Scale effect of the testing furnace on the oxidation of silicon nitride ceramics

Maeda, Masafumi; Nakamura, Kazuo; Tsuge, Akira

doi:10.1007/bf00730723

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…The pitfalls are apparatus related: Temperature and atmosphere constancy have to be guaranteed, crosscontamination must be avoided, and interaction with furnace linings and crucible material minimized. The danger of those points is often underestimated; there are reports of different results from a mere change in the furnace size [27].…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Thermodynamic data suggest that a two-step oxidation 2 Si3N4 + 1; O2 H 3 Si2N20 + N2 Si2N20 + 14 O2 + 2 SiOz + N2 (26) (27) and and accordingly a duplex layer in a oxygen potential gradient, developing in a scale, is favored. However, the discussion of the correct kinetics, the presence or absence of a sublayer of Si2N20, the activation energy, and other issues are still not settled [14,.…”

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confidence: 99%

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Corrosion of Hard Materials

Nickel¹,

Gogotsi²

2000

Handbook of Ceramic Hard Materials

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Corrosion may be defined as the physical and chemical alteration of a material due to its interaction with the environment of interest. It must be emphasized that corrosion resistance is not a material property but a system property and real environments have a high variability in both chemical and physical boundary conditions.Corrosive alteration leads to a change in the desired original properties and so corrosion usually, but not exclusively, has adverse effects and causes a decrease in strength, toughness, hardness, and increases wear. There are many reasons for the degradation of properties by corrosion. Decrease of the cross-section carrying the load, pitting, stress induced by phase changes, and grain separation are some of the common features.Some hard materials, namely Sic and Si3N4, are designed to serve at high temperatures, where corrosion resistance is an essential feature. This is the reason why a large proportion of the ceramic literature on corrosion, including recent textbooks [ 1-51, deals with these materials.In order to react with the environment, the material must not be in equilibrium with it. The hard materials covered in this chapter are non-oxides and hence this condition is fulfilled for all of them in almost every application environment, including ambient air. The applicability of hard materials thus rests on the kinetics of the processes.Before discussing individual materials we will introduce important terms and concepts in corrosion like attack modes, media classes, location of attack, kinetics, and their parameters. We feel that this is necessary for understanding of the discussion of the materials, because there is no generally accepted standard procedure that allows us to compare the corrosion behavior of materials as easily as other properties like mechanical strength or hardness. Corrosive MediaThe compositional variability of environments is so vast that only very few attempts have been made to classify corrosion behavior from the point-of-view of the discrete environment at hand. A noteworthy exception is the Dechema handbook [6],in which valuable information may be found if the corrosive agent is simple and known (e.g. acetates, chlorine, steam). However, its main thrust is on the corrosion of metals.

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Section: Experimental Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Corrosion of Hard Materials

Nickel¹,

Gogotsi²

2000

Handbook of Ceramic Hard Materials

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“…The E 4.1 /L p value decreases with increasing packing density. 16 In all cases, fast weight loss begins at 1500°C. SN-YM in Table VI shows that this is indeed the case.…”

Section: B Effect Of Packing Density and Sintering Timementioning

confidence: 98%

Effects of powder bed conditions on the liquid-phase sintering of Si₃N₄

et al. 2002

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The effects of the active and passive protection mechanisms of powder beds on the sintering of Si 3 N 4 were investigated. Shrinkage, density, and coloring behavior of sintered samples were analyzed using different compositions and packing conditions of powder beds based on BN and Si 3 N 4 with different additives. Y 2 O 3 additive in the powder bed influences the weight change and phase formation behavior of the samples, although it has a very low vapor pressure at the sintering temperature. When MgO/Y 2 O 3 was used as sintering additives, the packing density and thickness of the powder bed had a much stronger effect than in the case of Al 2 O 3 /Y 2 O 3 . For the optimization of the powder bed conditions, the vapor pressure and chemical stability of sintering additives at the sintering temperature has to be considered. a) Delegated to Max-Planck-Institut fü r Metallforschung by Hanyang University.

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