高压物理学报

The High Pressure Conlidation and Magnetism of Amorphous Fe40Ni38Mo4B18 (2826MB) Powder

LIU Yong, SHEN Zhong-Yi, YIN Xiu-Jun, ZHANG Yun, ZHAO Jian-Gao

1988, 2(4): 289-295 . doi: 10.11858/gywlxb.1988.04.001

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Abstract:
The feasibility to prepare the glassy alloy bulk was investigated by consolidating amorphous soft-magnetic Fe40Ni38Mo4B18 powder under high pressure and at elevated temperatures. The dependence of consolidating pressure and temperature on soft-magnetic properties of the pressed samples were examined by measuring the comples permeability instead of the magnetic field. The experimental results show that the compacting temperature has more effect on the magnetic properties in comparison to the pressure within the range of the experiments.

A Study on the High Temperature-High Pressure Stability and the X-Ray Phase Analysis for Compounds R2Fe4/3W2/3O7 with Pyrochlore Structure

WANG Yi-Feng, SU Wen-Hui, QIAN Zheng-Nan, MA Xian-Feng, YAN Xue-Wei

1988, 2(4): 296-304 . doi: 10.11858/gywlxb.1988.04.002

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Abstract:
The compounds R2Fe4/3W2/3O7 (R=Er, Yb, Dy) treated with high temperature-high pressure have been studied by X-ray diffraction and PSPC. It is found that under the condition of 3.7 GPa and 1 200 ℃, the compounds with hexagonal pyrochlore structure synthesized under atmospheric pressure and high temperature and decompose into a polyphase compound system (R2WO6, RFeO3, WO3 and Fe2O3). It is also found that under the condition of same high temperature but high pressure, the mixture of R2O3, Fe2O3 and WO3 composed to same polyphase compound system too. The stable zone of compound R2Fe4/3W2/3O7 under high pressure is described in this paper.

Numerical Analysis for Dynamic Damage Processes and LY-12 Aluminum Spallations

DONG Yu-Bin, ZAHNG Wan-Jia, JING Fu-Qian, HAN Jun-Wan, CHEN Da-Nian, SU Lin-Xiang, FENG Jia-Bo

1988, 2(4): 305-312 . doi: 10.11858/gywlxb.1988.04.003

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Abstract:
In Ref.[1], a damage-level function is proposed for analyzing the dynamic fracture processes of expanding cylindrical shell. In this paper, we extend the model to the case of planar geometry and perform numerical simulation for the dynamic damage processes under uniaxial strain case. The studied material is LY-12 aluminum and a kind of constitutive equation with viscous effect is utilized. The calculated free-surface velocity versue time relation is consistent with the experimental results. The calculated results also indicate that the spall strength c and the critical damage-level at fracture plane, c, are both monotone increase function of strain rate c', respectively. This kind of c~c' relation has been reported in many other articles, for example in Ref.[2-3]. The relation c~c' can be expressed as c'exp(-11.4c)=2 100 s-1 in the strain -rate range from 105 s-1 to 106 s-1. We think this expression could be used as a kind of spall criterion. The damage-level profiles in the spalled layer are also given from the numerical results, and the specific feature of the profiles is qualitatively in accord with that of the micro-photographic results from recovery specimens reported by Barbee, et al.

Effect of Pressure on Electrical Resistance of Ten Rare-Earth Metals

DONG Wei-Yi, LIN Ze-Shou, DENG Ke-Jun

1988, 2(4): 313-318 . doi: 10.11858/gywlxb.1988.04.004

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Abstract:
The pressure equipment used in this investigation was a Drickamer-type apparatus with sintered diamond compacts. The pressure calibration was established by using p vs. (L. Go) calibration diagram. The electrical resistance behavior of ten rare-earth metals (Pr, Nd, Sm, Gd, Tb, Dy, Ho, Tm, Lu and Yb) was studied under high pressure up to 43 GPa and at room temperature. Some kinks and slope changes are found on the resistance vs. pressure curves and many of them are first experimentally discovered, which are perhaps related to the hcpSm-typedhcpfcc phase transitions. These new phase transition pressure are 14.0 GPa for Lu from hcp-Sm-type, 7.0 GPa for Gd, 12.0 GPa for Tb, 12.5 GPa for Dy, 13.0 GPa for Ho, 17.5 GPa for Tm, and 26.0 GPa for Lu from Sm-type to dhcp, 12.0 GPa for Sm, 17.5 GPa for Gd, 18.0 GPa for Tb, 22.0 GPa for Dy, 24.0 GPa for Ho, and 31.0 GPa for Tm from dhcp to fcc, respectively. For Gd and Tb there is a slope change on each R vs p curve at 22.0 and 24.5 GPa respectively. We believe that these two changes are associated with the phase transition from fcc to a new phase, dfcc, three slope changes at 14.5, 18.6 and 25.0 GPa are also found for Yb. The first change is related to valence change from divalent to trivalent, which is in agreement with the value calculated by Johansson et al. The second and the third changes should indicate hcp to Sm-type and Sm-type to dhcp transitions respectively.

Investigation on Superconductivity of Metallic Hydrogen

PANG Xiao-Feng

1988, 2(4): 319-326 . doi: 10.11858/gywlxb.1988.04.005

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Abstract:
The strong-coupling superconductivity theory has been used to study the superconductivity of metallic hydrogen in this paper. As a result, the values of the isotope effect, the thermodynamic critical magnetic field and the specific heat as well as the relationship between the functional derivatives of Tc, Hc and with respect to effective phonon spectrum 2F() with have been obtained. The relation between some parameters of superconductivity and the electron-photon interactions is also illustrated.

