Applied Mechanics and Materials Vols. 110-116

Abstract: In this paper, a linear model of thermoelastic damping in annular microplate is considered for calculating the quality factor of this damping. In this model clamped boundary condition is applied in inner and outer circular edges. In the results, there are critical radius and thickness which are calculated analytically and in these dimensions, the thermoelastic damping becomes maximal. The critical radius and thickness depend on material properties, vibration modes and frequencies, dimensions of microplate.

Abstract: In this paper, thermal characteristics of miniature heat pipes with grooved wick and water-based multiwalled carbon nanotubes(MWCNT) nanofluids(0.1, 0.2, and 0.5 vol.%) as working fluids are experimentally investigated. The thermal conductivity and thermal resistances are measured and compared with those of DI water. The thermal conductivity of water-based MWCNT nandfluids is enhanced by up to 29% compared with that of DI water. Experiments are performed under the same evaporation temperature condition. The thermal resistance of heat pipe is reduced from 30% to 35.2% as the volume fraction of nanoparticles inceasing from 0.1% to 0.5%. Finally, based on the experimental results, we present the reduction of the thermal resistances of the heat pipes compared with conventional heat pipes cannot be explained by only the thermal conductivity of water-based MWCNT nanofluids.

Abstract: The physical properties of nano-Mn3O4 is Characterize by theory base clusters of Physical Chemistry, Including the lattice structure, catalytic properties, the phenomenon of giant magnetic and giant magnetoresistance, N dimensional wave function is approximation to be expressed as variational parameters of nonlinear multivariate function by Density Functional Theory, Extreme functional is obtained by Wavelet analysis ,And analyzed the data characteristics on relationship between Particle size, concentration, temperature, magnetic field strength of a4 , a5 and time, Compared with bulk materials, nano materials, bond angles, bond length parameters, Resolved electron spin states and relativistic effects of the problem, Correction of the uneven distribution of electron density because the error caused.

Abstract: The performance and characteristics of Double Gate MOSFET with high dielectric constant (high-κ) gate stack have been analyzed and compared with those of conventional pure SiO₂ gate MOSFET. Quantum Ballistic Transport Model has been used to demonstrate the performance of the device in terms of threshold voltage, drain current in both low and high drain voltage regions and subthreshold swing. The effect of temperature on the threshold voltage and subthreshold characteristics has also been observed. This work reveals that improved performance of this structure can be achieved by scaling the gate length and illustrates its superiority over SiO₂ gate MOSFETs in achieving long-term ITRS goals.

Abstract: Silver nanoparticles were synthesized by a sonochemistry method by using silver stearate and triphenylphosphine as silver precursor and reduction accelerator respectively. The experimental conditions that influence the formation and organization of the particles were investigated, and the particles were characterized by TEM. Results showed that well-ordered two-dimentional (2D)-monolayer was formed after solvent evaporation on a carbon-coated copper TEM grid at the optimal experimental conditions which was that the mole percentage of the amount of reducing agent and triphenylphosphine to silver precursor was 10% and 50% respectively, and the ultrasound power was set at 60% (relative to the maximum ultrasound power value of the machine).

Abstract: The nano-Ru/[Bmim][BF₄] catalyst was prepared for benzene selective hydrogenation in 1-n-butyl-3- methylimidazolium tetrafluoroborate [Bmim][BF₄] by chemical reduction method. TEM analysis of these nanoparticles sho wed the monodisperse Ru⁰ particles which were prepared by positive dropping method dispersed in the ionic liquids with diameters less than 5nm. The Ru⁰ particles which were prepared by reverse dropping method agglomerated with diameters more than 10nm. KBH₄ was the suitable reductant. The optimum loading of Ru was 1.5%. The hydrogenation activity of Ru/ [Bmim] [BF₄] was high and the selectivity of cyclohexene was very low. Selectivity of cyclohexene was only 14.5% at 27.3 % benzene conversion.

Abstract: The single perovskite BiFeO₃ nanoparticles were prepared by a sol-gel process. The BiFeO₃ nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy, and Brunauer-Emmett-Teller (BET) method. It was found that the prepared BiFeO₃ nanoparticles show the large specific surface area of 136 m²/g, and narrow band gap of 2.12 eV. Consequently, BiFeO₃ nanoparticles show high visible-light photocatalytic activity for decomposition of methylene blue in comparison with the commercial Degussa P25. It is concluded that the large specific surface area and the narrow band gap contribute to the high visible-light photocatalytic activity through enhanced adsorption capability and visible-light absorption.

Abstract: Uniformly distributed and quasi-perpendicular patterned ZnO nanowires were synthesized on Ag electrodes coated Si substrate by thermal evaporation. Field emission (FE) measurements show that its turn-on field is 3.65V/µm at current density of 10µA/cm2 and its the threshold field at current density of 1mA/cm2 is about 6.56 V/µm at an emitter-anode gap of 400µm. and the fluctuation of FE current density is smaller than 10% for 3.5h at electric field of 6V/µm. The low turn-on field and good stability indicates that it offers advantages as field emitter for much potential application.

Abstract: Anisotropic hydrogels based on acrylamide were prepared by frontal photopolymerization. First hydrophilic microgels (HM) were spreparaed by inverse emulsion photopolymerization, and secondly hydrophilic reactive microgels (HRM) with C=C double bonds were synthesis by chemical modification of the HM used N-methylolacrylamide, Last, HRM hydrogels were synthesis by frontal photopolymerization using HRM as crosslinkers. Only one direction of the HRM hydrogels show excellent fracture strength and tensile elongation but the other two directions show little fracture strength and tensile elongation. The reason of the high mechanical performance in the given direction is that the hydrogels are crosslinked by HRM as a new crosslinking agent instead of the conventional crosslinking agents and these nanoparticles can self-assemble into anisotropic structures and the structure can be stabilized by free radical polymerization. The anisotropic hydrogels could use potential materials such as artificial muscles tissue.

Abstract: In the paper, ZnO nanopowders were synthesized by one-step hydrothermal synthesis using zinc acetate and sodium hydroxide as raw materials. The influences of molar concentration of NaOH and synthesis temperature on the properties of ZnO nanopowders were investigated. XRD and FSEM were used to characterize ZnO nanopowders. The results showed that; when the molar concentration of NaOH was 0.05 mol/L, 1mol/L and 2mol/L, ZnO micrometer powders were obtained. When the molar concentration of NaOH was 4mol/L, ZnO nanorods or nanosheets were obtained with different reaction temperature. When the temperature was 220°C, ZnO nanorods with the length of 500nm and diameter of 100nm, were synthesised. Pure ZnO nanopowders can be obtained at lower temperature of 100°C by using one-step hydrothermal synthesis. When the synthesis temperature was 100°C and the molar concentration of NaOH was 4mol/L, ZnO nanosheets were produced. The length, width and thickness of ZnO nanosheets were about 800 nm, 500nm and 80nm, respectively.