Fluorographene Research Articles

Metal ion-crosslinked thermoconductive sugar-functionalized graphene fluoride-based cellulose papers with enhanced mechanical properties and electrical insulation

Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics. In this study, we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugar-functionalized graphene fluoride (SGF) and cellulose nanofibers (CNF) by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties. The facile sugar-assisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride. Thanks to the good dispersibility of the SGF sheets in water, the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration. We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers. Ca2+ or Al3+ ion-crosslinked SGF/ CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking. SGF/CNF-Ca2+ and SGF/CNF-Al3+ papers at 50 wt% of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m–1 K–1, and tensile strengths of 121.5 and 135.7 MPa, respectively. A thermal percolation value was observed at 12.6 vol% of SGF filler content. In addition, the SGF/CNF papers exhibited electrical insulation properties. These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport. High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.

Self-Assembled MXene@Fluorographene Hybrid for High Dielectric Constant and Low Loss Ferroelectric Polymer Composite Films.

Modern electrical applications urgently need flexible polymer films with a high dielectric constant (εr) and low loss. Recently, the MXene-filled percolative composite has emerged as a potential material choice because of the promised high εr. Nevertheless, the typically accompanied high dielectric loss hinders its applications. Herein, a facile and effective surface modification strategy of cladding Ti3C2Tx MXene (T = F or O; FMX) with fluorographene (FG) via self-assembly is proposed. The obtained FMX@FG hybrid yields high εr (up to 108 @1 kHz) and low loss (loss tangent tan δ = 1.16 @ 1 kHz) in a ferroelectric polymer composite at a low loading level (the equivalent of 1.5 wt % FMX), which is superior to its counterparts in our work (e.g., FMX: εr = 104, tan δ = 10.71) and other studies. It is found that the FG layer outside FMX plays a critical role in both the high dielectric constant and low loss from experimental characterizations and finite element simulations. For one thing, FG with a high F/C ratio would induce a favorable structure of high β-phase crystallinity, extensive microcapacitor networks, and abundant interfacial dipoles in polymer composites that account for the high εr. For another, FG, as a highly insulating layer, can inhibit the formation of conductive networks and inter-FMX electron tunneling, which is responsible for conduction loss. The results demonstrate the potential of a self-assembled FMX@FG hybrid for high εr and low loss polymer composite films and offer a new strategy for designing advanced polymer composite dielectrics.

Janus polyurethane composite film with highly aligned graphene fluoride and liquid metal: A versatile technique for thermal management and electromagnetic interference shielding

Flexible and multi-functional thermoconductive polymer composites have significant potential for application in advanced electronics. However, achieving a composite with necessary requirements such as flexibility, thermal conductivity, electromagnetic interference (EMI) shielding, and electrical insulation are challenging. The concept of Janus materials has provided the requirements of advanced electronics by forming a layered structure in polyurethane via sedimentation of liquid metal (LM) and graphene fluoride (GF). The fillers in the polyurethane were elongated and aligned along the draw direction using a stretching-induced filler alignment approach, which enhanced in-plane thermal conductivity and EMI shielding performance simultaneously. The Janus composite film exhibited electrical conductivity on one side and insulation on the other side, demonstrating the true nature of the Janus structure, while the film showed superior thermal conductivity (9.62 W·m−1·K−1) and EMI shielding effectiveness (55 dB) at a draw ratio of 2. These findings provide a novel approach to fabricating multifunctional composites for electronics applications.

Efficient heavy metal ion removal by fluorographene nanochannel templated molecular sieve: a molecular dynamics simulation study

