. Reactive cluster model of metallic glasses

    SciTech Connect

    Jones, Travis E.; Miorelli, Jonathan; Eberhart, Mark E.

    2014-02-28

    Though discovered more than a half century ago metallic glasses remain a scientific enigma. Unlike crystalline metals, characterized by short, medium, and long-range order, in metallic glasses short and medium-range order persist, though long-range order is absent. This fact has prompted research to develop structural descriptions of metallic glasses. Among these are cluster-based models that attribute amorphous structure to the existence of clusters that are incommensurate with crystalline periodicity. Not addressed, however, are the chemical factors stabilizing these clusters and promoting their interconnections. We have found that glass formers are characterized by a rich cluster chemistry that above the glass transformation temperature promotes exchange as well as static and vibronic sharing of atoms between clusters. The vibronic mechanism induces correlated motions between neighboring clusters and we hypothesize that the distance over which these motions are correlated mediates metallic glass stability and influences critical cooling rates.

  13. Nanometer-scale investigation of compositional and structural evolution during crystallization of melt-spun Co84Nb10B6 metallic glass

    NASA Astrophysics Data System (ADS)

    Lusby, Thomas Alan

    2000-08-01

    Nanocrystalline materials are increasingly showing progress in the quest to control the properties of a solid. As the building blocks of matter approach sizes on the order of 100 nanometers or less, nearly every physical property of the material is altered. One class of nanocrystalline material that has received considerable attention in recent decades and especially in the last several years is that of the metallic glass. This research project was performed in order to obtain a better understanding of the formation of nanocrystalline structure in a Co-based metallic glass. Ribbons of a Co84Nb10B6 metallic glass were rapidly quenched by the melt spinning technique. Field Ion Microscopy (FIM), Atom Probe Field Ion Microscopy (APFIM) and Transmission Electron Microscopy (TEM) were applied to study the micro-structural and nanocompositional changes of Co84Nb10B6 due to annealing. The as-quenched metallic glass was determined to be amorphous by FIM and APFIM. Subsequent annealing at various temperatures and times produced specimens in different stages of phase separation and nanocrystallinity. Crystal nuclei in specimens annealed for one hour at 500, 550, and 600 C were constant in size (4 nm) but increased in number density with increasing temperature. Annealing at 700 C for one hour produced a fully crystalline, three-phase material. The phases consist of a nanocrystalline boride phase, a nanocrystalline Co3Nb phase, both with average grain sizes of 20--50 nm, and a relatively pure cobalt matrix. The various phases exhibited significantly different field evaporation and imaging behavior in the FIM. Prior to this work, it was hypothesized that boron atoms segregating to grain boundaries played a role in limiting the grain growth of this nanocrystalline material. The composition fluctuations across several grain boundaries were analyzed and there was no evidence of boron accumulation. The results of this work suggest another mechanism must be keeping the grains of this

  14. The failure rate of adhesively retained composite core build-ups in comparison with metal-added glass ionomer core build-ups.

    PubMed

    Stober, Thomas; Rammelsberg, P

    2005-01-01

    The purpose of this study was to evaluate the clinical performance of two adhesively retained composite core materials and compare them with a metal-added glass ionomer. The main objective evaluated was total or partial loss of build-ups during the treatment prior to crown cementation. In 187 patients, 315 vital and non-vital teeth were built up after randomisation with either Rebilda D (RD), Rebilda SC (RSC) or Ketac Silver Aplicap (KSA). The composites were applied in the total-etch-technique with the corresponding dentin bonding agent. The metal-added glass ionomer was used with a conditioner. One group of patients was treated by experienced dentists, the other by dental students, in order to evaluate the effects of different levels of experience. Data were analysed using Mann-Whitney-U-Test and binomial logistic regression. The early failure rate (partial or total loss) of core build-ups before crown cementation was significantly higher for KSA (28.8%), as compared to RSC (15.3%, p=0.037) and RD (15%, p=0.025). Most failures were observed during the removal of the temporary crowns. The rate of replacements was between 3.0 (RD/dentists) and 20.4% (KSA/students). Furthermore, we found that build-ups made by students had a significantly higher risk of loss than those made by dentists (p=0.028). Adhesively retained self-curing composites show a better clinical short-term performance and can be recommended as core build-up materials.

  15. Hardening of shear band in metallic glass.

    PubMed

    Wang, J G; Hu, Y C; Guan, P F; Song, K K; Wang, L; Wang, G; Pan, Y; Sarac, B; Eckert, J

    2017-08-01

    Strain hardening, originating from defects such as the dislocation, avails conventional metals of high engineering reliability in applications. However, the hardenability of metallic glass is a long-standing concern due to the lack of similar defects. In this work, we carefully examine the stress-strain relationship in three bulk monolithic metallic glasses. The results show that hardening is surely available in metallic glasses if the effective load-bearing area is considered instantly. The hardening is proposed to result from the remelting and ensuing solidification of the shear-band material under a hydrostatic pressure imposed by the normal stress during the shear banding event. This applied-pressure quenching densifies the metallic glass by discharging the free volume. On the other hand, as validated by molecular dynamics simulations, the pressure promotes the icosahedral short-range order. The densification and icosahedral clusters both contribute to the increase of the shear strength and therefore the hardening in metallic glasses.

  16. Development of high volume fraction SiCP/Al composite-bismuthate glass metal plus dielectric films optics Au-mirror

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Qu, Shengguan; Li, Xiang-Long

    2017-01-01

    This paper reports the development of high volume fraction SiCP/Al composite-bismuthate glass multilayer films optics Au-mirror with high reflectivity in a wavelength range of 760 to 1000 nm. Multilayer films were fabricated using an radio frequency-magnetron sputtering deposition system. The measured reflectivity of Ta2O5/SiO2/Au/Cr metal plus dielectric films optics Au-mirror could reach up to ≥97%. Then, on the basis of experiments, a Φ75-mm high volume fraction SiCP/Al composite-bismuthate glass multilayer optical Au-mirror for a wavelength range of 760 to 1000 nm was manufactured. The tested results indicate that a peak-to-valley value of 0.854λ (λ=632.8 nm) was achieved on the Au-mirror surface, and the slope deviation error for the flat surface was lower than 0.153λ root mean square. The surface roughness of Ta2O5/SiO2/Au/Cr multilayer thin films was 1.30 nm (Ra).

  17. Bulk metallic glass coating of polymer substrates

    NASA Astrophysics Data System (ADS)

    Soinila, Erno; Sharma, Parmanand; Heino, Markku; Pischow, Kaj; Inoue, Akihisa; Hänninen, Hannu

    2009-01-01

    Bulk Metallic Glass (BMG) alloy with the composition of Zr55Cu30Al10Ni5 was deposited by sputtering as thin films on several different engineering polymers and polymer composites. Polycarbonate, polymethyl methacrylate, polyamide 12, polyarylamide (50GF=50 % glass fibers), polyphenylene sulfide (30GF) and polybutylene terephthalate (30GF) were used as substrates. The microstructure of the deposited BMG coatings was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of XRD and SEM studies were consistent with amorphous microstructure. Elemental compositions of the coatings were verified by energy dispersive spectroscopy (EDS). Mechanical properties of the coatings were compared to copper mould cast BMG using nano- indentation tests with similar results. According to the cross-cut tape tests good adhesion was achieved between the studied BMG alloy and all other polymer substrates except polycarbonate. Nano-indentation results showed similar mechanical properties for coating and cast BMG. The results of this study look promising as they open new opportunities for BMG- polymer composite applications.

  18. Metal etching composition

    NASA Technical Reports Server (NTRS)

    Otousa, Joseph E. (Inventor); Thomas, Clark S. (Inventor); Foster, Robert E. (Inventor)

    1991-01-01

    The present invention is directed to a chemical etching composition for etching metals or metallic alloys. The composition includes a solution of hydrochloric acid, phosphoric acid, ethylene glycol, and an oxidizing agent. The etching composition is particularly useful for etching metal surfaces in preparation for subsequent fluorescent penetrant inspection.

  19. High-Entropy Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Wang, W. H.

    2014-10-01

    The high-entropy alloys are defined as solid-solution alloys containing five or more than five principal elements in equal or near-equal atomic percent. The concept of high mixing entropy introduces a new way for developing advanced metallic materials with unique physical and mechanical properties that cannot be achieved by the conventional microalloying approach based on only a single base element. The metallic glass (MG) is the metallic alloy rapidly quenched from the liquid state, and at room temperature it still shows an amorphous liquid-like structure. Bulk MGs represent a particular class of amorphous alloys usually with three or more than three components but based on a single principal element such as Zr, Cu, Ce, and Fe. These materials are very attractive for applications because of their excellent mechanical properties such as ultrahigh (near theoretical) strength, wear resistance, and hardness, and physical properties such as soft magnetic properties. In this article, we review the formation and properties of a series of high-mixing-entropy bulk MGs based on multiple major elements. It is found that the strategy and route for development of the high-entropy alloys can be applied to the development of the MGs with excellent glass-forming ability. The high-mixing-entropy bulk MGs are then loosely defined as metallic glassy alloys containing five or more than five elements in equal or near-equal atomic percent, which have relatively high mixing entropy compared with the conventional MGs based on a single principal element. The formation mechanism, especially the role of the mixing entropy in the formation of the high-entropy MGs, is discussed. The unique physical, mechanical, chemical, and biomedical properties of the high-entropy MGs in comparison with the conventional metallic alloys are introduced. We show that the high-mixing-entropy MGs, along the formation idea and strategy of the high-entropy alloys and based on multiple major elements, might provide

  20. Combinatorial Strategies for the Development of Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Ding, Shiyan

    The systematic identification of multi-component alloys out of the vast composition space is still a daunting task, especially in the development of bulk metallic glasses that are typically based on three or more elements. In order to address this challenge, combinatorial approaches have been proposed. However, previous attempts have not successfully coupled the synthesis of combinatorial libraries with high-throughput characterization methods. The goal of my dissertation is to develop efficient high-throughput characterization methods, optimized to identify glass formers systematically. Here, two innovative approaches have been invented. One is to measure the nucleation temperature in parallel for up-to 800 compositions. The composition with the lowest nucleation temperature has a reasonable agreement with the best-known glass forming composition. In addition, the thermoplastic formability of a metallic glass forming system is determined through blow molding a compositional library. Our results reveal that the composition with the largest thermoplastic deformation correlates well with the best-known formability composition. I have demonstrated both methods as powerful tools to develop new bulk metallic glasses.

  1. Prominent β-relaxations in yttrium based metallic glasses

    SciTech Connect

    Luo, P.; Lu, Z.; Zhu, Z. G.; Li, Y. Z.; Bai, H. Y.; Wang, W. H.

    2015-01-19

    Most metallic glasses (MGs) exhibit weak slow β-relaxation. We report the prominent β-relaxation in YNiAl metallic glass with a wide composition range. Compared with other MGs, the MGs show a pronounced β-relaxation peak and high β-relaxation peak temperature, and the β-relaxation behavior varies significantly with the changes of the constituent elements, which is attributed to the fluctuations of chemical interactions between the components. We demonstrate the correlation between the β-relaxation and the activation of flow units for mechanical behaviors of the MG and show that the MG is model system for studying some controversial issues in glasses.

  2. Understanding the deformation mechanism of individual phases of a ZrTi-based bulk metallic glass matrix composite using in situ diffraction and imaging methods

    SciTech Connect

    Huang, Yongjiang E-mail: yjhuang@hit.edu.cn; Khong, J. C.; Mi, J. E-mail: yjhuang@hit.edu.cn; Connolley, Thomas

    2014-01-20

    The plasticity of a ZrTi-based bulk metallic glass composite consisting of glassy matrix and crystalline dendritic phase was studied in-situ under identical tensile loading conditions using scanning electron microscopy and synchrotron X-ray diffraction. A generic procedure was developed to separate the diffraction information of the crystalline phases away from that of the matrix and to precisely calculate the microscopic strains of the two phases at different macroscopic load steps. In this way, the time-evolved quantitative links between shear bands nucleation/propagation and the corresponding microscopic stress fields around them are established, providing more quantitative understanding on (1) how the shear bands are driven by the local stress field, and (2) the critical stresses required for the shear bands to nucleate in the crystalline phase, propagate through the crystalline/matrix interface, and finally into the matrix.

  3. Fiber glass-bioactive glass composite for bone replacing and bone anchoring implants.

    PubMed

    Vallittu, Pekka K; Närhi, Timo O; Hupa, Leena

    2015-04-01

    Although metal implants have successfully been used for decades, devices made out of metals do not meet all clinical requirements, for example, metal objects may interfere with some new medical imaging systems, while their stiffness also differs from natural bone and may cause stress-shielding and over-loading of bone. Peer-review articles and other scientific literature were reviewed for providing up-dated information how fiber-reinforced composites and bioactive glass can be utilized in implantology. There has been a lot of development in the field of composite material research, which has focused to a large extent on biodegradable composites. However, it has become evident that biostable composites may also have several clinical benefits. Fiber reinforced composites containing bioactive glasses are relatively new types of biomaterials in the field of implantology. Biostable glass fibers are responsible for the load-bearing capacity of the implant, while the dissolution of the bioactive glass particles supports bone bonding and provides antimicrobial properties for the implant. These kinds of combination materials have been used clinically in cranioplasty implants and they have been investigated also as oral and orthopedic implants. The present knowledge suggests that by combining glass fiber-reinforced composite with particles of bioactive glass can be used in cranial implants and that the combination of materials may have potential use also as other types of bone replacing and repairing implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  4. Mechanical failure and glass transition in metallic glasses

    SciTech Connect

    Egami, Takeshi

    2011-01-01

    The current majority view on the phenomenon of mechanical failure in metallic glasses appears to be that it is caused by the activity of some structural defects, such as free-volumes or shear transformation zones, and the concentration of such defects is small, only of the order of 1%. However, the recent results compel us to revise this view. Through molecular dynamics simulation it has been shown that mechanical failure is the stress-induced glass transition. According to our theory the concentration of the liquid-like sites (defects) is well over 20% at the glass transition. We suggest that the defect concentration in metallic glasses is actually very high, and percolation of such defects causes atomic avalanche and mechanical failure. In this article we discuss the glass transition, mechanical failure and viscosity from such a point of view.

  5. Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr-Cu-Al bulk metallic glass composites.

    PubMed

    González, Sergio; Pérez, Pablo; Rossinyol, Emma; Suriñach, Santiago; Dolors Baró, Maria; Pellicer, Eva; Sort, Jordi

    2014-06-01

    The microstructure and mechanical properties of Zr48Cu48 - x Al4M x (M ≡ Fe or Co, x = 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4 material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys with x = 0.5 (5.5% in Zr48Cu47.5Al4Co0.5 and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4 or the alloys with x = 1. Slight variations in the Young's modulus (around 5-10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite-martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr-Cu-Al-(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications.

  6. Boron Nitride Nanotubes-Reinforced Glass Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam; Hurst, Janet B.; Choi, Sung R.

    2005-01-01

    Boron nitride nanotubes of significant lengths were synthesized by reaction of boron with nitrogen. Barium calcium aluminosilicate glass composites reinforced with 4 weight percent of BN nanotubes were fabricated by hot pressing. Ambient-temperature flexure strength and fracture toughness of the glass-BN nanotube composites were determined. The strength and fracture toughness of the composite were higher by as much as 90 and 35 percent, respectively, than those of the unreinforced glass. Microscopic examination of the composite fracture surfaces showed pullout of the BN nanotubes. The preliminary results on the processing and improvement in mechanical properties of BN nanotube reinforced glass matrix composites are being reported here for the first time.

  7. Unusual fast secondary relaxation in metallic glass

    PubMed Central

    Wang, Q.; Zhang, S.T.; Yang, Y.; Dong, Y.D.; Liu, C.T.; Lu, J.

    2015-01-01

    The relaxation spectrum of glassy solids has long been used to probe their dynamic structural features and the fundamental deformation mechanisms. Structurally complicated glasses, such as molecular glasses, often exhibit multiple relaxation processes. By comparison, metallic glasses have a simple atomic structure with dense atomic packing, and their relaxation spectra were commonly found to be simpler than those of molecular glasses. Here we show the compelling evidence obtained across a wide range of temperatures and frequencies from a La-based metallic glass, which clearly shows two peaks of secondary relaxations (fast versus slow) in addition to the primary relaxation peak. The discovery of the unusual fast secondary relaxation unveils the complicated relaxation dynamics in metallic glasses and, more importantly, provides us the clues which help decode the structural features serving as the ‘trigger' of inelasticity on mechanical agitations. PMID:26204999

  8. Statistical thermodynamics and atomic structure of metallic glasses

    NASA Astrophysics Data System (ADS)

    Lass, Eric Andrew

    -containing binary, ternary, and quaternary Zr-and Fe-based metallic glass forming systems. In binary alloys, strong chemical short-range ordering (CSRO) effects are observed, occurring most prominently at compositions which experimentally show the best glass formability (GFA). Partial coordination numbers calculated using CAM correlate well with those determined by neutron and x-ray scattering experiments. Experimentally, Cu-Zr binary glasses exhibit a well-defined glass transition temperature, Tg, while Ni-Zr glasses do not. CAM suggests that the local atomic structure around Cu and Ni atoms is responsible for this difference. Fe-P alloys are shown to have a greater degree of Fe-Fe metallic bonding than Fe-B alloys, possibly elucidating the increased ductility in Fe-based glasses containing P. When BDs are included in CAM, the defect concentration surrounding one particular species in a system is observed to reach a constant value at Tg. Compositional changes in the values of T g predicted by CAM are in excellent agreement with those determined experimentally for both Cu- and Ni-Zr alloys. Using a combination of atomic structural differences and thermodynamic stability of the various phases, an understanding is gained of the difference between glass-forming and non-glass-forming systems. Similarly promising results are observed in ternary metallic glasses. CAM shows the CSRO around Cu atoms in ternary Cu-Zr-Al and Cu-Zr-Ti alloys reaches a maximum near compositions with high GFA. Similar to the binary system, the Zr BD concentration reaches a critical level at experimentally observed Tgs. The use of three-body atomic bonding energies is beneficial in describing ternary interactions in metallic glasses, compared to pair-wise bonding used in other models. Fe-(Mo)-B-P alloys exhibit increased glass stability over their binary counterparts. Replacing 1 at% Fe with Mo in Fe-B-P alloys shows increased stability of the amorphous phase, brought on by the creation of a strong network of Mo

  9. Effects of chemical composition and test conditions on the dynamic tensile response of Zr-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, F.; Laws, K.; Martinez, D.; Trujillo, C. P.; Brown, A. D.; Cerreta, E. K.; Hazell, P. J.; Ferry, M.; Quadir, M. Z.; Jiang, J.; Escobedo, J. P.

    2017-01-01

    The effects of impact velocity and temperature on the dynamic mechanical behavior of two bulk metallic (BMG) alloys with slightly different elemental compositions (Zr55Cu30Ni5Al30 and Zr46Cu38Ag8Al38) have been investigated. Bullet-shaped samples were accelerated by a gas gun to speeds in the 400˜600m/s range and tested at both room temperature and 250°C. The samples impacted steel extrusion dies which subjected the bullets to high strains at relatively high strain-rates. The extruded fragments were subsequently soft recovered by using low density foams and examined by means of optical/scanning electron microscopy and differential scanning calorimetry. It was found that shear banding was the dictating mechanism responsible for the fracture of all BMGs. At room temperature, the Zr55Cu30Ni5Al30 alloy exhibited a higher resistance to fragmentation than the Zr46Cu38Ag8Al38 alloy. At 250°C, significant melting was observed in the recovered fragments of both alloys, which indicates that the BMG glassy structure undergoes a melting process and deformation likely occurs homogeneously.

  10. Glass ceramic-to-metal seals

    DOEpatents

    Not Available

    1982-04-19

    A glass ceramic composition prepared by subjecting a glass composition comprising, by weight, 65 to 80% SiO/sub 2/, 8 to 16% Li/sub 2/O, 2 to 8% Al/sub 2/O/sub 3/, 1 to 8% K/sub 2/O, 1 to 5% P/sub 2/O/sub 5/ and 1.5 to 7% B/sub 2/O/sub 3/, to the following processing steps of heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein, holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii, cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein, and thermally treating the glass composition at a temperature and for a time period sufficient to caus growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient and products containing said composition.

  11. Large size metallic glass gratings by embossing

    NASA Astrophysics Data System (ADS)

    Ma, J.; Yi, J.; Zhao, D. Q.; Pan, M. X.; Wang, W. H.

    2012-09-01

    Bulk metallic glasses have excellent thermoforming ability in their wide supercooled liquid region. We show that large-size metallic glass grating (˜8 × 8 mm2) with fine periodicity and ultra smooth surface feature can be readily fabricated by hot embossing. The method for fabrication of gratings is proved to be much cheaper, and requires low pressure and short time (less than 30 s). The metallic glass gratings exhibit comparable optical properties such as rainbow-like spectrum when shone by fluorescent lamp light.

  12. "Work-Hardenable" ductile bulk metallic glass.

    PubMed

    Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  13. 'Work-Hardenable' Ductile Bulk Metallic Glass

    SciTech Connect

    Das, Jayanta; Eckert, Juergen; Tang Meibo; Wang Weihua; Kim, Ki Buem; Baier, Falko; Theissmann, Ralf

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (<1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive 'work hardening' and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The 'work-hardening' capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  14. Superconducting Metallic Glass Transition-Edge-Sensors

    NASA Technical Reports Server (NTRS)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  15. Cyclic Deformation in Metallic Glasses.

    PubMed

    Sha, Z D; Qu, S X; Liu, Z S; Wang, T J; Gao, H

    2015-10-14

    Despite the utmost importance and decades of experimental studies on fatigue in metallic glasses (MGs), there has been so far little or no atomic-level understanding of the mechanisms involved. Here we perform molecular dynamics simulations of tension-compression fatigue in Cu50Zr50 MGs under strain-controlled cyclic loading. It is shown that the shear band (SB) initiation under cyclic loading is distinctly different from that under monotonic loading. Under cyclic loading, SB initiation takes place when aggregates of shear transformation zones (STZs) accumulating at the MG surface reach a critical size comparable to the SB width, and the accumulation of STZs follows a power law with rate depending on the applied strain. It is further shown that almost the entire fatigue life of nanoscale MGs under low cycle fatigue is spent in the SB-initiation stage, similar to that of crystalline materials. Furthermore, a qualitative investigation of the effect of cycling frequency on the fatigue behavior of MGs suggests that higher cycling frequency leads to more cycles to failure. The present study sheds light on the fundamental fatigue mechanisms of MGs that could be useful in developing strategies for their engineering applications.

  16. Glass transition in binary eutectic systems: best glass-forming composition.

    PubMed

    Wang, Li-Min; Li, Zijing; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

    2010-09-23

    The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

  17. Composition-dependent structural and electronic properties of Mg(95-x)Zn(x)Ca5 metallic glasses: an ab initio molecular dynamics study.

    PubMed

    Li, S N; Liu, J B; Li, J H; Wang, J; Liu, B X

    2015-02-26

    Recent progress in the synthesis of Mg-based metallic glasses (MGs) has allowed them to be considered as potential candidates for biodegradable and bioabsorbable implant materials. In this work, we use the Mg-Zn-Ca system as a representative to investigate the effect of composition on the atomic-level structure and local chemical environment in Mg-based MGs from ab initio molecular dynamics simulations. The results suggest that the short-range order of Mg(95-x)Zn(x)Ca5 (x = 21, 25, 29, and 33) MGs is characterized by Zn-centered icosahedral and icosahedral-like clusters, which show an increasing number and a rising tendency to interpenetrate each other with the enrichment of Zn constituents. A considerable degree of charge transfer between Zn and the surrounding Mg/Ca atoms is observed through electronic structure and bonding character analysis. At Zn-rich compositions, a percolated Zn-Zn network extended throughout the entire sample is formed, upon which the accumulated charges around Zn atoms are associated into a continuous conductivity path. Such results may shed light on the improved corrosion resistance of the Zn-rich Mg-Zn-Ca MGs.

  18. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    The results of research for the origination of graphite-fiber reinforced glass matrix composites are presented. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a glass matrix.

  19. Room temperature homogeneous flow in a bulk metallic glass with low glass transition temperature

    SciTech Connect

    Zhao, K.; Xia, X. X.; Bai, H. Y.; Zhao, D. Q.; Wang, W. H.

    2011-04-04

    We report a high entropy metallic glass of Zn{sub 20}Ca{sub 20}Sr{sub 20}Yb{sub 20}(Li{sub 0.55}Mg{sub 0.45}){sub 20} via composition design that exhibiting remarkable homogeneous deformation without shear banding under stress at room temperature. The glass also shows properties such as low glass transition temperature (323 K) approaching room temperature, low density and high specific strength, good conductivity, polymerlike thermoplastic manufacturability, and ultralow elastic moduli comparable to that of bones. The alloy is thermally and chemically stable.

  20. Ultrahigh stability of atomically thin metallic glasses

    SciTech Connect

    Cao, C. R.; Huang, K. Q.; Zhao, N. J.; Sun, Y. T.; Bai, H. Y.; Gu, L. E-mail: dzheng@iphy.ac.cn Zheng, D. N. E-mail: dzheng@iphy.ac.cn Wang, W. H. E-mail: dzheng@iphy.ac.cn

    2014-07-07

    We report the fabrication and study of thermal stability of atomically thin ZrCu-based metallic glass films. The ultrathin films exhibit striking dynamic properties, ultrahigh thermal stability, and unique crystallization behavior with discrete crystalline nanoparticles sizes. The mechanisms for the remarkable high stability and crystallization behaviors are attributed to the dewetting process of the ultrathin film. We demonstrated a promising avenue for understanding some fundamental issues such as glassy structure, crystallization, deformation, and glass formation through atomic resolution imaging of the two dimensional like metallic glasses.

  1. Glasses, ceramics, and composites from lunar materials

    NASA Technical Reports Server (NTRS)

    Beall, George H.

    1992-01-01

    A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

  2. Glasses, ceramics, and composites from lunar materials

    NASA Astrophysics Data System (ADS)

    Beall, George H.

    1992-02-01

    A variety of useful silicate materials can be synthesized from lunar rocks and soils. The simplest to manufacture are glasses and glass-ceramics. Glass fibers can be drawn from a variety of basaltic glasses. Glass articles formed from titania-rich basalts are capable of fine-grained internal crystallization, with resulting strength and abrasion resistance allowing their wide application in construction. Specialty glass-ceramics and fiber-reinforced composites would rely on chemical separation of magnesium silicates and aluminosilicates as well as oxides titania and alumina. Polycrystalline enstatite with induced lamellar twinning has high fracture toughness, while cordierite glass-ceramics combine excellent thermal shock resistance with high flexural strengths. If sapphire or rutile whiskers can be made, composites of even better mechanical properties are envisioned.

  3. Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr–Cu–Al bulk metallic glass composites

    PubMed Central

    González, Sergio; Pérez, Pablo; Rossinyol, Emma; Suriñach, Santiago; Dolors Baró, Maria; Pellicer, Eva; Sort, Jordi

    2014-01-01

    The microstructure and mechanical properties of Zr48Cu48 − xAl4Mx (M ≡ Fe or Co, x = 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4 material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys with x = 0.5 (5.5% in Zr48Cu47.5Al4Co0.5 and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4 or the alloys with x = 1. Slight variations in the Young’s modulus (around 5–10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite–martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr–Cu–Al–(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications. PMID:27877691

  4. Amorphous Metals and Composites as Mirrors and Mirror Assemblies

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C. (Inventor); Davis, Gregory L. (Inventor); Agnes, Gregory S. (Inventor); Shapiro, Andrew A. (Inventor)

    2016-01-01

    A mirror or mirror assembly fabricated by molding, pressing, assembling, or depositing one or more bulk metal glass (BMG), bulk metal glass composite (BMGMC), or amorphous metal (AM) parts and where the optical surface and backing of the mirror can be fabricated without machining or polishing by utilizing the unique molding capabilities of this class of materials.

  5. Formation of nanostructured metallic glass thin films upon sputtering.

    PubMed

    Ketov, Sergey V; Joksimovic, Rastko; Xie, Guoqiang; Trifonov, Artem; Kurihara, Kazue; Louzguine-Luzgin, Dmitri V

    2017-01-01

    Morphology evolution of the multicomponent metallic glass film obtained by radio frequency (RF) magnetron sputtering was investigated in the present work. Two modes of metallic glass sputtering were distinguished: smooth film mode and clustered film mode. The sputtering parameters, which have the most influence on the sputtering modes, were determined. As a result, amorphous Ni-Nb thin films with a smooth surface and nanoglassy structure were deposited on silica float glass and Si substrates. The phase composition of the target appeared to have a significant influence on the chemical composition of the deposited amorphous thin film. The differences in charge transport and nanomechanical properties between the smooth and nanoglassy Ni-Nb film were also determined.

  6. Major element composition of Luna 20 glasses.

    NASA Technical Reports Server (NTRS)

    Warner, J.; Reid, A. M.; Ridley, W. I.; Brown, R. W.

    1972-01-01

    Ten per cent of the 50 to 150-micron size fraction of Luna 20 soil is glass. A random suite of 270 of these glasses has been analyzed by electron microprobe techniques. The major glass type forms a strong cluster around a mean value corresponding to Highland basalt (anorthositic gabbro) with 70% normative feldspar. Minor glass groups have the compositions of mare basalts and of low-K Fra Mauro type basalts. The glass data indicate that Highland basalt is the major rock type in the highlands north of Mare Fecunditatis.

  7. Structure of glasses containing transition metal ions. Progress report, February 1, 1979-January 31, 1980

    SciTech Connect

    White, W B; Furukawa, T; Tsong, I S.T.; Fox, K; Herman, J S; Houser, C; Nelson, C

    1980-02-01

    New normal coordinate calculations were used to relate the vibrational frequencies of silicate glasses to Si-O force constants. These appear to account for the observed frequency shifts with degree of silica polymerization. Raman spectroscopy has been used to elucidate the structure of sodium borosilicate glasses and of sodium aluminosilicate glasses. Structures of compositionally complex glasses can be understood if spectra are measured on many glasses spaced at small compositional intervals. Optical absorption spectra were used to investigate the structural setting of iron in alkali silicate glasses. Research on the alkali-hydrogen exchange in alkali silicate glasses was completed and additional work on ternary glasses is under way. A series of appendices present completed work on the structural investigations of alkali borosilicate glasses, on the structural setting of transition metal ions in glasses, and on the diffusion of hydrogen in alkali silicate glasses.

  8. Glass transition temperature of bulk metallic glasses: A linear connection with the mixing enthalpy

    NASA Astrophysics Data System (ADS)

    Li, Xuelian; Bian, Xiufang; Hu, Lina; Wu, Yuqin; Guo, Jing; Zhang, Junyan

    2007-05-01

    A linear relationship is found between the glass transition temperature Tg and the absolute value of the mixing enthalpy, |ΔHchem|, for bulk metallic glass systems. The increasing (or lowering) of Tg with an admixture of metals or other elements manifests itself in the larger (or smaller) of |ΔHchem| in a given system. The results indicate that the composition dependence of Tg results from the change of excess entropy (Sex) during thermal excitation. The |ΔHchem|, which relates to the strength of interaction among different atoms, corresponds to part of the Sex at Tg [Sex(Tg)]. The glass transition temperatures for Cu-Zr (Hf)-, Zr-Cu-, and La-Al-based glassy alloys are correlated with the interaction intensity between their based binary eutectic compositions, respectively.

  9. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1985-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  10. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1984-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  11. Metallic glass as a temperature sensor during ion plating

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Spalvins, T.; Buckley, D. H.

    1985-01-01

    The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

  12. Characterization of Al/crystallized Al-based metallic glass composites produced by repeated roll bonding process

    NASA Astrophysics Data System (ADS)

    Alizadeh, Morteza; Khoramkhorshid, Saba; Taghvaei, Amir Hossein; Gokuldoss, Prashanth Konda

    2017-07-01

    Devitrified Al84Gd6Ni7Co3 glassy particles have been used to reinforce Al-matrix composites through repeated roll bonding (RRB) process. Microstructural characterization of the produced composites after various rolling cycles was performed by scanning electron microscopy. Mechanical properties of the fabricated composites were evaluated by the tensile and microhardness tests. The results indicate that the RRB process is successful to produce composites with the negligible amount of flaws and porosity, and it is followed by homogeneous distribution of Al84Gd6Ni7Co3 particles in the Al matrix after nine rolling passes. Elongation of the composites improves significantly upon RRB cycles and the tensile strength and microhardness of them increase more than two times compared to unreinforced Al. According to fractography results, the enhanced mechanical properties are correlated with formation of excellent bonding at the interface of Al84Gd6Ni7Co3 particles and Al matrix. The theoretical values of composites hardness and yield strength calculated based on iso-strain model show a good agreement with respect to the experimental results.

  13. Shaping metallic glasses by electromagnetic pulsing

    PubMed Central

    Kaltenboeck, Georg; Demetriou, Marios D.; Roberts, Scott; Johnson, William L.

    2016-01-01

    With damage tolerance rivalling advanced engineering alloys and thermoplastic forming capabilities analogous to conventional plastics, metallic glasses are emerging as a modern engineering material. Here, we take advantage of their unique electrical and rheological properties along with the classic Lorentz force concept to demonstrate that electromagnetic coupling of electric current and a magnetic field can thermoplastically shape a metallic glass without conventional heating sources or applied mechanical forces. Specifically, we identify a process window where application of an electric current pulse in the presence of a normally directed magnetic field can ohmically heat a metallic glass to a softened state, while simultaneously inducing a large enough magnetic body force to plastically shape it. The heating and shaping is performed on millisecond timescales, effectively bypassing crystallization producing fully amorphous-shaped parts. This electromagnetic forming approach lays the groundwork for a versatile, time- and energy-efficient manufacturing platform for ultrastrong metals. PMID:26853460

  14. Wetting of metals and glasses on Mo

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Saiz, Eduardo; Lopez-Esteban, Sonia; Benhassine, Mehdi; de Coninck, Joel; Rauch, Nicole; Ruehle, Manfred

    2008-01-08

    The wetting of low melting point metals and Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. The selected metals (Au, Cu, Ag) form a simple eutectic with Mo. Metal spreading occurs under nonreactive conditions without interdiffusion or ridge formation. The metals exhibit low (non-zero) contact angles on Mo but this requires temperatures higher than 1100 C in reducing atmospheres in order to eliminate a layer of adsorbed impurities on the molybdenum surface. By controlling the oxygen activity in the furnace, glass spreading can take place under reactive or nonreactive conditions. We have found that in the glass/Mo system the contact angle does not decrease under reactive conditions. In all cases, adsorption from the liquid seems to accelerate the diffusivity on the free molybdenum surface.

  15. Shaping metallic glasses by electromagnetic pulsing

    NASA Astrophysics Data System (ADS)

    Kaltenboeck, Georg; Demetriou, Marios D.; Roberts, Scott; Johnson, William L.

    2016-02-01

    With damage tolerance rivalling advanced engineering alloys and thermoplastic forming capabilities analogous to conventional plastics, metallic glasses are emerging as a modern engineering material. Here, we take advantage of their unique electrical and rheological properties along with the classic Lorentz force concept to demonstrate that electromagnetic coupling of electric current and a magnetic field can thermoplastically shape a metallic glass without conventional heating sources or applied mechanical forces. Specifically, we identify a process window where application of an electric current pulse in the presence of a normally directed magnetic field can ohmically heat a metallic glass to a softened state, while simultaneously inducing a large enough magnetic body force to plastically shape it. The heating and shaping is performed on millisecond timescales, effectively bypassing crystallization producing fully amorphous-shaped parts. This electromagnetic forming approach lays the groundwork for a versatile, time- and energy-efficient manufacturing platform for ultrastrong metals.

