Separation Of Sheets Research Articles

Highly selective ion transport by freestanding Zn-Imidazole complex intercalated graphene oxide membrane for enhanced blue energy harvesting

Generating electricity from seawater by utilizing nanofluidic structures is an appealing strategy for achieving zero-emission energy goals. A nanofluidic channel that is atomically small, tunable, and mechanically stable is the key to solving this problem. In this paper, for the first time, we report the construction of centimeter-sized freestanding zinc-imidazole complex (ZnIm) intercalated graphene oxide (GO) membrane (GO-ZnIm) having uniform 2D nanofluidic channels with interlayer spacing of 9 Å. The pristine GO membrane rapidly disintegrates in an aqueous medium due to membrane swelling; however, treatment with an aqueous zeolitic imidazole framework (ZIF-8) suspension, rendering ZnIm complex, provides long-term stability by restricting the excessive interlayer separation of GO sheets. From ion transport, diffusion, and variable load studies, it is observed that, besides stabilizing the GO membrane, intercalation of ZnIm significantly improves average cation selectivity (from 0.46 for GO to 0.74 for GO-ZnIm, measured up to 1000 concentration gradient) and experimental power density (from 1.7 Wm−2 for GO to 10.8 Wm−2 for GO-ZnIm, at 1000 concentration gradient). Moreover, the practical applicability of the GO-ZnIm membrane has also been investigated under artificial estuary conditions at ambient temperature, rendering an osmotic power density of 4.5 Wm−2, which is very close to the commercial benchmark of 5 Wm−2. A mechanically robust and flexible membrane made up of cost-effective components (GO and ZnIm), able to deliver an osmotic power density close to commercial benchmark at ambient temperature is the main highlight of the present GO-ZnIm membrane, which can be a promising candidate for applications such as separation, desalination, and blue energy harvesting.

Heat Treatment at 1000 °C under Reducing Atmosphere of Commercial Vermiculites

With the purpose of obtaining synthetic materials from other natural sources for industrial and technological applications, a thermal alteration study was carried out with commercial vermiculites of different purity and origin. For this objective, samples were subjected to 1000 °C in a furnace both at ambient and reduced (N2/Ar) atmospheres. The thermal behavior and physicochemical properties of the different vermiculites were investigated by X-ray diffraction (XRD), thermal analysis (TG and DTG), and scanning electron microscopy (SEM), and their textural parameters were analyzed by BET treatment. The transformations undergone by the investigated commercial vermiculites subjected to heating treatments caused textural and structural changes in them. There was a decrease in the specific surface area, adsorption capacity, and pore volume values for the samples treated with in situ heating at 1000 °C, both at ambient and reduced atmospheres, and the samples were treated with ex situ abrupt heating at 1000 °C at ambient conditions. There was a decrease in the specific surface area, adsorption capacity, and pore volume values for the samples treated with in situ heating at 1000 °C, both in ambient and reduced atmospheres, which was not observed in the samples treated with an ex situ abrupt heating at 1000 °C at ambient conditions. This corroborated with our findings that the expansion in the first type of thermal treatment produced less separation of the exfoliation sheets than the expansion in the second type of thermal treatment. These textural changes, together with the structural ones, could play a fundamental role in the choice of industrial and technological applications for which these materials could be used.

Terahertz nondestructive stratigraphic reconstruction of paper stacks based on adaptive sparse deconvolution

Characterizing the number of sheets in a stack of paper typically involves mechanical separation of the individual sheets. Here, we explore an nondestructive method that can be applied to the intact paper stack. Namely, terahertz time-of-flight tomography, together with post signal-processing technique sparse deconvolution based on a two-step iterative shrinkage-thresholding algorithm (SD/TWIST), is employed to reconstruct the stratigraphy of stacks of sheets of paper with multilayered structure in a nondestructive and noncontact manner. The double-Gaussian mixture model (DGMM) is also incorporated to suppress dispersion in the reflected THz echoes. The effectiveness and accuracy of the proposed adaptive sparse-deconvolution method are verified experimentally and numerically. Compared with the commonly used frequency wavelet-domain deconvolution (FWDD) method and previous implementations of sparse deconvolution based on an iterative-shrinkage and thresholding algorithm (SD/IST), the proposed sparse-deconvolution approach can provide a clearer and rapid stratigraphic reconstruction of the paper stacks studied, while ensuring accurate thickness information for each paper sheet in the presence of noise, revealing the potential usage of real-time THz tomographic-image processing.

