Reaction thermodynamics in the SiO2-SiC system

Борисов, В. Г.; Yudin, B. F.

doi:10.1007/bf01295401

Cited by 13 publications

(5 citation statements)

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“…SiO 2 impurity can be removed by reaction between SiC and SiO 2 at temperatures above 1700 • C. This processing is often called as self-cleaning of SiC [22]. B 2 O 3 will be vaporized significantly at temperatures above 1200 • C. Unlike B 2 O 3 , HfO 2 with melting point of 2810 • C has very low vapor pressure in the sintering temperature range.…”

Section: Oxygen Contentmentioning

confidence: 98%

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Liu

Zhang

et al. 2015

Journal of the European Ceramic Society

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Section: Oxygen Contentmentioning

confidence: 98%

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Liu

Zhang

et al. 2015

Journal of the European Ceramic Society

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“…These are, respectively, works on H 2 /N 2 O mixtures, on N 2 O at high concentration, and on N 2 O diluted in inert gases. It should be mentioned that there are several works − related to the title reaction which will not be further discussed here. These early studies have been criticized and discounted in BDH73; see the discussion there regarding reaction R1.…”

Section: Evaluation Of Literature Datamentioning

confidence: 99%

Kinetics of the O(³P) + N₂O Reaction. 2. Interpretation and Recommended Rate Coefficients

and

Anderson

2000

J. Phys. Chem. A

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The reaction O( 3 P) + N 2 O is important to models of NO x pollutant and propellant chemistry and to the understanding of the thermal decomposition of N 2 O, which has historically played a key role in the development of unimolecular reaction theory. The reaction has two important product channels: ). Rate coefficients of these reactions have been the subject of several reviews. However, clear reasons why many of the evaluated, nonretained data differ from recommendations have not previously been known. There has been a great deal of controversy over the rate coefficients, particularly for reaction R2. Here, the relevant data are critically evaluated using detailed chemical modeling as an important tool. The results explain many of the discrepancies. Some of the data of central importance in earlier evaluations are shown to be incorrect. Additionally, some important features of the global behavior of the mixtures studied, which had previously not been understood, are explained, and the possible effects of hypothetical H 2 O contamination on N 2 O shock tube studies was quantitatively investigated. It is shown that the bulk of the rate coefficient results remaining after the evaluations can be combined with the intermediate temperature results for k tot ) k 1 + k 2 from FGFAM (Fontijn, A.; Goumri, A.; Fernandez, A.; Anderson, W. R.; Meagher, N. E. J. Phys. Chem., preceding paper in this issue) to obtain fitted recommendations: k 1 ) 1.52 × 10 -10 exp(-13 930/T) cm 3 molecule -1 s -1 (1370-4080 K); k 2 ) 6.13 × 10 -12 exp(-8,020/T) cm 3 molecule -1 s -1 (1075-3340 K). Until recently, it was believed rate coefficients of the two product channels were approximately equal over a very wide temperature range. In contrast, the present study has led to the conclusion that reaction R2 dominates below, and reaction R1 above, 1840 K.

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“…Except for major parts of HfC and SiC, green pellets of HfC–SiC always contain some oxygen impurities (HfO 2 and SiO 2 ) and residual free carbon (C), the reactions would occur at different temperatures during sintering process of HfC–SiC, according to thermodynamic calculation and previous report:

\begin{matrix} {SiO}_{2} + 3 C & \to SiC + 2 CO (g) (T > 1530^{\circ} C, P_{CO} \\ = 1 atm, Δ G < 0) \end{matrix}

SiC + 2 {SiO}_{2} \to 3 SiO (g) + CO (g) (T > ˜ 1700^{\circ} C, P_{SiO} = 3 P_{CO} = 0.25 atm, Δ G < 0)

\begin{matrix} {HfO}_{2} + (3 - x) C & \to {HfC}_{1 - x} + 2 CO(g) ({for HfC}_{1.0}, \\ T > 1650^{\circ} C, P_{CO} = 1 atm, Δ G < 0) \end{matrix}

(3 - x) HfC + x {HfO}_{2 <...>}

…”

Section: Resultsmentioning

confidence: 94%

Pressureless Sintering of Hafnium Carbide–Silicon Carbide Ceramics

2013

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HfC-30 vol%SiC ceramics with a relative density of 99.7% was obtained by pressureless sintering at 2300°C for 0.5 h. The resultant ceramics showed fine microstructure with HfC grain size around 1 lm. The hardness (20.5 ± 0.2 GPa), bending strength (396 ± 56 MPa), and fracture toughness (2.81 ± 0.18 MPaÁm 1/2 ) of HfC-30 vol%SiC ceramics were at least 20% higher than those of monolithic HfC ceramics. The influences of SiC particle size, volume fraction, and the oxide impurity on the microstructure evolution of HfC-based ceramics were examined. The results indicate that SiC addition and the oxygen impurity introduced by ball milling play opposite roles in the HfC grain growth during sintering. The oxide impurity introduced by ball milling caused the HfC grain coarsening, whereas SiC particles inhibited the grain growth of HfC significantly.

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Reaction thermodynamics in the SiO2-SiC system

Cited by 13 publications

References 5 publications

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Kinetics of the O(³P) + N₂O Reaction. 2. Interpretation and Recommended Rate Coefficients

Pressureless Sintering of Hafnium Carbide–Silicon Carbide Ceramics

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Reaction thermodynamics in the SiO2-SiC system

Cited by 13 publications

References 5 publications

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Densification, microstructure evolution and mechanical properties of WC doped HfB2–SiC ceramics

Kinetics of the O(3P) + N2O Reaction. 2. Interpretation and Recommended Rate Coefficients

Pressureless Sintering of Hafnium Carbide–Silicon Carbide Ceramics

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Kinetics of the O(³P) + N₂O Reaction. 2. Interpretation and Recommended Rate Coefficients