Transmission Electron Microscopy Investigations on a Polysiloxane Preceramic Polymer Pyrolyzed at High Temperature in Argon

Abstract

A commercially available methylphenylvinylhydrogen polysiloxane preceramic polymer was cross-linked and pyrolyzed in argon in order to study if this compound could be used as an organic precursor for the manufacture of silicon carbide parts by photopolymerisation-based three-dimensional printing. X-Ray diffraction experiments and transmission electron microscopy observations showed that the pyrolyzed material was constituted by an interconnected polycrystalline network made of faulted/twinned β-SiC grains surrounded by an amorphous and porous second phase mainly constituted (at least 80 at%) of carbon. The free carbon residual content was estimated to be around 17.2 wt%. Additional efforts are then required to be able to use such a preceramic polymer to manufacture SiC parts by photopolymerisation-based three-dimensional printing.

Silicon Carbide Precursor: Structure Analysis and Thermal Behavior from Polymer Cross-Linking to Pyrolyzed Ceramics

“…Finally, an observation using transmission electron microscopy of the ceramic converted at 1700 • C reported in a previous work [21] confirmed the presence of the SiC crystalline phase and residual carbon-rich phase (Figure 13). The final composition of the ceramic obtained from the conversion of the Silres H62C polysiloxane resin at 1700 • C in argon gave a solid compound made of 82.15 wt% SiC, 0.69 wt% SiO 2 and 17.16 wt% of free C. The results obtained using the Scherrer equation from XRD give smaller-sized particles than the observation using TEM which shows an average particle size of 122 nm, accessed by image analysis.…”

“…A signal with a broad peak width for Silres H62C treated at 1400 • C was then observed, indicating the progressive apparition of a crystalline phase between 1200 and 1400 • C. Five distinct and fine peaks were finally observed for 35.6, 41.3, 59.9, 71.7 and 75.4 • on the diffractogram of the materials pyrolyzed at 1700 • C. All diffraction peaks were associated with the cubic silicon carbide (3C-SiC) crystalline phase. The crystallite size calculated from the Scherrer equation using the (111) peak was 73 nm at 1700 • C. Finally, an observation using transmission electron microscopy of the ceramic converted at 1700 °C reported in a previous work [21] confirmed the presence of the SiC crystalline phase and residual carbon-rich phase (Figure 13). The final composition of the ceramic obtained from the conversion of the Silres H62C polysiloxane resin at 1700 °C in In addition, a small peak to the left of the main peak was observed at 33.7 • .…”

“…In addition, in a previous investigation, the Silres H62C resin treated at 1700 • C in argon was characterized using transmission electron microscopy (TEM). This characterization showed that the ceramics obtained are made of carbon-enriched SiC [21]. However, this promising polymer for the printing of SiC parts is only rarely referenced alone in the literature and is often associated with Silres MK polysiloxane [22][23][24].…”