Applied Mechanics and Materials Vol. 577

Abstract: Carbon nanotubes (CNTs) are the ultimate reinforcing materials for the development of an entirely new class of composites. However, they have the complicated shapes and do not usually appear as straight reinforcements when introduced in polymer matrices. This decreases nanotube’s effectiveness in enhancing the matrix mechanical properties. In this paper, nanostructure having hexagonal representative volume element (RVE), theory of elasticity of anisotropic materials and finite element method (FEM) are used to investigate the effect of helical CNT morphology on effective mechanical properties of nanocomposites. CNT with different helical angles are modeled to estimate the nanocomposite mechanical properties. The results of helical nanotube models are compared with the effective mechanical properties of nanocomposites reinforced with straight nanotubes.

Abstract: In this paper, the prenyl alcohol was catalyzed synthesized by using isoprene and dichloroacetic acid as raw material and sodium dichloroacetate as catalyst. The obtained product was mainly characterized by FT-IR and GC. Furthermore, the olefine acid ratio, reaction time, amount of catalyst, saponification time, NaOH concentration and distilled water consumption were systematically investigated during the work. The optimum reaction conditions were as follows: the olefine acid ratio was 1:2, reaction time was 2h, amount of catalyst was 1.5g, saponification time was 2h, NaOH concentration was 4mol/L and amount of distilled water was 0.2mL, the yield of prenyl alcohol was 26%

Abstract: The anodic aluminum oxide (AAO) films were prepared by anodization method from the 15 vol. % sulphuric acid solution, and prepared AAO films were heat-treated in the ranges of 25~1000°C. AAO films were characterized by EDAX, SEM and XRD techniques, respectively. The crystal phases of prepared AAO film is amorphous. The apertures of AAO film are in 25~30 nm. AAO films are amorphous when heat treatment temperatures of AAO films are below 800 °C. After the AAO film being heat-treated in the ranges of 850°C~900 °C, the heat-treated AAO film are γ-Al₂O₃ film. When the AAO film is heat-treated at 950 °C, the part of γ-Al₂O₃ change into α-Al₂O₃, and the heat-treated AAO film are mixed film of γ-Al₂O₃ and α-Al₂O₃. After the AAO film being heat-treated at 1000 °C, the heat-treated AAO film is α-Al₂O₃ film.

Abstract: Mo-Ni coatings were prepared on Ni alloy by electrodeposition method. The effects of electrodeposition temperature, current density, stir speed and electrodeposition time on deposition rate and microhardness of Mo-Ni coating were researched, respectively. Deposition rate of Mo-Ni coating decreases with the increase of electrodeposition temperature in 35 °C ~ 60 °C. Deposition rate and microhardness of Mo-Ni coating increases with the increase of current density respectively in 15 A/dm² ~ 17.5 A/dm². Deposition rate and microhardness of Mo-Ni coating decreases with the increase of stir speed respectively in 200 r/min to 400 r/min. Deposition rate and microhardness of Mo-Ni coating decreases with the increase of electrodeposition time respectively in 30 min ~ 40 min. When electrodeposition parameters: temperature 35 °C, current density 17.5 A/dm², stir speed 200 r/mi, pH 5 and time 30 min, deposition rate and microhardness of Mo-Ni coatin are as high as 0.269 mg/ cm²·min and 502.4 HV respectively.

Abstract: Co-doped ZnO nanoparticles were fabricated by an electrodeposition method. The XPS results show Co ions have doped into the ZnO crystal lattices successfully. The as-grown sample has no ferromagnetism at room temperature. But after an ammine plasma treatment the room temperature ferromagnetism were detected on Co_0.04Zn_0.96O nanoparticles. The Hall measurement reveals after the treatment the resistivity increase by three orders of magnitude. Although the aspect conductivity is n type, some holes generated by N doping play an important role to induce the ferromagnetic properties for Co doped ZnO sample.

Abstract: Tree-like transgranular cracks were found at the bottom of a expansion joint bellow that had been used for heat-supply network at 90°C and 0.8MPa. A failure analysis was conducted, including visual, microstructural, compositional, and mechanical characterization, to determine the cause and source of the degradation. Branched, brittle cracks were observed in the failure region and exhibited transgranular propagation. The results showed that the concentration of the chloride in the deposit was 248 ppm in the intermittent wet/dry cycles situation. It was determined that the likely cause of failure was neutral pH, Concentrated chloride-induced stress corrosion cracking.

Abstract: In a direct injection turbocharged diesel engine, four fuels with different sulfur content is used to study the effects of emission characteristics in diesel engine. Results show that the smoke emission have certain relations with sulfur content on fuel, the smoke emission decreases remarkably with the decreases of fuel sulfur content, and the sulfur content on fuel has a greater influence on the smoke emission at low load of the diese1 engine, the NO_x emissions has no significant change when the engine fuelled with different sulfur content on fuel, while the CO and HC emissions will drop significantly.

Abstract: Characteristics of diesel engine emission are studied on emulsified diesel oil with diethyl ether through elucidation on their mechanism of exhaust emission reduction. The amount of emission pollutants changes with various engine loads. Comparison is made on the emission effect of engines fueled with diesel oil and emulsified diesel oil respectively. Experiment shows that emulsified diesel oil with 10% of diethyl ether can significantly brought down the emission of NOx and smoke intensity on high load, particularly the emission of HC and CO on low load.

Abstract: Rheological properties and friction resistance properties of CO₂-emulsified viscoelastic surfactant fracturing fluid were investigated on the large-scale test loop of foam fracturing fluid. When the velocity is below 2.8 m·s^-1, the friction pressure drop gradient gradually decreases with the increase of foam quality, however, when the velocity is above 2.8 m·s^-1, the friction pressure drop gradient of VES-CO₂ with higher foam quality is higher than lower foam quality. In addition, frictional pressure drop gradient of the pure CO₂ is higher than the VES-CO₂ fracturing fluid system when the velocity is more than 1.6 m·s^-1. And frictional resistance coefficient decreases with the increase of foam quality and increases slightly with the increase of temperature. Experimental correlation between frictional resistance coefficient and Reynolds number is obtained and has high precision.