Addition Of Fluoride Research Articles

2‐Quinolyl Benzodiazaborine: A Tunable Platform for Aggregation‐Induced Emission Luminogens via Formation of Dimeric Borate Crystals with Acid Additives

Abstract2‐Quinolyl benzodiazaborine (DAB) was synthesized and its conversion to a borate species was investigated. Addition of carboxylic acids and hydrogen fluoride led to facile formation of a stable borate derivative, whose structure was unambiguously characterized by single crystal X‐ray diffraction analysis. The borates show intense aggregation‐induced emission (AIE) in crystals, which is thought to be derived from a rigid dimeric structure with intermolecular hydrogen bonding.

Viscosity of conventional cryolite-alumina melts

The study covers the viscosity of NaF–AlF3–CaF2–Al2O3 conventional cryolite-alumina melts with a cryolite ratio CR = 2.3 depending on the CaF2, Al2O3 content and temperature. The viscosity of cryolite-alumina electrolyte samples prepared under laboratory conditions and electrolyte samples of industrial electrolytic cells was measured by the rotary method using the FRS 1600 rheometer («Anton Paar», Austria). The laminar flow region of the melt determined according to the dependence of viscosity on shear rate at a constant temperature was 10–15 s–1 for all the studied samples. The temperature dependence of cryolite-alumina melt viscosity was measured at a shear rate of 12 ± 1 s–1 in the temperature range from liquidus to 1020 °C. It was shown that the change in the viscosity of all samples in the investigated temperature range (50–80 °С) can be described by a linear equation. The average temperature coefficient of linear equations describing the viscosity of cryolite-alumina electrolytes prepared in laboratory conditions was 0.005 mPа· s/°С, which is 2 times less compared to industrial cell electrolytes. Thus, the change in the viscosity of industrial cell electrolytes with increasing temperature is more significant. Both alumina and calcium fluoride additives increase the cryolite melt viscosity. The viscosity of samples prepared with the conventional composition NaF–AlF3–5%CaF2–4%Al2O3 (CR = 2.3) is equal to 3.11 ± 0.04 mPа· s at an electrolysis operating temperature of 960 °C, while the viscosity of industrial cell electrolytes with the same cryolite ratio is 10–15 % higher and falls in the range of 3.0–3.7 mPа· s depending on the electrolyte composition.

The mechanism for tuning the corrosion resistance and pore density of plasma electrolytic oxidation (PEO) coatings on Mg alloy with fluoride addition

Here we prepared PEO coatings on Mg alloys in silicate–NaOH–phosphate electrolyte containing different concentrations of NaF addition. The detailed microstructural characterizations combining with potentiodynamic polarization and electrochemical impedance spectra (EIS) were employed to investigate the roles of fluoride in the growth and corrosion properties of PEO coating on Mg. The result shows the introduction of NaF led to a fluoride-containing nanolayer (FNL) formed at the Mg/coating interface. The FNL consists of MgO nanoparticles and insoluble MgF2 nanoparticles (containing rutile phase and cubic phase). The increase in the NaF concentration of the electrolyte increases the thickness and the MgF2 content in the FNL. When anodized in the electrolyte containing 2 g/L NaF, the formed FNL has the highest thickness of 100–200 nm along with the highest value of x of ∼0.6 in (MgO)1-x(MgF2)x resulted in the highest corrosion performance of PEO coating. In addition, when anodized in the electrolyte containing a low NaF concentration (0.4–0.8 g/L), the formed FNL was thin and discontinuous, which would decrease the pore density and increase the coating's uniformness simultaneously.

