高压物理学报

A Method of Solving One-Dimension Rigid-Thermo-Visco-Plastic Flow with Cylindrical Symmetry

LI Xiao-Jie, LI Yong-Chi

1996, 10(2): 81-86 . doi: 10.11858/gywlxb.1996.02.001

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Abstract:
Assuming the material incompressible, the partial differential control equations of one-dimension cylindrical flow can be reduced into the ordinary differential equations. These equations can then be solved by using available method for ordinary differential equations. As an example, the collapse of a copper pipe subjected to external inward compressions were analyzed with a thermo-visco-plastic constitutive relation and its velocity, stress and temperature fields were also shown in the paper.

Influence of High Pressure on Crystal Field Parameters for GdOBr:Er

LI Hong-Nian, CHI Yuan-Bin, WANG Li-Zhong, LIU Shen-Xin

1996, 10(2): 87-96 . doi: 10.11858/gywlxb.1996.02.002

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Abstract:
The fluorescence spectra of GdOBr:Eu at room temperature and under high pressure up to 12 GPa were measured and analyzed. 43 lines were observed at ambient pressure in the wavenumber of 13 000～21 500 cm-1. From the fluorescence spectra, the major part of the 7F0～5 and all the 5D0~2 stark levels were determined. Under pressures, the 5D0~2 stark levels shift downwards, but the 7F0～5 stark levels shift upwards or downwards irregularly. The crystal field simulation calculation is conducted on the 49 7F states. The five nonzero crystal field parameters obtained at ambient pressure are as follows: B02=-1 124.0 cm-1, B04=-969.6 cm-1, B44=827.9 cm-1, B06=889.6 cm-1 and B46=377.0 cm-1. Under high pressures, B04 and B06 increase with pressure. While B46 decreases with pressure, B02 and B44 show somewhat irregular variations with perssure. From the crystal field parameters, crystal field strength S was deduced. At ambient pressure, S =445.0 cm-1. Under high pressures it decreases with pressure till about 8 GPa, then increases with pressure till 12 GPa.

The Crystallization of BN and the Synthesis of cBN at High Pressure and Temperature

MA Xian-Feng, YAN Xue-Wei

1996, 10(2): 97-101 . doi: 10.11858/gywlxb.1996.02.003

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Abstract:
The crystallization of amorphous, turbostratic and low crystalline degree hexagonal BN was found at high pressure and temperature and the conversion behavior of various BN with different crystallinity to cBN were studied. Results show that the synthesis of cBN is getting difficult as the crystallinity of starting BN material becomes worse (i.e. G.I value increase). When synthesizing cBN using hexagonal BN doped with B, we found that B can hinder the conversion to cBN. The existence of high nitrogen vacancies in low crystallinity BN may explain why it is difficult to transform to cBN. When BN crystallizes at high pressure and temperature, boron escapes which hinders the conversion of hBN to cBN.

The Influence of Impurities in Liner Materials on the Behavior of Shaped Charge Jets

WANG Tie-Fu, ZHAO Tong-Hu, RUAN Wen-Jun, WANG Lei

1996, 10(2): 102-106 . doi: 10.11858/gywlxb.1996.02.004

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Abstract:
In this paper, the influence of impurities on the behavior of shaped charge jets was investigated by fire tests of depleted uranium shaped charge liner. The results of these tests indicate that impurity carbon have an important influence on the behavior of depleted uranium shaped charge jet. As the content of impurity carbon increases, the penetration depths of depleted uranium shaped charge decreased dramatically. The reason we suggest is that harmful impurities can affect the ductility of materials in different ways, such as inhibiting the dislocation movement and reducing the slip mobility, etc.

Studies on the Recrystallization of Graphite during the Process of Diamond Growth under Excess Pressure

LUO Xiang-Jie, LUO Bo-Cheng, LUO Jun-Yi, CHEN Shi-Tu, DING Li-Ye

1996, 10(2): 107-113 . doi: 10.11858/gywlxb.1996.02.005

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Abstract:
Characteristics of co-growing of recrystallized graphite have been reported during the epitaxial growth process of diamond seed under excess pressure. Spontaneous diamond nucleation was inhibited by recrystallized graphite grains which abundantly distributed in lower temperature zone of metal solvent discs. Numerous recrystallized graphite grains, which were in strata structure but disordered each other, occurred with some amorphous carbon. Those phenomena have been considered to be related to the condition under long time lower excess pressure: plentiful carbon in metal solvent discs, high temperature and high pressure are suitable for well recrystallization but insufficient for graphitization. It has also been discussed that the active carbon atoms rather than recrystallized graphite grains might play as a source of carbon for epitaxial growth of diamond under lower excess pressure.

The Mechanism of the Negative Bias-Enhanced Nucleation of Diamond

YANG Guo-Wei

1996, 10(2): 114-121 . doi: 10.11858/gywlxb.1996.02.006

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Abstract:
The mechanism of substrates negative bias-enhanced nucleation of diamond, in the growth of diamond thin films by plasma CVD methods is suggested. A relationship between the effect of bias-enhanced nucleation and deposition condition such as the reaction pressures and carbon fractions are obtained from the model. The model reasonably explains why the bias-enhanced nucleation of diamond increase with the decrease of reaction pressures and the increase of carbon fraction, as the bias is enhanced. The model is also in accordance with the reported data.

