Search Results (8)

Li/fluorinated carbon (CF_x) batteries have attracted considerable attention in the field of energy storage owing to their excellent energy density and long storage life. However, the development of CF_x cathodes is restricted by their poor conductivity at high degrees of fluorination. Herein, ZIF-8-based fluorinated carbon with a well-developed network structure was fabricated via gas-phase fluorination and acid treatment. Moreover, treatment at a low fluorination temperature of 180 °C for 4 h and acid washing endowed the obtained fluorinated carbon (HFG@ZIF-8) with a high F/C (1.62), favorable specific surface area (207 m² g⁻¹), unique porous channels, and highly electrochemically active C–F bonds, resulting in a maximum specific capacity (1143.4 mAh g⁻¹) and energy density (2614.8 Wh kg⁻¹) at 0.02 C. The superior Li⁺ transport efficiency, with diffusion coefficients ranging from 1.47 × 10⁻¹¹ to 1.93 × 10⁻¹⁷ cm² s⁻¹, enables HFG@ZIF-8 to deliver 453.4 mAh g⁻¹ at 5 C with no voltage delay. Therefore, this work provides an innovative strategy for the preparation of high-performance CF_x cathodes. Full article

The fabrication of semiconductor devices with three-dimensional architectures imposes unprecedented demands on advanced plasma dry etching processes. These include the simultaneous requirements of high throughput, high material selectivity, and precise profile control. In conventional reactive ion etching (RIE), fluorocarbon plasma provides both accelerated ion species and reactive neutrals that etch the feature front, while the CF_x radicals promote polymerization that protects sidewalls and enhance selectivity to the amorphous carbon layer (ACL) mask. In this work, we present computational results on the role of CF₄ addition to hydrogen fluoride (HF) plasma for next-generation RIE, specifically cryogenic etching. Simulations were performed by varying the CF₄ concentration in the HF plasma to evaluate its influence on ion densities, neutral species concentration, and electron density. The results show that the densities of CF_x (x = 1–3) ions and radicals increase significantly with CF₄ addition (up to 20%), while the overall plasma density and the excited HF species remain nearly unchanged. The results of plasma density and atomic fluorine density are consistent with the experimental observations of the HF/CF₄ plasma using an absorption probe and the actimetry method. It was verified that the gas-phase reaction model proposed in this study can accurately reproduce the plasma characteristics of the HF/CF₄ system. The coupling of HF-based etchants with CF_x radicals enables polymerization that preserves SiO₂ etching throughput while significantly enhancing etch selectivity against the ACL mask from 1.86 to 5.07, with only a small fraction (~10%) of fluorocarbon gas added. The plasma simulation provides new insights into enhancing the etching performance of HF-based cryogenic plasma etching by controlling the CF₂ radicals and HF reactants through the addition of fluorocarbon gases. Full article

This review compiles data from 77 articles on the tribological properties of fluorinated carbons CFx. Covalent grafting of fluorine atoms improves the tribological properties. The C-F bonding plays a key role in reducing friction. The tribological stability of CFx, along with their ability to form protective films from the very first cycles, provides a significant advantage in reducing wear and extending the lifespan of mechanical components. The role of the presence of fluorine atoms, their content, their distribution in the carbon lattice, and the C-F bonding, as well as the dimensionality and the size of the materials, are discussed. Some ways of improving lubrication performance and investigating friction-reducing properties and mechanisms are proposed. Full article

Fluorinated carbon cathode materials have extremely high theoretical specific energy among known cathode materials of lithium primary batteries. Nevertheless, current fluorinated carbon cannot meet the performance demands of future applications due to the rate performance. This work innovatively applies hollow carbon spheres with a porous structure as carbon sources to prepare fluorinated hollow porous carbon spheres (FHPCS) with high energy density and power density. The porous structure provides more reaction sites for the fluorination process and also shortens the diffusion path of lithium ions during the discharge. Additionally, the hollow porous structure offers more interfacial contact areas and reduces volumetric expansion during discharge reactions. The Li/CF_x primary battery has a maximum specific energy of 2007 Wh kg⁻¹ and a maximum power density of 30,400 W kg⁻¹ and can have a capacity retention rate of 80.8% at a current density of 16 A g⁻¹. In addition, FHPCS also has the highest specific energy of 1999 Wh kg⁻¹ and 1711 Wh kg⁻¹ in Na/CF_x and K/CF_x primary batteries, respectively. The diffusion efficiency of an alkali metal ion is analyzed by the different discharge depths with electrochemical impedance spectroscopy and galvanostatic intermittent titration technique. This effort introduces a new high-performance fluorinated carbon featuring a hollow porous structure and puts forward an innovative approach to designing fluorinated carbon materials. Full article