Magnetorheological effect and sensing performance of graphite sheet filled PDMS based magnetorheological elastomer under compression

In order to study the effect of large-sized graphite (Gr) sheet on the magnetorheological (MR) effect and sensing characteristics of MR elastomer (MRE), isotropic and anisotropic Gr-filled MRE samples with different carbonyl iron powder (CIP) contents were fabricated. The effect of Gr sheet on the microstructure, MR effect and sensing characteristics of the MRE samples were experimentally tested, and the mechanisms behind discussed. The results show that in the anisotropic MRE samples, the addition of Gr sheets results in the short particle chains formed between Gr sheets, thus leading to the high MR effect and low resistivity than those of isotropic counterparts. The non-monotonic resistivity responses of the Gr-filled MRE samples during compression were observed owing to the interlayer separation of Gr sheets and the reconstruction of conductive network. A higher piezoresistive response was observed from the isotropic Gr-filled MRE sample filled with the CIP content below the percolation threshold. The resistivities of the Gr-filled MRE samples decline with increasing the applied magnetic field. The isotropic sample filled with lower CIP content shows the higher magnetoresistive effect from the view point of absolute change in resistivity. While for the relative change in resistivity, the anisotropic sample filled with the higher CIP content has the higher magnetoresistive effect.

Fabrication and characterization of copper and copper alloys reinforced with graphene

The consistent rise in current density within electrical wires leads to progressively more substantial heat losses attributed to the Joule effect. Consequently, mitigating the electrical resistivity of copper wires becomes imperative. To attain this objective, the development of a composite material that incorporates a more conductive reinforcement, like graphene, holds great promise. The conception of a copper/graphene composite using a powder metallurgy-based approach is presented. An optimum graphene quantity of 0.06 vol.% was obtained by calculation in order to limit the phenomenon of overlapping layers. This synthesis technique enables the dispersion of graphene and the meticulous control of the interface through the growth of CuO(Cu) nanoparticles that are tightly bonded to the reinforcement. The increase in the hardness of the various materials with separation of the graphene sheets by ultrasonic treatment (55.3 to 67.6 HV) was obtained. It is an indicator of the correct distribution of the reinforcement. The influence on the electrical properties of dendritic copper (ρe = 2.30 µΩ.cm) remains limited, resulting in a modest reduction in electrical resistance of around 1.4%. Nevertheless, for flake copper (2.71 µΩ.cm) and brass (7.66 µΩ.cm), we achieved a more substantial reduction of 2.7% and 10%, respectively. With the improvement of graphene quality, there exists a greater potential for further enhancing the electrical properties.

Impact of Preprocessing of Graphene Additive via Ultrasonication on the Electrochemical Performance of Activated Carbon‐Based Supercapacitors

This article investigates the influence of the addition method of graphene to activated carbon (AC) on the electrochemical performance of the fabricated electric double‐layer capacitors (EDLCs). To do so, the same graphene material is introduced to the other electrode slurry materials either in the form of a powder (GP) or a suspension (GL). It is discovered that the introduction of graphene already dispersed by ultrasonic in a suspension to AC has a better effect on the electrochemical performance of the fabricated EDLCs than directly employing its powder. GL EDLC achieves the highest capacitance of 54 F g−1 at a current density of 0.05 A g−1 in an organic electrolyte, which is much better than the GP EDLC (41.9 F g−1) and about 77% more than AC EDLC. Moreover, after cycling at various current densities (2000 cycles), GL EDLC maintains 28.8 F g−1 of its capacitance with 99.4% coulombic efficiency at a current density of 1 A g−1. Finally, GL EDLC exhibits 35.8 and 21.4 Wh kg−1 energy densities at 50.2 and 1102.8 W kg−1 power densities, respectively. The better performance of GL EDLC in comparison with GP EDLC is ascribed to better graphene dispersion.

Experiments on Nd:YAG pulsed laser welding of thin sheets

Laser welding of thin sheets raises a number of issues arising from the difficulty to maintain a good contact between the components to be joined. A set of experiments were performed using a Nd:YAG PE-W500II laser welding equipment, aiming to identify solutions to avoid local separation of thin sheets due to the induced thermal influence. The welding results were analysed by optical and scanning electron microscopy. The effects of the current intensity and pulse width had a decisive influence on the quality of the resulting welded joint. Furthermore, the use of a device that ensures good localized contact in the area to be welded, also leading to increased local energy dissipation, was essential to achieve high-quality microwelds.

