المؤلفون: Poloni, Erik, Bouville, Florian, Schmid, Alexander L., Pelissari, Pedro I. B. G. B., Pandolfelli, Victor C., Sousa, Marcelo L. C., Tervoort, Elena, Christidis, George, Shklover, Valery, Leuthold, Juerg, Studart, André R.

المصدر: Carbon 195 (2022) 80-91

مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Materials Science

الوصف: Porous carbon ablators offer cost-effective thermal protection for aerospace vehicles during re-entry into planetary atmospheres. However, the exploration of more distant planets requires the development of ablators that are able to withstand stronger thermal radiation conditions. Here, we report the development of bio-inspired porous carbon insulators with pore sizes that are deliberately tuned to enhance heat-shielding performance by increasing scattering of high-temperature thermal radiation. Pore size intervals that promote scattering are first estimated using an established model for the radiative contribution to the thermal conductivity of porous insulators. On the basis of this theoretical analysis, we identify a polymer additive that enables the formation of pores in the desired size range through the polymerization-induced phase separation of a mixture of phenolic resin and ethylene glycol. Optical and electron microscopy, porosimetry and mechanical tests are used to characterize the structure and properties of porous insulators prepared with different resin formulations. Insulators with pore sizes in the optimal scattering range reduce laser-induced damage of the porous structures by up to 42%, thus offering a promising and simple route for the fabrication of carbon ablators for enhanced thermal protection at high temperatures.
Comment: 34 pages, 9 figures

الوصول الحر: http://arxiv.org/abs/2110.04244Test

المؤلفون: Poloni, Erik, id_orcid:0 000-0002-6982-0643, Galinski, Henning, Bouville, Florian, id_orcid:0 000-0002-1527-5045, Wilts, Bodo, Braginsky, Leonid, Bless, David, Shklover, Valery, Sicher, Alba, Studart, André R.

المصدر: Advanced Optical Materials, 11 (7)

مصطلحات موضوعية: alumina, epoxy, manufacturing, reflective materials, titania

الوصف: The reflection of light from distributed microplatelets is an effective approach to creating color and controlling the optical properties in paints, security features, and optical filters. However, predictive tools for the design and manufacturing of such composite materials are limited due to the complex light-matter interactions that determine their optical response. Here, the optical reflectance of individual reflective microplatelets and of polymer-based composites containing these engineered platelets as an aligned, dispersed phase are experimentally studied and analytically calculated. Transfer-matrix calculations are used to interpret the effect of the platelet architecture, the number of platelets, and their size distribution on the experimentally measured reflectance of composites prepared using a previously established magnetic alignment technique. It is demonstrated that the reflectance of the composites can be understood as the averaged response of an array of Fabry-Perot resonators, in which the microplatelets act as semi-transparent flat reflectors and the polymer as cavity medium. By using an analytical model and computer simulations to describe the interaction of light with platelets embedded in a polymer matrix, this work provides useful tools for the design and fabrication of composites with tailored optical reflectance. ; ISSN:2195-1071

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000916708800001; info:eu-repo/grantAgreement/SNF/Projekte MINT/160184; http://hdl.handle.net/20.500.11850/597491Test

الإتاحة: https://doi.org/20.500.11850/597491Test
https://doi.org/10.3929/ethz-b-000597491Test
https://doi.org/10.1002/adom.202201989Test
https://hdl.handle.net/20.500.11850/597491Test

المؤلفون: Poloni, Erik, id_orcid:0 000-0002-6982-0643, Bouville, Florian, id_orcid:0 000-0002-1527-5045, Schmid, Alexander L., Pelissari, Pedro I.B.G.B., Pandolfelli, Victor C., Sousa, Marcelo L.C., Tervoort, Elena, Christidis, George, id_orcid:0 000-0001-6725-2083, Shklover, Valery, Leuthold, Juerg, id_orcid:0 000-0003-0111-8169, Studart, André R.

