scholarly journals Application of equilibrium phase diagrams for calculation of segregation kinetics during two-component melt cooling

2020 ◽  
Vol 63 (2) ◽  
pp. 129-134
Author(s):  
A. D. Drozin ◽  
E. Yu. Kurkina
Keyword(s):  
Liquid Phase ◽  
Equilibrium State ◽  
Cross Section ◽  
Diffusion Coefficients ◽  
Solid Phase ◽  
Equilibrium Phase ◽  
Minimum Size ◽  
Two Component ◽  
Solid Phases ◽  
Liquid And Solid Phases

According to the equilibrium state diagrams, when the melt is cooled to a certain temperature below liquidus, compositions of liquid and solid phases are uniquely determined by corresponding curves in the diagram. However, it does not happen in reality. For equilibrium (which the diagram describes), it is necessary that the melt is maintained indefinitely at each temperature, or thermal conductivity of liquid and solid phases, and the diffusion coefficients of their components, are infinitely large. We made an attempt to find out how these processes occur in reality. In this work, we consider the growth of individual crystal during cooling of a two-component melt. Mathematical model is constructed based on the following. 1. The melt area with volume corresponding to one grain, the periphery of which is cooled according to a certain law, is considered. 2. At the initial instant of time, a crystal nucleus of a certain minimum size is in the liquid. 3. At the surface of crystal, compositions of liquid and solid phases correspond to equilibrium state diagram at a given temperature on its surface. 4. Changes in temperature and composition in liquid and solid phases occur according to the laws of heat conduction and diffusion, respectively. As the melt gets cold and the crystal grows, the liquid phase is enriched in one component and depleted in another, the solid phase – on the contrary. Since the diffusion coefficients of the components in the solid phase are small, the composition of the crystal does not have time to completely equalize its cross section. The model proposed in the work allows us to study this phenomenon, to calculate for each cooling mode how the composition of the crystal will vary over its cross section. The calculations have shown that the temperature equalization occurs almost instantly, and composition of the liquid phase equalizes much slower. Equalization of the solid phase composition does not occur in the foreseeable time. The results of the work will help to improve technology of generation of alloys with an optimal structure.

scholarly journals Solid-liquid phase equilibria in the ternary systems H2O+ZnCl2+NaCl at temperatures of 298, 313 and 333 K

2021 ◽  
pp. 53-53
Author(s):  
Sevilay Demirci ◽  
Vedat Adiguze ◽  
Omer Sahin
Keyword(s):  
Liquid Phase ◽  
Phase Equilibria ◽  
Solid Phase ◽  
Ternary Systems ◽  
Viscosity Data ◽  
Isothermal Method ◽  
Chloride Water ◽  
Solid Phases ◽  
Solid Liquid ◽  
Liquid And Solid Phases

In this study, an economic separation method was suggested with the use of phase equilibria in order to ensure the recycling of ZnCl2 whose industrial waste amount is very high and to prevent it to form an environmental pollution. Sodium chloride-zinc chloride-water systems were examined with the isothermal method at temperatures of 298, 313 and 333 K. The analyses of the liquid and solid phases were used to determine the composition of the solid phase using the Schreinemakers graphic method. The solid-liquid phase equilibrium and viscosity data belonging to all ternary systems were identified and the solubility and viscosity changes with temperature were compared. The viscosity values were inversely proportional to the temperature as the amount of ZnCl2 in the solution increased. NaCl, 2NaCl ZnCl2 nH2O (n: 2, 0), ZnCl2 salts were observed at 298, 313, 333 K in the solid phases which are at equilibrium with the liquid phase at the invariant point.

scholarly journals Solid-liquid phase equilibria of (H2O-Mn(H2PO2)2-MnCl2-NaCl), (H2O-Mn(H2PO2)2-MnCl2) and (H2O-NaCl- MnCl2) systems at 323.15 K

2020 ◽  
pp. 59-59
Author(s):  
Vedat Adiguzel ◽  
Wei Liu ◽  
Asadullah Memon ◽  
Hongtao Zhou ◽  
Imran Akbar ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Phase Equilibria ◽  
Quaternary System ◽  
Invariant Point ◽  
Solid Phase ◽  
Ternary Systems ◽  
Invariant Curves ◽  
Saturation Method ◽  
Solid Liquid ◽  
Liquid And Solid Phases

The solid-liquid phase equilibria (SLE) and densities of H2O-NaCl- -MnCl2-Mn(H2PO2)2 quaternary system, H2O-NaCl-MnCl2 and H2O-MnCl2- -Mn(H2PO2)2 ternary systems were investigated at 323.15 K by the isothermal solution saturation method. The analyses of the liquid and solid phases were used to determine the composition of the solid phase using the Schreinemakers graphic method. The ternary systems contain one invariant point, two invariant curves and two crystallization regions. In the quaternary system, there is one invariant point, three invariant curves, and three crystallization areas corresponding to NaCl, MnCl2 4H2O, and Mn(H2PO2)2H2O. The crystallization area of Mn(H2PO2)2 H2O, being the largest in comparison with those of other salts, occupied 80.75 % of the total crystallization area.

