Effect of zirconia content on the oxidation behavior of silicon carbide/zirconia/mullite composites
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Citations
Synthesis and structure-property relationships of a new family of layered carbides in Zr-Al(Si)-C and Hf-Al(Si)-C systems
Dependence of Oxidation Modes on Zirconia Content in Silicon Carbide/Zirconia/Mullite Composites
Retention of SiC during development of SiC-MxSiyOz composites [M = Al, Zr, Mg] by reaction bonding in air
Modeling of oxidation behavior of SiC-reinforced ceramic matrix composites
Phase Evolution in Silicon Carbide-Whisker-Reinforced Mullite/Zirconia Composite during Long-Term Oxidation at 1000° to 1350°C
References
Oxidation of Silicon Carbide‐Reinforced Oxide‐Matrix Composites at 1375° to 1575°C
Mechanical and Microstructural Characterization of Mullite and Mullite‐SiC‐Whisker and ZrO2‐Toughened‐Mullite—SiC‐Whisker Composites
Transport Processes in Composite Media
Effects of Oxygen Partial Pressure on the Oxidation of Silicon Carbide
Oxidation Behavior of SiC‐Whisker‐Reinforced Alumina‐Zirconia Composites
Related Papers (5)
Dependence of Oxidation Modes on Zirconia Content in Silicon Carbide/Zirconia/Mullite Composites
Oxidation of Silicon Carbide‐Reinforced Oxide‐Matrix Composites at 1375° to 1575°C
Compositional dependence of phase formation mechanisms at the interface between titanium and calcia-stabilized zirconia at 1550°C
Frequently Asked Questions (17)
Q2. What is the diffusivity of SiCp in a matrix?
The oxygen diffusivity in a matrix with >20 vol% ZrO2 should be very close to that in ZrO2, which leads to a rapid increase in the oxidation rate of SiC particles.
Q3. What is the effect of the interaction between the matrix and the oxide product?
In addition, the formation of ZrSiO4, as a result of the interaction between the matrix and the oxide product, would lead to a reduction of the oxidation rate.
Q4. Why does the oxidation rate in SiC particles increase as the ZrO2 content?
Because the oxygen diffusivity in the matrix now becomes much faster than that in the silica layer around SiC, the oxygen will pass over partially oxidized SiC particles and continuously diffuse into the inner region, leading to the oxidation of more SiC particles and, thus, a deep oxidation zone.
Q5. What is the definition of the silica layer in a SiC-containing composite?
the silica layer of an individual SiC particle in a SiC-containing composite means the layer of SiO2 that is formed as a result of the oxidation reaction occurring on the surface of the SiC particle.
Q6. At what temperature is the diffusivity of SiCp in mullite?
At 1000°C, the diffusivity in ZrO2 is between 10−9 and 10−5 cm2/s; this value is dependent on crystal structure, additives, and the stoichiometry.
Q7. Why is the oxidation rate in SiO2 so low?
Because the oxygen diffusivity slowly increases as the ZrO2 content increases in the range of f < fc, according to the effective medium theory,33,34it is inferred that the oxidation rate will also slowly increase as the ZrO2 content increases.
Q8. What is the definition of the oxidation zone of a SiC-containing composite?
the oxidation zone of a SiC-containing composite after exposure in an oxidizing environment is defined as the zone from the outermost surface of the composite to the depth where no oxidation of the incorporated SiC particles can be detected.
Q9. What is the effect of ZrSiO4 on the oxidation rate of si?
the substitution of ZrO2 by ZrSiO4 will slow the oxygen diffusion in the matrix, which leads to a decrease in the oxidation rate.
Q10. Why were the specimens drawn from the furnace not reloaded?
Specimens drawn from the furnace were not reloaded for further oxidation, to avoid the formation of extended cracks due to thermal shock.
Q11. What is the order of Dm in a SiC-containing composite?
percolation theory predicts that Dm has the approximate order of D1 if f < fc and has the approximate order of D2 if f > fc (where D1 and D2 are the diffusivities of a certain species in the two phases, Dm is the diffusivity of that species in the composite, and f is the volume fraction of the second phase).
Q12. Why did the cross-sectional samples exhibit a distinct structure?
The cross-sectional samples clearly exhibited a distinct layered structure; this layering was due to the different extent of oxidation at various depths, which caused a change in composition.
Q13. How deep did the SiC particles oxidize?
The SiC particles were slightly oxidized, even at a depth of >600 mm, which indicates a much-larger oxidized depth than that of the MZY15/SiC composite exposed for 500 h.IV.
Q14. What is the oxidation zone of SiCp/ZrO2/mullite?
Because oxygen diffusivity in ZrO2 is much higher than that in mullite (Table II) and using mullite and ZrO2 as the first and second phases, respectively, the relationships of oxygen diffusivity in ZrO2/mullite matrices would beDmatrix O ≈ order of DzirconiaO (if f > fc) (2a)Dmatrix O ≈ order of DmulliteO (if f < fc) (2b)where the superscript denotes the diffusing species (oxygen).
Q15. How is the inward diffusion of oxygen controlled?
That is, the inward diffusion of oxygen may be controlled by either diffusion through the ZrO2-containing matrix or diffusion through the silica layer, depending on which one is slower.
Q16. What is the reason why the weight gain at 1200°C did not increase?
The fact that the weight gain at 1200°C did not increase (or even slightly decrease) when the ZrO2 content was >80 vol% (Fig. 2) may be attributed to the fact that more ZrSiO4 formed at higher ZrO2 contents, as determined by XRD (Fig. 4).V. Summary
Q17. What was the composition of the MZY50/SiC composite?
The as-hot-pressed sample consisted of four major phases: mullite, monoclinic ZrO2 (m-ZrO2), tetragonal ZrO2 (t-ZrO2), and SiC (Fig. 3(a)).