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A new ternary compound CsC24 (C2H4)x
GOO8-6223/91 $3.00 + .OO Copyright 0 1991Pergamon Press plc
Carbon Vol. 29, No.?, pp. 283-285, 1991 Primed in Great
Britam
LETTERS TO THE EDITOR
A new ternary
compound
C&24
(CZH~)~
(Received 10 October 1990; accepted 12 October 1990) Key Words - Cs-GIC, ethylene, absorption
It is known that 2nd stage alkali-metal graphite intercalation compounds (AM-GICs) are physiintercalated by a variety of molecules such as Hz. N2, Ar, and CIQ at low temperatures [l]. Very recently, physi-intercalation of n-(&H14 around room temperature has been reported by Goldman et al. [Z]. We have been studying the interaction of aliphatic hy~~~bons with AM-GICs, and reported some results on the physisorption of C2Hg and C3H8 [3]. In this communication we report our preliminary results of the formation of a new ternary compound csc24 (c2H4)x (x - 1.2). The 2nd stage CsC24 sample prepared from natural graphite flakes or grafoil (Union Carbide, GTA grade) was contacted with ethylene gas at 273.15K in an evacuated vessel. Prompt absorption of C2H4 by the CsC24 sample was observed and the amount of absorbed gas was measured by both the pressure change of the gas and the weight increase of the sample. The final composition was around Cs(C24H4)1.2. The most remarkable feature of this new ternary compound is its unusual stability. It does not decompose by evacuation not only at room temperature, but at high temperatures up to 850K. When we exposed the sample to air, on1 a very slow weight increase (AW/WAt - 2 x lo- 3 h- ry) was observed and its dark blue color was unchanged even after a few weeks. The results of X-ray diffraction analysis are shown in Fig. 1 and Table 1. Its repeat distance in the c-axis direction is
isotherm,
ternary GIC
Table 1. X-ray diffraction pattern of csC24(C$4)~,? AC
yro
(001)
dcti
1.010
2
001
1.010
0.502
1
002
0.505
0.337
100
003
0.337
0.169
5
006
0.168
x0.1
Diffraction Fig. 1 X-ray diffmctogram
’ i 30 angle
I 28(clegrees)
of C&24 (C&)1.2 283
(nm)
considered to be about 1.01 nm, which can be compared with that of 0.94 nm for the 2nd stage CsC24. It should be noted here that when the absorption experiments of C2H4 on CsC24 were performed at 194K, it showed an isotherm of the normal physisorption, as shown in Fig. 2. The final composition in this case was roughly CsC&+(C2H4)2. The isotherms of C2H6 and C3H8 for C&24 are also shown in Fig. 2 for compa~son. The C2H4 molecules absorbed by the CsC24 sample were released easily by evacuation so long as the sample was kept at the low
003
I
= 1.01 nm
dabs (nm)
(CuKa radiation).
284
Department of Nuclear Engineering University of Tokyo Hongo, Bunkyo-ku Tokyo, 113 JAPAN
Y. TAKAHASHI
Department of Industrial Chemistry Tokyo Natio~l College of Technology Kunugida, Hachioji Tokyo, 193 JAPAN
N. AKUZAWA
K. 01 T. TERAI
REFERENCES 1.
Fig. 2 Absorption isotherms of C2H4, C2Hg and C3H8 in CsC24. NG/NQ shows moles of the gases absorbed per Cs atom.O; C2H4, 194K, A; C$&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.
Carbon Vol. 29, No.?, pp. 283-285, 1991 Primed in Great
Britam
LETTERS TO THE EDITOR
A new ternary
compound
C&24
(CZH~)~
(Received 10 October 1990; accepted 12 October 1990) Key Words - Cs-GIC, ethylene, absorption
It is known that 2nd stage alkali-metal graphite intercalation compounds (AM-GICs) are physiintercalated by a variety of molecules such as Hz. N2, Ar, and CIQ at low temperatures [l]. Very recently, physi-intercalation of n-(&H14 around room temperature has been reported by Goldman et al. [Z]. We have been studying the interaction of aliphatic hy~~~bons with AM-GICs, and reported some results on the physisorption of C2Hg and C3H8 [3]. In this communication we report our preliminary results of the formation of a new ternary compound csc24 (c2H4)x (x - 1.2). The 2nd stage CsC24 sample prepared from natural graphite flakes or grafoil (Union Carbide, GTA grade) was contacted with ethylene gas at 273.15K in an evacuated vessel. Prompt absorption of C2H4 by the CsC24 sample was observed and the amount of absorbed gas was measured by both the pressure change of the gas and the weight increase of the sample. The final composition was around Cs(C24H4)1.2. The most remarkable feature of this new ternary compound is its unusual stability. It does not decompose by evacuation not only at room temperature, but at high temperatures up to 850K. When we exposed the sample to air, on1 a very slow weight increase (AW/WAt - 2 x lo- 3 h- ry) was observed and its dark blue color was unchanged even after a few weeks. The results of X-ray diffraction analysis are shown in Fig. 1 and Table 1. Its repeat distance in the c-axis direction is
isotherm,
ternary GIC
Table 1. X-ray diffraction pattern of csC24(C$4)~,? AC
yro
(001)
dcti
1.010
2
001
1.010
0.502
1
002
0.505
0.337
100
003
0.337
0.169
5
006
0.168
x0.1
Diffraction Fig. 1 X-ray diffmctogram
’ i 30 angle
I 28(clegrees)
of C&24 (C&)1.2 283
(nm)
considered to be about 1.01 nm, which can be compared with that of 0.94 nm for the 2nd stage CsC24. It should be noted here that when the absorption experiments of C2H4 on CsC24 were performed at 194K, it showed an isotherm of the normal physisorption, as shown in Fig. 2. The final composition in this case was roughly CsC&+(C2H4)2. The isotherms of C2H6 and C3H8 for C&24 are also shown in Fig. 2 for compa~son. The C2H4 molecules absorbed by the CsC24 sample were released easily by evacuation so long as the sample was kept at the low
003
I
= 1.01 nm
dabs (nm)
(CuKa radiation).
284
Department of Nuclear Engineering University of Tokyo Hongo, Bunkyo-ku Tokyo, 113 JAPAN
Y. TAKAHASHI
Department of Industrial Chemistry Tokyo Natio~l College of Technology Kunugida, Hachioji Tokyo, 193 JAPAN
N. AKUZAWA
K. 01 T. TERAI
REFERENCES 1.
Fig. 2 Absorption isotherms of C2H4, C2Hg and C3H8 in CsC24. NG/NQ shows moles of the gases absorbed per Cs atom.O; C2H4, 194K, A; C$&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.