Fluorination Process Research Articles

Mn(IV)‐Substituted Metal(II) Hexafluorido Metallates(IV): Synthesis, Crystal Structures, and Luminescence Properties

AbstractWe synthesized 16 novel red‐emitting Mn(IV)‐substituted phosphors of the compositions MgGeF6 : Mn, MgPbF6 : Mn, CaMF6 : Mn (M=Ge, Sn, Pb, Zr, Hf), SrSnF6 : Mn, “SrTiF6 : Mn”, BaPbF6 : Mn, ZnMF6 : Mn (M=Sn, Pb, Zr, Hf), and CdMF6 : Mn (M=Pb, Hf) using a dry‐chemical fluorination process completely avoiding hydrofluoric acid. In comparison with the commonly used red‐emitter K2SiF6 : Mn (KSF) with its emission maximum at 630.8 nm, all above Ca and Sr compounds and CdHfF6 : Mn show a blue‐shift of their emission maxima, the compound SrSnF6 : Mn even by 4.2 nm down to 626.6 nm. The compounds were characterized by powder X‐ray diffraction, IR and emission spectroscopy. We additionally present the crystal structures of the unsubstituted compounds CaZrF6, CaHfF6, CaPbF6, CdZrF6, CdHfF6, and MgHfF6, which all crystallize isotypic in the NaSbF6 structure type. The compound “SrTiF6” was characterized by powder XRD and studied with evolutionary structure prediction methods, but its crystal structure could not yet be solved.

Adsorption of HF on gibbsite calcined at various temperatures: A solid-state NMR study of low-level fluorinated systems

The fluorination mechanism of low-level fluorinated materials obtained by calcination of Bayer gibbsite at different temperatures was studied by 27Al and 19F solid-state NMR spectroscopy and X-ray diffraction. Gibbsite was calcined at 400, 600, 800, and 1000 °C followed by treatment with anhydrous HF/N2 gas at 100 °C. Three types of Al–F species on the surface of fluorinated gibbsite calcined at 400, 600, and 800 °C are proposed on the basis of the 19F magic angle spinning (MAS) NMR spectra, which show peaks at about −132, −137, and −163 ppm, while the spectrum of fluorinated gibbsite calcined at 1000 °C showed five additional peaks, at about −139, −164, −176, −183, and −191 ppm. The fluorination process in aluminas is based on elementary exchange reactions in which F− replaces surface –OH groups according to their basicity. The 27Al MAS NMR and 19F-27Al cross-polarization–MAS experiments confirmed the presence of octahedral Al species.

Distribution, Sources, and Risk Assessment of Polyfluoroalkyl Substances in Main Rivers and Soils of Tianjin

Rapid urbanization and industrialization may potentially impact the spatial distribution and transmission of polyfluoroalkyl substances (PFASs). Tianjin, a typical industrialized city with a high urbanization level around Bohai Bay, was selected to evaluate the spatial distribution and ecological risks of PFASs. Water and soil samples were systematically collected and analyzed by using solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS-MS) methods. The results showed that all 12 PFASs were detected in water and soils, and the detection rates of the other congeners were low. The concentrations of ΣPFASs in water ranged from 3.93 to 357.85 ng ·L-1, and the levels of ΣPFASs in soils ranged from 4.60 to 63.85 ng ·g-1. PFBA was the major component in water and soils, and the contribution of PFBA was 37% and 67% in water and soils, respectively. The spatial difference in ΣPFASs in the water bodies was significant. ΣPFAS concentrations in the surface water were higher in the north (mean value of 63.83 ng ·L-1) than in the south (mean value of 51.71 ng ·L-1) and higher in the eastern coastal area (mean value of 71.36 ng ·L-1) than in the western area (mean value of 36.08 ng ·L-1). ΣPFAS concentrations from upstream to downstream of the rivers showed an increasing trend. The highest PFAS concentration was found in the Chaobai River, and the lowest was detected in the South Canal. The spatial distribution of PFASs in soils was higher in the south (mean value of 13.33 ng ·g-1) than in the north (mean value of 6.38 ng ·g-1) and higher in the eastern coastal region (mean value of 11.45 ng ·g-1) than in the western region (mean value of 6.94 ng ·g-1). The soil concentrations of ΣPFASs in the Haihe River Basin were the highest. The source analysis results showed that the emulsification of rubber products, food packaging process, paper surface treatment, fire extinguishing agent use, and electrochemical fluorination process in industrial production were the main sources of PFASs in the soils in the study area. PFOS/PFOA, PFOA/PFNA, and PFHpA/PFOA analyses showed that the main source of PFASs in water bodies was the degradation of precursors. ΣPFASs in a few areas originated from the direct emissions from production, but the atmospheric deposition was small. The results of the ecological risk evaluation indicated that the exposure concentrations of PFASs in water and soils in the study area were at a low ecological risk level. However, the long-term ecological effects of PFASs cannot be ignored because of their long-distance transport capability and high food chain (web) accumulation capability.

