3/25/2023 0 Comments Fotonica 2016In particular, silver as highly IR reflecting metal and aluminium nitride as transparent insulating material, have been alternated in a very simple and highly effective coating formulation. Once defined optical requirements of high visible transmittance and low emissivity (< 5%), proper materials have been selected as metals and ceramics to create the optical filter. Sputtering process parameters, layers sequence of the stacked structure and thicknesses of the layers have been selected by means. Optically selective low-emissive (low-E) filters, constituted of different ultrathin layers and suitable to an effective employment in glazing technology for low energy consumption buildings have been designed and fabricated on glass by means of sputtering technique. This last solution well agrees with low-E coated polymeric films applied on glass when it is necessary to realize a low cost energy saving intervention on pre-existing windows. Furthermore, it has been also verified that substitution of glass pane with polycarbonate pane as substrate largely improved long term coating stability. In particular, substitution of antireflective silicon oxide by tailored aluminium oxide or oxy-nitride with optimized hydrophobic properties can safeguard air stability. In this work different approaches have been proposed to improve coating stability without worsening all the optimal low-E performances. Starting from single layers characterization an undesired AlN hydrolytic reaction has been recognized as the most dangerous phenomenon in terms of overall coating degradation. Sputtering process parameters, layers sequence of the stacked structure, thicknesses of each layer and photo-thermal properties have been tailored to obtain visible transmittance as high as possible, coupled with very low thermal emissivity values. In our previous work an optically selective low-E filter, suitable to an effective purpose in glazing technology for mild to hot climates, has been designed and fabricated on glass by sputtering technique adopting transparent insulating aluminium nitride layers as template to grow very thin uniformly continuous silver films and using silicon oxide as final effective antireflective layer. Clearly, solving the problem of coating stability in moist atmosphere offers the possibility to place it also out of the protective gap. As most low-E coatings contain silver thin films as metal layers, they are generally exposed to inert gas inside the gap of double pane windows to prevent coating. Integration with low-E coated glass largely enhance heat flow control through glazing units. To meet today's energy saving standards, low-emission (low-E) coatings for windows are commonly utilized in multi-pane glazing units. This last solution well agrees with low-E coated polymeric films. Furthermore, it has been also verified that substitution of glass with polycarbonate largely improved long term coating stability. In particular, substitution of silicon oxide by aluminum oxide or oxy-nitride with optimized hydrophobic properties can safeguard air stability. An undesired AlN hydrolytic reaction has been recognized as the most dangerous phenomenon in terms of overall degradation. Sputtering process parameters, layers sequence, thicknesses of layers have been optimized to obtain visible transmittance as high as possible, coupled with very low emissivity values. In our previous work a low-E filter has been fabricated on glass by sputtering technique adopting aluminum nitride layers as template to grow very thin uniformly continuous silver films. Solving the problem of coating stability in air offers the possibility to place it also out of protective gaps. As most low-E coatings contain silver thin films, they are generally exposed to inert gas to prevent degradation. To meet today's energy saving standards, low-emission coatings for windows are commonly utilized in multi-pane glazing units to largely enhance heat flow control through windows.
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