A one-dimensional fluid model is proposed to simulate the dual-frequency capacitively coupled plasma for Ar discharges. The influences of the low frequency on the plasma density, electron temperature, sheath voltage d...A one-dimensional fluid model is proposed to simulate the dual-frequency capacitively coupled plasma for Ar discharges. The influences of the low frequency on the plasma density, electron temperature, sheath voltage drop, and ion energy distribution at the powered electrode are investigated. The decoupling effect of the two radio-frequency sources on the plasma parameters, especially in the sheath region, is discussed in detail.展开更多
The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and t...The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.展开更多
We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electro...We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electromagnetic wave propagating only once in previous work on the plasma layer, a general formula of total power absorption by the plasma layer with an infinite time of reflections between the atmosphere-plasma interface and the metal surface has been derived for the first time. Effects of plasma parameters, especially the dependence of the fraction of positive ions, negative ions and electrons in plasmas on the power absorption processes are discussed. The results show that the existence of negative ions significantly reduces the power absorption of the electromagnetic wave. Absorptions of electromagnetic waves are calculated.展开更多
Ternary Sm-based Sm-Al-Co alloys at specific compositions designed using an e/a-and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-...Ternary Sm-based Sm-Al-Co alloys at specific compositions designed using an e/a-and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-casting method.Four composi-tions of bulk metallic glasses(BMGs)are Sm50Al25Co25,Sm52Al24Co24,Sm54Al23Co23 and Sm56Al22Co22,which all satisfy a constant conduction electron concentration of 1.5.Among them,the BMG exhibiting the largest reduced glass transition temperature(Trg)is Sm50Al25Co25,which reaches 0.648.The glass transition temperature Tg and the onset crystallization temperature Tx of this alloy are respectively 579 and 640 K at a heating rate of 20 K/min.展开更多
The two-dimensional energy balance in a coaxial plasma opening switch （POS） is studied based on the single-fluid magnetohydrodynarnic （MHD） equations coupled with the generalized Ohm＇s law. The energy transfers b...The two-dimensional energy balance in a coaxial plasma opening switch （POS） is studied based on the single-fluid magnetohydrodynarnic （MHD） equations coupled with the generalized Ohm＇s law. The energy transfers between the plasma and the magnetic field are considered during the penetration of the magnetic field as the Ohmic heating is included in the energy-balance equation. The focus is on the energy partition between the magnetic-field energy and the dissipated magnetic-field energy in a high-density POS with different rise-in-time electric currents at the generator boundary. The simulation code is tested in two cases： the constant-in-time current case and the linear rise-in-time current case. For the sinusoidally rise-in-time current similar to that of the experiments, it is shown that at the end of the conduction phase the dissipated magnetic-field energy is 36.5% of the input electromagnetic energy, which is consistent with the experimental results.展开更多
Plasma behaviour and the scaling relations in a coaxial plasma opening switch （POS） using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydrodynamic （MHD） equations in conjuncti...Plasma behaviour and the scaling relations in a coaxial plasma opening switch （POS） using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydrodynamic （MHD） equations in conjunction with the generalized Ohm＇s law. The vacuum region on the right of POS is included in the model and the influence of downstream flow on the conduction characteristics is discussed. It is found that with the penetration of magnetic field, the pure hydrogen plasma is pushed downstream significantly; and POS still conducts current after the magnetic field arrives at the load edge of POS, which is different from the previous experimental results in a multispecies POS. It is because that the noticeable downstream plasma in the pure hydrogen POS may continue to conduct the current, while in the multispecies POS, the downstream plasma is unimportant so that the conduction phase ends soon after the magnetic field reaches the load edge. The scaling relation obtained from the simulations including the downstream region is consistent with the experimental results.展开更多
In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Bolt...In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.展开更多
Effects of tearing modes are inves shows that the effect of the m = 0 harmonics on the early quasi-linear stage of m = 1 double tigated. The numerical calculation with the harmonics m = 0 included the m = 0 harmonics ...Effects of tearing modes are inves shows that the effect of the m = 0 harmonics on the early quasi-linear stage of m = 1 double tigated. The numerical calculation with the harmonics m = 0 included the m = 0 harmonics on the mode is negligible in the linear stage. As the mode begins to grow nonlinearly, both the current and flow profiles are pinched due to the m = 0 harmonics. To make a comparison we also carry out the calculation with m = 0 harmonics turned off. The profiles of the total current, poloidal magnetic field, and poloidal shear velocity in the cases with or without the m = 0 harmonics are compared and discussed. In addition, the formation of a poloidal velocity shear is found and its mechanism is investigated.展开更多
