WorldWideScience

Sample records for crystal melting endotherm

  1. 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)

  2. 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.

  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. Melting temperature evolution of non-reorganized crystals. Poly(3-hydroxybutyrate)

    International Nuclear Information System (INIS)

    Righetti, Maria Cristina; Di Lorenzo, Maria Laura

    2011-01-01

    In the present study the correlation between the melting behaviour of poly(3-hydroxybutyrate) (PHB) original, non-reorganized crystals and the crystallinity increase during isothermal crystallization is presented and discussed. Since the reorganization processes modify the melting curve of original crystals, it is necessary to prevent and hinder all the processes that influence and increase the lamellar thickness. PHB exhibits melting/recrystallization on heating, the occurring of lamellar thickening in the solid state being excluded. The first step of the study was the identification of the scanning rate which inhibits PHB recrystallization at sufficiently high T c . For the extrapolated onset and peak temperatures of the main melting endotherm, which is connected to fusion of dominant lamellae, a double dependence on the crystallization time was found. The crystallization time at which T onset and T peak change their trends was found to correspond to the spherulite impingement time, so that the two different dependencies were put in relation with primary and secondary crystallizations respectively. The increase of both T onset and T peak at high crystallization times after spherulite impingement was considered an effect due to crystal superheating and an indication of a stabilization process of the crystalline phase. Such stabilization, which produces an increase of the melting temperature, is probably connected with the volume filling that occurs after spherulite impingement.

  5. Morphology, melting behavior, and non-isothermal crystallization of poly(butylene terephthalate)/poly(ethylene-co-methacrylic acid) blends

    International Nuclear Information System (INIS)

    Huang, J.-W.; Wen, Y.-L.; Kang, C.-C.; Yeh, M.-Y.; Wen, S.-B.

    2007-01-01

    The morphology, melting behavior, and non-isothermal crystallization of poly(butylene terephthalate) (PBT) and poly(ethylene-co-methacrylic acid) (PEMA) blends were studied with scanning electron microscopy, X-ray diffraction and differential scanning calorimetry (DSC). PEMA forms immiscible, yet compatible, blends with PBT. Subsequent DSC scans on melt-crystallized samples exhibited two melting endotherms (T mI and T mII ). The presence of PEMA would facilitate the recrystallization during heating scan and retard PBT molecular chains to form a perfect crystal in cooling crystallization. The dispersion phases of molten PEMA acts as nucleating agents to enhance the crystallization rate of PBT. The solidified PBT could act as nucleating agents to enhance the crystallization of PEMA, but also retard the molecular mobility to reduce crystallization rate. The U* and K g of Hoffman-Lauritzen theory were also determined by Vyazovkin's methods to support the interpretation

  6. 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....

  7. 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.

  8. Mutual interaction between high and low stereo-regularity components for crystallization and melting behaviors of polypropylene blend fibers

    Science.gov (United States)

    Kawai, Kouya; Kohri, Youhei; Takarada, Wataru; Takebe, Tomoaki; Kanai, Toshitaka; Kikutani, Takeshi

    2016-03-01

    Crystallization and melting behaviors of blend fibers of two types of polypropylene (PP), i.e. high stereo-regularity/high molecular weight PP (HPP) and low stereo-regularity/low molecular weight PP (LPP), was investigated. Blend fibers consisting of various HPP/LPP compositions were prepared through the melt spinning process. Differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC) and wide-angle X-ray diffraction (WAXD) analysis were applied for clarifying the crystallization and melting behaviors of individual components. In the DSC measurement of blend fibers with high LPP composition, continuous endothermic heat was detected between the melting peaks of LPP at around 40 °C and that of HPP at around 160 °C. Such endothermic heat was more distinct for the blend fibers with higher LPP composition indicating that the melting of LPP in the heating process was hindered because of the presence of HPP crystals. On the other hand, heat of crystallization was detected at around 90 °C in the case of blend fibers with LPP content of 30 to 70 wt%, indicating that the crystallization of HPP component was taking place during the heating of as-spun blend fibers in the DSC measurement. Through the TMDSC analysis, re-organization of the crystalline structure through the simultaneous melting and re-crystallization was detected in the cases of HPP and blend fibers, whereas re-crystallization was not detected during the melting of LPP fibers. In the WAXD analysis during the heating of fibers, amount of a-form crystal was almost constant up to the melting in the case of single component HPP fibers, whereas there was a distinct increase of the intensity of crystalline reflections from around 100 °C, right after the melting of LPP in the case of blend fibers. These results suggested that the crystallization of HPP in the spinning process as well as during the conditioning process after spinning was hindered by the presence of LPP.

  9. Mutual interaction between high and low stereo-regularity components for crystallization and melting behaviors of polypropylene blend fibers

    International Nuclear Information System (INIS)

    Kawai, Kouya; Takarada, Wataru; Kikutani, Takeshi; Kohri, Youhei; Takebe, Tomoaki; Kanai, Toshitaka

    2016-01-01

    Crystallization and melting behaviors of blend fibers of two types of polypropylene (PP), i.e. high stereo-regularity/high molecular weight PP (HPP) and low stereo-regularity/low molecular weight PP (LPP), was investigated. Blend fibers consisting of various HPP/LPP compositions were prepared through the melt spinning process. Differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC) and wide-angle X-ray diffraction (WAXD) analysis were applied for clarifying the crystallization and melting behaviors of individual components. In the DSC measurement of blend fibers with high LPP composition, continuous endothermic heat was detected between the melting peaks of LPP at around 40 °C and that of HPP at around 160 °C. Such endothermic heat was more distinct for the blend fibers with higher LPP composition indicating that the melting of LPP in the heating process was hindered because of the presence of HPP crystals. On the other hand, heat of crystallization was detected at around 90 °C in the case of blend fibers with LPP content of 30 to 70 wt%, indicating that the crystallization of HPP component was taking place during the heating of as-spun blend fibers in the DSC measurement. Through the TMDSC analysis, re-organization of the crystalline structure through the simultaneous melting and re-crystallization was detected in the cases of HPP and blend fibers, whereas re-crystallization was not detected during the melting of LPP fibers. In the WAXD analysis during the heating of fibers, amount of a-form crystal was almost constant up to the melting in the case of single component HPP fibers, whereas there was a distinct increase of the intensity of crystalline reflections from around 100 °C, right after the melting of LPP in the case of blend fibers. These results suggested that the crystallization of HPP in the spinning process as well as during the conditioning process after spinning was hindered by the presence of LPP.

  10. Mutual interaction between high and low stereo-regularity components for crystallization and melting behaviors of polypropylene blend fibers

    Energy Technology Data Exchange (ETDEWEB)

    Kawai, Kouya; Takarada, Wataru; Kikutani, Takeshi, E-mail: kikutani.t.aa@m.titech.ac.jp [Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Kohri, Youhei; Takebe, Tomoaki [Performance Materials Laboratories, Idemitsu Kosan Co.,Ltd. (Japan); Kanai, Toshitaka [KT Polymer (Japan)

    2016-03-09

    Crystallization and melting behaviors of blend fibers of two types of polypropylene (PP), i.e. high stereo-regularity/high molecular weight PP (HPP) and low stereo-regularity/low molecular weight PP (LPP), was investigated. Blend fibers consisting of various HPP/LPP compositions were prepared through the melt spinning process. Differential scanning calorimetry (DSC), temperature modulated DSC (TMDSC) and wide-angle X-ray diffraction (WAXD) analysis were applied for clarifying the crystallization and melting behaviors of individual components. In the DSC measurement of blend fibers with high LPP composition, continuous endothermic heat was detected between the melting peaks of LPP at around 40 °C and that of HPP at around 160 °C. Such endothermic heat was more distinct for the blend fibers with higher LPP composition indicating that the melting of LPP in the heating process was hindered because of the presence of HPP crystals. On the other hand, heat of crystallization was detected at around 90 °C in the case of blend fibers with LPP content of 30 to 70 wt%, indicating that the crystallization of HPP component was taking place during the heating of as-spun blend fibers in the DSC measurement. Through the TMDSC analysis, re-organization of the crystalline structure through the simultaneous melting and re-crystallization was detected in the cases of HPP and blend fibers, whereas re-crystallization was not detected during the melting of LPP fibers. In the WAXD analysis during the heating of fibers, amount of a-form crystal was almost constant up to the melting in the case of single component HPP fibers, whereas there was a distinct increase of the intensity of crystalline reflections from around 100 °C, right after the melting of LPP in the case of blend fibers. These results suggested that the crystallization of HPP in the spinning process as well as during the conditioning process after spinning was hindered by the presence of LPP.

  11. 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)

  12. Unsolved problems of crystallization and melting of flexible macromolecules

    International Nuclear Information System (INIS)

    Wunderlich, B.

    1992-01-01

    The thermodynamics, kinetics, and computer simulations of crystallization and melting is discussed. The thermodynamics is shown to be well understood, although for many specific crystals not enough details for full description are available. Experiments on the crystallization kinetics of poly(ethylene) and poly(oxyethylene) in the presence of crystal nuclei as a function of molecular mass revealed that with increasing mass, the crystallization behavior deviates increasingly from that of small, rigid molecules. Instead of showing a continuously changing, linear crystallization rate with temperature through the equilibrium melting temperature, T m 0 , these flexible macromolecules show a region of practically zero crystallization rate between T m 0 and about (T m 0 - 15) K, creating a temperature region of metastability in the melt that cannot be broken by nucleation with pregrown crystals. Molecular Nucleation was proposed as a cooperative process to be of overriding importance for the description of polymer crystallization, and to be at the center of segregation of molecules of lower molecular mass by growing crystal fronts. Initial efforts to model sufficiently large crystals using Monte Carlo and molecular dynamics methods are presented. Some of the short-time intermediates in the melting, crystallization, and annealing processes seem to have little similarity to commonly assumed models of crystallization and melting and are presented as discussion topics

  13. 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.

  14. 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.

  15. Spent oxide fuel regeneration by crystallization in molybdate melts

    International Nuclear Information System (INIS)

    Ustinov, O.A.; Sukhanov, L.P.; Yakunin, S.A.

    2006-01-01

    Paper describes a procedure to regenerate spent oxide fuel by its crystallization in molybdate melts. Paper presents the process procedures to regenerate spent fuel of both fast and thermal neutron reactors. One analyzes the advantages of the elaborated procedure [ru

  16. Development and melt growth of novel scintillating halide crystals

    Science.gov (United States)

    Yoshikawa, Akira; Yokota, Yuui; Shoji, Yasuhiro; Kral, Robert; Kamada, Kei; Kurosawa, Shunsuke; Ohashi, Yuji; Arakawa, Mototaka; Chani, Valery I.; Kochurikhin, Vladimir V.; Yamaji, Akihiro; Andrey, Medvedev; Nikl, Martin

    2017-12-01

    Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed.

  17. UHMW Ziegler–Natta polyethylene: Synthesis, crystallization, and melt behavior

    KAUST Repository

    Atiqullah, Muhammad

    2017-04-26

    The fabrication of normal and UHMW PE end-products involves melting and crystallization of the polymer. Therefore, the melt behavior and crystallization of as-synthesized UHMW PE, and NMW PE and E-1-hexene copolymer have been studied using a new nonisothermal crystallization model, Flory\\'s equilibrium theory and ethylene sequence length distribution concept (SLD), Gibbs–Thompson equation, and DSC experiments. By using this approach, the effects of MW, 1-hexene incorporation, ethylene SLD, the level of undercooling θ, and crystal surface free energy D on crystallite stability, relative crystallinity α, instantaneous crystallinity χ, the crystallization kinetic triplet, crystallization entropy, and lamellar thickness distribution (LTD) have been evaluated. Consequently, this study reports insightful new results, interpretations, and explanations regarding the melting and crystallization of the aforementioned polymers. The UHMW PE results significantly differ from the NMW PE and E-1-hexene copolymer ones. Ethylene sequences shorter than the so called minimum crystallizable ethylene sequence length, irrespective of E-1-hexene copolymer MW, can also crystallize. Additionally, the polymer preparation shows that the catalyst coordination environment and symmetry, as well as achiral ethylene versus prochiral α-olefin steric encumbrance and competitive diffusion affect the synthesis of UHMW PE, particularly the corresponding UHMW copolymers.

  18. Melting of anisotropic colloidal crystals in two dimensions

    International Nuclear Information System (INIS)

    Eisenmann, C; Keim, P; Gasser, U; Maret, G

    2004-01-01

    The crystal structure and melting transition of two-dimensional colloids interacting via an anisotropic magnetic dipole-dipole potential are studied. Anisotropy is achieved by tilting the external magnetic field inducing the dipole moments of the colloidal particles away from the direction perpendicular to the particle plane. We find a centred rectangular lattice and a two-step melting similar to the phase transitions of the corresponding isotropic crystals via a quasi-hexatic phase. The latter is broadened compared to the hexatic phase for isotropic interaction potential due to strengthening of orientational order

  19. Melting of anisotropic colloidal crystals in two dimensions

    Science.gov (United States)

    Eisenmann, C.; Keim, P.; Gasser, U.; Maret, G.

    2004-09-01

    The crystal structure and melting transition of two-dimensional colloids interacting via an anisotropic magnetic dipole-dipole potential are studied. Anisotropy is achieved by tilting the external magnetic field inducing the dipole moments of the colloidal particles away from the direction perpendicular to the particle plane. We find a centred rectangular lattice and a two-step melting similar to the phase transitions of the corresponding isotropic crystals via a quasi-hexatic phase. The latter is broadened compared to the hexatic phase for isotropic interaction potential due to strengthening of orientational order.

  20. Investigating the vortex melting phenomenon in BSCCO crystals ...

    Indian Academy of Sciences (India)

    reveal complex patterns in the formation and evolution of the vortex solid–liquid interface ... images of the melting process in a BSCCO crystal (Tc =90 K) of area 0.35×0.27 mm2 .... For example, at 20 Oe the valley in the form of an arc along.

  1. Iron single crystal growth from a lithium-rich melt

    Science.gov (United States)

    Fix, M.; Schumann, H.; Jantz, S. G.; Breitner, F. A.; Leineweber, A.; Jesche, A.

    2018-03-01

    α -Fe single crystals of rhombic dodecahedral habit were grown from a Li84N12Fe∼3 melt. Crystals of several millimeter along a side form at temperatures around T ≈ 800 ° C. Upon further cooling the growth competes with the formation of Fe-doped Li3N. The b.c.c. structure and good sample quality of α -Fe single crystals were confirmed by X-ray and electron diffraction as well as magnetization measurements and chemical analysis. A nitrogen concentration of 90 ppm was detected by means of carrier gas hot extraction. Scanning electron microscopy did not reveal any sign of iron nitride precipitates.

  2. Modeling and simulation of Si crystal growth from melt

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lijun; Liu, Xin; Li, Zaoyang [National Engineering Research Center for Fluid Machinery and Compressors, School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Miyazawa, Hiroaki; Nakano, Satoshi; Kakimoto, Koichi [Research Institute for Applied Mechanics, Kyushu University, Kasuga 816-8580 (Japan)

    2009-07-01

    A numerical simulator was developed with a global model of heat transfer for any crystal growth taking place at high temperature. Convective, conductive and radiative heat transfers in the furnace are solved together in a conjugated way by a finite volume method. A three-dimensional (3D) global model was especially developed for simulation of heat transfer in any crystal growth with 3D features. The model enables 3D global simulation be conducted with moderate requirement of computer resources. The application of this numerical simulator to a CZ growth and a directional solidification process for Si crystals, the two major production methods for crystalline Si for solar cells, was introduced. Some typical results were presented, showing the importance and effectiveness of numerical simulation in analyzing and improving these kinds of Si crystal growth processes from melt. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Melting and crystallization of Gesub(1-x)Tesub(x)

    International Nuclear Information System (INIS)

    Korzhuev, M.A.; Petrov, L.A.; Teplov, O.A.; Demenskij, G.K.

    1983-01-01

    The purpose of the paper is to investigate melting and crystallization processes of Gesub(1-x)Tesub(x) alloys of different composition. The alloys for investigation have been prepared from pure components using synthesis in quartz ampules during 3 hours at 1150 K with the subsequent homogenizing at 600 K during 3000 hours. Investigations have been conducted in the 750-1090 temperature range. Ranges of transformations, maximum temperature of sample heat release Tsub(max), thermal effect theta, entropy δS=theta/Tsub(max) are computed. The obtained theta and δS values agree with the data of works of other authors. Part of Ge-Te diagrams near the melting temperature, melting curves and curves of thermal degree of Atheta(T)/theta transformation during melting, crystallization and Ge separation from solid solution in alloys of different composition are presented. The results agree with phase diagram and prove mechanism of non-stoichiometric defect formation in GeTe

  4. Transparent phosphosilicate glasses containing crystals formed during cooling of melts

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; He, W.

    2011-01-01

    The effect of P2O5-SiO2 substitution on spontaneous crystallization of SiO2-Al2O3-P2O5- Na2O-MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P2O5 leads...... to amorphous phase separation (APS), i.e., phosphate- and silicate-rich phases. It is due to the tendency of Mg2+ to form [MgO4] linking with [SiO4]. Molar substitution of P2O5 for SiO2 enhances the network polymerization of silicate-rich phase in the melts, and thereby the spontaneous crystallization of cubic...... Na2MgSiO4 is also enhanced during cooling of the melts. In addition, the sizes of the local crystalline and separated glassy domains are smaller than the wavelength of the visible light, and this leads to the transparency of the obtained glasses containing crystals....

  5. Magnetic Control in Crystal Growth from a Melt

    Science.gov (United States)

    Huang, Yue

    Control of bulk melt crystal growth techniques is desirable for producing semiconductors with the highest purity and ternary alloys with tunable electrical properties. Because these molten materials are electrically conducting, external magnetic fields are often employed to regulate the flow in the melt. However, complicated by the coupled flow, thermal, electromagnetic and chemical physics, such magnetic control is typically empirical or even an educated guess. Two magnetic flow control mechanisms: flow damping by steady magnetic fields, and flow stirring by alternating magnetic fields, are investigated numerically. Magnetic damping during optically-heated float-zone crystal growth is modeled using a spectral collocation method. The Marangoni convection at the free melt-gas interface is suppressed when exposed to a steady axial magnetic field, measured by the Hartmann number Ha. As a result, detrimental flow instabilities are suppressed, and an almost quiescent region forms in the interior, ideal for single crystal growth. Using normal mode linear stability analyses, dominant flow instabilities are determined in a range applicable to experiments (up to Ha = 300 for Pr = 0.02, and up to Ha = 500 for Pr = 0.001). The hydrodynamic nature of the instability for small Prandtl number Pr liquid bridges is confirmed by energy analyses. Magnetic stirring is modeled for melt crystal growth in an ampule exposed to a transverse rotating magnetic field. Decoupled from the flow field at small magnetic Reynolds number, the electromagnetic field is first solved via finite element analysis. The flow field is then solved using the spectral element method. At low to moderate AC frequencies (up to a few kHz), the electromagnetic body force is dominant in the azimuthal direction, which stirs a steady axisymmetric flow primarily in the azimuthal direction. A weaker secondary flow develops in the meridional plane. However, at high AC frequencies (on the order of 10 kHz and higher), only

  6. 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...

  7. Shrink, twist, ripple and melt: Studies of frustrated liquid crystals

    Science.gov (United States)

    Fernsler, Jonathan G.

    Complex structures can arise out of a simple system with more than one competing influence on its behavior. The protypical example of this is the two-dimensional triangular lattice Ising model. The ferromagnetic model has two simple degenerate ground states of all spins up or down, but the antiferromagnetic model is a frustrated system. Its geometry does not allow satisfaction of the antiferro condition everywhere, which produces complex ordered structures with dimerization of the spins [1]. Without frustration, the complex structures and phase behavior are lost. All of the topics discussed in this thesis concern smectic liquid crystals. Liquid crystals are perhaps uniquely adept at manifesting frustrated phases. Their combination of periodicity in one or more dimensions allows ordered structures, yet their fluid nature in remaining dimensions allows creation of defects and extraordinarily complex structures in ways that a normal crystal could not tolerate. Liquid crystals contain a huge menagerie of frustrated phases and effects including the polarization modulated [2], vortex lattice [3], twist grain boundary [4], and blue [5] phases, as well as frustrated structures such as cholesteric or SmC* helix unwinding [6], defect lattices in thin films [7], and bend melted grain boundary defects [8], arising from boundary conditions and field effects. In this thesis, we study four liquid crystal systems that show unusual phase behavior or complex structures, deriving from the effects of frustration. Frustration, despite some human prejudices against the word, leaves nature all the more interesting and beautiful.

  8. Effect of cooling rate on crystallization in an aluminophosphosilicate melt

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; Yue, Yuanzheng

    2011-01-01

    The effect of cooling rate on spontaneous crystallization behavior of an alumino-phospho-silicate melt is studied by means of differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and viscometry. The cooling rates of 160, 2100 and 12000 K/s are attained by subjecting ......, the opalescence of the glass can be tuned by adjusting the cooling rate. This makes the production of opal glasses or transparent glass ceramics more efficient and energy saving, since the conventional isothermal treatment procedure can be left out....

  9. Crystallization and Melt Removal at Arenal Volcano, Polytopic Vector Analysis

    Science.gov (United States)

    Hidalgo, P. J.; Vogel, T. A.; Bolge, L. L.; Ehrlich, R.; Alvarado, G. E.

    2007-12-01

    Tephra sequences ET3 and ET4 from Arenal volcano in Costa Rica have recently been interpreted to be a product of crystal fractionation by Bolge and coworkers in a series of papers (2004, 2006). The two tephra units are part of a sequence of 22 tephra units that represent a 7000 year span of the Arenal volcano activity. The tephro- stratigraphy has been described extensively by Melson (1982; 1994). The ET3 and ET4 tephras were interpreted (based on major- and trace-element, isotopic analyses of whole rocks and microchemical analyses of individual phases) as clear evidence of crystal separation by gravity settling (Bolge et al., 2004, 2006). The lower ET4 tephra sequence (andesitic and crystal poor) and the upper ET3 tephra (basaltic and crystal rich) represent an inverted snapshot of the magma chamber with contrasting geochemical properties. The ET3 sequence (deeper part of the magma chamber) has nearly constant composition with only a few elements varying stratigraphically (best represented by CaO). This is consistent with gradually decreasing amounts of melt in the upper part of ET3. The lower ET4 tephra (upper part of the magma chamber) contains large chemical gradients in both incompatible and compatible elements. In the present study we use whole-rock geochemical data from the recent tephra sequences ET3 and ET4 as inputs to Polytopic Vector Analysis (PVA) (for a review of this method see Vogel and coworkers, in press). With this method we produce a three end member solution that is consistent with crystallization of Olivine, plagioclase and pyroxene from the most mafic end member (EM1) resulting in a crystal rich mush zone. As crystallization progresses the compositions of the liquids are driven towards an intermediate end member (EM3), which has an intermediate composition liquid. At EM3 composition, rapid depletion of FeO, MgO and TiO2 by crystallization of Fe-Ti oxides, rapidly drives the liquid composition towards the silicic EM1 (incompatible element

  10. Textures and melt-crystal-gas interactions in granites

    Directory of Open Access Journals (Sweden)

    Jean-Louis Vigneresse

    2015-09-01

    Full Text Available Felsic intrusions present ubiquitous structures. They result from the differential interactions between the magma components (crystal, melt, gas phase while it flows or when the flow is perturbed by a new magma injection. The most obvious structure consists in fabrics caused by the interactions of rotating grains in a flowing viscous melt. New magma inputs through dikes affect the buk massif flow, considered as global within each mineral facies. A review of the deformation and flow types developing in a magma chamber identifis the patterns that could be expected. It determines their controlling parameters and summarizes the tools for their quantification. Similarly, a brief review of the rheology of a complex multi-phase magma identifies and suggests interactions between the different components. The specific responses each component presents lead to instability development. In particular, the change in vorticity orientation, associated with the switch between monoclinic to triclinic flow is a cause of many instabilities. Those are preferentially local. Illustrations include fabric development, shear zones and flow banding. They depend of the underlying rheology of interacting magmas. Dikes, enclaves, schlieren and ladder dikes result from the interactions between the magma components and changing boundary conditions. Orbicules, pegmatites, unidirectional solidification textures and miarolitic cavities result from the interaction of the melt with a gaseous phase. The illustrations examine what is relevant to the bulk flow, local structures or boundary conditions. In each case a field observation illustrates the instability. The discussion reformulates instability observations, suggesting new trails for ther description and interpretation in terms of local departure to a bulk flow. A brief look at larger structures and at their evolution tries to relate these instabilities on a broader scale. The helical structures of the Říčany pluton, Czech

  11. Model of coordination melting of crystals and anisotropy of physical and chemical properties of the surface

    Science.gov (United States)

    Bokarev, Valery P.; Krasnikov, Gennady Ya

    2018-02-01

    Based on the evaluation of the properties of crystals, such as surface energy and its anisotropy, the surface melting temperature, the anisotropy of the work function of the electron, and the anisotropy of adsorption, were shown the advantages of the model of coordination melting (MCM) in calculating the surface properties of crystals. The model of coordination melting makes it possible to calculate with an acceptable accuracy the specific surface energy of the crystals, the anisotropy of the surface energy, the habit of the natural crystals, the temperature of surface melting of the crystal, the anisotropy of the electron work function and the anisotropy of the adhesive properties of single-crystal surfaces. The advantage of our model is the simplicity of evaluating the surface properties of the crystal based on the data given in the reference literature. In this case, there is no need for a complex mathematical tool, which is used in calculations using quantum chemistry or modeling by molecular dynamics.

  12. Crystallization and melting behavior of multi-walled carbon nanotube-reinforced nylon-6 composites

    NARCIS (Netherlands)

    Phang, In Yee; Ma, Jianhua; Shen, Lu; Liu, Tianxi; Zhang, Wei-De

    2006-01-01

    The crystallization and melting behavior of neat nylon-6 (PA6) and multi-walled carbon nanotubes (MWNTs)/PA6 composites prepared by simple melt-compounding was comparatively studied. Differential scanning calorimetry (DSC) results show two crystallization exotherms (TCC, 1 and TCC, 2) for PA6/MWNTs

  13. Investigation of melt structure and crystallization processes by high-temperature Raman spectroscopy method

    International Nuclear Information System (INIS)

    Voron'ko, Yu.K.; Kudryavtsev, A.B.; Osiko, V.V.; Sobol', A.A.

    1988-01-01

    A review of studies dealing with the melts of alkali, rare earth and other element phosphates, gallates, germanates, niobates and tungstates, which are carried out by the method of high-temperature Raman spectroscopy, is given. The effect of the melt structure on the mechanism of the substance cystallization is considered. It is shown that vitrification and supercooling of the melt, as well as its crystallization in the from of metastable structures, are related to the effect of nonconformity between the melt and crystal strucure. The effect of nonconformity between anion motives in the melt and crystal creates obstacles for equilibrium structure nucleation, which results in the formation mainly of metastable forms with lattice structure for from the structure of the melt, though cases of equilibrium phase crystallization are also possible. 37 refs.; 13 figs.; 2 tabs

  14. Endothermic technology for domestic houses

    International Nuclear Information System (INIS)

    Virk, G.S.

    2005-01-01

    The paper introduces the endothermic energy systems being developed for buildings. These use the concept of solar assisted heat pumps where thermal energy is harvested using large integrated solar collectors connected to energy stores. The low grade energy is upgraded using heat pumps to provide thermal energy effectively to a wide variety of applications for space heating and cooling and hot water. The domestic housing sector is focused upon here and a current EC funded project aimed at assessing the potential of the endothermic technology for providing the thermal energy for space heating and cooling and hot water is presented. (author)

  15. Composition dependence of spontaneous crystallization of phosphosilicate glass melts during cooling

    DEFF Research Database (Denmark)

    Liu, S.J.; Zhu, C.F.; Zhang, Y.F.

    2012-01-01

    Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type and crystallizat......Crystallization behavior of alumino-phospho-silicate melts during cooling is studied by means of the differential scanning calorimetry, X-ray diffractometry and viscometry. The results show a pronounced impact of alkaline earth oxide, alkali oxide and fluoride on the crystal type...... and crystallization degree. It is found that adding NaF into the studied compositions slightly decreases melt fragility and improves both the glass-forming ability and melt workability. This effect is associated with the unique structural role of NaF compared to the other modifier oxides. It is also found...

  16. 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.

  17. Kinetic approach in numerical modeling of melting and crystallization at laser cladding with powder injection

    Energy Technology Data Exchange (ETDEWEB)

    Mirzade, F. Kh., E-mail: fmirzade@rambler.ru [Institute on Laser and Information Technology, Russian Academy of Sciences, 1 Svyatoozerskaya Street, Shatura, Moscow Region 140700 (Russian Federation); Niziev, V.G.; Panchenko, V. Ya.; Khomenko, M.D.; Grishaev, R.V. [Institute on Laser and Information Technology, Russian Academy of Sciences, 1 Svyatoozerskaya Street, Shatura, Moscow Region 140700 (Russian Federation); Pityana, S.; Rooyen, Corney van [CSIR-National Laser Centre, Building 46A, Meiring Nauder Road, Brummeria, Pretoria (South Africa)

    2013-08-15

    The numerical model of laser cladding with coaxial powder injection includes the equations for heat transfer, melting and crystallization kinetics. It has been shown that the main parameters influencing the melt pool dynamics and medium maximum temperature are mass feed rate, laser power and scanning velocity. It has been observed that, due to the phase change occurring with superheating/undercooling, the melt zone has the boundary distinguished from melting isotherm. The calculated melt pool dimensions and dilution are in a good agreement with the experimental results for cladding of 431 martensitic stainless steel onto carbon steel substrate.

  18. Temperature fluctuations in a LiNbO 3 melt during crystal growth

    Science.gov (United States)

    Suzuki, Tetsuro

    2004-10-01

    Variations in temperature induced by forced convection on the surface of a LiNbO3 melt during crystal growth have been studied. Temperature measurements on the melt surface of single crystals growing (∅ 50 mm) at rotation rates of 15-40 rpm on an RF-heated Czochralski puller has revealed that the melt surface continuously alternates between a steady and unsteady state of flow. This was attributed to the intermittently turbulent flow mode at intermediate rotation rates. The fluctuation period is thought to depend on the thickness of its boundary layer. The boundary layer varies in thickness due to the melt flow, which stops as the interface moves toward the crystal and resumes once the interface reverts to its former position. By contrast, at above 60 rpm, the melt surface temperature drops without fluctuation, indicating that turbulent flow is dominant at faster rotation rates.

  19. Heat and mass transfer in semiconductor melts during single-crystal growth processes

    Science.gov (United States)

    Kakimoto, Koichi

    1995-03-01

    The quality of large semiconductor crystals grown from melts is significantly affected by the heat and mass transfer in the melts. The current understanding of the phenomena, especially melt convection, is reviewed starting from the results of visualization using model fluids or silicon melt, and continuing to the detailed numerical calculations needed for quantitative modeling of processing with solidification. The characteristics of silicon flows are also reviewed by focusing on the Coriolis force in the rotating melt. Descriptions of flow instabilities are included that show the level of understanding of melt convection with a low Prandtl number. Based on hydrodynamics, the origin of the silicon flow structure is reviewed, and it is discussed whether silicon flow is completely turbulent or has an ordered structure. The phase transition from axisymmetric to nonaxisymmetric flow is discussed using different geometries. Additionally, surface-tension-driven flow is reviewed for Czochralski crystal growth systems.

  20. The hardness of synthetic products obtained from cooled and crystallized basaltic melts (in Romanian)

    OpenAIRE

    Daniela Ogrean

    2001-01-01

    The Hardness of Synthetic Products Obtained from Cooled and Crystallized Basaltic Melts. Hardness is one of the main properties of the products obtained from cooled and crystallized basaltic melts under a controlled thermal regime. It influences the abrasion tear resistance of the resulted material. The microhardness measurements on the samples (bricks, boards, gutters, armour plates, tubes) indicated Vickers hardness value between 757–926 for the materials obtained from Şanovita basalts (Tim...

  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. Effects of Humidity and Surfaces on the Melt Crystallization of Ibuprofen

    Directory of Open Access Journals (Sweden)

    Il Won Kim

    2012-08-01

    Full Text Available Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with –CH3, –OH, and –COOH functional groups. Effects of the humidity were studied at room temperature (18–20 °C with relative humidity 33%, 75%, and 100%. Effects of the surfaces were observed at −20 °C (relative humidity 36% to enable close monitoring with slower crystal growth. The nucleation time of ibuprofen was faster at high humidity conditions probably due to the local formation of the unfavorable ibuprofen melt/water interface. The crystal morphologies of ibuprofen were governed by the nature of the surfaces, and they could be associated with the growth kinetics by the Avrami equation. The current study demonstrated the effective control of the melt crystallization of ibuprofen through the melt/atmosphere and melt/surface interfaces.

  3. Effects of humidity and surfaces on the melt crystallization of ibuprofen.

    Science.gov (United States)

    Lee, Dong-Joo; Lee, Suyang; Kim, Il Won

    2012-01-01

    Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with -CH(3), -OH, and -COOH functional groups. Effects of the humidity were studied at room temperature (18-20 °C) with relative humidity 33%, 75%, and 100%. Effects of the surfaces were observed at -20 °C (relative humidity 36%) to enable close monitoring with slower crystal growth. The nucleation time of ibuprofen was faster at high humidity conditions probably due to the local formation of the unfavorable ibuprofen melt/water interface. The crystal morphologies of ibuprofen were governed by the nature of the surfaces, and they could be associated with the growth kinetics by the Avrami equation. The current study demonstrated the effective control of the melt crystallization of ibuprofen through the melt/atmosphere and melt/surface interfaces.

  4. Organisation and melting of solution grown truncated lozenge polyethylene single crystals

    NARCIS (Netherlands)

    Loos, J.; Tian, M.

    2003-01-01

    Morphological features and the melting behaviour of truncated lozenge crystals have been studied. For the crystals investigated, the heights of the (110) and the (200) sectors were measured to be 14.5 and 12.7 nm, respectively, using atomic force microscopy (AFM) in contact and non-contact mode.

  5. Solid-melt interface structure and growth of Cu alloy single crystals

    International Nuclear Information System (INIS)

    Tomimitsu, Hiroshi; Kamada, Kohji.

    1983-01-01

    Crystal-melt interface behavior during the growth of Cu-base solid solutions by the Bridgman method is discussed on the basis of experimental evidence obtained by neutron diffraction topography. Advantages of neutron diffraction topography for the characterization of large single crystals, such as dealt with in this paper, are emphasized. Evidence was odserved of extremely regular crystal growth along directions, irrespective of the macroscopic growth direction. This contrasts with the previously believed (110) normal growth which is a conclusion of growth theory based on molecular kinetics at the solid-melt interface. In consequence, we believe that the kinetics at the interface is a minor factor in the meltgrowth of metal single crystals. Revised melt-growth theory should include both the growth and the formation of the regular structure as evidenced by neutron diffraction topography. (author)

  6. 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.

  7. Isothermal crystallization and melting behavior of polypropylene/layered double hydroxide nanocomposites

    International Nuclear Information System (INIS)

    Lonkar, Sunil P.; Singh, R.P.

    2009-01-01

    The effect of layered double hydroxide (LDH) nanolayers on the crystallization behavior of polypropylene (PP) was studied based on the preparation of nanocomposites by a melt intercalation method. The isothermal crystallization kinetics and subsequent melting behavior of PP/LDH hybrids were studied with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). Studies revealed that the LDH promoted heterogeneous nucleation, accelerating the crystallization of PP. The Avrami equation successfully describes the isothermal crystallization kinetics of PP/LDH hybrids and signifies heterogeneous nucleation in crystal growth of PP. The varying values of Avrami exponent (n) and half crystallization time (t 1/2 ) of PP and PP/LDH hybrids describes overall crystallization behavior. The crystallite size (D hkl ) and distribution of different crystallites in PP varied in presence of LDH. A significant increase in melting temperature is observed for PP/LDH hybrids. The POM showed that smaller and less perfect crystals were formed in nanocomposites because of molecular interaction between PP chains and LDH. The value of fold surface free energy (σ e ) of PP chains decreased with increasing LDH content. Finally, the overall results signify that LDH at nanometer level acted as nucleating agent and accelerate the overall crystallization process of PP.

  8. A Study of the Crystallization, Melting, and Foaming Behaviors of Polylactic Acid in Compressed CO2

    Directory of Open Access Journals (Sweden)

    Chul B. Park

    2009-12-01

    Full Text Available The crystallization and melting behaviors of linear polylactic acid (PLA treated by compressed CO2 was investigated. The isothermal crystallization test indicated that while PLA exhibited very low crystallization kinetics under atmospheric pressure, CO2 exposure significantly increased PLA’s crystallization rate; a high crystallinity of 16.5% was achieved after CO2 treatment for only 1 min at 100 °C and 6.89 MPa. One melting peak could be found in the DSC curve, and this exhibited a slight dependency on treatment times, temperatures, and pressures. PLA samples tended to foam during the gas release process, and a foaming window as a function of time and temperature was established. Based on the foaming window, crystallinity, and cell morphology, it was found that foaming clearly reduced the needed time for PLA’s crystallization equilibrium.

  9. Full melting of a two-dimensional complex plasma crystal triggered by localized pulsed laser heating

    Science.gov (United States)

    Couëdel, L.; Nosenko, V.; Rubin-Zuzic, M.; Zhdanov, S.; Elskens, Y.; Hall, T.; Ivlev, A. V.

    2018-04-01

    The full melting of a two-dimensional plasma crystal was induced in a principally stable monolayer by localized laser stimulation. Two distinct behaviors of the crystal after laser stimulation were observed depending on the amount of injected energy: (i) below a well-defined threshold, the laser melted area recrystallized; (ii) above the threshold, it expanded outwards in a similar fashion to mode-coupling instability-induced melting, rapidly destroying the crystalline order of the whole complex plasma monolayer. The reported experimental observations are due to the fluid mode-coupling instability, which can pump energy into the particle monolayer at a rate surpassing the heat transport and damping rates in the energetic localized melted spot, resulting in its further growth. This behavior exhibits remarkable similarities with impulsive spot heating in ordinary reactive matter.

  10. UHMW Ziegler–Natta polyethylene: Synthesis, crystallization, and melt behavior

    KAUST Repository

    Atiqullah, Muhammad; Adamu, Sagir; Emwas, Abdul-Hamid M.

    2017-01-01

    nonisothermal crystallization model, Flory's equilibrium theory and ethylene sequence length distribution concept (SLD), Gibbs–Thompson equation, and DSC experiments. By using this approach, the effects of MW, 1-hexene incorporation, ethylene SLD, the level

  11. Infrared laser-induced chaos and conformational disorder in a model polymer crystal: Melting vs ablation

    International Nuclear Information System (INIS)

    Sumpter, B.G.; Noid, D.W.; Voth, G.A.; Wunderlich, B.

    1990-01-01

    Molecular dynamics-based computer simulations are presented for the interaction of one and two infrared (IR) laser beams with a model polymer surface. When a single laser beam system is studied over a wide range of intensities, only melting of the polymer, or melting followed by bond dissociation, is observed for up to 100 picoseconds. In contrast, the two-laser simulation results exhibit a marked difference in the energy absorption behavior of the irradiated polymer which, in turn, results in multiple bond dissociations. The results for the one- and two-laser cases studied can be divided into four different classes of physical behavior: (a) the polymer remains in the solid state; (b) the polymer crystal melts; (c) the polymer ablates, but with significant melting (charring); or (d) the polymer ablates with minimal melting. Damage to the model polymer crystal from absorption of energy from either one or two lasers occurs through a mechanism that involves the competition between the absorption of energy and internal energy redistribution. The rate of energy loss from the absorption site(s) relative to the rate of absorption of energy from the radiation field determines rather the polymer melts or ablates (low absorption rates lead to melting or no change and high rates lead to ablation). A sufficiently large rate of energy absorption is only obtainable through the use of two lasers. Two lasers also significantly decrease the total laser intensity required to cause polymer crystal melting. The differences between the one- and two-laser cases are studied by adapting novel signal/subspace techniques to analyze the dynamical changes in the mode spectrum of the polymer as it melts

  12. Effects of Humidity and Surfaces on the Melt Crystallization of Ibuprofen

    OpenAIRE

    Lee, Dong-Joo; Lee, Suyang; Kim, Il Won

    2012-01-01

    Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with –CH3, –OH, and –COOH functional groups. Effects of the humidity were studied at room temperature (18–20 °C) with relative humidity 33%, 75%, and 100%. Effects of t...

  13. Paramagnetic resonance of LaGaO3: Mn single crystals grown by floating zone melting

    Science.gov (United States)

    Vazhenin, V. A.; Potapov, A. P.; Artyomov, M. Yu.; Salosin, M. A.; Fokin, A. V.; Gil'mutdinov, I. F.; Mukhamedshin, I. R.

    2016-02-01

    The EPR spectrum of Mn-doped lanthanum gallate single crystals grown by floating zone melting with optical heating has been studied. In contrast to the crystals grown according to the Czochralski method, no manganese is found in these crystals even after high-temperature annealing in air. The spectral characteristics of Fe3+ and Gd3+ centers in crystals prepared by various methods have been compared in the rhombohedral phase, and the fourth-rank nondiagonal parameters of the Fe3+ trigonal centers have been determined, as well.

  14. Growth of binary solid solution single crystals and calculation of melt surface displacement velocity

    International Nuclear Information System (INIS)

    Agamaliyev, Z.A.; Tahirov, V.I.; Hasanov, Z.Y.; Quliyev, A.F.

    2007-01-01

    A binary solid solution single crystal growth method has been worked out. Cylinder feeding alloy with complex content distribution and truncated cone crucible are used. Second component distribution coefficient is more than unit. Content distribution along grown crystal is found by solving continuity equation. After reaching dynamic equilibrium state second component concentration in grown crystal is saturated the value of which is less than the average ona in the feeding alloy. Using the method Ge-Si perfect single crystals has been grown. Calculation method of melt surface displacement velocity has been offered as well

  15. 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.

  16. Raman spectroscopy study of the crystal - melt phase transition of lanthanum, cerium and neodymium trichlorides

    International Nuclear Information System (INIS)

    Zakir'yanova, I.D.; Salyulev, A.B.

    2007-01-01

    Systematic structural studies of crystalline (over a wide temperature range) and molten LaCl 3 , CeCl 3 , and NdCl 3 salts (near the crystal-melt phase transition temperature) are conducted employing Raman spectroscopy. A change in the trend of temperature dependences of characteristic frequencies is revealed in the pre-melting region of the compounds. This is attributed to an increase in the number of crystal defects due to weakening of a part of Ln-Cl bonds and decreasing of coordination number of chloride anions in the vicinity of rare earth cation [ru

  17. A study on effective thermal conductivity of crystalline layers in layer melt crystallization

    International Nuclear Information System (INIS)

    Kim, Kwang-Joo; Ulrich, Joachim

    2002-01-01

    An effective thermal conductivity in layer melt crystallization was explored based on a model considering inclusions inside a crystalline layer during crystal growth, molecular diffusion of inclusions migration due to temperature gradient and heat generation due to recrystallization of inclusions in the crystalline layer. The effective thermal conductivity increases with time, in general, as a result of compactness of the layer. Lower cooling temperature, i.e. greater supercooling, results in a more porous layer with lower effective thermal conductivity. A similar result is seen for the parameter of melt temperature, but less pronounced. A high concentration of the melt results in a high effective thermal conductivity while low concentration yields low effective thermal conductivity. At higher impurity levels in the melt phase, constitutional supercooling becomes more pronounced and unstable growth morphologies occur more easily. Cooling rate and Reynolds number also affect the effective thermal conductivity. The predictions of an effective thermal conductivity agree with the experimental data. The model was applied to estimate the thermal conductivities of the crystalline layer during layer melt crystallization. (author)

  18. Crystal structure determination and thermal behavior upon melting of p-synephrine

    Energy Technology Data Exchange (ETDEWEB)

    Rosa, Frédéric [Unité de Technologies Chimiques et Biologiques pour la Santé, U1022 INSERM, UMR8258 CNRS, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Sorbonne Paris Cité, 4 Avenue de l' Observatoire, 75006 Paris (France); Négrier, Philippe [Laboratoire Ondes et Matière d' Aquitaine, Université de Bordeaux, UMR CNRS 5798, 351 cours de la Libération, 33 405 Talence Cedex (France); Corvis, Yohann [Unité de Technologies Chimiques et Biologiques pour la Santé, U1022 INSERM, UMR8258 CNRS, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Sorbonne Paris Cité, 4 Avenue de l' Observatoire, 75006 Paris (France); Espeau, Philippe, E-mail: philippe.espeau@parisdescartes.fr [Unité de Technologies Chimiques et Biologiques pour la Santé, U1022 INSERM, UMR8258 CNRS, Faculté des Sciences Pharmaceutiques et Biologiques, Université Paris Descartes, Sorbonne Paris Cité, 4 Avenue de l' Observatoire, 75006 Paris (France)

    2016-05-20

    Highlights: • The refinement of the crystal structure is achieved from X-ray powder diffraction. • P-Synephrine is revealed to be a racemic compound. • Degradation during melting can be bypassed using high DSC scan rates. • The temperature and enthalpy of melting are then proposed for this compound. - Abstract: The crystal structure of p-synephrine was solved from a high-resolution X-ray powder diffraction pattern optimized by energy-minimization calculations using the Dreiding force field. The title compound crystallizes in a monoclinic system (space group P2{sub 1}/c, Z = 4, with a = 8.8504(11) Å, b = 12.1166(15) Å, c = 9.7820(11) Å, β = 122.551(2)°, V = 884.21(19) Å{sup 3} and d = 1.256 g cm{sup −3}). Since p-synephrine degrades upon melting, its melting data were determined from DSC experiments carried out as a function of the heating rate. This method allowed determining a melting temperature and enthalpy equal to 199.8 ± 1.3 °C and 57 ± 3 kJ mol{sup −1}, respectively.

  19. The synergy of modeling and novel experiments for melt crystal growth research

    Science.gov (United States)

    Derby, Jeffrey J.

    2018-05-01

    Computational modeling and novel experiments, when performed together, can enable the identification of new, fundamental mechanisms important for the growth of bulk crystals from the melt. In this paper, we present a compelling example of this synergy via the discovery of previously unascertained physical mechanisms that govern the engulfment of silicon carbide particles during the growth of crystalline silicon.

  20. Melt extraction during heating and cooling of felsic crystal mushes in shallow volcanic systems: An experimental study

    Science.gov (United States)

    Pistone, M.; Baumgartner, L. P.; Sisson, T. W.; Bloch, E. M.

    2017-12-01

    The dynamics and kinetics of melt extraction in near-solidus, rheologically stalled, felsic crystal mushes (> 50 vol.% crystals) are essential to feeding many volcanic eruptions. At shallow depths (volatile-saturated and may be thermally stable for long time periods (104-107 years). In absence of deformation, residual melt can segregate from the mush's crystalline framework stimulated by: 1) gas injecting from hot mafic magmas into felsic mushes (heating / partial melting scenario), and 2) gas exsolving from the crystallizing mush (cooling / crystallizing scenario). The conditions and efficiency of melt extraction from a mush in the two scenarios are not well understood. Thus, we conducted high-temperature (700 to 850 °C) and -pressure (1.1 kbar) cold seal experiments (8-day duration) on synthetic felsic mushes, composed of water-saturated (4.2 wt.%) rhyodacite melt bearing different proportions of added quartz crystals (60, 70, and 80 vol%; 68 mm average particle size). High-spatial resolution X-ray tomography of run products show: 1) in the heating scenario (> 750 °C) melt has not segregated due to coalescence of vesicles (≤ 23 vol%) and large melt connectivity (> 7 vol% glass) / low pressure gradient for melt movement up to 80 vol% crystals; 2) in the cooling scenario (≤ 750 °C) vesicle (< 11 vol%) coalescence is limited or absent and limited amount of melt (3 to 11 vol%) segregated from sample center to its outer periphery (30 to 100 mm melt-rich lenses), testifying to the efficiency of melt extraction dictated by increasing crystallinity. These results suggest that silicic melt hosted within a crystal-rich mush can accumulate rapidly due to the buildup of modest gas pressures during crystallization at temperatures near the solidus.

  1. Features of bicrystal growth during the directional crystallization of metal melts

    Energy Technology Data Exchange (ETDEWEB)

    Gubernatorov, V. V.; Sycheva, T. S., E-mail: sych@imp.uran.ru; Gundyrev, V. M.; Akshentsev, Yu. N. [Russian Academy of Sciences, M.N. Mikheev Institute of Metal Physics, Ural Branch (Russian Federation)

    2017-03-15

    The factors responsible for the formation of different configurations of boundaries between adjacent crystallites during their growth from melt by Bridgman and Czochralski methods have been considered by an of example Fe–20 wt % Ga alloy and Ni bicrystals. It is found that the configuration of intercrystallite boundary is related to the features of crystallite growth, caused by the strained state of intercrystallite and interphase (crystal–melt) boundaries, the difference in the linear thermal expansion coefficients of the crystallite boundaries and bulk, and the shape (geometry) of the bicrystal cross section. It is suggested that the strained state of boundaries and the formation of substructure in crystallites during directional crystallization from metal melt are significantly affected by their deformation under the melt weight.

  2. Thermal gravimetric analysis of the CsCuCl3, Cs2CuCl4 and Cs2CuCl4x2H2O crystals

    International Nuclear Information System (INIS)

    Soboleva, L.V.; Vasil'eva, M.G.

