Activation Energy Of Viscous Flow Research Articles

Effects of viscous flow activation energies and viscosities on waterborne light-diffusion dip-coatings

PurposeThis paper aims to prepare good waterborne light-diffusion dip-coatings (WLDDC) for the glass lampshade inner walls of LED lamp tubes, the effects of viscosities and viscous flow activation energies on these dip-coatings were investigated.Design/methodology/approachThe WLDDC were prepared using white pigments, light-diffusion agents, additives and an acrylic emulsion. The dip-coatings were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and a digital rotational viscometer, respectively. The effects of shear rates, temperatures and solids contents on the viscosities of the dip-coatings were studied. The viscous flow activation energies of these dip-coatings and the emulsion were calculated, compared and studied, respectively.FindingsThe results showed that the non-Newtonian behaviors of these dip-coatings were more prominent than that of the acrylic emulsion. When the temperature was maintained to be a constant and the shear rate was increased, the viscosity decreased and the shear stress increased. When the shear rate was maintained to be a constant, the viscosity decreased with increasing temperatures. The viscous flow activation energies of these dip-coatings decreased with the increasing shear rates. The higher solid contents of WLDDC were, the more its viscosity would decrease with the increasing shear rates, the more prominent its non-Newtonian behaviors would show.Practical implicationsA sample of good WLDDC with balanced properties was illustrated.Originality/valueThis investigation benefits to investigate waterborne environment-friendly dip-coatings for the inner glass walls of lamp tubes. This research provides an approach to optimize the viscosity parameters of light-diffusion dip-coatings.

Kinetic Processes in Amorphous Materials Revealed by Thermal Analysis: Application to Glassy Selenium

It is expected that viscous flow is affecting the kinetic processes in a supercooled liquid, such as the structural relaxation and the crystallization kinetics. These processes significantly influence the behavior of glass being prepared by quenching. In this paper, the activation energy of viscous flow is discussed with respect to the activation energy of crystal growth and the structural relaxation of glassy selenium. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and hot-stage infrared microscopy were used. It is shown that the activation energy of structural relaxation corresponds to that of the viscous flow at the lowest value of the glass transition temperature obtained within the commonly achievable time scale. The temperature-dependent activation energy of crystal growth, data obtained by isothermal and non-isothermal DSC and TMA experiments, as well as direct microscopic measurements, follows nearly the same dependence as the activation energy of viscous flow, taking into account viscosity and crystal growth rate decoupling due to the departure from Stokes–Einstein behavior.

Effect of Viscous Flow Activation Energy on the Gas-Assisted Extrusion Forming of Plastic Micro-Tube

In this paper, the effect of viscous flow activation energy on the gas-assisted extrusion (GAE) forming of the plastic micro-tube was investigated by numerical method. The three-phase fluids geometric model was built and same boundary conditions were imposed in the model. Under different viscous flow activation energies (VFAE), the influence of VFAE on the size changes of plastic micro-tube in the GAE were obtained. Moreover, the flow velocities, pressure, temperature, and viscosity distributions of melt were also gotten and analyzed. Results show that with the increase of viscous flow activation energy, the inner and outer radiuses all synchronously increase due to the increase of radial velocity and axial velocity. In addition, the temperature distribution slightly increases, which results in the decrease of the pressure and viscosity of melt.

Effect of CaF2, B2O3 and the CaO/SiO2 mass ratio on the viscosity and structure of B2O3‐containing calcium‐silicate‐based melts

AbstractThe relationship between the viscosity and structure of B2O3‐containing calcium‐silicate‐based mold fluxes and the effects of fluidizers including CaF2, CaO, and B2O3 on the viscosity and their correlation with the structural aspects were studied using a rheometer with Fourier transformation infrared and Raman spectroscopy. The viscosity decreased with increasing CaF2 addition up to 28 wt% at a fixed CaO/SiO2 ratio of 0.3, which was related to depolymerization. Furthermore, CaF2 addition also affected the apparent activation energy for viscous flow, which decreased with increasing CaF2 content to 105.1 from 151.1 kJ/mol. At higher C/S ratios, the viscosity decreased in the presence of greater Ca2+ and O2− supplied from CaO, which subsequently increased the activation energy to 149.7 from 122.0 kJ/mol. With regard to the B2O3‐melt, polymerization of the network structure was observed by comparing the B2O3‐free to 4.4 wt% B2O3 content. However, the viscosity was relatively constant with increasing B2O3 addition. However, the viscosity decreased due to greater simplification of the network structure above 4.4 wt% B2O3. The break temperature decreased with greater B2O3 addition as the crystallization was inhibited. Furthermore, the apparent activation energy decreased as depolymerization of the network structures occurred above 4.4 wt% B2O3.

