Preparation methods for carbon-carbon composites

The preparation of carbon/carbon (C/C) composites primarily involves steps such as liquid-phase impregnation, chemical vapor deposition (CVD), and heat treatment; these methods effectively enhance the material's properties and density.

1. Preparation Principles

C/C composites utilize carbon fibers or graphite fibers as reinforcement. A preform is impregnated and filled with organic substances—such as resin or pitch—and subsequently heat-treated to convert the organics into carbon, thereby yielding the composite material. Key steps include preform preparation, densification, and final high-temperature heat treatment.

2. Main Preparation Methods

Liquid-phase impregnation: The preform is impregnated with liquid-phase precursors (e.g., pitch or resin) and subjected to high-temperature treatment to convert them into carbon. This method offers a high carbon yield; the resulting C/C composites are easily graphitized and exhibit excellent ablation and thermal shock resistance.

Chemical Vapor Deposition (CVD): A carbon source is deposited onto the preform via gas-phase reactions in an inert atmosphere, forming a dense carbon matrix. While suitable for producing high-performance materials, this method entails higher costs and longer processing times.

Heat treatment: The impregnated preform undergoes high-temperature heat treatment to remove organic matter and form the carbon matrix. The temperature and duration of this process significantly influence the final material's properties.

3. Specific Steps

Preform preparation: Suitable carbon fibers (e.g., PAN-based carbon fibers) are selected to fabricate the preform; common methods include filament winding and compression molding.

Impregnation: The preform is immersed in resin or pitch to ensure the organic material fully fills the preform's pores.

Heat treatment: High-temperature heat treatment is conducted in an inert atmosphere to convert the organic matter into carbon, resulting in a dense C/C composite.

Post-processing: Mechanical machining or surface treatment is performed as needed to enhance the material's performance and adaptability.

4. Application Fields

Due to their exceptional thermal stability and ablation resistance, C/C composites are widely used in aerospace, automotive, and medical sectors, particularly as structural materials for high-temperature and high-stress environments. Through the methods described above, carbon/carbon composites with excellent properties can be effectively produced to meet the demands of various fields.