    1977-01-01

    The thermal characteristics of crystals of Cs 2 CuCl 4 , Cs 2 CuCl 4 x2H 2 O, and CsCuCl 3 were investigated thermogravimetrically. The derivatogram of the Cs 2 CuCl 4 crystal is characterized by the presence of a single endothermal effect at 505 deg C. The derivatogram of the Cs 2 CuCl 4 x2H 2 O crystal contains three endothermal effects: at 40, 135, and 480 deg C. The derivatogram of the CsCuCl 3 crystal shows the presence of two endothermal effects at 142 and 455 deg C. The thermogravimetric data on Cs 2 CuCl 4 and CsCuCl 3 crystals reveal crystal decomposition on melting; hence, these crystals cannot be grown from melts

  3. Competition of the connectivity with the local and the global order in polymer melts and crystals

    Energy Technology Data Exchange (ETDEWEB)

    Bernini, S.; Puosi, F.; Barucco, M.; Leporini, D., E-mail: dino.leporini@df.unipi.it [Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa (Italy)

    2013-11-14

    The competition between the connectivity and the local or global order in model fully flexible chain molecules is investigated by molecular-dynamics simulations. States with both missing (melts) and high (crystal) global order are considered. Local order is characterized within the first coordination shell (FCS) of a tagged monomer and found to be lower than in atomic systems in both melt and crystal. The role played by the bonds linking the tagged monomer to FCS monomers (radial bonds), and the bonds linking two FCS monomers (shell bonds) is investigated. The detailed analysis in terms of Steinhardt's orientation order parameters Q{sub l} (l = 2 − 10) reveals that increasing the number of shell bonds decreases the FCS order in both melt and crystal. Differently, the FCS arrangements organize the radial bonds. Even if the molecular chains are fully flexible, the distribution of the angle formed by adjacent radial bonds exhibits sharp contributions at the characteristic angles θ ≈ 70°, 122°, 180°. The fractions of adjacent radial bonds with θ ≈ 122°, 180° are enhanced by the global order of the crystal, whereas the fraction with 70° ≲ θ ≲ 110° is nearly unaffected by the crystallization. Kink defects, i.e., large lateral displacements of the chains, are evidenced in the crystalline state.

  4. Crystallization kinetics in Si-1 at%Sn during rapid solidification in undercooled melt

    Science.gov (United States)

    Kuribayashi, K.; Ozawa, S.; Nagayama, K.; Inatomi, Y.

    2017-06-01

    In order to elucidate the cause of the morphological transition of crystals growing in an undercooled melt of semiconducting materials, we carried out the containerless solidification of undoped Si and Si-1 at%Sn using a CO2 laser-equipped electromagnetic levitator (EML). The crystallization of these materials was successfully achieved under controlled undercooling. The relation between the shape of growing crystals and the degree of undercooling in Si-1 at%Sn was similar to that in undoped Si; that is, plate-like needle crystals were observed at low undercooling, whereas at medium and high undercooling the shape of growing crystals changed to massive dendrites. The grain-size of as-solidified samples of Si-1 at%Sn was remarkably small compared with that of undoped Si. The surface morphologies of samples solidified by dropping the melt onto a chill plate of mirror-polished silicon consisted of typical twin-related dendrites. On the other hand, samples that were dropped from the undercooled state consisted of twin-free dendrites. The nucleation rate of two-dimensional nuclei calculated on the basis of two mechanisms, which are the twin-plane re-entrant edge mechanism and the twin-free mechanism, suggested that the morphological transition to twin-free dendrites from twin-related dendrites occurs when the degree of undercooling becomes larger than the critical value. These results indicate that the cause of the morphological transition of Si growing in the undercooled melt is not the roughening transition of the crystal-melt interface but the transition of the nucleation kinetics to the twin-free mechanism from the twin-related mechanism.

  5. The glass transition, crystallization and melting in Au-Pb-Sb alloys

    Science.gov (United States)

    Lee, M. C.; Allen, J. L.; Fecht, H. J.; Perepezko, J. H.; Ohsaka, K.

    1988-01-01

    The glass transition, crystallization and melting of Au(55)Pb(22.5)Sb(22.5) alloys have been studied by differential scanning calorimetry DSC. Crystallization on heating above the glass transition temperature Tg (45 C) begins at 64 C. Further crystallization events are observed at 172 C and 205 C. These events were found to correspond to the formation of the intermetallic compounds AuSb2, Au2Pb, and possibly AuPb2, respectively. Isothermal DSC scans of the glassy alloy above Tg were used to monitor the kinetics of crystallization. The solidification behavior and heat capacity in the glass-forming composition range were determined with droplet samples. An undercooling level of 0.3T(L) below the liquidus temperature T(L) was achieved, resulting in crystallization of different stable and metastable phases. The heat capacity C(P) of the undercooled liquid was measured over an undercooling range of 145 C.

  6. Glass Transition, Crystallization of Glass-Forming Melts, and Entropy

    Directory of Open Access Journals (Sweden)

    Jürn W. P. Schmelzer

    2018-02-01

    Full Text Available A critical analysis of possible (including some newly proposed definitions of the vitreous state and the glass transition is performed and an overview of kinetic criteria of vitrification is presented. On the basis of these results, recent controversial discussions on the possible values of the residual entropy of glasses are reviewed. Our conclusion is that the treatment of vitrification as a process of continuously breaking ergodicity with entropy loss and a residual entropy tending to zero in the limit of zero absolute temperature is in disagreement with the absolute majority of experimental and theoretical investigations of this process and the nature of the vitreous state. This conclusion is illustrated by model computations. In addition to the main conclusion derived from these computations, they are employed as a test for several suggestions concerning the behavior of thermodynamic coefficients in the glass transition range. Further, a brief review is given on possible ways of resolving the Kauzmann paradox and its implications with respect to the validity of the third law of thermodynamics. It is shown that neither in its primary formulations nor in its consequences does the Kauzmann paradox result in contradictions with any basic laws of nature. Such contradictions are excluded by either crystallization (not associated with a pseudospinodal as suggested by Kauzmann or a conventional (and not an ideal glass transition. Some further so far widely unexplored directions of research on the interplay between crystallization and glass transition are anticipated, in which entropy may play—beyond the topics widely discussed and reviewed here—a major role.

  7. Anisotropic Defect-Mediated Melting of Two-Dimensional Colloidal Crystals

    Science.gov (United States)

    Eisenmann, C.; Gasser, U.; Keim, P.; Maret, G.

    2004-09-01

    The melting transition of anisotropic two-dimensional (2D) crystals is studied in a model system of superparamagnetic colloids. The anisotropy of the induced dipole-dipole interaction is varied by tilting the external magnetic field off the normal to the particle plane. By analyzing the time-dependent Lindemann parameter as well as translational and orientational order we observe a 2D smecticlike phase. The Kosterlitz-Thouless-Halperin-Nelson-Young scenario of isotropic melting is modified: dislocation pairs and dislocations appear with different probabilities depending on their orientation with respect to the in-plane field.

  8. Crystal growth nucleation and Fermi energy equalization of intrinsic spherical nuclei in glass-forming melts

    Directory of Open Access Journals (Sweden)

    Robert F Tournier

    2009-01-01

    Full Text Available The energy saving resulting from the equalization of Fermi energies of a crystal and its melt is added to the Gibbs free-energy change ΔG2ls associated with a crystal formation in glass-forming melts. This negative contribution being a fraction ε ls(T of the fusion heat is created by the electrostatic potential energy −U0 resulting from the electron transfer from the crystal to the melt and is maximum at the melting temperature Tm in agreement with a thermodynamics constraint. The homogeneous nucleation critical temperature T2, the nucleation critical barrier ΔG2ls*/kBT and the critical radius R*2ls are determined as functions of εls(T. In bulk metallic glass forming melts, εls(T and T2 only depend on the free-volume disappearance temperature T0l, and εls(Tm is larger than 1 (T0l>Tm/3; in conventional undercooled melts εls(Tm is smaller than 1 (T0l>Tm/3. Unmelted intrinsic crystals act as growth nuclei reducing ΔG2ls*/kBT and the nucleation time. The temperature-time transformation diagrams of Mg65Y10 Cu25, Zr41.2Ti13.8 Cu12.5Ni10Be22.5, Pd43Cu27 Ni10P20, Fe83B17 and Ni melts are predicted using classic nucleation models including time lags in transient nucleation, by varying the intrinsic nucleus contribution to the reduction of ΔG2ls*/kBT. The energy-saving coefficient ε nm(T of an unmelted crystal of radius Rnm is reduced when Rnm LtR*2ls; εnm is quantified and corresponds to the first energy level of one s-electron moving in vacuum in the same spherical attractive potential −U0 despite the fact that the charge screening is built by many-body effects.

  9. Crystal nucleation and dendrite growth of metastable phases in undercooled melts

    International Nuclear Information System (INIS)

    Herlach, Dieter

    2011-01-01

    Research highlights: → Homogenous nucleation. → Effects of convection on dendrite growth kinetics. → Description of disorder trapping validated by experiment. - Abstract: An undercooled melt possesses an enhanced free enthalpy that opens up the possibility to crystallize metastable crystalline solids in competition with their stable counterparts. Crystal nucleation selects the crystallographic phase whereas the growth dynamics controls microstructure evolution. We apply containerless processing techniques such as electromagnetic and electrostatic levitation to containerlesss undercool and solidify metallic melts. Owing to the complete avoidance of heterogeneous nucleation on container-walls a large undercooling range becomes accessible with the extra benefit that the freely suspended drop is direct accessible for in situ observation of crystallization far away from equilibrium. Results of investigations of maximum undercoolability on pure zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Rapid dendrite growth is measured as a function of undercooling by a high-speed camera and analysed within extended theories of non-equilibrium solidification. In such both supersaturated solid solutions and disordered superlattice structure of intermetallics are formed at high growth velocities. A sharp interface theory of dendrite growth is capable to describe the non-equilibrium solidification phenomena during rapid crystallization of deeply undercooled melts. Eventually, anomalous growth behaviour of Al-rich Al-Ni alloys is presented, which may be caused by forced convection.

  10. The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts

    Science.gov (United States)

    Kolzenburg, S.; Di Genova, D.; Giordano, D.; Hess, K. U.; Dingwell, D. B.

    2018-04-01

    Storage and transport of silicate melts in the Earth's crust and their emplacement on the planet's surface occur almost exclusively at sub-liquidus temperatures. At these conditions, the melts undergo crystallization under a wide range of cooling-rates, deformation-rates, and oxygen fugacities (fO2). Oxygen fugacity is known to influence the thermodynamics and kinetics of crystallization in magmas and lavas. Yet, its influence on sub-liquidus rheology remains largely uncharted. We present the first rheological characterization of crystallizing lavas along natural cooling paths and deformation-rates and at varying fO2. Specifically, we report on apparent viscosity measurements for two crystallizing magmatic suspensions 1) at log ⁡ fO2 of -9.15 (quartz-fayalite-magnetite buffer, QFM, -2.1) and 2) in air. These fugacities span a range of reduced to oxidized conditions pertinent to magma migration and lava emplacement. We find that: 1) crystallization at constant cooling-rates results in a quasi-exponential increase in the apparent viscosity of the magmatic suspensions until they achieve their rheological cut off temperature (Tcutoff), where the melt effectively solidifies 2) the rheological departure and Tcutoff increase with increasing fO2 and 3) increasing fO2 results in decreased crystallization-rates. Based on the experimental results and by comparison with previous rheological isothermal studies we propose a generalisation of the effect of fO2 on the dynamic rheological evolution of natural magmatic and volcanic suspensions. We further discuss the implications for magmatic transport in plumbing and storage systems (e.g. conduits, dikes and magma chambers) and during lava flow emplacement.

  11. Crystal growth kinetics in undercooled melts of pure Ge, Si and Ge-Si alloys

    Science.gov (United States)

    Herlach, Dieter M.; Simons, Daniel; Pichon, Pierre-Yves

    2018-01-01

    We report on measurements of crystal growth dynamics in semiconducting pure Ge and pure Si melts and in Ge100-xSix (x = 25, 50, 75) alloy melts as a function of undercooling. Electromagnetic levitation techniques are applied to undercool the samples in a containerless way. The growth velocity is measured by the utilization of a high-speed camera technique over an extended range of undercooling. Solidified samples are examined with respect to their microstructure by scanning electron microscopic investigations. We analyse the experimental results of crystal growth kinetics as a function of undercooling within the sharp interface theory developed by Peter Galenko. Transitions of the atomic attachment kinetics are found at large undercoolings, from faceted growth to dendrite growth. This article is part of the theme issue `From atomistic interfaces to dendritic patterns'.

  12. The hardness of synthetic products obtained from cooled and crystallized basaltic melts (in Romanian

    Directory of Open Access Journals (Sweden)

    Daniela Ogrean

    2001-04-01

    Full Text Available The Hardness of Synthetic Products Obtained from Cooled and Crystallized Basaltic Melts. Hardness is one of the main properties of the products obtained from cooled and crystallized basaltic melts under a controlled thermal regime. It influences the abrasion tear resistance of the resulted material. The microhardness measurements on the samples (bricks, boards, gutters, armour plates, tubes indicated Vickers hardness value between 757–926 for the materials obtained from Şanovita basalts (Timiş district and between 539–958 respectively, in case of the Racoş basalts (Braşov district. There is a certain variation of the hardness within the same sample, in various measurement points, within the theoretical limits of the hardnesses of the pyroxenes and that of the spinels.

  13. Crystal nucleus formation on the cathode under conditions of supersaturation of melt by lower valent forms

    International Nuclear Information System (INIS)

    Kaliev, K.A.; Aksent'ev, A.G.; Baraboshkin, A.N.

    1979-01-01

    Nucleation on the cathode of sodium-tungsten bronzes forom the Na 2 WO 4 -WO 3 melt, containing 40 mol.% WO 3 is studied. It has been found that in the initial period the cathode deposition of sodium-tungsten bronze is preceeded by the formation of tungsten soluble lower reduced forms, the concentration of which can considerably exceed the equilibrium one because of excessive overstress of oxide bronze crystal nucleation. The polarization of cathode and change of its potential at the crystal nucleation of sodium-tungsten bronze and switching-off of the electrolysis current has been studied

  14. Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

    Science.gov (United States)

    Su, Ching-Hua (Inventor)

    2013-01-01

    The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

  15. Crystallization and melting behavior of nanoclay-containing polypropylene/poly(trimethylene terephthalate blends

    Directory of Open Access Journals (Sweden)

    S. H. Jafari

    2012-02-01

    Full Text Available This contribution concerns preparation and characterization of polypropylene (PP/poly(trimethylene terephthalate (PTT melt-mixed blends in the presence of organically-modified montmorillonite nanoclays and functional compatibilizers. Immiscibility and nanocomposite formation were confirmed via transmission electron microscopy. An intercalated structure was observed by wide angle X-ray diffraction technique. Crystallization, and melting characteristics were studied by differential scanning calorimetry in both isothermal and non-isothermal modes, supplemented by temperature modulated DSC (TMDSC. A concurrent crystallization was found for both polymeric components in the blends. Whereas blending favored PP crystallizability, it interrupted that of PTT. The addition compatibilizers interfered with rate, temperature, and degree of crystallization of PP and PTT. On the contrary, nanoclays incorporation increased crystallizability of each individual component. However, as for blend nanocomposite samples, the way the crystallization behavior changed was established to depend on the type of nanoclay. Based on kinetic analysis, isothermal crystallization nucleation followed athermal mechanism, while that of non-isothermal obeyed thermal mode. Addition of nanoclays shifted nucleation mechanism from athermal to thermal mode.

  16. Crystallization in melts of short, semiflexible hard polymer chains: An interplay of entropies and dimensions

    Science.gov (United States)

    Shakirov, T.; Paul, W.

    2018-04-01

    What is the thermodynamic driving force for the crystallization of melts of semiflexible polymers? We try to answer this question by employing stochastic approximation Monte Carlo simulations to obtain the complete thermodynamic equilibrium information for a melt of short, semiflexible polymer chains with purely repulsive nonbonded interactions. The thermodynamics is obtained based on the density of states of our coarse-grained model, which varies by up to 5600 orders of magnitude. We show that our polymer melt undergoes a first-order crystallization transition upon increasing the chain stiffness at fixed density. This crystallization can be understood by the interplay of the maximization of different entropy contributions in different spatial dimensions. At sufficient stiffness and density, the three-dimensional orientational interactions drive the orientational ordering transition, which is accompanied by a two-dimensional translational ordering transition in the plane perpendicular to the chains resulting in a hexagonal crystal structure. While the three-dimensional ordering can be understood in terms of Onsager theory, the two-dimensional transition can be understood in terms of the liquid-hexatic transition of hard disks. Due to the domination of lateral two-dimensional translational entropy over the one-dimensional translational entropy connected with columnar displacements, the chains form a lamellar phase. Based on this physical understanding, orientational ordering and translational ordering should be separable for polymer melts. A phenomenological theory based on this understanding predicts a qualitative phase diagram as a function of volume fraction and stiffness in good agreement with results from the literature.

  17. 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

  18. Crystallization and melting behavior of isotactic polypropylene composites filled by zeolite supported β-nucleator

    International Nuclear Information System (INIS)

    Jiang, Juan; Li, Gu; Tan, Nanshu; Ding, Qian; Mai, Kancheng

    2012-01-01

    Highlights: ► The supported calcium pimelate β-zeolite was prepared. ► The β-nucleation of zeolite was enhanced dramatically through reaction. ► High β-phase content iPP composites were obtained by introducing the β-zeolite into iPP. - Abstract: In order to prepare the zeolite filled β-iPP composites, the calcium pimelate as β-nucleator supported on the surface of zeolite (β-zeolite) was prepared by the interaction between calcified zeolite and pimelic acid. The β-nucleation, crystallization behavior and melting characteristic of zeolite, calcified zeolite and β-zeolite filled iPP composites were investigated by differential scanning calorimetry and wide-angle X-ray diffractometer. The results indicated that addition of the zeolite and calcified zeolite as well as β-zeolite increased the crystallization temperature of iPP. The zeolite and calcified zeolite filled iPP composites mainly crystallized in the α-crystal form and the strong β-heterogeneous nucleation of β-zeolite results in the formation of only β-crystal in β-zeolite filled iPP composites. The zeolite filled β-iPP composites with high β-crystal contents (above 0.90) can be easily obtained by adding β-zeolite into iPP matrix.

  19. Phase relations study on the melting and crystallization regions of the Bi-2223 high temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2004-09-01

    Full Text Available The melting and solidification behavior of Bi2Sr2Ca2Cu3 O10 (Bi-2223 precursors has been studied. Nominal compositions corresponding to excess of liquid, Ca2CuO3 and CuO have been investigated. Each sample was made by packing a precursor powder into a silver crucible, in order to approximately simulate the situation found in 2223 silver-sheathed tapes. The samples were partially melted and then slow-cooled, being quenched from different temperatures and analyzed through X-ray diffraction (XRD and scanning electron microscopy (SEM/EDS. The precursors decomposed peritectically during melting, forming liquid and solid phases. Very long plates with compositions falling in the vicinity of the 2223 primary phase field formed upon slow-cooling. The 2223 phase may have been formed and the results suggest that long grains of this phase might be obtained by melting and crystallization if the exact peritectic region and the optimum processing conditions are found.

  20. Study of melting of molecular crystals by a modified Pople-Karasz model

    Science.gov (United States)

    Yazıcı, Mustafa; Özgan, Şükrü; Keskin, Mustafa

    2005-02-01

    A new modified model that combines the modified models of Chandrasekhar et al. with those of Keskin and Özgan, which are based on the Pople-Karasz theory, is applied to study the thermodynamics of melting and solid-solid transitions of molecular crystals. The thermodynamic properties of the disordered system are evaluated relative to those of the perfectly ordered one using the lowest approximation of the cluster-variation method, which is identical to the mean-field approximation. A good agreement is found between the present modified theory and the available experimental data. For melting transitions the agreement is excellent and much better than with the calculations of the Pople-Karasz theory and its previous modified theories. Approximate agreement is obtained for the solid-solid transitions. However, for these transition the experimental agreement with the present modified theory is still better than previous modified theories except at zero and low pressures.

  1. Predicting body temperature of endotherms during shuttling

    NARCIS (Netherlands)

    Rodriguez-Girones, M.A.

    2002-01-01

    This paper presents two models that can be used to predict the temporal dynamics of body temperature in endotherms. A first-order model is based on the assumption that body temperature is uniform at all times, while a second-order model is based on the assumption that animals can be divided in a

  2. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    International Nuclear Information System (INIS)

    Schebarchov, D.; Schulze, T. P.; Hendy, S. C.

    2014-01-01

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level

  3. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schebarchov, D., E-mail: Dmitri.Schebarchov@gmail.com [University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Schulze, T. P., E-mail: schulze@math.utk.edu [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300 (United States); Hendy, S. C. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand); Department of Physics, University of Auckland, Auckland 1010 (New Zealand)

    2014-02-21

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.

  4. 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

  5. Study to Determine the Feasibility of Utilizing Skull-Melting Techniques for the Growth of Single Crystals of Yttrium Vanadate

    Science.gov (United States)

    1986-04-01

    these conditions and the sublimation product (IrO 2 ) contaminates the melt and resultant crystal. The goal of this program is to explore the...element; if the skull-melting operation is carried out under oxidizing conditions, the combustion products of high-purity graphite (CO 2 and CO) do not...polycrstalline ingots. Subsequent annealing of 16 S’ .1i" these 0 2 -defficient ingots in air at 1200 degrees C resulted in powdering and disintergration

  6. Energetics of thermoregulation by an industrious endotherm.

    Science.gov (United States)

    Meehan, Timothy D

    2012-01-01

    Thermoregulation by modern industrial humans is unique among endothermic animals, in that it is largely accomplished by controlling the temperature of our external environment. The objective of this study was to view the relationship between thermoregulatory energy use and environmental temperature in modern humans from the perspective of comparative physiology. Monthly residential energy use estimates from the US Energy Information Administration were divided by the annual number of American households from the US Census Bureau, giving average monthly energy consumption per American household for the years 2006 through 2010. Monthly energy consumption was then plotted against average monthly temperature across the United States from the National Climatic Data Center. The resulting graph bore a striking resemblance to a classic Scholander-Irving curve, exhibiting clear upper (22°C) and lower (15°C) critical temperatures, and an increase in energy use as temperatures extend above (90 W °C(-1) increase) or below (244 W °C(-1) decrease) those critical temperatures. Allometric equations from comparative physiology indicate that the energetic costs of our current thermoregulatory habits are ∼30 to 50 times those predicted for an endotherm of our size. Modern humans have redefined what it means to be a homeothermic endotherm, using large quantities of extrametabolic energy to regulate the temperature of our surroundings. Despite this sophistication, the signal of our individual physiology is readily discernible in national data on energy consumption. Copyright © 2012 Wiley Periodicals, Inc.

  7. PA6 and Kevlar fiber reinforced isotactic polypropylene: Structure, mechanical properties and crystallization and melting behavior

    International Nuclear Information System (INIS)

    Zhao, Songfang; Cheng, Lei; Guo, Yong; Zheng, Yuying; Li, Baoming

    2012-01-01

    Highlights: ► KF was modified with caprolactam using toluenediisocyanate (TDI) as bridge. ► Modified KF improves interfacial interaction of iPP/KF/PA6 composites. ► Fiber and nylon 6 inhibited the crystallization of PP continuous phase. -- Abstract: To improve the thermal and mechanical properties of isotactic polypropylene (iPP), iPP/Kevlar fiber (KF)/polyamide 6 (PA6) composites were prepared via the melt-extrusion method on twin-screw extruder. Kevlar fiber was modified with caprolactam using toluenediisocyanate (TDI) as bridge. The microstructure of modified KF was successfully characterized by Fourier transform infrared (FT-IR), X-ray photoelectron spectrometer (XPS) and scanning electron microscopy (SEM), the results showed that KF was bonded with caprolactam and became coarser. Then the modified KF was introduced into iPP, the composites have better mechanical and thermal properties, implying that modification of KF was helpful to improve the interfacial interaction of iPP/KF/PA6 composites. Besides, the crystallization curves indicated that crystallization behavior of PA6 in the composites was homogeneous and fractional. Furthermore, compatibilizer content played an important role in the mechanical and thermal properties of composites.

  8. Oxygen Barrier Properties and Melt Crystallization Behavior of Poly(ethylene terephthalate/Graphene Oxide Nanocomposites

    Directory of Open Access Journals (Sweden)

    Anna Szymczyk

    2015-01-01

    Full Text Available Poly(ethylene terephthalate nanocomposites with low loading (0.1–0.5 wt% of graphene oxide (GO have been prepared by using in situ polymerization method. TEM study of nanocomposites morphology has shown uniform distribution of highly exfoliated graphene oxide nanoplatelets in PET matrix. Investigations of oxygen permeability of amorphous films of nanocomposites showed that the nanocomposites had better oxygen barrier properties than the neat PET. The improvement of oxygen permeability for PET nanocomposite films over the neat PET is approximately factors of 2–3.3. DSC study on the nonisothermal crystallization behaviors proves that GO acts as a nucleating agent to accelerate the crystallization of PET matrix. The evolution of the lamellar nanostructure of nanocomposite and neat PET was monitored by SAXS during nonisothermal crystallization from the melt. It was found that unfilled PET and nanocomposite with the highest concentration of GO (0.5 wt% showed almost similar values of the long period (L=11.4 nm for neat PET and L=11.5 nm for PET/0.5GO.

  9. 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

  10. Crystallization and mechanical properties of reinforced PHBV composites using melt compounding: Effect of CNCs and CNFs.

    Science.gov (United States)

    Jun, Du; Guomin, Zhao; Mingzhu, Pan; Leilei, Zhuang; Dagang, Li; Rui, Zhang

    2017-07-15

    Nanocellulose reinforced poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites were prepared using melt compounding. The effects of nanocellulose types (CNCs and CNFs) and nanocellulose content (1, 2, 3, 4, 5, 6 and 7wt%) on the crystallization, thermal and mechanical properties of PHBV composites were systematically compared in this study. The thermal stability of PHBV composites was improved by both CNCs and CNFs. CNFs with a higher thermal stability leaded to a higher thermal stability of PHBV composites. Both CNCs and CNFs induced a reduction in the crystalline size of PHBV spherulites. Furthermore, CNCs could act as a better nucleating agent for PHBV than did CNFs. CNCs and CNFs showed reinforcing effects in PHBV composites. At the equivalent content of nanocellulose, CNCs led to a higher tensile modulus of PHBV composites than did CNFs. 1wt% CNCs/PHBV composites exhibited the most optimum mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Solid-solid phase transformation via internal stress-induced virtual melting, significantly below the melting temperature. Application to HMX energetic crystal.

    Science.gov (United States)

    Levitas, Valery I; Henson, Bryan F; Smilowitz, Laura B; Asay, Blaine W

    2006-05-25

    We theoretically predict a new phenomenon, namely, that a solid-solid phase transformation (PT) with a large transformation strain can occur via internal stress-induced virtual melting along the interface at temperatures significantly (more than 100 K) below the melting temperature. We show that the energy of elastic stresses, induced by transformation strain, increases the driving force for melting and reduces the melting temperature. Immediately after melting, stresses relax and the unstable melt solidifies. Fast solidification in a thin layer leads to nanoscale cracking which does not affect the thermodynamics or kinetics of the solid-solid transformation. Thus, virtual melting represents a new mechanism of solid-solid PT, stress relaxation, and loss of coherence at a moving solid-solid interface. It also removes the athermal interface friction and deletes the thermomechanical memory of preceding cycles of the direct-reverse transformation. It is also found that nonhydrostatic compressive internal stresses promote melting in contrast to hydrostatic pressure. Sixteen theoretical predictions are in qualitative and quantitative agreement with experiments conducted on the PTs in the energetic crystal HMX. In particular, (a) the energy of internal stresses is sufficient to reduce the melting temperature from 551 to 430 K for the delta phase during the beta --> delta PT and from 520 to 400 K for the beta phase during the delta --> beta PT; (b) predicted activation energies for direct and reverse PTs coincide with corresponding melting energies of the beta and delta phases and with the experimental values; (c) the temperature dependence of the rate constant is determined by the heat of fusion, for both direct and reverse PTs; results b and c are obtained both for overall kinetics and for interface propagation; (d) considerable nanocracking, homogeneously distributed in the transformed material, accompanies the PT, as predicted by theory; (e) the nanocracking does not

  12. Lubricating and waxy esters, I. Synthesis, crystallization, and melt behavior of linear monoesters.

    Science.gov (United States)

    Bouzidi, Laziz; Li, Shaojun; Di Biase, Steve; Rizvi, Syed Q; Narine, Suresh S

    2012-01-01

    Four pure jojoba wax-like esters (JLEs), having carbon chain length of 36, 40 (two isomers) and 44, were prepared by Steglish esterification of fatty acids (or acid chlorides) with fatty alcohols at room temperature. Calorimetric and diffraction data was used to elucidate the phase behavior of the esters. The primary thermal parameters (crystallization and melting temperatures) obtained from the DSC of the symmetrical molecules correspond well with the carbon numbers of the JLEs. However, the data also suggests that carbon number is not the only factor since the symmetry of the molecule also plays a significant role in the phase behavior. Overall, the JLEs show very little polymorphic activity at the experimental conditions used, suggesting that they are likely to transform the same way during melting as well as crystallization, a characteristic which may be useful in designing new waxes and lubricants. The XRD data clearly show that the solid phase in all samples consists of a mixture of a β-phase and a β'-phase; fully distinguishable by their characteristic diffraction peaks. Subtle differences between the subcell patterns and phase development of the samples were observed. Different layering of the samples was also observed, understandably because of the chain length differences between the compounds. The long spacings were perfectly linearly proportional to the number of carbon atoms. The length of the ester layers with n carbon atoms can be calculated by a formula similar to that used for the layers in linear alkane molecules. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  13. Morphological Development of Melt Crystallized Poly(propylene oxide) by In Situ AFM: Formation of Banded Spherulites

    NARCIS (Netherlands)

    Beekmans, L.G.M.; Hempenius, Mark A.; Vancso, Gyula J.

    2004-01-01

    The morphology of poly(propylene oxide) (PPO) crystals grown from the melt was investigated. The spherulites of the optically pure S polymers displayed a regular pattern of concentric rings as observed by polarizing optical microscopy, while the stereocopolymer developed irregularly banded, or

  14. Effect of Feed Melting, Temperature History, and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass

    Czech Academy of Sciences Publication Activity Database

    Izák, Pavel; Hrma, P.; Arey, B. W.; Plaisted, T. J.

    2001-01-01

    Roč. 289, 1-3 (2001), s. 17-29 ISSN 0022-3093 Grant - others:DOE(US) DE/06/76RL01830 Keywords : feed melting * crystalization * high-level waste glass Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.363, year: 2001

  15. On determination of melt composition by liquidus curves for a number of oxide systems for crystal formation

    International Nuclear Information System (INIS)

    Soboleva, L.V.

    1991-01-01

    Consideration is given to liquidus curves in 31 phase diagrams of a series of borate, aluminate, silicate, germanate, titanate and other systems with unlimited mutual solubility in liquid state. Proposed optimal compositions of melts for preparation of crystals of compounds, forming in these systems, were calculated

  16. Ultrafast characterization of phase-change material crystallization properties in the melt-quenched amorphous phase.

    Science.gov (United States)

    Jeyasingh, Rakesh; Fong, Scott W; Lee, Jaeho; Li, Zijian; Chang, Kuo-Wei; Mantegazza, Davide; Asheghi, Mehdi; Goodson, Kenneth E; Wong, H-S Philip

    2014-06-11

    Phase change materials are widely considered for application in nonvolatile memories because of their ability to achieve phase transformation in the nanosecond time scale. However, the knowledge of fast crystallization dynamics in these materials is limited because of the lack of fast and accurate temperature control methods. In this work, we have developed an experimental methodology that enables ultrafast characterization of phase-change dynamics on a more technologically relevant melt-quenched amorphous phase using practical device structures. We have extracted the crystallization growth velocity (U) in a functional capped phase change memory (PCM) device over 8 orders of magnitude (10(-10) 10(8) K/s), which reveals the extreme fragility of Ge2Sb2Te5 in its supercooled liquid phase. Furthermore, these crystallization properties were studied as a function of device programming cycles, and the results show degradation in the cell retention properties due to elemental segregation. The above experiments are enabled by the use of an on-chip fast heater and thermometer called as microthermal stage (MTS) integrated with a vertical phase change memory (PCM) cell. The temperature at the PCM layer can be controlled up to 600 K using MTS and with a thermal time constant of 800 ns, leading to heating rates ∼10(8) K/s that are close to the typical device operating conditions during PCM programming. The MTS allows us to independently control the electrical and thermal aspects of phase transformation (inseparable in a conventional PCM cell) and extract the temperature dependence of key material properties in real PCM devices.

  17. Crystallization and Martensitic Transformation Behavior of Ti-Ni-Si Alloy Ribbons Prepared via Melt Spinning.

    Science.gov (United States)

    Park, Ju-Wan; Kim, Yeon-Wook; Nam, Tae-Hyun

    2018-09-01

    Ti-(50-x)Ni-xSi (at%) (x = 0.5, 1.0, 3.0, 5.0) alloy ribbons were prepared via melt spinning and their crystallization procedure and transformation behavior were investigated using differential scanning calorimtry, X-ray diffraction, and transmission electron microscopy. Ti-Ni-Si alloy ribbons with Si content less than 1.0 at% were crystalline, whereas those with Si content more than 3.0 at% were amorphous. Crystallization occurred in the sequence of amorphous →B2 → B2 → Ti5Si4 + TiNi3 → B2 + Ti5Si4 + TiNi3 + TiSi in the Ti-47.0Ni-3.0Si alloy and amorphous →R → R + Ti5Si4 + TiNi3 → R + Ti5Si4 + TiNi3 + TiSi in the Ti-45.0Ni-5.0Si alloy. The activation energy for crystallization was 189 ±8.6 kJ/mol for the Ti-47Ni-3Si alloy and 212±8.6 kJ/mol for the Ti-45Ni-5Si alloy. One-stage B2-R transformation behavior was observed in Ti-49.5Ni-0.5Si, Ti-49.0Ni-1.0Si, and Ti-47.0Ni- 3.0Si alloy ribbons after heating to various temperatures in the range of 873 K to 1073 K. In the Ti-45.0Ni-5.0Si alloy, one-stage B2-R transformation occurred after heating to 893 K, two-stage B2-R-B19' occurred after heating to 973 K, and two-stage B2-R-B19' occurred on cooling and one-stage B19'-B2 occurred on heating, after heating to 1073 K.

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

    Energy Technology Data Exchange (ETDEWEB)

    Orava, J.; Greer, A. L., E-mail: alg13@cam.ac.uk [WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan and Department of Materials Science and Metallurgy, 27 Charles Babbage Road, University of Cambridge, Cambridge CB3 0FS (United Kingdom)

    2014-06-07

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

  19. Crystallization of nuclear glass under a thermal gradient: application to the self-crucible produced in the skull melting process

    International Nuclear Information System (INIS)

    Delattre, O.

    2013-01-01

    In the context of the vitrification of high level nuclear waste, a new industrial process has been launched in 2010 at the La Hague factory: The skull melting process. This setup applies thermal gradients to the melt, which leads to the formation of a solid layer of glass: the 'self-crucible'. The question would be to know whether these thermal gradients have an impact or not on the crystallization behaviour of the considered glasses in the self crucible. In order to answer that question, the crystallization of two glass compositions of nuclear interest has been investigated with an image analysis based method in isothermal and thermal gradient heat treatments conditions. The isothermal experiments allow for the quantification (growth speed, nucleation, crystallized fraction) of the crystallization of apatites (660 C-900 C) and powellites (630 C-900 C). The comparison of the results obtained through these two types of experimentations allows us to conclude that there is no impact of the thermal gradient on the crystallization of the studied glass compositions. In order to complete the image analysis study (based on surfaces), in and ex situ microtomography experiments have been performed at ESRF (Grenoble) on the ID19 beamline. This study allowed us to follow the crystallization of apatites in a simplified glass and to confirm the reliability of the image analysis method based on the analysis of surfaces. (author) [fr

  20. X-ray and DSC studies on the melt-recrystallization process of poly(butylene naphthalate)

    International Nuclear Information System (INIS)

    Yasuniwa, Munehisa; Tsubakihara, Shinsuke; Fujioka, Takashi

    2003-01-01

    Melt-recrystallization in the heating process of poly(butylene naphthalate) (PBN) was studied with X-ray analysis and differential scanning calorimetry (DSC). DSC melting curve of an isothermally crystallized sample showed double endothermic peaks. With increasing the temperature, wide-angle X-ray diffraction (WAXD) patterns of the sample were obtained successively. Crystal structure did not change during the double melting process. The X-ray diffraction intensity decreased gradually in the temperature region up to about 200 deg. C, and then increased distinctly before steep decrease due to the final melting. This increase is interpreted as a proof of recrystallization. The temperature derivative curve of the diffraction intensity was similar to the DSC melting curve

  1. Flux pinning and vortex dynamics in YBCO: Melt-textured crystals

    International Nuclear Information System (INIS)

    Zhao, Y.; Choi, C.H.; Zhang, H.; Xu, M.; Andrikidis, C.

    1996-01-01

    Full text: Flux pinning and vortex dynamics in Melt-Textured-Growth (MTG) YBa 2 Cu 3 O 7-y (Y123) crystals have been studied by measurements of magnetization from 4 to 90 K and up to 5 T, ac susceptibility, I-V characteristics, and TEM and SEM analyses. A fishtail or peak effect in the field dependence of the superconducting current density is observed in samples annealed in oxygen for a long time. It is found that the fishtail effect is sensitive to the oxygen distribution and dopants such as Nd at Y site or Ni at Cu(2) site, suggesting that the fishtail effect is independent of the magnetic impurities, but closely related to the microstructural defects. TEM analysis shown these samples have needle shape defects with high density. The irreversibility line determined by I-V curve is consistent with that by magnetization and the I-V curves are found to obey the scaling behaviour of the vortex-glass transition. The mechanisms of fishtail effect and high critical current density of the samples are discussed

  2. The influence of sol on the behavior of melting and nonisothermal crystallization kinetic of radiation cross-linking HDPE

    International Nuclear Information System (INIS)

    Deng Pengyang; Xie Hongfeng; Deng Mingxiao; Zhong Xiaoguang

    2000-01-01

    By using DSC, the behavior of second melting and nonisothermal crystallization of pure gel pure sol and sol-gel blend of radiation crosslinking HDPE was studied. The authors found that, because of the existence of sol, there is notable difference between pure gel and pure sol or sol-gel blend. Under the same dose, the melting point and crystallization temperature of pure sol and sol-gel blend are higher than that of pure gel. At the same time, the authors also found that the Avrami exponent of original PE, pure sol and sol-gel blend is the similar to each other and different to that of pure gel, which means that the procedure of nucleation and growth of these samples is the same and also different to that of pure gel

  3. Influence of clusters in melt on the subsequent glass-formation and crystallization of Fe–Si–B metallic glasses

    Directory of Open Access Journals (Sweden)

    Shaoxiong Zhou

    2015-04-01

    Full Text Available The liquid structure of seven representative Fe–Si–B alloys has been investigated by ab initio molecular dynamics simulation focusing on the role of clusters in terms of glass-forming ability (GFA and crystallization. It is demonstrated that the type of primary phase precipitated from amorphous state under heat treatment is determined by the relative fraction and role of various clusters in melt. The alloy melt shows higher stability and resultantly larger GFA when there is no dominant cluster or several clusters coexist, which explains the different GFAs and crystallization processes at various ratios of Si and B in the Fe–Si–B system. The close correlation among clusters, crystalline phase and GFA is also studied.

  4. Growth from the melt of high-quality In2O3 and Ga2O3 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fornari, Roberto; Galazka, Zbigniew; Uecker, Reinhard; Irmscher, Klaus [Leibniz Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin (Germany)

    2013-07-01

    Because of their interesting properties semiconducting oxides, in particular Ga{sub 2}O{sub 3} In{sub 2}O{sub 3}, have recently received much attention. However, as they were deposited as films on hetero-substrates their quality was quite poor. The growth of high-quality bulk Ga{sub 2}O{sub 3} and In{sub 2}O{sub 3} and manufacture of the corresponding substrates can allow the deposition of high-quality epilayers with lower residual carrier density and fewer extended defects. For this reason IKZ has undertaken an effort to grow large single crystals of these oxide compounds from the melt. Transparent semiconducting Ga{sub 2}O{sub 3} single crystals with diameter of about 20 mm and 50-60 mm long were grown by the Czochralski method along the b-axis, using an Iridium crucible and a dynamic protective atmosphere to minimize the dissociation of Ga{sub 2}O{sub 3} melt and ingot. In the case of In{sub 2}O{sub 3} the Czochralski technique is not applicable and it was necessary to develop a novel melt growth method. This new method indeed supplied crystals from which oriented substrates could be prepared. In this presentation the melt growth of Ga{sub 2}O{sub 3} and In{sub 2}O{sub 3} single crystals will be reviewed. An important feature of both materials is given by their strong sensitivity to thermal processing: the free carrier concentration and the absorption spectra drastically vary as a function of annealing temperature, duration and ambient. The possible causes are discussed.

  5. Effect of Feed Melting, Temperature History and Minor Component Addition on Spinel Crystallization in High-Level Waste Glass

    International Nuclear Information System (INIS)

    Izak, Pavel; Hrma, Pavel R.; Arey, Bruce W.; Plaisted, Trevor J.

    2001-01-01

    This study was undertaken to help design mathematical models for high-level waste (HLW) glass melter that simulate spinel behavior in molten glass. Spinel, (Fe,Ni,Mn) (Fe,Cr)2O4, is the primary solid phase that precipitates from HLW glasses containing Fe and Ni in sufficient concentrations. Spinel crystallization affects the anticipated cost and risk of HLW vitrification. To study melting reactions, we used simulated HLW feed, prepared with co-precipitated Fe, Ni, Cr, and Mn hydroxides. Feed samples were heated up at a temperature-increase rate (4C/min) close to that which the feed experiences in the HLW glass melter. The decomposition, melting, and dissolution of feed components (such as nitrates, carbonates, and silica) and the formation of intermediate crystalline phases (spinel, sodalite (Na8(AlSiO4)6(NO2)2), and Zr-containing minerals) were characterized using evolved gas analysis, volume-expansion measurement, optical microscope, scanning electron microscope, thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Nitrates and quartz, the major feed components, converted to a glass-forming melt by 880C. A chromium-free spinel formed in the nitrate melt starting from 520C and Sodalite, a transient product of corundum dissolution, appeared above 600C and eventually dissolved in glass. To investigate the effects of temperature history and minor components (Ru,Ag, and Cu) on the dissolution and growth of spinel crystals, samples were heated up to temperatures above liquidus temperature (TL), then subjected to different temperature histories, and analyzed. The results show that spinel mass fraction, crystals composition, and crystal size depend on the chemical and physical makeup of the feed and temperature history

  6. (nBuCp)2ZrCl2-catalyzed Ethylene-4M1P Copolymerization: Copolymer Backbone Structure, Melt Behavior, and Crystallization

    KAUST Repository

    Atiqullah, Muhammad; Adamu, Sagir; Malaibari, Zuhair O.; Al-Harthi, Mamdouh A.; Emwas, Abdul-Hamid M.

    2016-01-01

    The judicious design of methylaluminoxane (MAO) anions expands the scope for developing industrial metallocene catalysts. Therefore, the effects of MAO anion design on the backbone structure, melt behavior, and crystallization of ethylene−4-methyl-1

  7. Nonisothermal melt-crystallization kinetics for in situ prepared poly(ethylene terephthalate)/monmorilonite (PET/OMMT)

    International Nuclear Information System (INIS)

    Antoniadis, G.; Paraskevopoulos, K.M.; Vassiliou, A.A.; Papageorgiou, G.Z.; Bikiaris, D.; Chrissafis, K.

    2011-01-01

    Highlights: → The melting temperature of the nanocomposites was shifted slightly to higher temperatures. → OMMT can act as nucleating agent. → The samples present lower activation energy compared to that of neat PET. → They crystallized by mechanisms with different activation energies. - Abstract: Poly(ethylene terephthalate) (PET) montmorillonite nanocomposites were prepared by in situ polymerization containing 0.5, 1, 2 and 5 wt% of organically modified montmorillonite (OMMT). In order to prepare exfoliated nanocomposites a new thermally stable modifier for montmorillonite nanoparticles like chlorohexadecane triphenylphosphine (CHDTPP) was synthesized. The preparation of nanocomposites was carried out using the two-stage melt polycondensation method. As verified by TEM micrographs, the dispersion of OMMT nanoparticles into the PET matrix was homogeneous while these were dispersed in the exfoliated form, proving the effectiveness of the modifier. The influence of OMMT nanomaterials on the thermal behaviour of PET and its non-isothermal crystallization was studied. Furthermore, the crystallization kinetics of PET and its nanocomposites were investigated by DSC. The activation energy was calculated using the Friedman's method. The Avrami exponent was calculated and analyzed. The effect of OMMT nanoparticles on spherulite growth rate of PET in all nanocomposites was also evaluated using the modified Lauritzen-Hoffman equation. From all these results it was found that OMMT nanoparticles can act as nucleating agents enhancing the crystallization rate of PET. The dispersion of OMMT nanoparticles in exfoliate form plays also an important role.

  8. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    International Nuclear Information System (INIS)

    Jahangir, Vafa; Riahifar, Reza; Sahba Yaghmaee, Maziar

    2016-01-01

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  9. A thermodynamic model for predicting surface melting and overheating of different crystal planes in BCC, FCC and HCP pure metallic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jahangir, Vafa, E-mail: vafa.jahangir@yahoo.com; Riahifar, Reza, E-mail: reza_rfr@yahoo.com; Sahba Yaghmaee, Maziar, E-mail: fkmsahba@uni-miskolc.hu

    2016-03-31

    In order to predict as well as study the surface melting phenomena in contradiction to surface overheating, a generalized thermodynamics model including the surface free energy of solid and the melt state along with the interfacial energy of solid–liquid (melt on substrate) has been introduced. In addition, the effect of different crystal structures of surfaces in fcc, bcc and hcp metals was included in surface energies as well as in the atomistic model. These considerations lead us to predict surface melting and overheating as two contradictory melting phenomena. The results of the calculation are demonstrated on the example of Pb and Al thin films in three groups of (100), (110) and (111) surface planes. Our conclusions show good agreement with experimental results and other theoretical investigations. Moreover, a computational algorithm has been developed which enables users to investigate the surface melt or overheating of single component metallic thin film with variable crystal structures and different crystalline planes. This model and developed software can be used for studying all related surface phenomena. - Highlights: • Investigating the surface melting and overheating phenomena • Effect of crystal orientations, surface energies, geometry and different atomic surface layers • Developing a computational algorithm and its related code (free-software SMSO-Ver1) • Thickness and orientation of surface plane dominate the surface melting or overheating. • Total excess surface energy as a function of thickness and temperature explains melting.

  10. Initial crystallization and growth in melt processing of large-domain YBa2Cu3Ox for magnetic levitation

    International Nuclear Information System (INIS)

    Shi, D.

    1994-10-01

    Crystallization temperature in YBa 2 Cu 3 O x (123) during peritectic reaction has been studied by differential thermal analysis (DTA) and optical microscopy. It has been found that YBa 2 Cu 3 O x experiences partial melting near 1,010 C during heating while crystallization takes place at a much lower temperature range upon cooling indicating a delayed nucleation process. A series of experiments have been conducted to search for the initial crystallization temperature in the Y 2 BaCuO x + liquid phase field. The authors have found that the slow-cool period (1 C/h) for the 123 grain texturing can start at as low as 960 C. This novel processing has resulted in high-quality, large-domain, strongly pinned 123 magnetic levitators

  11. Melt growth of zinc aluminate spinel single crystal by the micro-pulling down method under atmospheric pressure

    Science.gov (United States)

    Kamada, K.; Shoji, Y.; Yamaji, A.; Kurosawa, S.; Yokota, Yuui; Ohashi, Y.; Kim, Kyoung Jin; Ivanov, M.; Kochurikhin, V. V.; Yoshikawa, A.

    2018-06-01

    ZnAl2O4 crystals were grown using few starting compositions with various ZnO:AlO3/2 ratio using an Ir wire seed and Ir + Re crucible under ordinary pressure with Ar + 2%O2 atmosphere by the radiofrequency heating μ-PD furnace. The ZnAl2O4 spinel single crystal with 4 mm diameter could be successfully grown by the μ-PD method by optimization of starting melt composition considering with Zinc oxide evaporation. During 10 min of growth under normal pressure the formation of ZnAl2O4 single phase observed even at high vapor pressure of ZnO. The transmittance spectra and X-ray locking curve were measured for evaluating of grown ZnAl2O4 crystals quality.

  12. Magma transport and olivine crystallization depths in Kīlauea’s East Rift Zone inferred from experimentally rehomogenized melt inclusions

    Science.gov (United States)

    Tuohy, Robin M; Wallace, Paul J.; Loewen, Matthew W; Swanson, Don; Kent, Adam J R

    2016-01-01

    Concentrations of H2O and CO2 in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO2concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO2 is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai‘i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO2 in shrinkage bubbles. The measured CO2 concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n=10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n=38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO2 values than naturally quenched inclusions, indicating at least partial dissolution of CO2 from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO2 in the vapor bubbles suggests that 55-85% of the dissolved CO2 in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at <6 km depth, with the majority of olivine in the 1-3 km depth range. These depths are consistent with the interpretation that the Kīlauea Iki magma was supplied from Kīlauea’s summit magma reservoir (∼2-5 km depth). In contrast, olivine from Kapoho, which was the rift zone extension of the Kīlauea Iki eruption, crystallized over a much wider range of depths (∼1-16 km). The wider depth range requires magma transport during the Kapoho eruption from deep beneath the

  13. Magma transport and olivine crystallization depths in Kīlauea's east rift zone inferred from experimentally rehomogenized melt inclusions

    Science.gov (United States)

    Tuohy, Robin M.; Wallace, Paul J.; Loewen, Matthew W.; Swanson, Donald A.; Kent, Adam J. R.

