Activation Energy Of Viscous Flow Research Articles

Viscosity of sodium–borate melts containing mechanically activated REM oxide additions

The viscosity of sodium–borate melts containing 1 wt % mechanically activated lanthanide group REM oxide is measured in the temperature range 950–1650 K using an oscillating viscometer. The dependences of the viscosity on temperature and composition are determined. The logarithmic dependences have high- and low-temperature portions with different viscous flow activation energies. It is found that the melt structure changes as a function of composition and temperature.

Kinetic Viscosity of Molten High Entropy Alloys Cu–Sn–In–Bi–Pb

By means of torsional oscillation was studied temperature dependence of kinematic viscosity of equiatomic alloys Cu–Sn–In–Bi–Pb in the range of 600–1300 °C during heating and cooling regimes. There was detected discrepancy of temperature dependence for kinematic viscosity, corresponding to regimes of heating and cooling, as well as stepwise variation of characteristics of viscous flow (activation energy of viscous flow and entropy factor in Arrhenius equation) during sample heating.

Photophysics and Rotational Dynamics of a Hydrophilic Molecule in a Room Temperature Ionic Liquid.

We have studied the photophysics and rotational diffusion of hydrophilic solute 7-(N, N'-diethylamino)coumarin-3-carboxylic acid (7-DCCA) in a room temperature ionic liquid methyltrioctylammonium bis(trifluoromethylsulfonyl) imide ([N1888 ][NTf2 ]). Comparison of activation energies of viscous flow and nonradiative decay shows that the photophysical properties of 7-DCCA are not guided by the bulk viscosity of the medium but are dependent on the specific solute solvent interaction and structural heterogeneity of the medium. The rotational relaxation behaviour of 7-DCCA in [N1888 ][NTf2] shows significant deviation from the Stokes Einstein Debye hydrodynamic model of rotational diffusion. This is indicative of the influence of specific solute solvent interaction on the rotational relaxation behaviour of 7-DCCA. Comparison of activation energy of rotational relaxation with activation energy of viscous flow clearly reinforces our assumption that the structural heterogeneity of the medium and specific solute solvent interaction plays a dominant role on the rotational diffusion instead of bulk viscosity.

Correlation Between Superheated Liquid Fragility And Onset Temperature Of Crystallization For Al-Based Amorphous Alloys

Abstract Amorphous alloys or metallic glasses have attracted significant interest in the materials science and engineering communities due to their unique physical, mechanical, and chemical properties. The viscous flow of amorphous alloys exhibiting high strain rate sensitivity and homogeneous deformation is considered to be an important characteristic in thermoplastic forming processes performed within the supercooled liquid region because it allows superplastic-like deformation behavior. Here, the correlation between the superheated liquid fragility, and the onset temperature of crystallization for Al-based alloys, is investigated. The activation energy for viscous flow of the liquid is also investigated. There is a negative correlation between the parameter of superheated liquid fragility and the onset temperature of crystallization in the same Al-based alloy system. The activation energy decreases as the onset temperature of crystallization increases. This indicates that the stability of a superheated liquid can affect the thermal stability of the amorphous alloy. It also means that a liquid with a large superheated liquid fragility, when rapidly solidified, forms an amorphous alloy with a low thermal stability.

The effect of lithium on the viscosity of pegmatite forming liquids

Viscosity experiments were conducted to investigate the effect of Li2O on the viscosity of pegmatite forming melts and the possible difference to K2O. The individual effects of Li2O and K2O on melt viscosity were investigated by adding the same molar proportion of both components to a starting composition representing natural pegmatite forming melts. The viscosity experiments on hydrous melts (~1 to ~6wt.% H2O) were carried out in the low temperature range at ambient pressure using the micropenetration technique and in the high temperature range at 200–300MPa pressure using the falling sphere method.The addition of Li2O and K2O results in a decrease of melt viscosity and, on a molar basis, the effect of Li2O is comparable to that of K2O. Viscosity-related properties such as activation energy of viscous flow, melt fragility and glass transition temperature are affected in a similar way by both alkali oxides. The observed effects of alkalis on the viscosity of melt are smaller when compared to an equal molar amount of OH− groups at low water content but become equal with increasing water content. Finally, it is shown that the low viscosity of pegmatite forming melts can only be explained by the combined effects of H2O, F and of non-charge balancing alkalis.

