Applied Mechanics and Materials Vols. 313-314

Abstract: Behavior of sodium metal subject to geometrical constraints has been studied at variable temperatures. A porous medium, Vycor glass of an average pore size of 9.2 nm, was loaded with Na by vacuum vaporization. Synchrotron X-ray powder diffraction of the specimen revealed the existence of close-packed phases such as FCC, HCP, 9R and 4H already at room temperature whereas the bulk BCC phase of Na was completely absent. In contrast, close-packed phases in bulk sodium are only observed at temperatures below 35 K upon cooling. This result can be qualitatively understood in view of earlier zero Kelvin calculations from which it is well known that the differences of structural energies between BCC and close-packed phases are very small. As a consequence, also various close-packed structures can be formed at ambient temperature under certain conditions and environments. The lattice expansion in the restricted geometry has been determined in the range of 160 K to 300 K and compared with the bulk metal. Confined Na exhibits smaller lattice expansion as compared to that of the bulk which likewise can be explained as being due to confinement.

Abstract: Tensile and compressive creep tests of the extruded magnesium alloy AZ91D were carried out in vacuum at 150°C under constant engineering stresses ranged from 60 to 150 MPa. From the test results, the secondary creep rate in tension was found to be significantly higher than that in compression. Moreover, the estimation method of creep curve under a constant true stress was proposed by considering the reduction of cross sectional area during tensile loading where the specimen cross-sectional area and length were measured periodically until the end of creep test. The creep curve under a constant true stress obtained in the present study was still different between tensile and compressive loadings. Therefore, it should be noted that the different creep curves and creep exponents should be used in the creep deformation analysis of structures.

Abstract: The purpose of this study is to investigate the strength and mechanical properties of concrete by partial replacement of cement with nano-pigment particles. Nano-pigment particles with the average diameter of 120 nm were used with ten different contents of 0.5%, 0.1%, 1.5% and 4.0% by weight. have been investigated by scan electron microscopy(SEM) ,¬X-ray diffraction(XRD).The results showed that the use of nano- pigment particles up to maximum replacement level of 4.0% produces concrete with improved strength and mechanical properties The SEM study of the microstructures between the cement mortar mixed with the nano-pigment particles and the plain cement mortar showed that the nano-pigment particles as a partial replacement of cement up to 4 wt% could accelerate C–S–H gel formation as a result of the increased crystalline Ca(OH)2 amount at the early ages of hydration.

Abstract: The results of studies relating to the use of porous silicon as the basis for the creation of nanostructured getter layers for MEMS are presented. New technical solutions, in which the porous silicon with pores of micro- and nanometer range is used as a matrix for the deposition of reactive metals or metal alloys, were developed. The research results can be used to create getters for MEMS, as well as in other areas which require the creation of structures with a developed surface.

Abstract: BCNO nanomaterials were obtained by mixing charcoal with boric acid and urea, and then heat treated at high temperatures. Their microstructures and electromagnetic parameters were characterized and discussed. TEM analysis revealed the analogues of few-layered graphenes after doption. Aditional ammonia treatment was also studied, which could lower the real part of the permittivity and adjust the reflectivity peaks.

Abstract: Poly (vinylidene fluoride-hexafluoro propylene) (PVDF-HFP), Poly (methyl methacrylate)-grafted natural rubber (MG49) (70/30) complexed with different compositions of lithium trifluoromethane sulfonate (LiCF3SO3) based solid polymer electrolyte has been prepared using solution casting method. This work has demonstrated that conductivity values were found to depend upon the concentration of LiCF3SO3. The highest ionic conductivity was 1.97×10ˉ4 S cm-1at 25 wt. % of LiCF3SO3 at room temperature. X-ray diffraction (XRD) indicates decrease in the degree of crystallinity by increasing of salt concentration.

Abstract: A new intercalation of Indium and Zinc Phthalocyanine(ZnPc) thin films is developed by using thermal co-evaporation method. Optical characteristics of In-doped ZnPc are studied in comparison with pristine ZnPc, which shows improvement on optical absorption at the visible spectrum. The presence of a new phase transition upon Indium doping is examined and consequently support the idea of the intercalated phase upon doping. A Schottky diode made of Indium doped ZnPc is fabricated in order to measure its electrical properties, its photo-current spectrum confirms the existence of phase transition.

Abstract: The Al2O3 films were deposited onto Al2O3-TiC and Si (100) substrates by RF sputtering technique by varying powers sputter target, substrate bias voltages and fixed process pressure 25 mTorr which aim to achieve high deposition rate and investigated film properties onto different types. Result showed significant power sputter target to deposition rate both substrates and film properties depend on type of substrate. The power sputter target at 8kW and substrate bias voltage at -150 V is optimum deposition condition to provide deposition rate is 53.97nm/min for Al2O3-TiC substrate and 51.50nm/min for Si substrate. The Al2O3 film deposited onto Al2O3-TiC substrate surface morphology displayed rather roughness than Al2O3 film deposited onto Si substrate which verified from SEM and AFM as 0.99 nm (Ra) versus 0.46 nm (Ra). The film stress, hardness, reduces modulus and breakdown voltage (BDV) of Al2O3 film deposited were higher than Al2O3 film deposited on Al2O3-TiC substrates which were correspond to surface morphology.

Abstract: The adsorption and photocatalytic reactions of ethylene and oxygen were investigated by sol-gel routed TiO2 particles. The dependence of ethylene –free oxygen concentrations, oxygen-free ethylene concentrations and the molar ratio of C2H4:O2 in the gas mixture on adsorption and photocatalytic reaction rates were examined. The increase of ethylene –free oxygen concentrations or oxygen-free ethylene concentrations can enhance the adsorption rates while decreasing photoreaction rates. The presence of ethylene and oxygen can increase adsorption rates leading to enhance photocatalytic rates. The photocatalytic rates of ethylene oxidation and oxygen reduction were 10-8 mol. s-1.g-1 evenly at C2H4:O2 molar ratio equal to 3:1.

Abstract: The bolt load loss behavior of AZ91D magnesium alloy bolted joints with a conventional SCM435 steel bolt and an A5056 aluminum bolt was investigated at elevated temperature. The A5056 bolt could reduce the bolt load loss compared to the SCM435 bolt due to smaller mismatch of thermal expansion between the bolt material and the plates. The mismatch of thermal expansion between bolt material and AZ91D plates was found to induce the compressive creep deformation in the AZ91D plates which performed as the main mechanism of bolt load loss. At higher tightening stress, the bolt load loss could be intensified by additional plastic deformation in bolt occurred during the test. Moreover, it is suggested that the plastic deformation could be reduced by decreasing the friction condition in the bolted joint.