Methods for tailoring the surface topography of a nanocrystalline or amorphous metal or alloy and articles formed by such methods

Abstract

Electrochemical etching tailors topography of a nanocrystalline or amorphous metal or alloy, which may be produced by any method including, by electrochemical deposition. Common etching methods can be used. Topography can be controlled by varying parameters that produce the item or the etching parameters or both. The nanocrystalline article has a surface comprising at least two elements, at least one of which is metal, and one of which is more electrochemically active than the others. The active element has a definite spatial distribution in the workpiece, which bears a predecessor spatial relationship to the specified topography. Etching removes a portion of the active element preferentially, to achieve the specified topography. Control is possible regarding: roughness, color, particularly along a spectrum from silver through grey to black, reflectivity and the presence, distribution and number density of pits and channels, as well as their depth, width, size. Processing parameters that have been correlated in the Ni—W system to topography features include, for both the deposition phase and the etching phase of a nanocrystalline surface: duty cycle, current density, deposition duration, plating chemistry, polarity ratio. The relative influence of the processing parameters can be noted and correlated to establish a relationship between values for processing parameters and degree of topography feature. Control can be established over the topography features. Correlation can be made for any such system that exhibits a definite spatial distribution of an active element that bears a predecessor spatial relationship to a desired topography feature.

Description

RELATED DOCUMENTS[0001]The benefit of U.S. Provisional application No. 60 / 859,067, filed on Nov. 15, 2006, is hereby claimed, and its entire disclosure is hereby incorporated fully herein, by reference.INTRODUCTION[0002]Metals and alloys with nanocrystalline or amorphous structures often exhibit superior physical and / or functional properties, such as high strength, high corrosion-resistance and low coefficient of friction. They may also have desirable magnetic, electronic, optical, or biological properties in specific applications. For these reasons, nanocrystalline or amorphous metals and alloys are gaining wide usage throughout many industries.[0003]Nanocrystalline metal refers to a metallic body in which the number-average size of the crystalline grains is less than one micrometer. The number-average size of the crystalline grains provides equal statistical weight to each grain. The number-average size of the crystalline grains is calculated as the sum of all spherical equivalent...

AI Technical Summary

Benefits of technology

[0123]A related embodiment of an invention hereof uses a high deposition duty cycle and a low etching current density to achieve a black surface with relatively narrower and shallower channels. Rather than a low etching current density, a low etching duty cycle has a similar effect of reducing the width or depth of channels.

[0126]Yet another related invention is a method using a low deposition duty cycle with a low etching duty cycle, which achieves a plurality of pits that are relatively narrower, or shallower, or having a higher number density, or any of these three properties. Rather than using a low etching duty cycle, a low etching current density may be used to similar effect.

Problems solved by technology

The regions of the chromium film that are not covered by the sleeve are etched, leading to the formation of pits on the chromium film.

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