高压物理学报

An Ideal n=3 Phase Ca4Mn3O10 of Ruddlesden-Popper Series Obtained by Solid-State Reaction under High Pressure

YU Ri-Cheng, ZHU Jia-Lin, LI Feng-Ying, LIU Zhen-Xing, JIN Chang-Qing, LI Shu-You, I.G.Voigt Martin

2002, 16(3): 161-166 . doi: 10.11858/gywlxb.2002.03.001

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Abstract:
An ideal n=3 member of Ruddlesden Popper (RP) phase Ca4Mn3O10with a space group of I4/mmm was obtained by solid-state reaction under high pressure. This phase was studied by transmission electron microscopy. An approximate model of the structure was proposed. Simulation work was carried out based on this model, and the simulated images were compared with the experimental ones.

Relation of Hydrostatic Pressure to Both Ionic Conductivity and Permittivity of Nanophase CaF2

SU Fang, SUN Wei, SUN Ming-Li

2002, 16(3): 167-175 . doi: 10.11858/gywlxb.2002.03.002

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Abstract:
A nanophase solid CaF2 with a clean interface and an average grain size of 14 nm was prepared by evaporating in inert gas and compacting in situ in high vacuum. Under different hydrostatic pressures ranging from 0.1 MPa to 2.20 GPa, the ionic conductivity () and permittivity () of the resulting product were measured to determine their relation to pressure. The results show: (1) The change caused by the pressure in the ionic migration channel (equal to, greater or smaller than the optimum) is the main factor that affects the peak of the ionic conductivity-pressure curve. (2) When pressure goes up from 0.66 GPa, lg drops linearly along 3 line segments, which may be ascribed to three kinds of free volumes in the nanometer-sized crystalline materials. (3) Polarization of space charge on the boundary layer is the main cause of the high relative permittivity of nanophase CaF2, which illustrates the effect of pressure on permittivity. In order to obtain a compact bulk with higher fluorine ionic conductivity, a higher pressure of 0.66 GPa is recommended in the preparation of the nanophase material.

Compressional Velocity and Attenuation in Amphibolite at 2.0 GPa and up to 1 200 ℃

YUE Lan-Xiu, XIE Hong-Sen, LIU Cong-Qiang, WU Feng-Chang

2002, 16(3): 176-182 . doi: 10.11858/gywlxb.2002.03.003

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Abstract:
Compressional wave velocity and attenuation in amphibolite collected from Kudi, Xinjiang Province were measured at high pressure (2.0 GPa) and high temperature (up to 1 200 ℃). The experimental results show that vp and Q values decrease with the increase of temperature. At the beginning of increasing temperature, vp decreases slowly, and then decreases rapidly with the higher temperature. Because of amphiboliteps anisotropy, the temperature at which vp decreases quickly in different directions is different. The temperature is 812 ℃ in x and y and 673 ℃ in z. However, the temperature at which Q decreases quickly is about 812 ℃ at the three directions. It can be concluded from the experimental results of minerals that as the temperature is higher than 647 ℃, the melt appears. The scope of vp decreasing with temperature in x and y directions is not various than before. It increases in z direction. However, the melt does not affect Q values. As the temperature is higher than 812 ℃, the melt is more than before, vp and Q values decrease more quickly. Therefore, partial melting is the main reason for elastic wave velocity decreasing and attenuation increasing.

PbTe Syntheses by High-Pressure and High-Temperature Approach

ZHU Pin-Wen, JIA Xiao-Peng, CHEN Hai-Yong, CHEN Li-Xue, LI Dong-Mei, GUO Wei-Li, MA Hong-An, REN Guo-Zhong, ZOU Guang-Tian

2002, 16(3): 183-187 . doi: 10.11858/gywlxb.2002.03.004

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Abstract:
In this paper, lead telluride was successfully synthesized by a high-pressure and high-temperature (HPHT) method. XRD results show that the samples are polycrystalline with rock salt structure. The orientation of PbTe samples is varying with the increasing synthesis pressure. Scanning electric microscope (SEM) results show that the synthesized PbTe samples possess high orientation. The electrical resistivities of PbTe samples are about 1～2 magnitudes lower than those of the samples sintered at ambient pressure, and decrease with the increase of the synthesis pressure. The thermal conductivities of the PbTe samples synthesized by HPHT are lower than those of the samples fabricated at ambient pressure. These results indicate that thermoelectric properties of PbTe samples can be improved by high-pressure and high-temperature approach.

FeS2 Ban Gap Modulation under Pressure Perturbation

XIAO Qi, QIU Guan-Zhou, HU Yue-Hua, WANG Dian-Zuo

2002, 16(3): 188-193 . doi: 10.11858/gywlxb.2002.03.005

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Abstract:
The electronic structure of iron pyrite FeS2 under external pressure was studied using self-consistent pseudopotential method based on density functional theory. The results indicate that, with compressibility increasing, the width of band gap becomes wider, and that the interaction between Fe d electrons and S p electrons is stronger, and length of FeS bond becomes shorter. The results are conflict to the rule of metallization of nonconductors at high pressure.

Application of T-p Distribution to Equation of State at High Pressures

GENG Hua-Yun, WU-Qiang, TAN Hua

2002, 16(3): 194-198 . doi: 10.11858/gywlxb.2002.03.006

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Abstract:
A new framework for equation of state in which pressure is as an independent variable are discussed simply by using a T-p distribution in this paper. Then applications of this distribution to the free volume model and Harmonic oscillator model for liquid are given. The Wu-Jing parameters for these two models are also obtained.