Influence of molecular weight on structure and rheological properties of microcrystalline chitosan mixtures

In the present work, the atomic force microscopy (AFM) studies and rheological properties of aqueous solutions of microcrystalline chitosan (MCCh), polyacrylamide (PAM) and their mixtures at different weight ratios have been investigated. Flow measurements were carried out using on solutions of native polymers and their mixtures with various weight fractions of components. It has been observed that the polymer solutions and their mixtures exhibited the non-Newtonian behavior with shear-thinning and/or shear-thickening areas. Rheological parameters from power law and activation energy of viscous flow are determined and discussed. The AFM images showed difference in surface properties films for the native polymers and their mixtures. The roughness of the mixtures increases with the increase of MCCh content. This may indicate a strong interaction between the polymeric components.

Viscosity of high-entropy melts in Cu-Sn-Pb-Bi-Ga, G-Sn, Cu-Pb, Cu-Ga, and Cu-Bi equiatomic compositions

Temperature dependences of kinematic viscosity of high-entropy melts (HEM) of the composition, at %, Cu-20Sn-20Pb-20Bi-20Ga, Cu-50Sn, Cu-50Pb, Cu-50Ga, and Cu-50Bi are investigated in a temperature range from 1550 to 1300°C. It is shown that melt overheating above a definite temperature (t hom) leads to the appearance of viscosity hysteresis, which indicates a variation in the structural state of the HEM. The values of t hom for all studied samples are in limits of 925–1185°C. It is found that heating the HEM to definite temperatures (t*) leads to a variation in the activation energy of viscous flow (E) and entropy multiplier (A) in the Arrhenius equation: ν = Aexp[E/(RT)]. Entropy of viscous flow (ΔS #) for studied HEMs is investigated in terms of the Airing theory. It is revealed that the magnitude of ΔS# for a five-component Cu-Sn-Pb-Bi-Ga melt in a cooling mode is smaller than during heating by a factor of 2.6. The rheological characteristics of HEMs allow us to consider these melts promising functional materials: solders, heat carriers, and electric contacts.

Effect of Oligomer Structure on the Diffraction Efficiency of Holographic Recording Media

The development of new materials possessing photoconductance in the visible and near-IR regions holds great importance for the use of such materials in photoelectric solar energy converters, light emitters, light beam modulators and switches, and devices for recording, storage, and for the treatment of optical information. In addition to inorganic semiconductors, organic oligomers and their derived composites (OC) hold promise for practical application [1-8]. Most of the experience in the development of OC with hole-type conductance has been accumulated for electrographic and holographic information media [9-11]. These OC were tested in holographic recording media (HRM) for the photothermoplastic (PTP) method of recording optical information [12]. HRM for the PTP method of hologram recording should possess suitable rheological properties, high electrical resistance in the dark, and high photoconductance. Our studies over many years have indicated that the rheological properties are more important than photoconductance in the photosensitivity of the recoding layer of photothermoplastic material. Thus, the viscosity, surface tension, brittle temperature, and viscous flow activation energy are the major factors determining the photosensitivity of the oligomer films. The softening temperature and viscosity of oligomer photoconductors decrease with decreasing length of its main chain and increasing distance between bulky carbazolyl substituents. The presence of oxygen or silicon hinge atoms enhances the number of allowed conformations of the individual units, which permits lowering the softening temperature of the oligomer and increasing elasticity of the oligomer films. However, there is only sparse information in the literature on the effect of the shape oftheoligomermoleculesontheaboveproperties.Inthiswork,wecarriedoutacomparativestudyofthediffractionefficiency of holograms in HRM derived from linear and radial oligomers. The sensitivity of the recording layer of a photothermoplastic material is largely a function of the capacity of the oligomer photoconductor to undergo deformation upon the action of a surface charge. Since one of the factors inhibiting deformation is viscosity in the melt, a decrease in this viscosity should lead to a significant increase in the sensitivity of the recording layer. The distinguishing feature of radial, i.e., star-shaped, polymers is lower viscosity in melts and solutions relative to their linear analogs. This property led to the choice of radial siloxane oligomers for the creation of highly-sensitive HRM for the PTP method of hologram recording.

