高压物理学报

Effects of Pressure on the Recrystallized Graphite

HE Yi-Xing, HAO Zhao-Yin, WANG De-Rong, CHEN Yu-Fei

1992, 6(3): 161-168 . doi: 10.11858/gywlxb.1992.03.001

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Abstract:
Three sorts of recrystallized graphite grains (petal, sphere-like and piece) is the alloy have been observed with microscope. We found that the amount and morphology of the three sorts of recrystallized graphite grains varied with pressures and concluded that the existence of sphere-like recrystallized graphite grains is absolutely necessary for the transformation of graphite to diamond.

The Phase Transition of La2CuO4+ Synthesized in High Oxygen Pressure

ZHOU Jian-Shi

1992, 6(3): 169-174 . doi: 10.11858/gywlxb.1992.03.002

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Abstract:
In this paper, La2CuO4+ compound with superconducting phase content over 30%, has been obtained by using high oxygen pressure 2.3 PGa techniques, which is the highest oxygen pressure exerted so far on the La2CuO4. It is noteworthy that the excess oxygen content determined by iodimetric titration (=0.050.01) is not consistent with that determined by TGA (in N2, =0.143). The product obtained by high oxygen pressure is heated in air at different temperatures, then quenched to room temperature. The superconductor shows a first order phase transition at temperatures between 200~300 ℃, and after this transition, the sample transformed to antiferromagnetic semiconductor. TGA and DSC also confirm the presence of this transition. The variation in the oxygen content before and after the phase transition just matches the value obtained by titration. These excess oxygen, which is responsible for the superconductivity, leads to a transformation from Cu2+ to Cu(2+2)+, and this rules out the possibility that the superconductivity is caused by superoxide.

The Surface Impurities Depth-Profiling on the Diamond

ZHANG Shu-Da, ZHU Yao-Hua

1992, 6(3): 175-179 . doi: 10.11858/gywlxb.1992.03.003

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Abstract:
The surface impurities on the diamond were determined and analyzed by the secondary ion mass spectroscopy (SIMS). In order to obtain the depth-profiling of the surface impurities, the ion erosion method was used. The total erosion time was 6 400 s by Ar+ at 15 keV, and N, Na, Mg and Si were chosen as the impurities to be observed. The results indicate that the concentration maximums of the various impurities are situated in a thin layer near the most outward surface and its erosion time correspond to less than 6.5 min; the concentrations for a given impurity, at the most outward surfaces of two different samples, may differ enormously; if the erosion time exceed 30 min, however, this concentration difference in different samples is not large. Also variations in impurities concentrations are not obvious as the erosion time (i. e. as the depth) increases, in the same sample.

A Study on Adiabatic Shear Banding of TC4-Titanium Alloy under Planar Shock Compression

GONG Zi-Zheng, FU Shi-Qin, JING Fu-Qian

1992, 6(3): 180-191 . doi: 10.11858/gywlxb.1992.03.004

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Abstract:
Investigations for adiabatic shear banding (ASB) of a TC4-titanium alloy under planar shock compression were performed by using a compressed gas gun of 57 mm bore diameter, and symmetric impact technique. The stresses in the target, from 3 to 15 GPa, were designed above the Hugoniot elastic limit, HEL=2.85 GPa, of the target material. Microstructural features of the recovered sample were examined metallographically by using scanning electron microscope. Results indicated: (1) ASB emerges only if the stress in target is not less than 5.87 GPa (or impact velocity 500 m/s), a stress far above HEL. It implies that the ASB formation, resulted from heterogeneous energy deposition, is merely a stage in the material yielding process. Results from X-ray diffraction analysis indicated that phase transition occurred in ASB, and also in matrix material but with weaker degree and rather dispersive manner; (2) The angle between ASB and shock compression direction is about 45, consistent with the theoretical prediction of maximum shear direction for isotropic medium, which is just the case of TC4-titanium alloy; (3) Spherical and elliptic voids appeared in ASB and increased both in number and in size with increasing shock stress in target, showing the typical features of the dynamic damage for ductile materials; (4) A few ASB branches appeared at stress of 15 GPa, with an angle of about 15 inclined to the main ASB; and (5) microstructure of ASB, characterized by the appearance of tiny and lengthy crystallites with preferred orientation parallel to the bounds of ASB, is significantly different from that of the matrix material. Accordingly, we believe that a melting and recrystallization process happened in ASB during its development. Calculations for ASB temperature and the melting temperature at corresponding shock stress showed that the above arguments are reasonable.

The Effect of Different Additives on the Microstructure and Property of Sintered Diamond with Fine Grain Size

LI Shang-Jie, WANG Li-Wei, TAN Shu-Zhen

1992, 6(3): 192-197 . doi: 10.11858/gywlxb.1992.03.005

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Abstract:
The difference in the microstructures of the sintered bodies of diamonds with Si-Ti-B as additives and with nickel as additives was investigated. Effect of the two different additives in the sintering process at high temperature and ultra-high pressures was discussed. The wear resistance and oxidation resistance of sintered diamond with different additives were measured.

