Fidelis, Clara Lana
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Fidelis, Clara Lana
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Fidelis, Clara Lana
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Item-typ:Veröffentlichung, Macro/mesoporous SiOC ceramics of anisotropic structure for cryogenic engineering(Elsevier, 2017-09-01); ; ; ; Macro/mesopore SiOC ceramic monoliths of anisotropic structure were prepared by freeze casting, using methy phenyl polysiloxane (H44) or methy polysiloxane (MK) and (3-aminopropyl)triethoxysilane (APTES) as precursors. Influence of pyrolysis and testing temperature on compressive strength was investigated. Monoliths pyrolyzed at 700 °C had the highest compressive strength both at 77 K (14.0 ± 4.3 MPa) and 293 K (7.7 ± 1.8 MPa), regardless of precursors. Compressive strength of monolith in parallel direction is around twice as much as perpendicular direction. Compressive strength of both monoliths in liquid nitrogen (77 K) was around twice of that in air (293 K) probably due to low temperature and liquid resistance. Anisotropic expansion was observed, and the shrinkage in parallel direction was almost twice of that in perpendicular direction, which can be verified by the Schapery equation. Monolith made from H44 showed a much higher coefficient of thermal expansion at 77 K than monolith made from MK and APTES, probably due to difference in composition and measurement condition. Thermal conductivities and specific heat capacities displayed an upward trend from low to warmer temperature. The minimum and maximum values for thermal conductivity are 0.2 and 1.2 W m− 1 K− 1. The maximum heat conductivities might be determined mainly by the macroporosity and the thermal conductivity of the hybrid material.Wissenschaftlicher ArtikelBand:13497 121 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Water-based freeze casting: Adjusting hydrophobic polymethylsiloxane for obtaining hierarchically ordered porous SiOC(Wiley, 2017-05-07); ; ; ; The hydrophobic properties of methyl poly siloxane (MK) were pushed into the“hydrophilic”range by cross-linking it with (3-aminopropyl)triethoxysilane(APTES) and subsequent pyrolysis to enable water-based freeze casting. Fillerproperties are investigated by varying the ratios of MK to APTES (1:1, 1:2, 1:3,1:4, 1:5), and pyrolysis temperatures (400°C, 500°C, 600°C) for the purpose ofdetermining an optimal set of characteristics for freeze casting. Additionally, fillerselection for this purpose is facilitated by analysis of zeta potential values andvapor adsorption. It was found that water-based freeze casting with hybrid fillers,followed by a pyrolysis step (600°C-700°C), leads to a SiOC ceramic monolithwith a lamellar pore morphology and a hierarchically ordered micro/meso/macrop-ore structure. Samples pyrolyzed at 1000°C contain mesopores, having a SSA ashigh as 51.6 m2/g. The hierarchically porous structure is very promising for appli-cations involving gas or liquid transportation.Wissenschaftlicher ArtikelBand:100Heft:5113 191