Preparation, characterization, and physical properties of graphene nanosheets and films obtained from low-temperature expandable graphite

Abstract

Graphene nanosheets have been prepared from low-temperature expandable graphite by ball milling and subsequent ultrasonication. The as-prepared graphene nanosheets were characterized by ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy, atomic force microscopy, differential thermal analysis, etc. The graphene concentration in the suspensions could be increased proportionally by simply extending the milling and ultrasonication duration. The graphene morphology changed from ribbons to single-and few-layer nanosheets with a porous nature. After milling for 40 h, the average number of stacking layers was estimated to be 3.5 for the graphene nanosheets. The lateral dimension of the defect-free crystallites decreased with the milling time, whereas the structural defects mainly from the graphene edges increased accordingly. The exfoliation process was interpreted in terms of complex factors, including weak interlayer attraction, shear-induced dislocation bands, and acoustic cavitation of ultrasonic irradiation. The sheet resistance of the graphene films dramatically decreased after the thermal treatments, especially in reducing atmospheres. This facile approach appears promising for its potential applications in functional composite materials.

Preparation and tribological properties of eco‐friendly as‐exfoliated graphene in grease

“…The UV-vis spectra shown in Figure 1C confirm that the absorbance peaks of F I G U R E 1 A, XRD patterns, B, FTIR, C, UV-vis, D, Raman spectra of GO and GN-900-C the GN-900-C suspension appear at 265 nm compared to GO (230 nm), which is assigned to the π!π* transitions of aromatic C─C bonds. 2,22 It is worth noting that the UV absorption peak of GN-900-C is stronger than GO due to the addition of H 2 C 2 O 4 to assist in expansion and exfoliation. This phenomenon implies that more graphene nanosheets were uniformly dispersed within the solvent due to enhanced exfoliation.…”

“…In the past, many novel methods could prepare the high-quality graphene nanosheets, including the supercritical fluid exfoliation, mechanical exfoliation, solvothermal synthesis, liquid phase expansion, electrochemical exfoliation methods etc. [1][2][3][4][5][6][7] Li et al 1 prepared high-quality graphene by supercritical CO 2 fluid exfoliation method. More than 90% of the graphene nanosheets were less than 10 layers thick and had no oxygen-containing functional groups on the surface.…”

“…However, these expansion-exfoliation methods above still existed the unsatisfied issues for the large-scale and green production, such as solvent pollution, toxic element residual and larger thickness. [2][3][4][5][6][7] Consequently, it was imperative to develop the expansion-exfoliation agent without toxic residual and solvent pollution while guaranteeing to prepare the highquality graphene nanosheets from graphene oxide (GO).…”

Effect of Ammonium Bicarbonate on Intercalation and Exfoliation of Graphite Materials

“…The G peak at 1580 cm -1 is caused by the stretching of the sp 2 -type C-C bond in the hexagonal ring structure of the graphite lattice [14], and the G′ peak (2D peak) at 2700 cm -1 is attributed to the vibration of the two-photon lattice. The information in the figure shows that NG and EG have high crystallinity and few defects, while GO has a large number of defects and low crystallinity [15]. EG and GO have different degrees of interlayer oxidation, and GO has a higher degree of oxidation.…”

Surface-Modified Graphene for Mid-Infrared Detection

“…The engineering of band structure of graphene sheet has been extensively studied. Band gap about 0.5 eV can be formed in nanoribbons with the width about 10 nm [20][21][22]. In this method, controling the value of band gap which is strongly affected by the structure of nano ribbons edges is difficult.…”