Optimization for size separation of graphene oxide sheets by flow/hyperlayer field-flow fractionation

Graphene oxide (GO)-a chemical derivative of graphene with numerous oxygen functional groups on its surface-has attracted considerable interest because of its intriguing properties in relation to those of pristine graphene. In addition to the inherent wide lateral size distribution of GO sheets arising from the typical oxidative exfoliation of graphite, control of the lateral size of GO is critical for desired GO-based applications. Herein, flow/hyperlayer field-flow fractionation (flow/hyperlayer FFF) is optimized to separate GO sheets by lateral dimensions. Optimized fractionation is achieved by investigating the influences of carrier solvent, channel thickness, and flow rate conditions on the steric/hyperlayer separation of GO sheets by flow FFF. Due to the strong hydrodynamic lift forces of extremely thin GO sheets, a thick flow FFF channel (w=350 μm) and a very low field strength are required to retain the GO sheets within the channel. GO sheets with narrow size fractions are successfully collected from two different graphite sources during flow/hyperlayer FFF runs and are examined to verify the size evolution. Considering the average lateral diameter of the GO fraction calculated on the basis of the assumption of a circular disk shape, the retention of the GO sheets is 2.2-5.0 times faster than that of spherical particles of the same diameter. This study demonstrates that through flow/hyperlayer FFF, the size distribution of GO sheets can be determined and narrow size fractions can be collected (which is desirable for GO-based applications), which are commonly influenced by the GO lateral dimension.

Metal-organic frameworks/ hydrotalcite/graphene oxide sandwich composites derived Fe-Ce@GSL hierarchical materials as highly efficient catalysts for rechargeable Zn-air batteries

The fabrication of efficient bi-functional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applied in energy storage and conversion devices like Zn-air batteries to solve the growing energy and environmental crises has attracted great attentions. In this work, the Fe-Ce@GSL catalysts have developed by first constructing the MOF/LDH/GO templates with multi-stage mixed growth method followed by calcining the template at high temperature. Fe-Ni-LDH (hydrotalcite) plays the role of linking the metal organic frameworks (Fe-Ce-MOF) and graphene oxides (GO), avoiding the separation of MOFs derivatives and GO sheets during pyrolysis process. Rare-earth metal oxide (CeO2) featuring with abundant oxygen vacancies dispersed on the surface of transition-metal oxide can efficiently improve the stability of catalysts. The optimal Fe7-Ce1@GSL-800 catalysts exhibit excellent ORR/OER performances with the potential gap between ORR (E1/2 = 0.87 V) and OER (EJ=10 = 1.59 V) of 0.720 V. The aqueous Zn-air battery assembled with Fe7-Ce1@GSL-800 catalysts exhibits outstanding performances with high open circuit voltage (1.56 V), large specific capacity (801.1 mAh/g@10 mA.cm−2), and good charge–discharge cycle performances (>500 h). The Fe7-Ce1@GSL-800 based solid-state Zn-air battery also delivers an excellent performance with high specific capacity (791.7 mAh/g@5 mA.cm−2) and long cycle stability (>230 h).

Wide-Range Size Fractionation of Graphene Oxide by Flow Field-Flow Fractionation

Many interesting properties of 2D materials and their assembled structures are strongly dependent on the lateral size and size distribution of 2D materials. Accordingly, effective size separation of polydisperse 2D sheets is critical for desirable applications. Here, we introduce flow field-flow fractionation (FlFFF) for a wide-range size fractionation of graphene oxide (GO) up to 100 μm. Two different separation mechanisms are identified for FlFFF, including normal mode and steric/hyperlayer mode, to size fractionate wide size-distributed GOs while employing a crossflow field for either diffusion or size-controlled migration of GO. Obviously, the 2D GO sheet reveals size separation behavior distinctive from typical spherical particles arising from its innate planar geometry. We also investigate 2D sheet size-dependent mechanical and electrical properties of three different graphene fibers produced from size-fractionated GOs. This FlFFF-based size selection methodology can be used as a generic approach for effective wide-range size separation for 2D materials, including rGO, TMDs, and MXene.

