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hybrid sandwich actuating mechanism. Collection of techni- [14] Crowley ED. Stemming leaks with spiral-wound gaskets.cal papers – AIAA/ASME/ASCE/AHS/ASC Structures, Chemical Engineer 1993;100(7):139–42.Structural Dynamics & Materials Conference, Reston, Vir- [15] Jones WF, Seth BB. Replacing asbestos steam path gaskets.ginia, USA, AIAA 1998;3:1822–1830. Power Engineer 1992;96(3):43–5.

[9] Shane JH, Russell RJ, Bochman RA. Flexible graphite [16] Bazergui A, Winter JR. Room temperature and elevatedmaterials of expanded particles compressed together. US temperature tests of a metal corrugated gasket with flexiblePatent 3 404 061, 1968. graphite fill. American Society of Mechanical Engineers,

[10] Flitney RK. Soft packings. Tribology Int 1986;19:181. Pressure Vessels & Piping Division, New York, USA:[11] Derenne M, Marchand L, Payne JR. Characterization be- ASME, vol. 158, 1989:33–40.

haviour of flexible graphite sheet gasket materials. In: [17] Hirschvogel A. Sealed joints with regard to corrosiveProceedings of the International Conference on Pressure processes. Analysis of bolted joints. American Society ofVessel Technology, Fatigue /Fracture, NDE, Materials and Mechanical Engineers, Pressure Vessels and Piping Division,Manufacturing, Vol. 1, New York, USA: ASME, 1996, pp. New Jersey, USA: ASME, vol. 367, 1998:81–87.125–46. [18] Chynoweth E. Seal of approval – graphite foil does the job

[12] Derenne M, Marchand L, Payne JR. Elevated temperature safely. Process Engineer (London) 1987;68(7):63–4.characterization of flexible graphite sheet materials for bolted [19] Luo X, Chung DDL. Electromagnetic interference shieldingflanged joints. Weld Res Council Bull 1997;419:1–86. reaching 130 dB using flexible graphite. Carbon

[13] Mueller RT. Recent buckling experiences with spiral wound 1996;34(10):1293–4.flexible graphite filled gaskets. Computer technology–1996: [20] Parks SW. Damping behavior of aluminum and zinc–applications and methodology. American Society of Me- aluminum metal-matrix composites. M.S. Project Report,chanical Engineers, Pressure Vessels and Piping Division. Department of Mechanical and Aerospace Engineering, StateNew York, USA: ASME vol. 326, 1996:23–34. University of New York at Buffalo, 1995.

Formation of carbon nanotubes from jet fuel on superalloys atmoderate temperature and high pressure

a,b , a a*Semih Eser , Orhan Altin , Bhabendra K. PradhanaLaboratory for Hydrocarbon Process Chemistry, The Energy Institute, University Park, PA 16802, USA

bDepartment of Energy and Geo-Environmental Engineering, College of Earth and Mineral Sciences, The Pennsylvania StateUniversity, 209 Academic Projects Building, University Park, PA 16802, USA

Received 24 November 1999; accepted 30 March 2000

Keywords: A. Carbon nanotubes, Carbon onions; B. High pressure; C. TEM, Electron diffraction

Carbon nanostructures, particularly carbon nanotubes, trolysis [4], template carbonization [5,6], and laser-ablationhave created much interest among many researchers [7]. All these processes take place at relatively high

26because of the unusual structure and properties of these temperatures (.950 K) and low pressures (10 –760carbon materials. Carbon nanotubes are nanometer wide Torr).needle-like cylindrical tubes of concentric graphitic carbon There are some reports in the literature on the formationwith diameters as small as 1 nm and a length up to many of carbon tubes and shells in the filamentuous carbonmicrometers. They consists of either a single layer of deposits. Smith et al. [8] reported the formation ofgraphite that has been rolled into a cylinder (single-walled graphitic tube structures upon steam reforming of n-butanenanotubes) or multi layers of concentric graphite sheets on Ni /MgO catalysts at 923 K. Audier et al. [9] observed(multi-walled nanotubes). After their discovery by Iijima truncated multi-shell carbon tubes in the deposit obtained[1], carbon nanotubes have been prepared by various from heating a mixture of CO and CO to 873 K at2

