Process for manufacturing boron nitride fiber felt using a Fourdrinier machine

A process for producing boron nitride-bonded boron nitride fiber mats, comprising the steps of:

• blending boron nitride fibers and boron oxide fibers in a ratio by weight of about 50-99% of boron nitride fibers and about 1-50% of boron oxide fibers, said fibers having a length of from about 0.1 inch to about 1.0 foot, with CCl.sub.2 F--CClF.sub.2 to form a homogeneous slurry;
• distributing said slurry in an essentially uniformly thick layer upon the moving screen of a Fourdrinier machine;
• suctioning essentially all of said Freon from said slurry-supporting surface of said screen, yielding a boron nitride and boron oxide fiber felt;
• heating said felt in an anhydrous gas selected from the group consisting of inert gases, nitrogen, ammonia, air, and mixtures thereof, to a sufficient temperature to fuse said boron oxide fibers to said boron nitride fibers;
• and
• heating the fused felt in an anhydrous ammonia atmosphere to a sufficient temperature, and for a sufficient time to convert essentially all boron oxide in the fibers to boron nitride.