Effects of different polymer precursors on the characteristics of SiOC bulk ceramics

Preparation of SiCf/Si–O–C composites by impregnation pyrolysis of polysiloxane and its electromagnetic wave absorption properties

“…With the annealing temperature rising, part of Si-O-C matrix is decomposed, producing amorphous SiO 2 , SiC, and highly ordered free carbon at 1300 • C. In addition, the carbothermal reaction between the SiO 2 and free carbon is simultaneously activated to form β-SiC. 21 The nanocrystalline β-SiC generated can serve as initial crystal nucleus providing the basis for growth of SiC nanowires in the next stage. It is widely accepted that SiC nanowires are formed in the composites without catalysts following a vapor-solid growth mechanism.…”

“…Studies have shown that with the addition of catalysts or annealing temperature above 1100 • C, the interior of Si-O-C ceramics prepared from different precursors react in situ to generate second phases and nanostructures in an argon atmosphere, which is a good method for complex permittivity tuning. 21,22 Ding et al 23,24 prepared Si-O-C composites possessing various heterostructures by using FeCl 3 as the catalyst at different temperatures, which have good EMW absorption performance at X-and Ku-band. The reports show that annealing plays a key role to modulate the electrical properties and microstructures of Si-O-C ceramics derived from polysiloxanes, 25,26 whereas there are few publications about the annealing temperature effects on EMW absorption properties of SiC f /Si-O-C composites, although it may be an effective strategy.…”

Electrically conductive and thermally stable SiC‐TiC containing nanocomposites via flash pyrolysis

“…36,37 When a pure SiOC system is C-deficient, the electrical conductivity only depends on the amorphous SiOC matrix. With the increase in the C content of precursor side groups, 38 pyrolysis or annealing temperature, 19,39 or transition metal catalyst content, 40 the nucleation of segregated carbon and its sp 2 hybridization (sp 3 -to-sp 2 transition) are facilitated. As a result, drastically increased conductivity can be achieved through the coalescence of conducting graphitic C nanodomains beyond the percolation threshold.…”

Macromonomers as a Novel Way to Investigate and Tailor Silicon-Oxycarbide-Based Materials Obtained from Polymeric Preceramic Precursors

“…In the latter, either commercially available polysiloxanes [18,19], networked organosilicon polymers [20,21], or polysilsesquioxane gels obtained using the sol-gel method [22,23] can be annealed at temperatures exceeding 700 • C [24]. The last route is especially interesting for scientists, as it allows the easy customization of the preceramic polymer atom content by mixing small alkoxysilanes with a variable number of Si-C bonds [25], as well as different organic side groups [26]. The problem is that monomers with two or three Si-C bonds have a greater tendency to form volatile oligomers that can evaporate before the glass transition, thus effectively lowering the carbon content in the preceramic material [27].…”