techniques, including carbon arc-discharge [1], catalytic atmospheric pressure in the presence of iron–cobalt andpyrolysis of hydrocarbons [2,3], condensed-phase elec- iron–nickel alloys. Oberlin et al. [10] observed the forma-

tion of hollow carbon fibers upon pyrolysis of a mixture ofbenzene and hydrogen at 1373 K. In all these cases, metalparticles were found in the carbon tubes. There has been*Corresponding author. Tel.: 11-814-863-0989; fax: 11-814-

865-3573. no report of carbon nanotube, or nanoparticle formation atE-mail address: sxe2@psu.edu (S. Eser). pressures much above the atmospheric pressure and at

0008-6223/00/$ – see front matter 2000 Elsevier Science Ltd. All rights reserved.PI I : S0008-6223( 00 )00112-3

Letters to the Editor / Carbon 38 (2000) 1499 –1524 1513

temperatures below 873 K. We have observed carbon The deposit samples were found to contain fullerenicnanotubes and nanoparticles in the carbonaceous deposit carbon structures consisting of carbon nanotubes withfrom heating of a jet fuel (JP-8) over superalloys (Inconel conical and spheroidal caps, and multi-shell tube tips600 and Inconel 718) below 773 K and 3.5 MPa. These similar to those observed in arc-discharge deposits [1].conditions are relevant to the propulsion system of an These multishell nanotubes consist of four to 20 concentricadvanced aircraft using jet fuel as a coolant [11]. This is graphitic shells with external diameters ranging from 5 tothe first report of carbon nanostructures (nanotubes) that 15 nm. In addition to nanotubes, carbon nanoparticlesare produced under such high pressure and low tempera- those resemble carbon onions [1,13,14] were also observedture. No metal particles appeared to be associated with the in the deposit samples.nanostructures observed under HRTEM. Harris [15] observed some carbon nanotubes and

Any form of undesired carbon deposition from stressed graphitic structures as contaminants on evaporated carbonfuel is detrimental to the operation of an aircraft. To study films supported on copper grids. To make sure that carbonthe mechanisms of carbon deposition on metal surfaces, nanostructures observed in this work were not contami-thermal stressing of a military jet fuel (JP-8) was carried nants, an unused grid was carefully examined underout in a glass-lined flow-through reactor in the presence of HRTEM. No nanostructures were observed on the unusedsuperalloy coupons. The experimental set-up was de- grid. The examination of the same grid after samplescribed elsewhere [12]. The experiments were performed at placement showed the presence of nanostructures confirm-a constant external wall temperature of 773 K and fuel ing that the observed nanostructures were present in thepressure of 3.5 MPa. The composition and specifications of deposit samples. Ando [16] reported the presence of sp1-JP-8 fuel are very similar to those of the commercial jet bonded carbyne, but observed no nanostructures on thefuel, Jet A. The two superalloys used in this study have the same type of grids used in this study.following compositions: Inconel 600: Ni:74.4, Fe:8, Fig. 1a shows a TEM image of multishell carbonCr:15.5, Cu:0.5, Mn:1.0, Si:0.5, C:0.15, S:0.0015%wt.; nanotubes similar to those produced by arc-dischargeInconel 718: Ni:52.5, Fe:18.5, Cr:19, Nb:5.13, Mo:3.05, evaporation of graphite [1]. This image shows the cappedTi:0.9, Al:0.5, Cu:0.15, Mn:0.15, Si:0.18, C:0.04, end of the carbon nanotubes with spheroidal and conicalS:0.0008%wt. After 5 h of stressing at a fuel flow rate of 4 caps. The inset picture displays the selective area diffrac-

3cm /min, the superalloy coupons were cooled down under tion (SAD) pattern for the carbon nanotubes shown in Fig.nitrogen flow. Samples of the carbon deposit on the foils 1a. The pattern shows the diffraction from carbon 002were sonicated with ethanol, drops of the dispersion wereplaced on holey carbon TEM grid (Type B, Oken ShojiCo., Japan) and examined in a high resolution transmissionelectron microscope (JEOL JEM-2010) operating at 200keV.