  16. Shaping metallic glasses by electromagnetic pulsing.

    PubMed

    Kaltenboeck, Georg; Demetriou, Marios D; Roberts, Scott; Johnson, William L

    2016-02-08

    With damage tolerance rivalling advanced engineering alloys and thermoplastic forming capabilities analogous to conventional plastics, metallic glasses are emerging as a modern engineering material. Here, we take advantage of their unique electrical and rheological properties along with the classic Lorentz force concept to demonstrate that electromagnetic coupling of electric current and a magnetic field can thermoplastically shape a metallic glass without conventional heating sources or applied mechanical forces. Specifically, we identify a process window where application of an electric current pulse in the presence of a normally directed magnetic field can ohmically heat a metallic glass to a softened state, while simultaneously inducing a large enough magnetic body force to plastically shape it. The heating and shaping is performed on millisecond timescales, effectively bypassing crystallization producing fully amorphous-shaped parts. This electromagnetic forming approach lays the groundwork for a versatile, time- and energy-efficient manufacturing platform for ultrastrong metals.

  17. Alloy with metallic glass and quasi-crystalline properties

    SciTech Connect

    Xing, Li-Qian; Hufnagel, Todd C.; Ramesh, Kaliat T.

    2004-02-17

    An alloy is described that is capable of forming a metallic glass at moderate cooling rates and exhibits large plastic flow at ambient temperature. Preferably, the alloy has a composition of (Zr, Hf).sub.a Ta.sub.b Ti.sub.c Cu.sub.d Ni.sub.e Al.sub.f, where the composition ranges (in atomic percent) are 45.ltoreq.a.ltoreq.70, 3.ltoreq.b.ltoreq.7.5, 0.ltoreq.c.ltoreq.4, 3.ltoreq.b+c.ltoreq.10, 10.ltoreq.d.ltoreq.30, 0.ltoreq.e.ltoreq.20, 10.ltoreq.d+e.ltoreq.35, and 5.ltoreq.f.ltoreq.15. The alloy may be cast into a bulk solid with disordered atomic-scale structure, i.e., a metallic glass, by a variety of techniques including copper mold die casting and planar flow casting. The as-cast amorphous solid has good ductility while retaining all of the characteristic features of known metallic glasses, including a distinct glass transition, a supercooled liquid region, and an absence of long-range atomic order. The alloy may be used to form a composite structure including quasi-crystals embedded in an amorphous matrix. Such a composite quasi-crystalline structure has much higher mechanical strength than a crystalline structure.

  18. Glass matrix composites from coal flyash and waste glass

    SciTech Connect

    Boccaccini, A.R.; Buecker, M.; Bossert, J.; Marszalek, K.

    1997-12-31

    Glass matrix composites have been fabricated from waste materials by means of powder technology. Flyash from coal power stations and waste glass, residue of float glass production, were used. Commercial alumina platelets were employed as the reinforcing component. For flyash contents up to 20% by weight nearly fully dense compacts could be fabricated by using relatively low sintering temperatures (650 C). For higher flyash contents the densification was hindered due to the presence of crystalline particles in the as-received flyash, which jeopardized the viscous flow densification mechanism. The addition of alumina platelets resulted in better mechanical properties of the composites than those of the unreinforced matrix, despite a residual porosity present. Young`s modulus, modulus of rupture, hardness and fracture toughness increase with platelet volume fraction. The low brittleness index of the composites suggests that the materials have good machinability. A qualitative analysis of the wear behavior showed that the composite containing 20% by volume platelet addition has a higher wear resistance than the unreinforced matrix. Overall, the results indicate that the materials may compete with conventional glasses and glass-ceramics in technical applications.

  19. Microstructure, mechanical and bio-corrosion properties of Mn-doped Mg-Zn-Ca bulk metallic glass composites.

    PubMed

    Wang, Jingfeng; Huang, Song; Li, Yang; Wei, Yiyun; Xi, Xingfeng; Cai, Kaiyong

    2013-10-01

    The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg69-xZn27Ca4Mnx (x=0, 0.5 and 1at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg69Zn27Ca4 alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545 MPa to 364 MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37 °C revealed that the Mn-doped Mg-Zn-Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg-Zn-Ca alloys extracts were higher than that of pure Mg. Mg68.5Zn27Ca4Mn0.5 exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Fabrication of metallic glass structures

    DOEpatents

    Cline, Carl F.

    1986-01-01

    Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature range.

  1. Fabrication of metallic glass structures

    DOEpatents

    Cline, C.F.

    1983-10-20

    Amorphous metal powders or ribbons are fabricated into solid shapes of appreciable thickness by the application of compaction energy. The temperature regime wherein the amorphous metal deforms by viscous flow is measured. The metal powders or ribbons are compacted within the temperature regime.

  2. Bioactive glass coatings for orthopedic metallic implants

    SciTech Connect

    Lopez-Esteban, Sonia; Saiz, Eduardo; Fujino, Sigheru; Oku, Takeo; Suganuma, Katsuaki; Tomsia, Antoni P.

    2003-06-30

    The objective of this work is to develop bioactive glass coatings for metallic orthopedic implants. A new family of glasses in the SiO2-Na2O-K2O-CaO-MgO-P2O5 system has been synthesized and characterized. The glass properties (thermal expansion, softening and transformation temperatures, density and hardness) are in line with the predictions of established empirical models. The optimized firing conditions to fabricate coatings on Ti-based and Co-Cr alloys have been determined and related to the glass properties and the interfacial reactions. Excellent adhesion to alloys has been achieved through the formation of 100-200 nm thick interfacial layers (Ti5Si3 on Ti-based alloys and CrOx on Co-Cr). Finally, glass coatings, approximately 100 mu m thick, have been fabricated onto commercial Ti alloy-based dental implants.

  3. Glass matrix composites. I - Graphite fiber reinforced glass

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Bacon, J. F.

    1978-01-01

    An experimental program is described in which graphite fibers of Hercules HMS and HTS, Thornel 300, and Celanese DG-12 were used to reinforce, both uniaxially and biaxially, borosilicate pyrex glass. Composite flexural strength distribution, strength as a function of test temperature, fracture toughness and oxidative stability were determined and shown to be primarily a function of fiber type and the quality of fiber-matrix bond formed during composite fabrication. It is demonstrated that the graphite fiber reinforced glass system offers unique possibilities as a high performance structural material.

  4. Structural rejuvenation in bulk metallic glasses

    DOE PAGES

    Tong, Yang; Iwashita, T.; Dmowski, Wojciech; ...

    2015-01-05

    Using high-energy X-ray diffraction we study structural changes in bulk metallic glasses after uniaxial compressive homogeneous deformation at temperatures slightly below the glass transition. We observe that deformation results in structural disordering corresponding to an increase in the fictive, or effective, temperature. However, the structural disordering saturates after yielding. Lastly, examination of the experimental structure and molecular dynamics simulation suggests that local changes in the atomic connectivity network are the main driving force of the structural rejuvenation.

  5. Structural rejuvenation in bulk metallic glasses

    SciTech Connect

    Tong, Yang; Iwashita, T.; Dmowski, Wojciech; Bei, Hongbin; Yokoyama, Y.; Egami, Takeshi

    2015-01-05

    Using high-energy X-ray diffraction we study structural changes in bulk metallic glasses after uniaxial compressive homogeneous deformation at temperatures slightly below the glass transition. We observe that deformation results in structural disordering corresponding to an increase in the fictive, or effective, temperature. However, the structural disordering saturates after yielding. Lastly, examination of the experimental structure and molecular dynamics simulation suggests that local changes in the atomic connectivity network are the main driving force of the structural rejuvenation.

  6. Thulium-based bulk metallic glass

    SciTech Connect

    Yu, H. B.; Yu, P.; Wang, W. H.; Bai, H. Y.

    2008-04-07

    We report the formation and properties of a thulium-based bulk metallic glass (BMG). Compared with other known rare-earth (RE) based BMGs, Tm-based BMGs show features of excellent glass formation ability, considerable higher elastic modulus, smaller Poisson's ratio, high mechanical strength, and intrinsic brittleness. The reasons for the different properties between the Tm-based and other RE-based BMGs are discussed. It is expected that the Tm-based glasses with the unique properties are appropriate candidates for studying some important issues in BMGs.

  7. Lithium and Sodium Resistance of Alkali Metal Vapor Resistant Glasses

    NASA Astrophysics Data System (ADS)

    Kishinevski, Anatoly; Hall, Matthew

    2014-05-01

    A common challenge in atomic physics is that of containing an alkali metal vapor at an elevated temperature and concurrently being able to excite and probe atomic transitions within. Typically glass is used as the material to construct the container, as it is easy to manipulate into any geometry and offers thermal, mechanical, and optical properties that no other material is capable. Unfortunately it has been well established that alkali metal gasses/vapors react readily with silica containing glass and results in a progressive darkening of the material. As the darkening reaction progresses, the optical transmission properties of the glass progressively degrade to an eventual point of uselessness. Alkali metals have been used extensively in frequency standards and magnetometers. The finite life of these alkali metal vapor-containing devices has been accepted despite varying attempts by different teams to solve this problem. As a viable solution, it has been identified there exist a family of glass compositions that contain a marginal amount of silica, may be lampworked using traditional glassblowing techniques, and that offer substantially better alkali vapor resistance. The evaluation of these glasses and their resistance to sodium and lithium vapor at varying pressures and temperatures are discussed.

  8. EFFECTS OF TEST TEMPERATURE ON FLOW OF METALLIC GLASSES

    SciTech Connect

    A.S. NOURI; Y. LIU; P. WESSELING; J. LEWANDOWSKI

    2006-04-12

    Micro-hardness experiments were conducted over a range of temperatures using a Nikon QM micro-hardness machine on a number of metallic glass (e.g. Zr-, Fe-, Al-) systems. Although high micro-hardness was exhibited at room temperature, significant hardness reductions were exhibited near the glass transition temperature, T{sub g}. The effects of changes in test temperature on the micro-hardness will be reported. The effects of exposure time on the hardness evolution at a given temperature will also be summarized to illustrate some of the differences in behavior of the systems shown. The extreme softening near T{sub g}, characteristic of bulk metallic glass systems, enables the exploration of novel deformation processing. In order to develop deformation processing windows, the evaluation of bulk metallic glass mechanical properties under quasi-static conditions and the determination of flow properties at different temperatures and strain rates are reported. The use of such information to create layered/composite bulk metallic glasses will be summarized.

  9. Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Mortensen, Andreas; Llorca, Javier

    2010-08-01

    In metal matrix composites, a metal is combined with another, often nonmetallic, phase to produce a novel material having attractive engineering attributes of its own. A subject of much research in the 1980s and 1990s, this class of materials has, in the past decade, increased significantly in variety. Copper matrix composites, layered composites, high-conductivity composites, nanoscale composites, microcellular metals, and bio-derived composites have been added to a palette that, ten years ago, mostly comprised ceramic fiber- or particle-reinforced light metals together with some well-established engineering materials, such as WC-Co cermets. At the same time, research on composites such as particle-reinforced aluminum, aided by novel techniques such as large-cell 3-D finite element simulation or computed X-ray microtomography, has served as a potent vehicle for the elucidation of the mechanics of high-contrast two-phase elastoplastic materials, with implications that range well beyond metal matrix composites.

  10. Key factors affecting mechanical behavior of metallic glass nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Li, Qi-Kai; Li, Mo

    2017-01-01

    Both strengthening and weakening trends with decreasing diameter have been observed for metallic glass nanowires, sometimes even in the samples with the same chemical composition. How to reconcile the results has reminded a puzzle. Since the detailed stress state and microstructure of metallic glass nanowires may differ from each other significantly depending on preparation, to discover the intrinsic size effect it is necessary to study metallic glass nanowires fabricated differently. Here we show the complex size effects from one such class of metallic glass nanowires prepared by casting using molecular dynamics simulations. As compared with the nanowires of the same composition prepared by other methods, the cast nanowires deform nearly homogeneously with much lower strength but better ductility; and also show strengthening in tension but weakening in compression with decreasing wire diameter. The subtle size dependence is shown to be related to the key factors including internal and surface stress state, atomic structure variation, and presence of various gradients. The complex interplay of these factors at decreasing size leads to the different deformation behaviors.

  11. Key factors affecting mechanical behavior of metallic glass nanowires.

    PubMed

    Zhang, Qi; Li, Qi-Kai; Li, Mo

    2017-01-30

    Both strengthening and weakening trends with decreasing diameter have been observed for metallic glass nanowires, sometimes even in the samples with the same chemical composition. How to reconcile the results has reminded a puzzle. Since the detailed stress state and microstructure of metallic glass nanowires may differ from each other significantly depending on preparation, to discover the intrinsic size effect it is necessary to study metallic glass nanowires fabricated differently. Here we show the complex size effects from one such class of metallic glass nanowires prepared by casting using molecular dynamics simulations. As compared with the nanowires of the same composition prepared by other methods, the cast nanowires deform nearly homogeneously with much lower strength but better ductility; and also show strengthening in tension but weakening in compression with decreasing wire diameter. The subtle size dependence is shown to be related to the key factors including internal and surface stress state, atomic structure variation, and presence of various gradients. The complex interplay of these factors at decreasing size leads to the different deformation behaviors.

  12. Key factors affecting mechanical behavior of metallic glass nanowires

    PubMed Central

    Zhang, Qi; Li, Qi-Kai; Li, Mo

    2017-01-01

    Both strengthening and weakening trends with decreasing diameter have been observed for metallic glass nanowires, sometimes even in the samples with the same chemical composition. How to reconcile the results has reminded a puzzle. Since the detailed stress state and microstructure of metallic glass nanowires may differ from each other significantly depending on preparation, to discover the intrinsic size effect it is necessary to study metallic glass nanowires fabricated differently. Here we show the complex size effects from one such class of metallic glass nanowires prepared by casting using molecular dynamics simulations. As compared with the nanowires of the same composition prepared by other methods, the cast nanowires deform nearly homogeneously with much lower strength but better ductility; and also show strengthening in tension but weakening in compression with decreasing wire diameter. The subtle size dependence is shown to be related to the key factors including internal and surface stress state, atomic structure variation, and presence of various gradients. The complex interplay of these factors at decreasing size leads to the different deformation behaviors. PMID:28134292

  13. Structural considerations in design of lightweight glass-fiber composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Faddoul, J. R.

    1973-01-01

    The development of structurally efficient, metal-lined, glass-fiber composite pressure vessels. Both the current state-of-the-art and current problems are discussed along with fracture mechanics considerations for the metal liner. The design concepts used for metal-lined, glass-fiber, composite pressure vessels are described and the structural characteristics of the composite designs are compared with each other and with homogeneous metal pressure vessels. Specific design techniques and available design data are identified. Results of a current program to evaluate flaw growth and fracture characteristics of the metal liners are reviewed and the impact of these results on composite pressure vessel designs is discussed.

  14. Celsian Glass-Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Dicarlo, James A.

    1996-01-01

    Glass-ceramic matrix reinforced fiber composite materials developed for use in low dielectric applications, such as radomes. Materials strong and tough, exhibit low dielectric properties, and endure high temperatures.

  15. Cooling rates for glass containing lunar compositions

    NASA Technical Reports Server (NTRS)

    Fang, C. Y.; Yinnon, H.; Uhlmann, D. R.

    1983-01-01

    Cooling rates required to form glassy or partly-crystalline bodies of 14 lunar compositions have been estimated using a previously introduced, simplified model. The calculated cooling rates are found to be in good agreement with cooling rates measured for the same compositions. Measurements are also reported of the liquidus temperature and glass transition temperature for each composition. Inferred cooling rates are combined with heat flow analyses to obtain insight into the thermal histories of samples 15422, 14162, 15025, 74220, 74241, 10084, 15425, and 15427. The critical cooling rates required to form glasses of 24 lunar compositions, including the 14 compositions of the present study, are suggested to increase systematically with increasing ratio of total network modifiers/total network formers in the compositions. This reflects the importance of melt viscosity in affecting glass formation.

  16. Bulk Metallic Glasses Deform via Slip Avalanches

    NASA Astrophysics Data System (ADS)

    Antonaglia, James; Wright, Wendelin J.; Gu, Xiaojun; Byer, Rachel R.; Hufnagel, Todd C.; LeBlanc, Michael; Uhl, Jonathan T.; Dahmen, Karin A.

    2014-04-01

    For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model. We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs). Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality. The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses.

  17. Bulk metallic glasses deform via slip avalanches.

    PubMed

    Antonaglia, James; Wright, Wendelin J; Gu, Xiaojun; Byer, Rachel R; Hufnagel, Todd C; LeBlanc, Michael; Uhl, Jonathan T; Dahmen, Karin A

    2014-04-18

    For the first time in metallic glasses, we extract both the exponents and scaling functions that describe the nature, statistics, and dynamics of slip events during slow deformation, according to a simple mean field model. We model the slips as avalanches of rearrangements of atoms in coupled shear transformation zones (STZs). Using high temporal resolution measurements, we find the predicted, different statistics and dynamics for small and large slips thereby excluding self-organized criticality. The agreement between model and data across numerous independent measures provides evidence for slip avalanches of STZs as the elementary mechanism of inhomogeneous deformation in metallic glasses.

  18. Crystallization of heavy metal fluoride glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Bruce, Allan J.; Doremus, R. H.; Moynihan, C. T.

    1984-01-01

    The kinetics of crystallization of a number of fluorozirconate glasses were studied using isothermal and dynamic differential scanning calorimetry and X-ray diffraction. The addition of the fluorides LiF, NaF, AlF3, LaF3 to a base glass composition of ZrF4-BaF2 reduced the tendency to crystallize, probably by modifying the viscosity-temperature relation. ZrF4-BaF2-LaF3-AlF3-NaF glass was the most stable against devitrification and perhaps is the best composition for optical fibers with low scattering loss. Some glasses first crystallize out into metastable beta-BaZr2F10 and beta-BaZrF6 phases, which transform into the most stable alpha-phases when heated to higher temperatures. The size of the crystallites was estimated to be about 600 A from X-ray diffraction.

  19. Crystallization of heavy metal fluoride glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Bruce, Allan J.; Doremus, R. H.; Moynihan, C. T.

    1984-01-01

    The kinetics of crystallization of a number of fluorozirconate glasses were studied using isothermal and dynamic differential scanning calorimetry and X-ray diffraction. The addition of the fluorides LiF, NaF, AlF3, LaF3 to a base glass composition of ZrF4-BaF2 reduced the tendency to crystallize, probably by modifying the viscosity-temperature relation. ZrF4-BaF2-LaF3-AlF3-NaF glass was the most stable against devitrification and perhaps is the best composition for optical fibers with low scattering loss. Some glasses first crystallize out into metastable beta-BaZr2F10 and beta-BaZrF6 phases, which transform into the most stable alpha-phases when heated to higher temperatures. The size of the crystallites was estimated to be about 600 A from X-ray diffraction.

  20. Mechanical properties of bioactive glasses, glass-ceramics and composites.

    PubMed

    Thompson, I D; Hench, L L

    1998-01-01

    The application of bioactive glass and glass-ceramics has been widely documented over the past twenty years but the high modulus and low fracture toughness has made them less applicable for clinical, load bearing, applications. The development of non-resorbable polyethylene and polysulphone matrices for these materials has improved the mechanical properties. However, the primary concern of whether the bioactivity of the composites is reduced is still unresolved. The more recent development of resorbable carrier systems, dextran and collagen, for bioactive glasses does not introduce such problems, hence making this form of composite suitable for novel soft tissue applications. The development of a simple quality index has enabled some of the materials described within this paper to be ranked by their ability to replace bone, thus enabling possible new research directions to be emphasized.

  1. Chemical constraints on fly ash glass compositions

    SciTech Connect

    John H. Brindle; Michael J. McCarthy

    2006-12-15

    The major oxide content and mineralogy of 75 European fly ashes were examined, and the major element composition of the glass phase was obtained for each. Correlation of compositional trends with the glass content of the ash was explored. Alkali content was deduced to have a major influence on glass formation, and this in turn could be related to the probable chemistry of clay minerals in the source coals. Maximal glass content corresponded to high aluminum content in the glass, and this is in accordance with the theoretical mechanism of formation of aluminosilicate glasses, in which network-modifying oxides are required to promote tetrahedral coordination of aluminum in glass chain structures. Iron oxide was found to substitute for alkali oxides where the latter were deficient, and some indications of preferred eutectic compositions were found. The work suggests that the proportion of the glass phase in the ash can be predicted from the coal mineralogy and that the utility of a given ash for processing into geopolymers or zeolites is determined by its source. 23 refs., 7 figs., 1 tab.

  2. Predicting Novel Bulk Metallic Glasses via High- Throughput Calculations

    NASA Astrophysics Data System (ADS)

    Perim, E.; Lee, D.; Liu, Y.; Toher, C.; Gong, P.; Li, Y.; Simmons, W. N.; Levy, O.; Vlassak, J.; Schroers, J.; Curtarolo, S.

    Bulk metallic glasses (BMGs) are materials which may combine key properties from crystalline metals, such as high hardness, with others typically presented by plastics, such as easy processability. However, the cost of the known BMGs poses a significant obstacle for the development of applications, which has lead to a long search for novel, economically viable, BMGs. The emergence of high-throughput DFT calculations, such as the library provided by the AFLOWLIB consortium, has provided new tools for materials discovery. We have used this data to develop a new glass forming descriptor combining structural factors with thermodynamics in order to quickly screen through a large number of alloy systems in the AFLOWLIB database, identifying the most promising systems and the optimal compositions for glass formation. National Science Foundation (DMR-1436151, DMR-1435820, DMR-1436268).

  3. The properties of metal-reinforced glass ionomer materials.

    PubMed

    Chung, K H

    1993-01-01

    The physical properties and bond strengths of two glass ionomer materials reinforced with silver and amalgam alloy powders were compared with those of a conventional material from the same manufacture as well as two commercially available products. The diametral tensile strength, hardness and bonding strength are improved with the addition of either commercial available silver particles or fabricated high-copper amalgam alloy powders to the glass. Simple mixture of the metal or alloy powders with the glass ionomer cement seems to be feasible to improve the properties of the regular cement. However, further studies in formulating an optimal composition of metal or alloy, setting characteristics and long-term clinical evaluation are necessary before proposing uses for this new material.

  4. Design of Cu8Zr5-based bulk metallic glasses

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu-Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100-xNbx, where x =1.5 and 2.5at.%, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.

  5. Ni- and Be-free Zr-based bulk metallic glasses with high glass-forming ability and unusual plasticity.

    PubMed

    Zhu, Shengli; Xie, Guoqiang; Qin, Fengxiang; Wang, Xinmin; Inoue, Akihisa

    2012-09-01

    We developed Ni- and Be-free Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ bulk metallic glasses with large glass-forming ability and unusual plasticity. The alloys have large critical diameters (larger than 10 mm) in a wide composition range (x=0-20). The Zr₅₀Cu₃₅Al₇Pd₅Nb₃ and Zr₅₅Cu₃₀Al₇Pd₅Nb₃ alloys exhibit the largest critical diameter (between 18 and 20 mm). The Zr(45+x)Cu(40-x)Al₇Pd₅Nb₃ bulk metallic glasses also have large plastic elongation in wide composition range (x=10-17). The Zr₆₂Cu₂₃Al₇Pd₅Nb₃ bulk metallic glass exhibits significant plasticity (over 20% of plastic elongation). With increasing Zr content, the compressive strength decreases except for the Zr₆₇Cu₁₈Al₇Pd₅Nb₃ alloy. The fragility parameters were calculated to evaluate the glass-forming ability and plasticity. The fragility exhibits more sensitive correlation with plasticity than glass-forming ability. The ZrCuAlPdNb bulk metallic glasses have high crystallization activation energies of above 300 kJ/mol. The ZrCuAlPdNb bulk metallic glasses are favorable for application to biomaterials.

  6. Graphite fiber reinforced thermoplastic glass matrix composites for use at 1000 F

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Minford, E. J.

    1985-01-01

    The fabrication and properties of the graphite fiber reinforced glass matrix composite system are described. By reinforcing borosilicate glass with graphite fibers it has been possible to develop a composite whose properties can be compared favorably with resin matrix counterparts. Both high elastic modulus and strength can be obtained and maintained to temperatures of approximately 600 C. In addition, composite dimensional stability is superior to resin or metal matrix systems due to the low thermal expansion behavior of the glass matrix.

  7. Metal matrix composite structures

    SciTech Connect

    Krivov, G.A.; Beletsky, V.M.; Gribkov, A.N.

    1993-12-31

    High strength-weight properties, stiffness and fatigue resistance characteristics together with low sensitivity to stress concentration make metal matrix composites (MMC) rather promising for their use in structures. Metal matrix composites consist of a matrix (aluminum, magnesium, titanium and their alloys are the most frequently used) and reinforcers (carbon and boron fibers, high-strength steel wire, silicon carbide whiskers, etc.). This work considers various types of MMC and their applications in structures. The methods of structure production from metal matrix CM of aluminum-boron system with the help of machining, deformation, part joining by welding and riveting are given.

  8. Hard metal composition

    DOEpatents

    Sheinberg, Haskell

    1986-01-01

    A composition of matter having a Rockwell A hardness of at least 85 is formed from a precursor mixture comprising between 3 and 10 weight percent boron carbide and the remainder a metal mixture comprising from 70 to 90 percent tungsten or molybdenum, with the remainder of the metal mixture comprising nickel and iron or a mixture thereof. The composition has a relatively low density of between 7 to 14 g/cc. The precursor is preferably hot pressed to yield a composition having greater than 100% of theoretical density.

  9. Hard metal composition

    DOEpatents

    Sheinberg, H.

    1983-07-26

    A composition of matter having a Rockwell A hardness of at least 85 is formed from a precursor mixture comprising between 3 and 10 wt % boron carbide and the remainder a metal mixture comprising from 70 to 90% tungsten or molybdenum, with the remainder of the metal mixture comprising nickel and iron or a mixture thereof. The composition has a relatively low density of between 7 and 14 g/cc. The precursor is preferably hot pressed to yield a composition having greater than 100% of theoretical density.

  10. Research on graphite reinforced glass matrix composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.; Thompson, E. R.

    1978-01-01

    A composite that can be used at temperatures up to 875 K with mechanical properties equal or superior to graphite fiber reinforced epoxy composites is presented. The composite system consist of graphite fiber, uniaxially or biaxially, reinforced borosilicate glass. The mechanical and thermal properties of such a graphite fiber reinforced glass composite are described, and the system is shown to offer promise as a high performance structural material. Specific properties that were measured were: a modified borosilicate glass uniaxially reinforced by Hercules HMS graphite fiber has a three-point flexural strength of 1030 MPa, a four-point flexural strength of 964 MPa, an elastic modulus of 199 GPa and a failure strain of 0.0052. The preparation and properties of similar composites with Hercules HTS, Celanese DG-102, Thornel 300 and Thornel Pitch graphite fibers are also described.

  11. Statistical Mechanics of Metallic Glasses and Liquids

    NASA Astrophysics Data System (ADS)

    Egami, T.; Levashov, V. A.; Morris, J. R.; Haruyama, O.

    2010-07-01

    It is difficult to formulate the statistical mechanical theory of liquids and glasses, because phonons, which are the basis for the statistical mechanics of lattice dynamics in crystals, are strongly scattered and have a very short lifetime in liquids and glasses. Instead computer simulation and the “free-volume” theory are most frequently used in explaining experimental results on metallic glasses. However, both of them suffer from serious problems, as discussed in this article. We propose an alternative approach based upon the dynamics of the atomic level stresses. We review recent progress with this approach and show that it is possible to calculate thermodynamic quantities, including the glass transition temperature and the kinetics of structural relaxation, by this approach.

  12. Atomic-Scale Mechanisms of the Glass-Forming Ability in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Yang, L.; Guo, G. Q.; Chen, L. Y.; Huang, C. L.; Ge, T.; Chen, D.; Liaw, P. K.; Saksl, K.; Ren, Y.; Zeng, Q. S.; LaQua, B.; Chen, F. G.; Jiang, J. Z.

    2012-09-01

    The issue, composition dependence of glass-forming ability (GFA) in metallic glasses (MG), has been investigated by systematic experimental measurements coupled with theoretical calculations in Cu-Zr and Ni-Nb alloy systems. It is found that the atomic-level packing efficiency strongly relates to their GFA. The best GFA is located at the largest difference in the packing efficiency of the solute-centered clusters between the glassy and crystal alloys in both MG systems. This work provides an understanding of GFA from atomic level and will shed light on the development of new MGs with larger critical sizes.

  13. Glass-metal objects from archaeological excavation: corrosion study

    NASA Astrophysics Data System (ADS)

    Greiner-Wronowa, Elżbieta; Zabiegaj, Dominika; Piccardo, Paolo

    2013-12-01

    This paper contributes to the investigations on history, technology, and degradation of middle age objects (metallic rings with mounted glass beads) recently excavated under the Main Square in Krakow (Poland). Moreover, they were discovered in soil layers differing by chemical composition and microclimate parameters. Historical material is indeed very limited in terms of quantity and sample size, and the following nondestructive analyses were applied: scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), X-ray diffraction (XRD), and X-ray fluorescence spectroscopy (XRF). The glass and the metal were separately tested. Metallography on cross-sections (by both optical and scanning electron microscopy) was applied only on microfragments sampled from metallic rings. The achieved results pointed out how the local microclimate affected the degradation of the analyzed rings developing locally different corrosion processes. Each tested glass of "ring eye" shows a specific chemical composition. All glass pieces were covered by silica gel, and locally more advanced corrosion has been found.

  14. Characteristics of Johari-Goldstein relaxations in bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Qiao, Jichao; Casalini, Riccardo; Pelletier, Jean-Marc; Kato, Hidemi; Yao, Yao; Yao'S Group Team; Chemistry Division, Naval Research Laboratory Team; Pvmh, Mateis, Insa de Lyon Team; Kato'S Lab Team

    2015-03-01

    The dynamics of Pd-based metallic glasses was studied by mechanical spectroscopy and modulated differential scanning calorimetry. The results show the change in composition has a significant effect on the α relaxation dynamics. All Pd-based metallic glasses have similar fragilities, 59 < m <67, and Kohlrausch stretched exponents, 0.59 <βKWW <0.60. The values of m and βKWW correlate well with the general relation proposed by Böhmer et al. for other glassy materials and the substitution of the Ni with Cu induced a large change in the time constant of the β relaxation, τβ. The activation energy, Uβ, of the β relaxation was generally independent of chemical composition. In all cases, 25 glass formers. From the heat capacity and mechanical loss, the number of dynamically correlated units, Ncwere obtained; significantly larger Nc values for these metallic glasses were observed compared with glassy materials.

  15. Producing Metallic Glasses With Acoustic Leviation

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Feng, I. A.

    1983-01-01

    Acoustic fields support and cool liquid particles. Levitated by sound energy, liquid drop in acoustic standing-wave field surrounded by acousticically-induced jet streams. Streaming gas cools drow below its freezing point in small fraction of second. Allows new amorphous alloys including "metallic glass" to be formed.

  16. Metallic Glass Cooling Inside The TEMPUS Furnace

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A sample of advanced metallic glass alloy cools down during an experiment with the TEMPUS furnace on STS-94, July 7, 1997, MET:5/23:35 (approximate). The sequence shows the sample glowing, then fading to black as scientists began the process of preserving the liquid state, but lowering the temperature below the normal solidification temperature of the alloy. This process is known as undercooling. (10 second clip covering approximately 50 seconds.) TEMPUS (stands for Tiegelfreies Elektromagnetisches Prozessiere unter Schwerelosigkeit (containerless electromagnetic processing under weightlessness). It was developed by the German Space Agency (DARA) for flight aboard Spacelab. The DARA project scientist was Igon Egry. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). DARA and NASA are exploring the possibility of flying an advanced version of TEMPUS on the International Space Station. (1.1MB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300188.html.

  17. Metallic Glass Cooling Inside The TEMPUS Furnace

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A sample of advanced metallic glass alloy cools down during an experiment with the TEMPUS furnace on STS-94, July 7, 1997, MET:5/23:35 (approximate). The sequence shows the sample glowing, then fading to black as scientists began the process of preserving the liquid state, but lowering the temperature below the normal solidification temperature of the alloy. This process is known as undercooling. (10 second clip covering approximately 50 seconds.) TEMPUS (stands for Tiegelfreies Elektromagnetisches Prozessiere unter Schwerelosigkeit (containerless electromagnetic processing under weightlessness). It was developed by the German Space Agency (DARA) for flight aboard Spacelab. The DARA project scientist was Igon Egry. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). DARA and NASA are exploring the possibility of flying an advanced version of TEMPUS on the International Space Station. (1.1MB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300188.html.

  18. Atomic structure of biodegradable Mg-based bulk metallic glass.

    PubMed

    Christie, J K

    2015-05-21

    We have used highly accurate first-principles molecular dynamics simulations to elucidate the structure of Mg60Zn35Ca5 and Mg72Zn23Ca5 bulk metallic glasses, which are candidate materials for biomedical implants; these two compositions exhibit different behaviours when implanted. The environments of each species are different, and average coordination numbers are ∼13 for Mg, ∼11 for Zn and ∼18-19 for Ca. A wide range of local environments were found and icosahedral motifs, often seen in bulk metallic glasses, were among the most common for both Mg and Zn. Through the computation of a chemical short-range order parameter, a moderate avoidance of Zn-Zn bonding over Zn-Mg or Zn-Ca was observed. No statistically significant difference in structure was observed between the two compositions.

  19. Dimensionally Stable Graphite-Fiber/Glass Composites

    NASA Technical Reports Server (NTRS)

    Harris, Robert; Bergen, George J.; Studer, Philip A.

    1992-01-01

    Method of making composites of glass matrices reinforced by graphite fibers provides for control of proportions, orientations, and distributions of fibers in matrices and for fused bonds between fibers and matrices. Enables fabrication of composites of high specific strength and dimensional stability. Method particularly suitable for making low-thermal-expansion platforms for optical instruments.

  20. Influence of temperature and glass composition on aluminum nitride contact angle

    NASA Astrophysics Data System (ADS)

    Tarnovskiy, R.; Ditts, A.

    2016-11-01

    Results of research of different glass compositions for possibility of their application in metallization pastes intended for ceramics based on aluminum nitride are presented in this article. It includes research of contact angle of aluminum nitride with glasses of different compositions at different temperatures and different roughness of ceramics.

  1. Mechanical heterogeneity and mechanism of plasticity in metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, J. G.; Zhao, D. Q.; Pan, M. X.; Shek, C. H.; Wang, W. H.

    2009-01-01

    The mechanical heterogeneity is quantified based on the spatial nanohardness distributions in three bulk metallic glasses with different plasticities. It is found that the metallic glass with high mechanical heterogeneity is more plastic. We propose that the appropriate mechanical heterogeneity makes the metallic glasses meliorate their plasticity by increasing inelastic strained area and promoting energy dissipation.

  2. Aluminum Metal Matrix Composites

    SciTech Connect

    Hunt, Warren; Herling, Darrell R.

