WorldWideScience

Sample records for melting points

  1. Melting point of yttria

    International Nuclear Information System (INIS)

    Skaggs, S.R.

    1977-06-01

    Fourteen samples of 99.999 percent Y 2 O 3 were melted near the focus of a 250-W CO 2 laser. The average value of the observed melting point along the solid-liquid interface was 2462 +- 19 0 C. Several of these same samples were then melted in ultrahigh-purity oxygen, nitrogen, helium, or argon and in water vapor. No change in the observed temperature was detected, with the exception of a 20 0 C increase in temperature from air to helium gas. Post test examination of the sample characteristics, clarity, sphericity, and density is presented, along with composition. It is suggested that yttria is superior to alumina as a secondary melting-point standard

  2. Calculation of melting points of oxides

    International Nuclear Information System (INIS)

    Bobkova, O.S.; Voskobojnikov, V.G.; Kozin, A.I.

    1975-01-01

    The correlation between the melting point and thermodynamic parameters characterizing the strength of oxides and compounds is given. Such thermodynamic paramters include the energy and antropy of atomization

  3. Nanotexturing of surfaces to reduce melting point.

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Ernest J.; Zubia, David (University of Texas at El Paso El Paso, TX); Mireles, Jose (Universidad Aut%C3%94onoma de Ciudad Ju%C3%94arez Ciudad Ju%C3%94arez, Mexico); Marquez, Noel (University of Texas at El Paso El Paso, TX); Quinones, Stella (University of Texas at El Paso El Paso, TX)

    2011-11-01

    This investigation examined the use of nano-patterned structures on Silicon-on-Insulator (SOI) material to reduce the bulk material melting point (1414 C). It has been found that sharp-tipped and other similar structures have a propensity to move to the lower energy states of spherical structures and as a result exhibit lower melting points than the bulk material. Such a reduction of the melting point would offer a number of interesting opportunities for bonding in microsystems packaging applications. Nano patterning process capabilities were developed to create the required structures for the investigation. One of the technical challenges of the project was understanding and creating the specialized conditions required to observe the melting and reshaping phenomena. Through systematic experimentation and review of the literature these conditions were determined and used to conduct phase change experiments. Melting temperatures as low as 1030 C were observed.

  4. Making Sense of Boiling Points and Melting Points

    Indian Academy of Sciences (India)

    GENERAL | ARTICLE. The boiling and melting points of a pure substance are char- ... bonds, which involves high energy and hence high temperatures. Among the .... with zero intermolecular force at all temperatures and pressures, which ...

  5. Low-melting point heat transfer fluid

    Science.gov (United States)

    Cordaro, Joseph Gabriel; Bradshaw, Robert W.

    2010-11-09

    A low-melting point, heat transfer fluid made of a mixture of five inorganic salts including about 29.1-33.5 mol % LiNO.sub.3, 0-3.9 mol % NaNO.sub.3, 2.4-8.2 mol % KNO.sub.3, 18.6-19.9 mol % NaNO.sub.2, and 40-45.6 mol % KNO.sub.2. These compositions can have liquidus temperatures below 80.degree. C. for some compositions.

  6. Realization of Copper Melting Point for Thermocouple Calibrations

    Directory of Open Access Journals (Sweden)

    Y. A. ABDELAZIZ

    2011-08-01

    Full Text Available Although the temperature stability and uncertainty of the freezing plateau is better than that of the melting plateau in most of the thermometry fixed points, but realization of melting plateaus are easier than that of freezing plateaus for metal fixed points. It will be convenient if the melting points can be used instead of the freezing points in calibration of standard noble metal thermocouples because of easier realization and longer plateau duration of melting plateaus. In this work a comparison between the melting and freezing points of copper (Cu was carried out using standard noble metal thermocouples. Platinum - platinum 10 % rhodium (type S, platinum – 30 % rhodium / platinum 6 % rhodium (type B and platinum - palladium (Pt/Pd thermocouples are used in this study. Uncertainty budget analysis of the melting points and freezing points is presented. The experimental results show that it is possible to replace the freezing point with the melting point of copper cell in the calibration of standard noble metal thermocouples in secondary-level laboratories if the optimal methods of realization of melting points are used.

  7. Double melting in polytetrafluoroethylene γ-irradiated above its melting point

    International Nuclear Information System (INIS)

    Serov, S.A.; Khatipov, S.A.; Sadovskaya, N.V.; Tereshenkov, A.V.; Chukov, N.A.

    2012-01-01

    Highlights: ► PTFE irradiation leads to formation of double melting peaks in DSC curves. ► This is connected to dual crystalline morphology typical for PTFE. ► Two crystalline types exist in the PTFE irradiated in the melt. - Abstract: PTFE irradiation above its melting point leads to formation of double melting and crystallization peaks in DSC curves. Splitting of melting peaks is connected to dual crystalline morphology typical for PTFE irradiated in the melt. According to electron microscopy, two crystalline types with different size and packing density exist in the irradiated PTFE.

  8. Automated realization of the gallium melting and triple points

    Science.gov (United States)

    Yan, X.; Duan, Y.; Zhang, J. T.; Wang, W.

    2013-09-01

    In order to improve the automation and convenience of the process involved in realizing the gallium fixed points, an automated apparatus, based on thermoelectric and heat pipe technologies, was designed and developed. This paper describes the apparatus design and procedures for freezing gallium mantles and realizing gallium melting and triple points. Also, investigations on the melting behavior of a gallium melting point cell and of gallium triple point cells were carried out while controlling the temperature outside the gallium point cells at 30 °C, 30.5 °C, 31 °C, and 31.5 °C. The obtained melting plateau curves show dentate temperature oscillations on the melting plateaus for the gallium point cells when thermal couplings occurred between the outer and inner liquid-solid interfaces. The maximum amplitude of the temperature fluctuations was about 1.5 mK. Therefore, the temperature oscillations can be used to indicate the ending of the equilibrium phase transitions. The duration and amplitude of such temperature oscillations depend on the temperature difference between the setting temperature and the gallium point temperature; the smaller the temperature difference, the longer the duration of both the melting plateaus and the temperature fluctuations.

  9. Estimating the melting point, entropy of fusion, and enthalpy of ...

    Science.gov (United States)

    The entropies of fusion, enthalies of fusion, and melting points of organic compounds can be estimated through three models developed using the SPARC (SPARC Performs Automated Reasoning in Chemistry) platform. The entropy of fusion is modeled through a combination of interaction terms and physical descriptors. The enthalpy of fusion is modeled as a function of the entropy of fusion, boiling point, and fexibility of the molecule. The melting point model is the enthlapy of fusion divided by the entropy of fusion. These models were developed in part to improve SPARC's vapor pressure and solubility models. These models have been tested on 904 unique compounds. The entropy model has a RMS of 12.5 J mol-1K-1. The enthalpy model has a RMS of 4.87 kJ mol-1. The melting point model has a RMS of 54.4°C. Published in the journal, SAR and QSAR in Environmental Research

  10. Quantitative structure-property relationships for prediction of boiling point, vapor pressure, and melting point.

    Science.gov (United States)

    Dearden, John C

    2003-08-01

    Boiling point, vapor pressure, and melting point are important physicochemical properties in the modeling of the distribution and fate of chemicals in the environment. However, such data often are not available, and therefore must be estimated. Over the years, many attempts have been made to calculate boiling points, vapor pressures, and melting points by using quantitative structure-property relationships, and this review examines and discusses the work published in this area, and concentrates particularly on recent studies. A number of software programs are commercially available for the calculation of boiling point, vapor pressure, and melting point, and these have been tested for their predictive ability with a test set of 100 organic chemicals.

  11. Melting point of high-purity germanium stable isotopes

    Science.gov (United States)

    Gavva, V. A.; Bulanov, A. D.; Kut'in, A. M.; Plekhovich, A. D.; Churbanov, M. F.

    2018-05-01

    The melting point (Tm) of germanium stable isotopes 72Ge, 73Ge, 74Ge, 76Ge was determined by differential scanning calorimetry. With the increase in atomic mass of isotope the decrease in Tm is observed. The decrease was equal to 0.15 °C per the unit of atomic mass which qualitatively agrees with the value calculated by Lindemann formula accounting for the effect of "isotopic compression" of elementary cell.

  12. Low-melting point inorganic nitrate salt heat transfer fluid

    Science.gov (United States)

    Bradshaw, Robert W [Livermore, CA; Brosseau, Douglas A [Albuquerque, NM

    2009-09-15

    A low-melting point, heat transfer fluid made of a mixture of four inorganic nitrate salts: 9-18 wt % NaNO.sub.3, 40-52 wt % KNO.sub.3, 13-21 wt % LiNO.sub.3, and 20-27 wt % Ca(NO.sub.3).sub.2. These compositions can have liquidus temperatures less than 100 C; thermal stability limits greater than 500 C; and viscosity in the range of 5-6 cP at 300 C; and 2-3 cP at 400 C.

  13. Binding Energy, Vapor Pressure and Melting Point of Semiconductor Nanoparticles

    International Nuclear Information System (INIS)

    H. H. Farrell; C. D. Van Siclen

    2007-01-01

    Current models for the cohesive energy of nanoparticles generally predict a linear dependence on the inverse particle diameter for spherical clusters, or, equivalently, on the inverse of the cube root of the number of atoms in the cluster. Although this is generally true for metals, we find that for the group IV semiconductors, C, Si and Ge, this linear dependence does not hold. Instead, using first principles, density functional theory calculations to calculate the binding energy of these materials, we find a quadratic dependence on the inverse of the particle size. Similar results have also been obtained for the metallic group IV elements Sn and Pb. This is in direct contradiction to current assumptions. Further, as a consequence of this quadratic behavior, the vapor pressure of semiconductor nanoparticles rises more slowly with decreasing size than would be expected. In addition, the melting point of these nanoparticles will experience less suppression than experienced by metal nanoparticles with comparable bulk binding energies. This non-linearity also affects sintering or Ostwald ripening behavior of these nanoparticles as well as other physical properties that depend on the nanoparticle binding energy. The reason for this variation in size dependence involves the covalent nature of the bonding in semiconductors, and even in the 'poor' metals. Therefore, it is expected that this result will hold for compound semiconductors as well as the elemental semiconductors

  14. The Melting Point of Palladium Using Miniature Fixed Points of Different Ceramic Materials: Part II—Analysis of Melting Curves and Long-Term Investigation

    Science.gov (United States)

    Edler, F.; Huang, K.

    2016-12-01

    Fifteen miniature fixed-point cells made of three different ceramic crucible materials (Al2O3, ZrO2, and Al2O3(86 %)+ZrO2(14 %)) were filled with pure palladium and used to calibrate type B thermocouples (Pt30 %Rh/Pt6 %Rh). A critical point by using miniature fixed points with small amounts of fixed-point material is the analysis of the melting curves, which are characterized by significant slopes during the melting process compared to flat melting plateaus obtainable using conventional fixed-point cells. The method of the extrapolated starting point temperature using straight line approximation of the melting plateau was applied to analyze the melting curves. This method allowed an unambiguous determination of an electromotive force (emf) assignable as melting temperature. The strict consideration of two constraints resulted in a unique, repeatable and objective method to determine the emf at the melting temperature within an uncertainty of about 0.1 μ V. The lifetime and long-term stability of the miniature fixed points was investigated by performing more than 100 melt/freeze cycles for each crucible of the different ceramic materials. No failure of the crucibles occurred indicating an excellent mechanical stability of the investigated miniature cells. The consequent limitation of heating rates to values below {± }3.5 K min^{-1} above 1100° C and the carefully and completely filled crucibles (the liquid palladium occupies the whole volume of the crucible) are the reasons for successfully preventing the crucibles from breaking. The thermal stability of the melting temperature of palladium was excellent when using the crucibles made of Al2O3(86 %)+ZrO2(14 %) and ZrO2. Emf drifts over the total duration of the long-term investigation were below a temperature equivalent of about 0.1 K-0.2 K.

  15. Noise temperature measurements for the determination of the thermodynamic temperature of the melting point of palladium

    Energy Technology Data Exchange (ETDEWEB)

    Edler, F.; Kuhne, M.; Tegeler, E. [Bundesanstalt Physikalisch-Technische, Berlin (Germany)

    2004-02-01

    The thermodynamic temperature of the melting point of palladium in air was measured by noise thermometric methods. The temperature measurement was based on noise comparison using a two-channel arrangement to eliminate parasitic noises of electronic components by cross correlation. Three miniature fixed points filled with pure palladium (purity: {approx}99.99%, mass: {approx}90 g) were used to realize the melts of the fixed point metal. The measured melting temperature of palladium in air amounted to 1552.95 deg C {+-} 0.21 K (k = 2). This temperature is 0.45 K lower than the temperature of the melting point of palladium measured by radiation thermometry. (authors)

  16. On the correlation between hydrogen bonding and melting points in the inositols

    Directory of Open Access Journals (Sweden)

    Sándor L. Bekö

    2014-01-01

    Full Text Available Inositol, 1,2,3,4,5,6-hexahydroxycyclohexane, exists in nine stereoisomers with different crystal structures and melting points. In a previous paper on the relationship between the melting points of the inositols and the hydrogen-bonding patterns in their crystal structures [Simperler et al. (2006. CrystEngComm 8, 589], it was noted that although all inositol crystal structures known at that time contained 12 hydrogen bonds per molecule, their melting points span a large range of about 170 °C. Our preliminary investigations suggested that the highest melting point must be corrected for the effect of molecular symmetry, and that the three lowest melting points may need to be revised. This prompted a full investigation, with additional experiments on six of the nine inositols. Thirteen new phases were discovered; for all of these their crystal structures were examined. The crystal structures of eight ordered phases could be determined, of which seven were obtained from laboratory X-ray powder diffraction data. Five additional phases turned out to be rotator phases and only their unit cells could be determined. Two previously unknown melting points were measured, as well as most enthalpies of melting. Several previously reported melting points were shown to be solid-to-solid phase transitions or decomposition points. Our experiments have revealed a complex picture of phases, rotator phases and phase transitions, in which a simple correlation between melting points and hydrogen-bonding patterns is not feasible.

  17. On the correlation between hydrogen bonding and melting points in the inositols

    DEFF Research Database (Denmark)

    Bekö, Sándor L; Alig, Edith; Schmidt, Martin U

    2014-01-01

    Inositol, 1,2,3,4,5,6-hexahydroxycyclohexane, exists in nine stereoisomers with different crystal structures and melting points. In a previous paper on the relationship between the melting points of the inositols and the hydrogen-bonding patterns in their crystal structures [Simperler et al. (2006...... ▶). CrystEngComm 8, 589], it was noted that although all inositol crystal structures known at that time contained 12 hydrogen bonds per molecule, their melting points span a large range of about 170 °C. Our preliminary investigations suggested that the highest melting point must be corrected for the effect...... ordered phases could be determined, of which seven were obtained from laboratory X-ray powder diffraction data. Five additional phases turned out to be rotator phases and only their unit cells could be determined. Two previously unknown melting points were measured, as well as most enthalpies of melting...

  18. Evaluation of melting point of UO2 by molecular dynamics simulation

    International Nuclear Information System (INIS)

    Arima, Tatsumi; Idemitsu, Kazuya; Inagaki, Yaohiro; Tsujita, Yuichi; Kinoshita, Motoyasu; Yakub, Eugene

    2009-01-01

    The melting point of UO 2 has been evaluated by molecular dynamics simulation (MD) in terms of interatomic potential, pressure and Schottky defect concentration. The Born-Mayer-Huggins potentials with or without a Morse potential were explored in the present study. Two-phase simulation whose supercell at the initial state consisted of solid and liquid phases gave the melting point comparable to the experimental data using the potential proposed by Yakub. The heat of fusion was determined by the difference in enthalpy at the melting point. In addition, MD calculations showed that the melting point increased with pressure applied to the system. Thus, the Clausius-Clapeyron equation was verified. Furthermore, MD calculations clarified that an addition of Schottky defects, which generated the local disorder in the UO 2 crystal, lowered the melting point.

  19. Determination of melting point of mixed-oxide fuel irradiated in a fast breeder reactor

    International Nuclear Information System (INIS)

    Tachibana, Toshimichi

    1985-01-01

    The melting point of fuel is important to set its in-reactor maximum temperature in fuel design. The fuel melting point measuring methods are broadly the filament method and the capsule sealing method. The only instance of measuring the melting point of irradiated mixed oxide (U, Pu)O 2 fuel by the filament method is by GE in the United States. The capsule sealing method, while the excellent means, is difficult in weld sealing the irradiated fuel in a capsule within the cell. In the fast reactor development program, the remotely operated melting point measuring apparatus in capsule sealing the mixed (U, Pu)O 2 fuel irradiated in the experimental FBR Joyo was set in the cell and the melting point was measured, for the first time in the world. (Mori, K.)

  20. Our Educational Melting Pot: Have We Reached the Boiling Point?

    Science.gov (United States)

    Lauderdale, Katherine Lynn, Ed.; Bonilla, Carlos A., Ed.

    The articles and excerpts in this collection illustrate the complexity of the melting pot concept. Multiculturalism has become a watchword in American life and education, but it may be that in trying to atone for past transgressions educators and others are simply going too far. These essays illustrate some of the problems of a multicultural…

  1. Effect of grain size on the melting point of confined thin aluminum films

    Energy Technology Data Exchange (ETDEWEB)

    Wejrzanowski, Tomasz; Lewandowska, Malgorzata; Sikorski, Krzysztof; Kurzydlowski, Krzysztof J. [Materials Design Division, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

    2014-10-28

    The melting of aluminum thin film was studied by a molecular dynamics (MD) simulation technique. The effect of the grain size and type of confinement was investigated for aluminum film with a constant thickness of 4 nm. The results show that coherent intercrystalline interface suppress the transition of solid aluminum into liquid, while free-surface gives melting point depression. The mechanism of melting of polycrystalline aluminum thin film was investigated. It was found that melting starts at grain boundaries and propagates to grain interiors. The melting point was calculated from the Lindemann index criterion, taking into account only atoms near to grain boundaries. This made it possible to extend melting point calculations to bigger grains, which require a long time (in the MD scale) to be fully molten. The results show that 4 nm thick film of aluminum melts at a temperature lower than the melting point of bulk aluminum (933 K) only when the grain size is reduced to 6 nm.

  2. Applicability of low-melting-point microcrystalline wax to develop temperature-sensitive formulations.

    Science.gov (United States)

    Matsumoto, Kohei; Kimura, Shin-Ichiro; Iwao, Yasunori; Itai, Shigeru

    2017-10-30

    Low-melting-point substances are widely used to develop temperature-sensitive formulations. In this study, we focused on microcrystalline wax (MCW) as a low-melting-point substance. We evaluated the drug release behavior of wax matrix (WM) particles using various MCW under various temperature conditions. WM particles containing acetaminophen were prepared using a spray congealing technique. In the dissolution test at 37°C, WM particles containing low-melting-point MCWs whose melting was starting at approx. 40°C (Hi-Mic-1045 or 1070) released the drug initially followed by the release of only a small amount. On the other hand, in the dissolution test at 20 and 25°C for WM particles containing Hi-Mic-1045 and at 20, 25, and 30°C for that containing Hi-Mic-1070, both WM particles showed faster drug release than at 37°C. The characteristic drug release suppression of WM particles containing low-melting-point MCWs at 37°C was thought attributable to MCW melting, as evidenced by differential scanning calorimetry analysis and powder X-ray diffraction analysis. Taken together, low-melting-point MCWs may be applicable to develop implantable temperature-sensitive formulations that drug release is accelerated by cooling at administered site. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. An assessment of the melting, boiling, and critical point data of the alkali metals

    International Nuclear Information System (INIS)

    Ohse, R.W.; Babelot, J.-F.; Magill, J.

    1985-01-01

    The paper reviews the measured melting, boiling and critical point data of alkali metals. A survey of the static heat generation methods for density and pressure-volume-temperature measurements is given. Measured data on the melting and boiling temperatures of lithium, sodium, potassium, rubidium and caesium are summarised. Also measured critical point data for the same five alkali metals are presented, and discussed. (U.K.)

  4. Melting point of polymers under high pressure Part I: Influence of the polymer properties

    International Nuclear Information System (INIS)

    Seeger, Andreas; Freitag, Detlef; Freidel, Frank; Luft, Gerhard

    2004-01-01

    The pressure dependence of the melting point of various polymers including homo- and copolymers (HDPE, LDPE, PP and ethylene vinyl acetate copolymers (EVA)) was investigated under nitrogen atmosphere up to 330 MPa within a high pressure differential thermal analysis cell designed by our group. The properties of the polymers (vinylacetate content, melt flow index, molecular weight, isotactic index, crystallinity, density, and frequency of branching) have been correlated with the change of the melting point under pressure (dT m /dp). It could be shown that the melting point always increases linearly with pressure up to 330 MPa. The pressure dependence was found to be in the range of 11-17 K/(100 MPa). From these results it is possible to approximate dT m /dp using the enthalpy of fusion of the polymers at ambient pressure

  5. Some thermophysical properties of ruthenium in the neighbourhood of the melting point

    International Nuclear Information System (INIS)

    Sheindlin, A.E.; Kats, S.A.; Berezin, B.Ya.; Chekhovskoy, V.Ya.; Kenisarin, M.M.

    1975-01-01

    The technique of levitation calorimetry has been used to study for the first time thermophysical properties of ruthenium in the neighbourhood of the melting point. To measure enthalpy a copper block calorimeter with an istohermal jacket has been used. Basing on the values measured the equations for enthalpy of solid and liquid ruthenium within the temperature ranges of 2,270-2,607 K and 2,607-2,760 K respectively have been obtained by the least squares method. In addition the melting temperature of ruthenium and its brightness temperature at the melting point, the wavelength being 0.65 micron, have been measured. The results of the measurements have been used to calculate the heat and entropy of fusion, the specific heat of solid and that of liquid ruthenium and its normal spectral emissivity at the melting point

  6. An assessment of the melting, boiling, and critical point data of the alkali metals

    International Nuclear Information System (INIS)

    Ohse, R.W.; Babelot, J.F.; Magill, J.

    1985-01-01

    The measured melting, boiling and critical point data of the alkali metals are reviewed. Emphasis has been given to the assessment of the critical point data. The main experimental techniques for measurements in the critical region are described. The selected data are given. Best estimates of the critical constants of lithium are given. (author)

  7. Origin of melting point depression for rare gas solids confined in carbon pores

    International Nuclear Information System (INIS)

    Morishige, Kunimitsu; Kataoka, Takaaki

    2015-01-01

    To obtain insights into the mechanism of the melting-point depression of rare gas solids confined in crystalline carbon pores, we examined the freezing and melting behavior of Xe and Ar confined to the crystalline pores of ordered mesoporous carbons as well as compressed exfoliated graphite compared to the amorphous pores of ordered mesoporous silicas, by means of X-ray diffraction. For the Xe and Ar confined to the crystalline carbon pores, there was no appreciable thermal hysteresis between freezing and melting. Furthermore, the position of the main diffraction peak did not change appreciably on freezing and melting. This strongly suggests that the liquids confined in the carbon pores form a multilayered structure parallel to the smooth walls. For the Xe and Ar confined to the amorphous silica pores, on the other hand, the position of the main diffraction peak shifted into higher scattering angle on freezing suggested that the density of the confined solid is distinctly larger than for the confined liquid. Using compressed exfoliated graphite with carbon walls of higher crystallinity, we observed that three-dimensional (3D) microcrystals of Xe confined in the slit-shaped pores melted to leave the unmelted bilayers on the pore walls below the bulk triple point. The lattice spacing of the 3D microcrystals confined is larger by ∼0.7% than that of the bilayer next to the pore walls in the vicinity of the melting point

  8. Origin of melting point depression for rare gas solids confined in carbon pores

    Energy Technology Data Exchange (ETDEWEB)

    Morishige, Kunimitsu, E-mail: morishi@chem.ous.ac.jp; Kataoka, Takaaki [Department of Chemistry, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 700-0005 (Japan)

    2015-07-21

    To obtain insights into the mechanism of the melting-point depression of rare gas solids confined in crystalline carbon pores, we examined the freezing and melting behavior of Xe and Ar confined to the crystalline pores of ordered mesoporous carbons as well as compressed exfoliated graphite compared to the amorphous pores of ordered mesoporous silicas, by means of X-ray diffraction. For the Xe and Ar confined to the crystalline carbon pores, there was no appreciable thermal hysteresis between freezing and melting. Furthermore, the position of the main diffraction peak did not change appreciably on freezing and melting. This strongly suggests that the liquids confined in the carbon pores form a multilayered structure parallel to the smooth walls. For the Xe and Ar confined to the amorphous silica pores, on the other hand, the position of the main diffraction peak shifted into higher scattering angle on freezing suggested that the density of the confined solid is distinctly larger than for the confined liquid. Using compressed exfoliated graphite with carbon walls of higher crystallinity, we observed that three-dimensional (3D) microcrystals of Xe confined in the slit-shaped pores melted to leave the unmelted bilayers on the pore walls below the bulk triple point. The lattice spacing of the 3D microcrystals confined is larger by ∼0.7% than that of the bilayer next to the pore walls in the vicinity of the melting point.

  9. Estimating the physicochemical properties of polyhalogenated aromatic and aliphatic compounds using UPPER: part 1. Boiling point and melting point.

    Science.gov (United States)

    Admire, Brittany; Lian, Bo; Yalkowsky, Samuel H

    2015-01-01

    The UPPER (Unified Physicochemical Property Estimation Relationships) model uses enthalpic and entropic parameters to estimate 20 biologically relevant properties of organic compounds. The model has been validated by Lian and Yalkowsky on a data set of 700 hydrocarbons. The aim of this work is to expand the UPPER model to estimate the boiling and melting points of polyhalogenated compounds. In this work, 19 new group descriptors are defined and used to predict the transition temperatures of an additional 1288 compounds. The boiling points of 808 and the melting points of 742 polyhalogenated compounds are predicted with average absolute errors of 13.56 K and 25.85 K, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Preparation of 147Pm metal and the determination of the melting point and phase transformation temperatures

    International Nuclear Information System (INIS)

    Angelini, P.; Adair, H.L.

    1976-07-01

    The promethium metal used in the determination of the melting point and phase transformation temperatures was prepared by reduction of promethium oxide with thorium metal at 1600 0 C and distilling the promethium metal into a quartz dome. The melting point and phase transformation temperatures of promethium metal were found to be 1042 +- 5 0 C and 890 +- 5 0 C, respectively. The ratio for the heat of the high-temperature transformation to the heat of fusion was determined to be 0.415

  11. Molecular dynamics calculations of the thermal expansion properties and melting points of Si and Ge

    International Nuclear Information System (INIS)

    Timon, V; Brand, S; Clark, S J; Abram, R A

    2006-01-01

    The thermal expansion properties and melting points of silicon and germanium are calculated using molecular dynamics simulations within the density functional theory framework. An isothermal-isobaric (NPT) ensemble is considered in a periodic system with a relatively small number of particles per unit cell to obtain the thermal expansion data over a range of temperatures, and it is found that the calculated thermal expansion coefficients and bond lengths agree well with experimental data. Also, the positions of discontinuities in the potential energy as a function of temperature are in good agreement with the experimental melting points

  12. Effect of deposition rate on melting point of copper film catalyst substrate at atomic scale

    Science.gov (United States)

    Marimpul, Rinaldo; Syuhada, Ibnu; Rosikhin, Ahmad; Winata, Toto

    2018-03-01

    Annealing process of copper film catalyst substrate was studied by molcular dynamics simulation. This copper film catalyst substrate was produced using thermal evaporation method. The annealing process was limited in nanosecond order to observe the mechanism at atomic scale. We found that deposition rate parameter affected the melting point of catalyst substrate. The change of crystalline structure of copper atoms was observed before it had been already at melting point. The optimum annealing temperature was obtained to get the highest percentage of fcc structure on copper film catalyst substrate.

  13. A density functional theory based approach for predicting melting points of ionic liquids.

    Science.gov (United States)

    Chen, Lihua; Bryantsev, Vyacheslav S

    2017-02-01

    Accurate prediction of melting points of ILs is important both from the fundamental point of view and from the practical perspective for screening ILs with low melting points and broadening their utilization in a wider temperature range. In this work, we present an ab initio approach to calculate melting points of ILs with known crystal structures and illustrate its application for a series of 11 ILs containing imidazolium/pyrrolidinium cations and halide/polyatomic fluoro-containing anions. The melting point is determined as a temperature at which the Gibbs free energy of fusion is zero. The Gibbs free energy of fusion can be expressed through the use of the Born-Fajans-Haber cycle via the lattice free energy of forming a solid IL from gaseous phase ions and the sum of the solvation free energies of ions comprising IL. Dispersion-corrected density functional theory (DFT) involving (semi)local (PBE-D3) and hybrid exchange-correlation (HSE06-D3) functionals is applied to estimate the lattice enthalpy, entropy, and free energy. The ions solvation free energies are calculated with the SMD-generic-IL solvation model at the M06-2X/6-31+G(d) level of theory under standard conditions. The melting points of ILs computed with the HSE06-D3 functional are in good agreement with the experimental data, with a mean absolute error of 30.5 K and a mean relative error of 8.5%. The model is capable of accurately reproducing the trends in melting points upon variation of alkyl substituents in organic cations and replacement one anion by another. The results verify that the lattice energies of ILs containing polyatomic fluoro-containing anions can be approximated reasonably well using the volume-based thermodynamic approach. However, there is no correlation of the computed lattice energies with molecular volume for ILs containing halide anions. Moreover, entropies of solid ILs follow two different linear relationships with molecular volume for halides and polyatomic fluoro

  14. Estimating the melting point, entropy of fusion, and enthalpy of fusion of organic compounds via SPARC

    Science.gov (United States)

    The entropies of fusion, enthalies of fusion, and melting points of organic compounds can be estimated through three models developed using the SPARC (SPARC Performs Automated Reasoning in Chemistry) platform. The entropy of fusion is modeled through a combination of interaction ...

  15. Palm-Based Standard Reference Materials for Iodine Value and Slip Melting Point

    Directory of Open Access Journals (Sweden)

    Azmil Haizam Ahmad Tarmizi

    2008-01-01

    Full Text Available This work described study protocols on the production of Palm-Based Standard Reference Materials for iodine value and slip melting point. Thirty-three laboratories collaborated in the inter-laboratory proficiency tests for characterization of iodine value, while thirty-two laboratories for characterization of slip melting point. The iodine value and slip melting point of palm oil, palm olein and palm stearin were determined in accordance to MPOB Test Methods p3.2:2004 and p4.2:2004, respectively. The consensus values and their uncertainties were based on the acceptability of statistical agreement of results obtained from collaborating laboratories. The consensus values and uncertainties for iodine values were 52.63 ± 0.14 Wijs in palm oil, 56.77 ± 0.12 Wijs in palm olein and 33.76 ± 0.18 Wijs in palm stearin. For the slip melting points, the consensus values and uncertainties were 35.6 ± 0.3 ° C in palm oil, 22.7 ± 0.4 ° C in palm olein and 53.4 ± 0.2 ° C in palm stearin. Repeatability and reproducibility relative standard deviations were found to be good and acceptable, with values much lower than that of 10%. Stability of Palm-Based Standard Reference Materials remained stable at temperatures of -20 ° C, 0 ° C, 6 ° C and 24 ° C upon storage for one year.

  16. Melting point gram-atomic volumes and enthalpies of atomization for liquid elements

    International Nuclear Information System (INIS)

    Lamoreaux, R.H.

    1976-01-01

    Values of the gram-atomic volumes and enthalpies of atomization to the monatomic ideal gas state for liquid elements at their melting points are collected to facilitate predictions of the behavior of mixed systems. Estimated values are given for experimentally undetermined quantities

  17. The Relationship between Lattice Enthalpy and Melting Point in Magnesium and Aluminium Oxides. Science Notes

    Science.gov (United States)

    Talbot, Christopher; Yap, Lydia

    2013-01-01

    This "Science Note" presents a study by Christopher Talbot and Lydia Yap, who teach IB Chemistry at Anglo-Chinese School (Independent), Republic of Singapore, to pre-university students. Pre-university students may postulate the correlation between the magnitude of the lattice enthalpy compound and its melting point, since both…

  18. Explaining Melting and Evaporation below Boiling Point. Can Software Help with Particle Ideas?

    Science.gov (United States)

    Papageorgiou, George; Johnson, Philip; Fotiades, Fotis

    2008-01-01

    This paper reports the findings of a study exploring the use of a software package to help pupils understand particulate explanations for melting and evaporation below boiling point. Two matched classes in a primary school in Greece (ages 11-12, n = 16 and 19) were involved in a short intervention of six one hour lessons. Covering the same…

  19. Self-diffusion at the melting point: From H2 and N2 to liquid metals

    International Nuclear Information System (INIS)

    Armstrong, B.H.

    1992-01-01

    A nominal lower bound to the mean free diffusion time at the melting point T m was obtained earlier which provided a factor-two type estimate for self-diffusion coefficients of the alkali halides, alkali metals, eight other metals, and Ar. The argument was based on the classical Uncertainty Principle applied to the solid crystal, whereby maximum-frequency phonons lose validity as collective excitations and degenerate into aperiodic, single-particle diffusive motion at the melting point. Because of the short time scale of this motion, the perfect-gas diffusion equation and true mass can be used to obtain the self-diffusion coefficient in the Debye approximation to the phonon spectrum. This result for the self-diffusion coefficient also yields the scale factor that determines the order of magnitude of liquid self-diffusion coefficients, which has long been an open question. The earlier theory is summarized and clarified, and the results extended to the more complex molecular liquids H 2 and N 2 . It is also demonstrated that combining Lindemann's melting law with the perfect-gas diffusion equation estimate yields a well-known empirical expression for liquid-metal self-diffusion at T m . Validity of the self-diffusion estimate over a melting temperature range from 14 to more than 1,300 K and over a wide variety of crystals provides strong confirmation for the existence of the specialized diffusive motion at the melting point, as well as confirmation of a relation between the phonon spectrum of the solid crystal and diffusive motion in the melt. 21 refs., 2 tabs

  20. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.com [Department of Physics, College of Science, University of Salahaddin-Erbil, Arbil, Kurdistan (Iraq)

    2012-11-15

    Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å{sup 3} for bulk to 57 Å{sup 3} for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10{sup −6} K{sup −1} for a bulk crystal down to a minimum value of 0.1 × 10{sup −6} K{sup −1} for a 6 nm diameter nanoparticle.

  1. Models for mean bonding length, melting point and lattice thermal expansion of nanoparticle materials

    International Nuclear Information System (INIS)

    Omar, M.S.

    2012-01-01

    Graphical abstract: Three models are derived to explain the nanoparticles size dependence of mean bonding length, melting temperature and lattice thermal expansion applied on Sn, Si and Au. The following figures are shown as an example for Sn nanoparticles indicates hilly applicable models for nanoparticles radius larger than 3 nm. Highlights: ► A model for a size dependent mean bonding length is derived. ► The size dependent melting point of nanoparticles is modified. ► The bulk model for lattice thermal expansion is successfully used on nanoparticles. -- Abstract: A model, based on the ratio number of surface atoms to that of its internal, is derived to calculate the size dependence of lattice volume of nanoscaled materials. The model is applied to Si, Sn and Au nanoparticles. For Si, that the lattice volume is increases from 20 Å 3 for bulk to 57 Å 3 for a 2 nm size nanocrystals. A model, for calculating melting point of nanoscaled materials, is modified by considering the effect of lattice volume. A good approach of calculating size-dependent melting point begins from the bulk state down to about 2 nm diameter nanoparticle. Both values of lattice volume and melting point obtained for nanosized materials are used to calculate lattice thermal expansion by using a formula applicable for tetrahedral semiconductors. Results for Si, change from 3.7 × 10 −6 K −1 for a bulk crystal down to a minimum value of 0.1 × 10 −6 K −1 for a 6 nm diameter nanoparticle.

  2. New Approach in Filling of Fixed-Point Cells: Case Study of the Melting Point of Gallium

    Science.gov (United States)

    Bojkovski, J.; Hiti, M.; Batagelj, V.; Drnovšek, J.

    2008-02-01

    The typical way of constructing fixed-point cells is very well described in the literature. The crucible is loaded with shot, or any other shape of pure metal, inside an argon-filled glove box. Then, the crucible is carefully slid into a fused-silica tube that is closed at the top with an appropriate cap. After that, the cell is removed from the argon glove box and melted inside a furnace while under vacuum or filled with an inert gas like argon. Since the metal comes as shot, or in some other shape such as rods of various sizes, and takes more volume than the melted material, it is necessary to repeat the procedure until a sufficient amount of material is introduced into the crucible. With such a procedure, there is the possibility of introducing additional impurities into the pure metal with each cycle of melting the material and putting it back into the glove box to fill the cell. Our new approach includes the use of a special, so-called dry-box system, which is well known in chemistry. The atmosphere inside the dry box contains less than 20 ppm of water and less than 3 ppm of oxygen. Also, the size of the dry box allows it to contain a furnace for melting materials, not only for gallium but for higher-temperature materials as well. With such an approach, the cell and all its parts (pure metal, graphite, fused-silica tube, and cap) are constantly inside the controlled atmosphere, even while melting the material and filling the crucible. With such a method, the possibility of contaminating the cell during the filling process is minimized.

  3. Evaluation of methods for characterizing the melting curves of a high temperature cobalt-carbon fixed point to define and determine its melting temperature

    Science.gov (United States)

    Lowe, David; Machin, Graham

    2012-06-01

    The future mise en pratique for the realization of the kelvin will be founded on the melting temperatures of particular metal-carbon eutectic alloys as thermodynamic temperature references. However, at the moment there is no consensus on what should be taken as the melting temperature. An ideal melting or freezing curve should be a completely flat plateau at a specific temperature. Any departure from the ideal is due to shortcomings in the realization and should be accommodated within the uncertainty budget. However, for the proposed alloy-based fixed points, melting takes place over typically some hundreds of millikelvins. Including the entire melting range within the uncertainties would lead to an unnecessarily pessimistic view of the utility of these as reference standards. Therefore, detailed analysis of the shape of the melting curve is needed to give a value associated with some identifiable aspect of the phase transition. A range of approaches are or could be used; some purely practical, determining the point of inflection (POI) of the melting curve, some attempting to extrapolate to the liquidus temperature just at the end of melting, and a method that claims to give the liquidus temperature and an impurity correction based on the analytical Scheil model of solidification that has not previously been applied to eutectic melting. The different methods have been applied to cobalt-carbon melting curves that were obtained under conditions for which the Scheil model might be valid. In the light of the findings of this study it is recommended that the POI continue to be used as a pragmatic measure of temperature but where required a specified limits approach should be used to define and determine the melting temperature.

  4. Inverse shear viscosity (fluidity) scaled with melting point properties: Almost 'universal' behaviour of heavier alkalis

    International Nuclear Information System (INIS)

    Tankeshwar, K.; March, N.H.

    1997-07-01

    Some numerical considerations relating to the potential of mean force at the melting point of Rb metal are first presented, which argue against the existence of a well defined activation energy for the shear viscosity of this liquid. Therefore, a scaling approach is developed, based on a well established formula for the viscosity η m of sp liquid metals at their melting points T m . This approach is shown to lead to an 'almost' universal plot of scaled fluidity η -1 η m against (T/T m ) 1/2 for the liquid alkali metals, excluding Li. This metal is anomalous because it is a strong scattering liquid, in marked contrast to the other alkali metals. (author). 9 refs, 3 figs, 1 tab

  5. Degradation mechanism and thermal stability of urea nitrate below the melting point

    International Nuclear Information System (INIS)

    Desilets, Sylvain; Brousseau, Patrick; Chamberland, Daniel; Singh, Shanti; Feng, Hongtu; Turcotte, Richard; Anderson, John

    2011-01-01

    Highlights: → Decomposition mechanism of urea nitrate. → Spectral characterization of the decomposition mechanism. → Thermal stability of urea nitrate at 50, 70 and 100 o C. → Chemical balance of decomposed products released. - Abstract: Aging and degradation of urea nitrate below the melting point, at 100 o C, was studied by using thermal analysis and spectroscopic methods including IR, Raman, 1 H and 13 C NMR techniques. It was found that urea nitrate was completely degraded after 72 h at 100 o C into a mixture of solids (69%) and released gaseous species (31%). The degradation mechanism below the melting point was clearly identified. The remaining solid mixture was composed of ammonium nitrate, urea and biuret while unreacted residual nitric and isocyanic acids as well as traces of ammonia were released as gaseous species at 100 o C. The thermal stability of urea nitrate, under extreme storage conditions (50 o C), was also examined by isothermal nano-calorimetry.

  6. Determination of melting point of vegetable oils and fats by differential scanning calorimetry (DSC technique.

    Directory of Open Access Journals (Sweden)

    Nassu, Renata Tieko

    1999-02-01

    Full Text Available Melting point of fats is used to characterize oils and fats and is related to their physical properties, such as hardness and thermal behaviour. The present work shows the utilization of DSC technique on the determination of melting point of fats. In a comparison with softening point (AOCS method Cc 3-25, DSC values were higher than those obtained by AOCS method. It has occurred due to the fact that values obtained by DSC technique were taken when the fat had melted completely. DSC was also useful for determining melting point of liquid oils, such as soybean and cottonseed ones.

    El punto de fusión de grasas es usado para caracterizar aceites y grasas, y está relacionado con sus propiedades físicas, tales como dureza y comportamiento térmico. El presente trabajo muestra la utilización de la técnica de Calorimetría Diferencial de Barrido (DSC en la determinación del punto de fusión de grasas. En comparación con el punto de ablandamiento (AOCS método Cc 3-25, los valores de DSC fueron más altos que los obtenidos por los métodos de AOCS. Esto ha ocurrido debido al hecho que los valores obtenidos por la técnica de DSC fueron tomados cuando la grasa había fundido completamente. DSC fue también útil para determinar puntos de fusión de aceites líquidos, tales como los de soya y algodón.

  7. Palm-Based Standard Reference Materials for Iodine Value and Slip Melting Point

    Directory of Open Access Journals (Sweden)

    Azmil Haizam Ahmad Tarmizi

    2008-01-01

    Full Text Available This work described study protocols on the production of Palm-Based Standard Reference Materials for iodine value and slip melting point. Thirty-three laboratories collaborated in the inter-laboratory proficiency tests for characterization of iodine value, while thirty-two laboratories for characterization of slip melting point. The iodine value and slip melting point of palm oil, palm olein and palm stearin were determined in accordance to MPOB Test Methods p3.2:2004 and p4.2:2004, respectively. The consensus values and their uncertainties were based on the acceptability of statistical agreement of results obtained from collaborating laboratories. The consensus values and uncertainties for iodine values were 52.63 ± 0.14 Wijs in palm oil, 56.77 ± 0.12 Wijs in palm olein and 33.76 ± 0.18 Wijs in palm stearin. For the slip melting points, the consensus values and uncertainties were 35.6 ± 0.3 °C in palm oil, 22.7 ± 0.4 °C in palm olein and 53.4 ± 0.2 °C in palm stearin. Repeatability and reproducibility relative standard deviations were found to be good and acceptable, with values much lower than that of 10%. Stability of Palm-Based Standard Reference Materials remained stable at temperatures of –20 °C, 0 °C, 6 °C and 24 °C upon storage for one year.

  8. SHORT COMMUNICATION: Correlation between the Resistance Ratios of Platinum Resistance Thermometers at the Melting Point of Gallium and the Triple Point of Mercury

    Science.gov (United States)

    Singh, Y. P.; Maas, H.; Edler, F.; Zaidi, Z. H.

    1994-01-01

    A set of resistance ratios (W) for platinum resistance thermometers was obtained at the triple point of Hg and the melting point of Ga in order to study their relationship. It was found that using measured values for one of the fixed points, a linear equation will predict the value of the other. These measurements also indicate that the fixed points of Hg and of Ga are inconsistent by about 1,5 mK in the sense that either the melting point of Ga or the triple point of Hg was assigned too high a value on the ITS-90.

  9. Melting heat transfer in boundary layer stagnation-point flow towards a stretching/shrinking sheet

    International Nuclear Information System (INIS)

    Bachok, Norfifah; Ishak, Anuar; Pop, Ioan

    2010-01-01

    An analysis is carried out to study the steady two-dimensional stagnation-point flow and heat transfer from a warm, laminar liquid flow to a melting stretching/shrinking sheet. The governing partial differential equations are converted into ordinary differential equations by similarity transformation, before being solved numerically using the Runge-Kutta-Fehlberg method. Results for the skin friction coefficient, local Nusselt number, velocity profiles as well as temperature profiles are presented for different values of the governing parameters. Effects of the melting parameter, stretching/shrinking parameter and Prandtl number on the flow and heat transfer characteristics are thoroughly examined. Different from a stretching sheet, it is found that the solutions for a shrinking sheet are non-unique.

  10. Evaluation of thermal physical properties for fast reactor fuels. Melting point and thermal conductivities

    International Nuclear Information System (INIS)

    Kato, Masato; Morimoto, Kyoichi; Komeno, Akira; Nakamichi, Shinya; Kashimura, Motoaki; Abe, Tomoyuki; Uno, Hiroki; Ogasawara, Masahiro; Tamura, Tetsuya; Sugata, Hirotada; Sunaoshi, Takeo; Shibata, Kazuya

    2006-10-01

    Japan Atomic Energy Agency has developed a fast breeder reactor (FBR), and plutonium and uranium mixed oxide (MOX) having low density and 20-30%Pu content has used as a fuel of the FBR, Monju. In plutonium, Americium has been accumulated during long-term storage, and Am content will be increasing up to 2-3% in the MOX. It is essential to evaluate the influence of Am content on physical properties of MOX on the development of FBR in the future. In this study melting points and thermal conductivities which are important data on the fuel design were measured systematically in wide range of composition, and the effects of Am accumulated were evaluated. The solidus temperatures of MOX were measured as a function of Pu content, oxygen to metal ratio (O/M) and Am content using thermal arrest technique. The sample was sealed in a tungsten capsule in vacuum for measuring solidus temperature. In the measurements of MOX with Pu content of more than 30%, a rhenium inner capsule was used to prevent the reaction between MOX and tungsten. In the results, it was confirmed that the melting points of MOX decrease with as an increase of Pu content and increase slightly with a decrease of O/M ratio. The effect of Am content on the fuel design was negligible small in the range of Am content up to 3%. Thermal conductivities of MOX were evaluated from thermal diffusivity measured by laser flash method and heat capacity calculated by Neumann- Kopp's law. The thermal conductivity of MOX decreased slightly in the temperature of less than 1173K with increasing Am content. The effect of Am accumulated in long-term storage fuel was evaluated from melting points and thermal conductivities measured in this study. It is concluded that the increase of Am in the fuel barely affect the fuel design in the range of less than 3%Am content. (author)

  11. A noise thermometry investigation of the melting point of gallium at the NIM

    Science.gov (United States)

    Zhang, J. T.; Xue, S.

    2006-06-01

    This paper describes a study of the melting point of gallium with the new NIM Johnson noise thermometer (JNT). The new thermometer adopts the structure of switching correlator and commutator with the reference resistor maintained at the triple point of water. The electronic system of the new thermometer is basically the same as the current JNT, but the preamplifiers have been improved slightly. This study demonstrates that examining the characteristics of the noise signals in the frequency domain is of critical importance in constructing an improved new thermometer, where a power spectral analysis is found to be critical in establishing appropriate grounding for the new thermometer. The new JNT is tested on measurements of the thermodynamic temperature of the melting point of gallium, which give the thermodynamic temperature of 302.9160 K, with an overall integration time of 190 h and a combined standard uncertainty of 9.4 mK. The uncertainty analysis indicates that a standard combined uncertainty of 3 mK could be achieved with the new thermometer over an integration period of 1750 h.

  12. Fluid–fluid–solid triple point on melting curves at high temperatures

    International Nuclear Information System (INIS)

    Norman, G E; Saitov, I M

    2016-01-01

    An analysis is presented of experimental data where fluid-fluid phase transitions are observed for different substances at high temperatures with triple points on melting curves. Viscosity drops point to the structural character of the transition, whereas conductivity jumps remind of both semiconductor-to-metal and plasma nature. The slope of the phase equilibrium dependencies of pressure on temperature and the consequent change of the specific volume, which follows from the Clapeyron-Clausius equation, are discussed. P(V, T) surfaces are presented and discussed for the phase transitions considered in the vicinity of the triple points. The cases of abnormal P(T) dependencies on curves of phase equilibrium are in the focus of discussion. In particular, a P(V, T) surface is presented when both fluid-fluid and melting P(T) curves are abnormal. Particular attention is paid to warm dense hydrogen and deuterium, where remarkable contradictions exist between data of different authors. The possible connection of the P(V, T) surface peculiarities with the experimental data uncertainties is outlined. (paper)

  13. Pressure Dependence of Molar Volume near the Melting Point in Benzene

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The pressure dependence of the molar volume was at constant temperatures close to the melting point in benzene. The molar volume of benzene was calculated using experimental data for the thermal expansivity for constant temperatures of 25℃, 28.5℃, 40℃, and 51℃ at various pressures for both the solid and liquid phases. The predictions are in good agreement with the observed volumes in both the solid and liquid phases of benzene. The predicted values of the molar volume for a constant temperature of 28.5℃ in the liquid phase of benzene agree well with experimental data in the literature.

  14. Theoretical Understanding the Relations of Melting-point Determination Methods from Gibbs Thermodynamic Surface and Applications on Melting Curves of Lower Mantle Minerals

    Science.gov (United States)

    Yin, K.; Belonoshko, A. B.; Zhou, H.; Lu, X.

    2016-12-01

    The melting temperatures of materials in the interior of the Earth has significant implications in many areas of geophysics. The direct calculations of the melting point by atomic simulations would face substantial hysteresis problem. To overcome the hysteresis encountered in the atomic simulations there are a few different melting-point determination methods available nowadays, which are founded independently, such as the free energy method, the two-phase or coexistence method, and the Z method, etc. In this study, we provide a theoretical understanding the relations of these methods from a geometrical perspective based on a quantitative construction of the volume-entropy-energy thermodynamic surface, a model first proposed by J. Willard Gibbs in 1873. Then combining with an experimental data and/or a previous melting-point determination method, we apply this model to derive the high-pressure melting curves for several lower mantle minerals with less computational efforts relative to using previous methods only. Through this way, some polyatomic minerals at extreme pressures which are almost unsolvable before are calculated fully from first principles now.

  15. Effect of nitrogen pressure on melting point of ZrNsub(x)

    International Nuclear Information System (INIS)

    Eronyan, M.A.; Avarbeh, R.G.; Nikol'skaya, T.A.

    1976-01-01

    The investigations were performed in an airtight water-cooled chamber in the nitrogen pressure range of 10 -3 -100 atm and at 2600-3700 0 C. The nitrogen pressure in the range 10 -3 -10 -2 atm was measured by a differential oil-pressure gauge, in the range 10 -2 -10 -1 atm by a differential mercury-pressure gauge, and in the range from 0.1 to 100 atm by a membrane manometer. The temperature of the specimens was measured to within +-1% by an optical pyrometer. The nitrogen and oxygen contents of ZrNsub(x) were determined by extraction gas chromatography to within 0.2 and 0.05 wt.% for nitrogen and oxygen, respectively. The dependence of the incongruent melting point of ZrNsub(x) on the equilibrium pressure of nitrogen in the range 10 -3 -60 atm was established. It was found that the pressure of oxygen as impurity in ZrNsub(x) greatly reduces its melting point

  16. Melting heat transfer in stagnation point flow of carbon nanotubes towards variable thickness surface

    Directory of Open Access Journals (Sweden)

    T. Hayat

    2016-01-01

    Full Text Available This work concentrates on the mathematical modeling for stagnation point flow of nanofluids over an impermeable stretching sheet with variable thickness. Carbon nanotubes [single-wall carbon nanotubes (SWCNTs and multi-wall carbon nanotubes (MWCNTs] as the nanoparticles are utilized. Water and kerosene oil are taken as the base fluids. Heat transfer through melting effect is discussed. Transformation procedure is adapted to obtain the non-linear ordinary differential equations from the fundamental laws of mass, linear momentum and energy. The optimal values of convergence control parameters and corresponding individual and total residual errors for SWCNTs and MWCNTs are computed by means of homotopy analysis method (HAM based BVPh 2.0. Characteristics of different involved parameters on the velocity, temperature, skin friction coefficient and Nusselt number are discussed. Higher velocity profile is observed for wall thickness parameter in case of water carbon nanotubes when compared with the kerosene oil carbon nanotubes.

  17. Molten salt oxidation as a technique for decommissioning: selection of low melting point salt mixtures

    International Nuclear Information System (INIS)

    Lainetti, Paulo E.O.; Garcia, Vitor F.; Benvegnu, Guilherme

    2013-01-01

    During the 70 and 80 years, IPEN built several facilities in pilot scale, destined to the technological domain of the Nuclear Fuel Cycle. In the nineties, radical changes in the Brazilian nuclear policy determined the interruption of the activities and the shut-down of pilot plants. Nowadays, IPEN has been facing the problem of the dismantling and decommissioning of its Nuclear Fuel Cycle old facilities. The facility CELESTE-I of the IPEN is a laboratory where reprocessing studies were accomplished during the decade of 80 and in the beginning of the 90s. The last operations occurred in 92-93. The research activities generated radioactive wastes in the form of organic and aqueous solutions of different compositions and concentrations. For the treatment of these liquid wastes it was proposed a study of waste thermal decomposition based on the molten salt oxidation process.Decomposition tests of different organic wastes have been performed in laboratory equipment developed at IPEN, in the range of temperatures of 900 to 1020 deg C, demonstrating the complete oxidation of the compounds. The reduction of the process temperatures would be of crucial importance. Besides this, the selection of lower melting point salt mixtures would have an important impact in the reduction of equipment costs. Several experiments were performed to determine the most suitable salt mixtures, optimizing costs and melting temperatures as low as possible. This paper describes the main characteristics of the molten salt oxidation process, besides the selection of salt mixtures of binary and ternary compositions, respectively Na 2 CO 3 - NaOH and Na 2 CO 3 - K 2 CO 3 -Li 2 CO 3 . (author)

  18. CADASTER QSPR Models for Predictions of Melting and Boiling Points of Perfluorinated Chemicals.

    Science.gov (United States)

    Bhhatarai, Barun; Teetz, Wolfram; Liu, Tao; Öberg, Tomas; Jeliazkova, Nina; Kochev, Nikolay; Pukalov, Ognyan; Tetko, Igor V; Kovarich, Simona; Papa, Ester; Gramatica, Paola

    2011-03-14

    Quantitative structure property relationship (QSPR) studies on per- and polyfluorinated chemicals (PFCs) on melting point (MP) and boiling point (BP) are presented. The training and prediction chemicals used for developing and validating the models were selected from Syracuse PhysProp database and literatures. The available experimental data sets were split in two different ways: a) random selection on response value, and b) structural similarity verified by self-organizing-map (SOM), in order to propose reliable predictive models, developed only on the training sets and externally verified on the prediction sets. Individual linear and non-linear approaches based models developed by different CADASTER partners on 0D-2D Dragon descriptors, E-state descriptors and fragment based descriptors as well as consensus model and their predictions are presented. In addition, the predictive performance of the developed models was verified on a blind external validation set (EV-set) prepared using PERFORCE database on 15 MP and 25 BP data respectively. This database contains only long chain perfluoro-alkylated chemicals, particularly monitored by regulatory agencies like US-EPA and EU-REACH. QSPR models with internal and external validation on two different external prediction/validation sets and study of applicability-domain highlighting the robustness and high accuracy of the models are discussed. Finally, MPs for additional 303 PFCs and BPs for 271 PFCs were predicted for which experimental measurements are unknown. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Improvement of gel strength and melting point of fish gelatin by addition of coenhancers using response surface methodology.

    Science.gov (United States)

    Koli, Jayappa M; Basu, Subrata; Nayak, Binay B; Kannuchamy, Nagalakshmi; Gudipati, Venkateshwarlu

    2011-08-01

    Fish gelatin is a potential alternative to mammalian gelatin. However, poor gel strength and low melting point limit its applications. The study was aimed at improving these properties by adding coenhancers in the range obtained from response surface methodology (RSM) by using Box-Behnken design. Three different coenhancers, MgSO₄, sucrose, and transglutaminase were used as the independent variables for improving the gel strength and melting point of gelatin extracted from Tiger-toothed croaker (Otolithes ruber). Addition of coenhancers at different combinations resulted gel strength and melting point in the range of 150.5 to 240.5 g and 19.5 to 22.5 °C, respectively. The optimal concentrations of coenhancers for predicted maximum gel strength (242.8 g) obtained by RSM were 0.23 M MgSO₄, 12.60% sucrose (w/v), and 5.92 mg/g transglutaminase and for predicted maximum melting point (22.57 °C), the values were 0.24 M MgSO₄, 10.44% sucrose (w/v), and 5.72 mg/g transglutaminase. By addition of coenhancers at these optimal concentrations in verification experiments, the gel strength and melting point were improved from 170 to 240.89 g and 20.3 to 22.7 °C, respectively. These experimental values agreed well with the predicted values demonstrating the fitness of the models. Results from the present study clearly revealed that the addition of coenhancers at a particular combination can improve the gel strength and melting point of fish gelatin to enhance its range of applications. There is a growing interest in the use of fish gelatin as an alternative to mammalian gelatin. However, poor gel strength and low melting point of fish gelatin have limited its commercial applications. The gel strength and melting point of fish gelatin can be increased by incorporation of coenhancers such as magnesium sulphate, sucrose, and transglutaminase. Results of this work help to produce the fish gelatin suitable for wide range of applications in the food industry. © 2011 Institute

  20. Creating Stiff, Tough, and Functional Hydrogel Composites with Low-Melting-Point Alloys.

    Science.gov (United States)

    Takahashi, Riku; Sun, Tao Lin; Saruwatari, Yoshiyuki; Kurokawa, Takayuki; King, Daniel R; Gong, Jian Ping

    2018-04-01

    Reinforcing hydrogels with a rigid scaffold is a promising method to greatly expand the mechanical and physical properties of hydrogels. One of the challenges of creating hydrogel composites is the significant stress that occurs due to swelling mismatch between the water-swollen hydrogel matrix and the rigid skeleton in aqueous media. This stress can cause physical deformation (wrinkling, buckling, or fracture), preventing the fabrication of robust composites. Here, a simple yet versatile method is introduced to create "macroscale" hydrogel composites, by utilizing a rigid reinforcing phase that can relieve stress-induced deformation. A low-melting-point alloy that can transform from a load-bearing solid state to a free-deformable liquid state at relatively low temperature is used as a reinforcing skeleton, which enables the release of any swelling mismatch, regardless of the matrix swelling degree in liquid media. This design can generally provide hydrogels with hybridized functions, including excellent mechanical properties, shape memory, and thermal healing, which are often difficult or impossible to achieve with single-component hydrogel systems. Furthermore, this technique enables controlled electrochemical reactions and channel-structure templating in hydrogel matrices. This work may play an important role in the future design of soft robots, wearable electronics, and biocompatible functional materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Temperature calibration procedure for thin film substrates for thermo-ellipsometric analysis using melting point standards

    International Nuclear Information System (INIS)

    Kappert, Emiel J.; Raaijmakers, Michiel J.T.; Ogieglo, Wojciech; Nijmeijer, Arian; Huiskes, Cindy; Benes, Nieck E.

    2015-01-01

    Highlights: • Facile temperature calibration method for thermo-ellipsometric analysis. • The melting point of thin films of indium, lead, zinc, and water can be detected by ellipsometry. • In-situ calibration of ellipsometry hot stage, without using any external equipment. • High-accuracy temperature calibration (±1.3 °C). - Abstract: Precise and accurate temperature control is pertinent to studying thermally activated processes in thin films. Here, we present a calibration method for the substrate–film interface temperature using spectroscopic ellipsometry. The method is adapted from temperature calibration methods that are well developed for thermogravimetric analysis and differential scanning calorimetry instruments, and is based on probing a transition temperature. Indium, lead, and zinc could be spread on a substrate, and the phase transition of these metals could be detected by a change in the Ψ signal of the ellipsometer. For water, the phase transition could be detected by a loss of signal intensity as a result of light scattering by the ice crystals. The combined approach allowed for construction of a linear calibration curve with an accuracy of 1.3 °C or lower over the full temperature range

  2. Point, surface and volumetric heat sources in the thermal modelling of selective laser melting

    Science.gov (United States)

    Yang, Yabin; Ayas, Can

    2017-10-01

    Selective laser melting (SLM) is a powder based additive manufacturing technique suitable for producing high precision metal parts. However, distortions and residual stresses within products arise during SLM because of the high temperature gradients created by the laser heating. Residual stresses limit the load resistance of the product and may even lead to fracture during the built process. It is therefore of paramount importance to predict the level of part distortion and residual stress as a function of SLM process parameters which requires a reliable thermal modelling of the SLM process. Consequently, a key question arises which is how to describe the laser source appropriately. Reasonable simplification of the laser representation is crucial for the computational efficiency of the thermal model of the SLM process. In this paper, first a semi-analytical thermal modelling approach is described. Subsequently, the laser heating is modelled using point, surface and volumetric sources, in order to compare the influence of different laser source geometries on the thermal history prediction of the thermal model. The present work provides guidelines on appropriate representation of the laser source in the thermal modelling of the SLM process.