A Comparative Study of Gas-phase Fluorination and Nano-Al2O3 Doping on Space Charge Behavior and Trap Level in Epoxy Resin

In this work, the effect of gas-phase fluorination concurrent with nano-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> doping on space charge distribution, as well as trap level and density of epoxy resin, is investigated. Epoxy resins with different concentrations of Al2O3 nano-fillers (0, 1, 3, and 5 wt%) are prepared and fluorinated by a gas mixture of F2/N2 (20/80 v/v) for 30 min at 40 °C and 0.05 MPa. Fourier-transform infrared (FTIR) spectroscopy confirms the breakage of molecular-chain during the gas-phase fluorination process. The space charge behavior is observed by the pulsed electroacoustic (PEA) method before and after fluorination. PEA results indicate that 30-minute fluorination is useful against space charge injection into the bulk of epoxy resin/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> nanocomposites. The trap density and trap energy level distribution are determined by isothermal surface potential decay (ISPD) measurement. The results indicate that fluorination introduces shallow traps on the surface, which can increase the conductivity of surface, and, thus, the trap depth is considerably reduced after fluorination. Moreover, it is found that incorporating 1 wt% nano-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> particles into epoxy resin can level up the energy level of deep traps. However, further increasing the nano-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> concentration, e.g., 3 and 5 wt%, promises the overlap of interaction zones between polymer matrix and nanoparticles, reducing the trap energy level.

Plasma electrolytic fluorination on Al alloys: Coating growth and plasma discharge behavior

The plasma electrolytic fluorination (PEF) process was conducted on 6061 Al alloy in the NH4F-EG non-aqueous electrolyte at room temperature. The microstructure and composition of the resultant coating were characterized by SEM, EDS, XRD and XPS. Also the coating growth and plasma discharge behavior were investigated by means of a well-designed jig, digital camera and OES, in order to understand the process characteristics. Results showed that the coating was dominantly composed of AlF3, and characterized by a flake-like microstructure accompanying with some micro-pores and numerous micro-cracks. The internal of the coating was porous with a compact barrier layer near the substrate/coating interface. The fluorination of the substrate contributed the inward growth of the coating. PEF discharge sparks were characterized by tiny size and weak intensity during the whole process, of which the plasma electron temperature was about (3510 ± 110) K. Also, the discharge behavior and coating growth mechanism of the PEF process on Al alloy were discussed.

Copper catalyzed late-stage C(sp3)-H functionalization of nitrogen heterocycles

Nitrogen heterocycle represents a ubiquitous skeleton in natural products and drugs. Late-stage C(sp3)-H bond functionalization of N-heterocycles with broad substrate scope remains a challenge and of particular significance to modern chemical synthesis and pharmaceutical chemistry. Here, we demonstrate copper-catalysed late-stage C(sp3)-H functionalizaion of N-heterocycles using commercially available catalysts under mild reaction conditions. We have investigated 8 types of N-heterocycles which are usually found as medicinally important skeletons. The scope and utility of this approach are demonstrated by late-stage C(sp3)-H modification of these heterocycles including a number of pharmaceuticals with a broad range of nucleophiles, e.g. methylation, arylation, azidination, mono-deuteration and glycoconjugation etc. Preliminary mechanistic studies reveal that the reaction undergoes a C-H fluorination process which is followed by a nucleophilic substitution.

