The ZrB<sub>2</sub> Volatility Diagram

Fahrenholtz, William G.

doi:10.1111/j.1551-2916.2005.00599.x

Cited by 229 publications

(141 citation statements)

References 15 publications

Supporting

Mentioning

134

Contrasting

Order By: Relevance

“…However, the oxidation resistance of ZrB 2 is very poor at temperatures above 1400°C due to the volatilization of B 2 O 3 , which results in formation of a porous, non-protective ZrO 2 layer. [4,5] Numerous investigations to improve the oxidation resistance of ZrB 2 have been reported. [4,[6][7][8][9][10][11] It was found that SiC addition provided improved oxidation resistance by promoting the formation of borosilicate glass.…”

Section: Introductionmentioning

confidence: 99%

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Zhang

Kurokawa

2015

Oxid Met

View full text Add to dashboard Cite

The oxidation behavior of ZrB 2 -SiC composites with different SiC addition was investigated at 1273 K and 1473 K in air for 12 h in this study. The SiC addition contents ranged from 0 to 30wt%. The results showed that when ZrB 2 -SiC composites were oxidized at 1273 K in air, a two-oxide layer-structure forms: a continuous glassy layer and a ZrO 2 layer contained unoxidized SiC. When SiC content is 5wt% and 10wt%, the glassy layer is mainly composed by B 2 O 3 . When SiC content is 20wt% and 30wt%, a borosilicate glass could be formed on the top layer, which could improve the oxidation resistance of ZrB 2 . When ZrB 2 -SiC composites were oxidized at 1473 K in air, the oxide layer was composed of ZrO 2 and SiO 2 and unreacted SiC. Additionally, when SiC addition content was higher than 10wt%, a continuous borosilicate glass layer could be formed on the top of the oxide layer at 1473 K. With the increase of SiC content in ZrB 2 , the oxide layer thickness decreased at both 1273 K and 1473 K.

show abstract

Section: Introductionmentioning

confidence: 99%

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Zhang

Kurokawa

2015

Oxid Met

View full text Add to dashboard Cite

show abstract

“…The crystalline oxide phase ZrO 2 (c) formed is often highly porous-although in arc jet testing above 2000 K it appears that ZrO 2 (c) could sinter into a less porous compact layer, 16,17 thereby potentially becoming protective also. Whether the in situ formed ZrO 2 (c), when fully dense, is as a significant barrier to oxygen diffusion as SiO 2 (l) in open-circuit condition, is an interesting question that depends on its electronic conductivity, which in turn depends on how the charge defects are compensated inside the crystal, related to the amount of impurities.…”

mentioning

confidence: 99%

“…SiO 2 ðlÞ þ COðgÞ (2) respectively. Intense research is ongoing to characterize and enhance this scale as a barrier against oxygen [11][12][13][14][15][16][17][18][19][20][21][22][23] (the scale microstructure can be seen in, for example, Fig. 4 of Opila et al 15 ), which apparently is superior to that of either monolithic diboride or SiC at the intended high temperatures (see Fig.…”

mentioning

confidence: 99%

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB₂+SiC and Oxygen Transport Mechanisms

Lenosky

Först

et al. 2008

Journal of the American Ceramic Society

View full text Add to dashboard Cite

Refractory diboride with silicon carbide additive has a unique oxide scale microstructure with two condensed oxide phases (solid+liquid), and demonstrates oxidation resistance superior to either monolithic diboride or silicon carbide. We rationalize that this is because the silica‐rich liquid phase can retreat outward to remove the high SiO gas volatility region, while still holding onto the zirconia skeleton mechanically by capillary forces, to form a “solid pillars, liquid roof ” scale architecture and maintain barrier function. Basic assessment of the oxygen carriers in the borosilicate liquid in oxygen‐rich condition is performed using first‐principles calculations. It is estimated from entropy and mobility arguments that above a critical temperature TC∼1500°C, the dominant oxygen carriers should be network defects, such as peroxyl linkage or oxygen‐deficient centers, instead of molecular O2* as in the Deal–Grove model. These network defects will lead to sublinear dependence of the oxidation rate with external oxygen partial pressure. The present work suggests that there could be significant room in improving the high‐temperature oxidation resistance by refining the oxide scale microstructure as well as controlling the glass chemistry.

show abstract

“…A volatility diagram [2,[14][15][16][17][18][19] plots the vapor pressure of the predominant gaseous species in equilibrium with the various condensed phases as a function of oxygen partial pressure and temperature, so it is appropriate for understanding the oxidation behaviors of UHTCs when more than one gaseous species is involved. Thermodynamic calculations have been conducted on the volatility diagrams by Lou and coworkers [15,16] to study the gas-solid interactions for material systems such as Mg-O, Al-O, Si-O, Si-N, Si-N-O and Si-C-O.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Calculation of HfB2 Volatility Diagram

Zhang

Zeng

et al. 2011

J. Phase Equilib. Diffus.

View full text Add to dashboard Cite

The thermodynamics of the oxidation of HfB 2 at temperatures of 1000, 1500, 2000, and 2500 K have been studied using volatility diagrams. Both the equilibrium oxygen partial pressure (P O 2 ) for the HfB 2 (s) to HfO 2 (s) plus B 2 O 3 (l) and the partial pressures of B-O vapor species formed due to B 2 O 3 (l) volatilization increase with increasing temperature. Vapor pressures of the predominant gaseous species also increase with P O 2 . At 1000 K, the predominant vapor transition sequence is predicted be BO(g) fi B 2 O 2 (g) fi B 2 O 3 (g) fi BO 2 (g) with increasing P O 2 , and the predominant gas is BO 2 (g) with a pressure of 1.27310 26 Pa under the condition of P O 2 = 20 kPa. At higher temperatures of 1500, 2000, and 2500 K, the system undergoes vapor transitions in the same sequence of B(g) fi BO(g) fi B 2 O 2 (g) fi B 2 O 3 (g) fi BO 2 (g). Under the same condition of P O 2 = 20 kPa, the predominant vapor species is B 2 O 3 (g) with pressures of 2.38, 4.49310 3 , and 3.55310 5 Pa, respectively. Volatilization of B 2 O 3 (l) may produce porous HfO 2 scale, which is consistent with the experimental observations of HfB 2 oxidation in air. The present volatility diagram of HfB 2 shows that HfB 2 exhibits oxidation behavior similar to ZrB 2 , and factors other than volatility of gaseous species affect the oxidation rate.

show abstract

The ZrB₂ Volatility Diagram

Cited by 229 publications

References 15 publications

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB₂+SiC and Oxygen Transport Mechanisms

Thermodynamic Calculation of HfB2 Volatility Diagram

Contact Info

Product

Resources

About

The ZrB2 Volatility Diagram

Cited by 229 publications

References 15 publications

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Effect of SiC Addition on Oxidation Behavior of ZrB2 at 1273 K and 1473 K

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB2+SiC and Oxygen Transport Mechanisms

Thermodynamic Calculation of HfB2 Volatility Diagram

Contact Info

Product

Resources

About

The ZrB₂ Volatility Diagram

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB₂+SiC and Oxygen Transport Mechanisms