Transparent thermal insulation

Transparent soaps, 22 747-748 cast-mature process for, 22 749 Transparent thermal insulation,... 

One of the most promising applications of SiOa aerogels is their use as transparent thermal insulation. Extensive studies of transparent aerogels have shown that the thermal resistance as well as the solar transmission are sufficiently high to make these materials most suitable for passive solar usage [72]. However,... 

During recent years, there have been new developments in the area of spacer textiles ITV Denkendorf has developed a process in which two separated textile fabric layers, covered by transparent foils, are connected by a spacer fabric. Due to this specific construction, an air space is created which provides a high degree of heat and acoustic insulation. Spacer fabrics, laminated or coated with transparent foil on both sides, are increasingly used for transparent thermal insulation. Woven spacer fabrics can be produced up to 600 mm in width and are used, sometimes with filUng, for sound damping (Fig. 2.8). 

Transparent thermal insulating material and CFC-substituted high-performance thermal insulating material (Fricke, 1988 Wittwer, 1992 Svendsen, 1992)... 

Thermal Insulation. In addition to their low thermal conductivity, as discussed in the section above, siUca aerogels can be prepared to be highly transparent in the visible spectmm region. Thus, they are promising materials as superinsulating window-spacer. To take further advantage of its... 

Silica aerogels, a newly developing type of material, also have been produced as thermal insulations with superinsulation characteristics. The nanometer-size cells limit the gas phase conduction that can take place. The aerogels are transparent to visible light, so they have potential as window insulation. The use of superinsulations at present is limited by cost and the need to have a design that protects the evacuated packets or aerogels from mechanical damage. 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toll producers is often economically viable despite high cost, especially for aerospace and microelectronic applications. For the majority of industrial applications, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement in some applications such as multilayer thermal insulation blankets for satellites and protective coatings for solar cells and other space components (93). For interlayer dielectric applications in semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors used in those devices (94). 

Ceramics used for thermal insulation of microwave caskets include alumina, aluminosilicates, mullite, and fused silica, each of which is relatively transparent to microwave radiation and thus have low dielectric loss at room temperature. The insulating materials included in the casket are typically in the form of ceramic fibers, fiberboard, or a granular bed of ceramic... 

Another method for measuring thermal diffusivity is the flash method developed by Parker et al. [48] and successfully used for the thermal diffusivity measurement of solid materials [49]. A high intensity short duration heat pulse is absorbed in the front surface of a thermally insulated sample of a few millimeters thick. The sample is coated with absorbing black paint if the sample is transparent to the heat pulse. The resulting temperature of the rear surface is measured by a thermocouple or infrared detector, as a function of time and is recorded either by an oscilloscope or a computer having a data acquisition system. The thermal diffusivity is calculated from this time-temperature curve and the thickness of the sample. This method is commercialized now, and there are ready made apparatus with sample holders for fluids. There is only one publication on nanofluids with this method. Shaikh et al. [50] measured thermal conductivity of carbon nanoparticle doped PAO oil. 

As a class, ceramics are hard, wear-resistant, brittle, prone to thermal shock, refractory, electrically and thermally insulative, intrinsically transparent. 

Although the aerogel loses its optical transparency by this measure, its thermal insulation is strongly enhanced. Total conductivities for nonevacuated aerogels of the order of 0.014 W/(m K) are achievable. This is considerably lower than in CFC-blown polyurethane (PU) foams, the best nonevacuated thermal insulators available today [48]. 

The pottant is the vibration damping, elastomeric material that immediately surrounds both sides of the fragile solar cell wafers and their electrical contacts and interconnects. It must be soft, transparent, electrically insulating, weather resistant, chemically inert and form strong and stable adhesive bonds to the surfaces it touches. It protects the cells from stresses due to thermal expansion differences and external impact and isolates them electrically. The pottant also helps protect the circuit metallic contacts and interconnects from the corrosive effects of moisture, salt, smog, etc. 

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