Advanced Materials Research Vol. 669

Abstract: Through SEM observation from natural and experimental examples of rocky materials, nanocoating texture was found on the shear slip surface (plane, lamellae). Our researching suggested that the nanocoating possesses some textural characteristics including granular, delaminating and rheological one. In general, single nano-sized grain (40-80 nm in diameter) with moderate roundness and sphericity could aggregate into the compound grain, and thickness of the nanocoating (thin shell, film) might reach from μm to cm scale in different rocky materials. Development of the nanocoating textures of shear slip surface could be subdivided into three stages, i.e. strain hardness, strain softening and strain decaying stage, and its forming mechanism is quite similar to the “tribological white layer” which is very common phenomena in metallography. Furthermore, it is determined that the nanocoating lamellae in rocky materials might be capable to constitute a shelter for a reservoir.

Abstract: Use Nanoscale α-Al2O3 as raw materials, prepared by high temperature solid state reaction, we produced the Lithium Aluminate (Li5AlO4) which can directly absorb CO2 at a temperature between 450°C and 650°C. Respectively use the method of scanning electron microscopy (SEM)、X-ray powder diffractometer (XRD) and thermogravimetric analyzer (TG) for the morphology、structure and the performance of CO2 absorption analysises. The results show that the synthesized Lithium Aluminate (Li5AlO4) materials have a performance of CO2 absorption.

Abstract: In this paper Fe2O3 precursor coating on the surface of carbon balls was prepared by hydrothermal method using Fe(NO3)3·9H20 and glucose as the raw materials. After calcination Fe2O3 hollow sphere could be achieved. The influence of pH value on the preparation of hollow Fe2O3 spheres was studied using XRD and SEM respectively. The results show that the pH value has no effect on the formation of Fe2O3 phase, but has a giant influence on the morphology of the hollow spheres. The Fe2O3 hollow spheres were achieved when the pH value was between 3 and 7. The particles with sheet and block structure form when pH7. The mechanism was studied, When 3

Abstract: Hydrothermal synthesis of Cu-saponite was achieved using copper nitrate and sodium silicate as the raw materials. The mixtures of starting materials were treated under hydrothermal conditions at 60–230°C for 6–48h. The effect of different synthetic parameters such as hydrothermal temperature and hydrothermal time on the structure development of Cu-saponite was discussed. All the samples were characterized by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM) and nitrogen physisorption techniques. The results of the study showed that the obtained Cu-saponite exhibited better crystallinity at 200°C for 36h. Both increasing hydrothermal temperature and the duration of hydrothermal treatment yielded better crystallized Cu-saponite as determined by XRD. SEM micrographs revealed plate-like shape of the synthetic Cu-saponite. The results of nitrogen physisorption measurements showed different synthesis conditions resulted in different adsorption-desorption isotherms.

Abstract: SiO₂/polyaniline (PANI) nanocomposites were obtained by chemical oxidative polymerization using ammonium peroxydisulfate as oxidizing agent. The FE-SEM and TEM images showed that nanocomposites presented the core-shell structure with raspberry morphology. The electrorheological (ER) effect of those materials was enhanced by using the ammonium hydroxide to deprotonate the corresponding PANI base. It was found that the yield stress of those ER fluids and its near linear dependence on the electric field were different from the conventional ER fluids.

Abstract: Abstract. The phonon spectrum of zigzag h-BN nanoribbons with the edges passivated by hydrogen atoms under tensile strain along the axis direction were calculated by first-principle calculations. It is found that the uniaxial strain can lead to a narrow frequency range of lattice vibration modes. But it hardly affects the two highest frequency modes due to the vibration of B-H or N-H bonds. In particular, the strain usually promotes the softening of phonon modes. It means that more phonons should be activated at a given temperature. This may result in the changes of thermal properties, such as, heat capacity and vibration entropy.

Abstract: The geometrical and electronic structures of pure graphene and S-doped graphene have been investigated using plane wave pseudopotential method with generalized gradient approximation based on the density functional theory. The local structure change, Mulliken population, density of states, and electron density difference of S-doped graphene have been calculated. It can be observed that the Fermi level shifts towards the conduction band after the doping of sulfur atom. The results also suggest that there are chemical bonds formed between the sulfur and carbon atoms, and the charges transfer from the doped sulfur atom to graphene.

Abstract: High energy ball milling was used to preparation SiC/Al composites flakes. The research found the milling parameter of high energy milling was the ball/powder ration is 20:1, the rotary speed is 800 r/min, the milling time is 100min.Also researched the molding process of SiC/Al composites, the change of grain size and the weight fraction of the SiC, The research also found the mechanical properties of SiC/Al composites affected by the molding process. It was found that to reduce particle size and increasing of weight fraction of SiC, tensile strength of the SiC/Al composites increased. When the weight fraction of SiC in the SiC/Al composites is about 16%, the mechanical properties of SiC/Al composites about the hardness and tensile strength also get the high-point, the hardness and tensile strength is about 95HB and 248MPa.

Abstract: Micro-particles and nano-wires, small outgrowths were found to appear on upper film surface when metal thin film is confined between two Si3N4 layers deposited by magnetron sputtering and is annealed at an appropriate temperature. The stress evolution during this process is monitored by multi-beam optic stress sensor, and is qualitatively interpreted in terms of elastic and plastic deformation, as well as bulk diffusion. Additionally, the interface constraint effect among different layers is explored. Stress relaxation of nano-sandwiched thin films behaves in different stress modes. As a comparative study, Si3N4/Zn/Si3N4 sandwiches were prepared and studied by the same method. Experimental results show that the pertinent geometry is strongly dependent on material types and stress states of the substrates. Finally, an appropriate mode was suggested to interpret this phenomenon.

Abstract: A grinding tool without kinematic pairs, of compactness and low cost, based on the defect that it is difficult to improve the precision of kinematic pairs of traditional grinding methods, is presented in the paper. The operating principle based on elastic waves was analyzed. The grinding tool would realize the ultra-precision machining theoretically and experimentally. Components of the prototype were manufactured, assembled, and tested for the grinding performance to validate the concepts of the precision machining and confirm the simulation results of modal and harmonic analysis. The test results show that the performance of the proposed grinding tool can meet the requirements of the precision grinding. It is confirmed that this prototype can realize the accurate ultra-low-stress and the removal of material under ultra-low-stress circumstance. The research is aimed at exploring new methods and new theories of ultra-precision surface machining and giving a new solution to the problem of ultra-precision surface machining.