Multi-Metallic Template Fluorination Mmtf for the Preparation of Ternary Metal Fluoride and Their First Use As Cathodes in Solid State Lithium Batteries

There is an urgent need in exploring new cathode materials for Lithium batteries in order to increase their capacities. Conversion type cathodes are relevant replacement candidates and especially metal fluorides such as FeF3 with a theoretical capacity of 712 mAh g-1 for three electrons at a voltage of 2.74 V vs. Li+/Li or CuF2 with a theoretical capacity of 528 mAh g-1 for two electrons at 3.55 V vs. Li+/Li. However, important voltage hysteresis, dissolution in organic electrolytes and poor reversibility hinder their use as reliable cathode materials in Lithium batteries. In this work, compatibility of fluorides with a PEO/LiTFSI (Poly Ethylene Oxide impregnated with Lithium bis(trifluoromethanesulfonyl)imide) solid electrolyte membrane is evaluated to avoid dissolution of active materials in organic liquid electrolytes often encountered with fluorides. Additionally, a general synthesis method is used to prepare ternary metal fluorides. Indeed, ternary metal fluorides were recently explored1–3 as a solution to buffer volume expansion occurring during conversion, hence greatly reducing voltage hysteresis and improving cyclability. These materials are usually prepared by planetary ball milling or by hydrofluoric acid HF-assisted fluorination, both methods not scalable for industrial purpose. In this work, we propose Multi-Metallic Template Fluorination MMTF as a general synthesis way to prepare ternary metal fluorides in a scalable way suitable for industrial applications.Prussian Blue Analogs are particularly relevant fluorination templates: these compounds can be easily prepared in great quantities by coprecipitation, enabling industrial applications. Additionally, a wide variety of compositions can be synthesized while their open structure facilitates gas solid fluorination process used. Multi Metallic Template Fluorination MMTF on PBA therefore enables the preparation of fluoride compounds with desired metallic stoichiometry by tuning it in the pristine PBA. For electrochemical applications considered in this work, Copper based Prussian Blue Analog CuPBA of general formula Cu3[Fe(CN)6]2.xH2O is chosen to combine properties of copper and iron redox centers in a ternary metal fluoride cathode. By monitoring thermal transformations of CuPBA using ThermoGravimetric Analyses coupled to Mass Spectrometry (TGA MS) and XRD, different temperature domains are identified under air, assessing that the CuPBA template can be maintained up to 170 °C while oxides are formed at 350 °C. Fluorination temperatures are selected in consequence: structures of fluorinated products are characterized by combined XAS and XRD analyses. Results indicate the formation of an anti-perovskite [Cu(H2O)4]3.(FeF6)2 phase at low temperatures, showing that Multi Metallic Template Fluorination can proceed in a topotactic manner by maintaining a Multi Metallic Template in the fluorinated product. After a severe change in the local order identified by XAS at 200 °C and especially around copper cations, a biphasic CuF2/FeF3 product is formed at high temperatures.Electrochemical signature of different CuPBA fluorination products are investigated by Cyclic Voltammetry (CV) and galvanostatic measurements with a solid electrolyte membrane. Comparisons with a mechanical milling CuF2/FeF3 reference but also with pristine CuF2 and FeF3 commercial references cycled in the same conditions are presented. Results reveal that CuPBA fluorinated at 350 °C is able to match a CuF2/FeF3 mechanical milling reference and even perform slightly better. Both materials perform much better than the mere addition of CuF2 and FeF3 signatures, confirming the superiority of ternary metal fluorides as cathode materials over binary metal fluorides stated in literature. Better performances of CuPBA Multi Metallic Template Fluorination MMTF product at high temperatures over mechanical milling reference are explained by an homogeneous dispersion of copper and iron redox centers present in the initial CuPBA template resulting in a better distribution of CuF2 and FeF3 domains in the fluorinated product at 350 °C than in the mechanical milling reference.The first discharge capacity approaches the maximum theoretical capacity of 600 mAh g-1 and highlights the possibility to dramatically increase the capacity of Lithium batteries by potentially doubling the capacity reached with classical NMC electrodes. Multi Metallic Template Fluorination therefore enables the preparation of complex fluorinated cathodes in a scalable way for industry with interesting features over a simple mechanical milling.The Multi Metallic Template Fluorination MMTF approach detailed in this work can be adapted to a wide range of multi metallic templates such as Metal Organic Frameworks and Layered Double Hydroxides for the preparation of mixed metal fluorides with unique features such as particular structures and/or morphologies depending on the desired application and in a scalable way.(1) Villa et al. ACS Appl. Mater. Interfaces 2019, 11 (1), 647–654.(2) Wang et al. Nat Commun 2015, 6 (1), 6668.(3) Ding et al. ACS Appl. Mater. Interfaces 2019, 11 (4), 3852–3860. Figure 1