M-Phenylene linked macrocycle composed of electron-rich dithienogermole and electron-deficient tricoordinate boron units

Incorporation of non-conventional elements into π-conjugated systems is a powerful tool to control the electronic structures. In this work, electron-deficient tricoordinate boron units were combined with electron-rich dithienogermole units to provide an element-hybrid conjugated macrocycle with m-phenylene linkers. In contrast to the absorption spectra which were unaffected by solvent polarity, the element-hybrid macrocycle exhibited clear solvatochromism in the fluorescence spectra originating from the charge transfer (CT) transition between the dithienogermole and tricoordinate boron units. The addition of fluoride to the solution of the macrocycle resulted in the stoichiometric formation of tetracoordinate borate species. Interestingly, the fluorescence was intensified by the addition of fluoride, and the mechanism was confirmed by fluorescence spectroscopy and TD-DFT calculations.

A Facile Method to Determine the Native Contents of 4'-O-Methylpyridoxine and 4'-O-Methylpyridoxine-5'-glucoside in Ginkgo biloba Seeds.

4'-O-Methylpyridoxine (MPN) and MPN-5'-glucoside (MPNG) are collectively known as ginkgotoxin, which are the main toxic ingredients of excessive consumption of Ginkgo biloba seeds. Water extraction is the generally adopted sample preparation method for high-performance liquid chromatography determination of ginkgotoxin. However, endogenous enzymes such as glycosidases in Ginkgo biloba seeds can hydrolyze MPNG to MPN in the process of water extraction, which will result in the measured contents of MPN and MPNG but not their natural contents in Ginkgo biloba seeds. In this work, inhibitors for the endogenous enzymes were first screened, and it was found that silver fluoride could effectively inhibit endogenous enzymes such as glucosidase and phosphatase. The optimized concentration of silver fluoride was 25 mmol/L, which could effectively inhibit the endogenous enzymes for more than 60 h. A new sample preparation method based on water extraction with 25 mmol/L silver fluoride addition was thus developed. This method was employed to determine the native contents of MPN and MPNG in the exotesta and kernel of five Ginkgo biloba seed cultivars. The result showed that the contents of MPNG in the exotesta and kernel of five cultivars were significantly higher than those of MPN. MPNG was present at high content in raw seeds, which was the main form of ginkgotoxin in seeds. The method established in this work is simple and effective and can be used to accurately quantify the native contents of MPN and MPNG.

Synthesis of NiS2 nanomaterial as wide range pressure sensor

With the vigorous development of industry and information technology, people's requirements for sensors are becoming more and more diversified and universal. It is still a challenge to find a new type of pressure sensor with low cost, simple preparation, wider pressure test range, and higher sensitivity. Hereby, we report a novel flexible pressure sensor with a wide pressure detection range and robust mechanical properties, taking advantage of transition metal sulfide NiS2, adsorbed in melamine sponge as the active substance. The flexible sensor deforms under pressure with a internal microstructure change and a corresponding conductivity ramping. The addition of elastic polyvinylidene fluoride after curing improves the impact resistance and enables higher stability. Experiments show that the resistance pressure sensor responds within a wide range of 50 kPa with a high sensitivity of below 0.0345 kPa−1 and a fast response time of 0.64 s. Its excellent performance makes the sensor promising for wearable electronics and health monitoring devices.

Effect of Zinc Fluoride addition on structure of barium Borate glasses for nonlinear optical applications

A series of Zinc Barium Borate Oxyfluoride glasses with composition 60B 2 O 3 -(40-x)BaO-xZnF 2 , where x = 0, 10, 20, 30, and 40 mol% are prepared using the conventional melt quench method. Density and molar volume was found to decrease with the increase in ZnF 2 content. The optical band gap was found to vary between 5.76 and 5.14 eV. Such a wide bandgap of the prepared samples makes them a potential candidate as Supercontinuum sources. Fourier transform infrared (FTIR) and Raman spectroscopy were used together to see the structural changes incurred in the material. Raman spectroscopy confirms the Non-bridging Oxygen variation while FTIR gives insights into borate structural units' changes, including the Boron coordination. Non-bridging Oxygen species were found to decrease initially with the addition of ZnF 2 and thereby cause network loosening. FTIR studies indicate a nonlinear variation in the coordination of Boron with the addition of ZnF 2 . Nonlinear absorption and refraction have been measured to establish the potential of the prepared samples as supercontinuum sources. The origin of nonlinearity in the samples is explained from the insights obtained using structural investigations. • BZB glasses possess wide bandgap and are a potential Supercontinuum source. • Zinc acts as a network former at low concentrations. • Creation of NBO increases nonlinear coefficients. • Nonlinear refractive index values are of the order of 10 −14 cm 2 W −1 .

