Publication Date:
2012-03-16
Description:
( Ca , Dy ) co-stabilized α-Sialon with elongated grains was prepared from SiO 2 – AlN – CaF 2 – Dy 2 O 3 powders by carbothermal reduction-nitridation (CRN) at 1700°C. Detailed investigations on the formation process of ( Ca , Dy )-α-Sialon elongated grains performed under various firing conditions revealed that the big quartz particles were initially reduced and decomposed gradually by carbon, and a large number of ball-shaped particles consisting of amorphous ( Si , Al , Ca , Dy ) x ( O , N ) y were formed. With increasing temperature, nitrogen continuously diffused into the liquid to form nitrogen-rich solid balls. Further increasing the temperature to 1700°C and held for 2 h, hollow α-Sialon spheres with nanometric particles were obtained from nitrogen-rich solid balls. Subsequently, the framework structure of hollow spheres was destroyed at 1700°C for 3 h, and ( Ca , Dy )-α-Sialon grains grew up continuously by consuming nanometric particles in the rough interface via Ostwald ripening and growth stages moving on the smooth interface. Finally, ( Ca , Dy )-α-Sialon developed well-defined crystalline elongated grains because the growth rate of rough surfaces is more rapid than that of smooth surfaces.
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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