Papers by Keyword: Interface

Abstract: Although metal matrix composites (MMC) for the high temperature structural material have been investigated extensively for many years, applications of MMC have been still limited. Among many combinations between the ceramic fibers and the matrix materials, combination of SiC fiber and TiAl based intermetallic compounds has been expected to be one of the best combination, since both SiC fiber and TiAl have demonstrated the capabilities of the low density heat resistant materials. SiC fiber reinforced TiAl composites have been successfully fabricated using hot press method. Optimum temperature and pressure have been determined. SiC/TiAl composite having relatively low fiber volume fraction shows nearly an ideal elastic property applying the law of mixture. Effects of interface layers on the mechanical properties of composites have been studied in detail. Micro-indentation on a single fiber was carried out to examine the pull out strength of SiC fiber quantitatively. Estimated shear stress on the interface was 145-195MPa, those values are quite reasonable since the tensile strength of TiAl matrix was 420MPa and the maximum shear stress would be the half of tensile strength according to Schmid law. Three-point bending tests have been carried out to evaluate the mechanical properties of composites. Fiber volume fraction 8.9% specimen shows ideal bending stiffness compare with the calculated values based on the low of mixture. Reaction layers and the interface between SiC fiber and TiAl have been analyzed by SEM-EDS and XRD. At least two or more reaction layers have been identified. These reaction layers can be explained based on the Si-Ti-C ternary equilibrium phase diagram at 1373K. Optimum conditions of interface structure will be discussed

Abstract: This article aims to study the Performance footing on loose sand soil reinforced with geogrid layers The Load Settlement behavior of the footing under various conditions such as different eccentric value (e), depth of the first geogrid layer (u/B), and vertical spacing between geogrid layers (z/B) was studied. This study presents, the numerical modeling utilizes the finite element package (PLAXIS version 8.2). The soil vertical stress displacement, axial force and footing displacement are discussed by means of a set of finite element results and the validation. The Load carrying decrease with increasing eccentricity values were shown. The optimal spacing between any successive reinforcement layer (z/B) is equivalent to (0.5) for different eccentricity value (e). The PLAXIS output show the failure mechanism developed, and maximum axial force that will be reached in geogrid and footing and the total stress distribution at failure.

Abstract: Wide bandgap semiconductor technology has been generating a great deal of attention due to its fundamental advantages in high power electronics. Understanding and effective control of interfacial properties belong to a group of critical issues requiring progress. In this work, we report progress in wide bandgap interface characterization, achieved using photo-ionization of deep traps under a non-equilibrium condition created by corona-charge bias in deep depletion. This characterization capability is demonstrated on oxidized n-type epitaxial SiC with deep interfacial traps invisible in standard C-V. These traps, initially present at high density, are shown to be reduced by half after a wet anneal. The photo-ionization technique is incorporated in commercially available non-contact C-V (CnCV) metrology [1,2] providing a non-invasive, cost and time saving metrology that benefits development research as well as device fabrication.

Abstract: For precise investigation of distribution for impurity or composition at SiO₂/SiC interface, dual-beam Time-of-flight Secondary ion mass spectrometry (TOF-SIMS) with low energy sputtering beam was available. In addition to the experimental profiles, simulation using MRI model, in which Mixing, Roughness and Information depth were employed as parameters, enabled to acquire a more authentic distribution at the SiO₂/SiC interface. Slight discrepancy on depth profiles between samples with different surface roughness was duplicated on the convoluted profiles in the simulation. Moreover, reconstructed profile of nitrogen indicated a real distribution with less impact of mixing and roughness, although that may contain uncertainty due to incompletion in the simulation model or variation of the distribution owing to detection species in the experiment. From the result of carbon profiles of both experimental and convoluted profiles, the relative discrepancy on the carbon distribution between samples was clarified, which suggested the possibility that a carbon thin layer at the SiO₂/SiC interface would be found in the future.

Abstract: Total hip replacement is surgical procedure which is widely performed in most of the developed countries due to rapid aging. The extensive application of titanium alloy as hip prosthesis can be seen because of its suitable properties such as good biocompatibility, light weight and high strength. However, coating or bond is required as titanium alloy ineffective to be adhered directly with human bone. Hydroxyapatite (HAp) is common coating material used to bond Ti-6Al-4V hip prosthesis with human bone. HAp-Ti-6Al-4V interface is a possible fretting wear region which is subjected to significant contact pressure. HAp-Ti-6Al-4V interface fretting fatigue delamination leads to contact pressure which can accelerate fretting wear behaviour of HAp coating. Present paper discusses the influence of delamination length and fatigue stress ratio on contact pressure distribution at interface of HAp-Ti-6Al-4V using finite element methodology. A simple two-dimensional finite element contact configuration consisting Ti-6Al-4V substrate, HAp coating and contact pad (representing bone) is employed to examine under static analysis. The finite element predicted results highlighted that contact pressure can be promoted under increased delamination length condition and stress ratio of 0.1 (tension-tension). Contact pressure can accelerate HAp coating fretting wear behaviour.

