A coupled model on fluid flow, heat transfer and solidification in continuous casting mold

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Xu-bin Zhang

2017-11-01

Full Text Available Fluid flow, heat transfer and solidification of steel in the mold are so complex but crucial, determining the surface quality of the continuous casting slab. In the current study, a 2D numerical model was established by Fluent software to simulate the fluid flow, heat transfer and solidification of the steel in the mold. The VOF model and k-ε model were applied to simulate the flow field of the three phases (steel, slag and air, and solidification model was used to simulate the solidification process. The phenomena at the meniscus were also explored through interfacial tension between the liquid steel and slag as well as the mold oscillation. The model included a 20 mm thick mold to clarify the heat transfer and the temperature distribution of the mold. The simulation results show that the liquid steel flows as upper backflow and lower backflow in the mold, and that a small circulation forms at the meniscus. The liquid slag flows away from the corner at the meniscus or infiltrates into the gap between the mold and the shell with the mold oscillating at the negative strip stage or at the positive strip stage. The simulated pitch and the depth of oscillation marks approximate to the theoretical pitch and measured depth on the slab.

Molecular Dynamics Simulation of Binary Fluid in a Nanochannel

International Nuclear Information System (INIS)

Mullick, Shanta; Ahluwalia, P. K.; Pathania, Y.

2011-01-01

This paper presents the results from a molecular dynamics simulation of binary fluid (mixture of argon and krypton) in the nanochannel flow. The computational software LAMMPS is used for carrying out the molecular dynamics simulations. Binary fluids of argon and krypton with varying concentration of atom species were taken for two densities 0.65 and 0.45. The fluid flow takes place between two parallel plates and is bounded by horizontal walls in one direction and periodic boundary conditions are imposed in the other two directions. To drive the flow, a constant force is applied in one direction. Each fluid atom interacts with other fluid atoms and wall atoms through Week-Chandler-Anderson (WCA) potential. The velocity profile has been looked at for three nanochannel widths i.e for 12σ, 14σ and 16σ and also for the different concentration of two species. The velocity profile of the binary fluid predicted by the simulations agrees with the quadratic shape of the analytical solution of a Poiseuille flow in continuum theory.

Homogeneous nucleation ahead of the solid-liquid interface during rapid solidification of binary alloys

International Nuclear Information System (INIS)

Smith, P.M.; Elmer, J.W.

1996-01-01

In recent rapid solidification experiments on Al-5%Be alloys, a Liquid Phase Nucleation (LPN) model was developed to explain the formation of periodic arrays of randomly-oriented Be-rich particles in an Al-rich matrix. In the LPN model, Be droplets were assumed to nucleate in the liquid ahead of the solid-liquid interface, but no justification for this was given. Here the authors present a model which considers the geometric constraints (imposed by proximity to the interface) on the number of solute atoms available to form a nucleus. Calculations based on this model predict that nucleation of second-phase particles can be most likely a short distance ahead of the interface in immiscible binary systems such as Al-Be. As part of the nucleation calculations, a semi-empirical method of calculating solid-liquid surface tensions in binary systems was developed, and is presented in the Appendix

General characteristics of eutectic alloy solidification mechanisms

International Nuclear Information System (INIS)

Lemaignan, Clement.

1977-01-01

The eutectic alloy sodification was studied in binary systems: solidification of non facetted - non facetted eutectic alloy (theoretical aspects, variation of the lamellar spacing, crystallographic relation between the various phases); solidification of facetted - non facetted eutectic alloy; coupled growth out of eutectic alloy; eutectic nucleation [fr

Solidification paths of multicomponent monotectic aluminum alloys

Energy Technology Data Exchange (ETDEWEB)

Mirkovic, Djordje; Groebner, Joachim [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Street 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, Rainer [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Street 42, D-38678 Clausthal-Zellerfeld (Germany)], E-mail: schmid-fetzer@tu-clausthal.de

2008-10-15

Solidification paths of three ternary monotectic alloy systems, Al-Bi-Zn, Al-Sn-Cu and Al-Bi-Cu, are studied using thermodynamic calculations, both for the pertinent phase diagrams and also for specific details concerning the solidification of selected alloy compositions. The coupled composition variation in two different liquids is quantitatively given. Various ternary monotectic four-phase reactions are encountered during solidification, as opposed to the simple binary monotectic, L' {yields} L'' + solid. These intricacies are reflected in the solidification microstructures, as demonstrated for these three aluminum alloy systems, selected in view of their distinctive features. This examination of solidification paths and microstructure formation may be relevant for advanced solidification processing of multicomponent monotectic alloys.

Crystal Growth and Fluid Mechanics Problems in Directional Solidification

Science.gov (United States)

Tanveer, Saleh A.; Baker, Gregory R.; Foster, Michael R.

2001-01-01

Our work in directional solidification has been in the following areas: (1) Dynamics of dendrites including rigorous mathematical analysis of the resulting equations; (2) Examination of the near-structurally unstable features of the mathematically related Hele-Shaw dynamics; (3) Numerical studies of steady temperature distribution in a vertical Bridgman device; (4) Numerical study of transient effects in a vertical Bridgman device; (5) Asymptotic treatment of quasi-steady operation of a vertical Bridgman furnace for large Rayleigh numbers and small Biot number in 3D; and (6) Understanding of Mullins-Sererka transition in a Bridgman device with fluid dynamics is accounted for.

Finite-element solidification modelling of metals and binary alloys

International Nuclear Information System (INIS)

Mathew, P.M.

1986-12-01

In the Canadian Nuclear Fuel Waste Management Program, cast metals and alloys are being evaluated for their ability to support a metallic fuel waste container shell under disposal vault conditions and to determine their performance as an additional barrier to radionuclide release. These materials would be cast to fill residual free space inside the container and allowed to solidify without major voids. To model their solidification characteristics following casting, a finite-element model, FAXMOD-3, was adopted. Input parameters were modified to account for the latent heat of fusion of the metals and alloys considered. This report describes the development of the solidification model and its theoretical verification. To model the solidification of pure metals and alloys that melt at a distinct temperature, the latent heat of fusion was incorporated as a double-ramp function in the specific heat-temperature relationship, within an interval of +- 1 K around the solidification temperature. Comparison of calculated results for lead, tin and lead-tin eutectic melts, unidirectionally cooled with and without superheat, showed good agreement with an alternative technique called the integral profile method. To model the solidification of alloys that melt over a temperature interval, the fraction of solid in the solid-liquid region, as calculated from the Scheil equation, was used to determine the fraction of latent heat to be liberated over a temperature interval within the solid-liquid zone. Comparison of calculated results for unidirectionally cooled aluminum-4 wt.% copper melt, with and without superheat, showed good agreement with alternative finite-difference techniques

A numerical analysis of an anisotropic phase-field model for binary-fluid mixtures in the presence of magnetic-field

OpenAIRE

Belmiloudi , Aziz; Rasheed , Amer

2015-01-01

In this paper we propose a numerical scheme and perform its numerical analysis devoted to an anisotropic phase-field model with convection under the influence of magnetic field for the isother-mal solidification of binary mixtures in two-dimensional geometry. Precisely, the numerical stability and error analysis of this approximation scheme which is based on mixed finite-element method are performed. The particular application of a nickelcopper (NiCu) binary alloy, with real physical paramete...

Hydrodynamic 'memory' of binary fluid mixtures

International Nuclear Information System (INIS)

Kalashnik, M. V.; Ingel, L. Kh.

2006-01-01

A theoretical analysis is presented of hydrostatic adjustment in a two-component fluid system, such as seawater stratified with respect to temperature and salinity. Both linear approximation and nonlinear problem are investigated. It is shown that scenarios of relaxation to a hydrostatically balanced state in binary fluid mixtures may substantially differ from hydrostatic adjustment in fluids that can be stratified only with respect to temperature. In particular, inviscid two-component fluids have 'memory': a horizontally nonuniform disturbance in the initial temperature or salinity distribution does not vanish even at the final stage, transforming into a persistent thermohaline 'trace.' Despite stability of density stratification and convective stability of the fluid system by all known criteria, an initial temperature disturbance may not decay and may even increase in amplitude. Moreover, its sign may change (depending on the relative contributions of temperature and salinity to stable background density stratification). Hydrostatic adjustment may involve development of discontinuous distributions from smooth initial temperature or concentration distributions. These properties of two-component fluids explain, in particular, the occurrence of persistent horizontally or vertically nonuniform temperature and salinity distributions in the ocean, including discontinuous ones

nth-Nearest neighbour distribution functions of a binary fluid mixture ...

Indian Academy of Sciences (India)

Administrator

for ob- taining the NND functions for single component flu- ids, to binary fluid mixtures. The MD simulation and computation details are presented in section 4. Results are elaborated in section 5 and conclusions are provided in section 6. 2. n-Particle distribution function. Considering a binary system of Nα and Nβ particles.

Choice of optimal working fluid for binary power plants at extremely low temperature brine

Science.gov (United States)

Tomarov, G. V.; Shipkov, A. A.; Sorokina, E. V.

2016-12-01

The geothermal energy development problems based on using binary power plants utilizing lowpotential geothermal resources are considered. It is shown that one of the possible ways of increasing the efficiency of heat utilization of geothermal brine in a wide temperature range is the use of multistage power systems with series-connected binary power plants based on incremental primary energy conversion. Some practically significant results of design-analytical investigations of physicochemical properties of various organic substances and their influence on the main parameters of the flowsheet and the technical and operational characteristics of heat-mechanical and heat-exchange equipment for binary power plant operating on extremely-low temperature geothermal brine (70°C) are presented. The calculation results of geothermal brine specific flow rate, capacity (net), and other operation characteristics of binary power plants with the capacity of 2.5 MW at using various organic substances are a practical interest. It is shown that the working fluid selection significantly influences on the parameters of the flowsheet and the operational characteristics of the binary power plant, and the problem of selection of working fluid is in the search for compromise based on the priorities in the field of efficiency, safety, and ecology criteria of a binary power plant. It is proposed in the investigations on the working fluid selection of the binary plant to use the plotting method of multiaxis complex diagrams of relative parameters and characteristic of binary power plants. Some examples of plotting and analyzing these diagrams intended to choose the working fluid provided that the efficiency of geothermal brine is taken as main priority.

Calculation of solidification microstructure maps for the system Al-Fe-Si

International Nuclear Information System (INIS)

Gilgien, P.

1996-01-01

Computer programs have been developed in order to calculate solidification microstructure maps for binary and ternary alloys. These programs are based on recent analytical models for the constrained growth of dendrites and eutectics. Due to the importance of phase diagrams data, programs for the calculation of growth kinetics are coupled with ThermoCalc, a commercial software for phase diagram calculations. These programs have been used to calculate a solidification microstructure map for the Al-Fe system from 0 to 4 at%Fe. Comparison of the calculated results with an experimental solidification microstructure map from the literature shows that all microstructure transitions were predicted. Nevertheless there remain significant discrepancies between some calculated and experimental transition velocities. The programs were also used to calculate solidification microstructure maps in the Al-rich corner of the Al-Fe-Si system (0 to 8 at% Fe and 0 to 8 at% Si). In this case also, calculated results were in satisfactory agreement with experimental solidification microstructure maps, although the comparison was only partial since experimental ternary microstructure maps are less complete than for the binary system, and because the available thermodynamic database does not, as yet, include metastable phases. Laser surface remelting experiments were carried out on an Al-4 at% Fe alloy in order to link results from the literature, obtained at high solidification rates by laser surface remelting and at low solidification rates by Bridman experiments. Finally, Bridman experiments were carried out with an Al-2.63 wt% Fe alloy in order to determine the critical velocity at which a planar Al-Al 13 Fe 4 eutectic front is destabilised in a cellular eutectic by a small amount of Si. The critical solidification velocity thus obtained was in agreement with a criterion of constitutional undercooling. (author) figs., tabs., refs

Three-dimensional phase-field simulations of directional solidification

Science.gov (United States)

Plapp, Mathis

2007-05-01

The phase-field method has become the method of choice for simulating microstructural pattern formation during solidification. One of its main advantages is that time-dependent three-dimensional simulations become feasible, which makes it possible to address long-standing questions of pattern stability and pattern selection. Here, a brief introduction to the phase-field model and its implementation is given, and its capabilities are illustrated by examples taken from the directional solidification of binary alloys. In particular, the morphological stability of hexagonal cellular arrays and of eutectic lamellar patterns is investigated.

Advanced modeling of solidification

International Nuclear Information System (INIS)

Bousquet-Melou, P.; Fichot, F.; Goyeau, B.; Gobin, D.; Quintard, M.

2001-01-01

A theoretical and numerical macroscopic modeling of the solidification of binary mixtures is presented. The growth of a solid-liquid region (mushy zone), represented by a non-homogeneous porous medium, is considered. A macroscopic model for momentum, heat and mass transfer during solidification is derived using the volume averaging method, and the effective transport properties (permeability, effective diffusivities, mass exchange coefficients) are defined by associated closure problems (set of microscopic balance equations). Consequently, the effects of the dendritic geometry (tortuosity) and of microscopic transfer phenomena (dispersion, interfacial exchange) are introduced in the averaged balance equations and in the representation of the effective transport coefficients. This closure method provides an original approach of solidification modeling. The resulting macroscopic model is based on the local thermal equilibrium assumption (one-temperature model) while a two-phase description of macroscopic species transfer is introduced using solid and liquid mass exchange coefficients. The phase diagram is used to predict the solid and liquid equilibrium concentrations at the solid-liquid interface. This two-phase approach extends the classical limiting cases that correspond to the lever-rule and Scheil descriptions. (authors)

Grain Floatation During Equiaxed Solidification of an Al-Cu Alloy in a Side-Cooled Cavity: Part II—Numerical Studies

Science.gov (United States)

Kumar, Arvind; Walker, Mike J.; Sundarraj, Suresh; Dutta, Pradip

2011-08-01

In this article, a single-phase, one-domain macroscopic model is developed for studying binary alloy solidification with moving equiaxed solid phase, along with the associated transport phenomena. In this model, issues such as thermosolutal convection, motion of solid phase relative to liquid and viscosity variations of the solid-liquid mixture with solid fraction in the mobile zone are taken into account. Using the model, the associated transport phenomena during solidification of Al-Cu alloys in a rectangular cavity are predicted. The results for temperature variation, segregation patterns, and eutectic fraction distribution are compared with data from in-house experiments. The model predictions compare well with the experimental results. To highlight the influence of solid phase movement on convection and final macrosegregation, the results of the current model are also compared with those obtained from the conventional solidification model with stationary solid phase. By including the independent movement of the solid phase into the fluid transport model, better predictions of macrosegregation, microstructure, and even shrinkage locations were obtained. Mechanical property prediction models based on microstructure will benefit from the improved accuracy of this model.

Evolution of solidification texture during additive manufacturing

Science.gov (United States)

Wei, H. L.; Mazumder, J.; DebRoy, T.

2015-01-01

Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components. PMID:26553246

Integral solution of equiaxed solidification with an interface kinetics model for nuclear waste management

International Nuclear Information System (INIS)

Naterer, G.F.

1996-01-01

In this paper, a one-dimensional analysis of energy and species transport during binary dendritic solidification is presented and compared to experimental results. The paper's objective is a continuation of previous studies of solidification control for the waste management of nuclear materials in the underground disposal concept. In the present analysis, interface kinetics at the solid - liquid interface accounts for recalescent thermal behaviour during solidification. The theoretical results were compared to available experimental results and the agreement appears fair although some discrepancies have been attributed to uncertainties with thermophysical properties. (author)

Simulating the Effect of Space Vehicle Environments on Directional Solidification of a Binary Alloy

Science.gov (United States)

Westra, D. G.; Heinrich, J. C.; Poirier, D. R.

2003-01-01

Space microgravity missions are designed to provide a microgravity environment for scientific experiments, but these missions cannot provide a perfect environment, due to vibrations caused by crew activity, on-board experiments, support systems (pumps, fans, etc.), periodic orbital maneuvers, and water dumps. Therefore, it is necessary to predict the impact of these vibrations on space experiments, prior to performing them. Simulations were conducted to study the effect of the vibrations on the directional solidification of a dendritic alloy. Finite element ca!cu!attie?ls were dme with a simd2titcr based on a continuum model of dendritic solidification, using the Fractional Step Method (FSM). The FSM splits the solution of the momentum equation into two steps: the viscous intermediate step, which does not enforce continuity; and the inviscid projection step, which calculates the pressure and enforces continuity. The FSM provides significant computational benefits for predicting flows in a directionally solidified alloy, compared to other methods presently employed, because of the efficiency gains in the uncoupled solution of velocity and pressure. finite differences, arises when the interdendritic liquid reaches the eutectic temperature and concentration. When a node reaches eutectic temperature, it is assumed that the solidification of the eutectic liquid continues at constant temperature until all the eutectic is solidified. With this approach, solidification is not achieved continuously across an element; rather, the element is not considered solidified until the eutectic isotherm overtakes the top nodes. For microgravity simulations, where the convection is driven by shrinkage, it introduces large variations in the fluid velocity. When the eutectic isotherm reaches a node, all the eutectic must be solidified in a short period, causing an abrupt increase in velocity. To overcome this difficulty, we employed a scheme to numerically predict a more accurate value

Fluid mechanics of directional solidification at reduced gravity

Science.gov (United States)

Chen, C. F.

1992-01-01

The primary objective of the proposed research is to provide additional groundbased support for the flight experiment 'Casting and Solidification Technology' (CAST). This experiment is to be performed in the International Microgravity Laboratory-1 (IML-1) scheduled to be flown on a space shuttle mission scheduled for 1992. In particular, we will provide data on the convective motion and freckle formation during directional solidification of NH4Cl from its aqueous solution at simulated parameter ranges equivalent to reducing the gravity from the sea-level value down to 0.1 g or lower. The secondary objectives of the proposed research are to examine the stability phenomena associated with the onset of freckles and the mechanisms for their subsequent growth and decline (to eventual demise of some) by state-of-the-art imaging techniques and to formulate mathematical models for the prediction of the observed phenomena.

Species redistribution during solidification of nuclear fuel waste metal castings

Energy Technology Data Exchange (ETDEWEB)

Naterer, G F; Schneider, G E [Waterloo Univ., ON (Canada)

1994-12-31

An enthalpy-based finite element model and a binary system species redistribution model are developed and applied to problems associated with solidification of nuclear fuel waste metal castings. Minimal casting defects such as inhomogeneous solute segregation and cracks are required to prevent container corrosion and radionuclide release. The control-volume-based model accounts for equilibrium solidification for low cooling rates and negligible solid state diffusion for high cooling rates as well as intermediate conditions. Test problems involving nuclear fuel waste castings are investigated and correct limiting cases of species redistribution are observed. (author). 11 refs., 1 tab., 13 figs.

Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients

Energy Technology Data Exchange (ETDEWEB)

Dan Wendt; Greg Mines

2011-10-01

Effect of Mixed Working Fluid Composition on Binary Cycle Condenser Heat Transfer Coefficients Dan Wendt, Greg Mines Idaho National Laboratory The use of mixed working fluids in binary power plants can provide significant increases in plant performance, provided the heat exchangers are designed to take advantage of these fluids non-isothermal phase changes. In the 1980's testing was conducted at DOE's Heat Cycle Research Facility (HCRF) where mixtures of different compositions were vaporized at supercritical pressures and then condensed. This testing had focused on using the data collected to verify that Heat Transfer Research Incorporated (HTRI) codes were suitable for the design of heat exchangers that could be used with mixtures. The HCRF data includes mixture compositions varying from 0% to 40% isopentane and condenser tube orientations of 15{sup o}, 60{sup o}, and 90{sup o} from horizontal. Testing was performed over a range of working fluid and cooling fluid conditions. Though the condenser used in this testing was water cooled, the working fluid condensation occurred on the tube-side of the heat exchanger. This tube-side condensation is analogous to that in an air-cooled condenser. Tube-side condensing heat transfer coefficient information gleaned from the HCRF testing is used in this study to assess the suitability of air-cooled condenser designs for use with mixtures. Results of an air-cooled binary plant process model performed with Aspen Plus indicate that that the optimal mixture composition (producing the maximum net power for the scenario considered) is within the range of compositions for which data exist. The HCRF data is used to assess the impact of composition, tube orientation, and process parameters on the condensing heat transfer coefficients. The sensitivity of the condensing coefficients to these factors is evaluated and the suitability of air-cooled condenser designs with mixtures is assessed. This paper summarizes the evaluation

Effect of Temperature and Fluid Flow on Dendrite Growth During Solidification of Al-3 Wt Pct Cu Alloy by the Two-Dimensional Cellular Automaton Method

Science.gov (United States)

Gu, Cheng; Wei, Yanhong; Liu, Renpei; Yu, Fengyi

2017-12-01

A two-dimensional cellular automaton-finite volume model was developed to simulate dendrite growth of Al-3 wt pct Cu alloy during solidification to investigate the effect of temperature and fluid flow on dendrite morphology, solute concentration distribution, and dendrite growth velocity. Different calculation conditions that may influence the results of the simulation, including temperature and flow, were considered. The model was also employed to study the effect of different undercoolings, applied temperature fields, and forced flow velocities on solute segregation and dendrite growth. The initial temperature and fluid flow have a significant impact on the dendrite morphologies and solute profiles during solidification. The release of energy is operated with solidification and results in the increase of temperature. A larger undercooling leads to larger solute concentration near the solid/liquid interface and solute concentration gradient at the same time-step. Solute concentration in the solid region tends to increase with the increase of undercooling. Four vortexes appear under the condition when natural flow exists: the two on the right of the dendrite rotate clockwise, and those on the left of the dendrite rotate counterclockwise. With the increase of forced flow velocity, the rejected solute in the upstream region becomes easier to be washed away and enriched in the downstream region, resulting in acceleration of the growth of the dendrite in the upstream and inhibiting the downstream dendrite growth. The dendrite perpendicular to fluid flow shows a coarser morphology in the upstream region than that of the downstream. Almost no secondary dendrite appears during the calculation process.

Phase-field modelling of β(Ti) solidification in Ti-45at.%Al: columnar dendrite growth at various gravity levels

Science.gov (United States)

Viardin, A.; Berger, R.; Sturz, L.; Apel, M.; Hecht, U.

2016-03-01

The effect of solutal convection on the solidification of γ titanium aluminides, specifically on β(Ti) dendrite growth, is not well known. With the aim of supporting directional solidification experiments under hyper-gravity using a large diameter centrifuge, 2D-phase field simulations of β(Ti) dendrite growth have been performed for the binary alloy Ti-45at.%Al and various gravity scenarios. Both, the direction and magnitude of the gravity vector were varied systematically in order to reveal the subtle interplay between the convective flow pattern and mushy zone characteristics. In this presentation, gravity effects are discussed for early dendrite growth. For selected cases the evolution on longer timescales is also analyse of and oscillatory modes leading to dynamically stable steady state growth are outlined. In a dedicated simulation series forced flow is superimposed, as to mimic thermally driven fluid flow expected to establish on the macroscopic scale (sample size) in the centrifugal experiments. Above a certain threshold this flow turns dominant and precludes solutally driven convective effects.

Development of sodium disposal technology. Experiment of sodium compound solidification process

International Nuclear Information System (INIS)

Matsumoto, Toshiyuki; Ohura, Masato; Yatoh, Yasuo

2007-07-01

A large amount of sodium containing radioactive waste will come up at the time of final shutdown/decommission of FBR plant. The radioactive waste is managed as solid state material in a closed can in Japan. As for the sodium, there is no established method to convert the radioactive sodium to solid waste. Further, the sodium is highly reactive. Thus, it is recommended to convert the sodium to a stable substance before the solidification process. One of the stabilizing methods is conversion of sodium into sodium hydroxide solution. These stabilization and solidification processes should be safe, economical, and efficient. In order to develop such sodium disposal technology, nonradioactive sodium was used and a basic experiment was performed. Waste-fluid Slag Solidification method was employed as the solidification process of sodium hydroxide solution. Experimental parameters were mixing ratio of the sodium hydroxide and the slag solidification material, temperature and concentration of the sodium hydroxide. The best parameters were obtained to achieve the maximum filling ratio of the sodium hydroxide under a condition of enough high compressive strength of the solidified waste. In a beaker level test, the solidified waste was kept in a long term and it was shown that there was no change of appearance, density, and also the compressive strength was kept at a target value. In a real scale test, homogeneous profiles of the density and the compressive strength were obtained. The compressive strength was higher than the target value. It was shown that the Waste-fluid Slag Solidification method can be applied to the solidification process of the sodium hydroxide solution, which was produced by the stabilization process. (author)

Uniform phases in fluids of hard isosceles triangles: One-component fluid and binary mixtures

Science.gov (United States)

Martínez-Ratón, Yuri; Díaz-De Armas, Ariel; Velasco, Enrique

2018-05-01

We formulate the scaled particle theory for a general mixture of hard isosceles triangles and calculate different phase diagrams for the one-component fluid and for certain binary mixtures. The fluid of hard triangles exhibits a complex phase behavior: (i) the presence of a triatic phase with sixfold symmetry, (ii) the isotropic-uniaxial nematic transition is of first order for certain ranges of aspect ratios, and (iii) the one-component system exhibits nematic-nematic transitions ending in critical points. We found the triatic phase to be stable not only for equilateral triangles but also for triangles of similar aspect ratios. We focus the study of binary mixtures on the case of symmetric mixtures: equal particle areas with aspect ratios (κi) symmetric with respect to the equilateral one, κ1κ2=3 . For these mixtures we found, aside from first-order isotropic-nematic and nematic-nematic transitions (the latter ending in a critical point): (i) a region of triatic phase stability even for mixtures made of particles that do not form this phase at the one-component limit, and (ii) the presence of a Landau point at which two triatic-nematic first-order transitions and a nematic-nematic demixing transition coalesce. This phase behavior is analogous to that of a symmetric three-dimensional mixture of rods and plates.

On the role of solidification modelling in Integrated Computational Materials Engineering “ICME”

International Nuclear Information System (INIS)

Schmitz, G J; Böttger, B; Apel, M

2016-01-01

Solidification during casting processes marks the starting point of the history of almost any component or product. Integrated Computational Materials Engineering (ICME) [1-4] recognizes the importance of further tracking the history of microstructure evolution along the subsequent process chain. Solidification during joining processes in general happens quite late during production, where the parts to be joined already have experienced a number of processing steps which affected their microstructure. Reliable modelling of melting and dissolution of these microstructures represents a key issue before eventually modelling ‘re’-solidification e.g. during welding or soldering. Some instructive examples of microstructure evolution during a joining process obtained on the basis of synthetic and simulated initial microstructures of an Al-Cu binary model system are discussed. (paper)

Thermosolutal convection during dendritic solidification

Science.gov (United States)

Heinrich, J. C.; Nandapurkar, P.; Poirier, D. R.; Felicelli, S.

1989-01-01

This paper presents a mathematical model for directional solidification of a binary alloy including a dendritic region underlying an all-liquid region. It is assumed initially that there exists a nonconvecting state with planar isotherms and isoconcentrates solidifying at a constant velocity. The stability of this system has been analyzed and nonlinear calculations are performed that show the effect of convection in the solidification process when the system is unstable. Results of calculations for various cases defined by the initial temperature gradient at the dendrite tips and varying strength of the gravitational field are presented for systems involving lead-tin alloys. The results show that the systems are stable for a gravitational constant of 0.0001 g(0) and that convection can be suppressed by appropriate choice of the container's size for higher values of the gravitational constant. It is also concluded that for the lead-tin systems considered, convection in the mushy zone is not significant below the upper 20 percent of the dendritic zone, if al all.

Binary non-additive hard sphere mixtures: fluid demixing, asymptotic decay of correlations and free fluid interfaces

International Nuclear Information System (INIS)

Hopkins, Paul; Schmidt, Matthias

2010-01-01

Using a fundamental measure density functional theory we investigate both bulk and inhomogeneous systems of the binary non-additive hard sphere model. For sufficiently large (positive) non-additivity the mixture phase separates into two fluid phases with different compositions. We calculate bulk fluid-fluid coexistence curves for a range of size ratios and non-additivity parameters and find that they compare well to simulation results from the literature. Using the Ornstein-Zernike equation, we investigate the asymptotic, r→∞, decay of the partial pair correlation functions, g ij (r). At low densities a structural crossover occurs in the asymptotic decay between two different damped oscillatory modes with different wavelengths corresponding to the two intra-species hard-core diameters. On approaching the fluid-fluid critical point there is a Fisher-Widom crossover from exponentially damped oscillatory to monotonic asymptotic decay. Using the density functional we calculate the density profiles for the planar free fluid-fluid interface between coexisting fluid phases. We show that the type of asymptotic decay of g ij (r) not only determines the asymptotic decay of the interface profiles, but is also relevant for intermediate and even short-ranged behaviour. We also determine the surface tension of the free fluid interface, finding that it increases with non-additivity, and that on approaching the critical point mean-field scaling holds.

Microstructure and corrosion properties of as sub-rapid solidification Mg-Zn-Y-Nd alloy in dynamic simulated body fluid for vascular stent application.

Science.gov (United States)

Wang, Jun; Wang, Liguo; Guan, Shaokang; Zhu, Shijie; Ren, Chenxing; Hou, Shusen

2010-07-01

Magnesium alloy stent has been employed in animal and clinical experiment in recent years. It has been verified to be biocompatible and degradable due to corrosion after being implanted into blood vessel. Mg-Y-Gd-Nd alloy is usually used to construct an absorbable magnesium alloy stent. However, the corrosion resistant of as cast Mg-Y-Gd-Nd alloy is poor relatively and the control of corrosion rate is difficult. Aiming at the requirement of endovascular stent in clinic, a new biomedical Mg-Zn-Y-Nd alloy with low Zn and Y content (Zn/Y atom ratio 6) was designed, which exists quasicrystals to improve its corrosion resistance. Additionally, sub-rapid solidification processing was applied for preparation of corrosion-resisting Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys. Compared with the as cast sample, the corrosion behavior of alloys in dynamic simulated body fluid (SBF) (the speed of body fluid: 16 ml/800 ml min(-1)) was investigated. The results show that as sub-rapid solidification Mg-Zn-Y-Nd alloy has the better corrosion resistance in dynamic SBF due to grain refinement and fine dispersion distribution of the quasicrystals and intermetallic compounds in alpha-Mg matrix. In the as cast sample, both Mg-Zn-Y-Nd and Mg-Y-Gd-Nd alloys exhibit poor corrosion resistance. Mg-Zn-Y-Nd alloy by sub-rapid solidification processing provides excellent corrosion resistance in dynamic SBF, which open a new window for biomedical materials design, especially for vascular stent application.

Dendritic solidification in undercooled Ni-Zr-Al melts: Experiments and modeling

Energy Technology Data Exchange (ETDEWEB)

Galenko, P.K., E-mail: Peter.Galenko@dlr.de [Institut fuer Materialsphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), D-51170 Koeln (Germany); Reutzel, S.; Herlach, D.M. [Institut fuer Materialsphysik im Weltraum, Deutsches Zentrum fuer Luft- und Raumfahrt (DLR), D-51170 Koeln (Germany); Fries, S.G. [ICAMS, Ruhr-Universitaet Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany)] [SGF Scientific Consultancy, Arndtstr 9, D-52064 Aachen (Germany); Steinbach, I. [ICAMS, Ruhr-Universitaet Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany); Apel, M. [ACCESS eV, Intzestrasse 5, D-52072 Aachen (Germany)

2009-12-15

The kinetics of dendritic solidification in a ternary Ni{sub 98}Zr{sub 1}Al{sub 1} alloy is investigated experimentally in a range of melt undercoolings 40K{<=}{Delta}T{<=}320K. The growth velocity is measured for samples processed by the electromagnetic levitation technique using a high-speed video camera. With {Delta}T{<=}220K the measured growth rates are the same as those of a binary Ni{sub 99}Zr{sub 1} alloy. In the regime of rapid solidification, especially within the regime of thermal dendritic growth at {Delta}T{>=}220K, growth rates are decreased. Sharp-interface modeling predicts growth rates over the whole range of undercooling. Phase-field simulations give quantitative predictions for the dendritic growth velocity in the solute-controlled growth regime. Results show that the composition and temperature dependency of the thermodynamic data, e.g. liquidus slope and solute partition coefficient, are important for describing the alloys. Our findings give improved sharp-interface model predictions compared to calculations based on an approximation of the thermodynamic data derived from binary phase diagrams.

Modeling and optimization of geothermal power plants using the binary fluid cycle

Energy Technology Data Exchange (ETDEWEB)

Walter, R.A.

1976-09-01

A computer simulation of a binary fluid cycle power plant for use with geothermal energy sources, and the subsequent optimization of this power plant type over a range of geothermal source conditions are described. The optimization technique employed for this analysis was based upon the principle of maximum use of geothermal energy.

Modeling of solidification of MMC composites during gravity casting process

Directory of Open Access Journals (Sweden)

R. Zagórski

2013-04-01

Full Text Available The paper deals with computer simulation of gravity casting of the metal matrix composites reinforced with ceramics (MMC into sand mold. The subject of our interest is aluminum matrix composite (AlMMC reinforced with ceramic particles i.e. silicon carbide SiC and glass carbon Cg. The created model describes the process taking into account solidification and its influence on the distribution of reinforcement particles. The computer calculation has been carried out in 2D system with the use of Navier-Stokes equations using ANSYS FLUENT 13. The Volume of Fluid approach (VOF and enthalpy method have been used to model the air-fluid free surface (and also volume fraction of particular continuous phases and the solidification of the cast, respectively.

Self-consistent theory of steady-state lamellar solidification in binary eutectic systems

International Nuclear Information System (INIS)

Nash, G.E.; Glicksman, M.E.

1976-01-01

The potential theoretic methods developed recently at NRL for solving the diffusion equation are applied to the free-boundary problem describing lamellar eutectic solidification. Using these techniques, the original boundary value problem is reduced to a set of coupled integro-differential equations for the shape of the solid/liquid interface and various quantities defined on the interface. The behavior of the solutions is discussed in a qualitative fashion, leading to some interesting inferences regarding the nature of the eutectic solidification process. Using the information obtained from the analysis referred to above, an approximate theory of the lamellar-rod transition is formulated. The predictions of the theory are shown to be in qualitative agreement with experimental observations of this transition. In addition, a simplified version of the general integro-differential equations is developed and is used to assess the effect of interface curvature on the interfacial solute concentrations, and to check the new theory for consistency with experiment

Turbidity of a Binary Fluid Mixture: Determining Eta

Science.gov (United States)

Jacobs, Donald T.

1996-01-01

A ground based (1-g) experiment is in progress that will measure the turbidity of a density-matched, binary fluid mixture extremely close to its liquid-liquid critical point. By covering the range of reduced temperatures t equivalent to (T-T(sub c)) / T(sub c) from 10(exp -8) to 10(exp -2), the turbidity measurements will allow the critical exponent eta to be determined. No experiment has precisely determined a value of the critical exponent eta, yet its value is significant to theorists in critical phenomena. Relatively simple critical phenomena, as in the liquid-liquid system studied here, serve as model systems for more complex systems near a critical point.

Buoyancy-driven instability in a vertical cylinder: Binary fluids with Soret effect. I - General theory and stationary stability results

Science.gov (United States)

Hardin, G. R.; Sani, R. L.; Henry, D.; Roux, B.

1990-01-01

The buoyancy-driven instability of a monocomponent or binary fluid completely contained in a vertical circular cylinder is investigated, including the influence of the Soret effect for the binary mixture. The Boussinesq approximation is used, and the resulting linear stability problem is solved using a Galerkin technique. The analysis considers fluid mixtures ranging from gases to liquid metals. The flow structure is found to depend strongly on both the cylinder aspect ratio and the magnitude of the Soret effect. The predicted stability limits are shown to agree closely with experimental observations.

Three-dimensional granular model of semi-solid metallic alloys undergoing solidification: Fluid flow and localization of feeding

International Nuclear Information System (INIS)

Sistaninia, M.; Phillion, A.B.; Drezet, J.-M.; Rappaz, M.

2012-01-01

A three-dimensional (3-D) granular model which simulates fluid flow within solidifying alloys with a globular microstructure, such as that found in grain refined Al alloys, is presented. The model geometry within a representative volume element (RVE) consists of a set of prismatic triangular elements representing the intergranular liquid channels. The pressure field within the liquid channels is calculated using a finite elements (FEs) method assuming a Poiseuille flow within each channel and flow conservation at triple lines. The fluid flow is induced by solidification shrinkage and openings at grain boundaries due to deformation of the coherent solid. The granular model predictions are validated against bulk data calculated with averaging techniques. The results show that a fluid flow simulation of globular semi-solid materials is able to reproduce both a map of the 3-D intergranular pressure and the localization of feeding within the mushy zone. A new hot cracking sensitivity coefficient is then proposed. Based on a mass balance performed over a solidifying isothermal volume element, this coefficient accounts for tensile deformation of the semi-solid domain and for the induced intergranular liquid feeding. The fluid flow model is then used to calculate the pressure drop in the mushy zone during the direct chill casting of aluminum alloy billets. The predicted pressure demonstrates that deep in the mushy zone where the permeability is low the local pressure can be significantly lower than the pressure predicted by averaging techniques.

A scaling analysis of alloy solidification in presence of electromagnetic stirring

International Nuclear Information System (INIS)

Kumar, Arvind; Dutta, Pradip

2006-01-01

Application of electromagnetic stirring (EMS) during continuous casting shears off the dendrites from the solidification front to produce billets with a non-dendritic microstructure. In the present study, a systematic approach to the scaling analysis of momentum, energy and species conservation equations pertaining to the case of the solidification of a binary alloy in the presence of EMS is outlined. With suitable choices of non-dimensionalizing parameters, the governing equations coupled with appropriate boundary conditions are first scaled, and then the relative significance of various terms appearing in them are analysed. In the physical domain two regions are identified, one where the electromagnetic forces play a dominant role in the momentum equations, and the other where the inertia and viscous effects play major roles. Using the scaling predictions, the influence of various processing parameters on the system variables can be utilized for the selection of appropriate electromagnetic forces to shear off the dendrites from the solidification area. For the sake of assessment of the scaling analysis, the predictions are validated against corresponding computational results

Improving geothermal power plants with a binary cycle

Science.gov (United States)

Tomarov, G. V.; Shipkov, A. A.; Sorokina, E. V.

2015-12-01

The recent development of binary geothermal technology is analyzed. General trends in the introduction of low-temperature geothermal sources are summarized. The use of single-phase low-temperature geothermal fluids in binary power plants proves possible and expedient. The benefits of power plants with a binary cycle in comparison with traditional systems are shown. The selection of the working fluid is considered, and the influence of the fluid's physicochemical properties on the design of the binary power plant is discussed. The design of binary power plants is based on the chemical composition and energy potential of the geothermal fluids and on the landscape and climatic conditions at the intended location. Experience in developing a prototype 2.5 MW Russian binary power unit at Pauzhetka geothermal power plant (Kamchatka) is outlined. Most binary systems are designed individually for a specific location. Means of improving the technology and equipment at binary geothermal power plants are identified. One option is the development of modular systems based on several binary systems that employ the heat from the working fluid at different temperatures.

Low-temperature susceptibility of concentrated magnetic fluids

Science.gov (United States)

Pshenichnikov, Alexander F.; Lebedev, Alexander V.

2004-09-01

The initial susceptibility of concentrated magnetic fluids (ferrocolloids) has been experimentally investigated at low temperatures. The results obtained indicate that the interparticle dipole-dipole interactions can increase the susceptibility by several times as compared to the Langevin value. It is shown that good agreement between recent theoretical models and experimental observations can be achieved by introducing a correction for coefficients in the series expansion of susceptibility in powers of density and aggregation parameter. A modified equation for equilibrium susceptibility is offered to sum over corrections made by Kalikmanov (Statistical Physics of Fluids, Springer-Verlag, Berlin, 2001) and by B. Huke and M. Lücke (Phys. Rev. E 67, 051403, 2003). The equation gives good quantitative agreement with the experimental data in the wide range of temperature and magnetic particles concentration. It has been found that in some cases the magnetic fluid solidification occurs at temperature several tens of kelvins higher than the crystallization temperature of the carrier liquid. The solidification temperature of magnetic fluids is independent of particle concentration (i.e., magneto-dipole interparticle interactions) and dependent on the surfactant type and carrier liquid. This finding allows us to suggest that molecular interactions and generation of some large-scale structure from colloidal particles in magnetic fluids are responsible for magnetic fluid solidification. If the magnetic fluid contains the particles with the Brownian relaxation mechanism of the magnetic moment, the solidification manifests itself as the peak on the "susceptibility-temperature" curve. This fact proves the dynamic nature of the observed peak: it arises from blocking the Brownian mechanism of the magnetization relaxation.

Thermodynamic database of multi-component Mg alloys and its application to solidification and heat treatment

Directory of Open Access Journals (Sweden)

Guanglong Xu

2016-12-01

Full Text Available An overview about one thermodynamic database of multi-component Mg alloys is given in this work. This thermodynamic database includes thermodynamic descriptions for 145 binary systems and 48 ternary systems in 23-component (Mg–Ag–Al–Ca–Ce–Cu–Fe–Gd–K–La–Li–Mn–Na–Nd–Ni–Pr–Si–Sn–Sr–Th–Y–Zn–Zr system. First, the major computational and experimental tools to establish the thermodynamic database of Mg alloys are briefly described. Subsequently, among the investigated binary and ternary systems, representative binary and ternary systems are shown to demonstrate the major feature of the database. Finally, application of the thermodynamic database to solidification simulation and selection of heat treatment schedule is described.

Modelling of solidification processing and continuous strip casting for copper-base alloys

Energy Technology Data Exchange (ETDEWEB)

Mahmoudi, Jafar [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Materials Processing

2000-04-01

An experimental and numerical study was carried out to investigate the solidification process in a copper continuous strip casting process. Heat flow and solidification process has been experimentally studied. Cooling curves during solidification were registered using a thermocouple of type K connected to a data acquisition system. Temperature measurements in the mould and cooling water were also performed. The numerical model considers a generalized set of mass, momentum and heat equations that is valid for the solid, liquid and solidification interval in the cast. A k-{epsilon} turbulence model, produced with the commercial program CFX, is used to analyse the solidification process of pure copper in the mould region of the caster. The fluid flow, temperature and heat flux distributions in the mould region of the caster were computed. The shape and location of the solidification front were also determined. The effects of the parameters such as heat transfer coefficient, casting speed, casting temperature, heat of fusion and specific heat on the shape and location of the solidification front and the heat transport at the mould-cast interface were investigated. The predicted temperature and heat flux distributions were compared with experimental measurements, and reasonable agreement was obtained. The solidification behaviour of pure copper and different copper base alloys has been studied. A series of solidification experiments using DTA furnace, mirror furnace and levitation technique were performed on different copper-base alloys. The undercooling, cooling rates of the liquid and the solid states, solidification times and temperatures were evaluated from the curves. The cooling curves for different samples were simulated using a FEM solidification program. It was found that the calculated values of the heat of fusion were much lower than the tabulated ones. The fraction of solid formed before quenching, in the DTA experiments, has been observed to be much higher

Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 1: Formulation and analysis

Science.gov (United States)

Maples, A. L.; Poirier, D. R.

1980-01-01

The physical and numerical formulation of a model for the horizontal solidification of a binary alloy is described. It can be applied in an ingot. The major purpose of the model is to calculate macrosegregation in a casting ingot which results from flow of interdendritic liquid during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, was modeled as flow through a porous medium. The symbols used are defined. The physical formulation of the problem leading to a set of equations which can be used to obtain: (1) the pressure field; (2) the velocity field: (3) mass flow and (4) solute flow in the solid plus liquid zone during solidification is presented. With these established, the model calculates macrosegregation after solidification is complete. The numerical techniques used to obtain solution on a computational grid are presented. Results, evaluation of the results, and recommendations for future development of the model are given. The macrosegregation and flow field predictions for tin-lead, aluminum-copper, and tin-bismuth alloys are included as well as comparisons of some of the predictions with published predictions or with empirical data.

Solidification process of a tool steel with niobium

International Nuclear Information System (INIS)

Makray, E.T.; Bresciani Filho, E.; Martinez Nazar, A.M.

1984-01-01

The solidification process of M2 high speed steel where tungsten was totally substituted by niobium was analysed. It occurs through a eutectic type reaction, in four steps. It was verified that one can apply the Coupled Zone Concept to explain the solification mechanism of this alloy: there is a primary phase (NbC), which is envolved by the other phase (ferrite) as a halo in order to send the composition back to the coupled growth region, where the binary eutectic forms. The last step is the formation of other compounds at the grain boundary. (Author) [pt

Diffusion in Poiseuille and Couette flows of binary mixtures of incompressible newtonian fluids

International Nuclear Information System (INIS)

Caetano Filho, E.; Qassim, R.Y.

1981-07-01

Using the continuum theory of binary mixtures of incompressible Newtonian fluids, Poiseuille and Couette flows are studied with a view to determining whether diffusion occurs in such flows. It is shown that diffusion is absent in the Couette case. However, in Poiseuille flow there are significant differences between the velocities of the species comprising the mixture. This result is in broad agreement with that of Mills for similar mixtures of nonuniform composition. (Author) [pt

Binary Mixture of Perfect Fluid and Dark Energy in Modified Theory of Gravity

Science.gov (United States)

Shaikh, A. Y.

2016-07-01

A self consistent system of Plane Symmetric gravitational field and a binary mixture of perfect fluid and dark energy in a modified theory of gravity are considered. The gravitational field plays crucial role in the formation of soliton-like solutions, i.e., solutions with limited total energy, spin, and charge. The perfect fluid is taken to be the one obeying the usual equation of state, i.e., p = γρ with γ∈ [0, 1] whereas, the dark energy is considered to be either the quintessence like equation of state or Chaplygin gas. The exact solutions to the corresponding field equations are obtained for power-law and exponential volumetric expansion. The geometrical and physical parameters for both the models are studied.

Origin of grain orientation during solidification of an aluminum alloy

International Nuclear Information System (INIS)

Wei, H.L.; Elmer, J.W.; DebRoy, T.

2016-01-01

The evolution of grain morphology during solidification of a moving aluminum alloy pool is simulated by considering heat transfer, flow of liquid metal in the molten pool and solidification parameters. The computationally efficient model consists of a 3D coupled heat transfer and fluid flow simulation to predict the molten pool shape and temperature field, and a 2D model of grain formation in the molten pool. The results demonstrate that columnar grains grow in a curved pattern rather than along straight lines from the fusion boundary towards the center of the molten pool. The calculated results are validated with independent experimental data. The computed ratio of local temperature gradient to solidification rate, G/R, is used to model the columnar to equiaxed transition during solidification. The simulated results show that only curved columnar grains are formed when the scanning speed is low (2.0 mm/s). In contrast, a transition from curved columnar to equiaxed morphologies occurs at the higher scanning speeds of 8.0 mm/s and 11.5 mm/s, with higher equiaxed grain fraction at higher speed. The similarities between the physical processes governing fusion welding and additive manufacturing (AM) make the model capable of predicting grain orientation in both processes.

Microstructure Formations in the Two-Phase Region of the Binary Peritectic Organic System TRIS-NPG

Science.gov (United States)

Mogeritsch, Johann; Ludwig, Andreas

2012-01-01

In order to prepare for an onboard experiment on the International Space Station (ISS), systematic directional solidification experiments with transparent hypoperitectic alloys were carried out at different solidification rates around the critical velocity for morphological stability of both solid phases. The investigations were done in the peritectic region of the binary transparent organic TRIS-NPG system where the formation of layered structures is expected to occur. The transparent appearance of the liquid and solid phase enables real time observations of the dynamic of pattern formation during solidification. The investigations show that frequently occurring nucleation events govern the peritectic solidification morphology which occurs at the limit of morphological stability. As a consequence, banded structures lead to coupled growth even if the lateral growth is much faster compared to the growth in pulling direction.

The effects of solidification on sill propagation dynamics and morphology

Science.gov (United States)

Chanceaux, L.; Menand, T.

2016-05-01

Sills are an integral part of the formation and development of larger plutons and magma reservoirs. Thus sills are essential for both the transport and the storage of magma in the Earth's crust. However, although cooling and solidification are central to magmatism, their effects on sills have been so far poorly studied. Here, the effects of solidification on sill propagation dynamics and morphology are studied by means of analogue laboratory experiments. Hot fluid vegetable oil (magma analogue), that solidifies during its propagation, is injected as a sill in a colder layered gelatine solid (elastic host rock analogue). The injection flux and temperature are maintained constant during an experiment and systematically varied between each experiment, in order to vary and quantify the amount of solidification between each experiments. The oil is injected directly at the interface between the two gelatine layers. When solidification effects are small (high injection temperatures and fluxes), the propagation is continuous and the sill has a regular and smooth surface. Inversely, when solidification effects are important (low injection temperatures and fluxes), sill propagation is discontinuous and occurs by steps of surface-area creation interspersed with periods of momentary arrest. The morphology of these sills displays folds, ropy structures on their surface, and lobes with imprints of the leading fronts that correspond to each step of area creation. These experiments show that for a given, constant injected volume, as solidification effects increase, the area of the sills decreases, their thickness increases, and the number of propagation steps increases. These results have various geological and geophysical implications. The morphology of sills, such as lobate structures (interpretation of 3D seismic studies in sedimentary basin) and ropy flow structures (field observations) can be related to solidification during emplacement. Moreover, a non-continuous morphology

Radioactive gas solidification apparatus

International Nuclear Information System (INIS)

Kobayashi, Yoshihiro; Seki, Eiji; Yabu, Tomohiko; Matsunaga, Hiroyuki.

1990-01-01

Handling of a solidification container from the completion for the solidifying processing to the storage of radioactive gases by a remote control equipment such as a manipulator requires a great cost and is difficult to realize. In a radioactive gas solidification device for injection and solidification in accumulated layers of sputtered metals by glow discharge, radiation shieldings are disposed surrounding the entire container, and cooling water is supplied to a cooling vessel formed between the container and the shielding materials. The shielding materials are divided into upper and lower shielding materials, so that solidification container can be taken out from the shielding materials. As a result, the solidification container after the solidification of radioactive gases can be handled with ease. Further, after-heat can be removed effectively from the ion injection electrode upon solidifying treatment upon storage, to attain a radioactive gas solidifying processing apparatus which is safe, economical and highly reliable. (N.H.)

The solidification behavior of dilute aluminium-scandium alloys

International Nuclear Information System (INIS)

Norman, A.F.; Prangnell, P.B.; McEwen, R.S.

1998-01-01

The solidification behavior of dilute Sc containing Al alloys has been investigated. In binary Al-Sc alloys, Sc additions greater than the eutectic composition (0.55 wt%) were found to produce a remarkable refinement in the grain size of aluminum castings, of two orders of magnitude, due to the formation of the primary Al 3 Sc intermetallic phase during solidification. The refinement in grain size only occurred in hypereutectic compositions and was shown to be far greater than can be achieved by conventional Al grain refiners. Grain refinement by the addition of Sc is accompanied by a change in growth morphology from dendritic, in the large unrefined grains, to fine spherical grains with a divorced eutectic appearing on the grain boundaries in the refined castings. Similar levels of refinement were observed in Al-Sc-Zr and Al-Cu-Sc alloys. In the latter, a change in the segregation behavior of Cu was observed, from a strongly interdendritic segregation pattern to a more homogeneous distribution. The supersaturated Al-Sc solid solution can decompose via a discontinuous precipitation reaction to form coherent rod-like precipitates of the L1 2 Al 3 Sc phase

A mesoscale granular model for the mechanical behavior of alloys during solidification

Energy Technology Data Exchange (ETDEWEB)

Vernede, Stephane [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland); Alcan Centre de Recherches de Voreppe, ZI Centr' Alp, 725 rue Aristide Berges, BP 27, Voreppe FR-38341 (France)], E-mail: stephane.vernede@alcan.com; Dantzig, Jonathan A. [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland); Department of Mechanical Science and Engineering, University of Illinois, 1206 West Green Street Urbana, IL 61801 (United States); Rappaz, Michel [Computational Materials Laboratory, Ecole Polytechnique Federale de Lausanne, Station 12, Lausanne CH-1015 (Switzerland)

2009-03-15

We present a two-dimensional granular model for the mechanical behavior of an ensemble of globular grains during solidification. The grain structure is produced by a Voronoi tessellation based on an array of predefined nuclei. We consider the fluid flow caused by grain movement and solidification shrinkage in the network of channels that is formed by the faces of the grains in the tessellation. We develop the governing equations for the flow rate and pressure drop across each channel when the grains are allowed to move, and we then assemble the equations into a global expression that conserves mass and force in the system. We show that the formulation is consistent with dissipative formulations of non-equilibrium thermodynamics. Several example problems are presented to illustrate the effect of tensile strains and the availability of liquid to feed the deforming microstructure. For solid fractions below g{sub s}=0.97, we find that the fluid is able to feed the deformation at low strain, even if external feeding is not permitted. For solid fractions above g{sub s}=0.97, clusters of grains with 'dry' boundaries form and fluid flow becomes highly localized.

Elimination of Hot Tears in Steel Castings by Means of Solidification Pattern Optimization

DEFF Research Database (Denmark)

Kotas, Petr; Tutum, Cem Celal; Thorborg, Jesper

2012-01-01

A methodology of how to exploit the Niyama criterion for the elimination of various defects such as centerline porosity, macrosegregation, and hot tearing in steel castings is presented. The tendency of forming centerline porosity is governed by the temperature distribution close to the end...... of the solidification interval, specifically by thermal gradients and cooling rates. The physics behind macrosegregation and hot tears indicate that these two defects also are dependent heavily on thermal gradients and pressure drop in the mushy zone. The objective of this work is to show that by optimizing...... the solidification pattern, i.e., establishing directional and progressive solidification with the help of the Niyama criterion, macrosegregation and hot tearing issues can be both minimized or eliminated entirely. An original casting layout was simulated using a transient three-dimensional (3-D) thermal fluid model...

Inspection method for solidification product of radioactive waste and method of preparing solidification product of radiation waste

International Nuclear Information System (INIS)

Izumida, Tatsuo; Tamada, Shin; Matsuda, Masami; Kamata, Shoji; Kikuchi, Makoto.

1993-01-01

A powerful X-ray generation device using an electron-ray accelerator is used for inspecting presence or absence of inner voids in solidification products of radioactive wastes during or after solidification. By installing the X-ray CT system and the radioactive waste solidifying facility together, CT imaging for solidification products is conducted in a not-yet cured state of solidifying materials during or just after the injection. If a defect that deteriorates the durability of the solidification products should be detected, the solidification products are repaired, for example, by applying vibrations to the not-yet cured solidification products. Thus, since voids or cracks in the radioactive wastes solidification products, which were difficult to be measured so far, can be measured in a short period of time accurately thereby enabling to judge adaptability to the disposal standards, inspection cost for the radioactive waste solidification product can be saved remarkably. Further, the inside of the radioactive waste solidification products can be evaluated correctly and visually, so that safety in the ground disposal storage of the radioactive solidification products can be improved remarkably. (N.H.)

Radioactive gas solidification treatment device

International Nuclear Information System (INIS)

Igarashi, Ryokichi; Watanabe, Yu; Seki, Eiji.

1992-01-01

In a radioactive gas solidification treatment device by using sputtering, spiral pipelines are disposed with a gap therebetween for cooling an ion injection electrode by passing cooling water during operation of the solidification treatment. During the operation of the solidification treatment, cooling water is passed in the pipelines to cool the ion injection electrode. During storage, a solidification vessel is cooled by natural heat dissipation from an exposed portion at the surface of the solidification vessel. Accordingly, after-heat of radioactive gas solidified in a metal accumulation layer can be removed efficiently, safely and economically to improve the reliability. (N.H.)