Environmental water contamination, particularly by heavy metal ions, has emerged as a worldwide concern due to their non-biodegradable nature and propensity to accumulate in soil and living organisms, posing a significant risk to human health. Therefore, the effective removal of heavy metal ions from wastewater is of utmost importance for both public health and environmental sustainability. In this study, we propose and design a membrane consisting of fluorographene (F-GRA) nanochannels to investigate its heavy metal ion removal capacity through molecular dynamics simulation. Although many previous studies have revealed the good performance of lamellar graphene membranes for desalination, how the zero-charged graphene functionalized by fluorine atoms (fully covered by negative charges) affects the heavy metal ion removal capacity is still unknown. Our F-GRA membrane exhibits an exceptional water permeability accompanied by an ideal heavy metal ion rejection rate. The superior performance of F-GRA membrane in removing heavy metal ions can be attributed to the negative charge of the F-GRA surface, which results in electrostatic attraction to positively charged ions that facilitates the optimal ion capture. Our analysis of the potential of mean force further reveals that water molecule exhibits the lowest free energy barrier relative to ions when passing through the F-GRA channel, indicating that water transport is energetically more favorable than ion. Additional simulations of lamellar graphene membranes show that graphene membranes have higher water permeabilities compared with F-GRA membranes, while robustly compromising the heavy meal ion rejection rates, and thus F-GRA membranes show better performances. Overall, our theoretical research offers a potential design approach of F-GRA membrane for heavy metal ions removal in future industrial wastewater treatment.

Multilayered silver nanowires and graphene fluoride-based aramid nanofibers for excellent thermoconductive electromagnetic interference shielding materials with low-reflection

Multilayered films composed of alternating layers of graphene fluoride (GF) and silver nanowires (AgNWs) in an aramid nanofiber (ANF) matrix were fabricated. The films were prepared by sequential vacuum filtration of GF@ANF and AgNWs@ANF suspensions to obtain multilayered composite architectures. The multilayered GF@ANF/AgNWs@ANF films exhibited exceptional mechanical flexibility and strength, with tensile strength up to 130 MPa and 5000 bending cycles with negligible performance deterioration. The films displayed remarkably high electromagnetic interference (EMI) shielding effectiveness up to 54 dB in X-band frequencies, attributed to the multiple internal reflections in the multilayered structure. EMI shielding was dominated by absorption rather than reflection, enabling attenuation of incident microwaves without secondary pollution. The multilayered films also exhibited ultrahigh in-plane thermal conductivity of up to 45 W/mK, owing to the thermally conductive GF and AgNWs networks. The EMI shielding effectiveness and thermal conductivity were retained after temperature and bending cycling. The composite films also demonstrated excellent flame retardancy. This study provides an effective route toward concurrent enhancement of multi-functional properties through architectural engineering at the nanoscale. The combination of robust EMI shielding, mechanical flexibility, thermal management, and fire safety highlights the potential of rationally designed multilayered composites for practical applications in 5 G wearable electronics devices, communications systems, and radar technologies.

Polyurethane composite films with self-assembled graphene fluoride: Constructing conductive pathways for thermal management with electrical insulation

Polymer composites incorporating carbon-based fillers have been demonstrated to have high thermal conductivity (TC), yet their high electrical conductivity restricts their utility in electronic devices. As a solution to this issue, we report graphene fluoride (GF) incorporated thermoplastic polyurethane (TPU) composites that are both thermally conductive and electrically insulating. The TPU composites, engineered for both high TC and electrical insulation while maintaining flexibility, were fabricated using a combination of electrospinning, dip-coating, and hot-pressing techniques. This study aimed to investigate the effects of various dip-coating cycles on the in-plane thermal conductivity (λ∥) of GF@TPU composites. Noticeably, GF@TPU composites exhibited an outstanding TC, reaching up to 13.5 W m−1 K−1 with 10 vol% GF loading, marking a 75-fold increase compared to the neat TPU films. Moreover, the GF@TPU composites exhibited an electrically insulating property of 6.5 × 1010 Ω/m. This work provides a promising strategy to make thermally conductive composites with electrical insulation for thermal management in smart electronics.

