Pulsed Electric Current Sintering of Silicon Nitride

Pulsed electric current sintering (PECS) has been used to densify α-Si 3 N 4 powder doped with oxide additives of Y 2 O 3 and Al 2 O 3 . A full density (>99%) was achieved with virtually no transformation to β-phase, resulting in a microstructure with fine equiaxed grains. With further holding at the sintering temperature, the α-to-β phase transformation took place, concurrent with an exaggerated grain growth of a limited number of elongated β-grains in a fine-grained matrix, leading to a distinct bimodal grain size distribution. The average grain size was found to obey a cubic growth law, indicating that the growth is diffusion-controlled. In contrast, the densification by hot pressing was accompanied by a significant degree of the phase transformation, and the subsequent grain growth gave a broad normal size distribution. The apparent activation energy for the phase transformation was as high as 1000 kJ/mol for PECS, almost twice the value for hot pressing (∼500 kJ/mol), thereby causing the retention of α-phase during the densification by PECS.

[1]  Hua-Tay Lin,et al.  Microstructural Design of Silicon Nitride with Improved Fracture Toughness: I, Effects of Grain Shape and Size , 2005 .

[2]  K. Hirao,et al.  Microstructural Design of Silicon Nitride with Improved Fracture Toughness: II, Effects of Yttria and Alumina Additives , 2005 .

[3]  K. Hirota,et al.  Fabrication, Microstructure, and Mechanical Properties of Cr2O3/ZrO2(2.5Y) Composite Ceramics in the Cr2O3‐Rich Region , 2005 .

[4]  J. Groza,et al.  Field‐Assisted Sintering of Nanocrystalline Titanium Nitride , 2004 .

[5]  M. Toriyama,et al.  Very Rapid Densification of Nanometer Silicon Carbide Powder by Pulse Electric Current Sintering , 2004 .

[6]  T. Ohji,et al.  Strengthening of Porous Alumina by Pulse Electric Current Sintering and Nanocomposite Processing , 2004 .

[7]  A. Mukherjee,et al.  Thermal and Electrical Properties in Plasma‐Activation‐Sintered Silicon Carbide with Rare‐Earth‐Oxide Additives , 2004 .

[8]  T. Hirai,et al.  Consolidation of Eutectic Powder of Al2O3–GdAlO3 , 2004 .

[9]  M. Toriyama,et al.  Densification Behavior in Microwave-Sintered Silicon Nitride at 28 GHz , 2004 .

[10]  T. Ohji,et al.  High‐Strength Porous Alumina Ceramics by the Pulse Electric Current Sintering Technique , 2004 .

[11]  Jow-Lay Huang,et al.  Microstructure in Silicon Nitride Containing β‐Phase Seeding: III, Grain Growth and Coalescence , 2004 .

[12]  I. Chen,et al.  Microstructure Control of In‐Situ‐Toughened α‐SiAlON Ceramics , 2004 .

[13]  J. Groza,et al.  Surface effects in field-assisted sintering , 2001 .

[14]  T. Hirai,et al.  Densification of Al_2O_3 powder using spark plasma sintering , 2000 .

[15]  N. Murayama,et al.  Comparison between Pulse Electric Current Sintering and Hot Pressing of Silicon Nitride Ceramics , 1999 .

[16]  M. Nygren,et al.  Superfast Densification of Oxide/Oxide Ceramic Composites , 1999 .

[17]  Jenn‐Ming Yang,et al.  MICROSTRUCTURE AND PROPERTIES OF NANOSEMICRYSTALLINE SI3N4 CERAMICS WITH DOPED SINTERING ADDITIVES : PART II. PHASE TRANSFORMATION AND MICROSTRUCTURAL CONTROL , 1998 .

[18]  Y. Kinemuchi,et al.  Effects of Coated Carbon on Si3N4 Powder for the Surface Reaction during Pulsed Electric Current Sintering , 1998 .

[19]  S. Risbud,et al.  Influence of initial crystal structure and electrical pulsing on densification of nanocrystalline alumina powder , 1998 .

[20]  K. Yamazaki,et al.  Effect of TiO_2 doping on rapid densification of alumina by plasma activated sintering , 1996 .

[21]  S. Risbud,et al.  Rapid consolidation processing of silicon nitride powders , 1996 .

[22]  T. Nishimura,et al.  Influence of Phase Transformation on Densification Behavior and Grain Growth of Fine Silicon Nitride Powder , 1996 .

[23]  Koji Tanaka,et al.  Effect of Spark Plasma Sintering on Densification and Mechanical Properties of Silicon Carbide , 1995 .

[24]  A. Mukherjee,et al.  Plasma activated sintering of nanocrystalline γ-Al2O3 , 1995 .

[25]  G. Thomas,et al.  Phase transformation and microstructural changes of Si3N4 during sintering , 1995 .

[26]  Moon J. Kim,et al.  Retention of nanostructure in aluminum oxide by very rapid sintering at 1150 °C , 1995 .

[27]  T. Nishimura,et al.  Fabrication of silicon nitride nano-ceramics by spark plasma sintering , 1995 .

[28]  Kiyoshi Hirao,et al.  Microstructure Control of Silicon Nitride by Seeding with Rodlike β‐Silicon Nitride Particles , 1994 .

[29]  Takahiro Tanaka,et al.  Usefulness of Spark Plasma Sintering on Densification and Mechanical Properties of Alumina Whisker/Zirconia Composites , 1994 .

[30]  S. Risbud,et al.  Clean grain boundaries in aluminium nitride ceramics densified without additives by a plasma-activated sintering process , 1994 .

[31]  Michael J. Hoffmann,et al.  Grain Growth Studies of Silicon Nitride Dispersed in an Oxynitride Glass , 1993 .

[32]  M. Hoffmann,et al.  Grain growth kinetics of Si3N4 during α/ß-transformation , 1993 .

[33]  T. Tien,et al.  Kinetics of β-Si3N4 Grain Growth in Si3N4 Ceramics Sintered under High Nitrogen Pressure , 1993 .

[34]  K. Yamazaki,et al.  Plasma activated sintering of additive-free AlN powders to near-theoretical density in 5 minutes , 1992 .

[35]  M. Mitomo,et al.  Microstructural Development During Gas‐Pressure Sintering of α‐Silicon Nitride , 1992 .

[36]  R. Brook,et al.  Hot‐Pressing of Si3N4 with Y2O3 and Li2O as Additives , 1978 .

[37]  R. Brook,et al.  Hot-pressing and the α-β phase transformation in silicon nitride , 1978 .