Oxide Melt Research Articles

Modeling the viscosity of silicate melts containing Fe oxide: Fe saturation condition

Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing iron oxide. In the present study, the viscosity experimental data under the reduced atmosphere, which is Fe saturation condition were critically reviewed and three pairs of adjustable model parameters related to ‘FeO’ were optimized to best reproduce all experimental data in the FeO–SiO2–Al2O3–CaO–MgO–Na2O–MnO–Ti2O3–TiO2 system. The viscosities of a wide compositional and temperature range of binary, ternary and multicomponent melts were well reproduced by the present model within the scatter of experimental data.

From melt to crystals: The effects of cooling on Fe[sbnd]Ti oxide nanolites crystallisation and melt polymerisation at oxidising conditions

The state and properties of magma are crucial controls on the eruptive behaviour of volcanic systems. Nowhere is the importance of the link between the state and properties more dramatically expressed than in the rheology of multiphase magmatic systems, and it is magma rheology in turn that exerts a primary control on eruption style. Magmas ascending to shallow levels are subjected to decompression that leads to volatile loss and melt viscosity increase as well as the nucleation and growth of microlites and nanolites. Yet the effects of nanolites on magma rheology have only been investigated to date in a reconnaissance fashion. In order to better constrain the influence of cooling on FeTi oxide nanolite crystallisation and silicate melt structure, we conducted magma cooling experiments at controlled cooling rates of 0.1 − 50 K min−1. All experiments were run in air at 1 bar on a Fe-rich rhyolitic magma at superliquidus starting conditions. We analysed the resultant glasses via micro-Raman spectrometry to monitor the structural changes in the melt induced during the transition from a crystal-free melt to a nanolite-bearing magma, as well as the process of nanolite crystallisation itself. The Raman spectral data indicate that nanolite formation together with a concomitant increase in melt polymerisation occur at cooling rates of 0.5 K min−1 or less. The timescales for nanolite formation are estimated to be on the order of 104s for both dynamic crystallisation and isothermal crystallisation. Our experimental results, obtained at oxidising conditions and slow cooling rates, provide insights into the formation of FeTi oxide nanolites and structural changes of silicate melts that can also be observed and are expected in equivalent natural volcanic systems. The higher degree of melt polymerisation and the higher load of crystals both due to the formation of nanolites in Fe-rich rhyolites are likely to cause increases in the magma viscosity. In addition the nanolites likely provide sites for heterogeneous bubble nucleation in these degassing magmas. Taken together these effects may have the potential to shift shallow magmas from an effusive eruption style into conditions favourable for an explosive eruption.

Expansion of Temperature Range Showing Low Frictional Properties in TiB<sub>2</sub>-MoS<sub>2</sub> Composite Films

The TiB2-MoS2 composite films had been produced by DC magnetron sputtering for developing new lubricious films used at high temperatures. The composite films had excellent frictional properties with a friction coefficient of about 0.07 at R.T. even in dry conditions. Furthermore, the friction coefficients of the composite films became as low as 0.01 at 200 ˚C, although those of TiN-MoS2 composite films were above 0.2 at high temperatures. However, the frictional properties of the TiB2-MoS2 composite films deteriorated due to desorption of B by heating above 500 ˚C. Therefore, it was required to improve the frictional properties at above 500 ˚C for applying them to sliding parts used at high temperatures. In this study, B was excessively added to the composite films in order to prevent the desorption of B in heat treatments of 500 ˚C. The TiB4.4-MoS2 composite films showed a low friction coefficient of 0.03 at 200 ˚C and the excellent wear properties were maintained after heating at 500 ˚C. The formation and melting of boron oxide on the sliding surface was thought to be a reason for the low friction coefficients even after heating at 500 ˚C.

A model for multicomponent diffusion in oxide melts

A general flux equation for multicomponent diffusion in oxide melts is presented. An explicit method was developed to calculate the gradients of single-ion activities from those of oxides with the constraints of local equilibrium and electroneutrality. This resolves ambiguity in quantifying the thermochemical driving force for ionic diffusion. A model equation for multicomponent ionic diffusion was derived within the framework of non-equilibrium thermodynamics by de Groot and Mazur. The proposed model takes empirically measurable quantities as input variables, so the diffusion calculations are consistent with thermochemical data, as furnished by the CALPHAD (CALculation of PHAse Diagrams) method, as well as ionic mobility measurements. Although the model is derived for oxides, it can be applied to diffusion in other concentrated liquid electrolytes, such as chloride and fluoride melts. Formulas for multicomponent ionic diffusion in various reference frames are presented with respect to mole fraction.