    2004-02-01

    Metal matrix composites comprise a relatively wide range of materials defined by the metal matrix, reinforcement type, and reinforcement geometry. In the area of the matrix, most metallic systems have been explored for use in metal matrix composites, including Al, Be, Mg, Ti, Fe, Ni, Co, and Ag. By far, the largest usage is in aluminum matrix composites. From a reinforcement perspective, the materials used are typically ceramics since they provide a very desirable combination of stiffness, strength, and relatively low density. Candidate reinforcement materials include SiC, Al2O3, B4C, TiC, TiB2, graphite, and a number of other ceramics. In addition, there has been work on metallic materials as reinforcements, notably W and steel fibers. The morphology of the reinforcement material is another variable of importance in metal matrix composites. The three major classes of reinforcement morphology are continuous fiber, chopped fiber or whisker, and particulate. Typically, the selection of the reinforcement morphology is determined by the desired property/cost combination. Generally, continuous fiber reinforced MMCs provide the highest properties in the direction of the fiber orientation but are the most expensive. Chopped fiber and whisker reinforced materials can produce significant property improvements in the plane or direction of their orientation, at somewhat lower cost. Particulates provide a comparatively more moderate but isotropic increase in properties and are typically available at the lowest cost. By adding to the three variables of metallic matrix, reinforcement material, and reinforcement morphology the further options of reinforcement volume fraction, orientation, and matrix alloy composition and heat treatment, it is apparent that there is a very wide range of available material combinations and resultant properties. This paper will focus on how MMCs have been applied in specific application areas.

  3. Preparation of fullerene/glass composites

    DOEpatents

    Mattes, B.R.; McBranch, D.W.; Robinson, J.M.; Koskelo, A.C.; Love, S.P.

    1995-05-30

    Synthesis of fullerene/glass composites is described. A direct method for preparing solid solutions of C{sub 60} in silicon dioxide (SiO{sub 2}) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these ``guests`` in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C{sub 60}. Depending upon the preparative procedure, C{sub 60} dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C{sub 60} in a solid glass matrix, is generated by the present method.

  4. Preparation of fullerene/glass composites

    DOEpatents

    Mattes, Benjamin R.; McBranch, Duncan W.; Robinson, Jeanne M.; Koskelo, Aaron C.; Love, Steven P.

    1995-01-01

    Synthesis of fullerene/glass composites. A direct method for preparing solid solutions of C.sub.60 in silicon dioxide (SiO.sub.2) glass matrices by means of sol-gel chemistry is described. In order to produce highly concentrated fullerene-sol-gel-composites it is necessary to increase the solubility of these "guests" in a delivery solvent which is compatible with the starter sol (receiving solvent). Sonication results in aggregate disruption by treatment with high frequency sound waves, thereby accelerating the rate of hydrolysis of the alkoxide precursor, and the solution process for the C.sub.60. Depending upon the preparative procedure, C.sub.60 dispersed within the glass matrix as microcrystalline domains, or dispersed as true molecular solutions of C.sub.60 in a solid glass matrix, is generated by the present method.

  5. Plasma-sprayed metal-glass fluoride coatings for lubrication to 1170 K (1650 F)

    NASA Technical Reports Server (NTRS)

    Sliney, H. E.

    1974-01-01

    Plasma spray of Nichrome matrix composite contains dispersed glass for oxidation protection and calcium fluoride for lubrication. Coatings can be applied to bearing journals and bearing bores. Coating was easily machinable and had excellent bond strength on substrate metal.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Stability of Glass Fiber-Plastic Composites

    DTIC Science & Technology

    1974-11-01

    differs between the two main sources ( Owens - Corning and Ferro Corporation) from which samples were obtained for this research program. However...according to published work by Humphrey (8) of Owens - Corning , the approximate composition of S-glass (994) is 65% S1Ü2, 25% A1203 and 10% MgO. From the...fibers. S-glass fibers furnished by both Owens - Corning and Ferro Cor- poration were utilized and the results analyzed using scanning electron 34

  8. Glass/polymer composites and methods of making

    DOEpatents

    Samuels, W. D.; Exarhos, Gregory J.

    1995-01-01

    The present invention relates to new glass/polymer composites and methods for making them. More specifically, the invention is glass/polymer composites having phases that are at the molecular level and thereby practicably indistinguishable. The invention further discloses making molecular phase glass/polymer composites by mixing a glass and a polymer in a compatible solvent.

  9. Glass/polymer composites and methods of making

    DOEpatents

    Samuels, W.D.; Exarhos, G.J.

    1995-06-06

    The present invention relates to new glass/polymer composites and methods for making them. More specifically, the invention is glass/polymer composites having phases that are at the molecular level and thereby practicably indistinguishable. The invention further discloses making molecular phase glass/polymer composites by mixing a glass and a polymer in a compatible solvent.

  10. GLASS COMPOSITION AND PROCESS OF MAKING

    DOEpatents

    Bishay, A.M.

    1962-09-01

    Glass compositions are described which are suitable for scintillators of thermal-neutron counters. The glass consists of from 70 to 75 mole% of B/sub 2/O/ sub 3/, from 7 to 9 mole% of Ce/sub 2/O/sub 3/, and from 23 to 16 mole% of Al/sub 2/O/sub 3/ plus Na/sub 2 /O in a mole ratio of 1 to 1.5. The process of making the glass from cerous oxalate, ammonium pentaborate, sodium carbonate, and hydrated alumina in a nonoxidizing atmosphere at 1400-1500 deg C is given. (AEC)

  11. Tetraethyl orthosilicate-based glass composition and method

    DOEpatents

    Wicks, G.G.; Livingston, R.R.; Baylor, L.C.; Whitaker, M.J.; O`Rourke, P.E.

    1997-06-10

    A tetraethyl orthosilicate-based, sol-gel glass composition with additives selected for various applications is described. The composition is made by mixing ethanol, water, and tetraethyl orthosilicate, adjusting the pH into the acid range, and aging the mixture at room temperature. The additives, such as an optical indicator, filler, or catalyst, are then added to the mixture to form the composition which can be applied to a substrate before curing. If the additive is an indicator, the light-absorbing characteristics of which vary upon contact with a particular analyte, the indicator can be applied to a lens, optical fiber, reagent strip, or flow cell for use in chemical analysis. Alternatively, an additive such as alumina particles is blended into the mixture to form a filler composition for patching cracks in metal, glass, or ceramic piping. 12 figs.

  12. Tetraethyl orthosilicate-based glass composition and method

    DOEpatents

    Wicks, George G.; Livingston, Ronald R.; Baylor, Lewis C.; Whitaker, Michael J.; O'Rourke, Patrick E.

    1997-01-01

    A tetraethyl orthosilicate-based, sol-gel glass composition with additives selected for various applications. The composition is made by mixing ethanol, water, and tetraethyl orthosilicate, adjusting the pH into the acid range, and aging the mixture at room temperature. The additives, such as an optical indicator, filler, or catalyst, are then added to the mixture to form the composition which can be applied to a substrate before curing. If the additive is an indicator, the light-absorbing characteristics of which vary upon contact with a particular analyte, the indicator can be applied to a lens, optical fiber, reagant strip, or flow cell for use in chemical analysis. Alternatively, an additive such as alumina particles is blended into the mixture to form a filler composition for patching cracks in metal, glass, or ceramic piping.

  13. R&D on glass fiber reinforced epoxy resin composites for superconducting Tokamak.

    PubMed

    Hu, Nannan; Wang, Ke; Ma, Hongming; Pan, Wanjiang; Chen, Qingqing

    2016-01-01

    The glass fiber reinforced epoxy resin composites play an important role in superconducting Tokamak, which are used to insulate the metal components, such as superconducting winding, cooling pipes, metal electrodes and so on. For the components made of metal and glass fiber reinforced epoxy resin composites, thermal shrinkage leads to non-ignorable thermal stress, therefore, much attention should be paid on the thermal shrinkage rate of glass fiber reinforced epoxy resin composites. The structural design of glass fiber reinforced epoxy resin composites should aim at reducing thermal stress. In this paper, the density, glass fiber content and thermal shrinkage rate of five insulation tubes were tested. The testing results will be applied in structural design and mechanical analysis of isolators for superconducting Tokamak.

  14. Method for forming glass-to-metal seals

    DOEpatents

    Kramer, Daniel P.; Massey, Richard T.

    1986-01-01

    A method for forming a glass-to-metal seal in which the glass has a higher melting point than the metal. The molten glass is vacuum injection molded onto the metal, thus melting a very thin layer of the surface of the metal long enough to form a seal, but not long enough to cause a distortion in the shape of the metal component.

  15. Method for forming glass-to-metal seals

    DOEpatents

    Kramer, D.P.; Massey, R.T.

    1985-08-26

    Disclosed is a method for forming a glass-to-metal seal in which the glass has a higher melting point than the metal. The molten glass is vacuum injection molded onto the metal, thus melting a very thin layer of the surface of the metal long enough to form a seal, but not long enough to cause a distortion in the shape of the metal component.

  16. Atomic Transport in Metallic Glasses.

    DTIC Science & Technology

    1983-11-01

    creep, amorphous metals, canpositionally modulated films, structural relaxation, iso-configurational flow, bimolecular kinetics, Stokes-Einstein relation ...34 731471 60 rcoe F I iov s isasso Einstain relation from the viscosity. - S/N8CUN@4* 40 CLASSIPICATIOOW OF T04lS PAGEL(010 fON41 EW PREFACE This report...12- tion, B is related to the macroscopic interdiffusion coefficient, B, by r 2 K 13 I+ -.1 (2) where f; is the second derivative, with respect to

  17. Structural aspects of elastic deformation of a metallic glass

    SciTech Connect

    Hufnagel, T. C.; Ott, R. T.; Almer, J.

    2006-02-01

    We report the use of high-energy x-ray scattering to measure strain in a Zr{sub 57}Ti{sub 5}Cu{sub 20}Ni{sub 8}Al{sub 10} bulk metallic glass in situ during uniaxial compression in the elastic regime up to stresses of approximately 60% of the yield stress. The strains extracted in two ways--directly from the normalized scattering data and from the pair correlation functions--are in good agreement with each other for length scales greater than 4 A. The elastic modulus calculated on the basis of this strain is in good agreement with that reported for closely related amorphous alloys based on macroscopic measurements. The strain measured for atoms in the nearest-neighbor shell, however, is smaller than that for more distant shells, and the effective elastic modulus calculated from the strain on this scale is therefore larger, comparable to crystalline alloys of similar composition. These observations are in agreement with previously proposed models in which the nominally elastic deformation of a metallic glass has a significant anelastic component due to atomic rearrangements in topologically unstable regions of the structure. We also observe that the distribution of the atomic-level stresses in the glass becomes more uniform during loading. This implies that the stiffness of metallic glasses may have an entropic contribution, analogous to the entropic contribution in rubber elasticity.

  18. Spinodal Decomposition of Ni-Nb-Y metallic Glasses

    SciTech Connect

    Mattern, Norbert; G, Goerigk; Vainio, U; Miller, Michael K; Gemming, T; Eckert, J

    2009-01-01

    Phase-separated Ni-Nb-Y metallic glasses were prepared by rapid quenching from the melt. The early stages of decomposition were characterized in Ni-Nb-Y alloys with Ni contents of more than 60 at.%. Strongly correlated chemical fluctuations with a nanometer length scale were found to exist in the as-quenched state. The observed fluctuation lengths range from 5 to 12 nm, depending on the actual composition of the glass. The 'frozen-in' early stages of decomposition occur in the deeply undercooled melt due to the reduction in the critical temperature of liquid-liquid phase separation with Ni content. Annealing of the phase-separated Ni{sub 70}Nb{sub 15}Y{sub 15} glass below the crystallization temperature leads to an increase in the amplitude of the fluctuations. However, the wavelength was unchanged, which provides evidence for the spinodal character of the decomposition.

  19. Research on Graphite Reinforced Glass Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bacon, J. F.; Prewo, K. M.

    1977-01-01

    This report contains the results obtained in the first twelve months of research under NASA Langley Contract NAS1-14346 for the origination of graphite-fiber reinforced glass matrix composites. Included in the report is a summary of the research by other investigators in this area. The method selected to form the composites consisted of pulling the graphite fiber through a slurry containing powdered glass, winding up the graphite fiber and the glass it picks up on a drum, drying, cutting into segments, loading the tape segment into a graphite die, and hot pressing. During the course of the work, composites were made with a variety of graphite fibers in a C.G.W. 7740 (Pyrex) glass matrix. The graphite fibers used included Hercules HMS, Hercules HTS, Thornel 300S, and Celanese DG-102 and, of these, the Hercules HMS and Celanese DG-102 graphite fibers in C.G.W. 7740 gave the most interesting but widely different results. Hercules HMS fiber in C.G.W. 7740 glass (Pyrex) showed an average four-point flexural strength of 848 MPa or 127,300 psi. As the test temperature was raised from room temperature to 560 C in argon or vacuum, the strength was higher by 50 percent. However, in air, similar tests at 560 C gave a severe loss in strength. These composites also have good thermal cycle properties in argon or vacuum, greatly increased toughness compared to glass, and no loss in strength in a 100 cycle fatigue test. Celanese DG-102 fiber in C.G.W. 7740 glass (Pyrex) had a much lower flexural strength but did not suffer any loss in this strength when samples were heated to 560 C in air for 4 hrs.

  20. Advances in photo-thermo-refractive glass composition modifications

    NASA Astrophysics Data System (ADS)

    Ivanov, S. A.; Ignatiev, A. I.; Nikonorov, N. V.

    2015-05-01

    The novel photo-thermo-refractive (PTR) glass developed in ITMO University is a very promising optical material for photonic and plasmonic applications. In this paper authors represent study of tin influence on photo thermo inducted crystallization process and make a comparison of the optical and holographic properties of the new and classic composition of glass. Also during this work was made overall optimization of chemical composition namely was optimized concentration of halides, fluorides, bromides which are responsible for crystalline phase properties. Ions of antimony, which playing key role in catching and transferring electrons emitted during the UV exposure and subsequent heating. Also was lowered the concentration of stray impurity ions which a capable to catch photo-electrons. Optical spectra show that new composition of PTR glass has no absorption band in visible range caused by metal nano particles of silver. That allows recording of pure phase holograms in wide spectral range. Furthermore new PTR glass allows receiving refractive index modulation up to 1500 ppm. And the UV exposures needed to achieve maximum changes in refraction index are 6-7 times lower than in classic glass.

  1. Microgravity metal processing: from undercooled liquids to bulk metallic glasses

    PubMed Central

    Hofmann, Douglas C; Roberts, Scott N

    2015-01-01

    Bulk metallic glasses (BMGs) are a novel class of metal alloys that are poised for widespread commercialization. Over 30 years of NASA and ESA (as well as other space agency) funding for both ground-based and microgravity experiments has resulted in fundamental science data that have enabled commercial production. This review focuses on the history of microgravity BMG research, which includes experiments on the space shuttle, the ISS, ground-based experiments, commercial fabrication and currently funded efforts. PMID:28725709

  2. Foamed Bulk Metallic Glass (Foam) Investigation

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This soldering iron has an evacuated copper capsule at the tip that contains a pellet of Bulk Metallic Glass (BMG) aboard the International Space Station (ISS). Prior to flight, researchers sealed a pellet of bulk metallic glass mixed with microscopic gas-generating particles into the copper ampoule under vacuum. Once heated in space, such as in this photograph, the particles generated gas and the BMG becomes a viscous liquid. The released gas made the sample foam within the capsule where each microscopic particle formed a gas-filled pore within the foam. The inset image shows the oxidation of the sample after several minutes of applying heat. Although hidden within the brass sleeve, the sample retained the foam shape when cooled, because the viscosity increased during cooling until it was solid.

  3. Phonon dispersion relation of metallic glasses

    NASA Astrophysics Data System (ADS)

    Crespo, Daniel; Bruna, Pere; Valles, Araceli; Pineda, Eloi

    2016-10-01

    Experimental data on the phase sound speed of metallic glasses show anomalies in the terahertz range, reflecting an underlying complex behavior of their phonon dispersion spectrum not yet explained. We determine the phonon dispersion curve of metallic glasses by means of massive molecular dynamics simulations, allowing us to obtain the low-q region behavior with unprecedented detail. Results confirm that the sound speed is constant below the THz range, down to the macroscopic limit. On the contrary, a hardening of the sound speed, more notable in the transverse case, is found in the THz range. This behavior is modeled in terms of a relaxation model. The model gives quantitative agreement and allows us to determine a new threshold frequency ωh, at the end of the boson-peak region. Above ωh the shear modulus increases dramatically, reflecting the end of the amorphous-like acoustic propagation region characterized by the excess density of vibrational states.

  4. Solid oxide fuel cell having a glass composite seal

    DOEpatents

    De Rose, Anthony J.; Mukerjee, Subhasish; Haltiner, Jr., Karl Jacob

    2013-04-16

    A solid oxide fuel cell stack having a plurality of cassettes and a glass composite seal disposed between the sealing surfaces of adjacent cassettes, thereby joining the cassettes and providing a hermetic seal therebetween. The glass composite seal includes an alkaline earth aluminosilicate (AEAS) glass disposed about a viscous glass such that the AEAS glass retains the viscous glass in a predetermined position between the first and second sealing surfaces. The AEAS glass provides geometric stability to the glass composite seal to maintain the proper distance between the adjacent cassettes while the viscous glass provides for a compliant and self-healing seal. The glass composite seal may include fibers, powders, and/or beads of zirconium oxide, aluminum oxide, yttria-stabilized zirconia (YSZ), or mixtures thereof, to enhance the desirable properties of the glass composite seal.

  5. Delocalized Plastic Flow in Proton-Irradiated Monolithic Metallic Glasses

    PubMed Central

    Heo, Jaewon; Kim, Sunghwan; Ryu, Seunghwa; Jang, Dongchan

    2016-01-01

    Creating new materials with novel properties through structural modification is the Holy Grail of materials science. The range of targetable structures for amplification of mechanical properties in metallic glasses would include types of atomic short range orders at the smallest scale through compositions or morphologies of phases in composites. Even though the usefulness of the latter approach has been successfully demonstrated in the past decades, the feasibility of the former has been incompletely proved with only marginal property improvements reported within experimentally-accessible atomic-level structural changes. Here, we report the significant enhancement of deformability in Zr-based monolithic metallic glass only through the atomic disordering by proton irradiation without altering any other structural traits. Metallic glass nanopillars that originally failed catastrophically without any notable plasticity become capable of attaining more than 30% uniaxial plastic strain accommodated by homogeneous deformation when irradiated to ~1 displacement per atom (DPA). We discuss the atomistic origin of this improved plasticity in terms of density and spatial distributions of icosahedral short range order influenced by irradiation. PMID:26988265

  6. Delocalized Plastic Flow in Proton-Irradiated Monolithic Metallic Glasses.

    PubMed

    Heo, Jaewon; Kim, Sunghwan; Ryu, Seunghwa; Jang, Dongchan

    2016-03-18

    Creating new materials with novel properties through structural modification is the Holy Grail of materials science. The range of targetable structures for amplification of mechanical properties in metallic glasses would include types of atomic short range orders at the smallest scale through compositions or morphologies of phases in composites. Even though the usefulness of the latter approach has been successfully demonstrated in the past decades, the feasibility of the former has been incompletely proved with only marginal property improvements reported within experimentally-accessible atomic-level structural changes. Here, we report the significant enhancement of deformability in Zr-based monolithic metallic glass only through the atomic disordering by proton irradiation without altering any other structural traits. Metallic glass nanopillars that originally failed catastrophically without any notable plasticity become capable of attaining more than 30% uniaxial plastic strain accommodated by homogeneous deformation when irradiated to ~1 displacement per atom (DPA). We discuss the atomistic origin of this improved plasticity in terms of density and spatial distributions of icosahedral short range order influenced by irradiation.

  7. Structural considerations in design of lightweight glass-fiber composite pressure vessels

    NASA Technical Reports Server (NTRS)

    Faddoul, J. R.

    1973-01-01

    The design concepts used for metal-lined glass-fiber composite pressure vessels are described, comparing the structural characteristics of the composite designs with each other and with homogeneous metal pressure vessels. Specific design techniques and available design data are identified. The discussion centers around two distinctly different design concepts, which provide the basis for defining metal lined composite vessels as either (1) thin-metal lined, or (2) glass fiber reinforced (GFR). Both concepts are described and associated development problems are identified and discussed. Relevant fabrication and testing experience from a series of NASA-Lewis Research Center development efforts is presented.

  8. Crystallization of Beryllium-Boron Metallic Glasses

    SciTech Connect

    Jankowski, A F; Wall, M A; Nieh, T G

    2002-02-14

    Prior studies of evaporation and sputter deposition show that the grain size of pure beryllium can be dramatically refined through the incorporation of metal impurities. Recently, the addition of boron at a concentration greater than 11% is shown to serve as a glassy phase former in sputter deposited beryllium. Presently, thermally induced crystallization of the beryllium-boron metallic glass is reported. The samples are characterized during an in-situ anneal treatment with bright field imaging and electron diffraction using transmission electron microscopy. A nanocrystalline structure evolves from the annealed amorphous phase and the crystallization temperature is affected by the boron concentration.

  9. Effects of Composition Changes on Strength, Bend Ductility, Toughness, and Flex-Bending Fatigue of Iron-Based Metallic Glass Ribbons

    NASA Astrophysics Data System (ADS)

    El-Shabasy, Adel B.; Hassan, Hala A.; Lewandowski, John J.

    2012-08-01

    Vickers microhardness, nanohardness, tension tests, notch and fatigue precrack toughness tests, and controlled monotonic and cyclic strain experiments via bending over mandrels of different diameter have been performed on two different chemistries of Fe-based (Fe-Si-B) metallic glass ribbons. The tensile strengths of Fe73.5Cu1Nb3Si13.5B9 were 2000 ± 100 MPa and 1640 ± 35 MPa for Fe78Si9B13, which is consistent with the microhardness trends. High notch toughness ( e.g., 89 ± 0.9 MPam1/2 - Fe73.5Cu1Nb3Si13.5B9; 94.5 ± 5.5 MPam1/2 - Fe78Si9B13) and fatigue precracked toughness of 76 MPam1/2 for the Fe73.5Cu1Nb3Si13.5B9 and 80 MPam1/2 for the Fe78Si9B13 were obtained. Flex-bending cyclic fatigue tests revealed a fatigue limit of 385 MPa for Fe78Si9B13 ribbons, whereas the more brittle behavior of the Fe73.5Cu1Nb3Si13.5B9 ribbons prevented the generation of flex-bending fatigue data. These results are discussed in the light of recent work on metallic glass systems.

  10. Flash Joule heating for ductilization of metallic glasses.

    PubMed

    Okulov, I V; Soldatov, I V; Sarmanova, M F; Kaban, I; Gemming, T; Edström, K; Eckert, J

    2015-07-29

    Metallic glasses (MGs) inherit their amorphous structure from the liquid state, which predetermines their ability to withstand high loads approaching the theoretical limit. However, the absence of slip systems makes them very sensitive to the type of loading and extremely brittle in tension. The latter can be improved by precipitation of ductile crystals, which suppress a catastrophic propagation of shear bands in a glassy matrix. Here we report a novel approach to obtain MG-matrix composites with tensile ductility by flash Joule heating applied to Cu47.5Zr47.5Al5 (at.%) metallic glass. This homogeneous, volumetric and controllable rapid heat treatment allows achieving uniformly distributed metastable B2 CuZr crystals in the glassy matrix. It results in a significant tensile strain of 6.8±0.5%. Moreover, optimized adjustment of the heat-treatment conditions enables tuning of microstructure to achieve desired mechanical properties.

  11. Plastic Deformation in Zirconium Based Metallic Glasses via Nanoindentation

    NASA Astrophysics Data System (ADS)

    Melgarejo-Pinto, Zenon Humberto

    Since the discovery in 1960 of Au-Si amorphous alloy by rapidly quenching with cooling rates up to 106 K/s metallic glasses became as an important research topic in the materials science community because of their intriguing processing routes, structure and properties. Recently, new multicomponent glassy- alloy systems, bulk metallic glasses (BMGs), appeared with lower critical cooling rates (103 to 1 K/s) and superlative properties, such as corrosion resistance, biocompatibility, and high strength/modulus ratio. Nevertheless, low temperature brittleness remains a concern. This brittleness comes from the tendency of plastic deformation to concentrate into extremely narrow shear bands. The present research pursues a better understanding of plastic deformation in metallic glasses (MGs) by studying, via nanoindentation, the effect of thermal history, composition, and loading paths on the mechanical behavior of Zr-based MGs. Differential scanning calorimeter (DSC) analysis helps to assess structural relaxation near glass transition temperature (T g). Broadband nanoindentation creep (BNC) and load transient nanoindentation experiments contribute to characterize the hardness-strain rate behavior and indentation size effects, respectively. As-cast Zr 50Cu45Al5 (at. %) metallic glasses evidenced hardness-strain rate loading path dependence, which gradually disappears by effect of the annealing treatments. Back-stresses effect is theorized as the cause of load path dependence behavior. Relaxation effect at low and high strain rates in BNC traces and load ramps "overshoots" in transient experiments enabled to confirm structural changes during mechanical deformation, which is not considered by thermal activation models of deformation. Most of the Zr-based metallic glasses exhibited measurable overshoot indentation size effect. Nonetheless, creep fraction size effect was observed just in as-cast Zr50Cu45Al5 alloys. Rheological mechanical model helps to both characterize the

  12. Friction behavior of glass and metals in contact with glass in various environments

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1973-01-01

    Sliding friction experiments have been conducted for heat-resistant glass and metals in contact with glass. These experiments were conducted in various environments including vacuum, moist air, dry air, octane, and stearic acid in hexadecane. Glass exhibited a higher friction force in moist air than it did in vacuum when in sliding contact with itself. The metals, aluminum, iron, and gold, all exhibited the same friction coefficient when sliding on glass in vacuum as glass sliding on glass. Gold-to-glass contacts were extremely sensitive to the environment despite the relative chemical inertness of gold.

  13. Polymeric, Metallic, and Other Glasses in Introductory Chemistry

    ERIC Educational Resources Information Center

    Hawkes, Stephen J.

    2008-01-01

    Non-ceramic glasses are not adequately discussed in introductory chemistry. Such glasses include polycarbonate, which many corrective lenses are made of, amber, enamel, gelatin, hard candy, coal, refrigerated glycerol, and metallic glasses that have been marketed in recent decades. What is usually discussed in elementary texts is siliceous glass,…

  14. Polymeric, Metallic, and Other Glasses in Introductory Chemistry

    ERIC Educational Resources Information Center

    Hawkes, Stephen J.

    2008-01-01

    Non-ceramic glasses are not adequately discussed in introductory chemistry. Such glasses include polycarbonate, which many corrective lenses are made of, amber, enamel, gelatin, hard candy, coal, refrigerated glycerol, and metallic glasses that have been marketed in recent decades. What is usually discussed in elementary texts is siliceous glass,…

  15. A Process for Making Bulk Heavy Metal Fluoride Glasses.

    DTIC Science & Technology

    This invention relates to the preparation of glasses, and, in particular, relates to the preparation of heavy metal fluoride glasses with...reproducible high optical qualities. Considerable effort has been expended to develop heavy metal fluoride glasses ( HMFG ) as a viable family of infrared

  16. Molybdenum sealing glass-ceramic composition

    DOEpatents

    Eagan, Robert J.

    1976-01-01

    The invention relates to a glass-ceramic composition having low hydrogen and helium permeability properties, along with high fracture strength, a thermal coefficient of expansion similar to that of molybdenum, and adaptable for hermetically sealing to molybdenum at temperatures of between about 900.degree. and about 950.degree.C. to form a hermatically sealed insulator body.

  17. Bulk formation of metallic glasses and amorphous silicon from the melt

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1984-01-01

    Procedures and compositions for producing metallic glasses in bulk at slow cooling rates were investigated. An attempt was made to form the amorphous phase of the tetrahedrally coordinated elements (Si or Ge) by undercooling the melt. The crystal nucleation behavior of pure liquids and glass formers were examined.

  18. Glass Former Effects on Photoluminescence and Optical Properties of Some Heavy Metal Oxide Glasses Doped with Transition Metal Ions

    NASA Astrophysics Data System (ADS)

    Marzouk, M. A.; Abo-Naf, S. M.; Zayed, H. A.; Hassan, N. S.

    2017-03-01

    Heavy metal oxide (PbO and Bi2O3) glasses doped with transition metal (TM) ions (TiO2, V2O5, Cr2O3, and MnO2) and having low content of common glass formers (B2O3, SiO2, or P2O5) were prepared by the conventional melt annealing method. Ultraviolet, visible absorption, and photoluminescence properties of these glasses were measured, and the data were employed to investigate the prepared glassy samples. The optical absorption spectra of TiO2 and V2O5 exhibited three bands centered at about 240, 305, and 380 nm, followed by a broad asymmetrical near-visible band centered at 425-432 nm, while Cr2O3 and MnO2 exhibited an extended visible peak at 517-548 nm. Results showed that the luminescence intensity changed with different transition metal oxides. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (ΔE) were calculated. The calculated values of the optical energy gap were found to be dependent on the glass composition. The changing values of optical band gap and band tail can be related to the structural changes that are taking place in the glass samples. The variations of the luminescence intensity, values of optical band gap, band tail, and refractive index gave an indication of the potential use of the prepared glasses to design novel optical functional materials with higher optical performance.

  19. Fracture and deformation of a zirconium based bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Flores, Katharine Marie

    the design of metallic glass matrix composites. A ductile particle reinforcement phase blocks the propagation of shear bands and distributes plastic deformation over a larger volume, giving rise to extensive stable crack growth at stress intensities double the intrinsic toughness of the unreinforced bulk metallic glass.

  20. Thermo-mechanical relaxation of stresses in a glass-metal junction

    NASA Astrophysics Data System (ADS)

    Lyubimova, O. N.; Solonenko, E. P.

    2016-10-01

    This work deals with the evaluation of the stress-strain state in an infinite layered cylindrical junction of glass with steel. Structural changes in the glass behavior are described by the Tool-Narayanaswamy-Mazurin-Moynihan model. The relaxation processes in the glass have been presented by the temperature regime depending of the fictive temperature Tf, the relaxation time τ' or the viscosity η and the thermal expansion coefficient α(1). The calculations of the stress components in the glass have been made by using the viscoelastic model. The presented model allows to find the optimal annealing conditions for the creation of the glass- metal composite material.

  1. Spectral descriptors for bulk metallic glasses based on the thermodynamics of competing crystalline phases

    PubMed Central

    Perim, Eric; Lee, Dongwoo; Liu, Yanhui; Toher, Cormac; Gong, Pan; Li, Yanglin; Simmons, W. Neal; Levy, Ohad; Vlassak, Joost J.; Schroers, Jan; Curtarolo, Stefano

    2016-01-01

    Metallic glasses attract considerable interest due to their unique combination of superb properties and processability. Predicting their formation from known alloy parameters remains the major hindrance to the discovery of new systems. Here, we propose a descriptor based on the heuristics that structural and energetic ‘confusion' obstructs crystalline growth, and demonstrate its validity by experiments on two well-known glass-forming alloy systems. We then develop a robust model for predicting glass formation ability based on the geometrical and energetic features of crystalline phases calculated ab initio in the AFLOW framework. Our findings indicate that the formation of metallic glass phases could be much more common than currently thought, with more than 17% of binary alloy systems potential glass formers. Our approach pinpoints favourable compositions and demonstrates that smart descriptors, based solely on alloy properties available in online repositories, offer the sought-after key for accelerated discovery of metallic glasses. PMID:27480126

  2. Spectral descriptors for bulk metallic glasses based on the thermodynamics of competing crystalline phases

    NASA Astrophysics Data System (ADS)

    Perim, Eric; Lee, Dongwoo; Liu, Yanhui; Toher, Cormac; Gong, Pan; Li, Yanglin; Simmons, W. Neal; Levy, Ohad; Vlassak, Joost J.; Schroers, Jan; Curtarolo, Stefano

    2016-08-01

    Metallic glasses attract considerable interest due to their unique combination of superb properties and processability. Predicting their formation from known alloy parameters remains the major hindrance to the discovery of new systems. Here, we propose a descriptor based on the heuristics that structural and energetic `confusion' obstructs crystalline growth, and demonstrate its validity by experiments on two well-known glass-forming alloy systems. We then develop a robust model for predicting glass formation ability based on the geometrical and energetic features of crystalline phases calculated ab initio in the AFLOW framework. Our findings indicate that the formation of metallic glass phases could be much more common than currently thought, with more than 17% of binary alloy systems potential glass formers. Our approach pinpoints favourable compositions and demonstrates that smart descriptors, based solely on alloy properties available in online repositories, offer the sought-after key for accelerated discovery of metallic glasses.

  3. Glass-ceramic hermetic seals to high thermal expansion metals

    DOEpatents

    Kramer, D.P.; Massey, R.T.

    1987-04-28

    A process for forming glass-ceramic materials from an alkaline silica-lithia glass composition comprising 60-72 mole-% SiO/sub 2/, 18-27 mole-% Li/sub 2/O, 0-5 mole-% Al/sub 2/O/sub 3/, 0-6 mole-% K/sub 2/O, 0-3 mole-% B/sub 2/O/sub 3/, and 0.5-2.5 mole-% P/sub 2/O/sub 5/, which comprises heating said glass composition at a first temperature within the 950-1050/degree/C range for 5-60 minutes, and then at a devitrification temperature within the 700-900/degree/C range for about 5-300 minutes to obtain a glass-ceramic having a thermal expansion coefficient of up to 210 x 10/sup /minus/7///degree/C. These ceramics form strong, hermetic seals with high expansion metals such as stainless steel alloys. An intermediate nucleation heating step conducted at a temperature within the range of 675-750/degree/C for 10-120 minutes may be employed between the first stage and the devitrification stage. 1 fig., 2 tabs.

  4. Nanostructured metal-polyaniline composites

    DOEpatents

    Wang, Hsing-Lin; Li, Wenguang; Bailey, James A.; Gao, Yuan

    2010-08-31

    Metal-polyaniline (PANI) composites are provided together with a process of preparing such composites by an electrodeless process. The metal of the composite can have nanoscale structural features and the composites can be used in applications such as catalysis for hydrogenation reactions and for analytical detection methods employing SERS.

  5. Fatigue evaluation of composite-reinforced, integrally stiffened metal panels

    NASA Technical Reports Server (NTRS)

    Dumesnil, C. E.

    1973-01-01

    The fatigue behavior of composite-reinforced, integrally stiffened metal panels was investigated in combined metal and composite materials subjected to fatigue loading. The systems investigated were aluminum-graphite/epoxy, and aluminum-S glass/epoxy. It was found that the composite material would support the total load at limit stress after the metal had completely failed, and the weight of the composite-metal system would be equal to that of an all metal system which would carry the same total load at limit stress.

  6. A predictive structural model for bulk metallic glasses

    PubMed Central

    Laws, K. J.; Miracle, D. B.; Ferry, M.

    2015-01-01

    Great progress has been made in understanding the atomic structure of metallic glasses, but there is still no clear connection between atomic structure and glass-forming ability. Here we give new insights into perhaps the most important question in the field of amorphous metals: how can glass-forming ability be predicted from atomic structure? We give a new approach to modelling metallic glass atomic structures by solving three long-standing problems: we discover a new family of structural defects that discourage glass formation; we impose efficient local packing around all atoms simultaneously; and we enforce structural self-consistency. Fewer than a dozen binary structures satisfy these constraints, but extra degrees of freedom in structures with three or more different atom sizes significantly expand the number of relatively stable, ‘bulk' metallic glasses. The present work gives a new approach towards achieving the long-sought goal of a predictive capability for bulk metallic glasses. PMID:26370667

  7. A predictive structural model for bulk metallic glasses.

    PubMed

    Laws, K J; Miracle, D B; Ferry, M

    2015-09-15

    Great progress has been made in understanding the atomic structure of metallic glasses, but there is still no clear connection between atomic structure and glass-forming ability. Here we give new insights into perhaps the most important question in the field of amorphous metals: how can glass-forming ability be predicted from atomic structure? We give a new approach to modelling metallic glass atomic structures by solving three long-standing problems: we discover a new family of structural defects that discourage glass formation; we impose efficient local packing around all atoms simultaneously; and we enforce structural self-consistency. Fewer than a dozen binary structures satisfy these constraints, but extra degrees of freedom in structures with three or more different atom sizes significantly expand the number of relatively stable, 'bulk' metallic glasses. The present work gives a new approach towards achieving the long-sought goal of a predictive capability for bulk metallic glasses.

