- Email: [email protected]
CO2-laser-assisted deposition of carbon coating on the surface of carbon fibers
284
Department of Nuclear Engineering University of Tokyo Hongo, Bunkyo-ku Tokyo, 113 JAPAN
Y. TAKAHASHI
Department of Industrial Chemistry Tokyo Natio~l College of Technology Kunugida, Hachioji Tokyo, 193 JAPAN
N. AKUZAWA
K. 01 T. TERAI
REFERENCES 1.
Fig. 2 Absorption isotherms of C2H4, C2Hg and C3H8 in CsC24. NG/NQ shows moles of the gases absorbed per Cs atom.O; C2H4, 194K, A; C$&j, 194K,tJ; C3Ht3,273K.
2. 3.
K. Watanabe, T. Kondow, M. Soma, T. Onishi and K. Tamaru, Proc. R. Sot. (London), Ser A333,51 (1973). M. Goldman, H. Pilliere and F. Beguin, Synth. Met., 34, 59 (1989). K. Oi, T. Terai and Y. Takahashi, TANSO, to be published.
temperature of 194K. On the other hand, when the sample temperature was raised to room temperature without evacuation, a considerable part of the absorbed C2H4 molecules was found to remain and to form a stable compound almost similar to that stated above. We are now studying the structure and the properties of this compound in more detail
COz-laser-assisted
deposition
of carbon coating on the surface of carbon fibers
(Received 29 Mw 1990; accepted in revisedfonn 2 October 1990) Key Words
- Carbon fibers, laser, carbon deposition,
PyroIytic carbon deposition on carbon fibers (CF) is a promising method for modifying the surface characteristics of the fiber [1,2]. The drawbacks of traditional deposition methods are as follows: 1. Deposition is usually performed under high temperatures which sometimes reduces the fiber strength. 2. Coating thickness is large; thick coatings usually have lower strength and yidd poor adhesion with the matrix. There have been a number of reports discussing carbon pyrolysis with the assistance of a laser [3]. Laser radiation has the following advantages: 1. Laser energy can be focused on local areas on the surface of the fiber. 2. Fast Iocal heating and cooling takes place only in radiated areas. 3. Specific physical and chemical processes occur when laser radiation contacts the material. Besides, diamond and other high-pressure phases of carbon were synthesized with assistance of laser radiation 141. We have developed a laser-assisted method of carbon deposition on the surface of continuously pulled yarn in methane. In this case, the fiber is placed in a laser affected zone for a short period of time which does
adhesion
not cause any damage. The schematic diagram of the apparatus is shown in fig. 1. The fiber is irradiated in methane with a laser beam whose diameter is equal to the fiber width (-2 mm). The fiber was irradiated bv a 0.07 kW CO? laser with wavelength 1Opm. ’ The fiber surface temperature was measured by a pyrometer and was equal 1723 K (fixed fiber) or 2023 K (moving fiber). The fiber pulling speed was 40 cm/mm and could be changed over a wide range. Fibers in the form of planar bundles were irradiated on both sides through double rewinding. Yarn breaking strength and breaking load were measured before and after irradiation. Fiber adhesion was measured by interlaminar shear strength of an epoxy composite produced from irradiated and original fibers: shear strength was measured by the short beam shear test. The properties of original and irradiated fibers are shown in Table 1. The treatment does not reduce the fiber strength; instead, the strength increases. The fiber eIasticity decreases slightly, but this does not lead to any The significant losses in composite properties. in;erlaminar shear strength -of the carbon composite produced from irradiated coated fibers improves greatly by a factor of 2.5.
285
MIRROR DEPOSITION CHAMBER OBSERVATION
:AM
KC1 WINDOW
HALF-
SILVERED
MANOMETER
PYROMETER
Fig 1. A schematic drawing of the apparatus used for coating carbon fibers in methane using a laser
TABLE 1 Influence of Laser Irradiation in Methane on Carbon Fiber Properties
Item
Fifi;Tipe
Breaking Load (H) based on 30 tests
Composite Modulus of elasticity 10-3 kg/mm2
Interlaminar shear strength (T) kg/mm2
1
Initial
15.8 f 0.99
11.7
1.6
2
Irradiated
25.6 f 1.2
10.7
4.3
The increase in strength of the yarn produced by irradiation in methane is caused by the compacting of individual filaments in yarn undergoing carbon deposition. The thin carbon film produced on the CF surface under the laser beam has a good adhesion both to the fibers and binder. The carbon film obtained nrovides an increase of the interlaminar shear strength of the composite by more than 2.5 times. The composition and structure of the carbon film formed on the surface of CF are being studied. This thin layer of pryocarbon should also pro;ide good adhesion between fiber and matrix in a carbon - carbon composite, and should prevent the reduction of fiber strength during contact with metal in fabricating composites containing a metal matrix. Department of Physics I 17936, Moscow Institute of Steel and Alloys Moscow, Leninksy Prospect, 4 USSR
M. DIGILOV G. NEIMAN
REFERENCES 1. 2. 3. 4.
D.T. Pinchin, R.T. Woodhams, J. of Materials Science, 9, 300 (1974). S. Jasenko, J. Machinowski, Carbon, 19, 205 ,1o0,\ [l-/01,. R.L. Hanson, Carbon, 16, 159 (1978). M. Alam, T. DebRoy, R. Roy, E. Breval, Carbon, 27, 289 (1989).
