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Reactive Melt Infiltration of Silicon-Niobium Alloys in Microporous CarbonsStudies of the reactive melt infiltration of silicon-niobium alloys in microporous carbon preforms prepared by the pyrolysis of a polymer precursor have been carried out using modeling, Differential Thermal Analysis (DTA), and melt infiltration. Mercury porosimetry results indicate a very narrow pore size distribution with virtually all the porosity within the carbon preforms open to infiltrants. The morphology and amount of the residual phases (niobium disilicide and silicon) in the infiltrated material can be tailored according to requirements by careful control of the properties (pore size and pore volume) of the porous carbon preforms and alloy composition. The average room temperature four-point flexural strength of a reaction-formed silicon carbide material (made by the infiltration of medium pore size carbon preform with Si - 5 at. % Nb alloy) is 290 +/- 40 MPa (42 +/- 6 ksi) and the fracture toughness is 3.7 +/- 0.3 MPa square root of m. The flexural strength decreases at high temperatures due to relaxation of residual thermal stresses and the presence of free silicon in the material.
Document ID
19950028435
Acquisition Source
Glenn Research Center
Document Type
Reprint (Version printed in journal)
Authors
Singh, M.
(NASA Lewis Research Center Cleveland, OH, United States)
Behrendt, D. R.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
August 16, 2013
Publication Date
July 1, 1994
Publication Information
Publication: Journal of Materials Research
Volume: 9
Issue: 7
ISSN: 0884-2914
Subject Category
Materials Processing
Report/Patent Number
E-8251
Accession Number
95A60034
Distribution Limits
Public
Copyright
Other

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