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Opening and tuning of the band gap of bilayer graphene (BLG) is of particular importance for its utilization in nanoelectronics. We presented here the electronic structures of two types of stoichiometrically half-fluorinated BLGs (i.e. C2Fs) as well as those under biaxial compressive and tensile strains. Our results reveal that both C2Fs are semiconductor with large direct band gaps in their unstrained configurations. Under biaxial compressive strains, the band gaps of both C2Fs can be reduced. However, by applying biaxial tensile strains, both C2Fs undergo a direct-to-indirect band gap transition. Electronic nature of the strain-tuned band gaps has been discussed.

National Natural Science Foundation [10774124]; Natural Science Foundation of Fujian Province of China [2008J04018]

The structural and electronic properties of anode materials LiMN (M = Ni, Co, Cu) for lithium ion batteries have been studied by the first-principles method. The calculations reveal different bonding characteristics for LiMN (M = Ni, Co, Cu). The Li–N bond on the LiN planes shows covalent mixed with ionic characters, with the covalent interaction strengthened and ionic one weakened gradually from LiNiN to LiCoN and then to LiCuN. In the direction of N–M chains, the bonding characteristics are analogous on the whole. The N–M bonding shows both ionic and covalent characters again, while the covalent interaction slightly weakened in sequence. Electronic structure calculations suggest that LiMN (M = Ni, Co, Cu) are all metallic, where the LiNiN is of anisotropic conductivity along the directions of N–Ni chains, while for LiCoN and LiCuN, electrons can also be feebly conductive on the LiN planes besides along the linear N–Co and N–Cu chains.

A room temperature fast curing epoxy resin nano-adhesive was prepared and modified by nano-SiO2 and liquid rubber CTBN. It shows good shear strength value and heat-durability and also meets the conditions of room temperature and short solidified time. Compared with conventional resin mixing method, adhesive modified by nanomaterial can achieve better heat-durability. Compound cation/nonionic surfactants were used for modifying nano-SiO2 and solution mix method was used for preparation of nano-SiO2 epoxy resin adhesive. The effects of nano-SiO2 to adhesive’s mechanical property and heat-durability were investigated. Adhesive with 2wt% nano-SiO2 shows improved properties which shear strength value is 17.9 MPa and vitrification point is 216.5°C. Micropores and grains of nano-SiO2/liquid rubber CTBN modifying system were observed using scanning electron microscope. Adhesives were investigated using infrared spectroscopy analysis. Nano-SiO2 modified using compound surfactant has higher reacting activity and accelerates the reaction of adhesive. It can be used as catalyst.

High temperature tribological behavior of nano-Al2O3 in different base oils were tested by a SRV multifunctional test system. The results show that the nano-Al2O3 particles can obviously improve the antiwear and friction reducing properties of the base oil under high temperature and high load. The friction coefficients of the base oil with added nano-Al2O3 are reduced about 35%, and abrasion loss reduces about 60%. When temperature is 500°C and load is 500N the pure base oil has lost lubricative function, but the base oil with added nano-Al2O3 can still remain the lower friction coefficients. Tribological behavior should be similar to the “ball bearing” lubrication action of the nano-Al2O3 particles, so the movement between the two tribological pairs becomes sliding/rolling.

A new technology, duplex ion nitrocarburizing and sulphurizing technology (DINS), for friction reduction and anti-scuffing applications of diesel engine cylinder was studied. Duplex ion nitrocarburized-sulphurized layer was prepared on the surface of CrMoCu alloy cast iron by using the DINS process. The morphology, phase structure and tribological behaviors under sulphur contained additive lubrication were investigated. Results show that the sulphide surface layer of the duplex layer is mainly composed of close-packed hexagonal structured FeS phase and cubic structured FeS2 phase. The nitrocarburized sub-surface layer of the duplex layer is mainly composed of Fe2C and Fe3N phases. The harder nitrocarburized layer can provide effective support to the softer sulphide layer and avoid its lamellar tear. The synergistic effect between the duplex layer and the sulphur contained additive lubricant, resulted in 10% and 33.3% reduction in coefficient of friction and wear volume, respectively, compared with those of the sulphurized surface, and 25% and 50.1% reduction, respectively, compared with those of the plain surface. Bench test of diesel engine further demonstrated that the DINS process can provide the treated cylinder with superior properties in anti-scuffing and friction reduction, so that it can be used to prolong the service life of the cylinder.