Activation energy for the viscoelastic flow: Analysis of the microstructure-at-rest of (water- and milk-based) fruit beverages

Fresh fruit beverages are a tasty way to follow the recommendations of World Health Organization. A study on the rheological behaviour of water-based and milk-based fruit beverages with emphasis on the temperature effect was made. The power law model adjusted data of apparent viscosity. The flow index of each beverage was practically constant with temperature variation. Then, one could discuss the variation with temperature of the consistency index. This parameter decreased around 40% in both cases in the temperature interval 5–30 °C. The stability of beverages against the sedimentation of the fruit pulp was clearly affected by the increase of temperature. Viscoelastic moduli were obtained in the linear region. Temperature dependency of both moduli was described in the interval 5–30 °C. The activation energy for linear viscoelastic flow was slightly higher than the activation energy for viscous flow. This result was interpreted as an indication of the strength of the microstructure-at-rest.

Research on Polymer Viscous Flow Activation Energy and Non-Newtonian Index Model Based on Feature Size

The viscous flow activation energy and non-Newtonian index properties of polymer based on feature size were studied through a series of experiments on the rheological properties of amorphous polymer polymethyl methacrylate (PMMA), semi-crystalline polymer polypropylene (PP), and crystalline polymer high-density polyethylene (HDPE) using capillary die with hole diameters of φ0.3 mm, φ0.5 mm, φ1.0 mm, and φ2.0 mm. The results show that the viscous flow activation energy of PMMA decreases with the feature size under microscopic scale. And the viscous flow activation energy of PP and HDPE increases with hole diameters of the die. Under macroscopic scale, the difference in viscous flow activation energy of all polymer materials is significantly reduced with hole diameters of the die. For the non-Newtonian index of the three polymer materials, it decreases with the feature size under the microscopic scale while it increases or does not change with the feature size under the macroscopic scale. At the same time, for different high polymer materials, the viscous flow activation energy model (SVAE model) and non-Newtonian index model (SNNE model) based on feature size were established. Finally, the accuracy and effectiveness of the SVAE model and the SNNE model are verified by comparing with the traditional model and reference data. The viscous flow activation energy and non-Newtonian index values of the polymer material can be calculated conveniently and accurately.

In situ Viscometry of Primitive Lunar Magmas at High Pressure and High Temperature

Understanding the dynamics of the magmatic evolution of the interior of the Moon requires accurate knowledge of the viscosity () of lunar magmas at high pressure (P) and high temperature (T) conditions. Although the viscosities of terrestrial magmas are relatively well documented, and their relation to magma composition well studied, the viscosities of lunar titano-silicate melts are not well known. Here, we present an experimentally measured viscosity dataset for three end member compositions, characterized by a wide range of titanium contents, at lunar-relevant pressure-temperature range of 1.1 – 2.4 GPa and 1830 - 2090 K. In-situ viscometry using the falling sphere technique shows that the viscosity of lunar melts varies between  0.13 and 0.87 Pa-s depending on temperature, pressure and composition. Viscosity decreases with increasing temperature with activation energies for viscous flow of Ea = 201 kJ/mol and Ea = 106 kJ/mol for low-titanium (Ti) and high-Ti melts, respectively. Pressure is found to mildly increase the viscosity of these intermediate polymerized melts by a factor of  1.5 between 1.1 and 2.4 GPa. Viscosities of low-Ti and high-Ti magmas at their respective melting temperatures are very close. However at identical P-T conditions ( 1.3 GPa,  1840 K) low-Ti magmas are about a factor of three more viscous than high-Ti magmas, reflecting structural effects of Si and Ti on melt viscosity. Measured viscosities differ significantly from empirical models based on measurements of the viscosity of terrestrial basalts, with largest deviations observed for the most Ti-rich and Si-poor composition. Viscosity coefficients for these primitive lunar melts are found to be lower than those of common terrestrial basalts, giving them a high mobility throughout the lunar mantle and onto the surface of the Moon despite their Fe and Ti-rich compositions.

Influence of absorbed dose and temperature on physical properties of bis(2-ethylhexyl) diglycolamic acid (HDEHDGA) in n-dodecane

N,N-di-2-Ethylhexyl diglycolamic acid (HDEHDGA) in n-dodecane is being emerged as a promising solvent for the separations at the back-end of nuclear fuel cycle. Present paper deals with the evaluation of its density, viscosity and inter facial tension, and their dependency on absorbed dose, temperature and composition. The experimental data was used to calculate apparent molar volume, excess molar volume, viscosity deviation, activation energy for viscous flow, enthalpy and entropy changes of activation. Redlich–Kister type equation was solved for these properties, the coefficients of third degree polynomial that fitted with the experimental data, and their dependency on temperature and absorbed dose was studied.

