Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?

Bhattacharjee, Jayanta K.; Mirzaev, S. Z.; Kaatze, U.

doi:10.1007/s10765-012-1167-3

Cited by 11 publications

(12 citation statements)

References 41 publications

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“…Figure 9 shows that the experimental η s (0) data of the 2,6-dimethylpyridinewater mixture nicely fit to the relation obtained from an analysis of Eq. 12, using the measured static shear viscosities η s0 along with mutual diffusion coefficients of the system [54]. With the triethylamine-water mixture of critical composition, the η s (0) data are somewhat smaller than the corresponding η bg values, indicating another dispersion in η s below the frequency range of measurement [60].…”

Section: Critical Mixtures: Background Viscosity and Viscosity Relaxamentioning

confidence: 97%

“…Due to critical fluctuations in the local composition, such mixtures near the critical temperature T c exhibit an additional contribution in their shear viscosity [54]. As an example, the static shear viscosity η s0 of the 2,6-dimethylpyridine-water mixture of critical composition [18] is displayed in a range of temperatures in Fig.…”

Section: Critical Mixtures: Background Viscosity and Viscosity Relaxamentioning

confidence: 99%

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High-Frequency Shear Viscosity of Low-Viscosity Liquids

Kaatze

Behrends

2014

Int J Thermophys

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A thickness shear quartz resonator technique is described to measure the shear viscosity of low-viscosity liquids in the frequency range from 6 MHz to 130 MHz. Examples of shear-viscosity spectra in that frequency range are presented to show that various molecular processes are accompanied by shear-viscosity relaxation. Among these processes are conformational variations of alkyl chains, with relaxation times τ η of about 0.3 ns for n-pentadecane and n-hexadecane at 25 • C. These variations can be well represented in terms of a torsional oscillator model. Also featured briefly are shear-viscosity relaxations associated with fluctuations of hydrogen-bonded clusters in alcohols, for which τ η values between 0.3 ns (n-hexanol) and 1.5 ns (n-dodecanol) have been found at 25 • C. In addition, the special suitability of high-frequency shearviscosity spectroscopy to the study of critically demixing mixtures is demonstrated by some illustrative examples. Due to slowing, critical fluctuations do not contribute to the shear viscosity at sufficiently high frequencies of measurements so that the non-critical background viscosity η bg of critical systems can be directly determined from highfrequency shear-viscosity spectroscopy. Relaxations in η bg appear also in the shearviscosity spectra with, for example, τ η ≈ 2 ns for the critical triethylamine-water binary mixture at temperatures between 10 • C and 18 • C. Such relaxations noticeably influence the relaxation rate of order parameter fluctuations. They may be also the U. Kaatze (B) 2089 reason for the need of a special mesoscopic viscosity when mutual diffusion coefficients of critical polymer solutions are discussed in terms of mode-coupling theory.

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Section: Critical Mixtures: Background Viscosity and Viscosity Relaxamentioning

confidence: 97%

Section: Critical Mixtures: Background Viscosity and Viscosity Relaxamentioning

confidence: 99%

High-Frequency Shear Viscosity of Low-Viscosity Liquids

Kaatze

Behrends

2014

Int J Thermophys

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“…Another model-free method was later proposed by Vyazovkin for nonisothermal thermogravimetry experiments with a linear heating rate in which the activation energy E α * can be evaluated at any particular value of α by minimizing the following objective function [12,37,[43][44][45][46]:…”

Section: Calculation Of Kinetic Parametersmentioning

confidence: 99%

Thermal Decomposition Reaction of Ferrocene in the Presence of Oxalic Acid

Rooj

Roy

Bhattacharjee

2017

Int. J. Chem. Kinet.

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Thermal decomposition of ferrocene [(C 5 H 5 ) 2 Fe] in the presence of oxalic acid [(COOH) 2 ·2H 2 O] samples-prepared by grinding the mixtures of ferrocene and oxalic acid at different weight ratios-is reported in this work. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetics as well as thermodynamic parameters. Model-free (integral isoconversional) methods are employed to analyze thermogravimetric data. The most probable reaction mechanisms for thermal reactions have been identified. Based on the values of the activation energy E α * and reaction rate A α for different steps of decomposition, the values of S*, H*, and G* for the formation of activated complex from the precursor are estimated. Besides, this work has proposed reaction pathways indicating the formation of hematite (α-Fe 2 O 3 ) as the solid end-product of thermal decomposition of the samples.

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“…This information finds applications across a wide range of solid-state reactions. Thermogravimetric (TG) analysis is a common method for obtaining conversion data from the thermal solid-state reactions, which result in the change of sample mass upon heating under isothermal or nonisothermal conditions [4][5][6][7][8][9]. Nonisothermal thermogravimetry with a linear heating rate is the most frequently used technique for thermal analysis of materials [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…Thermogravimetric (TG) analysis is a common method for obtaining conversion data from the thermal solid-state reactions, which result in the change of sample mass upon heating under isothermal or nonisothermal conditions [4][5][6][7][8][9]. Nonisothermal thermogravimetry with a linear heating rate is the most frequently used technique for thermal analysis of materials [7][8][9][10]. In nonisothermal TG, model-fitting and model-free methods have been used quite commonly for the evaluation of kinetic parameters despite severe criticism recently raised on the use of the activation model for the interpretation of the kinetics of heterogeneous solid-state reactions [11].…”

Section: Introductionmentioning

confidence: 99%

Kinetic Analysis of Nonisothermal Decomposition of Acetyl Ferrocene

Das

Bhattacharjee

2018

Int J of Chemical Kinetics

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The work deals with thermal decomposition of acetyl ferrocene in nitrogen atmosphere based on nonisothermal thermogravimetry. It presents a mathematical analysis of nonisothermal thermogravimetric data using multiheating rates to estimate reaction kinetic parameters. Model free (integral isoconversional) methods are employed to analyze the thermogravimetric data. The decomposition is a multistep process. The activation energy Eα of decomposition is conversion (α) dependent. The average values of activation energy are Eα = 49.87, 106.28, and 183.35 kJ mol−1 for three major steps of decomposition. The most probable reaction mechanism function, g(α), for thermal reactions has been identified by the master plot method, and the stepwise reaction mechanisms are found to be different for different steps. The estimated values of the activation energy Eα and g(α) have been utilized in the determination of the reaction rate Aα of thermal decomposition. The α‐dependent reaction rate values are determined and are found to lie in the range of 5.2 × 105 to 3.2 × 104 min−1, 1.7 × 1015 to 7.8 × 106 min−1, and 3.8 × 108 to 1.4 × 107 min−1 for three different steps. Based on the values of Eα, g(α), and Aα, the thermodynamic triplets (ΔS, ΔH, ΔG) associated with the decomposition reactions have been estimated. Estimated kinetic parameters have been used to construct the conversion curves, and those have been successfully compared with the experimentally observed ones.

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Does the Viscosity Exponent Derive from Ultrasonic Attenuation Spectra?

Cited by 11 publications

References 41 publications

High-Frequency Shear Viscosity of Low-Viscosity Liquids

High-Frequency Shear Viscosity of Low-Viscosity Liquids

Thermal Decomposition Reaction of Ferrocene in the Presence of Oxalic Acid

Kinetic Analysis of Nonisothermal Decomposition of Acetyl Ferrocene

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