Fig. 1. HRTEM images of the carbon deposited on superalloys at773 K and 3.5 MPa from a JP-8 jet fuel, dispersed by sonication:(a) multi-shell nanotubes with spheroidal and conical caps in thedeposit on Inconel 600. Inset picture shows the SAD pattern for Fig. 2. The micrograph shows the tip of a nanotube with a conicalthe nanotube taken from the TEM image (a). cap. The interlayer spacing is 0.34 nm.

1514 Letters to the Editor / Carbon 38 (2000) 1499 –1524

Fig. 3. (a) A typical carbon onion structure observed in the Fig. 4. (a) A nanotube observed in the deposit on Inconel 600; (b)deposit on Inconel 600; (b) multi-shell carbon nanoparticles nanocapsules observed in the deposit on Inconel 718.(onion type structure) with an interlayer spacing 0.34 nm in thedeposit on Inconel 718.

planes as a pair of bright spots along with diffraction from nanotubes we observed do not appear to contain any metal100 and 110 planes as rings. Fig. 2 shows a high resolution particles, as usually seen in the nanotubes from catalyticTEM micrograph of the carbon nanotubes, showing the tip pyrolysis of hydrocarbons. These results add new in-of a multi-shell nanotube with an interlayer spacing of 0.34 formation and pose new questions regarding the formationnm which is close to that of graphite. In this figure, the mechanisms of ordered nanostructures [18]. It is likely thatconical end of the nanotubes with the individual end caps the unique compositions of the two superalloys are respon-separated by a large distance than the interlayer spacing. sible for nanotube and nanoparticle formation under verySuch structures have been described by Iijima [17]. Fig. 3a different physical conditions than those reported in theand b show the TEM micrographs of polyhedral graphitic literature. A better understanding of the role of metalnanoparticles with hollow cores. These particles are similar surfaces and pressure on nanostructure formation mayin structure to carbon onions produced in hydrocarbon point to more economical processes for mass production offlames [11]. Fig. 4 shows disordered layers on the surface nanotubes.of a multi-wall nanotube with graphitic structure producedon Inconel 600 (Fig. 4a) and a bundle of nanocapsules withspheroidal caps produced on Inconel 718 (Fig. 4b). Acknowledgements

Our observations clearly indicate that ordered carbonstructures formed at lower temperatures and much higher This work was funded through the US Air Forcepressures than previously reported for highly energetic Research Laboratory (AFRL)/Aero Propulsion and Powerprocesses. It is also interesting that the multi-shell Directorate, Wright Patterson AFB. We thank Prof. H.H.

Letters to the Editor / Carbon 38 (2000) 1499 –1524 1515

CH, Lee YH, Kim SG, Rinzler AG, Colbert DT, ScuseriaSchobert of Penn State for his support, and Dr. T. EdwardsGE, Tomanek D, Fisher JE, Smalley RE. Scienceof AFRL/APPD for his interest. We wish to express our1996;273:483–7.gratitude to Prof. Akira Tomita of Tohoku University,

[8] Smith DJ, McCartney MR, Tracz E, Borowiecki T. Ultramic-Japan for his advice and helpful discussions.roscopy 1990;34:54–9.

[9] Audier M, Oberlin A, Coulon M. J Crystal Growth1981;55:549–56.

References [10] Oberlin A, Endo M, Koyama T. J Crystal Growth1976;32:335–49.

