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Nitridation of siliconSilicon powders with three levels of impurities, principally Fe, were sintered in He or H2. Non-densifying mechanisms of material transport were dominant in all cases. High purity Si showed coarsening in He while particle growth was suppressed in H2. Lower purity powder coarsened in both He and H2. The same three Si powders and Si /111/ single crystal wafers were nitrided in both N2 and N2/H2 atmospheres. Hydrogen increased the degree of nitridation of all three powders and the alpha/beta ratio of the lower purity powder. Some Si3N4 whiskers and open channels through the surface nitride layer were observed in the presence of Fe, correlating with the nitridation-enhancing effects of Fe. Thermodynamic calculations showed that when SiO2 is present on the Si, addition of H2 to the nitriding atmosphere decreases the amount of SiO2 and increases the partial pressure of Si-containing vapor species, that is, Si and SiO. Large amounts of NH3 and SiH4 were also predicted to form.
Document ID
19820007324
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Shaw, N. J.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 4, 2013
Publication Date
October 1, 1981
Subject Category
Nonmetallic Materials
Report/Patent Number
E-921
NASA-TM-82722
Accession Number
82N15197
Funding Number(s)
PROJECT: RTOP 505-33-12
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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