High hydrophobic poly(lactic acid) foams impregnating one-step Si–F modified lignin nanoparticles for oil/organic solvents absorption

In this work, the hydrophobic lignin nanoparticles (LNP) were synthesized by a synchronous modification of silanization and fluorination process. Thermogravimetric analyser, fourier-transform-infrared-spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to confirm the surface modified LNP (m-LNP). The maximum degradation temperature of m-LNP was 85 °C higher than that of origin LNP. Then the bio-based PLA foams were prepared via freezing-dry method by impregnating various amount of m-LNP. The results showed that a high hydrophobicity (141° of contact angle) and porosity structure (94% of porosity) were constructed when the m-LNP content increased to 6 wt% (PLA-6L). Afterwards, the absorption capacities of the PLA composite foams towards various oil/organic solvents are measured. The composite foams reached their saturated adsorption capacity in quite short time and exhibited good recyclability due to the two factors: high hydrophobicity and high porosity. Thus, the bio-based PLA/m-LNP composite foams could be used as the eco-benign and efficient absorbents for petroleum leakage, oil spills and toxic organic solvents in water contamination field.

BxCyNz nanotubes decorated with tracks of fluorine: atomic structure, stability and electronic properties

The structural and electronic properties of fluorinated armchair (7,7) and zigzag (10,0) BxCyNz nanotubes were investigated using ab initio calculations within the scope of generalized gradient approximation and density functional theory. The selected tube structures consist of segregated C and BN phases, arranged in diametrically opposite ribbons, on which the effects of F adsorption on top of B atoms were studied. It was found that the fluorination on the outer side is more stable than on the inner side, by an energetic difference of approximately 1 eV for the armchair structures. Moreover, the results indicate that all arrangements of fluorine atoms are energetically favorable. It is shown that the fluorination process induces significant modifications on the electronic band structures of the nanotubes, producing no magnetic features.

Tuning of superdiamagnetism in La2CuO4 by solid-state electrochemical fluorination and defluorination

Here, we demonstrate the electrochemical fluorination of La2CuO4 in an all-solid-state cell. This method of fluorine intercalation is controllable and reproducible, offering a precise adjustment of hole doping and thus tuning of superdiamagnetic (i.e., the perfect diamagnetic behavior of a superconductor) properties. The fluorinated La2CuO4Fx samples showed an increase in Tc and in diamagnetic response with increasing fluorine content with x up to ∼0.2. The fluorination process could also be reversed, as fluorine could be electrochemically deintercalated from La2CuO4Fx under re-formation of the antiferromagnetic insulator La2CuO4, returning the samples to a non-superdiamagnetic state. This method offers a convenient way of studying the detailed effects of hole doping in La2CuO4 and shows that tuning of material properties by electrochemical fluorination can also be extended to the field of superconductors.

