Synthesis of Si{sub 3}N{sub 4} fibres by a gas-phase process
Conference
·
OSTI ID:99130
- Eidgenoessische Materialpruefungs- und Forschungsanstalt, Duebendorf (Switzerland)
A gas-phase process has been developed to produce Si{sub 3}N{sub 4}-fibres for high temperature applications. The reaction 3SiO{sub 2}+4NH{sub 3} {yields} Si{sub 3}N{sub 4}+6H{sub 2}O operates at temperatures above 1400{degrees}C by evaporation of SiO and dissociation of NH{sub 3} into active nitrogen and hydrogen atoms. Active hydrogen can crack the SiO-bonds while the nitrogen atoms react with unbounded Si atoms thus forming Si{sub 3}N{sub 4} fibres. The growth process and the fibre yield is influenced by the substrate material. The reaction time, the gas flow rate in the reaction chamber and the type of metallic additives which are added to the silica. Depending on the reaction parameters the fibres grow amorphous or crystalline with straight or helical coiled shape. Tensile strength measurements of amorphous fibres have values up to 5 GPa.
- OSTI ID:
- 99130
- Report Number(s):
- CONF-940911--
- Country of Publication:
- United States
- Language:
- English
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