Science.gov

Sample records for form glasses manufactured

  1. Method for manufacturing glass frit

    DOEpatents

    Budrick, Ronald G.; King, Frank T.; Nolen, Jr., Robert L.; Solomon, David E.

    1977-01-01

    A method of manufacturing a glass frit for use in the manufacture of uniform glass microspheres to serve as containers for laser fusion fuel to be exposed to laser energy which includes the formation of a glass gel which is then dried, pulverized, and very accurately sized to particles in a range of, for example, 125 to 149 micrometers. The particles contain an occluded material such as urea which expands when heated. The sized particles are washed, dried, and subjected to heat to control the moisture content prior to being introduced into a system to form microspheres.

  2. Determination of the Structure of Vitrified Hydroceramic/CBC Waste Form Glasses Manufactured from DOE Reprocessing Waste

    SciTech Connect

    Scheetz, B.E.; White, W. B.; Chesleigh, M.; Portanova, A.; Olanrewaju, J.

    2005-05-31

    The selection of a glass-making option for the solidification of nuclear waste has dominated DOE waste form programs since the early 1980's. Both West Valley and Savannah River are routinely manufacturing glass logs from the high level waste inventory in tank sludges. However, for some wastes, direct conversion to glass is clearly not the optimum strategy for immobilization. INEEL, for example, has approximately 4400 m{sup 3} of calcined high level waste with an activity that produces approximately 45 watts/m{sup 3}, a rather low concentration of radioactive constituents. For these wastes, there is value in seeking alternatives to glass. An alternative approach has been developed and the efficacy of the process demonstrated that offers a significant savings in both human health and safety exposures and also a lower cost relative to the vitrification option. The alternative approach utilizes the intrinsic chemical reactivity of the highly alkaline waste with the addition of aluminosilicate admixtures in the appropriate proportions to form zeolites. The process is one in which a chemically bonded ceramic is produced. The driving force for reaction is derived from the chemical system itself at very modest temperatures and yet forms predominantly crystalline phases. Because the chemically bonded ceramic requires an aqueous medium to serve as a vehicle for the chemical reaction, the proposed zeolite-containing waste form can more adequately be described as a hydroceramic. The hydrated crystalline materials are then subject to hot isostatic pressing (HIP) which partially melts the material to form a glass ceramic. The scientific advantages of the hydroceramic/CBC approach are: (1) Low temperature processing; (2) High waste loading and thus only modest volumetric bulking from the addition of admixtures; (3) Ability to immobilize sodium; (4) Ability to handle low levels of nitrate (2-3% NO{sub 3}{sup -}); (5) The flexibility of a vitrifiable waste; and (6) A process that

  3. Manufacturing laser glass by continuous melting

    SciTech Connect

    Campbell, J H; Suratwala, T; krenitsky, S; Takeuchi, K

    2000-07-01

    A novel, continuous melting process is being used to manufacture meter-sized plates of laser glass at a rate 20-times faster, 5-times cheaper, and with 2-3 times better optical quality than with previous one-at-a-time, ''discontinuous'' technology processes. This new technology for manufacturing laser glass, which is arguably the most difficult continuously-melted optical material ever produced, comes as a result of a $60 million, six-year joint R&D program between government and industry. The glasses manufactured by the new continuous melting process are Nd-doped phosphate-based glasses and are marketed under the product names LG-770 (Schott Glass Technologies) and LHG-8 (Hoya Corporation USA). With this advance in glass manufacturing technology, it is now possible to construct high-energy, high-peak-power lasers for use in fusion energy development, national defense, and basic physics research that would have been impractical to build using the old melting technology. The development of continuously melted laser glass required technological advances that have lead to improvements in the manufacture of other optical glass products as well. For example, advances in forming, annealing, and conditioning steps of the laser glass continuous melting process are now being used in manufacture of other large-size optical glasses.

  4. GlassForm

    Energy Science and Technology Software Center (ESTSC)

    2011-09-16

    GlassForm is a software tool for generating preliminary waste glass formulas for a given waste stream. The software is useful because it reduces the number of verification melts required to develop a suitable additive composition. The software includes property models that calculate glass properties of interest from the chemical composition of the waste glass. The software includes property models for glass viscosity, electrical conductivity, glass transition temperature, and leach resistance as measured by the 7-daymore » product consistency test (PCT).« less

  5. Bubble formation in additive manufacturing of glass

    NASA Astrophysics Data System (ADS)

    Luo, Junjie; Gilbert, Luke J.; Peters, Daniel C.; Bristow, Douglas A.; Landers, Robert G.; Goldstein, Jonathan T.; Urbas, Augustine M.; Kinzel, Edward C.

    2016-05-01

    Bubble formation is a common problem in glass manufacturing. The spatial density of bubbles in a piece of glass is a key limiting factor to the optical quality of the glass. Bubble formation is also a common problem in additive manufacturing, leading to anisotropic material properties. In glass Additive Manufacturing (AM) two separate types of bubbles have been observed: a foam layer caused by the reboil of the glass melt and a periodic pattern of bubbles which appears to be unique to glass additive manufacturing. This paper presents a series of studies to relate the periodicity of bubble formation to part scan speed, laser power, and filament feed rate. These experiments suggest that bubbles are formed by the reboil phenomena why periodic bubbles result from air being trapped between the glass filament and the substrate. Reboil can be detected using spectroscopy and avoided by minimizing the laser power while periodic bubbles can be avoided by a two-step laser melting process to first establish good contact between the filament and substrate before reflowing the track with higher laser power.

  6. "S" Glass Manufacturing Technology Transfer

    SciTech Connect

    Buckner, Dean, A.; McCollister, Howard, L.

    1988-06-01

    A glass-ceramic-to metal sealing technology patented by Sandia National Laboratories, Albuquerque (SNLA) was developed by MRC-Mound for use in the manufacture of weapon components. Successful implementation attracted increasingly widespread weapon use of this technology. "S-glass" manufacturing technology was transferred to commercial vendors to ensure that weapons production schedules would be met in the coming years. Such transfer also provided sources of this fledgling technology for the Department of Defense (DOD), aerospace and other commercial uses. The steps involved in the technology transfer are described, from the initial cooperative development work of Sandia and Mound scientists and technologists to the final phase of qualifying commercial vendors for component manufacture.

  7. SOURCE ASSESSMENT: GLASS CONTAINER MANUFACTURING PLANTS

    EPA Science Inventory

    The report summarizes results of a study to gather and analyze background information and technical data related to air emissions from glass container manufacturing operations. It covers emissions from three plant areas: raw materials preparation and handling, glass melting, and ...

  8. Glasses formed by hypervelocity impact

    NASA Technical Reports Server (NTRS)

    Stoeffler, D.

    1984-01-01

    This paper presents description, classification, and geological setting of impact glasses, which are formed as a result of meteorite impacts with the planetary surface, and discusses the impact-glass formation process in the context of cratering mechanics. Impact glasses can be classified as belonging to two major groups: (1) mineral glasses, which are identical in composition to a mineral, and (2) rock glasses, which have the composition of a rock or a mixture of various rocks. Rock glasses may be (1) melt ejecta, (2) parts of a coherent melt layer inside the crater cavity, or (3) dikes or veins. The composition of rock glasses at a particular crater can be matched by that of the target. In nonporous rocks, the formation of rock glasses requires peak pressures in excess of 60-80 GPa, while mineral glasses are formed in the pressure range of about 25 to 55 GPa; in porous rocks, interstitial glass forms at pressures as low as 5 GPa.

  9. Glass shell manufacturing in space

    NASA Technical Reports Server (NTRS)

    Nolen, R. L.; Downs, R. L.; Ebner, M. A.

    1982-01-01

    Highly-uniform, hollow glass spheres, which are used for inertial-confinement fusion targets, are formed from metal-organic gel powder feedstock in a drop-tower furnace. The modelling of this gel-to-sphere transformation has consisted of three phases: gel thermochemistry, furnance-to-gel heat transfer, and gravity-driven degradation of the concentricity of the molten shell. The heat transfer from the furnace to the free-falling gel particle was modelled with forced convection. The gel mass, dimensions, and specific heat as well as furnace temperature profile and furnace gas conductivity, were controlled variables. This model has been experimentally verified. In the third phase, a mathematical model was developed to describe the gravity-driven degradation of concentricity in molten glass shells.

  10. Glass shell manufacturing in space

    NASA Technical Reports Server (NTRS)

    Downs, R. L.; Ebner, M. A.; Nolen, R. L., Jr.

    1981-01-01

    Highly-uniform, hollow glass spheres (shells), which are used for inertial confinement fusion targets, were formed from metal-organic gel powder feedstock in a vertical furnace. As a result of the rapid pyrolysis caused by the furnace, the gel is transformed to a shell in five distinct stages: (a) surface closure of the porous gel; (b) generation of a closed-cell foam structure in the gel; (c) spheridization of the gel and further expansion of the foam; (d) coalescence of the closed-cell foam to a single-void shell; and (e) fining of the glass shell. The heat transfer from the furnace to the falling gel particle was modeled to determine the effective heating rate of the gel. The model predicts the temperature history for a particle as a function of mass, dimensions, specific heat, and absorptance as well as furnace temperature profile and thermal conductivity of the furnace gas. A model was developed that predicts the gravity-induced degradation of shell concentricity in falling molten shells as a function of shell characteristics and time.

  11. Containerless Manufacture of Glass Optical Fibers

    NASA Technical Reports Server (NTRS)

    Naumann, R. J.; Ethridge, E. C.

    1985-01-01

    Contamination and crystallization reduced in proposed process. Solid optical fiber drawn from an acoustically levitated lump of molten glass. New material added in solid form, melted and then moved into main body of molten glass. Single axis acoustic levitation furnances levitate glass melts at temperature up to about 700 degrees C. Processing in unit limited to low-melting temperature glasses.

  12. Manufacturing unique glasses in space

    NASA Technical Reports Server (NTRS)

    Happe, R. P.

    1976-01-01

    An air suspension melting technique is described for making glasses from substances which to date have been observed only in the crystalline condition. A laminar flow vertical wind tunnel was constructed for suspending oxide melts that were melted using the energy from a carbon dioxide laser beam. By this method it is possible to melt many high-melting-point materials without interaction between the melt and crucible material. In addition, space melting permits cooling to suppress crystal growth. If a sufficient amount of under cooling is accompanied by a sufficient increase in viscosity, crystallization will be avoided entirely and glass will result.

  13. Additive manufacturing of glass for optical applications

    NASA Astrophysics Data System (ADS)

    Luo, Junjie; Gilbert, Luke J.; Bristow, Douglas A.; Landers, Robert G.; Goldstein, Jonathan T.; Urbas, Augustine M.; Kinzel, Edward C.

    2016-04-01

    Glasses including fused quartz have significant scientific and engineering applications including optics, communications, electronics, and hermetic seals. This paper investigates a filament fed process for Additive Manufacturing (AM) of fused quartz. Additive manufacturing has several potential benefits including increased design freedom, faster prototyping, and lower processing costs for small production volumes. However, current research in AM of glasses is limited and has focused on non-optical applications. Fused quartz is studied here because of its desirability for high-quality optics due to its high transmissivity and thermal stability. Fused quartz also has a higher working temperature than soda lime glass which poses a challenge for AM. In this work, fused quartz filaments are fed into a CO2 laser generated melt pool, smoothly depositing material onto the work piece. Single tracks are printed to explore the effects that different process parameters have on the morphology of printed fused quartz. A spectrometer is used to measure the thermal radiation incandescently emitted from the melt pool. Thin-walls are printed to study the effects of layer-to-layer height. Finally, a 3D fused quartz cube is printed using the newly acquired layer height and polished on each surface. The transmittance and index homogeneity of the polished cube are both measured. These results show that the filament fed process has the potential to print fused quartz with optical transparency and of index of refraction uniformity approaching bulk processed glass.

  14. SOURCE ASSESSMENT: PRESSED AND BLOWN GLASS MANUFACTURING PLANTS

    EPA Science Inventory

    This report summarizes the results of a study to gather and analyze background information and technical data related to air emissions from glass manufacturers producing pressed and blown glassware. This includes all glassware except flat glass, glass containers, and fiber glass....

  15. 40 CFR 426.80 - Applicability; description of the glass container manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... glass container manufacturing subcategory. 426.80 Section 426.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Container Manufacturing Subcategory § 426.80 Applicability; description of the glass...

  16. 40 CFR 426.80 - Applicability; description of the glass container manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... glass container manufacturing subcategory. 426.80 Section 426.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Container Manufacturing Subcategory § 426.80 Applicability; description of the glass...

  17. Wafer-level manufacturing technology of glass microlenses

    NASA Astrophysics Data System (ADS)

    Gossner, U.; Hoeftmann, T.; Wieland, R.; Hansch, W.

    2014-08-01

    In high-tech products, there is an increasing demand to integrate glass lenses into complex micro systems. Especially in the lighting industry LEDs and laser diodes used for automotive applications require encapsulated micro lenses. To enable low-cost production, manufacturing of micro lenses on wafer level base using a replication technology is a key technology. This requires accurate forming of thousands of lenses with a diameter of 1-2 mm on a 200 mm wafer compliant with mass production. The article will discuss the technical aspects of a lens manufacturing replication process and the challenges, which need to be solved: choice of an appropriate master for replication, thermally robust interlayer coating, choice of replica glass, bonding and separation procedure. A promising approach for the master substrate material is based on a lens structured high-quality glass wafer with high melting point covered by a coating layer of amorphous silicon or germanium. This layer serves as an interlayer for the glass bonding process. Low pressure chemical vapor deposition and plasma enhanced chemical vapor deposition processes allow a deposition of layer coatings with different hydrogen and doping content influencing their chemical and physical behavior. A time reduced molding process using a float glass enables the formation of high quality lenses while preserving the recyclability of the mother substrate. The challenge is the separation of the replica from the master mold. An overview of chemical methods based on optimized etching of coating layer through small channels will be given and the impact of glass etching on surface roughness is discussed.

  18. 40 CFR 426.40 - Applicability; description of the plate glass manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... plate glass manufacturing subcategory. 426.40 Section 426.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Plate Glass Manufacturing Subcategory § 426.40 Applicability; description of the plate...

  19. 40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float...

  20. 40 CFR 426.100 - Applicability; description of the glass tubing (Danner) manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... glass tubing (Danner) manufacturing subcategory. 426.100 Section 426.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Tubing (Danner) Manufacturing Subcategory § 426.100...

  1. 40 CFR 426.30 - Applicability; description of the rolled glass manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... rolled glass manufacturing subcategory. 426.30 Section 426.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Rolled Glass Manufacturing Subcategory § 426.30 Applicability; description of the rolled...

  2. 40 CFR 426.80 - Applicability; description of the glass container manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... glass container manufacturing subcategory. 426.80 Section 426.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Container Manufacturing Subcategory § 426.80 Applicability; description of the...

  3. 40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float...

  4. 40 CFR 426.80 - Applicability; description of the glass container manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... glass container manufacturing subcategory. 426.80 Section 426.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Container Manufacturing Subcategory § 426.80 Applicability; description of the...

  5. 40 CFR 426.80 - Applicability; description of the glass container manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... glass container manufacturing subcategory. 426.80 Section 426.80 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Container Manufacturing Subcategory § 426.80 Applicability; description of the...

  6. 40 CFR 426.20 - Applicability; description of the sheet glass manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... sheet glass manufacturing subcategory. 426.20 Section 426.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Sheet Glass Manufacturing Subcategory § 426.20 Applicability; description of the sheet...

  7. 40 CFR 426.40 - Applicability; description of the plate glass manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... plate glass manufacturing subcategory. 426.40 Section 426.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Plate Glass Manufacturing Subcategory § 426.40 Applicability; description of the plate...

  8. 40 CFR 426.20 - Applicability; description of the sheet glass manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... sheet glass manufacturing subcategory. 426.20 Section 426.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Sheet Glass Manufacturing Subcategory § 426.20 Applicability; description of the sheet...

  9. 40 CFR 426.100 - Applicability; description of the glass tubing (Danner) manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... glass tubing (Danner) manufacturing subcategory. 426.100 Section 426.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Tubing (Danner) Manufacturing Subcategory § 426.100...

  10. 40 CFR 426.30 - Applicability; description of the rolled glass manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... rolled glass manufacturing subcategory. 426.30 Section 426.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Rolled Glass Manufacturing Subcategory § 426.30 Applicability; description of the rolled...

  11. 40 CFR 426.100 - Applicability; description of the glass tubing (Danner) manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... glass tubing (Danner) manufacturing subcategory. 426.100 Section 426.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Tubing (Danner) Manufacturing Subcategory § 426.100...

  12. Glass fiber manufacturing and fiber safety: the producer's perspective.

    PubMed Central

    Bender, J R; Hadley, J G

    1994-01-01

    Historically, the potential health effects of airborne fibers have been associated with the dose, dimension, and durability. Increasing focus is being placed on the latter category. Concern about airborne fiber safety could be reduced by manufacturing fibers that are not respirable; however, due to performance and manufacturing constraints on glasswool insulations, this is not possible today. These products are an important part of today's economy and as a major manufacturer, Owens-Corning is committed to producing and marketing materials that are both safe and effective in their intended use. To this end, manufacturing technology seeks to produce materials that generate low concentrations of airborne fibers, thus minimizing exposure and irritation. The range of fiber diameters is controlled to assure effective product performance and, as far as possible, to minimize respirability. Glass compositions are designed to allow effective fiber forming and ultimate product function. Fiber dissolution is primarily a function of composition; this too, can be controlled within certain constraints. Coupled with these broad parameters is an extensive product stewardship program to assure the safety of these materials. This article will discuss the factors that influence glasswool insulation production, use, and safety. PMID:7882953

  13. Thin transparent films formed from powdered glass

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Glass film less than five mils thick is formed from powdered glass dispersed in an organic liquid, deposited on a substrate, and fused into place. The thin films can be cut and shaped for contact lenses, optical filters and insulating layers.

  14. Advances in solid dosage form manufacturing technology.

    PubMed

    Andrews, Gavin P

    2007-12-15

    Currently, the pharmaceutical and healthcare industries are moving through a period of unparalleled change. Major multinational pharmaceutical companies are restructuring, consolidating, merging and more importantly critically assessing their competitiveness to ensure constant growth in an ever-more demanding market where the cost of developing novel products is continuously increasing. The pharmaceutical manufacturing processes currently in existence for the production of solid oral dosage forms are associated with significant disadvantages and in many instances provide many processing problems. Therefore, it is well accepted that there is an increasing need for alternative processes to dramatically improve powder processing, and more importantly to ensure that acceptable, reproducible solid dosage forms can be manufactured. Consequently, pharmaceutical companies are beginning to invest in innovative processes capable of producing solid dosage forms that better meet the needs of the patient while providing efficient manufacturing operations. This article discusses two emerging solid dosage form manufacturing technologies, namely hot-melt extrusion and fluidized hot-melt granulation. PMID:17855217

  15. SUMMARY REPORT ON EMISSIONS FROM THE GLASS MANUFACTURING INDUSTRY

    EPA Science Inventory

    This project was undertaken to evaluate emissions rates from typical glass manufacturing furnaces. The effort concentrated on the container segment of the industry, however, tests were also conducted on the pressed blown, and flat glass segments of the industry. The quantitative ...

  16. Titanium sealing glasses and seals formed therefrom

    DOEpatents

    Brow, Richard K.; McCollister, Howard L.; Phifer, Carol C.; Day, Delbert E.

    1997-01-01

    Alkaline-earth lanthanoborate sealing-glass compositions containing CaO, La.sub.2 O.sub.3, B.sub.2 O.sub.3, TiO.sub.2 and Al.sub.2 O.sub.3 in various combinations of mole-% are provided. These sealing-glass compositions are useful for forming hermetic glass-to-metal seals with titanium and titanium alloys that have a high aqueous durability for component or device applications requiring exposure to moisture, water or body fluids. Particular applications of the titanium sealing-glass compositions include forming glass-to-metal seals for lithium batteries and implanted biomedical devices (e.g. batteries, pacemakers, defibrillators, pumps).

  17. Titanium sealing glasses and seals formed therefrom

    DOEpatents

    Brow, R.K.; McCollister, H.L.; Phifer, C.C.; Day, D.E.

    1997-12-02

    Alkaline-earth lanthanoborate sealing-glass compositions containing CaO, La{sub 2}O{sub 3}, B{sub 2}O{sub 3}, TiO{sub 2} and Al{sub 2}O{sub 3} in various combinations of mole-% are provided. These sealing-glass compositions are useful for forming hermetic glass-to-metal seals with titanium and titanium alloys that have a high aqueous durability for component or device applications requiring exposure to moisture, water or body fluids. Particular applications of the titanium sealing-glass compositions include forming glass-to-metal seals for lithium batteries and implanted biomedical devices (e.g. batteries, pacemakers, defibrillators, pumps). 2 figs.

  18. 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.

  19. Hollow microspheres of silica glass and method of manufacture

    DOEpatents

    Downs, Raymond L.; Miller, Wayne J.

    1982-01-01

    A method of manufacturing gel powder suitable for use as a starting material in the manufacture of hollow glass microspheres having a high concentration of silica. The powder is manufactured from a gel containing boron in the amount of about 1% to 20% (oxide equivalent mole percent), alkali metals, specifically potassium and sodium, in an amount exceeding 8% total, and the remainder silicon. Preferably, the ratio of potassium to sodium is greater than 1.5.

  20. Modeling the glass forming ability of metals

    NASA Astrophysics Data System (ADS)

    Cheney, Justin Lee

    A design protocol for the discovery of novel metallic glass compositions has been developed using a multi-model approach. By using a series of modeling criteria, all aspects of vitrification in metals can be simultaneously analyzed, and optimum compositions for metallic glass formation can be accurately determined. The modeling tools used focus on three aspects common among good glass forming alloy: compositional proximity to a deep eutectic, development of strong chemical interactions in the liquid state, and an ordered local topology in the amorphous state. It was shown that metallic glasses have the tendency to form two separate local topologies, that based on solvent-solute clustering, and that based on solute-solute clustering. A chemical short range order parameter model was used to evaluate constituent element interactions, and distinguish between these two structure types. In solvent-solute clusters, metallic glass design involves maximizing the packing density in the cluster structure; in the solute-solute cluster case, metallic glass design requires maximizing the elastic strain as a function of the solute composition. A quantification method, termed the alpha parameter, was developed to determine the depth of a eutectic, and rank alloy compositions among a large multi-dimensional composition space. This modeling approach was shown to accurately predict the wide range of metallic glass types represented in the literature. Furthermore, novel metallic glass compositions were developed according to this model. These novel compositions are among the most cost-effective bulk metallic glasses, which belong to three distinct alloy systems, Fe-Cr-Mo-C-B-W, Fe-Nb-Cr-B, and Ti-Ni-Cu-Si-Sn.

  1. Method for heating, forming and tempering a glass sheet

    DOEpatents

    Boaz, Premakaran Tucker; Sitzman, Gary W.

    1998-01-01

    A method for heating, forming and tempering a glass sheet including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet.

  2. Method for heating, forming and tempering a glass sheet

    DOEpatents

    Boaz, P.T.; Sitzman, G.W.

    1998-10-27

    A method for heating, forming and tempering a glass sheet is disclosed including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet. 2 figs.

  3. Correlation functions for glass-forming systems

    PubMed

    Jacobs

    2000-07-01

    We present a simple, linear, partial-differential equation for the density-density correlation function in a glass-forming system. The equation is written down on the basis of fundamental and general considerations of linearity, symmetry, stability, thermodynamic irreversibility and consistency with the equation of continuity (i.e. , conservation of matter). The dynamical properties of the solutions show a change in behavior characteristic of the liquid-glass transition as a function of one of the parameters (temperature). The equation can be shown to lead to the simplest mode-coupling theory of glasses and provides a partial justification of this simplest theory. It provides also a method for calculating the space dependence of the correlation functions not available otherwise. The results suggest certain differences in behavior between glassy solids and glass-forming liquids which may be accessible to experiment. A brief discussion is presented of how the method can be applied to other systems such as sandpiles and vortex glasses in type II superconductors. PMID:11088609

  4. Method for heating and forming a glass sheet

    DOEpatents

    Boaz, P.T.

    1997-08-12

    A method for heating and forming a glass sheet includes the steps of heating a glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, cooling an outer surface of the glass sheet to at least a third predetermined temperature and forming the glass sheet using forming rollers to a predetermined configuration. 5 figs.

  5. Method for heating and forming a glass sheet

    DOEpatents

    Boaz, Premakaran Tucker

    1997-01-01

    A method for heating and forming a glass sheet includes the steps of heating a glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, cooling an outer surface of the glass sheet to at least a third predetermined temperature and forming the glass sheet using forming rollers to a predetermined configuration.

  6. Additive manufacturing of tools for lapping glass

    NASA Astrophysics Data System (ADS)

    Williams, Wesley B.

    2013-09-01

    Additive manufacturing technologies have the ability to directly produce parts with complex geometries without the need for secondary processes, tooling or fixtures. This ability was used to produce concave lapping tools with a VFlash 3D printer from 3D Systems. The lapping tools were first designed in Creo Parametric with a defined constant radius and radial groove pattern. The models were converted to stereolithography files which the VFlash used in building the parts, layer by layer, from a UV curable resin. The tools were rotated at 60 rpm and used with 120 grit and 220 grit silicon carbide lapping paste to lap 0.750" diameter fused silica workpieces. The samples developed a matte appearance on the lapped surface that started as a ring at the edge of the workpiece and expanded to the center. This indicated that as material was removed, the workpiece radius was beginning to match the tool radius. The workpieces were then cleaned and lapped on a second tool (with equivalent geometry) using a 3000 grit corundum aluminum oxide lapping paste, until a near specular surface was achieved. By using lapping tools that have been additively manufactured, fused silica workpieces can be lapped to approach a specified convex geometry. This approach may enable more rapid lapping of near net shape workpieces that minimize the material removal required by subsequent polishing. This research may also enable development of new lapping tool geometry and groove patterns for improved loose abrasive finishing.

  7. 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.

  8. 40 CFR 426.40 - Applicability; description of the plate glass manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... plate glass manufacturing subcategory. 426.40 Section 426.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Plate Glass Manufacturing Subcategory § 426.40 Applicability; description of the plate...

  9. 40 CFR 426.30 - Applicability; description of the rolled glass manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... rolled glass manufacturing subcategory. 426.30 Section 426.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Rolled Glass Manufacturing Subcategory § 426.30 Applicability; description of the rolled...

  10. 40 CFR 426.30 - Applicability; description of the rolled glass manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... rolled glass manufacturing subcategory. 426.30 Section 426.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Rolled Glass Manufacturing Subcategory § 426.30 Applicability; description of the rolled...

  11. 40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float...

  12. 40 CFR 426.40 - Applicability; description of the plate glass manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... plate glass manufacturing subcategory. 426.40 Section 426.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Plate Glass Manufacturing Subcategory § 426.40 Applicability; description of the plate...

  13. 40 CFR 426.100 - Applicability; description of the glass tubing (Danner) manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... glass tubing (Danner) manufacturing subcategory. 426.100 Section 426.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Tubing (Danner) Manufacturing Subcategory § 426.100 Applicability; description of the...

  14. 40 CFR 426.100 - Applicability; description of the glass tubing (Danner) manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... glass tubing (Danner) manufacturing subcategory. 426.100 Section 426.100 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GLASS MANUFACTURING POINT SOURCE CATEGORY Glass Tubing (Danner) Manufacturing Subcategory § 426.100 Applicability; description of the...

  15. 40 CFR 426.20 - Applicability; description of the sheet glass manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... sheet glass manufacturing subcategory. 426.20 Section 426.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Sheet Glass Manufacturing Subcategory § 426.20 Applicability; description of the sheet...

  16. 40 CFR 426.30 - Applicability; description of the rolled glass manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... rolled glass manufacturing subcategory. 426.30 Section 426.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Rolled Glass Manufacturing Subcategory § 426.30 Applicability; description of the rolled...

  17. 40 CFR 426.40 - Applicability; description of the plate glass manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... plate glass manufacturing subcategory. 426.40 Section 426.40 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Plate Glass Manufacturing Subcategory § 426.40 Applicability; description of the plate...

  18. 40 CFR 426.20 - Applicability; description of the sheet glass manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... sheet glass manufacturing subcategory. 426.20 Section 426.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Sheet Glass Manufacturing Subcategory § 426.20 Applicability; description of the sheet...

  19. 40 CFR 426.20 - Applicability; description of the sheet glass manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... sheet glass manufacturing subcategory. 426.20 Section 426.20 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Sheet Glass Manufacturing Subcategory § 426.20 Applicability; description of the sheet...

  20. 40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float...

  1. 40 CFR 426.50 - Applicability; description of the float glass manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... float glass manufacturing subcategory. 426.50 Section 426.50 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS (CONTINUED) GLASS MANUFACTURING POINT SOURCE CATEGORY Float Glass Manufacturing Subcategory § 426.50 Applicability; description of the float...

  2. Innovative hybrid optics: combining the thermal stability of glass with low manufacturing cost of polymers

    NASA Astrophysics Data System (ADS)

    Doushkina, Valentina

    2010-08-01

    Innovative hybrid glass-polymer optical solutions on a component, module, or system level offer thermal stability of glass with low manufacturing cost of polymers reducing component weight, enhancing the safety and appeal of the products. Narrow choice of polymer materials is compensated by utilizing sophisticated optical surfaces such as refractive, reflective, and diffractive substrates with spherical, aspherical, cylindrical, and freeform prescriptions. Current advancements in polymer technology and injection molding capabilities placed polymer optics in the heart of many high tech devices and applications including Automotive Industry, Defense & Aerospace; Medical/Bio Science; Projection Displays, Sensors, Information Technology, Commercial and Industrial. This paper is about integration of polymer and glass optics for enhanced optical performance with reduced number of components, thermal stability, and low manufacturing cost. The listed advantages are not achievable when polymers or glass optics are used as stand-alone. The author demonstrates that integration of polymer and glass on component or optical system level on one hand offers high resolution and diffraction limited image quality, similar to the glass optics with stable refractive index and stable thermal performance when design is athermalized within the temperature range. On the other hand, the integrated hybrid solution significantly reduces cost, weight, and complexity, just like the polymer optics. The author will describe the design and analyzes process of combining glass and polymer optics for variety of challenging applications such as fast optics with low F/#, wide field of view lenses or systems, free form optics, etc.

  3. Method for forming silicon on a glass substrate

    DOEpatents

    McCarthy, Anthony M.

    1995-01-01

    A method by which single-crystal silicon microelectronics may be fabricated on glass substrates at unconventionally low temperatures. This is achieved by fabricating a thin film of silicon on glass and subsequently forming the doped components by a short wavelength (excimer) laser doping procedure and conventional patterning techniques. This method may include introducing a heavily boron doped etch stop layer on a silicon wafer using an excimer laser, which permits good control of the etch stop layer removal process. This method additionally includes dramatically reducing the remaining surface roughness of the silicon thin films after etching in the fabrication of silicon on insulator wafers by scanning an excimer laser across the surface of the silicon thin film causing surface melting, whereby the surface tension of the melt causes smoothing of the surface during recrystallization. Applications for this method include those requiring a transparent or insulating substrate, such as display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard and high temperature electronics.

  4. Polyamorphic transitions in network glasses and glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Kieffer, John

    2006-03-01

    Over the past two decades, we have witnessed increasing evidence for the occurrence of polyamorphism, i.e., the existence of more than one thermodynamically and structurally distinct non-crystalline state of a given substance. This concept is manifest predominantly through the transitions between different polyamorphic states, as we are still not able to unequivocally describe a given amorphous structure. However, if substantiated, the concept of polyamorphism should facilitate such a description, since it implies that polyamorphic states are uniquely defined and a distinctive structural character must exist for each state. We have observed polyamorphic transitions in a number of glass-forming systems, e.g., when probing their high-frequency visco-elastic response as a function of temperature,[1] or when compacting such systems at high pressures. We have carried out molecular dynamics simulations to reveal explanations for the phenomena observed in experiments.[2] In this presentation we discuss reversible and irreversible transitions in silica glass, their relation to the anomalous thermo-mechanical properties of this material, and the effects of permanent densification on structure and properties. We present an unusual transition in boron oxide glass, which is continuous upon compression and discontinuous upon decompression.[3] We show how the manifestations of polyamorphic transitions and their are related to structural transformations in the crystalline counterparts of these materials, and how this can even lead to the discovery of previously unknown metastable crystalline phases. [1] J. Kieffer, J.E. Masnik, O. Nickolayev, and J.D. Bass, Phys. Rev. B 58, 694 (1998). [2] L. Huang, and J. Kieffer, Phys. Rev. B 69, 224203 and 224204 (2004). [3] J.D. Nicholas, S.V. Sinogeikin, J. Kieffer, and J.D. Bass, Phys. Rev. Letters 92, 215701 (2004).

  5. An overview on mirrors for Cherenkov telescopes manufactured by glass cold-shaping technology

    NASA Astrophysics Data System (ADS)

    Canestrari, Rodolfo; Sironi, Giorgia

    2015-09-01

    The cold glass-slumping technique is a low cost processing developed at INAF-Osservatorio Astronomico di Brera for the manufacturing of mirrors for Cherenkov telescopes. This technology is based on the shaping of thin glass foils by means of bending at room temperature. The glass foils are thus assembled into a sandwich structure for retaining the imposed shape by the use of a honeycomb core. The mirrors so manufactured employ commercial off-the-shelf materials thus allowing a competitive cost and production time. They show very low weight, rigidity and environmental robustness. In this contribution we give an overview on the most recent results achieved from the adoption of the cold-shaping technology to different projects of Cherenkov telescopes. We show the variety of optical shapes implemented ranging from those spherical with long radius of curvature up to the most curved free form ones.

  6. Development of a compression molding process for three-dimensional tailored free-form glass optics

    NASA Astrophysics Data System (ADS)

    Yi, Allen Y.; Huang, Chunning; Klocke, Fritz; Brecher, Christian; Pongs, Guido; Winterschladen, Markus; Demmer, Axel; Lange, Sven; Bergs, Thomas; Merz, Michael; Niehaus, Frank

    2006-09-01

    Because of the limitation of manufacturing capability, free-form glass optics cannot be produced in a large volume using traditional processes such as grinding, lapping, and polishing. Very recently compression molding of glass optics became a viable manufacturing process for the high-volume production of precision glass optical components. An ultraprecision diamond-turning machine retrofitted with a fast tool servo was used to fabricate a free-form optical mold on a nickel-plated surface. A nonuniform rational B-spline trajectory generator was developed to calculate the computer numerical control machine tool path. A specially formulated glass with low transition temperature (Tg) was used, since the nickel alloy mold cannot withstand the high temperatures required for regular optical glasses. We describe the details of this process, from optical surface geometry, mold making, molding experiment, to lens measurement.

  7. Development of a compression molding process for three-dimensional tailored free-form glass optics.

    PubMed

    Yi, Allen Y; Huang, Chunning; Klocke, Fritz; Brecher, Christian; Pongs, Guido; Winterschladen, Markus; Demmer, Axel; Lange, Sven; Bergs, Thomas; Merz, Michael; Niehaus, Frank

    2006-09-01

    Because of the limitation of manufacturing capability, free-form glass optics cannot be produced in a large volume using traditional processes such as grinding, lapping, and polishing. Very recently compression molding of glass optics became a viable manufacturing process for the high-volume production of precision glass optical components. An ultraprecision diamond-turning machine retrofitted with a fast tool servo was used to fabricate a free-form optical mold on a nickel-plated surface. A nonuniform rational B-spline trajectory generator was developed to calculate the computer numerical control machine tool path. A specially formulated glass with low transition temperature (Tg) was used, since the nickel alloy mold cannot withstand the high temperatures required for regular optical glasses. We describe the details of this process, from optical surface geometry, mold making, molding experiment, to lens measurement. PMID:16912790

  8. Prediction of glass forming ability and glass forming range for electrodeposited binary Co-W alloys

    NASA Astrophysics Data System (ADS)

    Singh, Ashish; Iyer, Nikhilesh; Harimkar, Sandip P.

    2012-05-01

    This paper reports on the transition of crystalline to amorphous structure with increasing W content in electrodeposited binary Co-W alloys. The glass forming ability of the electrodeposited Co-based alloys, including Co-W alloy, is analyzed using deep eutectic criteria based on reduced liquidus temperature and relative composition ratio. MD simulations based on solid solution models indicated glass forming ability above 20 at. % W for Co-rich Co-W alloys, which is in good agreement with the experimental observations.

  9. Nonlinear energy response of glass forming materials

    NASA Astrophysics Data System (ADS)

    Tagawa, Fumitaka; Odagaki, Takashi

    2008-01-01

    A theory for the nonlinear energy response of a system subjected to a heat bath is developed when the temperature of the heat bath is modulated sinusoidally. The theory is applied to a model glass forming system, where the landscape is assumed to have 20 basins and transition rates between basins obey a power law distribution. It is shown that the statistics of eigenvalues of the transition rate matrix, the glass transition temperature Tg, the Vogel-Fulcher temperature T0 and the crossover temperature Tx can be determined from the first- and second-order ac specific heats, which are defined as coefficients of the first- and second-order energy responses. The imaginary part of the first-order ac specific heat has a broad peak corresponding to the distribution of the eigenvalues. When the temperature is decreased below Tg, the frequency of the peak decreases and the width increases. Furthermore, the statistics of eigenvalues can be obtained from the frequency dependence of the first-order ac specific heat. The second-order ac specific heat shows extrema as a function of the frequency. The extrema diverge at the Vogel-Fulcher temperature T0. The temperature dependence of the extrema changes significantly near Tg and some extrema vanish near Tx.

  10. 24 CFR 3280.403 - Standard for windows and sliding glass doors used in manufactured homes.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... glass doors used in manufactured homes. 3280.403 Section 3280.403 Housing and Urban Development... AND SAFETY STANDARDS Testing § 3280.403 Standard for windows and sliding glass doors used in manufactured homes. (a) Scope. This section sets the requirements for prime windows and sliding glass...

  11. 24 CFR 3280.403 - Standard for windows and sliding glass doors used in manufactured homes.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... glass doors used in manufactured homes. 3280.403 Section 3280.403 Housing and Urban Development... AND SAFETY STANDARDS Testing § 3280.403 Standard for windows and sliding glass doors used in manufactured homes. (a) Scope. This section sets the requirements for prime windows and sliding glass...

  12. 24 CFR 3280.403 - Standard for windows and sliding glass doors used in manufactured homes.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... glass doors used in manufactured homes. 3280.403 Section 3280.403 Housing and Urban Development... AND SAFETY STANDARDS Testing § 3280.403 Standard for windows and sliding glass doors used in manufactured homes. (a) Scope. This section sets the requirements for prime windows and sliding glass...

  13. 24 CFR 3280.403 - Standard for windows and sliding glass doors used in manufactured homes.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... glass doors used in manufactured homes. 3280.403 Section 3280.403 Housing and Urban Development... AND SAFETY STANDARDS Testing § 3280.403 Standard for windows and sliding glass doors used in manufactured homes. (a) Scope. This section sets the requirements for prime windows and sliding glass...

  14. Inorganic glasses, glass-forming liquids and amorphizing solids

    NASA Astrophysics Data System (ADS)

    Greaves, G. N.; Sen, S.

    2007-01-01

    We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of relaxation in different dynamical regimes, spectroscopic studies of atomic-scale mechanisms of viscous flow in inorganic glass-formers and the signatures of relaxational behaviour embedded in the low-frequency vibrational dynamics of glasses including the Boson peak and the Two-Level Systems (TLS) that control conformational transformation. We conclude this review by extending concepts of the dynamics of the glass transition from the supercooled liquid in order to understand the solid-state amorphization of crystals under temperature and pressure and to determine the thermodynamic limits of the crystalline and glassy state.

  15. Thermodynamic and Viscous Behaviour of Glass Forming Melts and Glass Forming Ability

    SciTech Connect

    Dubey, K. S.

    2010-06-29

    The bulk metallic glasses (BMGs) have achieved a great interest due to their scientific and potential technological applications and these are among the most extensively studied advanced materials. The understanding of the glass forming ability (GFA) of these multicomponent metallic alloys is an essential parameter to develop new non-crystalline materials which is an outstanding problem for being adequately solved. The Gibbs free energy difference ({Delta}G) between the undercooled melt and the corresponding equilibrium solid phases and the viscosity ({eta}) of the undercooled melts are essential parameters for understanding the nucleation and growth processes. The present article deals with the procedures for obtaining the expressions for {Delta}G as well as the expressions for obtaining the temperature dependence of viscosity of the undercooled melts. The method for evaluation of the Kauzmann temperature T{sub k} and its importance has also been discussed. The glass forming ability (GFA) of materials is explained in terms of ratio of specific heat difference {Delta}C{sub p}{sup m} and entropy difference {Delta}S{sub m} at the melting temperature T{sub m}. The role of various thermodynamic quantities in GFA of materials has also been discussed. The discussion is confined to simple, oxide, polymeric and bulk metallic glasses.

  16. Thermodynamic and Viscous Behaviour of Glass Forming Melts and Glass Forming Ability

    NASA Astrophysics Data System (ADS)

    Dubey, K. S.

    2010-06-01

    The bulk metallic glasses (BMGs) have achieved a great interest due to their scientific and potential technological applications and these are among the most extensively studied advanced materials. The understanding of the glass forming ability (GFA) of these multicomponent metallic alloys is an essential parameter to develop new non-crystalline materials which is an outstanding problem for being adequately solved. The Gibbs free energy difference (ΔG) between the undercooled melt and the corresponding equilibrium solid phases and the viscosity (η) of the undercooled melts are essential parameters for understanding the nucleation and growth processes. The present article deals with the procedures for obtaining the expressions for ΔG as well as the expressions for obtaining the temperature dependence of viscosity of the undercooled melts. The method for evaluation of the Kauzmann temperature Tk and its importance has also been discussed. The glass forming ability (GFA) of materials is explained in terms of ratio of specific heat difference ΔCpm and entropy difference ΔSm at the melting temperature Tm. The role of various thermodynamic quantities in GFA of materials has also been discussed. The discussion is confined to simple, oxide, polymeric and bulk metallic glasses.

  17. Leaching behavior of glass ceramic nuclear waste forms

    NASA Astrophysics Data System (ADS)

    Lokken, R. O.

    1981-11-01

    Glass ceramic waste forms were investigated as alternatives to borosilicate glasses for the immobilization of high-level radioactive waste. Three glass ceramic systems were investigated, including basalt, celsian, and fresnoite, each containing 20 wt percent simulated high-level waste calcine. Static leach tests were performed on seven glass ceramic materials and one parent glass (before recrystallization). Samples were leached at 90 C for 3 to 28 days in deionized water and silicate water. The results, expressed in normalized elemental mass loss, show comparable releases from celsian and fresnoite glass ceramics. Basalt glass ceramics demonstrated the lowest normalized elemental losses with a nominal release less than 2 grams per square meter when leached in polypropylene containers. The releases from basalt glass ceramics when leached in silicate water were nearly identical with those in deionized water. The overall leachability of celsian and fresnoite glass ceramics was improved when silicate water was used as the leachant.

  18. 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.

  19. 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.

  20. Method for forming silicon on a glass substrate

    DOEpatents

    McCarthy, A.M.

    1995-03-07

    A method by which single-crystal silicon microelectronics may be fabricated on glass substrates at unconventionally low temperatures. This is achieved by fabricating a thin film of silicon on glass and subsequently forming the doped components by a short wavelength (excimer) laser doping procedure and conventional patterning techniques. This method may include introducing a heavily boron doped etch stop layer on a silicon wafer using an excimer laser, which permits good control of the etch stop layer removal process. This method additionally includes dramatically reducing the remaining surface roughness of the silicon thin films after etching in the fabrication of silicon on insulator wafers by scanning an excimer laser across the surface of the silicon thin film causing surface melting, whereby the surface tension of the melt causes smoothing of the surface during recrystallization. Applications for this method include those requiring a transparent or insulating substrate, such as display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard and high temperature electronics. 15 figs.

  1. High precision droplet based new form manufacturing

    SciTech Connect

    Aceves,S; Hadjiconstantinou, N; Miller, W O; Orme, M; Sahai, V; Shapiro, A B

    1999-09-16

    In collaboration with the University of California at Irvine (UCI), we are working on a new technology that relies on the precise deposition of nanoliter molten-metal droplets that are targeted onto a substrate by electrostatic charging and deflection. By this way, three-dimensional (3D) structural materials can be manufactured microlayer by microlayer. Because the volume of the droplets are small, they rapidly solidify on impact, bringing forth a material component with fine grain structures which lead to enhanced material properties (e.g., strength). UCI is responsible for an experimental investigation of the manufacturing feasibility of this process. LLNL has unique expertise in the computational modeling of 3D heat transfer and solid mechanics and has the large-scale computer resources necessary to model this large system. Process modeling will help move this technology from the bench-top to an industrial process. Applications at LLNL include rapid prototyping of metal parts and manufacturing new alloys by co-jetting different metals.

  2. 40 CFR 426.130 - Applicability; description of the hand pressed and blown glass manufacturing subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 30 2011-07-01 2011-07-01 false Applicability; description of the hand... CATEGORY Hand Pressed and Blown Glass Manufacturing Subcategory § 426.130 Applicability; description of the hand pressed and blown glass manufacturing subcategory. The provisions of this subpart are...

  3. 40 CFR 426.130 - Applicability; description of the hand pressed and blown glass manufacturing subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Applicability; description of the hand... POINT SOURCE CATEGORY Hand Pressed and Blown Glass Manufacturing Subcategory § 426.130 Applicability; description of the hand pressed and blown glass manufacturing subcategory. The provisions of this subpart...

  4. 40 CFR 426.130 - Applicability; description of the hand pressed and blown glass manufacturing subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 31 2012-07-01 2012-07-01 false Applicability; description of the hand... POINT SOURCE CATEGORY Hand Pressed and Blown Glass Manufacturing Subcategory § 426.130 Applicability; description of the hand pressed and blown glass manufacturing subcategory. The provisions of this subpart...

  5. 40 CFR 426.130 - Applicability; description of the hand pressed and blown glass manufacturing subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Applicability; description of the hand... CATEGORY Hand Pressed and Blown Glass Manufacturing Subcategory § 426.130 Applicability; description of the hand pressed and blown glass manufacturing subcategory. The provisions of this subpart are...

  6. 40 CFR 426.130 - Applicability; description of the hand pressed and blown glass manufacturing subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Applicability; description of the hand... POINT SOURCE CATEGORY Hand Pressed and Blown Glass Manufacturing Subcategory § 426.130 Applicability; description of the hand pressed and blown glass manufacturing subcategory. The provisions of this subpart...

  7. 24 CFR 3280.403 - Standard for windows and sliding glass doors used in manufactured homes.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... glass doors used in manufactured homes. 3280.403 Section 3280.403 Housing and Urban Development... AND SAFETY STANDARDS Testing § 3280.403 Standard for windows and sliding glass doors used in... the requirements for prime windows and sliding glass doors except for windows used in entry...

  8. Method of forming crystalline silicon devices on glass

    DOEpatents

    McCarthy, A.M.

    1995-03-21

    A method is disclosed for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics. 7 figures.

  9. Method of forming crystalline silicon devices on glass

    DOEpatents

    McCarthy, Anthony M.

    1995-01-01

    A method for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics.

  10. Effects of manufacturing method on surface mineralization of bioactive glasses

    NASA Astrophysics Data System (ADS)

    Pirayesh, Hamidreza

    Amorphous bioactive glass powders are used as bone-filling materials in many medical applications. Bioactivity is achieved through ion exchange with bodily fluids, leading to surface apatite mineral formation---a necessity for tissue development. Traditional fabrication is by melt-casting and grinding, however sol-gel synthesis is another method which directly produces powders with higher specific surface area and potential for increased ion exchange rates. In this study sol-gel derived powders were manufactured and compared with melt-cast powders to determine the effects of crystallinity, composition, and specific surface area on apatite formation. Powders were immersed in simulated body fluid as a function of time and the evolution of apatite minerals was characterized. Apatite formation was most significantly affected by powder composition, followed by specific surface area; merely having sodium in the powder was more influential than altering the surface area and/or atomic structure, yet high specific surface area was found to enhance reactions on crystalline powders.

  11. New Insights into the Fragility Dilemma in Glass Forming Liquids

    NASA Astrophysics Data System (ADS)

    McKenna, Gregory B.; Huang, Dinghai

    2001-03-01

    A compilation of data for small molecule organic, polymeric and inorganic glass forming liquids shows that the original expectation, that there be a positive correlation between the thermodynamic measure of fragility (the heat capacity ratio between the liquid and the crystal) and the dynamic fragility index m, is not generally true. The results are consistent with three classes of behavior: 1) a decrease in m with increasing heat capacity ratio for the polymeric glass formers; 2)a nearly constant value of m independent of the heat capacity ratio for small molecule organics and hydrogen bonding small molecules; 3) an increasing value of m with increasing heat capacity ratio for inorganic glass formers as originally considered by Angell. The results suggest the possibility that "universality" of "glassiness" may not be true. We suggest the existence of "free volume" glass formers and "entropy" glass formers as separate classes of glass formers.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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.

  13. 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

    2015-01-01

    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. PMID:25580857

  14. 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

    2011-09-01

    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 (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. PMID:21873237

  15. 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

  16. Zirconium fluoride glass - Surface crystals formed by reaction with water

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.; Bansal, N. P.; Bradner, T.; Murphy, D.

    1984-01-01

    The hydrated surfaces of a zirconium barium fluoride glass, which has potential for application in optical fibers and other optical elements, were observed by scanning electron microscopy. Crystalline zirconium fluoride was identified by analysis of X-ray diffraction patterns of the surface crystals and found to be the main constituent of the surface material. It was also found that hydrated zirconium fluorides form only in highly acidic fluoride solutions. It is possible that the zirconium fluoride crystals form directly on the glass surface as a result of its depletion of other ions. The solubility of zirconium fluoride is suggested to be probably much lower than that of barium fluoride (0.16 g/100 cu cm at 18 C). Dissolution was determined to be the predominant process in the initial stages of the reaction of the glass with water. Penetration of water into the glass has little effect.

  17. 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.

  18. 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. PMID:24089782

  19. Manufacturing and testing a thin glass mirror shell with piezoelectric active control

    NASA Astrophysics Data System (ADS)

    Spiga, D.; Barbera, M.; Collura, A.; Basso, S.; Candia, R.; Civitani, M.; Di Bella, M.; Di Cicca, G.; Lo Cicero, U.; Lullo, G.; Pelliciari, C.; Riva, M.; Salmaso, B.; Sciortino, L.; Varisco, S.

    2015-09-01

    Optics for future X-ray telescopes will be characterized by very large aperture and focal length, and will be made of lightweight materials like glass or silicon in order to keep the total mass within acceptable limits. Optical modules based on thin slumped glass foils are being developed at various institutes, aiming at improving the angular resolution to a few arcsec HEW. Thin mirrors are prone to deform, so they require a careful integration to avoid deformations and even correct forming errors. On the other hand, this offers the opportunity to actively correct the residual deformation: a viable possibility to improve the mirror figure is the application of piezoelectric actuators onto the non-optical side of the mirrors, and several groups are already at work on this approach. The concept we are developing consists of actively integrating thin glass foils with piezoelectric patches, fed by voltages driven by the feedback provided by X-rays. The actuators are commercial components, while the tension signals are carried by a printed circuit obtained by photolithography, and the driving electronic is a multi-channel low power consumption voltage supply developed inhouse. Finally, the shape detection and the consequent voltage signal to be provided to the piezoelectric array are determined in X-rays, in intra-focal setup at the XACT facility at INAF/OAPA. In this work, we describe the manufacturing steps to obtain a first active mirror prototype and the very first test performed in X-rays.

  20. Containerless processing of glass forming melts in space

    NASA Technical Reports Server (NTRS)

    Day, D. E.; Ray, C. S.

    1988-01-01

    The near weightlessness of a material in the reduced gravity environment of space offers the opportunity of melting and cooling glass forming compositions without a container. This reduces the heterogeneous nucleation/crystallization which usually occurs at the walls of the container, thereby, extending the range of glass forming compositions. Based primarily on this idea, containerless glass forming experiments, which used a single axis acoustic levitator/furnace (SAAL), were conducted on SPAR rocket flights, 6 and 8, and on Space Shuttle mission, STS-7 and STS-61A. The experiments on the Space Shuttle were designed to include other studies related to melt homogenization and mixing, development of techniques for preparing uncontaminated preflight samples, and simple shaping experiments.

  1. Glass technology involved in the manufacture of magnetometer components

    NASA Technical Reports Server (NTRS)

    Bergen, G.

    1972-01-01

    Glass technology has developed quicker and less costly techniques in sealing and vacuum processing which result in improved lamps and bulbs, thus producing a less costly and more reliable instrument package.

  2. High-temperature oxygen sensors for glass-forming melts.

    PubMed

    Baucke, F G

    1996-09-01

    Electrochemical sensors are reported for the on-line measurement of oxygen partial pressures of oxidic glass-forming melts on a laboratory and technical scale. Based on the principle of solid electrolyte cells without transference, they are principally simple units. The extreme chemical and temperature conditions of their applications, however, demanded extensive fundamental investigations and resulted in specific forms of reference and measuring electrodes, a thermo-dynamic procedure of verifying the correct functioning of such cells, and a method of measuring thermoelectric voltages of non-isothermal glass melts. PMID:15048355

  3. Dynamical Heterogeneity in Glass-Forming Liquids

    NASA Astrophysics Data System (ADS)

    Glotzer, S. C.; Donati, C.

    1998-03-01

    The dynamical properties of cold, dense liquids differ dramatically from what is expected from extrapolation of their high temperature behavior. Recently, it has been proposed that such liquids may be dynamically heterogeneous over time scales which increase as the liquid cools. It has been suggested that, e.g., this is a mechanism for the stretched exponential decay of relaxation functions. Using extensive molecular dynamics simulations, we have investigated several supercooled liquids [1-4] ([1] W. Kob, C. Donati, S.J. Plimpton, P.H. Poole and S.C. Glotzer, PRL) 79 2827 (1997); [2] C. Donati, S.J. Plimpton, J.F. Douglas, W. Kob, P.H. Poole, and S.C. Glotzer, preprint; [3] Glotzer, Donati, Sciortino, unpublished; [4] Donati, Mountain, Glotzer, unpublished. to determine the extent and character of their dynamical heterogeneity. In the case of a binary Lennard-Jones mixture, e.g., we find [1] that particles of similar mobility form highly ramified clusters which grow with decreasing temperature [1]. Remarkably, their size appears to diverge as a power law at the mode coupling dynamical critical point [2]. We further find that the dynamical heterogeneity is related to the local potential energy landscape [2].

  4. 46 CFR 53.10-15 - Manufacturers' data report forms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Vessel Code (incorporated by reference; see 46 CFR 53.01-1) must be made available to the marine... 46 Shipping 2 2013-10-01 2013-10-01 false Manufacturers' data report forms. 53.10-15 Section 53.10-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING...