Improvement Viscosity Index of Lubricating Engine Oil Using Low Molecular Weight Compounds

the effect of polarity of solvent on the viscosity and viscosity index of lubricating engine oil has been studied using ethanol as an example of polar solvent and toluene as an example of non-polar solvent at different solvent ratios and ambient temperature and additionally other experiments have been done at five different temperatures including 100 oC. So that, the activation energy of viscous flow (Ea) was calculated, and for this purpose Arrhenius viscosity-temperature dependence has been applied and the results were 42.128, 29.256 and 35.417KJ/mole for lubricating engine oil mixed with ethanol, toluene and no additives in turn. It additionally shows that adding polar solvent to lubrication engine oil viscosity increases this may be due to the fact of strong inter molecular forces that found in polar molecules such as hydrogen bonding in ethanol makes the solution forces stronger as a result higher viscosity. However, adding non-polar solvent decreases viscosity because of small size of toluene and both paraffinic lubricating oil and toluene have same London dispersion inter molecular forces. Last not least, the result shows that engine oil mixed with non-polar molecule gives more temperature stability than that of polar molecule giving viscosity index (VI) 366 and 580 respectively.

The Effect of Titanium Carbonitride on the Viscosity of High-Titanium-Type Blast Furnace Slag

In this paper, the effect of titanium carbonitride (Ti(C,N)) on the viscosity of high-titanium-type blast furnace slags was investigated. The different Ti(C,N) contents were achieved by adjusting the reduction degree of TiO2 to reflect the real characteristics of the high-titanium slag. The results show that the viscosity of the slag increased with the increasing Ti(C,N) content and decreased with the rising temperature. A deviation between the measured and the fitted viscosity appeared as the content of the Ti(C,N) was beyond 4 wt%. Furthermore, the apparent viscous flow activation energy of the slag ranged from 106.13 kJ/mol to 235.46 kJ/mol by varying the Ti(C,N) contents from 0 wt% to 4.97 wt%, which was evidently different from the results of previous studies. The optical microscope and energy dispersive X-ray spectroscopy (EDS) analysis show that numerous bubble cavities were embedded in the slags and the Ti(C,N) particles agglomerated in the solidified samples. This phenomenon further indicates that the high-titanium slag is a polyphase dispersion system, which consists of liquid slag, solid Ti(C,N) particles and bubbles.

Melt viscosity of nanocrystalline alloys in the model of free volume

In this paper we investigated the viscosity and density of melts Fe73.5Cu1M3Si13,5B9 where M = Nb, Mo, V, Cr. It is shown that the lowest viscosity and activation energy of viscous flow has a melt with Nb, whose atomic radius is the largest. It is shown that the free volume of the melt is higher during cooling compared to heating, and it indicates irreversible structural changes in the melt. The critical temperature Tk = 1770 K is found, above which the activation energy of the viscous flow changes.

COMPOSITIONS BASED ON AQUEOUS SOLUTIONS OF CHITOSAN AND GLUTAR ALDEHYDE FOR EMBOLIZATION OF BLOOD VESSELS

The article investigates the aqueous solutions of food chitosan and glutaraldehyde to determine the feasibility of their use as components of an embolizing composition. It was shown on the basis of experimental flow curves, viscosity and velocity curves that test solutions have low viscosity and exhibit Newtonian flow behavior. The activation energy of viscous flow of the fluids was estimated in the temperature range of 25-37 °C within the Arrhenius - Frenkel - Eyring equation. It varies within a narrow range: 17-24 kJ/mol. When mixing the aqueous solutions of food chitosan and glutaraldehyde, chemical interaction of the solutes occurs. It is accompanied by an increase in viscosity and formation of a covalently crosslinked gel. Using a simple exponential equation the effective rate constant of the chemical process was calculated. It varies in a wide range: 1.9-82.7∙103 1/s. These values can be used when selecting an optimal region of food chitosan-glutaraldehyde ratios and concentrations of their aqueous solutions to generate embolizing agents. The conditions at which gel formation takes place over forty seconds were determined. Differential scanning calorimetry indicated a negligible thermal effect of food chitosan reaction with glutaraldehyde in the aqueous medium, which ensures no thermal burn during the formation of an embolus in the blood vessel in situ. As a result of the work elastic solid gels suitable for use as embolizing agents were obtained.

