NIST Standard Reference Database 30
Last Update to Data Content: 2002
"Fracture of Yttria-Doped, Sintered Reaction-Bonded Silicon Nitride," R.K. Govila, J.A. Mangels, and J.R. Baer, Journal of the American Ceramic Society, Vol. 68 [7], pp. 413-418 (1985), published by American Ceramic Society.Language: English
"Silicon powder was combined with yttrium oxide powder and made into an aqueous slip. Rectangular billets of dimensions 75 mm by 50 mm by 25 mm and green density of 1.52 g/cm3 were cast. They were dried and nitrided by using the "nitrogen/demand" cycle. The nitrided density of the billets was 2.35 g/cm3. The nitrided billets were then imbedded in a mixture of silicon nitride, yttria, and boron nitride packing powder and sintered in a water-cooled graphite furnace using a two-stage sintering cycle. The maximum sintering temperature was 1975 °C and the maximum nitrogen pressure was about 10 MPa."
"Flexural test specimens (about 32 mm long by 6 mm wide by 3 mm thick) were machined from the billets. All faces were ground lengthwise using 320 grit diamond wheels; the edges were chamfered (lengthwise) to prevent notch effects. For flexural strength evaluation, specimens were tested in 1/4-point, 4-point bending (inner span is one-half of outer-span) in a testing machine using specially designed self-aligning ceramic fixtures made from hot-pressed SiC. The outer and inner knife edges of the testing fixture were spaced 10 mm and 9.5 mm apart, respectively. The high-temperature bend tests were conducted in air by using a rapid temperature response furnace attached to the testing machine head. In high-temperature tests, specimens were held at the test temperature for 15 min, to achieve equilibrium, before testing was begun. No preload was applied on test specimens for either room-temperature of high-temperature tests. All specimens were tested at a machine crosshead of 0.5 mm/min. ... Static oxidation tests were carried out at 700 °C, 1000 °C, 1200 °C, and 1400 °C in air by exposing several flexural type specimens at the test temperature... These specimens were further tested in four-point bending at 200 °C after the 300 h exposure."
| Amount of Element ( formula units ) | Element ( no unit ) |
|---|---|
| 3 | Si |
| 4 | N |
| Test Temperature ( °C ) | Oxidation Temperature ( °C ) | Flexural Strength ( MPa ) |
|---|---|---|
| 20 | -- | 696 ± 83 |
| 500 | -- | 689 ± 50 |
| 800 | -- | 684 ± 63 |
| 1000 | -- | 608 ± 80 |
| 1200 | -- | 536 ± 55 |
| 1300 | -- | 519 ± 20 |
| 1400 | -- | 472 ± 52 |
| 20 | 700 | 770 ± 37 |
| 20 | 1000 | 641 ± 98 |
| 20 | 1200 | 703 ± 110 |
| 20 | 1400 | 682 ± 110 |
Data were obtained from Tables I and II, and Figure 5 of the paper.
| Temperature ( °C ) | Weibull Modulus ( no unit ) |
|---|---|
| 20 | 10 |
| Temperature ( °C ) | Weibull Strength ( MPa ) |
|---|---|
| 20 | 727 |