Showing papers on "Graphite published in 2014"
TL;DR: Expanded graphite is reported as a Na-ion battery anode, prepared through a process of oxidation and partial reduction on graphite, which has an enlarged interlayer lattice distance yet retains an analogous long-range-ordered layered structure to graphite.
Abstract: Graphite, as the most common anode for commercial Li-ion batteries, has been reported to have a very low capacity when used as a Na-ion battery anode. It is well known that electrochemical insertion of Na(+) into graphite is significantly hindered by the insufficient interlayer spacing. Here we report expanded graphite as a Na-ion battery anode. Prepared through a process of oxidation and partial reduction on graphite, expanded graphite has an enlarged interlayer lattice distance of 4.3 A yet retains an analogous long-range-ordered layered structure to graphite. In situ transmission electron microscopy has demonstrated that the Na-ion can be reversibly inserted into and extracted from expanded graphite. Galvanostatic studies show that expanded graphite can deliver a high reversible capacity of 284 mAh g(-1) at a current density of 20 mA g(-1), maintain a capacity of 184 mAh g(-1) at 100 mA g(-1), and retain 73.92% of its capacity after 2,000 cycles.
1,432 citations
TL;DR: The described electrochemical exfoliation of graphene sheets into aqueous solutions of different inorganic salts shows great promise for the industrial-scale synthesis of high-quality graphene for numerous advanced applications.
Abstract: Mass production of high-quality graphene sheets is essential for their practical application in electronics, optoelectronics, composite materials, and energy-storage devices. Here we report a prompt electrochemical exfoliation of graphene sheets into aqueous solutions of different inorganic salts ((NH4)2SO4, Na2SO4, K2SO4, etc.). Exfoliation in these electrolytes leads to graphene with a high yield (>85%, ≤3 layers), large lateral size (up to 44 μm), low oxidation degree (a C/O ratio of 17.2), and a remarkable hole mobility of 310 cm2 V–1 s–1. Further, highly conductive graphene films (11 Ω sq–1) are readily fabricated on an A4-size paper by applying brush painting of a concentrated graphene ink (10 mg mL–1, in N,N′-dimethylformamide). All-solid-state flexible supercapacitors manufactured on the basis of such graphene films deliver a high area capacitance of 11.3 mF cm–2 and an excellent rate capability of 5000 mV s–1. The described electrochemical exfoliation shows great promise for the industrial-scale ...
1,137 citations
TL;DR: This work shows that formation of GO from graphite constitutes three distinct independent steps, and that the reaction can be stopped at each step, and the corresponding intermediate products can be isolated, characterized, and stored under appropriate conditions.
Abstract: Despite intensive research, the mechanism of graphene oxide (GO) formation remains unclear. The role of interfacial interactions between solid graphite and the liquid reaction medium, and transport of the oxidizing agent into the graphite, has not been well-addressed. In this work, we show that formation of GO from graphite constitutes three distinct independent steps. The reaction can be stopped at each step, and the corresponding intermediate products can be isolated, characterized, and stored under appropriate conditions. The first step is conversion of graphite into a stage-1 graphite intercalation compound (GIC). The second step is conversion of the stage-1 GIC into oxidized graphite, which we define as pristine graphite oxide (PGO). This step involves diffusion of the oxidizing agent into the preoccupied graphite galleries. This rate-determining step makes the entire process diffusive-controlled. The third step is conversion of PGO into conventional GO after exposure to water, which involves hydroly...
681 citations
TL;DR: In this article, the synthesis methods employed for the doping of different types of carbon materials with various elements and the characterization techniques used to investigate their physicochemical properties such as degree of graphitization, dopant content and surface area are reviewed.
Abstract: Carbon materials such as graphite, graphene, carbon nanotubes and ordered mesoporous carbon have attracted a lot of attention for their use in fuel cells, due to beneficial properties like high conductivity, high mechanical and chemical stability and, for the latter, high surface area. Doping these materials with nitrogen or, less commonly, other elements alters their (electronic) properties, making them particularly suitable for application as electrocatalysts for the oxygen reduction reaction (ORR) in a fuel cell. This paper reviews the synthesis methods employed for the doping of these different types of carbon materials with various elements and the characterization techniques used to investigate their physicochemical properties such as degree of graphitization, dopant content, dopant configuration and surface area. Furthermore, their application as electrocatalysts for the oxygen reduction in a fuel cell is reviewed. Finally, the possible mechanisms for the ORR on N-doped carbon materials are critically discussed and compared to the mechanisms of commercial Pt/C electrocatalysts.