Low-level radwaste solidification

International Nuclear Information System (INIS)

Naughton, M.D.; Miller, C.C.; Nelson, R.A.; Tucker, R.F.

1983-01-01

This paper reports on a study of ''Advanced Low-Level Radioactive Waste Treatment Systems'' conducted under an EPRI contract. The object of the study is to identify advanced lowlevel radwaste treatment systems that are commercially available or are expected to be in the near future. The current state-ofthe-art in radwaste solidification technology is presented. Related processing technologies, such as the compaction of dry active waste (DAW), containers available for radwaste disposal, and the regulatory aspects of radwaste transportation and solidification, are described. The chemical and physical properties of the currently acceptable solidification agents, as identified in the Barnwell radwaste burial site license, are examined. The solidification agents investigated are hydraulic cements, thermoplastic polymers, and thermosetting polymers. It is concluded that solidification processes are complex and depend not only on the chemical and physical properties of the binder material and the waste, but also on how these materials are mixed

Numerical modeling of two-phase binary fluid mixing using mixed finite elements

KAUST Repository

Sun, Shuyu

2012-07-27

Diffusion coefficients of dense gases in liquids can be measured by considering two-phase binary nonequilibrium fluid mixing in a closed cell with a fixed volume. This process is based on convection and diffusion in each phase. Numerical simulation of the mixing often requires accurate algorithms. In this paper, we design two efficient numerical methods for simulating the mixing of two-phase binary fluids in one-dimensional, highly permeable media. Mathematical model for isothermal compositional two-phase flow in porous media is established based on Darcy\\'s law, material balance, local thermodynamic equilibrium for the phases, and diffusion across the phases. The time-lag and operator-splitting techniques are used to decompose each convection-diffusion equation into two steps: diffusion step and convection step. The Mixed finite element (MFE) method is used for diffusion equation because it can achieve a high-order and stable approximation of both the scalar variable and the diffusive fluxes across grid-cell interfaces. We employ the characteristic finite element method with moving mesh to track the liquid-gas interface. Based on the above schemes, we propose two methods: single-domain and two-domain methods. The main difference between two methods is that the two-domain method utilizes the assumption of sharp interface between two fluid phases, while the single-domain method allows fractional saturation level. Two-domain method treats the gas domain and the liquid domain separately. Because liquid-gas interface moves with time, the two-domain method needs work with a moving mesh. On the other hand, the single-domain method allows the use of a fixed mesh. We derive the formulas to compute the diffusive flux for MFE in both methods. The single-domain method is extended to multiple dimensions. Numerical results indicate that both methods can accurately describe the evolution of the pressure and liquid level. © 2012 Springer Science+Business Media B.V.

Solidification method of radioactive wastes

Energy Technology Data Exchange (ETDEWEB)

Baba, Tsutomu; Chino, Koichi; Sasahira, Akira; Ikeda, Takashi

1992-07-24

Metal solidification material can completely seal radioactive wastes and it has high sealing effect even if a trace amount of evaporation should be caused. In addition, the solidification operation can be conducted safely by using a metal having a melting point of lower than that of the decomposition temperature of the radioactive wastes. Further, the radioactive wastes having a possibility of evaporation and scattering along with oxidation can be solidified in a stable form by putting the solidification system under an inert gas atmosphere. Then in the present invention, a metal is selected as a solidification material for radioactive wastes, and a metal, for example, lead or tin having a melting point of lower than that of the decomposition temperature of the wastes is used in order to prevent the release of the wastes during the solidification operation. Radioactive wastes which are unstable in air and scatter easily, for example, Ru or the like can be converted into a stable solidification product by conducting the solidification processing under an inert gas atmosphere. (T.M.).

Calculation of interfacial tensions with gradient theory. I. Pure and Pseudo-Pure Fluids. II. Binary Systems

DEFF Research Database (Denmark)

Zuo, You-Xiang; Stenby, Erling Halfdan

1997-01-01

.26% at low pressure, and that of naphtha reformate cuts was 3.6%. In addition, the gradient theory was used to predict interfacial tensions for binary systems in the near-critical region. The results show excellent agreement between the predicted and experimental IFTs at high and moderate levels, while....... A consistent procedure for the estimation of properties associated to lumped systems. Fluid Phase Equilibria, 87: 89-197] was used to lump a mixture into one pseudocomponent, and its IFTs were calculated by means of the method of pure fluids. On the basis of the SRK EOS, the overall AAD of mixtures was 3...

Influence of the type of working fluid in the lower cycle and superheated steam parameters in the upper cycle on effectiveness of operation of binary power plant

Directory of Open Access Journals (Sweden)

Stachel Aleksander A.

2015-03-01

Full Text Available In the paper presented have been the results of the analysis of effectiveness of operation of binary power plant consisting of combined two Clausius-Rankine cycles, namely the binary cycle with water as a working fluid in the upper cycle and organic substance as a working fluid in the lower cycle, as well as a single fluid component power plant operating also in line with the C-R cycle for superheated steam, with water as a working fluid. The influence of the parameters of superheated steam in the upper cycle has been assessed as well as the type of working fluid in the lower cycle. The results of calculations have been referred to the single-cycle classical steam power plant operating at the same parameters of superheated steam and the same mass flow rate of water circulating in both cycles. On the basis of accomplished analysis it has been shown that the binary power plant shows a greater power with respect to the reference power plant.

Liquid-liquid phase separation and solidification behavior of Al55Bi36Cu9 monotectic alloy with different cooling rates

Science.gov (United States)

Bo, Lin; Li, Shanshan; Wang, Lin; Wu, Di; Zuo, Min; Zhao, Degang

2018-03-01

The cooling rate has a significant effect on the solidification behavior and microstructure of monotectic alloy. In this study, different cooling rate was designed through casting in the copper mold with different bore diameters. The effects of different cooling rate on the solidification behavior of Al55Bi36Cu9 (at.%) immiscible alloy have been investigated. The liquid-liquid phase separation of Al55Bi36Cu9 immiscible alloy melt was investigated by resistivity test. The solidification microstructure and phase analysis of Al55Bi36Cu9 immiscible alloy were performed by the SEM and XRD, respectively. The results showed that the liquid-liquid phase separation occurred in the solidification of Al55Bi36Cu9 monotectic melt from 917 °C to 653 °C. The monotectic temperature, liquid phase separation temperature and immiscibility zone of Al55Bi36Cu9 monotectic alloy was lower than those of Al-Bi binary monotectic alloy. The solidification morphology of Al55Bi36Cu9 monotectic alloy was very sensitive to the cooling rate. The Al/Bi core-shell structure formed when Al55Bi36Cu9 melt was cast in the copper mold with a 8 mm bore diameter.

Solidification microstructure development

Indian Academy of Sciences (India)

Unknown

A majority of manufacturing processes involve melting and solidification of metals and ... In such a case (for example, chill casting), the solidification thickness (S) is ... (5). Here, LX is the system length scale in one dimension and DS is the solute diffusivity in solid. Thermal and solutal diffusivities are finite and usually very ...

Free energy change of off-eutectic binary alloys on solidification

Science.gov (United States)

Ohsaka, K.; Trinh, E. H.; Lin, J.-C.; Perepezko, J. H.

1991-01-01

A formula for the free energy difference between the undercooled liquid phase and the stable solid phase is derived for off-eutectic binary alloys in which the equilibrium solid/liquid transition takes place over a certain temperature range. The free energy change is then evaluated numerically for a Bi-25 at. pct Cd alloy modeled as a sub-subregular solution.

Numerical simulation of convection and inclusion distribution during solidification in a heavy steel ingot

International Nuclear Information System (INIS)

Lin, Rui; Shen, Houfa

2015-01-01

Inclusions content in the steel ingot is an important index for homogeneity, and it becomes more serious for heavy steel ingots which are used for major equipment. However, knowledge about the formation of inclusion in steel ingot is limited, and modeling of inclusion distribution is still challenging, so it is of great significance to research the behavior of inclusion. In this paper, fluid flow during solidification is numerically simulated based on the equilibrium equations of mass, momentum and energy, and then inclusion distribution is modeled according to the Lagrangian Stokes trajectory method. The Results show that the inclusion distribution in the steel ingot is influenced by the flow pattern which is affected by the solidification pattern. Therefore, inclusion distribution could be controlled by the solidification front with the optimization of heat transfer condition such as the hot top design of steel ingot for the high quality steel production. (paper)

Plastic solidification of radioactive wastes

International Nuclear Information System (INIS)

Moriyama, Noboru

1981-01-01

Over 20 years have elapsed after the start of nuclear power development, and the nuclear power generation in Japan now exceeds the level of 10,000 MW. In order to meet the energy demands, the problem of the treatment and disposal of radioactive wastes produced in nuclear power stations must be solved. The purpose of the plastic solidification of such wastes is to immobilize the contained radionuclides, same as other solidification methods, to provide the first barrier against their move into the environment. The following matters are described: the nuclear power generation in Japan, the radioactive wastes from LWR plants, the position of plastic solidification, the status of plastic solidification in overseas countries and in Japan, the solidification process for radioactive wastes with polyethylene, and the properties of solidified products, and the leachability of radionuclides in asphalt solids. (J.P.N.)

Numerical Simulation on the Origin of Solidification Cracking in Laser Welded Thick-Walled Structures

Directory of Open Access Journals (Sweden)

Nasim Bakir

2018-06-01

Full Text Available One of the main factors affecting the use of lasers in the industry for welding thick structures is the process accompanying solidification cracks. These cracks mostly occurring along the welding direction in the welding center, and strongly affect the safety of the welded components. In the present study, to obtain a better understanding of the relation between the weld pool geometry, the stress distribution and the solidification cracking, a three-dimensional computational fluid dynamic (CFD model was combined with a thermo-mechanical model. The CFD model was employed to analyze the flow of the molten metal in the weld pool during the laser beam welding process. The weld pool geometry estimated from the CFD model was used as a heat source in the thermal model to calculate the temperature field and the stress development and distributions. The CFD results showed a bulging region in the middle depth of the weld and two narrowing areas separating the bulging region from the top and bottom surface. The thermo-mechanical simulations showed a concentration of tension stresses, transversally and vertically, directly after the solidification during cooling in the region of the solidification cracking.

Advances in Solidification Processing

Directory of Open Access Journals (Sweden)

Hugo F. Lopez

2015-08-01

Full Text Available Melt solidification is the shortest and most viable route to obtain components, starting from the design to the finished products. Hence, a sound knowledge of the solidification of metallic materials is essential for the development of advanced structural metallic components that drive modern technological societies. As a result, there have been innumerable efforts and full conferences dedicated to this important subject [1–6]. In addition, there are various scientific journals fully devoted to investigating the various aspects which give rise to various solidification microstructures [7–9]. [...

Solidification Sequence of Spray-Formed Steels

Science.gov (United States)

Zepon, Guilherme; Ellendt, Nils; Uhlenwinkel, Volker; Bolfarini, Claudemiro

2016-02-01

Solidification in spray-forming is still an open discussion in the atomization and deposition area. This paper proposes a solidification model based on the equilibrium solidification path of alloys. The main assumptions of the model are that the deposition zone temperature must be above the alloy's solidus temperature and that the equilibrium liquid fraction at this temperature is reached, which involves partial remelting and/or redissolution of completely solidified droplets. When the deposition zone is cooled, solidification of the remaining liquid takes place under near equilibrium conditions. Scanning electron microscopy (SEM) and optical microscopy (OM) were used to analyze the microstructures of two different spray-formed steel grades: (1) boron modified supermartensitic stainless steel (SMSS) and (2) D2 tool steel. The microstructures were analyzed to determine the sequence of phase formation during solidification. In both cases, the solidification model proposed was validated.

Elimination of Hot Tears in Steel Castings by Means of Solidification Pattern Optimization

Science.gov (United States)

Kotas, Petr; Tutum, Cem Celal; Thorborg, Jesper; Hattel, Jesper Henri

2012-06-01

A methodology of how to exploit the Niyama criterion for the elimination of various defects such as centerline porosity, macrosegregation, and hot tearing in steel castings is presented. The tendency of forming centerline porosity is governed by the temperature distribution close to the end of the solidification interval, specifically by thermal gradients and cooling rates. The physics behind macrosegregation and hot tears indicate that these two defects also are dependent heavily on thermal gradients and pressure drop in the mushy zone. The objective of this work is to show that by optimizing the solidification pattern, i.e., establishing directional and progressive solidification with the help of the Niyama criterion, macrosegregation and hot tearing issues can be both minimized or eliminated entirely. An original casting layout was simulated using a transient three-dimensional (3-D) thermal fluid model incorporated in a commercial simulation software package to determine potential flaws and inadequacies. Based on the initial casting process assessment, multiobjective optimization of the solidification pattern of the considered steel part followed. That is, the multiobjective optimization problem of choosing the proper riser and chill designs has been investigated using genetic algorithms while simultaneously considering their impact on centerline porosity, the macrosegregation pattern, and primarily on hot tear formation.

Solidification and casting

CERN Document Server

Cantor, Brian

2002-01-01

INDUSTRIAL PERSPECTIVEDirect chillcasting of aluminium alloysContinuous casting of aluminium alloysContinuous casting of steelsCastings in the automotive industryCast aluminium-silicon piston alloysMODELLING AND SIMULATIONModelling direct chill castingMold filling simulation of die castingThe ten casting rulesGrain selection in single crystal superalloy castingsDefects in aluminium shape castingPattern formation during solidificationPeritectic solidificationSTRUCTURE AND DEFECTSHetergeneous nucleation in aluminium alloysCo

Fundamental Metallurgy of Solidification

DEFF Research Database (Denmark)

Tiedje, Niels

2004-01-01

The text takes the reader through some fundamental aspects of solidification, with focus on understanding the basic physics that govern solidification in casting and welding. It is described how the first solid is formed and which factors affect nucleation. It is described how crystals grow from...

Diffusivities of an Al-Fe-Ni melt and their effects on the microstructure during solidification

International Nuclear Information System (INIS)

Zhang Lijun; Du Yong; Steinbach, Ingo; Chen Qing; Huang Baiyun

2010-01-01

A systematical investigation of the diffusivities in an Al-Fe-Ni melt was presented. Based on the experimental and theoretical data about diffusivities, the temperature- and composition-dependent atomic mobilities were evaluated for the elements in Al-Ni, Al-Fe, Fe-Ni and Al-Fe-Ni melts via an effective approach. Most of the reported diffusivities can be reproduced well by the obtained atomic mobilities. In particular, for the first time the ternary diffusivity of the liquid in a ternary system is described in conjunction with the established atomic mobilities. The effect of the atomic mobilities in a liquid on microstructure and microsegregation during solidification was demonstrated with one Al-Ni binary alloy. The simulation results indicate that accurate databases of mobilities in the liquid phase are much needed for the quantitative simulation of microstructural evolution during solidification by using various approaches, including DICTRA and the phase-field method.

Characteristics of Cement Solidification of Metal Hydroxide Waste

Directory of Open Access Journals (Sweden)

Dae-Seo Koo

2017-02-01

Full Text Available To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

Characteristics of cement solidification of metal hydroxide waste

Energy Technology Data Exchange (ETDEWEB)

Koo, Dae Seo; Sung, Hyun Hee; Kim, Seung Soo; Kim, Gye Nam; Choi, Jong Won [Dept. of Decontemination Decommission Technology Development, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2017-02-15

To perform the permanent disposal of metal hydroxide waste from electro-kinetic decontamination, it is necessary to secure the technology for its solidification. The integrity tests on the fabricated solidification should also meet the criteria of the Korea Radioactive Waste Agency. We carried out the solidification of metal hydroxide waste using cement solidification. The integrity tests such as the compressive strength, immersion, leach, and irradiation tests on the fabricated cement solidifications were performed. It was also confirmed that these requirements of the criteria of Korea Radioactive Waste Agency on these cement solidifications were met. The microstructures of all the cement solidifications were analyzed and discussed.

An adjoint-based framework for maximizing mixing in binary fluids

Science.gov (United States)

Eggl, Maximilian; Schmid, Peter

2017-11-01

Mixing in the inertial, but laminar parameter regime is a common application in a wide range of industries. Enhancing the efficiency of mixing processes thus has a fundamental effect on product quality, material homogeneity and, last but not least, production costs. In this project, we address mixing efficiency in the above mentioned regime (Reynolds number Re = 1000 , Peclet number Pe = 1000) by developing and demonstrating an algorithm based on nonlinear adjoint looping that minimizes the variance of a passive scalar field which models our binary Newtonian fluids. The numerical method is based on the FLUSI code (Engels et al. 2016), a Fourier pseudo-spectral code, which we modified and augmented by scalar transport and adjoint equations. Mixing is accomplished by moving stirrers which are numerically modeled using a penalization approach. In our two-dimensional simulations we consider rotating circular and elliptic stirrers and extract optimal mixing strategies from the iterative scheme. The case of optimizing shape and rotational speed of the stirrers will be demonstrated.

Fractal growth in impurity-controlled solidification in lipid monolayers

DEFF Research Database (Denmark)

Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.

1987-01-01

A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

A binary mixture operated heat pump

International Nuclear Information System (INIS)

Hihara, E.; Saito, T.

1991-01-01

This paper evaluates the performance of possible binary mixtures as working fluids in high- temperature heat pump applications. The binary mixtures, which are potential alternatives of fully halogenated hydrocarbons, include HCFC142b/HCFC22, HFC152a/HCFC22, HFC134a/HCFC22. The performance of the mixtures is estimated by a thermodynamic model and a practical model in which the heat transfer is considered in heat exchangers. One of the advantages of binary mixtures is a higher coefficient of performance, which is caused by the small temperature difference between the heat-sink/-source fluid and the refrigerant. The mixture HCFC142b/HCFC22 is promising from the stand point of thermodynamic performance

The dynamics of the rapid solidification of two successive aluminum particles in molten state

Science.gov (United States)

Zirari, M.; El-Hadj, A. Abdellah; Bacha, N.

2013-12-01

A finite element method is used to simulate coating deposition in the thermal spraying process. The model uses a method based on a fixed-grid Eulerian control volume to solve the fluid dynamics and energy conservation equations. A volume-of-fluid algorithm was used to track free surface deformation. The specific heat method (SHM) is used for the solidification phenomenon. This work deals mainly numerically, the problem related to solidification during impact of two identical aluminium drops, impacting successively on the same point and time-shifted, onto a smooth steel substrate. In the first part of this study, a completely melted particle, sprayed onto substrate tool steel H13 is considered in the objective of identification. Then, we examine four possible cases of successive impacts of two particles and their effects on the sprawl dynamics in different states (fully and/or partially melted). It was found that the internal energy in conjunction with the metallurgical state of the droplet play a key role in the final morphology of the coating.

Simulation of spreading with solidification: assessment synthesis of Thema code

Energy Technology Data Exchange (ETDEWEB)

Spindler, B.; Veteau, J.M. [CEA Grenoble, Direction de l' Energie Nucleaire, Dept. de Technologie Nucleaire, Service d' Etudes Thermohydrauliques et Technologiques, 38 (France)

2004-07-01

After a presentation of the models included in THEMA code, which simulates the spreading of a fluid with solidification, the whole assessment calculations are presented. The first series concerns the comparison with analytical or numerical solutions: dam break, conduction for the heat transfer in the substrate, crust growth. The second series concerns the comparison with the CORINE isothermal tests (simulating fluid at low temperature). The third series concerns the CORINE tests with heat transfer. The fourth series concerns the tests with simulating materials at medium or high temperature (RIT, KATS). The fifth series concerns the tests with prototypical materials (COMAS, FARO, VULCANO). Finally the blind simulations of the ECOKATS tests are presented. All the calculations are performed with the same physical models (THEMA version 2.5), without any variable tuning parameter according to the test under consideration. Sensitivity studies concern the influence of the viscosity model in the solidification interval, and for the tests with prototypical materials the inlet temperature and the solid fraction. The relative difference between the calculated and measured spreading areas is generally less than 20 % except for the test with prototypical materials, for which the assessment is not easy due to the large experimental uncertainties. The level of validation of THEMA is considered as satisfactory, taking into account the required accuracy. (authors)

Simulation of spreading with solidification: assessment synthesis of Thema code

International Nuclear Information System (INIS)

Spindler, B.; Veteau, J.M.

2004-01-01

After a presentation of the models included in THEMA code, which simulates the spreading of a fluid with solidification, the whole assessment calculations are presented. The first series concerns the comparison with analytical or numerical solutions: dam break, conduction for the heat transfer in the substrate, crust growth. The second series concerns the comparison with the CORINE isothermal tests (simulating fluid at low temperature). The third series concerns the CORINE tests with heat transfer. The fourth series concerns the tests with simulating materials at medium or high temperature (RIT, KATS). The fifth series concerns the tests with prototypical materials (COMAS, FARO, VULCANO). Finally the blind simulations of the ECOKATS tests are presented. All the calculations are performed with the same physical models (THEMA version 2.5), without any variable tuning parameter according to the test under consideration. Sensitivity studies concern the influence of the viscosity model in the solidification interval, and for the tests with prototypical materials the inlet temperature and the solid fraction. The relative difference between the calculated and measured spreading areas is generally less than 20 % except for the test with prototypical materials, for which the assessment is not easy due to the large experimental uncertainties. The level of validation of THEMA is considered as satisfactory, taking into account the required accuracy. (authors)

The solidification velocity of nickel and titanium alloys

Science.gov (United States)

Altgilbers, Alex Sho

2002-09-01

The solidification velocity of several Ni-Ti, Ni-Sn, Ni-Si, Ti-Al and Ti-Ni alloys were measured as a function of undercooling. From these results, a model for alloy solidification was developed that can be used to predict the solidification velocity as a function of undercooling more accurately. During this investigation a phenomenon was observed in the solidification velocity that is a direct result of the addition of the various alloying elements to nickel and titanium. The additions of the alloying elements resulted in an additional solidification velocity plateau at intermediate undercoolings. Past work has shown a solidification velocity plateau at high undercoolings can be attributed to residual oxygen. It is shown that a logistic growth model is a more accurate model for predicting the solidification of alloys. Additionally, a numerical model is developed from simple description of the effect of solute on the solidification velocity, which utilizes a Boltzmann logistic function to predict the plateaus that occur at intermediate undercoolings.

Onset of Soret-driven convection of binary fluid in square cavity heated from above at different gravity levels

Science.gov (United States)

Lyubimova, Tatyana; Zubova, Nadezhda

The instability of incompressible viscous binary fluid with the Soret effect in square cavity heated from above is studied for different gravity levels. The no slip and zero mass flux conditions are imposed on all the boundaries. The horizontal boundaries are perfectly conductive, they are maintained at constant different temperatures and vertical boundaries are adiabatic. The calculations are performed for water - isopropanol mixture 90:10. Initial conditions correspond to the motionless state with uniform distribution of components and uniform temperature gradient directed upward. For binary fluid under consideration the separation parameter is negative therefore the Soret effect leads to the accumulation of heavy component in the upper part of cavity, moreover, the rate of accumulation is independent of the gravity level. The linear stability of the unsteady motionless state is studied numerically by solving linearized equations for small perturbations. To determine the time t* for the onset of instability, the criterion suggested in [1] is used. The dependence of t* on the gravity level is obtained. The work was done under financial support of Government of Perm Region, Russia (Contract C-26/212). 1. Shliomis M.I., Souhar M. Europhysics Letters. 2000. Vol. 49 (1), pp. 55-61.

Numerical study of impact and solidification of a droplet over a deposited frozen splat

International Nuclear Information System (INIS)

Ghafouri-Azar, R.; Mostaghimi, J.; Chandra, S.

2002-01-01

The impact and solidification of a molten tin droplet on another solidified splat was studied for varying offset spacing using a three-dimensional model of droplet impact. It was found the final shapes of impinging droplets were sensitive to the offset distance. The model applies a fixed-grid Eulerian control volume method to solve the fluid dynamics and heat transfer in the droplet. The model employs a Volume of Fluid (VOF) algorithm to track free surface deformation. Predictions of droplet shapes during impact from the model agreed well with experimental photographs. (author)

Radioactive waste solidification material

International Nuclear Information System (INIS)

Nishihara, Yukio; Wakuta, Kuniharu; Ishizaki, Kanjiro; Koyanagi, Naoaki; Sakamoto, Hiroyuki; Uchida, Ikuo.

1992-01-01

The present invention concerns a radioactive waste solidification material containing vermiculite cement used for a vacuum packing type waste processing device, which contains no residue of calcium hydroxide in cement solidification products. No residue of calcium hydroxide means, for example, that peak of Ca(OH) 2 is not recognized in an X ray diffraction device. With such procedures, since calcium sulfoaluminate clinker and Portland cement themselves exhibit water hardening property, and slugs exhibit hydration activity from the early stage, the cement exhibits quick-hardening property, has great extension of long term strength, further, has no shrinking property, less dry- shrinkage, excellent durability, less causing damages such as cracks and peeling as processing products of radioactive wastes, enabling to attain highly safe solidification product. (T.M.)

Numerical study on morphology and solidification characteristics of successive droplet depositions on a substrate

Science.gov (United States)

Adaikalanathan, Vimalan

Successive droplet impingement finds extensive applications in additive manufacturing technologies such as 3D printing, Liquid Metal Jetting and Net Form Manufacturing. Deposition, deformation and solidification of droplets are the constitutive stages in the process which determine the final outcome. Detailed knowledge about the flow behaviour, phase transformation and free surface deformation is required to have a complete understanding and optimization of the process parameters. Experimental research in this field is only limited to imaging techniques and post solidification analysis which only provide superficial information while overlooking most of the governing phenomenon. Knowledge of the physics governing the fluid and thermal behaviours can be applied to study the process with real time data pertaining to flow field, temperature profiles and solidification. However, free surface tracking, surface tension modelling, non-isothermal solidification and convection dominant heat transfer pose mathematical challenges in the solution of the governing equations. Moreover, deposition of droplets on pre-solidified splats or non-flat surfaces requires accurate special attention. The objective of the present work is to model the successive droplet impacts and simultaneous solidification and deformation. The highly non-linear flow field governed by the Navier Stokes equation is solved using a Two Step Projection method. The surface tension effects are accounted for through a Continuum Surface Force technique. One of the crucial elements in the study is the interface tracking algorithm. A Coupled Level Set Volume of Fluid (CLSVOF) method is formulated to give an accurate orientation of the drastically deforming interface and also facilitates generation of multiple droplets in a fixed domain at a user defined frequency, thereby conserving computational resources. The phase change is modelled using an enthalpy formulation of the energy equation with an implicit source term

Investigation of the effect of different refrigerants on performances of binary geothermal power plants

International Nuclear Information System (INIS)

Basaran, Anil; Ozgener, Leyla

2013-01-01

Highlights: • Working fluid selection plays a key role on binary cycle performance. • Selected refrigerants were analyzed in the sample cycle under the same working conditions. • Energy and exergy efficiencies of binary cycle were calculated for 8 refrigerants. - Abstract: The paper tries to review the argument of the use of working fluids for binary cycle power plants and has been dedicated to this specific argument with a more general perspective. Binary cycle that allows the production of electricity from geothermal energy sources is one of these systems. In this cycle, thermal energy obtained from geothermal sources is transferred to second working fluid. Therefore, selection of second working fluid plays a key role on the cycle performance. In this study, a sample geothermal binary power cycle was modeled and 12 refrigerants that are HFC, HC, and zoetrope refrigerant mixtures were selected as working fluid. Energy and exergy efficiencies of binary cycle were calculated for 12 refrigerants. Dry type fluids of investigated refrigerants R 236ea, R 600, R 600a, and R 227ea showed higher energy and exergy efficiencies, respectively. On the other hand, R 143a, R 415A, R 290, and R 413A that are wet fluids indicated lower energy and exergy efficiencies, respectively

Method of plastic solidification of radioactive wastes

International Nuclear Information System (INIS)

Oikawa, Yasuo; Tokimitsu, Fujio.

1986-01-01

Purpose: To prevent occurrence of deleterious cracks to the inside and the surface of solidification products, as well as eliminate gaps between the products and the vessel inner wall upon plastic solidification processing for powdery or granular radioactive wastes. Method: An appropriate amount of thermoplastic resins such as styrenic polymer or vinyl acetate type polymer as a low shrinking agent is added and mixed with unsaturated polyester resins to be mixed with radioactive wastes so as to reduce the shrinkage-ratio to 0 % upon curing reaction. Thus, a great shrinkage upon hardening the mixture is suppressed to prevent the occurrence of cracks to the surface and the inside of the solidification products, as well as prevent the gaps between the inner walls of a drum can vessel and the products upon forming solidification products to the inside of the drum can. The resultant solidification products have a large compression strength and can sufficiently satisfy the evaluation standards as the plastic solidification products of radioactive wastes. (Horiuchi, T.)

Study of the influence of gravity on the thermodynamic equilibrium of a liquid alloy, and on its solidification: application to eutectic Al-Ge and monotectic Al-In alloys

International Nuclear Information System (INIS)

Vinet, Bernard

1981-01-01

After having recalled the meaning of gravity, this research thesis addresses the study of movements within the Earth gravity field to assess accelerations for a centrifuged system, and to describe conditions which create weightlessness. The various actions of gravity on fluid phases are analysed by highlighting phenomena of convection and segregation. In a second part, the author addresses the issue of local order. The third part addresses the influence of gravity conditions on the distribution of components of a binary liquid alloy in thermodynamic equilibrium. The fourth part addresses experimental means. The next parts address the eutectic Al-Ge alloy and the monotectic Al-In alloy. Results obtained for liquid alloy are presented, and the author analyse segregations which appeared during solidification in gravity conditions between 40 and 100 g. The influence of these conditions of the structure of both alloys is then studied

Method of storing solidification products

International Nuclear Information System (INIS)

Tani, Yutaro.

1985-01-01

Purpose: To enable to efficiently and satisfactorily cool and store solidification products of liquid wastes generated from the reactor spent fuel reprocessing process by a simple facility. Method: Liquid wastes generated from the reactor spent fuel reprocessing process are caused to flow from the upper opening to the inside of a spherical canistor. The opening of the spherical canistor is welded with a lid by a remote control and the liquid wastes are tightly sealed within the spherical canistor as glass solidification products. Spherical canistors having the solidification products tightly sealed therein are sent into and stored in a hopper by the remote control. Further, a blower is driven upon storing to suck cooling air from the cooling air intake port to the inside of the hopper to absorb the decay heat of radioactive materials in the solidification products and the air is discharged from the duct and through the stack to the atmosphere. (Kawakami, Y.)

Generalized Einstein relation for the mutual diffusion coefficient of a binary fluid mixture.

Science.gov (United States)

Felderhof, B U

2017-08-21

The method employed by Einstein to derive his famous relation between the diffusion coefficient and the friction coefficient of a Brownian particle is used to derive a generalized Einstein relation for the mutual diffusion coefficient of a binary fluid mixture. The expression is compared with the one derived by de Groot and Mazur from irreversible thermodynamics and later by Batchelor for a Brownian suspension. A different result was derived by several other workers in irreversible thermodynamics. For a nearly incompressible solution, the generalized Einstein relation agrees with the expression derived by de Groot and Mazur. The two expressions also agree to first order in solute density. For a Brownian suspension, the result derived from the generalized Smoluchowski equation agrees with both expressions.

Micro-scale thermocapillary convection with solidification

International Nuclear Information System (INIS)

Yang, W.J.; Liu, J.C.; Chai, A.T.

1991-01-01

This paper reports on an experimental study performed on heat transfer in sessile drops of lysozyme solutions with solidification. Solidification inside the sessile drop is initiated by means of the center cooling method. The internal flow behavior and solidification front movement are observed using a microscope-video monitor system. Results are obtained for lysozyme, and buffer solutions, and water, representing media possessing surface tension coefficients. It is disclosed that the time history of the solidification front movement can be divided into two stages; initial and stable. In the stable stage, the front movement x follows the power-law behavior x = Ct n . C is an empirical constant, and t denotes time. The exponent n takes on a value close to unity in the stable stage

Method of processing solidification product of radioactive waste

International Nuclear Information System (INIS)

Daime, Fumiyoshi.

1988-01-01

Purpose: To improve the long-time stability of solidification products by providing solidification products with liquid tightness, gas tightness, abrasion resistance, etc., of the products in the course of the solidification for the treatment of radioactive wastes. Method: The surface of solidification products prepared by mixing solidifying agents with powder or pellets is entirely covered with high molecular polymer such as epoxy resin. The epoxy resin has excellent properties such as radiation-resistance, heat resistance, water proofness and chemical resistance, as well as have satisfactory mechanical properties. This can completely isolate the solidification products of radioactive wastes from the surrounding atmosphere. (Yoshino, Y.)

Solidification process for toxic and hazardous wastes. Second part: Cement solidification matrices

International Nuclear Information System (INIS)

Donato, A.; Arcuri, L.; Dotti, M.; Pace, A.; Pietrelli, L.; Ricci, G.; Basta, M.; Cali, V.; Pagliai, V.

1989-05-01

This paper reports the second part of a general study carried out at the Nuclear Fuel Division aiming at verifying the possible application of the radioactive waste solidification processes to industrial hazardous wastes (RTN). The cement solidification of several RTN types has been taken into consideration, both from the technical and from the economic point of view. After a short examination of the Italian juridical and economical situation in the field, which demonstrates the need of the RTN solidification, the origin and characteristics of the RTN considered in the study and directly provided by the producing industries are reviewed. The laboratory experimental results of the cementation of RTN produced by gold manufacturing industries and by galvanic industries are reported. The cementation process can be considered a very effective mean for reducing both the RTN management costs and the environmental impact of RTN disposal. (author)

Simulation of the solidification in a channel of a water-cooled glass flow

Directory of Open Access Journals (Sweden)

G. E. Ovando Chacon

2014-12-01

Full Text Available A computer simulation study of a laminar steady-state glass flow that exits from a channel cooled with water is reported. The simulations are carried out in a two-dimensional, Cartesian channel with a backward-facing step for three different angles of the step and different glass outflow velocities. We studied the interaction of the fluid dynamics, phase change and thermal behavior of the glass flow due to the heat that transfers to the cooling water through the wall of the channel. The temperature, streamline, phase change and pressure fields are obtained and analyzed for the glass flow. Moreover, the temperature increments of the cooling water are characterized. It is shown that, by reducing the glass outflow velocity, the solidification is enhanced; meanwhile, an increase of the step angle also improves the solidification of the glass flow.

Solidification and vitrification life-cycle economics study

International Nuclear Information System (INIS)

Gimpel, R.F.

1992-01-01

Solidification (making concrete) and vitrification (making glass) are frequently the treatment methods recommended for treating inorganic or radioactive wastes. Ex-situ solidification and vitrification are the competing methods for treating in excess of 450 000 cm 3 of low-level radioactive and mixed wastes at the Fernald Environmental Management Project (FEMP) located near Cincinnati, Ohio. This paper summarizes a detailed study done to: (1) compare the economics of the solidification and vitrification processes, (2) determine if the stigma assigned to vitrification is warranted and, (3) determine if investing millions of dollars into vitrification development, along with solidification development, at Fernald is warranted

Solidification and vitrification life-cycle economics study

International Nuclear Information System (INIS)

Gimpel, R.F.

1992-01-01

Solidification (making concrete) and vitrification (making glass) are frequently the treatment methods recommended for treating inorganic or radioactive wastes. Solidification is generally perceived as the most economical treatment method, whereas vitrification is considered (by many) as the most effective of all treatment methods. Unfortunately, vitrification has acquired the stigma that it is too expensive to receive further consideration as an alternative to solidification in high volume treatment applications. Ex situ solidification and vitrification are the competing methods for treating in excess of 450,000 m 3 of low-level radioactive and mixed waste at the Fernald Environmental Management Project (FEMP or simply, Fernald) located near Cincinnati, Ohio. This paper s a detailed study done to: compare the economics of the solidification and vitrification processes; determine if the stigma assigned to vitrification is warranted; determine if investing millions of dollars into vitrification development, along with solidification development, at Fernald is warranted. Common parameters were determined and detailed life-cycle cost estimates were made. Incorporating the unit costs into a computer spreadsheet allowed 'what if' scenarios to be performed. Some scenarios investigated included variation of: remediation times, amount of wastes treated, treatment efficiencies, electrical and material costs and escalation

Solidification process for sludge residue

International Nuclear Information System (INIS)

Pearce, K.L.

1998-01-01

This report investigates the solidification process used at 100-N Basin to solidify the N Basin sediment and assesses the N Basin process for application to the K Basin sludge residue material. This report also includes a discussion of a solidification process for stabilizing filters. The solidified matrix must be compatible with the Environmental Remediation Disposal Facility acceptance criteria

Phase-field simulation of peritectic solidification closely coupled with directional solidification experiments in an Al-36 wt% Ni alloy

International Nuclear Information System (INIS)

Siquieri, R; Emmerich, H; Doernberg, E; Schmid-Fetzer, R

2009-01-01

In this work we present experimental and theoretical investigations of the directional solidification of Al-36 wt% Ni alloy. A phase-field approach (Folch and Plapp 2005 Phys. Rev. E 72 011602) is coupled with the CALPHAD (calculation of phase diagrams) method to be able to simulate directional solidification of Al-Ni alloy including the peritectic phase Al 3 Ni. The model approach is calibrated by systematic comparison to microstructures grown under controlled conditions in directional solidification experiments. To illustrate the efficiency of the model it is employed to investigate the effect of temperature gradient on the microstructure evolution of Al-36 wt% Ni during solidification.

Manufacture history results of an investigation of the bitumen solidification object towards the check of an abandonment object

International Nuclear Information System (INIS)

Kogawa, Noboru; Kondo, Toshiyuki

2001-08-01

In order to make this book reflect in the investigation which turned the bitumen solidification object to maintenance of the abandonment object technical standard on condition of carrying out subterranean disposal in the future, it created for the purpose of utilizing as precious sources of information, such as a nuclide inventory in the living body, group-izing of the past campaign required for typical solidification object selection, and information offer at the time of disposal examination. A development operation history collected so that histories including the shift action in an institution of the formation of discharge reduction of the characteristic of solidification object manufacture outlines, such as composition of the process of an institution and a solidification object and a storage actual result, the contents of an examination of the past campaign, and the solidification object manufactured based on topics or radioactive iodine and radioactive carbon etc., such as the past contents of an examination/operation, may grasp comprehensively in creation, and it carried out as the composition stared the trend of future disposal fixedly. It was a period (for 16 years) until an bituminization demonstration facility processing institution will start a cold examination from April (Showa 57), 1982, and it starts a hot examination from May 4, it starts solidification processing technical development operation from October 6 and it results in the fire explosion accident on March 11 (Heisei 9), 1997, and low level radioactivity concentration waste fluid was processed 7,438m 3 and 29,967 bitumen solidification objects were manufactured. According to the accident, it is necessary to hand it down to future generations with processing technology while the bitumen solidification object manufactured in 15 years although the bituminization demonstration facility processing institution came to close the mission holds information precious when considering future disposal

''New ' technology of solidification of liquid radioactive waste'

International Nuclear Information System (INIS)

Sytyl, V.A.; Svistova, L.M.; Spiridonova, V.P.

1998-01-01

It is generally accepted that the best method of processing of radioactive waste is its solidification and then storage. At present time, three methods of solidification of radioactive waste are widely used in the world: cementation, bituminous grouting and vitrification. But they do not solve the problem of ecologically processing of waste because of different disadvantages. General disadvantages are: low state of filling, difficulties in solidification of the crystalline hydrated forms of radioactive waste; particular sphere of application and economical difficulties while processing the great volume of waste. In connection with it the urgent necessity is emerging: to develop less expensive and ecologically more reliable technology of solidification of radioactive waste. A new method of solidification is presented with its technical schema. (N.C.)

Marangoni-buoyancy convection in binary fluids under varying noncondensable concentrations

Science.gov (United States)

Li, Yaofa; Yoda, Minami

2014-11-01

Marangoni-buoyancy convection in binary fluids in the presence of phase change is a complex and poorly understood problem. Nevertheless, this flow is of interest in evaporative cooling because solutocapillary stresses could reduce film dryout. Convection was therefore studied in methanol-water (MeOH-H2O) layers of depth h ~ 1 - 3 mm confined in a sealed rectangular cell driven by horizontal temperature differences of ~6° C applied over ~ 5 cm. Particle-image velocimetry (PIV) was used to study how varying the fraction of noncondensables (i.e., air) ca from ~ 7 mol% to ambient conditions in the vapor space affects soluto- and thermocapillary stresses in this flow. Although solutocapillary stresses can be used to drive the flow towards hot regions, solutocapillarity appears to have the greatest effect on the flow at small ca, because noncondensables suppress phase change and hence the gradient in the liquid-phase composition at the interface. Surprisingly, convection at ca ~ 50 % leads to a very weak flow and significant condensation in the central portion of the layer i.e., away from the heated and cooled walls). Supported by ONR.

Method of reprocessing radioactive asphalt solidification products

International Nuclear Information System (INIS)

Nakaya, Iwao; Murakami, Tadashi; Miyake, Takafumi; Inagaki, Yuzo.

1986-01-01

Purpose: To obtain heat-stable solidification products and decrease the total volume thereof by modifying the solidified form by the reprocessing of existent radioactive asphalt solidification products. Method: Radioactive asphalt solidification products are heated into a fluidized state. Then, incombustible solvents such as perchloroethylene or trichloroethylene are added to a dissolving tank to gradually dissolve the radioactive asphalt solidification products. Thus, organic materials such as asphalts are transferred into the solvent layer, while inorganic materials containing radioactive materials remain as they are in the separation tank. Then, the inorganic materials containing the radioactive materials are taken out and then solidified, for example, by converting them into a rock or glass form. (Kawakami, Y.)

In Situ Study of Microstructure Evolution in Solidification of Hypereutectic Al-Si Alloys with Application of Thermal Analysis and Neutron Diffraction

Science.gov (United States)

Sediako, Dimitry G.; Kasprzak, Wojciech

2015-09-01

Understanding of the kinetics of solid-phase evolution in solidification of hypereutectic aluminum alloys is a key to control their as-cast microstructure and resultant mechanical properties, and in turn, to enhance the service characteristics of actual components. This study was performed to evaluate the solidification kinetics for three P-modified hypereutectic Al-19 pct Si alloys: namely, Al-Si binary alloy and with the subsequent addition of 2.8 pct Cu and 2.8 pct Cu + 0.7 pct Mg. Metallurgical evaluation included thermodynamic calculations of the solidification process using the FactSage™ 6.2 software package, as well as experimental thermal analysis, and in situ neutron diffraction. The study revealed kinetics of solid α-Al, solid Si, Al2Cu, and Mg2Si evolution, as well as the individual effects of Cu and Mg alloying additions on the solidification path of the Al-Si system. Various techniques applied in this study resulted in some discrepancies in the results. For example, the FactSage computations, in general, resulted in 281 K to 286 K (8 °C to 13 °C) higher Al-Si eutectic temperatures than the ones recorded in the thermal analysis, which are also ~278 K (~5 °C) higher than those observed in the in situ neutron diffraction. None of the techniques can provide a definite value for the solidus temperature, as this is affected by the chosen calculation path [283 K to 303 K (10 °C to 30 °C) higher for equilibrium solidification vs non-equilibrium] for the FactSage analysis; and further complicated by evolution of secondary Al-Cu and Mg-Si phases that commenced at the end of solidification. An explanation of the discrepancies observed and complications associated with every technique applied is offered in the paper.

In situ synchrotron x-ray characterization of microstructure formation in solidification processing of Al-based metallic alloys

International Nuclear Information System (INIS)

Billia, Bernard; Nguyen-Thi, Henri; Mangelinck-Noel, Nathalie

2010-01-01

The microstructure formed during the solidification step has a major influence on the properties of materials processed by major techniques (casting, welding ...). In situ and real-time characterization by synchrotron X-ray imaging is the method of choice to unveil the dynamical formation of the solidification microstructure in metallic alloys, and thus provide precise data for the critical validation of the theoretical predictions that is needed for sound advancement of modeling and numerical simulation. After a description of the experimental procedure used at the European Synchrotron Radiation Facility (ESRF), dynamical phenomena in the formation of the grain structure and dendritic or equiaxed solidification microstructure in Al-based alloys are presented. Beyond fluid flow interaction, earth gravity induces stresses, deformation and fragmentation in the dendritic mush. Settling of dendrite arms and equiaxed grains thus occurs, in particular in the columnar to equiaxed transition. Other types of stresses and strains are caused by the mere formation of the solidification microstructure itself. In white-beam X-ray topography, stresses and strains are manifested by specific contrasts and breaking of the Laue images into several pieces. Finally, quantitative analysis of the grey level in radiographs enables the analysis of solute segregation, which noticeably results in solutal poisoning of growth when equiaxed grains are interacting. (author)

Application of the cubic-plus-association (CPA) equation of state to model the fluid phase behaviour of binary mixtures of water and tetrahydrofuran

DEFF Research Database (Denmark)

Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

2013-01-01

The complex fluid phase behaviour, of the binary system comprised of water and tetrahydrofuran (THF) is modelled by use of the cubic-plus-association (CPA) equation of state. A total of seven modelling approaches are analysed, differing only in their way of describing THF and its interactions...

Solidification of Hypereutectic Thin Wall Ductile Cast Iron

DEFF Research Database (Denmark)

Pedersen, Karl Martin; Tiedje, Niels Skat

2006-01-01

solidification. The first stage, which was relatively short, had none or very little recalescence. Further under cooling, followed by reheating during recalescence, was necessary to initiate the second part of the eutectic solidification. Both the secondary under cooling and recalescence was larger in the 3 mm...... a higher Si content in the ferrite around the larger nodules compared to the ferrite around the rest of the nodules. This indicates that solidification took place along the following path: The solidification starts with nucleation and growth of primary graphite nodules. This probably starts during...

Optimization of Magnetically Driven Directional Solidification of Silicon Using Artificial Neural Networks and Gaussian Process Models

Czech Academy of Sciences Publication Activity Database

Dropka, N.; Holeňa, Martin

2017-01-01

Roč. 471, 1 August (2017), s. 53-61 ISSN 0022-0248 R&D Projects: GA ČR GA17-01251S Institutional support: RVO:67985807 Keywords : computer simulation * fluid flows * magnetic fields * directional solidification * semiconducting silicon Subject RIV: IN - Informatics, Computer Science OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.751, year: 2016

Low level waste solidification practice in Japan

International Nuclear Information System (INIS)

Sakata, S.; Kuribayashi, H.; Kono, Y.

1981-01-01

Both sea dumping and land isolation are planned to be accomplished for low level waste disposal in Japan. The conceptual design of land isolation facilities has been completed, and site selection will presently get underway. With respect to ocean dumping, safety surveys are being performed along the lines of the London Dumping Convention and the Revised Definitions and Recommendations of the IAEA, and the review of Japanese regulations and applicable criteria is being expedited. This paper discusses the present approach to waste solidification practices in Japan. It reports that the bitumen solidification process and the plastic solidification process are being increasingly used in Japan. Despite higher investment costs, both processes have advantages in operating cost, and are comparable to the cement solidification process in overall costs

Relationships Between Solidification Parameters in A319 Aluminum Alloy

Science.gov (United States)

Vandersluis, E.; Ravindran, C.

2018-03-01

The design of high-performance materials depends on a comprehensive understanding of the alloy-specific relationships between solidification and properties. However, the inconsistent use of a particular solidification parameter for presenting materials characterization in the literature impedes inter-study comparability and the interpretation of findings. Therefore, there is a need for accurate expressions relating the solidification parameters for each alloy. In this study, A319 aluminum alloy castings were produced in a permanent mold with various preheating temperatures in order to control metal cooling. Analysis of the cooling curve for each casting enabled the identification of its liquidus, Al-Si eutectic, and solidus temperatures and times. These values led to the calculation of the primary solidification rate, total solidification rate, primary solidification time, and local solidification time for each casting, which were related to each other as well as to the average casting SDAS and material hardness. Expressions for each of their correlations have been presented with high coefficients of determination, which will aid in microstructural prediction and casting design.

Mesoscopic electrohydrodynamic simulations of binary colloidal suspensions

NARCIS (Netherlands)

Rivas, Nicolas; Frijters, Stefan; Pagonabarraga, Ignacio; Harting, Jens

2018-01-01

A model is presented for the solution of electrokinetic phenomena of colloidal suspensions in fluid mixtures. We solve the discrete Boltzmann equation with a Bhatnagar-Gross-Krook collision operator using the lattice Boltzmann method to simulate binary fluid flows. Solvent-solvent and solvent-solute

Heat transfer and fluid flow during laser spot welding of 304 stainless steel

CERN Document Server

He, X; Debroy, T

2003-01-01

The evolution of temperature and velocity fields during laser spot welding of 304 stainless steel was studied using a transient, heat transfer and fluid flow model based on the solution of the equations of conservation of mass, momentum and energy in the weld pool. The weld pool geometry, weld thermal cycles and various solidification parameters were calculated. The fusion zone geometry, calculated from the transient heat transfer and fluid flow model, was in good agreement with the corresponding experimentally measured values for various welding conditions. Dimensional analysis was used to understand the importance of heat transfer by conduction and convection and the roles of various driving forces for convection in the weld pool. During solidification, the mushy zone grew at a rapid rate and the maximum size of the mushy zone was reached when the pure liquid region vanished. The solidification rate of the mushy zone/liquid interface was shown to increase while the temperature gradient in the liquid zone at...

Physical and numerical modelling of corium spreading with solidification in safety studies of pressurized water reactors; Modelisation physique et numerique de l`etalement d`un fluide avec solidification dans le cadre des etudes de surete pour les reacteurs eau sous pression

Energy Technology Data Exchange (ETDEWEB)

Eberle Patrick [Service d`Etude et de Modelisation en Thermohydrolique, CEA/DRN/DTP/SMTH, Grenoble (France)]|[Grenoble-1 Univ., 74 Annecy (France)

1997-12-12

In the frame of severe accidents of nuclear pressurized water reactor, it is important to understand and to model phenomena of corium spreading with solidification. The first part of the study describes experiments with simulating materials as well as simple models of the literature. We deduce a model where the equations of conservation are averaged over the volume. This model gives interesting results for continuous spreading but it is not convenient for discontinuous phenomena. A more precise model is then necessary. In the second part of this study, we present a complete model from which the basic idea is to average the conservation equations over the fluid height, supposing the characteristic fluid thickness is small in comparison with the characteristic spreading length. This model describes the thermalhydraulic aspects of the spreading as well as the mechanical behaviour of the upper crust. The liquid phases are supposed to be stratified and have a Newtonian fluid behaviour. The dynamical crust model takes into account a non-linear behaviour law. This law depends on the deformation tensor whereas the liquid behaviour low, depends on the rate of deformation tensor, so it is necessary to link this two notions by supplementary equations. The operation of averaging the equations gives terms at the interfaces which must be determined by constitutive laws. We deduce laws by fixing the velocity and temperature profile in the fluid height. The previous system of equations is discretized by finite volumes and semi-implicit methods. The discretized models are included in the specific code THEMA. The results of the model show good agreement with available experimental results. (author) 9 refs., 45 figs., 42 tabs.

On the Role of Mantle Overturn during Magma Ocean Solidification

Science.gov (United States)

Boukaré, C. E.; Parmentier, E.; Parman, S. W.

2017-12-01

Solidification of potential global magma ocean(s) (MO) early in the history of terrestrial planets may play a key role in the evolution of planetary interiors by setting initial conditions for their long-term evolution. Constraining this initial structure of solid mantles is thus crucial but remains poorly understood. MO fractional crystallization has been proposed to generate gravitationally unstable Fe-Mg chemical stratification capable of driving solid-state mantle overturn. Fractional solidification and overturn hypothesis, while only an ideal limiting case, can explain important geochemical features of both the Moon and Mars. Current overturn models consider generally post-MO overturn where the cumulate pile remains immobile until the end of MO solidification. However, if the cumulate pile overturns during MO solidification, the general picture of early planet evolution might differ significantly from the static crystallization models. We show that the timing of mantle overturn can be characterized with a dimensionless number measuring the ratio of the MO solidification time and the purely compositional overturn timescale. Syn-solidification overturn occurs if this dimensionless parameter, Rc, exceeds a critical value. Rc is mostly affected by the competition between the MO solidification time and mantle viscosity. Overturn that occurs during solidification can result in smaller scales of mantle chemical heterogeneity that could persist for long times thus influencing the whole evolution of a planetary body. We will discuss the effects of compaction/percolation on mantle viscosity. If partially molten cumulate do not have time to compact during MO solidification, viscosity of cumulates would be significantly lower as the interstitcial melt fraction would be large. Both solid mantle remelting during syn-solidification overturn and porous convection of melt retained with the cumulates are expected to reduce the degree of fractional crystallization. Syn-solidification

Organic alloy systems suitable for the investigation of regular binary and ternary eutectic growth

Science.gov (United States)

Sturz, L.; Witusiewicz, V. T.; Hecht, U.; Rex, S.

2004-09-01

Transparent organic alloys showing a plastic crystal phase were investigated experimentally using differential scanning calorimetry and directional solidification with respect to find a suitable model system for regular ternary eutectic growth. The temperature, enthalpy and entropy of phase transitions have been determined for a number of pure substances. A distinction of substances with and without plastic crystal phases was made from their entropy of melting. Binary phase diagrams were determined for selected plastic crystal alloys with the aim to identify eutectic reactions. Examples for lamellar and rod-like eutectic solidification microstructures in binary systems are given. The system (D)Camphor-Neopentylglycol-Succinonitrile is identified as a system that exhibits, among others, univariant and a nonvariant eutectic reaction. The ternary eutectic alloy close to the nonvariant eutectic composition solidifies with a partially faceted solid-liquid interface. However, by adding a small amount of Amino-Methyl-Propanediol (AMPD), the temperature of the nonvariant eutectic reaction and of the solid state transformation from plastic to crystalline state are shifted such, that regular eutectic growth with three distinct nonfaceted phases is observed in univariant eutectic reaction for the first time. The ternary phase diagram and examples for eutectic microstructures in the ternary and the quaternary eutectic alloy are given.

Propagative selection of tilted array patterns in directional solidification

Science.gov (United States)

Song, Younggil; Akamatsu, Silvère; Bottin-Rousseau, Sabine; Karma, Alain

2018-05-01

We investigate the dynamics of tilted cellular/dendritic array patterns that form during directional solidification of a binary alloy when a preferred-growth crystal axis is misoriented with respect to the temperature gradient. In situ experimental observations and phase-field simulations in thin samples reveal the existence of a propagative source-sink mechanism of array spacing selection that operates on larger space and time scales than the competitive growth at play during the initial solidification transient. For tilted arrays, tertiary branching at the diverging edge of the sample acts as a source of new cells with a spacing that can be significantly larger than the initial average spacing. A spatial domain of large spacing then invades the sample propagatively. It thus yields a uniform spacing everywhere, selected independently of the initial conditions, except in a small region near the converging edge of the sample, which acts as a sink of cells. We propose a discrete geometrical model that describes the large-scale evolution of the spatial spacing profile based on the local dependence of the cell drift velocity on the spacing. We also derive a nonlinear advection equation that predicts the invasion velocity of the large-spacing domain, and sheds light on the fundamental nature of this process. The models also account for more complex spacing modulations produced by an irregular dynamics at the source, in good quantitative agreement with both phase-field simulations and experiments. This basic knowledge provides a theoretical basis to improve the processing of single crystals or textured polycrystals for advanced materials.

Finite element modelling of solidification phenomena

Indian Academy of Sciences (India)

Unknown

Abstract. The process of solidification process is complex in nature and the simulation of such process is required in industry before it is actually undertaken. Finite element method is used to simulate the heat transfer process accompanying the solidification process. The metal and the mould along with the air gap formation ...

Efficient estimation of diffusion during dendritic solidification

Science.gov (United States)

Yeum, K. S.; Poirier, D. R.; Laxmanan, V.

