Fluorination Treatment Research Articles

Multifunctional Textiles Based on Three-Dimensional Hierarchically Structured TiO2 Nanowires.

The development of three-dimensional (3D) micro-/nanostructures with multiscale hierarchy offers new potential for the improvement of the pristine textile properties. In this work, a polyester fabric coated with 3D hierarchically structured rutile TiO2 nanowires (THNWP) was fabricated by a facile hydrothermal strategy. The THNWP samples exhibit markedly improved photocatalytic activities and antibacterial properties owing to their 3D hierarchical architecture constructed by one-dimensional nanowire structures, good crystallinity, excellent light-harvesting capability, and fast electron-transfer rate. Furthermore, the unique 3D hierarchical nanostructures also combine with the monofilament to produce ternary-scale hierarchy, which endows the fabric surface with outstanding superamphiphobicity after further facile fluorination treatment. The supportive air-pockets trapped within the unique ternary-scale architectures are proved to be the crucial factor in the achievement of high liquid repellency, and the highest performing superamphiphobic surface is capable of repelling liquids down to a minimal surface tension of 23.4 mN m-1. We envision that our findings may possess great potential in the bottom-up design of high-performance textiles.

P‐18: Student Poster: Non‐Oxidizing Pre‐Annealing for Enhanced Fluorination of an Indium‐Gallium‐Zinc Oxide Thin‐Film Transistor

Different processes have been investigated for the fluorination of amorphous indium‐gallium‐zinc oxide (IGZO) thin‐film transistors (TFTs) and the reliability of the resulting TFTs subjected to a positive gate‐bias thermal stress has been compared. It is shown that the negative shift of the turn‐on voltage of a TFT improved with an increase in the fluorination time. Such improvement correlates well with the annihilation of oxygen‐related defects in the fluorinated channels. However, further extension of the fluorination time has been found to lead to degradation of some device characteristics. An alternative process has been proposed, involving the addition of a non‐oxidizing anneal before the fluorination treatment. More positive shift of the turn‐on voltage and improvement in reliability have been obtained, without the TFT suffering from degradation in other device characteristics.

A fluorinated polymer sponge with superhydrophobicity for high-performance biomechanical energy harvesting

Human body contains various biomechanical energy, which emerges as a pervasive and sustainable energy resource for wearable electronics in the era of Internet of Things. We have developed a fluorinated polymer sponge based triboelectric nanogenerator (FPS-TENG) that provides stable electrical output over a wide range of ambient humidity. The humidity resistance due to excellent hydrophobic property of the fluorinated polymer sponge can overcome the adverse effects of moisture. The FPS-TENG also exhibits high durability even after enduring heavy abrasion. The output voltage of the FPS-TENG is three times higher than that of the pristine polymer film (PPF) based TENG. When assembled with hydrophobic copper (HC) contact electrodes, the FPS-TENG retains almost 90% electrical output over 20–85% relative humidity. Moreover, super durability is achieved by quasi-bulk-phase functionalization. After 1 mm-thickness abrasion of the fluorinated polymer sponge, the output voltage is degraded by only 10%. Under the optimal operating conditions, the FPS-TENG delivers a maximum power density of 0.89 W m −2 at a load resistance of 10 MΩ. The fluorination enhanced triboelectrification and the surface superhydrophobicity induced humidity-stability make the FPS-TENG a sustainable power source for the wearable bioelectronics in the era of Internet of Things. • Moisture-resistant triboelectric nanogenerator was developed. • Fluorination treatment effectively improves hydrophobicity. • Quasi-bulk-phase functionalization enables super durability. • Parametric experimental results yield optimal material design.

Topographical selective deposition: A comparison between plasma-enhanced atomic layer deposition/sputtering and plasma-enhanced atomic layer deposition/quasi-atomic layer etching approaches

In this work, we focus on the development of topographically selective deposition (TSD) leading to local deposition on the vertical sidewalls of 3D structures. A proof of concept is provided for the TSD of Ta2O5. The TSD process relies on plasma-enhanced atomic layer deposition (PEALD) alternating with quasi-atomic layer etching (ALE). Quasi-ALE involves a fluorination treatment followed by a directional Ar+ sputtering step. We show that the fluorination treatment allows a significant decrease in the incident kinetic energy of the subsequent directional Ar+ sputtering step. Conversely, when no fluorination step is carried out, TSD requires high incident kinetic energies during the directional Ar+ sputtering step, which, in turn, leads to detrimental plasma-induced damage on horizontal surfaces, such as roughness, also promoting by-product redeposition. The benefits and shortcomings of these two TSD approaches—PEALD/quasi-ALE and PEALD/energetic Ar+ sputtering—are compared in light of potential bottom-up technological developments.

