Si3N4 ceramic was jointed to Si3N4 ceramic using a filler alloy of Cu-Zn-Ti at 1123-1323K for 0.3-2.7ks. Ti content in the Cu-Zn-Ti filler alloy was 15%（molar fraction）. The effect of bonding parameters on t...Si3N4 ceramic was jointed to Si3N4 ceramic using a filler alloy of Cu-Zn-Ti at 1123-1323K for 0.3-2.7ks. Ti content in the Cu-Zn-Ti filler alloy was 15%（molar fraction）. The effect of bonding parameters on the microstructure and mechanical properties of the Si3N4/Si3N4 joint were investigated. The results indicate that with increasing brazing temperature from 1123K to 1323K and brazing time from 0.3ks to 2.7ks, the thickness of the interfacial reaction layer between the filler alloy and the Si3N4 ceramic and the size and amount of the reactant products in the filler alloy increase, leading to an increase in shear strength of the joint from 163MPa to 276MPa. It is also found that the fracture behavior of the Si3N4/Si3N4 joint greatly depends on the microstructure of the joint.展开更多
Si3N4-SiC composite ceramics were fabricated by chemical vapor infiltration using porous Si3N4 ceramic as preform. The average grain size of SiC was 30 nm. Relationship between SiC content and relative complex permitt...Si3N4-SiC composite ceramics were fabricated by chemical vapor infiltration using porous Si3N4 ceramic as preform. The average grain size of SiC was 30 nm. Relationship between SiC content and relative complex permittivity of Si3N4-SiC within the frequency range of 8.2-12.4 GHz (X-band) was investigated. The average real part of relative complex permittivity ε of Si3N4-SiC increased from 3.7 to 14.9 and the relative imaginary part ε increased from 0.017 to 13.4 when the content of SiC increased from 0 to 10 vol.%. The Si3N4-SiC ceramic with 3 vol.% SiC achieved a reflection loss below 10 dB (90% absorption) at 8.6-11.4 GHz, and the minimum value was 27.1 dB at 9.8 GHz when the sample thickness was 2.5 mm. The excellent microwave absorbing abilities of Si3N4-SiC ceramic were attributed to the interfacial polarization at interface between Si3N4 and SiC and at grain boundary between SiC nanocrystals.展开更多
文摘Si3N4 ceramic was jointed to Si3N4 ceramic using a filler alloy of Cu-Zn-Ti at 1123-1323K for 0.3-2.7ks. Ti content in the Cu-Zn-Ti filler alloy was 15%（molar fraction）. The effect of bonding parameters on the microstructure and mechanical properties of the Si3N4/Si3N4 joint were investigated. The results indicate that with increasing brazing temperature from 1123K to 1323K and brazing time from 0.3ks to 2.7ks, the thickness of the interfacial reaction layer between the filler alloy and the Si3N4 ceramic and the size and amount of the reactant products in the filler alloy increase, leading to an increase in shear strength of the joint from 163MPa to 276MPa. It is also found that the fracture behavior of the Si3N4/Si3N4 joint greatly depends on the microstructure of the joint.
基金financial support from the National University Student Innovation Program fund (No. 101069911)supported by the Research Fund of State Key Laboratory of Solidification Processing in Northwestern Polytechnical University (No. KB200920)+1 种基金the China Postdoctoral Science Foundation (No. 20110491683)the 111 Project(B08040)
文摘Si3N4-SiC composite ceramics were fabricated by chemical vapor infiltration using porous Si3N4 ceramic as preform. The average grain size of SiC was 30 nm. Relationship between SiC content and relative complex permittivity of Si3N4-SiC within the frequency range of 8.2-12.4 GHz (X-band) was investigated. The average real part of relative complex permittivity ε of Si3N4-SiC increased from 3.7 to 14.9 and the relative imaginary part ε increased from 0.017 to 13.4 when the content of SiC increased from 0 to 10 vol.%. The Si3N4-SiC ceramic with 3 vol.% SiC achieved a reflection loss below 10 dB (90% absorption) at 8.6-11.4 GHz, and the minimum value was 27.1 dB at 9.8 GHz when the sample thickness was 2.5 mm. The excellent microwave absorbing abilities of Si3N4-SiC ceramic were attributed to the interfacial polarization at interface between Si3N4 and SiC and at grain boundary between SiC nanocrystals.
