Chloride Fluoride Research Articles

Chemical Investigation on the Mechanism and Kinetics of the Atmospheric Degradation Reaction of Trichlorofluoroethene by OH⋅ and Its Subsequent Fate in the Presence of O2 /NOx.

The M06-2X/6-311++G(d,p) level of theory was used to examine the degradation of Trichlorofluoroethene (TCFE) initiated by OH⋅ radicals. Additionally, the coupled-cluster single-double with triple perturbative [CCSD(T)] method was employed to refine the single-point energies using the complete basis set extrapolation approach. The results indicated that OH-addition is the dominant pathway. OH⋅ adds to both the C1 and C2 carbons, resulting in the formation of the C(OH)Cl2 -⋅CClF and ⋅CCl2 -C(OH)ClF species. The associated barrier heights were determined to be 1.11 and -0.99 kcal mol-1 , respectively. Furthermore, the energetic and thermodynamic parameters show that pathway 1 exhibits greater exothermicity and exergonicity compared to pathway 2, with differences of 8.11 and 8.21 kcal mol-1 , correspondingly. The primary pathway involves OH addition to the C2 position, with a rate constant of 6.2×10-13 cm3 molecule-1 sec-1 at 298 K. This analysis served to estimate the atmospheric lifetime, along with the photochemical ozone creation potential (POCP) and ozone depletion potential (ODP). It yielded an atmospheric lifetime of 8.49 days, an ODP of 4.8×10-4 , and a POCP value of 2.99, respectively. Radiative forcing efficiencies were also estimated at the M06-2X/6-311++G(d,p) level. Global warming potentials (GWPs) were calculated for 20, 100, and 500 years, resulting in values of 9.61, 2.61, and 0.74, respectively. TCFE is not expected to make a significant contribution to the radiative forcing of climate change. The results obtained from the time-dependent density functional theory (TDDFT) indicated that TCFE and its energized adducts are unable to photolysis under sunlight in the UV and visible spectrum. Secondary reactions involve the [TCFE-OH-O2 ]⋅ peroxy radical, leading subsequently to the [TCFE-OH-O]⋅ alkoxy radical. It was found that the alkoxy radical resulting from the peroxy radical can lead to the formation of phosgene (COCl2 ) and carbonyl chloride fluoride (CClFO), with phosgene being the primary product.

Electrodeposition of Ti in Molten Alkali Metal Fluoride–Chloride Mixtures: Comparative Study of Li, Na, K, and Cs Systems

1. IntroductionTitanium (Ti) is a metal with excellent properties such as high corrosion resistance and biocompatibility. However, it is still not widely used due to its high production cost and poor workability. If Ti films can be plated on a variety of substrates, the excellent surface properties of Ti can be imparted, and it is expected to be applied in a wider range of fields.We have previously studied Ti electrodeposition using KF–KCl [1-3] and LiF–LiCl [4,5] melts and reported that smooth Ti films were obtained. Here, fluoride–chloride melts containing a single cation, such as KF–KCl and LiF–LiCl, were used so that differences due to cations could be compared. As a result, we have already reported that the electrodeposition potential of Ti differs significantly between the K- and Li-based systems [4]. Therefore, in this study, we investigated the electrodeposition of Ti and the electrochemical behavior of Ti(III) ions in the CsF-CsCl and NaF-NaCl melts. This allowed us to systematically compare the effects of cations on titanium electrodeposition for the Li-, Na-, K-, and Cs-based systems.2. ExperimentalThe experiments were conducted in eutectic CsF–CsCl and NaF–NaCl melts in an Ar glove box. A2TiF6 (A = Cs, Na) and sponge Ti were added to the melts and Ti(IV) ions were converted to Ti(III) ions by comproportionation reaction. Ni plate, Mo and Au flag electrodes were used as the working electrodes. The counter and reference electrodes were Ti rods. The potential of the reference electrode was calibrated by A+/A (A = Cs, Na) potential measured at a Mo electrode. The electrochemical behavior of Ti(III) was studied by cyclic voltammetry. Samples prepared by galvanostatic electrolysis of Ni plate substrates were analyzed by X-ray diffraction (XRD) after washing with distilled water.3. Result and DiscussionFigure 1 (a) shows cyclic voltammograms measured at a Mo flag electrode in the negative potential region in molten CsF–CsCl at 823 K. After the addition of Ti(III) ions, cathodic currents around 0.3 V were larger than those before the addition, and a current shoulder was observed at 0.3 V. Furthermore, a sample prepared by galvanostatic electrolysis at a cathodic current density of 25 mA cm−2 was confirmed to be Ti metal by XRD. Considering that the potential during the electrodeposition was around 0.3 V, the cathodic currents around 0.3 V in the CV were confirmed to beTi(III) + 3e− → Ti(0).Figure 1 (b) shows cyclic voltammograms measured at a Au flag electrode in the positive potential region in molten CsF–CsCl containing Ti(III) ions at 823 K. A pair of redox currents were observed around 1.7 V. The number of electrons transferred was 0.86 which was calculated from the difference in the cathodic and anodic peak potentials. This result indicates that the redox reaction around 1.7 V isTi(IV) + e− ⇄ Ti(III).Here, the formal potential of Ti(IV)/Ti(III) was calculated to be 1.63 V from the average values of the cathodic and anodic peak potentials.We compared the obtained potentials of Ti(III)/Ti(0) and Ti(IV)/Ti(III) to those previously reported in KF–KCl and LiF–LiCl melts [2,4]. Figure 2 shows the comparison of the Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials in CsF–CsCl, KF–KCl, and LiF–LiCl melts. All potentials were calibrated using F2/F− potential for comparison because Ti(III) ions exist as fluoro-complexes in the melts. Both Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials were negative in the order of Li-, K-, Cs-based systems. Such potential differences are explained by the interactions of alkaline cations (A+) and fluoride ions (F−); smaller cations interact more strongly with F−, resulting in reduced stability of Ti fluoro-complexes. At the meeting, we will compare and discuss all the results, including those obtained with NaF-NaCl melts.AcknowledgmentA part of this work was supported by JSPS KAKENHI Grant Number 22K14507. A part of this study was conducted as a collaboration with Sumitomo Electric Industries, Ltd.