Kinetic fragility of pure TeO2 glass

Pure TeO2 glass was prepared in a flash differential scanning calorimeter by applying fast quenching rates to a TeO2 melt. Matching cooling and heating rates of up to 30,000 K s−1 were then used to determine the respective fictive temperatures, corresponding to viscosity values as low as 105.3 Pa s. The interdependence between calorimetric data and viscosity was verified and fine-tuned for this compositional system utilizing sodium tellurite glasses. The fragility index of pure TeO2 (m = 64) is by far the highest reported for a single-component oxide melt.

Цифровое моделирование электромагнитных процессов в технологических индукционных устройствах

Development of an electrical calculation method plays the leading role in simulating induction devices. In modeling electrical devices and complexes, it is often necessary to simultaneously solve both chain and field problems, i.e., to deal with both lumped and distributed parameters. The article considers the method of integral equations for induction systems with non-magnetic and ferromagnetic loading, which is based on the theory of long-range action. The method’s key statement is that the field at any point is determined as the sum of the fields produced by all sources, including primary and secondary ones. Another finite element method is based on the theory of short-range action, which describes the electromagnetic wave propagation from point to point, its refraction and reflection at the boundaries of media. The article substantiates the development of a combined method based on using the method of integral equations for calculating the input parameters of inductors (an external problem) and the finite element method for calculating the field distribution in the load (an internal problem). The combined method has well proven itself in modeling induction heating and melting of metals and oxides, heating a tape in a transverse magnetic field, induction plasmatrons, and casting aluminum into an electromagnetic crystallizer.

Synthesis of Lanthanum Hexaboride in a Chloride–Oxide Melt

We have demonstrated the feasibility of lanthanum hexaboride powder synthesis from a chloride–oxide melt via electrochemical codeposition of its components on an inert cathode. The synthesis temperature, electrolyte composition, and current density have been optimized. The phase composition of the synthesized powder has been determined by X-ray diffraction. Using scanning electron microscopy, the powder has been shown to have cubic morphology and its particle size has been determined. The particle size distribution of the powder has been determined by particle size analysis.

A New Class of Entropy Stabilized Oxides: Commensurately Modulated A <sub>6</sub>B <sub>2</sub>O <sub>17</sub> (A = Zr, Hf, B = Nb, Ta) Structures

High entropy oxides (HEOs) have experienced a meteoric rise in the past decade. Here, we report a new class of entropy stabilized A6B2O17 (A = Zr, Hf; B = Nb, Ta) oxides whose enthalpies of formation have been determined by high temperature oxide melt solution calorimetry. All four compounds have endothermic enthalpies of formation from binary oxides (AO2 and B2O5), indicating that these modulated phases are entropy stabilized. The unfavorable energetics of formation are counterbalanced by large configurational entropy arising from cation disorder. The calculated configurational entropy per formula unit for A6B2O17 is 4.50R J/mol·K, which is ~2.8 times higher than the maximum configurational entropy value of 1.61R for an equimolar five cation containing “high entropy oxide”. Based on X-ray and neutron diffraction data, measured enthalpies of formation and calculated configurational entropies, one can infer that all four compounds have a high degree of disorder.