VISCOSITY OF HIGH-ENTROPY MELTS IN CU–SN–PB–BI–GA, CU–SN, CU–PB, CU–GA, AND CU–BI EQUIATOMIC COMPOSITIONS

Temperature dependences of kinematic viscosity of high-entropy melts (HEM) of the composition, at %: Cu–20Sn–20Pb–20Bi–20Ga, Cu–50Sn, Cu–50Pb, Cu–50Ga, and Cu–50Bi are investigated in a temperature range from 1550 to 1300 °C. It is shown that melt overheating above a definite temperature (thom) leads to the appearance of viscosity hysteresis, which indicates the variation in the structural state of the HEM. Values of thom for all studied samples are in limits of 925–1185 °C. It is found that heating of the HEM to definite temperatures (t*) leads to the variation in activation energy of viscous flow (Е) and entropy multiplier (A) in the Arrhenius equation: v = Aexp[E/(RT)]. Entropy of viscous flow (ΔS≠) for studied HEM is investigated in terms of the Airing theory. It is revealed that the magnitude of ΔS≠ for a five-component Cu–Sn–Pb–Bi–Ga melt in a cooling mode is smaller than during heating by a factor of 2,6. The found rheological characteristics of HEMs allow us to consider these melts as promising functional materials: solders, heat carriers, electric contacts.

Rheological properties of mesophase pitch investigated by the Giseeler fluidity method

The Giseeler fluidity method was used to investigate the rheological properties of pitch with and without heat treatment from room temperature to 520 °C. Results show that the fluidity has a good repeatability at different temperatures under different heating rates. The fluidity of the raw pitch slowly increases from 253 to 282 °C, then increases exponentially from 282 to 311 °C near the softening temperature, and finally remains unchanged from 311 to 498 °C. This changing pattern of fluidity with temperature has also been found for heat-treated mesophase pitch and can be formulated by the Arrhenius equation, from which the viscous flow activation energy can be obtained. The toluene-insoluble fraction increases from 67.3 to 88.7% with heat-treatment time and the flow activation energy of the treated mesophase pitch in the Newtonian fluid region at low temperature range is between 203.6 and 294 kJ/mol.

The activation energy of the viscous flow of layers of saturated hydrocarbons with quasi macroscopic cross-borderstructure

Influence of temperature on the viscosity coefficient in shear flow micron layers of saturated hydrocarbons n-heptadecane, n-hexadecane and n-tridecane. Such heterophasic interlayers (which are including epitropnye liquid crystal layers) activation energy of viscous flow 2÷3 times higher than that of liquids in the "volume".

Intrinsic viscosity and rheological properties of natural and substituted guar gums in seawater

The intrinsic viscosity and rheological properties of guar gum (GG), hydroxypropyl guar (HPG) and carboxymethyl guar (CMG) in seawater and the effects of shear rate, concentration, temperature and pH on these properties were investigated. An intrinsic viscosity-increasing effect was observed with GG and HPG in seawater (SW) compared to deionized water (DW), whereas the intrinsic viscosity of CMG in seawater was much lower than that in DW due to a screening effect that reduced the repulsion between the polymer chains. Regardless of the functional groups, all sample solutions was well characterized by a modified Cross model that exhibited the transition from Newtonian to pseudoplastic in the low shear rate range at the concentrations of interest to industries, and their viscosity increased with the increase in their concentration but decreased with the increase in temperature. In contrast to nonionic GG or HPG, anionic CMG had a slightly decreased viscosity property in SW, exhibiting polyelectrolyte viscosity behavior. The α value in the zero-shear rate viscosity vs. concentration power–law equation for the samples gave the order of CMG>HPG>GG while the SW solution of CMG had the lowest viscous flow activation energy and exhibited a strong pH-dependent viscosity by a different shear rate.

Effect of lanthanide group REM oxides activated mechanically on the viscosity of borate melts

The viscosity of borate melts containing 1 wt % lanthanide group REM oxide is studied by an oscillatory viscometer in the temperature range 1100–1700 K. The activation energy of viscous flow is calculated. The zigzag-shaped dependence of the viscosity on the atomic number of a lanthanide in a number of melts obeys the series periodicity (tetrad effect). The deviations from the tetrad effect are due to the formation of divalent rare-earth element ions.