  3. New encapsulation method using low-melting-point alloy for sealing micro heat pipes

    Energy Technology Data Exchange (ETDEWEB)

    Li, Congming; Wang, Xiaodong; Zhou, Chuanpeng; Luo, Yi; Li, Zhixin; Li, Sidi [Dalian University of Technology, Dalian (China)

    2017-06-15

    This study proposed a method using Low-melting-point alloy (LMPA) to seal Micro heat pipes (MHPs), which were made of Si substrates and glass covers. Corresponding MHP structures with charging and sealing channels were designed. Three different auxiliary structures were investigated to study the sealability of MHPs with LMPA. One structure is rectangular and the others are triangular with corner angles of 30° and 45°, respectively. Each auxiliary channel for LMPA is 0.5 mm wide and 135 μm deep. LMPA was heated to molten state, injected to channels, and then cooled to room temperature. According to the material characteristic of LMPA, the alloy should swell in the following 12 hours to form strong interaction force between LMPA and Si walls. Experimental results show that the flow speed of liquid LMPA in channels plays an important role in sealing MHPs, and the sealing performance of triangular structures is always better than that of rectangular structure. Therefore, triangular structures are more suitable in sealing MHPs than rectangular ones. LMPA sealing is a plane packaging method that can be applied in the thermal management of high-power IC device and LEDs. Meanwhile, implanting in commercialized fabrication of MHP is easy.

  4. New encapsulation method using low-melting-point alloy for sealing micro heat pipes

    International Nuclear Information System (INIS)

    Li, Congming; Wang, Xiaodong; Zhou, Chuanpeng; Luo, Yi; Li, Zhixin; Li, Sidi

    2017-01-01

    This study proposed a method using Low-melting-point alloy (LMPA) to seal Micro heat pipes (MHPs), which were made of Si substrates and glass covers. Corresponding MHP structures with charging and sealing channels were designed. Three different auxiliary structures were investigated to study the sealability of MHPs with LMPA. One structure is rectangular and the others are triangular with corner angles of 30° and 45°, respectively. Each auxiliary channel for LMPA is 0.5 mm wide and 135 μm deep. LMPA was heated to molten state, injected to channels, and then cooled to room temperature. According to the material characteristic of LMPA, the alloy should swell in the following 12 hours to form strong interaction force between LMPA and Si walls. Experimental results show that the flow speed of liquid LMPA in channels plays an important role in sealing MHPs, and the sealing performance of triangular structures is always better than that of rectangular structure. Therefore, triangular structures are more suitable in sealing MHPs than rectangular ones. LMPA sealing is a plane packaging method that can be applied in the thermal management of high-power IC device and LEDs. Meanwhile, implanting in commercialized fabrication of MHP is easy.

  5. 46 CFR 153.488 - Design and equipment for tanks carrying high melting point NLSs: Category B.

    Science.gov (United States)

    2010-10-01

    ... (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS... equipment for tanks carrying high melting point NLSs: Category B. Unless waived under § 153.491, for a ship to have its Certificate of Inspection or Certificate of Compliance endorsed allowing a tank to carry...

  6. Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

    Science.gov (United States)

    Tsang, Floris Y.

    1980-01-01

    Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

  7. Fabrication and Optimization of a PAGATA Gel Dosimeter: Increasing the Melting Point of the PAGAT Gel Dosimeter with Agarose Additive

    Directory of Open Access Journals (Sweden)

    Bakhtiar Azadbakht

    2010-12-01

    Full Text Available Introduction: The PAGAT polymer gel dosimeter melts at 30 ˚C and even at room temperature during the summer, so it needs to be kept in a cool place such as a refrigerator. To increase the stability of the PAGAT gel, different amounts of agarose were added to the PAGAT gel composition and the PAGATA gel was manufactured. Material and Methods: The PAGATA gel vials were irradiated using a Co-60 machine. Then, the samples were evaluated using a 1.5 T Siemens MRI scanner. The ingredients of the PAGATA normoxic gel dosimeter were 4.5% N-N' methylen-bis-acrylamide, 4.5% acrylamide, 4.5% gelatine, 5 mM tetrakis (THPC, 0.01 mM hydroquinone (HQ, 0.5% agarose and 86% de-ionized water (HPLC. Results: Melting point and sensitivity of the PAGAT gel dosimeter with addition of 0.0, 0.3, 0.5, 1.0, 1.5 and 2.0% of agarose were measured, in which the melting points were increased to 30, 82, 86, 88, 89 and 90°C and their sensitivities found to be 0.113, 0.1059, 0.125, 0.122, 0.115 and 0.2  respectively. Discussion and Conclusions: Adding agarose increased the sensitivity and background R2 of the evaluated samples. The optimum amount of agarose was found to be 0.5% regarding these parameters and also the melting point of the gel dosimeter. A value of 0.5% agarose was found to be an optimum value considering the increase of sensitivity to 0.125 and melting point to 86°C but at the expense of increasing the background R2 to 4.530.

  8. Study on the Melting Point Depression of Tin Nanoparticles Manufactured by Modified Evaporation Method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun Jin; Beak, Il Kwon; Kim, Kyu Han; Jang, Seok Pil [Korea Aerospace University, Goyang (Korea, Republic of)

    2014-08-15

    In the present study, the melting temperature depression of Sn nanoparticles manufactured using the modified evaporation method was investigated. For this purpose, a modified evaporation method with mass productivity was developed. Using the manufacturing process, Sn nanoparticles of 10 nm size was manufactured in benzyl alcohol solution to prevent oxidation. To examine the morphology and size distribution of the nanonoparticles, a transmission electron microscope was used. The melting temperature of the Sn nanoparticles was measured using a Differential scanning calorimetry (DSC) which can calculate the endothermic energy during the phase changing process and an X-ray photoelectron spectroscopy (XPS) used for observing the manufactured Sn nanoparticle compound. The melting temperature of the Sn nanoparticles was observed to be 129 ℃, which is 44 ℃ lower than that of the bulk material. Finally, the melting temperature was compared with the Gibbs Thomson and Lai's equations, which can predict the melting temperature according to the particle size. Based on the experimental results, the melting temperature of the Sn nanoparticles was found to match well with those recommended by the Lai's equation.

  9. Steady distribution structure of point defects near crystal-melt interface under pulling stop of CZ Si crystal

    Science.gov (United States)

    Abe, T.; Takahashi, T.; Shirai, K.

    2017-02-01

    In order to reveal a steady distribution structure of point defects of no growing Si on the solid-liquid interface, the crystals were grown at a high pulling rate, which Vs becomes predominant, and the pulling was suddenly stopped. After restoring the variations of the crystal by the pulling-stop, the crystals were then left in prolonged contact with the melt. Finally, the crystals were detached and rapidly cooled to freeze point defects and then a distribution of the point defects of the as-grown crystals was observed. As a result, a dislocation loop (DL) region, which is formed by the aggregation of interstitials (Is), was formed over the solid-liquid interface and was surrounded with a Vs-and-Is-free recombination region (Rc-region), although the entire crystals had been Vs rich in the beginning. It was also revealed that the crystal on the solid-liquid interface after the prolonged contact with the melt can partially have a Rc-region to be directly in contact with the melt, unlike a defect distribution of a solid-liquid interface that has been growing. This experimental result contradicts a hypothesis of Voronkov's diffusion model, which always assumes the equilibrium concentrations of Vs and Is as the boundary condition for distribution of point defects on the growth interface. The results were disscussed from a qualitative point of view of temperature distribution and thermal stress by the pulling-stop.

  10. A preliminary view on adsorption of organics on ice at temperatures close to melting point

    Science.gov (United States)

    Kong, Xiangrui; Waldner, Astrid; Orlando, Fabrizio; Artiglia, Luca; Ammann, Markus; Bartels-Rausch, Thorsten

    2016-04-01

    -level spectroscopies to reveal the behaviour of adsorption and dissociation on ice. Additionally, pure ice and amine doped ice will be compared for their surface structure change at different temperatures, which will indicate the differences of surface disordering caused by different factors. For instance, we will have a chance to know better if impurities will cause local disordering, i.e. forming hydration shell, which challenges the traditional picture of a homogenous disordered doped ice surface. The findings of this study could not only improve our understanding of how acidic organics adsorb to ice, and of their chemical properties on ice, but also have potentials to know better the behaviour of pure ice at temperatures approaching to the melting point.

  11. Progress of HDDR NdFeB powders modulated by the diffusion of low melting point elements and their alloys

    Directory of Open Access Journals (Sweden)

    Lyu Meng

    2017-12-01

    Full Text Available The hydrogenation-disproportionation-desorption-recombination (HDDR process is the main technique for the fabrication of anisotropic NdFeB magnetic powder.But the intrinsic coercivity (HC of HDDR magnetic powder is low.The addition of heavy rare earth element Dy could improve its HC.It was found that the added Dy is mainly distributed in the grain boundary of HDDR magnets,which regulates grain boundary phase and increases the thickness of grain boundary to improve the anisotropy field (HA and HC of the magnets.However,Dy becomes scarcer and more expensive,which limits the practical application of HDDR magnets.To reduce the dependence on heavy rare earth elements and cost,researchers replaced the heavy rare earth element Dy by low melting point elements and their alloys through grain boundary diffusion technique.During diffusion process low melting point metal exists as liquid phase that increases the diffusion coefficient of diffusion medium as well as its contact area with grain boundary phases of HDDR magnets,and benefits its diffusion along grain boundaries and regulation of grain boundary phase.The modified grain boundary in magnets improve HC.This review paper focuses on the research progress in improving HC of HDDR NdFeB magnets by low melting point elements and their alloys.

  12. Airborne concentrations of toxic metals resulting from the use of low melting point lead alloys to construct radiotherapy shielding

    International Nuclear Information System (INIS)

    McCullough, E.C.; Senjem, D.H.

    1981-01-01

    Determinations of airborne concentrations of lead, cadmium, bismuth, and tin were made above vessels containing a fusible lead alloy (158 0 F melting point) commonly used for construction of radiotherapy blocks. Fume concentrations were determined by collection on a membrane filter and analysis by atomic absorption spectrophotometry. Samples were obtained for alloy temperatures of 200 0 , 400 0 , and 600 0 F. In all instances, concentrations were much lower than the applicable occupational limits for continuous exposure. The results of this study indicate that the use of a vented hood as a means of reducing air concentrations of toxic metals above and near vessels containing low temperature melting point lead allows commonly used in construction of radiotherapy shields appears unjustifiable. However, proper handling procedures should be observed to avoid entry into the body via alternate pathways (e.g., ingestion or skin absorption). Transmission data of a non-cadmium containing lead alloy with a melting point of 203 0 F was ascertained and is reported on

  13. Point, surface and volumetric heat sources in the thermal modelling of selective laser melting

    NARCIS (Netherlands)

    Yang, Y.; Ayas, C.; Brabazon, Dermot; Naher, Sumsun; Ul Ahad, Inam

    2017-01-01

    Selective laser melting (SLM) is a powder based additive manufacturing technique suitable for producing high precision metal parts. However, distortions and residual stresses within products arise during SLM because of the high temperature gradients created by the laser heating. Residual stresses

  14. Calculation procedure for formulating lauric and palmitic fat blends based on the grouping of triacylglycerol melting points

    Directory of Open Access Journals (Sweden)

    B. P. Nusantoro

    2018-01-01

    Full Text Available A calculation procedure for formulating lauric and palmitic fat blends has been developed based on grouping TAG melting points. This procedure offered more flexibility in choosing the initial fats and oils and eventually gave deeper insight into the existing chemical compositions and better prediction on the physicochemical properties and microstructure of the fat blends. The amount of high, medium and low melting TAGs could be adjusted using the given calculation procedure to obtain the desired functional properties in the fat blends. Solid fat contents and melting behavior of formulated fat blends showed particular patterns with respect to ratio adjustments of the melting TAG groups. These outcomes also suggested that both TAG species and their quantity had a significant influence on the crystallization behavior of the fat blends. Palmitic fat blends, in general, were found to exhibit higher SFC values than those of Lauric fat blends. Instead of the similarity in crystal microstructure, lauric fat blends were stabilized at β polymorph while palmitic fat blends were stabilized at β’ polymorph.

  15. Structure and thermal expansion of Lu2O3 and Yb2O3 up to the melting points

    Science.gov (United States)

    Pavlik, Alfred; Ushakov, Sergey V.; Navrotsky, Alexandra; Benmore, Chris J.; Weber, Richard J. K.

    2017-11-01

    Knowledge of thermal expansion and high temperature phase transformations is essential for prediction and interpretation of materials behavior under the extreme conditions of high temperature and intense radiation encountered in nuclear reactors. Structure and thermal expansion of Lu2O3 and Yb2O3 were studied in oxygen and argon atmospheres up to their melting temperatures using synchrotron X-ray diffraction on laser heated levitated samples. Both oxides retained the cubic bixbyite C-type structure in oxygen and argon to melting. In contrast to fluorite-type structures, the increase in the unit cell parameter of Yb2O3 and Lu2O3 with temperature is linear within experimental error from room temperature to the melting point, with mean thermal expansion coefficients (8.5 ± 0.6) · 10-6 K-1 and (7.7 ± 0.6) · 10-6 K-1, respectively. There is no indication of a superionic (Bredig) transition in the C-type structure or of a previously suggested Yb2O3 phase transformation to hexagonal phase prior to melting.

  16. Calculation procedure for formulating lauric and palmitic fat blends based on the grouping of triacylglycerol melting points

    International Nuclear Information System (INIS)

    Nusantoro, B.P.; Yanty, N.A.M.; Van de Walle, D.; Hidayat, C.; Danthine, S.; Dewettinck, K.

    2017-01-01

    A calculation procedure for formulating lauric and palmitic fat blends has been developed based on grouping TAG melting points. This procedure offered more flexibility in choosing the initial fats and oils and eventually gave deeper insight into the existing chemical compositions and better prediction on the physicochemical properties and microstructure of the fat blends. The amount of high, medium and low melting TAGs could be adjusted using the given calculation procedure to obtain the desired functional properties in the fat blends. Solid fat contents and melting behavior of formulated fat blends showed particular patterns with respect to ratio adjustments of the melting TAG groups. These outcomes also suggested that both TAG species and their quantity had a significant influence on the crystallization behavior of the fat blends. Palmitic fat blends, in general, were found to exhibit higher SFC values than those of Lauric fat blends. Instead of the similarity in crystal microstructure, lauric fat blends were stabilized at β polymorph while palmitic fat blends were stabilized at β’ polymorph. [es

  17. On the yield of cold and ultracold neutrons for liquid hydrogen at low temperatures near the melting point

    CERN Document Server

    Morishima, N

    1999-01-01

    The neutron scattering cross sections for liquid hydrogen in the temperature range from the melting point to the boiling point are calculated. It is shown that lowering the temperature results in a significant increase in the yield of cold neutrons: for instance, a 44% increase for an incident neutron energy of 19.4 meV. The major cause of this increment is the para-to-ortho transition of a hydrogen molecule though accompanied by an appreciable increase in the density. The results of the cold- and ultracold-neutron yields are discussed in connection with the experimental results of Altarev et al. at the WWR-M reactor.

  18. Surface Observation and Pore Size Analyses of Polypropylene/Low-Melting Point Polyester Filter Materials: Influences of Heat Treatment

    Directory of Open Access Journals (Sweden)

    Lin Jia-Horng

    2016-01-01

    Full Text Available This study proposes making filter materials with polypropylene (PP and low-melting point (LPET fibers. The influences of temperatures and times of heat treatment on the morphology of thermal bonding points and average pore size of the PP/LPET filter materials. The test results indicate that the morphology of thermal bonding points is highly correlated with the average pore size. When the temperature of heat treatment is increased, the fibers are joined first with the thermal bonding points, and then with the large thermal bonding areas, thereby decreasing the average pore size of the PP/LPET filter materials. A heat treatment of 110 °C for 60 seconds can decrease the pore size from 39.6 μm to 12.0 μm.

  19. The thermal expansion of gold: point defect concentrations and pre-melting in a face-centred cubic metal.

    Science.gov (United States)

    Pamato, Martha G; Wood, Ian G; Dobson, David P; Hunt, Simon A; Vočadlo, Lidunka

    2018-04-01

    On the basis of ab initio computer simulations, pre-melting phenomena have been suggested to occur in the elastic properties of hexagonal close-packed iron under the conditions of the Earth's inner core just before melting. The extent to which these pre-melting effects might also occur in the physical properties of face-centred cubic metals has been investigated here under more experimentally accessible conditions for gold, allowing for comparison with future computer simulations of this material. The thermal expansion of gold has been determined by X-ray powder diffraction from 40 K up to the melting point (1337 K). For the entire temperature range investigated, the unit-cell volume can be represented in the following way: a second-order Grüneisen approximation to the zero-pressure volumetric equation of state, with the internal energy calculated via a Debye model, is used to represent the thermal expansion of the 'perfect crystal'. Gold shows a nonlinear increase in thermal expansion that departs from this Grüneisen-Debye model prior to melting, which is probably a result of the generation of point defects over a large range of temperatures, beginning at T / T m > 0.75 (a similar homologous T to where softening has been observed in the elastic moduli of Au). Therefore, the thermodynamic theory of point defects was used to include the additional volume of the vacancies at high temperatures ('real crystal'), resulting in the following fitted parameters: Q = ( V 0 K 0 )/γ = 4.04 (1) × 10 -18  J, V 0 = 67.1671 (3) Å 3 , b = ( K 0 ' - 1)/2 = 3.84 (9), θ D = 182 (2) K, ( v f /Ω)exp( s f / k B ) = 1.8 (23) and h f = 0.9 (2) eV, where V 0 is the unit-cell volume at 0 K, K 0 and K 0 ' are the isothermal incompressibility and its first derivative with respect to pressure (evaluated at zero pressure), γ is a Grüneisen parameter, θ D is the Debye temperature, v f , h f and s f are the vacancy formation volume, enthalpy and entropy

  20. The effect of correlated and point defects on the vortex lattice melting transition in single-crystal YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fendrich, J.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G.W.; Giapintzakis, J.

    1994-01-01

    The vortex melting transition T m in several untwinned and twinned crystals is measured resistively in fields up to 8T. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the magnetoresistance at B m supporting a first-order phase transition. The anisotropy of twin boundary pinning and its reduction of the 'kink' in ρ(T) associated with the first-order melting transition is discussed in samples with very dilute twin boundaries. We also report on the direct suppression of the the melting transition by intrinsic pinning for H parallel ab and by electron-irradiation-induced point defects. (orig.)

  1. The effect of correlated and point defects on the vortex lattice melting transition in single crystal YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G.W.; Fendrich, J. Giapintzakis, J.

    1993-08-01

    The vortex melting transition T m in several untwinned and twinned crystals measured resistively in fields up to 8 Tesla. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the magnetoresistance at B m supporting a first order phase transition. The anisotropy of twin boundary pinning and its reduction of the ''kink'' in ρ(T) associated with the first order melting transition is discussed in samples with very dilute twin boundaries. We also report on direct suppression of melting transition by intrinsic pinning for H parallel ab and by electron-irradiation-induced point defects

  2. Development of high melting point, environmentally friendly solders, using the calphad approach

    DEFF Research Database (Denmark)

    Chidambaram, Vivek; Hald, John; Hattel, Jesper Henri

    2008-01-01

    An attempt has been made using the CALPHAD approach via Thermo-Calc to explore the various possible chemical compositions that adhere to the melting criterion i.e. 270-350 degrees C, required to replace the traditionally used high lead content solders for first level packaging applications. Vario...... tension have also been considered. Special focus has been given to toxicity related issues since the main ideology of looking for an alternative to high lead containing solders is not related to technical issues but due to environmental concerns.......An attempt has been made using the CALPHAD approach via Thermo-Calc to explore the various possible chemical compositions that adhere to the melting criterion i.e. 270-350 degrees C, required to replace the traditionally used high lead content solders for first level packaging applications. Various...... of promising solder alloy candidates. The ternary combinations that satisfied the primary solidification requirement were scrutinized taking into account the commercial interests i.e. availability, cost-effectiveness, recyclability and toxicity issues. Technical issues like manufacturability and surface...

  3. Building optimal regression tree by ant colony system-genetic algorithm: Application to modeling of melting points

    Energy Technology Data Exchange (ETDEWEB)

    Hemmateenejad, Bahram, E-mail: hemmatb@sums.ac.ir [Department of Chemistry, Shiraz University, Shiraz (Iran, Islamic Republic of); Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz (Iran, Islamic Republic of); Shamsipur, Mojtaba [Department of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Zare-Shahabadi, Vali [Young Researchers Club, Mahshahr Branch, Islamic Azad University, Mahshahr (Iran, Islamic Republic of); Akhond, Morteza [Department of Chemistry, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2011-10-17

    Highlights: {yields} Ant colony systems help to build optimum classification and regression trees. {yields} Using of genetic algorithm operators in ant colony systems resulted in more appropriate models. {yields} Variable selection in each terminal node of the tree gives promising results. {yields} CART-ACS-GA could model the melting point of organic materials with prediction errors lower than previous models. - Abstract: The classification and regression trees (CART) possess the advantage of being able to handle large data sets and yield readily interpretable models. A conventional method of building a regression tree is recursive partitioning, which results in a good but not optimal tree. Ant colony system (ACS), which is a meta-heuristic algorithm and derived from the observation of real ants, can be used to overcome this problem. The purpose of this study was to explore the use of CART and its combination with ACS for modeling of melting points of a large variety of chemical compounds. Genetic algorithm (GA) operators (e.g., cross averring and mutation operators) were combined with ACS algorithm to select the best solution model. In addition, at each terminal node of the resulted tree, variable selection was done by ACS-GA algorithm to build an appropriate partial least squares (PLS) model. To test the ability of the resulted tree, a set of approximately 4173 structures and their melting points were used (3000 compounds as training set and 1173 as validation set). Further, an external test set containing of 277 drugs was used to validate the prediction ability of the tree. Comparison of the results obtained from both trees showed that the tree constructed by ACS-GA algorithm performs better than that produced by recursive partitioning procedure.

  4. Character of changes in the thermodynamic properties of alloyed melts of rare-earth metals with low-melting-point p- and d-metals

    International Nuclear Information System (INIS)

    Yamshchikov, L.F.; Zyapaev, A.A.; Raspopin, S.P.

    2003-01-01

    Published data on thermodynamic characteristics of lanthanides in liquid-metal melts of gallium, indium and zinc were systematized. The monotonous change from lanthanum to lutetium was ascertained for activity values and activity coefficients of trivalent lanthanides in the melts, which permits calculating the values for the systems of fusible metals, where no experimental data are available [ru

  5. Solid Lipid Nanoparticle Formulations of Docetaxel Prepared with High Melting Point Triglycerides: In Vitro and in Vivo Evaluation

    Science.gov (United States)

    2015-01-01

    Docetaxel (DCX) is a second generation taxane. It is approved by the U.S. Food and Drug Administration for the treatment of various types of cancer, including breast, non-small cell lung, and head and neck cancers. However, side effects, including those related to Tween 80, an excipient in current DCX formulations, can be severe. In the present study, we developed a novel solid lipid nanoparticle (SLN) composition of DCX. Trimyristin was selected from a list of high melting point triglycerides as the core lipid component of the SLNs, based on the rate at which the DCX was released from the SLNs and the stability of the SLNs. The trimyristin-based, PEGylated DCX-incorporated SLNs (DCX-SLNs) showed significantly higher cytotoxicity against various human and murine cancer cells in culture, as compared to DCX solubilized in a Tween 80/ethanol solution. Moreover, in a mouse model with pre-established tumors, the new DCX-SLNs were significantly more effective than DCX solubilized in a Tween 80/ethanol solution in inhibiting tumor growth without toxicity, likely because the DCX-SLNs increased the concentration of DCX in tumor tissues, but decreased the levels of DCX in major organs such as liver, spleen, heart, lung, and kidney. DCX-incorporated SLNs prepared with one or more high-melting point triglycerides may represent an improved DCX formulation. PMID:24621456

  6. Printing low-melting-point alloy ink to directly make a solidified circuit or functional device with a heating pen.

    Science.gov (United States)

    Wang, Lei; Liu, Jing

    2014-12-08

    A new method to directly print out a solidified electronic circuit through low-melting-point metal ink is proposed. A functional pen with heating capability was fabricated. Several typical thermal properties of the alloy ink Bi 35 In 48.6 Sn 16 Zn 0.4 were measured and evaluated. Owing to the specifically selected melting point of the ink, which is slightly higher than room temperature, various electronic devices, graphics or circuits can be manufactured in a short period of time and then rapidly solidified by cooling in the surrounding air. The liquid-solid phase change mechanism of the written lines was experimentally characterized using a scanning electron microscope. In order to determine the matching substrate, wettability between the metal ink Bi 35 In 48.6 Sn 16 Zn 0.4 and several materials, including mica plate and silicone rubber, was investigated. The resistance-temperature curve of a printed resistor indicated its potential as a temperature control switch. Furthermore, the measured reflection coefficient of a printed double-diamond antenna accords well with the simulated result. With unique merits such as no pollution, no requirement for encapsulation and easy recycling, the present printing approach is an important supplement to current printed electronics and has enormous practical value in the future.

  7. Confinement in Melts of Chains with Junction Points, but No Ends

    Science.gov (United States)

    Foster, Mark; He, Qiming; Zhou, Yang; Zhang, Fan; Huang, Chongwen; Narayanan, Suresh

    Measurements of surface fluctuations of 4-arm star and ''8-shaped'' analogs of the same polystyrene (PS) chain show that elimination of chain ends is much more important in dictating the fragility in a thin film than is the introduction of a branch point in the molecule. Both the viscosities derived from surface fluctuations and rheological measurements for the 8-shaped PS manifest a lower value than the 4-arm star PS analog, with the discrepancy increasing as the temperature approaches the glass transition temperature, Tg , bulk. Comparison among different chain topologies shows the effect of the number of chain ends and junction point on the viscosity. The viscosity behavior of the 8-shaped PS is quite different from that of the star analog, but similar to that of the simple cycle analog. The fragility of the 8-shaped molecule in the thin film is reduced relative to that in the bulk, manifesting a nanoconfinement effect. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

  8. A powerful way of cooling computer chip using liquid metal with low melting point as the cooling fluid

    Energy Technology Data Exchange (ETDEWEB)

    Li Teng; Lv Yong-Gang [Chinese Academy of Sciences, Beijing (China). Cryogenic Lab.; Chinese Academy of Sciences, Beijing (China). Graduate School; Liu Jing; Zhou Yi-Xin [Chinese Academy of Sciences, Beijing (China). Cryogenic Lab.

    2006-12-15

    With the improvement of computational speed, thermal management becomes a serious concern in computer system. CPU chips are squeezing into tighter and tighter spaces with no more room for heat to escape. Total power-dissipation levels now reside about 110 W, and peak power densities are reaching 400-500 W/mm{sup 2} and are still steadily climbing. As a result, higher performance and greater reliability are extremely tough to attain. But since the standard conduction and forced-air convection techniques no longer be able to provide adequate cooling for sophisticated electronic systems, new solutions are being looked into liquid cooling, thermoelectric cooling, heat pipes, and vapor chambers. In this paper, we investigated a novel method to significantly lower the chip temperature using liquid metal with low melting point as the cooling fluid. The liquid gallium was particularly adopted to test the feasibility of this cooling approach, due to its low melting point at 29.7 C, high thermal conductivity and heat capacity. A series of experiments with different flow rates and heat dissipation rates were performed. The cooling capacity and reliability of the liquid metal were compared with that of the water-cooling and very attractive results were obtained. Finally, a general criterion was introduced to evaluate the cooling performance difference between the liquid metal cooling and the water-cooling. The results indicate that the temperature of the computer chip can be significantly reduced with the increasing flow rate of liquid gallium, which suggests that an even higher power dissipation density can be achieved with a large flow of liquid gallium and large area of heat dissipation. The concept discussed in this paper is expected to provide a powerful cooling strategy for the notebook PC, desktop PC and large computer. It can also be extended to more wide area involved with thermal management on high heat generation rate. (orig.)

  9. Bayesian inference as a tool for analysis of first-principles calculations of complex materials: an application to the melting point of Ti2GaN

    International Nuclear Information System (INIS)

    Davis, Sergio; Gutiérrez, Gonzalo

    2013-01-01

    We present a systematic implementation of the recently developed Z-method for computing melting points of solids, augmented by a Bayesian analysis of the data obtained from molecular dynamics simulations. The use of Bayesian inference allows us to extract valuable information from limited data, reducing the computational cost of drawing the isochoric curve. From this Bayesian Z-method we obtain posterior distributions for the melting temperature T m , the critical superheating temperature T LS and the slopes dT/dE of the liquid and solid phases. The method therefore gives full quantification of the errors in the prediction of the melting point. This procedure is applied to the estimation of the melting point of Ti 2 GaN (one of the so-called MAX phases), a complex, laminar material, by density functional theory molecular dynamics, finding an estimate T m of 2591.61 ± 89.61 K, which is in good agreement with melting points of similar ceramics. (paper)

  10. Simultaneous feature selection and parameter optimisation using an artificial ant colony: case study of melting point prediction

    Directory of Open Access Journals (Sweden)

    Nigsch Florian

    2008-10-01

    Full Text Available Abstract Background We present a novel feature selection algorithm, Winnowing Artificial Ant Colony (WAAC, that performs simultaneous feature selection and model parameter optimisation for the development of predictive quantitative structure-property relationship (QSPR models. The WAAC algorithm is an extension of the modified ant colony algorithm of Shen et al. (J Chem Inf Model 2005, 45: 1024–1029. We test the ability of the algorithm to develop a predictive partial least squares model for the Karthikeyan dataset (J Chem Inf Model 2005, 45: 581–590 of melting point values. We also test its ability to perform feature selection on a support vector machine model for the same dataset. Results Starting from an initial set of 203 descriptors, the WAAC algorithm selected a PLS model with 68 descriptors which has an RMSE on an external test set of 46.6°C and R2 of 0.51. The number of components chosen for the model was 49, which was close to optimal for this feature selection. The selected SVM model has 28 descriptors (cost of 5, ε of 0.21 and an RMSE of 45.1°C and R2 of 0.54. This model outperforms a kNN model (RMSE of 48.3°C, R2 of 0.47 for the same data and has similar performance to a Random Forest model (RMSE of 44.5°C, R2 of 0.55. However it is much less prone to bias at the extremes of the range of melting points as shown by the slope of the line through the residuals: -0.43 for WAAC/SVM, -0.53 for Random Forest. Conclusion With a careful choice of objective function, the WAAC algorithm can be used to optimise machine learning and regression models that suffer from overfitting. Where model parameters also need to be tuned, as is the case with support vector machine and partial least squares models, it can optimise these simultaneously. The moving probabilities used by the algorithm are easily interpreted in terms of the best and current models of the ants, and the winnowing procedure promotes the removal of irrelevant descriptors.

  11. Simultaneous feature selection and parameter optimisation using an artificial ant colony: case study of melting point prediction.

    Science.gov (United States)

    O'Boyle, Noel M; Palmer, David S; Nigsch, Florian; Mitchell, John Bo

    2008-10-29

    We present a novel feature selection algorithm, Winnowing Artificial Ant Colony (WAAC), that performs simultaneous feature selection and model parameter optimisation for the development of predictive quantitative structure-property relationship (QSPR) models. The WAAC algorithm is an extension of the modified ant colony algorithm of Shen et al. (J Chem Inf Model 2005, 45: 1024-1029). We test the ability of the algorithm to develop a predictive partial least squares model for the Karthikeyan dataset (J Chem Inf Model 2005, 45: 581-590) of melting point values. We also test its ability to perform feature selection on a support vector machine model for the same dataset. Starting from an initial set of 203 descriptors, the WAAC algorithm selected a PLS model with 68 descriptors which has an RMSE on an external test set of 46.6 degrees C and R2 of 0.51. The number of components chosen for the model was 49, which was close to optimal for this feature selection. The selected SVM model has 28 descriptors (cost of 5, epsilon of 0.21) and an RMSE of 45.1 degrees C and R2 of 0.54. This model outperforms a kNN model (RMSE of 48.3 degrees C, R2 of 0.47) for the same data and has similar performance to a Random Forest model (RMSE of 44.5 degrees C, R2 of 0.55). However it is much less prone to bias at the extremes of the range of melting points as shown by the slope of the line through the residuals: -0.43 for WAAC/SVM, -0.53 for Random Forest. With a careful choice of objective function, the WAAC algorithm can be used to optimise machine learning and regression models that suffer from overfitting. Where model parameters also need to be tuned, as is the case with support vector machine and partial least squares models, it can optimise these simultaneously. The moving probabilities used by the algorithm are easily interpreted in terms of the best and current models of the ants, and the winnowing procedure promotes the removal of irrelevant descriptors.

  12. Crack repair welding by CMT brazing using low melting point filler wire for long-term used steam turbine cases of Cr-Mo-V cast steels

    Energy Technology Data Exchange (ETDEWEB)

    Kadoi, Kota, E-mail: kadoi@hiroshima-u.ac.jp [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 (Japan); Murakami, Aoi; Shinozaki, Kenji; Yamamoto, Motomichi [Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 (Japan); Matsumura, Hideo [Chugoku Electric Power Co., 3-9-1 Kagamiyama, Higashi-Hiroshima 739-0046 (Japan)

    2016-06-01

    Surface melting by gas tungsten arc (GTA) welding and overlaying by cold metal transfer (CMT) brazing using low melting point filler wire were investigated to develop a repair process for cracks in worn cast steel of steam turbine cases. Cr-Mo-V cast steel, operated for 188,500 h at 566 °C, was used as the base material. Silver and gold brazing filler wires were used as overlaying materials to decrease the heat input into the base metal and the peak temperature during the welding thermal cycle. Microstructural analysis revealed that the worn cast steel test samples contained ferrite phases with intragranular precipitates of Cr{sub 7}C{sub 3}, Mo{sub 2}C, and CrSi{sub 2} and grain boundary precipitates of Cr{sub 23}C{sub 6} and Mo{sub 2}C. CMT brazing using low melting point filler wire was found to decrease the heat input and peak temperature during the thermal cycle of the process compared with those during GTA surface melting. Thus, the process helped to inhibit the formation of hardened phases such as intermetallics and martensite in the heat affected zone (HAZ). Additionally, in the case of CMT brazing using BAg-8, the change in the hardness of the HAZ was negligible even though other processes such as GTA surface melting cause significant changes. The creep-fatigue properties of weldments produced by CMT brazing with BAg-8 were the highest, and nearly the same as those of the base metal owing to the prevention of hardened phase formation. The number of fracture cycles using GTA surface melting and CMT brazing with BAu-4 was also quite small. Therefore, CMT brazing using low melting point filler wire such as BAg-8 is a promising candidate method for repairing steam turbine cases. However, it is necessary to take alloy segregation during turbine operation into account to design a suitable filler wire for practical use.

  13. Predicting critical temperatures of ionic and non-ionic fluids from thermophysical data obtained near the melting point

    Science.gov (United States)

    Weiss, Volker C.

    2015-10-01

    In the correlation and prediction of thermophysical data of fluids based on a corresponding-states approach, the critical temperature Tc plays a central role. For some fluids, in particular ionic ones, however, the critical region is difficult or even impossible to access experimentally. For molten salts, Tc is on the order of 3000 K, which makes accurate measurements a challenging task. Room temperature ionic liquids (RTILs) decompose thermally between 400 K and 600 K due to their organic constituents; this range of temperatures is hundreds of degrees below recent estimates of their Tc. In both cases, reliable methods to deduce Tc based on extrapolations of experimental data recorded at much lower temperatures near the triple or melting points are needed and useful because the critical point influences the fluid's behavior in the entire liquid region. Here, we propose to employ the scaling approach leading to universal fluid behavior [Román et al., J. Chem. Phys. 123, 124512 (2005)] to derive a very simple expression that allows one to estimate Tc from the density of the liquid, the surface tension, or the enthalpy of vaporization measured in a very narrow range of low temperatures. We demonstrate the validity of the approach for simple and polar neutral fluids, for which Tc is known, and then use the methodology to obtain estimates of Tc for ionic fluids. When comparing these estimates to those reported in the literature, good agreement is found for RTILs, whereas the ones for the molten salts NaCl and KCl are lower than previous estimates by 10%. The coexistence curve for ionic fluids is found to be more adequately described by an effective exponent of βeff = 0.5 than by βeff = 0.33.

  14. CATALYST-FREE REACTIONS UNDER SOLVENT-FEE CONDITIONS: MICROWAVE-ASSISTED SYNTHESIS OF HETEROCYCLIC HYDRAZONES BELOW THE MELTING POINT OF NEAT REACTANTS: JOURNAL ARTICLE

    Science.gov (United States)

    NRMRL-CIN-1437 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Catalyst-free Reactions under Solvent-fee Conditions: Microwave-assisted Synthesis of Heterocyclic Hydrazones below the Melting Point of Neat Reactants. Published in: Chemical Communications 18:1716-1717 (200...

  15. Thermal property prediction and measurement of organic phase change materials in the liquid phase near the melting point

    International Nuclear Information System (INIS)

    O’Connor, William E.; Warzoha, Ronald; Weigand, Rebecca; Fleischer, Amy S.; Wemhoff, Aaron P.

    2014-01-01

    Highlights: • Liquid-phase thermal properties for five phase change materials were estimated. • Various liquid phase and phase transition thermal properties were measured. • The thermal diffusivity was found using a best path to prediction approach. • The thermal diffusivity predictive method shows 15% agreement for organic PCMs. - Abstract: Organic phase change materials (PCMs) are a popular choice for many thermal energy storage applications including solar energy, building envelope thermal barriers, and passive cooling of portable electronics. Since the extent of phase change during a heating or cooling process is dependent upon rapid thermal penetration into the PCM, accurate knowledge of the thermal diffusivity of the PCM in both solid and liquid phases is crucial. This study addresses the existing gaps in information for liquid-phase PCM properties by examining an approach that determines the best path to prediction (BPP) for the thermal diffusivity of both alkanes and unsaturated acids. Knowledge of the BPP will enable researchers to explore the influence of PCM molecular structure on bulk thermophysical properties, thereby allowing the fabrication of optimized PCMs. The BPP method determines which of the tens of thousands of combinations of 22 different available theoretical techniques provides best agreement with thermal diffusivity values based on reported or measured density, heat capacity, and thermal conductivity for each of five PCMs (heneicosane, tricosane, tetracosane, oleic acid, and linoleic acid) in the liquid phase near the melting point. Separate BPPs were calibrated for alkanes based on heneicosane and tetracosane, and for the unsaturated acids. The alkane and unsaturated acid BPPs were then tested on a variety of similar materials, showing agreement with reported/measured thermal diffusivity within ∼15% for all materials. The alkane BPP was then applied to find that increasing the length of alkane chains decreases the PCM thermal

  16. Magnetic properties and densification of Manganese-Zinc soft ferrites (Mn1-xZnxFe2O4) doped with low melting point oxides

    International Nuclear Information System (INIS)

    Shokrollahi, H.

    2008-01-01

    Mn-Zn ferrites have high electrical resistivity, low power loss and high initial permeability up to several MHz range. Oxide additives can greatly affect the magnetic properties of these ferrites. The effects of the additives on the sintering behaviour and magnetic properties of Mn-Zn ferrites are different. Some low melting point additives such as Bi 2 O 3 enhance the sintering by forming a liquid phase in the ferrites. The additive V 2 O 5 enhances the sintering by increasing bulk diffusion due to the increased vacancy concentration which is accompanied by the solubility of V 5+ in the ferrites. Some additives are cations that are soluble in the host lattice and enter regular positions on the tetrahedral or octahedral sites. This paper investigates the effect of several low melting point oxides on the magnetic properties, microstructure and densification of Mn-Zn soft ferrites

  17. The effect of coconut oil and palm oil as substituted oils to cocoa butter on chocolate bar texture and melting point

    Science.gov (United States)

    Limbardo, Rebecca Putri; Santoso, Herry; Witono, Judy Retti

    2017-05-01

    Cocoa butter has responsibility for dispersion medium to create a stable chocolate bar. Due to the economic reason, cocoa butter is partially or wholly substituted by edible oils e.g palm oil and coconut oil. The objective of the research was to observe the effect of oil substitution in the chocolate bar towards its melting point and texture. The research were divided in three steps which were preliminary research started with fat content analysis in cocoa powder, melting point analysis of substituted oils anc cocoa butter, and iodine number analysis in vegetable fats (cocoa butter, coconut oil, and palm oil), chocolate bar production with substitution 0%, 20%, 40%, 60%, 80%, and 100%wt of cocoa butter with each of substituted oils, and analysis process to determine the chocolate bar melting point with DSC and chocolate bar hardness with texture analyser. The increasement of substituted oils during substitution in chocolate bar would reduce the melting point of chocolate bar from 33.5°C to 31.6°C in palm oil substitution with cocoa butter and 33.5°C to 30.75°C in coconut oil substitution. The hardness of chocolate with palm oil were around 88.5 to 139 g on the 1st cycle and 22.75 to 132 g on the 2nd cycle. The hardness of chocolate with coconut oil were around 74.75 to 152.5 g on the 1st cycle and 53.25 to 132 g on the 2nd cycle. Maximum amount of fats substitution to produce a stable texture chocolate bar is 60% wt.

  18. Specific heat measurements on metals up to their melting point; Mesure de la chaleur specifique des metaux jusqu'a leur temperature de fusion

    Energy Technology Data Exchange (ETDEWEB)

    Affortit, Ch [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1967-07-15

    We have built an apparatus to measure the specific heat of metal up to the melting point. The method is the pulse-heating method, where the specimen is heated very rapidly (1/10 s) from room temperature to the melting point by a very intense d.c. current (1000 A). The simultaneous measurements of intensity, voltage and temperature in the specimen allows a calculation of the specific heat. We have obtained good results for niobium, tungsten, tantalum and uranium. The accuracy is around 3 to 5 per cent and allows a measurement of the heat of formation of vacancies near the melting temperature. (author) [French] Nous avons construit un appareil permettant la mesure de la chaleur specifique des metaux jusqu'a leur temperature de fusion. La methode utilisee est la methode dite de chauffage instantane, L'echantillon est echauffe tres rapidement (1/10 s) de la temperature ambiante a la temperature de fusion par le passage d'un courant tres intense ({approx} 1000 A). L'enregistrement simultane de l'intensite du courant, de la difference de potentiel aux bornes de l'echantillon et de la temperature, permet de calculer la chaleur specifique. Nous avons obtenu de bons resultats pour le niobium, le tungstene tantale et l'uranium. La precision de la methode est de l'ordre de 3 a 5 pour cent et permet une mesure de la chaleur de formation des lacunes au voisinage de la fusion. (auteur)

  19. Effect of low-melting point phases on the microstructure and properties of spark plasma sintered and hot deformed Nd-Fe-B alloys

    Science.gov (United States)

    Zhang, Li; Wang, Meiyu; Yan, Xueliang; Lin, Ye; Shield, Jeffrey

    2018-04-01

    The effect of adding a low melting point Pr-Cu-Al alloy during spark plasma sintering of melt-spun Nd-Fe-B ribbons is investigated. Regions of coarse grains were reduced and overall grain refinement was observed after the addition of Pr68Cu25Al7, leading to an enhancement of coercivity from 12.7 kOe to 20.4 kOe. Hot deformation of the samples in the spark plasma sintering system resulted in the formation of platelet-like grains, producing crystallographic alignment and magnetic anisotropy. The hot deformation process improved the remanence and energy product but reduced the coercivity. The decrease of coercivity resulted from grain growth and aggregation of Pr and Nd elements at triple-junction phases.

  20. Poly(1,4-cyclohexanedimethylene 2,6-naphthalate polyester with high melting point: Effect of different synthesis methods on molecular weight and properties

    Directory of Open Access Journals (Sweden)

    N. Kasmi

    2018-03-01

    Full Text Available In the current manuscript, a new approach for the synthesis of poly(1,4- cyclohexanedimethylene 2,6-naphthalate (PCHDMN derived from dimethyl 2,6-naphthalenedicarboxylate (2,6-DMN and 1,4-Cyclohexanedimethanol (CHDM via melt polycondensation method is introduced. The effect of three different synthesis pathways, polycondensation time and temperature on polyesters molecular weight increase has been investigated. All of the prepared samples were characterized measuring their intrinsic viscosity (IV, thermal properties and morphology with differential scanning calorimetry (DSC and wide-angle X-ray diffraction (WAXD, respectively. The results demonstrated the effectiveness of the synthesis pathway proposed for the preparation of PCHDMN, resulting in high molecular weight (IV value around 0.5 dL/g and much shorter reaction time. Melt polycondensation temperatures above melting point of polyester should be avoided to be used due to the decomposition of polyester. This was proved by thermogravimetric analysis (TGA and Pyrolysis-gas chromatography–mass spectroscopy analysis (Py-GC/MS.

  1. Using Paraffin with -10 deg C to 10 deg C Melting Point for Payload Thermal Energy Storage in SpaceX Dragon Trunk

    Science.gov (United States)

    Choi, Michael K.

    2013-01-01

    A concept of using paraffin wax phase change material (PCM) with a melting point between -10 deg C and 10 deg C for payload thermal energy storage in a Space Exploration Technologies (SpaceX) Dragon trunk is presented. It overcomes the problem of limited heater power available to a payload with significant radiators when the Dragon is berthed to the International Space Station (ISS). It stores adequate thermal energy to keep a payload warm without power for 6 hours during the transfer from the Dragon to an ExPRESS logistics carrier (ELC) on the ISS.

  2. Influence of Immersion Conditions on The Tensile Strength of Recycled Kevlar®/Polyester/Low-Melting-Point Polyester Nonwoven Geotextiles through Applying Statistical Analyses

    Directory of Open Access Journals (Sweden)

    Jing-Chzi Hsieh

    2016-05-01

    Full Text Available The recycled Kevlar®/polyester/low-melting-point polyester (recycled Kevlar®/PET/LPET nonwoven geotextiles are immersed in neutral, strong acid, and strong alkali solutions, respectively, at different temperatures for four months. Their tensile strength is then tested according to various immersion periods at various temperatures, in order to determine their durability to chemicals. For the purpose of analyzing the possible factors that influence mechanical properties of geotextiles under diverse environmental conditions, the experimental results and statistical analyses are incorporated in this study. Therefore, influences of the content of recycled Kevlar® fibers, implementation of thermal treatment, and immersion periods on the tensile strength of recycled Kevlar®/PET/LPET nonwoven geotextiles are examined, after which their influential levels are statistically determined by performing multiple regression analyses. According to the results, the tensile strength of nonwoven geotextiles can be enhanced by adding recycled Kevlar® fibers and thermal treatment.

  3. Temperature dependence of the mechanical properties of melt-processed Dy-Ba-Cu-O bulk superconductors evaluated by three point bending tests

    International Nuclear Information System (INIS)

    Katagiri, K; Nyilas, A; Sato, T; Hatakeyama, Y; Hokari, T; Teshima, H; Iwamoto, A; Mito, T

    2006-01-01

    Dy-Ba-Cu-O bulk superconductor has an excellent capability of trapping magnetic flux and lower heat conductivity at cryogenic temperatures as compared with Y-Ba-Cu-O bulk superconductor. The Young's modulus and the bending strength in the range from room temperature to 7 K were measured by the three-point bending tests using specimens cut from a melt-processed Dy-Ba-Cu-O bulk superconductor. They were tested in a helium gas flow type cryostat at Forschungszentrum Karlsruhe and in a liquid nitrogen bath at Iwate University. The Young's modulus was calculated by either the slope of stress-strain curve or that of the load-deflection curve of the specimen. Although the bending strength measured in the two institutes coincided well, there was a significant discrepancy in the Young's modulus. The Young's modulus and bending strength increased with decrease of temperature down to 7 K. The amount of increase in the Young's modulus and the bending strength were about 32% and 36% of those at room temperature, respectively. The scatter of data for each run was significant and did not depend on temperature. The temperature dependence of the Young's modulus coincided with that in Y-Ba-Cu-O obtained by ultrasonic velocity. The temperature dependence of the Young's modulus and the bending strength was discussed from the view point of interatomic distance of the bulk crystal

  4. Structural phases arising from reconstructive and isostructural transitions in high-melting-point oxides under hydrostatic pressure: A first-principles study

    Science.gov (United States)

    Tian, Hao; Kuang, Xiao-Yu; Mao, Ai-Jie; Yang, Yurong; Xu, Changsong; Sayedaghaee, S. Omid; Bellaiche, L.

    2018-01-01

    High-melting-point oxides of chemical formula A B O3 with A =Ca , Sr, Ba and B =Zr , Hf are investigated as a function of hydrostatic pressure up to 200 GPa by combining first-principles calculations with a particle swarm optimization method. Ca- and Sr-based systems: (1) first undergo a reconstructive phase transition from a perovskite state to a novel structure that belongs to the post-post-perovskite family and (2) then experience an isostructural transition to a second, also new post-post-perovskite state at higher pressures, via the sudden formation of a specific out-of-plane B -O bond. In contrast, the studied Ba compounds evolve from a perovskite phase to a third novel post-post-perovskite structure via another reconstructive phase transition. The original characteristics of these three different post-post-perovskite states are emphasized. Unusual electronic properties, including significant piezochromic effects and an insulator-metal transition, are also reported and explained.

  5. Carbon-13 isotope fractionation in the decarboxylation of phenylpropiolic (PPA) below and above its melting point and in the decarboxylation of PPA in phenylacetylene medium

    International Nuclear Information System (INIS)

    Zielinski, M.; Zielinska, A.; Papiernik-Zielinska, H.

    2000-01-01

    C-13 isotope fractionation in the decarboxylation of pure phenylpropiolic acid (PPA) below and above its melting point and the decarboxylation of PPA in phenylacetylene solutions has been investigated in sealed under vacuum reaction vessels. The reactive PPA undergoing decarboxylation polymerizes with the liquid product, phenylacetylene in reaction cage producing a condensation compound, which does not decarboxylate measurably in the 120-190 o C. Especially low final carbon dioxide yields (about 11%) have been obtained in the decarboxylation of PPA in phenylacetylene solution at 132 o C and below this temperature. The carbon dioxide is depleted in carbon-13. The ratio of the carbon isotope ratios of carboxylic carbon of PPA before decarboxylation, R( 13 C/ 12 C so ), and of the first portions of carbon dioxide obtained at partial decarboxylation R( 13 C/ 12 C) pf , located in the range 1.007-1.010, indicates that the pure kinetic fractionation of 13 C in the elementary decarboxylation step is negligible and the C-13 fractionation in the condensed phase dimer/monomer equilibria contributes mainly to the resultant experimental carbon isotope fractionation. A preliminary discussion of the experimental isotope findings is presented. (author)

  6. Method of melting solid waste

    International Nuclear Information System (INIS)

    Ootsuka, Katsuyuki; Mizuno, Ryokichi; Kuwana, Katsumi; Sawada, Yoshihisa; Komatsu, Fumiaki.

    1982-01-01

    Purpose: To enable the volume reduction treatment of a HEPA filter containing various solid wastes, particularly acid digestion residue, or an asbestos separator at a relatively low temperature range. Method: Solid waste to be heated and molten is high melting point material treated by ''acid digestion treatment'' for treating solid waste, e.g. a HEPA filter or polyvinyl chloride, etc. of an atomic power facility treated with nitric acid or the like. When this material is heated and molten by an electric furnace, microwave melting furnace, etc., boron oxide, sodium boride, sodium carbonate, etc. is added as a melting point lowering agent. When it is molten in this state, its melting point is lowered, and it becomes remarkably fluid, and the melting treatment is facilitated. Solidified material thus obtained through the melting step has excellent denseness and further large volume reduction rate of the solidified material. (Yoshihara, H.)

  7. Filament stretching rheometry of polymer melts

    DEFF Research Database (Denmark)

    Hassager, Ole; Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz

    2005-01-01

    The Filament Stretching Rheometry (FSR) method developed by Sridhar, McKinley and coworkers for polymer solutions has been extended to be used also for polymer melts. The design of a melt-FSR will be described and differences to conventional melt elongational rheometers will be pointed out. Results...

  8. Cold Storage Stability of Blend Oil from Soybean Oil and Palm Oil with Different Melting Points%大豆油调和不同熔点棕榈液油的冷藏试验

    Institute of Scientific and Technical Information of China (English)

    吴苏喜; 刘立萍; 李慧; Ooi Cheng KEAT

    2012-01-01

    In order to provide references for preparing blend oil from soybean oil and palm oil with different melting points, the effects of different types and amounts of anti-crystallization agent and soybean oil-to-palm oil ratio on the cold storage stability of blend oil were studied. The best anti-crystallization agent was hydroxyl stearin at a dose of 0.025%. The blend oil A composed of 70% soybean oil, 30% palm olein with melting point of 10 ℃ and 0.025% hydroxy stearin could be kept transparent for more than 16 hours at 0 ℃ and more than 72 h at 5℃. The blend oil B composed of 70% soybean oil, 30% palm olein with melting point of 18 ℃ and 0.025% hydroxy stearin could be kept transparent for more than 30 h at 10℃. The blend oil C composed of 60% soybean oil, 40% palm olein with melting point of 18 ℃ and 0.025% hydroxy stearin could be kept transparent for more than 20 h at 15℃. The blend oil D composed of 60% soybean oil, 40% μm olein with melting point of 24℃ and 0.025% hydroxy stearin could be kept transparent for more than 10 h.%为了制备适应不同储存温度的豆油.棕榈液油调和油,以大豆油与不同熔点棕榈液油为原料,采用冷藏试验方法优化抑晶剂种类、用量和调和油配方。结果表明,羟基硬脂精是效果最佳的抑晶剂,其最佳添加量为0.025%;调和油1(豆油70%+10℃棕榈油30%+羟基硬脂精0.025%)在0℃环境下储存可保持16h以上澄清透亮,在5℃条件可保持72h以上澄清透亮;调和油2(豆油70%+18℃棕榈油30%+羟基硬脂精0.025%)在10℃环境下可保持30h以上澄清透亮;调和油3(豆油60%+18℃棕榈油40%+羟基硬脂精0.025%)在15℃环境下可保持20h以上澄清透亮;调和油4(豆油60%+24℃棕榈油40%+羟基硬脂精0.025%)在20℃环境下可保持10h以上澄清透亮。

  9. Design of Low-Melting Point Compositions Suitable for Transient Liquid Phase Sintering of PM Steels Based on a Thermodynamic and Kinetic Study

    Science.gov (United States)

    Bernardo, Elena; de Oro, Raquel; Campos, Mónica; Torralba, José Manuel

    2014-04-01

    The possibility of tailoring the characteristics of a liquid metal is an important asset in a wide number of processing techniques. For most of these processes, the nature and degree of the interaction between liquid and solid phases are usually a focus of interest since they determine liquid properties such as wettability and infiltration capacity. Particularly, within the powder metallurgy (PM) technology, it is considered one of the key aspects to obtain high performance steels through liquid phase sintering. In this work, it is proved how thermodynamic and kinetics software is a powerful tool to study the liquid/solid interactions. The assessment of different liquid phase promoters for transient liquid phase sintering is addressed through the use of ThermoCalc and DICTRA calculations. Besides melting temperatures, particular attention is given to the solubility phenomena between the phases and the kinetics of these processes. Experimental validation of thermodynamic results is carried out by wetting and infiltration experiments at high temperatures. Compositions presenting different liquid/solid solubility are evaluated and directly correlated to the behavior of the liquid during a real sintering process. Therefore, this work opens the possibility to optimize liquid phase compositions and predict the liquid behavior from the design step, which is considered of high technological value for the PM industry.

  10. Melting method for miscellaneous radioactive solid waste and melting furnace

    International Nuclear Information System (INIS)

    Osaki, Toru; Furukawa, Hirofumi; Uda, Nobuyoshi; Katsurai, Kiyomichi

    1998-01-01

    A vessel containing miscellaneous solid wastes is inserted in a crucible having a releasable material on the inner surface, they are induction-heated from the outside of the crucible by way of low temperature heating coils to melt low melting point materials in the miscellaneous wastes within a temperature range at which the vessel does not melt. Then, they are induction-heated by way of high temperature heating coils to melt the vessel and not yet melted materials, those molten materials are cooled, solidified molten material and the releasable material are taken out, and then the crucible is used again. Then, the crucible can be used again, so that it can be applied to a large scaled melting furnace which treats wastes by a unit of drum. In addition, since the cleaning of the used crucible and the application of the releasable material can be conducted without interrupting the operation of the melting furnace, the operation cycle of the melting furnace can be shortened. (N.H.)

  11. On high-pressure melting of tantalum

    Science.gov (United States)

    Luo, Sheng-Nian; Swift, Damian C.

    2007-01-01

    The issues related to high-pressure melting of Ta are discussed within the context of diamond-anvil cell (DAC) and shock wave experiments, theoretical calculations and common melting models. The discrepancies between the extrapolations of the DAC melting curve and the melting point inferred from shock wave experiments, cannot be reconciled either by superheating or solid-solid phase transition. The failure to reproduce low-pressure DAC melting curve by melting models such as dislocation-mediated melting and the Lindemann law, and molecular dynamics and quantum mechanics-based calculations, undermines their predictions at moderate and high pressures. Despite claims to the contrary, the melting curve of Ta (as well as Mo and W) remains inconclusive at high pressures.

  12. Coercivity enhancement of NdFeB sintered magnets by low melting point Dy{sub 32.5}Fe{sub 62}Cu{sub 5.5} alloy modification

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Liping; Ma, Tianyu, E-mail: maty@zju.edu.cn; Zhang, Pei; Jin, Jiaying; Yan, Mi, E-mail: mse_yanmi@zju.edu.cn

    2014-04-15

    To improve coercivity without sacrificing other magnetic performance of NdFeB sintered magnets, a low melting point Dy{sub 32.5}Fe{sub 62}Cu{sub 5.5} alloy was introduced as an intergranular additive. Magnetic properties and microstructure of the magnets with different Dy{sub 32.5}Fe{sub 62}Cu{sub 5.5} contents were studied. At the optimum addition of 3 wt%, coercivity H{sub cj} was enhanced from 12.7 to 15.2 kOe, the maximum magnetic energy product (BH){sub max} was simultaneously increased from 46.6 to 47.8 MG Oe, accompanied by a slight reduction in remanence B{sub r}. Further investigation on microstructure and grain boundary composition indicated that the enhanced H{sub cj} and (BH){sub max} could be attributed to the refined and uniform 2:14:1 phase grains, continuous grain boundaries and a (Nd,Dy){sub 2}Fe{sub 14}B hardening shell surrounding the 2:14:1 phase grains. - Highlights: • Low melting-point Dy{sub 32.5}Fe{sub 62}Cu{sub 5.5} alloy was introduced to NdFeB magnets. • The doped magnet exhibits enhanced coercivity and maximum energy product. • (Nd,Dy){sub 2}Fe{sub 14}B shell was expected to form in the surface of Nd{sub 2}Fe{sub 14}B grains. • The continuous grain boundary layer formed between neighboring Nd{sub 2}Fe{sub 14}B grains.

  13. Quantitative PCR high-resolution melting (qPCR-HRM) curve analysis, a new approach to simultaneously screen point mutations and large rearrangements: application to MLH1 germline mutations in Lynch syndrome.

    Science.gov (United States)

    Rouleau, Etienne; Lefol, Cédrick; Bourdon, Violaine; Coulet, Florence; Noguchi, Tetsuro; Soubrier, Florent; Bièche, Ivan; Olschwang, Sylviane; Sobol, Hagay; Lidereau, Rosette

    2009-06-01

    Several techniques have been developed to screen mismatch repair (MMR) genes for deleterious mutations. Until now, two different techniques were required to screen for both point mutations and large rearrangements. For the first time, we propose a new approach, called "quantitative PCR (qPCR) high-resolution melting (HRM) curve analysis (qPCR-HRM)," which combines qPCR and HRM to obtain a rapid and cost-effective method suitable for testing a large series of samples. We designed PCR amplicons to scan the MLH1 gene using qPCR HRM. Seventy-six patients were fully scanned in replicate, including 14 wild-type patients and 62 patients with known mutations (57 point mutations and five rearrangements). To validate the detected mutations, we used sequencing and/or hybridization on a dedicated MLH1 array-comparative genomic hybridization (array-CGH). All point mutations and rearrangements detected by denaturing high-performance liquid chromatography (dHPLC)+multiplex ligation-dependent probe amplification (MLPA) were successfully detected by qPCR HRM. Three large rearrangements were characterized with the dedicated MLH1 array-CGH. One variant was detected with qPCR HRM in a wild-type patient and was located within the reverse primer. One variant was not detected with qPCR HRM or with dHPLC due to its proximity to a T-stretch. With qPCR HRM, prescreening for point mutations and large rearrangements are performed in one tube and in one step with a single machine, without the need for any automated sequencer in the prescreening process. In replicate, its reagent cost, sensitivity, and specificity are comparable to those of dHPLC+MLPA techniques. However, qPCR HRM outperformed the other techniques in terms of its rapidity and amount of data provided.

  14. Petrological Geodynamics of Mantle Melting I. AlphaMELTS + Multiphase Flow: Dynamic Equilibrium Melting, Method and Results

    Directory of Open Access Journals (Sweden)

    Massimiliano Tirone

    2017-10-01

    with time, the melt and solid composition approach the composition that is found from a dynamic batch melting model which assumes the velocities of melt and residual solid to be the same. Time dependent melt fluctuations can be observed under certain conditions. In this case the composition of the melt that reaches the top side of the model (exit point may vary to some extent. A consistent result of the model under various conditions is that the volume of the first melt that arrives at the exit point is substantially larger than any later melt output. The analogy with large magma emplacements associated to continental break-up or formation of oceanic plateaus seems to suggest that these events are the direct consequence of a dynamic two-phase flow process. Even though chemical equilibrium between melt and the residual solid is imposed locally in space, bulk composition of the whole system (solid+melt varies with depth and may also vary with time, mainly as the result of the changes of the melt abundance. Potential factors that can influence the melting process such as bulk composition, temperature and mantle upwelling velocity at the top boundary (passive flow or bottom boundary (active flow should be addressed more systematically before the DEM model in this study and the dynamic fractional melting (DFM model that will be introduced in the second installment can be applied to interpret real petrological data. Complete data files of most of the simulations and four animations are available following the data repository link provided in the Supplementary Material.

