Molded Carbon–Carbon Composites Based on Microcomposite Technology
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A one-step, cost-effective processing methodology based on compression molding of a mixture of graphite particles and short fibers, both coated with a soluble polyimide adhesive was developed. This technique shows a considerable potential in decreasing the complexity of the current carbon–carbon fabrication procedures. The new process eliminates additional infiltration and densification steps following the initial carbonization, which reduces the processing time from 5 weeks to 3–5 days and saves energy. The structure and properties of the new carbon–carbon composites were characterized using optical and electronic microscopy, thermal analysis, density and porosity measurements, and mechanical properties (hardness and flexural strength).
The flexural strengths ranged from 20–45 MPa. The densities ranged from 1.9 to 2.2 g/cc (which is close to pure graphite) while the porosity was as low as 3%. The CTE was approximately ± 1 ppm/○C (R.T. to 550○C). The thermal stability of the carbonized and graphitized specimens when heated in flowing air up to 500○C and flowing nitrogen up to 1000○C showed no observable weight loss.
There are numerous applications for these materials which include: optical mirrors, medical implants, thermal radiators and parts for rotating equipment, etc.
A car piston was successfully molded using a mixture of polymer coated graphite powder, flakes and chopped fibers.
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