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Unusual cavity shapes resulting from multistep mass transport controlled dissolution: Numerical simulation and experimental investigation with titanium using oxide film laser lithography

Authors
  • Chauvy, P.-F.1
  • Landolt, D.1
  • 1 Institute of Materials – LMCH, Swiss Federal Institute of Technology Lausanne, Lausanne EPFL, CH-1015, Switzerland , Lausanne EPFL
Type
Published Article
Journal
Journal of Applied Electrochemistry
Publisher
Kluwer Academic Publishers
Publication Date
Feb 01, 2003
Volume
33
Issue
2
Pages
135–142
Identifiers
DOI: 10.1023/A:1024034404509
Source
Springer Nature
Keywords
License
Yellow

Abstract

The shape evolution of cavities produced by multistep electrochemical micromachining is investigated both theoretically and experimentally. A boundary element code is used for 2D simulation of the shape evolution as a function of applied charge. A two-step process is simulated by assuming that metal dissolves from a small area at the bottom of a hemicylindrical groove protected by an insulating film. Similarly, the shape evolution in a three-step process is numerically simulated. The simulation shows that multistep isotropic etching can yield buried cavities with a narrow opening as well as large aspect ratio cavities. It also permits one to achieve aspect ratios larger than one. Electrochemical micromachining experiments were carried out with titanium using oxide film laser lithography (OFLL) for patterning the surface. Metal dissolution from the irradiated line features on the oxide was carried out in an electropolishing electrolyte starting from a flat surface or from preformed grooves. The resulting cavity shapes observed with a microscope corresponded well to the theoretical predictions. The experiments thus confirmed that isotropic etching involving two or three subsequent anodization–irradiation–dissolution steps can yield high aspect ratio cavities and partly occluded cavities. Possible implications of the present results for the shape evolution of corrosion pits are discussed.

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