Efficient and Accurate Methods for the Computation of Thermodynamic and Transport Properties of Multitemperature Thermal Plasma. Part I: Thermodynamic and Heavy Particle Transport Properties

In this paper we present numerical efficient methods for the computation ofthermodynamic and transport properties of nonequilibrium thermalplasmas. Thermodynamic properties of mono- and diatomic speciesare calculated directly from partition functions. The evaluation oftransport properties is based on the kinetic theory using the classicalChapman–Enskog approach to solve the heavy particle Boltzmannequation. A multitemperature model is used to consider thermalnonequilibrium.     

New Method to Calculate Thermodynamic and Transport Properties of a Multi-Temperature Plasma: Application to N2 Plasma

Multi-temperature thermal plasmas have often to be considered to account for the nonequilibrium effects. Recently André et al. have developed the calculation of concentrations in a multi-temperature plasma by artificially separating the partition functions into a product by assuming that the excitation energies are those of the lower levels (electronic, vibration, and rotation). However, at equilibrium, differences, increasing with temperature, can be observed between partition functions calculated rigorously and with their method. This paper presents a modified method where it has been assumed that the preponderant rotational energy is that of the vibrational level v=0 of the ground electronic state and the preponderant vibrational energy is that of the ground electronic state. The internal partition function can then be expressed as a product of series expressions. At equilibrium for N ₂ and N ₂ ⁺ partition functions the values calculated with our method differ by less than 0.1% from those calculated rigorously. The calculation has been limited to three temperatures: heavy species T_h , electrons T_e , and vibrational T _v temperatures. The plasma composition has been calculated by minimizing the Gibbs free enthalpy with the steepest descent numerical technique. The nonequilibrium properties have been calculated using the method of Devoto, modified by Bonnefoi and Aubreton. The ratio =T_e/T_h was varied between 1 and 2 as well as the ratio _v =T _v /T _h for a nitrogen plasma. At equilibrium the corresponding equilibrium transport properties of Ar and N ₂ are in good agreement with those of Devoto and Murphy except for T>10,000 K where we used a different interaction potential for N–N ⁺ . The effects of _v and _e on thermodynamic and transport properties of N ₂ are then discussed.     

An Alternative Quantitative Analysis of Non-Equilibrium Transport Coefficients in Argon Plasmas

To describe plasmas in non-local thermal equilibrium (non-LTE) four parameters need to be used, which are usually besides the pressure and the electron temperature, the electron density and the atom temperature. In the approach presented here it is argued that the use of four other variables is preferable. These four parameters are the total pressure, the ratio of the electron density and the squares root of the total pressure, and two specific non-equilibrium parameters. The non-equilibrium parameters are chosen such that they describe deviations from ionization–recombination equilibrium, and deviations from temperature equilibrium.It appears that the influence of deviations from complete LTE on the transport coefficients is often small when the parameters are scaled with the electron density and the pressure. In this way, the non-LTE transport properties can be estimated by using complete LTE transport coefficients without losing much accuracy.     

Reactions of Nonequilibrium Oxygen Plasmas with Liquid Olefins

The oxidation of 13 liquid olefins with either high-voltage or radio frequency (RF) glow discharges has been studied. The reactions were carried out by making the oxygen plasma reach the low vapor pressure substrate. Product formation has proved to be selective—epoxides, aldehydes, ketones, and low quantities of carboxylic acids being the most important species. Fragmentation products were only observed in the traps of the RF system for the most volatile olefin of this study. This indicates that, except for this case, the most relevant interaction of this study has been the heterogeneous reaction of the plasma with the liquid. Total conversion, i.e., mass transformed against initial mass of substrate, has been studied as a function of temperature of the liquid and oxygen flow rate in the reactor, this ranging from 15 to 53.6 mmol/hr in the high-voltage system and 13 to 270 mmol/hr in the RF device. The optimum conversions were 27 to 99%. A correlation between these results and the behavior of the O( ³ P) population in the discharge allows us to conclude that this is the most relevant species to the oxidation process. A discussion relating the structures of the olefins with the composition of the mixtures produced by the oxidation is also presented.     