The characteristics of collisional radio-frequency (rf) sheath dynamics over an elec-trode with a cylindrical hole is simulated by means of a self-consistent model which consists of two-dimensional time-dependent flui...The characteristics of collisional radio-frequency (rf) sheath dynamics over an elec-trode with a cylindrical hole is simulated by means of a self-consistent model which consists of two-dimensional time-dependent fluid equations coupled with Poisson equation. In addition, an equivalent-circuit model is coupled to the fluid equations in order to self-consistently determine re-lationship between the instantaneous potential at the rf-biased electrode and the sheath thickness. Two-dimensional profiles of the potential, the ion fluid velocity, and the distributions of the ion and electron densities within the sheath are computed under various discharge conditions, such as the discharge powers and the gas pressures. The results show that the existence of the cylindrical hole on the electrode significantly affects the sheath structure and generates a potential trap in the horizontal direction, which is particularly strong when the sheath thickness is comparable to the depth of the hole. Moreover, it is found that the collisional effects have a significant influence on the sheath characteristics.展开更多
The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean an...The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean antiprism that characterizes the local structure of the Cu10Zr7 crystalline phase.This cluster composition almost superposes with Cu-Zr eutectic Cu0.56Zr0.44.A se-ries of alloys along the cluster line(Cu6Zr5)1-xMx were examined for their glass forming abilities.Alloy rods with a diameter of 3 mm were prepared by copper mould suction casting method and analyzed by XRD and thermal analysis.The Cu-Zr based bulk metallic glasses were discovered with minor Nb,Sn,Mo,Ta additions(≤2at%)and Al,Ti,Ag(8at%≤concentration≤9at%).The alloying mechanism was discussed in the light of atomic size,cluster-linking structure and electron concentration factors.展开更多
Acoustic breathing modes of dusty plasmas have been investigated in a cylindrical system with an axial symmetry. The linear wave solution and a 'dispersion' relation were derived. It was found that in an infin...Acoustic breathing modes of dusty plasmas have been investigated in a cylindrical system with an axial symmetry. The linear wave solution and a 'dispersion' relation were derived. It was found that in an infinite area, the mode is reduced to a 'classical' dust acoustic wave in the region away from the center. If the dusty plasma is confined in a finite region, however, the breathing (or heart-beating) behavior would be found as observed in many experiments.展开更多
基金National Natural Science Foundation of China(No.10635010)
文摘A one-dimensional fluid model is proposed to simulate the dual-frequency capacitively coupled plasma for Ar discharges. The influences of the low frequency on the plasma density, electron temperature, sheath voltage drop, and ion energy distribution at the powered electrode are investigated. The decoupling effect of the two radio-frequency sources on the plasma parameters, especially in the sheath region, is discussed in detail.
文摘The sheath structures of strongly electronegative plasmas are investigated on basis of the accurate Bohm criterion obtained by Sagdeev potential. It is found that the presheath transition between the bulk plasma and the sheath almost does not exist there, and that distributions of electrons, negative and positive ions in the sheath form a pure positive ion sheath near the boundary of the electrode. Furthermore, the density distribution of space net charge has a peak near the sheath edge, the spatial potential within the sheath falls faster, and the sheath thickness becomes thinner.
文摘We have studied the absorption, reflection, and transmission of electromagnetic waves in an unmagnetized uniform plasma layer covering a metal surface in atmosphere conditions. Instead of the absorption of the electromagnetic wave propagating only once in previous work on the plasma layer, a general formula of total power absorption by the plasma layer with an infinite time of reflections between the atmosphere-plasma interface and the metal surface has been derived for the first time. Effects of plasma parameters, especially the dependence of the fraction of positive ions, negative ions and electrons in plasmas on the power absorption processes are discussed. The results show that the existence of negative ions significantly reduces the power absorption of the electromagnetic wave. Absorptions of electromagnetic waves are calculated.
基金This work was financially supported by the National Natural Science Foundation of China(No.50401020,50671018 and 50631010)the Provincial Science and Technology Foundation of Liaoning(No.20061067).
文摘Ternary Sm-based Sm-Al-Co alloys at specific compositions designed using an e/a-and cluster-related criteria exhibit high glass forming abilities and form bulk glassy rods of 3 mm in diameter by a copper mold suction-casting method.Four composi-tions of bulk metallic glasses(BMGs)are Sm50Al25Co25,Sm52Al24Co24,Sm54Al23Co23 and Sm56Al22Co22,which all satisfy a constant conduction electron concentration of 1.5.Among them,the BMG exhibiting the largest reduced glass transition temperature(Trg)is Sm50Al25Co25,which reaches 0.648.The glass transition temperature Tg and the onset crystallization temperature Tx of this alloy are respectively 579 and 640 K at a heating rate of 20 K/min.
基金supported by the National Science Foundation of China(No.10376003)
文摘The two-dimensional energy balance in a coaxial plasma opening switch （POS） is studied based on the single-fluid magnetohydrodynarnic （MHD） equations coupled with the generalized Ohm＇s law. The energy transfers between the plasma and the magnetic field are considered during the penetration of the magnetic field as the Ohmic heating is included in the energy-balance equation. The focus is on the energy partition between the magnetic-field energy and the dissipated magnetic-field energy in a high-density POS with different rise-in-time electric currents at the generator boundary. The simulation code is tested in two cases： the constant-in-time current case and the linear rise-in-time current case. For the sinusoidally rise-in-time current similar to that of the experiments, it is shown that at the end of the conduction phase the dissipated magnetic-field energy is 36.5% of the input electromagnetic energy, which is consistent with the experimental results.