Measurement of thermophysical properties of binary system of (water + ascorbic acid) and ternary systems of (water + ascorbic acid + glycerol) and (water + ascorbic acid + d-sorbitol) at T = 293.15 K to 323.15 K and atmospheric pressure

Ascorbic acid, d-sorbitol, and glycerol are used as important food additives. In this research work, the thermophysical properties (viscosities and refractive indices) of binary solution of (water + ascorbic acid) and ternary solutions of [(water + ascorbic acid + glycerol)] and [(water + ascorbic acid + d-sorbitol)] were measured in different mass fractions of ascorbic acid (0.03 to 0.21) at temperatures (T = 293.15, 303.15, 313.15, and 323.15) K and atmospheric pressure. For mixtures of this study, the experimental values of viscosity and refractive index increase by increasing solute concentration and decrease by temperature growth. The experimental values of viscosity were correlated with the Jones-Dole and Kampmeyer-Girifalco equations. Also, the experimental values of refractive index were correlated with a semi-empirical equation which its constant, Kr, was suggested and introduced by Koohyar in 2018. Finally, derived thermodynamic properties (change of refractive index on mixing, ΔnD, and activation energy for viscous flow, Ea(vis)) were obtained using refractive index and viscosity data. The obtained data were applied for investigation on interaction between solute and solvent molecules in studied mixtures of this research work.

Perfluoropolyether (PFPE)-Based Vitrimers with Ionic Conductivity

Ion-conducting low-Tg perfluoropolyether (PFPE)-based vitrimers were obtained via thermally initiated polyaddition and in situ N-alkylation in the presence of a fluorinated cross-linker. Both reactions were quantified by differential scanning calorimetry (DSC) employing the Vyazovkin method (74 ± 1 kJ mol–1 for the polyaddition and 140 kJ mol–1 for the N-alkylation). The viscous flow activation energy was found to be 161 ± 23 kJ mol–1, in good correlation with the activation energy calculated by DSC for the N-alkylation. The creep behavior at elevated temperature is typical of a viscoelastic liquid and the relaxation times range from 2.5 h at 170 °C to 4 min at 210 °C. The topology freezing transition temperatures found via thermal creep experiment and relaxometry were in absolute agreement (ca. 110 °C). The network is stable under acidic and basic environments and can recover its mechanical properties after two recyclings. Three samples were prepared by varying the cross-linker loading, and the most stab...

Thermal characterizations and investigation of the drawing region in Ge-As-S glasses for IR optical fibers

Several glass compositions of the Ge-As-S ternary system were prepared and their thermal and physical properties were investigated as Tg, Td, theoretical drawing temperature Ts, viscous flow activation energy, density, visible and IR absorption coefficients. The measured values, which are in excellent agreement with the literature, were used to explore the drawing capability of the glass samples. In this work, we report wide range of Ge-As-S optical fiber compositions using the classical preform-to-fiber drawing technique. We show the possibility to obtain optical fibers with sulfur concentration ranging from 35 to 75%, and germanium concentration as high as 35%. In addition, based on the drawing tests we present a fiber drawing domain in the Ge-As-S ternary diagram. The attenuation losses measured at 1310 nm wavelength were between 8.4 and 12.3 dB/m.

Exploring the phase diagram of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesufonyl)imide

X-ray diffraction and Raman scattering measurements of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesufonyl)imide, [Pyrr1,4][NTf2], were performed in a wide range of temperature and pressure. Pressure dependence of glass transition Tg(p), cold-crystallization Tcc(p), and melting Tm(p) temperatures were obtained from atmospheric pressure up to ca. 2.0 GPa. The temperature dependence of Raman spectra within the Tcc < T < Tm range at atmospheric pressure unveils conformational dynamics of [Pyrr1,4]+ while [NTf2]- remains in the transoid conformation characteristic of the crystal. The different pressure dependence of Tcc(p) and Tm(p) implies that these curves merge at ca. 330 K and 1.0 GPa. Upon the assumption that the Tg(p) curve belongs to isochronous states, Tg(p) is discussed in terms of thermodynamic scaling using low-temperature and high-pressure extrapolations of an empirical equation of state. The ratio between constant volume and constant pressure activation energies for viscous flow, EV/Ep, increases only slightly in the pressure range investigated in this work. The results obtained under simultaneous variation of temperature and pressure highlight the complex interplay between glass transition and crystallization of [Pyrr1,4][NTf2].

