WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 14Citation - Scopus: 14Microstructural Development of Interface Layers Between Co-Sintered Alumina and Spinel Compacts(Elsevier Ltd., 2011) Yalamaç, Emre; Carry, Claude; Akkurt, SedatTests were performed to investigate the microstructure of the interface between alumina and spinel materials after high temperature thermal treatment (1500°C). The first test involved co-sintering of co-pressed alumina and spinel compacts. Microstructures were investigated by SEM, EDS, WDS and EBSD. A microstructurally distinct layer with columnar grains of up to 40μm length and 5μm width was observed after 16h at 1500°C. Growth rate of the columnar spinel grains from parent spinel towards alumina follows parabolic kinetics, controlled by a mixed process of O2- ion diffusion and interface reaction. Diffusion couples of spinel and alumina were investigated. Same columnar spinel grains were observed at the interface which grew into alumina during thermal treatment with the same kinetics as in co-sintering experiments. The shape of the phase boundaries between spinel and alumina can be a further indication of the direction of their growth.Article Citation - WoS: 13Citation - Scopus: 15Analysis of a Corner Layer Problem in Anisotropic Interfaces(Southwest Missouri State University, 2006) Alikakos, N. D.; Bates, P. W.; Cahn, J. W.; Fife, P. C.; Fusco, G.; Tanoğlu, GamzeWe investigate a model of anisotropic diffuse interfaces in ordered FCC crystals introduced recently by Braun et al and Tanoglu et al [3, 18, 19], focusing on parametric conditions which give extreme anisotropy. For a reduced model, we prove existence and stability of plane wave solutions connecting the disordered FCC state with the ordered Cu3Au state described by solutions to a system of three equations. These plane wave solutions correspond to planar interfaces. Different orientations of the planes in relation to the crystal axes give rise to different surface energies. Guided by previous work based on numerics and formal asymptotics, we reduce this problem in the six dimensional phase space of the system to a two dimensional phase space by taking advantage of the symmetries of the crystal and restricting attention to solutions with corresponding symmetries. For this reduced problem a standing wave solution is constructed that corresponds to a transition that, in the extreme anisotropy limit, is continuous but not differentiable. We also investigate the stability of the constructed solution by studying the eigenvalue problem for the linearized equation. We find that although the transition is stable, there is a growing number 0(1/ε), of critical eigenvalues, where 1/ε ≫ 1 is a measure of the anisotropy. Specifically we obtain a discrete spectrum with eigenvalues λn = ε2/3 μn with μn ∼ Cn2/3, as n → +∞. The scaling characteristics of the critical spectrum suggest a previously unknown microstructural instability.Article Citation - WoS: 12Citation - Scopus: 12Dispersion of Organophilic Ag Nanoparticles in Ps-Pmma Blends(Elsevier Ltd., 2015) Tüzüner, Şeyda; Demir, Mustafa Muammer.Abstract The preparation of stable composites with well-controlled particle location is one of the challenges in formulating new polymer/nanoparticle mixtures. In this study, cetyltriammonium bromide (CTAB)-capped monodisperse Ag nanoparticles were prepared and mixed with an equimass blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in solution. The surface of the blend film without nanoparticles showed spherical pits with a size of 4.5 μm in diameter. The integration of CTAB-capped nanoparticles into the blend film developed surface bumps with a size of 0.4 μm in diameter. The organophilic Ag nanoparticles were distributed heterogeneously in the immiscible PS-PMMA blend. When the diameter of particle domains reached approximately 20 nm, particles were preferentially located at the interface of the PS and PMMA domains. Larger particle domains with a diameter of 90 nm were found to be in the PMMA-rich phase. Isothermal post-treatment of the PS-PMMA/Ag composite films directs the particle domains into PS domains. Thermodynamic factors that contribute to the observed morphologies are discussed.