Preparation of finely macroporous SiOC foams with high mechanical properties and with hierarchical porosity via pyrolysis of a siloxane/epoxide composite

0443898 - ÚMCH 2016 RIV GB eng J - Journal Article
Strachota, Adam - Černý, Martin - Chlup, Zdeněk - Rodzen, Krzysztof - Depa, Katarzyna - Halasová, Martina - Šlouf, Miroslav - Schweigstillová, Jana
Preparation of finely macroporous SiOC foams with high mechanical properties and with hierarchical porosity via pyrolysis of a siloxane/epoxide composite.
Ceramics International. Roč. 41, č. 7 (2015), s. 8402-8410. ISSN 0272-8842. E-ISSN 1873-3956
R&D Projects: GA ČR GAP107/12/2445
Institutional support: RVO:61389013 ; RVO:67985891 ; RVO:68081723
Keywords : silicon oxycarbide * foams * pyrolysis
Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass; JI - Composite Materials (USMH-B); JL - Materials Fatigue, Friction Mechanics (UFM-A)
Impact factor: 2.758, year: 2015

Mechanically strong SiOC foams were prepared via pyrolysis of polysiloxane composites, into which 20–70 wt% of epoxy powder were incorporated as sacrificial filler. The chosen epoxy filler degrades practically quantitatively during the pyrolysis in nitrogen, due to a high content of polyoxypropylene chains. The pyrolysis of the composite precursors yielded SiOC foams with apparent densities between 1.31 and 0.62 g/cm3, which corresponded to macro-porosities of 35–69%. A hierarchical porosity was obtained due to a relatively wide distribution of the sacrificial filler grains size. Compressive strength between 15 and 38 MPa was achieved, depending on the apparent density of the SiOC foams: the best result was obtained for the foam with 56% porosity. In the case of denser foams, their strength was reduced by the presence of pyrolysis cracks, while at 70% porosity, the thinner pore walls led to a reduced strength. The elastic modulus of the most promising foam (56% porosity) was found to be 10 GPa.
Permanent Link: http://hdl.handle.net/11104/0247160