Advanced Materials Research Vols. 139-141

Abstract: In this paper, the effects of immersion time on the electrochemical impedance spectroscopy model of nano-sized titanium modified epoxy coating immersed in 3.5(wt.%) sodilum chloride solution has been studied using electrochemical impedance spectroscopy(EIS). Through the analysis of the spectra of the coating at different immersion times, the results showed that the spectrum was different at the different immersion times. Therefore, the equivalent electrical circuit was varied with the increasing immersion time and there were the characteristics of the powder in the equivalent electrical circuits (electrochemical impedance spectroscopy model). By the study on the evlolution of impedance model in the given system, it was found that the nano-sized powder played an important part during the electrolyte diffusing to the surface of the substrate and the electrolyte reacting with the substrate

Abstract: The growth mechanism of Onion-like fullerenes (OLFs) synthesized by arc discharge in liquid benzene was discussed. HRTEM was employed to characterize the morphologies and microstructures of the products. Results showed that the typical OLFs were highly crystallized with uniform diameter of 10-30nm. The growth of OLFs depended on the appropriate temperature gradient and quenching zone provided by the bubbles. The aromatic debris could act as graphite fragments composed of hexagonal carbon rings. The reducing of dangling bonds on the edges of graphite fragments would lower the energy of the system, resulting in formation of a close-caged structure at suitable temperature gradient by the auto-curling of graphite fragments. Based on the impact of the innermost core shape, such as C60 shape, quasi-spherical or polyhedral hollow concentric OLFs was formed. Adding ferrocene, ferrocene directly influenced the morphology and yield of OLFs.

Abstract: Bismuth sulfide (Bi2S3) nanorods were successfully fabricated by sonochemical aqueous solution. The morphology, crystallinity and composition of samples at various growth stages were investigated by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). The results showed that the Bi2S3 nuclei had an obvious tendency to arrange themselves in rod-like arrays over extended length scales under soft template. Moreover the crystallinity would be reinforced with the elongation of the aging periods. The growth mode of particle−to−particle by self-assembly under soft template was proposed. The band gap energy of Bi2S3 nanorods was estimated at about 1.36 eV by UV-Vis absorption spectroscopy.

Abstract: Carbon fiber reinforced plastics (CFRP) are typical difficult-to-cut materials because of their anisotropic mechanical properties and poor heat conductivity. Drilling is the most common process in the manufacturing of CFRP products in which delamination is the most potentially damaging defect. In the present work the delamination damage around drilled hole of multi-directional CFRP is analyzed by means of infiltration inspection method with gold chloride solution, and the effects of drill rotational rate and feed as well as drill geometry on delamination are investigated, the damage degrees in laminas near the hole entrance and the hole exit are compared. The experiment proves the infiltration method is applicable for the investigation. The results show that the nearer the distance to the hole entrance or exit, the larger the remains area of infiltration agent is; the remains mark near the hole exit is larger and more irregular than that near the hole entrance, and it has the largest length in the direction along fiber length; a chisel-free drill, a high drill rotation rate combining with a small feed brings on the decrease of delamination damage.

Abstract: A progressive damage method is adopted to predict the structural strength of a woven out-of plane composite bonded π joint. A 3D progressive damage model is established and analyzed via a user defined subroutine embedded into the general FEA package. The numerical prediction gives the information of damage onset, damage propagation and final failure pattern, initial and final failure strength. Three samples of woven composite π joint under tensile load are tested to verify the numerical results. The numerical prediction agrees well with the experimental outcomes. All the numerical and experimental results provide insight into the basic understanding of static strength of woven composite bonded π joint.

Abstract: Pure Al2O3/AlB12/Al composite ceramic powders have been synthesized using high frequency induction heating method. This method starts from Al and B2O3 powder mixtures, after which Al2O3/AlB12/AlN composite ceramics were fabricated by hot-press sintering at 16000C for 2h under the protection of a N2 atmosphere. The bending strength and the fracture toughness of the ceramics were measured by the three-point bending method and the indentation fracture method, respectively. The results show that the pure Al2O3/AlB12/Al composite ceramic powders can be successfully synthesized by high frequency induction heating method. Al2O3 and AlB12 phases were formed by the liquid-liquid reaction mechanism and the liquid-solid reaction mechanism, respectively. The bending strength and the fracture toughness of the Al2O3/AlB12/AlN composite ceramics were 549.48MPa and 5.96MPa.m1/2, respectively. These values are 56.99% and 49% greater than those of the pure Al2O3 ceramic (350MPa and 4MPa.m1/2).

Abstract: A new method of carbon nanotube with electroless plating of nickel is proposed. It is shown that in a certain condition, the compacted and well-distributed coating of nickel is obtained without the process of sensitization and activation. Upon the surface treatment of the carbon nanotube, the CNT-consolidated composites for copper-based electrical contact have been made in the way of powder metallurgy. Some important mechanical properties and physical properties, including sliding wear property, electrical conductivity and fusion resistance, were investigated. The experiment results showed that Carbon nanotube inside the composite was uniformly distributed and a proper addition of CNT effectively improves the comprehensive property of the composites. When the carbon nanotube takes up 4vol. % in the material, it is highly effective in improving its sliding wear property and fusion resistance; though its electrical conductivity drops. Its overall properties meet the requirements of electrical contact materials

Abstract: The present study focuses on the penetrating resistance of the laminated composite with stepwise graded foam target struck normally by conical-nosed projectiles. The dynamic cavity expansion theory is applied to formulate analytical model. Experimental results verify that this model on account of rigid-perfectly plastic-locking model is suitable for analyzing penetration depth of the projectile into a cellular target. The difference types of foam configurations, with identical areal density, were arranged according to the density of the respective foam. The penetrating process can be divided into 7 stages. Penetrating depth; the effect of mass density and the change of graded/layered core structures of the difference configurations are analyzed. It is found that composite target have a higher penetrating resistance than the monolithic foam material target of equal mass. The analytical results show great potential to reasonable structures for absorbing the dynamics energy and improving the overall penetrating resistance.

Abstract: Carbon fiber paper was modified by adding carbon nanotubes to make it reach the demand of gas diffusion layer (GDL) by the process of impregnation with phenolic resin solution dispersed with carbon nanotubes, molding, and carbonization. The properties of modified carbon fiber paper, thickness, density, porosity, gas permeability, specific resistance and tensile strength, were characterized. The results indicate that surface treatment is helpful to disperse carbon nanotubes in phenolic resin. Phenolic resin is used to bond the carbon fibers, and carbon nanotube could reduce the specific resistance of the carbon fiber paper. When carbon nanotube content is 5 %, modified carbon fiber paper is prepared with thickness of 0.30 mm, density of 0.43 g/cm3, porosity of 77 %, gas permeability of 2400 mL•mm/(cm2•h•mmAq), specific resistance of 0.020 Ω•cm and tensile strength of 15 MPa, which basically qualifies for the application requirement.

Abstract: . Zn1-xMnxO films are prepared by radio frequency (RF) magnetron sputtering method. The wurtzite ZnO crystal can be well retained up to a Mn composition of 6.7% and doped Mn ions substituted into Zn sites of ZnO host lattice. All the samples show high transparency over the wavelengths from 450 to 800 nm. Optical transmittance study showed an increase in the bandgap (Eg) with increase in Mn atomic fraction x following Eg=3.26+1.43x eV. Furthermore, the midgap absorption around 420 nm (3 eV) in Mn doped ZnO films suggest that there are impurity levels created by doped Mn ions. The room temperature resistivities of the samples show an increase with the increase of Mn content, which indicates that the doped element is at the status of deep levels.