[1] Iijima S. Nature 1991;354:56–8. [11] Linne DD, Meyer ML, Edwards T, Eitman DA. Paper AIAA[2] Terrones M, Grobert N, Olivares J, Zhang JP, Terrones H, 97-3041. 33rd AIAA/ASME/SAE/ASEE Joint Propulsion

Kordatos K, Hsu WK, Hare JP, Townsend PD, Prassides K, Conference, July 6–9, 1997.Cheetham AK, Kroto HW, Walton DRM. Nature [12] Altin O, Eser S. Ind Eng Chem Res 2000;39:642–5.1997;388:52–5. [13] Howard JB, Das Chowdhury K, Vander Sande JB. Nature

[3] Andrews R, Jacques D, Rao AM, Derbyshire F, Qian D, Fan 1994;376:603.X, Dickey EC, Chen J. Chem Phys Lett 1999;303:467–74. [14] Ugarte D. Nature 1992;359:707–9.

[4] Hsu WK, Hare JP, Terrones H, Kroto HW, Walton DRM. [15] Harris PJF. J Microsc 1996;186:88–90.Nature 1995;377:687. [16] Ando Y. Carbon 1995;33:171–5.

[5] Kyotani T, Tsai LF, Tomita A. Chem Mater 1995;7:1427–8. [17] Iijima S, Ichihashi T, Ando Y. Nature 1992;356:776–8.[6] Kyotani T, Pradhan BK, Tomita A. Bull Chem Soc Jpn [18] Ebbesen TW. Acc Chem Res 1988;31:558–66.

1999;72:1957–70.[7] Thess A, Lee R, Nikolaev P, Dai HJ, Petit P, Robert J, Xu

A TG-MS study of poly(vinyl butyral) /phenol-formaldehyderesin blend fiber

*Jun-ichi Ozaki , Wataru Ohizumi, Asao OyaFaculty of Engineering, Gunma University, 1-5-1, Tenjin-cho, Kiryu, Gunma 376-8515, Japan

Received 18 December 1999; accepted 5 May 2000

Keywords: A. Carbon fibers; B. Carbonization; C. Thermal analysis; D. Chemical structure

materials for such functional carbon materials. In thisOne of the factors needed for designing carbon materialssense, polymer alloys are attractive materials and we areis the selection of raw materials. Accumulated data on thestudying the carbonization of polymer blends. In thiscarbonization of organic polymers enable the manufactur-paper, we present a TG-MS observation of a polymering of various types of carbon products, ranging fromblend consisting of phenol formaldehyde (PF) resin andcarbon fibers to glassy carbons [1]. Polymer alloys such aspoly(vinyl butyral) (PVB), which was a candidate to give ablock copolymers, graft copolymers, physical blends andporous polymer fiber without physical activation by steamchemical blends, are essentially multi-component polymeror carbon dioxide [4].systems, which sometimes show superior properties to the

Details of the sample preparation procedure are de-properties of each component polymer [2]. This fact givesscribed elsewhere [5]. Two samples were made, one is theus an expectation of widening the spectrum of the avail-pristine PF fiber and another is the polymer blend fiber ofable raw materials for carbonization, and hence of manu-PF and PVB. These samples were subjected to FT-IR andfacturing a variety of carbon materials.TG-MS measurements with an FT-IR spectrometer (Per-We are interested in the preparation of electronically orkin-Elmer, 1650) and with an experimental apparatuschemically functional carbons by modifying the carboniza-consisting of a TG/DTA analyzer (Rigaku Thermoplustion processes [3–5]. Beside this, we also believe some8160) coupled with a quadrupole mass spectrometernovel polymer or organic materials would be suitable(Hewlett Packard, Mass Selective Detector 5973), respec-tively. FT-IR spectra were recorded for KBr disks of the*Corresponding author. Tel.: 181-277-30-1352; fax: 181-

277-1353. samples. For TG-MS measurements, about 4 mg of sampleE-mail address: jozaki@chem.gunma-u.ac.jp (J.-i. Ozaki). was taken onto a platinum pan, and was pyrolyzed in a

0008-6223/00/$ – see front matter 2000 Elsevier Science Ltd. All rights reserved.PI I : S0008-6223( 00 )00113-5