Sub-fluorinated carbon nanofibers (F-CNFs) can be described as a non-fluorinated core surrounded by a fluorocarbon lattice. The core ensures the electron flux in the cathode during the electrochemical discharge in the primary lithium battery, which allows a high-power density to be reached. The ball-milling in an inert gas (Ar) of these F-CNFs adds a second level of conductive sp² carbons, i.e., a dual sub-fluorination. The opening of the structure changes, from one initially similar multi-walled carbon nanotube to small lamellar nanoparticles after milling. The power densities are improved by the dual sub-fluorination, with values of 9693 W/kg (3192 W/kg for the starting material). Moreover, the over-potential of low depth of discharge, which is typical of covalent CFx, is suppressed thanks to the ball-milling. The energy density is still high during the ball-milling, i.e., 2011 and 2006 Wh/kg for raw and milled F-CNF, respectively. Full article

Lithium/carbon fluoride (Li/CF_x) batteries have been widely researched due to their high theoretical specific energy. To create a high-performance electrode, the fluorinated hard carbon (FHC) is prepared by direct gas-phase fluorination. It has a high F/C ratio of 0.95 based on the gravimetric method. Selecting hard carbon (HC) with a high surface area as the carbon source allows for FHC to achieve suitable interlayer spacing and specific surface area, as well as abundant pore structures to facilitate rapid lithium ion transportation. Additionally, a composite of graphene and carbon nanotubes (CNTs) is coated on the surface of FHC, enhancing electron transport speed. The resulting FHC&C exhibits a very high energy density of 1256 Wh kg⁻¹ and an excellent power density of 72,929 W kg⁻¹ at a high rate of 40 C. Moreover, compared to commercial CF_x, FHC&C exhibits higher energy and power densities, thus presenting a promising practical application prospect. Full article

TaN thin-film coatings are well known for their good mechanical properties, acceptable toughness, as well as good biocompatibility. However, the friction coefficient of these films is sometimes too high, or the hemocompatibility is poor. The purpose of this study is to reduce the friction coefficient and increase the hydrophobicity of TaN coatings by introducing carbon and fluorine into the coatings. This study has never been conducted by other researchers. Fluorine-containing tantalum carbonitride (i.e., F–TaC_xN_y) top layers were deposited on TaN/Ta interlayers by reactive sputtering with fixed nitrogen and various hexafluoroethane (C₂F₆) mass flow rates. During the deposition process, C₂F₆ gas with various mass flow rates was added. After deposition, these F–TaC_xN_y multi-layered films were then characterized using XRD, XPS, FTIR, FESEM, WDS, a nano-indenter, a water contact-angle measurement system, and a tribometer. The tribological tests were carried out in the environment with and without humidity. The surface energies of the films were examined with water contact-angle variation. According to structural analysis, TaN phase would transform to TaC_xN_y with the increase in the C₂F₆ mass flow rate, which would result in a decrease in the friction coefficient and an increase in hydrophobicity. The films’ hardness (H, increased at most by 20%), elastic modulus (E), and H/E ratio first increased then decreased, most likely due to the increase in relatively soft C–F bonding. According to the results obtained from tribotesting, it was found that an increase in carbon and fluorine contents in the films reduces the friction by more than 30%, and wear rate by more than 50%. More importantly, the effects of moisture on the friction coefficient can be minimized to almost nothing. In a water contact-angle study, the contact angle increased from 60° to 85° with the increase in C₂F₆ mass flow rates. This evidence illustrated that hemocompatibility of the TaN thin film can be significantly enhanced through the formation of Ta–C and C–F_x bonding. The chemical composition and bonding status of these films, especially the existence of C–F_x bonds, were studied by FTIR and XPS. In sum, with the increased C₂F₆ mass flow rate, the carbon and fluorine contents in the films increased, while the nitrogen content decreased. The structure, bonding status, and compositions varied accordingly. The tribological behaviors were significantly improved. Furthermore, by carrying out tribotesting in humid air and a dry argon environment, it was confirmed that the greater the fluorine content, the less sensitive the films would be to environment change. This is attributable to the induced lower surface energy and reduced adsorption to water vapor due to the increase in C–F_x bonds. The successfully fabricated and studied F–TaC_xN_y films could be applied in many areas such as artificial blood vessels, or precision components in an atmospheric or vacuum environment. Full article

Fluorinated graphitic layers with good mechanical and chemical stability, polar C–F bonds, and tunable bandgap are attractive for a variety of applications. In this work, we investigated the photolysis of fluorinated graphites with interlayer embedded acetonitrile, which is the simplest representative of the acetonitrile-containing photosensitizing family. The samples were continuously illuminated in situ with high-brightness non-monochromatized synchrotron radiation. Changes in the compositions of the samples were monitored using X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NEXAFS N K-edge spectra showed that acetonitrile dissociates to form HCN and N₂ molecules after exposure to the white beam for 2 s, and the latter molecules completely disappear after exposure for 200 s. The original composition of fluorinated matrices CF_0.3 and CF_0.5 is changed to CF_0.10 and GF_0.17, respectively. The highly fluorinated layers lose fluorine atoms together with carbon neighbors, creating atomic vacancies. The edges of vacancies are terminated with the nitrogen atoms and form pyridinic and pyrrolic units. Our in situ studies show that the photolysis products of acetonitrile depend on the photon irradiation duration and composition of the initial CF_x matrix. The obtained results evaluate the radiation damage of the acetonitrile-intercalated fluorinated graphites and the opportunities to synthesize nitrogen-doped graphene materials. Full article