Papers by Keyword: Bilayer

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Authors: Chetan P. Nikhare
Abstract: Lightweight design for vehicle industry is not anymore an optional condition but a mandatory need to reduce the fuel consumption and adhere to environmental regulations. To achieve this goal many single parts have been removed and complex design have been implied. This includes implementation of tailored-welded blanks and multi-layer materials. Due to the increase use of dissimilar materials in a component it is also called as hybrid components. It was observed that due to use of hybrid component the part weight decrease and thus increase fuel efficiency. To continue this aspect, in this bilayer tube flaring is investigated. The metal tubular material from inside and polymer from outside is considered for flaring. The flaring behavior of the tube is analyzed and compared with the single metal layer. The strength difference and effect of that on the formability is discussed and resulted. It was observed that due to contact of lower strength material from outside the formability of the metal tube increased and failure is delayed.
Authors: Carlos Morón, Alfonso Garcia, Enrique Tremps, Jose Andrés Somolinos
Abstract: Related with the detection of weak magnetic fields, the anisotropic magnetoresistive (AMR) effect is widely utilized in sensor applications. Exchange coupling between an antiferromagnet (AF) and the ferromagnet (FM) has been known as a significant parameter in the field sensitivity of magnetoresistance because of pinning effects on magnetic domain in FM layer by the bias field in AF. In this work we have studied the thermal evolution of the magnetization reversal processes in nanocrystalline exchange biased Ni80Fe20/Ni-O bilayers with large training effects and we report the anisotropic magnetoresistance ratio arising from field orientation in the bilayer.
Authors: Ming Yuan Lu, Hong Tao Xie, Han Huang
Abstract: This review summarized the research works on the characterisation of interfacial adhesion in thin film/substrate bilayer structure by use of indentation testing. It focused on the delamination mechanics between a thin film and a substrate induced by indentation and the quantitative characterisation of interfacial strength in such bilayer systems. Three major techniques were introduced, namely conventional indentation, cross-sectional indentation and acoustic emission assisted indentation. A number of theoretical models and finite element simulation studies were discussed, in association with the experimental investigations. Key words: Thin film, bilayer, delamination, adhesion, indentation, acoustic emission
Authors: Yang Do Kim, Jang Hee Lee, Jae Hyoung Koo, Ho Jung Chang, Hyeong Tag Jeon
Abstract: ZrO2/Al2O3 bilayer structure was investigated as one of potential replacements for SiO2 gate dielectric. Al2O3 and ZrO2 films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al2O3 film exhibited an amorphous structure without interlayer formation while ZrO2 film showed a randomly oriented polycrystalline structure with amorphous phase of interlayer. ZrO2/Al2O3bilayer film exhibited no interfacial layer between Si substrate and Al2O3 layers. The flat band voltage and hysteresis of ZrO2/Al2O3bilayer film were 0.8 V and 150 mV, respectively, with fully reversible hysteresis. The measured leakage current of ZrO2/Al2O3bilayer film was 1.2E-6 A/cm2 with EOT value of 1.4 nm. ZrO2/Al2O3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al2O3 and ZrO2 films.
Authors: Yu Du, Xiao Qing Tian, Jian Bin Xu
Abstract: The structures and magnetic properties of monolayer and bilayer of transitional metallo-porphine (MP) species (M = Mn, Fe, Co, Ni, Cu) on the Ag (111) substrate are investigated by DFT based first-principle method. The MP monolayer has a distortion about 10° towards the substrate due to strong interaction between adsorbed molecule and substrate. The molecule-substrate interaction could quench the magnetic moment of the adsorbed molecule. For MP bilayer adsorption on the Ag (111), the top layer remains its planar structure and magnetic moment due to the screening of substrate effects by bottom layer, meanwhile the bottom layer has strong structural distortions and obvious variations of magnetic moment.
