The Effect of Thickness of Aluminium Films on Optical Reflectance

Abstract

In Uganda and Africa at large, up to 90% of the total energy used for food preparation and water pasteurization is from fossil fuels particularly firewood and kerosene which pollute the environment, yet there is abundant solar energy throughout the year, which could also be used. Uganda is abundantly rich in clay minerals such as ball clay, kaolin, feldspar, and quartz from which ceramic substrates were developed. Aluminium films of different thicknesses were deposited on different substrates in the diffusion pump microprocessor vacuum coater (Edwards AUTO 306). The optical reflectance of the aluminium films was obtained using a spectrophotometer (SolidSpec-3700/DUV-UV-VIS-NIR) at various wave lengths. The analysis of the results of the study revealed that the optical reflectance of the aluminium films was above 50% and increased with increasing film thickness and wavelength. Thus, this method can be used to produce reflector systems in the technology of solar cooking and other appliances which use solar energy.

Aluminum Coated Micro Glass Spheres to Increase the Infrared Reflectance

“…To show this more clearly, in Figure 14d the reflectance values of each sphere type at a wavelength of 15 µm is plotted against the layer thickness. A similar behavior was observed by Lugolole et al [20]. Interestingly, a similar layer thicknesses of approx.…”

“…Despite the coated layer, for both types of spheres, no or less reflectance increase can be observed. This behavior was already established by Lugolole et al [20], where the lowest reflectance was achieved with the sample, which has a rough surface. Das et al [28], Moushumy et al [29], and Sharma et al [30] also show numerical simulations of different nano-structured gratings on GaAs substrates, that the surface structure has a significant influence on the reflection behavior.…”

“…It also exhibits a high reflectance in the mid-wave infrared range but is better recyclable and also cheaper than silver. In addition to a low oxidation potential, aluminum films have a good thermal stability and a good adherence to substrates [20]. Thus, none or less influence on the reflection behavior by degradation of aluminum is expected.…”

Deposition of Al Thin Film on Steel Substrate: The Role of Thickness on Crystallization and Grain Growth

“…R. Lugolole et al reported that when Al film was deposited on a ceramic substrate, the reflectance increased with increasing film thickness. The maximum reflectance was reached when the thickness was about 750 nm [25].…”

Advantages of Electrochemical Polishing of Metals and Alloys in Ionic Liquids

“…Aluminum is a typical example proving this phenomenon. The aluminum oxide film is assumed to produce a dull finish on the metal surface, owing to its considerable thickness (~0.5-1 µm) [13,14]. The light scattering on natural oxidized copper is also due to the oxide film, the thickness of which was calculated to be about 627 nm [15].…”