Thermodynamic Modeling of Iron and Nickel Reduction from B2O3-CaO-FeO-NiO Melts


 
 
 At present, during solving theoretical and applied problems of metallurgical technologies improving, thermodynamic modeling (TDM) methods are widely used to calculate multicomponent and multiphase systems. However, existing methodology TДM are intended for the balance analysis in the ”closed” systems. The authors of [9] proposed a technique that allows, using TDMs, to describe metal reduction processes during gas bubbling of multicomponent oxide melts in approximation to “open” real systems. The applicability of the methods is estimated using the example of joint Nickel and Iron reduction modeling in the B2O3-CaO-FeO-NiO system by Carbon monoxide for ”open” and ”closed” systems. The data obtained comparison for ”open” and ”closed” systems show that the consecutive output of products (gas and metal) from working medium promotes achievement of the best parameters for Nickel extraction to alloy and to its residual content in oxide melt. Using this technique, the TДM process of joint reduction of Nickel and Iron in system B2O3-CaO-FeO-NiO by Carbon monoxide in ”open” system was undertaken at various temperatures in the 1273-1773K interval.
 Keywords: thermodynamic modeling, ”closed” system, ”open” system, joint reduction, Carbon monoxide, oxide melt, gas bubbling
 
 

Radiation damage and thermal annealing in tunnel structured hollandite materials

Three tunnel structured hollandite samples (Cs1.33Ga1.33Ti6.67O16, Cs1.33Fe1.33Ti6.67O16, and Cs1.33Zn0.67Ti7.33O16) with demonstrated thermodynamic stability and chemical durability were synthesized and irradiated by a 1.1 GeV Au ion beam in order to study effects of B-site dopants on radiation stability. A crystalline-to-amorphous transformation induced by the high-energy ion irradiation was confirmed by complementary characterization techniques sensitive to different length-scales, such as powder X-ray diffraction, Raman spectroscopy and neutron total scattering. High-temperature oxide melt solution calorimetry was performed to determine the energy landscape before and after ion irradiation. Together, structural and thermodynamic analyses demonstrated distinctly different radiation responses of the hollandite with different B-site dopants; the Ga-substituted hollandite exhibited the smallest enthalpy of damage indicating the best radiation stability among the three samples. The hypothesized origin of the different radiation responses is the structural feature in the binary oxide form of the respective B-site dopants (e.g., Ga2O3versus Fe2O3/ZnO for Ga and Fe/Zn dopants, respectively). Moreover, thermal analysis (i.e., differential scanning calorimetry) was conducted to investigate structural changes from the irradiation induced damaged states after thermal annealing. Results of thermal analysis revealed that the annealing-induced structural evolution of the radiation damaged hollandite structure is complex and decoupled at different length-scales. The long-range periodic structure (nanometers) was not recovered after thermal annealing and structural changes over a shorter range (≤ ∼3 Å) occurred in multiple steps during the annealing process.

Thermodynamic analysis on tin precipitation behavior in Ti-bearing peritectic steel after magnesium treatment

TiN, which is ubiquitous in Ti-bearing steel, has a critical influence on both the mechanical properties and the welding process of steel, and therefore researche on the precipitation behavior of TiN in molten steel bath is of great significance. In this paper, Ti-bearing peritectic steel was taken as the study object and FactSage was adopted to explore how the precipitation behavior of typical inclusions in steel was affected by the steel composition. Furthermore, microsegregation models were used to analyze the precipitation process of TiN at solidification front, and the calculation results were finally verified by scanning electron microscope (SEM). Research showed that a multitude of dispersed particles of high melting oxide MgAl2O4 or MgO always existed in molten steel after magnesium treatment. In consideration of the segregation and enrichment of solute elements at the solidification front, the Ohnaka microsegregation model was employed to compute the precipitation during solidification. In the event of the solid fraction reaching 0.95 or more, the concentration product of [Ti][N] at the solidification front exceeded the equilibrium concentration product, then TiN began to precipitate. MgO or MgAl2O4 cores were generally found in TiN particles of peritectic steel after the magnesium treatment, which was consistent with the thermodynamic calculation results. Moreover, the average size of TiN particles was reduced by approximately 49%. This demonstrated that Mg-rich high melting inclusions were formed after the magnesium treatment, by which the heterogeneous nucleation of TiN was promoted it; therefore, favorable nucleation sites were provided for further refining the high-temperature ferrite phase.