Abstract: Fluxing and tinning processes are usually used to improve the adhesion of the Al bearing layer on steel substrate. Commonly after grinding the surface of the steel substrate, it is briefly immersed in flux solution followed by coating steel surface with either pure Sn (in a process known as tinning process) to promote adhesion between the bearing alloys and the steel. The current work is designated to investigate the influence of tinning material for carbon steel substrate using simultaneous fluxing and tinning mixture technique. The influence of three different tinning materials on the interface structure and shear strength of cast Al-Sn bearing alloy/steel bimetal composite is evaluated for compound casting technique. Sn pure, Sn-3Cu alloy and Sn-7.5Sb-3Cu powder alloys mixed individually with flux are used as tinning materials. It was found that using of different tinning materials have a significant effect on the bonding of interface area and the shear strength of interface as well. The shear strength of the bimetal fabricated using tinning mixture contains Sn+3% Cu with flux significantly increases by 59% compared to that fabricated using tinning mixture contains pure Sn. This increment is mainly due to the improvements of the interface bond structure and lower percentage of tin oxides. Such kind of phenomena can be explained in the fact that Cu minimizes the possibility of Sn oxidation during tinning process and during preheating of tinned steel substrate before casting of Al12Sn4Si1Cu bearing alloy as well.

Abstract: The mechanical behaviour and adhesion properties of thermal oxide scales are key issues for steel processing and long-term durability. This chapter aims at taking up the various aspects to be considered for such studies. The first part is devoted to a description of the origin of stress and stress quantification. Then, description of mechanical failure and damaging patterns of thermal oxide scales will be given. Finally, definitions of adhesion energy as well as quantitative methods to measure adhesion energy will be proposed. An appendix describing the hypotheses and the constitutive equations for plane stress analysis, which suits to oxide scales, is also given The purpose is enriched by references in particular to Alain Galerie’s co-workers’ publications.

Abstract: Inverted organic light-emitting diodes (IOLEDs) have a bottom cathode, making them convenient to integrate with the preferred n-type active matrix OLED driving technologies. Furthermore, inverted OLEDs show much better air-stability compared with conventional OLEDs, due to the very reactive and sensitive of alkali doped electron injection layer (EIL) towards ambient oxygen and moisture. For inverted OLEDs, the bottleneck to limit their efficiency and stability is the interface at cathode/EIL and light emitting layer (EML)/charge transporting layer. In this paper, we have investigated the effect of different electron/hole transporting layers on the turn-on voltage, efficiency roll-off and power consumption of inverted orange OLEDs. We found that the device exhibits extremely-low efficiency roll-off and a significant lifetime improvement.

Abstract: Novel copper-nanocarbons – Cu-fullerene soot/reduced graphene oxide composites with 0-5 wt.% carbon additions were fabricated by spray drying method and hot pressing procedure. In order to obtain the homogeneity of composites, the spray drying integrating with shear mixing was adopted. The microstructure and properties of the composite materials were investigated and compared to Cu–graphite composite, which was prepared under the standard technology. The interface, depending on the nanocarbons addition, prevents copper aggregation, and inhibits the copper grain growth. The compact composites hardness was significantly higher as compared with Cu-CNTs and Cu-Graphite composites of the same carbon concentration with small reduction of the thermal conductivity.

Abstract: After intensifying the knowledge of hygric permeance (HP) in multi-layered test samples, which were subjected to the imbibition process, a significant set of HP values (with different interface types) was experimentally achieved. This was done in order to develop a new model which allows estimating more correctly the hygric permeance. The idea is predicts the HP with several scenarios, i.e., different interfaces (perfect contact, hydraulic contact and air space interface), interfaces heights and materials studied, in the attempt to estimate the HP without the need to resort to the measurement by the experimental route in the attempt to estimate the HP without the need to resort to the measurement by the experimental route and even with possible measurement, generator automatic calculation (without human opinion/criteria). In this paper, the Hygric Permeance will be calculated by two different methods, gravimetric and gamma ray methods, and a new methodology proposes. The maximum flows transmitted were determined by the slope of the mass variation per contact area in function of the time involved. When having interface, the calculations admit that the first layer is saturated and that all the increased weight stems becomes from the relative humidity that penetrates the interface. The new methodology proposed is analysis of the prevision mathematical model that describes the mass variation per contact area in function of the time, after the “knee point”. This work it is the first attempt to provide a set of values that refer from hygric permeance in masonry of building walls, these being random values experimentally determined.