Obtained Viscosity Values Research Articles

Viscosity experiments of slag-spinel suspensions: The effect of volume fraction, particle size, and shear rate

Heterogeneous slag viscosity measurements have a wide variety of parameters, such as particle size, shape, solid volume fraction, and shear rate, which affect the final measured viscosity. Often, some of these parameters are neglected or predicted via models, since it is experimentally difficult to determine them during high-temperature slag viscosity measurements. In this work, a viscosity apparatus was used, which allows quenching of the sample after measurement. This way, all relevant parameters could be experimentally determined. The viscosities of three datasets were studied with various spinel sizes: small (13 μm), medium (34 μm), and large particles (76 μm). Within each dataset, the composition of the liquid slag matrix was kept constant to uniquely measure the effect of solids. Shear thinning, i.e., a decreasing viscosity with increasing shear rate, was observed for all samples, even at a low vol. % of 1.8. Moreover, stronger shear thinning was observed at a higher vol. % and for smaller spinel particles. On the basis of these results, the phenomenon of shear thinning was discussed and mainly attributed to the particle–particle orientation in the suspension. The obtained viscosity values were used to optimize a Krieger–Dougherty equation, which describes the viscosity increase caused by the presence of a certain vol. % of spinel particles, with a certain size and at a specific shear rate.

Probing molecular interactions in mixed system of green solvent ethyl lactate with oligomers of polyethylene glycol

Polyethylene glycol and its oligomers are potential hydrogen bond donors that act as a green, effective, non-toxic, non-corrosive and recyclable molecular component for extractive desulfurization of liquid fuels and variety of other applications. The aim of this investigation is to explore the molecular interactions via variations in viscosity that occur on mixing these glycols with green solvent ethyl lactate. Dynamic viscosities (η) for pure solvents and binary mixtures of ethyl lactate and glycols oligomers (mono/di/tri/tetra-ethylene glycol) were measured at varying temperatures T/(K) = (298.15–313.15; with an interval of 5). Viscosity deviations (Δη) along with excess thermodynamic parameters of activation for viscous flow as Gibbs free energy (ΔG∗E), Enthalpy (ΔH∗E) and Entropy (ΔS∗E) were derived from experimental data. The Δη and ΔG∗E values were further correlated using Redlich-Kister polynomial expression. The experimentally obtained viscosity values were compared with 10 generalised literature models (Arrhenius, Kendall, Kendall-Monroe, Grunberg-Nissan, Hind, Katti-Chaudhri, Heric, McAllister three-body, McAllister four-body and Jouyban-Acree models). The average standard deviation percentages (ASD %) were calculated for all the models to compare the quality of correlation with experimental data. The minimal ASD % for McAllister four-body and Jouyban-Acree models in the working systems indicate that the multiparameter relations have the best capability of reproducing the experimental values. The temperature induced variations were also discussed together with molecular interactions. Further, quantum mechanical density-functional theory and graph theoretical approaches were used to explore the extent of interactions among the components.

Dynamic Viscosity of the NaF-KF-NdF3 Molten System.

The dynamic viscosity (η) of the molten system (NaF-KF)eut-NdF3 containing NdF3 in an amount from 0 to 15 mol.% was studied by rotational viscometry using a high-temperature rheometer, FRS 1600. Viscosity measurements were carried out in the temperature range from liquidus to 1153 K. The measurement procedure was tested on the (LiF-NaF-KF)eut melt. The choice of the parameter shear rate was carried out according to the viscosity and flow curves. Viscosity does not depend on shear rate, and therefore the investigated melts behave like Newtonian fluids, in the range of 9–19 s−1. The experimentally obtained viscosity values for (NaF-KF)eut-NdF3 melts in a wide temperature range are described by an exponential equation. In the coordinates ln(η) = f(1/T), they are straight lines; however, their temperature coefficients are noticeably different, which indicates significant impacts of composition and temperature.

