Investigation of Microstructure and Phase Composition of Chromic Oxide, AZS/Cr and High-alumina Refractories after Exposure of Basalt and Aluminaboronsilicate Glasses Melts

The microstructure and phase composition of high-alumina,chromic oxide,and AZS/Cr refractories containing 30%and 60%(by mass)Cr_(2)O_(3) after exposure to aluminaboronsilicate glasses and basalt melts depending on the type of melts and temperature have been studied.The mechanisms of refractory corrosion by the used melts and the factors contributing to the inhibition of corrosion development have been investigated by the method of petrographic analysis.On the basis of obtained results,the use of high-alumina,chromic oxide,and AZS/Cr refractories in the sections of glass furnace linings,experiencing the intensive impact of aluminaboronsilicate glasses and basalt melts,has been confirmed and scientifically substantiated.

Raman spectroscopy and ionic structure of Na_3AlF_(6-)Al_2O_3 melts

Raman spectrum of molten cryolite was recorded. Based on the new understanding of the scattering coefficients, contents of various structural entities in acidic NaF-AlF3 melts at 942-1 024 ℃ in previous research were reanalyzed. The new quantitative analysis results show that when cryolite ratio（CR） is less than 2, AlF4- is the dominant anion in the melts, and its mole fraction is about 0.70 for melts with CR=1.5 and 0.50 for melts with CR=2. When CR is more than 2.5, the mole fraction of AlF6^3- is relatively large, which is around 0.45 for melts with CR=2.5. Ionic structure of Na3AlF6-Al2O3 melts was investigated by UV-Raman spectroscopy. Octahedral AlF6^3- and tetrahedral AlF4- are proved to exist with possible partial replacement of F- by O^2-. Al2O2F4^2- with a large scattering coefficient also exists in the melts in which alumina concentration is more than 4% （mass fraction）. The increase of temperature causes blue-shift of the bands in the Raman spectra.

Local structure of calcium silicate melts from classical molecular dynamics simulation and a newly constructed thermodynamic model

The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Qi from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Qi were obtained, denoted as Qi-Ca-Qj and Qi-[Ob]-Qj, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.

Rheological Behavior for Polymer Melts and Concentrated Solutions——Part Ⅶ: A Quantitative Verification for the Molecular Theory of Non-linear Viscoelasticity with Entanglement Constraints in Polymer Melts

Based on the molecular theory of non-linear viscoelasticity with constrained entanglements in polymer melts, the material functions in simple shear flow were formulated, the theoretical relations between. eta((gamma) over dot), psi (10)((gamma) over dot) and shear rate ((gamma) over dot), and topologically constrained dimension number n ' and a were derived. Linear viscoelastic parameters (eta (0) and G(N)(0)) and topologically constrained dimension number (n ' a and <(<upsilon>)over bar>) as a function of the primary molecular weight (M-n), molecular weight between entanglements (M-C) and the entanglement sites sequence distribution in polymer chain were determined. A new method for determination of viscoelastic parameters (eta (0), psi (10), G(N)(0) and J(e)(0)), topologically constrained dimension number (n ', a and v) and molecular weight (M-n, M-c and M-e) from the shear flow measurements was proposed. It was used to determine those parameters and structures of HDPE, making a good agreement between these values and those obtained by other methods. The agreement affords a quantitative verification for the molecular theory of nonlinear viscoelasticity with constrained entanglement in polymer melts.

Rheological Behaviour for Polymer Melts and Concentrated Solutions Part Ⅰ:A New Multiple Reptation Model to Predict the Nonlinear Visco-elasticity with Nagai Chain Constraints in Entangled Polymer Melts

An approach of stochastically statistical mechanics and a unified molecular theory of nonlinear viscoelasticity with constraints of Nagai chain entanglement for polymer melts have been proposed. A multimode model structure for a single polymer chain with n tail segments and N reversible entanglement sites on the test polymer chain is developed. Based on the above model structure and the mechanism of molecular flow by the dynamical reorganization of entanglement sites, the probability distribution function of the end-to-end vectr for a single polymer chain at entangled state and the viscoelastic free energy of deformation for polymer melts are calculated by using the method of the stochastically statistical mechanics. The four types of stress-strain relation and the memory function are derived from this thery. The above theoretical relations are verified by the experimentaf data for various polymer melts. These relations are found to be in good agreement with the experimental results

Electrochemical codeposition of Mg-Li-Gd alloys from LiCl-KCl-MgCl_2-Gd_2O_3 melts