  5. 46 CFR 53.10-15 - Manufacturers' data report forms.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Vessel Code (incorporated by reference; see 46 CFR 53.01-1) must be made available to the marine... 46 Shipping 2 2011-10-01 2011-10-01 false Manufacturers' data report forms. 53.10-15 Section 53.10-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING...

  6. 46 CFR 53.10-15 - Manufacturers' data report forms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Vessel Code (incorporated by reference; see 46 CFR 53.01-1) must be made available to the marine... 46 Shipping 2 2014-10-01 2014-10-01 false Manufacturers' data report forms. 53.10-15 Section 53.10-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING...

  7. 46 CFR 53.10-15 - Manufacturers' data report forms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Vessel Code (incorporated by reference; see 46 CFR 53.01-1) must be made available to the marine... 46 Shipping 2 2012-10-01 2012-10-01 false Manufacturers' data report forms. 53.10-15 Section 53.10-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING...

  8. 46 CFR 53.10-15 - Manufacturers' data report forms.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Vessel Code (incorporated by reference; see 46 CFR 53.01-1) must be made available to the marine... 46 Shipping 2 2010-10-01 2010-10-01 false Manufacturers' data report forms. 53.10-15 Section 53.10-15 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING...

  9. Correlating structural and dynamic fragility in glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Voylov, Dmitry; Griffin, Philip; Mercado, Brandon; Keum, Jong; Novikov, Vladimir; Sokolov, Alexei

    The glass transition was attracting wide interest over the last several decades, but still remains the topic of intensive research and discussions. One of the most intriguing and well-known observations is a drastic change of dynamic properties with only slight variations of structure upon cooling down to the glass transition temperature Tg. This has led many to believe that the changes of dynamics during approach to Tg have no structural signatures which would be significant and common to different types of glass-forming liquids. Here we demonstrate analysis of temperature dependence of the main diffraction peak in a static structure factor of various glass-formers. We show that the relative changes of its width with temperature correlates with fragility of these materials. This observation was analyzed using Adam-Gibbs approach establishing a connection between the structural and dynamical properties of glass-forming materials. We acknowledge partial financial support from the Division of Materials Science and Engineering, U.S. Department of Energy, Office of Basic Energy Sciences.

  10. Shockwave Absorption using Network-forming Ionic glass

    NASA Astrophysics Data System (ADS)

    Lee, Jaejun; Yang, Ke; Moore, Jeffrey; Sottos, Nancy; MURI SWED Collaboration

    2015-06-01

    Network-forming ionic glasses composed of di-ammonium cations and citrate anions exhibit significant potential for dissipation of shock wave energy. The long alkyl side chains in the di-ammonium cation form a soft matrix, while the negatively charged heads of anions segregate into hard nanophase domains. Similar to polyurea, which has microphase separation of soft and hard domains, we hypothesize that shock wave dissipation of the ionic glass occurs by bond breaking in the hard domains and/or pressure-induced phase transition. By employing size-tunable alkyl side chains in the cations, we examine the effect of the relative soft domain size on energy dissipation. A series of thin film (ca. 50 μm) ionic glass specimens are subjected to laser-induced compressive stress waves and the transmitted response measured interferometrically. Structural changes of the ionic glass due to shock wave impact are characterized by x-ray diffraction. When compared directly to polyurea films of identical thickness and geometry, the ionic glass showed superior shock-wave mitigating performance. ONR MURI program.

  11. Manufacture of large glass honeycomb mirrors. [for astronomical telescopes

    NASA Technical Reports Server (NTRS)

    Angel, J. R. P.; Hill, J. M.

    1982-01-01

    The problem of making very large glass mirrors for astronomical telescopes is examined, and the advantages of honeycomb mirrors made of borosilicate glass are discussed. Thermal gradients in the glass that degrade the figure of thick borosilicate mirrors during use can be largely eliminated in a honeycomb structure by internal ventilation (in air) or careful control of the radiation environment (in space). It is expected that ground-based telescopes with honeycomb mirrors will give better images than those with solid mirrors. Materials, techniques, and the experience that has been gained making trial mirrors and test castings as part of a program to develop 8-10-m-diameter lightweight mirrors are discussed.

  12. Length scales for fragile glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Mountain, Raymond D.

    1995-04-01

    Molecular dynamics simulation results are used to demonstrate the existence of a growing length in supercooled, fragile glass-forming liquids. This length is the longest wavelength, propagating shear wave the fluid can support. Explicit results are reported for an equimolar soft-sphere mixture. A possible connection between this length and the size of locally rigid clusters is discussed.

  13. Undercooling Limits and Thermophysical Properties in Glass Forming Alloys

    NASA Technical Reports Server (NTRS)

    Rhim, Won-Kyu; Ohsaka, Kenichi; Spjut, R. Erik

    1999-01-01

    The primary objective of this program is to produce deeply undercooled metallic liquids and to identify factors that limit undercooling and glass formation. The main research objectives are: (1) Investigating undercooling limits in glass-forming alloys and identifying factors that affect undercooling; (2) Measuring thermophysical properties and investigating the validity of the classical nucleation theory and other existing theories in the extreme undercooled states; and (3) To investigate the limits of electrostatic levitation technology in the ground base and to identify thermophysical parameters that might require reduced-g environment.

  14. Metal and Glass Manufactures Reduce Costs by Increasing Energy Efficiency in Process Heating Systems

    SciTech Connect

    2004-05-01

    Process heating plays a key role in producing steel, aluminum, and glass and in manufacturing products made from these materials. Faced with regulatory and competitive pressures to control emissions and reduce operating costs, metal and glass manufacturers are considering a variety of options for reducing overall energy consumption. As 38% of the energy used in U.S. industrial plants is consumed for process heating applications, metal and glass manufacturers are discovering that process heating technologies provide significant opportunities for improving industrial productivity, energy efficiency, and global competitiveness. This fact sheet is the first in a series to describe such opportunities that can be realized in industrial systems by conducting plant-wide assessments (PWA).

  15. Dynamics of Glass Forming Liquids with Randomly Pinned Particles

    PubMed Central

    Chakrabarty, Saurish; Karmakar, Smarajit; Dasgupta, Chandan

    2015-01-01

    It is frequently assumed that in the limit of vanishing cooling rate, the glass transition phenomenon becomes a thermodynamic transition at a temperature TK. However, with any finite cooling rate, the system falls out of equilibrium at temperatures near Tg(>TK), implying that the very existence of the putative thermodynamic phase transition at TK can be questioned. Recent studies of systems with randomly pinned particles have hinted that the thermodynamic glass transition may be observed for liquids with randomly pinned particles. This expectation is based on the results of approximate calculations that suggest that the thermodynamic glass transition temperature increases with increasing concentration of pinned particles and it may be possible to equilibrate the system at temperatures near the increased transition temperature. We test the validity of this prediction through extensive molecular dynamics simulations of two model glass-forming liquids in the presence of random pinning. We find that extrapolated thermodynamic transition temperature TK does not show any sign of increasing with increasing pinning concentration. The main effect of pinning is found to be a rapid decrease in the kinetic fragility of the system with increasing pin concentration. Implications of these observations for current theories of the glass transition are discussed. PMID:26206070

  16. Comparison of mechanical properties of glass-bonded sodalite and borosilicate glass high-level waste forms

    SciTech Connect

    O'Holleran, T. P.; DiSanto, T.; Johnson, S. G.; Goff, K. M.

    2000-05-09

    Argonne National Laboratory has developed a glass-bonded sodalite waste form to immobilize the salt waste stream from electrometallurgical treatment of spent nuclear fuel. The waste form consists of 75 vol.% crystalline sodalite and 25 vol.% glass. Microindentation fracture toughness measurements were performed on this material and borosilicate glass from the Defense Waste Processing Facility using a Vickers indenter. Palmqvist cracking was confined for the glass-bonded sodalite waste form, while median-radial cracking occurred in the borosilicate glass. The elastic modulus was measured by an acoustic technique. Fracture toughness, microhardness, and elastic modulus values are reported for both waste forms.

  17. Comparison of radiation-induced transmission degradation of borosilicate crown optical glass from four different manufacturers

    NASA Astrophysics Data System (ADS)

    Gusarov, Andrei; Doyle, Dominic; Glebov, Leonid; Berghmans, Francis

    2005-09-01

    Space-born optical systems must be tolerant to radiation to guarantee that the required system performance is maintained during prolonged mission times. The radiation-induced absorption in optical glasses is often related with the presence of impurities, which are, intentionally or not, introduced during the manufacturing process. Glass manufacturers use proprietary fabrication processes and one can expect that the radiation sensitivity of nominally identical optical glasses from different manufacturers is different. We studied the gamma-radiation induced absorption of several crown glasses with nd ≈ 1.516 and vd ≈ 64, i.e. NBK7 (Schott), S-BSL7 (Ohara), BSC 517642 (Pilkington) and K8 (Russia). NBK7 recently replaced the well-known BK7. We therefore also compared the radiation response of NBK7 and BK7 glass. Our results show that whereas the glasses are optically similar before irradiation, they show a different induced absorption after irradiation and also different post-radiation recovery kinetics. Taking these differences into account can help to improve the radiation tolerance of optical systems for space applications.

  18. Medium-range structure and glass forming ability in Zr–Cu–Al bulk metallic glasses

    DOE PAGESBeta

    Zhang, Pei; Maldonis, Jason J.; Besser, M. F.; Kramer, M. J.; Voyles, Paul M.

    2016-03-05

    Fluctuation electron microscopy experiments combined with hybrid reverse Monte Carlo modeling show a correlation between medium-range structure at the nanometer scale and glass forming ability in two Zr–Cu–Al bulk metallic glass (BMG) alloys. Both Zr50Cu35Al15 and Zr50Cu45Al5 exhibit two nanoscale structure types, one icosahedral and the other more crystal-like. In Zr50Cu35Al15, the poorer glass former, the crystal-like structure is more stable under annealing below the glass transition temperature, Tg, than in Zr50Cu45Al5. Variable resolution fluctuation microscopy of the MRO clusters show that in Zr50Cu35Al15 on sub-Tg annealing, the crystal-like clusters shrink even as they grow more ordered, while icosahedral-like clustersmore » grow. Furthermore, the results suggest that achieving better glass forming ability in this alloy system may depend more on destabilizing crystal-like structures than enhancing non-crystalline structures.« less

  19. Will it form a stable glass? How the stability of vapor deposited glasses depends on molecular structure

    NASA Astrophysics Data System (ADS)

    Tylinski, Michael; Beasley, Madeleine; Chua, Yeong Zen; Schick, Christoph; Ediger, Mark

    Over the past nine years physical vapor deposition has been used to prepare molecular glasses with exceptional properties. When heated, transformation of these highly stable glasses takes orders of magnitude longer than the transformation of liquid-cooled glasses. Until recently, it appeared that most organic molecules could form stable glasses when vapor deposited. We test the generality of stable glass formation by vapor-depositing a wide range of small organic molecules, including hydroxyl, carbonyl, phosphate, aromatic, and aliphatic functional groups. When prepared under conditions expected to yield highly stable glasses, we observe glasses with a wide range of kinetic stabilities, depending on the functional groups in the molecule. In general, alcohols and molecules with long aliphatic chains do not form highly stable glasses while aromatic molecules do. We also test the hypothesis that the surface mobility during deposition determines if a molecule is able to create highly stable glasses.

  20. Low sintering temperature glass waste forms for sequestering radioactive iodine

    DOEpatents

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  1. 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.

  2. 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.

  3. Precipitation of nanocrystals in glasses by electron irradiation: An alternative path to form glass ceramics?

    SciTech Connect

    Jiang, N.; Wu, B.; Qiu, J.; Spence, J. C. H.

    2007-04-16

    This letter demonstrates an alternative method to form gallium silicate glass ceramics using high-energy electron irradiation. Compared with glass ceramics obtained from the conventional thermal treatment method, the distribution and crystal sizes of the precipitated Ga{sub 2}O{sub 3} nanoparticles are the same. An advantage of this method is that the spatial distribution of the precipitated nanoparticles can be easily controlled. However, optically active dopants Ni{sup 2+} ions do not participate in the precipitation during electron irradiation.

  4. Advanced manufacturing by spray forming: Aluminum strip and microelectromechanical systems

    SciTech Connect

    McHugh, K.M.

    1994-12-31

    Spray forming is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. By combining rapid solidification processing with product shape control, spray forming can reduce manufacturing costs while improving product quality. INEL is developing a unique spray-forming method based on de Laval (converging/diverging) nozzle designs to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Properties of the spray-formed material are tailored by controlling the characteristics of the spray plume and substrate. Two examples are described: high-volume production of aluminum alloy strip, and the replication of micron-scale features in micropatterned polymers during the production of microelectromechanical systems.

  5. Relaxational Dynamics of a Model Glass-forming Metallic Liquid

    NASA Astrophysics Data System (ADS)

    Jaiswal, Abhishek; O'Keeffe, Stephanie; Podlesnyak, Andrey; Ehlers, Georg; Mills, Rebecca; Lokshin, Konstantin; Dmowski, Wojciech; Egami, Takeshi; Zhang, Yang

    2015-03-01

    Understanding the diffusional behavior of multi-component glass-forming metallic liquids is of critical importance to the development of novel alloy systems such as bulk metallic glasses (BMG). However, such diffusions are highly activated and complicated because of structural disorder induced by quenching, and chemical disorders induced by size mismatch. Herein, we report temperature and wave-vector transfer (Q) dependence of two-step collective relaxations in the BMG (LM601: ZrCuNiAl) melt measured by quasi-elastic neutron scattering. Q-dependence of both fast and slow relaxation time, and the adiabatic sound speed are found to obey the principle of de Gennes narrowing. The measured spectra show a distinct vibrational mode at around 15 meV. Classical Molecular Dynamics (MD) simulation of CuZrAl system, using EAM potential shows that this acoustic mode arises from local vibrations of Al in the cage formed by Cu and Zr atoms. Furthermore, we observed a breakdown of Stokes-Einstein relation in the MD simulated system well above its melting temperature. Accompanied dynamical clustering was detected using unsupervised machine learning techniques. These mechanisms in tandem can be responsible for the excellent glass-forming ability of this material.

  6. Transition from glass to graphite in manufacture of composite aircraft structure

    NASA Technical Reports Server (NTRS)

    Buffum, H. E.; Thompson, V. S.

    1978-01-01

    The transition from fiberglass reinforced plastic composites to graphite reinforced plastic composites is described. Structural fiberglass design and manufacturing background are summarized. How this experience provides a technology base for moving into graphite composite secondary structure and then to composite primary structure is considered. The technical requirements that must be fulfilled in the transition from glass to graphite composite structure are also included.

  7. Dielectric Relaxation of Materials that Form Ultra-Stable Glasses

    NASA Astrophysics Data System (ADS)

    Richert, Ranko

    2015-03-01

    Physical vapor deposition of glass forming materials onto substrates at temperatures around 0.8 Tg produces glasses of high density and low enthalpy. Using interdigitated electrode cells as substrates, such stable glasses can be studied by dielectric spectroscopy in situ. This technique is applied to monitor the dynamics of stable films upon their conversion to the ordinary supercooled liquid state. The dielectric loss during transformation indicates that the softening proceeds by a growth front mechanism and generates the ordinary liquid state without forming intermediates. The same technique is also used to assess the residual dynamics of the stable glassy state. We observe that processes such as the Johari-Goldstein beta relaxation are strongly suppressed in this stable state, consistent with the relatively low fictive temperature of these glassy states. coauthors: Hai-Bin Yu, Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85278; Michael Tylinski, and Mark D. Ediger, Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706.

  8. Theory of specific heat in glass-forming systems.

    PubMed

    Hentschel, H G E; Ilyin, Valery; Procaccia, Itamar; Schupper, Nurith

    2008-12-01

    Experimental measurements of the specific heat in glass-forming systems are obtained from the linear response to either slow cooling (or heating) or to oscillatory perturbations with a given frequency about a constant temperature. The latter method gives rise to a complex specific heat with the constraint that the zero frequency limit of the real part should be identified with thermodynamic measurements. Such measurements reveal anomalies in the temperature dependence of the specific heat, including the so called "specific heat peak" in the vicinity of the glass transition. The aim of this paper is to provide theoretical explanations of these anomalies in general and a quantitative theory in the case of a simple model of glass formation. We first present interesting simulation results for the specific heat in a classical model of a binary mixture glass former. We show that in addition to the formerly observed specific heat peak there is a second peak at lower temperatures which was not observable in earlier simulations. Second, we present a general relation between the specific heat, a caloric quantity, and the bulk modulus of the material, a mechanical quantity, and thus offer a smooth connection between the liquid and amorphous solid states. The central result of this paper is a connection between the micromelting of clusters in the system and the appearance of specific heat peaks; we explain the appearance of two peaks by the micromelting of two types of clusters. We relate the two peaks to changes in the bulk and shear moduli. We propose that the phenomenon of glass formation is accompanied by a fast change in the bulk and the shear moduli, but these fast changes occur in different ranges of the temperature. Last, we demonstrate how to construct a theory of the frequency dependent complex specific heat, expected from heterogeneous clustering in the liquid state of glass formers. A specific example is provided in the context of our model for the dynamics of

  9. Energy Saving Method of Manufacturing Ceramic Products from Fiber Glass Waste

    SciTech Connect

    Michael J. Haun

    2005-07-15

    The U.S. fiber glass industry disposes of more than 260,000 tons of industrial fiber glass waste in landfills annually. New technology is needed to reprocess this industrial waste into useful products. A low-cost energy-saving method of manufacturing ceramic tile from fiber glass waste was developed. The technology is based on sintering fiber glass waste at 700-900 degrees C to produce products which traditionally require firing temperatures of >1200 degrees C, or glass-melting temperatures >1500 degrees C. The process also eliminates other energy intensive processing steps, including mining and transportation of raw materials, spray-drying to produce granulated powder, drying pressed tile, and glazing. The technology completely transforms fiber glass waste into a dense ceramic product, so that all future environmental problems in the handling and disposal of the fibers is eliminated. The processing steps were developed and optimized to produce glossy and matte surface finishes for wall and floor tile applications. High-quality prototype tile samples were processed for demonstration and tile standards testing. A Market Assessment confirmed the market potential for tile products produced by the technology. Manufacturing equipment trials were successfully conducted for each step of the process. An industrial demonstration plant was designed, including equipment and operating cost analysis. A fiber glass manufacturer was selected as an industrial partner to commercialize the technology. A technology development and licensing agreement was completed with the industrial partner. Haun labs will continue working to transfer the technology and assist the industrial partner with commercialization beyond the DOE project.

  10. Are polymers standard glass-forming systems? The role of intramolecular barriers on the glass-transition phenomena of glass-forming polymers

    NASA Astrophysics Data System (ADS)

    Colmenero, J.

    2015-03-01

    Traditionally, polymer melts have been considered archetypal glass-formers. This has been mainly due to the fact that these systems can easily be obtained as glasses by cooling from the melt, even at low cooling rates. However, the macromolecules, i.e. the structural units of polymer systems in general, are rather different from the standard molecules. They are long objects (‘chains’) made by repetition of a given chemical motif (monomer) and have intra-macromolecular barriers that limit their flexibility. The influence of these properties on, for instance, the glass-transition temperature of polymers, is a topic that has been widely studied by the polymer community almost from the early times of polymer science. However, in the framework of the glass-community, the relevant influence of intra-macromolecular barriers and chain connectivity on glass-transition phenomena of polymers has started to be recognized only recently. The aim of this review is to give an overview and to critically revise the results reported on this topic over the last years. From these results, it seems to be evident that there are two different mechanisms involved in the dynamic arrest in glass-forming polymers: (i) the intermolecular packing effects, which dominate the dynamic arrest of low molecular weight glass-forming systems; and (ii) the effect of intra-macromolecular barriers combined with chain connectivity. It has also been shown that the mode coupling theory (MCT) is a suitable theoretical framework to discuss these questions. The values found for polymers for the central MCT parameter—the so-called λ-exponent—are of the order of 0.9, clearly higher than the standard values (λ ≈ 0.7) found in systems where the dynamic arrest is mainly driven by packing effects (‘standard’ glass-formers). Within the MCT, this is a signature of the presence of two competing mechanisms of dynamic arrest, as it has been observed in short-ranged attractive colloids or two component

  11. Are polymers standard glass-forming systems? The role of intramolecular barriers on the glass-transition phenomena of glass-forming polymers.

    PubMed

    Colmenero, J

    2015-03-18

    Traditionally, polymer melts have been considered archetypal glass-formers. This has been mainly due to the fact that these systems can easily be obtained as glasses by cooling from the melt, even at low cooling rates. However, the macromolecules, i.e. the structural units of polymer systems in general, are rather different from the standard molecules. They are long objects ('chains') made by repetition of a given chemical motif (monomer) and have intra-macromolecular barriers that limit their flexibility. The influence of these properties on, for instance, the glass-transition temperature of polymers, is a topic that has been widely studied by the polymer community almost from the early times of polymer science. However, in the framework of the glass-community, the relevant influence of intra-macromolecular barriers and chain connectivity on glass-transition phenomena of polymers has started to be recognized only recently. The aim of this review is to give an overview and to critically revise the results reported on this topic over the last years. From these results, it seems to be evident that there are two different mechanisms involved in the dynamic arrest in glass-forming polymers: (i) the intermolecular packing effects, which dominate the dynamic arrest of low molecular weight glass-forming systems; and (ii) the effect of intra-macromolecular barriers combined with chain connectivity. It has also been shown that the mode coupling theory (MCT) is a suitable theoretical framework to discuss these questions. The values found for polymers for the central MCT parameter--the so-called λ-exponent--are of the order of 0.9, clearly higher than the standard values (λ ≈ 0.7) found in systems where the dynamic arrest is mainly driven by packing effects ('standard' glass-formers). Within the MCT, this is a signature of the presence of two competing mechanisms of dynamic arrest, as it has been observed in short-ranged attractive colloids or two component mixtures with

  12. Design considerations and manufacturing limitations of Insert Precision Glass Molding (IPGM)

    NASA Astrophysics Data System (ADS)

    Symmons, Alan; Auz, Bryan

    2012-10-01

    Precision glass molding (PGM) directly into metallic structures is a process similar to the plastic injection molding process of insert molding, however fundamental differences exist due to the processing temperatures, nature of materials and manufacturing requirements. Despite some limitations, insert precision glass molding (IPGM) extends many benefits to the product designer. IPGM occurs at the glass transition temperature of the glass therefore materials must be matched by their thermal properties so that undue stress is not exerted on the glass during processing or significant inherent stress left in the part after processing. Either of these conditions could lead to cracking, birefringence or failures due to thermal cycling during operation. This paper will discuss the techniques and specific design considerations that must be taken into account when designing for IPGM. Design aspects such as interface diameters, wall thicknesses, aspect ratios and material properties will be analyzed. The optical and mechanical performance and properties of the glass and holder assembly will also be reviewed, including strength of the assembly, quality of the sealing interface (hermeticity), optical to mechanical alignment and impact on optical quality. The review includes both chalcogenide and traditional oxide based moldable glasses.

  13. Ion Dynamics of Glass-Forming Nitrate Melts

    NASA Astrophysics Data System (ADS)

    Kamiyama, T.; Goshi, M.; Nakamura, Y.; Shibata, K.; Suzuki, K.

    We have studied the RbNO3-Sr(NO3)2 and Mg(NO3)2-NaNO3 systems in the regime of normal liquid and supercooled liquid from measurements of some dynamical properties. In the periodic table the difference is only in the sizes of the cations, though the ratio of the cationic radii is nearly equal. It has been found that in these glass-forming systems the monovalent cations are main charge carriers, due to the strong correlation between the divalent cations and the nitrate anions. The long range translational motion of the monovalent cation is correlated with the liquid structural motion.

  14. Microcraters formed in glass by low density projectiles

    NASA Technical Reports Server (NTRS)

    Mandeville, J.-C.; Vedder, J. F.

    1971-01-01

    Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene (p = 1.06 g/cu cm) with masses between 0.7 and 62 picograms and velocities between 2 and 14 km/s. The morphology of the craters depended on the velocity and the angle of incidence of the projectiles and these are discussed in detail. It was found that the transitions in morphology of the craters formed by polystyrene spheres occurred at higher velocities than they did for more dense projectiles.

  15. Microcraters formed in glass by low density projectiles

    NASA Technical Reports Server (NTRS)

    Mandeville, J.-C.; Vedder, J. F.

    1971-01-01

    Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene with masses between 0.7 and 62 picograms and velocities between 2 and 14 kilometers per second. The morphology of the craters depends on the velocity and angle of incidence of the projectiles. The transitions in morphology of the craters formed by polystyrene spheres occur at higher velocities than they do for more dense projectiles. For oblique impact, the craters are elongated and shallow with the spallation threshold occuring at higher velocity. For normal incidence, the total displaced mass of the target material per unit of projectile kinetic energy increases slowly with the energy.

  16. A new Energy Saving method of manufacturing ceramic products from waste glass

    SciTech Connect

    Haun Labs

    2002-07-05

    This final report summarizes the activities of the DOE Inventions and Innovations sponsored project, ''A New Energy Saving Method of Manufacturing Ceramic Products from Waste Glass.'' The project involved an innovative method of lowering energy costs of manufacturing ceramic products by substituting traditional raw materials with waste glass. The processing method is based on sintering of glass powder at {approx}750 C to produce products which traditionally require firing temperatures of >1200 C, or glass-melting temperatures >1500 C. The key to the new method is the elimination of previous processing problems, which have greatly limited the use of recycled glass as a ceramic raw material. The technology is aligned with the DOE-OIT Glass Industry Vision and Roadmap, and offers significant energy savings and environmental benefits compared to current technologies. A U.S. patent (No. 6,340,650) covering the technology was issued on January 22, 2002. An international PCT Patent Application is pending with designations made for all PCT regions and countries. The goal of the project was to provide the basis for the design and construction of an energy-efficient manufacturing plant that can convert large volumes of waste glass into high-quality ceramic tile. The main objectives of the project were to complete process development and optimization; construct and test prototype samples; and conduct market analysis and commercialization planning. Two types of ceramic tile products were targeted by the project. The first type was developed during the first year (Phase I) to have a glazed-like finish for applications where slip resistance is not critical, such as wall tile. The processing method optimized in Phase I produces a glossy surface with a translucent appearance, without the extra glazing steps required in traditional tile manufacturing. The second type of product was developed during the second year (Phase II). This product was designed to have an unglazed appearance

  17. Glass Forming Ability of Sub-Alkaline Silicate Melts

    NASA Astrophysics Data System (ADS)

    Vetere, F. P.; Iezzi, G.; Behrens, H.; Holtz, F.; Ventura, G.; Misiti, V.; Mollo, S.; Perugini, D.

    2014-12-01

    The glass forming ability (GFA) and critical cooling rate (Rc) of six natural sub-alkaline melts from basalt to rhyolite (i.e., B100, B80R20, B60R40, B40R60, B20R80, and R100) have been quantified through cooling-induced solidification experiments of 9000, 1800, 180, 60, 7 and 1 °C/h conducted at ambient pressure and air buffering conditions, in a temperature range between 1300 °C (superliquidus region) and 800 °C (glass transition region), The phase proportion in each run-product was determined by image analysis on about 500 BS-SEM microphotographs. The phase assemblage consists of glass, clinopyroxene, spinel, and plagioclase with the occurrence of sporadic olivine, orthopyroxene and melilite. Both the glass and crystalline fractions are well correlated with the composition of residual melt. Generally, the amount of crystals decreases with increasing cooling rate. However, some exceptions occurs showing no correlations or even opposite trends. For the example of, Al2O3 and CaO in clinopyroxenes from B100, B80R20, B60R40 and B40R60, their concentrations scale as a function of both cooling rate and the degree of clinopyroxene crystallization. The value of Rc changes of 5 order of magnitude from <1 to ~9000 °C/h when the melt composition changes from R100 to B100, respectively. The most important Rc variations are measured between B80R20 and B60R40, levelling off towards B100. This trend scales with NBO/T (non bridging oxygen per tetrahedron) and can be modelled by the following master sigmoid equation: Rc = a / 1+e-(NBO/T-xo/b), where a, b and xo are fitting parameters equal to 9214, 0.040 and 0.297, respectively. Our data can be used to retrieve the solidification conditions of aphyric, degassed and oxidised lavas. Indeed, the relationship between crystal content and cooling kinetics suggests that the solidification path is more complex than previously assumed and strongly non-linear. This finding has also implications to design glass-ceramics based on natural

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  19. Characteristic free volumes of bulk metallic glasses: Measurement and their correlation with glass-forming ability

    SciTech Connect

    Hu Qiang; Zeng Xierong; Fu, M. W.

    2011-03-01

    A convenient method is proposed for the measurement of the characteristic free volumes, viz., the amount of excess free volume annihilation in structural relaxation V{sub f-sr} and the amount of new free volume production in glass transition V{sub f-gt} of bulk metallic glasses (BMGs) by thermal dilation (DIL) test. Through the DIL tests, the characteristic free volumes are found to be sensitive to the change of glass forming ability (GFA). The Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} BMG has a quite small V{sub f-sr}. For a series of Fe-Cr-Mo-C-B-(Er) BMGs, Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 2} with the largest GFA is identified to have the largest V{sub f-gt} and smallest V{sub f-sr}. The correlation between V{sub f-sr} and the squares of critical diameters of these iron-based BMGs can be fitted as a negative exponential function with high accuracy.

  20. Fragility correlates thermodynamic and kinetic properties of glass forming liquids

    SciTech Connect

    Reddy, C.Narayana; Viswanatha, R.; Chethana, B.K.; Gowda, V.C.Veeranna; Rao, K.J.

    2015-03-15

    Graphical abstract: The suggested new fragility parameter correlates viscosity and configurational entropy. - Highlights: • A new fragility function, F=ΔT/ΔC{sub p}×C{sub p}{sup l}/T{sub g} has been proposed. • A three parameter viscosity function using the new F reproduces Angell fragility plot. • A new ΔC{sub p} function is derived which directly relates Adam–Gibbs function with the fragility based viscosity function. - Abstract: In our earlier communication we proposed a simple fragility determining function, ([NBO]/V{sub m}{sup 3}T{sub g}), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, ΔC{sub p}/C{sub p}{sup l}, introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both ΔC{sub p} and ΔT and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters ΔC{sub p}, C{sub p}{sup l}, T{sub g} and T{sub m}. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam–Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the ΔC{sub p} versus ln(T{sub r}) curves and hence the configurational entropy.

  1. Consolidated waste forms: glass marbles and ceramic pellets

    SciTech Connect

    Treat, R.L.; Rusin, J.M.

    1982-05-01

    Glass marbles and ceramic pellets have been developed at Pacific Northwest Laboratory as part of the multibarrier concept for immobilizing high-level radioactive waste. These consolidated waste forms served as substrates for the application of various inert coatings and as ideal-sized particles for encapsulation in protective matrices. Marble and pellet formulations were based on existing defense wastes at Savannah River Plant and proposed commercial wastes. To produce marbles, glass is poured from a melter in a continuous stream into a marble-making device. Marbles were produced at PNL on a vibratory marble machine at rates as high as 60 kg/h. Other marble-making concepts were also investigated. The marble process, including a lead-encapsulation step, was judged as one of the more feasible processes for immobilizing high-level wastes. To produce ceramic pellets, a series of processing steps are required, which include: spray calcining - to dry liquid wastes to a powder; disc pelletizing - to convert waste powders to spherical pellets; sintering - to densify pellets and cause desired crystal formation. These processing steps are quite complex, and thereby render the ceramic pellet process as one of the least feasible processes for immobilizing high-level wastes.

  2. Configurational entropy of glass-forming systems from graph isomorphism

    NASA Astrophysics Data System (ADS)

    Zhou, Yuxing; Milner, Scott

    The configurational entropy plays a central role in the thermodynamic scenarios of glass transition, such as Adam-Gibbs theory and random first-order transition theory. By definition, the configurational entropy Sc is the difference between the entropy of liquid and the vibrational entropy with structural rearrangement restricted, both of which can be obtained by means of thermodynamic integration. On the other hand, Sc is essentially a measure of the number of basins in the energy landscape, and therefore it can also be estimated by explicitly enumerating inherent structures. To this end, we first coarse-grain the vibrational motions by mapping configurations to Voronoi diagrams and then categorize them using canonical labelling. The Voronoi graph entropy is calculated as SG /kB = - ∑pi log (pi) , where pi is the probability of finding distinct graph i. We find for an n-particle subsystem of glass-forming hard-disk/sphere fluids, SG (n) scales linearly with n, and Sc can be estimated from the slope.

  3. Spectral, electrochemical and thermal characteristics of glass forming hydrazine derivatives

    NASA Astrophysics Data System (ADS)

    Bijak, Katarzyna; Sek, Danuta; Siwy, Mariola; Grucela-Zajac, Marzena; Janeczek, Henryk; Wiacek, Malgorzata; Malecki, Grzegorz; Schab-Balcerzak, Ewa

    2014-11-01

    The azines being condensation products of benzophenone hydrazone with triphenylamine substituted with different numbers of aldehyde groups and also with terephthaldicarboxaldehyde were prepared. Their spectral, thermal and electronic properties that is, orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT) and estimated by electrochemical measurements were explored. The prepared hydrazine derivatives exhibited glass-forming properties with glass-transition temperatures in the range of 10-98 °C and high thermal stability with decomposition temperatures placed between 231 and 337 °C. The photoluminescence (PL) studies showed that all investigated compounds both in solid state as blends with PMMA and in NMP solution emitted blue light, however, with different intensity. Relative PL intensity of azines was investigated in NMP in relation to rhodamine-B used as a standard. Moreover, the stability of azines during doping with acid and ferric chloride was spectroscopically demonstrated via repeated doping/dedoping in solution and in film. All compounds are electrochemically active. Depend on chemical structure of azines they undergo reversible or irreversible electrochemical oxidation and reduction processes. The LUMO levels were found in the range from -2.66 to -3.0 eV. They exhibited energy band gap (Eg) estimated electrochemically from 2.57 to 3.22 eV.

  4. Molecular cooperativity in the dynamics of glass-forming systems

    NASA Astrophysics Data System (ADS)

    Hong, Liang; Gujrati, Purushottam; Novikov, Vladimier; Sokolov, Alexei

    2010-03-01

    The mechanism behind the sharp slowing down of the main structural relaxation in a glass-forming liquid upon approaching the glass transition remains a great puzzle. Most of the theories relate this mechanism to the cooperativity in molecular motion. On the other hand, the collective vibration in the pico-second time region, the so-called boson peak, is also described as a cooperative process. In our recent work (L. Hong, et al., J. Chem. Phys., in print), we demonstrated that the collective vibrations and the main structural relaxation involve a similar length scale of cooperative molecular motions. More importantly, we found that the cooperativity length scale in different materials directly correlates to only one part of the mechanism of slowing down the structural relaxation, i.e., the dependence of the structural relaxation on volume. In this presentation, we will further demonstrate that this correlation holds true not only for different chemical species, but also for the same chemical specie with different molecular weight or under pressure. The results are compared to predictions of theoretical models.

  5. Glass transition temperature and topological constraints of sodium borophosphate glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Jiang, Qi; Zeng, Huidan; Liu, Zhao; Ren, Jing; Chen, Guorong; Wang, Zhaofeng; Sun, Luyi; Zhao, Donghui

    2013-09-01

    Sodium borophosphate glasses exhibit intriguing mixed network former effect, with the nonlinear compositional dependence of their glass transition temperature as one of the most typical examples. In this paper, we establish the widely applicable topological constraint model of sodium borophosphate mixed network former glasses to explain the relationship between the internal structure and nonlinear changes of glass transition temperature. The application of glass topology network was discussed in detail in terms of the unified methodology for the quantitative distribution of each coordinated boron and phosphorus units and glass transition temperature dependence of atomic constraints. An accurate prediction of composition scaling of the glass transition temperature was obtained based on topological constraint model.

  6. Heterogeneous nucleation in a glass-forming alloy

    NASA Astrophysics Data System (ADS)

    Wall, J. J.; Liu, C. T.; Rhim, W.-K.; Li, J. J. Z.; Liaw, P. K.; Choo, H.; Johnson, W. L.

    2008-06-01

    Nucleation in the undercooled liquid state in the bulk metallic glass-forming composition Zr52.5Cu17.9Ni14.6Al10Ti5 (VIT-105), produced using high purity (PA) and commercial purity (CA) raw materials was investigated using electrostatic levitation and ex situ neutron diffraction. The CA material was observed to have a lower density than the PA sample and crystallized at relatively shallow undercooling. The densities of the samples at temperatures above the solidus showed an oxygen-dependent hysteresis associated with the state change, indicating the presence of oxygen-stabilized intermetallics. The PA alloy exhibited three distinct crystallization modes dependent on the thermal history of the melt, one of which showed a net volume expansion.

  7. Structural disorder in metallic glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Pan, Shao-Peng; Feng, Shi-Dong; Wang, Li-Min; Qiao, Jun-Wei; Niu, Xiao-Feng; Dong, Bang-Shao; Wang, Wei-Min; Qin, Jing-Yu

    2016-06-01

    We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be directly correlated with potential energy and structural relaxation at the atomic level. Some straightforward relationships between QNA and other properties (per-atom potential energy and α-relaxation time) are introduced to reflect structure-property relationship in metallic liquids. We believe that the new structural parameter can well reflect structure disorder in metallic liquids and play an important role in understanding various properties in metallic liquids.

  8. Structural disorder in metallic glass-forming liquids

    PubMed Central

    Pan, Shao-Peng; Feng, Shi-Dong; Wang, Li-Min; Qiao, Jun-Wei; Niu, Xiao-Feng; Dong, Bang-Shao; Wang, Wei-Min; Qin, Jing-Yu

    2016-01-01

    We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be directly correlated with potential energy and structural relaxation at the atomic level. Some straightforward relationships between QNA and other properties (per-atom potential energy and α-relaxation time) are introduced to reflect structure-property relationship in metallic liquids. We believe that the new structural parameter can well reflect structure disorder in metallic liquids and play an important role in understanding various properties in metallic liquids. PMID:27278113

  9. Structural disorder in metallic glass-forming liquids.

    PubMed

    Pan, Shao-Peng; Feng, Shi-Dong; Wang, Li-Min; Qiao, Jun-Wei; Niu, Xiao-Feng; Dong, Bang-Shao; Wang, Wei-Min; Qin, Jing-Yu

    2016-01-01

    We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be directly correlated with potential energy and structural relaxation at the atomic level. Some straightforward relationships between QNA and other properties (per-atom potential energy and α-relaxation time) are introduced to reflect structure-property relationship in metallic liquids. We believe that the new structural parameter can well reflect structure disorder in metallic liquids and play an important role in understanding various properties in metallic liquids. PMID:27278113

  10. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    SciTech Connect

    Lan, Si; Wei, Xiaoya; Wu, Xuelian; Wang, Xun-Li; Zhou, Jie; Lu, Zhaoping; Feygenson, Mikhail; Neuefeind, Jörg

    2014-11-17

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr{sub 56}Cu{sub 36}Al{sub 8}, an average glass former, follows continuous nucleation and growth, while that of Zr{sub 46}Cu{sub 46}Al{sub 8}, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  11. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    DOE PAGESBeta

    Lan, Si; Wei, Xiaoya; Zhou, Jie; Lu, Zhaoping; Wu, Xuelian; Feygenson, Mikhail; Neuefeind, Jorg C.; Wang, Xun-Li

    2014-11-18

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr56Cu36Al8, an average glass former, follows continuous nucleation and growth, while that of Zr46Cu46Al8, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  12. 19 CFR 146.52 - Manipulation, manufacture, exhibition or destruction; Customs Form 216.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 19 Customs Duties 2 2013-04-01 2013-04-01 false Manipulation, manufacture, exhibition or... Merchandise in a Zone § 146.52 Manipulation, manufacture, exhibition or destruction; Customs Form 216. (a... application) on Customs Form 216 for permission to manipulate, manufacture, exhibit, or destroy merchandise...

  13. 19 CFR 146.52 - Manipulation, manufacture, exhibition or destruction; Customs Form 216.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 19 Customs Duties 2 2011-04-01 2011-04-01 false Manipulation, manufacture, exhibition or... Merchandise in a Zone § 146.52 Manipulation, manufacture, exhibition or destruction; Customs Form 216. (a... application) on Customs Form 216 for permission to manipulate, manufacture, exhibit, or destroy merchandise...

  14. 19 CFR 146.52 - Manipulation, manufacture, exhibition or destruction; Customs Form 216.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Manipulation, manufacture, exhibition or... Merchandise in a Zone § 146.52 Manipulation, manufacture, exhibition or destruction; Customs Form 216. (a... application) on Customs Form 216 for permission to manipulate, manufacture, exhibit, or destroy merchandise...

  15. 19 CFR 146.52 - Manipulation, manufacture, exhibition or destruction; Customs Form 216.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 19 Customs Duties 2 2012-04-01 2012-04-01 false Manipulation, manufacture, exhibition or... Merchandise in a Zone § 146.52 Manipulation, manufacture, exhibition or destruction; Customs Form 216. (a... application) on Customs Form 216 for permission to manipulate, manufacture, exhibit, or destroy merchandise...

  16. 19 CFR 146.52 - Manipulation, manufacture, exhibition or destruction; Customs Form 216.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 19 Customs Duties 2 2014-04-01 2014-04-01 false Manipulation, manufacture, exhibition or... Merchandise in a Zone § 146.52 Manipulation, manufacture, exhibition or destruction; Customs Form 216. (a... application) on Customs Form 216 for permission to manipulate, manufacture, exhibit, or destroy merchandise...

  17. Temperature accelerated dynamics in glass-forming materials.

    PubMed

    Tsalikis, Dimitrios G; Lempesis, Nikolaos; Boulougouris, Georgios C; Theodorou, Doros N

    2010-06-17

    In this work we propose a methodology for improving dynamical sampling in molecular simulations via temperature acceleration. The proposed approach combines the novel methods of Voter for temperature-accelerated dynamics with the multiple histogram reweighting method of Ferrenberg and Swendsen, its dynamical extension by Nieto-Draghi et al., and with hazard plot analysis, allowing optimal sampling with small computational cost over time scales inaccessible to classical molecular dynamics simulations by utilizing the "inherent structure" idea. The time evolution of the system is viewed as a succession of transitions between "basins" in its potential energy landscape, each basin containing a local minimum of the energy (inherent structure). Applying the proposed algorithm to a glass-forming material consisting of a mixture of spherical atoms interacting via Lennard-Jones potentials, we show that it is possible to perform an exhaustive search and evaluate rate constants for basin-to-basin transitions that cover several orders of magnitude on the time scale, far beyond the abilities of any competitive dynamical study, revealing an extreme ruggedness of the potential energy landscape in the vicinity of the glass transition temperature. By analyzing the network of inherent structures, we find that there are characteristic distances and rate constants related to the dynamical entrapment of the system in a neighborhood of basins (a metabasin), whereas evidence to support a random energy model is provided. The multidimensional configurational space displays a self-similar character depicted by a fractal dimension around 2.7 (+/-0.5) for the set of sampled inherent structures. Only transitions with small Euclidean measure can be considered as localized. PMID:20491458

  18. Waste vitrification: prediction of acceptable compositions in a lime-soda-silica glass-forming system

    SciTech Connect

    Gilliam, T.M.; Jantzen, C.M.

    1996-10-01

    A model is presented based upon calculated bridging oxygens which allows the prediction of the region of acceptable glass compositions for a lime-soda-silica glass-forming system containing mixed waste. The model can be used to guide glass formulation studies (e.g., treatability studies) or assess the applicability of vitrification to candidate waste streams.

  19. Free-form glass reflectors for non-trivial illumination applications with extended sources

    NASA Astrophysics Data System (ADS)

    Heßling, Thomas; Geyer, Ulf; Hellwig, Ansgar; Hübner, Marc C.

    2012-10-01

    The field of illumination optics has an increasing demand for free-form optics that produce arbitrary light distributions. In various applications an asymmetric, e.g. rectangular illumination can be beneficial, such as street lights, shop lights or architectural lighting. Yet there are only very few construction methods for free-form surfaces, especially using extended sources. One such method utilizes a manifold of conic sections to derive a source-target mapping for a particular source and target distribution. Although it relies on the assumption of a point source it can be adapted to work with real, extended sources. We implemented the algorithm to construct glass reflectors for almost arbitrary light distributions, either prescribed in the near- or far-field. Starting with a point source, an initial surface is optimized in a second process with a feedback loop to produce the desired result with the actual extended source. Our method is quite robust and was used to design for example an asymmetrical street light reflector. It was manufactured at Auer Lighting GmbH out of borosilicate glass. Measured target distributions are in excellent agreement with the simulations. These promising results show that this particular design method can be applied to real world applications. It is a powerful tool whenever a highly optimized reflector for a non-trivial illumination is required.

  20. Development of thermally formed glass optics for astronomical hard X-ray telescopes.

    PubMed

    Craig, W; Hailey, C; Jimenez-Garate, M; Windt, D; Harrison, F; Mao, P; Christensen, F; Hussain, A

    2000-08-14

    The next major observational advance in hard X-ray/soft gamma-ray astrophysics will come with the implementation of telescopes capable of focusing 10-200 keV radiation. Focusing allows high signal-to-noise imaging and spectroscopic observations of many sources in this band for the first time. The recent development of depth-graded multilayer coatings has made the design of telescopes for this bandpass practical, however the ability to manufacture inexpensive substrates with appropriate surface quality and figure to achieve sub-arcminute performance has remained an elusive goal. In this paper, we report on new, thermally-formed glass micro-sheet optics capable of meeting the requirements of the next-generation of astronomical hard X-ray telescopes. PMID:19407863

  1. Highly conductive electrolyte composites containing glass and ceramic, and method of manufacture

    DOEpatents

    Hash, M.C.; Bloom, I.D.

    1992-10-13

    An electrolyte composite is manufactured by pressurizing a mixture of sodium ion conductive glass and an ionically conductive compound at between 12,000 and 24,000 pounds per square inch to produce a pellet. The resulting pellet is then sintered at relatively lower temperatures (800--1200 C), for example 1000 C, than are typically required (1400 C) when fabricating single constituent ceramic electrolytes. The resultant composite is 100 percent conductive at 250 C with conductivity values of 2.5 to 4[times]10[sup [minus]2](ohm-cm)[sup [minus]1]. The matrix exhibits chemical stability against sodium for 100 hours at 250 to 300 C. 1 figure.

  2. Analysis of Glass-Filled Nylon in Laser Powder Bed Fusion Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Slotwinski, John; LaBarre, Erin; Forrest, Ryan; Crane, Emily

    2016-03-01

    At the Johns Hopkins University Applied Physics Laboratory (APL), glass bead-filled polyamide (a.k.a. nylon) (GFN) is being used frequently for functional parts and systems, built using a laser-based powder bed fusion (PBF) additive manufacturing (AM) system. Since these parts have performance requirements, it is important to understand the mechanical properties of the additively-made GFN as a function of build orientation and build parameters. In addition, the performance of the AM system used to manufacture these parts must be evaluated in order to understand its capabilities, especially in order to determine the dimensional precision and repeatability of features built with this system. This paper summarizes recent APL efforts to characterize the GFN powder, the mechanical properties of parts made with GFN, and the performance of the laser PBF machine while running GFN using an AM test artifact.

  3. Fast dynamics in glass forming systems: Vibrations vs relaxation

    SciTech Connect

    Sokolov, A.P.

    1997-12-31

    Two contributions specific for the spectra of the fast dynamics in glass forming systems, a broad quasielastic scattering and the boson peak, are analyzed. It is shown that the vibrational contribution (the boson peak) decreases strongly in fragile systems. Some speculations about dependence of the degree of fragility (a la Angell) on peculiarity of the spectrum of fast dynamics are presented. The existence of some intrinsic relation between the broad quasielastic contribution and the boson peak is demonstrated from analysis of the recent neutron and Raman scattering data. It is shown that this relation can be explained in framework of the model of damped oscillator. The model ascribes the quasielastic contribution to the scattering of light or neutrons on the vibrations around the boson peak, which are damped by some relaxation channel and have a quasielastic part in their response function. It is demonstrated that the model can explain many peculiar properties of the fast dynamics in the Raman, neutron and far-infrared absorption spectra.

  4. Cooperative Molecular Motion in Glass-Forming Liquids

    NASA Astrophysics Data System (ADS)

    Donati, C.; Douglas, J. F.; Glotzer, S. C.

    1998-03-01

    The slowing down of dynamics as a liquid cools was explained by Adam and Gibbs as arising from cooperative molecular motion. Specifically, they proposed that significant motion by molecules in a dense fluid could only occur if the molecules rearranged their positions in a cooperative manner. However, this type of collective motion has not yet been detected experimentally in glass-forming liquids, and has only recently been shown in molecular dynamics simulations [1]. Using extensive molecular dynamics simulations, we have investigated several supercooled liquids [1-3] ([1] C. Donati, J.F. Douglas, W. Kob, S.J. Plimpton, P.H. Poole and S.C. Glotzer, preprints; [2] Glotzer, Donati, Sciortino, unpublished; [3] Donati, Mountain, Glotzer, unpublished.) to determine the nature of the collective particle motion, and to test whether cooperative molecular motion may be a mechanism for dynamical heterogenity. In the case of a binary LJ mixture [1] we find that the most mobile molecules in this dynamically heterogeneous, supercooled liquid move cooperatively in string-like structures (``strings'') whose mean length and radius of gyration increase as the liquid is cooled. We discuss our results in the context of the Adam-Gibbs picture and other models.

  5. Kinetics of Nucleation and Crystal Growth in Glass Forming Melts in Microgravity

    NASA Technical Reports Server (NTRS)

    Day, Delbert E.; Ray, Chandra S.

    1999-01-01

    The following list summarizes the most important results that have been consistently reported for glass forming melts in microgravity: (1) Glass formation is enhanced for melts prepared in space; (2) Glasses prepared in microgravity are more chemically homogeneous and contain fewer and smaller chemically heterogeneous regions than identical glasses prepared on earth; (3) Heterogeneities that are deliberately introduced such as Pt particles are more uniformly distributed in a glass melted in space than in a glass melted on earth; (4) Glasses prepared in microgravity are more resistant to crystallization and have a higher mechanical strength and threshold energy for radiation damage; and (5) Glasses crystallized in space have a different microstructure, finer grains more uniformly distributed, than equivalent samples crystallized on earth. The preceding results are not only scientifically interesting, but they have considerable practical implications. These results suggest that the microgravity environment is advantageous for developing new and improved glasses and glass-ceramics that are difficult to prepare on earth. However, there is no suitable explanation at this time for why a glass melted in microgravity will be more chemically homogeneous and more resistant to crystallization than a glass melted on earth. A fundamental investigation of melt homogenization, nucleation, and crystal growth processes in glass forming melts in microgravity is important to understanding these consistently observed, but yet unexplained results. This is the objective of the present research. A lithium disilicate (Li2O.2SiO2) glass will be used for this investigation, since it is a well studied system, and the relevant thermodynamic and kinetic parameters for nucleation and crystal growth at 1-g are available. The results from this research are expected to improve our present understanding of the fundamental mechanism of nucleation and crystal growth in melts and liquids, and to lead

  6. Structure of Glass-Forming Melts - Lanthanide in Borosilicates

    SciTech Connect

    Li, Hong; Li, Liyu; Qian, Morris; Strachan, Denis M.; Wang, Zheming

    2004-05-17

    Over the past few years, we studied several complex Na2O-Al2O3-B2O3-SiO2 glass systems to answer key questions: effects of melt chemistry on solubility of lanthanide oxides; lanthanide solution behavior, and intermediate-range ordering in the melts. This paper summarizes our currently understanding on rare earth elements in borosilicate glasses, covering solution behavior, solubility limits, crystalization and phase separation.

  7. Kinetics of phase transformations in glass forming systems

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.

    1994-01-01

    A nucleation rate like curve for a glass can be determined from the functional dependence of the maximum height of its DTA crystallization peak, (delta T)(sub p), on the nucleation temperature, T(sub n). This nucleation rate curve provides information for the temperature range where nucleation for the glass can occur and the temperature where the nucleation rate is a maximum. However, this curve does not provide information for the nucleation rate, I, for the glass at different temperatures. A method for estimating I at different temperatures from (delta T)(sub p) was developed using a Li2O.2SiO2 (LS2) glass. Also, the dielectric constant (epsilon) and the loss factor (tan delta) of a glass-ceramic depend, in part, upon the amount of crystallinity which, in turn, depends upon the nucleation density in the starting glass. It is therefore expected that epsilon and tan delta should have a relationship with nucleation density and hence on the nucleation rate.

  8. Non-equilibrium dynamics of glass-forming liquid mixtures

    NASA Astrophysics Data System (ADS)

    Sánchez-Díaz, Luis Enrique; Lázaro-Lázaro, Edilio; Olais-Govea, José Manuel; Medina-Noyola, Magdaleno

    2014-06-01

    The non-equilibrium self-consistent generalized Langevin equation theory of irreversible processes in glass-forming liquids [P. Ramírez-González and M. Medina-Noyola, Phys. Rev. E 82, 061503 (2010)] is extended here to multi-component systems. The resulting theory describes the statistical properties of the instantaneous local particle concentration profiles nα(r, t) of species α in terms of the coupled time-evolution equations for the mean value overline{n}_α ({r},t) and for the covariance σ _{α β }({r},{r}^' };t)equiv overline{δ n_α ({r},t)δ n_β ({r}^' },t)} of the fluctuations δ n_α ({r},t) = n_α ({r},t)- overline{n}_α ({r},t). As in the monocomponent case, these two coarse-grained equations involve a local mobility function bα(r, t) for each species, written in terms of the memory function of the two-time correlation function C_{α β }({r},{r}^' };t,t^' }) equiv overline{δ n_α ({r},t)δ n_β ({r}^' },t^' })}. If the system is constrained to remain spatially uniform and subjected to a non-equilibrium preparation protocol described by a given temperature and composition change program T(t) and overline{n}_α (t), these equations predict the irreversible structural relaxation of the partial static structure factors Sαβ(k; t) and of the (collective and self) intermediate scattering functions Fαβ(k, τ; t) and F^S_{α β }(k,τ ;t). We illustrate the applicability of the resulting theory with two examples involving simple model mixtures subjected to an instantaneous temperature quench: an electroneutral binary mixture of equally sized and oppositely charged hard-spheres, and a binary mixture of soft-spheres of moderate size-asymmetry.

  9. Spinel dissolution via addition of glass forming chemicals. Results of preliminary experiments

    SciTech Connect

    Fox, K. M.; Johnson, F. C.

    2015-11-01

    Increased loading of high level waste in glass can lead to crystallization within the glass. Some crystalline species, such as spinel, have no practical impact on the chemical durability of the glass, and therefore may be acceptable from both a processing and a product performance standpoint. In order to operate a melter with a controlled amount of crystallization, options must be developed for remediating an unacceptable accumulation of crystals. This report describes preliminary experiments designed to evaluate the ability to dissolve spinel crystals in simulated waste glass melts via the addition of glass forming chemicals (GFCs).

  10. Verification of plunger cooling for glass forming in real working mode

    NASA Astrophysics Data System (ADS)

    Starý, Michal; Salač, Petr

    2012-04-01

    The article presents results of experimental verification of plunger watercooling for glass forming in a working cycle which has been set by a real working mode. Results have been submitted in the form of confrontation of the temperature distributions across classical and optimized plunger surfaces. During the experiment, the glass was replaced by a tin bath.

