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Large melting point hysteresis of Ge nanocrystals embedded inSiO2

Description: The melting behavior of Ge nanocrystals embedded within SiO{sub 2} is evaluated using in situ transmission electron microscopy. The observed melting point hysteresis is large ({+-} 17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.
Date: May 4, 2006
Creator: Xu, Q.; Sharp, I.D.; Yuan, C.W.; Yi, D.O.; Liao, C.Y.; Glaeser,A.M. et al.
Partner: UNT Libraries Government Documents Department

Morphological, rheological and electrochemical studies ofpoly(ethylene oxide) electrolytes containing fumed silicananoparticles

Description: In this paper, the rheology and crystallization of composite Poly(Ethylene Oxide) (PEO) electrolytes were studied by dynamic mechanical analysis, DSC and polarized light microscopy. The effects of fumed silica nanoparticles on the conductivities of the polymer electrolytes at temperatures above and below their melting point were measured and related to their rheology and crystallization behavior, respectively. The electrolyte/electrode interfacial properties and cycling performances of the composite polymer electrolytes in Li/Li cells are also discussed. The measured electrochemical properties were found to depend heavily on the operational environments and sample processing history.
Date: June 1, 2003
Creator: Xie, Jiangbing; Kerr, John B.; Duan, Robert G. & Han, Yongbong
Partner: UNT Libraries Government Documents Department

MOLTEN SALT COMPOSITIONS

Description: A list of fused-salt mixtures which are of importance in molten salt research is presented. The list is a revision and extension of the list published in ORNL CF-57-6-81. The liquidus temperatures given are believed to be within lO C of the correct values. (auth)
Date: June 12, 1958
Creator: Blakely, J.P.
Partner: UNT Libraries Government Documents Department

Wetting of metals and glasses on Mo

Description: The wetting of low melting point metals and Si-Ca-Al-Ti-O glasses on molybdenum has been investigated. The selected metals (Au, Cu, Ag) form a simple eutectic with Mo. Metal spreading occurs under nonreactive conditions without interdiffusion or ridge formation. The metals exhibit low (non-zero) contact angles on Mo but this requires temperatures higher than 1100 C in reducing atmospheres in order to eliminate a layer of adsorbed impurities on the molybdenum surface. By controlling the oxygen activity in the furnace, glass spreading can take place under reactive or nonreactive conditions. We have found that in the glass/Mo system the contact angle does not decrease under reactive conditions. In all cases, adsorption from the liquid seems to accelerate the diffusivity on the free molybdenum surface.
Date: January 8, 2008
Creator: Saiz, Eduardo; Tomsia, Antoni P.; Saiz, Eduardo; Lopez-Esteban, Sonia; Benhassine, Mehdi; de Coninck, Joel et al.
Partner: UNT Libraries Government Documents Department

Pysico-chemical properties of hydrophobic ionic liquids containing1-octylpyridinium, 1-octyl-2-methylpyridinium or1-octyl-4-methylpyridinium cations

Description: This paper reports synthesis of some ionic liquids based on cations 1-octylpyridinium, 1-octyl-2-methylpyridinium or 1-octyl-4-methylpyridinium and anions dicyanamide [N(CN)2]-, bis(trifluoromethylsulfonyl)imide [Tf2N]-, bis(pentafluoroethylsulfonyl)imide [BETI]-, trifluoromethyl sulfonate [TfO]-, nonafluorobutyl sulfonate [NfO]-, tetrafluoroborate [BF4]-, trifluorophenylborate [BF3Ph]- or hexafluoroarsenate [AsF6]-. Melting points, decomposition temperatures, densities, mutual solubilities with water, and viscosities have been measured. Unlike similar ionic liquids containing imidazolium cations, pyridinium ionic liquids studied here are nearly immiscible in water. Viscosities are similar and water content is slightly lower than those for ionic liquids containing imidazolium cations.
Date: September 15, 2006
Creator: Papaiconomou, Nicolas; Salminen, Justin; Lee, Jong-Min & Prausnitz, John M.
Partner: UNT Libraries Government Documents Department

Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory

Description: We present valence photoelectron emission spectra of liquid water in comparison with gas-phase water, ice close to the melting point, low temperature amorphous and crystalline ice. All aggregation states have major electronic structure changes relative to the free molecule, with rehybridization and development of bonding and anti-bonding states accompanying the hydrogen bond formation. Sensitivity to the local structural order, most prominent in the shape and splitting of the occupied 3a{sub 1} orbital, is understood from the electronic structure averaging over various geometrical structures, and reflects the local nature of the orbital interaction.
Date: April 29, 2008
Creator: Nordlund, Dennis; Odelius, Michael; Bluhm, Hendrik; Ogasawara, Hirohito; Pettersson, Lars G.M. & Nilsson, Anders
Partner: UNT Libraries Government Documents Department

Melting of transition metals at high pressure and the influence of liquid frustration. I. The late metals Cu, Ni and Fe

Description: This report focuses on the role that frustration, or preferred liquid local causes ordering, plays in the melting of transition metals. Specifically, Cu, Ni and Fe. It is proposed that for liquids of metals with partially filled d-bands (Ni and Fe) frustration caused by Peierls/Jahn-Teller distortion and pressure-induced s-d electron promotion provides a mechanism for creating and enhancing the stability of local structures. At the most elementary level, liquid structures are essentially impurities that lower the freezing point. In the case of transition metals with partially filled d-bands, the application of pressure induces s-d electron promotion increases the concentration of local structures. This leads to melting slopes for Ni and Fe that are considerably lower than measured for Cu, and lower than for theoretical predictions employing models in which liquid structures are neglected.
Date: March 15, 2007
Creator: Ross, M; Boehler, R & Errandonea, D
Partner: UNT Libraries Government Documents Department

The effect of lattice temperature on surface damage in fused silica optics

Description: We examine the effect of lattice temperature on the probability of surface damage initiation for 355nm, 7ns laser pulses for surface temperatures below the melting point to temperatures well above the melting point of fused silica. At sufficiently high surface temperatures, damage thresholds are dramatically reduced. Our results indicate a temperature activated absorption and support the idea of a lattice temperature threshold of surface damage. From these measurements, we estimate the temperature dependent absorption coefficient for intrinsic silica.
Date: October 31, 2007
Creator: Bude, J; Guss, G; Matthews, M & Spaeth, M L
Partner: UNT Libraries Government Documents Department

Properties of some ionic liquids based on1-methyl-3-octylimidazolium and 4-methyl-N-butylpyridinium cations.

Description: Syntheses are reported for ionic liquids containing 1-methyl-3octylimidazolium and 4-methyl-N-butylpyridinium cations, and trifluoromethansulfonate, dicyanamide, bis(trifluoromethylsulfonyl)imide, and nonafluorobutanesulfonate anions. Densities, melting points and glass transition points, solubility in water as well as polarities have been measured. Ionic liquids based on pyridinium cations exhibit higher melting points, lower solubility in water, and higher polarity than those based on imidazolium cations.
Date: September 29, 2005
Creator: Papaiconomou, Nicolas; Yakelis, Neal; Salminen, Justin; Bergman,Robert & Prausnitz, John M.
Partner: UNT Libraries Government Documents Department

New Target Results from the FNAL Antiproton Source

Description: Nickel and compressed rhenium powder targets have been installed in the FNAL antiproton source target station. Ni was chosen for its high melting point energy and resistance to stress wave fractures. As well, compressed powdered rhenium segments were constrained by a thin-wall Ti jacket to insure resistance to stress fractures. The {bar p} yield of these new targets is compared with that of copper - the previous standard production target. The target depletion characteristics of nickel and rhenium for a beam intensity of 1.6 x 10{sup 12} protons per pulse are also presented.
Date: January 1, 1992
Creator: O'Day, S.; Bieniosek, F.; Anderson, K. & /Fermilab
Partner: UNT Libraries Government Documents Department