  15. Multiscale Models of Melting Arctic Sea Ice

    Science.gov (United States)

    2014-09-30

    Sea ice reflectance or albedo , a key parameter in climate modeling, is primarily determined by melt pond and ice floe configurations. Ice - albedo ...determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a...bifurcation points. Ising model for melt ponds on Arctic sea ice Y. Ma, I. Sudakov, and K. M. Golden Abstract: The albedo of melting

  16. Methods for Melting Temperature Calculation

    Science.gov (United States)

    Hong, Qi-Jun

    Melting temperature calculation has important applications in the theoretical study of phase diagrams and computational materials screenings. In this thesis, we present two new methods, i.e., the improved Widom's particle insertion method and the small-cell coexistence method, which we developed in order to capture melting temperatures both accurately and quickly. We propose a scheme that drastically improves the efficiency of Widom's particle insertion method by efficiently sampling cavities while calculating the integrals providing the chemical potentials of a physical system. This idea enables us to calculate chemical potentials of liquids directly from first-principles without the help of any reference system, which is necessary in the commonly used thermodynamic integration method. As an example, we apply our scheme, combined with the density functional formalism, to the calculation of the chemical potential of liquid copper. The calculated chemical potential is further used to locate the melting temperature. The calculated results closely agree with experiments. We propose the small-cell coexistence method based on the statistical analysis of small-size coexistence MD simulations. It eliminates the risk of a metastable superheated solid in the fast-heating method, while also significantly reducing the computer cost relative to the traditional large-scale coexistence method. Using empirical potentials, we validate the method and systematically study the finite-size effect on the calculated melting points. The method converges to the exact result in the limit of a large system size. An accuracy within 100 K in melting temperature is usually achieved when the simulation contains more than 100 atoms. DFT examples of Tantalum, high-pressure Sodium, and ionic material NaCl are shown to demonstrate the accuracy and flexibility of the method in its practical applications. The method serves as a promising approach for large-scale automated material screening in which

  17. Thermodynamics of freezing and melting

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Costigliola, Lorenzo; Bailey, Nicholas

    2016-01-01

    phases at a single thermodynamic state point provide the basis for calculating the pressure, density and entropy of fusion as functions of temperature along the melting line, as well as the variation along this line of the reduced crystalline vibrational mean-square displacement (the Lindemann ratio...

  18. Experimental results for TiO2 melting and release using cold crucible melting

    International Nuclear Information System (INIS)

    Hong, S. W.; Min, B. T.; Park, I. G.; Kim, H. D.

    2000-01-01

    To simulate the severe accident phenomena using the real reactor material which melting point is about 2,800K, the melting and release method for materials with high melting point should be developed. This paper discusses the test results for TiO 2 materials using the cold crucible melting method to study the melting and release method of actual corium. To melt and release of few kg of TiO2, the experimental facility is manufactured through proper selection of design parameters such as frequency and capacity of R.F generator, crucible size and capacity of coolant. The melting and release of TiO 2 has been successfully performed in the cold crucible of 15cm in inner diameter and 30cm in height with 30kW RF power generator of 370 KHz. In the melt delivery experiment, about 2.6kg of molten TiO2, 60% of initial charged mass, is released. Rest of it is remained in the watercage in form of the rubble crust formed at the top of crucible and melt crust formed at the interface between the water-cage and melt. Especially, in the melt release test, the location of the working coil is important to make the thin crust at the bottom of the crucible

  19. Lipídios estruturados obtidos a partir da mistura de gordura de frango, sua estearina e triacilgliceróis de cadeia média: II- pontos de amolecimento e fusão Structured lipids from chicken fat, its stearin, and medium chain triacyglycerol blends: II- softening and melting points

    Directory of Open Access Journals (Sweden)

    Ming Chih Chiu

    2008-01-01

    Full Text Available The aim of the present work is to investigate the effects of blending and chemical interesterification reactions on the softening and melting behavior of chicken fat, its stearin and medium chain triacylglycerols, and blends thereof in various ratios. Chemical interesterification is a promising alternative to the current processes of modifying the physical properties of fats. In the experimental design 7 samples corresponding to 7 different blend proportions were used. The results were represented in triangular diagrams. The addition of stearin influenced the softening and melting points. The mixture response surface methodology proved to be an extremely useful tool for the optimization of the fat mixtures.

  20. Melting under shock compression

    International Nuclear Information System (INIS)

    Bennett, B.I.

    1980-10-01

    A simple model, using experimentally measured shock and particle velocities, is applied to the Lindemann melting formula to predict the density, temperature, and pressure at which a material will melt when shocked from room temperature and zero pressure initial conditions

  1. Subsequent bilateral comparison to CCT-K3, CIPM key comparison CCT-K3.1: Comparison of standard platinum resistance thermometers at the triple point of water (T = 273.16 K) and at the melting point of gallium (T = 302.9146 K)

    Science.gov (United States)

    Picard, S.; Nonis, M.; Solve, S.; Allisy-Roberts, P. J.; Renaot, E.; Martin, C.

    2011-01-01

    A comparison of standard platinum resistance thermometers (SPRTs) has been carried out between the BIPM and the Laboratoire commun de métrologie LNE-CNAM using the melting point of gallium and the triple point of water. The temperature difference at Ga between the BIPM and the LNE-CNAM was determined as 108 µK with an associated combined standard uncertainty of 223 µK. This outcome indicates a present temperature difference of the BIPM of -65 µK with respect to an Average Reference Value from an earlier comparison, with an associated uncertainty of uc = 262 µK. It should be noted that the present BIPM scale is not independent, but traceable to cells used in KC7. The comparison results validate the re-establishment of thermometer calibrations at the BIPM for internal use. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  2. Melting of Dense Sodium

    International Nuclear Information System (INIS)

    Gregoryanz, Eugene; Degtyareva, Olga; Hemley, Russell J.; Mao, Ho-kwang; Somayazulu, Maddury

    2005-01-01

    High-pressure high-temperature synchrotron diffraction measurements reveal a maximum on the melting curve of Na in the bcc phase at ∼31 GPa and 1000 K and a steep decrease in melting temperature in its fcc phase. The results extend the melting curve by an order of magnitude up to 130 GPa. Above 103 GPa, Na crystallizes in a sequence of phases with complex structures with unusually low melting temperatures, reaching 300 K at 118 GPa, and an increased melting temperature is observed with further increases in pressure

  3. Vacancies in quantal Wigner crystals near melting

    International Nuclear Information System (INIS)

    Barraza, N.; Colletti, L.; Tosi, M.P.

    1999-04-01

    We estimate the formation energy of lattice vacancies in quantal Wigner crystals of charged particles near their melting point at zero temperature, in terms of the crystalline Lindemann parameter and of the static dielectric function of the fluid phase near freezing. For both 3D and 2D crystals of electrons our results suggest the presence of vacancies in the ground state at the melting density. (author)

  4. Model of interfacial melting

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.; Zuckermann, Martin J.

    1987-01-01

    A two-dimensional model is proposed to describe systems with phase transitions which take place in terms of crystalline as well as internal degrees of freedom. Computer simulation of the model shows that the interplay between the two sets of degrees of freedom permits observation of grain-boundar......-boundary formation and interfacial melting, a nonequilibrium process by which the system melts at the boundaries of a polycrystalline domain structure. Lipid membranes are candidates for systems with pronounced interfacial melting behavior....

  5. Melt inclusions: Chapter 6

    Science.gov (United States)

    ,; Lowenstern, J. B.

    2014-01-01

    Melt inclusions are small droplets of silicate melt that are trapped in minerals during their growth in a magma. Once formed, they commonly retain much of their initial composition (with some exceptions) unless they are re-opened at some later stage. Melt inclusions thus offer several key advantages over whole rock samples: (i) they record pristine concentrations of volatiles and metals that are usually lost during magma solidification and degassing, (ii) they are snapshots in time whereas whole rocks are the time-integrated end products, thus allowing a more detailed, time-resolved view into magmatic processes (iii) they are largely unaffected by subsolidus alteration. Due to these characteristics, melt inclusions are an ideal tool to study the evolution of mineralized magma systems. This chapter first discusses general aspects of melt inclusions formation and methods for their investigation, before reviewing studies performed on mineralized magma systems.

  6. Force induced DNA melting

    International Nuclear Information System (INIS)

    Santosh, Mogurampelly; Maiti, Prabal K

    2009-01-01

    When pulled along the axis, double-strand DNA undergoes a large conformational change and elongates by roughly twice its initial contour length at a pulling force of about 70 pN. The transition to this highly overstretched form of DNA is very cooperative. Applying a force perpendicular to the DNA axis (unzipping), double-strand DNA can also be separated into two single-stranded DNA, this being a fundamental process in DNA replication. We study the DNA overstretching and unzipping transition using fully atomistic molecular dynamics (MD) simulations and argue that the conformational changes of double-strand DNA associated with either of the above mentioned processes can be viewed as force induced DNA melting. As the force at one end of the DNA is increased the DNA starts melting abruptly/smoothly above a critical force depending on the pulling direction. The critical force f m , at which DNA melts completely decreases as the temperature of the system is increased. The melting force in the case of unzipping is smaller compared to the melting force when the DNA is pulled along the helical axis. In the case of melting through unzipping, the double-strand separation has jumps which correspond to the different energy minima arising due to sequence of different base pairs. The fraction of Watson-Crick base pair hydrogen bond breaking as a function of force does not show smooth and continuous behavior and consists of plateaus followed by sharp jumps.

  7. Size-dependent melting of nanoparticles: Hundred years of ...

    Indian Academy of Sciences (India)

    point depression of nanoparticles and the variation is linear with the inverse of the particle size. An attempt to ... Different expressions can be derived by assuming different melting hypothesis that explains different variations. ... process, the entire solid is in equilibrium with entire melted particles [1,15] which corresponds to ...

  8. Vacancies und melting curves of metals at high pressure

    International Nuclear Information System (INIS)

    Gorecki, T.

    1977-01-01

    The vacancy mechanism of the melting process is utilized as a starting point in derivation of the pressure dependence of melting temperature for metals. The results obtained for the initial slope of the melting curve are compared with experimental data for 45 metals (including U, Np, Pu, rare earths) and in most cases the agreement is very good. An on-linearity of the fusion curve and appearence of the maximum on the melting curve at a pressure approximately equal to the bulk modulus is also predicted with qualitative agreement with existing experimental data. (orig./GSC) [de

  9. Theoretical study of a melting curve for tin

    International Nuclear Information System (INIS)

    Feng, Xi; Ling-Cang, Cai

    2009-01-01

    The melting curve of Sn has been calculated using the dislocation-mediated melting model with the 'zone-linking method'. The results are in good agreement with the experimental data. According to our calculation, the melting temperature of γ-Sn at zero pressure is about 436 K obtained by the extrapolation of the method from the triple point of Sn. The results show that this calculation method is better than other theoretical methods for predicting the melting curve of polymorphic material Sn. (condensed matter: structure, thermal and mechanical properties)

  10. Melting temperature of graphite

    International Nuclear Information System (INIS)

    Korobenko, V.N.; Savvatimskiy, A.I.

    2001-01-01

    Full Text: Pulse of electrical current is used for fast heating (∼ 1 μs) of metal and graphite specimens placed in dielectric solid media. Specimen consists of two strips (90 μm in thick) placed together with small gap so they form a black body model. Quasy-monocrystal graphite specimens were used for uniform heating of graphite. Temperature measurements were fulfilled with fast pyrometer and with composite 2-strip black body model up to melting temperature. There were fulfilled experiments with zirconium and tungsten of the same black body construction. Additional temperature measurements of liquid zirconium and liquid tungsten are made. Specific heat capacity (c P ) of liquid zirconium and of liquid tungsten has a common feature in c P diminishing just after melting. It reveals c P diminishing after melting in both cases over the narrow temperature range up to usual values known from steady state measurements. Over the next wide temperature range heat capacity for W (up to 5000 K) and Zr (up to 4100 K) show different dependencies of heat capacity on temperature in liquid state. The experiments confirmed a high quality of 2-strip black body model used for graphite temperature measurements. Melting temperature plateau of tungsten (3690 K) was used for pyrometer calibration area for graphite temperature measurement. As a result, a preliminary value of graphite melting temperature of 4800 K was obtained. (author)

  11. Plasma arc melting of titanium-tantalum alloys

    International Nuclear Information System (INIS)

    Dunn, P.; Patterson, R.A.; Haun, R.

    1994-01-01

    Los Alamos has several applications for high temperature, oxidation and liquid-metal corrosion resistant materials. Further, materials property constraints are dictated by a requirement to maintain low density; e.g., less than the density of stainless steel. Liquid metal compatibility and density requirements have driven the research toward the Ti-Ta system with an upper bound of 60 wt% Ta-40 wt% Ti. Initial melting of these materials was performed in a small button arc melter with several hundred grams of material; however, ingot quantities were soon needed. But, refractory metal alloys whose constituents possess very dissimilar densities, melting temperatures and vapor pressures pose significant difficulty and require specialized melting practices. The Ti-Ta alloys fall into this category with the density of tantalum 16.5 g/cc and that of titanium 4.5 g/cc. Melting is further complicated by the high melting point of Ta(3020 C) and the relatively low boiling point of Ti(3287 C). Previous electron beam melting experience with these materials resulted, in extensive vaporization of the titanium and poor chemical homogeneity. Vacuum arc remelting(VAR) was considered as a melting candidate and discarded due to density and vapor pressure issues associated with electron beam. Plasma arc melting offered the ability to supply a cover gas to deal with vapor pressure issues as well as solidification control to help with macrosegregation in the melt and has successfully produced high quality ingots of the Ti-Ta alloys

  12. Applications of nonequilibrium melting concept to damage-accumulation processes

    International Nuclear Information System (INIS)

    Lam, N.Q.; Okamoto, P.R.

    1998-01-01

    The authors recent study of crystalline-to-amorphous transformation led to the successful development of a unified thermodynamic description of disorder-induced amorphization and heat-induced melting, based on a generalized version of the Lindemann melting criterion. The generalized criterion requires that the melting temperature of a defective crystal decreases with increasing static atomic disorder. Hence, any crystal can melt at temperatures below the melting point of its perfect crystalline state when driven far from equilibrium by introducing critical amounts of misfitting solute atoms and lattice imperfections, radiation damage, and/or tensile stresses. This conceptual approach to nonequilibrium melting provides new insight into long-standing materials problems such as brittle fracture, embrittlement, and environmentally-induced cracking, for example irradiation-assisted stress corrosion cracking

  13. Vacancies and a generalised melting curve of metals

    International Nuclear Information System (INIS)

    Gorecki, T.

    1979-01-01

    The vacancy mechanism of the melting process is used as a starting point for deriving an expression for the pressure dependence of the melting temperature of metals. The results obtained for the initial slope of the melting curve are compared with experimental data for 45 metals and in most cases the agreement is very good. The nonlinearity of the melting curve and the appearance of a maximum on the melting curve at a pressure approximately equal to the bulk modules is also predicted, with qualitative agreement with experimental data. A relation between bonding energy, atomic volume, and bulk modulus of metals is established. On the basis of this relation and the proposed vacancy mechanism, a generalised equation for the pressure dependence of the melting temperature of metals is derived. (author)

  14. Melting the vacuum

    International Nuclear Information System (INIS)

    Rafelski, J.

    1998-01-01

    Results presented at the Quark Matter 97 conference, held in December in Tsukuba, Japan, have provided new insights into the confinement of quarks in matter. The current physics paradigm is that the inertial masses of protons and neutrons, and hence of practically all of the matter around us, originate in the zero-point energy caused by the confinement of quarks inside the small volume of the nucleon. Today, 25 years after Harald Fritzsch, Heinrich Leutwyler and Murray Gell-Mann proposed quantum chromodynamics (QCD) as a means for understanding strongly interacting particles such as nucleons and mesons, our understanding of strong interactions and quark confinement remains incomplete. Quarks and the gluons that bind them together have a ''colour'' charge that may be red, green or blue. But quarks are seen in particles that are white: baryons such as protons and neutrons consist of three quarks with different colour charges, while mesons consist of a quark and an antiquark, and again the colour charge cancels out. To prove that confinement arises from quark-gluon fluctuations in the vacuum that quantum theories dictate exists today, we need to find a way of freeing the colour charge of quarks. Experiments must therefore ''melt'' the vacuum to deconfine quarks and the colour charge. By colliding nuclei at high energies, we hope to produce regions of space filled with free quarks and gluons. This deconfined phase is known as the quark-gluon plasma. At the Tsukuba meeting, Scott Pratt of Michigan State University in the US discussed measurements that show that the hot dense state of matter created in these collisions exists for only 2x10 -23 s. So does the quark gluon plasma exist? No-one doubts that it did at one time, before the vacuum froze into its current state about 20 into the life of the universe, causing the nucleons to form as we know them today. The issue is whether we can recreate this early stage of the universe in laboratory experiments. And if we did

  15. Melting of gold microclusters

    International Nuclear Information System (INIS)

    Garzon, I.L.; Jellinek, J.

    1991-01-01

    The transition from solid-like to liquid-like behavior in Au n , n=6, 7, 13, clusters is studied using molecular dynamics simulations. A Gupta-type potential with all-neighbour interactions is employed to incorporate n-body effects. The melting-like transition is described in terms of short-time averages of the kinetic energy per particle, root-mean-square bond length fluctuations and mean square displacements. A comparison between melting temperatures of Au n and Ni n clusters is presented. (orig.)

  16. GLASS MELTING PHENOMENA, THEIR ORDERING AND MELTING SPACE UTILISATION

    Directory of Open Access Journals (Sweden)

    Němec L.

    2013-12-01

    Full Text Available Four aspects of effective glass melting have been defined – namely the fast kinetics of partial melting phenomena, a consideration of the melting phenomena ordering, high utilisation of the melting space, and effective utilisation of the supplied energy. The relations were defined for the specific melting performance and specific energy consumption of the glass melting process which involve the four mentioned aspects of the process and indicate the potentials of effective melting. The quantity “space utilisation” has been treated in more detail as an aspect not considered in practice till this time. The space utilisation was quantitatively defined and its values have been determined for the industrial melting facility by mathematical modelling. The definitions of the specific melting performance and specific energy consumption have been used for assessment of the potential impact of a controlled melt flow and high space utilisation on the melting process efficiency on the industrial scale. The results have shown that even the partial control of the melt flow, leading to the partial increase of the space utilisation, may considerably increase the melting performance, whereas a decrease of the specific energy consumption was determined to be between 10 - 15 %.

  17. MELT-IIIB: an updated version of the melt code

    International Nuclear Information System (INIS)

    Tabb, K.K.; Lewis, C.H.; O'Dell, L.D.; Padilla, A. Jr.; Smith, D.E.; Wilburn, N.P.

    1979-04-01

    The MELT series is a reactor modeling code designed to investigate a wide variety of hypothetical accident conditions, particularly the transient overpower sequence. MELT-IIIB is the latest in the series

  18. Melt electrospinning of biodegradable polyurethane scaffolds

    Science.gov (United States)

    Karchin, Ari; Simonovsky, Felix I.; Ratner, Buddy D.; Sanders, Joan E.

    2014-01-01

    Electrospinning from the melt, in contrast to from solution, is an attractive tissue engineering scaffold manufacturing process as it allows for the formation of small diameter fibers while eliminating potentially cytotoxic solvents. Despite this, there is a dearth of literature on scaffold formation via melt electrospinning. This is likely due to the technical challenges related to the need for a well-controlled high temperature setup and the difficulty in developing an appropriate polymer. In this paper, a biodegradable and thermally stable polyurethane (PU) is described specifically for use in melt electrospinning. Polymer formulations of aliphatic PUs based on (CH2)4-content diisocyanates, polycaprolactone (PCL), 1,4-butanediamine and 1,4-butanediol (BD) were evaluated for utility in the melt electrospinning process. The final polymer formulation, a catalyst-purified PU based on 1,4-butane diisocyanate, PCL and BD in a 4/1/3 molar ratio with a weight-average molecular weight of about 40 kDa, yielded a nontoxic polymer that could be readily electrospun from the melt. Scaffolds electrospun from this polymer contained point bonds between fibers and mechanical properties analogous to many in vivo soft tissues. PMID:21640853

  19. Arctic melt ponds and bifurcations in the climate system

    Science.gov (United States)

    Sudakov, I.; Vakulenko, S. A.; Golden, K. M.

    2015-05-01

    Understanding how sea ice melts is critical to climate projections. In the Arctic, melt ponds that develop on the surface of sea ice floes during the late spring and summer largely determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a bifurcation point - an irreversible critical threshold as the system warms, by incorporating geometric information about melt pond evolution. This study is based on a bifurcation analysis of the energy balance climate model with ice-albedo feedback as the key mechanism driving the system to bifurcation points.

  20. `Technology for Advanced Treatment of High Melting Point Metal-Based Material,` local research and development of important technology for fiscal 1997. Development of materials creation technology for high efficiency power generator components; 1997 nendo juyo chiiki gijutsu kenkyu kaihatsu. `Koyuten kinzokukei buzai no kodo kako gijutsu` (kokoritsu hatsuden`yo buzai sosei gijutsu kaihatsu)

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    Efforts are made for the creation of high melting point metal-base materials to replace the currently-used Ni-base superalloys for the turbine to withstand higher operating temperatures. The main efforts made in fiscal 1997 are outlined. As in fiscal 1996, Nb-base solution alloys, in which solution reinforcement elements such as Mo and W are alloyed, are manufactured by button arc melting and tested for mechanical properties and texture/characteristics. In the designing and evaluation for a strongest Nb-base composite material, Nb-base composite materials are manufactured by use of particle dispersion-strengthening attained by addition of intermetallic compounds or elements to contribute to the formation of oxides, carbides, or nitrides. Nb-base composite materials may also be manufactured by use of eutectic-strengthening attained by utilizing crystallization in the process of coagulation. The resultant Nb-base composite materials are evaluated for their dynamic characteristics at high temperatures. In the development and evaluation of technologies for creating Nb-base materials for high-temperature components, larger specimens as heavy as several kg are tested in line with small specimens for basic studies, and the results are utilized for alloy designing for high-temperature materials. 50 refs., 97 figs., 15 tabs.

  1. Fuel Rod Melt Progression Simulation Using Low-Temperature Melting Metal Alloy

    International Nuclear Information System (INIS)

    Seung Dong Lee; Suh, Kune Y.; GoonCherl Park; Un Chul Lee

    2002-01-01

    downwards a blockage may be formed and grow both radially and axially. The velocity of the melt can be calculated from a force balance between the gravity and frictional losses at the melt-rod interface. When the heater rod is uncovered completely, the melt progression is initiated at the mid-point, which is the hot spot in the rod. However, the melting location is elevated as the water level rises because of the downward heat transfer. Considering the melt flow as a film, the steady-state film thickness on the cylindrical heater rod and the average velocity are computed. The steady-state film flow rate is determined in terms of the density, film thickness, and film velocity. (authors)

  2. Erythritol: crystal growth from the melt.

    Science.gov (United States)

    Lopes Jesus, A J; Nunes, Sandra C C; Ramos Silva, M; Matos Beja, A; Redinha, J S

    2010-03-30

    The structural changes occurring on erythritol as it is cooled from the melt to low temperature, and then heated up to the melting point have been investigated by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), X-ray powder diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). By DSC, it was possible to set up the conditions to obtain an amorphous solid, a crystalline solid, or a mixture of both materials in different proportions. Two crystalline forms have been identified: a stable and a metastable one with melting points of 117 and 104 degrees C, respectively. The fusion curve decomposition of the stable form revealed the existence of three conformational structures. The main paths of the crystallization from the melt were followed by PLTM. The texture and colour changes allowed the characterization of the different phases and transitions in which they are involved on cooling as well as on heating processes. The type of crystallization front and its velocity were also followed by microscopic observation. These observations, together with the data provided by PXRD, allowed elucidating the transition of the metastable form into the stable one. The structural changes occurring upon the cooling and subsequent heating processes, namely those arising from intermolecular hydrogen bonds, were also accompanied by infrared spectroscopy. Particular attention was given to the spectral changes occurring in the OH stretching region. Copyright (c) 2009 Elsevier B.V. All rights reserved.

  3. The melting curve of tetrahydrofuran hydrate in D2O

    International Nuclear Information System (INIS)

    Hanley, H.J.M.; Meyers, G.J.; White, J.W.; Sloan, E.D.

    1989-01-01

    Melting points for the tetrahydrofuran/D 2 O hydrate in equilibrium with the air-saturated liquid at atmospheric pressure are reported. The melting points were measured by monitoring the absorbance of the solution. Overall, the melting-point phase boundary curve is about 2.5 K greater than the corresponding curve for the H 2 O hydrate, with a congruent melting temperature of 281 ± 0.5 K at a D 2 O mole fraction of 0.936. The phase boundary is predicted to within 5% if the assumption is made that the THF occupancy in the D 2 O and H 2 O hydrates is the same. The authors measure an occupancy of 99.9%. The chemical potential of the empty lattice in D 2 O is estimated to be 5% greater than in H 2 O

  4. Melting of polydisperse hard disks

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2004-01-01

    The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find

  5. Thermodynamics of Oligonucleotide Duplex Melting

    Science.gov (United States)

    Schreiber-Gosche, Sherrie; Edwards, Robert A.

    2009-01-01

    Melting temperatures of oligonucleotides are useful for a number of molecular biology applications, such as the polymerase chain reaction (PCR). Although melting temperatures are often calculated with simplistic empirical equations, application of thermodynamics provides more accurate melting temperatures and an opportunity for students to apply…

  6. Volume dependence of the melting temperature for alkali metals with Debye's model

    International Nuclear Information System (INIS)

    Soma, T.; Kagaya, H.M.; Nishigaki, M.

    1983-01-01

    Using the volume dependence of the Grueneisen constant at higher temperatures, the volume effect on the melting temperature of alkali metals is studied by Lindeman's melting law and Debye's model. The obtained melting curve increases as a function of the compressed volume and shows the maximum of the melting point at the characteristic volume. The resultant data are qualitatively in agreement with the observed tendency for alkali metals. (author)

  7. Pavement Snow Melting

    Energy Technology Data Exchange (ETDEWEB)

    Lund, John W.

    2005-01-01

    The design of pavement snow melting systems is presented based on criteria established by ASHRAE. The heating requirements depends on rate of snow fall, air temperature, relative humidity and wind velocity. Piping materials are either metal or plastic, however, due to corrosion problems, cross-linked polyethylene pipe is now generally used instead of iron. Geothermal energy is supplied to systems through the use of heat pipes, directly from circulating pipes, through a heat exchanger or by allowing water to flow directly over the pavement, by using solar thermal storage. Examples of systems in New Jersey, Wyoming, Virginia, Japan, Argentina, Switzerland and Oregon are presented. Key words: pavement snow melting, geothermal heating, heat pipes, solar storage, Wyoming, Virginia, Japan, Argentina, Klamath Falls.

  8. Transient fuel melting

    International Nuclear Information System (INIS)

    Roche, L.; Schmitz, F.

    1982-10-01

    The observation of micrographic documents from fuel after a CABRI test leads to postulate a specific mode of transient fuel melting during a rapid nuclear power excursion. When reaching the melt threshold, the bands which are characteristic for the solid state are broken statistically over a macroscopic region. The time of maintaining the fuel at the critical enthalpy level between solid and liquid is too short to lead to a phase separation. A significant life-time (approximately 1 second) of this intermediate ''unsolide'' state would have consequences on the variation of physical properties linked to the phase transition solid/liquid: viscosity, specific volume and (for the irradiated fuel) fission gas release [fr

  9. Melt Adsorption as a Manufacturing Method for Fine Particles of Wax Matrices without Any Agglomerates.

    Science.gov (United States)

    Shiino, Kai; Fujinami, Yukari; Kimura, Shin-Ichiro; Iwao, Yasunori; Noguchi, Shuji; Itai, Shigeru

    2017-01-01

    We have focused on melt adsorption as manufacture method of wax matrices to control particles size of granules more easily than melt granulation. The purpose of present study was to investigate the possibility of identifying a hydrophobic material with a low melting point, currently used as a meltable binder of melt granulation, to apply as a novel carrier in melt adsorption. Glyceryl monostearate (GM) and stearic acid (SA) were selected as candidate hydrophobic materials with low melting points. Neusilin US2 (US2), with a particle diameter of around 100 µm was selected as a surface adsorbent, while dibasic calcium phosphate dihydrate (DCPD), was used as a non-adsorbent control to prepare melting granules as a standard for comparison. We prepared granules containing ibuprofen (IBU) by melt adsorption or melt granulation and evaluated the particle size, physical properties and crystallinity of granules. Compared with melt granulation using DCPD, melt adsorption can be performed over a wide range of 14 to 70% for the ratio of molten components. Moreover, the particle size; d50 of obtained granules was 100-200 µm, and these physical properties showed good flowability and roundness. The process of melt adsorption did not affect the crystalline form of IBU. Therefore, the present study has demonstrated for the first time that melt adsorption using a hydrophobic material, GM or SA, has the potential capability to control the particle size of granules and offers the possibility of application as a novel controlled release technique.

  10. Molecular dynamics simulations of the melting curve of NiAl alloy under pressure

    International Nuclear Information System (INIS)

    Zhang, Wenjin; Peng, Yufeng; Liu, Zhongli

    2014-01-01

    The melting curve of B2-NiAl alloy under pressure has been investigated using molecular dynamics technique and the embedded atom method (EAM) potential. The melting temperatures were determined with two approaches, the one-phase and the two-phase methods. The first one simulates a homogeneous melting, while the second one involves a heterogeneous melting of materials. Both approaches reduce the superheating effectively and their results are close to each other at the applied pressures. By fitting the well-known Simon equation to our melting data, we yielded the melting curves for NiAl: 1783(1 + P/9.801) 0.298 (one-phase approach), 1850(1 + P/12.806) 0.357 (two-phase approach). The good agreement of the resulting equation of states and the zero-pressure melting point (calc., 1850 ± 25 K, exp., 1911 K) with experiment proved the correctness of these results. These melting data complemented the absence of experimental high-pressure melting of NiAl. To check the transferability of this EAM potential, we have also predicted the melting curves of pure nickel and pure aluminum. Results show the calculated melting point of Nickel agrees well with experiment at zero pressure, while the melting point of aluminum is slightly higher than experiment

  11. Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization

    Science.gov (United States)

    Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

    2016-03-01

    Organic semiconductors including rubrene, Alq3, copper phthalocyanine and pentacene are crystallized by the eutectic melt crystallization. Those organic semiconductors form good eutectic systems with the various volatile crystallizable additives such as benzoic acid, salicylic acid, naphthalene and 1,3,5-trichlorobenzene. Due to the formation of the eutectic system, organic semiconductors having originally high melting point (Tm > 300 °C) are melted and crystallized at low temperature (Te = 40.8-133 °C). The volatile crystallizable additives are easily removed by sublimation. For a model system using rubrene, single crystalline rubrene nanowires are prepared by the eutectic melt crystallization and the eutectic-melt-assisted nanoimpinting (EMAN) technique. It is demonstrated that crystal structure and the growth direction of rubrene can be controlled by using different volatile crystallizable additives. The field effect mobility of rubrene nanowires prepared using several different crystallizable additives are measured and compared.

  12. Behavior of nuclides at plasma melting of TRU wastes

    International Nuclear Information System (INIS)

    Amakawa, Tadashi; Adachi, Kazuo

    2001-01-01

    Arc plasma heating technique can easily be formed at super high temperature, and can carry out stable heating without any effect of physical and chemical properties of the wastes. By focussing to these characteristics, this technique was experimentally investigated on behavior of TRU nuclides when applying TRU wastes forming from reprocessing process of used fuels to melting treatment by using a mimic non-radioactive nuclide. At first, according to mechanism determining the behavior of TRU nuclides, an element (mimic nuclide) to estimate the behavior was selected. And then, to zircaloy with high melting point or steel can simulated to metal and noncombustible wastes and fly ash, the mimic nuclide was added, prior to melting by using the arc plasma heating technique. As a result, on a case of either melting sample, it was elucidated that the nuclides hardly moved into their dusts. Then, the technique seems to be applicable for melting treatment of the TRU wastes. (G.K.)

  13. Mechanical properties of melt-derived erbium oxide

    International Nuclear Information System (INIS)

    Neuman, A.D.; Blacic, M.J.; Platero, M.; Romero, R.S.; McClellan, K.J.; Petrovic, J.J.

    1998-01-01

    Erbium oxide (Er 2 O 3 ) is a rare earth oxide that is chemically and thermally stable and has a melting point of 2,430 C. There is relatively little information available regarding single crystal growth of erbia or the properties of erbia. In this study, erbia single crystals have been grown in a Xenon Optical Floating Zone Unit (XeOFZ) capable of melting materials at temperatures up to 3,000 C. Erbia was melt synthesized in the XeOFZ unit in a container less fashion, proving for little chance of contamination. Crystals were grown in compressed air and in reducing atmospheres. A recurring problem with melt synthesis of erbia is the appearance of flakes at the edges of the melt zone during growth; these flakes disrupt the growth process. The processing details and an initial survey of the physical properties of erbia single crystals is discussed

  14. Emerging melt quality control solution technologies for aluminium melt

    Directory of Open Access Journals (Sweden)

    Arturo Pascual, Jr

    2009-11-01

    Full Text Available The newly developed “MTS 1500” Melt Treatment System is performing the specifi cally required melt treatment operations like degassing, cleaning, modification and/or grain refinement by an automated process in one step and at the same location. This linked process is saving time, energy and metal losses allowing - by automated dosage of the melt treatment agents - the production of a consistent melt quality batch after batch. By linking the MTS Metal Treatment System with sensors operating on-line in the melt, i.e., with a hydrogen sensor “Alspek H”, a fully automated control of parts of the process chain like degassing is possible. This technology does guarantee a pre-specifi ed and documented melt quality in each melt treatment batch. Furthermore, to ensure that castings are consistent and predictable there is a growing realization that critical parameters such as metal cleanliness must be measured prior to casting. There exists accepted methods for measuring the cleanliness of an aluminum melt but these can be both slow and costly. A simple, rapid and meaningful method of measuring and bench marking the cleanliness of an aluminum melt has been developed to offer the foundry a practical method of measuring melt cleanliness. This paper shows the structure and performance of the integrated MTS melt treatment process and documents achieved melt quality standards after degassing, cleaning, modifi cation and grain refi nement operations under real foundry conditions. It also provides an insight on a melt cleanliness measuring device “Alspek MQ” to provide foundry men better tools in meeting the increasing quality and tighter specifi cation demand from the industry.

  15. Method of melt-decontaminating alumium contaminated with radioactivity

    International Nuclear Information System (INIS)

    Uda, Tatsuhiko; Iba, Hajime; Miura, Noboru; Kawasaki, Katsuo.

    1986-01-01

    Purpose: To enable optimum deontamination for radioactive-contaminated aluminum by further improving the decontaminating effect of the slag agent added to radioactive contaminated materials. Method: The slag agent is mainly composed of chloride type slags having a high reactivity for mainly incorporating uranium compounds and easily reacting near the melting point of aluminum and incorporated with fluorides for weakening the deliquescent characteristic to the chloride materials. Further, those slag agents are selected which can be treated at a low temperature in order to prevent the uranium compounds once incorporated into the slags from re-melting into the molten aluminum. Typically, a slag agent comprising 14 LiF, 76 KCl - 10 BaCl 2 is preferred. The basicity of the slag agent ranges from 0.5 to 2 and the melting point is 700 deg C. The melting decontaminating efficiency for the radioactive-contaminated aluminum can thus be improved. (Horiuchi, T.)

  16. Equation for the melting curve of solids under high pressure

    International Nuclear Information System (INIS)

    Boguslavskii, Yu.Ya.

    1982-01-01

    Simon's equation of the melting curve is obtained using the Clausius-Clapeyron equation in the linear approximation of the pressure dependence of the melting entropy and the volume change at the melting point. The constants in Simon's equation are calculated in this approximation for the alkali metals Li, Na, K, Rb, Cs and also for hydrogen, H 2 , and argon. It is shown that one can obtain the constants of Simon's equation in a pressure range which is wider than the region of the thermodynamical validity of Simon's equation by averaging the values of the constants determined in different points of the melting curves. The constants obtained by this manner agree well with the experimental data. (author)

  17. Petrological Geodynamics of Mantle Melting II. AlphaMELTS + Multiphase Flow: Dynamic Fractional Melting

    Science.gov (United States)

    Tirone, Massimiliano

    2018-03-01

    In this second installment of a series that aims to investigate the dynamic interaction between the composition and abundance of the solid mantle and its melt products, the classic interpretation of fractional melting is extended to account for the dynamic nature of the process. A multiphase numerical flow model is coupled with the program AlphaMELTS, which provides at the moment possibly the most accurate petrological description of melting based on thermodynamic principles. The conceptual idea of this study is based on a description of the melting process taking place along a 1-D vertical ideal column where chemical equilibrium is assumed to apply in two local sub-systems separately on some spatial and temporal scale. The solid mantle belongs to a local sub-system (ss1) that does not interact chemically with the melt reservoir which forms a second sub-system (ss2). The local melt products are transferred in the melt sub-system ss2 where the melt phase eventually can also crystallize into a different solid assemblage and will evolve dynamically. The main difference with the usual interpretation of fractional melting is that melt is not arbitrarily and instantaneously extracted from the mantle, but instead remains a dynamic component of the model, hence the process is named dynamic fractional melting (DFM). Some of the conditions that may affect the DFM model are investigated in this study, in particular the effect of temperature, mantle velocity at the boundary of the mantle column. A comparison is made with the dynamic equilibrium melting (DEM) model discussed in the first installment. The implications of assuming passive flow or active flow are also considered to some extent. Complete data files of most of the DFM simulations, four animations and two new DEM simulations (passive/active flow) are available following the instructions in the supplementary material.

  18. Vortex melting and the liquid state in YBa2Cu3Ox

    International Nuclear Information System (INIS)

    Crabtree, G. W.

    1998-01-01

    The experimental vortex phase diagram of YBa 2 Cu 3 O x is reviewed, with emphasis on first order vortex melting, the upper and lower critical points on the melting line, and the effect of disorder arising from twin boundary and point defect pinning

  19. Logistics Reduction: Heat Melt Compactor

    Data.gov (United States)

    National Aeronautics and Space Administration — The Advanced Exploration Systems (AES) Logistics Reduction (LR) project Heat Melt Compactor (HMC) technology is a waste management technology. Currently, there are...

  20. Melting in trivalent metal chlorides

    International Nuclear Information System (INIS)

    Saboungi, M.L.; Price, D.L.; Scamehorn, C.; Tosi, M.P.

    1990-11-01

    We report a neutron diffraction study of the liquid structure of YCl 3 and combine the structural data with macroscopic melting and transport data to contrast the behaviour of this molten salt with those of SrCl 2 , ZnCl 2 and AlCl 3 as prototypes of different melting mechanisms for ionic materials. A novel melting mechanism for trivalent metal chlorides, leading to a loose disordered network of edge-sharing octahedral units in the liquid phase, is thereby established. The various melting behaviours are related to bonding character with the help of Pettifor's phenomenological chemical scale. (author). 25 refs, 4 figs, 3 tabs

  1. Melting of contaminated metallic waste

    International Nuclear Information System (INIS)

    Lee, Y.-S.; Cheng, S.-Y.; Kung, H.-T.; Lin, L.-F.

    2004-01-01

    Approximately 100 tons of contaminated metallic wastes were produced each year due to maintenance for each TPC's nuclear power reactor and it was roughly estimated that there will be 10,000 tons of metallic scraps resulted from decommissioning of each reactor in the future. One means of handling the contaminated metal is to melt it. Melting process owns not only volume reduction which saves the high cost of final disposal but also resource conservation and recycling benefits. Melting contaminated copper and aluminum scraps in the laboratory scale have been conducted at INER. A total of 546 kg copper condenser tubes with a specific activity of about 2.7 Bq/g was melted in a vacuum induction melting facility. Three types of products, ingot, slag and dust were derived from the melting process, with average activities of 0.10 Bq/g, 2.33 Bq/g and 84.3 Bq/g respectively. After the laboratory melting stage, a pilot plant with a 500 kg induction furnace is being designed to melt the increasingly produced contaminated metallic scraps from nuclear facilities and to investigate the behavior of different radionuclides during melting. (author)

  2. Glass forming ability of calcium aluminosilicate melts

    DEFF Research Database (Denmark)

    Moesgaard, Mette; Yue, Yuanzheng

    2011-01-01

    The glass forming ability (GFA) of two series of calcium aluminosilicate melts is studied by measuring their viscous behavior and crystallization tendency. The first series consists of five compositions on the joining line between the eutectic point of anorthite-wollastonite-tridymite and that of......The glass forming ability (GFA) of two series of calcium aluminosilicate melts is studied by measuring their viscous behavior and crystallization tendency. The first series consists of five compositions on the joining line between the eutectic point of anorthite......-wollastonite-tridymite and that of anorthite-wollastonite-gehlenite. The series includes the eutectic compositions as end members. The second series consists of five compositions on a line parallel to the joining line on the alumina rich side. In the present work, GFA is described in terms of glass stability, i.e., the ability of a glass...... to resist crystallization during reheating. In addition, the fragility index (m) is derived by fitting the viscosity data with the Avramov-Milchev equation. The results show that m is inversely proportional to the glass stability for the two series of melts, implying that m is an indirect measure of GFA...

  3. Calculation procedure for formulating lauric and palmitic fat blends based on the grouping of triacylglycerol melting points; Procedimiento de cálculo para la formulación de mezclas de grasas lauricas y palmíticas basadas en el agrupamiento de puntos de fusión de triacilgliceroles

    Energy Technology Data Exchange (ETDEWEB)

    Nusantoro, B.P.; Yanty, N.A.M.; Van de Walle, D.; Hidayat, C.; Danthine, S.; Dewettinck, K.

    2017-07-01

    A calculation procedure for formulating lauric and palmitic fat blends has been developed based on grouping TAG melting points. This procedure offered more flexibility in choosing the initial fats and oils and eventually gave deeper insight into the existing chemical compositions and better prediction on the physicochemical properties and microstructure of the fat blends. The amount of high, medium and low melting TAGs could be adjusted using the given calculation procedure to obtain the desired functional properties in the fat blends. Solid fat contents and melting behavior of formulated fat blends showed particular patterns with respect to ratio adjustments of the melting TAG groups. These outcomes also suggested that both TAG species and their quantity had a significant influence on the crystallization behavior of the fat blends. Palmitic fat blends, in general, were found to exhibit higher SFC values than those of Lauric fat blends. Instead of the similarity in crystal microstructure, lauric fat blends were stabilized at β polymorph while palmitic fat blends were stabilized at β’ polymorph. [Spanish] Se ha desarrollado un procedimiento de cálculo para la formulación de mezclas de grasas lauricas y palmíticas basándose en la agrupación de puntos de fusión de TAG. Este procedimiento ofreció más flexibilidad en la elección de las grasas y aceites iniciales y, dio una visión más profunda de las composiciones químicas existentes y una mejor predicción sobre las propiedades físico-químicas y la microestructura de las mezclas de grasas. La cantidad de TAGs de fusión alta, media y baja se pudo ajustar usando el procedimiento de cálculo dado para obtener las propiedades funcionales deseadas en las mezclas de grasas. El contenido de grasa sólida y el comportamiento de fusión de las mezclas de grasas formuladas mostraron patrones particulares con respecto a los ajustes de relación de los grupos de fusión de TAG. Estos resultados tambi

  4. Controllable irregular melting induced by atomic segregation in bimetallic clusters with fabricating different initial configurations

    International Nuclear Information System (INIS)

    Li Guojian; Liu Tie; Wang Qiang; Lue Xiao; Wang Kai; He Jicheng

    2010-01-01

    The melting process of Co, Co-Cu and Co-Ni clusters with different initial configurations is studied in molecular dynamics by a general embedded atom method. An irregular melting, at which energy decreases as the temperature increase near the melting point, is found in the onion-like Co-Cu-Co clusters, but not in the mixed Co-Cu and onion-like Co-Ni-Co clusters. From the analysis of atomic distributions and energy variation, the results indicate the irregular melting is induced by Cu atomic segregation. Furthermore, this melting can be controlled by doping hetero atoms with different surface energies and controlling their distributions.

  5. Waste glass melting stages

    International Nuclear Information System (INIS)

    Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

    1994-01-01

    Three simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600 degrees C to 1000 degrees C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentru Karlsruhe (KfK) in Germany were used. The samples were thin sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. The behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied. 2 refs., 8 tabs

  6. Waste glass melting stages

    International Nuclear Information System (INIS)

    Anderson, L.D.; Dennis, T.; Elliott, M.L.; Hrma, P.

    1993-04-01

    Three different simulated nuclear waste glass feeds, consisting of dried waste and glass frit, were heat treated for 1 hour in a gradient furnace at temperatures ranging from approximately 600 degrees C--1000 degrees C. Simulated melter feeds from the Hanford Waste Vitrification Plant (HWVP), the Defense Waste Processing Facility (DWPF), and Kernforschungszentrum Karlsruhe (KfK) in Germany were used. The samples were thin-sectioned and examined by optical microscopy to investigate the stages of the conversion from feed to glass. Various phenomena were seen, such as frit softening, bubble formation, foaming, bubble motion and removal, convective mixing, and homogenization. Behavior of different feeds was similar, although the degree of gas generation and melt homogenization varied

  7. Observation of melting in 30 angstrom diameter CdS nanocrystals

    International Nuclear Information System (INIS)

    Goldstein, A.N.; Colvin, V.L.; Alivisatos, A.P.

    1991-01-01

    In this paper temperature dependent electron diffraction studies on 30 Angstrom diameter CdS nanocrystals are described. The linear thermal expansion coefficient of the nanocrystals is 2.75 * 10 -5 Angstrom/K, and the melting point is 575 K. These data are in contrast to bulk CdS which has a melting point of 1750 K and a linear expansion coefficient of 5.5 * 10 -6 Angstrom/K. The observed depression in the melting point of these semiconductor clusters is similar to effects observed in metals and molecular crystals, indicating that the phenomenon of reduced melting point in small systems is a general one regardless of the type of material. The observation of melting point depression in these clusters also has far reaching implications for the preparation of highly crystalline clusters of CdS, as well as for the use of these nanocrystals as precursors to thin films

  8. Epoxy resins and low melting point alloy composites

    OpenAIRE

    Ł. Wierzbicki; J. Stabik

    2011-01-01

    Purpose: The goal of this work was to describe manufacturing process of polymer matrix composite materials reinforced with Wood’s alloy particles and to observe changes of structure.Design/methodology/approach: Polymer matrix composite materials reinforced with the Wood’s alloy particles fabricating method was developed during the investigations, making it possible to obtain materials with good mechanical, electrical and thermal properties . Microscopic examination of samples cross- sections ...

  9. Rhenium corrosion in chloride melts

    International Nuclear Information System (INIS)

    Stepanov, A.D.; Shkol'nikov, S.N.; Vetyukov, M.M.

    1989-01-01

    The results investigating rhenium corrosion in chloride melts containing sodium, potassium and chromium ions by a gravimetry potentials in argon atmosphere in a sealing quarth cell are described. Rhenium corrosion is shown to be rather considerable in melts containing CrCl 2 . The value of corrosion rate depending on temperature is determined

  10. UNCONSTRAINED MELTING AND SOLIDIFICATION INSIDE ...

    African Journals Online (AJOL)

    2015-09-01

    Sep 1, 2015 ... There is a large number of experimental and numerical works on melting and solidification of PCM[6-10], and also its usage as thermal management in building [11-14], electronic devices [15-16] and solar energy. [17-20].Most investigated geometries in melting and freezing process are sphere (spherical.

  11. Development of metal-carbon eutectic cells for application as high temperature reference points in nuclear reactor severe accident tests: Results on the Fe-C, Co-C, Ti-C and Ru-C alloys' melting/freezing transformation temperature under electromagnetic induction heating

    International Nuclear Information System (INIS)

    Parga, Clemente J.; Journeau, Christophe; Parga, Clemente J.; Tokuhiro, Akira

    2012-01-01

    With the aim of reducing the high temperature measurement uncertainty of nuclear reactor severe accident experimental tests at the PLINIUS platform in Cadarache Research Centre, France, a variety of graphite cells containing a metal-carbon eutectic mix have been tested to assess the melting/freezing temperature reproducibility and their feasibility as calibration cells for thermometers. The eutectic cells have been thermally cycled in an induction furnace to assess the effect of heating/cooling rate, metal purity, graphite crucible design, and binary system constituents on the eutectic transformation temperature. A bi-chromatic pyrometer was used to perform temperature measurements in the graphite cell black cavity containing the metal-carbon eutectic mix. The eutectic points analyzed are all over 1100 C and cover an almost thousand degree span, i.e. from the Fe-Fe 3 C to the Ru-C eutectic. The induction heating permitted the attainment of heating and cooling rates of over 200 C/min under an inert atmosphere. The conducted tests allowed the determination of general trends and peculiarities of the solid. liquid transformation temperature under non-equilibrium and non-steady-state conditions of a variety of eutectic alloys (Fe-C, Co-C, Ti-C and Ru-C binary systems). (authors)

  12. Fiscal 1999 achievement report. Important regional technology research and development--Advanced machining technology for high-melting point metal based members (Development of creating technology for high-efficiency power generating members); 1999 nendo koyuten kinzokukei buzai no kodo kako gijutsu seika hokokusho. Kokoritsu hatsuden'yo buzai sosei gijutsu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-01

    Research and development is conducted concerning technologies of creating high-melting point metal based members for the purpose of enabling gas turbines to withstand still higher temperatures. In the research which deals mainly with Nb, solid solution state is enhanced, high-temperature strength and tenacity are improved by enhanced composition and diffusion, and surfaces are modified in terms of resistance to oxidation and corrosion by the technologies of multi-layer coating and slope-structured coating. In the designing and evaluation of high-strength Nb based solid solution alloys, alloys excellent in high-temperature strength and room-temperature tenacity are obtained, which contain 5-30at% Mo and 5-15at% W. In the designing and evaluation of Nb based composite materials, it is found that it strengthens the composition of Nb based enhanced solid solution alloys to add Si to Nb alloys for the precipitation of silicides in the Nb based solid solution alloy matrices. In the study of the creation technology for and evaluation of Nb based ultrahigh-temperature members, experiments are conducted with attention focused on the discharge plasma sintering method. In the development of technologies for providing oxidation resisting capability, studies are conducted about ion implantation and ion plating. (NEDO)

  13. Experiments on melt droplets falling into a water pool

    Energy Technology Data Exchange (ETDEWEB)

    Okkonen, T.; Sehgal, B.R. [Royal Inst. of Tech., Stockholm (Sweden). Div. of Nuclear Power Safety

    1998-01-01

    This paper presents experimental data and analysis related to melt droplets falling into a water pool. A binary CaO-B{sub 2}O{sub 3} melt mixture is used to study the influence of melt superheat and water subcooling on droplet deformation and fragmentation. For the conditions studied (We {<=} 1000), the surface tension of the melt droplet and the film boiling stability greatly affect the fragmentation behaviour. If the melt temperature is between the liquidus and solidus point (mushy zone) or if the film boiling is stable due to a relatively low subcooling, the droplet deformation and fragmentation are mitigated. This behaviour can be related to the effective Weber number (We) of the melt droplet upon entry into the water pool. Similar phenomena can be expected also for interactions of corium (UO{sub 2}-ZrO{sub 2}) and water, which are characterized by a potentially fast transformation of melt into the mushy zone and by particularly stable film boiling. (author)

  14. A metastable liquid melted from a crystalline solid under decompression

    Science.gov (United States)

    Lin, Chuanlong; Smith, Jesse S.; Sinogeikin, Stanislav V.; Kono, Yoshio; Park, Changyong; Kenney-Benson, Curtis; Shen, Guoyin

    2017-01-01

    A metastable liquid may exist under supercooling, sustaining the liquid below the melting point such as supercooled water and silicon. It may also exist as a transient state in solid-solid transitions, as demonstrated in recent studies of colloidal particles and glass-forming metallic systems. One important question is whether a crystalline solid may directly melt into a sustainable metastable liquid. By thermal heating, a crystalline solid will always melt into a liquid above the melting point. Here we report that a high-pressure crystalline phase of bismuth can melt into a metastable liquid below the melting line through a decompression process. The decompression-induced metastable liquid can be maintained for hours in static conditions, and transform to crystalline phases when external perturbations, such as heating and cooling, are applied. It occurs in the pressure-temperature region similar to where the supercooled liquid Bi is observed. Akin to supercooled liquid, the pressure-induced metastable liquid may be more ubiquitous than we thought.

  15. DEPENDENCY OF SULFATE SOLUBILITY ON MELT COMPOSITION AND MELT POLYMERIZATION

    International Nuclear Information System (INIS)

    JANTZEN, CAROL M.

    2004-01-01

    Sulfate and sulfate salts are not very soluble in borosilicate waste glass. When sulfate is present in excess it can form water soluble secondary phases and/or a molten salt layer (gall) on the melt pool surface which is purported to cause steam explosions in slurry fed melters. Therefore, sulfate can impact glass durability while formation of a molten salt layer on the melt pool can impact processing. Sulfate solubility has been shown to be compositionally dependent in various studies, (e.g. , B2O3, Li2O, CaO, MgO, Na2O, and Fe2O3 were shown to increase sulfate solubility while Al2O3 and SiO2 decreased sulfate solubility). This compositional dependency is shown to be related to the calculated melt viscosity at various temperatures and hence the melt polymerization

  16. Plasma arc melting of zirconium

    International Nuclear Information System (INIS)

    Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

    1997-01-01

    Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming

  17. Transition from two-dimensional to three-dimensional melting in Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Mukhopadhyay, M.K.; Sanyal, M.K.; Datta, A.; Mukherjee, M.; Geue, Th.; Grenzer, J.; Pietsch, U.

    2004-01-01

    Results of energy-dispersive x-ray reflectivity and grazing incidence diffraction studies of Langmuir-Blodgett films exhibited evolution of conventional three-dimensional melting from continuous melting, characteristic of two-dimensional systems, as a function of deposited monolayers. Continuous expansion followed by a sharp phase transition of the in-plane lattice was observed before the melting point and found to be independent of number of deposited layers. Evolution of conventional melting with an increase in the number of monolayers could be quantified by measuring stiffness against tilting of the vertical stack of molecules, which are kept together by an internal field. The internal field as defined in this model reduces as the in-plane lattice expands and the sample temperature approaches melting point. The sharpness of the melting transition, which has been approximated by a Langevin function, increases with the number of deposited monolayers

  18. Microcanonical Monte Carlo approach for computing melting curves by atomistic simulations

    OpenAIRE

    Davis, Sergio; Gutiérrez, Gonzalo

    2017-01-01

    We report microcanonical Monte Carlo simulations of melting and superheating of a generic, Lennard-Jones system starting from the crystalline phase. The isochoric curve, the melting temperature $T_m$ and the critical superheating temperature $T_{LS}$ obtained are in close agreement (well within the microcanonical temperature fluctuations) with standard molecular dynamics one-phase and two-phase methods. These results validate the use of microcanonical Monte Carlo to compute melting points, a ...

  19. Nitrogen Control in VIM Melts

    Science.gov (United States)

    Jablonski, P. D.; Hawk, J. A.

    NETL has developed a design and control philosophy for the addition of nitrogen to austenitic and ferritic steels. The design approach uses CALPHAD as the centerpiece to predict the level to which nitrogen is soluble in both the melt and the solid. Applications of this technique have revealed regions of "exclusion" in which the alloy, while within specification limits of prescribed, cannot be made by conventional melt processing. Furthermore, other investigations have found that substantial retrograde solubility of nitrogen exists, which can become problematic during subsequent melt processing and/or other finishing operations such as welding. Additionally, the CALPHAD method has been used to adjust primary melt conditions. To that end, nitrogen additions have been made using chrome nitride, silicon nitride, high-nitrogen ferrochrome as well as nitrogen gas. The advantages and disadvantages of each approach will be discussed and NETL experience in this area will be summarized with respect to steel structure.

  20. Theoretical melting curve of caesium

    International Nuclear Information System (INIS)

    Simozar, S.; Girifalco, L.A.; Pennsylvania Univ., Philadelphia

    1983-01-01

    A statistical-mechanical model is developed to account for the complex melting curve of caesium. The model assumes the existence of three different species of caesium defined by three different electronic states. On the basis of this model, the free energy of melting and the melting curve are computed up to 60 kbar, using the solid-state data and the initial slope of the fusion curve as input parameters. The calculated phase diagram agrees with experiment to within the experimental error. Other thermodynamic properties including the entropy and volume of melting were also computed, and they agree with experiment. Since the theory requires only one adjustable constant, this is taken as strong evidence that the three-species model is satisfactory for caesium. (author)

  1. Melting curves of gammairradiated DNA

    International Nuclear Information System (INIS)

    Hofer, H.; Altmann, H.; Kehrer, M.

    1978-08-01

    Melting curves of gammairradiated DNA and data derived of them, are reported. The diminished stability is explained by basedestruction. DNA denatures completely at room temperature, if at least every fifth basepair is broken or weakened by irradiation. (author)

  2. Pressure melting and ice skating

    Science.gov (United States)

    Colbeck, S. C.

    1995-10-01

    Pressure melting cannot be responsible for the low friction of ice. The pressure needed to reach the melting temperature is above the compressive failure stress and, if it did occur, high squeeze losses would result in very thin films. Pure liquid water cannot coexist with ice much below -20 °C at any pressure and friction does not increase suddenly in that range. If frictional heating and pressure melting contribute equally, the length of the wetted contact could not exceed 15 μm at a speed of 5 m/s, which seems much too short. If pressure melting is the dominant process, the water films are less than 0.08 μm thick because of the high pressures.

  3. Melting in super-earths.

    Science.gov (United States)

    Stixrude, Lars

    2014-04-28

    We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

  4. Numerical simulations of the melting behavior of bulk and nanometer-sized Cu systems

    International Nuclear Information System (INIS)

    Manai, G.; Delogu, F.

    2007-01-01

    Molecular dynamics simulations have been employed to investigate the melting mechanisms of four different Cu systems consisting of a surface-free crystalline bulk, a semi-crystal terminating with a free surface and two unsupported particles with a radius of about 4 and 8 nm, respectively. Starting from a relaxed configuration at 300 K, the systems were gradually heated up to the characteristic melting points. The surface-free bulk system underwent homogeneous melting at the limit of superheating, whereas the melting of the semi-crystal and of the nanometer-sized particles occurred with heterogeneous features. In these latter cases, the structural and energetic properties revealed a two-state character with a definite difference between disordered surface layers and bulk-like interiors. In addition, the melting point and the latent heat of fusion of the nanometer-sized particles were significantly depressed with respect to the ones of the semi-crystal, approximately corresponding to the equilibrium values. Pre-melting phenomena took place at the free surfaces at temperatures significantly below the melting point, determining the formation of a solid-liquid interface. Numerical findings indicate that in all the cases the onset of melting is connected with the proliferation and migration of lattice defects and that an intimate relationship exists between homogeneous and heterogeneous melting mechanisms

  5. Molecular dynamics simulation of UO2 nanocrystals melting under isolated and periodic boundary conditions

    International Nuclear Information System (INIS)

    Boyarchenkov, A.S.; Potashnikov, S.I.; Nekrasov, K.A.; Kupryazhkin, A.Ya.

    2012-01-01

    Highlights: ► We perform MD simulation of UO 2 nanocrystals melting (in range of 768–49 152 ions). ► T(P) melting curves intersect zero near −20 GPa and saturate near 25 GPa. ► Reciprocal size dependences of nanocrystal melting point decrease nonlinearly. ► Linear and parabolic extrapolations to macroscopic values are considered. ► Melting point and density jump are reproduced, but heat of fusion is underestimated. - Abstract: Melting of uranium dioxide (UO 2 ) nanocrystals has been studied by molecular dynamics (MD) simulation. Ten recent and widely used sets of pair potentials were assessed in the rigid ion approximation. Both isolated (in vacuum) and periodic boundary conditions (PBC) were explored. Using barostat under PBC the pressure dependences of melting point were obtained. These curves intersected zero near −20 GPa, saturated near 25 GPa and increased nonlinearly in between. Using simulation of surface under isolated boundary conditions (IBC) recommended melting temperature and density jump were successfully reproduced. However, the heat of fusion is still underestimated. These melting characteristics were calculated for nanocrystals of cubic shape in the range of 768–49 152 particles (volume range of 10–1000 nm 3 ). The obtained reciprocal size dependences decreased nonlinearly. Linear and parabolic extrapolations to macroscopic values are considered. The parabolic one is found to be better suited for analysis of the data on temperature and heat of melting.

  6. Glacial melting in Himalaya

    Directory of Open Access Journals (Sweden)

    Kavita Tariyal

    2013-07-01

    Full Text Available Mountains are amongst the most flimsy environments on Earth. They are prosperous repositories of biodiversity, water and providers of ecosystem goods and services on which downstream communities, both regional and global, rely. The transport of atmospheric pollutants and climate-altering substances can significantly impact high mountain areas, which are generally considered “clean” regions. The snow glaciers of the Himalayas, considered the “third pole”, one of the largest stores of water on the planet and accelerated melting could have far-reaching effects, such as flooding in the short-term and water shortages in the long-term as the glaciers shrink. The data available on temperature in Himalayas indicate that warming during last 3-4 decades has been more than the global average over the last century. Some of the values indicate that the Himalayas are warming 5-6 times more than the global average. Mountain systems are seen globally as the prime sufferers from climate change. There is a severe gap in the knowledge of the short and long-term implications of the impact of climate change on water and hazards in the Himalayas, and their downstream river basins. Most studies have excluded the Himalayan region because of its extreme and complex topography and the lack of adequate rain gauge data. There is an urgent need to close the knowledge gap by establishing monitoring schemes for snow, ice and water; downscaling climate models; applying hydrological models to predict water availability; and developing basin wide scenarios, which also take water demand and socioeconomic development into account. Climate change induced hazards such as floods, landslides and droughts will impose considerable stresses on the livelihoods of mountain people and downstream populations. Enhancing resilience and promoting adaptation in mountain areas have thus become among the most important priorities of this decade. It is important to strengthen local

  7. On melting dynamics and the glass transition. II. Glassy dynamics as a melting process.

    Science.gov (United States)

    Krzakala, Florent; Zdeborová, Lenka

    2011-01-21

    There are deep analogies between the melting dynamics in systems with a first-order phase transition and the dynamics from equilibrium in super-cooled liquids. For a class of Ising spin models undergoing a first-order transition--namely p-spin models on the so-called Nishimori line--it can be shown that the melting dynamics can be exactly mapped to the equilibrium dynamics. In this mapping the dynamical--or mode-coupling--glass transition corresponds to the spinodal point, while the Kauzmann transition corresponds to the first-order phase transition itself. Both in mean field and finite dimensional models this mapping provides an exact realization of the random first-order theory scenario for the glass transition. The corresponding glassy phenomenology can then be understood in the framework of a standard first-order phase transition.

