Melting System Research Articles

Stability Analysis of Thermocapillary Convection of B<sub>2</sub>O<sub>3</sub>/Sapphire Melt in an Annular Pool

Aiming at the thermocapillary convection stability of sapphire crystal grown by liquid-encapsulated Czochralski method, by non-linear numerical simulation, obtained the flow function and temperature distribution of R-Z cross section, as well as the velocity and temperature distribution at liquid-liquid interface and monitoring point of B2O3/sapphire melt in annular two liquid system, covered with solid upper wall and in microgravity. By means of linear stability analysis, obtained the neutral stability curve and critical stability parameters of the system, and revealed the temperature fluctuation of the liquid-liquid interface. The calculated results of B2O3/sapphire melt were compared with 5cSt silicone oil/HT-70. The results show that under the same geometrical conditions, the flow of B2O3/sapphire melt system is more unstable than 5cSt silicone oil/HT-70, there are two unstable flow patterns, radial three-dimensional steady flow cell and hydrothermal waves near the hot wall. The larger the ratio of Pr number of upper and lower fluid layers is, the better the effect of restraining the flow of lower fluid layers is.

First-principles investigation of equilibrium iron isotope fractionation in Fe1−xSx alloys at Earth's core formation conditions

Iron is one of the most abundant non-volatile elements in the solar system. As a major component of planetary metallic alloys, its immiscibility with silicates plays a major role in planetary formation and differentiation. Information about these processes can be gained by studying the equilibrium Fe isotope fractionation between metal alloys and molten silicates at conditions of core formation. In particular, recent attention has been paid to 56Fe/54Fe equilibrium isotope fractionation at conditions relevant to Earth's core formation and the influence that light elements (O, H, C, Ni, Si and S) have had in this process. Most of these experimental studies relied on the measurement of Fe isotope fractionation from quenched phases of silicate melts and molten iron alloys. The experimental works are extremely challenging, and may suffer different drawbacks. To overcome this, we use ab-initio computational methods to perform a systematic study of the 56Fe/54Fe equilibrium isotope fractionation in molten and solid Fe1−xSx alloys at conditions of the core formation (60 GPa, 3000 K). We show for the first time, that equilibrium isotope fractionation factors from solid systems can be used as proxies for molten systems with differences between these two methods less than 0.01‰ at the relevant P-T conditions. Additionally, we discuss the effect of sulphur concentration on the equilibrium Fe isotope fractionation and show that although there are some structural changes due to atom substitutions, the wide range of studied concentrations produces β-factors that are constant within ∼0.02‰. Finally, we discuss the implications of our results for the interpretation of recent experiments and the understanding of core crystallisation processes.

Implementation of active probe rheology simulation technique for determining the viscoelastic moduli of soft matter

Although bead microrheology experiments are routinely used to characterize the viscoelasticity of complex matter, their simulation analog—probe rheology molecular simulations—has been scarcely used since the system characteristics required for its robust implementation are not established in the literature. We address this issue by analyzing an active probe rheology simulation setup consisting of a probe particle that is subjected to an external oscillatory force and a harmonic trapping force. We identify a set of eight conditions of the system properties that must be satisfied for the successful implementation of the probe rheology technique in molecular simulations. Among these criteria, the two most important are as follows: (1) The spring force constant for the trapping force should be sufficiently large such that the peak in the Fourier transform of the probe displacement occurs at the same frequency as that of the applied force. (2) System parameters should be chosen such that the magnitude of the external force used to drive the probe motion should be comparable to the magnitude of the hydrodynamic friction force experienced by the probe particle in the viscoelastic medium. Furthermore, a scaling relation that can be used to determine the frequency at which inertial effects set in for a given probe size is also established. The validity of our procedure is demonstrated by applying it to determine the viscoelastic properties of a weakly entangled polymer melt system.