    2016-07-01

    Concentrations of H2O and CO2 in olivine-hosted melt inclusions can be used to estimate crystallization depths for the olivine host. However, the original dissolved CO2 concentration of melt inclusions at the time of trapping can be difficult to measure directly because in many cases substantial CO2 is transferred to shrinkage bubbles that form during post-entrapment cooling and crystallization. To investigate this problem, we heated olivine from the 1959 Kīlauea Iki and 1960 Kapoho (Hawai'i) eruptions in a 1-atm furnace to temperatures above the melt inclusion trapping temperature to redissolve the CO2 in shrinkage bubbles. The measured CO2 concentrations of the experimentally rehomogenized inclusions (⩽590 ppm for Kīlauea Iki [n = 10]; ⩽880 ppm for Kapoho, with one inclusion at 1863 ppm [n = 38]) overlap with values for naturally quenched inclusions from the same samples, but experimentally rehomogenized inclusions have higher within-sample median CO2 values than naturally quenched inclusions, indicating at least partial dissolution of CO2 from the vapor bubble during heating. Comparison of our data with predictions from modeling of vapor bubble formation and published Raman data on the density of CO2 in the vapor bubbles suggests that 55-85% of the dissolved CO2 in the melt inclusions at the time of trapping was lost to post-entrapment shrinkage bubbles. Our results combined with the Raman data demonstrate that olivine from the early part of the Kīlauea Iki eruption crystallized at <6 km depth, with the majority of olivine in the 1-3 km depth range. These depths are consistent with the interpretation that the Kīlauea Iki magma was supplied from Kīlauea's summit magma reservoir (∼2-5 km depth). In contrast, olivine from Kapoho, which was the rift zone extension of the Kīlauea Iki eruption, crystallized over a much wider range of depths (∼1-16 km). The wider depth range requires magma transport during the Kapoho eruption from deep beneath the summit

  14. Kyropoulos method for growth of nonlinear optical organic crystal ABP (4-aminobenzophenone) from the melt

    Science.gov (United States)

    Pan, Shoukui; Okano, Y.; Tsunekawa, S.; Fukuda, T.

    1993-03-01

    The Kyropoulus method was used to grow nonlinear optical organic crystals ABP (4-aminobenzophenone). The crystals were characterized by nonlinear optical measurements and had a large effect of frequency doubling.

  15. Melting and crystallization behavior of partially miscible high density polyethylene/ethylene vinyl acetate copolymer (HDPE/EVA) blends

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yang; Zou, Huawei, E-mail: hwzou@163.com; Liang, Mei, E-mail: liangmeiww@163.com; Cao, Ya

    2014-06-01

    Highlights: • HDPE/EVA blends undergo phase separation, making it an interesting topic to investigate the relationships between miscibility and crystallization. • Influences from blending on the crystallization kinetics were successfully evaluated by Friedman's and Khanna's method. • X-ray diffraction studies revealed that blending with EVA the unit length of the unit cell of the HDPE increases. • Thermal fractionation method was successfully used to characterize the co-crystallization in HDPE/EVA blends. - Abstract: Crystallization studies on HDPE/EVA blends and the individual components were performed with differential scanning calorimetry (DSC) technique and wide angle X-ray scattering (WAXS). Influences of blending on the crystallization kinetics of each component in HDPE/EVA mixture were evaluated by Friedman's activation energy and Khanna's crystallization rate coefficient (CRC). The addition of more HDPE into the EVA matrix causes more heterogeneous nucleation while the addition of EVA would hinder the nucleation of HDPE at the beginning of cooling process. Inter-molecular interaction in the melt facilitated the crystallization of both EVA and HDPE components. X-ray diffraction studies revealed that HDPE and EVA have orthorhombic unit cell. Blending with EVA did not affect the crystalline structure of HDPE. In addition, a little shift of (1 1 0), (2 0 0) and (0 2 0) crystalline peaks toward lower 2θ values of samples indicating a little increase of unit cell parameters of the orthorhombic unit cell of polyethylene. Thermal fractionation results showed that co-crystallization took place in the HDPE/EVA blend. All those results indicated that the polymer pair we choose was partially miscible.

  16. Real-time qualitative study of forsterite crystal - Melt lithium distribution by laser-induced breakdown spectroscopy

    Science.gov (United States)

    Lebedev, V. F.; Makarchuk, P. S.; Stepanov, D. N.

    2017-11-01

    A factor of lithium distribution between single-crystal forsterite (Cr,Li:Mg2SiO4) and its melt are studied by laser-induced breakdown spectroscopy. Lithium content in the crystalline phase is found to achieve a saturation at relatively low Li concentration in the melt (about 0.02%wt.). An algorithm and software are developed for real-time analysis of the studied spectra of lithium trace amounts at wide variation of the plasma radiation intensity. The analyzed plasma spectra processing method is based on the calculation of lithium emission part in the total emission of the target plasma for each recorded spectrum followed by the error estimation for the series of measurements in the normal distribution approximation.

  17. 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.)

  18. 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

  19. Morphological Features of Diamond Crystals Dissolved in Fe0.7S0.3 Melt at 4 GPa and 1400°C

    Science.gov (United States)

    Sonin, V. M.; Zhimulev, E. I.; Pomazanskiy, B. S.; Zemnuhov, A. L.; Chepurov, A. A.; Afanasiev, V. P.; Chepurov, A. I.

    2018-01-01

    An experimental study of the dissolution of natural and synthetic diamonds in a sulfur-bearing iron melt (Fe0.7S0.3) with high P-T parameters (4 GPa, 1400°C) was performed. The results demonstrated that under these conditions, octahedral crystals with flat faces and rounded tetrahexahedral diamond crystals are transformed into rounded octahedroids, which have morphological characteristics similar to those of natural diamonds from kimberlite. It was suggested that, taking into account the complex history of individual natural diamond crystals, including the dissolution stages, sulfur-bearing metal melts up to sulfide melts were not only diamond-forming media during the early evolution of the Earth, but also natural solvents of diamond in the mantle environment before the formation of kimberlitic melts.

  20. In-situ temperature field measurements and direct observation of crystal/melt at vertical Bridgman growth of lead chloride under stationary and dynamic arrangement

    Czech Academy of Sciences Publication Activity Database

    Král, Robert; Nitsch, Karel

    2015-01-01

    Roč. 427, Oct (2015), 7-15 ISSN 0022-0248 R&D Projects: GA MŠk(CZ) LH14266 Institutional support: RVO:68378271 Keywords : single crystal growth * temperature field measurements * crystal/melt interface * lead chloride * vertical Bridgman method Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.462, year: 2015

  1. Influence of gravitational and vibrational convection on the heat- and mass transfer in the melt during crystal growing by Bridgman and floating zone methods

    Science.gov (United States)

    Fedorov, Oleg

    2016-07-01

    Space materials science is one of the priorities of different national and international space programs. The physical processes of heat and mass transfer in microgravity (including effect of g-jitter) is far from complete clarity, especially for important practical technology for producing crystals from the melt. The idea of the impact on crystallizing melt by low frequency vibration includes not only the possibility to suppress unwanted microaccelerations, but also to actively influence the structure of the crystallization front. This approach is one of the most effective ways to influence the quality of materials produced in flight conditions. The subject of this work is the effect of vibrations on the thermal and hydrodynamic processes during crystal growth using Bridgman and floating zone techniques, which have the greatest prospect of practical application in space. In the present approach we consider the gravitational convection, Marangoni convection, as well as the effect of vibration on the melt for some special cases. The results of simulation were compared with some experimental data obtained by the authors using a transparent model substance - succinonitrile (Bridgman method), and silicon (floating zone method). Substances used, process parameters and characteristics of the experimental units correspond the equipment developed for onboard research and serve as a basis for selecting optimum conditions vibration exposure as a factor affecting the solidification pattern. The direction of imposing vibrations coincides with the axis of the crystal, the frequency is presented by the harmonic law, and the force of gravity was varied by changing its absolute value. Mathematical model considered axisymmetric approximation of joint convective-conductive energy transfer in the system crystal - melt. Upon application of low-frequency oscillations of small amplitude along the axis of growing it was found the suppression of the secondary vortex flows near the

  2. The Silicon Environment in Silica Polymorphs, Aluminosilicate Crystals and Melts: An In Situ High Temperature XAS Study

    International Nuclear Information System (INIS)

    Cormier, L.; Neuville, D. R.; Roux, J.; Ligny, D. de; Henderson, G. S.; Flank, A.-M.; Lagarde, P.

    2007-01-01

    High temperature X-ray absorption spectroscopy at the Si K-edge has been used to obtain in situ information on SiO2 phase transitions upon heating. Important modifications are observed for the XANES spectra of the high temperature polymorphs, in relation to disordering of the SiO4 tetrahedra beyond the short-range correlations. This paper also presents the XANES spectra of anorthite (CaAl2Si2O8) from room temperature up to the melt (1900 K). This study shows the possibilities for determining the Si environment in crystals and glasses up to the liquid state using in situ XANES measurements

  3. Comparative study of crystallized melt-spun iron-boron alloys by Moessbauer effect and resistivity measurements

    International Nuclear Information System (INIS)

    Arshad, M.; Siddique, M.; Anwar-ul-Islam, M.; Butt, N.M.; Ashfaq, A.; Shamim, A.

    1993-01-01

    Moessbauer study of two as-quenched, melt-spun iron-boron completely crystallized alloys, Fe/sub 72/01/B/sub 28/ and Fe/sub 88/01/B/sub 12/, indicates the presence of alpha-Fe, Fe/sub 2/B and Fe/sub 3/B. The percentage of these phases is different in the two alloys. Resistivity measurements show to phase transformation of Fe/sub 3/B and Fe/sub 2/B, respectively. (author)

  4. Effects of tellurium concentration on the structure of melt-grown ZnSe crystals

    International Nuclear Information System (INIS)

    Atroshchenko, Lyubov V.; Galkin, Sergey N.; Rybalka, Irina A.; Voronkin, Evgeniy F.; Lalayants, Alexandr I.; Ryzhikov, Vladimir D.; Fedorov, Alexandr G.

    2005-01-01

    It has been shown that isovalent doping by tellurium positively affects the structural perfection of ZnSe crystals related to the completeness of the wurtzite-sphalerite phase transition. The optimum concentration range of tellurium in ZnSe crystals is 0.3-0.6 mass %. X-ray diffraction studies have shown that in ZnSe 1-x Te x crystals at tellurium concentrations below 0.3 mass % twinning and packing defects occur, while tellurium concentrations above 0.6 mass % lead to formation of tetragonal crystal lattice

  5. Growth of congruently melting Ca0.59Sr0.41F2 crystals and study of their properties

    Science.gov (United States)

    Karimov, D. N.; Komar'kova, O. N.; Sorokin, N. I.; Bezhanov, V. A.; Chernov, S. P.; Popov, P. A.; Sobolev, B. P.

    2010-05-01

    Homogeneous crystals of Ca0.59Sr0.41F2 alloy (sp. gr., Fm bar 3 m, a = 0.56057 nm), corresponding to the point of minimum in the melting curve in the CaF2-SrF2 phase diagram, have been grown by the vertical Bridgman method. The optical, mechanical, electrical, and thermophysical properties of Ca0.59Sr0.41F2 and MF2 crystals ( M = Ca, Sr) have been studied and comparatively analyzed. Ca0.59Sr0.41F2 crystals are transparent in the range of 0.133-11.5 μm, have refractive index n D = 1.436, microhardness H μ = 2.63 ± 0.10 GPa, ion conductivity σ = 5 × 10-5 S/cm at 825 K, and thermal conductivity k = 4.0 W m-1 K-1 at 300 K. It is shown that the optical properties of Ca0.59Sr0.41F2 crystals are intermediate between those of CaF2 and SrF2, whereas their mechanical and electrical characteristics are better than the latter compounds.

  6. Melting and crystallization of in-situ polymerized cyclic butylene terephthalates with and without organoclay: a modulated DSC study

    Directory of Open Access Journals (Sweden)

    2007-02-01

    Full Text Available The polymerization of cyclic butylene terephthalate oligomers (CBT were studied in presence (in 5 wt.% and absence of an organoclay (Cloisite® 30B by modulated DSC (MDSC. The organoclay containing samples were produced by dry and melt blending, respectively. The first heating, causing the polymerization of the CBT catalyzed by an organotin compound, was followed by cooling prior to the second heating. The MDSC scans covered the temperature interval between 0 and 260°C. The aim of this protocol was to study the crystallization and melting behavior of the resulting polybutylene terephthalate (pCBT and its organoclay modified nanocomposites. It was found that the thermal behaviors of the polymerizing and polymerized CBT (pCBT were strongly affected by the sample preparation. The organoclay suppressed the crystallization of the pCBT produced during the first heating. However, results from the second heating suggest that more perfect crystallites were formed in the organoclay modified pCBT variants. The organoclay also affected the conversion and mean molecular mass of the resulting pCBT which were slightly lower than those of the plain pCBT polymerized under identical conditions.

  7. Crystal structure and magnetic properties of a nitrogenated melt-spun Sm[sub 2]Fe[sub 17] compound

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Choong-Jin [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of); Lee, Woo-Young [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of); Choi, Seung-Duck [Electromagnetic Materials Laboratory, Research Institute of Industrial Science and Technology, P.O. Box 135, 790-330 Pohang (Korea, Republic of)

    1994-05-15

    Sm[sub 2]Fe[sub 17]N[sub 2.9] compound powders were prepared from parent alloys of Sm[sub 2]Fe[sub 17] which were made by both arc melting and rapid solidification processes. The cast Sm[sub 2]Fe[sub 17] contained mixed phases of SmFe[sub 3] and [alpha]-Fe, and correspondingly formed less Sm[sub 2]Fe[sub 17]N[sub x] with a rather large amount of residual [alpha]-Fe after nitrogenation. The melt-spun Sm[sub 2]Fe[sub 17] compound, however, was single phase and exhibited a negligible amount of residual [alpha]+Fe after nitrogenation. The residual amount of free iron was found to increase as a function of milling time and to impede the development of promising permanent magnetic properties. The melt-spun Sm[sub 2]Fe[sub 17]N[sub x] compound powders exhibited a coercivity value [sub i]H[sub c] of 5 kOe, which is double that of the as-cast Sm[sub 2]Fe[sub 17]N[sub x] powders and a high remanence B[sub r]=60 e.m.u. g[sup -1]. The average magnetic moment of Fe atoms in the crystal is estimated to be 2.29 [mu][sub B] and the Fe atom in the 6c site exhibits the highest magnetic moment of 2.65 [mu][sub B]. The expansion in the c axial direction of the nitrogenated crystal was found to be mainly due to extension of Sm(6c)-Fe(c) and Fe(18f)-Fe(18f) distances. ((orig.))

  8. The melt growth of large LuAP single crystals for PET scanners

    International Nuclear Information System (INIS)

    Petrosyan, Ashot; Ovanesyan, Karine; Shirinyan, Grigory; Butaeva, Tatyana; Derdzyan, Marina; Pedrini, Christian; Dujardin, Christophe; Garnier, Nicolas; Kamenskikh, Irina

    2005-01-01

    Performance properties of LuAP, a material of highly promising potential for future PET scanners, are presented, as they relate to crystal growth and composition. The light yield measured in 2x2x10 mm 3 elements with 0.4-0.5% Ce and cut from large size crystals (100 mm long and 15 mm in diameter) grown by the Bridgman technique is improved to 40% LSO. The ratio between light yield measured in vertical and horizontal arrangements in the best crystals is near 90%. The role of chemical purity in respect to divalent impurities is studied

  9. Numerical analysis of transport phenomena in Y-Ba-Cu-O melt during growth of superconducting crystal Y123 by Czochralski method

    Science.gov (United States)

    Szmyd, J. S.; Suzuki, K.

    2003-10-01

    In 1993, at the Superconductivity Research Laboratory (SRL), International Superconductivity Technology Centre (ISTEC), in Tokyo, continuous growth of large single crystals of YBa 2Cu 3O 7- x (Y123) was achieved by the application of a modified Czochralski method. This paper presents the numerical computations of the flow, thermal and Y concentration fields in the Ba-Cu-O melt for Y123 single crystal growth by this modified method. The finite volume method was used to calculate the fluid flow, heat transfer and yttrium distribution in the melt with staggered numerical grid. The flow in the melt was modelled as an incompressible Newtonian and Boussinesque fluid. Calculations are presented for a combined flow regime of buoyancy-driven natural convection and crystal-rotation-driven forced convection.

  10. An ordered metallic glass solid solution phase that grows from the melt like a crystal

    International Nuclear Information System (INIS)

    Chapman, Karena W.; Chupas, Peter J.; Long, Gabrielle G.; Bendersky, Leonid A.; Levine, Lyle E.; Mompiou, Frédéric; Stalick, Judith K.; Cahn, John W.

    2014-01-01

    We report structural studies of an Al–Fe–Si glassy solid that is a solid solution phase in the classical thermodynamic sense. We demonstrate that it is neither a frozen melt nor nanocrystalline. The glass has a well-defined solubility limit and rejects Al during formation from the melt. The pair distribution function of the glass reveals chemical ordering out to at least 12 Å that resembles the ordering within a stable crystalline intermetallic phase of neighboring composition. Under isothermal annealing at 305 °C the glass first rejects Al, then persists for approximately 1 h with no detectable change in structure, and finally is transformed by a first-order phase transition to a crystalline phase with a structure that is different from that within the glass. It is possible that this remarkable glass phase has a fully ordered atomic structure that nevertheless possesses no long-range translational symmetry and is isotropic

  11. SEPARATION OF CsCl FROM LiCl-CsCl MOLTEN SALT BY COLD FINGER MELT CRYSTALLIZATION

    Directory of Open Access Journals (Sweden)

    JOSHUA R. VERSEY

    2014-06-01

    Full Text Available This study provides a fundamental understanding of a cold finger melt crystallization technique by exploring the heat and mass transfer processes of cold finger separation. A series of experiments were performed using a simplified LiCl-CsCl system by varying initial CsCl concentrations (1, 3, 5, and 7.5 wt%, cold finger cooling rates (7.4, 9.8, 12.3, and 14.9 L/min, and separation times (5, 10, 15, and 30 min. Results showed a potential recycling rate of 0.36 g/min with a purity of 0.33 wt% CsCl in LiCl. A CsCl concentrated drip formation was found to decrease crystal purity especially for smaller crystal formations. Dimensionless heat and mass transfer correlations showed that separation production is primarily influenced by convective transfer controlled by cooling gas flow rate, where correlations are more accurate for slower cooling gas flow rates.

  12. The influence of heterogeneous nucleation on the surface crystallization of guaifenesin from melt extrudates containing Eudragit L10055 or Acryl-EZE.

    Science.gov (United States)

    Bruce, Caroline D; Fegely, Kurt A; Rajabi-Siahboomi, Ali R; McGinity, James W

    2010-05-01

    The objective of this study was to investigate the influence of talc and humidity conditions during storage on the crystal growth of guaifenesin on the surface of melt-extruded matrix tablets. Tablets consisted of the model drug guaifenesin in a matrix of either Acryl-EZE(R) or Eudragit(R) L10055 and either no talc, 25% or 50% talc. After processing, the hot-melt-extruded matrix tablets were supersaturated with amorphous guaifenesin, which resulted in the development of guaifenesin drug crystals on exposed surfaces of the tablet during storage (all tablets were stored at 24 degrees C). A previously developed, quantitative test was used to assay for surface guaifenesin. In tablets with a drug-to-polymer ratio of 19:81, talc-containing tablets exhibited an earlier onset of crystal growth (storage at 17% relative humidity). The presence of talc also increased the amount of surface crystallization and was independent of the talc concentration, since the talc levels used in this study exceeded the critical nucleant concentration. Additional non-melting components did not have an additive effect on surface crystal growth. High humidity during storage (78%) increased guaifenesin crystallization, but moisture uptake of tablets did not correlate with increased drug recrystallization. When storage at 17% relative humidity was interrupted for 3days by storage at 78% relative humidity before the tablets were returned to their previous low RH storage conditions, crystal growth quickly increased during the high RH interval and remained at an elevated level throughout the remaining storage period. A similar intermediate period of low, 17% relative humidity in tablets stored before and after that time at 78% RH did not affect surface crystallization levels. The effects of humidity and talc on the crystallization of guaifenesin from melt-extruded dosage forms supersaturated with amorphous drug were ascribed to heterogeneous nucleation.

  13. Thermal Analysis, Mechanical and Rheological Behaviour of Melt Manufactured Polyethylene/Liquid Crystal Polymer Blends

    Directory of Open Access Journals (Sweden)

    Ilze ELKSNITE

    2011-07-01

    Full Text Available Modification of properties of conventional thermoplastics with thermotropic liquid crystal polymers, from one hand, allows decrease their viscosities, substantially facilitating processing conditions, and, from another hand, allows increase their exploitation properties. Orientation of the labile structure of liquid crystal polymer in extrusion or injection moulding causes specific reinforcement (so-called self-reinforcement to occur in the blends containing liquid crystal polymer. Up to now the effect of self-reinforcement is mostly investigated in the blends, containing considerable amount of liquid crystal polymer. In this research the effect of minor amounts of liquid crystalline co-polyester modifier on the properties of polyethylene is investigated. Various compositions of laboratory synthesized hydroxybenzoic acid /polyethylene terephtalate copolymer containing polyethylene composites have been manufactured by thermoplastic blending. It has been observed that 1 modulus of elasticity, yield strength and ultimate strength increase with raising the content of liquid crystalline modifier; 2 void content in the investigated polyethylene/liquid crystal copolymer composites is not greater that 1 %; 3 addition of liquid crystalline co-polyester modifier improves arrangement of PE crystalline phase.http://dx.doi.org/10.5755/j01.ms.17.2.483

  14. Effects of emulsifier addition on the crystallization and melting behavior of palm olein and coconut oil.

    Science.gov (United States)

    Maruyama, Jessica Mayumi; Soares, Fabiana Andreia Schafer De Martini; D'Agostinho, Natalia Roque; Gonçalves, Maria Inês Almeida; Gioielli, Luiz Antonio; da Silva, Roberta Claro

    2014-03-12

    Two commercial emulsifiers (EM1 and EM2), containing predominantly monoacylglycerols (MAGs), were added in proportiond of 1.0 and 3.0% (w/w) to coconut oil and palm olein. EM1 consisted of approximately 90% MAGs, whereas EM2 consisted of approximately 50% MAGs. The crystallization behavior of these systems was evaluated by differential scanning calorimetry (DSC) and microscopy under polarized light. On the basis of DSC results, it was clear that the addition of EM2 accelerated the crystallization of coconut oil and delayed the crystallization of palm olein. In both oils EM2 addition led to the formation of smaller spherulites, and these effects improved the possibilities for using these fats as ingredients. In coconut oil the spherulites were maintained even at higher temperatures (20 °C). The addition of EM1 to coconut oil changed the crystallization pattern. In palm olein, the addition of 3.0% (w/w) of this emulsifier altered the pattern of crystallization of this fat.

  15. Numerical simulation of the oxygen concentration distribution in silicon melt for different crystal lengths during Czochralski growth with a transverse magnetic field

    Science.gov (United States)

    Chen, Jyh-Chen; Chiang, Pei-Yi; Nguyen, Thi Hoai Thu; Hu, Chieh; Chen, Chun-Hung; Liu, Chien-Cheng

    2016-10-01

    A three-dimensional simulation model is used to study the oxygen concentration distribution in silicon crystal during the Czochralski growth process under a transverse uniform magnetic field. The flow, temperature, and oxygen concentration distributions inside the furnace are calculated for different crystal lengths. There is significant variation in the flow structure in the melt with the growth length. The results show that in the initial stages, there is a decrease in the oxygen concentration at the crystal-melt interface as the length of the growing crystal increases. As the crystal lengthens further, a minimum value is reached after which the oxygen concentration increases continuously. This trend is consistent with that shown in the experimental results. The variation of the oxygen concentration with the growth length is strongly related to the depth of the melt in the crucible and the flow structure inside the melt. Better uniformity of the axial oxygen concentration can be achieved by proper adjustment of the crucible rotation rate during the growth process.

  16. Cavity Pull Rod: Device to Promote Single Crystal Growth from the Melt

    Science.gov (United States)

    Goldsby, Jon (Inventor)

    2017-01-01

    A pull rod for use in producing a single crystal from a molten alloy is provided that includes an elongated rod having a first end and a second end, a first cavity defined at the first end and a second cavity defined at the first end and in communication with the first cavity. The first cavity receives the molten alloy and the second cavity vents a gas from the molten alloy to thereby template a single crystal when the pull rod is dipped into and extracted from the molten alloy.

  17. Partial reactive crystallization of variable CO2-bearing siliceous MORB-eclogite-derived melt in fertile peridotite and genesis of alkalic basalts with signatures of crustal recycling

    Science.gov (United States)

    Mallik, A.; Dasgupta, R.

    2013-12-01

    The presence of heterogeneity in the form of recycled altered oceanic crust (MORB-eclogite) has been proposed in the source of HIMU ocean island basalts (OIBs) [1]. Partial melts of recycled oceanic crust, however, are siliceous and Mg-poor and thus do not resemble the major element compositions of alkalic OIBs that are silica-poor and Mg-rich. In an upwelling heterogenous mantle, MORB-eclogite undergoes melting deeper than volatile-free peridotite, hence, andesitic partial melt derived from eclogite will react with subsolidus peridotite. We have examined the effect of such a melt-rock reaction under volatile-free conditions at 1375 °C, 3 GPa by varying the melt-rock ratio from 8 to 50 wt.% [2]. We concluded that the reacted melts reproduce certain major element characteristics of oceanic basanites, but not nephelinites. Also, the melt-rock reaction produces olivine and garnet-bearing websteritic residue. Because presence of CO2 has been invoked in the source of many HIMU ocean islands, the effect of CO2 on such a melt-rock reaction needs to be evaluated. Accordingly, we performed reaction experiments on mixtures of 25% and 33% CO2-bearing andesitic partial melt and peridotite at 1375 °C, 3 GPa by varying the dissolved CO2 content of the reacting melts from 1 to 5 wt.% (bulk CO2 from 0.25 to 1.6 wt.%) [3, this study]. Owing to melt-rock reaction, with increasing CO2 in the bulk mixture, (a) modes of olivine and cpx decrease while melt, opx and garnet increase, (b) reacted melts evolve to greater degree of Si-undersaturation (from andesite through basanite to nephelinite), (c) enhanced crystallization of garnet take place with higher CO2 in the melt, reducing alumina content of the reacted melts, and (d) CaO and MgO content of the reacted melts increase, without affecting FeO* and Na2O contents (indicating greater propensity of Ca2+ and Mg2+ over Fe2+ and Na+ to enter silicate melt as carbonate). For a given melt-MgO, the CO2-bearing reacted melts are a better

  18. Seed crystals with improved properties for melt processing superconductors for practical applications

    Science.gov (United States)

    Veal, Boyd W.; Paulikas, Arvydas; Balachandran, Uthamalingam; Zhong, Wei

    1997-01-01

    A method of fabricating bulk superconducting material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta. comprising heating compressed powder oxides and/or carbonates of R and Ba and Cu present in mole ratios to form RBa.sub.2 Cu.sub.3 O.sub.7-.delta. in physical contact with an oxide single crystal seed to a temperature sufficient to form a liquid phase in the RBa.sub.2 Cu.sub.3 O.sub.7-.delta. while maintaining the single crystal seed solid to grow the superconducting material and thereafter cooling to provide a material including RBa.sub.2 Cu.sub.3 O.sub.7-.delta.. R is a rare earth or Y or La and the single crystal seed has a lattice mismatch with RBa.sub.2 Cu.sub.3 O.sub.7-.delta. of less than about 2% at the growth temperature. The starting material may be such that the final product contains a minor amount of R.sub.2 BaCuO.sub.5.

  19. Melt, fluid and crystal inclusions in olivine phenocrysts from Kerguelen plume-derived picritic basalts: evidence for interaction with the Kerguelen Plateau lithosphere.

    NARCIS (Netherlands)

    Borisova, A.U.; Nikogosian, I.; Shimizu, N.; Weis, D.; Scoates, J.S.; Touret, J.L.R.; Damasceno, D.

    2002-01-01

    Melt, fluid and crystal inclusions have been studied in olivine phenocrysts from a suite of picritic basalts dredged during the "Marion Dufresne" MD 109 cruise (Dredge 6) from a seamount located between the Kerguelen Archipelago and Heard Island (Southern Indian Ocean). A two-stage polybaric

  20. Registration of melting and crystallization process of MCMgLi8Ca5 alloy with use of ATND method

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2009-04-01

    Full Text Available Among lightweight metal alloys, magnesium is the lightest structural material with density of 1.74 g/cm3, having many attractive physical and mechanical properties combined with processing advantages. Therefore, it represents very attractive material for large amountof applications starting from automotive industry as the main user, up to other industry fields like sports, robotic electronics, armaments, and textile ones, or production of audio-video equipment. Furthermore, addition of lithium, that has density of 0,53 g/cm3, reduces density of the resulting Mg-Li alloys to the same level as polymeric materials. On metallic matrix of magnesium alloys with lithium are also manufactured composites reinforced with e.g. ceramic fiber, which are used as a lightweight and resistant structure materials. Therefore, Mg-Li alloys become an alternative material assuring low density, improved ductility and corrosion resistance.The paper presents an attempt of implementation of the ATND method to monitoring of crystallization process of MCMgLi8Ca5 alloys.Investigated magnesium alloys were produced in the Foundry Research Institute. Registration of melting and crystallization processes wasmade with use of the ATND method. Results of the preliminary tests are shown in a graphical form.

  1. 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

  2. Investigation of the crystallization process of titanium alloy ingots produced by vacuum arc melting method

    International Nuclear Information System (INIS)

    Tetyukhin, V.V.; Kurapov, V.N.; Trubin, A.N.; Demchenko, M.V.; Lazarev, V.G.; Ponedilko, S.V.; Dubrovina, N.T.; Kurapova, L.A.

    1978-01-01

    The process of crystallization and hardening of the VT3-1 and VT9 titanium alloys ingots during the vacuum-arc remelting (VAR) has been studied. In order to investigate the kinetics of the hole shape changing and the peculiarities of the ingot formation during the VAR, the radiography method has been used. It is established that the VAR of the titanium alloy ingots is basically a continuous process. An intense heating of the liquid bath mirror and the availability of high temperature gradients in the hole are the typical features of the VAR process

  3. Fission Product Separation from Pyrochemical Electrolyte by Cold Finger Melt Crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Versey, Joshua R. [Univ. of Idaho, Moscow, ID (United States)

    2013-08-01

    This work contributes to the development of pyroprocessing technology as an economically viable means of separating used nuclear fuel from fission products and cladding materials. Electrolytic oxide reduction is used as a head-end step before electrorefining to reduce oxide fuel to metallic form. The electrolytic medium used in this technique is molten LiCl-Li2O. Groups I and II fission products, such as cesium (Cs) and strontium (Sr), have been shown to partition from the fuel into the molten LiCl-Li2O. Various approaches of separating these fission products from the salt have been investigated by different research groups. One promising approach is based on a layer crystallization method studied at the Korea Atomic Energy Research Institute (KAERI). Despite successful demonstration of this basic approach, there are questions that remain, especially concerning the development of economical and scalable operating parameters based on a comprehensive understanding of heat and mass transfer. This research explores these parameters through a series of experiments in which LiCl is purified, by concentrating CsCl in a liquid phase as purified LiCl is crystallized and removed via an argon-cooled cold finger.

  4. Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field

    Science.gov (United States)

    Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar

    2000-01-01

    This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.

  5. Determination of the crystal-melt interface kinetic coefficient from molecular dynamics simulations

    International Nuclear Information System (INIS)

    Monk, J; Mendelev, M I; Yang, Y; Asta, M; Hoyt, J J; Sun, D Y

    2010-01-01

    The generation and dissipation of latent heat at the moving solid–liquid boundary during non-equilibrium molecular dynamics (MD) simulations of crystallization can lead to significant underestimations of the interface mobility. In this work we examine the heat flow problem in detail for an embedded atom description of pure Ni and offer strategies to obtain an accurate value of the kinetic coefficient, μ. For free-solidification simulations in which the entire system is thermostated using a Nose–Hoover or velocity rescaling algorithm a non-uniform temperature profile is observed and a peak in the temperature is found at the interface position. It is shown that if the actual interface temperature, rather than the thermostat set point temperature, is used to compute the kinetic coefficient then μ is approximately a factor of 2 larger than previous estimates. In addition, we introduce a layered thermostat method in which several sub-regions, aligned normal to the crystallization direction, are indepently thermostated to a desired undercooling. We show that as the number of thermostats increases (i.e., as the width of each independently thermostated layer decreases) the kinetic coefficient converges to a value consistent with that obtained using a single thermostat and the calculated interface temperature. Also, the kinetic coefficient was determined from an analysis of the equilibrium fluctuations of the solid–liquid interface position. We demonstrate that the kinetic coefficient obtained from the relaxation times of the fluctuation spectrum is equivalent to the two values obtained from free-solidification simulations provided a simple correction is made for the contribution of heat flow controlled interface motion. Finally, a one-dimensional phase field model that captures the effect of thermostats has been developed. The mesoscale model reproduces qualitatively the results from MD simulations and thus allows for an a priori estimate of the accuracy of a

  6. Interfacial free energy of the NaCl crystal-melt interface from capillary wave fluctuations.

    Science.gov (United States)

    Benet, Jorge; MacDowell, Luis G; Sanz, Eduardo

    2015-04-07

    In this work we study, by means of molecular dynamics simulations, the solid-liquid interface of NaCl under coexistence conditions. By analysing capillary waves, we obtain the stiffness for different orientations of the solid and calculate the interfacial free energy by expanding the dependency of the interfacial free energy with the solid orientation in terms of cubic harmonics. We obtain an average value for the solid-fluid interfacial free energy of 89 ± 6 mN m(-1) that is consistent with previous results based on the measure of nucleation free energy barriers [Valeriani et al., J. Chem. Phys. 122, 194501 (2005)]. We analyse the influence of the simulation setup on interfacial properties and find that facets prepared as an elongated rectangular stripe give the same results as those prepared as squares for all cases but the 111 face. For some crystal orientations, we observe at small wave-vectors a behaviour not consistent with capillary wave theory and show that this behavior does not depend on the simulation setup.

  7. Effects of Undercooling and Cooling Rate on Peritectic Phase Crystallization Within Ni-Zr Alloy Melt

    Science.gov (United States)

    Lü, P.; Wang, H. P.

    2018-04-01

    The liquid Ni-16.75 at. pct Zr peritectic alloy was substantially undercooled and containerlessly solidified by an electromagnetic levitator and a drop tube. The dependence of the peritectic solidification mode on undercooling was established based on the results of the solidified microstructures, crystal growth velocity, as well as X-ray diffraction patterns. Below a critical undercooling of 124 K, the primary Ni7Zr2 phase preferentially nucleates and grows from the undercooled liquid, which is followed by a peritectic reaction of Ni7Zr2+L → Ni5Zr. The corresponding microstructure is composed of the Ni7Zr2 dendrites, peritectic Ni5Zr phase, and inter-dendritic eutectic. Nevertheless, once the liquid undercooling exceeds the critical undercooling, the peritectic Ni5Zr phase directly precipitates from this undercooled liquid. However, a negligible amount of residual Ni7Zr2 phase still appears in the microstructure, indicating that nucleation and growth of the Ni7Zr2 phase are not completely suppressed. The micromechanical property of the peritectic Ni5Zr phase in terms of the Vickers microhardness is enhanced, which is ascribed to the transition of the peritectic solidification mode. To suppress the formation of the primary phase completely, this alloy was also containerlessly solidified in free fall experiments. Typical peritectic solidified microstructure forms in large droplets, while only the peritectic Ni5Zr phase appears in smaller droplets, which gives an indication that the peritectic Ni5Zr phase directly precipitates from the undercooled liquid by completely suppressing the growth of the primary Ni7Zr2 phase and the peritectic reaction due to the combined effects of the large undercooling and high cooling rate.

  8. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    International Nuclear Information System (INIS)

    Mtangi, W.; Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M.; Nyamhere, C.

    2012-01-01

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8±0.3) meV that has been suggested as Zn i related and possibly H-complex related and (54.5±0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X Zn . The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60×10 17 cm −3 at 200 °C to 4.37×10 18 cm -3 at 800 °C.

  9. Annealing and surface conduction on Hydrogen peroxide treated bulk melt-grown, single crystal ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Mtangi, W., E-mail: wilbert.mtangi@up.ac.za [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nel, J.M.; Auret, F.D.; Chawanda, A.; Diale, M. [University of Pretoria, Physics Department, Pretoria 0002 (South Africa); Nyamhere, C. [Nelson Mandela Metropolitan University, Physics Department, P.O. Box 77000, Port Elizabeth 6031 (South Africa)

    2012-05-15

    We report on the studies carried out on hydrogen peroxide treated melt-grown, bulk single crystal ZnO samples. Results show the existence of two shallow donors in the as-received ZnO samples with energy levels (37.8{+-}0.3) meV that has been suggested as Zn{sub i} related and possibly H-complex related and (54.5{+-}0.9) meV, which has been assigned to an Al-related donor. Annealing studies performed on the hydrogen peroxide treated samples reveal the existence of a conductive channel in the samples in which new energy levels have been observed, Zn vacancies, related to the Group I elements, X{sub Zn}. The surface donor volume concentration of the conductive channel was calculated from a theory developed by Look (2007) . Results indicate an increase in the surface volume concentration with increasing annealing temperature from 60 Multiplication-Sign 10{sup 17} cm{sup -3} at 200 Degree-Sign C to 4.37 Multiplication-Sign 10{sup 18} cm{sup -3} at 800 Degree-Sign C.

  10. Vacancy formation energies in close-packed crystals correlated with melting temperature via thermodynamics and liquid structure

    International Nuclear Information System (INIS)

    Rashid, R.I.M.A.; March, N.H.

    1988-08-01

    In earlier work, the vacancy formation energy E v in close-packed crystals, in units of the thermal energy k B T m at the melting temperature T m , has been connected with compressibility and specific heats, plus terms dependent on the liquid structure at T m . Here, this connection has been examined quantitatively for (a) the insulating condensed rare gases Ne, Ar and Kr, and (b) a variety of close-packed metals. For case (a), E v /k B T m can be calculated directly from thermodynamic data to obtain agreement with experiment for Ar and Kr, though not for Ne. A 'residual' contribution is estimated for Ar and Kr from diffraction and computer experiments on the density dependence of the liquid pair correlation function and is shown to be very small. Agreement is less impressive for case (b) for the eight close-packed metals for which all data required is known, the thermodynamic formula giving an average value E v /k B T m =7.8+-1.1 whereas experiment yields 9.4+-1.8. However, for the body-centred cubic alkalis the thermodynamic average value of 4.5+-0.5 is much lower than the experimental value 11.5+-2.0 consistent with the known role of ionic relaxation round the vacancy in such open structures. (author). 16 refs, 2 tabs

  11. separation of strontium and cesium from ternary and quaternary lithium chloride-potassium chloride salts via melt crystallization

    Directory of Open Access Journals (Sweden)

    Ammon N. Williams

    2015-12-01

    Full Text Available Separation of cesium chloride (CsCl and strontium chloride (SrCl2 from the lithium chloride-potassium chloride (LiCl-KCl salt was studied using a melt crystallization process similar to the reverse vertical Bridgeman growth technique. A ternary SrCl2-LiCl-KCl salt was explored at similar growth rates (1.8–5 mm/h and compared with CsCl ternary results to identify similarities. Quaternary experiments were also conducted and compared with the ternary cases to identify trends and possible limitations to the separations process. In the ternary case, as much as 68% of the total salt could be recycled per batch process. In the quaternary experiments, separation of Cs and Sr was nearly identical at the slower rates; however, as the growth rate increased, SrCl2 separated more easily than CsCl. The quaternary results show less separation and rate dependence than in both ternary cases. As an estimated result, only 51% of the total salt could be recycled per batch. Furthermore, two models have been explored to further understand the growth process and separation. A comparison of the experimental and modeling results reveals that the nonmixed model fits reasonably well with the ternary and quaternary data sets. A dimensional analysis was performed and a correlation was identified to semipredict the segregation coefficient.

  12. Separation of strontium and cesium from ternary and quaternary lithium chloride-potassium chloride salts via melt crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Ammon n.; Pack, Michael [Dept. of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond (United States); Phongikaroon, Spathorn [Dept. of Chemical and Materials Engineering and Nuclear Engineering Program, University of Idaho, Idaho Falls (United States)

    2015-12-15

    Separation of cesium chloride (CsCl) and strontium chloride (SrCl{sub 2}) from the lithium chloride-potassium chloride (LiCl-KCl) salt was studied using a melt crystallization process similar to the reverse vertical Bridgeman growth technique. A ternary SrCl2-LiCl-KCl salt was explored at similar growth rates (1.8-5 mm/h) and compared with CsCl ternary results to identify similarities. Quaternary experiments were also conducted and compared with the ternary cases to identify trends and possible limitations to the separations process. In the ternary case, as much as 68% of the total salt could be recycled per batch process. In the quaternary experiments, separation of Cs and Sr was nearly identical at the slower rates; however, as the growth rate increased, SrCl{sub 2} separated more easily than CsCl. The quaternary results show less separation and rate dependence than in both ternary cases. As an estimated result, only 51% of the total salt could be recycled per batch. Furthermore, two models have been explored to further understand the growth process and separation. A comparison of the experimental and modeling results reveals that the nonmixed model fits reasonably well with the ternary and quaternary data sets. A dimensional analysis was performed and a correlation was identified to semipredict the segregation coefficient.

  13. Thermal behavior and melt fragility number of Cu100-x Zrx glassy alloys in terms of crystallization and viscous flow

    Science.gov (United States)

    Russew, K.; Stojanova, L.; Yankova, S.; Fazakas, E.; Varga, L. K.

    2009-01-01

    Six Cu100-xZrx amorphous alloys (x in the range 35.7 - 60 at. percent) were prepared via chill block melt spinning (CBMS) method under low pressure Helium atmosphere. Their crystallization and viscous flow behavior was studied with the aid of Perkin Elmer DSC 2C and Perkin Elmer TMS 2 devices, respectively. The viscous flow temperature dependencies at a heating rate of 20 K min-1 were interpreted on the basis of the f ree volume model. The DSC and TMS data were used to determine the fragility number m of Angell in three different ways as a function of alloy composition. It has been shown that the fragility number goes over a maximum and has a minimum at x very near to the alloy composition Cu64Zr36 in good agreement with the results of Donghua Xu et al. and Wang D et al. The experimental techniques and model interpretation used provide a tool for understanding the glass forming ability (GFA) and relaxation phenomena in metallic glasses.

  14. Incomparable hardness and modulus of biomimetic porous polyurethane films prepared by directional melt crystallization of a solvent

    Science.gov (United States)

    An, Suyeong; Kim, Byoungsoo; Lee, Jonghwi

    2017-07-01

    Porous materials with surprisingly diverse structures have been utilized in nature for many functional purposes. However, the structures and applications of porous man-made polymer materials have been limited by the use of processing techniques involving foaming agents. Herein, we demonstrate for the first time the outstanding hardness and modulus properties of an elastomer that originate from the novel processing approach applied. Polyurethane films of 100-μm thickness with biomimetic ordered porous structures were prepared using directional melt crystallization of a solvent and exhibited hardness and modulus values that were 6.8 and 4.3 times higher than those of the random pore structure, respectively. These values surpass the theoretical prediction of the typical model for porous materials, which works reasonably well for random pores but not for directional pores. Both the ordered and random pore structures exhibited similar porosities and pore sizes, which decreased with increasing solution concentration. This unexpectedly significant improvement of the hardness and modulus could open up new application areas for porous polymeric materials using this relatively novel processing technique.

  15. Thermal behavior and melt fragility number of Cu100-x Zrx glassy alloys in terms of crystallization and viscous flow

    International Nuclear Information System (INIS)

    Russew, K; Stojanova, L; Yankova, S; Fazakas, E; Varga, L K

    2009-01-01

    Six Cu 100-x Zr x amorphous alloys (x in the range 35.7 - 60 at. percent) were prepared via chill block melt spinning (CBMS) method under low pressure Helium atmosphere. Their crystallization and viscous flow behavior was studied with the aid of Perkin Elmer DSC 2C and Perkin Elmer TMS 2 devices, respectively. The viscous flow temperature dependencies at a heating rate of 20 K min -1 were interpreted on the basis of the f ree volume model. The DSC and TMS data were used to determine the fragility number m of Angell in three different ways as a function of alloy composition. It has been shown that the fragility number goes over a maximum and has a minimum at x very near to the alloy composition Cu 64 Zr 36 in good agreement with the results of Donghua Xu et al. and Wang D et al. The experimental techniques and model interpretation used provide a tool for understanding the glass forming ability (GFA) and relaxation phenomena in metallic glasses.

  16. Solubility of rare earth-iron borates in the Bi2O3-B2O3 melt and their crystallization

    International Nuclear Information System (INIS)

    Al'shinskaya, L.I.; Leonyuk, N.I.; Nadezhnaya, T.B.; Timchenko, T.I.

    1979-01-01

    The temperature dependence of solubility of RFe 3 (BO 3 ) 4 (R=Y, Gd, Nd, Er) double borates in the Bi 2 O 3 -B 2 O 3 solution-melt is studied. The solubility curves in the range from 25 to 52 mol% are plotted. The character of curves is almost similar. At equal temperatures YFe 3 (BO 3 ) 4 and ErFe 3 (BO 3 ) 4 have the highest solubility and GaFe 3 (BO 3 ) 4 - the lowest one. It is shown that in the Bi 2 O 3 -B 2 O 3 base solution-melt the wide temperature range of monophase crystallization of rare earth - iron borates exists and the stratification is not observed. Thus, for the first time obtained are the crystals of rare earth-iron borates suitable for the investigation of their physical properties

  17. Ikaite crystals in melting sea ice - implications for pCO2 and pH levels in Arctic surface waters

    Science.gov (United States)

    Rysgaard, S.; Glud, R. N.; Lennert, K.; Cooper, M.; Halden, N.; Leakey, R. J. G.; Hawthorne, F. C.; Barber, D.

    2012-08-01

    A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3·6H2O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km2 (0.5-1 m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2 m per week and resulted in an estimated 3.8 ppm decrease of pCO2 in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 10.6 mmol m-2 sea ice d-1 or to 3.3 ton km-2 ice floe week-1. This is markedly higher than the estimated primary production within the ice floe of 0.3-1.3 mmol m-2 sea ice d-1. Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO2 uptake.

  18. Ikaite crystals in melting sea ice – implications for pCO2 and pH levels in Arctic surface waters

    Directory of Open Access Journals (Sweden)

    R. J. G. Leakey

    2012-08-01

    Full Text Available A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air–sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO3·6H2O in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km2 (0.5–1 m thick drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice floe thickness by 0.2 m per week and resulted in an estimated 3.8 ppm decrease of pCO2 in the ocean surface mixed layer. This corresponds to an air–sea CO2 uptake of 10.6 mmol m−2 sea ice d−1 or to 3.3 ton km−2 ice floe week−1. This is markedly higher than the estimated primary production within the ice floe of 0.3–1.3 mmol m−2 sea ice d−1. Finally, the presence of ikaite in sea ice and the dissolution of the mineral during melting of the sea ice and mixing of the melt water into the surface oceanic mixed layer accounted for half of the estimated pCO2 uptake.

  19. Crystallization and melting behavior of poly(ethylene oxide) and its blend with styrene-based ionomer using time-resolved SAXS/WAXS experiments

    Energy Technology Data Exchange (ETDEWEB)

    Slusarczyk, CzesLaw, E-mail: cslusarczyk@ath.bielsko.pl [Institute of Textile Engineering and Polymer Materials, University of Bielsko-BiaLa, ul. Willowa 2, 43-309 Bielsko-BiaLa (Poland)

    2011-10-15

    Time-resolved synchrotron wide- and small-angle X-ray scattering experiments were used to investigate the crystallization behavior and microstructure development of neat poly(ethylene oxide) (PEO) and its 50/50 blend with ionomer containing 6.4 mol% of sodium acrylate. The apparent lateral crystal sizes D{sub (120)} and D{sub (112)/(004)} were derived from the WAXS profiles. It was found that D{sub (120)} and D{sub (112)/(004)} of PEO in the blend are almost independent of temperature and are smaller when compared to those of neat PEO sample. The evolution of morphological parameters extracted from time-resolved SAXS profiles such as the long period L, the lamellar crystal thickness l{sub C} and the amorphous layer thickness l{sub A}, shows that the crystallization process of neat PEO follows the nucleation theory. The lamellar crystal thickness l{sub C} shows a single linear dependence on inverse supercooling, over the whole temperature range investigated. In contrast, the crystallization process of PEO in the blend (i.e. in the presence of interactions with the ionomer) follows the nucleation theory only in the narrow supercooling range. It was found also that the morphology of the blend consists of a broad population of lamellar crystal thicknesses. During heating lamellae melt in the reversed sequence of their formation.

  20. Phase transition control, melt growth of (Gd,RE)F{sub 3} single crystal and their luminescent properties

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, Akira, E-mail: yosikawa@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Jouini, Anis [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); BerlinSolar GmbH, Magnusstrasse 11, D-12489 Berlin (Germany); Kamada, Kei [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Boulon, Georges [Physical Chemistry of Luminescent Materials, Claude Bernard/Lyon 1 University, UMR 5620 CNRS, Villeurbanne (France); Nikl, Martin [Institute of Physics AS CR, Cukrovarnicka 10, Prague 16253 (Czech Republic); Saito, Fumio [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2009-12-15

    Rare-earth sesquifluorides with no absorption in visible spectral region, such as LaF{sub 3}, GdF{sub 3}, LuF{sub 3}, YF{sub 3}, ScF{sub 3}, are the topic of intense study as a host for luminescence materials. However, except Nd:LaF{sub 3}, they are not studied as a host for laser materials. The main obstacle troubling further study of GdF{sub 3}, LuF{sub 3}, YF{sub 3}, ScF{sub 3} single crystal is the fact that there is first-order phase transition (LaF{sub 3} type{leftrightarrow}{beta}-YF{sub 3} type for GdF{sub 3}, {alpha}-YF{sub 3} type{leftrightarrow}{beta}-YF{sub 3} type for the rest) between the room and melting temperature.To prevent the phase transition, first of all, we have tried to make solid solution between GdF{sub 3} and YF{sub 3} in such a way that the average cation radii can be shifted to the size that does not have phase transition. Ce{sup 3+} perturbed luminescence was observed in the Ce- and Sr-codoped GdF{sub 3}-YF{sub 3} system. Similar solid solution concept was applied to the combination between GdF{sub 3} and YbF{sub 3}. The emission spectrum of Yb{sup 3+} that exhibits broad bands around 1 {mu}m was observed. Room temperature up-conversion luminescence spectra of Pr{sup 3+}-doped Gd{sub 1-x}Yb{sub x}F{sub 3} were studied and visible emission from Pr{sup 3+} was obtained under infrared laser pumping in the Yb{sup 3+} broad absorption band at 935.5 nm.

