Synthesis of silica-supported ZnO pigments for thermal control coatings and analysis of their reflection model / Vahid Heydari in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 15, N° 1 (01/2018)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 15, N° 1 (01/2018) . - p. 223-230 Titre : Synthesis of silica-supported ZnO pigments for thermal control coatings and analysis of their reflection model Type de document : texte imprimé Auteurs : Vahid Heydari, Auteur ; Zaker Bahreini, Auteur Année de publication : 2018 Article en page(s) : p. 223-230 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Industries aérospatiales -- Matériaux Isolation thermique Kubelka-Munk, Théorie de La théorie de Kubelka-Munk (du nom de Paul Kubelka et Franz Munk) décrit les propriétés d'absorption de la lumière et de diffusion de la lumière des systèmes pigmentés, tels que les peintures ou les colorants dans les tissus textiles. La théorie peut prédire à partir de mesures d'épaisseurs à deux couches comment la couleur fonctionne à d'autres épaisseurs de couche. Cela permet aux fabricants de peinture d'estimer combien de pigments ils doivent ajouter à une peinture, de sorte que la peinture est opaque à une certaine épaisseur du travail. Avec l'aide de la théorie, l'effet de couleur du mélange de deux colorants peut être prédit si les paramètres des colorants individuels sont déterminés au moyen de mesures spectroscopiques. Les résultats sont meilleurs que l'utilisation naïve du mélange de couleurs soustractif. Oxyde de zinc Pigments -- Synthèse Réflectance Revêtements protecteurs Silice La silice est la forme naturelle du dioxyde de silicium (SiO2) qui entre dans la composition de nombreux minéraux. La silice existe à l'état libre sous différentes formes cristallines ou amorphes et à l'état combiné dans les silicates, les groupes SiO2 étant alors liés à d'autres atomes (Al : Aluminium, Fe : Fer, Mg : Magnésium, Ca : Calcium, Na : Sodium, K : Potassium...). Les silicates sont les constituants principaux du manteau et de l'écorce terrestre. La silice libre est également très abondante dans la nature, sous forme de quartz, de calcédoine et de terre de diatomée. La silice représente 60,6 % de la masse de la croûte terrestre continentale. Index. décimale : 667.9 Revêtements et enduits Résumé : A spacecraft in orbit undergoes extreme temperature cycling, space radiations, and other extreme conditions that can potentially raise the temperature of spacecraft to harmful levels. Hardware and sensitive detectors utilized in spacecrafts require that temperatures be maintained within specified ranges. Thermal control coatings (TCCs) help to maintain the thermal equilibrium of the spacecraft at a level acceptable for vital components. This is done by employing the diffused reflection of all effective ultraviolet (UV), visible (VIS), and near-IR (NIR) wavelengths of solar radiation and emitting the infrared (IR) energy. The most commonly used TCCs have utilized potassium silicate as the binder and ZnO as the pigment (Z-93), but absorption of UV light by ZnO pigment affects the ideal scheme of these TCCs. In the present study, silica-supported zinc oxide particles with different ZnO contents were synthesized as pigments for white thermal control coatings and the optimized one was selected based on the experimental determination of the optical properties of the prepared coatings. The results revealed that the optimized TCCs containing pigment with the zinc to silicon ratio of 1.91 had better reflection and emission properties in comparison with Z-93, due to the improvement in the refractive index and the dispersion quality of pigment. Then, the scattering properties (S) of the synthesized pigments and ZnO in TCC were investigated based on the reflectance data, according to the Kubelka–Munk analysis. The general trend in scattering coefficients for each formulation showed the same shape, such that with the increase in S values, the zinc to silicon ratio of pigments was raised too. Also, this trend revealed that scattering was more efficient at longer rather than shorter wavelengths. For Z-93, this trend was completely opposite. Also, S values for Z-93 in the wavelength range of 200–400 nm were around zero, while for the prepared coatings, this was not the case. Finally, the statistical nonlinear regression method was utilized to prepare a model for reflectance as a function of the zinc to silicon ratio of pigments and the wavelength of light. Note de contenu : - MATERIALS AND METHODS : Materials - Synthesis of silica-supported ZnO samples - Preparation of the paint samples - RESULTS AND DISCUSSION : Characterization of pigment particles - Reflectance spectra and thermal emission of the prepared coatings - Kubelka-Munk analysis - Gauss-Newton nonlinear regression method for the modeling of reflectance and scattering date DOI : 10.1007/s11998-017-9969-7 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-017-9969-7.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30114 [article]

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Synthesis of Zn-SBA-15 as a new pigment for spacecraft white thermal control coatings / Vahid Heydari in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 13, N° 4 (07/2016)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 13, N° 4 (07/2016) . - p. 727–733 Titre : Synthesis of Zn-SBA-15 as a new pigment for spacecraft white thermal control coatings Type de document : texte imprimé Auteurs : Vahid Heydari, Auteur ; Zaker Bahreini, Auteur ; Masoud Heidari, Auteur ; Alireza Sedrpoushan, Auteur Année de publication : 2016 Article en page(s) : p. 727–733 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Absorption Industries aérospatiales -- Matériaux Photométrie Pigments -- Synthèse Radiométrie Rayonnement solaire Revêtements:Peinture Santa Barbara Amorphous-15 Santa Barbara Amorphous-15 (SBA-15) is a highly stable mesoporous silica sieve developed by researchers at the University of California at Santa Barbara. It gets it high hydrothermal and mechanical stability from a framework of uniform hexagonal pores that feature a narrow pore-size distribution and a tunable pore diameter of 5nm to 15nm, but, most significantly, from its relatively thick walls, which range between 3.1nm and 6.4nm. SBA mesoporous silica 15 has a high internal surface area, which lends itself to various applications, including environmental adsorption and separation, advanced optics, and catalysts. (ACS Materials) Satellites artificiels Index. décimale : 667.9 Revêtements et enduits Résumé : Thermal control coatings (TCCs) help to maintain the thermal equilibrium of spacecraft at a level acceptable for vital components, usually around 20°C. This is done by either minimizing the solar absorbance or maximizing the thermal emittance. In the present study, with the aim of introducing new TCCs with enhanced optical properties, two TCCs were prepared by incorporating presynthesized pigments including SBA-15 (mesoporous material) and Zn-SBA-15 into potassium silicate binder. After application and drying, the TCC containing SBA-15 showed very low hiding power, so optical tests for this TCC were not done. The results of solar absorptance measurements revealed that the TCC containing Zn-SBA-15 was a proper reflector in the ultraviolet (UV) radiation range, making it much less susceptible to solar radiation in comparison with conventional TCCs. Also, thermal emittance tests demonstrated that the surface of this TCC had greater ability to emit heat. Furthermore, lower pigment-to-binder ratio and dry film thickness were attainable with this TCC, leading to weight reduction, improvement of mechanical properties, and lower porosity. Note de contenu : - MATERIALS AND METHODS : Materials - Equipment - Preparation of pigments - Preparation of paints - RESULTS AND DISCUSSION : X-ray diffraction - Scanning electron microscopy - Reflectometry DOI : 10.1007/s11998-015-9778-9 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-015-9778-9.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=26752 [article]

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