Papers by Author: Enikõ Horváth

Abstract: The deformation of ceramic matrix composites (CMC) is controlled by several processes occurring in the matrix, in the enforcing phase, at the interfaces between different phases and at the surface of the body. The main tool to study morphology features of CMC-s is high resolution scanning electron microscopy (SEM). In this study destructive chemical methods such as chemical etching and burning of combustible phases were used to prepare samples for SEM investigations from three types of materials. I. SiC skeletons of C/C-SiC structures prepared of 2D woven fabric and chopped fiber bodies were produced by chemical elimination of the constituents: Si, reinforcing C- fibers and amorphous carbon. II. Silicon-nitride reaction bonded silicon-carbide samples with finishing surface oxide films – as produced and aged - were handled by HF etchants. Etching revealed cristobalite crystallites at the interface between ceramics and oxide film, and cracks in the glassy surface layer. III. Microstructure and pore structure of Si3N4 ceramics, carbon nanotube reinforced Si3N4 (CNT/Si3N4), and C/Si3N4 with graphite and carbon black addition were examined by HF etching.

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Abstract: The aim of this study was to find if nanocrystal layers obtained by well-established nanotechnology are able to induce deposition of hydroxyapatite [Ca10(PO4)6(OH)2]. It is known that nanosized objects and porous structures influence biological events and they may be used to create biologically integrated multifunctional devices including biomaterials and sensors. In this work, sequential physical vapour deposition of CdSe and SiO, or SiOx film was used to modify glass substrates. To study the ability of the nanostructured surfaces to induce hydroxyapatite deposition, samples were immersed in a simulated body fluid and simultaneously irradiated with a scanning laser beam for a few minutes. This resulted in a porous sponge-like non homogeneous hydroxyapatite layer, consisting of networks of aggregates of nano dimensions on the modified surfaces. Analysis showed higher Ca and P contents in the stripes of the laser-substrate interaction, which indicated the influence of the laser energy. The method of laser-liquid-solid interaction used has led to a synergistic effect due to the simultaneous use of the nanostructured substrate, aqueous solution and laser energy.