Вивчення змочування та кінетики просочення оксидних волокон розплавами свинцю та його сплавів

The effect of metal coverings on wetting of oxide fibers by lead, bismuth, tin-lead-bismuth-cadmium alloy in vacuum 2·10-3 Pa in the temperature range 400–600 oC was studied by the sessile drop method using the capillary purification method of melt. Oxide fibers plaits that have been placed on a silicon oxide substrate as wetting substrates used. Titanium and nickel powders were used as metal coatings. There is no wetting. The contact angles are close to or greater than 90 degrees and only in the case of the lead-titanium melt system at 600 oC the value of the angle is 15, respectively. The use of a dropper allows separate heating of the melt and the substrate, capillary and thermo vacuum cleaning of the melt, as well as thermo vacuum cleaning of the coatings surface. This is a model scheme of the impregnation process of non-metallic frames with matrix melts in the manufacture of composite materials by spontaneous free impregnation. The metal titanium, nickel powder coatings for the method of spon¬taneous free impregnation was used. The study of the kinetics of impregnation of plaits of oxide fibers with melts of lead and tin-lead-bismuth-cadmium alloy was performed at 600–700 oC. The metal melt impregnates metal powders well. The rate of impregnation is quite high 1,1–1,8 mm/s. The obtained results allow the use of titanium pastes for the manufacture of composites from oxide materials with lead matrices. Composites were made. Oxide fiberglass made of CRT waste was selected as the reinforcing material. Lead was chosen as the matrix metal. Despite the fact that lead is a harmful material, but its use as a matrix phase for composites from the action of ionizing radiation is indispensable. Keywords: spontaneous free impregnation, composites, lead melts, oxide fibers, wetting, metal coverings.

Термодинамічні властивості розплавів системи In—Tb

The method of isoportic calorimetry investigated the thermochemical properties of the melt In—Tb system in the range of compositions 0 < xIn < 0,4 at 1625 ± 1 K. The obtained data were extrapolated on a non-investigated concentration interval, given that when xTb = 1 integral and partial to Tb enthalpia mixing is zero. It was established that the first partial for Terbium and the minimum enthalpy of mixing is –145 ± 7 and –40,1 ± 0,2 kJ/mol respectively. Comparison of ΔHmin, the melt of five previously investigated In—Ln systems from the serial number Ln (zLn), together with the data obtained in this papper, showed that they are described by one trend line. For ΔHmin In—Eu (Yb) melts (Yb) are very slight deviations from the trend line. But for dimensional factor, these deviations from the trend line are more significant. Enthalpia of the formation of some In—Ln intermetallides are known, with most of them relate to the LnIn3 compound. But there is no full reconciliation between these data. The results of the most modern work exhibit less dependence on the serial number of lanthanides and are more exothermic for heavy lanthanides, compared with other data. Comparing thermochemical properties of double Sn (Sb) —REM melt systems. It has been established that the energy of the interaction between the data p-elements and REM increases in such a sequence: In-REM → Sn—REM → Sb—REM. This is due to the fact that the stibium is the best acceptor of electrons. Keywords: thermochemical properties, melts, compounds, In, Tb.

Experimental Study on the Influence of Buried Geothermal Pipes on the Temperature Field of Concrete Roads

