Entropy and Nonlinear Nonequilibrium Thermodynamic Relation for Heat Conducting Steady States

Among various possible routes to extend entropy and thermodynamics to nonequilibrium steady states (NESS), we take the one which is guided by operational thermodynamics and the Clausius relation. In our previous study, we derived the extended Clausius relation for NESS, where the heat in the original relation is replaced by its "renormalized" counterpart called the excess heat, and the Gibbs-Shannon expression for the entropy by a new symmetrized Gibbs-Shannon-like expression. Here we concentrate on Markov processes describing heat conducting systems, and develop a new method for deriving thermodynamic relations. We first present a new simpler derivation of the extended Clausius relation, and clarify its close relation with the linear response theory. We then derive a new improved extended Clausius relation with a "nonlinear nonequilibrium" contribution which is written as a correlation between work and heat. We argue that the "nonlinear nonequilibrium" contribution is unavoidable, and is determined uniquely once we accept the (very natural) definition of the excess heat. Moreover it turns out that to operationally determine the difference in the nonequilibrium entropy to the second order in the temperature difference, one may only use the previous Clausius relation without a nonlinear term or must use the new relation, depending on the operation (i.e., the path in the parameter space). This peculiar "twist" may be a clue to a better understanding of thermodynamics and statistical mechanics of NESS.Comment: 31 pages, 4 figure

Representation of nonequilibrium steady states in large mechanical systems

Recently a novel concise representation of the probability distribution of heat conducting nonequilibrium steady states was derived. The representation is valid to the second order in the ``degree of nonequilibrium'', and has a very suggestive form where the effective Hamiltonian is determined by the excess entropy production. Here we extend the representation to a wide class of nonequilibrium steady states realized in classical mechanical systems where baths (reservoirs) are also defined in terms of deterministic mechanics. The present extension covers such nonequilibrium steady states with a heat conduction, with particle flow (maintained either by external field or by particle reservoirs), and under an oscillating external field. We also simplify the derivation and discuss the corresponding representation to the full order.Comment: 27 pages, 3 figure

Tensile properties of Co-based oxide dispersion strengthened superalloys

Tensile properties of a novel Co-20Cr-5Al-2.4Hf-1.5Y(2)O(3) (wt%) oxide dispersion strengthened (ODS) superalloy were studied through a comparing investigation with Co-20Cr-5Al (wt%) alloy. Both the Co-based alloys (with and without oxide particles) were fabricated by mechanical alloying (MA), spark plasma sintering (SPS), hot rolling and the final annealing at 1200 degrees C. Due to the ultrafine grains of 500 nm in the ODS superalloy and 1.2 mu m in the ODS free alloy, the metastable fcc structure predominates at room temperature. Tensile testing was conducted at room temperature and 1000 degrees C. Strain-induced twinning deformation was evidenced by transmission electron microscopy and was found to significantly enhance the ultimate tensile strength (UTS) of the two alloys at room temperature. The Co-based ODS superalloy exhibits a superior tensile strength of 2.85 GPa at room temperature, which is associated with the distribution of twins and fine Y-Hf oxides. At 1000 degrees C, since the ultrafine grain size in the ODS superalloys, an easy grain boundary deformation occurred and resulted in a significant reduction in the UTS value. (C) 2017 Elsevier B.V. All rights reserved

Effect of Cr and Y2O3 on the oxidation behavior of Co-based oxide dispersion strengthened superalloys at 900 °C

In order to study the effect of Cr and Y2O3 addition on the oxidation behavior of novel Co-20Cr-10Al (wt.%) oxide dispersion strengthened (ODS) superalloys, an isothermal oxidation test was carried out at 900 degrees C in air. The addition of Cr altered the oxide scale from the multilayered scale with an external Co oxide/CoAl2O4 and an inner Al2O3 to a single Al2O3 scale. Y2O3 addition increased oxidation mass gain slightly but improved spallation resistance of the external Al2O3 scale

Tensile properties of Co-added FeCrAl oxide dispersion strengthened alloy

The Co-added FeCrAl oxide-dispersion-strengthened (ODS) alloy developed by the authors enables easy and precise control of the grain morphology and hardness using alpha/gamma phase transformation during manufacturing. The tensile properties of the transformable Co-added FeCrAl-ODS alloy were evaluated, focusing on the oxide dispersion strengthening and B2-type CoAl ordered strengthening at both ambient and elevated temperatures. The oxide particles and B2-type CoAl precipitate were characterized using transmission electron microscopy, and strengthening mechanisms for the oxide particles and CoAl-precipitate were evaluated by hardness and tensile tests at room temperature, 300 degrees C, and 500 degrees C. The theoretically estimated values showed good agreement with the experimental results at RT and 300 degrees C. However, the order strengthening by CoAl precipitates was significantly reduced at 500 degrees C, which was attributed to the increase of thermally activated slip in the body-centered cubic matrix. The slip weakened the dislocation interaction with CoAl precipitates with the same slip system

Corrosion-resistant materials for liquid LiPb fusion blanket in elevated temperature operation

The corrosion tests of CVD-SiC, FeCrAl alloy (APMT, Fe-22Cr-5Al) and ODS FeCrAlZr alloy (NF12, Fe-11.6Cr-6.2Al) were performed in liquid LiPb up to 1173 K for 250 h. High-purity LiPb was synthesized by melting and mixing of Pb and Li granules at 623 K under vacuum condition. CVD-SiC revealed corrosion resistance, though SiC chemically reacted with impurities dissolved in liquid LiPb and formed complex oxides. The α-Al2O3 layer which was formed on the surfaces of the FeCrAl alloys by the pre-oxidation treatment chemically reacted with liquid LiPb at 1023 K and 1173 K, and the layer chemically transformed into γ-LiAlO2

Reduction of MHD pressure drop by electrical insulating oxide layers in liquid breeder blanket of fusion reactors

The electrical conductivity of the α-Al2O3 layer formed on FeCrAl alloy APMT (Fe-21Cr-5Al-3Mo) in air atmosphere at 1273 K and 1373 K was measured in a temperature range between room temperature and 1073 K. Low electrical conductivity of the α-Al2O3 layer was clarified in the measurement temperature range. Low electrical conductivity of the ZrO2 layer formed on the Zr metal in air atmosphere at 873 K was also measured. Numerical simulation was performed with three-dimensional thermo-fluid code to clarify the reduction of magnetohydrodynamic (MHD) pressure drop with the electrical insulating α-Al2O3 and ZrO2 layers in liquid blankets of magnetic confinement fusion reactors. The MHD pressure drop is significantly reduced when the four inner surfaces of the duct are electrically insulated by the oxide layers. The electrical insulation of the three inner surfaces is also effective to reduce the MHD pressure drop when the magnetic field is parallel to the conductive wall of the flow duct. However, the MHD pressure drop is induced in the three-surface insulation duct when the magnetic field makes an angle with the conductive wall of the duct