Oxide Sensor Development By Square Wave Voltammetry for Molten Fluoride Salts

A fundamental understanding of oxide concentration is critical for operation of advanced nuclear reactors which use molten salts. Molten fluoride salts have been proposed as fuel solvents, coolants, and tritium breeding blankets in fission and fusion nuclear reactors due to their high temperature operation and favorable neutron-interaction properties. An electrochemical sensor which can measure the real-time concentration of oxide anions in the salt melt could be used to identify air ingress to the system. Additionally, similar electrochemical analyses used in the development of a sensor could be used to study the fundamental properties and behavior of oxides in molten fluoride salts. These properties include the activity coefficient, diffusion coefficient, and solubility of oxides. Understanding of these properties could, in turn, inform sensor development.A further understanding salt chemistry can also help predict and control the effects of oxide concentration on salt corrosion. Material integrity under exposure to high-temperature molten salts is an impactful technical challenge for the design of nuclear reactors that employ molten salts. Oxide anion concentration and complexation of cations and anions in the melt can influence corrosion. Therefore, electrochemical oxide sensors for molten fluoride salts would be instrumental in corrosion studies. Fundamental understanding of oxide chemistry in fluorides would also advance understanding of corrosion mechanisms in fluoride salts.Cyclic voltammetry, square wave voltammetry, and chronopotentiometry have been previously used to study the electrochemical behavior of oxides in fluoride salt melts. Square wave voltammetry (SWV) is particularly useful in this application because it limits the noise caused by oxygen bubbling from the oxidation of O2- anions, as found by Massot et al.. Titrations of known additions of oxide to the melt have previously been used to show that the intensity of the SWV oxide oxidation peak is linear with oxide concentration.Oxides have yet to be studied electrochemically in 2LiF-BeF2 (FLiBe) or LiF-NaF-KF (FLiNaK) molten salts, which are of interest for nuclear reactors. FLiBe is a likely coolant and solvent candidate for molten salt nuclear reactors. FLiNaK has been studied as a surrogate salt with similar thermo-physical properties to FLiBe. It is easier to handle experimentally since it presents no beryllium health hazard, but its chemical and neutronic behavior are different. FLiNaK is often used in salt loops for reactor design, safety analysis, component testing, and corrosion testing. Therefore, availability of oxide electrochemical sensors for FLiBe and FLiNaK would be instrumental in reactor operation as well as reactor development.This talk will summarize the application of SWV to quantification of oxides in FLiBe and FLiNaK melts. It will also discuss the available chemical and thermodynamic information for oxides in FLiBe and FLiNaK. Ultimately, an understanding of oxide behavior and a quantification of oxide concentration in molten fluoride salts will aide in the development of an electrochemical sensor for detecting leaks in molten salt reactors.

Solubility of Rare Earth Oxides in Fused Alkali and Alkaline Earth Halides

Melts based on mixtures of alkali and/or alkaline earth halides are considered as prospective media for electrowinning rare earth metals as well as for pyrochemical reprocessing spent nuclear fuels. Fluoride or mixed fluoride-chloride baths can be operated at high temperatures yielding molten rare earth metals (REMs) thus simplifying separation of the metal and salt. One of the problems in using fluoride melts is possible formation of fluorine at the anode. This can be avoided by adding a rare earth oxide to the melt both as the source of REM and oxide ions. The latter will be oxidized to oxygen producing carbon mono- or dioxide at the anode. The limiting factor for feeding the electrolysis bath with REM oxides is their solubility in the halide melt.The aim of the present study was determining the effect of temperature and melt composition on solubility of REM oxides in fused halides. The experiments were performed in CaCl2–CaF2 mixtures containing 20 or 75 mol. % CaF2; BaCl2–BaF2 mixtures containing 15 or 73 mol. % BaF2; equimolar CaF2–BaF2 mixture and NaCl–NaF eutectic mixture (34 mol. % NaF). Solubility of REM oxides was determined by the method of isothermal saturation. Time required for reaching the equilibrium between solid REM oxides and fused salts was determined in a preliminary set of experiments. To compare the behavior of 4f- and 5f-elements, solubility of uranium dioxide was also measured.The measurements were performed at the temperatures up to 1400 oC under argon atmosphere. The lower limit of the temperature range varied from 700 to 1100 oC depending on the melting temperatures of the salt mixtures used. Oxides of yttrium, lanthanum, cerium, praseodymium, neodymium and samarium were selected for the study. To assess a possible mutual influence of rare earth elements on solubility of their oxides in fused salts the solubility of a mixture of REM oxides was determined in a separate series of experiments and concentrations of individual REMs in the melt was determined.Solubility of REM oxides increased with increasing temperature and an example of effect of temperature on solubility of neodymium oxide in various melts is shown in Fig.Fig. Concentration of neodymium in alkali and alkaline halide based melts saturated with Nd2O3. Melt: CaCl2–CaF2 20 mol. % (1); CaCl2–CaF2 75 mol. % (2); BaCl2–BaF2 73 mol. % (3); BaCl2–BaF2 15 mol. % (4); CaF2–BaF2 50 mol. % (5; and NaCl–NaF 34 mol. % (6). Figure 1