Anodizing of AS12 alloy in alkaline media

The anodizing of AS12 alloys in various alkaline media is investigated over a large potential range (0–600 V) in order to provide a deep understanding of the mechanisms involved and judiciously chose chemical conditions enabling efficient micro-arc anodizing. Combined in situ stationary electrochemical methods, electrochemical impedance spectroscopy and TEM observations reveal that silicon in the aluminium matrix modifies the composition and the electrochemical properties of the duplex nanostructure grown at the early stages of the anodizing, therefore hindering micro-arc anodizing initiation. The addition of fluorides to the electrolyte, or silicates to a lesser extend, reinforces the resistive properties of the internal anodic layer and favors the efficiency of the anodizing process. The corrosion resistance of AS12, evaluated in NaCl 0.1 M by electrochemical techniques and salt spray test, is improved by the presence of the oxide coating and the nature of the additive incorporated compounds as well.

Study on Adding Ammonium Hydrogen Fluoride to Improve Manganese Leaching Efficiency of Ammonia Leaching Low-Grade Rhodochrosite

The ammonia leaching method for treating low-grade rhodochrosite has the advantages of a good impurity removal effect and low environmental pollution. In this paper, aiming at the low leaching efficiency of low-grade rhodochrosite treated by the ammonia leaching method, studies on enhancing the leaching efficiency of manganese by using ammonium hydrogen fluoride as an additive are carried out. The effects of different ammonia concentrations, leaching temperatures, leaching times, liquid-solid ratios, stirring rates, and the addition of ammonium hydrogen fluoride on the leaching efficiency of manganese with and without ammonium hydrogen fluoride as an additive were comparatively studied, and the parameters of ammonia concentration, ammonia leaching temperature, and ammonium hydrogen fluoride dosage were optimized in the experimental study. The results indicated that ammonium hydrogen fluoride as an additive in the treatment of low-grade rhodochrosite by the ammonia leaching method could effectively increase the leaching efficiency of manganese, and the optimal process parameters were obtained. Meanwhile, the addition of ammonium hydrogen fluoride didn’t affect the quality of the steamed ammonia product.

Dissolved valence state of iron fluorides and their effect on Ni-based alloy in FLiNaK salt

In this study, the stable dissolved valence state of iron fluorides in molten LiF - NaF - KF (FLiNaK) salt and their effect on GH3535 alloy were systematically investigated. Results of in situ ultraviolet–visible (UV–Vis) absorption spectroscopy and electrochemical analysis indicated that Fe (II) in molten FLiNaK salt is unstable and gets converted to more stable Fe (III) through the disproportionation reaction: 3 Fe (II) = 2 Fe (III) + Fe. Thus, the corrosion of GH3535 alloy is aggravated by the addition of iron fluorides due to the redox reaction: Fe (III) + Cr = Fe + Cr (III), resulting in the formation of the Cr-depletion layer and Fe-rich layer.

Discrete Heteropolynuclear Yb/Er Assemblies: Switching on Molecular Upconversion Under Mild Conditions.

