Preparation and examination of multilayer graphene nanosheets by exfoliation of graphite in high efficient attritor mill

Work Function Modulation of Few-Layer Graphene by Swift Heavy Ion Irradiation

Here, we report the structural and electronic modification induced in chemical vapor deposited graphene by using swift heavy ions (70 MeV Ni⁶⁺).Raman spectroscopy was used to quantify the irradiation-induced modification in vibrational properties. The increase in defect density with fluence causes an increase in the intensity ratio of its characteristic Raman D and G band. The increase in defect density also results in a decrease in crystallite size. The changes in the crystal structure are observed from X-rays diffraction measurement. Swift heavy ion irradiation induced defect, modified the surface roughness and surface potential of graphene thin film as measured from atomic force microscopy and scanning Kelvin probe microscopy respectively. The increase in the work function, surface roughness as well as defect concentration with fluence, indicate the possibility of linear correlation between them. Presence of defects in graphene sheets strongly affects surface electronic and optical properties of the material that can be used to tailor the optoelectronics device performance.

Graphene Nanoplatelets Hybrid Flame Retardant Containing Ionic Liquid and Ammonium Polyphosphate for Modified Bismaleimide Resin: Excellent Flame Retardancy, Thermal Stability, Water Resistance and Unique Dielectric Properties

To achieve the requirements of modified bismaleimide resin composites in electronic industry and high energy storage devices, flame retardancy, water resistance and dielectric properties must be improved. Hence, a highly efficient multifunctional graphene nanoplatelets hybrid flame retardant is prepared by ionic liquid graphite and ammonium polyphosphate. The preparation processes of the flame retardants are simple, low energy consumption and follow the green chemical concept of 100% utilization of raw materials, compared with chemical stripping. The bismaleimide resin containing 10 wt.% of the flame retardant show good flame retardancy, resulting in the limiting oxygen index increases to above 43%, and the peak heat release rate, total heat release and total smoke release decrease by 41.8%, 47.8% and 52.3%, respectively. After soaking, mass loss percentage of the modified bismaleimide resin only decreases by 0.96%, the dielectric constant of the composite increases by 39.4%, and the dielectric loss decreases with the increase of frequency. The hybrid flame retardants show multifunctional effect in the modified bismaleimide resin, due to the physical barrier, the chemical char-formation, hydrophobicity and strong conductivity attributed to co-work of Graphene nanoplatelets, ammonium polyphosphate and ionic liquid.

Graphite Nanoplatelets from Waste Chicken Feathers

Graphite nanoplatelets (GNPs), a functional 2D nanofiller for polymer nanocomposites, utilize natural graphite as a raw material due to its stacked graphene layers and outstanding material properties upon successful exfoliation into nano-thick sheets. However, the increasing demand for natural graphite in many industrial applications necessitates the use of graphite from waste resources. We synthesized GNPs from waste chicken feathers (WCFs) by graphitizing carbonized chicken feathers and exfoliating the graphitic carbon by high-speed homogenization and sonication. We then separated GNP from non-exfoliated carbon by centrifugation. This paper describes the morphology, chemical, and crystalline properties of WCF and its carbon derivatives, as well as the structural features of WCF-derived carbons. We obtained GNPs that have a 2D structure with huge variations in particle size and thickness. The GNP shows the presence of carbonyl groups, which are mostly attached at the edges of the stacked graphene sheets. Defects in the GNP are higher than in graphene synthesized from direct exfoliation of natural graphite but lower than in graphene oxide and reduced graphene oxide. To produce GNP of high quality from WCF, restacking of graphene sheets and concentration of carbonyls must be minimized.

Enhancing Electrocatalytic Activity through Liquid-Phase Exfoliation of NiFe Layered Double Hydroxide Intercalated with Metal Phthalocyanines in the Presence of Graphene

Earth-abundant transition-metal-based catalysts are attractive for alkaline water electrolysis. However, their catalytic properties are often limited by their poor electrical conductivity. Here, we present a strategy for enhancing the electrical conductivity of NiFe layered double hydroxide (LDH) in order to further improve its properties as an electrocatalyst for the oxygen evolution reaction (OER) in alkaline media. We show that NiFe LDH containing metal tetrasulfonate phthalocyanine in the interlayers between the NiFe oxide galleries can be coupled with graphene during liquid-phase exfoliation by taking advantage of their π-π stacking capabilities. A substantial enhancement in the electrocatalytic activity of NiFe LDH with respect to the OER was observed. Moreover, the activity and selectivity of the catalyst materials towards the oxygen reduction reaction were investigated, demonstrating that both the metal hydroxide layer and the interlayer species contribute to the electrocatalytic performance of the composite material.

Melt compounding with graphene to develop functional, high-performance elastomers

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer-ethylene-propylene-diene monomer rubber (EPDM)-using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment.

Preparation and Characterization of Multilayer Graphene by Mechanical Milling and Related Applications for Ceramic Composites

As graphene nanomaterials present exceptional mechanical, thermal and electric properties therefore it can be an excellent reinforcement material for ceramic composites. The research of ceramic composites incorporated with carbon-based fillers has focused on carbon nanotubes until now. In this work silicon nitride-based nanocomposites have been prepared with different ammount (1 and 3 wt%) of multilayer graphene (MLG) made by mechanical milling-based method as well as exfoliated graphite nanoplatelets (xGnP) and nanographene platelets (Angstron) in comparison. The morphology and microstructure of the sintered samples were studied by scanning electron microscope and transmission electron microscope. Phase compositions were determined by X-ray diffractometer. The bending strength and elastic modulus of MLG-silicon nitride composites showed enhanced values compared to the other graphene reinforced silicon nitride ceramic composites.