My research is on using 3D printing to make conductive 3D copper structures. The images attached are microscopy images of the copper surface of my 3D printed parts. Occasionally surface oxides form on the surface which are visible under the microscope as a spectacular blueish glimmer. This effect is similar to the common bluing of steel which can be seen on metal pipes which endure heating cycles such as hot water pipes.
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CC BY 4.0
<span class="int-own-work" lang="en">Own work</span>