Absorption and Photocataly tic Degradation of Machine Oil by Exfoliated Graphite-Supported Nanometer TiO2 Material

By loading nanometer anatase onto exfoliated graphite with the sol-gel method, exfoliated graphite-TiO2 composite （EG-TiO2） can be prepared, which can adsorb oil and can also degrade oil. In a technologic condition for preparing EG-TiO2, the impregnated number of times is the most important factor to influence oil-adsorbing capability, that is, when the impregnated number of times increases, the amount of saturation-adsorbed oil decreases. The study of EG-TiO2 photocatalytic degradation of machine oil based on the weight-loss method and infrared spectrum method indicates that EG-TiO2 has obvious effect of photocatalytic degradation for machine oil. Its performance is superior to pure nanometer TiO2 powder because nanometer TiO2 in EG-TiO2 has three-dimension laminar structure and comparatively high adsorption capability.

Sorption Behaviours of Exfoliated Graphite

Exfoliated graphite (EG) is selected as a new kind of sorbent to sorb heavy oil spilled. In order to make use of EG more effectively, some basic experiments are performed to investigate its sorption properties, i.e. , specific sorption, height of saturation layer, sorption time constant. In the present experiments, A grade heavy oil is employed as a standard sorbate. It is concluded that 1) under the condition that the area of solid (filter bottom) liquid (heavy oil) interface is a constant, specific sorption usually decreases when the amount of EG filled or the apparent bulk density increase; however, the specific sorption initially increases when the apparent bulk density is too low and the amount of EG filled is too much; 2) under the condition that the apparent bulk density of EG filled is a constant, the sorption time constant tends to increase when the amount of EG filled increases; however, for a constant amount of EG filled, the sorption time constant will decrease when the apparent bulk density increases.

Environment-friendly preparation of exfoliated graphite and functional graphite sheets

Exfoliated graphite(EG)is promising oil sorbent as well as an intermediate product for the preparation of flexible graphite films(FGFs).It has been a critical challenge to energy conservation and pollution abatement for the traditional EG production technique.Here,we propose a simple and effective preparation method to acquire EG in which flake graphite is intercalated and exfoliated at room temperature,not involving any pollutant emission.The influence factors in the preparation process were explored,such as the amount of H_(2)SO_(4)and H_(2)O_(2),the temperature for the preparation of room temperature exfoliated graphite(RTEG).In contrast to the EG by high temperature exfoliation(HTEG),RTEG exhibits a homogeneous structure and a significantly increased volume and surface area.Moreover,EG blocks with high oil sorption capacity and excellent reuse performance can be obtained by RTEG method.Especially,FGFs fabricated by RTEG has high flexibility,thermal conductivity and electrical conductivity.It suggests that this environment-friendly technology is suitable for large-scale industrial implementation of graphite-based oil sorbents and flexible materials.

High electromechanical reponses of ultra-high-density aligned nano-porous microwave exfoliated graphite oxide/polymer nanocomposites ionic actuators

High elastic energy density and high-efficiency ionic electromechanical actuators were prepared from aligned activated microwave exfoliated graphite oxide(A-aMEGO)/polymer nano-composites,and the electromechanical performance was characterized.The elastic modulus and elastic energy density of the ionic actuators can be tuned over a wide range by varying the polymer(poly(vinylidene fluoride/chlorotrifluoroethylene)[P(VDF-CTFE)])concentration in the nano-composite actuators.The A-aMEGO/P(VDF-CTFE)nano-composite actuators with 35 wt.%of polymer content exhibit an elastic energy density higher than 5 J/cm^(3) and an electromechanical conversion efficiency higher than 3.5%,induced under 4 V.The results show the promise of high-density highly aligned graphene electrodes for high-performance ionic electromechanical transduction devices.

Molecular simulation and experimental investigation of thermal conductivity of flexible graphite film

Flexible graphite film(FGF),as a traditional interface heat dissipation material,has high anisotropy.It is a challenge to enhance both in-plane and through-plane thermal conductivity of FGF.For this reason,the effects of oxygen content,layer spacing,density and particle size on the in-plane and through-plane thermal conductivity of FGF were studied by both molecular simulation and experimental investigation.The simulation results indicate that the ways to improve the thermal conductivity of FGF include reducing oxygen content and layer spacing,increasing the density and matching the size of graphite sheets.The FGF prepared from room temperature exfoliated graphite(RTFGF)has a wide range of adjustable density(1.3–2.0 g/cm^(3))and thickness(50–400μm).The thermal conductivity of the RTFGF is significantly improved after heat treatment owing to reduced oxygen content and layer spacing,which is consistent with the simulation results.Moreover,RTFGF with both high in-plane(518 W·m^(-1)·K^(-1))and through-plane(7.2 W·m^(-1)·K^(-1))thermal conductivity can be obtained by particle size matching of graphite.

Microwave Synthesis of Large Few-Layer Graphene Sheets in Aqueous Solution of Ammonia

Few-layer graphene (FLG) sheets with sizes exceeding several micrometers have been synthesized by exfoliation of expanded graphite in aqueous solution of ammonia under microwave irradiation, with an overall yield approaching 8 wt.%. Transmission electron microscopy (in bright-field and dark-field modes) together with electron diffraction patterns and atomic force microscopy confirmed that this graphene material consisted mostly of mono-, bi- or few-layer graphene (less than ten layers). The high degree of surface reduction was confirmed by X-ray photoelectron and infrared spectroscopies. In addition, the high stability of the FLG in the liquid medium facilitates the deposition of the graphene material onto several substrates via low-cost solution-phase processing techniques, opening the way to subsequent applications of the material.