The salts {[Ln2 Ln*(Hhmq)3 (OAc)3 (hfac)2 ]+ [Ln*(hfac)3 (OAc)(MeOH)]- } (Hhmq=2-methanolquinolin-8-oxide, hfac=hexafluoroacetylacetonate; Ln, Ln*=Er, Gd, Yb) feature a discrete heteronuclear cation consisting of two types of lanthanide atoms. The quinolinoxy O-atom serves as a μ2 -bridge to two Ln atoms and as a μ3 -bridge to all three atoms, with metal⋅⋅⋅metal distances being around 3.7 Å. For 1 ([Yb2 Er]+ ), near-infrared downshifted luminescence is switched to competitive upconversion luminescence upon irradiation by a 980 nm laser under an extremely low excitation power (0.288 W cm-2 ) through introduction of fluoride ions. The stability of 1 after addition of fluoride was confirmed by powder X-ray diffraction and multistage mass spectrometry, associated with the 1 H NMR of 6 ([La2 Eu]+ ). More importantly, the at least 20-fold enhancement of the quantum yield in non-deuterated solvents at room temperature under low power densities (2 W cm-2 ) is the highest among the few molecular examples reported.

Discrete Heteropolynuclear Yb/Er Assemblies: Switching on Molecular Upconversion Under Mild Conditions

AbstractThe salts {[Ln2Ln*(Hhmq)3(OAc)3(hfac)2]+ [Ln*(hfac)3(OAc)(MeOH)]−} (Hhmq=2‐methanolquinolin‐8‐oxide, hfac=hexafluoroacetylacetonate; Ln, Ln*=Er, Gd, Yb) feature a discrete heteronuclear cation consisting of two types of lanthanide atoms. The quinolinoxy O‐atom serves as a μ2‐bridge to two Ln atoms and as a μ3‐bridge to all three atoms, with metal⋅⋅⋅metal distances being around 3.7 Å. For 1 ([Yb2Er]+), near‐infrared downshifted luminescence is switched to competitive upconversion luminescence upon irradiation by a 980 nm laser under an extremely low excitation power (0.288 W cm−2) through introduction of fluoride ions. The stability of 1 after addition of fluoride was confirmed by powder X‐ray diffraction and multistage mass spectrometry, associated with the 1H NMR of 6 ([La2Eu]+). More importantly, the at least 20‐fold enhancement of the quantum yield in non‐deuterated solvents at room temperature under low power densities (2 W cm−2) is the highest among the few molecular examples reported.

Fluoride-doped MWCNT/Si3N4 composite with improved mechanical and structural properties

The addition of carbon nanotubes (CNT) in ceramic composites has stimulated a substantial interest due to their high mechanical, thermal and electrical properties. This approach used fluoride additives (AlF3 and MgF2) to prepare multi-walled carbon nanotubes/silicon nitride (MWCNT/Si3N4) composite densified at 1700 °C for 1 h by hot press (HP) sintering. The microstructural analyses of MWCNT/Si3N4 composites indicate that the fluoride additives have substantially improved densification and the transformation of α-Si3N4 to β-Si3N4. As observed, the mechanical properties, i.e. flexural strength, fracture toughness, Young's modulus and hardness of MWCNT/Si3N4 composites are improved with an increasing concentration of MWCNT. These results attributed to the highly dense composites, strong interfacial interaction and the pull-out mechanism of MWCNT and β-Si3N4. The maximum values of fracture toughness flexural strength, Young's modulus, and hardness were 12.76 ± 1.15 MPa.m0.5, 883 ±46 MPa, 260 ±9 GPa, and 26.4 ± 1.3 GPa, respectively. The improved mechanical properties also ascribed to the synergistic strengthening and toughening influence of MWCNT and β-Si3N4.

Unveiling Roles of Tin Fluoride Additives in High‐Efficiency Low‐Bandgap Mixed Tin‐Lead Perovskite Solar Cells