CONSTITUTION OF URANIUM AND THORIUM ALLOYS

Description: A compilation of constitution diagrams of uranium and thorium alloys is presented. The transformation and melting temperatures of the base metal are discussed, followed by the various alloys in alphabetical order. References are included on each alloy. (J.R.D.)
Date: June 1, 1958
Creator: Rough, F.A. & Bauer, A.A.
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: This progress report on the Department of Energy project DE-FG-97FT97263 entitled, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures,'' covers the period April-September 1998. The specific aims of the project for this period were to identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal, evaluate various impregnation or catalyst addition methods to improve catalyst dispersion, and evaluate gasification performance in a bench-scale fixed bed reactor. The project is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (Georgia Tech) with CAU as the prime contractor. Several single salt catalysts and binary and ternary eutectic catalysts were investigated at Clark Atlanta University. Physical mixing and incipient wetness methods were investigated as catalyst addition techniques. Gasification was carried out using TGA at CAU and UTSI and with a fixed-bed reactor at UTSI. The results showed better gasification activity in the presence of the catalysts tested. The eutectic salt studies showed clear agreement between the melting points of the prepared eutectics and reported literature values. The order of catalytic activity observed was ternary > binary > single salt. With the soluble single salt catalysts, the incipient wetness method was found to give better results than physical mixing technique. Also, catalyst preparation conditions such as catalyst loading, drying time and temperature were found to influence the gasification rate. Based on the Clark Atlanta University studies on Task 1, the project team selected the 43.5%Li{sub 2}CO{sub 3}-31.5%Na{sub 2}CO{sub 3}-25%K{sub 2}CO{sub 3} ternary eutectic and the 29%Na{sub 2}CO{sub 3}-71%K{sub 2}CO{sub 3} and 2.3%KNO{sub 3}-97.7%K{sub 2}CO{sub 3} binary eutectic for the fixed bed studies at UTSI. The eutectic salts were found to be highly insoluble in aqueous medium. As a result the technique of adding the eutectic to the raw coal ...
Date: October 1, 1998
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: This progress report on the Department of Energy project DE-FG-97FT97263 entitled, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures'', covers the period April-September 1998. The specific aims of the project for this period were to identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal, evaluate various impregnation or catalyst addition methods to improve catalyst dispersion, and evaluate gasification performance in a bench-scale fixed bed reactor. The project is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (Georgia Tech) with CAU as the prime contractor. Several single salt catalysts and binary and ternary eutectic catalysts were investigated at Clark Atlanta University. Physical mixing and incipient wetness methods were investigated as catalyst addition techniques. Gasification was carried out using TGA at CAU and UTSI and with a fixed-bed reactor at UTSI. The results showed better gasification activity in the presence of the catalysts tested. The eutectic salt studies showed clear agreement between the melting points of the prepared eutectics and reported literature values. The order of catalytic activity observed was ternary > binary > single salt. With the soluble single salt catalysts, the incipient wetness method was found to give better results than physical mixing technique. Also, catalyst preparation conditions such as catalyst loading, drying time and temperature were found to influence the gasification rate. Based on the Clark Atlanta University studies on Task 1, the project team selected the 43.5%Li{sub 2}CO{sub 3}-31.5%Na{sub 2}CO{sub 3}-25%K{sub 2}CO{sub 3} ternary eutectic and the 29%Na{sub 2}CO{sub 3}-71%K{sub 2}CO{sub 3} and 2.3% KNO{sub 3}-97.7%K{sub 2}CO{sub 3} binary eutectic for the fixed bed studies at UTSI. The eutectic salts were found to be highly insoluble in aqueous medium. As a result the technique of adding the eutectic to the raw ...
Date: April 1, 2000
Partner: UNT Libraries Government Documents Department