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.

Understanding the kinetics and atmospheric degradation mechanism of chlorotrifluoroethylene (CF2CFCl) initiated by OH radicals.

The atmospheric degradation of chlorotrifluoroethylene (CTFE) by OH˙ was investigated using density functional theory (DFT). The potential energy surfaces were also defined in terms of single-point energies derived from the linked cluster CCSD(T) theory. With an energy barrier of -2.62 to -0.99 kcal mol-1 using the M06-2x method, the negative temperature dependence was determined. The OH˙ attack on Cα and Cβ atoms (labeled pathways R1 and R2, respectively) shows that reaction R2 is 4.22 and 4.42 kcal mol-1, respectively, more exothermic and exergonic than reaction R1. The main pathway should be the addition of OH˙ to the β-carbon, resulting in ˙CClF-CF2OH species. At 298 K, the calculated rate constant was 9.87 × 10-13 cm3 molecule-1 s-1. The TST and RRKM calculations of rate constants and branching ratios were performed at P = 1 bar and in the fall-off pressure regime over the temperature range of 250-400 K. The formation of HF and ˙CClF-CFO species via the 1,2-HF loss process is the most predominant pathway both kinetically and thermodynamically. With increasing temperature and decreasing pressure, the regioselectivity of unimolecular processes of energized adducts [CTFE-OH]˙ gradually decreases. Pressures greater than 10-4 bar are often adequate for assuring saturation of the estimated unimolecular rates when compared to the RRKM rates (in high-pressure limit). Subsequent reactions involve the addition of O2 to the [CTFE-OH]˙ adducts at the α-position of the OH group. The [CTFE-OH-O2]˙ peroxy radical primarily reacts with NO and then directly decomposes into NO2 and oxy radicals. "Carbonic chloride fluoride", "carbonyl fluoride", and "2,2-difluoro-2-hydroxyacetyl fluoride" are predicted to be stable products in an oxidative atmosphere.

Electrodeposition of crystalline Si in molten alkali metal fluoride–chloride mixtures: Comparative study of Li, Na, K, and Cs systems

A comparative study was conducted on the electrodeposition of Si using molten salts of AF–ACl–A2SiF6 (A = Li, Na, K, Cs, AF–ACl = 50:50 mol%) at 1073 K. Cyclic voltammetry revealed that the electrodeposition potential of Si was negative in the order of Na > K > Cs systems with reference to Cl2/Cl−, and almost the same as with reference to F2/F−. In the Li system, no cathodic current peak was observed, owing to the formation of the Li–Si alloy. In the Na and Li systems, the cathodic peak current density decreased with time owing to the decomposition of SiF62− ions. The differences in the Si electrodeposition and thermal stability of SiF62− ions can be explained by the interactions of alkaline cations and F− ions; smaller cations interact more strongly with F−, resulting in the reduced thermal stability of SiF62−. Electrodeposited Si was confirmed to be crystalline by XRD, and its morphology was film-like in the K and Cs systems, and whisker-like in the Na system. A difference in nucleation and growth was observed between the K and Na systems, which explains the difference in the morphology of the Si deposits.