AbstractLow‐bandgap mixed tin–lead perovskite solar cells (PSCs) have been attracting increasing interest due to their appropriate bandgaps and promising application to build efficient all‐perovskite tandem cells, an effective way to break the Shockley–Queisser limit of single‐junction cells. Tin fluoride (SnF2) has been widely used as a basis along with various strategies to improve the optoelectronic properties of low‐bandgap SnPb perovskites and efficient cells. However, fully understanding the roles of SnF2 in both films and devices is still lacking and fundamentally desired. Here, the functions of SnF2 in both low‐bandgap (FASnI3)0.6(MAPbI3)0.4 perovskite films and efficient devices are unveiled. SnF2 regulates the growth mode of low‐bandgap SnPb perovskite films, leading to highly oriented topological growth and improved crystallinity. Meanwhile, SnF2 prevents the oxidation of Sn2+ to Sn4+ and reduces Sn vacancies, leading to reduced background hole density and defects, and improved carrier lifetime, thus largely decreasing nonradiative recombination. Additionally, the F− ion preferentially accumulates at hole transport layer/perovskite interface with high SnF2 content, leading to more defects. This work provides in‐depth insights into the roles of SnF2 additives in low‐bandgap SnPb films and devices, assisting in further investigations into multiple additives and approaches to obtain efficient low‐bandgap PSCs.

Oral health for all-how can the development of dental public health in Germany be sustainably enhanced?

Public health promotes health through organised efforts of society. Oral and maxillofacial diseases and conditions are important public health problems due to the large burden of disease and oral health inequity caused by social determinants. Caries, periodontitis, traumatic dental injuries or carcinomas of the mouth and throat can be reduced by increased public health efforts. One example for ahighly effective public health measure like the health-promoting modification of the product range is the addition of fluoride to toothpastes, which is largely responsible for the impressive caries decline.However, the full potential of dental public health is not yet unlocked. It therefore appears necessary to create structures such as an "oral health institution" at the federal level and through statutory mandate. Its assignment should be "oral health for all" through changes in the social and economic environments to make them conducive to oral health. By this, the already established individual and group prophylaxis would be complemented with apopulation-based approach. The institution's tasks on the federal and on the federal states level should be to influence policies relevant to oral health, communication, collaboration, advanced training and research. Subdivisions of the proposed institution could provide oral health education for groups not yet reached. This would be an essential contribution to effectively addressing existing oral health problems across the population as well as for deprived and vulnerable groups.

Defect passivation in CH3NH3PbI3 films using alkali metal fluoride additives for highly efficient perovskite solar cells

Solution-processed organic/inorganic hybrid halide perovskites are a class of very promising photovoltaic materials because of their extraordinary optoelectronic properties. However, numerous intrinsic defects within perovskite films limit the performance enhancement of perovskite solar cells (PSCs). Herein, we introduce three different alkali metal fluoride additives into the perovskite precursor to modulate the defect behaviors. The addition of alkali metal fluorides, especially potassium fluoride (KF), significantly passivates grain boundaries and point defects within bulk perovskite films, contributing to increased carrier lifetime and reduced defect state density. By optimizing the concentration of additives, the PSC device with 1% KF added has realized a significantly enhanced power conversion efficiency of 20.11%, and ignorable hysteresis.

A Review of the Melt Structure and Crystallization Behavior of Non‐Reactive Mold Flux for the Casting of Advanced High‐Strength Steels

The non‐reactive CaO–Al2O3‐based mold flux system is proposed to avoid the reaction problems during the casting process of advanced high‐strength steels, when conventional CaO–SiO2‐based mold flux system is applied. However, new problems such as low consumption and insufficient lubrication are introduced during the industrials of CaO–Al2O3‐based mold fluxes, which is closely associated with its melt structure and crystallization behavior. Herein, the studies on the melt structure and crystallization property of CaO–Al2O3‐based mold fluxes are summarized and discussed. The structural roles of Al2O3, B2O3, and SiO2 in CaO–Al2O3‐based mold flux system are quite complex because the structural transformation occurs in aluminate network structure, such as [AlO4]5− and [AlO5]7−, and borate network structure, such as [BO3]3− and [BO4]5−, in the system. In addition, it is suggested that the addition of basic metal oxides and fluorides will strengthen the stability of network structure, due to the charge compensation effect of Li+ and Ba2+, and the strong electrostatic attraction between Al3+ and F−. On the contrary, many Al‐bearing crystal phases with high melting point precipitate in the CaO–Al2O3‐based melt, which will improve the crystallization ability of slag and deteriorate its lubrication performance.