Heat Transfer in Induction Melting of Aluminum Oxide in Cold Crucible

Abstract This article aims to explain the mechanism of heat transfer between melt and cold crucible (CC) in processes referred to as induction skull melting (ISM). Several experiments were performed for this purpose. In these experiments, all relevant electrical and mechanical quantities that affect the heat transfer between the melt and the cold crucible were monitored. Firstly, this article deals with the description of the equipment used in the experiments. Aluminum oxide was considered as experimental material (EM). Therefore, the article also deals with the design of a suitable cold crucible for its melting. Subsequently, the article deals with the implementation of the experiment itself and its phases. Finally, based on the data obtained during melting processes, this paper deals with the calculation of the real heat transfer from the melt to the cold crucible. The main contribution of this article is a comprehensive view of the values of mechanical and electrical quantities that accompany the melting of the considered experimental material (EM) in the designed cold crucible. In conclusion, the values of thermal quantities obtained in the performed experiments are compared with numerical simulation.

ТЕРМОДИНАМИЧЕСКОЕ МОДЕЛИРОВАНИЕ ФАЗОВЫХ РАВНОВЕСИЙ В ОКСИДНОЙ СИСТЕМЕ FEO-SRO-SIO2

Oxide systems with strontium oxide as one of the main components are used more and more widely in different industries. The effect of adding SrO on slug, flux, and the properties of glass and even ceramic with magnetic behaviour is intensively studied today. However, there is only a limited amount of data on phase diagrams for oxide strontium-bearing systems in academic literature, in particular for triple and multi-component systems. This research involved a thermodynamic simulation of phase equilibria and further construction of phase diagrams for double oxide systems FeO–SrO, FeO–SiO2, SrO–SiO2, and the calculation of coordinates of the liquidus surface projection of the phase diagram for a triple oxide system FeO–SrO–SiO2. The simulation was conducted using the sub-regular ionic solution theory approximation. The study has identified energy parameters of the theory for every of the researched systems. The estimated data on the position of liquidus lines in double oxide systems are comparable to those published in academic literature, thus confirming that the performed simulation is correct. Information on the phase diagram of the triple oxide system FeO–SrO–SiO2 is not presented in the academic literature and have been calculated for the first time. The present paper also analyses the data on the temperatures, enthalpy and entropy of silicate formation Fe2SiO4, Sr3SiO5, Sr2SiO4, SrSiO3 from the components of oxide melt of systems FeO–SiO2 and SrO–SiO2 respectively. For example, in the case of Fe2SiO4, the enthalpy of the compound formation from the components of the oxide melt was 63600 J/mol; in case of the silicate Sr3SiO5 – 181675 J/mol; in case of the compound Sr2SiO4 – 169576 J/mol; and for SrSiO3 – 155697 J/mol.

Redox-structure dependence of molten iron oxides

The atomic structural arrangements of liquid iron oxides affect the thermophysical and thermodynamic properties associated with the steelmaking process and magma flows. Here, the structures of stable and supercooled iron oxide melts have been investigated as a function of oxygen fugacity and temperature, using x-ray diffraction and aerodynamic levitation with laser heating. Total x-ray structure factors and their corresponding pair distribution functions were measured for temperatures ranging from 1973 K in the stable melt, to 1573 K in the deeply supercooled liquid region, over a wide range of oxygen partial pressures. Empirical potential structure refinement yields average Fe–O coordination numbers ranging from ~4.5 to ~5 over the region FeO to Fe2O3, significantly lower than most existing reports. Ferric iron is dominated by FeO4, FeO5 and FeO6 units in the oxygen rich melt. For ferrous iron under reducing conditions FeO4 and FeO5 units dominate, in stark contrast to crystalline FeO.

