高压物理学报

Influence of Pressure-Transmitting Media on the Lattice Vibration and Phase Transition Pressure-High Pressure Raman Spectra Studies of -Bi2O3

LIU Zhen-Xian, CUI Qi-Liang, ZHAO Yong-Nian, ZOU Guang-Tian

1990, 4(2): 81-86 . doi: 10.11858/gywlxb.1990.02.001

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Abstract:
High pressure Raman spectra of -Bi2O3 were measured by using a 4∶1 methanol-ehanol mixture and solid argon as pressure-transmitting media respectively. The experimental results show that the shift rates of Raman lines in the sample are distinctly affected by the pressure-transmitting media. We firmly believed that -Bi2O3 probably undergoes a structural phase transition. The phase transition pressure are 23.1 GPa and 20.4 GPa under quasi-hydrostatic condition and nonhydrostatic condition respectively.

Undercooling of Liquid Bismuth and Formation of Bismuth-Ⅱ at Normal Pressure

QIN Zhi-Cheng, XU Xiao-Ping, WANG Zhao-Xing, CHEN Hong, WANG Wen-Kui

1990, 4(2): 87-90 . doi: 10.11858/gywlxb.1990.02.002

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Abstract:
This paper studied the undercooling of liquid bismuth and the formation possibility of bismuth-Ⅱ phase at normal pressure by using a high clean and containerless environment provided by a five meters long drop-tube and an alternate approach to heat and cool the molten bismuth in helium atmosphere. The two methods have allowed the ability of undercooling for liquid bismuth to be extended through controlling of the droplet size and cooling rate. The result of X-ray diffraction indicated that the undercooling samples have a monoclinic lattice with the lattice parameters a=0.696 8 nm, b=0.628 6 nm, c=0.339 7 nm and =110.33. To make a comparison between the volume of unite cell and that of the bismuth-Ⅱ (monoclinic lattice) obtained by Brugger at 2.6 GPa, the latter has a compression of 9.34% relative to the former, the result is in good agreement with Bridgman's.

The properties of Electrical Resistance in Cu100-xZrx Metallic Glasses System under Pressure Loading

HAN Shun-Hui, JIN Rong-Ying, SHEN Bao-Gen, HAN Han

1990, 4(2): 91-95 . doi: 10.11858/gywlxb.1990.02.003

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Abstract:
The pressure dependence of electric resistance for Cu100-xZrx (x=70, 75) metallic glasses has been measured under pressure from 0 to 0.8 GPa and at room temperature. In two samples, the pressure coefficients of resistance p are negative. The contribution of d-wave phase shift 2(EF) under pressure loading to p are calculated and discussed with the measured value of p and generalized Ziman theory.

The Change of Metal Inclusions and Its Influence on the Strength of Synthetic Diamond

DING Li-Ye, CHEN Jiang-Hua, WEI Xiao-Li

1990, 4(2): 96-104 . doi: 10.11858/gywlxb.1990.02.004

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Abstract:
At a temperature of about 1 000 ℃, larger defect areas in the crystal lattice of synthetic diamond will be formed with changes in the shape, in the composition and in the structure of metal inclusion. So it is the basic cause of the strength loss of synthetic diamonds heated at high temperatures. The size of defect areas increases with changes above. To a series of synthetic diamond samples-heated at different temperatures and in argon atmosphere, strength values have been measured. All the results supported the conclusion above. It was also supported that the heating stability of synthetic diamond is strongly influenced by metal inclusions which make it easier for diamond to return to graphite at a lower temperature of about 1 000 ℃.

Experimental on Sintering Diamond with Direct Bonding between Diamond Particles

HONG Shi-Ming, LUO Xiang-Jie, CHEN Shu-Xin, JIANG Ren-Zhu, GOU Qing-Quan

1990, 4(2): 105-113 . doi: 10.11858/gywlxb.1990.02.005

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Abstract:
Diamond powder was placed on the pure Ni or alloy Ni70Mn25Co5 substrate and held at high pressure of 6.3 GPa and high temperature of 1 440 to 1 650 ℃ for 3 to 40 minutes. Composition and microstructure of the sintering diamond were studied by the scanning electron microscopy, X-ray diffraction and Raman spectroscopy. It was observed clearly that the continuous phase between diamond particles was produced extensively in the region where metal was filtrated sufficient. No carbide or graphite was detected in that region and other places. Homogeneous and compact microstructure with the continuous phase between diamond particles was observed in all the sample with the size of 7 mm2 mm, which was sintered using diamond powder with the grain size of 7 to 14 m and the Ni70Mn25Co5 alloy as a substrate.

Measurement of the Vaporization Pressure on Aluminum Target Irradiated by Laser Beam

YUAN Yong-Hua, LIU Chang-Ling, HAN Li-Shi, GUI Yuan-Zhen, LI Qi-Min

1990, 4(2): 114-117 . doi: 10.11858/gywlxb.1990.02.006

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Abstract:
The characteristics of aluminum target vapor expansion induced by the focused beam of neodymium-glass pulsed laser operated in the normal mode are investigated in this paper. Under laser flux about 10 MW/cm2, the Mach-dish characteristic parameters were measured by a time-integrated photo of the free jet, then the vapor pressure on target in the atmosphere is calculated. It is about 3.6 MPa. The time-integrated photo is compared with the high-speed photo of the free jet development, it is shown that the Mach-dish indeed occurred in the process of the target irradiated by the focused laser beam.