Snow removal is a critical security issue for concrete roads, but geothermal methods can be an environmentally friendly and efficient alternative to traditional approaches for snow removal. In order to obtain fully the change rule of the temperature field of the concrete road under geothermal conditions, observe the relationship between temperature rise and time, and better apply the geothermal buried pipe technology to road snow and ice melting, two concrete road models with the dimension of 1 m × 2 m × 0.45 m are made. The model experiments are carried out under the conditions of 0.8 m/s, 0.85 m/s, and 0.9 m/s of pipeline flow velocity, 15 cm and 25 cm of buried pipe depth, and 10 cm and 15 cm of pipe space. The influence of flow velocity, the buried pipe depth, and space on the internal and surface temperature field of concrete road is studied. The results show that, in the flow velocity test, the temperature of the four-layer measuring points shows an upward trend under different flow velocities. With the increase of initial flow velocity, the temperature rise of the first layer measuring points gradually increases. The temperature rise value of the first layer corresponding to 0.9 m/s is 11.66°C, 4.32°C, and 3.13°C higher than 0.8 m/s and 0.85 m/s, respectively; in the buried depth test, the first layer temperature rise at 15 cm is 1.85°C higher than that at 25 cm; in the space test, when the buried pipe space increases from 10 cm to 15 cm, the temperature rise value of the first layer decreases by 1.2°C. From the above three influencing factors experiments, it can be obtained that the temperature rise stage of the first layer measuring points can be divided into the rapid temperature rise stage within 0–2 hours, the temperature rise one with 2 h–6 h, and stable temperature stage after 6 h. Experimental observation shows that road temperature will be higher than 8°C within 1 h–1.2 h, which can eliminate the road icing temperature conditions to ensure that the road does not freeze. After opening the snow melting system for 6 h, the surface temperature of the road tends to be stable, and there is no significant change. In practical application, open the system 1.5 h in advance so that it can prevent road snow and freezing. After opening the system for 6 h or stopping snowfall and rainfall within 6 h, close the system, and the residual temperature stored in the concrete road is used for deicing and snow melting. Ensuring that the road surface temperature is above 0°C, the heating system is turned on intermittently to save energy. The research provides theoretical support for preventing road snow and freezing.

A novel contactless, feedbackless and sensorless power delivery link to electromagnetic levitation melting system residing in sealed compartment

The paper presents practical considerations and guidelines for designing an improved-efficiency contactless inductive power transfer link, delivering DC power in step-down mode to an electromagnetic levitation melting system residing in a sealed compartment. The proposed arrangement employs none-series compensated inductive power transfer link operating at the so-called “load-independent-voltage-output” frequency, allowing feedback-less and sensor-less design. However, the output voltage of a system operating at such frequency remains influenced by the load to some extent, residing within a certain range with boundary values (minimum and maximum) corresponding to maximum (rated) and minimum load, respectively. Consequently, the proposed contactless power delivery system is first analyzed using both first harmonic approximation (frequency-domain) based approach and differential equations (time-domain) based method to obtain corresponding output voltage bounds. Then, coil-to-coil efficiency and optimal load matching factor are determined. Comparison with both typically utilized symmetrical series-series and recently proposed series-none compensation topologies reveals the superiority of none-series compensation topology in terms of coil-to-coil efficiency for the whole range of coupling coefficients. Simulations and experiments of 400 V, 1 kW none-to-series compensated inductive wireless power transfer link, delivering contactless energy to a 250 V electromagnetic levitation melting system, demonstrate excellent matching and accurately validate the presented analysis.

Influence of Selected Model Parameters on the Electromagnetic Levitation Melting Efficiency

The article presents the results of multivariate calculations for the levitation metal melting system. The research had two main goals. The first goal of the multivariate calculations was to find the relationship between the basic electrical and geometric parameters of the selected calculation model and the maximum electromagnetic buoyancy force and the maximum power dissipated in the charge. The second goal was to find quasi-optimal conditions for levitation. The choice of the model with the highest melting efficiency is very important because electromagnetic levitation is essentially a low-efficiency process. Despite the low efficiency of this method, it is worth dealing with it because is one of the few methods that allow melting and obtaining alloys of refractory reactive metals. The research was limited to the analysis of the electromagnetic field modeled three-dimensionally. From among of 245 variants considered in the article, the most promising one was selected characterized by the highest efficiency. This variant will be a starting point for further work with the use of optimization methods.