Redox-mediated regulation of an evolutionarily conserved cross-β structure formed by the TDP43 low complexity domain

A methionine-rich low complexity (LC) domain is found within a C-terminal region of the TDP43 RNA-binding protein. Self-association of this domain leads to the formation of labile cross-β polymers and liquid-like droplets. Treatment with H2O2 caused phenomena of methionine oxidation and droplet melting that were reversed upon exposure of the oxidized protein to methionine sulfoxide reductase enzymes. Morphological features of the cross-β polymers were revealed by H2O2-mediated footprinting. Equivalent TDP43 LC domain footprints were observed in polymerized hydrogels, liquid-like droplets, and living cells. The ability of H2O2 to impede cross-β polymerization was abrogated by the prominent M337V amyotrophic lateral sclerosis-causing mutation. These observations may offer insight into the biological role of TDP43 in facilitating synapse-localized translation as well as aberrant aggregation of the protein in neurodegenerative diseases.

Parageneses of TiB2 in corundum xenoliths from Mt. Carmel, Israel: Siderophile behavior of boron under reducing conditions

Abstract Titanium diboride (TiB2) is a minor but common phase in melt pockets trapped in the corundum aggregates that occur as xenoliths in Cretaceous basaltic volcanoes on Mt. Carmel, north Israel. These melt pockets show extensive textural evidence of immiscibility between metallic (Fe-Ti-C-Si) melts, Ca-Al-Mg-Si-O melts, and Ti-(oxy)nitride melts. The metallic melts commonly form spherules in the coexisting oxide glass. Most of the observed TiB2 crystallized from the Fe-Ti-C silicide melts and a smaller proportion from the oxide melts. The parageneses in the melt pockets of the xenoliths require fO2 ≤ ΔIW-6, probably generated through interaction between evolved silicate melts and mantle-derived CH4+H2 fluids near the crust-mantle boundary. Under these highly reducing conditions boron, like carbon and nitrogen, behaved mainly as a siderophile element during the separation of immiscible metallic and oxide melts. These parageneses have implications for the residence of boron in the peridotitic mantle and for the occurrence of TiB2 in other less well-constrained environments such as ophiolitic chromitites.

Influence of technological parameters on the vanadium valence form in slags

The multivalence of vanadium in oxide melts is considered. It is shown that the vanadium oxidation state in the slags is determined by the slag and metal compositions as well as the oxidation potential of the gas phase. Using a polymer model, vanadium valence form fractions were calculated depending on technological parameters. Calculations show that in an air atmosphere, vanadium in the slag should be predominantly in the tetravalent and trivalent state, and in contact with the molten iron, mainly in the trivalent and partly divalent state. Upon contact with pig iron, VO oxide becomes the main form of vanadium in the slag. Slag basicity and temperature have a significant effect on the relationship of vanadium forms. The suggested design-basis using the polymer model can be useful in accomplishment of the thermodynamic calculations for the vanadium equilibrium distribution between metal and slag in the iron and steel production. It allows us to describe the dependence of the vanadium oxidation state on the free oxygen activity in the slag and the gas phase oxidation potential.

Effect of Milling Parameter on the Surface State of Ultra-high strength Steel 16Co14Ni10Cr2Mo

The machining mechanism and process parameters of ultra-high strength steel 16Co14Ni10Cr2Mo are still lack of complete understanding. By changing the milling condition, the influence of process parameters on cutting force, such as Radial milling depth, Axial milling depth, Feed per tooth and milling speed, is studied,and in the meanwhile that the surface morphology and hardness of 16Co14Ni10Cr2Mo after machining are analyzed. Indicating that the milling force increases with the increase of axial milling depth, feed rate and radial milling depth. With the increase of milling speed, the milling force reduces. The effect of axial cutting depth and radial cutting depth on cutting force is maximum. For 16Co14Ni10Cr2Mo ultra-high strength steel, it is suitable to use small cutting depth and high milling speed. On the surface of milling material, partial melting and partial oxidation of chips occur. When the milling speed and feed rate increased, the surface hardness of the material did not change significantly, and there was no work hardening.