  8. NATURAL FIBER OR GLASS REINFORCED POLYPROPYLENE COMPOSITES?

    SciTech Connect

    Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

    2008-08-28

    Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

  9. Natural Fiber or Glass Reinforced Polypropylene Composites?

    NASA Astrophysics Data System (ADS)

    Lorenzi, W.; Di Landro, L.; Casiraghi, A.; Pagano, M. R.

    2008-08-01

    Problems related to the recycle of conventional composite materials are becoming always more relevant for many industrial fields. Natural fiber composites (NFC) have recently gained much attention due to their low cost, environmental gains (eco-compatibility), easy disposal, reduction in volatile organic emissions, and their potential to compete with glass fiber composites (GFC). Interest in natural fibers is not only based over ecological aspects. NFC have good mechanical performances in relation to their low specific weight and low price. A characterization of mechanical properties, dynamic behavior, and moisture absorption is presented.

  10. Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten

    NASA Astrophysics Data System (ADS)

    Martin, Morgana

    2008-10-01

    The research involved performing controlled impact experiments on BMG composites consisting of amorphous Zr57Nb5Cu 15:4Ni12:6Al10 (LM106 or Vitreloy106) with crystalline tungsten reinforcement particles. Monolithic LM106 was also examined to aid in the understanding of the composite. The mechanical behavior of the composite was investigated over a range of strain rates (10-3 s -1 to 106 s-1), stress states (compression, compression-shear, tension), and temperatures (RT to 600°C) to determine the dependence of mechanical properties and deformation and failure modes (i.e., homogeneous deformation vs. inhomogeneous shear banding) on these parameters. Mechanical testing in the quasi-static to intermediate strain-rate regimes was performed using an Instron, Drop Weight Tower, and Split Hopkinson Pressure Bar, respectively. High-strain-rate mechanical properties of the BMG-matrix composite and monolithic BMG were investigated using dynamic compression (reverse Taylor) and dynamic tension (spall) impact experiments performed using a gas gun instrumented with velocity interferometry and high-speed digital photography. These experiments provided information about dynamic strength and deformation modes, and allowed for validation of constitutive models via comparison of experimental and simulated transient deformation profiles and free surface velocity traces. Hugoniot equation of state measurements were performed on the monolithic BMG to investigate the high pressure phase stability of the glass and the possible implications of a high pressure phase transformation on mechanical properties. Specimens were recovered for post-impact microstructural and thermal analysis to gain information about the mechanisms of dynamic deformation and fracture, and to examine for possible shock-induced phase transformations of the amorphous phase. For the composite, mechanical testing revealed positive strain-rate sensitivity of its yield stress and negative strain-rate sensitivity of its

  11. Metallic glass alloys of Zr, Ti, Cu and Ni

    DOEpatents

    Lin, Xianghong; Peker, Atakan; Johnson, William L.

    1997-01-01

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM.sub.1-x Ti.sub.x).sub.a Cu.sub.b (Ni.sub.1-y Co.sub.y).sub.c wherein x is from 0.1 to 0.3, y.cndot.c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b.

  12. Hard and fragile holmium-based bulk metallic glasses

    SciTech Connect

    Luo, Q.; Zhao, D.Q.; Pan, M.X.; Wang, R.J.; Wang, W.H.

    2006-05-01

    A family of holmium-based bulk metallic glasses (BMGs) with high glass-forming ability is obtained. The Ho-based BMGs exhibit much larger elastic moduli and high thermal stability in contrast to other known rare-earth (RE)-based BMGs. In particular, the BMGs show a large value of fragility. It is expected that the hard RE-based glasses with high glass-forming ability and fragile behaviors make them the appropriate candidate for glass transition study.

  13. Stability of bulk metallic glass structure

    SciTech Connect

    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

  14. High temperature glass coatings for superalloys and refractory metals

    NASA Technical Reports Server (NTRS)

    Chapman, J. W.; Grekila, R. B.; Hirayama, C.; Mattox, D. M.

    1970-01-01

    New glasses are used as protective coatings on metals and alloys susceptible to oxidation at high temperatures in oxidizing atmospheres. Glasses are stable and solid at temperatures up to 1000 deg C, adhere well to metal surfaces, and are usable for metals with broad range of expansion coefficients.

  15. Thermomechanical Behavior of Molded Metallic Glass Nanowires

    NASA Astrophysics Data System (ADS)

    Magagnosc, Daniel J.; Chen, Wen; Kumar, Golden; Schroers, Jan; Gianola, Daniel S.

    2016-01-01

    Metallic glasses are disordered materials that offer the unique ability to perform thermoplastic forming operations at low thermal budget while preserving excellent mechanical properties such as high strength, large elastic strain limits, and wear resistance owing to the metallic nature of bonding and lack of internal defects. Interest in molding micro- and nanoscale metallic glass objects is driven by the promise of robust and high performance micro- and nanoelectromechanical systems and miniature energy conversion devices. Yet accurate and efficient processing of these materials hinges on a robust understanding of their thermomechanical behavior. Here, we combine large-scale thermoplastic tensile deformation of collections of Pt-based amorphous nanowires with quantitative thermomechanical studies of individual nanowires in creep-like conditions to demonstrate that superplastic-like flow persists to small length scales. Systematic studies as a function of temperature, strain-rate, and applied stress reveal the transition from Newtonian to non-Newtonian flow to be ubiquitous across the investigated length scales. However, we provide evidence that nanoscale specimens sustain greater free volume generation at elevated temperatures resulting in a flow transition at higher strain-rates than their bulk counterparts. Our results provide guidance for the design of thermoplastic processing methods and methods for verifying the flow response at the nanoscale.

  16. Thermomechanical Behavior of Molded Metallic Glass Nanowires

    PubMed Central

    Magagnosc, Daniel J.; Chen, Wen; Kumar, Golden; Schroers, Jan; Gianola, Daniel S.

    2016-01-01

    Metallic glasses are disordered materials that offer the unique ability to perform thermoplastic forming operations at low thermal budget while preserving excellent mechanical properties such as high strength, large elastic strain limits, and wear resistance owing to the metallic nature of bonding and lack of internal defects. Interest in molding micro- and nanoscale metallic glass objects is driven by the promise of robust and high performance micro- and nanoelectromechanical systems and miniature energy conversion devices. Yet accurate and efficient processing of these materials hinges on a robust understanding of their thermomechanical behavior. Here, we combine large-scale thermoplastic tensile deformation of collections of Pt-based amorphous nanowires with quantitative thermomechanical studies of individual nanowires in creep-like conditions to demonstrate that superplastic-like flow persists to small length scales. Systematic studies as a function of temperature, strain-rate, and applied stress reveal the transition from Newtonian to non-Newtonian flow to be ubiquitous across the investigated length scales. However, we provide evidence that nanoscale specimens sustain greater free volume generation at elevated temperatures resulting in a flow transition at higher strain-rates than their bulk counterparts. Our results provide guidance for the design of thermoplastic processing methods and methods for verifying the flow response at the nanoscale. PMID:26787400

  17. Thermomechanical Behavior of Molded Metallic Glass Nanowires.

    PubMed

    Magagnosc, Daniel J; Chen, Wen; Kumar, Golden; Schroers, Jan; Gianola, Daniel S

    2016-01-20

    Metallic glasses are disordered materials that offer the unique ability to perform thermoplastic forming operations at low thermal budget while preserving excellent mechanical properties such as high strength, large elastic strain limits, and wear resistance owing to the metallic nature of bonding and lack of internal defects. Interest in molding micro- and nanoscale metallic glass objects is driven by the promise of robust and high performance micro- and nanoelectromechanical systems and miniature energy conversion devices. Yet accurate and efficient processing of these materials hinges on a robust understanding of their thermomechanical behavior. Here, we combine large-scale thermoplastic tensile deformation of collections of Pt-based amorphous nanowires with quantitative thermomechanical studies of individual nanowires in creep-like conditions to demonstrate that superplastic-like flow persists to small length scales. Systematic studies as a function of temperature, strain-rate, and applied stress reveal the transition from Newtonian to non-Newtonian flow to be ubiquitous across the investigated length scales. However, we provide evidence that nanoscale specimens sustain greater free volume generation at elevated temperatures resulting in a flow transition at higher strain-rates than their bulk counterparts. Our results provide guidance for the design of thermoplastic processing methods and methods for verifying the flow response at the nanoscale.

  18. DWPF waste glass Product Composition Control System

    SciTech Connect

    Brown, K.G.; Postles, R.L.

    1992-01-01

    The Defense Waste Processing Facility (DWPF) will be used to blend aqueous radwaste (PHA) with solid radwaste (Sludge) in a waste receipt vessel (the SRAT). The resulting SRAT material is transferred to the SME an there blended with ground glass (Frit) to produce a batch of melter feed slurry. The SME material is passed to a hold tank (the MFT) which is used to continuously feed the DWPF melter. The melter. The melter produces a molten glass wasteform which is poured into stainless steel canisters for cooling and, ultimately, shipment to and storage in a geologic repository. The Product Composition Control System (PCCS) is the system intended to ensure that the melt will be processible and that the glass wasteform will be acceptable. This document provides a description of this system.

  19. DWPF waste glass Product Composition Control System

    SciTech Connect

    Brown, K.G.; Postles, R.L.

    1992-07-01

    The Defense Waste Processing Facility (DWPF) will be used to blend aqueous radwaste (PHA) with solid radwaste (Sludge) in a waste receipt vessel (the SRAT). The resulting SRAT material is transferred to the SME an there blended with ground glass (Frit) to produce a batch of melter feed slurry. The SME material is passed to a hold tank (the MFT) which is used to continuously feed the DWPF melter. The melter. The melter produces a molten glass wasteform which is poured into stainless steel canisters for cooling and, ultimately, shipment to and storage in a geologic repository. The Product Composition Control System (PCCS) is the system intended to ensure that the melt will be processible and that the glass wasteform will be acceptable. This document provides a description of this system.

  20. Slip avalanche in nanoscratching of metallic glasses

    NASA Astrophysics Data System (ADS)

    Han, D. X.; Wang, G.; Ren, J. L.; Song, S. X.; Li, J.; Yi, J.; Jia, Y. D.; Xu, H.; Chan, K. C.; Liaw, P. K.

    2017-09-01

    Slip avalanches, similar to discrete earthquake events, of Zr-, Co-, and Ce-based metallic glasses during nanoscratching were investigated. Differing from the conventional continuum approach, mean-field theory, which is an inherently-discrete model, was applied to analytically compute intermittent slip avalanches. Mean-field theory was first connected with the potential energy barrier and concentration of free volume in order to study the stick-slip behavior. The results suggest that the motion behavior of free volume affects the critical slip avalanche size.

  1. New Class of Plastic Bulk Metallic Glass

    NASA Astrophysics Data System (ADS)

    Chen, L. Y.; Fu, Z. D.; Zhang, G. Q.; Hao, X. P.; Jiang, Q. K.; Wang, X. D.; Cao, Q. P.; Franz, H.; Liu, Y. G.; Xie, H. S.; Zhang, S. L.; Wang, B. Y.; Zeng, Y. W.; Jiang, J. Z.

    2008-02-01

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

  2. Glass former composition and method for immobilizing nuclear waste using the same

    DOEpatents

    Cadoff, Laurence H.; Smith-Magowan, David B.

    1988-01-01

    An alkoxide glass former composition has silica-containing constituents present as solid particulates of a particle size of 0.1 to 0.7 micrometers in diameter in a liquid carrier phase substantially free of dissolved silica. The glass former slurry is resistant to coagulation and may contain other glass former metal constituents. The immobilization of nuclear waste employs the described glass former by heating the same to reduce the volume, mixing the same with the waste, and melting the resultant mixture to encapsulate the waste in the resultant glass.

  3. An Assessment of Binary Metallic Glasses: Correlations Between Structure, Glass Forming Ability and Stability (Preprint)

    DTIC Science & Technology

    2009-04-01

    through 3.5) and physical properties of the constituent elements (Sections 3.6 and 3.7) on the thermal stability and thickness of binary metallic glasses...containing alkali metals , inert gas and halogen elements were not found in this assessment. Most metallic elements have been used to produce binary metallic ... properties such as partial pair distribution functions recommend binary metallic glasses for more extensive characterization. There are surprisingly few

  4. Stochastic metallic-glass cellular structures exhibiting benchmark strength.

    PubMed

    Demetriou, Marios D; Veazey, Chris; Harmon, John S; Schramm, Joseph P; Johnson, William L

    2008-10-03

    By identifying the key characteristic "structural scales" that dictate the resistance of a porous metallic glass against buckling and fracture, stochastic highly porous metallic-glass structures are designed capable of yielding plastically and inheriting the high plastic yield strength of the amorphous metal. The strengths attainable by the present foams appear to equal or exceed those by highly engineered metal foams such as Ti-6Al-4V or ferrous-metal foams at comparable levels of porosity, placing the present metallic-glass foams among the strongest foams known to date.

  5. Effect of Zr on microstructure of metallic glass coatings prepared by gas tunnel type plasma spraying.

    PubMed

    Kobayashi, A; Kuroda, T; Kimura, H; Inoue, A

    2012-06-01

    Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared.

  6. SCOPING MELTING STUDIES OF HIGH ALUMINA WASTE GLASS COMPOSITIONS

    SciTech Connect

    Kroll, Jared O.; Schweiger, Michael J.; Vienna, John D.

    2015-09-04

    Glass property models will be used at the Hanford Tank Waste Treatment and Immobilization Plant to formulate durable high-level waste glasses for disposal. A major effort is focused on expanding glass property models to cover a broader range of wastes and higher waste-loaded glasses. As a part of this effort, a statistically designed matrix of high-alumina glass compositions was developed. Forty five compositions were selected from the matrix to evaluate glass properties. Of these compositions, thirty three produced homogeneous glasses. The other twelve compositions contained segregated phases and high crystallinity; these were iteratively modified in an attempt to produce homogeneous glass samples while altering the original composition as little as possible. This paper focuses on the characterization of the twelve inhomogeneous compositions and their modifications using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy.

  7. Correlations between elastic moduli and molar volume in metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, J. Q.; Wang, W. H.; Yu, H. B.; Bai, H. Y.

    2009-03-01

    We report clear correlations between bulk modulus (K) and average molar volume Vm, and between Poisson's ratio ν and Vm for various bulk metallic glasses. The origin for the correlations between elastic moduli and Vm are discussed. The established correlation, associated with Poisson's ratio ν, and since the ν correlates with plasticity of metallic glasses, indicates that the average molar volume is important factor to be considered for plastic metallic glasses searching. The found correlations also suggest a close relation between the mechanical properties and the short-range atomic bonding, and assist in understanding deformation behavior in metallic glasses.

  8. Spin-exchange interaction between transition metals and metalloids in soft-ferromagnetic metallic glasses

    NASA Astrophysics Data System (ADS)

    Das, Santanu; Choudhary, Kamal; Chernatynskiy, Aleksandr; Choi Yim, Haein; Bandyopadhyay, Asis K.; Mukherjee, Sundeep

    2016-06-01

    High-performance magnetic materials have immense industrial and scientific importance in wide-ranging electronic, electromechanical, and medical device technologies. Metallic glasses with a fully amorphous structure are particularly suited for advanced soft-magnetic applications. However, fundamental scientific understanding is lacking for the spin-exchange interaction between metal and metalloid atoms, which typically constitute a metallic glass. Using an integrated experimental and molecular dynamics approach, we demonstrate the mechanism of electron interaction between transition metals and metalloids. Spin-exchange interactions were investigated for a Fe-Co metallic glass system of composition [(Co1-x Fe x )0.75B0.2Si0.05]96Cr4. The saturation magnetization increased with higher Fe concentration, but the trend significantly deviated from simple rule of mixtures. Ab initio molecular dynamics simulation was used to identify the ferromagnetic/anti-ferromagnetic interaction between the transition metals and metalloids. The overlapping band-structure and density of states represent ‘Stoner type’ magnetization for the amorphous alloys in contrast to ‘Heisenberg type’ in crystalline iron. The enhancement of magnetization by increasing iron was attributed to the interaction between Fe 3d and B 2p bands, which was further validated by valence-band study.

  9. Magnetic behavior of Gd4Co3 metallic glass

    NASA Astrophysics Data System (ADS)

    Zhang, Ji Liang; Zheng, Zhi Gang; Cao, Wen Huan; Shek, Chan Hung

    2013-01-01

    Metallic glass was successfully fabricated of the Gd4Co3 intermetallic composition. Analysis of the magnetization-temperature data showed that the moment per Gd atom was larger than its theoretical value and indicated the contribution from the Co moment. The maximum magnetic entropy change of glassy Gd4Co3 was determined as -7.2 J kg-1 K-1 at 50 kOe and -3.8 J kg-1 K-1 at 20 kOe, which are both much larger than those of its crystalline state.

  10. Sink property of metallic glass free surfaces

    SciTech Connect

    Shao, Lin; Fu, Engang; Price, Lloyd; Chen, Di; Chen, Tianyi; Wang, Yongqiang; Xie, Guoqiang; Lucca, Don A.

    2015-03-16

    When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences. For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.

  11. Sink property of metallic glass free surfaces

    DOE PAGES

    Shao, Lin; Fu, Engang; Price, Lloyd; ...

    2015-03-16

    When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences.more » For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.« less

  12. Second virial coefficient and mechanical moduli of metallic glasses

    NASA Astrophysics Data System (ADS)

    Cao, Wan Qiang

    2013-10-01

    The relationship between the bulk, shear moduli and second virial coefficient of amorphous materials is derived according to their dependences with the radial distribution function. Lennard-Jones-Gaussian potential is used to investigate the relationship between second virial coefficient and temperature, where Lennard-Jones potential represents interactions with the nearest neighbor atoms, and Gaussian potential is responsible for the multi-atom interactions including the next nearest neighbor atoms and heterogeneous structures for a metallic glass. The results show that deep potential well formed by Gaussian potential causes a large second virial coefficient at low temperatures, which is very obvious for the larger fragility glasses. The quadratic form relationship of shear modulus and compositions is proposed, and confirmed by the experimental results of PdxNi100-x-20P20 alloy.

  13. DWPF (Defense Waste Processing Facility) glass composition control based on glass properties

    SciTech Connect

    Carter, J T; Brown, K G; Bickford, D F

    1988-01-01

    The Defense Waste Processing Facility (DWPF) will immobilize Savannah River Plant (SRP) High Level Waste as a durable borosilicate glass for permanent disposal in a civilian repository. The DWPF will be controlled based on glass composition. The waste glass physical and chemical properties, such as viscosity, liquidus temperature, and durability are functions of glass chemistry. Preliminary models have been developed to evaluate the effects of feed composition variability on the glass properties. These properties are presently being related to the waste glass composition in order to develop process control paradigms that include batching algorithms, hold points, and transfer limits. 3 refs., 6 tabs.

  14. Intermediate-range order in simple metal-phosphate glasses: The effect of metal cations on the phosphate anion distribution

    SciTech Connect

    Sales, B.C.; Boatner, L.A.; Ramey, J.O.

    1997-06-01

    The technique of high-performance liquid chromatography (HPLC) has been used to probe the phosphate anion distribution in a variety of metal phosphate glasses including glasses made with trivalent metal cations (Al, In, Ga, La). The composition of each glass was chosen so that the average phosphate chain length was between 2 and 4 PO{sub 4} tetrahedra. The widths of the resulting phosphate anion distributions were determined directly from an analysis of the HPLC chromatograms. Literature values for the free energy of formation of the crystalline metal-orthophosphate compounds with respect to P{sub 2}O{sub 5} and the metal oxide, were compared to the chromatogram widths. It was found that the smaller the energy of formation, the wider the distribution of phosphate chains, and the greater the ease of glass formation.

  15. Glass formation, chemical properties and surface analysis of Cu-based bulk metallic glasses.

    PubMed

    Qin, Chunling; Zhao, Weimin; Inoue, Akihisa

    2011-01-01

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

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

    PubMed Central

    Qin, Chunling; Zhao, Weimin; Inoue, Akihisa

    2011-01-01

    This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs). In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni) and Cu–Zr–Ag–Al–(Nb) bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS) analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance. PMID:21731441

  17. Metallic threaded composite fastener

    NASA Technical Reports Server (NTRS)

    Dunn, Thomas J. (Inventor)

    1992-01-01

    A metallic threaded composite fastener, particularly suited for high temperature applications, has a body member made of high temperature resistant composite material with a ceramic coating. The body member has a head portion configured to be installed in a countersunk hole and a shank portion which is noncircular and tapered. One part of the shank may be noncircular and the other part tapered, or the two types of surface could be combined into a frustum of a noncircular cone. A split collar member made of high strength, high temperature tolerant metal alloy is split into two halves and the interior of the halves are configured to engage the shank. The exterior of the collar has a circumferential groove which receives a lock ring to secure the collar halves to the shank. In the assembled condition torque may be transmitted from the body to the split collar by the engaged noncircular portions to install and remove the fastener assembly into or from a threaded aperture and shear loads in the collar threads are transferred to the shank tapered portion as a combination of radial compression and axial tension loads. Thus, tension loads may be applied to the fastener shank without damaging the ceramic coating.

  18. Bulk Formation of Metallic Glasses and Amorphous Silicon from the Melt

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1985-01-01

    By using metallic glass compositions with a high relative glass transition temperature, such as Pd40Ni40P20, homogeneous nucleation also becomes negligible. Large (5g) masses of this alloys were obtained using a molten B2O3 flux. Presently, bulk glass formation in iron based glasses is being investigated. It is expected that if an undercooling of about 250K can be achieved in a Ge or Si melt, formation of the amorphous semiconductor phase (rather than the crystal) may be kinetically favored. The volumetric behavior of undercooled liquid Ga droplet dispersion is investigated by dilatometry. A theoretical model (both analytical and numerical) was developed for transient nucleation in glass forming melts. The model, originally designed for isothermal conditions, was extended to continuous quenching. It is being applied to glass formation in various metallic and oxide systems. A further refinement will be the inclusion of diffusion controlled interfacial rearrangements governing the growth of the crystal embryos.

  19. Bulk Formation of Metallic Glasses and Amorphous Silicon from the Melt

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1985-01-01

    By using metallic glass compositions with a high relative glass transition temperature, such as Pd40Ni40P20, homogeneous nucleation also becomes negligible. Large (5g) masses of this alloys were obtained using a molten B2O3 flux. Presently, bulk glass formation in iron based glasses is being investigated. It is expected that if an undercooling of about 250K can be achieved in a Ge or Si melt, formation of the amorphous semiconductor phase (rather than the crystal) may be kinetically favored. The volumetric behavior of undercooled liquid Ga droplet dispersion is investigated by dilatometry. A theoretical model (both analytical and numerical) was developed for transient nucleation in glass forming melts. The model, originally designed for isothermal conditions, was extended to continuous quenching. It is being applied to glass formation in various metallic and oxide systems. A further refinement will be the inclusion of diffusion controlled interfacial rearrangements governing the growth of the crystal embryos.

  20. Metal Nanoparticle Aerogel Composites

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Ignont, Erica; Snow, Lanee; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have fabricated sol-gels containing gold and silver nanoparticles. Formation of an aerogel produces a blue shift in the surface plasmon resonance as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping this blue shift does not obey effective medium theories. Annealing the samples in a reducing atmosphere at 400 C eliminates this discrepancy and results in narrowing and further blue shifting of the plasmon resonance. Metal particle aggregation also results in a deviation from the predictions of effective medium theories, but can be controlled through careful handling and by avoiding the use of alcohol. By applying effective medium theories to the heterogeneous interlayer surrounding each metal particle, we extend the technique of immersion spectroscopy to inhomogeneous materials characterized by spatially dependent dielectric constants, such as aerogels. We demonstrate that the shift in the surface plasmon wavelength provides the average fractional composition of each component (air and silica) in this inhomogeneous layer, i.e. the porosity of the aerogel or equivalently, for these materials, the catalytic dispersion. Additionally, the kinetics suggest that collective particle interactions in coagulated metal clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  1. Metal Nanoparticle Aerogel Composites

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Ignont, Erica; Snow, Lanee; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have fabricated sol-gels containing gold and silver nanoparticles. Formation of an aerogel produces a blue shift in the surface plasmon resonance as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping this blue shift does not obey effective medium theories. Annealing the samples in a reducing atmosphere at 400 C eliminates this discrepancy and results in narrowing and further blue shifting of the plasmon resonance. Metal particle aggregation also results in a deviation from the predictions of effective medium theories, but can be controlled through careful handling and by avoiding the use of alcohol. By applying effective medium theories to the heterogeneous interlayer surrounding each metal particle, we extend the technique of immersion spectroscopy to inhomogeneous materials characterized by spatially dependent dielectric constants, such as aerogels. We demonstrate that the shift in the surface plasmon wavelength provides the average fractional composition of each component (air and silica) in this inhomogeneous layer, i.e. the porosity of the aerogel or equivalently, for these materials, the catalytic dispersion. Additionally, the kinetics suggest that collective particle interactions in coagulated metal clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  2. Dimensionally stable metallic hydride composition

    DOEpatents

    Heung, Leung K.

    1994-01-01

    A stable, metallic hydride composition and a process for making such a composition. The composition comprises a uniformly blended mixture of a metal hydride, kieselguhr, and a ballast metal, all in the form of particles. The composition is made by subjecting a metal hydride to one or more hydrogen absorption/desorption cycles to disintegrate the hydride particles to less than approximately 100 microns in size. The particles are partly oxidized, then blended with the ballast metal and the kieselguhr to form a uniform mixture. The mixture is compressed into pellets and calcined. Preferably, the mixture includes approximately 10 vol. % or more kieselguhr and approximately 50 vol. % or more ballast. Metal hydrides that can be used in the composition include Zr, Ti, V, Nb, Pd, as well as binary, tertiary, and more complex alloys of La, Al, Cu, Ti, Co, Ni, Fe, Zr, Mg, Ca, Mn, and mixtures and other combinations thereof. Ballast metals include Al, Cu and Ni.

  3. Nanoscale size effects in crystallization of metallic glass nanorods.

    PubMed

    Sohn, Sungwoo; Jung, Yeonwoong; Xie, Yujun; Osuji, Chinedum; Schroers, Jan; Cha, Judy J

    2015-09-01

    Atomistic understanding of crystallization in solids is incomplete due to the lack of appropriate materials and direct experimental tools. Metallic glasses possess simple metallic bonds and slow crystallization kinetics, making them suitable to study crystallization. Here, we investigate crystallization of metallic glass-forming liquids by in-situ heating metallic glass nanorods inside a transmission electron microscope. We unveil that the crystallization kinetics is affected by the nanorod diameter. With decreasing diameters, crystallization temperature decreases initially, exhibiting a minimum at a certain diameter, and then rapidly increases below that. This unusual crystallization kinetics is a consequence of multiple competing factors: increase in apparent viscosity, reduced nucleation probability and enhanced heterogeneous nucleation. The first two are verified by slowed grain growth and scatter in crystallization temperature with decreasing diameters. Our findings provide insight into relevant length scales in crystallization of supercooled metallic glasses, thus offering accurate processing conditions for predictable metallic glass nanomolding.

  4. Thermal behaviors of liquid La-based bulk metallic glasses

    SciTech Connect

    Zhang, D. W.; Wang, X. D. E-mail: jiangjz@zju.edu.cn; Lou, H. B.; Cao, Q. P.; Jiang, J. Z. E-mail: jiangjz@zju.edu.cn; Wang, L. W.; Zhang, D. X.

    2014-12-14

    Thermal behaviors of liquid La-based bulk metallic glasses have been measured by using the dilatometer with a self-sealed sample cell. It is demonstrated that the strong glass forming liquid not only has the small thermal expansion coefficient but also shows the slow variation rate. Moreover, the strong glass former has relatively dense atomic packing and also small density change in the liquid state. The results suggest that the high glass forming ability of La-based metallic glasses would be closely related to the slow atomic rearrangements in liquid melts.

  5. Application of the model of delocalized atoms to metallic glasses

    NASA Astrophysics Data System (ADS)

    Sanditov, D. S.; Darmaev, M. V.; Sanditov, B. D.

    2017-01-01

    The parameters of the model of delocalized atoms applied to metallic glasses have been calculated using the data on empirical constants of the Vogel-Fulcher-Tammann equation (for the temperature dependence of viscosity). It has been shown that these materials obey the same glass-formation criterion as amorphous organic polymers and inorganic glasses. This fact qualitatively confirms the universality of the main regularities of the liquid-glass transition process for all amorphous materials regardless of their origin. The energy of the delocalization of an atom in metallic glasses, Δɛ e ≈ 20-25 kJ/mol, coincides with the results obtained for oxide inorganic glasses. It is substantially lower than the activation energies for a viscous flow and for ion diffusion. The delocalization of an atom (its displacement from the equilibrium position) for amorphous metallic alloys is a low-energy small-scale process similar to that for other glass-like systems.

  6. Responses of bone-forming cells on pre-immersed Zr-based bulk metallic glasses: Effects of composition and roughness.

    PubMed

    Huang, L; Cao, Z; Meyer, H M; Liaw, P K; Garlea, E; Dunlap, J R; Zhang, T; He, W

    2011-01-01

    Bulk metallic glasses (BMGs) demonstrate attractive properties for potential biomedical applications, owing to their amorphous structure. The present work has investigated the biocompatibility of Zr-based BMGs by studying the cellular behavior of bone-forming mouse MC3T3-E1 pre-osteoblast cells. A Ti-6Al-4V alloy was used as a reference material. Pre-immersion treatment was performed on BMG samples in phosphate-buffered saline prior to cell experiments. The effects of 1at.% yttrium alloying and surface roughness on cellular behavior were examined. The general biosafety of Zr-based BMGs for MC3T3-E1 cells was revealed as normal cell responses. Pre-immersion treatment was found to effectively reduce the surface concentrations of alloying elements. Micro-alloying with 1 at.% yttrium did not significantly affect cell adhesion and proliferation, but slightly decreased alkaline phosphatase (ALP) activity on rough surfaces. Lower cell adhesion and proliferation were found on smooth surfaces of Zr-based BMGs compared to their rougher counterparts. Higher ALP activity was detected on rougher surfaces. To obtain a mechanistic understanding surface free energy was correlated with cell adhesion. Copyright © 2010 Acta Materialia Inc. All rights reserved.

  7. Biocompatible Ni-free Zr-based bulk metallic glasses with high-Zr-content: compositional optimization for potential biomedical applications.

    PubMed

    Hua, Nengbin; Huang, Lu; Chen, Wenzhe; He, Wei; Zhang, Tao

    2014-11-01

    The present study designs and prepares Ni-free Zr60+xTi2.5Al10Fe12.5-xCu10Ag5 (at.%, x=0, 2.5, 5) bulk metallic glasses (BMGs) by copper mold casting for potential biomedical application. The effects of Zr content on the in vitro biocompatibility of the Zr-based BMGs are evaluated by investigating mechanical properties, bio-corrosion behavior, and cellular responses. It is found that increasing the content of Zr is favorable for the mechanical compatibility with a combination of low Young's modulus, large plasticity, and high notch toughness. Electrochemical measurements demonstrate that the Zr-based BMGs are corrosion resistant in a phosphate buffered saline solution. The bio-corrosion resistance of BMGs is improved with the increase in Zr content, which is attributed to the enrichment in Zr and decrease in Al concentration in the surface passive film of alloys. Regular cell responses of mouse MC3T3-E1 cells, including cell adhesion and proliferation, are observed on the Zr-Ti-Al-Fe-Cu-Ag BMGs, which reveals their general biosafety. The high-Zr-based BMGs exhibit a higher cell proliferation activity in comparison with that of pure Zr and Ti-6Al-4V alloy. The effects of Zr content on the in vitro biocompatibility can be used to guide the future design of biocompatible Zr-based BMGs. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Glass Fiber Resin Composites and Components at Arctic Temperatures

    DTIC Science & Technology

    2015-06-01

    3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE GLASS FIBER RESIN COMPOSITES AND COMPONENTS AT ARCTIC TEMPERATURES 5...temperatures. This thesis focuses on the tensile properties of GFRC, resin , and glass fiber used in previous NPS-related composite research. The...conduct previous composite experiments at arctic temperatures. 14. SUBJECT TERMS Composite , glass fiber, resin 15. NUMBER OF PAGES 63

  9. Hidden topological order and its correlation with glass-forming ability in metallic glasses.

    PubMed

    Wu, Z W; Li, M Z; Wang, W H; Liu, K X

    2015-01-12

    Unlike the well-defined long-range periodic order that characterizes crystals, so far the inherent atomic packing mode in glassy solids remains mysterious. Based on molecular dynamics simulations, here we find medium-range atomic packing orders in metallic glasses, which are hidden in the diffraction data in terms of structure factors or pair correlation functions. The analysis of the hidden orders in various metallic glasses indicates that the glassy and crystalline solids share a nontrivial structural homology in short-to-medium range, and the hidden orders are formulated by inheriting partial crystalline orders during glass formation. As the number of chemical components increases, more hidden orders are often developed in a metallic glass and entangled topologically. We use this phenomenon to explain the geometric frustration in glass formation and the glass-forming ability of metallic alloys.

  10. Modified glass fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Cao, Yumei

    A high ratio of strength to density and relatively low-cost are some of the significant features of glass fibre reinforced polymer composites (GFRPCs) that made them one of the most rapidly developed materials in recent years. They are widely used as the material of construction in the areas of aerospace, marine and everyday life, such as airplane, helicopter, boat, canoe, fishing rod, racket, etc. Traditionally, researchers tried to raise the mechanical properties and keep a high strength/weight ratio using all or some of the following methods: increasing the volume fraction of the fibre; using different polymeric matrix material; or changing the curing conditions. In recent years, some new techniques and processing methods were developed to further improve the mechanical properties of glass fibre (GF) reinforced polymer composite. For example, by modifying the surface condition of the GF, both the interface strength between the GF and the polymer matrix and the shear strength of the final composite can be significantly increased. Also, by prestressing the fibre during the curing process of the composite, the tensile, flexural and the impact properties of the composite can be greatly improved. In this research project, a new method of preparing GFRPCs, which combined several traditional and modern techniques together, was developed. This new method includes modification of the surface of the GF with silica particles, application of different levels of prestressing on the GF during the curing process, and the change of the fibre volume fraction and curing conditions in different sets of experiments. The results of the new processing were tested by the three-point bend test, the short beam shear test and the impact test to determine the new set of properties so formed in the composite material. Scanning electronic microscopy (SEM) was used to study the fracture surface of the new materials after the mechanical tests were performed. By taking advantages of the

  11. Lunar glass compositions - Apollo 16 core sections 60002 and 60004

    NASA Technical Reports Server (NTRS)

    Meyer, H. O. A.; Tsai, H.-M.