RETRACTED: Fabrication of a superhydrophobic surface on Al alloy 5052 via combined anodic oxidation and fluorination treatment

AbstractIn this study, a superhydrophobic surface was successfully prepared on Al alloy 5052 using a simple anodic oxidation method followed by fluorination treatment. This study demonstrates the construction of rough structure of Al oxide by an anodic oxidation reaction, which improves the superhydrophobicity of the alloy. The top, tilt, and cross‐views of the samples were characterized by field‐emission scanning electron microscopy and focused ion beam. The chemical composition of the samples was analyzed by energy‐dispersive X‐ray spectroscopy and Fourier‐transform infrared spectroscopy. The structure of the surface was effectively modified as the anodization time increased. The optimum anodic oxidation reaction was carried out for 4 min in a 0.2‐M H3PO4 aqueous electrolyte at 50°C under a constant voltage of 120 V to create a pore‐and‐dendrite hybrid nanostructure. The water contact angle values were maximized in the hybrid nanostructure because their solid fraction area was smaller than that in the porous structure. Corrosion measurements proved that the superhydrophobic surface can significantly inhibit the corrosion of the substrate alloy with an inhibition efficiency of 99.99%. In addition, the prepared superhydrophobic sample exhibited good self‐cleaning properties.

Degradation Characteristics of Electrospun Gas Diffusion Layers with Custom Pore Structures for Polymer Electrolyte Membrane Fuel Cells.

Electrospinning has been demonstrated to be a versatile technique for producing hydrophobic gas diffusion layers (GDLs) with customized pore structures for the enhanced performance of polymer electrolyte membrane (PEM) fuel cells. However, the degradation characteristics of custom hydrophobic electrospun GDLs (eGDLs) have not yet been explored. Here, for the first time, we investigate the degradation characteristics of custom hydrophobic eGDLs via an ex situ accelerated degradation protocol using H2O2. The surface contact angle of degraded eGDLs (44 ± 12°) was lower than that of pristine eGDLs (137 ± 6°). The loss of hydrophobicity was attributed to the degradation (via hydrolysis) of the fluorinated monolayers (formed via a direct fluorination treatment) on the electrospun carbon fiber surfaces as evidenced by the reduction in surface fluorine content. Degradation of the surface monolayers affected fuel cell performance under multiple operating conditions. At 100% relative humidity (RH), the loss of monolayers led to higher liquid water content and lower cell voltages compared to the pristine eGDL. At 50% RH, the degraded eGDL led to lower cell voltages due to the lower electrical conductivity of the degraded materials. The lower electrical conductivity was attributed to the oxidation of carbon fibers upon loss of the monolayers. Our results indicate the importance of designing robust hydrophobic surface treatments for the advancement of customized GDLs for effective long-term fuel cell operation.

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.

Lubricant-infused titania surfaces with high underwater transparency for antifouling applications: A combined experimental and molecular dynamics study

Marine optical instruments are usually blinded by biofouling. Biomimetic slippery lubricant-infused surfaces have been used for antifouling applications. Herein, lubricant-infused titania surfaces on glass substrates were fabricated, involving the formation of nanostructured surfaces via a sol–gel process of alkoxide, followed by fluorination treatment and then lubricant infusion. Molecular dynamics (MD) simulations directly suggested the adsorption behavior of fluorinate molecules on titania surfaces and the interaction between the fluorinated surface and lubricant molecules. The MD simulation results also illustrated the different interactions between as-prepared surfaces and water molecules, indicating the formation of stable lubricant-infused surfaces. The lubricant-infused surfaces showed a high transparency up to 87% throughout the visible-light region, and exhibited excellent antifouling performance by declining adhesion by 94% Phaeodactylum tricornutum. The results would show great potential of lubricant-infused surfaces for antifouling applications of marine optical instruments with high transparency.

