High Fluorine Content Research Articles

Fluorine incorporation into calcite, aragonite and vaterite CaCO3: Computational chemistry insights and geochemistry implications

The abundant occurrence of calcium carbonate minerals in marine sediments and their high fluorine content suggests that fluorine is a good candidate for reconstructing paleoceanographic parameters. However, the potential of fluorine as a paleoproxy had hardly been explored, and fundamental insights into the behaviour of fluorine in biogenic carbonates and marine sediments is required. A first-principles modelling approach is used here to analyse the incorporation mechanisms of fluorine into crystalline calcium carbonates. We compute F incorporation into the CaCO3 lattice via a number of mechanisms, but concentrate on comparison of the energetics of the two easiest substitution mechanisms: replacing one oxygen atom within the carbonate group to form a (CO2F)− group as against a substitution involving replacement of the CO3 group by two fluorine ions to form a CaF2 defect. These incorporation mechanisms are fundamentally different from that of iodine into calcium carbonates, where a carbon atom is replaced. Our simulations suggest that the substitution of CO32- by F22- is the most favoured and that fluorine is preferentially incorporated into the three naturally-occurring polymorphs of calcium carbonate in the order vaterite ⪆ aragonite ≫ calcite. These results explain the previously-reported preponderance of fluorine in aragonite corals, and lend support to the use of F/Ca as a proxy for ocean pCO2.

Particulate matter emissions from flex-fuel vehicles with direct fuel injection

Otto cycle vehicles with gasoline direct injection (GDI) can reduce fuel consumption by 5–20%. In compliance with current legislation in Brazil, this technology was introduced to the domestic market in the form of a first flex-fuel GDI vehicle in 2013. However, despite gains in efficiency, studies in the literature have shown that GDI engines tend to have higher particulate matter emissions than port fuel injection (PFI) engines. This paper provides measurements of the emissions of GDI flex-fuel vehicles fuelled with gasoline containing 22% anhydrous ethanol (E22), hydrous ethanol (E100) and a 50% mixture of both (E61). The blending fuels were tested in accordance with the recommendations made in the widely known FTP 75 and HWFET cycles. The particulate-matter emissions formed during the combustion process were closely linked to fuel-type properties. The results showed the particles that adhere to sampling filters have higher concentrations of fluorine and carbon and lower amounts of silicon and oxygen, as well as sizes of around 2 μm. The black carbon emissions tend to increase directly with the gasoline content in the fuel. The results also provided evidence that the HWFET test cycle showed a higher emission rate of total particulate matter than the FTP 75 test cycle, and that overall, there were higher emissions for E22 than E100.

The source, enrichment and precipitation of ore-forming elements for porphyry Mo deposit: Evidences from melt inclusions, biotite and fluorite in Dasuji deposit, China

The Dasuji ore deposit is a large-scale porphyry Mo deposit at the northern margin of the North China Craton, China. Four stages of hydrothermal veins were recognized in the deposit, from early to late: K-feldspar–quartz veins (stage 1), quartz–molybdenite veins (stage 2), quartz–carbonate–pyrite–galena–sphalerite veins and fluorite veins (stage 3), and carbonate–quartz ± fluorite veins (stage 4). The melt inclusions in the earliest K-feldspar–quartz veins retain information about the ore-forming magma. Melt inclusions in quartz were studied in detail to investigate the magmatic evolution. In chondrite- and primitive-mantle-normalized trace element diagrams, all the inclusions have negative Ba, Sr, and Eu, and positive Pb anomalies. The inclusions have uniform (La/Sm)N ratios, and Sr concentrations decrease with decreasing Ba content, indicating the magma experienced significant fractionation, particularly of plagioclase and biotite. With increasing SiO2, Mo concentrations gradually increased, whereas Cu concentrations first increased and then decreased, suggesting that magmatic evolution was beneficial for Mo, but not Cu, enrichment. This indicates that highly fractionated magmas are conducive to the formation of porphyry Mo ore deposits rather than Cu ore deposits. The high F contents in biotite (up to 4.03 wt%) and pervasive occurrence of fluorite are indicative of a high-F magmatic–hydrothermal system. The disappearance of magnetite means the decrease of oxygen fugacity during stage 2, which promotes molybdenite precipitation. The contents of trace elements in fluorite before the stage 4 changed little, indicating that the fluid system was closed prior to this stage. The highly fractionated granitic magmatic system with high oxygen fugacity and high fluorine content potentially contain new porphyry Mo deposit.

