Thesis of Mehran Jaberi Zamharir

Investigation of nano SiC particles on densification behavior and mechanical properties of ZrB2-based composite

By Mehran Jaberi Zamharir

Supervisor: Dr. M. Gassemi Kakroudi

Advisor: Dr. M. Rezvani

University of Tabriz

September 2015

Abstract: ZrB2–25 vol% SiC ceramic composites were prepared by hot pressing in order to investigate the effects of processing parameters and SiC particle size (20 nm, 200 nm and 5 µm) on the densification behavior, the average ZrB2 grain size and Vickers hardness. At this study, an experimental design technique (Taguchi method) was used to specify the significance of four factors and to obtain the optimal conditions. The experimental procedure included nine tests for four parameters with three levels which were employed to optimize the process parameters. The statistical analyses recognized the hot pressing pressure and temperature as the most consequential parameters affecting the density and hardness of ZrB2–SiC composites. The SiC particle size and holding time were specified as the most effective parameters on the average ZrB2 grain size. The relative density, average ZrB2 grain size, Vickers hardness and fracture toughness of the sample, hot pressed at optimal conditions (1850 °C, 90 min, 16 MPa and 200 nm), reached about 5.36 g/cm3, 10.03 µm, ~17.1 GPa and 5.9 MPa.m1/2, respectively. The confirmation test, performed under optimum conditions, indicated that the experimental outcomes were equal with the expected values from the Taguchi prediction. Finally, the mechanisms of enhanced densification and fracture toughness of the hot pressed ZrB2–SiC ceramic composites were discussed.