Mechanisms of Fatty Acid and Triglyceride Dispersant Bonding in Non-Aqueous Dispersions of NiO


  • Supported by the Air Force Research Labs under UES subcontract # S-932-19-MR002.

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Infrared spectroscopy was used to identify the mechanism of fatty acid and triglyceride dispersant bonding to NiO in 2-butanol for a series of triglyceride and straight chain fatty acid dispersants with systematically varied chain lengths and degrees of unsaturation. The extent of NiO deflocculation was measured using laser diffraction particle size analysis. The relative stabilities of the fatty acid/NiO dispersions were assessed through settling tests. Diffuse reflectance infrared spectroscopy indicates that the straight chain fatty acids chemisorb to NiO as alkoxides with most of the adsorbed moieties in an η2 configuration. A small fraction of the adsorbed straight chain fatty acids are either chemisorbed through the hydroxyl oxygen in an η1 configuration or physisorbed as dimers. Glycerol trioleate and Menhaden fish oil both exhibit some chemisorption through the carbonyl oxygen. Despite similarities in adsorption mechanism, the dispersants differ in their abilities to break up NiO aggregates and to prevent re-aggregation. Dispersant characteristics favoring stability of the NiO/2-butanol dispersion are longer carbon chain length and higher degree of unsaturation. The triglyceride structure provides a weak improvement in stability. These results are discussed in the context of recent work developing non-aqueous inks for inkjet printing of solid oxide fuel cells.