Tungsten mineralization during the evolution of a magmatic-hydrothermal system: Mineralogical evidence from the Xihuashan rare-metal granite in South China

Abstract Tungsten deposits are usually associated with granitic intrusions that record a long and complex evolution of the magmatic-hydrothermal system. However, the genetic link between magmatic-hydrothermal evolution and tungsten mineralization remains unclear. The Xihuashan tungsten deposit in South China, an important vein-type wolframite deposit, is closely associated with greisen and multi-phase intrusive activity that produced biotite granite, two-mica granite, and muscovite granite. From the biotite granite to the two-mica granite to the muscovite granite, micas vary from siderophyllite to lithian siderophyllite, with decreasing K/Rb and Nb/Ta ratios and increasing Rb and Cs contents. The zoned micas in the muscovite granite and greisen display fluorine-depleted rims, reflecting subsolidus replacement by external aqueous fluids. The presence of siderite indicates a Fe-, Mn-, and CO2-rich fluid under reducing conditions. The micas in the greisen have higher-F contents and lower Fe3+/Fe2+ ratios than those in the muscovite granite, suggesting that the fluids contributing to greisen formation had a relatively high-fluorine content and were reduced. The increase of CO2 in the fluid enhanced its ability to unlock W from melts/rocks into fluids. The reducing environment also facilitated the tungsten mineralization. During greisenization, the pH value of the fluid increased, which destabilized the polymeric tungstates to form WO42–. The mixture of W-rich solution and Fe-, Mn-rich external fluid eventually precipitated as vein-type wolframite in favorable locations. An empirical equation (Li2O = 0.0748 × F2 + 0.0893 × F) was introduced for estimating the Li2O contents of hydrothermal micas using the F contents determined by EPMA.

Synthesis and energetic properties of trifluoromethyl-substituted 2-nitro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives

5-Amino-3-nitro-1,2,4-triazole (ANTA) is a potential intermediate for the synthesis of high performance energetic materials. Now we describe the construction of 5,7-disubstituted-2-nitro-[1,2,4]triazolo[1,5-a]pyrimidine with high fluorine content and considerable energy. The new compounds were fully characterized by multinuclear NMR (1H, 13C, 19F), and infrared spectroscopy, elemental analysis and differential scanning calorimetry (DSC). The structure of 2a is supported by single crystal X-ray diffraction analysis. Measured crystal densities, calculated heats of formation and energetic properties have been investigated. Based on Explo5 calculations, highly fluorinated compound 2b has detonation properties comparable with TNT.

Robust perfluorinated porous organic networks: Succinct synthetic strategy and application in chlorofluorocarbons adsorption

Fluorinated porous organic networks (F-PONs) have demonstrated unique properties and applications, but approaches capable of affording F-PONs with high fluorine content and robust nanoporous architecture under metal-free and easy handling conditions are still rarely reported. Herein, using polydivinylbenzene (PDVB) as an easily available precursor, a novel and straightforward approach was developed to afford F-PONs via a dehydrative Friedel-Crafts reaction using perfluorinated benzylic alcohols as the cross-linking agent promoted by Bransted acid (trifluoromethanesulfonic acid). The afforded material (F-PDVB) featured high fluorine content (22 at.%), large surface area (771 m2·g−1), and good chemical/thermal stability, rendering them as promising candidates for the adsorption of CO2, hydrocarbons, fluorocarbons, and chlorofluorocarbons, with weight capacities up to 520 wt.% being achieved. This simple methodology can be extended to fabricate fluorinated hyper-crosslinked polymers (F-HCPs) from rigid aromatic monomers. The progress made in this work will open new opportunities to further expand the involvement of fluorinated materials in large scale applications.

