高压物理学报

Some Problems of Fracture Waves in Brittle Materials under Shock Loading

ZHANG Guan-Ren

1998, 12(2): 81-86 . doi: 10.11858/gywlxb.1998.02.001

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Abstract:
In this paper, some problems of fracture waves in glasses and rocks under shock loading are discussed, such as whether its formation mechanism is crack growth or phase transformation, why it begins from the surface of glasses, and what is its propagation velocity.

The Three-Body and Four-Body Interactions between Hydrogen Molecules at High Temperatures and Densities

LIU Fu-Sheng, CAI Ling-Cang, JING Fu-Qian

1998, 12(2): 87-91 . doi: 10.11858/gywlxb.1998.02.002

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Abstract:
To describe the complicate three-body and four-body interactions between hydrogen molecules at high temperatures and densities, an effective helium-atom model is presented to approximate electron cloud distribution of rotating hydrogen molecule at the outer space, on the basis of the average pair potential of Ree and Bender. The calculation results for three-body potentials are in good agreement with the CI calculations of Ree and Bender. The four-body ones are also given in this article.

The Structure and Phase Transition for CsBr under Ultra-High Pressure

WANG Li-Jun, CHEN Liang-Chen, LI Feng-Ying, GU Hui-Cheng, ZHOU Lei, CHE Rong-Zheng

1998, 12(2): 92-96 . doi: 10.11858/gywlxb.1998.02.003

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Abstract:
In situ energy dispersive X-ray diffraction measurements on CsBr under pressure up to 115 GPa have been performed by using pressure device－diamond anvil cell (DAC) with synchrotron source. It is determined that the structure of CsBr is changed from simple cubic phase to tetragonal phase at about 53 GPa marked by the splitting of its strongest diffraction line (110) into two parts: (011) and (110). The lattice parameter ratio c/a has been measured from p=0 to the maximum pressure (corresponds to V/V0 range of 1～0.463). No pressure-induced metallization transition has been observed at higher pressure up to 115 GPa.

In-Situ Measure and Control of Oxygen Fugacity at High-Temperature and High-Pressure

LI He-Ping, XIE Hong-Sen, GUO Jie, ZHANG Yue-Ming, XU Zu-Ming, XU Ji-An

1998, 12(2): 97-102 . doi: 10.11858/gywlxb.1998.02.004

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Abstract:
By inserting a solid oxygen-specific electrolyte between a sample and an oxygen reservoir, and applying a DC power between the oxygen reservoir and the sample oxygen can be pumped out from or poured into the sample in situ independent of temperature and pressure. By installing an oxygen sensor into the sample cell, the oxygen fugacity in the sample can be monitored in situ. In this way, the oxygen fugacity in the sample can be conveniently controlled in situ independent of temperature and pressure. Our experiments in which a Ni-O system was used as the sample show that this method is very successful. Undoubtedly, the method is of great significance to high-pressure experimental studies.

Phase Evolution of Germanium during Solidification at High Pressure

HE Duan-Wei, LI Jiao-Jun, ZHANG Fu-Xiang, ZHANG Ming, LIU Ri-Ping, XU Ying-Fan, WANG Wen-Kui

1998, 12(2): 103-108 . doi: 10.11858/gywlxb.1998.02.005

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Abstract:
In this paper the phase evolution in the solidification process of germanium under high pressure is investigated. Data obtained on electrical resistance changes, and in situ differential thermal measurements, as well as X-ray diffraction results enable us to arrive at the phase relations and transformation processes occurred during solidification at high pressure. Under high pressure above 4 GPa, the metallic germanium phase is first solidified from the melt and then transformed into Ge Ⅰ phase and/or Ge Ⅲ phase. The kinetics of the non-equilibrium transitions is also briefly discussed.

