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Elastic Properties of Selected Transition Metals at Extreme Conditions: High Pressure and High Temperature.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Elastic Properties of Selected Transition Metals at Extreme Conditions: High Pressure and High Temperature./
作者:	Qi, Xintong.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
面頁冊數:	183 p.
附註:	Source: Dissertations Abstracts International, Volume: 81-06, Section: B.
Contained By:	Dissertations Abstracts International81-06B.
標題:	Geophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13811321
ISBN:	9781687998989

Elastic Properties of Selected Transition Metals at Extreme Conditions: High Pressure and High Temperature.
Qi, Xintong.

Elastic Properties of Selected Transition Metals at Extreme Conditions: High Pressure and High Temperature. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 183 p.

Source: Dissertations Abstracts International, Volume: 81-06, Section: B.

Thesis (Ph.D.)--State University of New York at Stony Brook, 2019.

This item must not be sold to any third party vendors.

The d - block transition metals have great importance in scientific research with their unique electronic configurations. 5d transition metals, such as hafnium (Hf), tantalum (Ta) and tungsten (W), are important engineering materials in nuclear science and the aerospace industry due to their high mechanical, chemical and thermal stabilities. Pressure and temperature can change the physical and chemical properties of materials. Therefore, it is crucial to understand the behavior of these transition metals under high pressure and/or high temperature conditions. Experimental studies on the elasticity of bulk and shear moduli of these metals, as well as their pressure and temperature derivatives, are still limited to low pressure at room temperature or moderate temperature at room pressure. Comprehensive investigations of their thermoelastic properties are still needed for a better understanding of their phase diagrams, electronic structures and the development of theoretical modeling in computational physics. In this dissertation, I employed ultrasonic interferometry technique in the multi-anvil large volume press (LVP) and synchrotron radiation facilities (e.g. X-ray diffraction and X-ray radiography) to measure the compressional and shear wave velocities for 5d transition metals Hf, Ta and W under high pressure and high temperature conditions. First-principles calculations were also performed as complementary to the experimental results using density functional theory (DFT).Acoustic wave velocities of polycrystalline hafnium have been measured up to 13.5 GPa and 1073 K, and up to 10.4 GPa at room temperature. The hcp phase of hafnium exhibited a weak pressure dependence of the shear wave velocity up to 10 GPa beyond which the velocity exhibited a continuous decrease with increasing pressure. The softening of the shear properties resulted from the weakening and subsequent softening of the elastic constants C44 under pressure, which can be interpreted as a precursor to the thermodynamically drive α-ω phase transition in Group IV transition metals. The simultaneous high-pressure and high-temperature experiments provided the most self-consistent and complete dataset for the thermoelastic properties of hafnium. The unit-cell volumes of hafnium at temperature up to 2000 K and atmospheric pressure were calculated using the currently determined thermal expansion and are in good agreement with previous experimental results.The compressional and shear wave velocities of sintered polycrystalline tantalum were measured up to 13.6 GPa at room temperature. With the measured shear modulus and its pressure derivative, the upper and lower bound for the yield strength of Ta were assessed using the Steinberg-Guinan model. As compared with the experimentally measured strength at strain rates of ~106 /s from literature, the Steinberg strength model provides a reasonable prediction for annealed Ta to ~17 GPa. DFT calculations have been conducted up to 200 GPa. The bcc phase of tantalum remained stable in the entire range of 0 - 200 GPa, with pronounced softening in C44 and the shear wave velocity VS at 80 GPa and stiffening after 180 GPa. Subtle changes of slope were also observed in C11 and the compressional wave velocity VP. Such anomalies were also found in Group V transition metals vanadium (V) and niobium (Nb), which were primarily due to the cross sections of the Fermi surfaces shrinking with pressure.Ultrasonic measurements on polycrystalline tungsten were performed to 10.4 GPa and 1073 K in conjunction with synchrotron X-radiation, and up to 13 GPa at room temperature. Different equations of state (EOS) have been utilized for analysis of the P-V-T data: (1) the Birch-Murnaghan EOS, (2) the Vinet EOS, (3) the 3rd order finite strain EOS, and (4) a thermal pressure EOS, which provided a complete dataset of thermoelastic parameters, including temperature and pressure derivatives of bulk and shear moduli, and thermal expansion of tungsten. Other mechanical properties such as Young's modulus, Poisson's ratio and the ductility/brittleness have also been investigated based on the measured velocity data.Iron (Fe) is the predominant component of the Earth's core. The behavior of iron under high pressure and temperature conditions is essential to constrain our knowledge of the chemical composition and dynamics of the Earth's core and those of other terrestrial planets. Due to the limitations of current experimental techniques, direct measurements on the elasticity and sound velocity of iron under the Earth's conditions are not feasible. Birch's law, a linear relationship between density and velocity, thus offers a simple means to extrapolate the experimental results to much higher densities and has been used in many previous studies to compare with the seismic models such as the Preliminary Reference Earth Model (PREM).[1] In this study, I have conducted successful ultrasonic measurements on iron at simultaneous high pressure and high temperature conditions. Appearance of peaks of hcp-Fe was observed on the initial cold compression at pressure above 14 GPa. With increasing temperature to 673 K, the bcc-Fe fully transformed to the hcp phase. The elastic properties of hcp-Fe were obtained by fitting the unit-cell volume data to the high-temperature 3rd order Birch-Murnaghan EOS. A modified Birch's law based on the framework of finite strain theory was presented and tested using the elasticity data of transition metals over a wide range of compression. With further detailed analysis of the sound velocities of Fe, the present results can offer valuable information for theoretical modeling the anharmonic terms in the interatomic potential quantitatively and provide important constrains on the chemical composition of the Earth's inner core.

