Papers by Author: Ferhat Kara

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Authors: M.S. Başpınar, Wolfgang Schulle, Ferhat Kara
Authors: E. Ayas, Alpagut Kara, Ferhat Kara
Abstract: An effective approach for preparing electrically conductive SiAlON-TiN composites was developed. Granules of a designed composition of α- SiAlON was obtained by spray drying and coated with varying amounts of TiO2 powder homogenously by mechanical mixing. Fully dense composites were obtained by spark plasma sintering (SPS) under a pressure of 50 MPa at 1650°C for 5min. According to the SEM analysis, unique microstructures containing continuously segregated in-situ formed TiN phase in 3-D were achieved. Additionally, XRD studies revealed that all TiO2 was successfully converted to TiN. The resistivity of the α-β SiAlON (1x1011 .m) was drastically reduced with the addition of only 5 vol. % TiO2 (2x10-4 .m).
Authors: N. Çalış, Alpagut Kara, Ferhat Kara, Hasan Mandal
Authors: Nurcan Calis Acikbas, Ferhat Kara, Hasan Mandal
Abstract: - SiAlON ceramics were produced from different starting Si3N4 powders including β-Si3N4 and α-Si3N4 powders and mixtures of these powders. Gas pressure sintering was used for sintering. After sintering, resultant fracture toughness values were correlated with microstructure and starting powders. By optimizing chemistry and process parameters; - SiAlON ceramics with reasonable fracture toughness can be produced from rather coarse β-Si3N4 powder. This could improve the economic viability of SiAlON ceramics since -Si3N4 powders are less costly.
Authors: K. Alptekin, Ferhat Kara
Authors: M. Cavac, Ferhat Kara
Authors: N.C. Acikbas, Alpagut Kara, Servet Turan, Ferhat Kara, Hasan Mandal, Bernd Bitterlich
Abstract: 25α:75β SiAlON composition was designed with different cations and at different molar ratios. Effect of the type of cations both on the composition and the type of intergranular phase investigated after gas pressure sintering and further post sintering heat treatment.
Authors: A. Kalemtas, Nurcan Calis Acikbas, Ferhat Kara, Hasan Mandal, Kristoffer Krnel, Tomaž Kosmač
Abstract: In the present study, interactions between AlN and SiAlON laminated couples were investigated after gas pressure (GPS) and spark plasma sintering (SPS) by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) with the aim to produce laminated composites. In the laminated couples sintered by GPS, a significant reaction zone (~100-150 μm), containing a high aspect ratio of elongated polytypoid grains, was observed at the interface. However, in the case of laminated couples sintered by SPS, a considerably thin reaction region (~2-3 μm) was observed, elongated polytypoid grain formations were also detected.
Authors: Gürsoy Arslan, Ferhat Kara, Servet Turan
Authors: Hasan Mandal, Ferhat Kara, Servet Turan, Alpagut Kara
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