Experimental study and modeling of the wettability of fluorine graphene. Corrosion behavior of the fluorine graphene layer on a copper substrate

Fluorographene (FG) is a high-quality 2D insulator, which is effectively used as the atomically thin tunnel barrier. To date, the most common idea is that the complete fluorination of graphene (G) leads to an increase in hydrophobicity. We have shown that in reality fluorination leads to superhydrophilicity and to a significant increase in the defectiveness of the graphene layer. Without hydrocarbons, as well as due to the high defectiveness and superhydrophilicity, the corrosion current of FG is an order of magnitude higher than for pure copper and two orders of magnitude higher than for G synthesized on copper. The simulation results confirm experimental data on FG superhydrophilicity after prolonged fluorination. Thus, in order to achieve high hydrophilicity, it is not necessary to create hydroxyl groups on the surface of FG. A higher concentration of fluorine (the C/F composition ratio) is realized on a thicker copper plate with a graphene layer, compared to thin copper foil. Different fluorine concentrations are associated with different sizes of crystal grains, their orientation, as well as defectiveness and the number of graphene layers. The corrosive effect leads to a decrease in roughness and a multiple decrease in the amount of F on the FG.

Fluorographene and carbon nanotubes fillers reinforced nitrile butadiene rubber with enhanced mechanical, wear and oil resistant properties

AbstractIn this work, we prepared nitrile butadiene rubber (NBR) composites with fluorographene (FG) and carbon nanotubes (CNTs) as hybrid fillers by a solution‐blending method. The resulting composites xFG/yCNTs‐NBR, where x and y represent the loading of FG and CNTs respectively, show significantly improved physical and mechanical properties. The hybrid fillers can form a filler network in the rubber matrix, leading to efficient energy dissipation. As a result, when the mass ratio of FG to CNTs is 1:1 and the total filler loading is 20 phr, the tensile strength of 10FG/10CNTs‐NBR is as high as 12.1 MPa. Furthermore, due to inherent lubricating and oil‐repelling effects of FG, 10FG/10CNTs‐NBR shows an abrasion resistance index (ARI) of 187% and a volume change of 2.38% after 72 h of soaking in aviation oil, which are 24% higher and 48% lower than the corresponding values of unfilled NBR composites, respectively. These results indicate that the hybrid fillers can effectively enhance the mechanical, wear and oil resistant properties of the elastomer composites, which is conductive for application of the NBR‐based composites.

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics

Thermoconductive Graphene Fluoride Cross-Linked Aramid Nanofiber Composite Films with Enhanced Mechanical Flexibility and Flammable Retardancy for Thermal Management in Wearable Electronics

Multilayered graphene fluoride and Ti3C2Tx MXene-based aramid nanofiber films with excellent thermal conductivity and electromagnetic interference shielding performance

Thermally conductive electromagnetic interference (EMI) shielding materials with excellent thermal conductivity, EMI shielding effectiveness (SE), and electrical insulation are pivotal for ensuring the operation and performance of next-generation electronic devices, safeguarding them against external electromagnetic waves and mitigating excessive heat generation. In this study, multilayered graphene fluoride (GF) and Ti3C2Tx MXene (MX)-based aramid nanofiber (ANF) films, in which the MX@ANF layer was sandwiched between GF@ANF layers, were fabricated using the alternating vacuum filtration method. The resultant multilayered films with increased GF and MX contents showed an upsurge in thermal conductivity and EMI SE while maintaining excellent electrical insulation, thermal stability, and mechanical flexibility. The GF50/MX75 film with 50 wt% GF content and 75 wt% MX content in each layer exhibited an excellent EMI SE of ∼41 dB in the X-band frequency, along with a superior specific shielding effectiveness of 3818 dB·cm2/g, an outstanding in-plane thermal conductivity of 85 W/m·K, and mechanical strength of 70 MPa. The notable properties of the GF/MX films are attributed to the well-ordered alignment of the GF and MX sheets and their strong interaction with ANF, which facilitates phonon and electron conduction. Furthermore, the multilayered GF/MX films exhibited excellent heat dissipation capabilities and flame retardancy. Owing to their exceptional performance, multilayered GF/MX films offer a compelling opportunity to advance EMI shielding and thermal management materials to the forefront of next-generation electronics.

