Introduction Of Fluoride Research Articles

Isoreticular Contraction of Cage-like Metal-Organic Frameworks with Optimized Pore Space for Enhanced C2H2/CO2 and C2H2/C2H4 Separations.

The C2H2 separation from CO2 and C2H4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine- and carboxylic acid-functionalized linkers and introducing a fluoride- and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C2H2 adsorption capacity, and selective C2H2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride- and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C2H2 binding sites, thus rendering the adequate ability for practical C2H2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C-H···O, C-H···F, and other van der Waals forces play a critical role in the selective C2H2 separation.

High‐Performance Perovskite Solar Cells with Low Open‐Circuit Voltage Loss and Excellent Stability after p‐F‐PEAI Posttreatment

Photoelectric properties of perovskite solar cells (PSCs) are closely linked to defects on the surface of perovskite in the preparation process, which have a significant impact on the open‐circuit voltage (VOC) of devices. It is necessary for high‐performance PSCs to suppress the non‐radiative recombination at the interface and improve the charge transfer. Herein, phenylethyl ammonium iodide containing fluorine (p‐F‐PEAI) is utilized to treat the perovskite film, which can optimize the energy‐level alignment between perovskite layer and hole‐transport layer to promote charge transfer and reduce non‐radiative recombination by passivating interface defects and inhibiting the generation of Pb0. The introduction of fluoride can enhance the electropositivity of −NH3+ to obtain excellent passivation and moisture resistance. The p‐F‐PEAI‐modified PSCs achieve a superior power conversion efficiency of 22.56% with remarkable VOC (1.20 V) and maintain 96% of the initial optimal value after 1000 h without encapsulation.

Crowding of neodymium ions as a structural feature of fluorophosphate glasses

The rare-earth element of neodymium is used as a doping agent for a variety of alloys, as the base element for super magnets and in cryogenic industry. Inorganic glass industry represents a separate application for neodymium oxide. Having a high quantum yield of luminescence, such glasses are essential for the production of high-power optical quantum generators. Fluorophosphate glasses have a complex composition, specific physicochemical properties and spectral characteristics, and demonstrate specific matrix forming patterns when modifiers or glass forming agents are introduced. The current structural description of fluorophosphate glasses is lacking, which gives relevance to further studies into the structure of Ba(PO3)2 based pseudobinary glass system and barium fluoroaluminate. Microadditions of neodymium oxide were introduced as an activator during glass synthesis. Such glasses can be used as laser material. The authors examined the absorption and luminescence spectra of glass specimens containing neodymium. It is shown that fluorophosphate glasses are structurally heterogeneous systems that contain two typical activator coordination environments; introduction of fluorides in Ba(PO3)2 glass leads to neodymium ion segregation in the phosphate glass matrix. Specimens of crystallization resistant optical glass have been obtained. The paper describes optimum compositions of neodymium activated fluorophosphate glasses that retain the advantages of phosphate glass systems while shorter neodymium luminescence lifetimes have no noticeable impact on the glass performance.

A Green and Cost-Effective Synthesis of Hierarchical SAPO-34 through Dry Gel Conversion and Its Performance in a Methanol-to-Olefin Reaction

In this work, a low-cost and high-performance methanol-to-olefin (MTO) catalyst was synthesized by dry gel conversion (DGC). Using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) to prepare the dry gel, nano-SAPO-34 in a range of 50–500 nm was synthesized under the effect of the vapor of triethylamine (TEA) and H2O. The TEAOH consumption using this method was only 7.5% of that in the hydrothermal synthesis (HTS), and the yield of nano-SAPO-34 products was up to 94%. When scaling up to the pilot test, obvious heterocrystals appeared with the decrease in SiO2 content in the dry gel. Our results showed that the heterocrystals were completely eliminated after the introduction of fluoride into the dry gel. A low acid density nanosheet-SAPO-34 molecular sieve product with good micropore, mesopore, and macropore connectivity was obtained. The obtained multikilogram-scale molecular sieve sample can be directly shaped to obtain MTO microsphere catalysts by spray drying without separation and washing. No wastewater was produced during the whole process, demonstrating an entirely green production way. The MTO performance of the microsphere catalysts was tested in a fluidized bed reactor, and results showed that the catalysts exhibited the characteristics of a slow carbon deposition rate and a high activity utilization ratio. Their lifetime was extended by 14%, and their selectivity (C2= + C3=) was increased by 1.55%, so they are very suitable for industrial application. This work has provided the theoretical and practical basis for the industrial production and application of DGC in the future.