CATALYTIC GASIFICATION OF COAL USING EUTECTIC SALT MIXTURES

Description: The project, ''Catalytic Gasification of Coal Using Eutectic Salt Mixtures'', is being conducted jointly by Clark Atlanta University (CAU), the University of Tennessee Space Institute (UTSI) and the Georgia Institute of Technology (GT). The aims of the project are to: identify appropriate eutectic salt mixture catalysts for the gasification of Illinois No.6 coal; evaluate various impregnation or catalyst addition methods to improve catalyst dispersion; evaluate effects of major process variables (e.g., temperature, system pressure, etc.) on coal gasification; evaluate the recovery, regeneration and recycle of the spent catalysts in a bench-scale fixed bed reactor; and conduct thorough analysis and modeling of the gasification process to provide a better understanding of the fundamental mechanisms and kinetics of the process. The eutectic catalysts increased gasification rate significantly. The methods of catalyst preparation and addition had significant effect on the catalytic activity and coal gasification. The incipient wetness method gave more uniform catalyst distribution than that of physical mixing for the soluble catalysts resulting in higher gasification rates for the incipient wetness samples. The catalytic activity increased by varying degrees with catalyst loading. The above results are especially important since the eutectic catalysts (with low melting points) yield significant gasification rates even at low temperatures. Among the ternary eutectic catalysts studied, the system 39% Li{sub 2}CO{sub 3}-38.5% Na{sub 2}CO{sub 3}-22.5% Rb{sub 2}CO{sub 3} showed the best activity and will be used for further bench scale fixed-bed gasification reactor in the next period. Based on the Clark Atlanta University studies in the previous reporting period, the project team selected the 43.5% Li{sub 2}CO{sub 3}-31.5% Na{sub 2}CO{sub 3}-25% K{sub 2}CO{sub 3} ternary eutectic and the 29% Na{sub 2}CO{sub 3}-71% K{sub 2}CO{sub 3} binary eutectic for the fixed-bed studies at UTSI during this reporting period. Temperature was found to have a significant effect on the rate ...
Date: April 1, 1999
Partner: UNT Libraries Government Documents Department

Synthesis and casting of a lithium-bismuth compound for an ion-replacement electrorefiner.

Description: The intermetallic compound Li{sub 3}Bi played an integral part in the demonstration of an ion replacement electrorefining method developed at Argonne National Laboratory. The Li{sub 3}Bi compound was generated in a tilt-pour casting furnace using high-purity lithium and bismuth metals as the initial charge. At first, small-scale ({approximately}20 g) experiments were conducted to determine the materials synthesis parameters. In the end, four larger-scale castings (500 g to 1250 g) were completed in a tantalum crucible. The metals were heated slowly to melt the charge, and the formation reaction proceeded vigorously above the melting point of bismuth ({approximately}270 C). For the large-scale melts, the furnace power was temporarily turned off at this point. After several minutes, the tantalum crucible stopped glowing, and the furnace power was turned on. The temperature was then increased to {approximately}1200 C to melt and homogenize the compound, and liquid Li{sub 3}Bi was cast into cold stainless steel molds. Approximately 3.7 kg of Li{sub 3}Bi was generated by this method.
Date: November 23, 1998
Creator: McDeavitt, S. M.
Partner: UNT Libraries Government Documents Department

An Evaluation of Liquidus Temperature as a Function of Waste Loading for a Tank 42 "Sludge Only"/Frit 200 Flowsheet

Description: 'The waste glass produced in the SRS Defense Waste Processing Faiclity (DWPF) process must comply with Waste Acceptance Product Specifications (WAPS) and process control requirements by demonstrating, to a high degree of confidence, that melter feed will produce glass satisfying all quality and processing requirements.'
Date: May 10, 1999
Creator: Peeler, D.
Partner: UNT Libraries Government Documents Department

Thermodynamic and kinetic characteristics of variations in shapes of ridges formed on {l_brace}100{r_brace} lithium fluoride surfaces

Description: channels with widths in the range form 5 {mu}m were formed in {l_brace}100{r_brace} surfaces of LiF single crystals by a photolithographic technique. Specimens annealed at or above 0.90 T{mu}m, where T{mu} is the melting point, and then quenched showed the channels and the ridges between them develop rounded profiles. Evolution of these profiles was evaluated for the various channel widths and for interchannel ridge spacings of 5 to 100 {mu}m in terms of: (a) an accepted theoretical model for a surface diffusion controlled process, and (b) a model which assumes that shape changes depend only on the relative energies of attachment of atoms in surface sites with various surface curvatures. Either model is consistent with the experimental observations to within the reproducibility in measurements.
Date: December 1, 1991
Creator: Bullard, J. W.; Glaeser, A. M. & Searcy, A. W.
Partner: UNT Libraries Government Documents Department

