Mixture Of KF Research Articles

Corrosion of Ceramic and Carbon-Based Materials in FLiNaK

Corrosion resistance of ceramic and carbon materials was studied in molten salt systems based on LiF–NaF–KF mixture in the temperature range 550–750°C. The rates of corrosion of silicon nitride, boron nitride, carbon-carbon composites, and high density graphite in the fluoride electrolyte were determined. The mechanisms of materials degradation after the contact with molten FLiNaK are proposed, and the effect of the salt media and the temperature on the mechanical properties of ceramic and carbon materials is considered.

Corrosion of Metallic Materials in the Molten FLiNaK

Corrosion resistance of molybdenum, tantalum, and nickel-based alloys was studied in molten salt systems based on LiF–NaF–KF mixture in the temperature range 550–750°C. The rates of corrosion of these materials were determined, the nature of the degradation of the surface of materials established, and the effect of the salt medium and temperature on the corrosive properties of metals and nickel-based alloys considered.

ChemInform Abstract: Ion Mobility, Conductivity, Structure, and Phase Transitions in K0.7M0.3SbF4 Compounds with M: Rb, NH4.

AbstractThe title compounds are obtained upon solvent evaporation of aqueous solutions containing a 0.5:0.5:1 molar mixture of KF, RbF, SbF3 or a 0.3:0.7:1 molar mixture of KF, NH4F, and SbF3, respectively.

An Ion-Specific Effect on Polymer-Protein Interaction Enhances Resolution of Nanopore-Based Detection

Poly(ethyleneglycol) (PEG) oligomers partition into acqueous transmembrane channels formed by alpha-Hemolysin (aHL) and Aerolysin (AeL) proteins and transiently bind the pore to induce reductions in conductance, i.e. resistive pulses, the amplitude of which is strongly related to polymer chain length. Histograms of such data for PEG yield mass spectrograms with single monomer resolution between approximately 20 and 60 repeat units (r.u.). For chain lengths <20 the duration of resistive pulses becomes too short (e.g.<50 µs) to be fully resolved using state-of-the art electrophysiological recording technology. Recently, computational reconstruction of unresolved events has revealed the presence in a sample of PEG species down to 9 r.u. from data acquired with a bandwidth of 0-100 kHz(1), showing that small PEGs also interact with the pore. We were interested in prolonging the interaction of pore and polymer in order to enable a quantitative detection of PEG species <20 r.u. Krasilnikov and coworkers reported in 2011 (2) that the anion species in the electrolyte strongly affected the dwell times of the aHL pore by PEG, with strongly hydrated F- promoting long-lasting events. Here, using 1:1 mixtures of KF and KCl (4 M) solutions, we report direct resolution of PEG oligomers down to 8 r.u. from data obtained at filter settings of 20 kHz (see figure), due to a significant increase in the characteristic dwell times (tau) of events: for PEG28 tau increased from approx. 1.5 ms in 4M KCl to 7 ms in 4M 1:1 KCl/KF while tau for PEG12 was not directly measurable in KCl (estimated at 18 µs in Ref. 1) but found at ca. 90 µs in KCl/KF.(1) Balijepalli et al. ACS Nano 2014, 8, 1547-1553.(2) Rodrigues et al. Biophys. J. 2011, 100, 2929-2935.

Sono-synthesis of biodiesel from soybean oil by KF/γ-Al2O3 as a nano-solid-base catalyst

In this work, biodiesel has successfully prepared via ultrasonic method in a short time and low temperature by nano-solid-base catalyst (KF/γ-Al2O3). The catalyst was obtained by calcination of a mixture of KF and γ-Al2O3(mKF/mγ-Al2O3=70%) at 500°C for 3h. Nano-solid-base catalyst was characterized with scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermal gravimetry (TG) and the Hammett indicator methods. The TEM image depicted nanoparticles and uniform dispersion of active phase over alumina. The XRD analysis confirmed the formation of potassium aluminum fluoride (K3AlF6) and potassium oxide, active catalyst for transesterification. The transesterification of soybean oil with methanol was performed by using both low frequency ultrasonic reactor (20kHz) and mechanical stirring in the presence of KF/γ-Al2O3. The influence of various parameters such as ultrasonic power, oil/methanol molar ratio, catalyst concentration, time, and temperature were studied on the biodiesel formation. The maximum yield (95%) was achieved by applying 45W acoustic power, molar ratio of alcohol to oil at 12:1, catalyst concentration of 2.0wt%, 40min sonication, and temperature of 50°C. The transesterification was performed in 360min using mechanical stirring with 76% yield. The results confirm that ultrasound significantly accelerates the transesterification reaction in comparison with the mechanical stirring.