المصدر: Carbon, 195

مصطلحات موضوعية: Radiative heat, Porosity, Heat shields, Thermal protection systems

الوصف: Porous carbon ablators offer cost-effective thermal protection for aerospace vehicles during re-entry into planetary atmospheres. However, the exploration of more distant planets requires the development of ablators that are able to withstand stronger thermal radiation conditions. Here, we report the development of bio-inspired porous carbon insulators with pore sizes that are deliberately tuned to enhance heat-shielding performance by increasing scattering of high-temperature thermal radiation. Pore size intervals that promote scattering are first estimated using an established model for the radiative contribution to the thermal conductivity of porous insulators. On the basis of this theoretical analysis, we identify a polymer additive that enables the formation of pores in the desired size range through the polymerization-induced phase separation of a mixture of phenolic resin and ethylene glycol. Optical and electron microscopy, porosimetry and mechanical tests are used to characterize the structure and properties of porous insulators prepared with different resin formulations. Insulators with pore sizes in the optimal scattering range reduce laser-induced damage of the porous structures by up to 42%, thus offering a promising and simple route for the fabrication of carbon ablators for enhanced thermal protection at high temperatures. ; ISSN:0008-6223

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000804763900009; info:eu-repo/grantAgreement/SNF/Projekte MINT/160184; http://hdl.handle.net/20.500.11850/544003Test

الإتاحة: https://doi.org/20.500.11850/544003Test
https://doi.org/10.3929/ethz-b-000544003Test
https://doi.org/10.1016/j.carbon.2022.03.062Test
https://hdl.handle.net/20.500.11850/544003Test

المؤلفون: Christidis, George, id_orcid:0 000-0001-6725-2083, Koch, Ueli, id_orcid:0 000-0001-8796-2146, Poloni, Erik, id_orcid:0 000-0002-6982-0643, De Leo, Eva, Cheng, Bojun, id_orcid:0 000-0001-5551-4242, Koepfli, Stefan M., id_orcid:0 000-0003-0291-2065, Dorodnyy, Alexander, Bouville, Florian, id_orcid:0 000-0002-1527-5045, Fedoryshyn, Yuriy M., Shklover, Valery, Leuthold, Juerg, id_orcid:0 000-0003-0111-8169

المساهمون: Caspani, Lucia, Tauke-Pedretti, Anna, Leo, F., Yang, B.

المصدر: OSA Advanced Photonics Congress (AP) 2020 (IPR, NP, NOMA, Networks, PVLED, PSC, SPPCom, SOF)

مصطلحات موضوعية: Aerospace engineering, High Temperature Materials, Reflectors, Photonic Additives, Thermal protection, info:eu-repo/classification/ddc/600, Technology (applied sciences)

الوصف: Metal-dielectric platelets are introduced as additives to heat protection systems. The platelets feature high reflectivity across 700 nm and thermal stability up to 1000°C. Impregnating aerospace heat shields improves thermal reflectivity by a factor 11.

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/isbn/978-1-943580-79-8; info:eu-repo/grantAgreement/SNF/Projekte MINT/160184; http://hdl.handle.net/20.500.11850/456252Test; urn:isbn:978-1-943580-79-8

الإتاحة: https://doi.org/20.500.11850/456252Test
https://doi.org/10.3929/ethz-b-000456252Test
https://doi.org/10.1364/NOMA.2020.NoTu2C.4Test
https://hdl.handle.net/20.500.11850/456252Test

المؤلفون: Christidis, George, id_orcid:0 000-0001-6725-2083, Koch, Ueli, id_orcid:0 000-0001-8796-2146, Gusarov, Andrey V., Shklover, Valery, Leuthold, Juerg, id_orcid:0 000-0003-0111-8169

المصدر: International Journal of Thermal Sciences, 170

مصطلحات موضوعية: Photonic Additives, Reflectance Enhancement, Thermal radiation, Radiative Transfer, Numerical modelling, Monte Carlo, info:eu-repo/classification/ddc/530, info:eu-repo/classification/ddc/600, info:eu-repo/classification/ddc/621.3, Physics, Technology (applied sciences), Electric engineering