  8. 3He melting pressure temperature scale

    DEFF Research Database (Denmark)

    Halperin, W.P.; Archie, C.N.; Richardson, R.C.

    1976-01-01

    temperatures. The A feature of the melting curve which suggests itself as a thermometric fixed point is found to be T//A equals 2. 75 plus or minus 0. 11 mK. The agreement between this value and independent measurements of T//A, based on nuclear or electronic paramagnetism, Johnson noise thermometry...

  9. Numerical simulation of hot-melt extrusion processes for amorphous solid dispersions using model-based melt viscosity.

    Science.gov (United States)

    Bochmann, Esther S; Steffens, Kristina E; Gryczke, Andreas; Wagner, Karl G

    2018-03-01

    Simulation of HME processes is a valuable tool for increased process understanding and ease of scale-up. However, the experimental determination of all required input parameters is tedious, namely the melt rheology of the amorphous solid dispersion (ASD) in question. Hence, a procedure to simplify the application of hot-melt extrusion (HME) simulation for forming amorphous solid dispersions (ASD) is presented. The commercial 1D simulation software Ludovic ® was used to conduct (i) simulations using a full experimental data set of all input variables including melt rheology and (ii) simulations using model-based melt viscosity data based on the ASDs glass transition and the physical properties of polymeric matrix only. Both types of HME computation were further compared to experimental HME results. Variation in physical properties (e.g. heat capacity, density) and several process characteristics of HME (residence time distribution, energy consumption) among the simulations and experiments were evaluated. The model-based melt viscosity was calculated by using the glass transition temperature (T g ) of the investigated blend and the melt viscosity of the polymeric matrix by means of a T g -viscosity correlation. The results of measured melt viscosity and model-based melt viscosity were similar with only few exceptions, leading to similar HME simulation outcomes. At the end, the experimental effort prior to HME simulation could be minimized and the procedure enables a good starting point for rational development of ASDs by means of HME. As model excipients, Vinylpyrrolidone-vinyl acetate copolymer (COP) in combination with various APIs (carbamazepine, dipyridamole, indomethacin, and ibuprofen) or polyethylene glycol (PEG 1500) as plasticizer were used to form the ASDs. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Apparatus and methods for investigations into acoustic properties of electronic melts

    International Nuclear Information System (INIS)

    Glazov, V.M.; Timoshenko, V.I.; Kim, S.G.

    1985-01-01

    Apparatus and highly sensitive methods of systematic investigations into acoustic properties of electronic melts are described. A variant of a measuring cell to investigate agressive melts is presented. A new technique for the reception of an acoustic contact with high transmission capacity of ultrasonic wave based on utilization of clarified layers of liquid boron anhydride is described. Results of calibration tests on lead and aluminium melts point to a good agreement with literature data. High sensitivity of the above technique allows one to reveal thin structural effects in melts

  11. Melting of superheated molecular crystals

    Science.gov (United States)

    Cubeta, Ulyana; Bhattacharya, Deepanjan; Sadtchenko, Vlad

    2017-07-01

    Melting dynamics of micrometer scale, polycrystalline samples of isobutane, dimethyl ether, methyl benzene, and 2-propanol were investigated by fast scanning calorimetry. When films are superheated with rates in excess of 105 K s-1, the melting process follows zero-order, Arrhenius-like kinetics until approximately half of the sample has transformed. Such kinetics strongly imply that melting progresses into the bulk via a rapidly moving solid-liquid interface that is likely to originate at the sample's surface. Remarkably, the apparent activation energies for the phase transformation are large; all exceed the enthalpy of vaporization of each compound and some exceed it by an order of magnitude. In fact, we find that the crystalline melting kinetics are comparable to the kinetics of dielectric α-relaxation in deeply supercooled liquids. Based on these observations, we conclude that the rate of non-isothermal melting for superheated, low-molecular-weight crystals is limited by constituent diffusion into an abnormally dense, glass-like, non-crystalline phase.

  12. Improved capacitive melting curve measurements

    International Nuclear Information System (INIS)

    Sebedash, Alexander; Tuoriniemi, Juha; Pentti, Elias; Salmela, Anssi

    2009-01-01

    Sensitivity of the capacitive method for determining the melting pressure of helium can be enhanced by loading the empty side of the capacitor with helium at a pressure nearly equal to that desired to be measured and by using a relatively thin and flexible membrane in between. This way one can achieve a nanobar resolution at the level of 30 bar, which is two orders of magnitude better than that of the best gauges with vacuum reference. This extends the applicability of melting curve thermometry to lower temperatures and would allow detecting tiny anomalies in the melting pressure, which must be associated with any phenomena contributing to the entropy of the liquid or solid phases. We demonstrated this principle in measurements of the crystallization pressure of isotopic helium mixtures at millikelvin temperatures by using partly solid pure 4 He as the reference substance providing the best possible universal reference pressure. The achieved sensitivity was good enough for melting curve thermometry on mixtures down to 100 μK. Similar system can be used on pure isotopes by virtue of a blocked capillary giving a stable reference condition with liquid slightly below the melting pressure in the reference volume. This was tested with pure 4 He at temperatures 0.08-0.3 K. To avoid spurious heating effects, one must carefully choose and arrange any dielectric materials close to the active capacitor. We observed some 100 pW loading at moderate excitation voltages.

  13. Automatic Control of Silicon Melt Level

    Science.gov (United States)

    Duncan, C. S.; Stickel, W. B.

    1982-01-01

    A new circuit, when combined with melt-replenishment system and melt level sensor, offers continuous closed-loop automatic control of melt-level during web growth. Installed on silicon-web furnace, circuit controls melt-level to within 0.1 mm for as long as 8 hours. Circuit affords greater area growth rate and higher web quality, automatic melt-level control also allows semiautomatic growth of web over long periods which can greatly reduce costs.

  14. Tipping Point

    Medline Plus

    Full Text Available ... en español Blog About OnSafety CPSC Stands for Safety The Tipping Point Home > 60 Seconds of Safety (Videos) > The Tipping Point The Tipping Point by ... danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe ...

  15. Magnetic susceptibility of semiconductor melts

    International Nuclear Information System (INIS)

    Kutvitskij, V.A.; Shurygin, P.M.

    1975-01-01

    The temperature dependences chi of various alloys confirm the existence of cluster formations in molten semiconductors, the stability of these formations in melts being considerably affected by the anion nature. The concentrational dependences of the magnetic susceptibility for all the investigated systems exhibit the diamagnetism maxima corresponding to the compound compositions. Heating the melt causes ''smearing'' the maxima, which is related with the cluster structure dissociation. The existence of the maxima concentrational dependence chi corresponding to BiTe and BiSe is found in the isotherms. The non-linear dependence of chi on the composition shows the absence of a single-valued relation between the phase diagram and the chi-diagram for melts

  16. Predicting the enthalpies of melting and vaporization for pure components

    Science.gov (United States)

    Esina, Z. N.; Korchuganova, M. R.

    2014-12-01

    A mathematical model of the melting and vaporization enthalpies of organic components based on the theory of thermodynamic similarity is proposed. In this empirical model, the phase transition enthalpy for the homological series of n-alkanes, carboxylic acids, n-alcohols, glycols, and glycol ethers is presented as a function of the molecular mass, the number of carbon atoms in a molecule, and the normal transition temperature. The model also uses a critical or triple point temperature. It is shown that the results from predicting the melting and vaporization enthalpies enable the calculation of binary phase diagrams.

  17. Dense Pure Tungsten Fabricated by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Dianzheng Wang

    2017-04-01

    Full Text Available Additive manufacturing using tungsten, a brittle material, is difficult because of its high melting point, thermal conductivity, and oxidation tendency. In this study, pure tungsten parts with densities of up to 18.53 g/cm3 (i.e., 96.0% of the theoretical density were fabricated by selective laser melting. In order to minimize balling effects, the raw polyhedral tungsten powders underwent a spheroidization process before laser consolidation. Compared with polyhedral powders, the spherical powders showed increased laser absorptivity and packing density, which helped in the formation of a continuous molten track and promoted densification.

  18. Estimation of structural strength of 38KhN3MFA steel, melted using different methods

    International Nuclear Information System (INIS)

    Kudrya, A.V.; Mochalov, B.V.; Fadeev, Yu.I.

    1982-01-01

    Quantity of steel melted by different methods using criteria of fracture mechanics is evaluated. Three technological variants of the 38KhN3MFA steel melting: acid Martin steel prepared by the duplex-process (melt 1); the main Martin steel melting with deoxidation and alloying in a ladle by liquid alloy and treatment with synthetic slag with argon purging after production (melt 2) and its electroslag remelt - ESP process (melt 3) are investigated. The analysis of the investigated melts has revealed that crack resistances of the acid Martin steel is higher than that of other melts at practically similar standard mechanical properties with 0.35 probability at 0.05 significance level in the low-tempered state; in the tempered state the best crack resistance is observed in the ESP main Martin steel. Metal of the main Martin melting has lower crack resistance as compared with other meltings at both strength levels. The results of the work point out the necessity of applying the criteria of fracture mechanics for obtaining an objective evaluation of the steel quality

  19. Thermophysical and Optical Properties of Semiconducting Ga2Te3 Melt

    Science.gov (United States)

    Li, Chao; Su, Ching-Hua; Lehoczky, Sandor L.; Scripa, Rosalie N.; Ban, Heng

    2005-01-01

    The majority of bulk semiconductor single crystals are presently grown from their melts. The thermophysical and optical properties of the melts provide a fundamental understanding of the melt structure and can be used to optimize the growth conditions to obtain higher quality crystals. In this paper, we report several thermophysical and optical properties for Ga2Te3 melts, such as electrical conductivity, viscosity, and optical transmission for temperatures ranging from the melting point up to approximately 990 C. The conductivity and viscosity of the melts are determined using the transient torque technique. The optical transmission of the melts is measured between the wavelengths of 300 and 2000 nm by an dual beam reversed-optics spectrophotometer. The measured properties are in good agreement with the published data. The conductivities indicate that the Ga2Te3 melt is semiconductor-like. The anomalous behavior in the measured properties are used as an indication of a structural transformation in the Ga2Te3 melt and discussed in terms of Eyring's and Bachinskii's predicted behaviors for homogeneous melts.

  20. On the rapid melt quenching

    International Nuclear Information System (INIS)

    Usatyuk, I.I.; Novokhatskij, I.A.; Kaverin, Yu.F.

    1994-01-01

    Specific features of instrumentation of traditionally employed method of melt spinning (rapid quenching), its disadvantages being discussed, were analyzed. The necessity of the method upgrading as applied to the problems of studying fine structure of molten metals and glasses was substantiated. The principle flowsheet of experimental facility for extremely rapid quenching of the melts of metals is described, specificity of its original functional units being considered. The sequence and character of all the principal stages of the method developed were discussed. 18 refs.; 3 figs

  1. Flux lattice melting in high-Tc superconductors

    International Nuclear Information System (INIS)

    Houghton, A.; Pelcovits, R.A.; Sudbo, A.

    1989-01-01

    We derive the wave-vector-dependent elastic moduli for a flux line lattice in compounds with underlying tetragonal crystalline symmetry. We find that it is essential to retain wave-vector dependence of the moduli when dealing with compounds where κ is large, as it is in the high-T c materials. We use our results to establish a Lindemann criterion for flux lattice melting, which we then compare with experimental data on two materials, and find excellent agreement. The melting curves are suppressed well below the mean-field superconducting-normal transition line and are linear in temperature over a wide range of magnetic fields. The point H=0, T=T c is approached as 1-T/T c ∼H 1/2 . The degree of suppression of the melting curves among the different compounds is accounted for in the main by differences in mass anisotropy

  2. Electrical conductivity and viscosity of borosilicate glasses and melts

    DEFF Research Database (Denmark)

    Ehrt, Doris; Keding, Ralf

    2009-01-01

    , 0 to 62·5 mol% B2O3, and 25 to 85 mol% SiO2. The glass samples were characterised by different methods. Refractive indices, density and thermal expansion were measured. Phase separation effects were investigated by electron microscopy. The electrical conductivity of glasses and melts were determined......Simple sodium borosilicate and silicate glasses were melted on a very large scale (35 l Pt crucible) to prepare model glasses of optical quality in order to investigate various properties depending on their structure. The composition of the glass samples varied in a wide range: 3 to 33·3 mol% Na2O...... by impedance measurements in a wide temperature range (250 to 1450°C). The activation energies were calculated by Arrhenius plots in various temperature regions: below the glass transition temperature, Tg, above the melting point, Tl, and between Tg and Tl. Viscosity measurements were carried out...

  3. Acoustic detection of melt particles

    International Nuclear Information System (INIS)

    Costley, R.D. Jr.

    1988-01-01

    The Reactor Safety Research Department at Sandia National Laboratories is investigating a type of Loss of Coolant Accident (LOCA). In this particular type of accident, core meltdown occurs while the pressure within the reactor pressure vessel (RPV) is high. If one of the instrument tube penetrations in the lower head fails, melt particles stream through the cavity and into the containment vessel. This experiment, which simulates this type accident, was performed in the Surtsev Direct Heating Test Facility which is approximately a 1:10 linear scaling of a large dry containment volume. A 1:10 linear scale model of the reactor cavity was placed near the bottom of the Surtsey vessel so that the exit of the cavity was at the vertical centerline of the vessel. A pressure vessel used to create the simulated molten core debris was located at the scaled height of the RPV. In order to better understand how the melt leaves the cavity and streams into the containment an array of five acoustic sensors was placed directly in the path of the melt particles about 30 feet from the exit of the sealed cavity. Highly damped, broadband sensors were chosen to minimize ringing so that individual particle hits could be detected. The goal was to count the signals produced by the individual particle hits to get some idea of how the melt particles left the cavity. This document presents some of the results of the experiment. 9 figs

  4. Melting of Pb clusters encapsulated in large fullerenes

    International Nuclear Information System (INIS)

    Delogu, Francesco

    2011-01-01

    Graphical abstract: Encapsulation significantly increases the melting point of nanometer-sized Pb particles with respect to the corresponding unsupported ones. Highlights: → Nanometer-sized Pb particles are encapsulated in fullerene cages. → Their thermal behavior is studied by molecular dynamics simulations. → Encapsulated particles undergo a pressure rise as temperature increases. → Encapsulated particles melt at temperatures higher than unsupported ones. - Abstract: Molecular dynamics simulations have been employed to explore the melting behavior of nanometer-sized Pb particles encapsulated in spherical and polyhedral fullerene cages of suitable size. The encapsulated particles, as well as the corresponding unsupported ones for comparison, were submitted to a gradual temperature rise. Encapsulation is shown to severely affect the thermodynamic behavior of Pb particles due to the different thermal expansion coefficients of particles and cages. This determines a volume constraint that induces a rise of pressure inside the fullerene cages, which operate for particles as rigid confinement systems. The result is that surface pre-melting and melting processes occur in encapsulated particles at temperatures higher than in unsupported ones.

  5. Effect of tellurium on viscosity and liquid structure of GaSb melts

    Energy Technology Data Exchange (ETDEWEB)

    Ji Leilei [School of Material Science and Engineering, Jinan University, Jinan 250022 (China); Geng Haoran [School of Material Science and Engineering, Jinan University, Jinan 250022 (China)], E-mail: mse_genghr@ujn.edu.cn; Sun Chunjing [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Teng Xinying; Liu Yamei [School of Material Science and Engineering, Jinan University, Jinan 250022 (China)

    2008-04-03

    The behavior of GaSb melt with tellurium addition was investigated using viscometer and differential scanning calorimetry (DSC). Normally, the viscosity of all melts measured decreased with the increasing temperature. However, anomalous transition points were observed in the temperature dependence of viscosity for Ga-Sb-Te system. Corresponded with the abnormal points on the viscosity-temperature curves, there were thermal effect peaks on the DSC curves. Furthermore, viscous activation energy and flow units of these melts and their structural features were discussed in this paper.

  6. Fixed Points

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 5. Fixed Points - From Russia with Love - A Primer of Fixed Point Theory. A K Vijaykumar. Book Review Volume 5 Issue 5 May 2000 pp 101-102. Fulltext. Click here to view fulltext PDF. Permanent link:

  7. Tipping Point

    Medline Plus

    Full Text Available ... OnSafety CPSC Stands for Safety The Tipping Point Home > 60 Seconds of Safety (Videos) > The Tipping Point ... 24 hours a day. For young children whose home is a playground, it’s the best way to ...

  8. Tipping Point

    Medline Plus

    Full Text Available ... 60 Seconds of Safety (Videos) > The Tipping Point The Tipping Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe Flash ...

  9. Fundamentals of Melt infiltration for the Preparation of Supported Metal Catalysts.The Case of Co/SiO2 Fischer-Tropsch Synthesis

    NARCIS (Netherlands)

    Eggenhuisen, T.M.|info:eu-repo/dai/nl/313959498; den Breejen, J.P.|info:eu-repo/dai/nl/304837318; Verdoes, D.; de Jongh, P.E.|info:eu-repo/dai/nl/186125372; de Jong, K.P.|info:eu-repo/dai/nl/06885580X

    2013-01-01

    We explored melt infiltration of mesoporous silica supports to prepare supported metal catalysts with high loadings and controllable particle sizes. Melting of Co(NO3)2 ·6H2O in the presence of silica supports was studied in situ with differential scanning calorimetry. The melting point depression

  10. Transient Cooperative Processes in Dewetting Polymer Melts.

    Science.gov (United States)

    Chandran, Sivasurender; Reiter, Günter

    2016-02-26

    We compare the high velocity dewetting behavior, at elevated temperatures, of atactic polystyrene (aPS) and isotactic polystyrene (iPS) films, with the zero shear bulk viscosity (η_{bulk}) of aPS being approximately ten times larger than iPS. As expected, for aPS the apparent viscosity of the films (η_{f}) derived from high-shear dewetting is less than η_{bulk}, displaying a shear thinning behavior. Surprisingly, for iPS films, η_{f} is always larger than η_{bulk}, even at about 50 °C above the melting point, with η_{f}/η_{bulk} following an Arrhenius behavior. The corresponding activation energy of ∼160±10  kJ/mol for iPS films suggests a cooperative motion of segments which are aligned and agglomerated by fast dewetting.

  11. Fission Product Release from Spent Nuclear Fuel During Melting

    International Nuclear Information System (INIS)

    Howell, J.P.; Zino, J.F.

    1998-09-01

    The Melt-Dilute process consolidates aluminum-clad spent nuclear fuel by melting the fuel assemblies and diluting the 235U content with depleted uranium to lower the enrichment. During the process, radioactive fission products whose boiling points are near the proposed 850 degrees C melting temperature can be released. This paper presents a review of fission product release data from uranium-aluminum alloy fuel developed from Severe Accident studies. In addition, scoping calculations using the ORIGEN-S computer code were made to estimate the radioactive inventories in typical research reactor fuel as a function of burnup, initial enrichment, and reactor operating history and shutdown time.Ten elements were identified from the inventory with boiling points below or near the 850 degrees C reference melting temperature. The isotopes 137Cs and 85Kr were considered most important. This review serves as basic data to the design and development of a furnace off-gas system for containment of the volatile species

  12. On melting of boron phosphide under pressure

    OpenAIRE

    Solozhenko, Vladimir; Mukhanov, V. A.

    2015-01-01

    Melting of cubic boron phosphide, BP, has been studied at pressures to 9 GPa using synchrotron X-ray diffraction and electrical resistivity measurements. It has been found that above 2.6 GPa BP melts congruently, and the melting curve exhibits negative slope (–60 ± 7 K/GPa), which is indicative of a higher density of the melt as compared to the solid phase.

  13. SAXS study of transient pre-melting in chain-folded alkanes

    International Nuclear Information System (INIS)

    Ungar, G.; Wills, H.H.

    1990-01-01

    A pronounced pre-melting effect is observed in chain-folded crystals of pure monodisperse n-alkane C 246 H 494 . The effect is reversible on a short time scale, but at longer times the once-folded chain crystals are irreversibly lost as slow chain extension proceeds by solid diffusion well below the melting point. The melting process is thus monitored by rapid time-resolved small-angle X-ray (SAXS) measurements, using synchrotron radiation. The results show that the observed pronounced broadening of the DSC melting endotherm for chain-folded crystals is entirely due to genuine pre-melting of lamellar surfaces. Although a significant portion of material is already molten below the final melting point of chain-folded crystals T F , no recrystallization in the chain-extended form can occur until the cores of the crystalline lamellae melt at T F . Pre-melting of extended chain crystals is significantly less pronounced than that of folded chain crystals

  14. Compositions of melts for growth of functional single crystals of complex oxides and other compounds

    Science.gov (United States)

    Soboleva, L. V.

    2008-12-01

    The melt compositions ( M c) are calculated for growing crystals with valuable physical properties. The calculation is based on the compositions of the invariant points of the liquidus curves for 33 congruently and 12 incongruently melting solid phases of 42 fusibility diagrams of binary systems. These systems include Na, Ca, Ba, Mg, and Y aluminates; Bi and Pb germanates; Li, K, Ba, and Bi borates; Ba, Fe, Sr, and Bi titanates; Li, K, Cs, Ba, Zn, Ca niobates; Li, Pb, and Gd molibdates; Pb and Nd tungstates; etc. More than 60 studies with data on the experimentally found melt compositions ( M e) for growing the noted crystals are analyzed. It is shown that the melt compositions M c and M e for growth of congruently and incongruently melting crystals are similar. Large-size stoichiometric crystals of high optical quality are grown using these melt compositions. Nonstoichiometric crystals of low structural quality are grown from melt compositions either corresponding to the stoichiometric ratio of the components ( M s) or similar to the compositions at invariant points ( M i). In these cases, a large difference is observed between the melt compositions M c, M s, and M e.

  15. Dew Point

    OpenAIRE

    Goldsmith, Shelly

    1999-01-01

    Dew Point was a solo exhibition originating at PriceWaterhouseCoopers Headquarters Gallery, London, UK and toured to the Centre de Documentacio i Museu Textil, Terrassa, Spain and Gallery Aoyama, Tokyo, Japan.

  16. Tipping Point

    Medline Plus

    Full Text Available ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe Flash ...

  17. Tipping Point

    Science.gov (United States)

    ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe Flash ...

  18. Tipping Point

    Medline Plus

    Full Text Available ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head ... see news reports about horrible accidents involving young children and furniture, appliance and tv tip-overs. The ...

  19. Tipping Point

    Medline Plus

    Full Text Available ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head ... TV falls with about the same force as child falling from the third story of a building. ...

  20. Tipping Point

    Medline Plus

    Full Text Available ... Tipping Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture ... about horrible accidents involving young children and furniture, appliance and tv tip-overs. The force of a ...

  1. Supercoil Formation During DNA Melting

    Science.gov (United States)

    Sayar, Mehmet; Avsaroglu, Baris; Kabakcioglu, Alkan

    2009-03-01

    Supercoil formation plays a key role in determining the structure-function relationship in DNA. Biological and technological processes, such as protein synthesis, polymerase chain reaction, and microarrays relys on separation of the two strands in DNA, which is coupled to the unwinding of the supercoiled structure. This problem has been studied theoretically via Peyrard-Bishop and Poland-Scheraga type models, which include a simple representation of the DNA structural properties. In recent years, computational models, which provide a more realtistic representaion of DNA molecule, have been used to study the melting behavior of short DNA chains. Here, we will present a new coarse-grained model of DNA which is capable of simulating sufficiently long DNA chains for studying the supercoil formation during melting, without sacrificing the local structural properties. Our coarse-grained model successfully reproduces the local geometry of the DNA molecule, such as the 3'-5' directionality, major-minor groove structure, and the helical pitch. We will present our initial results on the dynamics of supercoiling during DNA melting.

  2. Reaction- and melting behaviour of LWR-core components UO2, Zircaloy and steel during the meltdown period

    International Nuclear Information System (INIS)

    Hofmann, P.

    1976-07-01

    The reaction behaviour of the UO 2 , Zircaloy-4 and austenitic steel core components was investigated as a function of temperature (till melting temperatures) under inert and oxidizing conditions. Component concentrations varied between that of Corium-A (65 wt.% UO 2 , 18% Zry, 17% steel) and that of Corium-E (35 wt.% UO 2 , 10% Zry, 55% steel). In addition, Zircaloy and stainless steel were used with different degrees of oxidation. The paper describes systematically the phases that arise during heating and melting. The integral composition of the melts and the qualitative as well as quantitative analysis of the phases present in solidified corium are given. In some cases melting points have been determined. The reaction and melting behaviour of the corium specimens strongly depends on the concentration and on the degree of oxidation of the core components. First liquid phases are formed at the Zry-steel interface at about 1,350 0 C. The maximum temperatures of about 2,500 0 C for the complete melting of the corium-specimens are well below the UO 2 melting point. Depending on the steel content and/or degree of oxidation of Zry and steel, a homogeneous metallic or oxide melt or two immiscible melts - one oxide and the other metallic - are obtained. During the melting experiments performed under inert gas conditions the chemical composition of the molten specimens generally change by evaporation losses of single elements, especially of uranium, zirconium and oxygen. The total weight losses go up to 30%; under oxidizing conditions they are substantially smaller due to the occurrence of different phases. In air or water vapor, the occurrence of the phases and the melting behaviour of the core components are strongly influenced by the oxidation rate and the oxygen supply to the surface of the melt. In the case of the hypothetical core melting accident, a heterogeneous melt (oxide and metallic) is probable after the meltdown period. (orig./RW) [de

  3. Eutectic melting temperature of the lowermost Earth's mantle

    Science.gov (United States)

    Andrault, D.; Lo Nigro, G.; Bolfan-Casanova, N.; Bouhifd, M.; Garbarino, G.; Mezouar, M.

    2009-12-01

    Partial melting of the Earth's deep mantle probably occurred at different stages of its formation as a consequence of meteoritic impacts and seismology suggests that it even continues today at the core-mantle boundary. Melts are important because they dominate the chemical evolution of the different Earth's reservoirs and more generally the dynamics of the whole planet. Unfortunately, the most critical parameter, that is the temperature profile inside the deep Earth, remains poorly constrained accross the planet history. Experimental investigations of the melting properties of materials representative of the deep Earth at relevant P-T conditions can provide anchor points to refine past and present temperature profiles and consequently determine the degree of melting at the different geological periods. Previous works report melting relations in the uppermost lower mantle region, using the multi-anvil press [1,2]. On the other hand, the pyrolite solidus was determined up to 65 GPa using optical observations in the laser-heated diamond anvil cell (LH-DAC) [3]. Finally, the melting temperature of (Mg,Fe)2SiO4 olivine is documented at core-mantle boundary (CMB) conditions by shock wave experiments [4]. Solely based on these reports, experimental data remain too sparse to draw a definite melting curve for the lower mantle in the relevant 25-135 GPa pressure range. We reinvestigated melting properties of lower mantle materials by means of in-situ angle dispersive X-ray diffraction measurements in the LH-DAC at the ESRF [5]. Experiments were performed in an extended P-T range for two starting materials: forsterite and a glass with chondrite composition. In both cases, the aim was to determine the onset of melting, and thus the eutectic melting temperatures as a function of pressure. Melting was evidenced from drastic changes of diffraction peak shape on the image plate, major changes in diffraction intensities in the integrated pattern, disappearance of diffraction rings

  4. Direct contact heat transfer characteristics between melting alloy and water

    International Nuclear Information System (INIS)

    Kinoshita, Izumi; Nishi, Yoshihisa; Furuya, Masahiro

    1995-01-01

    As a candidate for an innovative steam generator for fast breeder reactors, a heat exchanger with direct contact heat transfer between melting alloy and water was proposed. The evaluation of heat transfer characteristics of this heat exchanger is one of the research subjects for the design and development of the steam generator. In this study, the effect of the pressure on heat transfer characteristics and the required degree of superheating of melting alloy above water saturation temperature are evaluated during the direct contact heat transfer experiment by injecting water into Wood's alloy. In the experiment, the pressure, the temperature of the Wood's alloy, the flow rate of feed water, and the depth of the feed water injection point are varied as parameters. As a result of the experiment, the product of the degree of Wood's alloy superheating above water saturation temperature and the depth of the feed water injection point is constant for each pressure. This constant increases as the pressure rises. (author)

  5. NMR investigations of the melting behaviour of mesogen compounds

    International Nuclear Information System (INIS)

    Limmer, S.; Grande, S.; Loesche, A.

    1977-01-01

    Proton NMR spectra of mesogen compounds in the solid phase are recorded. Between 20 and 40 K and 4 and 12 K below the melting point they exhibit a very narrow central line with a structure caused by the chemical shift, which is superimposed to the broad structureless line normally expected from polycrystalline solid phases. It is concluded that it originates from ''quasi-liquid'' molecules whose intensity grows drastically with increasing temperature and involves a maximum of about 2.5% of the whole intensity of the spectrum. In the region close to the melting point appears another lineshape, the so-called ''super-Lorentzian'' line, whose intensity increases still stronger than that of the narrow line. It can be shown that it is due to the existence of mesomorphic clusters the directors of which are statistically distributed in the sample. The impurity dependence of these effects is investigated and an attempt is made to explain them. (author)

  6. The surface quasiliquid melt acceleration and the role of thermodynamic phase in the thermal decomposition of crystalline organic explosives

    Energy Technology Data Exchange (ETDEWEB)

    Henson, Bryan F [Los Alamos National Laboratory

    2010-01-01

    We show that melt acceleration in the thermal decomposition of crystalline organic solids is a manifestation of the surface quasiliquid phase. We derive a single universal rate law for melt acceleration that is a simple function of the metastable liquid activity below the melting point, and has a zero order term proportional to the quasiliquid thickness. We argue that the underlying mechanisms of this model will provide a molecular definition for the stability of the class of secondary explosives.

  7. String-like cooperative motion in homogeneous melting.

    Science.gov (United States)

    Zhang, Hao; Khalkhali, Mohammad; Liu, Qingxia; Douglas, Jack F

    2013-03-28

    Despite the fundamental nature and practical importance of melting, there is still no generally accepted theory of this ubiquitous phenomenon. Even the earliest simulations of melting of hard discs by Alder and Wainwright indicated the active role of collective atomic motion in melting and here we utilize molecular dynamics simulation to determine whether these correlated motions are similar to those found in recent studies of glass-forming (GF) liquids and other condensed, strongly interacting, particle systems. We indeed find string-like collective atomic motion in our simulations of "superheated" Ni crystals, but other observations indicate significant differences from GF liquids. For example, we observe neither stretched exponential structural relaxation, nor any decoupling phenomenon, while we do find a boson peak, findings that have strong implications for understanding the physical origin of these universal properties of GF liquids. Our simulations also provide a novel view of "homogeneous" melting in which a small concentration of interstitial defects exerts a powerful effect on the crystal stability through their initiation and propagation of collective atomic motion. These relatively rare point defects are found to propagate down the strings like solitons, driving the collective motion. Crystal integrity remains preserved when the permutational atomic motions take the form of ring-like atomic exchanges, but a topological transition occurs at higher temperatures where the rings open to form linear chains similar in geometrical form and length distribution to the strings of GF liquids. The local symmetry breaking effect of the open strings apparently destabilizes the local lattice structure and precipitates crystal melting. The crystal defects are thus not static entities under dynamic conditions, such as elevated temperatures or material loading, but rather are active agents exhibiting a rich nonlinear dynamics that is not addressed in conventional "static

  8. Industrial opportunities of controlled melt flow during glass melting, part 1: Melt flow evaluation

    Czech Academy of Sciences Publication Activity Database

    Dyrčíková, Petra; Hrbek, Lukáš; Němec, Lubomír

    2014-01-01

    Roč. 58, č. 2 (2014), s. 111-117 ISSN 0862-5468 R&D Projects: GA TA ČR TA01010844 Institutional support: RVO:67985891 Keywords : glass melting * controlled flow * space utilization Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.435, year: 2014 http://www.ceramics-silikaty.cz/2014/pdf/2014_02_111.pdf

  9. The melting mechanism in binary Pd0.25Ni0.75 nanoparticles: molecular dynamics simulations

    Science.gov (United States)

    Domekeli, U.; Sengul, S.; Celtek, M.; Canan, C.

    2018-02-01

    The melting mechanism for Pd0.25Ni0.75 alloy nanoparticles (NPs) was investigated using molecular dynamics (MD) simulations with quantum Sutton-Chen many-body potentials. NPs of six different sizes ranging from 682 to 22,242 atoms were studied to observe the effect of size on the melting point. The melting temperatures of the NPs were estimated by following the changes in both the thermodynamic and structural quantities such as the total energy, heat capacity and Lindemann index. We also used a thermodynamics model to better estimate the melting point and to check the accuracy of MD simulations. We observed that the melting points of the NPs decreased as their sizes decreased. Although the MD simulations for the bulk system yielded higher melting temperatures because of the lack of a seed for the liquid phase, the melting temperatures determined for both the bulk material and the NPs are in good agreement with those predicted from the thermodynamics model. The melting mechanism proceeds in two steps: firstly, a liquid-like shell is formed in the outer regions of the NP with increasing temperature. The thickness of the liquid-like shell increases with increasing temperature until the shell reaches a critical thickness. Then, the entire Pd-Ni NP including core-related solid-like regions melts at once.

  10. Structure of Cd-Ga melts. Pt. 2

    International Nuclear Information System (INIS)

    Hermann, G.; Rainer-Harbach, G.; Steeb, S.

    1980-01-01

    X-ray small-angle scattering experiments were performed on nine melts of the Cd-Ga system at different temperatures up to 440 0 C. Evaluation of the data follows the Ornstein-Zernike theory of critical scattering, thus yielding correlation lengths xi of concentration fluctuations and the long-wavelenght limit Ssub(C)sub(C)(0) of the Bhatia-Thornton structure factor. Studies of the concentration and temperature dependence of xi and Ssub(C)sub(C)(0) indicate that the critical point occurs at csub(c) = 50.0 +- 1.0 at% Ga and Tsub(c) = 295.2 +- 0.1 0 C. For a melt with the critical concentration, Ssub(C)sub(C)(0) increases up to 3500 times the ideal Ssup(i)sup(d)sub(c)sub(c)(0) = csub(A)csub(B). This indicates a strong segregation tendency. In the vicinity of the critical point of the Cd-Ga system, experimental correlation lengths xi > 100 Angstroem were obtained. The critical-point exponents ν and γ were determined. It follows that the behaviour of a critical Cd-Ga melt satisfies the prediction of the classical mean-field theory for higher temperatures, whereas, within experimental accuracy, the lattice-gas predictions are satisfied upon approaching the critical temperature. (orig.)

  11. ELM-induced transient tungsten melting in the JET divertor

    Science.gov (United States)

    Coenen, J. W.; Arnoux, G.; Bazylev, B.; Matthews, G. F.; Autricque, A.; Balboa, I.; Clever, M.; Dejarnac, R.; Coffey, I.; Corre, Y.; Devaux, S.; Frassinetti, L.; Gauthier, E.; Horacek, J.; Jachmich, S.; Komm, M.; Knaup, M.; Krieger, K.; Marsen, S.; Meigs, A.; Mertens, Ph.; Pitts, R. A.; Puetterich, T.; Rack, M.; Stamp, M.; Sergienko, G.; Tamain, P.; Thompson, V.; Contributors, JET-EFDA

    2015-02-01

    The original goals of the JET ITER-like wall included the study of the impact of an all W divertor on plasma operation (Coenen et al 2013 Nucl. Fusion 53 073043) and fuel retention (Brezinsek et al 2013 Nucl. Fusion 53 083023). ITER has recently decided to install a full-tungsten (W) divertor from the start of operations. One of the key inputs required in support of this decision was the study of the possibility of W melting and melt splashing during transients. Damage of this type can lead to modifications of surface topology which could lead to higher disruption frequency or compromise subsequent plasma operation. Although every effort will be made to avoid leading edges, ITER plasma stored energies are sufficient that transients can drive shallow melting on the top surfaces of components. JET is able to produce ELMs large enough to allow access to transient melting in a regime of relevance to ITER. Transient W melt experiments were performed in JET using a dedicated divertor module and a sequence of IP = 3.0 MA/BT = 2.9 T H-mode pulses with an input power of PIN = 23 MW, a stored energy of ˜6 MJ and regular type I ELMs at ΔWELM = 0.3 MJ and fELM ˜ 30 Hz. By moving the outer strike point onto a dedicated leading edge in the W divertor the base temperature was raised within ˜1 s to a level allowing transient, ELM-driven melting during the subsequent 0.5 s. Such ELMs (δW ˜ 300 kJ per ELM) are comparable to mitigated ELMs expected in ITER (Pitts et al 2011 J. Nucl. Mater. 415 (Suppl.) S957-64). Although significant material losses in terms of ejections into the plasma were not observed, there is indirect evidence that some small droplets (˜80 µm) were released. Almost 1 mm (˜6 mm3) of W was moved by ˜150 ELMs within 7 subsequent discharges. The impact on the main plasma parameters was minor and no disruptions occurred. The W-melt gradually moved along the leading edge towards the high-field side, driven by j × B forces. The evaporation rate determined

  12. ELM-induced transient tungsten melting in the JET divertor

    International Nuclear Information System (INIS)

    Coenen, J.W.; Clever, M.; Knaup, M.; Arnoux, G.; Matthews, G.F.; Balboa, I.; Meigs, A.; Bazylev, B.; Autricque, A.; Dejarnac, R.; Horacek, J.; Komm, M.; Coffey, I.; Corre, Y.; Gauthier, E.; Devaux, S.; Krieger, K.; Frassinetti, L.; Jachmich, S.; Marsen, S.

    2015-01-01

    The original goals of the JET ITER-like wall included the study of the impact of an all W divertor on plasma operation (Coenen et al 2013 Nucl. Fusion 53 073043) and fuel retention (Brezinsek et al 2013 Nucl. Fusion 53 083023). ITER has recently decided to install a full-tungsten (W) divertor from the start of operations. One of the key inputs required in support of this decision was the study of the possibility of W melting and melt splashing during transients. Damage of this type can lead to modifications of surface topology which could lead to higher disruption frequency or compromise subsequent plasma operation. Although every effort will be made to avoid leading edges, ITER plasma stored energies are sufficient that transients can drive shallow melting on the top surfaces of components. JET is able to produce ELMs large enough to allow access to transient melting in a regime of relevance to ITER. Transient W melt experiments were performed in JET using a dedicated divertor module and a sequence of I P  = 3.0 MA/B T  = 2.9 T H-mode pulses with an input power of P IN  = 23 MW, a stored energy of ∼6 MJ and regular type I ELMs at ΔW ELM  = 0.3 MJ and f ELM  ∼ 30 Hz. By moving the outer strike point onto a dedicated leading edge in the W divertor the base temperature was raised within ∼1 s to a level allowing transient, ELM-driven melting during the subsequent 0.5 s. Such ELMs (δW ∼ 300 kJ per ELM) are comparable to mitigated ELMs expected in ITER (Pitts et al 2011 J. Nucl. Mater. 415 (Suppl.) S957–64). Although significant material losses in terms of ejections into the plasma were not observed, there is indirect evidence that some small droplets (∼80 µm) were released. Almost 1 mm (∼6 mm 3 ) of W was moved by ∼150 ELMs within 7 subsequent discharges. The impact on the main plasma parameters was minor and no disruptions occurred. The W-melt gradually moved along the leading edge towards the high-field side, driven by j

  13. Experimental study of simulant melt stream-water thermal interaction in pool and narrow geometries

    International Nuclear Information System (INIS)

    Narayanan, K.S.; Jasmin Sudha, A.; Murthy, S.S.; Rao, E.H.V.M.; Lydia, G.; Das, S.K.; Harvey, J.; Kannan, S.E.

    2005-01-01

    Full text of publication follows: Small scale experiments were carried out to investigate the thermal interaction characteristics of a few kilograms of Sn Pb, Bi and Zn as hot melt, in the film boiling region of water in an attempt to simulate a coherent fuel coolant interaction during a postulated severe accident in a nuclear reactor. Melt stream solidification and detached debris generation were studied with different melt superheat up to 200 deg. C, at different coolant temperatures of 30 deg. C, 50 deg. C, 70 deg. C, 90 deg. C, in pool geometry and in long narrow coolant column. The material was heated in an Alumina crucible and poured through a hot stainless steel funnel with a nozzle diameter of 7.7 mm, into the coolant. A stainless steel plate was used to collect the solidified mass after the interaction. Temperature monitoring was done in the coolant column close to the melt stream. The melt stream movement inside the coolant was imaged using a video camera at 25 fps. Measured melt stream entry velocity was around 1.5 m/sec. For low melt superheat and low coolant temperature, solidified porous tree like structure extended from the collector plate up to the melt release point. For water temperature of 70 deg. C, the solidified bed height at the center was found to decrease with increase in the melt superheat up to 150 deg. C. Fragmentation was found to occur when the melt superheat exceeded 200 deg. C. Particle size distribution was obtained for the fragmented debris. In 1D geometry, with 50 deg. C superheat, columnar solidification was observed with no fine debris. The paper gives the details of the results obtained in the experiments and highlights the role of Rayleigh-Taylor, Kelvin-Helmholtz instabilities and the melt physical properties on the fragmentation kinetics. (authors)

  14. Electron beam melting of sponge titanium

    International Nuclear Information System (INIS)

    Kanayama, Hiroshi; Kusamichi, Tatsuhiko; Muraoka, Tetsuhiro; Onouye, Toshio; Nishimura, Takashi

    1991-01-01

    Fundamental investigations were done on electron beam (EB) melting of sponge titanium by using 80 kW EB melting furnace. Results obtained are as follows: (1) To increase the melting yield of titanium in EB melting of sponge titanium, it is important to recover splashed metal by installation of water-cooled copper wall around the hearth and to decrease evaporation loss of titanium by keeping the surface temperature of molten metal just above the melting temperature of titanium without local heating. (2) Specific power consumption of drip melting of pressed sponge titanium bar and hearth melting of sponge titanium are approximately 0.9 kWh/kg-Ti and 0.5-0.7 kWh/kg-Ti, respectively. (3) Ratios of the heat conducted to water-cooled mould in the drip melting and to water-cooled hearth in the hearth melting to the electron beam input power are 50-65% and 60-65%, respectively. (4) Surface defects of EB-melted ingots include rap which occurs when the EB output is excessively great, and transverse cracks when the EB output is excessively small. To prevent surface defects, the up-down withdrawal method is effective. (author)

  15. Determining the thermodynamic melting parameters of sulfamethoxazole, trimethoprim, urea, nicodin, and their double eutectics by differential scanning calorimetry

    Science.gov (United States)

    Agafonova, E. V.; Moshchenskii, Yu. V.; Tkachenko, M. L.

    2013-08-01

    The literature data on the thermodynamic melting characteristics of sulfamethoxazole, urea, trimethoprim, and nicodin are analyzed for individual compounds. Their enthalpies and melting points, either individually or in the composition of eutectics, are found by means of DSC. The entropies of fusion and the cryoscopic constants of individual compounds are calculated.

  16. Eruption style at Kīlauea Volcano in Hawai‘i linked to primary melt composition

    Science.gov (United States)

    Sides. I.R.,; Edmonds, M.; Maclennan, J.; Swanson, Don; Houghton, Bruce F.

    2014-01-01

    Explosive eruptions at basaltic volcanoes have been linked to gas segregation from magmas at shallow depths in the crust. The composition of primary melts formed at greater depths was thought to have little influence on eruptive style. Ocean island basaltic volcanoes are the product of melting of a geochemically heterogeneous mantle plume and are expected to give rise to heterogeneous primary melts. This range in primary melt composition, particularly with respect to the volatile components, will profoundly influence magma buoyancy, storage and eruption style. Here we analyse the geochemistry of a suite of melt inclusions from 25 historical eruptions at the ocean island volcano of Kīlauea, Hawai‘i, over the past 600 years. We find that more explosive styles of eruption at Kīlauea Volcano are associated statistically with more geochemically enriched primary melts that have higher volatile concentrations. These enriched melts ascend faster and retain their primary nature, undergoing little interaction with the magma reservoir at the volcano’s summit. We conclude that the eruption style and magma-supply rate at Kīlauea are fundamentally linked to the geochemistry of the primary melts formed deep below the volcano. Magmas might therefore be predisposed towards explosivity right at the point of formation in their mantle source region.

  17. Liquid structure and temperature invariance of sound velocity in supercooled Bi melt

    International Nuclear Information System (INIS)

    Emuna, M.; Mayo, M.; Makov, G.; Greenberg, Y.; Caspi, E. N.; Yahel, E.; Beuneu, B.

    2014-01-01

    Structural rearrangement of liquid Bi in the vicinity of the melting point has been proposed due to the unique temperature invariant sound velocity observed above the melting temperature, the low symmetry of Bi in the solid phase and the necessity of overheating to achieve supercooling. The existence of this structural rearrangement is examined by measurements on supercooled Bi. The sound velocity of liquid Bi was measured into the supercooled region to high accuracy and it was found to be invariant over a temperature range of ∼60°, from 35° above the melting point to ∼25° into the supercooled region. The structural origin of this phenomenon was explored by neutron diffraction structural measurements in the supercooled temperature range. These measurements indicate a continuous modification of the short range order in the melt. The structure of the liquid is analyzed within a quasi-crystalline model and is found to evolve continuously, similar to other known liquid pnictide systems. The results are discussed in the context of two competing hypotheses proposed to explain properties of liquid Bi near the melting: (i) liquid bismuth undergoes a structural rearrangement slightly above melting and (ii) liquid Bi exhibits a broad maximum in the sound velocity located incidentally at the melting temperature

  18. Tin in granitic melts: The role of melting temperature and protolith composition

    Science.gov (United States)

    Wolf, Mathias; Romer, Rolf L.; Franz, Leander; López-Moro, Francisco Javier

    2018-06-01

    Granite bound tin mineralization typically is seen as the result of extreme magmatic fractionation and late exsolution of magmatic fluids. Mineralization, however, also could be obtained at considerably less fractionation if initial melts already had enhanced Sn contents. We present chemical data and results from phase diagram modeling that illustrate the dominant roles of protolith composition, melting conditions, and melt extraction/evolution for the distribution of Sn between melt and restite and, thus, the Sn content of melts. We compare the element partitioning between leucosome and restite of low-temperature and high-temperature migmatites. During low-temperature melting, trace elements partition preferentially into the restite with the possible exception of Sr, Cd, Bi, and Pb, that may be enriched in the melt. In high-temperature melts, Ga, Y, Cd, Sn, REE, Pb, Bi, and U partition preferentially into the melt whereas Sc, V, Cr, Co, Ni, Mo, and Ba stay in the restite. This contrasting behavior is attributed to the stability of trace element sequestering minerals during melt generation. In particular muscovite, biotite, titanite, and rutile act as host phases for Sn and, therefore prevent Sn enrichment in the melt as long as they are stable phases in the restite. As protolith composition controls both the mineral assemblage and modal contents of the various minerals, protolith composition eventually also controls the fertility of a rock during anatexis, restite mineralogy, and partitioning behavior of trace metals. If a particular trace element is sequestered in a phase that is stable during partial melting, the resulting melt is depleted in this element whereas the restite becomes enriched. Melt generation at high temperature may release Sn when Sn-hosts become unstable. If melt has not been lost before the breakdown of Sn-hosts, Sn contents in the melt will increase but never will be high. In contrast, if melt has been lost before the decomposition of Sn

  19. Chemical decontamination and melt densification

    International Nuclear Information System (INIS)

    Dillon, R.L.; Griggs, B.; Kemper, R.S.; Nelson, R.G.

    1976-01-01

    Preliminary studies on the chemical decontamination and densification of Zircaloy, stainless steel, and Inconel undissolved residues remaining after dissolution of the UO 2 --PuO 2 spent fuel material from sheared fuel bundles are reported. The studies were made on cold or very small samples to demonstrate the feasibility of the processes developed before proceeding to hot cell demonstrations with kg level of the sources. A promising aqueous decontamination method for Zr alloy cladding was developed in which oxidized surfaces are conditioned with HF prior to leaching with ammonium oxalate, ammonium citrate, ammonium fluoride, and hydrogen peroxide. Feasibility of molten salt decontamination of oxidized Zircaloy was demonstrated. A low melting alloy of Zircaloy, stainless steel, and Inconel was obtained in induction heated graphite crucibles. Segregated Zircaloy cladding sections were directly melted by the inductoslag process to yield a metal ingot suitable for storage. Both Zircaloy and Zircaloy--stainless steel--Inconel alloys proved to be highly satisfactory getters and sinks for recovered tritium

  20. Monitoring of polymer melt processing

    International Nuclear Information System (INIS)

    Alig, Ingo; Steinhoff, Bernd; Lellinger, Dirk

    2010-01-01

    The paper reviews the state-of-the-art of in-line and on-line monitoring during polymer melt processing by compounding, extrusion and injection moulding. Different spectroscopic and scattering techniques as well as conductivity and viscosity measurements are reviewed and compared concerning their potential for different process applications. In addition to information on chemical composition and state of the process, the in situ detection of morphology, which is of specific interest for multiphase polymer systems such as polymer composites and polymer blends, is described in detail. For these systems, the product properties strongly depend on the phase or filler morphology created during processing. Examples for optical (UV/vis, NIR) and ultrasonic attenuation spectra recorded during extrusion are given, which were found to be sensitive to the chemical composition as well as to size and degree of dispersion of micro or nanofillers in the polymer matrix. By small-angle light scattering experiments, process-induced structures were detected in blends of incompatible polymers during compounding. Using conductivity measurements during extrusion, the influence of processing conditions on the electrical conductivity of polymer melts with conductive fillers (carbon black or carbon nanotubes) was monitored. (topical review)

  1. Experimental evidence for flux-lattice melting. [in high-Tc superconductors

    Science.gov (United States)

    Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.

    1991-01-01

    A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.

  2. Features of melting of indium monohalides

    Energy Technology Data Exchange (ETDEWEB)

    Dmitriev, V S; Smirniv, V A [AN SSSR, Chernogolovka. Inst. Fiziki Tverdogo Tela

    1980-12-01

    The character of InCl, InBr and InI melting is investigated by the methods of DTA, calorimetry, conductometry and chemical analysis. Partial decomposition of monohalogenides during melting according to the reactions of disproportionation is shown. The presence of disproportionation products (In/sup 0/ and In/sup 3 +/) is manifested in the properties of solid monohalogenides, prepared by the crystallization from melt, in their photosensitivity and electroconductivity.

  3. Comparative Study on Two Melting Simulation Methods: Melting Curve of Gold

    International Nuclear Information System (INIS)

    Liu Zhong-Li; Li Rui; Sun Jun-Sheng; Zhang Xiu-Lu; Cai Ling-Cang

    2016-01-01

    Melting simulation methods are of crucial importance to determining melting temperature of materials efficiently. A high-efficiency melting simulation method saves much simulation time and computational resources. To compare the efficiency of our newly developed shock melting (SM) method with that of the well-established two-phase (TP) method, we calculate the high-pressure melting curve of Au using the two methods based on the optimally selected interatomic potentials. Although we only use 640 atoms to determine the melting temperature of Au in the SM method, the resulting melting curve accords very well with the results from the TP method using much more atoms. Thus, this shows that a much smaller system size in SM method can still achieve a fully converged melting curve compared with the TP method, implying the robustness and efficiency of the SM method. (paper)

  4. Modelling of the controlled melt flow in a glass melting space – Its melting performance and heat losses

    Czech Academy of Sciences Publication Activity Database

    Jebavá, Marcela; Dyrčíková, Petra; Němec, Lubomír

    2015-01-01

    Roč. 430, DEC 15 (2015), s. 52-63 ISSN 0022-3093 Institutional support: RVO:67985891 Keywords : glass melt flow * mathematical modelling * energy distribution * space utilizatios * melting performance Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.825, year: 2015

  5. Melting and Sintering of Ashes

    DEFF Research Database (Denmark)

    Hansen, Lone Aslaug

    1997-01-01

    -1300°C, and a trend of higher fusion temperatures with increasing contents of Al-silicates and quartz was found.c) Fly ashes, bottom ashes and deposits from coal/straw co-firing were all found to consist mainly of metal-alumina and alumina-silicates. These ashes all melt in the temperature range 1000......The thesis contains an experimental study of the fusion and sintering of ashes collected during straw and coal/straw co-firing.A laboratory technique for quantitative determination of ash fusion has been developed based on Simultaneous Thermal Analysis (STA). By means of this method the fraction......, the biggest deviations being found for salt rich (i.e. straw derived) ashes.A simple model assuming proportionality between fly ash fusion and deposit formation was found to be capable of ranking deposition rates for the different straw derived fly ashes, whereas for the fly ashes from coal/straw co-firing...

  6. Resistance–temperature relation and atom cluster estimation of In–Bi system melts

    International Nuclear Information System (INIS)

    Geng, Haoran; Wang Zhiming; Zhou Yongzhi; Li Cancan

    2012-01-01

    Highlights: ► A testing device was adopted to measure the electrical resistivity of In–Bi system melts. ► A basically linear relation exists between the resistivity and temperature of In x Bi 100−x melts in measured temperature range. ► Based on Novakovic's assumption, the content of InBi atomic cluster in In x Bi 100−x melt is estimated with ρ ≈ ρ InBi x InBi + ρ m (1 − x InBi ) equation. - Abstract: A testing device for the resistivity of high-temperature melt was adopted to measure the l resistivity of In–Bi system melts at different temperatures. It can be concluded from the analysis and calculation of the experimental results that the resistivity of In x Bi 100−x (x = 0–100) melt is in linear relationship with temperature within the experiment temperature range. The resistivity of the melt decreases with the increasing content of In. The fair consistency of resistivity of In–Bi system melt is found in the heating and cooling processes. On the basis of Novakovic's assumption, we approximately estimated the content of InBi atom clusters in In x Bi 100−x melts with the resistivity data by equation ρ ≈ ρ InBi x InBi + ρ m (1 − x InBi ). In the whole components interval, the content corresponds well with the mole fraction of InBi clusters calculated by Novakovic in the thermodynamic approach. The mole fraction of InBi type atom clusters in the melts reaches the maximum at the point of stoichiometric composition In 50 Bi 50 .

  7. A Unified Theory of Melting, Crystallization and Glass Formation

    DEFF Research Database (Denmark)

    Cotterill, R. M. J.; Jensen, F. J.; Damgaard Kristensen, W.

    1975-01-01

    In recent years, dislocations have been involved in theories of melting, in models of the liquid state, and in calculations of the viscosity of glasses. Particularly noteworthy are the Mott-Gurney model of a liquid as a polycrystal with a grain size (i. e. a dislocation network size) of near......-atomic dimensions, and the demonstration by Kotze and Kuhlmann-Wilsdorf that the solid-liquid interfacial energy is proportional to the grain boundary energy for a number of elements. These developments suggest the possibility of a relatively simple picture of crystallization and glass formation. In the liquid...... state dislocations, at the saturation density, are in constant motion and the microscopic grain boundary structure that they form is constantly changing due to dislocation-dislocation interaction. As the liquid is cooled below the melting point the free energy favors the crystalline form and grains...

  8. Devitrification of defense nuclear waste glasses: role of melt insolubles

    International Nuclear Information System (INIS)

    Bickford, D.F.; Jantzen, C.M.

    1985-01-01

    Time-temperature-transformation (TTT) curves have been determined for simulated nuclear waste glasses bounding the compositional range in the Defense Waste Processing Facility (DWPF). Formulations include all of the minor chemical elements such as ruthenium and chromium which have limited solubility in borosilicate glasses. Heterogeneous nucleation of spinel on ruthenium dioxide, and subsequent nucleation of acmite on spinel is the major devitrification path. Heterogeneous nucleation on melt insolubles causes more rapid growth of crystalline devitrification phases, than in glass free of melt insolubles. These studies point out the importance of simulating waste glass composition and processing as accurately as possible to obtain reliable estimates of glass performance. 11 refs., 8 figs., 1 tab

  9. Melt and vapor characteristics in an electron beam evaporator

    Energy Technology Data Exchange (ETDEWEB)

    Blumenfeld, L.; Fleche, J.L.; Gonella, C.; Soubbaramayer

    1994-12-31

    Two different approaches have been compared for the calculation of the free surface temperature Ts in cerium or copper evaporation experiments: the first method considers properties of the melt: an empirical law is used to take into account turbulent thermal convection, instabilities and characterization of the free surface. The second method considers the vapor flow expansion and connects Ts to the measured terminal temperature and terminal mean parallel velocity of the vapor jet, by direct simulation Monte Carlo calculations including an atom-atom inelastic collision algorithm. The agreement between the two approaches is better for cerium than for copper in the high characterization case. The analysis, from the point of view of the properties of the melt, of the terminal parameters of the vapor jet for the high beam powers shows that Ts and the Knudsen number at the vapour source reach a threshold when the beam power increases. (author). 12 figs., 1 tab., 21 refs.

  10. The melting and crystallization behavior of irradiated poly(1-butene)

    International Nuclear Information System (INIS)

    Markovic, V.; Silverman, J.

    1982-01-01

    Isotactic poly(1-butene) samples were melted and crystallized. This treatment leaves the polymer in the unstable crystalline form, known as Modification II. The transformation to stable Modification I normally has a half life of 1 day. Samples were irradiated within 30 min after crystallization with high doses of electrons delivered in intervals up to a few minutes. This permitted measurements of radiation effects on Modification II under circumstances where the II-I crystal transformation was negligibly small. Similar measurements were performed on stable Modification I, which was obtained by waiting for the completion of the II-I transformation; for this stable crystalline form, relatively low dose rate γ-exposures serve as well as high dose rate electron beams in measuring radiation effects. DSC and IR absorption measurements were performed. The effect of radiation on the fusion endotherms, melting points, IR spectra, and some aspects of the kinetics of crystalline transformation are presented. (author)

  11. Hydrogen effect on different melts of steel 03Cr10Ni10Mo2(Ti,Al)

    International Nuclear Information System (INIS)

    Hruby, J.; Novosad, P.; Axamit, R.

    1984-01-01

    The effect of hydrogen on martensitic 03Cr10Ni10Mo2(Ti,Al) steel was studied following vacuum induction melting and electroslag remelting with and without the effect of radiation. Under the influence of hydrogen and under the same parameters of catodic hydrogen charging of steel after vacuum induction melting shows a 20 - 30% reduction in total ductility. Steels after electroslag remelting show a higher reduction in total ductility - within the range of 26 - 33%, i.e., 33 - 43% for different melts, and contraction Z shows a reduction of 23 - 59%. Electroslag remelted steels show a greater reduction in plasticity owing to hydrogen than steels melted in vacuum induction furnaces. The reduction of the yield point and the breaking strength owing to hydrogen are more explicit than in steel after vacuum melting. In non-irradiated hydrogenated samples a higher yield point was evident. (B.S.)

  12. Reaction of soda-lime-silica glass melt with water vapour at melting temperatures

    Czech Academy of Sciences Publication Activity Database

    Vernerová, Miroslava; Kloužek, Jaroslav; Němec, Lubomír

    2015-01-01

    Roč. 416, MAY 15 (2015), s. 21-30 ISSN 0022-3093 R&D Projects: GA TA ČR TA01010844 Institutional support: RVO:67985891 Keywords : glass melt * sulfate * water vapour * bubble nucleation * melt foaming * glass melting Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.825, year: 2015

  13. High-pressure melting curve of KCl: Evidence against lattice-instability theories of melting

    International Nuclear Information System (INIS)

    Ross, M.; Wolf, G.

    1986-01-01

    We show that the large curvature in the T-P melting curve of KCl is the result of a reordering of the liquid to a more densely packed arrangement. As a result theories of melting, such as the instability model, which do not take into account the structure of the liquid fail to predict the correct pressure dependence of the melting curve

  14. Size-dependent melting modes and behaviors of Ag nanoparticles: a molecular dynamics study

    Science.gov (United States)

    Liang, Tianshou; Zhou, Dejian; Wu, Zhaohua; Shi, Pengpeng

    2017-12-01

    The size-dependent melting behaviors and mechanisms of Ag nanoparticles (NPs) with diameters of 3.5-16 nm were investigated by molecular dynamics (MD). Two distinct melting modes, non-premelting and premelting with transition ranges of about 7-8 nm, for Ag NPs were demonstrated via the evolution of distribution and transition of atomic physical states during annealing. The small Ag NPs (3.5-7 nm) melt abruptly without a stable liquid shell before the melting point, which is characterized as non-premelting. A solid-solid crystal transformation is conducted through the migration of adatoms on the surface of Ag NPs with diameters of 3.5-6 nm before the initial melting, which is mainly responsible for slightly increasing the melting point of Ag NPs. On the other hand, surface premelting of Ag NPs with diameters of 8-16 nm propagates from the outer shell to the inner core with initial anisotropy and late isotropy as the temperature increases, and the close-packed facets {111} melt by a side-consumed way which is responsible for facets {111} melting in advance relative to the crystallographic plane {111}. Once a stable liquid shell is formed, its size-independent minimum thickness is obtained, and a three-layer structure of atomic physical states is set up. Lastly, the theory of point defect-pair (vacancy-interstitial) severing as the mechanism of formation and movement of the solid-liquid interface was also confirmed. Our study provides a basic understanding and theoretical guidance for the research, production and application of Ag NPs.