Effectively simultaneous naked-eye detection of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin extracted from red cabbage as chelating agent

Simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) using cyanidin as a chelating agent was investigated in terms of both quantitative and qualitative detections. Cyanidin was extracted and purified from red cabbage which is a local plant in Thailand. The selectivity of this method was examined by regulating the pH of cyanidin solution operated together with masking agents. It was found that Cu(II), Pb(II), Al(III) and Fe(III) simultaneously responded with the color change at pH 7, pH 6, pH 5 and pH 4, respectively. KF, DMG and the mixture of KF and DMG were used as masking agents for the determination of Fe(III), Al(III) and Pb(II), respectively. Results from naked-eye detection were evaluated by comparing with those of inductively coupled plasma (ICP), and there was no significant difference noticed. Cyanidin using as a multianalyte reagent could be employed for simultaneous determination of Cu(II), Pb(II), Al(III) and Fe(III) at the lowest concentration at 50, 80, 50 and 200μM, respectively, by slightly varying pHs. Moreover, the proposed method could be potentially applied for real water samples with simplicity, rapidity, low cost and environmental safety.

ChemInform Abstract: Triangular Exchange Interaction Patterns in K3Fe6F19: An Iron Potassium Fluoride with a Complex Tungsten Bronze Related Structure.

AbstractK3Fe6F19 is synthesized from a stoichiometric mixture of KF, FeF2, and FeF3 (Ag tube, N2, 550—650 °C, 12 h) and characterized by single crystal XRD, powder neutron diffraction, and magnetic measurements.

Computational Thermodynamic Modeling of Hot Corrosion of Alloys Haynes 242 and HastelloyTM N for Molten Salt Service in Advanced High Temperature Reactors

Computational Thermodynamic Modeling of Hot Corrosion of Alloys Haynes 242 and HastelloyTM N for Molten Salt Service in Advanced High Temperature Reactors An evaluation of thermodynamic aspects of hot corrosion of the superalloys Haynes 242 and HastelloyTM N in the eutectic mixtures of KF and ZrF4 is carried out for development of Advanced High Temperature Reactor (AHTR). This work models the behavior of several superalloys, potential candidates for the AHTR, using computational thermodynamics tool (ThermoCalc), leading to the development of thermodynamic description of the molten salt eutectic mixtures, and on that basis, mechanistic prediction of hot corrosion.

ChemInform Abstract: Crystal Structure, Dielectric Properties of (K0.5Na0.5)NbO3 Single Crystal Grown by Flux Method Using B2O3 Flux.

AbstractSingle crystals of the title compound are prepared from mixtures of Na2CO3, K2CO3, and Nb2O5 using mixtures of KF, NaF, and B2O3 as flux (1150 °C, 24 h).

ChemInform Abstract: The Cubic [Ti8F36]4‐ Anion Found in the Crystal Structures of K4Ti8F36·8HF and Rb4Ti8F36·6HF.

AbstractSingle crystals of the title compounds are prepared by slow evaporation of anhydrous HF solutions containing mixtures of KF or RbF and TiF4.

ChemInform Abstract: Flux Synthesis, Crystal Structure, and Photoluminescence of a Heterometallic Uranyl‐Europium Germanate with U=O—Eu Linkage: K4 [(UO2)Eu2(Ge2O7)2

AbstractCrystals of the new title compound are synthesized from UO3, Eu2O3, and GeO2 using a mixture of KF and MoO3 as flux (Pt crucible, 950 °C, 48 h).

ChemInform Abstract: Preparation and Characterization of a Stable FeSO4F‐Based Framework for Alkali Ion Insertion Electrodes.

AbstractKMSO4F (M: Fe, Co, Ni) is prepared by ball milling of equimolar mixtures of KF and MSO4 for one hour followed by heating (Parr reactor, 270—290 °C, 40—45 h).

Flagellin-PAc Fusion Protein is a High-efficacy Anti-caries Mucosal Vaccine

We previously demonstrated that an anti-caries DNA vaccine intranasally administered with recombinant flagellin protein as a mucosal adjuvant enhanced salivary IgA response and conferred better protection against caries. However, the relatively weak immunogenicity of DNA vaccines and the necessity for a large quantity of antigens remain significant challenges. Here, we fused the flagellin derived from E. coli (KF) and target antigen PAc containing the A-P fragment of PAc from S. mutans (rPAc) to produce a single recombinant protein (KF-rPAc). The abilities of KF-rPAc to induce rPAc-specific mucosal and systemic responses and protective efficiency against caries following intranasal immunization were compared with those of rPAc alone or a mixture of rPAc and KF (KF + rPAc) in rats. Results showed that KF-rPAc promoted significantly higher rPAc-specific antibodies in serum as well as in saliva than did an equivalent dose of rPAc alone or a mixture of KF + rPAc. Intranasal immunization of 8.5 µg KF-rPAc could achieve 64.2% reduction of dental caries in rats. In conclusion, our study demonstrated that flagellin and PAc fusion strategy is promising for anti-caries vaccine development, and KF-rPAc could be used as an anti-caries mucosal vaccine.

