Seamless Joining of Silicon Nitride Ceramics

Abstract

High-strength joining of Si 3 N 4 ceramics has been achieved by developing a process that effectively eliminates the seam, and may allow for fabrication of large or complex silicon nitride bodies. This approach to joining is based on the concept that when sintering aids are effective in bonding individual grains, they could be equally effective in joining bulk pieces of Si 3 N 4 . Optimization of the process led to Si 3 N 4 /Si 3 N 4 joints with room-temperature bend strengths as high as 950 MPa, corresponding to more than 90% of the bulk strength of the Si 3 N 4 . At elevated temperatures of 1000°and 1200°C joint strengths of 666 and 330 MPa, respectively, were obtained, which are the highest values reported to date for these temperatures. These bend strengths are also more that 90% of the strength of bulk Si 3 N 4 measured at these temperatures.

Joining of silicon nitride by microwave local heating

“…5) Most silicon nitrides joined by glass with no or low pressure (<0.01 MPa) exhibited strengths in the range 400600 MPa, 9),11),12) whereas silicon nitride joined by glass under optimized conditions had a strength of over 900 MPa. 13) Therefore, the strength obtained in this study (446 MPa) is comparable to the moderate results previously reported. Therefore, microwave local heating can achieve a joint strength comparable to those obtained by conventional resistance furnace heating.…”

Semi-homogeneous joining of silicon nitride using oxynitride glass insert containing silicon nitride powder and post-heat treatment

“…6) A glass composed of the 2Re 2 O 3 SiO 2 (Re 2 O 3 = Y 2 O 3 , Yb 2 O 3 ) system was used as an insert, and joining was performed. Although a high strength was achieved under optimized joining temperatures and time, the glass remained at the joined interface.…”

Microstructure and Properties of Porous Si3N4/Dense Si3N4 Joints Bonded Using RE–Si–Al–O–N (RE = Y or Yb) Glasses

“…Currently, the bonding of ceramics with oxide or oxynitride glass adhesives has been successful [14][15][16][17]. Since the sintering aids contribute to excellent bonding between Si 3 N 4 grains during the synthesis process, they should also be applicable for the joining of bulk materials.…”