  1. Ikaite crystals in melting sea ice – implications for pCO2 and pH levels in Arctic surface waters

    DEFF Research Database (Denmark)

    Rysgaard, Søren; Glud, R.N.; Lennert, K.

    2012-01-01

    A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO 2 exchange. This has been complicated by the recent discoveries of ikaite (a polymorph of CaCO 3•6H 2O) in Arctic and Antarctic sea ice, which indicate that multiple...... chemical transformations occur in sea ice with a possible effect on CO 2 and pH conditions in surface waters. Here, we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from a melting 1.7 km 2 (0.5-1 m thick) drifting ice floe in the Fram Strait...... during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced...

  2. Equation of liquidus curve of primary crystallization of congruently melting of Asub(m)Bsub(n) compound in regular solutions approximation

    International Nuclear Information System (INIS)

    Glazov, V.M.; Pavlova, L.M.; Moskvinova, N.A.

    1975-01-01

    A general solution was obtained for the Prigozhin and Defey equation on the basis of which a liquidus equation was derived describing the primary crystallization of Asub(m)Bsub(n)-type compounds. The Prigozhin and Defey equation described a general case of the melting process of having a narrow homogeneity region at a certain temperature T:(Asub(m)Bsub(n))sub(s) reversible m(A)sub(L) n(B)sub(L). They have obtained a differential equation for the liquids curve describing the equilibrium state between the primary Asub(m)Bsub(n) crystals and the liquid solution. The obtained equation was tested by a comparison with the experimental liquidus curves corresponding to the primary crystallization of gallium and indium sesquitellurides in Ga-Te and In-Te systems. The liquidus curves were made more precise by means of a detailed thermographic study of a series of melts located to the right and left of Ga 2 Te 3 and In 2 Te 3 compounds. Computer calculations of liquidus curves corresponding to the primary crystallization of Ga 2 Te 3 and In 2 Te 3 were carried out with the aid of the last of the above-mentioned equations. The obtained results show that the derived equations can be used in studying the nature of intermolecular reactions in systems in which congruent intermediate phases of complex composition are present

  3. 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

  4. Morphological Transition in the Cellular Structure of Single Crystals of Nickel-Tungsten Alloys near the Congruent Melting Point

    International Nuclear Information System (INIS)

    Azhazha, V.M.; Ladygin, A.N.; Sverdlov, V.Ja.; Zhemanyuk, P.D.; Klochikhin, V.V.

    2005-01-01

    The structure and microhardness of single crystals of nickel-tungsten alloys containing 25-36 wt % W are investigated. The temperature gradient at the crystallization front and the velocity of the crystallization front are the variable parameters of directional crystallization. It is found that, when the velocity of the crystallization front is 4 mm/min, the morphology of the cellular structure of the single crystals grown from nickel-tungsten alloys changes from square cells to hexagonal cells at a tungsten content of greater than or equal to 31 wt %. As the velocity of the crystallization front increases to 10 mm/min, no morphological transition occurs. It is shown that impurities play an important role in the formation of a cellular structure with cells of different types

  5. Gelatinized wheat starch influences crystallization behaviour and structure of roll-in shortenings in laminated bakery products.

    Science.gov (United States)

    Mattice, Kristin D; Marangoni, Alejandro G

    2018-03-15

    One hydrogenated and one non-hydrogenated shortening were baked with isolated components of a croissant matrix, including crystalline wheat starch, gelatinized wheat starch, gluten, and formed gluten network. The impact of the matrix components on fat crystallization was analyzed for polymorphism using powder X-ray diffraction, solid fat content by pulsed nuclear magnetic resonance and thermal behaviour by differential scanning calorimetry. When compared to results obtained from croissants prepared with the respective shortenings, samples containing gelatinized wheat starch displayed notably similar results: polymorphic conversion, from the β' to β form over storage, and visually broader peaks in the melting endotherms indicating a greater temperature was required to completely melt all of the fat. All other component mixtures behaved similar to the respective fats in bulk. The measured rate of crystallization was greater in samples containing gelatinized wheat starch, indicating that the gelatinized starch could act as a nucleation site to speed crystallization. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Oscillations of the crystal-melt interface caused by harmonic oscillations of the pulling rate for the cylindrical phase of crystal growth

    Science.gov (United States)

    Vasil'ev, M. G.

    2017-02-01

    A technique for measuring the crystal cross-sectional area with a weight sensor based on the difference between its readings at the extreme rod positions in the stepwise and continuous modes of modulation of the pulling rate is proposed for the low-thermal gradient Czochralski method. A change in the crystallization rate at harmonic oscillations of the pulling rate is estimated with the aim of conserving the quality of the growing crystal for this measurement method.

  7. Controlling the crystallization and magnetic properties of melt-spun Pr2Fe14B/α-Fe nanocomposites by Joule heating

    Science.gov (United States)

    Jin, Z. Q.; Cui, B. Z.; Liu, J. P.; Ding, Y.; Wang, Z. L.; Thadhani, N. N.

    2004-05-01

    Pr2Fe14B/α-Fe based nanocomposites have been prepared through crystallization of melt-spun amorphous Pr7Tb1Fe85Nb0.5Zr0.5B6 ribbons by means of ac Joule heating while simultaneously monitoring room-temperature electrical resistance R. The R value shows a strong variation with respect to applied current I, and is closely related to the amorphous-to-nanocrystalline phase transformation. The curve of R versus I allows one to control the crystallization behavior during Joule heating and to identify the heat-treatment conditions for optimum magnetic properties. A coercivity of 550 kA/m and a maximum energy product of 128 kJ/m3 have been obtained upon heating the amorphous ribbons at a current of 2.0 A. These properties are around 30% higher than the values of samples prepared by conventionally (furnace) annealed amorphous ribbons.

  8. The Effect of Filler-Polymer Interactions on Cold-Crystallization Kinetics in Crosslinked, Silica Filled PDMS/PDPS Copolymer Melts

    International Nuclear Information System (INIS)

    Chien, A; DeTeresa, S; Thompson, L; Cohenour, R; Balazs, B; Maxwell, R S

    2006-01-01

    Crystallization in a series of variable crosslink density poly(dimethyl-diphenyl) siloxanes random block copolymers reinforced through a mixture of precipitated and fumed silica fillers has been studied by Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and X-ray Diffraction (XRD). The silicone composite studied was composed of 94.6 mol% Dimethoylsiloxane, 5.1 mol% diphenylsiloxane, and 0.3 mol% methyl-vinyl siloxane (which formed crosslinking after a peroxide cure). The polymer was filled with a mixture of 21.6 wt. % fumed silica and 4.0 wt. % precipitated silica previously treated with 6.8 wt. % ethoxy-endblocked siloxane processing aid. The base composite was characterized by a molecular weight between crosslinks in the polymer network of ∼24 kDa and an overall molecular weight (including the influence of the silica fillers) between crosslinks of ∼11 kDa. Molecular weight between crosslinks and filler-polymer interaction strength were then modified by exposure to γ-irradiation in either air or vacuum. The unirradiated material exhibited crystallization at -80 C as measured by DSC with a 16% crystallization as measured by XRD. Isothermal DMA experiments illustrated that crystallization at -85 C occurred over a 1.8 hour period in silica-filled systems and 2.2-2.6 hours in unfilled systems. The onset of crystallization typically occurred after a 30-minute incubation/nucleation period. The crystallization kinetics were dependent on crosslink density. Changes in molecular weight of a factor of two did not, however, change the amount of crystallization. Irradiation in vacuum resulted in faster overall crystallization rates compared to air irradiation for the same crosslink density, likely due to a reduction in the interaction between the polymer chains and the silica filler surface. Modulated differential scanning calorimetry contrasted the crystallization and melting behavior of pure PDMS versus the PDMS/PDPS base copolymer and helped

  9. (nBuCp)2ZrCl2-catalyzed Ethylene-4M1P Copolymerization: Copolymer Backbone Structure, Melt Behavior, and Crystallization

    KAUST Repository

    Atiqullah, Muhammad

    2016-01-08

    The judicious design of methylaluminoxane (MAO) anions expands the scope for developing industrial metallocene catalysts. Therefore, the effects of MAO anion design on the backbone structure, melt behavior, and crystallization of ethylene−4-methyl-1-pentene (E−4M1P) copolymer were investigated. Ethylene was homopolymerized, as well as copolymerized with 4M1P, using (i) MAO anion A (unsupported [MAOCl2]−) premixed with dehydroxylated silica, (nBuCp)2ZrCl2, and Me2SiCl2; and (ii) MAO anion B (Si−O−Me2Si−[MAOCl2]−) supported with (nBuCp)2ZrCl2 on Me2SiCl2-functionalized silica. Unsupported Me2SiCl2, opposite to the supported analogue, acted as a co-chain transfer agent with 4M1P. The modeling of polyethylene melting and crystallization kinetics, including critical crystallite stability, produced insightful results. This study especially illustrates how branched polyethylene can be prepared from ethylene alone using particularly one metallocene-MAO ion pair, and how a compound, that functionalizes silica as well as terminates the chain, can synthesize ethylene−α-olefin copolymers with novel structures. Hence, it unfolds prospective future research niches in polyethyne systhesis. This article is protected by copyright. All rights reserved.

  10. Development of crystal texture in R-lean RFeCoNbB (R = Nd, Pr) alloy during melt spinning processes

    International Nuclear Information System (INIS)

    Li, Wei; Li, Lanlan; Liu, Yanguo; Zhang, Xiangyi

    2012-01-01

    Highlights: ► We study the texture development during the melt spinning processes of R-lean alloys. ► A strong (0 0 l) texture parallel to the ribbon plane for (Nd,Pr) 2 Fe 14 B is obtained. ► The texture for R 2 Fe 14 B crystals can develop by a seeding effect of α-Fe texture. ► The anisotropic nanocomposite magnet yields M r = 0.78M s and large (BH) max = 25.2 MGOe. - Abstract: The formation of crystal texture of R 2 Fe 14 B nanocrystals in R–Fe–B (R = rare earth) alloys with low R content ( 2 Fe 14 B nanocrystals during the melt spinning processes of Nd 3.6 Pr 5.4 Fe 80 Co 3 NbB 7 by effectively employing the seeding effect of α-Fe nanocrystal texture. The (Nd,Pr) 2 Fe 14 B nanocrystals produced from the R-lean alloy at a wheel speed of 18 m/s show a strong (0 0 l) texture parallel to the ribbon plane, which yields a high remanence M r = 0.78M s and a large energy product (BH) max = 25.2 MGOe for the α-Fe/(Nd,Pr) 2 Fe 14 B nanocomposite ribbons. The present study provides a promising approach to prepare anisotropic nanocomposite magnets from R-lean alloys.

  11. Survey of appropriate endothermic processes for association with the HTR

    International Nuclear Information System (INIS)

    Brown, G.; Harrison, G.E.; Gent, C.W.; Plummer, J.

    1975-01-01

    Emphasis is placed on association of the HTR system as a heat source with chemical processes requiring temperatures up to 850 to 900 0 C, corresponding to a reactor coolant temperature of 950 0 C, though processes requiring temperatures up to 1100 0 C and above are reviewed. Particular attention is given to processes for the production of hydrogen-containing gases, including coal/lignite gasification which has been the subject of a recent study. Rising fuel prices make the HTR an attractive proposition if design concepts and materials can be developed to match the requirements. Other appropriate endothermic processes considered are oil processing, including tar sands and shales, and also energy production. Since the full temperature range of the reactor system must be utilised mention is made of low grade heat uses. Even very large chemical works have relatively small energy requirement by nuclear heat standards and adoption of the HTR as a heat source is likely only if it is associated with a large chemical/metallurgical complex or with the processing of a natural resource. (author)

  12. Crystal structure and nanotopographical features on the surface of heat-treated and anodized porous titanium biomaterials produced using selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Amin Yavari, S., E-mail: s.aminyavari@tudelft.nl [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft (Netherlands); FT Innovations BV, Braamsluiper 1, 5831 PW Boxmeer (Netherlands); Wauthle, R. [KU Leuven, Department of Mechanical Engineering, Section Production Engineering, Machine Design and Automation (PMA), Celestijnenlaan 300B, 3001 Leuven (Belgium); LayerWise NV, Kapeldreef 60, Leuven (Belgium); Böttger, A.J. [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft (Netherlands); Schrooten, J. [Department of Metallurgy and Materials Engineering, KU Leuven, Kasteelpark Arenberg 44 PB 2450, 3001 Heverlee (Belgium); Weinans, H. [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft (Netherlands); Department of Orthopedics and Department of Rheumatology, UMC Utrecht, Heidelberglaan 100, 3584 CX Utrecht (Netherlands); Zadpoor, A.A. [Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology (TU Delft), Mekelweg 2, 2628 CD Delft (Netherlands)

    2014-01-30

    Porous titanium biomaterials manufactured using additive manufacturing techniques such as selective laser melting are considered promising materials for orthopedic applications where the biomaterial needs to mimic the properties of bone. Despite their appropriate mechanical properties and the ample pore space they provide for bone ingrowth and osseointegration, porous titanium structures have an intrinsically bioinert surface and need to be subjected to surface bio-functionalizing procedures to enhance their in vivo performance. In this study, we used a specific anodizing process to build a hierarchical oxide layer on the surface of porous titanium structures made by selective laser melting of Ti6Al4V ELI powder. The hierarchical structure included both nanotopographical features (nanotubes) and micro-features (micropits). After anodizing, the biomaterial was heat treated in Argon at different temperatures ranging between 400 and 600 °C for either 1 or 2 h to improve its bioactivity. The effects of applied heat treatment on the crystal structure of TiO{sub 2} nanotubes and the nanotopographical features of the surface were studied using scanning electron microscopy and X-ray diffraction. It was shown that the transition from the initial crystal structure, i.e. anatase, to rutile occurs between 500 and 600 °C and that after 2 h of heat treatment at 600 °C the crystal structure is predominantly rutile. The nanotopographical features of the surface were found to be largely unchanged for heat treatments carried out at 500 °C or below, whereas they were partially or largely disrupted after heat treatment at 600 °C. The possible implications of these findings for the bioactivity of porous titanium structures are discussed.

  13. DETERMINATION OF VICKERS MICROHARDNESS IN β-Ga2O3 SINGLE CRYSTALS GROWN FROM THEIR OWN MELT

    Directory of Open Access Journals (Sweden)

    L. I. Guzilova

    2015-05-01

    Full Text Available The results of microhardness measurements of β-Ga2O3 single crystals for (001 crystallographic face are reported. The crystals were grown by the free crystallization with the "Garnet-2M" equipment. Microhardness values ​​ were determined by the Vickers method at varying loads. A four-sided diamond pyramid was used as an indenter. The average value of gallium oxide microhardness was equal to 8.91 GPa. We have carried out comparison of the values ​​obtained with the microhardness for the other wide bandgap semiconductors - epitaxial GaN layers grown on 6H-SiC and GaP layers grown on GaP:S. The findings are usable for machining process development of β-Ga2O3 single crystal substrates. In particular, silicon carbide and electrocorundum may be recommended for β-Ga2O3 machine processing.

  14. Effect of Chain Conformation on the Single-Molecule Melting Force in Polymer Single Crystals: Steered Molecular Dynamics Simulations Study.

    Science.gov (United States)

    Feng, Wei; Wang, Zhigang; Zhang, Wenke

    2017-02-28

    Understanding the relationship between polymer chain conformation as well as the chain composition within the single crystal and the mechanical properties of the corresponding single polymer chain will facilitate the rational design of high performance polymer materials. Here three model systems of polymer single crystals, namely poly(ethylene oxide) (PEO), polyethylene (PE), and nylon-66 (PA66) have been chosen to study the effects of chain conformation, helical (PEO) versus planar zigzag conformation (PE, PA66), and chain composition (PE versus PA66) on the mechanical properties of a single polymer chain. To do that, steered molecular dynamics simulations were performed on those polymer single crystals by pulling individual polymer chains out of the crystals. Our results show that the patterns of force-extension curve as well as the chain moving mode are closely related to the conformation of the polymer chain in the single crystal. In addition, hydrogen bonds can enhance greatly the force required to stretch the polymer chain out of the single crystal. The dynamic breaking and reformation of multivalent hydrogen bonds have been observed for the first time in PA66 at the single molecule level.

  15. The roles of fractional crystallization, magma mixing, crystal mush remobilization and volatile-melt interactions in the genesis of a young basalt-peralkaline rhyolite suite, the greater Olkaria volcanic complex, Kenya Rift valley

    Science.gov (United States)

    Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.

    2008-01-01

    The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All

  16. Pinning performance of (Nd,Eu,Gd)-123 superconductors: Comparison of melt-textured pellet and single crystal

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Jurek, Karel; Muralidhar, M.; Das, P.; Koblischka, M.R.; Wolf, T.

    2008-01-01

    Roč. 151, č. 1 (2008), s. 25-30 ISSN 0921-5107 R&D Projects: GA ČR GA202/05/0173; GA MŠk 1P05ME728 Institutional research plan: CEZ:AV0Z10100520 Keywords : high-temperature superconductors * cuprous oxides * superconductivity perovskites, * (Nd,Eu,Gd)BaCuO * ternary compounds * melt-textured materials Subject RIV: BM - Solid Matter Physics ; Magnetism

  17. Raman spectroscopy study of the crystal - melt phase transition of lanthanum, cerium and neodymium trichlorides; Issledovanie fazovogo perekhoda kristall-rasplav trikhloridov lantana, tseriya i neodima metodom spektroskopii KRS

    Energy Technology Data Exchange (ETDEWEB)

    Zakir' yanova, I D; Salyulev, A B [UrO RAN, Inst. Vysokotemperaturnoj Ehlektrokhimii, Ekaterinburg (Russian Federation)

    2007-09-15

    Systematic structural studies of crystalline (over a wide temperature range) and molten LaCl{sub 3}, CeCl{sub 3}, and NdCl{sub 3} salts (near the crystal-melt phase transition temperature) are conducted employing Raman spectroscopy. A change in the trend of temperature dependences of characteristic frequencies is revealed in the pre-melting region of the compounds. This is attributed to an increase in the number of crystal defects due to weakening of a part of Ln-Cl bonds and decreasing of coordination number of chloride anions in the vicinity of rare earth cation.

  18. Hydrothermal synthesis, crystal structure and luminescence property ...

    Indian Academy of Sciences (India)

    The design and construction of ... dination polymers. It is difficult to design coordination .... The first endotherm at about 180 ... graphic data for coordination polymer 1. ... Sheldrick G M 1997 SHELXS-97: Program for solution of crystal structures ...

  19. Influence of clay content on the melting behavior and crystal structure of nonisothermal crystallized poly(L-lactic acid)/nanocomposites

    Czech Academy of Sciences Publication Activity Database

    Ublekov, F.; Baldrian, Josef; Kratochvíl, Jaroslav; Steinhart, M.; Nedkov, E.

    2012-01-01

    Roč. 124, č. 2 (2012), s. 1643-1648 ISSN 0021-8995 Institutional research plan: CEZ:AV0Z40500505 Keywords : biopolymers * nanocomposite s * crystal structures Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.395, year: 2012

  20. Neutron diffraction study on the crystal and magnetic structures of arc-melted PrFe10.5Mo1.1C0.4 alloy

    International Nuclear Information System (INIS)

    Du Honglin; Xue Yanjie; Zhang Baisheng; Mao Weihua; Yang Jinbo; Cheng Benpei; Yang Yingchang

    1999-01-01

    The crystal and magnetic structures, especially the site occupation of C atoms in the crystal cell of arc-melted PrFe 10.5 Mo 1.1 C 0.4 permanent magnetic alloy have been determined by means of powder neutron diffraction study. Rietveld analysis of the neutron diffraction data indicates that Mo atoms prefers the 8i site, about 76 percent of the C atoms occupy the 8i substitution site, and the other part of C atoms enter the 2b interstitial site. The exact molecular formula should be Pr(Fe 10.575 Mo 1.250 C 0.1.75 C 0.055 . It seems that the site occupation of C atoms in the ThMn 12 -type carbides depends not only on the kind of substitutional transition metals, but also on the components of the substitutional transition metals in the compounds. There are still amount of work to make systematic studies on the relation between them. The effect of C atoms on the magnetic properties is also discussed. (author)

  1. Crystal Growth in Al72.9Ge27.1 Alloy Melt under Acoustic Levitation Conditions

    International Nuclear Information System (INIS)

    Yan Na; Dai Fu-Ping; Wang Wei-Li; Wei Bing-Bo

    2011-01-01

    The nonequilibrium solidification of liquid Al 72.9 Ge 27.1 hypoeutectic alloy is accomplished by using single-axis acoustic levitation. A maximum undercooling of 112K (0.16T L ) is obtained for the alloy melt at a cooling rate of 50 K/s. The primary (Al) phase displays a morphological transition from coarse dendrite under a normal conditions to equiaxed grain under acoustic levitation. In the (Al)+(Ge) eutectic, the (Ge) phase exhibits a conspicuous branched growth morphology. Both the primary (Al) dendrites and (Al)+(Ge) eutectics are well refined and the solute content of the primary (Al) phase is extended under acoustic levitation. The calculated and experimental results indicate that the solute trapping effect becomes more intensive with the enhancement of bulk undercooling. (cross-disciplinary physics and related areas of science and technology)

  2. On the Crystallization of Compacted and Chunky Graphite from Liquid Multicomponent Iron-Carbon-Silicon-Based Melts

    Science.gov (United States)

    Stefanescu, D. M.; Huff, R.; Alonso, G.; Larrañaga, P.; De la Fuente, E.; Suarez, R.

    2016-08-01

    Extensive SEM work was carried out on deep-etched specimens to reveal the evolution of compacted and chunky graphite in magnesium-modified multicomponent Fe-C-Si alloys during early solidification and at room temperature. The findings of this research were then integrated in the current body of knowledge to produce an understanding of the crystallization of compacted and chunky graphite. It was confirmed that growth from the liquid for both compacted and chunky graphite occurs radially from a nucleus, as foliated crystals and dendrites. The basic building blocks of the graphite aggregates are hexagonal faceted graphite platelets with nanometer height and micrometer width. Thickening of the platelets occurs through growth of additional graphene layers nucleated at the ledges of the graphite prism. Additional thickening resulting in complete joining of the platelets may occur from the recrystallization of the amorphous carbon that has diffused from the liquid through the austenite, once the graphite aggregate is enveloped in austenite. With increasing magnesium levels, the foliated graphite platelets progressively aggregate along the c-axis forming clusters. The clusters that have random orientation, eventually produce blocky graphite, as the spaces between the parallel platelets disappear. This is typical for compacted graphite irons and tadpole graphite. The chunky graphite aggregates investigated are conical sectors of graphite platelets stacked along the c-axis. The foliated dendrites that originally develop radially from a common nucleus may aggregate along the c-axis forming blocky graphite that sometimes exhibits helical growth. The large number of defects (cavities) observed in all graphite aggregates supports the mechanism of graphite growth as foliated crystals and dendrites.

  3. Ce-doped LuAG single-crystal fibers grown from the melt for high-energy physics

    CERN Document Server

    Xu, X; Moretti, F; Pauwels, K; Lecoq, P; Auffray, E; Dujardin, C

    2014-01-01

    Under a stationary stable regime undoped and Ce-doped LuAG (Lu3Al5O12) single-crystal fibers were grown by a micro-pulling-down technique. The meniscus length corresponding to the equilibrium state was <200 mu m. Fluctuations in the fiber composition and pulling rate were found to have a significant effect on the properties of the fibers grown. A great improvement in the performance was found in samples containing low Ce concentrations (<= 0.1 at.\\%) and produced using pulling rates <0.5 mm min(-1). Under such conditions a good lateral surface fiber quality was obtained and light propagation was significantly improved. Conversely, a high Ce concentration and a high pulling rate resulted in a strong degradation of the fiber surface quality causing defects to appear and a decrease in light output. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  4. Numerical simulation of flow and melting characteristics of seawater-ice crystals two-phase flow in inlet straight pipe of shell and tube heat exchanger of polar ship

    Science.gov (United States)

    Xu, Li; Huang, Chang-Xu; Huang, Zhen-Fei; Sun, Qiang; Li, Jie

    2018-05-01

    The ice crystal particles are easy to enter into the seawater cooling system of polar ship together with seawater when it sails in the Arctic. They are easy to accumulate in the pipeline, causing serious blockage of the cooling pipe. In this study, the flow and melting characteristics of ice particles-seawater two-phase flow in inlet straight pipe of shell-and-tube heat exchanger were numerically simulated by using Eulerian-Eulerian two-fluid model coupled with the interphase heat and mass transfer model. The influences of inlet ice packing factor, ice crystal particle diameter, and inlet velocity on the distribution and melting characteristics of ice crystals were investigated. The degree of asymmetry of the distribution of ice crystals in the cross section decreases gradually when the IPF changes from 5 to 15%. The volume fractions of ice crystals near the top of the outlet cross section are 19.59, 19.51, and 22.24% respectively for ice packing factor of 5, 10 and 15%. When the particle diameter is 0.5 mm, the ice crystals are gradually stratified during the flow process. With particle diameters of 1.0 and 2.0 mm, the region with the highest volume fraction of ice crystals is a small circle and the contours in the cloud map are compact. The greater the inlet flow velocity, the less stratified the ice crystals and the more obvious the turbulence on the outlet cross section. The average volume fraction of ice crystals along the flow direction is firstly rapidly reduced and then stabilized after 300 mm.

  5. Rb2Na(NO33: A Congruently Melting UV-NLO Crystal with a Very Strong Second-Harmonic Generation Response

    Directory of Open Access Journals (Sweden)

    Guohong Zou

    2016-04-01

    Full Text Available Crystals of congruently melting noncentrosymmetric (NCS mixed alkali metal nitrate, Rb2Na(NO33, have been grown through solid state reactions. The material possesses layers with NaO8 hexagonal bipyramids and NO3 triangular units. Rb+ cations are residing in the interlayer space. Each NaO8 hexagonal bipyramid shares its corners and edges with two and three NO3 units, respectively, in order to fulfill a highly dense stacking in the unit cell. The NaO8 groups share their six oxygen atoms in equatorial positions with three different NO3 groups to generate a NaO6-NO3 layer with a parallel alignment. The optimized arrangement of the NO3 groups and their high density in the structure together produce a strong second-harmonic generation (SHG response. Powder SHG measurements indicate that Rb2Na(NO33 has a strong SHG efficiency of five times that of KH2PO4 (KDP and is type I phase-matchable. The calculated average nonlinear optical (NLO susceptibility of Rb2Na(NO33 turns out to be the largest value among the NLO materials composed of only [NO3]− anion. In addition, Rb2Na(NO33 exhibits a wide transparency region ranging from UV to near IR, which suggests that the compound is a promising NLO material.

  6. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils

    International Nuclear Information System (INIS)

    Bootello, M.A.; Garces, R.; Martinez-Force, E.; Salas, J.J.

    2016-01-01

    The composition and distribution of fatty acids in triacylglycerol (TAG) molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the Sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.

  7. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  8. Thermalization calorimetry: A simple method for investigating glass transition and crystallization of supercooled liquids

    Directory of Open Access Journals (Sweden)

    Bo Jakobsen

    2016-05-01

    Full Text Available We present a simple method for fast and cheap thermal analysis on supercooled glass-forming liquids. This “Thermalization Calorimetry” technique is based on monitoring the temperature and its rate of change during heating or cooling of a sample for which the thermal power input comes from heat conduction through an insulating material, i.e., is proportional to the temperature difference between sample and surroundings. The monitored signal reflects the sample’s specific heat and is sensitive to exo- and endothermic processes. The technique is useful for studying supercooled liquids and their crystallization, e.g., for locating the glass transition and melting point(s, as well as for investigating the stability against crystallization and estimating the relative change in specific heat between the solid and liquid phases at the glass transition.

  9. Formamidinium iodide: crystal structure and phase transitions

    Directory of Open Access Journals (Sweden)

    Andrey A. Petrov

    2017-04-01

    Full Text Available At a temperature of 100 K, CH5N2+·I− (I, crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C—N bond lengths are 1.301 (7 and 1.309 (8 Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10 Å. The cation and anion of I form a tight ionic pair by a strong N—H...I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N—H...I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction. Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525 K, and one broad endothermic peak at ∼605 K. The first and second peaks are related to solid–solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387 K are estimated as 2.60 and 2.75 kJ mol−1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100–346 K, orthorhombic (346–387 K and cubic (387–525 K polymorphic modifications.

  10. Are Chicken Embryos Endotherms or Ectotherms? A Laboratory Exercise Integrating Concepts in Thermoregulation and Metabolism

    Science.gov (United States)

    Hiebert, Sara M; Noveral, Jocelyne

    2007-01-01

    This investigative laboratory exercise uses the different relations between ambient temperature and metabolic rate in endotherms and ectotherms as a core concept to answer the following question: What thermoregulatory mode is employed by chicken embryos? Emphasis is placed on the physiological concepts that can be taught with this exercise,…

  11. Growth and structural characterization of single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) obtained by the partial melting technique

    Science.gov (United States)

    Yamaki, K.; Bamba, Y.; Mochiku, T.; Funahashi, S.; Matsushita, Y.; Irie, A.

    2018-05-01

    In this study, cubic single crystals of the magnetic superconductor Ru1-xSr2-yGd1+yCu2+xO8-δ (RuGd-1212) with typical dimensions of 100-150 μm in length were grown by the partial melting technique. Multiple 00l reflections were first observed by XRD measurements of the bulk RuGd-1212 single crystals. The resistivity of the obtained crystals was roughly estimated to be ∼24-80 mΩ cm and no superconducting transition was observed down to 4.2 K. From the XRD measurements and refinement of the crystal structure, it was apparent that the Ru and Sr sites of the single-crystal RuGd-1212 were partially substituted by Cu and Gd, respectively. Oxygen defects were found to be minor (δ ≈ 0.1). The lattice parameters a and c of the single crystals were found to be larger and smaller, respectively, than those of a polycrystalline sample.

  12. Long term aging of selenide glasses: evidence of sub-Tg endotherms and pre-Tg exotherms

    Science.gov (United States)

    Chen, Ping; Boolchand, P.; Georgiev, D. G.

    2010-02-01

    Long term aging, extending from months to several years, is studied on several families of chalcogenide glasses including the Ge-Se, As-Se, and Ge-As-Se systems. Special attention is given to the As-Se binary, a system that displays a rich variety of aging behavior intimately tied to sample synthesis conditions and the ambient environment in which samples are aged. Calorimetric (modulated DSC) and Raman scattering experiments are undertaken. Our results show all samples display a sub-Tg endotherm typically 10-70 °C below Tg in glassy networks possessing a mean coordination number r in the 2.25 < r < 2.45 range. Two sets of AsxSe100-x samples aged for eight years were compared, set A consisted of slow cooled samples aged in the dark, and set B consisted of melt-quenched samples aged at laboratory environment. Samples of set B in the As concentration range, 35% < x < 60%, display a pre-Tg exotherm, but the feature is not observed in samples of set A. The aging behavior of set A presumably represents intrinsic aging in these glasses, while that of set B is extrinsic due to the presence of light. The reversibility window persists in both sets of samples, but is less well defined in set B. These findings contrast with a recent study by Golovchak et al (2008 Phys. Rev. B 78 014202), which finds the onset of the reversibility window moved up to the stoichiometric composition (x = 40%). Here we show that the up-shifted window is better understood as resulting due to demixing of As4Se4 and As4Se3 molecules from the backbone, i.e., nanoscale phase separation (NSPS). We attribute sub-Tg endotherms to compaction of the flexible part of the networks upon long term aging, while the pre-Tg exotherm is to NSPS. The narrowing and sharpening of the reversibility window upon aging is interpreted as the slow 'self-organizing' stress relaxation of the phases just outside the intermediate phase, which itself is stress free and displays little aging.

  13. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils

    Directory of Open Access Journals (Sweden)

    Bootello, M. A.

    2016-09-01

    Full Text Available The composition and distribution of fatty acids in triacylglycerol (TAG molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.La composición y distribución de los ácidos grasos en las moléculas de triglicéridos se consideran factores determinantes en las propiedades físicas de los aceites y grasas. La distribución de ácidos grasos en un determinado aceite o grasa puede caracterizarse mediante un coeficiente de asimetría α, calculado a partir de las composiciones de triglicéridos y de ácidos grasos en la posición sn-2 de la molécula de triglicérido mediante hidrólisis con lipasa. El aceite de girasol alto oleico-alto esteárico es una grasa estable y saludable, adecuada para reemplazar a los aceites vegetales hidrogenados y fracciones de palma en muchos productos alimentarios, como grasas plásticas y grasas de confitería. En el presente trabajo, se formularon diferentes aceites alto oleico-alto esteárico con diferente distribución de los ácidos grasos saturados en

  14. Exothermic or Endothermic Decomposition of Disubstituted Tetrazoles Tuned by Substitution Fashion and Substituents.

    Science.gov (United States)

    Jia, Yu-Hui; Yang, Kai-Xiang; Chen, Shi-Lu; Huang, Mu-Hua

    2018-01-11

    Nitrogen-rich compounds such as tetrazoles are widely used as candidates in gas-generating agents. However, the details of the differentiation of the two isomers of disubstituted tetrazoles are rarely studied, which is very important information for designing advanced materials based on tetrazoles. In this article, pairs of 2,5- and 1,5-disubstituted tetrazoles were carefully designed and prepared for study on their thermal decomposition behavior. Also, the substitution fashion of 2,5- and 1,5- and the substituents at C-5 position were found to affect the endothermic or exothermic properties. This is for the first time to the best of our knowledge that the thermal decomposition properties of different tetrazoles could be tuned by substitution ways and substitute groups, which could be used as a useful platform to design advanced materials for temperature-dependent rockets. The aza-Claisen rearrangement was proposed to understand the endothermic decomposition behavior.

  15. Kinetic analysis of overlapping multistep thermal decomposition comprising exothermic and endothermic processes: thermolysis of ammonium dinitramide.

    Science.gov (United States)

    Muravyev, Nikita V; Koga, Nobuyoshi; Meerov, Dmitry B; Pivkina, Alla N

    2017-01-25

    This study focused on kinetic modeling of a specific type of multistep heterogeneous reaction comprising exothermic and endothermic reaction steps, as exemplified by the practical kinetic analysis of the experimental kinetic curves for the thermal decomposition of molten ammonium dinitramide (ADN). It is known that the thermal decomposition of ADN occurs as a consecutive two step mass-loss process comprising the decomposition of ADN and subsequent evaporation/decomposition of in situ generated ammonium nitrate. These reaction steps provide exothermic and endothermic contributions, respectively, to the overall thermal effect. The overall reaction process was deconvoluted into two reaction steps using simultaneously recorded thermogravimetry and differential scanning calorimetry (TG-DSC) curves by considering the different physical meanings of the kinetic data derived from TG and DSC by P value analysis. The kinetic data thus separated into exothermic and endothermic reaction steps were kinetically characterized using kinetic computation methods including isoconversional method, combined kinetic analysis, and master plot method. The overall kinetic behavior was reproduced as the sum of the kinetic equations for each reaction step considering the contributions to the rate data derived from TG and DSC. During reproduction of the kinetic behavior, the kinetic parameters and contributions of each reaction step were optimized using kinetic deconvolution analysis. As a result, the thermal decomposition of ADN was successfully modeled as partially overlapping exothermic and endothermic reaction steps. The logic of the kinetic modeling was critically examined, and the practical usefulness of phenomenological modeling for the thermal decomposition of ADN was illustrated to demonstrate the validity of the methodology and its applicability to similar complex reaction processes.

  16. Molecular-scale hydrophobic interactions between hard-sphere reference solutes are attractive and endothermic.

    Science.gov (United States)

    Chaudhari, Mangesh I; Holleran, Sinead A; Ashbaugh, Henry S; Pratt, Lawrence R

    2013-12-17

    The osmotic second virial coefficients, B2, for atomic-sized hard spheres in water are attractive (B2 attractive with increasing temperature (ΔB2/ΔT attractive and endothermic at moderate temperatures. Hydrophobic interactions between atomic-sized hard spheres in water are more attractive than predicted by the available statistical mechanical theory. These results constitute an initial step toward detailed molecular theory of additional intermolecular interaction features, specifically, attractive interactions associated with hydrophobic solutes.

  17. The role of liquid-liquid immiscibility and crystal fractionation in the genesis of carbonatite magmas: insights from Kerimasi melt inclusions

    Science.gov (United States)

    Guzmics, Tibor; Zajacz, Zoltán; Mitchell, Roger H.; Szabó, Csaba; Wälle, Markus

    2015-02-01

    We have reconstructed the compositional evolution of the silicate and carbonate melt, and various crystalline phases in the subvolcanic reservoir of Kerimasi Volcano in the East African Rift. Trace element concentrations of silicate and carbonate melt inclusions trapped in nepheline, apatite and magnetite from plutonic afrikandite (clinopyroxene-nepheline-perovskite-magnetite-melilite rock) and calciocarbonatite (calcite-apatite-magnetite-perovskite-monticellite-phlogopite rock) show that liquid immiscibility occurred during the generation of carbonatite magmas from a CO2-rich melilite-nephelinite magma formed at relatively high temperatures (1,100 °C). This carbonatite magma is notably more calcic and less alkaline than that occurring at Oldoinyo Lengai. The CaO-rich (32-41 wt%) nature and alkali-"poor" (at least 7-10 wt% Na2O + K2O) nature of these high-temperature (>1,000 °C) carbonate melts result from strong partitioning of Ca (relative to Mg, Fe and Mn) in the immiscible carbonate and the CaO-rich nature (12-17 wt%) of its silicate parent (e.g., melilite-nephelinite). Evolution of the Kerimasi carbonate magma can result in the formation of natrocarbonatite melts with similar composition to those of Oldoinyo Lengai, but with pronounced depletion in REE and HFSE elements. We suggest that this compositional difference results from the different initial parental magmas, e.g., melilite-nephelinite at Kerimasi and a nephelinite at Oldoinyo Lengai. The difference in parental magma composition led to a significant difference in the fractionating mineral phase assemblage and the element partitioning systematics upon silicate-carbonate melt immiscibility. LA-ICP-MS analysis of coeval silicate and carbonate melt inclusions provides an opportunity to infer carbonate melt/silicate melt partition coefficients for a wide range of elements. These data show that Li, Na, Pb, Ca, Sr, Ba, B, all REE (except Sc), U, V, Nb, Ta, P, Mo, W and S are partitioned into the carbonate

  18. Common metabolic constraints on dive duration in endothermic and ectothermic vertebrates

    Directory of Open Access Journals (Sweden)

    April Hayward

    2016-10-01

    Full Text Available Dive duration in air-breathing vertebrates is thought to be constrained by the volume of oxygen stored in the body and the rate at which it is consumed (i.e., “oxygen store/usage hypothesis”. The body mass-dependence of dive duration among endothermic vertebrates is largely supportive of this model, but previous analyses of ectothermic vertebrates show no such body mass-dependence. Here we show that dive duration in both endotherms and ectotherms largely support the oxygen store/usage hypothesis after accounting for the well-established effects of temperature on oxygen consumption rates. Analyses of the body mass and temperature dependence of dive duration in 181 species of endothermic vertebrates and 29 species of ectothermic vertebrates show that dive duration increases as a power law with body mass, and decreases exponentially with increasing temperature. Thus, in the case of ectothermic vertebrates, changes in environmental temperature will likely impact the foraging ecology of divers.

  19. Amino acid composition in endothermic vertebrates is biased in the same direction as in thermophilic prokaryotes

    Directory of Open Access Journals (Sweden)

    Wang Guang-Zhong

    2010-08-01

    Full Text Available Abstract Background Among bacteria and archaea, amino acid usage is correlated with habitat temperatures. In particular, protein surfaces in species thriving at higher temperatures appear to be enriched in amino acids that stabilize protein structure and depleted in amino acids that decrease thermostability. Does this observation reflect a causal relationship, or could the apparent trend be caused by phylogenetic relatedness among sampled organisms living at different temperatures? And do proteins from endothermic and exothermic vertebrates show similar differences? Results We find that the observed correlations between the frequencies of individual amino acids and prokaryotic habitat temperature are strongly influenced by evolutionary relatedness between the species analysed; however, a proteome-wide bias towards increased thermostability remains after controlling for phylogeny. Do eukaryotes show similar effects of thermal adaptation? A small shift of amino acid usage in the expected direction is observed in endothermic ('warm-blooded' mammals and chicken compared to ectothermic ('cold-blooded' vertebrates with lower body temperatures; this shift is not simply explained by nucleotide usage biases. Conclusion Protein homologs operating at different temperatures have different amino acid composition, both in prokaryotes and in vertebrates. Thus, during the transition from ectothermic to endothermic life styles, the ancestors of mammals and of birds may have experienced weak genome-wide positive selection to increase the thermostability of their proteins.

  20. Emergence of traveling wave endothermic reaction in a catalytic fixed bed under microwave heating

    International Nuclear Information System (INIS)

    Gerasev, Alexander P.

    2017-01-01

    This paper presents a new phenomenon in a packed bed catalytic reactor under microwave heating - traveling wave (moving reaction zones) endothermic chemical reaction. A two-phase model is developed to simulate the nonlinear dynamic behavior of the packed bed catalytic reactor with an irreversible first-order chemical reaction. The absorbed microwave power was obtained from Lambert's law. The structure of traveling wave endothermic chemical reaction was explored. The effects of the gas velocity and microwave power on performance of the packed bed catalytic reactor were presented. Finally, the effects of the change in the location of the microwave source at the packed bed reactor was demonstrated. - Highlights: • A new phenomenon - traveling waves of endothermic reaction - is predicted. • The physical and mathematical model of a packed bed catalytic reactor under microwave heating is presented. • The structure of the traveling waves is explored. • The configuration of heating the packed bed reactor via microwave plays a key role.

  1. 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.

  2. The fluid flow of Czochralski melt under the electromagnetic field

    OpenAIRE

    加藤, 拓哉; 二條久保, 裕; 岩本, 光生; 齋藤, 晋一; 赤松, 正人; 尾添, 紘之; Takuya, Katoh; Yuu, Nijoukubo; Mitsuo, Iwamoto; Shinichi, Saitoh; Masato, Akamatsu; Hiroyuki, Ozoe; 大分大院; 大分大工; 大分大工

    2009-01-01

    The silicon single crystal is use for the semiconductor device and it is mainly manufactured by the Czochralski crystal growing method. Under the Cz method, the forced convection and natural convection caused by the crystal rotation and the temperature difference between the crystal and crucible. In traditional system, the melt convection is controlled by the heater power, the crystal and crucible rotation. We apply Lorentz force to control the melt convection in this study, the Lorentz force...

  3. 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.

  4. Synthesis and characterization of L-tyrosine hydrochloride crystals submitted to high and low temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Santos, C.A.A.S.; Facanha Filho, P.F.; Ribeiro, L.H.L.; Victor, F.M.S.; Abreu, D.C.; Santos, A.O. dos; Carvalho, J.O.; Soares, R.A.; Sousa, J.C.F.; Lima, R.C.; Cavaignac, A.O. [Universidade Federal do Maranhao (UFMA), MA (Brazil)

    2016-07-01

    Full text: New materials are emerging and generate advances in nonlinear optics that studies the phenomena related to changes in optical properties when occurs interaction of light with the matter. Semi organic crystals present such properties. The goal is this work is to produce semi organic single crystal of L-tyrosine hydrochloride (LTHCl) and verify their thermal stability when subjected to high and low temperatures. The single crystals of LTHCl were produced for solubilization of amino acid L-tyrosine in hydrochloric acid using slow solvent evaporation technique at a constant temperature of 25 deg C. The X-ray diffraction (XRD) and refining by the Rietveld method were used to confirm the structure of the material. The thermal stability was investigated using DSC, TGA-DTA. The LTHCl crystal belongs to the monoclinic system, with two molecules per unit cell. The refinement by the Rietveld method showed good results with Rwp= 8.49% and Rp= 6.29% with S=1.13. Thermal analysis shown an endothermic event at about 160°C, which can be associated with phase transition occurred in LTHCl crystal. It was also observed that the crystal melting point occurs at a temperature of 230°C. No water of crystallization was found in the crystal structure, which was confirmed by Raman spectroscopy and thermal analysis. From the Raman spectroscopy experiments in function of temperature, no significant changes was observe in the behavior of vibrational normal modes between temperatures of -253 and 170 deg C. Finally, a monoclinic crystal system LTHCl is stable up to 160°C at high temperatures and -253°C at low temperatures. Therefore, our investigation has proved that LTHCl crystals can be used in this range of temperature without the lost of their nonlinear optical properties. (author)

  5. Observations of crystallization and melting in poly(ethylene oxide)/poly(methyl methacrylate) blends by hot-stage atomic-force microscopy

    NARCIS (Netherlands)

    Pearce, R.; Vancso, Gyula J.

    1998-01-01

    The binary blend of poly(ethylene oxide)/atactic poly(methyl methacrylate) is examined using hot-stage atomic-force microscopy (AFM) in conjunction with differential scanning calorimetry and optical microscopy. It was found possible to follow in real time the melting process, which reveals itself to

  6. Calorimetric determination of inhibition of ice crystal growth by antifreeze protein in hydroxyethyl starch solutions.

    Science.gov (United States)

    Hansen, T N; Carpenter, J F

    1993-01-01

    Differential scanning calorimetry and cryomicroscopy were used to investigate the effects of type I antifreeze protein (AFP) from winter flounder on 58% solutions of hydroxyethyl starch. The glass, devitrification, and melt transitions noted during rewarming were unaffected by 100 micrograms/ml AFP. Isothermal annealing experiments were undertaken to detect the effects of AFP-induced inhibition of ice crystal growth using calorimetry. A premelt endothermic peak was detected during warming after the annealing procedure. Increasing the duration or the temperature of the annealing for the temperature range from -28 and -18 degrees C resulted in a gradual increase in the enthalpy of the premelt endotherm. This transition was unaffected by 100 micrograms/ml AFP. Annealing between -18 and -10 degrees C resulted in a gradual decrease in the premelt peak enthalpy. This process was inhibited by 100 micrograms/ml AFP. Cryomicroscopic examination of the samples revealed that AFP inhibited ice recrystallization during isothermal annealing at -10 degrees C. Annealing at lower temperatures resulted in minimal ice recrystallization and no visible effect of AFP. Thus, the 100 micrograms/ml AFP to have a detectable influence on thermal events in the calorimeter, conditions must be used that result in significant ice growth without AFP and visible inhibition of this process by AFP. Images FIGURE 8 PMID:7690257

  7. Seasonal bone growth and physiology in endotherms shed light on dinosaur physiology.

    Science.gov (United States)

    Köhler, Meike; Marín-Moratalla, Nekane; Jordana, Xavier; Aanes, Ronny

    2012-07-19

    Cyclical growth leaves marks in bone tissue that are in the forefront of discussions about physiologies of extinct vertebrates. Ectotherms show pronounced annual cycles of growth arrest that correlate with a decrease in body temperature and metabolic rate; endotherms are assumed to grow continuously until they attain maturity because of their constant high body temperature and sustained metabolic rate. This apparent dichotomy has driven the argument that zonal bone denotes ectotherm-like physiologies, thus fuelling the controversy on dinosaur thermophysiology and the evolution of endothermy in birds and mammal-like reptiles. Here we show, from a comprehensive global study of wild ruminants from tropical to polar environments, that cyclical growth is a universal trait of homoeothermic endotherms. Growth is arrested during the unfavourable season concurrently with decreases in body temperature, metabolic rate and bone-growth-mediating plasma insulin-like growth factor-1 levels, forming part of a plesiomorphic thermometabolic strategy for energy conservation. Conversely, bouts of intense tissue growth coincide with peak metabolic rates and correlated hormonal changes at the beginning of the favourable season, indicating an increased efficiency in acquiring and using seasonal resources. Our study supplies the strongest evidence so far that homeothermic endotherms arrest growth seasonally, which precludes the use of lines of arrested growth as an argument in support of ectothermy. However, high growth rates are a distinctive trait of mammals, suggesting the capacity for endogenous heat generation. The ruminant annual cycle provides an extant model on which to base inferences regarding the thermophysiology of dinosaurs and other extinct taxa.

  8. Endothermic decompositions of inorganic monocrystalline thin plates. II. Displacement rate modulation of the reaction front

    Science.gov (United States)

    Bertrand, G.; Comperat, M.; Lallemant, M.

    1980-09-01

    Copper sulfate pentahydrate dehydration into trihydrate was investigated using monocrystalline platelets with (110) crystallographic orientation. Temperature and pressure conditions were selected so as to obtain elliptical trihydrate domains. The study deals with the evolution, vs time, of elliptical domain dimensions and the evolution, vs water vapor pressure, of the {D}/{d} ratio of ellipse axes and on the other hand of the interface displacement rate along a given direction. The phenomena observed are not basically different from those yielded by the overall kinetic study of the solid sample. Their magnitude, however, is modulated depending on displacement direction. The results are analyzed within the scope of our study of endothermic decomposition of solids.

  9. Determination of Critical Properties of Endothermic Hydrocarbon Fuel RP-3 Based on Flow Visualization

    Science.gov (United States)

    Wang, Ning; Zhou, Jin; Pan, Yu; Wang, Hui

    2014-01-01

    The critical pressure and temperature of an endothermic hydrocarbon fuel RP-3 were determined by flow visualization. The flow pattern images of RP-3 at different pressures and temperatures were obtained. The critical pressure is identified by disappearance of the phase change while the critical temperature is determined by appearance of the opalescence phenomenon under the critical pressure. The opalescence phenomenon is unique to the critical point. The critical pressure and temperature of RP-3 are determined to be 2.3 MPa and 646 K, respectively.

