Papers by Keyword: Interface Structure

Abstract: Three alternate TiN/AlN nanostructured multilayers with the TiN layer thicknesses of 60, 70, and 120 Å and the AlN layer thickness of 10 Å were fabricated using dc reactive magnetron sputtering. Microstructural characterizations of the three nano-scale films were performed using nonpolarized specular neutron reflectometry. The results showed that the three TiN/AlN multilayer thin films were typical superlattice films and the thicknesses of the TiN layer and AlN layer in the multilayers were consistent with the design thickness nearly. The interface roughness was asymmetric in all the samples. The interface of AlN growing on TiN was much sharper than that of TiN growing on AlN and the latter was the diffusion interface in the TiN/AlN multilayer films.

Abstract: The effects of rolling deformation on the interface bonding strength and microstructure of bimetallic clad plates were simulated. The composition and sub-structure of the interface were analyzed by electron probe micro-analyzer (EPMA) and transmission electron microscope (TEM). The results showed that the interfacial bonding strength of clad plates was significantly depend on the deformation process, and the bonding time was also a significant factor on bonding effect apart from total strain in the two-stage rolling. Chromium, nickel and other alloying elements have a significant diffusion zone at the bonding interface with a diffusion width of about 10µm. High resolution TEM analysis confirmed that there was an sound metallurgical bonding at the interface, and the structure of martensite in transition zone and matrix approximately meet the coherent relationship of(200) Ferrite // (111) Martensite and [020] Ferrite // [211]Martensite.

Abstract: In current research composite copper/tantalum were used as interlayer for explosive welding of titanium and Ni-based alloy sheets. Defects such as cracks coupled with brittle intermetallics compounds were not detected at the interface of dissimilar materials by metallographic analysis. Strength test of obtained composite material reveals growth of yield strength in 2 times in comparison with Ni-based alloy.

Abstract: Morphology and structure of the interface in Ni/Ge thin films being due to the mutual diffusion of these elements are investigated with the help of atomic force microscope, high resolution electron microscope and micro-diffraction. Strong effect of interface in magnetic behavior of Ni layers is demonstrated and explained by formation of magnetic order in the interface and rough boundaries between layers.

Abstract: In order to study the mechanistic differences between recycled aggregate concrete (RAC)and normal aggregate concrete(NAC), the magnifier and scanning electron microscope were used to observe the meso-interfacial structure and microstructure of interfacial transition zone morphology of the RAC respectively, and analysed differences between RAC and NAC; Secondly, the finite element software ABAQUS was used to simulation the simplified model of RAC. The above analysis results show that, there existe a transition zone in the interface, the aggregate-new mortar interface as well as the new-old mortar interface has been obvious cracks before loading, this part is the weak link of RAC ;After loading, the crack occurs first in the old interface, then appeared at the new interface, and then develop to the old mortar, finally, there formed a through crack.

Abstract: The formation of epitaxial graphene on SiC(000-1) in a disilane environment is studied. The higher graphitization temperature required, compared to formation in vacuum, results in more homogeneous thin films of graphene. Some areas of the surface display unique electron reflectivity curves not seen in vacuum-prepared samples. Using selected area diffraction, these areas are found to have a graphene/SiC interface structure with a graphene-like buffer layer [analogous to what occurs on SiC(0001) surfaces].

Abstract: The fundamental aspects of thermal oxidation and oxide interface grown on 4H-SiC(0001) Si-face and (000-1) C-face substrates were investigated by means of high-resolution x-ray photoelectron spectroscopy (XPS) using synchrotron radiation together with electrical measurements of SiC-MOS capacitors. We found that, for both cases, there existed no distinct C-rich transition layer despite the literature. In contrast, atomic scale roughness causing degradation of SiC-MOS devices, such as negative fixed charge and electrical defects just at the oxide interface, was found to be introduced as thermal oxidation progressed, especially for the (000-1) C-face substrate.

Abstract: First principle calculations have been performed to study the interface structure effect on physical properties of the Fe/BaTiO₃/Fe junction. It is identified that Fe on top of the TiO₂- terminated plane with two Fe atoms adsorbed on the two O top sites is the most stable interface. The interface structure is found to affect the ferroelectric behavior of BaTiO₃ layer. With BaO-terminated interface, BaTiO₃ shows larger Ti-O distance compared with TiO₂-teminated interface. In addition, there is a sizable difference in magnetic moments on interfacial atoms at the two interfaces.

Abstract: The joining process of SiCp/A356 composites is investigated. The two substrates are heated up to the melt temperature of Zn27Al filler metal by a resistance heating plate. At the time, a stirrer is introduced into the liquid weld seam in order to mix filler metal and two sides of substrates into a single uniform joint. After stirring, specimens are sectioned for the analysis of macro- and micro-structures along the weld region. The research shows that two typical joint interfaces with oxide film and without one were found. So, oxide film on the substrate wasn’t completely disrupted during stirring brazing at 500°C.And, the tensile strength of joint is only 50MPa.

Abstract: Using analysis methods of stretching test，SEM，EDS and microhardness test to investigate and research the mechanical properties, the fracture mechanism，the reacting phases are produced and the distribution range of vacuum diffusion bonding joints of Ti-6Al-4V/Cu/304. The results show that when bonding pressure is 5.0 MPa, the tensile strenght of the joint increases at first, but decreases with the increasing of bonding temperature and time, When bonding temperature is 1223K, bonding time is 3.6ks, there is a maximum tensile strength that is 163 Mpa. However, it will be disadvantageous to the performance of the joints, when bonding temperature and time extended overly. Using Copper foil as the interlayer, the intermetallic compounds did not generate in interface of Cu/304，Therefore, it formed multi-phase transition organizations by solid solution, intermetallic compounds in interface of Titanium alloy/Cu，such as Ti_xCu_y, Ti_xFe_y and so on. The effect of Ti_xCu_y on strength of the joints is slightly larger than Ti_xFe_y compound. The fracture mainly happened in the titanium alloy side Ti₂Cu intermetallic compound in region Ⅱfor the source dehiscence, developping inⅡ-Ⅲ area junction weak intermetallic compounds of diffusion layer. It is brittle fracture. Therefore, it is the main way to improve the joint strength by improving the interface structure of titanium alloy/Cu side.