    1975-01-01

    Approximately 500 glasses between 1 mm and 125 microns in size have been analyzed from fourteen samples from the Apollo 16 core sections 60002 and 60004. The majority of glasses have compositions comparable to those found in previous studies of lunar surface soils; however, two new and distinct glass compositions that are probably derived in part from mare material occur in the core samples. The major glass composition in all samples is that of Highland Basalt glass, but it also appears that high-K Fra Mauro Basalt (KREEP) glass is more common at the Apollo 16 site than was previously thought. The relative abundance of glasses within the core samples is random in distribution: each sample is characterized by a particular assemblage and distribution of the constituent glass compositions.

  12. Quantifying the origin of metallic glass formation

    PubMed Central

    Johnson, W. L.; Na, J. H.; Demetriou, M. D.

    2016-01-01

    The waiting time to form a crystal in a unit volume of homogeneous undercooled liquid exhibits a pronounced minimum τX* at a ‘nose temperature' T* located between the glass transition temperature Tg, and the crystal melting temperature, TL. Turnbull argued that τX* should increase rapidly with the dimensionless ratio trg=Tg/TL. Angell introduced a dimensionless ‘fragility parameter', m, to characterize the fall of atomic mobility with temperature above Tg. Both trg and m are widely thought to play a significant role in determining τX*. Here we survey and assess reported data for TL, Tg, trg, m and τX* for a broad range of metallic glasses with widely varying τX*. By analysing this database, we derive a simple empirical expression for τX*(trg, m) that depends exponentially on trg and m, and two fitting parameters. A statistical analysis shows that knowledge of trg and m alone is therefore sufficient to predict τX* within estimated experimental errors. Surprisingly, the liquid/crystal interfacial free energy does not appear in this expression for τX*. PMID:26786966

  13. Quantifying the origin of metallic glass formation

    NASA Astrophysics Data System (ADS)

    Johnson, W. L.; Na, J. H.; Demetriou, M. D.

    2016-01-01

    The waiting time to form a crystal in a unit volume of homogeneous undercooled liquid exhibits a pronounced minimum τX* at a `nose temperature' T* located between the glass transition temperature Tg, and the crystal melting temperature, TL. Turnbull argued that τX* should increase rapidly with the dimensionless ratio trg=Tg/TL. Angell introduced a dimensionless `fragility parameter', m, to characterize the fall of atomic mobility with temperature above Tg. Both trg and m are widely thought to play a significant role in determining τX*. Here we survey and assess reported data for TL, Tg, trg, m and τX* for a broad range of metallic glasses with widely varying τX*. By analysing this database, we derive a simple empirical expression for τX*(trg, m) that depends exponentially on trg and m, and two fitting parameters. A statistical analysis shows that knowledge of trg and m alone is therefore sufficient to predict τX* within estimated experimental errors. Surprisingly, the liquid/crystal interfacial free energy does not appear in this expression for τX*.

  14. Glass Fiber Reinforced Metal Pressure Vessel Design Guide

    NASA Technical Reports Server (NTRS)

    Landes, R. E.

    1972-01-01

    The Engineering Guide presents curves and general equations for safelife design of lightweight glass fiber reinforced (GFR) metal pressure vessels operating under anticipated Space Shuttle service conditions. The high composite vessel weight efficiency is shown to be relatively insensitive to shape, providing increased flexibility to designers establishing spacecraft configurations. Spheres, oblate speroids, and cylinders constructed of GFR Inconel X-750, 2219-T62 aluminum, and cryoformed 301 stainless steel are covered; design parameters and performance efficiencies for each configuration are compared at ambient and cryogenic temperature for an operating pressure range of 690 to 2760 N/sq cm (1000 to 4000 psi). Design variables are presented as a function of metal shell operating to sizing (proof) stress ratios for use with fracture mechanics data generated under a separate task of this program.

  15. Sliding induced crystallization of metallic glass

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Sliding friction and wear experiments, electron microscopy, and diffraction studies were conducted with an Fe67Co18B14Si1 ferrous-base metallic glass in sliding contact with aluminum oxide at room temperature in air. The results indicate that the amorphous alloy can be crystallized during the sliding process. Crystallization of the wear surface causes high friction. Plastic flow occurred on the amorphous alloy with sliding, and the flow film of the alloy transferred to the aluminum oxide surface. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris, and powdery and whiskery oxide debris. Generation of oxide wear debris particles on an alloy can cause transitions in friction behavior.

  16. Cavitation instability in bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Dai, L. H.; Huang, X.; Ling, Z.

    2015-09-01

    Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs) usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones) mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD) simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs) at atomic scale.

  17. Polaronic Transport in Phosphate Glasses Containing Transition Metal Ions

    NASA Astrophysics Data System (ADS)

    Henderson, Mark

    such glasses because the two network formers will tend to separate into different phases, making it difficult to obtain homogenous samples. The PSF system proved easier to study than other systems. The hopping in this system seems to be dominated by the Greaves mid-range mechanism. In addition, in samples containing the same proportion of iron, conductivities were found to not depend noticeably on composition, supporting the use of models focusing on the transition metal ions in calculating conductivity. Despite ostensibly changing the structural and metrical properties of the network, the ratio of the concentration of the network formers only appears to have an effect on the conductivity through changing the inter-atomic distance of iron. The numerical model adds to the evidence for the dominating contribution on the nearest-neighbor ordering of TI ions on the electrical properties of a glass; especially interesting is the reproducibility of the mixed-transition ion effect (MTE) in a numerical model where ensemble averages are taken over possible arrangements. It was also determined that the disorder arising from the spread between two types of traps can lead to a MIT as function of population. Finally, an outline of the notion of invariance in TI glasses is extended from work done by other authors, creating an opportunity for further research.

  18. The formation of silver metal nanoparticles by ion implantation in silicate glasses

    NASA Astrophysics Data System (ADS)

    Vytykacova, S.; Svecova, B.; Nekvindova, P.; Spirkova, J.; Mackova, A.; Miksova, R.; Böttger, R.

    2016-03-01

    It has been shown that glasses containing silver metal nanoparticles are promising photonics materials for the fabrication of all-optical components. The resulting optical properties of the nanocomposite glasses depend on the composition and structure of the glass, as well as on the type of metal ion implanted and the experimental procedures involved. The main aim of this article was to study the influence of the conditions of the ion implantation and the composition of the glass on the formation of metal nanoparticles in such glasses. Four various types of silicate glasses were implanted with Ag+ ions with different energy (330 keV, 1.2 MeV and 1.7 MeV), with the fluence being kept constant (1 × 1016 ions cm-2). The as-implanted samples were annealed at 600 °C for 1 h. The samples were characterised in terms of: the nucleation of metal nanoparticles (linear optical absorption), the migration of silver through the glass matrix during the implantation and post-implantation annealing (Rutherford backscattering spectroscopy), and the oxidation state of silver (photoluminescence in the visible region).

  19. PIXE characterization of tissues surrounding metallic prostheses coated with biological glasses

    NASA Astrophysics Data System (ADS)

    Barbotteau, Y.; Irigaray, J. L.; Moretto, Ph.

    2004-01-01

    Biological glasses can be used as coatings for metallic prostheses in order to prevent corrosion. According to their composition, these glasses have different properties. We studied, in vivo, two glasses referred to as BVA and BVH. They are used as coatings of Ti6Al4V metallic implant. BVA glass disappears after 3 months of implantation and is replaced by bone. Prostheses initially coated by this glass have a larger osseous contact perimeter compared to the uncoated prostheses. This ensures a better anchoring of the implant and limits the micro-motions which cause wear debris. BVH glass keeps a constant composition during implantation and it is used like a layer which isolates metal implant from biological environment. In order to characterize the bony environment surrounding implants, we have used PIXE and RBS methods. This paper shows results of the behavior of bony tissue under micro-beam, the quality tests of new bone which replaces the BVA glass coating and the evaluation of corrosion effects. Titanium release in bony tissues begins when the metal surface of the prosthesis is exposed to biological fluids. After a few months of implantation, the titanium contamination is stabilized and remains localized within the first tens of micrometers of surrounding bone.

  20. EXAFS studies of the local atomic environment in metal-metal glasses

    SciTech Connect

    Wong, J.; Lytle, F. W.; Liebermann, H. H.; Tanner, L. E.

    1980-01-01

    The interatomic distances and nearest neighbor coordinations of constituent atoms in a series of metal-metal glasses: M'/sub 100-x/M''/sub x/ where M' = Zr, Nb, M'' = Fe, Ni, Cu and x varies from 30 to 60 at %, have been determined using the EXAFS technique in conjunction with the x-ray synchrotron source at Stanford. Fourier transforms of the EXAFS signals clearly indicate there are like as well as unlike atom pairs in the first coordination shell about both the M' and M'' atoms. The ratio of like and unlike pairs scales linearly with composition and is indicative of random mixing in these binary glasses. The M'-M'' separation are shorter than sum of the Goldschmidt radii and implies chemical interaction between the M' and M'' atoms.

  1. Filled glass composites for sealing of solid oxide fuel cells.

    SciTech Connect

    Tandon, Rajan; Widgeon, Scarlett Joyce; Garino, Terry J.; Brochu, Mathieu; Gauntt, Bryan D.; Corral, Erica L.; Loehman, Ronald E.

    2009-04-01

    Glasses filled with ceramic or metallic powders have been developed for use as seals for solid oxide fuel cells (SOFC's) as part of the U.S. Department of Energy's Solid State Energy Conversion Alliance (SECA) Program. The composites of glass (alkaline earth-alumina-borate) and powders ({approx}20 vol% of yttria-stabilized zirconia or silver) were shown to form seals with SOFC materials at or below 900 C. The type and amount of powder were adjusted to optimize thermal expansion to match the SOFC materials and viscosity. Wetting studies indicated good wetting was achieved on the micro-scale and reaction studies indicated that the degree of reaction between the filled glasses and SOFC materials, including spinel-coated 441 stainless steel, at 750 C is acceptable. A test rig was developed for measuring strengths of seals cycled between room temperature and typical SOFC operating temperatures. Our measurements showed that many of the 410 SS to 410 SS seals, made using silver-filled glass composites, were hermetic at 0.2 MPa (2 atm.) of pressure and that seals that leaked could be resealed by briefly heating them to 900 C. Seal strength measurements at elevated temperature (up to 950 C), measured using a second apparatus that we developed, indicated that seals maintained 0.02 MPa (0.2 atm.) overpressures for 30 min at 750 C with no leakage. Finally, the volatility of the borate component of sealing glasses under SOFC operational conditions was studied using weight loss measurements and found by extrapolation to be less than 5% for the projected SOFC lifetime.

  2. Vitrification and waste glass compositional limits

    SciTech Connect

    Chapman, C.C.; Whittington, K.F.; Peters, R.D.

    1994-08-01

    The most important issue when evaluating the suitability of a waste stream for vitrification is the composition of the waste. Appropriate analytical data are required to ensure that adequate information is available for evaluating and implementing the technology. Although vitrification can be used to immobilize almost any waste stream through dilution of the waste with glass formers, it may be too costly for certain limiting conditions. This report provides guidelines of these limit sand the consequent analytical requirements that are necessary for appropriate qualitative cost estimates.

  3. Cross-craft interactions between metal and glass working: slag additions to early Anglo-Saxon red glass

    NASA Astrophysics Data System (ADS)

    Peake, James R. N.; Freestone, Ian C.

    Opaque red glass has been extensively studied over the years, but its compositional complexity and variability means that the way in which it was manufactured is still not fully understood. Previous studies have suggested the use of metallurgical by-products in its manufacture, but until now the evidence has been limited. SEM-EDS analysis of glass beads from the early Anglo-Saxon cemetery complex at Eriswell, southeast England, has provided further insights into the production and technology of opaque red glass, which could only have been possible through invasive sampling. The matrix of the red glasses contains angular particles of slag, the main phases of which typically correspond to either fayalite (Fe2SiO4) or kirschsteinite (CaFeSiO4), orthosilicate (olivine-type) minerals characteristic of some copper- and iron-smelting slags. This material appears to have been added in part as a reducing agent, to promote the precipitation of sub-micrometer particles of the colorant phase, copper metal. Its use represents a sophisticated, if empirical, understanding of materials and can only have resulted through deliberate experimentation with metallurgical by-products by early glass workers. Slag also seems to have been added as a source of iron to colour `black' glass. The compositions of the opaque red glasses appear to be strongly paralleled by Merovingian beads from northern Europe and Anglo-Saxon beads from elsewhere in England, suggesting that this technology is likely to have been quite widespread.

  4. Predicting the glass transition temperature of bioactive glasses from their molecular chemical composition.

    PubMed

    Hill, Robert G; Brauer, Delia S

    2011-10-01

    A recently published paper (M.D. O'Donnell, Acta Biomaterialia 7 (2011) 2264-2269) suggests that it is possible to correlate the glass transition temperature (T(g)) of bioactive glasses with their molar composition, based on iterative least-squares fitting of published T(g) data. However, we show that the glass structure is an important parameter in determining T(g). Phase separation, local structural effects and components (intermediate oxides) which can switch their structural role in the glass network need to be taken into consideration, as they are likely to influence the glass transition temperature of bioactive glasses. Although the model suggested by O'Donnell works reasonably well for glasses within the composition range presented, it is oversimplified and fails for glasses outside certain compositional boundaries.

  5. Developing and Characterizing Bulk Metallic Glasses for Extreme Applications

    NASA Astrophysics Data System (ADS)

    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

  6. Metal particle manipulation by laser irradiation in borosilicate glass.

    PubMed

    Hidai, Hirofumi; Yamazaki, Takato; Itoh, Sho; Hiromatsu, Kuniaki; Tokura, Hitoshi

    2010-09-13

    We propose a new technique of manipulating a metal particle in borosilicate glass. A metal particle that is heated by laser illumination heats the surrounding glass by radiation and conduction. A softened glass enabled metal particle migration. A 1-µm-thick platinum film was deposited on the back surface of a glass plate and irradiated with a green CW laser beam through the glass. As a result, the platinum film was melted and implanted into the glass as a particle. Platinum particles with diameters of 3 to 50 μm migrated at speeds up to 10 mm/s. In addition to platinum particles, nickel and austenitic stainless steel (SUS304) particles can be implanted.

  7. Ultra-stiff metallic glasses through bond energy density design

    NASA Astrophysics Data System (ADS)

    Schnabel, Volker; Köhler, Mathias; Music, Denis; Bednarcik, Jozef; Clegg, William J.; Raabe, Dierk; Schneider, Jochen M.

    2017-07-01

    The elastic properties of crystalline metals scale with their valence electron density. Similar observations have been made for metallic glasses. However, for metallic glasses where covalent bonding predominates, such as metalloid metallic glasses, this relationship appears to break down. At present, the reasons for this are not understood. Using high energy x-ray diffraction analysis of melt spun and thin film metallic glasses combined with density functional theory based molecular dynamics simulations, we show that the physical origin of the ultrahigh stiffness in both metalloid and non-metalloid metallic glasses is best understood in terms of the bond energy density. Using the bond energy density as novel materials design criterion for ultra-stiff metallic glasses, we are able to predict a Co33.0Ta3.5B63.5 short range ordered material by density functional theory based molecular dynamics simulations with a high bond energy density of 0.94 eV Å-3 and a bulk modulus of 263 GPa, which is 17% greater than the stiffest Co-B based metallic glasses reported in literature.

  8. Separating the configurational and vibrational entropy contributions in metallic glasses

    NASA Astrophysics Data System (ADS)

    Smith, Hillary L.; Li, Chen W.; Hoff, Andrew; Garrett, Glenn R.; Kim, Dennis S.; Yang, Fred C.; Lucas, Matthew S.; Swan-Wood, Tabitha; Lin, J. Y. Y.; Stone, M. B.; Abernathy, D. L.; Demetriou, Marios D.; Fultz, B.

    2017-09-01

    Glassy materials exist in nature and play a critical role in technology, but key differences between the glass, liquid and crystalline phases are not well understood. Over several decades there has been controversy about the specific heat absorbed as a glass transforms to a liquid--does this originate from vibrational entropy or configurational entropy? Here we report direct in situ measurements of the vibrational spectra of strong and fragile metallic glasses in the glass, liquid and crystalline phases. For both types of material, the measured vibrational entropies of the glass and liquid show a tiny excess over the crystal, representing less than 5% of the total excess entropy measured with step calorimetry. These results reveal that the excess entropy of metallic glasses is almost entirely configurational in origin, consistent with the early theories of Gibbs and co-workers describing the glass transition as a purely configurational transition.

  9. Metallic glass alloys of Zr, Ti, Cu and Ni

    DOEpatents

    Lin, X.; Peker, A.; Johnson, W.L.

    1997-04-08

    At least quaternary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3} K/s. Such alloys comprise titanium from 19 to 41 atomic percent, an early transition metal (ETM) from 4 to 21 atomic percent and copper plus a late transition metal (LTM) from 49 to 64 atomic percent. The ETM comprises zirconium and/or hafnium. The LTM comprises cobalt and/or nickel. The composition is further constrained such that the product of the copper plus LTM times the atomic proportion of LTM relative to the copper is from 2 to 14. The atomic percentage of ETM is less than 10 when the atomic percentage of titanium is as high as 41, and may be as large as 21 when the atomic percentage of titanium is as low as 24. Furthermore, when the total of copper and LTM are low, the amount of LTM present must be further limited. Another group of glass forming alloys has the formula (ETM{sub 1{minus}x}Ti{sub x}){sub a} Cu{sub b} (Ni{sub 1{minus}y}Co{sub y}){sub c} wherein x is from 0.1 to 0.3, y{center_dot}c is from 0 to 18, a is from 47 to 67, b is from 8 to 42, and c is from 4 to 37. This definition of the alloys has additional constraints on the range of copper content, b. 2 figs.

  10. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2003-09-23

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste uranium oxides The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  11. Crystal nucleation and glass formation in metallic alloy melts

    NASA Technical Reports Server (NTRS)

    Spaepen, F.

    1984-01-01

    Homogeneous nucleation, containerless solidification, and bulk formation of metallic glasses are discussed. Homogeneous nucleation is not a limiting factor for metallic glass formation at slow cooling rates if the reduced glass transition temperature is high enough. Such glasses can be made in bulk if heterogeneous nucleants are removed. Containerless processing eleminates potential sources of nucleants, but as drop tube experiments on the Pd-Si alloys show, the free surface may still be a very effective heterogeneous nucleant. Combination of etching and heating in vacuum or fluxing can be effective for cleaning fairly large ingots of nucleants. Reduced gravity processing has a potentially useful role in the fluxing technique, for example to keep large metallic ingots surrounded by a low density, low fluidity flux if this proved difficult under ground conditions. For systems where heterogeneous nucleants in the bulk of the ingot need gravity to segregate to the flux-metal interface, reduced gravity processing may not be appropriate for bulk glass formation.

  12. Characterization of activation energy for flow in metallic glasses

    NASA Astrophysics Data System (ADS)

    Wang, J. Q.; Wang, W. H.; Liu, Y. H.; Bai, H. Y.

    2011-01-01

    The molar volume (Vm) scaled flow activation energy (ΔE), namely as the activation energy density ρE=ΔE/Vm, is proposed to describe the flow of metallic glasses. Based on the energy landscape, both the shear and bulk moduli are critical parameters accounting for the ρE of both homogeneous and inhomogeneous flows in metallic glasses. The expression of ρE is determined experimentally to be a simple expression of ρE=(10)/(11)G+(1)/(11)K. The energy density perspective depicts a realistic picture for the flow in metallic glasses and is suggestive for understanding the glass transition and deformation in metallic glasses.

  13. Electromagnetic vibration process for producing bulk metallic glasses.

    PubMed

    Tamura, Takuya; Amiya, Kenji; Rachmat, Rudi S; Mizutani, Yoshiki; Miwa, Kenji

    2005-04-01

    It is known that the cooling rate from the liquid state is an important factor in the production of bulk metallic glasses. However, the effects of other factors such as electric and magnetic fields have not been thoroughly investigated. Here, we present a new method for producing bulk metallic glasses by using electromagnetic vibrations with simultaneous imposition of an alternating electric current and a magnetic field. This method was found to be effective in enhancing apparent glass-forming ability in Mg65-Cu25-Y10 (atomic percent) alloys. Indeed, larger bulk metallic glasses could be obtained by the electromagnetic vibration process under the same cooling conditions. We presume that disappearance or decrement of clusters by the electromagnetic vibrations applied to the liquid state cause suppression of crystal nucleation. This electromagnetic vibration process should be effective in other bulk metallic glass systems if the clusters in the liquid state cause the crystal nucleation.

  14. Stress Concentration in Glass-Epoxy Composite Plates.

    DTIC Science & Technology

    FIBER REINFORCED COMPOSITES, * GLASS REINFORCED PLASTICS, *STRESS CONCENTRATION, STRESS STRAIN RELATIONS, LOAD DISTRIBUTION, FIBERGLASS , MANUFACTURING, THESES, HOLES(OPENINGS), STRAIN GAGES, EPOXY COMPOUNDS, WEAR RESISTANCE.

  15. Exploring a wider range of Mg–Ca–Zn metallic glass as biocompatible alloys using combinatorial sputtering

    DOE PAGES

    Li, Jinyang; Gittleson, Forrest S.; Liu, Yanhui; ...

    2017-06-30

    In order to bypass the limitation of bulk metallic glasses fabrication, we synthesized thin film metallic glasses to study the corrosion characteristics of a wide atomic% composition range, Mg(35.9-63%)Ca(4.1-21%)Zn(17.9-58.3%), in simulated body fluid. We highlight a clear relationship between Zn content and corrosion current such that Zn-medium metallic glasses exhibit minimum corrosion. In addition, we found higher Zn content leads to a poor in vitro cell viability. Finally, these results showcase the benefit of evaluating a larger alloy compositional space to probe the limits of corrosion resistance and prescreen for biocompatible applications.

  16. Preparation of high density heavy metal fluoride glasses with extended ultraviolet and infra red ranges, and such high density heavy metal fluoride glasses

    NASA Technical Reports Server (NTRS)

    Martin, Steven W. (Inventor); Huebsch, Jesse (Inventor)

    2001-01-01

    A heavy metal fluoride glass composition range (in mol percent) consisting essentially of: (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24)InF.sub.3 or GaF.sub.3.(4-16)CdF.sub.2.(6-24)YbF.sub.3.(4-22)ZnF.sub.2. In an alternative embodiment, a heavy metal fluoride glass composition range (in mol percent) comprises (16-30)BaF.sub.2.(8-26)HfF.sub.4.(6-24) of (0-24)InF.sub.3, (0-24)GaF.sub.3 and (0-19)AlF.sub.3.(1-16)CdF.sub.2.(6-24)YbF.sub.3.(4-26)ZnF.sub.2. A preferred heavy metal fluoride glass produced in accordance with the present invention comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.7InF.sub.3.5GaF.sub.3.10CdF.sub.2.18YbF.sub.3. 16ZnF.sub.2. A preferred heavy metal fluoride glass has maximum thickness of most preferably about 3 mm. Another preferred heavy metal fluoride glass comprises a composition (in mol %) and comprises about 26BaF.sub.2.18HfF.sub.4.12AlF.sub.3.10CdF.sub.2.18YbF.sub.3.16ZnF.sub.2.

  17. The correlation between shear elastic modulus and glass transition temperature of bulk metallic glasses

    SciTech Connect

    Lu Zhibin; Li Jiangong; Shao Hang; Ni Xia; Gleiter, H.

    2009-03-02

    Based on Varshni equation, the shear elastic modulus at the glass transition temperature [G(T{sub g})] and the shear elastic modulus at 0 K [G(0)] were calculated from the elastic modulus measured at room temperature for various bulk metallic glasses (BMGs). The G(T{sub g})/G(0) ratios for various BMGs are almost the same and have a value around 0.85. This unique correlation implies that the glass transition occurs when the shear modulus of a BMG decreases to about 85% of G(0). This correlation between shear modulus and glass transition is of significance in understanding the glass transition of BMGs.

  18. Compositional Models of Glass/Melt Properties and their Use for Glass Formulation

    DOE PAGES

    Vienna, John D.; USA, Richland Washington

    2014-12-18

    Nuclear waste glasses must simultaneously meet a number of criteria related to their processability, product quality, and cost factors. The properties that must be controlled in glass formulation and waste vitrification plant operation tend to vary smoothly with composition allowing for glass property-composition models to be developed and used. Models have been fit to the key glass properties. The properties are transformed so that simple functions of composition (e.g., linear, polynomial, or component ratios) can be used as model forms. The model forms are fit to experimental data designed statistically to efficiently cover the composition space of interest. Examples ofmore » these models are found in literature. The glass property-composition models, their uncertainty definitions, property constraints, and optimality criteria are combined to formulate optimal glass compositions, control composition in vitrification plants, and to qualify waste glasses for disposal. An overview of current glass property-composition modeling techniques is summarized in this paper along with an example of how those models are applied to glass formulation and product qualification at the planned Hanford high-level waste vitrification plant.« less

  19. Compositional Models of Glass/Melt Properties and their Use for Glass Formulation

    SciTech Connect

    Vienna, John D.; USA, Richland Washington

    2014-12-18

    Nuclear waste glasses must simultaneously meet a number of criteria related to their processability, product quality, and cost factors. The properties that must be controlled in glass formulation and waste vitrification plant operation tend to vary smoothly with composition allowing for glass property-composition models to be developed and used. Models have been fit to the key glass properties. The properties are transformed so that simple functions of composition (e.g., linear, polynomial, or component ratios) can be used as model forms. The model forms are fit to experimental data designed statistically to efficiently cover the composition space of interest. Examples of these models are found in literature. The glass property-composition models, their uncertainty definitions, property constraints, and optimality criteria are combined to formulate optimal glass compositions, control composition in vitrification plants, and to qualify waste glasses for disposal. An overview of current glass property-composition modeling techniques is summarized in this paper along with an example of how those models are applied to glass formulation and product qualification at the planned Hanford high-level waste vitrification plant.

  20. Clustered field evaporation of metallic glasses in atom probe tomography.

    PubMed

    Zemp, J; Gerstl, S S A; Löffler, J F; Schönfeld, B

    2016-03-01

    Field evaporation of metallic glasses is a stochastic process combined with spatially and temporally correlated events, which are referred to as clustered evaporation (CE). This phenomenon is investigated by studying the distance between consecutive detector hits. CE is found to be a strongly localized phenomenon (up to 3nm in range) which also depends on the type of evaporating ions. While a similar effect in crystals is attributed to the evaporation of crystalline layers, CE of metallic glasses presumably has a different - as yet unknown - physical origin. The present work provides new perspectives on quantification methods for atom probe tomography of metallic glasses.

  1. The plastic yield and flow behavior in metallic glasses

    NASA Astrophysics Data System (ADS)

    Thamburaja, Prakash; Klusemann, Benjamin; Adibi, Sara; Bargmann, Swantje

    2015-02-01

    Metallic glasses have vast potential applications as components in microelectronics- and nanoelectronics-type devices. The design of such components through computer simulations requires the input of a faithful set of continuum-based constitutive equations. However, one long-standing controversial issue in modeling the plastic behavior of metallic glasses at the continuum level is the use of the most appropriate plastic yield criterion and flow rule. Guided by a series of molecular dynamics simulations conducted at low-homologous temperatures under homogeneous deformations, we quantitatively prove that the continuum plastic behavior in metallic glasses is most accurately described by a von Mises-type plastic yield criterion and flow rule.

  2. Elastocapillary bundling of high aspect-ratio metallic glass nanowires

    NASA Astrophysics Data System (ADS)

    Hu, Zhonglue; Uzun, Ceren; Dong, Ziye; Li, Wei; Bernussi, Ayrton A.; Kumar, Golden

    2017-07-01

    Collapsing and bundling of wet nanostructures can be a desirable or an unwanted phenomenon depending on the target application. We study the effect of the aspect-ratio and solvent surface tension on bundling of Pt-based metallic glass nanowires prepared by thermoplastic molding. The results show that the bundling can be quantitatively described by the competition between the Laplacian capillary force and the elastic restoring force. Supercritical CO2 drying can prevent bundling to form vertically aligned metallic glass nanowires with high aspect-ratios (>15). Optical measurements and simulations reveal that the diffuse reflectance of metallic glass nanowires strongly depends on their profile (vertical or bundled).

  3. Process for direct conversion of reactive metals to glass

    DOEpatents

    Rajan, John B.; Kumar, Romesh; Vissers, Donald R.

    1990-01-01

    Radioactive alkali metal is introduced into a cyclone reactor in droplet form by an aspirating gas. In the cyclone metal reactor the aspirated alkali metal is contacted with silica powder introduced in an air stream to form in one step a glass. The sides of the cyclone reactor are preheated to ensure that the initial glass formed coats the side of the reactor forming a protective coating against the reactants which are maintained in excess of 1000.degree. C. to ensure the formation of glass in a single step.

  4. The shells of atomic structure in metallic glasses

    NASA Astrophysics Data System (ADS)

    Pan, S. P.; Feng, S. D.; Qiao, J. W.; Dong, B. S.; Qin, J. Y.

    2016-02-01

    We proposed a scheme to describe the spatial correlation between two atoms in metallic glasses. Pair distribution function in a model iron was fully decomposed into several shells and can be presented as the spread of nearest neighbor correlation via distance. Moreover, angle distribution function can also be decomposed into groups. We demonstrate that there is close correlation between pair distribution function and angle distribution function for metallic glasses. We think that our results are very helpful understanding the atomic structure of metallic glasses.

  5. Exploring Mg-Zn-Ca-Based Bulk Metallic Glasses for Biomedical Applications Based on Thermodynamic Approach

    NASA Astrophysics Data System (ADS)

    Ramya, M.; Sarwat, Syed Ghazi; Udhayabanu, V.; Raj, Baldev; Ravi, K. R.

    2015-12-01

    Magnesium (Mg)-based metallic glasses are considered as possible candidates in orthopedic implant applications. This paper aims to theoretically predict the glass-forming ability (GFA) in Mg-Zn-Ca alloy using a newly proposed thermodynamic model ( P HHS), and the consistency of this model is verified through experimental analysis. P HHS is based on thermodynamic parameters such as enthalpy of chemical mixing, elastic enthalpy, and configurational entropy, thus incorporating the pivotal effects, i.e., electron transfer effects, effect of atomic size mismatch, and effect of randomness, which aid to high GFA. In essence, P HHS can be visualized as the energy barrier that exists between the transformations of random atomic structure of glass to ordered crystalline structure. When the P HHS value is more negative, the energy barrier will be high, supporting easy glass formation. Various Mg-Zn-Ca metallic glass compositions displayed almost an expected and supporting trend, where the critical diameter of the metallic glass rod increased with a more negative P HHS value. Among the predicted Mg-Zn-Ca systems, the Mg60Zn35Ca5 composition shows deviation from the expected trend. This discrepancy has been clearly elucidated using a eutectic phase diagram. In addition to the consistency of the P HHS parameter to verifying the GFA of various compositions, the unique ability of this model is to predict unexplored Mg-Zn-Ca glass-forming compositions using contour development. Thus, proving P HHS parameter to be used as an efficient tool in predicting new glass-forming compositions.

  6. The Prospects for Mechanical Ratcheting of Bulk Metallic Glasses

    SciTech Connect

    Wright, W; Dauskardt, R H; Nix, W D

    2003-11-12

    The major mechanical shortcoming of metallic glasses is their limited ductility at room temperature. Monolithic metallic glasses sustain only a few percent plastic strain when subjected to uniaxial compression and essentially no plastic strain under tension. Here we describe a room temperature deformation process that may have the potential to overcome the limited ductility of monolithic metallic glasses and achieve large plastic strains. By subjecting a metallic glass sample to cyclic torsion, the glass is brought to the yield surface; the superposition of a small uniaxial stress (much smaller than the yield stress) should then produce increments in plastic strain along the tensile axis. This accumulation of strain during cyclic loading, commonly known as ratcheting, has been extensively investigated in stainless and carbon steel alloys, but has not been previously studied in metallic glasses. We have successfully demonstrated the application of this ratcheting technique of cyclic torsion with superimposed tension for polycrystalline Ti-6Al-4V. Our stability analyses indicate that the plastic deformation of materials exhibiting elastic--perfectly plastic constitutive behavior such as metallic glasses should be stable under cyclic torsion, however, results obtained thus far are inconclusive.

  7. General nanomoulding with bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Liu, Ze; Schroers, Jan

    2015-04-01

    Bulk metallic glasses (BMGs) are ideal for nanomoulding as they possess desirable strength for molds as well as for moldable materials and furthermore lack intrinsic size limitations. Despite their attractiveness, only recently Pt-based BMGs have been successfully molded into pores ranging 10-100 nm (Kumar et al 2009 Nature 457 868-72). Here, we introduce a quantitative theory, which reveals previous challenges in filling nanosized pores. This theory considers, in addition to a viscous and a capillary term, also oxidation, which becomes increasingly more important on smaller length scales. Based on this theory we construct a nanomoulding processing map for BMG, which reveals the limiting factors for BMG nanomoulding. Based on the quantitative prediction of the processing map, we introduce a strategy to reduce the capillary effect through a wetting layer, which allows us to mold non-noble BMGs below 1 μm in air. An additional benefit of this strategy is that it drastically facilitates demoulding, one of the main challenges of nanomoulding in general.

  8. Atomistic simulation of nanoformed metallic glass

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Da

    2015-07-01

    The effects of forming speed and temperature on the forming mechanism and mechanics of Cu50Zr25Ti25 metallic glass are studied using molecular dynamics simulations based on the second-moment approximation of the many-body tight-binding potential. These effects are investigated in terms of atomic trajectories, flow field, slip vectors, internal energy, radial distribution function, and elastic recovery of nanoimprint lithography (NIL) patterns. The simulation results show that a shear transformation zone (STZ) forms at the substrate surface underneath the mold during the forming process. The STZ area increases with mold displacement (D). The movement speed of substrate atoms underneath the mold increases with increasing D value. The movement directions of substrate atoms underneath the mold are more agreeable for a larger D value. The stick-slip phenomenon becomes more obvious with increasing D value and imprint speed. The substrate energy increases with increasing imprint speed and temperature. Great NIL pattern transfer is obtained with unloading at low temperatures (e.g., room temperature).

  9. Status of Gr/glass composites technology at UTOS

    NASA Technical Reports Server (NTRS)

    Mayor, Ramon A.

    1988-01-01

    The TSC (Thermally Stable Composite) refers to a family of graphite reinforced glass matrix composite materials developed by UTOS. This fiber matrix combination exhibits low coefficients of thermal expansion (CTE), exceptional dimensional stability, high specific strength and stiffness, adequate fracture toughness, and space environment compatibility. The dimensional stability of a TSC mirror structure was experimentally characterized at the Steward Observatory. Preliminary results indicate that TSC is significantly more thermally stable than most current structural composite materials. In addition, the use of lower CTE glass matrix materials, such as 96 percent silica glass, have the potential for producing graphite/glass panels with expansion rates and stability comparable to that of fused silica.

  10. Ammonia-treated phosphate glasses useful for sealing to metals

    SciTech Connect

    Brow, R.K.; Day, D.E.

    1990-12-31

    A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.

  11. Ammonia-treated phosphate glasses useful for sealing to metals

    DOEpatents

    Brow, R.K.; Day, D.E.

    1991-09-03

    A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.

  12. High expansion coefficient glasses can be sealed to common metals

    NASA Technical Reports Server (NTRS)

    Camp, F. E.; Champman, J. W.; Hirayama, C.