Fluorinated graphite nanosheets for ultrahigh-capacity lithium primary batteries

Traditional fluorinated carbon (CFx) batteries are greatly limited in their applications mostly because of inferior rate performances, initial voltage delay and low fluorine-to-carbon ratio below one. This work innovatively applies graphite nanosheets (NSs) as carbon source and optimizes the fluorination process at temperature range of 250–400 °C to prepare CFx NSs. Specifically, the edge defects and –CF2, –CF3 perfluorinated functional group active sites are introduced into NSs in the form of covalent/semi-covalent/semi-ionic bonds by adjusting the temperature which also breaks the limit of fluorocarbon ratio to achieve ultra-thin microstructure with high performances. In the battery assembly process, a series of discharge electrolytes are introduced to improve the quality and realize the ultrahigh specific capacity. The optimized CFx-400 °C NSs deliver an excellent specific capacity of 921 mAh·g−1 at a current density of 10 mA·g−1 with a high energy density value of 2210 Wh·kg−1. Moreover, the new electrolytes are selected which not only serve as electrolytes but also can be loaded on CFx surface for various discharge reactions without affecting the actual battery function. Thus, the lightweight tabs and current collectors are selected to control the loading of active material and injection coefficient. The presented battery design strategy provides a new strategy to achieve an ultrahigh specific energy density of 1116 Wh·kg−1.

Sulfur [18F]Fluoride Exchange Click Chemistry Enabled Ultrafast Late-Stage Radiosynthesis.

The lack of efficient [18F]fluorination processes and target-specific organofluorine chemotypes remains the major challenge of fluorine-18 positron emission tomography (PET). We report here an ultrafast isotopic exchange method for the radiosynthesis of novel PET agent aryl [18F]fluorosulfate enabled by the emerging sulfur fluoride exchange (SuFEx) click chemistry. The method has been applied to the fully automated 18F-radiolabeling of 25 structurally and functionally diverse aryl fluorosulfates with excellent radiochemical yield (83-100%, median 98%) and high molar activity (280 GBq μmol-1) at room temperature in 30 s. The purification of radiotracers requires no time-consuming HPLC but rather a simple cartridge filtration. We further demonstrate the imaging application of a rationally designed poly(ADP-ribose) polymerase 1 (PARP1)-targeting aryl [18F]fluorosulfate by probing subcutaneous tumors in vivo.

Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics.

The characterization of fluorinated carbon fibers by water sorption has been broadly investigated in this work. In brief, a pitch-based activated carbon fiber (ACF) was submitted to a fluorination process under different conditions of partial pressure (F2:N2 ratio) and temperature. This led to samples with varied fluorine content and C-F type bonding. The effect of the fluorination treatment on the textural properties of the ACF was studied by means of nitrogen and carbon dioxide adsorption at −196 and 0°C, respectively, while the changes induced in the surface chemistry of the materials were analyzed by XPS. Also, the affinity and stability of the materials toward water was evaluated by single and cycling isotherms. The obtained results show that a mild fluorination not only can preserve most of the textural properties of the parent ACF, but enhance the water uptake at the first stages of the water sorption process, together with a shift in the upswing of the water isotherms toward lower relative humidities. This indicates that fluorination under certain conditions can actually enhance the surface hydrophilicity of carbon materials with specific properties. On the contrary, higher partial pressures led to highly fluorinated fibers with lower porosity and more hydrophobic character. Moreover, they presented a lower chemical stability as demonstrated by a change in the shape of the water isotherms after two consecutive measurements. The kinetics of water sorption in the ACFs provided further insights into the different sorption phenomena involved. Hence, water sorption can definitely help to tailor the water affinity, stability and performance of fluorinated porous carbon materials under humid conditions.

