NaF System Research Articles

Расчет удельной электропроводности расплавов смесей LiF+NaF

The calculation of the specific electrical conductivity of lithium and sodium fluorides mixtures melts is presented. The Iinterest in the LiF–NaF system melts is determined by their practical significance. Melts of LiF+NaF mixtures are used in heat-storing compositions and in metallurgy. They are part of various multicomponent systems. The specific electrical conductivity calculation by isoconcentration, isothermal and interpolation methods is given for LiF+NaF mixtures melts of various compositions using known reference data for the temperature range 1020...1340 K. A calculation has been performed for the eutectic composition. The resulting analytical equations have been used to describe and calculate the specific electrical conductivity of the eutectic mixture for temperatures 5°, 10°, 50°, 75°, 100° above the liquidus. The specific electrical conductivity of the eutectic mixture melt is calculated on isotherms by interpolation for the isoconcentration dependences of hypoeutectic and hypereutectic mixtures. Isotherms of electrical conductivity (1020...1340 K) of melts depending on the content of LiF and NaF components are described by a third-degree polynomial. Depending on the temperature, the coefficients in the resulting equation change linearly. A comparison has been made of the values of specific electrical conductivity ϰ(LiF+NaF), calculated from the obtained equations. The description of ϰ(LiF+NaF) by isoconcentration and isothermal methods has showed satisfactory convergence of calculation results and makes it possible to calculate the specific electrical conductivity of LiF+NaF mixtures melts of any given composition, including eutectic.

Crystallization behavior of fluorozirconate glasses as monitored by 35Cl NMR

The 35Cl nuclear magnetic resonance (NMR) spectroscopy was first used to study the crystallization of erbium-doped fluorochlorozirconate glass in the ZrF4–BaF2–BaCl2–LaF3–AlF3–NaF system. It has been shown that crystallization results in the increasing homogeneity of electronic structure on chlorine atoms and a narrowing of the NMR line. The glass being crystallized, erbium cations are displaced into the fluoride phase.

Enhanced ionic conductivity of NASICON-type NaTi2(PO4)3 solid electrolytes with sodium-ion conduction: based on NaF-assisted synthesis

The ceramic composite electrolytes in the NaTi2(PO4)3–NaF system were characterised by thermal analysis, X-ray diffraction, Fourier infrared absorption spectroscopy, scanning electron microscope, and impedance spectroscopy. X-ray diffraction confirmed that the ceramic composites have a Na Super Ionic Conductor (NASICON) structure. The scanning electron images showed that the addition of NaF significantly improved the microscopic morphology of the NaTi2(PO4)3 crystals and made the packing of crystal grains closer. The addition of NaF in a certain proportion is beneficial to the growth of crystals, making the crystal grains more compact and improving the density of the solid electrolytes. The ionic conductivity analysis was carried out by alternating current (AC) impedance spectroscopy. The conductivity can be effectively improved when a certain proportion of NaF is added to the ceramic composites. The maximum total conductivity is about 1.50 × 10−5 S·cm−1 obtained when the molar ratio of NaF to NaTi2(PO4)3 reaches 0.4.

Spatiotemporal characteristics and earthquake statistics of the 2020 and 2022 adjacent earthquake sequences in North Aegean Sea (Greece)

The two moderate earthquakes that occurred close and to the north of the North Aegean Trough (NAT) on 26 September 2020 (Mw5.3) and 16 January 2022 (Mw5.4), both followed by aftershock activity, are examined. Seismic activity along the NAT and its parallel branches is continuous and remarkable, with numerous strong instrumental (M≥6.0) earthquakes. Yet, the frequency of moderate (5.0≤M<6.0) earthquakes outside these major fault branches is rather rare and therefore their investigation provides the optimal means to decipher the seismotectonic properties of the broader area. The temporal and spatial proximity of the two seismic excitations from late September of 2020 through early 2022, intrigues for exhaustive investigation of seismic activity with the employment of earthquake relocation techniques, moment tensor solutions and statistical analysis. Our research revealed that this seismic activity purely falls inside the Mainshock – Aftershock type, with fast aftershock decay rates and moderate productivity. According to our findings, the two seismic sequences, despite their close proximity, exhibit distinctive features as a result of the intricate stress field generated at the western termination of the NAF system in an extensional domain.

