高压物理学报

High Pressure X-Ray Study on NiO Isothermal Equation of State up to 50 GPa

YANG Hai-Bin, LI Ming-Hui, WANG Li-Zhong, ZOU Guang-Tian

1990, 4(4): 241-245 . doi: 10.11858/gywlxb.1990.04.001

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Abstract:
The isothermal compression behavior of NiO was studied using the in-situ high pressure X-ray diffraction method with the diamond anvil cell up to 50 GPa. The Murnaghan equation of state for NiO was used to fit the experimental data with the least square method, and the equation parameters are: B0=223 GPa, B0'=4.21. The pressure dependence of the ratio c/a of NiO indexed by hexagonal lattice can be expressed approximately as c/a=2.450~1.56910-3(GPa) in the range of our experimental pressures. No phase transition was observed under high pressure and room temperature in present experiment.

The Influences of Cool- and Hot-Pressure Treatment on the Phase Transition and Superconductivity of YBa2Cu3O7-

SUN Bao-Quan, WANG Yi-Feng, LIU Hong-Jian, LI Li-Ping, SU Wen-Hui

1990, 4(4): 246-253 . doi: 10.11858/gywlxb.1990.04.002

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Abstract:
In this paper, the influence of cool- and hot-pressure treatment were studied on the phase transition region from or thorhombic to tetragonal and superconductivity in YBa2Cu3O7-. After the cool pressure treatment of 2.2~5.2 GPa, the samples remained the orthorhombic structure, but lost their superconductivities and kept up the semiconductivity in the region from 98 K to room temperature. If the samples are sintered in air, their zero resistance states will be regained. When the samples were sealed hermetically into a Cu bowl, there was no separation of Cu in the samples within the region of hot-pressure temperature from 250 ℃ up to 950 ℃. After the hot-pressure treatment (2.2 GPa, 250~950 ℃), the samples were in semiconductiviting state in the region of 98 K to room temperature. If the samples are followed by an after-treatment in oxygen, the zero resistance state can be observed (at about 86 K). In the process of hot-pressure treatment, it was found that the transition region of orthorhombic to tetragonal is in the 450~950 ℃, 950 ℃ is the end temperature of transition, which is higher than that of samples obtained by sintering in oxygen, air, nitrogen and vacuum. And about 400 ℃ is the onset temperature of transition, which is lower than that in nitrogen, air and oxygen. Therefore the phase transition region is widened, and the end temperature of T0-t raises. These are related to that the Cu bowl restrains the reduction role under high pressure. If the quenching rate under high pressure is slowed (102 ℃/s), or the samples are followed by an after-treatment in O2, the YBa2Cu3O7- both with high density and Tc can be obtained. The deficiency and hole of oxygen are also discussed here.

Pressure Dependence of Crystallization Temperature of a Silica Contained Oxide Ionic Glass

SHEN Zhong-Yi, CHEN Li-Quan, ZHANG Yun, YIN Xiu-Jun, LIU Yong, WANG Chao-Ying, Cros C

1990, 4(4): 254-258 . doi: 10.11858/gywlxb.1990.04.003

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Abstract:
The crystallization behavior of amorphous lithium ionic conductor 0.3Li2O-0.67SiO2-0.03V2O5 has been studied under ambient and high pressures. There were two steps for the crystallization of the amorphous material. Li2Si2O5 was formed in the first step at 560 ℃ under ambient pressure while the precipitation of SiO2 occurred in the second one. The temperature of the first crystallization step Tx1 was greatly influenced by pressure. With the increasing pressure, it increased from 560 ℃ at ambient pressure to 620 ℃, the maximum, at 0.3 GPa and then dropped sharply to 528 ℃ at 0.4 GPa. After that Tx1 increased gradually with a rate of 29 ℃/GPa up to 2 GPa, the highest pressure applied. An explanation will also be given.

Perimeter-Area Relation of Fractal Island

LONG Qi-Wei

1990, 4(4): 259-262 . doi: 10.11858/gywlxb.1990.04.004

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Abstract:
The relationship of perimeter with area (P/A relation) of fractal island is discussed. It is shown that Mandelbrot's fractal relation between Koch perimeter and area does not hold in the island with finite self-similar generations. This might be the reason why the fractal dimension measured with P/A relation varied with the length of yardstick in previous work.

Effect of Hydrostatic Pressure on Lithium Ionic Conductivity in Amorphous Li+ Conductor

SU Fang, XU Wei, SU Jun

1990, 4(4): 263-269 . doi: 10.11858/gywlxb.1990.04.005

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Abstract:
Ionic conductivity and activation volume of the bulk piece and powder of amorphous lithium ionic conductor B2O3-0.7Li2O-0.7LiCl-0.10Al2O3 were investigated in the hydrostatic pressure range from 0 to 2.21 GPa. For the hydrostatic pressure dependence of ionic conductivity of the bulk piece, a preliminary microscopic explanation was given by considering the physical picture of ionic transport passages. Effect of hydrostatic pressure on ionic conductivity of the amorphous powder consists of three changes in bulk-conductivity, contact-conductivity and boundary layer-conductivity with the same phase. Specially, the latter can increase the ionic conductivity 2.5~16 times. The experimental results show that there is a possibility of further enhancing the ionic conductivity for above material.