Modern and early Holocene ice shelf sediment facies from Petermann Fjord and northern Nares Strait, northwest Greenland

Based on sediment cores and geophysical data collected from Petermann Fjord and northern Nares Strait, NW Greenland, an Arctic ice shelf sediment facies is presented that distinguishes sub and pro ice shelf environments. Sediment cores were collected from sites beneath the present day Petermann Ice Tongue (PIT) and in deglacial sediments of northern Nares Strait with a focus on understanding the glacial and oceanographic history over the last 11,000 cal yr BP. The modern sub ice shelf sediment facies in Petermann Fjord is laminated and devoid of coarse clasts (IRD) due to strong basal melting that releases debris (debris filtering) from the basal ice at the grounding zone driven by buoyant subglacial meltwater and entrained Atlantic Water. Laminated sediments in the deep basin proximal to the gounding zone comprise layers of fine mud formed by suspension settling from turbid meltwater plumes (plumites) interrupted by normally graded very fine sand to medium silt layers with sharp basal contacts and rip-up clasts of mud, interpreted as turbidites. An inner fjord sill limits distribution of sediment gravity flows from the grounding zone to the deep inner fjord basin, such that sites on the inner sill and beyond the ice tongue largely only comprise plumites. Bioturbation and foraminiferal abundances increase with distance from the grounding zone. The benthic foraminiferal species, Elphidium clavatum is absent beneath the ice tongue, but dominant in the turbid meltwater influenced environment beyond the ice tongue. The very sparse IRD in sediments beneath the PIT and in the fjord beyond the PIT derives mainly from englacial debris in the ice tongue, side valley glaciers, rock falls from the steep fjord walls and sea ice.We use the modern ice shelf sediment facies characteristics to infer the past presence of ice shelves in northern Nares Strait using analyses of sediment cores from several cruises (OD1507, HLY03, 2001LSSL, RYDER19). On bathymetric highs, bioturbated mud with dispersed IRD overlies a 10–15 m thick, distinctly laminated silt and clay unit with rare coarse clasts and sparse foraminifera which forms a sediment drape of nearly uniform thickness. We interpret these laminated sediments to represent glaciomarine deposition by meltwater plumes emanating from ice streams that terminated in floating ice shelves. IRD layers, shifts in sediment composition (qXRD, MS and XRF) and faunal assemblage changes in the laminated unit document periods of ice-shelf instability sometimes, but not always, coupled with grounding zone retreat. Our deglacial reconstruction, including ice shelves, begins ∼10.7 cal ka BP, with confluent ice streams grounded in Hall Basin fronted by the Robeson Channel ice shelf. Ice shelf breakup and grounding zone retreat to relatively stable grounding zones at Kennedy Channel and the mouth of Petermann Fjord was accomplished by 9.4 cal ka BP when the Hall Basin ice shelf was established. This ice shelf broke up and reformed once prior to the final break up at 8.5 to 8.4 cal ka BP marking ice stream collapse, separation of Greenland and Innuitian ice sheets, and the opening of Nares Strait for Arctic-Atlantic throughflow. The Petermann ice shelf remained in Hall Basin until the Petermann Glacier retreated from the fjord mouth ∼7.1 cal ka BP. The resilience of these northern ice streams to strong early Holocene insolation and subsurface Atlantic Water advection is attributed to their northern aspect, buttressing by narrow passages, and high ice flux from the Greenland Ice Sheet (GIS).

The synergic effects of metakaolin and polycarboxylate-ether on dispersion of graphene oxide in cementitious environments and macro-level properties of graphene oxide modified cement composites

Studying the effects of pozzolanic materials such as silica fume, fly ash, and metakaolin (MK) on dispersion of graphene oxide (GO) in cementitious environments has attracted interest in recent years. In this research, the potential of MK particles as an impediment against GO agglomeration in high alkaline environments is investigated. Despite the exhibited results in previous studies that the particles of pozzolans can inhibit the agglomeration of GO in cementitious environments by consuming Ca(OH)2 besides the mechanical separation of GO sheets, the results of the present study revealed that MK particles alone could not prevent GO nanosheets from clustering, physically or chemically. However, based on UV–vis spectroscopy and SEM-EDS analysis results, the incorporation of MK particles with Polycarboxylate-ether (PCE) significantly ameliorates the dispersion and time-dependent stability of GO nanosheets in simulated cement pore solution. Indeed, in this case, the anchoring characteristic of the negative surface charge of MK particles besides the steric hindrance effect of PCE’s side chains can reduce the possibility of the interaction between GO nanosheets and calcium ions in cementitious environments. Moreover, the improved stability of MK-PCE modified GO suspensions ensures the permanence of the desired dispersion of GO in the alkaline medium of cement composites, which is advantageous for enhancing the mechanical and transport properties of cement composites. In this research, the results of compressive strength, flexural strength, flexural modulus, toughness, and ultrasonic pulse velocity tests on MK-GO incorporated cement paste samples after 28 days of curing showed an enhancement by 27.6%, 36.3%, 49.8%, 42.0%, and 5.0%, respectively compared to the reference sample. This improvement is primarily due to the beneficial effects of MK-PCE to make GO play a better reinforcing role in cement composites.