Beyond dissolution: Xerostomia rinses affect composition and structure of biomimetic dental mineral in vitro.

Xerostomia, known as dry mouth, is caused by decreased salivary flow. Treatment with lubricating oral rinses provides temporary relief of dry mouth discomfort; however, it remains unclear how their composition affects mineralized dental tissues. Therefore, the objective of this study was to analyze the effects of common components in xerostomia oral rinses on biomimetic apatite with varying carbonate contents. Carbonated apatite was synthesized and exposed to one of the following solutions for 72 hours at varying pHs: water-based, phosphorus-containing (PBS), mucin-like containing (MLC), or fluoride-containing (FC) solutions. Post-exposure results indicated that apatite mass decreased irrespective of pH and solution composition, while solution buffering was pH dependent. Raman and X-ray diffraction analysis showed that the addition of phosphorus, mucin-like molecules, and fluoride in solution decreases mineral carbonate levels and changed the lattice spacing and crystallinity of bioapatite, indicative of dissolution/recrystallization processes. The mineral recrystallized into a less-carbonated apatite in the PBS and MLC solutions, and into fluorapatite in FC. Tap water did not affect the apatite lattice structure suggesting formation of a labile carbonate surface layer on apatite. These results reveal that solution composition can have varied and complex effects on dental mineral beyond dissolution, which can have long term consequences on mineral solubility and mechanics. Therefore, clinicians should consider these factors when advising treatments for xerostomia patients.

An expedient synthesis of cyanoformates via DAST-mediated C[sbnd]C bond cleavage of α-oximino-β-ketoesters

A new protocol to synthesize cyanoformates was developed using simple β-ketoesters as substrates. (Diethylamino)sulfur trifluoride (DAST) was used as a dual-role reagent to activate the oxime moiety and to donate a fluoride. The key intermediates, α-oximino-β-ketoesters, were prepared by highly efficient acid-assisted oximation of β-ketoesters. Then, the deconstruction of α-oximino-β-ketoesters by the fluorinative CC bond cleavage was demonstrated to provide cyanoformates. In this event, the fluoride addition followed by the CC bond cleavage selectively occurred in the ketones over esters. Due to simple and mild reaction conditions, variously functionalized cyanoformates were exemplified.

PrF3-NdF3-DyF3-LiF electrolyte system for preparation of Pr-Nd-Dy alloy by electrolysis

The application of Pr-Nd-Dy alloy in the field of high-performance Nd-Fe-B permanent magnet materials has great potential. The composition of the PrF3-NdF3-DyF3-LiF (PND-LiF) electrolyte system used in the production of Pr-Nd-Dy alloys, the distribution of F, Li, RE and other elements in the electrolyte and their occurrence state were studied in this paper. The effect of temperature and lithium fluoride addition on electrolyte conductivity was revealed using the continuous conductivity cell constant (CVCC) method. The thermal analysis method was used to study the influence of lithium fluoride addition on the electrolyte's liquidus temperature and the optimal process conditions for the production of Pr-Nd-Dy alloy were determined. The results show that the overall distribution of praseodymium neodymium fluoride and lithium fluoride is uniform in the electrolyte and dysprosium fluoride is distributed between praseodymium-neodymium fluoride and lithium fluoride. Praseodymium-neodymium oxide is embedded in praseodymium neodymium fluoride in spotty pattern. The electrolyte's conductivity is increased as the temperature and lithium fluoride addition are going up, while the liquidus temperature is going down with increasing lithium fluoride addition. The best electrolysis process conditions for the PND-LiF system to produce praseodymium neodymium dysprosium alloy are as follows: temperature 1050 °C and 15.56 wt% PrF3-62.22 wt% NdF3-11.11 wt% DyF3-11.11 wt% LiF.