Characteristics of Solid Argon and 4∶1 Methanol-Ethanol Mixture as Pressure-Transmitting Media under High Pressure and Low Temperature

LIU Zhen-Xian, LI Guo-Hua, HAN He-Xiang, WANG Zhao-Ping

1992, 6(3): 198-205 . doi: 10.11858/gywlxb.1992.03.006

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Abstract:
Characteristics of solid argon and 4∶1 methanol-ethanol mixture were systematically studied by using ruby fluorescence technique under high pressure and low temperature (77 K) in the gasket diamond anvil cells. The pressure distribution was determined by measuring the special shifts of the R1 line of ruby at different positions within the sample chamber. Experimental results showed that the values of |p/p| and p/p which reflect the degree of inhomogeneity in solid argon medium are less than 3% and 2% in the pressure range from 0 to 16 GPa, respectively. Under high pressure, the shape of ruby R lines is similar to that at ambient pressure except for broadening with increasing pressure, which indicates solid argon is an excellent pressure-transmitting medium under high pressure and low temperature. On the other hand, the values of |p/p| and p/p are larger than 3% and 2% in 4∶1 methanol-ethanol mixture, respectively, except for the initial pressure. Moreover, the shaper of ruby R lines at different positions are also different under higher mean pressures. These results indicate the methanol-ethanol mixture can not be used as a good pressure-transmitting medium under high pressure and low temperature.

A Study of Raman Spectra and the Soft Mode Phase Transition under Hydrostatic Pressure in Ba2-xLaxTi4O11

MENG Jin-Fang, ZOU Guang-Tian, CUI Qi-Liang, ZHAO Yong-Nian, LI Dong-Mei

1992, 6(3): 206-211 . doi: 10.11858/gywlxb.1992.03.007

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Abstract:
The Raman spectra of Ba2-xLaxTi4O11 under hydrostatic pressure have been completed. The behavior of the coupled soft mode is found. Through comparing the result of Ba2Ti4O11 obtained by termodynamics with the experimental data, it is believed that the coupling is one between q0 soft optical phonon with Bg symmetry and a acoustic phonon mode. The phase transition occurring in Ba2-xLaxTi4O11 is a secondary order one driven by the soft mode.

Formation of Bulk Metallic Glass Zr60Ni20Al20 by High Pressure Quenching

MAO Zi-Li, CHEN Hong, WANG Wen-Kui

1992, 6(3): 212-216 . doi: 10.11858/gywlxb.1992.03.008

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Abstract:
A bulk Zr60Ni20Al20 amorphous alloy was prepared by using high pressure quenching technique. The crystal growth velocity of the undercooled alloy melts at high pressure was estimated much smaller than at normal pressure, confirming that the high pressure quenching facilitates the formation of metallic glass by suppressing the crystal growth.

On the Boat Deformation in BN Diffusionless Phase Transition

XU Xiao-Wei, ZOU Guang-Tian

1992, 6(3): 217-220 . doi: 10.11858/gywlxb.1992.03.009

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Abstract:
The model of boat deformation is a diffusionless phase transition model describing rBNwBN transition under high static pressure, the boat deformation is easier than the chair deformation on the diffusionless phase transition of rBN.

A Study of the Emission Spectra from Shock Tube Wall under Detonation

LI Zhao-Ning, DENG Xiang-Dong, HU Dong, WANG Yong-Guo, CHENG Xin-Lu, SUN Zhu-Mei, GOU Qing-Quan

1992, 6(3): 221-225 . doi: 10.11858/gywlxb.1992.03.010

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Abstract:
The KODAK-2485 film is used to study the impurity spectrum appeared in the detonation spectrum of four hydracarbon fuels (heptane, isooctane, M-17 and W-11 emulsification) mixed with oxygen (or nitrogen). The emission spectra consists of the continuous emission spectra from detonation products, spectral lines of Fe, Cr, Mn atom, and a series of strong and complex bands in the range 550~660 nm, in which exist orange bands for FeO molecules.

An EPR Investigation of Nitrogen Impurities in Synthesized Diamond

ZHAN Rui-Yun, TANG Gong-Ben, LIU Ya-Yan, LIU Gui-Zhen, XU Jie, SUN Wan-Ming

1992, 6(3): 226-229 . doi: 10.11858/gywlxb.1992.03.011

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Abstract:
EPR technique has been used to study the electronic structure of nitrogen impurities in synthesized diamond with pretreated graphite. The observed hyperfine splitting lines of 14N reveals the presence of for types of substitution nitrogen. A quantitative way has been proosed to estimate the spin concentration of the nitrogen impurities. The analytical result indicates that the spin concentration of nitrogen in diamond synthesized with pretreated graphite is higher than that of synthesized with normal graphite.

A Study of the Intensity High Density Polyethylene at Static High Pressure

YANG Guang-Qun, WANG Hui, WU Rui-Qi

1992, 6(3): 230-234 . doi: 10.11858/gywlxb.1992.03.012

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Abstract:
High density polyethylene was crystallized at static high pressure from 1 GPa to 2 GPa. The Young's modulus of the sample treated by high-pressure compression was measured with the compression method. The results show that the Young's modulus is increased both with the pressure and the crystallinity, and its maximum value is 1.46 GPa. The formation of the extended-chain crystal is an important factor for the increase of Young's modulus.

Experimental Study on the Self-Sharpening Property of PDC

YANG BAO-De, MIAO Qing-Wei

1992, 6(3): 235-239 . doi: 10.11858/gywlxb.1992.03.013

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Abstract:
The rate of penetration of PDC bits relates closely to its self-sharpening property. This relation can be tested through rig test which is performed with standard PDC test bit. At the same time the average rate of penetration (v) and average rate of change in ROP () can describe the self-sharpening property of PDC. From the analyses, it is thought that different sloughing forms of polycrystalline layers are microscopic evidence for different self-sharpening of PDC. From macroscopic view, the self-sharpening of PDC depends on the mutually interdependent relation of double layers on wear resistance.

1992 Vol. 6, No. 3

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