    1970-01-01

    New series of high expansion coefficient glasses can be sealed by fusion onto hot surfaces of metals and alloys. Glasses have relatively low working temperatures, good chemical durability, and can be used in electrical insulators and feedthroughs to fluid or vacuum systems.

  13. Replacement of oxide glass with metallic glass for Ag screen printing metallization on Si emitter

    NASA Astrophysics Data System (ADS)

    Kim, Se Yun; Jee, Sang Soo; Lim, Ka Ram; Kim, Won Tae; Kim, Do Hyang; Lee, Eun-Sung; Kim, Young Hwan; Lee, Sang Mock; Lee, Jun Ho; Eckert, Jürgen

    2011-05-01

    Cu-Zr-based metallic glass (MG) has been applied as a binding agent of Ag paste for front contact formation in Si solar cell by screen printing process. Use of electroconductive MG binder significantly improves the quality of the contact by the formation of highly dense 10-50 nm size Ag crystallites and the noncorrugation of the emitter surface with a very shallow Ag crystallite penetration depth of 10-30 nm. Nanoscale Ag crystallites form on the emitter surface by local Si-Cu-Ag eutectic melting, leading to the formation of pyramidal pits on the Si emitter surface, followed by precipitation of Ag crystallites during cooling.

  14. Glass-ceramic composition for hermetic seals

    DOEpatents

    Ballard, Jr., Clifford P.

    1979-01-01

    The invention relates to a glass-ceramic composition having a high fracture strength adaptable for hermetically sealing to chromium bearing iron or nickel base alloys at temperatures of between about 950.degree. C to about 1100.degree. C to form a hermetically sealed insulator body, comprising from about 55 to about 65 weight percent SiO.sub.2, from about 0 to about 5 weight percent Al.sub.2 O.sub.3, from about 6 to about 11 weight % Li.sub.2 O, from about 25 to about 32 weight percent BaO, from about 0.5 to about 1.0 weight percent CoO and from about 1.5 to about 3.5 weight percent P.sub.2 O.sub.5.

  15. Polyamorphism in Yb-based metallic glass induced by pressure

    DOE PAGES

    Li, Liangliang; Luo, Qiang; Li, Renfeng; ...

    2017-04-25

    The Yb62.5Zn15Mg17.5Cu5 metallic glass is investigated using synchrotron x-ray total scattering method up to 38.4 GPa. The polyamorphic transformation from low density to high density with a transition region between 14.1 and 25.2 GPa is observed, accompanying with a volume collapse reflected by a discontinuousness of isothermal bulk modulus. This collapse is caused by that distortional icosahedron short range order precedes to perfect icosahedron, which might link to Yb 4f electron delocalization upon compression, and match the result of in situ electrical resistance measurement under high pressure conditions. Furthermore, this discovery in Yb-based metallic glass, combined with the previous reportsmore » on other metallic glass systems, demonstrates that pressure induced polyamorphism is the general behavior for typical lanthanide based metallic glasses.« less

  16. Polyamorphism in Yb-based metallic glass induced by pressure.

    PubMed

    Li, Liangliang; Luo, Qiang; Li, Renfeng; Zhao, Haiyan; Chapman, Karena W; Chupas, Peter J; Wang, Luhong; Liu, Haozhe

    2017-04-25

    The Yb62.5Zn15Mg17.5Cu5 metallic glass is investigated using synchrotron x-ray total scattering method up to 38.4 GPa. The polyamorphic transformation from low density to high density with a transition region between 14.1 and 25.2 GPa is observed, accompanying with a volume collapse reflected by a discontinuousness of isothermal bulk modulus. This collapse is caused by that distortional icosahedron short range order precedes to perfect icosahedron, which might link to Yb 4f electron delocalization upon compression, and match the result of in situ electrical resistance measurement under high pressure conditions. This discovery in Yb-based metallic glass, combined with the previous reports on other metallic glass systems, demonstrates that pressure induced polyamorphism is the general behavior for typical lanthanide based metallic glasses.

  17. Polyamorphism in Yb-based metallic glass induced by pressure

    PubMed Central

    Li, Liangliang; Luo, Qiang; Li, Renfeng; Zhao, Haiyan; Chapman, Karena W.; Chupas, Peter J.; Wang, Luhong; Liu, Haozhe

    2017-01-01

    The Yb62.5Zn15Mg17.5Cu5 metallic glass is investigated using synchrotron x-ray total scattering method up to 38.4 GPa. The polyamorphic transformation from low density to high density with a transition region between 14.1 and 25.2 GPa is observed, accompanying with a volume collapse reflected by a discontinuousness of isothermal bulk modulus. This collapse is caused by that distortional icosahedron short range order precedes to perfect icosahedron, which might link to Yb 4f electron delocalization upon compression, and match the result of in situ electrical resistance measurement under high pressure conditions. This discovery in Yb-based metallic glass, combined with the previous reports on other metallic glass systems, demonstrates that pressure induced polyamorphism is the general behavior for typical lanthanide based metallic glasses. PMID:28440339

  18. Localized crystallization in shear bands of a metallic glass.

    PubMed

    Yan, Zhijie; Song, Kaikai; Hu, Yong; Dai, Fuping; Chu, Zhibing; Eckert, Jürgen

    2016-01-13

    Stress-induced viscous flow is the characteristic of atomic movements during plastic deformation of metallic glasses in the absence of substantial temperature increase, which suggests that stress state plays an important role in mechanically induced crystallization in a metallic glass. However, it is poorly understood. Here, we report on the stress-induced localized crystallization in individual shear bands of Zr60Al15Ni25 metallic glass subjected to cold rolling. We find that crystallization in individual shear bands preferentially occurs in the regions neighboring the amorphous matrix, where the materials are subjected to compressive stresses demonstrated by our finite element simulations. Our results provide direct evidence that the mechanically induced crystallization kinetics is closely related with the stress state. The crystallization kinetics under compressive and tensile stresses are interpreted within the frameworks of potential energy landscape and classical nucleation theory, which reduces the role of stress state in mechanically induced crystallization in a metallic glass.

  19. Localized crystallization in shear bands of a metallic glass

    PubMed Central

    Yan, Zhijie; Song, Kaikai; Hu, Yong; Dai, Fuping; Chu, Zhibing; Eckert, Jürgen

    2016-01-01

    Stress-induced viscous flow is the characteristic of atomic movements during plastic deformation of metallic glasses in the absence of substantial temperature increase, which suggests that stress state plays an important role in mechanically induced crystallization in a metallic glass. However, it is poorly understood. Here, we report on the stress-induced localized crystallization in individual shear bands of Zr60Al15Ni25 metallic glass subjected to cold rolling. We find that crystallization in individual shear bands preferentially occurs in the regions neighboring the amorphous matrix, where the materials are subjected to compressive stresses demonstrated by our finite element simulations. Our results provide direct evidence that the mechanically induced crystallization kinetics is closely related with the stress state. The crystallization kinetics under compressive and tensile stresses are interpreted within the frameworks of potential energy landscape and classical nucleation theory, which reduces the role of stress state in mechanically induced crystallization in a metallic glass. PMID:26758530

  20. Universal structural parameter to quantitatively predict metallic glass properties

    SciTech Connect

    Ding, Jun; Cheng, Yong-Qiang; Sheng, Howard; Asta, Mark; Ritchie, Robert O.; Ma, Evan

    2016-12-12

    Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parameter correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales.

  1. Universal structural parameter to quantitatively predict metallic glass properties

    PubMed Central

    Ding, Jun; Cheng, Yong-Qiang; Sheng, Howard; Asta, Mark; Ritchie, Robert O.; Ma, Evan

    2016-01-01

    Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce ‘flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parameter correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales. PMID:27941922

  2. Universal structural parameter to quantitatively predict metallic glass properties

    DOE PAGES

    Ding, Jun; Cheng, Yong-Qiang; Sheng, Howard; ...

    2016-12-12

    Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parametermore » correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales.« less

  3. Universal structural parameter to quantitatively predict metallic glass properties.

    PubMed

    Ding, Jun; Cheng, Yong-Qiang; Sheng, Howard; Asta, Mark; Ritchie, Robert O; Ma, Evan

    2016-12-12

    Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce 'flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parameter correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales.

  4. Elasticity dominates strength and failure in metallic glasses

    SciTech Connect

    Liu, Z. Q.; Qu, R. T.; Zhang, Z. F.

    2015-01-07

    Two distinct deformation mechanisms of shearing and volume dilatation are quantitatively analyzed in metallic glasses (MGs) from the fundamental thermodynamics. Their competition is deduced to intrinsically dominate the strength and failure behaviors of MGs. Both the intrinsic shear and normal strengths give rise to the critical mechanical energies to activate destabilization of amorphous structures, under pure shearing and volume dilatation, respectively, and can be determined in terms of elastic constants. By adopting an ellipse failure criterion, the strength and failure behaviors of MGs can be precisely described just according to their shear modulus and Poisson's ratio without mechanical testing. Quantitative relations are established systematically and verified by experimental results. Accordingly, the real-sense non-destructive failure prediction can be achieved in various MGs. By highlighting the broad key significance of elasticity, a “composition-elasticity-property” scheme is further outlined for better understanding and controlling the mechanical properties of MGs and other glassy materials from the elastic perspectives.

  5. Universal structural parameter to quantitatively predict metallic glass properties

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Cheng, Yong-Qiang; Sheng, Howard; Asta, Mark; Ritchie, Robert O.; Ma, Evan

    2016-12-01

    Quantitatively correlating the amorphous structure in metallic glasses (MGs) with their physical properties has been a long-sought goal. Here we introduce `flexibility volume' as a universal indicator, to bridge the structural state the MG is in with its properties, on both atomic and macroscopic levels. The flexibility volume combines static atomic volume with dynamics information via atomic vibrations that probe local configurational space and interaction between neighbouring atoms. We demonstrate that flexibility volume is a physically appropriate parameter that can quantitatively predict the shear modulus, which is at the heart of many key properties of MGs. Moreover, the new parameter correlates strongly with atomic packing topology, and also with the activation energy for thermally activated relaxation and the propensity for stress-driven shear transformations. These correlations are expected to be robust across a very wide range of MG compositions, processing conditions and length scales.

  6. General 2.5 power law of metallic glasses

    PubMed Central

    Zeng, Qiaoshi; Lin, Yu; Liu, Yijin; Zeng, Zhidan; Shi, Crystal Y.; Zhang, Bo; Lou, Hongbo; Sinogeikin, Stanislav V.; Kono, Yoshio; Kenney-Benson, Curtis; Park, Changyong; Yang, Wenge; Wang, Weihua; Sheng, Hongwei; Mao, Ho-kwang; Mao, Wendy L.

    2016-01-01

    Metallic glass (MG) is an important new category of materials, but very few rigorous laws are currently known for defining its “disordered” structure. Recently we found that under compression, the volume (V) of an MG changes precisely to the 2.5 power of its principal diffraction peak position (1/q1). In the present study, we find that this 2.5 power law holds even through the first-order polyamorphic transition of a Ce68Al10Cu20Co2 MG. This transition is, in effect, the equivalent of a continuous “composition” change of 4f-localized “big Ce” to 4f-itinerant “small Ce,” indicating the 2.5 power law is general for tuning with composition. The exactness and universality imply that the 2.5 power law may be a general rule defining the structure of MGs. PMID:26831105

  7. LIQUID METAL COMPOSITIONS CONTAINING URANIUM

    DOEpatents

    Teitel, R.J.

    1959-04-21

    Liquid metal compositions containing a solid uranium compound dispersed therein is described. Uranium combines with tin to form the intermetallic compound USn/sub 3/. It has been found that this compound may be incorporated into a liquid bath containing bismuth and lead-bismuth components, if a relatively small percentage of tin is also included in the bath. The composition has a low thermal neutron cross section which makes it suitable for use in a liquid metal fueled nuclear reactor.

  8. Compressive behavior of bulk metallic glass under different conditions --- Coupled effect of temperature and strain rate

    NASA Astrophysics Data System (ADS)

    Yin, Weihua

    Metallic glass was first reported in 1960 by rapid quenching of Au-Si alloys. But, due to the size limitation, this material did not attract remarkable interest until the development of bulk metallic glasses (BMGs) with specimen sizes in excess of 1 mm. BMGs are considered to be promising engineering materials because of their ultrahigh strength, high elastic limit and wear resistance. However, they usually suer from a strong tendency for localized plastic deformation with catastrophic failure. Many basic questions, such as the origin of shear softening and the strain rate eect remain unclear. In this thesis, the mechanical behavior of the Zr55Al 10Ni5Cu30 bulk metallic glass and a metallic glass composite is investigated. The stress-strain relationship for Zr55Al10Ni 5Cu30 over a wide range of strain rate (5x10 --5 to 2x103 s--1) was investigated in uniaxial compression loading using both MTS servo-hydraulic system (quasi-static) and compression Kolsky bar system (dynamic). The effect of the strain rate on the fracture stress at room temperature was discussed. Based on the experimental results, the strain rate sensitivity of the bulk metallic glass changes from a positive value to a negative value at high strain rate, which is a consequence of the significant adiabatic temperature rise during the dynamic testing. In order to characterize the temperature eect on the mechanical behavior of the metallic glass, a synchronically assembled heating unit was designed to be attached onto the Kolsky bar system to perform high temperature and high strain rate mechanical testing. A transition from inhomogeneous deformation to homogeneous deformation has been observed during the quasi-static compressive experiments at testing temperatures close to the glass transition temperature. However, no transition has been observed at high strain rates at all the testing temperatures. A free volume based model is applied to analyze the stress-strain behavior of the homogeneous

  9. A nanometallic nickel-coated, glass-fibre-based structural health monitoring system for polymer composites

    NASA Astrophysics Data System (ADS)

    Balaji, R.; Sasikumar, M.

    2017-09-01

    Glass-fibre-reinforced polymer matrix composites are widely used in various industries because of their unique high strength to weight ratio. Unlike metals, strain-induced and damage states of composites are complicated to predict under real-time loading due to their anisotropic nature. With that focus, a piezoresistive nanomaterial-based structural health monitoring system for laminated polymer composites is proposed to measure the strain induced in the composite under real-time loading. Nanometallic nickel-coated glass fibres are embedded into the polymer composites to monitor the strain and damage induced in them. The nanometallic nickel is coated over the glass fibre by a dip coating technique using epoxy as the binding agent. A microcontroller-based electrical resistance measurement system is used to measure the piezoresistive variation in the coated glass fibre under real-time loading. Using the piezoresistance variation of the embedded nanometallic nickel-coated glass fibre, the real-time strain and damage induced in the composite can be correlated. The piezoresistive response of the coated glass fibre is descibed in two phases, the deformation phase and the failure phase, which clearly show the various states of strain and damage induced in the composites.

  10. Predicting the Glass-Forming-Ability of Alloys by Molecular Dynamics Simulation: A Working Example of Ti-Co Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Kao, Su-Wen; Yang, Ke-Chin; Wang, Shuo-Hong; Hwang, Chi-Chuan; Lee, Pee-Yew; Huang, Rong-Tan; Chin, Tsung-Shune

    2009-06-01

    Predicting the glass-forming-ability (GFA) of alloys before experimental trials has long been a pursuit in the exploration of bulk metallic glasses (BMGs). Researchers can determine GFA criteria, such as reduced glass-transition temperature (Trg) and gamma factor concluded only from experimental data in prepared amorphous metals, but not beforehand. This study predicts the GFA of binary TixCo100-x system, where x = 60, 70, 77 and 84 (hyper-eutectic, eutectic to hypo-eutectic compositions) by calculating their Trg using molecular dynamics simulation with modified tight-binding potentials. The same compositions were also melted and injection-cast into 1 mm rods. Experiment tests confirm that the compositions Ti60Co40 and Ti70Co30, having calculated Trg> 0.5, were able to produce BMGs. Both calculation and differential thermal analysis indicate that Ti-Co BMGs have exceptionally high glass-transition temperatures.

  11. Composite and Nanocomposite Metal Foams

    PubMed Central

    Duarte, Isabel; Ferreira, José M. F.

    2016-01-01

    Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams. PMID:28787880

  12. Composite and Nanocomposite Metal Foams.

    PubMed

    Duarte, Isabel; Ferreira, José M F

    2016-01-28

    Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams.

  13. Quantitative NDE applied to composites and metals

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.; Winfree, William P.; Parker, F. Raymond; Heath, D. Michele; Welch, Christopher S.

    1989-01-01

    Research at the NASA/Langley Research Center concerning quantitative NDE of composites and metals is reviewed. The relationship between ultrasonics and polymer cure is outlined. NDE models are presented, which can be used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The models can be used to determine the glass transition temperature, the degree of cure, and the cure rate. The application of the model to control autoclave processing of composite materials is noted. Consideration is given to the use of thermal diffusion models combined with controlled thermal input measurements to determine the thermal diffusivity of materials. Also, a two-dimensional physical model is described that permits delaminations in samples of Space Shuttle Solid Rocket Motors to be detected in thermograms in the presence of cooling effects and uneven heating.

  14. Quantitative NDE applied to composites and metals

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.; Winfree, William P.; Parker, F. Raymond; Heath, D. Michele; Welch, Christopher S.

    1989-01-01

    Research at the NASA/Langley Research Center concerning quantitative NDE of composites and metals is reviewed. The relationship between ultrasonics and polymer cure is outlined. NDE models are presented, which can be used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The models can be used to determine the glass transition temperature, the degree of cure, and the cure rate. The application of the model to control autoclave processing of composite materials is noted. Consideration is given to the use of thermal diffusion models combined with controlled thermal input measurements to determine the thermal diffusivity of materials. Also, a two-dimensional physical model is described that permits delaminations in samples of Space Shuttle Solid Rocket Motors to be detected in thermograms in the presence of cooling effects and uneven heating.

  15. Plasticity in the Supercooled Liquid Region of Bulk Metallic Glasses

    SciTech Connect

    Nieh, T G; Wadsworth, J; Liu, C T; Ice, G E

    2000-10-30

    Intensive efforts have been carried out over the past decade to develop means to slow down the phase transformation kinetics during the forming of metallic glasses. As a result of these efforts, some metallic glasses can now be fabricated in bulk forms (BMG) from the liquid state at cooling rates on the order of 1-10 K/s, which is close to that of conventional casting. This enables the production of bulk amorphous alloys with a thickness of {approx}10 mm. While advances in amorphous metallic alloy development have been impressive, they have been made largely through experience [1]. Three main conclusions drawn from this study are: (1) Bulk metallic glasses generally have excellent mechanical formability in the supercooled liquid region. (2) Bulk metallic glasses may not be necessarily behave like a Newtonian fluid (i.e. m=1). The non-Newtonian behavior is associated with glass instability during deformation. (3) Multi-component Bulk metallic glasses can be used as the precursor of a nanocrystalline solid. However, the nanocrystalline solid is not necessarily superplastic. The non-superplastic behavior is caused by the difficult strain accommodation at grain triple junctions.

  16. Guided evolution of bulk metallic glass nanostructures: A platform for designing three-dimensional electrocatalytic surfaces

    DOE PAGES

    Doubek, Gustavo; Sekol, Ryan C.; Li, Jinyang; ...

    2015-12-22

    Precise control over catalyst surface composition and structure is necessary to improve the function of electrochemical systems. To that end, bulk metallic glass (BMG) alloys with atomically dispersed elements provide a highly processable, nanoscale platform for electrocatalysis and surface modification. Here we report on nanostructures of Pt-based BMGs that are modified with various subtractive and additive processes to improve their electrochemical performance.

  17. Methods of Fabricating a Layer of Metallic Glass-Based Material Using Immersion and Pouring Techniques

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas (Inventor)

    2015-01-01

    Systems and methods in accordance with embodiments of the invention implement layers of metallic glass-based materials. In one embodiment, a method of fabricating a layer of metallic glass includes: applying a coating layer of liquid phase metallic glass to an object, the coating layer being applied in a sufficient quantity such that the surface tension of the liquid phase metallic glass causes the coating layer to have a smooth surface; where the metallic glass has a critical cooling rate less than 1000 K/s; and cooling the coating layer of liquid phase metallic glass to form a layer of solid phase metallic glass.

  18. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses

    PubMed Central

    Kohara, S.; Akola, J.; Morita, H.; Suzuya, K.; Weber, J. K. R.; Wilding, M. C.; Benmore, C. J.

    2011-01-01

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth’s mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO3) composition is a good glass former, whereas the forsterite (Mg2SiO4) composition is at the limit of glass formation. Here, the structure of MgSiO3 and Mg2SiO4 composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg2SiO4 glass is associated with a topologically ordered and very narrow ring distribution. The MgOx polyhedra have a variety of irregular shapes in MgSiO3 and Mg2SiO4 glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgOx-MgOx polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg2+ remains similar. This unusual structure-property relation of Mg2SiO4 glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity. PMID:21873237

  19. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses.

    PubMed

    Kohara, S; Akola, J; Morita, H; Suzuya, K; Weber, J K R; Wilding, M C; Benmore, C J

    2011-09-06

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth's mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO(3)) composition is a good glass former, whereas the forsterite (Mg(2)SiO(4)) composition is at the limit of glass formation. Here, the structure of MgSiO(3) and Mg(2)SiO(4) composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg(2)SiO(4) glass is associated with a topologically ordered and very narrow ring distribution. The MgO(x) polyhedra have a variety of irregular shapes in MgSiO(3) and Mg(2)SiO(4) glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgO(x)-MgO(x) polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg(2+) remains similar. This unusual structure-property relation of Mg(2)SiO(4) glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity.

  20. Fast Surface Dynamics of Metallic Glass Enable Superlatticelike Nanostructure Growth.

    PubMed

    Chen, L; Cao, C R; Shi, J A; Lu, Z; Sun, Y T; Luo, P; Gu, L; Bai, H Y; Pan, M X; Wang, W H

    2017-01-06

    Contrary to the formation of complicated polycrystals induced by general crystallization, a modulated superlatticelike nanostructure, which grows layer by layer from the surface to the interior of a Pd_{40}Ni_{10}Cu_{30}P_{20} metallic glass, is observed via isothermal annealing below the glass transition temperature. The generation of the modulated nanostructure can be solely controlled by the annealing temperature, and it can be understood based on the fast dynamic and liquidlike behavior of the glass surface. The observations have implications for understanding the glassy surface dynamics and pave a way for the controllable fabrication of a unique and sophisticated nanostructure on a glass surface to realize the properties' modification.

  1. Fast Surface Dynamics of Metallic Glass Enable Superlatticelike Nanostructure Growth

    NASA Astrophysics Data System (ADS)

    Chen, L.; Cao, C. R.; Shi, J. A.; Lu, Z.; Sun, Y. T.; Luo, P.; Gu, L.; Bai, H. Y.; Pan, M. X.; Wang, W. H.

    2017-01-01

    Contrary to the formation of complicated polycrystals induced by general crystallization, a modulated superlatticelike nanostructure, which grows layer by layer from the surface to the interior of a Pd40Ni10Cu30P20 metallic glass, is observed via isothermal annealing below the glass transition temperature. The generation of the modulated nanostructure can be solely controlled by the annealing temperature, and it can be understood based on the fast dynamic and liquidlike behavior of the glass surface. The observations have implications for understanding the glassy surface dynamics and pave a way for the controllable fabrication of a unique and sophisticated nanostructure on a glass surface to realize the properties' modification.

  2. Ceramic-glass-metal seal by microwave heating

    DOEpatents

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

    1983-10-04

    A method for producing a ceramic-glass-metal seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic and metal workpieces. The slurry and workpieces are then insulated and microwaved at a power, time and frequency sufficient to cause a liquid-phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by diffusion rather than by wetting of the reactants.

  3. Ceramic-glass-metal seal by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1985-01-01

    A method for producing a ceramic-glass-metal seal by microwaving mixes a slurry of glass sealing material and coupling agent and applies same to ceramic and metal workpieces. The slurry and workpieces are then insulated and microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by diffusion rather than by wetting of the reactants.

  4. Patch electrode glass composition affects ion channel currents.

    PubMed

    Furman, R E; Tanaka, J C

    1988-02-01

    The influence of patch electrode glass composition on macroscopic IV relations in inside-out patches of the cGMP-activated ion channel from rod photoreceptors was examined for a soda lime glass, a Kovar sealing glass, a borosilicate glass, and several soft lead glasses. In several glasses the shape or magnitude of the currents changed as the concentration of EGTA or EDTA was increased from 200 microM to 10 mM. The changes in IV response suggest that, at low concentrations of chelator, divalent cations are released from the electrode glass and interact with the cGMP-activated channel. Possible mechanisms are discussed to explain the observations, and several comments are made concerning the choice of a glass for patching.

  5. Prediction of glass durability as a function of glass composition and test conditions: Thermodynamics and kinetics

    SciTech Connect

    Jantzen, C M

    1988-01-01

    The long-term durability of nuclear waste glasses can be predicted by comparing their performance to natural and ancient glasses. Glass durability is a function of the kinetic and thermodynamic stability of glass in solution. The relationship between the kinetic and thermodynamic aspects of glass durability can be understood when the relative contributions of glass composition and imposed test conditions are delineated. Glass durability has been shown to be a function of the thermodynamic hydration free energy which can be calculated from the glass composition. Hydration thermodynamics also furnishes a quantitative frame of reference to understand how various test parameters affect glass durability. Linear relationships have been determined between the logarithmic extent of hydration and the calculated hydration free energy for several different test geometries. Different test conditions result in different kinetic reactivity parameters such as the exposed glass surface area (SA), the leachant solution volume (V), and the length of time that the glass is in the leachant (t). Leachate concentrations are known to be a function of the kinetic test parameter (SAV)t. The relative durabilities of glasses, including pure silica, obsidians, nuclear waste glasses, medieval window glasses, and frit glasses define a plane in three dimensional ..delta..G/sub hyd/-concentration-(SAV)t space. At constant kinetic conditions, e.g., test geometry and test duration, the three dimensional plane is intersected at constant (SAV)t and the ..delta..G/sub hyd/-concentration plots have similar slopes. The slope represents the natural logarithm of the theoretical slope, (12.303 RT), for the rate of glass dissolution. 53 refs., 4 figs.

  6. Atomic-scale heterogeneity of a multicomponent bulk metallic glass with excellent glass forming ability.

    PubMed

    Fujita, T; Konno, K; Zhang, W; Kumar, V; Matsuura, M; Inoue, A; Sakurai, T; Chen, M W

    2009-08-14

    We report the atomic structure of a multicomponent Cu45Zr45Ag10 bulk metallic glass investigated by state-of-the-art experimental and computational techniques. In comparison with a binary Cu50Zr50 metallic glass, Zr-rich interpenetrating clusters centered by paired and stringed Ag atoms and Cu-rich icosahedra are widely observed in the ternary Cu45Zr45Ag10 alloy. The atomic-scale heterogeneity caused by chemical short- and medium-range order is found to play a key role in stabilizing the liquid phase and in improving the glass forming ability of the multicomponent alloy.

  7. Mechanical behaviour of degradable phosphate glass fibres and composites-a review.

    PubMed

    Colquhoun, R; Tanner, K E

    2015-12-23

    Biodegradable materials are potentially an advantageous alternative to the traditional metallic fracture fixation devices used in the reconstruction of bone tissue defects. This is due to the occurrence of stress shielding in the surrounding bone tissue that arises from the absence of mechanical stimulus to the regenerating bone due to the mismatch between the elastic modulus of bone and the metal implant. However although degradable polymers may alleviate such issues, these inert materials possess insufficient mechanical properties to be considered as a suitable alternative to current metallic devices at sites of sufficient mechanical loading. Phosphate based glasses are an advantageous group of materials for tissue regenerative applications due to their ability to completely degrade in vivo at highly controllable rates based on the specific glass composition. Furthermore the release of the glass's constituent ions can evoke a therapeutic stimulus in vivo (i.e. osteoinduction) whilst also generating a bioactive response. The processing of these materials into fibres subsequently allows them to act as reinforcing agents in degradable polymers to simultaneously increase its mechanical properties and enhance its in vivo response. However despite the various review articles relating to the compositional influences of different phosphate glass systems, there has been limited work summarising the mechanical properties of different phosphate based glass fibres and their subsequent incorporation as a reinforcing agent in degradable composite materials. As a result, this review article examines the compositional influences behind the development of different phosphate based glass fibre compositions intended as composite reinforcing agents along with an analysis of different potential composite configurations. This includes variations in the fibre content, matrix material and fibre architecture as well as other novel composites designs.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Design and Fabrication of E-Glass /carbon/graphite epoxy hybrid composite leaf spring

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, T.; Raja, M.; Jothi Prakash, V. M.; Gnanavel, C.

    2017-03-01

    The Automobile Industry has shown increase interest for replacement of steel leaf spring with that of composite leaf spring. Substituting composite materials for conventional metallic materials has many advantages because of higher specific stiffness, strength and fatigue resistance etc. This work deals with the replacement of conventional steel leaf spring with a hybrid Composite leaf spring using E -Glass/Carbon/Graphite/Epoxy. The hybrid composite is obtained by introducing more than one fiber in the reinforcement phase. The hybrid composite is fabricated by the vacuum bag technique. The result shows that introduction of carbon and graphite fiber in the reinforcement phase increases the stiffness of the composite.

  10. A microscopic continuum model for defect dynamics in metallic glasses

    NASA Astrophysics Data System (ADS)

    Acharya, Amit; Widom, Michael

    2017-07-01

    Motivated by results of the topological theory of glasses accounting for geometric frustration, we develop the simplest possible continuum mechanical model of defect dynamics in metallic glasses that accounts for topological, energetic, and kinetic ideas. A geometrical description of ingredients of the structure of metallic glasses using the concept of local order based on Frank-Kasper phases and the notion of disclinations as topological defects in these structures is proposed. This novel kinematics is incorporated in a continuum mechanical framework capable of describing the interactions of disclinations and also of dislocations (interpreted as pairs of opposite disclinations). The model is aimed towards the development of a microscopic understanding of the plasticity of such materials. We discuss the expected predictive capabilities of the model vis-a-vis some observed physical behaviors of metallic glasses.

  11. Composite materials based on wastes of flat glass processing.

    PubMed

    Gorokhovsky, A V; Escalante-Garcia, J I; Gashnikova, G Yu; Nikulina, L P; Artemenko, S E

    2005-01-01

    Glass mirrors scrap and poly (vinyl) butiral waste (PVB) obtained from flat glass processing plants were investigated as raw materials to produce composites. The emphasis was on studying the influence of milled glass mirror waste contents on properties of composites produced with PVB. The characterization involved: elongation under rupture, water absorption, tensile strength and elastic modulus tests. The results showed that the composite containing 10 wt% of filler powder had the best properties among the compositions studied. The influence of the time of exposure in humid atmosphere on the composite properties was investigated. It was found that the admixture of PVB iso-propanol solution to the scrap of glass mirrors during milling provided stabilization of the properties of the composites produced.

  12. Flexural behavior of a glass fiber reinforced wood fiber composite

    SciTech Connect

    Smulski, S.J.

    1985-01-01

    The static and dynamic flexural properties of a wood fiber matrix internally reinforced with continuous glass fibers were investigated. When modeled as sandwich composite, the static flexural modulus of elasticity (MOE) of glass fiber reinforced hardboard could be successfully predicted from the static flexural MOE of the wood fiber matrix, and the tensile MOE and effective volume fraction of the glass fiber reinforcement. Under the same assumption, the composite modulus of rupture (MOR) was a function of the reinforcement tensile MOE and effective volume fraction, and the matrix stress at failure. The composite MOR was predicted on this basis with limited success. The static flexural modulus of elasticity, dynamic modulus of elasticity, and modulus of rupture of glass fiber reinforced hardboard increased with increasing effective reinforcement volume fraction. The logarithmic decrement of the composite decreased with increasing effective reinforcement volume fraction. The short-term flexural creep behavior of glass fiber reinforced hardboard was accurately described by a 4-element linear viscoelastic model.

  13. Surface modification of bioactive glasses and preparation of PDLLA/bioactive glass composite films.

    PubMed

    Gao, Yuan; Chang, Jiang

    2009-08-01

    In order to improve the homogeneous dispersion of particles in the polymeric matrix, 45S5, mesoporous 58S, and 58S bioactive glasses were surface modified by esterification reactions with dodecyl alcohol at reflux temperature of 260 degrees C (named as m-45S5, m-mesoporous 58S, and m-58S, respectively). The modified particles showed better hydrophobicity and longer time of suspension in organic matrix. The PDLLA/bioactive glass composite films were fabricated using surface modified bioactive glass particles through solvent casting-evaporation method. Surface morphology, mechanical property, and bioactivity were investigated. The results revealed that the inorganic particle distribution and tensile strength of the composite films with modified bioactive glass particles were significantly improved while great bioactive properties were maintained. Scanning electron microscopy (SEM) observation illustrated that the modified bioactive glass particles were homogeneously dispersed in the PDLLA matrix. The maximum tensile strengths of composite films with modified bioactive glass particles were higher than that of composite films with unmodified bioactive glass particles. The bioactivity of the composite films were evaluated by being soaked in the simulated body fluid (SBF) and the SEM observation of the films suggested that the modified composite films were still bioactive in that they could induce the formation of HAp on its surface and the distribution of HAp was even more homogeneous on the film. The results mentioned above indicated that the surface modification of bioactive glasses with dodecyl alcohol was an effective method to prepare PDLLA/bioactive glass composites with enhanced properties. By studying the comparisons of modification effects among the three types of bioactive glasses, we could get the conclusion that the size and morphology of the inorganic particles would greatly affect the modification effects and the properties of composites.

  14. Some developments on ceramic-to-metal and glass-ceramics-to-metal seals and related studies

    NASA Astrophysics Data System (ADS)

    Kothiyal, G. P.; Goswami, M.; Shrikhande, V. K.

    2008-05-01

    Seals and coatings based on ceramics and glass-ceramics find numerous applications in different disciplines of science and technology including space, accelerators, nuclear energy, chemical industry. Ceramic-to-metal (CM) seals based on conventional design (using brazing alloys) and glass-ceramics have been prepared. While Ag-Cu brazing alloy has been used in conventional CM seal, we have employed lithium zinc silicate (LZS) and lithium aluminum silicate (LAS) glass-ceramics for glass-ceramics-to-metal (GCM) seals. LZS glass-ceramics based on two different compositions; (a) LZSL composition (wt.%)- Li2O: 12.65, ZnO: 1.85, SiO2: 74.4, Al2O3: 3.8, K2O: 2.95, P2O5: 3.15, and B2O3: 1.2 (low ZnO) and (b) LZSH composition (wt.%)- Li2O: 8.9, ZnO: 24.03, SiO2: 53.7, Na2O: 5.42, P2O5: 2.95, and B2O3: 5.0 (high ZnO) were prepared with desired sealing characteristics for matched type seals. In addition, (wt.%) 12.6Li2O-71.7SiO2-5.1Al2O3-4.9K2O-3.2B2O3-2.5P2O5 (LAS-GC) was investigated for compressive type of seal. LZS glass-ceramics-to-Cu as well as SS-321 seals were found to withstand a vacuum of 10-6 Torr with leak rate 10-9 Torr. 1/s and LAS GC-to-SS304 seal showed high pressure endurance of 12000psi. In order to understand the mechanism of sealing, glass-ceramics-to-metal interface study has also been carried out.

  15. Surface characteristics of metallic glass spheres of Au(55)Pb(22.5)Sb(22.5)

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Kendall, J. M.