Influence of Fluorine Content on the Crystallisation of Potassium and Barium Fluorphlogopite Glass-Ceramics

The influence of fluorine content on the nucleation and crystallization behaviour of fluormica glass-ceramics based on 8SiO2-3Al2O3-(6-X)MgO-XMgF2-(K2O/BaO) were investigated. Fluoride reduced the glass transition temperature (Tg), as well as the first peak crystallisation temperature (Tp1) in both potassium and barium series. High fluoride content (X ≥ 2) promoted bulk crystal nucleation in the potassium series. The first crystallisation peak corresponded to the crystallization of potassium fluorphlogopite in glasses with X ≥ 2.0. However, in barium glasses surface crystallization was more dominant regardless of the fluorine content with kinoshitalite found to be the main mica phase. The formulations were designed to have high aluminium content to reduce volatilisation of SiF4, therefore only small weight loss was evident from the DTA/TGA analysis, <5% in fine samples; the frit samples showed much lower weight loss. In the potassium series, the weight loss increased with increase in fluoride content. In barium series the weight loss was independent of fluoride content. No evidence was found of precursor crystal phases, such as chondrodite (2Mg2SiO4.MgF2,), or norbergite (MgSiO4.MgF2). Owing to the high alumina and silica content in both series, other aluminium and silica rich phases, e.g. cordierite and mullite, crystallised in addition to the main phase of Phlogopite. Cordierite (5SiO2.2Al2O3.2MgO) was formed readily at low fluoride content of all glasses at high temperatures. Microstructural imaging of the developed glass-ceramic showed that the growth and coarsening of the microstructure was faster in glass compositions with higher fluorine contents and with potassium rather than barium.

Moisture Barrier Properties of Silicone Rubber Surface Layers Fluorinated at Different Temperatures

In this study, direct fluorination is used to modify the surface of silicone rubber. Moisture barrier properties of the SIR surface layers fluorinated at different temperatures are evaluated by moisture absorption experiments at a temperature of 30 or 60°C and at a relative humidity of 75 or 97%. Physicochemical characteristics of the fluorinated SIR surface layers are investigated on the basis of ATR-IR, XPS and SEM techniques. The moisture absorption measurements show that the fluorinated surface layer has a distinct moisture barrier to the entry of water into the interior of SIR at each humidity and temperature condition, and a close association of the barrier properties with fluorination temperature or physicochemical characteristics of the fluorinated layer. The barrier is particularly significant for such a surface layer fluorinated at a lower temperature, which has higher fluorine content and compactness although a small thickness, compared to the surface layer fluorinated at higher temperatures. In addition, fitting analysis of the experimental data further shows a lower apparent diffusivity of the surface fluorinated samples than the unfluorinated sample.

High-pressure vibrational spectra of humite-group minerals: Fluorine effect on thermodynamic properties and hydrogen bonds

The humite-group minerals could be potential water carriers as the dehydration products of serpentine in subduction slabs. Fluorine is an important element incorporated into the crystal structures through the substitution mechanism of OH− = F−, and has significant impacts on the thermodynamic properties. We conducted in situ high-pressure Raman and Fourier transform infrared (FTIR) measurements on natural F-bearing clinohumite, humite and norbergite samples, up to approximately 19GPa. The isothermal mode Grüneisen and intrinsic anharmonic parameters were calculated for both the lattice and OH-stretching modes, and the anharmonic contribution to the heat capacities was further evaluated for these hydrous phases. As compared with the OH-clinohumite sample, the anharmonic contribution is larger in magnitude for the F-bearing clinohumite, while such anharmonic contributions are even more significant in the humite and norbergite samples with higher fluorine concentrations. Both the Raman and FTIR spectra indicate that the OH-stretching modes above 3450 cm−1, which are controlled by the neighboring HH, systematically show positive pressure dependences. On the other hand, the OH bands below 3450 cm−1 shift to lower frequencies at elevated pressure, due to F− or Ti4+ substitutions. The F− substitution of OH− group could alleviate local HH repulsion effect, and create new H sites with shorter hydrogen bond lengths. These hydrogen bond would get shorter (negative pressure dependences), and are likely to participate in the hydrogen bond symmetrization at high pressure.

