高压物理学报

High Pressure Induced Phase Transitions and Chemical Reaction of Trans, Trans-Dibenzylideneacetone

TANG Xu-Dong, ZHANG Zeng-Ming, ZHAO Zhi, WANG Zhong-Ping, DING Ze-Jun

2009, 23(6): 401-406 . doi: 10.11858/gywlxb.2009.06.001

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Abstract:
By using a diamond anvil cell the trans, trans-Dibenzylideneacetone molecular crystal was studied with high pressure Raman, fluorescence spectroscopy and EDXRD at room temperature. A crystalline to crystalline phase transition is found at 1.0~1.3 GPa; meanwhile, a pressure induced chemical reaction is observed and the reaction is completed around 6.5 GPa. The EDXRD spectra show that a new covalent bond produces in this chemcial reaction process. The possible chemical reaction paths are suggested as the openning of C=C bond of the molecule and then combination between adjacent molecules. Another crystalline to crystalline phase transition forms around 11 GPa. After the pressure is released, the newly formed phase of material can remain stable at ambient conditions.

Temperature Calibration for 3 GPa Molten Salt Medium Triaxial Pressure Vessel

HAN Liang, ZHOU Yong-Sheng, DANG Jia-Xiang, HE Chang-Rong, YAO Wen-Ming

2009, 23(6): 407-414 . doi: 10.11858/gywlxb.2009.06.002

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Abstract:
A triaxial deformation apparatus with 3 GPa molten salt medium pressure vessel was developed to study the mechanical behavior of the rock under high temperature and ultra-high pressure. It is based on the conventional Griggs design and the molten salt cell concept is after the concept of Green and Borch (1989) and Rybacki et al (1998). The pressure vessel is improved with respect to systems described previously by the use of different salt mixtures with low eutectic temperatures, and by a mechanically stable arrangement of the thermocouples. In this study, we focus on the temperatures distribution around the sample under confined pressure of 500 MPa. The experimental results show that there is a good linear correlation between temperatures monitored by the upper thermocouple (at the upper 1/3 position of the sample center, outside the sample) and others. Based on the linear slopes, we can identify temperature difference in positions of sample. The temperature difference between the upper and the lower thermocouple (at the lower 1/3 position of the sample center, outside the sample) is so small that both of them can be used as temperature controller for the heating system. The temperature in the center of the sample is by 4% lower than the ones monitored by the upper thermocouple. The temperature in the bottom of the sample is by 5% lower than that in the center of the sample. The temperature in the lower quarter of the sample is by 2% lower than that in the center of the sample. The temperature distribution in the sample show that vertical temperature gradient in the sample is constant (16 ℃/mm at 900 ℃). The temperature controlling resolution and temperature distribution in the pressure vessel are similar to the same type apparatuses in other laboratories of the world.

Detonation Synthesis of Carbon Encapsulated Cobalt/Nickel Nanoparticles

LUO Ning, LI Xiao-Jie, YAN Hong-Hao, WANG Xiao-Hong, WANG Li-He

2009, 23(6): 415-420 . doi: 10.11858/gywlxb.2009.06.003

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Abstract:
Carbon encapsulated cobalt and nickel magnetic nanoparticles have been synthesized successfully via detonation technique under nitrogen gas in explosion vessel. The gelatine dynamics are mainly made up of RDX explosive, mixed with nitrate cobalt or nitrate nickel, some orgnatic carbon materials at a proportion. Some testing methods such as XRD, TEM, VSM were carried out on the detonation soot, so as to characterize their morphology and properties. The results of experiments showed that the detonation products consisted of carbon encapsulated cobalt and nickel nanomaterials, with the perfect core shell structure. The size of carbon encapsulated cobalt particles distributed between 30 and 50 nm, and the grain of carbon encapsulated nickel nanoparticles was 25~60 nm. At room temperature, they exhibited good soft magnetism.

