A highly ordered metal nanohole array (platinum and gold) was fabricated by a two-step replication of the honeycomb structure of anodic porous alumina. Preparation of the negative porous structure of porous alumina followed by the formation of the positive structure with metal resulted in a honeycomb metallic structure. The metal hole array of the film has a uniform, closely packed honeycomb structure approximately 70 nanometers in diameter and from 1 to 3 micrometers thick. Because of its textured surface, the metal hole array of gold showed a notable color change compared with bulk gold.

https://science.sciencemag.org/content/sci/268/5216/1466.full.pdf

Ordered Metal Nanohole Arrays Made by a Two-Step Replication of Honeycomb Structures of Anodic Alumina

A highly ordered gold nanodot array was fabricated by vacuum evaporation using an anodic porous alumina membrane with through-holes of nanometer scale as a mask. This technique resulted in an orderly arrangement of Au dots with a diameter of approximately 40 nm over a large area on a Si substrate.

https://iopscience.iop.org/article/10.1143/JJAP.35.L126/pdf

Fabrication of gold nanodot array using anodic porous alumina as an evaporation mask

Large cell-sized anodic porous alumina with long-range ordering was fabricated using phosphoric acid solution. Self-ordering of the anodic alumina took place under long-period constant voltage anodization at 195 V, which generated the self-ordered anodic porous alumina with a cell size of 500 nm.

https://iopscience.iop.org/article/10.1143/JJAP.37.L1340/pdf

Self-Ordering of Cell Configuration of Anodic Porous Alumina with Large-Size Pores in Phosphoric Acid Solution

https://www.oocities.org/gazerwho/Bacteriaasworkersintheliving.pdf

Bacteria as workers in the living factory: metal-accumulating bacteria and their potential for materials science.

This report describes the concentrating solar power (CSP) systems using solar absorbers to convert concentrated sunlight to thermal electric power. It is possible to achieve solar absorber surfaces for efficient photothermal conversion having high solar absorptance (a) for solar radiation and a low thermal emittance (e) at the operational temperature. A low reflectance (?'' 0) at wavelengths (?) 3 mm and a high reflectance (?'' 1) at l 3 mm characterize spectrally selective surfaces. The operational temperature ranges of these materials for solar applications can be categorized as low temperature (T 400 C). High- and mid-temperature applications are needed for CSP applications. For CSP applications, the ideal spectrally selective surface would be low-cost and easy to manufacture, chemically and thermally stable in air at elevated operating temperatures (T= 500 C), and have a solar absorptance= 0.98 and a thermal emittance= 0.05 at 500 C.

/pdf/review-of-mid-to-high-temperature-solar-selective-absorber-3b1c7v216u.pdf

Review of Mid- to High-Temperature Solar Selective Absorber Materials

Spectrally selective surfaces on Al metal sheets were prepared by dc anodization in dilute phosphoric acid followed by black coloration via ac electrolysis in a bath containing NiSO4. These coatings had good durability, as found from several accelerated tests. The optical performance was studied by the recording of hemispherical reflectance or specular reflectance in conjunction with diffuse light scattering. From these results we extracted a solar absorptance of 0.93–0.96 and a corresponding thermal emittance of 0.10–0.20. The structure of the coatings was investigated by scanning electron microscopy on fractured specimens, Auger electron spectroscopy combined with depth profiling by sputtering, and atomic absorption analysis. Based on this information, a multilayer model was formulated, its most conspicuous feature being a sheath near to the Al interface comprised of metallic Ni particles in an Al2O3 matrix. The optical properties of this layer were described either by the Maxwell Garnett theory or the ...

Nickel pigmented anodic aluminum oxide for selective absorption of solar energy

Nickel pigmented anodic aluminium oxide for selective absorption of solar energy

Ni pigmentation of anodic Al2O3 is obtained by electrolytic coloration. Durable coatings with good spectral selectivity (a/e≃8) are produced. Scanning electron microscopy, Auger depth profiling, and atomic absorption analysis lead to the formulation of a detailed structural model, its most essential feature being a thin layer comprising a mixture of Ni and Al2O3 located near the bottom of the anodic film. Experimental spectral reflectance data agree well with computer calculations, provided the optical properties of the metal‐insulator layer are described with the Bruggeman effective medium theory.

O. Hunderi

Papers

Nickel pigmented anodic aluminum oxide for selective absorption of solar energy

Nickel pigmented anodic aluminium oxide for selective absorption of solar energy

Spectrally selective surfaces of Ni‐pigmented anodic Al2O3