Fluorinated SnO2/ER as an antistatic coating for enhancing the surface insulating strength of epoxy insulators

AbstractThe surface coating of epoxy resin has been widely used in the composite materials with micron scale fillers, but the related research on the composite coating filled with nanoparticles is still rare. SnO2 is a common antistatic additive in composite materials, and it is also a semiconductor material, capable of uniform voltage. In this paper, nano‐SnO2 powder was considered as the filler of coating materials. By analyzing the microscopic test results, the flashover voltage, surface charge dissipation, and surface conductivity of the coating sample, the effects of coating treatment and nano‐SnO2 fluorination on the surface insulation properties of epoxy insulators were studied. It is found that the flashover voltage and surface charge dissipation rate of the coating sample can be improved by both coating treatment and fluorination treatment, thus improving the surface insulation performance of epoxy insulators. The modification process and test results have guiding significance for improving the surface insulation performance of epoxy insulators.

A Simple Way to Achieve Self-Cleaning Surfaces with Unique Antifouling Property

Self-cleaning surfaces may have wide applications such as microfluidic devices, lab-on-a-chip, sensors, microreactors, air purification, and antimicrobial fields. In this article, by using a combination of femtosecond (fs) laser irradiation and fluorination technique, self-cleaning stainless steel surfaces with unique antifouling property were obtained. New insight is developed through a detailed analysis of the antifouling behavior of the self-cleaning surfaces. The surface free energy and its polar and disperse components were calculated by using the Owens–Wendt-–Rabel–Kaelble (OWRK) method. X-ray photoelectron spectroscopy was employed to analyse the surface elemental compositions and functional groups. The antifouling property of the surface was recorded by using a high speed camera. Water sliding angles (SAs) were reduced by fluorination treatment, resulting in low adhesive superhydrophobic surfaces with the self-cleaning property. The influences of micro/nanostructures, fluorination, and their combination on the surface free energy were investigated. The interaction process between water droplets and pollutants (inorganic and organic particles) on the treated surface was explored. The antifouling property of an optimized specimen (CA = 162° and SA = 1°) was tested and compared with the untreated sample.

New inorganic coating-based triboelectric nanogenerators with anti-wear and self-healing properties for efficient wave energy harvesting

As a new approach of collecting friction energy, triboelectric nanogenerators (TENGs) have shown promising applications in many fields. However, the most TENGs based on organic polymer materials often suffer from durability problems of aging, wear, and low output performance. Here, a novel inorganic coating TENG based on normal microarc oxidation coating (FM-TENG) is constructed and designed for wave energy collection and in situ self-powered cathodic protection against corrosion. After fluorination treatment, FM-TENG exhibits good output performance with a maximum short-circuit current density of 3 mA/m2 and power density of 2 mW/m2, which is 3–5 times larger than that of Teflon film-based TENG that is commonly used as the best solid–liquid triboelectrification material. As a high-output coating, TENG can be easily coated on the surface of marine equipment, such as ships, to collect wave energy in situ for energy supply or self-powered cathodic protection. More importantly, TENG with inorganic coating as the friction material possesses high wear resistance and long-term stability. When FM-TENG is damaged in a complex marine environment, it can self-healing by releasing fluoride in the pores of the microarc oxidation coating, and a self-healing FM-TENG is achieved. This new type of inorganic coating TENG has great potential applications in the field of ocean wave energy harvesting, energy supply, and self-powered devices.

Omniphobic PVDF nanofibrous membrane for superior anti-wetting performance in direct contact membrane distillation

Membrane wetting caused by low surface tension pollutants in feed solution has been a major challenge for membrane distillation (MD), and omniphobic membranes have been proposed as a promising solution to address this challenge due to their strong repellence towards liquids with a broad range of surface tensions. In this study, we report a nanoparticle-free strategy to fabricate omniphobic polyvinylidene fluoride (PVDF) nanofibrous membranes for robust MD desalination. A solvent-thermal induced roughening method was used to create multiscale hierarchical nanofin structures on electrospun PVDF nanofibers, followed by a polydopamine-anchored surface fluorination treatment to reduce the surface energy of the nanofibrous membrane. We show that the as-prepared membrane exhibited super repellence (>150°) to diverse liquids with surface tension ranging from 73 to 30 mN m−1. Moreover, the omniphobic membrane maintained stable salt rejection and water flux in direct contact MD processes in the presence of sodium dodecyl sulfate surfactant (up to 0.4 mM) or mineral oil (up to 480 mg L−1), demonstrating its promising potential in practical water reclamation from MD applications.

