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Converting Anisotropic Photon Absorbers into Isotropic Absorbers

IP.com Disclosure Number: IPCOM000086799D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR

Abstract

Anisotropic photon absorbers with a high A/E (4 to 10), i.e., the ratio of the absorptance in visible wavelengths to the emittance in infrared wavelengths, have been shown by the use of tungsten dendritic surfaces.* There are applications where isotropic photon absorbing surfaces with good stability are needed. A process is described herein to produce such surfaces.

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Converting Anisotropic Photon Absorbers into Isotropic Absorbers

Anisotropic photon absorbers with a high A/E (4 to 10), i.e., the ratio of the absorptance in visible wavelengths to the emittance in infrared wavelengths, have been shown by the use of tungsten dendritic surfaces.* There are applications where isotropic photon absorbing surfaces with good stability are needed. A process is described herein to produce such surfaces.

The process transforms tungsten dendritic surfaces (anisotropic absorbers) to an isotropic absorbing surface by oxidizing and then reducing the tungsten. The process used is to air oxidize the tungsten dendritic surface at about 650 degrees C to produce a yellow-green WO(3) surface. When the surface is uniformly coated, it is then reduced in hydrogen at about 800 degrees C for about 30 min. The surface produced by this process is uniformly black in all directions. Scanning electron microscope (SEM] examination of the surface showed a very fine porous structure on the dendrites that appeared to "flower", i.e., the dendrite peels back in layers giving a flowery appearance.

Exemplary uses for such enhanced surface area trapping surfaces are: 1. Coated chambers where optical dumps are needed, i.e., high energy laser studies. An optical "dump" is a

surface into which light enters and does not reflect. 2. Catalytic surfaces. * Applied Phys. Letters 26, 557-559 (1975).

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