Hydrogen Fluoride Research Articles

High-performance Li/LiNi0.8Co0.1Mn0.1O2 batteries enabled by optimizing carbonate-based electrolyte and electrode interphases via triallylamine additive

Lithium (Li) metal batteries (LMBs), paired with high-energy–density cathode materials, are promising to meet the ever-increasing demand for electric energy storage. Unfortunately, the inferior electrode–electrolyte interfaces and hydrogen fluoride (HF) corrosion in the state-of-art carbonate-based electrolytes lead to dendritic Li growth and unsatisfactory cyclability of LMBs. Herein, a multifunctional electrolyte additive triallylamine (TAA) is proposed to circumvent those issues. The TAA molecule exhibits strong nucleophilicity and contains three unsaturated carbon–carbon double bonds, the former for HF elimination, the later for in-situ passivation of aggressive electrodes. As evidenced theoretically and experimentally, the preferential oxidation and reduction of carbon–carbon double bonds enable the successful regulation of components and morphologies of electrode interfaces, as well as the binding affinity to HF effectively blocks HF corrosion. In particular, the TAA-derived electrode interfaces are packed with abundant lithium-containing inorganics and oligomers, which diminishes undesired parasitic reactions of electrolyte and detrimental degradation of electrode materials. When using the TAA-containing electrolyte, the cell configuration with Li anode and nickel-rich layered oxide cathode and symmetrical Li cell deliver remarkably enhanced electrochemical performance with regard to the additive-free cell. The TAA additive shows great potential in advancing the development of carbonate-based electrolytes in LMBs.

Effect of SiO2 Coating on Microstructure and Electrochemical Properties of LiNi0.5Mn1.5O4 Cathode Material

Abstract We present a simple method for producing SiO2-modified LiNi0.5Mn1.5O4 (LNMO) cathode materials. Manganese carbonate was directly mixed with nickel nitrate and lithium hydroxide, and a spherical structure LNMO cathode material was prepared by two-step calcination, then ethyl orthosilicate and LNMO powder were simply mixed in solid and liquid phases to prepare SiO2-coated LNMO material. The effect of SiO2 coating on the structure of LNMO was studied by diffraction of X-rays, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis and differential scanning calorimetry. An amorphous SiO2 coating layer developed on the surface of the LNMO particles in the modification and this could alleviate the strike of hydrogen fluoride (HF) caused by electrolyte decomposition as well as the development of a solid electrolyte interphase. The electrochemical performance of the coated material was as follows: when the amount of SiO2 was 0 wt%, 1 wt%, 2 wt%, and 3 wt%, the initial discharge capacity of the sample was 98.2, 84.1, 101.3, and 89.8mAh/g, respectively. After 50 charge−discharge cycles, the capacity retention rates are 92.7%, 66.8%, 97.9%, and 93.8%, respectively. The cyclic stability of the samples can be significantly improved when the SiO2 coating amount is 2 wt% and 3 wt%, indicating that SiO2 coating can not only improve the discharge-specific capacity of the material but also improve its cyclic stability.

Corrosion studies on low-cost solid lubricant coated stainless steel specimen

AISI 304 stainless steel is widely used in industries owing to its many desirable qualities like excellent formability, drawability and resistance to corrosion. However, AISI 304 stainless steel corrodes when exposed to halide environment such as chloride and fluoride. This study is primarily focused to assess the anti-corrosion properties of AISI 304 steel when coated with CaF2 solid lubricant. CaF2 solid lubricant was synthesized from the discarded egg-shells by ion exchange method by treating the egg-shell powder with hydrogen fluoride solution. Thermal spray coating method was used to coat the synthesized CaF2 solid lubricant on the AISI 304 stainless steel specimen. Slurry erosion test and electrochemical impedance spectroscopy test were conducted on the coated and uncoated specimen to assess the corrosion resistance. From the experimental results, the corrosion rate of the coated specimen was found to be very effective compared to the uncoated specimen.

Concentration of hydrofluoric acid during processing columbite and loparite concentrates

The results of modeling the concentration of hydrofluoric acid on the example of processing columbite and loparite concentrates are presented. It is shown that when optimizing the rectification process, it is necessary to use the electrolyte NRTL vapor-liquid equilibrium model and use the total energy consumption going to the separation of the mixture as an optimization criterion. The information about the work on the extraction of anhydrous hydrogen fluoride from hydrofluoric acid is presented.