    1983-01-01

    It is pointed out that the production of metallic glasses of high atomic number is currently of considerable importance for inertial confinement fusion (ICF) target applications. In connection with the present investigation, spherules of the alloy Au(55)Pb(22.5)Sb(22.5) were produced. Metallic glass was formed on solidification. With the aid of X-ray diffraction studies, it was established that the spheres were completely amorphous. A near-surface phase separation on spheres of the metallic glass could be observed. Energy dispersive spectroscopy (EDS) measurements showed that the average composition of the surface differed from that of the bulk.

  16. Impact of ion irradiation on the thermal, structural, and mechanical properties of metallic glasses

    SciTech Connect

    Mayr, S.G.

    2005-04-01

    The impact of ion-beam irradiation on the thermal, structural, and mechanical properties of metallic glasses is investigated using the model glass, CuTi, in molecular dynamics computer simulations. It is found that ion-beam bombardment successively modifies the compositional and structural order toward a universal steady state, which proves to be independent of the initial relaxation state and thermal history of the unirradiated sample. This is reflected by key materials properties, including enthalpy, structural and compositional short-range order, as well as Young's modulus and fracture behavior. The results are interpreted within the framework of competing dynamics, where radiation-induced plastic relaxation counteracts ion-beam disordering.

  17. Evolution of shear banding flows in metallic glasses characterized by molecular dynamics

    SciTech Connect

    Yao, Li; Luan, Yingwei

    2016-06-21

    To reveal the evolution of shear banding flows, one-dimensional nanostructure metallic glass composites have been studied with molecular dynamics. The inherent size determines the initial thickness of shear bands, and the subsequent broadening can be restricted to some extent. The vortex-like flows evoke the atomic motion perpendicular to the shear plane, which accelerates the interatomic diffusion. The reduction of local strain rate causes the flow softening for monolithic Cu-Zr glass, but the participation of Cu-atoms in the shear banding flow gradually leads to the shear hardening for the composites.

  18. Calcium and zinc containing bactericidal glass coatings for biomedical metallic substrates.

    PubMed

    Esteban-Tejeda, Leticia; Díaz, Luis A; Prado, Catuxa; Cabal, Belén; Torrecillas, Ramón; Moya, José S

    2014-07-23

    The present work presents new bactericidal coatings, based on two families of non-toxic, antimicrobial glasses belonging to B2O3-SiO2-Na2O-ZnO and SiO2-Na2O-Al2O3-CaO-B2O3 systems. Free of cracking, single layer direct coatings on different biomedical metallic substrates (titanium alloy, Nb, Ta, and stainless steel) have been developed. Thermal expansion mismatch was adjusted by changing glass composition of the glass type, as well as the firing atmosphere (air or Ar) according to the biomedical metallic substrates. Formation of bubbles in some of the glassy coatings has been rationalized considering the reactions that take place at the different metal/coating interfaces. All the obtained coatings were proven to be strongly antibacterial versus Escherichia coli (>4 log).

  19. Calcium and Zinc Containing Bactericidal Glass Coatings for Biomedical Metallic Substrates

    PubMed Central

    Esteban-Tejeda, Leticia; Díaz, Luis A.; Prado, Catuxa; Cabal, Belén; Torrecillas, Ramón; Moya, José S.

    2014-01-01

    The present work presents new bactericidal coatings, based on two families of non-toxic, antimicrobial glasses belonging to B2O3–SiO2–Na2O–ZnO and SiO2–Na2O–Al2O3–CaO–B2O3 systems. Free of cracking, single layer direct coatings on different biomedical metallic substrates (titanium alloy, Nb, Ta, and stainless steel) have been developed. Thermal expansion mismatch was adjusted by changing glass composition of the glass type, as well as the firing atmosphere (air or Ar) according to the biomedical metallic substrates. Formation of bubbles in some of the glassy coatings has been rationalized considering the reactions that take place at the different metal/coating interfaces. All the obtained coatings were proven to be strongly antibacterial versus Escherichia coli (>4 log). PMID:25056542

  20. High strength glass-ceramic to metal seals

    SciTech Connect

    Haws, L D; Kramer, D P; Moddeman, W E; Wooten, G W

    1986-12-01

    In many applications, ceramics are joined to other materials, especially metals. In such cases, interfacial strength is as important as the strength of each constituent material. Examples are presented for tailoring materials and processes to optimize the glass-ceramic-to-metal seal. Means for detecting defects, nondestructively, are also identified.

  1. The grindability of glass fibre reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Chockalingam, P.

    The use of glass fibre-reinforced polymer (GFRP) composite materials is extensive due to their favourable mechanical properties and near net shape production. However, almost all composite structures require post-processing operations such as grinding to meet surface finish requirements during assembly. Unlike that of conventional metal, grinding of GFRP composite needs special tools and parameters due to the abrasive nature of fibres and the delamination of the workpiece. Therefore, proper selection of the tools and parameters is important. This research aims to investigate the effects of wheel speed, feed, depth of cut, grinding wheel and coolant on the grindability of chopped strand mat (CSM) GFRP. Grinding was carried out in a precision CNC (Master-10HVA) high-speed machining centre under three conditions, namely dry, and wet conditions with synthetic coolant and emulsion coolant, using alumina wheel (OA46QV) and CBN wheel (B46QV). The grinding experiments were conducted per the central composite design of design of experiments. The grindability aspects investigated were surface area roughness (Sa) and cutting force ratio (µ). The responses were analyzed by developing fuzzy logic models. The surface area roughness and cutting force ratio values predicted by the fuzzy logic models are mostly in good agreement with experimental data, and hence conclusion was made that these models were reliable.

  2. Metal coated glasses by sputtering and their microfouling properties

    NASA Astrophysics Data System (ADS)

    Kougo, T.; Kanematsu, H.; Wada, N.; Hihara, T.; Minekawa, M.; Fujita, Y.

    2014-02-01

    Some elements as contaminant tend to be concentrated in biofilm. In order to prevent the fogging of glass, it is very important to control biofilm formation by metal dissolution. In this study, Metals were deposited on glass substrate by Helicon-wave-excited-plasma sputtering process. Sample was very thin metals layer like as half mirror, it could transmit light. The results of biofilm formation test, biofilm formation were inhibited on Cu, Sn and Cr, and light transmission of these samples was not degradation. It could be said that inhibition of biofilm formation was effective to suppressing cloudiness.

  3. Glass/Ceramic Composites for Sealing Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Choi, Sung R.

    2007-01-01

    A family of glass/ceramic composite materials has been investigated for use as sealants in planar solid oxide fuel cells. These materials are modified versions of a barium calcium aluminosilicate glass developed previously for the same purpose. The composition of the glass in mole percentages is 35BaO + 15CaO + 5Al2O3 + 10B2O3 + 35SiO2. The glass seal was found to be susceptible to cracking during thermal cycling of the fuel cells. The goal in formulating the glass/ ceramic composite materials was to (1) retain the physical and chemical advantages that led to the prior selection of the barium calcium aluminosilicate glass as the sealant while (2) increasing strength and fracture toughness so as to reduce the tendency toward cracking. Each of the composite formulations consists of the glass plus either of two ceramic reinforcements in a proportion between 0 and 30 mole percent. One of the ceramic reinforcements consists of alumina platelets; the other one consists of particles of yttria-stabilized zirconia wherein the yttria content is 3 mole percent (3YSZ). In preparation for experiments, panels of the glass/ceramic composites were hot-pressed and machined into test bars.

  4. Formation of bulk metallic glass by fluxing

    NASA Technical Reports Server (NTRS)

    Kui, H. W.; Turnbull, D.; Greer, A. L.

    1984-01-01

    Bulk specimens (0.4-4 g mass) of the alloy Pd40Ni40P20 have been undercooled consistently to the glass state, with no detectable superficial crystallinity, in a molten flux of dehydrated boron oxide. The minimum dimension of the most massive glass specimen, so formed, was 1.0 cm. The absence of crystallinity in the specimens was confirmed by X-ray diffraction, scanning electron microscopy, and calorimetry.

  5. High-throughput drawing and testing of metallic glass nanostructures.

    PubMed

    Hasan, Molla; Kumar, Golden

    2017-03-02

    Thermoplastic embossing of metallic glasses promises direct imprinting of metal nanostructures using templates. However, embossing high-aspect-ratio nanostructures faces unworkable flow resistance due to friction and non-wetting conditions at the template interface. Herein, we show that these inherent challenges of embossing can be reversed by thermoplastic drawing using templates. The flow resistance not only remains independent of wetting but also decreases with increasing feature aspect-ratio. Arrays of assembled nanotips, nanowires, and nanotubes with aspect-ratios exceeding 1000 can be produced through controlled elongation and fracture of metallic glass structures. In contrast to embossing, the drawing approach generates two sets of nanostructures upon final fracture; one set remains anchored to the metallic glass substrate while the second set is assembled on the template. This method can be readily adapted for high-throughput fabrication and testing of nanoscale tensile specimens, enabling rapid screening of size-effects in mechanical behavior.

  6. A comparative study of the mechanical performance of Glass and Glass/Carbon hybrid polymer composites at different temperature environments

    NASA Astrophysics Data System (ADS)

    Shukla, M. J.; Kumar, D. S.; Mahato, K. K.; Rathore, D. K.; Prusty, R. K.; Ray, B. C.

    2015-02-01

    Glass Fiber Reinforced Polymer (GFRP) composites have been widely accepted as high strength, low weight structural material as compared to their metallic counterparts. Some specific advanced high performance applications such as aerospace components still require superior specific strength and specific modulus. Carbon Fiber Reinforced Polymer (CFRP) composites exhibit superior specific strength and modulus but have a lower failure strain and high cost. Hence, the combination of both glass and carbon fiber in polymer composite may yield optimized mechanical properties. Further the in-service environment has a significant role on the mechanical performance of this class of materials. Present study aims to investigate the mechanical property of GFRP and Glass/Carbon (G/C hybrid) composites at room temperature, in-situ and ex-situ temperature conditions. In-situ testing at +70°C and +100°C results in significant loss in inter-laminar shear strength (ILSS) for both the composites as compared to room temperature. The ILSS was nearly equal for both the composite systems tested in-situ at +100°C and effect of fiber hybridisation was completely diminished there. At low temperature ex-situ conditioning significant reduction in ILSS was observed for both the systems. Further at -60°C G/C hybrid exhibited 32.4 % higher ILSS than GFRP. Hence this makes G/C hybrid a better choice of material in low temperature environmental applications.

  7. Relating Dynamic Properties to Atomic Structure in Metallic Glasses

    SciTech Connect

    Sheng, H.W.; Ma, E.; Kramer, Matthew J.

    2012-07-18

    Atomic packing in metallic glasses is not completely random but displays various degrees of structural ordering. While it is believed that local structures profoundly affect the properties of glasses, a fundamental understanding of the structure–property relationship has been lacking. In this article, we provide a microscopic picture to uncover the intricate interplay between structural defects and dynamic properties of metallic glasses, from the perspective of computational modeling. Computational methodologies for such realistic modeling are introduced. Exploiting the concept of quasi-equivalent cluster packing, we quantify the structural ordering of a prototype metallic glass during its formation process, with a new focus on geometric measures of subatomic “voids.” Atomic sites connected with the voids are found to be crucial in terms of understanding the dynamic, including vibrational and atomic transport, properties. Normal mode analysis is performed to reveal the structural origin of the anomalous boson peak (BP) in the vibration spectrum of the glass, and its correlation with atomic packing cavities. Through transition-state search on the energy landscape of the system, such structural disorder is found to be a facilitating factor for atomic diffusion, with diffusion energy barriers and diffusion pathways significantly varying with the degree of structural relaxation/ordering. The implications of structural defects for the mechanical properties of metallic glasses are also discussed.

  8. Correlation between medium-range order structure and glass-forming ability for Al-based metallic glasses

    SciTech Connect

    Wu, N. C.; Yan, M.; Zuo, L.; Wang, J. Q.

    2014-01-28

    To clarify the correlation of medium-range order (MRO) structure with glass forming ability (GFA) of Al-based metallic glasses, Al{sub 86}Ni{sub 14-a}Y{sub a} (a = 2∼9 at. %) metallic glasses were analyzed by x-ray diffraction in detail and further verified by synchrotron high-energy x-ray diffraction. The prepeak that reflects the MRO structural evolution was found to be much sensitive to alloy composition. We have proposed an icosahedral supercluster MRO structure model in Al-TM (transition metal)-RE (rare earth metal) system, which consists of 12 RE(TM)-centered clusters on the vertex of icosahedral supercluster, one RE(TM)-centered clusters in the center, and TM(RE) atoms located at RE(TM)-centered cluster tetrahedral interstices in the icosahedral supercluster. It was indicated that the MRO structural stability mainly depends on the interaction of efficient dense packing and electrochemical potential equalization principle. The Al{sub 86}Ni{sub 9}Y(La){sub 5} alloys present good GFA due to the combination of the two structural factors.

  9. Computational studies of the glass-forming ability of model bulk metallic glasses.

    PubMed

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2013-09-28

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate R(c) below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing R(c), and thus good glass-formers possess small values of R(c). We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change R(c) significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ~10(11) K/s, which is several orders of magnitude higher than R(c) for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  10. Computational studies of the glass-forming ability of model bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2013-09-01

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate Rc below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing Rc, and thus good glass-formers possess small values of Rc. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change Rc significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ˜1011 K/s, which is several orders of magnitude higher than Rc for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  11. Ultra-Short Pulsed Laser Engineered Metal-Glass Nanocomposites

    NASA Astrophysics Data System (ADS)

    Stalmashonak, Andrei; Seifert, Gerhard; Abdolvand, Amin

    Glasses and other dielectrics containing metallic nanoparticles are very promising materials for applications in optoelectronics due to their unique linear and non-linear optical properties. These properties are dominated by the strong surface plasmon resonance (SPR) of the metal nanoparticles. The SPR occurs when the electron and light waves couple with each other at a metal-dielectric interface. These are regarded as the collective oscillation of the nanoparticle (NP) electrons.

  12. Partial Coordination Numbers in Binary Metallic Glasses (Postprint)

    DTIC Science & Technology

    2011-12-07

    AFRL-RX-WP-JA-2015-0115 PARTIAL COORDINATION NUMBERS IN BINARY METALLIC GLASSES (POSTPRINT) Daniel B. Miracle AFRL/RXCM Kevin Laws...Approved for public release; distribution unlimited. See additional restrictions described on inside pages STINFO COPY ©2011 The Minerals , Metals...2011 The Minerals , Metals & Materials Society and ASM International. The U.S. Government is joint author of the work and has the right to use

  13. Apatite- and monazite-bearing glass-crystal composites for the immobilization of low-level nuclear and hazardous wastes

    SciTech Connect

    Wronkiewicz, D.J.; Wolf, S.F.; DiSanto, T.S.

    1995-12-31

    This study demonstrates that glass-crystal composite waste forms can be produced from waste streams containing high proportions of phosphorus, transition metals, and/or halides. The crystalline phases produced in crucible-scale melts include apatite, monazite, spinels, and a Zr-Si-Fe-Ti phase. These phases readily incorporated radionuclide and toxic metals into their crystal structures, while corrosion tests have demonstrated that glass-crystal composites can be up to 300-fold more durable than simulated high-level nuclear waste glasses, such as SRL 202U.

  14. Innovative Technologies to Manufacture Hybrid Metal Foam/Composite Components

    SciTech Connect

    Carrino, L.; Durante, M.; Franchitti, S.; Sorrentino, L.; Tersigni, L.

    2011-01-17

    The aim of this paper is to verify the technological feasibility to realize hybrid metal-foam/composite component and the mechanical performances of the final structure. The hybrid component is composed by a cylindrical core in aluminum foam, the most used between those commercially available, and an outer layer in epoxy/S2-glass, manufactured by filament winding technology.A set of experimental tests have been carried out, to the aim to estimate the improvement of the hybrid component characteristics, compared to the sum of the single components (metal foam cylinder and epoxy/S2-glass tube).

  15. Multifunctional methacrylate-based coatings for glass and metal surfaces

    NASA Astrophysics Data System (ADS)

    Pospiech, Doris; Jehnichen, Dieter; Starke, Sandra; Müller, Felix; Bünker, Tobias; Wollenberg, Anne; Häußler, Liane; Simon, Frank; Grundke, Karina; Oertel, Ulrich; Opitz, Michael; Kruspe, Rainer

    2017-03-01

    In order to prevent freshwater biofouling glass and metal surfaces were coated with novel transparent methacrylate-based copolymers. The multifunctionality of the copolymers, such as adhesion to the substrate, surface polarity, mechanical long-term stability in water, and ability to form metal complexes was inserted by the choice of suitable comonomers. The monomer 2-acetoacetoxy ethyl methacrylate (AAMA) was used as complexing unit to produce copper(II) complexes in the coating's upper surface layer. The semifluorinated monomer 1H,1H,2H,2H-perfluorodecyl methacrylate was employed to adjust the surface polarity and wettability. Comprehensive surface characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and contact angle measurements showed that surface compositions and properties can be easily adjusted by varying the concentrations of the comonomers. The formation of copper(II) complexes along the copolymer chains and their stability against washing out with plenty of water was proven by XPS. Copolymers containing semifluorinated comonomers significantly inhibited the growth of Achnanthidium species. Copolymers with copper-loaded AAMA-sequences were able to reduce both the growth of Achnanthidium spec. and Staphylococcus aureus.

  16. Formation and atomic configuration of binary metallic glasses studied by ion beam mixing and molecular dynamics simulation

    SciTech Connect

    Tai, K. P.; Gao, N.; Dai, X. D.; Li, J. H.; Liu, B. X.

    2007-06-15

    Metallic glasses are obtained in an immiscible Ag-Nb system with overall composition ranging from 25 to 90 at. % of Nb by ion beam mixing. Interestingly, the diffraction analysis shows that the formed Nb-rich metallic glass features are two distinct atomic configurations. In atomistic modeling, an n-body Ag-Nb potential is derived, under the assistance of ab initio calculation, and then applied in molecular dynamics simulations. An atomic configuration is discovered, i.e., an icositetrahedral ordering, and as well as an icosahedral ordering observed in the Ag-Nb metallic glasses and in some previously reported systems. Simulations confirm that the two dominate local atomic packing units are formed through a structural phase transition from the Nb-based bcc and fcc solid solutions, respectively, suggesting a concept of structural heredity that the crystalline structure of the constituent metals play a decisive role in determining the atomic structure of the resultant metallic glasses.

  17. Carbon Fiber Reinforced Glass Matrix Composites for Space Based Applications.

    DTIC Science & Technology

    1987-08-31

    Nardone , "Carbon Fiber Reinforced Glass Matrix Composites for Space Based Applications", Office of Naval Research Contract N00014-85-C-0332, Report R86... Nardone and K M. Prewo, "Tensile Performance of Carbon Fiber Reinforced Glass", J. Mater. Sci. accepted for publication, 1987. 27. R. F. Cooper and K

  18. Glass fiber addition strengthens low-density ablative compositions

    NASA Technical Reports Server (NTRS)

    Chandler, H. H.

    1974-01-01

    Approximately 15% of E-glass fibers was added to compositions under test and greatly improved char stability. Use of these fibers also reduced thermal strains which, in turn, minimized char shrinkage and associated cracks, subsurface voids, and disbonds. Increased strength allows honeycomb core reinforcement to be replaced by equivalent amount of glass fibers.

  19. Correlation Between Local Structure and Boson Peak in Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Ahmad, Azkar Saeed; Zhao, Xiangnan; Xu, Mingxiang; Zhang, Dongxian; Hu, Junwen; Fecht, Hans J.; Wang, Xiaodong; Cao, Qingping; Jiang, J. Z.

    2017-01-01

    We made a systematic study of the boson peak for six different Zr-based metallic glasses and found a universal correlation between average local atomic structure and boson peak. It is found that the boson peak can be decomposed into six characteristic vibratory modes, i.e., Debye's vibratory mode and five Einstein's vibratory modes. By using the Ioffe-Regel condition over all studied Zr-based metallic glasses, we reveal that atomic pair correlation function exactly maps on the low-temperature dynamics and the origin of the boson peak, which is the sum of vibrations of local density fluctuation domains in the glasses. In addition, it is found that the Debye's type oscillators are the major contributors to the low-temperature specific heat capacities. This study opens a new way of understanding the relationship of the physical properties with the atomic arrangements in glasses.

  20. Influence of environment on the corrosion of glass-metal connections

    NASA Astrophysics Data System (ADS)

    Szala, Barbara; Greiner-Wronowa, Elżbieta; Piccardo, Paolo; Kwaśniak-Kominek, Monika; Bajda, Tomasz

    2014-09-01

    `Glass sensors' of the eighteenth century Backer glass and the sixteenth century enamel from Limoges have been chosen for a series of experiments. Combinations of these materials with different base materials such as copper and bronze has been investigated. To create surface changes on the `glass sensor', a corrosion process was induced in a controlled environment. A variety of corrosive agents such as hydrochloric acid, sulfuric acid, water and formaldehyde were used. The sample immersed in the corrosive solution was exposed alternately to light and high temperature for a total of 38 weeks. During this period, macroscopic and microscopic observations were made and series of tests such as SEM/EDS and Raman spectroscopy were performed on the surface of the samples. ICP-MS methods were used to determine the change in the chemical composition of the solutions where the samples had corroded. The primary aim of this study was to identify the impact of a number of external corrosive variables such as temperature, humidity and local environment to identify the most damaging environments for glass-metal objects. The obtained results showed the chemical and physical phenomena acting on the surface of the glass, metal or in the place of their joints. Information obtained on this study was used to explain the influence of the environment on the surface of glass-metal materials. Results can be used in the design of conservation work as well as for sustainable conservation.

  1. Recent advances in bulk metallic glasses for biomedical applications.

    PubMed

    Li, H F; Zheng, Y F

    2016-05-01

    With a continuously increasing aging population and the improvement of living standards, large demands of biomaterials are expected for a long time to come. Further development of novel biomaterials, that are much safer and of much higher quality, in terms of both biomedical and mechanical properties, are therefore of great interest for both the research scientists and clinical surgeons. Compared with the conventional crystalline metallic counterparts, bulk metallic glasses have unique amorphous structures, and thus exhibit higher strength, lower Young's modulus, improved wear resistance, good fatigue endurance, and excellent corrosion resistance. For this purpose, bulk metallic glasses (BMGs) have recently attracted much attention for biomedical applications. This review discusses and summarizes the recent developments and advances of bulk metallic glasses, including Ti-based, Zr-based, Fe-based, Mg-based, Zn-based, Ca-based and Sr-based alloying systems for biomedical applications. Future research directions will move towards overcoming the brittleness, increasing the glass forming ability (GFA) thus obtaining corresponding bulk metallic glasses with larger sizes, removing/reducing toxic elements, and surface modifications. Bulk metallic glasses (BMGs), also known as amorphous alloys or liquid metals, are relative newcomers in the field of biomaterials. They have gained increasing attention during the past decades, as they exhibit an excellent combination of properties and processing capabilities desired for versatile biomedical implant applications. The present work reviewed the recent developments and advances of biomedical BMGs, including Ti-based, Zr-based, Fe-based, Mg-based, Zn-based, Ca-based and Sr-based BMG alloying systems. Besides, the critical analysis and in-depth discussion on the current status, challenge and future development of biomedical BMGs are included. The possible solution to the BMG size limitation, the brittleness of BMGs has been

  2. Processing and characterization of continuous fiber-reinforced glass and glass-ceramic matrix composites

    SciTech Connect

    Wang, Shaio-Wen.

    1990-01-01

    An investigation of the processing and mechanical behavior, particularly damage evolution and failure mechanisms, of continuous fiber reinforced glass and glass-ceramic composites was conducted. The processing effort utilized a slurry infiltration/hot pressing technique to fabricate carbon fiber reinforced borosilicate glass and Nicalon SiC fiber reinforced borosilicate glass composites. A slurry infiltration prepregging setup was designed and successfully operated. Processing parameters including slurry composition, binder burnout cycle and hot pressing schedule were systematically studied and optimized. Mechanical behavior studies were conducted on Nicalon SiC/Calcium Aluminosilicate (CAS) composites. The nature and the strength of the fiber/matrix interface was first characterized using a variety of fiber indentation test methods and transmission electron microscopy.

  3. Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers.

    PubMed

    Al-Sabagh, Ahmed; Taha, Eman; Kandil, Usama; Nasr, Gamal-Abdelnaser; Reda Taha, Mahmoud

    2016-09-10

    In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

  4. Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers

    PubMed Central

    Al-Sabagh, Ahmed; Taha, Eman; Kandil, Usama; Nasr, Gamal-Abdelnaser; Reda Taha, Mahmoud

    2016-01-01

    In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites. PMID:28335298

  5. Composite material based on fluoroplast and low melting oxyfluoride glass

    NASA Astrophysics Data System (ADS)

    Ignatieva, L. N.; Savchenko, N. N.; Lalayan, V. M.; Zverev, G. A.; Goncharuk, V. K.; Ustinov, A. Yu.; Shaulov, A. Yu.; Berlin, A. A.; Bouznik, V. M.

    2016-05-01

    The present work summarizes the results of studies of the samples fabricated through extrusion blending of mixtures composed of the perfluorocarbon polymer (polyvinylidene fluoride, PVDF), which presently undergoes intensive studies, and the inorganic glass (BF-glass) of the composition 3B2O3-97(40SnF2-30SnO-30P2O5). It is revealed as a result of application of the suggested technique the composite material whose structure depends on the component ratio in the mixture (from individual areas formed by each component to homogeneously distributed composite particles) has been fabricated. The peculiarities of formation of composites were studied on the basis of the results of studying their morphology, molecular structure and phase composition. It was revealed the preservation of the polymer molecular structure and the absence of interaction with the glass in the fabricated samples. We found that in the process of sample fabrication there occur melting of the mixture, mixing of particles and changing of the phase compositions. The polymer partially and the glass almost completely crystallize in the process of composite fabrication. Glass crystals fill polymer cavities forming agglomerates. Along with the increase of the amount of inorganic component crystals, the polymer monolithic nature is disrupted and an inversion occurs at a certain component ratio: polymer particles are located between crystals of the inorganic component, mixing with them and covering them. The glass crystallization is facilitated through pre-crushing in extruder mill.

  6. Redox systematics in model glass compositions from West Valley

    SciTech Connect

    Schreiber, H.D.; Schreiber, C.W.; Ward, C.C.

    1993-12-31

    At a processing temperature of 1150{degrees}C for model West Valley glass composition, the prescribed range of oxygen fugacities needed to achieve an [Fe{sup 2+}]/[Fe{sup 3+}] of 0.1 to 0.5 is 10{sup -4} to 10{sup -7} atm. Establishment of the Fe{sup 2+}-Fe{sup 0} equilibrium, resulting in metal precipitation from the melt, occurs at oxygen fugacities lower than 10{sup -11} atm at this temperature. The target processing range as defined by the iron redox ratio is equally valid at both lower and higher temperatures ({+-}100{degrees}C). Elevations of the concentrations of redox-active components to 1 wt% Cr{sub 2}O{sub 3}, 1 wt% NiO, 1 wt% CeO{sub 2}, and 4 wt% Mn{sub 2}O{sub 3} in the waste glass will not affect the redox limits as established by the iron redox ratio of 0.1 to 0.5; these limits provide sufficiently large margins of safety to assure no stabilization of reduced or oxidized forms of these elements.

  7. Monitoring and analyzing waste glass compositions

    DOEpatents

    Schumacher, Ray F.

    1994-01-01

    A device and method for determining the viscosity of a fluid, preferably molten glass. The apparatus and method uses the velocity of rising bubbles, preferably helium bubbles, within the molten glass to determine the viscosity of the molten glass. The bubbles are released from a tube positioned below the surface of the molten glass so that the bubbles pass successively between two sets of electrodes, one above the other, that are continuously monitoring the conductivity of the molten glass. The measured conductivity will change as a bubble passes between the electrodes enabling an accurate determination of when a bubble has passed between the electrodes. The velocity of rising bubbles can be determined from the time interval between a change in conductivity of the first electrode pair and the second, upper electrode pair. The velocity of the rise of the bubbles in the glass melt is used in conjunction with other physical characteristics, obtained by known methods, to determine the viscosity of the glass melt fluid and, hence, glass quality.

  8. Monitoring and analyzing waste glass compositions

    DOEpatents

    Schumacher, R.F.

    1994-03-01

    A device and method are described for determining the viscosity of a fluid, preferably molten glass. The apparatus and method use the velocity of rising bubbles, preferably helium bubbles, within the molten glass to determine the viscosity of the molten glass. The bubbles are released from a tube positioned below the surface of the molten glass so that the bubbles pass successively between two sets of electrodes, one above the other, that are continuously monitoring the conductivity of the molten glass. The measured conductivity will change as a bubble passes between the electrodes enabling an accurate determination of when a bubble has passed between the electrodes. The velocity of rising bubbles can be determined from the time interval between a change in conductivity of the first electrode pair and the second, upper electrode pair. The velocity of the rise of the bubbles in the glass melt is used in conjunction with other physical characteristics, obtained by known methods, to determine the viscosity of the glass melt fluid and, hence, glass quality. 2 figures.

  9. Testing composite-to-metal tubular lap joints

    SciTech Connect

    Guess, T.R.; Reedy, E.D. Jr.; Slavin, A.M.

    1993-11-01

    Procedures were developed to fabricate, nondestructively evaluate, and mechanically test composite-to-metal tubular joints. The axially loaded tubular lap joint specimen consisted of two metal tubes bonded within each end of a fiberglass composite tube. Joint specimens with both tapered and untapered aluminum adherends and a plain weave E-glass/epoxy composite were tested in tension, compression, and flexure. Other specimens with tapered and untapered steel adherends and a triaxially reinforced E-glass/epoxy composite were tested in tension and compression. Test results include joint strength and failure mode data. A finite element analysis of the axially loaded joints explains the effect of adherend geometry and material properties on measured joint strength. The flexural specimen was also analyzed; calculated surface strains are in good agreement with measured values, and joint failure occurs in the region of calculated peak peel stress.

  10. Rejuvenation of metallic glasses by non-affine thermal strain.

    PubMed

    Ketov, S V; Sun, Y H; Nachum, S; Lu, Z; Checchi, A; Beraldin, A R; Bai, H Y; Wang, W H; Louzguine-Luzgin, D V; Carpenter, M A; Greer, A L

    2015-08-13

    When a spatially uniform temperature change is imposed on a solid with more than one phase, or on a polycrystal of a single, non-cubic phase (showing anisotropic expansion-contraction), the resulting thermal strain is inhomogeneous (non-affine). Thermal cycling induces internal stresses, leading to structural and property changes that are usually deleterious. Glasses are the solids that form on cooling a liquid if crystallization is avoided--they might be considered the ultimate, uniform solids, without the microstructural features and defects associated with polycrystals. Here we explore the effects of cryogenic thermal cycling on glasses, specifically metallic glasses. We show that, contrary to the null effect expected from uniformity, thermal cycling induces rejuvenation, reaching less relaxed states of higher energy. We interpret these findings in the context that the dynamics in liquids become heterogeneous on cooling towards the glass transition, and that there may be consequent heterogeneities in the resulting glasses. For example, the vibrational dynamics of glassy silica at long wavelengths are those of an elastic continuum, but at wavelengths less than approximately three nanometres the vibrational dynamics are similar to those of a polycrystal with anisotropic grains. Thermal cycling of metallic glasses is easily applied, and gives improvements in compressive plasticity. The fact that such effects can be achieved is attributed to intrinsic non-uniformity of the glass structure, giving a non-uniform coefficient of thermal expansion. While metallic glasses may be particularly suitable for thermal cycling, the non-affine nature of strains in glasses in general deserves further study, whether they are induced by applied stresses or by temperature change.

  11. Glass-to-Metal Seal Against Liquid Helium

    NASA Technical Reports Server (NTRS)

    Watkins, John L.; Gatewood, John R.

    1987-01-01

    Simple compression joint with indium gasket forms demountable seal for superfluids. Seal developed for metal lid on glass jar used in experiments on liquid helium. Glass container allows contents to be viewed for such purposes as calibration of liquid-level detectors and adjustments of displacement plungers. Seal contains liquid helium even when temperature drops below 2.19K. Made from inexpensive, commercially available materials and parts.

  12. Relaxation Behavior of Ca-Based Bulk Metallic Glasses (Postprint)

    DTIC Science & Technology

    2009-09-03

    DD-MM-YY) 2. REPORT TYPE 3. DATES COVERED (From - To) April 2014 Interim 19 March 2014 – 31 March 2014 4. TITLE AND SUBTITLE RELAXATION...liquids.[2 4] Almost all bulk metallic glasses show intermediate fragile behavior.[ 5 ] Slow kinet- ics of crystallization due to high viscosity/high...on u is used to calculate the activation enthalpy of structural relax- ation, DHg, at the glass transition: [17] DHg ¼ R d lnu d 1 . Tcalg ½ 5

  13. Strain gradient drives shear banding in metallic glasses

    NASA Astrophysics Data System (ADS)

    Tian, Zhi-Li; Wang, Yun-Jiang; Chen, Yan; Dai, Lan-Hong

    2017-09-01

    Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.

  14. Polyimide fiber-glass composite resists high temperatures

    NASA Technical Reports Server (NTRS)

    Gilwee, W. J.; Rosser, R. W.; Parker, J. A.

    1973-01-01

    Composites synthesized from bismaleimide have superior strength and oxidation resistance at elevated temperatures when compared with similar composites prepared with epoxy or silicon polymers of similar cost. Polyimide synthesis technique and processing method yield essentially void-free fiber-glass reinforced composites.

  15. Chemical Composition Measurements of LAWA44 Glass Samples

    SciTech Connect

    Fox, K.; Edwards, T.; Riley, W.

    2016-11-15

    DOE is building the Hanford Tank Waste Treatment and Immobilization Plant (WTP) at the Hanford Site in Washington to remediate 55 million gallons of radioactive waste that is temporarily stored in 177 underground tanks. Both low-activity and high-level wastes will then be vitrified into borosilicate glass using Joule-heated ceramic melters. Efforts are being made to increase the loading of Hanford tank wastes in the glass. One area of work is enhancing waste glass composition/property models and broadening the compositional regions over which those models are applicable. In this report, the Savannah River National Laboratory provides chemical analysis results for several samples of a simulated low-activity waste glass, LAWA44, provided by the Pacific Northwest National Laboratory as part of an ongoing development task. The measured chemical composition data are reported and compared with the targeted values for each component for each glass. A detailed review showed no indications of errors in the preparation or measurement of the study glasses. All of the measured sums of oxides for the study glasses fell within the interval of 97.9 to 102.6 wt %, indicating acceptable recovery of the glass components. Comparisons of the targeted and measured chemical compositions showed that the measured values for the glasses met the targeted concentrations within 10% for those components present at more than 5 wt %. It was noted that the measured B2O3 concentrations are somewhat above the targeted values for the study glasses. No obvious trends were observed with regard to the multiple melting steps used to prepare the study glasses, indicating that any potential effects of volatility were below measurable thresholds.