Mg-Li-Gd alloys were prepared by electrochemical codeposition from LiCl-KCl-MgCl 2 -Gd 2 O 3 melts on molybdenum electrode with constant current density at 823 and 973 K. The microstructure of the Mg-Li-Gd alloys was analyzed by X-ray diffraction （XRD）, optical microscopy （OM） and scanning electron microscopy （SEM）. The results show that magnesium and gadolinium deposit mainly in the first 30 min, and the alloy obtained contains 96.53% Mg, 0.27% Li and 3.20% Gd （mass fraction）. Then, the reduction of lithium ions occurs quickly. The composition of alloy can be adjusted by controlling electrolysis time or Gd 2 O 3 concentration in LiCl-KCl melts. With the addition of Gd into Mg-Li alloys, the corrosion resistance of the alloys is enhanced. XRD results suggest that Mg 3 Gd and Mg 2 Gd can be formed in Mg-Li-Gd alloys. The distribution of Gd element in Mg-Li-Gd alloys indicates that Gd element mainly distributes at the grain boundaries of Mg-Li-Gd alloys.

Electrochemical Deposition and Nucleation of Aluminum on Tungsten in Aluminum Chloride-Sodium Chloride Melts

Electrochemical deposition and nucleation of aluminum on tungsten electrode from AlCl3-NaCl melts were studied by cyclic voltammetry, chronopotentiometry and chronoamperometry. Cyclic voltammetry and chronopotentiometry analyses showed that Al （Ⅲ） was reduced at 200℃ in two consecutive steps in an electrolyte of molten AlCl3-NaCl system with a composition 52：48 molar ratio. The current-time characteristics of nucleation aluminum on tungsten showed a strong dependence on overpotentials. Chronoamperometry showed that the deposition process of aluminum on tungsten was controlled by an instantaneous nucleation with a hemispherical diffusion-controlled growth mechanism. The results could lead to a better understanding of the AlCl3-NaCl melt system that has technological importance in electrodeposition of metals as well as in rechargeable batteries.

APPLICABILITY OF THE MASS ACTION LAW IN COMBINATION WITH THE COEXISTENCE THEORY OF METALLIC MELTS INVOLVING COMPOUND TO BINARY METALLIC MELTS

Based on the atomicity and molecularity as well as the consistency ofthermodynamic properties and activities of metallic melts with their structures, the coexistencetheory of metallic melts structure involving compound has been suggested. According to this theory,the calculating models of mass action concentrations for different binary metallic melts have beenformulated. The calculated mass action concentrations agree well with corresponding measuredactivities, which confirms that the suggested theory can reflect the structural characteristics ofmetallic melts involving compound and that the mass action law is widely applicable to this kind ofmetallic melts.

Identification of structural entities in NdF_3-LiF melts with cryoscopic method

Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.

Time-dependent Diffusion Coefficient and Conventional Diffusion Constant of Nanoparticles in Polymer Melts by Mode-coupling Theory

Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa- tion is adopted to describe the diffusion dynamics. Mode-coupling theory is employed to calculate the memory kernel of friction. For simplicity, only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism. The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure. The effect of nanoparticle size and that of the polymer size are clarified explicitly. The structural functions, the friction kernel, as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length. We find that for small nanoparticles or short chain polymers, the characteristic short time non-Markov diffusion dynamics becomes more prominent, and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant. This constant due to the microscopic contributions will decrease with the increase of nanoparticle size, while increase with polymer size. Furthermore, our result of diffusion constant from mode- coupling theory is compared with the value predicted from the Stokes-Einstein relation. It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers. Inversely, when nanonparticle is big, or polymer chain is short, the hydrodynamic contribution might play a significant role.

Zircon saturation model in silicate melts:a review and update

Zircon stability in silicate melts-which can be quantitatively constrained by laboratory measurements of zircon saturation-is important for understanding the evolution of magma.Although the original zircon saturation model proposed by Watson and Harrison(Earth Planet Sci Lett 64(2):295-304,1983) is widely cited and has been updated recently,the three main models currently in use may generate large uncertainties due to extrapolation beyond their respective calibrated ranges.This paper reviews and updates zircon saturation models developed with temperature and compositional parameters.All available data on zircon saturation ranging in composition from mafic to silicic(and/or peralkaline to peraluminous)at temperatures from 750 to 1400℃ were collected to develop two refined models(1 and 2) that may be applied to the wider range of compositions.Model 1 is given by lnCZr(melt)=(14.297±0.308)+(0.964 ± 0.066).M-(11113±374)/r,and model 2 given by lnCZr(melt)=(18.99±0.423)-(1.069±0.102)·lnG-(12288±593)/T,where CZr(melt) is the Zr concentration of the melt in ppm and parameters M [=(Na+K+2 Ca)/(Al·Si)](cation ratios) and G [=(3·Al2 O3+SiO2)/(Na2-O+K2 O+CaO+MgO+FeO)](molar proportions)represent the melt composition.The errors are at one sigma,and T is the temperature in Kelvin.Before applying these models to natural rocks,it is necessary to ensure that the zircon used to date is crystallized from the host magmatic rock.Assessment of the application of both new and old models to natural rocks suggests that model 1 may be the best for magmatic temperature estimates of metaluminous to peraluminous rocks and that model 2 may be the best for estimating magmatic temperatures of alkaline to peralkaline rocks.