Weldable and electrochemically stable composite of graphene and polyvinylidene fluoride as a current collector for promoting reversible lithium plating/stripping

Cu foils are physically heavy and chemically inappropriate for lithium metal rechargeable batteries with lithium-metal-free negatrode (LMFRBs). Physically light carbon-based current collectors (CBCCs) with high conductivity and strong resistance toward corrosion by air or electrolyte can replace Cu foil as a preferable deposition substrate for Li. However, welding problems, lithiation or electrolyte penetration-induced mechanical strength reduction, and lithiophobility-induced fragile SEI largely limit the application of CBCCs. In this work, we prepare lightweight graphene/polyvinylidene fluoride (PVDF) composite sheet via a coating and etching process to address the above issues. Cu tabs are bonded firmly to this CBCC with acceptable resistance, guaranteeing practical application. Tightly stacked graphene nanosheets mitigate lithiation and extra Li consumption (SEI), while PVDF as the binder reinforces the mechanical strength of CBCC by hindering the electrolyte penetration. Therefore, this composite CBCC satisfies the basic requirements i.e., sufficient conductivity and mechanical strength, and viable tab welding, needed for pouch cell application. In addition, as a film-forming polymer with a low Fermi level, PVDF helps form Li–F-rich and highly insulating SEI and suppresses electron transfer to the electrolyte, which induces uniform Li+ flux and alleviates electrolyte decomposition. The stable interface and robust SEI give rise to uniform and more reversible Li plating/stripping. The assembled LMFRB using this composite CBCC achieves remarkable capacity retention of 80% after ∼50 cycles with a high plating capacity of 4 mAh cm−2.

Functionalization of graphene fluoride with 2-phenylbenzimidazole

The interaction of graphene fluoride with 2-phenylbenzimidazole afforded a new benzimidazole-functionalized graphene material. It was shown that carrying out the reaction in sulfolane in the presence of pyridine provides a higher degree of functionalization. The formation of the target product was confirmed by elemental analysis, IR and Raman spectroscopy.

Study of Thermal Conductivity of Fluorinated Graphene

With the rapid development of technology and the advent of the 5G era in recent years, the heat dissipation of electronic devices has received great attention. However, the high intrinsic conductivity of ordinary graphene materials limits their potential applications in electronic packaging materials because of their poor thermal management. The results show that fluorinated graphene has excellent heat resistance, corrosion resistance, and strong wear resistance. It can also play a role in lubrication and is commonly used in high-temperature coatings, wear-resistant lubrication coatings and corrosion-resistant coatings because it does not react easily with other substances. Due to the strong electronegativity of fluorine, fluorinated graphene has strong stability and oxidation resistance at high temperatures. Therefore, in this paper, a fluorinated graphene with high compressibility, high thermal conductivity, and high electrical insulation was developed by hydrothermal method assisted by hydrofluoric acid, and the effect on the thermal conductivity of fluorinated graphene was investigated by changing the fluorine-to-carbon ratio (F/C) by adjusting the hydrofluoric acid content. The structure of fluorinated graphene was characterized by SEM and XRD, which proved to be porous and a customized interconnected graphene network with adjustable fluorine coverage. The prepared fluorinated graphene has good insulating properties with a minimum conductivity of 4×10-7 S cm-1 and a thermal conductivity of 1.254 W m-1 K-1, which has been confirmed by the electrical conductivity test results. Meanwhile, because of the porous structure of graphene fluoride, we prepared epoxy resin/fluorinated graphene nanocomposites by vacuum-assisted infiltration process using epoxy resin as the filler material. This material and fluorinated graphene showed outstanding thermal performance during the typical cooling process. The conclusion shows that graphene fluoride and epoxy resin/fluorinated graphene nanocomposites are promising for electronic packaging.

