摘要:
This invention is related to a polymorphic B Form of 3-(cyclopropylmethoxy)-4-[4-(methylsulfonyl)phenyl]-5,5-dimethyl-5H-furan-2-one characterized by the following parameters: cristalline system Trigonal space group R-3 description hexagonal unit-cell dimensions a (Å) 18.183 b (Å) 18.183 c (Å) 26.950 &agr; (°) 90 &bgr; (°) 90 &ggr; (°) 120 unit-cell volume (Å3) 7716.5 number of molecules per unit-cell Z 18 Temperature of measurement (° K) 293 calculated specific gravity 1.303 weight absorption coefficient (cm−1) 2.11.
摘要:
Ceramic fibers based on silicon carbide, silicon nitride or silicon carbonitride are treated with hydrofluoric acid, e.g., with a 3% to 30% aqueous solution of HF, to strip surface impurities therefrom, to reduce critical surface defects and to enhance the rupture strength thereof.
摘要:
Novel boron/nitrogen compounds having the formula (1): ##STR1## and the products of the at least partial reduction thereof, are converted into BN ceramic materials by thermally polymerizing same, whether or not in the presence of suitable polymerization catalyst, and then pyrolyzing the boron/nitrogen polymers thus obtained.