The Flyer Plate Velocity in Explosive Welding under the Critical Conditions

WANG Zhi-Ping, HE Zhi, FU Ming-Lin, LIU Shu

1996, 10(2): 122-129 . doi: 10.11858/gywlxb.1996.02.007

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Abstract:
By analyzing the parameters, it is found that the critical velocity of flyer plate impacting with the parent plate depends principally on the properties of flyer plate and almost has nothing to do with the explosives and its detonation parameters under critical conditions. The results were tentatively proved by the semi-cylindrical tests.

Study on the Emission Spectra from Fast Reaction of Aluminum Powder

LI Zhao-Ning, GOU Qing-Quan, WANG Yong-Guo, HU Dong

1996, 10(2): 130-136 . doi: 10.11858/gywlxb.1996.02.008

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Abstract:
Optical multichannel analyzer (OMA) was used to investigate the emission spectra from the fast reaction of aluminum powders driven by hydrogen-oxygen detonation in shock tube. The spectra from the reactions of two sizes of aluminum powders throughout of the 240～850 nm wavelength region has been determined experimentally with a resolution of 0.6 nm at various pressures. Higher resolution (0.071 nm resolution) spectroscopic were also made in several region of interest in the 240～850 nm wavelength region. The spectra measurements in this study were dominated by continuum radiation. The intense blue-green emission of the AlO B2+X2+ transition was also present.

A Embryonic Form of wBN Crystal in Zone of cBN Growth

ZHANG Tie-Chen, YU San, GUO Wei-Li, LIU Jian-Ting, ZOU Guang-Tian, LI Dong-Mei

1996, 10(2): 137-140 . doi: 10.11858/gywlxb.1996.02.009

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Abstract:
In the present paper, embryonic form of wBN crystal was observed in hBN-catalyst system after treatments under static high pressure(～5.0 GPa) and high temperature (～1500 ℃), the size of the embryonic crystal was about 20～30 nm. It is larger than the critical nuclei and smaller than the critical crystal. The phase of wBN was determined by the electron diffraction.

A Discussion on Some Problem in Fractal Descriptions of Some Fracture Problems

GAO Feng, XIE He-Ping

1996, 10(2): 141-144 . doi: 10.11858/gywlxb.1996.02.010

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Abstract:
Fractal geometry can provide quantitative methods to describe numerous irregular and complicated phenomena in nature, and has widely been used in many scientific fields. However people find that many similar experiments produce contradictory results, and thus make exploration from views of fractal range, size correlation, self-affine farctal and multifractal concepts. However, we find that many contradictory results are originated from poor understanding of fractal concepts and physical mechanical definitions, some of them are discussed in details in the paper.

Application of Aluminum in Correcting the Elastic Wave Velocity Measurement of Materials at High Pressure

XU You-Sheng, XIE Hong-Sen, ZHANG Yue-Ming, XU Ji-An, SONG Mao-Shuang, XU Zu-Ming

1996, 10(2): 145-150 . doi: 10.11858/gywlxb.1996.02.011

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Abstract:
A lot of wave velocity data for minerals and rocks have been obtained since the method of elastic wave velocity measurement has been established in YJ-30MN press fitted with a wedge-type cubic anvil at high pressure and high temperature. Many geological problems have been explained by using this velocity data. However, the accuracy of elastic velocity data under high pressure has not been resolved. The travel time of the upper and lower anvils is still not corrected. In this paper we calculate the relation between the velocities and pressures of aluminum according to the elastic theory and elastic constants of aluminum .Then the real travel time of the anvils is inferred from the relation between velocities and pressures. The corrected velocities for iron, which is non linear with pressure, is well consistent with other lower pressure data. Henceforward, the real travel time of the anvils can be emended according to the velocities of standard aluminum and iron before experiment. In this way the more accurate velocity data can be obtained under high pressure after corrected.

Effect of Filament Temperature on in Situ Absorption Spectrum and Diamond Film Growth

CUI Jing-Biao, MA Yu-Rong, FANG Rong-Chuan

1996, 10(2): 151-156 . doi: 10.11858/gywlxb.1996.02.012

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Abstract:
In situ infrared absorption spectroscopy has been used to study chemical vapor deposition (CVD) diamond growth process. The effects of filament temperature on in situ infrared absorption and diamond film growth are investigated. We find that the absorption of CH4 radicals is always exist while that of C2H2 can only be detected at filament temperatures higher than a threshold value, 1 700 ℃. High filament temperature results in more C2H2 formation and CH4 decomposition. At the same time, diamond films prepared at high filament temperature will have a higher diamond content and growth rate. We conclude that more decomposition in CH4 will lead to high concentration C2H2 and hydrocarbon formation radicals which may benefit the high quality diamond film growth and promote growth rate.

A New Method of Manganin Piezoresistance Measurement

WANG Xiang, FU Qiu-Wei

1996, 10(2): 157-160 . doi: 10.11858/gywlxb.1996.02.013

PDF (786)

Abstract:
Different techniques in commonly used piezoelectric manganin gauge measurement with constant current supply are briefly discussed, along with their advantages and disadvantages. A new method with higher fidelity and accuracy by using digital oscilloscope is introduced, which can improve not only the accuracy in pressure measurement, but also extend the applicable pressure range for the small-resistance gauge to as low as 0.17 GPa.

1996 Vol. 10, No. 2

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