Snow melting on a road unit as affected by thermal fluids in different embedded pipes

Snow melting on a road unit circulating thermal fluids was experimentally conducted in the severely cold region of China, Harbin. The performances (snow-free area ratio, average road-surface temperature, and energy consumption) at different embedded pipe depths (60, 80, and 100 mm) with snow thickness of 43 mm at the ambient temperatures of −7.93 to −9.36 °C were presented and discussed. It was observed that the snow-melting process could be divided into three periods according to the snow-free area ratio: (a) starting period (0), (b) rapid period (0–0.7), and (c) slow period (0.7–1.0). The average road-surface temperatures for the starting, rapid, and slow periods fluctuated mainly in the ranges of −4–0, 0–1, and 1–10 °C, respectively. The energy consumption gradually decreased over time with the averages of 1170.8–1959.7 W/m2. The results also revealed that the embedded pipe depth of 80 mm could be adopted in the hydronic road-heating system. The contents presented in this work can guide the design of a hydronic road-heating system for snow melting in severely cold regions.

A novel flameless oxidation and in-chamber melting system coupled with advanced scrubbers for a laboratory waste plant

This is the first study integrate the flameless oxidation (FO) and in-chamber melting (ICM) processes in a primary chamber of a laboratory waste incinerator to improve energy and emission performances. Two liquid burners created a twin-cyclonic fluid field that achieved the FO and ICM in the same chamber. The first cyclone provided a well-mixed and lower temperature FO to reduce auxiliary diesel consumption, NOx and PM emissions by 25.8%, 30.9%, and 79.2%, respectively, from the original system. The hot gases produced by FO enhance the ICM process and transformed the bottom ashes to stabler slags, in turn meeting the regulations for nonhazardous wastes. The other cyclone enhanced the drying and water–gas shift reaction in the drying zone by recirculating the CO and enthalpy from FO and ICM. Eventually, the residual CO, hydrocarbons, and H2 were sent to the secondary chamber for further oxidation. A computational fluid dynamic simulation supported the fluid field assumption posed in this study. Moreover, advanced scrubbers were employed after thermal treatments to reduce HCl and SO2 by 81.8% and 38.8% and further retarded the corrosion rate in the baghouse supporting cage by 87.7%. The precursors of condensable particulate matter were reduced by condensation and finally removed in the baghouse. Nevertheless, the emissions of the high- and mid-molecular-weight polycyclic aromatic hydrocarbons were greatly reduced by 60.8–93.1% and 80.2–99.9%, respectively. Consequently, the new system reduced annual emissions by 40.7–87.6% and operating costs by 41.5%, allowing recovery of the remodification investment in 20.5 months.

CHARMM-GUI Polymer Builder for Modeling and Simulation of Synthetic Polymers.

Molecular modeling and simulations are invaluable tools for polymer science and engineering, which predict physicochemical properties of polymers and provide molecular-level insight into the underlying mechanisms. However, building realistic polymer systems is challenging and requires considerable experience because of great variations in structures as well as length and time scales. This work describes Polymer Builder in CHARMM-GUI (http://www.charmm-gui.org/input/polymer), a web-based infrastructure that provides a generalized and automated process to build a relaxed polymer system. Polymer Builder not only provides versatile modeling methods to build complex polymer structures, but also generates realistic polymer melt and solution systems through the built-in coarse-grained model and all-atom replacement. The coarse-grained model parametrization is generalized and extensively validated with various experimental data and all-atom simulations. In addition, the capability of Polymer Builder for generating relaxed polymer systems is demonstrated by density calculations of 34 homopolymer melt systems, characteristic ratio calculations of 170 homopolymer melt systems, a morphology diagram of poly(styrene-b-methyl methacrylate) block copolymers, and self-assembly behavior of amphiphilic poly(ethylene oxide-b-ethylethane) block copolymers in water. We hope that Polymer Builder is useful to carry out innovative and novel polymer modeling and simulation research to acquire insight into structures, dynamics, and underlying mechanisms of complex polymer-containing systems.