Density and volume properties of MF-K2ZrF6 (M = Li, Na, and K)

Critical evaluation of volume properties (based on density measurements using Archimedean method) of the zirconium-based fluorides melts MF-K2ZrF6 (M = Li, Na, and K) revealed the different properties of KF system in contrast to LiF and NaF systems. Excess molar volume adopts negative values in the entire concentration range for all three investigated systems. Partial molar volumes of K2ZrF6 were obtained by using two different approaches - simple polynomial regression analysis and multicomponent polynomial regression in the form of the Redlich-Kister equation. Finally, the excess partial molar volume of K2ZrF6 in KF shows smaller overall volume contraction that adopts 60% of volume contraction in LiF or NaF systems. The obtained data of density, molar volumes and partial molar volumes were compared with accessible literate data after recalculation to the MF-ZrF4 coordinates.

Molecular dynamics simulations and FTIR spectroscopy investigations on the hydration, transport, and dielectric properties of the NaF(aq) system at various concentrations

Sodium fluoride has many applications in various fields, such as dentistry, geochemistry, and rechargeable battery technology. Indeed, the determination of the hydration structures, dynamics, and dielectric properties of the NaF electrolyte in aqueous solutions is a crucial element in order to optimize its performance and predict its intervention mechanisms in industrial processes. In this study, we used the molecular dynamics approach to study the NaF(aq) binary system at different concentrations ranging from 0.1 to 1.0 mol.kg−1 using the OPLS-AA force field combined with the extended simple point load water model (SPC/E). Thus, the ions were represented as charged Lennard-Jones particles. The radial distribution functions (RDF) have been calculated to analyze the hydration shell structures of different ion pairs. The microstructures, self-diffusion coefficient, and dielectric constant were determined by molecular dynamics at various concentrations. Moreover, our FTIR spectroscopy data confirm the results obtained from molecular simulations.

Optical Properties of Fluorozirconate Glasses Doped with Chromium Ions

Chromium trifluoride-doped fluoride glasses in the ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) system with partial substitution of fluorine for chlorine have been synthesized. The spectral data obtained confirm that chromium ions enter the glass structure and exhibit broadband luminescence caused by the 4T2 → 4A2 transition in the Cr3+ ion. The observed long-wavelength shift of the broadband luminescence band and Cr3+absorption bands in fluoride–chloride glass compared to fluoride glass corresponds to the expected behavior of the Cr3+ luminescence and absorption spectra when fluoride ions are replaced by chloride ions, which should lead to a weakening of the strength of the crystal field acting on Cr3+ ions. At room temperature, the luminescence of Cr3+ ions at 888 and 908 nm is strongly quenched due to the thermally stimulated nonradiative transition from the 4T2 excited state to the 4A2 ground state.

Study on diffusion kinetics of chromium and nickel electrochemical co-deposition in a NaCl–KCl–NaF–Cr2O3–NiO molten salt

Abstract The process of preparing surface composite by molten salt co-deposition is the result of the mass transfer of active particles in molten salt, electrochemical reduction, and solid diffusion. In this study, we prepared Cr–Ni alloy/low-carbon steel surface composites in NaCl, KCl, NaF, Cr2O3, and NiO melt salt system successfully, and analyzed the entire diffusion dynamics process, aiming to find out the limiting links and provide ideas for further improving the preparation efficiency. The results show that chromium and nickel ions are simultaneously reduced on the cathode surface through two and one steps, respectively. And an alloy layer with Fe content of 64.52 wt%, Ni content of 28.96 wt%, and Cr content of 6.52 wt% is formed on the surface of low-carbon steel substrate. The average diffusion coefficients of chromium and nickel atoms in the surface composites are 1.16 × 10−14 and 1.44 × 10−14 m2·s−1. The mass transfer process in molten salt is the limiting link in the whole preparation process.

Distribution of trace elements between phases in the Carbonate–Phosphate System with Fluorine at 500 MPa

