Fluorination Of Surfaces Research Articles

Preparation of multifunctional ceramic foams for sound absorption, waterproofing, and antibacterial applications.

Using porous materials for sound absorption is an effective approach to alleviating noise pollution, although their hydrophilic properties potentially cause concerns regarding public safety and health risks. This work provides a facile strategy for establishing a multifunctional ceramic system by using sponges as the sintering template, adjusting the pore structure of ceramic foams by varying the ceramic slurry weights and fluorinating the sintered ceramic foams via hydrolysis and condensation processes to provide low surface energy. The obtained porous ceramic foams demonstrate sound-absorbing, waterproof, and antibacterial properties. The results reveal that the increase in ceramic slurry weight decreases the pore size and porosity due to the formation of more compact structures, and the decrease in porosity compromises the sound absorption performance. In the middle-range sound frequency, the maximum sound absorption coefficient reached 0.92. In addition, the fluorination of the rough ceramic surfaces endows the ceramic foams with waterproof properties, which enables them to float on water and display the silver mirror phenomenon. In addition, due to the waterproof property reducing the contact area between the ceramic surface and the bacterial suspension, as well as the lipophilic fluorine chain disrupting the bacterial structures, these ceramic foams exhibited antibacterial rates above 95%. In addition, the mechanisms underlying the sound-absorbing, waterproof, and antibacterial properties of these porous ceramic foams are elucidated. Therefore, this work provides a facile approach to developing a multifunctional ceramic system. Their practical features make these ceramic foams more significant in the field of noise reduction.

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.

Selective Fluorination of the Surface of Polymeric Materials after Stereolithography 3D Printing.

With the microfluidics community embracing 3D resin printing as a rapid fabrication method, controlling surface chemistry has emerged as a new challenge. Fluorination of 3D-printed surfaces is highly desirable in many applications due to chemical inertness, low friction coefficients, antifouling properties, and the potential for selective hydrophobic patterning. Despite sporadic reports, silanization methods have not been optimized for covalent bonding with polymeric resins. As a case study, we tested the silanization of a commercially available (meth)acrylate-based resin (BV-007A) with a fluoroalkyl trichlorosilane. Interestingly, plasma oxidation was unnecessary for silanization of this resin and indeed was ineffective. Solvent-based deposition in a fluorinated oil (FC-40) generated significantly higher contact angles than deposition in ethanol or gas-phase deposition, yielding hydrophobic surfaces with contact angle >110° under optimized conditions. Attenuated total reflectance-Fourier transform infrared spectroscopy indicated that the increase in the contact angle correlated with consumption of a carbonyl moiety, suggesting covalent bonding of silane without plasma oxidation. Consistent with a covalent bond, silanization was resistant to mechanical damage and hydrolysis in methanol and was stable over long-term storage. When tested on a suite of photocrosslinkable resins, this silanization protocol generated highly hydrophobic surfaces (contact angle > 110°) on three resins and moderate hydrophobicity (90-100°) on the remainder. Selective patterning of hydrophobic regions in an open 3D-printed microchannel was possible in combination with simple masking techniques. Thus, this facile fluorination strategy is expected to be applicable for resin-printed materials in a variety of contexts including micropatterning and multiphase microfluidics.

Sustainable approach for the development of durable superhydrophobic metallic surfaces

In the present work, we devised a facile, and environmental imprinting and hot-water treatments for developing a durable self-cleaning aluminum surface. The micro and nanostructured surfaces were composed of pillars and ellipsoidal flakes, respectively. The fluorination (vapor deposition) of surfaces imparted superhydrophobicity (θs > 150°), with high adhesion observed for micro-patterned surface, while nano and hierarchical surfaces exhibited low hysteresis and tilting angles (θ < 5°). The nanostructured (ΔE=-0.3J/m) surface has shown the prevalence of stable Cassie state compared to hierarchical (ΔE=-0.07J/m) counterpart. The nanostructured surface has also exhibited higher durability under static and dynamic conditions than the hierarchical counterpart.

