Thermodynamics of hypoelasticity

A thermodynamic framework for hypoelasticity is constructed based on a modified Gibbs Function which depends on the stress deviator and specific volume. In the hypoelastic equations considered here, the stress deviator is obtained from a rate equation involving the corotational derivative and coefficients which depend on the invariants of the stress deviator as well as specific volume. Non-negative entropy production is enforced, leading to a non-dissipative condition in the sense that entropy is produced only by heat transfer. The resulting conditions lead to relations among the coefficients in the rate equation. These relations underdetermine the coefficients, so that there is leeway in specifying these coefficients. An example of a set of rate equations which satisfy the thermodynamics is presented.     

Zur Problematik individueller thermodynamischer Aktivitätskoeffizienten einzelner Ionensorten in Elektrolytlösungen hoher Konzentration

On the Individual Thermodynamic Activity Coefficients of Single Ion Species in Electrolyte Solutions at High Concentrations The individual activity coefficients of the single ion species, which are produced by dissociation of aqueous electrolytes, are necessary for the thermodynamic treatment of equilibrations and processes involving electrolytes. The determination of these values is one of the basic quests of electrochemistry and a controversial topic. This problem is unsolvable using classical thermodynamics. In this paper a mathematical method is shown, which can be used to split the mean activity coefficients into the values for the individual ion species of an electrolyte. For this determination the mean activity coefficients have to be expressed in the power form of equation. The concept based on the adaptation of a product function for the concentration development of the mean activity coefficients to the experimental data and their separation into factor functions of a predefined structure, which represent the concentration development of the individual activity coefficients of the single ion species of the electrolyte. This mathematical method was used to calculate the individual activity coefficients of the single ion species of alkali chlorides, alkaline earth chlorides, alkaline earth perchlorates, hydrohalic acids and alkali hydroxides. In summary, all the calculated single ion activity coefficients are in good agreement with the expected theoretical considerations. A proportionality to the reciprocal diameter of the unhydrated cation is clearly recognizable. The calculated individual activity coefficients correspond in every case with the assumption about their size, which can be reproduced using a variety of electrochemical investigations and experiments.     

Melting of microinclusions close packed in an elastic matrix

A novel representation is proposed of the liquid state in a microcavity, the collective nature of that state being taken into account. In this case a microinclusion undergoing melting is described as a single two-level system. The phase transition of melting in a close-packed system of such inclusions embedded in an elastic medium is described rigorously within the framework of the self-consistent approach. When an additional intermediate premelting state is taken into account, the curve of the steady-state phase transition with a critical point that happens on the phase diagram can be transformed in different ways, depending on the values of the specific parameters. In the simplest case shortening of the straight line takes place; bending is also possible. There is a region of the parameters where the critical line is split. In the latter case the existence of the triple point is also possible. The results obtained are in agreement with the experimental data.     

Thermodynamics of electrolyte solutions: Activity and osmotic coefficients of aqueous NaCl in the NaCl-MgCl2-H2O system at different temperatures by the EMF method

The activity and osmotic coefficients of aqueous NaCI in the NaCl-MgCl₂-H₂O system at 25, 35 and 45°C and total ionic strengths of 0.5, 1, 2 and 3 were obtained by an EMF method using a sodium ion-selective electrode and an Ag/AgCl electrode. The Harned coefficients and Pitzer binary and ternary interaction coefficients were also determined.     

Synthesis,Characterization and Migration of Ionic Polyferrocenyl Compounds of 5‐Ferrocenyl‐1H‐tetrazole and Their Effects During Combustion

Eighteen ionic polyferrocenyl compounds with 5‐ferrocenyl‐1H‐tetrazolate as anion and mono‐ and dinuclear ferrocenyl‐alkylammonium as cations were synthesized and characterized by ¹H NMR, ¹³C NMR, FT‐IR, and UV/Vis spectroscopy, and elemental analysis. Molecular structures of three compounds were further confirmed by single‐crystal X‐ray diffraction. Their thermal stability was evaluated by TG and DSC and found that they are of high thermal stability. The cyclic voltammetry analysis suggested that each of the compounds exhibits only an irreversible redox wave of the ferrocene units in the molecule. Both migration and volatility test results showed that, on comparison with those of Catocene, all tested compounds exhibit much more excellent anti‐migration ability and most of the tested compounds have lower volatility. Their effects on the thermal disintegration of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were measured by DSC. The results revealed that most of the compounds exhibit significant catalytic effects on the thermal degradation of AP and RDX. Particularly, most of the compounds containing one ferrocene unit in their cations show higher activity than that of Catocene. These compounds can be used as alternatives to Catocene in the composite solid propellants.     