Lateral Unstability of a Jet Produced by Shaped Charge

LI Mao-Sheng

1988, 2(4): 327-334 . doi: 10.11858/gywlxb.1988.04.006

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Abstract:
Based on the gas dynamics with lateral gas-solid two phase flow and the stability analysis to the vibrating elastic-plastic bar, the vibration phenomenon during jet penetration could be explained in this paper.

A Diamond Anvil Cell with External Heater and Pressure Measurement by Using Ruby at High Temperature

WANG Li-Jun, HU Jing-Zhu, CHE Rong-Zheng, TANG Ru-Ming, CHEN Liang-Chen

1988, 2(4): 335-339 . doi: 10.11858/gywlxb.1988.04.007

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Abstract:
The techniques of diamond anvil cell used in our laboratory with external heater under high pressure and high temperature are described in this paper. The pressure and the temperature can be up to 20 GPa and 350 ℃, respectively. The high pressure phase of LiIO3, phase has been determined in situ by using X-ray diffraction analysis in this device. The pressure measurement with ruby at high temperature in this device is discussed. According to the LiIO3 data of X-ray diffraction analysis, it is shown that the dropping part of p-T curve is corresponding to the occurrence of to phase transition of LiIO3 under high pressure and high temperature. We suppose that one can estimate the phase transition temperature and pressure as well as the decreasing value of pressure caused by phase transition from p-T curve for some materials.

An Improvement on Resistance Measuring Technique of Insulant under Shock Compression

GU Cheng-Gang, XIE Pan-Hai, WANG Jin-Gui, JING Fu-Qian

1988, 2(4): 340-345 . doi: 10.11858/gywlxb.1988.04.008

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Abstract:
An improvement technique, in comparison with that of the Mitchell, et al, on measuring the resistance of insulant under shock compression is proposed in this paper. The main point of the improvement is adding a circuit branch with an etalon resistance connected in series in it, for monitoring the shock-wave arrival time entering the sample, in the measuring electrical circuit. Advantages of the improvement are: (1) it is in favor of enhancing the sample resistance signal magnitude, or extending the upper measurable emits of the sample resistance; (2) the etalon resistance could be used to check the measured value of the sample resistance; and (3) the shock velocities in the sample were obtained simultaneously. A measurement of Teflon specimen is given as an example. A brief discussion of the characteristics of the improvement is given.

Flash X-Ray Radiographic Image Restoration by Wiener Filter Method

LIU Rui-Gen, WU Shi-Fa

1988, 2(4): 346-353 . doi: 10.11858/gywlxb.1988.04.009

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Abstract:
Some blurred images taken by a flash X-ray system have been restored successfully. A radiography model is built by the approximation of LSI system. United PSF is presented to describe the blur effect of the system and measured by pinhole or step sample experiment successfully. Before calculation, some pre-processing is necessary for giving a good result, which includes the adjusting of nonlinear information and the weakening of various noises. Wiener filter method requires that the signal-to-noise ratio (SNR) of the blurred image can be lifted up to 30~50. If the blurred image is a section and without a blurred boundary, it is necessary to add a blurred boundary approximately. Let pn(u,v)/pf(u,v)k, result shows that the restoration is as good as that in the case pn(u,v)/pf(u,v) is accurate, so long as we select an appropriate k, k can be obtained by 1~2 times test. Generally k=0.1~0.001. A restoration result is given with k=0.002.

The Pressure Dependence of Ionic Conductivity of Amorphous Lithium Ionic Conductor

SU Fang, XU Wei

1988, 2(4): 354-359 . doi: 10.11858/gywlxb.1988.04.010

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Abstract:
The ionic conductivity and the activation volume of amorphous lithium ionic conductors B2O3-0.7Li2O-0.7LiCl-xAl2O3 (x=0.05 and 0.15) under pressure from the atmosphere to 0.80 GPa were investigated for the first time. It is found that their activation volumes have changed from negative to positive under a certain pressure. The first microcosmic explanation is given by the physics picture of the ionic transport passages. Moreover, the two kinds of specimen i. e., the whole large piece and the tablet of powder are compared; the effect of alumina content on the phase transformation pressure is discussed. The pressure relaxation has been observed, the ionic conductivity when unloading to the atmosphere increases by 10.4 times compared to the original one.

A High Sensitive Method of Differential Thermal Analysis DTA under High Pressure

ZHANG Yun, YIN Xiu-Jun, SHEN Zhong-Yi, LIU Yong, ZHOU Wei-Ya

1988, 2(4): 360-364 . doi: 10.11858/gywlxb.1988.04.011

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Abstract:
We set up a sensitive high pressure DTA measuring method on a piston-cylinder apparatus with 20 mm inner diameter. By repeated experiments and improvements, this method is proved to be enough sensitive and efficient. The main point of this method can be stated as follows: the sample capsule is made of a material which is used as one pole of a thermocouple and the wire of another pole is welded on the centre of the capsule. Such an arrangement to receive signals from the heat released. In this new sample assembly, as a result of much higher detecting efficiency, the quantity of sample can be reduced from several hundred milligrams to tens of milligram so the space being seized of the sample in pressure chamber is reduced to about 0.5 mm in the axial direction. For this reason the temperature homogeneity in the sample is essentially improved and the baseline of DTA curve become basically flatted. By substitution of the plate thermocouple for the point junction form, the latent heat on transition is received far more sufficiently and the differential thermal signals are enhanced obviously. We have successfully distinguished very closely situated transition in high pressure phase diagram determination of ternary alloy systems by this method. Many experimental results on various substances show that present new assembly is rational instructure and possess a sensible and simple part arrangement.

1988 Vol. 2, No. 4

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