高压物理学报

Research on Complex Impedance Spectra of Nanophase Ionic Conductor under Hydrostatic Pressure

SU Fang, XIE Bin, ZHAO Ming-Wen, WU Xi-Jun

1995, 9(2): 81-88 . doi: 10.11858/gywlxb.1995.02.001

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Abstract:
A nanophase soild CaF2 which has clean interface and average graininess 16 nm was prepared with the method of evaporation in inert gas and being pressed in high vacuum, complex impedance spectra of nanophase CaF2 were measured precisely using 70 frequencies from 100 kHz to 100 Hz under the different hydrostatic pressure from 0.1～2 400 MPa. Variations of both ionic conductivity and dielectric constant in nanophasc CaF2 with pressure were given. It is indicated in final discussion that passage for migration of fluorine ions being compressed is the main factor of changing pressure-effect on ionic conductivity. Under low pressure the passage sizes much larger than optimum, so movement of F- is not the fastest. Under 1 263 MPa pressure, the passage size reaches its optimum, migration of F- is the easiest, hence reaches maximum. When pressure is over 1 263 MPa, the passage size becomes smaller and smaller than optimum, migration of F- gets more and more difficult, so that diminishes rapidly. Besides, polarization of space charge on interface layer is the cause which makes relative dielectric constant of nanophase CaF2 larger. From the role of interface we can understand the pressure effect of the dielectric constant.

Synthesis and Characterization of Boron Suboxide B7O under High Pressure and High Temperature

LIU Xiao-Yang, ZHAO Xu-Dong, HOU Wei-Min, SU Wen-Hui

1995, 9(2): 89-95 . doi: 10.11858/gywlxb.1995.02.002

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Abstract:
The red-brown boron-rich solid B7O has been synthesized by means of oxidation of boron with zinc oxide under conditions of 3.5 GPa and 1 200 ℃ for 30 min. The product after leached in hydrochroric acid has been characterized by XRD, XPS, IR, SIMS and chemical analysis. The results of SIMS and chemical analysis show that the chemical formula is B7O. The results of X-ray powder diffraction indicates that the crystal structure of the sample can be classified as hexagonal symmetry with lattice constants of =0.543 5 nm and c=1.2415 nm.

Dynamic Fracture of TC4 and TC9 Titanium Alloy under High Strain Rates

ZHUANG Shi-Ming, FENG Shu-Ping, WANG Chun-Yan, SUN Cheng-Wei

1995, 9(2): 96-106 . doi: 10.11858/gywlxb.1995.02.003

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Abstract:
The experimental and numerical simulation results of dynamic failure of TC4 and TC9 titanium alloys under shock loadings induced by short pulse duration laser beam and electric gun drived Mylar plane flyer impacting the specimen is reported in this paper. The detail metallurgical analysis of recovered specimen indicates that for both loading conditions, the strain rate about 106 s-1 by electric gun drived flyer impacting target and the strain rate over 107 s-1 by short pulse duration laser beam loading, the failure and fracture of TC4 and TC9 titanium alloys are all ductile in the course of microvoid nucleation, growth and coalescence. The numerical investigation by one dimensional code SSS shows that to some extent the nucleation and growth (NAG) damage model can be used to describe the failure of TC4 and TC9 titanium alloys under high strain rates.

Thermal Shock Wave Induced by Impulsive X-Ray

TANG Wen-Hui, ZHANG Ruo-Qi, ZHAO Guo-Min

1995, 9(2): 107-111 . doi: 10.11858/gywlxb.1995.02.004

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Abstract:
Shock wave induced by impulsive X-ray, which is also called thermal shock wave, is simulated in this paper. Our study indicates that the mechanical mechanism of shock wave induced by impulsive X-ray can be classified as the following two categories: (1) it is generated by the blow-off of the surface layer of the radiated material; (2) it is caused by thermal deformation.

Theoretical Calculation for the Hugoniot Curves of Liquid Helium

LIU Fu-Sheng, GOU Qing-Quan, JING Fu-Qian

1995, 9(2): 112-116 . doi: 10.11858/gywlxb.1995.02.005

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Abstract:
The variational fluid perturbation theory is used to calculate the single and double shock Hugoniot curves of liquid helium by means of a two-body potential function. It is found that the theoretical predictions are 30%～50% higher than the measurements at the same volume. It shows that the effective potential of two atoms, which are at high densities and temperatures, is much lower than that of two isolated ones. The physical mechanism which probably causes this unusual soften phenomena and its theoretical treatment methods are discussed as well.