Uncertain Problem in Application of Fractal to Fracture Toughness

DONG Lian-Ke, WANG Xiao-Wei, WANG Ke-Gang, Lü Guo-Hao

1990, 4(2): 118-122 . doi: 10.11858/gywlxb.1990.02.007

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Abstract:
In this paper, we have introduced the geometrical criterion and physical criterion both of which have solved the uncertainties of fractal dimension and the value of yardstick based on the principle of consistency among physics, fractal and fracture mechanics. We have solved the uncertain problem in application of fractal to the fracture toughness. These viewpoints in this paper will have special meaning for applications of fractal to other fields.

Laser-Supported Detonation Waves in Metal Target Vapor

LIU Cheng-Hai, PEI Wen-Bing, YAN Jun, FAN Fu-Ru

1990, 4(2): 123-129 . doi: 10.11858/gywlxb.1990.02.008

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Abstract:
A physical model for laser metal-vapor interactions has been developed and used to study numerically the laser supported detonation waves (LSDWs) in vapor in front of metal targets, and some good results about LSDWs, such as ignition mechanism, threshold, propagation law and so on, have been obtained numerically with the model. A power law between LSDWs threshold and laser pulse duration, Ith-1/2, has been obtained. Some useful results about the LSDWs shield effects have also been obtained. In the developing phase of LSDWs, the optical thickness of the front of LSDWs may reach 5~10 in order of magnitude. It is shown that the LSDWs are able to play a very strong shield role.

Calculation for the Thermal Stress Damage in the Thin Plate of Al Irradiated by CW Laser Beam

PENG Jian, ZHAO Yi-Jun, ZHANG Zheng-Wen, YUAN Jian-Min

1990, 4(2): 130-136 . doi: 10.11858/gywlxb.1990.02.009

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Abstract:
The parameters of the material of Al such as the thermal coupling coefficient conductivity, yield strength and so on, will change with the change of temperature induced by laser heating. It will influence the physical and mechanical properties of the material. The large thermal stress can result in the damage of the structure of material. Specially, in the case of the action of very large preload being present, the material structure can be yielded, deformed or fractured due to the action of the thermal stress and the preload, that is , the material structure may be damaged before the melt through of it. The damage effects of thermal stress in the thin plate of Al loaded induced by laser beam is calculated by using the method of finite element. The damage thresholds dependence on the preloads, laser power densities and wavelength are given out. The change of parameters mentioned above with the temperature is considered in the calculation. The results are in agreement with the experimental result given by Medford.

A Study on the Formation of Quasi-Crystal Al80Mn14Si6 under High Static Pressure

CHU Shu-Cheng, XU Da-Peng, SU Wen-Hui, ZHANG Qiang

1990, 4(2): 137-142 . doi: 10.11858/gywlxb.1990.02.010

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Abstract:
By using the method of quenching in fusing state under high static pressure (MQFSHP), the samples of Al80Mn14Si6 alloy rapidly quenched were gained under pressure of 2.8 and 3.1 GPa respectively. The quenched samples were examined by X-ray diffraction and electron diffraction. Results show that they contain icosahedra phase, non-crystal, intermediate metastable phase. After the quenched samples were heated to 350 ℃ maintained for 1 h, there occurred no detectable crystallization of Ⅰ-phase in them, but for the case of 500 ℃/h, the samples crystallized completely into a stable -Al73Si10Mn17. In this paper, the applicability of MQFSHP to the quasi-crystal formation has also been discussed.

The Electronic Structure of Metal Lithium at High Pressures

HUANG Chun-Jia

1990, 4(2): 143-149 . doi: 10.11858/gywlxb.1990.02.011

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Abstract:
This paper has evaluated the energy bands using the orthogonalized plane wave method and has calculated the density-of-states as well as the Fermi energy by the nearly free electron model for metal lithium at pressures of 0, 2, 4 GPa. The energy and the density-of-states in the region close to the Fermi surface rise evidently as the pressure increase. The higher the pressure, the more the Fermi surface is distorted from the sphere characteristic of the free electron.

Experimental Studies on the Dynamic Quasi-Isentropic Compression of Oxygen Free-Copper

DING Feng, HUANG Shi-Hui, JING Fu-Qian, DONG Yu-Bin, LI Ze-Ren

1990, 4(2): 150-156 . doi: 10.11858/gywlxb.1990.02.012

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Abstract:
The experiments of quasi-isentropic compression of oxygen free-copper were performed in a two-stage light gas gun by means of the composite flyer, in which the shock impedance increased from the impact surface to the rear interface. The impact velocity was 2.51 km/s. The compression time attained was about 1 s. Using the Lagrangian analysis technique a quasi-isentropic stress-strain relation of oxygen free-copper was obtained from the laser interferometric measurements of the free surface velocity histories on the different thickness specimens. The preliminary results show that quasi-isentrope is located above the Hugoniot at stress lower than 32 GPa, which is contrary to the expectation, and falls back below the Hugoniot at the stress higher than 32 GPa. The phenomenon, which was similar to the results of aluminum and tungsten reported by Barker and Chhabildas et al., was attributed to the furth increasing of dynamic strength of the specimen with the lower strain rate, arising from the quasi-isentropic compressing process, at low stresses, comparing with the shock-loading condition.

A New Measurement Technique for p-V Relationship

BAO Zhong-Xing, ZHANG Zhi-Ting

1990, 4(2): 157-160 . doi: 10.11858/gywlxb.1990.02.013

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Abstract:
The p-V relationships for Fe and Bi up to 4.5 GPa have been measured using a new measurement technique established by us. The experimental results showed that the accuracy of the p-V relationship measurement and the working efficiency can be increased by using the new measurement technique.

1990 Vol. 4, No. 2

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