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7735067 
Journal Article 
Fabrication of pressureless sintered Si3N4 ceramic balls by powder injection molding 
Gal, C; Song, GiW; Baek, WH; Kim, H; Lee, D; Lim, KiW; Park, S 
2019 
1 
Ceramics International
ISSN: 0272-8842
EISSN: 1873-3956 
Elsevier Ltd 
45 
5 
6418-6424 
English 
WOS:000459365500154 
Pressureless sintered Si3N4 ceramic balls were fabricated by powder injection molding technology. Yttria and alumina as a sintering aid were added to improve the sintered density. The mixing was performed with twin-screw extrude mixer to fabricate the homogeneous feedstock. The rheological behavior of Si3N4 feedstock was analyzed with Power Law-Arrhenius model and moldability index. With the optimized injection molding parameters, green parts without defects were obtained. A two-step debinding process was applied to remove the binders in the green parts. Solvent debinding was firstly conducted in n-hexane at 50 °C for 5 h. The optimized thermal debinding was secondly conducted in air atmosphere based on TGA experiment results. The sintering was conducted in nitrogen atmosphere at 1750 and 1800 °C for 4 h. Embedding powder (Si3N4:BN = 1:1) was used to avoid dissociation of silicon nitride. The balls with 5 mm diameter were finally fabricated with no defects. The relative density and mechanical properties including 3-point bending strength, Vickers hardness and fracture toughness had a higher value at the sintering temperature of 1800 °C than at 1750 °C. It indicates that the Si3N4 ceramic balls with high physical and mechanical properties can be successfully fabricated by optimized PIM process. © 2018 Elsevier Ltd and Techna Group S.r.l. 
Si3N4; Injection molding; Sintering; Mechanical property