Transparent heat mirror

Transparent heat mirrors have optical properties which enable them to have high transmission of the visible radiation and high reflectivity of infrared radiation. 

Transmittance and reflectance of a transparent heat mirror using a thin metal-dielectric film combination [62]. 

There are basically two ways to achieve high visual transmittance simultaneously with high infrared reflectance. One is the use of the interference effect in all-dielectric multilayers, the other is the use of intrinsic optical properties of electrically conducting films such as Au, Ag, and others which have high infrared reflection with relatively low visual absorption. Their suitability as transparent heat mirror can be improved by antireflection coating for the visible. Figure 25 shows an example for such types of heat mirrors, according to Fan et al. [102]. 

A further type of coating suited for transparent heat mirrors is a semiconducting film such as Inx-Sny-Oz, which combines good visual transmittance with high infrared reflectivity [103-105]. 

Such transparent heat mirrors have important application, for example, in combination with cold light mirrors as thermal radiation shields in projection and illumination techniques and potential applications also in solar energy collection, window insulation, etc. 

The deposition of TiN and ZrN on glass for windows represents a combination of ornamental application with the economic constraint of energy saving in buildings. ZrN layers, especially, have been found to exhibit favorable properties for transparent heat mirrors, i.e. windows which transmit visible light but reflect heat radiation [114). 

Karlsson B, Ribbing C-G. Optical properties of transparent heat mirrors based on TiN, ZrN and HfN. Proc Soc Photo Opt Instrum Eng 1982 324 52. 

Fig. 10.2 Schematic diagram of a reflected interference microscope 1 - tight source, 2 - heat reflecting filter, 3 - coUimator, 4 - diaphragm, 5 - light filter, 6 - photo film, 7 - projection ocular, 8 - semi-transparent silvered mirror, 9 - aperture diaphragm, 10- auxiliary lens, 11 - immersion lens, 12 - sample under investigation, 13 - substrate...

Another type of structures for metal-dielectric mirrors are metallodielectric multilayers. In this case alternating quarterwave or subwavelength stacks of metal and dielectric are deposited. Typical for such multilayers is alow reflection in visible, but large in infrared wavelength range. Thus they basically behave as low-pass optical filters. Such stmctures were denoted in literature as heat mirrors. First heat mirrors were fabricated as early as in 1950s [252]. The simplest heat mirrors consist of three layers only, dielectric-metal-dielectric or, alternatively, dielectric-transparent conductive oxide-dielectric [253]. Full multilayer metal-dielectric reflectors with binary but also ternary layers were also considered [254]. Because of their high reflectance in infrared, but also because of their plasmonic properties [255] metal-dielectric multilayer mirrors are of interest for cavity enhancement of infrared detectors. 

InpOo SnOoi ZnO and Cd2Sn0 as transparent conductors RE. ARE, RS, RIBS, CVD spray pyrolysis Solar cells, heat mirrors, display devices, gas sensors Hear resistant coatings... 

Decomposed by cone. HCl with evolution of Cl3. A solution of OSO4 is not decomposed by light and can be Indefinitely stored in transparent bottles. Toxic the vapor first irritates the respiratory passages and (particularly) the eyes. Decomposed in a stream of Hs at red heat, forming a mirror. 

Figure 25.9 Scheme of the reactor housing (left) and photograph (middle) ofthe heat-shielded reactor under operation (gold mirror becomes transparent) [40] and different reactor sizes (right inset magnification of microchannel structure) [47]. 

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