Thermal Stability Of Graphene Research Articles

Performance of graphene Oxide/SiO2 Nanocomposite-based: Antibacterial Activity, dye and heavy metal removal

Nanocomposite materials have been successfully applied to remediation of organic and inorganic contaminants from polluted water. The present study investigates the synthesis, characterizations, and adsorptive performances of graphene oxide/SiO2 nanocomposite-based adsorbent. Graphene oxide/SiO2 was used for the adsorption of methylene blue (MB) and Cr (VI) ion from wastewater. Furthermore, the antibacterial activity performance of synthesized nanocomposite was studied. The adsorption consideration has been performed by various adsorption parameters in our laboratory. X-ray crystallography (XRD), Scanning electron microscope (SEM), Energy Dispersive X-ray Analysis (EDX) and, thermal gravimetric analysis (TGA) methods were applied in the characterization, morphological structure, crystallinity, and thermal stability of graphene oxide/SiO2. Maximum capacities of adsorption of graphene oxide/SiO2-based adsorbent had been evaluated by the Langmuir isotherm model for MB and Cr (VI) ion as 555.50 and 181.81 mg/g, respectively. Generally, adsorption experiments revealed that the performances of graphene oxide/SiO2 nanocomposite for all adsorbents have been found in the order MB > Cr (VI). Furthermore, antibacterial activity study against gram-positive and gram-negative bacteria showed and proved that graphene oxide/SiO2 composite showed a remarkable ability to kill bacteria.

MnO2-graphene based composites for supercapacitors: Synthesis, performance and prospects

Supercapacitors stand out among some traditional energy storage devices due to their advantages such as long cycle stability, fast charge-discharge performance and high-power density. Therefore, it is necessary to explore high-performance electrode materials for application in supercapacitors. Manganese dioxide (MnO 2 ) has high theoretical capacitance and high energy density, however, the deterioration of volume expansion and low conductivity directly affect its wide application. Graphene has attracted great interest owing to its invention. The combination of graphene and MnO 2 can not only highlight the low resistance, large specific surface area and thermal stability of graphene, but also solve the shortcomings of MnO 2 alone as an electrode material. The proposal of composite materials has also promoted the development and application of electrode materials in supercapacitors. Hence, this review aims to summarize the synthetic strategies and research progress of MnO 2 -graphene based multi-element composites, including the combination of MnO 2 -graphene with various carbon materials, transition metal oxides and conducting polymers, respectively. Finally, the possible development directions of MnO 2 -graphene based composite electrode materials in the future are also prospected. • Focusing on the synthesis strategy and electrochemical performance. • Multi-composites exert synergistic effects and offer significant performance. • MnO 2 -graphene based composites still have a promising future in other fields.

Graphene oxide‐containing isocyanate‐based polyimide foams: Enhanced thermal stability and flame retardancy

AbstractIsocyanate‐based graphene oxide‐containing polyimide foams were synthesized by a semi‐prepolymer method. In this method, while the first solution containing pre‐polymer was derived from pyromellitic dianhydride and excess polymethylene polyphenylene isocyanate (PM200), the second solution contains dianhydride derivatives, water, catalysts, surfactants, and graphene oxide. PIFs were prepared with 0%, 0.25%, 0.50%, 0.75%, and 1% graphene oxide by weight, respectively. PIFs exhibited a minimum side reaction and urea generation was not seen for all PIFs instead of imide bonding. The addition of graphene oxide (GO) leads to a more close‐packed structure. Therefore, crosslinking density and thermal stability of graphene oxide‐containing polyimide foams increased. Upon the addition of 1% GO, almost seven times higher compression strength was obtained compared to neat PIFs. Also, LOI values supported the theory that thermally stable and flame retardant PIFs can be synthesized via the isocyanate‐based process with GO.