  11. Glass Ceramic Waste Forms for Combined CS+LN+TM Fission Products Waste Streams

    SciTech Connect

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna; Sickafus, Kurt E.

    2010-09-23

    In this study, glass ceramics were explored as an alternative waste form for glass, the current baseline, to be used for immobilizing alkaline/alkaline earth + lanthanide (CS+LN) or CS+LN+transition metal (TM) fission-product waste streams generated by a uranium extraction (UREX+) aqueous separations type process. Results from past work on a glass waste form for the combined CS+LN waste streams showed that as waste loading increased, large fractions of crystalline phases precipitated upon slow cooling.[1] The crystalline phases had no noticeable impact on the waste form performance by the 7-day product consistency test (PCT). These results point towards the development of a glass ceramic waste form for treating CS+LN or CS+LN+TM combined waste streams. Three main benefits for exploring glass ceramics are: (1) Glass ceramics offer increased solubility of troublesome components in crystalline phases as compared to glass, leading to increased waste loading; (2) The crystalline network formed in the glass ceramic results in higher heat tolerance than glass; and (3) These glass ceramics are designed to be processed by the same melter technology as the current baseline glass waste form. It will only require adding controlled canister cooling for crystallization into a glass ceramic waste form. Highly annealed waste form (essentially crack free) with up to 50X lower surface area than a typical High-Level Waste (HLW) glass canister. Lower surface area translates directly into increased durability. This was the first full year of exploring glass ceramics for the Option 1 and 2 combined waste stream options. This work has shown that dramatic increases in waste loading are achievable by designing a glass ceramic waste form as an alternative to glass. Table S1 shows the upper limits for heat, waste loading (based on solubility), and the decay time needed before treatment can occur for glass and glass ceramic waste forms. The improvements are significant for both combined waste

  12. Preparation, glass forming ability, crystallization and deformation of (zirconium, hafnium)-copper-nickel-aluminum-titanium-based bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Gu, Xiaofeng

    Multicomponent Zr-based bulk metallic glasses are the most promising metallic glass forming systems. They exhibit great glass forming ability and fascinating mechanical properties, and thus are considered as potential structural materials. One potential application is that they could be replacements of the depleted uranium for making kinetic energy armor-piercing projectiles, but the density of existing Zr-based alloys is too low for this application. Based on the chemical and crystallographic similarities between Zr and Hf, we have developed two series of bulk metallic glasses with compositions of (HfxZr1-x) 52.5Cu17.9Ni14.6Al10Ti5 and (HfxZr1-x) 57Cu20Ni8Al10Ti5 ( x = 0--1) by gradually replacing Zr by Hf. Remarkably increased density and improved mechanical properties have been achieved in these alloys. In these glasses, Hf and Zr play an interchangeable role in determining the short range order. Although the glass forming ability decreases continuously with Hf addition, most of these alloys remain bulk glass-forming. Recently, nanocomposites produced from bulk metallic glasses have attracted wide attention due to improved mechanical properties. However, their crystalline microstructure (the grain size and the crystalline volume fraction) has to be optimized. We have investigated crystallization of (Zr, Hf)-based bulk metallic glasses, including the composition dependence of crystallization paths and crystallization mechanisms. Our results indicate that the formation of high number density nanocomposites from bulk metallic glasses can be attributed to easy nucleation and slowing-down growth processes, while the multistage crystallization behavior makes it more convenient to control the microstructure evolution. Metallic glasses are known to exhibit unique plastic deformation behavior. At low temperature and high stress, plastic flow is localized in narrow shear bands. Macroscopic investigations of shear bands (e.g., chemical etching) suggest that the internal

  13. Determination of different valence forms of cerium in glasses using potentiometric titration

    SciTech Connect

    Chesnokova, S.M.; Danilova, I.Yu.; Andreev, P.A.

    1987-09-01

    This paper describes a potentiometric method for the quantitative determination of two cerium oxide forms--cerium dioxide and dicerium trioxide--in glasses where the oxides form a major constituent. The method uses hydroquinone as a reducing agent. Cerium valences are also determined. The sensitivity of the method is tested by analyzing known synthetic mixtures simulating the composition of the glasses. The method has been used to determine the total concentration of cerium and to monitor the redox regime in glass melting furnaces during the melting of cerium-containing glasses.

  14. 46 CFR 54.10-25 - Manufacturers' data report forms (modifies UG-120).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... ENGINEERING PRESSURE VESSELS Inspection, Reports, and Stamping § 54.10-25 Manufacturers' data report forms... completed in duplicate and certified by the manufacturer for each pressure vessel required to be shop.... (b) Data forms for those parts of a pressure vessel requiring inspection, which are furnished...

  15. 46 CFR 54.10-25 - Manufacturers' data report forms (modifies UG-120).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... ENGINEERING PRESSURE VESSELS Inspection, Reports, and Stamping § 54.10-25 Manufacturers' data report forms... completed in duplicate and certified by the manufacturer for each pressure vessel required to be shop.... (b) Data forms for those parts of a pressure vessel requiring inspection, which are furnished...

  16. Direct hot slumping and accurate integration process to manufacture prototypal x-ray optical units made of glass

    NASA Astrophysics Data System (ADS)

    Civitani, M.; Ghigo, M.; Basso, S.; Proserpio, L.; Spiga, D.; Salmaso, B.; Pareschi, G.; Tagliaferri, G.; Burwitz, V.; Hartner, G.; Menz, B.; Bavdaz, M.; Wille, E.

    2013-09-01

    X-ray telescopes with very large collecting area, like the proposed International X-ray Observatory (IXO, with around 3 m2 at 1 keV), need to be composed of a large number high quality mirror segments, aiming at achieving an angular resolution better than 5 arcsec HEW (Half-Energy-Width). A possible technology to manufacture the modular elements that will compose the entire optical module, named X-ray Optical Units (XOUs), consists of stacking in Wolter-I configuration several layers of thin foils of borosilicate glass, previously formed by hot slumping. The XOUs are subsequently assembled to form complete multi-shell optics with Wolter-I geometry. The achievable global angular resolution of the optic relies on the required surface shape accuracy of slumped foils, on the smoothness of the mirror surfaces and on the correct integration and co-alignment of the mirror segments. The Brera Astronomical Observatory (INAF-OAB) is leading a study, supported by ESA, concerning the implementation of the IXO telescopes based on thin slumped glass foils. In addition to the opto-mechanical design, the study foresees the development of a direct hot slumping thin glass foils production technology. Moreover, an innovative assembly concept making use of Wolter-I counter-form moulds and glass reinforcing ribs is under development. The ribs connect pairs of consecutive foils in an XOU stack, playing a structural and a functional role. In fact, as the ribs constrain the foil profile to the correct shape during the bonding, they damp the low-frequency profile errors still present on the foil after slumping. A dedicated semirobotic Integration MAchine (IMA) has been realized to this scope and used to build a few integrated prototypes made of several layers of slumped plates. In this paper we provide an overview of the project, we report the results achieved so far, including full illumination intra-focus X-ray tests of the last integrated prototype that are compliant with a HEW of

  17. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    SciTech Connect

    Lan, Si; Wei, Xiaoya; Zhou, Jie; Lu, Zhaoping; Wu, Xuelian; Feygenson, Mikhail; Neuefeind, Jorg C.; Wang, Xun-Li

    2014-11-18

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr56Cu36Al8, an average glass former, follows continuous nucleation and growth, while that of Zr46Cu46Al8, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  18. Non-equilibrium dynamics of glass-forming liquid mixtures

    SciTech Connect

    Sánchez-Díaz, Luis Enrique; Lázaro-Lázaro, Edilio; Olais-Govea, José Manuel; Medina-Noyola, Magdaleno

    2014-06-21

    The non-equilibrium self-consistent generalized Langevin equation theory of irreversible processes in glass-forming liquids [P. Ramírez-González and M. Medina-Noyola, Phys. Rev. E 82, 061503 (2010)] is extended here to multi-component systems. The resulting theory describes the statistical properties of the instantaneous local particle concentration profiles n{sub α}(r, t) of species α in terms of the coupled time-evolution equations for the mean value n{sup ¯}{sub α}(r,t) and for the covariance σ{sub αβ}(r,r{sup ′};t)≡δn{sub α}(r,t)δn{sub β}(r{sup ′},t){sup ¯} of the fluctuations δn{sub α}(r,t)=n{sub α}(r,t)−n{sup ¯}{sub α}(r,t). As in the monocomponent case, these two coarse-grained equations involve a local mobility function b{sub α}(r, t) for each species, written in terms of the memory function of the two-time correlation function C{sub αβ}(r,r{sup ′};t,t{sup ′})≡δn{sub α}(r,t)δn{sub β}(r{sup ′},t{sup ′}){sup ¯}. If the system is constrained to remain spatially uniform and subjected to a non-equilibrium preparation protocol described by a given temperature and composition change program T(t) and n{sup ¯}{sub α}(t), these equations predict the irreversible structural relaxation of the partial static structure factors S{sub αβ}(k; t) and of the (collective and self) intermediate scattering functions F{sub αβ}(k, τ; t) and F{sub αβ}{sup S}(k,τ;t). We illustrate the applicability of the resulting theory with two examples involving simple model mixtures subjected to an instantaneous temperature quench: an electroneutral binary mixture of equally sized and oppositely charged hard-spheres, and a binary mixture of soft-spheres of moderate size-asymmetry.

  19. Anomalies in the Thermophysical Properties of Undercooled Glass-Forming Alloys

    NASA Technical Reports Server (NTRS)

    Hyers, Robert W.; Rogers, Jan R.; Kelton, Kenneth F.; Gangopadhyay, Anup

    2008-01-01

    The surface tension, viscosity, and density of several bulk metallic glass-forming alloys have been measured using noncontact techniques in the electrostatic levitation facility (ESL) at NASA Marshall Space Flight Center. All three properties show unexpected behavior in the undercooled regime. Similar deviations were previously observed in titanium-based quasicrystal-forming alloys,but the deviations in the properties of the glass-forming alloys are much more pronounced. New results for anomalous thermophysical properties in undercooled glass-forming alloys will be presented and discussed.

  20. Multiple glass singularities and isodynamics in a core-softened model for glass-forming systems.

    PubMed

    Gnan, Nicoletta; Das, Gayatri; Sperl, Matthias; Sciortino, Francesco; Zaccarelli, Emanuela

    2014-12-19

    We investigate the slow dynamics of a simple glass former whose interaction potential is the sum of a hard core and a square shoulder repulsion. According to mode coupling theory, the competition between the two repulsive length scales gives rise to a complex dynamic scenario: besides the fluid-glass line, the theory predicts a glass-glass line in the temperature-packing fraction plane with two end points. Interestingly, for critical values of the square-shoulder parameters, such end points can be accessed from the liquid phase. We verify, via extensive numerical simulations, the existence of both points through the observation of an unconventional subdiffusive/logarithmic dynamical behavior. Unexpectedly, we also discover that the simultaneous presence of two end points generates special loci in the state diagram along which the dynamics is identical at all length and time scales. PMID:25554913

  1. Highly conductive electrolyte composites containing glass and ceramic, and method of manufacture

    DOEpatents

    Hash, Mark C.; Bloom, Ira D.

    1992-01-01

    An electrolyte composite is manufactured by pressurizing a mixture of sodium ion conductive glass and an ionically conductive compound at between 12,000 and 24,000 pounds per square inch to produce a pellet. The resulting pellet is then sintered at relatively lower temperatures (800.degree. C.-1200.degree. C.), for example 1000.degree. C., than are typically required (1400.degree. C.) when fabricating single constituent ceramic electrolytes. The resultant composite is 100 percent conductive at 250.degree. C. with conductivity values of 2.5 to 4.times.10.sup.-2 (ohm-cm).sup.-1. The matrix exhibits chemical stability against sodium for 100 hours at 250.degree. to 300.degree. C.

  2. Manufacture of mirror glass substrates for the NuSTAR mission

    NASA Astrophysics Data System (ADS)

    Zhang, William W.

    2009-08-01

    The NuSTAR (Nuclear Spectroscopy Telescope Array) observatory (Harrison et al. 2009), expected to be launched into an equatorial low earth orbit in 2011, will have two mirror assemblies capable of imaging X-rays in the hard X-ray band between 5 keV and 80 keV. It will be the first X-ray observatory using multilayer coatings to significantly expand the bandwidth of the typical X-ray telescope of 0.1 keV to 10 keV. The mirror assemblies use a segmented design to simplify the construction process, as such they require 4,680 mirror substrates coated with appropriately designed multilayers to enhance reflectivity for hard X-rays. These substrates are produced by slumping commercially available thin glass sheets. In this paper we report on our work of manufacturing these substrates at NASA Goddard Space Flight Center.

  3. A Case of Complicated Silicosis with a Complex Clinical Course in a Glass Manufacturing Worker

    PubMed Central

    2014-01-01

    We reported a case of complicated silicosis that occurred in a glass manufacturing plant worker who had presumably been exposed to low-concentration free silica for almost 20 years. To the best of our knowledge this report is the first in the Republic of Korea. The physician’s first impression was cancer since the enlargement of neck and supraclavicuar lymph nodes had clearly progressed and metastasis was suspected in ultrasonography. However, it turned out to be reactive hyperplasia and anthracosis. Although lung cancer was suspected and tests were performed in 2 hospitals due to repetitive cough and dyspnea, along with weight loss of approximately 10% over the course of 7 months, the patient was eventually diagnosed with complicated silicosis and pneumothorax occurred after 1 year. Herein, we report this case with a literature review. PMID:24914413

  4. Effect of glass composition on waste form durability: A critical review

    SciTech Connect

    Ellison, A.J.G.; Mazer, J.J.; Ebert, W.L.

    1994-11-01

    This report reviews literature concerning the relationship between the composition and durability of silicate glasses, particularly glasses proposed for immobilization of radioactive waste. Standard procedures used to perform durability tests are reviewed. It is shown that tests in which a low-surface area sample is brought into contact with a very large volume of solution provide the most accurate measure of the intrinsic durability of a glass composition, whereas high-surface area/low-solution volume tests are a better measure of the response of a glass to changes in solution chemistry induced by a buildup of glass corrosion products. The structural chemistry of silicate and borosilicate glasses is reviewed to identify those components with the strongest cation-anion bonds. A number of examples are discussed in which two or more cations engage in mutual bonding interactions that result in minima or maxima in the rheologic and thermodynamic properties of the glasses at or near particular optimal compositions. It is shown that in simple glass-forming systems such interactions generally enhance the durability of glasses. Moreover, it is shown that experimental results obtained for simple systems can be used to account for durability rankings of much more complex waste glass compositions. Models that purport to predict the rate of corrosion of glasses in short-term durability tests are evaluated using a database of short-term durability test results for a large set of glass compositions. The predictions of these models correlate with the measured durabilities of the glasses when considered in large groupings, but no model evaluated in this review provides accurate estimates of durability for individual glass compositions. Use of these models in long-term durability models is discussed. 230 refs.

  5. Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

    NASA Technical Reports Server (NTRS)

    Turnbull, D.

    1979-01-01

    Crystal nucleation behavior in metallic alloys known to form glasses in melt quenching was characterized and from this characterization the possibility that massive amounts of certain alloys could be slow cooled to the glass state was assessed. Crystal nucleation behavior of pure liquid metals was examined experimentally, under containerless conditions, and theoretically.

  6. Talc-silicon glass-ceramic waste forms for immobilization of high- level calcined waste

    SciTech Connect

    Vinjamuri, K.

    1993-06-01

    Talc-silicon glass-ceramic waste forms are being evaluated as candidates for immobilization of the high level calcined waste stored onsite at the Idaho Chemical Processing Plant. These glass-ceramic waste forms were prepared by hot isostatically pressing a mixture of simulated nonradioactive high level calcined waste, talc, silicon and aluminum metal additives. The waste forms were characterized for density, chemical durability, and glass and crystalline phase compositions. The results indicate improved density and chemical durability as the silicon content is increased.

  7. Kinetics of Nucleation and Crystal Growth in Glass Forming Melts in Microgravity

    NASA Technical Reports Server (NTRS)

    Day, Delbert E.; Ray, Chandra S.

    2003-01-01

    This flight definition project has the specific objective of investigating the kinetics of nucleation and crystal growth in high temperature inorganic oxide, glass forming melts in microgravity. It is related to one1 of our previous NASA projects that was concerned with glass formation for high temperature containerless melts in microgravity. The previous work culminated in two experiments which were conducted aboard the space shuttle in 1983 and 1985 and which consisted of melting (at 1500 C) and cooling levitated 6 to 8 mm diameter spherical samples in a Single Axis Acoustic Levitator (SAAL) furnace. Compared to other types of materials, there have been relatively few experiments, 6 to 8, conducted on inorganic glasses in space. These experiments have been concerned with mass transport (alkali diffusion), containerless melting, critical cooling rate for glass formation, chemical homogeneity, fiber pulling, and crystallization of glass forming melts. One of the most important and consistent findings in all of these experiments has been that the glasses prepared in microgravity are more resistant to crystallization (better glass former) and more chemically homogeneous than equivalent glasses made on earth (1g). The chemical composition of the melt appears relatively unimportant since the same general results have been reported for oxide, fluoride and chalcogenide melts. These results for space-processed glasses have important implications, since glasses with a higher resistance to crystallization or higher chemical homogeneity than those attainable on earth can significantly advance applications in areas such as fiber optics communications, high power laser glasses, and other photonic devices where glasses are the key functional materials. The classical theories for nucleation and crystal growth for a glass or melt do not contain any parameter that is directly dependent upon the g-value, so it is not readily apparent why glasses prepared in microgravity should be

  8. Kinetics of phase transformation in glass forming systems

    NASA Technical Reports Server (NTRS)

    Ray, Chandra S.

    1994-01-01

    The objectives of this research were to (1) develop computer models for realistic simulations of nucleation and crystal growth in glasses, which would also have the flexibility to accomodate the different variables related to sample characteristics and experimental conditions, and (2) design and perform nucleation and crystallization experiments using calorimetric measurements, such as differential scanning calorimetry (DSC) and differential thermal analysis (DTA) to verify these models. The variables related to sample characteristics mentioned in (1) above include size of the glass particles, nucleating agents, and the relative concentration of the surface and internal nuclei. A change in any of these variables changes the mode of the transformation (crystallization) kinetics. A variation in experimental conditions includes isothermal and nonisothermal DSC/DTA measurements. This research would lead to develop improved, more realistic methods for analysis of the DSC/DTA peak profiles to determine the kinetic parameters for nucleation and crystal growth as well as to assess the relative merits and demerits of the thermoanalytical models presently used to study the phase transformation in glasses.

  9. Machinable glass-ceramics forming as a restorative dental material.

    PubMed

    Chaysuwan, Duangrudee; Sirinukunwattana, Krongkarn; Kanchanatawewat, Kanchana; Heness, Greg; Yamashita, Kimihiro

    2011-01-01

    MgO, SiO(2), Al(2)O(3), MgF(2), CaF(2), CaCO(3), SrCO(3), and P(2)O(5) were used to prepare glass-ceramics for restorative dental materials. Thermal properties, phases, microstructures and hardness were characterized by DTA, XRD, SEM and Vickers microhardness. Three-point bending strength and fracture toughness were applied by UTM according to ISO 6872: 1997(E). XRD showed that the glass crystallized at 892°C (second crystallization temperature+20°C) for 3 hrs consisted mainly of calcium-mica and fluorapatite crystalline phases. Average hardness (3.70 GPa) closely matched human enamel (3.20 GPa). The higher fracture toughness (2.04 MPa√m) combined with the hardness to give a lower brittleness index (1.81 µm(-1/2)) which indicates that they have exceptional machinability. Bending strength results (176.61 MPa) were analyzed by Weibull analysis to determine modulus value (m=17.80). Machinability of the calcium mica-fluorapatite glass-ceramic was demonstrated by fabricating with CAD/CAM. PMID:21597218

  10. Kinetics of Nucleation and Crystal Growth in Glass Forming Melts in Microgravity

    NASA Technical Reports Server (NTRS)

    Day, Delbert E.; Ray, Chandra S.

    2001-01-01

    This flight definition project has the specific objective of investigating the kinetics of nucleation and crystal growth in high temperature inorganic oxide, glass forming melts in microgravity. It is related to one of our previous NASA projects that was concerned with glass formation for high temperature containerless melts in microgravity. The previous work culminated in two experiments which were conducted aboard the space shuttle in 1983 and 1985 and which consisted of melting (at 1500 C) and cooling levitated 6 to 8 mm diameter spherical samples in a Single Axis Acoustic Levitator (SAAL) furnace. Compared to other types of materials, there have been relatively few experiments, 6 to 8, conducted on inorganic glasses in space. These experiments have been concerned with mass transport (alkali diffusion), containerless melting, critical cooling rate for glass formation, chemical homogeneity, fiber pulling, and crystallization of glass forming melts. One of the most important and consistent findings in all of these experiments has been that the glasses prepared in microgravity are more resistant to crystallization (better glass former) and more chemically homogeneous than equivalent glasses made on Earth (1 g). The chemical composition of the melt appears relatively unimportant since the same general results have been reported for oxide, fluoride and chalcogenide melts. These results for space-processed glasses have important implications, since glasses with a higher resistance to crystallization or higher chemical homogeneity than those attainable on Earth can significantly advance applications in areas such as fiber optics communications, high power laser glasses, and other photonic devices where glasses are the key functional materials.

  11. Accurate glass forming for high-temperature solar applications. Final report

    SciTech Connect

    1980-10-01

    Development work was undertaken to thermally form glass for solar concentrators. Sagging and pressing glass to parabolic shapes was investigated with goal of achieving slope errors less than 2.0 mr RMS and costs of $1.25/ft/sup 2/. In addition, a laminating process was investigated to overcome the problem of silvering of a curved surface and to reduce corrosion of the silver. Thermal sagging is a process in which glass is shaped by heating the glass until it is sufficiently soft to deform under its own weight and conform to a mold. For cylindrical parabolic shapes, a method for producing low cost high accuracy molds was developed using castable ceramics and a grinder. Thermal conditions were established for a commercial glass bending furnace to obtain good replication of the mold. The accuracy and cost goals were met for glass size up to 30 x 30 x 0.125 inches and for low iron and regular iron float and sheet glasses. Lamination of two curved pieces of glass using automotive technology was investigated. A silver film was placed between two layers of polyvinyl and butyral (PVB) and this was used to bond two sheets of glass. Economically, and technically, the process appears feasible. However, the non-uniform thickness of PBV cause distortion in the reflected image. More work is needed to assess accuracy of curved laminated composites. Thermal pressing of glass is accomplished by heating the glass until it is soft and mechanically stamping the shape. Equipment was built and operated to determine important parameters in pressing. Control of thermal stresses in the glass is critical to preventing cracks. No glass pieces were produced without cracks.

  12. Roll forming technology for manufacturing axisymmetric automotive components

    SciTech Connect

    Syn, C.K.; Lesuer, D.R.; Bieh, T.G.; Yang, H.s.; Brown, K.R.; Kaibyshev, R.O.; Petrov, E.N.

    1997-10-28

    A unique roll forming technology that permits complex axisymmetric components, such as automobile wheels and turbine disks, to be formed in a single forming operation, has been developed by two Russian Institute, the Institute of Technical Physics of the Russian Federal Nuclear Center and the Institute for Metals Superplasticity Problems. This process was used to fabricate automobile wheels from a Russian AVT alloy, a 6010 aluminum alloy equivalent. The process included steps of isothermal roll forming of preforms into wheels shapes, all at 430C for the AVT alloy. The microstructure and mechanical properties were evaluated at various locations in the finished wheels by optical metallography and tensile testing at elevated temperatures. Tensile properties were obtained by stain-rate change tests and tensile tests to failure at high strain rates. Microstructure and mechanical propertied of the preforms and blanks were also evaluated. The results indicate that dynamically recovered microstructures were developed during the processing, which showed relatively high strain rate sensitivity and rendered sufficiently plasticity at the elevated temperature for wheel fabrication process.

  13. Localized Excitations and the Morphology of Cooperatively Rearranging Regions in a Colloidal Glass-Forming Liquid

    NASA Astrophysics Data System (ADS)

    Gokhale, Shreyas; Ganapathy, Rajesh; Nagamanasa, K. Hima; Sood, A. K.

    2016-02-01

    We develop a scheme based on a real space microscopic analysis of particle dynamics to ascertain the relevance of dynamical facilitation as a mechanism of structural relaxation in glass-forming liquids. By analyzing the spatial organization of localized excitations within clusters of mobile particles in a colloidal glass former and examining their partitioning into shell-like and corelike regions, we establish the existence of a crossover from a facilitation-dominated regime at low area fractions to a collective activated hopping-dominated one close to the glass transition. This crossover occurs in the vicinity of the area fraction at which the peak of the mobility transfer function exhibits a maximum and the morphology of cooperatively rearranging regions changes from stringlike to a compact form. Collectively, our findings suggest that dynamical facilitation is dominated by collective hopping close to the glass transition, thereby constituting a crucial step towards identifying the correct theoretical scenario for glass formation.

  14. Percolation Model for Slow Dynamics in Glass-Forming Materials

    NASA Astrophysics Data System (ADS)

    Lois, Gregg; Blawzdziewicz, Jerzy; O'Hern, Corey S.

    2009-01-01

    We identify a link between the glass transition and percolation of regions of mobility in configuration space. We find that many hallmarks of glassy dynamics, for example, stretched-exponential response functions and a diverging structural relaxation time, are consequences of the critical properties of mean-field percolation. Specific predictions of the percolation model include the range of possible stretching exponents 1/3≤β≤1 and the functional dependence of the structural relaxation time τα and exponent β on temperature, density, and wave number.

  15. Correlation between relaxations and plastic deformation, and elastic model of flow in metallic glasses and glass-forming liquids

    SciTech Connect

    Wang Weihua

    2011-09-01

    We study the similarity and correlations between relaxations and plastic deformation in metallic glasses (MGs) and MG-forming liquids. It is shown that the microscope plastic events, the initiation and formation of shear bands, and the mechanical yield in MGs where the atomic sites are topologically unstable induced by applied stress, can be treated as the glass to supercooled liquid state transition induced by external shear stress. On the other hand, the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to describe the flow based on the energy landscape theory. That is, the flow activation energy density is linear proportional to the instantaneous elastic moduli, and the activation energy density {rho}{sub E} is determined to be a simple expression of {rho}{sub E}=(10/11)G+(1/11)K. The model indicates that both shear and bulk moduli are critical parameters accounting for both the homogeneous and inhomogeneous flows in MGs and MG-forming liquids. The elastic model is experimentally certified. We show that the elastic perspectives offers a simple scenario for the flow in MGs and MG-forming liquids and are suggestive for understanding the glass transition, plastic deformation, and nature and characteristics of MGs.

  16. Correlation between relaxations and plastic deformation, and elastic model of flow in metallic glasses and glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Wang, Wei Hua

    2011-09-01

    We study the similarity and correlations between relaxations and plastic deformation in metallic glasses (MGs) and MG-forming liquids. It is shown that the microscope plastic events, the initiation and formation of shear bands, and the mechanical yield in MGs where the atomic sites are topologically unstable induced by applied stress, can be treated as the glass to supercooled liquid state transition induced by external shear stress. On the other hand, the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to describe the flow based on the energy landscape theory. That is, the flow activation energy density is linear proportional to the instantaneous elastic moduli, and the activation energy density ρE is determined to be a simple expression of ρE=10/11G +1/11K. The model indicates that both shear and bulk moduli are critical parameters accounting for both the homogeneous and inhomogeneous flows in MGs and MG-forming liquids. The elastic model is experimentally certified. We show that the elastic perspectives offers a simple scenario for the flow in MGs and MG-forming liquids and are suggestive for understanding the glass transition, plastic deformation, and nature and characteristics of MGs

  17. The production of advanced glass ceramic HLW forms using cold crucible induction melter

    SciTech Connect

    Rutledge, V.J.; Maio, V.

    2013-07-01

    Cold Crucible Induction Melters (CCIM) will favorably change how High-Level radioactive Waste (from nuclear fuel recovery) is treated in a near future. Unlike the existing Joule-Heated Melters (JHM) currently in operation for the glass-based immobilization of High-Level Waste (HLW), CCIM offers unique material features that will increase melt temperatures, increase throughput, increase mixing, increase loading in the waste form, lower melter foot prints, eliminate melter corrosion and lower costs. These features not only enhance the technology for producing HLW forms, but also provide advantageous attributes to the waste form by allowing more durable alternatives to glass. It is concluded that glass ceramic waste forms that are tailored to immobilize fission products of HLW can be can be made from the HLW processed with the CCIM. The advantageous higher temperatures reached with the CCIM and unachievable with JHM allows the lanthanides, alkali, alkaline earths, and molybdenum to dissolve into a molten glass. Upon controlled cooling they go into targeted crystalline phases to form a glass ceramic waste form with higher waste loadings than achievable with borosilicate glass waste forms. Natural cooling proves to be too fast for the formation of all targeted crystalline phases.

  18. Microstructural characterization of halite inclusions in a surrogate glass bonded ceramic waste form

    SciTech Connect

    Luo, J. S.; Zyryanov, V. N.; Ebert, W. L.

    2000-05-12

    A glass-bonded ceramic waste form is being developed to immobilize high-level chloride waste salts generated during the conditioning of spent sodium-bonded nuclear fuel for disposal. The waste salt is loaded into zeolite cavities, mixed with a borosilicate glass, and consolidated at 800--900 C by hot isostatic pressing. During this process, small amounts of halite are generated, whereas the zeolite converts to the mineral sodalite, which retains most of the waste salt. In this work, optical microscopy, scanning electron microscopy, and transmission electron microscopy2048e used to characterize the halite inclusions in the final waste form. The halite inclusions were detected within micron- to submicron-sized pores that form within the glass phase in the vicinity of the sodalite/glass interface. The chemical nature and distribution of the halite inclusions were determined. The particular microstructure of the halite inclusions has been related to the corrosion of the ceramic waste form.

  19. Microcraters formed in glass by projectiles of various densities

    NASA Technical Reports Server (NTRS)

    Vedder, J. F.; Mandeville, J.-C.

    1974-01-01

    An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.

  20. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness.

    PubMed

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-14

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point. PMID:27083733

  1. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

    NASA Astrophysics Data System (ADS)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

  2. Development of iodine waste forms using low-temperature sintering glass.

    SciTech Connect

    Krumhansl, James Lee; Nenoff, Tina Maria; Garino, Terry J.; Rademacher, David

    2010-06-01

    This presentation will describe our recent work on the use of low temperature-sintering glass powders mixed with either AgI or AgI-zeolite to produce a stable waste form. Radioactive iodine ({sup 129}I, half-life of 1.6 x 10{sup 7} years) is generated in the nuclear fuel cycle and is of particular concern due to its extremely long half-life and its effects on human health. As part of the DOE/NE Advanced Fuel Cycle Initiative (AFCI), the separation of {sup 129}I from spent fuel during fuel reprocessing is being studied. In the spent fuel reprocessing scheme under consideration, the iodine is released in gaseous form and collected using Ag-loaded zeolites, to form AgI. Although AgI has extremely low solubility in water, it has a relatively high vapor pressure at moderate temperatures (>550 C), thus limiting the thermal processing. Because of this, immobilization using borosilicate glass is not feasible. Therefore, a bismuth oxide-based glasses are being studied due to the low solubility of bismuth oxide in aqueous solution at pH > 7. These waste forms were processed at 500 C, where AgI volatility is low but the glass powder is able to first densify by viscous sintering and then crystallize. Since the glass is not melted, a more chemically stable glass can be used. The AgI-glass mixture was found to have high iodine leach resistance in these initial studies.

  3. Linking Slow Dynamics and Local Structure in Simple Models of Glass-Forming Liquids

    NASA Astrophysics Data System (ADS)

    Coslovich, D.; Pastore, G.

    2008-07-01

    Establishing a relation between the dynamical features of supercooled liquids, their structural properties and the nature of intermolecular interactions is a key issue in the description of the glass transition. To investigate this point we perform molecular dynamics simulations for three model glass-forming liquids with different types of local order. Our results show that the roughness of the energy landscape, estimated from the amplitude of average energy barriers, and the localization of unstable modes provide useful means to rationalize the link between structure and dynamics in glass-forming liquids.

  4. Diffusion in confinement as a microscopic relaxation mechanism in glass-forming liquids

    SciTech Connect

    Mamontov, Eugene

    2012-01-01

    Using quasielastic neutron scattering, we compare dynamics in single-element liquids, glass-forming selenium and non glass-forming gallium. There is a single jump-diffusion process in gallium, whereas in selenium there is also a faster, spatially localized process. The fast and slow processes describe {beta}- and {alpha}-relaxation, respectively. We then analyze an archetypical glass-former, glycerol, to show that the two-component fit, with {beta}- and {alpha}-relaxations explicitly separated, yields the correct value for the translational diffusion coefficient and provides information on the spatial localization of the {beta}-relaxation that is not experimentally accessible otherwise.

  5. 46 CFR 54.10-25 - Manufacturers' data report forms (modifies UG-120).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... ENGINEERING PRESSURE VESSELS Inspection, Reports, and Stamping § 54.10-25 Manufacturers' data report forms... prior to inspection of the pressure vessel. (Approved by the Office of Management and Budget...

  6. Reaction sintered glass: A durable matrix for spinel-forming nuclear waste compositions

    NASA Astrophysics Data System (ADS)

    Gong, W. L.; Lutze, W.; Ewing, R. C.

    2000-01-01

    Glass formation by reaction sintering under isostatic pressure is an innovative process to vitrify refractory-rich high-level radioactive waste. We used a typical defense waste composition, containing spinel-forming components such as ˜4 wt% of Cr 2O 3, ˜23 wt% Al 2O 3, ˜13 wt% Fe 2O 3, and ˜9 wt% UO 2, with CeO 2 simulating UO 2. Reaction sintered silicate glasses with waste loading up to 45 wt% were prepared within three hours, by hot pressing at 800°C. The glass former was amorphous silica. Simulated waste was added as calcined oxides. The reaction sintered glass samples were characterized using scanning and analytical electron microscopy. The results show that extensive reaction sintering took place and a continuous glass phase formed. Waste components such as Na 2O, CaO, MnO 2, and Fe 2O 3, dissolved completely in the continuous glass phase. Cr 2O 3, Al 2O 3, and CeO 2 were only partially dissolved due to incomplete dissolution (Al 2O 3) or super-saturation and reprecipitation (Cr 2O 3 and CeO 2). The precipitation mechanism is related to a time dependent alkali content in the developing glass phase. Short-term corrosion tests in water showed that the glasses are chemically more durable than melted nuclear waste glasses. Based on hydration energies calculations, the long-term chemical durability of our reaction sintered glasses is expected to be comparable to that of rhyolitic and tektite glasses.

  7. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

    NASA Astrophysics Data System (ADS)

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer; Thorpe, Steven John

    2015-09-01

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal-transition metal and transition metal-metalloid (TM-M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM-M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  8. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

    SciTech Connect

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer Thorpe, Steven John

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal–transition metal and transition metal–metalloid (TM–M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM–M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  9. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses.

    PubMed

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer; Thorpe, Steven John

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal-transition metal and transition metal-metalloid (TM-M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM-M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator. PMID:26395721

  10. Corrosion behavior of a glass-bonded sodalite ceramic waste form and its constituents.

    SciTech Connect

    Lewis, M. A.; Ebert, W. L.; Morss, L.

    1999-06-18

    A ceramic waste form (CWF) of glass bonded sodalite is being developed as a waste form for the long-term immobilization of fission products and transuranic elements from the U.S. Department of Energy's activities on spent nuclear fuel conditioning. A durable waste form was prepared by hot isostatic pressing (HIP) a mixture of salt-loaded zeolite powders and glass frit. During HIP the zeolite is converted to sodalite, and the resultant CWF is been completed for durations of up to 182 days. Four dissolution modes were identified: dissolution of free salt, dissolution of the aluminosilicate matrix of sodalite and the accompanying dissolution of occluded salt, dissolution of the boroaluminosilicate matrix of the glass, and ion exchange. Synergies inherent to the CWF were identified by comparing the results of the tests with pure glass and sodalite with those of the composite CWF.

  11. Dropwise additive manufacturing of pharmaceutical products for solvent-based dosage forms.

    PubMed

    Hirshfield, Laura; Giridhar, Arun; Taylor, Lynne S; Harris, Michael T; Reklaitis, Gintaras V

    2014-02-01

    In recent years, the US Food and Drug Administration has encouraged pharmaceutical companies to develop more innovative and efficient manufacturing methods with improved online monitoring and control. Mini-manufacturing of medicine is one such method enabling the creation of individualized product forms for each patient. This work presents dropwise additive manufacturing of pharmaceutical products (DAMPP), an automated, controlled mini-manufacturing method that deposits active pharmaceutical ingredients (APIs) directly onto edible substrates using drop-on-demand (DoD) inkjet printing technology. The use of DoD technology allows for precise control over the material properties, drug solid state form, drop size, and drop dynamics and can be beneficial in the creation of high-potency drug forms, combination drugs with multiple APIs or individualized medicine products tailored to a specific patient. In this work, DAMPP was used to create dosage forms from solvent-based formulations consisting of API, polymer, and solvent carrier. The forms were then analyzed to determine the reproducibility of creating an on-target dosage form, the morphology of the API of the final form and the dissolution behavior of the drug over time. DAMPP is found to be a viable alternative to traditional mass-manufacturing methods for solvent-based oral dosage forms. PMID:24311373

  12. Annual book of ASTM standards. Part 17. Refractories, glass, and other ceramic materials; manufactured carbon and graphite products

    SciTech Connect

    Not Available

    1980-01-01

    The standards are assembled in each part in alphanumeric sequence of their ASTM designation numbers. Each part has two tables of contents: a list of the standards in alphanumeric sequence of their ASTM designations; and a list of the standards classified according to subject. A subject index of the standards and tentatives in each part appears at the back of each volume. This part contains standards concerning refractories; glass and glass products; ceramic whitewares; porcelain enamel and related ceramic-metal systems; ceramics for electronics; manufactured carbon and graphite products; and general methods of testing.

  13. Fast and slow crystal growth kinetics in glass-forming melts

    NASA Astrophysics Data System (ADS)

    Orava, J.; Greer, A. L.

    2014-06-01

    Published values of crystal growth rates are compared for supercooled glass-forming liquids undergoing congruent freezing at a planar crystal-liquid interface. For the purposes of comparison pure metals are considered to be glass-forming systems, using data from molecular-dynamics simulations. For each system, the growth rate has a maximum value Umax at a temperature Tmax that lies between the glass-transition temperature Tg and the melting temperature Tm. A classification is suggested, based on the lability (specifically, the propensity for fast crystallization), of the liquid. High-lability systems show "fast" growth characterized by a high Umax, a low Tmax / Tm, and a very broad peak in U vs. T / Tm. In contrast, systems showing "slow" growth have a low Umax, a high Tmax / Tm, and a sharp peak in U vs. T / Tm. Despite the difference of more than 11 orders of magnitude in Umax seen in pure metals and in silica, the range of glass-forming systems surveyed fit into a common pattern in which the lability increases with lower reduced glass-transition temperature (Tg / Tm) and higher fragility of the liquid. A single parameter, a linear combination of Tg / Tm and fragility, can show a good correlation with Umax. For all the systems, growth at Umax is coupled to the atomic/molecular mobility in the liquid. It is found that, across the diversity of glass-forming systems, Tmax / Tg = 1.48 ± 0.15.

  14. Manufacturing an active X-ray mirror prototype in thin glass.

    PubMed

    Spiga, D; Barbera, M; Collura, A; Basso, S; Candia, R; Civitani, M; Di Bella, M S; Di Cicca, G; Lo Cicero, U; Lullo, G; Pelliciari, C; Riva, M; Salmaso, B; Sciortino, L; Varisco, S

    2016-01-01

    Adjustable mirrors equipped with piezo actuators are commonly used at synchrotron and free-electron laser (FEL) beamlines, in order to optimize their focusing properties and sometimes to shape the intensity distribution of the focal spot with the desired profile. Unlike them, X-ray mirrors for astronomy are much thinner in order to enable nesting and reduce the areal mass, and the application of piezo actuators acting normally to the surface appears much more difficult. There remains the possibility to correct the deformations using thin patches that exert a tangential strain on the rear side of the mirror: some research groups are already at work on this approach. The technique reported here relies on actively integrating thin glass foils with commercial piezoceramic patches, fed by voltages driven by the feedback provided by X-rays, while the tension signals are carried by electrodes on the back of the mirror, obtained by photolithography. Finally, the shape detection and the consequent voltage signal to be provided to the piezoelectric array will be determined by X-ray illumination in an intra-focal setup at the XACT facility. In this work, the manufacturing steps for obtaining a first active mirror prototype are described. PMID:26698046

  15. Transport properties of glass-forming liquids suggest that dynamic crossover temperature is as important as the glass transition temperature

    PubMed Central

    Mallamace, Francesco; Branca, Caterina; Corsaro, Carmelo; Leone, Nancy; Spooren, Jeroen; Chen, Sow-Hsin; Stanley, H. Eugene

    2010-01-01

    It is becoming common practice to partition glass-forming liquids into two classes based on the dependence of the shear viscosity η on temperature T. In an Arrhenius plot, ln η vs 1/T, a strong liquid shows linear behavior whereas a fragile liquid exhibits an upward curvature [super-Arrhenius (SA) behavior], a situation customarily described by using the Vogel–Fulcher–Tammann law. Here we analyze existing data of the transport coefficients of 84 glass-forming liquids. We show the data are consistent, on decreasing temperature, with the onset of a well-defined dynamical crossover η×, where η× has the same value, η× ≈ 103 Poise, for all 84 liquids. The crossover temperature, T×, located well above the calorimetric glass transition temperature Tg, marks significant variations in the system thermodynamics, evidenced by the change of the SA-like T dependence above T× to Arrhenius behavior below T×. We also show that below T× the familiar Stokes–Einstein relation D/T ∼ η-1 breaks down and is replaced by a fractional form D/T ∼ η-ζ, with ζ ≈ 0.85. PMID:21148100

  16. Evidence for non-diverging time-scales in glass-forming liquids

    NASA Astrophysics Data System (ADS)

    McKenna, Gregory

    2013-03-01

    One perceived important signature of the ``ideal'' glass transition and of the complex fluid nature of glass-forming liquids remains the apparent divergence of the dynamics at temperatures above zero Kelvin. Recently, however, this perception has been increasingly challenged both through experiments and in new theories of the dynamics of glass forming systems. In this presentation we summarize some of the prior evidence suggesting that time scales actually do not diverge in glasses that are aged into equilibrium, perhaps 15 K below the conventional glass transition temperature Tg. We then show new results from an extremely densified glass, 20 Ma old Jamaican amber, in which we were able to obtain the upper bound to the relaxation times through a step-wise temperature scan in which the stress relaxation response of the amber was measured both below and above the fictive temperature TF . We find that in the case of the upper bound responses at T>TF , there is a strong deviation of the response from the Super-Arrhenius Vogel-Fulcher behavior and this persists to the fictive temperature which is some 33.8 K below Tg. The results are compared to the parabolic model of Chandler and co-workers and we find the model to be consistent with our results if the value of Tx in the model is taken to be the calorimetric glass transition temperature. The significance of the results will be discussed. We acknowledge NSF grants DMR-0804438 and DMR-1207070 for support of this work

  17. Summary Report: Glass-Ceramic Waste Forms for Combined Fission Products

    SciTech Connect

    Crum, Jarrod V.; Riley, Brian J.; Turo, Laura A.; Tang, Ming; Kossoy, Anna

    2011-09-23

    Glass-ceramic waste form development began in FY 2010 examining two combined waste stream options: (1) alkaline earth (CS) + lanthanide (Ln), and (2) + transition metal (TM) fission-product waste streams generated by the uranium extraction (UREX+) separations process. Glass-ceramics were successfully developed for both options however; Option 2 was selected over Option 1, at the conclusion of 2010, because Option 2 immobilized all three waste streams with only a minimal decrease in waste loading. During the first year, a series of three glass (Option 2) were fabricated that varied waste loading-WL (42, 45, and 50 mass%) at fixed molar ratios of CaO/MoO{sub 3} and B{sub 2}O{sub 3}/alkali both at 1.75. These glass-ceramics were slow cooled and characterized in terms of phase assemblage and preliminary irradiation stability. This fiscal year, further characterization was performed on the FY 2010 Option 2 glass-ceramics in terms of: static leach testing, phase analysis by transmission electron microscopy (TEM), and irradiation stability (electron and ion). Also, a new series of glass-ceramics were developed for Option 2 that varied the additives: Al{sub 2}O{sub 3} (0-6 mass%), molar ratio of CaO/MoO{sub 3} and B{sub 2}O{sub 3}/alkali (1.75 to 2.25) and waste loading (50, 55, and 60 mass%). Lastly, phase pure powellite and oxyapatite were synthesized for irradiation studies. Results of this fiscal year studies showed compositional flexibility, chemical stability, and radiation stability in the current glass-ceramic system. First, the phase assemblages and microstructure of all of the FY 2010 and 2011 glass-ceramics are very similar once subjected to the slow cool heat treatment. The phases identified in these glass-ceramics were oxyapatite, powellite, cerianite, and ln-borosilicate. This shows that variations in waste loading or additives can be accommodated without drastically changing the phase assemblage of the waste form, thus making the processing and performance

  18. High Temperature In Situ Compression of Thermoplastically Formed Nano-scale Metallic Glass

    NASA Astrophysics Data System (ADS)

    Mridha, Sanghita; Arora, Harpreet Singh; Lefebvre, Joseph; Bhowmick, Sanjit; Mukherjee, Sundeep

    2016-05-01

    The mechanical behavior of nano-scale metallic glasses was investigated by in situ compression tests in a scanning electron microscope. Platinum-based metallic glass nano-pillars were fabricated by thermoplastic forming. The nano-pillars and corresponding bulk substrate were tested in compression over the range of room temperature to glass transition. Stress-strain curves of the nano-pillars were obtained along with in situ observation of their deformation behavior. The bulk substrate as well as nano-pillars showed an increase in elastic modulus with temperature which is explained by diffusive rearrangement of atomic-scale viscoelastic units.

  19. An electromotive force series in a borosilicate glass-forming melt

    NASA Technical Reports Server (NTRS)

    Schreiber, H. D.; Balazs, G. B.; Carpenter, B. E.; Kirkley, J. E.; Minnix, L. M.; Jamison, P. L.

    1984-01-01

    An electromotive force series for redox couples was defined as a function of oxygen fugacity in a borosilicate melt at 1150 C. The resulting order of relative reduction potentials can be used to estimate the amounts of redox species in glass during processing. The electromotive force series in this melt is comparable to those in other silicate glass-forming melts and in aqueous systems but differs in detail because of interaction of the solvents with individual redox couples.

  20. Characterization and durability testing of a glass-bonded ceramic waste form.

    SciTech Connect

    Johnson, S. G.

    1998-05-18

    Argonne National Laboratory is developing a glass bonded ceramic waste form for encapsulating the fission products and transuranics from the conditioning of metallic reactor fuel. This waste form is currently being scaled to the multi-kilogram size for encapsulation of actual high level waste. This paper will present characterization and durability testing of the ceramic waste form. An emphasis on results from application of glass durability tests such as the Product Consistency Test and characterization methods such as X-ray diffraction and scanning electron microscopy. The information presented is based on a suite of tests utilized for assessing product quality during scale-up and parametric testing.

  1. Method of making nanostructured glass-ceramic waste forms

    SciTech Connect

    Gao, Huizhen; Wang, Yifeng; Rodriguez, Mark A.; Bencoe, Denise N.

    2014-07-08

    A waste form for and a method of rendering hazardous materials less dangerous is disclosed that includes fixing the hazardous material in nanopores of a nanoporous material, reacting the trapped hazardous material to render it less volatile/soluble, and vitrifying the nanoporous material containing the less volatile/soluble hazardous material.

  2. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability

    PubMed Central

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A.S.

    2015-01-01

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12 h at temperatures 20 °C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20 °C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π–π interactions reduce the inherent physical stability of amorphous drugs. PMID:26341321

  3. How much time is needed to form a kinetically stable glass? AC calorimetric study of vapor-deposited glasses of ethylcyclohexane

    NASA Astrophysics Data System (ADS)

    Chua, Y. Z.; Ahrenberg, M.; Tylinski, M.; Ediger, M. D.; Schick, C.

    2015-02-01

    Glasses of ethylcyclohexane produced by physical vapor deposition have been characterized by in situ alternating current chip nanocalorimetry. Consistent with previous work on other organic molecules, we observe that glasses of high kinetic stability are formed at substrate temperatures around 0.85 Tg, where Tg is the conventional glass transition temperature. Ethylcyclohexane is the least fragile organic glass-former for which stable glass formation has been established. The isothermal transformation of the vapor-deposited glasses into the supercooled liquid state was also measured. At seven substrate temperatures, the transformation time was measured for glasses prepared with deposition rates across a range of four orders of magnitude. At low substrate temperatures, the transformation time is strongly dependent upon deposition rate, while the dependence weakens as Tg is approached from below. These data provide an estimate for the surface equilibration time required to maximize kinetic stability at each substrate temperature. This surface equilibration time is much smaller than the bulk α-relaxation time and within two orders of magnitude of the β-relaxation time of the ordinary glass. Kinetically stable glasses are formed even for substrate temperatures below the Vogel and the Kauzmann temperatures. Surprisingly, glasses formed in the limit of slow deposition at the lowest substrate temperatures are not as kinetically stable as those formed near 0.85 Tg.

  4. Glass-Ceramic Waste Forms for Uranium and Plutonium Residues Wastes - 13164

    SciTech Connect

    Stewart, Martin W.A.; Moricca, Sam A.; Zhang, Yingjie; Day, R. Arthur; Begg, Bruce D.; Scales, Charlie R.; Maddrell, Ewan R.; Hobbs, Jeff

    2013-07-01

    A program of work has been undertaken to treat plutonium-residues wastes at Sellafield. These have arisen from past fuel development work and are highly variable in both physical and chemical composition. The principal radiological elements present are U and Pu, with small amounts of Th. The waste packages contain Pu in amounts that are too low to be economically recycled as fuel and too high to be disposed of as lower level Pu contaminated material. NNL and ANSTO have developed full-ceramic and glass-ceramic waste forms in which hot-isostatic pressing is used as the consolidation step to safely immobilize the waste into a form suitable for long-term disposition. We discuss development work on the glass-ceramic developed for impure waste streams, in particular the effect of variations in the waste feed chemistry glass-ceramic. The waste chemistry was categorized into actinides, impurity cations, glass formers and anions. Variations of the relative amounts of these on the properties and chemistry of the waste form were investigated and the waste form was found to be largely unaffected by these changes. This work mainly discusses the initial trials with Th and U. Later trials with larger variations and work with Pu-doped samples further confirmed the flexibility of the glass-ceramic. (authors)

  5. Effects of partitioned enthalpy of mixing on glass-forming ability

    SciTech Connect

    Song, Wen-Xiong; Zhao, Shi-Jin

    2015-04-14

    We explore the inherent reason at atomic level for the glass-forming ability of alloys by molecular simulation, in which the effect of partitioned enthalpy of mixing is studied. Based on Morse potential, we divide the enthalpy of mixing into three parts: the chemical part (Δ E{sub nn}), strain part (Δ E{sub strain}), and non-bond part (Δ E{sub nnn}). We find that a large negative Δ E{sub nn} value represents strong AB chemical bonding in AB alloy and is the driving force to form a local ordered structure, meanwhile the transformed local ordered structure needs to satisfy the condition (Δ E{sub nn}/2 + Δ E{sub strain}) < 0 to be stabilized. Understanding the chemical and strain parts of enthalpy of mixing is helpful to design a new metallic glass with a good glass forming ability. Moreover, two types of metallic glasses (i.e., “strain dominant” and “chemical dominant”) are classified according to the relative importance between chemical effect and strain effect, which enriches our knowledge of the forming mechanism of metallic glass. Finally, a soft sphere model is established, different from the common hard sphere model.

  6. A Laser Deposition Strategy for the Efficient Identification of Glass-Forming Alloys

    NASA Astrophysics Data System (ADS)

    Tsai, Peter; Flores, Katharine M.

    2015-09-01

    Compositionally graded Cu-Zr specimens covering a wide composition range (30 to 60 at. pct Zr) were fabricated by direct laser deposition. By observing the surface topography of the as-fabricated specimens with differential interference contrast microscopy, primarily amorphous regions corresponding to compositions of high glass-forming ability were rapidly identified. Electron diffraction results confirmed the relationship between surface topography and atomic structure. The compositional widths of the amorphous regions were observed to narrow with increasing heat input from the laser, enabling further identification of local maxima in the glass-forming landscape of Cu-Zr alloys. In this work, we report two peaks in the glass-forming ability, located at Cu64.7Zr35.3 and Cu50.2Zr49.8. These two compositions find excellent agreement with previously reported results based on casting of discrete compositions.

  7. Planar Waveguides Formed by Ag Na Ion Exchange in Nonlinear Optical Glasses: Diffusion and Optical Properties

    NASA Astrophysics Data System (ADS)

    Martin, Marc; Videau, Jean J.; Canioni, Lionel; Adamietz, Frédéric; Sarger, Laurent; Le Flem, Gilles

    2000-01-01

    All-optical communication systems are the subject of intense research related to the integration of nonlinear optical materials. In sodiocalcic borophosphate glasses that contain niobium oxide and exhibit high nonlinear optical indices, planar waveguides have been formed by a Ag Na ion-exchange technique. WKB analysis has been used to characterize the diffusion profiles of silver ions exchanged in glass substrate samples chemically by an electron microprobe technique and optically by an M -line technique. These methods permit the Ag penetration depth and diffusion profile shape and index profiles to be determined. The results are analyzed and discussed in relation to Ca 2 concentration and exchange conditions in glasses. The Ag diffusion in these glasses can be almost entirely controlled for index-profile engineering.

  8. Form birefringence induced in multicomponent glass by femtosecond laser direct writing.

    PubMed

    Cao, Jing; Mazerolles, Léo; Lancry, Matthieu; Solas, Denis; Brisset, François; Poumellec, Bertrand

    2016-06-15

    We demonstrate a new kind of form birefringence in lithium niobium silicate glass induced by femtosecond laser direct writing. By combining electron backscatter diffraction and transmission electron microscopy, we reveal a self-assembled nanostructure consisting of periodic phase change: nonlinear optical nanocrystals embedded in a network of "walls" in a vitreous phase. These "walls" are aligned perpendicular to the laser polarization direction. This self-organized nanostructure may successfully explain the origin of the laser-induced birefringence in this multicomponent glass quite differently from pure silica. These findings highlight a spectacular modification of glass, and enable construction of a high contrast three-dimensional refractive index and birefringent structures at the micrometer scale in multicomponent glasses. PMID:27304277

  9. Revealing the role of molecular rigidity on the fragility evolution of glass-forming liquids

    PubMed Central

    Yildirim, C.; Raty, J.-Y.; Micoulaut, M.