Transport and Thermodynamic Properties of Ethylammonium Nitrate–Water Binary Mixtures: Effect of Temperature and Composition

Physical properties such as densities, ρ, viscosities, η, and conductivities, κ, have been measured for the binary mixtures of the ionic liquid ethylammonium nitrate, EtNH3NO3, with water over the entire molar fraction range at various temperatures ranging from 293.15 to 318.15 K and under ambient pressure. Strong effects of the composition and temperature on these properties have been observed. Experimental densities and viscosities were used to calculate the corresponding excess properties. The variations of excess molar volume and excess Gibbs energy against the ionic liquid fraction show complementary extrema (minima and maxima with opposite signs). The excess molar volumes and excess viscosity deviations are well fitted using the Redlich–Kister polynomial. Moreover, the viscosity was found to be temperature dependent and followed the Arrhenius law. Variations of the activation energies for viscous flow versus the ionic liquid content revealed a modification in the medium’s structure. The conductivity–temperature relationship was found to be better represented by the Vogel–Tammann–Fulcher model than with the Arrhenius equation. In addition, variations of the conductivity with composition are well described by the Casteel–Amis equation. The impact of addition of the ionic liquid to water on the viscosity and the conductivity have been also examined using Walden’s rule, which shows that viscosity is highly correlated to conductivity for ionic liquid molar fractions higher than ca. 0.2. Activation thermodynamic parameters for viscous flow, calculated from the viscosity data, reveal that changes in the medium structure occur at ca. 0.2 and 0.8 molar fractions of ionic liquid.

About activation energy of viscous flow of glasses and melts

ABSTRACTData on a viscous flow model based on network defects – broken bonds termed configurons – were analysed. An universal equation has been derived for the variable activation energy of viscous flow Q(T) of the generic Frenkel equation of viscosity η(T)=A∙exp(Q/RT) which is known to have two constant asymptotes – high QH at low temperatures and low QL at high temperatures. The defect model of flow used by e.g. Doremus, Mott, Nemilov, Sanditov states that higher the concentration of defects (e.g. configurons) the lower the viscosity. We have used the configuron percolation theory (CPT) which treats glass–liquid transition as a percolation-type phase transition. Additionally the CPT results in a continuous temperature relationship for viscosity valid for both glassy and liquid amorphous materials. We show that a particular result of CPT is the universal temperature relationship for the activation energy of viscous flow: Q(T)=QL+RT∙ln[1+exp(-Sd/R) exp((QH-QL)/RT)] which depends on asymptotic energies QL (for the liquid phase) and QH (for the glassy phase), and on entropy of configurons Sd. This equation has two asymptotes, namely Q(T<<Tg) = QH, and Q(T>>Tg) = QL. Moreover we demonstrate that the equation for Q(T) practically coincides in the transition range of temperatures with known Sanditov equation.

Acoustic, Thermal and Molecular Interactions of Polyethylene Glycol (2000, 3000, 6000)

Polyethylene Glycol (PEG) is a condensation polymer of ethylene oxide and water. PEG find its application as emulsifying agents, detergents, soaps, plasticizers, ointments, etc. Though the chemical and physical properties of PEG are known, still because of their uses in day to day life, it becomes necessary to study few physical properties like ultrasonic velocity, viscosity and hence adiabatic compressibility, free length, etc. In the present study, an attempt has been made to compute the activation energy and hence to analyse the molecular interactions of aqueous solutions of Polyethylene Glycol of molar mass 2000, 3000 and 6000 at different concentrations (2%, 4%, 6%, 8% and 10%) at different temperatures (303K, 308K, 313K, 318K) by determining relative viscosity, ultrasonic velocity and density. Various parameters like adiabatic compressibility, viscous relaxation time, inter molecular free length, free volume, internal pressure, etc are calculated at 303K and the results are discussed in the light of polymer-solvent interaction. This study helps to understand the behavior of macro-molecules with respect to changing concentration and temperature. Furthermore, viscosity and activation energy results are correlated to understand the increased entanglement of the polymer chains due to the increase in the concentration of a polymer solution that leads to an increase in viscosity and an increase in the activation energy of viscous flow.

Rheological Properties of Casting Solutions for Starch Edible Films Production

Rheological properties of corn starch and sodium alginate blend solutions have been measured at different polymer ratios in the temperature range from 303 to 343 K bya R/S Brook field rheometer with аcoaxial cylinder measuring unit. Dynamic viscosity of blends has been shown to decrease with shear rate increase and to increase with sodium alginate content increase. The influence of shear rate on activation energy of viscous flow depends on sodium alginate content and is different for below and over 5% (mass) content. Applicability of Ostwald-de-Waele, Herschel-Bulkley, Bingham and Casson models for the description of CS:SA blend solutions flow has been analyzed. Rheological properties of CS:SA blend solutions allow one to look at them as an alternative to starch solutions for edible films casting and production by dry method.

