NIST Standard Reference Database 30
Last Update to Data Content: 2002
"Fundamental Studies of Corrosion of Nonoxide Structural Ceramics," R.E. Tressler and K.E. Spear, Projects Within the Center for Advanced Materials, pp. 125-143 (1990), edited by J.R. Hellmann and B.K. Kennedy, published by Center for Advanced Materials, Pennsylvania State University.Language: English
Material (1): SiC platelets were grown by Acheson furnace synthesis. The platelets were 99.98 % (mass fraction) SiC in the hexagonal 4H polytype. The trace impurity elements were Ti (0.006 %); V (0.013 %); Fe (0.001 %). Material (2): The CVD Si3N4 was deposited on a graphite substrate. Material (3): Hexoloy SA is a siliconized, sintered, α-silicon carbide containing a mixture of cyrstal polytypes 6H and 15R and the following impurities: Al; B; Fe; Ti; Ca; Mg; V; Cu; Ni; Cr; Mn.
Specimens were first oxidized in one atmosphere of molecular oxygen, isotope 16, at 1200 °C {SiC: 180 min for 0 ppm and 50 ppm Na+ ions and 150 min for 1000 ppm implanted Na+ ions; Si3N4: 420 min}. Then, a second oxidation was performed in molecular oxygen, enriched to 20% isotope 18, at 1100 °C {SiC: 30 min; Si3N4: 60 min}. Then, oxygen isotope profiles were measured by secondary ion mass spectrometry using a cesium, isotope 133, primary ion beam with an accelerating voltage of 5.03 kV and a raster of 250 µm.Oxidation test
The authors cite Z. Zheng et al., J. Electrochem. Soc., Vol. 137(3), 854-858 (1990), and summarize the procedure as follows. Specimens were ground with diamond grinding disks and polished to a finish of 0.1 µm. Specimens were cleaned by successive treatments in trichloroethylene, acetone, dilute 10% HCl acid solution, and buffered HF acid. Specimens were rinsed with dionized water after each of these treatments. Then, specimens were stored in a glass dessicator. Next, specimens were preheated in extra dry oxygen (3 ppm H2O) at 1150 °C in a horizontal fused silica tube furnace heated by molybdenum disilicide heating elements, to produce a layer of SiO2 approximately 300 Å thick. Na+ ions were implanted into the specimens using a multilayer implantation technique with a beam energy from 25 keV to 180 keV. Specimens were oxidized in a horizontal mullite tube furnace heated by molybdenum disilicide heating elements. Specimens were placed on a sintered alpha silicon carbide holder and pushed in and pulled out of the furnace with a quartz pushrod. Temperatures were maintained within 2 °C and measured by Pt/Pt 10% Rh thermocouples. The thickness of the oxide layer was measured using a monochromatic ellipsometer using a helium-neon laser with a wavelength of 6328 Å. Parabolic oxidation rates were calculated from oxide thickness versus oxidation time data. Activation energy was computed from measurements of parabolic oxidation rates at 1100 °C, 1200 °C, and 1300 °C.
| Amount of Element ( formula units ) |
Element ( no unit ) |
|---|---|
| 1 | Si |
| 1 | C |
| Temperature ( °C ) |
Na+ implant ( ppm ) |
Corrosion Activtn Energy ( kJ/mol ) |
|---|---|---|
| 1200 | 0 | 123 |
| 1200 | 50 | 144 |
| 1200 | 1000 | 128 |
| Temperature ( °C ) |
Na+ implant ( ppm ) |
Diffusing Species |
Diffusion Coefficient ( mm2 h-1 ) |
|---|---|---|---|
| 1100 | 0 | O2 | -8.19 |
| 1200 | 0 | O2 | -7.85 |
| 1300 | 0 | O2 | -7.62 |
| 1100 | 50 | O2 | -8.05 |
| 1200 | 50 | O2 | -7.64 |
| 1300 | 50 | O2 | -7.35 |
| 1100 | 1000 | O2 | -7.92 |
| 1200 | 1000 | O2 | -7.59 |
| 1300 | 1000 | O2 | -7.30 |
| Amount of Element ( formula units ) |
Element ( no unit ) |
|---|---|
| 3 | Si |
| 4 | N |
| Temperature ( °C ) |
Na+ implant ( ppm ) |
Corrosion Activtn Energy ( kJ/mol ) |
|---|---|---|
| 1200 | 0 | 460 |
| 1200 | 50 | 404 |
| 1200 | 1000 | 384 |
| Amount of Element ( formula units ) |
Element ( no unit ) |
|---|---|
| 1 | Si |
| 1 | C |
| Mass Fraction of Impurity ( % ) |
Impurity ( no unit ) |
|---|---|
| 3.00 | Al |
| 0.04 | B |
| 0.01 | Fe |
| 0.01 | Ti |
| 0.04 | Ca |
| 0.01 | Mg |
| 0.005 | V |
| 0.01 | Cu |
| 0.003 | Ni |
| 0.02 | Cr |
| 0.005 | Mn |
| Temperature ( °C ) |
Na+ implant ( ppm ) |
Corrosion Activtn Energy ( kJ/mol ) |
|---|---|---|
| 1200 | -- | 123 |
| Density ( g cm-3 ) |
|---|
| 3.16 |
No measurement details were noted.