高压物理学报

Study of Phase Composition of a Siilcon Nitride (Si3N4)-Rare-Earth Oxide Ceramic Sintered under High Pressures

SHEN Zhong-Yi, SUN Ji-Rong, LIU Shi-Chao, LIU Yong, HUANG Zhen-Kun, SUN Wei-Ying

1993, 7(1): 1-10 . doi: 10.11858/gywlxb.1993.01.001

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Abstract:
The phase compositions of silicon nitride-rare-earth oxide ceramic (3-Si3N4+0.5La2O3+0.5Pr6O11 (mol.%)) sintered in a pressure range from 5 to 7 GPa, temperature from 600 ℃ to 1 800 ℃ has been studied by X-ray diffraction and SEM observation. The observed results show that the phase forming rule at high p-T is different from that of Si3N4-Al2O3-AlN system. Under high pressure and below 1 600 ℃, the sintering products are mixture of Si3N4 and the polymorphs of the rare-earth oxides. Si3N4 remains -structure even when certain amount of rare earth oxides has dissolved in. when the temperature exceeds 1 600 ℃ and pressure is above 6 GPa, a new single phase belonging to orthorhombic system is formed with lattice parameters a=1.298 3 nm, b=0.814 0 nm, c=0.428 5 nm.

Two Kinds of Different Effect of Pressure on Magnetism in Amorphous Alloys with Fe-Base

SU Fang, SU Jun, XU Wei

1993, 7(1): 11-22 . doi: 10.11858/gywlxb.1993.01.002

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Abstract:
The paper introduces in detail the experimental method to measure the saturation intensity of magnetization Bs and the maximum magnetic permeability max of amorphous alloy under hydrostatic pressures from 0.000 1 to 2.3 GPa. The results show that Bs and max of three amorphous alloys are different from each other, can be classified into two kinds. (1) The first kind of pressure effect on magnetism: general trendBs decreases when pressure increases, but in some pressure ranges Bs presents an anomalous rise, such as even decrease of Bs in amorphous alloy Fe75Ni5Si5B15, drop-rise-drop again of Bs in amorphous alloy (Fe0.85Co0.15)Cu0.4Si4.4B13.2. (2) The second kind of pressure effect on magnetism: Both Bs and max of amorphous alloy Fe78.75Cu1.25Si5B15 rise weakly when pressure increases. This is a new result. Respectively we discussed (1) and (2) by exchange-role theory of located electron-mode and rigid band theory of itinerant electron mode.

Studies of Dynamic Damage Behavior in LY12 Aluminum Alloy under the Condition of High Loading Rate

WANG Ze-Ping, HUANG Feng-Lei, DING Jing, HOU Min

1993, 7(1): 23-32 . doi: 10.11858/gywlxb.1993.01.003

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Abstract:
A new ductile dynamic failure model, based on a porous element consisting of a single spherical void of radius a in a sphere of radius b subjected to internal pressure pg and external stress r=-p+(-1)pg is developed in this paper. Work-hardening, rate-dependent contribution and inertial effects are considered in the model. Stress controlling mechanism is adopted while considering the contribution of void nucleation to rate of porosity . The mathematical model presented here is incorporated in a hydrodynamic two dimensional finite-difference computer code, to simulate two dimensional spallation of LY12 aluminum alloy. Comparison of numerical calculation with experimental results shows that the model described the process of spall experiment successfully. The future improvement of the model is discussed.

Effect of Pressure on the Superconducting Transition Temperature of the Single Phase Bi-Pb-Sr-Ca-Cu-O Sample with Tc=110 K

HAN Shun-Hui, DAI Xiang, CHEN Qi, HAN Han, ZHI Jin-Biao

1993, 7(1): 33-36 . doi: 10.11858/gywlxb.1993.01.004

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Abstract:
Measurements have been made on the electrical resistance of single phase Bi-Pb-Sr-Ca-Cu-O samples with superconducting onset temperature Tcon=110 K and final temperature Tcfi=106 K, under hydrostatic pressures up to 1 GPa and temperatures from 80 to 300 K. An increase in Tc with pressure, at a rate of dTc/dp=2 K/GPa, and a constant slope of (1/R(300 K)) under different pressures, were observed. A possible explanation for the pressure behavior is presented.

Study on quasicrystal Formation and Stability of Al65Co20Mn15 by Quenching under High Static Pressure

YU Ri-Cheng, XU Da-Peng, SU Wen-Hui, LIU Wei-Na, GE Zhong-Jiu, PANG Yan-Xin, TENG Qi-Fa, CHU Shu-Cheng

1993, 7(1): 37-41 . doi: 10.11858/gywlxb.1993.01.005

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Abstract:
In this paper, by using a method of quenching at fusing state under high static pressure, the formation of quasicrystal in Al65Co20Mn15 alloy has been investigated for the first time. X-ray and electron diffraction patterns have been observed and the stability of quasicrystal has been studied.