Melting of hydrous pyroxenites with alkali amphiboles in the continental mantle:1.Melting relations and major element compositions of melts

Melting experiments on ultramafic rocks rich in the hydrous minerals phlogopite or phlogopite+K-rich terite,some including 5%of accessory phases,have been conducted at 15 and 50 kbar.The assemblages represent probable source components that contribute to melts in cratonic regions,but whose melt compositions are poorly known.A main series of starting compositions based on MARID xenoliths consisted of a third each of clinopyroxene(CPX),phlogopite(PHL)and K-richterite(KR)with or without 5%ilmenite,rutile or apatite.Additional experiments were run without KR and with higher proportions of accessory phases.Melt traps were used at near-solidus temperatures to facilitate accurate analysis of wellquenched melts,for which reversal experiments demonstrate equilibrium.Results show that KR melts rapidly and completely within 50°C of the solidus,so that melts reflect the composition of the amphibole and its melting reaction.Melts have high SiO_(2) and especially K_(2)O but low CaO and Al_(2)O_(3) relative to basaltic melts produced from peridotites at similar pressures.They have no counterparts amongst natural rocks,but most closely resemble leucite lamproites at 15 kbar.KR and PHL melt incongruently to form olivine(OL)and CPX at 15 kbar,promoting SiO2 contents of the melt,whereas orthopyroxene OPX is increasingly stable at lower lithosphere pressures,leading to an increase in Mg O and decrease in SiO_(2) in melts,which resemble olivine lamproites.Melts of mica pyroxenites without KR are richer in CaO and Al_(2)O_(3) and do not resemble lamproites.These experiments show that low CaO and Al_(2)O_(3) in igneous rocks is not necessarily a sign of a depleted peridotite source.Accessory phases produce melts exceptionally rich in P_(2)O_(5) or TiO_(2) depending on the phases present and are unlike any melts seen at the Earth’s surface,but may be important agents of metasomatism seen in xenoliths.The addition of the 5%accessory phases ilmenite,rutile or apatite result in melting temperatures a few ten of degrees lower;at least two of these appear essential to explain the compositions of many alkaline igneous rocks on cratons.Melting temperatures for CPX+PHL+KR mixtures are close to cratonic geotherms at depths>130 km:minor perturbations of the stable geotherm at>150 km will rapidly lead to 20%melting.Melts of hydrous pyroxenites with a variety of accessory phases will be common initial melts at depth,but will change if reaction with wall-rocks occurs,leading to volcanism that contains chemical components of peridotite even though the temperature in the source region remains well below the melting point of peridotite.At higher temperatures,extensive melting of peridotite will dilute the initial alkaline melts:this is recognizable as alkaline components in basalts and,in extreme cases,alkali picrites.Hydrous pyroxenites are,therefore,components of most mantle-derived igneous rocks:basaltic rocks should not be oversimplified as being purely melts of peridotite or of mixtures of peridotite and dry pyroxenite without hydrous phases.

Rheological Behaviour for Polymer Melts and Concentrated SolutionsPart Ⅱ: Material Function with Nagai Chain Constraints and Determination of Their Parameters from Flow Curves

An integral constitutive equation and a set of material functions for describing the strain history of polymer melts were formulated in terms of the Cauchy-Green and Finger tensors. A simple memory function and the dependence of ηo and τt on M3.4 were derived from the theory of non-linear viscoelasticity with constraints of entanglements for polymer melts and substituted into the Oldroye-Walters-Fredickson constitutive equation. An integral constitutive equation for polymer melts was consequently obtained. Some material functions of the constitutive equation related to certain 'test flow' are examined as follows : (1) simple steady shear flow; (2) steady elongation flow; (3) small-amplitude oscillatory shear flow; (4) stress growth upon the inception of steady shear elongation flow; (5) stress relaxation (modulus and compllance). These theoretical relations for simple steady shear flow were compared with experimental data from our laboratory and references for various polymer melts and concentrated solutions. A good agreement between the theory and experiment was achieved.

Electrochemical process for recovery of metallic Mn from waste LiMn_(2)O_(4)-based Li-ion batteries in NaCl−CaCl_(2)melts

new method is proposed for the recovery of Mn via the direct electrochemical reduction of LiMn_(2)O_(4) from the waste of lithium-ion batteries in NaCl−CaCl_(2) melts at 750°C.The results show that the LiMn_(2)O_(4) reduction process by the electrochemical method on the coated electrode surface occurs in three steps:Mn(IV)→Mn(III)→Mn(II)→Mn.The products of this electro-deoxidation are CaMn2O4,MnO,(MnO)x(CaO)1−x,and Mn.Metal Mn appears when the electrolytic voltage increases to 2.6 V,which indicates that increasing the voltage may promote the deoxidation reaction process.With the advancement of the three-phase interline(3PI),electric deoxygenation gradually proceeds from the outer area of the crucible to the core.At high voltage,the kinetic process of the reduction reaction is accelerated,which generates double 3PIs at different stages.