The distributions of Ti, Zr, Nb, La, Sm, Yb, and Y were experimentally studied between phosphate and carbonate melts with various Ca and Na concentrations and equilibrium solid phases: apatite (in 12 experiments) and buchwaldite, CaNaPO4 (in two experiments). The experiments were carried out in an internally heated pressure vessel at a pressure of 500 MPa in the CaCO3 + NaPO3 + NaF system with variable proportions of phosphate and carbonate, and with the addition of H2O, H2C2O4 and mixture of trace-element oxides. The temperatures in runs V-1-8 were conducted as 1000 °C for melting for 24 h, then for crystallization at 650 °C for 7 days, and quenching; the temperatures in runs VI-1-5 - 1000 °C for 1 day and immediate quenching. The proportion of phosphate and carbonate in the starting mixtures was expressed as χ(P2O5) (mol. %), where χP2O5=nP2O5nP2O5+nCaO×100%. The experimental products were analyzed by electron probe microanalysis. The following two types of quenched melts were obtained depending on χ(P2O5): (i) calcite-rich melt with 20 mol% Na2O at χ(P2O5) < 30% and (ii) sodic carbonate–phosphate melt with a low CaO concentration at χ(P2O5) > 30%. The solubilities of ZrO2, TiO2, and Nb2O5 in the calcite-rich quenched melts at 650 °C were low and limited by the crystallization of Zr, Ti, and Nb oxides. At the temperatures 1000 °C these oxides are dissolved in the melts, and their concentrations in the melts increased with increasing χ(P2O5). The TiO2 and ZrO2 distribution coefficients between apatite and melt are 0.06–0.2 and 0.4–1.0, respectively. The REE distribution coefficients between apatite and coexisting melt rich in Ca carbonate increase with increasing χ(P2O5) from 1.3 to 3.3 for La2O3, from 0.4 to 3.4 for Sm2O3, from 1.4 to 1.9 for Yb2O3, and from 0.8 to 2.9 for Y2O3. The REE distribution coefficients between apatite and the sodic carbonate–phosphate melt increase by a few orders of magnitude with increasing χ(P2O5), particularly significantly for La2O3 and Sm2O3, to 110 and 75, respectively, and to >32 and 20 for Yb2O3 and Y2O3. The TiO2 and ZrO2 distribution coefficients between buchwaldite and melt do not depend on χ(P2O5) and are 0.1 and 1.05, respectively. The REE distribution coefficients between buchwaldite and melt coexisting with it in the experiments are 1.5 times lower than the distribution coefficients between apatite and melt and increase from ∼1.1 for all REE at χ(P2O5) = 25.8%, to 3.6, 2.9, 3.2, and 2.0, respectively, for La2O3, Sm2O3, Yb2O3 и Y2O3 at χ(P2O5) = 41.7%.

Efficient Cryptographic Hardware for Safety Message Verification in Internet of Connected Vehicles

An important security requirement in automotive networks is to authenticate, sign, and verify thousands of short messages per second by each vehicle. This requirement mandates the use of a high speed Elliptic Curve Cryptography (ECC) hardware. The Residue Number Systems (RNS) provide a natural parallelism and carry-free operations that could speed-up long integer arithmetics of cryptographic algorithms. In this article, we propose a high-speed RNS Montgomery modular reduction units with parallel computing to reduce the latency of the field modular operations. We propose a fully RNS-based ECC scalar multiplication co-processor for NIST-P256r1 and Brainpool256r1 standard curves and improved the scalar multiplication speed using NAF and DBC numbering systems. Compared to the literature, our scheme provides faster computation without compromising the security level. The performance of our fully RNS-ECC point multiplication meets the requirements of the automotive industry.

Segregation Melting in the LiAlSi2O6–Na2SO4–NaF System as a Method for the Preparation of Lithium Fluoride

Segregation Melting in the LiAlSi2O6–Na2SO4–NaF System as a Method for the Preparation of Lithium Fluoride

Preparation and characterization of glasses from the binary sodium fluoroborate system NaF–B2O3 within the range (10–50 mol% NaF) assessed by structural FTIR, optical and thermal properties and effects of gamma irradiation

Extended glasses from the binary system (NaF-B2O3) with (10→50 mol% NaF) were synthesized by the traditional melting-annealing route. These unfamiliar glasses with high extended NaF contents than Na2O were characterized by multi-techniques including optical and FTIR spectral analysis beside measurements of their thermal expansion parameters. The optical (UV–visible) spectra of the glasses reveal obvious transparency except for the appearance of distinct UV absorption due to unavoidable trace ferric ions impurities present within the laboratory chemicals. Structural FTIR spectra indicate that NaF primarily acts the same as Na2O progressively converting some of the BO3 units to produce tetrahedral (BO3F) units and then at a high percent of NaF is assumed to form additional (NaF4) groups and hence the intensity of the bands within the range 800–1200 cm−1 due to combined tetrahedral groups (BO4 + NaF4) is always higher than that for the peaks at the range 1200–1600 cm−1due to vibrational BO3 groups. The thermal expansion data reveal that the dilatometric softening temperature primarily increases due to the formation of compact tetrahedral (BO3F) groups. It is obvious that this unfamiliar (NaF–B2O3) glass does not show an anomalous behavior as that reported for (Na2O–B2O3) glassy system and other alkali-B2O3 glasses in their thermal expansion properties. Gamma irradiation did not show any distinct variations in the FTIR spectra indicating the stability of the structural building groups in this NaF–B2O3 glass system. On the other hand, the optical spectra show the displacement of one of the two broad bands in the UV spectra which is assumed to be due to a photochemical reaction between some Fe3+ ions present as trace impurities and formed freed electrons during the irradiation process.

