Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1985-10-31
1988-04-05
Bell, James J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
428240, 428297, 428323, 428408, 428903, 501 95, 501 96, B32B 516, C04B 3502
Patent
active
047358505
ABSTRACT:
A porous substrate formed from an agglomeration of fibers preferably has a carbonaceous composition. A binder is applied to the substrate. The binder may illustratively be an acrylic or beeswax to vaporize and form pyrolized carbon during pyrolysis or may illustratively be a phenolic resin, a furfural resin or pitch to form pyrolyzed carbon on the fibers during pyrolysis. A mixture of particles having the same approximate size as the diameter of the fibers is then applied to the fibers to become mechanically locked in the substrate pores. The mixture may contain (a) a first material (preferably a compound containing boron) which oxidizes and melts at a relatively low temperature and is relatively viscous when melted, (b) a second material (preferably a compound containing silicon) which oxidizes and has an increased melting temperature and is more viscous than the first material when melted and (c) a refractory material (preferably a compound containing zirconium) having a considerably higher melting temperature oxide than the first and second materials. The first material may be obtained from group 3a of the periodic table, the second material from group 4a of the periodic table and the third material from groups 4b and 5b of the periodic table. An impermeable coating such as a carbide, oxide or a nitride is thereafter applied to the substrate. The impermeable coating tends to crack at elevated temperatures. The adjacent particles in the mixture melt and flow into the cracks to inhibit crack amplification. The ease of flow is dependent upon the proportions of the first, second and third materials in the mixture. The particles displaced in the mixture from the cracks remain mechanically locked to the substrate.
REFERENCES:
patent: 3594049 (1971-07-01), Turner
patent: 4397901 (1983-08-01), Warren
Bell James J.
Roston Ellsworth R.
Schwartz Charles H.
Science Applications International Corporation
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