  15. Permeability and 3-D melt geometry in shear-induced high melt fraction conduits

    Science.gov (United States)

    Zhu, W.; Cordonnier, B.; Qi, C.; Kohlstedt, D. L.

    2017-12-01

    Observations of dunite channels in ophiolites and uranium-series disequilibria in mid-ocean ridge basalt suggest that melt transport in the upper mantle beneath mid-ocean ridges is strongly channelized. Formation of high melt fraction conduits could result from mechanical shear, pyroxene dissolution, and lithological partitioning. Deformation experiments (e.g. Holtzman et al., 2003) demonstrate that shear stress causes initially homogeneously distributed melt to segregate into an array of melt-rich bands, flanked by melt-depleted regions. At the same average melt fraction, the permeability of high melt fraction conduits could be orders of magnitude higher than that of their homogenous counterparts. However, it is difficult to determine the permeability of melt-rich bands. Using X-ray synchrotron microtomography, we obtained high-resolution images of 3-dimensional (3-D) melt distribution in a partially molten rock containing shear-induced high melt fraction conduits. Sample CQ0705, an olivine-alkali basalt aggregate with a nominal melt fraction of 4%, was deformed in torsion at a temperature of 1473 K and a confining pressure of 300 MPa to a shear strain of 13.3. A sub-volume of CQ0705 encompassing 3-4 melt-rich bands was imaged. Microtomography data were reduced to binary form so that solid olivine is distinguishable from basalt glass. At a spatial resolution of 160 nm, the 3-D images reveal the shape and connectedness of melt pockets in the melt-rich bands. Thin melt channels formed at grain edges are connected at large melt nodes at grain corners. Initial data analysis shows a clear preferred orientation of melt pockets alignment subparallel to the melt-rich band. We use the experimentally determined geometrical parameters of melt topology to create a digital rock with identical 3-D microstructures. Stokes flow simulations are conducted on the digital rock to obtain the permeability tensor. Using this digital rock physics approach, we determine how deformation

  16. Recent Changes in the Arctic Melt Season

    Science.gov (United States)

    Stroeve, Julienne; Markus, Thorsten; Meier, Walter N.; Miller, Jeff

    2007-01-01

    Melt-season duration, melt-onset and freeze-up dates are derived from satellite passive microwave data and analyzed from 1979 to 2005 over Arctic sea ice. Results indicate a shift towards a longer melt season, particularly north of Alaska and Siberia, corresponding to large retreats of sea ice observed in these regions. Although there is large interannual and regional variability in the length of the melt season, the Arctic is experiencing an overall lengthening of the melt season at a rate of about 2 weeks decade(sup -1). In fact, all regions in the Arctic (except for the central Arctic) have statistically significant (at the 99% level or higher) longer melt seasons by greater than 1 week decade(sup -1). The central Arctic shows a statistically significant trend (at the 98% level) of 5.4 days decade(sup -1). In 2005 the Arctic experienced its longest melt season, corresponding with the least amount of sea ice since 1979 and the warmest temperatures since the 1880s. Overall, the length of the melt season is inversely correlated with the lack of sea ice seen in September north of Alaska and Siberia, with a mean correlation of -0.8.

  17. Niobium interaction with chloride-carbonate melts

    International Nuclear Information System (INIS)

    Kuznetsov, S.A.; Kuznetsova, S.V.

    1996-01-01

    Niobium interaction with chloride-carbonate melt NaCl-KCl-K 2 CO 3 (5 mass %) in the temperature range of 973-1123 K has been studied. The products and niobium corrosion rate have been ascertained, depending on the temperature of melt and time of allowance. Potentials of niobium corrosion have been measured. Refs. 11, figs. 3, tabs. 2

  18. Attenuation in Melting Layer of Precipitation

    NARCIS (Netherlands)

    Klaassen, W.

    1988-01-01

    A model of the melting layer is employed on radar measurements to simulate the attenuation of radio waves at 12, 20 and 30GHz. The attenuation in the melting layer is simulated to be slightly larger than that of rain with the same path length and precipitation intensity. The result appears to depend

  19. Multiscale approach to equilibrating model polymer melts

    DEFF Research Database (Denmark)

    Svaneborg, Carsten; Ali Karimi-Varzaneh, Hossein; Hojdis, Nils

    2016-01-01

    We present an effective and simple multiscale method for equilibrating Kremer Grest model polymer melts of varying stiffness. In our approach, we progressively equilibrate the melt structure above the tube scale, inside the tube and finally at the monomeric scale. We make use of models designed...

  20. Disordering and Melting of Aluminum Surfaces

    DEFF Research Database (Denmark)

    Stoltze, Per; Nørskov, Jens Kehlet; Landman, U.

    1988-01-01

    We report on a molecular-dynamics simulation of an Al(110) surface using the effective-medium theory to describe the interatomic interactions. The surface region is found to start melting ≅200 K below the bulk melting temperature with a gradual increase in the thickness of the disordered layer as...

  1. Size and temperature consideration in the liquid layer growth from nanovoids and the melting model construction

    International Nuclear Information System (INIS)

    Li, H.; Liang, X.H.; Li, M.

    2014-01-01

    A new model for the solid melting point T m (D) from nanovoids is proposed through considering the liquid layer growth behavior. This model, which does not have any adjustable parameter, introduces the classical thermodynamic treatment, i.e., the liquid nucleation and growth theory, for nanoparticle melting. With increased void diameter D, T m (D) approaches to T m0 . Moreover, T m (D) > T m0 for a small void (T m0 is the bulk melting point). In other words, the solid can be significantly superheated especially when D decreases, even if the difference of interface energy is larger than zero. This finding can be expected from the negatively curved surface of the void. The model predictions are consistent with the molecular dynamic (MD) simulation results for argon solids. Moreover, the growth of liquid layer from void surface relies on both size and temperature, which directly determine liquid layer thickness, and only when liquid layer thickness reaches to a critical value, can void become instable. - Highlights: • A united model for the crystal melting point from nanovoids is established. • Melting point increases with decreased void size. • The result is expected from the negatively curved surface of the void. • The prediction is agreed well with the MD simulation results

  2. Shape evolution of a melting nonspherical particle

    Science.gov (United States)

    Kintea, Daniel M.; Hauk, Tobias; Roisman, Ilia V.; Tropea, Cameron

    2015-09-01

    In this study melting of irregular ice crystals was observed in an acoustic levitator. The evolution of the particle shape is captured using a high-speed video system. Several typical phenomena have been discovered: change of the particle shape, appearance of a capillary flow of the melted liquid on the particle surface leading to liquid collection at the particle midsection (where the interface curvature is smallest), and appearance of sharp cusps at the particle tips. No such phenomena can be observed during melting of spherical particles. An approximate theoretical model is developed which accounts for the main physical phenomena associated with melting of an irregular particle. The agreement between the theoretical predictions for the melting time, for the evolution of the particle shape, and the corresponding experimental data is rather good.

  3. Melting Can Hinder Impact-Induced Adhesion

    Science.gov (United States)

    Hassani-Gangaraj, Mostafa; Veysset, David; Nelson, Keith A.; Schuh, Christopher A.

    2017-10-01

    Melting has long been used to join metallic materials, from welding to selective laser melting in additive manufacturing. In the same school of thought, localized melting has been generally perceived as an advantage, if not the main mechanism, for the adhesion of metallic microparticles to substrates during a supersonic impact. Here, we conduct the first in situ supersonic impact observations of individual metallic microparticles aimed at the explicit study of melting effects. Counterintuitively, we find that under at least some conditions melting is disadvantageous and hinders impact-induced adhesion. In the parameter space explored, i.e., ˜10 μ m particle size and ˜1 km /s particle velocity, we argue that the solidification time is much longer than the residence time of the particle on the substrate, so that resolidification cannot be a significant factor in adhesion.

  4. Modeling the summertime evolution of sea-ice melt ponds

    DEFF Research Database (Denmark)

    Lüthje, Mikael; Feltham, D.L.; Taylor, P.D.

    2006-01-01

    We present a mathematical model describing the summer melting of sea ice. We simulate the evolution of melt ponds and determine area coverage and total surface ablation. The model predictions are tested for sensitivity to the melt rate of unponded ice, enhanced melt rate beneath the melt ponds...

  5. Angular forces and melting in bcc transition metals: A case study of molybdenum

    International Nuclear Information System (INIS)

    Moriarty, J.A.

    1994-01-01

    Both the multi-ion and effective pair potentials also permit a large amount of supercooling of the liquid before the onset of freezing. With v 2 eff a bcc structure is nucleated at freezing, while with the multi-ion potentials an amorphous glasslike structure is obtained, which appears to be related to the energetically competitive A15 structure. In our second approach to melting, the multi-ion potentials have been used to obtain accurate solid and liquid free energies from quasiharmonic lattice dynamics and MD calculations of thermal energies and pressures. The resulting ion-thermal melting curve exactly overlaps the dynamically observed melting point, indicating that no superheating of the solid occurred in our MD simulations. To obtain a full melting curve, electron-thermal contributions to the solid and liquid free energies are added in terms of the density of electronic states at the Fermi level, ρ(E F ). Here the density of states for the solid has been calculated with the linear-muffin-tin-orbital method, while for the liquid tight-binding calculations have been used to justify a simple model. In the liquid ρ(E F ) is increased dramatically over the bcc solid, and the net effect of the electron-thermal contributions is to lower the calculated melting temperatures by about a factor of 2. A full melting curve to 2 Mbar has thereby been obtained and the calculated melting properties near zero pressure are in generally good agreement with experiment

  6. Heat transfer in melt ponds with convection and radiative heating: observationally-inspired modelling

    Science.gov (United States)

    Wells, A.; Langton, T.; Rees Jones, D. W.; Moon, W.; Kim, J. H.; Wilkinson, J.

    2016-12-01

    Melt ponds have key impacts on the evolution of Arctic sea ice and summer ice melt. Small changes to the energy budget can have significant consequences, with a net heat-flux perturbation of only a few Watts per square metre sufficient to explain the thinning of sea ice over recent decades. Whilst parameterisations of melt-pond thermodynamics often assume that pond temperatures remain close to the freezing point, recent in-situ observations show more complex thermal structure with significant diurnal and synoptic variability. We here consider the energy budget of melt ponds and explore the role of internal convective heat transfer in determining the thermal structure within the pond in relatively calm conditions with low winds. We quantify the energy fluxes and temperature variability using two-dimensional direct numerical simulations of convective turbulence within a melt pond, driven by internal radiative heating and surface fluxes. Our results show that the convective flow dynamics are modulated by changes to the incoming radiative flux and sensible heat flux at the pond surface. The evolving pond surface temperature controls the outgoing longwave emissions from the pond. Hence the convective flow modifies the net energy balance of a melt pond, modulating the relative fractions of the incoming heat flux that is re-emitted to the atmosphere or transferred downward into the sea ice to drive melt.

  7. Study on plasma melting treatment of crucibles, ceramic filter elements, asbestos, and fly ash

    International Nuclear Information System (INIS)

    Hoshi, Akiko; Nakasio, Nobuyuki; Nakajima, Mikio

    2004-01-01

    The Japan Atomic Energy Research Institute (JAERI) decided to adopt an advanced volume reduction program for low-level radioactive wastes. In this program, inorganic wastes are converted to stable glassy products suitable for disposal by a plasma melting system in the Waste Volume Reduction Facilities (WVRF). High melting point wastes such as refractories are excluded from the plasma melting treatment in the WVRF, and wastes difficult to handle such as asbestos are also excluded. However, it is describable to apply the plasma melting treatment to these wastes for stabilization and volume reduction from the viewpoint of disposal. In this paper, plasma melting test of crucibles, ceramic filter elements, asbestos, and simulated fly ashes were carried out as a part of technical support for WVRF. The plasma melting treatment was applicable for crucibles and asbestos because homogeneous and glassy products were obtained by controlling of waste and loading condition. It was found that SiC in ceramic filter elements was volatile with a plasma torch with inert gas, and adding reducer was ineffective against stabilizing volatile metals such as Zn, Pb in a solidified product in the melting test of simulated fly ash. (author)

  8. Volatile diffusion in silicate melts and its effects on melt inclusions

    Directory of Open Access Journals (Sweden)

    P. Scarlato

    2005-06-01

    Full Text Available A compendium of diffusion measurements and their Arrhenius equations for water, carbon dioxide, sulfur, fluorine, and chlorine in silicate melts similar in composition to natural igneous rocks is presented. Water diffusion in silicic melts is well studied and understood, however little data exists for melts of intermediate to basic compositions. The data demonstrate that both the water concentration and the anhydrous melt composition affect the diffusion coefficient of water. Carbon dioxide diffusion appears only weakly dependent, at most, on the volatilefree melt composition and no effect of carbon dioxide concentration has been observed, although few experiments have been performed. Based upon one study, the addition of water to rhyolitic melts increases carbon dioxide diffusion by orders of magnitude to values similar to that of 6 wt% water. Sulfur diffusion in intermediate to silicic melts depends upon the anhydrous melt composition and the water concentration. In water-bearing silicic melts sulfur diffuses 2 to 3 orders of magnitude slower than water. Chlorine diffusion is affected by both water concentration and anhydrous melt composition; its values are typically between those of water and sulfur. Information on fluorine diffusion is rare, but the volatile-free melt composition exerts a strong control on its diffusion. At the present time the diffusion of water, carbon dioxide, sulfur and chlorine can be estimated in silicic melts at magmatic temperatures. The diffusion of water and carbon dioxide in basic to intermediate melts is only known at a limited set of temperatures and compositions. The diffusion data for rhyolitic melts at 800°C together with a standard model for the enrichment of incompatible elements in front of growing crystals demonstrate that rapid crystal growth, greater than 10-10 ms-1, can significantly increase the volatile concentrations at the crystal-melt interface and that any of that melt trapped

  9. Mineral conversion and microstructure change in the melting process of Shenmu coal ash

    Energy Technology Data Exchange (ETDEWEB)

    Yang Jianguo; Deng Furong; Zhao Hong; Cen Kefa [Zhejiang University, Hangzhou (China). State Key Laboratory of Clean Energy Utilization

    2007-05-15

    China has rich reserves of Shenmu coal, which has the typical characteristic of low-melting-point ash. If used in the pulverized-coal boiler of a power plant, Shenmu coal would cause serious slagging. In order to solve the slagging problem of Shenmu coal, the melting mechanism of Shenmu coal ash was studied. One of the Shenmu coals - Wenjialiang coal - was selected for the study. Using thermogravimetry-differential scanning colorimetry (TG-DSC) methods, the change of the coal ash's physicochemistry with temperature was studied. The typical temperature points in the melting process were obtained. Ash samples of the different temperature points were prepared in a high-temperature furnace with parameters similar to those used in the TG-DSC test, and were then cooled quickly in water. Later, the ash samples were analyzed using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) methods in detail. Wenjialiang coal ash started to melt at 980{sup o}C. The ash was found to melt to a great extent at 1200{sup o}C and formed a multiform microstructure. At 1260{sup o}C, it was found to melt into a dense body with many pores, and formed a piece of vitreous body at 1340{sup o}C. Anorthite and gehlenite are the intermediate products that exist between 980 and 1340{sup o}C. They may be the main cause of the ash having low melting points, so that they could convert into a eutectic at low temperatures.

  10. Effects of Melt Processing on Evolution of Structure in PEEK

    Science.gov (United States)

    Georgiev, Georgi; Dai, Patrick Shuanghua; Oyebode, Elizabeth; Cebe, Peggy; Capel, Malcolm

    1999-01-01

    We report on the effects of melt processing temperature on structure formation in Poly(ether-ether-ketone), PEEK. Real time Small Angle X-ray Scattering, SAXS, and thermal analysis are used to follow the melting behavior after various stages of processing. Assignment of peaks to structural entities within the material, the relative perfection of the crystals, and the possibility of their reorganization, are all influenced by the melt processing history. With the advent of high intensity synchrotron sources of X-radiation, polymer scientists gain a research tool which, when used along with thermal analysis, provides additional structural information about the crystals during growth and subsequent melting. PEEK is an engineering thermoplastic polymer with a very high glass transition temperature (145 C) and crystal melting point (337 C). PEEK has been the subject of recent studies by X-ray scattering in which melt and cold crystallization were followed in real-time. X-ray scattering and thermal studies have been used to address the formation of dual endothermic response which has been variously ascribed to lamellar insertion, dual crystal populations, or melting followed by re-crystallization. Another important issue is whether all of the amorphous phase is located in interlamellar regions, or alternatively whether some is located in "pockets" away from the crystalline lamellar stacks. The interpretation of scattering from lamellar stacks varies depending upon whether such amorphous pockets are formed. Some groups believe all of the amorphous phase is interlamellar. This leads to selection of a smaller thickness for the crystals. Other groups suggest that most amorphous phase is not interlamellar, and this leads to the suggestion that the crystal thickness is larger than the amorphous layer within the stacks. To investigate these ideas, we used SAXS and Differential Scanning Calorimetry to compare results of single and dual stage melt crystallization of PEEK using a

  11. Viscosity measurements on metal melts at high pressure and viscosity calculations for the earth's core

    International Nuclear Information System (INIS)

    Mineev, Vladimir N; Funtikov, Aleksandr I

    2004-01-01

    A review is given of experimental and calculated data on the viscosity of iron-based melts on the melting curve. The interest in these data originates in the division of opinion on whether viscosity increases rather moderately or considerably in the high-pressure range. This disagreement is especially pronounced in the interpretation of the values of molten iron and its compounds in the environment of the earth's outer core. The conclusion on a substantial rise in viscosity mostly follows from the universal law, proposed by Brazhkin and Lyapin [1], of viscosity changing along the metal melting curve in the high-pressure range. The review analyzes available experimental and computational data, including the most recent ones. Data on viscosity of metals under shock wave compression in the megabar pressure range are also discussed. It is shown that data on viscosity of metal melts point to a small increase of viscosity on the melting curve. Specifics are discussed of the phase diagram of iron made more complex by the presence of several phase transitions and by the uncertainty in the position of the melting curve in the high-pressure range. Inaccuracies that arise in extrapolating the results of viscosity measurements to the pressure range corresponding to the earth's core environment are pointed out. (reviews of topical problems)

  12. The importance of accurate interaction potentials in the melting of argon nanoclusters

    Science.gov (United States)

    Pahl, E.; Calvo, F.; Schwerdtfeger, P.

    The melting temperatures of argon clusters ArN (N = 13, 55, 147, 309, 561, and 923) and of bulk argon have been obtained from exchange Monte Carlo simulations and are compared using different two-body interaction potentials, namely the standard Lennard-Jones (LJ), Aziz and extended Lennard-Jones (ELJ) potentials. The latter potential has many advantages: while maintaining the computational efficiency of the commonly used LJ potential, it is as accurate as the Aziz potential but the computer time scales more favorably with increasing cluster size. By applying the ELJ form and extrapolating the cluster data to the infinite system, we are able to extract the melting point of argon already in good agreement with experimental measurements. By considering the additional Axilrod-Teller three-body contribution as well, we calculate a melting temperature of T meltELJ = 84.7 K compared to the experimental value of T meltexp = 83.85 K, whereas the LJ potential underestimates the melting point by more than 7 K. Thus melting temperatures within 1 K accuracy are now feasible.

  13. Melting of iron nanoparticles embedded in silica prepared by mechanical milling

    International Nuclear Information System (INIS)

    Ding, Peng; Ma, Ji; Cao, Hui; Liu, Yi; Wang, Lianwen; Li, Jiangong

    2013-01-01

    Highlights: • Melting of metallic nanoparticles was studied for some eight elements. • This slim range of materials is successfully expanded to iron. • A mechanical-milled iron–silica composite is employed. • For iron particles of 15 nm in diameter, the melting point depression is 30 K. • The measured data is in agreement with our theoretical calculations. -- Abstract: For decades, experimental studies on the size-dependent melting of metals are regretfully limited to some eight archetypal examples. In this work, to expand this slim range of materials, the melting behavior of Fe nanoparticles embedded in SiO 2 prepared by using mechanical milling are investigated. Effects of factors in sample preparation on the size, isolation and thermal stability of Fe nanoparticles are systematically studied. On this basis, the size-dependent melting of Fe is successfully traced: for Fe nanoparticles with a diameter of about 15 nm, the melting point depression is 30 °C in comparison with bulk Fe, in accordance with our recent theoretical prediction

  14. Endmembers of Ice Shelf Melt

    Science.gov (United States)

    Boghosian, A.; Child, S. F.; Kingslake, J.; Tedesco, M.; Bell, R. E.; Alexandrov, O.; McMichael, S.

    2017-12-01

    Studies of surface melt on ice shelves have defined a spectrum of meltwater behavior. On one end the storage of meltwater in persistent surface ponds can trigger ice shelf collapse as in the 2002 event leading to the disintegration of the Larsen B Ice Shelf. On the other, meltwater export by rivers can stabilize an ice shelf as was recently shown on the Nansen Ice Shelf. We explore this dichotomy by quantifying the partitioning between stored and transported water on two glaciers adjacent to floating ice shelves, Nimrod (Antarctica) and Peterman (Greenland). We analyze optical satellite imagery (LANDSAT, WorldView), airborne imagery (Operation IceBridge, Trimetrogon Aerial Phototography), satellite radar (Sentinel-1), and digital elevation models (DEMs) to categorize surface meltwater fate and map the evolution of ice shelf hydrology and topographic features through time. On the floating Peterman Glacier tongue a sizable river exports water to the ocean. The surface hydrology of Nimrod Glacier, geometrically similar to Peterman but with ten times shallower surface slope, is dominated by storage in surface lakes. In contrast, the Nansen has the same surface slope as Nimrod but transports water through surface rivers. Slope alone is not the sole control on ice shelf hydrology. It is essential to track the storage and transport volumes for each of these systems. To estimate water storage and transport we analyze high resolution (40 cm - 2 m) modern and historical DEMs. We produce historical (1957 onwards) DEMs with structure-from-motion photogrammetry. The DEMs are used to constrain water storage potential estimates of observed basins and water routing/transport potential. We quantify the total volume of water stored seasonally and interannually. We use the normalize difference water index to map meltwater extent, and estimate lake water depth from optical data. We also consider the role of stored water in subsurface aquifers in recharging surface water after

  15. Three-Phase Melting Curves in the Binary System of Carbon Dioxide and Water

    Science.gov (United States)

    Abramson, E. H.

    2017-10-01

    Invariant, three-phase melting curves, of ice VI in equilibrium with solid CO2, of ice VII in equilibrium with solid CO2, and of solid CO2 in simultaneous equilibrium with a majority aqueous and a majority CO2 fluid, were explored in the binary system of carbon dioxide and water. Diamond-anvil cells were used to develop pressures of 5 GPa. Water exhibits a large melting temperature depression (73°C less than its pure melting temperature of 253°C at 5 GPa) indicative of large concentrations of CO2 in the aqueous solution. The melting point of water-saturated CO2 does not show a measureable departure from that of the pure system at temperatures lower than ∼200°C and only 10°C at 5 GPa (from 327°C).

  16. Melting of iron at the Earth's core conditions by molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Y. N. Wu

    2011-09-01

    Full Text Available By large scale molecular dynamics simulations of solid-liquid coexistence, we have investigated the melting of iron under pressures from 0 to 364 GPa. The temperatures of liquid and solid regions, and the pressure of the system are calculated to estimate the melting point of iron. We obtain the melting temperature of iron is about 6700±200K under the inner-outer core boundary, which is in good agreement with the result of Alfè et al. By the pair analysis technique, the microstructure of liquid iron under higher pressures is obviously different from that of lower pressures and ambient condition, indicating that the pressure-induced liquid-liquid phase transition may take place in iron melts.

  17. Thermophysical properties of liquid Ni around the melting temperature from molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Rozas, R. E. [Institut für Theoretische Physik II: Soft Matter, Heinrich Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf (Germany); Department of Physics, University of Bío-Bío, Av. Collao 1202, P.O. Box 5C, Concepción (Chile); Demiraǧ, A. D.; Horbach, J. [Institut für Theoretische Physik II: Soft Matter, Heinrich Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf (Germany); Toledo, P. G. [Chemical Engineering Department and Surface Analysis Laboratory (ASIF), University of Concepción, P.O. Box 160-C, Correo 3, Concepción (Chile)

    2016-08-14

    Thermophysical properties of liquid nickel (Ni) around the melting temperature are investigated by means of classical molecular dynamics (MD) simulation, using three different embedded atom method potentials to model the interactions between the Ni atoms. Melting temperature, enthalpy, static structure factor, self-diffusion coefficient, shear viscosity, and thermal diffusivity are compared to recent experimental results. Using ab initio MD simulation, we also determine the static structure factor and the mean-squared displacement at the experimental melting point. For most of the properties, excellent agreement is found between experiment and simulation, provided the comparison relative to the corresponding melting temperature. We discuss the validity of the Hansen-Verlet criterion for the static structure factor as well as the Stokes-Einstein relation between self-diffusion coefficient and shear viscosity. The thermal diffusivity is extracted from the autocorrelation function of a wavenumber-dependent temperature fluctuation variable.

  18. Movement of liquid beryllium during melt events in JET with ITER-like wall

    International Nuclear Information System (INIS)

    Sergienko, G; Huber, A; Brezinsek, S; Coenen, J W; Mertens, Ph; Philipps, V; Samm, U; Arnoux, G; Matthews, G F; Nunes, I; Riccardo, V; Sirinelli, A; Devaux, S

    2014-01-01

    The ITER-like wall recently installed in JET comprises solid beryllium limiters and a combination of bulk tungsten and tungsten-coated carbon fibre composite divertor tiles without active cooling. During a beryllium power handling qualification experiment performed in limiter configuration with 5 MW neutral beam injection input power, accidental beryllium melt events, melt layer motion and splashing were observed locally on a few beryllium limiters in the plasma contact areas. The Lorentz force is responsible for the observed melt layer movement. To move liquid beryllium against the gravity force, the current flowing from the plasma perpendicularly to the limiter surface must be higher than 6 kA m −2 . The thermo-emission current at the melting point of beryllium is much lower. The upward motion of the liquid beryllium against gravity can be due to a combination of the Lorentz force from the secondary electron emission and plasma pressure force. (paper)

  19. Evaluation of Melt Behavior with initial Melt Velocity under SFR Severe Accidents

    Energy Technology Data Exchange (ETDEWEB)

    Heo, Hyo; Bang, In Cheol [UNIST, Ulsan (Korea, Republic of); Jerng, Dong Wook [Chung-Ang Univ, Seoul (Korea, Republic of)

    2015-10-15

    In the current Korean sodium-cooled fast reactor (SFR) program, early dispersion of the molten metallic fuel within a subchannel is suggested as one of the inherent safety strategies for the initiating phase of hypothetical core disruptive accident (HCDA). The safety strategy provides negative reactivity driven by the melt dispersal, so it could reduce the possibility of the recriticality event under a severe triple or more fault scenario for SFR. Since the behavior of the melt dispersion is unpredictable, it depends on the accident condition, particularly core region. While the voided coolant channel region is usually developed in the inner core, the unvoided coolant channel region is formed in the outer core. It is important to confirm the fuel dispersion with the core region, but there are not sufficient existing studies for them. From the existing studies, the coolant vapor pressure is considered as one of driving force to move the melt towards outside of the core. There is a complexity of the phenomena during intermixing of the melt with the coolant after the horizontal melt injections. It is too difficult to understand the several combined mechanisms related to the melt dispersion and the fragmentation. Thus, it could be worthwhile to study the horizontal melt injections at lower temperature as a preliminary study in order to identify the melt dispersion phenomena. For this reason, it is required to clarify whether the coolant vapor pressure is the driving force of the melt dispersion with the core region. The specific conditions to be well dispersed for the molten metallic fuel were discussed in the experiments with the simulant materials. The each melt behavior was compared to evaluate the melt dispersion under the coolant void condition and the boiling condition. As the results, the following results are remarked: 1. The upward melt dispersion did not occur for a given melt and coolant temperature in the nonboiling range. Over current range of conditions

  20. Evaluation of Melt Behavior with initial Melt Velocity under SFR Severe Accidents

    International Nuclear Information System (INIS)

    Heo, Hyo; Bang, In Cheol; Jerng, Dong Wook

    2015-01-01

    In the current Korean sodium-cooled fast reactor (SFR) program, early dispersion of the molten metallic fuel within a subchannel is suggested as one of the inherent safety strategies for the initiating phase of hypothetical core disruptive accident (HCDA). The safety strategy provides negative reactivity driven by the melt dispersal, so it could reduce the possibility of the recriticality event under a severe triple or more fault scenario for SFR. Since the behavior of the melt dispersion is unpredictable, it depends on the accident condition, particularly core region. While the voided coolant channel region is usually developed in the inner core, the unvoided coolant channel region is formed in the outer core. It is important to confirm the fuel dispersion with the core region, but there are not sufficient existing studies for them. From the existing studies, the coolant vapor pressure is considered as one of driving force to move the melt towards outside of the core. There is a complexity of the phenomena during intermixing of the melt with the coolant after the horizontal melt injections. It is too difficult to understand the several combined mechanisms related to the melt dispersion and the fragmentation. Thus, it could be worthwhile to study the horizontal melt injections at lower temperature as a preliminary study in order to identify the melt dispersion phenomena. For this reason, it is required to clarify whether the coolant vapor pressure is the driving force of the melt dispersion with the core region. The specific conditions to be well dispersed for the molten metallic fuel were discussed in the experiments with the simulant materials. The each melt behavior was compared to evaluate the melt dispersion under the coolant void condition and the boiling condition. As the results, the following results are remarked: 1. The upward melt dispersion did not occur for a given melt and coolant temperature in the nonboiling range. Over current range of conditions

  1. Viscosity of ring polymer melts

    KAUST Repository

    Pasquino, Rossana

    2013-10-15

    We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

  2. Viscosity of ring polymer melts

    KAUST Repository

    Pasquino, Rossana; Vasilakopoulos, Thodoris C.; Jeong, Youncheol; Lee, Hyojoon; Rogers, Simon A.; Sakellariou, Georgios; Allgaier, Jü rgen B.; Takano, Atsushi; Brá s, Ana Rita E; Chang, Taihyun; Gooß en, Sebastian; Pyckhout-Hintzen, Wim; Wischnewski, Andreas; Hadjichristidis, Nikolaos; Richter, Dieter R.; Rubinstein, Michael H.; Vlassopoulos, Dimitris

    2013-01-01

    We have measured the linear rheology of critically purified ring polyisoprenes, polystyrenes, and polyethyleneoxides of different molar masses. The ratio of the zero-shear viscosities of linear polymer melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed as a function of the number of entanglements Z. In the unentangled regime η0,linear/η 0,ring is virtually constant, consistent with the earlier data, atomistic simulations, and the theoretical expectation η0,linear/ η0,ring = 2. In the entanglement regime, the Z-dependence of ring viscosity is much weaker than that of linear polymers, in qualitative agreement with predictions from scaling theory and simulations. The power-law extracted from the available experimental data in the rather limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z 1.2±0.3, is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z 1.6±0.3) and the simulations (η0,linear/ η0,ring ∼ Z2.0±0.3). Nevertheless, the present collection of state-of-the-art experimental data unambiguously demonstrates that rings exhibit a universal trend clearly departing from that of their linear counterparts, and hence it represents a major step toward resolving a 30-year-old problem. © 2013 American Chemical Society.

  3. Dynamics of Melting and Melt Migration as Inferred from Incompatible Trace Element Abundance in Abyssal Peridotites

    Science.gov (United States)

    Peng, Q.; Liang, Y.

    2008-12-01

    To better understand the melting processes beneath the mid-ocean ridge, we developed a simple model for trace element fractionation during concurrent melting and melt migration in an upwelling steady-state mantle column. Based on petrologic considerations, we divided the upwelling mantle into two regions: a double- lithology upper region where high permeability dunite channels are embedded in a lherzolite/harzburgite matrix, and a single-lithology lower region that consists of partially molten lherzolite. Melt generated in the single lithology region migrates upward through grain-scale diffuse porous flow, whereas melt in the lherzolite/harzburgite matrix in the double-lithology region is allowed to flow both vertically through the overlying matrix and horizontally into its neighboring dunite channels. There are three key dynamic parameters in our model: degree of melting experienced by the single lithology column (Fd), degree of melting experienced by the double lithology column (F), and a dimensionless melt suction rate (R) that measures the accumulated rate of melt extraction from the matrix to the channel relative to the accumulated rate of matrix melting. In terms of trace element fractionation, upwelling and melting in the single lithology column is equivalent to non-modal batch melting (R = 0), whereas melting and melt migration in the double lithology region is equivalent to a nonlinear combination of non-modal batch and fractional melting (0 abyssal peridotite, we showed, with the help of Monte Carlo simulations, that it is difficult to invert for all three dynamic parameters from a set of incompatible trace element data with confidence. However, given Fd, it is quite possible to constrain F and R from incompatible trace element abundances in residual peridotite. As an illustrative example, we used the simple melting model developed in this study and selected REE and Y abundance in diopside from abyssal peridotites to infer their melting and melt migration

  4. Fundamental Aspects of Selective Melting Additive Manufacturing Processes

    Energy Technology Data Exchange (ETDEWEB)

    van Swol, Frank B. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Miller, James E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-12-01

    Certain details of the additive manufacturing process known as selective laser melting (SLM) affect the performance of the final metal part. To unleash the full potential of SLM it is crucial that the process engineer in the field receives guidance about how to select values for a multitude of process variables employed in the building process. These include, for example, the type of powder (e.g., size distribution, shape, type of alloy), orientation of the build axis, the beam scan rate, the beam power density, the scan pattern and scan rate. The science-based selection of these settings con- stitutes an intrinsically challenging multi-physics problem involving heating and melting a metal alloy, reactive, dynamic wetting followed by re-solidification. In addition, inherent to the process is its considerable variability that stems from the powder packing. Each time a limited number of powder particles are placed, the stacking is intrinsically different from the previous, possessing a different geometry, and having a different set of contact areas with the surrounding particles. As a result, even if all other process parameters (scan rate, etc) are exactly the same, the shape and contact geometry and area of the final melt pool will be unique to that particular configuration. This report identifies the most important issues facing SLM, discusses the fundamental physics associated with it and points out how modeling can support the additive manufacturing efforts.

  5. Corium melt researches at VESTA test facility

    Directory of Open Access Journals (Sweden)

    Hwan Yeol Kim

    2017-10-01

    Full Text Available VESTA (Verification of Ex-vessel corium STAbilization and VESTA-S (-small test facilities were constructed at the Korea Atomic Energy Research Institute in 2010 to perform various corium melt experiments. Since then, several tests have been performed for the verification of an ex-vessel core catcher design for the EU-APR1400. Ablation tests of an impinging ZrO2 melt jet on a sacrificial material were performed to investigate the ablation characteristics. ZrO2 melt in an amount of 65–70 kg was discharged onto a sacrificial material through a well-designed nozzle, after which the ablation depths were measured. Interaction tests between the metallic melt and sacrificial material were performed to investigate the interaction kinetics of the sacrificial material. Two types of melt were used: one is a metallic corium melt with Fe 46%, U 31%, Zr 16%, and Cr 7% (maximum possible content of U and Zr for C-40, and the other is a stainless steel (SUS304 melt. Metallic melt in an amount of 1.5–2.0 kg was delivered onto the sacrificial material, and the ablation depths were measured. Penetration tube failure tests were performed for an APR1400 equipped with 61 in-core instrumentation penetration nozzles and extended tubes at the reactor lower vessel. ZrO2 melt was generated in a melting crucible and delivered down into an interaction crucible where the test specimen is installed. To evaluate the tube ejection mechanism, temperature distributions of the reactor bottom head and in-core instrumentation penetration were measured by a series of thermocouples embedded along the specimen. In addition, lower vessel failure tests for the Fukushima Daiichi nuclear power plant are being performed. As a first step, the configuration of the molten core in the plant was investigated by a melting and solidification experiment. Approximately 5 kg of a mixture, whose composition in terms of weight is UO2 60%, Zr 10%, ZrO2 15%, SUS304 14%, and B4C 1%, was melted in a

  6. Melting technique for vanadium containing steels

    Energy Technology Data Exchange (ETDEWEB)

    Grishanov, M P; Gutovskij, I B; Vakhrushev, A S

    1980-04-28

    To descrease cost price of high-quality vanadium steels a method of their melting in open-hearth furnaces with acid lining using slag-metal fraction of vanadium, which is loaded in the content of 2.1-4.7% of melting mass, is suggested. Introduction of slag-metal fraction of vanadium ensures the formation of slag with composition that guarantees the necessary content of vanadium in steel and does not require introduction of expensive vanadium-containing ferroalloys into the melt.

  7. Melt processed high-temperature superconductors

    CERN Document Server

    1993-01-01

    The achievement of large critical currents is critical to the applications of high-temperature superconductors. Recent developments have shown that melt processing is suitable for producing high J c oxide superconductors. Using magnetic forces between such high J c oxide superconductors and magnets, a person could be levitated.This book has grown largely out of research works on melt processing of high-temperature superconductors conducted at ISTEC Superconductivity Research Laboratory. The chapters build on melt processing, microstructural characterization, fundamentals of flux pinning, criti

  8. Technological properties and structure of titanate melts

    International Nuclear Information System (INIS)

    Morozov, A.A.

    2002-01-01

    Power substantiation of existence of tough stream of complex anion ([TiO 6 ] 8- ) as a prevalent unit in titanate melts is given on the base of up-to-date knowledge about structure of metallurgical slags and results of investigations of thermophysical properties of these melts. It is shown that high crystallization ability of titanate melts at technological temperatures is determined by heterogeneity of liquid state - by presence up to 30 % of dispersed particles of solid phase solutions in matrix liquid [ru

  9. Bayesian estimation of core-melt probability

    International Nuclear Information System (INIS)

    Lewis, H.W.

    1984-01-01

    A very simple application of the canonical Bayesian algorithm is made to the problem of estimation of the probability of core melt in a commercial power reactor. An approximation to the results of the Rasmussen study on reactor safety is used as the prior distribution, and the observation that there has been no core melt yet is used as the single experiment. The result is a substantial decrease in the mean probability of core melt--factors of 2 to 4 for reasonable choices of parameters. The purpose is to illustrate the procedure, not to argue for the decrease

  10. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    and their diameter. The variation in melting temperature has little influence on the overall bubble volume. However, the size distribution of the bubbles varies with the melting temperature. When the melt is slowly cooled, the bubble volume increases, implying decreased solubility of the gaseous species. Mass...... spectroscopy analysis of gases liberated during heating of the glass reveals that small bubbles contain predominantly CH4, CO and CO2, whereas large bubbles bear N2, SO2 and H2S. The methodology utilised in this work can, besides mapping the bubbles in a glass, be applied to shed light on the sources of bubble...

  11. Melting of 2D monatomic solids: Lennard-Jones system

    International Nuclear Information System (INIS)

    Yi, Y.M.; Guo, Z.C.

    1987-09-01

    The Lennard-Jones interaction has been introduced into the Collins mix lattice of 2D liquids. By means of rigorous calculation of the total potential and the free area, the Gibbs functions for 2D liquid and solid have been derived. The melting line obtained from the phase transition equation agrees quite well with the result of recent computer simulation experiments. The obtained reduced temperature of the triple point T* t =0.438 agrees with the data measured in experiments of some inert gas monolayers adsorbed on graphite as well as in computer simulation experiments. (author). 11 refs, 7 figs, 3 tabs

  12. Shear melting and high temperature embrittlement: theory and application to machining titanium.

    Science.gov (United States)

    Healy, Con; Koch, Sascha; Siemers, Carsten; Mukherji, Debashis; Ackland, Graeme J

    2015-04-24

    We describe a dynamical phase transition occurring within a shear band at high temperature and under extremely high shear rates. With increasing temperature, dislocation deformation and grain boundary sliding are supplanted by amorphization in a highly localized nanoscale band, which allows for massive strain and fracture. The mechanism is similar to shear melting and leads to liquid metal embrittlement at high temperature. From simulation, we find that the necessary conditions are lack of dislocation slip systems, low thermal conduction, and temperature near the melting point. The first two are exhibited by bcc titanium alloys, and we show that the final one can be achieved experimentally by adding low-melting-point elements: specifically, we use insoluble rare earth metals (REMs). Under high shear, the REM becomes mixed with the titanium, lowering the melting point within the shear band and triggering the shear-melting transition. This in turn generates heat which remains localized in the shear band due to poor heat conduction. The material fractures along the shear band. We show how to utilize this transition in the creation of new titanium-based alloys with improved machinability.

  13. Realization of the Temperature Scale in the Range from 234.3 K (Hg Triple Point) to 1084.62°C (Cu Freezing Point) in Croatia

    Science.gov (United States)

    Zvizdic, Davor; Veliki, Tomislav; Grgec Bermanec, Lovorka

    2008-06-01

    This article describes the realization of the International Temperature Scale in the range from 234.3 K (mercury triple point) to 1084.62°C (copper freezing point) at the Laboratory for Process Measurement (LPM), Faculty of Mechanical Engineering and Naval Architecture (FSB), University of Zagreb. The system for the realization of the ITS-90 consists of the sealed fixed-point cells (mercury triple point, water triple point and gallium melting point) and the apparatus designed for the optimal realization of open fixed-point cells which include the gallium melting point, tin freezing point, zinc freezing point, aluminum freezing point, and copper freezing point. The maintenance of the open fixed-point cells is described, including the system for filling the cells with pure argon and for maintaining the pressure during the realization.

  14. Microstructures and microhardness evolutions of melt-spun Al-8Ni-5Nd-4Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Karakoese, Ercan, E-mail: ekarakose@karatekin.edu.tr [Karatekin University, Faculty of Sciences, Department of Physics, 18100 Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I (Turkey); Keskin, Mustafa [Erciyes University, Faculty of Sciences, Department of Physics, 38039 Kayseri (Turkey)

    2012-03-15

    Al-Ni-Nd-Si alloy with nominal composition of Al-8 wt.%Ni-5 wt.%Nd-4 wt.%Si was rapidly solidified by using melt-spinning technique to examine the influence of the cooling rate/conditions on microstructure and mechanical properties. The resulting conventional cast (ingot) and melt-spun ribbons were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy together with energy dispersive spectroscopy, differential scanning calorimetry, differential thermal analysis and Vickers microhardness tester. The ingot alloys consists of four phases namely {alpha}-Al, intermetallic Al{sub 3}Ni, Al{sub 11}Nd{sub 3} and fcc Si. Melt-spun ribbons are completely composed of {alpha}-Al phase. The optical microscopy and scanning electron microscopy results show that the microstructures of rapidly solidified ribbons are clearly different from their ingot alloy. The change in microhardness is discussed based on the microstructural observations. - Highlights: Black-Right-Pointing-Pointer Rapid solidification allows a reduction in grain size, extended solid solution ranges. Black-Right-Pointing-Pointer We observed the matrix lattice parameter increases with increasing wheel speed. Black-Right-Pointing-Pointer Melt-spun ribbons consist of partly amorphous phases embedded in crystalline phases. Black-Right-Pointing-Pointer The solidification rate is high enough to retain most of alloying elements in the Al matrix. Black-Right-Pointing-Pointer The rapid solidification has effect on the phase constitution.

  15. Cloud screening and melt water detection over melting sea ice using AATSR/SLSTR

    Science.gov (United States)

    Istomina, Larysa; Heygster, Georg

    2014-05-01

    With the onset of melt in the Arctic Ocean, the fraction of melt water on sea ice, the melt pond fraction, increases. The consequences are: the reduced albedo of sea ice, increased transmittance of sea ice and affected heat balance of the system with more heat passing through the ice into the ocean, which facilitates further melting. The onset of melt, duration of melt season and melt pond fraction are good indicators of the climate state of the Arctic and its change. In the absence of reliable sea ice thickness retrievals in summer, melt pond fraction retrieval from satellite is in demand as input for GCM as an indicator of melt state of the sea ice. The retrieval of melt pond fraction with a moderate resolution radiometer as AATSR is, however, a non-trivial task due to a variety of subpixel surface types with very different optical properties, which give non-unique combinations if mixed. In this work this has been solved by employing additional information on the surface and air temperature of the pixel. In the current work, a concept of melt pond detection on sea ice is presented. The basis of the retrieval is the sensitivity of AATSR reflectance channels 550nm and 860nm to the amount of melt water on sea ice. The retrieval features extensive usage of a database of in situ surface albedo spectra. A tree of decisions is employed to select the feasible family of in situ spectra for the retrieval, depending on the melt stage of the surface. Reanalysis air temperature at the surface and brightness temperature measured by the satellite sensor are analyzed in order to evaluate the melting status of the surface. Case studies for FYI and MYI show plausible retrieved melt pond fractions, characteristic for both of the ice types. The developed retrieval can be used to process the historical AATSR (2002-2012) dataset, as well as for the SLSTR sensor onboard the future Sentinel-3 mission (scheduled for launch in 2015), to keep the continuity and obtain longer time sequence

  16. Electron beam melting of bearing materials

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmied, G.; Schuler, A. (Technische Univ., Vienna (Austria). Inst. fuer Allgemeine Elektrotechnik); Elsinger, G.; Koroschetz, F. (MIBA Gleitlager AG, Laakirchen (Austria)); Tschegg, E.K. (Technische Univ., Vienna (Austria). Inst. fuer Angewandte und Technische Physik)

    1990-06-01

    This paper reports on a surface treatment method for the bearing materials AlSn6 which permits the use of this material without the overlay usually required. Microstructural refinement is achieved by means of a surface melting technique using an electron beam with successive rapid solidification. Extremely fine tin precipitates are formed in the melted surface layer which lead to significantly better tribological properties of the bearing material. Tests compared the tribological properties for AlSn6 bearings treated by the surface melting technique with those of untreated bearings. Whereas all untreated bearings failed by seizure after only 2 h of testing, 30% of the tested bearings which had been surface melted survived the entire testing program without damage.

  17. Extraction of scandium by organic substance melts

    International Nuclear Information System (INIS)

    Gladyshev, V.P.; Lobanov, F.I.; Zebreva, A.I.; Andreeva, N.N.; Manuilova, O.A.; Il'yukevich, Yu.A.

    1984-01-01

    Regularities of scandium extraction by the melts of octadecanicoic acid, n-carbonic acids of C 17 -C 20 commerical fraction and mixtures of tributylphosphate (TBP) with paraffin at (70+-1) deg C have been studied. The optimum conditions for scandium extraction in the melt of organic substances are determined. A scheme of the extraction by the melts of higher carbonic acids at ninitial metal concentrations of 10 -5 to 10 -3 mol/l has been suggested. The scandium compound has been isolated in solid form, its composition having been determined. The main advantages of extraction by melts are as follows: a possibility to attain high distribution coefficients, distinct separation of phases after extraction, the absence of emulsions, elimination of employing inflammable and toxic solvents, a possibility of rapid X-ray fluorescence determinatinon of scandium directly in solid extract

  18. Vertical melting of a stack of membranes

    Science.gov (United States)

    Borelli, M. E. S.; Kleinert, H.; Schakel, A. M. J.

    2001-02-01

    A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures, the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.

  19. Selective Laser Ablation and Melting, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this project Advratech will develop a new additive manufacturing (AM) process called Selective Laser Ablation and Melting (SLAM). The key innovation in this...

  20. Energy Saving Melting and Revert Reduction Technology (E-SMARRT): Melting Efficiency Improvement

    Energy Technology Data Exchange (ETDEWEB)

    Principal Investigator Kent Peaslee; Co-PI’s: Von Richards, Jeffrey Smith

    2012-07-31

    Steel foundries melt recycled scrap in electric furnaces and typically consume 35-100% excess energy from the theoretical energy requirement required to pour metal castings. This excess melting energy is multiplied by yield losses during casting and finishing operations resulting in the embodied energy in a cast product typically being three to six times the theoretical energy requirement. The purpose of this research project was to study steel foundry melting operations to understand energy use and requirements for casting operations, define variations in energy consumption, determine technologies and practices that are successful in reducing melting energy and develop new melting techniques and tools to improve the energy efficiency of melting in steel foundry operations.

  1. Basal melting driven by turbulent thermal convection

    Science.gov (United States)

    Rabbanipour Esfahani, Babak; Hirata, Silvia C.; Berti, Stefano; Calzavarini, Enrico

    2018-05-01

    Melting and, conversely, solidification processes in the presence of convection are key to many geophysical problems. An essential question related to these phenomena concerns the estimation of the (time-evolving) melting rate, which is tightly connected to the turbulent convective dynamics in the bulk of the melt fluid and the heat transfer at the liquid-solid interface. In this work, we consider a convective-melting model, constructed as a generalization of the Rayleigh-Bénard system, accounting for the basal melting of a solid. As the change of phase proceeds, a fluid layer grows at the heated bottom of the system and eventually reaches a turbulent convection state. By means of extensive lattice-Boltzmann numerical simulations employing an enthalpy formulation of the governing equations, we explore the model dynamics in two- and three-dimensional configurations. The focus of the analysis is on the scaling of global quantities like the heat flux and the kinetic energy with the Rayleigh number, as well as on the interface morphology and the effects of space dimensionality. Independently of dimensionality, we find that the convective-melting system behavior shares strong resemblances with that of the Rayleigh-Bénard one, and that the heat flux is only weakly enhanced with respect to that case. Such similarities are understood, at least to some extent, considering the resulting slow motion of the melting front (with respect to the turbulent fluid velocity fluctuations) and its generally little roughness (compared to the height of the fluid layer). Varying the Stefan number, accounting for the thermodynamical properties of the material, also seems to have only a mild effect, which implies the possibility of extrapolating results in numerically delicate low-Stefan setups from more convenient high-Stefan ones. Finally, we discuss the implications of our findings for the geophysically relevant problem of modeling Arctic ice melt ponds.

  2. Uniaxial Elongational viscosity of bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The startup and steady uniaxial elongational viscosity have been measured for three bidisperse polystyrene (PS) melts, consisting of blends of monodisperse PS with molecular weights of 52 kg/mole or 103 kg/mole and 390 kg/mole. The bidisperse melts have a maximum in the steady elongational...... viscosity, of up to a factor of 7 times the Trouton limit of 3 times the zero-shear viscosity....

  3. Shock induced melting of lead (experimental study)

    International Nuclear Information System (INIS)

    Mabire, Catherine; Hereil, Pierre L.

    2002-01-01

    To investigate melting on release of lead, two shock compression measurements have been carried out at 51 GPa. In the first one, a pyrometric measurement has been performed at the Pb/LiF interface. In the second one, the Pb/LiF interface velocity has been recorded using VISAR measurement technique. VISAR and radiance profile are in good agreement and seem to show melting on release of lead

  4. Electrodepositions on Tantalum in Alkali Halide Melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

    2013-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO3 melts carbonate ions seems to be reduced to carbon in...

  5. Electrodepositions on Tantalum in alkali halide melts

    DEFF Research Database (Denmark)

    Barner, Jens H. Von; Jensen, Annemette Hindhede; Christensen, Erik

    2012-01-01

    Surface layers of tantalum metal were electrodeposited on steel from K 2TaF7-LiF-NaF-KF melts. With careful control of the oxide contents dense and adherent deposits could be obtained by pulse plating. In NaCl-KCl-NaF-Na2CO3 and NaCl-KCl-Na2CO 3 melts carbonate ions seems to be reduced to carbon ...

  6. Melting Behavior of Organic Nanocrystals Grown in Sol-gel Matrices

    International Nuclear Information System (INIS)

    Sanz, N.; Boudet, A.; Ibanez, A.

    2002-01-01

    We have characterized the thermal stability of organic nanocrystals grown in the pores of sol-gel matrices. The structure has been measured with transmission electron microscopy (TEM) analysis. Depending on the nature of organic molecules and sol-gel matrices, we have modified the dye-matrix interactions and the interfacial structure between nanocrystals and gel-glasses. When the dye-matrix interactions are weak (Van der Waals' bonds), the corresponding interfacial structure observed by TEM is sharp and the nanocrystals melt below the bulk melting point. On the other hand, when the dye-matrix interactions are strong (hydrogen bonds), the interfacial structure is fuzzy and a great superheating of organic nanocrystals is observed in comparison to the bulk melting point of the dye

  7. Melt spreading code assessment, modifications, and application to the EPR core catcher design

    International Nuclear Information System (INIS)

    Farmer, M.T.

    2009-01-01

    of: (1) comparison to an analytical solution for the dam break problem, (2) water spreading tests in a 1/10 linear scale model of the Mark I containment by Theofanous et al., and (3) steel spreading tests by Suzuki et al. that were also conducted in a geometry similar to the Mark I. The objective of this work was to utilize the MELTSPREAD code to check the assumption of uniform melt spreading in the EPR core catcher design. As a starting point for the project, the code was validated against the worldwide melt spreading database that emerged after the code was originally written in the very early 1990's. As part of this exercise, the code was extensively modified and upgraded to incorporate findings from these various analytical and experiment programs. In terms of expanding the ability of the code to analyze various melt simulant experiments, the options to input user-specified melt and/or substrate material properties was added. The ability to perform invisicid and/or adiabatic spreading analysis was also added so that comparisons with analytical solutions and isothermal spreading tests could be carried out. In terms of refining the capability to carry out reactor material melt spreading analyses, the code was upgraded with a new melt viscosity model; the capability was added to treat situations in which solid fraction buildup between the liquidus-solidus is non-linear; and finally, the ability to treat an interfacial heat transfer resistance between the melt and substrate was incorporated. This last set of changes substantially improved the predictive capability of the code in terms of addressing reactor material melt spreading tests. Aside from improvements and upgrades, a method was developed to fit the model to the various melt spreading tests in a manner that allowed uncertainties in the model predictions to be statistically characterized. With these results, a sensitivity study was performed to investigate the assumption of uniform spreading in the EPR core

  8. Depth and degree of melting of komatiites

    Science.gov (United States)

    Herzberg, Claude

    1992-04-01

    High pressure melting experiments have permitted new constraints to be placed on the depth and degree of partial melting of komatiites. Komatiites from Gorgona Island were formed by relatively low degrees of pseudoinvariant melting involving L + Ol + Opx + Cpx + Gt on the solidus at 40 kbar, about 130 km depth. Munro-type komatiites were separated from a harzburgite residue (L + Ol + Opx) at pressures that were poorly constrained, but were probably around 50 kbar, about 165 km depth; the degree of partial melting was less than 40 percent. Secular variations in the geochemistry of komatiites could have formed in response to a reduction in the temperature and pressure of melting with time. The 3.5 Ga Barberton komatiites and the 2.7 Ga Munro-type komatiities could have formed in plumes that were hotter than the present-day mantle by 500 deg and 300 deg, respectively. When excess temperatures are this size, melting is deeper and volcanism changes from basaltic to momatiitic. The komatiities from Gorgona Island, which are Mesozoic in age, may be representative of komatiities that are predicted to occur in oceanic plateaus of Cretaceous age throughout the Pacific (Storey et al., 1991).

  9. The melting and solidification of nanowires

    International Nuclear Information System (INIS)

    Florio, B. J.; Myers, T. G.

    2016-01-01

    A mathematical model is developed to describe the melting of nanowires. The first section of the paper deals with a standard theoretical situation, where the wire melts due to a fixed boundary temperature. This analysis allows us to compare with existing results for the phase change of nanospheres. The equivalent solidification problem is also examined. This shows that solidification is a faster process than melting; this is because the energy transfer occurs primarily through the solid rather than the liquid which is a poorer conductor of heat. This effect competes with the energy required to create new solid surface which acts to slow down the process, but overall conduction dominates. In the second section, we consider a more physically realistic boundary condition, where the phase change occurs due to a heat flux from surrounding material. This removes the singularity in initial melt velocity predicted in previous models of nanoparticle melting. It is shown that even with the highest possible flux the melting time is significantly slower than with a fixed boundary temperature condition.

  10. The melting and solidification of nanowires

    Science.gov (United States)

    Florio, B. J.; Myers, T. G.

    2016-06-01

    A mathematical model is developed to describe the melting of nanowires. The first section of the paper deals with a standard theoretical situation, where the wire melts due to a fixed boundary temperature. This analysis allows us to compare with existing results for the phase change of nanospheres. The equivalent solidification problem is also examined. This shows that solidification is a faster process than melting; this is because the energy transfer occurs primarily through the solid rather than the liquid which is a poorer conductor of heat. This effect competes with the energy required to create new solid surface which acts to slow down the process, but overall conduction dominates. In the second section, we consider a more physically realistic boundary condition, where the phase change occurs due to a heat flux from surrounding material. This removes the singularity in initial melt velocity predicted in previous models of nanoparticle melting. It is shown that even with the highest possible flux the melting time is significantly slower than with a fixed boundary temperature condition.

  11. The melting and solidification of nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Florio, B. J., E-mail: brendan.florio@ul.ie [University of Limerick, Mathematics Applications Consortium for Science and Industry (MACSI), Department of Mathematics and Statistics (Ireland); Myers, T. G., E-mail: tmyers@crm.cat [Centre de Recerca Matemàtica (Spain)

    2016-06-15

    A mathematical model is developed to describe the melting of nanowires. The first section of the paper deals with a standard theoretical situation, where the wire melts due to a fixed boundary temperature. This analysis allows us to compare with existing results for the phase change of nanospheres. The equivalent solidification problem is also examined. This shows that solidification is a faster process than melting; this is because the energy transfer occurs primarily through the solid rather than the liquid which is a poorer conductor of heat. This effect competes with the energy required to create new solid surface which acts to slow down the process, but overall conduction dominates. In the second section, we consider a more physically realistic boundary condition, where the phase change occurs due to a heat flux from surrounding material. This removes the singularity in initial melt velocity predicted in previous models of nanoparticle melting. It is shown that even with the highest possible flux the melting time is significantly slower than with a fixed boundary temperature condition.

  12. On melting criteria for complex plasma

    International Nuclear Information System (INIS)

    Klumov, Boris A

    2011-01-01

    The present paper considers melting criteria for a plasma crystal discovered in dust plasma in 1994. Separate discussions are devoted to three-dimensional (3D) and two-dimensional (2D) systems. In the 3D case, melting criteria are derived based on the properties of local order in a system of microparticles. The order parameters are constructed from the cumulative distributions of the microparticle probability distributions as functions of various rotational invariants. The melting criteria proposed are constructed using static information on microparticle positions: a few snapshots of the system that allow for the determination of particle coordinates are enough to determine the phase state of the system. It is shown that criteria obtained in this way describe well the melting and premelting of 3D complex plasmas. In 2D systems, a system of microparticles interacting via a screened Coulomb (i.e., Debye-Hueckel or Yukawa) potential is considered as an example, using molecular dynamics simulations. A number of new order parameters characterizing the melting of 2D complex plasmas are proposed. The order parameters and melting criteria proposed for 2D and 3D complex plasmas can be applied to other systems as well. (methodological notes)

  13. Rapakivi texture formation via disequilibrium melting in a contact partial melt zone, Antarctica

    Science.gov (United States)

    Currier, R. M.

    2017-12-01

    In the McMurdo Dry Valleys of Antarctica, a Jurassic aged dolerite sill induced partial melting of granite in the shallow crust. The melt zone can be traced in full, from high degrees of melting (>60%) along the dolerite contact, to no apparent signs of melting, 10s of meters above the contact. Within this melt zone, the well-known rapakivi texture is found, arrested in various stages of development. High above the contact, and at low degrees of melting, K-feldspar crystals are slightly rounded and unmantled. In the lower half of the melt zone, mantles of cellular textured plagioclase appear on K-feldspar, and thicken towards the contact heat source. At the highest degrees of melting, cellular-textured plagioclase completely replaces restitic K-feldspar. Because of the complete exposure and intact context, the leading models of rapakivi texture formation can be tested against this system. The previously proposed mechanisms of subisothermal decompression, magma-mixing, and hydrothermal exsolution all fail to adequately describe rapakivi generation in this melt zone. Preferred here is a closed system model that invokes the production of a heterogeneous, disequilibrium melt through rapid heating, followed by calcium and sodium rich melt reacting in a peritectic fashion with restitic K-feldspar crystals. This peritectic reaction results in the production of plagioclase of andesine-oligoclase composition—which is consistent with not just mantles in the melt zone, but globally as well. The thickness of the mantle is diffusion limited, and thus a measure of the diffusive length scale of sodium and calcium over the time scale of melting. Thermal modeling provides a time scale of melting that is consistent with the thickness of observed mantles. Lastly, the distribution of mantled feldspars is highly ordered in this melt zone, but if it were mobilized and homogenized—mixing together cellular plagioclase, mantled feldspars, and unmantled feldspars—the result would be

  14. Fatigue behavior of porous biomaterials manufactured using selective laser melting.

    Science.gov (United States)

    Yavari, S Amin; Wauthle, R; van der Stok, J; Riemslag, A C; Janssen, M; Mulier, M; Kruth, J P; Schrooten, J; Weinans, H; Zadpoor, A A

    2013-12-01

    Porous titanium alloys are considered promising bone-mimicking biomaterials. Additive manufacturing techniques such as selective laser melting allow for manufacturing of porous titanium structures with a precise design of micro-architecture. The mechanical properties of selective laser melted porous titanium alloys with different designs of micro-architecture have been already studied and are shown to be in the range of mechanical properties of bone. However, the fatigue behavior of this biomaterial is not yet well understood. We studied the fatigue behavior of porous structures made of Ti6Al4V ELI powder using selective laser melting. Four different porous structures were manufactured with porosities between 68 and 84% and the fatigue S-N curves of these four porous structures were determined. The three-stage mechanism of fatigue failure of these porous structures is described and studied in detail. It was found that the absolute S-N curves of these four porous structures are very different. In general, given the same absolute stress level, the fatigue life is much shorter for more porous structures. However, the normalized fatigue S-N curves of these four structures were found to be very similar. A power law was fitted to all data points of the normalized S-N curves. It is shown that the measured data points conform to the fitted power law very well, R(2)=0.94. This power law may therefore help in estimating the fatigue life of porous structures for which no fatigue test data is available. It is also observed that the normalized endurance limit of all tested porous structures (<0.2) is lower than that of corresponding solid material (c.a. 0.4). © 2013.