Single step fluorination of dialkylphosphites: trichloroacetonitrile–KF as an efficient reagent for the synthesis of dialkyl fluorophosphates

The use of trichloroacetonitrile and KF mixture is described as an efficient reagent for the direct conversion of dialkylphosphites to their corresponding dialkyl fluorophosphates via in situ formation of dialkyl chlorophosphates in one-pot.

KF-Silica as a stationary phase for the chromatographic removal of tin residues from organic compounds.

Through the simple expedient of using a mixture of KF and silica as the stationary phase in column chromatography, levels of organotin impurities from tributyltin hydride mediated reductions have been reduced from stoichiometric levels to approximately 30 ppm.

Energetics of formation of KFGdF3 binary-intermediate compounds

Abstract Enthalpies of formation were measured for KGdF 4 , K 2 GdF 5 and KGd 2 F 7 using the transposed temperature drop calorimetry method. These compounds were synthesized by conventional solid state reaction methods using mixtures of KF and GdF 3 . The measured enthalpies of formation from fluorides for KGdF 4 , K 2 GdF 5 and KGd 2 F 7 were − 22.3, − 16.1 and − 18.3 kJ mol −1 , respectively. From these measurements, enthalpies of formation from the elements were computed to be − 2290.0, − 2852.4 and − 3985.2 kJ mol −1 for the respective compounds. These enthalpies were compared with estimated values calculated by two methods previously reported to be effective for multicomponent oxides. Estimated values compare favorably with measured data, with deviations ranging from 0.5 to 2.9%. The errors of 0.5–2.9% correspond to a 16–85 kJ mol −1 uncertainty range for Δ f H 0 of ternary fluorides from binary fluorides. One of these methods, based on the summation of Δ f H 0 values for the constituent binary fluorides, is recommended for the KGdF compounds.

Poly(ether ketone)s by Fluoride Catalyst Systems

KF or a mixture of KF and N-neopentyl-4-(dialkylamino)-pyridinium chlorides were used as catalysts to improve poly(ether ketone) syntheses of dichloroaryl monomers such as 1,4-bis(4-chlorobenzoyl)benzene (1) via nucleophilic displacement. Polymers of increased molecular weight within a significantly reduced reaction time can be obtained by this method, as demonstrated with condensations of 2,2-bis(4-hydroxyphenyl)pentane (4) or 2,2-bis(4-hydroxyphenyl)heptane (5) with 1. Furthermore, high molecular weight semicrystalline poly(ether ether ketone)s, commonly known as PEEKK, were synthesized by fluoride anion assisted polycondensation of 1

Saturation vapour pressure and thermodynamic properties of potassium solutions in molten binary mixtures of its halides

The saturation vapour pressure of potassium solutions in molten binary mixtures of KF + KCl, KF + KBr, KF + KI, KCl + KI with molar ratios of their components being 3:1, 1:1, 1:3, and in equimolar mixtures of KCl + KBr and KBr + KI was measured as a function of temperature and the metal concentration by a statistical method. A device with a sylphon zero-manometer was used, the gas space of which was minimized to reduce changes in the composition of the melts caused by the evaporation of their components. Potassium partial pressure was determined. It deviates from additive quantities towards greater values. The deviations grow as the molar ratio of lighter and heavier halide anions replacing each other in the melts increases. The potassium activity coefficient calculated from experimental data as a function of temperature and the composition of the melts is much greater than unity. It diminishes as the metal concentration and the molar fraction of the heavier salt components are raised. Potassium partial excess Gibbs energy was computed for all the melts under study.

Investigation of the Corrosion and Passivation Processes of Magnesium in the Molten 2 HF ‐ KF Mixture by AC Impedance Spectroscopy

Metallic magnesium is chemically corroded by the mixture at 80°C, with the formation of a passivating microporous magnesium fluoride layer as revealed by electron scanning micrograph and cyclic voltammetry. A more compact layer can be obtained electrochemically. The corrosion mechanism has been studied by ac impedance measurements. The reaction pathway involves oxidation, desorption, diffusion, and precipitation steps. Kinetic parameters (charge and mass transfer) have been determined by a computerized simulation method.

X-ray diffraction study of molten eutectic LiF–NaF–KF mixture

The structure of molten eutectic LiF–NaF–KF (46.5; 11.5; 42.0 mol%) mixture at 520 °C has been investigated using the radial-distribution function based on X-ray scattered intensity data and analysed by the correlation method. The nearest-neighbour distances of unlike-ions, Li–F, Na–F and K–F, were 1.83, 2.18 and 2.59 A, respectively, and their respective coordination numbers were 3.3, 3.8 and 4.0. These values are almost the same as those in the pure melts. The result indicates that in the ternary mixture the short-range structures of unlike ion pairs do not change on mixing nor in binary melts.