Correlation analysis and benchmark dose study on bone metabolic biochemical index of low doses of exposed hydrogen fluoride workers

Objective: To analyze correlation of occupational hydrogen fluoride exposure to low doses of bone metabolism index through occupational epidemiological investigation and benchmark dose calculation. Methods: In May 2021, using cluster sampling method, 237 workers exposed to hydrogen fluoride in a company were selected as the contact group, and 83 workers not exposed to hydrogen fluoride in an electronics production company were selected as the control group. The external exposure dose and urinary fluoride concentration, blood and urine biochemical indicators of the workers was measured.The relationship between external dose and internal dose of hydrogen fluoride was analyzed. The external dose, urinary fluoride was used as exposure biomarkers, while serum osteocalcin (BGP), serum alkaline phosphatase (AKP) and urinary hydroxyproline (HYP) were used as effect biomarkers for bone metabolism of hydrogen fluoride exposure. The benchmark dose calculation software (BMDS1.3.2) was used to calculate benchmark dose (BMD) . Results: Urine fluoride concentration in the contact group was correlated with creatinine-adjusted urine fluoride concentration (r=0.69, P=0.001). There was no significant correlation between the external dose of hydrogen fluoride and urine fluoride in the contact group (r=0.03, P=0.132). The concentrations of urine fluoride in the contact group and the control group were (0.81±0.61) and (0.45±0.14) mg/L, respectively, and the difference between the two groups was statistically significant (t=5.01, P=0.025). Using BGP, AKP and HYP as effect indexes, the urinary BMDL-05 values were 1.28, 1.47 and 1.08 mg/L, respectively. Conclusion: Urinary fluoride can sensitively reflect the changes in the effect indexes of biochemical indexes of bone metabolism. BGP and HYP can be used as early sensitive effect indexes of occupational hydrogen fluoride exposure.

Process Understanding Enables Control of Hydrogen Fluoride Formation in a Nitroarene Reduction

Process Understanding Enables Control of Hydrogen Fluoride Formation in a Nitroarene Reduction

Perturbation theoretical approaches to strong light-matter coupling in ground and excited electronic states for the description of molecular polaritons.

Quantum chemical methods for the description of molecular polaritonic states in the strong coupling regime based on the Pauli-Fierz Hamiltonian are introduced. Based on a quantum electrodynamic Hartree-Fock (QED-HF) reference, a QED Møller-Plesset perturbation theory of second order for the electronic ground state and a second order quantum electrodynamic algebraic diagrammatic construction scheme for the polarization propagator [QED-ADC(2)] for excited electronic states have been derived, implemented, and tested for polaritons in hydrogen fluoride. Analogous approaches based on a standard non-polaritonic HF reference are also presented and thoroughly compared, both algebraically and numerically, to those based on the QED-HF reference. Furthermore, a promising route to approximate QED-ADC methods based on a unitary transformation of the algebraic expression into a restricted state space is outlined showing excellent agreement in second order with QED-ADC(2). All presented novel methods are compared to and tested against other existing abinitio approaches, mostly QED coupled cluster theory, including single and double excitations, and show qualitative agreement at a reduced computational effort.

The role of silanol groups on the reaction of SiO2 and anhydrous hydrogen fluoride gas

AbstractIt is essential to etch SiO2 for producing silica glass components, semiconductor devices, and so on. Although wet‐etching with hydrogen fluoride (HF) solutions is usually employed for this purpose, it faces a drawback that microstructures stick during the drying of the solution. To overcome this problem, we have developed a dry‐etching technique with gaseous HF at high temperatures. In the present study, an interesting phenomenon was found that silicon thermal oxides were much less etched than vitreous silica by gaseous HF. Such difference had not been found in wet‐ or humid HF gas etching. Because their bulk chemical formulae are the same (SiO2), it was suggested that the surface species affected the reaction rate. In fact, preprocessing with water vapor plasma remarkably increased the etching rate on the thermal oxides layer, and vacuum heating almost completely suppressed the reaction on the vitreous silica and the plasma‐treated thermal oxides. These results indicate that the surface silanol groups enhance the reaction between SiO2 and gaseous HF. Based on the results, a model of chain reaction for SiO2 and gaseous HF was proposed, where the surface silanol groups act as the reaction center.

