Macro/mesoporous SiOC ceramics of anisotropic structure for cryogenic engineering
Veröffentlichungsdatum
2017-09-01
Zusammenfassung
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.
Schlagwörter
Macropore
;
Polymer derived ceramics
;
Cryogenic temperature
;
Thermal properties
;
Compressive strength
;
Mimenima
Verlag
Elsevier
Institution
Institute
Dokumenttyp
Artikel/Aufsatz
Zeitschrift/Sammelwerk
Band
134
Startseite
207
Endseite
217
Zweitveröffentlichung
Ja
Dokumentversion
Postprint
Sprache
Englisch
Dateien![Vorschaubild]()
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Name
H. Zhang, C.L. Fidelis, M. Wilhelm, Z. Xie, K. Rezwan, Macro-mesoporous SiOC ceramics anisotopic_2017_accepted version_Deckblatt_pdfa1.pdf
Size
1.29 MB
Format
Adobe PDF
Checksum
(MD5):82b554afd0bc59b8f3d753e0af91254b