Prediction of sound velocity and compressibility via molecular simulation at fixed entropy

A molecular-level simulation route is proposed to compute the isentropic thermodynamic properties in a fluid system by Monte Carlo simulation at fixed entropy. The method involves computation of the pressure response of a system to an infinitesimal change in system density by introduction of a single molecule, while retaining the system volume as well as the absolute molar entropy. The probability for accepting a change in temperature during the Monte Carlo moves was weighted against the argument proposed by Smith et al. [W.R. Smith, M. Lísal, I. Nezbeda, Chem. Phys. Lett. 426 (2006) 436–440]. Application to fluid argon has confirmed superior accuracy for the technique within the gas state to yield results within 1.2% of the measured values for the range of thermodynamic conditions investigated.     

Adsorption of fluoride on synthetic siderite from aqueous solution

The study has investigated the feasibility of using synthetic siderite for F⁻ removal from aqueous solution. Batch experiments were performed to test effects of adsorbent dosage, contact time, initial F⁻ concentration, temperature, solution pH, and coexisting anions on F⁻ removal. Results show that the kinetic rate of F⁻ adsorption was high in the first 2 h, and thereafter significantly decreased. The kinetic data was better fitted to the pseudo-second order kinetic model than the pseudo-first order kinetic model. In comparison with Langmuir isotherm, both Freundlich and Redlich-Peterson isotherms better described the adsorption process, which indicates that the multilayer adsorption should be involved in the process of F⁻ removal. Thermodynamic study manifests that F⁻ adsorption on synthetic siderite was spontaneous and exothermic in nature. The synthetic siderite had high adsorption capacity for F⁻ removal, which was up to 1.775 mg/g in the batch with an adsorbent dosage of 5 g/L and an initial F⁻ concentration of 20 mg/L at 25 °C. The adsorption was relatively independent on solution pH between 4 and 9. The presence of Cl⁻ and NO₃⁻ had less impact on F⁻ adsorption, while PO₄³⁻ significantly affected F⁻ removal from aqueous solution. Results of X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggest that the high adsorption capacity possibly arose from both coprecipitation of ferric hydroxide with F⁻ and adsorption of F⁻ on the fresh goethite.     

新型Salen型配合物的合成和表征及轴向配位热力学

采用金属模板法合成了四个新型Salen型单、双核金属配合物,并用元素分析、核磁共振(1HNMR)、电喷雾质谱(ESI-MS)、傅里叶变换红外光谱(FT-IR)等手段进行了表征.使用紫外-可见(UV-Vis)光谱滴定法和圆二色(CD)光谱研究了主体金属镍配合物与咪唑类含氮小分子的轴向配位反应热力学性质.结果表明:主体与咪唑(Im)和N-甲基咪唑(N-MeIm)的配位数是2,而与2-Et-4-MeIm和2-MeIm的配位数是1;轴配体系的热力学数据显示主体与咪唑类配体的平衡常数按K苓(Im)K苓(N-MeIm)K苓(2-Et-4-MeIm)K苓(2-MeIm)顺序依次减小;测得的△rHm苓和△rSm苓数据表明该轴向配位反应为放热、熵增加过程.     

磁性多壁碳纳米管吸附水中双氯芬酸的热力学与动力学

研究了磁化多壁碳纳米管(MWCNTs)对于水中非甾体抗炎药双氯芬酸的吸附过程.结果表明,双氯芬酸的吸附量随磁性MWCNTs投加量的增加而增大,而且吸附剂量增加到一定阶段后,双氯芬酸的吸附量达到平衡.在磁性MWCNTs的量为0.7g·L-1时,水溶液中双氯芬酸被磁性MWCNTs吸附的量达到最大,为33.37mg·g-1,对应的双氯芬酸去除率为98.1%.双氯芬酸的去除率随溶液pH的增加先增大后下降,随温度的升高而下降.用准一级、准二级模型进行了动力学分析.回归结果表明,准二级模型更准确地反映了吸附动力学.通过实验确定了Langmuir和Freundlich等温线的线性相关系数与标准偏差,结果揭示出Langmuir等温线与实验数据有很好的拟合度.对热力学参数的计算表明,ΔG00,意味着磁性MWCNTs对双氯芬酸的吸附是自发的;ΔH00,指明吸附是一个放热的物理吸附过程,温度低对吸附有利;ΔS00,代表该吸附是熵增过程.     

Unruh effect and holography

We study the Unruh effect on the dynamics of quarks and mesons in the context of AdS₅/CFT₄ correspondence. We adopt an AdS₅ metric with the boundary Rindler horizon extending into a bulk Rindler-like horizon, which yields the thermodynamics with Unruh temperature verified by computing the boundary stress tensor. We then embed in it a probe fundamental string and a D7 brane in such a way that they become the dual of an accelerated quark and a meson in Minkowski space, respectively. Using the standard procedure of holographic renormalization, we calculate the chiral condensate, and also the spectral functions for both the accelerated quark and meson. Especially, we extract the corresponding strength of random force of the Langevin dynamics and observe that it can characterize the phase transition of meson melting. This result raises an issue toward a formulation of complementarity principle for the Rindler horizon. We find most of the dynamical features are qualitatively similar to the ones in the thermal bath dual to the AdS black hole background, though they could be quite different quantitatively.