Authors: Dmitry Andreevich Maslov, Yuri Borislavovich Kudasov
Abstract: Charge ordering of nonstoichiometric LuFe2O4+δ is discussed. Properties of triangular bilayer are investigated via mean field theory with Coulomb interaction between sites. It is shown that low temperature state of bilayer has dipole moment essentially under any doping parameter. Correlation between sites in neighbor layers is estimated and dimer partially disordered antiferroelectric phase is extended for the case of nonstoichiometric samples. Competition of correlation effect with bilayer interaction and external electric field is discussed. Phase diagrams for doped specimen are presented. The results of investigation are used to clarify a significant surface impact.
Authors: Hélder M.C. Barbosa, Marta M. D. Ramos, Helena M.G. Correia
Abstract: The actual interest on polymer light emitting diodes (PLEDs) is based on the fact that they are easy to process, which reduces the cost of fabrication and thus opening a new branch in the electronic market – the low-cost electronics. However, these devices present a limited efficiency compared to their inorganic counterparts mainly due to the unbalanced charge injection, which reduces the fluorescence emission. One of the first strategies to improve PLEDs efficiency was using a bilayer structure composed by two polymers to improve charge injection and transport, and at the same time tune charge recombination zone to reduce the effect of the electrodes on exciton quenching. Although this is a very ingenious device architecture some of these bilayer devices showed a lower efficiency than it was expected. The reason for that is attributed to the dissolution of the first polymer layer by the solvent used for the deposition of the second polymer layer, which do not allow to create a define polymer/polymer interface. Although cross-linking the first polymer layer can solve this problem, there is not a clear understanding why the presence of a graded interface between both polymer layers can lead to a change on PLED efficiency. In order to clarify the effect of a graded polymer/polymer interface as compared to a sharp one on the functioning of a PLED, we performed computer experiments using a mesoscopic model of a bilayer PLED developed by us that considers the morphology of both polymers at nanoscale and their properties at molecular scale. The results present in this work show clearly a significant change on the charge recombination profile within the polymer device depending on the type of interface formed between the two polymers, which can be a plausible explanation for the loss of efficiency in the bilayer 7-CN-PPV/PPV LED.
Authors: Tarek Qasim, Mark Bush, Xiao Zhi Hu
Abstract: This paper aims to assess the effect of shape irregularity on contact damage in a brittle coating on a stiff metal substrate. Hertzian contact damage in a dental porcelain layer over a Ni-Cr alloy substrate in both curved and flat geometries was studied using finite element analysis and experimental investigation. Three failure modes were examined with varying porcelain layer thickness: cone cracking at the top surface of the porcelain, interface cracking at the layer/substrate interface and plastic deformation below the contact area in the substrate. It is shown that curvature has very little effect on the initiation of surface cone cracks in this system, but substantial effect on the initiation of interface radial cracks. In particular, curvature reduces the critical load for the onset of interface cracks
Authors: Bing Zhou, Xiao Hong Jiang, A.V. Rogachev, Rui Qi Shen
Abstract: Diamond-like carbon (DLC) bilayer films with Cu interlayer were prepared on silicon substrate by direct-current and pulsed cathode arc plasma technique, and annealed at various temperatures in vacuum. Structure, morphology and mechanical properties of the bilayer films were investigated by Raman spectroscopy, Auger electron spectroscopy, scanning electron microscopy and atomic force microscopy, surface profilometer and Vickers sclerometer. The results show that Cu interlayer changes the bilayer microstructure, including the thickness and element distribution of diffusion layer, the relative fraction of sp3/sp2 bonding and growth model of bilayer. A simple three-layer model was used to describe the interdiffusion between Cu and C layer. Cu interlayer could be more effective against graphitization upon annealing. Morphological characteristics of the films were studied by analyzing the surface features of substrate. Cu/DLC bilayer exhibits highly dispersed nano-agglomerates with smaller size on the surface due to low surface energy of Cu interlayer. The stress and hardness of the films were affected accordingly. Cu/DLC bilayer shows a relatively high hardness at low annealing temperature but the stress almost no change. By changing Cu interlayer and annealing temperature, excellent DLC films could be designed for the protective, hard, lubricating and wear resistant coatings on mechanical, electronic and optical applications.
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