    2016-01-01

    If quenched fast enough, a liquid is able to avoid crystallization and will remain in a metastable supercooled state down to the glass transition, with an important increase in viscosity upon further cooling. There are important differences in the way liquids relax as they approach the glass transition, rapid or slow variation in dynamic quantities under moderate temperature changes, and a simple means to quantify such variations is provided by the concept of fragility. Here, we report molecular dynamics simulations of a typical network-forming glass, Ge–Se, and find that the relaxation behaviour of the supercooled liquid is strongly correlated to the variation of rigidity with temperature and the spatial distribution of the corresponding topological constraints, which ultimately connect to the fragility minima. This permits extending the fragility concept to aspects of topology/rigidity, and to the degree of homogeneity of the atomic-scale interactions for a variety of structural glasses. PMID:27025348

  10. Revealing the role of molecular rigidity on the fragility evolution of glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Yildirim, C.; Raty, J.-Y.; Micoulaut, M.

    2016-03-01

    If quenched fast enough, a liquid is able to avoid crystallization and will remain in a metastable supercooled state down to the glass transition, with an important increase in viscosity upon further cooling. There are important differences in the way liquids relax as they approach the glass transition, rapid or slow variation in dynamic quantities under moderate temperature changes, and a simple means to quantify such variations is provided by the concept of fragility. Here, we report molecular dynamics simulations of a typical network-forming glass, Ge-Se, and find that the relaxation behaviour of the supercooled liquid is strongly correlated to the variation of rigidity with temperature and the spatial distribution of the corresponding topological constraints, which ultimately connect to the fragility minima. This permits extending the fragility concept to aspects of topology/rigidity, and to the degree of homogeneity of the atomic-scale interactions for a variety of structural glasses.

  11. Magnitude and risk factors of injuries in a glass bottle manufacturing plant.

    PubMed

    Bazroy, Joy; Roy, Gautam; Sahai, Ajit; Soudarssanane, M B

    2003-01-01

    A study was conducted in a glass bottle manufacturing plant in Pondicherry, India, to assess the magnitude and identify the risk factors of work-related injuries between January and December 1998. Three hundred and seventy-seven injuries were reported among 341 permanent workers followed up for one year (incidence=1,105.5/1,000 workers/yr). A higher load of injuries was noted in the first half of the night shifts and the second half of the other three shifts. Injuries were higher in the second half of the week and during the first half of the year. Hands and wrists were the most common sites of injury (40.6%), whereas the eye, foot, ankles and other body parts had 30%, 14.6%, 10.6% and 4.2% of injuries respectively. The commonest type of injury was cuts and lacerations (50.1%); injuries to the eye (due to foreign bodies, chemicals and welding sparks) accounted for 30%, sprains 8% and burns 7.1% of the injuries. A cohort of 75 workers chosen from the 341 permanent workers were followed up for the one year for identification of risk factors. Significant risk factors were age (less than 30 yr) and experience (less than 2 yr). Technical factors responsible for injury were a hazardous worksite in 37 (38.5%) cases, inadequate protection with safety wear in 32 (33%) cases and proximity to machines in 14 (14.6%) cases. Human factors identified were non-use of protective wear in 43 (45%), overconfidence in 18 (18.7%) and timing error while working with machines in 11 (11.4%) episodes. PMID:14605429

  12. XAF/XANES studies of plutonium-loaded sodalite/glass composite waste forms.

    SciTech Connect

    Aase, S. B.; Kropf, A. J.; Lewis, M. A.; Reed, D. T.; Richmann, M. K.

    1999-07-14

    A sodalite/glass ceramic waste form has been developed to immobilize highly radioactive nuclear wastes in chloride form, as part of an electrochemical cleanup process. Simulated waste forms have been fabricated which contain plutonium and are representative of the salt from the electrometallurgical process to recover uranium from spent nuclear fuel. X-ray absorption fine structure spectroscopy (XAFS) and x-ray absorption near-edge spectroscopy (XANES) studies were performed to determine the location, oxidation state and form of the plutonium within these waste forms. Plutonium, in the non-fission-element case, was found to segregate as plutonium(IV) oxide with a crystallite size of at least 20 nm. With fission elements present, the crystallite size was about 2 nm. No plutonium was observed within the sodalite or glass in the waste form.

  13. The Production of Advanced Glass Ceramic HLW Forms using Cold Crucible Induction Melter

    SciTech Connect

    Veronica J Rutledge; Vince Maio

    2013-10-01

    Cold Crucible Induction Melters (CCIMs) will favorably change how High-Level radioactive Waste (from nuclear fuel recovery) is treated in the 21st century. Unlike the existing Joule-Heated Melters (JHMs) currently in operation for the glass-based immobilization of High-Level Waste (HLW), CCIMs offer unique material features that will increase melt temperatures, increase throughput, increase mixing, increase loading in the waste form, lower melter foot prints, eliminate melter corrosion and lower costs. These features not only enhance the technology for producing HLW forms, but also provide advantageous attributes to the waste form by allowing more durable alternatives to glass. This paper discusses advantageous features of the CCIM, with emphasis on features that overcome the historical issues with the JHMs presently utilized, as well as the benefits of glass ceramic waste forms over borosilicate glass waste forms. These advantages are then validated based on recent INL testing to demonstrate a first-of-a-kind formulation of a non-radioactive ceramic-based waste form utilizing a CCIM.

  14. The fragility of Al Ni-based glass-forming melts

    NASA Astrophysics Data System (ADS)

    Si, Pengchao; Bian, Xiufang; Zhang, Junyan; Li, Hui; Sun, Minhua; Zhao, Yan

    2003-08-01

    In the original description of fragility, Angell (1988 J. Phys. Chem. Solids 49 863) determined the degree of fragility from the curvature on an Arrhenius plot. This paper discusses a new measurement of the fragility value. The fragility of Al-Ni-based glass-forming melts, which is seldom reported in this field, can be analysed by using data from their viscosity and thermal properties. The fragility is observed to be very high, which is in very good agreement with the low glass-forming ability of Al-Ni-based alloys.

  15. Atomic dynamics in Zr-(Co,Ni)-Al metallic glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Yuan, C. C.; Yang, F.; Kargl, F.; Holland-Moritz, D.; Simeoni, G. G.; Meyer, A.

    2015-06-01

    The microscopic transport and the macroscopic flow behavior of Zr-(Co,Ni)-Al melts are systemically investigated using containerless processing techniques. A remarkable decrease of the Co, Ni self-diffusion coefficient and increase of the melt viscosity upon alloying Al, are observed. In contrast to many other metallic glass-forming liquids, the average packing fraction of the melt derived from the measured macroscopic density decreases. Our study indicates that chemical interactions of Al with transition metal atoms play an important role in slowing down liquid dynamics of metal melts, which also contribute to their improved glass-forming ability.

  16. 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.

  17. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    SciTech Connect

    Moreau, P.; Gregoire, S.; Lochegnies, D.; Cesar de Sa, J.

    2007-05-17

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication...). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  18. Integration Of Heat Transfer Coefficient In Glass Forming Modeling With Special Interface Element

    NASA Astrophysics Data System (ADS)

    Moreau, P.; César de Sá, J.; Grégoire, S.; Lochegnies, D.

    2007-05-01

    Numerical modeling of the glass forming processes requires the accurate knowledge of the heat exchange between the glass and the forming tools. A laboratory testing is developed to determine the evolution of the heat transfer coefficient in different glass/mould contact conditions (contact pressure, temperature, lubrication…). In this paper, trials are performed to determine heat transfer coefficient evolutions in experimental conditions close to the industrial blow-and-blow process conditions. In parallel of this work, a special interface element is implemented in a commercial Finite Element code in order to deal with heat transfer between glass and mould for non-meshing meshes and evolutive contact. This special interface element, implemented by using user subroutines, permits to introduce the previous heat transfer coefficient evolutions in the numerical modelings at the glass/mould interface in function of the local temperatures, contact pressures, contact time and kind of lubrication. The blow-and-blow forming simulation of a perfume bottle is finally performed to assess the special interface element performance.

  19. Inelastic Neutron Scattering Studies of the Dynamics of Glass-Forming Materials in Confinement

    NASA Astrophysics Data System (ADS)

    Zorn, Reiner

    2015-03-01

    The study of the dynamics of glass-forming liquids in nanoscopic confinement may contribute to the understanding of the glass transition. Especially, the question of a cooperativity length scale may be addressed. In this presentation, results obtained by inelastic neutron scattering are presented. The first experiments were done to study the α relaxation of glass-forming liquids and polymers in nanoporous silica. Neutron scattering is a suitable method to study such composite materials because the scattering of the liquid component can be emphasized by proper choice of isotopes. By combining time-of-flight spectroscopy and backscattering spectroscopy it is possible to cover the large dynamical range spanned by the dynamics of glass-forming materials. The experiments demonstrated a broadening of the spectrum of relaxation times with faster as well as slower components compared to the bulk. In later experiments `soft' confinement in a microemulsion was used to reduce surface effects. In this system a definite acceleration of the dynamics was observed. In all cases the glass-specific fast vibrational dynamics (boson peak) was also studied, revealing a characteristic confinement dependence which allows conclusions on its nature. Finally, studies were carried out on polymers by neutron spin echo spectroscopy with the aim of observing the confinement effect on polymer specific dynamics (Rouse motion). These studies showed that a comparatively simple model is able to explain the deviation from bulk behavior.

  20. Product stewardship and science: safe manufacture and use of fiber glass.

    PubMed

    Hesterberg, Thomas W; Anderson, Robert; Bernstein, David M; Bunn, William B; Chase, Gerald A; Jankousky, Angela Libby; Marsh, Gary M; McClellan, Roger O

    2012-03-01

    This paper describes a proactive product stewardship program for glass fibers. That effort included epidemiological studies of workers, establishment of stringent workplace exposure limits, liaison with customers on safe use of products and, most importantly, a research program to evaluate the safety of existing glass fiber products and guide development of new even safer products. Chronic inhalation exposure bioassays were conducted with rodents and hamsters. Amosite and crocidolite asbestos produced respiratory tract cancers as did exposure to "biopersistent" synthetic vitreous fibers. "less biopersistent" glass fibers did not cause respiratory tract cancers. Corollary studies demonstrated the role of slow fiber dissolution rates and biopersistence in cancer induction. These results guided development of safer glass fiber products and have been used in Europe to regulate fibers and by IARC and NTP in classifying fibers. IARC concluded special purpose fibers and refractory ceramic fibers are "possibly carcinogenic to humans" and insulation glass wool, continuous glass filament, rock wool and slag wool are "not classifiable as to their carcinogenicity to human." The NTP's 12th report on carcinogens lists "Certain Glass Wool Fibers (Inhalable)" as "reasonably anticipated to be a human carcinogen." "Certain" in the descriptor refers to "biopersistent" glass fibers and excludes "less biopersistent" glass fibers. PMID:22266014

  1. High glass-forming ability correlated with fragility of Mg-Cu(Ag)-Gd alloys

    NASA Astrophysics Data System (ADS)

    Zheng, Qiang; Xu, Jian; Ma, Evan

    2007-12-01

    We report bulk metallic glasses with critical diameter (Dc) in the 20-27mm range over a relatively wide composition range in the Mg-Cu-Ag-Gd quaternary system. Such an extraordinary glass-forming ability is correlated with the relatively strong liquid behavior of these alloys in terms of Angell's [Science 267, 1924 (1995)] fragility concept. The relaxation time of the ternary Mg61Cu28Gd11 and quaternary Mg59.5Cu22.9Ag6.6Gd11 alloys was measured. In terms of the fragility parameter D*, the Mg59.5Cu22.9Ag6.6Gd11 alloy with a critical diameter of 27mm under copper mold casting has a D* of 25, higher than all the bulk metallic glass-forming alloys reported so far. The implications of these findings are discussed.

  2. Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy

    SciTech Connect

    Shen Jun; Chen Qingjun; Sun Jianfei; Fan Hongbo; Wang Gang

    2005-04-11

    It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16 mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500 MPa and Vickers hardness of 1253 kg mm{sup -2}.

  3. Secondary phases formed during nuclear waste glass-water interactions: Thermodynamic and derived properties

    SciTech Connect

    McKenzie, W.F.

    1992-08-01

    The thermodynamic properties of secondary phases observed to form during nuclear waste glass-water interactions are of particular interest as it is with the application of these properties together with the thermodynamic properties of other solid phases, fluid phases, and aqueous species that one may predict the environmental consequences of introducing radionuclides contained in the glass into groundwater at a high-level nuclear waste repository. The validation of these predicted consequences can be obtained from laboratory experiments and field observations at natural analogue sites. The purpose of this report is to update and expand the previous compilation (McKenzie, 1991) of thermodynamic data retrieved from the literature and/or estimated for secondary phases observed to form (and candidate phases from observed chemical compositions) during nuclear waste glass-water interactions. In addition, this report includes provisionally recommended thermodynamic data of secondary phases.

  4. Linking structure to fragility in bulk metallic glass-forming liquids

    SciTech Connect

    Wei, Shuai E-mail: m.stolpe@mx.uni-saarland.de; Stolpe, Moritz E-mail: m.stolpe@mx.uni-saarland.de; Gross, Oliver; Gallino, Isabella; Hembree, William; Busch, Ralf; Evenson, Zach; Bednarcik, Jozef; Kruzic, Jamie J.

    2015-05-04

    Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T{sub g}. The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic length scales. A more fragile behavior results from a more pronounced thermally induced dilatation of the structure on a length scale of about 3 to 4 atomic diameters, coupled with shallower temperature dependence of structural changes in the nearest neighbor environment. These findings shed light on the structural origin of viscous slowdown during undercooling of bulk metallic glass-forming liquids and demonstrate the promise of predicting the properties of bulk metallic glasses from the atomic scale structure.

  5. Evolution of collective motion in a model glass-forming liquid during physical aging

    NASA Astrophysics Data System (ADS)

    Shavit, Amit; Douglas, Jack F.; Riggleman, Robert A.

    2013-03-01

    At temperatures moderately below their glass transition temperature, the properties of many glass-forming materials can evolve slowly with time in a process known as physical aging whereby the thermodynamic, mechanical, and dynamic properties all drift towards their equilibrium values. In this work, we study the evolution of the thermodynamic and dynamic properties during physical aging for a model polymer glass. Specifically, we test the relationship between an estimate of the size of the cooperative rearrangements taking the form of strings and the effective structural relaxation time predicted by the Adam-Gibbs relationship for both an equilibrium supercooled liquid and the same fluid undergoing physical aging towards equilibrium after a series of temperature jumps. We find that there is apparently a close correlation between a structural feature of the fluid, the size of the string-like rearrangements, and the structural relaxation time, although the relationship for the aging fluid appears to be distinct from that of the fluid at equilibrium.

  6. Fast and slow crystal growth kinetics in glass-forming melts

    SciTech Connect

    Orava, J.; Greer, A. L.

    2014-06-07

    Published values of crystal growth rates are compared for supercooled glass-forming liquids undergoing congruent freezing at a planar crystal-liquid interface. For the purposes of comparison pure metals are considered to be glass-forming systems, using data from molecular-dynamics simulations. For each system, the growth rate has a maximum value U{sub max} at a temperature T{sub max} that lies between the glass-transition temperature T{sub g} and the melting temperature T{sub m}. A classification is suggested, based on the lability (specifically, the propensity for fast crystallization), of the liquid. High-lability systems show “fast” growth characterized by a high U{sub max}, a low T{sub max} / T{sub m}, and a very broad peak in U vs. T / T{sub m}. In contrast, systems showing “slow” growth have a low U{sub max}, a high T{sub max} / T{sub m}, and a sharp peak in U vs. T / T{sub m}. Despite the difference of more than 11 orders of magnitude in U{sub max} seen in pure metals and in silica, the range of glass-forming systems surveyed fit into a common pattern in which the lability increases with lower reduced glass-transition temperature (T{sub g} / T{sub m}) and higher fragility of the liquid. A single parameter, a linear combination of T{sub g} / T{sub m} and fragility, can show a good correlation with U{sub max}. For all the systems, growth at U{sub max} is coupled to the atomic/molecular mobility in the liquid. It is found that, across the diversity of glass-forming systems, T{sub max} / T{sub g} = 1.48 ± 0.15.

  7. Fast and slow crystal growth kinetics in glass-forming melts.

    PubMed

    Orava, J; Greer, A L

    2014-06-01

    Published values of crystal growth rates are compared for supercooled glass-forming liquids undergoing congruent freezing at a planar crystal-liquid interface. For the purposes of comparison pure metals are considered to be glass-forming systems, using data from molecular-dynamics simulations. For each system, the growth rate has a maximum value U(max) at a temperature T(max) that lies between the glass-transition temperature T(g) and the melting temperature T(m). A classification is suggested, based on the lability (specifically, the propensity for fast crystallization), of the liquid. High-lability systems show "fast" growth characterized by a high U(max), a low T(max)/T(m), and a very broad peak in U vs. T/T(m). In contrast, systems showing "slow" growth have a low U(max), a high T(max)/T(m), and a sharp peak in U vs. T/T(m). Despite the difference of more than 11 orders of magnitude in U(max) seen in pure metals and in silica, the range of glass-forming systems surveyed fit into a common pattern in which the lability increases with lower reduced glass-transition temperature (T(g)/T(m)) and higher fragility of the liquid. A single parameter, a linear combination of T(g)/T(m) and fragility, can show a good correlation with U(max). For all the systems, growth at U(max) is coupled to the atomic/molecular mobility in the liquid. It is found that, across the diversity of glass-forming systems, T(max)/T(g) = 1.48 ± 0.15. PMID:24908023

  8. Sub-second thermoplastic forming of bulk metallic glasses by ultrasonic beating

    NASA Astrophysics Data System (ADS)

    Ma, Jiang; Liang, Xiong; Wu, Xiaoyu; Liu, Zhiyuan; Gong, Feng

    2015-12-01

    The work proposed a novel thermoplastic forming approach-the ultrasonic beating forming (UBF) method for bulk metallic glasses (BMGs) in present work. The rapid forming approach can finish the thermoplastic forming of BMGs in less than one second, avoiding the time-dependent crystallization and oxidation to the most extent. Besides, the UBF is also proved to be competent in the fabrication of structures with the length scale ranging from macro scale to nano scale. Our results propose a novel route for the thermoplastic forming of BMGs and have promising applications in the rapid fabrication of macro to nano scale products and devices.

  9. Sub-second thermoplastic forming of bulk metallic glasses by ultrasonic beating

    PubMed Central

    Ma, Jiang; Liang, Xiong; Wu, Xiaoyu; Liu, Zhiyuan; Gong, Feng

    2015-01-01

    The work proposed a novel thermoplastic forming approach–the ultrasonic beating forming (UBF) method for bulk metallic glasses (BMGs) in present work. The rapid forming approach can finish the thermoplastic forming of BMGs in less than one second, avoiding the time-dependent crystallization and oxidation to the most extent. Besides, the UBF is also proved to be competent in the fabrication of structures with the length scale ranging from macro scale to nano scale. Our results propose a novel route for the thermoplastic forming of BMGs and have promising applications in the rapid fabrication of macro to nano scale products and devices. PMID:26644149

  10. 46 CFR 52.01-145 - Manufacturers' data report forms (modifies PG-112 and PG-113).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-145 Manufacturers' data report forms... I of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 52.01-1) must be made available to the marine inspector for review. The Authorized Inspector's National...

  11. 46 CFR 52.01-145 - Manufacturers' data report forms (modifies PG-112 and PG-113).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-145 Manufacturers' data report forms... I of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 52.01-1) must be made available to the marine inspector for review. The Authorized Inspector's National...

  12. 46 CFR 52.01-145 - Manufacturers' data report forms (modifies PG-112 and PG-113).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-145 Manufacturers' data report forms... I of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 52.01-1) must be made available to the marine inspector for review. The Authorized Inspector's National...

  13. 46 CFR 52.01-145 - Manufacturers' data report forms (modifies PG-112 and PG-113).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) MARINE ENGINEERING POWER BOILERS General Requirements § 52.01-145 Manufacturers' data report forms... I of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 52.01-1) must be made available to the marine inspector for review. The Authorized Inspector's National...

  14. 46 CFR 52.01-145 - Manufacturers' data report forms (modifies PG-112 and PG-113).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Manufacturers' data report forms (modifies PG-112 and PG-113). 52.01-145 Section 52.01-145 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... I of the ASME Boiler and Pressure Vessel Code (incorporated by reference; see 46 CFR 52.01-1)...

  15. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    NASA Astrophysics Data System (ADS)

    Tang, Ming; Kossoy, Anna; Jarvinen, Gordon; Crum, Jarrod; Turo, Laura; Riley, Brian; Brinkman, Kyle; Fox, Kevin; Amoroso, Jake; Marra, James

    2014-05-01

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (∼1-5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  16. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    SciTech Connect

    Tang, Ming; Kossoy, Anna; Jarvinen, G. D.; Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Brinkman, Kyle; Fox, Kevin M.; Amoroso, Jake; Marra, James C.

    2014-02-03

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (~1–5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  17. A novel parameter to describe the glass-forming ability of alloys

    NASA Astrophysics Data System (ADS)

    Park, E. S.; Ryu, C. W.; Kim, W. T.; Kim, D. H.

    2015-08-01

    In this paper, we propose a new parameter for glass-forming ability (GFA) based on the combination of thermodynamic (stability of stable and metastable liquids by ΔTm = Tmmix - Tl and ΔTx = Tx - Tg, respectively) and kinetic (resistance to crystallization by Tx) aspects for glass formation. The parameter is defined as ɛ = (ΔTm + ΔTx + Tx)/Tmmix without directly adding Tg while considering the whole temperature range for glass formation up to Tmmix, which reflects the relative position of crystallization curve in continuous cooling transformation diagram. The relationship between the ɛ parameter and critical cooling rate (Rc) or maximum section thickness for glass formation (Zmax) clearly confirms that the ɛ parameter exhibits a better correlation with GFA than other commonly used GFA parameters, such as ΔTx (=Tx - Tg), K (=[Tx - Tg]/[Tl - Tx]), ΔT*(=(Tmmix - Tl)/Tmmix), Trg (=Tg/Tl), and γ (=[Tx]/[Tl + Tg]). The relationship between the ɛ parameter and Rc or Zmax is also formulated and evaluated in the study. The results suggest that the ɛ parameter can effectively predict Rc and Zmax for various glass-forming alloys, which would permit more widespread uses of these paradigm-shifting materials in a variety of industries.

  18. Asymmetric crystallization during cooling and heating in model glass-forming systems.

    PubMed

    Wang, Minglei; Zhang, Kai; Li, Zhusong; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2015-03-01

    We perform molecular dynamics (MD) simulations of the crystallization process in binary Lennard-Jones systems during heating and cooling to investigate atomic-scale crystallization kinetics in glass-forming materials. For the cooling protocol, we prepared equilibrated liquids above the liquidus temperature Tl and cooled each sample to zero temperature at rate Rc. For the heating protocol, we first cooled equilibrated liquids to zero temperature at rate Rp and then heated the samples to temperature T>Tl at rate Rh. We measured the critical heating and cooling rates Rh* and Rc*, below which the systems begin to form a substantial fraction of crystalline clusters during the heating and cooling protocols. We show that Rh*>Rc* and that the asymmetry ratio Rh*/Rc* includes an intrinsic contribution that increases with the glass-forming ability (GFA) of the system and a preparation-rate dependent contribution that increases strongly as Rp→Rc* from above. We also show that the predictions from classical nucleation theory (CNT) can qualitatively describe the dependence of the asymmetry ratio on the GFA and preparation rate Rp from the MD simulations and results for the asymmetry ratio measured in Zr- and Au-based bulk metallic glasses (BMG). This work emphasizes the need for and benefits of an improved understanding of crystallization processes in BMGs and other glass-forming systems. PMID:25871112

  19. Asymmetric crystallization during cooling and heating in model glass-forming systems

    NASA Astrophysics Data System (ADS)

    Wang, Minglei; Zhang, Kai; Li, Zhusong; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-03-01

    We perform molecular dynamics (MD) simulations of the crystallization process in binary Lennard-Jones systems during heating and cooling to investigate atomic-scale crystallization kinetics in glass-forming materials. For the cooling protocol, we prepared equilibrated liquids above the liquidus temperature Tl and cooled each sample to zero temperature at rate Rc. For the heating protocol, we first cooled equilibrated liquids to zero temperature at rate Rp and then heated the samples to temperature T >Tl at rate Rh. We measured the critical heating and cooling rates Rh* and Rc*, below which the systems begin to form a substantial fraction of crystalline clusters during the heating and cooling protocols. We show that Rh*>Rc* and that the asymmetry ratio Rh*/Rc* includes an intrinsic contribution that increases with the glass-forming ability (GFA) of the system and a preparation-rate dependent contribution that increases strongly as Rp→Rc* from above. We also show that the predictions from classical nucleation theory (CNT) can qualitatively describe the dependence of the asymmetry ratio on the GFA and preparation rate Rp from the MD simulations and results for the asymmetry ratio measured in Zr- and Au-based bulk metallic glasses (BMG). This work emphasizes the need for and benefits of an improved understanding of crystallization processes in BMGs and other glass-forming systems.

  20. Microstructural characterization of halite inclusion in a glass-bonded ceramic waste form.

    SciTech Connect

    Luo, J. S.; Ebert, W. L.

    2000-12-14

    A glass-bonded ceramic waste form is being developed to immobilize radioactively contaminated chloride waste salts generated during the conditioning of spent sodium-bonded nuclear fuel for disposal. The waste salt is first mixed with zeolite A to occlude the salt into cavities in the zeolite structure. The salt-loaded zeolite is then mixed with a borosilicate glass and consolidated by hot isostatic pressing. During this process, the zeolite converts to the mineral sodalite, which retains most of the waste salt, and small amounts of halite are generated. Halite inclusions have been observed within micron- to submicron-sized pores that form within the glass phase in the vicinity of the sodalite/glass interface. These inclusions are important because they may contain small amounts of radionuclide contaminants (eg {sup 135}Cs and {sup 129}I),and may affect the corrosion behavior of the waste form. Optical microscopy, scanning electron microscopy, and transmission electron microscopy were used to characterize the chemical nature and distribution of halite inclusions in the waste form.

  1. Nanoscale physical properties of polymer glasses formed by solvent-assisted laser deposition

    NASA Astrophysics Data System (ADS)

    Shepard, Kimberly; Arnold, Craig; Priestley, Rodney

    2015-03-01

    High-energy, low-density nanostructured polymer glasses are formed via the solvent-assisted laser deposition technique MAPLE (Matrix Assisted Pulsed Laser Evaporation). During film deposition, micro- to nano-size polymer/solvent clusters are ejected via laser ablation from a frozen dilute polymer solution. During flight to the substrate under vacuum, the clusters experience rapid cooling and solvent stripping, forming polymer nanoglobules. Bulk polymer films are formed via the gradual assembly of these spherical-like nanostructured building blocks (i.e. nanoglobules). The MAPLE process thus enables investigation of the exceptional properties of glasses formed under extreme processing conditions. In the bulk state, we probe the effect of process parameters and chemical identity of the thermal behavior of a series of methacrylate polymers. We also employ multiple techniques to directly measure the properties of the polymer nanoglobules and connect the results to the global film properties. This talk will address nanoscale dilatometry via AFM, in which the volume of an individual polymer nanoglobule is tracked as it is heated through its glass transition, as well as Flash DSC analysis of the thermal properties of nanogram size MAPLE-deposited polymer glasses. We then discuss these findings in the context of the material's unconventional route to the glassy state.

  2. Connection between the packing efficiency of binary hard spheres and the glass-forming ability of bulk metallic glasses.

    PubMed

    Zhang, Kai; Smith, W Wendell; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2014-09-01

    We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate R, size ratio α, and number fraction x(S) of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate R(c), below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with α≳0.8 that do not demix, R(c) decreases strongly with Δϕ(J), as R(c)∼exp(-1/Δϕ(J)(2)), where Δϕ(J) is the difference between the average packing fraction of the amorphous packings and random crystal structures at R(c). Systems with α≲0.8 partially demix, which promotes crystallization, but we still find a strong correlation between R(c) and Δϕ(J). We show that known metal-metal BMGs occur in the regions of the α and x(S) parameter space with the lowest values of R(c) for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing α to increase packing efficiency, while maximizing α to prevent demixing. PMID:25314450

  3. Dropwise additive manufacturing of pharmaceutical products for melt-based dosage forms.

    PubMed

    Içten, Elçin; Giridhar, Arun; Taylor, Lynne S; Nagy, Zoltan K; Reklaitis, Gintaras V

    2015-05-01

    The US Food and Drug Administration introduced the quality by design approach and process analytical technology guidance to encourage innovation and efficiency in pharmaceutical development, manufacturing, and quality assurance. As part of this renewed emphasis on the improvement of manufacturing, the pharmaceutical industry has begun to develop more efficient production processes with more intensive use of online measurement and sensing, real-time quality control, and process control tools. Here, we present dropwise additive manufacturing of pharmaceutical products (DAMPP) as an alternative to conventional pharmaceutical manufacturing methods. This mini-manufacturing process for the production of pharmaceuticals utilizes drop on demand printing technology for automated and controlled deposition of melt-based formulations onto edible substrates. The advantages of drop-on-demand technology, including reproducible production of small droplets, adjustable drop sizing, high placement accuracy, and flexible use of different formulations, enable production of individualized dosing even for low-dose and high-potency drugs. In this work, DAMPP is used to produce solid oral dosage forms from hot melts of an active pharmaceutical ingredient and a polymer. The dosage forms are analyzed to show the reproducibility of dosing and the dissolution behavior of different formulations. PMID:25639605

  4. Composition dependence of the glass forming ability in binary mixtures: The role of demixing entropy.

    PubMed

    Nandi, Ujjwal Kumar; Banerjee, Atreyee; Chakrabarty, Suman; Bhattacharyya, Sarika Maitra

    2016-07-21

    We present a comparative study of the glass forming ability of binary systems with varying composition, where the systems have similar global crystalline structure (CsCl+fcc). Biased Monte Carlo simulations using umbrella sampling technique show that the free energy cost to create a CsCl nucleus increases as the composition of the smaller particles is decreased. We find that systems with comparatively lower free energy cost to form CsCl nucleus exhibit more pronounced pre-crystalline demixing near the liquid/crystal interface. The structural frustration between the CsCl and fcc crystal demands this demixing. We show that closer to the equimolar mixture, the entropic penalty for demixing is lower and a glass forming system may crystallize when seeded with a nucleus. This entropic penalty as a function of composition shows a non-monotonic behaviour with a maximum at a composition similar to the well known Kob-Anderson (KA) model. Although the KA model shows the maximum entropic penalty and thus maximum frustration against CsCl formation, it also shows a strong tendency towards crystallization into fcc lattice of the larger "A" particles which can be explained from the study of the energetics. Thus for systems closer to the equimolar mixture although it is the requirement of demixing which provides their stability against crystallization, for KA model it is not demixing but slow dynamics and the presence of the "B" particles make it a good glass former. The locally favoured structure around "B" particles is quite similar to the CsCl structure and the incompatibility of CsCl and fcc hinders the fcc structure growth in the KA model. Although the glass forming binary systems studied here are quite similar, differing only in composition, we find that their glass forming ability cannot be attributed to a single phenomenon. PMID:27448892

  5. Composition dependence of the glass forming ability in binary mixtures: The role of demixing entropy

    NASA Astrophysics Data System (ADS)

    Nandi, Ujjwal Kumar; Banerjee, Atreyee; Chakrabarty, Suman; Bhattacharyya, Sarika Maitra

    2016-07-01

    We present a comparative study of the glass forming ability of binary systems with varying composition, where the systems have similar global crystalline structure (CsCl+fcc). Biased Monte Carlo simulations using umbrella sampling technique show that the free energy cost to create a CsCl nucleus increases as the composition of the smaller particles is decreased. We find that systems with comparatively lower free energy cost to form CsCl nucleus exhibit more pronounced pre-crystalline demixing near the liquid/crystal interface. The structural frustration between the CsCl and fcc crystal demands this demixing. We show that closer to the equimolar mixture, the entropic penalty for demixing is lower and a glass forming system may crystallize when seeded with a nucleus. This entropic penalty as a function of composition shows a non-monotonic behaviour with a maximum at a composition similar to the well known Kob-Anderson (KA) model. Although the KA model shows the maximum entropic penalty and thus maximum frustration against CsCl formation, it also shows a strong tendency towards crystallization into fcc lattice of the larger "A" particles which can be explained from the study of the energetics. Thus for systems closer to the equimolar mixture although it is the requirement of demixing which provides their stability against crystallization, for KA model it is not demixing but slow dynamics and the presence of the "B" particles make it a good glass former. The locally favoured structure around "B" particles is quite similar to the CsCl structure and the incompatibility of CsCl and fcc hinders the fcc structure growth in the KA model. Although the glass forming binary systems studied here are quite similar, differing only in composition, we find that their glass forming ability cannot be attributed to a single phenomenon.

  6. Scaling out the density dependence of the α relaxation in glass-forming polymers

    NASA Astrophysics Data System (ADS)

    Alba-Simionesco, C.; Cailliaux, A.; Alegría, A.; Tarjus, G.

    2004-10-01

    We show that the density and temperature dependences of the α-relaxation time of several glass-forming polymers can be described through a single scaling variable X = e(ρ)/T, where e(ρ) is well fitted by a power law ρx, x being a species-specific parameter. This implies that "fragility" is an intrinsic, density-independent property of a glass-former characterizing its super-Arrhenius slowing-down of relaxations, and it leads us to propose a modification of the celebrated Angell plot.

  7. Nonlinear dielectric response at the excess wing of glass-forming liquids.

    PubMed

    Bauer, Th; Lunkenheimer, P; Kastner, S; Loidl, A

    2013-03-01

    We present nonlinear dielectric measurements of glass-forming glycerol and propylene carbonate applying electrical fields up to 671 kV/cm. The measurements extend to sufficiently high frequencies to allow for the investigation of the nonlinear behavior in the regime of the so-far mysterious excess wing, showing up in the loss spectra of many glass formers as a second power law at high frequencies. Surprisingly, we find a complete lack of nonlinear behavior in the excess wing, in marked contrast to the α relaxation where, in agreement with previous reports, a strong increase of dielectric constant and loss is found. PMID:23521298

  8. Structures and Dynamics of Glass-Forming Colloidal Liquids under Spherical Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Bo; Cheng, Xiang

    2016-03-01

    Recent theories predict that when a supercooled liquid approaches the glass transition, particle clusters with a special "amorphous order" nucleate within the liquid, which lead to static correlations dictating the dramatic slowdown of liquid relaxation. The prediction, however, has yet to be verified in 3D experiments. Here, we design a colloidal system, where particles are confined inside spherical cavities with an amorphous layer of particles pinned at the boundary. Using this novel system, we capture the amorphous-order particle clusters and demonstrate the development of a static correlation. Moreover, by investigating the dynamics of spherically confined samples, we reveal a profound influence of the static correlation on the relaxation of colloidal liquids. In analogy to glass-forming liquids with randomly pinned particles, we propose a simple relation for the change of the configurational entropy of confined colloidal liquids, which quantitatively explains our experimental findings and illustrates a divergent static length scale during the colloidal glass transition.

  9. Correlation between thermodynamic and kinetic fragilities in nonpolymeric glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Senkov, Oleg N.; Miracle, Daniel B.

    2008-03-01

    A phenomenological relationship between reduced excess heat capacity of supercooled liquid ΔCpexc(Tg)/ΔSm at the glass transition temperature Tg, fragility index m, and reduced glass transition temperature Trg=Tg/Tm, where Tm is the melting (liquidus) temperature, was derived for fragile nonpolymeric glass-forming liquids under the assumptions that the fragile behavior of these liquids is described by the Vogel-Fulcher-Tammann (VFT) equation; the excess heat capacity of liquid is inversely proportional to the absolute temperature and the VFT temperature T0 is equal to the Kauzmann temperature TK. It was found that ΔCpexc(Tg)/ΔSm is a composite function of m and Trg, which indicates that the empirical correlation ΔCpexc(Tg)/ΔSm=0.025m recently identified by Wang et al. [J. Chem Phys. 125, 074505 (2006)] is probably valid only for liquids which have nearly the same values of Trg.

  10. Understanding glass-forming ability through sluggish crystallization of atomically thin metallic glassy films

    SciTech Connect

    Sun, Y. T.; Cao, C. R.; Huang, K. Q.; Zhao, N. J.; 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

    2014-08-04

    The glass-forming ability (GFA) of an alloy, closely related to its ability to resist crystallization, is a crucial issue in condensed matter physics. So far, the studies on GFA are mostly statistical and empirical guides. Benefiting from the ultrahigh thermal stability of ultrathin metallic glassy film and high resolution spherical aberration-corrected transmission electron microscope, the crystallization of atomically thin ZrCu and its microalloyed ZrCuAl glasses with markedly different GFA was investigated at the atomic scale. We find the Zr diffusivity estimated from the density of nuclei is dramatically decreased by adding of Al, which is the major reason for the much better GFA of the ZrCuAl metallic glass.

  11. Superheated liquid fragility and thermodynamic refinement for evaluation of metallic glass-forming ability

    NASA Astrophysics Data System (ADS)

    Meng, Q. G.; Zhang, S. G.; Xia, M. X.; Li, J. G.; Zhou, J. K.

    2007-01-01

    Based on the super-Arrhenius equation and Angell's fragility concept [J. Non-Cryst. Solids 131, 13 (1991)], the expression of the fragility parameter for superheated liquid is deduced as M =E∞/kBTl, where E∞ is the activation energy, kB the Boltzmann constant, and Tl the liquidus temperature. It exhibits a negative correlation with the glass-forming ability (GFA) of the referenced metallic glasses in the same system rather than in the different systems, while the parameter ɛ based on order-disorder competition is just the opposite. The refined fragility parameter M* (=M/ɛ) gives a much better reflection of the GFA for the metallic glasses.

  12. Structures and Dynamics of Glass-Forming Colloidal Liquids under Spherical Confinement.

    PubMed

    Zhang, Bo; Cheng, Xiang

    2016-03-01

    Recent theories predict that when a supercooled liquid approaches the glass transition, particle clusters with a special "amorphous order" nucleate within the liquid, which lead to static correlations dictating the dramatic slowdown of liquid relaxation. The prediction, however, has yet to be verified in 3D experiments. Here, we design a colloidal system, where particles are confined inside spherical cavities with an amorphous layer of particles pinned at the boundary. Using this novel system, we capture the amorphous-order particle clusters and demonstrate the development of a static correlation. Moreover, by investigating the dynamics of spherically confined samples, we reveal a profound influence of the static correlation on the relaxation of colloidal liquids. In analogy to glass-forming liquids with randomly pinned particles, we propose a simple relation for the change of the configurational entropy of confined colloidal liquids, which quantitatively explains our experimental findings and illustrates a divergent static length scale during the colloidal glass transition. PMID:26991205

  13. Molecular cooperativity in the dynamics of glass-forming systems: A new insight

    NASA Astrophysics Data System (ADS)

    Hong, L.; Gujrati, P. D.; Novikov, V. N.; Sokolov, A. P.

    2009-11-01

    The mechanism behind the steep slowing down of molecular motions upon approaching the glass transition remains a great puzzle. Most of the theories relate this mechanism to the cooperativity in molecular motion. In this work, we estimate the length scale of molecular cooperativity ξ for many glass-forming systems from the collective vibrations (the so-called boson peak). The obtained values agree well with the dynamic heterogeneity length scale estimated using four-dimensional NMR. We demonstrate that ξ directly correlates to the dependence of the structural relaxation on volume. This dependence presents only one part of the mechanism of slowing down the structural relaxation. Our analysis reveals that another part, the purely thermal variation in the structural relaxation (at constant volume), does not have a direct correlation with molecular cooperativity. These results call for a conceptually new approach to the analysis of the mechanism of the glass transition and to the role of molecular cooperativity.

  14. Theoretical study of miscibility and glass-forming trends in mixtures of polystyrene spheres

    NASA Technical Reports Server (NTRS)

    Shih, W.-H.; Stroud, D.

    1984-01-01

    A theoretical study of glass-forming trends and miscibility in mixtures of polystyrene spheres (polyballs) of different diameters, suspended in an aqueous solution, is presented. The polyballs are assumed to be charged and to interact via a Debye-Hueckel screened Coulomb potential. The Helmholtz free energy is calculated from a variational principle based on the Gibbs-Bogoliubov inequality, in which a mixture of hard spheres of different diameters is chosen as the reference system. It is found that when the charges of the two types of polyballs are sufficiently different, the variationally determined ratio of hard-sphere diameters differs substantially, leading to packing difficulties characteristic of glass formation. The experimentally observed range of glass formation corresponds to a ratio of hard-sphere diameters of 0.8 or less. Calculations of the free energy as a function of concentration indicate that the liquid polyball mixture is stable against the phase separation, even for widely different polyball charges.

  15. Development and testing of matrices for the encapsulation of glass and ceramic nuclear waste forms.

    SciTech Connect

    Wald, J.W.; Brite, D.W.; Gurwell, W.E.; Buckwalter, C.Q.; Bunnell, L.R.; Gray, W.J.; Blair, H.T.; Rusin, J.M.

    1982-02-01

    This report details the results of research on the matrix encapsulation of high level wastes at PML over the past few years. The demonstrations and tests described were designed to illustrate how the waste materials are effected when encapsulated in an inert matrix. Candidate materials evaluated for potential use as matrices for encapslation of pelletized ceramics or glass marbles were categorized into four groups: metals, glasses, ceramics, and graphite. Two processing techniques, casting and hot pressing, were investigated as the most promising methods of formation or densification of the matrices. The major results reported deal with the development aspects. However, chemical durability tests (leach tests) of the matrix materials themselves and matrix-waste form composites are also reported. Matrix waste forms can provide a low porosity, waste-free barrier resulting in increased leach protection, higher impact strength and improved thermal conductivity compared to unencapsulated glass or ceramic waste materials. Glass marbles encapsulated in a lead matrix offer the most significant improvement in waste form stability of all combinations evaluated. This form represents a readily demonstrable process that provides high thermal conductivity, mechanical shock resistance, radiation shielding and increased chemical durability through both a chemical passivation mechanism and as a physical barrier. Other durable matrix waste forms evaluated, applicable primarily to ceramic pellets, involved hot-pressed titanium or TiO/sub 2/ materials. In the processing of these forms, near 100% dense matrices were obtained. The matrix materials had excellent compatibility with the waste materials and superior potential chemical durability. Cracking of the hot-pressed ceramic matrix forms, in general, prevented the realization of their optimum properties.

  16. The glass-forming ability of model metal-metalloid alloys.

    PubMed

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

    2015-03-14

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σS/σL and number fraction xS of the metalloid species. We show that the regime in the space of σS/σL and xS where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys. PMID:25770548

  17. The correlation between fragility, density, and atomic interaction in glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Wang, Lijin; Guan, Pengfei; Wang, W. H.

    2016-07-01

    The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as RI, RII, and RIII, respectively, with qualitatively disparate dynamic behaviors: RI which can be described by "softness makes strong glasses," RII where fragility is independent of softness and can only be tuned by density, and RIII with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses.

  18. The correlation between fragility, density, and atomic interaction in glass-forming liquids.

    PubMed

    Wang, Lijin; Guan, Pengfei; Wang, W H

    2016-07-21

    The fragility that controls the temperature-dependent viscous properties of liquids as the glass transition is approached, in various glass-forming liquids with different softness of the repulsive part of atomic interactions at different densities, is investigated by molecular dynamic simulations. We show that the landscape of fragility in purely repulsive systems can be separated into three regions denoted as RI, RII, and RIII, respectively, with qualitatively disparate dynamic behaviors: RI which can be described by "softness makes strong glasses," RII where fragility is independent of softness and can only be tuned by density, and RIII with constant fragility, suggesting that density plays an unexpected role for understanding the repulsive softness dependence of fragility. What is more important is that we unify the long-standing inconsistence with respect to the repulsive softness dependence of fragility by observing that a glass former can be tuned more fragile if nonperturbative attraction is added into it. Moreover, we find that the vastly dissimilar influences of attractive interaction on fragility could be estimated from the structural properties of related zero-temperature glasses. PMID:27448894

  19. The glass-forming ability of model metal-metalloid alloys

    SciTech Connect

    Zhang, Kai; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O’Hern, Corey S.

    2015-03-14

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σ{sub S}/σ{sub L} and number fraction x{sub S} of the metalloid species. We show that the regime in the space of σ{sub S}/σ{sub L} and x{sub S} where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  20. Length scales in glass-forming liquids and related systems: a review

    NASA Astrophysics Data System (ADS)

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-01-01

    The central problem in the study of glass-forming liquids and other glassy systems is the understanding of the complex structural relaxation and rapid growth of relaxation times seen on approaching the glass transition. A central conceptual question is whether one can identify one or more growing length scale(s) associated with this behavior. Given the diversity of molecular glass-formers and a vast body of experimental, computational and theoretical work addressing glassy behavior, a number of ideas and observations pertaining to growing length scales have been presented over the past few decades, but there is as yet no consensus view on this question. In this review, we will summarize the salient results and the state of our understanding of length scales associated with dynamical slow down. After a review of slow dynamics and the glass transition, pertinent theories of the glass transition will be summarized and a survey of ideas relating to length scales in glassy systems will be presented. A number of studies have focused on the emergence of preferred packing arrangements and discussed their role in glassy dynamics. More recently, a central object of attention has been the study of spatially correlated, heterogeneous dynamics and the associated length scale, studied in computer simulations and theoretical analysis such as inhomogeneous mode coupling theory. A number of static length scales have been proposed and studied recently, such as the mosaic length scale discussed in the random first-order transition theory and the related point-to-set correlation length. We will discuss these, elaborating on key results, along with a critical appraisal of the state of the art. Finally we will discuss length scales in driven soft matter, granular fluids and amorphous solids, and give a brief description of length scales in aging systems. Possible relations of these length scales with those in glass-forming liquids will be discussed.

  1. Length scales in glass-forming liquids and related systems: a review.

    PubMed

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-01-01

    The central problem in the study of glass-forming liquids and other glassy systems is the understanding of the complex structural relaxation and rapid growth of relaxation times seen on approaching the glass transition. A central conceptual question is whether one can identify one or more growing length scale(s) associated with this behavior. Given the diversity of molecular glass-formers and a vast body of experimental, computational and theoretical work addressing glassy behavior, a number of ideas and observations pertaining to growing length scales have been presented over the past few decades, but there is as yet no consensus view on this question. In this review, we will summarize the salient results and the state of our understanding of length scales associated with dynamical slow down. After a review of slow dynamics and the glass transition, pertinent theories of the glass transition will be summarized and a survey of ideas relating to length scales in glassy systems will be presented. A number of studies have focused on the emergence of preferred packing arrangements and discussed their role in glassy dynamics. More recently, a central object of attention has been the study of spatially correlated, heterogeneous dynamics and the associated length scale, studied in computer simulations and theoretical analysis such as inhomogeneous mode coupling theory. A number of static length scales have been proposed and studied recently, such as the mosaic length scale discussed in the random first-order transition theory and the related point-to-set correlation length. We will discuss these, elaborating on key results, along with a critical appraisal of the state of the art. Finally we will discuss length scales in driven soft matter, granular fluids and amorphous solids, and give a brief description of length scales in aging systems. Possible relations of these length scales with those in glass-forming liquids will be discussed. PMID:26684508

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  3. Onset of Cooperative Dynamics in an Equilibrium Glass-Forming Metallic Liquid.

    PubMed

    Jaiswal, Abhishek; O'Keeffe, Stephanie; Mills, Rebecca; Podlesynak, Andrey; Ehlers, Georg; Dmowski, Wojciech; Lokshin, Konstantin; Stevick, Joseph; Egami, Takeshi; Zhang, Yang

    2016-02-18

    Onset of cooperative dynamics has been observed in many molecular liquids, colloids, and granular materials in the metastable regime on approaching their respective glass or jamming transition points, and is considered to play a significant role in the emergence of the slow dynamics. However, the nature of such dynamical cooperativity remains elusive in multicomponent metallic liquids characterized by complex many-body interactions and high mixing entropy. Herein, we report evidence of onset of cooperative dynamics in an equilibrium glass-forming metallic liquid (LM601: Zr51Cu36Ni4Al9). This is revealed by deviation of the mean effective diffusion coefficient from its high-temperature Arrhenius behavior below TA ≈ 1300 K, i.e., a crossover from uncorrelated dynamics above TA to landscape-influenced correlated dynamics below TA. Furthermore, the onset/crossover temperature TA in such a multicomponent bulk metallic glass-forming liquid is observed at approximately twice of its calorimetric glass transition temperature (Tg ≈ 697 K) and in its stable liquid phase, unlike many molecular liquids. PMID:26798946

  4. Onset of cooperative dynamics in equilibrium glass-forming metallic liquids

    NASA Astrophysics Data System (ADS)

    Jaiswal, Abhishek; Zhang, Yang

    Onset of cooperative dynamics has been observed in the metastable regime of many molecular liquids, colloids, and granular materials approaching their respective glass or jamming transition points. It is also considered to play a significant role in the emergence of slow dynamics. However, the nature of such dynamical cooperativity remains elusive in multicomponent metallic liquids characterized by complex many-body interactions and high mixing entropy. Herein, we report indications of the onset of cooperative dynamics in an equilibrium glass-forming metallic liquid (ZrCuNiAl). This is revealed by deviation of the experimentally measured mean diffusion coefficient from its high temperature Arrhenius behavior below To ~ 1300 K, i.e., a crossover from uncorrelated dynamics above To to landscape-influenced correlated dynamics below To. The onset/crossover in this system is observed at approximately twice of its calorimetric glass transition temperature (Tg ~ 697 K) and in the stable liquid phase, unlike many molecular liquids. Furthermore, we show the presence of such a dynamical onset phenomenon in ten other glass-forming metallic liquids, universally occurring at approximately twice of their Tg and in their liquid phases.

  5. Radiation damage of a glass-bonded zeolite waste form using ion irradiation.

    SciTech Connect

    Allen, T. R.; Storey, B. G.

    1997-12-05

    Glass-bonded zeolite is being considered as a candidate ceramic waste form for storing radioactive isotopes separated from spent nuclear fuel in the electrorefining process. To determine the stability of glass-bonded zeolite under irradiation, transmission electron microscope samples were irradiated using high energy helium, lead, and krypton. The major crystalline phase of the waste form, which retains alkaline and alkaline earth fission products, loses its long range order under both helium and krypton irradiation. The dose at which the long range crystalline structure is lost is about 0.4 dpa for helium and 0.1 dpa for krypton. Because the damage from lead is localized in such a small region of the sample, damage could not be recognized even at a peak damage of 50 dpa. Because the crystalline phase loses its long range structure due to irradiation, the effect on retention capacity needs to be further evaluated.

  6. PTFE-coated foamed glass blocks form a floating tank cover that prevents acid emissions

    SciTech Connect

    Sandberg, H.W.; Wickersham, C.P.; Gaines, A.

    1983-02-01

    Foamed glass blocks, coated with a 10-mil thickness of PTFE fluoropolymer, covering open-top tanks that collect 72% sulfuric acid at about 320/sup 0/F, are discussed. The covers are efficient in preventing a mist of sulfuric acid to form over the tanks. The insulating properties have reduced the loss of heat from the tanks. The PTFE coating has not been affected by constant exposure to the acid.

  7. A new US manufacturing capability of glass preforms for fiber optics in defense programs. Final project report

    SciTech Connect

    Nath, D.K.

    1992-06-01

    The present project is a part of the program to develop ``A New US Manufacturing Capability of Fiber Optics in Defense Programs.`` The scope of the program extends beyond the limit of defense needs, impacting profoundly on important national issues such as, health industry vis-a-vis medical and insurance infrastructure as well as a great segment of commercial-industrial complex. At present, the glass preform -- critical raw material to produce the optical fiber, is 100% imported from Germany and Japan. Objectively, to create a domestic source, a cooperative project participated by Los Alamos and Polymicro began in the summer of 1991 to develop the cladding part of the glass preform. The goal was achieved by developing 0{center_dot}2NA preform, that was fabricated by Modified Chemical Vapor Deposition (MCVD) of born and fluorine doped silica glass as cladding layer on a silica substrate tube and collapsing the tube on a solid silica rod as the core. The preform was finally drawn into 200 micron core optical fiber and delivered to Los Alamos National Laboratory.

  8. Tellurite glass as a waste form for a simulated mixed chloride waste stream: Candidate materials selection and initial testing

    SciTech Connect

    Riley, Brian J.; Rieck, Bennett T.; McCloy, John S.; Crum, Jarrod V.; Sundaram, S. K.; Vienna, John D.

    2012-02-02

    Tellurite glasses have been researched widely for the last 60 years since they were first introduced by Stanworth. These glasses have been primarily used in research applications as glass host materials for lasers and as non-linear optical materials, though many other uses exist in the literature. Tellurite glasses have long since been used as hosts for various, and even sometimes mixed, halogens (i.e., multiple chlorides or even chlorides and iodides). Thus, it was reasonable to expect that these types of glasses could be used as a waste form to immobilize a combination of mixed chlorides present in the electrochemical separations process involved with fuel separations and processing from nuclear reactors. Many of the properties related to waste forms (e.g., chemical durability, maximum chloride loading) for these materials are unknown and thus, in this study, several different types of tellurite glasses were made and their properties studied to determine if such a candidate waste form could be fabricated with these glasses. One of the formulations studied was a lead tellurite glass, which had a low sodium release and is on-par with high-level waste silicate glass waste forms.

  9. Universal scaling between structural relaxation and vibrational dynamics in glass-forming liquids and polymers

    NASA Astrophysics Data System (ADS)

    Larini, L.; Ottochian, A.; de Michele, C.; Leporini, D.

    2008-01-01

    If liquids, polymers, bio-materials, metals and molten salts can avoid crystallization during cooling or compression, they freeze into a microscopically disordered solid-like state, a glass. On approaching the glass transition, particles become trapped in transient cages-in which they rattle on picosecond timescales-formed by their nearest neighbours; the particles spend increasing amounts of time in their cages as the average escape time, or structural relaxation time τα, increases from a few picoseconds to thousands of seconds through the transition. Owing to the huge difference between relaxation and vibrational timescales, theoretical studies addressing the underlying rattling process have challenged our understanding of the structural relaxation. Numerical and experimental studies on liquids and glasses support the theories, but not without controversies (for a review see ref. 21). Here we show computer simulations that, when compared with experiments, reveal the universal correlation of the structural relaxation time (as well as the viscosity η) and the rattling amplitude from glassy to low-viscosity states. According to the emerging picture the glass softens when the rattling amplitude exceeds a critical value, in agreement with the Lindemann criterion for the melting of crystalline solids and the free-volume model.