НОВЫЕ ИЗОТОПНО-ГЕОХИМИЧЕСКИЕ ДАННЫЕ ПО ТЕРМАЛЬНЫМ ВОДАМ ТАЛЬСКОГО МЕСТОРОЖДЕНИЯ (МАГАДАНСКАЯ ОБЛАСТЬ)

In this paper, we summarize new data on the chemical and isotopic composition of thermal wa-ters of the Talskoye deposit in the Magadan Oblast. We were the first to obtain the data on the content of stable oxygen (δ18O) and hydrogen (δD) isotopes in thermal and background waters, as well as oxygen (δ18O) and carbon in bicarbonate ion (δ13C), even though this is the largest ex-ploited deposit of low-mineralized alkaline nitric thermal waters in the region. The thermal water is fresh (M = 980 mg/l), alkaline (pH = 8.9), hydrocarbonate-chloride-sulphate sodium with a high content of fluorine (up to 17 mg/l) and silicic acid (up to 152 mg/l). The deposit is fed by atmospheric precipitation; we did not find traces of melting underground ice supply. A sequential scheme for calculating the temperature of a deep reservoir was applied, which allowed the temperature of water formation to be constrained at 108 °C suggesting an input of fluids rich in potassium and sulfate ion.

Diferenciação oxidativa em dispositivos temporários de ancoragem de Ti6Al4V e aço 316L – estudo piloto

The aim of this pilot study was to test the hypothesis that temporary anchoring devices (TADs) made of 316L steel are more resistant to corrosion even in fluorine environment than DATs manufactured in addition to titanium alloys, for this Potentiostat electrochemical measurements were performed. Materials and Methods: Four pieces of each material were tested in each test set, an application of Fusayama artificial saliva was used as an electrolytic solution in this study of in vitro corrosion, without fluorine in its composition and in a second moment with 1500ppM of fluorine in its composition. In the test, a cathodic polarization was performed by increasing this voltage for 5 minutes or until the corrosion pins were obtained. In artificial saliva containing up to 1500ppmF- this test was repeated with new samples of each material in artificial saliva solution without fluorine. Results: The results of the induction current scale were inserted into OriginPro8 software for making value graphs. As there was a small number of samples, in order not to violate the study’s reliability no statistical test was performed. Among all metal alloys currently used the Ti6Al4V alloy showed good resistance to corrosion in artificial saliva. However, the corrosion of these alloys occurs in contact with high fluorine concentration, unlike 316L steel alloy, which in addition to corrosion makes surface passivation.

Orthodontic Brackets and Wires Wear in Different Conditions: A Review

Metallic ions release from orthodontic brackets and wires mostly depends on quality (chemical composition) and the medium to which it is exposed, e.g. acid, alkali, substances with high fluorine concentration, etc. Among a heterogenous group of research, it was reported that stainless steel, which is used in orthodontic stuff, is the material that suffers most wear. It was apparent that dissolutions with acid pH, alcohols, fluorides, and chlorides aggravate the orthodontic material corrosion. Otherwise, nickel release from brackets and wires can cause allergic reactions to patients. This review addressed corrosion and wear of orthodontic brackets, wires and arches exposed to different media: beverages (juices), mouthwashes, artificial saliva, etc., and the possible health effects that can be caused by releasing of metallic ions under several conditions.

Development of a robust method for the determination of fluorine in liquid petroleum products

A robust method for the determination of total fluorine in liquid petroleum products is developed. The methodology is based on the oxidative pyrohydrolytic combustion of the sample, followed by the analysis of the evolved gases absorbed in an absorbing solution by ion chromatography. The detection limit reached for fluorine is 0.5 mg·kg−1 and the quantification limit is 1.4 mg·kg−1, thanks to the optimisation of different variables: combustion variables (temperature and time), sampling loop, and sample weight. The validation process has been developed by calculation of the uncertainty of the measurement and the analysis of spiked samples as there are no certified reference materials. The new methodology set up permits the determination of fluorine over organic materials from the refining industry of different matrices such as fuel oil, acid soluble oil, etc., containing from very low to high fluorine concentrations in a relatively short time, which makes the methodology suitable to be used as a control method. With this methodology, there is no need of sample preparation which implies the no use of acids for that, thus being environmentally friendly.