Advanced Na[Ni0.25Fe0.5Mn0.25]O2/C Cathode / EMS Electrolyte / Fe3O4 Anode for Sodium-Ion Batteries

Lithium is an attractive battery material because it is the lightest metal, but its resources are concentrated in large quantities mainly in South America with an associated risk of dependence on a single geographic area.1 In addition, the price of lithium-ion batteries is affected by the high cost of their active materials, commonly based on cobalt compounds. As a result, there is an increasing interest worldwide in developing low cost and sustainable energy storage systems that do not use lithium or cobalt. Among them, rechargeable sodium batteries, due to the almost infinite supply of the metal, are the most appealing as immediate alternatives to lithium batteries. Recently reported results2-4 have triggered an increasing industrial and academic interest in sodium-ion batteries operating at room temperature. Pioneering work by Hagenmuller et al. and Yamamoto et al. introduced O3-type NaMO2 (M = Ni, Co, and Fe) in which Na+ could be inserted into a host structure. Since then, interest in developing sodium batteries declined because of the fast development and market domination of lithium-ion batteries. However, recent increasing demands for low-cost energy storage have renewed interest in sodium-based batteries and, accordingly, the O3 type NaMO2 compounds are being revisited as a cathode material due to the facile synthesis and structural stability, including Na-Ni0.5Mn0.5O2, NaCoO2, NaCrO2, NaMnxM1 − xO2 (M =Co, Ni), Na[Ni1/3Fe1/3O1/3]O2, and NaxVO2. At present, the electrochemical performance of these cathode materials has been limited due to the lack of electrolytes capable of withstanding voltages above 3.9 V versus Na/Na+. In response, we have developed a sodium-ion battery that has an electrolyte of NaClO4 in a mixture of ethyl methanesulfonate electrolyte (EMS) and fluoroethylene carbonate (FEC) additive for increasing the stability and conductivity, along with an anode of carbon-coated Fe3O4 and a cathode of O3-type layered Na[Ni0.25Fe0.5Mn0.25]O2. The electrolyte is a key component if sodium-ion batteries are to become competitive with or surpass lithium-ion batteries. The main requirement is a wide anodic stability window in order to allow complete desodiation of the cathode. A common choice has been 1 M sodium perchlorate in propylene carbonate (NaClO4−PC) with selected additives. For instance, as suggested by Komaba et al., the addition of a small amount of FEC to the PC-based solvent contributes to improved cycleability of sodium batteries, possibly because of a positive effect induced by the fluorination of the anode surfaces. (1) Scrosati, B.; Garche, J. J. Power Sources 2010, 195, 2419−2430. (2) Fouassier, C.; Matejka, G.; Reau, J.-M.; Hagenmuller, P. J. Solid State Chem. 1973, 6, 532−537. (3) Delmas, C.; Fouassier, C.; Hagenmuller, P. Physica B+C 1980, 99,81−85. (4) Braconnier, J.-J.; Delmas, C.; Fouassier, C.; Hagenmuller, P. Mater. Res. Bull. 1980, 15, 1797−1804.

Surface fluorination of polystyrene particles via CF4 plasma irradiation using a barrel-plasma-treatment system

In this study, polystyrene powder was subjected to CF4 plasma-treatment using a polygonal barrel-plasma-treatment system to enhance the hydrophobicity of the particles. The characterization of the treated samples showed that the orange-peel-like surface of the particles was changed into rugged structures by the CF4 plasma-treatment. The plasma-treatment using our system also resulted in the fluorination of the particle surfaces. The contact angle of a water droplet loaded on the sample treated at a radio frequency (RF) power of 150W for 10min (149.1°) was significantly larger than that on the untreated sample (123.6°): both the contact angle value and the fluorine content of sample depended on the RF power. These results indicate that the hydrophobicity of the polystyrene powder was improved by our system, allowing preparation of stable liquid marbles, including CuCl2 solutions, which can be used as NH3 gas sensors.