594 citations
TL;DR: This work has grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide.
Abstract: Graphitic carbon nitride has been predicted to be structurally analogous to carbon-only graphite, yet with an inherent bandgap. We have grown, for the first time, macroscopically large crystalline thin films of triazine-based, graphitic carbon nitride (TGCN) using an ionothermal, interfacial reaction starting with the abundant monomer dicyandiamide. The films consist of stacked, two-dimensional (2D) crystals between a few and several hundreds of atomic layers in thickness. Scanning force and transmission electron microscopy show long-range, in-plane order, while optical spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations corroborate a direct bandgap between 1.6 and 2.0 eV. Thus TGCN is of interest for electronic devices, such as field-effect transistors and light-emitting diodes.
531 citations
TL;DR: In this article, the influence of graphite on the wear behavior of Al 7075/Al 2 O 3 /5.% graphite hybrid composite was investigated and the results revealed the effectiveness of incorporating graphite in the composite for gaining wear reduction.
Abstract: This work investigated the influence of graphite on the wear behavior of Al 7075/Al 2 O 3 /5 wt.% graphite hybrid composite. The investigation reveals the effectiveness of incorporation of graphite in the composite for gaining wear reduction. The Al 7075 (aluminium alloy 7075) reinforced with Al 2 O 3 –graphite were investigated. The composites were fabricated using liquid metallurgy route. Ceramic particles along with solid lubricating materials were incorporated into aluminium alloy matrix to accomplish reduction in both wear resistance and coefficient of friction. The Al 7075/Al 2 O 3 /graphite hybrid composite was prepared with 5 wt.% graphite particles addition and 2, 4, 6 and 8 wt.% of Al 2 O 3 . The hardness, tensile strength, flexural strength and compression strength of the Al 7075–Al 2 O 3 –graphite hybrid composites are found to be increased by increased weight percentage of ceramic phase. The wear properties of the hybrid composites containing graphite exhibited the superior wear-resistance properties.
468 citations
TL;DR: A thin polymer shell helps V2O5 a lot and an excellent high-rate capability and ultrastable cycling up to 1000 cycles are demonstrated.
Abstract: A thin polymer shell helps V2O5 a lot. Short V2O5 nanobelts are grown directly on 3D graphite foam as a lithium-ion battery (LIB) cathode material. A further coating of a poly(3,4-ethylenedioxythiophene) (PEDOT) thin shell is the key to the high performance. An excellent high-rate capability and ultrastable cycling up to 1000 cycles are demonstrated.
429 citations
TL;DR: DFT calculations elucidated the mechanism by which the charged edge carbon atoms result in the higher ORR activity and provided a direct way to identify the active sites of carbon materials for the ORR.
Abstract: Carbon-based metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline medium have been extensively investigated with the aim of replacing the commercially available, but precious platinum-based catalysts. For the proper design of carbon-based metal-free electrocatalysts for the ORR, it would be interesting to identify the active sites of the electrocatalyst. The ORR was now studied with an air-saturated electrolyte solution droplet (diameter ca. 15 μm), which was deposited at a specified position either on the edge or on the basal plane of highly oriented pyrolytic graphite. Electrochemical measurements suggest that the edge carbon atoms are more active than the basal-plane ones for the ORR. This provides a direct way to identify the active sites of carbon materials for the ORR. Ball-milled graphite and carbon nanotubes with more exposed edges were also prepared and showed significantly enhanced ORR activity. DFT calculations elucidated the mechanism by which the charged edge carbon atoms result in the higher ORR activity.
427 citations
TL;DR: In this article, the phase composition, microstructure, magnetic properties and electromagnetic (EM)-wave absorbability of carbon nanofibers with ferromagnetic metal nanoparticles (CNF-M, M = Fe, Co, and Ni) were studied.