基金National Natural Science Foundation of China(No.10376003)
文摘Plasma behaviour and the scaling relations in a coaxial plasma opening switch （POS） using hydrogen plasma are studied self-consistently based on the two-dimensional magnetohydrodynamic （MHD） equations in conjunction with the generalized Ohm＇s law. The vacuum region on the right of POS is included in the model and the influence of downstream flow on the conduction characteristics is discussed. It is found that with the penetration of magnetic field, the pure hydrogen plasma is pushed downstream significantly; and POS still conducts current after the magnetic field arrives at the load edge of POS, which is different from the previous experimental results in a multispecies POS. It is because that the noticeable downstream plasma in the pure hydrogen POS may continue to conduct the current, while in the multispecies POS, the downstream plasma is unimportant so that the conduction phase ends soon after the magnetic field reaches the load edge. The scaling relation obtained from the simulations including the downstream region is consistent with the experimental results.
文摘In this paper we investigate the dust surface potential at the sheath edge of electronegative dusty plasmas theoretically, using the standard fluid model for the sheath and treating electrons and negative ions as Boltzmann particles but positive ions and dust grains as cold fluids. The dust charging model is self-consistently coupled with the sheath formation criterion by the dust surface potential and the ion Mach number, moreover the dust density variation is taken into account. The numerical results reveal that the dust number density and negative ion number density as well as its temperature can significantly affect the dust surface potential at the sheath edge.
基金supported by the National Natural Science Function of China(Nos.40390150,40390155,10575018)
文摘Effects of tearing modes are inves shows that the effect of the m = 0 harmonics on the early quasi-linear stage of m = 1 double tigated. The numerical calculation with the harmonics m = 0 included the m = 0 harmonics on the mode is negligible in the linear stage. As the mode begins to grow nonlinearly, both the current and flow profiles are pinched due to the m = 0 harmonics. To make a comparison we also carry out the calculation with m = 0 harmonics turned off. The profiles of the total current, poloidal magnetic field, and poloidal shear velocity in the cases with or without the m = 0 harmonics are compared and discussed. In addition, the formation of a poloidal velocity shear is found and its mechanism is investigated.
基金The project supported by the National Natural Science Foundation of China(No.19975008 and 10275009)and by MOEC (Ministry of Education,China)Grant for Cross-Century Excellent ScholarSupport from the Natural Sciences and Engineering Research Council of C
文摘The characteristics of collisional radio-frequency (rf) sheath dynamics over an elec-trode with a cylindrical hole is simulated by means of a self-consistent model which consists of two-dimensional time-dependent fluid equations coupled with Poisson equation. In addition, an equivalent-circuit model is coupled to the fluid equations in order to self-consistently determine re-lationship between the instantaneous potential at the rf-biased electrode and the sheath thickness. Two-dimensional profiles of the potential, the ion fluid velocity, and the distributions of the ion and electron densities within the sheath are computed under various discharge conditions, such as the discharge powers and the gas pressures. The results show that the existence of the cylindrical hole on the electrode significantly affects the sheath structure and generates a potential trap in the horizontal direction, which is particularly strong when the sheath thickness is comparable to the depth of the hole. Moreover, it is found that the collisional effects have a significant influence on the sheath characteristics.
基金This paper was financially supported by the National Natural Science Foundation of China(No.50401020,50671018 and 50631010)the Provincial Science and Technology Foundation of Liaoning(No.20061067).
文摘The bulk metallic glass formation in the Cu-Zr-M ternary systems by alloying of a binary basic Cu6Zr5 cluster was inves-tigated,where M stands for Sn,Mo,Ta,Nb,Ag,Al and Ti.The Cu6Zr5 cluster is a capped Archimedean antiprism that characterizes the local structure of the Cu10Zr7 crystalline phase.This cluster composition almost superposes with Cu-Zr eutectic Cu0.56Zr0.44.A se-ries of alloys along the cluster line(Cu6Zr5)1-xMx were examined for their glass forming abilities.Alloy rods with a diameter of 3 mm were prepared by copper mould suction casting method and analyzed by XRD and thermal analysis.The Cu-Zr based bulk metallic glasses were discovered with minor Nb,Sn,Mo,Ta additions(≤2at%)and Al,Ti,Ag(8at%≤concentration≤9at%).The alloying mechanism was discussed in the light of atomic size,cluster-linking structure and electron concentration factors.
基金The project supported by the National Nature Science Foundation of China(No.10175013)andInternational Collaboration Funds(No.10010760807,10160420799)
文摘Acoustic breathing modes of dusty plasmas have been investigated in a cylindrical system with an axial symmetry. The linear wave solution and a 'dispersion' relation were derived. It was found that in an infinite area, the mode is reduced to a 'classical' dust acoustic wave in the region away from the center. If the dusty plasma is confined in a finite region, however, the breathing (or heart-beating) behavior would be found as observed in many experiments.