1989-01-01

A very efficient finite difference method has been developed to estimate the solute redistribution during solidification with diffusion in the solid. This method is validated by comparing the computed results with the results of an analytical solution derived by Kobayashi (1988) for the assumptions of a constant diffusion coefficient, a constant equilibrium partition ratio, and a parabolic rate of the advancement of the solid/liquid interface. The flexibility of the method is demonstrated by applying it to the dendritic solidification of a Pb-15 wt pct Sn alloy, for which the equilibrium partition ratio and diffusion coefficient vary substantially during solidification. The fraction eutectic at the end of solidification is also obtained by estimating the fraction solid, in greater resolution, where the concentration of solute in the interdendritic liquid reaches the eutectic composition of the alloy.

Solidification microstructures of aluminium-uranium alloys

International Nuclear Information System (INIS)

Ambrozio Filho, F.; Vieira, R.R.

1976-01-01

The solidification of microstrutures of aluminium-uranium alloys in the range of 4 to 20% uranium is investigated. The solidification was obtained both in ingot molds and under controlled directional solidification. The conditions for the presence of primary crystals and eutectic are discussed and an analysis of the influence of variables (growth rate and thermal gradient in the liquid) on the alloy structure is made. The effect of cooling rate on the alloy structures has been determined. It is found that the resulting structure can be derived from the kinectics concept, as required by the coupled-zone theory. Suggestions on the qualitative intervals of composition and temperatures with eutectic growth are presented [pt

Polymer solidification national program

International Nuclear Information System (INIS)

Kalb, P.D.; Colombo, P.

1993-04-01

Brookhaven National Laboratory (BNL) has developed several new and innovative polymer processes for the solidification of low-level radioactive, hazardous and mixed wastes streams. Polyethylene and modified sulfur cement solidification technologies have undergone steady, gradual development at BNL over the past nine years. During this time they have progressed through each of the stages necessary for logical technology maturation: from process conception, parameter optimization, waste form testing, evaluation of long-term durability, economic analysis, and scale-up feasibility. This technology development represents a significant investment which can potentially provide DOE with both short- and long-term savings

Thermodynamic description of the Al-Cu-Mg-Mn-Si quinary system and its application to solidification simulation

International Nuclear Information System (INIS)

Chang, Keke; Liu, Shuhong; Zhao, Dongdong; Du, Yong; Zhou, Liangcai; Chen, Li

2011-01-01

By means of the first-principles calculations, the enthalpy of formation for the quaternary phase in the Al-Cu-Mg-Si system was computed. A set of self-consistent thermodynamic parameters for the Al-Cu-Mg-Si and Al-Cu-Mn-Si systems was then obtained using CALPHAD approach taking into account the reliable experimental data and the first-principles calculations. The thermodynamic database for the Al-Cu-Mg-Mn-Si system was developed based on the constituent binary, ternary, and quaternary systems. Comprehensive comparisons between the calculated and measured phase diagrams and invariant reactions showed that the experimental information was satisfactorily accounted for by the present thermodynamic description. The obtained database was used to describe the solidification behavior of Al alloys B319.1 (90.2Al-6Si-3.5Cu-0.3Mg, in wt.%) and B319.1 + xMn (x = 0.5-2, in wt.%) under Gulliver-Scheil non-equilibrium condition. The reliability of the present thermodynamic database was also verified by the good agreement between calculation and experiment for Gulliver-Scheil non-equilibrium solidification.

Osmotic Suppression of Positional Fluctuation of a Trapped Particle in a Near-Critical Binary Fluid Mixture in the Regime of the Gaussian Model

Science.gov (United States)

Fujitani, Youhei

2017-11-01

Suppose a spherical colloidal particle surrounded by a near-critical binary fluid mixture in the homogeneous phase. The particle surface usually preferentially attracts one component of the mixture, and the resultant concentration gradient, which causes the osmotic pressure, becomes significant in the ambient near-criticality. The concentration profile is deformed by the particle motion, and can generate a nonzero force exerted on the moving particle. This link was previously shown to slightly suppress the positional equal-time correlation of a particle trapped by a harmonic potential. This previous study presupposed a small fluctuation amplitude of a particle much larger than the correlation length, a weak preferential attraction, and the Gaussian model for the free-energy functional of the mixture. In the present study, we calculate the equal-time correlation without assuming the weak preferential attraction and show that the suppression becomes much more distinct in some range of the trap stiffness because of the increased induced mass. This suggests the possible experimental usage of a trapped particle as a probe for local environments of a near-critical binary fluid mixture.

Solidification with back-diffusion of irregular eutectics

Directory of Open Access Journals (Sweden)

M. Trepczyńska-Łent

2008-10-01

Full Text Available The definition of the α - parameter back-diffusion has been introduced in the work. The alternative models of solidification were describedtaking into consideration back-diffusion process. The possibility of using those models for eutectic alloys solidification is worthyof interest.

Solidification control in continuous casting of steel

Indian Academy of Sciences (India)

Unknown

Solidification in continuous casting (CC) technology is initiated in a water- ..... to fully austenitic solidification, and FP between 0 and 1 indicates mixed mode. ... the temperature interval (LIT – TSA) corresponding to fs = 0⋅9 → 1, is in reality the.

Solidification at the micro-scale

International Nuclear Information System (INIS)

Howe, A.

2003-01-01

The experimental determination and computer simulation of the micro-segregation accompanying the solidification of alloys continues to be a subject of much academic and industrial interest. Both are subject to progressively more sophisticated analyses, and a discussion is offered regarding the development and practical use of such studies. Simple steels are particularly difficult targets for such work: solidification does not end conveniently in a eutectic, the rapid diffusion particularly in the delta-ferrite phase obscures most evidence of what had occurred at the micro-scale during solidification, and one or more subsequent solid state phase transformations further obscure such details. Also, solidification at the micro-scale is inherently variable: the usual, dendrite morphologies encountered are, after all, instabilities in growth behaviour, and therefore such variability should be expected. For questions such as the relative susceptibility of different grades to particular problems, it is the average, typical behaviour that is of interest, whereas for other questions such as the on-set of macro-segregation, the local variability is paramount. Depending on the question being asked, and indeed the accuracy with which validatory data are available, simple pseudo-analytical equations employing various limiting assumptions, or sophisticated models which remove the need for most such limitations, could be appropriate. This paper highlights the contribution to such studies of various collaborative research forums within the European Union with which the author is involved. (orig.) [de

Solidification behaviors of a single-crystal superalloy under lateral constraints

International Nuclear Information System (INIS)

Zhuangqi Hu; Huaming Wang

1993-01-01

The effect of lateral constraints ahead of solidification interface on the solidification behaviors of a newly developed hot corrosion resistant single-crystal nickel-base superalloy was investigated under commercial single-crystal production conditions. The lateral constraints or section variations ahead of solidification front were found to have drastic influences both on the modes of solidification and the profiles of solute segregation. As lateral constraints were imposed ahead of the directionally solidifying interface, the solidification microstructure of the single-crystal superalloy changed suddenly, through a γ/γ' eutectic-free zone which is characterized by an extremely-fine and highly-developed dendrite network, from the original well-branched dendritic structure to a fine cellular-dendrite or regular cell structure, accompanying which the primary arm spacing, the severity of segregation and the amount of microporosity decreased remarkably. The newly formed cellular dendrite or cell structure transforms always gradually to the initial coarse dendrite structure as the lateral constraint is finally released whether gradually or sharply. Moreover, an abnormal porosity zone was readily observed in the initial section beneath and away from the eutectic-free zone. The solidification microstructural changes were attributed to the drastic dynamical changes in local solidification cooling conditions and in momentum transport during solidification due to the presence of lateral constraint

Plastic solidification system at Hamaoka Nuclear Power Station

International Nuclear Information System (INIS)

Okajima, Hiroyuki; Iokibe, Hiroyuki; Tsukiyama, Shigeru; Suzuki, Michio; Yamaguchi, Masato

1987-01-01

In Unit 1 and 2 of the Hamaoka Nuclear Power Station, radioactive waste was previously solidified in cement. By this method, the quantity of waste thus treated is relatively small, resulting in large number of the solidified drums. In order to solve this problem, the solidification facility using a thermosetting resin was employed, which is in operation since January 1986 for Unit 1, 2 and 3. As compared with the cement solidification, the solidified volume of concentrated liquid is about 1/12 and of spent-resin slurry is about 1/4 in plastic solidification. The following are described: course leading to the employment, the plastic solidification facility, features of the facility, operation results so far with the facility, etc. (Mori, K.)

Solidification of oils and organic liquids

International Nuclear Information System (INIS)

Clark, D.E.; Colombo, P.; Neilson, R.M. Jr.

1982-07-01

The suitability of selected solidification media for application in the disposal of low-level oil and other organic liquid wastes has been investigated. In the past, these low-level wastes (LLWs) have commonly been immobilized by sorption onto solid absorbents such as vermiculite or diatomaceous earth. Evolving regulations regarding the disposal of these materials encourage solidification. Solidification media which were studied include Portland type I cement; vermiculite plus Portland type I cement; Nuclear Technology Corporation's Nutek 380-cement process; emulsifier, Portland type I cement-sodium silicate; Delaware Custom Materiel's cement process; and the US Gypsum Company's Envirostone process. Waste forms have been evaluated as to their ability to reliably produce free standing monolithic solids which are homogeneous (macroscopically), contain < 1% free standing liquids by volume and pass a water immersion test. Solidified waste form specimens were also subjected to vibratory shock testing and flame testing. Simulated oil wastes can be solidified to acceptable solid specimens having volumetric waste loadings of less than 40 volume-%. However, simulated organic liquid wastes could not be solidified into acceptable waste forms above a volumetric loading factor of about 10 volume-% using the solidification agents studied

Noble gas, binary mixtures for commercial gas-cooled reactor systems

International Nuclear Information System (INIS)

El-Genk, M. S.; Tournier, J. M.

2007-01-01

Commercial gas cooled reactors employ helium as a coolant and working fluid for the Closed Brayton Cycle (CBC) turbo-machines. Helium has the highest thermal conductivity and lowest dynamic viscosity of all noble gases. This paper compares the relative performance of pure helium to binary mixtures of helium and other noble gases of higher molecular weights. The comparison is for the same molecular flow rate, and same operating temperatures and geometry. Results show that although helium is a good working fluid because of its high heat transfer coefficient and significantly lower pumping requirement, a binary gas mixture of He-Xe with M = 15 gm/mole has a heat transfer coefficient that is ∼7% higher than that of helium and requires only 25% of the number stages of the turbo-machines. The binary mixture, however, requires 3.5 times the pumping requirement with helium. The second best working fluid is He-Kr binary mixture with M = 10 gm/mole. It has 4% higher heat transfer coefficient than He and requires 30% of the number of stages in the turbo-machines, but requires twice the pumping power

Tidal and magnetic interactions in close binary stars

International Nuclear Information System (INIS)

Campbell, C.G.

1983-03-01

The thesis investigates the nature of non-synchronous motions in members of close binary stars under the influence of gravitational and magnetic fields existing in these systems, and the evolution of such motions in different classes of binaries. Largely convective stars are considered and a solution is found for the fluid flow associated with the non-synchronous rotation of such a secondary in a close binary system, taking tidal and rotational forces into account. The tidal velocity field is calculated for a low mass white dwarf secondary star in a twin - degenerate binary. It is found that the synchronisation times can be comparable to the lifetime of the binary so that some asynchronism may remain present. (U.K.)

Phase selection and microstructure in directional solidification of glass forming Pd-Si-Cu alloys

Science.gov (United States)

Huo, Yang

Phase selection and microstructure formation during the rapid solidification of alloy melts has been a topic of substantial interest over the last several decades, attributed mainly to the access to novel structures involving metastable crystalline and non-crystalline phases. In this work, Bridgeman type directional solidification was conducted in Pd-Si-Cu glass forming system to study such cooling rate dependent phase transition and microstructure formation. The equilibrium state for Pd-Si-Cu ternary system was investigated through three different works. First of all, phase stabilities for Pd-Si binary system was accessed with respects of first-principles and experiments, showing Pd5Si, Pd9Si2, Pd3Si and Pd 2Si phase are stable all way to zero Kevin while PdSi phase is a high temperature stable phase, and Pd2Si phase with Fe2P is a non-stoichiometry phase. A thermodynamic database was developed for Pd-Si system. Second, crystal structures for compounds with ternary compositions were studied by XRD, SEM and TEM, showing ordered and disordered B2/bcc phases are stable in Pd-rich part. At last, based on many phase equilibria and phase transitions data, a comprehensive thermodynamic discrption for Pd-Si-Cu ternary system was first time to be developed, from which different phase diagrams and driving force for kinetics can be calculated. Phase selection and microstructure formation in directional solidification of the best glass forming composition, Pd 77.5Si16.5Cu6, in this system with growth velocities from 0.005 to 7.5mm/s was systematically studied and the solidification pathways at different conditions were interpreted from thermodynamic simulation. The results show that for growth velocities are smaller than 0.1mm/s Pd 3Si phase is primary phase and Pd9Si2 phase is secondary phase, the difficulty for Pd9Si2 phase nucleation gives rise to the formation of two different eutectic structure. For growth velocities between 0.4 and 1mm/s, instead of Pd3Si phase, Pd9Si2

Instabilities in rapid directional solidification under weak flow

Science.gov (United States)

Kowal, Katarzyna N.; Davis, Stephen H.; Voorhees, Peter W.

2017-12-01

We examine a rapidly solidifying binary alloy under directional solidification with nonequilibrium interfacial thermodynamics viz. the segregation coefficient and the liquidus slope are speed dependent and attachment-kinetic effects are present. Both of these effects alone give rise to (steady) cellular instabilities, mode S , and a pulsatile instability, mode P . We examine how weak imposed boundary-layer flow of magnitude |V | affects these instabilities. For small |V | , mode S becomes a traveling and the flow stabilizes (destabilizes) the interface for small (large) surface energies. For small |V | , mode P has a critical wave number that shifts from zero to nonzero giving spatial structure. The flow promotes this instability and the frequencies of the complex conjugate pairs each increase (decrease) with flow for large (small) wave numbers. These results are obtained by regular perturbation theory in powers of V far from the point where the neutral curves cross, but requires a modified expansion in powers of V1 /3 near the crossing. A uniform composite expansion is then obtained valid for all small |V | .

Spinodal decomposition in fluid mixtures

International Nuclear Information System (INIS)

Kawasaki, Kyozi; Koga, Tsuyoshi

1993-01-01

We study the late stage dynamics of spinodal decomposition in binary fluids by the computer simulation of the time-dependent Ginzburg-Landau equation. We obtain a temporary linear growth law of the characteristic length of domains in the late stage. This growth law has been observed in many real experiments of binary fluids and indicates that the domain growth proceeds by the flow caused by the surface tension of interfaces. We also find that the dynamical scaling law is satisfied in this hydrodynamic domain growth region. By comparing the scaling functions for fluids with that for the case without hydrodynamic effects, we find that the scaling functions for the two systems are different. (author)

Containerless solidification of acoustically levitated Ni-Sn eutectic alloy

Energy Technology Data Exchange (ETDEWEB)

Geng, D.L.; Xie, W.J.; Wei, B. [Northwestern Polytechnical University, Department of Applied Physics, Xi' an (China)

2012-10-15

Containerless solidification of Ni-18.7at%Sn eutectic alloy has been achieved with a single-axis acoustic levitator. The temperature, motion, and oscillation of the sample were monitored by a high speed camera. The temperature of the sample can be determined from its image brightness, although the sample moves vertically and horizontally during levitation. The experimentally observed frequency of vertical motion is in good agreement with theoretical prediction. The sample undergoes shape oscillation before solidification finishes. The solidification microstructure of this alloy consists of a mixture of anomalous eutectic plus regular lamellar eutectic. This indicates the achievement of rapid solidification under acoustic levitation condition. (orig.)

Solidification microstructures and solid-state parallels: Recent developments, future directions

Energy Technology Data Exchange (ETDEWEB)

Asta, M. [Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, CA 95616 (United States); Beckermann, C. [Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, IA 52242 (United States); Karma, A. [Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115 (United States); Kurz, W. [Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland)], E-mail: wilfried.kurz@epfl.ch; Napolitano, R. [Department of Materials Science and Engineering, Iowa State University, and Ames Laboratory USDOE, Ames, IA 50011 (United States); Plapp, M. [Physique de la Matiere Condensee, Ecole Polytechnique, CNRS, 91128 Palaiseau (France); Purdy, G. [Department of Materials Science and Engineering, McMaster University, Hamilton, Ont., L8S 4L7 (Canada); Rappaz, M. [Institute of Materials, Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne (Switzerland); Trivedi, R. [Department of Materials Science and Engineering, Iowa State University, and Ames Laboratory USDOE, Ames, IA 50011 (United States)

2009-02-15

Rapid advances in atomistic and phase-field modeling techniques as well as new experiments have led to major progress in solidification science during the first years of this century. Here we review the most important findings in this technologically important area that impact our quantitative understanding of: (i) key anisotropic properties of the solid-liquid interface that govern solidification pattern evolution, including the solid-liquid interface free energy and the kinetic coefficient; (ii) dendritic solidification at small and large growth rates, with particular emphasis on orientation selection; (iii) regular and irregular eutectic and peritectic microstructures; (iv) effects of convection on microstructure formation; (v) solidification at a high volume fraction of solid and the related formation of pores and hot cracks; and (vi) solid-state transformations as far as they relate to solidification models and techniques. In light of this progress, critical issues that point to directions for future research in both solidification and solid-state transformations are identified.

Noble gas binary mixtures for gas-cooled reactor power plants

International Nuclear Information System (INIS)

El-Genk, Mohamed S.; Tournier, Jean-Michel

2008-01-01

This paper examines the effects of using noble gases and binary mixtures as reactor coolants and direct closed Brayton cycle (CBC) working fluids on the performance of terrestrial nuclear power plants and the size of the turbo-machines. While pure helium has the best transport properties and lowest pumping power requirement of all noble gases and binary mixtures, its low molecular weight increases the number of stages of the turbo-machines. The heat transfer coefficient for a He-Xe binary mixture having a molecular weight of 15 g/mole is 7% higher than that of helium, and the number of stages in the turbo-machines is 24-30% of those for He working fluid. However, for the same piping and heat exchange components design, the loop pressure losses with He-Xe are ∼3 times those with He. Consequently, for the same reactor exit temperature and pressure losses in piping and heat exchange components, the higher pressure losses in the nuclear reactor decrease the net peak efficiency of the plant with He-Xe working fluid (15 g/mole) by a little more than ∼2% points, at higher cycle compression ratio than with He working fluid

Solidification effects on sill formation: An experimental approach

Science.gov (United States)

Chanceaux, L.; Menand, T.

2014-10-01

Sills represent a major mechanism for constructing continental Earth's crust because these intrusions can amalgamate and form magma reservoirs and plutons. As a result, numerous field, laboratory and numerical studies have investigated the conditions that lead to sill emplacement. However, all previous studies have neglected the potential effect magma solidification could have on sill formation. The effects of solidification on the formation of sills are studied and quantified with scaled analogue laboratory experiments. The experiments presented here involved the injection of hot vegetable oil (a magma analogue) which solidified during its propagation as a dyke in a colder and layered solid of gelatine (a host rock analogue). The gelatine solid had two layers of different stiffness, to create a priori favourable conditions to form sills. Several behaviours were observed depending on the injection temperature and the injection rate: no intrusions (extreme solidification effects), dykes stopping at the interface (high solidification effects), sills (moderate solidification effects), and dykes passing through the interface (low solidification effects). All these results can be explained quantitatively as a function of a dimensionless temperature θ, which describes the experimental thermal conditions, and a dimensionless flux ϕ, which describes their dynamical conditions. The experiments reveal that sills can only form within a restricted domain of the (θ , ϕ) parameter space. These experiments demonstrate that contrary to isothermal experiments where cooling could not affect sill formation, the presence of an interface that would be a priori mechanically favourable is not a sufficient condition for sill formation; solidification effects restrict sill formation. The results are consistent with field observations and provide a means to explain why some dykes form sills when others do not under seemingly similar geological conditions.

Investigation of waste heat recovery of binary geothermal plants using single component refrigerants

Science.gov (United States)

Unverdi, M.

2017-08-01

In this study, the availability of waste heat in a power generating capacity of 47.4 MW in Germencik Geothermal Power Plant has been investigated via binary geothermal power plant. Refrigerant fluids of 7 different single components such as R-134a, R-152a, R-227ea, R-236fa, R-600, R-143m and R-161 have been selected. The binary cycle has been modeled using the waste heat equaling to mass flow rate of 100 kg/s geothermal fluid. While the inlet temperature of the geothermal fluid into the counter flow heat exchanger has been accepted as 110°C, the outlet temperature has been accepted as 70°C. The inlet conditions have been determined for the refrigerants to be used in the binary cycle. Finally, the mass flow rate of refrigerant fluid and of cooling water and pump power consumption and power generated in the turbine have been calculated for each inlet condition of the refrigerant. Additionally, in the binary cycle, energy and exergy efficiencies have been calculated for 7 refrigerants in the availability of waste heat. In the binary geothermal cycle, it has been found out that the highest exergy destruction for all refrigerants occurs in the heat exchanger. And the highest and lowest first and second law efficiencies has been obtained for R-600 and R-161 refrigerants, respectively.

Ensemble averaged multi-phase Eulerian model for columnar/equiaxed solidification of a binary alloy: II. Simulation of the columnar-to-equiaxed transition (CET)

International Nuclear Information System (INIS)

Ciobanas, A I; Fautrelle, Y

2007-01-01

A new multi-phase Eulerian model for the columnar and equiaxed dendritic solidification has been developed. In this paper we first focus on the numerical simulation of quasi-steady solidification experiments in order to obtain corresponding CET maps. We have identified three main zones on the CET map: the pure columnar, the pure equiaxed zone and finally the mixed columnar+equiaxed zone. The mixed c/e zone was further quantified by means of a columnar fraction ε c which quantifies in a rigorous way the two coexisting structures. Since it intrinsically includes the solutal and the mechanical blocking effects, the new ensemble model unifies the semi-empirical Hunt's approach (pure mechanical blocking mechanism) and the Martorano et al approach (pure solutal blocking mechanism). Secondly the present model was used to simulate unidirectional solidification experiments. It was found that the columnar front evolved in a quasi-steady state until a time very close to the critical CET moment. It is also found that the equiaxed nucleation undercooling is close to the maximum columnar dendrite tip undercooling and that the CET is virtually independent of the equiaxed zone ahead of the columnar front. If the equiaxed zone is not taken into account it is observed that the columnar front velocity exhibits a sudden increase at the beginning of the solidification followed by a quasi-plateau corresponding to a quasi-state at the columnar tips and finally, above a critical time, an oscillatory evolution. The beginning of the oscillatory evolution of the columnar front was well correlated with the CET position measured in the experiments. We also find that this oscillatory evolution of the columnar front is very favourable for the fragmentation of the columnar dendrites and thus for the CET. In this respect, it seems that the unsteady regime of the columnar front with respect to the local cooling conditions represents the main cause for the CET phenomena, at least for the non

Chemical radwaste solidification processes

International Nuclear Information System (INIS)

Malloy, C.W.

1979-01-01

Some of these processes and their problems are briefly reviewed: early cement systems; urea-formaldehyde; Dow solidification process; low-viscosity chemical agents (POLYPAC); and water-extensible polyester. 9 refs

Modeling and analysis of advanced binary cycles

Energy Technology Data Exchange (ETDEWEB)

Gawlik, K.

1997-12-31

A computer model (Cycle Analysis Simulation Tool, CAST) and a methodology have been developed to perform value analysis for small, low- to moderate-temperature binary geothermal power plants. The value analysis method allows for incremental changes in the levelized electricity cost (LEC) to be determined between a baseline plant and a modified plant. Thermodynamic cycle analyses and component sizing are carried out in the model followed by economic analysis which provides LEC results. The emphasis of the present work is on evaluating the effect of mixed working fluids instead of pure fluids on the LEC of a geothermal binary plant that uses a simple Organic Rankine Cycle. Four resources were studied spanning the range of 265{degrees}F to 375{degrees}F. A variety of isobutane and propane based mixtures, in addition to pure fluids, were used as working fluids. This study shows that the use of propane mixtures at a 265{degrees}F resource can reduce the LEC by 24% when compared to a base case value that utilizes commercial isobutane as its working fluid. The cost savings drop to 6% for a 375{degrees}F resource, where an isobutane mixture is favored. Supercritical cycles were found to have the lowest cost at all resources.

An adaptive mesh refinement-multiphase lattice Boltzmann flux solver for simulation of complex binary fluid flows

Science.gov (United States)

Yuan, H. Z.; Wang, Y.; Shu, C.

2017-12-01

This paper presents an adaptive mesh refinement-multiphase lattice Boltzmann flux solver (AMR-MLBFS) for effective simulation of complex binary fluid flows at large density ratios. In this method, an AMR algorithm is proposed by introducing a simple indicator on the root block for grid refinement and two possible statuses for each block. Unlike available block-structured AMR methods, which refine their mesh by spawning or removing four child blocks simultaneously, the present method is able to refine its mesh locally by spawning or removing one to four child blocks independently when the refinement indicator is triggered. As a result, the AMR mesh used in this work can be more focused on the flow region near the phase interface and its size is further reduced. In each block of mesh, the recently proposed MLBFS is applied for the solution of the flow field and the level-set method is used for capturing the fluid interface. As compared with existing AMR-lattice Boltzmann models, the present method avoids both spatial and temporal interpolations of density distribution functions so that converged solutions on different AMR meshes and uniform grids can be obtained. The proposed method has been successfully validated by simulating a static bubble immersed in another fluid, a falling droplet, instabilities of two-layered fluids, a bubble rising in a box, and a droplet splashing on a thin film with large density ratios and high Reynolds numbers. Good agreement with the theoretical solution, the uniform-grid result, and/or the published data has been achieved. Numerical results also show its effectiveness in saving computational time and virtual memory as compared with computations on uniform meshes.

Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

Directory of Open Access Journals (Sweden)

Zhang Xian-Ping

2015-01-01

Full Text Available As an eco-friendly working fluid, carbon dioxide or R744 is expected to substitute for the existing working fluids used in heat pump systems. It is, however, challenged by the much higher heat rejection pressure in transcritical cycle compared with the traditional subcritical cycle using freons. There exists a worldwide tendency to utilize blend refrigerants as alternatives. Therefore, a new binary blend R744/R161 in this research is proposed in order to decrease the heat rejection pressure. Meanwhile, on mixing R744 with R161, the flammability and explosivity of R161 can be suppressed because of the extinguishing effect of R744. A transcritical thermodynamic model is developed, and then the system performances of heat pump using R744/R161 blend are investigated and compared with those of pure R744 system under the same operation conditions. The variations of heat rejection pressure, heating coefficient of performance, unit volumetric heating capacity, discharge temperature of compressor and the mass fraction of R744/R161 are researched. The results show that R744/R161 mixture can reduce the heat rejection pressure of transcritical heat pump system.

Determination for the Entrapment Criterion of Non-metallic Inclusions by the Solidification Front During Steel Centrifugal Continuous Casting

Science.gov (United States)

Wang, Qiangqiang; Zhang, Lifeng

2016-06-01

In the current study, the three-dimensional fluid flow, heat transfer, and solidification in steel centrifugal continuous casting strands were simulated. The volume of fluid model was used to solve the multiphase phenomena between the molten steel and the air. The entrapment and final distribution of inclusions in the solidified shell were studied with the discussion on the effect of rotation behavior of the caster system. Main results indicate that after applying the rotation of the shell, the fluid flow transformed from a recirculation flow to a rotation flow in the mold region and was driven to flow around in the casting direction. As the distance below the meniscus increased, the distribution of the tangential speed of the flow and the centrifugal force along one diameter of the strand became symmetrical gradually. The jet flow from the nozzle hardly impinged on the same location on the shell due to the rotation of the shell during solidification. Thus, the shell thickness on the same height was uniform around, and the thinning shell and a hot spot on the surface of shell were avoided. Both of the measurement and the calculation about the distribution of oxide inclusions along the radial direction indicated the number of inclusions at the side and the center was more than that at the quarter on the cross section of billet. With a larger diameter, inclusions tended to be entrapped toward the center area of the billet.

Polymer Solidification Technology - Technical Issues and Challenges

International Nuclear Information System (INIS)

Jensen, Charles; Kim, Juyoul

2010-01-01

Many factors come into play, most of which are discovered and resolved only during full-scale solidification testing of each of the media commonly used in nuclear power plants. Each waste stream is unique, and must be addressed accordingly. This testing process is so difficult that Diversified's Vinyl Ester Styrene and Advanced Polymer Solidification are the only two approved processes in the United States today. This paper summarizes a few of the key obstacles that must be overcome to achieve a reliable, repeatable process for producing an approved Stable Class B and C waste form. Before other solidification and encapsulation technologies can be considered compliant with the requirements of a Stable waste form, the tests, calculations and reporting discussed above must be conducted for both the waste form and solidification process used to produce the waste form. Diversified's VERI TM and APS TM processes have gained acceptance in the UK. These processes have also been approved and gained acceptance in the U. S. because we have consistently overcome technical hurdles to produce a complaint product. Diversified Technologies processes are protected intellectual property. In specific instances, we have patents pending on key parts of our process technology

Homogeneous Free Cooling State in Binary Granular Fluids of Inelastic Rough Hard Spheres

Science.gov (United States)

Santos, Andrés

2011-05-01

In a recent paper [A. Santos, G. M. Kremer, and V. Garzó, Prog. Theor. Phys. Suppl. 184, 31-48 (2010)] the collisional energy production rates associated with the translational and rotational granular temperatures in a granular fluid mixture of inelastic rough hard spheres have been derived. In the present paper the energy production rates are explicitly decomposed into equipartition rates (tending to make all the temperatures equal) plus genuine cooling rates (reflecting the collisional dissipation of energy). Next the homogeneous free cooling state of a binary mixture is analyzed, with special emphasis on the quasi-smooth limit. A previously reported singular behavior (according to which a vanishingly small amount of roughness has a finite effect, with respect to the perfectly smooth case, on the asymptotic long-time translational/translational temperature ratio) is further elaborated. Moreover, the study of the time evolution of the temperature ratios shows that this dramatic influence of roughness already appears in the transient regime for times comparable to the relaxation time of perfectly smooth spheres.

Progress on Numerical Modeling of the Dispersion of Ceramic Nanoparticles During Ultrasonic Processing and Solidification of Al-Based Nanocomposites

Science.gov (United States)

Zhang, Daojie; Nastac, Laurentiu

2016-12-01

In present study, 6061- and A356-based nano-composites are fabricated by using the ultrasonic stirring technology (UST) in a coreless induction furnace. SiC nanoparticles are used as the reinforcement. Nanoparticles are added into the molten metal and then dispersed by ultrasonic cavitation and acoustic streaming assisted by electromagnetic stirring. The applied UST parameters in the current experiments are used to validate a recently developed magneto-hydro-dynamics (MHD) model, which is capable of modeling the cavitation and nanoparticle dispersion during UST processing. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, and electromagnetic field, as well as the complex interaction between the nanoparticles and both the molten and solidified alloys by using ANSYS Maxwell and ANSYS Fluent. Molecular dynamics (MD) simulations are conducted to analyze the complex interactions between the nanoparticle and the liquid/solid interface. The current modeling results demonstrate that a strong flow can disperse the nanoparticles relatively well during molten metal and solidification processes. MD simulation results prove that ultrafine particles (10 nm) will be engulfed by the solidification front instead of being pushed, which is beneficial for nano-dispersion.

Solidification paths in modified Inconel 625 weld overlay material

DEFF Research Database (Denmark)

Chandrasekaran, Karthik; Tiedje, Niels Skat; Hald, John

2009-01-01

Inconel 625 is commonly used for overlay welding to protect the base metal against high temperature corrosion. The efficiency of corrosion protection depends on effective mixing of the overlay weld with the base metal and the subsequent segregation of alloy elements during solidification....... Metallographic analysis of solidified samples of Inconel 625 with addition of selected elements is compared with thermodynamic modelling of segregation during solidification. The influence of changes in the melt chemistry on the formation of intermetallic phases during solidification is shown. In particular...

Investigating Dark Energy with Black Hole Binaries

International Nuclear Information System (INIS)

Mersini-Houghton, Laura; Kelleher, Adam

2009-01-01

The accelerated expansion of the universe is ascribed to the existence of dark energy. Black holes accrete dark energy. The accretion induces a mass change proportional to the energy density and pressure of the background dark energy fluid. The time scale during which the mass of black holes changes considerably is long relative to the age of the universe, thus beyond detection possibilities. We propose to take advantage of the modified black hole masses for exploring the equation of state w[z] of dark energy, by investigating the evolution of supermassive black hole binaries on a dark energy background. Deriving the signatures of dark energy accretion on the evolution of binaries, we find that dark energy imprints on the emitted gravitational radiation and on the changes in the orbital radius of the binary can be within detection limits for certain supermassive black hole binaries. This talk describes how binaries can provide a useful tool in obtaining complementary information on the nature of dark energy.

Control of segregation in squeeze cast Al-4.5Cu binary alloy

Energy Technology Data Exchange (ETDEWEB)

Durrant, G. [Oxford Univ. (United Kingdom). Dept. of Materials; Gallerneault, M. [Alcan International Ltd., Kingston, ON (Canada); Cantor, B. [Oxford Univ. (United Kingdom). Dept. of Materials

1997-10-01

The high pressure applied in squeeze casting allows Al alloys of wrought composition to be cast to near net-shape, although their long freezing range leads to the segregation of alloying elements. In this paper we present results on the squeeze casting and gravity casting of a model Al-4.5 wt%Cu alloy. Squeeze cast Al-4.5Cu has a normal segregation pattern with eutectic macrosegregates towards the centre of the billet, whereas gravity cast material has a typical inverse segregation pattern. Normal segregation in squeeze cast Al-4.5Cu is due to large temperature gradients during solidification. Segregation can be minimized by releasing the applied pressure during solidification to allow backflow of the interdendritic fluid, or by the addition of grain refiner to remove the large columnar dendritic growth structure. (orig.)

Excess molar volumes and isentropic compressibilities of binary ...

Indian Academy of Sciences (India)

Excess molar volume; binary liquid mixtures; isentropic compressibility; intermolecular interactions. ... mixtures are essential for fluid flow, mass flow and heat transfer processes in chemical ... Experimentally determined values of density(ρ).

Simulations of rapid pressure-induced solidification in molten metals

International Nuclear Information System (INIS)

Patel, Mehul V.; Streitz, Frederick H.

2004-01-01

The process of interest in this study is the solidification of a molten metal subjected to rapid pressurization. Most details about solidification occurring when the liquid-solid coexistence line is suddenly transversed along the pressure axis remain unknown. We present preliminary results from an ongoing study of this process for both simple models of metals (Cu) and more sophisticated material models (MGPT potentials for Ta). Atomistic (molecular dynamics) simulations are used to extract details such as the time and length scales that govern these processes. Starting with relatively simple potential models, we demonstrate how molecular dynamics can be used to study solidification. Local and global order parameters that aid in characterizing the phase have been identified, and the dependence of the solidification time on the phase space distance between the final (P,T) state and the coexistence line has been characterized

Directional Solidification and Liquidus Projection of the Sn-Co-Cu System

Science.gov (United States)

Chen, Sinn-Wen; Chang, Jui-Shen; Pan, Kevin; Hsu, Chia-Ming; Hsu, Che-Wei

2013-04-01

This study investigates the Sn-Co-Cu ternary system, which is of interest to the electronics industry. Ternary Sn-Co-Cu alloys were prepared, their as-solidified microstructures were examined, and their primary solidification phases were determined. The primary solidification phases observed were Cu, Co, Co3Sn2, CoSn, CoSn2, Cu6Sn5, Co3Sn2, γ, and β phases. Although there are ternary compounds reported in this ternary system, no ternary compound was found as the primary solidification phase. The directional solidification technique was applied when difficulties were encountered using the conventional quenching method to distinguish the primary solidification phases, such as Cu6Sn5, Cu3Sn, and γ phases. Of all the primary solidification phases, the Co3Sn2 and Co phases have the largest compositional regimes in which alloys display them as the primary solidification phases. There are four class II reactions and four class III reactions. The reactions with the highest and lowest reaction temperatures are both class III reactions, and are L + CoSn2 + Cu6Sn5 = CoSn3 at 621.5 K (348.3 °C) and L + Co3Sn2 + CoSn = Cu6Sn5 at 1157.8 K (884.6 °C), respectively.

Incorporating interfacial phenomena in solidification models

Science.gov (United States)

Beckermann, Christoph; Wang, Chao Yang

1994-01-01

A general methodology is available for the incorporation of microscopic interfacial phenomena in macroscopic solidification models that include diffusion and convection. The method is derived from a formal averaging procedure and a multiphase approach, and relies on the presence of interfacial integrals in the macroscopic transport equations. In a wider engineering context, these techniques are not new, but their application in the analysis and modeling of solidification processes has largely been overlooked. This article describes the techniques and demonstrates their utility in two examples in which microscopic interfacial phenomena are of great importance.

Fundamentals of convection in non-Newtonian fluids

International Nuclear Information System (INIS)

Chen, J.L.S.; Ekmann, J.M.; Peterson, G.P.

1987-01-01

There are five papers in this book. They are: Pressure Drop and Heat Transfer in Viscoelastic Duct Flow - A New Look, A Heat Transfer Correlation for Viscoelastic Pipe Flows under Constant Wall Heat Flux, Three-Dimensional Solidification and Flow of Polymers in Curved Square Ducts, Natural Convecon Heat Transfer Between a Power-Law Fluid and a Permeable Isothermal Vertical Wall, and On Nonisothermal Flows of Bingham Plastics

Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

International Nuclear Information System (INIS)

Gorny, Anton; Manickaraj, Jeyakumar; Cai, Zhonghou; Shankar, Sumanth

2013-01-01

Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al 13 Fe 4 , τ 5 -Al 8 Fe 2 Si and τ 6 -Al 9 Fe 2 Si 2 phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s −1 . Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ 5 -Al 8 SiFe 2 and τ 6 -Al 9 Fe 2 Si 2 . The τ 5 -Al 8 SiFe 2 phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ 6 -Al 9 Fe 2 Si 2 through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al 13 Fe 4 binary phase precludes the evolution of the τ 5 during solidification and subsequently transforms into the τ 6 phase during solidification. These observations are anomalous to the publications as prior art and simulation predictions of thermodynamic phase diagrams of these alloys, wherein, only one intermetallic phases in the �

Rapid solidification growth mode transitions in Al-Si alloys by dynamic transmission electron microscopy

International Nuclear Information System (INIS)

Roehling, John D.; Coughlin, Daniel R.; Gibbs, John W.; Baldwin, J. Kevin; Mertens, James C.E.; Campbell, Geoffrey H.; Clarke, Amy J.; McKeown, Joseph T.

2017-01-01

In situ dynamic transmission electron microscope (DTEM) imaging of Al-Si thin-film alloys was performed to investigate rapid solidification behavior. Solidification of alloys with compositions from 1 to 15 atomic percent Si was imaged during pulsed laser melting and subsequent solidification. Solely α-Al solidification was observed in Al-1Si and Al-3Si alloys, and solely kinetically modified eutectic growth was observed in Al-6Si and Al-9Si alloys. A transition in the solidification mode in eutectic and hypereutectic alloys (Al-12Si and Al-15Si) from nucleated α-Al dendrites at lower solidification velocities to planar eutectic growth at higher solidification velocities was observed, departing from trends previously seen in laser-track melting experiments. Comparisons of the growth modes and corresponding velocities are compared with previous solidification models, and implications regarding the models are discussed.

A unified momentum equation approach for computing thermal residual stresses during melting and solidification

Science.gov (United States)

Yeo, Haram; Ki, Hyungson

2018-03-01

In this article, we present a novel numerical method for computing thermal residual stresses from a viewpoint of fluid-structure interaction (FSI). In a thermal processing of a material, residual stresses are developed as the material undergoes melting and solidification, and liquid, solid, and a mixture of liquid and solid (or mushy state) coexist and interact with each other during the process. In order to accurately account for the stress development during phase changes, we derived a unified momentum equation from the momentum equations of incompressible fluids and elastoplastic solids. In this approach, the whole fluid-structure system is treated as a single continuum, and the interaction between fluid and solid phases across the mushy zone is naturally taken into account in a monolithic way. For thermal analysis, an enthalpy-based method was employed. As a numerical example, a two-dimensional laser heating problem was considered, where a carbon steel sheet was heated by a Gaussian laser beam. Momentum and energy equations were discretized on a uniform Cartesian grid in a finite volume framework, and temperature-dependent material properties were used. The austenite-martensite phase transformation of carbon steel was also considered. In this study, the effects of solid strains, fluid flow, mushy zone size, and laser heating time on residual stress formation were investigated.

Modeling of multiphase flow with solidification and chemical reaction in materials processing

Science.gov (United States)

Wei, Jiuan

on SPH method and macroscopic model based on FVM, FEM and FDM, can be applied to even more complicated system. In the mesoscopic model by SPH method, some fundamental mesoscopic phenomena, such as the microstructure evolution, interface morphology represented by high resolution, particle entrapment in solidification can be studied. In the macroscopic model, the heat transfer, fluid flow, species transport can be modeled, and the simulation results provided the velocity, temperature and species boundary condition necessary for the mesoscopic model. This part falls into the region of future work. (Abstract shortened by UMI.)

Multi-scale Modeling of Dendritic Alloy Solidification

OpenAIRE

Dagner, Johannes

2009-01-01

Solidification of metallic melts is one of the most important processes in material science. The microstructure, which is formed during freezing, determines the mechanical properties of the final product largely. Many physical phenomena influence the solidification process and hence the resulting microstructure. One important parameter is influence of melt flow, which may modify heat and species transport on a large range of length- and time-scales. On the micro-scale, it influences the conce...

Application of the Method of Direct Solidification for Obtaining New Materials

International Nuclear Information System (INIS)

Grankin, S.S.

2007-01-01

The influence of the method of direct solidification on the formation of the material structure has been considered. The main methods of single crystal growth have been described. A considerable influence of the crystal growth parameters (temperature gradient at the front of solidification and the speed of moving of the front of solidification) on the type of the structure and morphology of single crystals has been shown. The examples of application of the method of direct solidification in experimental and industrial production are showed: production of directly crystallized blades for turbines of nuclear power plants and gas-turbine engines

Polyethylene solidification of low-level wastes

International Nuclear Information System (INIS)

Kalb, P.D.; Colombo, P.

1985-02-01

This topical report describes the results of an investigation on the solidification of low-level radioactive waste in polyethylene. Waste streams selected for this study included those which result from advanced volume reduction technologies (dry evaporator concentrate salts and incinerator ash) and those which remain problematic for solidification using contemporary agents (ion exchange resins). Four types of commercially available low-density polyethylenes were employed which encompass a range of processing and property characteristics. Process development studies were conducted to ascertain optimal process control parameters for successful solidification. Maximum waste loadings were determined for each waste and polyethylene type. Property evaluation testing was performed on laboratory-scale specimens to assess the potential behavior of actual waste forms in a disposal environment. Waste form property tests included water immersion, deformation under compressive load, thermal cycling and radionuclide leaching. Recommended waste loadings of 70 wt % sodium sulfate, 50 wt % boric acid, 40 wt % incinerator ash, and 30 wt % ion exchange resins, which are based on process control and waste form performance considerations are reported. 37 refs., 33 figs., 22 tabs

Convection Effects During Bulk Transparent Alloy Solidification in DECLIC-DSI and Phase-Field Simulations in Diffusive Conditions

Science.gov (United States)

Mota, F. L.; Song, Y.; Pereda, J.; Billia, B.; Tourret, D.; Debierre, J.-M.; Trivedi, R.; Karma, A.; Bergeon, N.

2017-08-01

To study the dynamical formation and evolution of cellular and dendritic arrays under diffusive growth conditions, three-dimensional (3D) directional solidification experiments were conducted in microgravity on a model transparent alloy onboard the International Space Station using the Directional Solidification Insert in the DEvice for the study of Critical LIquids and Crystallization. Selected experiments were repeated on Earth under gravity-driven fluid flow to evidence convection effects. Both radial and axial macrosegregation resulting from convection are observed in ground experiments, and primary spacings measured on Earth and microgravity experiments are noticeably different. The microgravity experiments provide unique benchmark data for numerical simulations of spatially extended pattern formation under diffusive growth conditions. The results of 3D phase-field simulations highlight the importance of accurately modeling thermal conditions that strongly influence the front recoil of the interface and the selection of the primary spacing. The modeling predictions are in good quantitative agreements with the microgravity experiments.

Effect Of Natural Convection On Directional Solidification Of Pure Metal

Directory of Open Access Journals (Sweden)

Skrzypczak T.

2015-06-01

Full Text Available The paper is focused on the modeling of the directional solidification process of pure metal. During the process the solidification front is sharp in the shape of the surface separating liquid from solid in three dimensional space or a curve in 2D. The position and shape of the solid-liquid interface change according to time. The local velocity of the interface depends on the values of heat fluxes on the solid and liquid sides. Sharp interface solidification belongs to the phase transition problems which occur due to temperature changes, pressure, etc. Transition from one state to another is discontinuous from the mathematical point of view. Such process can be identified during water freezing, evaporation, melting and solidification of metals and alloys, etc.

Weld solidification cracking in 304 to 304L stainless steel

Energy Technology Data Exchange (ETDEWEB)

Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Martinez, Raymond J [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory

2010-01-01

A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

Weld solidification cracking in 304 to 204L stainless steel

Energy Technology Data Exchange (ETDEWEB)

Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory

2010-09-15

A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found.This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GTAW showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

Steady-state and dynamic models for particle engulfment during solidification

Science.gov (United States)

Tao, Yutao; Yeckel, Andrew; Derby, Jeffrey J.

2016-06-01

Steady-state and dynamic models are developed to study the physical mechanisms that determine the pushing or engulfment of a solid particle at a moving solid-liquid interface. The mathematical model formulation rigorously accounts for energy and momentum conservation, while faithfully representing the interfacial phenomena affecting solidification phase change and particle motion. A numerical solution approach is developed using the Galerkin finite element method and elliptic mesh generation in an arbitrary Lagrangian-Eulerian implementation, thus allowing for a rigorous representation of forces and dynamics previously inaccessible by approaches using analytical approximations. We demonstrate that this model accurately computes the solidification interface shape while simultaneously resolving thin fluid layers around the particle that arise from premelting during particle engulfment. We reinterpret the significance of premelting via the definition an unambiguous critical velocity for engulfment from steady-state analysis and bifurcation theory. We also explore the complicated transient behaviors that underlie the steady states of this system and posit the significance of dynamical behavior on engulfment events for many systems. We critically examine the onset of engulfment by comparing our computational predictions to those obtained using the analytical model of Rempel and Worster [29]. We assert that, while the accurate calculation of van der Waals repulsive forces remains an open issue, the computational model developed here provides a clear benefit over prior models for computing particle drag forces and other phenomena needed for the faithful simulation of particle engulfment.

Phase-field modeling of microstructural pattern formation during directional solidification of peritectic alloys without morphological instability

International Nuclear Information System (INIS)

Shing Lo, Tak; Karma, Alain; Plapp, Mathis

2001-01-01

During the directional solidification of peritectic alloys, two stable solid phases (parent and peritectic) grow competitively into a metastable liquid phase of larger impurity content than either solid phase. When the parent or both solid phases are morphologically unstable, i.e., for a small temperature gradient/growth rate ratio (G/v p ), one solid phase usually outgrows and covers the other phase, leading to a cellular-dendritic array structure closely analogous to the one formed during monophase solidification of a dilute binary alloy. In contrast, when G/v p is large enough for both phases to be morphologically stable, the formation of the microstructure becomes controlled by a subtle interplay between the nucleation and growth of the two solid phases. The structures that have been observed in this regime (in small samples where convection effects are suppressed) include alternate layers (bands) of the parent and peritectic phases perpendicular to the growth direction, which are formed by alternate nucleation and lateral spreading of one phase onto the other as proposed in a recent model [R. Trivedi, Metall. Mater. Trans. A 26, 1 (1995)], as well as partially filled bands (islands), where the peritectic phase does not fully cover the parent phase which grows continuously. We develop a phase-field model of peritectic solidification that incorporates nucleation processes in order to explore the formation of these structures. Simulations of this model shed light on the morphology transition from islands to bands, the dynamics of spreading of the peritectic phase on the parent phase following nucleation, which turns out to be characterized by a remarkably constant acceleration, and the types of growth morphology that one might expect to observe in large samples under purely diffusive growth conditions

Rate of solidification of aluminium casting in varying wall thickness of cylindrical metallic moulds

Directory of Open Access Journals (Sweden)

Katsina Christopher BALA

2014-02-01

Full Text Available The quality of final casting mainly depends on the rate of solidification as rapid solidification produces fine grains structures with better mechanical properties. The analysis of heat transfer during the casting and solidification of aluminium alloy as well as the experimental investigation of the rate of solidification in varying thicknesses of cylindrical metallic mould was carried out. The temperature variation with time of the casting was recorded from which cooling curves were obtained for the determination of solidification time of the cast. The results showed that as the cylindrical mould thickness increases the solidification time decreases due to the chilling effect of the mould.

Numerical modelling of thermal and fluid flow phenomena in the mould channel

Directory of Open Access Journals (Sweden)

L. Sowa

2007-12-01

Full Text Available In the paper, a mathematical and a numerical model of the solidification of a cylindrical slender shaped casting, which take into account the process of filling the mould cavity with molten metal, has been proposed. Pressure and velocity fields were obtained by solving the momentum equations and the continuity equation, while the thermal fields were obtained by solving the heat conduction equation containing the convection term. Next, the numerical analysis of the solidification process of metals alloy in a cylindrical mould channel has been made. In the model one takes into account interdependence the heat transfer and fluid flow phenomena. Coupling of the thermal and fluid flow phenomena has been taken into consideration by the changes of the fluidity function and thermophysical parameters of alloy with respect to the temperature. The influence of the pressure and the temperature of metal pouring on the solid phase growth kinetics were estimated. The problem has been solved by the finite element method.

Solidification at the High and Low Rate Extreme

Energy Technology Data Exchange (ETDEWEB)

Meco, Halim [Iowa State Univ., Ames, IA (United States)

2004-12-19

The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the low growth rates can be utilized for the study of the intrinsic growth behavior of a certain phase growing from the melt. Although the length scales associated with certain processes, such as capillarity, and the diffusion of heat and solute, are different at low and high rate extremes, the phenomena that govern the selection of a certain microstructural length scale or a growth mode are the same. Consequently, one can analyze the solidification phenomena at both high and low rates by using the same governing principles. In this study, we examined the microstructural control at both low and high extremes. For the high rate extreme, the formation of crystalline products and factors that control the microstructure during rapid solidification by free-jet melt spinning are examined in Fe-Si-B system. Particular attention was given to the behavior of the melt pool at different quench-wheel speeds. Since the solidification process takes place within the melt-pool that forms on the rotating quench-wheel, we examined the influence of melt-pool dynamics on nucleation and growth of crystalline solidification products and glass formation. High-speed imaging of the melt-pool, analysis of ribbon microstructure, and measurement of ribbon geometry and surface character all indicate upper and lower limits for melt-spinning rates for which nucleation can be avoided, and fully amorphous ribbons can be achieved. Comparison of the relevant time scales reveals that surface-controlled melt

Predicting diffusivities in dense fluid mixtures

Directory of Open Access Journals (Sweden)

C. DARIVA

1999-09-01

Full Text Available In this work the Enskog solution of the Boltzmann equation, as corrected by Speedy, together with the Weeks-Chandler-Andersen (WCA perturbation theory of liquids is employed in correlating and predicting self-diffusivities of dense fluids. Afterwards this theory is used to estimate mutual diffusion coefficients of solutes at infinite dilution in sub and supercritical solvents. We have also investigated the behavior of Fick diffusion coefficients in the proximity of a binary vapor-liquid critical point since this subject is of great interest for extraction purposes. The approach presented here, which makes use of a density and temperature dependent hard-sphere diameter, is shown to be excellent for predicting diffusivities in dense pure fluids and fluid mixtures. The calculations involved highly nonideal mixtures as well as systems with high molecular asymmetry. The predicted diffusivities are in good agreement with the experimental data for the pure and binary systems. The methodology proposed here makes only use of pure component information and density of mixtures. The simple algebraic relations are proposed without any binary adjustable parameters and can be readily used for estimating diffusivities in multicomponent mixtures.

Defect generation during solidification of aluminium foams

International Nuclear Information System (INIS)

Mukherjee, M.; Garcia-Moreno, F.; Banhart, J.

2010-01-01

The reason for the frequent occurrence of cell wall defects in metal foams was investigated. Aluminium foams often expand during solidification, a process which is referred as solidification expansion (SE). The effect of SE on the structure of aluminium foams was studied in situ by X-ray radioscopy and ex situ by X-ray tomography. A direct correlation between the magnitude of SE and the number of cell wall ruptures during SE and finally the number of defects in the solidified foams was found.

Plastic solidification system for radioactive waste

International Nuclear Information System (INIS)

Kani, Jiro; Irie, Hiromitsu; Obu, Etsuji; Nakayama, Yasuyuki; Matsuura, Hiroyuki.

1979-01-01

The establishment of a new solidification system is an important theme for recent radioactive-waste disposal systems. The conditions required of new systems are: (1) the volume of the solidified product to be reduced, and (2) the property of the solidified product to be superior to the conventional ones. In the plastic solidification system developed by Toshiba, the waste is first dried and then solidified with thermosetting resin. It has been confirmed that the property of the plastic solidified product is superior to that of the cement-or bitumen-solidified product. Investigation from various phases is being carried on for the application of this method to commercial plants. (author)

Orbital Decay in Binaries with Evolved Stars

Science.gov (United States)

Sun, Meng; Arras, Phil; Weinberg, Nevin N.; Troup, Nicholas; Majewski, Steven R.

2018-01-01

Two mechanisms are often invoked to explain tidal friction in binary systems. The ``dynamical tide” is the resonant excitation of internal gravity waves by the tide, and their subsequent damping by nonlinear fluid processes or thermal diffusion. The ``equilibrium tide” refers to non-resonant excitation of fluid motion in the star’s convection zone, with damping by interaction with the turbulent eddies. There have been numerous studies of these processes in main sequence stars, but less so on the subgiant and red giant branches. Motivated by the newly discovered close binary systems in the Apache Point Observatory Galactic Evolution Experiment (APOGEE-1), we have performed calculations of both the dynamical and equilibrium tide processes for stars over a range of mass as the star’s cease core hydrogen burning and evolve to shell burning. Even for stars which had a radiative core on the main sequence, the dynamical tide may have very large amplitude in the newly radiative core in post-main sequence, giving rise to wave breaking. The resulting large dynamical tide dissipation rate is compared to the equilibrium tide, and the range of secondary masses and orbital periods over which rapid orbital decay may occur will be discussed, as well as applications to close APOGEE binaries.

Multiscale modeling of the solidification microstructure evolution in the presence of ultrasonic stirring

International Nuclear Information System (INIS)

Nastac, Laurentiu

2012-01-01

Ultrasonic treatment (UST) was studied to improve the quality of cast ingots as well as to control the solidification microstructure evolution. Ultrasonically-induced cavitation consists of the formation of small cavities (bubbles) in the molten metal followed by their growth, pulsation and collapse. These cavities are created by the tensile stresses that are produced by acoustic waves in the rarefaction phase. The cavitation threshold pressure for nucleation of the bubbles may decrease with increasing the amount of dissolved gases and especially with the amount of inclusions in the melt. A UST model was developed to predict the ultrasonic cavitation and acoustic streaming. The developed UST modeling approach is based on the numerical solution of Lilley model (that is founded on Lighthills's acoustic analogy), fluid flow, and heat transfer equations, and mesoscopic modeling of the grain structure. The UST model was applied to study the solidification of Al-based alloys) under the presence of ultrasound. It is found that the predicted ultrasonic cavitation region is relatively small, the acoustic streaming is strong and thus the created/survived bubbles/nuclei are transported into the bulk liquid quickly. The predicted grain size under UST condition is at least one order of magnitude lower than that without UST, which is in excellent agreement with the experimental data.