Thermodynamic and Transport Properties of Argon/Helium Plasmas at Atmospheric Pressure

Plasma Chemistry and Plasma Processing - Because of the importance of having reliable transport coefficients for argon/helium mixtures available, viscosities and thermal conductivities of such...     

盐湖卤水协同萃取提锂及基础热力学性质

为了充分利用盐湖卤水中丰富的锂资源,提出了以磷酸三丁酯（TBP）-乙酸丁酯（BA）-FeCl₃-260^#磺化煤油体系协同萃取提锂的方法。针对该体系,考察了卤水酸度、n_Fe/n_Li比以及温度对协同萃取过程的影响。根据锂离子及其它主要离子萃取率的变化,确定了最优萃取条件为：pH=2,n_Fe/n_Li=3.0,T=20℃。在最优条件下,单级萃取率达到90%左右。同时,研究了萃取过程的热焓、吉布斯自由能及熵变等基础热力学性质。结果表明,在选定的萃取体系和条件下,锂的萃取反应为放热反应,萃取过程为熵减过程。     

盐湖卤水协同萃取提锂及基础热力学性质

为了充分利用盐湖卤水中丰富的锂资源,提出了以磷酸三丁酯(TBP)-乙酸丁酯(BA)-FeCl3-260#磺化煤油体系协同萃取提锂的方法。针对该体系,考察了卤水酸度、nFe/nLi比以及温度对协同萃取过程的影响。根据锂离子及其它主要离子萃取率的变化,确定了最优萃取条件为:pH=2,nFe/nLi=3.0,T=20℃。在最优条件下,单级萃取率达到90%左右。同时,研究了萃取过程的热焓、吉布斯自由能及熵变等基础热力学性质。结果表明,在选定的萃取体系和条件下,锂的萃取反应为放热反应,萃取过程为熵减过程。     

聚合物-卟啉钴复合膜的氧气促进输送性能

综述了聚合物－卟啉钴复合膜的氧气促进输送性能。讨论了卟啉钴的结构及与氧的结合性能，聚合物－卟啉钴复合膜的氧气促进输送特性，影响聚合物－卟啉钴复合膜氧气透过性能的因素及卟啉钴的不可逆氧化反应机理。     

Theoretical Study on Intermolecular Interactions and Thermodynamic Properties of Nitroamine Dimers

Ab initio self-consistent field(SCF) and Mφller-Plesset correlation correction methods employing 6-31G^** basis set have been applied to the optimizations of nitroamine dimers.The binding energies have been corrected for the basis set superposition error (BSSE) and the zero-point energy.Theree optimized dimers have been obtained.The BSSE corrected binding energy of the most stable dimer is predicted to be -31.85kJ/mol at the MP4/6-31G^**//MP2/6-31G^** level.The energy barriers of the Walden conversion for -NH2 group are 19.7kJ/mol and 18.3kJ/mol for monomer and the most stable dimer,respectively.The molecular interaction makes the internal rotation around N1-N2 even more difficult.The thermodynamic properties of nitroamine and its dimers at different temperatures have been calculated on the basis of vibrational analyses.The change of the Gibbs free energy for the aggregation from monomer to the most stable dimer at standard pressure and 298.2 K is predicted to be 14.05kJ/mol.     

超临界CO2微乳/反胶束体系热力学行为与应用*

超临界微乳/反胶束体系极大地拓展了超临界流体的溶剂特性,是超临界流体技术研究的热点课题。选择合适的表面活性剂,通过调控操作条件,可以方便地控制其增溶特性,作为一种新兴绿色溶剂,在化学反应、材料制备、萃取分离等领域都有潜在的应用前景。本文阐述了超临界CO₂微乳/反胶束系统的基本概念,总结和归纳了关于热力学性质、表面活性剂选择、相行为、水力学尺寸计算、聚团颗粒间相互作用力等理论研究成果。在此基础上,还就该领域的一些应用进行了分析讨论。     

