Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina she...Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.展开更多
The time-dependent entropy of a single free quantum particle in the non-relativistic regime is studied in detail for the process started from a fully coherent quantum state to thermodynamic equilibrium with its surrou...The time-dependent entropy of a single free quantum particle in the non-relativistic regime is studied in detail for the process started from a fully coherent quantum state to thermodynamic equilibrium with its surroundings at a finite temperature. It is shown that the entropy at the end of the process converges to a universal constant, as a result of thermal interaction.展开更多
We report model calculations of the time-dependent internal energy and entropy for a single quasi-free massive quantum particle at a constant temperature. We show that the whole process started from a fully coherent q...We report model calculations of the time-dependent internal energy and entropy for a single quasi-free massive quantum particle at a constant temperature. We show that the whole process started from a fully coherent quantum state to thermodynamic equilibrium can be understood, based on statistics of diffracted matter waves. As a result of thermal interaction between the particle and its surroundings, the motion of the particle shows new feature.展开更多
A new process of producing magnesium by thermal vacuum reduction using dolomite and magnesite as materials and silicocalcium as reductant was studied in this study. The reduction process of MgO by silicocalcium was an...A new process of producing magnesium by thermal vacuum reduction using dolomite and magnesite as materials and silicocalcium as reductant was studied in this study. The reduction process of MgO by silicocalcium was analyzed by phases analysis of reduction slag through X-ray diffraction （XRD） and the factors influencing the reduction ratio of MgO were investigated. The experi- mental results show that when using silicocalcium as reductant, the reduction ratio of MgO can be over 93 %. In the reduction process, calcium in silicocalcium takes part in the reduction reaction of MgO firstly below 1,000 ℃ and it makes CaSi2 decompose. It also releases elemental silicon which has more reactive activity and improves the reduction reaction of MgO. That is the main cause that the reduction ratio of MgO using silicocalcium as reductant is 8 %-10 % higher than that by Pidgeon process using fer- rosilicon as reductant under the same conditions.展开更多
To investigate the electrodeposition mechanism of Ti^4＋, electrochemistry experiments were conducted using a KF-KCl-K2Ti6O13 molten salt at a Cu electrode at 950 ℃. Transient electrochemical techniques such as cycli...To investigate the electrodeposition mechanism of Ti^4＋, electrochemistry experiments were conducted using a KF-KCl-K2Ti6O13 molten salt at a Cu electrode at 950 ℃. Transient electrochemical techniques such as cyclic voltammetry（CV） and square-wave voltammetry were used in this study. The main phases and compositions of the product were analyzed by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy-dispersive spectrometry（EDS）. The resulting product has the structure of metallic Ti. The results indicate that Ti^4＋ is reduced to metallic Ti by a two-step mechanism, corresponding to the reduction pathway： Ti^4＋→ Ti^2＋→ Ti. Moreover, Cu-Ti alloy could be obtained by the potentiostatic electrolysis at a Cu electrode.展开更多
The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiom...The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^（-2）,but the current density is above 200 mA·cm^（-2） under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.展开更多
基金supported by the National Key Research and Development Program of China(No.2021YFC29003205)the National Natural Science Foundation of China(Nos.21878045,51504058)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.N2225019)Natural Science Foundation of Liaoning Province,China(No.2022-MS-106)。
基金financial supports from the National Natural Science Foundation of China (Nos.51774080,22078056)the National Key R&D Program of China (No.2018YFC1901905)。
基金the National Natural Science Foundation of China(Grant No.11802160)。
文摘Rupturing the alumina shell(shell-breaking)is a prerequisite for releasing energy from aluminum powder.Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell.COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650℃in vacuum.The simulation results show that the thermal stability time and shell-breaking response time of 10μm–100μm aluminum particles are 0.15μs–11.44μs and 0.08μs–3.94μs,respectively.They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes.When the particle size is less than 80μm,the shell-breaking response is a direct result of compressive stress overload.When the particle size is between80μm and 100μm,the shell-breaking response is a direct result of tensile stress overload.This article provides useful guidance for research into the energy release of aluminum powder.
文摘The time-dependent entropy of a single free quantum particle in the non-relativistic regime is studied in detail for the process started from a fully coherent quantum state to thermodynamic equilibrium with its surroundings at a finite temperature. It is shown that the entropy at the end of the process converges to a universal constant, as a result of thermal interaction.
文摘We report model calculations of the time-dependent internal energy and entropy for a single quasi-free massive quantum particle at a constant temperature. We show that the whole process started from a fully coherent quantum state to thermodynamic equilibrium can be understood, based on statistics of diffracted matter waves. As a result of thermal interaction between the particle and its surroundings, the motion of the particle shows new feature.
基金financially supported by the Industrial Research Project of Liaoning Province(No.2011221002)the Project of High Technology Plan of Magnesium Materials of Liaoning(No.MYF2011-34)
文摘A new process of producing magnesium by thermal vacuum reduction using dolomite and magnesite as materials and silicocalcium as reductant was studied in this study. The reduction process of MgO by silicocalcium was analyzed by phases analysis of reduction slag through X-ray diffraction （XRD） and the factors influencing the reduction ratio of MgO were investigated. The experi- mental results show that when using silicocalcium as reductant, the reduction ratio of MgO can be over 93 %. In the reduction process, calcium in silicocalcium takes part in the reduction reaction of MgO firstly below 1,000 ℃ and it makes CaSi2 decompose. It also releases elemental silicon which has more reactive activity and improves the reduction reaction of MgO. That is the main cause that the reduction ratio of MgO using silicocalcium as reductant is 8 %-10 % higher than that by Pidgeon process using fer- rosilicon as reductant under the same conditions.
基金financially supported by the State Key Development Program for Basic Research of China (973 Program, Grant No.2013CB632606-1)
文摘To investigate the electrodeposition mechanism of Ti^4＋, electrochemistry experiments were conducted using a KF-KCl-K2Ti6O13 molten salt at a Cu electrode at 950 ℃. Transient electrochemical techniques such as cyclic voltammetry（CV） and square-wave voltammetry were used in this study. The main phases and compositions of the product were analyzed by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy-dispersive spectrometry（EDS）. The resulting product has the structure of metallic Ti. The results indicate that Ti^4＋ is reduced to metallic Ti by a two-step mechanism, corresponding to the reduction pathway： Ti^4＋→ Ti^2＋→ Ti. Moreover, Cu-Ti alloy could be obtained by the potentiostatic electrolysis at a Cu electrode.
基金financially supported by the National Basic Research Program of China(No.2013CB632606-1)the National Natural Science Foundation of China(No.51204044)
文摘The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^（-2）,but the current density is above 200 mA·cm^（-2） under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.