  10. Evolution of mammalian endothermic metabolism: leaky membranes as a source of heat

    International Nuclear Information System (INIS)

    Else, P.L.; Hulbert, A.J.

    1987-01-01

    O 2 consumption was measured at 37/degrees/C in tissue slices of liver, kidney, and brain from Amphilbolurus vitticeps and Rattus norvegicus (a reptile and mammal with same weight and body temperature) both in the presence and absence of ouabain. O 2 consumption of the mammalian tissues was two to four times that of the reptilian tissues and the mammalian tissues used three to six times the energy for Na + -K + transport than the reptilian tissues. Passive permeability to 42 K + was measured at 37/degrees/C in liver and kidney slices, and passive permeability to 22 Na + was measured at 37/degrees/C in isolated and cultured liver cells from each species. The mammalian cell membrane was severalfold leakier to both these ions than was the reptilian cell membrane, and thus the membrane pumps must use more energy to maintain the transmembrane ion gradients. It is postulated that this is a general difference between the cells of ectotherms and endotherms and thus partly explains the much higher levels of metabolism found in endothermic mammals

  11. 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.

  12. Low-field dc magnetization investigations in a Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystal: observation of a magnetic phase transition at the vortex melting line

    Energy Technology Data Exchange (ETDEWEB)

    Revaz, B. [Geneva Univ. (Switzerland). Dept. de Physique de la Matiere Condensee; Triscone, G. [Geneva Univ. (Switzerland). Dept. de Physique de la Matiere Condensee; Fabrega, L. [Geneva Univ. (Switzerland). Dept. de Physique de la Matiere Condensee; Junod, A. [Geneva Univ. (Switzerland). Dept. de Physique de la Matiere Condensee; Muller, J. [Geneva Univ. (Switzerland). Dept. de Physique de la Matiere Condensee

    1996-03-20

    The mixed-state magnetization M(H parallel c, T) of a Bi-2212 single crystal has been investigated with high resolution using a SQUID magnetometer. In the high-temperature region (50 K < T < T{sub c} = 80.2 K), we found that the slope {partial_derivative}M/{partial_derivative}H vertical stroke {sub T} vs. H shows a positive step at H{sub trans}(T) {approx} H{sub 0} x (1 - T/T{sub c}){sup n} with H{sub 0} = 2340 Oe and n = 1.28. This observation is compatible with a first-order phase transition with a distribution of internal fields, and is attributed to the melting of the 3D vortex lattice. The estimated entropy jump is 1 k{sub B}/vortex/layer CuO. However, when T is lower than 50 K, we observe radical changes in M(H); the 3D melting line divides into a decoupling line at a temperature-independent field and the onset of the irreversibility. (orig.).

  13. Low-field dc magnetization investigations in a Bi2Sr2CaCu2O8 single crystal: observation of a magnetic phase transition at the vortex melting line

    International Nuclear Information System (INIS)

    Revaz, B.; Triscone, G.; Fabrega, L.; Junod, A.; Muller, J.

    1996-01-01

    The mixed-state magnetization M(H parallel c, T) of a Bi-2212 single crystal has been investigated with high resolution using a SQUID magnetometer. In the high-temperature region (50 K c = 80.2 K), we found that the slope ∂M/∂H vertical stroke T vs. H shows a positive step at H trans (T) ∼ H 0 x (1 - T/T c ) n with H 0 = 2340 Oe and n = 1.28. This observation is compatible with a first-order phase transition with a distribution of internal fields, and is attributed to the melting of the 3D vortex lattice. The estimated entropy jump is 1 k B /vortex/layer CuO. However, when T is lower than 50 K, we observe radical changes in M(H); the 3D melting line divides into a decoupling line at a temperature-independent field and the onset of the irreversibility. (orig.)

  14. Preparation and optimization of thermoelectric properties of Bi2Te3 based alloys using the waste particles as raw materials from the cutting process of the zone melting crystal rods

    Science.gov (United States)

    Xiang, Qiusheng; Fan, Xi'an; Han, Xuewu; Zhang, Chengcheng; Hu, Jie; Feng, Bo; Jiang, Chengpeng; Li, Guangqiang; Li, Yawei; He, Zhu

    2017-12-01

    The p-type Bi2Te3 alloys were prepared using the waste particles from the cutting process of the zone melting crystal rods as the main raw materials by impurity removal process including washing, carbon monoxide reduction and vacuum metallurgical process. The thermoelectric properties of the Bi2Te3 based bulk materials were optimized by component adjustment, second smelting and resistance pressing sintering (RPS) process. All evidences confirmed that most of impurities from the line cutting process and the oxidation such as Sb2O3, Bi2O3 and Bi2Te4O11 could be removed by carbon monoxide reduction and vacuum metallurgical process adopted in this work, and the recycling yield was higher than 97%. Appropriate component adjustment treatment was used to optimize the carrier content and corresponding thermoelectric properties. Lastly, a Bi0.36Sb1.64Te3 bulk was obtained and its power factor (PF) could reach 4.24 mW m-1 K-2 at 300 K and the average PF value was over 3.2 mW m-1 K-2 from 300 K to 470 K, which was equivalent with the thermoelectric performance of the zone melting products from high purity elements Bi, Te and Sb. It was worth mentioning that the recovery process introduced here was a simple, low-cost, high recovery rate and green recycling technology.

  15. Petrogenesis of basaltic volcanic rocks from the Pribilof Islands, Alaska, by melting of metasomatically enriched depleted lithosphere, crystallization differentiation, and magma mixing

    Science.gov (United States)

    Chang, J.M.; Feeley, T.C.; Deraps, M.R.

    2009-01-01

    The Pribilof Islands, Alaska, are located in the Bering Sea in a continental intraplate setting. In this study we examine the petrology and geochemistry of volcanic rocks from St. Paul (0??54-0??003 Ma) and St. George (2??8-1??4 Ma) Islands, the two largest Pribilof Islands. Rocks from St. George can be divided into three groups: group 1 is a high-MgO, low-SiO. 2 suite composed primarily of basanites; group 2 is a high-MgO, high-SiO 2 suite consisting predominantly of alkali basalts; group 3 is an intermediate- to low-MgO suite that includes plagioclase-phyric subalkali basalts and hawaiites. Major and trace element geochemistry suggests that groups 1 and 2 formed by small-degree partial melting of amphibole-bearing to amphibole-free garnet peridotite. Group 1 rocks were the earliest melts produced from the most hydrous parts of the mantle, as they show the strongest geochemical signature of amphibole in their source. The suite of rocks from St. Paul ranges from 14??4 to 4??2 wt % MgO at relatively constant SiO 2 contents (43??1-47??3 wt %). The most primitive St. Paul rocks are modeled as mixtures between magmas with compositions similar to groups 1 and 2 from St. George Island, which subsequently fractionated olivine, clinopyroxene, and spinel to form more evolved rocks. Plagioclase-phyric group 3 rocks from St. George are modeled as mixtures between an evolved melt similar to the evolved magmas on St. Paul and a fractionated group 2 end-member from St. George. Mantle potential temperatures estimated for primitive basanites and alkali basalts are ???1400??C and are similar to those of mid-ocean ridge basalts (MORB). Similarly, 87Sr/. 86Sr and 143Nd/. 144Nd values for all rocks are MORB-like, in the range of 0??702704-0??703035 and 0??513026-0??513109, respectively. 208Pb/. 204Pb vs 206Pb/. 204Pb values lie near the MORB end-member but show a linear trend towards HIMU (high time-integrated 238U/. 204Pb). Despite isotopic similarities to MORB, many of the major and

  16. Applications of endothermic research technology to the high speed civil transport

    Science.gov (United States)

    Glickstein, M. R.; Spadaccini, L. J.

    1997-01-01

    The success of strategies for controlling emissions and enhancing performance in High Speed Research applications may be increased by more effective utilization of the heat sink afforded by the fuel in the vehicle thermal management system. This study quantifies the potential benefits associated with the use of supercritical preheating and endothermic cracking of jet fuel prior to combustion to enhance the thermal management capabilities of the propulsion systems in the High Speed Civil Transport (HSCT). A fuel-cooled thermal management system, consisting of plate-fin heat exchangers and a small auxiliary compressor, is defined for the HSCT, integrated with the engine, and an assessment of the effect on engine performance, weight, and operating cost is performed. The analysis indicates significant savings due a projected improvement in fuel economy, and the potential for additional benefit if the cycle is modified to take full advantage of all the heat sink available in the fuel.

  17. Comparison of Mitochondrial Reactive Oxygen Species Production of Ectothermic and Endothermic Fish Muscle

    Directory of Open Access Journals (Sweden)

    Lilian Wiens

    2017-09-01

    Full Text Available Recently we demonstrated that the capacity of isolated muscle mitochondria to produce reactive oxygen species, measured as H2O2 efflux, is temperature-sensitive in isolated muscle mitochondria of ectothermic fish and the rat, a representative endothermic mammal. However, at physiological temperatures (15° and 37°C for the fish and rat, respectively, the fraction of total mitochondrial electron flux that generated H2O2, the fractional electron leak (FEL, was far lower in the rat than in fish. Those results suggested that the elevated body temperatures associated with endothermy may lead to a compensatory decrease in mitochondrial ROS production relative to respiratory capacity. To test this hypothesis we compare slow twitch (red muscle mitochondria from the endothermic Pacific bluefin tuna (Thunnus orientalis with mitochondria from three ectothermic fishes [rainbow trout (Oncorhynchus mykiss, common carp (Cyprinus carpio, and the lake sturgeon (Acipenser fulvescens] and the rat. At a common assay temperature (25°C rates of mitochondrial respiration and H2O2 efflux were similar in tuna and the other fishes. The thermal sensitivity of fish mitochondria was similar irrespective of ectothermy or endothermy. Comparing tuna to the rat at a common temperature, respiration rates were similar, or lower depending on mitochondrial substrates. FEL was not different across fish species at a common assay temperature (25°C but was markedly higher in fishes than in rat. Overall, endothermy and warming of Pacific Bluefin tuna red muscle may increase the potential for ROS production by muscle mitochondria but the evolution of endothermy in this species is not necessarily associated with a compensatory reduction of ROS production relative to the respiratory capacity of mitochondria.

  18. Can foraging ecology drive the evolution of body size in a diving endotherm?

    Directory of Open Access Journals (Sweden)

    Timothée R Cook

    Full Text Available Within a single animal species, different morphs can allow for differential exploitation of foraging niches between populations, while sexual size dimorphism can provide each sex with access to different resources. Despite being potentially important agents of evolution, resource polymorphisms, and the way they operate in wild populations, remain poorly understood. In this study, we examine how trophic factors can select for different body sizes between populations and sexes in a diving endotherm. Dive depth and duration are positively related to body size in diving birds and mammals, a relationship explained by a lower mass-specific metabolic rate and greater oxygen stores in larger individuals. Based on this allometry, we predict that selection for exploiting resources situated at different depths can drive the evolution of body size in species of diving endotherms at the population and sexual level. To test this prediction, we studied the foraging ecology of Blue-eyed Shags, a group of cormorants with male-biased sexual size dimorphism from across the Southern Ocean. We found that mean body mass and relative difference in body mass between sexes varied by up to 77% and 107% between neighbouring colonies, respectively. Birds from colonies with larger individuals dived deeper than birds from colonies with smaller individuals, when accounting for sex. In parallel, males dived further offshore and deeper than females and the sexual difference in dive depth reflected the level of sexual size dimorphism at each colony. We argue that body size in this group of birds is under intense selection for diving to depths of profitable benthic prey patches and that, locally, sexual niche divergence selection can exaggerate the sexual size dimorphism of Blue-eyed Shags initially set up by sexual selection. Our findings suggest that trophic resources can select for important geographic micro-variability in body size between populations and sexes.

  19. The dynamics of ice melting in the conditions of crybot movement

    Directory of Open Access Journals (Sweden)

    Zakharova Ekaterina

    2017-01-01

    Full Text Available The mathematical modeling results of the simultaneous processes of heat and mass transfer under the conditions of intense phase changes (melting of ice during the movement of cryobot have been given. The spatial unevenness of the melting rate of ice has been taken into account. It has been established that the rate of passage of the cryobot depends essentially on its temperature. According to the results of the numerical simulation, considerable cooling of the cryobot sheath has been established. The latter is due to the high endothermic effect of melting ice.

  20. 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

  1. Fast neutron induced flux pinning in Tl-based high-Tc single crystals and thin films, highly textured tapes and melt-textured bulk 123-superconductors

    International Nuclear Information System (INIS)

    Brandstaetter, G.; Samadi Hosseinalli, G.; Kern, C.; Sauerzopf, F.M.; Schulz, G.W.; Straif, W.; Yang, X.; Weber, H.W.; Hu, Q.Y.

    1999-01-01

    Various compounds (TI-2223, TI-1223, TI-2212) as well as material forms (single crystals, thin films, ceramics, tapes) of TI-based high temperature superconductors were investigated by magnetic and transport techniques. TI-2223 has a very 'low lying' irreversibility line (H parallel e) and negligible critical current densities J c at 77 K. However, the irreversibility line shifts to higher fields and temperatures and J c is strongly enhanced, even at 77 K, after fast neutron irradiation. In contrast, the related TI-1223 compound has a much steeper irreversibility line (H parallel c) similar to that of Y-123. J c is significant up to 77 K, even in the unirradiated state, and can be largely improved by neutron irradiation. Transport measurements made on TI-1223 tapes still show much lower critical current densities. TI-2212 and Tl-2223 thin films have J c 's at 77 K, which are comparable to those of TI-1223 single crystals. Transport measurements on highly textured Bi-2223 tapes as well as flux profile measurements on Nd-123 bulk superconductors confirm the beneficial effects of neutron induced defects (collision cascades) for flux pinning. (author)

  2. Using Different Conceptual Change Methods Embedded within 5E Model: A Sample Teaching of Endothermic-Exothermic Reactions

    Science.gov (United States)

    Turk, Fatma; Calik, Muammer

    2008-01-01

    Since Widodo, Duit and Muller (2002) addressed that there is a gap between teacher's theoretical knowledge and their practical classroom constructivist behavior, we presented a sample teaching activity about Endothermic-Exothermic Reactions for teacher usage. Therein, the aim of this study is to design a 5E model to include students' alternative…

  3. Effects of reagent translational and vibrational energy on the dynamics of endothermic reactions

    International Nuclear Information System (INIS)

    Krajnovich, D.; Zhang, Z.; Huisken, F.; Shen, Y.R.; Lee, Y.T.

    1981-07-01

    The endothermic reactions Br + CH 3 I → CH 3 + IBr (ΔH 0 0 = 13 kcal/mole) and Br + CF 3 I → CF 3 + IBr (ΔH 0 0 = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF 3 I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF 3 I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrational energy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF 3 I

  4. Effects of reagent translational and vibrational energy on the dynamics of endothermic reactions

    Energy Technology Data Exchange (ETDEWEB)

    Krajnovich, D.; Zhang, Z.; Huisken, F.; Shen, Y.R.; Lee, Y.T.

    1981-07-01

    The endothermic reactions Br + CH/sub 3/I ..-->.. CH/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 13 kcal/mole) and Br + CF/sub 3/I ..-->.. CF/sub 3/ + IBr (..delta..H/sub 0//sup 0/ = 11 kcal/mole) have been studied by the crossed molecular beams method. Detailed center-of-mass contour maps of the IBr product flux as a function of recoil velocity and scattering angle are derived. For both systems it is found that the IBr product is sharply backward scattered with respect to the incident Br dirction, and that most of the available energy goes into product translation. Vibrational enhancement of the Br + CF/sub 3/I reaction was investigated by using the infrared multiphoton absorption process to prepare highly vibrationally excited CF/sub 3/I. At a collision energy of 31 kcal/mole (several times the barrier height), reagent vibrational energy appears to be less effective than an equivalent amount of (additional) translational energy in promoting reaction. More forward scattered IBr is produced in reactions of Br with vibrationally hot CF/sub 3/I.

  5. Helium crystals

    International Nuclear Information System (INIS)

    Lipson, S.G.

    1987-01-01

    Hexagonal close-packed helium crystals in equilibrium with superfluid have been found to be one of the few systems in which an anisotropic solid comes into true thermodynamic equilibrium with its melt. The discovery of roughening transitions at the liquid-solid interface have shown this system to be ideal for the study of the statistical mechanics of interface structures. We describe the effect of roughening on the shape and growth of macroscopic crystals from both the theoretical and experimental points of view. (author)

  6. 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.

  7. 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

  8. Flux free growth of large FeSe1/2Te1/2 superconducting single crystals by an easy high temperature melt and slow cooling method

    Directory of Open Access Journals (Sweden)

    P. K. Maheshwari

    2015-09-01

    Full Text Available We report successful growth of flux free large single crystals of superconducting FeSe1/2Te1/2 with typical dimensions of up to few cm. The AC and DC magnetic measurements revealed the superconducting transition temperature (Tc value of around 11.5K and the isothermal MH showed typical type-II superconducting behavior. The lower critical field (Hc1 being estimated by measuring the low field isothermal magnetization in superconducting regime is found to be above 200Oe at 0K. The temperature dependent electrical resistivity ρ(T  showed the Tc (onset to be 14K and the Tc(ρ = 0 at 11.5K. The electrical resistivity under various magnetic fields i.e., ρ(TH for H//ab and H//c demonstrated the difference in the width of Tc with applied field of 14Tesla to be nearly 2K, confirming the anisotropic nature of superconductivity. The upper critical and irreversibility fields at absolute zero temperature i.e., Hc2(0 and Hirr(0 being determined by the conventional one-band Werthamer–Helfand–Hohenberg (WHH equation for the criteria of normal state resistivity (ρn falling to 90% (onset, and 10% (offset is 76.9Tesla, and 37.45Tesla respectively, for H//c and 135.4Tesla, and 71.41Tesla respectively, for H//ab. The coherence length at the zero temperature is estimated to be above 20Å ´ by using the Ginsburg-Landau theory. The activation energy for the FeSe1/2Te1/2 in both directions H//c and H//ab is determined by using Thermally Activation Flux Flow (TAFF model.

  9. Determination of constant of chemical reaction rate in the process of steel treatment in the endothermal atmosphere

    International Nuclear Information System (INIS)

    Gyulikhandanov, E.L.; Kislenkov, V.V.

    1978-01-01

    The high-temperature method was applied to measuring a relative variation in the electrical resistance of a thin steel foil prepared from the 12KhN3A, 18Kh2N4VA, 20KhGNR, and 20Kh3MVF steels during its carburization and decarburization, and determined was the temperature dependence of the reaction rate of the interaction of the endothermal atmosphere of different compositions with the analloyed γ-Fe. A connection has been established between the reaction rate constant and the thermodynamic activity of carbon in the alloyed austenite at the temperature of about 925 deg C, corresponding to the cementation temperature. This provides the quantitative estimation of the above value for any alloyed steels and with the presence of numerical values of diffusion coefficients; this also enables one to carry out an accurate calculation of the distribution of carbon throughout the depth of a layer when effecting the cementation in the endothermal atmosphere

  10. 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.

  11. 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

  12. Model validation and parametric study of fluid flows and heat transfer of aviation kerosene with endothermic pyrolysis at supercritical pressure

    Directory of Open Access Journals (Sweden)

    Keke Xu

    2015-12-01

    Full Text Available The regenerative cooling technology is a promising approach for effective thermal protection of propulsion and power-generation systems. A mathematical model has been used to examine fluid flows and heat transfer of the aviation kerosene RP-3 with endothermic fuel pyrolysis at a supercritical pressure of 5 MPa. A pyrolytic reaction mechanism, which consists of 18 species and 24 elementary reactions, is incorporated to account for fuel pyrolysis. Detailed model validations are conducted against a series of experimental data, including fluid temperature, fuel conversion rate, various product yields, and chemical heat sink, fully verifying the accuracy and reliability of the model. Effects of fuel pyrolysis and inlet flow velocity on flow dynamics and heat transfer characteristics of RP-3 are investigated. Results reveal that the endothermic fuel pyrolysis significantly improves the heat transfer process in the high fluid temperature region. During the supercritical-pressure heat transfer process, the flow velocity significantly increases, caused by the drastic variations of thermophysical properties. Under all the tested conditions, the Nusselt number initially increases, consistent with the increased flow velocity, and then slightly decreases in the high fluid temperature region, mainly owing to the decreased heat absorption rate from the endothermic pyrolytic chemical reactions.

  13. 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

  14. 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

  15. 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.

  16. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)

    2016-05-06

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  17. Mechanistic variables can enhance predictive models of endotherm distributions: the American pika under current, past, and future climates.

    Science.gov (United States)

    Mathewson, Paul D; Moyer-Horner, Lucas; Beever, Erik A; Briscoe, Natalie J; Kearney, Michael; Yahn, Jeremiah M; Porter, Warren P

    2017-03-01

    How climate constrains species' distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modeling of endotherm distributions remains limited in this literature. Using the American pika (Ochotona princeps) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat-balance model, to convert macroclimate data to pika-specific surface activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8-19% less habitat loss in response to annual temperature increases of ~3-5 °C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect

  18. Mechanistic variables can enhance predictive models of endotherm distributions: The American pika under current, past, and future climates

    Science.gov (United States)

    Mathewson, Paul; Moyer-Horner, Lucas; Beever, Erik; Briscoe, Natalie; Kearney, Michael T.; Yahn, Jeremiah; Porter, Warren P.

    2017-01-01

    How climate constrains species’ distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modeling of endotherm distributions remains limited in this literature. Using the American pika (Ochotona princeps) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat-balance model, to convert macroclimate data to pika-specific surface activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8–19% less habitat loss in response to annual temperature increases of ~3–5 °C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect

  19. 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

  20. Reaction Norms in Natural Conditions: How Does Metabolic Performance Respond to Weather Variations in a Small Endotherm Facing Cold Environments?

    Science.gov (United States)

    Petit, Magali; Vézina, François

    2014-01-01

    Reaction norms reflect an organisms' capacity to adjust its phenotype to the environment and allows for identifying trait values associated with physiological limits. However, reaction norms of physiological parameters are mostly unknown for endotherms living in natural conditions. Black-capped chickadees (Poecile atricapillus) increase their metabolic performance during winter acclimatization and are thus good model to measure reaction norms in the wild. We repeatedly measured basal (BMR) and summit (Msum) metabolism in chickadees to characterize, for the first time in a free-living endotherm, reaction norms of these parameters across the natural range of weather variation. BMR varied between individuals and was weakly and negatively related to minimal temperature. Msum varied with minimal temperature following a Z-shape curve, increasing linearly between 24°C and −10°C, and changed with absolute humidity following a U-shape relationship. These results suggest that thermal exchanges with the environment have minimal effects on maintenance costs, which may be individual-dependent, while thermogenic capacity is responding to body heat loss. Our results suggest also that BMR and Msum respond to different and likely independent constraints. PMID:25426860

  1. Heat storage in Asian elephants during submaximal exercise: behavioral regulation of thermoregulatory constraints on activity in endothermic gigantotherms.

    Science.gov (United States)

    Rowe, M F; Bakken, G S; Ratliff, J J; Langman, V A

    2013-05-15

    Gigantic size presents both opportunities and challenges in thermoregulation. Allometric scaling relationships suggest that gigantic animals have difficulty dissipating metabolic heat. Large body size permits the maintenance of fairly constant core body temperatures in ectothermic animals by means of gigantothermy. Conversely, gigantothermy combined with endothermic metabolic rate and activity likely results in heat production rates that exceed heat loss rates. In tropical environments, it has been suggested that a substantial rate of heat storage might result in a potentially lethal rise in core body temperature in both elephants and endothermic dinosaurs. However, the behavioral choice of nocturnal activity might reduce heat storage. We sought to test the hypothesis that there is a functionally significant relationship between heat storage and locomotion in Asian elephants (Elephas maximus), and model the thermoregulatory constraints on activity in elephants and a similarly sized migratory dinosaur, Edmontosaurus. Pre- and post-exercise (N=37 trials) measurements of core body temperature and skin temperature, using thermography were made in two adult female Asian elephants at the Audubon Zoo in New Orleans, LA, USA. Over ambient air temperatures ranging from 8 to 34.5°C, when elephants exercised in full sun, ~56 to 100% of active metabolic heat production was stored in core body tissues. We estimate that during nocturnal activity, in the absence of solar radiation, between 5 and 64% of metabolic heat production would be stored in core tissues. Potentially lethal rates of heat storage in active elephants and Edmontosaurus could be behaviorally regulated by nocturnal activity.

  2. Thermal sensitivity of immune function: evidence against a generalist-specialist trade-off among endothermic and ectothermic vertebrates

    Science.gov (United States)

    Butler, Michael W.; Stahlschmidt, Zachary R.; Ardia, Daniel R.; Davies, Scott; Davis, Jon; Guillette, Louis J.; Johnson, Nicholas; McCormick, Stephen D.; McGraw, Kevin J.; DeNardo, Dale F.

    2013-01-01

    Animal body temperature (Tbody) varies over daily and annual cycles, affecting multiple aspects of biological performance in both endothermic and ectothermic animals. Yet a comprehensive comparison of thermal performance among animals varying in Tbody (mean and variance) and heat production is lacking. Thus, we examined the thermal sensitivity of immune function (a crucial fitness determinant) in Vertebrata, a group encompassing species of varying thermal biology. Specifically, we investigated temperature-related variation in two innate immune performance metrics, hemagglutination and hemolysis, for 13 species across all seven major vertebrate clades. Agglutination and lysis were temperature dependent and were more strongly related to the thermal biology of species (e.g., mean Tbody) than to the phylogenetic relatedness of species, although these relationships were complex and frequently surprising (e.g., heterotherms did not exhibit broader thermal performance curves than homeotherms). Agglutination and lysis performance were positively correlated within species, except in taxa that produce squalamine, a steroidal antibiotic that does not lyse red blood cells. Interestingly, we found the antithesis of a generalist-specialist trade-off: species with broader temperature ranges of immune performance also had higher peak performance levels. In sum, we have uncovered thermal sensitivity of immune performance in both endotherms and ectotherms, highlighting the role that temperature and life history play in immune function across Vertebrata.

  3. Calorimetric and diffractometric evidence for the sequential crystallization of buffer components and the consequential pH swing in frozen solutions.

    Science.gov (United States)

    Sundaramurthi, Prakash; Shalaev, Evgenyi; Suryanarayanan, Raj

    2010-04-15

    Sequential crystallization of succinate buffer components in the frozen solution has been studied by differential scanning calorimetry and X-ray diffractometry (both laboratory and synchrotron sources). The consequential pH shifts were monitored using a low-temperature electrode. When a solution buffered to pH pK(a)(2), the freeze-concentrate pH first decreased and then increased due to the sequential crystallization of the basic (disodium succinate) followed by the acidic (monosodium succinate and succinic acid) buffer components. XRD provided direct evidence of the crystallization events in the frozen buffer solutions, including the formation of disodium succinate hexahydrate [Na(2)(CH(2)COO)(2).6H(2)O]. When the frozen solution was warmed in a differential scanning calorimeter, multiple endotherms attributable to the melting of buffer components and ice were observed. When the frozen solutions were dried under reduced pressure, ice sublimation was followed by dehydration of the crystalline hexahydrate to a poorly crystalline anhydrate. However, crystalline succinic acid and monosodium succinate were retained in the final lyophiles. The pH and the buffer salt concentration of the prelyo solution influenced the crystalline salt content in the final lyophile. The direction and magnitude of the pH shift in the frozen solution depended on both the initial pH and the buffer concentration. In light of the pH-sensitive nature of a significant fraction of pharmaceuticals (especially proteins), extreme care is needed in both the buffer selection and its concentration.

  4. Energy intake functions and energy budgets of ectotherms and endotherms derived from their ontogenetic growth in body mass and timing of sexual maturation.

    Science.gov (United States)

    Werner, Jan; Sfakianakis, Nikolaos; Rendall, Alan D; Griebeler, Eva Maria

    2018-05-07

    Ectothermic and endothermic vertebrates differ not only in their source of body temperature (environment vs. metabolism), but also in growth patterns, in timing of sexual maturation within life, and energy intake functions. Here, we present a mathematical model applicable to ectothermic and endothermic vertebrates. It is designed to test whether differences in the timing of sexual maturation within an animal's life (age at which sexual maturity is reached vs. longevity) together with its ontogenetic gain in body mass (growth curve) can predict the energy intake throughout the animal's life (food intake curve) and can explain differences in energy partitioning (between growth, reproduction, heat production and maintenance, with the latter subsuming any other additional task requiring energy) between ectothermic and endothermic vertebrates. With our model we calculated from the growth curves and ages at which species reached sexual maturity energy intake functions and energy partitioning for five ectothermic and seven endothermic vertebrate species. We show that our model produces energy intake patterns and distributions as observed in ectothermic and endothermic species. Our results comply consistently with some empirical studies that in endothermic species, like birds and mammals, energy is used for heat production instead of growth, and with a hypothesis on the evolution of endothermy in amniotes published by us before. Our model offers an explanation on known differences in absolute energy intake between ectothermic fish and reptiles and endothermic birds and mammals. From a mathematical perspective, the model comes in two equivalent formulations, a differential and an integral one. It is derived from a discrete level approach, and it is shown to be well-posed and to attain a unique solution for (almost) every parameter set. Numerically, the integral formulation of the model is considered as an inverse problem with unknown parameters that are estimated using a

  5. Lattice stability and high-pressure melting mechanism of dense hydrogen up to 1.5 TPa

    KAUST Repository

    Geng, Hua Y.; Hoffmann, R.; Wu, Q.

    2015-01-01

    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

  6. 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...

  7. 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....

  8. 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)

  9. Premature melt solidification during mold filling and its influence on the as-cast structure

    Science.gov (United States)

    Wu, M.; Ahmadein, M.; Ludwig, A.

    2018-03-01

    Premature melt solidification is the solidification of a melt during mold filling. In this study, a numerical model is used to analyze the influence of the pouring process on the premature solidification. The numerical model considers three phases, namely, air, melt, and equiaxed crystals. The crystals are assumed to have originated from the heterogeneous nucleation in the undercooled melt resulting from the first contact of the melt with the cold mold during pouring. The transport of the crystals by the melt flow, in accordance with the socalled "big bang" theory, is considered. The crystals are assumed globular in morphology and capable of growing according to the local constitutional undercooling. These crystals can also be remelted by mixing with the superheated melt. As the modeling results, the evolutionary trends of the number density of the crystals and the volume fraction of the solid crystals in the melt during pouring are presented. The calculated number density of the crystals and the volume fraction of the solid crystals in the melt at the end of pouring are used as the initial conditions for the subsequent solidification simulation of the evolution of the as-cast structure. A five-phase volume-average model for mixed columnar-equiaxed solidification is used for the solidification simulation. An improved agreement between the simulation and experimental results is achieved by considering the effect of premature melt solidification during mold filling. Finally, the influences of pouring parameters, namely, pouring temperature, initial mold temperature, and pouring rate, on the premature melt solidification are discussed.

  10. Thermoregulation of water foraging honeybees--balancing of endothermic activity with radiative heat gain and functional requirements.

    Science.gov (United States)

    Kovac, Helmut; Stabentheiner, Anton; Schmaranzer, Sigurd

    2010-12-01

    Foraging honeybees are subjected to considerable variations of microclimatic conditions challenging their thermoregulatory ability. Solar heat is a gain in the cold but may be a burden in the heat. We investigated the balancing of endothermic activity with radiative heat gain and physiological functions of water foraging Apis mellifera carnica honeybees in the whole range of ambient temperatures (T(a)) and solar radiation they are likely to be exposed in their natural environment in Middle Europe. The mean thorax temperature (T(th)) during foraging stays was regulated at a constantly high level (37.0-38.5 °C) in a broad range of T(a) (3-30 °C). At warmer conditions (T(a)=30-39 °C) T(th) increased to a maximal level of 45.3 °C. The endothermic temperature excess (difference of T(body)-T(a) of living and dead bees) was used to assess the endogenously generated temperature elevation as a correlate of energy turnover. Up to a T(a) of ∼30 °C bees used solar heat gain for a double purpose: to reduce energetic expenditure and to increase T(th) by about 1-3 °C to improve force production of flight muscles. At higher T(a) they exhibited cooling efforts to get rid of excess heat. A high T(th) also allowed regulation of the head temperature high enough to guarantee proper function of the bees' suction pump even at low T(a). This shortened the foraging stays and this way reduced energetic costs. With decreasing T(a) bees also reduced arrival body weight and crop loading to do both minimize costs and optimize flight performance. Copyright © 2010 Elsevier Ltd. All rights reserved.

  11. Synthesis and Characterization of Solution and Melt Processible Poly(Acrylonitrile-Co-Methyl Acrylate) Statistical Copolymers

    Science.gov (United States)

    Pisipati, Padmapriya

    (acrylonitrile-co-methyl acrylate) of Mw = 200 kg/mol to 160 0C as measured via DSC. Glycerin, ethylene glycol and glycerin/water combinations were investigated as potential plasticizers for high molecular weight (˜200,000 g/mol), high acrylonitrile (93-96 mole:mole %) content poly(acrylonitrile-co-methyl acrylate) statistical copolymers. Pure glycerin (25 wt %) induced crystallization followed by a reduced "Tm" of about 213 0C via DSC. However this composition did not melt process well. A lower M W (˜35 kg/mol) copolymer did extrude with no apparent degradation. Our hypothesis is that the hydroxyl groups in glycerin (or water) disrupt the strong dipole-dipole interactions between the chains enabling the copolymer endothermic transition (Tm) to be reduced and enable melting before the onset of degradation. Additionally high molecular weight (Mw = 200-230 kg/mol) poly(acrylonitrile-co-methyl acrylate) copolymers with lower acrylonitrile content (82-85 wt %) were synthesized via emulsion copolymerization and successfully melt pressed. These materials will be further investigated for their utility in packaging applications.

  12. Role of crucible partition in improving Czochralski melt conditions

    Science.gov (United States)

    Jafri, I. H.; Prasad, V.; Anselmo, A. P.; Gupta, K. P.

    1995-09-01

    Many of the inhomogeneities and defects in the crystal grown from a pool of melt are because of the inherent unsteady growth kinetics and flow instabilities of the process. A scaled up version of the Czochralski process induces oscillatory and turbulent conditions in the melt, thereby resulting in the production of non-uniform silicon crystals. This numerical study reveals that a crucible partition shorter than the melt height can significantly improve the melt conditions. The obstruction at the bottom of the crucible is helpful but the variations in heat flux and flow patterns remain random. However, when the obstruction is introduced at the top of the melt, the flow conditions become much more desirable and oscillations are greatly suppressed. It is also found that a full-melt height partition or a double-crucible may not be a good choice. An optimal size of the blockage and its location to produce the most desirable process conditions will depend on the growth parameters including the melt height and the crucible diameter. These findings should be particularly useful in designing a solid polysilicon pellets-feed continuous Czochralski process for Si crystals.

  13. 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.

  14. 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...

  15. Molecular morphology and crystallization in the quantum limit

    DEFF Research Database (Denmark)

    Bohr, Jakob

    2002-01-01

    The effects of phonons on crystallization and crystal morphology are investigated. It is shown that the commensuration of the lattice vibrations with the lattice will favor certain crystal morphologies. Vibrational effects can also be important for the molecular structure of chain molecules...... protein are estimated to differ by several electron volts. For a biomolecule, such energy is significant and may contribute to cold denaturing as seen for proteins. This is consistent with the empirical observation that cold denaturation is exothermic and hot denaturation endothermic....

  16. Protein Internal Dynamics Associated With Pre-System Glass Transition Temperature Endothermic Events: Investigation of Insulin and Human Growth Hormone by Solid State Hydrogen/Deuterium Exchange.

    Science.gov (United States)

    Fang, Rui; Grobelny, Pawel J; Bogner, Robin H; Pikal, Michael J

    2016-11-01

    Lyophilized proteins are generally stored below their glass transition temperature (T g ) to maintain long-term stability. Some proteins in the (pure) solid state showed a distinct endotherm at a temperature well below the glass transition, designated as a pre-T g endotherm. The pre-T g endothermic event has been linked with a transition in protein internal mobility. The aim of this study was to investigate the internal dynamics of 2 proteins, insulin and human growth hormone (hGH), both of which exhibit the pre-T g endothermic event with onsets at 50°C-60°C. Solid state hydrogen/deuterium (H/D) exchange of both proteins was characterized by Fourier transform infrared spectroscopy over a temperature range from 30°C to 80°C. A distinct sigmoidal transition in the extent of H/D exchange had a midpoint of 56.1 ± 1.2°C for insulin and 61.7 ± 0.9°C for hGH, suggesting a transition to greater mobility in the protein molecules at these temperatures. The data support the hypothesis that the pre-T g event is related to a transition in internal protein mobility associated with the protein dynamical temperature. Exceeding the protein dynamical temperature is expected to activate protein internal motion and therefore may have stability consequences. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  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. Basal metabolic rate of endotherms can be modeled using heat-transfer principles and physiological concepts: reply to "can the basal metabolic rate of endotherms be explained by biophysical modeling?".

    Science.gov (United States)

    Roberts, Michael F; Lightfoot, Edwin N; Porter, Warren P

    2011-01-01

    Our recent article (Roberts et al. 2010 ) proposes a mechanistic model for the relation between basal metabolic rate (BMR) and body mass (M) in mammals. The model is based on heat-transfer principles in the form of an equation for distributed heat generation within the body. The model can also be written in the form of the allometric equation BMR = aM(b), in which a is the coefficient of the mass term and b is the allometric exponent. The model generates two interesting results: it predicts that b takes the value 2/3, indicating that BMR is proportional to surface area in endotherms. It also provides an explanation of the physiological components that make up a, that is, respiratory heat loss, core-skin thermal conductance, and core-skin thermal gradient. Some of the ideas in our article have been questioned (Seymour and White 2011 ), and this is our response to those questions. We specifically address the following points: whether a heat-transfer model can explain the level of BMR in mammals, whether our test of the model is inadequate because it uses the same literature data that generated the values of the physiological variables, and whether geometry and empirical values combine to make a "coincidence" that makes the model only appear to conform to real processes.

  19. 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.

  20. Hypermetabolic Conversion of Plant Oil into Water: Endothermic Biochemical Process Stimulated by Juvenile Hormone in the European Firebug, L.

    Directory of Open Access Journals (Sweden)

    Karel Sláma

    2016-01-01

    Full Text Available The physiological and biochemical mechanisms that enable insects to feed on dry food to secure enough water for larval growth were investigated. The study was carried out with a plethora of physiological methods, ranging from the simple volumetric determination of O 2 consumption and water intake to more advanced methods such as scanning microrespirography and thermovision imaging of insect's body temperature. The experiments were done on the European firebug, Pyrrhocoris apterus , which feeds exclusively on dry linden seeds. In order to survive, it needs to drink water or suck a sap from plants occasionally. It was found that the young larval instars compensate the occasional water deficiency by the increased production of metabolic water. The juvenile hormone (JH-dependent production of metabolic water, which was previously found in other species consuming dry food, was achieved in P. apterus by total metabolic combustion of the dietary lipid (neutral seed oil. The water-producing, hypermetabolic larvae were heated from inside by endothermic energy released from the uncoupling of oxidation from oxidative phosphorylation. The “warm”, hypermetabolic larvae burning the dietary oil into CO 2 and water showed the increased rates of respiratory metabolism. Microrespirographic recording of these larvae revealed the ratio of the respiratory quotient (RQ, CO 2 /O 2 of 0.7, which indicated the breakdown of a pure triglyceride. The warm hypermetabolic larvae could be easily spotted and distinguished from the “cold” larvae on the screen of a thermovision camera. The last instar larvae lacking the JH were always only cold. They metabolized a carbohydrate substrate exclusively (RQ = 1.0, while the dietary lipid was stored in the fat body. In comparison with the hypermetabolic larvae of some other species fed on dry food, which exhibited the highest rates of O 2 consumption ever recorded in a living organism (10–20 mL O 2 /g per hour, the metabolic

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Oscillatory convection in low aspect ratio Czochralski melts

    Science.gov (United States)

    Anselmo, A.; Prasad, V.; Koziol, J.; Gupta, K. P.

    1993-11-01

    Modeling of the crucible in bulk crystal growth simulations as a right circular cylinder may be adequate for high aspect ratio melts but this may be unrealistic when the melt height is low. Low melt height is a unique feature of a solid feed continuous Czochralski growth process for silicon single crystals currently under investigation. At low melt heights, the crucible bottom curvature has a dampening effect on the buoyancy-induced oscillations, a source of inhomogeneities in the grown crystal. The numerical results demonstrate how the mode of convection changes from vertical wall-dominated recirculating flows to Benard convection as the aspect ratio is lowered. This phenomenon is strongly dependent on the boundary condition at the free surface of the melt, which has been generally considered to be either adiabatic or radiatively cooled. A comparison of the flow oscillations in crucibles with and without curved bottoms at aspect ratios in the range of 0.25 to 0.50, and at realistic Grashof numbers (10 7 < Gr < 10 8) illustrate that changing the shape of the crucible may be an effective means of suppressing oscillations and controlling the melt flow.

  6. Influence of crystal–melt interface shape on self-seeding and single ...

    Indian Academy of Sciences (India)

    Unknown

    Self-seeding; orientation; interface shape; antimonide crystals; VDS technique. 1. Introduction ... fundamental characteristics of source materials, various crystal growth models ... to the temperature 50°C above the melting temperature of the crystals ..... Gadkari D B, Lal K B, Shah A P and Arora B M 1997 J. Cryst. Growth 173 ...

  7. Correlations between entropy and volume of melting in halide salts

    International Nuclear Information System (INIS)

    Akdeniz, Z.; Tosi, M.P.

    1991-09-01

    Melting parameters and transport coefficients in the melt are collated for halides of monovalent, divalent and trivalent metals. A number of systems show a deficit of entropy of melting relative to the linear relationships between entropy change and relative volume change on melting that are found to be approximately obeyed by a majority of halides. These behaviours are discussed on the basis of structural and transport data. The deviating systems are classified into three main classes, namely (i) fast-ion conductors in the high-temperature crystal phase such as AgI, (ii) strongly structured network-like systems such as ZnCl 2 , and (iii) molecular systems melting into associated molecular liquids such as SbCl 3 . (author). 35 refs, 1 fig., 3 tabs

  8. Melt-quenched glasses of metal-organic frameworks

    DEFF Research Database (Denmark)

    Bennett, T.D.; Yue, Yuanzheng; Li, P.

    2016-01-01

    Crystalline solids dominate the field of metal−organic frameworks (MOFs), with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration to framework chemistry and topology to expand...... of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic nonmetallic, organic, and metallic), and retain the basic metal−ligand connectivity of crystalline MOFs, which connects their mechanical...... the phenomenon of the melting of 3D MOFs, linking crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to facilitate the melting...

  9. Thermophysical Properties of Selected II-VI Semiconducting Melts

    Science.gov (United States)

    Li, C.; Su, Ching-Hua; Lehoczky, S. L.; Scripa, R. N.; Ban, H.; Lin, B.

    2004-01-01

    Thermophysical properties are essential for the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the II-VI semiconductor melts are scarce. This paper reports the results of the temperature dependence of melt density, viscosity and electrical conductivity of selected II-VI compounds, including HgTe, HgCdTe and HgZnTe. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. The results were compared with and showed good agreement with the existing data in the literature.

  10. A continuous Czochralski silicon crystal growth system

    Science.gov (United States)

    Wang, C.; Zhang, H.; Wang, T. H.; Ciszek, T. F.

    2003-03-01

    Demand for large silicon wafers has driven the growth of silicon crystals from 200 to 300 mm in diameter. With the increasing silicon ingot sizes, melt volume has grown dramatically. Melt flow becomes more turbulent as melt height and volume increase. To suppress turbulent flow in a large silicon melt, a new Czochralski (CZ) growth furnace has been designed that has a shallow melt. In this new design, a crucible consists of a shallow growth compartment in the center and a deep feeding compartment around the periphery. Two compartments are connected with a narrow annular channel. A long crystal may be continuously grown by feeding silicon pellets into the dedicated feeding compartment. We use our numerical model to simulate temperature distribution and velocity field in a conventional 200-mm CZ crystal growth system and also in the new shallow crucible CZ system. By comparison, advantages and disadvantages of the proposed system are observed, operating conditions are determined, and the new system is improved.

  11. Features of Crystallization of Rapidly Quenched Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 Alloys from Melt with High-Temperature Shape Memory Effect

    Science.gov (United States)

    Pushin, A. V.; Pushin, V. G.; Kuntsevich, T. E.; Kuranova, N. N.; Makarov, V. V.; Uksusnikov, A. N.; Kourov, N. I.

    2017-12-01

    A comparative study of the structure and the chemical and phase composition of Ni45Ti32Hf18Cu5 and Ni25Ti32Hf18Cu25 amorphous alloys obtained by fast-quenching of melt stream by spinning has been carried out by transmission and scanning electron microscopy and X-ray diffraction. The critical temperatures of their devitrification were determined by the data of temperatures measurements of electrical resistance. The features of the formation of ultrafine structure and the phase transformation at the vitrification depending on the regimes of heat treatment and chemical composition of alloy have been established.

  12. 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

  13. 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)

  14. Phosphorus zoning as a recorder of crystal growth kinetics

    DEFF Research Database (Denmark)

    Baziotis, I.; Asimow, P.D.; Ntaflos, T.

    2017-01-01

    spectrometry. The petrogenetic history of each vein involves melt intrusion, cooling accompanied by both wall-rock reaction and crystallization, quench of melt to a glass, and possibly later modifications. Exotic secondary olivine crystals in the veins display concentric phosphorus (P)-rich zoning, P...

  15. Preparation of TiC single crystals

    International Nuclear Information System (INIS)

    Scheerer, B.; Fink, J.; Reichardt, W.

    1975-07-01

    TiC single crystals were prepared by vertical zone melting for measurements of the phonon dispersion by inelastic neutron scattering. The influence of the starting material and of the growing conditions on the growth of the crystal were studied. The crystals were characterized by chemical methods, EMX and neutron diffraction. It was possible to grow single crystals with a volume of up to 0.6 cm 3 and mosaic spread of less then 0.4 0 . (orig.) [de

  16. Development of silicon growth techniques from melt with surface heating

    Science.gov (United States)

    Kravtsov, Anatoly

    2018-05-01

    The paper contains literary and personal data on the development history of silicon-growing technology with volumetric and surface melt heating. It discusses the advantages and disadvantages of surface-heating technology. Examples are given of the implementation of such processes in the 60s-70s of the last century, and the reasons for the discontinuation of the relevant work. It describes the main solutions for the implementation of crystal growth process with the electron-beam heating of the melt surface, implemented by KEPP EU (Latvia). It discusses differences in the management of the growth process for the crystals with constant diameters compared to the Czochralski method. It lists geometrical and electro-physical properties of the obtained crystals. It describes the possible use of such crystals and the immediate challenges of technology development.

  17. How low can you go? An adaptive energetic framework for interpreting basal metabolic rate variation in endotherms.

    Science.gov (United States)

    Swanson, David L; McKechnie, Andrew E; Vézina, François

    2017-12-01

    Adaptive explanations for both high and low body mass-independent basal metabolic rate (BMR) in endotherms are pervasive in evolutionary physiology, but arguments implying a direct adaptive benefit of high BMR are troublesome from an energetic standpoint. Here, we argue that conclusions about the adaptive benefit of BMR need to be interpreted, first and foremost, in terms of energetics, with particular attention to physiological traits on which natural selection is directly acting. We further argue from an energetic perspective that selection should always act to reduce BMR (i.e., maintenance costs) to the lowest level possible under prevailing environmental or ecological demands, so that high BMR per se is not directly adaptive. We emphasize the argument that high BMR arises as a correlated response to direct selection on other physiological traits associated with high ecological or environmental costs, such as daily energy expenditure (DEE) or capacities for activity or thermogenesis. High BMR thus represents elevated maintenance costs required to support energetically demanding lifestyles, including living in harsh environments. BMR is generally low under conditions of relaxed selection on energy demands for high metabolic capacities (e.g., thermoregulation, activity) or conditions promoting energy conservation. Under these conditions, we argue that selection can act directly to reduce BMR. We contend that, as a general rule, BMR should always be as low as environmental or ecological conditions permit, allowing energy to be allocated for other functions. Studies addressing relative reaction norms and response times to fluctuating environmental or ecological demands for BMR, DEE, and metabolic capacities and the fitness consequences of variation in BMR and other metabolic traits are needed to better delineate organismal metabolic responses to environmental or ecological selective forces.

  18. An endothermic chemical process facility coupled to a high temperature reactor. Part I: Proposed accident scenarios within the chemical plant

    International Nuclear Information System (INIS)

    Brown, Nicholas R.; Seker, Volkan; Revankar, Shripad T.; Downar, Thomas J.

    2012-01-01

    Highlights: ► The paper identifies possible transient and accident scenarios in a coupled PBMR and thermochemical sulfur cycle based hydrogen plant. ► Key accidents scenarios were investigated through qualitative reasoning. ► The accidents were found to constitute loss of heat sink event for the nuclear reactor. - Abstract: Hydrogen generation using a high temperature nuclear reactor as a thermal driving vector is a promising future option for energy carrier production. In this scheme, the heat from the nuclear reactor drives an endothermic water-splitting plant, via coupling, through an intermediate heat exchanger. Quantitative study of the possible operational or accident events within the coupled plant is largely absent from the literature. In this paper, seven unique case studies are proposed based on a thorough review of possible events. The case studies are: (1) feed flow failure from one section of the chemical plant to another with an accompanying parametric study of the temperature in an individual reaction chamber, (2) product flow failure (recycle) within the chemical plant, (3) rupture or explosion within the chemical plant, (4) nuclear reactor helium inlet overcooling due to a process holding tank failure, (5) helium inlet overcooling as an anticipated transient without emergency nuclear reactor shutdown, (6) total failure of the chemical plant, (7) control rod insertion in the nuclear reactor. The qualitative parameters of each case study are outlined as well as the basis in literature. A previously published modeling scheme is described and adapted for application as a simulation platform for these transient events. The results of the quantitative case studies are described within part II of this paper.

