Liangsen Liu

A facile strategy to prepare functionalized graphene via intercalation, grafting and self-exfoliation of graphite oxide

A facile method of successive intercalation, grafting and exfoliation of graphite oxide in monomers by γ-ray irradiation to obtain functionalized graphene nanosheets was reported. The monolayer percentage of functionalized graphene nanosheets was sharply increased and the agglomeration showed a significant decrease.

Oxidation and disorder in few-layered graphene induced by the electron-beam irradiation

Structural changes caused by an electron beam with the high irradiation energy of 5 MeV were investigated in few-layered graphene. Both the original and the irradiated few-layered graphene were characterized by x-ray diffraction, Raman spectroscopy, and x-ray photoelectron spectroscopy. It was found that a typical diffraction peak of graphene oxide emerged and this may be attributed to a partial oxidation in few-layered graphene which was induced by the irradiation. In addition, the graphitic structure of few-layered graphene was found to be disordered according to the increased intensity ratio of D to G band.

Modifying graphite oxide nanostructures in various media by high-energy irradiation

The alterations of GO nanostructures after γ-ray irradiation in water, air and styrene with an absorbed dose of 200 kGy are systematically investigated. The interlayer structures of the ultimate products are confirmed to be remarkably different from each other due to the distinct changes of functional groups on single-sheets in various media. After irradiation in water, oxygen groups in graphite oxide are shown to be obviously decreased owing to the generation of reductive radicals by the decomposition of water molecules, which is reflected in the decrease of graphite oxide interlayer spacing. The interlayer distance of graphite oxide irradiated in air is found to be significantly increased, which may be attributed to the increase of the hydroxyl groups and the topological defects. However, the graphite oxide seems to be mainly exfoliated and functionalized by the intercalation of the monomers and the grafting of polystyrene chains when irradiated in styrene. It is expected that γ-ray irradiation in different media should be a promising strategy for manipulating nanostructures and properties of graphite oxide for improving its applicability in fields of composites, catalysts and sensors.

Modification of surface functionality and interlayer spacing of multi-walled carbon nanotubes using γ-rays

The surface functionality and interlayer spacing changes induced by γ-ray irradiation were investigated in multi-walled carbon nanotubes (MWCNTs). The modification effect of MWCNTs irradiated in air and epoxy chloropropane (ECP) was characterized by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. The results indicated that γ-ray irradiation in two different media improved the amount of oxygen-containing functional groups on nanotube surface, and the irradiation in ECP was more efficient. Compared with the pristine MWCNTs, the MWCNTs irradiated in air exhibited a decrease in width of G band and intensity ratio of D to G band in the Raman spectra and an increase in intensity and diffraction angle of (002) characteristic x-ray peak. However, the MWCNTs tended to show the opposite behaviors in Raman spectra and x-ray diffraction patterns after they were irradiated in ECP. This preliminary study suggests that γ-ray irradiation in air can meaningfully decrease the interlayer distanc...

Improving dielectric properties of poly(vinylidene fluoride) composites: effects of surface functionalization of exfoliated graphene

To investigate the effects of surface functionalization of exfoliated graphene (EG) on the crystalline form of β-phase and dielectric properties of poly(vinylidene fluoride) (PVDF), we prepared PVDF-based composites reinforced by different functionalized EG. The X-ray photoelectron spectroscopy results indicated that a wide variety of chemical functional groups such as C–OH, C–O–C, C=O, COOH and C–F could be introduced on the surface of modified EG. As confirmed by results of Fourier transform infrared spectrum and X-ray diffraction, the β-phase PVDF can be produced in the composites with the incorporation of functionalized EG. In the frequency ranging from 102 to 107 Hz, the dielectric permittivity of PVDF composites shows an obvious increase owing to a variation of the carbonyl group (C=O) content. Among all the composites, the EG grafted with polymethyl methacrylate/PVDF composite has the highest dielectric permittivity and dielectric loss.

