Structural evolutions in polymer-derived carbon-rich amorphous silicon carbide

Area of Science:

• Materials Science
• Ceramics Engineering
• Nanotechnology

Background:

• Polycarbosilane-derived amorphous silicon carbide (SiC) is a promising material with tunable properties.
• Understanding its structural evolution during pyrolysis is crucial for optimizing its performance.

Purpose of the Study:

• To investigate the semiquantitative structural evolutions in carbon-rich amorphous SiC derived from polycarbosilane.
• To elucidate the transformation mechanisms of the Si-containing matrix and free-carbon phases with increasing pyrolysis temperature.

Main Methods:

• Combined experimental and analytical techniques for semiquantitative investigation.
• Analysis of structural changes in the Si-containing matrix and free-carbon phases.
• Characterization of defects and phase transitions during pyrolysis.

Main Results:

• The material consists of a Si-containing matrix (SiC4, SiCxOx-4, Si-C-C-Si/Si-C-H defects) and a free-carbon phase.
• Increasing pyrolysis temperature orders the matrix (SiC2O2 to SiCO3) and initiates β-SiC crystallization above 1250 °C.
• Free carbon transitions from amorphous to nanocrystalline graphite, with cluster size initially decreasing then increasing, and C-dangling bonds continuously decreasing.

Conclusions:

• The structural evolution involves matrix ordering, crystallization, and transformation of free carbon.
• Carbon cluster growth is explained by Ostwald ripening and a 2D grain growth model.
• The decrease in C-dangling bonds is directly linked to the lateral growth of carbon clusters.