Resilience of Fluorinated Indium-Gallium-Zinc Oxide Thin-Film Transistor Against Hydrogen-Induced Degradation

Thin-film transistors (TFTs) based on amorphous indium-gallium-zinc oxide (IGZO) with or without plasma fluorination treatment were fabricated and the sensitivity of their characteristics to hydrogen exposure was compared. Consistent with the lower hydrogen content revealed using secondary ion-mass spectrometry, TFTs built with fluorinated IGZO were shown to exhibit improved intrinsic resilience against hydrogen-induced degradation. Further enhanced by the incorporation of aluminum oxide as a hydrogen diffusion-barrier, such resilience is beneficial to the integration of fluorinated IGZO TFTs with hydrogen-containing devices, such as photodiodes based on amorphous hydrogenated silicon and TFTs based on low-temperature polycrystalline silicon.

Atomic Layer Deposition of High-k Insulators on Epitaxial Graphene: A Review

Due to its excellent physical properties and availability directly on a semiconductor substrate, epitaxial graphene (EG) grown on the (0001) face of hexagonal silicon carbide is a material of choice for advanced applications in electronics, metrology and sensing. The deposition of ultrathin high-k insulators on its surface is a key requirement for the fabrication of EG-based devices, and, in this context, atomic layer deposition (ALD) is the most suitable candidate to achieve uniform coating with nanometric thickness control. This paper presents an overview of the research on ALD of high-k insulators on EG, with a special emphasis on the role played by the peculiar electrical/structural properties of the EG/SiC (0001) interface in the nucleation step of the ALD process. The direct deposition of Al2O3 thin films on the pristine EG surface will be first discussed, demonstrating the critical role of monolayer EG uniformity to achieve a homogeneous Al2O3 coverage. Furthermore, the ALD of several high-k materials on EG coated with different seeding layers (oxidized metal films, directly deposited metal-oxides and self-assembled organic monolayers) or subjected to various prefunctionalization treatments (e.g., ozone or fluorine treatments) will be presented. The impact of the pretreatments and of thermal ALD growth on the defectivity and electrical properties (doping and carrier mobility) of the underlying EG will be discussed.

Filler fluorination of nanoTiO2/ER composites and their surface insulation properties: a comparison of dielectric barrier discharge and chemical solution fluorination

NanoTiO2/epoxy resin composites, a kind of dielectric materials with excellent thermal, mechanical and electrical properties, has extensive promise in the insulation area of power system. Although the semiconductor property of TiO2 filler can suppress the electric field mutations in the epoxy insulation devices, the doping of TiO2 will have bad influence on the charge transmission, thus weakening the surface insulation. To solve this problem, filler fluorination with dielectric barrier discharge (DBD) plasma and chemical methods were designed to modify the TiO2 filler. The effects of two fluorination methods on the micro-structures, electrical parameters, and insulation properties of the materials were studied. The results have shown that both DBD plasma and chemical fluorination methods can effectively introduce fluorine into TiO2 filler and its epoxy composites, decreasing its dielectric constant and volume resistivity. Through doping the fluorinated TiO2 nanoparticles, the direct current flashover voltage and charge dissipation rate of the composites can be at best increased to 1.5 times and 4.6 times of the pure epoxy, respectively. The enhanced surface insulation properties were explained by the trap effect and the change of electrical parameters (containing dielectric constant and volume conductivity) brought by fluorination treatments. The study results of two types of filler fluorinations have guiding significance for nano-modification of epoxy insulation composites.

Physical Modeling of p-Type Fluorinated Al-Doped Tin-Oxide Thin Film Transistors

Fabrication, physical modeling and dynamic response of p-type Al-doped SnOx active channel thin film transistors (TFTs) are presented for the potential application of ultra-high definition (UHD) displays. After deposition of Al-doped SnOx active layer using reactive co-sputtering, the channel was treated with plasma fluorination which improve the device performance of high ION/IOFF ratio of > 106, low subthreshold swing of ~100 mV/dec and high field-effect mobility (μFE) of 4.8 cm 2 V -1 s -1 . To understand the origin of such high performance, physical modeling and numerical simulations were performed using density of state (DOS) model of defects/traps of oxide semiconductor. This model describes the modifications of donor-like tail states and acceptor-like Gaussian defect states due to Al doping on SnO x and fluorine treatment. To evaluate the device performance for UHD large scale displays, the dynamic responses of p-type TFT pixel circuit for various requirements are simulated with physical models. These results suggest that the Al-doped SnO x TFTs are potential candidates for future high-definition displays and many applications in transparent electronics.

