Accession Number : ADA332683

Title :   Development of Short Range Repulsive Inter-Particle Forces in Aqueous Si3N4 Slurries with Chem-Adsorbed Silanes

Corporate Author : CALIFORNIA UNIV SANTA BARBARA

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

PDF Url : ADA332683

Report Date : 1997

Pagination or Media Count : 32

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 polyethylene glycol 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 :   *ADSORPTION, *SLURRIES, *SILANES, *CHEMISORPTION, *SILICON NITRIDES, *AQUEOUS SOLUTIONS, STRESSES, STABILITY, DISPERSING, METHYL RADICALS, WATER, PROCESSING, LITHIUM, PARTICLES, RESIDUALS, HIGH DENSITY, CHLORIDES, CLAY, AMMONIUM COMPOUNDS, FLOW, SALTS, HYDROLYSIS, PACKING DENSITY, VISCOSITY, COLLOIDS, PLASTICS, PH FACTOR, SEDIMENTATION, YTTRIUM OXIDES, POLYETHYLENE, GLYCOLS, ELECTRIC DOUBLE LAYER.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Polymer Chemistry
      Coatings, Colorants and Finishes

Distribution Statement : APPROVED FOR PUBLIC RELEASE