Article with gradient property and processes for selective etching
View Patent ↗An article includes a substrate; and a coating disposed on the substrate that includes a microporous layer; a gradient in a density of a volume of the microporous layer, and a plurality of dendritic veins that are anisotropically disposed in the coating. A process for forming a coating includes disposing an activating catalyst on a substrate; introducing an activatable etchant; introducing an etchant oxidizer, performing an oxidation-reduction reaction between the substrate, the activatable etchant, and the etchant oxidizer in a presence of the activating catalyst, the oxidation-reduction reaction occurring in a liquid medium including the activatable etchant; and the etchant oxidizer, forming an etchant product comprising atoms from the substrate; removing a portion of the etchant product from the substrate; and forming a dendritic vein in the substrate to form the coating, the dendritic vein being anisotropically disposed in the coating.
1. A process for forming a coating, the process comprising:
disposing an activating catalyst on a substrate;
introducing an activatable etchant;
introducing an etchant oxidizer;
performing an oxidation-reduction reaction between the substrate, the activatable etchant, and the etchant oxidizer in a presence of the activating catalyst, the oxidation-reduction reaction occurring in a liquid medium comprising:
the activatable etchant; and
the etchant oxidizer;
forming an etchant product comprising a plurality of atoms from the substrate;
removing a portion of the etchant product from the substrate; and
forming a dendritic vein in the substrate to form the coating, the dendritic vein being anisotropically disposed in the coating,
wherein the coating comprises a uniform gradient in an index of refraction of the coating that varies from 1 to 3.9.
2. The process of claim 1 , further comprising forming a gradient in a density of a volume of the coating.
3. The process of claim 2 , further comprising controlling a reflectivity of coating.
4. The process of claim 3 , wherein the coating has a reflectivity tuned from 10% to 0.01% at a wavelength from 30 nm to 10 cm.
5. The process of claim 2 , wherein a temperature of the substrate during the oxidation-reduction reaction is less than 150° C.
6. A process for forming a coating, the process comprising:
disposing an activating catalyst on a substrate;
introducing an activatable etchant;
subjecting the activating catalyst and the activatable etchant to an electric potential;
performing an electrochemical reaction between the substrate and the activatable etchant in a presence of the activating catalyst and the electric potential, the electrochemical reaction occurring in a liquid medium comprising:
the activatable etchant; and
an etchant oxidizer;
forming an etchant product comprising a plurality of atoms from the substrate;
removing a portion of the etchant product from the substrate; and
forming a plurality of dendritic veins in the substrate to form the coating, the plurality of dendritic veins being anisotropically disposed in the coating,
wherein the coating comprises a uniform gradient in an index of refraction of the coating that varies from 1 to 3.9.
7. The process of claim 6 , wherein a temperature of the substrate during the electrochemical reaction is less than 150° C.