  15. Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology.

    Science.gov (United States)

    Chen, Fengchen; Su, Xin; Ye, Qing; Fu, Jianfeng

    2018-01-01

    A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

  16. Experimental Investigation of Concrete Runway Snow Melting Utilizing Heat Pipe Technology

    Directory of Open Access Journals (Sweden)

    Fengchen Chen

    2018-01-01

    Full Text Available A full scale snow melting system with heat pipe technology is built in this work, which avoids the negative effects on concrete structure and environment caused by traditional deicing chemicals. The snow melting, ice-freezing performance and temperature distribution characteristics of heat pipe concrete runway were discussed by the outdoor experiments. The results show that the temperature of the concrete pavement is greatly improved with the heat pipe system. The environment temperature and embedded depth of heat pipe play a dominant role among the decision variables of the snow melting system. Heat pipe snow melting pavement melts the snow completely and avoids freezing at any time when the environment temperature is below freezing point, which is secure enough for planes take-off and landing. Besides, the exportation and recovery of geothermal energy indicate that this system can run for a long time. This paper will be useful for the design and application of the heat pipe used in the runway snow melting.

  17. Low melting high lithia glass compositions and methods

    Science.gov (United States)

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

    2000-01-01

    The invention relates to methods of vitrifying waste and for lowering the melting point of glass forming systems by including lithia formers in the glass forming composition in significant amounts, typically from about 0.16 wt % to about 11 wt %, based on the total glass forming oxides. The lithia is typically included as a replacement for alkali oxide glass formers that would normally be present in a particular glass forming system. Replacement can occur on a mole percent or weight percent basis, and typically results in a composition wherein lithia forms about 10 wt % to about 100 wt % of the alkali oxide glass formers present in the composition. The present invention also relates to the high lithia glass compositions formed by these methods. The invention is useful for stabilization of numerous types of waste materials, including aqueous waste streams, sludge solids, mixtures of aqueous supernate and sludge solids, combinations of spent filter aids from waste water treatment and waste sludges, supernate alone, incinerator ash, incinerator offgas blowdown, or combinations thereof, geological mine tailings and sludges, asbestos, inorganic filter media, cement waste forms in need of remediation, spent or partially spent ion exchange resins or zeolites, contaminated soils, lead paint, etc. The decrease in melting point achieved by the present invention desirably prevents volatilization of hazardous or radioactive species during vitrification.

  18. Wetting and surface tension of bismate glass melt

    International Nuclear Information System (INIS)

    Shim, Seung-Bo; Kim, Dong-Sun; Hwang, Seongjin; Kim, Hyungsun

    2009-01-01

    Lead oxide glass frits are used widely in the electronics industry for low-temperature firing. On the other hand, one of the low-sintering and low-melting lead-free glass systems available, the bismate glass system, is considered to be an alternative to lead oxide glass. In order to extend the applications of Bi 2 O 3 glasses, this study examined the thermophysical properties of low-melting Bi 2 O 3 -B 2 O 3 -ZnO-BaO-Al 2 O 3 -SiO 2 glass frits with various ZnO/B 2 O 3 ratios. The fundamental thermal properties, such as glass transition temperature and softening point, were examined by differential thermal analysis and a glass softening point determination system. The wetting angles, viscosities and surface tension of the various bismate glasses on an alumina substrate were measured using hot-stage microscopy and the sessile drop method. These thermophysical properties will be helpful in understanding the work of adhesion and the liquid spread kinetics of glass frits.

  19. Determination of the liquidus temperature of tin using the heat pulse-based melting and comparison with traditional methods

    Science.gov (United States)

    Joung, Wukchul; Park, Jihye; Pearce, Jonathan V.

    2018-06-01

    In this work, the liquidus temperature of tin was determined by melting the sample using the pressure-controlled loop heat pipe. Square wave-type pressure steps generated periodic 0.7 °C temperature steps in the isothermal region in the vicinity of the tin sample, and the tin was melted with controllable heat pulses from the generated temperature changes. The melting temperatures at specific melted fractions were measured, and they were extrapolated to the melted fraction of unity to determine the liquidus temperature of tin. To investigate the influence of the impurity distribution on the melting behavior, a molten tin sample was solidified by an outward slow freezing or by quenching to segregate the impurities inside the sample with concentrations increasing outwards or to spread the impurities uniformly, respectively. The measured melting temperatures followed the local solidus temperature variations well in the case of the segregated sample and stayed near the solidus temperature in the quenched sample due to the microscopic melting behavior. The extrapolated melting temperatures of the segregated and quenched samples were 0.95 mK and 0.49 mK higher than the outside-nucleated freezing temperature of tin (with uncertainties of 0.15 mK and 0.16 mK, at approximately 95% level of confidence), respectively. The extrapolated melting temperature of the segregated sample was supposed to be a closer approximation to the liquidus temperature of tin, whereas the quenched sample yielded the possibility of a misleading extrapolation to the solidus temperature. Therefore, the determination of the liquidus temperature could result in different extrapolated melting temperatures depending on the way the impurities were distributed within the sample, which has implications for the contemporary methodology for realizing temperature fixed points of the International Temperature Scale of 1990 (ITS-90).

  20. Estimation of a melting probe's penetration velocity range to reach icy moons' subsurface ocean

    Science.gov (United States)

    Erokhina, Olga; Chumachenko, Eugene

    2014-05-01

    In modern space science one of the actual branches is icy satellites explorations. The main interest is concentrated around Jovian's moons Europa and Ganymede, Saturn's moons Titan and Enceladus that are covered by thick icy layer according to "Voyager1", "Voyager2", "Galileo" and "Cassini" missions. There is a big possibility that under icy shell could be a deep ocean. Also conditions on these satellites allow speculating about possible habitability, and considering these moons from an astrobiological point of view. One of the possible tasks of planned missions is a subsurface study. For this goal it is necessary to design special equipment that could be suitable for planetary application. One of the possible means is to use a melting probe which operates by melting and moves by gravitational force. Such a probe should be relatively small, should not weight too much and should require not too much energy. In terrestrial case such kind of probe has been successfully used for glaciers study. And it is possible to extrapolate the usage of such probe to extraterrestrial application. One of the tasks is to estimate melting probe's penetration velocity. Although there are other unsolved problems such as analyzing how the probe will move in low gravity and low atmospheric pressure; knowing whether hole will be closed or not when probe penetrate thick enough; and considering what order could be a penetration velocity. This study explores two techniques of melting probe's movement. One of them based on elasto-plastic theory and so-called "solid water" theory, and other one takes phase changing into account. These two techniques allow estimating melting probe's velocity range and study whole process. Based on these technique several cases of melting probe movement were considered, melting probe's velocity range estimated, influence of different factors studied and discussed and an easy way to optimize parameters of the melting probe proposed.

  1. Melting of size-selected gallium clusters with 60-183 atoms.

    Science.gov (United States)

    Pyfer, Katheryne L; Kafader, Jared O; Yalamanchali, Anirudh; Jarrold, Martin F

    2014-07-10

    Heat capacities have been measured as a function of temperature for size-selected gallium cluster cations with between 60 and 183 atoms. Almost all clusters studied show a single peak in the heat capacity that is attributed to a melting transition. The peaks can be fit by a two-state model incorporating only fully solid-like and fully liquid-like species, and hence no partially melted intermediates. The exceptions are Ga90(+), which does not show a peak, and Ga80(+) and Ga81(+), which show two peaks. For the clusters with two peaks, the lower temperature peak is attributed to a structural transition. The melting temperatures for clusters with less than 50 atoms have previously been shown to be hundreds of degrees above the bulk melting point. For clusters with more than 60 atoms the melting temperatures decrease, approaching the bulk value (303 K) at around 95 atoms, and then show several small upward excursions with increasing cluster size. A plot of the latent heat against the entropy change for melting reveals two groups of clusters: the latent heats and entropy changes for clusters with less than 94 atoms are distinct from those for clusters with more than 93 atoms. This observation suggests that a significant change in the nature of the bonding or the structure of the clusters occurs at 93-94 atoms. Even though the melting temperatures are close to the bulk value for the larger clusters studied here, the latent heats and entropies of melting are still far from the bulk values.

  2. Edge-melting: nanoscale key-mechanism to explain nanoparticle formation from heated TEM grids

    Energy Technology Data Exchange (ETDEWEB)

    Cesaria, Maura, E-mail: maura.cesaria@le.infn.it [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, Via Arnesano, 73100 Lecce (Italy); Taurino, Antonietta; Catalano, Massimo [Institute for Microelectronics and Microsystems, IMM-CNR, Via Monteroni, 73100 Lecce (Italy); Caricato, Anna Paola; Martino, Maurizio [Department of Mathematics and Physics “E. De Giorgi”, University of Salento, Via Arnesano, 73100 Lecce (Italy)

    2016-03-01

    Graphical abstract: - Highlights: • Nanoparticle formation from metal grids explained by edge melting as key mechanism. • The inconsistency of bulk phenomenology invoking the vapor pressure is discussed. • Surface-melting and size-dependent evaporation are questioned as unsatisfactory. • Edge-melting: edges, corners, facets invoked as highly thermally unstable surfaces. • The polycrystalline nature of the really occurring metal grids is accounted for. - Abstract: In this study, we examine at both experimental and fundamental levels, the experimental evidence of nanoparticle formation in transmission electron microscopy (TEM) metal grids annealed at temperatures lower than the melting point of the corresponding metal bulk material. Our experimental investigation considers the most thermally unstable TEM grids (i.e. Cu-grids) and inspects the possible sources and mechanisms of contamination of thin films, conventionally deposited on carbon-coated Cu-grids. The investigations are supported by morphological–compositional analyses performed in different regions of the TEM sample. Then, a general model is formulated and discussed in order to explain the grid thermal instability, based on the critical role of edge-melting (i.e. melting initiated at edges and corners of the grid bars), the enhanced rate of evaporation from a liquid surface and the polycristallinity of the grid bars. Hence, we totally disregard conventional arguments such as bulk evaporation and metal vapor pressure and, in order to emphasize and clarify the alternative point of view of our model, we also overview the nano-scale melting phenomenology relevant to our discussion and survey the discrepancies reported in the literature.

  3. Melt migration modeling in partially molten upper mantle

    Science.gov (United States)

    Ghods, Abdolreza

    The objective of this thesis is to investigate the importance of melt migration in shaping major characteristics of geological features associated with the partial melting of the upper mantle, such as sea-floor spreading, continental flood basalts and rifting. The partial melting produces permeable partially molten rocks and a buoyant low viscosity melt. Melt migrates through the partially molten rocks, and transfers mass and heat. Due to its much faster velocity and appreciable buoyancy, melt migration has the potential to modify dynamics of the upwelling partially molten plumes. I develop a 2-D, two-phase flow model and apply it to investigate effects of melt migration on the dynamics and melt generation of upwelling mantle plumes and focusing of melt migration beneath mid-ocean ridges. Melt migration changes distribution of the melt-retention buoyancy force and therefore affects the dynamics of the upwelling plume. This is investigated by modeling a plume with a constant initial melt of 10% where no further melting is considered. Melt migration polarizes melt-retention buoyancy force into high and low melt fraction regions at the top and bottom portions of the plume and therefore results in formation of a more slender and faster upwelling plume. Allowing the plume to melt as it ascends through the upper mantle also produces a slender and faster plume. It is shown that melt produced by decompressional melting of the plume migrates to the upper horizons of the plume, increases the upwelling velocity and thus, the volume of melt generated by the plume. Melt migration produces a plume which lacks the mushroom shape observed for the plume models without melt migration. Melt migration forms a high melt fraction layer beneath the sloping base of the impermeable oceanic lithosphere. Using realistic conditions of melting, freezing and melt extraction, I examine whether the high melt fraction layer is able to focus melt from a wide partial melting zone to a narrow region

  4. Multivariate data analysis for finding the relevant fatty acids contributing to the melting fractions of cream

    DEFF Research Database (Denmark)

    Buldo, Patrizia; Larsen, Mette Krogh; Wiking, Lars

    2013-01-01

    :0 and palmitoleic acid (C16:1) in milk fat, whereas it decreased the amount of stearic acid (C18:0) and C18:1 trans fatty acid. Average data on the melting behaviour of cream separated the farms into two groups where the main differences in feeding were the amounts of maize silage and rapeseed cake used. CONCLUSION......BACKGROUND: The melting behaviour and fatty acid composition of cream from a total of 33 cows from four farms were analysed. Multivariate data analysis was used to identify the fatty acids that contributed most to the melting points and to differentiate between creams from different practical...... feeding regimes. RESULTS: It was demonstrated that the melting point of the medium melting fraction of milk fat was positively correlated with palmitic acid (C16:0), whereas it was negatively correlated with oleic acid (C18:1 cis9), conjugated linoleic acid (CLA cis9 trans11), vaccenic acid (C18:1 trans11...

  5. Influence of repetitive pulsed laser irradiation on the surface characteristics of an aluminum alloy in the melting regime

    International Nuclear Information System (INIS)

    Choi, Sung Ho; Jhang, Kyung Young

    2015-01-01

    We have investigated the influence of repetitive near-infrared (NIR) pulsed laser shots in the melting regime on the surface characteristics of an aluminum 6061-T6 alloy. Characteristics of interest include surface morphology, surface roughness, and surface hardness in the melted zone as well as the size of the melted zone. For this study, the proper pulse energy for inducing surface melting at one shot is selected using numerical simulations that calculate the variation in temperature at the laser beam spot for various input pulse energies in order to find the proper pulse energy for raising the temperature to the melting point. In this study, 130 mJ was selected as the input energy for a Nd:YAG laser pulse with a duration of 5 ns. The size of the melted zone measured using optical microscopy (OM) increased logarithmically with an increasing shot number. The surface morphology observed by scanning electron microscopy (SEM) clearly showed a re-solidified microstructure evolution after surface melting. The surface roughness and hardness were measured by atomic force microscopy (AFM) and nano-indentation, respectively. The surface roughness showed almost no variation due to the surface texturing after laser shots over 10. The hardness inside the melted zone was lower than that outside the zone because the β'' phase was transformed to a β phase or dissolved into a matrix.

  6. Using ice melting and ice rolling technologies to remove ice from sub-transmission and transmission lines at Manitoba Hydro

    International Nuclear Information System (INIS)

    Farias, A. R.

    1999-01-01

    Development of an of an Ice Storm Management program by Manitoba Hydro to reduce ice storm damage to its 8 kV feeders to 115 kV transmission lines, is discussed. The program consists of the de-icing of overhead lines, either by ice melting, or ice rolling. Ice melting involves the placement of a three-phase short at a calculated point. The term ice rolling denotes a process of mechanically stripping the ice from conductors. The most recent major ice storm experienced by Manitoba Hydro was in the winter of 1997/1998. During the period from February 6 to February 17, 1998, a total of 83 'ice melt' procedures were performed to melt the ice from 2,628 km of overhead line (7,883 km of conductor), in addition to 'ice rolling'. This paper describes Manitoba Hydro's 25-years' experience with ice melting and it also describes the advantages and disadvantages of both ice melting and ice rolling. Although not a panacea to combat the effects of ice storms, ice melting was found to be the most effective way of removing ice from overhead transmission and sub-transmission lines. Ice rolling was also found to be effective. Other tools that have been found to be useful by various utilities in combating ice storm damage include improved structure and line design, system design that provide more redundancies and emergency sources, and standby generators at critical load points

  7. Equilibrium triple point pressure and pressure-temperature phase diagram of polyethylene

    NARCIS (Netherlands)

    Hikosaka, M.; Tsukijima, K.; Rastogi, S.; Keller, A.

    1992-01-01

    The equil. triple point and pressure and temp. phase diagrams of polyethylene were obtained by in situ optical microscopic and x-ray observations of the melting temp. of hexagonal and orthorhombic isolated extended-chain single crystals at high pressure. The melting temps. of extended-chain crystals

  8. Shock melting method to determine melting curve by molecular dynamics: Cu, Pd, and Al

    International Nuclear Information System (INIS)

    Liu, Zhong-Li; Zhang, Xiu-Lu; Cai, Ling-Cang

    2015-01-01

    A melting simulation method, the shock melting (SM) method, is proposed and proved to be able to determine the melting curves of materials accurately and efficiently. The SM method, which is based on the multi-scale shock technique, determines melting curves by preheating and/or prepressurizing materials before shock. This strategy was extensively verified using both classical and ab initio molecular dynamics (MD). First, the SM method yielded the same satisfactory melting curve of Cu with only 360 atoms using classical MD, compared to the results from the Z-method and the two-phase coexistence method. Then, it also produced a satisfactory melting curve of Pd with only 756 atoms. Finally, the SM method combined with ab initio MD cheaply achieved a good melting curve of Al with only 180 atoms, which agrees well with the experimental data and the calculated results from other methods. It turned out that the SM method is an alternative efficient method for calculating the melting curves of materials

  9. Shock melting method to determine melting curve by molecular dynamics: Cu, Pd, and Al.

    Science.gov (United States)

    Liu, Zhong-Li; Zhang, Xiu-Lu; Cai, Ling-Cang

    2015-09-21

    A melting simulation method, the shock melting (SM) method, is proposed and proved to be able to determine the melting curves of materials accurately and efficiently. The SM method, which is based on the multi-scale shock technique, determines melting curves by preheating and/or prepressurizing materials before shock. This strategy was extensively verified using both classical and ab initio molecular dynamics (MD). First, the SM method yielded the same satisfactory melting curve of Cu with only 360 atoms using classical MD, compared to the results from the Z-method and the two-phase coexistence method. Then, it also produced a satisfactory melting curve of Pd with only 756 atoms. Finally, the SM method combined with ab initio MD cheaply achieved a good melting curve of Al with only 180 atoms, which agrees well with the experimental data and the calculated results from other methods. It turned out that the SM method is an alternative efficient method for calculating the melting curves of materials.

  10. Energy Saving Melting and Revert Reduction Technology: Melting Efficiency in Die Casting Operations

    Energy Technology Data Exchange (ETDEWEB)

    David Schwam

    2012-12-15

    This project addressed multiple aspects of the aluminum melting and handling in die casting operations, with the objective of increasing the energy efficiency while improving the quality of the molten metal. The efficiency of melting has always played an important role in the profitability of aluminum die casting operations. Consequently, die casters need to make careful choices in selecting and operating melting equipment and procedures. The capital cost of new melting equipment with higher efficiency can sometimes be recovered relatively fast when it replaces old melting equipment with lower efficiency. Upgrades designed to improve energy efficiency of existing equipment may be well justified. Energy efficiency is however not the only factor in optimizing melting operations. Melt losses and metal quality are also very important. Selection of melting equipment has to take into consideration the specific conditions at the die casting shop such as availability of floor space, average quantity of metal used as well as the ability to supply more metal during peaks in demand. In all these cases, it is essential to make informed decisions based on the best available data.

  11. Olivine/melt transition metal partitioning, melt composition, and melt structure—Melt polymerization and Qn-speciation in alkaline earth silicate systems

    Science.gov (United States)

    Mysen, Bjorn O.

    2008-10-01

    The two most abundant network-modifying cations in magmatic liquids are Ca 2+ and Mg 2+. To evaluate the influence of melt structure on exchange of Ca 2+ and Mg 2+ with other geochemically important divalent cations ( m-cations) between coexisting minerals and melts, high-temperature (1470-1650 °C), ambient-pressure (0.1 MPa) forsterite/melt partitioning experiments were carried out in the system Mg 2SiO 4-CaMgSi 2O 6-SiO 2 with ⩽1 wt% m-cations (Mn 2+, Co 2+, and Ni 2+) substituting for Ca 2+ and Mg 2+. The bulk melt NBO/Si-range ( NBO/Si: nonbridging oxygen per silicon) of melt in equilibrium with forsterite was between 1.89 and 2.74. In this NBO/Si-range, the NBO/Si(Ca) (fraction of nonbridging oxygens, NBO, that form bonds with Ca 2+, Ca 2+- NBO) is linearly related to NBO/Si, whereas fraction of Mg 2+- NBO bonds is essentially independent of NBO/Si. For individual m-cations, rate of change of KD( m-Mg) with NBO/Si(Ca) for the exchange equilibrium, mmelt + Mg olivine ⇌ molivine + Mg melt, is linear. KD( m-Mg) decreases as an exponential function of increasing ionic potential, Z/ r2 ( Z: formal electrical charge, r: ionic radius—here calculated with oxygen in sixfold coordination around the divalent cations) of the m-cation. The enthalpy change of the exchange equilibrium, Δ H, decreases linearly with increasing Z/ r2 [Δ H = 261(9)-81(3)· Z/ r2 (Å -2)]. From existing information on (Ca,Mg)O-SiO 2 melt structure at ambient pressure, these relationships are understood by considering the exchange of divalent cations that form bonds with nonbridging oxygen in individual Qn-species in the melts. The negative ∂ KD( m-Mg) /∂( Z/ r2) and ∂(Δ H)/∂( Z/ r2) is because increasing Z/ r2 is because the cations forming bonds with nonbridging oxygen in increasingly depolymerized Qn-species where steric hindrance is decreasingly important. In other words, principles of ionic size/site mismatch commonly observed for trace and minor elements in crystals, also

  12. Viscosity characteristics of selected volcanic rock melts

    Science.gov (United States)

    Hobiger, Manuel; Sonder, Ingo; Büttner, Ralf; Zimanowski, Bernd

    2011-02-01

    A basic experimental study of the behavior of magma rheology was carried out on remelted volcanic rocks using wide gap viscometry. The complex composition of magmatic melts leads to complicated rheologic behavior which cannot be described with one simple model. Therefore, measurement procedures which are able to quantify non-Newtonian behavior have to be employed. Furthermore, the experimental apparatus must be able to deal with inhomogeneities of magmatic melts. We measured the viscosity of a set of materials representing a broad range of volcanic processes. For the lower viscous melts (low-silica compositions), non-Newtonian behavior is observed, whereas the high-silica melts show Newtonian behavior in the measured temperature and shear rate range (T = 1423 K - 1623 K, γ˙ = 10 - 2 s - 1 - 20 s - 1 ). The non-Newtonian materials show power-law behavior. The measured viscosities η and power-law indexes m lie in the intervals 8 Pa s ≤ η ≤ 210 3 Pa s, 0.71 ≤ m ≤ 1.0 (Grímsvötn basalt), 0.9 Pa s ≤ η ≤ 350 Pa s, 0.61 ≤ m ≤ 0.93 (Hohenstoffeln olivine-melilitite), and 8 Pa s ≤ η ≤ 1.510 4 Pa s, 0.55 ≤ m ≤ 1.0 (Sommata basalt). Measured viscosities of the Newtonian high-silica melts lie in the range 10 4 Pa s ≤ η ≤ 310 5 Pa s.

  13. SLUDGE MASS REDUCTION: PRIMARY COMPOSITIONAL FACTORS THAT INFLUENCE MELT RATE FOR FUTURE SLUDGE BATCH PROJECTIONS

    International Nuclear Information System (INIS)

    Newell, J; Miller, D; Stone, M; Pickenheim, B

    2008-01-01

    510 based system without Al-dissolution relative to the Frit 418 based system with Al-dissolution. Though the without aluminum dissolution scenario suggests a slightly higher melt rate with frit 510, several points must be taken into consideration: (1) The MRF does not have the ability to assess liquid feeds and, thus, rheology impacts. Instead, the MRF is a 'static' test bed in which a mass of dried melter feed (SRAT product plus frit) is placed in an 'isothermal' furnace for a period of time to assess melt rate. These conditions, although historically effective in terms of identifying candidate frits for specific sludge batches and mapping out melt rate versus waste loading trends, do not allow for assessments of the potential impact of feed rheology on melt rate. That is, if the rheological properties of the slurried melter feed resulted in the mounding of the feed in the melter (i.e., the melter feed was thick and did not flow across the cold cap), melt rate and/or melter operations (i.e., surges) could be negatively impacted. This could affect one or both flowsheets. (2) Waste throughput factors were not determined for Frit 510 and Frit 418 over multiple waste loadings. In order to provide insight into the mission life versus canister count question, one needs to define the maximum waste throughput for both flowsheets. Due to funding limitations, the melt rate testing only evaluated melt rate at a fixed waste loading. (3) DWPF will be processing SB5 through their facility in mid-November 2008. Insight into the over arching questions of melt rate, waste throughput, and mission life can be obtained directly from the facility. It is recommended that processing of SB5 through the facility be monitored closely and that data be used as input into the decision making process on whether to implement Al-dissolution for future sludge batches

  14. Monitoring device for glass melting furnace

    International Nuclear Information System (INIS)

    Endo, Noboru; Asano, Naoki; Higuchi, Tatsuo; Koyama, Mayumi; Hanado, Shinji.

    1995-01-01

    The device of the present invention can monitor, from a remote place, a liquid surface in a glass melting furnace for use in a solidification treatment, for example, of high level radioactive wastes. Namely, a vertical sleeve is disposed penetrating a ceiling wall of a melting vessel. A reflection mirror is disposed above the vertical sleeve and flex an optical axis. A monitoring means is disposed on the optical axis of the reflecting mirror at a spaced position. The monitoring means may have an optical telescopic means, a monitoring camera by way of a half mirror and an illumination means. The reflection mirror may be made of a metal. The monitoring device thus constituted suffer from no effects of high temperature and high radiation dose rate, thereby enabling to easily monitor the liquid surface in the melting furnace. (I.S.)

  15. Entangled Polymer Melts in Extensional Flow

    DEFF Research Database (Denmark)

    Hengeller, Ludovica

    Many commercial materials derived from synthetic polymers exhibit a complex response under different processing operations such as fiber formation, injection moulding,film blowing, film casting or coatings. They can be processed both in the solid or in the melted state. Often they may contain two...... or more different polymers in addition to additives, fillers or solvents in order to modify the properties of the final product. Usually, it is also desired to improve the processability. For example the supplement of a high molecular weight component improves the stability in elongational flows....... Understanding the behaviour of polymer melts and solutions in complex non-linearflows is crucial for the design of polymeric materials and polymer processes. Through rheological characterization, in shear and extensional flow, of model polymer systems,i.e. narrow molar mass distribution polymer melts...

  16. APPARATUS FOR MELTING AND POURING METAL

    Science.gov (United States)

    Harris, F.A.

    1958-02-25

    This patent relates to a crucible for melting and pouring a metal under controlled atmospheric conditions. The crucible has a frangible plug in the bottom and a retaining device to prevent the entrance of the broken portions of the plug into the mold without interfering with the flow of the melt. After the charge has been melted, a knockout rod is lowered through the charge and forced against the frangible plug sufficiently to break off the closure disk along a previously scored line. The disk drops onto a retaining grid large enough to permit the flow of metal around the disk and into the mold below. Thts arrangement elimnates the entry of broken portions of the plug into the mold, thereby elimnating a common cause of imperfect castings.

  17. Analysis of picosecond pulsed laser melted graphite

    International Nuclear Information System (INIS)

    Steinbeck, J.; Braunstein, G.; Speck, J.; Dresselhaus, M.S.; Huang, C.Y.; Malvezzi, A.M.; Bloembergen, N.

    1986-01-01

    A Raman microprobe and high resolution TEM have been used to analyze the resolidified region of liquid carbon generated by picosecond pulse laser radiation. From the relative intensities of the zone center Raman-allowed mode for graphite at 1582 cm -1 and the disorder-induced mode at 1360 cm -1 , the average graphite crystallite size in the resolidified region is determined as a function of position. By comparison with Rutherford backscattering spectra and Raman spectra from nonosecond pulsed laser melting experiments, the disorder depth for picosecond pulsed laser melted graphite is determined as a function of irradiating energy density. Comparisons of TEM micrographs for nanosecond and picosecond pulsed laser melting experiments show that the structure of the laser disordered regions in graphite are similar and exhibit similar behavior with increasing laser pulse fluence

  18. Selective Laser Melting of Pure Copper

    Science.gov (United States)

    Ikeshoji, Toshi-Taka; Nakamura, Kazuya; Yonehara, Makiko; Imai, Ken; Kyogoku, Hideki

    2018-03-01

    Appropriate building parameters for selective laser melting of 99.9% pure copper powder were investigated at relatively high laser power of 800 W for hatch pitch in the range from 0.025 mm to 0.12 mm. The highest relative density of the built material was 99.6%, obtained at hatch pitch of 0.10 mm. Building conditions were also studied using transient heat analysis in finite element modeling of the liquidation and solidification of the powder layer. The estimated melt pool length and width were comparable to values obtained by observations using a thermoviewer. The trend for the melt pool width versus the hatch pitch agreed with experimental values.

  19. Prereduction and melting of domestic titaniferous materials

    Science.gov (United States)

    Nafziger, R. H.; Jordan, R. R.

    1983-03-01

    Two domestic ilmenites and one titaniferous magnetite were prereduced by the United States Department of the Interior, Bureau of Mines, in a batch rotary kiln with coal char to assess the feasibility of this technique in improving melting operations and subsequent electric furnace processing. All three prereduced titaniferous materials were melted satisfactorily in an electric arc furnace to produce iron as a metal suitable for further refining to steel; metallizations ranging from 63 to 83 pct of the iron oxides were achieved. The ilmenites yielded titanium enriched slags that were amenable to further processing by conventional methods. Prereduction decreased electrode consumption during furnace operation and also conserved expensive electrical energy that otherwise must be used to reduce and melt totally the entire titaniferous materials charge.

  20. Scrap uranium recycling via electron beam melting

    International Nuclear Information System (INIS)

    McKoon, R.

    1993-11-01

    A program is underway at the Lawrence Livermore National Laboratory (LLNL) to recycle scrap uranium metal. Currently, much of the material from forging and machining processes is considered radioactive waste and is disposed of by oxidation and encapsulation at significant cost. In the recycling process, uranium and uranium alloys in various forms will be processed by electron beam melting and continuously cast into ingots meeting applicable specifications for virgin material. Existing vacuum processing facilities at LLNL are in compliance with all current federal and state environmental, safety and health regulations for the electron beam melting and vaporization of uranium metal. One of these facilities has been retrofitted with an auxiliary electron beam gun system, water-cooled hearth, crucible and ingot puller to create an electron beam melt furnace. In this furnace, basic process R ampersand D on uranium recycling will be performed with the goal of eventual transfer of this technology to a production facility

  1. Properties of melt-grown single crystals of 'YB/sub 68/'

    Energy Technology Data Exchange (ETDEWEB)

    Slack, G A; Oliver, D W; Brower, G D; Young, J D [General Electric Co., Schenectady, N.Y. (USA). Research and Development Center

    1977-01-01

    Single crystals of yttrium boride YB/sub n/ with n = 61 +- 3 were grown from the melt. Precision density and lattice parameter measurements indicate a congruent melting point at n = 61.7 and a stoichiometric composition at n = 68. Measurements of elastic constants, acoustic attenuation, electrical resistivity and optical absorption are presented. High resolution transmission electron microscopy reveals a complex crystal structure similar to that found by using X-rays. A comparison of the properties of YB/sub n/ with those of ..beta..-boron show that there are many similarities.

  2. Method for preparation of melts of alkali metal chlorides with highly volatile polyvalent metal chlorides

    International Nuclear Information System (INIS)

    Salyulev, A.B.; Kudyakov, V.Ya.

    1990-01-01

    A method for production of alkali metal (Cs, Rb, K) chloride melts with highly volatile polyvalent metal chlorides is suggested. The method consists, in saturation of alkali metal chlorides, preheated to the melting point, by volatile component vapours (titanium tetrachloride, molybdenum or tantalum pentachloride) in proportion, corresponding to the composition reguired. The saturation is realized in an evacuated vessel with two heating areas for 1-1.5 h. After gradual levelling of temperature in both areas the product is rapidly cooled. 1 fig.; 1 tab

  3. Mathematical model of melt flow channel granulator

    Directory of Open Access Journals (Sweden)

    A. A. Kiselev

    2016-01-01

    Full Text Available Granulation of carbohydrate-vitamin-mineral supplements based on molasses is performed at a high humidity (26 %, so for a stable operation of granulator it is necessary to reveal its melt flow pattern. To describe melt non-isothermal flow in the granulator a mathematical model with following initial equations: continuity equation, motion equation and rheological equation – was developed. The following assumptions were adopted: the melt flow in the granulator is a steady laminar flow; inertial and gravity forces can be ignored; melt is an incompressible fluid; velocity gradient in the flow direction is much smaller than in the transverse direction; the pressure gradient over the cross section of the channel is constant; the flow is hydrodynamically fully developed; effects impact on the channel inlet and outlet may be neglected. Due to the assumptions adopted, it can be considered that in this granulator only velocity components in the x-direction are significant and all the members of the equation with the components and their derivatives with respect to the coordinates y and z can be neglected. The resulting solutions were obtained: the equation for the mean velocity, the equation for determining the volume flow, the formula for calculating of mean time of the melt being in the granulator, the equation for determining the shear stress, the equation for determining the shear rate and the equation for determining the pressure loss. The results of calculations of the equations obtained are in complete agreement with the experimental data; deviation range is 16–19 %. The findings about the melt movement pattern in granulator allowed developing a methodology for calculating a rational design of the granulator molding unit.

  4. 50-kg large-size cold crucible levitation melting apparatus; Teibu shuto kino wo motsu 50kg kyu korudo kurushiburu fuyo yokai shochi no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, S. [Fuji Electric Co. Ltd., Tokyo (Japan); Tadano, E. [Fuji Electric Corporate Research and Development Ltd., Kanagawa (Japan)

    1997-06-25

    With an increase in the degree of industrial techniques and the development of high-technology products in recent years, it has been demanded that the quality of high-purity metal materials be improved. The levitation melting method is a new melting method in which a metal material is melted by induction heating while the material is levitated in a water-cooled copper crucible. This paper made clear the principle of the levitation melting method and describes some problems in the development of a 50 kg-class large-capacity levitation melting apparatus and solutions to the problems. The development of a 50 kg-class levitation melting apparatus having a bottom discharging function was carried out on the basis of the results of discussion of the above-mentioned problems, and the noncontact melting of 50 kg cast iron and the noncontact bottom discharging of molten iron succeeded. This enabled the noncontact process of from the melting of a high-purity metal material and a metal of a high melting point to the casting of the molten metal. Since a continuous casting apparatus is provided under the crucible, the casting of an ingot and a rod material becomes possible. When a metal material is levitation-melted in superhigh vacuum, production of a superhigh-purity metal and a new metal material can be attained since the material is not contaminated by the atmosphere. 9 refs., 11 figs., 4 tabs.

  5. Structure of polyvalent metal halide melts

    International Nuclear Information System (INIS)

    Tosi, M.P.

    1990-12-01

    A short review is given of recent progress in determining and understanding the structure of molten halide salts involving polyvalent metal ions. It covers the following three main topics: (i) melting mechanisms and types of liquid structure for pure polyvalent-metal chlorides; (ii) geometry and stability of local coordination for polyvalent metal ions in molten mixtures of their halides with alkali halides; and (iii) structure breaking and electron localization on addition of metal to the melt. (author). 28 refs, 3 figs, 1 tab

  6. Chemical reactions in solvents and melts

    CERN Document Server

    Charlot, G

    1969-01-01

    Chemical Reactions in Solvents and Melts discusses the use of organic and inorganic compounds as well as of melts as solvents. This book examines the applications in organic and inorganic chemistry as well as in electrochemistry. Organized into two parts encompassing 15 chapters, this book begins with an overview of the general properties and the different types of reactions, including acid-base reactions, complex formation reactions, and oxidation-reduction reactions. This text then describes the properties of inert and active solvents. Other chapters consider the proton transfer reactions in

  7. Stress Relaxation in Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf

    2010-01-01

    We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements...... and into the terminal relaxation regime for Z=10. Using the known (Rouse) mobility of unentangled chains and the melt entanglement length determined via the primitive path analysis of the microscopic topological state of our systems, we have performed parameter-free tests of several different tube models. We find...

  8. Electrochemistry of uranium in sodium chloroaluminate melts

    International Nuclear Information System (INIS)

    D'olieslager, W.; Meuris, F.; Heerman, L.

    1990-01-01

    The electrochemical behaviour of uranium was studied in basic, NaCl-saturated NaAlCl 4 melts at 175 deg C. Solutions of UO 3 exhibit two oxidation/reduction waves (cyclic voltammetry). Analysis of the peak currents (cyclic voltammetry), the limiting currents (pulse polarography) and the non-linear log i-t curves (anodic controlled potential coulometry) leads to the conclusion that uranium(IV) in the basic chloroaluminate melt exists as two different species in slow equilibrium with one another, of which only one species can be oxidized to U(VI). (author) 16 refs.; 7 figs.; 3 tabs

  9. Microstructure and mechanical behavior of pulsed laser surface melted AISI D2 cold work tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Yasavol, N. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Abdollah-zadeh, A., E-mail: zadeh@modares.ac.ir [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Ganjali, M. [Materials and Energy Research Center, P.O. Box 14155-4777, Karaj (Iran, Islamic Republic of); Alidokht, S.A. [Department of Materials Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Melted zone contained fine dendrites in the bottom and equiaxed grains on the top. Black-Right-Pointing-Pointer Microstructural refinements of PLSM led to microhardness enhancement. Black-Right-Pointing-Pointer Higher scanning rate and lower laser energy were more effective to refine the microstructure. - Abstract: D2 cold work tool steel (CWTS) was subjected to pulse laser surface melting (PLSM) at constant frequency of 20 Hz Nd: YAG laser with different energies, scanning rate and pulse durations radiated to the surface. Characterizing the PLSM, with optical and field emission scanning electron microscopy, electron backscattered diffraction and surface hardness mapping technique was used to evaluate the microhardness and mechanical behavior of different regions of melting pool. Increasing laser energy and reducing the laser scanning rate results in deeper melt pool formation. Moreover, PLSM has led to entirely dissolution of the carbides and re-solidification of cellular/dendritic structure of a fine scale surrounded by a continuous interdendritic network. This caused an increase in surface microhardness, 2-4 times over that of the base metal.

  10. Finite element modeling of melting and fluid flow in the laser-heated diamond-anvil cell

    Science.gov (United States)

    Gomez-Perez, N.; Rodriguez, J. F.; McWilliams, R. S.

    2017-04-01

    The laser-heated diamond anvil cell is widely used in the laboratory study of materials behavior at high-pressure and high-temperature, including melting curves and liquid properties at extreme conditions. Laser heating in the diamond cell has long been associated with fluid-like motion in samples, which is routinely used to determine melting points and is often described as convective in appearance. However, the flow behavior of this system is poorly understood. A quantitative treatment of melting and flow in the laser-heated diamond anvil cell is developed here to physically relate experimental motion to properties of interest, including melting points and viscosity. Numerical finite-element models are used to characterize the temperature distribution, melting, buoyancy, and resulting natural convection in samples. We find that continuous fluid motion in experiments can be explained most readily by natural convection. Fluid velocities, peaking near values of microns per second for plausible viscosities, are sufficiently fast to be detected experimentally, lending support to the use of convective motion as a criterion for melting. Convection depends on the physical properties of the melt and the sample geometry and is too sluggish to detect for viscosities significantly above that of water at ambient conditions, implying an upper bound on the melt viscosity of about 1 mPa s when convective motion is detected. A simple analytical relationship between melt viscosity and velocity suggests that direct viscosity measurements can be made from flow speeds, given the basic thermodynamic and geometric parameters of samples are known.

  11. Deformation, static recrystallization, and reactive melt transport in shallow subcontinental mantle xenoliths (Tok Cenozoic volcanic field, SE Siberia)

    Science.gov (United States)

    Tommasi, Andréa; Vauchez, Alain; Ionov, Dmitri A.

    2008-07-01

    Partial melting and reactive melt transport may change the composition, microstructures, and physical properties of mantle rocks. Here we explore the relations between deformation and reactive melt transport through detailed microstructural analysis and crystallographic orientation measurements in spinel peridotite xenoliths that sample the shallow lithospheric mantle beneath the southeastern rim of the Siberian craton. These xenoliths have coarse-grained, annealed microstructures and show petrographic and chemical evidence for variable degrees of reaction with silicate melts and fluids, notably Fe-enrichment and crystallization of metasomatic clinopyroxene (cpx). Olivine crystal preferred orientations (CPO) range from strong to weak. [010]-fiber patterns, characterized by a point concentration of [010] normal to the foliation and by dispersion of [100] in the foliation plane with a weak maximum parallel to the lineation, predominate relative to the [100]-fiber patterns usually observed in lithospheric mantle xenoliths and peridotite massifs. Variations in olivine CPO patterns or intensity are not correlated with modal and chemical compositions. This, together with the analysis of microstructures, suggests that reactive melt percolation postdated both deformation and static recrystallization. Preferential crystallization of metasomatic cpx along (010) olivine grain boundaries points to an influence of the preexisting deformation fabrics on melt transport, with higher permeability along the foliation. Similarity between orthopyroxene (opx) and cpx CPO suggests that cpx orientations may be inherited from those of opx during melt-rock reaction. As observed in previous studies, reactive melt transport does not weaken olivine CPO and seismic anisotropy in the upper mantle, except in melt accumulation domains. In contrast, recovery and selective grain growth during static recrystallization may lead to development of [010]-fiber olivine CPO and, if foliations are

  12. A characterization of Greenland Ice Sheet surface melt and runoff in contemporary reanalyses and a regional climate model

    Directory of Open Access Journals (Sweden)

    Richard eCullather

    2016-02-01

    Full Text Available For the Greenland Ice Sheet (GrIS, large-scale melt area has increased in recent years and is detectable via remote sensing, but its relation to runoff is not known. Historical, modeled melt area and runoff from Modern-Era Retrospective Analysis for Research and Applications (MERRA-Replay, the Interim Re-Analysis of the European Centre for Medium Range Weather Forecasts (ERA-I, the Climate Forecast System Reanalysis (CFSR, the Modèle Atmosphérique Régional (MAR, and the Arctic System Reanalysis (ASR are examined. These sources compare favorably with satellite-derived estimates of surface melt area for the period 2000-2012. Spatially, the models markedly disagree on the number of melt days in the interior of the southern part of the ice sheet, and on the extent of persistent melt areas in the northeastern GrIS. Temporally, the models agree on the mean seasonality of daily surface melt and on the timing of large-scale melt events in 2012. In contrast, the models disagree on the amount, seasonality, spatial distribution, and temporal variability of runoff. As compared to global reanalyses, time series from MAR indicate a lower correlation between runoff and melt area (r2 = 0.805. Runoff in MAR is much larger in the second half of the melt season for all drainage basins, while the ASR indicates larger runoff in the first half of the year. This difference in seasonality for the MAR and to an extent for the ASR provide a hysteresis in the relation between runoff and melt area, which is not found in the other models. The comparison points to a need for reliable observations of surface runoff.

  13. Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Du, Kang, E-mail: du126kang@126.com; Zhu, Qiang, E-mail: zhu.qiang@grinm.com; Li, Daquan, E-mail: lidaquan@grinm.com; Zhang, Fan, E-mail: sk_zf@163.com

    2015-08-15

    Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al{sub 2}Cu. The fine particles were determined being Al{sub 2}Cu, Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 8}Mg{sub 3}FeSi{sub 2}. Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed.

  14. Study of formation mechanism of incipient melting in thixo-cast Al–Si–Cu–Mg alloys

    International Nuclear Information System (INIS)

    Du, Kang; Zhu, Qiang; Li, Daquan; Zhang, Fan

    2015-01-01

    Mechanical properties of thixo-cast Al–Si–Cu–Mg alloys can be enhanced by T61 heat treatment. Copper and magnesium atoms in aluminum matrix can form homogeneously distributed precipitations after solution and aging treatment which harden the alloys. However, microsegregation of these alloying elements could form numerous tiny multi-compound phases during solidification. These phases could cause incipient melting defects in subsequent heat treatment process and degrade the macro-mechanical properties of productions. This study is to present heterogeneous distribution of Cu, Si, and Mg elements and formation of incipient melting defects (pores). In this study, incipient melting pores that occurred during solution treatment at various temperatures, even lower than common melting points of various intermetallic phases, were identified, in terms of a method of investigating the same surface area in the samples before and after solution treatment in a vacuum environment. The results also show that the incipient melting mostly originates at the clusters with fine intermetallic particles while also some at the edge of block-like Al 2 Cu. The fine particles were determined being Al 2 Cu, Al 5 Cu 2 Mg 8 Si 6 and Al 8 Mg 3 FeSi 2 . Tendency of the incipient melting decreases with decreases of the width of the clusters. The formation mechanism of incipient melting pores in solution treatment process was discussed using both the Fick law and the LSW theory. Finally, a criterion of solution treatment to avoid incipient melting pores for the thixo-cast alloys is proposed. - Highlights: • In-situ comparison technique was used to analysis the change of eutectic phases. • The ralationship between eutectic phase size and incipient melting was studied. • Teat treatment criterion for higher incipient melting resistance was proposed

  15. The Microwave Properties of Simulated Melting Precipitation Particles: Sensitivity to Initial Melting

    Science.gov (United States)

    Johnson, B. T.; Olson, W. S.; Skofronick-Jackson, G.

    2016-01-01

    A simplified approach is presented for assessing the microwave response to the initial melting of realistically shaped ice particles. This paper is divided into two parts: (1) a description of the Single Particle Melting Model (SPMM), a heuristic melting simulation for ice-phase precipitation particles of any shape or size (SPMM is applied to two simulated aggregate snow particles, simulating melting up to 0.15 melt fraction by mass), and (2) the computation of the single-particle microwave scattering and extinction properties of these hydrometeors, using the discrete dipole approximation (via DDSCAT), at the following selected frequencies: 13.4, 35.6, and 94.0GHz for radar applications and 89, 165.0, and 183.31GHz for radiometer applications. These selected frequencies are consistent with current microwave remote-sensing platforms, such as CloudSat and the Global Precipitation Measurement (GPM) mission. Comparisons with calculations using variable-density spheres indicate significant deviations in scattering and extinction properties throughout the initial range of melting (liquid volume fractions less than 0.15). Integration of the single-particle properties over an exponential particle size distribution provides additional insight into idealized radar reflectivity and passive microwave brightness temperature sensitivity to variations in size/mass, shape, melt fraction, and particle orientation.

  16. Melting of KCl and pressure calibration from in situ ionic conductivity measurements in a multi-anvil apparatus

    Science.gov (United States)

    Li, J.; Dong, J.; Zhu, F.

    2017-12-01

    Melting plays an unparalleled role in planetary differentiation processes including the formation of metallic cores, basaltic crusts, and atmospheres. Knowledge of the melting behavior of Earth materials provides critical constraints for establishing the Earth's thermal structure, interpreting regional seismic anomalies, and understanding the nature of chemical heterogeneity. Measuring the melting points of compressed materials, however, have remained challenging mainly because melts are often mobile and reactive, and temperature and pressure gradients across millimeter or micron-sized samples introduce large uncertainties in melting detection. Here the melting curve of KCl was determined through in situ ionic conductivity measurements, using the multi-anvil apparatus at the University of Michigan. The method improves upon the symmetric configuration that was used recently for studying the melting behaviors of NaCl, Na2CO3, and CaCO3 (Li and Li 2015 American Mineralogist, Li et al. 2017 Earth and Planetary Science Letters). In the new configuration, the thermocouple and electrodes are placed together with the sample at the center of a cylindrical heater where the temperature is the highest along the axis, in order to minimize uncertainties in temperature measurements and increase the stability of the sample and electrodes. With 1% reproducibility in melting point determination at pressures up to 20 GPa, this method allows us to determine the sample pressure to oil load relationship at high temperatures during multiple heating and cooling cycles, on the basis of the well-known melting curves of ionic compounds. This approach enables more reliable pressure measurements than relying on a small number of fixed-point phase transitions. The new data on KCl bridge the gap between the piston-cylinder results up to 4 GPa (Pistorius 1965 J. of Physics and Chemistry of Solids) and several diamond-anvil cell data points above 20 GPa (Boehler et al. 1996 Physical Review). We

  17. Recent Changes in Arctic Sea Ice Melt Onset, Freeze-Up, and Melt Season Length

    Science.gov (United States)

    Markus, Thorsten; Stroeve, Julienne C.; Miller, Jeffrey

    2010-01-01

    In order to explore changes and trends in the timing of Arctic sea ice melt onset and freeze-up and therefore melt season length, we developed a method that obtains this information directly from satellite passive microwave data, creating a consistent data set from 1979 through present. We furthermore distinguish between early melt (the first day of the year when melt is detected) and the first day of continuous melt. A similar distinction is made for the freeze-up. Using this method we analyze trends in melt onset and freeze-up for 10 different Arctic regions. In all regions except for the Sea of Okhotsk, which shows a very slight and statistically insignificant positive trend (O.4 days/decade), trends in melt onset are negative, i.e. towards earlier melt. The trends range from -1.0day/decade for the Bering Sea to -7.3 days/decade for the East Greenland Sea. Except for the Sea of Okhotsk all areas also show a trend towards later autumn freeze onset. The Chukchi/Beaufort Seas and Laptev/East Siberian Seas observe the strongest trends with 7 days/decade. For the entire Arctic, the melt season length has increased by about 20 days over the last 30 years. Largest trends of over 1O days/decade are seen for Hudson Bay, the East Greenland Sea the Laptev/East Siberian Seas, and the Chukchi/Beaufort Seas. Those trends are statistically significant a1 the 99% level.

  18. A quasimechanism of melt acceleration in the thermal decomposition of crystalline organic solids

    Energy Technology Data Exchange (ETDEWEB)

    Henson, Bryan F [Los Alamos National Laboratory

    2009-01-01

    It has been know for half a century that many crystalline organic solids undergo an acceleration in the rate of thermal decomposition as the melting temperature is approached. This acceleration terminates at the melting point, exhibiting an Arrhenius-like temperature dependence in the faster decomposition rate from the liquid phase. This observation has been modeled previously using various premelting behaviors based on e.g. freezing point depression induced by decomposition products or solvent impurities. These models do not, however, indicate a mechanism for liquid formation and acceleration which is an inherent function of the bulk thermodynamics of the molecule. Here we show that such an inherent thermodynamic mechanism for liquid formation exists in the form of the so-called quasi-liquid layer at the solid surface. We explore a kinetic mechanism which describes the acceleration of rate and is a function of the free energies of sublimation and vaporization. We construct a differential rate law from these thermodynamic free energies and a normalized progress variable. We further construct a reduced variable formulation of the model which is a simple function of the metastable liquid activity below the melting point, and show that it is applicable to the observed melt acceleration in several common organic crystalline solids. A component of the differential rate law, zero order in the progress variable, is shown to be proportional to the thickness of the quasiliquid layer predicted by a recent thermodynamic theory for this phenomenon. This work therefore serves not only to provide new insight into thermal decomposition in a broad class or organic crystalline solids, but also further validates the underlying thermodynamic nature of the phenomenon of liquid formation on the molecular surface at temperatures below the melting point.

  19. Thermal interaction in crusted melt jets with large-scale structures

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Ken-ichiro; Sotome, Fuminori; Ishikawa, Michio [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering

    1998-01-01

    The objective of the present study is to experimentally observe thermal interaction which would be capable of triggering due to entrainment, or entrapment in crusted melt jets with `large-scale structure`. The present experiment was carried out by dropping molten zinc and molten tin of 100 grams, of which mass was sufficient to generate large-scale structures of melt jets. The experimental results show that the thermal interaction of entrapment type occurs in molten-zinc jets with rare probability, and the thermal interaction of entrainment type occurs in molten tin jets with high probability. The difference of thermal interaction between molten zinc and molten tin may attribute to differences of kinematic viscosity and melting point between them. (author)

  20. Melting curves of molecular hydrogen and molecular deuterium under high pressures between 20 and 373 K

    International Nuclear Information System (INIS)

    Diatschenko, V.; Chu, C.W.; Liebenberg, D.H.; Young, D.A.; Ross, M.; Mills, R.L.

    1985-01-01

    We determined the melting curve of molecular hydrogen and molecular deuterium at closely spaced intervals from 20 to 373 K by two different techniques using high-pressure diamond cells. The cells were loaded with liquid at low temperature or with compressed gas at room temperature. Empirical functions for the melting curves were evaluated from least-squares fits of the data. Values of the compressibility and Debye temperature were computed at melting, and the results are compared with those calculated from various theoretical models. The good agreement shows that the models are generally valid, although small systematic deviations may point the way toward refinements in modeling. Our study also demonstrates the need to determine a one-piece intermolecular potential valid over a wide pressure range by refitting all experimental data, including the shock data recently made available

  1. Neutralization of Hydroxide Ion in Melt-Grown NaCl Crystals

    Science.gov (United States)

    Otterson, Dumas A.

    1961-01-01

    Many recent studies of solid-state phenomena, particularly in the area of crystal imperfections, have involved the use of melt-grown NaCl single crystals. Quite often trace impurities in these materials have had a prominent effect on these phenomena. Trace amounts of hydroxide ion have been found in melt-grown NaCl crystals. This paper describes a nondestructive method of neutralizing the hydroxide ion in such crystals. Crystals of similar hydroxide content are maintained at an elevated temperature below the melting point of NaCl in a flowing atmosphere containing. dry hydrogen chloride. Heat treatment is continued until an analysis of the test specimens shows no excess hydroxide ion. A colorimetric method previously described4 is used for this analysis.

  2. Structure and dynamics of ion clusters in linear octupole traps: Phase diagrams, chirality, and melting mechanisms

    International Nuclear Information System (INIS)

    Yurtsever, E.; Onal, E. D.; Calvo, F.

    2011-01-01

    The stable structures and melting dynamics of clusters of identical ions bound by linear octupole radiofrequency traps are theoretically investigated by global optimization methods and molecular dynamics simulations. By varying the cluster sizes in the range of 10-1000 ions and the extent of trap anisotropy by more than one order of magnitude, we find a broad variety of stable structures based on multiple rings at small sizes evolving into tubular geometries at large sizes. The binding energy of these clusters is well represented by two contributions arising from isotropic linear and octupolar traps. The structures generally exhibit strong size effects, and chiral arrangements spontaneously emerge in many crystals. Sufficiently large clusters form nested, coaxial tubes with different thermal stabilities. As in isotropic octupolar clusters, the inner tubes melt at temperatures that are lower than the overall melting point.

  3. Study on melting conditions of radioactive miscellaneous solid waste. Contract research

    International Nuclear Information System (INIS)

    Fukui, Toshiki; Nakashio, Nobuyuki; Isobe, Motoyasu; Otake, Atsushi; Wakui, Takuji; Nakashima, Mikio; Hirabayashi, Takakuni

    2001-02-01

    Improvement of fluidity of molten slag is one of the most important factors for plasma melting treatment of low level radioactive miscellaneous wastes generated from nuclear facilities. In general, it is considered that elevating molten slag temperature of addition of flux is of certain use in improvement of fluidity of molten slag. However, these ways are not necessarily suitable from the viewpoints of refractory erosion or reduction of waste volume. In this report, we suggested that fluidity of molten slag could be improved by controlling chemical compositions of molten slag. On the Basic of the investigation using phase diagram and viscosity data, FeO was selected as a key component for improving fluidity: Viscosity and melting point of molten slag decreased with increasing relative concentration of FeO in molten slag. Accordingly, we concluded that it is important to adjust basicity of molten slag for melting treatment of low-level radioactive miscellaneous solid wastes. (author)

  4. Impact of melting heat transfer and nonlinear radiative heat flux mechanisms for the generalized Burgers fluids

    Directory of Open Access Journals (Sweden)

    Waqar Azeem Khan

    Full Text Available The present paper deals with the analysis of melting heat and mass transfer characteristics in the stagnation point flow of an incompressible generalized Burgers fluid over a stretching sheet in the presence of non-linear radiative heat flux. A uniform magnetic field is applied normal to the flow direction. The governing equations in dimensional form are reduced to a system of dimensionless expressions by implementation of suitable similarity transformations. The resulting dimensionless problem governing the generalized Burgers is solved analytically by using the homotopy analysis method (HAM. The effects of different flow parameters like the ratio parameter, magnetic parameter, Prandtl number, melting parameter, radiation parameter, temperature ratio parameter and Schmidt number on the velocity, heat and mass transfer characteristics are computed and presented graphically. Moreover, useful discussions in detail are carried out with the help of plotted graphs and tables. Keywords: Generalized Burgers fluid, Non-linear radiative flow, Magnetic field, Melting heat transfer

  5. Experiments on transient melting of tungsten by ELMs in ASDEX Upgrade

    Science.gov (United States)

    Krieger, K.; Balden, M.; Coenen, J. W.; Laggner, F.; Matthews, G. F.; Nille, D.; Rohde, V.; Sieglin, B.; Giannone, L.; Göths, B.; Herrmann, A.; de Marne, P.; Pitts, R. A.; Potzel, S.; Vondracek, P.; ASDEX-Upgrade Team; EUROfusion MST1 Team

    2018-02-01

    Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using the divertor manipulator II (DIM-II) system (Herrmann et al 2015 Fusion Eng. Des. 98-9 1496-9). Designed as near replicas of the geometries used also in separate experiments on the JET tokamak (Coenen et al 2015 J. Nucl. Mater. 463 78-84 Coenen et al 2015 Nucl. Fusion 55 023010; Matthews et al 2016 Phys. Scr. T167 7), the samples featured a misaligned leading edge and a sloped ridge respectively. Both structures protrude above the default target plate surface thus receiving an increased fraction of the parallel power flux. Transient melting by ELMs was induced by moving the outer strike point to the sample location. The temporal evolution of the measured current flow from the samples to vessel potential confirmed transient melting. Current magnitude and dependency from surface temperature provided strong evidence for thermionic electron emission as main origin of the replacement current driving the melt motion. The different melt patterns observed after exposures at the two sample geometries support the thermionic electron emission model used in the MEMOS melt motion code, which assumes a strong decrease of the thermionic net current at shallow magnetic field to surface angles (Pitts et al 2017 Nucl. Mater. Energy 12 60-74). Post exposure ex situ analysis of the retrieved samples show recrystallization of tungsten at the exposed surface areas to a depth of up to several mm. The melt layer transport to less exposed surface areas leads to ratcheting pile up of re-solidified debris with zonal growth extending from the already enlarged grains at the surface.

  6. Rotational melting in displacive quantum paraelectrics

    International Nuclear Information System (INIS)

    Martonak, R.; Tosatti, E.

    1994-06-01

    Displacive quantum paraelectrics are discussed as possible realizations of rotational quantum melting. The phenomenology of SrTiO 3 and KTaO 3 is discussed in this light. Both old and fresh theoretical work on two-dimensional lattice models for quantum paraelectricity is reviewed. (author). 73 refs, 15 figs

  7. Using Melting Ice to Teach Radiometric Dating.

    Science.gov (United States)

    Wise, Donald Underkofler

    1990-01-01

    Presented is an activity in which a mystery setting is used to motivate students to construct their own decay curves of melting ice used as an analogy to radioactive decay. Procedures, materials, apparatus, discussion topics, presentation, and thermodynamics are discussed. (CW)

  8. Models and observations of Arctic melt ponds

    Science.gov (United States)

    Golden, K. M.

    2016-12-01

    During the Arctic melt season, the sea ice surface undergoes a striking transformation from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is largely determined by the complex evolution of melt pond configurations. In fact, ice-albedo feedback has played a significant role in the recent declines of the summer Arctic sea ice pack. However, understanding melt pond evolution remains a challenge to improving climate projections. It has been found that as the ponds grow and coalesce, the fractal dimension of their boundaries undergoes a transition from 1 to about 2, around a critical length scale of 100 square meters in area. As the ponds evolve they take complex, self-similar shapes with boundaries resembling space-filling curves. I will outline how mathematical models of composite materials and statistical physics, such as percolation and Ising models, are being used to describe this evolution and predict key geometrical parameters that agree very closely with observations.

  9. Melting Metal on a Playing Card

    Science.gov (United States)

    Greenslade, Thomas B., Jr.

    2016-01-01

    Many of us are familiar with the demonstration of boiling water in a paper cup held over a candle or a Bunsen burner; the ignition temperature of paper is above the temperature of 100°C at which water boils under standard conditions. A more dramatic demonstration is melting tin held in a playing card. This illustration is from Tissandier's book on…

  10. The atmospheric boundary layer over melting glaciers

    NARCIS (Netherlands)

    Oerlemans, J.

    1998-01-01

    Results from a number of glacio-meteorological experiments carried out over melting glaciers are summarized. It is shown that in summer the microclimate of a glacier tongue is dominated by katabatic flow, initiated by the downward sensible heat flux. Characteristic obstacle height is an

  11. Radiation polymerized hot melt pressure sensitive adhesives

    International Nuclear Information System (INIS)

    Pastor, S.D.; Skoultchi, M.M.

    1977-01-01

    Hot melt pressure sensitive adhesive compositions formed by copolymerizing at least one 3-(chlorinated aryloxy)-2-hydroxypropyl ester of an alpha, beta unsaturated carboxylic acid with acrylate based copolymerizable monomers, are described. The resultant ethylenically saturated prepolymer is heated to a temperature sufficient to render it fluid and flowable. This composition is coated onto a substrate and exposed to ultraviolet radiation

  12. Can Text Messages Mitigate Summer Melt?

    Science.gov (United States)

    Castleman, Benjamin L.; Page, Lindsay C.

    2013-01-01

    Higher education officials have long been familiar with the concept of "summer melt," where students who have paid a deposit to attend one college or university instead matriculate at a different institution, usually presumed to be of comparable quality. In previous research, drawing on longitudinal data from various urban school…

  13. Linking Polymer Dynamics to Melt Processing

    Indian Academy of Sciences (India)

    Ashish Lele

    Linking Polymer Dynamics to Melt Processing. Ashish Lele. NaUonal Chemical Laboratory, Pune ak.lele@ncl.res.in www.cfpegroup.net. Mid-‐Year MeeUng July 2-‐3, 2010. Indian Academy of Sciences, Bangalore ...