  16. Investigation of waterborne epoxies for E-glass composites

    NASA Astrophysics Data System (ADS)

    Jensen, Robert Eric

    Research is presented which encompasses a study of epoxies based on diglycidyl ether of bisphenol A (DGEBA) cured with 2-ethyl-4-methylimidazole (EMI-24) in the presence of the nonionic surfactant Triton X-100. Interest in this epoxy system is due partially to the potential application as a waterborne replacement for solvent cast epoxies in E-glass laminated printed circuit boards. This research has revealed that the viscoelastic behavior of the cured epoxy is altered when serving as the matrix in a glass composite. The additional constraining and coupling of the E-glass fibers to the segmental motion of the epoxy matrix results in an increased level of viscoelastic cooperativity. Current research has determined that the cooperativity of an epoxy/E-glass composite is also sensitive to the surface chemistry of the glass fibers. Model single-ply epoxy/E-glass laminates were constructed in which the glass was pretreated with either 3-aminopropyltriethoxysilane (APS) or 3-glycidoxypropyltrimethoxysilane (GPS) coupling agents. Dynamic mechanical analysis (DMA) was then used to create master curves of the storage modulus (E') in the frequency domain. The frequency range of the master curves and resulting cooperativity plots clearly varied depending on the surface treatment of the glass fibers. It was determined that the surfactant has surprisingly little effect in the observed trends in cooperativity of the composites. However, the changes in cooperativity due to the surface pretreatment of the glass were lessened by the aqueous phase of the waterborne resin. Moisture uptake experiments were also performed on epoxy samples that were filled with spherical glass beads as well as multi-ply laminated composites. No increases in the diffusion constant could be attributed to the surfactant. However, the surfactant did enhance the final equilibrium moisture uptake levels. These equilibrium moisture uptake levels were also sensitive to the surface pretreatment of the E-glass.

  17. Relaxation Behavior of Ca-Based Bulk Metallic Glasses (Preprint)

    DTIC Science & Technology

    2009-04-01

    Almost all bulk metallic glasses show intermediate fragile behavior [ 5 The fragile behavior of supercooled glass forming liquids can generally be...transition [17 ( )calgg Td dRH 1 lnϕ −=∆ ]: ( 5 ) where R is the gas constant. The calorimetric fragility index mc is then often calculated as: mc...temperatures of the start and the end of the glass transition, respectively, and τg = 1000 s. Equation (6) is equivalent to Equation 4 5 (2) only if ∆Tg

  18. Ordering and dimensional crossovers in metallic glasses and liquids

    NASA Astrophysics Data System (ADS)

    Chen, David Z.; An, Qi; Goddard, William A.; Greer, Julia R.

    2017-01-01

    The atomic-level structures of liquids and glasses are amorphous, lacking long-range order. We characterize the atomic structures by integrating radial distribution functions (RDF) from molecular dynamics (MD) simulations for several metallic liquids and glasses: C u46Z r54 , N i80A l20 , N i33.3Z r66.7 , and P d82S i18 . Resulting cumulative coordination numbers (CN) show that metallic liquids have a dimension of d =2.55 ±0.06 from the center atom to the first coordination shell and metallic glasses have d =2.71 ±0.04 , both less than 3. Between the first and second coordination shells, both phases crossover to a dimension of d =3 , as for a crystal. Observations from discrete atom center-of-mass position counting are corroborated by continuously counting Cu glass- and liquid-phase atoms on an artificial grid, which accounts for the occupied atomic volume. Results from Cu grid analysis show short-range d =2.65 for Cu liquid and d =2.76 for Cu glass. Cu grid structures crossover to d =3 at ξ ˜8 Å (˜3 atomic diameters). We study the evolution of local structural dimensions during quenching and discuss its correlation with the glass transition phenomenon.

  19. Major element compositions of Luna 20 glass particles.

    NASA Technical Reports Server (NTRS)

    Glass, B. P.

    1973-01-01

    Major element analyses of nineteen Luna 20 glass particles indicate that most of the Luna 20 glasses have Al2O3 contents greater than 21 wt % and compositions similar to Apollo 16 and Luna 20 rocks and soils. Three of the glass particles have low Al2O3 (less than 13 wt %) and high FeO (greater than 18 wt %) contents and were probably derived from one of the adjacent maria. The low glass content of the Luna 20 soil indicates that it is relatively young or less mature than most mare soils that have been studied.

  20. Melt-Quenched Hybrid Glasses from Metal-Organic Frameworks.

    PubMed

    Tao, Haizheng; Bennett, Thomas D; Yue, Yuanzheng

    2017-05-01

    While glasses formed by quenching the molten states of inorganic non-metallic, organic, and metallic species are known, those containing both inorganic and organic moieties are far less prevalent. Network materials consisting of inorganic nodes linked by organic ligands do however exist in the crystalline or amorphous domain. This large family of open framework compounds, called metal-organic frameworks (MOFs) or coordination polymers, has been investigated intensively in the past two decades for a variety of applications, almost all of which stem from their high internal surface areas and chemical versatility. Recently, a selection of MOFs has been demonstrated to undergo melting and vitrification upon cooling. Here, these recent discoveries and the connections between the fields of MOF chemistry and glass science are summarized. Possible advantages and applications for MOF glasses produced by utilizing the tunable chemistry of the crystalline state are also highlighted. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    PubMed Central

    Chen, Na; Martin, Laura; Luzguine-Luzgin, Dmitri V.; Inoue, Akihisa

    2010-01-01

    Alloying addition, as a means of improving mechanical properties and saving on costs of materials, has been applied to a broad range of uses and products in the metallurgical fields. In the field of bulk metallic glasses (BMGs), alloying additions have also proven to play effective and important roles in promoting glass formation, enhancing thermal stability and improving plasticity of the materials. Here, we review the work on the role of alloying additions in glass formation and performance improvement of BMGs, with focus on our recent results of alloying additions in Pd-based BMGs. PMID:28883386

  2. Ceramic fiber reinforced glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1993-01-01

    A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous chemical vapor deposition (CVD)-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite which is heated to burn out organic constituents. The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

  3. Structural origins of the boson peak in metals: From high-entropy alloys to metallic glasses

    NASA Astrophysics Data System (ADS)

    Brink, Tobias; Koch, Leonie; Albe, Karsten

    2016-12-01

    The boson peak appears in all amorphous solids and is an excess of vibrational states at low frequencies compared to the phonon spectrum of the corresponding crystal. Until recently, the consensus was that it originated from "defects" in the glass. The nature of these defects is still under discussion, but the picture of regions with locally disturbed short-range order and/or decreased elastic constants has gained some traction. Recently, a different theory was proposed: The boson peak was attributed to the first van Hove singularity of crystal lattices which is only smeared out by the disorder. This new viewpoint assumes that the van Hove singularity is simply shifted by the decreased density of the amorphous state and is therefore not a glass-specific anomaly. In order to resolve this issue, we use computer models of a four-component alloy, alternatively with chemical disorder (high-entropy alloy), structural disorder, and reduced density. Comparison to a reference glass of the same composition reveals that the boson peak consists of additional vibrational modes which can be induced solely by structural disorder. While chemical disorder introduces fluctuations of the elastic constants, we find that those do not lead to sufficient local softening to induce these modes. A boson peak due to a reduction of density could be excluded for the present metallic system.

  4. Development of metal hydride composites

    SciTech Connect

    Congdon, J.W.

    1992-12-01

    Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydride granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.

  5. Effect of mixed transition metal ions on DC conductivity in lithium bismuth borate glasses

    SciTech Connect

    Khasa, S.; Yadav, Arti Dahiya, M. S.; Seema,; Ashima; Agarwal, A.

    2015-06-24

    The DC conductivities of glasses having composition x(2NiO·V{sub 2}O{sub 5})·(30-x)Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (with x=0, 2, 5, 7 and 10, i.e. NVLBB glasses) and glass samples having composition 7NiO·23 Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} and 7V{sub 2}O{sub 5}·23Li{sub 2}O·20Bi{sub 2}O{sub 3}·50B{sub 2}O{sub 3} (NLBB and VLBB respectively) are investigated as a function of temperature. Conductivity for glasses containing higher percentage of lithium ions is predominantly ionic and in glasses containing higher percentage of transition metal (TM) ions is predominantly electronic. The observed increase in conductivity with x and peak-like behavior at x=7 in NVLBB glasses due to competitive transport of small polaron contributing to a significant structural change in NVLBB glasses. Variation of molar volume and density was also observed with x. In NVLBB glasses, as x increases density increases except a slight decrease at x=7. Also density increases in NLBB whereas in case of VLBB it decreases in comparison to NVLBB1 glass composition. Mott’s small polaron hopping (SPH) model has been applied to analyze the high temperature conductivity data and activation energy.

  6. Innovative approach to the design of low-cost Zr-based BMG composites with good glass formation.

    PubMed

    Cheng, Jia-Lin; Chen, Guang; Liu, Chain-Tsuan; Li, Yi

    2013-01-01

    The high manufacturing cost for metallic glasses hampers actual commercial applications of this class of fascinating materials. In this letter, the effect of oxygen impurity on the glass forming ability and tensile properties of Zr-BMG composites were studied. Our results have demonstrated that oxygen was absorbed and concentrated only in the precipitated β-Zr phase, leading that the remainder molten metal retains good glass forming ability. The high oxygen concentration in the β-Zr phase induces a significant solid-solution strengthening effect, this resulting in an enhanced strength of the BMG composites without sacrificing their overall ductility. Based on this alloying strategy, we have successfully developed the low-cost Zr-based BMG composites with excellent tensile properties and good glass forming ability, using the low grade industrial raw materials processed under industrial vacuum systems. This finding is expected to greatly cut down the manufacturing cost and greatly promote the commercial applications of the BMG composites.

  7. Formation of alkali-metal nanoparticles in alkali-silicate glasses under electron irradiation and thermal processing

    NASA Astrophysics Data System (ADS)

    Bochkareva, E. S.; Sidorov, A. I.; Ignat'ev, A. I.; Nikonorov, N. V.; Podsvirov, O. A.

    2017-02-01

    Experiments and numerical simulation show that the irradiation of alkali-containing glasses using electrons at an energy of 35 keV and the subsequent thermal processing at a temperature above the vitrification point lead to the formation of spherical metal (lithium, sodium, and potassium) nanoparticles with oxide sheaths that exhibit plasmon resonances in the visible spectral range. Glasses containing two alkali metals exhibit mutual effect of metals on the formation of nanoparticles with two compositions due to the difference of ion radii and mobilities of metal ions.

  8. Failure behavior of a glass-fiber reinforced thermoplastic composite

    NASA Astrophysics Data System (ADS)

    Liang, Jiaai; Kalyanasundaram, Shankar

    2017-05-01

    In this work, experiments were conducted to stamp form glass-fiber reinforced thermoplastics with different widths of hour-glass shapes. A forming limit diagram (FLD) is established based on the experimental data for this material, depicting strain forming limits at different deformation modes. The material system involved in the study is a glass-fiber reinforced polypropylene composite (TWINTEX®) with a fiber orientation of 0°/90° along the warp and weft directions. In this study, the conventional FLD method is adapted to use on thermoplastic composites and it is found that the major principle strain limit is the highest when the strain ratio is around -0.5.

  9. Mechanical properties of woven glass fiber-reinforced composites.

    PubMed

    Kanie, Takahito; Arikawa, Hiroyuki; Fujii, Koichi; Ban, Seiji

    2006-06-01

    The aim of this investigation was to measure the flexural and compressive strengths and the corresponding moduli of cylindrical composite specimens reinforced with woven glass fiber. Test specimens were made by light-curing urethane dimethacrylate oligomer with woven glass fiber of 0.18-mm standard thickness. Tests were conducted using four reinforcement methods and two specimen diameters. Flexural strength and modulus of woven glass fiber-reinforced specimens were significantly greater than those without woven glass fiber (p < 0.01). Likewise, compressive strength of reinforced specimens was significantly greater than those without woven glass fiber (p < 0.01), except for specimens reinforced with woven glass fiber oriented at a tilt direction in the texture (p > 0.05). In terms of comparison between the two specimen diameters, no statistically significant differences in flexural strength and compressive strength (p > 0.05) were observed.

  10. Structural features of plastic deformation in bulk metallic glasses

    SciTech Connect

    Scudino, S. Shakur Shahabi, H.; Stoica, M.; Kühn, U.; Kaban, I.; Escher, B.; Eckert, J.; Vaughan, G. B. M.

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  11. Atomistic mechanisms of cyclic hardening in metallic glass

    NASA Astrophysics Data System (ADS)

    Deng, Chuang; Schuh, Christopher A.

    2012-06-01

    Molecular dynamics with an embedded-atom method potential is used to simulate the nanoindentation of Cu63.5Zr36.5 metallic glasses. In particular, the effects of cyclic loading within the nominal elastic range on the overall strength and plasticity of metallic glass are studied. The simulated results are in line with the characteristics of experimentally observed hardening effects. In addition, analysis based on local von Mises strain suggests that the hardening is induced by confined microplasticity and stiffening in regions of the originally preferred yielding path, requiring a higher applied load to trigger a secondary one.

  12. Nanoscale patterning of metal nanoparticle distribution in glasses

    PubMed Central

    2013-01-01

    We show that electric field imprinting technique allows for patterning of metal nanoparticles in the glass matrix at the subwavelength scale. The formation of glass-metal nanocomposite strips with a width down to 150 nm is demonstrated. The results of near-field microscopy of imprinted patterns are in good agreement with the performed numerical modeling. Atomic force microscopy reveals that imprinting also results in the formation of nanoscale surface profile with the height going down with the decrease of the strip width. The experiments prove the applicability of this technique for the fabrication of nanoscale plasmonic components. PMID:23724801

  13. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1986-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  14. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1988-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  15. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, R.C.

    1985-02-11

    Disclosed are: amorphous metallic precipitates having the formula (M/sub 1/)/sub a/(M/sub 2/)/sub b/ wherein M/sub 1/ is at least one transition metal, M/sub 2/ is at least one main group metal and the integers ''a'' and ''b'' provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  16. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2000-01-01

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  17. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2003-10-07

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  18. Low melting high lithia glass compositions and methods

    DOEpatents

    Jantzen, Carol M.; Pickett, John B.; Cicero-Herman, Connie A.; Marra, James C.

    2004-11-02

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  19. Mechanical evaluation of SiC particle reinforced oxynitride glass and glass-ceramic composites

    SciTech Connect

    Rouxel, T.; Lavelle, C. . Lab. de Materiaux Ceramiques et Traitements de Surface); Garnier, C.; Verdier, P.; Laurent, Y. . Lab. de Chimie des Materiaux)

    1994-07-01

    In silicon oxynitride glasses, the nitrogen occupies anion sites and is bonded to three silicons. Hence, replacement of divalent oxygen ions by trivalent nitrogen ones results in a considerable improvement of the mechanical resistance. In this exploratory work, the authors investigate some basic mechanical properties at room temperature of composite materials prepared by adding some SiC particles to a highly refractory Y-Mg-Si-Al-O-N oxynitride glass. Taking advantage of both constituents, the brittle particulate composites exhibit much better fracture strength and toughness and higher elastic moduli than the glassy matrix. Due to the easy crystallization of the selected glass, a further improvement is attainable through a crystallization treatment of the matrix. Fracture toughness and Young's modulus as high as 5.4 MPa.m[sup 0.5] and 215 GPa respectively have been measured on the glass-ceramic composite containing 50 vol.% SiC.

  20. Relationship between structure, dynamics, and mechanical properties in metallic glass-forming alloys

    NASA Astrophysics Data System (ADS)

    Cheng, Y. Q.; Sheng, H. W.; Ma, E.

    2008-07-01

    Using Cu-Zr models, we demonstrate icosahedral ordering as a microscopic origin of the non-Arrhenius dynamical slowing down in metallic supercooled liquids. This correlation between the structural and dynamical heterogeneities underlies the evolution of the energy barrier for relaxation upon undercooling, as well as the eventual glass transition that leads to the formation of bulk metallic glasses (MGs). Our analysis of the energy barrier to plastic relaxation in MGs relates their macroscopic strength and plasticity to the local structures developed in the MGs. The structure-dynamics perspective explains not only the composition-dependent mechanical properties but also the known correlation between the strength of MGs and the glass transition temperature.

  1. Designing heavy metal oxide glasses with threshold properties from network rigidity

    SciTech Connect

    Chakraborty, Shibalik; Boolchand, P.; Malki, M.; Micoulaut, M.

    2014-01-07

    Here, we show that a new class of glasses composed of heavy metal oxides involving transition metals (V{sub 2}O{sub 5}–TeO{sub 2}) can surprisingly be designed from very basic tools using topology and rigidity of their underlying molecular networks. When investigated as a function of composition, such glasses display abrupt changes in network packing and enthalpy of relaxation at T{sub g}, underscoring presence of flexible to rigid elastic phase transitions. We find that these elastic phases are fully consistent with polaronic nature of electronic conductivity at high V{sub 2}O{sub 5} content. Such observations have new implications for designing electronic glasses which differ from the traditional amorphous electrolytes having only mobile ions as charge carriers.

  2. Fracture behavior of glass fiber reinforced polymer composite

    SciTech Connect

    Avci, A.; Arikan, H.; Akdemir, A

    2004-03-01

    Chopped strand glass fiber reinforced particle-filled polymer composite beams with varying notch-to-depth ratios and different volume fractions of glass fibers were investigated in Mode I fracture using three-point bending tests. Effects of polyester resin content and glass fiber content on fracture behavior was also studied. Polyester resin contents were used 13.00%%, 14.75%, 16.50%, 18.00% and 19.50%, and glass fiber contents were 1% and 1.5% of the total weight of the polymer composite system. Flexural strength of the polymer composite increases with increase in polyester and fiber content. The critical stress intensity factor was determined by using several methods such as initial notch depth method, compliance method and J-integral method. The values of K{sub IC} obtained from these methods were compared.

  3. Structural Anisotropy in Metallic Glasses Induced by Mechanical Deformation

    SciTech Connect

    Dmowski, Wojtek; Egami, Takeshi

    2008-01-01

    Metallic glasses have been studied vigorously since the first report on amorphous gold-silicon alloy back in 1960.[1] Initially soft magnetic properties were the most promising features for industrial applications. The recent development of bulk metallic glasses (BMGs)[2 5] initiated interests in engineering applications such as structural or biomedical materials because of attractive properties such as high strength,[6] high elasticity,[7,8] and good corrosion resistance,[9,10] among others. In addition, high temperature processing of BMGs allows for near-net-shape formability,[11 13] which could simplify and possibly reduce the cost of the final product. The glasses retain the disordered atomic structure of a liquid, and ideally are isotropic solids. Frequently because of processing conditions, such as directional heat flow, some structural anisotropy is produced during quenching, and has been observed by structural investigations. Usually, annealing at high temperatures results in an isotropic structure. Also, formation of uniaxial magnetic anisotropy[14] had been observed in studies of creep deformed ferromagnetic metallic glasses. Samples with a near-zero magnetostriction coefficient had been studied to establish the origin of the magnetic anisotropy. It was concluded that anisotropy resulted from the atomic level anisotropy[15] and not the heterogeneous internal stress distribution. Indeed X-ray diffraction study of the creep deformed metallic glass showed bond anisotropy.[ 16,17] Such structural studies had been cumbersome and lengthy because they required measurement of many orientations with high statistics. Recently we have shown that use of an area detector and high energy X-rays at a synchrotron source can speed up data collection without compromising statistics.[18] In this contribution, we present data showing structural anisotropy in glassy samples after homogenous (creep) and inhomogeneous (compression) mechanical deformation. The observation of the

  4. Highly evolved rhyolitic glass compositions from the Toba Caldera, Sumatra

    SciTech Connect

    Chesner, C.A.

    1985-01-01

    The quartz latite to rhyolitic ash flow tuffs erupted form the Toba Caldera, perhaps the largest caldera on earth (100 by 30 kms), provide the unique opportunity to study a highly differentiated liquid in equilibrium with numerous mineral phases. Not only are the rocks very crystal rich (30-50%), but at present a minimum of 15 co-existing mineral phases have been identified. Both whole-rock and glass analyses were made by XRF techniques providing data on both major and trace elements. Whole rock chemistry of individual pumices from the youngest eruption at Toba (75,000 years ago), are suggestive of the eruption of two magma compositions across a boundary layer in the magma chamber. Glass chemistry of the pumices also show two distinct liquid compositions. The more silicic pumices, which have the most evolved glass compositions, are similar to the whole rock chemistry of the few aplitic pumices and cognate granitic xenoliths that were collected. This highly evolved composition resulted from the removal of up to 15 mineral phases and may be a fractionation buffered, univariant composition. The glasses from the less silicic pumices are similar to the whole rock chemistry of the more silicic pumice, thus falling nicely on a fractionation trend towards the univariant composition for these rocks. This set of glass compositions allows an independent test for the origin of distal ashes thought to have erupted from Toba and deposited in Malaysia, the Indian Ocean, and as far away as India.

  5. Calcium phosphate glasses: silanation process and effect on the bioactivity behavior of glass-PMMA composites.

    PubMed

    Alonso, Lizette Morejón; García-Menocal, José Ángel Delgado; Aymerich, Mariona Tarragó; Guichard, Julio Ándrés Álvarez; García-Vallés, Maite; Manent, Salvador Martínez; Ginebra, Maria-Pau

    2014-02-01

    This article presents the results of a study of the efficiency of silanation process of calcium phosphate glasses particles and its effect on the bioactivity behavior of glass- poly(methyl methacrylate) (PMMA) composites. Two different calcium phosphate glasses: 44.5CaO-44.5P2 O5 -11Na2 O (BV11) and 44.5CaO-44.5P2 O5 -6Na2 O-5TiO2 (G5) were synthesized and treated with silane coupling agent. The glasses obtained were characterized by Microprobe and BET while the efficiency of silanation process was determined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Thermal Analysis (DTA and TG) techniques. The content of coupling agent chemically tightly bond to the silanated glasses ascended to 1.69 ± 0.02 wt % for BV11sil glass and 0.93 ± 0.01 wt % for G5sil glass. The in vitro bioactivity test carried out in Simulated Body Fluid (SBF) revealed certain bioactive performance with the use of both silanated glasses in a 30% (by weight) as filler of the PMMA composites because of a superficial deposition of an apatite-like layer with low content of CO3 (2-) and HPO4 (2-) in its structure after soaking for 30 days occurred.

  6. High-rate squeezing process of bulk metallic glasses

    PubMed Central

    Fan, Jitang

    2017-01-01

    High-rate squeezing process of bulk metallic glasses from a cylinder into an intact sheet achieved by impact loading is investigated. Such a large deformation is caused by plastic flow, accompanied with geometrical confinement, shear banding/slipping, thermo softening, melting and joining. Temperature rise during the high-rate squeezing process makes a main effect. The inherent mechanisms are illustrated. Like high-pressure torsion (HPT), equal channel angular pressing (ECAP) and surface mechanical attrition treatments (SMAT) for refining grain of metals, High-Rate Squeezing (HRS), as a multiple-functions technique, not only creates a new road of processing metallic glasses and other metallic alloys for developing advanced materials, but also directs a novel technology of processing, grain refining, coating, welding and so on for treating materials. PMID:28338092

  7. High-rate squeezing process of bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Fan, Jitang

    2017-03-01

    High-rate squeezing process of bulk metallic glasses from a cylinder into an intact sheet achieved by impact loading is investigated. Such a large deformation is caused by plastic flow, accompanied with geometrical confinement, shear banding/slipping, thermo softening, melting and joining. Temperature rise during the high-rate squeezing process makes a main effect. The inherent mechanisms are illustrated. Like high-pressure torsion (HPT), equal channel angular pressing (ECAP) and surface mechanical attrition treatments (SMAT) for refining grain of metals, High-Rate Squeezing (HRS), as a multiple-functions technique, not only creates a new road of processing metallic glasses and other metallic alloys for developing advanced materials, but also directs a novel technology of processing, grain refining, coating, welding and so on for treating materials.

  8. Theoretical study on the composition location of the best glass formers in Cu-Zr amorphous alloys.

    PubMed

    Wang, Da; Zhao, Shi-Jin; Liu, Li-Min

    2015-01-29

    This study combines the molecular dynamics (MD) simulations and first-principles approach to explain the experimental observation that the best glass formers of Cu-Zr bulk metallic glasses (BMGs) have the compositions Cu50Zr50 and Cu64Zr36. These two best glass formers are first calculated to be most abundantly composed of Cu6Zr7 and Cu8Zr5 icosahedral clusters when compared in the compositional range of CuxZr100-x (45 ≤ x ≤ 70), and then these two icosahedral clusters are calculated to have the lowest formation energy among the icosahedral clusters CuxZr13-x (3 ≤ x ≤ 10), as well as possessing some characteristics in electronic structure and chemical hardness. Through understanding the properties of specific icosahedral clusters in metallic glasses, the structural and energetic contribution to the glass-forming ability are systematically discussed.

  9. Superconducting property of Zr-Co-Al-Nb metallic glasses

    NASA Astrophysics Data System (ADS)

    Okai, D.; Nagai, R.; Motoyama, G.; Kimura, H. M.; Inoue, A.

    2011-11-01

    The superconducting property of Zr55Co(30-x)Al15Nbx (x = 0-20 at.%) metallic glasses fabricated by rapid solidification was investigated. The Zr55Co(30-x)Al15Nbx (x = 5-20 at.%) metallic glasses with a mixture structure of amorphous and nanocrystal phases exhibited superconductivity of Tc,on = 1.8-2.6 K. The maximum Tc,on = 2.6 K was obtained for the Zr55Co10Al15Nb20 metallic glass. This was attributable to the superconducting property of nanocrystalline particles contained in the Zr55Co10Al15Nb20 alloy. The increase of Nb element in the Zr55Co(30-x)Al15Nbx alloy led to the increase of Tc,on and the decrease of glass transition temperature. The glass transition temperature was between 704 and 749 K for the Zr55Co(30-x)Al15Nbx (x = 0-20 at.%) alloys. The temperature interval of supercooled liquid state was between 51 and 68 K for the Zr55Co(30-x)Al15Nbx (x = 0-20 at.%) alloys.

  10. Revealing the nanoparticles aspect ratio in the glass-metal nanocomposites irradiated with femtosecond laser

    PubMed Central

    Chervinskii, S.; Drevinskas, R.; Karpov, D. V.; Beresna, M.; Lipovskii, A. A.; Svirko, Yu. P.; Kazansky, P. G.

    2015-01-01

    We studied a femtosecond laser shaping of silver nanoparticles embedded in soda-lime glass. Comparing experimental absorption spectra with the modeling based on Maxwell Garnett approximation modified for spheroidal inclusions, we obtained the mean aspect ratio of the re-shaped silver nanoparticles as a function of the laser fluence. We demonstrated that under our experimental conditions the spherical shape of silver nanoparticles changed to a prolate spheroid with the aspect ratio as high as 3.5 at the laser fluence of 0.6 J/cm2. The developed approach can be employed to control the anisotropy of the glass-metal composites. PMID:26348691

  11. Evolution of elastic heterogeneity during aging in metallic glasses.

    PubMed

    Fan, Yue; Iwashita, Takuya; Egami, Takeshi

    2014-06-01

    The properties of glasses vary widely depending on the way they are prepared, even though their structures appear similar. We show that the local potential energy landscape (PEL) sensitively reflects the stability differences through simulation of local structural excitation in a model metallic glass. It is observed that the spectrum of local structural excitation develops a pseudogap at low energies as the glass becomes more stable. We also demonstrate that the spatial variation of the atomic level shear modulus, rather than the distribution of the magnitude of the single atom shear modulus, is more closely related to the nature of the PEL and the stabilities of glasses. In particular, local aggregation of atoms with low shear modulus greatly contributes to instability of the system.

  12. Evolution of elastic heterogeneity during aging in metallic glasses

    NASA Astrophysics Data System (ADS)

    Fan, Yue; Iwashita, Takuya; Egami, Takeshi

    2014-06-01

    The properties of glasses vary widely depending on the way they are prepared, even though their structures appear similar. We show that the local potential energy landscape (PEL) sensitively reflects the stability differences through simulation of local structural excitation in a model metallic glass. It is observed that the spectrum of local structural excitation develops a pseudogap at low energies as the glass becomes more stable. We also demonstrate that the spatial variation of the atomic level shear modulus, rather than the distribution of the magnitude of the single atom shear modulus, is more closely related to the nature of the PEL and the stabilities of glasses. In particular, local aggregation of atoms with low shear modulus greatly contributes to instability of the system.

  13. Bioactivity of thermal plasma synthesized bovine hydroxyapatite/glass ceramic composites

    NASA Astrophysics Data System (ADS)

    Yoganand, C. P.; Selvarajan, V.; Rouabhia, Mahmoud; Cannillo, Valeria; Sola, Antonella

    2010-02-01

    Bone injuries and failures often require the inception of implant biomaterials. Research in this area is receiving increasing attention worldwide. A variety of artificial bone materials, such as metals, polymeric materials, composites and ceramics, are being explored to replace diseased bones. Calcium phosphate ceramics are currently used as biomaterials for many applications in both dentistry and orthopedics. Bioactive silicate-based glasses show a higher bioactive behaviour than calcium phosphate materials. It is very interesting to study the mixtures of HA and silicate-based glasses. In the present study; natural bovine hydroxyapatite / SiO2-CaO-MgO glass composites were produced using the Transferred arc plasma (TAP) melting method. TAP melting route is a brisk process of preparation of glass-ceramics in which the raw materials are melted in the plasma and crystallization of the melt occurs while cooling down at a much faster rate in relatively short processing times compared to the conventional methods of manufacture of glass ceramics/composites. It is well known that; one essential step to the understanding of the biological events occurring at the bone tissue/material interface is the biological investigation by in vitro tests. Cell lines are commonly used for biocompatibility tests, and are very efficient because of their reproducibility and culture facility. In this study, we report the results of a study on the response of primary cultures of human fibroblast cells to TAP melted bioactive glass ceramics.

  14. Soldering of Thin Film-Metallized Glass Substrates

    SciTech Connect

    Hosking, F.M.; Hernandez, C.L.; Glass, S.J.

    1999-03-31

    The ability to produce reliable electrical and structural interconnections between glass and metals by soldering was investigated. Soldering generally requires premetallization of the glass. As a solderable surface finish over soda-lime-silicate glass, two thin films coatings, Cr-Pd-Au and NiCr-Sn, were evaluated. Solder nettability and joint strengths were determined. Test samples were processed with Sn60-Pb40 solder alloy at a reflow temperature of 210 C. Glass-to-cold rolled steel single lap samples yielded an average shear strength of 12 MPa. Solder fill was good. Control of the Au thickness was critical in minimizing the formation of AuSn{sub 4} intermetallic in the joint, with a resulting joint shear strength of 15 MPa. Similar glass-to-glass specimens with the Cr-Pd-Au finish failed at 16.5 MPa. The NiCr-Sn thin film gave even higher shear strengths of 20-22.5 MPa, with failures primarily in the glass.

  15. Diffusion between glass and metals for optical fiber preform extrusion

    NASA Astrophysics Data System (ADS)

    Yeo, Felicia Yan Xin; Zhang, Zhifeng; Kumar Chakkathara Janardhanan Nair, Dileep; Zhang, Yilei

    2015-07-01

    When silica is extruded, diffusion of metal atoms into silica results contamination to the silica being heated, and thus is a serious concern for the glass extrusion process, such as extrusion of glass fiber preform. This paper examines diffusion between fused silica and two high strength metals, the stainless steel SS410 and the superalloy Inconel 718, at 1000 °C and under the normal atmosphere condition by SEM and Electron Dispersion Spectrum. It is found that diffusion occurs between silica and SS410, and at the same time, SS410 is severely oxidized during diffusion experiment. On the contrary, the diffusion between Inconel 718 and silica is unnoticeable, suggesting excellent high temperature performance of Inconel 718 for glass extrusion.

  16. Kinetics, Thermodynamics, and Structure of Bulk Metallic Glass Forming Liquids

    NASA Astrophysics Data System (ADS)

    Busch, Ralf; Gallino, Isabella

    2017-09-01

    Bulk metallic glass forming melts are viscous liquids compared with pure metals and conventional alloys. They show intermediate kinetic fragility and low thermodynamic driving force for crystallization, leading to sluggish crystallization kinetics, leaving time for good glass forming ability and bulk casting thickness. We relate the kinetics to the thermodynamics of the supercooled liquid using the Adam-Gibbs equation. The kinetic fragility is also connected to the structural changes in the liquid and can be quantitatively linked to the robustness of medium-range order in the supercooled liquid with increasing temperature. Liquid-liquid transitions from fragile behavior at high temperature to strong behavior at low temperature in the supercooled liquid and in the vicinity of the glass transition emerge as a common phenomenon.

  17. Ammonia-treated phosphate glasses useful for sealing to metals metals

    DOEpatents

    Brow, Richard K.; Day, Delbert E.

    1991-01-01

    A method of improving surface-dependent properties of phosphate glass such as durability and wear resistance without significantly affecting its thermal expansion coefficient is provided which comprises annealing the glass in a dry ammonia atmosphere at temperatures approximating the transition temperature of the glass. The ammonia annealing treatment of the present invention is carried out for a time sufficient to allow incorporation of a thin layer of nitrogen into the surface of the phosphate glass, and the treatment improves the durability of the glass without the reduction in the thermal expansion coefficient that has restricted the effectiveness of prior ammonia treatments. The improved phosphate glass resulting from this method is superior in wear resistance, yet maintains suitable thermal expansion properties so that it may be used effectively in a variety of applications requiring hermetic glass-metal seals.

  18. Phase transformations and thermodynamics of aluminum-based metallic glasses

    NASA Astrophysics Data System (ADS)

    Gao, Changhua (Michael)

    This thesis examines the thermodynamics and associated kinetics and phase transformations of the glass forming Al-Ni-Gd and Al-Fe-Gd systems. In order to fully understand the unique glass forming ability (GFA) of Al-based metallic glasses, the ternary Al-Fe-Gd and Al-Ni-Gd systems in their Al-rich corners were examined experimentally to assist in a thermodynamic assessment. The solid-state phase equilibria are determined using XRD and TEM-EDS techniques. While this work basically confirms the solid-state equilibria in Al-Fe-Gd reported previously, the ternary phase in Al-Ni-Gd system has been identified to be Al15Ni3Gd2 rather than Al16Ni 3Gd reported in the literature. DTA analysis of 24 alloys in the Al-Fe-Gd system and 42 alloys in the Al-Ni-Gd system have yielded critical temperatures pertaining to the solid-liquid transition. Based on these data and information from the literature, a self-consistent thermodynamic database for these systems has been developed using the CALPHAD technique. Parameters describing the Gibbs free energy for various phases of the Al-Gd, Al-Fe-Gd and Al-Ni-Gd systems are manually optimized in this study. Once constructed, the database is used to calculate driving forces for nucleation of crystalline phases which can qualitatively explain the phase formation sequence during crystallization at low temperatures. It was also confirmed that alloy compositions with the lowest Gibbs free energy difference between the equilibrium state and undercooled liquid state exhibit better GFA than other chemistries. Based on 250°C isothermal devitrification phase transformations of 17 Al-Ni-Gd alloys, a phase formation sequence map is constructed. Fcc-Al nanocrystals are formed first in most of the alloys studied, but eutectic crystallization of a metastable phase and fcc-Al is also observed. Addition of Al or Ni promotes fcc-Al phase formation, while increasing Gd suppresses it. The continuous heating DSC scans revealed that crystallization in Al

  19. Producing Magnesium Metallic Glass By Disintegrated Melt Deposition

    SciTech Connect

    Shanthi, M.; Gupta, M.; Jarfors, A. E. W.; Tan, M. J.

    2011-01-17

    Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their low density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties.

  20. Structural anisotropy in metallic glasses induced by mechanical deformation

    SciTech Connect

    Dmowski, W.; Egami, T.

    2009-03-06

    We observed structural anisotropy in metallic glasses samples deformed by homogenous mechanical creep and by inhomogeneous compression using high energy X-ray diffraction. Pair distribution function analysis indicates bond anisotropy in the first atomic shell. This suggests that mechanical deformation involves rearrangements in a cluster of atoms by a bond reformation.