  10. Interfacial Free Energy Controlling Glass-Forming Ability of Cu-Zr Alloys

    PubMed Central

    Kang, Dong-Hee; Zhang, Hao; Yoo, Hanbyeol; Lee, Hyun Hwi; Lee, Sooheyong; Lee, Geun Woo; Lou, Hongbo; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jianzhong

    2014-01-01

    Glass is a freezing phase of a deeply supercooled liquid. Despite its simple definition, the origin of glass forming ability (GFA) is still ambiguous, even for binary Cu-Zr alloys. Here, we directly study the stability of the supercooled Cu-Zr liquids where we find that Cu64Zr36 at a supercooled temperature shows deeper undercoolability and longer persistence than other neighbouring compositions with an equivalent driving Gibbs free energy. This observation implies that the GFA of the Cu-Zr alloys is significantly affected by crystal-liquid interfacial free energy. In particular, the crystal-liquid interfacial free energy of Cu64Zr36 in our measurement was higher than that of other neighbouring liquids and, coincidently a molecular dynamics simulation reveals a larger glass-glass interfacial energy value at this composition, which reflects more distinct configuration difference between liquid and crystal phase. The present results demonstrate that the higher crystal-liquid interfacial free energy is a prerequisite of good GFA of the Cu-Zr alloys. PMID:24893772

  11. Interfacial Free Energy Controlling Glass-Forming Ability of Cu-Zr Alloys

    NASA Astrophysics Data System (ADS)

    Kang, Dong-Hee; Zhang, Hao; Yoo, Hanbyeol; Lee, Hyun Hwi; Lee, Sooheyong; Lee, Geun Woo; Lou, Hongbo; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jianzhong

    2014-06-01

    Glass is a freezing phase of a deeply supercooled liquid. Despite its simple definition, the origin of glass forming ability (GFA) is still ambiguous, even for binary Cu-Zr alloys. Here, we directly study the stability of the supercooled Cu-Zr liquids where we find that Cu64Zr36 at a supercooled temperature shows deeper undercoolability and longer persistence than other neighbouring compositions with an equivalent driving Gibbs free energy. This observation implies that the GFA of the Cu-Zr alloys is significantly affected by crystal-liquid interfacial free energy. In particular, the crystal-liquid interfacial free energy of Cu64Zr36 in our measurement was higher than that of other neighbouring liquids and, coincidently a molecular dynamics simulation reveals a larger glass-glass interfacial energy value at this composition, which reflects more distinct configuration difference between liquid and crystal phase. The present results demonstrate that the higher crystal-liquid interfacial free energy is a prerequisite of good GFA of the Cu-Zr alloys.

  12. Anomalously slow crystal growth of the glass-forming alloy CuZr

    NASA Astrophysics Data System (ADS)

    Tang, Chunguang; Harrowell, Peter

    2013-06-01

    Our ability to exploit the benefits of metallic glasses depends on identifying alloys of high glass-forming ability (GFA). So far, the established empirical correlations of GFA (ref. ) are statistical guides at best and lack a microscopic rationale. Although simulations have the potential to provide this physical insight into the maximum crystallization rate, crystal nucleation is often too slow to be observed. In contrast, measuring the growth rate of a planar crystal surface represents an accessible route to understanding ordering kinetics. Here we use molecular dynamics simulations to show that the crystal growth rate for an important binary glass former, CuZr, is significantly slower than that of a poor glass former, NiAl. In accounting for this difference, we find that the crystal/liquid interface in NiAl exhibits a significantly greater width than that of CuZr. Our results suggest that the crystal/liquid interfacial structure exerts an important influence on the GFA of alloys.

  13. Mineralogy and thermodynamic properties of magnesium phyllosilicates formed during the alteration of a simplified nuclear glass

    NASA Astrophysics Data System (ADS)

    Debure, Mathieu; De Windt, Laurent; Frugier, Pierre; Gin, Stéphane; Vieillard, Philippe

    2016-07-01

    The precipitation of crystallized magnesium phyllosilicates generally sustains the alteration rate of nuclear waste containment glass. However, glass alteration slows down to a residual rate as soon as Mg disappears from the solution. The identification of the phyllosilicates formed is therefore crucial for modeling the long-term behavior of nuclear glass. This study deals with batch alteration of the simplified nuclear glass ISG in presence of magnesium, and the characterization of the secondary phases. Morphological, chemical and structural analyses (MET, EDX, XRD) were performed to determine the nature and structure of the precipitated phases identified as trioctahedral smectites. Analyses conducted on the secondary phases proved the presence of Al, Na and Ca in the Mg-phyllosilicate phases. Such elements had been suspected but never quantitatively measured. The experimental results were then used to determine the thermodynamic solubility constants for each precipitated secondary phase at various temperatures. The calculated values were consistent with those available for sodium and magnesium saponites in the existing thermodynamic databases.

  14. 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.

  15. Forensic Identification of Automobile Window Glass Manufacturers in Japan Based on the Refractive Index, X-ray Fluorescence, and X-ray Absorption Fine Structure.

    PubMed

    Funatsuki, Atsushi; Takaoka, Masaki; Shiota, Kenji; Kokubu, Daisuke; Suzuki, Yasuhiro

    2016-01-01

    In this study, 3 automobile window glass manufacturers were identified based on refractive index, XRF, and XAFS analyses. The samples were classified into the corresponding groups using XRF, which should be the first step for identification. Samples having different manufacturing times showed differences in the refractive index. Based on XAFS, the amplitude of the EXAFS spectra and the intensities of Fourier transforms differed between manufacturers. In the scheme for manufacturer identification proposed in this study, performing XRF and refractive index studies is the first step. The concentrations of CeO2, MgO, Al2O3, and K2O allowed us to distinguish among manufacturers. Secondly, for samples containing cerium, we discriminated between manufacturer based on the amplitude of the EXAFS spectra and the intensities of Fourier transforms. As a result, the manufacturers of the 75 samples used in this study were multilaterally identified. PMID:26860567

  16. Bulk Forming of Industrial Micro Components in Conventional Metals and Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Arentoft, M.; Paldan, N. A.; Eriksen, R. S.; Gastaldi, T.; Wert, J. A.; Eldrup, M.

    2007-04-01

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

  17. Bulk Forming of Industrial Micro Components in Conventional Metals and Bulk Metallic Glasses

    SciTech Connect

    Arentoft, M.; Paldan, N. A.; Eriksen, R. S.; Gastaldi, T.; Wert, J. A.; Eldrup, M.

    2007-04-07

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

  18. Fracture toughness measurements on a glass bonded sodalite high-level waste form.

    SciTech Connect

    DiSanto, T.; Goff, K. M.; Johnson, S. G.; O'Holleran, T. P.

    1999-05-19

    The electrometallurgical treatment of metallic spent nuclear fuel produces two high-level waste streams; cladding hulls and chloride salt. Argonne National Laboratory is developing a glass bonded sodalite waste form to immobilize the salt waste stream. The waste form consists of 75 Vol.% crystalline sodalite (containing the salt) with 25 Vol.% of an ''intergranular'' glassy phase. Microindentation fracture toughness measurements were performed on representative samples of this material using a Vickers indenter. Palmqvist cracking was confirmed by post-indentation polishing of a test sample. Young's modulus was measured by an acoustic technique. Fracture toughness, microhardness, and Young's modulus values are reported, along with results from scanning electron microscopy studies.

  19. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials

    NASA Astrophysics Data System (ADS)

    Khamzin, A. A.; Popov, I. I.; Nigmatullin, R. R.

    2013-06-01

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures.

  20. The influence of the secondary relaxation processes on the structural relaxation in glass-forming materials.

    PubMed

    Khamzin, A A; Popov, I I; Nigmatullin, R R

    2013-06-28

    In the frame of fractional-kinetic approach, the model of the structural α-relaxation in the presence of the secondary β-relaxation processes is suggested. The model is based on the rigorous bond between β-processes with α-process and leads to the generalized and justified expression for the complex dielectric permittivity (CDP). It allows to form a new sight on the problem of the fitting of multi-peak structure of the dielectric loss spectra in glass-forming materials. The consistency of the CDP expressions obtained is based on a good fit of experimental data for binary methanol-water mixtures. PMID:23822251

  1. Hydrotalcite formed by alteration of R7T7 nuclear waste glass and basaltic glass in salt brine at 190{degrees}C

    SciTech Connect

    Abdelouas, A.; Crovisier, J.L.; Lutze, W.; Mueller, R.; Bernotat, W.

    1994-12-31

    The R7T7 and synthetic basaltic glasses were submitted to corrosion in a saline MgCl{sub 2} dominated solution at 190{degrees}C. For both glasses, the early alteration product is a hydrotalcite-like compound in which HPO{sub 4}{sup 2{minus}}, SO{sub 4}{sup 2{minus}} and Cl{sup {minus}} substitutes to CO{sub 3}{sup 2{minus}}. The measured d{sub 003} spacing is 7.68 {angstrom} for the hydrotalcite formed from R7T7 glass and 7.62 {angstrom} for the hydrotalcite formed from basaltic glass which reflect the high aluminium content. Chemical microanalyses show that the hydrotalcite is subsequently covered by a silica-rich gel which evolves into saponite after few months.

  2. Influence of manufacturing factors on physical stability and solubility of solid dispersions containing a low glass transition temperature drug.

    PubMed

    Sakurai, Atsushi; Sako, Kazuhiro; Maitani, Yoshie

    2012-01-01

    In this study, we investigated the effect of manufacturing factors such as particle size, water content and manufacturing method on the physical stability and solubility of solid dispersion formulations of a low-glass-transition-temperature (T(g)) drug. Solid dispersions were prepared from polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC) by hot melt extrusion or spray drying. Water content of solid dispersions prepared by hot melt extrusion determined by dynamic moisture sorption measurement was increased drastically with relative humidity below a certain level of particle size. The blends with a lower water content (0.8%) prepared by hot melt extrusion during storage were more stable than those with a higher water content (3.5%) prepared by spray drying, which caused rapid recrystallization. Physical stability in the hot melt blends may be attributed to reduced molecular mobility due to a higher T(g). Dissolution study revealed that solid dispersions prepared by hot melt extrusion with the smallest particle size showed decreased solubility, attributed to reduced wetting properties (surface energy), which is not predictable by the Noyes-Whitney equation. Taken together, these results indicate that the control of particle size concerned in water content or wetting properties is critical to ensuring the physical stability or enhancing solubility of low-T(g) drugs. Further, hot melt extrusion, which can reduce water content, is a suitable manufacturing method for solid dispersions of low-T(g) drugs. PMID:23124559

  3. Effect of aluminum and silicon reactants and HIP soak time on characteristics of glass-ceramic waste forms

    SciTech Connect

    Vinjamuri, K.

    1993-04-01

    The high level liquid waste (HLLW) from nuclear fuel reprocessing is being calcined into solid granules and being stored onsite at the Idaho Chemical Processing Plant (ICPP) since 1963. Final disposal of the calcined waste in a geologic repository requires further consolidation of the calcine in to a solid waste form. One of the solid waste forms being considered for immobilization of the ICPP calcines is the glass-ceramic. The glass-ceramic waste form is a promising option because it can potentially reduce the calcined high level waste (HLW) volume significantly compared to glass waste forms while maintaining similar leach rates. Based on technical evaluations, and laboratory and pilot plant mockup tests, the Environmental Protection Agency (EPA) believes that the glass-ceramic process is more efficient than the glass process for ICPP calcine waste forms. The EPA has determined that the glass-ceramic waste form technology is an acceptable technology to meet the Best Demonstrated Acceptable Technology (BDAT) for ICPP HLW calcine. In this progress report, the impact of aluminum and silicon reactants and HIP soak time on leach rates, microstructure and phase composition of glass-ceramic waste forms are discussed.

  4. Characterisation and durability of glass composite waste forms immobilising spent clinoptilolite

    SciTech Connect

    Juoi, J.M.; Ojovan, M.I.

    2007-07-01

    Simulated spent clinoptilolite was immobilised in a monolithic glass composite wasteform (GCM) produced by a pressureless sintering for 2 hours at relative low temperatures 750 deg. C. The GCM utilises the high durability of alkali borosilicate glass to encapsulate the Cs-impregnated clinoptilolite (Cs-Clino). With this approach mobile radionuclides are retained by a multi-barrier system, comprising the crystalline form of the clinoptilolite and the borosilicate glass Wastes loading ranging from 1:1 up to 1:10 glass to Cs-clino volume ratios corresponding to 37- 88 mass % were studied. Water durability of GCM was assessed in 7, 14 and 28 days leaching tests in deionised water at 40 deg. C based on ASTM C1220-98 standard. It was found that the normalised leaching rates of Cs remaining below 6.35 10{sup -6} g/cm{sup 2} day in a GCM with 73 mass % waste during a leaching test for 7 days. However, at higher waste loading of {>=}80 mass %, the normalised leaching rate of Cs was as high as 9.06 10{sup -4} g/cm{sup 2} day. The normalised leaching rate of Cs decreased within the 28 days of leaching. Microstructure and Energy Dispersive X-ray (EDS) analysis of the GCM with 1:1 glass to Cs-clino vol. ratio shows that there were no changes in phases identified as well as elements present in GCM after 28 days leaching test. The compression strength of the GCM was found to be in a range from 85.5 at waste loading 80 mass % - 394.2 MPa at waste loading 37 mass %. (authors)

  5. Glass sealing

    SciTech Connect

    Brow, R.K.; Kovacic, L.; Chambers, R.S.

    1996-04-01

    Hernetic glass sealing technologies developed for weapons component applications can be utilized for the design and manufacture of fuel cells. Design and processing of of a seal are optimized through an integrated approach based on glass composition research, finite element analysis, and sealing process definition. Glass sealing procedures are selected to accommodate the limits imposed by glass composition and predicted calculations.

  6. Liquid-liquid transition in a strong bulk metallic glass-forming liquid.

    PubMed

    Wei, Shuai; Yang, Fan; Bednarcik, Jozef; Kaban, Ivan; Shuleshova, Olga; Meyer, Andreas; Busch, Ralf

    2013-01-01

    Polymorphic phase transitions are common in crystalline solids. Recent studies suggest that phase transitions may also exist between two liquid forms with different entropy and structure. Such a liquid-liquid transition has been investigated in various substances including water, Al2O3-Y2O3 and network glass formers. However, the nature of liquid-liquid transition is debated due to experimental difficulties in avoiding crystallization and/or measuring at high temperatures/pressures. Here we report the thermodynamic and structural evidence of a temperature-induced weak first-order liquid-liquid transition in a bulk metallic glass-forming system Zr(41.2)Ti(13.8)Cu(12.5)Ni10Be(22.5) characterized by non- (or weak) directional bonds. Our experimental results suggest that the local structural changes during the transition induce the drastic viscosity changes without a detectable density anomaly. These changes are correlated with a heat capacity maximum in the liquid. Our findings support the hypothesis that the 'strong' kinetics (low fragility) of a liquid may arise from an underlying lambda transition above its glass transition. PMID:23817404

  7. Microcraters formed in hot glass by hypervelocity projectiles. [lunar environment simulation

    NASA Technical Reports Server (NTRS)

    Vedder, J. F.

    1976-01-01

    Microcraters were formed in heated soda-lime glass by the normal incidence of spheres of plastic or fused silica with diameters between 0.8 and 4.5 microns and velocities between 2.5 and 10 km/s. The morphology of the craters in targets at temperatures up to 800 C is little different from those formed in unheated glass. Spallation still occurs to the same extent and above the same velocity threshold, but the spalls sag and sharp edges become dull in a few seconds at temperatures above the softening point. There is a small increase in the flow of glass from the central pit into a narrow lip at the higher temperatures, but this lip is often removed by spallation, especially at the higher velocities of impact. There is no evidence of a splashed lip with strings of melt overlying the spalled area. The results in conjunction with other evidence suggest that most lunar craters of micrometer size with a smooth central pit, splashed lip, and a spallation zone are the result of primary impacts.

  8. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    SciTech Connect

    Chen, C. J.; Podlesnyak, A.; Mamontov, E.; Wang, W. H.; Chathoth, S. M.

    2015-09-28

    We've made extensive efforts to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. We have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Finally, our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.

  9. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    NASA Astrophysics Data System (ADS)

    Chen, C. J.; Podlesnyak, A.; Mamontov, E.; Wang, W. H.; Chathoth, S. M.

    2015-09-01

    Extensive efforts have been made to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. In this work, we have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.

  10. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    DOE PAGESBeta

    Chen, C. J.; Podlesnyak, A.; Mamontov, E.; Wang, W. H.; Chathoth, S. M.

    2015-09-28

    We've made extensive efforts to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. We have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Finally, our results indicate that atomic caging is themore » primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.« less

  11. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    SciTech Connect

    Chen, C. J.; Chathoth, S. M.; Podlesnyak, A.; Mamontov, E.; Wang, W. H.

    2015-09-28

    Extensive efforts have been made to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. In this work, we have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.

  12. Qualitative change in structural dynamics of some glass-forming systems

    NASA Astrophysics Data System (ADS)

    Novikov, Vladimir; Sokolov, Alexei

    Analysis of temperature dependence of structural relaxation time τ (T) in supercooled liquids revealed a qualitatively distinct feature - a sharp, cusp-like maximum in the second derivative of log τα (T) at some Tmax. It suggests that the super-Arrhenius temperature dependence of τα (T) in glass-forming liquids eventually crosses over to an Arrhenius behavior at Tglass transition to the new avenue - the origin of the limiting activation energy for structural relaxation at low T. The authors acknowledge the support from the NSF Chemistry program (grant CHE-1213444).

  13. Short-Time Beta Relaxation in Glass-Forming Liquids Is Cooperative in Nature

    NASA Astrophysics Data System (ADS)

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-02-01

    Temporal relaxation of density fluctuations in supercooled liquids near the glass transition occurs in multiple steps. Using molecular dynamics simulations for three model glass-forming liquids, we show that the short-time β relaxation is cooperative in nature. Using finite-size scaling analysis, we extract a growing length scale associated with beta relaxation from the observed dependence of the beta relaxation time on the system size. We find, in qualitative agreement with the prediction of the inhomogeneous mode coupling theory, that the temperature dependence of this length scale is the same as that of the length scale that describes the spatial heterogeneity of local dynamics in the long-time α -relaxation regime.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  15. Communication: High pressure specific heat spectroscopy reveals simple relaxation behavior of glass forming molecular liquid

    NASA Astrophysics Data System (ADS)

    Roed, Lisa Anita; Niss, Kristine; Jakobsen, Bo

    2015-12-01

    The frequency dependent specific heat has been measured under pressure for the molecular glass forming liquid 5-polyphenyl-4-ether in the viscous regime close to the glass transition. The temperature and pressure dependences of the characteristic time scale associated with the specific heat is compared to the equivalent time scale from dielectric spectroscopy performed under identical conditions. It is shown that the ratio between the two time scales is independent of both temperature and pressure. This observation is non-trivial and demonstrates the existence of specially simple molecular liquids in which different physical relaxation processes are both as function of temperature and pressure/density governed by the same underlying "inner clock." Furthermore, the results are discussed in terms of the recent conjecture that van der Waals liquids, like the measured liquid, comply to the isomorph theory.

  16. An important factor powerfully influencing the Al Ni-based alloys' glass-forming ability

    NASA Astrophysics Data System (ADS)

    Bo, Zhang; Xiufang, Bian; Chunxia, Fu; Na, Han; Jiankun, Zhou; Weimin, Wang

    2005-12-01

    In order to get better glass-forming abilities (GFAs), Ni atoms are partially replaced by Cu and Co atoms in Al84Ni12Zr4 alloys. Thermal analysis shows that the reduced crystallization temperature Trx has no direct correlation with the GFA of the alloys. However, it is notable that prepeaks have been found in the total structure factors of the amorphous Al84Ni(12-x)Zr4Cux and Al84Ni(12-x)Zr4Cox alloys. In addition, the results prove that the intensity of the prepeaks influences the GFA powerfully. The amorphous alloys with larger intensity of the prepeak show better GFA. The influence of prepeaks on the GFA can be explained by the atomic configuration difference among the liquid, crystal and glass states.

  17. Qualitative change in structural dynamics of some glass-forming systems

    DOE PAGESBeta

    Novikov, Vladimir N.; Sokolov, Alexei P.

    2015-12-14

    Analysis of the temperature dependence of the structural relaxation time Τα(T) in supercooled liquids revealed a qualitatively distinct feature a sharp, cusplike maximum in the second derivative of log Τα(T) at some Tmax. It suggests that the super-Arrhenius temperature dependence of Τα(T) in glass-forming liquids eventually crosses over to an Arrhenius behavior at T < Tmax, and there is no divergence of Τα(T) at nonzero T . Tmax can be above or below Tg, depending on the sensitivity of τ(T) to a change in the liquid's density quantified by the exponent γ in the scaling Τα(T) ~exp(A/Tρ–γ). Lastly, these resultsmore » might turn the discussion of the glass transition in a different direction toward the origin of the limiting activation energy for structural relaxation at low T.« less

  18. Evaluation of final waste forms and recommendations for baseline alternatives to group and glass

    SciTech Connect

    Bleier, A.

    1997-09-01

    An assessment of final waste forms was made as part of the Federal Facilities Compliance Agreement/Development, Demonstration, Testing, and Evaluation (FFCA/DDT&E) Program because supplemental waste-form technologies are needed for the hazardous, radioactive, and mixed wastes of concern to the Department of Energy and the problematic wastes on the Oak Ridge Reservation. The principal objective was to identify a primary waste-form candidate as an alternative to grout (cement) and glass. The effort principally comprised a literature search, the goal of which was to establish a knowledge base regarding four areas: (1) the waste-form technologies based on grout and glass, (2) candidate alternatives, (3) the wastes that need to be immobilized, and (4) the technical and regulatory constraints on the waste-from technologies. This report serves, in part, to meet this goal. Six families of materials emerged as relevant; inorganic, organic, vitrified, devitrified, ceramic, and metallic matrices. Multiple members of each family were assessed, emphasizing the materials-oriented factors and accounting for the fact that the two most prevalent types of wastes for the FFCA/DDT&E Program are aqueous liquids and inorganic sludges and solids. Presently, no individual matrix is sufficiently developed to permit its immediate implementation as a baseline alternative. Three thermoplastic materials, sulfur-polymer cement (inorganic), bitumen (organic), and polyethylene (organic), are the most technologically developed candidates. Each warrants further study, emphasizing the engineering and economic factors, but each also has limitations that regulate it to a status of short-term alternative. The crystallinity and flexible processing of sulfur provide sulfur-polymer cement with the highest potential for short-term success via encapsulation. Long-term immobilization demands chemical stabilization, which the thermoplastic matrices do not offer. Among the properties of the remaining

  19. Effect of local structures on crystallization in deeply undercooled metallic glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Jiang, S. Q.; Wu, Z. W.; Li, M. Z.

    2016-04-01

    The crystallization mechanism in deeply undercooled ZrCu metallic glass-forming liquids was investigated via molecular dynamics simulations. It was found that the crystallization process is mainly controlled by the growth of crystal nuclei formed by the BCC-like atomic clusters, consistent with experimental speculations. The crystallization rate is found to relate to the number of growing crystal nuclei in the crystallization process. The crystallization rate in systems with more crystal nuclei is significantly hindered by the larger surface fractions of crystal nuclei and their different crystalline orientations. It is further revealed that in the crystallization in deeply undercooled regions, the BCC-like crystal nuclei are formed from the inside of the precursors formed by the FCC-like atomic clusters, and growing at the expense of the precursors. Meanwhile, the precursors are expanding at the expense of the outside atomic clusters. This process is consistent with the so-called Ostwald step rule. The atomic structures of metallic glasses are found to have significant impact on the subsequent crystallization process. In the Zr85Cu15 system, the stronger spatial correlation of Cu atoms could hinder the crystallization processes in deeply undercooled regions.

  20. Ultra-miniature all-glass Fabry-Pérot pressure sensor manufactured at the tip of a multimode optical fiber

    NASA Astrophysics Data System (ADS)

    Pinet, Éric; Cibula, Edvard; Đonlagić, Denis

    2007-09-01

    The design and fabrication of an ultra-miniature all-glass pressure sensor with a diameter of 125 μm are presented. The sensor consists of a thin flexible silica membrane fused on a capillary tube section, which is assembled at the tip of a standard multimode fiber, thus forming a Fabry-Pérot air cavity whose length depends on applied pressure. Controlled polishing steps including on-line tuning of the diaphragm thickness during the manufacturing process achieve good repeatability and high sensitivity of the pressure sensor. The prototypes obtained with the described manufacturing method could easily have a sensitivity of ~2 nm/kPa (~0.3 nm/mmHg) with a record, so far, of ~5 nm/kPa (~0.7 nm/mmHg). The relatively simple fabrication technique using common and inexpensive equipments and materials combined with the fact that such sensitive sensors with multimode fiber could be interrogated with low-cost commercial interrogators (such as those using white-light interferometry) make this option very attractive for many applications involving pressure measurement. The sensor significant size reduction is valuable especially for the medical field, for applications such as minimally invasive patient health monitoring and diagnostics or small animals testing. Disposable sensors with ultra-miniature size will certainly open the way for new medical diagnostics and therapies.

  1. Tellurite glass as a waste form for mixed alkali-chloride waste streams: Candidate materials selection and initial testing

    NASA Astrophysics Data System (ADS)

    Riley, Brian J.; Rieck, Bennett T.; McCloy, John S.; Crum, Jarrod V.; Sundaram, S. K.; Vienna, John D.

    2012-05-01

    Tellurite glasses have historically been shown to host large concentrations of halides. They are here considered for the first time as a waste form for immobilizing chloride wastes, such as may be generated in the proposed molten alkali salt electrochemical separations step in nuclear fuel reprocessing. Key properties of several tellurite glasses are determined to assess acceptability as a chloride waste form. TeO2 glasses with other oxides (PbO, Al2O3 + B2O3, WO3, P2O5, or ZnO) were fabricated with and without 10 mass% of a simulated (non-radioactive) mixed alkali, alkaline-earth, and rare earth chloride waste. Measured chemical durability is compared for the glasses, as determined by the product consistency test (PCT), a common standardized chemical durability test often used to validate borosilicate glass waste forms. The glass with the most promise as a waste form is the TeO2-PbO system, as it offers good halide retention, a low sodium release (by PCT) comparable with high-level waste silicate glass waste forms, and a high storage density.

  2. The meaning of the "universal" WLF parameters of glass-forming polymer liquids

    NASA Astrophysics Data System (ADS)

    Dudowicz, Jacek; Douglas, Jack F.; Freed, Karl F.

    2015-01-01

    Although the Williams-Landell-Ferry (WLF) equation for the segmental relaxation time τ(T) of glass-forming materials is one of the most commonly encountered relations in polymer physics, its molecular basis is not well understood. The WLF equation is often claimed to be equivalent to the Vogel-Fulcher-Tammann (VFT) equation, even though the WLF expression for τ(T) contains no explicit dependence on the fragility parameter D of the VFT equation, while the VFT equation lacks any explicit reference to the glass transition temperature Tg, the traditionally chosen reference temperature in the WLF equation. The observed approximate universality of the WLF parameters C1 ( g ) and C2 ( g ) implies that τ(T) depends only on T-Tg, a conclusion that seems difficult to reconcile with the VFT equation where the fragility parameter D largely governs the magnitude of τ(T). The current paper addresses these apparent inconsistencies by first evaluating the macroscopic WLF parameters C1 ( g ) and C2 ( g ) from the generalized entropy theory of glass-formation and then by determining the dependence of C1 ( g ) and C2 ( g ) on the microscopic molecular parameters (including the strength of the cohesive molecular interactions and the degree of chain stiffness) and on the molar mass of the polymer. Attention in these calculations is restricted to the temperature range (Tg < T < Tg + 100 K), where both the WLF and VFT equations apply.

  3. Revealing the pure confinement effect in glass-forming liquids by dynamic mechanical analysis

    NASA Astrophysics Data System (ADS)

    Koppensteiner, J.; Schranz, W.; Carpenter, M. A.

    2010-01-01

    The dynamic mechanical response of mesoporous silica with coated inner surfaces confining the glass-forming liquid salol is measured as a function of temperature and frequency (1-100 Hz) for various pore sizes (2.4-7.3 nm). Compared to former results on natural pores, a distinct acceleration of dynamics due to the removal of surface-related retardation of molecular dynamics is found now, which can be fitted by a homogeneous relaxation using an unmodified Vogel-Fulcher-Tammann relation. This lubrication effect leads to a stronger decrease in the glass transition temperature Tg with decreasing pore size. The present data allow to quantify and separate competing side effects as surface bondings and negative pressure from the pure confinement induced acceleration of molecular dynamics with decreasing pore size. We analyze the dynamic elastic susceptibility data in terms of a recently proposed procedure [C. Dalle-Ferrier , Phys. Rev. E 76, 041510 (2007)], which relates the number Ncorr,T of molecules, whose dynamics is correlated with a local enthalpy fluctuation, to the three-point dynamic susceptibility χT . The observed increase of Ncorr,T with decreasing temperature strongly indicates that the size ξ of dynamic heterogeneities increases when approaching the glass transition.

  4. A novel parameter to describe the glass-forming ability of alloys

    SciTech Connect

    Park, E. S.; Ryu, C. W.; Kim, W. T.; Kim, D. H.

    2015-08-14

    In this paper, we propose a new parameter for glass-forming ability (GFA) based on the combination of thermodynamic (stability of stable and metastable liquids by ΔT{sub m} = T{sub m}{sup mix} − T{sub l} and ΔT{sub x} = T{sub x} − T{sub g}, respectively) and kinetic (resistance to crystallization by T{sub x}) aspects for glass formation. The parameter is defined as ε = (ΔT{sub m} + ΔT{sub x} + T{sub x})/T{sub m}{sup mix} without directly adding T{sub g} while considering the whole temperature range for glass formation up to T{sub m}{sup mix}, which reflects the relative position of crystallization curve in continuous cooling transformation diagram. The relationship between the ε parameter and critical cooling rate (R{sub c}) or maximum section thickness for glass formation (Z{sub max}) clearly confirms that the ε parameter exhibits a better correlation with GFA than other commonly used GFA parameters, such as ΔT{sub x} (=T{sub x} − T{sub g}), K (=[T{sub x} − T{sub g}]/[T{sub l} − T{sub x}]), ΔT*(=(T{sub m}{sup mix} − T{sub l})/T{sub m}{sup mix}), T{sub rg} (=T{sub g}/T{sub l}), and γ (=[T{sub x}]/[T{sub l} + T{sub g}]). The relationship between the ε parameter and R{sub c} or Z{sub max} is also formulated and evaluated in the study. The results suggest that the ε parameter can effectively predict R{sub c} and Z{sub max} for various glass-forming alloys, which would permit more widespread uses of these paradigm-shifting materials in a variety of industries.

  5. Statistical description of glass-forming alloys with chemical interaction: Application to Al-R systems

    NASA Astrophysics Data System (ADS)

    Ryltsev, R. E.; Son, L. D.

    2011-10-01

    The statistical model for describing network-forming systems, developed in our previous works, is applied to study of metallic alloys with chemical bonding. The model is based on the representation of the sum of statistical weights over all possible configurations for a thermoreversible network in the form of a functional integral over a scalar field. The mean-field solution of the model is derived, and for particular case of a binary alloy having single element of chemical short-range order A 2B-type, thermodynamic and structural properties have been analyzed. This analysis allows to plot the temperature-concentration phase diagram of the model representing two immiscibility gap meeting in the distectic point. It is shown that at some temperatures and concentrations, geometry percolation of the network of chemical bonds and thus a sol-gel transition may take place. The critical percolation line was plotted in common with phase diagram. Then, the structural transitions, glass-forming ability and magnetic properties of Al-R alloys are discussed in the frames of this conception. It is proposed that the range of easy glass formation is confined on the left by the minimal concentration for the sol-gel transition and on the right by the concentration corresponding to the fractal-to-Euclidian crossover in the structure of percolation cluster. Finally, the abnormal growth of Al-REM magnetic susceptibility occurring above melting point of Al 2R compound is also explained.

  6. DEVELOPMENT OF GLASS AND CRYSTALLINE CERAMIC FORMS FOR DISPOSITION OF EXCESS PLUTONIUM

    SciTech Connect

    Marra, James; Cozzi, A; Crawford, C.; Herman, C.; Marra, John; Peeler, D.

    2009-09-10

    In the aftermath of the Cold War, the United States Department of Energy (DOE) has identified up to 50 metric tons of excess plutonium that needs to be dispositioned. The bulk of the material is slated to be blended with uranium and fabricated into a Mixed Oxide (MOX) fuel for subsequent burning in commercial nuclear reactors. Excess plutonium-containing impurity materials making it unsuitable for fabrication into MOX fuel will need to be dispositioned via other means. Glass and crystalline ceramics have been developed and studied as candidate forms to immobilize these impure plutonium feeds. A titanate-based ceramic was identified as an excellent actinide material host. This composition was based on Synroc compositions previously developed for nuclear waste immobilization. These titanate ceramics were found to be able to accommodate extremely high quantities of fissile material and exhibit excellent aqueous durability. A lanthanide borosilicate (LaBS) glass was developed to accommodate high concentrations of plutonium and to be very tolerant of impurities yet still maintain good aqueous durability. Recent testing of alkali borosilicate compositions showed promise of using these compositions to disposition lower concentrations of plutonium using existing high level waste vitrification processes. The developed waste forms all appear to be suitable for Pu disposition. Depending on the actual types and concentrations of the Pu residue streams slated for disposition, each waste form offers unique advantages.

  7. Universal scaling of dielectric response of various liquid crystals and glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Gałązka, M.; Juszyńska-Gałązka, E.; Osiecka, N.; Bąk, A.

    2016-04-01

    We present a new generalized scaling relationship accounting both for the real and imaginary parts of the complex permittivity data. The generalized scaling procedure has been successfully used for various relaxation processes in liquid crystals (4-bromobenzylidene-4‧-pentyloxyaniline, 4-bromobenzylidene-4‧-hexyloxyaniline, 4‧-butyl-4-(2-methylbutoxy)-azoxybenzene, 4-ethyl-4‧-octylazoxybenzene), and in glass-forming liquids (glycerol, propylene carbonate, salol, cresolphthalein-dimethylether). As it is shown, one obtains common master-curve for liquid-like phases (isotropic liquid, cholesteric, nematic, smectic A), solid-like phases (smectic B, conformationally disorder crystal) and supercooled liquid phase.

  8. Health Impact of Elevated Levels of Lead Encountered in the Manufacture of Crystal Glass.

    PubMed

    Bilban, Marjan

    2015-12-01

    Lead is known to cause harmful effects in the haematopoietic, nervous, digestive, renal, and other organ systems, inhibiting a number of enzymes in the biosynthesis of haem, as well as other enzymes with haematological significance. Our study involved 151 employees involved with the cutting of crystal, i.e. leaded glass, who had been found using eco-monitoring to have been exposed to above normal levels of lead. Our bio-monitoring process followed the values of lead, delta-ALAD and EPP.The highest level of lead detected was 276 µg/L, the lowest level of delta-ALAD was 99 nkat/L), and the highest level of EPP was 14.2 nmol/gHb). We had found that contrary to expectations, lead levels were not correlated to haemoglobin levels, or to gender or age, but were instead based only on the post of the employee and their time spent working at the glassworks. The levels of haematopoiesis were directly proportional to the levels of lead, however, the correlation was not statistically significant or had perhaps been masked by the exposure due to the employee's post and gender. We had also found a significant correlation of lead levels to the levels of renal function. The study had indicated some health impacts of lead on the exposed glass workers, but also at least partly diverged from the results of previous studies, prompting us to continue our research. PMID:26987160

  9. Cerium, uranium, and plutonium behavior in glass-bonded sodalite, a ceramic nuclear waste form.

    SciTech Connect

    Lewis, M. A.; Lexa, D.; Morss, L. R.; Richmann, M. K.

    1999-09-03

    Glass-bonded sodalite is being developed as a ceramic waste form (CWF) to immobilize radioactive fission products, actinides, and salt residues from electrometallurgical treatment of spent nuclear reactor fuel. The CWF consists of about 75 mass % sodalite, 25 mass % glass, and small amounts of other phases. This paper presents some results and interpretation of physical measurements to characterize the CWF structure, and dissolution tests to measure the release of matrix components and radionuclides from the waste form. Tests have been carried out with specimens of the CWF that contain rare earths at concentrations similar to those expected in the waste form. Parallel tests have been carried out on specimens that have uranium or plutonium as well as the rare earths at concentrations similar to those expected in the waste forms; in these specimens UCl{sub 3} forms UO{sub 2} and PuCl{sub 3} forms PuO{sub 2}. The normalized releases of rare earths in dissolution tests were found to be much lower than those of matrix elements (B, Si, Al, Na). When there is no uranium in the CWF, the release of cerium is two to ten times lower than the release of the other rare earths. The low release of cerium may be due to its tetravalent state in uranium-free CWF. However, when there is uranium in the CWF, the release of cerium is similar to that of the other rare earths. This trivalent behavior of cerium is attributed to charge transfer or covalent interactions among cerium, uranium, and oxygen in (U,Ce)O{sub 2}.

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

    SciTech Connect

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

    2005-06-24

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

  11. Candidate glass-ceramic waste forms for immobilization of the calcines stored at the Idaho Chemical Processing Plant

    SciTech Connect

    Vinjamuri, K.

    1995-11-01

    Candidate glass-ceramic waste forms for immobilizaion of the major types of calcines stored at the Idaho Chemical Processing Plant (ICPP) were synthesized and characterized. The waste forms were prepared by hot isostatically pressing a mixture 70 wt% of precompacted simulated non-radioactive calcine and 30 wt% additives (Silica and Al or Ti metal powders). The types of calcines stored in stainless steel Bin Sets at the ICPP are fluorinel/sodium (Fl/Na), alumina, zirconia, zirconia/sodium (Zr/Na), and zirconia-alumina (Zr-AD. In addition to the silica additive, glass-ceramics for Fl/NA and alumina calcines were prepared and characterized using ICPP soil and clay additives. The characteristics of the waste forms including density, elastic properties, chemical durability, glass and crystalline phases, phases separation, and the microstructure were investigated. The 28-day MCC-1 test for chemical durability was used for all the waste forms. In addition, the Product Consistency Test (PCI) was conducted for the glass-ceramics, and the normalized elemental releases in g/m{sup 2} were compared with the Environmental Assessment (EA) glass. The characteristics of the soil and clay glass-ceramics appear to be as good as the waste forms prepared with silica. The glass-ceramic waste forms recommended are: 5Ti-Clay, or 5Ti-SoiL or 5Ti-Silica for the fluorinel/sodium calcine-, Clay or silica for the alumina calcine; and 5Ti-Silica for the zirconia, Zr/Na, and Zr-Al calcines. Soil- and clay-based glass- ceramics offer an opportunity to incorporate contaminated waste into durable low volume waste forms.

  12. Sealed glass coating of high temperature ceramic superconductors

    DOEpatents

    Wu, Weite; Chu, Cha Y.; Goretta, Kenneth C.; Routbort, Jules L.

    1995-01-01

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor.

  13. Magnetic Properties of Al-Gd-TM Glass-Forming Alloys

    NASA Astrophysics Data System (ADS)

    Uporov, Sergey; Estemirova, Svetlana; Bykov, Viktor; Mitrofanov, Valentin

    2016-01-01

    We report results of magnetic studies of glass-forming alloys with nominal composition of Al86Gd6TM8 (where TM = Cu, Ni, Co, Fe, Mn, Cr, Ti, Zr, Mo, Ta) synthesized by arc-melting. X-ray diffraction analysis and vibrating sample magnetometry were applied to characterize the prepared samples. All the alloys exhibit antiferromagnetic ordering at low temperatures. In some compositions, we observed metamagnetic transitions in external magnetic fields up to 3 T. Analysis of the paramagnetic susceptibility of the considered Al-Gd-TM systems has revealed non-magnetic behavior of the transition metals. We found that the magnetic properties of the studied samples can be described satisfactorily using only the Gd trivalent ions. But in some cases the magnetic moments of gadolinium are slightly larger than the theoretical values, probably, because of an additional contribution of the 5 d electrons. The obtained results are discussed in framework of the assumptions of the strong s- p- d hybridization and frustrated magnetic states of gadolinium. We argue that the hybridization might be one of the main factors improving the glass-forming ability in these ternary alloys.

  14. In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

    DOEpatents

    Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

    2004-03-23

    A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

  15. In-situ ductile metal/bulk metallic glass matrix composites formed by chemical partitioning

    DOEpatents

    Kim, Choong Paul; Hays, Charles C.; Johnson, William L.

    2007-07-17

    A composite metal object comprises ductile crystalline metal particles in an amorphous metal matrix. An alloy is heated above its liquidus temperature. Upon cooling from the high temperature melt, the alloy chemically partitions, forming dendrites in the melt. Upon cooling the remaining liquid below the glass transition temperature it freezes to the amorphous state, producing a two-phase microstructure containing crystalline particles in an amorphous metal matrix. The ductile metal particles have a size in the range of from 0.1 to 15 micrometers and spacing in the range of from 0.1 to 20 micrometers. Preferably, the particle size is in the range of from 0.5 to 8 micrometers and spacing is in the range of from 1 to 10 micrometers. The volume proportion of particles is in the range of from 5 to 50% and preferably 15 to 35%. Differential cooling can produce oriented dendrites of ductile metal phase in an amorphous matrix. Examples are given in the Zr--Ti--Cu--Ni--Be alloy bulk glass forming system with added niobium.

  16. Relaxation times and energy barriers of rubbing-induced birefringence in glass-forming polymers

    NASA Astrophysics Data System (ADS)

    Shiu, K. P.; Qin, Zongyi; Yang, Z.

    2008-12-01

    The relaxations of rubbing-induced birefringence (RIB) in several glass-forming polymers, including polycarbonate and polystyrene (PS) derivatives with various modifications to the phenyl ring side group, are studied. Significant relaxations of RIB are observed at temperatures well below the glass transition temperature T g . The relaxation times span a wide range from ˜ 10 s to probably geological time scale. Physical aging effects are absent in the RIB relaxations. The model proposed for the interpretation of RIB in PS describes well the RIB relaxations in all the polymers investigated here. The energy barriers are of the order of a few hundred kJ/mol and decrease with decreasing temperature, in opposition to the trend of Vogel-Fulcher form for polymer segmental relaxations above T g . The relaxation behaviors of different polymers are qualitatively similar but somewhat different in quantitative details, such as in the values of the saturated birefringence, the shape of the initial barrier density distribution functions, the rates of barrier decrease with decreasing temperature, and the dependence of relaxation times on temperature and parameter ξ , etc. The RIB relaxations are different from any of the other relaxations below T g that have been reported in the literature, such as dielectric relaxations or optical probe relaxations. A microscopic model for the relaxations of RIB is much desired.

  17. The effect of glass-forming sugars on vesicle morphology and water distribution during drying

    PubMed Central

    Vogl, C. J.; Miksis, M. J.; Davis, S. H.; Salac, D.

    2014-01-01

    Cryopreservation requires that stored materials be kept at extremely low temperatures and uses cryoprotectants that are toxic to cells at high concentrations. Lyopreservation is a potential alternative where stored materials can remain at room temperatures. That storage process involves desiccating cells filled with special glass-forming sugars. However, current desiccation techniques fail to produce viable cells, and researchers suspect that incomplete vitrification of the cells is to blame. To explore this hypothesis, a cell is modelled as a lipid vesicle to monitor the water content and membrane deformation during desiccation. The vesicle is represented as a moving, bending-resistant, inextensible interface and is tracked by a level set method. The vesicle is placed in a fluid containing a spatially varying sugar concentration field. The glass-forming nature is modelled through a concentration-dependent diffusivity and viscosity. It is found that there are optimal regimes for the values of the osmotic flow parameter and of the concentration dependence of the diffusivity to limit water trapping in the vesicle. Furthermore, it is found that the concentration dependencies of the diffusivity and viscosity can have profound effects on membrane deformations, which may have significant implications for vesicle damage during the desiccation process. PMID:25142522

  18. Is there a connection between fragility of glass forming systems and dynamic heterogeneity/cooperativity?

    SciTech Connect

    Hong, L; Novikov, V. N.; Sokolov, Alexei P

    2011-01-01

    Although fragility of glass forming liquids is traditionally related to cooperativity in molecular motion, the connection between those parameters remains unclear. In this paper we present the estimates of cooperativity (heterogeneity) length scale obtained from the boson peak spectra. We demonstrate that agrees well with the dynamic heterogeneity length scale for the structural relaxation estimated by 4- dimensional NMR, justifying the use of . Presented analysis of large number of materials reveals no clear correlation between and fragility. However, there is a strong correlation between the cooperativity volume 3 and the activation volume measured at Tg. This observation suggests that only the volume (pressure) dependence of structural relaxation time correlates directly with the cooperativity size. However, the pure thermal (energetic) contribution to the structural relaxation, the so-called isochoric fragility, exhibits no correlation to the heterogeneity length scale , or the amount of structural units in 3. The presented results call for a revision of traditional view on the role of cooperativity/heterogeneity in structural relaxation of glass forming systems.

  19. Electrical and morphological properties of conducting layers formed from the silver-glass composite conducting powders prepared by spray pyrolysis.

    PubMed

    Jung, D S; Koo, H Y; Kang, Y C

    2010-03-01

    Ag-glass composite powders with various glass contents and excellent conducting properties were prepared by spray pyrolysis. Irrespective of the glass content, all the prepared powders were found to comprise spherical particles with nonaggregation characteristics. The crystal structure of the powder particles resembled that of pure Ag particles, irrespective of the glass content. Conducting layers formed from pure Ag did not melt even when sintered at 400 degrees C. On the other hand, conducting layers formed from composite powders containing 3 and 5 wt% glass melted when sintered at 400 degrees C. The optimum glass content of the composite powders was 3 wt% at sintering temperatures of 400 and 450 degrees C. However, the optimum glass content decreased to 1 wt% when the sintering temperature was increased to 550 degrees C. The lowest specific resistances of the conducting layers formed from the composite powders were 5.3 and 2.3 microohms-cm at sintering temperatures of 400 and 550 degrees C, respectively. PMID:20036371

  20. EXAFS/XANES studies of plutonium-loaded sodalite/glass waste forms

    NASA Astrophysics Data System (ADS)

    Richmann, Michael K.; Reed, Donald T.; Kropf, A. Jeremy; Aase, Scott B.; Lewis, Michele A.

    2001-09-01

    A sodalite/glass ceramic waste form is being developed to immobilize highly radioactive nuclear wastes in chloride form, as part of an electrochemical cleanup process. Two types of simulated waste forms were studied: where the plutonium was alone in an LiCl/KCl matrix and where simulated fission-product elements were added representative of the electrometallurgical treatment process used to recover uranium from spent nuclear fuel also containing plutonium and a variety of fission products. Extended X-ray absorption fine structure spectroscopy (EXAFS) and X-ray absorption near-edge spectroscopy (XANES) studies were performed to determine the location, oxidation state, and particle size of the plutonium within these waste form samples. Plutonium was found to segregate as plutonium(IV) oxide with a crystallite size of at least 4.8 nm in the non-fission-element case and 1.3 nm with fission elements present. No plutonium was observed within the sodalite in the waste form made from the plutonium-loaded LiCl/KCl eutectic salt. Up to 35% of the plutonium in the waste form made from the plutonium-loaded simulated fission-product salt may be segregated with a heavy-element nearest neighbor other than plutonium or occluded internally within the sodalite lattice.

  1. Kinetic and thermodynamic studies of the fragility of bulk metallic glass forming liquids

    NASA Astrophysics Data System (ADS)

    Gallino, Isabella; Schroers, Jan; Busch, Ralf

    2010-09-01

    The thermodynamic functions of the bulk metallic glass (BMG) forming Pd43Ni10Cu27P20 alloy are determined calorimetrically as a function of temperature. Along with eight other BMG forming alloys, the available experimental thermodynamic and viscosity data are reassessed. For each alloy, consistent Vogel-Fulcher-Tammann (VFT) fits of the viscosity measurements are established, and the temperature dependence of the configurational entropy is calculated from thermodynamic data. Together with the VFT fits, fits to the Adam-Gibbs equation are performed using this configurational entropy change. We find remarkable agreement between the Adam-Gibbs and VFT fits. Moreover, the temperature T0 is obtained from the VFT fits at which the viscous flow diverges. This T0 matches very well the temperature where the configurational entropy vanishes in the corresponding Adam-Gibbs fits.

  2. [Health status of workers exposed to styrene used in the manufacture of glass laminates].

    PubMed

    Kovarík, J; Pithartová, R; Ehler, E; Salandová, J; Kuzelová, M; Popler, A; Sírl, J; Ciharová, M

    1989-01-01

    A group of 37 workers exposed to styrene used in the plastic mass manufacture was investigated. No damage of the hepatic parenchyma, hematopoiesis or other internal affection was proved; irritative styrene effects were, however, observed, skin was attacked and higher genetic risk was evidenced. From the viewpoint of neurotoxicology, pseudoneurasthenic syndromes, predominantly inhibitory, could be seen, which was proved also by electroencephalography; higher incidence of lesion findings was also found in the risk group. Slight neuropathies of distal type, sensitive-motor, not dependent on the length of exposure were found by electromyography. Abnormalities in electrophysiological examinations appear earlier. The results obtained are significant for further preventive follow-up of persons under exposure. PMID:2638043

  3. Glass shell manufacturing in space. [residual gases in spherical shells made from metal-organic gels

    NASA Technical Reports Server (NTRS)

    Nolen, R. J.; Ebner, M. A.; Downs, R. L.

    1980-01-01

    Residual gases always found in glass shells are CO2, O2 and N2. In those cases where high water vapor pressure is maintained in the furnace, water is also found in the shells. Other evidence for the existence of water in shells is the presence of water-induced surface weathering of the interior shell surface. Water and CO2 are the predominant volatiles generated by the pyrolysis of both inorganic and hydrolyzed metal-organic gels. The pyrolysates of unhydrolyzed metal-organic gels also contain, in addition to water and CO2, significant levels of organic volatiles, such as ethanol and some hydrocarbons; on complete oxidation, these produce CO2 and water as well. Water is most likely the initial blowing agent, it is produced copiously during the initial stages of heating. In the later stages, CO2 becomes the dominant gas as H2O is lost at increasing rates. Water in the shell arises mainly from gel dehydration, CO2 by sodium bicarbonate/carbonate decomposition and carbon oxidation, and O2 and N2 by permeation of the ambient furnace air through the molten shell wall.

  4. A novel scalable manufacturing process for the production of hydrogel-forming microneedle arrays.

    PubMed

    Lutton, Rebecca E M; Larrañeta, Eneko; Kearney, Mary-Carmel; Boyd, Peter; Woolfson, A David; Donnelly, Ryan F

    2015-10-15

    A novel manufacturing process for fabricating microneedle arrays (MN) has been designed and evaluated. The prototype is able to successfully produce 14×14 MN arrays and is easily capable of scale-up, enabling the transition from laboratory to industry and subsequent commercialisation. The method requires the custom design of metal MN master templates to produce silicone MN moulds using an injection moulding process. The MN arrays produced using this novel method was compared with centrifugation, the traditional method of producing aqueous hydrogel-forming MN arrays. The results proved that there was negligible difference between either methods, with each producing MN arrays with comparable quality. Both types of MN arrays can be successfully inserted in a skin simulant. In both cases the insertion depth was approximately 60% of the needle length and the height reduction after insertion was in both cases approximately 3%. PMID:26302858

  5. A novel scalable manufacturing process for the production of hydrogel-forming microneedle arrays

    PubMed Central

    Lutton, Rebecca E.M.; Larrañeta, Eneko; Kearney, Mary-Carmel; Boyd, Peter; Woolfson, A.David; Donnelly, Ryan F.

    2015-01-01

    A novel manufacturing process for fabricating microneedle arrays (MN) has been designed and evaluated. The prototype is able to successfully produce 14 × 14 MN arrays and is easily capable of scale-up, enabling the transition from laboratory to industry and subsequent commercialisation. The method requires the custom design of metal MN master templates to produce silicone MN moulds using an injection moulding process. The MN arrays produced using this novel method was compared with centrifugation, the traditional method of producing aqueous hydrogel-forming MN arrays. The results proved that there was negligible difference between either methods, with each producing MN arrays with comparable quality. Both types of MN arrays can be successfully inserted in a skin simulant. In both cases the insertion depth was approximately 60% of the needle length and the height reduction after insertion was in both cases approximately 3%. PMID:26302858

  6. The new insight into dynamic crossover in glass forming liquids from the apparent enthalpy analysis

    NASA Astrophysics Data System (ADS)

    Martinez-Garcia, Julio Cesar; Martinez-Garcia, Jorge; Rzoska, Sylwester J.; Hulliger, Jürg

    2012-08-01

    One of the most intriguing phenomena in glass forming systems is the dynamic crossover (TB), occurring well above the glass temperature (Tg). So far, it was estimated mainly from the linearized derivative analysis of the primary relaxation time τ(T) or viscosity η(T) experimental data, originally proposed by Stickel et al. [J. Chem. Phys. 104, 2043 (1996), 10.1063/1.470961; Stickel et al. J. Chem. Phys. 107, 1086 (1997)], 10.1063/1.474456. However, this formal procedure is based on the general validity of the Vogel-Fulcher-Tammann equation, which has been strongly questioned recently [T. Hecksher et al. Nature Phys. 4, 737 (2008), 10.1038/nphys1033; P. Lunkenheimer et al. Phys. Rev. E 81, 051504 (2010), 10.1103/PhysRevE.81.051504; J. C. Martinez-Garcia et al. J. Chem. Phys. 134, 024512 (2011)], 10.1063/1.3514589. We present a qualitatively new way to identify the dynamic crossover based on the apparent enthalpy space (H_a^' = {{dln τ }/{d({1/T})}}) analysis via a new plot ln H_a^' vs. 1/T supported by the Savitzky-Golay filtering procedure for getting an insight into the noise-distorted high order derivatives. It is shown that depending on the ratio between the "virtual" fragility in the high temperature dynamic domain (mhigh) and the "real" fragility at Tg (the low temperature dynamic domain, m = mlow) glass formers can be splitted into two groups related to f < 1 and f > 1, (f = mhigh/mlow). The link of this phenomenon to the ratio between the apparent enthalpy and activation energy as well as the behavior of the configurational entropy is indicated.

  7. Manufacture of Alumina-Forming Austenitic Steel Alloys by Conventional Casting and Hot-Working Methods

    SciTech Connect

    Brady, M.P.; Yamamoto, Y.; Magee, J.H.

    2009-03-10

    Oak Ridge National Laboratory (ORNL) and Carpenter Technology Corporation (CarTech) participated in an in-kind cost share cooperative research and development agreement (CRADA) effort under the auspices of the Energy Efficiency and Renewable Energy (EERE) Technology Maturation Program to explore the feasibility for scale up of developmental ORNL alumina-forming austenitic (AFA) stainless steels by conventional casting and rolling techniques. CarTech successfully vacuum melted 301b heats of four AFA alloy compositions in the range of Fe-(20-25)Ni-(12-14)Cr-(3-4)Al-(l-2.5)Nb wt.% base. Conventional hot/cold rolling was used to produce 0.5-inch thick plate and 0.1-inch thick sheet product. ORNL subsequently successfully rolled the 0.1-inch sheet to 4 mil thick foil. Long-term oxidation studies of the plate form material were initiated at 650, 700, and 800 C in air with 10 volume percent water vapor. Preliminary results indicated that the alloys exhibit comparable (good) oxidation resistance to ORNL laboratory scale AFA alloy arc casting previously evaluated. The sheet and foil material will be used in ongoing evaluation efforts for oxidation and creep resistance under related CRADAs with two gas turbine engine manufacturers. This work will be directed to evaluation of AFA alloys for use in gas turbine recuperators to permit higher-temperature operating conditions for improved efficiencies and reduced environmental emissions. AFA alloy properties to date have been obtained from small laboratory scale arc-castings made at ORNL. The goal of the ORNL-CarTech CRADA was to establish the viability for producing plate, sheet and foil of the AFA alloys by conventional casting and hot working approaches as a first step towards scale up and commercialization of the AFA alloys. The AFA alloy produced under this effort will then be evaluated in related CRADAs with two gas turbine engine manufacturers for gas turbine recuperator applications.

