Hot-pressed ceramics of ultradisperse composite powders

Journal Article · Thu Sep 01 04:00:00 EDT 1994 · Refractories

DOI:https://doi.org/10.1007/BF02226846· OSTI ID:103030

Tkacheva, I I ^[1]

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1. ONPP Tekhnologiya, Kaluga (Russian Federation)

The regularities of variation of the microstructure, phase composition, degree of crystallinity, and properties of hot-pressed ceramics prepared from ultradisperse composite powders of the Si{sub 3}N{sub 4}-Y{sub 2}O{sub 3} system depending on the {beta}/{alpha} phase ratio in Si{sub 3}N{sub 4} and the concentration of Y{sub 2}O{sub 3} are discussed. An increase in the concentration of Y{sub 2}O{sub 3} in composite powders up to 15-18% and a decrease in the {beta}/{alpha} of Si{sub 3}N{sub 4} lead to a change of the composition of the secondary crystalline phases with an increase in their refractoriness (from silicon oxynitride and yttrium silicates to complex yttrium-silicon oxynitrides), a lower concentration of the vitreous phase, a higher degree of crystallinity, and a higher content of stretched grains in the structure of the ceramics. The presence of the high-melting phase of yttrium-silicon oxynitrides improves the phase and granular homogeneity of the structure that forms by the type of solid solutions, with an essentially similar composition of the grains and the intergranular phase. The formation of a high-melting fine-grained self-toughening structure with a coefficient of grain elongation up to 8-9 ensures a high and practically stable level of the mechanical properties of the synthesized materials at temperatures up to 1400-1500{degrees}C.

• Sponsoring Organization: USDOE
• OSTI ID: 103030
• Journal Information: Refractories, Journal Name: Refractories Journal Issue: 1-2 Vol. 35; ISSN 0034-3102; ISSN REFRAL
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ELONGATION
HOT PRESSING
MECHANICAL PROPERTIES
MELTING
MICROSTRUCTURE
PHASE STUDIES
POWDERS
SILICON NITRIDES
SOLID SOLUTIONS
YTTRIUM OXIDES