Sm7F12Cl2: synthesis and crystal structure of a new fluoride-rich samarium(II) fluoride chloride

Sm₇F₁₂Cl₂: synthesis and crystal structure of a new fluoride-rich samarium(II) fluoride chloride

Experimental Study of the Solubility of Natural Tantalite and Pyrochlore and Tantalum and Niobium Oxides in Hydrothermal Fluoride–Chloride Solutions

The concentration and temperature dependences of the solubility of tantalite, pyrochlore, and tantalum and niobium oxides in fluoride–chloride aqueous (mHF + mHCl) solutions at 300–550°C and 100 MPa (Co–CoO buffer) were studied experimentally. The initial concentration of HF varied from 0.01m to 2m, while the HCl concentration remained constant and was 0.5m. A comparative analysis of the equilibrium contents of Nb and Ta upon dissolution of tantalum and niobium oxides and natural tantalite and pyrochlore in fluoride, chloride, and mixed (mHF + mHCl) solutions was carried out.

Solubility of REM Oxides in Chloride–Fluoride and Fluoride Melts

Solubility of REM Oxides in Chloride–Fluoride and Fluoride Melts

Charge Transfer Kinetics of the Ti(IV)/Ti(III) Redox Couple in Chloride–Fluoride Melts

Charge Transfer Kinetics of the Ti(IV)/Ti(III) Redox Couple in Chloride–Fluoride Melts

Microstructural Master Alloys Features of Aluminum–Erbium System

Aluminum master alloys with rare earth metals are widely studied by many scientists around the world, but research on the production of Al-Er master alloys is still limited. The purpose of this work is to study the microstructure parameters of aluminum-erbium master alloys obtained by metallothermic reduction of salt mixtures containing erbium oxide or fluoride. The structural features were investigated by optical and scanning electron microscopy, and the dependence of the microhardness of the eutectic and solid solution fields of obtained master alloys on the content of erbium in the master alloy was determined. Studies have shown that master alloys obtained by metallothermic reduction of erbium compounds from chloride–fluoride melts are characterized by a uniform distribution of Al3Er intermetallic compounds in the volume of double eutectic [(Al) + Al3Er] and have a strong grain refinement effect. The analysis of the microstructure showed that the structure of the master alloys varies depending on the content of erbium. When the content of erbium in the master alloy is up to 6 wt.%, the eutectic structure is preserved. When the content of erbium in the master alloy is 8 wt.% or more, the structure becomes a solid solution with individual inclusions of various shapes and intermetallic compounds.

Electroreduction of Cobalt(II) Chloride and Cobalt(II) Fluoride Mixtures in a Thermally Activated Chemical Current Source

Electroreduction of Cobalt(II) Chloride and Cobalt(II) Fluoride Mixtures in a Thermally Activated Chemical Current Source

Secondary Reduction of Refractory Metal near Smooth Cathode during the Salt Melt Electrolysis. 3. Numerical Reproducing of Natural Experiment with the Nb Cathodic Reduction in KNaCl2–NaF–K3NbF7 Melt

In terms of the model of steady-state process of a refractory-metal ion secondary reduction with an alkali (or alkali-earth) metal formed on a smooth cathode during salt melt electrolysis, numerical reproducing of a natural experiment is carried out. The model calculations are based on the polarization measured during the cathodic reduction of Nb in chloride―fluoride melt: [Nb] = 2.4 mol %, 800°C, current density i up to 5.4 A/cm2. On a smooth cathode in the overvoltage range from 0.21 to 0.41 V (i = 0.75―1.17 A/cm2), the reduction mechanism is shown to completely change from primary to the secondary reduction. The secondary reduction zone is located inside the diffusion layer and moves away from the cathode with increasing i. Even at maximal i, this zone remains inside δ (δ is the thickness of the diffusion layer): with i = 0.96 A/cm2, the coordinate of the maximum of the secondary reduction rate xm = 0; with i = 5.4 A/cm2, xm = 0.93δ (in the experiment, the value of i at which xm ≥ δ was not achieved). At i = 5.4 A/cm2, the fraction of secondary reduction in the bulk is insignificant, ≈10−5 A/cm2. The δ vs. E curve is calculated: when E is shifted from the equilibrium value toward the negative values, |i| increased from zero and higher, whereas δ first decreased by an order of magnitude and then increased. Correspondingly, the limiting diffusion current is not constant at a constant Nb concentration in the bulk. This is the reason of uncertain limiting current on steady-state cathodic polarization curves during the electrolysis of metals in melts. A hypothesis is proposed on the dependence of the Nernst diffusion layer thickness near the cathode on the current density exceeding the limiting diffusion current density under the conditions of secondary reduction.