A Discussion on the Errors for the in Situ Magnetic Measurements in Hydrostatic High Pressure Vessel (2)－The Influence of Demagnetic Field

SU Fang, SU Xiao

1998, 12(2): 109-114 . doi: 10.11858/gywlxb.1998.02.006

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Abstract:
To study the influence of demagnetic field in the hydrostatic high pressure vessel, we selected 6 samples with different slice-number (n=1, 3, 5, 7, 10, 13) of amorphous alloy Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5 ribbon, inserted them into multiple electric solenoid and measured the magnetization, magnetic permeability and initial magnetization, respectively, at 400 Hz. We found that: (1) The more the slices of sample, the stronger the influence of demagnetic field was, which leaded in surprising errors of m and i. For the sample with 1 slice, we obtained the optimal values, m=4 430, i=3 396. (2) With the increase of slice number (n=1~13), we measured saturation magnetic induction Bs=0.837～0.762T, indicating the influence of demagnetic field on Bs was much small. (3) To reduce the error from demagnetic field, thinner sample could be used, for example thin film with 0.2 m thick. (4) To eliminate the error from demagnetic field, closed magnetic circuit must be adopted, such as ring rolled up by amorphous alloy ribbon.

The Synthesis of Sr1-xLaxTiO3 under High-Temperature and High-Pressure and Its XPS Study

LU Da-Yong, LI Li-Ping, CHE Yu-Lu, MIAO Ji-Peng, LIU Hong-Jian, SU Wen-Hui

1998, 12(2): 115-119 . doi: 10.11858/gywlxb.1998.02.007

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Abstract:
The perovskite oxides, Sr1-xLaxTiO3, were synthesized at high-temperature and high-pressure. XRD measurement shows that the samples with x0.5 are in single phase and belong to cubic phase structure. Cell volume increase at beginning of x, then decrease at x=0.4. XPS analysis indicates that Ti ions are in mixed valence. The influence of valence state of Ti ions on the lattice parameters is discussed.

A Theoretical Study on the Equation of State of Liquid Methane at High Temperature and High Densities

YANG Xin-Dao, LIU Fu-Sheng, LI Jian-Feng, JING Fu-Qian

1998, 12(2): 120-124 . doi: 10.11858/gywlxb.1998.02.008

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Abstract:
Equation of state and molecular dissociation reactions of liquid methane at high-temperature and high-pressure are investigated by Statistical Mechanics and Chemical Equilibrium method, with focus on the interactions between CH4 and H2, which apparently would affect the equilibrium of chemical reactions and EOS of shock compressed liquid methane. By using a set of optimized exp-6 potential parameters obtained from experimental Hugoniot data (pH, V), our theoretical calculation results agree satisfactorily with published experimental data. The repulsive part of our potential, however, is softer than that determined by ideal mixture rule, which implies attractive interaction between CH4 and H2 may exist under high pressure. The effect of the effective potential between CH4-H2 on the dissociation of CH4 molecules under shock compression is also discussed in this paper.

Temperature Changes with Time of Synthesizing Diamond by Low-Frequency Heating

XU Hong-Shan, CHEN Yu-Fei, WANG Yan-Di

1998, 12(2): 125-128 . doi: 10.11858/gywlxb.1998.02.009

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Abstract:
The effect of synthesizing diamond under high temperature and high pressure by low-frequency (50 Hz) heating differs from that of by industrial frequency heating. For industrial frequency heating, the constant heat is imported into the cell and the temperature is a spatial l distribution, while for low frequency heating, the pulsed heat is imported into the cell, and the temperature changes not only with spatial distribution but also with time in the cell. Some experimental phenomena and results are explained by temperature changes with time.

Effect of Different Preservative Substances on the Formation of Condensed Carbon in Detonation

CHEN Quan, MA Feng, CHEN Peng-Wan, YUN Shou-Rong, HUANG Feng-Lei

1998, 12(2): 129-133 . doi: 10.11858/gywlxb.1998.02.010

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Abstract:
In this paper, the comparison of the effect of different preservative materials on preserving the condensed carbon obtained from detonation soot shows that the surrounding substance has prominent importance on the formation of condensed carbon in detonation which not only take a preservative effect but also a cooling effect to compress graphitization. For carbon, different circumstance corresponds to different path on carbon phase diagram while detonation product expanding. This provides a clue of improving yield of ultrafine diamond (UFD) obtained from detonation soot. Also in this paper, it proposes the graphitization of graphite crystallite existing in soot and UFD as a criterion to evaluate the preservative effect of different substances.