Functionalization of Graphene Fluoride with 2-Phenylbenzimidazole

Functionalization of Graphene Fluoride with 2-Phenylbenzimidazole

Impact of Disorder and Defects on Bond Energies in Highly Fluorinated Graphene

Fluorinated graphite materials are of interest for an assortment of applications and can be synthesized under a variety of synthetic conditions from many different types of carbon. Due to such variations, structural disorders in the form of defects and polymorphism are often present. Here, we investigate the impact of local structural variations on the C–F bond dissociation energies (BDEs) in carbon-based fluoride materials using density functional theory (DFT) computational methods. Employing fluorographene (FG) cluster models, we determine the impact of different C–F bonding configurations in the core of each platelet on the equilibrium BDEs for each C–F bond. The introduction of structural disorder decreases the first C–F BDE by approximately 1 eV compared to the canonical arrangement of axial C–F bonds ordered as in a network of cyclohexane “chairs”. Variability of calculated BDEs among the different polymorphs decreases upon subsequent F removal. Common structural tendencies of the adiabatic defluorination pathways for each polymorph are identified. Our analysis suggests that at F/C ratios near 1.0, disorder in the local structure can play a significant role in the energetics of the initial carbon fluoride defluorination and that the influence of this configurational disorder diminishes with decreasing F/C ratios.

Dual 3D networks of graphene derivatives based polydimethylsiloxane composites for electrical insulating electronic packaging materials with outstanding electromagnetic interference shielding and thermal dissipation performances

Research on electronic packaging materials with high electromagnetic interference (EMI) shielding, thermal conductivity, and electrical insulating properties has been flourishing in recent years. In this work, dual three-dimensional (3D) structures of graphene nanoplatelets (GnP) and graphene fluoride (GF) were fabricated in the polydimethylsiloxane (PDMS) composites for electronic packaging materials with superior EMI shielding effectiveness (SE), thermal conductivity, and electrically insulating. The first 3D structure of the porous GnP@PDMS foams was fabricated using the sugar template method. The GF/PDMS solution was then infiltrated into the GnP@PDMS foam by the vacuum infiltration method to create the second 3D network of GF in the GnP@PDMS/GF composites. The prepared porous GnP30@PDMS foam exhibits an EMI SE of 51.26 dB with 30 wt% of GnP. In addition, the introduction of the second 3D network of GF/PDMS plays a vital role to improve the thermal conductivity and electrical insulating properties of the GnP30@PDMS/GF composites. The GnP30@PDMS/GF8 composites showed a thermal conductivity of 1.47 W·m−1·K−1 which is enhanced by 568 % in comparison to the pure PDMS and excellent electrical insulating properties as high as 2.82 × 10−10 S·cm−1 and maintained high EMI SE of 50.13 dB. The extraordinary EMI SE of the GnP@PDMS/GF composites is favorably correlated to the porous interconnected network of GnP while the enhanced thermal conductivity is attributed to the dual 3D thermoconductive channels of GnP and GF. Additionally, the GnP@PDMS/GF8 composites are demonstrated to have outstanding mechanical flexibility, thermal stability, and heat dissipating capability. Therefore, the developed GnP@PDMS/GF composites have great prospects in the field of electronic packaging materials.

Enhanced Breakdown Strength of Ferroelectric Polymer Films for Capacitive Energy Storage by Incorporating Oriented Fluorographene

Ever-increasing electrification scenarios call for high energy density (Ue) polymer nanodielectric films beyond the commercial benchmark biaxially oriented polypropylene. Ferroelectric polymers of intrinsic high dielectric constant εr, if integrated with improved breakdown strength (Eb) and dielectric loss from nanofillers, would be a promising paradigm for high-Ue polymer nanodielectrics. Yet, this expectation is still in its infancy because of the great challenge of increasing the Eb and needs introduction of new approaches. Here, fluorographene (FG), as a young halogen derivative of graphene, is employed as an emerging nanofiller to develop high-Eb polymer nanodielectrics. A dramatically enhanced Eb, which is 39.4% higher than that of a neat polymer film from casting, is achieved in a composite film along with a reduced dielectric loss by incorporating only 0.2 wt % FG with in-plane orientation from electrospinning. The origin of such a high Eb-reinforcing effect of FG is traced by both experimental characterizations and phase-field simulation. It is found that the in-plane oriented FG of appropriate loading level would induce both the favorable low crystallinity of the polymer matrix and the FG–polymer interface with deep traps and less defects. This, together with the high out-of-plane insulation of FG from a high fluorine/carbon ratio, regulates the charge behaviors and breakdown paths and thus significantly enhances the voltage endurance of composite films. The results demonstrate the remarkable Eb-reinforcing effect of emerging FG fillers in polymer nanodielectrics and offer a strategy toward high-Eb/high-Ue flexible dielectric capacitors.