Electrochemical Synthesis of Crystalline Niobium Oxide

Features of creation of porous nanostructured oxides of transition materials on an example of niobium are considered. It has been experimentally shown that variation in anodizing modes makes it possible to obtain non-porous and porous amorphous anodic oxide films (AOF) and films of the crystalline type. It is determined that the process of AOF formation on niobium, as well as its structure and properties depend on such parameters as the type of electrolyte, anodizing voltage, activator concentration, the duration of the process. It is confirmed that the presence of an activator in the electrolyte is a necessary and decisive factor in the process of forming a nanostructured anode oxide layer. To obtain a nanostructured surface of niobium oxide, a necessary condition is the introduction of fluoride into the electrolyte, but also an important task is to determine the type of compound with which F– ions are introduced into the electrolyte. It has been experimentally determined that the optimal solution for the rapid growth of porous crystalline oxide is a solution consisting of a background electrolyte in the form of 1M H2SO4 with the addition of a fluoride ion activator in the form of 0.5M NaF. The increase in the activator accelerates the formation of the crystal structure on the surface of niobium. It is shown that higher voltage and longer anodizing time leads to an increase in the size of microcones and their number on the surface of niobium. Optimal for the formation of porous crystalline oxide is a voltage of 60 V in the electrolyte 1M H2SO4 + 0.5M NaF for 2 hours.

Fluoridated dentifrices: towards a cavity free future

The introduction of fluoride represents an epoch making event in the field of dentistry. In spite of the overwhelming evidence on the beneficial effects of fluoride in reducing dental caries, this simple public health measure has not yet been fully implemented universally. Dental caries exerts social, physical, mental and financial burdens on a global scale with developing countries being affected the most. Prevention of dental caries should be the primary aim rather than emphasising only curative aspects. In this paper the beneficial effects of fluoride dentifrices in general and problems related to the implementation of fluoride as a community measure for a developing country like India are discussed.

Subsampling of Regional-Scale Database for improving Multivariate Analysis Interpretation of Groundwater Chemical Evolution and Ion Sources

Multivariate statistics are widely and routinely used in the field of hydrogeochemistry. Trace elements, for which numerous samples show concentrations below the detection limit (censored data from a truncated dataset), are removed from the dataset in the multivariate treatment. This study now proposes an approach that consists of avoiding the truncation of the dataset of some critical elements, such as those recognized as sensitive elements regarding human health (fluoride, iron, and manganese). The method aims to reduce the dataset to increase the statistical representativeness of critical elements. This method allows a robust statistical comparison between a regional comprehensive dataset and a subset of this regional database. The results from hierarchical Cluster analysis (HCA) and principal component analysis (PCA) were generated and compared with results from the whole dataset. The proposed approach allowed for improvement in the understanding of the chemical evolution pathways of groundwater. Samples from the subset belong to the same flow line from a statistical point of view, and other samples from the database can then be compared with the samples of the subset and discussed according to their stage of evolution. The results obtained after the introduction of fluoride in the multivariate treatment suggest that dissolved fluoride can be gained either from the interaction of groundwater with marine clays or from the interaction of groundwater with Precambrian bedrock aquifers. The results partly explain why the groundwater chemical background of the region is relatively high in fluoride contents, resulting in frequent excess in regards to drinking water standards.