Abstract: Carbon nanofibers with ferromagnetic metal nanoparticles (CNF–M, M = Fe, Co, and Ni) have been synthesized by carbonizing electrospun polyacrylonitrile nanofibers including metal acetylacetonate in an argon atmosphere, and their phase composition, microstructure, magnetic properties and electromagnetic (EM)-wave absorbability have been studied. The microstructure analysis shows that the in situ formed metal nanoparticles are well distributed along carbon-based nanofibers and encapsulated by ordered graphite layers. The investigation of magnetic properties and EM-wave absorbability reveals that the as-synthesized CNF–M has typical characteristics of ferromagnetic materials and exhibits excellent EM-wave absorption properties (reflection loss exceeding −20 dB) from the C-band to the Ku-band (4–18 GHz) over an absorber thickness of 1.1–5.0 mm due to the efficient complementarities of complex permeability and permittivity resulting from the magnetic metal nanoparticles and lightweight carbon, as well as the particular particle/graphite core/shell microstructures in CNF–M. Moreover, a minimum reflection loss value of −67.5, −63.1, and −61.0 dB is achieved at 16.6, 12.9, and 13.1 GHz with a matching thickness of 1.3, 1.6, and 1.7 mm for CNF–Fe, CNF–Co, and CNF–Ni, respectively. These magnetic carbon nanofibers are attractive candidates for the new type of high performance EM-wave absorbing materials.
397 citations
TL;DR: R-GOs are highly promising fillers for microwave attenuation in the carbon family and that r-GO composites are high-performance EMI shielding materials with application anticipated to many fields.
Abstract: In this work, reduced graphene oxide (r-GO) and graphite nanosheet (GN) were obtained via the chemical approach. Furthermore, r-GO composites and GN composites were prepared with a paraffin wax host. r-GO composites show high dielectric properties and electromagnetic interference shielding efficiency (EMI SE). Compared with the GN composites, the loss tangent and EMI SE of the r-GO composites with the same mass ratio are enhanced ∼5 to 10 times and ∼3 to 10 times, respectively. The enhanced attenuation capacity arises from higher specific surface area, clustered defects and residual bonds of the r-GOs, which increase the polarization loss, scattering and conductivity of the composite. Moreover, the higher conductivity of r-GO composites leads to higher EMI SE compared with that of GN composites. These results suggest that r-GOs are highly promising fillers for microwave attenuation in the carbon family and that r-GO composites are high-performance EMI shielding materials with application anticipated to many fields.
342 citations
TL;DR: In this article, the authors proposed a dual-graphite and dual-carbon energy storage system, where the graphite was used as both anode and cathode material in a so-called dual graphite or dual carbon cell, and an ionic liquid-based electrolyte mixture was used in combination with the SEI-forming additive ethylene sulfite.
Abstract: Recently, dual-ion cells based on the anion intercalation into a graphite positive electrode have been proposed as electrochemical energy storage devices. For this technology, in particular electrolytes which display a high stability vs. oxidation are required due to the very high operation potentials of the cathode, which may exceed 5 V vs. Li/Li+. In this work, we present highly promising results for the use of graphite as both the anode and cathode material in a so-called “dual-graphite” or “dual-carbon” cell. A major goal for this system is to find suitable electrolyte mixtures which exhibit not only a high oxidative stability at the cathode but also form a stable solid electrolyte interphase (SEI) at the graphite anode. As an electrolyte system, the ionic liquid-based electrolyte mixture Pyr14TFSI-LiTFSI is used in combination with the SEI-forming additive ethylene sulfite (ES) which allows stable and highly reversible Li+ ion and TFSI− anion intercalation/de-intercalation into/from the graphite anode and cathode, respectively. By addition of ES, also the discharge capacity for the anion intercalation can be remarkably increased from 50 mA h g−1 to 97 mA h g−1. X-ray diffraction studies of the anion intercalation into graphite are conducted in order to understand the influence of the electrolyte additive on the graphite structure and on the cell performance.
TL;DR: In this article, the dependence of graphitic fillers on the rheological, electrical, mechanical, thermal, dielectric and barrier properties of elastomer composites is discussed, giving special emphasis to particle size and mode of interactions with the matrix.
TL;DR: In this paper, LiNiNi1/3Mn 1/3Co1 /3O2/graphite cells at sub-ambient temperatures are studied by neutron diffraction at Stress-Spec, MLZ.
TL;DR: In this article, the worn surfaces of hybrid composites and base alloys were studied through SEM and EDS systems and some useful conclusions were made by using a pin-on-disc apparatus with various input parameters like applied load (10, 20, and 30 n), sliding speed (0.6, 0.8, and 1.0 n), and sliding distance (1000, 1500, and 2000 m).
