Presently, solar cells are covered with Ce-doped microsheet cover glasses that are attached with Dow Corning DC 93500 silicone adhesive. This general approach has been used from the beginning of space exploration, however, it is expensive and time consuming. Furthermore, as the voltage of solar arrays increases, significant arcing has occurred in solar arrays, leading to loss of satellite power. This problem could be ameliorated if the cover glass extended over the edges of the cell, but this would impact packing density. An alternative idea that might solve these issues and be less expensive and more protective is to develop a coating that could be applied over the entire array. Such a coating must be resistant to atomic oxygen for low earth orbits below about 700 km, it must be resistant to ultraviolet radiation for all earth and near-sun orbits and it must withstand the damaging effects of space radiation. Coating flexibility would be an additional advantage. We have been exploring the use of newly discovered polyoligomericsilsesquioxane (POSSreg) materials with metallic additives for these applications. This technology has several significant advantages: the glass-like composition of POSSreg provides excellent resistance to radiation and VUV and the POSS nano-building blocks can be incorporated into all known plastics using conventional polymerization or compounding techniques that can lead to tailored optically transparent materials with entirely new performance levels. We will report on the results of POSS coatings containing various additives (e.g. organic and metallic). Thick samples (150 mum) are being applied to various substrates and have been exposed to 2 MeV protons up to 10 15 P+/cm2 and UV/VUV irradiation up to 1000 hrs. The 2 MeV protons are absorbed within about 85 mum depth with ~2 mum straggle so the damage is contained entirely within the layer. Results of these tests with several POSSreg matrices will be presented
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Calculations and experimental data on the shielding effectiveness of a new kind of conformal coating against thermal neutrons typical of the natural environment are presented. This coating is shown to be capable of significantly reducing the thermal neutron threat to COTS ICs in a cost-effective manner.
A new method is described for effecting selective monofunctionalization of CH2CH)8Si8O12 2: reaction of 2 with triflic acid (TfOH) produces (TfOCH2CH2)(CH2 CH)7Si8O12 3, which reacts with nucleophiles (e.g. H2O or 2-mercaptopyridine) to produce (XCH2CH2)(CH2CH)7Si8O12 (4 X = OH, 5 X = SC5H4N); acylation of 4 with p-O2NC6H4COCl affords (p-O2NC6H4CO2- CH2CH2)(CH2CH)7Si8O12 6; catalytic hydrogenation of 4 affords (HOCH2CH2) Et7Si8O12 7.
In this work, organic-inorganic hybrid materials containing stable silanol functionalities were designed by incorporating cyclic tetravinylsiloxanetetraols into photopolymerized polymer networks via the thiol-ene reaction, with the intent of tailoring the thermal and mechanical properties of the resulting materials. The effects of the cyclic tetravinylsiloxanetetraols concentration on the thermomechanical properties and thermal stability of pentaerythritol triallyl ether/pentaerythritol tetra(3-mercaptopropionate) (APE-PETMP) and allyl isocyanurate/pentaerythritol tetra(3-mercaptopropionate) (TTT-PETMP) ternary networks were evaluated using dynamic thermomechanical analysis and thermogravimetric analysis, respectively. Photopolymerization kinetics were monitored using real-time FTIR. Interestingly, an increase in glass transition temperature was observed with the APE-PETMP networks while a decrease in glass transition temperature was observed for the TTT-PETMP networks with increasing concentration of [Vi(OH)SiO]4. These observations are discussed in terms of cross-link density and monomer rigidity.