Effect of Fluoride‐Modification on the Phillips Cr/SiO2 Catalyst for Ethylene Polymerization

AbstractIn this work, a fluoride‐modified Phillips catalyst was investigated by using combined experimental and computational methods. The addition of fluoride to the Phillips Cr/SiO2 catalyst can increase the activity of the catalyst calcined at a low temperature and the molecular weight of the polyethylene product. DFT calculations were performed to show that the difference of the Gibbs free energy barriers between chain transfer and chain propagation increased after the introduction of the fluoride onto the silica surface, which is in accordance with the increased molecular weight of the polyethylene produced by the fluoride‐modified Phillips Cr/F‐SiO2 catalyst. The computational results also reflect the increase of the activity of the ethylene/1‐hexene copolymerization after the introduction of fluoride, although the modification has little effect on the regioselectivity of the produced ethylene/1‐hexene copolymer. Moreover, copolymers produced by the fluoride‐modified Phillips catalyst with more short‐chain branches (SCBs) in the high‐molecular‐weight fraction and a significant enhancement of the environmental stress crack resistance can be explained from the results of the DFT calculations.

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

Abstract This study investigates the effects of aluminum (Al) and F interactions on the coagulation behaviors of Al salts, i.e., AlCl3 and polymer aluminum chloride (PACl) at different basicity (B) towards fluoride. These coagulants achieve the optimum fluoride removal over pH 6–7, and PACl exhibits higher removal efficiency than AlCl3 does over pH 4–9. The removal of fluoride is positively correlated with the content of either Al13 or Alb in Al-based coagulants over pH 4–9 and increases in the order: PACl2 > PACl1 > AlCl3. As for PACl, the increased B from 0 to 2.4 improves fluoride removal owing to the elevated ratios of Alb. However, at further increased B to 2.8, the formation of colloidal Al species (Alc) occurs and this effect adversely inhibits fluoride removal thereafter. The removal of fluoride by these coagulants increases with elevated initial fluoride concentrations ([F]0) from 0 to 20 mg/L. At high [F]0 of 80 mg/L, fluoride removal by AlCl3 decreases to as low as 13.1% owing to the formation of soluble Al–F complexes, as indicated from the high residual Al concentrations of 16 mg/L. Interestingly, this adverse effect can hardly be observed for PACl due to the stronger stability of Al13 or Alb. As for AlCl3 and PACl, the introduction of fluoride changes the Al species distribution to some extent owing to the Al–F complexation, as indicated by the analysis of electrospray ionization mass spectrometry. The possible Al–F complexes formed fluoride and different Al species are proposed thereafter. PACl with diverse Al species and high Alb or Al13 content shows higher removal efficiency towards fluoride than AlCl3 does, especially at high [F]0 or under acidic pH and alkaline pH conditions.

Calcium Orthophosphates (CaPo ) and Dentistry

Dental caries, also known as tooth decay or a cavity, remains a major public health problem in the most communities even though the prevalence of disease has decreased since the introduction of fluorides for dental care. In addition, there is dental erosion, which is a chemical wear of the dental hard tissues without the involvement of bacteria. Besides, there are other dental losses, which may be of a medical (decay or periodontal disease), age (population aging), traumatic (accident) or genetic (disorders) nature. All these cases clearly indicate that biomaterials to fill dental defects appear to be necessary to fulfill customers’ needs regarding the properties and the processing of the products. Bioceramics and glass-ceramics are widely used for these purposes, as dental inlays, onlays, veneers, crowns or bridges. Calcium orthophosphates (CaPO ) belong to bioceramics but they have some specific advantage over other types of bioceramics due to a chemical similarity to the inorganic part of both human and mammalian bones and teeth. Therefore, CaPO (both alone and as constituents of various formulations) are used in dentistry as both dental fillers and implantable scaffolds. This review provides brief knowledge on CaPO and describes in details current state-of-the-art on their applications in dentistry and dentistry-related fields. Among the recognized dental specialties, CaPO are most frequently used in periodontics; however, the majority of the publications on CaPO in dentistry are devoted to unspecified “dental” fields.