Solidification technique of radioactive elements. Research using zirconium phosphates

International Nuclear Information System (INIS)

Nakayama, Susumu; Ito, Katsuhiko

2005-01-01

Proton type zirconium phosphates HZr 2 (PO 4 ) 3 , NASICON type three-dimensional net work structure, is used for solidification of Cs in the high level radioactive waste. Two kinds of solidification methods such as the dry method and autoclave method are explained. Cs ion entered into 0.6nm space of HZr 2 (PO 4 ) 3 , and formed ionic bonding, which made the difficult situation to remove. When mixture of HZr 2 (PO 4 ) 3 and 23 kinds of M(NO 3 )n (M= Li, Na, K, Pb, Sr, Bi, Y, Mg, Ca, Sc, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, Ba, La, Ce, Tl, and Pb; n=1,2 or 3) was treated at 400-700degC by dry method, solidification of the subject metals was succeeded. Amount of solidification of Cs by autoclave at 250degC is almost same as the dry method and its leachability resistance increased 40 times than that of dry method after heat treatment in atmosphere at 700degC. (S.Y.)

A dendritic solidification experiment under large gravity - implications for the Earth's inner core solidification regime.

Science.gov (United States)

Deguen, R.; Alboussière, T.; Brito, D.; La Rizza, P.; Masson, J.

2009-05-01

The Earth's inner core solidification regime is usually thought to be dendritic, which should results in the formation of a mushy layer at the inner core boundary, possibly extending deep in the inner core. The release of latent heat and solute associated with crystallization provides an important boyancy source to drive thermo- chemical convection in the core. In the laboratory, two modes of convection associated with the crystallization of mushy layers have been observed. One is a boundary layer mode originating from the destabilisation of the chemical boundary layer present at the mush-liquid interface; the second is the so-called 'mushy layer mode' which involves the whole mushy layer. In the mushy layer mode, convection usually takes the form of narrow plumes rising through crystal free conduits called chimneys. One particularity of inner core crystallization is its extremely small solidification rate compared to typical outer core convective timescales. We have designed and build an experiment devoted to the study of crystallization under a large gravity field, using a centrifuge, of an aqueous solution of ammonium chloride, which is a good analogue to metallic alloys. The large gravity field allows to reach Rayleigh numbers much larger than in typical solidification experiments. Under large gravity fields, we observe the disappearance of chimney convection and show that the large gravity field promotes the boundary layer convection mode at the expent of the mushy layer mode. As the gravitationnal forcing is increased, convective heat and solute transport are significantly enhanced, which results in larger solid fraction directly below the mush-liquid interface. The increase in solid fraction results in a dramatic decrease of the permeability in the mushy layer, which eventually becomes subcritical in respect to the mushy layer mode. Because of the very slow solidification rate of the inner core, convective transport of heat and solute from the ICB is

Evolution of Fe based intermetallic phases in Al–Si hypoeutectic casting alloys: Influence of the Si and Fe concentrations, and solidification rate

Energy Technology Data Exchange (ETDEWEB)

Gorny, Anton; Manickaraj, Jeyakumar [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada); Cai, Zhonghou [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Shankar, Sumanth, E-mail: shankar@mcmaster.ca [Light Metal Casting Research Centre (LMCRC), Department of Mechanical Engineering, McMaster University, 1280 Main Street W, Hamilton, ON, Canada L8S 4L7 (Canada)

2013-11-15

Highlights: •Anomalous evolution of Fe based intermetallic phases in Al–Si–Fe alloys. •XRF coupled with nano-diffraction to confirm the nano-size Fe intermetallic phases. •Crystallography of the θ-Al{sub 13}Fe{sub 4}, τ{sub 5}-Al{sub 8}Fe{sub 2}Si and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} phases. •Peritectic reactions involving the Fe intermetallic phases in Al–Si–Fe alloys. -- Abstract: Al–Si–Fe hypoeutectic cast alloy system is very complex and reported to produce numerous Fe based intermetallic phases in conjunction with Al and Si. This publication will address the anomalies of phase evolution in the Al–Si–Fe hypoeutectic casting alloy system; the anomaly lies in the peculiarities in the evolution and nature of the intermetallic phases when compared to the thermodynamic phase diagram predictions and past publications of the same. The influence of the following parameters, in various combinations, on the evolution and nature of the intermetallic phases were analyzed and reported: concentration of Si between 2 and 12.6 wt%, Fe between 0.05 and 0.5 wt% and solidification rates of 0.1, 1, 5 and 50 K s{sup −1}. Two intermetallic phases are observed to evolve in these alloys under these solidification conditions: the τ{sub 5}-Al{sub 8}SiFe{sub 2} and τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2}. The τ{sub 5}-Al{sub 8}SiFe{sub 2} phase evolves at all levels of the parameters during solidification and subsequently transforms into the τ{sub 6}-Al{sub 9}Fe{sub 2}Si{sub 2} through a peritectic reaction when promoted by certain combinations of solidification parameters such as higher Fe level, lower Si level and slower solidification rates. Further, it is also hypothesized from experimental evidences that the θ-Al{sub 13}Fe{sub 4} binary phase precludes the evolution of the τ{sub 5} during solidification and subsequently transforms into the τ{sub 6} phase during solidification. These observations are anomalous to the publications as prior art and

Matemathical description of solidification cooling curves of pure metals

Directory of Open Access Journals (Sweden)

Arno Müller

1998-10-01

Full Text Available The introduction of an "incubation time" to the Schwarz classical mathematical description of metals solidification, resulted in a new model called Modified Schwarz Model. By doing so it was possible to identify and quantify the "delay time" that separates the two heat waves traveling independently in a casting during the solidification: the Supercooled / Superheated Liquid and the Solid / Liquid. The thermal shock produced in the initial stage of the undercooling generation process, can be used as an important parameter in the forecasting of the solidification's behavior of pure metals and alloys, when changing mold's materials, pouring and ambient temperatures. The hypercooling proneness degree of metals and alloys, can also be calculated.

Theoretical modeling of cellular and dendritic solidification microstructures

Science.gov (United States)

Song, Younggil

the invasion process starts with a group of cells, the leader cell can detach itself from the group and grow continuously as a misoriented solitary cell in the other grain with a different misorientation. We use PF simulations to investigate the GB morphology and dynamics of a solitary cell. Solidification experiments on earth are typically performed in a thin-sample geometry to avoid fluid convection. Thus, we consider various influences on cellular and dendritic array patterns in thin samples. First, we explore the influence of crystal orientation. When a grain in a thin-sample geometry is misoriented with respect to the temperature gradient, primary cells and dendrites drift laterally in both experiments and simulations. At the same time, grain boundaries are systematically formed at the edges of the misoriented grain. The misoriented primary branches move away from the divergent grain boundary. At this boundary, cells/dendrites are generated continuously, and their spacings are larger than the dynamically selected spacings. Primary branches run into the other convergent GB, which leads to their elimination. Thus, at a stationary state, a spacing distribution is uniform with the spacing selected at the divergent GB until it decreases near the convergent GB. We perform simulations to illustrate the global evolutions of a primary spacing. In addition, we suggest a simple geometrical model and a nonlinear advection equation for the dynamics of the primary spacing evolution, which can predict the slow evolution of a primary spacing in a quasi-2D array. Experimental observations point out that the primary spacing selection could be affected by the sample thickness; however, the detailed description for the link between the primary spacing selection and a sample thickness is still missing. Here, we use PF simulations to investigate the primary cellular and dendritic spacing selection mechanisms under the influence of a sample thickness. A thin-sample geometry can limit

Inverse thermal analysis method to study solidification in cast iron

DEFF Research Database (Denmark)

Dioszegi, Atilla; Hattel, Jesper

2004-01-01

Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... inverse thermal analysis was tested on both experimental and simulated data....

Fluids in porous media. IV. Quench effect on chemical potential.

Science.gov (United States)

Qiao, C Z; Zhao, S L; Liu, H L; Dong, W

2017-06-21

It appears to be a common sense to measure the crowdedness of a fluid system by the densities of the species constituting it. In the present work, we show that this ceases to be valid for confined fluids under some conditions. A quite thorough investigation is made for a hard sphere (HS) fluid adsorbed in a hard sphere matrix (a quench-annealed system) and its corresponding equilibrium binary mixture. When fluid particles are larger than matrix particles, the quench-annealed system can appear much more crowded than its corresponding equilibrium binary mixture, i.e., having a much higher fluid chemical potential, even when the density of each species is strictly the same in both systems, respectively. We believe that the insight gained from this study should be useful for the design of functionalized porous materials.

Choosing solidification or vitrification for low-level radioactive and mixed waste treatment

International Nuclear Information System (INIS)

Gimpel, R.F.

1992-01-01

Solidification (making concrete) and vitrification (making glass) are frequently the treatment methods recommended for treating inorganic or radioactive wastes. Solidification is generally perceived as the most economical treatment method. Whereas, vitrification is considered (by many) as the most effective of all treatment methods. Unfortunately, vitrification has acquired the stigma that it is too expensive to receive further consideration as an alternative to solidification in high volume treatment applications. Ironically, economic studies, as presented in this paper, show that vitrification may be more competitive in some high volume applications. Ex-situ solidification and vitrification are the competing methods for treating in excess of 450 000m 3 of low-level radioactive and mixed waste at the Fernald Environmental Management Project (FEMP or simply, Fernald) located near Cincinnati, Ohio. This paper summarizes how Fernald is choosing between solidification and vitrification as the primary waste treatment method

Choosing solidification or vitrification for low-level radioactive and mixed waste treatment

International Nuclear Information System (INIS)

Gimpel, R.F.

1992-01-01

Solidification (making concrete) and vitrification (making glass) are frequently the treatment methods recommended for treating inorganic or radioactive wastes. Solidification is generally perceived as the most economical treatment method. Whereas, vitrification is considered (by many) as the most effective of all treatment methods. Unfortunately, vitrification has acquired the stigma that it is too expensive to receive further consideration as an alternative to solidification in high volume treatment applications. Ironically, economic studies, as presented in this paper, show that vitrification may be more competitive in some high volume applications. Ex-situ solidification and vitrification are the competing methods for treating in excess of 450,000 m 3 of low-level radioactive and mixed waste at the Fernald Environmental Management Project (FEMP or simply, Fernald) located near Cincinnati, Ohio. This paper summarized how Fernald is choosing between solidification and vitrification as the primary waste treatment method

Microstructural evolution in Mg-Zn alloys during solidification: An experimental and simulation study

Science.gov (United States)

Paliwal, Manas; Jung, In-Ho

2014-05-01

A comprehensive microstructural evolution of Mg-1.5, 4.0 and 5.5 wt% Zn alloys with respect to the solidification parameters such as thermal gradient (G), solidification velocity (V), cooling rate (GV) and solute (Zn) content were investigated in the present study. Solidification techniques such as directional solidification and wedge casting were employed in order to obtain cooling rates between 0.05 and 250 K/s. Microstructural features such as secondary dendrite arm spacing (SDAS), primary dendrite arm spacing (PDAS), microsegregration along the secondary dendrites and secondary phase fractions were experimentally determined. A solidification model that incorporates solute back diffusion, secondary arm coarsening, dendrite tip undercooling and dynamically linked with accurate thermodynamic databases is used to explain the experimental results.

Predictive modeling of solidification during laser additive manufacturing of nickel superalloys: recent developments, future directions

Science.gov (United States)

Ghosh, Supriyo

2018-01-01

Additive manufacturing (AM) processes produce parts with improved physical, chemical, and mechanical properties compared to conventional manufacturing processes. In AM processes, intricate part geometries are produced from multicomponent alloy powder, in a layer-by-layer fashion with multipass laser melting, solidification, and solid-state phase transformations, in a shorter manufacturing time, with minimal surface finishing, and at a reasonable cost. However, there is an increasing need for post-processing of the manufactured parts via, for example, stress relieving heat treatment and hot isostatic pressing to achieve homogeneous microstructure and properties at all times. Solidification in an AM process controls the size, shape, and distribution of the grains, the growth morphology, the elemental segregation and precipitation, the subsequent solid-state phase changes, and ultimately the material properties. The critical issues in this process are linked with multiphysics (such as fluid flow and diffusion of heat and mass) and multiscale (lengths, times and temperature ranges) challenges that arise due to localized rapid heating and cooling during AM processing. The alloy chemistry-process-microstructure-property-performance correlation in this process will be increasingly better understood through multiscale modeling and simulation.

Multiscale modelling of solidification microstructures, including microsegregation and microporosity, in an Al-Si-Cu alloy

International Nuclear Information System (INIS)

Lee, P.D.; Chirazi, A.; Atwood, R.C.; Wang, W.

2004-01-01

Phase transition phenomena in metallic alloys involve complex physical processes occurring over a wide range of temporal, spatial and energy scales. Multiscale modelling is a powerful methodology for understanding these complex systems. In this paper, a multiscale model of grain and pore formation is presented during solidification. At the microscale, a combined stochastic-deterministic approach based on the cellular automata method is used to solve multicomponent diffusion in a three-phase system (liquid, solid and gas), simulating the nucleation and growth of both grains and pores. The impingement of the growing pores upon the developing solid is also solved to predict the tortuous shape of the porosity, a critical factor for fatigue properties. The micromodel is coupled with a finite element method (FEM) solution of the macroscale heat transfer and fluid flow in industrial castings through the temperature and pressure fields. The result model was used to investigate the influence of local solidification time, hydrogen content, local metallostatic pressure and alloy composition upon the predicted grain structure and pore morphology. Comparison of the model predictions to both laboratory and industrial scale castings are presented

Macrosegregation Resulting from Directional Solidification Through an Abrupt Change in Cross-Sections

Science.gov (United States)

Lauer, M.; Poirier, D. R.; Ghods, M.; Tewari, S. N.; Grugel, R. N.

2017-01-01

Simulations of the directional solidification of two hypoeutectic alloys (Al-7Si alloy and Al-19Cu) and resulting macrosegregation patterns are presented. The casting geometries include abrupt changes in cross-section from a larger width of 9.5 mm to a narrower 3.2 mm width then through an expansion back to a width of 9.5 mm. The alloys were chosen as model alloys because they have similar solidification shrinkages, but the effect of Cu on changing the density of the liquid alloy is about an order of magnitude greater than that of Si. The simulations compare well with experimental castings that were directionally solidified in a graphite mold in a Bridgman furnace. In addition to the simulations of the directional solidification in graphite molds, some simulations were effected for solidification in an alumina mold. This study showed that the mold must be included in numerical simulations of directional solidification because of its effect on the temperature field and solidification. For the model alloys used for the study, the simulations clearly show the interaction of the convection field with the solidifying alloys to produce a macrosegregation pattern known as "steepling" in sections with a uniform width. Details of the complex convection- and segregation-patterns at both the contraction and expansion of the cross-sectional area are revealed by the computer simulations. The convection and solidification through the expansions suggest a possible mechanism for the formation of stray grains. The computer simulations and the experimental castings have been part of on-going ground-based research with the goal of providing necessary background for eventual experiments aboard the ISS. For casting practitioners, the results of the simulations demonstrate that computer simulations should be applied to reveal interactions between alloy solidification properties, solidification conditions, and mold geometries on macrosegregation. The simulations also presents the

Solidification of ash from incineration of low-level radioactive waste

International Nuclear Information System (INIS)

Roberson, W.A.; Albenesius, E.L.; Becker, G.W.

1983-01-01

The safe disposal of both high-level and low-level radioactive waste is a problem of increasing national attention. A full-scale incineration and solidification process to dispose of suspect-level and low-level beta-gamma contaminated combustible waste is being demonstrated at the Savannah River Plant (SRP) and Savannah River Laboratory (SRL). The stabilized wasteform generated by the process will meet or exceed all future anticipated requirements for improved disposal of low-level waste. The incineration process has been evaluated at SRL using nonradioactive wastes, and is presently being started up in SRP to process suspect-level radioactive wastes. A cement solidification process for incineration products is currently being evaluated by SRL, and will be included with the incineration process in SRP during the winter of 1984. The GEM alumnus author conducted research in a related disposal solidification program during the GEM-sponsored summer internship, and upon completion of the Masters program, received full-time responsibility for developing the incineration products solidification process

Toxic and hazardous waste disposal. Volume 1. Processes for stabilization/solidification

International Nuclear Information System (INIS)

Pojasek, R.B.

1979-01-01

Processes for the stabilization and/or solidification of toxic, hazardous, and radioactive wastes are reviewed. The types of wastes classified as hazardous are defined. The following processes for the solidification of hazardous wastes are described: lime-based techniques; thermoplastic techniques; organic polymer techniques; and encapsulation. The following processes for the solidification of high-level radioactive wastes are described: calcination; glassification; and ceramics. The solidification of low-level radioactive wastes with asphalt, cement, and polymeric materials is also discussed. Other topics covered include: the use of an extruder/evaporator to stabilize and solidify hazardous wastes; effect disposal of fine coal refuse and flue gas desulfurization slurries using Calcilox additive stabilization; the Terra-Tite Process; the Petrifix Process; the SFT Terra-Crete Process; Sealosafe Process; Chemfix Process; and options for disposal of sulfur oxide wastes

Solidification of eutectic system alloys in space (M-19)

Science.gov (United States)

Ohno, Atsumi

1993-01-01

It is well known that in the liquid state eutectic alloys are theoretically homogeneous under 1 g conditions. However, the homogeneous solidified structure of this alloy is not obtained because thermal convection and non-equilibrium solidification occur. The present investigators have clarified the solidification mechanisms of the eutectic system alloys under 1 g conditions by using the in situ observation method; in particular, the primary crystals of the eutectic system alloys never nucleated in the liquid, but instead did so on the mold wall, and the crystals separated from the mold wall by fluid motion caused by thermal convection. They also found that the equiaxed eutectic grains (eutectic cells) are formed on the primary crystals. In this case, the leading phase of the eutectic must agree with the phase of the primary crystals. In space, no thermal convection occurs so that primary crystals should not move from the mold wall and should not appear inside the solidified structure. Therefore no equiaxed eutectic grains will be formed under microgravity conditions. Past space experiments concerning eutectic alloys were classified into two types of experiments: one with respect to the solidification mechanisms of the eutectic alloys and the other to the unidirectional solidification of this alloy. The former type of experiment has the problem that the solidified structures between microgravity and 1 g conditions show little difference. This is why the flight samples were prepared by the ordinary cast techniques on Earth. Therefore it is impossible to ascertain whether or not the nucleation and growth of primary crystals in the melt occur and if primary crystals influence the formation of the equiaxed eutectic grains. In this experiment, hypo- and hyper-eutectic aluminum copper alloys which are near eutectic point are used. The chemical compositions of the samples are Al-32.4mass%Cu (Hypo-eutectic) and Al-33.5mass%Cu (hyper-eutectic). Long rods for the samples are

Effects Disposal Condition and Ground Water to Leaching Rate of Radionuclides from Solidification Products

International Nuclear Information System (INIS)

Herlan Martono; Wati

2008-01-01

Effects disposal condition and ground water to leaching rate of radionuclides from solidification products have been studied. The aims of leaching test at laboratory to get the best composition of solidified products for continuous process or handling. The leaching rate of radionuclides from the many kinds of matrix from smallest to bigger are glass, thermosetting plastic, urea formaldehyde, asphalt, and cement. Glass for solidification of high level waste, thermosetting plastic and urea formaldehyde for solidification of low and intermediate waste, asphalt and cement for solidification of low and intermediate level waste. In shallow land burial, ground water rate is fast, debit is high, and high permeability, so the probability contact between solidification products and ground water is occur. The pH of ground water increasing leaching rate, but cation in the ground water retard leaching rate. Effects temperature radiation and radiolysis to solidification products is not occur. In the deep repository, ground water rate is slow, debit is small, and low permeability, so the probability contact between solidification products and ground water is very small. There are effect cooling time and distance between pits to rock temperature. Alfa radiation effects can be occur, but there is no contact between solidification products and ground water, so that there is not radiolysis. (author)

Effect of chemical composition and cooling conditions on solidification hot cracking of Ni-based alloys

International Nuclear Information System (INIS)

De Vito, Sophie

2000-01-01

Ni-based alloys 690 present solidification hot cracks during welding of vapour generators. Hot cracks are qualitatively known to be due to the formation of inter-dendritic liquid films and of secondary phases down to low temperatures. This study aims at establishing the link between thermodynamics, solidification and hot cracking. Experimental solidification paths of high purity alloys (with varying Nb and Si contents) are obtained from quenching during directional solidification and TIG-welding experiments. They are compared to Thermo-Calc computations, assuming no diffusion in the solid. From directional solidification samples, good agreement between computed and experimental solidification paths is shown in the quenched liquid. Secondary arms of dendrites are affected by solid state diffusion of Nb. Combined effect of diffusion and solute build-up in the liquid phase modifies micro-segregation in the solid region. Solidification paths from welding specimens are similar to those of the solid region of quenched samples. Nb solid state diffusion is negligible but undercooling compensates the effect of solid state diffusion in directional solidification. Evolution of liquid fraction at the end of the solidification is in accordance with the hot cracking classification of the alloys. Nb favours formation of inter-dendritic liquid films and eutectic-like phases down to low temperature. (author) [fr

Mixing process of a binary gas in a density stratified layer

Energy Technology Data Exchange (ETDEWEB)

Takeda, Tetsuaki [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment

1997-09-01

This study is to investigate the effect of natural convection on the mixing process by molecular diffusion in a vertical stratified layer of a binary fluid. There are many experimental and analytical studies on natural convection in the vertical fluid layer. However, there are few studies on natural convection with molecular diffusion in the vertical stratified layer of a binary gas. Experimental study has been performed on the combined phenomena of molecular diffusion and natural convection in a binary gas system to investigate the mixing process of the binary gas in a vertical slot consisting of one side heated and the other side cooled. The range of Rayleigh number based on the slot width was about 0 < Ra{sub d} < 7.5 x 10{sup 4}. The density change of the gas mixture and the temperature distribution in the slot was obtained and the mixing process when the heavier gas ingress into the vertical slot filled with the lighter gas from the bottom side of the slot was discussed. The experimental results showed that the mixing process due to molecular diffusion was affected significantly by the natural convection induced by the slightly temperature difference between both vertical walls even if a density difference by the binary gas is larger than that by the temperature difference. (author). 81 refs.

Nuclear waste solidification

Science.gov (United States)

Bjorklund, William J.

1977-01-01

High level liquid waste solidification is achieved on a continuous basis by atomizing the liquid waste and introducing the atomized liquid waste into a reaction chamber including a fluidized, heated inert bed to effect calcination of the atomized waste and removal of the calcined waste by overflow removal and by attrition and elutriation from the reaction chamber, and feeding additional inert bed particles to the fluidized bed to maintain the inert bed composition.

Nuclear waste solidification

International Nuclear Information System (INIS)

Bjorklund, W.J.

1977-01-01

High level liquid waste solidification is achieved on a continuous basis by atomizing the liquid waste and introducing the atomized liquid waste into a reaction chamber including a fluidized, heated inert bed to effect calcination of the atomized waste and removal of the calcined waste by overflow removal and by attrition and elutriation from the reaction chamber, and feeding additional inert bed particles to the fluidized bed to maintain the inert bed composition

Numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow

KAUST Repository

Zhu, Guangpu

2018-04-17

In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.

Numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow

KAUST Repository

Zhu, Guangpu; Kou, Jisheng; Sun, Shuyu; Yao, Jun; Li, Aifen

2018-01-01

In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.

Dipolar fluid-wall systems. Beyond the image potential

International Nuclear Information System (INIS)

Boudh-hir, M.E.

1989-02-01

The case of dipolar fluid in front of an ideal wall is examined. The surface-fluid system is introduced as a limit case of a binary mixture Using the diagrammatic development, the expansion of the one-particle distribution function is given. 16 refs

On the stable eutectic solidification of iron–carbon–silicon alloys

International Nuclear Information System (INIS)

Stefanescu, Doru M.; Alonso, Gorka; Larrañaga, Pello; Suarez, Ramon

2016-01-01

Extensive effort was expanded to elucidate the growth and morphology of the stable eutectic grains during early solidification of continuous cooled Fe–C–Si alloys. To this purpose, quenching experiments at successive stages during solidification have been carried out on five cast irons with various magnesium and titanium levels designed to produce graphite morphologies ranging from lamellar to mixed compacted–spheroidal. The graphite shape factors were measured on the metallographic samples, and their evolution as a function of the chemical composition and the solid fraction was analyzed. Extensive scanning electron microscopy was carried on to evaluate the change in graphite shape during early solidification, to establish the fraction of solid at which the transition from spheroidal-to-compacted-to-lamellar graphite occurs, and to outline the early morphology of the eutectic grains. It was confirmed that solidification of Mg containing irons started with the development of spheroidal graphite even at Mg levels as low as 0.013 mass%. Then, as solidification proceeds, when some spheroids developed one or more tails (tadpole graphite), the spheroidal-to-compacted graphite transition occurs. The new findings were then integrated in previous knowledge to produce an understanding of the eutectic solidification of these materials. It was concluded that in hypoeutectic lamellar graphite iron austenite/graphite eutectic grains can nucleate at the austenite/liquid interface or in the bulk of the liquid, depending on the sulfur content and on the cooling rate. When graphite nucleation occurs on the primary austenite, several eutectic grains can nucleate and grow on the same dendrite. The primary austenite continues growing as eutectic austenite and therefore the two have the same crystallographic orientation. Thus, a final austenite grain may include several eutectic grains. In eutectic irons the eutectic grains nucleate and grow mostly in the liquid. The eutectic

Functional Nanoclay Suspension for Printing-Then-Solidification of Liquid Materials.

Science.gov (United States)

Jin, Yifei; Compaan, Ashley; Chai, Wenxuan; Huang, Yong

2017-06-14

Additive manufacturing (AM) enables the freeform fabrication of complex structures from various build materials. The objective of this study is to develop a novel Laponite nanoclay-enabled "printing-then-solidification" additive manufacturing approach to extrude complex three-dimensional (3D) structures made of various liquid build materials. Laponite, a member of the smectite mineral family, is investigated to serve as a yield-stress support bath material for the extrusion printing of liquid build materials. Using the printing-then-solidification approach, the printed structure remains liquid and retains its shape with the help of the Laponite support bath. Then the completed liquid structures are solidified in situ by applying suitable cross-linking mechanisms. Finally, the solidified structures are harvested from the Laponite nanoclay support bath for any further processing as needed. Due to its chemical and physical stability, liquid build materials with different solidification/curing/gelation mechanisms can be fabricated in the Laponite bath using the printing-then-solidification approach. The feasibility of the proposed Laponite-enabled printing-then-solidification approach is demonstrated by fabricating several complicated structures made of various liquid build materials, including alginate with ionic cross-linking, gelatin with thermal cross-linking, and SU-8 with photo-cross-linking. During gelatin structure printing, living cells are included and the postfabrication cell viability is above 90%.

Containerless solidification of BiFeO3 oxide under microgravity

Science.gov (United States)

Yu, Jianding; Arai, Yasutomo; Koshikawa, Naokiyo; Ishikawa, Takehito; Yoda, Shinichi

1999-07-01

Containerless solidification of BiFeO3 oxide has been carried out under microgravity with Electrostatic Levitation Furnace (ELF) aboard on the sounding rocket (TR-IA). It is a first containerless experiment using ELF under microgravity for studying the solidification of oxide insulator material. Spherical BiFeO3 sample with diameter of 5mm was heated by two lasers in oxygen and nitrogen mixing atmosphere, and the sample position by electrostatic force under pinpoint model and free drift model. In order to compare the solidification behavior in microgravity with on ground, solidification experiments of BiFeO3 in crucible and drop tube were carried out. In crucible experiment, it was very difficult to get single BiFeO3 phase, because segregation of Fe2O3 occured very fast and easily. In drop tube experiment, fine homogeneous BiFeO3 microstructure was obtained in a droplet about 300 μm. It implies that containerless processing can promote the phase selection in solidification. In microgravity experiment, because the heating temperature was lower than that of estimated, the sample was heated into Fe2O3+liquid phase region. Fe2O3 single crystal grew on the surface of the spherical sample, whose sample was clearly different from that observed in ground experiments.

Solution of free-boundary problems using finite-element/Newton methods and locally refined grids - Application to analysis of solidification microstructure

Science.gov (United States)

Tsiveriotis, K.; Brown, R. A.

1993-01-01

A new method is presented for the solution of free-boundary problems using Lagrangian finite element approximations defined on locally refined grids. The formulation allows for direct transition from coarse to fine grids without introducing non-conforming basis functions. The calculation of elemental stiffness matrices and residual vectors are unaffected by changes in the refinement level, which are accounted for in the loading of elemental data to the global stiffness matrix and residual vector. This technique for local mesh refinement is combined with recently developed mapping methods and Newton's method to form an efficient algorithm for the solution of free-boundary problems, as demonstrated here by sample calculations of cellular interfacial microstructure during directional solidification of a binary alloy.

Microstructural investigation of D2 tool steel during rapid solidification

Science.gov (United States)

Delshad Khatibi, Pooya

Solidification is considered as a key processing step in developing the microstructure of most metallic materials. It is, therefore, important that the solidification process can be designed and controlled in such a way so as to obtain the desirable properties in the final product. Rapid solidification refers to the system's high undercooling and high cooling rate, which can yield a microstructure with unique chemical composition and mechanical properties. An area of interest in rapid solidification application is high-chromium, high-carbon tool steels which experience considerable segregation of alloying elements during their solidification in a casting process. In this dissertation, the effect of rapid solidification (undercooling and cooling rate) of D2 tool steel on the microstructure and carbide precipitation during annealing was explored. A methodology is described to estimate the eutectic and primary phase undercooling of solidifying droplets. The estimate of primary phase undercooling was confirmed using an online measurement device that measured the radiation energy of the droplets. The results showed that with increasing primary phase and eutectic undercooling and higher cooling rate, the amount of supersaturation of alloying element in metastable retained austenite phase also increases. In the case of powders, the optimum hardness after heat treatment is achieved at different temperatures for constant periods of time. Higher supersaturation of austenite results in obtaining secondary hardness at higher annealing temperature. D2 steel ingots generated using spray deposition have high eutectic undercooling and, as a result, high supersaturation of alloying elements. This can yield near net shape D2 tool steel components with good mechanical properties (specifically hardness). The data developed in this work would assist in better understanding and development of near net shape D2 steel spray deposit products with good mechanical properties.

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.

Geometrical modulus of a casting and its influence on solidification process

Directory of Open Access Journals (Sweden)

F. Havlicek

2011-10-01

Full Text Available Object: The work analyses the importance of the known criterion for evaluating the controlled solidification of castings, so called geometrical modulus defined by N. Chvorinov as the first one. Geometrical modulus influences the solidification process. The modulus has such specificity that during the process of casting formation it is not a constant but its initial value decreases with the solidification progress because the remaining melt volume can decrease faster than its cooling surface.Methodology: The modulus is determined by a simple calculation from the ratio of the casting volume after pouring the metal in the mould to the cooled mould surface. The solidified metal volume and the cooled surface too are changed during solidification. That calculation is much more complicated. Results were checked up experimentally by measuring the temperatures in the cross-section of heavy steel castings during cooling them.Results: The given experimental results have completed the original theoretical calculations by Chvorinov and recent researches done with use of numerical calculations. The contribution explains how the geometrical modulus together with the thermal process in the casting causes the higher solidification rate in the axial part of the casting cross-section and shortening of solidification time. Practical implications: Change of the geometrical modulus negatively affects the casting internal quality. Melt feeding by capillary filtration in the dendritic network in the casting central part decreases and in such a way the shrinkage porosity volume increases. State of stress character in the casting is changed too and it increases.

Solidification processing of intermetallic Nb-Al alloys

Science.gov (United States)

Smith, Preston P.; Oliver, Ben F.; Noebe, Ronald D.

1992-01-01

Several Nb-Al alloys, including single-phase NbAl3 and the eutectic of Nb2Al and NbAl3, were prepared either by nonconsumable arc melting in Ar or by zone processing in He following initial induction melting and rod casting, and the effect of the solidification route on the microstructure and room-temperature mechanical properties of these alloys was investigated. Automated control procedures and melt conditions for directional solidification of NbAl3 and the Nb2Al/Nb3Al eutectic were developed; high purity and stoichiometry were obtained. The effects of ternary additions of Ti and Ni are described.

Interface Pattern Selection in Directional Solidification

Science.gov (United States)

Trivedi, Rohit; Tewari, Surendra N.

2001-01-01

The central focus of this research is to establish key scientific concepts that govern the selection of cellular and dendritic patterns during the directional solidification of alloys. Ground-based studies have established that the conditions under which cellular and dendritic microstructures form are precisely where convection effects are dominant in bulk samples. Thus, experimental data can not be obtained terrestrially under pure diffusive regime. Furthermore, reliable theoretical models are not yet possible which can quantitatively incorporate fluid flow in the pattern selection criterion. Consequently, microgravity experiments on cellular and dendritic growth are designed to obtain benchmark data under diffusive growth conditions that can be quantitatively analyzed and compared with the rigorous theoretical model to establish the fundamental principles that govern the selection of specific microstructure and its length scales. In the cellular structure, different cells in an array are strongly coupled so that the cellular pattern evolution is controlled by complex interactions between thermal diffusion, solute diffusion and interface effects. These interactions give infinity of solutions, and the system selects only a narrow band of solutions. The aim of this investigation is to obtain benchmark data and develop a rigorous theoretical model that will allow us to quantitatively establish the physics of this selection process.

Heat transfer and solidification processes of alloy melt with undercooling: I. Experimental results

International Nuclear Information System (INIS)

Yoshioka, Hideaki; Tada, Yukio; Kunimine, Kanji; Furuichi, Taira; Hayashi, Yujiro

2006-01-01

The solidification process of Pb-Sn and Bi-Sn alloy melts is discussed to obtain a basic understanding of the essential phenomena of solidification with undercooling. First, from macroscopic observations, it is shown that the solidification process consists of the following three stages: (1) free growth with recalescence dissipation of thermal undercooling (2) expansion of crystals with the relaxation of constitutional undercooling or with the recovering process of interrupted quasi-steady heat conduction, and (3) equilibrium solidification. The specific features of free growth under non-uniform undercooling are also shown by comparison with the Lipton, Glicksman, and Kurz model. Next, from microscopic observations, the distribution of the solute concentration and the change of crystal morphology in the solidified materials were investigated quantitatively using scanning electron microscopy and energy-dispersive spectroscopy. Finally, the solidification path during the above three fundamental processes is dynamically represented on phase diagrams

Melting, solidification, remelting, and separation of glass and metal

International Nuclear Information System (INIS)

Ebadian, M.A.; Xin, R.C.; Liu, Y.Z.

1998-01-01

Several high-temperature vitrification technologies have been developed for the treatment of a wide range of mixed waste types in both the low-level waste and transuranic (TRU) mixed waste categories currently in storage at DOE sites throughout the nation. The products of these processes are an oxide slag phase and a reduced metal phase. The metal phase has the potential to be recycled within the DOE Complex. Enhanced slag/metal separation methods are needed to support these processes. This research project involves an experimental investigation of the melting, solidification, remelting, and separation of glass and metal and the development of an efficient separation technology. The ultimate goal of this project is to find an efficient way to separate the slag phase from the metal phase in the molten state. This two-year project commenced in October 1995 (FY96). In the first fiscal year, the following tasks were accomplished: (1) A literature review and an assessment of the baseline glass and metal separation technologies were performed. The results indicated that the baseline technology yields a high percentage of glass in the metal phase, requiring further separation. (2) The main melting and solidification system setup was established. A number of melting and solidification tests were conducted. (3) Temperature distribution, solidification patterns, and flow field in the molten metal pool were simulated numerically for the solidification processes of molten aluminum and iron steel. (4) Initial designs of the laboratory-scale DCS and CS technologies were also completed. The principal demonstration separation units were constructed. (5) An application for a patent for an innovative liquid-liquid separation technology was submitted and is pending

Modified sulfur cement solidification of low-level wastes

Energy Technology Data Exchange (ETDEWEB)

1985-10-01

This topical report describes the results of an investigation on the solidification of low-level radioactive wastes in modified sulfur cement. The work was performed as part of the Waste Form Evaluation Program, sponsored by the US Department of Energy's Low-Level Waste Management Program. Modified sulfur cement is a thermoplastic material developed by the US Bureau of Mines. Processing of waste and binder was accomplished by means of both a single-screw extruder and a dual-action mixing vessel. Waste types selected for this study included those resulting from advanced volume reduction technologies (dry evaporator concentrate salts and incinerator ash) and those which remain problematic for solidification using contemporary agents (ion exchange resins). Process development studies were conducted to ascertain optimal process control parameters for successful solidification. Maximum waste loadings were determined for each waste type and method of processing. Property evaluation testing was carried out on laboratory scale specimens in order to compare with waste form performance for other potential matrix materials. Waste form property testing included compressive strength, water immersion, thermal cycling and radionuclide leachability. Recommended waste loadings of 40 wt. % sodium sulfate and boric acid salts and 43 wt. % incinerator ash, which are based on processing and performance considerations, are reported. Solidification efficiencies for these waste types represent significant improvements over those of hydraulic cements. Due to poor waste form performance, incorporation of ion exchange resin waste in modified sulfur cement is not recommended.

Modified sulfur cement solidification of low-level wastes

International Nuclear Information System (INIS)

1985-10-01

This topical report describes the results of an investigation on the solidification of low-level radioactive wastes in modified sulfur cement. The work was performed as part of the Waste Form Evaluation Program, sponsored by the US Department of Energy's Low-Level Waste Management Program. Modified sulfur cement is a thermoplastic material developed by the US Bureau of Mines. Processing of waste and binder was accomplished by means of both a single-screw extruder and a dual-action mixing vessel. Waste types selected for this study included those resulting from advanced volume reduction technologies (dry evaporator concentrate salts and incinerator ash) and those which remain problematic for solidification using contemporary agents (ion exchange resins). Process development studies were conducted to ascertain optimal process control parameters for successful solidification. Maximum waste loadings were determined for each waste type and method of processing. Property evaluation testing was carried out on laboratory scale specimens in order to compare with waste form performance for other potential matrix materials. Waste form property testing included compressive strength, water immersion, thermal cycling and radionuclide leachability. Recommended waste loadings of 40 wt. % sodium sulfate and boric acid salts and 43 wt. % incinerator ash, which are based on processing and performance considerations, are reported. Solidification efficiencies for these waste types represent significant improvements over those of hydraulic cements. Due to poor waste form performance, incorporation of ion exchange resin waste in modified sulfur cement is not recommended

Performance of the mineral blended ester oil-based drilling fluid systems

Energy Technology Data Exchange (ETDEWEB)

Ismail, A.R.; Kamis, A.; Foo, K.S. [University Teknologi (Malaysia)

2001-06-01

A study was conducted in which the properties of ester oil-based drilling fluid systems were examined using a blended mixture of ester and synthetic mineral oil. Biodegradable invert emulsion ester-based fluids are preferred over mineral oil-based drilling fluids for environmental reasons, but they tend to cause alkaline hydrolysis resulting in solidification of the drilling fluid systems. The drilling fluid examined here consisted of Malaysian palm oil ester derivatives (methyl laureate ester or isopropyl laureate ester) blended with commercially available synthetic mineral oil. This mineral oil was added to reduce the problem of alkaline hydrolysis. This mixture, however, was found to be unstable and could not solve the problem at high temperature. The isopropyl laureate and mineral oil blended system was more stable towards the hydrolysis process up to 250 degrees F. In order to enhance the performance of an invert emulsion drilling fluid system, it was recommended that brine water content of the fluid system be lowered. 3 refs., 2 figs.

Stabilization/Solidification Remediation Method for Contaminated Soil: A Review

Science.gov (United States)

Tajudin, S. A. A.; Azmi, M. A. M.; Nabila, A. T. A.

2016-07-01

Stabilization/Solidification (S/S) is typically a process that involves a mixing of waste with binders to reduce the volume of contaminant leachability by means of physical and chemical characteristics to convert waste in the environment that goes to landfill or others possibly channels. Stabilization is attempts to reduce the solubility or chemical reactivity of the waste by changing the physical and chemical properties. While, solidification attempt to convert the waste into easily handled solids with low hazardous level. These two processes are often discussed together since they have a similar purpose of improvement than containment of potential pollutants in treated wastes. The primary objective of this review is to investigate the materials used as a binder in Stabilization/Solidification (S/S) method as well as the ability of these binders to remediate the contaminated soils especially by heavy metals.

MODELING SOLIDIFICATION-INDUCED STRESSES IN CERAMIC WASTE FORMS CONTAINING NUCLEAR WASTES

International Nuclear Information System (INIS)

Solbrig, Charles W.; Bateman, Kenneth J.

2010-01-01

The goal of this work is to produce a ceramic waste form (CWF) that permanently occludes radioactive waste. This is accomplished by absorbing radioactive salts into zeolite, mixing with glass frit, heating to a molten state 915 C to form a sodalite glass matrix, and solidifying for long-term storage. Less long term leaching is expected if the solidifying cooling rate doesn't cause cracking. In addition to thermal stress, this paper proposes that a stress is formed during solidification which is very large for fast cooling rates during solidification and can cause severe cracking. A solidifying glass or ceramic cylinder forms a dome on the cylinder top end. The temperature distribution at the time of solidification causes the stress and the dome. The dome height, ''the length deficit,'' produces an axial stress when the solid returns to room temperature with the inherent outer region in compression, the inner in tension. Large tensions will cause cracking of the specimen. The temperature deficit, derived by dividing the length deficit by the coefficient of thermal expansion, allows solidification stress theory to be extended to the circumferential stress. This paper derives the solidification stress theory, gives examples, explains how to induce beneficial stresses, and compares theory to experimental data.

Solidification of low-level wastes by inorganic binder

International Nuclear Information System (INIS)

Sasaki, M.T.; Shimojo, M.; Suzuki, K.; Kajikawa, A.; Karasawa, Y.

1995-01-01

The use of an alkali activated slag binder has been studied for solidification and stabilization of low-level wastes in nuclear power stations and spent fuel processing facilities. The activated slag effectively formed waste products having good physical properties with high waste loading for sodium sulfate, sodium nitrate, calcium pyrophosphate/phosphate and spent ion-exchange resins. Moreover, the results of the study suggest the slag has the ability to become a common inorganic binder for the solidification of various radioactive wastes. This paper also describes the fixation of radionuclides by the activated slag binder

Solidification in Multicomponent Multiphase Systems (SIMMS)

Science.gov (United States)

Rex, S.; Hecht, U.

2005-06-01

The multiphase microstructures that evolve during the solidification of multicomponent alloys are attracting widespread interest for industrial applications and fundamental research.Thermodynamic databases are now well-established for many alloy systems. Thermodynamic calculations provide all the required information about phase equilibria, forming an integral part of both dedicated and comprehensive microstructure models. Among the latter, phase-field modelling has emerged as the method of choice. Solidification experiments are intended to trigger model development or to serve as benchmarks for model validation. For benchmarking, microgravity conditions offer a unique opportunity for avoiding buoyancy-induced convection and buoyancy forces in bulk samples. However, diffusion and the free-energy of interfaces and its anisotropy need to be determined.The measurement of chemical diffusivities in the liquid state can equally benefit from microgravity experiments.

Measuring device for weight of glass of glass solidification product to be charged

International Nuclear Information System (INIS)

Yasutake, Nobuhiro; Arai, Masaki; Akashi, Ken-ichi

1998-01-01

The present invention provides a device for accurately calculating the weight of molten glass to be charged during manufacturing glass solidification products of radioactive liquid wastes. Namely, a discharge nozzle at the lower end of a glass melting furnace and an upper end of a vessel for glass solidification materials are connected by a connecting device extensible vertically in a cylindrical shape. Molten glasses are flown down by way of the connecting device and filled into the vessel for solidification products. A first scale is constituted so as to measure the weight of load, and the vessel for solidification products are loaded. A second scale is constituted so as to measure the own weight and a weight of load, and is interposed between a flange at the circumference of a charging port and the lower end of the connecting device, and has an opening for flowing down the molten glass at the central portion. With such a constitution, the first scale can weigh the total of the weight of molten glass charged to the vessel for solidification products, the weight of the vessel for solidification products, the counterforce from the connecting device and the weight of the second scale. If the measured value of the secondary scale and the weight of the vessel for solidification products are subtracted from the former value, the weight of the charged molten glass can be determined. (I.S.)

Growth kinetics in multicomponent fluids

International Nuclear Information System (INIS)

Chen, S.; Lookman, T.

1995-01-01

The hydrodynamic effects on the late-stage kinetics in spinodal decomposition of multicomponent fluids are examined using a lattice Boltzmann scheme with stochastic fluctuations in the fluid and at the interface. In two dimensions, the three- and four-component immiscible fluid mixture (with a 1024 2 lattice) behaves like an off-critical binary fluid with an estimated domain growth of t 0.4 +/= 0.03 rather than t 1/3 as previously estimated, showing the significant influence of hydrodynamics. In three dimensions (with a 256 3 lattice), we estimate the growth as t 0.96 +/= 0.05 for both critical and off-critical quenches, in agreement with phenomenological theory

PREFACE: Third International Conference on Advances in Solidification Processes (ICASP - 3)

Science.gov (United States)

Zimmermann, Gerhard; Ratke, Lorenz

2012-01-01

The 3rd International Conference on Advances in Solidification Processes was held in the Rolduc Abbey in the Netherlands a few kilometres away from Aachen. Around 200 scientists from 24 countries come in for the four day meeting. They found a stimulating but also relaxing environment and atmosphere, with beautiful weather and the medieval abbey inviting for walks, discussions, sitting outside and drinking a beer or wine. The contributions given at the conference reflected recent advances in various topics of solidification processes, ranging from fundamental aspects to applied casting technologies. In 20 oral sessions and a large poster session innovative results of segregation phenomena, microstructure evolution, nucleation and growth, phase formation, polyphase solidification, rapid solidification and welding, casting technology, thermophysics of molten alloys, solidification with forced melt flow and growth of single crystals and superalloys together with innovative diagnostic techniques were presented. Thereby, findings from experiments as well as from numerical modeling on different lengths scales were jointly discussed and contribute to new insight in solidification behaviour. The papers presented in this open access proceedings cover about half the oral and poster presentations given. They were carefully reviewed as in classical peer reviewed journals by two independent referees and most of them were revised and thus improved according to the reviewers comments. We think that this collection of papers presented at ICASP-3 gives an impression of the excellent contributions made. The papers embrace both the basic and applied aspects of solidification. We especially wish to express our appreciation for the team around Georg Schmitz and Margret Nienhaus organising this event and giving us their valued advice and support at every stage in preparing the conference. We also thank Lokasenna Lektorat for taking the task of checking all language-associated issues and

Microstructure and Corrosion Resistance Property of a Zn-AI-Mg Alloy with Different Solidification Processes

Directory of Open Access Journals (Sweden)

Jiang Guang-rui

2017-01-01

Full Text Available Zn-Al-Mg alloy coating attracted much attention due to its high corrosion resistance properties, especially high anti-corrosion performance at the cut edge. As the Zn-Al-Mg alloy coating was usually produced by hot-dip galvanizing method, solidification process was considered to influence its microstructure and corrosion properties. In this work, a Zn-Al-Mg cast alloy was melted and cooled to room temperature with different solidification processes, including water quench, air cooling and furnace cooling. Microstructure of the alloy with different solidification processes was characterized by scanning electron microscopy (SEM. Result shows that the microstructure of the Zn-Al-Mg alloy are strongly influenced by solidification process. With increasing solidification rate, more Al is remained in the primary crystal. Electrochemical analysis indicates that with lowering solidification rate, the corrosion current density of the Zn-Al-Mg alloy decreases, which means higher corrosion resistance.

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.

Solidification behavior of austenitic stainless steel filler metals

International Nuclear Information System (INIS)

David, S.A.; Goodwin, G.M.; Braski, D.N.

1980-02-01

Thermal analysis and interrupted solidification experiments on selected austenitic stainless steel filler metals provided an understanding of the solidification behavior of austenitic stainless steel welds. The sequences of phase separations found were for type 308 stainless steel filler metal, L + L + delta + L + delta + γ → γ + delta, and for type 310 stainless steel filler metal, L → L + γ → γ. In type 308 stainless steel filler metal, ferrite at room temperature was identified as either the untransformed primary delta-ferrite formed during the initial stages of solidification or the residual ferrite after Widmanstaetten austenite precipitation. Microprobe and scanning transmission electron microscope microanalyses revealed that solute extensively redistributes during the transformation of primary delta-ferrite to austenite, leading to enrichment and stabilization of ferrite by chromium. The type 310 stainless steel filler metal investigated solidifies by the primary crystallization of austenite, with the transformation going to completion at the solidus temperature. In our samples residual ferrite resulting from solute segregation was absent at the intercellular or interdendritic regions

On the relation between primary and eutectic solidification structures in gray iron

International Nuclear Information System (INIS)

Elmquist, L; Sonawane, P A

2012-01-01

The solidification of hypoeutectic gray cast iron starts with the nucleation of primary austenite crystals. Before graphite is nucleated, and the eutectic structure is formed, these crystals start to grow as columnar or equiaxed dendrites. However, very little is known about these dendrites, and especially how they influence the subsequent eutectic structure. Besides, it has previously been shown that the primary solidification structure influences the formation of defects. Shrinkage porosity was found between the dendrites, in the grain boundaries, and the formation of the primary solidification structure was found to influence problems related to metal expansion penetration. Therefore a better understanding about the formation of this structure is of importance. In this work, different inoculants and their influence on the formation of the micro- and macrostructures has been investigated. The inoculants considered are commercially used inoculants, i.e. inoculants used in the foundries, as well as different iron powders. The addition of iron powder is used to promote the primary solidification structure. It is shown that the nucleation of the dendrites is influenced by the amount of iron powder. Secondary dendrite arm spacing is a quantitative measurement in the microstructure related to these dendrites, which in turn depends on the solidification time. Eutectic cell size, on the other hand, is found to depend on secondary dendrite arm spacing. It is shown how the addition of inoculants influences both primary and eutectic solidification structures, and how they are related to each other.

Overview of the Tusas Code for Simulation of Dendritic Solidification

Energy Technology Data Exchange (ETDEWEB)

Trainer, Amelia J. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Newman, Christopher Kyle [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Francois, Marianne M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-01-07

The aim of this project is to conduct a parametric investigation into the modeling of two dimensional dendrite solidification, using the phase field model. Specifically, we use the Tusas code, which is for coupled heat and phase-field simulation of dendritic solidification. Dendritic solidification, which may occur in the presence of an unstable solidification interface, results in treelike microstructures that often grow perpendicular to the rest of the growth front. The interface may become unstable if the enthalpy of the solid material is less than that of the liquid material, or if the solute is less soluble in solid than it is in liquid, potentially causing a partition [1]. A key motivation behind this research is that a broadened understanding of phase-field formulation and microstructural developments can be utilized for macroscopic simulations of phase change. This may be directly implemented as a part of the Telluride project at Los Alamos National Laboratory (LANL), through which a computational additive manufacturing simulation tool is being developed, ultimately to become part of the Advanced Simulation and Computing Program within the U.S. Department of Energy [2].

Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

Energy Technology Data Exchange (ETDEWEB)

Osborne, Matthew G. [Iowa State Univ., Ames, IA (United States)

1998-02-23

A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100-1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was atomized under inert atmosphere and the subsequent particles were examined microscopically to determine solidification structure and rate. This dissertation details the experimental procedures used in producing the Al-Cu eutectic alloy particles, examination of the particle microstructures, and determination of the solidification characteristics (e.g., solidification rate) of various phases. Finally, correlations are proposed between the operation of the centrifugal atomizer and the observed solidification spacings.

Nucleation and solidification of thin walled ductile iron - Experiments and numerical simulation

DEFF Research Database (Denmark)

Pedersen, Karl Martin; Tiedje, Niels Skat

2005-01-01

Investigation of solidification of thin walled ductile cast iron has been performed based on experiments and numerical simulation. The experiments were based on temperature and microstructure examination. Results of the experiments have been compared with a 1-D numerical solidification model...

Simulation of dendritic growth of magnesium alloys with fluid flow

Directory of Open Access Journals (Sweden)

Meng-wu Wu

2017-11-01

Full Text Available Fluid flow has a significant impact on the microstructure evolution of alloys during solidification. Based on the previous work relating simulation of the dendritic growth of magnesium alloys with hcp (hexagonal close-packed structure, an extension was made to the formerly established CA (cellular automaton model with the purpose of studying the effect of fluid flow on the dendritic growth of magnesium alloys. The modified projection method was used to solve the transport equations of flow field. By coupling the flow field with the solute field, simulation results of equiaxed and columnar dendritic growth of magnesium alloys with fluid flow were achieved. The simulated results were quantitatively compared with those without fluid flow. Moreover, a comparison was also made between the present work and previous works conducted by others. It can be concluded that a deep understanding of the dendritic growth of magnesium alloys with fluid flow can be obtained by applying the present numerical model.

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.

Process gas solidification system

International Nuclear Information System (INIS)

1980-01-01

A process for withdrawing gaseous UF 6 from a first system and directing same into a second system for converting the gas to liquid UF 6 at an elevated temperature, additionally including the step of withdrawing the resulting liquid UF 6 from the second system, subjecting it to a specified sequence of flash-evaporation, cooling and solidification operations, and storing it as a solid in a plurality of storage vessels. (author)

Alternative solidification techniques for radioactive ion exchange resins and liquid concentrates

International Nuclear Information System (INIS)

Thegerstroem, C.

1980-01-01

Methods, that are used or are under development for solidification of radioactive ion exchange resins or liquid concentrates, utilize normally cement, bitumen or some polymere as matrix material. This report contains a review and a description of these solidification processes and their products, especially of relatively new techniques that are under development in different countries. It is possible that solidification in thermosetting resins will be more used in the future, especially when product quality requirements are high (for instance when solidifying medium level resins) or when special waste categories has to be solidified. However it is not probable that thermosetting resins will be extensively used in a broad application as matrix material. In that case the methods are to complicated and expensive compared to, for instance, solidification in concrete. Systems for incorporation in polyesteremulsions (Dow-process) have a potential as they are quite simple and can accept a large variation of liquid wastes. Some methods in an early stage of development (for instance Inert Carrier Radwaste Process) will have to be tested in active application before they can be further evaluated. (author)

Instabilities in vertically vibrated fluid-grain systems.

Science.gov (United States)

King, P J; Lopez-Alcaraz, P; Pacheco-Martinez, H A; Clement, C P; Smith, A J; Swift, M R

2007-03-01

When a bed of fluid-immersed fine grains is exposed to vertical vibration a wealth of phenomena may be observed. At low frequencies a horizontal bed geometry is generally unstable and the bed breaks spatial symmetry, acquiring a tilt. At the same time it undergoes asymmetric granular convection. Fine binary mixtures may separate completely into layers or patterns of stripes. The separated regions may exhibit instabilities in which they undergo wave-like motion or exhibit quasi-periodic oscillations. We briefly review these and a number of related behaviours, identifying the physical mechanisms behind each. Finally, we discuss the magneto-vibratory separation of binary mixtures which results from exposing each component to a different effective gravity and describe the influence of a background fluid on this process.

