高压物理学报

A New Thermodynamic Model for the Shock Compression Behavior Prediction for Porous Materials

WU Qiang, JING Fu-Qian

1996, 10(1): 1-5 . doi: 10.11858/gywlxb.1996.01.001

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Abstract:
Assuming that the specific heat at constant pressure cP is simply dependent on the pressure or remains constant, a new thermodynamic equation of state (EOS) is derived in this paper, which is very useful for the EOS studies, particularly in isobaric plane. Combining with Rankine-Hugoniot relations, our new EOS can be used to deduce the relation between porous Hugoniot and the solid one. Consequently, once the solid Hugoniot is known, this model can predict the Hugoniot behavior of materials with different initial porosities. In order to verify the validity of this model calculations are carried out for porous 2024 aluminum, copper and tungsten with different initial densities. Comparison with the corresponding experimental data demonstrates that this model has high accuracy in prediction of Hugoniots for porous materials in a wide pressure range.

Pressure Effect on the Critical Temperature of HgBa2Ca2Cu3O8+y

HAN Cui-Ying, SHAO Hui-Min, LIN Wei, SONG Wei, JIA Shun-Lian, YAO Xi-Xian

1996, 10(1): 6-11 . doi: 10.11858/gywlxb.1996.01.002

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Abstract:
The critical temperature Tc of the superconductor HgBa2Ca2Cu3O8+y (Hg-1223) sample is determined by four probe resistivity measurements under quasi-hydrostatic pressure up to 7.8 GPa. Tc increases from 130K at ambient pressure to 141 K under a pressure up to 5.4 GPa. dTc/dp=1.85 K/GPa at pressures below 5.4 GPa. The moving of some oxygen atoms and the coupling between CuO2 planes were used to analyzed the pressure effect on Tc of the high Tc superconductors.

The Preparation and Electron Spin Resonance Study of NiFe2O4 Nanosolids under High Pressure

SUI Yu, ZHENG Fan-Lei, XU Da-Peng, SU Wen-Hui

1996, 10(1): 12-18 . doi: 10.11858/gywlxb.1996.01.003

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Abstract:
In the present paper, the NiFe2O4 nanoparticles which were synthesized by the method of reserve drop coprecipitation, then compacted into nanosolids under different pressures. The variation of structure and interfacial states in NiFe2O4 nanosolids under different pressures are studied by XRD and ESR measurement for the first time. The experimental results indicate that, the structure of nanosolids has not changed obviously under the pressure up to 6.0 GPa; but the linewidth and g-factor values of their ESR spectra would increase significantly with increasing pressure up to 4.5 GPa and then turn to decrease under higher pressures. These variations could be interpreted by the change of magnetic interaction in the NiFe2O4 nanosolids under different pressures. These experimental results suggest that 4.5 GPa is the best forming pressure, under which the NiFe2O4 nanoparticles can be compacted into densest solid but their structure and nano-properties have not been destroyed.

- Phase Transition under Pressure, Constant Magnetic Permeability and Its Pressure as Well as Frequency Characteristic in Nanometer-Scale Powder of Invar Alloy

SU Fang, XIE Bin, CHEN Yun-Hong

1996, 10(1): 19-29 . doi: 10.11858/gywlxb.1996.01.004

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Abstract:
By means of evaporation and condensation, three kinds of nanometer-scale powder of invar alloy (Fe-30wt%Ni) were prepared. It is found out with the method of TEM and X-ray diffraction that their composition coincides with its matrix alloy, average grain size is 13.6 nm (powder 5T) and 27 nm (powder 5H) and 40 nm (powder 3K). Under room temperature and hydrostatic pressure of 43~28 different magnitudes ranging from 0.000 1 to 2.205 GPa, the magnetization curve and initial magnetization curve were measured to see their relation with pressure. The authors point out: (1) the three kinds of nanometer-scale powder of invar alloy (Fe-30wt%Ni) all possess constant magnetic permeability when H＝(20－132)(1000/4)A/m; (2) constant magnetic permeability, r varies with the pressure as follows: r＝3.83+0.253p-0.022 1p2-0.007 22p3, r＝3.93+1.20p-1.97p2+1.52p3-0.510p4+0.059 9p5, r＝5.96-0.276p+0.107p2-0.045 9p3 , r of powder 5T and 5H rises, but r of powder 3K decreases when pressure increases; (3) - Martensite phase transition under high pressure exists obviously in ultramicron 5H and 5T, but not in ultramicron 3K; (4) i of Fe-30wt%Ni alloy piece decreases in one order of magnitude in the frequency range from 200 kHz to 2 MHz, but when frequency range for their ultramicrons is over 30 MHz, the value of i does not decrease greatly so its frequency range extents two orders of magnitude as compared with its piece.

Synthesis Diamond of Perfect Cubic Morphology

LUO Jun-Yi, DING Li-Ye, LUO Xiang-Jie, CHEN Jiang-Hua, SUN Zhu-Mei, FU You-Kun

1996, 10(1): 30-36 . doi: 10.11858/gywlxb.1996.01.005

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Abstract:
Based upon the pre-study of relation between morphology and temperature in Ni70Mn25Co5-carbon system, synthesizing methods and growing rules of diamond have been studied experimentally by controlling the change of pressure and temperature in quasi-static way, in order that the regarded seeds of spontaneous crystals would grow epitaxially into perfect cubic morphology. The work is useful both theoretically and practically for the synthesizing of large form diamond crystals as heat-sink material by the reconstitution method.