ISBN: 9781687998989Subjects--Topical Terms:

535228
Geophysics.
Subjects--Index Terms:

elastic properties

Elastic Properties of Selected Transition Metals at Extreme Conditions: High Pressure and High Temperature.
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502 $a Thesis (Ph.D.)--State University of New York at Stony Brook, 2019.
506 $a This item must not be sold to any third party vendors.
520 $a The d - block transition metals have great importance in scientific research with their unique electronic configurations. 5d transition metals, such as hafnium (Hf), tantalum (Ta) and tungsten (W), are important engineering materials in nuclear science and the aerospace industry due to their high mechanical, chemical and thermal stabilities. Pressure and temperature can change the physical and chemical properties of materials. Therefore, it is crucial to understand the behavior of these transition metals under high pressure and/or high temperature conditions. Experimental studies on the elasticity of bulk and shear moduli of these metals, as well as their pressure and temperature derivatives, are still limited to low pressure at room temperature or moderate temperature at room pressure. Comprehensive investigations of their thermoelastic properties are still needed for a better understanding of their phase diagrams, electronic structures and the development of theoretical modeling in computational physics. In this dissertation, I employed ultrasonic interferometry technique in the multi-anvil large volume press (LVP) and synchrotron radiation facilities (e.g. X-ray diffraction and X-ray radiography) to measure the compressional and shear wave velocities for 5d transition metals Hf, Ta and W under high pressure and high temperature conditions. First-principles calculations were also performed as complementary to the experimental results using density functional theory (DFT).Acoustic wave velocities of polycrystalline hafnium have been measured up to 13.5 GPa and 1073 K, and up to 10.4 GPa at room temperature. The hcp phase of hafnium exhibited a weak pressure dependence of the shear wave velocity up to 10 GPa beyond which the velocity exhibited a continuous decrease with increasing pressure. The softening of the shear properties resulted from the weakening and subsequent softening of the elastic constants C44 under pressure, which can be interpreted as a precursor to the thermodynamically drive α-ω phase transition in Group IV transition metals. The simultaneous high-pressure and high-temperature experiments provided the most self-consistent and complete dataset for the thermoelastic properties of hafnium. The unit-cell volumes of hafnium at temperature up to 2000 K and atmospheric pressure were calculated using the currently determined thermal expansion and are in good agreement with previous experimental results.The compressional and shear wave velocities of sintered polycrystalline tantalum were measured up to 13.6 GPa at room temperature. With the measured shear modulus and its pressure derivative, the upper and lower bound for the yield strength of Ta were assessed using the Steinberg-Guinan model. As compared with the experimentally measured strength at strain rates of ~106 /s from literature, the Steinberg strength model provides a reasonable prediction for annealed Ta to ~17 GPa. DFT calculations have been conducted up to 200 GPa. The bcc phase of tantalum remained stable in the entire range of 0 - 200 GPa, with pronounced softening in C44 and the shear wave velocity VS at 80 GPa and stiffening after 180 GPa. Subtle changes of slope were also observed in C11 and the compressional wave velocity VP. Such anomalies were also found in Group V transition metals vanadium (V) and niobium (Nb), which were primarily due to the cross sections of the Fermi surfaces shrinking with pressure.Ultrasonic measurements on polycrystalline tungsten were performed to 10.4 GPa and 1073 K in conjunction with synchrotron X-radiation, and up to 13 GPa at room temperature. Different equations of state (EOS) have been utilized for analysis of the P-V-T data: (1) the Birch-Murnaghan EOS, (2) the Vinet EOS, (3) the 3rd order finite strain EOS, and (4) a thermal pressure EOS, which provided a complete dataset of thermoelastic parameters, including temperature and pressure derivatives of bulk and shear moduli, and thermal expansion of tungsten. Other mechanical properties such as Young's modulus, Poisson's ratio and the ductility/brittleness have also been investigated based on the measured velocity data.Iron (Fe) is the predominant component of the Earth's core. The behavior of iron under high pressure and temperature conditions is essential to constrain our knowledge of the chemical composition and dynamics of the Earth's core and those of other terrestrial planets. Due to the limitations of current experimental techniques, direct measurements on the elasticity and sound velocity of iron under the Earth's conditions are not feasible. Birch's law, a linear relationship between density and velocity, thus offers a simple means to extrapolate the experimental results to much higher densities and has been used in many previous studies to compare with the seismic models such as the Preliminary Reference Earth Model (PREM).[1] In this study, I have conducted successful ultrasonic measurements on iron at simultaneous high pressure and high temperature conditions. Appearance of peaks of hcp-Fe was observed on the initial cold compression at pressure above 14 GPa. With increasing temperature to 673 K, the bcc-Fe fully transformed to the hcp phase. The elastic properties of hcp-Fe were obtained by fitting the unit-cell volume data to the high-temperature 3rd order Birch-Murnaghan EOS. A modified Birch's law based on the framework of finite strain theory was presented and tested using the elasticity data of transition metals over a wide range of compression. With further detailed analysis of the sound velocities of Fe, the present results can offer valuable information for theoretical modeling the anharmonic terms in the interatomic potential quantitatively and provide important constrains on the chemical composition of the Earth's inner core.
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