Phase-field simulation of solidification in multicomponent alloys coupled with thermodynamic and diffusion mobility databases

International Nuclear Information System (INIS)

Zhang Ruijie; Jing Tao; Jie Wanqi; Liu Baicheng

2006-01-01

To simulate quantitatively the microstructural evolution in the solidification process of multicomponent alloys, we extend the phase-field model for binary alloys to multicomponent alloys with consideration of the solute interactions between different species. These interactions have a great influence not only on the phase equilibria but also on the solute diffusion behaviors. In the model, the interface region is assumed to be a mixture of solid and liquid with the same chemical potential, but with different compositions. The simulation presented is coupled with thermodynamic and diffusion mobility databases, which can accurately predict the phase equilibria and the solute diffusion transportation in the whole system. The phase equilibria in the interface and other thermodynamic quantities are obtained using Thermo-Calc through the TQ interface. As an example, two-dimensional computations for the dendritic growth in Al-Cu-Mg ternary alloy are performed. The quantitative solute distributions and diffusion matrix are obtained in both solid and liquid phases

Study of the thermal and kinetic parameters during directional solidification of zinc-aluminum eutectic alloys

International Nuclear Information System (INIS)

Gueijman, Sergio Fabian; Ares, Alicia Esther; Schvezov, Carlos Enrique

2008-01-01

Much work has been done recently on investigating zinc-based binary alloys, with different aluminum content, and modified or not with small amounts of other alloying elements. Some of these alloys have interesting properties, such as, the ZA alloys that have properties similar to some bronzes that are used in applications that require pieces with enough resistance to mechanical stresses. The longitudinal thermal gradients, the minimal gradients, the velocities of the liquid interphases, the velocities of the solid interphases and the accelerations of both interphases as a function of time and position were determined for each diluted alloy of the eutectic concentration considered (Zn-5%Al, % in weight), solidified horizontally with caloric extraction from both ends of the test pieces. The values obtained from the horizontal solidification with two directions of predominant caloric extraction are compared to previous values obtained for the same vertically solidified alloy system with a predominantly caloric extraction direction

Volumetric properties under pressure for the binary system ethanol plus toluene

DEFF Research Database (Denmark)

Zeberg-Mikkelsen, Claus Kjær; Lugo, Luis; García, Josefa

2005-01-01

. The VLE behavior of this binary system within the considered temperature range is represented satisfactory by the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state with a single interaction parameter, although no cross association between ethanol and toluene is taken...... into account. The densities of this binary system (pure compounds and mixtures) are satisfactory predicted by PC-SAFT with an overall AAD of 0.8%, but the behavior of the excess molar volume is not described correctly....

Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

Directory of Open Access Journals (Sweden)

Szymanek M.

2015-12-01

Full Text Available The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS. The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr refines their structure.

Microstructural Development in Al-Si Powder During Rapid Solidification

Energy Technology Data Exchange (ETDEWEB)

Genau, Amber Lynn [Iowa State Univ., Ames, IA (United States)

2004-01-01

Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

Effect of high-intensity ultrasonic irradiation on the modification of solidification microstructure in a Si-rich hypoeutectic Al-Si alloy

Energy Technology Data Exchange (ETDEWEB)

Das, A., E-mail: A.Das@swansea.ac.uk [Materials Research Centre, School of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom); Kotadia, H.R. [Brunel Centre for Advanced Solidification Technology, Brunel University, Uxbridge, UB8 3PH (United Kingdom)

2011-02-15

Effect of high-intensity ultrasound irradiation in modifying complex solidification microstructure is explored in a high Si containing Al-Si alloy and the origin of microstructural changes explained on the basis of nucleation and growth behaviour. Complete suppression of dendritic growth and dramatic refinement to globular morphology were observed for primary {alpha}-Al grains. Strong supportive evidence is presented towards enhanced and prolonged heterogeneous nucleation triggered by cavitation induced increase in the equilibrium melting point and effective dissipation of latent heat at the solidification front. Morphological evolution of eutectic Si and intermetallic particles is found to be dominated by coarsening and spherodisation from strong fluid flow in areas of intense cavitation near the ultrasonic radiator. Outside the region of direct energy transfer, Si particle morphology appears to be controlled predominantly by the imposed cooling conditions. Extremely fine and short Si-platelets observed in the intergranular spaces near the radiator are explained on the basis of probable rapid cooling of final liquid pockets of small volume and large surface area, rather than refinement through ultrasound.

Microwave solidification project overview

Energy Technology Data Exchange (ETDEWEB)

Sprenger, G.

1993-01-01

The Rocky Flats Plant Microwave Solidification Project has application potential to the Mixed Waste Treatment Project and the The Mixed Waste Integrated Program. The technical areas being addressed include (1) waste destruction and stabilization; (2) final waste form; and (3) front-end waste handling and feed preparation. This document covers need for such a program; technology description; significance; regulatory requirements; and accomplishments to date. A list of significant reports published under this project is included.

Microwave solidification project overview

International Nuclear Information System (INIS)

Sprenger, G.

1993-01-01

The Rocky Flats Plant Microwave Solidification Project has application potential to the Mixed Waste Treatment Project and the The Mixed Waste Integrated Program. The technical areas being addressed include (1) waste destruction and stabilization; (2) final waste form; and (3) front-end waste handling and feed preparation. This document covers need for such a program; technology description; significance; regulatory requirements; and accomplishments to date. A list of significant reports published under this project is included

Solute redistribution in dendritic solidification with diffusion in the solid

Science.gov (United States)

Ganesan, S.; Poirier, D. R.

1989-01-01

An investigation of solute redistribution during dendritic solidification with diffusion in the solid has been performed using numerical techniques. The extent of diffusion is characterized by the instantaneous and average diffusion parameters. These parameters are functions of the diffusion Fourier number, the partition ratio and the fraction solid. Numerical results are presented as an approximate model, which is used to predict the average diffusion parameter and calculate the composition of the interdendritic liquid during solidification.

Solidification of highly active liquid waste

International Nuclear Information System (INIS)

Morris, J.B.

1985-03-01

This document contains the annual progress reports on the following subjects: Joule ceramic melter; microwave vitrification; glass technology; identification, evaluation and review of potential alternative solidification processes; rotary kiln calcination; alternative glass feedstocks; volatile ruthenium trapping by solid adsorbents; irrigated baffle column dust scrubber. (author)

Centralized cement solidification technique for low-level radioactive wastes

International Nuclear Information System (INIS)

Matsuda, Masami; Nishi, Takashi; Izumida, Tatsuo; Tsuchiya, Hiroyuki.

1996-01-01

A centralized cement solidification system has been developed to enable a single facility to solidify such low-level radioactive wastes as liquid waste, spent ion exchange resin, incineration ash, and miscellaneous solid wastes. Since the system uses newly developed high-performance cement, waste loading is raised and deterioration of waste forms after land burial prevented. This paper describes the centralized cement solidification system and the features of the high-performance cement. Results of full-scale pilot plant tests are also shown from the viewpoint of industrial applicability. (author)

Utilization of coal fly ash in solidification of liquid radioactive waste from research reactor.

Science.gov (United States)

Osmanlioglu, Ahmet Erdal

2014-05-01

In this study, the potential utilization of fly ash was investigated as an additive in solidification process of radioactive waste sludge from research reactor. Coal formations include various percentages of natural radioactive elements; therefore, coal fly ash includes various levels of radioactivity. For this reason, fly ashes have to be evaluated for potential environmental implications in case of further usage in any construction material. But for use in solidification of radioactive sludge, the radiological effects of fly ash are in the range of radioactive waste management limits. The results show that fly ash has a strong fixing capacity for radioactive isotopes. Specimens with addition of 5-15% fly ash to concrete was observed to be sufficient to achieve the target compressive strength of 20 MPa required for near-surface disposal. An optimum mixture comprising 15% fly ash, 35% cement, and 50% radioactive waste sludge could provide the solidification required for long-term storage and disposal. The codisposal of radioactive fly ash with radioactive sludge by solidification decreases the usage of cement in solidification process. By this method, radioactive fly ash can become a valuable additive instead of industrial waste. This study supports the utilization of fly ash in industry and the solidification of radioactive waste in the nuclear industry.

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy

Science.gov (United States)

Wang, Changshuai; Su, Haijun; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

2017-09-01

Solidification characteristics and segregation behavior of a P-containing Ni-Fe-Cr-based alloy, considered as boiler and turbine materials in 700 °C advanced ultra-supercritical coal-fired power plants, have been investigated by differential thermal analysis and directional solidification quenching technique. Results reveal that P decreases the solidus temperature, but only has negligible influence on liquidus temperature. After P was added, the solidification sequence has no apparent change, but the width of the mushy zone increases and dendritic structures become coarser. Moreover, P increases the amount and changes the morphology of MC carbide. Energy-dispersive spectroscopy analysis reveals that P has obvious influence on the segregation behavior of the constitute elements with equilibrium partition coefficients (ki) far away from unity, whereas has negligible effect on the constituent elements with ki close to unity and has more influence on the final stage of solidification than at early stage. The distribution profiles reveal that P atoms pile up ahead of the solid/liquid (S/L) interface and strongly segregate to the interdendritic liquid region. The influence of P on solidification characteristics and segregation behavior of Ni-Fe-Cr-based alloy could be attributed to the accumulation of P ahead of the S/L interface during solidification.

Solidification of low-level waste - a dilemma for the small user

International Nuclear Information System (INIS)

Harris, S.; Gilmore, A.

1980-01-01

The requirement that radioactive waste for sea disposal must be solidified by the originator is discussed. Attempts to solidify small quantities of radioactive waste such as contaminated oils and labelled benzyopyrene with other solvents are described. Encapsulation media tested were concrete and interior and exterior grade Polyfilla (a plaster and cellulose based filler). Problems were presented by the difficulty of mixing the materials and by the maximum uptake of solvents while still allowing solidification. In all cases a soft crumbling material resulted. It is concluded that solidification processing on a small scale does not make economic or scientific sense and that if solidification is necessary it would be better carried out as a national operation by collecting liquids from users. (U.K.)

Mesoscopic electrohydrodynamic simulations of binary colloidal suspensions

Science.gov (United States)

Rivas, Nicolas; Frijters, Stefan; Pagonabarraga, Ignacio; Harting, Jens

2018-04-01

A model is presented for the solution of electrokinetic phenomena of colloidal suspensions in fluid mixtures. We solve the discrete Boltzmann equation with a Bhatnagar-Gross-Krook collision operator using the lattice Boltzmann method to simulate binary fluid flows. Solvent-solvent and solvent-solute interactions are implemented using a pseudopotential model. The Nernst-Planck equation, describing the kinetics of dissolved ion species, is solved using a finite difference discretization based on the link-flux method. The colloids are resolved on the lattice and coupled to the hydrodynamics and electrokinetics through appropriate boundary conditions. We present the first full integration of these three elements. The model is validated by comparing with known analytic solutions of ionic distributions at fluid interfaces, dielectric droplet deformations, and the electrophoretic mobility of colloidal suspensions. Its possibilities are explored by considering various physical systems, such as breakup of charged and neutral droplets and colloidal dynamics at either planar or spherical fluid interfaces.

Fluid bed dryer and Aeropep solidification system. Amendment 1 to topical report

International Nuclear Information System (INIS)

1975-01-01

Information is presented on interfaces between the aerojet fluid bed dryer and the liquid radwaste system, plant ventilation system, and radioactive solid waste handling system for BWR and PWR type reactors. (U.S.)

Evaporative lithographic patterning of binary colloidal films.

Science.gov (United States)

Harris, Daniel J; Conrad, Jacinta C; Lewis, Jennifer A

2009-12-28

Evaporative lithography offers a promising new route for patterning a broad array of soft materials. In this approach, a mask is placed above a drying film to create regions of free and hindered evaporation, which drive fluid convection and entrained particles to regions of highest evaporative flux. We show that binary colloidal films exhibit remarkable pattern formation when subjected to a periodic evaporative landscape during drying.

Exergoeconomic analysis and optimization of an evaporator for a binary mixture of fluids in an organic Rankine cycle

Science.gov (United States)

Li, You-Rong; Du, Mei-Tang; Wang, Jian-Ning

2012-12-01

This paper focuses on the research of an evaporator with a binary mixture of organic working fluids in the organic Rankine cycle. Exergoeconomic analysis and performance optimization were performed based on the first and second laws of thermodynamics, and the exergoeconomic theory. The annual total cost per unit heat transfer rate was introduced as the objective function. In this model, the exergy loss cost caused by the heat transfer irreversibility and the capital cost were taken into account; however, the exergy loss due to the frictional pressure drops, heat dissipation to surroundings, and the flow imbalance were neglected. The variation laws of the annual total cost with respect to the number of transfer units and the temperature ratios were presented. Optimal design parameters that minimize the objective function had been obtained, and the effects of some important dimensionless parameters on the optimal performances had also been discussed for three types of evaporator flow arrangements. In addition, optimal design parameters of evaporators were compared with those of condensers.

Analytical and Numerical Study of Soret and Dufour Effects on Double Diffusive Convection in a Shallow Horizontal Binary Fluid Layer Submitted to Uniform Fluxes of Heat and Mass

Directory of Open Access Journals (Sweden)

A. Lagra

2018-01-01

Full Text Available Combined Soret and Dufour effects on thermosolutal convection induced in a horizontal layer filled with a binary fluid and subject to constant heat and mass fluxes are investigated analytically and numerically. The thresholds marking the onset of supercritical and subcritical convection are predicted analytically and explicitly versus the governing parameters. The present investigation shows that different regions exist in the N-Du plane corresponding to different parallel flow regimes. The number, the extent, and the locations of these regions depend on whether SrDu>-(1+Le2/2Le2=f(Le or SrDu<-(1+Le2/2Le2. Conjugate effects of cross-phenomena on thresholds of fluid flow and heat and mass transfer characteristics are illustrated and discussed.

Retrofit of radwaste solidification systems in Spain

International Nuclear Information System (INIS)

Rorcillo, R.; Virzi, E.

1983-01-01

In order to meet current Spanish engineering criteria as well as to provide for likely future Spanish Regulatory requirements, utilities committed to a major policy change in the preferred radwaste solidification media. In the early 1970's Spanish utilities, following the United States experience, purchased inexpensive solidification systems which used urea formaldehyde (UF) as the binding matrix. By the late 1970's the Spanish utilities, seeing the deterioration of the UF position and slow progress toward its improvement, unilaterally changed their binding matrix to cement. This paper illustrates the implementation of this change at the ASCO Nuclear Plant. The problems of layout modifications, shortened delivery schedule and criteria unique for Spain are addressed. Also presented is the operating experience acquired during the pre-operational start-up of the ASCO I Radwaste System

Solidification processing of monotectic alloy matrix composites

Science.gov (United States)

Frier, Nancy L.; Shiohara, Yuh; Russell, Kenneth C.

1989-01-01

Directionally solidified aluminum-indium alloys of the monotectic composition were found to form an in situ rod composite which obeys a lambda exp 2 R = constant relation. The experimental data shows good agreement with previously reported results. A theoretical boundary between cellular and dendritic growth conditions was derived and compared with experiments. The unique wetting characteristics of the monotectic alloys can be utilized to tailor the interface structure in metal matrix composites. Metal matrix composites with monotectic and hypermonotectic Al-In matrices were made by pressure infiltration, remelted and directionally solidified to observe the wetting characteristics of the alloys as well as the effect on structure of solidification in the constrained field of the fiber interstices. Models for monotectic growth are modified to take into account solidification in these constrained fields.

Solidification Mapping of a Nickel Alloy 718 Laboratory VAR Ingot

Science.gov (United States)

Watt, Trevor J.; Taleff, Eric M.; Lopez, Felipe; Beaman, Joe; Williamson, Rodney

The solidification microstructure of a laboratory-scale Nickel alloy 718 vacuum arc remelted (VAR) ingot was analyzed. The cylindrical, 210-mm-diameter ingot was sectioned along a plane bisecting it length-wise, and this mid-plane surface was ground and etched using Canada's reagent to reveal segregation contrast. Over 350 photographs were taken of the etched mid-plane surface and stitched together to form a single mosaic image. Image data in the resulting mosaic were processed using a variety of algorithms to extract quantities such as primary dendrite orientation, primary dendrite arm spacing (PDAS), and secondary dendrite arm spacing (SDAS) as a function of location. These quantities were used to calculate pool shape and solidification rate during solidification using existing empirical relationships for Nickel Alloy 718. The details and outcomes of this approach, along with the resulting comparison to experimental processing conditions and computational models, are presented.

Analysis of weld solidification cracking in cast nickel aluminide alloys

International Nuclear Information System (INIS)

Santella, M.L.; Feng, Z.

1995-01-01

A study of the response of several nickel aluminide alloys to SigmaJig testing was done to examine their weld solidification cracking behavior and the effect of Zr concentration. The alloys were based on the Ni-8Al-7.7Cr-1.5Mo-0.003B wt% composition and contained Zr concentrations of 3, 4.5, and 6 wt%. Vacuum induction melted ingots with a diameter of 2.7 in and weight about 18 lb were made of each alloy, and were used to make 2 x 2 x 0.030 in specimens for the Sigmajig test. The gas tungsten arc welds were made at travel speeds of 10, 20, and 30 ipm with heat inputs of 2--2.5 kJ/in. When an arc was established before traveling onto the test specimen centerline cracking was always observed. This problem was overcome by initiating the arc directly on the specimens. Using this approach, the 3 wt% Zr alloy withstood an applied stress of 24 ksi without cracking at a welding speed of 10 ipm. This alloy cracked at 4 ksi applied at 20 ipm, and with no applied load at 30 ipm. Only limited testing was done on the remaining alloys, but the results indicate that resistance to solidification cracking increases with Zr concentration. Zirconium has limited solid solubility and segregates strongly to interdendritic regions during solidification where it forms a Ni solid solution-Ni 5 Zr eutectic. The volume fraction of the eutectic increases with Zr concentration. The solidification cracking behavior of these alloys is consistent with phenomenological theory, and is discussed in this context. The results from SigmaJig testing are analyzed using finite element modeling of the development of mechanical strains during solidification of welds. Experimental data from the test substantially agree with recent analysis results

Large Eddy Simulation of Transient Flow, Solidification, and Particle Transport Processes in Continuous-Casting Mold

Science.gov (United States)

Liu, Zhongqiu; Li, Linmin; Li, Baokuan; Jiang, Maofa

2014-07-01

The current study developed a coupled computational model to simulate the transient fluid flow, solidification, and particle transport processes in a slab continuous-casting mold. Transient flow of molten steel in the mold is calculated using the large eddy simulation. An enthalpy-porosity approach is used for the analysis of solidification processes. The transport of bubble and non-metallic inclusion inside the liquid pool is calculated using the Lagrangian approach based on the transient flow field. A criterion of particle entrapment in the solidified shell is developed using the user-defined functions of FLUENT software (ANSYS, Inc., Canonsburg, PA). The predicted results of this model are compared with the measurements of the ultrasonic testing of the rolled steel plates and the water model experiments. The transient asymmetrical flow pattern inside the liquid pool exhibits quite satisfactory agreement with the corresponding measurements. The predicted complex instantaneous velocity field is composed of various small recirculation zones and multiple vortices. The transport of particles inside the liquid pool and the entrapment of particles in the solidified shell are not symmetric. The Magnus force can reduce the entrapment ratio of particles in the solidified shell, especially for smaller particles, but the effect is not obvious. The Marangoni force can play an important role in controlling the motion of particles, which increases the entrapment ratio of particles in the solidified shell obviously.

Solidification of high-level radioactive wastes. Final report

International Nuclear Information System (INIS)

1979-06-01

A panel on waste solidification was formed at the request of the Nuclear Regulatory Commission to study the scientific and technological problems associated with the conversion of liquid and semiliquid high-level radioactive wastes into a stable form suitable for transportation and disposition. Conclusions reached and recommendations made are as follows. Many solid forms described in this report could meet standards as stringent as those currently applied to the handling, storage, and transportation of spent fuel assemblies. Solid waste forms should be selected only in the context of the total radioactive waste management system. Many solid forms are likely to be satisfactory for use in an appropriately designed system, The current United States policy of deferring the reprocessing of commercial reactor fuel provides additional time for R and D solidification technology for this class of wastes. Defense wastes which are relatively low in radioactivity and thermal power density can best be solidified by low-temperature processes. For solidification of fresh commercial wastes that are high in specific activity and thermal power density, the Panel recommends that, in addition to glass, the use of fully-crystalline ceramics and metal-matrix forms be actively considered. Preliminary analysis of the characteristics of spent fuel pins indicates that they may be eligible for consideration as a waste form. Because the differences in potential health hazards to the public resulting from the use of various solid form and disposal options are likely to be small, the Panel concludes that cost, reliability, and health hazards to operating personnel will be major considerations in choosing among the options that can meet safety requiremens. The Panel recommends that responsibility for all radioactive waste management operations (including solidification R and D) should be centralized

Solidification process for toxic and hazardous wastes. Second part: Cement solidification matrices; Inertizzazione di rifiuti tossici e nocivi (RTN). Parte seconda: Inertizzazione in matrici cementizie

Energy Technology Data Exchange (ETDEWEB)

Donato, A; Arcuri, L; Dotti, M; Pace, A; Pietrelli, L; Ricci, G [ENEA - Dipartimento Ciclo del Combustibile, Centro Ricerche Energia, Casaccia (Italy); Basta, M; Cali, V; Pagliai, V [ENEA - Dipartimento Ciclo del Combustibile, Centro Ricerche Energia, Saluggia (Italy)

1989-05-15

This paper reports the second part of a general study carried out at the Nuclear Fuel Division aiming at verifying the possible application of the radioactive waste solidification processes to industrial hazardous wastes (RTN). The cement solidification of several RTN types has been taken into consideration, both from the technical and from the economic point of view. After a short examination of the Italian juridical and economical situation in the field, which demonstrates the need of the RTN solidification, the origin and characteristics of the RTN considered in the study and directly provided by the producing industries are reviewed. The laboratory experimental results of the cementation of RTN produced by gold manufacturing industries and by galvanic industries are reported. The cementation process can be considered a very effective mean for reducing both the RTN management costs and the environmental impact of RTN disposal. (author)

Inertial effects in three-dimensional spinodal decomposition of a symmetric binary fluid mixture: a lattice Boltzmann study

Science.gov (United States)

Kendon, Vivien M.; Cates, Michael E.; Pagonabarraga, Ignacio; Desplat, J.-C.; Bladon, Peter

2001-08-01

The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary fluid mixture is studied numerically, using a thermodynamically consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecedented range of length and time scales when expressed in reduced physical units. (These are the length and time units derived from fluid density, viscosity, and interfacial tension.) Using eight large (2563) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 [less, similar] l [less, similar] 105, 10 [less, similar] t [less, similar] 108. Our data are consistent with the dynamical scaling hypothesis that l(t) is a universal scaling curve. We give the first detailed statistical analysis of fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the fluid velocity and velocity gradient fields. Using the conventional definition of Reynolds number for this problem, Re[phi] = ldl/dt, we attain values approaching 350. At Re[phi] [greater, similar] 100 (which requires t [greater, similar] 106) we find clear evidence of Furukawa's inertial scaling (l [similar] t2/3), although the crossover from the viscous regime (l [similar] t) is both broad and late (102 [less, similar] t [less, similar] 106). Though it cannot be ruled out, we find no indication that Re[phi] is self-limiting (l [similar] t1/2) at late times, as recently proposed by Grant & Elder. Detailed study of the velocity fields confirms that, for our most inertial runs, the RMS ratio of nonlinear to viscous terms in the Navier Stokes equation, R2, is of order 10, with the fluid mixture showing incipient turbulent characteristics. However, we cannot go far enough into the inertial regime to obtain a clear length separation of domain size, Taylor microscale, and Kolmogorov scale, as would be needed to test a

Solidification of radioactive waste in a cement/lime mixture

International Nuclear Information System (INIS)

Zhou, H.; Colombo, P.

1984-01-01

The suitability of a cement/lime mixture for use as a solidification agent for different types of wastes was investigated. This work includes studies directed towards determining the wasted/binder compositional field over which successful solidification occurs with various wastes and the measurement of some of the waste from properties relevant to evaluating the potential for the release of radionuclides to the environment. In this study, four types of low-level radioactive wastes were simulated for incorporation into a cement/lime mixture. These were boric acid waste, sodium sulfate wastes, aion exchange resins and incinerator ash. 7 references, 3 figures, 2 tables

Aluminum alloy weldability. Identification of weld solidification cracking mechanisms through novel experimental technique and model development

Energy Technology Data Exchange (ETDEWEB)

Coniglio, Nicolas

2008-07-01

solidification range, refinement in grain size from 63 to 51 {mu}m, centerline columnar grains disappearance, and decreased cooling rate from 113 to 89 C/s. Moreover, in order to make direct comparison with literature, castings of controlled mixtures of alloys 6060 and 4043 were also investigated, thereby simulating weld metal composition under controlled cooling conditions. Castings showed a different trend than welds with small increases in silicon content (i.e. increase in 4043 filler dilution) resulting in huge effect on microstructure, no effect on liquidus temperature, drop in solidus temperature from 577 C to 509 C, increase in quantity of interdendritic constituent from 2% to 14%, and different phase formation. Binary {beta}-Al{sub 5}FeSi, Mg{sub 2}Si, and Si phases are replaced with ternary {beta}-Al{sub 5}FeSi, {pi}-Al{sub 8}FeMg{sub 3}Si{sub 6}, and a low melting quaternary eutectic involving Mg{sub 2}Si, {pi}, and Si. Also, variation of the cooling conditions in castings revealed the existence of a critical cooling rate, above which the solidification path and microstructure undergo a major change. Cracking Model. Implementing the critical conditions for cracking into the Rappaz- Drezet-Gremaud (RDG) model revealed a pressure drop in the interdendritic liquid on the order of 10{sup -1} atm, originating primarily from straining conditions. Since, according to literature, a minimum of 1,760 atm is required to fracture pure aluminum liquid (theoretical), this demonstrates that cavitation as a liquid fracture mechanism is not likely to occur, even when accounting for dissolved hydrogen gas. Instead, a porosity-based crack initiation model has been developed based upon pore stability criteria, assuming that gas pores expand from pre-existing nuclei. Crack initiation is taken to occur when stable pores form within the coherent dendrite region, critical to crack initiation being weld metal hydrogen content. Following initiation, a mass-balance approach developed by Braccini

INEL studies concerning solidification of low-level waste in cement

International Nuclear Information System (INIS)

Mandler, J.W.

1989-01-01

The Idaho National Engineering Laboratory (INEL) has performed numerous studies addressing issues concerning the solidification of low-level radioactive waste in cement. These studies have been performed for both the Nuclear Regulatory Commission (NRC) and the Department of Energy (DOE). This short presentation will only outline the major topics addressed in some of these studies, present a few conclusions, and identify some of the technical concerns we have. More details of the work and pertinent results will be given in the Working Group sessions. The topics that have been addressed at the INEL which are relevant to this Workshop include (1) solidification of ion-exchange resins and evaporator waste in cement at commercial nuclear power plants, (2) leachability and compressive strength of power plant waste solidified in cement, (3) suggested guidelines for preparation of a solid waste process control program (PCP), (4) cement solidification of EPICOR-II resin wastes, and (5) performance testing of cement-solidified EPICOR-II resin wastes

Equation-of-State Modeling of Phase Equilibria in Petroleum Fluids

DEFF Research Database (Denmark)

Jørgensen, Marianne

1996-01-01

The Soave-Redlich-Kwong (SRK) equation of state was used to investigate and develop several aspects of the modeling of natural petroleum fluids.A new method was presented for numerical evaluation of PVT experiments. This method was used in the estimation of binary interaction parameters. A comphr......The Soave-Redlich-Kwong (SRK) equation of state was used to investigate and develop several aspects of the modeling of natural petroleum fluids.A new method was presented for numerical evaluation of PVT experiments. This method was used in the estimation of binary interaction parameters....... A comphrensive study of pseudoization procedures is presented. It is concluded that the compared methods exhibit results of comparable accuracy, and that six to eight pseudocomponents are needed for optimal representation of petroleum fluids.Finally, it is investigated how well the EOS can represent the VLLE...

Performance analysis a of solar driven organic Rankine cycle using multi-component working fluids

DEFF Research Database (Denmark)

Baldasso, E.; Andreasen, J. G.; Modi, A.

2015-01-01

suitable control strategy and both the overall annual production and the average solar to electrical efficiency are estimated with an annual simulation. The results suggest that the introduction of binary working fluids enables to increase the solar system performance both in design and part-load operation....... cycle. The purpose of this paper is to optimize a low temperature organic Rankine cycle tailored for solar applications. The objective of the optimization is the maximization of the solar to electrical efficiency and the optimization parameters are the working fluid and the turbine inlet temperature...... and pressure. Both pure fluids and binary mixtures are considered as possible working fluids and thus one of the primary aims of the study is to evaluate whether the use of multi-component working fluids might lead to increased solar to electrical efficiencies. The considered configuration includes a solar...

Self-rewetting fluids with suspended carbon nanostructures.

Science.gov (United States)

Savino, R; Di Paola, R; Gattia, D Mirabile; Marazzi, R; Antisari, M Vittori

2011-10-01

Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary or multi-component heat transfer fluids with peculiar surface tension properties and in particular to "self-rewetting fluids," i.e., liquids with a surface tension increasing with temperature and concentration. Thermophysical properties like surface tension, wettability and thermal conductivity, at different temperatures, have been measured not only for binary mixtures, but also for a number of ternary aqueous solutions with relatively low freezing point and for nanoparticles suspensions (so called nanofluids). Some of them interestingly exhibit the same anomalous positive surface tension gradient with temperature as binary self-rewetting solutions. Since in the course of liquid/vapour phase change, self-rewetting fluids behaviour induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, several interesting applications may be envisaged, e.g., the development of advanced wickless heat pipes for utilization in reduced gravity environments. The present work is dedicated to the study of the thermophysical properties of nanofluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesised by an homemade apparatus with an AC arc discharge in open air. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

In situ observations of graphite formation during solidification of cast iron

DEFF Research Database (Denmark)

Bjerre, Mathias Karsten

solidification and growth continues throughout solid state cooling and the eutectoid transformation. Years of research have greatly improved the understanding of the basic mechanisms that control graphite growth as well as the ability to control graphite morphology during industrial production of cast components......, the solidification of cast iron is studied with focus on formation and growth of spheroidal graphite. To this end, an experiment is conducted at the Diamond Light Source synchrotron facility in Harwell, UK: Employing an environmental cell devel-oped at the Manchester X-ray Imaging Facility at the University...... state growth presented in the present thesis. From the analysis it is clear that the presented data is of an unprecedented quality and that it represents a solid basis for validation of future models. Solidification simulations of a ductile cast iron component highlights the importance of the nucleation...

Physicochemical characterization of solidification agents used and products formed with radioactive wastes at LWR nuclear power plants

International Nuclear Information System (INIS)

Kibbey, A.H.; Godbee, H.W.

1978-01-01

Solidification of evaporator concentrates, filter sludges, and spent ion exchange resins used in LWR streams is discussed. The introduction of solidification agents to immobilize these sludges and resins can increase the volume of these wastes by a factor of slightly over 1 to greater than 2, depending on the binder chosen. The agents and methods used or proposed for use in solidification of LWR power plant wastes are generally suitable for treating most of the other-than-high-level wastes generated throughout the entire fuel cycle. Among the solidification agents most commonly used or suggested for use are the inorganic cements and organic plastics, which are listed and compared. A summary of considerations important in choosing a solidification agent is presented tabularly

Interaction of Multiple Particles with a Solidification Front: From Compacted Particle Layer to Particle Trapping.

Science.gov (United States)

Saint-Michel, Brice; Georgelin, Marc; Deville, Sylvain; Pocheau, Alain

2017-06-13

The interaction of solidification fronts with objects such as particles, droplets, cells, or bubbles is a phenomenon with many natural and technological occurrences. For an object facing the front, it may yield various fates, from trapping to rejection, with large implications regarding the solidification pattern. However, whereas most situations involve multiple particles interacting with each other and the front, attention has focused almost exclusively on the interaction of a single, isolated object with the front. Here we address experimentally the interaction of multiple particles with a solidification front by performing solidification experiments of a monodisperse particle suspension in a Hele-Shaw cell with precise control of growth conditions and real-time visualization. We evidence the growth of a particle layer ahead of the front at a close-packing volume fraction, and we document its steady-state value at various solidification velocities. We then extend single-particle models to the situation of multiple particles by taking into account the additional force induced on an entering particle by viscous friction in the compacted particle layer. By a force balance model this provides an indirect measure of the repelling mean thermomolecular pressure over a particle entering the front. The presence of multiple particles is found to increase it following a reduction of the thickness of the thin liquid film that separates particles and front. We anticipate the findings reported here to provide a relevant basis to understand many complex solidification situations in geophysics, engineering, biology, or food engineering, where multiple objects interact with the front and control the resulting solidification patterns.

Interacting binaries

International Nuclear Information System (INIS)

Eggleton, P.P.; Pringle, J.E.

1985-01-01

This volume contains 15 review articles in the field of binary stars. The subjects reviewed span considerably, from the shortest period of interacting binaries to the longest, symbiotic stars. Also included are articles on Algols, X-ray binaries and Wolf-Rayet stars (single and binary). Contents: Preface. List of Participants. Activity of Contact Binary Systems. Wolf-Rayet Stars and Binarity. Symbiotic Stars. Massive X-ray Binaries. Stars that go Hump in the Night: The SU UMa Stars. Interacting Binaries - Summing Up

Cement solidification of spent ion exchange resins produced by the nuclear industry

International Nuclear Information System (INIS)

Jaouen, C.; Vigreux, B.

1988-01-01

Cement solidification technology has been applied to spent ion exchange resins for many years in countries throughout the world (at reactors, research centers and spent fuel reprocessing plants). Changing specifications for storage of radioactive waste have, however, confronted the operators of such facilities with a number of problems. Problems related both to the cement solidification process (water/cement/resin interactions and chemical interactions) and to its utilization (mixing, process control, variable feed composition, etc.) have often led waste producers to prefer other, polymer-based processes, which are very expensive and virtually incompatible with water. This paper discusses research on cement solidification of ion exchange resins since 1983 and the development of application technologies adapted to nuclear service conditions and stringent finished product quality requirements

Long-lived magnetism from solidification-driven convection on the pallasite parent body

DEFF Research Database (Denmark)

Bryson, James F.J.; Nichols, Claire I. O.; Herrero-Albillos, Julia

2015-01-01

of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed.We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measuredmagnetic field......Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, themolten metallic cores ofmany small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally...... characteristics and cooling rates. Solidification-driven convectionwas probably commonamong small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among...

Solidification of ion exchange resin wastes

International Nuclear Information System (INIS)

1982-08-01

Solidification media investigated included portland type I, portland type III and high alumina cements, a proprietary gypsum-based polymer modified cement, and a vinyl ester-styrene thermosetting plastic. Samples formulated with hydraulic cement were analyzed to investigate the effects of resin type, resin loading, waste-to-cement ratio, and water-to-cement ratio. The solidification of cation resin wastes with portland cement was characterized by excessive swelling and cracking of waste forms, both after curing and during immersion testing. Mixed bed resin waste formulations were limited by their cation component. Additives to improve the mechanical properties of portland cement-ion exchange resin waste forms were evaluated. High alumina cement formulations dislayed a resistance to deterioration of mechanical integrity during immersion testing, thus providing a significant advantage over portland cements for the solidification of resin wastes. Properties of cement-ion exchange resin waste forms were examined. An experiment was conducted to study the leachability of 137 Cs, 85 Sr, and 60 Co from resins modified in portland type III and high alumina cements. The cumulative 137 Cs fraction release was at least an order of magnitude greater than that of either 85 Sr or 60 Co. Release rates of 137 Cs in high alumina cement were greater than those in portland III cement by a factor of two.Compressive strength and leach testing were conducted for resin wastes solidified with polymer-modified gypsum based cement. 137 Cs, 85 Sr, and 60 Co fraction releases were about one, two and three orders of magnitude higher, respectively, than in equivalent portland type III cement formulations. As much as 28.6 wt % dry ion exchange resin was successfully solidified using vinyl ester-styrene compared with a maximum of 25 wt % in both portland and gypsum-based cement

Processing and solidification of Savannah River Plant high-level waste

International Nuclear Information System (INIS)

Kelley, J.A.

1981-01-01

The entire flowsheet for processing and solidification of Savannah River Plant (SRP) high-level wastes has been demonstrated. A new small-scale integrated pilot plant is operating with actual radioactive wastes, and large-scale equipment is being demonstrated with nonradioactive simulated wastes. Design of a full-scale waste solidification plant is in progress. Plant construction is expected to begin in 1983, and startup is anticipated in 1988. The plant will poduce about 500 cans of glass per year with each can containing about 1.5 tons of glass

Some techniques for the solidification of radioactive wastes in concrete

International Nuclear Information System (INIS)

Colombo, P.; Neilson, R. Jr.

1976-06-01

Some techniques for the solidification of radioactive wastes in concrete are discussed. The sources, storage, volume reduction, and solidification of liquid wastes at Brookhaven National Laboratory (BNL) using the cement-vermiculite process is described. Solid waste treatment, shipping containers, and off-site shipments of solid wastes at BNL are also considered. The properties of low-heat-generating, high-level wastes, simulating those in storage at the Savannah River Plant (SRP), solidified in concrete were determined. Polymer impregnation was found to further decrease the leachability and improve the durability of these concrete waste forms

Hot tearing susceptibility of binary Mg–Y alloy castings

International Nuclear Information System (INIS)

Wang, Zhi; Huang, Yuanding; Srinivasan, Amirthalingam; Liu, Zheng; Beckmann, Felix; Kainer, Karl Ulrich; Hort, Norbert

2013-01-01

Highlights: ► Quantitatively and qualitatively assessing hot tearing susceptibility for different alloys. ► Monitoring the hot tearing propagation process. ► Detecting the hot tearing initiation/onset temperature. ► Recording the stress and strain evolution during the casting solidification and the subsequent cooling. - Abstract: The influence of Y content on the hot tearing susceptibility (HTS) of binary Mg–Y alloys has been predicted using thermodynamic calculations based on Clyne and Davies model. The calculated results are compared with experimental results determined using a constrained rod casting (CRC) apparatus with a load cell and data acquisition system. Both thermodynamic calculations and experimental measurements indicate that the hot tearing susceptibility as a function of Y content follows the “λ” shape. The experimental results show that HTS first increases with increase in Y content, reaches the maximum at about 0.9 wt.%Y and then decreases with further increase the Y content. The maximum susceptibility observed in Mg–0.9 wt.%Y alloy is attributed to its coarsened columnar microstructure, large solidification range and small amount of eutectic at the time of hot tearing. The initiation of hot cracks is monitored during CRC experiments. It corresponds to a drop in load increment on the force curves. The critical solid fractions at which the hot cracks are initiated are in the range from 0.9 to 0.99. It is also found that it decreases with increasing the content of Y. The hot cracks propagate along the dendritic or grain boundaries through the interdendritic separation or tearing of interconnected dendrites. Some of the formed cracks are possible to be healed by the subsequent refilling of the remained liquids

Diffuse-Interface Methods in Fluid Mechanics

Science.gov (United States)

Anderson, D. M.; McFadden, G. B.; Wheeler, A. A.

1997-01-01

The authors review the development of diffuse-interface models of hydrodynamics and their application to a wide variety of interfacial phenomena. The authors discuss the issues involved in formulating diffuse-interface models for single-component and binary fluids. Recent applications and computations using these models are discussed in each case. Further, the authors address issues including sharp-interface analyses that relate these models to the classical free-boundary problem, related computational approaches to describe interfacial phenomena, and related approaches describing fully-miscible fluids.

The melting and solidification of nanowires

International Nuclear Information System (INIS)

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

2016-01-01

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

The melting and solidification of nanowires

Science.gov (United States)

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

2016-06-01

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

The melting and solidification of nanowires

Energy Technology Data Exchange (ETDEWEB)

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

2016-06-15

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

The True Ultracool Binary Fraction Using Spectral Binaries

Science.gov (United States)

Bardalez Gagliuffi, Daniella; Burgasser, Adam J.; Schmidt, Sarah J.; Gagné, Jonathan; Faherty, Jacqueline K.; Cruz, Kelle; Gelino, Chris

2018-01-01

Brown dwarfs bridge the gap between stars and giant planets. While the essential mechanisms governing their formation are not well constrained, binary statistics are a direct outcome of the formation process, and thus provide a means to test formation theories. Observational constraints on the brown dwarf binary fraction place it at 10 ‑ 20%, dominated by imaging studies (85% of systems) with the most common separation at 4 AU. This coincides with the resolution limit of state-of-the-art imaging techniques, suggesting that the binary fraction is underestimated. We have developed a separation-independent method to identify and characterize tightly-separated (dwarfs as spectral binaries by identifying traces of methane in the spectra of late-M and early-L dwarfs. Imaging follow-up of 17 spectral binaries yielded 3 (18%) resolved systems, corroborating the observed binary fraction, but 5 (29%) known binaries were missed, reinforcing the hypothesis that the short-separation systems are undercounted. In order to find the true binary fraction of brown dwarfs, we have compiled a volume-limited, spectroscopic sample of M7-L5 dwarfs and searched for T dwarf companions. In the 25 pc volume, 4 candidates were found, three of which are already confirmed, leading to a spectral binary fraction of 0.95 ± 0.50%, albeit for a specific combination of spectral types. To extract the true binary fraction and determine the biases of the spectral binary method, we have produced a binary population simulation based on different assumptions of the mass function, age distribution, evolutionary models and mass ratio distribution. Applying the correction fraction resulting from this method to the observed spectral binary fraction yields a true binary fraction of 27 ± 4%, which is roughly within 1σ of the binary fraction obtained from high resolution imaging studies, radial velocity and astrometric monitoring. This method can be extended to identify giant planet companions to young brown

Ternary equilibria in bismuth--indium--lead alloys

International Nuclear Information System (INIS)

Liao, K.C.; Johnson, D.L.; Nelson, R.C.

1975-01-01

The liquidus surface is characterized by three binary equilibria. One binary extends from the Pb--Bi peritectic to the Pb--In peritectic. The other two extend from In--Bi eutectics, merge at 50 at. percent Bi and 30 at. percent Pb, and end at the Bi--Pb eutectic. Based on analysis of ternary liquidus contours and vertical sections, it is suggested that solidification for high lead and very high indium alloys occurs from two-phase equilibria. Solidification from all other alloys occurs from three-phase equilibria. Four-phase solidification does not occur in this system

Refractive index and solubility control of para-cymene solutions for index-matched fluid-structure interaction studies

Science.gov (United States)

Fort, Charles; Fu, Christopher D.; Weichselbaum, Noah A.; Bardet, Philippe M.

2015-12-01

To deploy optical diagnostics such as particle image velocimetry or planar laser-induced fluorescence (PLIF) in complex geometries, it is beneficial to use index-matched facilities. A binary mixture of para-cymene and cinnamaldehyde provides a viable option for matching the refractive index of acrylic, a common material for scaled models and test sections. This fluid is particularly appropriate for large-scale facilities and when a low-density and low-viscosity fluid is sought, such as in fluid-structure interaction studies. This binary solution has relatively low kinematic viscosity and density; its use enables the experimentalist to select operating temperature and to increase fluorescence signal in PLIF experiments. Measurements of spectral and temperature dependence of refractive index, density, and kinematic viscosity are reported. The effect of the binary mixture on solubility control of Rhodamine 6G is also characterized.

Closed solutions to a differential-difference equation and an associated plate solidification problem.

Science.gov (United States)

Layeni, Olawanle P; Akinola, Adegbola P; Johnson, Jesse V

2016-01-01

Two distinct and novel formalisms for deriving exact closed solutions of a class of variable-coefficient differential-difference equations arising from a plate solidification problem are introduced. Thereupon, exact closed traveling wave and similarity solutions to the plate solidification problem are obtained for some special cases of time-varying plate surface temperature.

NPP radioactive waste processing and solidification

International Nuclear Information System (INIS)

Nikiforov, A.S.; Polyakov, A.S.; Zakharova, K.P.

1983-01-01

The problems of proce-sing NPP intermediate level- and low-level liquid radioactive wastes (LRW) are considered. Various methods are compared of LWR solidification on the base of bituminization, cement grouting and inclusion into synthetic resins. It is concluded that the considered methods ensure radioactive radionuclides effluents into open hydronetwork at the level below the sanitary, standards

ENGINEERING BULLETIN: SOLIDIFICATION/STABILIZATION OF ORGANICS AND INORGANICS

Science.gov (United States)

Solidification refers to techniques that encapsulate hazardous waste into a solid material of high structural integrity. Encapsulation involves either fine waste particles (microencapsulation) or a large block or container of wastes (macroencapsulation). Stabilization refe...

Positive segregation as a function of buoyancy force during steel ingot solidification

International Nuclear Information System (INIS)

Radovic, Zarko; Jaukovic, Nada; Lalovic, Milisav; Tadic, Nebojsa

2008-01-01

We analyze theoretically and experimentally solute redistribution in the dendritic solidification process and positive segregation during solidification of steel ingots. Positive segregation is mainly caused by liquid flow in the mushy zone. Changes in the liquid steel velocity are caused by the temperature gradient and by the increase in the solid fraction during solidification. The effects of buoyancy and of the change in the solid fraction on segregation intensity are analyzed. The relationships between the density change, liquid fraction and the steel composition are considered. Such elements as W, Ni, Mo and Cr decrease the effect of the density variations, i.e. they show smaller tendency to segregate. Based on the modeling and experimental results, coefficients are provided controlling the effects of chemical composition, secondary dendrite arm spacing and the solid fraction.

Solidification and performance of cement doped with phenol

International Nuclear Information System (INIS)

Vipulanandan, C.; Krishnan, S.

1991-01-01

Treating mixed hazardous wastes using the solidification/stabilization technology is becoming a critical element in waste management planning. The effect of phenol, a primary constituent in many hazardous wastes, on the setting and solidification process of Type I Portland cement was evaluated. The leachability of phenol from solidified cement matrix (TCLP test) and changes in mechanical properties were studied after curing times up to 28 days. The changes in cement hydration products due to phenol were studied using the X-ray diffraction (XRD) powder technique. Results show that phenol interferes with initial cement hydration by reducing the formation of calcium hydroxide and also reduces the compressive strength of cement. A simple model has been proposed to quantify the phenol leached from the cement matrix during the leachate test

Continuous Solidification of Immiscible Alloys and Microstructure Control

Science.gov (United States)

Jiang, Hongxiang; Zhao, Jiuzhou

2018-05-01

Immiscible alloys have aroused considerable interest in last few decades due to their excellent physical and mechanical characteristics as well as potential industrial applications. Up to date, plenty of researches have been carried out to investigate the solidification of immiscible alloys on the ground or in space and great progress has been made. It is demonstrated that the continuous solidification technique have great future in the manufacturing of immiscible alloys, it also indicates that the addition of surface active micro-alloying or inoculants for the nucleation of the minority phase droplets and proper application of external fields, e.g., static magnetic field, electric current, microgravity field, etc. may promote the formation of immiscible alloys with an expected microstructure. The objective of this article is to review the research work in this field.

Metastable and unstable cellular solidification of colloidal suspensions

Science.gov (United States)

Deville, Sylvain; Maire, Eric; Bernard-Granger, Guillaume; Lasalle, Audrey; Bogner, Agnès; Gauthier, Catherine; Leloup, Jérôme; Guizard, Christian

2009-12-01

Colloidal particles are often seen as big atoms that can be directly observed in real space. They are therefore becoming increasingly important as model systems to study processes of interest in condensed-matter physics such as melting, freezing and glass transitions. The solidification of colloidal suspensions has long been a puzzling phenomenon with many unexplained features. Here, we demonstrate and rationalize the existence of instability and metastability domains in cellular solidification of colloidal suspensions, by direct in situ high-resolution X-ray radiography and tomography observations. We explain such interface instabilities by a partial Brownian diffusion of the particles leading to constitutional supercooling situations. Processing under unstable conditions leads to localized and global kinetic instabilities of the solid/liquid interface, affecting the crystal morphology and particle redistribution behaviour.

Effect of Chemical Composition on Susceptibility to Weld Solidification Cracking in Austenitic Weld Metal

Science.gov (United States)

Kadoi, Kota; Shinozaki, Kenji

2017-12-01

The influence of the chemical composition, especially the niobium content, chromium equivalent Creq, and nickel equivalent Nieq, on the weld solidification cracking susceptibility in the austenite single-phase region in the Schaeffler diagram was investigated. Specimens were fabricated using the hot-wire laser welding process with widely different compositions of Creq, Nieq, and niobium in the region. The distributions of the susceptibility, such as the crack length and brittle temperature range (BTR), in the Schaeffler diagram revealed a region with high susceptibility to solidification cracking. Addition of niobium enhanced the susceptibility and changed the distribution of the susceptibility in the diagram. The BTR distribution was in good agreement with the distribution of the temperature range of solidification (Δ T) calculated by solidification simulation based on Scheil model. Δ T increased with increasing content of alloying elements such as niobium. The distribution of Δ T was dependent on the type of alloying element owing to the change of the partitioning behavior. Thus, the solidification cracking susceptibility in the austenite single-phase region depends on whether the alloy contains elements. The distribution of the susceptibility in the region is controlled by the change in Δ T and the segregation behavior of niobium with the chemical composition.

Particle Trapping and Banding in Rapid Colloidal Solidification

KAUST Repository

Elliott, J. A. W.; Peppin, S. S. L.

2011-01-01

We derive an expression for the nonequilibrium segregation coefficient of colloidal particles near a moving solid-liquid interface. The resulting kinetic phase diagram has applications for the rapid solidification of clay soils, gels, and related

Formation of Nitrogen Bubbles During Solidification of Duplex Stainless Steels

Science.gov (United States)

Dai, Kaiju; Wang, Bo; Xue, Fei; Liu, Shanshan; Huang, Junkai; Zhang, Jieyu

2018-04-01

The nucleation and growth of nitrogen bubbles for duplex stainless steels are of great significance for the formation mechanism of bubbles during solidification. In the current study, numerical method and theoretical analysis of formula derivation were used to study the formation of nitrogen bubbles during solidification. The critical sizes of the bubble for homogeneous nucleation and heterogeneous nucleation at the solid-liquid interface during solidification were derived theoretically by the classical nucleation theory. The results show that the calculated values for the solubility of nitrogen in duplex stainless steel are in good agreement with the experimental values which are quoted by references: for example, when the temperature T = 1823 K and the nitrogen partial pressure P_{{N2 }} = 40P^{Θ} , the calculated value (0.8042 wt pct) for the solubility of Fe-12Cr alloy nitrogen in molten steel is close to the experimental value (0.780 wt pct). Moreover, the critical radii for homogeneous nucleation and heterogeneous nucleation are identical during solidification. On the one hand, with the increasing temperature or the melt depth, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. On the other hand, with the decreasing initial content of nitrogen or the cooling rate, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. Furthermore, when the melt depth is greater than the critical depth, which is determined by the technological conditions, the change in the Gibbs free energy for the nucleation is not conducive enough to form new bubbles.

Solidification of liquid concentrate and solid waste generated as by-products of the liquid radwaste treatment systems in light-water reactors

International Nuclear Information System (INIS)

Neilson, R.M. Jr.; Colombo, P.

1977-01-01

The treatment of liquid concentrate and solid waste produced in light-water reactors as by-products of liquid radwaste treatment systems consists of five basic operations: waste collection, waste pretreatment, solidification agent handling, mixing/packaging (solidification) and waste package handling. This paper will concern itself primarily with the solidification operation, however, the other operations enumerated as well as the types of wastes treated and their origins will be briefly described, especially with regards to their effects on solidification. During solidification, liquid concentrate and solid wastes are incorporated with a solidification agent to form a monolithic, free-standing solid. The basic solidification agent types either currently used in the United States or proposed for use include absorbants, hydraulic cement, urea-formaldehyde, other polymer systems, and bitumen. The operation, formulations and limitations of these agents as used for radwaste solidification will be discussed. Properties relevant to the evaluation of solidified waste forms will be identified and relative comparisons made for wastes solidified by various processes

Learning to assign binary weights to binary descriptor

Science.gov (United States)

Huang, Zhoudi; Wei, Zhenzhong; Zhang, Guangjun

2016-10-01

Constructing robust binary local feature descriptors are receiving increasing interest due to their binary nature, which can enable fast processing while requiring significantly less memory than their floating-point competitors. To bridge the performance gap between the binary and floating-point descriptors without increasing the computational cost of computing and matching, optimal binary weights are learning to assign to binary descriptor for considering each bit might contribute differently to the distinctiveness and robustness. Technically, a large-scale regularized optimization method is applied to learn float weights for each bit of the binary descriptor. Furthermore, binary approximation for the float weights is performed by utilizing an efficient alternatively greedy strategy, which can significantly improve the discriminative power while preserve fast matching advantage. Extensive experimental results on two challenging datasets (Brown dataset and Oxford dataset) demonstrate the effectiveness and efficiency of the proposed method.

Micromechanical modeling of stress-induced strain in polycrystalline Ni–Mn–Ga by directional solidification

International Nuclear Information System (INIS)

Zhu, Yuping; Shi, Tao; Teng, Yao

2015-01-01

Highlights: • A micromechanical model of directional solidification Ni–Mn–Ga is developed. • The stress–strain curves in different directions are tested. • The martensite Young’s moduli in different directions are predicted. • The macro reorientation strains in different directions are investigated. - Abstract: Polycrystalline ferromagnetic shape memory alloy Ni–Mn–Ga produced by directional solidification possess unique properties. Its compressive stress–strain behaviors in loading–unloading cycle show nonlinear and anisotropic. Based on the self-consistent theory and thermodynamics principle, a micromechanical constitutive model of polycrystalline Ni–Mn–Ga by directional solidification is developed considering the generating mechanism of the macroscopic strain and anisotropy. Then, the stress induced strains at different angles to solidification direction are calculated, and the results agree well with the experimental data. The predictive curves of martensite Young’s modulus and macro reorientation strain in different directions are investigated. It may provide theoretical guidance for the design and use of ferromagnetic shape memory alloy

Nonlinear hydrodynamic stability and transition; Proceedings of the IUTAM Symposium, Nice, France, Sept. 3-7, 1990

Science.gov (United States)

Theoretical and experimental research on nonlinear hydrodynamic stability and transition is presented. Bifurcations, amplitude equations, pattern in experiments, and shear flows are considered. Particular attention is given to bifurcations of plane viscous fluid flow and transition to turbulence, chaotic traveling wave covection, chaotic behavior of parametrically excited surface waves in square geometry, amplitude analysis of the Swift-Hohenberg equation, traveling wave convection in finite containers, focus instability in axisymmetric Rayleigh-Benard convection, scaling and pattern formation in flowing sand, dynamical behavior of instabilities in spherical gap flows, and nonlinear short-wavelength Taylor vortices. Also discussed are stability of a flow past a two-dimensional grid, inertia wave breakdown in a precessing fluid, flow-induced instabilities in directional solidification, structure and dynamical properties of convection in binary fluid mixtures, and instability competition for convecting superfluid mixtures.

Current high-level waste solidification technology

International Nuclear Information System (INIS)

Bonner, W.F.; Ross, W.A.

