Papers by Author: N.C. Acikbas

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.

Abstract: In this study, effect of seed addition on the microstructural development of Y-Sm α-SiAlON system has been investigated. Besides using pre-produced rod-like α-SiAlON seeds, growth in the glassy phase and harvested by chemical treatment, powdered Y-Sm/α-SiAlON was also used as nuclei. Microstructural results of both systems were compared with un-seeded samples. It was found that the powdered α-SiAlON addition has also caused the acicular α-SiAlON grain formation, which indicates the dominant effect of thermodynamic stability on the preferential growth of α-SiAlON grains in the c direction.

Abstract: In this study, textured α-SiAlON ceramic was produced by templated grain growth process. In order to enhance the alignment of the seeds, gated tape casting arrangement was utilized. Y-Ce codoped seeds were synthesized to induce the preferred orientation. For the production of the seeds, Ce3+ was used as a sintering additive due to its well-known effect on the formation of elongated α-SiAlON grains. In addition, Y3+ was used to stabilize Ce3+ in α-SiAlON structure. Gated tape casting arrangement was also used to enhance the alignment of the seeds in the green tape. After the lamination and sintering, preferentially aligned α-SiAlON grains were observed by the microstructural investigation. In addition, XRD results obtained from the planes parallel and perpendicular to the casting direction indicated the alignment of grains in α-SiAlON ceramics. Hardness measurements also confirmed that the alignment of the grains results in 8% increase in hardness value of the plane perpendicular to the casting direction with respect to that of the parallel one.