Incorporation of Reduced Graphene Oxides for Enhancing the Gas Sensing Characteristics

Incorporation of Reduced Graphene Oxides for Enhancing the Gas Sensing Characteristics

Molecular Dynamic Studies and Experimental Methods for Dispersion of Graphene Sheets with Different Strategies

Graphene sheets tend to self-associate in microscale aggregates. This occurs in products with less mechanical and electrical action. Recognizing this problem, extensive research has been evidenced in the literature on the development of dispersion technologies, based on both mechanical and chemical approaches. Chemically converted sheets wrapped in surfactants, the ability of surfactants to disperse graphene nanospheres in a medium, was evaluated by different research groups, using both experimental and molecular dynamics (DM) simulation methods; In this article we summarize these methods and techniques. The effect of the influencing factors that count the ions, the pH value and the surfactants in the separation and agglomeration of the gerata sheets is highlighted. Here, we reviewed the recent advances that have been made in the dispersion of graphene sheets in aqueous and organic media by non-covalent adsorption of surfactants and polymers. Graphene structure, properties, and mainly self-assembly are also studied.

In situ synthesis of MgWO4–GO nanocomposites and their catalytic effect on the thermal decomposition of HMX, RDX and AP

For solving phase separation of nanoparticles and graphene oxide (GO) in the application process, MgWO4–GO nanocomposites were successfully synthesized using three different dispersants via a facile solvothermal-assisted in situ synthesis method. The structure and morphology of the prepared samples were characterized by X-ray diffraction, Scanning electron microscopy, Transmission electron microscopy, Fourier transform infrared and Raman techniques. The experimental results show that MgWO4 nanoparticles are tightly anchored on the surfaces of GO sheets and the agglomeration of MgWO4 nanoparticles is significantly weakened. Additionally, MgWO4–GO nanocomposites are more stable than self-assembly MgWO4/GO, which there is no separation of MgWO4 nanoparticles and GO sheets by ultrasound after 10 min. The catalytic results show that, compared with bare MgWO4, MgWO4–GO nanocomposites present better catalytic activities on the thermal decomposition of cyclotetramethylenete tranitramine (HMX), cyclotrimethylene trinitramine (RDX) and ammonium perchlorate (AP). The enhanced catalytic activity is mainly attributed to the synergistic effect of MgWO4 nanoparticles and GO. MgWO4–GO prepared using urea as the dispersant has the smallest diameter and possesses the best catalytic action among the three MgWO4–GO nanocomposites, which make the decomposition temperature of HMX, RDX and AP reduce by 10.71, 11.09 and 66.6 °C, respectively, and the apparent activation energy of RDX decrease by 68.6 kJ mol−1.

(Invited) Graphene for Bioapplications: Toxicological Studies and Integration in 3D-Scaffolds

The biological applications of graphene materials are strongly conditioned by the need to handle these nanostructures under physiological conditions, essentially complex aqueous media. While the water stabilization of Graphene Oxide (GO) can be easily achieved, this material do not possess the electrical properties of graphene. On the other hand, the mechanical exfoliation of graphite has led to the efficient separation and stabilization of graphene sheets in water when water-soluble dispersant species are used in the exfoliation process. However, many surfactants may cause toxicity problems if they are not thoroughly removed. Our group has developed a facile and inexpensive ball milling process to exfoliate graphite and to prepare graphene dispersions in water. These aqueous suspensions can be freeze-dried, resulting in a soft powder that can be easily re-suspended in aqueous media, including cell culture media, at the desired concentration. We have also made sure that the redispersed solid retains the original properties of graphene. During this talk, we will discuss (i) studies of interaction of so-prepared solutions with cells; (ii) the use of graphene in hybrid hydrogels for drug delivery purposes and for 3D cell culture media.