1976-01-01

Technology has been developed in the U.S. and abroad for solidification of high-level waste from nuclear power production. Several processes have been demonstrated with actual radioactive waste and are now being prepared for use in the commercial nuclear industry. Conversion of the waste to a glass form is favored because of its high degree of nondispersibility and safety

Simulation of Microstructure during Laser Rapid Forming Solidification Based on Cellular Automaton

Directory of Open Access Journals (Sweden)

Zhi-jian Wang

2014-01-01

Full Text Available The grain microstructure of molten pool during the solidification of TC4 titanium alloy in the single point laser cladding was investigated based on the CAFE model which is the cellular automaton (CA coupled with the finite element (FE method. The correct temperature field is the prerequisite for simulating the grain microstructure during the solidification of the molten pool. The model solves the energy equation by the FE method to simulate the temperature distribution in the molten pool of the single point laser cladding. Based on the temperature field, the solidification microstructure of the molten pool is also simulated with the CAFE method. The results show that the maximum temperature in the molten pool increases with the laser power and the scanning rate. The laser power has a larger influence on the temperature distribution of the molten pool than the scanning rate. During the solidification of the molten pool, the heat at the bottom of the molten pool transfers faster than that at the top of the molten pool. The grains rapidly grow into the molten pool, and then the columnar crystals are formed. This study has a very important significance for improving the quality of the structure parts manufactured through the laser cladding forming.

Experimental and Theoretical Investigations of the Solidification of Eutectic Al-Si Alloy

Science.gov (United States)

Sen, S.; Catalina, A. V.; Rose, M. Franklin (Technical Monitor)

2001-01-01

The eutectic alloys have a wide spectrum of applications due to their good castability and physical and mechanical properties. The interphase spacing resulting during solidification is an important microstructural feature that significantly influences the mechanical behavior of the material. Thus, knowledge of the evolution of the interphase spacing during solidification is necessary in order to properly design the solidification process and optimize the material properties. While the growth of regular eutectics is rather well understood, the irregular eutectics such as Al-Si or Fe-graphite exhibit undercoolings and lamellar spacings much larger than those theoretically predicted. Despite of a considerable amount of experimental and theoretical work a clear understanding of the true mechanism underlying the spacing selection in irregular eutectics is yet to be achieved. A new experimental study of the solidification of the eutectic Al-Si alloy will be reported in this paper. The measured interface undercoolings and lamellar spacing will be compared to those found in the literature in order to get more general information regarding the growth mechanism of irregular eutectics. A modification of the present theory of the eutectic growth is also proposed. The results of the modified mathematical model, accounting for a non-isothermal solid/liquid interface, will be compared to the experimental measurements.

Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

Science.gov (United States)

Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

2013-10-01

We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

Binary Linear-Time Erasure Decoding for Non-Binary LDPC codes

OpenAIRE

Savin, Valentin

2009-01-01

In this paper, we first introduce the extended binary representation of non-binary codes, which corresponds to a covering graph of the bipartite graph associated with the non-binary code. Then we show that non-binary codewords correspond to binary codewords of the extended representation that further satisfy some simplex-constraint: that is, bits lying over the same symbol-node of the non-binary graph must form a codeword of a simplex code. Applied to the binary erasure channel, this descript...

Mobile concrete solidification systems for power reactor waste

International Nuclear Information System (INIS)

Tchemitcheff, E.; Bordas, Y.

1990-01-01

In late 1988 SGN received an order from Electricite de France (EDF) for the construction of a mobile concrete solidification system to process secondary system resins generated by the P'4 and N4 series PWR power plants in France. This order was placed in view of SGN's experience with low- and medium-level radioactive waste treatment and conditioning over a period of almost 20 years. In addition to the construction of fixed waste processing facilities using more conventional technologies, SGN has been involved in application of the mobile system concept to the bituminization process in the United States, which led to the construction and commissioning of two transportable systems in collaboration with its American licensee US Ecology. It has also conducted large-scale R ampersand D on LLW/MLW concrete solidification, particularly for ion exchange resins. 5 figs

Solidification processing of high-Tc superconductors

CERN Document Server

Shiohara, Y; Nakamura, Y; Izumi, T

2001-01-01

Recent progress in the solidification processing of RE-system (RE:Y, Sm, Nd etc.) oxide superconducting materials is reviewed. The superconducting YBa/sub 2/Cu/sub 3/O/sub y/(Y123) phase is solidified from Y/sub 2/BaCuO/sub 5/(Y211) and liquid phases, by a peritectic reaction. The solidified micro and macro structure can not be explained by the peritectic reaction with diffusion in the solid but rather by diffusion in the liquid. A solidification model for this reaction is developed. It is confirmed that the prediction from the model calculation is in good agreement with the experimental results. Furthermore, the basic idea is expanded to develop a novel single crystal pulling process. Y211 powders were placed at the bottom of the crucible as the solute source for the growth and a BaO-CuO composite (Ba to Cu cation ratio was 3 to 5) was placed on the layer of Y211 powders. Temperature gradient was provided in the melt. Large bulk single crystals were obtained by this technique, and the growth mechanism was al...

Evaluation of process alternatives for solidification of the West Valley high-level liquid wastes

International Nuclear Information System (INIS)

Holton, L.K.; Larson, D.E.

1982-01-01

The Department of Energy (DOE) established the West Valley Solidification Project (WVSP) in 1980. The project purpose is to demonstrate removal and solidification of the high-level liquid wastes (HLLW) presently stored in tanks at the Western New York Nuclear Service Center (WNYNSC), West Valley, New York. As part of this effort, the Pacific Northwest Laboratory (PNL) conducted a study to evaluate process alternatives for solidifcation of the WNYNSC wastes. Two process approaches for waste handling before solidification, together with solidification processes for four terminal and four interim waste forms, were considered. The first waste-handling approach, designated the salt/sludge separation process, involves separating the bulk of the nonradioactive nuclear waste constituents from the radioactive waste constituents, and the second waste-handling approach, designated the combined-waste process, involves no waste segregation prior to solidification. The processes were evaluated on the bases of their (1) readiness for plant startup by 1987, (2) relative technical merits, and (3) process cost. The study has shown that, based on these criteria, the salt/sludge separation process with a borosilicate glass waste form is preferred when producing a terminal waste form. It was also concluded that if an interim waste form is to be used, the preferred approach would be the combined waste process with a fused-salt waste form

Binary effectivity rules

DEFF Research Database (Denmark)

Keiding, Hans; Peleg, Bezalel

2006-01-01

is binary if it is rationalized by an acyclic binary relation. The foregoing result motivates our definition of a binary effectivity rule as the effectivity rule of some binary SCR. A binary SCR is regular if it satisfies unanimity, monotonicity, and independence of infeasible alternatives. A binary...

Oxygen and carbon transfer during solidification of semiconductor grade silicon in different processes

Science.gov (United States)

Ribeyron, P. J.; Durand, F.

2000-03-01

A model is established for comparing the solute distribution resulting from four solidification processes currently applied to semiconductor grade silicon: Czochralski pulling (CZ), floating zone (FZ), 1D solidification and electromagnetic continuous pulling (EMCP). This model takes into account solid-liquid interface exchange, evaporation to or contamination by the gas phase, container dissolution, during steady-state solidification, and in the preliminary preparation of the melt. For simplicity, the transfers are treated in the crude approximation of perfectly mixed liquid and boundary layers. As a consequence, only the axial ( z) distribution can be represented. Published data on oxygen and carbon transfer give a set of acceptable values for the thickness of the boundary layers. In the FZ and EMCP processes, oxygen evaporation can change the asymptotic behaviour of the reference Pfann law. In CZ and in 1D-solidification, a large variety of solute profile curves can be obtained, because they are very sensitive to the balance between crucible dissolution and evaporation. The CZ process clearly brings supplementary degrees of freedom via the geometry of the crucible, important for the dissolution phenomena, and via the rotation rate of the crystal and of the crucible, important for acting on transfer kinetics.

Solidification method for organic solution and processing method of aqueous solution

International Nuclear Information System (INIS)

Kamoshida, Mamoru; Fukazawa, Tetsuo; Yazawa, Noriko; Hasegawa, Toshihiko

1998-01-01

The relative dielectric constant of an organic solution containing polar ingredients is controlled to 13 or less to enable its solidification. The polarity of the organic solution can be evaluated quantitatively by using the relative dielectric constant. If the relative dielectric constant is high, it can be controlled by dilution using a non-polar organic solvent of low relative dielectric constant. With such procedures, solidification can be conducted by using an economical 12-hydroxy stearic acid, process of liquid wastes can be facilitated and the safety can be ensured. (T.M.)

Improved cement solidification of low and intermediate level radioactive wastes

International Nuclear Information System (INIS)

1993-01-01

Cementation was the first and is still the most widely applied technique for the conditioning of low and intermediate level radioactive wastes. Compared with other solidification techniques, cementation is relatively simple and inexpensive. However, the quality of the final cemented waste forms depends very much on the composition of the waste and the type of cement used. Different kinds of cement are used for different kinds of waste and the compatibility of a specific waste with a specific cement type should always be carefully evaluated. Cementation technology is continuously being developed in order to improve the characteristics of cemented waste in accordance with the increasing requirements for quality of the final solidified waste. Various kinds of additives and chemicals are used to improve the cemented waste forms in order to meet all safety requirements. This report is meant mainly for engineers and designers, to provide an explanation of the chemistry of cementation systems and to facilitate the choice of solidification agents and processing equipment. It reviews recent developments in cementation technology for improving the quality of cemented waste forms and provides a brief description of the various cement solidification processes in use. Refs, figs and tabs

Effect of alloying elements on solidification of primary austenite in Ni-Mn-Cu cast iron

Directory of Open Access Journals (Sweden)

A. Janus

2011-04-01

Full Text Available Within the research, determined were direction and intensity of alloying elements influence on solidification way (directional orvolumetric of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu. 50 cast shafts dia. 20 mm were analysed.Chemical composition of the alloy was as follows: 1.7 to 3.3 % C, 1.4 to 3.1 % Si, 2.8 to 9.9 % Ni, 0.4 to 7.7 % Mn, 0 to 4.6 % Cu, 0.14 to0.16 % P and 0.03 to 0.04 % S. The discriminant analysis revealed that carbon influences solidification of primary austenite dendrites most intensively. It clearly increases the tendency to volumetric solidification. Influence of the other elements is much weaker. This means that the solidification way of primary austenite dendrites in hypoeutectic austenitic cast iron Ni-Mn-Cu does not differ from that in an unalloyed cast iron.

Solidification of ion exchange resin wastes in hydraulic cement

International Nuclear Information System (INIS)

Neilson, R.M. Jr.; Kalb, P.; Fuhrmann, M.; Colombo, P.

1982-01-01

Work has been conducted to investigate the solidification of ion exchange resin wastes with portland cements. These efforts have been directed toward the development of acceptable formulations for the solidification of ion exchange resin wastes and the characterization of the resultant waste forms. This paper describes formulation development work and defines acceptable formulations in terms of ternary phase compositional diagrams. The effects of cement type, resin type, resin loading, waste/cement ratio and water/cement ratio are described. The leachability of unsolidified and solidified resin waste forms and its relationship to full-scale waste form behavior is discussed. Gamma irradiation was found to improve waste form integrity, apparently as a result of increased resin crosslinking. Modifications to improve waste form integrity are described. 3 tables

On the Lyapunov stability of a plane parallel convective flow of a binary mixture

Directory of Open Access Journals (Sweden)

Giuseppe Mulone

1991-05-01

Full Text Available The nonlinear stability of plane parallel convective flows of a binary fluid mixture in the Oberbeck-Boussinesq scheme is studied in the stress-free boundary case. Nonlinear stability conditions independent of Reynolds number are proved.

High-potential Working Fluids for Next Generation Binary Cycle Geothermal Power Plants

Energy Technology Data Exchange (ETDEWEB)

Zia, Jalal [GE Global Research; Sevincer, Edip; Chen, Huijuan; Hardy, Ajilli; Wickersham, Paul; Kalra, Chiranjeev; Laursen, Anna Lis; Vandeputte, Thomas

2013-06-29

A thermo-economic model has been built and validated for prediction of project economics of Enhanced Geothermal Projects. The thermo-economic model calculates and iteratively optimizes the LCOE (levelized cost of electricity) for a prospective EGS (Enhanced Geothermal) site. It takes into account the local subsurface temperature gradient, the cost of drilling and reservoir creation, stimulation and power plant configuration. It calculates and optimizes the power plant configuration vs. well depth. Thus outputs from the model include optimal well depth and power plant configuration for the lowest LCOE. The main focus of this final report was to experimentally validate the thermodynamic properties that formed the basis of the thermo-economic model built in Phase 2, and thus build confidence that the predictions of the model could be used reliably for process downselection and preliminary design at a given set of geothermal (and/or waste heat) boundary conditions. The fluid and cycle downselected was based on a new proprietary fluid from a vendor in a supercritical ORC cycle at a resource condition of 200°C inlet temperature. The team devised and executed a series of experiments to prove the suitability of the new fluid in realistic ORC cycle conditions. Furthermore, the team performed a preliminary design study for a MW-scale turbo expander that would be used for a supercritical ORC cycle with this new fluid. The following summarizes the main findings in the investigative campaign that was undertaken: 1. Chemical compatibility of the new fluid with common seal/gasket/Oring materials was found to be problematic. Neoprene, Viton, and silicone materials were found to be incompatible, suffering chemical decomposition, swelling and/or compression set issues. Of the materials tested, only TEFLON was found to be compatible under actual ORC temperature and pressure conditions. 2. Thermal stability of the new fluid at 200°C and 40 bar was found to be acceptable after 399

Development of high-level waste solidification technology 1

Energy Technology Data Exchange (ETDEWEB)

Kim, Joon Hyung; Kim, Hwan Young; Kim, In Tae [and others

1999-02-01

Spent nuclear fuel contains useful nuclides as valuable resource materials for energy, heat and catalyst. High-level wastes (HLW) are expected to be generated from the R and D activities and reuse processes. It is necessary to develop vitrification or advanced solidification technologies for the safe long-term management of high level wastes. As a first step to establish HLW vitrification technology, characterization of HLWs that would arise at KAERI site, glass melting experiments with a lab-scale high frequency induction melter, and fabrication and property evaluation of base-glass made of used HEPA filter media and additives were performed. Basic study on the fabrication and characterization of candidate ceramic waste form (Synroc) was also carried out. These HLW solidification technologies would be directly useful for carrying out the R and Ds on the nuclear fuel cycle and waste management. (author). 70 refs., 29 tabs., 35 figs.

Cross-Permeability of the Semisolid Region in Directional Solidification: A Combined Phase-Field and Lattice-Boltzmann Simulation Approach

Science.gov (United States)

Böttger, B.; Haberstroh, C.; Giesselmann, N.

2016-01-01

Based on the results of microstructure simulations, fluid flow through the semisolid region during directional solidification of the technical Ni-base alloy 718 has been studied. Three-dimensional microstructures at different positions in the semisolid region were obtained by using a multicomponent multiphase-field model that was online coupled to a commercial thermodynamic database. For the range of five different primary dendrite distances λ 1 between 50 µm and 250 µm, the flow velocity and the permeability perpendicular to the dendrite growth direction was evaluated by using a proprietary Lattice-Boltzmann model. The commercial CFD software ANSYS FLUENT was alternatively applied for reference. Consistent values of the average flow velocity along the dendrites were obtained for both methods. From the results of the fluid flow simulations, the cross-permeability was evaluated as a function of temperature and fraction liquid for each of the five different primary dendrite distances λ 1. The obtained permeability values can be approximated by a single analytical function of the fraction liquid and λ 1 and are discussed and compared with known relations from the literature.

Retrofit of existing Dow solidification system at quad cities nuclear station

International Nuclear Information System (INIS)

Dekitis, L.; Jarvis, N.; Petri, R.; Testa, J.

1983-01-01

Over the past year ATCOR has been involved in the design, testing and supply of an In-container Mixing System Retrofit for Commonwealth Edison's Quad Cities Nuclear Station Solidification System. The system supplied by DOW, itself a retrofit of a urea formaldehyde system, was based upon use of 50 cubic foot containers (liners). ATCOR's retrofit increased liner capacity to 170 cubic feet and allowed in-cask solidification of highly radioactive material. This paper discusses the reasons for the decision to replace equipment within the originally furnished system and the development of the ATCOR plan to proof-test this equipment prior to delivery at the site. Results of this pre-testing, and a comparison between pre-tested conditions and the actual in-plan start-up tests are presented. Development of improved instrumentation and mechanical modifications which enhance the reliability of the ATCOR/DOW process In-container Mixing System was provided as a part of this project. Test results are presented on instruments, controls and the unique method of mechanical attachment of the Mixing Head to the solidification container

Raft River binary-cycle geothermal pilot power plant final report

Energy Technology Data Exchange (ETDEWEB)

Bliem, C.J.; Walrath, L.F.

1983-04-01

The design and performance of a 5-MW(e) binary-cycle pilot power plant that used a moderate-temperature hydrothermal resource, with isobutane as a working fluid, are examined. Operating problems experienced and solutions found are discussed and recommendations are made for improvements to future power plant designs. The plant and individual systems are analyzed for design specification versus actual performance figures.

Macrosegregation and Grain Formation Caused by Convection Associated with Directional Solidification Through Cross-Section Increase

Science.gov (United States)

Ghods, Masoud; Lauer, Mark; Tewari, Surendra; Poirier, David; Grugel, Richard

2016-01-01

Cylindrical Al-7 wt% Silicon, Al-19 wt% Copper and Lead-6 wt% Antimony alloy samples were directionally solidified (DS) with liquid above, solid below, and gravity pointing down, in graphite crucibles having an abrupt cross-sectional increase. These alloys have similar solidification shrinkage but are expected to have different degrees of thermosolutal convection during solidification. Microstructures in the DS samples in the vicinity of the section change have been studied in order to examine the effect of convection associated with the combined influence of thermosolutal effects and solidification shrinkage. Extensive radial and axial macrosegregation associated with cross-section change is observed. It also appears that steepling and local primary alpha-phase remelting resulting from convection are responsible for stray grain formation at the reentrant corners. Preliminary results from a numerical model, which includes solidification shrinkage and thermosolutal convection in the mushy zone, indicate that these regions are prone to solutal remelting of dendrites.

Binary pulsars as probes of a Galactic dark matter disk

Science.gov (United States)

Caputo, Andrea; Zavala, Jesús; Blas, Diego

2018-03-01

As a binary pulsar moves through a wind of dark matter particles, the resulting dynamical friction modifies the binary's orbit. We study this effect for the double disk dark matter (DDDM) scenario, where a fraction of the dark matter is dissipative and settles into a thin disk. For binaries within the dark disk, this effect is enhanced due to the higher dark matter density and lower velocity dispersion of the dark disk, and due to its co-rotation with the baryonic disk. We estimate the effect and compare it with observations for two different limits in the Knudsen number (Kn). First, in the case where DDDM is effectively collisionless within the characteristic scale of the binary (Kn ≫ 1) and ignoring the possible interaction between the pair of dark matter wakes. Second, in the fully collisional case (Kn ≪ 1), where a fluid description can be adopted and the interaction of the pair of wakes is taken into account. We find that the change in the orbital period is of the same order of magnitude in both limits. A comparison with observations reveals good prospects to probe currently allowed DDDM models with timing data from binary pulsars in the near future. We finally comment on the possibility of extending the analysis to the intermediate (rarefied gas) case with Kn ∼ 1.

Tailored Working Fluids for Enhanced Binary Geothermal Power Plants

Energy Technology Data Exchange (ETDEWEB)

Mahmoud, Ahmad [United Technologies Research Center, East Hartford, CT (United States)

2013-01-29

United Technologies Research Center (UTRC), in collaboration with the Georgia Institute of Technology and the National Institute of Standards and Technology will evaluate and develop fundamental and component level models, conduct experiments and generate data to support the use of mixed or enhanced working fluids for geothermal power generation applications.

Mathematics applied to fluid mechanics and stability; Proceedings of the Conference, Rensselaer Polytechnic Institute, Troy, NY, Sept. 9-11, 1985

International Nuclear Information System (INIS)

Drew, D.A.; Flaherty, J.E.

1986-01-01

The mathematical analysis of fluid mechanics and stability and its applications in science and engineering are examined in reviews and reports. Topics addressed include Taylor-vortex flow, isothermal fluid-film lubrication theories, the morphology of spiral galaxies, rotating-fluid problems in ballistics, coupled Lorenz oscillators, the connection between chaos and turbulence, plane-front alloy solidification versus free-surface Benard convection, and the nonlinear stability of spiral flow between rotating cylinders with a small gap. Consideration is given to resonance conditions for forced two-dimensional channel flows, the secondary bifurcation of standing surface waves in rectangular basins, instability in the flow of granular materials, and the supercritical dynamics of baroclinic disturbances

Solidification of radioactive wastes with inorganic binders (literature survey)

International Nuclear Information System (INIS)

Rudolph, G.; Koester, R.

A survey is provided on solidification of radioactive waste solutions, sludges and tritium waste water through cement and other inorganic binders. A general survey of the possibilities described in the literature is followed by a somewhat more detailed description of the work carried on at four research establishments in the United States, Oak Ridge National Laboratory, Savannah River Laboratory, Brookhaven National Laboratory, and Atlantic Richfield Hanford Company, supplemented by personal information. Additional sections describe the experiences with various types of cement and the possibilities for improvement of solidification products through preliminary fixation of the toxic nuclides (transformation into insoluble products or absorption); there is a further possibility of post-treatment through polymer impregnation. Finally, definition and determination of leachability are provided and some results compiled. 74 references, 7 figures, 5 tables

Formulating food protein-stabilized indomethacin nanosuspensions into pellets by fluid-bed coating technology: physical characterization, redispersibility, and dissolution.

Science.gov (United States)

He, Wei; Lu, Yi; Qi, Jianping; Chen, Lingyun; Yin, Lifang; Wu, Wei

2013-01-01

Drug nanosuspensions are very promising for enhancing the dissolution and bioavailability of drugs that are poorly soluble in water. However, the poor stability of nanosuspensions, reflected in particle growth, aggregation/agglomeration, and change in crystallinity state greatly limits their applications. Solidification of nanosuspensions is an ideal strategy for addressing this problem. Hence, the present work aimed to convert drug nanosuspensions into pellets using fluid-bed coating technology. Indomethacin nanosuspensions were prepared by the precipitation-ultrasonication method using food proteins (soybean protein isolate, whey protein isolate, β-lactoglobulin) as stabilizers. Dried nanosuspensions were prepared by coating the nanosuspensions onto pellets. The redispersibility, drug dissolution, solid-state forms, and morphology of the dried nanosuspensions were evaluated. The mean particle size for the nanosuspensions stabilized using soybean protein isolate, whey protein isolate, and β-lactoglobulin was 588 nm, 320 nm, and 243 nm, respectively. The nanosuspensions could be successfully layered onto pellets with high coating efficiency. Both the dried nanosuspensions and nanosuspensions in their original amorphous state and not influenced by the fluid-bed coating drying process could be redispersed in water, maintaining their original particle size and size distribution. Both the dried nanosuspensions and the original drug nanosuspensions showed similar dissolution profiles, which were both much faster than that of the raw crystals. Fluid-bed coating technology has potential for use in the solidification of drug nanosuspensions.

The solidification of aluminum production waste in geopolymer matrix

Czech Academy of Sciences Publication Activity Database

Perná, Ivana; Hanzlíček, Tomáš

2014-01-01

Roč. 84, DEC 1 (2014), s. 657-662 ISSN 0959-6526 Institutional support: RVO:67985891 Keywords : aluminum waste * solidification * recycling * geopolymer Subject RIV: DM - Solid Waste and Recycling Impact factor: 3.844, year: 2014

Remotely operated facility for in situ solidification of fissile uranium

International Nuclear Information System (INIS)

McGinnis, C.P.; Collins, E.D.; Patton, B.D.

1986-01-01

A heavily shielded, remotely operated facility, located within the Radiochemical processing Plant at Oak Ridge National Laboratory (ORNL), has been designed and is being operated to convert approx.1000 kg of fissile uranium (containing approx.75% 235 U, approx.10% 233 U, and approx.140 ppM 232 U) from a nitrate solution (130 g of uranium per L) to a solid oxide form. This project, the Consolidated Edison Uranium Solidification Program (CEUSP), is being carried out in order to prepare a stable uranium form for longterm storage. This paper describes the solidification process selected, the equipment and facilities required, the experimental work performed to ensure successful operation, some problems that were solved, and the initial operations

Study of plastic solidification process on solid radioactive waste treatment

International Nuclear Information System (INIS)

Jing Weiguan; Zhang Yinsheng; Qian Wenju

1994-01-01

Comparisons between the plastic solidification conditions of incinerated ash and waste cation resin by using thermosetting plastic polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE), and identified physico-chemical properties and irradiation resistance of solidified products were presented. These solidified products have passed through different tests as compression strength, leachability, durability, stability, permeability and irradiation resistance (10 6 Gy) etc. The result showed that the solidified products possessed stable properties and met the storage requirement. The waste tube of radioimmunoassay, being used as solidification medium to contain incinerated ash, had good mechanical properties and satisfactory volume reduction. This process may develop a new way for disposal solid radioactive waste by means of re-using waste

Numerical investigation on natural convection and solidification of molten pool with OpenFOAM

International Nuclear Information System (INIS)

Wang Xi; Meng Zhaocan; Cheng Xu

2015-01-01

The in-vessel retention is adopted by the third generation nuclear power technology as an important severe accident mitigation strategy. The integrity of reactor pressure vessel depends on the heat flux distribution of molten pool. In present study, the solidification model in open source CFD software OpenFOAM was applied to simulate solidification and natural convection which was driven by internal heat source or temperature difference. The stratified molten pool heat transfer experiment carried out by Royal Institute of Technology was analyzed in the paper, and the solidified crust, temperature and heat flux distributions were obtained. The simulation results were compared with experimental data. It is shown that this numerical method can be used in the simulation of natural convection and solidification of molten pool, and it will probably be used in the analysis of molten corium behavior in reactor lower head. (authors)

External field effects on diffusion and solidification derived from the free-volume model

Science.gov (United States)

Miller, R. I.; Ruff, R. C.

1975-01-01

Expressions for the diffusion coefficient and the solidification rate from the free-volume model of liquids developed by Turnbull and Cohen have been used to estimate the effects which microgravity and magnetic fields will have on these quantities. The mathematical formalism describing changes of the diffusion coefficient and the solidification rate is the same for both the microgravity and magnetic field cases, but the difference between the magnitudes of the two effects is quite large. The change in the two parameters is found to be less than .0001% for the microgravity case and on the order of 0.1 to 1.1% for the magnetic field case for four representative materials. The diffusion coefficient and the solidification rate are found to increase under the influence of an applied magnetic field, and this is in agreement with experimental observations.

Rapid Solidification of AB{sub 5} Hydrogen Storage Alloys

Energy Technology Data Exchange (ETDEWEB)

Gulbrandsen-Dahl, Sverre

2002-01-01

This doctoral thesis is concerned with rapid solidification of AB{sub 5} materials suitable for electrochemical hydrogen storage. The primary objective of the work has been to characterise the microstructure and crystal structure of the produced AB{sub 5} materials as a function of the process parameters, e.g. the cooling rate during rapid solidification, the determination of which has been paid special attention to. The thesis is divided into 6 parts, of which Part I is a literature review, starting with a short presentation of energy storage alternatives. Then a general review of metal hydrides and their utilisation as energy carriers is presented. This part also includes more detailed descriptions of the crystal structure, the chemical composition and the hydrogen storage properties of AB{sub 5} materials. Furthermore, a description of the chill-block melt spinning process and the gas atomisation process is given. In Part II of the thesis a digital photo calorimetric technique has been developed and applied for obtaining in situ temperature measurements during chill-block melt spinning of a Mm(NiCoMnA1){sub 5} hydride forming alloy (Mm = Mischmetal of rare earths). Compared with conventional colour transmission temperature measurements, this technique offers a special advantage in terms of a high temperature resolutional and positional accuracy, which under the prevailing experimental conditions were found to be {+-}29 K and {+-} 0.1 mm, respectively. Moreover, it is shown that the cooling rate in solid state is approximately 2.5 times higher than that observed during solidification, indicating that the solid ribbon stayed in intimate contact with the wheel surface down to very low metal temperatures before the bond was broken. During this contact period the cooling regime shifted from near ideal in the melt puddle to near Newtonian towards the end, when the heat transfer from the solid ribbon to the wheel became the rate controlling step. In Part III of the

Investigation of solidification behavior of the Sn-rich ternary Sn–Bi–Zn alloys

Directory of Open Access Journals (Sweden)

S Mladenović

2017-03-01

Full Text Available Solidification properties and microstructure of six as-cast Sn–Bi–Zn alloys with 80 at.% of Sn and variable contents of Bi and Zn were experimentally investigated using the scanning electron microscopy (SEM with energy-dispersive X-ray spectroscopy (EDS and differential scanning calorimetry (DSC. The experimentally obtained results were compared with predicted phase equilibria according to the calculation of phase diagram (CALPHAD method and by the Scheil solidification simulation.

Analysis of capital and operating costs associated with high level waste solidification processes

International Nuclear Information System (INIS)

Heckman, R.A.; Kniazewycz, B.G.

1978-03-01

An analysis was performed to evaluate the sensitivity of annual operating costs and capital costs of waste solidification processes to various parameters defined by the requirements of a proposed Federal waste repository. Five process methods and waste forms examined were: salt cake, spray calcine, fluidized bed calcine, borosilicate glass, and supercalcine multibarrier. Differential cost estimates of the annual operating and maintenance costs and the capital costs for the five HLW solidification alternates were developed

Numerical analysis of the thermal and fluid flow phenomena of the fluidity test

Directory of Open Access Journals (Sweden)

L. Sowa

2010-01-01

Full Text Available In the paper, two mathematical and numerical models of the metals alloy solidification in the cylindrical channel of fluidity test, which take into account the process of filling the mould cavity with molten metal, has been proposed. Velocity and pressure fields were obtained by solving the momentum equations and the continuity equation, while the thermal fields were obtained by solving the heat conduction equation containing the convection term. Next, the numerical analysis of the solidification process of metals alloy in the cylindrical mould channel has been made. In the models one takes into account interdependence of the thermal and dynamical phenomena. Coupling of the heat transfer and fluid flow phenomena has been taken into consideration by the changes of the fluidity function and thermophysical parameters of alloy with respect to the temperature. The influence of the velocity or the pressure and the temperature of metal pouring on the solid phase growth kinetics were estimated. The problem has been solved by the finite element method.

Solidification Mechanism of the D-Gun Sprayed Fe-Al Particles

Directory of Open Access Journals (Sweden)

Wołczyński W.

2017-12-01

Full Text Available The detonation gas spraying method is used to study solidification of the Fe-40Al particles after the D-gun spraying and settled on the water surface. The solidification is divided into two stages. First, the particle solid shell forms during the particle contact with the surrounding air / gas. Usually, the remaining liquid particle core is dispersed into many droplets of different diameter. A single Fe-Al particle is described as a body subjected to a rotation and finally to a centrifugal force leading to segregation of iron and aluminum. The mentioned liquid droplets are treated as some spheres rotated freely / chaotically inside the solid shell of the particle and also are subjected to the centrifugal force. The centrifugal force, and first of all, the impact of the particles onto the water surface promote a tendency for making punctures in the particles shell. The droplets try to desert / abandon the mother-particles through these punctures. Some experimental evidences for this phenomenon are delivered. It is concluded that the intensity of the mentioned phenomenon depends on a given droplet momentum. The droplets solidify rapidly during their settlement onto the water surface at the second stage of the process under consideration. A model for the solidification mechanism is delivered.

Stabilization/solidification of synthetic Nigerian drill cuttings | Opete ...

African Journals Online (AJOL)

Stabilization/solidification of synthetic Nigerian drill cuttings. SEO Opete, IA Mangibo, ET Iyagba. Abstract. In the Nigerian oil and gas industry, large quantities of oily and synthetic drill cuttings are produced annually. These drill cuttings are heterogeneous wastes which comprises of hydrocarbons, heavy metals and ...

A Comparative study of solidification of Al-Cu alloy under flow of cylindrical radial heat and the unidirectional vertically

Directory of Open Access Journals (Sweden)

Jean Robert P. Rodrigues

2014-09-01

Full Text Available In spite of technological importance of solidification of metallic alloys under radial heat flow, relatively few studies have been carried out in this area. In this work the solidification of Al 4.5 wt% Cu cylinders against a steel massive mold is analyzed and compared with unidirectional solidification against a cooled mold. Initially temperature variations at different positions in the casting and in the mold were measured during solidification using a data acquisition system. These temperature variations were introduced in a numerical method in order to determine the variation of heat transfer coefficient at metal/mold interface by inverse method. The primary and secondary dendrite arm spacing variations were measured through optical microscopy. Comparisons carried out between experimental and numerical data showed that the numerical method describes well the solidification processes under radial heat flux.

Techniques for the solidification of high-level wastes

International Nuclear Information System (INIS)

1977-01-01

The problem of the long-term management of the high-level wastes from the reprocessing of irradiated nuclear fuel is receiving world-wide attention. While the majority of the waste solutions from the reprocessing of commercial fuels are currently being stored in stainless-steel tanks, increasing effort is being devoted to developing technology for the conversion of these wastes into solids. A number of full-scale solidification facilities are expected to come into operation in the next decade. The object of this report is to survey and compare all the work currently in progress on the techniques available for the solidification of high-level wastes. It will examine the high-level liquid wastes arising from the various processes currently under development or in operation, the advantages and disadvantages of each process for different types and quantities of waste solutions, the stages of development, the scale-up potential and flexibility of the processes

Thermodynamic assessment of liquid composition change during solidification and its effect on freckle formation in superalloys

International Nuclear Information System (INIS)

Long Zhengdong; Liu Xingbo; Yang Wanhong; Chang, K.-M.; Barbero, Ever

2004-01-01

The solidification macrosegregation, i.e. freckle, becomes more and more concerned with ever increasing demand for the large ingot size of superalloys. The evaluation of freckle formation is very difficult because of the less understanding of freckle formation mechanism and complex solidification behaviors of multi-component superalloys. The macrostructure of typical Nb-bearing and Ti-bearing superalloys in horizontally directional solidification and vacuum arc remelting (VAR) ingots were investigated to clarify the freckle formation mechanism. The thermodynamic approach was proposed to simulate the solidification behaviors. The relative Ra numbers, a reliable criterion, of freckle formation for some alloys were obtained based on the results of thermodynamic calculations. This thermodynamic approach was evaluated through comparison of the calculations from semi-experimental results. The Ra numbers obtained by thermodynamic approach are in good agreement with the ingot size capability of the industry melting shops, which is limited mainly by freckle defects

Microstructure and fractal characteristics of the solid-liquid interface forming during directional solidification of Inconel 718

Directory of Open Access Journals (Sweden)

WANG Ling

2007-08-01

Full Text Available The solidification microstructure and fractal characteristics of the solid-liquid interfaces of Inconel 718, under different cooling rates during directional solidification, were investigated by using SEM. Results showed that 5 μm/s was the cellular-dendrite transient rate. The prime dendrite arm spacing (PDAS was measured by Image Tool and it decreased with the cooling rate increased. The fractal dimension of the interfaces was calculated and it changes from 1.204310 to 1.517265 with the withdrawal rate ranging from 10 to 100 μm/s. The physical significance of the fractal dimension was analyzed by using fractal theory. It was found that the fractal dimension of the dendrites can be used to describe the solidification microstructure and parameters at low cooling rate, but both the fractal dimension and the dendrite arm spacing are needed in order to integrally describe the evaluation of the solidification microstructure completely.

Cadarache LOR (liquides organiques radioactifs) treatment by a solidification process using NOCHAR polymers

International Nuclear Information System (INIS)

Vaudey, Claire-Emilie; Renou, Sebastien; Kelley, Dennis; Cochaud, Chantal; Serrano, Roger

2013-01-01

In France, two options can be considered to handle the Very Low Level Waste (VLLW) and the Low Level Waste (LLW). The first one is the incineration at CENTRACO facility and the second one is the disposal at ANDRA sites. The waste acceptance in these two channels is dependent upon the adequacy between the waste characteristics (physical chemistry and radiological) and the channel specifications. If the waste characteristics and the channel specifications (presence of significant quantities of halogens, complexing agents, organic components... or/and high activity limits) are incompatible, an alternative solution have to be identify. It consists of a waste pre-treatment process. For Cadarache LOR (Liquides Organiques Radioactifs) waste streams, two radioactive scintillation cocktails have to be treated. They are composed of a mix of organic liquids and water: for the first one, 19 % of organic compounds (xylene, mesitylene, diphenyloxazole, TBP...) and 86.9 % of water, and for the second one, 23 % of organic compounds (TBP...) and 77 % of water. They contain halogens (chlorine and fluorine), complexants agents (nitrate, sulphate, oxalate and formate) and have got αβγ spectra with mass activities equal to some 100 Bq/g. Therefore, tritium is also present. As a consequence, in order for storage acceptance at the ANDRA site, it is necessary to pre-treat the waste. An adequate solution seems to be a solidification process using NOCHAR polymers. Indeed, NOCHAR polymers correspond to an important variety of products applied to the treatment of radioactive aqueous and organic liquids (solvent, oil, solvent/oil mixing ...) and sludge through a mechanical and chemical solidification process. For Cadarache LOR, N910 and N960 respectively dedicated to the organic and aqueous liquids solidification are considered. With the N910, the organic waste solidification occurs in two steps. As the organic liquid travels moves through the polymer strands, the strands swell and

Evaporative and Convective Instabilities for the Evaporation of a Binary Mixture in a Bilayer System

Science.gov (United States)

Guo, Weidong; Narayanan, Ranga

2006-11-01

Evaporative convection in binary mixtures arises in a variety of industrial processes, such as drying of paint and coating technology. There have been theories devoted to this problem either by assuming a passive vapor layer or by isolating the vapor fluid dynamics. Previous work on evaporative and convective instabilities in a single component bilayer system suggests that active vapor layers play a major role in determining the instability of the interface. We have investigated the evaporation convection in binary mixtures taking into account the fluid dynamics of both phases. The liquid mixture and its vapor are assumed to be confined between two horizontal plates with a base state of zero evaporation but with linear vertical temperature profile. When the vertical temperature gradient reaches a critical value, the evaporative instability, Rayleigh and Marangoni convection set in. The effects of vapor and liquid depth, various wave numbers and initial composition of the mixture on the evaporative and convective instability are determined. The physics of the instability are explained and detailed comparison is made between the Rayleigh, Marangoni and evaporative convection in pure component and those in binary mixtures.

Influences on Distribution of Solute Atoms in Cu-8Fe Alloy Solidification Process Under Rotating Magnetic Field

Science.gov (United States)

Zou, Jin; Zhai, Qi-Jie; Liu, Fang-Yu; Liu, Ke-Ming; Lu, De-Ping

2018-05-01

A rotating magnetic field (RMF) was applied in the solidification process of Cu-8Fe alloy. Focus on the mechanism of RMF on the solid solution Fe(Cu) atoms in Cu-8Fe alloy, the influences of RMF on solidification structure, solute distribution, and material properties were discussed. Results show that the solidification behavior of Cu-Fe alloy have influenced through the change of temperature and solute fields in the presence of an applied RMF. The Fe dendrites were refined and transformed to rosettes or spherical grains under forced convection. The solute distribution in Cu-rich phase and Fe-rich phase were changed because of the variation of the supercooling degree and the solidification rate. Further, the variation in solute distribution was impacted the strengthening mechanism and conductive mechanism of the material.

Statistical mechanics of homogeneous partly pinned fluid systems.

Science.gov (United States)

Krakoviack, Vincent

2010-12-01

The homogeneous partly pinned fluid systems are simple models of a fluid confined in a disordered porous matrix obtained by arresting randomly chosen particles in a one-component bulk fluid or one of the two components of a binary mixture. In this paper, their configurational properties are investigated. It is shown that a peculiar complementarity exists between the mobile and immobile phases, which originates from the fact that the solid is prepared in presence of and in equilibrium with the adsorbed fluid. Simple identities follow, which connect different types of configurational averages, either relative to the fluid-matrix system or to the bulk fluid from which it is prepared. Crucial simplifications result for the computation of important structural quantities, both in computer simulations and in theoretical approaches. Finally, possible applications of the model in the field of dynamics in confinement or in strongly asymmetric mixtures are suggested.

On the hot cracking susceptibility of a semisolid aluminium 6061 weld: Application of a coupled solidification- thermomechanical model

International Nuclear Information System (INIS)

Rajani, H R Zareie; Phillion, A B

2015-01-01

A coupled solidification-thermomechanical model is presented that investigates the hot tearing susceptibility of an aluminium 6061 semisolid weld. Two key phenomena are considered: excessive deformation of the semisolid weld, initiating a hot tear, and the ability of the semisolid weld to heal the hot tear by circulation of the molten metal. The model consists of two major modules: weld solidification and thermomechanical analysis. 1) By means of a multi-scale model of solidification, the microstructural evolution of the semisolid weld is simulated in 3D. The semisolid structure, which varies as a function of welding parameters, is composed of solidifying grains and a network of micro liquid channels. The weld solidification module is utilized to obtain the solidification shrinkage. The size of the micro liquid channels is used as an indicator to assess the healing ability of the semisolid weld. 2) Using the finite element method, the mechanical interaction between the weld pool and the base metal is simulated to capture the transient force field deforming the semisolid weld. Thermomechanical stresses and shrinkage stresses are both considered in the analysis; the solidification contractions are extracted from the weld solidification module and applied to the deformation simulation as boundary conditions. Such an analysis enables characterization of the potential for excessive deformation of the weld. The outputs of the model are used to study the effect of welding parameters including welding current and speed, and also welding constraint on the hot cracking susceptibility of an aluminium alloy 6061 semisolid weld. (paper)

Glass-solidification method for high level radioactive liquid waste

International Nuclear Information System (INIS)

Kawamura, Kazuhiro; Kometani, Masayuki; Sasage, Ken-ichi.

1996-01-01

High level liquid wastes are removed with precipitates mainly comprising Mo and Zr, thereafter, the high level liquid wastes are mixed with a glass raw material comprising a composition having a B 2 O 3 /SiO 2 ratio of not less than 0.41, a ZnO/Li 2 O ratio of not less than 1.00, and an Al 2 O 3 /Li 2 O ratio of not less than 2.58, and they are melted and solidified into glass-solidification products. The liquid waste content in the glass-solidification products can be increased up to about 45% by using the glass raw material having such a predetermined composition. In addition, deposition of a yellow phase does not occur, and a leaching rate identical with that in a conventional case can be maintained. (T.M.)

Influence of working fluids on startup mechanism and thermal performance of a closed loop pulsating heat pipe

International Nuclear Information System (INIS)

Patel, Vipul M.; Gaurav; Mehta, Hemantkumar B.

2017-01-01

Highlights: • Startup mechanism and thermal performance of a CLPHP is reported. • Influence of pure fluids, water-based binary fluids and surfactant solutions are investigated. • Startup heat flux is observed lower for acetone and higher for water compared to all other working fluids. • Thermal resistance is observed to decrease with increase in heat input irrespective of working fluids. • CLPHP is observed to perform better with acetone, water-acetone, water-45 PPM and water-60 PPM surfactant solutions. - Abstract: Development of efficient cooling system is a tricky and challenging task in the field of electronics. Pulsating heat pipe has a great prospect in the upcoming days for an effective cooling solution due to its excellent heat transfer characteristics. Experimental investigations are reported on a Closed Loop Pulsating Heat Pipe (CLPHP). The influence of working fluids on startup mechanism and thermal performance of a CLPHP are carried out on 2 mm, nine turn copper capillary. Total eleven (11) working fluids are prepared and investigated. Deionized (DI) Water (H_2O), ethanol (C_2H_6O), methanol (CH_3OH) and acetone (C_3H_6O) are used as pure fluids. The water-based mixture (1:1) of acetone, methanol and ethanol are used as binary fluids. Sodium Dodecyl Sulphate (SDS, NaC_1_2H_2_5SO_4) is used as a surfactant to prepare the water-based surfactant solutions of 30 PPM, 45 PPM, 60 PPM and 100 PPM. The filling ratio is kept as 50%. The vertical bottom heating position of a CLPHP is considered. Heat input is varied in the range of 10–110 W. Significant influence is observed for water-based binary fluids and surfactant solutions on startup mechanism and thermal performance of a CLPHP compared to DI water used as the pure working fluid.

Solidification of the polyester coatings with accelerated electron beam in air

International Nuclear Information System (INIS)

Braginskaya, A.E.; Duvakina, N.I.; Kontorov, D.S.; Kuznetsova, L.I.; Kuz'min, A.A.; Nikolaev, A.F.

1976-01-01

A study has been made to find lacquer-paint compositions which are able to solidify in the air under the action of the electron beam with formation of beautiful, glistening and firm coating on wood. As objects under study compositions on the basis of oligoethercrylates, vinyl-series monomers, non-saturated polyether resins of industrial makes and newly created polymer compositions have been used. Styrol, methylmethacrylate, dimethylacryl triglicol ether (TGM-3), α,w-dimethacrylbis (diglicol) phthalate (MDF) have been used as monomers. Solidification of lacquer-paint coatings by the electron beam has been made under the electron energy of 250-400 keV and the current density of 10-120 μA/cm 2 . Solidification of lacquers has been performed at the room temperature. The effect of reactive additives, of the nature of the monomer and the polyether on the radiational solidification process have been studied. As a result of these studies polyether compositions have been developed, which are able to solidify in the air under the action of electrons at the room temperature for a short time with formation of the glistening firm surface; these compositions can be used to obtain coatings on wood, paper, metal and other substrates

Two-dimensional time-resolved X-ray diffraction study of directional solidification in steels

International Nuclear Information System (INIS)

Yonemura, Mitsuharu

2009-01-01

Full text: The high intensity heat source used for fusion welding creates steep thermal gradients of 100 degree C/s from 1800 degree Celsius. Further, the influence of a preferred orientation is serious for observation of a directional solidification that follows the dendrite growth along the direction toward the moving heat source. Therefore, we observed the rapid solidification of weld metal at a time resolution of 0.01∼0.1seconds by the Two-Dimensional Time-Resolved X-ray Diffraction (2DTRXRD) system for real welding. The diffraction ring was dynamically observed by 2DTRXRD during arc-passing over the irradiation area of X-ray with synchrotron energy of 18 KeV. The arc power output was 10 V - 150 A, and a scan speed of the arc was 1.0 mm/s. The temperature rise of instruments was suppressed by the water-cooled copper plate under the sample. Further, the temperature distribution of the weld metal was measured by the thermocouple and related to the diffraction patterns. Consequently, solidification and solid phase transformation of low carbon steels and stainless steels were observed during rapid cooling by 2DTRXRD. In the low-carbon steel, the microstructure is formed in the 2 step process; (i) formation of crystallites and (ii) increase of crystallinity. In the stainless steel, the irregular interface layer of σ/y in the quenched metal after solidification is expected that it is easy for dendrites to move at the lower temperature. In the carbide precipitation stainless steel, it is easy for NbC to grow on σ phase with a little under cooling. Further, a mist-like pattern, which differs from the halo-pattern, in the fusion zone gave some indication of the possibilities to observe the nucleation and the early solidification by 2DTRXRD. (author)

Alkali metal and ammonium chlorides in water and heavy water (binary systems)

CERN Document Server

Cohen-Adad, R

1991-01-01

This volume surveys the data available in the literature for solid-fluid solubility equilibria plus selected solid-liquid-vapour equilibria, for binary systems containing alkali and ammonium chlorides in water or heavy water. Solubilities covered are lithium chloride, sodium chloride, potassium chloride, rubidium chloride, caesium chloride and ammonium chloride in water and heavy water.

Discussions on the non-equilibrium effects in the quantitative phase field model of binary alloys

International Nuclear Information System (INIS)

Zhi-Jun, Wang; Jin-Cheng, Wang; Gen-Cang, Yang

2010-01-01

All the quantitative phase field models try to get rid of the artificial factors of solutal drag, interface diffusion and interface stretch in the diffuse interface. These artificial non-equilibrium effects due to the introducing of diffuse interface are analysed based on the thermodynamic status across the diffuse interface in the quantitative phase field model of binary alloys. Results indicate that the non-equilibrium effects are related to the negative driving force in the local region of solid side across the diffuse interface. The negative driving force results from the fact that the phase field model is derived from equilibrium condition but used to simulate the non-equilibrium solidification process. The interface thickness dependence of the non-equilibrium effects and its restriction on the large scale simulation are also discussed. (cross-disciplinary physics and related areas of science and technology)

Solidification microstructures in a short fiber reinforced alloy composite containing different fiber fractions

Directory of Open Access Journals (Sweden)

JING Qing-xiu

2006-02-01

Full Text Available The solidification microstructures and micro-segregation of a fiber reinforced Al-9 Cu alloy, containing different volume fractions of Al2O3 short fibers about 6 μm diameter and made by squeeze casting have been studied. The results indicate that as volume fraction of fiber Vf increases, the size of final grains becomes finer in the matrix. If λf /λ＞1, the fibers have almost no influence on the solidification behavior of the matrix, so the final grains grow coarse, where λf is the average inter-fiber spacing and λ is the secondary dendrite arm spacing. While if λf /λ＜1, the growth of crystals in the matrix is affected significantly by the fibers and the grain size is reduced to the value of the inter-fiber spacing. The fibers influence the average length of a solidification volume element L of the matrix and also influence the solidification time θt of the matrix. As a result of fibers influencing L and θt, the micro-segregation in the matrix is improved when the composite contains more fibers, although the level of the improvement is slight. The Clyne-Kurz model can be used to semi-quantitatively analyze the relationship between Vf and the volume fraction fe of the micro-segregation eutectic structure.

A Three-Stage Mechanistic Model for Solidification Cracking During Welding of Steel

Science.gov (United States)

Aucott, L.; Huang, D.; Dong, H. B.; Wen, S. W.; Marsden, J.; Rack, A.; Cocks, A. C. F.

2018-03-01

A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of solidification cracking and subsequent analysis of fracture surfaces. Stage 1—Nucleation of inter-granular hot cracks: cracks nucleate inter-granularly in sub-surface where maximum volumetric strain is localized and volume fraction of liquid is less than 0.1; the crack nuclei occur at solute-enriched liquid pockets which remain trapped in increasingly impermeable semi-solid skeleton. Stage 2—Coalescence of cracks via inter-granular fracture: as the applied strain increases, cracks coalesce through inter-granular fracture; the coalescence path is preferential to the direction of the heat source and propagates through the grain boundaries to solidifying dendrites. Stage 3—Propagation through inter-dendritic hot tearing: inter-dendritic hot tearing occurs along the boundaries between solidifying columnar dendrites with higher liquid fraction. It is recommended that future solidification cracking criterion shall be based on the application of multiphase mechanics and fracture mechanics to the failure of semi-solid materials.

Corium spreading: hydrodynamics, rheology and solidification of a high-temperature oxide melt

International Nuclear Information System (INIS)

Journeau, Ch.

2006-06-01

In the hypothesis of a nuclear reactor severe accident, the core could melt and form a high- temperature (2000-3000 K) mixture called corium. In the hypothesis of vessel rupture, this corium would spread in the reactor pit and adjacent rooms as occurred in Chernobyl or in a dedicated core-catcher s in the new European Pressurized reactor, EPR. This thesis is dedicated to the experimental study of corium spreading, especially with the prototypic corium material experiments performed in the VULCANO facility at CEA Cadarache. The first step in analyzing these tests consists in interpreting the material analyses, with the help of thermodynamic modelling of corium solidification. Knowing for each temperature the phase repartition and composition, physical properties can be estimated. Spreading termination is controlled by corium rheological properties in the solidification range, which leads to studying them in detail. The hydrodynamical, rheological and solidification aspects of corium spreading are taken into account in models and computer codes which have been validated against these tests and enable the assessment of the EPR spreading core-catcher concept. (author)

Numerical simulation of boundary heat flow effects on directional solidification microstructure of a binary alloy

Directory of Open Access Journals (Sweden)

Xue Xiang

2010-08-01

Full Text Available The boundary heat flow has important significance for the microstructures of directional solidified binary alloy. Interface evolution of the directional solidified microstructure with different boundary heat flow was discussed. In this study, only one interface was allowed to have heat flow, and Neumann boundary conditions were imposed at the other three interfaces. From the calculated results, it was found that different boundary heat flows will result in different microstructures. When the boundary heat flow equals to 20 W·cm-2, the growth of longitudinal side branches is accelerated and the growth of transverse side branches is restrained, and meanwhile, there is dendritic remelting in the calculation domain. When the boundary heat flow equals to 40 W·cm-2, the growths of the transverse and longitudinal side branches compete with each other, and when the boundary heat flow equals to 100-200 W·cm-2, the growth of transverse side branches dominates absolutely. The temperature field of dendritic growth was analyzed and the relation between boundary heat flow and temperature field was also investigated.

Characterization for solidification and phase transformations of pure-titanium steel weld metal with time-resolved X-ray diffraction system

International Nuclear Information System (INIS)

Terasaki, Hidenori; Komizo, Yu-ichi; Nishino, Fumihiro; Ikeda, Masahiko

2007-01-01

Understanding and controlling solidification and phase transformation process of weld metal is essential for forming the microstructure with superior mechanical property. Recent evolution of analysis technique makes for solidification and phase transformation process to be in-situ analyzed, in direct and reciprocal lattice space. In the present work, unidirectional-solidification and phase transformation in the weld metal of commercial pure-titanium in Gas Tungsten Arc welding was in-situ observed by using Time-Resolved X-Ray Diffraction system with two-dimensional pixel detector. An undulator beam was used as a probe. Larger diffraction area could be detected in the time-resolution of 0.05 seconds, in unidirectional solidification and subsequent phase transformation process of pure-titanium weld metal. Furthermore, the microstructure formation during β-α phase transformation was in situ observed with High temperature Laser Scanning Confocal Microscopy. The crystal configurations in unidirectional solidification of weld metal and rapid change of phase ratio in reconstructive phase transformation were clearly analyzed. (author)

Numerical simulation of binary collisions using a modified surface tension model with particle method

International Nuclear Information System (INIS)

Sun Zhongguo; Xi Guang; Chen Xi

2009-01-01

The binary collision of liquid droplets is of both practical importance and fundamental value in computational fluid mechanics. We present a modified surface tension model within the moving particle semi-implicit (MPS) method, and carry out two-dimensional simulations to investigate the mechanisms of coalescence and separation of the droplets during binary collision. The modified surface tension model improves accuracy and convergence. A mechanism map is established for various possible deformation pathways encountered during binary collision, as the impact speed is varied; a new pathway is reported when the collision speed is critical. In addition, eccentric collisions are simulated and the effect of the rotation of coalesced particle is explored. The results qualitatively agree with experiments and the numerical protocol may find applications in studying free surface flows and interface deformation

Effect and kinetic mechanism of ultrasonic vibration on solidification of 7050 aluminum alloy

Directory of Open Access Journals (Sweden)

Ripeng Jiang

2014-07-01

Full Text Available The work described in this paper dealt with the effect of ultrasonic vibration on the solidification of 7050 aluminum alloy. Two experiments were carried out through introducing ultrasound into the semi-continuous direct-chill (DC casting of aluminum alloy and into alloy solidifying in a crucible, respectively. Results show that ultrasonic vibration can refine grains in the whole cross-section of a billet in the first experiment and is able to increase the cooling rate within the temperature range from 625 °C to 590 °C in the other one. The mechanism of particle resonance caused by ultrasonic vibration was illustrated on the basis of theoretical analysis of the kinetics and energy conversion during the solidification. It is demonstrated that the kinetic energy of resonant particles are mainly from the latent heat energy of solidification, which can shorten the cooling time, inhibit the crystal growth and then lead to the grain refinement.

