Nanotechnology: Novel Electrodeposited Nanocrystalline Metals and Composites

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9871980 Koch The focus of this research is to develop artifact-free nanocrystalline materials by electrodeposition. Electrochemical parameters that control the grain size and chemistry of copper and zinc nanocrystalline films are a central theme of the research. The effects of chemical addition agents to the bath and the waveform of a periodic, pulsed-current deposition are studied. For comparison purposes selected nanocrystalline samples are also prepared by mechanical attrition followed by powder compaction and by pulsed-laser ablation. Closely coupled with these processing studies is atomic level characterization of the nanocrystalline grain-boundary structure and chemistry using high-resolution transmission electron microscopy and analytical electron microscopy to provide feedback on the effects of processing variables. A goal of the synthesis and characterization studies is the processing of the nanocrystalline metals with a range of grain sizes from about 2 to 50 nm and the introduction of nanodispersoids at 1 to 10 volume percent. Into each nanocrystalline metal "hard" and "soft" (polystyrene) nanodispersoids are introduced during the electrodeposition process. This provides unique model systems to determine mechanical properties as a function of nanocrystalline grain size, test temperature, and strain rate. The influence of the nanoscale dispersoids on mechanical deformation and shear banding is of special interest. The data obtained should allow us to construct better models for the deformation and fracture behavior of nanocrystalline materials. This award is a selection under the NSF 98-20 initiative on Functional Nanocrystalline Materials. %%% In comparison to more conventional means to prepare nanocrystalline metals (e.g., gas phase condensation or mechanical attrition), electrodeposition has the following advantages: i) it is a relatively simple operation with low- cost equipment; ii) dense, void-free deposits can be prepared directly without need for consolidation; iii) current or plating-bath chemistry may be used to control grain size, and hence properties, of the nanocrystalline deposit; and iv) nanocomposites with unique properties can be formed by codeposition of nanoparticulates within the metal matrix. ***