  Quantitative microstructural analysis of Room Temperature Vulcanized (RTV)
silicone pyrolysis at high temperatures is presented. RTV is used as a bonding
agent in multiple industries, particularly filling gaps in ablative tiles for
hypersonic (re-)entry vehicles and fire prevention. Decomposition of RTV is
resolved in real time using in situ high-temperature X-ray computed
micro-tomography. Full tomographies are acquired every 90~seconds for four
different linear heating rates ranging from 7 to 54 C/min. The microstructure
is resolved below 5 micro-meters/pixel, allowing for a full quantitative
analysis of the micro-structural evolution and porous network development.
Results are highly heating rate dependent, and are evaluated for bulk sample
volume change, porosity, pore network size, and observed densification from
X-ray attenuation. The outcome of this work is critical to develop
multi-physics models for thermal response.