Calculation Models of Mass Action Concentrations for Metallic Melts Involving Monotectic

Based on the phase diagrams, measured activities as well asDeltaG(m) and DeltaG(xs), calculating models of mass action concentrations for metallic melts involving monotectic have been formulated. The calculated results agree with practice on the whole, showing that the models deduced generally can reflect the structural characteristics of these melts. The metastable compounds formed in the melts are of the types A(2)B(3), AB(2), A(2)B(3) or AB and A(2)B(3)+AB etc..

Microstructures and Corrosion Resistance of Al_2O_3-C Based Refractories to the Melts Containing Titania

The corrosion resistance of the Al2O3-C based refractories in melts containing titania has been studied by quasi-station immersion and rotary immersion. The corrosionrate is decreased with the addition of graphite carbon, and ZrO2 in the refractories . The corrosion, mechanism of Al2O3-C refractories, is. the oxidization of graphite carbon by the oxides of the melts the formation of deteriorate layer, For the Al2O3-C-ZrO2 refractories, the corrosion behavior is due to the, interaction between melts and refractories . The new compounds of FeO. SiO2, SiZrO4, FeO. 3 CaO, 2CaO. SiO2 and CaO. SiO2 are formed in the deteriorate layer.

AN IRREVERSIBILITY PHENOMENA IN ELECTRICAL CONDUCTIVITY OF THE MELTS IN SODIUM IRON PHOSPHATE SYSTEM

Theelectricalresistivityofsodium iron phosphate melts wasinvestigated asa functionoftem peratureand composition. Irreversibility was found in thetemperature dependent electricalresistivityinthe melts withlow Na2 Ocontentduringtheheating andcoolingcycle. Theirre versibility wasreduced withincreasing Na2 Ocontent. Theelectricalresistivity tendedto de creaseslightly withtime. Theelectricalconduction ofthe meltscontainingsimulatedindustry waste wassimilartothatofthe melts withsimilarsodacontent. Thetemperature dependent electricalresistivity and activation energy ofthese melts was discussed using the Motttheory and wascorrelatedtothe Fe(II) contentinthe melts

MODELING THE CHAIN CONFORMATION OF POLYMER MELTS IN CONTRACTION FLOW

A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction now.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocityprofiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction byusing the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation ofpolymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simpleshear flow, extensional flow, vortical flow, and mixed flow respectively.

Graphite Nucleation in Cast Iron Melts Based on Solidification Experiments and Microstructure Simulation

Microstructure strongly influences the mechanical properties of cast iron. By inoculating the melt with proper inoculants, foreign substrates are brought into the melt and eventually the graphite can crystallize on them. The elements and substrates that really play a role for nucleation are yet unknown. Until now there is very little knowledge about the fundamentals of nucleation, such as composition and morphology of nuclei. In this work we utilized EN-GJL-200 as a base material and examined several produced specimens. The specimens were cast with and without inoculants and quenched at different solidification states. Specimens were also examined with a high and low oxygen concentration, but the results showed that different oxygen contents have no influence on the nucleation in cast iron melts. Our research was focused on the microscopic examination and phase-field simulations. For studying the samples we applied different analytical methods, where SEM-EDS, -WDS were proved to be most effective. The simulations were conducted by using the software MICRESS, which is based on a multiphase-field model and has been coupled directly to the TCFE3 thermodynamic database from TCAB. On the basis of the experimental investigations a nucleation mechanism is proposed, which claims MnS precipitates as the preferred site for graphite nucleation. This theory is supported by the results of the phase-field simulations.

A RHEOLOGICAL MODEL FOR POLYMER MELTS WITH INTERNAL STRUCTURE IN FLOW FIELDS

Conceptually, an imagined conformation ellipsoid is supposed to represent the shape of a polymer chain for polymer melts in flow fields and to be equivalent to the volume element in a mathematical sense in continuum mechanics. A power law dependence of shear modulus of polymer melts on detC, referred to as envelope volume, is proposed. Based on those assumptions and the non-linear relation of shear modulus, a phenomenological viscoelastic model is derived. The model is tested in simple shear flow, simple elongational flow, oscillatory shear flow, and relaxation process after flow suddenly stopped. The results show that the model works well to predict the change of internal structure and viscoelastic performance of polymer melts in flow fields.