Possibility of Predicting Activation Energy for Viscous Flow in Five-Membered Naphthenes by Means of Structural Descriptors

In this paper, the possibility of predicting values apparent activation energy for viscous flow in five-membered naphthenes by the calculation method, namely, using the two-parameter dependence of structural descriptors, is investigated. We explore structural descriptors of the molecular graph, namely, a topological index and the sum of eigenvalues squares of the topological matrix. Interchangeability checking of topological descriptors was performed. We performed regression analysis, and constructed dependences of apparent activation energy on the sum of squares of eigenvalues and topological indices. This paper presents data for calculating apparent activation energy of viscous flow from the experimental data and from the dependence on the Wiener topological index and the squares sum of eigenvalues. It is shown that for compounds under consideration there is a kinetic compensation effect. Based on the studies carried out for compounds considered, it can be assumed that, the apparent activation energy of viscous flow and the associated Arrhenius constant (frequency factor) is determined by the topological characteristics of the molecules.

Реологические свойства композитов на основе гидроксида алюминия и смесей полиэтилена низкой и высокой плотности

The results of the study of the rheological characteristics of low- and high-density polyethylene blend in the ratio of 50 : 50 and its composites filled with aluminum hydroxide are presented. The influence of the concentration of aluminum hydroxide, temperature, and shear stress on the regularity of changes in the effective viscosity and shear rate has been established. Rheograms of low- and high-density polyethylene blend in the ratio of 50 : 50 and composites based on it are presented. The dependence of viscosity on temperature in Arrhenius coordinates is determined, according to which the “apparent” activation energy of viscous flow for the initial low- and high-density polyethylene blend and its composites filled with aluminum hydroxide varies in the range of 6–19 and 11–31 kJ/mol, respectively. A universal temperature-invariant characteristic of the viscosity properties of low-and high- density polyethylene blend in the ratio of 50 : 50 and its composites filled with aluminum hydroxide, which makes it possible to predict the change in the melt viscosity of composites in a wide range of shear rates and stresses, is drawn. It is shown that, with an increase in the concentration of aluminum hydroxide in the polymer mixture to 5 wt %, the value of the shear rate remains almost unchanged relative to the initial low- and high-density polyethylene blend (50/50). Rheological studies of the melt of polymer materials have been carried out in accordance with the standard ASTM D1238 on a CEAST MF50 capillary rheometer (INSTRON, Italy) in the temperature range of 190–250°C and in the load range of 3.8–21.6 kg.

Crystallization behavior of SiO2–P2O5–CaO–MgO–Na2O–K2O bioactive glass powder

Abstract The crystallization process of a bioactive silicate glass with 47.5SiO2-10Na2O-10K2O-10MgO-20CaO-2.5P2O5 molar composition was investigated by using nonisothermal differential t hermal a nalysis (DTA). T he DTA plots recorded at different heating rates exhibited a single crystallization peak. The activation energy for crystallization was estimated by applying the equations proposed by Kissinger and Matusita-Sakka. The Johnson-Mehl-Avrami exponent (n) was assessed by using the Ozawa and Augis-Bennett methods. The analyses suggest that a surface crystallization mechanism with one-dimensional crystal growth is predominant. The activation energy for viscous flow was also assessed (176 kJ/mol) and was found lower than the activation energy for crystallization (271 kJ/mol). This confirms the stability of 47.5B against crystallization and its good sinterability, which is a highly attractive feature for producing glass products of biomedical interest, such as bioactive porous scaffolds for bone repair.

Effects of basicity and CaF2 on the viscosity of CaF2–CaO–SiO2 slag for electroslag remelting process

Effects of the basicity and the CaF2 content on viscosity of CaF2–CaO–SiO2 slag with high CaF2 content for electroslag remelting process were investigated by the rotating cylinder method in the temperature ranging from 1773 to 1533 K. The relationship between the structure and the viscosity variation of the slag was also clarified by the Fourier transform infrared (FT-IR) spectroscopy of water-quenched slags. The results show that the viscosity gradually decreases with the increase in the basicity of the slag from 1 to 3 under the present experimental conditions. It is found that the CaO does not depolymerize all silicate complex anions for the slag with the basicity of 1 at 1773 K and there are still some bridging oxygens. With the increase in the basicity to 3, the silicate complex anions are almost completely depolymerized to simple ions. As the CaF2 content increases from 40 to 80 mass%, the viscosity of the slag decreases due to the dilution of CaF2 for the concentration of the silicate complex anions in unit volume of the slag. Moreover, the effect of the temperature on the viscosity is not remarkable. The activation energy of viscous flow exhibits the decrease from 40.4 to 26.7 kJ · mol−1 with the increase in the basicity from 1 to 3, and also the decrease from 66.6 to 31.0 kJ · mol−1 with the increase in the CaF2 content from 40 to 80 mass%.