Numerical Simulation of Explosive Particles Compaction

LIU Qun, CHEN Lang, LU Jian-Ying, ZHANG Ming

2009, 23(6): 421-426 . doi: 10.11858/gywlxb.2009.06.004

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Abstract:
Understanding the mechanics of explosives compaction can provide theoretical foundation to improve pressing technique and quality of explosive component. In this paper, a calculating model of explosive particles pressed to charge was developed. The explosive particles were considered as being the uniform diameter and arraying in order. With non-linear finite element calculating method, the numerical simulations of explosives compaction were conducted, and the deformation, mechanics and temperature of explosive particles were analyzed. The calculated results show that explosive particles compaction experiences two phases: displacement and deformation. In the displacement phase, the stress centralization appears on the contact surfaces between particles and constrained surface. In the plastic deformation phase, the stress in the particles increases sharply and tends to be uniform. The explosive particles temperature increases with pressing. When the explosive charge is close to the density of crystalline grains, the highest temperature occurs in the center of charge.

Hugoniot Relation of Unreacted JOB-9003 Explosive

FU Hua, TAN Duo-Wang, LI Jin-He, LI Tao

2009, 23(6): 427-432 . doi: 10.11858/gywlxb.2009.06.005

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Abstract:
The Hugoniot relation of unreacted JOB-9003 explosive was investigated experimentally by using Particle Velocity Matching Method. The PMMA flyer is driven by detonation wave which is attenuated with a thick plate. Magnetic gauges were used to respectively record the interface particle velocity u1 between the PMMA flyer and the explosive sample as well as u2 between the PMMA flyer and PMMA sample. Furthermore, considering unreacted explosives as composite and porous materials, the shock Hugoniot relation of JOB-9003 explosives are calculated by using Hugoniot calculation method for porous material, as the known shock Hugoniot of each component. The calculated results are in good agreement with the experimental data.

Numerical Analysis on Launch Property of Rarefaction Wave Gun

WANG Ying-Ze, ZHANG Xiao-Bing

2009, 23(6): 433-440 . doi: 10.11858/gywlxb.2009.06.006

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Abstract:
The launch property of the rarefaction wave gun and some influences of different factors on the launch property were studied. The two-phase flow interior ballistic model was established based on the launch mechanism of the rarefaction wave gun. The Mac-Cormack difference scheme was used in numerical calculations. Compared with the interior ballistic process of a closed chamber gun with the same caliber, the launch property was discussed in detail, and the influence of the different factors including loading conditions, venting time and structural parameters on the emission property was obtained.

Experimental Study on Deflagration-to-Detonation Transition in Two Pressed High-Density Explosives

WANG Jian, WEN Shang-Gang

2009, 23(6): 441-446 . doi: 10.11858/gywlxb.2009.06.007

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Abstract:
This paper deals with the experimental findings of the characteristic of deflagration-to-detonation transition in two kinds of pressed explosivesA and B. A series of tests are performed on the high-density explosives. Electrical pins and pressure sensors are used to measure the pressures and velocities of shock, flame, or detonation wave. The experimental results show that it's very difficult to obtain the transition in the pressed explosives. The phenomenon of low velocity detonation (LVD) is achieved under the confinement condition that the length of DDT tube is 400 mm. A deflagration-to-detonation transition in the pressed explosives of A is obtained under the stronger confinement condition that the length of DDT tube is 600 mm and the detonation-induced distance is slightly longer than 545 mm. It's also concluded that the pressed explosive of A is more sensitive to transit into detonation than the pressed explosive of B under the same experimental conditions.

Experimental Study on the Damage Effect of Compound Reactive Fragment Penetrating Diesel Oil Tank

XIE Chang-You, JIANG Jian-Wei, SHUAI Jun-Feng, MEN Jian-Bing, WANG Shu-You

2009, 23(6): 447-452 . doi: 10.11858/gywlxb.2009.06.008

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Abstract:
Two new kinds of compound reactive fragments were designed and prepared, and the penetration tests of the compound reactive fragments against oil tank with diesel oil were performed. The compound reactive fragment is composed of shell, bare reactive fragment and coping. Bare reactive fragments prepared by high-temperature sintering in a vacuum container have two kinds of formulations, one is mixed aluminum powder with PTFE, another is mixed titanium powder with PTFE. Fragments were fired using 12.7 mm ballistic gun, and the penetration process against oil tank were recorded by high-speed camera. The experimental results show that two kinds of compound reactive fragment can penetrate through 6 mm thick oil tank and have obvious ignition effects. Comparing with inert fragments, compound reactive fragments have better capability of penetration and ignition.