TEM Observation of Shear Bands in Ti-6Al-4V and AISI 6140 Steel

HU Ba-Yi, DONG Qing-Dong, HAN Chang-Sheng, ZHANG Hai-Ping

1996, 10(1): 37-43 . doi: 10.11858/gywlxb.1996.01.006

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Abstract:
The fragments contained adiabatic shear band (ASB) in Ti-6Al-4V and AISI 6140 steel were studied by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show the structure of shear bands in Ti-6Al-4V and AISI 6140 steel being microgranular with average diameter less than 0.3 m. The granula exhibit some preferred orientation, its electron diffraction patterns appear some discontinous rings. The dislocation density is very low in the ASB; adjacent matrix granulas are highly dislocated. No evidence of a phase transformation within the ASB is observed.

Numerical Simulation of the Temperature Distribution on a Tank Wall under an Intensive Laser Loading

ZHAO Jian-Heng, ZHANG Guan-Ren, LIU Xu-Fa

1996, 10(1): 44-49 . doi: 10.11858/gywlxb.1996.01.007

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Abstract:
A numerical model is presented to simulate the temperature distribution on the tank wall under an intensive laser loading. Thermal property parameters varying with temperature are included and the effect of the variation of the temperature distribution is studied in this paper.

Metallic Transitions in Several Kinds of Semiconductors at High Pressure

BAO Zhong-Xing, Tu C S, Anderson J R, Schmidt V H, Pinto N J

1996, 10(1): 50-55 . doi: 10.11858/gywlxb.1996.01.008

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Abstract:
Resistance-pressure (R-p) relationships in InP0.97As0.03, InP0.5As0.5, Ga0.76In0.24As and Ga0.24In0.76As at room temperature at high pressure have been studied in a diamond anvil cell using resistance measurement. Experimental results indicate that these samples all undergo metallic transitions in the measured pressure range, and their transition pressures are about 10.3, 9.7, 13.5~14.6 and 10~10.4 GPa, respectively. Some improvements were made on the measurement techniques.

Effects of Additive Li8SiN4 on cBN Crystal Morphology

ZHOU Yan-Ping, YAN Xue-Wei, MA Xian-Feng, ZHAO Ting-He, XIE Yun-Fen

1996, 10(1): 56-62 . doi: 10.11858/gywlxb.1996.01.009

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Abstract:
After adding Li8SiN4 into the catalytic system of Li-complex borom nitrides, the glossy transparent cBN brown crystals were synthesized under the conditions of high pressure and high temperature in the range 4.5～5.0 GPa and 1 500～1 800 ℃ respectively. The morphology of cBN crystals is studied. The result shows that the percentage of blocky cBN crystals synthesized with Li8SiN4 increases obviously, and except the partial tuncated tetragonal crystals, the most of them are tuncated octahedral crystals. The edges and corners of cBN crystals are accurate and sharp, and surfaces of them are dense and smooth.

Studies on Impact Fracture Toughness of Composite Materials PP/AT

DAI Lan-Hong

1996, 10(1): 63-68 . doi: 10.11858/gywlxb.1996.01.010

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Abstract:
Impact fracture toughness of composite materials PP/AT with packing particle AT: 0, 10wt%, 15wt%, 20wt%, 30wt% and 40wt% is studied by means of Charpy impact testing machine respectively. Results demonstrate that adding AT can increase fracture toughness of PP/AT under a certain range of AT fraction, and the best fraction is between 20wt% and 30wt%.

Mechanism of Sintering Clinopyroxene Solid Solution CaMgSi2O6-NaAlSi2O6

ZHAO Ting-He, MA Xian-Feng, YAN Xue-Wei, CUI Shuo-Jing

1996, 10(1): 69-75 . doi: 10.11858/gywlxb.1996.01.011

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Abstract:
The effects of variation of the temperature and pressure on the nucleation and crystal growth of penetrating fibrous grains of sintered polycrystalline CaMgSi2O6(Di)-NaAlSi2O6(Jd) have been investigated. A more distinct effect of the pressure appears on the crystallization of DiJd at the lower temperature than at the higher temperature. On the contrary, the pressure has a much more effect on the growth and texture of penetrating fibrous grains of DiJd at the gigher temperature than at the lower temperature. The grains of DiJd synthesized under the higher pressure are stronger, and more ordered and compact than that synthesized under the lower pressure. The critical temperatures of nucleation and growth of DiJd are increased with the elevated pressure. And the maximum rates of nucleation and growth are also increased and moved toward the high temperature with the elevated pressure.

Observation on Original Crystals of hBN and cBN by EMS

ZHANG Tie-Chen, YU San, GUO Wei-Li, LIU Jian-Ting, ZOU Guang-Tian, LI Dong-Mei

1996, 10(1): 76-80 . doi: 10.11858/gywlxb.1996.01.012

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Abstract:
In the paper, the original products of hBN-catalyst system after treatments under high pressure and high temperature were observed by EMS. hBN and cBN phases were determined by method of electron diffraction. The results show that self-structure of these crystals is already formed in size 200～300 nm. However, characteristic morphology of the crystals does not appear. We guess that the crystals are in original growth. We also deduce that the size of the critical grain of the crystals is about 100 nm.

1996 Vol. 10, No. 1

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