Emission and occupational health risk assessment of harmful contaminants in various processes in a typical semiconductor manufacturing industry building

Workers in semiconductor factories have occupational health risks from exposure to chemical substances. This work analyzed hazardous chemical substances in the key process of a semiconductor factory in China, and studied cancer and non-cancer health risks and occupational health risks of workers. Research results show that more than half of the processes contain compounds such as hydrogen fluoride, chlorine, hydrogen chloride, ammonia and 2-propanol, and their concentrations vary greatly depending on the process. The occupational exposure index (Ei) of some processes is greater than 1, which means that there are adverse occupational health risks, including wet etching (WETCH), physical vapour deposition (PVD), furnace process (FUR), chemicals storehouse (CS) and diffusion (from inspection area). The pollutants with a high contribution rate to Ei vary with the process, and WETCH (operating area) has the highest contribution rate of sulphuric acid (93.33%). The Hazard Quotient (HQi) of PVD and CS is far greater than 1, indicating that there is a non-cancer risk. The lifetime cancer risk (LCRi) of wastewater treatment and CS is greater than 10−4, which indicates a risk of cancer. The General Engineer has higher health risks than the Duty Engineer due to the higher exposure frequency.

Challenges in atomic layer etching of gallium nitride using surface oxidation and ligand-exchange

Two atomic layer etching (ALE) methods were studied for crystalline GaN, based on oxidation, fluorination, and ligand exchange. Etching was performed on unintentionally doped GaN grown by hydride vapor phase epitaxy. For the first step, the GaN surfaces were oxidized using either water vapor or remote O2-plasma exposure to produce a thin oxide layer. Removal of the surface oxide was addressed using alternating exposures of hydrogen fluoride (HF) and trimethylgallium (TMG) via fluorination and ligand exchange, respectively. Several HF and TMG super cycles were implemented to remove the surface oxide. Each ALE process was monitored in situ using multiwavelength ellipsometry. X-ray photoelectron spectroscopy was employed for the characterization of surface composition and impurity states. Additionally, the thermal and plasma-enhanced ALE methods were performed on patterned wafers and transmission electron microscopy (TEM) was used to measure the surface change. The x-ray photoelectron spectroscopy measurements indicated that F and O impurities remained on etched surfaces for both ALE processes. Ellipsometry indicated a slight reduction in thickness. TEM indicated a removal rate that was less than predicted. We suggest that the etch rates were reduced due to the ordered structure of the oxide formed on crystalline GaN surfaces.

Prediction of glassy silica etching with hydrogen fluoride gas by kinetic Monte Carlo simulations.

Understanding the surface properties of glass during the hydrogen fluoride (HF)-based vapor etching process is essential to optimize treatment processes in semiconductor and glass industries. In this work, we investigate an etching process of fused glassy silica by HF gas with kinetic Monte Carlo (KMC) simulations. Detailed pathways of surface reactions between gas molecules and the silica surface with activation energy sets are explicitly implemented in the KMC algorithm for both dry and humid conditions. The KMC model successfully describes the etching of the silica surface with the evolution of surface morphology up to the micron regime. The simulation results show that the calculated etch rate and surface roughness are in good agreement with the experimental results, and the effect of humidity on the etch rate is also confirmed. Development of roughness is theoretically analyzed in terms of surface roughening phenomena, and it is predicted that the values of growth and roughening exponents are 0.19 and 0.33, respectively, suggesting that our model belongs to the Kardar-Parisi-Zhang universality class. Furthermore, the temporal evolution of surface chemistry, specifically surface hydroxyls and fluorine groups, is monitored. The surface density of fluorine moieties is 2.5 times higher than that of the hydroxyl groups, implying that the surface is well fluorinated during vapor etching.

Separation of a Gas Mixture Containing Uranium Hexafluoride, Hydrogen Fluoride, and Chlorine Trifluoride

Separation of a Gas Mixture Containing Uranium Hexafluoride, Hydrogen Fluoride, and Chlorine Trifluoride

Polymeric Material Stability in a Hydrogen Fluoride Environment

Polymeric Material Stability in a Hydrogen Fluoride Environment

Crystal Growth and Crystal Structures of Gold(V) Compounds: Cu(AuF6)2, Ag(AuF6)2, and O2(CuF)3(AuF6)4 ⋅ HF

AbstractCrystal growth from anhydrous hydrogen fluoride solutions of M2+(M=Cu, Ag) and [AuF6]−gave M(AuF6)2salts (M=Cu, Ag). Similar attempts to prepare single crystals of the corresponding nickel, zinc and magnesium salts failed. The crystal structure of Cu(AuF6)2consists of layers of Cu2+cations connected by [AuF6]−anions, thus forming slabs. Only van der Waals interactions exist between adjacent slabs. The crystal structure of Ag(AuF6)2consists of a three‐dimensional framework in which Ag+cations are linked by [AuF6]−anions. Both structures are members of the MII(XVF6)2family, in which seven different structure types have been observed to date. In the crystal structure of O2(CuF)3(AuF6)4 ⋅ HF, the bridging AuF6units connect [−Cu−F−Cu−F−]∞chains to form stacks between which O2+cations and HF molecules are located.