Numerical Simulation Investigation in Hypervelocity Impact on Shield Structure Containing Aluminum Foam

JIA Bin, MA Zhi-Tao, PANG Bao-Jun

2009, 23(6): 453-459 . doi: 10.11858/gywlxb.2009.06.009

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Abstract:
Aluminum foam is a new type of material for shield of spacecrafts which bears fine characteristics when subjected to hypervelocity impact of space debris. A microstructure model of geometry for metallic foams was developed to simulate their manufacturing process. Numerical simulations on hypervelocity impact were carried out using self-programmed Smooth Particle Hydrodynamics, and the proposed model is validated by comparison with experimental results. Two Al-foam-containing shield structures against space debris were presented including Al-foam stuffed shield and Al-foam sandwiched shield. Ballistic limit curves of both shields were obtained respectively through numerical simulations. Analyses results indicate that the shield performance of Al-foam stuffed shield is better than that of Al-foam sandwiched shield for the majority of impact speed range referring to shield against space debris.

Experimental Investigation on Spherical Bubble Evolution Loaded by a Weak Planar Shock Wave

GUO Wen-Can, LIU Cang-Li, TAN Duo-Wang, LIU Jin-Hong, ZOU Li-Yong, ZHANG Guang-Sheng

2009, 23(6): 460-466 . doi: 10.11858/gywlxb.2009.06.010

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Abstract:
The interaction of a shock wave with a spherical gaseous interface (soap bubble) was observed directly by a high-speed camera. To trace the picture of the interface, white droplets were used to dye the test gas inside the bubble. Light gas bubble and heavy gas bubble under weak planar shock waves loading were studied. The geometrical characteristics of bubble evolution were obtained, and the ring-shaped structure in the light gas bubble was observed for the first time. We also analyzed the distribution of the displacement for the light gas bubble with the correlation method. The results agree quite well with the theoretical analysis. The successful usage of droplets encourages the introduction of more accurate diagnostic system like planar laser induced fluorescence (PLIF) or particle image velocimetry (PIV) into experiments in the future.

Thermodynamic Analysis of Cubic Boron Nitride Synthesized under HPHT

JI Xiao-Rui, YANG Da-Peng, YANG Xiao-Hong, ZHANG Tie-Chen, 

2009, 23(6): 467-470 . doi: 10.11858/gywlxb.2009.06.011

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Abstract:
We analyzed the relationships between growth condition and phase transition probability, and critical crystal radius respectively by thermodynamics. Then we calculated the critical grain radius rk for forming cBN crystal under high pressure and high temperature (HPHT). Under 6.0 GPa, 1 600 ℃, the rk is around 15 nm. In the thermodynamically stable region of cBN, the results show that under the same pressure, rk is increasing with the elevated temperature; under the same temperature, rk is decreasing with increasing pressure, and the smaller rk is, the higher phase transition probability is. These results are well consistent with experimental data.

High-Speed Photography and Pulsed in-Line Holography Diagnostics of Microjet

YE Yan, WANG Wei, LI Zuo-You, LI Jian, LIU Zhen-Qing, ZHONG Jie, LI Jun, SHANG Chang-Shui, LUO Zhen-Xiong, LI Xin-Zhu, LI Ze-Ren

2009, 23(6): 471-475 . doi: 10.11858/gywlxb.2009.06.012

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Abstract:
High-speed photography and pulsed in-line holography were applied in the diagnosis of microjet from shocked metal surface. Microjet loading driver, high-speed photography system, pulsed in-line holography system, and high-accuracy synchronization timing system were established. Shown as the experiment, the evolutionary images of microjet can be gained by high-speed photography, and the clear image of microjet can be gained by pulsed in-line holography. The two diagnosis methods are effective means for microjet.

One-Dimensional Numerical Simulation of a Flyer Accelerated by Electrically Exploded Metal Foil

HE Jia, ZHAO Jian-Heng, TAN Fu-Li, SUN Cheng-Wei

2009, 23(6): 476-480 . doi: 10.11858/gywlxb.2009.06.013

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Abstract:
We modified the one-dimensional hydrodynamic code named SSS for simulation of acceleration of Mylar flyer driven by electric explosion. Both simulated histories of discharging current and flyer are consistent with those of experimental results, which validates that the hydrodynamic code SSS with this new introduced model is reliable to simulate the electric explosion. The presented work will be much more helpful for understanding the physical process of electric explosion and optimization of the electric gun instrument itself.

2009 Vol. 23, No. 6

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