Search

The Ag–Cu phase diagram at nanoscale was reassessed by CALculation of PHAse Diagrams (CALPHAD) method, considering the surface effect on the chemical potential of pure substance and excess Gibbs free energy of mixtures. According to the reported thermodynamic properties of pure Ag and Cu nanoparticles (NPs), and the measured melting eutectic temperatures of Ag8Cu2, Ag7Cu3, Ag6Cu5 to Ag5Cu5 NPs, respectively, obtained in the previous works, self-consistent thermodynamic parameters including the size effect were obtained by thermodynamic optimization. Using the obtained thermodynamic parameters, four Ag–Cu nano phase diagrams were constructed, and thermodynamic properties were calculated. It was indicated that the calculated Ag–Cu nano phase diagrams agreed well with experimental data.

The high temperature tribological properties of surface-modified nano-diamond in colza oil were tested with SRV machine, and wear surface morphology was observed by using three dimension profiler. The results show that the modified nano-diamond by dimer ester possesses excellent anti-wear and friction reducing properties as lubricating oil additive. The friction coefficients of the modified nano-diamond by dimer ester are lower than those of nano-daimond and the modified nano-diamond by oleic ester when the temperature is lower than 200 °C, and its friction coefficients are very similar to nano-diamond's when the temperature is higher than 200 °C, but are better than that of the modified nano-diamond by oleic ester. The wear volume of the modified nano-diamond by dimer ester is far-forth lower than that of nano-daimond and the modified nano-diamond by oleic ester after the continuously heating test, and the wear volume decrease 60% than nano-diamond's.

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.

This study investigated the dependence of surface blistering and exfoliation phenomena on post-annealing time in H + -implanted Si〈1 1 1〉. Czochralski-grown n-type Si〈1 1 1〉 wafers were room-temperature ion-implanted with 40 keV hydrogen monomers to a fluence of 5×10 16 cm −2 , and followed by furnace annealing treatments at 400 and 500 °C for various durations ranging from 0.25 to 3 h. The corresponding analysis results for Si〈1 0 0〉 [1] (Liang et al., 2008); [2] (Bai, 2007) were adopted in order to make comparisons. The evolution of blister formation and growth for Si〈1 1 1〉 at 400 °C has a shorter characteristic time compared to Si〈1 0 0〉. However, there is a longer characteristic time when annealing takes place at 500 °C. In addition, no craters were observed for Si〈1 1 1〉 annealed at 400 °C while the opposite is true for Si〈1 0 0〉. The evolution of crater development for Si〈1 1 1〉 annealed at 500 °C has a longer characteristic time compared to Si〈1 0 0〉. These results are attributed to the fact that compared to Si〈1 0 0〉, Si〈1 1 1〉 has a smaller surface binding energy of silicon atoms and a larger areal number density of silicon atoms on the plane perpendicular to the incident-ion axis. Furthermore, Si〈1 1 1〉 has a greater areal number density, smaller diameter, and a similar covered-area fraction of optically-detectable blisters compared to Si〈1 0 0〉. However, Si〈1 1 1〉 has a lower areal number density and a smaller covered-area fraction of craters than does Si〈1 0 0〉. Increasing post-annealing temperature from low (e.g. 400 °C) to high (e.g. 500 °C) revealed that Si〈1 1 1〉 tends to create more blisters while Si〈1 0 0〉 tends to develop larger blisters as well as create more craters.

This study attempted to examine surface blistering characteristics induced by room-temperature implantation of 5 × 1016 cm− 2 40 keV hydrogen ions into Si wafers followed by furnace annealing treatments at various temperatures for a duration of 1 h. The results obtained in our previous work [1], in which Si wafers were used, were adopted for making comparisons. A comparison of Si and Si resulted in blister distributions with greater areal number densities, smaller diameters, similar covered-area fractions, higher threshold and saturation post-annealing temperatures, larger apparent activation energy levels, smaller hydrogen-trapping and oxygen-gettering depths, higher threshold post-annealing temperatures for hydrogen trapping and oxygen gettering, and lower SIMS peak intensities at hydrogen-trapping and oxygen-gettering depths. Furthermore, the K values for Si were less than those for Si when post-annealing temperatures ranged from 200 to 450 °C. Conversely, just the opposite was true when post-annealing temperatures ranged from 450 to 550 °C. In addition, the crater distributions achieved in Si had lower areal number densities and covered-area fractions, higher threshold and saturation post-annealing temperatures, and smaller crater depths compared to Si . In both Si and Si , areal number densities and covered-area fractions in the crater distributions were lower than those in the blister distributions.

In this study, a family of defect-free and structurally analogous sheet-tube frameworks (STFs) constructed by tailored graphene sheets and (3n, 3n) armchair single-walled carbon nanotubes (SWCNTs) was proposed. First-principles calculations have been employed to investigate the structural and electronic properties of two typical STFs, namely, STF(6, 6)-I and STF(6, 6)-II. The results show that both are energetically stable and two-dimensionally conductive on the graphene sheets, a result of charge transfer from the tubes to the graphene sheets. All other defect-free STFs have thus been expected to be energetically stable and similar in electronic behaviors as they are structurally analogous to STF(6, 6)-I or STF(6, 6)-II. In addition, the present STFs are all in porous networks with high surface areas, promising their potential applications in the field of energy storage. The two-dimensional (2-D) conductivity of STFs is also expected to find important potential application in nanoelectronics.

Low temperature ammonia plasma surface treatment on asphalt base carbon fiber is reported with 150°C for 60min, 200°C for 60min and without treatment. The surface topography, chemical composition and structural changes were followed by Atomic force microscope(AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, of which indicate the treatment could improve the density of carbonyl and amino functional group on the surface of carbon fiber, which can also changed carbon crystalline structure. The density of carbonyl and amino functional group was shown higher for the fibers treated at 150°C than for the fibers treated at 200°C which could be attributed to the temperature and introduced Si element factors.

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.

National 973 Program of China [2007CB209702]; National Natural Science Foundation of China [11004165]; Natural Science Foundation of Fujian Province of China [2008J04018]

An asymmetry metal–semiconductor–metal (MSM) structure has been demonstrated in SiGe/Si heterojunction photodetector (HPD) to suppress the dark current of conventional symmetry MSM structure, but the photocurrent are about the same for all symmetry and asymmetry structures. In our study, the Ni, Au, and Cr metals were employed and we found that the Ni/SiGe/Si/Au asymmetry MSM heterojunction photodetector exhibits the lowest dark current for all symmetry and asymmetry structures. Compared to symmetry Ni/SiGe/Si/Ni MSM HPD, the dark current of asymmetry Ni/SiGe/Si/Au MSM HPD was reduced by a magnitude of 127 at an applied reverse bias voltage of 5 V. Moreover, the photo to dark current ratio was also enhanced by 78.6 for the Ni/SiGe/Si/Au asymmetry one at 5 V reverse bias, which exhibits a photoresponsivity of 16.57 A/W.