Development of porous SiOC-based materials from a preceramic polymer and sucrose particles

MARIANO H. TALOU; M. ANDREA CAMERUCCI; JAVIER O. BOLAÑOS-RIVERA

Congreso; ICC7; 2018

Polymer-derived ceramics (PDCs) constitute a novel type of materials which are receiving special attention due to their ultrahigh-temperature relevant properties. These materials are defined as intrinsically complex nanostructured materials whose chemical compositions are unique, and their processing includes crosslinking and pyrolysis processes. The advantage of this processing resides in the possibility of fabricating ceramic parts by techniques conventionally used in the polymer manufacturing. However, the polymerceramic transformation is accompanied by removing of a large gas volume, which leads to a high volumetriccontraction and formation of cracks. Thus, the fabrication of PDCs in bulk constitutes a huge technological challenge. The addition of porogen along with particulate filler is considered as a possible way of solution and development of hierarchical porosity. In this work, a polysilsesquioxane (MP-POSS) with high concentration of SiOH groups synthetized by condensation of 3-ethacryloxypropyl-trimethoxysilane (molar ratio HCOOH/Si=0.055; 50°C, 5 days) and characterized by density measurement, ATR, RMN and DSC, was used as preceramic polymer. In addition, sucrose particles (D50=90μm) and SiOC powder (D50=30μm) were used as porogen and filler, respectively. Porous hybrid bodies were prepared by cross-linking (60°C, 1.5h, 10 vol% of triethylenetetramine) of MPPOSS/sucrose/filler (55/20/25 and 55/25/20 vol%) mixtures and heating (220°C, 2h), and characterized by porosity measurements and SEM. The pyrolysis was carried out at different temperatures (1000-1500°C) using controlled thermal cycles in N2. Porous SiOC-based materials (porosity=43-55%) were characterized by XRD, SEM/EDS, FTIR and Raman. All the materials (SiOxC(1-x/2)+C) presented amorphous freecarbon (clusters) and carbon bonded to Si, while those obtained from 1330°C shown the development of whiskers (SiOC0.5) with core-shell structure (nucleus of SiC and shell of amorphous silica).