Abstract: A filler powder comprised of an alumina powder coated with a silicon containing coating, wherein the silicon containing coating at most partially covers the surface of said coated alumina powder and the filler powder, when mixed with a thermosetting epoxy resin, has an average spiral flow length that is at least about 1.1 times greater than a comparable filler powder containing uncoated alumina powder mixed with the thermosetting resin. A preferred process for making the filler powder comprises: heating, simultaneously, an alumina powder with a second powder coated with an organo-silicate to a temperature for a time sufficient to volatilize, deposit and pyrolyze at least a portion of the organo-silicate on the alumina powder to form a silicon containing inorganic coating thereon.

Abstract: A method for producing dense aluminum nitride articles having enhanced thermal conductivity is disclosed. The method comprises the steps of forming a powder compact comprising AlN alone or in combination with other ceramic compounds, adding a densification aid, subsequently exposing the compact to an environment which serves to reduce the oxygen content of the compact, and then densifying the compact by sintering or hot-pressing to provide a dense article. The densified AlN article is found to have a high thermal conductivity.

Abstract: Moisture-resistant aluminum nitride powder which is treated with an yttrium-containing compound. The method of treating the aluminum nitride compound includes (a) thoroughly mixing a slurry containing aluminum nitride powder, an yttrium-containing compound, and a solvent for the yttrium-containing compound in the absence of any surfactant and (b) removing the solvent from the slurry. The moisture-resistant aluminum nitride powder may be used in aqueous formulations for making ceramic articles.

Abstract: A powder composition consisting essentially of an intimate mixture of boron carbide and titanium diboride, the mixture having an average particle size of less than about 0.5 micron, the particles being uniformly dispersed such that elemental analytical techniques show all discrete concentrations of boron carbide and titanium diboride to be less than or equal to about 0.5 micron in diameter, is disclosed. The powder is useful for making a densified ceramic composition comprising titanium diboride grains, having an average grain size of less than or equal to about 3 microns in diameter, uniformly dispersed with boron carbide grains, having an average grain size of less than about 5 microns in diameter. The densified composition exhibits improved hardness and toughness when compared wiht titanium diboride or boron carbide compositions.

Abstract: A powder composition consisting essentially of an intimate mixture of boron carbide and titanium diboride, the mixture having an average particle size of less than about 0.5 micron, the particles being uniformaly dispersed such that elemental analytical techniques show all discrete concentrations of boron carbide and titanium diboride to be less than or equal to about 0.5 micron in diameter, is disclosed. The powder is useful for making a densified ceramic composition comprising titanium diboride grains, having an average grain size of less than or equal to about 3 microns in diameter, uniformly dispersed with boron carbide grains, having an average grain size of less than about 5 microns in diameter. The densified composition exhibits improved hardness and toughness when compared with titanium diboride or boron carbide compositions.

Abstract: A sequence of temporally-spaced radiant energy pulses are applied to the front surface of the sample and the heat rise caused by each thermal pulse is measured at the second surface using a suitable thermocouple or infrared sensor. The temperature rise data for each pulse is digitized and stored in a two-state memory device such as a random access memory. The data from each successive pulse is coadded and statistically processed by averaging to derive a set of favored values indicative of the temperature of the sample as a function of time. The favored values data is further processed using a least squares curve fitting algorithm to determine a numerical value indicative of the diffusivity of the sample.

Abstract: Ultrafine, high purity B.sub.4 C is produced by BCl.sub.3, CH.sub.4 or C.sub.2 H.sub.4, and H.sub.2, using a CO.sub.2 laser, when a stoichiometric excess of H.sub.2 and about half the stoichiometric amount of CH.sub.4 or C.sub.2 H.sub.4 is employed.

Abstract: Ultrafine titanium diboride powder is produced by subjecting a gaseous mixture of BCl.sub.3, H.sub.2, and TiCl.sub.4 to an amount of laser radiation effective to convert at least a portion of the volatile boron and titanium sources to titanium diboride. The TiB.sub.2 powders consist primarily of monodispersed equiaxial particles having a diameter of about 0.025 micron to about 0.3 micron.