Papers by Keyword: Interface Layer

Abstract: The paper presents an analysis of positions, which a theory of a liquid wetting a solid surface is based on, using the sitting drop equilibrium as an example. Certain inconsistencies are indicated in these positions, which is the subject of the discussion. The paper explains why the interfacial tension of solid-gas has no effect on the equilibrium of a drop. It proposes a mechanism to form a liquid-solid interface layer, the tensor of interfacial tensions of which is represented as a pressure tensor. It is established that the surface tension of the interface layer is variable and changes in magnitude and direction depending on the wetting conditions. It is determined that it is not possible to present a range of phenomena accompanying the wetting of a solid surface with a liquid by examining the equilibrium of a three-phase contact line.

Abstract: Abstract. Designing highly protective and superior electrically conductive coatings from Cobalt-manganese doped/un-doped oxide materials (CMOs) is the main target of this study. The as-prepared nanopowders were synthesized via glycine nitrate process (GNP) at moderate annealing temperature afterword characterized using several techniques including X-rays diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and electrochemical impedance measurements at room temperature. The XRD results revealed a pure phase of spinel structure with particle size range 75-81 nm for the doped CMO samples. SEM micrographs exhibited morphology with fine aggregate of particles. The incorporation of different ions of Cu, Ni, Fe and Na into the CMOs structure showed a significant increase in the diffusivity of ions and remarkable improvement in the crystallinity. AC electrical conductivity was also measured for the compacted pellets after sintering at 850°C using the electrochemical impedance spectroscopy technique at room temperature. From the obtained results it could be concluded that the polarization resistance of pure and modified CMOs samples show similar behavior ranged from 5 to 6 k Ω.

Abstract: In order to save fuel consumption by reducing the weight of automobile body, the use of aluminum alloys has a great advantage. However, how to join aluminum alloys with steels becomes a big problem in the assembly lines. Cold metal transfer (CMT) is a promising joining process for steel/Al dissimilar materials. To evaluate the shear strength and to investigate the failure modes of CMT brazed lap joints of dissimilar materials, both experimental observation and numerical simulation are performed. A numerical model for the failure criteria of the interface layer failure between steel and aluminum is developed. The interface layer of CMT brazed lap joint can be modeled by the interface element. The failure stress and failure energy at the interface element are proposed as the failure criteria for the prediction of shear strength of CMT lap joints. If steel sheet thickness becomes thicker, stress distribution and concentration at interface layer elements have some change and shear strength at the interface layer can be improved. Then the failure occurring at the interface element may transfer to the fusion line at the side of the aluminum alloy sheet.

Abstract: Diffusion annealing experiments in Al-Ni cold rolled strip was conducted in nitrogen protection. The characterization of diffusion layers between pure Al and pure Ni metals has been analyzed. The analysis results show that the diffusion layers would be composed of solid-solution of Al in Ni marked as Ni (Al), Ni3Al and Ni5Al3 compounds. During diffusion processing, the diffusion speed of Al to Ni was faster than that of Ni to Al. This implied a possibility to form chemical connection of Al-Ni by solid-solution without intermetallic compounds formation to obtain good mechanical and electric properties through optimizing annealing temperature and holding time.

Abstract: Laminated copper films of the epoxy-bonded or diffusion-bonded to the base metal were used in order to investigate and analyze film fatigue behavior depending on the inevitable bonding interfaces for electric/functional parts used in MEMS. Fatigue damage was observed using SEM and crack initiation lives were evaluated at the notch root where the bonding interfaces could be observed directly through the thickness. These observations showed that the resin interface layer caused cracks without slips in a zig-zig pattern and also decreased fatigue crack initiation lives. On the other hand, fatigue damage was observed using an optical microscope on surface of the film with resin bonding or with diffusion bonded interfaces. In this case, many cracks were caused and propagated towards the width direction on the film bonded to the base steel with resin, while slip and cracks were caused along slip lines during fatigue on the film bonded to the base steel by diffusion. There was a significant difference in crack initiation behavior of the films between resin and diffusion bonded to base metals. This finding was not only for crack initiation site but also for roughness near the crack on the film. Using Eulerian equation of motion in continuum, this difference was discussed in terms of elastic displacement field with a wave caused from the base plate subjected to cyclic deformation. Such a wave motion enables us to understand the geometric effects of bonding interfaces on the fatigue damage behavior of the bonded film to base metal.

Abstract: Thermal oxidation process of silicon carbide in ultra-thin oxide regime has been studied by performing in-situ and real time spectroscopic ellipsometry. We found the thermal oxidation at 700°C forms no or extremely thin interface layers between SiC and oxide layers. In contrast, the oxidation at 850°C forms an interface layer of around 1 nm in thickness, having similar thickness and optical constants of the interface layers formed by the oxidation at higher temperature than 1000°C. To make clear the conditions no interface layer is formed, i.e., whether low temperature growth or thin oxide thickness is crucial, we have performed the oxidation at 850°C in the reduced oxygen pressure. Based on the results of these experiments, we discussed the origin of the formation of interface layers as well as the oxidation mechanism of SiC.

Abstract: In our early analytic reports [1,2] has been made the supposition that during the diffusion welding (DW) in subcontact area of SiC is formed the intermediate amorphous layer. In the present work are given the first results of transmission electron microscopy (TEM) and electron diffraction investigations of subcontact layers in n0-n- 4H-SiC. TEM examinations show that the boundary between aluminium and silicon carbide looks like stripy interface layer of ~ 25 nm thickness. This is the evidence that during diffusion welding in subcontact surface layer of SiC the shear micro deformations have been taking place and due to this process the plane inclusions of small-grained phase have been appeared. The image of contact area obtained in diffracted SiC rays (dark field) apparently confirms that stripy zone belongs to silicon carbide because the aluminium (black zone) fell out of contrast. Diffraction picture obtained from bulk zone of silicon carbide looks like monocrystallin, but the micro diffraction pattern obtained from the subcontact (stripy zone) gives a lot of concentric rings, that makes evidential the fact of existence of small-grained inclusions. Deciphering of this electron-diffraction pattern reveals the presence of such elements as residue SiC, Al, Si, as well as inclusions of graphite.

Abstract: The paper reviews recent progress and current challenges in implementing high-k dielectrics in microelectronics. Logic devices, non-volatile-memories, DRAMs and low power mixedsignal components are found to be the technologies where high-k dielectrics are implemented or will be introduced soon. Two gate architectures have to be considerd: MOS with metal as gate electrode and MIM. In particular, Hf-silicates for logic and NVM devices in conventional MOS architecture and ZrO2 for DRAM cells in MIM architecture are discussed.