The Refining Mechanism of Super Gravity on the Solidification Structure of Al-Cu Alloys

Directory of Open Access Journals (Sweden)

Yuhou Yang

2016-12-01

Full Text Available There is far less study of the refining effect of super gravity fields on solidification structures of metals than of the effects of electrical currents, magnetic and ultrasonic fields. Moreover, the refining mechanisms of super gravity are far from clear. This study applied a super gravity field to Al-Cu alloys to investigate its effect on refining their structures and the mechanism of interaction. The experimental results showed that the solidification structure of Al-Cu alloys can be greatly refined by a super gravity field. The major refining effect was mainly achieved when super gravity was applied at the initial solidification stage; only slight refinement could be obtained towards the end of solidification. No refinement was obtained by the super gravity treatment on pure liquid or solid stages. The effectiveness of super gravity results from its promoting the multiplication of crystal nuclei, which we call “Heavy Crystal Rain”, thereby greatly strengthening the migration of crystal nuclei within the alloy. Increasing the solute Cu content can increase nucleation density and restrict the growth of crystals, which further increases the refining effect of super gravity. Within this paper, we also discuss the motile behavior of crystals in a field of super gravity.

New knowledge on the temperature-entropy saturation boundary slope of working fluids

International Nuclear Information System (INIS)

Su, Wen; Zhao, Li; Deng, Shuai

2017-01-01

The slope of temperature-entropy saturation boundary of working fluids has a significant effect on the thermodynamic performance of cycle processes. However, for the working fluids used in cycles, few studies have been conducted to analyze the saturated slope from the molecular structure and mixture composition. Thus, in this contribution, an analytical expression on the slope of saturated curve is obtained based on the highly accurate Helmholtz energy equation. 14 pure working fluids and three typical binary mixtures are employed to analyze the influence of molecular groups and mixture compositions on the saturated slope, according to the correlated parameters of Helmholtz energy equation. Based on the calculated results, a preliminary trend is demonstrated that with an increase of the number of molecular groups, the positive liquid slope of pure fluids increases and the vapor slope appears positive sign in a narrow temperature range. Particularly, for the binary mixtures, the liquid slope is generally located between the corresponding pure fluids', while the vapor slope can be infinity by mixing dry and wet fluids ingeniously. It can be proved through the analysis of mixtures' saturated slope that three types of vapor slope could be obtained by regulating the mixture composition. - Highlights: • The saturated slope is derived from the Helmholtz function for working fluids. • The effect of molecular structure on the saturated slope is analyzed. • The variation of saturated slope with the mixture composition is investigated.

Application of the finite volume method in the simulation of saturated flows of binary mixtures

International Nuclear Information System (INIS)

Murad, M.A.; Gama, R.M.S. da; Sampaio, R.

1989-12-01

This work presents the simulation of saturated flows of an incompressible Newtonian fluid through a rigid, homogeneous and isotropic porous medium. The employed mathematical model is derived from the Continuum Theory of Mixtures and generalizes the classical one which is based on Darcy's Law form of the momentum equation. In this approach fluid and porous matrix are regarded as continuous constituents of a binary mixture. The finite volume method is employed in the simulation. (author) [pt

Real-time synchrotron x-ray observations of equiaxed solidification of aluminium alloys and implications for modelling

Science.gov (United States)

Prasad, A.; Liotti, E.; McDonald, S. D.; Nogita, K.; Yasuda, H.; Grant, P. S.; StJohn, D. H.

2015-06-01

Recently, in-situ observations were carried out by synchrotron X-ray radiography to observe the nucleation and growth in Al alloys during solidification. The nucleation and grain formation of a range of Al-Si and Al-Cu binary alloys were studied. When grain refiner was added to the alloys, the location of the nucleation events was readily observed. Once nucleation began it continued to occur in a wave of events with the movement of the temperature gradient across the field of view due to cooling. Other features observed were the settling of the primary phase grains in the Al-Si alloys and floating in the Al-Cu alloys, the effects of convection with marked fluctuation of the growth rate of the solid-liquid interface in the Al-Si alloys, and an absence of fragmentation. The microstructures are typical of those produced in the equiaxed zone of actual castings. These observations are compared with predictions arising from the Interdependence model. The results from this comparison have implications for further refinement of the model and simulation and modelling approaches in general. These implications will be discussed.

Application of the dual reciprocity boundary element method for numerical modelling of solidification process

Directory of Open Access Journals (Sweden)

E. Majchrzak

2008-12-01

Full Text Available The dual reciprocity boundary element method is applied for numerical modelling of solidification process. This variant of the BEM is connected with the transformation of the domain integral to the boundary integrals. In the paper the details of the dual reciprocity boundary element method are presented and the usefulness of this approach to solidification process modelling is demonstrated. In the final part of the paper the examples of computations are shown.

Solidification of hazardous and mixed radioactive waste at the Idaho National Engineering Laboratory

International Nuclear Information System (INIS)

Boehmer, A.M.; Larsen, M.M.

1986-01-01

EG and G Idaho has initiated a program to develop treatment options for the hazardous and mixed wastes generated at the Idaho National Engineering Laboratory (INEL). This program includes development of solidification methods for some of these wastes. Testing has shown that toxic wastes can be successfully solidified using cement, cement-silicate, or ENVIROSTONE binders to produce nontoxic stable waste forms for safe, long term disposal. This paper presents the results of the solidification development program conducted at the INEL by EG and G Idaho

Solidification of hazardous and mixed radioactive waste at the Idaho National Engineering Laboratory

International Nuclear Information System (INIS)

Boehmer, A.M.; Larsen, M.M.

1986-03-01

EG and G Idaho has initiated a program to develop treatment options for the hazardous and mixed wastes generated at the Idaho National Engineering Laboratory (INEL). This program includes development of solidification methods for some of these wastes. Testing has shown that toxic wastes can be successfully solidified using cement, cement-silicate, or ENVIROSTONE binders to produce nontoxic stable waste forms for safe, long term disposal. This paper presents the results of the solidification development program conducted at the INEL by EG and G Idaho

Method of processing radioactive liquid wastes by solidification with cement

International Nuclear Information System (INIS)

Yasumura, Keijiro; Matsuura, Hiroyuki.

1975-01-01

Object: To subject radioactive liquid wastes to a cement solidification treatment after heating and drying it by a thin film scrape-off drier to render it into the form of power, and then molding it into pellets for the treatment. Structure: Radioactive liquid wastes discharged from a nuclear power plant or nuclear reactor are supplied through a storage tank into a thin film scrape-off drier. In the drier, the radioactive liquid wastes are heated to separate the liquid, and the residue is taken out as dry powder from the scrape-off apparatus. The powder obtained in this way is molded into pellets of a desired form. These pellets are then packed in a drum can or similar container, into which cement paste is then poured for solidification. (Moriyama, K.)

Solidification of high temperature molten salts for thermal energy storage systems

Science.gov (United States)

Sheffield, J. W.

1981-01-01

The solidification of phase change materials for the high temperature thermal energy storage system of an advanced solar thermal power system has been examined theoretically. In light of the particular thermophysical properties of candidate phase change high temperature salts, such as the eutectic mixture of NaF - MgF2, the heat transfer characteristics of one-dimensional inward solidification for a cylindrical geometry have been studied. The Biot number for the solidified salt is shown to be the critical design parameter for constant extraction heat flux. A fin-on-fin design concept of heat transfer surface augmentation is proposed in an effort to minimize the effects of the salt's low thermal conductivity and large volume change upon fusing.

Alternative method of solidification for low-level class a radioactive waste

International Nuclear Information System (INIS)

Mayo, K.S.

1988-01-01

New solidification media have been developed that exhibit excellent spatial efficiency over the entire range of virtually all Class A liquid wastes. These new media are being used to incorporate from 41 to 48 gallons of liquid radioactive waste in a 55-gallon drum. To date, wastes processing at nuclear power plants and facilities include oils, evaporator bottoms, sludges, and ion-exchanges resins as well as combinations of these waste streams. This paper comparatively discusses the performance of solidification agents known as AQUASET TM and PETROSET TM with other currently available agents. It presents key advantages of using the AQUASET and PETROSET media over other media. These advantages include improvements in packaging efficiency, leachability, and repeatability

Joining of superalloy Inconel 600 by diffusion induced isothermal solidification of a liquated insert metal

International Nuclear Information System (INIS)

Egbewande, A.T.; Chukwukaeme, C.; Ojo, O.A.

2008-01-01

The effect of process variables on the microstructure of transient liquid phase bonded IN 600 using a commercial filler alloy was studied. Microstructural examination of bonded specimens showed that isothermal solidification of the liquated insert occurred during holding at the joining temperatures. In cases where the holding time was insufficient for complete isothermal solidification, the residual liquid transformed on cooling into a centerline eutectic product. The width of the eutectic decreased with increased holding time and an increase in initial gap width resulted in thicker eutectic width in specimens bonded at the same temperature and for equivalent holding times. In addition to the centerline eutectic microconstituent, precipitation of boron-rich particles was observed within the base metal region adjacent to the substrate-joint interface. Formation of these particles appeared to have influenced the rate of solidification of the liquated interlayer during bonding. In contrast to the conventional expectation of an increase in the rate of isothermal solidification with an increase in temperature, a decrease in the rate was observed with an increase in temperatures above 1160 deg. C. This could be related to a decrease in solubility of boron in nickel above the Ni-B eutectic temperature

Real-time X-ray transmission microscopy for fundamental studies solidification: Al-Al2Au eutectic

International Nuclear Information System (INIS)

Curreri, Peter A.; Kaukler, William F.; Sen, Subhayu

1998-01-01

High resolution real-time X-ray Transmission Microscopy, XTM, has been applied to obtain information fundamental to solidification of optically opaque metallic systems. We have previously reported the measurement of the solute profile in the liquid, phase growth, and detailed solid-liquid interfacial morphology of aluminum based alloys with exposure times less than 2 seconds. Recent advances in XTM furnace design have provided an increase in real-time magnification (during solidification) for the XTM from 40X to 160X. The increased magnification has enabled for the first time the XTM imaging of real-time growth of fibers and particles with diameters of 5 μm. We have previously applied this system to study the kinetics of formation and morphological evolution of secondary fibers and particles in Al-Bi monotectic alloys. In this paper we present the preliminary results of the first real-time observations of fiber morphology evolution in optically opaque bulk metal sample of Aluminum-Gold eutectic alloy. These studies show that the XTM can be applied to study the fundamentals of eutectic and monotectic solidification. We are currently attempting to apply this technology in the fundamentals of solidification in microgravity

Integrated System of Thermal/Dimensional Analysis for Quality Control of Metallic Melt and Ductile Iron Casting Solidification

Science.gov (United States)

Stan, Stelian; Chisamera, Mihai; Riposan, Iulian; Neacsu, Loredana; Cojocaru, Ana Maria; Stan, Iuliana

2018-03-01

The main objective of the present work is to introduce a specific experimental instrument and technique for simultaneously evaluating cooling curves and expansion or contraction of cast metals during solidification. Contraction/expansion analysis illustrates the solidification parameters progression, according to the molten cast iron characteristics, which are dependent on the melting procedure and applied metallurgical treatments, mold media rigidity and thermal behavior [heat transfer parameters]. The first part of the paper summarizes the performance of this two-mold device. Its function is illustrated by representative shrinkage tendency results in ductile cast iron as affected by mold rigidity (green sand and furan resin sand molds) and inoculant type (FeSi-based alloys), published in part previously. The second part of the paper illustrates an application of this equipment adapted for commercial foundry use. It conducts thermal analysis and volume change measurements in a single ceramic cup so that mold media as well as solidification conditions are constants, with cast iron quality as the variable. Experiments compared gray and ductile cast iron solidification patterns. Gray iron castings are characterized by higher undercooling at the beginning and at the end of solidification and lower graphitic expansion. Typically, ductile cast iron exhibits higher graphitic, initial expansion, conducive for shrinkage formation in soft molds.

The thermodynamic cycle models for geothermal power plants by considering the working fluid characteristic

Science.gov (United States)

Mulyana, Cukup; Adiprana, Reza; Saad, Aswad H.; M. Ridwan, H.; Muhammad, Fajar

2016-02-01

The scarcity of fossil energy accelerates the development of geothermal power plant in Indonesia. The main issue is how to minimize the energy loss from the geothermal working fluid so that the power generated can be increased. In some of geothermal power plant, the hot water which is resulted from flashing is flown to injection well, and steam out from turbine is condensed in condenser, while the temperature and pressure of the working fluid is still high. The aim of this research is how the waste energy can be re-used as energy source to generate electric power. The step of the research is started by studying the characteristics of geothermal fluid out from the well head. The temperature of fluid varies from 140°C - 250°C, the pressure is more than 7 bar and the fluid phase are liquid, gas, or mixing phase. Dry steam power plant is selected for vapor dominated source, single or multiple flash power plant is used for dominated water with temperature > 225°C, while the binary power plant is used for low temperature of fluid enthalpy, the calculated power of these double and triple flash power plant are 50% of W1+W2. At the last step, the steam out from the turbine of unit 3 with the temperature 150°C is used as a heat source for binary cycle power plant named unit 4, while the hot water from the flasher is used as a heat source for the other binary cycle named unit 5 resulted power W5+W6 or 15% of W1+W2. Using this integrated model the power increased 75% from the original one.

Initial stages of solidification of eutectic alloys

International Nuclear Information System (INIS)

Lemaignan, Clement

1980-01-01

The study of the various initial stages of eutectic solidification - i.e. primary nucleation, eutectic structure formation and stable growth conditions - was undertaken with various techniques including low angle neutron diffusion, in-situ electron microscopy on solidifying alloys and classical metallography. The results obtained allow to discuss the effect of metastable states during primary nucleation, of surface dendrite during eutectic nucleation and also of the crystallographic anisotropy during growth. (author) [fr

Binary Ice Technology - Processes and Applications for Energy Management of Buildings (Binäistechnologie - Verfahren und Anwendungen in der Technischen Gebäudeausrüstung)

DEFF Research Database (Denmark)

Paul, Joachim

2003-01-01

Binary Ice has stunning properties. Such liquid ice can be pumped and stored in a simple way, the fluid is energy efficient, has excellent heat transfer properties and is very well suited for air conditioning and air dehumidification. Furthermore Binary Ice is non toxic. Smaller pipes, less pumpi...

Rapid solidification for preparation of high Tc superconductors

International Nuclear Information System (INIS)

Yavari, A.R.

1988-01-01

High Tc superconducting oxides are prepared in two different ways using rapid solidification: by oxidation of microcrystalline or amorphous tapes obtained by quenching the liquid alloy and via crystallisation of the amorphous oxide obtained by rapid quenching of the oxide melt. This technique is applied for the first time to the BiCaSrCuO family [fr

Particle Trapping and Banding in Rapid Colloidal Solidification

KAUST Repository

Elliott, J. A. W.

2011-10-11

We derive an expression for the nonequilibrium segregation coefficient of colloidal particles near a moving solid-liquid interface. The resulting kinetic phase diagram has applications for the rapid solidification of clay soils, gels, and related colloidal systems. We use it to explain the formation of bandlike defects in rapidly solidified alumina suspensions. © 2011 American Physical Society.

Corium spreading: hydrodynamics, rheology and solidification of a high-temperature oxide melt; L'etalement du corium: hydrodynamique, rheologie et solidification d'unbain d'oxydes a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Journeau, Ch

2006-06-15

In the hypothesis of a nuclear reactor severe accident, the core could melt and form a high- temperature (2000-3000 K) mixture called corium. In the hypothesis of vessel rupture, this corium would spread in the reactor pit and adjacent rooms as occurred in Chernobyl or in a dedicated core-catcher s in the new European Pressurized reactor, EPR. This thesis is dedicated to the experimental study of corium spreading, especially with the prototypic corium material experiments performed in the VULCANO facility at CEA Cadarache. The first step in analyzing these tests consists in interpreting the material analyses, with the help of thermodynamic modelling of corium solidification. Knowing for each temperature the phase repartition and composition, physical properties can be estimated. Spreading termination is controlled by corium rheological properties in the solidification range, which leads to studying them in detail. The hydrodynamical, rheological and solidification aspects of corium spreading are taken into account in models and computer codes which have been validated against these tests and enable the assessment of the EPR spreading core-catcher concept. (author)

Solidification structure and dispersoids in rapidly solidified Ti-Al-Sn-Zr-Er-B alloys

International Nuclear Information System (INIS)

Rowe, R.G.; Broderick, T.F.; Koch, E.F.; Froes, F.H.

1986-01-01

The microstructure of melt extracted and melt spun titanium alloys containing erbium and boron revealed a duplex solidification structure of columnar grains leading to equiaxed and dendritic structures near the free surface of melt extracted and melt spun alloys. The solidification structure was revealed by apparent boride segregation to cellular, interdendritic and grain boundaries. Precipitation of needle or lath-like TiB particles occurred adjacent to Er/sub 2/O/sub 3/ dispesoid particles in as-rapidly solidified ribbon

Effect of blended materials on U(VI) retention characteristics for portland cement solidification product

International Nuclear Information System (INIS)

Tan Hongbin; Ma Xiaoling; Li Yuxiang

2006-01-01

Using the simulated groundwater as leaching liquid, the retention capability of U(VI) in solidification products with Portland cement, the Portland cement containing silica fume, the Portland cement containing metakaolin and the Portland cement containing fly ash was researched by leaching experiments at 25 degree C for 42 d. The results indicate silica fume and metakaolin as blended materials can improve the U(VI) retention capability of Portland cement solidification product, but fly ash can not. (authors)

Study and modeling of heat transfer during the solidification of semi-crystalline polymers

Energy Technology Data Exchange (ETDEWEB)

Le Goff, R.; Poutot, G.; Delaunay, D. [Laboratoire de Thermocinetique de l' ecole polytechnique de l' universite de Nantes, UMR CNRS 6607, rue Christian Pauc, BP 50609 44306 Nantes cedex 3 (France); Fulchiron, R.; Koscher, E. [Laboratoire des Materiaux Polymeres et des Biomateriaux, IMP/UMR CNRS 5627, Universite Claude Bernard, Lyon 1, 69622 Villeurbanne Cedex (France)

2005-12-01

Semi-crystalline polymers are materials whose behavior during their cooling is difficult to model because of the strong coupling between the crystallization, heat transfer, pressure and shear. Thanks to two original apparatus we study solidification of such a polymer without shear. Firstly the comparison between experimental results and a numerical model will permit to validate crystallization kinetic for cooling rate reachable by DSC. The second experiment makes it possible to analyze solidification for high cooling rate, corresponding to some manufacturing processes. It appears that crystallization has an influence on the thermal contact resistance. (author)

Hazardous and mixed waste solidification development conducted at the Idaho National Engineering Laboratory

International Nuclear Information System (INIS)

Boehmer, A.M.; Larsen, M.M.

1986-04-01

EG and G Idaho, Inc., has initiated a program to develop safe, efficient, cost-effective solidification treatment methods for the disposal of some of the hazardous and mixed wastes generated at the Idaho National Engineering Laboratory (INEL). Testing has shown that Extraction Procedure (EP) toxic wastes can be successfully solidified using cement, cement-silicate, or ENVIROSTONE binders to produce nontoxic stable waste forms for safe, long-term disposal as general or low-level waste, depending upon the radioactivity. The results of the solidification development program are presented in this report

ACOUSTIC EFFECTS ON BINARY AEROELASTICITY MODEL

Directory of Open Access Journals (Sweden)

Kok Hwa Yu

2011-10-01

Full Text Available Acoustics is the science concerned with the study of sound. The effects of sound on structures attract overwhelm interests and numerous studies were carried out in this particular area. Many of the preliminary investigations show that acoustic pressure produces significant influences on structures such as thin plate, membrane and also high-impedance medium like water (and other similar fluids. Thus, it is useful to investigate the structure response with the presence of acoustics on aircraft, especially on aircraft wings, tails and control surfaces which are vulnerable to flutter phenomena. The present paper describes the modeling of structural-acoustic interactions to simulate the external acoustic effect on binary flutter model. Here, the binary flutter model which illustrated as a rectangular wing is constructed using strip theory with simplified unsteady aerodynamics involving flap and pitch degree of freedom terms. The external acoustic excitation, on the other hand, is modeled using four-node quadrilateral isoparametric element via finite element approach. Both equations then carefully coupled and solved using eigenvalue solution. The mentioned approach is implemented in MATLAB and the outcome of the simulated result are later described, analyzed and illustrated in this paper.

Direct numerical simulations of fluid flow, heat transfer and phase changes

Science.gov (United States)

Juric, D.; Tryggvason, G.; Han, J.

1997-01-01

Direct numerical simulations of fluid flow, heat transfer, and phase changes are presented. The simulations are made possible by a recently developed finite difference/front tracking method based on the one-field formulation of the governing equations where a single set of conservation equations is written for all the phases involved. The conservation equations are solved on a fixed rectangular grid, but the phase boundaries are kept sharp by tracking them explicitly by a moving grid of lower dimension. The method is discussed and applications to boiling heat transfer and the solidification of drops colliding with a wall are shown.

Solidification of AM and AZ magnesium alloys characterized by heat-transfer modeled thermal and calorimetric analysis and microsegregation study of directionally solidified microstructure

Energy Technology Data Exchange (ETDEWEB)

Mirkovic, Djordje

2008-05-09

The micro-scale solidification of commercial Mg alloys of the AZ and AM series is in the focus of the present thesis. Two approaches of investigating solidification are implemented, complementary regarding temperature gradient and solidification rate, and also with respect to the generated microstructure. The first approach considers solidification under a negligible spatial temperature gradient. Here the solidification curves, i.e. fraction solid versus temperature, were determined by developing an improved heat-transfer modeling applicable on both differential thermal analysis (DTA) and differential scanning calorimetry (DSC) signals. The correlation between solidification enthalpy and fraction solid during solidification was tested in detail. A better evaluation of the measured DTA and DSC signals is attained through an independent measurement of the time constant as function of temperature for the applied equipment. A further improvement is achieved through a more impartial interpretation of the measured curves. Both improvements enable a better desmearing of measured signals and reduce the error induced by the operator. The novel tantalum encapsulation enabled appropriate handling of challenging Mg-alloys. The viability and limitations of thermal analysis in general to determine start and end of solidification of AZ magnesium alloys was also studied. The second approach is based on directional solidification in a high temperature gradient and at constant solidification rate, achieved by the Bridgman technique. The resulting dendritic microstructure and inherent microsegregation are studied in this work. The solute profiles, i.e. solute content versus solid phase fraction during solidification, are determined by an advanced treatment of the EPMA data. Problems that are demonstrated in this work are Al-loss and melt pollution due to reaction with typical sample container material made of unprotected steel. The development of an optimized boron nitride (BN

Solidification microstructure of centrifugally cast Inconel 625

Directory of Open Access Journals (Sweden)

Silvia Barella

2017-07-01

Full Text Available Centrifugal casting is a foundry process allowing the production of near net-shaped axially symmetrical components. The present study focuses on the microstructural characterization of centrifugally cast alloys featuring different chemical compositions for the construction of spheres applied in valves made of alloy IN625 for operation at high pressure. Control of the solidification microstructure is needed to assure the reliability of the castings. Actually, a Ni-base superalloy such as this one should have an outstanding combination of mechanical properties, high temperature stability and corrosion resistance. Alloys such as IN625 are characterised by a large amount of alloying elements and a wide solidification range, so they can be affected by micro-porosity defects, related to the shrinkage difference between the matrix and the secondary reinforcing phases (Nb-rich carbides and Laves phase. In this study, the microstructure characterization was performed as a function of the applied heat treatments and it was coupled with a calorimetric analysis in order to understand the mechanism ruling the formation of micro-porosities that can assure alloy soundness. The obtained results show that the presence of micro-porosities is governed by morphology and by the size of the secondary phases, and the presence of the observed secondary phases is detrimental to corrosion resistance.

Liquid–liquid equilibria for reservoir fluids+monoethylene glycol and reservoir fluids+monoethylene glycol+water: Experimental measurements and modeling using the CPA EoS

DEFF Research Database (Denmark)

Frost, Michael; Kontogeorgis, Georgios; Stenby, Erling Halfdan

2013-01-01

for critical temperature, pressure and acentric factor.This work presents new phase equilibrium data for binary MEG/reservoir fluid and ternary MEG/water/reservoir fluid systems, where two reservoir fluids from Statoil operated fields are used. The solubility data are reported over a range of temperatures......The complex phase equilibrium between reservoir fluids and associating compounds like water and glycols has become more and more important as the increasing global energy demand pushes the oil industry to use advanced methods to increase oil recovery, such as increasing the use of various chemicals...... to ensure a constant and safe production. The CPA equation of state has been successfully applied in the past to well defined systems and gas condensates, containing associating compounds. It has also been extended to reservoir fluids in presence of water and polar chemicals using modified correlations...

Economic analysis of a volume reduction/polyethylene solidification system for low-level radioactive wastes

International Nuclear Information System (INIS)

Kalb, P.D.; Colombo, P.

1985-01-01

A study was conducted at Brookhaven National Laboratory to determine the economic feasibility of a fluidized bed volume reduction/polyethylene solidification system for low-level radioactive wastes. These results are compared with the ''null'' alternative of no volume reduction and solidification of aqueous waste streams in hydraulic cement. The economic analysis employed a levelized revenue requirement (LRR) technique conducted over a ten year period. An interactive computer program was written to conduct the LRR calculations. Both of the treatment/solidification options were considered for a number of scenarios including type of plant (BWR or PWR) and transportation distance to the disposal site. If current trends in the escalation rates of cost components continue, the volume reduction/polyethylene solidification option will be cost effective for both BWRs and PWRs. Data indicate that a minimum net annual savings of $0.8 million per year (for a PWR shipping its waste 750 miles) and a maximum net annual savings of $9 million per year (for a BWR shipping its waste 2500 miles) can be achieved. A sensitivity analysis was performed for the burial cost escalation rate, which indicated that variation of this factor will impact the total levelized revenue requirement. The burial cost escalation rate which yields a break-even condition was determined for each scenario considered. 11 refs., 8 figs., 39 tabs

Solidification as low cost technology prior to land filling of industrial hazardous waste sludge.

Science.gov (United States)

El-Sebaie, O; Ahmed, M; Ramadan, M

2000-01-01

The aim of this study is to stabilize and solidify two different treated industrial hazardous waste sludges, which were selected from factories situated close to Alexandria. They were selected to ensure their safe transportation and landfill disposal by reducing their potential leaching of hazardous elements, which represent significant threat to the environment, especially the quality of underground water. The selected waste sludges have been characterized. Ordinary Portland Cement (OPC), Cement Kiln Dust (CKD) from Alexandria Portland Cement Company, and Calcium Sulphate as a by-product from the dye industry were used as potential solidification additives to treat the selected treated waste sludges from tanning and dyes industry. Waste sludges as well as the solidified wastes have been leach-tested, using the General Acid Neutralization Capacity (GANC) procedure. Concentration of concerning metals in the leachates was determined to assess changes in the mobility of major contaminants. The treated tannery waste sludge has an acid neutralization capacity much higher than that of the treated dyes waste sludge. Experiment results demonstrated the industrial waste sludge solidification mix designs, and presented the reduction of contaminant leaching from two types of waste sludges. The main advantages of solidification are that it is simple and low cost processing which includes readily available low cost solidification additives that will convert industrial hazardous waste sludges into inert materials.

Elemental analysis of the Al-Fe intermetallic prepared by fast solidification

International Nuclear Information System (INIS)

Sandoval J, R.A.; Lopez M, J.; Ramirez T, J.J.; Aspiazu F, J.; Villasenor S, P.

2003-01-01

Applying the PIXE technique samples of the Al-Fe intermetallic prepared by fast solidification, obtained starting from Al recycled were analyzed. The concentrations of the found elements are given. (Author)

Solidification of ion-exchange resins by hydrothermal hot-pressing

International Nuclear Information System (INIS)

Kaneko, M.

1993-01-01

The solidification reaction which easily occurs while continuously keeping the mixture of cation and anion exchange resins compressed under hydrothermal conditions has been demonstrated. Dehydration was considered to occur between sulphonic acid (-SO 3 H) from the cation exchange resin and quaternary ammonium [-CH 2 -N(CH 3 ) 3 OH] from anion-exchange resin-on terminal groups. The cation-and anion-exchange resins were mixed in a 1:1 weight ratio, put in a hot-pressing autoclave and compressed between pistons from the top and bottom at 600 kg cm -2 pressure. The material was continuously compressed during hydrothermal treatment at 200 kg cm -2 by a hydraulic jack and heated to a desired temperature with an induction heater. This system could be used for rapid temperature increasing up to 30 o c min -1 . The pressure and temperature were kept constant for 10 min. The autoclave was cooled to room temperature after the hydrothermal treatment. After the specimen was taken out, the ion-exchange radical reactions were estimated and the product structures were examined. The cation- and anion-exchange resin mixture was solidified. The resultant solidified body at a 300 o C reaction condition for 10 min had a 1.0 g cm -3 density and 700 kg cm -2 compressive strength, and the weight loss did not change in distilled water for 2 weeks. On the other hand, a solidification reaction did not occur at below 250 o C when only the cation or anion was solidified, but they were decomposed. These results suggest that a mixture of cation- and anion-exchange resins causes a solidification reaction under hydrothermal hot-pressing conditions at 300 o C. (author)

Rock solidification method

International Nuclear Information System (INIS)

Nakaya, Iwao; Murakami, Tadashi; Miyake, Takafumi; Funakoshi, Toshio; Inagaki, Yuzo; Hashimoto, Yasuhide.

1985-01-01

Purpose: To convert radioactive wastes into the final state for storage (artificial rocks) in a short period of time. Method: Radioactive burnable wastes such as spent papers, cloths and oils and activated carbons are burnt into ashes in a burning furnace, while radioactive liquid wastes such as liquid wastes of boric acid, exhausted cleaning water and decontaminating liquid wastes are powderized in a drying furnace or calcining furnace. These powders are joined with silicates as such as white clay, silica and glass powder and a liquid alkali such as NaOH or Ca(OH) 2 and transferred to a solidifying vessel. Then, the vessel is set to a hydrothermal reactor, heated and pressurized, then taken out about 20 min after and tightly sealed. In this way, radioactive wastes are converted through the hydrothermal reactions into aqueous rock stable for a long period of time to obtain solidification products insoluble to water and with an extremely low leaching rate. (Ikeda, J.)

Survey of agents and techniques applicable to the solidification of low-level radioactive wastes

International Nuclear Information System (INIS)

Fuhrmann, M.; Neilson, R.M. Jr.; Colombo, P.

1981-12-01

A review of the various solidification agents and techniques that are currently available or potentially applicable for the solidification of low-level radioactive wastes is presented. An overview of the types and quantities of low-level wastes produced is presented. Descriptions of waste form matrix materials, the wastes types for which they have been or may be applied and available information concerning relevant waste form properties and characteristics follow. Also included are descriptions of the processing techniques themselves with an emphasis on those operating parameters which impact upon waste form properties. The solidification agents considered in this survey include: hydraulic cements, thermoplastic materials, thermosetting polymers, glasses, synthetic minerals and composite materials. This survey is part of a program supported by the United States Department of Energy's Low-Level Waste Management Program (LLWMP). This work provides input into LLWMP efforts to develop and compile information relevant to the treatment and processing of low-level wastes and their disposal by shallow land burial

Survey of agents and techniques applicable to the solidification of low-level radioactive wastes

Energy Technology Data Exchange (ETDEWEB)

Fuhrmann, M.; Neilson, R.M. Jr.; Colombo, P.

1981-12-01

A review of the various solidification agents and techniques that are currently available or potentially applicable for the solidification of low-level radioactive wastes is presented. An overview of the types and quantities of low-level wastes produced is presented. Descriptions of waste form matrix materials, the wastes types for which they have been or may be applied and available information concerning relevant waste form properties and characteristics follow. Also included are descriptions of the processing techniques themselves with an emphasis on those operating parameters which impact upon waste form properties. The solidification agents considered in this survey include: hydraulic cements, thermoplastic materials, thermosetting polymers, glasses, synthetic minerals and composite materials. This survey is part of a program supported by the United States Department of Energy's Low-Level Waste Management Program (LLWMP). This work provides input into LLWMP efforts to develop and compile information relevant to the treatment and processing of low-level wastes and their disposal by shallow land burial.

Pulsars in binary systems: probing binary stellar evolution and general relativity.

Science.gov (United States)

Stairs, Ingrid H

2004-04-23

Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

Simulation of continuous cast steel product solidification

Directory of Open Access Journals (Sweden)

Ardelean, E.

2007-06-01

Full Text Available Primary cooling – inside the tundish – has a great impact over the thickness of the solidified steel crust. If on exiting the tundish the crust is too thin, it can punch and break, as a result of the ferrostatic pressure exerted from the inside by the liquid steel as well as because of the weight of the molten steel. The parameters that influence the amount of dissipated heat depend on the cooling water flow of the tundish, on the pressure and temperature of the cooling water but also on the overheating of the continuously cast steel. The secondary cooling takes place at the exit of the semi-finished product from the tundish, when the solidification is supposed to take place all along the cross section of the strand. In order to achieve it, in addition to a correctly managed primary cooling, it is necessary to obtain the proper correlation of the factors that influence the secondary cooling as well: the water flow rate long the three zones of the installation and its pressure in the secondary circuit. All these have in view a proper solidification length; an intense cooling can generate cracks due to the thermal stress, while a too slow cooling can generate a partial solidification of the strand up to the cropping machine area. The paper presents a mathematical simulation of the continuously cast steel solidification.

El enfriamiento primario del cristalizador tiene una gran importancia sobre el espesor de la costra de acero solidificado. Si al salir del cristalizador, esta costra es demasiado sutil, bajo la acción de la presión ferro estática ejercitada por el acero líquido del interior y gracias el peso propio del hilo, ésta, puede perforar resultando su rompimiento. Los parámetros que influenyen sobre la cantidad de calor cedida dependen del agua de enfriamiento del catalizador, de la presión y de la temperatura de agua de enfriamiento, pero también del sobrecalentamiento del acero fundido continuamente. A la salida del

Solidification of Waste Steel Foudry Dust with Portland Cement

Czech Academy of Sciences Publication Activity Database

Škvára, F.; Kaštánek, František; Pavelková, I.; Šolcová, Olga; Maléterová, Ywetta; Schneider, Petr

B89, č. 1 (2001), s. 67-81 ISSN 0304-3894 R&D Projects: GA ČR GA104/99/0440 Institutional research plan: CEZ:AV0Z4072921; CEZ:MSM 223100002 Keywords : solidification, * foundry dust * cement Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.497, year: 2001

Matching time and spatial scales of rapid solidification: dynamic TEM experiments coupled to CALPHAD-informed phase-field simulations

Science.gov (United States)

Perron, Aurelien; Roehling, John D.; Turchi, Patrice E. A.; Fattebert, Jean-Luc; McKeown, Joseph T.

2018-01-01

A combination of dynamic transmission electron microscopy (DTEM) experiments and CALPHAD-informed phase-field simulations was used to study rapid solidification in Cu-Ni thin-film alloys. Experiments—conducted in the DTEM—consisted of in situ laser melting and determination of the solidification kinetics by monitoring the solid-liquid interface and the overall microstructure evolution (time-resolved measurements) during the solidification process. Modelling of the Cu-Ni alloy microstructure evolution was based on a phase-field model that included realistic Gibbs energies and diffusion coefficients from the CALPHAD framework (thermodynamic and mobility databases). DTEM and post mortem experiments highlighted the formation of microsegregation-free columnar grains with interface velocities varying from ˜0.1 to ˜0.6 m s-1. After an ‘incubation’ time, the velocity of the planar solid-liquid interface accelerated until solidification was complete. In addition, a decrease of the temperature gradient induced a decrease in the interface velocity. The modelling strategy permitted the simulation (in 1D and 2D) of the solidification process from the initially diffusion-controlled to the nearly partitionless regimes. Finally, results of DTEM experiments and phase-field simulations (grain morphology, solute distribution, and solid-liquid interface velocity) were consistent at similar time (μs) and spatial scales (μm).

High Temperature Heat Pump Integration using Zeotropic Working Fluids for Spray Drying Facilities

DEFF Research Database (Denmark)

Zühlsdorf, Benjamin; Bühler, Fabian; Mancini, Roberta

2017-01-01

source and sink best possibly. Therefore, a set of six common working fluids is defined and the possible binary mixtures of these fluids are analyzed. The performance of the fluids is evaluated based on the energetic performance (COP) and the economic potential (NPV). The results show...... and show a large potential to reuse the excess heat from exhaust gases. This study analyses a heat pump application with an improved integration by choosing the working fluid as a mixture in such a way, that the temperature glide during evaporation and condensation matches the temperature glide of the heat...

Directional solidification and characterization of the Al Nb2 - Al3 Nb eutectic system

International Nuclear Information System (INIS)

Trevisan, Eduardo A.O.; Andreotti, Fabio; Caram, Rubens

1996-01-01

The manufacturing of components to operate at high temperatures requires the use of metallic materials which can keep satisfactory mechanical and chemical properties, even at temperatures beyond 1000 deg C. An interesting alternative is the use of directionally solidified eutectic alloys. The eutectic alloy solidification makes possible the production of 'in situ' composite. A potentially useful system for manufacturing structural materials is the Al-Nb eutectic system. The aim of this work is to present the directional solidification of the Al-Nb eutectic alloy. (author)

Phase transformation and liquid density redistribution during solidification of Ni-based superalloy Inconel 718

Directory of Open Access Journals (Sweden)

Wang Ling

2012-08-01

Full Text Available The influences of chemical segregation and phase transformation on liquid density variation during solidification of Ni-based supperalloy Inconel 718 were investigated using SEM and EDS. It was found that significant segregation in liquid prompts high Nb phase to precipitate directly from liquid, which results in the redistribution of alloy elements and liquid density in their vicinity. The term “inter-precipitate liquid density” is therefore proposed and this concept should be applied to determine the solidification behavior of superalloy Inconel 718.

Vertical solidification of dendritic binary alloys

Science.gov (United States)

Heinrich, J. C.; Felicelli, S.; Poirier, D. R.

1991-01-01

Three numerical techniques are employed to analyze the influence of thermosolutal convection on defect formation in directionally solidified (DS) alloys. The finite-element models are based on the Boussinesq approximation and include the plane-front model and two plane-front models incorporating special dendritic regions. In the second model the dendritic region has a time-independent volume fraction of liquid, and in the last model the dendritic region evolves as local conditions dictate. The finite-element models permit the description of nonlinear thermosolutal convection by treating the dendritic regions as porous media with variable porosities. The models are applied to lead-tin alloys including DS alloys, and severe segregation phenomena such as freckles and channels are found to develop in the DS alloys. The present calculations and the permeability functions selected are shown to predict behavior in the dendritic regions that qualitatively matches that observed experimentally.

AqSo_NaCl: Computer program to calculate p-T-V-x properties in the H2O-NaCl fluid system applied to fluid inclusion research and pore fluid calculation

Science.gov (United States)

Bakker, Ronald J.

2018-06-01

The program AqSo_NaCl has been developed to calculate pressure - molar volume - temperature - composition (p-V-T-x) properties, enthalpy, and heat capacity of the binary H2O-NaCl system. The algorithms are designed in BASIC within the Xojo programming environment, and can be operated as stand-alone project with Macintosh-, Windows-, and Unix-based operating systems. A series of ten self-instructive interfaces (modules) are developed to calculate fluid inclusion properties and pore fluid properties. The modules may be used to calculate properties of pure NaCl, the halite-liquidus, the halite-vapourus, dew-point and bubble-point curves (liquid-vapour), critical point, and SLV solid-liquid-vapour curves at temperatures above 0.1 °C (with halite) and below 0.1 °C (with ice or hydrohalite). Isochores of homogeneous fluids and unmixed fluids in a closed system can be calculated and exported to a.txt file. Isochores calculated for fluid inclusions can be corrected according to the volumetric properties of quartz. Microthermometric data, i.e. dissolution temperatures and homogenization temperatures, can be used to calculated bulk fluid properties of fluid inclusions. Alternatively, in the absence of total homogenization temperature the volume fraction of the liquid phase in fluid inclusions can be used to obtain bulk properties.

New insight on glass-forming ability and designing Cu-based bulk metallic glasses: The solidification range perspective

International Nuclear Information System (INIS)

Wu, Jili; Pan, Ye; Li, Xingzhou; Wang, Xianfei

2014-01-01

Highlights: • The equation, T rg = T g /T l , was rotationally modified to T rg = κ(T m /T l ) + C/T l . • The newly generalized equation suggests a way for describing glass-forming ability. • Several new Cu-based bulk metallic glasses were discovered by solidification range. - Abstract: In this paper, a new equation was rationally generalized from the reduced glass transition temperature. This equation indicates that solidification range can be used for describing glass-forming ability, which can be calculated with the aid of computational thermodynamic approach. Based on this scenario, several new Cu-based bulk metallic glasses in the ternary Cu–Zr–Ti alloy system were discovered. The as-cast samples were characterized by X-ray diffraction and transmission electronic microscopy. The results indicate that as-cast samples have monolithic amorphous nature. Thermal analysis validates that the smaller solidification range is closely related to the higher glass-forming ability, which is contributed to the effect of solidification time on the formation of bulk metallic glasses. This work also suggests that solidus can influence glass formation

Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

Science.gov (United States)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-02-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).

Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

Science.gov (United States)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-06-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).

X-Ray Radiographic Observation of Directional Solidification Under Microgravity: XRMON-GF Experiments on MASER12 Sounding Rocket Mission

Science.gov (United States)

Reinhart, G.; NguyenThi, H.; Bogno, A.; Billia, B.; Houltz, Y.; Loth, K.; Voss, D.; Verga, A.; dePascale, F.; Mathiesen, R. H.;

Trojan Binaries

Science.gov (United States)

Noll, K. S.

2017-12-01

The Jupiter Trojans, in the context of giant planet migration models, can be thought of as an extension of the small body populations found beyond Neptune in the Kuiper Belt. Binaries are a distinctive feature of small body populations in the Kuiper Belt with an especially high fraction apparent among the brightest Cold Classicals. The binary fraction, relative sizes, and separations in the dynamically excited populations (Scattered, Resonant) reflects processes that may have eroded a more abundant initial population. This trend continues in the Centaurs and Trojans where few binaries have been found. We review new evidence including a third resolved Trojan binary and lightcurve studies to understand how the Trojans are related to the small body populations that originated in the outer protoplanetary disk.

Microwave solidification development for Rocky Flats waste

Energy Technology Data Exchange (ETDEWEB)

Dixon, D.; Erle, R.; Eschen, V. [and others

1994-04-01

The Microwave Engineering Team at the Rocky Flats Plant has developed a production-scale system for the treatment of hazardous, radioactive, and mixed wastes using microwave energy. The system produces a vitreous final form which meets the acceptance criteria for shipment and disposal. The technology also has potential for application on various other waste streams from the public and private sectors. Technology transfer opportunities are being identified and pursued for commercialization of the microwave solidification technology.

Microwave solidification development for Rocky Flats waste

International Nuclear Information System (INIS)

Dixon, D.; Erle, R.; Eschen, V.

1994-04-01

The Microwave Engineering Team at the Rocky Flats Plant has developed a production-scale system for the treatment of hazardous, radioactive, and mixed wastes using microwave energy. The system produces a vitreous final form which meets the acceptance criteria for shipment and disposal. The technology also has potential for application on various other waste streams from the public and private sectors. Technology transfer opportunities are being identified and pursued for commercialization of the microwave solidification technology

Onset of solid state mantle convection and mixing during magma ocean solidification

Science.gov (United States)

Maurice, Maxime; Tosi, Nicola; Samuel, Henri; Plesa, Ana-Catalina; Hüttig, Christian; Breuer, Doris

2017-04-01

The fractional crystallization of a magma ocean can cause the formation of a compositional layering that can play a fundamental role for the subsequent long-term dynamics of the interior, for the evolution of geochemical reservoirs, and for surface tectonics. In order to assess to what extent primordial compositional heterogeneities generated by magma ocean solidification can be preserved, we investigate the solidification of a whole-mantle Martian magma ocean, and in particular the conditions that allow solid state convection to start mixing the mantle before solidification is completed. To this end, we performed 2-D numerical simulations in a cylindrical geometry. We treat the liquid magma ocean in a parametrized way while we self-consistently solve the conservation equations of thermochemical convection in the growing solid cumulates accounting for pressure-, temperature- and, where it applies, melt-dependent viscosity as well as parametrized yield stress to account for plastic yielding. By testing the effects of different cooling rates and convective vigor, we show that for a lifetime of the liquid magma ocean of 1 Myr or longer, the onset of solid state convection prior to complete mantle crystallization is likely and that a significant part of the compositional heterogeneities generated by fractionation can be erased by efficient mantle mixing.

Experimental Study on Melting and Solidification of Phase Change Material Thermal Storage

Science.gov (United States)

Ambarita, H.; Abdullah, I.; Siregar, C. A.; Siregar, R. E. T.; Ronowikarto, A. D.

2017-03-01

Melting and solidification process of Phase Change Materials (PCMs) are investigated experimentally. The tested PCMs are Paraffin wax and Steric acid which typically used for solar water heater. The objective is to explore the characteristics of the PCM when it is being melted and solidified. The experiments are performed in a glass box. One side of the box wall is heated while the opposite wall is kept constant and other walls are insulated. Temperature of the heated wall are kept constant at 80°C, 85°C, and 90°C, respectively. Every experiment is carried out for 600 minutes. Temperatures are recorded and the melting and solidification processes are pictured by using camera. The results show that the melting process starts from the upper part of the thermal storage. In the solidification process, it starts from the lower part of the thermal storage. As a thermal energy storage, Paraffin wax is better than Steric acid. This is because Paraffin wax can store more energy. At heat source temperature of 90°C, thermal energy stored by Paraffin wax and Stearic acid is 61.84 kJ and 57.39 kJ, respectively. Thus it is better to used Paraffin wax in the solar water heater as thermal energy storage.

Two-dimensional time-resolved x-ray diffraction study of dual phase rapid solidification in steels

Science.gov (United States)

Yonemura, Mitsuharu; Osuki, Takahiro; Terasaki, Hidenori; Komizo, Yuichi; Sato, Masugu; Toyokawa, Hidenori; Nozaki, Akiko

2010-01-01

The high intensity heat source used for fusion welding creates steep thermal gradients of 100 °C/s from 1800 °C. Further, the influence of preferred orientation is important for the observation of a directional solidification that follows the dendrite growth along the ⟨100⟩ direction toward the moving heat source. In the present study, we observed the rapid solidification of weld metal at a time resolution of 0.01-0.1 s by a two-dimensional time-resolved x-ray diffraction (2DTRXRD) system for real welding. The diffraction rings were dynamically observed by 2DTRXRD with synchrotron energy of 18 keV while the arc passes over the irradiation area of the x-rays. The arc power output was 10 V-150 A, and the scan speed of the arc was 1.0 mm/s. The temperature rise in instruments was suppressed by a water-cooled copper plate under the specimen. Further, the temperature distribution of the weld metal was measured by a thermocouple and correlated with the diffraction patterns. Consequently, solidification and solid phase transformation of low carbon steels and stainless steels were observed during rapid cooling by 2DTRXRD. In the low carbon steel, the microstructure is formed in a two step process, (i) formation of crystallites and (ii) increase of crystallinity. In stainless steel, the irregular interface layer of δ/γ in the quenched metal after solidification is expected to show the easy movement of dendrites at a lower temperature. In carbide precipitation stainless steel, it is easy for NbC to grow on δ phase with a little undercooling. Further, a mistlike pattern, which differs from the halo pattern, in the fusion zone gave some indication of the possibilities to observe the nucleation and the early solidification by 2DTRXRD.

Microscopic dynamics of binary mixtures and quasi-colloidal systems

International Nuclear Information System (INIS)

Smorenburg, H.E.

1996-01-01

In the study on the title subject two questions are addressed. One is whether the microscopic dynamics of binary mixtures and quasi-colloidal systems can be understood theoretically with kinetic theories for equivalent hard sphere mixtures. The other question that arises is whether the similarity in the dynamics of dense simple fluids and concentrated colloidal suspensions also holds for binary mixtures and quasi-colloidal systems. To answer these questions, we have investigated a number of binary gas mixtures and quasi-colloidal system with different diameter ratios and concentrations. We obtain the experimental dynamic structure factors S expt (κ,ω) of the samples from inelastic neutron scattering. We compare S expt (κ,ω) with the dynamic structure S HS (κ,ω) of an equivalent hard sphere fluid, that we calculate with the Enskog theory. In chapter 2, 3 and 4 we study dense He-Ar gas mixtures (diameter ratio R=1.4, and mass ratio M=10) at low and high Ar concentrations. Experiment and kinetic theory are in good agreement. In chapter 5 we study dilute quasi-colloidal suspensions of fullerene C60 molecules dissolved in liquid CS2. The diameter ratio R=2.2 is larger than in previous experiments while the mass ratio M=9.5 is more or less the same. We obtain the self diffusion coefficient D S of one C60 molecule in CS2 and find D s ≤D SE ≤D E , with D E obtained from kinetic theory and D SE from the Stokes-Einstein description. It appears that both descriptions are relevant but not so accurate. In chapter 6 we study three dense mixtures of neopentane in 40 Ar (diameter ratio R=1.7, mass ratio M=2) at low and high neopentane concentrations. At low concentration, we find a diffusion coefficient of neopentane in Ar, which is in good agreement with kinetic theory and in moderate agreement with the Stokes-Einstein description. At high concentration the collective translational dynamics of neopentane shows a similar behaviour as in dense colloids and simple fluids

Process control of Low and Intermediate-level radioactive wastes solidification

International Nuclear Information System (INIS)

1993-01-01

Safety guidelines issued by the Spanish Council of Nuclear Safety (CSN) with basic criteria which must be adopted for the control of the Process for wastes solidification, establishing, in addition, a series of protocols and basic contents to assist the elaboration of Process Control Programs

Solidification of low-level radioactive wastes in masonry cement

International Nuclear Information System (INIS)

Zhou, H.; Colombo, P.

1987-03-01

Portland cements are widely used as solidification agents for low-level radioactive wastes. However, it is known that boric acid wastes, as generated at pressurized water reactors (PWR's) are difficult to solidify using ordinary portland cements. Waste containing as little as 5 wt % boric acid inhibits the curing of the cement. For this purpose, the suitability of masonry cement was investigated. Masonry cement, in the US consists of 50 wt % slaked lime (CaOH 2 ) and 50 wt % of portland type I cement. Addition of boric acid in molar concentrations equal to or less than the molar concentration of the alkali in the cement eliminates any inhibiting effects. Accordingly, 15 wt % boric acid can be satisfactorily incorporated into masonry cement. The suitability of masonry cement for the solidification of sodium sulfate wastes produced at boiling water reactors (BWR's) was also investigated. It was observed that although sodium sulfate - masonry cement waste forms containing as much as 40 wt % Na 2 SO 4 can be prepared, waste forms with more than 7 wt % sodium sulfate undergo catastrophic failure when exposed to an aqueous environment. It was determined by x-ray diffraction that in the presence of water, the sulfate reacts with hydrated calcium aluminate to form calcium aluminum sulfate hydrate (ettringite). This reaction involves a volume increase resulting in failure of the waste form. Formulation data were identified to maximize volumetric efficiency for the solidification of boric acid and sodium sulfate wastes. Measurement of some of the waste form properties relevant to evaluating the potential for the release of radionuclides to the environment included leachability, compression strengths and chemical interactions between the waste components and masonry cement. 15 refs., 19 figs., 9 tabs

Development of Stable Solidification Method for Insoluble Ferrocyanides-13170

Energy Technology Data Exchange (ETDEWEB)

Ikarashi, Yuki; Masud, Rana Syed; Mimura, Hitoshi [Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Aramaki-Aza-Aoba6-6-01-2, Sendai, 980-8579 (Japan); Ishizaki, Eiji; Matsukura, Minoru [UNION SHOWA K.K. 17-20, Mita 2-chome, Minato-ku, Tokyo 108-0073 (Japan)

2013-07-01

The development of stable solidification method of insoluble ferrocyanides sludge is an important subject for the safety decontamination in Fukushima NPP-1. By using the excellent immobilizing properties of zeolites such as gas trapping ability and self-sintering properties, the stable solidification of insoluble ferrocyanides was accomplished. The immobilization ratio of Cs for K{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O saturated with Cs{sup +} ions (Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O) was estimated to be less than 0.1% above 1,000 deg. C; the adsorbed Cs{sup +} ions are completely volatilized. In contrast, the novel stable solid form was produced by the press-sintering of the mixture of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O and zeolites at higher temperature of 1,000 deg. C and 1,100 deg. C; Cs volatilization and cyanide release were completely depressed. The immobilization ratio of Cs, under the mixing conditions of Cs{sub 2}[CoFe(CN){sub 6}].nH{sub 2}O:CP= 1:1 and calcining temperature: 1,000 deg. C, was estimated to be nearly 100%. As for the kinds of zeolites, natural mordenite (NM), clinoptilolite (CP) and Chabazite tended to have higher immobilization ratio compared to zeolite A. This may be due to the difference in the phase transformation between natural zeolites and synthetic zeolite A. In the case of the composites (K{sub 2-X}Ni{sub X/2}[NiFe(CN){sub 6}].nH{sub 2}O loaded natural mordenite), relatively high immobilization ratio of Cs was also obtained. This method using zeolite matrices can be applied to the stable solidification of the solid wastes of insoluble ferrocyanides sludge. (authors)

Testing the Binary Black Hole Nature of a Compact Binary Coalescence.

Science.gov (United States)

Krishnendu, N V; Arun, K G; Mishra, Chandra Kant

2017-09-01

We propose a novel method to test the binary black hole nature of compact binaries detectable by gravitational wave (GW) interferometers and, hence, constrain the parameter space of other exotic compact objects. The spirit of the test lies in the "no-hair" conjecture for black holes where all properties of a Kerr black hole are characterized by its mass and spin. The method relies on observationally measuring the quadrupole moments of the compact binary constituents induced due to their spins. If the compact object is a Kerr black hole (BH), its quadrupole moment is expressible solely in terms of its mass and spin. Otherwise, the quadrupole moment can depend on additional parameters (such as the equation of state of the object). The higher order spin effects in phase and amplitude of a gravitational waveform, which explicitly contains the spin-induced quadrupole moments of compact objects, hence, uniquely encode the nature of the compact binary. Thus, we argue that an independent measurement of the spin-induced quadrupole moment of the compact binaries from GW observations can provide a unique way to distinguish binary BH systems from binaries consisting of exotic compact objects.

EMHD micro-pumping of a non-conducting shear-thinning fluid under EDL phenomena

International Nuclear Information System (INIS)

Gaikwad, Harshad; Borole, Chetan; Basu, Dipankar N.; Mondal, Pranab K.

2016-01-01

The Electro-Magneto-Hydrodynamic (EMHD) pumping of a binary fluid system constituted by one non-conducting shear-thinning fluid (top layer) by exploiting the transverse momentum exchange through the interfacial viscous shearing effect from a conducting Newtonian fluid layer (bottom layer) in a microfluidic channel is investigated. An externally applied electric field drives the conducting fluid layer under the influence of an applied magnetic field as well. The study reveals that the volume transport of shear-thinning fluid gets augmented for low magnetic field strength, higher electrical double layer (EDL) effect, low viscosity ratio and moderate potential ratio. It is also established that the volumetric flow rate reduces significantly for the higher magnetic field strength. (author)

Binary Masking & Speech Intelligibility

DEFF Research Database (Denmark)

Boldt, Jesper

The purpose of this thesis is to examine how binary masking can be used to increase intelligibility in situations where hearing impaired listeners have difficulties understanding what is being said. The major part of the experiments carried out in this thesis can be categorized as either experime......The purpose of this thesis is to examine how binary masking can be used to increase intelligibility in situations where hearing impaired listeners have difficulties understanding what is being said. The major part of the experiments carried out in this thesis can be categorized as either...... experiments under ideal conditions or as experiments under more realistic conditions useful for real-life applications such as hearing aids. In the experiments under ideal conditions, the previously defined ideal binary mask is evaluated using hearing impaired listeners, and a novel binary mask -- the target...... binary mask -- is introduced. The target binary mask shows the same substantial increase in intelligibility as the ideal binary mask and is proposed as a new reference for binary masking. In the category of real-life applications, two new methods are proposed: a method for estimation of the ideal binary...