Analysis of Activated Carbon from Bituminous Coal as the Primary Battery Cathode Potential Using Fluoric Acid

Activated carbon can generally be made from carbon-containing materials such as coal. The activation in activated carbon synthesis has different activation mechanisms and characteristics. The objective of this study was to analyze the quality and characterization of activated carbon in bituminous coal using a fluoride (HF) activator. The research method was carried out starting from the sample preparation stage, the chemical and physical activation carbonization stage, and the stage of testing the quality of coal-activated carbon. The results showed that each test obtained a moisture content ranging from 0.7% -1.61%. Ash content has a range of values ranging from 17.51% -25.74%, while volatile matter content ranges from 20.96% - 33.97%. The bound carbon content has a range of values ranging from 20.96% -33.97%, iodine numbers range from 3995.4455-4302, 0456 mg/g (all parameters follow SNI 06-3730-1995); and the degree of crystallinity obtained from the concentrations of 3.5 M and 5 M (duplo) has a degree of crystallinity of 26.6218 and 26.6014, respectively. Bituminous coal-activated carbon activated using Hydrogen Flouride (HF) with a temperature of 800 °C has optimal characteristics at a concentration of 5 M with a moisture content of 0.84. The volatile matter content is 18.60, while the iodine absorption capacity is 4.137.0704. The short carbon chain in degrees of crystallization is at an angle of 26.6014 2θ with two diffraction peaks forming a solid crystalline pattern. The surface morphology of activated carbon produces round, neat, and slightly impurities pore with a diameter of 8.81μm.

Fluorination of TiN, TiO2, and SiO2 Surfaces by HF toward Selective Atomic Layer Etching (ALE)

As semiconductor devices become miniaturized, the importance of the molecular-level understanding of the fabrication processes is growing. Titanium nitride (TiN) is an important material utilized in various architectural components of semiconductor devices requiring precise control over size and shape. A reported process for atomic layer etching (ALE) of TiN involves surface oxidation into titanium oxide (TiO2) and selective oxidized layer removal by hydrogen fluoride (HF). However, the chemical selectivity of these Ti-based materials in the etching process by HF remains unclear. In this study, computational chemistry methods utilizing density functional theory (DFT) calculations were applied to the fluorination reactions of TiN, TiO2, and SiO2 to identify and compare the surface chemical reactivity of these substrates toward etching processes. It is shown that the materials can be etched using HF, leaving TiF4 and SiF4 as the byproducts. However, while such a TiN reaction is thermodynamically hindered, the etching of TiO2 and SiO2 is suggested to be favorable. Our study provides theoretical insights into the fluorination reactivity of TiN, which has not been reported previously regardless of technological importance. Furthermore, we explore the etching selectivity between TiN, TiO2, and SiO2, which is a crucial factor in the ALE process conditions of TiN.

Sand Consolidation Using Enforced Calcium and Magnesium Fluoride Precipitation

Abstract Sand production is a common problem that interrupts hydrocarbon production from unconsolidated formations. Different chemical and mechanical methods are used to prevent solid production either by consolidating the sand particles or installing downhole screens. This study presents a novel approach for sand consolidation using enforced calcium and magnesium precipitation. The used chemicals are ammonium hydrogen fluoride, calcium oxide, and magnesium oxide solutions. In this work, different measurements were carried out to assess the performance of the new consolidation method. Also, the impact of soaking the consolidated sand in freshwater, toluene, and HCl was examined. The rock mineralogy was determined before and after each soaking treatment using X-ray diffraction (XRD) analysis. The nuclear magnetic resonance (NMR) technique was used to evaluate the pore system at different stages. In addition, scanning electron microscope (SEM) technique was used to examine the morphology and chemistry changes after each chemical treatment. Finally, the rock strength was measured before and after the treatment using a scratch test. Results indicate that the proposed chemical method can significantly improve the sand consolidation and increase the rock strength to 34 MPa (4931 psi). Soaking the consolidated sand sample in water and toluene showed minor alterations in the rock properties. However, using HCl lead to increasing rock permeability due to mineral dissolution. The strength measurements showed that the consolidated sand can withstand the water and toluene treatment, and the rock strength was reduced by less than 10%. Overall, a new chemical treatment is presented to improve the sand consolidated utilizing enforced calcium and magnesium precipitation. The consolidated sand sample showed very reasonable rock strength which can prevent sand migration.

