高压物理学报

High-Pressure Synthesis of Superconducting Pr1-xCaxBa2Cu3O7-

XIONG Yu-Feng, YAO Yu-Shu, HUANG Yun-Kai, JIA Shun-Lian, JIN Duo, ZHAO Zhong-Xian

1999, 13(2): 81-86 . doi: 10.11858/gywlxb.1999.02.001

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Abstract:
The new bulk superconductors Pr1-xCaxBa2Cu3O7- (0.4x0.6) have been synthesized under a high-pressure of 5 GPa and 1 000 ℃ for 30 min. The solubility of Ca in Pr-123 phase has much increased by the high pressure synthesis method, that effectively compensates the hole-filling by Pr on CuO2 planes and achieves superconducting.

Experimental Study and Theoretical Exploration on Interaction Potential and Mixing Law for Mixture of Carbon and Water

HU Dong, YANG Xiang-Dong, JING Fu-Qian, WANG Yong-Guo, LI Xiao-Chang, SUN Zhu-Mei, DONG Shi, SHI Shang-Chun

1999, 13(2): 87-92 . doi: 10.11858/gywlxb.1999.02.002

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Abstract:
The behavior of shock compression of the mixture of carbon and water is studied by means of loading technique of two stage light gas gun. It is found that the behavior in the mixture of graphite and water is different to the mixture of diamond and water below shock loading pressure of 19 GPa; as shock pressure is greater than 23 GPa, their compression Hugoniot is close, it shows that the more graphite has transited to diamond. The shock Hugoniot at 52.9 GPa shock pressure in the mixture of graphite and water is different abnormally, i.e. when the pressure rises, the volume expands, it related to produced gas because the carbon reacts with water under high pressure. The emission spectra above mentioned mixtures are observed by means of OMA spectrometer. The results show that the emission spectra on the obvious head radiation in the range from 350 nm to 750 nm as shock pressure is larger than 16.4 GPa. The spectrum bands of C2, CO, CO2 are obvious, when shock pressure is larger than 34 GPa, it shows that the carbon reacts with water. The choices of interaction potential and mixing law for the mixture of carbon and water are discussed.

Studies of EOS for Detonation Products: Liquid Nitrogen, Liquid Helium and Water

YANG Xiang-Dong, HU Dong, JING Fu-Qian

1999, 13(2): 93-102 . doi: 10.11858/gywlxb.1999.02.003

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Abstract:
The improved WCA theory and Ross's variation perturbation theory are used to study the shock-compression properties of liquid nitrogen, helium and water, while the exponential-six potential is used to calculate the free energy. Our study shows that in the calculation of shock-compression properties of high-temperature and high-density fluid, the inter-atomic many-body effects are much more important, which have softened the two-body potential.

Phase Diagram of Halloysite under High Pressure and Temperature and Its Geophysical Implications

GONG Zi-Zheng, XIE Hong-Sen, JING Fu-Qian, TAN Hua, BI Yan

1999, 13(2): 103-107 . doi: 10.11858/gywlxb.1999.02.004

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Abstract:
Hugoniot measurements for halloysite with two different initial densities have been performed at the shock pressures up to about 100 GPa. Three distinct regions appear along their Hugoniots. For the samples of 0=1.375 g/cm3, a low-pressure phase (LPP) exists within the shock pressure up to about 12.69 GPa, a mixed phase region (MP) begins at 12.69 GPa and ends at about 22.90 GPa, and then a high-pressure phase (HPP) occurs at shock pressures between 22.90 GPa and 46.64 GPa. The fitted linear D-u relations of its LPP and HPP can be expressed respectively as D=0.24+1.89u and D=2.47+1.12u, D is the shock wave velocity and u is the particle velocity (km/s). For the samples with 0=2.001 g/cm3, the pressure ranges of its LPP, MP are covering 0~35.77 GPa, 35.77~95.48 GPa, respectively, and no HPP obviously shows on its Hugoniot. The fitted linear D-u relations of its LPP and MP are D=1.73+1.72u and D=2.69+1.37u , respectively. p-T phase boundary is determined approximately by the Mie-Grneisen Equation of state using the present parameters. It is compared with the linear geothermal lines of 10 ℃/km and 4 ℃/km, and suggested that halloysite may be stable at depth about 50 km inupper mantle or as a transient phase in subducting slabs at depth of about 133 km.

Crystallization of Amorphous (Fe0.99Mo0.01)78Si9B13 Alloy Reacted with Al

YAO Bin, YANG Zhao-Hai, LIU Li, SU Wen-Hui

1999, 13(2): 108-114 . doi: 10.11858/gywlxb.1999.02.005

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Abstract:
Crystallization products of amorphous (Fe0.99Mo0.01)78Si9B13 (FMSB) alloy or pure amorphous FMSB alloy reacted with Al are different under high pressure. The amorphous FMSB alloy reacted with Al may start crystallization at Al/FMSB interface by reacting diffusely with Al. It crystallizes to -Fe (Al) and second-amorphous phase in the range from 3.0 to 5.0 GPa in the temperature range of 780 K to 900 K and to -Fe (Si), Fe3B or Fe2B beyond the range of 3.0 to 5.0 GPa between temperatures of 720 and 900 K. The effect of pressure and temperature on its crystallization process comes mainly from the change of Gibbs energy of -Fe solid solution with pressure, temperature and Al content.