الوصف: Photonic additives have been investigated as a means to enhance the efficiency of thermal protection systems (TPS) against the adverse effects of thermal radiation. State-of-the-art TPS consist of carbon fibers embedded in a phenolic resin matrix. During operation, the TPS is consumed because it is exposed to an excess heat flux, a large fraction of which is due to thermal radiation. Here, we show that a properly modeled and designed additive-impregnated TPS can block a considerable part of this heat influx and quantify how different control parameters, in particular the additives’ amount, placement and alignment, influence the achieved photonic enhancement. More specifically, the intrinsic reflectivity of 8.5% of a conventional TPS can been improved to values exceeding 85% by controllably inserting additives, consisting of a Ta/[SiO2/TiO2]6 heterostructure, here referred to as Type 1, an ideal, optimized, high and broadband reflector. Nevertheless, even simple, commercially available additives composed of TiO2/Al2O3/TiO2, here referred to as Type 2, provide a high reflectivity enhancement with values of up to 76%, when used in larger quantities. The simulations of this work are based on the Monte Carlo Ray Tracing (MCRT) method. The MCRT simulation method has been validated against experiment, using the structure and experiments from a literature reference. Our analysis method allows one to design and model the performance of photonically enhanced TPS that operate in high-flux, radiative conditions, like those expected in future aerospace re-entry missions or next-generation, gas turbines and thermophotovoltaic plants and provides a viable option for efficiently enhancing a TPS. ; ISSN:1290-0729 ; ISSN:1778-4166

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000685518600001; info:eu-repo/grantAgreement/SNF/Projekte MINT/160184; http://hdl.handle.net/20.500.11850/493596Test

الإتاحة: https://doi.org/20.500.11850/493596Test
https://doi.org/10.3929/ethz-b-000493596Test
https://doi.org/10.1016/j.ijthermalsci.2021.107146Test
https://hdl.handle.net/20.500.11850/493596Test

المؤلفون: Christidis, George, id_orcid:0 000-0001-6725-2083, Fabrichnaya, Olga B., Koepfli, Stefan M., id_orcid:0 000-0003-0291-2065, Poloni, Erik, id_orcid:0 000-0002-6982-0643, Winiger, Joel, Fedoryshyn, Yuriy M., Gusarov, Andrey V., Ilatovskaia, Mariia, Saenko, Ivan, Savinykh, Galina, Shklover, Valery, Leuthold, Juerg

المصدر: Journal of Materials Science, 56

مصطلحات موضوعية: Ceramics, info:eu-repo/classification/ddc/530, Physics

الوصف: The microstructural and optical reflectivity response of photonic SiO2/TiO2 nanomultilayers have been investigated as a function of temperature and up to the material system’s melting point. The nanomultilayers exhibit high, broadband reflectivities up to 1350 °C with values that exceed 75% for a 1 μm broad wavelength range (600–1600 nm). The optimized nanometer sized, dielectric multilayers undergo phase transformations from anatase TiO2 and amorphous SiO2 to the thermodynamically stable phases, rutile and cristobalite, respectively, that alter their structural morphology from the initial multilayers to that of a scatterer. Nonetheless, they retain their photonic characteristics, when characterized on top of selected substrate foils. The thermal behavior of the nanometer sized multilayers has been investigated by differential thermal analysis (DTA) and compared to that of commercially available, mm-sized, annealed powders. The same melting reactions were observed, but the temperatures were lower for the nm-sized samples. The samples were characterized using X-ray powder diffraction before DTA and after annealing at temperatures of 1350 and 1700 °C. The microstructural evolution and phase compositions were investigated by scanning electron microscopy and energy-dispersive X-ray spectroscopy measurements. The limited mutual solubility of one material to another, in combination with the preservation of their optical reflectivity response even after annealing, makes them an interesting material system for high-temperature, photonic coatings, such as photovoltaics, aerospace re-entry and gas turbines, where ultra-high temperatures and intense thermal radiation are present. ; ISSN:0022-2461 ; ISSN:1573-4803

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000705788000002; info:eu-repo/grantAgreement/SNF/Projekte MINT/160184; http://hdl.handle.net/20.500.11850/508913Test

الإتاحة: https://doi.org/20.500.11850/508913Test
https://doi.org/10.3929/ethz-b-000508913Test
https://doi.org/10.1007/s10853-021-06557-yTest
https://hdl.handle.net/20.500.11850/508913Test

المؤلفون: Leuthold, Juerg, id_orcid:0 000-0003-0111-8169, Dorodnyy, Alexander, Alarcon-Lladó, Esther, Shklover, Valery, Hafner, Christian, Fontcuberta i Morral, Anna

المصدر: ACS Photonics, 2 (9)