Reactivities of electrophilic N-F fluorinating reagents.

Electrophilic fluorination represents one of the most direct and useful methods available for the selective introduction of fluorine into organic compounds. Electrophilic fluorinating reagents of the N-F class have revolutionised the incorporation of fluorine atoms into both pharmaceutically- and agrochemically-important substrates. Since the earliest N-F reagents were commercialised in the 1990s, their reactivities have been investigated using qualitative and, more recently, quantitative methods. This review discusses the different experimental approaches employed to determine reactivities of N-F reagents, focussing on the kinetics studies reported in recent years. We make critical evaluations of the experimental approaches against each other, theoretical approaches, and their applicability towards practical problems. The opportunities for achieving more efficient synthetic electrophilic fluorination processes through kinetic understanding are highlighted.

Superhydrophobic polymer membrane coated by mineralized β-FeOOH nanorods for direct contact membrane distillation

Membrane wetting and fouling represent the foremost concerning issues confining membrane distillation in the treatment of industrial wastewater. This work presents a superhydrophobic poly(vinylidene fluoride) (PVDF) membrane with anti-fouling property, which was derived from the bioinspired adhesive, mineralization and fluorination process for the direct contact membrane distillation (DCMD). The synthesis of membrane was initiated by co-depositing polydopamine/polyethylenimine composite layer onto membrane substrates as “bio-glue” associated with β-FeOOH nanorods as hierarchical structure anchoring to form coordination complexes via the catechol group and Fe3+, then proceeded with the fluorination of 1H,1H,2H,2H-perfluorodecyltriethoxysilane to obtain the superhydrophobic PVDF membrane. Due to the unique micro-nano structure obtained, the resulting PVDF membrane, with a low sliding angle of 5.7° and a high water contact angle of 162°, conforms to the Cassie state. The membrane morphology, wetting behaviour, and anti-fouling performance were systematically characterized. The novel mineralized superhydrophobic membrane exhibited a steady flux and an outstanding salt rejection (99.9%) in treating high salinity and hardness containing-wastewater during 60-h-DCMD test, thus showing great potential for practical application in long-term DCMD.

Spatial distribution, sources and risk assessment of perfluoroalkyl substances in surface soils of a representative densely urbanized and industrialized city of China

As a representative densely urbanized and industrialized city of China, Ningbo has experienced extremely rapid development, with a wide variety of chemical, electronic, pharmaceutical, and paper manufacturing industries. However, limited data and researches are available regarding the levels and profiles of perfluoroalkyl substances (PFASs) in surface soils of Ningbo. The present study was launched to address the knowledge gap through analyzing 27 sites in five functional regions for 9 PFASs types. Results showed that concentrations of the total PFASs (∑PFASs) ranged from 0.63 to 25.6 ng·g−1, with an average of 10.1 ng·g−1. The concentrations of ∑PFASs in different functional regions were in the order of landfill sites > industrial areas > farmlands > residential communities > animal farms. Correlation analyses between soil physicochemical properties and PFASs content revealed that concentrations of ∑PFASs were negatively correlated with soil pH but positively correlated with soil organic matter. Principal component analysis indicated that fluorochemical industrial discharge, daily life discharge, atmospheric precipitation, and electrochemical fluorination process dominated factor loadings. In addition, the ecological risk assessment based on the risk quotient demonstrated that although the risk of PFOA contamination in landfill sites was highest, there are no risk of PFOA and PFOS contamination in the surface soil environment, but needs more supervision for the neighborhood of landfill sites to avoid additional risk. This work provides new data on the different PFAS profiles in soils impacted by different contamination sources within a densely urbanized and industrialized area, and the results obtained should be useful for delineating priority sites for remediation and restauration of polluted soils.

