Micro-scale mass-transfer variations during electrodeposition
Results of two studies on micro-scale mass-transfer enhancement are reported: (1) Profiled cross-sections of striated zinc surfaces deposited in laminar channel flow were analyzed with fast-fourier transforms (FFT) to determine preferred striation wavelengths. Striation frequency increases with current density until a minimum separation between striae of 150 {mu}m is reached. Beyond this point, independent of substrate used, striae meld together and form a relatively smooth, nodular deposit. Substrates equipped with artificial micron-sized protrusions result in significantly different macro-morphology in zinc deposits. Micro-patterned electrodes (MPE) with hemispherical protrusions 5 {mu}m in diameter yield thin zinc striae at current densities that ordinarily produce random nodular deposits. MPEs with artificial hemi-cylinders, 2.5 {mu}m in height and spaced 250 {mu}m apart, form striae with a period which matches the spacing of micron-sized ridges. (2) A novel, corrosion-resistant micromosaic electrode was fabricated on a silicon wafer. Measurements of mass-transport enhancement to a vertical micromosaic electrode caused by parallel bubble streams rising inside of the diffusion boundary-layer demonstrated the presence of two co-temporal enhancement mechanisms: surface-renewal increases the limiting current within five bubble diameters of the rising column, while bubble-induced laminar flows cause weaker enhancement over a much broader swath. The enhancement caused by bubble curtains is predicted accurately by linear superposition of single-column enhancements. Two columns of smaller H{sub 2} bubbles generated at the same volumetric rate as a single column of larger bubbles cause higher peak and far-field enhancements. 168 refs., 96 figs., 6 tabs.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5208259
- Report Number(s):
- LBL-30825; ON: DE92000907
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ZINC
ELECTRODEPOSITION
MASS TRANSFER
BUBBLES
ELECTRODES
FOURIER TRANSFORMATION
KINETICS
LAMINAR FLOW
MICROSTRUCTURE
SILICON
SUBSTRATES
SURFACES
CRYSTAL STRUCTURE
DEPOSITION
ELECTROLYSIS
ELEMENTS
FLUID FLOW
INTEGRAL TRANSFORMATIONS
LYSIS
METALS
SEMIMETALS
SURFACE COATING
TRANSFORMATIONS
360102* - Metals & Alloys- Structure & Phase Studies
360101 - Metals & Alloys- Preparation & Fabrication
400400 - Electrochemistry