Studies of Shock-Activation of Silicon Nitride Powder

LU Fang-Yun, CAI Qing-Yu, ZHOU Xin-Gui, CHEN Gang, ZHOU An-Chen

1999, 13(2): 115-119 . doi: 10.11858/gywlxb.1999.02.006

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Abstract:
In this paper, we have studied the surface and microscopic features of the silicon nitride powders, which have been activated by shock waves in two pressures: 15.7 GPa and 25.6 GPa, and the sintering features of the ceramics sintered from the activated powders. The results show that the shock-activation plays an apparent role on promoting densification of the powders during sintering.

An Analytic Solution for Flyer Plate Motion in Grazing Detonation

TAN Duo-Wang, SUN Cheng-Wei

1999, 13(2): 120-126 . doi: 10.11858/gywlxb.1999.02.007

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Abstract:
In this paper, an analytic solution is presented to calculate the flyer plate motion by grazing detonation. The solution was checked against experimental and finite element computer results, good agreement indicates that the solution can accurately describe the flyer plate motion. The solution is very simple, and is a quick and efficient tool for the usage in explosive welding.

High-Pressure Phase State of Enstatite and Its Application in Geophysics

HUO Hui, GONG Zi-Zheng, JING Fu-Qian

1999, 13(2): 127-132 . doi: 10.11858/gywlxb.1999.02.008

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Abstract:
By using Birch-Murnaghan and Grneisen equation of state, Hugoniots of both perovskite Mg0.86Fe0.14SiO3 and the mixture of magnesiow stite (Mg0.86Fe0.14O) and stishovite (SiO2) have been calculated in this work. When compared with experimental Hugoniots, the calculations demonstrate that the above mentioned two kinds of phase states are indeed possibly the high-pressure phases of enstatite when it is compressed to high pressure but to different temperatures. Besides, we further made corrections on the effect of temperature-difference due to Hugoniot and PREM estimations to deduce the density values relevant to lower mantle and found that Mg0.86Fe0.14SiO3 is more likely to be the main composition or phase state of the lower mantle. It shows an additional support to the opinion proposed by Knittle et al.

Electrical Properties and Metallic Transitions in Nanocrystals Si at High Pressure

BAO Zhong-Xing, HE Yu-Liang, WANG Wei-Xiang, LIU Cui-Xia, CHEN Wei

1999, 13(2): 133-137 . doi: 10.11858/gywlxb.1999.02.009

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Abstract:
The resistance pressure and capacitance-pressure relationships for nanocrystals Si with grain sizes of 15～18 nm and 80 nm at room temperature and up to 24 GPa have been studied in a diamond anvil cell using resistance and capacitance measurements established by us. The experimental results show that they undergo a metallic transition at about 19～17 GPa and 14 GPa, respectively.

Shock Activation of Titanium Oxide and Its Photocatalytic Activity

LIU Jian-Jun, YU Ying-Chun, LI Ying-Jun, HE Hong-Liang, TAN Hua, XU Kang

1999, 13(2): 138-142 . doi: 10.11858/gywlxb.1999.02.010

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Abstract:
The metal oxide catalyst TiO2 has been treated by shock wave, and then used as a photocatalyst for the dehydrogenation of H2S. Results show that, compared with the unshocked sample, the treated ones exhibit much higher photocatalytic activity within the experimental pressure range of 16～34 GPa, the activity has been increased by a factor of 2～3. Analyses of XRD and u.v. vis diffuse reflection spectra suggest that the enhancement may be attributed to the higher density of residual strain and dislocation defects and the degradation of energy gap of the shock treated TiO2.

Emission Spectra of Shock-Compressed Carbon-Water Mixtures

LI Jing-Ze, LI Xiao-Chang, WANG Yong-Guo, HU Dong, JING Fu-Qian

1999, 13(2): 143-146 . doi: 10.11858/gywlxb.1999.02.011

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Abstract:
Emission spectra of shock-compressed graphite-water mixtures and diamond-water mixtures have been recorded by using the optical multichannel system(OMA-Ⅲ) at a two stage gas gun. Emission has been observed under a broad but strong background in a spectral range between 350 nm and 750 nm from the shocked examples above 16.41 GPa. The shock products C2, CO, CO2 appear at pressure above 33 95 GPa, it shows that carbon has reacted with water.

Model of Structural Transformation in Synthesizing Nano-Crystalline Diamond with Pulsed-Laser Induced Liquid-Solid Interface Reaction

WANG Jin-Bin, YANG Guo-Wei

1999, 13(2): 147-151 . doi: 10.11858/gywlxb.1999.02.012

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Abstract:
The physical and chemical mechanisms of synthesizing diamond nanocrystallites with pulsed-laser induced liquid-solid interface reaction (PLIR) have been analyzed in this paper. At the initial stage of nano-crystalline diamond growth, the models of structural transformation from hexagonal to rhombohedral graphite at first and then to cubic diamond crystal nuclear, or from hexagonal graphite direct to cubic diamond have been developed. These models reasonably explain the physical and chemical mechanisms of synthesizing diamond nanocrystallites with pulsed-laser induced liquid-solid interface reaction from a kinetic view.

Multi-scaling Transport Equation on Fractals

ZENG Qiu-Hua, LI Hou-Qiang

1999, 13(2): 152-160 . doi: 10.11858/gywlxb.1999.02.013

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Abstract:
The general transport equation for multi-scaling disordered fractal media in three-dimensional case is derived from conservation of mass and on the basis of discussing Brownian motion, fractional Brownian motion and standard diffusion equation on fractals, the multiscaling fractional transport equation is obtained.

1999 Vol. 13, No. 2

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