| Expanded Graphite (EG) is a kind of graphite material with highly porous worm-like accordions, prepared by intercalating-expanding natural flake graphite. EG not only has some similar excellent properties with natural graphite, such as cold-heat resistance, corrosion resistance, self-lubricating and non-poison, but also has some properties which natural graphite does not have, such as softness, pliability, compression resilience, sorption, environment harmony, biology compatibility, radiation resistance. In the 1970s, EG was firstly compressed into seal materials with high temperature resistance and/or corrosion resistance. After that, people find that EG has numerous actual and potential applications, such as supports for various dispersed matters, and for uses in conductivity, lubrication, hydrogen storage, adsorption, electromagnetic interference shielding, vibration damping, thermal insulation, electrochemical application and stress sensing. In order to further develop the application field of EG, in the present paper, three new function materials on EG are prepared, including that loading photo-catalyst ZnO on EG and thus forming EG/ZnO composite;sonicating EG and thus forming graphite nanosheets; ball-milling and EG (or mixtures of EG and metal) and thus forming carbon nanostructure materials. We characterize the structures of the corresponding products, and investigate the sorption and decomposition capacities of EG/ZnO, as well as the anti-frication performances of the graphite nanosheets and the ball-milled products as lubricating oil additive. The main research works and results are listed as following.(1) Three EG/ZnO composites, marked as EG/ZnO-1, EG/ZnO-2 and EG/ZnO-3, are prepared by heating a mixture of zinc acetate and water-washed expandable graphite, zinc acetate and dried expandable graphite, zinc acetate and EG, respectively. The composites combine the sorption capacity of EG and the photo-decomposition capacity of ZnO. We characterize the structures of the composites, and investigate their sorption and decomposition capacities for spilled crude oil and for methyl orange in aqueous solution. Results show that: the ZnO doping method markedly influences the distribution of ZnO particles on EG, the structure as well as the sorption and decomposition capacities of the composites. Comparatively speaking, EG/ZnO-3 has the highest remove capacity for methyl orange, methyl orange in aqueous solution can be removed completely after UV irradiating for 2 h. However, its oil sorption capacity is only 26 g/g, which is lower compared with the 50 g/g of EG/ZnO-1 and EG/ZnO-2. Under UV irradiation, the decomposition of crude oil absorbed in EG/ZnO-1和EG/ZnO-2 is faster compared with that in pure EG, among them, the oil in EG/ZnO-2 is decomposed most fast.(2) Three EGs, marked as EG1, EG2 and EG3, are prepared by intercalating-expanding natural graphite, expandable graphite and EG, respectively. The resulting EGs are sonicated, forming three graphite nanosheets (marked as GN1, GN2 and GN3, respectively). We characterize the microstructures of the corresponding products, and investigate the anti-frication performances of the graphite nanosheets as lubricating oil additive.Results show that: compared with EG1, the growth of network pores on the worm-like particles of EG2 is more perfect. On the worm-like particles of EG3, numerous curved graphite sheets with micro scale are observed, and some are multi-layer cylinder-shaped. The average diameters and thicknesses of GN1, GN2 and GN3 are 16μm and 25 nm, 10μm and 11 nm as well as 8μm and 4.5 nm, respectively. The three graphite nanosheets as lubricating oil additive all have anti-frication effect, among them, the effect of GN2 is the most excellent, while GN1 and GN3 have the similar effects.(3) Three EGs, marked as EG600, EG800 and EG1000, are prepared by rapid heating of expandable graphite to 600, 800 and 1000℃, respectively. The resulting EGs are ball-milled, forming carbon nanostructure materials. We characterize the nanostructures of the corresponding products, and investigate the anti-frication performances of the ball-milled products as lubricating oil additive.Results show that: compared with natural graphite, during ball-milling EG1000 and EG600 show a lower decreasing degree of the crystallite thickness along the c-axis, among them, the decreasing degree of EG1000 is the lowest. In the ball-milled EG1000, plenty of in-plane defects are observed, which rarely occur in ball-milled natural graphite. The ball-milled EGs as lubricating oil additive have anti-frication effect, the effect is more excellent compared with natural graphite and EG without ball-milling.(4) By ball-milling the mixtures of EG and metal (Fe or Ni), it is found that: during ball-milling, the amorphization process of EG/metal system is accelerated with increasing the heating temperature of expandable graphite. In addition, metal carbide phase is produced in the ball-milled EG1000/metal system. The metal addition can restrains the amorphization process of EG600 in rate, but it promotes this process of EG1000. The subsequent annealing can increase the crystallization degree of ball-milled EG600, and the additional Ni is helpful for this process. Ball-milled EG partly keeps the pore structure of the original EG, but the Ni addition results in the disappearance of the pore structure. Ball-milled EG/Ni mixtures as lubricating oil additive have anti-frication effect, and the effect is associated with the crystallization degree of EG, better the crystallization degree, better the effect.
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