Department of Nuclear Engineering University of Tokyo Hongo, Bunkyo-ku Tokyo, 113 JAPAN
Y. TAKAHASHI
Department of Industrial Chemistry Tokyo Natio~l College of Technology Kunugida, Hachioji Tokyo, 193 JAPAN
N. AKUZAWA
K. 01 T. TERAI
REFERENCES 1.
Fig. 2 Absorption isotherms of C2H4, C2Hg and C3H8 in CsC24. NG/NQ shows moles of the gases absorbed per Cs atom.O; C2H4, 194K, A; C$&j, 194K,tJ; C3Ht3,273K.
2. 3.
K. Watanabe, T. Kondow, M. Soma, T. Onishi and K. Tamaru, Proc. R. Sot. (London), Ser A333,51 (1973). M. Goldman, H. Pilliere and F. Beguin, Synth. Met., 34, 59 (1989). K. Oi, T. Terai and Y. Takahashi, TANSO, to be published.
temperature of 194K. On the other hand, when the sample temperature was raised to room temperature without evacuation, a considerable part of the absorbed C2H4 molecules was found to remain and to form a stable compound almost similar to that stated above. We are now studying the structure and the properties of this compound in more detail
COz-laser-assisted
deposition
of carbon coating on the surface of carbon fibers
(Received 29 Mw 1990; accepted in revisedfonn 2 October 1990) Key Words
- Carbon fibers, laser, carbon deposition,
PyroIytic carbon deposition on carbon fibers (CF) is a promising method for modifying the surface characteristics of the fiber [1,2]. The drawbacks of traditional deposition methods are as follows: 1. Deposition is usually performed under high temperatures which sometimes reduces the fiber strength. 2. Coating thickness is large; thick coatings usually have lower strength and yidd poor adhesion with the matrix. There have been a number of reports discussing carbon pyrolysis with the assistance of a laser [3]. Laser radiation has the following advantages: 1. Laser energy can be focused on local areas on the surface of the fiber. 2. Fast Iocal heating and cooling takes place only in radiated areas. 3. Specific physical and chemical processes occur when laser radiation contacts the material. Besides, diamond and other high-pressure phases of carbon were synthesized with assistance of laser radiation 141. We have developed a laser-assisted method of carbon deposition on the surface of continuously pulled yarn in methane. In this case, the fiber is placed in a laser affected zone for a short period of time which does
adhesion
not cause any damage. The schematic diagram of the apparatus is shown in fig. 1. The fiber is irradiated in methane with a laser beam whose diameter is equal to the fiber width (-2 mm). The fiber was irradiated bv a 0.07 kW CO? laser with wavelength 1Opm. ’ The fiber surface temperature was measured by a pyrometer and was equal 1723 K (fixed fiber) or 2023 K (moving fiber). The fiber pulling speed was 40 cm/mm and could be changed over a wide range. Fibers in the form of planar bundles were irradiated on both sides through double rewinding. Yarn breaking strength and breaking load were measured before and after irradiation. Fiber adhesion was measured by interlaminar shear strength of an epoxy composite produced from irradiated and original fibers: shear strength was measured by the short beam shear test. The properties of original and irradiated fibers are shown in Table 1. The treatment does not reduce the fiber strength; instead, the strength increases. The fiber eIasticity decreases slightly, but this does not lead to any The significant losses in composite properties. in;erlaminar shear strength -of the carbon composite produced from irradiated coated fibers improves greatly by a factor of 2.5.
285
MIRROR DEPOSITION CHAMBER OBSERVATION
:AM
KC1 WINDOW
HALF-
SILVERED
MANOMETER
PYROMETER
Fig 1. A schematic drawing of the apparatus used for coating carbon fibers in methane using a laser
TABLE 1 Influence of Laser Irradiation in Methane on Carbon Fiber Properties
Item
Fifi;Tipe
Breaking Load (H) based on 30 tests
Composite Modulus of elasticity 10-3 kg/mm2
Interlaminar shear strength (T) kg/mm2
1
Initial
15.8 f 0.99
11.7
1.6
2
Irradiated
25.6 f 1.2
10.7
4.3
The increase in strength of the yarn produced by irradiation in methane is caused by the compacting of individual filaments in yarn undergoing carbon deposition. The thin carbon film produced on the CF surface under the laser beam has a good adhesion both to the fibers and binder. The carbon film obtained nrovides an increase of the interlaminar shear strength of the composite by more than 2.5 times. The composition and structure of the carbon film formed on the surface of CF are being studied. This thin layer of pryocarbon should also pro;ide good adhesion between fiber and matrix in a carbon - carbon composite, and should prevent the reduction of fiber strength during contact with metal in fabricating composites containing a metal matrix. Department of Physics I 17936, Moscow Institute of Steel and Alloys Moscow, Leninksy Prospect, 4 USSR
M. DIGILOV G. NEIMAN
REFERENCES 1. 2. 3. 4.
D.T. Pinchin, R.T. Woodhams, J. of Materials Science, 9, 300 (1974). S. Jasenko, J. Machinowski, Carbon, 19, 205 ,1o0,\ [l-/01,. R.L. Hanson, Carbon, 16, 159 (1978). M. Alam, T. DebRoy, R. Roy, E. Breval, Carbon, 27, 289 (1989).