Synthesis of Mg–Zn–Nd Master Alloy in Metallothermic Reduction of Neodymium from Fluoride–Chloride Melt

In the presented article, a differential thermal analysis was carried out and the temperatures of thermal effects were established that arise during the reduction of neodymium from a technological salt mixture KCl–NaCl–CaCl2–NdF3 with a magnesium–zinc alloy. The results of experimental studies on the reduction of neodymium from a fluoride–chloride melt in a shaft electric furnace at temperatures of 550, 600, 650, 700 °C are presented. In order to increase the degree of extraction of neodymium into the Mg–Zn–Nd master alloy, the study of the influence of technological parameters on the degree of extraction of neodymium was carried out. It was experimentally proven that when zinc is added to a reducing agent (magnesium), the degree of extraction of neodymium into the master alloy is 99.5–99.7%. The structure of the obtained master alloy samples, characterized by a uniform distribution of ternary intermetallic compounds (Mg3,4NdZn7) in the volume of a double magnesium–zinc eutectic, was studied by optical and electron microscopy.

Search for Flux Media for Crystallization of Epitaxial Fluorite Layers

The solubility of CaF2 in different chloride and chloride‒fluoride melts has been studied in order to choose appropriate fluxes for crystallization of epitaxial fluorite layers. It is shown that the advantages of the 0.6NaCl–0.4NaF composition over the well-known CaCl2–CaF2 flux are the high thermal stability, lower (by half) temperature gradient of solubility, and possibility for reducing the growth temperature by 100°С. Seed crystallization of fluorite in the CaF2–(0.6NaCl–0.4NaF) flux has been performed both using the temperature reduction method and under the temperature gradient conditions.

Highly efficient removal of phosphate by lanthanum modified nanochitosan-hierarchical ZSM-5 zeolite nanocomposite: characteristics and mechanism

In this study, nanochitosan-hierarchical ZSM-5 zeolite composite (NCS@ZSM-5-H) was synthesized via simple way at ambient temperature. The hierarchical ZSM-5 zeolite were prepared by hydrothermal processing without the use of zeolite seeding crystals or additional template. Lanthanum (La) was loaded onto the surface of samples to acquire a simply separable adsorbent for efficient separation of phosphate (P) from water. The synthesized materials are examined before and after adsorption of P by several characterization techniques. Results of adsorption experiments showed that NCS@ZSM-5-H/La is very effective in the adsorption of P species from aqueous solutions. Response surface methodology has been applied to optimize and model P uptake onto NCS@ZSM-5-H/La nanocomposite. A four-factor central composite design has been applied to find out the influence of different process parameters on P removal. Thermodynamic, isotherm, and kinetic studies were employed to understand the adsorption behavior. The P adsorption was not significantly by interfering anions of fluoride chloride, and sulfate but carbonate revealed further negative effects, indicating NCS@ZSM-5-H/La possessed highly selectivity to P. The NCS@ZSM-5-H/La was regenerated using 2.0 M NaOH, with up to ~ 80% recovery and the as-synthesized nanocomposite was reused in seven consecutive adsorption–desorption cycles without significant reduction in regeneration capacity.

Few-layer-graphene as intercalating agent for spray-pyrolysed fluorine-doped tin oxide transparent conducting electrode

In this work, the development of a robust method for the fabrication of a low-cost transparent conducting electrode (TCE) via the addition of graphene in the spray-pyrolysis of fluorine-doped tin oxide (FTO) is explained. Alcoholic suspensions of few-layer-graphene were produced via the liquid exfoliation of graphite in different alcoholic solutions as sonicating solvent. These mixtures were then mixed with ammonium fluoride and tin (II) chloride dihydrate precursors to fabricate graphene/FTO composite through spray pyrolysis. Graphene exfoliated with 50% aqueous ethanol proved to yield improved TCE properties with nearly two-fold enhancement in figure of merit (FOM) measured in terms of the ratio of optical transmittance and sheet resistance. Using optimized spraying conditions, graphene/FTO coatings still yielded slightly higher FOM compared to plain FTO. The increase in FOM is largely attributed to the decrease in sheet resistance with the incorporation of graphene flakes.

