Reactive atomization of silicon to form in situ oxide sintering aids
- Univ. of California, Irvine, CA (United States). Dept. of Chemical Engineering and Materials Science
- California State Polytechnic Univ., Pomona, CA (United States). Chemical and Materials Engineering Dept.
The present investigation demonstrated the feasibility of using reactive atomization to produce Si powder with in situ oxide sintering aids. With further process optimization, this powder may be an alternative starting material to the conventional, mechanically blended, Si-plus-oxide powder used to produce commercial sintered reaction bonded silicon nitride (SRBSN). In the reactive atomization approach, yttrium and aluminum additives were introduced into silicon metal during induction melting. Reactive atomization was accomplished using a N{sub 2}-5 pct O{sub 2} mixture as the atomization gas. During atomization, oxygen in the atomization gas reacted with Y and Al in the Si melt to produce Y{sub 2}O{sub 3} and Al{sub 2}O{sub 3}, which act as in situ sintering aids. The reactive atomized powder demonstrated a Gaussian distribution with a mean diameter of 36 {micro}M. The powder fines (<38 {micro}m) were used to produce cold isostatically pressed compacts that were subsequently reaction bonded and sintered. The results demonstrate that {beta}-Si{sub 3}N{sub 4} formed during reaction bonding and sintering. The density of the SRBSN was 77 pct of theoretical. Transmission electron microscopy (TEM) studies indicated the presence of a glassy phase on the grain boundaries, which is typical in SRBSN and indicative of the presence of the in situ sintering aids. A kinetic model was used to study the influence of processing parameters, such as droplet temperature and oxygen partial pressure, on the kinetics of oxide formation during reactive atomization. The results suggest that the volume fraction of oxides increases with increasing droplet temperature and oxygen partial pressure in the atomization gas mixture.
- OSTI ID:
- 282256
- Report Number(s):
- CONF-950201--
- Journal Information:
- Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 8 Vol. 27; ISSN 0360-2133; ISSN MTTABN
- Country of Publication:
- United States
- Language:
- English
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