Fluorinated Carbonate Electrolyte with Superior Oxidative Stability Enables Long‐Term Cycle Stability of Na2/3Ni1/3Mn2/3O2 Cathodes in Sodium‐Ion Batteries

AbstractLayered transition metal oxides are promising cathode materials for sodium‐ion batteries applicable for low‐cost energy storage systems. However, their cycle stability needs to be substantially improved to meet the requirements of practical applications. Specifically, the issues related to electrolyte stability and the formation of an unstable cathode–electrolyte interface (CEI) remain unsolved. Herein, it is shown that an electrolyte with high fluorine content may induce a robust fluorinated CEI on Na2/3Ni1/3Mn2/3O2 cathode, a representative transitional metal oxide, which can efficiently passivate its surface and suppress continuous electrolyte decomposition during cycling. As a result, the cells deliver a remarkably improved rate capability and cycle stability. Density functional simulations further validate the superior stability of fluorinated electrolyte on cathodes with low highest occupied molecule orbital energy and high dissociation energy barriers. This finding demonstrates the favorable role of fluorinated electrolytes for improving the long‐term cycle stability of Na2/3Ni1/3Mn2/3O2 cathode toward grid‐scale applications.

Etching of Si3N4 by SF6/H2 and SF6/D2 plasmas

Selective plasma etching of silicon nitride (Si3N4) over silicon oxide (SiO2) is one of critical steps in the nanofabrication processes, where a direct plasma etching of Si3N4 is required for some applications. It was reported recently that Si3N4 etching by remote plasma source can be initiated by the vibrationally excited HF(v) molecules at the low concentration of atomic fluorine. Generally, the main source of HF(v) in plasma is reaction of atomic fluorine with H2 molecule. Due to this fact, the kinetic isotope effect should be observed during Si3N4 etching if replace the H2 source gas on deuterium gas (D2). The data presented here are the Si3N4 and SiO2 etching by the SF6/H2 and SF6/D2 plasmas. A different amount of H2 and D2 have been added to the SF6 discharge during the Si3N4 and SiO2 etching. It was shown that at low H2/D2 flow rate the Si3N4 etch rate is lower in the SF6/D2 discharge. This one confirms the hypothesis about Si3N4 etching by HF(v) and indicates on the fact that HF(v) gives contribution to Si3N4 etching by the direct plasma (not only by the remote plasma) at relatively high concentration of atomic fluorine.

Microwave-assisted synthesis of hydroxyl modified fluorinated graphene with high fluorine content and its high load-bearing capacity as water lubricant additive for ceramic/steel contact

The fluorinated graphene (FG) has been reported in diverse applications for its unique chemical and physical properties, resulting from the 2D carbon-skeleton and decorated CF bonds. How to substitute the FG’s fluorine atom with other active functional groups and retain its fluorine content is still a challenge. In this work, a microwave-assisted liquid-phase synthetic route was introduced to obtain hydroxyl modified fluorinated graphene (HOFG) with high fluorine content. The as-prepared product exhibits excellent water dispersibility with far less fluorine loss than previously reported methods. It is found that the HOFG’s fluorine/oxygen (F/O) ratio plays a crucial role in the water dispersibility and lubricating property. The as-prepared HOFG exhibits excellent dispersibility at a high F/O ratio (35). Used as the water lubrication additive for ceramic-steel pair, the as-prepared HOFG significantly improves water’s load-bearing capacity from 250N to 600N. The friction-reduction and anti-wear ability of water are also improved with the addition of the HOFG samples. Compared with pure water, the aquous dispersion of HOFG-40M at a concentration of 1.5 mg/mL shows the best lubricating property with a nearly 20 % reduction of friction coefficient and a 30 % decrease of wear.

Fabrication of a fast curing super-hydrophobic FEVE/MMA coating and its property research

Because of its significant role in the field of self-cleaning, super-hydrophobic coatings have attracted more and more attention from researchers around the world, while the properties of environmental weather resistance and structure-stability often limit the application in daily life of which. In this study, a fast curing super-hydrophobic coating with good thermal tolerance as well as structure-stability and can be applied to a variety of surfaces conveniently was fabricated with fluorocarbon resin (FEVE), methyl methacrylate (MMA) and micro/nanometer scale powders via solution method. A scanning electron microscope (SEM) and a confocal laser scanning microscope (CLSM) were used to evaluate the coating micro morphology. The influence of material content ratio of each component on wettability was analyzed by contact angle measuring instrument. The composition testing of Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that the coating has a high fluorine content. And the test of friction, constant temperature and immersion experiments showed appropriate physical/chemical stability and weather fastness of the coating.

