LaMnO3 films doped with Ca, Ba, or Sr have been fabricated using the metalorganic decomposition technique. These films exhibit paramagnetic-to-ferromagnetic phase transitions at 250, 300, and 350 K, respectively. By measuring the film magnetization as a function of field and temperature we have determined the entropy change associated with these transitions. The large magnetization of these materials results in a total entropy change a factor of five less than that of gadolinium, the prototypical high-temperature magnetocaloric material. Improvements in film morphology and composition may provide a further increase in the magnetization and total entropy change in these materials.

The way in which chemically modified polymer surfaces (substrates) affect the activity of electroless catalysts was examined. Surfaces of three injection-molded styrene containing polymers [polystyrene (PS), poly(styrene-acrylonitrile) (SAN), and poly(acrylonitrile-butadiene-styrene) (ABS)] were modified by either plasma oxidation or by plasma oxidation followed by immersion in sodium hydroxide solution. After modification, two palladium catalyst systems (a two-step palladium catalyst and a commercial colloid catalyst) and six electroless baths were tested for activity in combinations with these surfaces. The activities ofthe two catalysts vary unpredictably and differently as the polymer, surface treatment, and electroless bath are changed. X-ray photoelectron spectroscopy results show only a weak correlation between surface composition and platability: (i) plasma-treated polymers show a net increase in surface oxygen, present mostly as carbonyl, (ii) immersing the plasma-exposed surfaces in alkaline solutions lowers oxygen and carbonyl concentrations. Some of these results differ from those previously obtained with photo-oxidized surfaces.

The surfaces of poly(styrene) (PS) and two polymers containing styrene, poly(styrene‐acrylonitrile) (SAN), and poly (acrylonitrile‐butadiene‐styrene) (ABS) were photo‐oxidized with 254 nm light and then treated with Pd‐ or Ag‐based electroless catalysts. These photo‐oxidized surfaces poisoned the Pd catalysts, hence inhibiting electroless metal plating, but the Ag‐based catalyst resisted deactivation by the modified surface. Results from x‐ray photoelectron spectroscopy (XPS) indicate that catalyst poisoning is due to photochemically produced carbonyl groups on the polymer surfaces, but show no spectroscopically significant change in the electroless catalysts. Treating irradiated polymers with alkaline solution restores platability and correlates with a loss of surface carbonyl groups by way of an alkaline decarbonylation reaction. Six electroless baths (two Cu and four Ni) were examined; the catalyst deactivation effect is independent of bath chemistry.

We present a combined experimental/theoretical study aimed at enhancing adhesion between a NiTi wire and a thermoplastic polyolefin (TPO) matrix in which it is embedded. NiTi wire surfaces were subjected to the following surface treatments prior to pull-out tests: (i) treatment with an acid etch or chemical conversion coating and (ii) application of a surface microgeometry to enhance mechanical interlocking between the wire and the TPO matrix. Nanometer to micron-scale NiTi wire surface features were examined with atomic force microscopy. The extent to which each treatment increased the pull-out force was quantified. Existing theoretical models of wire pull-out based upon strength of materials and linear elastic fracture mechanics are reviewed. Results from a finite element model (FEM), wherein the NiTi/TPO matrix interface is modeled with a cohesive zone model, suggest that the interface behavior strongly depends on the cohesive energy. The FEM model properly accounts for energy dissipation at the debonding front and inelastic deformation in a NiTi wire during pull-out. We demonstrate that residual stresses from the molding process significantly influence mode mixity at the debonding front.