Studies on Synthesis and Heat Resistant Character of cBN Crystals with Different Colors

ZHANG Tie-Chen, XU Xiao-Wei, GUO Wei-Li, MA Wen-Jun, GUO Xue-Bin, ZOU Guang-Tian

1990, 4(4): 270-275 . doi: 10.11858/gywlxb.1990.04.006

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Abstract:
In this paper, three types of cBN crystals with different colors were obtained under high pressure and high temperature using hBN as starting material and Mg, Mg3N2 and Mg-Mg3N2 popwders as catalysts respectively. We analysed the properties of the cBN crystals with different colors by TG-DTA and high temperature oxidization experiments, and discussed the mechanism of heat resistant character.

Detonation Temperature for Hydrogen-Oxygen Mixtures Using Multi-wavelength Pyrometer

LI Zhao-Ning, HU Dong, SUN Zhu-Mei, WANG Gui-Chao

1990, 4(4): 276-283 . doi: 10.11858/gywlxb.1990.04.007

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Abstract:
A multi-wavelength method that can be used to measure the detonation temperature for hydrogen-oxygen mixture in shock tube was described in this paper, with the entire field of view of the receiving fibers either filled by the gases or not. To calculate transverse temperature and longitudinal temperature, the continuum radiation at four wavelengths (406.4, 540, 636, 835 nm) was measured by two ways, one was that the receiving fibers were vertical to the direction of detonation wave, and the other was that the receiving fibers were parallel to the direction of detonation wave. If Planck equation is assumed to be suitable for product gases and the emissivity of the gases is assumed to be gray for the above four wavelengths, the transverse and longitudinal temperatures for six hydrogen-oxygen mixtures were calculated in the initial pressure range 0.020~0.053 MPa and the fitting errors were about 10%. The transverse temperature coincides with the longitudinal temperature in the experimental errors and the temperatures also coincide with the theoretical C-J temperature very well.

The Structure and Luminescence Characters of SrSiO3:Eu3+Bi3+ Synthesized by High Pressure and High Temperature

LIU Hong-Jian, WANG Yi-Feng, YANG Jing-Hai, LI Li-Ping, SU Wen-Hui, GUAN Zhong-Su, YU Bao-Gui

1990, 4(4): 284-290 . doi: 10.11858/gywlxb.1990.04.008

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Abstract:
The SrSiO3:Eu3+Bi3+ samples were firstly synthesized by high-pressure (HP) and high-temperature (HT) method under 3.15 GPa and 1 200 ℃. Comparing with those prepared under atmosphere pressure, the structure of the samples and the influence of pressure and temperature on the luminescence properties has been studied. It shows that the structure of the samples synthesized by HP and HT is of monoclinic, while the samples prepared under atmosphere pressure is of hexagonal. At the same time, for the samples synthesized by HP and HT the intensity and quantum luminescence efficiency decreased obviously, the half-width was broadened and the red shift of emission peak was enlarged to 756 cm-1. The variation of the luminescence characters is due to the pressure-induced changes of crystal field interactions.

Investigation of the Explosive Consolidations of Al-Li Alloy and Al Powders

ZHANG Deng-Xia, MA Cheng-Hui, AI Bao-Ren, ZHANG Jin-Yuan, ZHU Rui-Zhen, LIU Chun-Lan

1990, 4(4): 291-299 . doi: 10.11858/gywlxb.1990.04.009

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Abstract:
In this paper, explosive consolidation was investigated for rapidly solidified Al-Li alloy and Al powders. The density, microstructures and fracture morphologies of the sintering compacts were examined. The Al-Li alloy powder was prepared by argon gas atomization. The Al powders were prepared by water or nitrogen gas atomization. The powder was packed in a container and the explosive, also in powder form, was contained in a concentrically placed cardboard tube. The explosive was initiated on one end. By proper selection of the explosive parameter, the 1770 mm (Al-Li alloy) and the 100100 mm (Al) sintering cylindrical compacts have been obtained. They are defect-free and the densities of powder compacts were over 98% T. D. The microstructures and fracture morphologies show that the inter-particle bonding occurs and the bonding region consists of ultrafine grain. In the interior of particle the inherent microstructures are still retained. It is shown that the velocity and internal diameter of container, the powder strength and the characteristics of surface oxide layer are important in determining the effectiveness of the joints sintered.

The Effect of Pretreatment of Graphite on Diamond Synthesis

TANG Gong-Ben, SHI Feng, SUN Wan-Ming, CUI Shuo-Jing, SHI Chang-Huai, XIE Yun-Fen, WANG Zeng-Lin, NI Jia-Zuan

1990, 4(4): 300-304 . doi: 10.11858/gywlxb.1990.04.010

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Abstract:
This paper reports the effect of pretreatment of graphite on the diamond growth. Big size diamonds of good quality were synthesized, in which the inclusions of Ni, Mn, Co, Si were reduced and N content increased. It was found that the diamond grew on both side of catalytic disks. The pretreatment method not only improved the quality of diamond, but also might provide basis for understanding of the mechanism of graphite transformation to diamond.

1990 Vol. 4, No. 4

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