Light scattering from a binary-liquid entanglement gel

Science.gov (United States)

Xia, K.-Q.; Maher, J. V.

1987-09-01

Light-scattering experiments have been carried out on an entanglement gel with a binary-liquid mixture as solvent. The onset temperature for critical opalescence has a composition dependence which is similar to the coexistence curve of the free-liquid mixture. This system resembles previously reported work on the cross-linked gel polyacrylamide in two ways: (1) As temperature is lowered toward the critical temperature of the free-liquid mixture, the binary-fluid gel exhibits a strong and increasing light scattering over a broad temperature region of several kelvins, and (2) no appreciable temporal fluctuations are observed throughout this temperature region. Two added features are observed in the present, entanglement-gel measurements: (a) Gel samples with solvent composition both near and off the critical composition of the free-liquid mixture exhibit similar light-scattering behavior, and (b) a Lorentzian-squared fit to the light-scattering angular distributions yields a characteristic wave number which does not change with temperature and an amplitude which shows a very strong dependence on the temperature.

Solidification of saturated radioactive organic ion exchangers and of ash from incineration plant

International Nuclear Information System (INIS)

Timulak, J.; Krejci, F.; Pekar, A.; Gulis, G.; Breza, M.

1985-01-01

The study of bituminization of saturated radioactive organic ion exchangers was centred on finding the effect of the water content of ion exchangers on the process of solidification and on the water content of bituminization products, the optimization of temperature conditions in the process of bituminization, on seeking a suitable bitumen, on testing the radiation and thermal stability of the bituminization product, on finding its properties as well as the effects of nuclear radiation on these properties. Ion exchangers of Czechoslovak and Soviet make were used in all experiments. It was found that solidified ion exchangers must have a maximum moisture of 10%, and the temperature during solidification must not exceed 130 degC. The negative effect of boric acid on cement solidification may be removed by neutralization of esterification of this acid following its release from the ion exchangers by hydrochloric acid. Some other results of the experiments are tabulated. The obtained results describe the behaviour of the product only during a brief period of time as compared with the long time of long-term disposal. It will therefore be necessary to devote attention to finding the characteristics of long-term behaviour of products during disposal. (Z.M.)

Cement radwaste solidification studies third annual report

International Nuclear Information System (INIS)

Brown, D.J.; James, J.M.; Lee, D.J.; Smith, D.L.; Walker, A.T.

1982-03-01

This report summarises cement radwaste studies carried out at AEE Winfrith during 1981 on the encapsulation of medium and low active waste in cement. During the year more emphasis has been placed on the work which is directly related to the solidification of SGHWR active sludge. Information has been obtained on the properties of 220 dm 3 drums of cemented waste. The use of cement grouts for the encapsulation of solid items has also been investigated during 1981. (U.K.)

Interacting binary stars

CERN Document Server

Sahade, Jorge; Ter Haar, D

1978-01-01

Interacting Binary Stars deals with the development, ideas, and problems in the study of interacting binary stars. The book consolidates the information that is scattered over many publications and papers and gives an account of important discoveries with relevant historical background. Chapters are devoted to the presentation and discussion of the different facets of the field, such as historical account of the development in the field of study of binary stars; the Roche equipotential surfaces; methods and techniques in space astronomy; and enumeration of binary star systems that are studied

Interface stability during rapid directional solidification

International Nuclear Information System (INIS)

Hoglund, D.E.; Aziz, M.J.

1992-01-01

This paper reports that at the solidification velocities observed during pulsed laser annealing, the planar interface between solid and liquid is stabilized by capillarity and nonequilibrium effects such as solute trapping. The authors used Rutherford backscattering and electron microscopy to determine the nonequilibrium partition coefficient and critical concentration for breakdown of the planar interface as a function of interface velocity for Sn-implanted silicon. This allows the authors to test the applicability of the Mulliins-Sekerka stability theory to interfaces not in local equilibrium and to test the Coriell-Sekerka and other theories for oscillatory instabilities

Modélisation de la solidification par la méthode d’enthalpie

OpenAIRE

BENAMEUR, Benamar

2014-01-01

La modélisation numérique du phénomène de solidification à l’échelle macroscopique a une importance considérable dans la conception virtuelle des procédés d’élaboration des matériaux. Ce phénomène de solidification est caractérisé par la formation d’une frontière mobile qui sépare les deux phases liquide et solide au cours de changement de phase, ce qui nécessite des techniques appropriées pour suivre le mouvement de front et localiser sa position. Dans ce mémoire et afin de...

Modélisation de la solidification par la méthode d’enthalpie

OpenAIRE

BENAMEUR, Benamar

2013-01-01

La modélisation numérique du phénomène de solidification à l’échelle macroscopique a une importance considérable dans la conception virtuelle des procédés d’élaboration des matériaux. Ce phénomène de solidification est caractérisé par la formation d’une frontière mobile qui sépare les deux phases liquide et solide au cours de changement de phase, ce qui nécessite des techniques appropriées pour suivre le mouvement de front et localiser sa position. Dans ce mémoire et afin de...

Evidence of nonuniqueness and oscillatory solutions in computational fluid mechanics

International Nuclear Information System (INIS)

Nunziato, J.W.; Gartling, D.K.; Kipp, M.E.

1985-01-01

We will review some of our recent experiences in computing solutions for nonlinear fluids in relatively simple, two-dimensional geometries. The purpose of this discussion will be to display by example some of the interesting but difficult questions that arise when ill-behaved solutions are obtained numerically. We will consider two examples. As the first example, we will consider a nonlinear elastic (compressible) fluid with chemical reactions and discuss solutions for detonation and detonation failure in a two-dimensional cylinder. In this case, the numerical algorithm utilizes a finite-difference method with artificial viscosity (von Neumann-Richtmyer method) and leads to two, distinctly different, stable solutions depending on the time step criterion used. The second example to be considered involves the convection of a viscous fluid in a rectangular container as a result of an exothermic polymerization reaction. A solidification front develops near the top of the container and propagates down through the fluid, changing the aspect ratio of the region ahead of the front. Using a Galerkin-based finite element method, a numerical solution of the partial differential equations is obtained which tracks the front and correctly predicts the fluid temperatures near the walls. However, the solution also exhibits oscillatory behavior with regard to the number of cells in the fluid ahead of the front and in the strength of the cells. More definitive experiments and analysis are required to determine whether this oscillatory phenomena is a numerical artifact or a physical reality. 20 refs., 14 figs

Non azeotrope mixing refrigerating fluids condensation outside of an horizontal tubes stack; Condensation de melanges non azeotropes de fluides frigorigenes a l'exterieur d'un faisceau de tubes horizontaux

Energy Technology Data Exchange (ETDEWEB)

Signe, J.Ch.

1999-04-16

The development of non-azeotrope mixing, as regular refrigerating fluids substitute, calls in question the experience for the design of refrigerating and cooling machinery. Studies to better understand these fluids behaviour are necessary. The aim of this thesis is the knowledge enlargement on the pure fluids and non azeotrope mixing condensation, outside of a tubes stack, and to simulate the heat transfers. The tubes stack is a condenser, type TEMA X often used in refrigerating machinery. The binary mixing HFC 134a-HFC23, allows a large sliding scale. (A.L.B.)

Numerical Model for Solidification Zones Selection in the Large Ingots

Directory of Open Access Journals (Sweden)

Wołczyński W.

2015-12-01

Full Text Available A vertical cut at the mid-depth of the 15-ton forging steel ingot has been performed by curtesy of the CELSA - Huta Ostrowiec plant. Some metallographic studies were able to reveal not only the chilled undersized grains under the ingot surface but columnar grains and large equiaxed grains as well. Additionally, the structural zone within which the competition between columnar and equiaxed structure formation was confirmed by metallography study, was also revealed. Therefore, it seemed justified to reproduce some of the observed structural zones by means of numerical calculation of the temperature field. The formation of the chilled grains zone is the result of unconstrained rapid solidification and was not subject of simulation. Contrary to the equiaxed structure formation, the columnar structure or columnar branched structure formation occurs under steep thermal gradient. Thus, the performed simulation is able to separate both discussed structural zones and indicate their localization along the ingot radius as well as their appearance in term of solidification time.

A phase-field model for non-equilibrium solidification of intermetallics

International Nuclear Information System (INIS)

Assadi, H.

2007-01-01

Intermetallics may exhibit unique solidification behaviour-including slow growth kinetics, anomalous partitioning and formation of unusual growth morphologies-because of departure from local equilibrium. A phase-field model is developed and used to illustrate these non-equilibrium effects in solidification of a prototype B2 intermetallic phase. The model takes sublattice compositions as primary field variables, from which chemical long-range order is derived. The diffusive reactions between the two sublattices, and those between each sublattice and the liquid phase are taken as 'internal' kinetic processes, which take place within control volumes of the system. The model can thus capture solute and disorder trapping effects, which are consistent-over a wide range of the solid/liquid interface thickness-with the predictions of the sharp-interface theory of solute and disorder trapping. The present model can also take account of solid-state ordering and thus illustrate the effects of chemical ordering on microstructure formation and crystal growth kinetics

Solidification of Bi2Sr2Ca1Cu2Oy and Bi2Sr1.75Ca0.25CuOy

International Nuclear Information System (INIS)

Holesinger, T.G.; Miller, D.J.; Viswanathan, H.K.; Chumbley, L.S.

1993-01-01

The solidification processes for the compositions Bi 2 Sr 2 CaCu 2 O y (2212) and Bi 2 Sr 1.75 Ca 0.25 CuO y (2201) were determined as a function of oxygen partial pressure. During solidification in argon, the superconducting phases were generally not observed to form for either composition. In both cases, the solidus is lowered to approximately 750 degree C. Solidification of Bi 2 Sr 1.75 Ca 0.25 CuO y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 2-x Ca x O y (22x) and Cu 2 O while solidification of Bi 2 Sr 2 CaCu 2 O y in Ar resulted in a divorced eutectic structure of Bi 2 Sr 3-x Ca x O y (23x) and Cu 2 O. Solidification of Bi 2 Sr 1.75 Ca 0.25 CuO y in O 2 resulted in large grains of 2201 interspersed with small regions containing the eutectic structure of 22x and CuO/Cu 2 O. Solidification of Bi 2 Sr 2 CaCu 2 O y in partial pressures of 1%, 20%, and 100% oxygen resulted in multiphase samples consisting of 2212, 2201, some alkaline-earth cuprates, and both divorced eutectic structures found during solidification in Ar. For both compositions, these latter structures can be attributed to oxygen deficiencies present in the melt regardless of the overpressure of oxygen. These eutectic structures are unstable and convert into the superconducting phases during subsequent anneals in oxygen. The formation process of the 2212 phase during solidification from the melt was determined to proceed through an intermediate state involving the 2201 phase

Full Ionisation In Binary-Binary Encounters With Small Positive Energies

Science.gov (United States)

Sweatman, W. L.

2006-08-01

Interactions between binary stars and single stars and binary stars and other binary stars play a key role in the dynamics of a dense stellar system. Energy can be transferred between the internal dynamics of a binary and the larger scale dynamics of the interacting objects. Binaries can be destroyed and created by the interaction. In a binary-binary encounter, full ionisation occurs when both of the binary stars are destroyed in the interaction to create four single stars. This is only possible when the total energy of the system is positive. For very small energies the probability of this occurring is very low and it tends towards zero as the total energy tends towards zero. Here the case is considered for which all the stars have equal masses. An asymptotic power law is predicted relating the probability of full ionisation with the total energy when this latter quantity is small. The exponent, which is approximately 2.31, is compared with the results from numerical scattering experiments. The theoretical approach taken is similar to one used previously in the three-body problem. It makes use of the fact that the most dramatic changes in scale and energies of a few-body system occur when its components pass near to a central configuration. The position, and number, of these configurations is not known for the general four-body problem, however, with equal masses there are known to be exactly five different cases. Separate consideration and comparison of the properties of orbits close to each of these five central configurations enables the prediction of the form of the cross-section for full ionisation for the case of small positive total energy. This is the relation between total energy and the probability of total ionisation described above.

High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2005-2008)

DEFF Research Database (Denmark)

Fonseca, José; Dohrn, Ralf; Peper, Stephanie

2011-01-01

%) have carbon dioxide as one of the components. Information on 206 pure components, 535 ternary systems of which 355 (66%) contain carbon dioxide, 163 multicomponent and complex systems, and 207 systems with hydrates is given. A continuation of the review series is planned, covering the years from 2009...... points, the solubility of high-boiling substances in supercritical fluids, the solubility of gases in liquids and the solubility (sorption) of volatile components in polymers are included. Most of experimental data in the literature has been given for binary systems. Of the 1469 binary systems, 796 (54...

CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. I. S-TYPE BINARIES

Energy Technology Data Exchange (ETDEWEB)

Kaltenegger, Lisa [MPIA, Koenigstuhl 17, D-69117 Heidelberg (Germany); Haghighipour, Nader, E-mail: kaltenegger@mpia.de [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States)

2013-11-10

We have developed a comprehensive methodology for calculating the boundaries of the habitable zone (HZ) of planet-hosting S-type binary star systems. Our approach is general and takes into account the contribution of both stars to the location and extent of the binary HZ with different stellar spectral types. We have studied how the binary eccentricity and stellar energy distribution affect the extent of the HZ. Results indicate that in binaries where the combination of mass-ratio and orbital eccentricity allows planet formation around a star of the system to proceed successfully, the effect of a less luminous secondary on the location of the primary's HZ is generally negligible. However, when the secondary is more luminous, it can influence the extent of the HZ. We present the details of the derivations of our methodology and discuss its application to the binary HZ around the primary and secondary main-sequence stars of an FF, MM, and FM binary, as well as two known planet-hosting binaries α Cen AB and HD 196886.

CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. I. S-TYPE BINARIES

International Nuclear Information System (INIS)

Kaltenegger, Lisa; Haghighipour, Nader

2013-01-01

We have developed a comprehensive methodology for calculating the boundaries of the habitable zone (HZ) of planet-hosting S-type binary star systems. Our approach is general and takes into account the contribution of both stars to the location and extent of the binary HZ with different stellar spectral types. We have studied how the binary eccentricity and stellar energy distribution affect the extent of the HZ. Results indicate that in binaries where the combination of mass-ratio and orbital eccentricity allows planet formation around a star of the system to proceed successfully, the effect of a less luminous secondary on the location of the primary's HZ is generally negligible. However, when the secondary is more luminous, it can influence the extent of the HZ. We present the details of the derivations of our methodology and discuss its application to the binary HZ around the primary and secondary main-sequence stars of an FF, MM, and FM binary, as well as two known planet-hosting binaries α Cen AB and HD 196886

NOCHAR Polymers: An Aqueous and Organic Liquid Solidification Process for Cadarache LOR (Liquides Organiques Radioactifs) - 13195

International Nuclear Information System (INIS)

Vaudey, Claire-Emilie; Renou, Sebastien; Porco, Julien; Kelley, Dennis; Cochaud, Chantal; Serrano, Roger

2013-01-01

To handle the Very Low Level Waste (VLLW) and the Low Level Waste (LLW) in France, two options can be considered: the incineration at CENTRACO facility and the disposal facility on ANDRA sites. The waste acceptance in these radwaste routes is dependent upon the adequacy between the waste characteristics (physical chemistry and radiological) and the radwaste route specifications. If the waste characteristics are incompatible with the radwaste route specifications (presence of significant quantities of chlorine, fluorine, organic component etc or/and high activity limits), it is necessary to find an alternative solution that consists of a waste pre-treatment process. In the context of the problematic Cadarache LOR (Liquides Organiques Radioactifs) waste streams, two radioactive scintillation cocktails have to be treated. The first one is composed of organic liquids at 13.1 % (diphenyloxazol, mesitylene, TBP, xylene) and water at 86.9 %. The second one is composed of TBP at 8.6 % and water at 91.4 %. They contain chlorine, fluorine and sulphate and have got alpha/beta/gamma spectra with mass activities equal to some kBq.g -1 . Therefore, tritium is present and creates the second problematic waste stream. As a consequence, in order for disposal acceptance at the ANDRA site, it is necessary to pre-treat the waste. The NOCHAR polymers as an aqueous and organic liquid solidification process seem to be an adequate solution. Indeed, these polymers constitute an important variety of products applied to the treatment of radioactive aqueous and organic liquids (solvent, oil, solvent/oil mixing etc) and sludge through a mechanical and chemical solidification process. For Cadarache LOR, N910 and N960 respectively dedicated to the organic and aqueous liquids solidification are considered. With the N910, the organic waste solidification occurs in two steps. As the organic liquid travels moves through the polymer strands, the strands swell and immobilise the liquid. Then as the

Many-Body Effects on the Thermodynamics of Fluids, Mixtures, and Nanoconfined Fluids.

Science.gov (United States)

Desgranges, Caroline; Delhommelle, Jerome

2015-11-10

Using expanded Wang-Landau simulations, we show that taking into account the many-body interactions results in sharp changes in the grand-canonical partition functions of single-component systems, binary mixtures, and nanoconfined fluids. The many-body contribution, modeled with a 3-body Axilrod-Teller-Muto term, results in shifts toward higher chemical potentials of the phase transitions from low-density phases to high-density phases and accounts for deviations of more than, e.g., 20% of the value of the partition function for a single-component liquid. Using the statistical mechanics formalism, we analyze how this contribution has a strong impact on some properties (e.g., pressure, coexisting densities, and enthalpy) and a moderate impact on others (e.g., Gibbs or Helmholtz free energies). We also characterize the effect of the 3-body terms on adsorption isotherms and adsorption thermodynamic properties, thereby providing a full picture of the effect of the 3-body contribution on the thermodynamics of nanoconfined fluids.

Direct observation of spatially isothermal equiaxed solidification of an Al-Cu alloy in microgravity on board the MASER 13 sounding rocket

Science.gov (United States)

Murphy, A. G.; Mathiesen, R. H.; Houltz, Y.; Li, J.; Lockowandt, C.; Henriksson, K.; Melville, N.; Browne, D. J.

2016-11-01

For the first time, isothermal equiaxed solidification of a metallic alloy has been observed in situ in space, providing unique benchmark experimental data. The experiment was completed on board the MASER 13 sounding rocket, launched in December 2015, using a newly developed isothermal solidification furnace. A grain-refined Al-20 wt%Cu sample was fully melted and solidified during 360 s of microgravity and the solidification sequence was recorded using time-resolved X-radiography. Equiaxed nucleation, dendritic growth, solutal impingement, and eutectic transformation were thus observed in a gravity-free environment. Equiaxed nucleation was promoted through application of a controlled cooling rate of -0.05 K/s producing a 1D grain density of 6.5 mm-1, uniformly distributed throughout the field of view (FOV). Primary growth slowed to a visually imperceptible level at an estimated undercooling of 7 K, after which the cooling rate was increased to -1.0 K/s for the remainder of solidification and eutectic transformation, ensuring the sample was fully solidified inside the microgravity time window. The eutectic transformation commenced at the centre of the FOV proceeding radially outwards covering the entire FOV in 3 s Microgravity-based solidification is compared to an identical pre-flight ground-based experiment using the same sample and experiment timeline. The ground experiment was designed to minimise gravity effects, by choice of a horizontal orientation for the sample, so that any differences would be subtle. The first equiaxed nucleation occurred at an apparent undercooling of 0.6 K less than the equivalent event during microgravity. During primary equiaxed solidification, as expected, no buoyant grain motion was observed during microgravity, compared to modest grain rotation and reorientation observed during terrestrial-based solidification. However, when the cooling rate was increased from -0.05 K/s to -1.0 K/s during the latter stages of solidification, in

Solidification treatment of thiophene and BTEX contaminated soils

International Nuclear Information System (INIS)

Zarlinski, S.J.; Kingham, N.W.; Blevins, J.

1995-01-01

Contamination at the McColl Superfund Site, located in Fullerton, California, is due to the disposal, in pits, of spent sulfuric acid sludge from the production of aviation fuel. A treatability study was performed to evaluate the electiveness of in situ solidification treatment of materials contaminated with high concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX), as well as thiophene and other organic compounds. The contaminated materials were extremely acidic (pH<1) and had high organic and sulfur contents of greater than 70 percent and 10 percent, respectively. A total of 150 mixtures were screened to evaluate the effectiveness of 15 reagents. Based on the preliminary screening results, six mixtures were selected as being the most effective at treating the contaminated materials. Comprehensive evaluations of the candidate mixtures included (1) quantitative glovebag volatilization studies, (2) chemical characterization of the treated materials, (3) strength characterizations at multiple cure times of up to 60 days, (4) emissions monitoring of the treated materials at cure times of 7 and 14 days, and (5) the evaluation of oxidation reagents for treatment of the thiophene contamination. The treatability study demonstrated that solidification treatment is an effective alternative for remediation of the thiophene and BTEX contaminated materials

Wax solidification of drying agents containing tritiated water

International Nuclear Information System (INIS)

Mishikawa, M.; Kido, H.

1984-01-01

It is necessary to immobilize the tritium not to give any impact on the environmental biosphere because tritium may give profound effects in the metabolic pathway. One of the most probable methods of immobilizing tritium would be incorporation of tritiated water in solid forms. Any drying or dehydration technique would be effective in a tritium cleanup system for off-gas streams containing tritium or tritiated water. Commonly used drying agents such as activated alumina, silica gel, molecular sieves and calcium sulfate are of value for removal of water vapour from air or other gases. For long term tritium storage, however, these adsorptive materials should be enveloped to prevent contact with water or water vapour because the rate of leaching, evaporation or diffusion of tritium from these porous materials is so large. The beeswax solidification method of the packed bed of drying agents adsorbing tritiated water is developed in this study, where the wax solidification procedure is performed by pouring the melt of wax into the void space of the packed bed of the drying agents and successive gradual cooling. The observed values of diffusivity or permeability of tritium in the wax solidified materials are about one-thousandth of those obtained for the cement block. Effect of coating on the rate of leaching is also discussed

Crystallographic investigation of grain selection during initial solidification

International Nuclear Information System (INIS)

Esaka, H; Shinozuka, K; Kataoka, Y

2016-01-01

Normally, macroscopic solidified structure consists of chill, columnar and equiaxed zones. In a chill zone, many fine grains nucleate on the mold surface and grow their own preferred growth direction. Only a few of them continue to grow because of grain selection. In order to understand the grain selection process, crystallographic investigation has been carried out in the zone of initial solidification in this study. 10 g of Al-6 wt%Si alloy was melted at 850 °C and poured on the thick copper plate. Longitudinal cross section of the solidified shell was observed by a SEM and analyzed by EBSD. The result of EBSD mapping reveals that crystallographic orientation was random in the range of initial solidification. Further, some grains are elongated along their <100> direction. Columnar grains, whose growth directions are almost parallel to the heat flow direction, develop via grain selection. Here, a dendrite whose growth direction is close to the heat flow direction overgrows the other dendrite whose growth direction is far from the heat flow direction. However, sometimes we observed that dendrite, whose zenith angle is large, overgrew the other dendrite. It can be deduced that the time of nucleation on the mold surface is not constant. (paper)

Divorced Eutectic Solidification of Mg-Al Alloys

Science.gov (United States)

Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

2015-08-01

We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

Densities of Pb-Sn alloys during solidification

Science.gov (United States)

Poirier, D. R.

1988-01-01

Data for the densities and expansion coefficients of solid and liquid alloys of the Pb-Sn system are consolidated in this paper. More importantly, the data are analyzed with the purpose of expressing either the density of the solid or of the liquid as a function of its composition and temperature. In particular, the densities of the solid and of the liquid during dendritic solidification are derived. Finally, the solutal and thermal coefficients of volume expansion for the liquid are given as functions of temperature and composition.

Investigation on the formation of the preferred orientations in a TbDyFe alloy with directional solidification

International Nuclear Information System (INIS)

Jiang Chengbao; Xu Huibin

1999-01-01

The formation of the preferred orientations in a TbDyFe alloy was studied by transmission electron microscopy (TEM). It was found that there were several different preferred orientations in the experimental TbDyFe alloy with directional solidification. left angle 110 right angle, left angle 112 right angle and left angle 113 right angle preferred orientations were observed in this alloy solidified by our self-made super high gradient temperature directional solidification device. The preferred orientations changed with the variation of the solidification conditions. Two {111} twinning systems resulted in the left angle 110 right angle preferred orientation and a single {111} twinning system resulted in the left angle 112 right angle preferred orientation. The twinning displacement was observed and this formatted the left angle 113 right angle preferred orientation. (orig.)

Interacting binaries

CERN Document Server

Shore, S N; van den Heuvel, EPJ

1994-01-01

This volume contains lecture notes presented at the 22nd Advanced Course of the Swiss Society for Astrophysics and Astronomy. The contributors deal with symbiotic stars, cataclysmic variables, massive binaries and X-ray binaries, in an attempt to provide a better understanding of stellar evolution.

L2 droplet interaction with α-Al during solidification of hypermonotectic Al-8 wt.% Bi alloys

International Nuclear Information System (INIS)

Schaffer, P.L.; Mathiesen, R.H.; Arnberg, L.

2009-01-01

Studies of Al-based hypermonotectics have so far focused mainly on droplet motion and coagulation dynamics, with limited attention given to the interaction between droplets and the advancing solidification front which is decisive for the final distribution of the second phase within the α-Al matrix. The current work presents results from directional solidification experiments with Al-8 wt.% Bi alloys. It was found that droplets with large radii were frequently pushed and small droplets were engulfed. This is contradictory to the many models that have been proposed to explain pushing/engulfment of solid particles and can in part be ascribed to the fact that while solid-particle models only consider single, non-interacting particles that remain unaffected by solutal gradients ahead of the advancing solidification front, droplet-droplet interaction and local solute gradients have been found to be critical for droplet pushing/engulfment behaviour in hypermonotectic alloys.

The sequence of intermetallic formation and solidification pathway of an Al–13Mg–7Si–2Cu in-situ composite

Energy Technology Data Exchange (ETDEWEB)

Farahany, Saeed, E-mail: saeedfarahany@gmail.com [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Johor Bahru (Malaysia); Nordin, Nur Azmah; Ourdjini, Ali; Abu Bakar, TutyAsma; Hamzah, Esah; Idris, Mohd Hasbullah [Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 Johor Bahru (Malaysia); Hekmat-Ardakan, Alireza [École Polytechnique de Montréal, Dép. de Génie Chimique, P.O. Box 6079, Centre-ville, Montreal, Quebec H3C 3A7 (Canada)

2014-12-15

The phase transformation sequence and solidification behaviour of an Al–13Mg–7Si–2Cu in-situ composite was examined using a combination of computer-aided cooling curve thermal analysis and interrupted quenching techniques. Five different phases were identified by analysing the derivative cooling curves, the X-ray diffraction profile, optical and scanning electron microscopy images and the corresponding energy dispersive spectroscopy. It has been found that the solidification of this alloy begins with primary Mg{sub 2}Si precipitation and continues with the formation of eutectic Al–Mg{sub 2}Si, followed by Al{sub 5}FeSi and simultaneous precipitation of Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} and Al{sub 2}Cu complex intermetallic phases. The formation of the last three intermetallic compounds changes the solidification behaviour of these composites remarkably due to their complex eutectic formation reactions. The solidification of the alloy, calculated using the Factsage thermochemical analysis software, has demonstrated a good agreement with the experiments in terms of compound prediction, their weight fractions and reaction temperatures. - Highlights: • Solidification path of a commercial Al-13Mg-7Si-2Cu composite was characterized. • Five different phases were identified and then confirmed with EDS and XRD results. • Mg{sub 2}Si, Al-Mg{sub 2}Si,Al{sub 5}FeSi (β),Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) and Al{sub 2}Cu(θ) precipitated respectively. • Solidification was predicted using the Factsage thermochemical analysis software.

A coupled analysis of fluid flow, heat transfer and deformation behavior of solidifying shell in continuously cast beam blank

Energy Technology Data Exchange (ETDEWEB)

Lee, Jung Eui; Yeo, Tae Jung; Oh, Kyu Hwan; Yoon, Jong Kyu [School of Materials Science and Engineering, Seoul Nat` l Univ., Seoul (Korea, Republic of); Han, Heung Nam [Oxford Center for Advanced Materials and Composites, Department of Materials, Univ. of Oxford (United Kingdom)

1998-12-31

A mathematical model for a coupled analysis of fluid flow, heat transfer and deformation behavior in the continuously cast beam blank has been developed. The fluid flow, heat transfer and solidification in the mold region were analyzed with 3-dimensional finite difference method (FDM) based on control volume method. A body fitted coordinate system was introduced for the complex geometry of the beam blank. The effects of turbulence and natural convection of molten steel were taken into account in determining the fluid flow in the strand. The thermo-elasto-plastic deformation behavior in the cast strand and the formation of air gap between the solidifying shell and the mold were analyzed by the finite element method (FEM) using the 2-dimensional slice temperature profile calculated by the FDM. The heat flow between the strand and the mold was evaluated by the coupled analysis between the fluid flow-heat transfer analysis and the thermo-elasto-plastic stress analysis. In order to determine the solid fraction in the mushy zone, the microsegregation of solute element was assessed. The effects of fluid flow on the heat transfer, the solidification of steel and the distribution of shell thickness during the casting of the beam blank were simulated. The deformation behavior of the solidifying shell and the possibility of cracking of the strand were also investigated. The recirculating flows were developed in the regions of the web and the flange tip. The impinging of the inlet flow from the nozzle retarded the growing of solidifying shell in the regions of the fillet and the flange. The air gap between the strand and the mold was formed near the region of the corner of the flange tip. At the initial stage of casting, the probability of the surface cracking was high in the regions of the fillet and the flange tip. After the middle stage of casting, the internal cracking was predicted in the regions of the flange tip, and between the fillet and the flange tip. (author) 38

A coupled analysis of fluid flow, heat transfer and deformation behavior of solidifying shell in continuously cast beam blank

Energy Technology Data Exchange (ETDEWEB)

Lee, Jung Eui; Yeo, Tae Jung; Oh, Kyu Hwan; Yoon, Jong Kyu [School of Materials Science and Engineering, Seoul Nat`l Univ., Seoul (Korea, Republic of); Han, Heung Nam [Oxford Center for Advanced Materials and Composites, Department of Materials, Univ. of Oxford (United Kingdom)

1997-12-31

A mathematical model for a coupled analysis of fluid flow, heat transfer and deformation behavior in the continuously cast beam blank has been developed. The fluid flow, heat transfer and solidification in the mold region were analyzed with 3-dimensional finite difference method (FDM) based on control volume method. A body fitted coordinate system was introduced for the complex geometry of the beam blank. The effects of turbulence and natural convection of molten steel were taken into account in determining the fluid flow in the strand. The thermo-elasto-plastic deformation behavior in the cast strand and the formation of air gap between the solidifying shell and the mold were analyzed by the finite element method (FEM) using the 2-dimensional slice temperature profile calculated by the FDM. The heat flow between the strand and the mold was evaluated by the coupled analysis between the fluid flow-heat transfer analysis and the thermo-elasto-plastic stress analysis. In order to determine the solid fraction in the mushy zone, the microsegregation of solute element was assessed. The effects of fluid flow on the heat transfer, the solidification of steel and the distribution of shell thickness during the casting of the beam blank were simulated. The deformation behavior of the solidifying shell and the possibility of cracking of the strand were also investigated. The recirculating flows were developed in the regions of the web and the flange tip. The impinging of the inlet flow from the nozzle retarded the growing of solidifying shell in the regions of the fillet and the flange. The air gap between the strand and the mold was formed near the region of the corner of the flange tip. At the initial stage of casting, the probability of the surface cracking was high in the regions of the fillet and the flange tip. After the middle stage of casting, the internal cracking was predicted in the regions of the flange tip, and between the fillet and the flange tip. (author) 38

Continuum simulation of heat transfer and solidification behavior of AlSi10Mg in Direct Metal Laser Sintering Process

Science.gov (United States)

Ojha, Akash; Samantaray, Mihir; Nath Thatoi, Dhirendra; Sahoo, Seshadev

2018-03-01

Direct Metal Laser Sintering (DMLS) process is a laser based additive manufacturing process, which built complex structures from powder materials. Using high intensity laser beam, the process melts and fuse the powder particles makes dense structures. In this process, the laser beam in terms of heat flux strikes the powder bed and instantaneously melts and joins the powder particles. The partial solidification and temperature distribution on the powder bed endows a high cooling rate and rapid solidification which affects the microstructure of the build part. During the interaction of the laser beam with the powder bed, multiple modes of heat transfer takes place in this process, that make the process very complex. In the present research, a comprehensive heat transfer and solidification model of AlSi10Mg in direct metal laser sintering process has been developed on ANSYS 17.1.0 platform. The model helps to understand the flow phenomena, temperature distribution and densification mechanism on the powder bed. The numerical model takes into account the flow, heat transfer and solidification phenomena. Simulations were carried out for sintering of AlSi10Mg powders in the powder bed having dimension 3 mm × 1 mm × 0.08 mm. The solidification phenomena are incorporated by using enthalpy-porosity approach. The simulation results give the fundamental understanding of the densification of powder particles in DMLS process.

Eclipsing binaries in open clusters

DEFF Research Database (Denmark)

Southworth, John; Clausen, J.V.

2006-01-01

Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August......Stars: fundamental parameters - Stars : binaries : eclipsing - Stars: Binaries: spectroscopic - Open clusters and ass. : general Udgivelsesdato: 5 August...

CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. II. P-TYPE BINARIES

International Nuclear Information System (INIS)

Haghighipour, Nader; Kaltenegger, Lisa

2013-01-01

We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results

CALCULATING THE HABITABLE ZONE OF BINARY STAR SYSTEMS. II. P-TYPE BINARIES

Energy Technology Data Exchange (ETDEWEB)

Haghighipour, Nader [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii-Manoa, Honolulu, HI 96822 (United States); Kaltenegger, Lisa [MPIA, Koenigstuhl 17, Heidelberg, D-69117 (Germany)

2013-11-10

We have developed a comprehensive methodology for calculating the circumbinary habitable zone (HZ) in planet-hosting P-type binary star systems. We present a general formalism for determining the contribution of each star of the binary to the total flux received at the top of the atmosphere of an Earth-like planet and use the Sun's HZ to calculate the inner and outer boundaries of the HZ around a binary star system. We apply our calculations to the Kepler's currently known circumbinary planetary systems and show the combined stellar flux that determines the boundaries of their HZs. We also show that the HZ in P-type systems is dynamic and, depending on the luminosity of the binary stars, their spectral types, and the binary eccentricity, its boundaries vary as the stars of the binary undergo their orbital motion. We present the details of our calculations and discuss the implications of the results.

Simulating solidification in metals at high pressure: The drive to petascale computing

International Nuclear Information System (INIS)

Streitz, Frederick H; Glosli, James N; Patel, Mehul V; Chan, Bor; Yates, Robert K; Supinski, Bronis R de; Sexton, James; Gunnels, John A

2006-01-01

We investigate solidification in metal systems ranging in size from 64,000 to 524,288,000 atoms on the IBM BlueGene/L computer at LLNL. Using the newly developed ddcMD code, we achieve performance rates as high as 103 TFlops, with a performance of 101.7 TFlop sustained over a 7 hour run on 131,072 cpus. We demonstrate superb strong and weak scaling. Our calculations are significant as they represent the first atomic-scale model of metal solidification to proceed, without finite size effects, from spontaneous nucleation and growth of solid out of the liquid, through the coalescence phase, and into the onset of coarsening. Thus, our simulations represent the first step towards an atomistic model of nucleation and growth that can directly link atomistic to mesoscopic length scales

MCWASP XIV: International Conference on Modelling of Casting, Welding and Advanced Solidification Processes

International Nuclear Information System (INIS)

Yasuda, H

2015-01-01

The current volume represents contributed papers of the proceedings of the 14th international conference on ''Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP XIV)'', Yumebutai International Conference Center, Awaji island, Hyogo, Japan on 21 – 26 June, 2016. The first conference of the series 'Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP)' was started up in 1980, and this is the 14th conference. The participants are more than 100 scientists from industry and academia, coming from 19 countries. In the conference, we have 5 invited, 70 oral and 31 poster presentations on different aspects of the modeling. The conference deals with various casting processes (Ingot / shape casting, continuous casting, direct chill casting and welding), fundamental phenomena (nucleation and growth, dendritic growth, eutectic growth, micro-, meso- and macrostructure formation and defect formation), coupling problems (electromagnetic interactions, application of ultrasonic wave), development of experimental / computational methods and so on. This volume presents the cutting-edge research in the modeling of casting, welding and solidification processes. I would like to thank MAGMA Giessereitechnologie GmbH, Germany and SCSK Corporation, Japan for supporting the publication of contributed papers. Hideyuki Yasuda Conference Chairman Department of Materials Science and Engineering, Kyoto University Japan (preface)

Solidification of HLLW by glass-ceramic process

International Nuclear Information System (INIS)

Oguino, N.; Masuda, S.; Tsunoda, N.; Yamanaka, T.; Ninomiya, M.; Sakane, T.; Nakamura, S.; Kawamura, S.

1979-01-01

The compositions of glass-ceramics for the solidification of HLLW were studied, and the glass-ceramics in the diopside system was concluded to be the most suitable. Compared with the properties of HLW borosilicate glasses, those of diopside glass-ceramic were thought to be almost equal in leach rate and superior in thermal stability and mechanical strength. It was also found that the glass in this system can be crystallized simply by pouring it into a thermally insulated canister and then allowing it to cool to room temperature. 2 figures, 5 tables

Search for a solute-drag effect in dendritic solidification

International Nuclear Information System (INIS)

Eckler, K.; Herlach, D.M.; Aziz, M.J.

1994-01-01

The authors report the results of an indirect experimental test for the solute-drag effect in alloy solidification by fitting the data of Eckler et.al. for Ni-B dendrite tip velocities vs undercooling to models in several ways. The unknown equilibrium partition coefficient, k e , was varied as a fitting parameter. When they combine the dendrite growth model of Boettinger et al. with the Continuous Growth Model (CGM) of Aziz and Kaplan with solute drag, they cannot fit the data for any value of k e . When they combine dendrite growth theory with the CGM without solute drag, they obtain a reasonable fit to the data for k e = 4 x 10 -6 . When they combine dendrite growth theory with a new partial-solute-drag interpolation between the with-solute-drag and the without-solute-drag versions of the CGM, they obtain a still better fit to the data for k e = 2.8 x 10 - 4. This result points out the possibility of partial solute-drag during solidification and the importance of an independent determination of k e in order to distinguish between models

Interim solidification of SRP waste with silica, bentonite, or phosphoric acid

International Nuclear Information System (INIS)

Thompson, G.H.

1976-03-01

One option for interim waste management at the Savannah River Plant is in-tank solidification of the liquid waste solutions. This would reduce the mobility of these highly radioactive solutions until techniques for their long-term immobilization and storage are developed and implemented. Interim treatments must permit eventual retrieval of waste and subsequent incorporation into a high-integrity form. This study demonstrated the solidification of simulated alkaline waste solutions by reaction with silica, bentonite, and phosphoric acid. Alkaline waste can be solidified by reaction with silica gel, silica flour, or sodium silicate solution. Solidified products containing waste salt can be retrieved by slurrying with water. Alkaline supernate (solution in equilibrium with alkaline sludge in SRP waste tanks) can be solidified by reaction with bentonite to form cancrinite powder. The solidified waste can be retrieved by slurrying with water. Alkaline supernate can be solidified by partial evaporation and reaction with phosphoric acid. Water is incorporated into hydrated complexes of trisodium phosphate. The product is soluble, but actual plant waste would not solidify completely because of decay heat. Reaction of simulated alkaline waste solutions with silica gel, silica flour, or bentonite increases the volume by a factor of approximately 6 over that of evaporated waste; reaction with phosphoric acid results in a volume 1.5 times that of evaporated waste. At present, the best method for in-tank solidification is by evaporation, a method that contributes no additional solids to the waste and does not compromise any waste management options

[Recent advance in solidification/stabilization technology for the remediation of heavy metals-contaminated soil].

Science.gov (United States)

Hao, Han-zhou; Chen, Tong-bin; Jin, Meng-gui; Lei, Mei; Liu, Cheng-wu; Zu, Wen-pu; Huang, Li-mi

2011-03-01

Remediation of heavy metals-contaminated soil is still a difficulty and a hotspot of international research projects. At present, the technologies commonly adopted for the remediation of contaminated sites mainly include excavation, solidification/stabilization (S/S), soil washing, soil vapor extraction (SVE), thermal treatment, and bioremediation. Based on the S/S technical guidelines of Unite State Environmental Protection Agency (EPA) and United Kingdom Environment Agency (EA) and the domestic and foreign patents, this paper introduced the concepts of S/S and its development status at home and abroad, and discussed its future development directions. Solidification refers to a process that binds contaminated media with a reagent, changing the media's physical properties via increasing its compressive strength, decreasing its permeability, and encapsulating the contaminants to form a solid material. Stabilization refers to the process that involves a chemical reaction which reduces the leachability of a waste, chemically immobilizes the waste and reduces its solubility, making the waste become less harmful or less mobile. S/S technology includes cement solidification, lime pozzolanic solidification, plastic materials stabilization, vitrification, and regent-based stabilization. Stabilization (or immobilization) treatment processes convert contaminants to less mobile forms through chemical or thermal interactions. In stabilization technology, the aim of adding agents is to change the soil physical and chemical properties through pH control technology, redox potential technology, precipitation techniques, adsorption technology, and ion-exchange technology that change the existing forms of heavy metals in soil, and thus, reduce the heavy metals bioavailability and mobility. This review also discussed the S/S evaluation methods, highlighted the need to enhance S/S technology in the molecular bonding, soil polymers, and formulation of China's S/S technical guidelines.

Phase Equilibrium Calculations for Multi-Component Polar Fluid Mixtures with tPC-PSAFT

DEFF Research Database (Denmark)

Karakatsani, Eirini; Economou, Ioannis

2007-01-01

The truncated Perturbed-Chain Polar Statistical Associating Fluid Theory (tPC-PSAFT) is applied to a number of different mixtures, including binary, ternary and quaternary mixtures of components that differ substantially in terms of intermolecular interactions and molecular size. In contrast to m...

Close binary stars

International Nuclear Information System (INIS)

Larsson-Leander, G.

1979-01-01

Studies of close binary stars are being persued more vigorously than ever, with about 3000 research papers and notes pertaining to the field being published during the triennium 1976-1978. Many major advances and spectacular discoveries were made, mostly due to increased observational efficiency and precision, especially in the X-ray, radio, and ultraviolet domains. Progress reports are presented in the following areas: observational techniques, methods of analyzing light curves, observational data, physical data, structure and models of close binaries, statistical investigations, and origin and evolution of close binaries. Reports from the Coordinates Programs Committee, the Committee for Extra-Terrestrial Observations and the Working Group on RS CVn binaries are included. (Auth./C.F.)

Morphological variants of carbides of solidification origin in the rapidly solidified powder particles of hypereutectic iron alloy

International Nuclear Information System (INIS)

Kusy, M.; Grgac, P.; Behulova, M.; Vyrostkova, A.; Miglierini, M.

2004-01-01

The paper deals with the analysis of the morphological variants of solidification microstructures and vanadium rich M 4 C 3 carbide phases in the rapidly solidified (RS) powder particles from hypereutectic Fe-C-Cr-V alloy prepared by the nitrogen gas atomisation. Five main types of solidification microstructures were identified in RS particles: microstructure with globular carbides, microstructure with globular and star-like carbides, microstructure with primary carbides in the centres of eutectic colonies, microstructure with eutectic colonies without primary carbides and microstructure with eutectic spherulites. Based on the morphological features of carbide phases and the thermal history of RS particles, the microstructures were divided into two groups - microstructures morphologically affected and non-affected during the post-recalescence period of solidification. Thermophysical reasons for the morphologically different M 4 C 3 carbide phases development in the RS powder particles are discussed

Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

International Nuclear Information System (INIS)

Ahmed, Sazzad Hossain; Mian, Ahsan; Srinivasan, Raghavan

2016-01-01

In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

Science.gov (United States)

Ahmed, Sazzad Hossain; Mian, Ahsan; Srinivasan, Raghavan

2016-07-01

In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

Effect of process parameters on hardness, temperature profile and solidification of different layers processed by direct metal laser sintering (DMLS)

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Sazzad Hossain; Mian, Ahsan, E-mail: ahsan.mian@wright.edu; Srinivasan, Raghavan [Department of Mechanical and Materials Engineering, Wright State University, Dayton, Ohio 45435 (United States)

2016-07-12

In DMLS process objects are fabricated layer by layer from powdered material by melting induced by a controlled laser beam. Metallic powder melts and solidifies to form a single layer. Solidification map during layer formation is an important route to characterize micro-structure and grain morphology of sintered layer. Generally, solidification leads to columnar, equiaxed or mixture of these two types grain morphology depending on solidification rate and thermal gradient. Eutectic or dendritic structure can be formed in fully equiaxed zone. This dendritic growth has a large effect on material properties. Smaller dendrites generally increase ductility of the layer. Thus, materials can be designed by creating desired grain morphology in certain regions using DMLS process. To accomplish this, hardness, temperature distribution, thermal gradient and solidification cooling rate in processed layers will be studied under change of process variables by using finite element analysis, with specific application to Ti-6Al-4V.

Fluid flow and heat transfer modeling for castings

International Nuclear Information System (INIS)

Domanus, H.M.; Liu, Y.Y.; Sha, W.T.

1986-01-01

Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach. In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process. 14 refs., 13 figs

Sphere interaction in bounded shear flow of Oldroyd-B fluids

Science.gov (United States)

Chiu, Shang-Huan; Pan, Tsorng-Whay; Glowinski, Roland

2017-11-01

It is well-known that, up to the initial sphere displacement, binary encounters of spheres in bounded shear flow of a Newtonian fluid can have either swapping or non-swapping trajectories under creeping flow conditions. The motion of dilute sphere suspensions in bounded shear flow of Oldroyd-B fluids at zero Reynolds number has been studied. The pass and return trajectories of the two ball mass centers in a two wall driven shear flow are similar to those in a Newtonian fluid; but they lose the symmetry due to the effect of elastic force arising from viscoelastic fluids. A tumbling chain of two balls (a dipole) may occur, depending on the value of the Weissenberg number and the initial vertical displacement of the ball mass center to the middle plane between two walls. The two ball tumbling motion has also been compared with that of an ellipsoid in bounded shear flow Oldroyd-B fluids. This work was supported by NSF (Grant DMS-1418308).

Formation of bands of ultrafine beryllium particles during rapid solidification of Al-Be alloys: Modeling and direct observations

International Nuclear Information System (INIS)

Elmer, J.W.; Tanner, L.E.; Smith, P.M.; Wall, M.A.; Aziz, M.J.

1994-01-01

Rapid solidification of dilute hyper-eutectic and monotectic alloys sometimes produces a dispersion of ultrafine randomly-oriented particles that lie in arrays parallel to the advancing solidification front. The authors characterize this effect in Al-Be where Be-rich particles with diameters on the order of 10 nm form in arrays spaced approximately 25 nm apart, and they present a model of macroscopically steady state but microscopically oscillatory motion of the solidification front to explain this unusual microstructure. The proposed mechanism involves; (i) the build-up of rejected solute in a diffusional boundary layer which slows down the growing crystal matrix, (2) the boundary layer composition entering a metastable liquid miscibility gap, (3) homogeneous nucleation of solute rich liquid droplets in the boundary layer, and crystallization of these droplets, and (4) growth of the matrix past the droplets and its reformation into a planar interface. The size of the Be-rich particles is limited by the beryllium supersaturation in the diffusional boundary layer. A numerical model was developed to investigate this solidification mechanism, and the results of the model are in good agreement with experimental observations of rapidly solidified Al-5 at.% Be

Massive Black Hole Binary Evolution

Directory of Open Access Journals (Sweden)

Merritt David

2005-11-01

Full Text Available Coalescence of binary supermassive black holes (SBHs would constitute the strongest sources of gravitational waves to be observed by LISA. While the formation of binary SBHs during galaxy mergers is almost inevitable, coalescence requires that the separation between binary components first drop by a few orders of magnitude, due presumably to interaction of the binary with stars and gas in a galactic nucleus. This article reviews the observational evidence for binary SBHs and discusses how they would evolve. No completely convincing case of a bound, binary SBH has yet been found, although a handful of systems (e.g. interacting galaxies; remnants of galaxy mergers are now believed to contain two SBHs at projected separations of <~ 1kpc. N-body studies of binary evolution in gas-free galaxies have reached large enough particle numbers to reproduce the slow, “diffusive” refilling of the binary’s loss cone that is believed to characterize binary evolution in real galactic nuclei. While some of the results of these simulations - e.g. the binary hardening rate and eccentricity evolution - are strongly N-dependent, others - e.g. the “damage” inflicted by the binary on the nucleus - are not. Luminous early-type galaxies often exhibit depleted cores with masses of ~ 1-2 times the mass of their nuclear SBHs, consistent with the predictions of the binary model. Studies of the interaction of massive binaries with gas are still in their infancy, although much progress is expected in the near future. Binary coalescence has a large influence on the spins of SBHs, even for mass ratios as extreme as 10:1, and evidence of spin-flips may have been observed.

The structural and thermodynamical properties of binary ellipsoidal fluid mixture Gay-Berne interaction

Directory of Open Access Journals (Sweden)

M. Moradi

2007-06-01

Full Text Available  In this paper, a uniform classical fluid mixture comprising ellipsoidal molecules is studied. This mixture is composed of two types of ellipsoidal molecules interacting through the Gay-Berne potential with different sizes at temperature T. For this system, the Ornstein-Zernike equation using the Percus-Yevick closure relation is solved. Then the direct correlation function, pair correlation function and the pressure of the fluid at temperature T are calculated. The obtained results are in agreement with the previous theories and the results of molecular dynamic computer simulation.

Effect of liquid nitrogen flow rate on solidification of stagnant water in a horizontal tube

International Nuclear Information System (INIS)

Ibrahim, S.M.

1995-01-01

Five experiments are conducted to study the effect of liquid nitrogen flow rate on the solidification of stagnant water inside a horizontal stainless steel tube of inner diameter 19.6 cm and 12 mm thick. This tube simulates the down-comer of the nuclear reactor ET-R R-1. The apparatus design is mentioned more detail description. The results show that for the first experiment where the liquid nitrogen flow rate is 30 1/hr, the progress of solidification of water has stopped at a diameter of 12 cm. By increasing the flow rate from 30 1/hr to 40,50 and 60 1/hr, the time of freezing the water inside the tube is decreased from 86 to 67 and 60 minutes respectively. By increasing the liquid nitrogen flow rate to 70 1/hr, there is no much effect on the time of frozen. In all experiments, where the solidification is happened, the ice block formed inside the tube is subjected to a pressure of 3 at mg least, and is succeed to withstand this pressure without any leak. 7 figs

Effect of solidification parameters on mechanical properties of directionally solidified Al-Rich Al-Cu alloys

Science.gov (United States)

Çadırlı, Emin

2013-05-01

Al(100-x)-Cux alloys (x=3 wt%, 6 wt%, 15 wt%, 24 wt% and 33 wt%) were prepared using metals of 99.99% high purity in vacuum atmosphere. These alloys were directionally solidified under steady-state conditions by using a Bridgman-type directional solidification furnace. Solidification parameters (G, V and ), microstructure parameters (λ1, λ2 and λE) and mechanical properties (HV, σ) of the Al-Cu alloys were measured. Microstructure parameters were expressed as functions of solidification parameters by using a linear regression analysis. The dependency of HV, σ on the cooling rate, microstructure parameters and composition were determined. According to experimental results, the microhardness and ultimate tensile strength of the solidified samples was increased by increasing the cooling rate and Cu content, but decreased with increasing microstructure parameters. The microscopic fracture surfaces of the different samples were observed using scanning electron microscopy. Fractographic analysis of the tensile fracture surfaces showed that the type of fracture significantly changed from ductile to brittle depending on the composition.

Effect of the hypo and hyperstoichiometry of niobium about the solidification of steel with medium carbon content

International Nuclear Information System (INIS)

Kestenbach, H.-J.; Rodrigues, J.A.; Makray, E.T.

1984-01-01

The solidification sequency and the microstructure from carbon steel with 0.4%C and several content of Nb were investigated. Additions between 1 and 5% in Nb weight to obtain compositions hypo and hyperstoichiometric in relation to the niobium carbide formation were used. The metallographic observations were interpreted based in several solidifications reactions that could be occur in the iron rich region of the ternary diagram Fe-Nb-C. (E.G.) [pt

Quasi-Chemical PC-SAFT: An Extended Perturbed Chain-Statistical Associating Fluid Theory for Lattice-Fluid Mixtures.

Science.gov (United States)

Parvaneh, Khalil; Shariati, Alireza

2017-09-07

In this study, a new modification of the perturbed chain-statistical associating fluid theory (PC-SAFT) has been proposed by incorporating the lattice fluid theory of Guggenheim as an additional term to the original PC-SAFT terms. As the proposed model has one more term than the PC-SAFT, a new mixing rule has been developed especially for the new additional term, while for the conventional terms of the PC-SAFT, the one-fluid mixing rule is used. In order to evaluate the proposed model, the vapor-liquid equilibria were estimated for binary CO 2 mixtures with 16 different ionic liquids (ILs) of the 1-alkyl-3-methylimidazolium family with various anions consisting of bis(trifluoromethylsulfonyl) imide, hexafluorophosphate, tetrafluoroborate, and trifluoromethanesulfonate. For a comprehensive comparison, three different modes (different adjustable parameters) of the proposed model were compared with the conventional PC-SAFT. Results indicate that the proposed modification of the PC-SAFT EoS is generally more reliable with respect to the conventional PC-SAFT in all the three proposed modes of vapor-liquid equilibria, giving good agreement with literature data.

Recent Advances in Study of Solid-Liquid Interfaces and Solidification of Metals

Directory of Open Access Journals (Sweden)

Mohsen Asle Zaeem

2018-02-01

Full Text Available Solidification occurs in several material processing methods, such as in casting, welding, and laser additive manufacturing of metals, and it controls the nano- and microstructures, as well as the overall properties of the products[...

Solidification/stabilization of fly and bottom ash from medical waste incineration facility.

Science.gov (United States)

Anastasiadou, Kalliopi; Christopoulos, Konstantinos; Mousios, Epameinontas; Gidarakos, Evangelos

2012-03-15

In the present work, the stabilization/solidification of fly and bottom ash generated from incinerated hospital waste was studied. The objectives of the solidification/stabilization treatment were therefore to reduce the leachability of the heavy metals present in these materials so as to permit their disposal in a sanitary landfill requiring only a lower degree of environmental protection. Another objective of the applied treatment was to increase the mechanical characteristics of the bottom ash using different amounts of Ordinary Portland Cement (OPC) as a binder. The solidified matrix showed that the cement is able to immobilize the heavy metals found in fly and bottom ash. The TCLP leachates of the untreated fly ash contain high concentrations of Zn (13.2 mg/l) and Pb (5.21 mg/l), and lesser amounts of Cr, Fe, Ni, Cu, Cd and Ba. Cement-based solidification exhibited a compressive strength of 0.55-16.12 MPa. The strength decreased as the percentage of cement loading was reduced; the compressive strength was 2.52-12.7 MPa for 60% cement mixed with 40% fly ash and 6.62-16.12 MPa for a mixture of 60% cement and 40% bottom ash. The compressive strength reduced to 0.55-1.30 MPa when 30% cement was mixed with 70% fly ash, and to 0.90-7.95 MPa when 30% cement was mixed with 70% bottom ash, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.