Lithium isotope behavior during magmatic differentiation and fluid exsolution in the Jiajika granite–pegmatite deposit, Sichuan, China

The Jiajika lithium (Li) deposit in Sichuan Province is the largest pegmatite-type Li deposit in China. The petrogenesis and metallogenesis of the Jiajika granitic pegmatites remain debatable. This study presents the Li isotopic compositions of two-mica granites, Li-rich and Li-poor pegmatites, and muscovites in Li-poor and Li-rich pegmatites to unravel the Li enrichment mechanism in the Jiajika deposit. The two-mica granites have a lower average δ7Li values than those of the Li-rich and Li-poor pegmatites. The Li contents of the two-mica granites are almost the same as those of the Li-poor pegmatites but are much lower than those of the Li-rich pegmatites. Muscovites in the Li-rich pegmatites have higher average Li contents and δ7Li values than those of the Li-poor pegmatites. All these results indicate the Jiajika granitic pegmatites were the final products of the extreme fractional crystallization of two-mica granitic magmas rather than direct anatectic melts, and that the Li-poor pegmatites derived from early differentiation of the two-mica granitic magmas before they evolved into Li-rich pegmatites during the late stage of magmatic differentiation. The lower average δ7Li values of the more evolved Li-rich pegmatites compared with the Li-poor pegmatites may have been caused by fluid exsolution and kinetic diffusive fractionation during melt-fluid separation. We discovered that fluid exsolution during melt-fluid separation can cause significant Li isotopic fractionation, with 7Li enriched in a H2O-poor silicate-rich melt system. Considering the crystallization ages of the two-mica granites and granitic pegmatites and other geochemical evidence (e.g., major- and trace-element compositions), the magmatic differentiation and fluid exsolution in the late stage of the granitic magma evolution together with the Li-rich surrounding strata led to the multistage enrichments in lithium, thus contributing to the formation of the Jiajika large Li deposit.

Molecular Dynamics Simulation Study of the Effect of Ni, Fe, Cu on Cryolite Molten Salt System 78% Na<sub>3</sub>AlF<sub>6</sub>-9.5%AlF<sub>3</sub>-5.0%CaF<sub>2</sub>-7.5%-Al<sub>2</sub>O<sub>3</sub>

The effect of different additives Ni, Fe, Cu on the structure and properties of electrolyte system 78% Na3AlF6- -9.5%AlF3-5.0%CaF2-7.5%Al2O3 at 1200K and 1.01Mpa was studied by molecular dynamics method. The radial distribution function, coordination number, diffusion coefficient, conductivity, and viscosity of the system were discussed in detail. The results demonstrated that the order of the self-diffusion coefficient of ions in the electrolyte system is: Na+ > F- > O2- > Ca2+ >Al3+. The addition of Ni and Fe connected the free aluminum composite ion groups in the system through fluorine bridges, which enhanced the interaction between Al3+ and Al3+. The addition of Cu weakened the interaction between Al3 + and Al3+ and the F-. The interaction between Al3+ and Na+, [AlF7]4- ionic groups might appeared in the melt system. After adding NiO, Fe2O3, and Cu, the electrical conductivity of the system increased, and the viscosity decreased. The research work revealed the influence of Ni, Fe, Cu on the ion existence form, mobility, inter-ion interaction and diffusion mechanism of cryolite molten salt system, which has important guiding significance for aluminum electrolysis production.

Diffraction and luminescence analysis of extremely rapidly cooled molten system (LiF−CaF2)eut−xLnF3 (Ln=Sm and Gd)