Synthesis of a mineralizing agent for Portland cement from aluminum production waste

Priority directions in innovative technologies of the construction materials industry are the expansion of the use of mineral and chemical additives in the production of cements, as well as alternative raw materials and fuels in production processes. During the production of aluminum at the enterprise JSC RUSAL Krasnoyarsk, the method of electrolytic reduction of aluminum oxide or alumina dissolved in a cryolite-based melt generates fluorocarbon-containing (FCC) waste, which currently accumulates more than 16,000 tons per year. Due to the increased year-round generation of waste with a high content of carbon, fluorine and aluminum, it is urgent to develop technologies that will effectively use them as a new mineralizer product for the production of Portland cement clinker - calcium fluoride. This paper describes the thermal method of waste processing FCC for receipt of the mineralizing agent (fluorite). The disadvantage of FCC as a raw material is an increased concentration of alkali metals, whose oxides negatively affect the process of hydration of clinker minerals, and lead to the formation of efflorescence on products. To reduce their content, the finished fluorite was washed with water. Calcium fluoride as a mineralizing agent in the production of Portland cement, reduces the clinkerization temperature, increases the content of alite, changes the stability, polymorphism and reactivity of phases. The resulting fluorite with a high mass concentration of 73.9% CaF2 makes it possible to reduce the clinker formation temperature, which increases the energy efficiency of obtaining Portland cement. The technological process for removing alkaline components from the product will reduce the likelihood of destructive processes in concrete caused by the aggressive action of reactive silica aggregates and freezing and thawing processes.

Semi‐fluorinated polyarylenes: Microwave‐assisted synthesis and structure–property relationships

AbstractA series of three fluorine containing and three non‐fluorinated Diels–Alder step‐growth polyarylene polymers and copolymers was synthesized via conventional oil bath heating (days/weeks). A drastic time reduction was realized with a microwave‐assisted polymerization (hours). The polymers were characterized by multinuclear (1H, 13C, and 19F) NMR and attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, thermal analysis (thermogravimetric analysis [TGA], differential scanning calorimetry [DSC], and dynamic mechanical analysis [DMA]), gel permeation chromatography, X‐ray diffraction (XRD), water contact analysis, and refractive index (RI) measurements. The NMR spectra indicated a mixture of para and meta conformations through the polymer backbone increasing to more para with greater fluorine content. TGA revealed the fluorine‐containing polyarylenes possessed the highest char yields at almost 80% at 1000°C under nitrogen, and all the polyarylenes possessed onset of degradation temperatures above 550°C under nitrogen and air atmospheres. XRD analysis indicated more ordering for the fluorine‐containing polyarylenes which afforded the high char yields. DMA gave storage moduli values in the range of 1–10 GPa for the polyarylenes. Molecular weights for all samples were above 100 kg/mol. Water contact angles did not change with fluorine content due to the shielding effect of the pendant phenyl groups. However, the RI decreased to 1.6497 at 632.8 nm for the polyarylene with the highest fluorine content.

Fluorous phthalocyanines and subphthalocyanines

Incorporating fluorine atoms into a molecule can endow it with various unique properties that enable materials applications. Selective solubility in fluorous solvents is achieved by a high fluorine content and selective partitioning into perfluorinated liquids over organic and aqueous phases provides orthogonal opportunities for chemistry and materials assembly. Although there is a growing number of partially fluorinated molecules, there are insufficient structural design principles to produce diverse fluorous soluble dyes. Herein, we report the synthesis of six fluorous phthalocyanine and subphthalocyanine dyes, and study their properties in the fluorous phase. Phthalocyanines generally display limited solubility and we also observed apparent aggregation in the fluorous phase. However, the nonplanar subphthalocyanines showed greater solubility. Subphthalocyanines also displayed fluorescence in selected solvents, and their emissive properties were investigated. The materials described expand the library of fluorous dyes and provide insights for the design of new molecules with fluorous solubility.