Nanotechnology: Novel Electrodeposited Nanocrystalline Metals and Composites

9871980 Koch本研究的重点是通过电沉积技术开发无伪影纳米晶材料。控制铜和锌纳米晶薄膜晶粒尺寸和化学性质的电化学参数是研究的中心主题。研究了化学添加剂对镀液的影响以及周期性脉冲电流沉积的波形。为了比较，选择的纳米晶样品也通过机械磨损，然后粉末压实和脉冲激光烧蚀制备。与这些加工研究密切相关的是利用高分辨率透射电子显微镜和分析电子显微镜对纳米晶体晶界结构和化学的原子水平表征，以提供对加工变量影响的反馈。合成和表征研究的一个目标是处理晶粒尺寸范围从2到50纳米的纳米晶金属，并引入体积为1到10%的纳米分散体。在电沉积过程中，将“硬”和“软”（聚苯乙烯）纳米分散体引入每个纳米晶体金属中。这提供了独特的模型系统，以确定机械性能作为纳米晶晶粒尺寸，测试温度和应变速率的函数。纳米级分散体对机械变形和剪切带的影响是特别感兴趣的。获得的数据将使我们能够为纳米晶材料的变形和断裂行为建立更好的模型。该奖项是NSF 98-20功能性纳米晶体材料倡议下的一个选择。与更传统的制备纳米晶金属的方法（如气相冷凝或机械磨损）相比，电沉积具有以下优点：1)操作相对简单，设备成本低；Ii)致密、无空洞的沉积物可直接制备，无需固结；Iii)电流或镀液化学可用于控制晶粒尺寸，从而控制纳米晶沉积的性质；4)纳米颗粒在金属基体内共沉积可形成具有独特性能的纳米复合材料。＊＊＊

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. ***