TL;DR: In this paper, the performance of nitrogen-doped few-layer graphene/multi-walled carbon nanotube (FLG/MWCNT) composite catalyst has been investigated.
TL;DR: The in situ behaviour of the double resonance 2D band during the lithiation and delithiation of graphitic carbon has been reported, in keeping with the Daumas-Hérold model of electrochemically derived intercalation, where the graphene layers are flexible and deform around domains of intercalating lithium ions.
Abstract: The first and second order Raman spectra of graphite during the first lithiation and delithiation have been investigated in a typical lithium-ion battery electrolyte. In situ, real-time Raman measurements under potential control enable the probing of the graphitic negative electrode surface region during ion insertion and extraction. The experimental results reveal the staging formation of a single particle within a free standing graphitic electrode. In particular, the in situ behaviour of the double resonance 2D band during the lithiation and delithiation of graphitic carbon has not been previously reported. The 2D band was observed to shift from 2681 to 2611 cm−1 and the band shape transformed into a single Lorentzian from 0.24 to 0.15 V vs. Li/Li+, providing further information on the electronic structure and C–C bonding of stage 3 and 4 graphite intercalation compounds. The behaviour of the 2D band is in keeping with the Daumas–Herold model of electrochemically derived intercalation, where the graphene layers are flexible and deform around domains of intercalating lithium ions.
TL;DR: Aminotriazine systems were found to be the best partners in the preparation and stabilization of graphene layers in different solvents, while the equivalent benzene derivatives did not show comparable exfoliation ability.
Abstract: A ball-milling treatment can be employed to exfoliate graphite through interactions with commercially available melamine under solid conditions. This procedure allows the fast production of relatively large quantities of material with a low presence of defects. The milling treatment can be modulated in order to achieve graphene flakes with different sizes. Once prepared, the graphene samples can be redispersed in organic solvents, water, or culture media, forming stable dispersions that can be used for multiple purposes. In the present work, we have screened electron-rich benzene derivatives along with triazine derivatives in their respective ability to exfoliate graphite. The results suggest that the formation of a hydrogen-bonding network is important for the formation of multipoint interactions with the surfaces of graphene, which can be used for the exfoliation of graphite and the stabilization of graphene in different solvents. Aminotriazine systems were found to be the best partners in the preparati...
TL;DR: In this paper, the authors investigated 7075 aluminium alloy-graphite composites for their tribological and mechanical behavior under dry sliding conditions. And they found that the presence of 5-wt.% graphite in the composites can exhibit superior wear property as compared to base alloy.
Abstract: This work investigates 7075 aluminium alloy–graphite composites for its tribological and mechanical behaviour under dry sliding conditions. The conventional liquid casting technique was used for the fabrication of composite material and subjected to T6 heat treatment. The reinforcement content was chosen as 5, 10, 15 and 20 wt.% of graphite to identify its potential for self-lubricating property under dry sliding conditions. Wear tests were conducted by using pin on disc apparatus to evaluate the tribological behaviour of the composite and to determine the optimum content of graphite for its minimum wear rate. The wear rate decreases with addition of graphite content and reaches its minimum at 5 wt.% graphite. The wear mass loss was found to decrease with increasing sliding distance. The average coefficient of friction decreases with addition of graphite content and was found to be minimum at 5 wt.% graphite. The mechanical properties of the composites and base alloy were tested. The mechanical properties decrease with increasing graphite content as compared to base alloy. The worn surfaces were examined through SEM. The presence of 5 wt.% graphite in the composites can exhibit superior wear property as compared to base alloy.
TL;DR: In this paper, the van der Waals (vdW) density function was used for graphite intercalation of lithium, sodium and potassium in graphite by density functional theory.
Abstract: We report on the energetics of intercalation of lithium, sodium and potassium in graphite by density functional theory using recently developed van der Waals (vdW) density functionals. First stage intercalation compounds are well described by conventional functionals like GGA, but van der Waals functionals are crucial for higher stage intercalation compounds and graphite, where van der Waals interactions are important. The vdW-optPBE functional gave the best agreement with reported structure and energetics for graphite and LiC6 and was further applied for intercalation of Na and K. The enthalpy of formation of LiC6 and KC8 were found to be −16.4 and −27.5 kJ mol−1 respectively. NaC6 and NaC8 were unstable with positive enthalpies of formation (+20.8 and +19.9 kJ mol−1). The energetics of stacking of graphene and intercalant layers was investigated from first to fifth stage intercalation compounds. Higher stage compounds of Li and K were stable, but with less negative enthalpy of formation with increasing stage order. The higher stage Na compounds possessed positive enthalpy of formation, but lower in magnitude than the energy difference of 0.6 kJ mol−1 between graphite with AB and AA stacking. The abnormal behaviour of the lower stage Na intercalation compounds was rationalized by the lower energy involved in the formation of the chemical bond between carbon Na relative to the corresponding bond with Li or K. The chemical bond between alkali metal and carbon is characterized by charge transfer from the alkali-metal to carbon resulting in ionized alkali-metals. The intercalation induces only a subtle increase in the in-plane C–C bond lengths, with longer C–C bonds in the vicinity of the alkali metals but without breaking the hexagonal symmetry.