  19. Ultrafast endothermic transfer of non-radiative exciplex state to radiative excitons in polyfluorene random copolymer for blue electroluminescence

    Science.gov (United States)

    Moghe, Dhanashree A.; Dey, Amrita; Johnson, Kerr; Lu, L.-P.; Friend, Richard H.; Kabra, Dinesh

    2018-04-01

    We report a blue-emitting random copolymer (termed modified Aryl-F8) consisting of three repeat units of polydioctylfluorene (F8), Aryl-polydioctylfluorene (Aryl-F8), and an aromatic amine comonomer unit, poly(bis-N,Ν'-(4-butylphenyl)-bis-N,N'-phenyl-1,4 phenylenediamine) chemically linked to get an improved charge carrier balance without compromising on the photoluminescence (PL) quantum yield with respect to the Aryl-F8 homo-polymer. The measured photoluminescence quantum efficiency (˜70%) of the blue-emitting polymer is comparable to or greater than the individual monomer units. The time resolved PL spectra from the modified Aryl-F8 are similar to those of Arylated-poly(9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4 phenylenediamine) (PFB) even at a time scale of 100-250 ps, indicating an ultrafast energy transfer from the (Aryl-F8 or F8):Arylated-PFB interface to Arylated-PFB, i.e., endothermic transfer of non-radiative exciplex to a radiative molecular exciton. Furthermore, the presence of non-radiative exciplex is confirmed by the photoluminescence decay profile and temperature dependent PL spectra. The luminance efficiency achieved for the modified Aryl-F8 polymer light-emitting diodes is ˜11 cd A-1 with an external quantum efficiency (EQE) of ˜4.5%, whereas it is 0.05 cd/A with an EQE of ˜0.025% for Aryl-F8. Almost two orders of higher efficiency is achieved due to the improved charge carrier balance from the random copolymer without compromising on the photoluminescence yield.

  20. 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

  1. 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.)

  2. 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 %.

  3. Applications of disorder-induced melting concept to critical-solute-accumulation processes

    International Nuclear Information System (INIS)

    Lam, N.Q.; Okamoto, P.R.; Heuer, J.K.

    2001-01-01

    A generalized version of the Lindemann melting criterion has recently been used to develop a unified thermodynamic description of disorder-induced amorphization and heat-induced melting. This concept of amorphization as a melting process is based on the fact that the melting temperature of a defective crystal driven far from equilibrium will decrease relative to that of its defect-free equilibrium state. The broader view of melting provides a new perspective of damage-accumulation processes such as radiation damage, ion implantation, ion beam mixing, plastic deformation, and fracture. For example, within this conceptual framework, disorder-induced amorphization is simply polymorphous melting of a critically disordered crystal at temperatures below the glass transition temperature. In the present communication, we discuss the application of the concept to two specific cases: amorphous phase formation during ion implantation and solute segregation-induced intergranular fracture

  4. 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

  5. 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.

  6. Matrix effects on the crystallization behaviour of butter and roll-in shortening in laminated bakery products.

    Science.gov (United States)

    Mattice, Kristin D; Marangoni, Alejandro G

    2017-06-01

    Two hydrogenated roll-in shortenings (A & B), one non-hydrogenated roll-in shortening and butter were used to prepare croissants. The impact of the laminated dough matrix on fat crystallization was then investigated using powder X-ray diffraction (XRD), pulsed nuclear magnetic resonance (p-NMR) and differential scanning calorimetry (DSC). The fat contained within a croissant matrix has never before been analyzed using these techniques. In each case, XRD revealed that the polymorphism of a roll-in fat will be different when baked within the dough matrix than when simply heated and cooled on its own. Both hydrogenated roll-in shortenings and butter experienced only minor changes, largely retaining their β' polymorphs, but the non-hydrogenated shortening experienced significant conversion from β' to the β form. However, this conversion did not take place immediately upon cooling, but after approximately 24h of storage time. The fat contained within the croissants exhibited a significantly lower SFC than the same fats in bulk. Further, DSC results demonstrated that a greater temperature was required to completely melt all of the fat in a croissant than the same fat in bulk, observed visually as broader peaks in the melting endotherms. Analysis of croissant firmness over storage time, measured as the maximum force required to cut a croissant was used as an indication of potential sensory consequences. Results suggested that only croissants prepared with non-hydrogenated shortening experienced significant changes in firmness over one week of storage. These results indicate that there is an interaction between the shortenings and the ingredients of the croissant matrix, and given the differences observed between roll-in fats used, the extent of interaction is potentially influenced by the composition of the roll-in fat itself. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Ab initio molecular dynamics simulation of laser melting of silicon

    NARCIS (Netherlands)

    Silvestrelli, P.-L.; Alavi, A.; Parrinello, M.; Frenkel, D.

    1996-01-01

    The method of ab initio molecular dynamics, based on finite temperature density functional theory, is used to simulate laser heating of crystal silicon. We have found that a high concentration of excited electrons dramatically weakens the covalent bond. As a result, the system undergoes a melting

  8. Changes in density of aluminium, lead and zinc melts dependent on temperature

    International Nuclear Information System (INIS)

    Kazachkov, S.P.; Kochegura, N.M.; Markovskij, E.A.

    1979-01-01

    Density of aluminium, lead and zinc in various aggregate states has been studied in a wide temperature range. The density of the above metals was found to manifest temperature hysteresis after melting and cyclic change at the temperature of melting and crystallization. These phenomena are in agreement with the Stuart model of liquid state

  9. Dehydration and crystallization kinetics of zirconia-yttria gels

    International Nuclear Information System (INIS)

    Ramanathan, S.; Muraleedharan, R.V.; Roy, S.K.; Nayar, P.K.K.

    1995-01-01

    Zirconia and zirconia-yttria gels containing 4 and 8 mol% yttria were obtained by coprecipitation and drying at 373 K. The dehydration and crystallization behavior of the dried gels was studied by DSC, TG, and XRD. The gels undergo elimination of water over a wide temperature range of 373--673 K. The peak temperature of the endotherm corresponding to dehydration and the kinetic constants for the process were not influenced by the yttria content of the gel. The enthalpy of dehydration observed was in good agreement with the heat of vaporization data. The dehydration was followed by a sharp exothermic crystallization process. The peak temperature of the exotherm and the activation energy of the process increased with an increase in yttria content, while the enthalpy of crystallization showed a decrease. The ''glow effect'' reduced with increasing yttria content. Pure zirconia crystallizes in the tetragonal form while the zirconia containing 4 and 8 mol% yttria appears to crystallize in the cubic form

  10. 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

  11. Melting behaviour of raw materials and recycled stone wool waste

    DEFF Research Database (Denmark)

    Schultz-Falk, Vickie; Agersted, Karsten; Jensen, Peter Arendt

    2018-01-01

    Stone wool is a widely used material for building insulation, to provide thermal comfort along with fire stability and acoustic comfort for all types of buildings. Stone wool waste generated either during production or during renovation or demolition of buildings can be recycled back into the sto...... wool melt production. This study investigates and compares the thermal response and melting behaviour of a conventional stone wool charge and stone wool waste. The study combines differential scanning calorimetry (DSC), hot stage microscopy (HSM) and X-ray diffraction (XRD). DSC reveals...... that the conventional charge and stone wool waste have fundamentally different thermal responses, where the charge experiences gas release, phase transition and melting of the individual raw materials. The stone wool waste experiences glass transition, crystallization and finally melting. Both DSC and HSM measurements...

  12. Structure, morphology and melting hysteresis of ion-implanted nanocrystals

    International Nuclear Information System (INIS)

    Andersen, H.H.; Johnson, E.

    1995-01-01

    Investigations of nanosized metal and semimetal inclusions produced by ion implantation in aluminium are reviewed. The inclusions are from 1 nm to 15 nm in size and contain from 80 to 100,000 atoms. Embedded crystallites, which are topotactically aligned with the surrounding matrix, may not be produced in this size range by any other method. The inclusions offer unique possibilities for study of the influence of interfaces on the crystal structure of the inclusions as well as on their melting and solidification behaviour. Studies are made with transmission electron microscopy (TEM), electron- and x-ray diffraction and in situ RBS- channeling measurements. Bi, Cd, In, Pb and Tl inclusions all show a substantial melting/solidification temperature hysteresis, which, in all cases except for Bi, is placed around the bulk melting temperature, while bismuth melts below that temperature. (au) 46 refs

  13. Method of studying polymorphic transformations in melts of metals

    International Nuclear Information System (INIS)

    Magomedov, A.M.

    1986-01-01

    This paper presents a method used to study the dynamics of the change in the electrical properties of specimens during melting and crystallization and to quite accurately determine the phase transformation temperatures in melts. A block diagram of the unit for measuring the magnetoresistive effect in melts of metals is shown. The authors found that the strength of the magnetic field affects the magnitude of the jumps associated with the anomalies rather than the temperature range of the polymorphic transformations. The method described accurately determines the transformation temperatures for first- and second-order phase transformations; it does not require the use of complicated and expensive equipment. The measurement time is much shorter and the amount of material needed for studies is much smaller than with the use of any other method. The proposed method can be used to study melts of metals and construct phase deagrams of alloys

  14. 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

  15. 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…

  16. 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.

  17. 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

  18. 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.

  19. Control of heat transfer in continuous-feeding Czochralski-silicon crystal growth with a water-cooled jacket

    Science.gov (United States)

    Zhao, Wenhan; Liu, Lijun

    2017-01-01

    The continuous-feeding Czochralski method is an effective method to reduce the cost of single crystal silicon. By promoting the crystal growth rate, the cost can be reduced further. However, more latent heat will be released at the melt-crystal interface under a high crystal growth rate. In this study, a water-cooled jacket was applied to enhance the heat transfer at the melt-crystal interface. Quasi-steady-state numerical calculation was employed to investigate the impact of the water-cooled jacket on the heat transfer at the melt-crystal interface. Latent heat released during the crystal growth process at the melt-crystal interface and absorbed during feedstock melting at the feeding zone was modeled in the simulations. The results show that, by using the water-cooled jacket, heat transfer in the growing crystal is enhanced significantly. Melt-crystal interface deflection and thermal stress increase simultaneously due to the increase of radial temperature at the melt-crystal interface. With a modified heat shield design, heat transfer at the melt-crystal interface is well controlled. The crystal growth rate can be increased by 20%.

  20. 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.

  1. 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

  2. A new titanium-bearing calcium aluminosilicate phase. 2: Crystallography and crystal chemistry of grains formed in slowly cooled melts with bulk compositions of calcium-aluminium-rich inclusions

    Science.gov (United States)

    Barber, David J.; Beckett, John R.; Paque, Julie M.; Stolper, Edward

    1994-01-01

    The crystallography and crystal chemistry of a new calcium- titanium-aluminosilicate mineral (UNK) observed in synthetic analogs to calcium-aluminum-rich inclusions (CAIs) from carbonaceous chondrites was studied by electron diffraction techniques. The unit cell is primitive hexagonal or trigonal, with a = 0.790 +/- 0.02 nm and c = 0.492 +/- 0.002 nm, similar to the lattice parameters of melilite and consistent with cell dimensions for crystals in a mixer furnace slag described by Barber and Agrell (1994). The phase frequently displays an epitactic relationship in which melilite acts as the host, with (0001)(sub UNK) parallel (001)(sub mel) and zone axis group 1 0 -1 0(sub UNK) parallel zone axis group 1 0 0(sub mel). If one of the two space groups determined by Barber and Agrell (1994) for their sample of UNK is applicable (P3m1 or P31m), then the structure is probably characterized by puckered sheets of octahedra and tetrahedra perpendicular to the c-axis with successive sheets coordinated by planar arrays of Ca. In this likely structure, each unit cell contains three Ca sites located in mirror planes, one octahedrally coordinated cation located along a three-fold axis and five tetrahedrally coordinated cations, three in mirrors and two along triads. The octahedron contains Ti but, because there are 1.3-1.9 cations of Ti/formula unit, some of the Ti must also be in tetrahedral coordination, an unusual but not unprecedented situation for a silicate. Tetrahedral sites in mirror planes would contain mostly Si, with lesser amounts of Al while those along the triads correspondingly contain mostly Al with subordinate Ti. The structural formula, therefore, can be expressed as Ca(sub 3)(sup VIII)(Ti,Al)(sup VI)(Al,Ti,Si)(sub 2)(sup IV)(Si,Al)(sub 3)(sup IV)O14 with Si + Ti = 4. Compositions of meteoritic and synthetic Ti-bearing samples of the phase can be described in terms of a binary solid solution between the end-members Ca3TiAl2Si3O14 and Ca3Ti(AlTi)(AlSi2)O14. A Ti

  3. Gamma irradiation of melt processed biomedical PDLLA/HAP nanocomposites

    International Nuclear Information System (INIS)

    Dadbin, Susan; Kheirkhah, Yahya

    2014-01-01

    Poly(D-L lactide) PDLLA/hydroxyapatite (HAP) nanocomposites at various compositions were prepared by melt-compounding process and then subjected to gamma irradiation at a dose of 30 kGy. The morphology of the nanocomposites, characterized by transmission electron microscopy (TEM), displayed HAP nanoparticles at various sizes ranging from 10 to 100 nm distributed almost evenly within the polymer matrix. Differential scanning calorimetric (DSC) analysis of the irradiated nanocomposites showed an increase in the degree of crystallinity along with a melting peak split. The double melting peak suggested formation of different crystalline structures in the radiation exposed nanocomposites. Also the cold crystallization peak shifted to lower temperatures and became much sharper upon irradiation, indicating higher crystallization rate. The irradiated nanocomposites showed lower tensile strength and elongation at break, suggesting occurrence of some chain scission reactions in the PLA. - Highlights: • Biomedical polylactic acid/hydroxyapatite nanocomposites prepared by melt-compounding were gamma irradiated. • Transmission electron microscopy showed hydroxyapatite nanoparticles evenly distributed within polylactic acid ranging from 10 to 100 nm. • A halo appeared around hydroxyapatite particles showing interfacial interactions between polylactic acid and the particles. • Double melting peak appeared for polylactic acid in DSC thermograms upon gamma irradiation of the nanocomposites

  4. The Melting Behavior and Thermal Stability of Green Poly(L-lactic acid) with N, N, N, N'-Tetra(benzoyl) Ethylene Diamine Tetraacetic Acid Dihydrazide

    International Nuclear Information System (INIS)

    Cai, Y.; Qiang Xu, Q.; Ren, L.; Zhao, L.

    2015-01-01

    The thermal properties of green poly(L-lactic acid) (PLLA) with N, N, N, N'-tetra(benzoyl) ethylene diamine tetraacetic acid dihydrazide (NA) at different conditions were investigated. The melting behavior of PLLA/NA sample after isothermal crystallization at 100 degree C showed that the low-temperature melting peak shifted to high temperature with increasing of crystallization time. However, the high-temperature melting peak did not show any change. Meantime, the melting enthalpy of cold crystallization was higher than that of hot crystallization, and the difference between cold crystallization and hot crystallization increased from 0.31 J/g to 0.89 J/g with increasing of crystallization time. Heating or cooling rate affected the melting behavior of PLLA, the low-temperature and high-temperature melting peak shifted to low temperature with increasing of rate, and the ratio of melting peak area between low-temperature melting peak and high-temperature melting peak decreased. Thermal stability of PLLA/NA indicated that PLLA/NA only exhibited one decomposition stage as decomposition of PLLA. (author)

  5. Conversion of broadband thermal radiation in lithium niobate crystals of various compositions

    Science.gov (United States)

    Syuy, A. V.; Litvinova, M. N.; Goncharova, P. S.; Sidorov, N. V.; Palatnikov, M. N.; Krishtop, V. V.; Likhtin, V. V.

    2013-05-01

    The conversion of the broadband thermal radiation in stoichiometric ( R = 1) lithium niobate single crystals that are grown from melt with 58.6 mol % of LiO2, congruent ( R = Li/Nb = 0.946) melt with the K2O flux admixture (4.5 and 6.0 wt %), and congruent melt and in congruent single crystals doped with the Zn2+, Gd3+, and Er3+ cations is studied. It is demonstrated that the conversion efficiency of the stoichiometric crystal that is grown from the melt with 58.6 mol % of LiO2 is less than the conversion efficiency of congruent crystal. In addition, the stoichiometric and almost stoichiometric crystals and the doped congruent crystals exhibit the blue shift of the peak conversion intensity in comparison with a nominally pure congruent crystal. For the congruent crystals, the conversion intensities peak at 520 and 495 nm, respectively.

  6. Transition from Endothermic to Exothermic Dissolution of Hydroxyapatite Ca5(PO43OH–Johnbaumite Ca5(AsO43OH Solid Solution Series at Temperatures Ranging from 5 to 65 °C

    Directory of Open Access Journals (Sweden)

    Bartosz Puzio

    2018-06-01

    Full Text Available Five crystalline members of the hydroxyapatite (HAP; Ca5(PO43OH–johnbaumite (JBM; Ca5(AsO43OH series were crystallized at alkaline pH from aqueous solutions and used in dissolution experiments at 5, 25, 45, and 65 °C. Equilibrium was established within three months. Dissolution was slightly incongruent, particularly at the high-P end of the series. For the first time, the Gibbs free energy of formation ΔGf0, enthalpy of formation ΔHf0, entropy of formation Sf0, and specific heat of formation Copf were determined for HAP–JBM solid solution series. Based on the dissolution reaction, Ca5(AsO4m(PO43−mOH = 5Ca2+(aq + mAsO43−(aq + (3 − mPO43−(aq + OH−(aq, their solubility product Ksp,298.15 was determined. Substitution of arsenic (As for phosphorus (P in the structure of apatite resulted in a linear increase in the value of Ksp: from HAP logKsp,298.15 = −57.90 ± 1.57 to JBM logKsp,298.15 = −39.22 ± 0.56. The temperature dependence of dissolution in this solid solution series is very specific; in the temperature range of 5 °C to 65 °C, the enthalpy of dissolution ΔHr varied around 0. For HAP, the dissolution reaction at 5 °C and 25 °C was endothermic, which transitioned at around 40 °C and became exothermic at 45 °C and 65 °C.

  7. The Properties of Ammonium Dinitramine (ADN): Part 2: Melt Casting

    Science.gov (United States)

    Hahma, A.; Edvinsson, H.; Östmark, H.

    2010-04-01

    A melt casting technique for ammonium dinitramine (ADN) and ADN/aluminum was developed. ADN proved relatively easy to cast, when 1% of magnesium oxide was used as a stabilizer and crystallization kernels. Densities of ADN/MgO 99/1 were 92 to 97% of theoretical mean density (TMD) and those of ADN/Al/MgO 64/35/1 were between 95 and 99% of TMD. Sedimentation of Al in the melt was prevented and the particle wetting was ensured by selecting a suitable particle size for Al. No gelling agents or other additives were used. The casting process and factors influencing it are discussed.

  8. Effect of the distribution of saturated fatty acids in the melting and crystallization profiles of high-oleic high-stearic oils; Efecto de la distribución de los ácidos grasos saturados en los perfiles de fusión y cristalización de los aceites alto esteárico alto oleico

    Energy Technology Data Exchange (ETDEWEB)

    Bootello, M.A.; Garces, R.; Martinez-Force, E.; Salas, J.J.

    2016-07-01

    The composition and distribution of fatty acids in triacylglycerol (TAG) molecules are commonly considered as factors that determine the physical properties of a given oil or fat. The distribution of any fatty acid in fats and oils can be described through the α coefficient of asymmetry, which can be calculated from the TAG composition and fatty acid composition of the Sn-2 position of the TAGs determined through lipase hydrolysis. High-oleic high-stearic oils and fats are considered stable and healthy, and they are good substitutes for hydrogenated vegetable oils and palm fractions in many food products, such as spreads and confectionery. Here, different high-oleic high-stearic acid oils were formulated which contained different distributions of saturated fatty acids in their TAGs, while maintaining a similar fatty acid composition. The aim of this work was to discuss the possibility of using the α coefficient to predict the physical properties of fats in function of their chemical composition and their melting and crystallization behavior as examined by differential scanning calorimetry.

  9. 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.)

  10. Springer Handbook of Crystal Growth

    CERN Document Server

    Dhanaraj, Govindhan; Prasad, Vishwanath; Dudley, Michael

    2010-01-01

    Over the years, many successful attempts have been made to describe the art and science of crystal growth. Most modern advances in semiconductor and optical devices would not have been possible without the development of many elemental, binary, ternary, and other compound crystals of varying properties and large sizes. The objective of the Springer Handbook of Crystal Growth is to present state-of-the-art knowledge of both bulk and thin-film crystal growth. The goal is to make readers understand the basics of the commonly employed growth processes, materials produced, and defects generated. Almost 100 leading scientists, researchers, and engineers from 22 different countries from academia and industry have been selected to write chapters on the topics of their expertise. They have written 52 chapters on the fundamentals of bulk crystal growth from the melt, solution, and vapor, epitaxial growth, modeling of growth processes and defects, techniques of defect characterization as well as some contemporary specia...

  11. 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...

  12. 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

  13. 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)

  14. 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.)

  15. The density, compressibility and seismic velocity of hydrous melts at crustal and upper mantle conditions

    Science.gov (United States)

    Ueki, K.; Iwamori, H.

    2015-12-01

    Various processes of subduction zone magmatism, such as upward migration of partial melts and fractional crystallization depend on the density of the hydrous silicate melt. The density and the compressibility of the hydrous melt are key factors for the thermodynamic calculation of phase relation of the hydrous melt, and the geophysical inversion to predict physicochemical conditions of the melting region based on the seismic velocity. This study presents a new model for the calculations of the density of the hydrous silicate melts as a function of T, P, H2O content and melt composition. The Birch-Murnaghan equation is used for the equation of state. We compile the experimentally determined densities of various hydrous melts, and optimize the partial molar volume, compressibility, thermal expansibility and its pressure derivative, and K' of the H2O component in the silicate melt. P-T ranges of the calibration database are 0.48-4.29 GPa and 1033-2073 K. As such, this model covers the P-T ranges of the entire melting region of the subduction zone. Parameter set provided by Lange and Carmichael [1990] is used for the partial molar volume and KT value of the anhydrous silicate melt. K' of anhydrous melt is newly parameterized as a function of SiO2 content. The new model accurately reproduces the experimentally determined density variations of various hydrous melts from basalt to rhyolite. Our result shows that the hydrous melt is more compressive and less dense than the anhydrous melt; with the 5 wt% of H2O in melt, density and KT decrease by ~10% and ~30% from those of the anhydrous melt, respectively. For the application of the model, we calculated the P-wave velocity of the hydrous melt. With the 5 wt% of H2O, P-wave velocity of the silicate melt decreases by >10%. Based on the melt P-wave velocity, we demonstrate the effect of the melt H2O content on the seismic velocity of the partially molten zone of the subduction zone.

  16. Research and Development of Crystal Purification for Product of Uranium Crystallization Process

    Energy Technology Data Exchange (ETDEWEB)

    Yano, K. [Japan Atomic Energy Agency - JAEA (Japan)

    2009-06-15

    Uranium crystallization has been developed as a part of advanced aqueous reprocessing for FBR spent fuel. Although the purity of uranyl nitrate hexahydrate (UNH) crystal from the crystallization process is supposed to meet a specification of FBR blanket fuel, an improvement of its purity is able to reduce the cost of fuel fabrication and storage (in case interim storage of recovered uranium is required). In this work, UNH crystal purification was developed as additional process after crystallization. Contamination of the crystal is caused by mother solution and solid state impurities. They are inseparable by washing and filtration. Mother solution on the surface of UNH crystals is removable by washing, but it is difficult to remove that in an obstructed part of crystalline aggregate by washing. Major elements of solid state impurities are cesium and barium. Cesium precipitates with tetravalent plutonium as a double nitrate, Cs{sub 2}Pu(NO{sub 3}){sub 6}. Barium crystallizes as Ba(NO{sub 3}){sub 2} because of its low solubility in nitric acid solution. It is difficult to separate their particle from UNH crystal by solid-liquid separation such as simple filtration. As a kind of crystal purification, there are some methods using sweating. Sweating is a phenomenon that a crystal melts partly below its melting point and it is caused by depression of freezing point due to impurity. It is considerably applicable for removal of mother solution. Concerning the solid state impurities, which has higher melting point than that of UNH crystal, it is supposed that they are separable by melting UNH crystal and filtration. The behaviors of impurities and applicability of sweating and melting-filtration operations to the purification for UNH crystal were investigated experimentally on a beaker and an engineering scale. With regard to behaviors of impurities, the conditions of cesium and barium precipitation were surveyed and it was clarified that there were most impurities on the

  17. 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

  18. 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

  19. Endothermic decompositions of inorganic monocrystalline thin plates. I. Shape of polycrystalline product domains versus constraints and time

    Science.gov (United States)

    Bertrand, G.; Comperat, M.; Lallemant, M.; Watelle, G.

    1980-03-01

    Copper sulfate pentahydrate dehydration into trihydrate was investigated using monocrystalline platelets with varying crystallographic orientations. The morphological and kinetic features of the trihydrate domains were examined. Different shapes were observed: polygons (parallelograms, hexagons) and ellipses; their conditions of occurrence are reported in the (P, T) diagram. At first (for about 2 min), the ratio of the long to the short axes of elliptical domains changes with time; these subsequently develop homothetically and the rate ratio is then only pressure dependent. Temperature influence is inferred from that of pressure. Polygonal shapes are time dependent and result in ellipses. So far, no model can be put forward. Yet, qualitatively, the polygonal shape of a domain may be explained by the prevalence of the crystal arrangement and the elliptical shape by that of the solid tensorial properties. The influence of those factors might be modulated versus pressure, temperature, interface extent, and, thus, time.

  20. Application of the Billet Casting Method to Determine the Onset of Incipient Melting of 319 Al Alloy Engine Blocks

    Science.gov (United States)

    Lombardi, A.; Ravindran, C.; MacKay, R.

    2015-06-01

    The increased use of Al for automotive applications has resulted from the need to improve vehicle fuel efficiency. Aluminum alloy engine blocks fulfil the need of lightweighting. However, there are many challenges associated with thermo-mechanical mismatch between Al and the gray cast iron cylinder liners, which result in large tensile residual stress along the cylinder bores. This requires improced mechanical properties in this region to prevent premature engine failure. In this study, replicating billet castings were used to simulate the engine block solution heat treatment process and determine the onset of incipient melting. Microstructural changes during heat treatment were assessed with SEM and EDX, while thermal analysis was carried out using differential scanning calorimetry. The results suggest that solution heat treatment at 500 °C was effective in dissolving secondary phase particles, while solutionizing at 515 or 530 °C caused incipient melting of Al2Cu and Al5Mg8Cu2Si6. Incipient melting caused the formation ultra-fine eutectic clusters consisting of Al, Al2Cu, and Al5Mg8Cu2Si6 on quenching. In addition, DSC analysis found that incipient melting initiated at 507 °C for all billets, although the quantity of local melting reduced with microstructural refinement as evidenced by smaller endothermic peaks and energy absorption. The results from this study will assist in improving engine block casting integrity and process efficiency.

  1. Influence of initial microstructure of aluminium alloy charge after its melting on the hard metal inherited structure

    Directory of Open Access Journals (Sweden)

    Г. О. Іванов

    2016-07-01

    Full Text Available Metal properties heredity in the chain- initial hard state > liquid state > final solidified state has always been interesting for metallurgists. It is known that after the primary melting of charge there occurs microheterogenеous non-equilibrium melt with crystal-like groups of atoms and disordered area in it. With increase in temperature the melt approaches the equilibrium microhomogeneous state. The aim of this work is to study the charge microstructure influence on melt fluidity in the light of quasi-crystal model of liquid structure. Influence of isothermal heating on fluidity of aluminium melt, smelted from fine-grained and coarse-grained charge has been investigated. It has been stated that for coarse-grained metal additional melting of crystallization «genes» takes place in 1,4-quick time, as compared to fine-grained. The coefficients of exponential function for our experimental data have been calculated. It has been stated that the exponent depends on the charge microstructure, and multiplier depends on the soaking temperature. On the basis of A. Einstein equation for the calculation of liquid viscosity from the known fraction of admixtures and clean liquid viscosity an analogical equation for fluidity and calculation of quasi-crystals volume share in the melt have been derived. It has been found that the charge grain size affects the speed of quasi-crystals additional melting in the melt. The reference amount of quasi-crystals at the initial moment of large- and fine-grained charge melting has been calculated from our metallographic, experimental and estimated data

  2. 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

  3. 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.

  4. Cathodic processes during ruthenium electrodeposition from a chloride melt

    International Nuclear Information System (INIS)

    Sokol'skij, D.V.

    1985-01-01

    Cathodic processes occurring during the electrolysis of chloride melts in the presence of oxygen-containing impurities were studied. The experiments were carried out at 500, 550 600 and 680 deg C, ruthenium ions concentration in KCl-NaCl-CsCl eutectic melt being 0.4-1.5 mol% and BaO additions 4.8x10 -2 mol%. Temperature dependence of Ru(3) ion diffusion coefficient in the chloride melt (lg D=3.25-1508/T+-0.02) and activation energy of the diffusion process (6.9 k cal/mol) were determined. It is shown that changes of the shape of E, t-curve and the deviation of values determined in the cause of chronopotentiometric investigations from the corresponding values of reversable processes are related in many respects to the participation of oxygen-containing compounds in the cathodic process. Irreversibility of the cathodic process is also connected with metal crystallization during electrodeposition

  5. Crystal habit, characterization and pharmacological activity of various crystal forms of arteether

    Directory of Open Access Journals (Sweden)

    Renu Chadha

    2011-08-01

    Full Text Available The aim of this study was to investigate and characterize different crystal forms of arteether, a rapidly acting, highly potent antimalarial drug for the treatment of acute Plasmodium falciparum malaria. Six different crystal forms were prepared utilizing various polar and non-polar solvents. Scanning electron microscopy (SEM revealed differences in the surface characteristics of the six forms from those of a commercial sample. Differential scanning calorimetry (DSC revealed the absence of a desolvation endotherm indicating that the forms were neither hydrates nor solvates. Powder X-ray diffraction (PXRD patterns of the forms showed much weaker major peaks than in the commercial sample indicating them to be less crystalline. Solubility and dissolution studies showed that the most amorphous form was the most soluble and possessed the highest antimalarial activity.

  6. Phase relations, crystal structures and physical properties of nuclear fuels

    International Nuclear Information System (INIS)

    Tagawa, Hiroaki; Fujino, Takeo; Tateno, Jun

    1975-07-01

    Phase relations, crystal structures and physical properties of the compounds for nuclear fuels are presented, including melting point, thermal expansion, diffusion and magnetic and electric properties. Emphasis is on oxides, carbides and nitrides of thorium, uranium and plutonium. (auth.)

  7. 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).

  8. Ca/Al of plagioclase-hosted melt inclusions as an indicator for post-entrapment processes at mid-ocean ridges?

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, H.T.; Yang, Y.M.; Yan, Q.S.; Shi, Z.F.; Zhu, Z.W.; Su, W.C.; Qin, C.J.; Ye, J.

    2016-07-01

    The composition of melt inclusions in basalts erupted at mid-ocean ridges may be modified by post-entrapment processes, so the present composition of melt inclusions may not represent their original composition at the time of entrapment. By combining the melt inclusion composition in samples from the South Mid-Atlantic Ridge at 19°S analyzed in this study, and from the Petrological Database, we found that post-entrapment crystallization processes resulted in higher Ca/Al, Mg#[100×atomic Mg2+/(Mg2++Fe2+)], MgO and FeO contents, and lower CaO and Al2O3 contents of plagioclase-hosted melt inclusions relative to those hosted in olivine. In addition, melt inclusions hosted in plagioclase with anorthite content larger than 80mol.% had been modified more readily than others. By discussing the relationships between Ca/Al and fractional crystallization, post-entrapment crystallization, and the original melt composition, we propose that Ca/Al can be regarded as an indicator of the effect of post-entrapment processes on melt inclusion composition. Specifically, i) when Ca/Al<0.78, melt inclusion compositions corrected for fractional crystallization to Mg#=72 can represent the primary magma at mid-ocean ridges; ii) when 0.78melt inclusions are mainly modified by post-entrapment crystallization effects, and can reveal the original melt composition after correcting for these effects; iii) when Ca/Al>1.0, the compositions of melt inclusions do not reflect the original melt composition nor preserve information about the mantle source. According to these criteria, plagioclase-hosted melt inclusions with Ca/Al>1.0 in basalts from the South Mid-Atlantic Ridge at19°S cannot represent the composition of the melt at the moment of their entrapment. (Author)

  9. Chemistry and melting characteristics of fireside deposits taken from boiler tubes in waste incinerators

    International Nuclear Information System (INIS)

    Otsuka, Nobuo

    2011-01-01

    Highlights: → We examine tube deposits taken from boilers of municipal solid waste incinerators. → Literature survey is done on the corrosion mechanism of tube steels. → Chemical analyses, X-ray diffraction, DSC, and corrosion test were conducted. → Melting behavior of salt constituents affected the corrosiveness of the deposits. - Abstract: Twenty-three tube deposits taken from seven heat-recovery boilers of municipal solid waste incinerators were examined by chemical analyses and X-ray diffraction. These deposits were measured by Differential Scanning Calorimeter (DSC) in N 2 to investigate their melting characteristics. Sixteen deposits were used to evaluate their corrosiveness to carbon steel by high-temperature corrosion test conducted at 400 o C for 20 h in 1500 ppm HCl - 300 ppm SO 2 - 7.5%O 2 - 7.5%CO 2 - 20%H 2 O - N 2 . Total heat of endothermic reactions of the deposits taking place between 200 and 400 o C can be related to the corrosion rate of carbon steel at 400 o C. Corrosion initiated at temperatures when the deposits started to melt, became severe when fused salt constituents increased, and alleviated when the majority of the deposits became fused. The corrosion can be interpreted as fused salt corrosion caused by chloride and sulfate salts.

  10. A thermal model for czochralski silicon crystal growth with an axial magnetic field

    Science.gov (United States)

    Hjellming, L. N.

    1990-07-01

    This paper presents a thermal model for molten silicon in a Czochralski crystal puller system with an applied uniform axial magnetic field. The melt depth is treated as continually decreasing, which affects the thermal environment of the melt and crystal. The radiative heat loss and the input heat flux are treated as functions of time, with a constraint placed on the heat lost to the crystal from the melt. As the melt motion reaches a steady state rapidly, the temperature and flow fields are treated as instantaneously steady at each melt depth. The heat transport is a mixture of conduction and convection, and by considering the crystal and crucible to be rotating with the same angular velocity, the flows driven by buoyancy and thermocapillarity are isolated and provide the convective heat transport in the melt for the range of magnetic field strengths 0.2 ≤ B ≤ 1.0T.

  11. The effect of polycrystalline rod insertion in a low Prandtl number melt for continuous Czochralski system

    Science.gov (United States)

    Nam, Phil-Ouk; Son, Seung-Suk; Yi, Kyung-Woo

    2010-04-01

    The increased wafer size results in greater instabilities and complexities within the silicon melt, and melt flow control through the application of magnetic fields is not adequate to stabilize the melt. Therefore, continuous Czochralski systems are being studied as a solution to these issues, with higher productivity and no change in size. The purpose of this study is to observe the effects of polycrystalline rod insertion on the melt for a continuous Czochralski system. In order to observe flow patterns within the melt both broadly and specifically, we employ experimentation on a model system in tandem with numerical simulation. The rod insertion do not significantly affect near the crystal edge. In the melt height from 0.14 to 0.09 m, an asymmetric temperature distributions arise when the crystal rotation is counterclockwise direction (-15 rpm) and the crucible rotation is clockwise direction (3 rpm). The axis-symmetrical temperature distribution is formed at lower melt heights (0.08 and 0.07 m). When the melt height is 0.07 m, the axis-symmetric temperature distribution is maintained even after the rod insertion.

  12. Investigation of the dynamics and threshold behavior of endothermic negative ion-neutral reactions. Annual progress report, July 15, 1980-July 14, 1981

    International Nuclear Information System (INIS)

    Tiernan, T.O.; Wu, R.L.C.

    1981-01-01

    Modifications to a tandem mass spectrometer inlet system and ion source have been accomplished to facilitate introduction of solid organometallic compounds and oxidizing gases, which are potential sources of inorganic oxide molecular ions when these compounds are subjected to electron impact or microwave discharge. Experiments with a variety of organometallic compounds have resulted in successful production of PO - , PO 2 - , and FeO 2 - , which were utilized as projectile ions in studies of collision-induced dissociation and endothermic charge transfer reactions. Energy thresholds measured in the latter experiments yielded the bond dissociation energies, D 0 0 (O - - P) = 5.6 +- 0.1 eV and D 0 0 (O - - PO) = 7.4 +- 0.2 eV, the first direct experimental determinations of these quantities. Used in conjunction with other thermochemical data these results lead to the determination of ΔH 0 /sub f/(PO - ) = -1.0 +- 0.1 eV; ΔH 0 /sub f/(PO 2 - ) = -6.4 +- 0.2 eV; E.A. (PO) = 1.0 +- 0.1 eV; and E.A. (PO 2 ) = 3.3 +- 0.2 eV. From the threshold measured for the endothermic charge transfer reaction of FeO 2 - with NO 2 , 0.77 +- 0.2 eV, the electron affinity of FeO 2 was determined to be 3.1 +- 0.2 eV. Results are discussed

  13. Crystal nucleation in simple and complex fluids.

    Science.gov (United States)

    Oxtoby, David W

    2003-03-15

    The application of density-functional methods from statistical mechanics to the nucleation of crystals from the melt is described. Simple fluids such as metals, with sizes comparable with the range of their attractive forces, are compared with complex fluids such as colloidal suspensions and proteins dissolved in solution. A different mechanism for crystal nucleation is proposed in the latter case, in which density (concentration) changes before periodic crystalline order appears. This leads to a theoretical foundation for empirical observations on the 'crystallization window' in protein crystallization. Comparisons are made with the results of computer simulation via molecular dynamics.

  14. Shear effects on crystallization behaviors and structure transitions of isotactic poly-1-butene

    DEFF Research Database (Denmark)

    Li, Jingqing; Guan, Peipei; Zhang, Yao

    2014-01-01

    Different melt pre-shear conditions were applied to isotactic poly-1-butene (iP-1-B) and the effect on the crystallization behaviors and the crystalline structure transitions of iP-1-B were investigated. The polarized optical microscope observations during isothermal crystallization process...... revealed that the applied melt pre-shear within the experimental range could enhance the nucleation of crystal II and accelerate the diameter growth of the formed spherulites. If the applied melt pre-shear rate was large enough, Shish-Kebabs structure could be formed. After the isothermal crystallization...... was formed in the melt pre-sheared iP-1-B samples. Further investigations were applied with synchrotron radiation instruments. Wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) after the crystal transition showed that the applied melt pre-shear could result in orientated fine...

  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. Melting behavior of SnI4 reexamined

    Science.gov (United States)

    Fuchizaki, Kazuhiro

    2013-12-01

    The low-pressure crystalline phase of a molecular crystal, SnI4, has a rising melting curve that breaks abruptly at around 1.5 GPa, beyond which it becomes almost flat, with a slight maximum at about 3 GPa. Although the overall aspect of this melting curve can be captured by the Kumari-Dass-Kechin equation, the values for the parameters involved in the equation were definitely different from those predicted on the basis of the Clapeyron-Clausius relationship. On the other hand, the accuracy of our experimental data prevented us from judging whether the parameters are derivable from the Lindemann melting law, as shown independently by Kumari and Dass, and by Kechin. The Kraut-Kennedy and Magalinskii-Zubov relationships seem to be valid in the low-pressure region where the melting curve is rising. The breakdown of these relationships suggests a qualitative change in the intermolecular interaction upon compression, thereby making the melting behavior unusual.

  18. Deep and persistent melt layer in the Archaean mantle

    Science.gov (United States)

    Andrault, Denis; Pesce, Giacomo; Manthilake, Geeth; Monteux, Julien; Bolfan-Casanova, Nathalie; Chantel, Julien; Novella, Davide; Guignot, Nicolas; King, Andrew; Itié, Jean-Paul; Hennet, Louis

    2018-02-01

    The transition from the Archaean to the Proterozoic eon ended a period of great instability at the Earth's surface. The origin of this transition could be a change in the dynamic regime of the Earth's interior. Here we use laboratory experiments to investigate the solidus of samples representative of the Archaean upper mantle. Our two complementary in situ measurements of the melting curve reveal a solidus that is 200-250 K lower than previously reported at depths higher than about 100 km. Such a lower solidus temperature makes partial melting today easier than previously thought, particularly in the presence of volatiles (H2O and CO2). A lower solidus could also account for the early high production of melts such as komatiites. For an Archaean mantle that was 200-300 K hotter than today, significant melting is expected at depths from 100-150 km to more than 400 km. Thus, a persistent layer of melt may have existed in the Archaean upper mantle. This shell of molten material may have progressively disappeared because of secular cooling of the mantle. Crystallization would have increased the upper mantle viscosity and could have enhanced mechanical coupling between the lithosphere and the asthenosphere. Such a change might explain the transition from surface dynamics dominated by a stagnant lid on the early Earth to modern-like plate tectonics with deep slab subduction.

  19. Investigation of PEG crystallization in frozen PEG-sucrose-water solutions. I. Characterization of the nonequilibrium behavior during freeze-thawing.

    Science.gov (United States)

    Bhatnagar, Bakul S; Martin, Susan M; Teagarden, Dirk L; Shalaev, Evgenyi Y; Suryanarayanan, Raj

    2010-06-01

    Our objective was to characterize the nonequilibrium thermal behavior of frozen aqueous solutions containing PEG and sucrose. Aqueous solutions of (i) sucrose (10%, w/v) with different concentrations of PEG (1-20%, w/v), and (ii) PEG (10%, w/v) with different concentrations of sucrose (2-20%, w/v), were cooled to -70 degrees C at 5 degrees C/min and heated to 25 degrees C at 2 degrees C/min in a differential scanning calorimeter. Annealing was performed at temperatures ranging from -50 to -20 degrees C for 2 or 6 h. Similar experiments were also performed in the low-temperature stage of a powder X-ray diffractometer. A limited number of additional DSC experiments were performed wherein the samples were cooled to -100 degrees C. In unannealed systems with a fixed sucrose concentration (10%, w/v), the T'g decreased from -35 to -48 degrees C when PEG concentration was increased from 1% to 20% (w/v). On annealing at -25 degrees C, PEG crystallized. This was evident from the increase in T'g and the appearance of a secondary melting endotherm in the DSC. Low-temperature XRD provided direct evidence of PEG crystallization. Annealing at temperatures crystallization and a devitrification event was observed above the T'g. In unannealed systems with a fixed PEG concentration (10%, w/v), the T'g increased from -50 to -40 degrees C when sucrose concentration was increased from 5% to 50%, w/v. As the annealing time increased (at -25 degrees C), the T'g approached that of a sucrose-water system, reflecting progressive PEG crystallization. A second glass transition at approximately -65 degrees C was evident in unannealed systems [10%, w/v sucrose and 10 (or 20%), w/v PEG] cooled to -100 degrees C. Investigation of the nonequilibrium behavior of frozen PEG-sucrose-water ternary system revealed phase separation in the freeze-concentrate. Annealing facilitated PEG crystallization. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association

  20. The effect of melt composition on the partitioning of trace elements between titanite and silicate melt

    Science.gov (United States)

    Prowatke, S.; Klemme, S.

    2003-04-01

    the influence of the crystal lattice on partitioning with the effect of melt composition on trace element partition coefficients. [1] Nakada, S. (1991) Am. Mineral. 76: 548-560 [2] Green, T.H. and Pearson, N.J. (1986) Chem. Geol. 55: 105-119 [3] Tiepolo, M.; Oberti, R. and Vannucci, R. (2002) Chem. Geol. 191: 105-119

  1. A Feasibility Study on UO2/ZrO2 Mixture Melting using Induction Skull Melting Method

    International Nuclear Information System (INIS)

    Hong, S. W.; Kim, J. H.; Kim, H. D.

    1998-01-01

    Using ISM(Induction Skull Melting) method, which is usually used for the crystallization of refractory materials, a feasibility study on melting of the UO 2 /ZrO 2 mixture(w/o 8:2) is carried out. Frequency, one of main design parameters for ISM, is determined from electrical resistance of UO 2 /ZrO 2 mixture. Heat loss from the crucible for UO 2 /ZrO 2 20kg melting is predicted by comparison with the existing experimental data for UO , ZrO 2 , and ThO 2 . The analysis shows that melting and superheating of the UO 2 /ZrO 2 mixture using induction skull melting method is possible. To attain the superheat of 300K for 20 kg of UO 2 /ZrO 2 , 100kHz, 100 kW power input for induction coil, and 570L/min coolant flow rate are found to be required. The results of this feasibility study will be adopted for designing UO 2 /ZrO 2 furnace using actual corium material at KAERI

  2. 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.

  3. Characterization of the melting process of PTFE using positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Honda, Y; Nishijima, S

    2015-01-01

    Poly(tetrafluoroethylene) (PTFE) is a semi-crystalline polymer and the lifetime of ortho-positronium(o-Ps) is known to be able to be separated into two components due to annihilation in the crystal region and in the amorphous region. The melting process of PTFE was investigated using positron annihilation spectroscopy and X-ray diffraction. The results indicated that volume expansion with an increase of temperature is dominantly due to the expansion of the amorphous region and a Ps bubble is formed at melting in both regions. The o-Ps relating to the crystal region definitely remains on the surface of crystal at the time of annihilation. The production of lower energy electrons at melting was deduced by the analysis of the Doppler broadened annihilation photopeak, and the increase in the number of such electrons was found to have great influence on the formation of the o-Ps and annihilation processes of positron and o-Ps. (paper)

  4. 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.

  5. 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)

  6. 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)

  7. 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.

  8. Sulfur concentration at sulfide saturation (SCSS) in magmatic silicate melts

    Science.gov (United States)

    Liu, Yanan; Samaha, Naji-Tom; Baker, Don R.

    2007-04-01

    The sulfur concentration in silicate melts at sulfide saturation (SCSS) was experimentally investigated in a temperature range from 1150 to 1450 °C and a pressure range from 500 MPa to 1 GPa in a piston-cylinder apparatus. The investigated melt compositions varied from rhyolitic to basaltic and water concentrations varied from 0 to ˜9 wt%. All experiments were saturated with FeS melt or pyrrhotite crystals. Temperature was confirmed to have a positive effect on the SCSS. Experimental oxygen fugacities were either near the carbon-carbon monoxide buffer or one log unit above the nickel-nickel oxide buffer, and found to positively affect the SCSS. Combining our results with data from the literature we constructed a model to predict the SCSS in melts ranging in composition from komatiitic to rhyolitic, with water concentrations from 0 to 9 wt%, at pressures from 1 bar to 9 GPa and oxygen fugacities between ˜2 log units below the fayalite-magnetite-quartz buffer to ˜2 log units above it. The coefficients were obtained by multiple linear regression of experimental data and the best model found for the prediction of the SCSS is: ln(Sinppm)=11.35251-{4454.6}/{T}-0.03190{P}/{T}+0.71006ln(MFM)-1.98063[(MFM)(XO)]+0.21867ln(XO)+0.36192lnX where P is in bar, T is in K, MFM is a compositional parameter describing the melt based upon cation mole fractions: MFM={Na+K+2(Ca+Mg+Fe)}/{Si×(Al+Fe)}, XO is the mole fraction of water in the melt, and X is the mole fraction of FeO in the melt. This model was independently tested against experiments performed on anhydrous and hydrous melts in the temperature range from 800 to 1800 °C and 1-9 GPa. The model typically predicts the measured values of the natural log of the SCSS (in ppm) for komatiitic to rhyolitic (˜42 to ˜74 wt% SiO 2) melts to within 5% relative, but is less accurate for high-silica (>76 wt% SiO 2) rhyolites, especially those with molar ratios of iron to sulfur below 2. We demonstrate how this model can be used with

  9. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion....... As representative examples, a metal (Pt), an alloy (PtSn), and a metal carbide (beta-Mo2C) were supported on conventional and mesoporous zeolite carriers, respectively, and the degree of particle dispersion was compared by TEM imaging. On conventional zeolites, the supported material aggregated on the outer surface...

  10. MELTS_Excel: A Microsoft Excel-based MELTS interface for research and teaching of magma properties and evolution

    Science.gov (United States)

    Gualda, Guilherme A. R.; Ghiorso, Mark S.

    2015-01-01

    thermodynamic modeling software MELTS is a powerful tool for investigating crystallization and melting in natural magmatic systems. Rhyolite-MELTS is a recalibration of MELTS that better captures the evolution of silicic magmas in the upper crust. The current interface of rhyolite-MELTS, while flexible, can be somewhat cumbersome for the novice. We present a new interface that uses web services consumed by a VBA backend in Microsoft Excel©. The interface is contained within a macro-enabled workbook, where the user can insert the model input information and initiate computations that are executed on a central server at OFM Research. Results of simple calculations are shown immediately within the interface itself. It is also possible to combine a sequence of calculations into an evolutionary path; the user can input starting and ending temperatures and pressures, temperature and pressure steps, and the prevailing oxidation conditions. The program shows partial updates at every step of the computations; at the conclusion of the calculations, a series of data sheets and diagrams are created in a separate workbook, which can be saved independently of the interface. Additionally, the user can specify a grid of temperatures and pressures and calculate a phase diagram showing the conditions at which different phases are present. The interface can be used to apply the rhyolite-MELTS geobarometer. We demonstrate applications of the interface using an example early-erupted Bishop Tuff composition. The interface is simple to use and flexible, but it requires an internet connection. The interface is distributed for free from http://melts.ofm-research.org.

  11. Virtual Crystallizer

    Energy Technology Data Exchange (ETDEWEB)

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  12. single crystals

    Indian Academy of Sciences (India)

    2018-05-18

    May 18, 2018 ... Abstract. 4-Nitrobenzoic acid (4-NBA) single crystals were studied for their linear and nonlinear optical ... studies on the proper growth, linear and nonlinear optical ..... between the optic axes and optic sign of the biaxial crystal.

  13. Crystal Systems.

    Science.gov (United States)

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  14. 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.