Comprehensive approach to torque and lost circulation problems in geothermal wells in terms of drilling fluid

Drilling in a lost circulation zone has long been a challenge in geothermal wells due to its strong potential for high torque and wellbore instability. Particularly in deviated, extended reach and horizontal wells, frictional forces between drill string and wellbore or casing may be high enough to interfere with running the pipe in and out of the hole. These forces may also increase the torque and the stress on drill string which may end up with severe problems like stuck pipe and lost in hole. High-temperature high-pressure (HTHP) drilling fluids design, which minimize loss rates and friction values, is critical for the success in the face of these challenging drilling practices.The goal of this research is to provide a solution-oriented approach to torque and lost circulation problems in potential seepage and partial loss zones in geothermal wells; by developing efficient water-based drilling fluid compositions.Non-aqueous fluids (NAFs) are known to have the highest lubricity performance. However, application of these drilling fluid systems is limited because of high cost and environmental constraints. Hence, water-based drilling fluids are good candidates for replacing conventional NAFs. This paper investigates water-based drilling fluid compositions with high lubricity performance, HTHP resistance and high loss zone plugging performance.The design and selection of HTHP drilling fluid system have been the focus of experimental studies and worldwide field experience. Several chemical commercial lubricants are added in this fluid system to find the compositions for the highest lubricity performance closest to NAF systems. Also, considering the formation characteristics, environmental constraints, reservoir contamination concern and drilling limitations; proper fluid compositions are formulated to plug the potential seepage and partial loss zones and reduce the differential-sticking tendency by using proper lost circulation materials and lubricants.This study aims to encourage the geothermal drilling industry worldwide, to utilize the developed drilling fluid compositions with enhanced lubricity and loss zone plugging performance together to overcome related major drilling problems.Results reveal that lubricity and pore plugging characteristics of the selected compositions are highly innovative and noteworthy to be used in field applications for geothermal drilling industry.

Active Subaquatic Fault Segments in Lake Iznik Along the Middle Strand of the North Anatolian Fault, NW Turkey

AbstractThe seismic activity of the middle strand of the North Anatolian Fault (MNAF), Northwestern Turkey, is debated because of its quiescence during the instrumental period, in contrast to a significant historical activity documented by several chronicles over the last two millennia. Here, we focus on Lake Iznik, bordered by the MNAF, to get a new insight into its long‐term seismicity and its tectonic setting. The study of lacustrine sediment cores reveals 14 earthquake‐induced turbidites since their ages correspond to seismic events during the past two millennia. Bathymetry and high‐resolution seismic reflection data allow to describe two hitherto unknown subaquatic active fault structures (the South Boyalica and Iznik faults) that belong to the MNAF system. Sediment cores sampled on both sides of the Iznik Fault document an event deposit and a sedimentary unit vertically offset of ~40 cm interpreted as the last rupture during the 1065 CE destructive earthquake. Older events are supposed on this fault more than thousand years ago. Further studies will help to estimate the horizontal co‐seismic offset of this oblique‐slip fault and the calendar of older ruptures. The current seismic gap of thousand years on this segment greatly increases the seismic hazard in this region and must be considered in the seismic risk assessment of the NAF system.

Crystallization Behavior and Spectroscopic Properties of Erbium-Doped Chlorine-Substituted Fluorozirconate Glasses

We have prepared ErF3-doped glasses in the ZrF4–BaF2–LaF3–AlF3–NaF system containing chlorine ions substituted for fluorine ions. The crystallization behavior of the chlorine-substituted glasses has been studied at various BaCl2 and ErF3 concentrations. We have identified phases precipitating during heat treatment of the glasses and assessed the effect of chlorine substitution for fluoride on the optical absorption and IR luminescence in the glasses. The results demonstrate that chlorine substitution for fluorine causes the UV absorption edge of the glass to shift to longer wavelengths and produces an additional absorption in the visible spectral region. The formation of crystalline phases during heat treatment of the glasses leads to significant changes in the shape of the Er3+ luminescence bands at 0.98 and 1.55 μm.