Sensing non-ideal microheterogeneity in binary mixtures of dimethyl sulfoxide and water

We present a microscopic study of water–dimethyl sulfoxide (DMSO) binary mixtures using optical tweezers and thermal lens techniques. Binary mixtures of DMSO with water show anomalous behavior due to the specific hydrogen bonding ability of DMSO. We use a tightly focused femtosecond laser at a low average power to optically trap microspheres with diameters of 1 micron for use as probes. The binary mixture exhibits various viscosities, depending on its composition ratio, and hence different trapped particle characteristic frequencies (corner frequencies) due to Brownian motion. The power spectrum density method is used to obtain the corner frequency from forward-scattered data. Thus, using low-power optical tweezer experiments, we find that the maximum viscosity occurs at a DMSO mole fraction of 0.276. At higher powers, the propensity for trapping is highly diminished. It may be surprising to note that these viscosity values obtained from the corner frequencies do not exactly match those published in the literature. However, this deviation can be attributed to the thermal behavior of the binary mixture, which affects the Brownian motion and hence the obtained viscosity values. Studies at the microscopic level can thus provide a newer perspective on these already important binary mixtures. Intensity-dependent measurements further confirm the contribution of thermal effects in this study.

Influence of joints on creep processes involving rock masses: results from physical-analogue laboratory tests

Viscoplastic behavior of jointed rock masses still represents a main research topic due to the reduced possibilities of carrying on long-term tests on site as well as to the reduced representativeness of laboratory samples if compared to the scale of the study-case. Rock masses are often involved in creep processes as in the case of gravity-induced deformations affecting relevant portions of natural slopes. These processes can interact with main infrastructures, among which dams, pipelines, aqueducts, tunnels, highways and railways.This study is focused on laboratory tests performed to deduce the rheological behavior of a rock masses at a reduced scale for defining the influence of joint attitude and properties on viscoplasticity. A physics of reduction scaling of mechanical behavior (down-scaling) was preliminary applied to select the most adapt material for laboratory tests; the obtained results were then reported to the effective slope scale (up-scaling).The tested specimens were realized by an artificial moisture whose mechanical properties were scaled respect to limestones outcropping in a mountain ridge involved in already documented gravity-induced slope deformation that caused an intense rock mass jointing.Viscoplasticity was analyzed based on uniaxial compressive strength (UCS) and creep tests. The test results were then up-scaled according to an “equivalent continuum approach” and an equivalent viscosity for the outcropping rock mass was derived. The following performed up-scaling is representative for a creep process acting over a time interval of about 200 years.The obtained viscosity values for the equivalent rock range from 4.23·1018 up to 1.56·1019 Pa∙s and are in good agreement with the values derived by back-analysis through stress-strain numerical modeling of the gravity-induced slope deformation involving Mt. Rocchetta. The obtained results demonstrate that properties of pervasive joints are not negligible on rock mass creep acting at slope scale which can drive gravity-induced processes toward paroxysmal failures.

Modeling viscosity of moderate and light dead oils in the presence of complex aromatic structure

Crude oil viscosity measurements are very crucial in the field of petroleum industries. Difficulties associated with obtaining accurate measured viscosity values for reservoir oils have turned the light to estimate viscosity through empirical correlations to alleviate these laboratory difficulties. This work is a supplementary study for a previous research work, done on Egyptian heavy crude oil samples, to cover all types of reservoir oils. The proposed work started with evaluating the previously published viscosity correlations that considered as a useful method to provide preliminary values for viscous oil reservoirs characterization. The obtained viscosity values showed poor performance of applying these correlations, as these correlations depend only on oil specific gravity and operating temperature. Therefore, there is a need for correlating a new effective viscosity model using asphaltene content as one of the main representative parameters. Asphaltene is considered as a complex aromatic structure which causes problems in reservoir oils. In this work, laboratory measurements have been made on five-hundred database points of Egyptian moderate and light dead oil samples obtained from different locations to build accurate viscosity correlation model. The best fit accurate empirical correlation has been found using multiple least-square nonlinear regression analysis for ranges of viscosity measurements from 23.06 to 43.18 OAPI. Testing of the new proposed viscosity model, with another set of laboratory measured viscosity data, shows high performance and accuracy in predicting Egyptian moderate and light dead crude oils viscosity as compared with literature viscosity correlations.