  15. Simulation of viscous melt drop crystallization by the SPH method

    Directory of Open Access Journals (Sweden)

    Gerasimov Alexander V.

    2017-01-01

    Full Text Available Heat and mass transfer during absorption on a film of lithium bromide water solution flowing by a cooled wall in the steam atmosphere is numerically investigated in this paper. The self-similar solutions are using as the initial conditions for solving the problem beyond the entrance region. The key criteria characterizing heat and mass transfer in the film absorption with uniform velocity profile and with a constant thickness have been determined.

  16. 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

  17. 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

  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. Controlled localised melting in silicon by high dose germanium implantation and flash lamp annealing

    International Nuclear Information System (INIS)

    Voelskow, Matthias; Skorupa, Wolfgang; Pezoldt, Joerg; Kups, Thomas

    2009-01-01

    High intensity light pulse irradiation of monocrystalline silicon wafers is usually accompanied by inhomogeneous surface melting. The aim of the present work is to induce homogeneous buried melting in silicon by germanium implantation and subsequent flash lamp annealing. For this purpose high dose, high energy germanium implantation has been employed to lower the melting temperature of silicon in a predetermined depth region. Subsequent flash lamp irradiation at high energy densities leads to local melting of the germanium rich buried layer, whereby the thickness of the molten layer depends on the irradiation energy density. During the cooling down epitaxial crystallization takes place resulting in a largely defect-free layer. The combination of buried melting and dopant segregation has the potential to produce unusually buried doping profiles or to create strained silicon structures.

  20. 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

  1. Cooperative ring exchange and quantum melting of vortex lattices in atomic Bose-Einstein condensates

    International Nuclear Information System (INIS)

    Ghosh, Tarun Kanti; Baskaran, G.

    2004-01-01

    Cooperative ring exchange is suggested as a mechanism of quantum melting of vortex lattices in a rapidly rotating quasi-two-dimensional atomic Bose-Einstein condensate (BEC). Using an approach pioneered by Kivelson et al. [Phys. Rev. Lett. 56, 873 (1986)] for the fractional quantized Hall effect, we calculate the condition for quantum melting instability by considering large-correlated ring exchanges in a two-dimensional Wigner crystal of vortices in a strong 'pseudomagnetic field' generated by the background superfluid Bose particles. BEC may be profitably used to address issues of quantum melting of a pristine Wigner solid devoid of complications of real solids

  2. Buried melting in germanium implanted silicon by millisecond flash lamp annealing

    International Nuclear Information System (INIS)

    Voelskow, Matthias; Yankov, Rossen; Skorupa, Wolfgang; Pezoldt, Joerg; Kups, Thomas

    2008-01-01

    Flash lamp annealing in the millisecond range has been used to induce buried melting in silicon. For this purpose high dose high-energy germanium implantation has been employed to lower the melting temperature of silicon in a predetermined depth region. Subsequent flash lamp treatment at high energy densities leads to local melting of the germanium rich layer. The thickness of the molten layer has been found to depend on the irradiation energy density. During the cool-down period, epitaxial crystallization takes place resulting in a largely defect-free layer

  3. Pulsed melting of silicon (111) and (100) surfaces simulated by molecular dynamics

    International Nuclear Information System (INIS)

    Abraham, F.F.; Broughton, J.Q.

    1986-01-01

    The pulsed heating of Si (100) and (111) surfaces has been simulated by molecular dynamics. The (111) crystal-melt interface propagates by layer-by-layer growth whereas the (100) interface grows in a continuous fashion. The equilibrium crystal-melt interface is sharp for the (111) orientation and broad for the (100) orientation. These simulations are the first use of nonpairwise potentials to study interfaces between condensed phases, and the results support models of interfaces which heretofore had to be deduced from indirect experimental information

  4. Melting of the moving vortex lattice in the presence of disorder

    International Nuclear Information System (INIS)

    Koshelev, A.E.; Vinokur, V.M.

    1994-07-01

    The authors investigate the melting of the two-dimensional vortex lattice moving in an inhomogeneous environment under the applied current j. They predict the existence of a dynamic phase transition at some current j = j t (crystallization current) from the motion of the amorphous configuration at j t to the motion of the crystal at j > j t . j t exceeds essentially the critical current j c for strongly disordered systems and approaches j c with the decrease of the degree of disorder. They find that j t diverges as temperature approaches the melting temperature of the undisturbed lattice

  5. 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

  6. Hypermetabolic Conversion of Plant Oil into Water: Endothermic Biochemical Process Stimulated by Juvenile Hormone in the European Firebug, Pyrrhocoris apterus L.

    Science.gov (United States)

    Sláma, Karel; Lukáš, Jan

    2016-01-01

    The physiological and biochemical mechanisms that enable insects to feed on dry food to secure enough water for larval growth were investigated. The study was carried out with a plethora of physiological methods, ranging from the simple volumetric determination of O 2 consumption and water intake to more advanced methods such as scanning microrespirography and thermovision imaging of insect's body temperature. The experiments were done on the European firebug, Pyrrhocoris apterus , which feeds exclusively on dry linden seeds. In order to survive, it needs to drink water or suck a sap from plants occasionally. It was found that the young larval instars compensate the occasional water deficiency by the increased production of metabolic water. The juvenile hormone (JH)-dependent production of metabolic water, which was previously found in other species consuming dry food, was achieved in P. apterus by total metabolic combustion of the dietary lipid (neutral seed oil). The water-producing, hypermetabolic larvae were heated from inside by endothermic energy released from the uncoupling of oxidation from oxidative phosphorylation. The "warm", hypermetabolic larvae burning the dietary oil into CO 2 and water showed the increased rates of respiratory metabolism. Microrespirographic recording of these larvae revealed the ratio of the respiratory quotient (RQ, CO 2 /O 2 ) of 0.7, which indicated the breakdown of a pure triglyceride. The warm hypermetabolic larvae could be easily spotted and distinguished from the "cold" larvae on the screen of a thermovision camera. The last instar larvae lacking the JH were always only cold. They metabolized a carbohydrate substrate exclusively (RQ = 1.0), while the dietary lipid was stored in the fat body. In comparison with the hypermetabolic larvae of some other species fed on dry food, which exhibited the highest rates of O 2 consumption ever recorded in a living organism (10-20 mL O 2 /g per hour), the metabolic difference between the

  7. Monomial Crystals and Partition Crystals

    Science.gov (United States)

    Tingley, Peter

    2010-04-01

    Recently Fayers introduced a large family of combinatorial realizations of the fundamental crystal B(Λ0) for ^sln, where the vertices are indexed by certain partitions. He showed that special cases of this construction agree with the Misra-Miwa realization and with Berg's ladder crystal. Here we show that another special case is naturally isomorphic to a realization using Nakajima's monomial crystal.

  8. High porosity harzburgite and dunite channels for the transport of compositionally heterogeneous melts in the mantle: II. Geochemical consequences

    Science.gov (United States)

    Liang, Y.; Schiemenz, A.; Xia, Y.; Parmentier, E.

    2009-12-01

    channel drives part of the channel melt in the upper part of the dunite channel into the surrounding harzburgite, providing a physical mechanism for shallow level re-fertilization or mantle metasomatism. The presence of compacting waves in and around a dunite-harzburgite channel system further complicates the melt flow field and provides new mechanisms for melt-peridotite interaction in the mantle. In the presence of chemical heterogeneity, the assumption of local equilibrium between the melt and its surrounding crystals results in significant chromatographic fractionation for incompatible trace elements in the melt percolating in region (d), and moderate fractionation for melt flowing through the harzburgite channel. Chemical disequilibrium between the melt and crystals reduces the extent of chromatographic fractionation during melt percolation and may be needed to explain the observed geochemical data. Alternatively, compositionally heterogeneous melts may be extracted through the high porosity melt channels without interaction with the peridotite matrix. [1] Schiemenz et al. submitted to AGU Fall meeting, 2009.

  9. 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.

  10. Characteristics of bulk liquid undercooling and crystallization ...

    Indian Academy of Sciences (India)

    Characteristics of bulk liquid undercooling and crystallization behaviors ... cooling rate is fixed, the change of undercooling depends on the melt processing tem- ... solidification and a deep knowledge of undercooling of ... evolution, to obtain the information for the nucleation and ..... When cooling rate is fixed, the change.

  11. Meniscus Imaging for Crystal-Growth Control

    Science.gov (United States)

    Sachs, E. M.

    1983-01-01

    Silicon crystal growth monitored by new video system reduces operator stress and improves conditions for observation and control of growing process. System optics produce greater magnification vertically than horizontally, so entire meniscus and melt is viewed with high resolution in both width and height dimensions.

  12. 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

  13. Czochralski growth of gallium indium antimonide alloy crystals

    Energy Technology Data Exchange (ETDEWEB)

    Tsaur, S.C.

    1998-02-01

    Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub 1{minus}x}Sb{sub x}. Single crystals of Ga{sub 1{minus}x}In{sub x}Sb were grown with uniform

  14. Deep Crustal Melting and the Survival of Continental Crust

    Science.gov (United States)

    Whitney, D.; Teyssier, C. P.; Rey, P. F.; Korchinski, M.

    2017-12-01

    Plate convergence involving continental lithosphere leads to crustal melting, which ultimately stabilizes the crust because it drives rapid upward flow of hot deep crust, followed by rapid cooling at shallow levels. Collision drives partial melting during crustal thickening (at 40-75 km) and/or continental subduction (at 75-100 km). These depths are not typically exceeded by crustal rocks that are exhumed in each setting because partial melting significantly decreases viscosity, facilitating upward flow of deep crust. Results from numerical models and nature indicate that deep crust moves laterally and then vertically, crystallizing at depths as shallow as 2 km. Deep crust flows en masse, without significant segregation of melt into magmatic bodies, over 10s of kms of vertical transport. This is a major mechanism by which deep crust is exhumed and is therefore a significant process of heat and mass transfer in continental evolution. The result of vertical flow of deep, partially molten crust is a migmatite dome. When lithosphere is under extension or transtension, the deep crust is solicited by faulting of the brittle upper crust, and the flow of deep crust in migmatite domes traverses nearly the entire thickness of orogenic crust in Recognition of the importance of migmatite (gneiss) domes as archives of orogenic deep crust is applicable to determining the chemical and physical properties of continental crust, as well as mechanisms and timescales of crustal differentiation.

  15. RNA Crystallization

    Science.gov (United States)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  16. 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

  17. Crystallization mechanisms of acicular crystals

    Science.gov (United States)

    Puel, François; Verdurand, Elodie; Taulelle, Pascal; Bebon, Christine; Colson, Didier; Klein, Jean-Paul; Veesler, Stéphane

    2008-01-01

    In this contribution, we present an experimental investigation of the growth of four different organic molecules produced at industrial scale with a view to understand the crystallization mechanism of acicular or needle-like crystals. For all organic crystals studied in this article, layer-by-layer growth of the lateral faces is very slow and clear, as soon as the supersaturation is high enough, there is competition between growth and surface-activated secondary nucleation. This gives rise to pseudo-twinned crystals composed of several needle individuals aligned along a crystallographic axis; this is explained by regular over- and inter-growths as in the case of twinning. And when supersaturation is even higher, nucleation is fast and random. In an industrial continuous crystallization, the rapid growth of needle-like crystals is to be avoided as it leads to fragile crystals or needles, which can be partly broken or totally detached from the parent crystals especially along structural anisotropic axis corresponding to weaker chemical bonds, thus leading to slower growing faces. When an activated mechanism is involved such as a secondary surface nucleation, it is no longer possible to obtain a steady state. Therefore, the crystal number, size and habit vary significantly with time, leading to troubles in the downstream processing operations and to modifications of the final solid-specific properties. These results provide valuable information on the unique crystallization mechanisms of acicular crystals, and show that it is important to know these threshold and critical values when running a crystallizer in order to obtain easy-to-handle crystals.

  18. Crystal growth under external electric fields

    International Nuclear Information System (INIS)

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo

    2014-01-01

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal

  19. Crystal growth under external electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)

    2014-10-06

    This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.

  20. Quantum Hooke's Law to Classify Pulse Laser Induced Ultrafast Melting

    Science.gov (United States)

    Hu, Hao; Ding, Hepeng; Liu, Feng

    2015-02-01

    Ultrafast crystal-to-liquid phase transition induced by femtosecond pulse laser excitation is an interesting material's behavior manifesting the complexity of light-matter interaction. There exist two types of such phase transitions: one occurs at a time scale shorter than a picosecond via a nonthermal process mediated by electron-hole plasma formation; the other at a longer time scale via a thermal melting process mediated by electron-phonon interaction. However, it remains unclear what material would undergo which process and why? Here, by exploiting the property of quantum electronic stress (QES) governed by quantum Hooke's law, we classify the transitions by two distinct classes of materials: the faster nonthermal process can only occur in materials like ice having an anomalous phase diagram characterized with dTm/dP < 0, where Tm is the melting temperature and P is pressure, above a high threshold laser fluence; while the slower thermal process may occur in all materials. Especially, the nonthermal transition is shown to be induced by the QES, acting like a negative internal pressure, which drives the crystal into a ``super pressing'' state to spontaneously transform into a higher-density liquid phase. Our findings significantly advance fundamental understanding of ultrafast crystal-to-liquid phase transitions, enabling quantitative a priori predictions.

  1. Physical properties of some Sn-based melts

    Directory of Open Access Journals (Sweden)

    Ilinykh N.

    2011-05-01

    Full Text Available The physical properties (viscosity, density, electroresistivity and magnetic susceptibility of pure tin, copper, silver, some binary (Sn - Ag, Sn - Cu, Sn - Bi, Sn - Zn and ternary (Sn-Ag-Cu, Sn-BiAg, Sn-Bi-Zn alloys with near eutectic compositions are investigated in wide temperature ranges. The irreversible decrease of viscosity in pure tin melt is discovered at 820 °С during heating. The similar anomaly with the following hysteresis of dynamic viscosity was fixed for binary and ternary alloys but at higher temperatures – 900 °С and 950 °С respectively. For all the systems it was shown that the alloys with eutectic compositions differ significantly in their electric and magnetic properties from hypo- and hypereutectic ones. Qualitative and quantitative metallographic analysis for Sn-3.8wt.%Ag-0.7wt.%Cu samples, heated low and above characteristic temperatures, showed the influence of melt overheating on crystallization kinetics.

  2. AsS melt under pressure: one substance, three liquids.

    Science.gov (United States)

    Brazhkin, V V; Katayama, Y; Kondrin, M V; Hattori, T; Lyapin, A G; Saitoh, H

    2008-04-11

    An in situ high-temperature--high-pressure study of liquid chalcogenide AsS by x-ray diffraction, resistivity measurements, and quenching from melt is presented. The obtained data provide direct evidence for the existence in the melt under compression of two transformations: one is from a moderate-viscosity molecular liquid to a high-viscosity nonmetallic polymerized liquid at P approximately 1.6-2.2 GPa; the other is from the latter to a low-viscosity metallic liquid at P approximately 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.

  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. 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...

  5. Heterogeneously Catalyzed Endothermic Fuel Cracking

    Science.gov (United States)

    2016-08-28

    reactor was circumferentially delivered from a 4.2 kW array consisting of 4 independently PID controlled fiber insulated heaters (Zircar ceramics, FIH...the H-ZSM- 5 lattice and Brønsted acid site characteristics” Micropor . Mesopor. Mater., 222 (2016) 256−270. DISTRIBUTION A: Distribution...distribution on the H-ZSM-5 lattice and Brønsted acid site characteristics" Micropor . Mesopor. Mater., 222 (2016) 256-270. S. M. Opalka, H. Huang

  6. Unique Crystal Orientation of Poly(ethylene oxide) Thin Films by Crystallization Using a Thermal Gradient

    DEFF Research Database (Denmark)

    Gbabode, Gabin; Delvaux, Maxime; Schweicher, Guillaume

    2017-01-01

    Poly(ethylene oxide), (PEO), thin films of different thicknesses (220, 450, and 1500 nm) and molecular masses (4000, 8000, and 20000 g/mol) have been fabricated by spin-coating of methanol solutions onto glass substrates. All these samples have been recrystallized from the melt using a directional......, to significantly decrease the distribution of crystal orientation obtained after crystallization using the thermal gradient technique....

  7. Silicon Crystal Growth by the Electromagnetic Czochralski (EMCZ) Method

    Science.gov (United States)

    Watanabe, Masahito; Eguchi, Minoru; Hibiya, Taketoshi

    1999-01-01

    A new method for growing silicon crystals by using electromagnetic force to rotate the melt without crucible rotation has been developed. We call it electromagnetic Czochralski (EMCZ) growth. An electromagnetic force in the azimuthal direction is generated in the melt by the interaction between an electric current (I) through the melt in the radial direction and a vertical magnetic field (B). The rotation rate (ωm) of the silicon melt is continuously changed from 0 to over 105 rpm under I = 0 to 8 A and B = 0 to 0.1 T. Thirty-mm-diameter silicon single crystals free of dislocations could be grown under two conditions: I = 2.0 A and B = 0.05 T (ωm = 105 rpm); and I =0.2 A and B = 0.1 T (ωm = 15 rpm). The oxygen concentration in the crystals was 8 ×1017 atoms/cm3 for the high rotation rate and 1×1017 atoms/cm3 for the low rotation rate. The oxygen-concentration distributions in the radial direction in both crystals were more homogeneous than those in the crystals grown by conventional CZ and/or MCZ growth. This new crystal-growth method can be easily adopted for growing large-diameter silicon crystals.

  8. Composition and origin of rhyolite melt intersected by drilling in the Krafla geothermal field, Iceland

    Science.gov (United States)

    Zierenberg, R.A.; Schiffman, P.; Barfod, G.H.; Lesher, C.E.; Marks, N.E.; Lowenstern, Jacob B.; Mortensen, A.K.; Pope, E.C.; Bird, D.K.; Reed, M.H.; Friðleifsson, G.O.; Elders, W.A.

    2013-01-01

    The Iceland Deep Drilling Project Well 1 was designed as a 4- to 5-km-deep exploration well with the goal of intercepting supercritical hydrothermal fluids in the Krafla geothermal field, Iceland. The well unexpectedly drilled into a high-silica (76.5 % SiO2) rhyolite melt at approximately 2.1 km. Some of the melt vesiculated while extruding into the drill hole, but most of the recovered cuttings are quenched sparsely phyric, vesicle-poor glass. The phenocryst assemblage is comprised of titanomagnetite, plagioclase, augite, and pigeonite. Compositional zoning in plagioclase and exsolution lamellae in augite and pigeonite record changing crystallization conditions as the melt migrated to its present depth of emplacement. The in situ temperature of the melt is estimated to be between 850 and 920 °C based on two-pyroxene geothermometry and modeling of the crystallization sequence. Volatile content of the glass indicated partial degassing at an in situ pressure that is above hydrostatic (~16 MPa) and below lithostatic (~55 MPa). The major element and minor element composition of the melt are consistent with an origin by partial melting of hydrothermally altered basaltic crust at depth, similar to rhyolite erupted within the Krafla Caldera. Chondrite-normalized REE concentrations show strong light REE enrichment and relative flat patterns with negative Eu anomaly. Strontium isotope values (0.70328) are consistent with mantle-derived melt, but oxygen and hydrogen isotope values are depleted (3.1 and −118 ‰, respectively) relative to mantle values. The hydrogen isotope values overlap those of hydrothermal epidote from rocks altered by the meteoric-water-recharged Krafla geothermal system. The rhyolite melt was emplaced into and has reacted with a felsic intrusive suite that has nearly identical composition. The felsite is composed of quartz, alkali feldspar, plagioclase, titanomagnetite, and augite. Emplacement of the rhyolite magma has resulted in partial melting of

  9. Thermal-capillary analysis of Czochralski and liquid encapsulated Czochralski crystal growth. II - Processing strategies

    Science.gov (United States)

    Derby, J. J.; Brown, R. A.

    1986-01-01

    The pseudosteady-state heat transfer model developed in a previous paper is augmented with constraints for constant crystal radius and melt/solid interface deflection. Combinations of growth rate, and crucible and bottom-heater temperatures are tested as processing parameters for satisfying the constrained thermal-capillary problem over a range of melt volumes corresponding to the sequence occuring during the batchwise Czochralski growth of a small-diameter silicon crystal. The applicability of each processing strategy is judged by the range of existence of the solution, in terms of melt volume and the values of the axial and radial temperature gradients in the crystal.

  10. The melt inclusion record from the rhyolitic Kos Plateau Tuff (Aegean Arc)

    Science.gov (United States)

    Bachmann, Olivier; Wallace, Paul J.; Bourquin, Julie

    2010-02-01

    The >60 km3 rhyolitic Kos Plateau Tuff provides an exceptional probe into the behavior of volatile components in highly evolved arc magmas: it is crystal-rich (30-40 vol% crystals), was rapidly quenched by the explosive eruptive process, and contains abundant homogeneous melt inclusions in large quartz crystals. Several methods for measuring major, trace and volatile element concentrations (SIMS, FTIR, Raman spectroscopy, electron microprobe, LA-ICPMS) were applied to these melt inclusions. We found a ~2 wt% range of H2O contents (4.5-6.5 wt% H2O, measured independently by SIMS, FTIR, and Raman spectroscopy) and relatively low CO2 concentrations (15-140 ppm measured by FTIR, with most analyses <100 ppm). No obvious correlations between H2O, CO2, major and trace elements are observed. These observations require a complex, protracted magma evolution in the upper crust that included: (1) vapor-saturated crystallization in a chamber located between 1.5 and 2.5 kb pressure, (2) closed-system degassing (with up to 10 vol% exsolved gas) as melts percolated upwards through a vertically extensive mush zone (2-4 km thick), and (3) periodic gas fluxing from subjacent, more mafic and more CO2-rich magma, which is preserved as andesite bands in pumices. These processes can account for the range of observed H2O and CO2 values and the lack of correlation between volatiles and trace elements in the melt inclusions.

  11. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    ). The change of melt viscosity induced by crystallization of a NVP composition was measured in the temperature ranges from 1463 to 1229 °C. Results showed an increase in effective viscosity from 4.3 Pa s to 1090 Pa s as the crystal content increased from 0 vol% to ca. 25 vol.%. The crystallization processes in the nominally dry NVP began at 1308 °C. Interestingly, melts viscosity changes from 4 to 16 Pa s as temperature varies from 1463 to 1327 °C. The extreme Mercurian lava fluidity experimentally measured has revealed the potentiality of NVP lavas to cover huge areas as shown by satellite data. Keywords: Viscosity, Concentric cylinders, NVP, Mercury.

  12. Thermodynamic analysis of ANS binding to partially unfolded α-lactalbumin: correlation of endothermic to exothermic changeover with formation of authentic molten globules.

    Science.gov (United States)

    Kim, Ki Hyung; Yun, Soi; Mok, K H; Lee, E K

    2016-09-01

    A fluorescent reporter, 8-anilino-1-naphthalene sulfonic acid (ANS), can serve as a reference molecule for conformational transition of a protein because its aromatic carbons have strong affinity with hydrophobic cores of partially unfolded molten globules. Using a typical calcium-binding protein, bovine α-lactalbumin (BLA), as a model protein, we compared the ANS binding thermodynamics to the decalcified (10 mM EDTA treated) apo-BLA at two representative temperatures: 20 and 40 °C. This is because the authentic molten globule is known to form more heavily at an elevated temperature such as 40 °C. Isothermal titration calorimetry experiments revealed that the BLA-ANS interactions at both temperatures were entropy-driven, and the dissociation constants were similar on the order of 10(-4)  M, but there was a dramatic changeover in the binding thermodynamics from endothermic at 20 °C to exothermic at 40 °C. We believe that the higher subpopulation of authentic molten globules at 40 °C than 20 °C would be responsible for the results, which also indicate that weak binding is sufficient to alter the ANS binding mechanisms. We expect that the thermodynamic properties obtained from this study would serve as a useful reference for investigating the binding of other hydrophobic ligands such as oleic acid to apo-BLA, because oleic acid is known to have tumor-selective cytotoxicity when complexed with partially unfolded α-lactalbumin. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  13. A theoretical study on the use of microwaves in reducing energy consumption for an endothermic reaction: Role of metal coated bounding surface

    International Nuclear Information System (INIS)

    Bhattacharya, Madhuchhanda; Basak, Tanmay

    2013-01-01

    This work presents a theoretical analysis on savings of energy during an endothermic reaction under microwave heating compared to conventional heating and shows the use of metal coated bounding surface to enhance the energy savings in otherwise low saving zones. Main thrust of this work is the quantification of energy savings for various probable microwave heating scenarios that may arise either due to varying reactor dimension (2L) over thin, intermediate and thick regimes or due to varying dielectric properties of the reactor. The analysis considers detailed transport equations in conjunction with Helmholtz equation for microwave propagation within a semiinfinite batch reactor. Simulations show that use of microwave can significantly save energy (as high as 60%) depending on reactor configuration. Simulations also show efficient use of metal coated bounding surface to enhance energy savings for reactors with 2L/λ eff = 0.5n−0.25, where n = 1, 2, 3… and λ eff is wavelength of microwave within the reactor. The enhancement is found to be 2 and 1.5 times at 2L/λ eff = 0.25 and 0.75, respectively. Various regions of efficient use of metal coated bounding surface for different microwave heating scenarios have been identified in a series of master curves. - Highlights: • This work simulates chemical reaction under microwave radiation using detailed model. • Simulations are presented in presence or absence of metal coated bounding surface. • Savings of energy under microwave have been analyzed for various probable scenarios. • Simulations show significant savings of energy under microwave heating. • Simulations show the potential of metal coated bounding surface to further enhance energy savings

  14. An endothermic chemical process facility coupled to a high temperature reactor. Part II: Transient simulation of accident scenarios within the chemical plant

    International Nuclear Information System (INIS)

    Brown, Nicholas R.; Revankar, Shripad T.

    2012-01-01

    Highlights: ► Seven quantitative transient case studies were analyzed in a coupled PBMR and thermochemical sulfur cycle based hydrogen plant. ► Positive power excursion in the nuclear reactor were found for helium-inlet overcoolings. ► In all cases studied the maximum fuel temperatures in the nuclear reactor were 200 K below the design basis limit. - Abstract: Hydrogen generation using a high temperature nuclear reactor as a thermal driving vector is a promising future option for energy carrier production. In this scheme, the heat from the nuclear reactor drives an endothermic water-splitting plant, via coupling, through an intermediate heat exchanger. Transient study of the operational or accident events within the coupled plant is largely absent from the literature. In this paper, seven quantitative transient case studies are analyzed. The case studies consist of: (1) feed flow failure from one section of the chemical plant to another with an accompanying parametric study of the temperature in an individual reaction chamber, (2) product flow failure (recycle) within the chemical plant, (3) rupture or explosion within the chemical plant, (4) nuclear reactor helium inlet overcooling due to a process holding tank failure, (5) helium inlet overcooling as an anticipated transient without emergency nuclear reactor shutdown, (6) total failure of the chemical plant, (7) control rod insertion in the nuclear reactor. Various parametric studies based on the magnitude of the events were also performed. The only chemical plant initiated events that caused a positive power excursion in the nuclear reactor were helium-inlet overcoolings due to process holding tank failures or reaction chamber ruptures. Even for a severe sustained overcooling, the calculated maximum fuel temperatures in the nuclear reactor were 200 K below the design basis limit. The qualitative basis for the case studies and the analysis models are summarized in part I of this paper.

  15. A Cost-effectiveness Analysis of Surgery, Endothermal Ablation, Ultrasound-guided Foam Sclerotherapy and Compression Stockings for Symptomatic Varicose Veins.

    Science.gov (United States)

    Marsden, G; Perry, M; Bradbury, A; Hickey, N; Kelley, K; Trender, H; Wonderling, D; Davies, A H

    2015-12-01

    The aim was to investigate the cost-effectiveness of interventional treatment for varicose veins (VV) in the UK NHS, and to inform the national clinical guideline on VV, published by the National Institute of Health and Care Excellence. An economic analysis was constructed to compare the cost-effectiveness of surgery, endothermal ablation (ETA), ultrasound-guided foam sclerotherapy (UGFS), and compression stockings (CS). The analysis was based on a Markov decision model, which was developed in consultation with members of the NICE guideline development group (GDG). The model had a 5-year time horizon, and took the perspective of the UK National Health Service. Clinical inputs were based on a network meta-analysis (NMA), informed by a systematic review of the clinical literature. Outcomes were expressed as costs and quality-adjusted life years (QALYs). All interventional treatments were found to be cost-effective compared with CS at a cost-effectiveness threshold of £20,000 per QALY gained. ETA was found to be the most cost-effective strategy overall, with an incremental cost-effectiveness ratio of £3,161 per QALY gained compared with UGFS. Surgery and CS were dominated by ETA. Interventional treatment for VV is cost-effective in the UK NHS. Specifically, based on current data, ETA is the most cost-effective treatment in people for whom it is suitable. The results of this research were used to inform recommendations within the NICE guideline on VV. Copyright © 2015 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  16. Magnetostriction of Tb-Dy-Fe crystals

    International Nuclear Information System (INIS)

    Mei Wu; Okane, T.; Umeda, T.

    1998-01-01

    left angle 111 right angle -oriented twin free Tb-Dy-Fe single crystals, left angle 112 right angle - and left angle 110 right angle -oriented twinned ''single'' Tb-Dy-Fe crystals were prepared using floating zone melting crystal growth methods. Magnetostrictive performances of the crystals were investigated. Better low-field properties were observed in the left angle 110 right angle twinned crystals than in the left angle 112 right angle crystals. The highest properties were achieved in the left angle 111 right angle twin free single crystals. Even though there were still oxidized particles in the present left angle 111 right angle single crystals, a large magnetostrictive jump of 1700 ppm and a very low saturation magnetic field of 500 Oe were obtained. To understand magnetization and magnetostriction of different Tb-Dy-Fe crystals, theoretical modeling was carried out based on a simplified domain rotation model. Magnetization moment rotation paths of different domains were simulated and hence the resultant magnetostriction was obtained, which could adequately account for the experimental results of different crystals. The limitation of the domain rotation model was also discussed. (orig.)

  17. Melt density and the average composition of basalt

    Science.gov (United States)

    Stolper, E.; Walker, D.

    1980-01-01

    Densities of residual liquids produced by low pressure fractionation of olivine-rich melts pass through a minimum when pyroxene and plagioclase joint the crystallization sequence. The observation that erupted basalt compositions cluster around the degree of fractionation from picritic liquids corresponding to the density minimum in the liquid line of descent may thus suggest that the earth's crust imposes a density fiber on the liquids that pass through it, favoring the eruption of the light liquids at the density minimum over the eruption of denser more fractionated and less fractionated liquids.

  18. 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.

  19. Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

    Science.gov (United States)

    Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

    2006-09-01

    Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

  20. Basalt generation at the Apollo 12 site. Part 2: Source heterogeneity, multiple melts, and crustal contamination

    Science.gov (United States)

    Neal, Clive R.; Hacker, Matthew D.; Snyder, Gregory A.; Taylor, Lawrence A.; Liu, Yun-Gang; Schmitt, Roman A.

    1994-01-01

    The petrogenesis of Apollo 12 mare basalts has been examined with emphasis on trace-element ratios and abundances. Vitrophyric basalts were used as parental compositions for the modeling, and proportions of fractionating phases were determined using the MAGFOX prograqm of Longhi (1991). Crystal fractionation processes within crustal and sub-crustal magma chambers are evaluated as a function of pressure. Knowledge of the fractionating phases allows trace-element variations to be considered as either source related or as a product of post-magma-generation processes. For the ilmenite and olivine basalts, trace-element variations are inherited from the source, but the pigeonite basalt data have been interpreted with open-system evolution processes through crustal assimilation. Three groups of basalts have been examined: (1) Pigeonite basalts-produced by the assimilation of lunar crustal material by a parental melt (up to 3% assimilation and 10% crystal fractionation, with an 'r' value of 0.3). (2) Ilmenite basalts-produced by variable degrees of partial melting (4-8%) of a source of olivine, pigeonite, augite, and plagioclase, brought together by overturn of the Lunar Magma Ocean (LMO) cumulate pile. After generation, which did not exhaust any of the minerals in the source, these melts experienced closed-system crystal fractionation/accumulation. (3) Olivine basalts-produced by variable degrees of partial melting (5-10%) of a source of olivine, pigeonite, and augite. After generation, again without exhausting any of the minerals in the source, these melts evolved through crystal accumulation. The evolved liquid counterparts of these cumulates have not been sampled. The source compositions for the ilmenite and olivine basalts were calculated by assuming that the vitrophyric compositions were primary and the magmas were produced by non-modal batch melting. Although the magnitude is unclear, evaluation of these source regions indicates that both be composed of early- and

  1. Crystallization Mechanism and Kinetics of BaO-Li2O-ZrO2-SiO2 Glasses

    Directory of Open Access Journals (Sweden)

    Cristian Berto da Silveira

    2002-03-01

    Full Text Available Differential thermal analysis and scanning electron microscopy were used to determine the influence of the addition of BaO on the crystallization mechanism of Li2O-ZrO2-SiO2 systems. As the concentration of BaO in the samples increased, a transition occurred in the predominant crystallization mechanism, which passed from superficial to volumetric. To determine the maximum nucleation rate, the crystallization kinetics of the sample containing 20 mole % BaO, which showed the most uniform crystallization, was studied by counting the nuclei with an image analyzer. The first nuclei appeared at the first endothermic inflection point (at the start of Tg, at 440 °C, while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 °C. These results are similar to those observed for other materials that crystallize in volume, and confirm scanning electron microscopy data.

  2. 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.

  3. Shear-induced anisotropic plastic flow from body-centred-cubic tantalum before melting

    Science.gov (United States)

    Wu, Christine J.; Söderlind, Per; Glosli, James N.; Klepeis, John E.

    2009-03-01

    There are many structural and optical similarities between a liquid and a plastic flow. Thus, it is non-trivial to distinguish between them at high pressures and temperatures, and a detailed description of the transformation between these phenomena is crucial to our understanding of the melting of metals at high pressures. Here we report a shear-induced, partially disordered viscous plastic flow from body-centred-cubic tantalum under heating before it melts into a liquid. This thermally activated structural transformation produces a unique, one-dimensional structure analogous to a liquid crystal with the rheological characteristics of Bingham plastics. This mechanism is not specific to Ta and is expected to hold more generally for other metals. Remarkably, this transition is fully consistent with the previously reported anomalously low-temperature melting curve and thus offers a plausible resolution to a long-standing controversy about melting of metals under high pressures.

  4. Partial melting of UHP calc-gneiss from the Dabie Mountains

    Science.gov (United States)

    Liu, Penglei; Wu, Yao; Liu, Qiang; Zhang, Junfeng; Zhang, Li; Jin, Zhenmin

    2014-04-01

    Exhumation melting has been proposed for the ultra-high pressure (UHP) metamorphic rocks in the Dabie Mountains based on melting experiments. We document here the first petrological and mineralogical evidence demonstrating that the UHP calc-gneisses from the Ganjialing area in the Dabie Mountains experienced partial melting during early exhumation. The assemblage of garnet, phengite (Si = 3.65 pfu), coesite, rutile and carbonate preserved in the calc-gneisses indicates a peak metamorphic condition of 692-757 °C and 4.0-4.8 GPa. Partial melting is indicated by several lines of evidence: the melting textures of phengite, the feldspar-dominated films, bands, branches, blebs and veins, the euhedral K-feldspars, the intergrowth film of plagioclase and K-feldspar, the plagioclase + biotite intergrowth after garnet and the epidote poikiloblasts. Polyphase inclusions in garnet are characterized with wedge-like offshoots and serrate outlines whereas those in epidote display negative crystal shapes, which can be best interpreted by entrapment of former melts. We propose a wet melting reaction of Phn + Q ± Na-Cpx + H2O = Bt + Pl + Grt + felsic melts, which likely took place at ca.650-800 °C and ca.1.0-2.0 GPa, to interpret the melting event in the calc-gneisses. Chemical exchanges between garnet and melts produced new garnet domains with higher almandine, spessartine, MREE, HREE and Y but lower grossular, pyrope, P, Sc, Ti, V and Zr contents. Zr-in-rutile thermometer reveals a low temperature of 620-643 °C at 5 GPa, indicating a later reset for Zr in rutile. Healed fractures are suggested to be responsible for the formation of some polyphase inclusions in garnet.

  5. 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

    Full Text Available The complex process of melting in the Earth's interior is studied by combining a multiphase numerical flow model with the program AlphaMELTS which provides a petrological description based on thermodynamic principles. The objective is to address the fundamental question of the effect of the mantle and melt dynamics on the composition and abundance of the melt and the residual solid. The conceptual idea is based on a 1-D description of the melting process that develops along an ideal vertical column where local chemical equilibrium is assumed to apply at some level in space and time. By coupling together the transport model and the chemical thermodynamic model, the evolution of the melting process can be described in terms of melt distribution, temperature, pressure and solid and melt velocities but also variation of melt and residual solid composition and mineralogical abundance at any depth over time. In this first installment of a series of three contributions, a two-phase flow model (melt and solid assemblage is developed under the assumption of complete local equilibrium between melt and a peridotitic mantle (dynamic equilibrium melting, DEM. The solid mantle is also assumed to be completely dry. The present study addresses some but not all the potential factors affecting the melting process. The influence of permeability and viscosity of the solid matrix are considered in some detail. The essential features of the dynamic model and how it is interfaced with AlphaMELTS are clearly outlined. A detailed and explicit description of the numerical procedure should make this type of numerical models less obscure. The general observation that can be made from the outcome of several simulations carried out for this work is that the melt composition varies with depth, however the melt abundance not necessarily always increases moving upwards. When a quasi-steady state condition is achieved, that is when melt abundance does not varies significantly

  6. 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...

  7. Control of crystal growth in water purification by directional freeze crystallization

    Science.gov (United States)

    Conlon, William M. (Inventor)

    1996-01-01

    A Directional Freeze Crystallization system employs an indirect contact heat exchanger to freeze a fraction of liquid to be purified. The unfrozen fraction is drained away and the purified frozen fraction is melted. The heat exchanger must be designed in accordance with a Growth Habit Index to achieve efficient separation of contaminants. If gases are dissolved in the liquid, the system must be pressurized.

  8. Large-area photonic crystals

    Science.gov (United States)

    Ruhl, Tilmann; Spahn, Peter; Hellmann, Gotz P.; Winkler, Holger

    2004-09-01

    Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions. In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick. To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.

  9. Single-crystal growth of ceria-based materials

    International Nuclear Information System (INIS)

    Ulbrich, Gregor

    2015-01-01

    In this work it could be shown that Skull-Melting is a suitable method for growing ceria single crystals. Twenty different ceria-based single crystals could be manufactured. It was possible to dope ceria single crystals with Gd, Sm, Y, Zr, Ti, Ta, and Pr in different concentrations. Also co-doping with the named metals was realized. However, there remain some problems for growing ceria-based single crystals by Skull-Melting. As ignition metal zirconium was used because no ceria-based material works well. For that reason all single crystals show small zirconium contamination. Another problem is the formation of oxygen by the heat-induced reduction of ceria during the melting process. Because of that the skull of sintered material is often destroyed by gas pressure. This problem had to be solved individually for every single crystal. The obtained single crystals were characterized using different methods. To ensure the single crystal character the y were examined by Laue diffraction. All manufactured crystals are single crystals. Also powder diffraction patterns of the milled and oxidized samples were measured. For the determination of symmetry and metric the structural parameters were analyzed by the Rietveld method. All synthesized materials crystallize in space group Fm-3m known from calcium fluoride. The cubic lattice parameter a was determined for all crystals. In the case of series with different cerium and zirconium concentrations a linear correlation between cerium content and cubic lattice parameter was detected. The elemental composition was determined by WDX. All crystals show a homogeneous elemental distribution. The oxygen content was calculated because the WDX method isn't useful for determination.

  10. An Evaluation of Quantitative Methods of Determining the Degree of Melting Experienced by a Chondrule

    Science.gov (United States)

    Nettles, J. W.; Lofgren, G. E.; Carlson, W. D.; McSween, H. Y., Jr.

    2004-01-01

    Many workers have considered the degree to which partial melting occurred in chondrules they have studied, and this has led to attempts to find reliable methods of determining the degree of melting. At least two quantitative methods have been used in the literature: a convolution index (CVI), which is a ratio of the perimeter of the chondrule as seen in thin section divided by the perimeter of a circle with the same area as the chondrule, and nominal grain size (NGS), which is the inverse square root of the number density of olivines and pyroxenes in a chondrule (again, as seen in thin section). We have evaluated both nominal grain size and convolution index as melting indicators. Nominal grain size was measured on the results of a set of dynamic crystallization experiments previously described, where aliquots of LEW97008(L3.4) were heated to peak temperatures of 1250, 1350, 1370, and 1450 C, representing varying degrees of partial melting of the starting material. Nominal grain size numbers should correlate with peak temperature (and therefore degree of partial melting) if it is a good melting indicator. The convolution index is not directly testable with these experiments because the experiments do not actually create chondrules (and therefore they have no outline on which to measure a CVI). Thus we had no means to directly test how well the CVI predicted different degrees of melting. Therefore, we discuss the use of the CVI measurement and support the discussion with X-ray Computed Tomography (CT) data.

  11. 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.

  12. Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

    Science.gov (United States)

    Sanchez-Valle, Carmen; Malfait, Wim J.

    2016-04-01

    Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

  13. Experimental Partitioning of Chalcophile Elements between Mantle Silicate Minerals and Basaltic Melt at High Pressures and Temperatures - Implications for Sulfur Geochemistry of Mantle and Crust

    Science.gov (United States)

    Dasgupta, R.; Jego, S.; Ding, S.; Li, Y.; Lee, C. T.

    2015-12-01

    The behavior of chalcophile elements during mantle melting, melt extraction, and basalt differentiation is critical for formation of ore deposits and geochemical model and evolution of crust-mantle system. While chalcophile elements are strongly partitioned into sulfides, their behavior with different extent of melting, in particular, in the absence of sulfides, can only be modeled with complete knowledge of the partitioning behavior of these elements between dominant mantle minerals and basaltic melt with or without dissolved sulfide (S2-). However, experimental data on mineral-melt partitioning are lacking for many chalcophile elements. Crystallization experiments were conducted at 3 GPa and 1450-1600 °C using a piston cylinder and synthetic silicate melt compositions similar to low-degree partial melt of peridotite. Starting silicate mixes doped with 100-300 ppm of each of various chalcophile elements were loaded into Pt/graphite double capsules. To test the effect of dissolved sulfur in silicate melt on mineral-melt partitioning of chalcophile elements, experiments were conducted on both sulfur-free and sulfur-bearing (1100-1400 ppm S in melt) systems. Experimental phases were analyzed by EPMA (for major elements and S) and LA-ICP-MS (for trace elements). All experiments produced an assemblage of cpx + melt ± garnet ± olivine ± spinel and yielded new partition coefficients (D) for Sn, Zn, Mo, Sb, Bi, Pb, and Se for cpx/melt, olivine/melt, and garnet/melt pairs. Derived Ds (mineral/basalt) reveal little effect of S2- in the melt on mineral-melt partition coefficients of the measured chalcophile elements, with Ds for Zn, Mo, Bi, Pb decreasing by less than a factor of 2 from S-free to S-bearing melt systems or remaining similar, within error, between S-free and S-bearing melt systems. By combining our data with existing partitioning data between sulfide phases and silicate melt we model the fractionation of these elements during mantle melting and basalt

  14. Volcanic volatile budgets and fluxes inferred from melt inclusions from post-shield volcanoes in Hawaii and the Canary Islands

    Science.gov (United States)

    Moore, L.; Gazel, E.; Bodnar, R. J.; Carracedo, J. C.

    2017-12-01

    Pre-eruptive volatile contents of volcanic melts recorded by melt inclusions are useful for estimating rates of deep earth ingassing and outgassing on geologic timescales. Ocean island volcanoes may erupt melts derived from recycled material and thus have implications regarding the degree to which volatile-bearing phases like magnesite can survive subduction and be recycled by intraplate magmatism. However, melt inclusions affected by degassing will not reflect the original volatile content of the primary melt. Post-shield ocean island volcanoes are thought to erupt volatile-rich melts that ascend quickly, crystallizing in deep reservoirs and are more likely to reflect the composition of the primary melt. In this study, we compare melt inclusions from post-shield volcanoes, Haleakala (East Maui, Hawaii) and Tenerife (Canary Islands), to estimate the volatile budgets of two presumably plume-related ocean-island settings. Melt inclusions from Haleakala contain up to 1.5 wt% CO2, up to 1.3 wt% H2O, and about 2000 ppm of S. The CO2 concentration is similar to estimates for primary CO2 concentrations for Hawaii, suggesting that the melt inclusions in this study trapped a melt that underwent minimal degassing. Assuming a melt production rate of 2 km3/ka for postshield Hawaiian volcanism, the average fluxes of CO2 and S are about 80 t/year and 10 t/year respectively. Melt inclusions from Tenerife contain up to 1 wt% CO2, up to 2 wt% H2O, and about 4000 ppm of S. Assuming a melt production rate of 0.8 km3/ka for the northeast rift zone of Tenerife, the average fluxes of CO2 and S are about 20 t/year and 8 t/year respectively. The concentration of CO2 is lower than estimates of the primary melt CO2 content based on CO2/Nb from El Hierro. This may indicate that the inclusions trapped a melt that had degassed significantly, or that some of the CO2 in the inclusions has been sequestered in carbonate daughter crystals, which were observed in abundance.

  15. Deducing Water Concentrations in the Parent Magma of Cumulate Clinopyroxene and Olivine: Implications for a Hydrous Parent Melt of a Primitive Deccan Lava

    Science.gov (United States)

    Seaman, S. J.

    2017-12-01

    Water concentrations of clinopyroxene megacrysts in the Powai ankaramite flow, located near Mumbai, Deccan province, India, indicate that the parent magma of the flow hosted at least 4.3 wt.% water, an unusually high water concentration for a continental flood basalt magma. The Powai flow hosts clinopyroxene and olivine phenocrysts. Chatterjee and Sheth (2015) showed that phenocrysts in the flow were part of a cumulate layer intruded by basaltic melt at 6 kb and 1230oC, so the phenocrysts record characteristics of the cumulate parent melt. Clinopyroxene phenocrysts are oscillatorily zoned in water, Mg, Fe, and Ca concentrations, and have concentric bands 100-200 microns thick of 10-20 micron diameter melt inclusions. Olivine phenocrysts host only larger isolated melt inclusions. Zones in the cpx phenocrysts where melt inclusion-rich concentric bands occur have higher concentrations of water than inclusion-free zones. Water concentrations of cpx were used to calculate water concentrations in the melt from which the crystals formed using partition coefficients of Hauri et al. (2004). Water concentrations in the parent magma were between 4.3 and 8.2 wt. % based on water concentrations in cpx. Both Mg and Fe are relatively depleted in the water- and melt inclusion-rich zones in cpx, and Ca is enriched in these zones. Oscillatory zoning in cpx may be a result of repeated growth of cpx in water- richer and water-poorer boundary layers where water lowered melt viscosity and enhanced diffusion and crystal growth rates. Water-enhanced growth rates may have resulted in capture of melt inclusions preserved in water-rich cpx zones. Melt inclusions in olivine phenocrysts preserve lower water concentrations ( 1.2 wt. %) than those indicated by water concentration in cpx phenocrysts. This disparity may be evidence of water loss from melt inclusions in olivine (Gaetani et al., 2009) or may indicate that cpx and ol crystals did not crystallize from the same parent at the same time.

  16. Modification of steel 35 HL surge current during crystallization

    Directory of Open Access Journals (Sweden)

    Zhbanova O.M.

    2017-04-01

    Full Text Available The method of electro steel melt modification 35 HL variable polarity current pulses with a duration of more 10-3s frequency within the 5–33 Hz, 5–24 porosity meanders, strength 30–40 A at a voltage of 180–240 V during crystallization, which allows to obtain high-quality castings 35 HL steel grade. Show that electro melt processing improves the structure and reduces the physical heterogeneity of castings and increases the rate of dissolution of metallic impurities and other components in the melt, providing fine-grained structure and increases the homogeneity of metal carbides reduces the amount of manganese reduces gases and nonmetallic inclusions. Modifying steel 35 HL pulse current during crystallization of the melt increases the physical and mechanical properties of tempered steel, increasing yield strength by 30 %, the tensile strength at 7 % elongation of 1,5 % relative narrowing by 2 %, toughness at 20 %.

  17. Shear induced structures in crystallizing cocoa butter

    Science.gov (United States)

    Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.

    2004-03-01

    Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.

  18. Origin of migmatites by deformation-enhanced melt infiltration of orthogneiss: a new model based on quantitative microstructural analysis

    Czech Academy of Sciences Publication Activity Database

    Hasalová, P.; Schulmann, K.; Lexa, O.; Štípská, P.; Hrouda, F.; Ulrich, Stanislav; Haloda, J.; Týcová, P.

    2008-01-01

    Roč. 26, č. 1 (2008), s. 29-53 ISSN 0263-4929 Grant - others:GA AV ČR(CZ) IAA3111401; GA ČR(CZ) GA205/04/2065 Institutional research plan: CEZ:AV0Z30120515 Keywords : crystal size distribution * melt infiltration * melt topology * migmatites * quantitative textural analysis Subject RIV: DB - Geology ; Mineralogy Impact factor: 3.340, year: 2008

  19. Deep pooling of low degree melts and volatile fluxes at the 85°E segment of the Gakkel Ridge: Evidence from olivine-hosted melt inclusions and glasses

    Science.gov (United States)

    Shaw, Alison M.; Behn, Mark D.; Humphris, Susan E.; Sohn, Robert A.; Gregg, Patricia M.

