This site will look much better in a browser that supports web standards, but it is accessible to any browser or Internet device.
Fracture of Y-Al-Si-O-N Glass
Dennis N. Coon
Department of Mechanical Engineering
University of Wyoming
Laramie, WY 82071
The three-point bend strength of two glasses in the Al2O3 · ( ) Y2O3 · (3-x) SiO2 · (x/3) Si3N4 system was determined at temperatures up to 1000 °C. The average bend strength ranged from 100 to 150 MPa. Nitrogen content of the glasses ranged from 7.2 to 15.0 atomic%, however, nitrogen content had little influence on average bend strength. In addition, the bend strength changed little with temperature up to the glass transition temperature. Flaw sizes and mirror/mist radii were optically determined. The nitrogen content had no influence on the relationship between bend strength and flaw size or the relationship between bend strength and mirror/mist radius. The mirror/mist constant was calculated to be 1.5 ± 0.2 MPa•m-½. Fracture toughness was determined at room temperature using the indentation fracture technique. The indentation toughness of the glass containing 7.2 atomic% nitrogen was 1.32 ± 0.03 MPa•m½ and the indentation toughness of the glass containing 15 atomic% nitrogen was 1.31 ± 0.04 MPa•m½. Fracture toughness values calculated from bend test data agreed with indentation toughness results, and nitrogen content had little influence on fracture toughness determined from bend test data. The fracture toughness decreased slightly with test temperature, but was still about 1.2 to 1.3 MPa•m½ at 900 °C. Critical strain energy release rate was calculated for indentation and bend test data. Average critical strain energy release rate ranged from 6 to 8.5 J/m2, and test temperature had little effect on calculated critical strain energy release rate.