Advanced Materials Research Vols. 47-50

Abstract: The straight silica nano-rods with a diameter of about 200nm and smooth surface were synthesized by chemical vapor deposition method at 1300°C. The as-synthesized samples were characterized by means of scanning electron microscopy, energy dispersive x-ray, and transmission electron microscopy. The results show that as-synthesized silica nano-rods have a uniform size, well-defined shape, and smooth surface. However, the morphologies and microstructures of silica nano-rods are affected by synthesis conditions, such as the concentration of the SiOx and the the deposition temperature. On the basis of these experimental results, a possible growth mechanism of silica nano-rods in this process is proposed.

Abstract: A simple combustion technique is presented for the preparation of mono-sized silica nanoparticles by employing tetraethyl orthosilicates as precursor. The as-grown white powders were characterized by means of scanning electron microscopy. The results showed the size of silica nanoparticles were relative to the unique synthesis conditions. According to the observation and analysis of the scanning electron microscopy images, the possible growth mechanism of silica nanoparticles in this process is proposed.

Abstract: The straight Y-shaped silica nanorods have been synthesized on Si wafer by thermal chemical evaporation of mixed powders of silica and graphite at 1300°C and condensation on Si substrate without assistance of any catalyst. The synthesized samples were characterized by means of scanning electron microscopy, transmission electron microscopy. The results suggested that the straight Y-shaped silica nanorods have uniform diameter about 50-200nm and neat smooth surface. The growth of such silica nanorods may be a result of the fluctuation of external conditions causing a change in the growth direction of silica nanorods developed.

Abstract: Optimum height of the core and thickness of the composite faces of a sandwich panel under a defined loading have been computed in order to obtain the lowest weight of structure and its highest stiffness. Either by choosing adequate lay up sequence of multilayer composite faces, desired properties of the composite faces was chosen. The Genetic Algorithm (GA) based on statistics was used and to obtain the best methods of G.A., sensitivity analysis was carried out. In result, the influence of sensitivity analysis was found useful because it leaded to a better convergence of problem and decreased the execution time of the problem.

Abstract: The mixing situation of Co atoms implanting onto Cu(001) substrate is investigated with regard to incident energy and substrate temperature by molecular dynamics. The results indicate that higher substrate temperature and/or incident energy will result in higher intermixing between the incident atoms and the substrate atoms. Furthermore, the value of the first peak of the radial distribution function (RDF) becomes lower and wider for the Co-Cu system as the substrate temperature and/or incident energy are increased.

Abstract: In this paper, the three-dimensional charge redistribution of IPMC material under dynamic electric potentials with uncertainty in surface conductivity is studied. The governing equations of charge redistribution are derived from the Nernst-Planck equation, the Poisson equation, the mass conservation equation and the basic electrostatic equations. The surface conductivity is viewed as a Gaussian distribution. A travelling wave type analytical solution is obtained to account for the three-dimensional cation movement under the applied electric potentials.

Abstract: In this article, a novel InGaP/GaAs pnp δ-doped heterojunction bipolar transistor is first demonstrated. Though the valence band discontinuity at InGaP/GaAs heterojunction is relatively large, the addition of a δ-doped sheet between two spacer layers at the emitter-base junction effectively eliminates the potential spike and increases the confined barrier for electrons, simultaneously. Experimentally, a high current gain of 25 and an offset voltage of 100 mV are achieved. The offset voltage is much smaller than the conventional InGaP/GaAs pnp HBT. The proposed device could be used for linear amplifiers and low-power complementary integrated circuit applications.

Abstract: In this study, thermal post-buckling characteristics of functionally graded (FG) panels in hypersonic airflows are investigated. The volume fraction and the material properties of FGMs are continuously changed from ceramic to metal in the thickness direction agreeably to a simple power law distribution and a linear rule of mixture, respectively. Using the principle of virtual work, the governing equations are derived and the finite element method is applied to obtain the solutions. Based on the first-order shear deformation theory (FSDT), the FG panels are modeled by the von Karman strain-displacement relation for the structural non-linearity. Also, the third-order piston theory is employed to consider the aerodynamic non-linearity.

Abstract: Distributed pressure sensing schemes for human positioning and plantar mapping is desired to be unconstrained for human activity in their daily life in the form of a floor and mat. On the other hand, an optical fiber has several advantages such as lightweight, minimal material, and resistance to corrosion and electromagnetic interference. Additionally, a novel hetero-core optic fiber nerve sensor is only sensitive to be bending action of the sensor portion and the fiber transmission line is unaffected to external disturbance as pressure and temperature fluctuation because of its single-mode stable propagation scheme. Therefore, the hetero-core fiber optic sensor could be suitable for the distributed pressure sensing in human natural activity and be placed in various sites. In this paper, we proposed several smart mat applications in the form of a thin mat in the floor for human positioning and sole pressure mapping mat using the hetero-core optic fiber sensors. We successfully demonstrated the distributed pressure sensing mat using hetero-core sensors to detect human positioning with their circumstance and sole pressure mapping.

Abstract: Search of new physical tools for change of structure and properties in volume of a solid body an actual problem is. A composite material at which the chemical compound is constant on all volume, it is possible to make. Reinforcing devices in this material are the structures differing from matrix material on micro- and nano levels. If little-studied phenomenon - the superdeep penetration to use as the physical tool much factorial action in volume of a matrix material is implemented. Thus the design of a specific composite material and unusual properties can be received.