Role of Environmental Dynamic Polarizability in Static Excited State Properties of Embedded Molecular Systems: Application to Disordered Fluorographene Systems

We present an extension of the standard polarizable quantum mechanic/molecular mechanics (QM/MM) approach for treating environmental effects on excited state properties of embedded systems. A quantum polarizable atom model is derived from a full quantum description of the environment using perturbation theory for the system-environment coupling. Our model provides a more general description of the environment, including frequency-dependent atomic polarizabilities, without the loss of computational simplicity of the QM/MM approach. The classical polarizable atom description, used in the polarizable QM/MM approach, can be obtained as a limiting case of the present model. This result enables us to pinpoint approximations and assumptions about the system inherent to a classical polarizable atom description of the environment. We apply our method to fluorographene (FG)-based systems to investigate the effects of the FG sheet on excited state properties of impurities on the FG surface. The comparison to full quantum chemistry calculations and to the standard polarizable QM/MM approach on disordered fluorographene clusters reveals the importance of the frequency dependence of atomic polarizabilities for a proper treatment of the effects of the environment on both the transition energy shifts and the interaction energies.

Perfluoroalkyl-Functionalized Graphene Oxide as a Multifunctional Additive for Promoting the Energetic Performance of Aluminum.

Aluminum (Al) is a widely used metal fuel for energetic applications ranging from space propulsion and exploration, and materials processing, to power generation for nano- and microdevices due to its high energy density and earth abundance. Recently, the ignition and combustion performance of Al particles were found to be improved by graphene-based additives, such as graphene oxide (GO) and graphene fluoride (GF), as their reactions provide heat to accelerate Al oxidation, gas to reduce particle agglomeration, and fluorine-containing species to remove Al2O3. However, GF is not only expensive but also hydrophobic with poor mixing compatibility with Al particles. Herein, we report a multifunctional graphene-based additive for Al combustion, i.e., perfluoroalkyl-functionalized graphene oxide (CFGO), which integrates the benefits of GO and GF in one material. We compared the effects of CFGO to GO and GF on the ignition and combustion properties of nAl particles using thermogravimetric analysis, differential scanning calorimetry, temperature-jump ignition), Xe flash ignition, and constant-volume combustion test. These experiments confirm that CFGO generates fluorine-containing species, heat, and gases, which collectively lower the ignition threshold, augment the energy release rate, and reduce the combustion product agglomeration of nanosized Al particles, outperforming both GO and GF as additives. This work shows the great potential of using multifunctionalized graphene as an integrated additive for enhancing the ignition and combustion of metals.

Vertically interconnected network of graphene fluoride for highly thermoconductive and electrically insulating epoxy composites

AbstractGraphene fluoride (GF), a new graphene derivative, is an excellent candidate for thermal management applications, given its exceptional thermal conductivity and superb insulation properties. However, the fabrication of the vertically aligned graphene fluoride (VA‐GF) sheet network is challenging due to its hydrophobic property and complicated surface modification process. In this work, the freeze‐casting method was used to create VA‐GF scaffolds incorporating polyethyleneimine (PEI) as the dispersing agent and binder. Benefiting from the vertical alignment of the GF scaffold, the epoxy composites exhibited the through‐plane thermal conductivity (TC) of 0.96 W m−1 K−1 at 15 vol% of GF loading, corresponding to 465% and 146% enhancement over pure epoxy and randomly distributed GF/epoxy composites, respectively. As a function of frequency, the electrical conductivity of VA‐GF/epoxy composites was also explored at different filler contents. With increasing GF content and frequency, the electrical conductivity of the composites rose from 10−9 to 10−8 S m−1 between 103 and 106 Hz, demonstrating an insulating property of materials. The vertical alignment of GF in a polymer matrix provides an opportunity for the creation of composites with exceptional thermal conductivity in a through‐plane direction and electrical insulation properties, which promotes the development of thermal management materials for electronic devices.