Capsule structured Al/FeF3/AP energetic microspheres with enhanced combustion performance and energy release efficiency by a microexplosion reaction

The agglomeration and sintering of aluminum (Al) metal fuels lead to inadequate combustion and low energy release efficiency in the solid propellant systems. Herein, we assemble Al particles with gas generator of ferric trifluoride (FeF3) into capsule structured microspheres to detonate a microexplosion reaction by the evaporation-induced self-assembly technique, with encapsulating by ammonium perchlorate (AP) oxidant. The generated ternary Al/FeF3/AP microspheres achieved superior heat of combustion (12719.75 J g−1) and combustion temperature (1639.6 °C) owing to the full contact between components, reduced reaction transport distance, and the fierce shattering microexplosion combustion. Combustion mechanism analysis indicated that Al2O3 layer that hindered the oxidation reaction of Al was etched by the hydrogen fluoride (HF) from FeF3 decomposition, which caused the rapid splashing of nano Al clusters to detonate shattering microexplosion combustion. Furthermore, the ternary Al/FeF3/AP microspheres dramatically improve the combustion performance of hydroxy-terminated polybutadiene (HTPB)-based propellants and achieve a burning rate of 2.975 mm s−1, higher than most of the published HTPB/AP/Al propellants to date. The construction of Al/FeF3/AP microspheres exhibits a huge potential for the improvement of the propulsion power of rockets and weapons.

Degradation mechanism of FKM during thermo-oxidative aging from mechanical and network structure correlations

The thermal weak point of a peroxide-cured fluoroelastomer (FKM) in presence of triallylisocyanurate (TAIC) has been identified. To that purpose, the thermal stability was assessed by TGA measurements. In parallel, thermo-oxidative degradation was characterized after the aging of several samples at 250 °C for various durations. Specific attention has been directed to the structural evolution, evaluated by both FTIR and equilibrium swelling experiments. Experimental results highlight that TAIC, the system's crosslink node, is the thermal weak point of a peroxide-cured fluoroelastomer (FKM). Nonetheless, crosslinks are not entirely broken since the crosslinking density decreases with aging time before stabilizing for one week at 250 °C. This allows the material to retain some of its mechanical properties such as good elongation at break. For longest exposure times at 250 °C (beyond one week), chain scission mechanism becomes predominant leading to a loss of the mechanical properties. Regarding the degradation mechanism, TGA-FTIR results are rather in favor of a dehydrofluorination mechanism as hydrogen fluoride (HF) is detected upon the first times of thermo-oxidative aging. In a second step, chain scission starts to occur. Recombination reactions between double bonds provided by dehydrofluorination and macroradicals formed during chain scission could explain that FKM is still crosslinked after one week at 250 °C under air.

Surface modification strategy for constructing Fe-Nx species and FeF2/Fe3C nanoparticles co-anchored N, F co-doped carbon nanotubes for efficient oxygen reduction

Fe-N-C catalysts have served as ideal catalysts for oxygen reduction reaction (ORR), but the strong adsorption to ORR-relevant intermediates and less utilization of Fe-Nx sites endow those catalysts with inferior performance. Here, an efficient catalyst consisted of Fe-Nx species and FeF2/Fe3C nanoparticles co-anchored on N, F co-doped carbon nanotubes (Fe-NF-CNTs) has been constructed through a surface modification strategy. Sodium trifluoroacetate as functional linker modified on metal-organic framework surface promotes to form abundant and accessible active sites. FeF2/Fe3C nanoparticles and hydrogen fluoride generated in pyrolysis process facilitate to construct N, F co-doped CNTs with defects and holes. N, F co-doping modifies the adsorption characteristic of Fe-Nx sites, while CNTs improve the accessibility of active sites and the capability of material transport. Therefore, Fe-NF-CNTs exhibits outstanding activity (E1/2 = 0.85 V) and stabilization (ΔE = 6 mV, 10k cycles). Impressively, Fe-NF-CNTs delivers high power density (144 and 68 mW cm–2) and cycle stability (300 and 60 h) in liquid and flexible Zn-air batteries, respectively. This work provides a surface modification strategy to guide the tuning of electronic structure of efficient ORR catalysts designed for renewable green energy.