A MOF-derived multifunctional nano-porous fluorinated carbon for high performance lithium/fluorinated carbon primary batteries

For lithium/fluorinated carbon batteries, the carbon sources play a key role in improving the cell performances. In this work, we developed a new type of fluorinated carbon using Cr-MOF as precursor via a direct F2 fluorination method. The prepared samples not only keep the morphology of Cr-MOF but also contain plenty of in-situ fabricated nano-voids during the process of fluorination. Benefitting from the advantage of the nano-porous structure, the samples fluorinated at different temperatures show the highest energy density of 2110.7 W‧h kg−1 at a current density of 10 mA g−1 and a maximum power density of 6540 W kg−1 at 3000 mA g−1. Moreover, the MOF-derived fluorinated carbon cathodes possess an anti-swelling function (volume expansion is no more than 12%). This work delivers a new approach for designing advanced multifunctional fluorinated carbons.

Literature Review and Thermodynamic Modelling of Roasting Processes for Lithium Extraction from Spodumene

This review adds to the public domain literature on the extraction of lithium from mineral ores. The focus is on the pyrometallurgical pre-treatment of spodumene. Information on the phase transformation from α to β, the heat treatment methods as well as the behavior of various compounds in the roasting processes are evaluated. Insight into the chemical thermodynamics of the baking process is evaluated using HSC Chemistry software up to 1200 °C. It was observed that the alkaline, sulfation, chlorination (using Cl2 and CaCl2), carbonizing (to form Li2CO3) and fluorination processes were feasible either throughout or at a point within the temperature range considered. Chlorination using KCl and carbonizing to form Li2O are the processes found to be nonspontaneous throughout the temperatures considered.

A Fluorination Method for Improving Cation‐Disordered Rocksalt Cathode Performance

AbstractIn Li‐rich cation‐disordered rocksalt oxide cathodes (DRX), partial fluorine substitution in the oxygen anion sublattice can increase the capacity contribution from transition‐metal (TM) redox while reducing that from the less reversible oxygen redox. To date, limited fluorination substitution has been achieved by introducing LiF precursor during the solid‐state synthesis. To take full advantage of the fluorination effect, however, a higher F content is desired. In the present study, the successful use of a fluorinated polymeric precursor is reported to increase the F solubility in DRX and the incorporation of F content up to 10–12.5 at% into the rocksalt lattice of a model Li‐Mn‐Nb‐O (LMNO) system, largely exceeding the 7.5 at% limit achieved with LiF synthesis. Higher F content in the fluorinated‐DRX (F‐DRX) significantly improves electrochemical performance, with a reversible discharge capacity of ≈255 mAh g−1 achieved at 10 at% of F substitution. After 30 cycles, up to a 40% increase in capacity retention is achieved through the fluorination. The study demonstrates the feasibility of using a new and effective fluorination process to synthesize advanced DRX cathode materials.

Fluorination of Diamond Nanoparticles in Slow Neutron Reflectors Does Not Destroy Their Crystalline Cores and Clustering While Decreasing Neutron Losses.

If the wavelength of radiation and the size of inhomogeneities in the medium are approximately equal, the radiation might be intensively scattered in the medium and reflected from its surface. Such efficient nanomaterial reflectors are of great scientific and technological interest. In previous works, we demonstrated a significant improvement in the efficiency of reflection of slow neutrons from a powder of diamond nanoparticles by replacing hydrogen located on the surface of nanoparticles with fluorine and removing the residual sp2 amorphous shells of nanoparticles via the fluorination process. In this paper, we study the mechanism of this improvement using a set of complementary experimental techniques. To analyze the data on a small-angle scattering of neutrons and X-rays in powders of diamond nanoparticles, we have developed a model of discrete-size diamond nanospheres. Our results show that fluorination does not destroy either the crystalline cores of nanoparticles or their clustering in the scale range of 0.6–200 nm. This observation implies that it does not significantly affect the neutron scattering properties of the powder. We conclude that the overall increase in reflectivity from the fluorinated nanodiamond powder is primarily due to the large reduction of neutron losses in the powder caused by the removal of hydrogen contaminations.