    2010-01-01

    We present new analyses of volatile, major, and trace elements for a suite of glasses and melt inclusions from the 85°E segment of the ultra-slow spreading Gakkel Ridge. Samples from this segment include limu o pele and glass shards, proposed to result from CO 2-driven explosive activity. The major element and volatile compositions of the melt inclusions are more variable and consistently more primitive than the glass data. CO 2 contents in the melt inclusions extend to higher values (167-1596 ppm) than in the co-existing glasses (187-227 ppm), indicating that the melt inclusions were trapped at greater depths. These melt inclusions record the highest CO 2 melt concentrations observed for a ridge environment. Based on a vapor saturation model, we estimate that the melt inclusions were trapped between seafloor depths (˜ 4 km) and ˜ 9 km below the seafloor. However, the glasses are all in equilibrium with their eruption depths, which is inconsistent with the rapid magma ascent rates expected for explosive activity. Melting conditions inferred from thermobarometry suggest relatively deep (25-40 km) and cold (1240°-1325 °C) melting conditions, consistent with a thermal structure calculated for the Gakkel Ridge. The water contents and trace element compositions of the melt inclusions and glasses are remarkably homogeneous; this is an unexpected result for ultra-slow spreading ridges, where magma mixing is generally thought to be less efficient based on the assumption that steady-state crustal magma chambers are absent in these environments. All melts can be described by a single liquid line of descent originating from a pooled melt composition that is consistent with the aggregate melt calculated from a geodynamic model for the Gakkel Ridge. These data suggest a model in which deep, low degree melts are efficiently pooled in the upper mantle (9-20 km depth), after which crystallization commences and continues during ascent and eruption. Based on our melting model

  20. 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

  1. Crystal growth and doping

    International Nuclear Information System (INIS)

    Paorici, C.

    1980-01-01

    Section 1 contains a self-consistent review of the basic growth features. After a short introduction concerning the driving force acting in a crystallization process, three main topics are broadly discussed: (i) interface kinetics; (ii) transport kinetics, and (iii) growth stability conditions. On point (i), after definition of the nature of interface, using Temkin's model, the growth mechanisms predicted by Burton, Cabrera and Frank (BCF) and bidimensional nucleation theories are fully developed. On points (ii) and (iii), the differential equations of the constitutional (concentration) and thermal fields are presented and discussed in terms of relevant approximations, suitable boundary conditions and limit values expected in order to have growth stability. Section 2 reports various experimental procedures for growing bulk crystals from the melt, from solutions and from the vapour phase. The basic concepts of Section 1 are amply employed for a critical discussion of possibilities, advantages and drawbacks of the methods described. Along the same lines, in Section 3 the principal epitaxial deposition procedures are highlighted. Section 4 contains a brief account of doping and of stoichiometry-defect control procedures. There is a long, carefully chosen list of bibliographical references. (author)

  2. 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

  3. Apatite-Melt Partitioning at 1 Bar: An Assessment of Apatite-Melt Exchange Equilibria Resulting from Non-Ideal Mixing of F and Cl in Apatite

    Science.gov (United States)

    McCubbin, F. M.; Ustunisik, G.; Vander Kaaden, K. E.

    2016-01-01

    The mineral apatite [Ca5(PO4)3(F,Cl,OH)] is present in a wide range of planetary materials. Due to the presence of volatiles within its crystal structure (X-site), many recent studies have attempted to use apatite to constrain the volatile contents of planetary magmas and mantle sources. In order to use the volatile contents of apatite to precisely determine the abundances of volatiles in coexisting silicate melt or fluids, thermodynamic models for the apatite solid solution and for the apatite components in multi-component silicate melts and fluids are required. Although some thermodynamic models for apatite have been developed, they are incomplete. Furthermore, no mixing model is available for all of the apatite components in silicate melts or fluids, especially for F and Cl components. Several experimental studies have investigated the apatite-melt and apatite-fluid partitioning behavior of F, Cl, and OH in terrestrial and planetary systems, which have determined that apatite-melt partitioning of volatiles are best described as exchange equilibria similar to Fe-Mg partitioning between olivine and silicate melt. However, McCubbin et al. recently reported that the exchange coefficients may vary in portions of apatite compositional space where F, Cl, and OH do not mix ideally in apatite. In particular, solution calorimetry data of apatite compositions along the F-Cl join exhibit substantial excess enthalpies of mixing. In the present study, we conducted apatite-melt partitioning experiments in evacuated, sealed silica-glass tubes at approximately 1 bar and 950-1050 degrees Centigrade on a synthetic Martian basalt composition equivalent to the basaltic shergottite Queen Alexandria Range (QUE) 94201. These experiments were conducted dry, at low pressure, to assess the effects of temperature and apatite composition on the partitioning behavior of F and Cl between apatite and basaltic melt along the F-Cl apatite binary join, where there is non-ideal mixing of F and Cl

  4. Generalized melting criterion for beam-induced amorphization

    International Nuclear Information System (INIS)

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

    1993-09-01

    Recent studies have shown that the mean-square static atomic displacements provide a generic measure of the enthalpy stored in the lattice in the form of chemical and topological disorder, and that the effect of the displacements on the softening of shear elastic constants is identical to that of heating. This finding lends support to a generalized form of the Lindemann phenomenological melting criterion and leads to a natural interpretion of crystalline-to-amorphous transformations as defect-induced melting of metastable crystals driven beyond a critical state of disorder where the melting temperature falls below the glass-transition temperature. Application of the generalized Lindemann criterion to both the crystalline and amorphous phases indicates that the enthalpies of the two phases become identical when their shear moduli become equal. This thermo-elastic rule provides a basis for predicting the relative susceptibility of compounds to amorphization in terms of their elastic properties as measured by Debye temperatures. The present approach can explain many of the basic findings on beam-induced amorphization of intermetallic compounds as well as amorphous phase formation associated with ion implantation, ion-beam mixing and other solid-state processes

  5. Non-Equilibrium Solidification of Undercooled Metallic Melts

    Directory of Open Access Journals (Sweden)

    Dieter M. Herlach

    2014-06-01

    Full Text Available If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.

  6. Crystal Structure and Spectroscopic Characterization of K8(VO)2O(SO4)6:

    DEFF Research Database (Denmark)

    Rasmussen, Søren Birk; Rasmussen, Rikke Christina; Fehrmann, Rasmus

    2003-01-01

    Red and yellow dichroistic crystals of a vanadium(V) compound, potassium (mu-oxo, di-mu-suifato)bis(oxodisulfato-vanadate), K-8(VO)(2)O(SO4)(6), have been obtained from the ternary catalytic model melt system K2S2O7-K2SO4-V2O5. By slow cooling of the melt from 420 to 355 degreesC, crystal growth...

  7. 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

  8. 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)

  9. Formation of anorthosite on the Moon through magma ocean fractional crystallization

    Directory of Open Access Journals (Sweden)

    Tatsuyuki Arai

    2017-03-01

    Full Text Available Lunar anorthosite is a major rock of the lunar highlands, which formed as a result of plagioclase-floatation in the lunar magma ocean (LMO. Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite (mode of plagioclase >95 vol.% is a key to reveal the early magmatic evolution of the terrestrial planets. To form the pure lunar anorthosite, plagioclase should have separated from the magma ocean with low crystal fraction. Crystal networks of plagioclase and mafic minerals develop when the crystal fraction in the magma (φ is higher than ca. 40–60 vol.%, which inhibit the formation of pure anorthosite. In contrast, when φ is small, the magma ocean is highly turbulent, and plagioclase is likely to become entrained in the turbulent magma rather than separated from the melt. To determine the necessary conditions in which anorthosite forms from the LMO, this study adopted the energy criterion formulated by Solomatov. The composition of melt, temperature, and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the melt. When plagioclase starts to crystallize, the Mg# of melt becomes 0.59 at 1291 °C. The density of the melt is smaller than that of plagioclase for P > 2.1 kbar (ca. 50 km deep, and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase (1.8–3 cm. This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to crystallize. When the Mg# of melt becomes 0.54 at 1263 °C, the density of melt becomes larger than that of plagioclase even for 0 kbar. When the Mg# of melt decreases down to 0.46 at 1218 °C, the critical diameter of plagioclase to separate from the melt becomes 1.5–2.5 cm, which is nearly equal to the typical plagioclase of the lunar anorthosite. This suggests that plagioclase could separate from the

  10. Luna 24 ferrobasalt as a low-Mg primary melt

    International Nuclear Information System (INIS)

    Norman, M.; Ryder, G.

    1980-01-01

    Luna 24 very-low titanium (VLT) ferrobasalts, metabasalts, brown glasses and impact melts form a tight compositional cluster with no gradation to other groupings postulated for the Luna 24 core components. This suggests that the Luna 24 VLT ferrobasalt was extruded as a liquid of its own composition and was not derived by fractional crystallization from a more magnesian parent in a surface flow. Furthermore, the characteristics of the core lithologies are not easily visualized as components of such a differential flow, e.g. brown glasses. Gravitative settling models purporting to demonstrate the validity of the flow differentiation model are merely permissive. Subsurface fractionation requires that plagioclase, not olivine, be the liquidus phase. The high-Mg component in the Luna 24 core can be constrained, though not identified, chemically, and it has neither the major element, trace element, isotopic, nor mineralogical characteristics required of a possible parent to the Luna 24 VLT ferrobasalt. Thus models of fractionation lack a physical expression of the less differentiated compositions, contrary to the belief that the high-Mg component in the core is the parent material. The Luna 24 VLT ferrobasalt is probably a primary low-Mg melt from a plagioclase-bearing source region, and may have undergone little or no fractionation prior to eruption. Such a model is compatible with, and suggested by, chemical and experimental data. Caution against posulating that all Mg-poor melts are fractionated products, based on terrestrial models, is advised. The terrestrial oceanic situation of 'primary melts' with similar Mg/Fe is probably not valid for the Moon. (Auth.)

  11. 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

  12. 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

  13. 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)

  14. Impact-melt hygrometer for Mars: The case of shergottite Elephant Moraine (EETA) 79001

    Science.gov (United States)

    Liu, Yang; Chen, Yang; Guan, Yunbin; Ma, Chi; Rossman, George R.; Eiler, John M.; Zhang, Youxue

    2018-05-01

    We report volatile concentrations and hydrogen isotope compositions of impact melts and minerals in EETA 79001. We observed chemical changes in pyroxene, maskelynite (or feldspathic glass), and merrillite in contact with or inside impact melts. All pyroxene grains analyzed here are inside or close to impact melt pockets and contain 10-41 ppm H2O and enriched in D (δD = + 1729 to + 3707 ‰), with the highest values found in a grain enclosed in an impact melt pocket. Maskelynite or feldspathic glass contains 6.3 to 98 ppm H2O with δD values of +1604 to + 3938 ‰. The high H2O and δD values were obtained in those enclosed inside or in contact with the impact melts, whereas low H2O content (4 ppm) and terrestrial-like D/H value (δD of - 90 ± 82 ‰) were found in one maskelynite grain away from impact melts contains. Rims of ∼5 μm thickness of merrillite grains next to impact melts display Na-depletion by ∼0.9 wt%, and the sides in contact with impact melts show Mg-enrichment by ∼0.5 wt%. However, the H2O and δD values of merrillite interiors (39-242 ppm H2O and δD of +1682 to + 3884 ‰) do not show correlation with their proximity to the impact melts. Rather, δD and 1/H2O of merrillite form a negative trend different from that of impact melt pockets and maskelynite, suggesting post-crystallization or late-crystallization interactions with the crustal fluids. The impact melt pockets in EETA 79001 contain 121-646 ppm H2O, 4.3-13 ppm F, 13-50 ppm Cl, 707-2702 ppm S, and the δD values of +3368 to + 4639 ‰. The correlations between H2O, F, Cl, P2O5, and δD values of impact melts and feldspathic glass are consistent with mixing between a volatile-rich and high δD (+3000 to + 5000 ‰) endmember and a volatile-poor and low δD endmember. The volatile-poor and low δD endmember is consistent with magmatic volatiles stored in silicates. The volatile-rich and high δD endmember represents pre-impact alteration materials by subsurface water. Alteration

  15. Full-scale experiments on solid-pellets feed continuous Czochralski growth of silicon crystals

    Science.gov (United States)

    Anselmo, A.; Koziol, J.; Prasad, V.

    1996-06-01

    Two long-term solid-pellets feed continuous Czochralski growth experiments were performed in an industrial Czochralski crystal puller as an extension to our previous work [7]. The goals of these experiments were to examine how polysilicon pellets would melt in a standard Cz system, to discover the thermal effects the pellets would have on the overall melt, and to find if pellet addition could be an effective melt replenishment technique. These experiments demonstrate that the quality of the melt for the CCz growth is based heavily on the surface temperature of the melt. A novel characterization method ("impact severity") is developed to characterize the quality of the CCz melt. Stable feed rate and melt conditions were achieved for three different pull rates. These experiments demonstrate that the process is technically feasible, and can be retrofitted to the existing industrial systems. Several critical issues that need to be addressed to develop a successful CCz process are also discussed.

  16. 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

  17. Homogeneous crystal nucleation in polymers.

    Science.gov (United States)

    Schick, C; Androsch, R; Schmelzer, J W P

    2017-11-15

    The pathway of crystal nucleation significantly influences the structure and properties of semi-crystalline polymers. Crystal nucleation is normally heterogeneous at low supercooling, and homogeneous at high supercooling, of the polymer melt. Homogeneous nucleation in bulk polymers has been, so far, hardly accessible experimentally, and was even doubted to occur at all. This topical review summarizes experimental findings on homogeneous crystal nucleation in polymers. Recently developed fast scanning calorimetry, with cooling and heating rates up to 10 6 K s -1 , allows for detailed investigations of nucleation near and even below the glass transition temperature, including analysis of nuclei stability. As for other materials, the maximum homogeneous nucleation rate for polymers is located close to the glass transition temperature. In the experiments discussed here, it is shown that polymer nucleation is homogeneous at such temperatures. Homogeneous nucleation in polymers is discussed in the framework of the classical nucleation theory. The majority of our observations are consistent with the theory. The discrepancies may guide further research, particularly experiments to progress theoretical development. Progress in the understanding of homogeneous nucleation is much needed, since most of the modelling approaches dealing with polymer crystallization exclusively consider homogeneous nucleation. This is also the basis for advancing theoretical approaches to the much more complex phenomena governing heterogeneous nucleation.

  18. Ca/Al of plagioclase-hosted melt inclusions as an indicator for post-entrapment processes at mid-ocean ridges?

    International Nuclear Information System (INIS)

    Zhang, H.T.; Yang, Y.M.; Yan, Q.S.; Shi, Z.F.; Zhu, Z.W.; Su, W.C.; Qin, C.J.; Ye, J.

    2016-01-01

    The composition of melt inclusions in basalts erupted at mid-ocean ridges may be modified by post-entrapment processes, so the present composition of melt inclusions may not represent their original composition at the time of entrapment. By combining the melt inclusion composition in samples from the South Mid-Atlantic Ridge at 19°S analyzed in this study, and from the Petrological Database, we found that post-entrapment crystallization processes resulted in higher Ca/Al, Mg#[100×atomic Mg2+/(Mg2++Fe2+)], MgO and FeO contents, and lower CaO and Al2O3 contents of plagioclase-hosted melt inclusions relative to those hosted in olivine. In addition, melt inclusions hosted in plagioclase with anorthite content larger than 80mol.% had been modified more readily than others. By discussing the relationships between Ca/Al and fractional crystallization, post-entrapment crystallization, and the original melt composition, we propose that Ca/Al can be regarded as an indicator of the effect of post-entrapment processes on melt inclusion composition. Specifically, i) when Ca/Al 1.0, the compositions of melt inclusions do not reflect the original melt composition nor preserve information about the mantle source. According to these criteria, plagioclase-hosted melt inclusions with Ca/Al>1.0 in basalts from the South Mid-Atlantic Ridge at19°S cannot represent the composition of the melt at the moment of their entrapment. (Author)

  19. Role of local assembly in the hierarchical crystallization of associating colloidal hard hemispheres

    Science.gov (United States)

    Lei, Qun-li; Hadinoto, Kunn; Ni, Ran

    2017-10-01

    Hierarchical self-assembly consisting of local associations of simple building blocks for the formation of complex structures widely exists in nature, while the essential role of local assembly remains unknown. In this work, by using computer simulations, we study a simple model system consisting of associating colloidal hemispheres crystallizing into face-centered-cubic crystals comprised of spherical dimers of hemispheres, focusing on the effect of dimer formation on the hierarchical crystallization. We found that besides assisting the crystal nucleation because of increasing the symmetry of building blocks, the association between hemispheres can also induce both reentrant melting and reentrant crystallization depending on the range of interaction. Especially when the interaction is highly sticky, we observe a novel reentrant crystallization of identical crystals, which melt only in a certain temperature range. This offers another axis in fabricating responsive crystalline materials by tuning the fluctuation of local association.

  20. 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

  1. Steps and dislocations in cubic lyotropic crystals

    International Nuclear Information System (INIS)

    Leroy, S; Pieranski, P

    2006-01-01

    It has been shown recently that lyotropic systems are convenient for studies of faceting, growth or anisotropic surface melting of crystals. All these phenomena imply the active contribution of surface steps and bulk dislocations. We show here that steps can be observed in situ and in real time by means of a new method combining hygroscopy with phase contrast. First results raise interesting issues about the consequences of bicontinuous topology on the structure and dynamical behaviour of steps and dislocations

  2. Vitrification and Crystallization of Phase-Separated Metallic Liquid

    Directory of Open Access Journals (Sweden)

    Yun Cheng

    2017-02-01

    Full Text Available The liquid–liquid phase separation (LLPS behavior of Fe50Cu50 melt from 3500 K to 300 K with different rapid quenching is investigated by molecular dynamics (MD simulation based on the embedded atom method (EAM. The liquid undergoes metastable phase separation by spinodal decomposition in the undercooled regime and subsequently solidifies into three different Fe-rich microstructures: the interconnected-type structure is kept in the glass and crystal at a higher cooling rate, while the Fe-rich droplets are found to crystalize at a lower cooling rate. During the crystallization process, only Fe-rich clusters can act as the solid nuclei. The twinning planes can be observed in the crystal and only the homogeneous atomic stacking shows mirror symmetry along the twinning boundary. Our present work provides atomic-scale understanding of LLPS melt during the cooling process.

  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. Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

    Science.gov (United States)

    Wang, Zhong-Jie; Ni, Wen; Li, Ke-Qing; Huang, Xiao-Yan; Zhu, Li-Ping

    2011-08-01

    The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag (NS) and blast furnace slag (BFS) with a small amount of quartz sand was investigated. A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process. The results show that the iron-rich system has much lower melting temperature, glass transition temperature ( T g), and glass crystallization temperature ( T c), which can result in a further energy-saving process. The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C. The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample. The crystallization process can be completed in a few minutes. A distinct boundary between the crystallized part and the non-crystallized part exists during the process. In the non-crystallized part showing a black colour, some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to T c. In the crystallized part showing a khaki colour, a compact structure is formed by augite crystals.

  5. 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

  6. Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

    International Nuclear Information System (INIS)

    Firstov, G.S.; Koval, Yu.N.; Van Humbeeck, J.; Portier, R.; Vermaut, P.; Ochin, P.

    2006-01-01

    The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed

  7. Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Firstov, G.S. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine)]. E-mail: gfirst@imp.kiev.ua; Koval, Yu.N. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine); Van Humbeeck, J. [Department MTM, Catholic University of Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven) (Belgium); Portier, R. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Vermaut, P. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Ochin, P. [Centre d' Etudes de Chimie Metallurgique-CNRS UPR2801, 15 rue Georges Urbain, 94407 Vitry-sur-Seine (France)

    2006-11-25

    The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed.

  8. 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...

  9. Silicon crystal growth using a liquid-feeding Czochralski method

    Science.gov (United States)

    Shiraishi, Yutaka; Kurosaka, Shoei; Imai, Masato

    1996-09-01

    Silicon single crystals with uniformity along the growth direction were grown using a new continuous Czochralski (CCZ) method. Polycrystalline silicon rods used as charge materials are melted by carbon heaters over a crucible without contact between the raw material and other substances. Using this method, silicon crystals with diameters as large as 6 or 8 inch and good uniformity along the growth direction were grown.

  10. Defect reduction in seeded aluminum nitride crystal growth

    Science.gov (United States)

    Bondokov, Robert T.; Schowalter, Leo J.; Morgan, Kenneth; Slack, Glen A; Rao, Shailaja P.; Gibb, Shawn Robert

    2017-09-26

    Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density.ltoreq.100 cm.sup.-2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

  11. Discrete elastic model for two-dimensional melting.

    Science.gov (United States)

    Lansac, Yves; Glaser, Matthew A; Clark, Noel A

    2006-04-01

    We present a network model for the study of melting and liquid structure in two dimensions, the first in which the presence and energy of topological defects (dislocations and disclinations) and of geometrical defects (elemental voids) can be independently controlled. Interparticle interaction is via harmonic springs and control is achieved by Monte Carlo moves which springs can either be orientationally "flipped" between particles to generate topological defects, or can be "popped" in force-free shape, to generate geometrical defects. With the geometrical defects suppressed the transition to the liquid phase occurs via disclination unbinding, as described by the Kosterlitz-Thouless-Halperin-Nelson-Young model and found in soft potential two-dimensional (2D) systems, such as the dipole-dipole potential [H. H. von Grünberg, Phys. Rev. Lett. 93, 255703 (2004)]. By contrast, with topological defects suppressed, a disordering transition, the Glaser-Clark condensation of geometrical defects [M. A. Glaser and N. A. Clark, Adv. Chem. Phys. 83, 543 (1993); M. A. Glaser, (Springer-Verlag, Berlin, 1990), Vol. 52, p. 141], produces a state that accurately characterizes the local liquid structure and first-order melting observed in hard-potential 2D systems, such as hard disk and the Weeks-Chandler-Andersen (WCA) potentials (M. A. Glaser and co-workers, see above). Thus both the geometrical and topological defect systems play a role in melting. The present work introduces a system in which the relative roles of topological and geometrical defects and their interactions can be explored. We perform Monte Carlo simulations of this model in the isobaric-isothermal ensemble, and present the phase diagram as well as various thermodynamic, statistical, and structural quantities as a function of the relative populations of geometrical and topological defects. The model exhibits a rich phase behavior including hexagonal and square crystals, expanded crystal, dodecagonal quasicrystal

  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. Petrological constraints on melt generation beneath the Asal Rift (Djibouti) using quaternary basalts

    Science.gov (United States)

    Pinzuti, Paul; Humler, Eric; Manighetti, Isabelle; Gaudemer, Yves

    2013-08-01

    The temporal evolution of the mantle melting processes in the Asal Rift is evaluated from the chemical composition of 56 new lava flows sampled along 10 km of the rift axis and 9 km off-axis (i.e., erupted within the last 620 kyr). Petrological and primary geochemical results show that most of the samples of the inner floor of the Asal Rift are affected by plagioclase accumulation. Trace element ratios and major element compositions corrected for mineral accumulation and crystallization show a symmetric pattern relative to the rift axis and preserved a clear signal of mantle melting depth variations. While FeO, Fe8.0, Zr/Y, and (Dy/Yb)N decrease from the rift shoulders to the rift axis, SiO2, Na/Ti, Lu/Hf increase and Na2O and Na8.0 are constant across the rift. These variations are qualitatively consistent with shallow melting beneath the rift axis and deeper melting for off-axis lava flows. Na8.0 and Fe8.0 contents show that beneath the rift axis, melting paths are shallow, from 81 ± 4 to 43 ± 5 km. These melting paths are consistent with adiabatic melting in normal-temperature fertile asthenosphere, beneath an extensively thinned mantle lithosphere. On the contrary, melting on the rift shoulders (from 107 ± 7 to 67 ± 8 km) occurred beneath thicker lithosphere, requiring a mantle solidus temperature 100 ± 40°C hotter. In this geodynamic environment, the calculated rate of lithospheric thinning appears to be 4.0 ± 2.0 cm yr-1, a value close to the mean spreading rate (2.9 ± 0.2 cm yr-1) over the last 620 kyr.

  16. Containerless solidification of undercooled oxide and metallic eutectic melts

    International Nuclear Information System (INIS)

    Li Mingjun; Nagashio, Kosuke; Kuribayashi, Kazuhiko

    2004-01-01

    A high-speed video was employed to monitor the in situ recalescence of undercooled oxide Al 2 O 3 -36.8 at.% ZrO 2 and metallic Ni-18.7 at.% Sn eutectics that were processed on an aero-acoustic levitator and an electromagnetic levitator, respectively. For the oxide eutectic, the entire sample becomes brighter and brighter without any clear recalescence front during spontaneous crystallization. When the sample was seeded at desired undercoolings, crystallization started from the seeding point and then spread through the entire sample. Microstructures of the oxide solidified via both the spontaneous crystallization and external seeding consist of many independent eutectic colonies at the sample surface, indicating that copious nucleation takes place regardless of melt undercooling and solidification mode. For the metallic eutectics, two kinds of recalescence are visualized. The surface and cross sectional microstructures reveal that copious nucleation is also responsible for the formation of independent eutectic colonies distributing within the entire sample. It is not possible to measure the growth velocity of a single eutectic colony using optical techniques under the usual magnification. The conventional nucleation concept derived from single-phase alloys may not be applicable to the free solidification of the undercooled double-phase oxide and metallic eutectic systems

  17. 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

  18. Magnetophotonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, M [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Fujikawa, R [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Baryshev, A [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Khanikaev, A [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Lim, P B [CREST, Japan Science and Technology Agency, Saitama 332-0012, Japan (Japan); Uchida, H [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Aktsipetrov, O [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Fedyanin, A [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Murzina, T [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation); Granovsky, A [Lomonosov Moscow State University, Leninskie Gory, Moscow, 119992 (Russian Federation)

    2006-04-21

    When the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs. (topical review)

  19. Magnetophotonic crystals

    International Nuclear Information System (INIS)

    Inoue, M; Fujikawa, R; Baryshev, A; Khanikaev, A; Lim, P B; Uchida, H; Aktsipetrov, O; Fedyanin, A; Murzina, T; Granovsky, A

    2006-01-01

    When the constitutive materials of photonic crystals (PCs) are magnetic, or even only a defect introduced in PCs is magnetic, the resultant PCs exhibit very unique optical and magneto-optical properties. The strong photon confinement in the vicinity of magnetic defects results in large enhancement in linear and nonlinear magneto-optical responses of the media. Novel functions, such as band Faraday effect, magnetic super-prism effect and non-reciprocal or magnetically controllable photonic band structure, are predicted to occur theoretically. All the unique features of the media arise from the existence of magnetization in media, and hence they are called magnetophotonic crystals providing the spin-dependent nature in PCs. (topical review)

  20. 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.

  1. 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

  2. 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

  3. 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...

  4. 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...

  5. Combined electron beam and vacuum ARC melting for barrier tube shell material

    International Nuclear Information System (INIS)

    Worcester, S.A.; Woods, C.R.

    1989-01-01

    This patent describes a process of the type wherein zirconium tetrachloride is reduced to produce a metallic zirconium sponge. The sponge is distilled to generally remove residual magnesium and magnesium chloride, and the distilled sponge is melted to produce an ingot, the improvement for making a non-crystal bar material for use in lining the interior of zirconium alloy fuel element cladding which comprises: a. forming the distilled sponge into a consumable electrode; b. melting the consumable electrode in a multiple swept beam electron furnace with a feed rate between 1 and 20 inches per hour to form an intermediate ingot; and c. vacuum arc melting the intermediate ingot to produce a homogeneous final ingot, having 50-500 ppm iron

  6. Ionic conduction in polyether-based lithium arylfluorosulfonimide ionic melt electrolytes

    International Nuclear Information System (INIS)

    Herath, Mahesha B.; Creager, Stephen E.; Rajagopal, Rama V.; Geiculescu, Olt E.; DesMarteau, Darryl D.

    2009-01-01

    We report synthesis, characterization and ion transport in polyether-based ionic melt electrolytes consisting of Li salts of low-basicity anions covalently attached to polyether oligomers. Purity of the materials was investigated by HPLC analysis and electrospray ionization mass spectrometry. The highest ionic conductivity of 7.1 x 10 -6 S/cm at 30 deg. C was obtained for the sample consisting of a lithium salt of an arylfluorosulfonimide anion attached to a polyether oligomer with an ethyleneoxide (EO) to lithium ratio of 12. The conductivity order of various ionic melts having different polyether chain lengths suggests that at higher EO:Li ratios the conductivity of the electrolytes at room temperature is determined in part by the amount of crystallization of the polyether portion of the ionic melt.

  7. 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.

  8. Mechanisms of heterogeneous crystal growth in atomic systems: insights from computer simulations.

    Science.gov (United States)

    Gulam Razul, M S; Hendry, J G; Kusalik, P G

    2005-11-22

    In this paper we analyze the atomic-level structure of solid/liquid interfaces of Lennard-Jones fcc systems. The 001, 011, and 111 faces are examined during steady-state growth and melting of these crystals. The mechanisms of crystallization and melting are explored using averaged configurations generated during these steady-state runs, where subsequent tagging and labeling of particles at the interface provide many insights into the detailed atomic behavior at the freezing and melting interfaces. The interfaces are generally found to be rough and we observe the structure of freezing and melting interfaces to be very similar. Large structural fluctuations with solidlike and liquidlike characteristics are apparent in both the freezing and melting interfaces. The behavior at the interface observed under either growth or melting conditions reflects a competition between ordering and disordering processes. In addition, we observe atom hopping that imparts liquidlike characteristics to the solid side of the interfaces for all three crystal faces. Solid order is observed to extend as rough, three-dimensional protuberances through the interface, particularly for the 001 and 011 faces. We are also able to reconcile our different measures for the interfacial width and address the onset of asymmetry in the growth rates at high rates of crystal growth/melting.

  9. Growth of high-temperature superconductor crystals from flux

    International Nuclear Information System (INIS)

    Demianets, L.N.; Bykov, A.B.; Melnikov, O.K.; Stishov, S.M.

    1991-01-01

    Crystallization of high-temperature superconductors was studied in La-Sr-Cu-O, Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems. Platelet crystals YBa 2 Cu 3 Osub(6.5+x) were obtained by spontaneous crystallization from homogeneous nonstoichiometric melts enriched in barium and copper oxides. Lasub(2-x)Sr x CuO 4 was prepared by slow cooling of melts enriched in copper oxide. Bi 2 (Sr, Ca)sub(n+1)Cu n O y , (n=1;2) was obtained by melting zone travelling. The crystals show transition to superconducting state at T=93K, ΔT 0.2-0.5 K (Y, Ba cuprate), T=87K, ΔT 2K (Bi, Sr, Ca-cuprate). La, Sr-cuprate single crystals obtained by Czochralski method did not show transition to superconducting state. For flux-grown crystals T c was 5-26 K depending on the composition, growth and heat treatment. The short characterization of some accessory phases (Ba 3 Y 2 Cu 3 PtO 10 , Casub(1.75)Srsub(1.5)Cusub(0.75)PtO 6 , BaCuO 2 , Ba 41 Cu 44 O 84 Cl 2 ) is reported. (author). 15 ref s., 8 figs

  10. Immiscible iron- and silica-rich melt in basalt petrogenesis documented in the Skaergaard intrusion

    DEFF Research Database (Denmark)

    Jakobsen, Jakob Kløve; Veksler, Ilya; Tegner, Christian

    2005-01-01

    colored type contains 30.9 6 4.2 wt% FeOt and 40.7 6 3.6 wt% SiO2, whereas the light colored type contains 8.6 6 5.9 wt% FeOt and 65.6 6 7.3 wt% SiO2. Similar light colored melt inclusions in olivine and fine grained dark and light colored interstitial pockets also give evidence of crystallization from......Silicate liquid immiscibility in basalt petrogenesis is a contentious issue. Immiscible iron and silica-rich liquids were reported in melt inclusions of lunar basalt and in groundmass glasses of terrestrial volcanics. In fully crystallized plutonic rocks, however, silicate liquid immiscibility has...

  11. 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.

  12. 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.

  13. 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...

  14. Resistivity distribution of silicon single crystals using codoping

    Science.gov (United States)

    Wang, Jong Hoe

    2005-07-01

    Numerous studies including continuous Czochralski method and double crucible technique have been reported on the control of macroscopic axial resistivity distribution in bulk crystal growth. The simple codoping method for improving the productivity of silicon single-crystal growth by controlling axial specific resistivity distribution was proposed by Wang [Jpn. J. Appl. Phys. 43 (2004) 4079]. Wang [J. Crystal Growth 275 (2005) e73] demonstrated using numerical analysis and by experimental results that the axial specific resistivity distribution can be modified in melt growth of silicon crystals and relatively uniform profile is possible by B-P codoping method. In this work, the basic characteristic of 8 in silicon single crystal grown using codoping method is studied and whether proposed method has advantage for the silicon crystal growth is discussed.

  15. Crustal accretion along the global mid-ocean ridge system based on basaltic glass and olivine-hosted melt inclusion compositions

    Science.gov (United States)

    Wanless, V. D.; Behn, M. D.

    2015-12-01

    The depth and distribution of crystallization at mid-ocean ridges controls the overall architecture of the oceanic crust, influences hydrothermal circulation, and determines geothermal gradients in the crust and uppermost mantle. Despite this, there is no overall consensus on how crystallization is distributed within the crust/upper mantle or how this varies with spreading rate. Here, we examine crustal accretion at mid-ocean ridges by combining crystallization pressures calculated from major element barometers on mid-ocean ridge basalt (MORB) glasses with vapor-saturation pressures from melt inclusions to produce a detailed map of crystallization depths and distributions along the global ridge system. We calculate pressures of crystallization from >11,500 MORB glasses from the global ridge system using two established major element barometers (1,2). Additionally, we use vapor-saturation pressures from >400 olivine-hosted melt inclusions from five ridges with variable spreading rates to constrain pressures and distributions of crystallization along the global ridge system. We show that (i) crystallization depths from MORB glasses increase and become less focused with decreasing spreading rate, (ii) maximum glass pressures are greater than the maximum melt inclusion pressure, which indicates that the melt inclusions do not record the deepest crystallization at mid-ocean ridges, and (iii) crystallization occurs in the lower crust/upper mantle at all ridges, indicating accretion is distributed throughout the crust at all spreading rates, including those with a steady-state magma lens. Finally, we suggest that the remarkably similar maximum vapor-saturation pressures (~ 3000 bars) in melt inclusion from all spreading rates reflects the CO2 content of the depleted upper mantle feeding the global mid-ocean ridge system. (1) Michael, P. & W. Cornell (1998), Journal of Geophysical Research, 103(B8), 18325-18356; (2) Herzberg, C. (2004), Journal of Petrology, 45(12), 2389.

  16. Fabrication of radiation detector using PbI{sub 2} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Shoji, T; Sakamoto, K; Ohba, K; Suehiro, T; Hiratate, Y [Tohoku Inst. of Tech., Sendai (Japan)

    1996-07-01

    In this paper, we will discuss the PbI{sub 2} radiation detector fabricated from a crystal grown by the zone melting method and by the vapor phase method, together with characteristics of the crystal obtained by a XPS analyzer. (J.P.N.)

  17. Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

    KAUST Repository

    Palacios, Jordana; Mugica, Agurtzane; Zubitur, Manuela; Iturrospe, Amaia; Arbe, A.; Liu, Guoming; Wang, Dujin; Zhao, Junpeng; Hadjichristidis, Nikolaos; Muller, Alejandro

    2016-01-01

    The sequential crystallization of poly(ethylene oxide)-b-poly(e-caprolactone)-b-poly(L-lactide) (PEO-b-PCL-b-PLLA) triblock terpolymers, in which the three blocks are able to crystallize separately and sequentially from the melt, is presented. Two

  18. Domain structures of LiNbO3 crystals grown by a floating zone technique

    International Nuclear Information System (INIS)

    Kawakami, Shoji; Ishii, Eiichi; Tsuzuki, Akihiro; Sekiya, Tadashi; Torii, Yasuyoshi; Takahashi, Akio.

    1986-01-01

    LiNbO 3 single crystals were grown from the congruently melting composition by a floating zone technique. It was confirmed by etching that the single domain crystals were produced without applying any external electric field. When annealed above the Curie temperature, antiparallel domain appeared in the form of annual rings. (author)

  19. Self-Assembly and Crystallization of Conjugated Block Copolymers

    Science.gov (United States)

    Davidson, Emily Catherine

    This dissertation demonstrates the utility of molecular design in conjugated polymers to create diblock copolymers that robustly self-assemble in the melt and confine crystallization upon cooling. This work leverages the model conjugated polymer poly(3-(2'-ethyl)hexylthiophene) (P3EHT), which features a branched side chain, resulting in a dramatically reduced melting temperature (Tm 80°C) relative to the widely-studied poly(3-hexylthiophene) (P3HT) (Tm 200°C). This reduced melting temperature permits an accessible melt phase, without requiring that the segregation strength (chiN) be dramatically increased. Thus, diblock copolymers containing P3EHT demonstrate robust diblock copolymer self-assembly in the melt over a range of compositions and morphologies. Furthermore, confined crystallization in the case of both glassy (polystyrene (PS) matrix block) and soft (polymethylacrylate (PMA) matrix block) confinement is studied, with the finding that even in soft confinement, crystallization is constrained within the diblock microdomains. This success demonstrates the strategy of leveraging molecular design to decrease the driving force for crystallization as a means to achieving robust self-assembly and confined crystallization in conjugated block copolymers. Importantly, despite the relatively flexible nature of P3EHT in the melt, the diblock copolymer phase behavior appears to be significantly impacted by the stiffness (persistence length of 3 nm) of the P3EHT chain compared to the coupled amorphous blocks (persistence length 0.7 nm). In particular, it is shown that the synthesized morphologies are dominated by a very large composition window for lamellar geometries (favored at high P3EHT volume fractions); cylindrical geometries are favored when P3EHT is the minority fraction. This asymmetry of the composition window is attributed to impact of conformational asymmetry (the difference in chain stiffness, as opposed to shape) between conjugated and amorphous blocks

  20. Sequential crystallization and morphology of triple crystalline biodegradable PEO-b-PCL-b-PLLA triblock terpolymers

    KAUST Repository

    Palacios, Jordana

    2016-01-05

    The sequential crystallization of poly(ethylene oxide)-b-poly(e-caprolactone)-b-poly(L-lactide) (PEO-b-PCL-b-PLLA) triblock terpolymers, in which the three blocks are able to crystallize separately and sequentially from the melt, is presented. Two terpolymers with identical PEO and PCL block lengths and two different PLLA block lengths were prepared, thus the effect of increasing PLLA content on the crystallization behavior and morphology was evaluated. Wide angle X-Ray scattering (WAXS) experiments performed on cooling from the melt confirmed the triple crystalline nature of these terpolymers and revealed that they crystallize in sequence: the PLLA block crystallizes first, then the PCL block, and finally the PEO block. Differential scanning calorimetry (DSC) analysis further demonstrated that the three blocks can crystallize from the melt when a low cooling rate is employed. The crystallization process takes place from a homogenous melt as indicated by small angle X-Ray scattering (SAXS) experiments. The crystallization and melting enthalpies and temperatures of both PEO and PCL blocks decrease as PLLA content in the terpolymer increases. Polarized light optical microscopy (PLOM) demonstrated that the PLLA block templates the morphology of the terpolymer, as it forms spherulites upon cooling from the melt. The subsequent crystallization of PCL and PEO blocks occurs inside the interlamellar regions of the previously formed PLLA block spherulites. In this way, unique triple crystalline mixed spherulitic superstructures have been observed for the first time. As the PLLA content in the terpolymer is reduced the superstructural morphology changes from spherulites to a more axialitic-like structure.

  1. 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

  2. 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

  3. Melting and thermal history of poly(hydroxybutyrate-co-hydroxyvalerate) using step-scan DSC

    International Nuclear Information System (INIS)

    Gunaratne, L.M.W.K.; Shanks, R.A.

    2005-01-01

    Melting behaviour and crystal morphology of poly(3-hydroxybutyrate) (PHB) and its copolymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with various hydroxyvalerate (HV) contents [5 wt.% (PHB5HV), 8 wt.% (PHB8HV) and 12 wt.% (PHB12HV)] have been investigated by conventional DSC, step-scan differential scanning calorimetry (SDSC) and hot-stage polarised optical microscopy (HSPOM). Crystallisation behaviour of PHB and its copolymers were investigated by SDSC. Thermal properties were investigated after different crystallisation treatments, fast, medium and slow cooling. Multiple melting peak behaviour was observed for all polymers. SDSC data revealed that PHB and its copolymers undergo melting-recrystallisation-remelting during heating, as evidenced by exothermic peaks in the IsoK baseline (non-reversing signal). An increase in degree of crystallinity due to significant melt-recrystallisation was observed for slow-cooled copolymers. PHB5HV showed different crystal morphologies for various crystallisation conditions. SDSC proved a convenient and precise method for measurement of the apparent thermodynamic specific heat (reversing signal) HSPOM results showed that the crystallisation rates and sizes of spherulites were significantly reduced as crystallisation rate increased

  4. Formation peculiarities of superconducting Bi-Sr-Ca -cuprates from glass ceramic quenched melts

    International Nuclear Information System (INIS)

    Furmakova, O.E.; Zinov'ev, S.Yu.; Glushkova, V.B.; Bugakov, A.G.; Sulejmanov, S.Kh.

    1992-01-01

    Specimens of varying composition of the Bi-Sr-Ca-Cu-O system, X-ray amorphous Alakes and glass ceramic ingots were prepared by means of different rate quenching of melts. Crystallization temperatures of flakes were determined and sequence of phase formation in both types of specimens during annealing was studied. Microstructure and distribution of elements by volume of specimen in initial and annealed ingot were investigated

  5. Melting temperatures of MgO under high pressure determined by micro-texture observation

    Science.gov (United States)

    Kimura, T.; Ohfuji, H.; Nishi, M.; Irifune, T.

    2016-12-01

    Periclase (MgO) is the second abundant mineral after bridgmanite in the Earth's lower mantle, and its melting temperature (Tm) under pressure is important to constrain the chemical composition of ultra-deep magma formed near the mantle-core boundary. However, the melting behavior is highly controversial among previous studies: a laser-heated diamond anvil cell (LHDAC) study reported a melting curve with a dTm/dP of 30 K/GPa at zero pressure [1], while several theoretical computations gave substantially higher dTm/dP of 90 100 K/GPa [2,3]. We performed a series of LHDAC experiments for measurements of Tm of MgO under high pressure, using single crystal MgO as the starting material. The melting was detected by using micro-texture observations of the quenched samples. We found that the laser-heated area of the sample quenched from the Tm in previous LHDAC experiments [1] showed randomly aggregated granular crystals, which was not caused by melting, but by plastic deformation of the sample. This suggests that the Tms of their study were substantially underestimated. On the other hand, the sample recovered from the temperature higher by 1500-1700 K than the Tms in previous LHDAC experiments showed a characteristic internal texture comparable to the solidification texture typically shown in metal casting. We determined the Tms based on the observation of this texture up to 32 GPa. Fitting our Tms to the Simon equation yields dTm/dP of 82 K/GPa at zero pressure, which is consistent with those of the theoretical predictions (90 100 K/GPa) [2,3]. Extrapolation of the present melting curve of MgO to the pressure of the CMB (135 GPa) gives a melting temperature of 8900 K. The present steep melting slope offers the eutectic composition close to peridotite (in terms of Mg/Si ratio) throughout the lower mantle conditions. According to the model for sink/float relationship between the solid mantle and the magma [4], a considerable amount of iron (Fe/(Mg+Fe) > 0.24) is expected

  6. 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

  7. 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

  8. Annealing behavior of solution grown polyethylene single crystals

    NARCIS (Netherlands)

    Loos, J.; Tian, M.

    2006-01-01

    The morphology evolution of solution grown polyethylene single crystals has been studied upon annealing below their melting temperature by using atomic force microscopy (AFM). AFM investigations have been performed ex situ, which means AFM investigations at room temperature after the annealing

  9. Crystallization of poly(ethyleneterephthalate) modified with codiols

    NARCIS (Netherlands)

    Bouma, K.; Regelink, Marc; Gaymans, R.J.

    2001-01-01

    The nucleation of poly(ethylene terephthalate) (PET) by codiols and olefinic segments was studied. The codiols 1,5-pentanediol, 1,8-octanediol, 2,5-hexanediol, and 1,3-dihydroxymethyl benzene were copolymerized into PET in a concentration range of 0-10 mol %. The melting (Tm), crystallization (Tc),

  10. Growth of lead molybdate crystals by vertical Bridgman method

    Indian Academy of Sciences (India)

    Unknown

    The seeds were put in the seed wells, then the feed materials were filled in the cylinder of crucibles. The assembled crucible was sealed in order to prevent the volatilization of the melt during crystal growth. The cru- cible was installed in a refractory tube filled with Al2O3 powder to isolate it from external temperature fluctua-.

  11. Calorimetric studies of non-isothermal crystallization in amorphous

    Indian Academy of Sciences (India)

    Administrator

    the peak crystallization temperature. Amorphous alloys of Cu–Ti system are of special interest (Koster et al 1995) due to the fact that Cu–Ti is a congruently melting compound, which should allow static under-cooling experiments. Several works ... tion when mixed with another metal or rare earth metals. (Suzuki et al 2003).

  12. Crystal structure of (E-pent-2-enoic acid

    Directory of Open Access Journals (Sweden)

    Tim Peppel

    2015-05-01

    Full Text Available The molecule of the title compound, C5H8O2, a low-melting α,β-unsaturated carboxylic acid, is essentially planar [maximum displacement = 0.0239 (13 Å]. In the crystal, molecules are linked into centrosymmetric dimers via pairs of O—H...O hydrogen bonds.

  13. Crystallization and mechanical properties of biodegradable poly(p ...

    Indian Academy of Sciences (India)

    Effect of ome-POSS on the isothermal melt crystallization and dynamic mechanical properties of PPDO in the ... attracting more and more attention in recent times.12–14 Blen- ..... spent at Ts is enough to erase the crystalline memory of the.

  14. ZnO homoepitaxy on the O polar face of hydrothermal and melt-grown substrates by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, D.J. [Nanovation SARL, Orsay (France); Technical Univ. of Troyes (France); CNRS, Troyes (France); Hosseini Teherani, F. [Nanovation SARL, Orsay (France); Largeteau, A.; Demazeau, G. [ICMCB-CNRS, Bordeaux 1 University (Science and Technology), Pessac (France); Moisson, C.; Turover, D. [Novasic, Savoie Technolac, Arche Bat. 4, BP 267, Le Bourget du Lac (France); Nause, J. [Cermet Inc., Atlanta, GA (United States); Garry, G. [Thales Research, Domaine de Corbeville, Orsay (France); Kling, R.; Gruber, T. [Ulm University, Department of Semiconductor Physics, Ulm (Germany); Waag, A. [Braunschweig Technical University, Institute of Semiconductor Technology, Braunschweig (Germany); Jomard, F.; Galtier, P.; Lusson, A. [LPSC-CNRS, Meudon (France); Monteiro, T.; Soares, M.J.; Neves, A.; Carmo, M.C.; Peres, M. [University of Aveiro, Physics Department, Aveiro (Portugal); Lerondel, G.; Hubert, C. [Technical University of Troyes-CNRS (FRE2671), 12 rue Marie Curie, BP 2060, Troyes (France)

    2007-07-15

    2 cm diameter hydrothermal ZnO crystals were grown and then made into substrates using both mechanical and chemical-mechanical polishing (CMP). CMP polishing showed superior results with an (0002) {omega} scan full width half maximum (FWHM) of 67 arcsec and an root mean square (RMS) roughness of 2 Aa. In comparison, commercial melt-grown substrates exhibited broader X-ray diffraction (XRD) linewidths with evidence of sub-surface crystal damage due to polishing, including a downward shift of c-lattice parameter. Secondary ion mass spectroscopy revealed strong Li, Fe, Co, Al and Si contamination in the hydrothermal crystals as opposed to the melt-grown substrates, for which glow discharge mass spectroscopy studies had reported high levels of Pb, Fe, Cd and Si. Low temperature photoluminescence (PL) studies indicated that the hydrothermal crystal had high defect and/or impurity concentrations compared with the melt-grown substrate. The dominant bound exciton for the melt-grown substrate was indexed to Al. ZnO films were grown using pulsed laser deposition. The melt-grown substrates gave superior results with XRD (0002) {omega} and 2{theta}/{omega} WHM of 124 and 34 arcsec, respectively. Atomic force microscope measurements indicated a low RMS roughness (1.9 nm) as confirmed by fringes in the XRD 2{theta}/{omega} scan. It was suggested that the improvement in XRD response relative to the substrate might be due to ''healing'' of sub-surface polishing damage due to the elevated T{sub s} used for the growth. Indeed the c-lattice parameter for the homoepitaxial layer on the melt-grown substrate had become that which would be expected for strain-free ZnO. Furthermore, the stability of the PL peak positions relative to bulk ZnO, confirmed that the films appear practically strain free. (orig.)

  15. 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.

  16. 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.

  17. Mathematical modeling and numerical simulation of Czochralski Crystal Growth

    Energy Technology Data Exchange (ETDEWEB)

    Jaervinen, J.; Nieminen, R. [Center for Scientific Computing, Espoo (Finland)

    1996-12-31

    A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)

  18. Mathematical modeling and numerical simulation of Czochralski Crystal Growth

    Energy Technology Data Exchange (ETDEWEB)

    Jaervinen, J; Nieminen, R [Center for Scientific Computing, Espoo (Finland)

    1997-12-31

    A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)

  19. 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

  20. Systematic Study of the PbWO4 Crystal Short Term Instalibity Under Irradiation

    CERN Document Server

    Annenkov, Alexander; Chipaux, Rémi; Drobychev, Gleb; Fedorov, Andrey; Géléoc, Marie; Golubev, Nikolai; Korzhik, Mikhail; Lecoq, Paul; Ligun, A B; Missevitch, Oleg; Pavlenko, V B; Peigneux, Jean-Pierre; Singovsky, Alexander

    1997-01-01

    The effect of the irradiation on the lead tungstate ( PWO) scintillator properties has been studied at different irradiation facilities. Lead tungstate crystals grown with the tuning of oxides content in the melt to the stoichiometry of pure sheelite or sheelite-like type crystals and doped with heterovalent, trivalent and pentavalent impurities have been studied in order to optimize their resistance to irradiation. A combination of a selective cleaning of raw materials, a tuning of the melt from crystallization to crystallisation, and a destruction or compensation of the point structure defects has been used to minimize the short-term instability of PWO parameters under irradiation.