  8. PREFACE: Dynamic crossover phenomena in water and other glass-forming liquids Dynamic crossover phenomena in water and other glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin; Baglioni, Piero

    2012-02-01

    This special section has been inspired by the workshop on Dynamic Crossover Phenomena in Water and Other Glass-Forming Liquids, held during November 11-13, 2010 at Pensione Bencistà, Fiesole, Italy, a well-preserved 14th century Italian villa tucked high in the hills overlooking Florence. The meeting, an assembly of world renowned scientists, was organized as a special occasion to celebrate the 75th birthday of Professor Sow-Hsin Chen of MIT, a pioneer in several aspects of complex fluids and soft matter physics. The workshop covered a large variety of experimental and theoretical research topics of current interest related to dynamic crossover phenomena in water and, more generally, in other glass-forming liquids. The 30 invited speakers/lecturers and approximately 60 participants were a select group of prominent physicists and chemists from the USA, Europe, Asia and Mexico, who are actively working in the field. Some highlights of this special issue include the following works. Professor Yamaguchi's group and their collaborators present a neutron spin echo study of the coherent intermediate scattering function of heavy water confined in cylindrical pores of MCM-41-C10 silica material in the temperature range 190-298 K. They clearly show that a fragile-to-strong (FTS) dynamic crossover occurs at about 225 K. They attribute the FTS dynamic crossover to the formation of a tetrahedral-like structure, which is preserved in the bulk-like water confined to the central part of the cylindrical pores. Mamontov and Kolesnikov et al study the collective excitations in an aqueous solution of lithium chloride over a temperature range of 205-270 K using neutron and x-ray Rayleigh-Brillouin (coherent) scattering. They detect both the low-frequency and the high-frequency sounds known to exist in pure bulk water above the melting temperature. They also perform neutron (incoherent) and x-ray (coherent) elastic intensity scan measurements. Clear evidence of the crossover in the

  9. Effect of Minor al Addition on Glass-Forming Ability and Thermal Stability of Zr-Cu Binary Alloy

    NASA Astrophysics Data System (ADS)

    Yu, Z. H.; Ding, D.; Lu, T.; Xia, L.; Dong, Y. D.

    By adding 2 at.% Al element in Zr50Cu50 binary glass-forming alloy, we obtained Zr50Cu48Al2 glassy rods with diameter larger than 3 mm. The reduced glass transition temperature, parameter γ and the critical section thickness obtained from the differential scanning calorimetry (DSC) traces indicate the better glass-forming ability (GFA) of Zr50Cu48Al2 bulk metallic glass (BMG). The super-cooled liquid region and the continuous heating transformation diagram constructed from Vogel-Fulcher-Tammann fitting of crystallization temperature illustrate the enhanced thermal stability of the Zr50Cu48Al2 BMG. The mechanism of effect of minor Al addition on GFA was investigated in more detail from Angell's fragility concept and from the thermodynamic point of view respectively.

  10. A computational study of diffusion in a glass-forming metallic liquid

    SciTech Connect

    Wang, T.; Zhang, F.; Yang, L.; Fang, X. W.; Zhou, S. H.; Kramer, M. J.; Wang, C. Z.; Ho, K. M.; Napolitano, R. E.

    2015-06-09

    In this study, liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In our computational study, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general formulation for Al-Sm liquid, involving a diffusion mobility database that includes composition and temperature dependence. A Volmer-Fulcher-Tammann (VFT) equation is adopted for describing the non-Arrhenius behavior observed in the undercooled liquid. Furthermore, the composition dependence of diffusivity is found quite strong, even for the Al-rich region contrary to the sole previous report on this binary system. The model is used in combination with the available thermodynamic database to predict specific diffusivities and compares well with reported experimental data for 0.6 at.% and 5.6 at.% Sm in Al-Sm alloys.

  11. A computational study of diffusion in a glass-forming metallic liquid

    NASA Astrophysics Data System (ADS)

    Wang, T.; Zhang, F.; Yang, L.; Fang, X. W.; Zhou, S. H.; Kramer, M. J.; Wang, C. Z.; Ho, K. M.; Napolitano, R. E.

    2015-06-01

    Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general formulation for Al-Sm liquid, involving a diffusion mobility database that includes composition and temperature dependence. A Volmer-Fulcher-Tammann (VFT) equation is adopted for describing the non-Arrhenius behavior observed in the undercooled liquid. The composition dependence of diffusivity is found quite strong, even for the Al-rich region contrary to the sole previous report on this binary system. The model is used in combination with the available thermodynamic database to predict specific diffusivities and compares well with reported experimental data for 0.6 at.% and 5.6 at.% Sm in Al-Sm alloys.

  12. A computational study of diffusion in a glass-forming metallic liquid

    DOE PAGESBeta

    Wang, T.; Zhang, F.; Yang, L.; Fang, X. W.; Zhou, S. H.; Kramer, M. J.; Wang, C. Z.; Ho, K. M.; Napolitano, R. E.

    2015-06-09

    In this study, liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In our computational study, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a generalmore » formulation for Al-Sm liquid, involving a diffusion mobility database that includes composition and temperature dependence. A Volmer-Fulcher-Tammann (VFT) equation is adopted for describing the non-Arrhenius behavior observed in the undercooled liquid. Furthermore, the composition dependence of diffusivity is found quite strong, even for the Al-rich region contrary to the sole previous report on this binary system. The model is used in combination with the available thermodynamic database to predict specific diffusivities and compares well with reported experimental data for 0.6 at.% and 5.6 at.% Sm in Al-Sm alloys.« less

  13. Qualitative change in structural dynamics of some glass-forming systems

    SciTech Connect

    Novikov, Vladimir N.; Sokolov, Alexei P.

    2015-12-14

    Analysis of the temperature dependence of the structural relaxation time Τα(T) in supercooled liquids revealed a qualitatively distinct feature a sharp, cusplike maximum in the second derivative of log Τα(T) at some Tmax. It suggests that the super-Arrhenius temperature dependence of Τα(T) in glass-forming liquids eventually crosses over to an Arrhenius behavior at T < Tmax, and there is no divergence of Τα(T) at nonzero T . Tmax can be above or below Tg, depending on the sensitivity of τ(T) to a change in the liquid's density quantified by the exponent γ in the scaling Τα(T) ~exp(A/Tρ–γ). Lastly, these results might turn the discussion of the glass transition in a different direction toward the origin of the limiting activation energy for structural relaxation at low T.

  14. A computational study of diffusion in a glass-forming metallic liquid

    PubMed Central

    Wang, T.; Zhang, F.; Yang, L.; Fang, X. W.; Zhou, S. H.; Kramer, M. J.; Wang, C. Z.; Ho, K. M.; Napolitano, R. E.

    2015-01-01

    Liquid phase diffusion plays a critical role in phase transformations (e.g. glass transformation and devitrification) observed in marginal glass forming systems such as Al-Sm. Controlling transformation pathways in such cases requires a comprehensive description of diffusivity, including the associated composition and temperature dependencies. In the computational study reported here, we examine atomic diffusion in Al-Sm liquids using ab initio molecular dynamics (AIMD) and determine the diffusivities of Al and Sm for selected alloy compositions. Non-Arrhenius diffusion behavior is observed in the undercooled liquids with an enhanced local structural ordering. Through assessment of our AIMD result, we construct a general formulation for Al-Sm liquid, involving a diffusion mobility database that includes composition and temperature dependence. A Volmer-Fulcher-Tammann (VFT) equation is adopted for describing the non-Arrhenius behavior observed in the undercooled liquid. The composition dependence of diffusivity is found quite strong, even for the Al-rich region contrary to the sole previous report on this binary system. The model is used in combination with the available thermodynamic database to predict specific diffusivities and compares well with reported experimental data for 0.6 at.% and 5.6 at.% Sm in Al-Sm alloys. PMID:26055394

  15. Characteristic length scales of the secondary relaxations in glass-forming glycerol.

    PubMed

    Gupta, S; Mamontov, E; Jalarvo, N; Stingaciu, L; Ohl, M

    2016-03-01

    We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends on the time scale of the relaxation of interest. We use neutron backscattering to identify the characteristic length scale of 0.7 Å for the faster secondary relaxation described in the framework of the mode-coupling theory (MCT). Neutron spin-echo is employed to probe the slower secondary relaxation of the excess wing type at a low temperature ( ∼ 1.13T g . The characteristic length scale for this excess wing dynamics is approximately 4.7 Å. Besides the Q -dependence, the direct coupling of neutron scattering signal to density fluctuation makes this technique indispensable for measuring the length scale of the microscopic relaxation dynamics. PMID:27021657

  16. Localization model description of diffusion and structural relaxation in glass-forming Cu–Zr alloys

    NASA Astrophysics Data System (ADS)

    Douglas, Jack F.; Pazmino Betancourt, Beatriz A.; Tong, Xuhang; Zhang, Hao

    2016-05-01

    We test the localization model (LM) prediction of a parameter-free relationship between the α-structural relaxation time τ α and the Debye–Waller factor    for a series of simulated glass-forming Cu–Zr metallic liquids having a range of alloy compositions. After validating this relationship between the picosecond (‘fast’) and long-time relaxation dynamics over the full range of temperatures and alloy compositions investigated in our simulations, we show that it is also possible to estimate the self-diffusion coefficients of the individual atomic species (D Cu, D Zr) and the average diffusion coefficient D using the LM, in conjunction with the empirical fractional Stokes–Einstein (FSE) relation linking these diffusion coefficients to τ α . We further observe that the fragility and extent of decoupling between D and τ α strongly correlate with    at the onset temperature of glass-formation T A where particle caging and the breakdown of Arrhenius relaxation first emerge.

  17. Efficient measurement of point-to-set correlations and overlap fluctuations in glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Berthier, Ludovic; Charbonneau, Patrick; Yaida, Sho

    2016-01-01

    Cavity point-to-set correlations are real-space tools to detect the roughening of the free-energy landscape that accompanies the dynamical slowdown of glass-forming liquids. Measuring these correlations in model glass formers remains, however, a major computational challenge. Here, we develop a general parallel-tempering method that provides orders-of-magnitude improvement for sampling and equilibrating configurations within cavities. We apply this improved scheme to the canonical Kob-Andersen binary Lennard-Jones model for temperatures down to the mode-coupling theory crossover. Most significant improvements are noted for small cavities, which have thus far been the most difficult to study. This methodological advance also enables us to study a broader range of physical observables associated with thermodynamic fluctuations. We measure the probability distribution of overlap fluctuations in cavities, which displays a non-trivial temperature evolution. The corresponding overlap susceptibility is found to provide a robust quantitative estimate of the point-to-set length scale requiring no fitting. By resolving spatial fluctuations of the overlap in the cavity, we also obtain quantitative information about the geometry of overlap fluctuations. We can thus examine in detail how the penetration length as well as its fluctuations evolve with temperature and cavity size.

  18. Insights into Silicate and Oxide Melt Structure from Amorphous, Non-Glass-Forming Materials

    NASA Astrophysics Data System (ADS)

    Stebbins, J. F.

    2015-12-01

    Many silicate and oxide liquids of interest in the Earth sciences and in technology cannot readily be quenched to glasses, either because of low silica contents (and hence low viscosity at the melting point and accompanying liquid 'fragility') or because of liquid-liquid unmixing at high temperature. Although in-situ, high temperature structural tools have been in use for decades and are rapidly developing, many methods are still most informative for glass samples quenched to ambient pressure and temperature, e.g. high-resolution solid-state NMR. Amorphous oxides, including alumina and silicate compositions, have widespread technological applications. These are generally deposited by a variety of high-energy sputtering methods, as films of thicknesses of 10's to 100's of nm. Using Al-27, Si-29, and O-17 NMR, we have recently shown that for such films, very similar short-range structure is seen in materials made by very different kinetic pathways, such as sol-gel synthesis vs. ion-beam sputtering. This path-independent structure suggests that these materials pass through transient equilibrium states during their formation, probably that of deeply supercooled liquids just above glass transition temperatures. In the HfO2-SiO2 and ZrO2-SiO2 systems, for example, samples have well-resolved O-17 NMR spectra, allowing quantitation of O sites with only Hf(Zr) neighbors (so-called "free" oxide ions), with mixed Hf(Zr) and Si neighbors, and Si only. The observed oxygen speciation agrees well with a simple thermodynamic model of one of the most fundamental equilibria in silicate systems, namely the reaction of bridging (Si-O-Si) and "free" (e.g. OHf3 and OHf4) oxide ions to produce "non-bridging" oxygens (e.g. Si-OHf2). This new approach to sampling such structural equilibria in compositions far outside the range of normal glass-forming liquids may provide new insights into more geological compositions as well, as well as in more general models of silicate melt chemistry.

  19. Crystal nucleation in glass-forming alloy and pure metal melts under containerless and vibrationless conditions

    NASA Technical Reports Server (NTRS)

    Spaepen, F.; Turnbull, D.

    1982-01-01

    The undercooling behavior of large spheroids of Pd40Ni40P40 was investigated. By surface etching, supporting the specimens on a fused silica substrate, and successive heating and cooling, crystallization can be eliminated, presumable due to the removal of surface heterogeneities. By this method samples up to 3.2g with a 0.53 mm minor diameter, were made entirely glassy, except for some superficial crystals comprising less than 0.5% of the volume. These experiments show that a cooling rate of approximately 1 K/sec is adequate to avoid copious homogeneous nucleation in the alloy, and that by eliminating or reducing the effectiveness of heterogeneous nucleation sites, it is possible to form bulk samples of this metallic glass with virtually unlimited dimensions.

  20. Crystallization upon thermal annealing of a glass-forming liquid crystal in the nematic regime

    SciTech Connect

    Mastrangelo, J.C. |; Blanton, T.N.; Chen, S.H. |

    1995-04-24

    As an example of a novel class of glass-forming liquid crystals, compound (I) was synthesized and characterized to possess a nematic mesophase between {ital T}{sub {ital g}} and {ital T}{sub {ital c}} as the pristine crystal was heated beyond its {ital T}{sub {ital m}} followed by quenching to below room temperature. Differential scanning calorimetry (DSC) and x-ray diffraction techniques were employed to investigate its morphological stability. It was found that the nematic mesophase persists upon annealing for a period of up to 22 h without the appearance of new phases. However, after annealing in the nematic regime over a longer period of time, thermally activated phase transformations were observed, resulting in a new crystalline phase plus the pristine crystalline phase based on DSC thermal transition data and x-ray diffraction patterns.

  1. Electrorheological Source of Nonlinear Dielectric Effects in Molecular Glass-Forming Liquids.

    PubMed

    Samanta, Subarna; Richert, Ranko

    2016-08-11

    We have measured the dielectric relaxation spectra of eight glass-forming liquids in the presence of electric direct current (dc)-bias fields ranging from 100 to 500 kV/cm. For every sample, we observe two distinct field-induced effects: a reduction in the relaxation amplitude and an increase in the primary structural relaxation time that is associated with viscous flow. Whereas amplitude change is typical of the well-known dielectric saturation, the field-induced increase in viscosity is a source of nonlinear behavior that has been recognized only recently. We find that this electrorheological behavior occurs in all polar liquids of this study, and its magnitude is correlated with the field-induced change in thermodynamic entropy. It constitutes a significant source of nonlinear dielectric behavior, which occurs for both dc and alternating current fields. PMID:27404019

  2. Correlation of fragility with mechanical moduli in double-well potential for glass-forming liquid

    NASA Astrophysics Data System (ADS)

    Cao, Wan Qiang

    2012-02-01

    The shoving model and the Vogel-Fulcher relation are employed to derive correlation of the fragility with the mechanical moduli for glass-forming simple liquids. The result shows that a liquid with smaller fragility will have larger ratio of K∞/G∞ in dilute liquid system. Based on radial distribution function with the Lennard-Jones potential modified by the Gaussian potential with a second minimum, fragility of the supercooled simple liquid is derived from the correlation between viscosity and shear modulus via configurational entropy. The results demonstrate that the fragility is determined by two parts: thermodynamic components and mechanical moduli. For a weak Gaussian potential liquid, the fragility is proportional to the Tg, while for a strong one, the fragility is inversely proportional to the Tg, and the Gaussian potential will increase fragility.

  3. X-ray absorption fine structure of aged, Pu-doped glass and ceramic waste forms

    NASA Astrophysics Data System (ADS)

    Hess, N. J.; Weber, W. J.; Conradson, S. D.

    1998-04-01

    X-ray absorption spectroscopic (XAS) studies were performed on three compositionally identical, Pu-doped, borosilicate glasses prepared 15 years ago at different α-activities by varying the 239Pu/ 238Pu isotopic ratio. The resulting α-activities ranged from 1.9×10 7 to 4.2×10 9 Bq/g and have current, accumulated doses between 8.8×10 15 to 1.9×10 18 α-decays/g. Two ceramic, polycrystalline zircon (ZrSiO 4) samples prepared 16 years ago with 10.0 wt% Pu was also investigated. Varying the 239Pu/ 238Pu isotopic ratio in these samples resulted in α-activities of 2.5×10 8 and 5.6×10 10 Bq/g and current, accumulated doses of 1.2×10 17 and 2.8×10 19 α-decays/g. The multicomponent composition of the waste forms permitted XAS investigations at six absorption edges for the borosilicate glass and at three absorption edges for the polycrystalline zircons. For both waste forms, analysis of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectra indicates that the local environment around the cations exhibits different degrees of disorder as a result of the accumulated α-decay dose. In general, cations with short cation-oxygen bonds show little effect from self-radiation whereas cations with long cation-oxygen bonds show a greater degree of disorder with accumulated α-decay dose.

  4. Sustainable Energy Solutions Task 4.1 Intelligent Manufacturing of Hybrid Carbon-Glass Fiber-Reinforced Composite Wind Turbine Blades

    SciTech Connect

    Janet M Twomey, PhD

    2010-04-30

    EXECUTIVE SUMARY In this subtask, the manufacturability of hybrid carbon-glass fiber-reinforced composite wind turbine blades using Vacuum-Assisted Resin Transfer Molding (VARTM) was investigated. The objective of this investigation was to study the VARTM process and its parameters to manufacture cost-effective wind turbine blades with no defects (mainly eliminate dry spots and reduce manufacturing time). A 2.5-dimensional model and a 3-dimensional model were developed to simulate mold filling and part curing under different conditions. These conditions included isothermal and non-isothermal filling, curing of the part during and after filling, and placement of injection gates at different locations. Results from this investigation reveal that the process can be simulated and also that manufacturing parameters can be optimized to eliminate dry spot formation and reduce the manufacturing time. Using computer-based models is a cost-effective way to simulate manufacturing of wind turbine blades. The approach taken herein allows the design of the wind blade manufacturing processes without physically running trial-and-error experiments that are expensive and time-consuming; especially for larger blades needed for more demanding environmental conditions. This will benefit the wind energy industry by reducing initial design and manufacturing costs which can later be passed down to consumers and consequently make the wind energy industry more competitive.

  5. PREFACE: Dynamic crossover phenomena in water and other glass-forming liquids Dynamic crossover phenomena in water and other glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Chen, Sow-Hsin; Baglioni, Piero

    2012-02-01

    This special section has been inspired by the workshop on Dynamic Crossover Phenomena in Water and Other Glass-Forming Liquids, held during November 11-13, 2010 at Pensione Bencistà, Fiesole, Italy, a well-preserved 14th century Italian villa tucked high in the hills overlooking Florence. The meeting, an assembly of world renowned scientists, was organized as a special occasion to celebrate the 75th birthday of Professor Sow-Hsin Chen of MIT, a pioneer in several aspects of complex fluids and soft matter physics. The workshop covered a large variety of experimental and theoretical research topics of current interest related to dynamic crossover phenomena in water and, more generally, in other glass-forming liquids. The 30 invited speakers/lecturers and approximately 60 participants were a select group of prominent physicists and chemists from the USA, Europe, Asia and Mexico, who are actively working in the field. Some highlights of this special issue include the following works. Professor Yamaguchi's group and their collaborators present a neutron spin echo study of the coherent intermediate scattering function of heavy water confined in cylindrical pores of MCM-41-C10 silica material in the temperature range 190-298 K. They clearly show that a fragile-to-strong (FTS) dynamic crossover occurs at about 225 K. They attribute the FTS dynamic crossover to the formation of a tetrahedral-like structure, which is preserved in the bulk-like water confined to the central part of the cylindrical pores. Mamontov and Kolesnikov et al study the collective excitations in an aqueous solution of lithium chloride over a temperature range of 205-270 K using neutron and x-ray Rayleigh-Brillouin (coherent) scattering. They detect both the low-frequency and the high-frequency sounds known to exist in pure bulk water above the melting temperature. They also perform neutron (incoherent) and x-ray (coherent) elastic intensity scan measurements. Clear evidence of the crossover in the

  6. Chemical Principles Revisited: The Chemistry of Glass.

    ERIC Educational Resources Information Center

    Kolb, Doris; Kolb, Kenneth E.

    1979-01-01

    Presents a detailed discussion on the chemistry of glass. Topics discussed include: natural glass, early history, modern glass composition, raw materials for glass melting, chemically modified glasses, modern glass forming, glass ceramics, and new developments in glass research. (BT)

  7. Pressure and temperature dependent viscosity of two glass forming liquids: Glycerol and dibutyl phthalate

    NASA Astrophysics Data System (ADS)

    Cook, Richard L.; King, H. E., Jr.; Herbst, Chris A.; Herschbach, Dudley R.

    1994-04-01

    The pressure and temperature dependent viscosities of two glass forming liquids, glycerol and dibutyl phthalate (DBP), have been studied in the range P=0-3 GPa, T=0-125 °C, and η=101-1010 cP. These studies were made using a combination of a rolling-ball and a centrifugal-force diamond anvil cell viscometer. The majority of the results extend up to viscosities of 107 cP, with those at 22.5 °C going to 1010 cP. The overall precision of the data are approximately 10% or better throughout. This level of precision allows us to define a viscosity surface which can then be extrapolated to the glass transition along both temperature and pressure cuts. The T-dependence of viscosity is larger for glycerol than DBP but the P-dependence smaller for glycerol than for DBP, whereas the T-dependence is much more pressure sensitive for DBP. These data provide an assessment of the T-dependence of an isothermal model (free volume), the P-dependence of an isobaric model (Vogel-Tammann-Fulcher) and by extension that for isochoric conditions. Fragility parameters are evaluated for these three isometric conditions. For glycerol and (less conclusively) DBP under isobaric conditions, the fragility increases markedly at high pressure. Under isochoric conditions, the fragility for both glycerol and DBP increases with increasing density. This is dramatic for DBP, which goes from a strong to an intermediate-strength liquid. For the isothermal model, we derive a new measure of fragility. Using this, DBP shows a trend common to several liquids, a decrease in fragility with increasing temperature. Glycerol, however, becomes more fragile over the same temperature range. For glycerol, the trends towards increased fragility at elevated pressure and temperature are consistent with diminished hydrogen bonding under those conditions. The P-dependence of the glass transition is also determined over a wide range of T. The slope, dTg/dP, is positive with the pressure dependence for glycerol being

  8. Secondary relaxation dynamics in rigid glass-forming molecular liquids with related structures.

    PubMed

    Li, Xiangqian; Wang, Meng; Liu, Riping; Ngai, Kia L; Tian, Yongjun; Wang, Li-Min; Capaccioli, Simone

    2015-09-14

    The dielectric relaxation in three glass-forming molecular liquids, 1-methylindole (1MID), 5H-5-Methyl-6,7-dihydrocyclopentapyrazine (MDCP), and Quinaldine (QN) is studied focusing on the secondary relaxation and its relation to the structural α-relaxation. All three glass-formers are rigid and more or less planar molecules with related chemical structures but have dipoles of different strengths at different locations. A strong and fast secondary relaxation is detected in the dielectric spectra of 1MID, while no resolved β-relaxation is observed in MDCP and QN. If the observed secondary relaxation in 1MID is identified with the Johari-Goldstein (JG) β-relaxation, then apparently the relation between the α- and β-relaxation frequencies of 1MID is not in accord with the Coupling Model (CM). The possibility of the violation of the prediction in 1MID as due to either the formation of hydrogen-bond induced clusters or the involvement of intramolecular degree of freedom is ruled out. The violation is explained by the secondary relaxation originating from the in-plane rotation of the dipole located on the plane of the rigid molecule, contributing to dielectric loss at higher frequencies and more intense than the JG β-relaxation generated by the out-of-plane rotation. MDCP has smaller dipole moment located in the plane of the molecule; however, presence of the change of curvature of dielectric loss, ε″(f), at some frequency on the high-frequency flank of the α-relaxation reveals the JG β-relaxation in MDCP and which is in accord with the CM prediction. QN has as large an in-plane dipole moment as 1MID, and the absence of the resolved secondary relaxation is explained by the smaller coupling parameter than the latter in the framework of the CM. PMID:26374048

  9. Secondary relaxation dynamics in rigid glass-forming molecular liquids with related structures

    NASA Astrophysics Data System (ADS)

    Li, Xiangqian; Wang, Meng; Liu, Riping; Ngai, Kia L.; Tian, Yongjun; Wang, Li-Min; Capaccioli, Simone

    2015-09-01

    The dielectric relaxation in three glass-forming molecular liquids, 1-methylindole (1MID), 5H-5-Methyl-6,7-dihydrocyclopentapyrazine (MDCP), and Quinaldine (QN) is studied focusing on the secondary relaxation and its relation to the structural α-relaxation. All three glass-formers are rigid and more or less planar molecules with related chemical structures but have dipoles of different strengths at different locations. A strong and fast secondary relaxation is detected in the dielectric spectra of 1MID, while no resolved β-relaxation is observed in MDCP and QN. If the observed secondary relaxation in 1MID is identified with the Johari-Goldstein (JG) β-relaxation, then apparently the relation between the α- and β-relaxation frequencies of 1MID is not in accord with the Coupling Model (CM). The possibility of the violation of the prediction in 1MID as due to either the formation of hydrogen-bond induced clusters or the involvement of intramolecular degree of freedom is ruled out. The violation is explained by the secondary relaxation originating from the in-plane rotation of the dipole located on the plane of the rigid molecule, contributing to dielectric loss at higher frequencies and more intense than the JG β-relaxation generated by the out-of-plane rotation. MDCP has smaller dipole moment located in the plane of the molecule; however, presence of the change of curvature of dielectric loss, ɛ″(f), at some frequency on the high-frequency flank of the α-relaxation reveals the JG β-relaxation in MDCP and which is in accord with the CM prediction. QN has as large an in-plane dipole moment as 1MID, and the absence of the resolved secondary relaxation is explained by the smaller coupling parameter than the latter in the framework of the CM.

  10. Preparation and characterization of Fe-based bulk metallic glasses in plate form

    NASA Astrophysics Data System (ADS)

    Lavorato, G. C.; Fiore, G.; Castellero, A.; Baricco, M.; Moya, J. A.

    2012-08-01

    Amorphous alloys with composition (at%) Fe48Cr15Mo14C15B6Gd2 (alloy A) and Fe48Cr15Mo14C15B6Y2 (alloy B) were prepared either using pure elements (A and B1) and a commercial AISI430 steel as a base material (B2). When prepared from pure elements both alloys (A and B1) could be cast in plate form with a fixed thickness of 2 mm and variable lengths between 10 and 20 mm by means of copper-mold injection in air atmosphere. In the case of alloy B2, prepared using commercial grade raw materials, rods of 2 mm diameter were obtained. X-ray diffraction and scanning electron microscopy observations confirmed that an amorphous structure was obtained in all the as-cast samples. A minor fraction of crystalline phases (oxides and carbides) was detected on the as-cast surface. Differential scanning calorimetry measurements showed a glass transition temperature at 856 K for alloy A and 841 K for alloy B1, and an onset crystallization temperature of 887 K for alloy A and 885 K for alloy B1. In the case of alloy B2 a slightly different crystallization sequence was observed. Values of hardness (∼13 GPa) and the Young modulus (∼180 GPa) were measured by nanoindentation for both the alloys. The effects of adverse casting conditions (such as air atmosphere, non-conventional injection copper mold casting and partial replacement of pure elements with commercial grade raw materials) on the glass formation and properties of the alloy are discussed.

  11. Finite-size effects in the dynamics of glass-forming liquids.

    PubMed

    Berthier, Ludovic; Biroli, Giulio; Coslovich, Daniele; Kob, Walter; Toninelli, Cristina

    2012-09-01

    We present a comprehensive theoretical study of finite-size effects in the relaxation dynamics of glass-forming liquids. Our analysis is motivated by recent theoretical progress regarding the understanding of relevant correlation length scales in liquids approaching the glass transition. We obtain predictions both from general theoretical arguments and from a variety of specific perspectives: mode-coupling theory, kinetically constrained and defect models, and random first-order transition theory. In the last approach, we predict in particular a nonmonotonic evolution of finite-size effects across the mode-coupling crossover due to the competition between mode-coupling and activated relaxation. We study the role of competing relaxation mechanisms in giving rise to nonmonotonic finite-size effects by devising a kinetically constrained model where the proximity to the mode-coupling singularity can be continuously tuned by changing the lattice topology. We use our theoretical findings to interpret the results of extensive molecular dynamics studies of four model liquids with distinct structures and kinetic fragilities. While the less fragile model only displays modest finite-size effects, we find a more significant size dependence evolving with temperature for more fragile models, such as Lennard-Jones particles and soft spheres. Finally, for a binary mixture of harmonic spheres we observe the predicted nonmonotonic temperature evolution of finite-size effects near the fitted mode-coupling singularity, suggesting that the crossover from mode-coupling to activated dynamics is more pronounced for this model. Finally, we discuss the close connection between our results and the recent report of a nonmonotonic temperature evolution of a dynamic length scale near the mode-coupling crossover in harmonic spheres. PMID:23030918

  12. Five-fold symmetry as indicator of dynamic arrest in metallic glass-forming liquids

    PubMed Central

    Hu, Y. C.; Li, F. X.; Li, M. Z.; Bai, H. Y.; Wang, W. H.

    2015-01-01

    With sufficient high cooling rates, a variety of liquids, including metallic melts, will cross a glass transition temperature and solidify into glass accompanying a marked increase of the shear viscosity in approximately 17 orders of magnitude. Because of the intricate atomic structure and dynamic behaviours of liquid, it is yet difficult to capture the underlying structural mechanism responsible for the marked slowing down during glass transition, which impedes deep understanding of the formation and nature of glasses. Here, we report that a universal structural indicator, the average degree of five-fold local symmetry, can well describe the slowdown dynamics during glass transition. A straightforward relationship between structural parameter and viscosity (or α-relaxation time) is introduced to connect the dynamic arrest and the underlying structural evolution. This finding would be helpful in understanding the long-standing challenges of glass transition mechanism in the structural perspective. PMID:26387592

  13. Cesium Hydroxide Fusion Dissolution of Analytical Reference Glass-1 in Both Powder and Shard Form

    SciTech Connect

    Coleman, C.J.; Spencer, W.A.

    1998-04-01

    CsOH has been shown to be an effective and convenient dissolution reagent for Analytical Reference Glass-1 (ARG-1). This glass standard was prepared from nonradioactive DWPF Start-up Glass. Therefore, its composition is similar to DWPF product glass and many of the glass matrices prepared at SRTC.The principal advantage of the CsOH fusion dissolution is that the reagent does not add the alkali metals Li, Na, and K usually needed by SRS customers. Commercially available CsOH is quite pure so that alkali metals can be measured accurately, often without blank corrections. CsOH fusions provide a single dissolution method for applicable glass to replace multiple dissolution schemes used by most laboratories. For example, SRTC glass samples are most commonly dissolved with a Na{sub 2}O{sub 2}-NaOH fusion (ref.1) and a microwave- assisted acid dissolution with HNO{sub 3}-HF-H{sub 3}BO{sub 3}-HCl (ref.2). Othe laboratories use fusion methods based on KOH, LiBO{sub 2}, and Na{sub 2}CO{sub 3} CsOH fusion approach reduces by half not only the work in the dissolution laboratory, but also in the spectroscopy laboratories that must analyze each solution.Experiments also revealed that glass shards or pellets are rapidly attacked if the flux temperature is raised considerably above the glass softening point. The softening point of ARG-1 glass is near 650 degrees C. Fusions performed at 750 degrees C provided complete dissolutions and accurate elemental analyses of shards. Successful dissolution of glass shards was demonstrated with CsOH, Na{sub 2}O{sub 2}, NaOH, KOH, and RbOH. Ability to dissolve glass shards is of considerable practical importance. Crushing glass to a fine powder is a slow and tedious task, especially for radioactive glasses dissolved in shielded cells. CsOH fusion of glass powder or shards is a convenient, cost-effective dissolution scheme applicable in SRTC, the DWPF, and the commercial glass industry.

  14. Glass-forming property of hydroxyectoine is the cause of its superior function as a desiccation protectant

    PubMed Central

    Tanne, Christoph; Golovina, Elena A.; Hoekstra, Folkert A.; Meffert, Andrea; Galinski, Erwin A.

    2014-01-01

    We were able to demonstrate that hydroxyectoine, in contrast to ectoine, is a good glass-forming compound. Fourier transform infrared and spin label electron spin resonance studies of dry ectoine and hydroxyectoine have shown that the superior glass-forming properties of hydroxyectoine result from stronger intermolecular H-bonds with the OH group of hydroxyectoine. Spin probe experiments have also shown that better molecular immobilization in dry hydroxyectoine provides better redox stability of the molecules embedded in this dry matrix. With a glass transition temperature of 87°C (vs. 47°C for ectoine) hydroxyectoine displays remarkable desiccation protection properties, on a par with sucrose and trehalose. This explains its accumulation in response to increased salinity and elevated temperature by halophiles such as Halomonas elongata and its successful application in ``anhydrobiotic engineering'' of both enzymes and whole cells. PMID:24772110

  15. Invited Review Article: Review of post-process optical form metrology for industrial-grade metal additive manufactured parts.

    PubMed

    Stavroulakis, P I; Leach, R K

    2016-04-01

    The scope of this review is to investigate the main post-process optical form measurement technologies available in industry today and to determine whether they are applicable to industrial-grade metal additive manufactured parts. An in-depth review of the operation of optical three-dimensional form measurement technologies applicable to metal additive manufacturing is presented, with a focus on their fundamental limitations. Looking into the future, some alternative candidate measurement technologies potentially applicable to metal additive manufacturing will be discussed, which either provide higher accuracy than currently available techniques but lack measurement volume, or inversely, which operate in the appropriate measurement volume but are not currently accurate enough to be used for industrial measurement. PMID:27131645

  16. Invited Review Article: Review of post-process optical form metrology for industrial-grade metal additive manufactured parts

    NASA Astrophysics Data System (ADS)

    Stavroulakis, P. I.; Leach, R. K.

    2016-04-01

    The scope of this review is to investigate the main post-process optical form measurement technologies available in industry today and to determine whether they are applicable to industrial-grade metal additive manufactured parts. An in-depth review of the operation of optical three-dimensional form measurement technologies applicable to metal additive manufacturing is presented, with a focus on their fundamental limitations. Looking into the future, some alternative candidate measurement technologies potentially applicable to metal additive manufacturing will be discussed, which either provide higher accuracy than currently available techniques but lack measurement volume, or inversely, which operate in the appropriate measurement volume but are not currently accurate enough to be used for industrial measurement.

  17. Additive Manufacturing Modeling and Simulation A Literature Review for Electron Beam Free Form Fabrication

    NASA Technical Reports Server (NTRS)

    Seufzer, William J.

    2014-01-01

    Additive manufacturing is coming into industrial use and has several desirable attributes. Control of the deposition remains a complex challenge, and so this literature review was initiated to capture current modeling efforts in the field of additive manufacturing. This paper summarizes about 10 years of modeling and simulation related to both welding and additive manufacturing. The goals were to learn who is doing what in modeling and simulation, to summarize various approaches taken to create models, and to identify research gaps. Later sections in the report summarize implications for closed-loop-control of the process, implications for local research efforts, and implications for local modeling efforts.

  18. Non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 bulk metallic glass investigated by differential scanning calorimetry

    NASA Astrophysics Data System (ADS)

    Gong, Pan; Zhao, Shaofan; Wang, Xin; Yao, Kefu

    2015-07-01

    The non-isothermal crystallization kinetics and glass-forming ability of Ti41Zr25Be28Fe6 glassy alloy were investigated by differential scanning calorimetry. The activation energies corresponding to the characteristic temperatures have been calculated by Kissinger and Ozawa equations. Based on Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall models, it has been found that the local activation energy is higher at the beginning of the crystallization process for the first exothermic peak. The local Avrami exponent indicates that the first-step crystallization is mainly a high-dimensional nucleation and growth with an increasing nucleation rate. According to the calculated fragility index, Ti41Zr25Be28Fe6 alloy can be classified as "strong glass former." The studied alloy also possesses a critical size up to centimeter order, and the high glass-forming ability is probably related to the relatively low Gibbs energy difference between the liquid and crystalline states. The critical cooling rate of Ti41Zr25Be28Fe6 glassy alloy has also been determined using Barandiaran-Colmenero's method.

  19. AC Calorimetry and Thermophysical Properties of Bulk Glass-Forming Metallic Liquids

    NASA Technical Reports Server (NTRS)

    Johnson, William L.

    2000-01-01

    Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.

  20. Structural signatures evidenced in dynamic crossover phenomena in metallic glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Hu, Y. C.; Li, F. X.; Li, M. Z.; Bai, H. Y.; Wang, W. H.

    2016-05-01

    Molecular dynamics simulations were performed to investigate dynamic evolution in metallic glass-forming liquids during quenching from high temperature above melting point down to supercooled region. Two crossover temperatures TA and TS (TA > TS) are identified, and their physical meanings are clarified. TA and TS are found to be not only the sign of dynamic crossover phenomena but also the manifestation of two key structure correlation lengths ξ s . As temperature decreases below TA, ξ s goes beyond the nearest-neighbor distance, resulting in the Arrhenius-to-non-Arrhenius transition of structural relaxation time and the failure of Stokes-Einstein (SE) relation. As TS is traversed, the increase rate of ξ s reaches the maximum, leading to the simultaneous appearance of dynamical heterogeneity and fractional SE relation. It is further found that structure correlation increases much faster than dynamic correlation, playing a role of structural precursor for dynamic evolution in liquids. Thus, a structural link is established for deeper understanding dynamic crossover phenomena.

  1. On-line measurements to control the forming process of glass vials

    NASA Astrophysics Data System (ADS)

    Angrilli, Francesco; Bianchini, Gianandrea; Fanti, Giulio; Mozzi, Massimo

    1993-02-01

    The most relevant parameters to control the quality of glass vials are the internal and external diameters of the mouth and the height of the rim. A low cost vision system based on a 486 PC, a frame grabber, 4 CCD cameras (768 X 512 pixels) and I/O device to control the production of vials, by adjusting the flames temperature in the moulding section of the machine, has been developed and tested. A 24 mandrel machine rotating at about 300 rpm with a production capability of about 4200 pieces/hour had to be monitored with an accuracy of +/- 0.02 mm in the measure of the mouth diameters and +/- 0.04 mm on the rim height. In order to minimize the time delay required for the machine temperature compensation, the measurements had to be taken during the forming process. The system must be fast enough to follow the process, able to take into account the temperature variation of different classes of vials and far enough from the high temperature of the flames. A direct calibration procedure, using a reference vial, and a pyrometer to check the temperature range was derived. A long focus lens coupled with a bellow to put the system away from the flames was adopted. The algorithm implemented for the measurements and the machine temperature control is presented.

  2. The atomic-scale mechanism for the enhanced glass-forming-ability of a Cu-Zr based bulk metallic glass with minor element additions

    PubMed Central

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

    2014-01-01

    It is known that the glass forming-ability (GFA) of bulk metallic glasses (BMGs) can be greatly enhanced via minor element additions. However, direct evidence has been lacking to reveal its structural origin despite different theories hitherto proposed. Through the high-resolution transmission-electron-microscopy (HRTEM) analysis, here we show that the content of local crystal-like orders increases significantly in a Cu-Zr-Al BMG after a 2-at% Y addition. Contrasting the previous studies, our current results indicate that the formation of crystal-like order at the atomic scale plays an important role in enhancing the GFA of the Cu-Zr-Al base BMG. PMID:24721927

  3. Improvement of glass forming ability and magnetic properties of a Gd55Al20Co25 bulk metallic glass by minor Fe substitution for Co

    NASA Astrophysics Data System (ADS)

    Guan, Q.; Yu, P.; Chan, K. C.; Xia, L.

    2015-11-01

    Gd55Al20Co25 bulk metallic glass (BMG) exhibits good glass forming ability (GFA) and excellent magneto-caloric effect (MCE). In order to further improve the GFA and MCE of the Gd55Al20Co25 BMG, we attempted to add small amount of Fe as a replacement of Co in the BMG and obtained Gd55Al20Co23Fe2 glassy rod using a traditional suction casting method. The Gd55Al20Co23Fe2 BMG shows a better GFA and MCE than the Gd55Al20Co25 BMG. The magneto-caloric behavior of the Gd55Al20Co23Fe2 BMG was investigated by studying the field dependence of the magnetic entropy change peak and the refrigeration capacity.

  4. Dielectric Response of Glass-Forming Liquids in the Nonlinear Regime

    NASA Astrophysics Data System (ADS)

    Samanta, Subarna

    Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be 'slaved' to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein beta-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the

  5. Thermal deformation compensation in the molding of aspheric glass lenses

    NASA Astrophysics Data System (ADS)

    Lee, Dong-kil; Oh, Jun-girl; Jang, Won-Gun; Kim, Yang-gyu; Lee, Kwanghoon; Park, Anjin; Yang, Young-Soo

    2014-06-01

    Generally, aspheric glass lenses are manufactured using a glass molding press (GMP) method and a tungsten carbide mold core. This study analyzes the thermal deformation that occurs during the GMP process, and the results were applied to compensate an aspheric glass lens. After the compensation process, the form accuracy of aspheric glass lenses improved from ˜3.7 to ˜0.35 μm. The compensated lens complied with the actual specifications.

  6. Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering

    SciTech Connect

    Gupta, S.; Arend, N.; Lunkenheimer, P.; Loidl, A.; Stingaciu, L.; Jalarvo, N.; Mamontov, E.; Ohl, M.

    2015-01-22

    The relaxational dynamics in glass-forming glycerol and glycerol mixed with LiCl is investigated using different neutron scattering techniques. The performed neutron spin echo experiments, which extend up to relatively long relaxation time scales of the order of 10 ns, should allow for the detection of contributions from the so-called excess wing. This phenomenon, whose microscopic origin is controversially discussed, arises in a variety of glass formers and, until now, was almost exclusively investigated by dielectric spectroscopy and light scattering. In conclusion, we show here that the relaxational process causing the excess wing can also be detected by neutron scattering, which directly couples to density fluctuations.

  7. Development of a new process for manufacturing precision gobs out of new developed low Tg optical glasses for precise pressing of aspherical lenses; Technical Digest

    NASA Astrophysics Data System (ADS)

    Jaschek, Rainer; Klein, Christopher; Schenk, Christian; Schneider, Klaus; Freund, Jochen; Simone, Ritter

    2005-05-01

    Aspherical lenses or refractive elements out of optical glass can be produced either by grinding and polishing of glass or by precise molding of glass preforms. The first process is applied for lenses with larger geometries and smaller production quantities. On the other hand, precise molding is used for volume production of lenses within a diameter range between 1 mm and around 30 mm. The addressed products can be found in the consumer markets (digital imaging, digital projection and digital storage). Different preform types can be used for precise molding: polished spherical near shape preforms, polished balls, polished discs and precision gobs. The latter are made directly from the glass melt. This paper describes a newly developed process, which results in fire-polished gobs with very low surface roughness and excellent volume accuracy. Since precision gobs are mostly made for precise molding, they must meet specific process requirements apart form their optical values, such as allowing low molding temperatures and shorter process cycles times. Therefore, this paper also describes the latest results in the development of low Tg glasses, which are designed for the volume production of precision molded optical components. Beside the important parameters like nd, nd as well as Tg, other properties like chemical durability, devitrification resistance, thermal expansion and conductivity coefficients are important for optimizing the precise molding process. The characteristics of three new low Tg glasses in the FK-, PK- as well as SK-region are presented. These glasses are environmentally friendly, since they are free of lead and arsenic.

  8. Manufacturing technologies

    NASA Astrophysics Data System (ADS)

    The Manufacturing Technologies Center is at the core of Sandia National Laboratories' advanced manufacturing effort which spans the entire product realization process. The center's capabilities in product and process development are summarized in the following disciplines: (1) mechanical - rapid prototyping, manufacturing engineering, machining and computer-aided manufacturing, measurement and calibration, and mechanical and electronic manufacturing liaison; (2) electronics - advanced packaging for microelectronics, printed circuits, and electronic fabrication; and (3) materials - ceramics, glass, thin films, vacuum technology, brazing, polymers, adhesives, composite materials, and process analysis.

  9. An Electrochemical Sensing Platform Based on Liquid-Liquid Microinterface Arrays Formed in Laser-Ablated Glass Membranes.

    PubMed

    Alvarez de Eulate, Eva; Strutwolf, Jörg; Liu, Yang; O'Donnell, Kane; Arrigan, Damien W M

    2016-03-01

    Arrays of microscale interfaces between two immiscible electrolyte solutions (μITIES) were formed using glass membranes perforated with microscale pores by laser ablation. Square arrays of 100 micropores in 130 μm thick borosilicate glass coverslips were functionalized with trichloro(1H,1H,2H,2H-perfluorooctyl)silane on one side, to render the surface hydrophobic and support the formation of aqueous-organic liquid-liquid microinterfaces. The pores show a conical shape, with larger radii at the laser entry side (26.5 μm) than at the laser exit side (11.5 μm). The modified surfaces were characterized by contact angle measurements and X-ray photoelectron spectroscopy. The organic phase was placed on the hydrophobic side of the membrane, enabling the array of μITIES to be located at either the wider or narrower pore mouth. The electrochemical behavior of the μITIES arrays were investigated by tetrapropylammonium ion transfer across water-1,6-dichlorohexane interfaces together with finite element computational simulations. The data suggest that the smallest microinterfaces (formed on the laser exit side) were located at the mouth of the pore in hemispherical geometry, while the larger microinterfaces (formed on the laser entry side) were flatter in shape but exhibited more instability due to the significant roughness of the glass around the pore mouths. The glass membrane-supported μITIES arrays presented here provide a new platform for chemical and biochemical sensing systems. PMID:26853853

  10. Coincidence of collective relaxation anomaly and specific heat peak in a bulk metallic glass-forming liquid

    NASA Astrophysics Data System (ADS)

    Jaiswal, Abhishek; Podlesynak, Andrey; Ehlers, Georg; Mills, Rebecca; O'Keeffe, Stephanie; Stevick, Joseph; Kempton, James; Jelbert, Glenton; Dmowski, Wojciech; Lokshin, Konstantin; Egami, Takeshi; Zhang, Yang

    2015-07-01

    The study of relaxational behavior of multicomponent metallic liquids still holds the key to understanding and improving the glass-forming abilities of bulk metallic glasses. Herein, we report measurements of the collective relaxation times in a melted bulk metallic glass (LM 601 Zr51Cu36Ni4Al9 ) in the kinetic regime (Q : 1.5 -4.0 Å-1) using quasielastic neutron scattering. The results reveal an unusual slope change in the Angell plots of the collective relaxation time of this metallic liquid around 950 ∘C , beyond the melting point of the material. Specific heat capacity measurement also reveals the presence of a peak around the same temperature. The coincidence is rationalized using Adams-Gibbs theory, and motivates more careful experimental and computational studies of the metallic liquids in the future.

  11. Coincidence of collective relaxation anomaly and specific heat peak in a bulk metallic glass-forming liquid

    SciTech Connect

    Jaiswal, Abhishek; Podlesynak, Andrey; Ehlers, Georg; Mills, Rebecca; O'Keeffe, Stephanie; Stevick, Joseph; Kempton, James; Jelbert, Glenton; Dmowski, Wojciech; Lokshin, Konstantin; Egami, Takeshi; Zhang, Yang

    2015-07-21

    The study of multicomponent metallic liquids' relaxational behavior is still the key to understanding and improving the glass-forming abilities of bulk metallic glasses. Here, we report measurements of the collective relaxation times in a melted bulk metallic glass (LM601Zr51Cu36Ni4Al9) in the kinetic regime (Q: 1.5–4.0Å–1) using quasielastic neutron scattering. The results reveal an unusual slope change in the Angell plots of this metallic liquid's collective relaxation time around 950°C, beyond the material's melting point. Measurement of specific heat capacity also reveals a peak around the same temperature. Adams-Gibbs theory is used to rationalize the coincidence, which motivates more careful experimental and computational studies of the metallic liquids in the future.

  12. Coincidence of collective relaxation anomaly and specific heat peak in a bulk metallic glass-forming liquid

    DOE PAGESBeta

    Jaiswal, Abhishek; Podlesynak, Andrey; Ehlers, Georg; Mills, Rebecca; O'Keeffe, Stephanie; Stevick, Joseph; Kempton, James; Jelbert, Glenton; Dmowski, Wojciech; Lokshin, Konstantin; et al

    2015-07-21

    The study of multicomponent metallic liquids' relaxational behavior is still the key to understanding and improving the glass-forming abilities of bulk metallic glasses. Here, we report measurements of the collective relaxation times in a melted bulk metallic glass (LM601Zr51Cu36Ni4Al9) in the kinetic regime (Q: 1.5–4.0Å–1) using quasielastic neutron scattering. The results reveal an unusual slope change in the Angell plots of this metallic liquid's collective relaxation time around 950°C, beyond the material's melting point. Measurement of specific heat capacity also reveals a peak around the same temperature. Adams-Gibbs theory is used to rationalize the coincidence, which motivates more careful experimentalmore » and computational studies of the metallic liquids in the future.« less

  13. Quantitative relations between cooperative motion, emergent elasticity, and free volume in model glass-forming polymer materials

    PubMed Central

    Pazmiño Betancourt, Beatriz A.; Hanakata, Paul Z.; Starr, Francis W.; Douglas, Jack F.

    2015-01-01

    The study of glass formation is largely framed by semiempirical models that emphasize the importance of progressively growing cooperative motion accompanying the drop in fluid configurational entropy, emergent elasticity, or the vanishing of accessible free volume available for molecular motion in cooled liquids. We investigate the extent to which these descriptions are related through computations on a model coarse-grained polymer melt, with and without nanoparticle additives, and for supported polymer films with smooth or rough surfaces, allowing for substantial variation of the glass transition temperature and the fragility of glass formation. We find quantitative relations between emergent elasticity, the average local volume accessible for particle motion, and the growth of collective motion in cooled liquids. Surprisingly, we find that each of these models of glass formation can equally well describe the relaxation data for all of the systems that we simulate. In this way, we uncover some unity in our understanding of glass-forming materials from perspectives formerly considered as distinct. PMID:25713371

  14. Nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass: Insights from molecular dynamics simulations.

    PubMed

    Kilymis, D A; Delaye, J-M; Ispas, S

    2016-07-28

    We have carried out classical molecular dynamics simulations in order to get insight into the atomistic mechanisms of the deformation during nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass. In terms of the glass hardness, we have found that the primary factor affecting the decrease of hardness after irradiation is depolymerization rather than free volume, and we argue that this is a general trend applicable to other borosilicate glasses with similar compositions. We have analyzed the changes of the short- and medium-range structures under deformation and found that the creation of oxygen triclusters is an important mechanism in order to describe the deformation of highly polymerized borosilicate glasses and is essential in the understanding of the folding of large rings under stress. We have equally found that the less polymerized glasses present a higher amount of relative densification, while the analysis of bond-breaking during the nanoindentation has showed that shear flow is more likely to appear around sodium atoms. The results provided in this study can be proven to be useful in the interpretation of experimental results. PMID:27475379

  15. Nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass: Insights from molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Kilymis, D. A.; Delaye, J.-M.; Ispas, S.

    2016-07-01

    We have carried out classical molecular dynamics simulations in order to get insight into the atomistic mechanisms of the deformation during nanoindentation of the pristine and irradiated forms of a sodium borosilicate glass. In terms of the glass hardness, we have found that the primary factor affecting the decrease of hardness after irradiation is depolymerization rather than free volume, and we argue that this is a general trend applicable to other borosilicate glasses with similar compositions. We have analyzed the changes of the short- and medium-range structures under deformation and found that the creation of oxygen triclusters is an important mechanism in order to describe the deformation of highly polymerized borosilicate glasses and is essential in the understanding of the folding of large rings under stress. We have equally found that the less polymerized glasses present a higher amount of relative densification, while the analysis of bond-breaking during the nanoindentation has showed that shear flow is more likely to appear around sodium atoms. The results provided in this study can be proven to be useful in the interpretation of experimental results.

  16. Unique local structures of Ca, Ti, Fe and Zr in natural glasses formed by meteorite impact

    NASA Astrophysics Data System (ADS)

    Yoshiasa, Akira; Tobase, Tsubasa; Okube, Maki; Wang, Ling; Isobe, Hiroshi; Mashimo, Tsutomu; Graduate School of Science; Technology Collaboration; Materials; Structures Laboratory, Tokyo Institute of Technology Collaboration

    2015-06-01

    The local structures of cation in tektite from six strewn fields, impact-related glass, and non-impact-related glass were studied by Ca, Ti, Fe and Zr K-edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). Shock compression also causes local structural changes of gest and minor elements as well as transition of host structures. How to be left a record is peculiar by each element. The XAFS measurements were performed at the beam lines BL-NW10A and BL-9C, KEK, Japan. The comparison of XANES spectra and bonding distances between crystalline reference minerals and natural glasses was done. Based on the different valence states of iron, the degrees of oxidation states were estimated. The local structures of Ca, Ti and Zr ions are useful probe for physical conditions and formation process of glasses. Tektites experienced high quenching rates and a reduced atmospheric environment when they were ejected into outer space. Other impact-related glass, which was remained close to the crater, experienced a more complicated environment. The local structural changes of cation in the impact-related glass are rich in a variety. Analysis of local structure is help to compare their formation process and distinguish them.

