مرکز منطقه ای اطلاع رساني علوم و فناوري

Abstract :

Silicon nitride (Si3N4) ceramics have common application areas due to their marvelous thermomechanic properties. These materials are used heavily in cutting tools, ball bearings, motor valves and the other wear resistant tools. The microstructural growth of Si3N4 ceramic is controlled by three different parameters; properties of initial Si3N4 powders, compositions of sintering reagents and sintering conditions. Generally, MgO, Y2O3, Al2O3 and rare earth oxides are used as sintering additives. In this study, α-phase rich Si3N4 powders were synthesized containing sintering additive by carbothermal reduction and nitridation. The starting agent for silicon source was high-purity synthetic silica. MgO and Y2O3 powders were premixed (wt. %4 Y2O3 - %6 MgO, %5 Y2O3 - %5 MgO and %6 Y2O3 - %4 MgO) in the starting reactants depending on the final powder composition and the type and amount of the secondary phases desired for sintering. The synthesis was carried out in a tube furnace at different temperature (1400°C, 1450°C and 1475°C-3h) ranges under nitrogen gas atmosphere.In this way, the sintering additives dispersed in the structure more homogeneously and sinterable the starting material is produced. Having completed synthesis process, α-Si3N4 powder properties were examined by using XRD, SEM, etc.