scholarly journals Formation of Interfacial Reaction Layers in Al2O3/SS 430 Brazed Joints Using Cu-7Al-3.5Zr Alloys

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 990 ◽  
Author(s):  
Hoejun Heo ◽  
Hyeonim Joung ◽  
Keeyoung Jung ◽  
Chung-Yun Kang
Keyword(s):  
Liquid Phase ◽  
Interfacial Reaction ◽  
Eutectic Temperature ◽  
Liquid Phases ◽  
430 Stainless Steel ◽  
Brazed Joints ◽  
Solid Phases ◽  
Α Al2o3 ◽  
Kinetics Of ◽  
Liquid And Solid Phases

The formation of interfacial reaction layers was investigated in an α-Al2O3/430 stainless steel (SS430) joint brazed using a Cu-7Al-3.5Zr active brazing alloy. Brazing was conducted at above its eutectic temperature of 945 °C and below liquidus 1045 °C, where liquid and solid phases of the brazing alloys coexists. At 1000 °C, the liquid phase of the brazing alloy was wet onto the α-Al2O3 surface. Zr in the liquid phase reduced α-Al2O3 to form a continuous ZrO2 layer. As the dwell time increased, Zr in the liquid phases near α-Al2O3 interface was used up to thicken the reaction layers. The growth kinetics of the layer obeys the parabolic rate law with a rate constant of 9.25 × 10−6 cm·s−1/2. It was observed that a number of low yield strength Cu-rich particles were dispersed over the reaction layer, which can release the residual stress of the joint resulting in reduction of crack occurrence.

The Vibrational Spectra and Structure of Dimethyl Carbonate and its Conformational Behavior

1975 ◽  
Vol 53 (9) ◽  
pp. 1378-1386 ◽  
Author(s):  
J. E. Katon ◽  
M. D. Cohen
Keyword(s):  
Liquid Phase ◽  
Infrared Spectra ◽  
Dimethyl Carbonate ◽  
Solid Phase ◽  
Equilibrium Mixture ◽  
Vibrational Assignment ◽  
Enthalpy Difference ◽  
Oriented Polycrystalline ◽  
Phase Data ◽  
Liquid And Solid Phases

The infrared spectra of dimethyl carbonate in the liquid and solid phases and the Raman spectrum of the liquid phase are reported. The evidence suggests that dimethyl carbonate exists as an equilibrium mixture of at least two conformers in the liquid state. An experimental value for the enthalpy difference of the two conformers of 2.6 ± 0.5 kcal/mol is obtained from the temperature dependency of the infrared spectrum.Dimethyl carbonate crystallizes as an oriented polycrystalline film and polarized infrared spectra of the solid have been obtained. These have been utilized, along with the liquid phase data to obtain an improved vibrational assignment. There appears to be a solid–solid phase change in dimethyl carbonate in the vicinity of 140 K, but the details of this change are not known.

THE DISTRIBUTION OF CHLOROPHYLL IN RUMEN CONTENTS AND THE ONSET OF BLOAT IN CATTLE

1986 ◽  
Vol 66 (1) ◽  
pp. 97-102 ◽  
Author(s):  
W. MAJAK ◽  
J. W. HALL ◽  
R. E. HOWARTH
Keyword(s):  
Particulate Matter ◽  
Liquid Phase ◽  
Key Words ◽  
Rumen Fluid ◽  
Gas Production ◽  
Solid Phases ◽  
Relationship Of ◽  
The Relationship ◽  
Liquid And Solid Phases ◽  
Chlorophyll Concentrations

Chlorophyll levels in rumen contents from the dorsal and ventral sac were examined before alfalfa ingestion to determine the relationship of chloroplast particles to the onset of pasture bloat in cattle. Chlorophyll concentrations were significantly higher in cattle that subsequently bloated than in those that did not. The higher levels were observed in both the liquid and solid phases of rumen contents from cattle predisposed to bloat but the liquid phase showed a greater increase. Chlorophyll levels were uniformly distributed in the rumen with little or no difference between samples obtained from the ventral and dorsal sacs. In agreement with previous results, animals predisposed to bloat showed higher rates of gas production and greater buoyancy of particulate matter in prefeeding rumen fluid. The results suggest that chloroplast particles in the rumen have a slower rate of clearance in bloating animals than in nonbloating ones. Key words: Bloat, alfalfa, cattle, rumen, chlorophyll, chloroplast particles

Computational Model of Phase Transformations in Thermo-Chemical Cathodes Using Kinetic Approach