Confinement of fluorine anions in nickel-based catalysts for greatly enhancing oxygen evolution activity.

Herein, we highlighted fluorine-anion-modification as a useful method for enhancing OER catalytic activity. Fluorine-anion-doped Ni foam exhibits an almost 10-fold enhancement in OER catalytic activity. Moreover, fluorine-anion-modification could be used as a general method to greatly increase the OER activity of NiAl LDHs. The strongly electronegative F anion is favorable to build weak metal-fluorine bonds, which easily break to form active species of nickel oxides/hydroxides, enhancing OER catalytic performance.

The synergistic effect of nitrogen and fluorine co-doping in graphene quantum dot catalysts for full water splitting and supercapacitor

Development of efficient electrochemical catalysts is crucial for clean energy technologies such as water splitting, and batteries, etc. Despite large amounts of electrocatalyst research, it remains a challenge to eco-friendly non-metal catalyst showing high performance as much as novel metal. To achieve high performance as much as noble-metal, carbon nanomaterials (CNMs) have been attracted as a candidate to the widespread application using electrochemical reaction. Herein, we report nitrogen, and fluorine co-doped graphene quantum dot (N,F-GQDs) synthesized by two-step functionalizing method for highly efficient overall water splitting. N,F-GQDs demonstrate electrocatalytic effect toward HER, and OER, and is fabricated as two-electrode full-water splitting showing good stability at various potential points. Furthermore, due to fluorine treatment, prepared N,F-GQDs exhibits enhanced electrochemical reaction property, which can induce capacitance due to the large difference of electronegativity between fluorine and carbon. N,F-GQDs is applied for the anode of super capacitance in the three-electrode system and reveal specific capacitance of 270 F g−1 at 1 mV s−1 from CV curves, and GCD capacitance of 244 F g−1 at 3 mA cm−2. This work provides a new avenue for enhancing both activities of the electrocatalytic and electrochemical reaction.

Omniphobic Nanofibrous Membrane with Pine-Needle-Like Hierarchical Nanostructures: Toward Enhanced Performance for Membrane Distillation.

Wetting and fouling phenomena are the main concerns for membrane distillation (MD) in treating high-salinity industrial wastewater. This work developed an omniphobic membrane by growing titanium dioxide (TiO2) nanorods on polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofibers using a hydrothermal technique. The TiO2 nanorods form a uniform pine-needle-like hierarchical nanostructure on PVDF-HFP fibers. A further fluorination treatment provides the membrane with a low-surface-energy omniphobic surface, displaying contact angles of 168° and 153° for water and mineral oil, respectively. Direct contact MD experiments demonstrated that the resulting membrane shows a high and stable salt rejection of >99.9%, while the pristine PVDF-HFP nanofibrous membrane suffers a rejection decline caused by intense pore wetting and oil fouling in the desalination process in the presence of surfactant and mineral oil. The superior antiwetting and antifouling behaviors were ascribed to a nonwetting Cassie-Baxter state established by the accumulation of a great deal of air in the hydrophobized hierarchical re-entrant structures. The development of omniphobic membranes with pine-needle-like hierarchical nanostructures provides an approach to mitigate membrane wetting and fouling in the MD process for the water reclamation from industrial wastewater.

Plasma fluorination of BaTiO3 for enhancement of interfacial adhesion and surface insulation of epoxy resin

Composite dielectrics with excellent electrical properties are integral to today’s energy industries and power infrastructure. Epoxy resin filled with inorganic nano-fillers has been extensively studied for its excellent performances. In this paper, barium titanate (BaTiO3) nanoparticles are selected as the fillers and fluorinated by plasma treatment. The morphology, element content and chemical bond of BaTiO3 and fluorinated BaTiO3 fillers are characterized by SEM, EDS, XPS and FTIR, respectively. The influence of filler concentration and fluorination on flashover voltage of epoxy resin composites was studied. We found that the fluorinated BTO could improve the compatibility of filler and matrix and surface insulation of epoxy resin composites. Finally, the relationship between filler concentration, dielectric constant, fluorination treatment and charge dissipation was analyzed, and the trap distribution on the surface of composites was calculated by isothermal surface potential decay method. Fluorinated BaTiO3 particles as fillers blended with epoxy resin have great engineering application potential.