TL;DR: In this article, the tetraalkylammonium cations are intercalated into pristine graphite to form few-layer graphene flakes, which are then used for graphite rod electrode fabrication.
TL;DR: The graphene/polyaniline hybrid exhibited a breakthrough in the improvement of microwave absorption and the interactions between polyanilines and graphene were confirmed by Fourier transform infrared spectroscopy and Raman spectra.
Abstract: A new method is introduced for the preparation of graphene/polyaniline hybrids using a one-step intercalation polymerization of aniline inside the expanded graphite. The structural and morphological characterizations were performed by X-ray diffraction analysis, transmission electron microscopy and field emission scanning electron microscopy. Both the experimental and first-principles simulated results show that the aniline cation formed by aniline and H+ tends to be drawn towards the electron-enriched zone and to intercalate into the interlayer of graphite. Subsequently, an in situ polymerization leads to the separation of graphite into graphene sheet, resulting from the exothermic effect and more vigorous movements of the chain molecules of polyaniline. The interactions between polyaniline and graphene were confirmed by Fourier transform infrared spectroscopy and Raman spectra. In addition, the graphene/polyaniline hybrid exhibited a breakthrough in the improvement of microwave absorption.
TL;DR: The enhanced capability of the CSS-based graphite/PEDOT/MnO2 network electrode has high potential for low-cost, high-performance, and flexible supercapacitors.
Abstract: A facile and low-cost method is presented to synthesize graphite/PEDOT/MnO2 composites with controlled network structures on commercial supercapacitor separator (CSS) membranes for high-performance supercapacitors, in which pencil lead and a cellulose-based commercial supercapacitor separator membrane were applied as the graphite source and the flexible substrate, respectively. The dependence of PEDOT and MnO2 loading on the structural formation, the electrochemical performance of the hybrid electrode, and the formation mechanism of MnO2 nanowires are systematically investigated. The optimized electrode possesses a high areal capacitance of 316.4 mF/cm2 at a scan rate of 10 mV/s and specific capacitance of 195.7 F/g at 0.5 A/g. The asymmetric supercapacitor device assembled using optimized CSS/Graphite/PEDOT/MnO2 electrode and activated carbon electrode exhibits a high energy density of 31.4 Wh/kg at a power density of 90 W/kg and maintains 1 Wh/kg at 4500 W/kg. After 2000 cycles, the device retains 81.1%...
TL;DR: Six coal samples of different ranks have been used to prepare single-layer graphene quantum dots (S-GQDs), which showed excitation-dependent fluorescence and excellent electrochemiluminescence and might be more suitable for preparing other CNMs that were contained in CoalB, although those CNMs were difficult to separate from each other in the authors' experiment.
Abstract: Six coal samples of different ranks have been used to prepare single-layer graphene quantum dots (S-GQDs). After chemical oxidation and a series of centrifugation separation, every coal could be treated into two fractions, namely, CoalA and CoalB. According to the characterization results of TEM, AFM, XRD, Raman and FTIR, CoalA was revealed to be mainly composed of S-GQDs, which have an average height of about 0.5 nm and an average plane dimension of about 10 nm. The obtained S-GQDs showed excitation-dependent fluorescence and excellent electrochemiluminescence. CoalB was found to be some other carbon-based nanomaterials (CNMs), including agglomerated GQDs, graphene oxide, carbon quantum dots and agglomerated carbon nanocrystals. Generally, low-ranked coals might be more suitable for the preparation of S-GQDs. The production yield of S-GQDs from the six investigated coals decreased from 56.30% to 14.66% when the coal rank increased gradually. In contrast, high-ranked coals had high production yield of CoalB and might be more suitable for preparing other CNMs that were contained in CoalB, although those CNMs were difficult to separate from each other in our experiment.