Analysis of solar radiation heat transfer of architectural fabric membrane material

In recent years, the application of membrane structures in industrial storage buildings has been widely praised due to its light weight, high transparency, self-cleaning, and other advantages. The textile membranes consist of polyester fiber substrate and polyvinyl chloride or polyvinylidene fluoride flame-retardant coatings. It occupies the main market of architectural membrane materials in China. However, the fabric membrane material has high heat transfer coefficient, poor thermal insulation, and high light transmittance performance, being affected significantly by solar radiation intensity. These thermal optical properties are lead to a poor indoor thermal environment of industrial storage buildings. This article aims to overcome the difficulties in analyzing the fabric membrane materials solar radiation heat transfer. The complexity of heat transfer is mainly caused by the hourly solar radiation and the curved roofing of fabric membrane structure industrial storage building. Therefore, a solar radiation heat transfer model was established using MATLAB program. In this article, the different directions hourly heat gained of an actual membrane structures storage building located at Wuhan in China was calculated. The calculation results of solar radiation heat gained between the grid generation method with MATLAB and the projection method were compared. This study may provide a reference for analyze the solar radiation heat transfer and design of the practical fabric membrane structures building application.

Electrochemical Production of Tungsten Powders from Tungsten Hardmetal Waste

Hardmetals intended to perform in harsh operating conditions are developed with the use of metallic powders, in particular, tungsten powders. The growing consumption of tungsten in industry necessitates the improvement of techniques employed to produce it from industrial waste. The objective of this research effort was to reduce metallic tungsten (as a powder) from chloride and chloride–fluoride melts and determine the factors influencing its particle size. The starting material was tungsten oxide (WO3) produced electrochemically from processed raw material (VK-6 tungsten carbide pseudoalloy). The melts were KCl–NaCl–CsBr and NaCl–KCl–CsBr–Na3WO3F3 eutectic mixtures. When the melt with a high WO2F42− content was subjected to electrolysis, tungsten precipitated as a superfine powder. The precipitate morphology showed that the tungsten particle size was dependent on electrolysis conditions. A relatively inexpensive and effective method of producing tungsten powders was developed upon the research.

Effect of the Technological Parameters of the Aluminothermic Reduction of Erbium Oxide in Chloride–Fluoride Melts on the Transition of Erbium to a Master Alloy

The methods used for the preparation of an Al–Er master alloy as a promising addition to aluminum alloys for enhancing their physical and mechanical characteristics are analytically reviewed. Thermodynamic analysis of the processes that occur during master alloy fabrication in chloride–fluoride melts containing erbium oxide is carried out. Since the data on erbium complexes are lacking or restricted, the thermodynamic values are determined by indirect methods. The study of the phase composition of the chloride–fluoride melts shows that the melting of a salt mixture results in the fluorination of erbium oxide and the formation of the KEr3F10 complex, which is a precursor for erbium reduction and intermetallic compound Al3Er formation. The effect of the flux composition and the technological parameters of aluminothermic reduction on the transition of erbium to the master alloy is studied.

Tin–Nickel–Titania Composite Coatings

The effect of titania nanoparticles synthesized by direct oxidation of titanium powder on the cathodic polarization of the electrodeposition of Sn, Ni, and a Sn–Ni alloy in a fluoride–chloride electrolyte has been assessed using voltammetry. The morphology and phase composition of the coatings obtained have been studied by scanning electron microscopy and X-ray diffraction. The pH of the electrolyte has been shown to have a crucial effect on its stability and the quality of the coatings. The optimal pH of the electrolyte for the deposition process is 3.0 ± 0.1 and the optimal current density is 1.0 ± 0.1 A/dm2. The coprecipitation of nickel and tin into an alloy has been shown to be accompanied by a depolarization effect, due to the formation of NiSn2 and Ni3Sn2 intermetallic compounds. The addition of titanium dioxide shifts the alloy reduction process to more negative potentials. The addition of 2 g/L of titanium dioxide to an electrolyte leads to the incorporation of 0.7 wt % TiO2 into the composition of the coating.