Beyond equilibrium thermodynamics in the low temperature plasma processor
Beyond equilibrium thermodynamics in the low temperature plasma processor
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DOI：
10.1116/1.5022470
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发表时间：
2018-06
影响因子：
1.4
通讯作者：
E. Thimsen
中科院分区：
文献类型：
--
作者：
E. Thimsen
低温等离子体是开放驱动的热力学系统，能够增加流过它们的质量的自由能。关于低温等离子体的一个有趣的事情是，不同的物种在太空中的同一位置具有不同的温度。由于不能假设热平衡，平衡热力学的许多熟悉的结果不能以其熟悉的形式应用于预测，例如，化学反应的方向。从经典的热平衡处理的角度来看，非常意想不到的气相化学反应（CO2离解，NO，N2 H4，O3合成）和固体材料转化（表面活化，尺寸聚焦，和超掺杂）的低温等离子体促进的例子。缺乏一个已知的化学反应平衡标准，防止低温等离子体的预测动力学模型的评估，以确保它们符合热力学定律。有一个通用的方法来预测在低温等离子体中的化学反应平衡或替代方法来建立一个拟议的动力学模型的热力学容许性的需要。为了达到这些目的，在这项工作中探讨了两个想法。第一个想法是低温等离子体中的化学反应在中性气体温度和电子温度之间的中间有效温度下朝向热平衡状态进行。有效温度假设很简单，令人惊讶的是，它足以解释某些系统，但它缺乏普遍性。非平衡可逆-不可逆耦合通用方程（GENERIC）是一个通用的超越平衡热力学框架，可用于严格建立一组动态建模方程（如动力学模型）的热力学容许性，而无需知道系统趋向的最终状态。GENERIC的使用通过使用来自文献的双温度流体动力学模型的示例来描述。在这项工作中提出的GENERIC分析的结论是，超局域平衡的概念在物理上是允许的，并可以应用于描述低温等离子体，提供适当的条款包括不同的物种之间的内部能量和动量的交换，可能有不同的温度和体积速度在空间中的同一位置。超局域平衡的概念有望在未来的工作中得到应用，重点是导出低温等离子体的平衡判据。低温等离子体是开放驱动的热力学系统，能够增加流经它们的质量的自由能。关于低温等离子体的一个有趣的事情是，不同的物种在太空中的同一位置具有不同的温度。由于不能假设热平衡，平衡热力学的许多熟悉的结果不能以其熟悉的形式应用于预测，例如，化学反应的方向。从经典的热平衡处理的角度来看，非常意想不到的气相化学反应（CO2离解，NO，N2 H4，O3合成）和固体材料转化（表面活化，尺寸聚焦，和超掺杂）的低温等离子体促进的例子。缺乏一个已知的化学反应平衡标准，防止低温等离子体的预测动力学模型的评估，以确保它们符合热力学定律。需要一个通用的…
Low temperature plasmas are open driven thermodynamic systems capable of increasing the free energy of the mass that flows through them. An interesting thing about low temperature plasmas is that different species have different temperatures at the same location in space. Since thermal equilibrium cannot be assumed, many of the familiar results of equilibrium thermodynamics cannot be applied in their familiar form to predict, e.g., the direction of a chemical reaction. From the perspective of classical processing governed by thermal equilibrium, examples of highly unexpected gas-phase chemical reactions (CO2 dissociation, NO, N2H4, O3 synthesis) and solid material transformations (surface activation, size-focusing, and hyperdoping) promoted by low temperature plasmas are presented. The lack of a known chemical reaction equilibrium criterion prevents assessment of predictive kinetics models of low temperature plasmas, to ensure that they comply with the laws of thermodynamics. There is a need for a general method to predict chemical reaction equilibrium in low temperature plasmas or an alternative method to establish the thermodynamic admissibility of a proposed kinetics model. Toward those ends, two ideas are explored in this work. The first idea is that chemical reactions in low temperature plasmas proceed toward a thermal equilibrium state at an effective temperature intermediate between the neutral gas temperature and the electron temperature. The effective temperature hypothesis is simple, and surprisingly is adequate for elucidation in some systems, but it lacks generality. The general equation for nonequilibrium reversible–irreversible coupling (GENERIC) is a general beyond equilibrium thermodynamics framework that can be used to rigorously establish the thermodynamic admissibility of a set of dynamic modeling equations, such as a kinetic model, without knowledge of the final state that the system is tending toward. The use of GENERIC is described by way of example using a two-temperature hydrodynamic model from the literature. The conclusion of the GENERIC analysis presented in this work is that the concept of superlocal equilibrium is thermodynamically admissible and may be applied to describe low temperature plasmas, provided that appropriate terms are included for exchange of internal energy and momentum between different species that may have different temperatures and bulk velocities at the same location in space. The concept of superlocal equilibrium is expected to be of utility in future work focused on deriving equilibrium criteria for low temperature plasmas.Low temperature plasmas are open driven thermodynamic systems capable of increasing the free energy of the mass that flows through them. An interesting thing about low temperature plasmas is that different species have different temperatures at the same location in space. Since thermal equilibrium cannot be assumed, many of the familiar results of equilibrium thermodynamics cannot be applied in their familiar form to predict, e.g., the direction of a chemical reaction. From the perspective of classical processing governed by thermal equilibrium, examples of highly unexpected gas-phase chemical reactions (CO2 dissociation, NO, N2H4, O3 synthesis) and solid material transformations (surface activation, size-focusing, and hyperdoping) promoted by low temperature plasmas are presented. The lack of a known chemical reaction equilibrium criterion prevents assessment of predictive kinetics models of low temperature plasmas, to ensure that they comply with the laws of thermodynamics. There is a need for a general...