مصطلحات موضوعية: Photovoltaics, Nanowire, Spectrum splitting, Photonic crystals

الوصف: Nanowire-based solar cells opened a new avenue for increasing conversion efficiency and rationalizing material use by growing different III–V materials on silicon substrates. Here, we propose a multiterminal nanowire solar cell design with a theoretical conversion efficiency of 48.3% utilizing an efficient lateral spectrum splitting between three different III–V material nanowire arrays grown on a flat silicon substrate. This allows choosing an ideal material combination to achieve the proper spectrum splitting as well as fabrication feasibility. The high efficiency is possible due to an enhanced absorption cross-section of standing nanowires and optimization of the geometric parameters. Furthermore, we propose a multiterminal contacting scheme that can be fabricated with a technology close to standard CMOS. As an alternative we also consider a single power source with a module level voltage matching. These new concepts open avenues for next-generation solar cells for terrestrial and space applications. ; ISSN:2330-4022

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000361505000010; http://hdl.handle.net/20.500.11850/104772Test

الإتاحة: https://doi.org/20.500.11850/104772Test
https://doi.org/10.3929/ethz-b-000104772Test
https://doi.org/10.1021/acsphotonics.5b00222Test
https://hdl.handle.net/20.500.11850/104772Test

المؤلفون: Dorodnyy, Alexander, Alarcon-Lladó, Esther, Shklover, Valery, Hafner, Christian, Fontcuberta i Morral, Anna, Leuthold, Juerg

المساهمون: European Research Council, Schweizerische Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Zeropower, Rat der Eidgenössischen Technischen Hochschule, Schweizerische Universitätskonferenz

المصدر: ACS Photonics ; volume 2, issue 9, page 1284-1288 ; ISSN 2330-4022 2330-4022

الإتاحة: https://doi.org/10.1021/acsphotonics.5b00222Test

المؤلفون: Christidis, George, Koch, Ueli, Poloni, Erik, De Leo, Eva, Cheng, Bojun, Koepfli, Stefan M., Dorodnyy, Alexander, Bouville, Florian, Fedoryshyn, Yuriy, Shklover, Valery, Leuthold, Juerg

الوصف: A simple and thermally stable photonic heterostructure exhibiting high average reflectivity (⟨R⟩ ≈ 88.8%) across a broad wavelength range (920–1450 nm) is presented. The design combines a thin, highly reflective and broadband metallic substrate (Ta) with an optimized dielectric coating (10 layers) to create an enhanced reflector with improved optical and thermal properties compared to its constituents. The heterostructure exhibits temperature-reversible reflective properties up to 1000 °C. In order to take advantage of the high reflectivity and temperature stable properties of this coating, in a wide range of non-photonic composite materials, we have fabricated heterostructure platelets as additives. By impregnating these additives into other types of materials, their response can be photonically enhanced. Platelets of such a heterostructure have been introduced inside an organic matrix to increase its broadband reflection performance. The platelet-impregnated matrix displays an average reflectivity improvement from 5% to an average of 55% over a 1000 nm range, making it a suitable additive for next generation thermal protection systems (TPS).

العلاقة: https://repository.hkust.edu.hk/ir/Record/1783.1-121857Test; ACS Applied Materials and Interfaces, v. 12, (8), February 2020, p. 9925-9934; https://doi.org/10.1021/acsami.9b20753Test; http://www.scopus.com/record/display.url?eid=2-s2.0-85081015928&origin=inwardTest; http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=LinksAMR&SrcApp=PARTNER_APP&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000517360000105Test

الإتاحة: https://doi.org/10.1021/acsami.9b20753Test
https://repository.hkust.edu.hk/ir/Record/1783.1-121857Test
http://www.scopus.com/record/display.url?eid=2-s2.0-85081015928&origin=inwardTest
http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=LinksAMR&SrcApp=PARTNER_APP&DestLinkType=FullRecord&DestApp=WOS&KeyUT=000517360000105Test

المؤلفون: Bhattacharya, Anup K., Reinhard, Patrick, Steurer, Walter, Shklover, Valery

المصدر: Journal of Materials Science, 46 (17)

الوصف: ISSN:0022-2461 ; ISSN:1573-4803

وصف الملف: application/application/pdf

العلاقة: info:eu-repo/semantics/altIdentifier/wos/000291359700014; http://hdl.handle.net/20.500.11850/37561Test

الإتاحة: https://doi.org/20.500.11850/3756110.3929/ethz-b-00003756110.1007/s10853-011-5524-6Test
https://hdl.handle.net/20.500.11850/37561Test