High Pressure Carbon Behavior Induced from Carbide Hugoniots
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99 Mat. Res. Soc. Symp. Proc. Vol. 499 ©1998 Materials Research Society
EXPERIMENTAL method was employed to measure shock velocity surface velocity. Inclined Figure mirror 1 illustrates our observing system schematically. Basedand on free streak records the shock conditions were calculated by the help of the free surface velocity approximation method as well as the impedance match method using the measured impact velocity. The NIRIM twostage light-gas gun was used to generate shock waves[5]. The projectile impact velocity was determined by three cw x-ray beam cutting method, and these signals were used as triggering source for Xe flash lamp and flash x-ray. We use an image converter streak camera(Ultra nac FS 501), which is triggered by a pin on the driver plate, and the streak rate has been calibrated against modulated laser diode trace. The starting carbides used in the present study are two kinds of sintered bodies, et-SiC and I3-SiC, and a single crystal of titanium carbide. The 13-SIC consists of 3C type and was provided by the Osaka Sumitomo Cement Co. The or-SiC was manufactured from Cercom and consists mainly of6H polytype[6]. The density and thickness are 3.195 g/cm3 and about 2.0 mm and 3.226 g/cm3 and about 2.5 mm, respectively. Titanium carbide single crystal has been prepared in NIRIM, using a modified zone leveling method[7]. The crystal is highly pure and nearly stoichiometric, being C/Ti = 0.95. The single crystal was sliced along [100] orientation to be about 3 mm thick and cut into pieces of about 10 mm X 8 mm. Both surfaces were polished flatly. The elastic properties of the TiC used in the present study has been measured[8] and the longitudinal and transverse sound velocities are 10.25 km/sec and 6.03 km/s along [100], respectively. The density and the bulk modulus are 4.856 g/cm3 and 239.9 GPa, respectively. RESULTS AND DISCUSSION HUGONIOTS OF DIAMOND-TYPE CARBIDES SiC is the only diamond-type carbide and displays various types of modifications. For o•-SiC, Hugoniot has been determined up to 160 GPa together with the data by Grady[9], as shown in Fig. 2. A phase transition has been detected at a pressure of 105 __.4 GPa, with a volume reduction of 15 ---3%. The onset transition pressure is higher by about 10 GPa than that claimed by Gust et al.[10]. It is worthwhile to note that the highest-pressure datum by McQueen et al.[11] is on an extrapolation of our compression curve for the high-pressure phase region. The 13-SIC also display a similar Hugoniot, indicating a phase transition at 119 GPa.
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driver plate • sa'•nple
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Fig. 1. Schematic illustration of optical
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method to measure the shock velocity and the f• surface velocity using inclined (IM) and flat(M I-M4) mirrors. Extinction of rettectivity of mirrors M1 and M2 indicates the arrival time ofshock wave on the boundary between driver plate and sample and mirrors M2 and M3 are used to read arrival time on the back ofthe sample. Inclined mirro gives a profile of free-surface Svelocity with time.
projectile trigger pin
Xe fla
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