Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
1998-12-31
2001-07-17
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
C428S299100, C428S297100, C428S325000, C428S446000, C428S698000, C554S141000, C554S141000, C554S141000, C554S145000
Reexamination Certificate
active
06261692
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing a carbon-carbon composite and a carbon-carbon composite prepared therefrom. More specifically, the present invention relates to a method for preparing a carbon-carbon composite which comprises the step of adding a ceramic-based oxidation inhibitor having a brittle-to-ductile transition (hereinafter referred to as “BDT”), to thereby eliminate high densification processes via re-impregnation and re-carbonization. Further, the present invention relates to a carbon-carbon composite comprising a ceramic powder added to a thermosetting matrix resin.
2. Description of the Prior Art
‘Carbon-carbon composites’ in the present invention refer to carbon fiber-reinforced composites, which are prepared by impregnating a carbon fiber as a reinforced material with a matrix resin having good heat stability and carbon yield. Such carbon-carbon composites are superior to metals in their specific strength and specific modulus. They also have good fatigue resistance, heat shock resistance, corrosion resistance, wear resistance, lightness, heat-electrical conductivity and dimensional stability. Moreover, they are the only ultrahigh temperature materials, that do not loss their physical properties at temperatures up to 2000° C. and maintain their mechanical properties up to 3400° C. under a reduced condition. They have been predominantly used as parts of aerospace aircraft (for example, nozzle of rockets, exhaust cones, reentry tips), brake linings for ultrasonic airplanes, high-speed trains and racing cars, body of high-temperature reactors, limiting materials and next generation materials.
U.S. Pat. No. 5,225,283 discloses a process of blending a silicon carbide and a cyclosiloxane monomer and then coating the resultant blend onto a carbon-carbon composite. The silicon carbide used therein acts only as a filler, and brings neither the simplification of manufacturing process nor good properties at high temperatures by employing a brittle-to-ductile transition at high temperature.
U.S. Pat. No. 5,380,556 discloses a process for manufacturing a carbon-carbon composite by treating the surface of matrix with silicon carbide.
U.S. Pat. No. 5,382,392 discloses a method of forming a carbon composite material by simultaneously applying a vertical compressive force and a variable lateral force to a mixture of carbon fiber and a carbon precursor material during carbonization of the mixture.
U.S. Pat. Nos. 5,401,440 and 5,759,622 disclose a method for manufacturing a carbon-carbon composite by using a mixture of phosphoric acid, metal phosphate, polyol and alkoxylated monovalent alcohol as a catalyst.
U.S. Pat. No. 5,556,704 discloses a method for manufacturing a carbon-carbon composite by applying a vertical compressive force and a variable lateral force simultaneously to a mixture of carbon fiber and a carbon precursor material during carbonization of the mixture.
In addition, several other conventional articles also disclose methods for manufacturing a carbon-carbon composite by adding various oxidation inhibitors. However, there is no disclosure of a method for manufacturing a carbon-carbon composite by using a ceramic-based material having a brittle-to-ductile transition behavior in a single process.
FIG. 1
is a flow chart illustrating conventional procedures generally used in the preparation of carbon-carbon composites. Among the several processes depicted in the flow chart, the process for obtaining carbon-carbon composites of high density from the carbonized composites in the preform requires the longest process time. As seen in
FIG. 1
, the prior art for manufacturing conventional carbon-carbon composites necessitates three to five times of high densification procedures such as re-impregnation processes. If desired, such densification procedures may be repeated more than those times. As seen from the repeated processes shown in
FIG. 1
, it would take a long time to prepare the final carbon-carbon composites having desired physical properties via many pathways in the laboratory or in the industrial facility.
Conventional carbon-carbon composites thus obtained contain many cracks and pores due to the gas formed by pyrolysis of a matrix during the carbonization procedure. In order to fill such cracked portions and pores, re-impregnation and re-carbonization processes are repeated several times, which renders the manufacturing process complicated and, as a result, increases process costs.
SUMMARY OF THE INVENTION
The present inventors have made extensive studies in order to overcome the above-mentioned problems caused in the preparation of a carbon-carbon composite. The present inventors have found that a carbon-carbon composite having improved mechanical properties can be obtained by a simple manufacturing process which comprises only adding ceramic powder as an oxidation inhibitor into a matrix resin and eliminates re-impregnation and re-carbonization processes. The present invention has been attained on the basis of such finding.
It is therefore an object of the present invention to overcome the above-mentioned problems.
It is another object of the present invention to provide a method for preparing a carbon-carbon composite, which comprises adding a ceramic-based oxidation inhibitor having a brittle-to-ductile transition and eliminates re-impregnation and re-carbonization needed for high densification processes.
It is a further object of the present invention to provide a carbon-carbon composite comprising ceramic powder added to a thermosetting matrix resin.
Accordingly, the present invention provides a carbon-carbon composite consisting of a carbon fiber as a reinforced material, ceramic powder as an oxidation inhibitor and a thermosetting resin.
The oxidation inhibitor used in the present invention can be ceramic powders such as MoSi
2
, TiSi
2
, SiC, Si
3
N
4
, SiGe or TiC and the thermosetting resin is preferably a phenol resin. The ceramic powder has particle size in the range of 0.01 to 1 &mgr;m. When the size is less than 0.1 &mgr;m, the workability of the process is poor. When the size exceeds 1 &mgr;m, a phase separation phenomenon may arise.
It is preferred that the ceramic powder is added in an amount of 2 to 20% by weight on the basis of the resin. If the amount is less than 2% by weight, the activity as a filler is insufficient. If the amount exceeds 20% by weight, a phase separation phenomenon may arise.
The present invention also provides a method for preparing a carbon-carbon composite comprising the following steps: (a) impregnating a carbon fiber with a thermosetting resin to give prepregs, (b) laminating the obtained prepregs to give a laminate, (c) curing the laminate to give a green body composite, and then (d) carbonizing the green body composite to give a carbon-carbon composite. According to the method of the present invention, ceramic powder is added to the thermosetting resin as an oxidation inhibitor.
The other objects and features of the present invention will become apparent to those skilled in the art from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention are given way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.
REFERENCES:
patent: 3787229 (1974-01-01), Rudness
patent: 4377652 (1983-03-01), Ohmura et al.
patent: 4975261 (1990-12-01), Takabatake
patent: 5216098 (1993-06-01), Ahmed et al.
patent: 5380556 (1995-01-01), Hocquellet
patent: 5739217 (1998-04-01), Hagiwara et al.
Cho Min-Seok
Lee Jae-Rock
Park Soo-Jin
Jones Deborah
Korea Research Institute of Chemical Technology
Miranda Lymarie
Pennie & Edmonds LLP
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