2012 ◽  
Vol 510-511 ◽  
pp. 9-14
Author(s):  
A.A. Kavokin ◽  
I.H. Kazmi ◽  
B. Munir
Keyword(s):  
Heat Equation ◽  
Solid Phase ◽  
State Diagram ◽  
Two Phase ◽  
One Dimensional ◽  
Self Similar Solution ◽  
Self Similar ◽  
Solid Phases ◽  
Kinetics Of ◽  
Liquid And Solid Phases

The paper presents the results of modeling of the processes of phases transformations occurring in cathode of plasmatron with zirconium insertion. Model describes temperature and liquid-solid phase transformation in cathode considering kinetics of transformation in accordance with a state diagram. The comparison between one-dimensional mathematical models was exploited for estimation of the kinetics coefficient. First model is based on well-known heat equation with Stefans condition on the free boundary between liquid and solid phases [. The standard analytical self-similar solution for two-phase case is applied. In the second model, for heat equation instead of Stefans conditions, differential equations of kinetics are used.

scholarly journals Solution of the direct alloy solidification problem including the phenomenon of material shrinkage

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 105-115 ◽  
Author(s):  
Edyta Hetmaniok ◽  
Damian Słota ◽  
Adam Zielonka
Keyword(s):  
Solid Phase ◽  
Heat Of Fusion ◽  
Solution Technique ◽  
Mass Balance Equation ◽  
Direct Alloy ◽  
Solidification Problem ◽  
Solid Phases ◽  
The Difference ◽  
Account Due ◽  
Liquid And Solid Phases

In the paper we describe the solution technique for solving the direct problem of the alloy solidifying within the casting mould with the phenomenon of material shrinkage taken into account. Due to the difference between densities of the liquid and solid phases, the shrinkage of metal often appears during the solidification. The investigated process is modeled by means of the solidification in the temperature interval basing on the heat conduction equation with the source element enclosed which includes the latent heat of fusion and the volume contribution of solid phase. Whereas the shrinkage of metal is modeled by the proper application of the mass balance equation.

scholarly journals Phases and Phase Transitions in the First Few Layers of Methane, Argon and Krypton Adsorbed on Graphite

1992 ◽  
Vol 280 ◽  
Author(s):  
David Goodstein ◽  
P. Day ◽  
M. LaMadrid ◽  
M. Lysek
Keyword(s):  
Phase Transitions ◽  
Phase Diagrams ◽  
Capillary Condensation ◽  
Equilibrium Phase ◽  
Scanning Calorimetry ◽  
Liquid Phases ◽  
Thermodynamic Measurements ◽  
Solid Phases ◽  
Liquid And Solid Phases

ABSTRACTThe equilibrium phase diagrams of monolayers of many substances adsorbed on graphite have long been studied as examples of 2-dimensional (2D) matter. One typically observes 2D gas and liquid phases, and solid phases that may be commensurate or incommensurate with the substrate lattice. Many experimental techniques have been used, but thermodynamic measurements are generally the most useful for tracing out phase boundaries.Recent advances in technique have made it possible to use thermodynamic measurements to study the phase diagrams of the second and higher layers, up to the fifth or sixth. These advances include ultra high resolution scanning calorimetry, and a detailed understanding of the role of capillary condensation in corners and pores of the graphite foam substrate. We find a rich array of phases and phase transitions in multilayer methane, argon and krypton. The second and third layers typically have distinct 2D gas, liquid and solid phases evidenced by 2D triple points and critical points. We observe phase transitions between solid phases that are commensurate and incommensurate with the layer below. We also observe melting of the first layer at higher temperatures, even when one to five additional layers are adsorbed on top of it.In argon and krypton, but not in methane, a strange new phenomenon is observed at temperatures above the gas-liquid critical point of the nth layer for n> 3. Below that temperature, nthlayer gas coexists with a condensed nth layer. At some temperature above it, a new coexistence region is observed in which a partial nth layer coexists with a partial n + 1st layer. This behavior is thought to be evidence for a theoretically predicted phase transition of the bulk interface, called the preroughening transition.

The Vibrational Spectra of Methyl Cyanoacetate and Methyl Cyanoacetate-d3

1974 ◽  
Vol 52 (17) ◽  
pp. 3057-3062 ◽  
Author(s):  
Deepali Sinha ◽  
J. E. Katon
Keyword(s):  
Liquid Phase ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Vibrational Assignment ◽  
Conformational Isomers ◽  
Solid Phases ◽  
Liquid And Solid Phases

The i.r. spectra of methyl cyanoacetate in both liquid and solid phases and of methyl cyanoacetate-d3 in the liquid phase have been recorded in the region 4000–250 cm−1. The Raman spectra of both the compounds in the liquid phase have also been recorded. A tentative vibrational assignment has been made both for the light and the heavy ester. Evidence is presented for the existence of conformational isomers in the liquid phase.

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