A combined electrolyte for anodizing and copper plating of aluminum and its alloys

The formulation of an effective combined electrolyte for anodizing and copper plating of aluminum and its alloys, characterized by decreased concentration of harmful components (sulfuric acid, copper sulfate), was developed. To obtain copper deposits of finely crystalline structure, introduction of fluorides into the electrolyte was suggested. The optimum operation conditions for the electrolyte were determined. The electroplated copper coatings exhibit high adhesion to the aluminum support without additional heat treatment, which allows considerable reduction of the process time, especially when depositing multilayered coatings, and saving of expendable materials.

~2 µm Luminescence properties and nonradiative processes of Tm3+ in silicate glass

Two novel Tm3+-doped silicate glasses (one with fluoride addition) with good thermal stability were prepared in this work. Luminescence properties of these two samples were compared. After the addition of fluoride, the luminescence intensity of 1.8µm was much improved whereas that of 1.47µm was reduced. The rates of nonradiative processes populating and depopulating 3F4 were calculated quantitatively and a new method of calculating the quenching rate of hydroxyls was proposed. It was found that multiphonon relaxation rate of 3F4→3H6 was really low and could be neglected in both samples. The addition of fluoride in glass could reduce the quenching rate of hydroxyls but raised the cross-relaxation (3H6+3H4→3F4+3F4) rate. Thus the quantum efficiency of 1.8µm luminescence was improved after the introduction of fluoride.

氟化物对Er3+/Yb3+共掺的碲酸盐玻璃上转换和红外发光性能的影响

Er3+/Yb3+ 共掺的碲酸盐玻璃由于其良好的上转换发光性能而得到广泛的研究。本文将氟化物引入碲酸盐玻璃中, 通过熔融法制备了量比为70TeO2-(30-x)ZnO-xZnF2-0.15Er2O3-1.5Yb2O3(x=0,5,10,15,20)的碲酸盐氧氟玻璃样品, 并测试其热稳定性、拉曼光谱以及受激发射光谱。实验结果表明, 随着氟化物含量的提高, Er3+离子的410,555,670 nm上转换发光和2~3 μm波段中红外发光得到增强, 并且红光提高强度比绿光和蓝光更明显。在分析了氟离子引入后对上转换与近中红外波段发光的内在影响机制发现: 碲酸盐玻璃系统中的氟化物一方面促进能量传递过程中Er3+离子的双光子吸收, 促进粒子跃迁至相应的高能级; 另一方面, 引入氟化物后的碲酸盐玻璃的最大能量声子态密度下降也是降低无辐射跃迁概率、提高上转换和中红外发射强度的重要原因。

Controlling the microporosity of SBA-15 silicate material by background salt solution

The structure of silicate material of the SBA-15 type has been studied under variable composition of a salt solution in synthesis. Ammonium and sodium chlorides, as well as ammonium fluoride, introduced into the composition of the reaction mixture both at the first stage of precipitation and at the second stage of the thermal treatment (TT), have been used as the salt additives. The mesostructure was controlled by X-ray diffraction, gas adsorption and transmission electron microscopy. It was found that the multiple increase of the ionic strength of the solutions in the presence of chloride salts disrupt the stoichiometry of the silicate-surfactant interaction at the first stage of formation of mesostructure and leads to the formation of an impurity of irregular structure. The ions of ammonium promote an increase in the microporosity of the silicate wall. The presence of sodium ions reduces microporosity. Small quantities of fluoride ions (F−: Si = 0.032) improve the ordering of the product at the stage of primary precipitation. At the ratio F−: Si = 0.16, the hexagonal mesostructure is not formed. The introduction of fluorides at the TT stage leads to a decrease of the silicate pore wall thickness, microporosity and hexagonality of the pore.