Fireside Corrosion in Oxy-Fuel Combustion of Coal

Description: The goal is to develop technologies for pulverized coal boilers with >90% CO{sub 2} capture and sequestration and <35% increase in the cost of electricity. Air-fired power plant experience shows a corrosion loss max at 680-700 C. Low melting point alkali metal trisulfates, such as (K,Na){sub 3}Fe(SO{sub 4}){sub 3}, become thermally unstable above this temperature range. Some overall conclusions are: (1) CO{sub 2} + 30% H{sub 2}O more corrosive than Ar + 30% H{sub 2}O; (2) Excess O{sub 2} in H{sub 2}O can, in some cases, greatly increase oxidation; (3) Coal ash is generally innocuous without SO{sub 3}3 in gas phase; and (4) Long-term exposures are starting to establish differences between air-firing and oxy-firing conditions.
Date: October 9, 2011
Creator: Holcomb, G. R.; Tylczak, J.; Meier, G. H.; Jung, K.; Mu, N.; Yanar, N. M. et al.
Partner: UNT Libraries Government Documents Department

Development of a machine protection system for the Superconducting Beam Test Facility at Fermilab

Description: Fermilab's Superconducting RF Beam Test Facility currently under construction will produce electron beams capable of damaging the acceleration structures and the beam line vacuum chambers in the event of an aberrant accelerator pulse. The accelerator is being designed with the capability to operate with up to 3000 bunches per macro-pulse, 5Hz repetition rate and 1.5 GeV beam energy. It will be able to sustain an average beam power of 72 KW at the bunch charge of 3.2 nC. Operation at full intensity will deposit enough energy in niobium material to approach the melting point of 2500 C. In the early phase with only 3 cryomodules installed the facility will be capable of generating electron beam energies of 810 MeV and an average beam power that approaches 40 KW. In either case a robust Machine Protection System (MPS) is required to mitigate effects due to such large damage potentials. This paper will describe the MPS system being developed, the system requirements and the controls issues under consideration.
Date: September 1, 2011
Creator: Warner, A.; Carmichael, L.; Church, M.; Neswold, R. & /Fermilab
Partner: UNT Libraries Government Documents Department

IRRADIATION EFFECTS ON URANIUM DIOXIDE MELTING

Description: Irradiated uranium dioxide with exposures to 11.25 at.% uranium burnup was examined microscopically at temperatures to 3000 deg C. Melting temperatures were measured and mass vaporization rates compared for UO/sub 2/ with 14 different exposures. (auth)
Date: March 1, 1962
Creator: Christensen, J.A.
Partner: UNT Libraries Government Documents Department

POLYPHENYLENESULFIED/MONTOMORILLONITE CLAY NANOCOMPOSITE COATINGS: THEIR EFFICACY IN PROTECTING STEEL AGAINST CORROSION.

Description: Nanoscale montomorillonite (MMT) clay fillers became dispersed in a polyphenylenesulfied (PPS) matrix through the processes of octadecylamine (ODA) intercalation {yields} molten PPS co-intercalation {yields} exfoliation. Cooling this molten exfoliated material led to the formation of a PPS/MMT nanocomposite. The MMT nanofiller conferred three advanced properties on the semi-crystalline PPS: First, it raised its melting point by nearly 40 C to 290 C; second, it increased its crystallization energy, implying that an excellent adherence of the nanofillers surfaces to PPS in terms of a good interfacial bond; and, third, it abated the degree of its hydrothermal oxidation due to sulfide {yields} sulfite linkage transformations. When this advanced PPS nanocomposite was used as a corrosion-preventing coating for carbon steel in a simulated geothermal environment at 300 C, a coating of {approx}150 {micro}m thickness adequately protected the steel against hot brine-caused corrosion. In contrast, an MMT-free PPS coating of similar thickness was not nearly as effective in mitigating corrosion as was the nanocompsite; in fact, the uptake of corrosive ionic electrolyte by the unmodified coating increased with an extending exposure time.
Date: June 1, 2006
Creator: SUGAMA, T. & GAWLIK, K.
Partner: UNT Libraries Government Documents Department