Study on the Curves of Melting Temperature Pressure of Al, Cu and Pb

ZHENG Wei-Tao, ZHANG Rui-Lin

1993, 7(1): 42-46 . doi: 10.11858/gywlxb.1993.01.006

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Abstract:
Based on the universal equation of state (UEOS) at temperature T proposed by Vinet et al., combined with Guina's melting model for metal, the method of calculating the curves of melting temperature-pressure for metals is given, and it is applied to the calculation of typical metals Al, Cu and Pb. The calculated results are in good agreement with experiments.

Relativistic Modification of TF Model

SUN Jiu-Xun

1993, 7(1): 47-53 . doi: 10.11858/gywlxb.1993.01.007

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Abstract:
In this paper, we take the relativistic energy moment relation instead of the classical one and get the modified TF equation, and then expand the modified formula at low temperature. We applied this formula to calculated U92 and compared with that of the unmodified.

Studies of the Influence of Nitrogen or Argon on OH, O2 Emission under High Temperature and High Pressure by Spectrographic Method

HU Dong, WANG Yong-Guo, LIU Cai-Xue, SUN Zhu-Mei

1993, 7(1): 54-60 . doi: 10.11858/gywlxb.1993.01.008

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Abstract:
The behavior of OH, O2 in the process of the reaction for hydrogen are successfully studied by using improved prism spectrograph. The results show that nitrogen and argon which are as third bodies can get energy from free-atoms and radicals, thus decrease the OH emission; but certain argon atoms may increases the OH emission. The measurements using improved prism spectrograph found that O2 emission always delays the OH emission which directly proves that O2 may be excited after the stop of reaction for the chain. Both OH emission and induction time are observed under the excitation of incident wave and reflection wave. The technique for improved prism spectrograph can be used to study emission behavior under excitation by shock wave or high temperature-high pressure generated by high speed reaction.

Spallation of Aluminum Targets Irradiated by Pulsed Laser Beam

ZHUANG Shi-Ming, WANG Chun-Yan, LUO Fu, SUN Cheng-Wei

1993, 7(1): 61-65 . doi: 10.11858/gywlxb.1993.01.009

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Abstract:
The experiments on spallation of aluminum targets irradiated by the Nd: glass laser beam with 4 ns FWHM and flux of (2~5)1011 W/cm2 are reported in this paper. The spall occurred under the supercritical condition, and the spall thicknesses of 0.1 mm and 0.2 mm thick aluminum target are (176) m and (355) m respectively. The threshold spall thickness as a function of target thickness has been estimated for the laser induced shock loading with the strain rate over 107 s-1, and the spall strength of aluminum can reach up to 5~6 GPa at such ultrahigh strain rate.

The Relationships between Thermal Conductivity and Pressure for Alkali Halide Crystals

YAN Zu-Tong

1993, 7(1): 66-70 . doi: 10.11858/gywlxb.1993.01.010

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Abstract:
In this paper, we point out that the expirical equation for the relationships between thermal conductivity and pressure p: =A+Bp or =A+Bp+Cp2, can be derived from the definition of Bridgman parameter: g=-(d ln/dlnV)T and Tait equation: V/V0=ln(1+p)/. The calculated results is in a very suitable agreement with the experimental results.

Studies of Structure Phase Transition of Pb by Pseudopotential Method

ZHAO Min, SUN Feng-Guo

1993, 7(1): 71-74 . doi: 10.11858/gywlxb.1993.01.011

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Abstract:
Using pseudopotential method, we calculated the crystal energy of Pb with fcc structure and diamond structure. The stability of both structures at high pressure was discussed.

Electronic Structure of TiB2 under High Pressures

WANG Xiao-Bing, TIAN De-Cheng

1993, 7(1): 75-80 . doi: 10.11858/gywlxb.1993.01.012

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Abstract:
The electronic structures of TiB2 in compression have been calculated by using the self-consistent LMTO-ASA method. All the relativistic effects except spin-orbit coupling are considered. The results indicate that as the degree of compression increases, Ti-B hybridization is enhanced and another pseudogap or deep valley in the electronic structure appears. This pseudogap is connected with the increased cohesion of crystal under high pressure. Charge transfer from Ti to B decreases with increase of compression, though this effect is insignificant within the compression range considered.

1993 Vol. 7, No. 1

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