∼2 μm fluorescence radiative dynamics and energy transfer between Er3+ and Tm3+ ions in silicate glass

A Er3+/Tm3+ co-doped silicate glass with good thermal stability is prepared by melt-quenching method. An efficient emission of ∼2μm is observed under different selective laser excitations. The optical absorption and transmission spectra, Raman spectra, and emission spectra are tested to characterize ∼2μm emission properties of Er3+/Tm3+ co-doped silicate glasses and a reasonable energy transfer mechanism of ∼2μm emission between Er3+ and Tm3+ ions is proposed. Based on the optical absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated. Intense ∼2μm emission is obtained from Er3+/Tm3+ co-doped silicate glasses due to the efficient energy transfer from Er3+ to Tm3+ ions. The energy transfer coefficient from Er3+ to Tm3+ ions can reach as high as 13.39×10−40cm6/s. In addition, the population of the OH groups is decreased and the ∼2μm emission is effectively enhanced with fluoride introduction. The emission property, together with good thermal property, indicates that Er3+/Tm3+ co-doped silicate glass is a potential kind of laser glass for efficient ∼2μm laser.

AgNa(VO2F2)2: A Trioxovanadium Fluoride with Unconventional Electrochemical Properties

We present structural and electrochemical analyses of a new double-wolframite compound: AgNa(VO2F2)2 or SSVOF. SSVOF is fully ordered and displays electrochemical characteristics that give insight into electrode design for energy storage beyond lithium-ion chemistries. The compound contains trioxovanadium fluoride octahedra that combine to form one-dimensional chain-like basic building units, characteristic of wolframite (NaWO4). The 1D chains are stacked to create 2D layers; the cations Ag(+) and Na(+) lie between these layers. The vanadium oxide-fluoride octahedra are ordered by the use of cations (Ag(+), Na(+)) that differ in polarizability. In the case of sodium-ion batteries, thermodynamically, the use of a sodium anode introduces a 300 mV loss in overall cell voltage as compared to a lithium anode; however, this can be counter-balanced by introduction of fluoride into the framework to raise the reduction potentials via an inductive effect. This allows sodium-ion batteries to have comparable voltages to lithium systems. With SSVOF as a baseline compound, we have identified new materials design rules for emerging sodium-ion systems that do not apply to lithium-ion systems. These strategies can be applied broadly to provide materials of interest for fundamental structural chemistry and appreciable voltages for sodium-ion electrochemistry.

Effective regime of microarc oxidation (MAO) on AZ 91 magnesium alloy

8 1 At the present time, the relative volume of produc� tion and use of magnesium alloys is continuously growing due to their lower density compared to other structural materials (1). Nevertheless the use of parts made of these Mg alloys require anticorrosive coatings on their surfaces. To obtain such protective coatings one of the most promising method consists of Microarc Oxidation (MAO) (2, 3) with a subsequent sealing or varnishing and painting of the surface since microarc coating (MAC) mostly serves as a high� porous layer for further finishing treatment on magne� sium alloys products. It was established (4-6) that the addition of fluo� rinecontaining chemical components in basic elec� trolytes leads to the improvement of the mechanical and tribological properties of microarc oxidation coat� ings formed on the surface of magnesium alloys, increases the efficiency of the MAO process and con� sequently reduces the power consumption of the pro� cess. In this work (3) it is shown that within alkaline phosphate electrolytes, the growth rate of microarc oxidation coating on the surface of AZ91 magnesium alloy is significantly higher (not less than 1.4 times) for a process conducted in the anodic regime than in the anodiccathodic regime. Thus, at the stage of sparking discharges, growth coverage is slowed down with the advent of microarc discharges on a surface of the working electrode. It is obvious that the performance of the process of microarc oxidation of magnesium alloys increases sig� nificantly if it is conducted by passing a direct current between the electrodes in basic electrolytes with the introduction of fluorides. Therefore, the main objec� tive of this work is the investigation of the process to obtain MAO precoats on the surface of magnesium 1 The article was translated by the authors. alloys. This work also aims at establishing technologi� cal parameters that allow us to conduct the process with higher performances. Therefore the optimal con� centration of ammonium fluoride in the base alkaline phosphate electrolyte, the current density and the shape of the current waveform in galvanostatic mode are investigated