Phase Equilibria in the NaF–NaCl–NaBr–Na2CrO4 System

We have studied phase equilibria in the quaternary system NaF–NaCl–NaBr–Na2CrO4. The results demonstrate that the continuous series of NaClxBr1 – x solid solutions persists in the system. The chemical composition and melting point (507°C) of a mixture with the composition corresponding to the quaternary minimum have been determined by differential thermal analysis, and its enthalpy of fusion (232 J/g) has been determined by differential scanning calorimetry. Its phase composition has been confirmed by X-ray diffraction. Theoretical and experimental techniques have been used to identify phase equilibria and the phase crystallization sequence and construct a 3D computer model of phase relations, which makes it possible to predict phase transformations for arbitrary representative points in the system studied.

Phase Complex of the Quinary Reciprocal System Li+,Na+,K+||F–,Cl–,Br– and Investigation of the Stable Tetrahedron LiF–NaF–KCl–KBr

The phase complex of the quinary reciprocal system Li+,Na+,K+||F–,Cl–,Br– was studied for the first time. Partition according to graph theory determined that the tree of phases of the system has linear structure and comprises stable polytopes: the pentatope LiF–NaF–KF–KBr–KCl, the hexatope LiF–NaBr–NaCl–KCl–KBr–NaF, and the heptatope NaCl–KCl–KBr–LiBr–LiCl–LiF–NaBr, connected by the stable tetrahedron LiF–NaF–KCl–KBr and the stable pentatope LiF–KBr–NaBr–NaCl–KCl. Phase equilibria in the stable tetrahedron LiF–NaF–KCl–KBr were studied by differential thermal analysis and confirmed by X-ray powder diffraction analysis. In the tetrahedron, there is monovariant phase equilibrium L ⇄ LiF + α + KClxBr1 – x, where α is a limited solid solution based on NaF (LiF–NaF system), and KClxBr1 – x is a continuous series of solid solutions based on KCl and KBr. A 3D computer model of the projection of the phase complex on the concentration tetrahedron was constructed using the KOMPAS 3D software. The crystallization volumes of equilibrium phases are determined.

Development of Wide-range Viscometer and the Viscosity Measurement for SiO&lt;sub&gt;2&lt;/sub&gt;–Na&lt;sub&gt;2&lt;/sub&gt;O–NaF System

Development of Wide-range Viscometer and the Viscosity Measurement for SiO&lt;sub&gt;2&lt;/sub&gt;–Na&lt;sub&gt;2&lt;/sub&gt;O–NaF System

Optical Properties and Electron Paramagnetic Resonance Spectra of Zirconium Fluoride- and Hafnium Fluoride-Based Glasses Activated with MnO2 and EuF2

We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese- and europium-activated fluorozirconate glasses in the ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) system and fluorohafnate glasses in the HfF4–BaF2–LaF3–AlF3–NaF (HBLAN) system in order to assess the oxidation state and spatial distribution of the activator ions. The manganese luminescence band has been shown to shift from the green (545 nm) to the red (610 nm) spectral region, and additional lines in the EPR spectrum of manganese have been observed to emerge in the EPR spectrum of manganese as a result of BaCl2 substitution for BaF2 in the ZBLAN glass. The ratio of the concentration of free activator ions to that of clustered ions has been estimated quantitatively. It has been shown that, at high doping levels, the manganese and europium ions in the glasses are predominantly clustered, and only a small part of them are present as isolated ions.

Sorption and desorption of BrF3 on NaF: Studies on thermodynamics and kinetics

Temperature dependence of bromine trifluoride vapor pressure over its adduct with sodium fluoride has been determined; the adduct normal dissociation temperature has been determined. Kinetics of sorption and desorption processes in BrF3(gas)–NaF(solid) system have been studied.The equation was proposed to illustrate the link between forward reaction rate (Ка) described by Arrhenius equation and experimental value (Ki):Ki= Kа⋅ (Pa/Peq)m,where Ki – observed reaction rate constant, Ka – forward reaction rate constant described by Arrhenius equation; Pa – partial pressure of BrF3; Peq – equilibrium pressure of BrF3 above BrF3⋅3NaF; m – factor characterizing the interaction area of BrF3 with NaF. The application of this equation makes possible to determine the true reaction rate values and reaction activation energy in chemisorption terms; it also helps to calculate the degree BrF3 sorption on NaF reaction at different temperatures and adsorbate pressures.The possibility of sorption-desorption separation of bromine trifluoride – uranium hexafluoride – iodine pentafluoride system with use of sodium fluoride was shown.