VUV Enhanced XeF2 Fluorination of Polymer Surfaces

Exposure of polyethylene and polystyrene to xenon difluoride (XeF2) in the presence of vacuum ultraviolet (VUV) irradiation emitted from O2,N2, Ar, Kr and Xe electrical discharges gives rise to surface fluorination. The extent of reaction is found to be governed by the synergistic effect between the VUV absorption characteristics of the XeF2 feed gas and the polymer substrate. Polystyrene in combination with krypton electrical discharge emission lines yields the most fluorinated surface.

Xenon difluoride plasma fluorination of polymer surfaces

Xenon difluoride (XeF 2) plasma treatment of a series of polymers containing different repeat units gives rise to varying levels of surface fluorination. Alkene and aromatic C–H bonds appear to be more susceptible towards reaction compared to their sp 3 counterparts. The extent of fluorine incorporation can be accounted for in terms of a structure–behaviour relationship derived from extended Huckel molecular orbital calculations. Comparison with CF 4 plasma modification shows that XeF 2 electrical discharges are more effective at fluorinating polymer surfaces.

Cold plasma treatment on starch foam reinforced with wood fiber for its surface hydrophobicity

Tray samples of starch foam reinforced with aspen wood fiber were produced using a lab model-baking machine. Surfaces of the trays were treated with CF4 and SF6 plasma to get hydrophobic properties on surfaces. Fluorine compounds were found in XPS analysis of plasma treated samples. Due to the hydrophobic fluorine-rich surface, the contact angle was increased up to 150° with distilled water. RF power and gas pressure were varied to evaluate the effects of each parameter on fluorination of surfaces. The fluorine concentrations of treated sample surfaces were ranged from 46.8% to 60.2%. CF4 treatment showed higher concentration of fluorine on surfaces than SF6 treatment did. Water liquid and vapor uptake tests showed that the fluorine-rich surfaces restricted the permeability of water into the inner-layer of the treated samples.

Halogenation of detonation-synthesised nanodiamond surfaces

Comparative chlorination and fluorination of detonation-synthesised nanodiamond surfaces was carried out by various methods and the hydrolytic stability of the halogenated surfaces was studied.

Fluorination mechanisms of Al2O3 and Y2O3 surfaces irradiated by high-density CF4∕O2 and SF6∕O2 plasmas

Fluorination of Al2O3 and Y2O3 surfaces was investigated by irradiating high-density, helicon-wave CF4∕O2 and SF6∕O2 plasmas. The Al2O3 surface bombarded by high-flux positive ions of the CF4∕O2 plasma was fluorinated significantly. On contrast, Y2O3 was less fluorinated than Al2O3 when they were irradiated by the same CF4∕O2 plasma. The analysis of the Al2O3 surface irradiated by the CF4∕O2 plasma suggests that the fluorination is triggered by reactions between fluorocarbon deposit and Al–O bonding with the assistance of ion bombardment. On the other hand, irradiation of the SF6∕O2 plasma induced less significant fluorination on the Al2O3 surface. This suggests a lower reaction probability between sulfur fluoride deposit and Al–O bonding. The difference in the fluorination of the Al2O3 and Y2O3 surfaces induced by the irradiations of the CF4∕O2 and SF6∕O2 plasmas is understood by comparing the bonding energies of C–O, S–O, Al–O, and Y–O.

Plasma fluorination of diamond-like carbon surfaces: mechanism and application tonanoimprint lithography

Diamond-like carbon (DLC) films, used as molds for nanoimprint lithography, weretreated with a fluorocarbon-based plasma in order to enhance their anti-adhesionproperties. While ellipsometry and atomic force microscope measurementsshowed negligible changes in thickness and surface roughness after plasmaprocessing, contact angle measurement found fluorine plasma-treated DLCsurfaces to be highly hydrophobic, with surface energy values reduced from∼45 mJ m−2 for untreatedfilms to ∼20–30 mJ m−2 after fluorination. X-ray photoelectron spectroscopy revealed a thin (from∼0.5 to∼3 nm) fluorocarbon layer on the DLC surface. Proposed mechanisms for the formation ofthis layer include two competing processes: etching of DLC and deposition offluorocarbon material, with one or the other mechanism dominant, depending on theplasma conditions. Fluorocarbon plasma-treated DLC molds for nanoimprintlithography were used to pattern sub-20 nm size features with a high degree ofrepeatability, demonstrating an extended lifetime of the anti-adhesion coating.