TL;DR: In this paper, ultrathin conformal coatings of the lithium ion conductor, lithium aluminum oxide (LiAlO2), were evaluated for their ability to improve the electrochemical stability of LiNi0.5Mn1.5O4/graphite Li-ion batteries.
Abstract: Ultrathin conformal coatings of the lithium ion conductor, lithium aluminum oxide (LiAlO2), were evaluated for their ability to improve the electrochemical stability of LiNi0.5Mn1.5O4/graphite Li-ion batteries. Electrochemical impedance spectroscopy confirmed the ion conducting character of the LiAlO2 films. Complementary simulations of the activation barriers in these layers match experimental results very well. LiAlO2 films were subsequently separately deposited onto LiNi0.5Mn1.5O4 and graphite electrodes. Increased electrochemical stability was observed, especially in the full cells, which was attributed to the role of the coatings as physical barriers against side reactions at the electrode–electrolyte interface. By comparing data from full cells where the coatings were applied to either electrode, the dominating failure mechanism was found to be the diffusion of transition metal ions from the cathode to the anode. The LiNi0.5Mn1.5O4/graphite full cell with less than 1 nm LiAlO2 on the positive electr...
TL;DR: In this article, the structure-sensitivity of the electrochemical corrosion of high surface area carbon (HSAC) used to support catalytic materials in PEMFC electrodes is investigated in model (liquid electrolyte, 96 h potentiostatic holds at different electrode potentials ranging from 0.40 to 1.40 V at T = 330 K) and real PEM FC operating conditions (solid polymer electrolyte and 12,860 h of operation at constant current).
Abstract: The electrochemical oxidation of carbon is a pivotal problem for low-temperature electrochemical generators, among which are proton-exchange membrane fuel cells (PEMFCs), and (non)aqueous-electrolyte Li–air batteries. In this contribution, the structure-sensitivity of the electrochemical corrosion of high-surface area carbon (HSAC) used to support catalytic materials in PEMFC electrodes is investigated in model (liquid electrolyte, 96 h potentiostatic holds at different electrode potentials ranging from 0.40 to 1.40 V at T = 330 K) and real PEMFC operating conditions (solid polymer electrolyte, 12,860 h of operation at constant current). Characterizations from Raman spectroscopy demonstrate that the disordered domains of HSAC supports (amorphous carbon and defective graphite crystallites) are preferentially oxidized at voltages related to the PEMFC cathode (0.40 1.00 V, witnessed during start-up and shut-down of PEMFC systems, accelerate this pheno...
TL;DR: This article showed that fresh graphitic surfaces are mildly hydrophilic and graphite becomes hydrophobic upon exposure to ambient air and showed that surface properties of graphite and fresh CVD graphene can be characterized by defect density and dynamic contact angle measurements.
TL;DR: Covalent carbon nitride polymers were applied as metal-free robust catalysts for the inactivation of Escherichia coli K-12 under visible light illumination, demonstrating that the creation of antibacterial function on the surface of conjugated polymers has now become possible.
TL;DR: GO membranes demonstrate the absence of "negative thermal expansion" and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders.
Abstract: The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of “negative thermal expansion” and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes.
TL;DR: In this paper, a hierarchical carbon/carbon composite paper was fabricated by depositing graphene oxide into the carbon fiber precursor followed by carbonization, which achieved a thermal conductivity of 977 W m−1 K−1 and favorable tensile strength of 15.3 MPa.
Abstract: As a low dimensional crystal, graphene attracts great attention as heat dissipation material due to its unique thermal transfer property exceeding the limit of bulk graphite. In this contribution, flexible graphene–carbon fiber composite paper is fabricated by depositing graphene oxide into the carbon fiber precursor followed by carbonization. In this full-carbon architecture, scaffold of one-dimensional carbon fiber is employed as the structural component to reinforce the mechanical strength, while the hierarchically arranged two-dimensional graphene in the framework provides a convenient pathway for in-plane acoustic phonon transmission. The as-obtained hierarchical carbon/carbon composite paper possesses ultra-high in-plane thermal conductivity of 977 W m−1 K−1 and favorable tensile strength of 15.3 MPa. The combined mechanical and thermal performances make the material highly desirable as lateral heat spreader for next-generation commercial portable electronics.