One-Dimensional Numerical Simulations of Underwater Spherical Explosions

LIANG Long-He, CAO Ju-Zhen, WANG Yuan-Shu

2002, 16(3): 199-203 . doi: 10.11858/gywlxb.2002.03.007

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Abstract:
The characteristics of underwater explosions such as pulsation law and pulsation cycle of bubbles, and pressure time histories of shock waves in water were investigated numerically. Numerical results of the characteristics are given in this paper.

High-Resolution Eulerian Hybird Algorithm for Multi-Component Compressible Materials

BAI Jing-Song, CHEN Sen-Hua, ZHONG Min

2002, 16(3): 204-212 . doi: 10.11858/gywlxb.2002.03.008

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Abstract:
A series of dynamic equations applicable for the interfacial vicinity of the multi-component compressible material were derived in this paper. Both the equations describing the material interface quality and the conservative Euler equations are incorporated and solved by using a high-resolution finite volume scheme. The interface positions are captured by applying level set method independently. Some examples of one and two-dimensional are presented.

Theoretical Calculation for Shock Compressional Properties of Liquid Nitrogen

MENG Chuan-Min, SHI Shang-Chun, DONG Shi, SUN Yue, JIAO Rong-Zhen, YANG Xiang-Dong

2002, 16(3): 213-216 . doi: 10.11858/gywlxb.2002.03.009

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Abstract:
For the liquid nitrogen, the modified WCA fluid perturbation theory is used to calculate the shock pressure and shock temperature with the exp-6 reference potential. The theory is generalized from multi-component system by adding the molecular dissociation fraction, which is related to volume. The theoretical results of pH and TH are in good agreement with those of experimental data up to 70 GPa. According to the theoretical and experimental data, the shock energy is partially absorbed by molecular dissociation.

Study on the Shock Compression Properties of Mixed Liquid N2 and CO

SUN Yue, MENG Chuan-Min, WU Guo-Dong, YANG Xiang-Dong

2002, 16(3): 217-223 . doi: 10.11858/gywlxb.2002.03.010

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Abstract:
The shock compression properties of a mixture of liquid N2 and CO mixed in equal volume were studied using a two-stage light gas gun. Five Hugoniot data were measured within 10～25 GPa. Comparing with known Hugoniot curves of simple substance N2 and CO, we found that the Hugoniot curve of mixture was just located between those of CO and N2 but closed to its dissociated curve. This predicates that shock compressed properties of mixture is not equal to the simple mean of its components.

Study of -FeSi2 at High Pressure

LI Yan-Chun, LIU Jing, CAO Li-Min, DONG Yu-Hui, LI Xiao-Dong, NAN Yun, GAO Zhen-Shan, WANG Wen-Kui

2002, 16(3): 224-226 . doi: 10.11858/gywlxb.2002.03.011

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Abstract:
The structure transformation of -FeSi2 at high pressure with Diamond Anvil Cell Apparatus was firstly studied by using in situ synchrotron radiation X-ray diffraction. Phase transition was found to be appeared at 4.3 GPa and completed at 25.8 GPa. After indexed, it is shown that the product of phase transition is tetragonal and its lattice constants are a=b=1.004 9 nm, c=0.339 4 nm.

The Effect of MgO on Growth of cBN in the Mg-hBN System

WANG Xian-Cheng, ZHANG Tie-Chen, JIA Xiao-Peng, ZOU Guang-Tian

2002, 16(3): 227-230 . doi: 10.11858/gywlxb.2002.03.012

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Abstract:
In this paper, we report a method with which yellow cBN crystals are synthesized successfully. hBN is used as raw material and magnesium powder as catalyzer. MgO is added appropriately at high pressure (5.0 GPa) and high temperature (1 500～1 800 K) with cubic anvil high-pressure apparatus. The synthesized crystals are of perfect shape and uniform color. The synthesis temperature of the cBN is reduced due to the existence of MgO.

Ferroelectric/Antiferroelectric Phase Transition Studies of PZT-95/5 Ceramics under Shock Loading

LIU Gao-Min, TAN Hua, YUAN Wan-Zong, WANG Hai-Yan, ZHANG Yi

2002, 16(3): 231-236 . doi: 10.11858/gywlxb.2002.03.013

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Abstract:
Shock-induced phase transition in PZT-95/5 ferroelectric ceramics was studied by using X-cut quartz gauge. The stress profile measured shows definitely a two-wave structure which indicates that the FE/AFE phase transition starts at stress about 0.5 GPa. SEM observations for the pre-shock green samples, both polarized and un-polarized, and for the post-shock recovered samples provide clearly the unique microscopic features resulting from the transition.

The Bandwidth of Optical Fiber and Its Restrictions on VISAR

PENG Qi-Xian, MA Ru-Chao, LI Ze-Ren, LIU Jun, LIU Yuan-Kun, DENG Xiang-Yang

2002, 16(3): 237-240 . doi: 10.11858/gywlxb.2002.03.014

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Abstract:
The effects of the optical fiber bandwidth on VISAR system were investigated. It was estimated that the index-stepped multi-mode optical fiber could only reach a bandwidth of several MHz#8226;km while the index-graded optical fiber could easily reach a bandwidth of several GHz#8226;km. The experimental results confirmed that the index-stepped optical fiber did restrict the time resolution of VISAR due to its limited band width. So using the index-graded optical fiber, instead of the index-stepped fiber, may be an effective way to free the VISAR from the restriction of optical fiber bandwidth and advance the VISAR system.

2002 Vol. 16, No. 3

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