Accession Number : ADA332911

Title :   Aqueous Processing of Si3N4 Powder with Chem-Adsorbed Silanes

Descriptive Note : Technical rept. for period ending Sep 96

Corporate Author : CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS

Personal Author(s) : Colic, Miroslav ; Franks, George V. ; Fisher, Matthew ; Lange, Fred F.

PDF Url : ADA332911

Report Date : 30 SEP 1996

Pagination or Media Count : 33

Abstract : Different chem-adsorbed silane molecules have been used to produce weakly attractive silicon nitride particle networks for aqueous colloidal processing. Silanes with diamino and polyethyleneglycol hydrophilic heads yielded slurries with the lowest viscosity, longest sedimentation stability and highest packing density. Chem-adsorbed silane molecules protected silicon nitride and yttrium oxide, a common processing aid, from hydrolysis at pH's between 5.5 and 11. A novel approach was used to produce short range repulsive potentials necessary to yield the weakly attractive networks. Addition of salt to dispersed silicon nitride slurries with particles coated with polyethyleneglycol-silane, caused the collapse of the 22 atoms long chains and residual electrical double layer. This produced a weakly attractive network which persisted during consolidation to yield a plastic body with a flow stress that was dependent on the counterion size. When 0.5 M tetramethylammonium chloride was used at pH 10, plastic bodies had a flow stress similar to clay, whereas lithium counterions produced bodies with a much higher flow stress.

Descriptors :   *SILANES, *COLLOIDS, *SILICON NITRIDES, STRESSES, PARTICLE SIZE, LITHIUM, SLURRIES, CLAY, HYDROLYSIS, PACKING DENSITY, VISCOSITY, YTTRIUM OXIDES, COAGULATION, ETHYLENE GLYCOL, ELECTRIC DOUBLE LAYER.

Subject Categories : Physical Chemistry
      Adhesives, Seals and Binders

Distribution Statement : APPROVED FOR PUBLIC RELEASE