正三角锯齿型石墨烯的电子输运特性

利用密度泛函理论和非平衡格林函数方法, 系统研究了正三角锯齿型石墨烯的电子输运特性. 研究表明: 正三角石墨烯的电流-电压(I-V)特性及整流效应与几何尺寸、边缘吸附原子的类型密切相关, 在其边缘吸附H原子和S原子的情况下, 小的正三角石墨烯有大的电流, 但有小的整流比; 改变边缘吸附原子的类型(用O原子替换H原子), 电流增大, 但其整流效应明显变低. 分析表明, 这种整流是由于正三角石墨烯前线轨道的空间分布不对称以及在正、负偏压下分子能级的非对称移动所致. 我们的研究对于认识正三角石墨烯的基本物性(电子结构及器件应用)有重要意义.     

氮化硼纳米管热输运性能的分子动力学模拟

采用基于声子散射理论的Boltzmann-Peierls声子传输方程(BTE)和非平衡态分子动力学模拟(NEMD)方法研究了氮化硼纳米管(BNNT)的热输运性能.分析了BNNT的热力耦合效应,通过BTE与NEMD两种方法相结合,分析了温度和长度对BNNT热输运性能的影响,并应用量子修正扩大了NEMD的研究范围.结果表明:随着拉伸或压缩应变的增加,BNNT热输运性能均呈降低的趋势.通过计算声子态密度(PDOS)在理论上分析了以上结果,发现在拉伸状态下,声子模式的变化是决定BNNT热输运性能变化的主要因素;在压缩状态下,热导率变化是由于模型发生明显的屈曲变形引起的.在低温段,BNNT的热输运性能受量子效应影响最初有一个线性增加的过程,当温度超过一定值时,其开始显著地降低;当BNNT长度小于120nm时,随着长度的增加,其弹道性能逐渐减弱,但仍主要体现为弹道特征,其热导率(κ)与长度(L)基本满足κ∝Lα这一关系.     

Calculation of Thermodynamic Properties and of Liquidus Line Positions for Na-K Alloys

A model of an ideal associated solution, containing self-associates of different sizes and shapes, was considered. Calculations of the thermodynamic properties of mixing of Na-K liquid alloys and of liquidus line positions were carried out. Possible modifications of the model are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Possible Mechanisms of String Formation in Complex Plasmas at Elevated Pressures

Possible mechanisms of particle attraction providing formation of the field aligned microparticle strings in complex plasmas at elevated gas pressures are theoretically investigated in the light of the Plasmakristall-4 (PK-4) experiment on board the International Space Station. The particle interaction energy is addressed by two different approaches: (i) using the dynamically screened wake potential for small Mach numbers derived by Kompaneets et al., in 2016, and (ii) introducing effect of polarization of the trapped ion cloud by discharge electric fields. Is is found that both approaches yield the particle interaction energy which is independent of the operational discharge mode. In the parameter space of the performed experiments, the first approach can provide onset of the particle attraction and string formation only at gas pressures higher than 40–45 Pa, whilst the mechanism based on the trapped ion effect yields attraction in the experimentally important pressure range 20–40 Pa and may reconcile theory and observations.     

Use of Liquid Precursors for Diamond Chemical Vapor Deposition--The Effects of Mass Transport and Oxygen

Thermal plasma chemical vapor deposition of diamond-utilizing liquidfeedstock injection has been shown to yield higher mass deposition rates,larger crystal size, and thicker films when compared to the use of gaseousfeedstock for equivalent operating conditions. Increased mass transport ofthe activated precursor species across the substrate diffusion boundarylayer and the presence of oxygen in liquid precursors are investigated aspotential reasons for the observed results. Comparisons of the variousprecursor systems investigated in this study are based on crystal size andfilm thickness as a function of radial postion, area of deposit, totalmass deposition rate, and the observed liquid precursor droplet trajectorieswithin the deposition chamber using a laser strobe video system. The resultsindicate that the mass transport in both the liquid and gaseous precursorsystems is greatly improved by the use of an inert carrier gas. Further, theuse of a liquid versus a gaseous precursor does not seem toresult in higher total deposition rates when the operating conditions forboth have been optimized. Finally, the presence of oxygen in the liquidfeedstock system is found to be at least partly responsible for theincreased growth rate, which is observed when comparing the plainhydrocarbon precursor cases with the oxygenated liquid precursorcase.     