Fluorocarbon Barriers on Starch Foam Tray Surfaces Through SF6 Cold Plasma Treatment

Starch foam trays were produced using a laboratory model-baking machine. Surfaces of the trays were treated with SF6 plasma to create fluorine-rich layers on the surfaces. RF power, gas pressure and reaction time were varied to evaluate the effects of each parameter on fluorination of surfaces. The fluorine concentrations of treated sample surfaces ranged from 43.6% to 57.9%. For reaction time dependence, the ratio of oxygen to carbon was decreased since hydroxyl groups might be replaced by fluoro-compounds. Gas pressure and RF power affected fluorination mechanism, which resulted in different shapes of carbon and fluorine ESCA high resolution spectra. Plasma-treated samples have higher contact angles and less uptakes of liquid and vapor water. AFM showed different morphology of untreated and SF6 plasma-treated surfaces.

Influence of reaction with XeF2 on surface adhesion of Al and Al2O3 surfaces

The change in surface adhesion after fluorination of Al and Al2O3 surfaces using XeF2 was investigated with atomic force microscopy. The chemical interaction between XeF2 and Al and Al2O3 surfaces was studied by in situ x-ray photoelectron spectroscopy. Fresh Al and Al2O3 surfaces were obtained by etching top silicon layers of Si∕Al and Si∕Al2O3 with XeF2. The surface adhesion and chemical composition were measured after the exposure to air or annealing (at 200°C under vacuum). The correlation between the adhesion force increase and presence of AlF3 on the surface was revealed.

Fluorination of mammalian cell surfaces via the sialic acid biosynthetic pathway

Metabolic oligosaccharide engineering has been employed to introduce fluorine-containing groups onto mammalian cell surfaces. Incubation of HeLa, Jurkat, and HL60 cells in culture with fluorinated sialic acid and mannosamine analogues resulted in cell-surface presentation of fluorinated glycans. Metabolic conversion of fluorinated precursors was detected and quantified by DMB-derivatization and HPLC ESI-MS analysis. Between 7% and 72% of total membrane-associated sialosides were fluorinated, depending on the precursor used and the cell type. Fluorination of mammalian cell surfaces provides a means for introducing a bioorthogonal surface for modulating noncovalent interactions such as those involved in cell adhesion.

Fluorination of polymethylmethaacrylate with tetrafluoroethane using DC glow discharge plasma

Fluorination of polymer surfaces has technological applications in various fields such as microelectronics, biomaterials, textile, packing, etc. In this study PMMA surfaces were fluorinated using DC glow discharge plasma. Tetrafluoroethane was used as the fluorinating agent. On the fluorinated PMMA surface, static water contact angle, surface energy, optical transmittance (UV–vis), XPS and AFM analyses were carried out. After the fluorination PMMA surface becomes hydrophobic with water contact angle of 107° without losing optical transparency. Surface energy of fluorine plasma-treated PMMA decreased from 35 mJ/cm 2 to 21.2 mJ/cm 2. RMS roughness of the fluorinated surface was 4.01 nm and XPS studies revealed the formation of C–CF x and CF 3 groups on the PMMA surface.

Effect of a low-pressure plasma treatment on water vapor diffusivity and permeability of poly(ethylene-co-vinyl alcohol) and polyethylene films

Poly(ethylene-co-vinyl alcohol) and polyethylene films have been modified by CF 4 microwave plasma. The influence of vinyl alcohol comonomer contents on the properties of these materials under CF 4 microwave plasma has been studied by means of surface energies, atomic force microscopy (AFM), SIMS and calorimetric measurements (DSC). The CF 4 plasma treatment improved the hydrophobicity and the roughness of the film surfaces while the bulk phase in the films were hardly changed. Pervaporation measurements were carried out to characterize the effects of these plasma treatments on water vapor transport through the films. Fluorination of the film surfaces, obtained by the CF 4 plasma treatment allows reducing water permeability of the films. The barrier effect to water in plasma treated layers of EVOH was improved significantly, especially with the sample containing 71 mol% of vinyl alcohol comonomer unit and for which an increase of crystallinity was observed. Such a surface modification with fluorinated groups leads to decrease in the water uptake at the film surface at the feed side so that the plasticization effect of the hydrophobic films by the sorbed water molecules was decreased during the water vapor permeation.