ВЯЗКОСТНЫЕ И ОПТИЧЕСКИЕ ХАРАКТЕРИСТИКИ ЩЕЛОЧНЫХ РАСТВОРОВ Na-КАРБОКСИМЕТИЛЦЕЛЛЮЛОЗЫ В ОБЛУЧЕННОЙ ЭЛЕКТРОМАГНИТНЫМ ПОЛЕМ ВОДЕ

It was established that low intensity exposure (1 W) ultra-high frequency electromagnetic fields (175–265 MHz) for the water leads to a change in its physical-chemical properties. It has been shown that a significant increase in the electric conductivity and pH of the water occurs at a certain frequency of the field (180, 210, 220 and 230 MHz) and the time of exposure – 3 hours, which is interpreted as a change in its supramolecular organization. A substantial reduction in the relative viscosity of a 0,2% alkaline solution of CMC-Na, prepared with water having been exposed to electromagnetic, it is most pronounced for the frequencies 210 and 220 MHz. The viscosity measurements were carried out in the temperature range 25–40 °C. The effect is maintained throughout the temperature range studied. From the temperature dependence of the viscosity is calculated activation energy of viscous flow. It established its decline compared with control samples. Showed a decrease in turbidity alkaline solutions Na-CMC, prepared on the water subjected to an electromagnetic field. The observed effects may be due to the more compact packaging of the macromolecules of the polymer due to the weakening of hydration as a result of the restructuring of the supramolecular structure of water under irradiation.

Influence of CaF2 on the Viscosity and Structure of Manganese Ferroalloys Smelting Slags

Addition of CaF2 to the CaO-SiO2-MnO (CaO/SiO2 = 0.5) system, which corresponds qualitatively to a silicomanganese ferroalloy smelting slag, affected not only the critical (crystallization) temperature (TCR) but also the viscosity at high temperatures, and its influence on slag properties was strongly dependent on the content of MnO in the slag. The viscosity of CaF2-free 10 mass pct MnO slag was relatively high, i.e., about 10 dPa s at 1773 K (1500 °C), but decreased continuously upon addition of CaF2 to the system. In contrast, the viscosity of the 40 pct MnO system was very low, i.e., 1 dPa s at 1773 K (1500 °C), and CaF2 did not have a large effect. This indicates that Mn2+ is a strong network modifier in manganese ferroalloy smelting slags. Nevertheless, CaF2 addition was very effective at decreasing the viscosity of low MnO slags at low temperatures. The activation energy for the viscous flow of silicate melts decreased linearly in response to CaF2 addition, but this tendency was less pronounced in the more basic composition of the slag. The effect of CaF2 on the viscosity and activation energy for viscous flow of melts was analyzed quantitatively using micro-Raman spectra of quenched glass samples and the silicate polymerization index, i.e., Q3/Q2 ratio. The polymerization index decreased continuously with increasing CaF2 content in less basic (10 pct MnO or C/S = 0.5) slags, whereas it was not affected by CaF2 content in highly basic (40 pct MnO and C/S = 1.0) slags. Bulk thermophysical properties of the CaO-SiO2-MnO-CaF2 slags were quantitatively correlated with the structural information of the slags.

Heterogeneous catalytic synthesis of poly(butylene succinate) by attapulgite‐supported Sn catalyst

ABSTRACTAn attapulgite‐supported Sn catalyst (Sn‐palgorskite) was successfully prepared by ion‐exchange co‐impregnation method. The catalytic effect of Sn‐attapulgite on the melt polycondensation reaction of poly(butylene succinate) (PBS) was examined by comparing with that of anhydrous SnCl2 and a blank experiment. The structures and properties of the PBS products synthesized with the three catalytic systems were characterized by means of Fourier transform‐infrared spectra (FT‐IR), viscosity measurements, wide angle X‐ray diffraction (WARD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Meanwhile, the acidolysis degradation behaviors of the PBS samples were also studied. It was found that the intrinsic viscosities and the number‐average molecular weights of the PBS were remarkably increased under the catalysis of Sn‐attapulgite, further leading to an increase in the decomposition temperature, the crystallization temperature, and the viscous flow activation energy, while a decrease in the melting temperature, the relative degree of crystallinity, and the rate of degradation. Additionally, no significant differences were observed in the crystal structures of all the samples, regardless of the reaction system with or without catalyst. The experiment results confirmed that Sn‐attapulgite was an effective heterogeneous catalyst for the synthesis of PBS, and the recycled Sn‐attapulgite still exhibited higher activity than anhydrous SnCl2 under identical reaction conditions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41729.