Simultaneous chemical reduction and surface functionalization of graphene oxide for efficient lubrication of steel–steel contact

Abstract

13 bonds due to the presence of oxygenated functionalities. 42,46 The π-π* peak red-shifted to 267 nm upon reduction to graphene with hydrazine and the absence of n-π* transitions at 310 nm indicates the removal of the oxygen functionality from GO after reduction by hydrazine. In GO-ODA, the π-π* transitions of graphitic C=C bonds shifted to 266 nm, and n-π* transitions of C-O bonds completely disappeared similar to graphene indicates the simultaneous formation of RGO and functionalization with ODA molecules. Fig 1: (a) FT-IR transmittance spectra of GO, GO-ODA, Graphene, (b) UV-Visible absorption spectra of GO and graphene in water and GO-ODA chloroform medium, (c) Raman spectra of GO, GO-ODA and graphene.Raman spectroscopy is a powerful nondestructive tool to distinguish order and disorder in the crystal structure of materials as Raman scattering is strongly dependent upon its electronic structure. The crystal structure of graphite is altered during the oxidation process of graphite to graphite oxide. However, the reduction process of GO to graphene and GO-ODA partially restored the ordered crystal structure and also repaired few of the structural defects in the

Lubrication of dry sliding metallic contacts by chemically prepared functionalized graphitic nanoparticles

“…However, with an ODA functionalization, the π → π* peak red shifted towards the restoration of the π → π* conjugation in the GO-ODA sample. However, the n → π* transition at 310 nm completely disappeared, suggesting that the oxygen-containing groups were reduced, leading to extended graphitization [43]. Similarly, the π → π* peaks of the GO-ANS appeared at 260 nm with the absence of characteristics of a n → π* transition.…”

“…Figure 12(a) showed a weak intensity Raman signal (G band peak at 1,596 cm −1 ) for the particle film generated with GO at the HS condition whereas at the LS condition, a Raman signal was visible at a much higher intensity at the respective D and G band peak position. The higher intensity signal indicates the presence of a significantly thicker particle film on the wear track [15,43]. The worn track, corresponding to the GO-ODA at LS condition, showed the characteristic |www.Springer.com/journal/40544 | Friction http://friction.tsinghuajournals.com G band at 1,588 cm −1 corresponding to the reduced form of the GO and the intensity was drastically reduced at the HS condition due to the removal of the particle film ( Fig.…”

“…Herein, a modified Hummer's method is employed for the preparation of GO from graphite flakes as reported in our previous study [43]. GO was used as the precursor to create the modified reduced graphene (r-GO) for solid lubrication purpose.…”

Tribological behavior of nanocarbon materials with different dimensions in aqueous systems

“…The FTIR spectrum of Oct-O-GO(1) revealed the characteristic bands of the alkyl groups corresponding to the modification with n-Octanol. In particular, the peaks at 2,853 cm −1 and 2,924 cm −1 are attributed to the symmetric and asymmetric stretching vibration of the alkyl groups, respectively [43]. Moreover, there were several characteristic bands of epoxy groups and no carboxyl groups in the FTIR spectrum of Oct-O-GO(1), which indicates that the carboxyl groups in Oct-O-GO(1) reacted with n-Octanol.…”

In situ synthesis of copper nanoparticles encapsulated by nitrogen-doped graphene at room temperature via solution plasma

“…31 In general, the G band refers to the stretching regions of C-C bonds, while the 2D band indicates a signature of graphitic sp 2 structures. 32 Besides, D band at 1350 cm À1 , which usually refers to the defects, was also observed. These defects can be obtained from vacancies of the atom, grain boundaries, and doping atoms in graphene, or amorphous parts.…”