Ultrahigh benzene adsorption capacity of graphene-MOF composite fabricated via MOF crystallization in 3D mesoporous graphene

Highly porous composites were synthesized via facile crystallization of a metal-organic framework (MOF) in mesopores of a three-dimensional (3D) graphene (MG). First, MG was prepared via facile thermal exfoliation of graphite oxide in air, which enabled sufficient separation of graphene sheets in the form of an interconnected 3D structure. Next, aluminum-based MOF [MOF520: Al8(OH)8(BTB)4(HCOO)4, BTB = 4,4′,4”-benzene-1,3,5-tryil-tribenzoate] was predominantly crystallized in mesopores of 3D structure having a large pore volume. The resulting MG-MOF composites possessed specific surface areas and pore volumes between those of MG (640 m2/g and 3.0 cm3/g) and MOF (3160 m2/g and 1.3 cm3/g). The composite consisting of MG and MOF with a weight ratio of 1:2 showed almost twice-larger benzene adsorption capacity, i.e., 24.5 mmol/g at 20 °C and relative pressure close to unity, in comparison to that of pure MOF. Although at the same conditions the pure MG captured an ultrahigh amount of benzene, i.e., 33.6 mmol/g, adsorption of this adsorbate at low and moderate relative pressures was much lower than that on pure MOF. Thus, the MG-MOF composites featured much better benzene adsorption performance in a wide range of relative pressures as compared to pure MG and MOF, respectively. Additionally, the composites featured better thermal stability in comparison to the pristine MOF. The use of MG in this synthesis method afforded the well-dispersed, small crystals of MOF, which is essential for the design of MOF-based composites.

Three-dimensional monolithic corrugated graphene/Ni foam for highly stable and efficient Li metal electrode

To expedite the commercialization of Li metal anodes by combining them with Li transition metal oxides to achieve a high operating voltage, a carbonate-based electrolyte should be used, which is unstable at low potentials. Therefore, hybrid engineering to prevent dendritic Li growth and increase the coulombic efficiency in highly reactive electrolytes is essential. Here, three-dimensional monolithic corrugated graphene on nickel foam electrode as a Li metal storage framework in carbonate electrolytes is reported. The electrode is fabricated using a simple acid-catalyzed hydrothermal method. This involves separation of few-layer graphene sheets and formation of corrugated graphene sheets on porous Ni foam. During the initial Li deposition, Li ions are inserted into the vertical edge plane boundaries between graphene sheets. Li metal deposits then nucleate and grow further underneath the graphene sheets. The corrugated graphene sheets unfold and function as an artificial solid electrolyte interphase layer that separates the Li deposits from the reactive electrolyte. Consequently, the dendritic Li growth is effectively prevented, and the coulombic efficiency is significantly improved. Electrochemical tests demonstrate the effectiveness of this material design concept, which provides a new route to the development of a Li metal electrode for use in highly reactive electrolytes.

Chemically Specific Multiscale Modeling of the Shear-Induced Exfoliation of Clay-Polymer Nanocomposites.

We recently showed, using chemically specific modeling and simulation, how the process of intercalation of polymers within clay sheets occurs, transforming the large-scale materials properties by a specific set of spatial and temporal processes that can lead to exfoliation. Here, we use the same hierarchal multiscale modeling scheme to understand the processes that occur during the shear-induced processing of clay–polymer nanocomposites. For both hydrophobic polymers (polyethylene) and hydrophilic polymers (poly(ethylene glycol)), we used free-energy methods to identify the lowest-free-energy separation of the clay sheets; the polymer molecules spontaneously intercalate into the clay interlayer from the surrounding polymer melt. We apply shear forces to investigate exfoliation and find that while exfoliation is promoted by shearing, it is the surfactant molecules that play the dominant role in resisting it.

Multi-layered graphenic structures as the effect of chemical modification of thermally treated anthracite

ABSTRACTGraphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal reduction and (2) cycloaddition of azomethine ylide. Distinct differences were found between both anthracite-derived graphenic materials. The oxidation Hummers process resulted in a wide variety of oxygen functional groups incorporated into the carbon layers, while subsequent thermal reduction caused separation of graphene sheets but reduced the oxygen moieties. The cycloaddition of azometine ylide led to the formation of functionalized graphene sheets containing mostly 3,4-bonded N-methyl-2-(3,4-dihydroxyphenyl)pyrrolidine groups. The first attempts of application of anthracite-derived fillers to epoxy composites showed the improvement of their mechanical and viscoelastic properties, comparable to composites with graphene nanofillers.