The Preparation and Characterization of Bulk Cu-Si Nanocrystalline Alloy under High Pressure

YAO Bin, DING Bing-Zhe, LI Dong-Jian, WANG Ai-Min, LI Shu-Ling, HU Zhuang-Qi, SU Wen-Hui, GENG Yi-Zhi, HU An-Guang, XIN Zhi-Ming, et al

1995, 9(2): 117-123 . doi: 10.11858/gywlxb.1995.02.006

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Abstract:
The Cu-Si nanocrystalline (NC) alloy was prepared by quenching the melted Cu70Si30 alloy at cooling rate 200 K/s under a pressure of 6 GPa. The bulk Cu70Si30NC alloy consists of -Cu5Si and an unknown phase. The crystal structure of the unknown phase is simple cubic system and lattice constant is 0.853 5 nm. The thermo stability of the bulk Cu70Si30NC alloy was carried out and an endothermic peak was observed, enthalpy of which is 2.667 5 J/g. The formation mechanism of the bulk Cu70Si30 alloy under high pressure was discussed.

Analytical Solutions of One-Dimensional Thermal Shock Wave

ZHOU Nan, QIAO Deng-Jiang

1995, 9(2): 124-132 . doi: 10.11858/gywlxb.1995.02.007

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Abstract:
By using Laplace transform, analytical solutions of one-dimensional thermal shockwave are derived at small strain for material with finite and infinite thickness subjected to X-ray pulse radiation.

High Temperature Elastic Moduli of TC4, 16Mn and Al2O3 Ceramic

ZHANG Shu-Hua

1995, 9(2): 133-138 . doi: 10.11858/gywlxb.1995.02.008

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Abstract:
The velocities of longitudinal and shear waves in TC4, 16Mn and Al2O3 ceramics were measured by a pulse-echo technique from 15～1 000 ℃. Adiabatic elastic moduli are calculated from these velocities. Regression equations of E, G vs temperature are given by the regression analysis. The melting temperatures are estimated in the paper.

X-Ray Diffraction Studies on CsBr under High Pressure

WANG Li-Jun, CHEN Liang-Chen, CHE Rong-Zheng, ZHOU Lei, WANG Ji-Fang

1995, 9(2): 139-143 . doi: 10.11858/gywlxb.1995.02.009

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Abstract:
In situ high pressure X-ray diffraction experiments have been carried out on CsBr using energy dispersion method with synchrotron radiation source. The pressure was generated by the high pressure device－diamond anvil cell (DAC). The pressures up to 64.4 GPa were determinded by the diffraction data of Pt used as an inner pressure standard, whose EOS is known. The results indicate that the original sample AsBr is in simple cubic structure at room temperature and atmosphere pressure, its lattice parameter =0.428 5 nm. The structure of CsBr is changed to tetragonal phase at high pressure, marked by the splitting of the diffraction lines (110) and (211) after 51.3 GPa.

Studies on Fluorescence Spectrum of Pyrophyllite Phase Transformation under High Temperature and Pressure

MA Yan-Zhang, MENG Jin-Fang, ZOU Guang-Tian, CHI Yuan-Bin

1995, 9(2): 144-148 . doi: 10.11858/gywlxb.1995.02.010

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Abstract:
The effects of high temperature and pressure on the fluorescence of pyrophyllite have been studied. It is found that the wave numbers of the two peaks at 14 428 cm-1 and 14 398 cm-1 decrease under high temperature and pressure respectively. When high temperature and pressure are exerted on pyrophyllite simultaneously, the decrease is much smaller than those when they are exerted separately. Only at the place closest to the synthesizing chamber, pyrophyllite transforms into a new state with the effects of both high pressure and temperature. It is believed that the pressure and temperature change the electron energy levels which make a change of the transition energy.

Research Survey on the Mechanism of the Synthesis of Ultrafine Diamond by Means of Explosives Detonation

ZHOU Gang, HUANG Feng-Lei, YUN Shou-Rong

1995, 9(2): 149-154 . doi: 10.11858/gywlxb.1995.02.011

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Abstract:
In the article, the mechanism of ultrafine diamond synthesized from the carbon of explosives, are given a systematic summary and analysis from three aspects, experimental explores theoretical research and numerical modeling. Some problems expected to be researched at present are proposed.

Studies of Phase Transformation between Diamond and Graphite

ZHANG Ya-Fei, CHEN Guang-Hua

1995, 9(2): 155-160 . doi: 10.11858/gywlxb.1995.02.012

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Abstract:
The phase transformation between diamond and graphite has been studied by calculating the transition probability of the carbon atoms over a potential barrier. For the first time, the boundaries of the proposed metastable regions of diamond and graphite have been estimated theoretically, and the currently used characteristic paths of pressure temperature for synthesizing diamond by high pressure and high temperature (HPHT) method can be understood.

1995 Vol. 9, No. 2

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