Synchrotron X-ray diffraction characterization of healthy and fluorotic human dental enamel

With the introduction of fluoride as the main anticaries agent used in preventive dentistry, and perhaps an increase in fluoride in our food chain, dental fluorosis has become an increasing world-wide problem. Visible signs of fluorosis begin to become obvious on the enamel surface as opacities, implying some porosity in the tissue. The mechanisms that conduct the formation of fluorotic enamel are unknown, but should involve modifications in the basic physical-chemistry reactions of demineralization and remineralisation of the enamel of the teeth, which is the same reaction of formation of the enamel's hydroxyapatite (HAp) in the maturation phase. The increase of the amount of fluoride inside of the apatite will result in gradual increase of the lattice parameters. The aim of this work is to characterize the healthy and fluorotic enamel in human tooth using Synchrotron X-ray diffraction. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the Brazilian Synchrotron Light Laboratory—LNLS, Campinas, Brazil. X-ray diffraction experiments were performed both in powder samples and polished surfaces. The powder samples were analyzed to obtain the characterization of a typical healthy enamel pattern. The polished surfaces were analyzed in specific areas that have been identified as fluorotic ones. X-ray diffraction data were obtained for all samples and these data were compared with the control samples and also with the literature data.

In vitro and in situ evidence supporting the utility of a bioadhesive fluoridated rinse in the management of dental erosion

The last 40 years or so have seen a dramatic reduction in the incidence of dental caries in the developed world that has mirrored the introduction of fluoridated dentifrices, and implementation of regional or national water fluoridation programmes. 1−4 The concomitant improvement in periodontal health has been augmented by improvements in preventative and restorative dentistry. 4 There is recent evidence, however, to suggest that caries prevalence in many populations has stabilised, and in some cases actually risen. 5 What is not in dispute is that the improvements in oral health observed over recent decades have resulted in adults retaining their dentition for longer. With average life expectancy increasing in most countries, educative efforts to promote the idea of “teeth for life”, in combination with improved oral care treatments and clinical management, are to be encouraged. A consequence of retaining the dentition for longer is that processes that result in tooth surface loss but are not disease related, such as erosion, abrasion and attrition, become more relevant. 6−8 It is concerning, therefore, that as we have seen impressive reductions in caries-related dental disease since the introduction of fluoride, at the very time that suppression of caries in children appears to be stabilising, the prevalence of

Calcium phosphate‐based remineralization systems: scientific evidence?

Dental caries remains a major public health problem in most communities even though the prevalence of disease has decreased since the introduction of fluorides. The focus in caries research has recently shifted to the development of methodologies for the detection of the early stages of caries lesions and the non-invasive treatment of these lesions. Topical fluoride ions, in the presence of calcium and phosphate ions, promote the formation of fluorapatite in tooth enamel by a process referred to as remineralization. The non-invasive treatment of early caries lesions by remineralization has the potential to be a major advance in the clinical management of the disease. However, for net remineralization to occur adequate levels of calcium and phosphate ions must be available and this process is normally calcium phosphate limited. In recent times three calcium phosphate-based remineralization systems have been developed and are now commercially available: a casein phosphopeptide stabilized amorphous calcium phosphate (Recaldent (CPP-ACP), CASRN691364-49-5), an unstabilized amorphous calcium phosphate (ACP or Enamelon) and a bioactive glass containing calcium sodium phosphosilicate (NovaMin). The purpose of this review was to determine the scientific evidence to support a role for these remineralization systems in the non-invasive treatment of early caries lesions. The review has revealed that there is evidence for an anticariogenic efficacy of the Enamelon technology for root caries and for the Recaldent technology in significantly slowing the progression of coronal caries and promoting the regression of lesions in randomized, controlled clinical trials. Hence the calcium phosphate-based remineralization technologies show promise as adjunctive treatments to fluoride therapy in the non-invasive management of early caries lesions.