Abstract
AbstractThe influence of the additive β-Si3N4 on the formation and oxidation of Si4Al2O2N6 during the sintering of Al, Si, and Al2O3 powders under flowing nitrogen atmosphere was examined. An increasing molar percentage of β-Si3N4 was shown to alter the morphology of Si4Al2O2N6 from a fiber-like to a rod-like structure and also shortened the time needed to form a dense, continuous oxide layer, which served as a barrier to the diffusion of O2. An optimal molar percentage of β-Si3N4 of 29.9 mol% was discovered, at which the grain growth was enhanced, and the surface area was, in turn, reduced, yielding superior resistance to oxidation. Our results provided a theoretical basis for the formation of β-SiAlON and demonstrated the potential of its use in high-temperature oxidizing environments.
Highlights
Introduction βSi3N4 has a hexagonal close-packed crystal structure, which is composed of covalently bonded [SiN4] tetrahedral subunits
In the present Al2O3–Al–Si–N2 system, Si and Al reacted with N2 to form Si3N4 and AlN, thereby nitrogen was introduced in to the structure, and Al2O3 provided Al–O units for the formation of β-SiAlON
Si4Al2O2N6 was prepared via high-temperature nitridation of a mixture of α-Al2O3, metal Al, and Si powders and β-Si3N4 as an additive
Summary
Introduction βSi3N4 has a hexagonal close-packed crystal structure, which is composed of covalently bonded [SiN4] tetrahedral subunits. Li et al found that β-SiAlON powder prepared using a combustion method displayed a weaker oxidation resistance with an increasing addition of diluents, which was attributed to a decrease in particle size [16]. It is known that the formation and mechanical properties of SiAlON ceramics is enhanced with an increasing molar content of β-Si3N4 in the precursor [22].
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