  17. Decoupling of relaxation and diffusion in random pinning glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Li, Yan-Wei; Zhu, You-Liang; Sun, Zhao-Yan

    2015-03-01

    We investigate numerically the relaxation and diffusion dynamics in three-dimensional Kob-Andersen glass-forming liquids in which part of the particles are randomly chosen and pinned permanently. We find that both the relaxation dynamics and diffusion dynamics slow down as increasing the pinning concentration (cpin) at fixed temperatures that we study. For higher temperature and lower cpin, the α relaxation time τ and the diffusion coefficient D have the scaling relationship D ˜ τ-1. However, this coupling behavior breaks down if cpin is further increased, and the scaling relationship is replaced by D ˜ τ-ν with ν < 1. At temperatures around the onset temperature of the bulk system, a transition from ν ˜ 0.75 to ν ˜ 0.61 with increasing cpin is found. However, at lower temperatures, ν ˜ 0.67 holds in the whole studied cpin range. By fitting the relaxation time as a function of cpin with Vogel-Fulcher-Tamman equation, we find that the change of scaling exponent ν is accompanied with the change of fragility parameter K at higher temperatures. However, at lower temperatures, pinning particles have little effect on the system's qualitative properties. Moreover, we investigate three measures of heterogeneity of dynamics and find that the relaxation and the diffusion motion of particles show different responses to the pinned particles, which may lead to the slower relaxation than diffusion and the decoupling of relaxation and diffusion. The string-like motion is found to saturate at the mode-coupling theory (MCT) crossover point, which indicates that other relaxation modes may exist below the MCT transition point.

  18. Decoupling of relaxation and diffusion in random pinning glass-forming liquids.

    PubMed

    Li, Yan-Wei; Zhu, You-Liang; Sun, Zhao-Yan

    2015-03-28

    We investigate numerically the relaxation and diffusion dynamics in three-dimensional Kob-Andersen glass-forming liquids in which part of the particles are randomly chosen and pinned permanently. We find that both the relaxation dynamics and diffusion dynamics slow down as increasing the pinning concentration (cpin) at fixed temperatures that we study. For higher temperature and lower cpin, the α relaxation time τ and the diffusion coefficient D have the scaling relationship D ∼ τ(-1). However, this coupling behavior breaks down if cpin is further increased, and the scaling relationship is replaced by D ∼ τ(-ν) with ν < 1. At temperatures around the onset temperature of the bulk system, a transition from ν ∼ 0.75 to ν ∼ 0.61 with increasing cpin is found. However, at lower temperatures, ν ∼ 0.67 holds in the whole studied cpin range. By fitting the relaxation time as a function of cpin with Vogel-Fulcher-Tamman equation, we find that the change of scaling exponent ν is accompanied with the change of fragility parameter K at higher temperatures. However, at lower temperatures, pinning particles have little effect on the system's qualitative properties. Moreover, we investigate three measures of heterogeneity of dynamics and find that the relaxation and the diffusion motion of particles show different responses to the pinned particles, which may lead to the slower relaxation than diffusion and the decoupling of relaxation and diffusion. The string-like motion is found to saturate at the mode-coupling theory (MCT) crossover point, which indicates that other relaxation modes may exist below the MCT transition point. PMID:25833596

  19. Novel bioactive Fe-based metallic glasses with excellent apatite-forming ability.

    PubMed

    Qin, Chunling; Hu, Qingfeng; Li, Yongyan; Wang, Zhifeng; Zhao, Weimin; Louzguine-Luzgin, Dmitri V; Inoue, Akihisa

    2016-12-01

    We demonstrate, for the first time, that the (Fe0.75B0.15Si0.1)100-xNbx (x=0, 1 and 3at.%) metallic glasses without toxic and allergic elements exhibit excellent apatite-forming ability in simulated body fluids (SBF), which is expected to be a new generation of biomaterials in stents and orthopedic implants. For the alloys without any surface treatment, spherical particles corresponding to octacalcium phosphate are spontaneously nucleated and precipitated throughout the alloy surface after immersion only for 1day, indicating that the present alloys possess an unusual high bioactivity. During the subsequent in-vitro immersion for 3days, SEM image reveals the typical 'cauliflower' morphology of bone-like hydroxyapatite (HA) with Ca/P ratio of 1.65. In addition, it is surprising to find that the in-vitro SBF immersion not only leads to the formation and growth of the apatite layer but also causes the progressive development of the underlying alloy substrate. Moreover, for the alloys immersed for 3 or 9days, the substrate alloy just beneath the apatite layer consists of a hierarchical nano/macro-porous structure through selective dissolution of the active components Fe and B in the surface. XPS analysis indicates that the apatite nucleation on the present alloys in SBF is attributed to the specific dissolution properties of the present alloys and the fast formation of Si-OH and Fe-OH or Nb-OH functional groups, followed by combination of these groups with Ca(2+) and phosphate ions. PMID:27612742

  20. Influence of an amorphous wall on the distribution of localized excitations in a colloidal glass-forming liquid

    NASA Astrophysics Data System (ADS)

    Gokhale, Shreyas; Hima Nagamanasa, K.; Sood, A. K.; Ganapathy, Rajesh

    2016-07-01

    Elucidating the nature of the glass transition has been the holy grail of condensed matter physics and statistical mechanics for several decades. A phenomenological aspect that makes glass formation a conceptually formidable problem is that structural and dynamic correlations in glass-forming liquids are too subtle to be captured at the level of conventional two-point functions. As a consequence, a host of theoretical techniques, such as quenched amorphous configurations of particles, have been devised and employed in simulations and colloid experiments to gain insights into the mechanisms responsible for these elusive correlations. Very often, though, the analysis of spatio-temporal correlations is performed in the context of a single theoretical framework, and critical comparisons of microscopic predictions of competing theories are thereby lacking. Here, we address this issue by analysing the distribution of localized excitations, which are building blocks of relaxation as per the dynamical facilitation (DF) theory, in the presence of an amorphous wall, a construct motivated by the random first-order transition theory (RFOT). We observe that spatial profiles of the concentration of excitations exhibit complex features such as non-monotonicity and oscillations. Moreover, the smoothly varying part of the concentration profile yields a length scale {ξc} , which we compare with a previously computed length scale {ξ\\text{dyn}} . Our results suggest a method to assess the role of dynamical facilitation in governing structural relaxation in glass-forming liquids.

  1. Natural glass from Deccan volcanic province: an analogue for radioactive waste form

    NASA Astrophysics Data System (ADS)

    Rani, Nishi; Shrivastava, J. P.; Bajpai, R. K.

    2015-11-01

    Deccan basaltic glass is associated with the differentiation centres of the vast basaltic magmas erupted in a short time span. Its suitability as a radioactive waste containment chiefly depends on alteration behaviour; however, detailed work is needed on this glass. Therefore, the basaltic glass was treated under hydrothermal-like conditions and then studied to understand its alteration. Moreover, comparison of these results with the naturally altered glass is also documented in this paper. Solutions as well as residue obtained after glass alteration experiments were analysed. Treated glass specimens show partial to complete release of all the ions during alteration; however, abundant release of Si and Na ions is noticed in case of almost all the specimens and the ionic release is of the order of Na > Si > K > Ca > Al = Mg > Fe > Mn > Ti. Scanning electron images of the altered residue show morphologies of smectite, montmorillonite and illite inside as well as outside of the secondary layers, and represent paragenesis of alteration minerals. It has been noticed that the octahedral cation occupancies of smectite are consistent with the dioctahedral smectite. The secondary layer composition indicates retention for Si, Al, and Mg ions, indicating their fixation in the alteration products, but remarkably high retention of Ti, Mn and Fe ions suggests release of very small amount of these elements into the solution. By evolution of the secondary layer and retention of less soluble ions, the obstructive effect of the secondary layer increases and the initial constant release rate begins slowly to diminish with the proceeding time. It has been found that devitrification of glass along the cracks, formation of spherulite-like structures and formation of yellowish brown palagonite, chlorite, calcite, zeolite and finally white coloured clays yielded after experiments that largely correspond to altered obsidian that existed in the natural environment since inception ~66 Ma ago.

  2. Continuing the Validation of CCIM Processability for Glass Ceramic HLLW Forms: Plan for Test AFY14CCIM-GC1

    SciTech Connect

    Vince Maio

    2014-04-01

    This test plan covers test AFY14CCIM-GC1which is the first of two scheduled FY-2014 test runs involving glass ceramic waste forms in the Idaho National Laboratory’s Cold Crucible Induction Melter Pilot Plant. The test plan is based on the successes and challenges of previous tests performed in FY-2012 and FY-2013. The purpose of this test is to continue to collect data for validating the glass ceramic High Level Liquid Waste form processability advantages using Cold Crucible Induction Melter technology. The major objective of AFYCCIM-GC1 is to complete additional proposed crucible pouring and post tapping controlled cooling experiments not completed during previous tests due to crucible drain failure. This is necessary to qualify that no heat treatments in standard waste disposal canisters are necessary for the operational scale production of glass ceramic waste forms. Other objectives include the production and post-test analysis of surrogate waste forms made from separate pours into the same graphite mold canister, testing the robustness of an upgraded crucible bottom drain and drain heater assembly, testing the effectiveness of inductive melt initiation using a resistive starter ring with a square wave configuration, and observing the tapped molten flow behavior in pans with areas identical to standard High Level Waste disposal canisters. Testing conditions, the surrogate waste composition, key testing steps, testing parameters, and sampling and analysis requirements are defined.

  3. Gel-like elasticity in glass-forming side-chain liquid-crystal polymers

    NASA Astrophysics Data System (ADS)

    Pozo, O.; Collin, D.; Finkelmann, H.; Rogez, D.; Martinoty, P.

    2009-09-01

    We study the complex shear modulus G of two side-chain liquid-crystal polymers (SCLCPs), a methoxy-phenylbenzoate substituted polyacrylate (thereafter called PAOCH3 ), and a cyanobiphenyl substituted polyacrylate supplied by Merck (thereafter called LCP105) using a piezoelectric rheometer. Two methods of filling the cell are used: (a) a capillary method, which can be used only at high temperature because of the low value of the viscosity, and (b) the classical one, thereafter called compression method, which consists in placing the sample between the two slides of the cell and to bring them closer. By filling the cell at high temperature either with the compression or the capillary method, we show that the response of both compounds is liquidlike ( G'˜f2 and G″˜f , where f is the frequency) for temperatures higher than a certain temperature T0 and gel-like (G'˜const,G″˜f) below T0 . This change in behavior from the conventional flow response to a gel-like response, when approaching the glass transition, is observed for nonsliding conditions and for very weak-imposed shear strains. It can be explained by a percolation-type mechanism of preglassy elastic clusters, which correspond to long-range and long-lived density fluctuations that are frozen at the time scale of the experiment. The sample response is therefore the sum of two contributions: one is due to the flow response of the polymer melt and the other to the elastic response of the network formed by the preglassy elastic clusters. By filling the cell below T0 with the compression method, both compounds exhibit a gel-type behavior by gently bringing closer the slides of the cell and an anomalous low-frequency behavior characterized by G'=const and G″=const by increasing the pressure used to bring closer the slides of the cell. A compression-assisted aggregation of the preglassy elastic clusters can explain both the increase in the low-frequency elastic plateau when the sample thickness is decreased

  4. Cryomilling-induced solid dispersion of poor glass forming/poorly water-soluble mefenamic acid with polyvinylpyrrolidone K12.

    PubMed

    Kang, Naewon; Lee, Jangmi; Choi, Ji Na; Mao, Chen; Lee, Eun Hee

    2015-06-01

    The effect of mechanical impact on the polymorphic transformation of mefenamic acid (MFA) and the formation of a solid dispersion of mefenamic acid, a poor glass forming/poorly-water soluble compound, with polyvinylpyrrolidone (PVP) K12 was investigated. The implication of solid dispersion formation on solubility enhancement of MFA, prepared by cryomilling, was investigated. Solid state characterization was conducted using powder X-ray diffraction (PXRD) and Fourier-transform infrared (FTIR) spectroscopy combined with crystal structure analysis. Apparent solubility of the mixtures in pH 7.4 buffer was measured. A calculation to compare the powder patterns and FTIR spectra of solid dispersions with the corresponding physical mixtures was conducted. Solid state characterization showed that (1) MFA I transformed to MFA II when pure MFA I was cryogenically milled (CM); and (2) MFA forms a solid dispersion when MFA was cryogenically milled with PVP K12. FTIR spectral analysis showed that hydrogen bonding facilitated by mechanical impact played a major role in forming solid dispersions. The apparent solubility of MFA was significantly improved by making a solid dispersion with PVP K12 via cryomilling. This study highlights the importance of cryomilling with a good hydrogen bond forming excipient as a technique to prepare solid dispersion, especially when a compound shows a poor glass forming ability and therefore, is not easy to form amorphous forms by conventional method. PMID:24849785

  5. Preparation of glass-forming materials from granulated blast furnace slag

    NASA Astrophysics Data System (ADS)

    Alonso, M.; Sáinz, E.; Lopez, F. A.

    1996-10-01

    Glass precursor materials, to be used for the vitrification of hazardous wastes, have been prepared from blast furnace slag powder through a sol-gel route. The slag is initially reacted with a mixture of alcohol (ethanol or methanol) and mineral acid (HNO3 or H2SO4) to give a sol principally consisting of Si, Ca, Al, and Mg alkoxides. Gelation is carried out with variable amounts of either ammonia or water. The gelation rate can be made as fast as desired by adding excess hydrolizing agent or else by distilling the excess alcohol out of the alkoxide solution. The resulting gel is first dried at low temperature and ground. The powder thus obtained is then heat treated at several temperatures. The intermediate and final materials are characterized by thermal analysis, infrared (IR) spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), and chemical analysis. From the results, the operating conditions yielding a variety of glass precursors differing in their composition are established. The method, in comparison with direct vitrification of slag, presents a number of advantages: (1) the glass precursor obtained devitrifies at higher temperatures; (2) it enables the adjustment, to a certain extent, of the chemical composition of the glass precursor; and (3) it permits recovering marketable materials at different stages of the process.

  6. Erbium doping into silicate glasses to form luminescent optical layers for photonics applications

    NASA Astrophysics Data System (ADS)

    Salavcova, Linda; Mackova, Anna; Oswald, Jiri; Svecova, Blanka; Janakova, Stanislava; Spirkova, Jarmila; Mika, Martin

    2007-05-01

    Here we summarise results of our research on the Er-containing thin surface layers in the silicate glasses and on the effect of the layers’ composition on their luminescence properties (emission at 1535 nm) in the wavelength region widely used in photonics. The optical layers were fabricated by Er3+ (melt)⇔Li+/Na+ (glass substrate) ion exchange in the specially designed Li2O containing silicate glasses using various conditions (including annealing of the samples) to obtain a set of layers with diverse distribution of the Er3+ ions. Changes in the chemical composition of the prepared layers were suggested to avoid the concentration quenching effect and to improve their luminescence properties; special attention was paid to presence of hydrogen in the layers that may decrease the emission intensity. Rutherford Backscattering Spectroscopy and Elastic Recoil Detection were used to obtain detailed information on migration of erbium and hydrogen through the glass matrix, respectively. Photoluminescence spectra of the fabricated samples were measured (excitation at 980 nm) to examine the desired emission around 1535 nm.

  7. The dynamic susceptibility in glass forming molecular liquids: The search for universal relaxation patterns II

    NASA Astrophysics Data System (ADS)

    Blochowicz, T.; Gainaru, C.; Medick, P.; Tschirwitz, C.; Rössler, E. A.

    2006-04-01

    The susceptibility spectra of ten molecular glass formers are completely interpolated by an extension of the generalized gamma distribution of correlation times. The data cover at least 15 decades in frequency and the interpolation includes both α peak and excess wing. It is shown that the line shape parameters and the time constant of the α relaxation are related to each other. Master curves are identified by a scaling procedure that involves only three parameters, namely, the glass transition temperature Tg, the fragility m, and the excess wing exponent at Tg. This holds independent of whether a further secondary relaxation peak is present or not. Above a crossover temperature Tx this unique evolution of the line shape parameters breaks down, and a crossover to a simple peak susceptibility without excess wing is observed. Here, the frequency-temperature superposition principle holds in good approximation up to temperatures well above the melting point. It turns out that the crossover coincides with the temperature at which the low-temperature Vogel-Fulcher law starts to fail upon heating. Thus, the so-called Stickel temperature gets a more physical meaning as it marks a qualitative change in the evolution of the susceptibility spectra of glass formers. Moreover, the interrelation of the line shape parameters can explain why the "Nagel scaling" works in some approximation. Our study demonstrates that the excess wing in molecular glass formers is a secondary relaxation, which is linked to the α process in a unique way.

  8. Multi-phase glass-ceramics as a waste form for combined fission products: alkalis, alkaline earths, lanthanides, and transition metals

    SciTech Connect

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna

    2012-04-01

    In this study, multi-phase silicate-based glass-ceramics were investigated as an alternate waste form for immobilizing non-fissionable products from used nuclear fuel. Currently, borosilicate glass is the waste form selected for immobilization of this waste stream, however, the low thermal stability and solubility of MoO{sub 3} in borosilicate glass translates into a maximum waste loading in the range of 15-20 mass%. Glass-ceramics provide the opportunity to target durable crystalline phases, e.g., powellite, oxyapatite, celsian, and pollucite, that will incorporate MoO{sub 3} as well as other waste components such as lanthanides, alkalis, and alkaline earths at levels 2X the solubility limits of a single-phase glass. In addition a glass-ceramic could provide higher thermal stability, depending upon the properties of the crystalline and amorphous phases. Glass-ceramics were successfully synthesized at waste loadings of 42, 45, and 50 mass% with the following glass additives: B{sub 2}O{sub 3}, Al{sub 2}O{sub 3}, CaO and SiO{sub 2} by slow cooling form from a glass melt. Glass-ceramics were characterized in terms of phase assemblage, morphology, and thermal stability. The targeted phases: powellite and oxyapatite were observed in all of the compositions along with a lanthanide borosilicate, and cerianite. Results of this initial investigation of glass-ceramics show promise as a potential waste form to replace single-phase borosilicate glass.

  9. Polymeric compositions and their method of manufacture. [forming filled polymer systems using cryogenics

    NASA Technical Reports Server (NTRS)

    Moser, B. G.; Landel, R. F. (Inventor)

    1972-01-01

    Filled polymer compositions are made by dissolving the polymer binder in a suitable sublimable solvent, mixing the filler material with the polymer and its solvent, freezing the resultant mixture, and subliming the frozen solvent from the mixture from which it is then removed. The remaining composition is suitable for conventional processing such as compression molding or extruding. A particular feature of the method of manufacture is pouring the mixed solution slowly in a continuous stream into a cryogenic bath wherein frozen particles of the mixture result. The frozen individual particles are then subjected to the sublimation.

  10. Effects of Cu, Fe and Co addition on the glass-forming ability and mechanical properties of Zr-Al-Ni bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Li, YanHui; Zhang, Wei; Dong, Chuang; Makino, Akihiro

    2012-12-01

    The thermal stability, glass-forming ability (GFA) and mechanical properties of Zr60Al15Ni25- x TM x (TM = Cu, Fe and Co, x = 0-10) bulk metallic glasses (BMGs) were systematically investigated. Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy. Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm. However, addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA. In addition, the plasticity of the BMG can be improved by adding of Cu, while the strength is decreased slightly. Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa. Addition of Co brings an increase of strength but a lower of plasticity, and additional Fe reduces the strength and plasticity simultaneously.

  11. Ergodicity and slowing down in glass-forming systems with soft potentials: No finite-temperature singularities

    NASA Astrophysics Data System (ADS)

    Eckmann, Jean-Pierre; Procaccia, Itamar

    2008-07-01

    The aim of this paper is to discuss some basic notions regarding generic glass-forming systems composed of particles interacting via soft potentials. Excluding explicitly hard-core interaction, we discuss the so-called glass transition in which a supercooled amorphous state is formed, accompanied by a spectacular slowing down of relaxation to equilibrium, when the temperature is changed over a relatively small interval. Using the classical example of a 50-50 binary liquid of N particles with different interaction length scales, we show the following. (i) The system remains ergodic at all temperatures. (ii) The number of topologically distinct configurations can be computed, is temperature independent, and is exponential in N . (iii) Any two configurations in phase space can be connected using elementary moves whose number is polynomially bounded in N , showing that the graph of configurations has the small world property. (iv) The entropy of the system can be estimated at any temperature (or energy), and there is no Kauzmann crisis at any positive temperature. (v) The mechanism for the super-Arrhenius temperature dependence of the relaxation time is explained, connecting it to an entropic squeeze at the glass transition. (vi) There is no Vogel-Fulcher crisis at any finite temperature T>0 .

  12. An experimental approach to manufacturing technology of historical glass (XIII-XV centuries). Comparison with current glassmaking technology.

    NASA Astrophysics Data System (ADS)

    Tarrago, Mariona; Gimeno, Domingo; Bazzocchi, Flavia; Garcia-Valles, Maite; Martinez, Salvador

    2015-04-01

    One of the major and less explored issues in the characterization of historical glasses is the determination of their viscosity as a function of temperature in order to constrain technological aspects of glass production. Until now, assumptions on temperatures have been based on mathematical models based on chemical compositions. Hence, the topic of this work is to explore the technology of stained glass production related to the workability and melting process of the glass by experimental laboratory measurements. This work presents the analysis of viscosity of glasses from different historical sites and chemical compositions: four from Santes Creus (Tarragona, XIII century), two of classical medieval stained glass window from Santa Maria de Pedralbes (Barcelona, mid XIV century), and three of evolved late-medieval type from Santa Maria del Mar (Barcelona first half of XV century), and one sample of soda-lime industrial glass by means of Hot-Stage Microscopy and glass transformation temperature Tg by dilatometry. These data are then compared to the predictions on theoretical viscosity obtained from mathematical models based on chemical composition. These samples are classified according to their major modifier in: Na-rich (12-17% of Na2O, between 65-77% of SiO2 and less than 3 % of K2O); Ca-rich (29% of CaO, 54% of SiO2, 4% of K2O, and 4% of Na2O); K-Ca-rich (17 to 21% of K2O, more than 14% of CaO, 49-55% of SiO2and less than 2% of Na2O); Na-Ca-rich (12-14% of Na2O, 9-15% of CaO, 57-71% of SiO2 and < 6% of K2O). Glass transition temperature (Tg) is correlated to chemical composition: 464-492 °C for Na-rich, 645 °C for Ca-rich, 582-586 °C for K-Ca-rich and 497-542 °C for Na-Ca-rich glasses. Experimental viscosity-temperature curves are traced using Tg and fixed viscosity points measured by Hot-Stage microscopy (according to German standard 51730) in order to provide more accurate insight into the phases of glass production process (melting, working, conditioning

  13. Thermal Imaging for Assessment of Electron-Beam Free Form Fabrication (EBF(sup 3)) Additive Manufacturing Welds

    NASA Technical Reports Server (NTRS)

    Zalameda, Joseph N.; Burke, Eric R.; Hafley, Robert A.; Taminger, Karen M.; Domack, Christopher S.; Brewer, Amy R.; Martin, Richard E.

    2013-01-01

    Additive manufacturing is a rapidly growing field where 3-dimensional parts can be produced layer by layer. NASA s electron beam free-form fabrication (EBF(sup 3)) technology is being evaluated to manufacture metallic parts in a space environment. The benefits of EBF(sup 3) technology are weight savings to support space missions, rapid prototyping in a zero gravity environment, and improved vehicle readiness. The EBF(sup 3) system is composed of 3 main components: electron beam gun, multi-axis position system, and metallic wire feeder. The electron beam is used to melt the wire and the multi-axis positioning system is used to build the part layer by layer. To insure a quality weld, a near infrared (NIR) camera is used to image the melt pool and solidification areas. This paper describes the calibration and application of a NIR camera for temperature measurement. In addition, image processing techniques are presented for weld assessment metrics.

  14. Optical and morphological characterizations of pyronin dye-poly (vinyl alcohol) thin films formed on glass substrates

    NASA Astrophysics Data System (ADS)

    Meral, Kadem; Arik, Mustafa; Onganer, Yavuz

    2016-04-01

    Thin films of pyronin dye mixed with poly(vinyl alcohol) (PVA) on glass substrate were prepared by using spin-coating technique. The optical and morphological properties of the thin films were studied by UV-Vis., steady-state fluorescence spectroscopies and atomic force microscopy (AFM). The thin films on glass substrate were fabricated at various [PVA]/[dye] (P/D) ratios. Hence, the monomeric and H-aggregates thin films of pyronin dye mixed with PVA were formed as a function of the dye and PVA concentration. It was determined that while the monomeric thin films showed strong fluorescence, the formation of H-aggregates in the thin film caused to decreasing the fluorescence intensity. AFM studies demonstrated that the morphology of the thin film was drastically varied with changing the optical property of the thin film such as monomeric and H-aggregates thin films.

  15. Multi-scale lattice Boltzmann and mode-coupling theory calculations of the flow of a glass-forming liquid.

    PubMed

    Papenkort, S; Voigtmann, Th

    2015-11-28

    We present a hybrid-lattice Boltzmann (LB) algorithm for calculating the flow of glass-forming fluids that are governed by integral constitutive equations with pronounced nonlinear, non-Markovian dependence of the stresses on the flow history. The LB simulation for the macroscopic flow fields is combined with the mode-coupling theory (MCT) of the glass transition as a microscopic theory, in the framework of the integration-through transients formalism. Using the combined LB-MCT algorithm, pressure-driven planar channel flow is studied for a schematic MCT model neglecting spatial correlations in the microscopic dynamics. The cessation dynamics after removal of the driving pressure gradient shows strong signatures of oscillatory flow both in the macroscopic fields and the microscopic correlation functions. PMID:26627963

  16. Excess wing in glass-forming glycerol and LiCl-glycerol mixtures detected by neutron scattering

    DOE PAGESBeta

    Gupta, S.; Arend, N.; Lunkenheimer, P.; Loidl, A.; Stingaciu, L.; Jalarvo, N.; Mamontov, E.; Ohl, M.

    2015-01-22

    The relaxational dynamics in glass-forming glycerol and glycerol mixed with LiCl is investigated using different neutron scattering techniques. The performed neutron spin echo experiments, which extend up to relatively long relaxation time scales of the order of 10 ns, should allow for the detection of contributions from the so-called excess wing. This phenomenon, whose microscopic origin is controversially discussed, arises in a variety of glass formers and, until now, was almost exclusively investigated by dielectric spectroscopy and light scattering. In conclusion, we show here that the relaxational process causing the excess wing can also be detected by neutron scattering, whichmore » directly couples to density fluctuations.« less

  17. Fragility and dynamical properties of glass-forming liquids above their Tg

    NASA Astrophysics Data System (ADS)

    Cutroni, M.; Mandanici, A.; Pelster, R.; Spanoudaki, A.

    2000-04-01

    A new broadband dielectric spectroscopy technique, operating from some Hz up to the microwave frequency region, has been used to study the collective dynamical aspects of some simple molecular liquids approaching their glass transition temperature. Accessing to the relaxational dynamics of metatoluidine (CH3C6H4NH2) on a mesoscopic timescale, a very high value of fragility has been obtained for this liquid in the classification scheme recently refined by Angell.

  18. Magnetic nanoparticles formed in glasses co-doped with iron and larger radius elements

    SciTech Connect

    Edelman, I.; Ivanova, O.; Ivantsov, R.; Velikanov, D.; Zabluda, V.; Zubavichus, Y.; Veligzhanin, A.; Zaikovskiy, V.; Stepanov, S.; Artemenko, A.; Curely, J.; Kliava, J.

    2012-10-15

    A new type of nanoparticle-containing glasses based on borate glasses co-doped with low contents of iron and larger radius elements, Dy, Tb, Gd, Ho, Er, Y, and Bi, is studied. Heat treatment of these glasses results in formation of magnetic nanoparticles, radically changing their physical properties. Transmission electron microscopy and synchrotron radiation-based techniques: x-ray diffraction, extended x-ray absorption fine structure, x-ray absorption near-edge structure, and small-angle x-ray scattering, show a broad distribution of nanoparticle sizes with characteristics depending on the treatment regime; a crystalline structure of these nanoparticles is detected in heat treated samples. Magnetic circular dichroism (MCD) studies of samples subjected to heat treatment as well as of maghemite, magnetite, and iron garnet allow to unambiguously assign the nanoparticle structure to maghemite, independently of co-dopant nature and of heat treatment regime used. Different features observed in the MCD spectra are related to different electron transitions in Fe{sup 3+} ions gathered in the nanoparticles. The static magnetization in heat treated samples has non-linear dependence on the magnetizing field with hysteresis. Zero-field cooled magnetization curves show that at higher temperatures the nanoparticles occur in superparamagnetic state with blocking temperatures above 100 K. Below ca. 20 K, a considerable contribution to both zero field-cooled and field-cooled magnetizations occurs from diluted paramagnetic ions. Variable-temperature electron magnetic resonance (EMR) studies unambiguously show that in as-prepared glasses paramagnetic ions are in diluted state and confirm the formation of magnetic nanoparticles already at earlier stages of heat treatment. Computer simulations of the EMR spectra corroborate the broad distribution of nanoparticle sizes found by 'direct' techniques as well as superparamagnetic nanoparticle behaviour demonstrated in the magnetization

  19. 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.

  20. 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.

  1. Aging of the Johari-Goldstein relaxation in the glass-forming liquids sorbitol and xylitol

    NASA Astrophysics Data System (ADS)

    Yardimci, Hasan; Leheny, Robert L.

    2006-06-01

    Employing frequency-dependent dielectric susceptibility we characterize the aging in two supercooled liquids, sorbitol and xylitol, below their calorimetric glass transition temperatures. In addition to the alpha relaxation that tracks the structural dynamics, the susceptibility of both liquids possesses a secondary Johari-Goldstein relaxation at higher frequencies. Following a quench through the glass transition, the susceptibility slowly approaches the equilibrium behavior. For both liquids, the magnitude of the Johari-Goldstein relaxation displays a dependence on the time since the quench, or aging time, that is quantitatively very similar to the age dependence of the alpha peak frequency. The Johari-Goldstein relaxation time remains constant during aging for sorbitol while it decreases slightly with age for xylitol. Hence, one cannot sensibly assign a fictive temperature to the Johari-Goldstein relaxation. This behavior contrasts with that of liquids lacking distinct Johari-Goldstein peaks for which the excess wing of the alpha peak tracks the main part of the peak during aging, enabling the assignment of a single fictive temperature to the entire spectrum. The aging behavior of the Johari-Goldstein relaxation time further calls into question the possibility that the relaxation time possesses stronger temperature dependence in equilibrium than is observed in the out-of-equilibrium state below the glass transition.

  2. A New Strewnfield of Splash-Form Impact Glasses in Atacama, Chile: A Mössbauer Study

    NASA Astrophysics Data System (ADS)

    Dos Santos, E.; Scorzelli, R. B.; Rochette, P.; Devouard, B.; Gattacceca, J.; Moustard, F.; Cournède, C.

    2015-07-01

    Recently, tektite-like glasses were discovered in the Atacama desert (Chile) and named atacamaites. The discovery of this new strewnfield allows us to extend the impact glass database and the understanding concerning these natural glasses.

  3. Structural ordering and glass forming of soft spherical particles with harmonic repulsions

    SciTech Connect

    Sun, Bin; Sun, Zhiwei; Ouyang, Wenze Xu, Shenghua

    2014-04-07

    We carry out dissipative particle dynamics simulations to investigate the dynamic process of phase transformation in the system with harmonic repulsion particles. Just below the melting point, the system undergoes liquid state, face-centered cubic crystallization, body-centered cubic crystallization, and reentrant melting phase transition upon compression, which is in good agreement with the phase diagram constructed previously via thermodynamic integration. However, when the temperature is decreased sufficiently, the system is trapped into an amorphous and frustrated glass state in the region of intermediate density, where the solid phase and crystal structure should be thermodynamically most stable.

  4. Chalcogenide glasses

    SciTech Connect

    Taylor, P.C.

    1987-08-15

    Although there are some significant exceptions, most important glass-forming systems contain elements from the sixth, or chalcogenide, column of the periodic table (oxygen, sulfur, selenium, or tellurium). The glasses that contain oxygen are typically insulators, while those that contain the heavier chalcogen elements are usually semiconductors. Even though oxygen is technically a chalcogen element, the term chalcogenide glass is commonly used to denote those largely covalent, semiconducting glasses contain sulfur, selenium, or tellurium as one of the constituents.

  5. Near-net-shape manufacturing: Spray-formed metal matrix composites and tooling

    NASA Technical Reports Server (NTRS)

    Mchugh, Kevin M.

    1994-01-01

    Spray forming is a materials processing technology in which a bulk liquid metal is converted to a spray of fine droplets and deposited onto a substrate or pattern to form a near-net-shape solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g. refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. The Idaho National Engineering Laboratory is developing a unique spray-forming method, the Controlled Aspiration Process (CAP), to produce near-net-shape solids and coatings of metals, polymers, and composite materials. Results from two spray-accompanying technical and economic benefits. These programs involved spray forming aluminum strip reinforced with SiC particulate, and the production of tooling, such as injection molds and dies, using low-melting-point metals.

  6. Modeling the collective relaxation time of glass-forming polymers at intermediate length scales: Application to polyisobutylene

    NASA Astrophysics Data System (ADS)

    Colmenero, Juan; Alvarez, Fernando; Khairy, Yasmin; Arbe, Arantxa

    2013-07-01

    In a recent paper [V. N. Novikov, K. S. Schweizer, and A. P. Sokolov, J. Chem. Phys. 138, 164508 (2013)], 10.1063/1.4802771 a simple analytical ansatz has been proposed to describe the momentum transfer (Q) dependence of the collective relaxation time of glass-forming systems in a wide Q-range covering the region of the first maximum of the static structure factor S(Q) and the so-called intermediate length scale regime. In this work we have generalized this model in order to deal with glass-forming systems where the atomic diffusive processes are sub-linear in nature. This is for instance the case of glass-forming polymers. The generalized expression considers a sub-linear jump-diffusion model and reduces to the expression previously proposed for normal diffusion. The generalized ansatz has been applied to the experimental results of the Q- and temperature-dependence of polyisobutylene (PIB), which were previously published. To reduce the number of free parameters of the model to only one, we have taken advantage of atomistic molecular dynamics simulations of PIB properly validated by neutron scattering results. The model perfectly describes the experimental results capturing both, Q- and temperature-dependences. Moreover, the model also reproduces the experimental Q-dependence of the effective activation energy of the collective relaxation time in the temperature range of observation. This non-trivial result gives additional support to the way the crossover between two different relaxation mechanisms of density fluctuations is formulated in the model.

  7. Effects of Zr and Si on the Glass Forming Ability and Compressive Properties of Ti-Cu-Co-Sn Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Tan; Wu, Yidong; Si, Jiajia; Hui, Xidong

    2015-06-01

    To succeed in finding novel Ti-based bulk metallic glasses, which are free from Be, Ni, and noble metallic elements, a comprehensive study was performed on the effects of Zr and Si on the microstructural evolution, glass-forming ability (GFA), and mechanical properties of Ti46Cu44- x Zr x Co7Sn3 ( x = 0, 5, 10, 12.5, and 16 at. pct) and Ti46Cu31.5Zr12.5- x Co7Sn3Si x ( x = 0.5, 1, and 1.5 at. pct) alloys. It is shown that with the increase of Zr, the sequence of phase formation is β-Ti + α-Ti + (Ti, Zr)3Cu4 ⇒ β-Ti + α-Ti + TiCu ⇒ β-Ti + Ti2Cu + glassglass ⇒ β-Ti + Ti2Cu + TiCuSn. The quinary Ti-Zr-Cu-Co-Sn alloy with 12.5 pct Zr exhibits the best GFA. The addition of 1 pct Si results in the improvement of the critical size of glassy rods up to 3 mm in diameter. The yield stress and Young's modulus of Z-series alloys increases, and the plastic strain decreases with the addition of Zr. The yield stress and ultimate compression stress of Ti46Zr11.5Cu31.5Co7Sn3Si1 glassy alloy reach 2477.9 and 2623.3 MPa, respectively. It was found that the addition of Si promotes the generation and multiplication of shear bands, resulting in certain plasticity in these kinds of glassy alloys.

  8. Thermal Evaporation Loss Measurements on Quasicrystal (Ti-Zr-Ni) and Glass Forming (Vit 106 and Vit 106a) Liquids

    NASA Astrophysics Data System (ADS)

    Blodgett, M. E.; Gangopadhyay, A. K.; Kelton, K. F.

    2015-04-01

    Thermal evaporation loss measurements made using the electrostatic levitation (ESL) technique for one binary Ti-Zr, two ternary Ti-Zr-Ni, and two glass-forming (Vit 106 and Vit 106a) alloy liquids are reported. The containerless environment enables measurements not only for the equilibrium liquids but also for the metastable supercooled liquids. The data follow the Langmuir equation when the activity coefficient of the solute atoms, a measure for the deviation from the ideal solution behavior, is taken into account. An estimate for the activity coefficient of Ni in the Ti-Zr liquid is made from these data, demonstrating the effectiveness of ESL for such measurements.

  9. Nanostructures formed in pure quartz glass under irradiation in the reactor core

    NASA Astrophysics Data System (ADS)

    Ibragimova, E. M.; Mussaeva, M. A.; Kalanov, M. U.

    2014-04-01

    Optical spectroscopy and X-ray diffraction techniques were used for studying nanoscale particles grown in pure SiO2 glass under irradiation with fast neutron fluencies within 6×1016-5·1019 cm-2 and gamma-quanta ~1.8×1020 cm-2 in the reactor core in water. The neutron irradiation results in destroying of the initial α- and β-quartz mesoscopic order of 1.7 and 1.2 nm sizes and growing of cristobalite and tridymite nanocrystals of 16 and 8 nm sizes in the thermal peaks of displacements reapectively. The point defects (oxygen deficient E‧s, E'1, E'2 and non-bridging oxygen centers) induced by the γ-irradiation are accumulated in the nanocrystals shell of 0.65-0.85 nm thickness. Interaction of close point defects at the nanocrystal-glass interface causes the splitting of optical absorption bands into the intensive (D~2-4) resonances characteristic for local interband electron transitions, having the width of 10-15 nm close to the nanocrystals' sizes and the energy depending on their structure.

  10. Dynamic heterogeneities, boson peak and activation volume in glass-forming liquids

    SciTech Connect

    Hong, L; Novikov, V. N.; Sokolov, Alexei P

    2011-01-01

    There are various arguments and models connecting the characteristic length associated with the boson peak vibrations to the length scale of dynamical heterogeneity Lhet. is usually defined as the ratio of the transverse sound velocity to the boson peak frequency. Here we present pressure, temperature, and molecular weight dependencies of , estimated using light scattering, in a few molecular and polymeric glass formers. These dependencies are compared with respective dependencies of the activation volume V # in the same materials. Good agreement is found for the pressure and molecular weight dependencies of and V # measured at the glass transition temperature Tg. These results provide more evidence for a possible relationship between the sensitivity of structural relaxation to density (activation volume) and the heterogeneity volume. However, contrary to the expectations for Lhet, does not decrease with temperature above Tg in most of the studied materials. The temperature dependence of is compared to that of Lhet in glycerol and orthoterphenyl (OTP) estimated from literature data. The analysis shows a clear difference in the behavior of (T) and V #(T) at temperatures above Tg, although V #(T)1/3 and Lhet(T) have similar temperature dependence. Possible reasons for the observed difference are discussed.

  11. Mineralogical textural and compositional data on the alteration of basaltic glass from Kilauea, Hawaii to 300 degrees C: Insights to the corrosion of a borosilicate glass waste-form. [Yucca Mountain Project

    SciTech Connect

    Smith, D.K.

    1990-01-01

    Mineralogical, textural and compositional data accompanying greenschist facies metamorphism (to 300{degrees}C) of basalts of the East Rift Zone (ERZ), Kilauea, Hawaii may be evaluated relative to published and experimental results for the surface corrosion of borosilicate glass. The ERZ alteration sequence is dominated by intermittent palagonite, interlayered smectite-chlorite, chlorite, and actinolite-epidote-anhydrite. Alteration is best developed in fractures and vesicles where surface reaction layers root on the glass matrix forming rinds in excess of 100 microns thick. Fractures control fluid circulation and the alteration sequence. Proximal to the glass surface, palagonite, Fe-Ti oxides and clays replace fresh glass as the surface reaction layer migrates inwards; away from the surface, amphibole, anhydrite, quartz and calcite crystallize from hydrothermal fluids in contact with the glass. The texture and composition of basaltic glass surfaces are similar to those of a SRL-165 glass leached statically for sixty days at 150 {degrees}C. While the ERZ reservoir is a complex open system, conservative comparisons between the alteration of ERZ and synthetic borosilicate glass are warranted. 31 refs., 2 figs.

  12. Sealed glass coating of high temperature ceramic superconductors

    DOEpatents

    Wu, W.; Chu, C.Y.; Goretta, K.C.; Routbort, J.L.

    1995-05-02

    A method and article of manufacture of a lead oxide based glass coating on a high temperature superconductor is disclosed. The method includes preparing a dispersion of glass powders in a solution, applying the dispersion to the superconductor, drying the dispersion before applying another coating and heating the glass powder dispersion at temperatures below oxygen diffusion onset and above the glass melting point to form a continuous glass coating on the superconductor to establish compressive stresses which enhance the fracture strength of the superconductor. 8 figs.

  13. Investigation of medium range order and glass forming ability of metallic glass Co69Fe x Si21‑x B10 (x  =  3, 5, and 7)

    NASA Astrophysics Data System (ADS)

    Srivastava, A. P.; Das, N.; Sharma, S. K.; Sinha, A. K.; Srivastava, D.; Pujari, P. K.; Dey, G. K.

    2016-06-01

    Metallic glass of composition Co69Fe x Si21‑x B10 (x  =  3, 5, and 7) was studied using spatially resolved x-ray diffraction and positron annihilation spectroscopy. It was observed that the solute centered clusters forming the metallic glasses were connected to a fractal network of a reduced dimension of 2.18. The medium range order in the present system is described with a correlation function and its validity is discussed. A theoretical estimation of its glass forming ability (GFA) complimented the observations made on the local structural changes due to variation in Si content. The distribution of open volume defects in the metallic glasses during processing was found to be related to the relative GFA of the alloy compositions.

  14. Application of high performance computing to automotive design and manufacturing: Composite materials modeling task technical manual for constitutive models for glass fiber-polymer matrix composites

    SciTech Connect

    Simunovic, S; Zacharia, T

    1997-11-01

    This report provides a theoretical background for three constitutive models for a continuous strand mat (CSM) glass fiber-thermoset polymer matrix composite. The models were developed during fiscal years 1994 through 1997 as a part of the Cooperative Research and Development Agreement, "Application of High-Performance Computing to Automotive Design and Manufacturing." The full derivation of constitutive relations in the framework of the continuum program DYNA3D and have been used for the simulation and impact analysis of CSM composite tubes. The analysis of simulation and experimental results show that the model based on strain tensor split yields the most accurate results of the three implemented models. The parameters used in the models and their derivation from the physical tests are documented.

  15. Understanding the dynamics of glass-forming liquids with random pinning within the random first order transition theory

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Saurish; Das, Rajsekhar; Karmakar, Smarajit; Dasgupta, Chandan

    2016-07-01

    Extensive computer simulations are performed for a few model glass-forming liquids in both two and three dimensions to study their dynamics when a randomly chosen fraction of particles are frozen in their equilibrium positions. For all the studied systems, we find that the temperature-dependence of the α relaxation time extracted from an overlap function related to the self-part of the density autocorrelation function can be explained within the framework of the Random First Order Transition (RFOT) theory of the glass transition. We propose a scaling description to rationalize the simulation results and show that our data for the α relaxation time for all temperatures and pin concentrations are consistent with this description. We find that the fragility parameter obtained from fits of the temperature dependence of the α relaxation time to the Vogel-Fulcher-Tammann form decreases by almost an order of magnitude as the pin concentration is increased from zero. Our scaling description relates the fragility parameter to the static length scale of RFOT and thus provides a physical understanding of fragility within the framework of the RFOT theory. Implications of these findings for the values of the exponents appearing in the RFOT theory are discussed.

  16. Understanding the dynamics of glass-forming liquids with random pinning within the random first order transition theory.

    PubMed

    Chakrabarty, Saurish; Das, Rajsekhar; Karmakar, Smarajit; Dasgupta, Chandan

    2016-07-21

    Extensive computer simulations are performed for a few model glass-forming liquids in both two and three dimensions to study their dynamics when a randomly chosen fraction of particles are frozen in their equilibrium positions. For all the studied systems, we find that the temperature-dependence of the α relaxation time extracted from an overlap function related to the self-part of the density autocorrelation function can be explained within the framework of the Random First Order Transition (RFOT) theory of the glass transition. We propose a scaling description to rationalize the simulation results and show that our data for the α relaxation time for all temperatures and pin concentrations are consistent with this description. We find that the fragility parameter obtained from fits of the temperature dependence of the α relaxation time to the Vogel-Fulcher-Tammann form decreases by almost an order of magnitude as the pin concentration is increased from zero. Our scaling description relates the fragility parameter to the static length scale of RFOT and thus provides a physical understanding of fragility within the framework of the RFOT theory. Implications of these findings for the values of the exponents appearing in the RFOT theory are discussed. PMID:27448896

  17. [Exposure to arsenic in the manufacture of glass rods. Results of the biological monitoring and preventive indications].

    PubMed

    Montagnani, R; Campagna, M; Gasparello, S; Hreiglich, A; Apostoli, P

    2006-01-01

    Nowadays arsenic trioxid is still used in the hand made glass production in Murano. In the last years, many industries have reduced its use but, in some specific lines of production, such as the "bacchetta di vetro" for the secondary "a lume" production, there is still a considerable use. Biological monitoring, carried out through urinary arsenic measurement, shows as workers employed in the mixture preparation and in the furnace work, are still significantly exposed to arsenic, despite the technical preventive measures adopted. We propose further measures to reduce this risk. PMID:16805446

  18. Pronounced asymmetry in the crystallization behavior during constant heating and cooling of a bulk metallic glass-forming liquid

    SciTech Connect

    Schroers, J.; Masuhr, A.; Johnson, W.L.; Busch, R.

    1999-11-01

    The crystallization behavior of the supercooled bulk metallic glass-forming Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} liquid was studied with different heating and cooling rates. A rate of about 1 K/s is sufficient to suppress crystallization of the melt upon cooling from the equilibrium liquid. Upon heating, in contrast, a rate of about 200 K/s is necessary to avoid crystallization. The difference between the critical heating and cooling rate is discussed with respect to diffusion-limited growth taking classical nucleation into account. The calculated asymmetry of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are exposed to different growth rates. thinsp {copyright} {ital 1999} {ital The American Physical Society}

  19. A combined arc-melting and tilt-casting furnace for the manufacture of high-purity bulk metallic glass materials

    NASA Astrophysics Data System (ADS)

    Soinila, E.; Pihlajamäki, T.; Bossuyt, S.; Hänninen, H.

    2011-07-01

    An arc-melting furnace which includes a tilt-casting facility was designed and built, for the purpose of producing bulk metallic glass specimens. Tilt-casting was chosen because reportedly, in combination with high-purity processing, it produces the best fatigue endurance in Zr-based bulk metallic glasses. Incorporating the alloying and casting facilities in a single piece of equipment reduces the amount of laboratory space and capital investment needed. Eliminating the sample transfer step from the production process also saves time and reduces sample contamination. This is important because the glass forming ability in many alloy systems, such as Zr-based glass-forming alloys, deteriorates rapidly with increasing oxygen content of the specimen. The challenge was to create a versatile instrument, in which high purity conditions can be maintained throughout the process, even when melting alloys with high affinity for oxygen. Therefore, the design provides a high-vacuum chamber to be filled with a low-oxygen inert atmosphere, and takes special care to keep the system hermetically sealed throughout the process. In particular, movements of the arc-melting electrode and sample manipulator arm are accommodated by deformable metal bellows, rather than sliding O-ring seals, and the whole furnace is tilted for tilt-casting. This performance of the furnace is demonstrated by alloying and casting Zr55Cu30Al10Ni5 directly into rods up to ø 10 mm which are verified to be amorphous by x-ray diffraction and differential scanning calorimetry, and to exhibit locally ductile fracture at liquid nitrogen temperature.

  20. Quasielastic neutron scattering studies on glass-forming ionic liquids with imidazolium cations

    SciTech Connect

    Kofu, Maiko; Inamura, Yasuhiro; Miyazaki, Kyoko; Yamamuro, Osamu; Tyagi, Madhusudan

    2015-12-21

    Relaxation processes for imidazolium-based ionic liquids (ILs) were investigated by means of an incoherent quasielastic neutron scattering technique. In order to clarify the cation and anion effects on the relaxation processes, ten samples were measured. For all of the samples, we found three relaxations at around 1 ps, 10 ps, and 100 ps-10 ns, each corresponding to the alkyl reorientation, the relaxation related to the imidazolium ring, and the ionic diffusion. The activation energy (E{sub a}) for the alkyl relaxation is insensitive to both anion and alkyl chain lengths. On the other hand, for the imidazolium relaxation and the ionic diffusion processes, E{sub a} increases as the anion size decreases but is almost independent of the alkyl chain length. This indicates that the ionic diffusion and imidazolium relaxation are governed by the Coulombic interaction between the core parts of the cations (imidazolium ring) and the anions. This is consistent with the fact that the imidazolium-based ILs have nanometer scale structures consisting of ionic and neutral (alkyl chain) domains. It is also found that there is a clear correlation between the ionic diffusion and viscosity, indicating that the ionic diffusion is mainly associated with the glass transition which is one of the characteristics of imidazolium-based ILs.

  1. Structural origin of enhanced slow dynamics near a wall in glass-forming systems

    NASA Astrophysics Data System (ADS)

    Watanabe, Keiji; Kawasaki, Takeshi; Tanaka, Hajime

    2011-07-01

    Spatial confinement is known to induce a drastic change in the viscosity, relaxation times, and flow profile of liquids near the glass (or jamming) transition point. The essential underlying question is how a wall affects the dynamics of densely packed systems. Here we study this fundamental problem, using experiments on a driven granular hard-sphere liquid and numerical simulations of polydisperse and bidisperse colloidal liquids. The nearly hard-core nature of the particle-wall interaction provides an ideal opportunity to study purely geometrical confinement effects. We reveal that the slower dynamics near a wall is induced by wall-induced enhancement of ‘glassy structural order’, which is a manifestation of strong interparticle correlations. By generalizing the structure-dynamics relation for bulk systems, we find a quantitative relation between the structural relaxation time at a certain distance from a wall and the correlation length of glassy structural order there. Our finding suggests that glassy structural ordering may be the origin of the slow glassy dynamics of a supercooled liquid.

  2. Quasielastic neutron scattering studies on glass-forming ionic liquids with imidazolium cations

    NASA Astrophysics Data System (ADS)

    Kofu, Maiko; Tyagi, Madhusudan; Inamura, Yasuhiro; Miyazaki, Kyoko; Yamamuro, Osamu

    2015-12-01

    Relaxation processes for imidazolium-based ionic liquids (ILs) were investigated by means of an incoherent quasielastic neutron scattering technique. In order to clarify the cation and anion effects on the relaxation processes, ten samples were measured. For all of the samples, we found three relaxations at around 1 ps, 10 ps, and 100 ps-10 ns, each corresponding to the alkyl reorientation, the relaxation related to the imidazolium ring, and the ionic diffusion. The activation energy (Ea) for the alkyl relaxation is insensitive to both anion and alkyl chain lengths. On the other hand, for the imidazolium relaxation and the ionic diffusion processes, Ea increases as the anion size decreases but is almost independent of the alkyl chain length. This indicates that the ionic diffusion and imidazolium relaxation are governed by the Coulombic interaction between the core parts of the cations (imidazolium ring) and the anions. This is consistent with the fact that the imidazolium-based ILs have nanometer scale structures consisting of ionic and neutral (alkyl chain) domains. It is also found that there is a clear correlation between the ionic diffusion and viscosity, indicating that the ionic diffusion is mainly associated with the glass transition which is one of the characteristics of imidazolium-based ILs.

  3. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

    SciTech Connect

    Zhang, Hao; Zhong, Cheng; Wang, Xiaodong; Cao, Qingping; Jiang, Jian-Zhong E-mail: jack.douglas@nist.gov; Douglas, Jack F. E-mail: jack.douglas@nist.gov; Zhang, Dongxian

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by “dynamic heterogeneity” in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔG{sub a} with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τ{sub α} can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract “cooperatively rearranging regions” of AG. We also find coexisting clusters of relatively “immobile” atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of “mobile” atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized (“immobile”) and wandering (“mobile”) particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  4. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys.

    PubMed

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-28

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations. PMID:25933773

  5. Role of string-like collective atomic motion on diffusion and structural relaxation in glass forming Cu-Zr alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Zhong, Cheng; Douglas, Jack F.; Wang, Xiaodong; Cao, Qingping; Zhang, Dongxian; Jiang, Jian-Zhong

    2015-04-01

    We investigate Cu-Zr liquid alloys using molecular dynamics simulation and well-accepted embedded atom method potentials over a wide range of chemical composition and temperature as model metallic glass-forming (GF) liquids. As with other types of GF materials, the dynamics of these complex liquids are characterized by "dynamic heterogeneity" in the form of transient polymeric clusters of highly mobile atoms that are composed in turn of atomic clusters exhibiting string-like cooperative motion. In accordance with the string model of relaxation, an extension of the Adam-Gibbs (AG) model, changes in the activation free energy ΔGa with temperature of both the Cu and Zr diffusion coefficients D, and the alpha structural relaxation time τα can be described to a good approximation by changes in the average string length, L. In particular, we confirm that the strings are a concrete realization of the abstract "cooperatively rearranging regions" of AG. We also find coexisting clusters of relatively "immobile" atoms that exhibit predominantly icosahedral local packing rather than the low symmetry packing of "mobile" atoms. These two distinct types of dynamic heterogeneity are then associated with different fluid structural states. Glass-forming liquids are thus analogous to polycrystalline materials where the icosahedrally packed regions correspond to crystal grains, and the strings reside in the relatively disordered grain boundary-like regions exterior to these locally well-ordered regions. A dynamic equilibrium between localized ("immobile") and wandering ("mobile") particles exists in the liquid so that the dynamic heterogeneity can be considered to be type of self-assembly process. We also characterize changes in the local atomic free volume in the course of string-like atomic motion to better understand the initiation and propagation of these fluid excitations.

  6. Electron Spin Relaxation Rates for Semiquinones between 25 and 295 K in Glass-Forming Solvents

    PubMed Central

    Kathirvelu, Velavan; Sato, Hideo; Eaton, Sandra S.; Eaton, Gareth R.