  14. Educating Multicultural Citizens: Melting Pot or Mosaic?

    Science.gov (United States)

    Entwistle, Harold

    2000-01-01

    Explores the educational metaphors of the melting pot (immigrants must assimilate into the mainstream culture) and the cultural mosaic (immigrants should retain their cultural identifies). Focuses on such issues as multiculturalism and justice for immigrants, social cohesion, the notion of cultural relativism, and differing conceptions of culture.…

  15. Needleless Melt-Electrospinning of Polypropylene Nanofibres

    Directory of Open Access Journals (Sweden)

    Jian Fang

    2012-01-01

    Full Text Available Polypropylene (PP nanofibres have been electrospun from molten PP using a needleless melt-electrospinning setup containing a rotary metal disc spinneret. The influence of the disc spinneret (e.g., disc material and diameter, operating parameters (e.g., applied voltage, spinning distance, and a cationic surfactant on the fibre formation and average fibre diameter were examined. It was shown that the metal material used for making the disc spinneret had a significant effect on the fibre formation. Although the applied voltage had little effect on the fibre diameter, the spinning distance affected the fibre diameter considerably, with shorter spinning distance resulting in finer fibres. When a small amount of cationic surfactant (dodecyl trimethyl ammonium bromide was added to the PP melt for melt-electrospinning, the fibre diameter was reduced considerably. The finest fibres produced from this system were 400±290 nm. This novel melt-electrospinning setup may provide a continuous and efficient method to produce PP nanofibres.

  16. Catastrophic failure of polymer melts during extension

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.

    2013-01-01

    Numerical flow modeling has been applied to study the break of monodisperse polymer melts during extension. These continuum mechanical based computations are within the ideas of the microstructural ’interchain pressure’ theory. Calculated breaks, a result of small initial sample imperfections, ag...

  17. Arctic Ice Melting: National Security Implications

    Science.gov (United States)

    2011-02-01

    be a curse rather than a good, and under no conditions can it either lead into freedom or constitute a proof for its existence. - Hannah ... Arendt 39 How will the domestic or foreign economic policies of the United States be affected by Arctic ice melting? Increased access to the

  18. INVESTIGATION OF THE METAL MELTING PROCESS

    Directory of Open Access Journals (Sweden)

    V. I. Timoshpolskij

    2006-01-01

    Full Text Available The nonlinear mathematical model of calculation of temperature fields in the process of metal melting is formulated and solved using the method of equivalent source taking into account nonlinearity of thermophysical properties of material and variable terms of heat exchange.

  19. Development of rheometer for semi-solid highmelting point alloys

    Directory of Open Access Journals (Sweden)

    LIU Wen

    2005-11-01

    Full Text Available A rheometer for semi-solid high-melting point alloys was developed based on the principle of a double-bucket rheometer, with which the solidifying of semi-solid high-melting point alloy melt could be effectively controlled by the control of temperature and the outer force-field; and different microstructures have also been obtained. This rheometer can be used to investigate the rheological behavior under different conditions by changing the Theological parameters. By way of full-duplex communication between the computer and each sensor, automatic control of the test equipment and real- timemeasurement of rheological parameters were realized. Finally, the influencing factors on torque are also quantitatively analyzed.

  20. Multicomponent Diffusion in Experimentally Cooled Melt Inclusions

    Science.gov (United States)

    Saper, L.; Stolper, E.

    2017-12-01

    Glassy olivine-hosted melt inclusions are compositionally zoned, characterized by a boundary layer depleted in olivine-compatible components that extends into the melt inclusion from its wall. The boundary layer forms in response to crystallization of olivine and relaxes with time due to diffusive exchange with the interior of the inclusion. At magmatic temperatures, the time scale for homogenization of inclusions is minutes to hours. Preservation of compositional gradients in natural inclusions results from rapid cooling upon eruption. A model of MgO concentration profiles that couples crystal growth and diffusive relaxation of a boundary layer can be used to solve for eruptive cooling rates [1]. Controlled cooling-rate experiments were conducted to test the accuracy of the model. Mauna Loa olivine containing >80 µm melt inclusions were equilibrated at 1225°C in a 1-atm furnace for 24 hours, followed by linear cooling at rates of 102 - 105 °C/hr. High-resolution concentration profiles of 40 inclusions were obtained using an electron microprobe. The model of [1] fits the experimental data with low residuals and the best-fit cooling rates are within 30% of experimental values. The initial temperature of 1225 °C is underestimated by 65°C. The model was modified using (i) MELTS to calculate the interface melt composition as a function of temperature, and (ii) a concentration-dependent MgO diffusion coefficient using the functional form of [2]. With this calibration the best-fit starting temperatures are within 5°C of the experimental values and the best-fit cooling rates are within 20% of experimental rates. The evolution of the CaO profile during cooling is evidence for strong diffusive coupling between melt components. Because CaO is incompatible in olivine, CaO concentrations are expected to be elevated in the boundary layer adjacent to the growing olivine. Although this is observed at short time scales, as the profile evolves the CaO concentration near the

  1. Partial melting of lower oceanic crust gabbro: Constraints from poikilitic clinopyroxene primocrysts

    Science.gov (United States)

    Leuthold, Julien; Lissenberg, C. Johan; O'Driscoll, Brian; Karakas, Ozge; Falloon, Trevor; Klimentyeva, Dina N.; Ulmer, Peter

    2018-03-01

    Successive magma batches underplate, ascend, stall and erupt along spreading ridges, building the oceanic crust. It is therefore important to understand the processes and conditions under which magma differentiates at mid ocean ridges. Although fractional crystallization is considered to be the dominant mechanism for magma differentiation, open-system igneous complexes also experience Melting-Assimilation-Storage-Hybridization (MASH, Hildreth and Moorbath, 1988) processes. Here, we examine crystal-scale records of partial melting in lower crustal gabbroic cumulates from the slow-spreading Atlantic oceanic ridge (Kane Megamullion; collected with Jason ROV) and the fast-spreading East Pacific Rise (Hess Deep; IODP expedition 345). Clinopyroxene oikocrysts in these gabbros preserve marked intra-crystal geochemical variations that point to crystallization-dissolution episodes of the gabbro eutectic assemblage. Kane Megamullion and Hess Deep clinopyroxene core1 primocrysts and their plagioclase inclusions indicate crystallization from high temperature basalt (>1160 and >1200°C, respectively), close to clinopyroxene saturation temperature (fundamental mechanisms for generating the wide compositional variation observed in mid-ocean ridge basalts. We furthermore propose that such processes operate at both slow- and fast-spreading ocean ridges. Thermal numerical modelling shows that the degree of lower crustal partial melting at slow-spreading ridges can locally increase up to 50%, but the overall crustal melt volume is low (less than ca. 5% of total mantle-derived and crustal melts; ca. 20% in fast-spreading ridges).

  2. Studies of melting, crystallization, and commensurate-incommensurate transitions in two dimensions: Third year progress report

    International Nuclear Information System (INIS)

    Mockler, R.C.; O'Sullivan, W.J.

    1988-09-01

    The free expansion melting of a 2D suspension of micron-size spheres contained between parallel silica plates has been analyzed in some detail. The translational and orientational correlation functions conform with KTHNY theory prediction of a two-step melting process. The visual observations and study of the defect structures and evolution strongly suggest the process is first order with two-phase coexistence taking the place of the intermediate (hexatic) phase. On the other hand, melting of a 2.88 μm monolayer on water is in accord with KTHNY including the observation of dislocation-pair unbinding at the first transition. However, there is no evidence of the dissociation of dislocation into free disclinations at the second transition (the defect structure is much too complex here). Dynamic light scattering experiments on a 2D crystal on the surface of water yield viscous damping factors, force constants and the Lame coefficients. 2D computer simulation, in collaboration with Noel Clark's group, reveal cooperative motion along chains of particles (''snakes''). They appear to be the principal cause of diffusion near the melting point and important in the melting process. 16 refs

  3. Molecular dynamics for near melting temperatures simulations of metals using modified embedded-atom method

    Science.gov (United States)

    Etesami, S. Alireza; Asadi, Ebrahim

    2018-01-01

    Availability of a reliable interatomic potential is one of the major challenges in utilizing molecular dynamics (MD) for simulations of metals at near the melting temperatures and melting point (MP). Here, we propose a novel approach to address this challenge in the concept of modified-embedded-atom (MEAM) interatomic potential; also, we apply the approach on iron, nickel, copper, and aluminum as case studies. We propose adding experimentally available high temperature elastic constants and MP of the element to the list of typical low temperature properties used for the development of MD interatomic potential parameters. We show that the proposed approach results in a reasonable agreement between the MD calculations of melting properties such as latent heat, expansion in melting, liquid structure factor, and solid-liquid interface stiffness and their experimental/computational counterparts. Then, we present the physical properties of mentioned elements near melting temperatures using the new MEAM parameters. We observe that the behavior of elastic constants, heat capacity and thermal linear expansion coefficient at room temperature compared to MP follows an empirical linear relation (α±β × MP) for transition metals. Furthermore, a linear relation between the tetragonal shear modulus and the enthalpy change from room temperature to MP is observed for face-centered cubic materials.

  4. Investigation of transient melting of tungsten by ELMs in ASDEX Upgrade

    International Nuclear Information System (INIS)

    Krieger, K; Sieglin, B; Balden, M; De Marne, P; Nille, D; Rohde, V; Faitsch, M; Giannone, L; Herrmann, A; Coenen, J W; Göths, B; Laggner, F; Matthews, G F; Dejarnac, R; Horacek, J; Komm, M; Pitts, R A; Ratynskaia, S; Thoren, E; Tolias, P

    2017-01-01

    Repetitive melting of tungsten by power transients originating from edge localized modes (ELMs) has been studied in the tokamak experiment ASDEX Upgrade. Tungsten samples were exposed to H-mode discharges at the outer divertor target plate using the Divertor Manipulator II system. The exposed sample was designed with an elevated sloped surface inclined against the incident magnetic field to increase the projected parallel power flux to a level were transient melting by ELMs would occur. Sample exposure was controlled by moving the outer strike point to the sample location. As extension to previous melt studies in the new experiment both the current flow from the sample to vessel potential and the local surface temperature were measured with sufficient time resolution to resolve individual ELMs. The experiment provided for the first time a direct link of current flow and surface temperature during transient ELM events. This allows to further constrain the MEMOS melt motion code predictions and to improve the validation of its underlying model assumptions. Post exposure ex situ analysis of the retrieved samples confirms the decreased melt motion observed at shallower magnetic field line to surface angles compared to that at leading edges exposed to the parallel power flux. (paper)

  5. Geochemical evidence for the melting of subducting oceanic lithosphere at plate edges

    Science.gov (United States)

    Yogodzinski, G. M.; Lees, J. M.; Churikova, T. G.; Dorendorf, F.; Wöerner, G.; Volynets, O. N.

    2001-01-01

    Most island-arc magmatism appears to result from the lowering of the melting point of peridotite within the wedge of mantle above subducting slabs owing to the introduction of fluids from the dehydration of subducting oceanic crust. Volcanic rocks interpreted to contain a component of melt (not just a fluid) from the subducting slab itself are uncommon, but possible examples have been recognized in the Aleutian islands, Baja California, Patagonia and elsewhere. The geochemically distinctive rocks from these areas, termed `adakites', are often associated with subducting plates that are young and warm, and therefore thought to be more prone to melting. But the subducting lithosphere in some adakite locations (such as the Aleutian islands) appears to be too old and hence too cold to melt. This implies either that our interpretation of adakite geochemistry is incorrect, or that our understanding of the tectonic context of adakites is incomplete. Here we present geochemical data from the Kamchatka peninsula and the Aleutian islands that reaffirms the slab-melt interpretation of adakites, but in the tectonic context of the exposure to mantle flow around the edge of a torn subducting plate. We conclude that adakites are likely to form whenever the edge of a subducting plate is warmed or ablated by mantle flow. The use of adakites as tracers for such plate geometry may improve our understanding of magma genesis and thermal structure in a variety of subduction-zone environments.

  6. Water- and Boron-Rich Melt Inclusions in Quartz from the Malkhan Pegmatite, Transbaikalia, Russia

    Directory of Open Access Journals (Sweden)

    Elena Badanina

    2012-11-01

    Full Text Available In this paper we show that the pegmatite-forming processes responsible for the formation of the Malkhan pegmatites started at magmatic temperatures around 720 °C. The primary melts or supercritical fluids were very water- and boron-rich (maximum values of about 10% (g/g B2O3 and over the temperature interval from 720 to 600 °C formed a pseudobinary solvus, indicated by the coexistence of two types of primary melt inclusions (type-A and type-B representing a pair of conjugate melts. Due to the high water and boron concentration the pegmatite-forming melts are metastable and can be characterized either as genuine melts or silicate-rich fluids. This statement is underscored by Raman spectroscopic studies. This study suggested that the gel state proposed by some authors cannot represent the main stage of the pegmatite-forming processes in the Malkhan pegmatites, and probably in all others. However there are points in the evolution of the pegmatites where the gel- or gel-like state has left traces in form of real gel inclusions in some mineral in the Malkhan pegmatite, however only in a late, fluid dominated stage.

  7. Focused ion beam structuring of low melting polymeric materials

    International Nuclear Information System (INIS)

    Schmied, R.

    2014-01-01

    This thesis focuses on heating effects during focused ion beam (FIB) processing of low melting polymers. The combined approach using experiments and simulations identifies the in part massive local temperatures as a convolution between intrinsic ion-matter effects and a considerable, technically-induced heating component. While the former is invariable, the latter has been minimized by an alternative process strategy which massively improves the morphological stability and minimizes chemical damage during FIB processing, thus opening new possibilities for application on sensitive, low melting materials. The study starts with systematic experimental investigations which strongly suggested the existence of a technically-induced heating component as a consequence of classically-used serpentine or raster-like patterning strategies. Based on these results, a combined simulation approach of ion trajectories and thermal spike model calculations have been employed to get a deeper insight into spatial and temporal temperature evolution. The results were then combined with the thermodynamic behavior of polymers by means of melting and volatizing temperatures. The comparison of these simulationbased predictions with real FIB experiments revealed very good agreement, proving the applicability of the approach used to describe the temperature evolution from a fundamental point of view. As a next step, these simulations were then applied to the dierent scanning strategies which further con rmed the existence of a technically-induced heating component via classically-used patterning approaches. Due to the deep insight gained via simulations, an alternative patterning strategy was developed, which was expected to minimize these avoidable influences. This new strategy was then evaluated using a multi-technique approach, which revealed strongly reduced chemical damage together with increasing morphological stabilities even for temperature-sensitive polymers. Finally, this alternative

  8. Induction melting of simulated transuranic waste

    International Nuclear Information System (INIS)

    Tenaglia, R.D.; McCall, J.L.

    1983-06-01

    Coreless induction melting was investigated as a method to melt and consolidate waste material representative of the transuranic waste (TRU) stored at the Idaho National Engineering Laboratory (INEL). Waste material was introduced onto the surface of a molten cast iron bath in a coreless induction furnace. Waste metallics were incorporated into the bath. Noncombustibles formed a slag which was poured or skimmed from the bath surface. Stack sampling was performed to characterize the off-gas and particulate matter evolved. Experimental melting tests were performed for a variety of types of wastes including metallics, chemical sludge, soil, concrete, and glass. Each test also included a representative level of combustible materials consisting of paper, wood, cloth, polyvinyl chloride and polyethylene. Metallic wastes were readily processed by induction melting with a minimum of slag production. Test waste consisting primarily of chemical sludge provided fluid slags which could be poured from the bath surface. Processing of wastes consisting of soil, concrete, or glass was limited by the inability to achieve fluid slags. It appears from test results that coreless induction melting is a feasible method to process INEL-type waste materials if two problems can be resolved. First, slag fluidity must be improved to facilitate the collection of slags formed from soil, concrete, or glass containing wastes. Secondly, refractory life must be further optimized to permit prolonged processing of the waste materials. The use of a chrome-bearing high-alumina refractory was found to resist slag line attach much better than a magnesia refractory, although some attack was still noted

  9. The succinonitrile triple-point standard: a fixed point to improve the accuracy of temperature measurements in the clinical laboratory.

    Science.gov (United States)

    Mangum, B W

    1983-07-01

    In an investigation of the melting and freezing behavior of succinonitrile, the triple-point temperature was determined to be 58.0805 degrees C, with an estimated uncertainty of +/- 0.0015 degrees C relative to the International Practical Temperature Scale of 1968 (IPTS-68). The triple-point temperature of this material is evaluated as a temperature-fixed point, and some clinical laboratory applications of this fixed point are proposed. In conjunction with the gallium and ice points, the availability of succinonitrile permits thermistor thermometers to be calibrated accurately and easily on the IPTS-68.

  10. Evaporative Heat Transfer Mechanisms within a Heat Melt Compactor

    Science.gov (United States)

    Golliher, Eric L.; Gotti, Daniel J.; Rymut, Joseph Edward; Nguyen, Brian K; Owens, Jay C.; Pace, Gregory S.; Fisher, John W.; Hong, Andrew E.

    2013-01-01

    This paper will discuss the status of microgravity analysis and testing for the development of a Heat Melt Compactor (HMC). Since fluids behave completely differently in microgravity, the evaporation process for the HMC is expected to be different than in 1-g. A thermal model is developed to support the design and operation of the HMC. Also, low-gravity aircraft flight data is described to assess the point at which water may be squeezed out of the HMC during microgravity operation. For optimum heat transfer operation of the HMC, the compaction process should stop prior to any water exiting the HMC, but nevertheless seek to compact as much as possible to cause high heat transfer and therefore shorter evaporation times.

  11. Ceramic filters analysis for aluminium melting through microtomography technique

    International Nuclear Information System (INIS)

    Rocha, Henrique de Souza; Lopes, Ricardo Tadeu; Jesus, Edgar Francisco Oliveira de; Oliveira, Luis Fernando de; Duhm, Rainer; Feiste, Karsten L.; Reichert, Christian; Reimche, Wilfried; Stegemann, Dieter

    2000-01-01

    In this work a ceramic filters analysis is done through the microtomography for improvement of the aluminium melting process through the filter porosity control. Microtomography were obtained of ceramic filters with pore dimensions of 10, 20 and 30 ppi. The data were calculated by using an reconstruction algorithm for divergent beam implemented in the Nuclear Instrumentation Laboratory of COPPE/UFRJ and analysed through cells and windows separation according to the defined by Ray. For the analyses the Image Pro program were used where the cells have been detached by sphere inserted, adjusting by nine points, in the filter cavities. So, the size of the answer sphere were considered as the cell size. The windows were measured by straight lines secant to the window intersections

  12. Electric melting furnace of solidifying radioactive waste by utilizing magnetic field and melting method

    International Nuclear Information System (INIS)

    Igarashi, Hiroshi.

    1990-01-01

    An electric melting furnace for solidification of radioactive wastes utilizing magnetic fields in accordance with the present invention comprises a plurality of electrodes supplying AC current to molten glass in a glass melting furnace and a plurality of magnetic poles for generating AC magnetic fields. Interactions between the current and the magnetic field, generated forces in the identical direction in view of time in the molten glass. That is, forces for promoting the flow of molten glass in the melting furnace are resulted due to the Fleming's left-hand rule. As a result, the following effects can be obtained. (1) The amount of heat ransferred from the molten glass to the starting material layer on the molten surface is increased to improve the melting performance. (2) For an identical melting performance, the size and the weight of the melting furnace can be reduced to decrease the amount of secondary wastes when the apparatus-life is exhausted. (3) Bottom deposits can be suppressed and prevented from settling and depositing to the reactor bottom by the promoted flow in the layer. (4) Further, the size of auxiliary electrodes for directly supplying electric current to heat the molten glass near the reactor bottom can be decreased. (I.S.)

  13. Can Nano-Particle Melt below the Melting Temperature of Its Free Surface Partner?

    International Nuclear Information System (INIS)

    Sui Xiao-Hong; Qin Shao-Jing; Wang Zong-Guo; Kang Kai; Wang Chui-Lin

    2015-01-01

    The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for a bulk system have been analyzed. The discrete phonon energy levels of pure size effect and the wave-vector shifts of boundary conditions are investigated in detail. Unlike in macroscopic thermodynamics, the integration volume of zero-mode of phonon for a nano-particle is not zero, and it plays an important role in pure size effect and boundary condition effect. We find that a nano-particle will have a rising melting temperature due to purely finite size effect; a lower melting temperature bound exists for a nano-particle in various environments, and the melting temperature of a nano-particle with free boundary condition reaches this lower bound. We suggest an easy procedure to estimation the melting temperature, in which the zero-mode contribution will be excluded, and only several bulk quantities will be used as input. We would like to emphasize that the quantum effect of discrete energy levels in nano-particles, which is not present in early thermodynamic studies on finite size corrections to melting temperature in small systems, should be included in future researches. (condensed matter: structural, mechanical, and thermal properties)

  14. Causes of Glacier Melt Extremes in the Alps Since 1949

    Science.gov (United States)

    Thibert, E.; Dkengne Sielenou, P.; Vionnet, V.; Eckert, N.; Vincent, C.

    2018-01-01

    Recent record-breaking glacier melt values are attributable to peculiar extreme events and long-term warming trends that shift averages upward. Analyzing one of the world's longest mass balance series with extreme value statistics, we show that detrending melt anomalies makes it possible to disentangle these effects, leading to a fairer evaluation of the return period of melt extreme values such as 2003, and to characterize them by a more realistic bounded behavior. Using surface energy balance simulations, we show that three independent drivers control melt: global radiation, latent heat, and the amount of snow at the beginning of the melting season. Extremes are governed by large deviations in global radiation combined with sensible heat. Long-term trends are driven by the lengthening of melt duration due to earlier and longer-lasting melting of ice along with melt intensification caused by trends in long-wave irradiance and latent heat due to higher air moisture.

  15. Sea Ice Melt Pond Data from the Canadian Arctic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set contains observations of albedo, depth, and physical characteristics of melt ponds on sea ice, taken during the summer of 1994. The melt ponds studied...

  16. Students' Understanding of Boiling Points and Intermolecular Forces

    Science.gov (United States)

    Schmidt, Hans-Jurgen; Kaufmann, Birgit; Treagust, David F.

    2009-01-01

    In introductory chemistry courses students are presented with the model that matter is composed of particles, and that weak forces of attraction exist between them. This model is used to interpret phenomena such as solubility and melting points, and aids in understanding the changes in states of matter as opposed to chemical reactions. We…

  17. A 2D double-porosity model for melting and melt migration beneath mid-oceanic ridges

    Science.gov (United States)

    Liu, B.; Liang, Y.; Parmentier, E.

    2017-12-01

    Several lines of evidence suggest that the melting and melt extraction region of the MORB mantle is heterogeneous consisting of an interconnected network of high permeability dunite channels in a low porosity harzburgite or lherzolite matrix. In principle, one can include channel formation into the tectonic-scale geodynamic models by solving conservation equations for a chemically reactive and viscously deformable porous medium. Such an approach eventually runs into computational limitations such as resolving fractal-like channels that have a spectrum of width. To better understand first order features of melting and melt-rock interaction beneath MOR, we have formulated a 2D double porosity model in which we treat the triangular melting region as two overlapping continua occupied by the low-porosity matrix and interconnected high-porosity channels. We use melt productivity derived from a thermodynamic model and melt suction rate to close our problem. We use a high-order accurate numerical method to solve the conservation equations in 2D for porosity, solid and melt velocities and concentrations of chemical tracers in the melting region. We carry out numerical simulations to systematically study effects of matrix-to-channel melt suction and spatially distributed channels on the distributions of porosity and trace element and isotopic ratios in the melting region. For near fractional melting with 10 vol% channel in the melting region, the flow field of the matrix melt follows closely to that of the solid because the small porosity (exchange between the melt and the solid. The smearing effect can be approximated by dispersion coefficient. For slowly diffusing trace elements (e.g., LREE and HFSE), the melt migration induced dispersion can be as effective as thermal diffusion. Therefore, sub-kilometer scale heterogeneities of Nd and Hf isotopes are significantly damped or homogenized in the melting region.

  18. FT-IR emissivity measurements of Nb melt using an electrostatic levitation furnace

    International Nuclear Information System (INIS)

    Sakata, K.; Watanabe, Y.; Okada, J.T.; Kumar, M.V.; Paradis, P.-F.; Ishikawa, T.

    2015-01-01

    Highlights: • Since molten Nb has a high melting point, its thermal properties were measured using FT-IR combined with an electrostatic levitator. • The measured ε_T of molten Nb at the melting temperature in this study was 0.29, and the C_p was calculated as 41.9 J ⋅ mol"−"1 ⋅ K"−"1. - Abstract: Total hemispherical emissivity (ε_T) and constant pressure heat capacity (C_p) of molten Nb, which has a high melting point, was measured using FT-IR combined with an electrostatic levitator. In order to heat the sample to temperatures higher than 2000 °C and avoid chemical reactions between the sample and a crucible, a containerless method was needed. By applying these methods, the measured ε_T of molten Nb at the melting temperature was 0.29, and the C_p was calculated as 41.9 J ⋅ mol"−"1 ⋅ K"−"1. Both data showed good agreement with the literature values. In addition, the result was compared with the Drude model and the difference of emissivity between Zr and Nb was discussed.

  19. Efficient approach to compute melting properties fully from ab initio with application to Cu

    Science.gov (United States)

    Zhu, Li-Fang; Grabowski, Blazej; Neugebauer, Jörg

    2017-12-01

    Applying thermodynamic integration within an ab initio-based free-energy approach is a state-of-the-art method to calculate melting points of materials. However, the high computational cost and the reliance on a good reference system for calculating the liquid free energy have so far hindered a general application. To overcome these challenges, we propose the two-optimized references thermodynamic integration using Langevin dynamics (TOR-TILD) method in this work by extending the two-stage upsampled thermodynamic integration using Langevin dynamics (TU-TILD) method, which has been originally developed to obtain anharmonic free energies of solids, to the calculation of liquid free energies. The core idea of TOR-TILD is to fit two empirical potentials to the energies from density functional theory based molecular dynamics runs for the solid and the liquid phase and to use these potentials as reference systems for thermodynamic integration. Because the empirical potentials closely reproduce the ab initio system in the relevant part of the phase space the convergence of the thermodynamic integration is very rapid. Therefore, the proposed approach improves significantly the computational efficiency while preserving the required accuracy. As a test case, we apply TOR-TILD to fcc Cu computing not only the melting point but various other melting properties, such as the entropy and enthalpy of fusion and the volume change upon melting. The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional and the local-density approximation (LDA) are used. Using both functionals gives a reliable ab initio confidence interval for the melting point, the enthalpy of fusion, and entropy of fusion.

  20. Fission Product Release from Molten Pool: ceramic melt tests

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, Yu.B.; Lopukh, D.B.; Petchenkov, A.Yu. [AO ' NP Sintez' , St. Petersburg (RU)] [and others

    1999-07-01

    Experimental results are presented on the volatilisation of UO{sub 2{+-}}{sub x}, SrO, BaO, CeO{sub 2} from corium melts. Corium melts were generated by high frequency induction melting in a cold crucible. The surface temperature of the melts was in the range from 1753 to 3023 K. Some results of the tests are discussed and a comparison with published data is made. (author)

  1. Modeling of evaporation processes in glass melting furnaces

    NARCIS (Netherlands)

    Limpt, van J.A.C.

    2007-01-01

    The majority of glass furnaces worldwide, apply fossil fuel combustion to transfer heat directly by radiation from the combustion processes to the melting batch and glass melt. During these high temperature melting processes, some glass components, such as: sodium, potassium, boron and lead species

  2. Elongational viscosity of monodisperse and bidisperse polystyrene melts

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Rasmussen, Henrik K.; Hassager, Ole

    2006-01-01

    The start-up and steady uniaxial elongational viscosity have been measured for two monodisperse polystyrene melts with molecular weights of 52 and 103 kg/mole, and for three bidisperse polystyrene melts. The monodisperse melts show a maximum in the steady elongational viscosity vs. the elongational...

  3. Melt behaviour, crystallinity and morphology of poly(p-dioxanone)

    NARCIS (Netherlands)

    Pezzin, APT; van Ekenstein, GOR; Duek, EAR

    The melt behaviour of poly(p-dioxanone) (PPD) has been studied by differential scanning calorimetry (DSC). Crystallinity and morphology were evaluated by modulated differential scanning calorimetry (MDSC) and polarizing optical microscopy. The melting curves showed two melting endotherms, a higher

  4. Prediction of waste glass melt rates

    International Nuclear Information System (INIS)

    Lee, L.

    1987-01-01

    Under contract to the Department of Energy, the Du Pont Company has begun construction of a Defense Waste Processing Facility to immobilize radioactive wastes now stored as liquids at the Department of Energy's Savannah River Plant. The immobilization process solidifies waste sludge by vitrification into a leach-resistant borosilicate glass. Development of this process has been the responsibility of the Savannah River Laboratory. As part of the development, a simple model was developed to predict the melt rates for the waste glass melter. This model is based on an energy balance for the cold cap and gives very good agreement with melt rate data obtained from experimental campaigns in smaller scale waste glass melters

  5. Melting of metallic intermediate level waste

    Energy Technology Data Exchange (ETDEWEB)

    Huutoniemi, Tommi; Larsson, Arne; Blank, Eva [Studsvik Nuclear AB, Nykoeping (Sweden)

    2013-08-15

    This report presents a feasibility study of a melting facility for core components and reactor internals. An overview is given of how such a facility for treatment of intermediate level waste might be designed, constructed and operated and highlights both the possibilities and challenges. A cost estimate and a risk analysis are presented in order to make a conclusion of the technical feasibility of such a facility. Based on the authors' experience in operating a low level waste melting facility, their conclusion is that without technical improvements such a facility is not feasible today. This is based on the cost of constructing and operating such a facility, in conjunction with the radiological risks associated with operation and the uncertain benefits to disposal and long term safety.

  6. Melting of metallic intermediate level waste

    International Nuclear Information System (INIS)

    Huutoniemi, Tommi; Larsson, Arne; Blank, Eva

    2013-08-01

    This report presents a feasibility study of a melting facility for core components and reactor internals. An overview is given of how such a facility for treatment of intermediate level waste might be designed, constructed and operated and highlights both the possibilities and challenges. A cost estimate and a risk analysis are presented in order to make a conclusion of the technical feasibility of such a facility. Based on the authors' experience in operating a low level waste melting facility, their conclusion is that without technical improvements such a facility is not feasible today. This is based on the cost of constructing and operating such a facility, in conjunction with the radiological risks associated with operation and the uncertain benefits to disposal and long term safety

  7. Contaminated metallic melt volume reduction testing

    International Nuclear Information System (INIS)

    Deichman, J.L.

    1981-01-01

    Laboratory scale metallic melts (stainless steel) were accomplished in support of Decontamination and Decommissioning's (D and D) contaminated equipment volume reduction and Low-Level Lead Site Waste programs. Six laboratory scale melts made with contaminated stainless steel provided data that radionuclide distribution can be predicted when proper temperature rates and ranges are employed, and that major decontamination occurs with the use of designed slagging materials. Stainless steel bars were contaminated with plutonium, cobalt, cesium and europium. This study was limited to stainless steel, however, further study is desirable to establish data for other metals and alloys. This study represents a positive beginning in defining the feasibility of economical volume reduction or conversion from TRU waste forms to LLW forms for a large portion of approximately 50 thousand tons of contaminated metal waste now being stored at Hanford underground or in deactivated facilities

  8. Precipitation of metal nitrides from chloride melts

    International Nuclear Information System (INIS)

    Slater, S.A.; Miller, W.E.; Willit, J.L.

    1996-01-01

    Precipitation of actinides, lanthanides, and fission products as nitrides from molten chloride melts is being investigated for use as a final cleanup step in treating radioactive salt wastes generated by electrometallurgical processing of spent nuclear fuel. The radioactive components (eg, fission products) need to be removed to reduce the volume of high-level waste that requires disposal. To extract the fission products from the salt, a nitride precipitation process is being developed. The salt waste is first contacted with a molten metal; after equilibrium is reached, a nitride is added to the metal phase. The insoluble nitrides can be recovered and converted to a borosilicate glass after air oxidation. For a bench-scale experimental setup, a crucible was designed to contact the salt and metal phases. Solubility tests were performed with candidate nitrides and metal nitrides for which there are no solubility data. Experiments were performed to assess feasibility of precipitation of metal nitrides from chloride melts

  9. In vessel core melt progression phenomena

    International Nuclear Information System (INIS)

    Courtaud, M.

    1993-01-01

    For all light water reactor (LWR) accidents, including the so called severe accidents where core melt down can occur, it is necessary to determine the amount and characteristics of fission products released to the environment. For existing reactors this knowledge is used to evaluate the consequences and eventual emergency plans. But for future reactors safety authorities demand decrease risks and reactors designed in such a way that fission products are retained inside the containment, the last protective barrier. This requires improved understanding and knowledge of all accident sequences. In particular it is necessary to be able to describe the very complex phenomena occurring during in vessel core melt progression because they will determine the thermal and mechanical loads on the primary circuit and the timing of its rupture as well as the fission product source term. On the other hand, in case of vessel failure, knowledge of the physical and chemical state of the core melt will provide the initial conditions for analysis of ex-vessel core melt progression and phenomena threatening the containment. Finally a good understanding of in vessel phenomena will help to improve accident management procedures like Emergency Core Cooling System water injection, blowdown and flooding of the vessel well, with their possible adverse effects. Research and Development work on this subject was initiated a long time ago and is still in progress but now it must be intensified in order to meet the safety requirements of the next generation of reactors. Experiments, limited in scale, analysis of the TMI 2 accident which is a unique source of global information and engineering judgment are used to establish and assess physical models that can be implemented in computer codes for reactor accident analysis

  10. Holographic picture of heavy vector meson melting

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Nelson R.F.; Diles, Saulo [Universidade Federal do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro, RJ (Brazil); Martin Contreras, Miguel Angel [Universidad de los Andes, High Energy Group, Department of Physics, Bogota (Colombia)

    2016-11-15

    The fraction of heavy vector mesons produced in a heavy ion collision, as compared to a proton-proton collision, serves as an important indication of the formation of a thermal medium, the quark-gluon plasma. This sort of analysis strongly depends on understanding the thermal effects of a medium like the plasma on the states of heavy mesons. In particular, it is crucial to know the temperature ranges where they undergo a thermal dissociation, or melting. AdS/QCD models are know to provide an important tool for the calculation of hadronic masses, but in general are not consistent with the observation that decay constants of heavy vector mesons decrease with excitation level. It has recently been shown that this problem can be overcome using a soft wall background and introducing an extra energy parameter, through the calculation of correlation functions at a finite position of anti-de Sitter space. This approach leads to the evaluation of masses and decay constants of S wave quarkonium states with just one flavor dependent and one flavor independent parameter. Here we extend this more realistic model to finite temperatures and analyze the thermal behavior of the states 1S, 2S and 3S of bottomonium and charmonium. The corresponding spectral function exhibits a consistent picture for the melting of the states where, for each flavor, the higher excitations melt at lower temperatures. We estimate for these six states the energy ranges in which the heavy vector mesons undergo a transition from a well-defined peak in the spectral function to complete melting in the thermal medium. A very clear distinction between the heavy flavors emerges, with the bottomonium state Υ(1S) surviving a deconfinement transition at temperatures much larger than the critical deconfinement temperature of the medium. (orig.)

  11. How ice shelf morphology controls basal melting

    Science.gov (United States)

    Little, Christopher M.; Gnanadesikan, Anand; Oppenheimer, Michael

    2009-12-01

    The response of ice shelf basal melting to climate is a function of ocean temperature, circulation, and mixing in the open ocean and the coupling of this external forcing to the sub-ice shelf circulation. Because slope strongly influences the properties of buoyancy-driven flow near the ice shelf base, ice shelf morphology plays a critical role in linking external, subsurface heat sources to the ice. In this paper, the slope-driven dynamic control of local and area-integrated melting rates is examined under a wide range of ocean temperatures and ice shelf shapes, with an emphasis on smaller, steeper ice shelves. A 3-D numerical ocean model is used to simulate the circulation underneath five idealized ice shelves, forced with subsurface ocean temperatures ranging from -2.0°C to 1.5°C. In the sub-ice shelf mixed layer, three spatially distinct dynamic regimes are present. Entrainment of heat occurs predominately under deeper sections of the ice shelf; local and area-integrated melting rates are most sensitive to changes in slope in this "initiation" region. Some entrained heat is advected upslope and used to melt ice in the "maintenance" region; however, flow convergence in the "outflow" region limits heat loss in flatter portions of the ice shelf. Heat flux to the ice exhibits (1) a spatially nonuniform, superlinear dependence on slope and (2) a shape- and temperature-dependent, internally controlled efficiency. Because the efficiency of heat flux through the mixed layer decreases with increasing ocean temperature, numerical simulations diverge from a simple quadratic scaling law.

  12. "Chemical contraction" in rubidium-bismuth melts

    Science.gov (United States)

    Khairulin, R. A.; Abdullaev, R. N.; Stankus, S. V.

    2017-10-01

    The density and thermal expansion of liquid rubidium and rubidium-bismuth alloy containing 25.0 at % Bi were measured by the gamma-ray attenuation technique at temperatures from liquidus to 1000 K. The results of this study were compared with the data obtained by other authors. The molar volume of the Rb75Bi25 melt strongly deviates from the additivity rule for ideal solutions.

  13. Selective laser melting of Al-12Si

    OpenAIRE

    Prashanth, Konda Gokuldoss

    2014-01-01

    Selective laser melting (SLM) is a powder-based additive manufacturing technique consisting of the exact reproduction of a three dimensional computer model (generally a computer-aided design CAD file or a computer tomography CT scan) through an additive layer-by-layer strategy. Because of the high degree of freedom offered by the additive manufacturing, parts having almost any possible geometry can be produced by SLM. More specifically, with this process it is possible to build parts with ext...

  14. BWR core melt progression phenomena: Experimental analyses

    International Nuclear Information System (INIS)

    Ott, L.J.

    1992-01-01

    In the BWR Core Melt in Progression Phenomena Program, experimental results concerning severe fuel damage and core melt progression in BWR core geometry are used to evaluate existing models of the governing phenomena. These include control blade eutectic liquefaction and the subsequent relocation and attack on the channel box structure; oxidation heating and hydrogen generation; Zircaloy melting and relocation; and the continuing oxidation of zirconium with metallic blockage formation. Integral data have been obtained from the BWR DF-4 experiment in the ACRR and from BWR tests in the German CORA exreactor fuel-damage test facility. Additional integral data will be obtained from new CORA BWR test, the full-length FLHT-6 BWR test in the NRU test reactor, and the new program of exreactor experiments at Sandia National Laboratories (SNL) on metallic melt relocation and blockage formation. an essential part of this activity is interpretation and use of the results of the BWR tests. The Oak Ridge National Laboratory (ORNL) has developed experiment-specific models for analysis of the BWR experiments; to date, these models have permitted far more precise analyses of the conditions in these experiments than has previously been available. These analyses have provided a basis for more accurate interpretation of the phenomena that the experiments are intended to investigate. The results of posttest analyses of BWR experiments are discussed and significant findings from these analyses are explained. The ORNL control blade/canister models with materials interaction, relocation and blockage models are currently being implemented in SCDAP/RELAP5 as an optional structural component

  15. Surface Hardening by Laser Skin Melting

    Science.gov (United States)

    1979-07-01

    typical cross-sectional view of a melt region. Various solutions includina Murakami’s reaqent, Vilella’s reagent and an oxalic acid solution were used...each type selectively revealinq different microstructu- ral features. A second etch in an oxalic acid /hydrochloric acid solution was used in the...genization due to vigorous hydrothermal mixing and liquid super- heating. Computations by Greenwald (13) from a heat flow model are graphically represented

  16. Bursting the bubble of melt inclusions

    Science.gov (United States)

    Lowenstern, Jacob B.

    2015-01-01

    Most silicate melt inclusions (MI) contain bubbles, whose significance has been alternately calculated, pondered, and ignored, but rarely if ever directly explored. Moore et al. (2015) analyze the bubbles, as well as their host glasses, and conclude that they often hold the preponderance of CO2 in the MI. Their findings entreat future researchers to account for the presence of bubbles in MI when calculating volatile budgets, saturation pressures, and eruptive flux.

  17. The electrical conductivity of sodium polysulfide melts

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Meihui [Univ. of California, Berkeley, CA (United States)

    1992-06-01

    The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na2S4 and Na2S5 were measured as a function of temperature (range: 300 to 360°C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.

  18. The electrical conductivity of sodium polysulfide melts

    Energy Technology Data Exchange (ETDEWEB)

    Meihui Wang.

    1992-06-01

    The sodium polysulfide melt has been described by a macroscopic model. This model considers the melt to be composed of sodium cations, monosulfide anions, and neutral sulfur solvent. The transport equations of concentrated-solution theory are used to derived the governing equations for this binaryelectrolyte melt model. These equations relate measurable transport properties to fundamental transport parameters. The focus of this research is to measure the electrical conductivity of sodium polysulfide melts and calculate one of fundamental transport parameters from the experimental data. The conductance cells used in the conductivity measurements are axisymmetric cylindrical cells with a microelectrode. The electrode effects, including double-layer capacity, charge transfer resistance, and concentration overpotential, were minimized by the use of the alternating current at an adequately high frequency. The high cell constants of the conductance cells not only enhanced the experimental accuracy but also made the electrode effects negligible. The electrical conductivities of sodium polysulfide Na{sub 2}S{sub 4} and Na{sub 2}S{sub 5} were measured as a function of temperature (range: 300 to 360{degree}C). Variations between experiments were only up to 2%. The values of the Arrhenius activation energy derived from the experimental data are about 33 kJ/mol. The fundamental transport parameter which quantifies the interaction within sodium cations and monosulfide anions are of interest and expected to be positive. Values of it were calculated from the experimental conductivity data and most of them are positive. Some negative values were obtained probably due to the experimental errors of transference number, diffusion coefficient, density or conductivity data.

  19. Vacuum induction melting of uranium ingots

    International Nuclear Information System (INIS)

    Hussain, M.M.; Bagchi, S.N.; Singh, S.P.

    1992-01-01

    Massive uranium ingot is produced from green salt (UF 4 ) using calciothermic reduction (CTR) or magnesiothermic reduction (MTR) process. CTR process has been replaced by MTR process at Trombay due to economic considerations. This paper highlights problems associated with the vacuum induction melting of MTR ingots and the remedial measures taken to produce good quality billets. Details of metallographic examination of inclusions in ingots and billets have been incorporated. (author). 3 figs

  20. Early warning of climate tipping points

    Science.gov (United States)

    Lenton, Timothy M.

    2011-07-01

    A climate 'tipping point' occurs when a small change in forcing triggers a strongly nonlinear response in the internal dynamics of part of the climate system, qualitatively changing its future state. Human-induced climate change could push several large-scale 'tipping elements' past a tipping point. Candidates include irreversible melt of the Greenland ice sheet, dieback of the Amazon rainforest and shift of the West African monsoon. Recent assessments give an increased probability of future tipping events, and the corresponding impacts are estimated to be large, making them significant risks. Recent work shows that early warning of an approaching climate tipping point is possible in principle, and could have considerable value in reducing the risk that they pose.

  1. Mantle melting and melt refertilization beneath the Southwest Indian Ridge: Mineral composition of abyssal peridotites

    Science.gov (United States)

    Chen, Ling; Zhu, Jihao; Chu, Fengyou; Dong, Yan-hui; Liu, Jiqiang; Li, Zhenggang; Zhu, Zhimin; Tang, Limei

    2017-04-01

    As one of the slowest spreading ridges of the global ocean ridge system, the Southwest Indian Ridge (SWIR) is characterized by discontinued magmatism. The 53°E segment between the Gallieni fracture zone (FZ) (52°20'E) and the Gazelle FZ (53°30'E) is a typical amagmatic segment (crustal thickness 1cm) Opx, and Mg-rich mineral compositions akin to harzburgite xenoliths that sample old continental lithospheric mantle (Kelemen et al., 1998). Melt refertilization model shows that Group 2 peridotites were affected by an enriched low-degree partial melt from the garnet stability field. These results indicate that depleted mantle which experiences ancient melting event are more sensitive to melt refertilization, thus may reduce the melt flux, leading to extremely thin crust at 53°E segment. This research was granted by the National Basic Research Programme of China (973 programme) (grant No. 2013CB429705) and the Fundamental Research Funds of Second Institute of Oceanography, State Oceanic Administration (JG1603, SZ1507). References: Johnson K T M, Dick H J B, Shimizu N. Melting in the oceanic upper mantle: An ion microprobe study of diopsides in abyssal peridotites[J]. Journal of Geophysical Research, 1990, 95(B3):2661-2678. Kelemen P B, Hart S R, Bernstein S. Silica enrichment in the continental upper mantle via melt/rock reaction[J]. Earth & Planetary Science Letters, 1998, 164(1-2):387-406. Zhou H, Dick H J. Thin crust as evidence for depleted mantle supporting the Marion Rise.[J]. Nature, 2013, 494(7436):195-200.

  2. Melts of garnet lherzolite: experiments, models and comparison to melts of pyroxenite and carbonated lherzolite

    Science.gov (United States)

    Grove, Timothy L.; Holbig, Eva S.; Barr, Jay A.; Till, Christy B.; Krawczynski, Michael J.

    2013-01-01

    Phase equilibrium experiments on a compositionally modified olivine leucitite from the Tibetan plateau have been carried out from 2.2 to 2.8 GPa and 1,380–1,480 °C. The experiments-produced liquids multiply saturated with spinel and garnet lherzolite phase assemblages (olivine, orthopyroxene, clinopyroxene and spinel ± garnet) under nominally anhydrous conditions. These SiO2-undersaturated liquids and published experimental data are utilized to develop a predictive model for garnet lherzolite melting of compositionally variable mantle under anhydrous conditions over the pressure range of 1.9–6 GPa. The model estimates the major element compositions of garnet-saturated melts for a range of mantle lherzolite compositions and predicts the conditions of the spinel to garnet lherzolite phase transition for natural peridotite compositions at above-solidus temperatures and pressures. We compare our predicted garnet lherzolite melts to those of pyroxenite and carbonated lherzolite and develop criteria for distinguishing among melts of these different source types. We also use the model in conjunction with a published predictive model for plagioclase and spinel lherzolite to characterize the differences in major element composition for melts in the plagioclase, spinel and garnet facies and develop tests to distinguish between melts of these three lherzolite facies based on major elements. The model is applied to understand the source materials and conditions of melting for high-K lavas erupted in the Tibetan plateau, basanite–nephelinite lavas erupted early in the evolution of Kilauea volcano, Hawaii, as well as younger tholeiitic to alkali lavas from Kilauea.

  3. Electric melting furnace for waste solidification

    International Nuclear Information System (INIS)

    Masaki, Toshio.

    1990-01-01

    To avoid electric troubles or reduction of waste processing performance even when platinum group elements are contained in wastes to be applied with glass solidification. For this purpose, a side electrode is disposed to the side wall of a melting vessel and a central electrode serving as a counter electrode is disposed about at the center inside the melting vessel. With such a constitution, if conductive materials are deposited at the bottom of the furnace or the bottom of the melting vessel, heating currents flow selectively between the side electrode and the central electrode. Accordingly, no electric currents flow through the conductive deposits thereby enabling to prevent abnormal heating in the bottom of the furnace. Further, heat generated by electric supply between the side electrode and the central electrode is supplied efficiently to raw material on the surface of the molten glass liquid to improve the processing performance. Further, disposition of the bottom electrode at the bottom of the furnace enables current supply between the central electrode and the bottom electrode to facilitate the temperature control for the molten glass in the furnace than in the conventional structure. (I.S.)

  4. Ionic diffusion in superionic-conductor melts

    International Nuclear Information System (INIS)

    Tankeshwar, K.; Tosi, M.P.

    1991-03-01

    The self-diffusion coefficients D + and D - of the two ionic species in molten AgI, CuCl, CuBr and CuI are evaluated and contrasted with those calculated for molten NaCl. The evaluation adopts a simple model for liquid state dynamics, earlier proposed by Zwanzig to justify the Stokes-Einstein formula for monatomic fluids, and by suitable approximations relates the self-diffusion coefficients to pair potentials and to the pair structure of the melt. The results offer an interpretation for molecular dynamics data showing that, whereas for a ''normal'' system such as NaCl the ratio D + /D - in the melt is of the order unity, a sizable difference between D + and D - persists in salts melting from a fast-cation conducting solid. This difference is explicitly related to liquid structure through differences in the structural backscattering of cations by cations and of halogens by halogens. The calculated magnitudes of D + /D - are quite satisfactory, while the absolute magnitudes of D + and D - are in good agreement with the data only for those salts (AgI, CuBr and NaCl) in which the masses of the two ionic species are not greatly different. (author). 21 refs, 2 tabs

  5. Melt propagation in dry core debris beds

    International Nuclear Information System (INIS)

    Dosanjh, S.S.

    1989-01-01

    During severe light water reactor accidents like Three Mile Island Unit 2, the fuel rods can fragment and thus convert the reactor core into a large particle bed. The postdryout meltdown of such debris beds is examined. A two-dimensional model that considers the presence of oxidic (UO 2 and ZrO 2 ) as well as metallic (e.g., zirconium) constituents is developed. Key results are that a dense metallic crust is created near the bottom of the bed as molten materials flow downward and freeze; liquid accumulates above the blockage and, if zirconium is present, the pool grows rapidly as molten zirconium dissolved both UO 2 and ZrO 2 particles; if the melt wets the solid, a fraction of the melt flows radially outward under the action of capillary forces and freezes near the radial boundary; in a nonwetting system, all of the melt flows into the bottom of the bed; and when zirconium and iron are in intimate contact and the zirconium metal atomic fraction is > 0.33, these metals can liquefy and flow out of the bed very early in the meltdown sequence

  6. Melt processing of Yb-123 tapes

    International Nuclear Information System (INIS)

    Athur, S. P.; Balachandran, U.; Salama, K.

    2000-01-01

    The innovation of a simple, scalable process for manufacturing long-length conductors of HTS is essential to potential commercial applications such as power cables, magnets, and transformers. In this paper the authors demonstrate that melt processing of Yb-123 tapes made by the PIT route is an alternative to the coated conductor and Bi-2223 PIT tape fabrication techniques. Ag-clad Yb-123 tapes were fabricated by groove rolling and subsequently, melt processed in different oxygen partial pressures in a zone-melting furnace with a gradient of 140 C/cm. The transition temperatures measured were found to be around 81 K undermost processing conditions. EPMA of the tapes processed under different conditions show the 123 phase to be Ba deficient and Cu and Yb rich. Critical current was measured at various temperatures from 77 K to 4.2 K. The J c increased with decrease in pO 2 . The highest I c obtained was 52 A at 4.2 K

  7. The kinetic fragility of natural silicate melts

    International Nuclear Information System (INIS)

    Giordano, Daniele; Dingwell, Donald B

    2003-01-01

    Newtonian viscosities of 19 multicomponent natural and synthetic silicate liquids, with variable contents of SiO 2 (41-79 wt%), Al 2 O 3 (10-19 wt%), TiO 2 (0-3 wt%), FeO tot (0-11 wt%); alkali oxides (5-17 wt%), alkaline-earth oxides (0-35 wt%), and minor oxides, obtained at ambient pressure using the high-temperature concentric cylinder, the low-temperature micropenetration, and the parallel plates techniques, have been analysed. For each silicate liquid, regression of the experimentally determined viscosities using the well known Vogel-Fulcher-Tammann (VFT) equation allowed the viscosity of all these silicates to be accurately described. The results of these fits, which provide the basis for the subsequent analysis here, permit qualitative and quantitative correlations to be made between the VFT adjustable parameters (A VFT , B VFT , and T 0 ). The values of B VFT and T 0 , calibrated via the VFT equation, are highly correlated. Kinetic fragility appears to be correlated with the number of non-bridging oxygens per tetrahedrally coordinated cation (NBO/T). This is taken to infer that melt polymerization controls melt fragility in liquid silicates. Thus NBO/T might form an useful ingredient of a structure-based model of non-Arrhenian viscosity in multicomponent silicate melts

  8. Vortex lattice melting, pinning and kinetics

    International Nuclear Information System (INIS)

    Doniach, S.; Ryu, S.; Kapitulnik, A.

    1994-01-01

    The phenomenology of the high T c superconductors is discussed both at the level of the thermodynamics of melting of the Abrikosov flux lattice and in terms of the melting and kinetics of the flux lattice for a pinned system. The authors review results on 3D melting obtained by a Monte Carlo simulation approach in which the 2D open-quotes pancakeclose quotes vortices are treated as statistical variables. The authors discuss pinning in the context of the strong pinning regime in which the vortex density given in terms of the applied field B is small compared to that represented by an effective field B pin measuring the pinning center density. The authors introduce a new criterion for the unfreezing of a vortex glass on increase of magnetic field or temperature, in the strong pinning, small field unit. The authors model this limit in terms of a single flux line interacting with a columnar pin. This model is studied both analytically and by computer simulation. By applying a tilt potential, the authors study the kinetics of the vortex motion in an external current and show that the resulting current-voltage characteristic follows a basic vortex glass-like scaling relation in the vicinity of the depinning transition

  9. Prediction of melt geometry in laser cutting

    Energy Technology Data Exchange (ETDEWEB)

    Tani, Giovanni; Tomesani, Luca; Campana, Giampaolo

    2003-03-15

    In this paper, an analytical model for the evaluation of the melt film geometry in laser cutting of steels is developed. Using as basis, a previous model for kerf geometry estimation developed by the authors, with both reactive and non-reactive process gases, the film thickness and velocity were determined as a function of the kerf depth in the cutting plate. Two criteria were then adopted to predict the quality of the laser cutting operation: the first is based on a minimum acceptable value of the ejection speed of the melt from the bottom of the kerf, the second on the occlusion of the kerf itself due to an excess of molten material in the boundary layer at the kerf width. These criteria determined a feasibility region in the domain of the process and material variables, such as cutting speed, assistant gas pressure, laser beam power and material characteristics. These factors may be successfully used to build a process-planning tool for parameters optimisation and setting, in order to achieve a satisfactory process quality. The model response is in excellent agreement with the feasibility regions reported from experimental data by various authors and demonstrates a relationship between the occurrence of dross adhesion and the two different mechanisms predicted for such a phenomenon were: unsatisfactory ejection speed of the melt film from the bottom of the kerf and occlusion of the kerf.

  10. Rock melting technology and geothermal drilling

    Science.gov (United States)

    Rowley, J. C.

    1974-01-01

    National awareness of the potential future shortages in energy resources has heightened interest in exploration and utilization of a variety of geothermal energy (GTE) reservoirs. The status of conventional drilling of GTE wells is reviewed briefly and problem areas which lead to higher drilling costs are identified and R and D directions toward solution are suggested. In the immediate future, an expanded program of drilling in GTE formations can benefit from improvements in drilling equipment and technology normally associated with oil or gas wells. Over a longer time period, the new rock-melting drill bits being developed as a part of the Los Alamos Scientific Laboratory's Subterrene Program offer new solutions to a number of problems which frequently hamper GTE drilling, including the most basic problem - high temperature. Two of the most favorable characteristics of rock-melting penetrators are their ability to operate effectively in hot rock and produce glass linings around the hole as an integral part of the drilling process. The technical advantages to be gained by use of rock-melting penetrators are discussed in relation to the basic needs for GTE wells.

  11. Using cocrystals to systematically modulate aqueous solubility and melting behavior of an anticancer drug.

    Science.gov (United States)

    Aakeröy, Christer B; Forbes, Safiyyah; Desper, John

    2009-12-02

    Five cocrystals of an anticancer compound have been assembled using a well-defined hydrogen-bond-based supramolecular approach that produced the necessary structural consistency in the resulting solids. These cocrystals contain aliphatic even-numbered dicarboxylic acids of increasing chain length, and as a result, the physical properties of the cocrystals can be related to the molecular structure of the acid. The melting points of the five cocrystals show an excellent correlation with the melting points of the individual acids, and it has also been shown that aqueous solubility can be increased by a factor of 2.5 relative to that of the individual drug. Consequently, cocrystals can offer a range of solid forms from which can be chosen an active ingredient where a particular physical property can be dialed in, provided that the cocrystals show considerable structural consistency and that systematic changes are made to the participating cocrystallizing agents.

  12. Oxidation effect on steel corrosion and thermal loads during corium melt in-vessel retention

    Energy Technology Data Exchange (ETDEWEB)

    Granovsky, V.S.; Khabensky, V.B.; Krushinov, E.V.; Vitol, S.A.; Sulatsky, A.A.; Almjashev, V.I. [Alexandrov Scientific-Research Technology Institute (NITI), Sosnovy Bor (Russian Federation); Bechta, S.V. [KTH, Stockholm (Sweden); Gusarov, V.V. [SPb State Technology University (SPbGTU), St. Petersburg (Russian Federation); Barrachin, M. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), St Paul lez Durance (France); Bottomley, P.D., E-mail: paul.bottomley@ec.europa.eu [EC-Joint Research Centre, Institute for Transuranium Elements (ITU), Karlsruhe (Germany); Fischer, M. [AREVA GmbH, Erlangen (Germany); Piluso, P. [Commissariat à l’Energie Atomique et aux Energies Alternatives (CEA), Cadarache, St Paul lez Durance (France)

    2014-10-15

    Highlights: • The METCOR facility simulates vessel steel corrosion in contact with corium. • Steel corrosion rates in UO{sub 2+x}–ZrO{sub 2}–FeO{sub y} coria accelerate above 1050 K. • However corrosion rates can also be limited by melt O{sub 2} supply. • The impact of this on in-vessel retention (IVR) strategy is discussed. - Abstract: During a severe accident with core meltdown, the in-vessel molten core retention is challenged by the vessel steel ablation due to thermal and physicochemical interaction of melt with steel. In accidents with oxidizing atmosphere above the melt surface, a low melting point UO{sub 2+x}–ZrO{sub 2}–FeO{sub y} corium pool can form. In this case ablation of the RPV steel interacting with the molten corium is a corrosion process. Experiments carried out within the International Scientific and Technology Center's (ISTC) METCOR Project have shown that the corrosion rate can vary and depends on both surface temperature of the RPV steel and oxygen potential of the melt. If the oxygen potential is low, the corrosion rate is controlled by the solid phase diffusion of Fe ions in the corrosion layer. At high oxygen potential and steel surface layer temperature of 1050 °C and higher, the corrosion rate intensifies because of corrosion layer liquefaction and liquid phase diffusion of Fe ions. The paper analyzes conditions under which corrosion intensification occurs and can impact on in-vessel melt retention (IVR)

  13. Coating and melt induced agglomeration in a poultry litter fired fluidized bed combustor

    International Nuclear Information System (INIS)

    Billen, Pieter; Creemers, Benji; Costa, José; Van Caneghem, Jo; Vandecasteele, Carlo

    2014-01-01

    The combustion of poultry litter, which is rich in phosphorus, in a fluidized bed combustor (FBC) is associated with agglomeration problems, which can lead to bed defluidization and consequent shutdown of the installation. Whereas earlier research indicated coating induced agglomeration as the dominant mechanism for bed material agglomeration, it is shown experimentally in this paper that both coating and melt induced agglomeration occur. Coating induced agglomeration mainly takes place at the walls of the FBC, in the freeboard above the fluidized bed, where at the prevailing temperature the bed particles are partially molten and hence agglomerate. In the ash, P 2 O 5 forms together with CaO thermodynamically stable Ca 3 (PO 4 ) 2 , thus reducing the amount of calcium silicates in the ash. This results in K/Ca silicate mixtures with lower melting points. On the other hand, in-bed agglomeration is caused by thermodynamically unstable, low melting HPO 4 2− and H 2 PO 4 − salts present in the fuel. In the hot FBC these salts may melt, may cause bed particles to stick together and may subsequently react with Ca salts from the bed ash, forming a solid bridge of the stable Ca 3 (PO 4 ) 2 between multiple particles. - Highlights: • Coating induced agglomeration not due to K phosphates, but due to K silicates. • Melt induced agglomeration due to H 2 PO 4 − and HPO 4 2− salts in the fuel. • Wall agglomeration corresponds to coating induced mechanism. • In-bed agglomeration corresponds to melt induced mechanism

  14. Transition metal ions in silicate melts. I. Manganese in sodium silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C; White, W B

    1980-01-01

    Optical absorption spectra obtained on glasses quenched from sodium silicate melts show Mn/sup 3 +/ to be the dominant species for melts heated in air and Mn/sup 2 +/ to be the dominant species for melts heated at P/sub O/sub 2// = 10/sup -17/ bar. The absorption spectrum of Mn/sup 3 +/ consists of an intense band at 20,000 cm/sup -1/ with a 15,000 cm/sup -1/ satellite possibly arising from the Jahn-Teller effect. The independence of the spectrum from melt composition and the high band intensity is offered as evidence for a distinct Mn/sup 3 +/ complex in the melt. The spectrum of Mn/sup 2 +/ is weak and many expected bands are not observed. A two-band luminescence spectrum from Mn/sup 2 +/ has been tentatively interpreted as due to Mn/sup 2 +/ in interstitial sites in the network and Mn/sup 2 +/ coordiated by non-bridging oxygens.

