Sodium-assisted oxidation of reaction-bonded silicon nitride

Mayer, Martin; Riley, F. L.

doi:10.1007/bf00544739

“…Mayer and Riley [22] mentioned that the oxidation rates in dry air at each temperature were the same within experimental error as those in wet air, the small quantity of water vapour in normal atmospheric air did not appear to have a significant effect on the reaction rates, and the slight irregular differences observed could be attributed to experimental error.…”

Section: Introductionmentioning

confidence: 89%

“…H20 ) and in wet air (approximately 1.5% H20) obtained by Mayer and Riley [22]. The effect of water vapour on the oxidation of silicon nitride is not as strong as that of silicon carbide [23].…”

Section: Oxidation In a Wet Atmospherementioning

confidence: 96%

Oxidation of silicon nitride in a wet atmosphere

Maeda

¹

,

Nakamura

²

,

Ohkubo

³

1989

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The effect of water vapour on oxidation was studied with hot-pressed silicon nitride containing both yttria and alumina as sintering aids in wet air flow with 10, 20, 30, and 40vo1% H20 at 1300°C for 10Oh. The oxidation kinetics were determined in a wet air flow with 20vo1% H20 and in a dry air flow at 1300 °C for oxidation times up to 360h. The water vapour in the atmosphere slightly influenced the oxidation and accelerated the reaction, and the weight gained on oxidation in a wet atmosphere had an increasing tendency with increasing water vapour content. The oxidation proceeded in a diffusion-controlled manner in both wet and dry atmospheres. The values of weight gained in wet oxidation varied to a greater degree than in dry oxidation. Water vapour had a strong effect on the devitrification of the amorphous oxide. This process was presumed to promote the rate of oxidation more than in dry atmosphere. The water vapour also had a strong roughening effect on the surface oxide layer grown during oxidation. The flexural strength at room temperature was degraded by oxidation in a wet atmosphere and it is presumed to be degraded by wet oxidation slightly and consecutively with time.

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“…In a situation where the supply of sodium is limited, the reaction will stop at some composition given by the liquidus Na20-SiO2/SiO2 line on the Na20-SiO2 phase diagram. A layered Na20-SiO2(1)-SiO2(s) structure will result (Mayer andRiley, 1978 and. This is shown in Figure 36.…”

Section: 9moltensaltcorrosionmentioning

confidence: 98%

Corrosion of Ceramic Materials

Opila

¹

,

Jacobson

²

2013

Materials Science and Technology

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The sections in this article are Introduction Experimental Techniques Oxidation of Silica‐Formers Properties of Silica Basic Oxidation Mechanisms of Silica Formers Oxidation of Silicon Oxidation of Pure Si C in Dry Oxygen Oxidation of Pure Si 3 N 4 in Dry Oxygen Oxidation of Si C and Si 3 N 4 in the Presence of Low Level Impurities Oxidation of Si C and Si 3 N 4 Containing Sintering Aids Oxidation of Silica Formers in Other Oxidants Oxidation of Si , Si C , and Si 3 N 4 in Water Vapor Oxidation of Si C in CO 2 Cyclic Oxidation of Silica‐Formers Effect of Oxidation on Fracture Strength of Silica‐Formers Volatility Direct Vaporization Oxide–Substrate Reactions Active Oxidation Molten Salt Corrosion Refractory Oxide Coatings on Silica‐Forming Ceramics Oxidation of Alumina‐Forming Non‐oxides Oxidation of AlN Oxidation of Al 4 C 3 Boria‐Forming Ceramics Transition Metal Carbides and Nitrides Transition Metal Carbides Transition Metal Nitrides Oxidation of Ceramics Forming Multi‐Component Scales Mixed Oxide Scales Transition Metal Borides Oxidation of Complex Systems Resulting in Mixed Oxide Scales Composites which form Compound Oxides SiC‐Reinforced Al 2 O 3 Si 2 N 2 OZrO 2 Ti B 2  Al 2 O 3 Composites which form Single Phase Oxide Solid Solutions Ceramic Matrix Composites Summary

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“…This oxidation is enhanced in the presence of Na which has been reported to result in Na2O-SiO2 silicate species which are then more readily oxidized than the Si3N4. 13) Gas phase corrosion has also been described in terms of the effects of Na together with HF. 14) Enhanced degradation in the gas phase is reported to be due to the presence of Na species resulting in the formation of volatile SiF4 through the following Eqs.…”

Section: Jcs-japanmentioning

confidence: 99%

Corrosion behavior of reaction bonded Si3N4-SiC and SiAlON-SiC composites in simulated aluminum smelting conditions

Jones

¹

,

Etzion

²

,

Metson

³

et al. 2008

J. Ceram. Soc. Japan

6

0

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Si3N4-SiC composites, which are widely used as sidewall refractories in aluminum smelting cells, have been produced by reaction bonding and their corrosion performance assessed in simulated aluminum electrochemical cell conditions. Additional samples were produced with the silicon nitride bonding phase replaced by β SiAlON with compositions ranging from Z = 1-4 in Si6-zAlzOzN8-z. The formation of the Si3N4 and SiAlON bonding phases were studied by reaction bonding of silicon powders in a nitrogen atmosphere at low temperatures to promote the formation of silicon nitride, followed by a higher heating step to produce β SiAlON composites of different composition. The corrosion performance was studied in a laboratory scale aluminum electrolysis cell where samples were exposed to both liquid attack from molten salt bath and corrosive gas attack. For the Si3N4 bonded samples, the corrosion resistance was shown to be strongly dependent on the environment during corrosion testing, with samples in the gas phase showing higher corrosion than those immersed in the bath. Samples that had been pre-soaked in the bath and then tested in the gas phase showed the highest corrosion due to the combined effects of bath penetration and gas attack. For the SiAlON bonded samples, the corrosion results showed similar trends but were complicated by the presence of a strongly adherent layer on the samples which influenced volume measurements. This layer is believed to be alumina and appears to form through an interaction with the SiAlON and the bath components, since no such layer was observed for the silicon nitride samples.

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Sodium-assisted oxidation of reaction-bonded silicon nitride

Cited by 60 publications

References 19 publications

Oxidation of silicon nitride in a wet atmosphere

Oxidation of silicon nitride in a wet atmosphere

Corrosion of Ceramic Materials

Corrosion behavior of reaction bonded Si3N4-SiC and SiAlON-SiC composites in simulated aluminum smelting conditions

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