Fluorination of epoxy surfaces by a physical method

To enhance the surface hydrophobicity of epoxy polymers, a simple physical method for the simultaneous surface fluorination during curing of epoxy resins was proposed and evaluated. Curing of epoxy resins against a polytetrafluoroethylene (PTFE) mold gave rise to fluorinated epoxy polymer surfaces due to the anchorage of PTFE molecules on the epoxy polymer surface. The modified epoxy surfaces were characterized using contact-angle measurements and X-ray photoelectron spectroscopy (XPS). The fluorinated epoxy resin surfaces are highly hydrophobic, exhibiting contact angles of similar magnitude to that of the pristine PTFE film surface. The PTFE mold can be used repeatedly to give fluorinated epoxy surfaces with large contact angles. Aging and solvent extraction tests indicated that the fluorinated epoxy surfaces were very stable. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 296–304, 2000

Plasma surface treatment of poly(acrylonitrile) films by fluorocarbon compounds

This paper concerns the use of the low-pressure plasma process to confer an hydrophobic character to poly(acrylonitrile) films, without altering their bulk properties. Plasma based fluorination processes using saturated fluorine compounds such as CF 4, C 6F 14 and mixtures CF 4/H 2 were used. Such treated polyacrylonitrile films were characterized by XPS analysis, infrared (ATR) spectroscopy and contact angle measurements. The use of CF 4 led to the fluorination of the film surfaces. Indeed, XPS spectra showed the presence of -CHF-, -CF 2- and -CF 3 groups. Moreover, the contact angle θ which was 63° for untreated PAN films increased to 115°. Fluorine incorporation in the PAN disappeared when hydrogen is added to CF 4. In the case of treatment by C 6F 14, fluorination was accompanied by a polymerization, as evidenced by XPS with the disappearance of the N 1s photopeak corresponding to the C≡N functions in PAN. By considering the deposition of F- containing layer thickness, it was possible in this latter case to follow the surface modifications by ATR-i.r. spectroscopy.

Fluorination of diamond — C 4F 9I and CF 3I photochemistry on diamond (100)

The radiation-induced decomposition of C 4F 9I and CF 3I overlayers at 119 K on diamond (100) surfaces has been shown to be an efficient route to fluorination of the diamond surface. X-ray photoelectron spectroscopy has been used for photoactivation as well as for studying the photodecomposition of the fluoroalkyl iodide molecules, the attachment of the photofragments to the diamond surface, and the thermal decomposition of the fluoroalkyl ligands. Measured chemical shifts agree well with ab initio calculations of both C 1s and F 1s binding energies. It is found that chemisorbed CF 3 groups on diamond (100) decompose by 300 K whereas C 4F 9 groups decompose over the range 300 to ∼ 700 K and this reactivity difference is rationalized on steric grounds. Both of these thermal decomposition processes produce surface CF bonds on the diamond. The surface CF species thermally decompose over a wide temperature range extending up to 1500 K. Hydrogen passivation of the diamond surface is ineffective in preventing free radical attack from the photodissociated products of the fluoroalkyl iodides; I atoms produced photolytically abstract H from surface CH bonds to yield hydrogen iodide at 119 K allowing diamond fluorination. The attachment of chemisorbed F species to the diamond (100) surface causes band bending as the surface states are occupied as a result of chemisorption. This results in a shift to higher binding energy of the diamond-related C 1s levels present in the surface and subsurface regions which are sampled by XPS on the diamond. The use of photoactivation of fluoroalkyl iodides for the fluorination of diamond surfaces provides a convenient route compared to other methods involving the action of atomic F, molecular F 2, XeF 2 and F-containing plasmas.