Pressure Measurement Techniques in Electrothermal-Chemical Gun

LI Hong-Tao, QIU Xu, RUI Hai-Yan, CHEN Lin

1998, 12(2): 134-140 . doi: 10.11858/gywlxb.1998.02.011

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Abstract:
This article reports the measurement method of the pressure in-bore with high transient and broad spectra. It also presented how to resist the strong electromagnetic disturbances. The measurement method includes the acoustical filter and optic-electric separation techniques. The quartz and the PVDF pressure transducers, which are used in the experiment, are showed to be an efficient one for measuring pressure with high transient. The measuring results show that the method is practical and efficient.

Diamond Synthesis Using VC as Carbon Source

LI Liang-Bin, JIANG Jin-Chun, YANG Xin-Dao, ZHONG Yu-Mao, ZHANG Xin-Yuan, HONG Shi-Ming

1998, 12(2): 141-144 . doi: 10.11858/gywlxb.1998.02.012

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Abstract:
A system of VC powder and Ni70Mn25Co5 alloy in weight ratio of 1∶6 was treated under high pressure of 6.0 GPa and high temperature of 1 500 ℃ for 20 min. X-ray diffraction of the sample indicates that diamond and graphite formed respectively with decomposition of the VC. Observation in SEI, WDX and EDX shows that many diamond crystals are synthesized, which have rugged surfaces mostly, and the average grain size is about 20 m。

Theoretical Isothermal Compression Curve for Solid Helium

CAI Ling-Cang, LIU Fu-Sheng, JING Fu-Qian

1998, 12(2): 145-149 . doi: 10.11858/gywlxb.1998.02.013

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Abstract:
Based on the theory of atomic cluster and taking account of the screening effects induced by nearest-neighbor and next nearest-neighbor atoms, we have calculated the many-body repulsive potential and isothermal compression curve for solid helium with hcp lattice configuration. The calculation result is in agreement with the experimental data that obtained from high static-pressure measurements covering pressure range of about 5～25 GPa, and therefore also more reasonable than those previously proposed. Discussions on the limitations of two-body potential of Aziz, three-body potential of Loubeyre, and equivalent potential of Ross and Young are also given in the paper.

Ultrasonic Measurements and Mechanical Parameters Evaluation for Tungsten Alloy

HUA Jin-Song, JING Fu-Qian, TAN Hua, ZHAO Zhi-Dan

1998, 12(2): 150-155 . doi: 10.11858/gywlxb.1998.02.014

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Abstract:
Longitudinal and transversal sound velocities of 93W alloy were measured by using a belt type and a cubic-type high pressure apparatus, respectively. Results show that under normal temperature and pressure conditions, this tungsten alloy materials have a longitudinal velocity (cL) of 5.135 km/s and transversal velocity (ct) of 2.987 km/s. Pressure dependence of longitudinal velocity is linear in the pressure range up to 3 GPa, with a form of cL=5.053+0.02p, where p is in unit of GPa. Bulk sound velocity calculated from these data is 3.86 km/s, which is quite close to the shock wave experiment results of 4.008 km/s. Other parameters under normal conditions are: shear modulus G=157.4 GPa, Young's modulus E=393.0 GPa, bulk modulus K=260.2 GPa, Lame coefficients =155.3, =157.4, Possion's rate =0.248.

The Effect of the Confinement Condition upon the Corner Effect in Cast TNT

LI Sheng-Cai, ZHAO Tong-Hu, FENG Chang-Gen

1998, 12(2): 156-159 . doi: 10.11858/gywlxb.1998.02.015

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Abstract:
In this paper, detonation wave corner-turning in cast TNT was studied by means of electric probe technique. The relative delay time of wave arrival in various directions was measured under different confinement condition. The results show that the relative delay time can be reduced by means of (1) using confinement material to raise the strength of the detonation wave in donor charge, and (2) using the initiation ability of the shock wave in confinement material.

1998 Vol. 12, No. 2

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