On the Use of Global Kinetics Models for the Investigation of Energy Deposition and Chemistry in RF Argon–Oxygen Plasmas Working in the Torr Regime

A global plasma model is used to investigate the chemistry and energy deposition in 13.56 MHz radio-frequency capacitively coupled oxygen–argon discharges under conditions usually used for the deposition of tin oxide films. These models are based on the solution of a stationary electron Boltzmann equation coupled to species balance equations including the vibrational kinetics equations of O₂. The results obtained showed that vibrational non equilibrium of O₂-molecule is not significant. The dissociation degree of O₂ was found to be around a few percents and the discharge was often moderately electronegative even for small O₂ contents in the feed gas. The ionization and energy dissipation mechanisms are mainly governed by the collisional processes involving O₂ for an oxygen feed gas composition greater than 20%. Results also showed that the predicted densities of the charged species and the electronegative character of the discharge are strongly linked to the assumption made on the homogeneity of the power deposition. On the contrary, the predicted density of O-atom is not sensitive to this assumption.     

含氟共聚物与钴卟啉复合膜的制备及促进氧输送性能

研究了甲基丙烯酸八氟戊酯-乙烯基咪唑共聚物与钴卟啉复合膜的制备及钴卟啉与氧络合、促进输送性能.共聚物中的咪唑基与钴卟啉的第五配位点在溶液中络合,制得的复合膜具有快速和可逆的氧结合特性.温度降低,钴卟啉与氧络合的平衡常数增加;膜中的钴卟啉与氧络合平衡常数大于N,N-二甲基甲酰胺(DMF)溶液中的平衡常数.钴卟啉与氧络合和选择性地促进氧的输送使共聚物/钴卟啉复合膜的氧渗透系数和氧/氮选择系数提高.     

Ab initio Study on the Intermolecular Interaction and Thermodynamic Properties of Methyl Nitrate Dimer

Three stable dimers of methyl nitrate have been obtained and their geometries have been fully optimized at the HF/6‐31G,. level. Binding energies have been calculated with correction for the basis set superposition error (BSSE) and zero point energy (ZPE). The cyclic overlap‐type structure, the binding energy of which is 11.97 kJ/mol at the MP4SDTQ/6‐31G. / HF/6‐31G. level, is the most stable. No intermolecular hydrogen bond was found, and the charge transfer between two subsystems is minute. The thermodynamic properties of methyl nitrate and its dimers have been calculated based on the vibrational analysis and statistical thermodynamics.     

Standard Chemical Thermodynamic Properties of Perfluoro N-Alkanes

The chemical thermodynamic properties C_p°, ΔH_f° S°, ΔG_r° and K_p of gaseous perfluoro n-alkanes, P(CF₂)n F(2≤n≤10), have been calculated from 298.15 to 1000 K using the Benson method with C_p° = a″;b/T + c/T², C_p°=a+bT+c+/T² and C_p°=a″ + bT +cT². Better results are obtained for C_p°=a+b/T+c/T². The calculated chemical thermodynamic properties of C₂ F₆ (g) are in excellent agreement with the literature data of Stull, Westrum, and Sinke under IBM/PC microcomputer with STEP data base management system.     

The Stabilities and Thermodynamic Properties of Triethylenetetraminehexaacetic Acid Chelates of the Tripositive Lanthanide Ions

The interaction between the decadentate ligand triethylenetetraminehexaacetic acid (TTHA or H₆Z) and tripositive rare-earth metal ions (Ln³⁺) has been investigated. The acid formation constants of the hydrogen chelates (LnHZ^2?, LnH₂Z-) and the formation constants of the normal chelates (LnZ^3?) have been evaluated at 15, 25 and 35°C, and at an ionic strength of 0.1 (KNO₃), the former by a titration method and the latter by a mercury indicator electrode technique. Enthalpy and entropy changes characterizing the formation of the normal chelates have been calculated at 25°C. These functions have been compared with corresponding values for related chelating agents.