  15. Lessons learnt from FARO/TERMOS corium melt quenching experiments

    Energy Technology Data Exchange (ETDEWEB)

    Magallon, D.; Huhtiniemi, I.; Hohmann, H. [Commission of the European Communities, Ispra (Italy). Joint Research Center

    1998-01-01

    The influence of melt quantity, melt composition, water depth and initial pressure on quenching is assessed on the basis of seven tests performed in various conditions in the TERMOS vessel of the FARO facility at JRC-Ispra. Tests involved UO{sub 2}-based melt quantities in the range 18-176 kg at a temperature of approximately 3000 K poured into saturated water. The results suggest that erosion of the melt jet column is an efficient contributor to the amount of break-up, and thus quenching, for large pours of corium melt. The presence of Zr metal in the melt induced a much more efficient quenching than in a similar test with no Zr metal, attributed to the oxidation of the Zr. Significant amounts of H{sub 2} were produced also in tests with pure oxidic melts (e.g. about 300 g for 157 kg melt). In the tests at 5.0 and 2.0 MPa good mixing with significant melt break-up and quenching was obtained during the penetration in the water. At 0.5 MPa, good penetration of the melt into the water could still be achieved, but a jump in the vessel pressurisation occurred when the melt contacted the bottom and part (5 kg) of the debris was re-ejected from the water. (author)

  16. Melting of glass by direct induction heating in ceramic container

    International Nuclear Information System (INIS)

    Ooka, Kazuo; Oguino, Naohiko; Kawanishi, Nobuo

    1981-01-01

    The direct induction melting, a process of glass melting by high frequency induction heating, was found to be the effective way of glass melting, especially desirable for the vitrification of High Level Radioactive Liquid Wastes, HLLW. A test instrument in the cold level was equipped with a high frequency oscillator of 65 kW anode output. The direct induction melting was successfully performed with two frequencies of 400 kHz and 3 MHz, and the operation conditions were determined in the five cases of ceramic pot inner diameters of 170, 200, 230, 280 and 325 mm. The start-up of the direct induction melting was carried out by induction heating using a silicon carbide rod which was inserted in raw material powders in the ceramic pot. After the raw material powders partly melted down and the direct induction in the melt began, the start-up rod was removed out of the melt. At this stage, the direct induction melting was successively performed by adjusting the output power of the oscillator and by supplying the raw materials. It was also found that the capacity of this type of melting was reasonably large and the operation could be remotely controlled. Both applied frequencies of 400 kHz and 3 MHz was found to be successful with this melting system, especially in the case of lower frequency which proved more preferable for the in-cell work. (author)

  17. Scanning the melting curve of tungsten by a submicrosecond wire-explosion experiment

    International Nuclear Information System (INIS)

    Kloss, A.; Hess, H.; Schneidenbach, H.; Grossjohann, R.

    1999-01-01

    Measurements of temperature and density during a wire-explosion experiment at atmospheric pressure are described. The measurements encompass a parameter range from the solid to near the critical point. The influence of a polytetra-fluoroethylene coating of the wire, necessary to prevent surface discharges, on the temperature and density measurements is investigated. The melting curve of tungsten up to 4,000 K is determined

  18. Rheo-electrical approximate simulation of monocrystal growth from the melt

    International Nuclear Information System (INIS)

    Vernois, G.

    1969-01-01

    On a two-dimensional model, the advantages of rheo-electrical simulation for studying monocrystal growth from the melt are pointed out. In the case of an opaque body, it is always possible to make a fairly exact model. As regards a transparent body, the simulation of radiation thermal exchange is fairly difficult. It is shown how the plans of a constant level complex crucible are established. (author) [fr

  19. Organic Crystal Engineering of Thermosetting Cyanate Ester Monomers: Influence of Structure on Melting Point

    Science.gov (United States)

    2016-05-27

    NUMBER 5f. WORK UNIT NUMBER Q16J 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NO. Air Force Research...SPONSOR/MONITOR’S ACRONYM(S) Air Force Research Laboratory (AFMC) AFRL/RQR 11. SPONSOR/MONITOR’S REPORT 5 Pollux Drive NUMBER(S) Edwards AFB...in purification , as well as decreased storability and “out time” due to the comparative ease with which moisture infiltrates liquids, leading to

  20. Enzyme modification of starch with amylomaltase results in increasing gel melting point

    DEFF Research Database (Denmark)

    Hansen, Michael Riis; Blennow, Per Gunnar Andreas; Pedersen, Sven

    2009-01-01

    -enzyme-modified starches and 2 gelatins were investigated using differential scanning calorimetry (DSC). AM modification generally increased gel peak temperature (Tp) and enthalpy of transition (¿H). The increase in Tp for the potato starches was from 65 to 74 °C, whereas for the maize starches it was elevated from 57...... to 70 °C. Only for the combined AM and branching enzyme (BE) modified pea starches decreased Tp (from 79 to 61 °C) was obtained. This effect was followed by a decreased gel formation and hence a fully gelatin comparable gel was not obtained. A two-component principal component analysis (PCA) model...

  1. The role of hydrogen bonds in the melting points of sulfonate-based protic organic salts

    DEFF Research Database (Denmark)

    Luo, Jiangshui

    2016-01-01

    There are three main types of interactions inside organic salts - electrostatic interaction, hydrogen bonding and van der Waals force [1-4]. While van der Waals force is relatively weak, it is hydrogen bonding and particularly electrostatic interaction that determine the lattice energies of ionic...

  2. Sorption activity investigation of ultrafine powders of high temperature melting point compounds in atmospheric pressure conditions

    International Nuclear Information System (INIS)

    Rudneva, V.V.

    2006-01-01

    A study is made in saturation with gas in the air for ultradispersed chromium carbonitride and boride powders synthesized in a nitrogen plasma jet according to three variants: from elements, from oxides, from chromium trichloride. It is established that in the air on temperature increasing the powders adsorb considerable amounts of oxygen and water vapor. This results in surface oxidation of powder particles and a loss in specific combination of properties. Preliminary vacuum heat treatment is shown to decrease sharply the rate of atmospheric gas adsorption. The quantity of adsorbed gases is dependent on a carbon monoxide concentration in a particle surface layer and the availability of adsorption centers. The number of such centers in the layer can be controlled by vacuum heat treatment conditions. The interaction of the powders with atmospheric gases is concluded to be of adsorption-diffusion nature [ru

  3. Melting Point and Viscosity Behavior of High Energy Density Missile Fuels

    Science.gov (United States)

    1982-09-01

    CLASSIFICATION OF THIS PAGE (f,n Date Eneed . etrahydrodi(cyclopentadiene) ( XTHDCPD or JP-lO). HNN and HXX each have two crystalline forms. The solid-solid...suggesting solid solution formation on crystallization. The experimental m.p. curves for the binary/isomer I - XTHDCPD system could be used to predict m.p...liquidus temperature, of any/fuel blend of HNN, HXX, isomer I and XTHDCPD of kno composition. It )as found that the maximum m.p. specification of -54 C

  4. A Non-Mercury Thermometer Alternative for Use in Older Melting Point Apparatuses

    Science.gov (United States)

    Ongley, Lois K.; Kern, Clayton S.; Woods, Barry W.

    2008-01-01

    The State of Maine seeks to eliminate most mercury use. This includes removing mercury thermometers from secondary schools and discouraging Hg use in other educational institutions. Alternatives to mercury thermometers in chemical laboratory work include non-mercury thermometers, temperature probes, and thermocouples. In organic chemistry mercury…

  5. Thermodynamics properties of lanthanide series near melting point-A pseudopotential approach

    Science.gov (United States)

    Suthar, P. H.; Gajjar, P. N.

    2018-04-01

    The present paper deals with computational study of thermodynamics properties for fifteen elements of lanthanide series. The Helmholtz free energy (F), Internal energy (E) and Entropy (S)have been computed using variational method based on the Gibbs-Bogoliubov (GB) along with Percus-Yevick hard sphere reference system and Gajjar's model potential. The local field correction function proposed by Taylor is applied to introduce the exchange and correlation effects in the study of thermodynamics of these metals. The present results in comparison with available theoretical and experimental are found to be in good agreement and confirm the ability of the model potential.

  6. Low melting point pyridinium ionic liquid pretreatment for enhancing enzymatic saccharification of cellulosic biomass.

    Science.gov (United States)

    Uju; Nakamoto, Aya; Shoda, Yasuhiro; Goto, Masahiro; Tokuhara, Wataru; Noritake, Yoshiyuki; Katahira, Satoshi; Ishida, Nobuhiro; Ogino, Chiaki; Kamiya, Noriho

    2013-05-01

    The potential of 1-hexylpyridinium chloride ([Hpy][Cl]), to pretreat cellulosic feedstocks was investigated using microcrystalline cellulose (Avicel) and Bagasse at 80 °C or 100 °C. Short [Hpy][Cl] pretreatments, conversion of pretreated Avicel to glucose was attained after 24h enzymatic saccharification under optimal conditions, whereas regenerated Bagasse showed 1-3-fold higher conversion than untreated biomass. FT-IR analysis of both Avicel and Bagasse samples pretreated with [Hpy][Cl] or 1-ethyl-3-methyimidazolium acetate ([Emim][OAc]) revealed that these ionic liquids behaved differently during pretreatment. [Hpy][Cl] pretreatment for an extended duration (180 min) released mono- and disaccharides without using cellulase enzymes, suggesting [Hpy][Cl] has capability for direct saccharification of cellulosic feedstocks. On the basis of the results obtained, [Hpy][Cl] pretreatment enhanced initial reaction rates in enzymatic saccharification by either crystalline polymorphic alteration of cellulose or partial degradation of the crystalline cellulosic fraction in biomass. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Stability of the composites: NiAl - cellular high-melting point metal

    International Nuclear Information System (INIS)

    Belomyttsev, M.Yu.; Kozlov, D.A.

    2006-01-01

    For sintered composite materials (CM) NiAl-W and NiAl-W-Mo the structure and mechanical properties are studied. A comparative analysis of the effect of hot deformation by compression at 1000-1300 Deg C on the integrity of microsamples themselves and tungsten shells of NiAl granules in CM with a cellular structure is accomplished. Local chemical composition of a NiAl/refractory metal interface in CM with cellular structure and free of it is determined. A CM structural state effect on compression yield strength at 1000 Deg C is estimated. The treatment is proposed which permits approaching cellular structured CM oxidation resistance at 1000-1100 Deg C to the level of heat stability of unalloyed NiAl or its alloy with Hf [ru

  8. Temperature calibration procedure for thin film substrates for thermo-ellipsometric analysis using melting point standards

    NARCIS (Netherlands)

    Kappert, Emiel; Raaijmakers, Michiel; Ogieglo, Wojciech; Nijmeijer, Arian; Huiskes, Cindy; Huiskes, C.; Benes, Nieck Edwin

    2015-01-01

    Precise and accurate temperature control is pertinent to studying thermally activated processes in thin films. Here, we present a calibration method for the substrate–film interface temperature using spectroscopic ellipsometry. The method is adapted from temperature calibration methods that are well

  9. Simulation of melt spreading in consideration of phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Spengler, C. [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Koeln (Germany)

    2002-07-01

    The analysis of melt spreading and relocation phenomena in the containment of LWR power plants in case of hypothetical severe accidents leading to core melting is an important issue for reactor safety investigations. For the simulation of melt spreading the code LAVA has been developed on the basis of a method from the related subject of volcanology by adding more detailed models for heat transfer phenomena and flow rheology. The development is supported by basic analysis of the spreading of gravity currents as well as experimental investigations of the rheology of solidifying melts. These exhibit strong non-Newtonian effects in case of a high content of solids in the freezing melt. The basic model assumption in LAVA is the ideal Bingham plastic approach to the non-Newtonian, shear-thinning characteristic of solidifying melts. For the recalculation of melt spreading experiments, the temperature-dependent material properties for solidifying melt mixtures have been calculated using correlations from the literature. With the parameters and correlations for the rheological material properties approached by results from literature, it was possible to recalculate successfully recent spreading experiments with simulant materials and prototypic reactor core materials. An application to the behaviour of core melt in the reactor cavity assumed a borderline case for the issue of spreading. This limit is represented by melt conditions (large solid fraction, low volume flux), under which the melt is hardly spreadable. Due to the persistent volume flux the reactor cavity is completely, but inhomogeneously filled with melt. The degree of inhomogeneity is rather small, so it is concluded, that for the long-term coolability of a melt pool in narrow cavities the spreading of melt will probably have only negligible influence. (orig.)

  10. Core melt retention and cooling concept of the ERP

    Energy Technology Data Exchange (ETDEWEB)

    Weisshaeupl, H [SIEMENS/KWU, Erlangen (Germany); Yvon, M [Nuclear Power International, Paris (France)

    1996-12-01

    For the French/German European Pressurized Water Reactor (EPR) mitigative measures to cope with the event of a severe accident with core melt down are considered already at the design stage. Following the course of a postulated severe accident with reactor pressure vessel melt through one of the most important features of a future design must be to stabilize and cool the melt within the containment by dedicated measures. This measures should - as far as possible - be passive. One very promising solution for core melt retention seems to be a large enough spreading of the melt on a high temperature resistant protection layer with water cooling from above. This is the favorite concept for the EPR. In dealing with the retention of a molten core outside of the RPV several ``steps`` from leaving the RPV to finally stabilize the melt have to gone through. These steps are: collection of the melt; transfer of the melt; distribution of the melt; confining; cooling and stabilization. The technical features for the EPR solution of a large spreading of the melt are: Dedicated spreading chamber outside the reactor pit (area about 150 m{sup 2}); high temperature resistant protection layers (e.g. Zirconia bricks) at the bottom and part of the lateral structures (thus avoiding melt concrete interaction); reactor pit and spreading compartment are connected via a discharge channel which has a slope to the spreading area and is closed by a steel plate, which will resist the core melt for a certain time in order to allow a collection of the melt; the spreading compartments is connected with the In-Containment Refuelling Water Storage Tank (IRWST) with pipes for water flooding after spreading. These pipes are closed and will only be opened by the hot melt itself. It is shown how the course of the different steps mentioned above is processed and how each of these steps is automatically and passively achieved. (Abstract Truncated)

  11. Lattice stability and high-pressure melting mechanism of dense hydrogen up to 1.5 TPa

    KAUST Repository

    Geng, Hua Y.

    2015-09-01

    © 2015 American Physical Society. Lattice stability and metastability, as well as melting, are important features of the physics and chemistry of dense hydrogen. Using ab initio molecular dynamics (AIMD), the classical superheating limit and melting line of metallic hydrogen are investigated up to 1.5 TPa. The computations show that the classical superheating degree is about 100 K, and the classical melting curve becomes flat at a level of 350 K when beyond 500 GPa. This information allows us to estimate the well depth and the potential barriers that must be overcome when the crystal melts. Inclusion of nuclear quantum effects (NQE) using path integral molecular dynamics (PIMD) predicts that both superheating limit and melting temperature are lowered to below room temperature, but the latter never reaches absolute zero. Detailed analysis indicates that the melting is thermally activated, rather than driven by pure zero-point motion (ZPM). This argument was further supported by extensive PIMD simulations, demonstrating the stability of Fddd structure against liquefaction at low temperatures.

  12. Recent results in characterization of melt-grown and quench-melt- grown YBCO superconductors

    International Nuclear Information System (INIS)

    Balachandran, U.; Poeppel, R.B.; Gangopadhyay, A.K.

    1992-02-01

    From the standpoint of applications, melt-grown (MG) and quench-melt-grown (QMG) bulk YBCO superconductors are of considerable interest. In this paper, we studied the intragranular critical current density (J c ), the apparent pinning potential (U o ), and the irreversibility temperature (T irr ) of MG and QMG samples and compared the results to those for conventionally sintered YBCO. A systematic increase in U o and a slower drop in J c with temperature indicate a systematic improvement in flux-pinning properties in progressing from the sintered YBCO to QMG and MG samples. Weaker pinning is observed in the QMG YBCO than in the MG samples

  13. Controlled tungsten melting and droplet ejection studies in ASDEX Upgrade

    International Nuclear Information System (INIS)

    Krieger, K; Lunt, T; Dux, R; Janzer, A; Müller, H W; Potzel, S; Pütterich, T; Yang, Z

    2011-01-01

    Tungsten rods of 1×1×3 mm 3 were exposed in single H-mode discharges at the outer divertor target plate of ASDEX Upgrade using the divertor manipulator system. Melting of the W rod at a pre-defined time was induced by moving the initially far away outer strike point close to the W-rod position. Visible light emissions of both the W pin and consecutively ejected W droplets were recorded by two fast cameras with crossed viewing cones. The time evolution of the local W source at the pin location was measured by spectroscopic observation of the WI line emission at 400.9 nm and compared to the subsequent increase of tungsten concentration in the confined plasma derived from tungsten vacuum UV line emission. Combining these measurements with the total amount of released tungsten due to the pin melt events and ejected droplets allowed us to derive an estimate of the screening factor for this type of tungsten source. The resulting values of the tungsten divertor retention in the range 10-20 agree with those found in previous studies using a W source of sublimated W(CO) 6 vapour at the same exposure location. Ejected droplets were found to be always accelerated in the general direction of the plasma flow, attributed to friction forces and to rocket forces. Furthermore, the vertically inclined target plates cause the droplets, which are repelled by the target plate surface potential due to their electric charge, to move upwards against gravity due to the centrifugal force component parallel to the target plate.

  14. 2D model for melt progression through rods and debris

    International Nuclear Information System (INIS)

    Fichot, F.

    2001-01-01

    During the degradation of a nuclear core in a severe accident scenario, the high temperatures reached lead to the melting of materials. The formation of liquid mixtures at various elevations is followed by the flow of molten materials through the core. Liquid mixture may flow under several configurations: axial relocation along the rods, horizontal motion over a plane surface such as the core support plate or a blockage of material, 2D relocation through a debris bed, etc.. The two-dimensional relocation of molten material through a porous debris bed, implemented for the simulation of late degradation phases, has opened a new way to the elaboration of the relocation model for the flow of liquid mixture along the rods. It is based on a volume averaging method, where wall friction and capillary effects are taken into account by introducing effective coefficients to characterize the solid matrix (rods, grids, debris, etc.). A local description of the liquid flow is necessary to derive the effective coefficients. Heat transfers are modelled in a similar way. The derivation of the conservation equations for the liquid mixture falling flow (momentum) in two directions (axial and radial-horizontal) and for the heat exchanges (energy) are the main points of this new model for simulating melt progression. In this presentation, the full model for the relocation and solidification of liquid materials through a rod bundle or a debris bed is described. It is implemented in the ICARE/CATHARE code, developed by IPSN in Cadarache. The main improvements and advantages of the new model are: A single formulation for liquid mixture relocation, in 2D, either through a rod bundle or a porous debris bed, Extensions to complex structures (grids, by-pass, etc..), The modeling of relocation of a liquid mixture over plane surfaces. (author)

  15. Quality improvement of melt extruded laminar systems using mixture design.

    Science.gov (United States)

    Hasa, D; Perissutti, B; Campisi, B; Grassi, M; Grabnar, I; Golob, S; Mian, M; Voinovich, D

    2015-07-30

    This study investigates the application of melt extrusion for the development of an oral retard formulation with a precise drug release over time. Since adjusting the formulation appears to be of the utmost importance in achieving the desired drug release patterns, different formulations of laminar extrudates were prepared according to the principles of Experimental Design, using a design for mixtures to assess the influence of formulation composition on the in vitro drug release from the extrudates after 1h and after 8h. The effect of each component on the two response variables was also studied. Ternary mixtures of theophylline (model drug), monohydrate lactose and microcrystalline wax (as thermoplastic binder) were extruded in a lab scale vertical ram extruder in absence of solvents at a temperature below the melting point of the binder (so that the crystalline state of the drug could be maintained), through a rectangular die to obtain suitable laminar systems. Thanks to the desirability approach and a reliability study for ensuring the quality of the formulation, a very restricted optimal zone was defined within the experimental domain. Among the mixture components, the variation of microcrystalline wax content played the most significant role in overall influence on the in vitro drug release. The formulation theophylline:lactose:wax, 57:14:29 (by weight), selected based on the desirability zone, was subsequently used for in vivo studies. The plasma profile, obtained after oral administration of the laminar extruded system in hard gelatine capsules, revealed the typical trend of an oral retard formulation. The application of the mixture experimental design associated to a desirability function permitted to optimize the extruded system and to determine the composition space that ensures final product quality. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    Cochain, B.

    2009-12-01

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na 2 O-B 2 O 3 -SiO 2 -FeO and Na 2 O-Al 2 O 3 -SiO 2 -FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe 3+ /ΣFe redox state implies a structural rearrangement of the BO 4 species in the glass network whereas the BO 3 and BO 4 relative proportions remain nearly constant. In all studied glasses and melts, Fe 3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe 3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO 3 and BO 4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  17. Ice shelf melt rates in Greenland and Antarctica using time-tagged digital imagery from World View and TanDEM-X

    Science.gov (United States)

    Charolais, A.; Rignot, E. J.; Milillo, P.; Scheuchl, B.; Mouginot, J.

    2017-12-01

    The floating extensions of glaciers, or ice shelves, melt vigorously in contact with ocean waters. Melt is non uniform, with the highest melt taking place in the deepest part of the cavity, where thermal forcing is the greatest because of 1) the pressure dependence of the freezing point of the seawater/ice mixture and 2) subglacial water injects fresh, buoyant, cold melt water to fuel stronger ice-ocean interactions. Melt also forms along preferential channels, which are not stationary, and create lines of weakness in the shelf. Ice shelf melt rates have been successfully measured from space over the entire Antarctic continent and on the ice shelves in Greenland using an Eulerian approach that combines ice thickness, ice velocity vectors, surface mass balance data, and measurements of ice thinning rates. The Eulerian approach is limited by the precision of the thickness gradients, typically of a few km, and requires significant spatial averaging to remove advection effects. A Lagrangian approach has been shown to be robust to advection effects and provides higher resolution details. We implemented a Lagrangian methodology for time-tagged World View DEMs by the Polar Geoscience Center (PGS) at the University of Minnesota and time-tagged TanDEM-X DEMs separated by one year. We derive melt rates on a 300-m grid with a precision of a few m/yr. Melt is strongest along grounding lines and along preferred channels. Channels are non-stationary because melt is not the same on opposite sides of the channels. Examining time series of data and comparing with the time-dependent grounding line positions inferred from satellite radar interferometry, we evaluate the magnitude of melt near the grounding line and even within the grounding zone. A non-zero melt rate in the grounding zone has vast implications for ice sheet modeling. This work is funded by a grant from NASA Cryosphere Program.

  18. Dynamics of upper mantle rocks decompression melting above hot spots under continental plates

    Science.gov (United States)

    Perepechko, Yury; Sorokin, Konstantin; Sharapov, Victor

    2014-05-01

    Numeric 2D simulation of the decompression melting above the hot spots (HS) was accomplished under the following conditions: initial temperature within crust mantle section was postulated; thickness of the metasomatized lithospheric mantle is determined by the mantle rheology and position of upper asthenosphere boundary; upper and lower boundaries were postulated to be not permeable and the condition for adhesion and the distribution of temperature (1400-2050°C); lateral boundaries imitated infinity of layer. Sizes and distribution of lateral points, their symmetry, and maximum temperature varied between the thermodynamic condition for existences of perovskite - majorite transition and its excess above transition temperature. Problem was solved numerically a cell-vertex finite volume method for thermo hydrodynamic problems. For increasing convergence of iterative process the method of lower relaxation with different value of relaxation parameter for each equation was used. The method of through calculation was used for the increase in the computing rate for the two-layered upper mantle - lithosphere system. Calculated region was selected as 700 x (2100-4900) km. The time step for the study of the asthenosphere dynamics composed 0.15-0.65 Ma. The following factors controlling the sizes and melting degree of the convective upper mantle, are shown: a) the initial temperature distribution along the section of upper mantleb) sizes and the symmetry of HS, c) temperature excess within the HS above the temperature on the upper and lower mantle border TB=1500-2000oC with 5-15% deviation but not exceed 2350oC. It is found, that appearance of decompression melting with HS presence initiate primitive mantle melting at TB > of 1600oC. Initial upper mantle heating influence on asthenolens dimensions with a constant HS size is controlled mainly by decompression melting degree. Thus, with lateral sizes of HS = 400 km the decompression melting appears at TB > 1600oC and HS

  19. Shear Melting of a Colloidal Glass

    Science.gov (United States)

    Eisenmann, Christoph; Kim, Chanjoong; Mattsson, Johan; Weitz, David A.

    2010-01-01

    We use confocal microscopy to explore shear melting of colloidal glasses, which occurs at strains of ˜0.08, coinciding with a strongly non-Gaussian step size distribution. For larger strains, the particle mean square displacement increases linearly with strain and the step size distribution becomes Gaussian. The effective diffusion coefficient varies approximately linearly with shear rate, consistent with a modified Stokes-Einstein relationship in which thermal energy is replaced by shear energy and the length scale is set by the size of cooperatively moving regions consisting of ˜3 particles.

  20. Pressure-induced melting of micellar crystal

    DEFF Research Database (Denmark)

    Mortensen, K.; Schwahn, D.; Janssen, S.

    1993-01-01

    that pressure improves the solvent quality of water, thus resulting in decomposition of the micelles and consequent melting of the micellar crystal. The combined pressure and temperature dependence reveals that in spite of the apparent increase of order on the 100 angstrom length scale upon increasing......Aqueous solutions of triblock copolymers of poly(ethylene oxide) and poly(propylene oxide) aggregate at elevated temperatures into micelles which for polymer concentrations greater-than-or-equal-to 20% make a hard sphere crystallization to a cubic micellar crystal. Structural studies show...... temperature (decreasing pressure) the overall entropy increases through the inverted micellar crystallization characteristic....

  1. Reversed Extension Flow of Polymer melts

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Nielsen, Jens Kromann

    2007-01-01

    The measurement of the startup of uni axial elongational flow (potentially until steady state) followed by reversed bi axial flow, both with a constant elongational rate was made possible using a Filament Stretching Rheometer (FSR). The filament stretching rheometer rheometer is surrounded...... by a thermostated environment and allows measurements on polymeric melts and liquids from room temperatures until 200 °C. In the experiments the Hencky strain at which the stress becomes zero (the recovery strain) of the reversed flow can be identified....

  2. Eddy-resolving simulations of the Fimbul Ice Shelf cavity circulation: Basal melting and exchange with open ocean

    Science.gov (United States)

    Hattermann, T.; Smedsrud, L. H.; Nøst, O. A.; Lilly, J. M.; Galton-Fenzi, B. K.

    2014-10-01

    Melting at the base of floating ice shelves is a dominant term in the overall Antarctic mass budget. This study applies a high-resolution regional ice shelf/ocean model, constrained by observations, to (i) quantify present basal mass loss at the Fimbul Ice Shelf (FIS); and (ii) investigate the oceanic mechanisms that govern the heat supply to ice shelves in the Eastern Weddell Sea. The simulations confirm the low melt rates suggested by observations and show that melting is primarily determined by the depth of the coastal thermocline, regulating deep ocean heat fluxes towards the ice. Furthermore, the uneven distribution of ice shelf area at different depths modulates the melting response to oceanic forcing, causing the existence of two distinct states of melting at the FIS. In the simulated present-day state, only small amounts of Modified Warm Deep Water enter the continental shelf, and ocean temperatures beneath the ice are close to the surface freezing point. The basal mass loss in this so-called state of "shallow melting" is mainly controlled by the seasonal inflow of solar-heated surface water affecting large areas of shallow ice in the upper part of the cavity. This is in contrast to a state of "deep melting", in which the thermocline rises above the shelf break depth, establishing a continuous inflow of Warm Deep Water towards the deep ice. The transition between the two states is found to be determined by a complex response of the Antarctic Slope Front overturning circulation to varying climate forcings. A proper representation of these frontal dynamics in climate models will therefore be crucial when assessing the evolution of ice shelf basal melting along this sector of Antarctica.

  3. Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

    Directory of Open Access Journals (Sweden)

    Seongsuk Lee

    2016-12-01

    Full Text Available The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP F13 Special Sensor Microwave/Imagers (SSMI and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily and monthly sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole even during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA.

  4. High DNA melting temperature predicts transcription start site location in human and mouse.

    LENUS (Irish Health Repository)

    Dineen, David G

    2009-12-01

    The accurate computational prediction of transcription start sites (TSS) in vertebrate genomes is a difficult problem. The physicochemical properties of DNA can be computed in various ways and a many combinations of DNA features have been tested in the past for use as predictors of transcription. We looked in detail at melting temperature, which measures the temperature, at which two strands of DNA separate, considering the cooperative nature of this process. We find that peaks in melting temperature correspond closely to experimentally determined transcription start sites in human and mouse chromosomes. Using melting temperature alone, and with simple thresholding, we can predict TSS with accuracy that is competitive with the most accurate state-of-the-art TSS prediction methods. Accuracy is measured using both experimentally and manually determined TSS. The method works especially well with CpG island containing promoters, but also works when CpG islands are absent. This result is clear evidence of the important role of the physical properties of DNA in the process of transcription. It also points to the importance for TSS prediction methods to include melting temperature as prior information.

  5. Identification of squid species by melting temperature shifts on fluorescence melting curve analysis (FMCA) using single dual-labeled probe

    Science.gov (United States)

    Koh, Eunjung; Song, Ha Jeong; Kwon, Na Young; Kim, Gi Won; Lee, Kwang Ho; Jo, Soyeon; Park, Sujin; Park, Jihyun; Park, Eun Kyeong; Hwang, Seung Yong

    2017-06-01

    Real time PCR is a standard method for identification of species. One of limitations of the qPCR is that there would be false-positive result due to mismatched hybridization between target sequence and probe depending on the annealing temperature in the PCR condition. As an alternative, fluorescence melting curve analysis (FMCA) could be applied for species identification. FMCA is based on a dual-labeled probe. Even with subtle difference of target sequence, there are visible melting temperature (Tm) shift. One of FMCA applications is distinguishing organisms distributed and consumed globally as popular food ingredients. Their prices are set by species or country of origin. However, counterfeiting or distributing them without any verification procedure are becoming social problems and threatening food safety. Besides distinguishing them in naked eye is very difficult and almost impossible in any processed form. Therefore, it is necessary to identify species in molecular level. In this research three species of squids which have 1-2 base pair differences each are selected as samples since they have the same issue. We designed a probe which perfectly matches with one species and the others mismatches 2 and 1 base pair respectively and labeled with fluorophore and quencher. In an experiment with a single probe, we successfully distinguished them by Tm shift depending on the difference of base pair. By combining FMCA and qPCR chip, smaller-scale assay with higher sensitivity and resolution could be possible, andc furthermore, enabling results analysis with smart phone would realize point-of-care testing (POCT).

  6. Additive Manufacturing Processes: Selective Laser Melting, Electron Beam Melting and Binder Jetting—Selection Guidelines

    Science.gov (United States)

    Konda Gokuldoss, Prashanth; Kolla, Sri; Eckert, Jürgen

    2017-01-01

    Additive manufacturing (AM), also known as 3D printing or rapid prototyping, is gaining increasing attention due to its ability to produce parts with added functionality and increased complexities in geometrical design, on top of the fact that it is theoretically possible to produce any shape without limitations. However, most of the research on additive manufacturing techniques are focused on the development of materials/process parameters/products design with different additive manufacturing processes such as selective laser melting, electron beam melting, or binder jetting. However, we do not have any guidelines that discuss the selection of the most suitable additive manufacturing process, depending on the material to be processed, the complexity of the parts to be produced, or the design considerations. Considering the very fact that no reports deal with this process selection, the present manuscript aims to discuss the different selection criteria that are to be considered, in order to select the best AM process (binder jetting/selective laser melting/electron beam melting) for fabricating a specific component with a defined set of material properties. PMID:28773031

  7. Additive Manufacturing Processes: Selective Laser Melting, Electron Beam Melting and Binder Jetting-Selection Guidelines.

    Science.gov (United States)

    Gokuldoss, Prashanth Konda; Kolla, Sri; Eckert, Jürgen

    2017-06-19

    Additive manufacturing (AM), also known as 3D printing or rapid prototyping, is gaining increasing attention due to its ability to produce parts with added functionality and increased complexities in geometrical design, on top of the fact that it is theoretically possible to produce any shape without limitations. However, most of the research on additive manufacturing techniques are focused on the development of materials/process parameters/products design with different additive manufacturing processes such as selective laser melting, electron beam melting, or binder jetting. However, we do not have any guidelines that discuss the selection of the most suitable additive manufacturing process, depending on the material to be processed, the complexity of the parts to be produced, or the design considerations. Considering the very fact that no reports deal with this process selection, the present manuscript aims to discuss the different selection criteria that are to be considered, in order to select the best AM process (binder jetting/selective laser melting/electron beam melting) for fabricating a specific component with a defined set of material properties.

  8. Do cracks melt their way through solids?

    International Nuclear Information System (INIS)

    Okamoto, P. R.

    1998-01-01

    Real-time, in situ fracture studies in the high-voltage electron microscope (HVEM) show that microscopically thin regions of amorphous NiTi form ahead of moving crack tips in the B2-NiTi intermetallic compound during tensile straining at temperatures equal to or below 600K. The upper cutoff temperature of 600K for this stress-induced melting (or amorphization) is identical to the upper cutoff temperatures reported in the literature for both heavy-ion-induced amorphization of the intermetallic NiTi and ion-beam-mixing-induced amorphization of Ni and Ti multilayer. These results, together with the fact that the higher crystallization temperatures (∼800K)of unrelaxed amorphous NiTi alloys obtained by rapid quenching can also be reduced to, but not lower than 600K, by heavy-ion irradiation, strongly suggest that structural relaxation processes enhanced or induced by dynamic atomic disordering allow the formation of a unique, fully-relaxed glassy state which is characterized by a unique isothermal crystallization temperature. We believe that this unique temperature is the Kauzmann glass-transition temperature, corresponding to the ideal glass having the same entropy as the crystalline state. As the glassy state with the lowest global free energy, the preferential formation of this ideal glass by disorder-induced amorphization processes can be understood as the most energetically-favored, kinetically-constrained melting response of crystalline materials driven far from equilibrium at low temperatures

  9. Molecular thermodynamics of polymer melts at interfaces

    International Nuclear Information System (INIS)

    Theodorou, D.N.

    1988-09-01

    A lattice model is developed for the prediction of structure and thermodynamic properties at free polymer melt surfaces and polymer melt/solid interfaces. Density variations in the interfacial region are taken into account by introducing voids in the lattice, in the spirit of the equation of state theory of Sanchez and Lacombe. Intramolecular energy (chain stiffness) effects are explicitly incorporated. The model is derived through a rigorous statistical mechanical and thermodynamic analysis, which is based on the concept of availability. Two cases are considered: ''full equilibrium,'' whereby the interfacial polymer is taken as free to exchange heat, work and mass with a bulk polymer phase at given temperature and pressure; and ''restricted equilibrium,'' whereby a thin polymer film is allowed to equilibrate locally in response to ambient temperature and pressure, but in which chains do not necessarily have the same chemical potential as in the unconstrained bulk. Techniques are developed for calculating surface tension, adhesion tension, density profiles, chain shape, bond orientation, as well as the distribution of segments of various orders in the interfacial region. 28 refs., 6 figs

  10. Melting curve of materials: theory versus experiments

    International Nuclear Information System (INIS)

    Alfe, D; Vocadlo, L; Price, G D; Gillan, M J

    2004-01-01

    A number of melting curves of various materials have recently been measured experimentally and calculated theoretically, but the agreement between different groups is not always good. We discuss here some of the problems which may arise in both experiments and theory. We also report the melting curves of Fe and Al calculated recently using quantum mechanics techniques, based on density functional theory with generalized gradient approximations. For Al our results are in very good agreement with both low pressure diamond-anvil-cell experiments (Boehler and Ross 1997 Earth Planet. Sci. Lett. 153 223, Haenstroem and Lazor 2000 J. Alloys Compounds 305 209) and high pressure shock wave experiments (Shaner et al 1984 High Pressure in Science and Technology ed Homan et al (Amsterdam: North-Holland) p 137). For Fe our results agree with the shock wave experiments of Brown and McQueen (1986 J. Geophys. Res. 91 7485) and Nguyen and Holmes (2000 AIP Shock Compression of Condensed Matter 505 81) and the recent diamond-anvil-cell experiments of Shen et al (1998 Geophys. Res. Lett. 25 373). Our results are at variance with the recent calculations of Laio et al (2000 Science 287 1027) and, to a lesser extent, with the calculations of Belonoshko et al (2000 Phys. Rev. Lett. 84 3638). The reasons for these disagreements are discussed

  11. Proton NMR relaxation in hydrous melts

    International Nuclear Information System (INIS)

    Braunstein, J.; Bacarella, A.L.; Benjamin, B.M.; Brown, L.L.; Girard, C.

    1976-01-01

    Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120 0 C. Although measured in different temperature ranges, spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd 2+ . At temperatures near 50 0 C, mean Arrhenius coefficients Δ H/sub T 1 / (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T 1 and T 2 in Ca(NO 3 ) 2 -2.8 H 2 O between -4 and 120 0 C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T 0 ) of 225 0 K, close to the value of T 0 for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

  12. Synthesis of ammonia using sodium melt.

    Science.gov (United States)

    Kawamura, Fumio; Taniguchi, Takashi

    2017-09-14

    Research into inexpensive ammonia synthesis has increased recently because ammonia can be used as a hydrogen carrier or as a next generation fuel which does not emit CO 2 . Furthermore, improving the efficiency of ammonia synthesis is necessary, because current synthesis methods emit significant amounts of CO 2 . To achieve these goals, catalysts that can effectively reduce the synthesis temperature and pressure, relative to those required in the Haber-Bosch process, are required. Although several catalysts and novel ammonia synthesis methods have been developed previously, expensive materials or low conversion efficiency have prevented the displacement of the Haber-Bosch process. Herein, we present novel ammonia synthesis route using a Na-melt as a catalyst. Using this route, ammonia can be synthesized using a simple process in which H 2 -N 2 mixed gas passes through the Na-melt at 500-590 °C under atmospheric pressure. Nitrogen molecules dissociated by reaction with sodium then react with hydrogen, resulting in the formation of ammonia. Because of the high catalytic efficiency and low-cost of this molten-Na catalyst, it provides new opportunities for the inexpensive synthesis of ammonia and the utilization of ammonia as an energy carrier and next generation fuel.

  13. Dynamics and Melting of Finite Plasma Crystals

    Science.gov (United States)

    Ludwig, Patrick; K"Ahlert, Hanno; Baumgartner, Henning; Thomsen, Hauke; Bonitz, Michael

    2009-11-01

    Interacting few-particle systems in external trapping potentials are of strong current interest since they allow to realize and control strong correlation and quantum effects [1]. Here, we present our recent results on the structural and thermodynamic properties of the crystal-like Wigner phase of complex plasma confined in a 3D harmonic potential. We discuss the linear response of the strongly correlated system to external excitations, which can be described in terms of normal modes [2]. By means of first-principle simulations the details of the melting phase transitions of these mesoscopic systems are systematically analysed with the melting temperatures being determined by a modified Lindemann parameter for the pair distance fluctuations [3]. The critical temperatures turn out to be utmost sensitive to finite size effects (i.e., the exact particle number), and form of the (screened) interaction potential.[4pt] [1] PhD Thesis, P. Ludwig, U Rostock (2008)[0pt] [2] C. Henning et al., J. Phys. A 42, 214023 (2009)[0pt] [3] B"oning et al., Phys. Rev. Lett. 100, 113401 (2008)

  14. Detection of structural heterogeneity of glass melts

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2004-01-01

    The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One is the hyp......The structural heterogeneity of both supercooled liquid and molten states of silicate has been studied using calorimetric method. The objects of this study are basaltic glasses and liquids. Two experimental approaches are taken to detect the structural heterogeneity of the liquids. One...... is the hyperquench-anneal-calorimetric scan approach, by which the structural information of a basaltic supercooled liquid and three binary silicate liquids is acquired. Another is the calorimetrically repeated up- and downscanning approach, by which the structural heterogeneity, the intermediate range order...... is discussed. The ordered structure of glass melts above the liquidus temperature is indirectly characterized by use of X-ray diffraction method. The new approaches are of importance for monitoring the glass melting and forming process and for improving the physical properties of glasses and glass fibers....

  15. Simulation of steam explosion in stratified melt-coolant configuration

    International Nuclear Information System (INIS)

    Leskovar, Matjaž; Centrih, Vasilij; Uršič, Mitja

    2016-01-01

    Highlights: • Strong steam explosions may develop spontaneously in stratified configurations. • Considerable melt-coolant premixed layer formed in subcooled water with hot melts. • Analysis with MC3D code provided insight into stratified steam explosion phenomenon. • Up to 25% of poured melt was mixed with water and available for steam explosion. • Better instrumented experiments needed to determine dominant mixing process. - Abstract: A steam explosion is an energetic fuel coolant interaction process, which may occur during a severe reactor accident when the molten core comes into contact with the coolant water. In nuclear reactor safety analyses steam explosions are primarily considered in melt jet-coolant pool configurations where sufficiently deep coolant pool conditions provide complete jet breakup and efficient premixture formation. Stratified melt-coolant configurations, i.e. a molten melt layer below a coolant layer, were up to now believed as being unable to generate strong explosive interactions. Based on the hypothesis that there are no interfacial instabilities in a stratified configuration it was assumed that the amount of melt in the premixture is insufficient to produce strong explosions. However, the recently performed experiments in the PULiMS and SES (KTH, Sweden) facilities with oxidic corium simulants revealed that strong steam explosions may develop spontaneously also in stratified melt-coolant configurations, where with high temperature melts and subcooled water conditions a considerable melt-coolant premixed layer is formed. In the article, the performed study of steam explosions in a stratified melt-coolant configuration in PULiMS like conditions is presented. The goal of this analytical work is to supplement the experimental activities within the PULiMS research program by addressing the key questions, especially regarding the explosivity of the formed premixed layer and the mechanisms responsible for the melt-water mixing. To

  16. Ferric iron partitioning between pyroxene and melt during partial melting of the Earth's upper mantle

    Science.gov (United States)

    Rudra, A.; Hirschmann, M. M.

    2017-12-01

    The oxidation state of the Earth's mantle influences melt production, volatile behavior, partitioning of key trace elements and possible saturation of alloy at depth. Average Fe3+/FeT ratios in MORBs indicate oxygen fugacitiy of the source regions is close to QFM, in contrast to a 3 log unit variation of fO2 recorded by abyssal peridotites. Quantification of the relationship between basalt and source Fe3+/FeT, oxygen fugacity, and melting requires constraints on Fe3+ partitioning between melt and mantle minerals and in particular the principal Fe3+ host, pyroxene. McCanta et al. (2004) investigated valence dependent partitioning of Fe between Martian ferroan pigeonites and melt, but behavior in terrestrial pyroxene compositions relevant to MORB petrogenesis has not been investigated. We are conducting 1 atm controlled fO2 experiments over 4 log unit variation of fO2 between ΔQFM = 2.5 to -1.5 to grow pyroxenes of variable tetrahedral and octahedral cationic population from andesitic melts of varying Mg#, alumina and alkali content. Dynamic crystallization technique facilitates growth of pyroxene crystals (100-200 um) that EPMA analyses show to be compositionally homogeneous and in equilibrium with the melt. Fe3+/FeT ratio of the synthetic pyroxenes have been analyzed by XAFS spectroscopy at the APS (GSECARS) synchrotron. To quantify the x-ray anisotropy in pyroxenes, we collected Fe K-edge XAFS spectra of oriented natural single crystals for a wide range compositions whose Fe3+/FeT ratios we determined by Mossbauer spectroscopy. We have collected both XANES and EXAFS spectral regions spanning from 7020-7220 eV to explore predictive capabilities of different spectral regions about ferric iron concentration and site occupancy. Our results will document the Fe3+ compatibility in pyroxenes of different compositions under a variety of fO2 conditions, which in turn will better constrain the interrelationship between mantle redox and melting.

  17. Premixing and steam explosion phenomena in the tests with stratified melt-coolant configuration and binary oxidic melt simulant materials

    Energy Technology Data Exchange (ETDEWEB)

    Kudinov, Pavel, E-mail: pavel@safety.sci.kth.se; Grishchenko, Dmitry, E-mail: dmitry@safety.sci.kth.se; Konovalenko, Alexander, E-mail: kono@kth.se; Karbojian, Aram, E-mail: karbojan@kth.se

    2017-04-01

    Highlights: • Steam explosion in stratified melt-coolant configuration is studied experimentally. • Different binary oxidic melt simulant materials were used. • Five spontaneous steam explosions were observed. • Instability of melt-coolant interface and formation of premixing layer was observed. • Explosion strength is influenced by melt superheat and water subcooling. - Abstract: Steam explosion phenomena in stratified melt-coolant configuration are considered in this paper. Liquid corium layer covered by water on top can be formed in severe accident scenarios with (i) vessel failure and release of corium melt into a relatively shallow water pool; (ii) with top flooding of corium melt layer. In previous assessments of potential energetics in stratified melt-coolant configuration, it was assumed that melt and coolant are separated by a stable vapor film and there is no premixing prior to the shock wave propagation. This assumption was instrumental for concluding that the amount of energy that can be released in such configuration is not of safety importance. However, several recent experiments carried out in Pouring and Under-water Liquid Melt Spreading (PULiMS) facility with up to 78 kg of binary oxidic corium simulants mixtures have resulted in spontaneous explosions with relatively high conversion ratios (order of one percent). The instability of the melt-coolant interface, melt splashes and formation of premixing layer were observed in the tests. In this work, we present results of experiments carried out more recently in steam explosion in stratified melt-coolant configuration (SES) facility in order to shed some light on the premixing phenomena and assess the influence of the test conditions on the steam explosion energetics.

  18. Melt-processing method for radioactive solid wastes

    International Nuclear Information System (INIS)

    Kobayashi, Hiroaki

    1998-01-01

    Radioactive solid wastes are charged into a water-cooled type cold crucible induction melting furnace disposed in high frequency coils, and high frequency currents are supplied to high frequency coils which surround the melting furnace to melt the solid wastes by induction-heating. In this case, heat plasmas are jetted from above the solid wastes to the solid wastes to conduct initial heating to melt a portion of the solid wastes. Then, high frequency currents are supplied to the high frequency coils to conduct induction heating. According to this method, even when waste components of various kinds of materials are mixed, a portion of the solid wastes in the induction melting furnace can be melted by the initial heating by jetting heat plasmas irrespective of the kinds and the electroconductivity of the materials of the solid wastes. With such procedures, entire solid wastes in the furnace can be formed into a molten state uniformly and rapidly. (T.M.)

  19. The matter of probability controlling melting of nuclear ship reactor

    International Nuclear Information System (INIS)

    Pihowicz, W.; Sobczyk, S.

    2008-01-01

    In the first part of this work beside description of split power, power of radioactivity disintegration and afterpower and its ability to extinguish, the genera condition of melting nuclear reactor core and its detailed versions were described. This paper also include the description of consequences melting nuclear reactor core both in case of stationary and mobile (ship) reactor and underline substantial differences. Next, fulfilled with succeed, control under melting of stationary nuclear reactor core was characterized.The middle part describe author's idea of controlling melting of nuclear ship reactor core. It is based on: - the suggestion of prevention pressure's untightness in safety tank of nuclear ship reactor by '' corium '' - and the suggestion of preventing walls of this tank from melting by '' corium ''. In the end the technological and construction barriers of the prevention from melting nuclear ship reactor and draw conclusions was presented. (author)

  20. Microstructures define melting of molybdenum at high pressures

    Science.gov (United States)

    Hrubiak, Rostislav; Meng, Yue; Shen, Guoyin

    2017-03-01

    High-pressure melting anchors the phase diagram of a material, revealing the effect of pressure on the breakdown of the ordering of atoms in the solid. An important case is molybdenum, which has long been speculated to undergo an exceptionally steep increase in melting temperature when compressed. On the other hand, previous experiments showed nearly constant melting temperature as a function of pressure, in large discrepancy with theoretical expectations. Here we report a high-slope melting curve in molybdenum by synchrotron X-ray diffraction analysis of crystalline microstructures, generated by heating and subsequently rapidly quenching samples in a laser-heated diamond anvil cell. Distinct microstructural changes, observed at pressures up to 130 gigapascals, appear exclusively after melting, thus offering a reliable melting criterion. In addition, our study reveals a previously unsuspected transition in molybdenum at high pressure and high temperature, which yields highly textured body-centred cubic nanograins above a transition temperature.

  1. Shallow Melt Apparatus for Semicontinuous Czochralski Crystal Growth

    Science.gov (United States)

    Wang, T.; Ciszek, T. F.

    2006-01-10

    In a single crystal pulling apparatus for providing a Czochralski crystal growth process, the improvement of a shallow melt crucible (20) to eliminate the necessity supplying a large quantity of feed stock materials that had to be preloaded in a deep crucible to grow a large ingot, comprising a gas tight container a crucible with a deepened periphery (25) to prevent snapping of a shallow melt and reduce turbulent melt convection; source supply means for adding source material to the semiconductor melt; a double barrier (23) to minimize heat transfer between the deepened periphery (25) and the shallow melt in the growth compartment; offset holes (24) in the double barrier (23) to increase melt travel length between the deepened periphery (25) and the shallow growth compartment; and the interface heater/heat sink (22) to control the interface shape and crystal growth rate.

  2. Influence of gas-generation on melt/concrete interaction

    International Nuclear Information System (INIS)

    Powers, D.A.

    1979-01-01

    Gases formed during the interaction of a high-temperature melt with concrete are shown to stem from the thermal dehydration and decarboxylation of the concrete. The kinetics of these decomposition reactions are described. Gases within the melt cause an apparent swelling of the melt. The observed swelling is not easily correlated to the rate of gas evolution. Metallic melts cause CO 2 /CO and H 2 O liberated from the melt to be reduced to CO and hydrogen. When these gases escape from the melt they assist in aerosol formation. As the gases cool they react along a pathway whose oxygen fugacity is apparently buffered by the iron-Wuestite equilibrium. Methane is a product of the gas-phase reaction. (orig./HP) [de

  3. Finite size melting of spherical solid-liquid aluminium interfaces

    DEFF Research Database (Denmark)

    Chang, J.; Johnson, Erik; Sakai, T.

    2009-01-01

    We have investigated the melting of nano-sized cone shaped aluminium needles coated with amorphous carbon using transmission electron microscopy. The interface between solid and liquid aluminium was found to have spherical topology. For needles with fixed apex angle, the depressed melting tempera...... to the conclusion that the depressed melting temperature is not controlled solely by the inverse radius 1/R. Instead, we found a direct relation between the depressed melting temperature and the ratio between the solid-liquid interface area and the molten volume.......We have investigated the melting of nano-sized cone shaped aluminium needles coated with amorphous carbon using transmission electron microscopy. The interface between solid and liquid aluminium was found to have spherical topology. For needles with fixed apex angle, the depressed melting...

  4. Effects of surface shape on the geometry and surface topography of the melt pool in low-power density laser melting

    KAUST Repository

    Kim, Youngdeuk; Kim, Wooseung

    2011-01-01

    The quantitative correlations between workpiece volume and melt pool geometry, as well as the flow and thermal features of the melt pool are established. Thermocapillary convections in melt pool with a deformable free surface are investigated

  5. The End of Points

    Science.gov (United States)

    Feldman, Jo

    2018-01-01

    Have teachers become too dependent on points? This article explores educators' dependency on their points systems, and the ways that points can distract teachers from really analyzing students' capabilities and achievements. Feldman argues that using a more subjective grading system can help illuminate crucial information about students and what…

  6. Demerit points systems.

    NARCIS (Netherlands)

    2006-01-01

    In 2012, 21 of the 27 EU Member States had some form of demerit points system. In theory, demerit points systems contribute to road safety through three mechanisms: 1) prevention of unsafe behaviour through the risk of receiving penalty points, 2) selection and suspension of the most frequent

  7. Optimization of the ultrasonic processing in a melt flow

    OpenAIRE

    Tzanakis, I; Lebon, GSB; Eskin, DG; Pericleous, K

    2016-01-01

    Ultrasonic cavitation treatment of melt significantly improves the downstream properties and quality of conventional and advanced metallic materials. However, the transfer of this technology to treating large melt volumes has been hindered by a lack of fundamental knowledge, allowing for the ultrasonic processing in the melt flow. In this study, we present the results of experimental validation of an advanced numerical model applied to the acoustic cavitation treatment of liquid aluminum duri...

  8. Melting of the Abrikosov flux lattice in anisotropic superconductors

    Science.gov (United States)

    Beck, R. G.; Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.; Kogan, V. G.

    1992-01-01

    It has been proposed that the Abrikosov flux lattice in high-Tc superconductors is melted over a significant fraction of the phase diagram. A thermodynamic argument is provided which establishes that the angular dependence of the melting temperature is controlled by the superconducting mass anisotropy. Using a low-frequency torsional-oscillator technique, this relationship has been tested in untwinned single-crystal YBa2Cu3O(7-delta). The results offer decisive support for the melting proposal.

  9. Retrograde Melting and Internal Liquid Gettering in Silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hudelson, Steve; Newman, Bonna K.; Bernardis, Sarah; Fenning, David P.; Bertoni, Mariana I.; Marcus, Matthew A.; Fakra, Sirine C.; Lai, Barry; Buonassisi, Tonio

    2011-07-01

    Retrograde melting (melting upon cooling) is observed in silicon doped with 3d transition metals, via synchrotron-based temperature-dependent X-ray microprobe measurements. Liquid metal-silicon droplets formed via retrograde melting act as efficient sinks for metal impurities dissolved within the silicon matrix. Cooling results in decomposition of the homogeneous liquid phase into solid multiple-metal alloy precipitates. These phenomena represent a novel pathway for engineering impurities in semiconductor-based systems.

  10. Differential melt scaling for oblique impacts on terrestrial planets

    Science.gov (United States)

    Abramov, Oleg; Wong, Stephanie M. Wong; Kring, David A. Kring

    2012-01-01

    Analytical estimates of melt volumes produced by a given projectile and contained in a given impact crater are derived as a function of impact velocity, impact angle, planetary gravity, target and projectile densities, and specific internal energy of melting. Applications to impact events and impact craters on the Earth, Moon, and Mars are demonstrated and discussed. The most probable oblique impact (45°) produces ∼1.6 times less melt volume than a vertical impact, and ∼1.6 and 3.7 times more melt volume than impacts with 30° and 15° trajectories, respectively. The melt volume for a particular crater diameter increases with planetary gravity, so a crater on Earth should have more melt than similar-size craters on Mars and the Moon. The melt volume for a particular projectile diameter does not depend on gravity, but has a strong dependence on impact velocity, so the melt generated by a given projectile on the Moon is significantly larger than on Mars. Higher surface temperatures and geothermal gradients increase melt production, as do lower energies of melting. Collectively, the results imply thinner central melt sheets and a smaller proportion of melt particles in impact breccias on the Moon and Mars than on Earth. These effects are illustrated in a comparison of the Chicxulub crater on Earth, linked to the Cretaceous–Tertiary mass extinction, Gusev crater on Mars, where the Mars Exploration Rover Spirit landed, and Tsiolkovsky crater on the Moon. The results are comparable to those obtained from field and spacecraft observations, other analytical expressions, and hydrocode simulations.

  11. Electron beam melting state-of-the-art 1984

    International Nuclear Information System (INIS)

    Bakish, R.

    1984-01-01

    In 1984 electron beam melting and refining appear poised for an important new growth phase. The driving force for this phase is improved production economics made possible by technological advances. There is also a new and exciting growth application for electron beam melting: its use for surface properties beneficiation. This article is based in part on the content of the Conference on Electron Beam Melting and Refining, The State-of-the-Art 1983, held in November 1983 in Reno, Nevada

  12. Melting and Pressure-Induced Amorphization of Quartz

    OpenAIRE

    Badro, James; Gillet, Philippe; Barrat, Jean-Louis

    1997-01-01

    It has recently been shown that amorphization and melting of ice were intimately linked. In this letter, we infer from molecular dynamics simulations on the SiO2 system that the extension of the quartz melting line in the metastable pressure-temperature domain is the pressure-induced amorphization line. It seems therefore likely that melting is the physical phenomenon responsible for pressure induced amorphization. Moreover, we show that the structure of a "pressure glass" is similar to that ...

  13. Computer-integrated electric-arc melting process control system

    OpenAIRE

    Дёмин, Дмитрий Александрович

    2014-01-01

    Developing common principles of completing melting process automation systems with hardware and creating on their basis rational choices of computer- integrated electricarc melting control systems is an actual task since it allows a comprehensive approach to the issue of modernizing melting sites of workshops. This approach allows to form the computer-integrated electric-arc furnace control system as part of a queuing system “electric-arc furnace - foundry conveyor” and consider, when taking ...

  14. Erosion of melt layers developed during a plasma disruption

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, A.; Konkashbaev, I.

    1995-01-01

    Material erosion of plasma-facing components during a tokamak disruption is a serious problem that limits reactor operation and economical reactor lifetime. In particular, metallic low-Z components such as Be will be subjected to severe melting during disruptions and edge localized modes (ELMs). Loss of the developed melt layer will critically shorten the lifetime of these components, severely contaminate the plasma, and seriously inhibit successful and reliable operation of the reactor. In this study mechanisms responsible for melt-layer loss during a disruption are modeled and evaluated. Implications of melt-layer loss on the performance of metallic facing components in the reactor environment are discussed. (orig.)

  15. The coupled response to slope-dependent basal melting

    Science.gov (United States)

    Little, C. M.; Goldberg, D. N.; Sergienko, O. V.; Gnanadesikan, A.

    2009-12-01

    Ice shelf basal melting is likely to be strongly controlled by basal slope. If ice shelves steepen in response to intensified melting, it suggests instability in the coupled ice-ocean system. The dynamic response of ice shelves governs what stable morphologies are possible, and thus the influence of melting on buttressing and grounding line migration. Simulations performed using a 3-D ocean model indicate that a simple form of slope-dependent melting is robust under more complex oceanographic conditions. Here we utilize this parameterization to investigate the shape and grounding line evolution of ice shelves, using a shallow-shelf approximation-based model that includes lateral drag. The distribution of melting substantially affects the shape and aspect ratio of unbuttressed ice shelves. Slope-dependent melting thins the ice shelf near the grounding line, reducing velocities throughout the shelf. Sharp ice thickness gradients evolve at high melting rates, yet grounding lines remain static. In foredeepened, buttressed ice shelves, changes in grounding line flux allow two additional options: stable or unstable retreat. Under some conditions, slope-dependent melting results in stable configurations even at high melt rates.

  16. The Melting Curve and Premelting of MgO

    OpenAIRE

    Cohen, R. E.; Weitz, J. S.

    1996-01-01

    The melting curve for MgO was obtained using molecular dynamics and a non-empirical, many-body potential. We also studied premelting effects by computing the dynamical structure factor in the crystal on approach to melting. The melting curve simulations were performed with periodic boundary conditions with cells up to 512 atoms using the ab-initio Variational Induced Breathing (VIB) model. The melting curve was obtained by computing $% \\Delta H_m$ and $\\Delta V_m$ and integrating the Clapeyro...

  17. The melting treatment of bulk scrap from decommissioning

    International Nuclear Information System (INIS)

    Deng Junxian; Deng Feng

    2014-01-01

    Large amount of radioactive scrap will come out from reactor decommissioning. The melting treatment can be used for the volume reduction, the recycle and reuse of the radioactive scrap to reduce the mass of the radioactive waste disposal and to reuse most of the metal. The melting treatment has the advantages in volume reduction, conditioning, radionuclide confinement, reduction of radioactivity concentration, easy monitoring of radioactivity; and the effective of decontamination for several radionuclide. Therefore to use the melting technology other decontamination technology should be performed ahead, the decontamination effect of the melting should be predicted, the utility of recycle and reuse should be defined, and the secondary waste should be controlled effectively. (authors)

  18. Erosion of melt layers developed during a plasma disruption

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, A.; Konkashbaev, I.

    1994-08-01

    Material erosion of plasma-facing components during a tokamak disruption is a serious problem that limits reactor operation and economical reactor lifetime. In particular, metallic low-Z components such as Be will be subjected to severe melting during disruptions and edge localized models (ELMs). Loss of the developed melt layer will critically shorten the lifetime of these components, severely contaminate the plasma, and seriously inhibit successful and reliable operation of the reactor. In this study mechanisms responsible for melt-layer loss during a disruption are modeled and evaluated. Implications of melt-layer loss on the performance of metallic facing components in the reactor environment are discussed

  19. Greenland ice sheet melt from MODIS and associated atmospheric variability.

    Science.gov (United States)

    Häkkinen, Sirpa; Hall, Dorothy K; Shuman, Christopher A; Worthen, Denise L; DiGirolamo, Nicolo E

    2014-03-16

    Daily June-July melt fraction variations over the Greenland ice sheet (GIS) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) (2000-2013) are associated with atmospheric blocking forming an omega-shape ridge over the GIS at 500 hPa height. Blocking activity with a range of time scales, from synoptic waves breaking poleward (days) to full-fledged blocks (≥5 days), brings warm subtropical air masses over the GIS controlling daily surface temperatures and melt. The temperature anomaly of these subtropical air mass intrusions is also important for melting. Based on the years with the greatest melt (2002 and 2012) during the MODIS era, the area-average temperature anomaly of 2 standard deviations above the 14 year June-July mean results in a melt fraction of 40% or more. Though the summer of 2007 had the most blocking days, atmospheric temperature anomalies were too small to instigate extreme melting. Short-term atmospheric blocking over Greenland contributes to melt episodesAssociated temperature anomalies are equally important for the meltDuration and strength of blocking events contribute to surface melt intensity.

  20. Induction melting for volume reduction of metallic TRU wastes

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.; Montgomery, D.R.; Katayama, Y.B.; Ross, W.A.

    1986-01-01

    Volume reduction of metallic transuranic wastes offers economic and safety incentives for treatment of wastes generated at a hypothetical commercial fuel reprocessing facility. Induction melting has been identified as the preferred process for volume reduction of spent fuel hulls, fuel assembly hardware, and failed equipment from a reprocessing plant. Bench-scale melting of Zircaloy and stainless steel mixtures has been successfully conducted in a graphite crucible inside a large vacuum chamber. A low-melting-temperature alloy forms that has demonstrated excellent leach resistance. The alloy can be used to encapsulate other metallic wastes that cannot be melted using the existing equipment design