Abstract Samples of (LiF−CaF2)eut−xSmF3(−xGdF3) (x=0.03−0.50) were prepared by spontaneous cooling as well by very fast cooling (using the rapid solidification processing (RSP) method) which provide two types of sample morphology: riffle-like and sphere-like fragments. All types of samples were studied by XRD, optical absorption and fluorescence spectroscopy. The presence of LiF stabilises the cubic cell dimension, and the content of lanthanide fluorides presents influence on phases formed, as well as the crystallinity of the system, in both the spontaneously and rapidly-cooled systems. The photoluminescence properties of the investigated systems are dependent on the lanthanide fluoride content. The intensity of the emission bands, corresponding to the Sm3+ ion, reaches the maximum when the Sm content is x(SmF3)=0.03. An even stronger dependence is observed of optical properties on the morphology of the samples, i.e. whether the samples are spontaneously cooled or processed by the RSP method followed by mechanical grinding. Mechanical grinding enhances the luminescent properties and leads to higher emission intensities. It is also shown that the photoluminescent spectroscopy is suitable for detection/approval of lowered local symmetry via significant splitting of spectral bands.

Genesis of Intermediate and Silicic Arc Magmas Constrained by Nb/Ta Fractionation

AbstractResolving the geochemical discrepancies in Nb/Ta between the bulk continental crust and its parental mantle melts can provide insights into the processes by which basaltic magmas differentiated into the felsic crust. Deep‐seated garnet pyroxenite cumulates (i.e., arclogite) have high Nb/Ta values due to the presence of high Nb/Ta‐rutile. For this reason, rutile‐bearing arclogites having Nb‐rich composition were proposed to complement the low Nb/Ta nature of the continental crust and evolved arc magmas, that is to say, continental arc magma evolution dominantly occurred in the stability field of garnet. However, this suggestion is challenged by the incomplete understanding of the role of rutile in the Nb/Ta fractionation during arc magma evolution due to insufficient partitioning data at low temperatures (T ≤ 1,000°C). Here, we determined Nb and Ta partitioning ratios in rutile‐felsic melt systems at 2.0 GPa, 850–1,000°C and ∼4–20 wt.% H2O. Our results confirm that equilibrium crystallization of rutile with respect to Nb and Ta will not impart lower Nb/Ta values to any derivative liquids, whereas diffusive fractionation of Nb/Ta in siliceous melts during the growth of rutile can reduce Nb/Ta ratios in melts. However, a positive correlation between Nb/Ta and Dy/Yb for mature continental arc magmas, incipient continental arc magmas, island arc magmas, and global arc magmas indicates that amphibole rather than rutile‐bearing arclogite was responsible for causing low Nb/Ta ratios of many evolved intermediate rocks. Accordingly, the chemical differentiation from primary basaltic to average andesitic compositions of the continental crust mainly occurred in the stability field of amphibole.

Electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on liquid gallium electrode

The aim of this work is to explore the electroseparation of uranium from lanthanides (La, Ce, Pr, Nd and Sm) on a liquid gallium electrode. Cyclic voltammetric results showed that in multi-component melt systems (U/Nd, U/La-Ce-Nd, and U/La-Ce-Pr-Nd-Sm), the reduction potentials of each lanthanides on the Ga cathode are identical and cannot be distinguished and resolved. The peak potential differences between the lanthanides and uranium are all at about 250 mV. The practical electroseparations in U/Nd, U/La-Ce-Nd and U/La-Ce-Pr-Nd-Sm systems were carried out by applying different electrochemical techniques as galvanostatic, potentiostatic and current pulse electrolysis. After electrolysis, the ICP-AES technique was used to determine the composition of molten salt and alloy deposits, and the actual separations factor of U over lanthanides in these multi-component systems were calculated and compared. The results showed that the separation factors of U/La and U/Sm can be both up to 1000, whilst that of U/Nd is relatively low with an average value of about 350. In addition, the separation factor obtained by the current pulse electrolysis is larger than that of galvanostatic and potentiostatic method, and the potentiostatic electrolysis provides the lowest one.