Evaluations of Discharge Capacity and Cycle Stability for a Graphene-added Li1.9Ni0.35Mn0.65O2 Cathode Fabricated by using Carbonate Co-precipitation

Li-rich cathode materials are receiving considerable attention for use inlithium-ion batteries (LIBs) owing to their high capacity of more 250 mAh/g or higher in the voltage range of 3.0–4.5 V. However, due to the sharply fading capacity and poor rate-capability of Li-rich cathode materials, numerous efforts have been made to improve the rate-capability. In this research, Li-rich Li1.9Ni0.35Mn0.65O2 cathode materials were prepared via a carbonate coprecipitation route, and graphene, which provides high conductivity and thermal stability, was used during the slurry mixing process. The structures and microstructures of those cathode materials were confirmed using confirmed usnig X-ray diffraction (XRD) and scanning electron microscopy (SEM). The discharge capacity and capacity retention were enhanced owing to the high electric conductivity and thermal stability of graphene.

Effect of Aliphatic and Aromatic Chain Extenders on Thermal Stability of Graphene Oxide/Polyurethane Hybrid Composites Prepared by Sol‐Gel Method

AbstractHybrid composites of graphene and polyurethane (PU) were prepared via sol‐gel method. The isocyanate‐terminated PUs with chain extenders of pyromellitic dianhydride (PMDA) and butanediol were reacted with (3‐aminopropyl) triethoxysilane (APTES) to obtain Polyurethane with PMDA chain extender (PUI) and Polyurethane with BD chain extender (PUBD), respectively. Sol‐gel reaction between the silane‐modified polyurethanes with APTES‐modified graphene oxide resulted in the hybrid composites with high thermal degradation temperature and char content. Results of Fourier‐transform infrared spectroscopy and proton nuclear magnetic resonance analysis confirmed chemical modification of graphene and successful preparation of the bifunctional silane‐modified PUI and PUBD, respectively. Based on the thermogravimetric analysis (TGA) results, PMDA chain extender resulted in higher degradation temperature and char content in the hybrid composites. In addition, siloxane networks formed by sol‐gel process resulted in synergistic effects on improving thermal stability of the PU materials. X‐ray diffraction results in addition to the scanning and transmission electron microscopy images confirmed successful oxidation of graphite and also its modification process.

Friction and Wear of Al2O3 + G Nanocomposite Produced via Spark Plasma Sintering

We report the effect of graphene (G) allotropic carbon modification in a content range of 0.5–2.0 wt % on the tribological, strength, and structural characteristics of an Al2O3/G nanocomposite produced by a 10-min plasma spark sintering (at a pressure of 50 MPa and a temperature of 1550°C) of a nanopowder mixture, previously subjected to ultrasonic dispersion in organic solvent. Its lubricant free friction and wear are tested at room temperature on a tribometer under a load of 20 N, at a roundabout motion of a ruby ball penetrator on a disk. The nanohardness and elastic modulus of the nanocomposite are determined via kinetic indentation. The fracture surface structure and friction track are monitored using a scanning electron microscope. The microstructure in the bulk of the nanocomposite was probed via dark- and bright-field transmission electron microscopy scanning of thin foils. The thermal stability of graphene was monitored via Raman spectroscopy. The introduction of graphene is shown to improve micro- and nanohardness, elasticity, and wear resistance by two to three orders of magnitude, as well as to slightly decrease the coefficient of friction. A graphene content of 2 wt % alters the mechanism of wear from brittle fracture to viscous shear owing to stronger coupling of matrix grains and the presence of agglomerates. A lack of degradation and the retention of graphene thermal stability are evidenced as well. The morphology of graphene particles reveals their preferential arrangement inside the corundum grains rather than at the grain boundaries.