Effects of ion irradiation on carbon nanotubes: a review

Ion irradiation with energetic particles can successfully be used for changing the properties of carbon nanotubes (CNTs) by functionalising, connecting, and creating defect structures in the CNTs. In this paper, we focus on the recent progress in our understanding of ion-irradiation-induced phenomena in CNTs. The production of defects (vacancies and interstitials) and the structural change of CNTs were reviewed. The ion induced modification of the properties was illustrated and the factors such as the substrate, the circumstance of the ion and the temperature which affect the defects and the properties of the ion-irradiated CNTs were also briefly investigated. By summarising the predecessors’ research, we point out the issues which still lack complete investigating and further outline the most promising ways of using beams of energetic particles for CNT-related nano-engineering.

Synergetic improvement of mechanical properties and surface activities in γ-irradiated carbon fibers revealed by radial positioning spectroscopy and mechanical model

The relationship between microstructures, surface activities, and mechanical properties of γ-irradiated carbon fibers has been evaluated quantitatively. X-ray photoelectron spectroscopy combined with argon ion sputtering indicated that the outer-surface part (∼10 nm) was functionalized and disordered by the grafting reaction; this led to an increase in the surface activity and loss of mechanical properties of γ-irradiated carbon fibers. The degree of covalent cross-linking between subsurface layers of graphene (∼1.5 μm) showed a more notable increase than that of the core (∼4 μm); this indicated that the sub-surface was mainly responsible for improvement in the tensile strength of γ-irradiated carbon fibers. Increases of 15.5% (argon) and 13.3% (epoxy chloropropane) in tensile strength were achieved. Moreover, interfacial shear strength of a single fiber in matrix increased by 19.15% (argon) and 75.03% (epoxy chloropropane). Therefore, this spatially resolved study paved a meaningful way to understand the relationship among microstructures, surface activities, and mechanical properties of γ-irradiated carbon fibers.

Modification and shaping of carbon nanotubes with an electron beam

Abstract The paper reviews the modification and shaping of electron beam irradiation on carbon nanotubes (CNTs), as well as how this could be potentially useful for electron beam modification of nanotubes. The influence of irradiation on the mechanical property, electrical property and field effect of CNTs is discussed. Several examples are given with particular emphasis on the cutting, shaping and welding of CNTs by the electron beam in an electron microscope. It is shown that the change of incident electron energy and ambient temperature will lead to the different irradiation results. It is expected that electron irradiation studies will continue to play an important role in the research on CNTs.

Small angle X-ray scattering study of microvoid evolution and pertinence of microvoid and mechanical properties in γ-irradiated CFs

To explore the mechanism of microvoid evolution and the pertinence of microvoid and mechanical behavior of carbon fibers (CFs) in γ-irradiation, T700 CFs were exposed to γ-rays under epoxy chloropropane (ECP) and argon (Ar) at room temperature. The results from small angle X-ray scattering (SAXS) showed that the average microvoid radius of the CFs decreased gradually from 4.8406 nm for pristine fibers to 3.6868 nm (ECP) and 3.4223 nm (Ar), indicating that γ-irradiation could obviously decrease the microvoid in CFs owing to annealing and rearrangement effects. More significantly, active media would enlarge the surface microvoid of fibers, thus the microvoid of CFs irradiated in ECP was overall larger than that in Ar. The tensile strength of CFs was increased from 5.74 GPa for the pristine fibers to 6.78 GPa (Ar) and 6.18 GPa (ECP) for the irradiated CFs along with a decrease in the microvoid. Therefore, this would provide a key to investigate the evolution of the CF microvoid during γ-irradiation, which was conducive to improving the mechanical properties of γ-irradiated CFs.

Surface and Composite Interface of Carbon Fibre Modified by Pre- irradiation

The γ-ray pre-irradiation induced method was employed to study the effect of chloroepoxypropane modification on the surface of carbon fibre (CF) and the interfacial properties of CF/epoxy. Systematic experimental work was conducted to determine the fibre surface topography, fibre surface energy, fibre tensile strength and interfacial adhesion of CF/epoxy before and after γ-ray pre-irradiation grafting. The roughness and surface energy were all found to increase significantly. The tensile strength of carbon fibres was improved marginally by γ-ray pre-irradiation. The surface modification of carbon fibres led to an improvement (at most 18.2%) of the interlaminar shear strength of CF/epoxy composites. The mechanisms of pre-irradiation of CF are proposed.