Papers by Keyword: Surface Evolution

Abstract: In this study, we report the effect of ZnO film thickness on its optical and structural properties. The sol solution was synthesized by sol-gel method and deposited on silicon substrates by spin coating technique. The ZnO films thickness was varied from 60 to 180 nm. The ZnO films obtained showed a highly preferred orientation along the (002) plane. It was also observed that the crystallite size was not affected by increasing thickness. Transmittance measurements indicated that the ZnO films have a high transparency in the visible range (~90 %), which remained constant with thickness. Morphological evolution measurements confirmed that the thinner ZnO film consist mostly of a porous layer which became homogeneous and compact to increase the thickness. Photoluminescence measurements exhibit a strong ultraviolet (UV) emission, and the emission intensity was improved with thickness due to crystallinity enhancement.

Abstract: Zirconia ceramic widely applied in the fields of electronics, instrumentations and mechanical manufacture for its good physical and chemical properties. The ultraprecision lapping technology for the Zirconia ceramic is studied in this paper, and the influence of the different lapping parameters such as slurry, load and lapping velocity on the surface roughness of Zirconia ceramic is discussed. The evolution of surface construction is observed with the microscope to analysis the material removal mechanism. An extremely smooth surface with roughness 6.55nm Ra is obtained in the ultraprecision process. It is also found that the gap in the material will limit improvement of surface roughness and a better surface roughness of 4.72nm Ra was observed when using more compactly material lapped by same method.

Abstract: Deep drawing is one of the most important processes applied in industrial production. Here the Finite-Element-Method (FEM) is an important tool in the development and optimization process. One aspect to optimize simulations is to consider real friction behavior. Thus the friction phenomenon has to be describable. In addition to contact normal pressure and velocity the surface topography and the lubricant amount have a great influence on friction. This paper illustrates the influence of surface evolution in real, inhomogeneous processes on the lubricant distribution. For this a rectangular cup with four different corner radii is used to evaluate local surface topographies and lubricant amounts in deep drawing. The lubricant amount is measured by fluorescence technique and the surface topography is evaluated by a confocal white-light microscope. Due to hydrodynamic effects the lubricant is squeezed out and displaced to adjacent regions. Further hydrostatic pressures built up in closed lubricant pockets force the lubricant to stay in the forming zone to bear a part of the load. In free forming zones without contact between the sheet and tool the surface roughens due to grain dislocations in the microstructure. This paper also presents the results of lubricant distribution and surface evolution by varying the initial lubricant amounts and drawing depth. It can be recognized that the different corner radii of the rectangle cup have a great influence on the surface evolution and lubricant distribution. Moreover it can be clearly seen that surface parameters correlate with the lubricant amount. By means of the described evaluation it is also possible to correlate these values with load histories consisting of contact pressures and strain evolution, evaluated in FEM. All the results contribute to a better understanding of the friction behavior in deep drawing and point out the inhomogeneous character of friction.

Abstract: The Fe3+,La3+ co-doped polyvinyl acetate(PVAc)/titanium dioxide(TiO2) composite nanofibers were firstly prepared by combining sol-gel method and electrospinning process, and then calcined under 300°Cand 600°C separately. The effect of calcination temperature on structures, surface morphologies, crystalline state, elemental composition and photocatalysis activity were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X-ray Diffraction (XRD) , energy dispersive X-ray spectroscopy (EDX) and ultraviolet-visible spectrophotometer(UV-Vis) respectively. The SEM and AFM images showed that the nanofibers were randomly distributed to form the fibrous web, the diameters and surface roughness of nanofibers were obviously changed as the calcination tempreture increasing. The EDX analysis and XRD spectra indicated the percentage of C,O,Ti elements varied as the increase of tempreture and the formation of anatase crystal form TiO2 nanofibers under 600°C.The UV-Vis curves revealed strong adsorption to methylene blue under 600°C calcination.

Abstract: The substructure evolution was observed in the range of scales from dozens nanometers to millimeters on the surface of the aluminum single crystalline plates under restricted cyclic tension. The self-similar systems of crossing bands that create the grid-like ordered structures on different scales are assumed to be clear manifestation of their self-organization. The selforganization of these grid-like structures is assumed to be inevitably related to the crystal structure defects (dislocations, point-like defects and their ensembles). The model is proposed for explanation of 2-dimensional rectangular "tweed" and 3-dimensional rhombic "pullover" pattern formations which are related to cooperative arrangement of crystal structure defects.