Manufacture of carbon/carbon composites by hot pressing

a carbon/carbon composite and hot pressing technology, applied in the field of carbon/carbon composite manufacturing, can solve the problems of increasing weight, increasing cost, and increasing complexity of carbon/carbon composites, and achieves fewer densification and carbonization cycles and less processing steps

Inactive Publication Date: 2005-01-06
GRAFTECH INT HLDG INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] An advantage of at least one embodiment of the present invention is that carbon-carbon composites, such as insulation and brake component materials, are formed in much shorter periods of time than by conventional hot pressing methods.
[0014] Another advantage of at least one embodiment of the present invention is that the density of the hot pressed material is higher than in conventional preforms, thereby enabling desired densities to be achieved with fewer densification and carbonization cycles.
[0015] Another advantage of at least one embodiment of the present invention is that a composite material is formed using fewer processing steps.

Problems solved by technology

This carbonization step is carried out in an inert atmosphere and often takes about eighty hours to complete.
The lengthy heating and infiltration times render such composites expensive and impractical for many applications.
Accordingly, sintered metal articles are commonly used for thermal applications, despite their greater weight and often poorer thermal stability and friction properties.

Method used

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  • Manufacture of carbon/carbon composites by hot pressing
  • Manufacture of carbon/carbon composites by hot pressing
  • Manufacture of carbon/carbon composites by hot pressing

Examples

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Effect test

example 1

Carbon / Carbon Composite Made by Dry Mixing of Precursor Materials

[0064] Mesophase pitch-based carbon fibers and a matrix material of milled pitch with 170° C. softening point and 70% coking yield were dry mixed at ambient temperature in a Sigma-type blender or similar type of mixer for about 5-15 minutes. The ratio of fibers to pitch matrix material was from 50-80 wt % fiber: 20-50 wt % pitch. The mixture was collected and charged into a mold box cavity (dimensions approximately 23×20 cm) of a hot press, as illustrated in FIG. 1. A pressure of up to about 140 kg / cm2 was applied to the mixture in the press. After pressing to compact the mixture, an electric current of about 1000-2000 amps (a power input of about 30-60 kW / kg) was passed through the mixture. The mix was held under the temperature and pressure conditions for about 5-10 minutes. The temperature of the mixture reached 800-900° C. This hot pressing process carbonizes and densifies the fiber / matrix mixture in a very short ...

example 2

Carbon / Carbon Composite Made by Hot Mixing of Precursor Materials

[0065] Various batches of mesophase pitch-based carbon fibers and a matrix material of milled pitch from Example 1 were hot mixed at a temperature of about 200° C. in a Sigma-type blender or similar type of mixer for about 30-45 minutes. The ratio of fibers to pitch matrix material was varied from about 50-80 wt % fiber:20-50 wt % pitch. During the hot mixing, the matrix material coated the fibers uniformly. The mixture was collected and charged into a mold box cavity of a hot press, and heated and pressed as described for Example 1. Alternatively, the mixture was compacted in a separate mold to a density of between about 0.5 and 1.0 g / cm3 prior to hot pressing.

[0066] A pressure of up to 140 kg / cm2 was applied to the mixture in the hot press. After pressing to compact the mixture, an electric current as high as 1500-2000 A (a power input of about 45-60 kW / kg) was passed through the mixture. The mix was held under the...

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Abstract

A mixture of carbon-containing fibers, such as mesophase or isotropic pitch fibers, and a suitable matrix material, such as a milled pitch, is compressed while resistively heating the mixture to form a carbonized composite material having a density of about 1.5 g/cm3, or higher. The composite material is formed in under ten minutes. This is a significantly shorter time than for conventional processes, which typically take several days and achieve a lower density material. Consequently, carbon/carbon composite materials having final densities of about 1.6-1.8 g/cm3, or higher are readily achieved with one or two infiltration cycles using a pitch or other carbonaceous material to fill voids in the composite and rebaking.

Description

[0001] This divisional application claims benefit of co-pending U.S. patent application Ser. No. 10 / 205,859 filed Jul. 26, 2002, entitled “Manufacture of Carbon / Carbon Composites by Hot Pressing” which is hereby incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present application relates to a method for forming carbon / carbon composites suited for use as friction-bearing and structural materials for high temperature applications. It finds particular application in conjunction with a composite material formed by resistance heating of carbon fiber / binder mixtures during application of a compressive force and will be described with particular reference thereto. It should be appreciated that the method has application in other areas where the combined effects of pressure and temperature are desired. [0004] 2. Discussion of the Art [0005] Carbon / carbon composites include those structures formed from a fiber reinforcement, which itself consi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C04B35/52C04B35/645C04B35/83H05B3/00H05B3/60H05B6/22
CPCC04B35/521C04B35/522C04B35/645C04B35/83C04B2235/48H05B6/22C04B2235/96C04B2235/9607H05B3/0004H05B3/60C04B2235/77
Inventor HUANG, DAILEWIS, IRWIN C.LEWIS, RICHARD T.CATE, WILLIAM DAVID
Owner GRAFTECH INT HLDG INC
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