Advanced Materials Research Vols. 1120-1121

Abstract: In this paper, a variety of methods to prepare nanometer thin films, such as LB film method, self-assembly method, vapor deposition method and oil-water two-phase interface deposition method, are first introduced and compared. Then the self-assembly method is used to prepare the silver liquid-like film for the magnetic fluid deformable mirror. The basic principle of configuration of the silver thin films is discussed and a large area of ordered and close-packed multilayer structures of encapsulated silver nanoparticles is fabricated. The results showed that the film has good reflectivity and stability.

Abstract: By means of solution polymerization, a series of cross-linked starch-g-polyacrylamide/ montmorillonite (St-g-PAM/MMT) nanocomposites were prepared and used to adsorb methylene blue (MB). The effects of different preparation conditions on the adsorption capacity of the nanocomposites were investigated. The experimental results demonstrated that the prepared St-g-PAM/MMT nanocomposites were effective adsorbents for removal of MB from aqueous solution. Furthermore, adsorption capacity increased with the MMT contents up to 14% and decreased as the MMT contents further increased. Adsorption capacity increased with the increasing of the ratio of starch to acrylamide, whereas adsorption capacity decreased with the increasing of crosslinking agent contents.

Abstract: Co₃O₄/Nitrogen-doped graphene (Co₃O₄/NG) composites were synthesized by a simple hydrothermal method. The Co₃O₄/NG composites show a better electrochemical performance than the Co₃O₄/graphene (Co₃O₄/G) composite. The specific capacitance of Co₃O₄/NG electrode is 428 F/g (290 F/g for Co₃O₄/G electrode) at a current density of 1 A/g. As the current density was increased from 1 to 8 A/g, the capacitance of Co₃O₄/NG still retained 57%, significantly larger than that of Co₃O₄/G (40%). Moreover, over 94% of the original capacitance was maintained after 500 cycles (72% for Co₃O₄/G electrode), indicating a good cycle stability of Co₃O₄/NG electrode materials.

Abstract: The purpose of this work was to produce nanocomposites of polylactic acid with oph-POSS (octaphenyl-Polyhedral Oligomeric Silsesquioxanes)-based biodegradable polyester and study morphology, thermal stability and degradation property. Oph-POSS was synthesized via limited-hydrolytic condensation of phenyl trimethoxysilane catalyzed by tetramethylammonium hydroxide. By adding different mass fractions of oph-POSS into the PLA matrix, oph-POSS/PLA nanocomposites were successfully prepared by the solution casting method using chloroform as solvent. SEM(scanning electron microscopy) observations indicated that oph-POSS were homogeneously dispersed in the PLA matrix. The biodegradation rate of oph-POSS/PLA composites was higher than that of neat PLA, moreover, the degradations of neat PLA and oph-POSS/PLA composites underwent the surface erosion mechanism. It was found that the existence of oph-POSS enhanced thermal stability slightly of nanocomposites relative to neat PLA; however, the thermal degradation mechanism of PLA remained unchanged.

Abstract: This paper mainly describes the preparation of carbon nanotubes (CNTs) reinforced BMI/DBA composites, as well as the effects of CNTs contents on mechanical properties of BMI/DBA/CNTs nanocomposites. The results indicated that with the level of hydroxy-modified carbon nanotubes increased, the mechanical properties of the BMI/DBA/CNTs nanocomposites first increase then decrease. When the content of hydroxyl-modified carbon nanotubes was added to 0.75wt%, the mechanical properties of obtained nanocomposites reached the maximum. In addition, the hydroxyl-modified carbon nanotubes were found to be compatible with the polymer matrix effectively.

Abstract: Nanocrystalline silicon (nc-Si) thin film on glass substrate is subjected to excimer laser crystallized by varying the laser energy density in the range of 50~600 mJ/cm². The effect of excimer laser crystallization on the structure of silicon film is investigated using Raman spectroscopy, X-ray diffraction, atomic force microscopy and scanning electron microscopy. The results show that polycrystalline silicon thin films can be obtained by excimer laser crystallization of nc-Si films. A laser threshold energy density of 200 mJ/cm² is estimated from the change of crystalline fraction and surface roughness of the treated films. The growth of grain is observed and the crystallization mechanism is discussed based on the super lateral growth model. The nanocrystalline silicon grains in the films act as seeds for lateral growth to large grains.

Abstract: Wettability is one of most important characteristics for governing the flow and distribution of reservoir fluids in the porous media,the wetting and spreading behavior of liquids on the solid surfaces changes if the wettability of solid surface is altered. Recent studies show the spreading behavior of liquids on solid surface can be significantly improved after nanofluid treatment. In order to investigate the influence of wettability alternation on enhancing oil recovery after nanofluid treatment,flushing oil experiment and contact angle measurement were conducted in the laboratory. The first experiment involved flushing crude oil with the nanofluid and conventional surfactants, respectively. In the second case, the contact angles of oil phase in nanofluid (conventional surfactant solutions)-crude oil-slide systems were measured after treating 36 hours. The results indicated that nanofluid can produce a better flushing efficiency compared with that of conventional surfactant, and the contact angles of oil phase increased from 33° to 118° after nanofluid treatment in nanofluid/crude-oil/slide system. The mechanism of enhanced oil recovery of nanofluid is mainly wettability alternation.

Abstract: Nano-indentation technology was brought to study microscopic mechanical properties of a single-crystalline diamond (SCD). Nano-indentation measurement was conducted on the {100} plane of SCD, and influences of various factors on measured results were analyzed, from which methods were confirmed to improve veracity of measurement. Properties of the indenter were checked with a fused silica sample both before and after indentation on diamond, which provided guarantee to veracity of results on diamond. It was found that tilt of diamond surface had so great influence that it could damage the indenter, and make the indentation curves anomalous. While damage of indenter could be avoided and valid measurement results could be obtained when tilt of diamondsurface was decreased below 0.10º and the maximal indentation force was less than 10 mN. Deformation of the diamond was almost full-elastic during indentation process. Indentation hardness of {100} plane of the SCD was about 70 GPa with standard deviation less than 3 GPa. And there had good reproducibility between two groups of measurements.

Abstract: Graphene is a two-dimensional material consisting of single atomic layers of graphite. Its quality is markedly different from conventional graphite and semiconductor material. In this paper, electrical conductivity and Hall Effect of the graphene were measured at room temperature by Var der Pauw method. An ohmic contact of the sample and the electrodes was constructed and tested before the measurement of Hall Effect. With the help of the Var der Pauw method, the Hall voltages of the samples were measured under the static magnetic field and different input currents. Sequentially, a series of Hall parameters of graphene were obtained. The results shown that the Hall coefficient R_H is 7.00*10^-7 m³/C; the carrier concentration n is 10.52*10²⁴ m^-3 that is fifteen orders of magnitude bigger than silicon; the Hall element production sensitivity K_H is 6.87*10² m²/C and the carrier mobility was 1,882.54 cm²·V^-1·s^-1 which is much bigger than silicon. The measurement results in this paper can provide some reference for graphene’s research and application in related areas.

Abstract: The AlN nucleation layer (NL) has been deposited on Si (111) substrate by metal-organic chemical vapor deposition (MOCVD). The result indicates that the growth mode of the AlN NL is in the form of 2-dimensional plane and 3-dimensional island. The proportion of 3-dimensional region increases gradually and the 2-dimensional region reduces correspondingly with the increase of growth time. The decrease of the coverage ratio of AlN grains in the 2-dimensional growth region is due to the effect of etching. AlN film with the single crystal orientation has been deposited on the optimized AlN NL.