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by using electrochemistry one can controllably form an oxide layer on top of metallic titanium, which gives the material a vivid color through thin film interference : chemicalreactiongifs

by using electrochemistry one can controllably form an oxide layer on top of metallic titanium, which gives the material a vivid color through thin film interference : chemicalreactiongifs

Explanation:

As the title says, this process is commonly called anodization. The basic idea is that you use the metal (in this case the titanium) as the anode in an electrochemical cell. In other words, the metal is the part where electrons are removed so that the material is oxidized. The basic reaction has the following formula:

Ti(s) + 2 H*2O(l) → TIO2* (s) + 4H+(aq) + 4e

As the right side of the equation shows, a key part of this process is that you form a thin oxide layer on the titanium. As a result of this layer the material tends to become vividly colored. This color is a result of a phenomenon called thin film interference. The key idea is shown in this diagram. As light hits the anodized slab, part of the beam will be reflected at the oxide/air interface and part at the metal/oxide interface. These two reflected waves can interfere either constructively (giving a strong reflection) or destructively (suppressing the reflection of that wavelength of light). As a result, some wavelengths will be reflected more strongly than others, giving the slab a a very colorful appearance. The spectrum that is reflected in turn will depend on the thickness of the oxide. This fact is convenient since you can vary the oxide thickness by changing parameters such as the voltage and duration to get a wide gamut of colors.


Source for the gif: this video