Friction and wear of nanocomposite Al2O3 + G processed by spark plasma sintering

The effect of allotropic carbon modification content, graphene (G), in the range of 0.5 – 2.0 wt.% on tribological, strength and structural characteristics of Al2O3/G nanocomposite processed by 10-min plasma spark sintering (pressure 50 MPa, temperature 1550 °C) of nanopowder mixture previously subjected to ultrasonic dispersion in organic solvent is studied. The results of tests for friction and wear without lubricant on a tribometer under a load of 20 N at room temperature and roundabout motion of a ruby ball penetrator on a disk are presented along with data on kinetic indentation with determination of the nanohardness and elastic module and observations of the fracture surface structure and friction track using a scanning microscope. Methods of the transmission electron microscopy of thin foils in dark and bright fields and Raman spectroscopy, respectively, were used to determine the microstructure in the bulk of a nanocomposite and prove the graphene thermal stability during plasma spark sintering. It is shown that introduction of graphene contributes to the increase of micro- and nanohardness, elastic modulus, wear resistance by two or three orders of magnitude and a slight decrease in the coefficient of friction. Increase in graphene content to 2 wt.% changes the wear mechanism from brittle breakage to viscous shear due to strengthening in coupling of matrix grains and presnrce of agglomerates. Lack of degradation and retention of graphene thermal stability are proved. The morphology of graphene particles indicates to their preferential arrangement inside the corundum grains and more rarely — on the grain boundaries.

Reprint of: Improvements on thermal stability of graphene and top gate graphene transistors by Ar annealing

Thermal annealing of graphene was studied to improve the thermal stability. During the annealing under an Ar atmosphere with temperature from 100 °C to 600 °C, graphene exhibits partial removal of PMMA residues, low density of defect cracks in SEM images and relatively low ID/IG ratios in Raman spectrum probing. For a top-gated graphene transistor with thermal annealing, it performs high carrier mobility up to 3500 cm2 V−1 s−1 and slightly asymmetric bipolar behaviours as well as slight Dirac point variation within ±0.2 V.

Improvements on thermal stability of graphene and top gate graphene transistors by Ar annealing

Thermal annealing of graphene was studied to improve the thermal stability. During the annealing under an Ar atmosphere with temperature from 100 °C to 600 °C, graphene exhibits partial removal of PMMA residues, low density of defect cracks in SEM images and relatively low ID/IG ratios in Raman spectrum probing. For a top-gated graphene transistor with thermal annealing, it performs high carrier mobility up to 3500 cm2 V−1 s−1 and slightly asymmetric bipolar behaviours as well as slight Dirac point variation within ±0.2 V.

Graphene–nickel interfaces: a review

Graphene on nickel is a prototypical example of an interface between graphene and a strongly interacting metal, as well as a special case of a lattice matched system. The chemical interaction between graphene and nickel is due to hybridization of the metal d-electrons with the π-orbitals of graphene. This interaction causes a smaller separation between the nickel surface and graphene (0.21 nm) than the typical van der Waals gap-distance between graphitic layers (0.33 nm). Furthermore, the physical properties of graphene are significantly altered. Main differences are the opening of a band gap in the electronic structure and a shifting of the π-band by ∼2 eV below the Fermi-level. Experimental evidence suggests that the ferromagnetic nickel induces a magnetic moment in the carbon. Substrate induced geometric and electronic changes alter the phonon dispersion. As a consequence, monolayer graphene on nickel does not exhibit a Raman spectrum. In addition to reviewing these fundamental physical properties of graphene on Ni(111), we also discuss the formation and thermal stability of graphene and a surface-confined nickel-carbide. The fundamental growth mechanisms of graphene by chemical vapor deposition are also described. Different growth modes depending on the sample temperature have been identified in ultra high vacuum surface science studies. Finally, we give a brief summary for the synthesis of more complex graphene and graphitic structures using nickel as catalyst and point out some potential applications for graphene-nickel interfaces.

Устойчивость графена и материалов на его основе при механических и термических воздействиях

Устойчивость графена и материалов на его основе при механических и термических воздействиях, Галашев А.Е., Рахманова О.Р.

Thermal Stability of Graphene and Nanotube Covalent Functionalization

We study kinetic factors governing the diffusion and desorption of covalently grafted phenyl and dichlorocarbene radicals on graphene and carbon nanotubes. Our ab initio calculations of reaction rates show that isolated phenyls can easily desorb and diffuse at room temperature. On the contrary, paired phenyls are expected to remain grafted to the surface up to a few hundred degrees Celsius. In the case of dichlorocarbene, no clustering is observed; at room temperature, the isolated radicals remain covalently attached to small-diameter nanotubes but desorb easily from graphene. Our results on the thermal behavior of side moieties on graphitic surfaces could be used to optimize the tradeoff between reactivity and conductance of nanotubes in the process of covalent functionalization.