Evaluation of fits of metal copings fabricated by using selective laser melting at various angles

Statement of problemInformation on the fabrication of metal by selective laser melting (SLM) systems positioned at different angles is sparse. PurposeThe purpose of this in vitro study was to evaluate the extent of marginal and internal gaps in metal copings fabricated at different angles by using an SLM fabrication system. Material and methodsA master metal model was produced and replicated (N=10) with silicone impressions and dental stone. Standard tessellation language (STL) files of the 10 coping designs were then obtained by using a model scanner and a 3D design software program on a scannable working die. Co-Cr alloy metal copings were fabricated by the SLM fabrication system at 45, 90, and 180 degrees. The marginal and internal gaps were measured by the silicone replica technique. The measured data were analyzed by using the nonparametric Kruskal-Wallis H test (α=.05). ResultsThe specimens fabricated at 180 degrees showed the best fit in terms of the marginal gap, while the worst fit was observed in the specimens fabricated at 90 degrees. Statistically significant differences were seen among the marginal gaps produced in the 3 groups (P<.001). In terms of internal fit, the axial wall gap showed the best fit, and the occlusal gap the worst. The best fit overall was 66 μm at the axial wall of the 180-degree group, and the worst in the 90-degree group, at 663 μm. Statistically significant differences were observed between the chamfers, axial walls, and the occlusal gaps of the 3 groups (P<.001). ConclusionsRestorations fabricated by using an SLM system at 180 degrees were clinically acceptable. However, more research is required to investigate the performance of metal copings produced at 45 and 90 degrees to evaluate their clinical acceptability.

Thermodynamic Properties of Gd–Sn and Gd–Sn–Ni Melt Systems

Enthalpies of mixing of liquid alloys are determined via isoperibol calorimetry for the Gd–Sn system throughout the range of concentrations at 1873, 1640, and 1510 K, and for the Gd–Sn–Ni system along the radial section with a constant ratio of atomic fractions of tin and nickel: xSn/xNi = 0.68/0.32 at 1873 ± 5 K up to xGd ∼ 0.25. It is found that the melts of the Gd–Sn system form with the release of a large amount of heat ( $$\Delta {{{H}}_{{\min }}}$$ = −68.4 ± 0.4 kJ/mol at xSn = 0.45). The calculations are performed using the geometric and analytical Redlich–Kister–Muggianu models of ΔH for melts of the ternary Gd–Sn–Ni system from similar data for binary boundary subsystems at 1873 K. The results show the minimum enthalpy of mixing of these ternary melts was established for the Gd0.55Sn0.45 alloy. It is shown that the experimentally investigated enthalpies of mixing of the Gd–Sn–Ni melts and calculated data using the Redlich–Kister–Muggianu model with ternary interaction parameter L = 500 kJ/mol agree satisfactorily with one another.

Study on Surface Temperature Variation of Several Pavement with Snow Melting System Using Hot Water Piping

Study on Surface Temperature Variation of Several Pavement with Snow Melting System Using Hot Water Piping

First-Principles Molecular Dynamics Simulation on High Silica Content Na3AlF6–Al2O3–SiO2 Molten Salt

A new method for the disposal of the spent refractory materials by adding them directly to electrolytic cells requires our better knowledge of the Na3AlF6–Al2O3–SiO2 melt system. The development of computational materials science offers us a new way to avoid the limitation of the experiment under a strong corrosive environment at high temperatures. First-principles simulation is applied to study the structure information, electronic properties, and transport properties of the system. The study reveals that the main Si and Al ions in the melt are complex ion groups such as [SiF2O2]2–, [SiFO3]3–, [SiF3O2]3–, [AlF2O2]3–, [AlF3O]2–, and [AlF4O]3–. Tangled structures like [SiAlO3F5]4– also exist in the melt. The average coordination number of Al–F and Si–F is 3.21 and 2.45, respectively. O ions mainly act as bridge ions in the melt. The bonding ability of Al with O ions is stronger than that of Si with O ions. Moreover, the Al–O bond is mainly covalent, while the Al–F bond is basically ionic characters. The order of diffusion ability of ions from large to small is Na, F, Al, Si, and O. Addition of SiO2 into the Na3AlF6–Al2O3 molten salt causes an increase of the viscosity and a decrease of ionic conductivity.