    2009-01-01

    Electron spin lattice relaxation rates for five semiquinones (2,5-di-t-butyl-1,4-benzosemiquinone, 2,5-di-t-amyl-1,4-benzosemiquinone, 2,5-di-phenyl-1,4-benzosemiquinone, 2,6-di-t-butyl-1,4-benzosemiquinone, tetrahydroxy-1,4-benzosemiquione) were studied by long-pulse saturation recovery EPR in 1:4 glycerol:ethanol, 1:1 glycerol:ethanol, and triethanolamine between 25 and 295 K. Although the dominant process changes with temperature, relaxation rates vary smoothly with temperature, even near the glass transition temperatures, and could be modeled as the sum of contributions that have the temperature dependence that is predicted for the direct, Raman, local mode and tumbling dependent processes. At 85 K, which is in a temperature range where the Raman process dominates, relaxation rates along the gxx (g~2.006) and gyy (g~2.005) axes are about 2.7 to 1.5 times faster than along the gzz axis (g = 2.0023). In highly viscous triethanolamine, contributions from tumbling-dependent processes are negligible. At temperatures above 100 K relaxation rates in triethanolamine are unchanged between X-band (9.5 GHz) and Q-band (34 GHz), so the process that dominates in this temperature interval was assigned as a local mode rather than a thermally-activated process. Because the largest proton hyperfine couplings are only 2.2 G, spin rotation makes a larger contribution than tumbling-dependent modulation of hyperfine anisotropy. Since g anisotropy is small, tumbling dependent modulation of g anisotropy make a smaller contribution than spin rotation at X-band. Although there was negligible impact of methyl rotation on T1, rotation of t-butyl or t-amyl methyl groups enhances spin echo dephasing between 85 and 150 K. PMID:19223213

  7. Bioactive glass combined with bisphosphonates provides protection against biofilms formed by the periodontal pathogen Aggregatibacter actinomycetemcomitans.

    PubMed

    Hiltunen, Anna K; Skogman, Malena E; Rosenqvist, Kirsi; Juvonen, Helka; Ihalainen, Petri; Peltonen, Jouko; Juppo, Anne; Fallarero, Adyary

    2016-03-30

    Biofilms play a pivotal role in the progression of periodontitis and they can be treated with antiseptics (i.e. chlorhexidine) or antibiotics, but these therapeutic alternatives are unable of ameliorating periodontal alveolar bone loss, which has been, on the other hand, successfully treated with bone-preserving agents. The improved bone formation achieved in animal models by the combination of two such agents: bioactive glass (BAG) and bisphosphonates has attracted the interest for further exploring dental applications. However, the antimicrobial effects that may result from combining them have not been yet investigated. Here, our aim was to explore the anti-biofilm effects that could result from combining BAG with bisphosphonates, particularly in a dental biofilm model. The experiments were performed with an oral cavity single-specie (Aggregatibacter actinomycetemcomitans) biofilm assay, which was optimized in this contribution. Risedronate displayed an intrinsic anti-biofilm effect, and all bisphosphonates, except clodronate, reduced biofilm formation when combined with BAG. In particular, the anti-biofilm activity of risedronate was significantly increased by the combination with BAG. Since it has been proposed that some of the antimicrobial effects of BAG are caused by local pH changes, studies of pH variations were performed to gain a mechanistic understanding. However, the observed anti-biofilm effects could not be explained with lowered pHs. Overall, these results do provide further support for the promising use of bisphosphonate-BAG combinations in dental applications. These findings are particularly relevant for patients undergoing cancer chemotherapy, or osteoporotic patients, which are known to be more vulnerable to periodontitis. In such cases, bisphosphonate treatment could play a double positive effect: local treatment of periodontitis (in combination with BAG) and systemic treatment of osteoporosis, prevention of hypercalcemia and metastases. PMID

  8. Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content

    PubMed Central

    Li, H. X.; Gao, J. E.; Wu, Y.; Jiao, Z. B.; Ma, D.; Stoica, A. D.; Wang, X. L.; Ren, Y.; Miller, M. K.; Lu, Z. P.

    2013-01-01

    The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general. PMID:23760427

  9. Microwave heating for production of a glass bonded ceramic high-level waste form.

    SciTech Connect

    O'Holleran, T. P.

    2002-07-30

    Argonne National Laboratory has developed a ceramic waste form to immobilize the salt waste from electrometallurgical treatment of spent nuclear fuel. The process is being scaled up to produce bodies of 100 Kg or greater. With conventional heating, heat transfer through the starting powder mixture necessitates long process times. Coupling of 2.45 GHz radiation to the starting powders has been demonstrated. The radiation couples most strongly to the salt occluded zeolite powder. The results of these experiments suggest that this ceramic waste form could be produced using microwave heating alone, or by using microwave heating to augment conventional heating.

  10. An alternative host matrix based on iron phosphate glasses for the vitrification of specialized nuclear waste forms. Annual progress report, September 15, 1996--September 14, 1997

    SciTech Connect

    Day, D.E.; Ray, C.S.; Marasinghe, K.

    1997-09-23

    'Objectives of this project are to: (1) investigate the glass composition and processing conditions that yield optimum properties for iron phosphate glasses for vitrifying radioactive waste, (2) determine the atomic structure of iron phosphate glasses and the structure-property relationships, (3) determine how the physical and structural properties of iron phosphate glasses are affected by the addition of simulated high level nuclear waste components, and (4) investigate the process and products of devitrification of iron phosphate waste forms. The glass forming ability of about 125 iron phosphate melts has been investigated in different oxidizing to reducing atmospheres using various iron oxide raw materials such as Fe{sub 2}O{sub 3}, FeO, Fe{sub 3}O{sub 4}, and FeC{sub 2}O{sub 4} 2H{sub 2}O. The chemical durability, redox equilibria between Fe(II) and Fe(III), crystallization behavior and structural features for these glasses and their crystalline forms have been investigated using a variety of techniques including Mossbauer spectroscopy, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Extended x-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analysis, differential thermal and thermogravimetric analysis (DTA/TGA), and X-ray and neutron diffraction.'

  11. Evidence of liquid–liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature

    PubMed Central

    Xu, Wei; Sandor, Magdalena T.; Yu, Yao; Ke, Hai-Bo; Zhang, Hua-Ping; Li, Mao-Zhi; Wang, Wei-Hua; Liu, Lin; Wu, Yue

    2015-01-01

    Liquid–liquid transition, a phase transition of one liquid phase to another with the same composition, provides a key opportunity for investigating the relationship between liquid structures and dynamics. Here we report experimental evidences of a liquid–liquid transition in glass-forming La50Al35Ni15 melt above its liquidus temperature by 27Al nuclear magnetic resonance including the temperature dependence of cage volume fluctuations and atomic diffusion. The observed dependence of the incubation time on the degree of undercooling is consistent with a first-order phase transition. Simulation results indicate that such transition is accompanied by the change of bond-orientational order without noticeable change in density. The temperature dependence of atomic diffusion revealed by simulations is also in agreement with experiments. These observations indicate the need of two-order parameters in describing phase transitions of liquids. PMID:26165855

  12. Evidence of liquid-liquid transition in glass-forming La50Al35Ni15 melt above liquidus temperature

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Sandor, Magdalena T.; Yu, Yao; Ke, Hai-Bo; Zhang, Hua-Ping; Li, Mao-Zhi; Wang, Wei-Hua; Liu, Lin; Wu, Yue

    2015-07-01

    Liquid-liquid transition, a phase transition of one liquid phase to another with the same composition, provides a key opportunity for investigating the relationship between liquid structures and dynamics. Here we report experimental evidences of a liquid-liquid transition in glass-forming La50Al35Ni15 melt above its liquidus temperature by 27Al nuclear magnetic resonance including the temperature dependence of cage volume fluctuations and atomic diffusion. The observed dependence of the incubation time on the degree of undercooling is consistent with a first-order phase transition. Simulation results indicate that such transition is accompanied by the change of bond-orientational order without noticeable change in density. The temperature dependence of atomic diffusion revealed by simulations is also in agreement with experiments. These observations indicate the need of two-order parameters in describing phase transitions of liquids.

  13. Viscosity-temperature Relation of Aggregation Energies in Glass Forming Process

    NASA Astrophysics Data System (ADS)

    Cao, Wan Q.; Shang, Xun Z.

    Based on the dynamics of vitrification process driven by the configurational entropy, a novel expression of viscosity- temperature relation with the form of Fermi-type function is deduced below melting temperature by supposed an exponential function of average aggregation energy with temperature. The 'molecular rearrangement' to form aggregated regions at temperatures below the melting temperature is major contribution to the aggregation energies for describing vitrification process. The expression of relaxation time or viscosity is confirmed with several super-cooled liquids in broad temperature region. The expression contains the Vogel-Fulcher relation in limited temperature region and can avoid Kauzmenn paradox. The derived fragility shows that a reduced temperature may be a common structural variable in comparing various glassy liquids.

  14. Manufacture of Alumina-Forming Austenitic Stainless Steel Alloys by Conventional Casting and Hot-Working Methods

    SciTech Connect

    Brady, M.P.; Yamamoto, Y.; Magee, J.H.

    2009-03-23

    Oak Ridge National Laboratory (ORNL) and Carpenter Technology Corporation (CarTech) participated in an in-kind cost share cooperative research and development agreement (CRADA) effort under the auspices of the Energy Efficiency and Renewable Energy (EERE) Technology Maturation program to explore the feasibility for scale up of developmental ORNL alumina-forming austenitic (AFA) stainless steels by conventional casting and rolling techniques. CarTech successfully vacuum melted 30lb heats of four AFA alloy compositions in the range of Fe-(20-25)Ni-(12-14)Cr-(3-4)Al-(1-2.5)Nb wt.% base. Conventional hot/cold rolling was used to produce 0.5-inch thick plate and 0.1-inch thick sheet product. ORNL subsequently successfully rolled the 0.1-inch sheet to 4 mil thick foil. Long-term oxidation studies of the plate form material were initiated at 650, 700, and 800 C in air with 10 volume percent water vapor. Preliminary results indicated that the alloys exhibit comparable (good) oxidation resistance to ORNL laboratory scale AFA alloy arc casting previously evaluated. The sheet and foil material will be used in ongoing evaluation efforts for oxidation and creep resistance under related CRADAs with two gas turbine engine manufacturers. This work will be directed to evaluation of AFA alloys for use in gas turbine recuperators to permit higher-temperature operating conditions for improved efficiencies and reduced environmental emissions.

  15. Fatigue analysis of computer-aided design/computer-aided manufacturing resin-based composite vs. lithium disilicate glass-ceramic.

    PubMed

    Ankyu, Shuhei; Nakamura, Keisuke; Harada, Akio; Hong, Guang; Kanno, Taro; Niwano, Yoshimi; Örtengren, Ulf; Egusa, Hiroshi

    2016-08-01

    Resin-based composite molar crowns made by computer-aided design/computer-aided manufacturing (CAD/CAM) systems have been proposed as an inexpensive alternative to metal-ceramic or all-ceramic crowns. However, there is a lack of scientific information regarding fatigue resistance. This study aimed to analyze the fatigue behavior of CAD/CAM resin-based composite compared with lithium disilicate glass-ceramic. One-hundred and sixty bar-shaped specimens were fabricated using resin-based composite blocks [Lava Ultimate (LU); 3M/ESPE] and lithium disilicate glass-ceramic [IPS e.max press (EMP); Ivoclar/Vivadent]. The specimens were divided into four groups: no treatment (NT); thermal cycling (TC); mechanical cycling (MC); and thermal cycling followed by mechanical cycling (TCMC). Thermal cycling was performed by alternate immersion in water baths of 5°C and 55°C for 5 × 10(4) cycles. Mechanical cycling was performed in a three-point bending test, with a maximum load of 40 N, for 1.2 × 10(6) cycles. In addition, LU and EMP molar crowns were fabricated and subjected to fatigue treatments followed by load-to-failure testing. The flexural strength of LU was not severely reduced by the fatigue treatments. The fatigue treatments did not significantly affect the fracture resistance of LU molar crowns. The results demonstrate the potential of clinical application of CAD/CAM-generated resin-based composite molar crowns in terms of fatigue resistance. PMID:27203408

  16. Thermoelectro-optical switching properties in glass-forming calamitic liquid crystal mixtures

    NASA Astrophysics Data System (ADS)

    Witko, Waclaw; Selbmann, C.; Koswig, H. D.

    1995-08-01

    The mixtures of liquid crystalline derivatives of (Beta) -naphtol esters forming glassy state above room temperature were studied. Nematic and chiral dopants were used to modify mixture properties. Several orienting layers were applied and the thickness of electro-optic cell was between 1.8 and 10 micrometers . Studies of thermo-electro-optical changes of molecular orientations are presented (viz. local cholesteric nematic phase transition and Freedericksz- effect). It is shown that the local change of orientation can be frozen into glassy state and long- time preserved without the orienting field. Relaxation processes appear after the temperature increases above T(subscript g$. The effects of changing molecular orientation stimulated by variations of electric field and temperature can be applied for reversible optical data storage and erasure. The temperature and thickness dependencies of cell parameters were also measured.

  17. A Spinodal Decomposition Model for the Prediction of the Glass-Forming Ability of Ternary Mg Alloys

    NASA Astrophysics Data System (ADS)

    Eshed, Eyal; Bamberger, Menachem; Katsman, Alexander

    2016-01-01

    The glass-forming ability (GFA) of two alloy systems, Mg-Y-La and Mg-Zn-Nd, was investigated using thermal and microstructural analysis. Rapid solidification was found to lead to microstructural refinement and partial amorphization of the most investigated alloys. The addition of Cu to the Mg-Y-La group was found to increase its tendency to undergo amorphization during rapid solidification, exemplified by the Mg86Y9.5Cu2.5La2 alloy exhibiting a pronounced crystallization peak in the differential scanning calorimetry trace. Two Mg-Zn-Nd alloys, Mg71Zn28Nd and Mg73.6Zn22.1Nd4.3, were found to exhibit significant amorphous behavior, with the former alloy being more amorphous than the latter. An innovative model predicting the GFA of alloys based on spinodal-like decomposition of supercooled alloys is formulated herein. New generalized thermo-kinetic criteria for spinodal decomposition of ternary alloys for time/space-correlated fluctuations were formulated. The time-dependent amplification factor of concentration fluctuations in ternary systems was found to provide adequate GFA evaluation for the compositions of both alloy systems: Mg-Y-La and Mg-Zn-Nd. The model was able to pinpoint the most amorphous alloy in each alloy system, and comparison between both systems pointed to Mg71Zn28Nd as having the best GFA, while also recognizing that it has a lower GFA than the widely known and highly glass-formable Mg65Cu25Y10 alloy. This model is expected to predict the GFA of any envisaged composition, thereby avoiding cumbersome trials.

  18. Novel glass-forming organic materials. 2. Structure and fluorescence of pyrene- and carbazole-containing cyclohexane, bicyclooctene, and adamantane

    SciTech Connect

    Mastrangelo, J.C.; Conger, B.M.; Chen, S.H.

    1997-01-01

    A series of novel glass-forming organic materials consisting of pyrenyl and carbazolyl groups attached to cyclohexane with a 1-axial-2-equatorial configuration, bicyclo[2.2.2]oct-7-ene with an all-exo configuration, and adamantane were synthesized and characterized. On the basis of proton NMR spectra, it was found that the rotation of pendant pyrenyl and carbazolyl groups is restricted in the bicyclic system presumably because of steric hindrance in the all-exo configuration. In contrast, free rotation was found to prevail in cyclohexane- and adamantane-based systems. Fluorescence spectra gathered in solution at room temperature show evidence exclusively for intramolecular excimer formation in pyrene-containing compounds up to a concentration of 10{sup -4} M. On the contrary, carbazole-containing compounds are not prone to excimer formation in the concentration range 10{sup -6}-10{sup -3} M, presumably because of the more stringent requirements of interchromophoric distance and orientation. Although both pyrene and carbazole are highly crystalline on their own, attachment to cyclic, bicyclic, and tricyclic central cores was found to contribute to an ease of vitrification of the hybrid systems with a T{sub g} ranging from 43 to 132 {degrees}C. Moreover, the quenched glasses of all seven model systems were found to possess morphological stability in view of the absence of recrystallization upon heating from 0 to 200 {degrees}C at a heating rate ranging from 0.2 to 20{degrees}C/min. Morphological stability was further supported by the absence of recrystallization upon prolonged thermal annealing at temperatures above T{sub g}. 24 refs., 6 figs.

  19. Glass microsphere lubrication

    NASA Technical Reports Server (NTRS)

    Geiger, Michelle; Goode, Henry; Ohanlon, Sean; Pieloch, Stuart; Sorrells, Cindy; Willette, Chris

    1991-01-01

    The harsh lunar environment eliminated the consideration of most lubricants used on earth. Considering that the majority of the surface of the moon consists of sand, the elements that make up this mixture were analyzed. According to previous space missions, a large portion of the moon's surface is made up of fine grained crystalline rock, about 0.02 to 0.05 mm in size. These fine grained particles can be divided into four groups: lunar rock fragments, glasses, agglutinates (rock particles, crystals, or glasses), and fragments of meteorite material (rare). Analysis of the soil obtained from the missions has given chemical compositions of its materials. It is about 53 to 63 percent oxygen, 16 to 22 percent silicon, 10 to 16 percent sulfur, 5 to 9 percent aluminum, and has lesser amounts of magnesium, carbon, and sodium. To be self-supporting, the lubricant must utilize one or more of the above elements. Considering that the element must be easy to extract and readily manipulated, silicon or glass was the most logical choice. Being a ceramic, glass has a high strength and excellent resistance to temperature. The glass would also not contaminate the environment as it comes directly from it. If sand entered a bearing lubricated with grease, the lubricant would eventually fail and the shaft would bind, causing damage to the system. In a bearing lubricated with a solid glass lubricant, sand would be ground up and have little effect on the system. The next issue was what shape to form the glass in. Solid glass spheres was the only logical choice. The strength of the glass and its endurance would be optimal in this form. To behave as an effective lubricant, the diameter of the spheres would have to be very small, on the order of hundreds of microns or less. This would allow smaller clearances between the bearing and the shaft, and less material would be needed. The production of glass microspheres was divided into two parts, production and sorting. Production includes the

  20. Size-dependent structure and magnetocaloric properties of Fe-based glass-forming alloy powders

    NASA Astrophysics Data System (ADS)

    Luo, Qiang; Ye, Fengxia; Huang, Changjun; Jiao, Jin; Rahman, Anisur; Yu, Peng; Li, Jie; Shen, Jun

    2016-04-01

    We investigated the influence of particle size on the microstructure and magnetocaloric effect of Fe-based alloy powders (11 μm to 100 μm in diameter). The degree of structure order varies with the powder size. The 11 μm to 18 μm powders show the largest peak magnetic entropy change (MEC). Increasing the degree of structure order tends to decrease the maximum MEC. Nevertheless, enhancement of refrigerant capacity and MEC (above 70 K) is achieved when the crystalline phase content is ˜50% (above 75 μm) in the 75 μm to 100 μm powders. Exponent n of the field dependence of MEC increases with the decrease in powder size above 22.5 K. The size dependence of the structure and properties is associated with the fact that a larger particle has a slower cooling rate and takes a longer time to form medium-to-long range ordered structures.

  1. Pulsed sub-microsecond dielectric barrier discharge treatment of simulated glass manufacturing industry flue gas: removal of SO2 and NOx

    NASA Astrophysics Data System (ADS)

    Khacef, A.; Cormier, J. M.

    2006-03-01

    Experiments were carried out to investigate the removal of SO2 and NOx from simulated glass manufacturing industry flue gas containing O2, N2, NO, NO2, CO2, SO2 and H2O using a sub-microsecond pulsed dielectric barrier discharge (DBD) at atmospheric pressure. Removal efficiencies of SO2 and NOx (NO+NO2) were achieved as a function of gas temperature for two specific energies and two initial NO, NO2 and SO2 concentrations. The higher SO2 and NOx removal efficiencies were achieved in a gas stream containing 163 ppm of SO2, 523 ppm of NO, 49 ppm of NO2, 14% of CO2, 8% of O2, 16% of H2O and N2 as balance. The experimental results were evaluated using the energy cost or W-value (eV/molecule removed). About 100% of SO2 and 36% of NOx were removed at a gas temperature of 100 °C with an energy cost of about 45 eV/molecule removed and 36 eV/molecule removed, respectively. These results indicate that DBD plasmas have the potential to remove SO2 and NOx from gas streams without additives.

  2. Reserve, thin form-factor, hypochlorite-based cells for powering portable systems: Manufacture (including MEMS processes), performance and characterization

    NASA Astrophysics Data System (ADS)

    Cardenas-Valencia, Andres M.; Biver, Carl J.; Langebrake, Larry

    This work focuses on fabrication routes and performance evaluation of thin form-factors, reserve cells, as a powering alternative for expendable and/or remotely operated systems. The catalytic decomposition of sodium hypochlorite solutions is revisited herein with two cost-effective anodes: zinc and aluminum. Aluminum, even though the most expensive of the utilized anodes, constituted cells with double the energy content (up to 55 Wh kg -1) than those fabricated with zinc. Even though the hypochlorite concentration in the solution limits the cells' operational life, attractive performances (1.0 V with a current of 10 mA) for the manufactured cells are obtained. It is shown that micro fabrication processes, allowing for close electrodes interspacing, provided high faradic and columbic efficiencies of up to 70 and 100%, respectively. Obtained specific energies (50-120 Wh kg -1) are in the same order of magnitude than batteries currently used for powering deployable systems. Experimental results show that a simple model that linearly relates over potentials and the electrical load, adequately describe all the cell designs. A mathematical model based on a kinetic-mechanistic scheme that relates the current output as a function of time agrees fairly well with results obtained activating cells with various concentrations of NaOCl solutions.

  3. Manufacturing of GLARE Parts and Structures

    NASA Astrophysics Data System (ADS)

    Sinke, J.

    2003-07-01

    GLARE is a hybrid material consisting of alternating layers of metal sheets and composite layers, requiring special attention when manufacturing of parts and structures is concerned. On one hand the applicable manufacturing processes for GLARE are limited, on the other hand, due to the constituents and composition of the laminate, it offers new opportunities for production. One of the opportunities is the manufacture of very large skin panels by lay-up techniques. Lay-up techniques are common for full composites, but uncommon for metallic structures. Nevertheless, large GLARE skin panels are made by lay-up processes. In addition, the sequences of forming and laminating processes, that can be selected, offer manufacturing options that are not applicable to metals or full composites. With respect to conventional manufacturing processes, the possibilities for Fibre Metal Laminates in general, are limited. The limits are partly due to the different failure modes, partly due to the properties of the constituents in the laminate. For machining processes: the wear of the cutting tools during machining operations of GLARE stems from the abrasive nature of the glass fibres. For the forming processes: the limited formability, expressed by a small failure strain, is related to the glass fibres. However, although these manufacturing issues may restrict the use of manufacturing processes for FMLs, application of these laminates in aircraft is not hindered.

  4. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    SciTech Connect

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  5. Maria Goeppert-Mayer Award Prize Talk--Computer simulation studies of emerging dynamical structure in glass-forming liquids and polymers

    NASA Astrophysics Data System (ADS)

    Glotzer, Sharon C.

    2000-03-01

    Computer simulations of soft materials and complex fluids have provided a wealth of information on these systems that elucidates and guides experimental investigation. Molecular dynamics (MD) computer simulation in particular provides a unique window into the complex microscopic processes that control, e.g., the transformation of a liquid to a glass. As the glass transition is approached, particles (atoms or molecules in the case of simple liquids, monomers in the case of polymer melts, or colloids in the case of colloidal suspensions) become temporarily localized and relaxation times increase by many orders of magnitude. At the same time, MD simulations have shown that the dynamics becomes increasingly correlated and spatially heterogeneous, developing a characteristic dynamical length scale which grows rapidly as the glass transition is approached, despite the fact that static density and composition correlations remain short-ranged. In this talk, we review our investigations of dynamical heterogeneity and correlated particle motion in several model glass-forming liquids and polymer melts using MD simulation. We compare our results with new experimental data on glass-forming colloidal suspensions, and address the possible implications of our findings for nano-confined fluids, filled polymers and nanocomposites.

  6. Effect of Nb Concentration on Thermal Stability and Glass-Forming Ability of Soft Magnetic (Fe,Co)-Gd-Nb-B Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Jia, Fei; Zhang, Xingguo; Xie, Guoqiang; Inoue, Akihisa

    2010-07-01

    Addition of a small amount of Nb to the (Fe,Co)-Gd-B glassy alloy in (Fe0.9Co0.1)71.5- x Nb x Gd3.5B25 increased the stabilization of supercooled liquid. The largest supercooled liquid region of 104 K was obtained for the x = 2 alloy. A distinct two-stage-like glass transition was observed with further incresing Nb content. The nanoscale (Fe,Co)23B6 phase precipitated in the glassy matrix after annealing, while the two-stage-like glass transition disappeared, indicating that the anomalous glass transition behavior originates from the exothermic reaction for the formation of the (Fe,Co)23B6 phase in the supercooled liquid region. The glass-forming ability (GFA) also increased by addition of Nb, leading to formation of the bulk glass form for the Nb-doped alloys. The best GFA with a diameter of over 3 mm was achieved for the x = 4 alloy. The (Fe,Co)-Gd-Nb-B glassy alloys exhibited good magnetic properties, i.e., rather high saturation magnetization of 0.81 to 1.22 T, low coercive force of 2.5 to 5.8 A/m, and low saturated magnetostriction of 9 to 19 × 10-6. In addition, the glassy alloys also possessed very high compressive fracture strength of 3842 to 3916 MPa and high Vickers hardness of 1025 to 1076.

  7. AN ALTERNATIVE HOST MATRIX BASED ON IRON PHOSPHATE GLASSES FOR THE VITRIFICATION OF SPECIALIZED NUCLEAR WASTE FORMS

    EPA Science Inventory

    Borosilicate glass is the only material currently approved and being used to vitrify high level nuclear waste. Unfortunately, many high level nuclear waste feeds in the U.S. contain components which are chemically incompatible with borosilicate glasses. Current plans call for vit...

  8. Retraction: Atomic-scale simulation to study the dynamical properties and local structure of Cu-Zr and Ni-Zr metallic glass-forming alloys.

    PubMed

    Yang, M H; Li, Y; Li, J H; Liu, B X

    2016-07-20

    Retraction of 'Atomic-scale simulation to study the dynamical properties and local structure of Cu-Zr and Ni-Zr metallic glass-forming alloys' by M. H. Yang et al., Phys. Chem. Chem. Phys., 2016, 18, 7169-7183. PMID:27402030

  9. A final report on hydrothermal testing of sup 99 Tc-doped glass waste form and waste package components

    SciTech Connect

    Schramke, J.A.; Thomas, L.E.; McKinley, S.G.; Simonson, S.A.; Coles, D.G.; Westinghouse Hanford Co., Richland, WA; Pacific Northwest Lab., Richland, WA )

    1984-07-01

    This document reports the results of four experiments using borosilicate glass doped with the key radionuclide {sup 99}Technicium. The experiments were performed in Dickson rocking autoclaves at 200{degree}C, 30MPa pressure for 3 months. Starting materials consisted of the doped glass (+ undoped borosilicate glass){center dot} in GR-3 groundwater. To simulate various possible interactions among waste package components, the glass-groundwater starting materials were run either alone, or combined with RUE-basalt, or cast steel or both. The Dickson autocalve allowed periodic sampling of the fluid, through which concentrations of dissolved species were monitored. In the glass-only experiment, Tc concentration increased until reaching an apparent steady-state concentration of 55 mg/1 after 1000 hours. In runs with basalt, steel or both, this concentration reached steady-state at three or more orders of magnitude below that. 29 refs., 23 figs., 8 tabs.

  10. Microscopic origin of slow dynamics at the good glass forming composition range in Zr1-xCux metallic liquids

    NASA Astrophysics Data System (ADS)

    Hao, S. G.; Wang, C. Z.; Kramer, M. J.; Ho, K. M.

    2010-03-01

    We have studied the structure and dynamics of a series of Zr1-xCux metallic liquids at temperatures of 1500 and 1300 K. We found that as the Cu composition increases, the Zr-Zr order undergoes considerable transition, which can be attributed to the different size of Zr and Cu atoms. The diffusivities of both Cu and Zr atoms become lower at the composition range corresponding to good glass forming region, i.e., 0.50≤x≤0.70. We found that the lower diffusivities for the intermediate composition range are correlated with the concentration of some specific clusters, including icosahedra, which can be screened out automatically and unbiasedly by using direct atomic dynamics analysis. Our analysis for the dynamic properties of high temperature liquids of ZrCu metallic alloys shows that the icosahedral clusters together with some other pentagon-rich Voronoi clusters are responsible for slowing dynamics. Cluster lifetime analysis indicates that the slow clusters mobility could be originated in their energy.

  11. Slow relaxations and stringlike jump motions in fragile glass-forming liquids: breakdown of the Stokes-Einstein relation.

    PubMed

    Kawasaki, Takeshi; Onuki, Akira

    2013-01-01

    We perform molecular dynamics simulation on a glass-forming liquid binary mixture with the soft-core potential in three dimensions. We investigate crossover of the configuration changes caused by stringlike jump motions. With lowering the temperature T, the motions of the particles composing strings become larger in sizes and displacements, while those of the particles surrounding strings become smaller. Then the contribution of the latter to time-correlation functions tends to be long-lived as T is lowered. As a result, the relaxation time τ(α) and the viscosity η grow more steeply than the inverse diffusion constant D(-1) at low T, leading to breakdown of the Stokes-Einstein relation. At low T, the diffusion occurs as activation processes and may well be described by short-time analysis of rare jump motions with broken bonds and large displacements. Some characteristic features of the Van Hove self-correlation function arise from escape jumps over high potential barriers. We also visualize the particle motions at string formation taking place in a very short time. PMID:23410336

  12. Slow relaxations and stringlike jump motions in fragile glass-forming liquids: Breakdown of the Stokes-Einstein relation

    NASA Astrophysics Data System (ADS)

    Kawasaki, Takeshi; Onuki, Akira

    2013-01-01

    We perform molecular dynamics simulation on a glass-forming liquid binary mixture with the soft-core potential in three dimensions. We investigate crossover of the configuration changes caused by stringlike jump motions. With lowering the temperature T, the motions of the particles composing strings become larger in sizes and displacements, while those of the particles surrounding strings become smaller. Then the contribution of the latter to time-correlation functions tends to be long-lived as T is lowered. As a result, the relaxation time τα and the viscosity η grow more steeply than the inverse diffusion constant D-1 at low T, leading to breakdown of the Stokes-Einstein relation. At low T, the diffusion occurs as activation processes and may well be described by short-time analysis of rare jump motions with broken bonds and large displacements. Some characteristic features of the Van Hove self-correlation function arise from escape jumps over high potential barriers. We also visualize the particle motions at string formation taking place in a very short time.

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

    SciTech Connect

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

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate R{sub c}, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. R{sub c} (or the corresponding critical casting thickness d{sub c}) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small R{sub c} < 10{sup −2} K/s, pure metals and most alloys are typically poor glass-formers with large R{sub c} > 10{sup 10} K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with R{sub c} approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10-2 K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 1010 K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness.

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

    PubMed

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

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc < 10(-2) K/s, pure metals and most alloys are typically poor glass-formers with large Rc > 10(10) K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting

  16. Correlation between Dynamic Heterogeneity and Medium-Range Order in Two-Dimensional Glass-Forming Liquids

    SciTech Connect

    Kawasaki, Takeshi; Araki, Takeaki; Tanaka, Hajime

    2007-11-23

    A glassy state of matter results if crystallization is avoided upon cooling or increasing density. However, the physical factors controlling the ease of vitrification and nature of the glass transition remain elusive. Using numerical simulations of polydisperse hard disks, we find a direct relation between medium-range crystalline ordering and the slow dynamics which characterizes the glass transition. This suggests an intriguing scenario that the strength of frustration controls both the ease of vitrification and nature of the glass transition. Vitrification may be a process of hidden crystalline ordering under frustration, at least in our system.

  17. Basaltic glass formed from hydrovolcanism and impact processes: Characterization and clues for detection of mode of origin from VNIR through MWIR reflectance and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Farrand, W. H.; Wright, S. P.; Rogers, A. D.; Glotch, T. D.

    2016-09-01

    incipiently devitrified glass spectra were selected for all of the surface types and formed close to 40% of the N. Acidalia Planitia spectral type.

  18. Size control of nanopores formed on SiO{sub 2} glass by swift-heavy-ion irradiation and its application to highly sensitive biomolecular detection

    SciTech Connect

    Nomura, Ken-ichi; Fujimaki, Makoto; Awazu, Koichi; Komatsubara, Tetsuro

    2011-09-15

    Swift-heavy-ion irradiation creates latent tracks in SiO{sub 2} glass and nanopores with a high aspect ratio can be formed along these ion paths by selective etching of the latent tracks using hydrogen fluoride (HF) vapor. Here we report that the size of nanopores can easily be controlled by simply changing the temperature of the HF solution generating the vapor and/or that of the SiO{sub 2} glass exposed to the vapor. Furthermore, this method of size control was used to produce SiO{sub 2} glass sheets with nanopores of different sizes and number densities for use as the waveguide layer in the sensing plates for a waveguide-mode sensor. In comparison with nonperforated plates, the increased surface area due to the formation of nanopores was found to create up to a tenfold increase in sensitivity.

  19. Picture Wall (Glass Structures)

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Photo shows a subway station in Toronto, Ontario, which is entirely glass-enclosed. The all-glass structure was made possible by a unique glazing concept developed by PPG Industries, Pittsburgh, Pennsylvania, one of the largest U.S. manufacturers of flat glass. In the TVS glazing system, transparent glass "fins" replace conventional vertical support members used to provide support for wind load resistance. For stiffening, silicone sealant bonds the fins to adjacent glass panels. At its glass research center near Pittsburgh, PPG Industries uses the NASTRAN computer program to analyze the stability of enclosures made entirely of glass. The company also uses NASTRAN to simulate stresses on large containers of molten glass and to analyze stress effects of solar heating on flat glass.

  20. Effect of Industrial Raw Materials on the Glass-Forming Ability, Magnetic and Mechanical Properties of Fe-Based Bulk Metallic Glasses

    NASA Astrophysics Data System (ADS)

    Cai, Yongqian; Ling, Haibo; Jiang, Tao

    2015-12-01

    Pseudo-ternary Fe78P13C9 (the real composition is Fe77.6Si1.4P12.7C8.3) bulk metallic glasses (BMGs) with the maximum diameter of 1.5 mm based on industrial raw materials has been prepared by J-quenching technique using the master alloys with fluxing treatment, whereas fully amorphous alloy rod with the diameter of 1.0 mm cannot be obtained by the same preparation method using the master alloy without fluxing treatment. It is indicated that the glass formation ability (GFA) of the present Fe-based alloys based on industrial raw materials can be greatly enhanced through fluxing treatment. For comparison, the amorphous alloy rod with the same composition based on the pure raw materials has also been prepared by the same preparation technique and the critical diameter for fully glass formation gets to 2.0 mm. The DSC result indicates that the present Fe-based BMG based on industrial raw materials reveals higher thermal stability compared with the BMG based on pure raw materials. The magnetic tests show that the saturation magnetizations of the present Fe-based BMGs prepared by pure raw materials and industrial raw material are around 1.40 T, and have no significant difference. Compressive tests show that the present Fe-based BMG based on industrial raw materials exhibits higher compressive fracture strength (3.11 GPa) and slightly less plastic strain (0.8 pct) compared with the BMG based on pure raw materials with the same composition.

  1. Enhancement of the fracture strength and glass-forming ability of CoFeTaB bulk glassy alloy

    NASA Astrophysics Data System (ADS)

    Shen, Baolong; Inoue, Akihisa

    2005-09-01

    Co43Fe20Ta5.5B31.5 bulk glassy alloy has the best glass-forming ability (GFA) among the Co-based glassy alloys, and the highest strength (the compressive true strength σf = 5185 MPa) among all known bulk crystalline and glassy alloys. With the aim of synthesizing new Co-based bulk glassy alloys with much higher strength and much larger GFA, we investigated the effect of Mo and Si additions on the enhancement of σf and GFA in the Co-(Fe, Mo, Ta)-(B, Si) system. The small amount of 2 at.% Mo added to the Co-Fe-Ta-B glassy alloy resulted in obtaining an ultrahigh true fracture strength of 5545 MPa and high Young's modulus (E) of 282 GPa. By further adding 1 and 2 at.% Si, Co-(Fe, Mo, Ta)-(B, Si) bulk glassy alloys were synthesized in the diameter range up to 3 mm, and they exhibited σf of over 4450 MPa and E of over 227 GPa. In addition, the ultrahigh-strength glassy alloys simultaneously exhibited excellent soft magnetic properties, i.e., saturation magnetization of 0.32-0.35 T, low coercive force of 0.7-1.1 A m-1, and high effective permeability of 3.9-4.77 × 104 at 1 kHz. The improvement of GFA and σf is interpreted to result from the enhanced atomic bonding nature by adding Mo and Si.

  2. Glass shell manufacturing in space

    NASA Technical Reports Server (NTRS)

    Nolen, R. L., Jr.; Ebner, M. A.; Downs, R. L.

    1980-01-01

    A heat transfer model was developed that mathematically describes the heating and calculates the thermal history of a gel particle in free-fall through the furnace. The model parameters that greatly affect the calculations were found to be gel particle mass, geometry, specific heat, and furnace gas. Empirical testing of the model has commenced. The code calculations and the initial empirical testing results both indicate that the gel-to-shell transformation occurs early and rapidly in the thermal history of the gel particle, and that for current work the heat transfer rate is not a limitation in shell production.

  3. Containerless processing of glass forming melts: D-1, MEA/A-2 experiment 81F01 conducted on STS-61A flight, October 1985

    NASA Technical Reports Server (NTRS)

    Day, D. E.; Ray, C. S.

    1986-01-01

    Results of experiment 81F01, which was conducted in the Material Experiment Assembly MEA/A-2 on the D-1 Spacelab Mission (STS-61A), are presented. The general plan of the experiment was to heat, melt, and quench six spherical samples of different glass forming compositions while they were levitated in a single axis acoustic levitator furnace (SAAL). In addition, two non-melting sintered alumina samples were used to check the operational characteristics of the SAAL under reduced gravity conditions. Three of the eight samples were levitated between 1250 and 1500 C before the lack of coolant created an over-temperature condition that caused the SAAL to shut down prematurely. Two of the three samples processed were calcia-gallia-silica and soda-lime-silica glass forming compositions. Evidence of a two to three times increase in the tendency for glass formation was obtained for the calcia-gallia-silica. The final glass appeared reasonably homogeneous even though it was made from hot pressed powders containing deliberate heterogeneities. A photographic record was obtained of the microgravity sample processing sequences.

  4. Absorption and luminescence of silver nanocomposite soda-lime glass formed by Ag{sup +}-Na{sup +} ion-exchange

    SciTech Connect

    Manikandan, D.; Mohan, S.; Nair, K.G.M

    2003-09-02

    Metal nanocomposite glasses are formed by a multi step methodology which involves incorporation of the metal ions into the glass by ion-exchange process followed by suitable treatments like low mass ion irradiation or thermal annealing resulting in the aggregation of the metal ions to form nano dimension metal clusters. These embedded metal nanoclusters are well investigated by the optical absorption spectroscopy which gives information regarding the size and shape of the metal clusters embedded in the dielectric matrix. The Ag{sup +} ion-exchanged and annealed soda-lime glasses exhibit photoluminescence around 445 nm at two excitation wavelengths. He{sup +} ion irradiation of the ion-exchanged soda-lime glass resulted in the formation of Ag metal nano crystallites with a thin metal film on the irradiated surface. The Glancing incidence X-ray diffraction study confirmed the formation of Ag nano crystals inside the dielectric matrix. Photoluminescence vanished in the irradiated samples with the neutralization of Ag{sup +} ions into Ag metal nano crystallites.

  5. Manufacturing High-Fidelity Lunar Agglutinate Simulants

    NASA Technical Reports Server (NTRS)

    Gutafson, R. J.; Edmunson, J. E.; Rickman, D. L.

    2010-01-01

    The lunar regolith is very different from many naturally occurring material on Earth because it forms in the unique, impact-dominated environment of the lunar surface. Lunar regolith is composed of five basic particle types: mineral fragments, pristine crystalline rock fragments, breccia fragments, glasses of various kinds, and agglutinates (glass-bonded aggregates). Agglutinates are abundant in the lunar regolith, especially in mature regoliths where they can be the dominant component.This presentation will discuss the technical feasibility of manufacturing-simulated agglutinate particles that match many of the unique properties of lunar agglutinates.

  6. Conceptual waste package interim product specifications and data requirements for disposal of borosilicate glass defense high-level waste forms in salt geologic repositories

    SciTech Connect

    Not Available

    1983-06-01

    The conceptual waste package interim product specifications and data requirements presented are applicable specifically to the normal borosilicate glass product of the Defense Waste Processing Facility (DWPF). They provide preliminary numerical values for the defense high-level waste form parameters and properties identified in the waste form performance specification for geologic isolation in salt repositories. Subject areas treated include containment and isolation, operational period safety, criticality control, waste form/production canister identification, and waste package performance testing requirements. This document was generated for use in the development of conceptual waste package designs in salt. It will be revised as additional data, analyses, and regulatory requirements become available.

  7. Laser glass process development for the next generation of ICF lasers

    NASA Astrophysics Data System (ADS)

    Thorne, Alfred J.; Hayden, Joseph S.

    1997-12-01

    The next generation of high energy laser systems for ICF research demands an unprecedented volume of laser glass to be produced over a limited manufacturing period while still meeting ambitious targets of internal quality and overall cost. To meet this challenge, Schott has conceived a continuous manufacturing unit capable of producing 5,000 meter class PH 4 slabs of platinum particle-free phosphate laser glass within a three-year time period. This manufacturing unit concept draws on years of prior production experience with phosphate laser glass and other high quality optical materials but still represents a significant departure from the proven discontinuous manufacturing technology successfully employed over the last ten years for platinum-free phosphate laser glass. In addition, Schott has developed a new phosphate laser glass that simultaneously offers improvements in properties that relate to both laser performance and to characteristics related to forming the glass into large, high quality slabs. In this paper we will describe the key technology issues addressed in the manufacturing development and present a brief description of the planned manufacturing method to be employed. Lastly, the status of the development will be reviewed including characterization of pilot production melts of the new laser glass and the schedule for completion of the development program.

  8. Processing FeB03 glass-ceramics in space

    NASA Technical Reports Server (NTRS)

    Li, C. T.

    1976-01-01

    The possibility of preparing FeBO3 glass-ceramic in space is explored. A transparent glass-ceramic of FeBO3, due to its unique properties could be an excellent material for magneto-optic applications which currently utilize high price materials such as single crystals of Ga-YIG. The unique magneto-optic properties of FeBO3 were found to come from glass-ceramic but not from the glass form. It was anticipated and later confirmed that the FeBO3 glass-ceramics could not be prepared on earth. Phase separation and iron valence reduction, were identified as the two terrestrial manufacturing obstacles. Since the phase separation problem could be overcome by space processing, the preparation of FeBO3 glass-ceramic in space appears attractive.

  9. Manufacture of ceramic tiles from fly ash

    DOEpatents

    Hnat, J.G.; Mathur, A.; Simpson, J.C.

    1999-08-10

    The present invention relates to a process for forming glass-ceramic tiles. Fly ash containing organic material, metal contaminants, and glass forming materials is oxidized under conditions effective to combust the organic material and partially oxidize the metallic contaminants and the glass forming materials. The oxidized glass forming materials are vitrified to form a glass melt. This glass melt is then formed into tiles containing metallic contaminants. 6 figs.

  10. Manufacture of ceramic tiles from fly ash

    DOEpatents

    Hnat, James G.; Mathur, Akshay; Simpson, James C.

    1999-01-01

    The present invention relates to a process for forming glass-ceramic tiles. Fly ash containing organic material, metal contaminants, and glass forming materials is oxidized under conditions effective to combust the organic material and partially oxidize the metallic contaminants and the glass forming materials. The oxidized glass forming materials are vitrified to form a glass melt. This glass melt is then formed into tiles containing metallic contaminants.

  11. Time-temperature-transformation diagram and microstructures of bulk glass forming Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20}

    SciTech Connect

    Loeffler, Joerg F.; Schroers, Jan; Johnson, William L.

    2000-07-31

    Isothermal crystallization studies were performed on the bulk glass forming alloy Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} in the undercooled liquid region between the glass transition and liquidus temperature, resulting in a complete time-temperature-transformation (TTT) diagram for crystallization. The TTT diagram shows a typical ''C'' shape with the nose at 50 s and 680 K. Assuming steady state nucleation and a diffusion-controlled growth rate, the TTT diagram was successfully fit over the entire range of the measurement. The microstructure after isothermal crystallization shows a modulation in Cu and P for all degrees of undercooling. The primary solidified phase is Cu{sub 3}Pd, which forms distinct dendrites at low undercooling. From additional constant cooling experiments, the critical cooling rate to bypass crystallization was determined to be 0.33 K/s. (c) 2000 American Institute of Physics.

  12. Medium-range icosahedral order in quasicrystal-forming Zr{sub 2}Pd binary metallic glass

    SciTech Connect

    Huang Li; Fang, X. W.; Wang, C. Z.; Ho, K. M.; Kramer, M. J.; Ding, Z. J.

    2011-06-06

    Medium-range order in Zr{sub 2}Pd metallic glass was studied using a combination of x-ray diffraction experiment and atomistic simulations. We show that, in contrast to earlier experimental interpretations, the icosahedral-like polyhedron is centered around Pd, rather than Zr. Furthermore, we find that the ordered icosahedral packing around Pd extends to the third shell in the way similar to that in the Bergman-type clusters. The existence of Bergman-type clusters sheds interesting light into the formation of nanoquasicrystal phase during crystallization process of Zr{sub 2}Pd metallic glass.

  13. MEA/A-1 experiment 81F01 conducted on STS-7 flight, June 1983. Containerless processing of glass forming melts

    NASA Technical Reports Server (NTRS)

    Day, D. E.; Ray, C. S.

    1983-01-01

    The space processing of containerless, glassforming melts on board the space shuttle flight STS-7 is investigated. Objectives include; (1) obtain quantitative evidence for the supression of heterogeneous nucleation/crystallization, (2) study melt homogenization without gravity driven convection, (3) procedural development for bubble free, high purity homogeneous melts inmicro-g, (4) comparative analysis of melts on Earth and in micro g, and (5) assess the apparatus for processing multicomponent, glass forming melts in a low gravity environment.

  14. Characterization of structural relaxation in inorganic glasses using length dilatometry

    NASA Astrophysics Data System (ADS)

    Koontz, Erick

    The processes that govern how a glass relaxes towards its thermodynamic quasi-equilibrium state are major factors in understanding glass behavior near the glass transition region, as characterized by the glass transition temperature (Tg). Intrinsic glass properties such as specific volume, enthalpy, entropy, density, etc. are used to map the behavior of the glass network below in and near the transition region. The question of whether a true thermodynamic second order phase transition takes place in the glass transition region is another pending question. Linking viscosity behavior to entropy, or viewing the glass configuration as an energy landscape are just a couple of the most prevalent methods used for attempting to understand the glass transition. The structural relaxation behavior of inorganic glasses is important for more than scientific reasons, many commercial glass processing operations including glass melting and certain forms of optical fabrication include significant time spent in the glass transition region. For this reason knowledge of structural relaxation processes can, at a minimum, provide information for annealing duration of melt-quenched glasses. The development of a predictive model for annealing time prescription has the potential to save glass manufacturers significant time and money as well as increasing volume throughput. In optical hot forming processes such as precision glass molding, molded optical components can significantly change in shape upon cooling through the glass transition. This change in shape is not scientifically predictable as of yet though manufacturers typically use empirical rules developed in house. The classification of glass behavior in the glass transition region would allow molds to be accurately designed and save money for the producers. The work discussed in this dissertation is comprised of the development of a dilatometric measurement and characterization method of structural relaxation. The measurement and

  15. JET divertor coils, manufacture, assembly and testing

    NASA Astrophysics Data System (ADS)

    Dolgetta, N.; Bertolini, E.; D'Urzo, C.; Last, J. R.; Laurenti, A.; Presle, P.; Sannazzaro, G.; Tait, J.; Tesini, A.

    1994-07-01

    Four coils have been built and installed in the JET vacuum vessel to produce divertor plasmas. The coils are copper with glass epoxy insulation and are enclosed in vacuum tight Inconel cases. At the coil contractor's factory, the coil parts were manufactured and process techniques qualified. In the JET vacuum vessel the conductor bars were brazed to form the coils, which were inserted in the casings and impregnated and cured with epoxy resin.

  16. Highly processable bulk metallic glass-forming alloys in the Pt-Co-Ni-Cu-P system

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Johnson, William L.

    2004-05-01

    Highly processable bulk metallic glass alloys in the Pt-Co-Ni-Cu-P system were discovered. The alloys show low liquidus temperature below 900 K, excellent processability with low critical cooling rate reflecting in maximum casting thicknesses in quartz tubes of up to 20 mm, and a large supercooled liquid region. The Pt57.5Cu14.7Ni5.3P22.5 composition has a liquidus temperature of 795 K, a glass transition temperature of 508 K with a supercooled liquid region of 98 K. For medical and jewelry applications a Ni-free alloy, Pt60Cu16Co2P22 was discovered with a liquidus temperature of 881 K, a glass transition temperature of 506 K, and a supercooled liquid region of 63 K. Glass formation was observed in a wider composition range. Vickers hardness of these alloys is in the 400 Hv range. The alloys can be processed in the supercooled liquid region in air without any measurable oxidation. In this region, a large processing window is available in which the material does not embrittle. Embrittlement in these alloys is correlated with crystallization. It can be avoided as long as substantial crystallization does not take place during isothermal processing in the supercooled liquid region. Also, liquid processing can be performed in air when flux with B2O3.

  17. Analysis of in vitro reaction layers formed on 48S4 glass for applications in biomaterial field

    NASA Astrophysics Data System (ADS)

    Mami, M.; Oudadesse, H.; Dorbez-Sridi, R.; Dietrich, E.; Rocherullé, J.

    2007-11-01

    The purpose of this work is to study the formation of hydroxyapatite (Ca{10} (PO{4})6(OH){2}) on the surface of glass 48S4 with chemical composition: SiO{2}: 48%, CaO: 30%, Na{2}O: 18% and P{2}O{5}: 4% in weight ratio. This selected composition presents phosphorus contributions lower than that in BioglasscircledR [Hench et al. J. Biomed. Mater. 36, 117 (1971)] developed by L. Hench. Comparison of the kinetic formation of hydroxyapatite on the glass surfaces of these two biomaterials was made. The Material was prepared by melting and rapid quenching. It shows a bioactive character. This phenomenon is confirmed by the “in vitro” formation of hydroxycarbonate apatite (HCA) layer on the surface of glass after immersion in the Simulated Body Fluid (SBF). Before immersion in SBF, The proposed composition of glass was analyzed using several physicochemical methods like XRD, FTIR, SEM, and EDS confirming the composition and its amorphous state well. The pellets were soaked in SBF for 2 h, 1, 3, 7 and 15 days at 37 °C. The analyses of SBF after each immersion time were carried out using ICP-OES method. Results show important exchanges of ions between the surface of glass and the SBF. They revealed the formation of an amorphous CaO-P{2}O{5}- rich layer on the surface of the specimens after 1 day in the solution and a crystalline HCA{ }layer after 3 days immersion time as will be shown by XRD, EDS and FTIR analysis. The cristallinity increases with immersion time. After 15 days immersion in SBF liquid, the specimens are still fully covered by hydroxycarbonate apatite (HCA) layer.

  18. Development of Tc(IV)-Incorporated Fe Minerals to Enhance 99Tc Retention in Glass Waste Form

    SciTech Connect

    Um, Wooyong; Luksic, Steven A.; Wang, Guohui; Kim, Dong-Sang; Schweiger, Michael J.; Hrma, Pavel R.; Kruger, Albert A.

    2015-03-17

    Iron minerals have been considered to be good hosts for Tc immobilization because the Tc(IV) ion substitutes for Fe(III) in the crystal structure of the Fe oxide due to similarities in (1) cation size [Tc(IV) = 78.5 pm ; Fe(III) = 69 or 78.5 pm], (2) metal-oxygen interatomic distance (Tc—O = 0.199 nm, Fe—O = 0.203 nm), (3) number of coordinating oxygen atoms (both 6-fold coordinated), and (4) the redox potential (Eh=ca. +20 mV at pH = 7) for a redox couple between Tc(VII)/Tc(IV) and Fe(III)/Fe(II). Magnetite, maghemite, and trevorite are iron oxide minerals and all belong to spinel mineral group. Laboratory testing shows that Tc can be removed from aqueous waste solutions by a process of Tc reduction from Tc(VII) to Tc(IV) followed by co-precipitation with iron oxide minerals during recrystallization of Fe(OH)2(s) used as an initial solid precursor. X-ray absorption near edge structure (XANES) spectroscopy confirmed that Tc was in the +4 oxidation state in final Tc-Fe minerals. The Tc-incorporated Fe minerals were also tested for Tc retention in glass melts at different temperatures between 600 – 1,000 oC in a furnace. After being cooled in air, the solid glass specimens collected at different temperatures were analyzed for Tc oxidation state using XANES and Tc retention using liquid scintillation counting (LSC). Even though Tc(IV) started to reoxidize at 600 oC, Tc retention in the final glass specimen prepared with Tc-incorporated Fe mineral even at high temperatures was at least two times higher than glass prepared with KTcO4 salt. Higher Tc retention in glass is considered to result from limited and delayed Tc volatilization process due to Fe mineral encapsulation for Tc. Therefore, the results showing the presence of Tc(IV) in the Fe mineral structure indicate strong possibility to enhance Tc retention in borosilicate glass as well as to reduce the remediation costs at the Hanford Site.

  19. Insights into the ultrahigh glass-forming ability of the Fe-Co-Cr-Mo-C-B-Y alloy system from the electronic-structure perspective

    NASA Astrophysics Data System (ADS)

    Lu, Y. Z.; Huang, Y. J.; Wang, G.; Shen, J.

    2012-08-01

    The effect of cobalt on the glass-forming ability (GFA) of Fe-Co-Cr-Mo-C-B-Y bulk metallic glasses has been investigated by using ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The alloy containing 7% Co (Co7 alloy) exhibits the highest binding energy and the minimum electronic density of states at the Fermi energy in the valence band spectrum and possesses the largest carbide and metal boride peak intensity in the C 1s and B 1s core-level spectrum. The origin of the ultrahigh GFA for the Co7 alloy has been discussed in terms of the unique electronic structures, which are closely related to the densest atomic packing, the smallest atomic clusters, the minimum electronic density of states at the Fermi energy, and the most numerous transition-metal-carbon and transition-metal-boron bonds.

  20. Phase-field-crystal modeling of glass-forming liquids: Spanning time scales during vitrification, aging, and deformation

    NASA Astrophysics Data System (ADS)

    Berry, Joel; Grant, Martin

    2014-06-01

    Two essential elements required to generate a glass transition within phase-field-crystal (PFC) models are outlined based on observed freezing behaviors in various models of this class. The central dynamic features of glass formation in simple binary liquids are qualitatively reproduced across 12 orders of magnitude in time by applying a physically motivated time scaling to previous PFC simulation results. New aspects of the equilibrium phase behavior of the same binary model system are also outlined, aging behavior is explored in the moderate and deeply supercooled regimes, and aging exponents are extracted. General features of the elastic and plastic responses of amorphous and crystalline PFC solids under deformation are also compared and contrasted.