Physicochemical properties of Al, Al-Mg and Al-Mg-Zn alloys

The effect of the addition of Mg and Zn to Al on its physicochemical properties was investigated. Using the discharge crucible method, three thermophysical properties (density, surface tension and viscosity) were determined for the Al, Al-Mg and Al-Mg-Zn alloys. The measurements were performed for Al and Al-Mg alloys in Krakow, in the temperature range from 723 to 1053K, and for the Al-Mg-Zn alloys in Edmonton in the temperature range of 773 to 973K. The obtained viscosity values of pure Al show good agreement with the literature data. The viscosity data of Al-Mg alloys are lower those for pure metal Al and Mg. The addition of Zn to an Al-Mg alloy caused a slight increase in viscosity. For Al-Mg alloys, the surface tension results were compared with the Butler model, and the viscosity with several models.

Effect of Using the Combination of Tween 80 and Ethanol on the Forming and Physical Stability of Microemulsion of Eucalyptus Oil as Antibacterial

: Objective: The purpose of this study was to determine the effect of increasing concentrations of the combination of tween 80 and ethanol to the formation and stability of the physical properties of eucalyptus oil micro-emulsion. Methods: This oil is formulated into a micro-emulsion by increasing the concentration of the combination of tween 80 and ethanol (1: 1) with various concentrations, ie 40%, 45%, and 50% as a component of surfactant and cosurfactant. The evaluation was done for 8 weeks covering organoleptic test, test phase separation, viscosity test, measurement of pH, density measurements, measurements of surface tension and particle size measurement. Results: The pH of micro-emulsion showed in the range 5.4 to 6.2. Viscosity results obtained viscosity values between 206.2 to 248 cps. Density measurement results were between 0.9839 to 0.9904 g/ml. The results of surface tension measurement results obtained between 35.83 to 37.10 dyne/cm. The results of particle size measurement results obtained from 23.83 to 30.43 nm. Conclusion: It can be concluded that the use of tween 80 and ethanol can form a micro-emulsion system of eucalyptus oil, and with increasing concentrations of the combination of tween 80 and ethanol can increase the stability of the physical properties of the micro-emulsion system.Key words: Antibacterial, Ethanol, Eucalyptus oil, Micro-emulsion, Stability of the physical properties, Tween 80.

Precise Viscosity Analysis of Alkali Metal Molten Salts at High Temperature

Recently, solar thermal energy has been attracted considerable attention as a renewable energy alternative to fossil fuels. The operation and efficiency of solar thermal energy plants employing thermal energy storage techniques have been proved at both experimental and commercial scales.1 In solar thermal energy plants, alkali metal molten salts have recently attracted as thermal storage media and heat transfer fluids, because these salts have a low melting point, high heat capacity, and moderate energy density.2 In addition, alkali metal molten salts are less expensive and more environmentally friendly than currently available high-temperature oils. However, many investigations are scarce focusing on thermophysical properties of molten salts at high temperature. In particular, the viscosity of alkali metal molten salts is few reported and the reported viscosities are shown larger difference by analysis method or other one. In this study, therefore, we are measured the viscosity of alkali metal molten salts at high temperature above 500 °C by rotation method using high temperature rheometer system (MCR 502, Anton Paar) and reliability of obtained viscosity values is evaluated.3 This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "energy carrier" (Funding agency: JST). References Q. Peng, X. Yang, J. Ding, X. Wei, and J. Yang, Appl. Energy, 112 (2013) 682.S.M. Flueckiger and S.V. Garimella, Sol. Energy, 86 (2012) 1631.S.W. Kim, K. Uematsu, K. Toda, and M. Sato, J. Ceram. Soc. Jpn., (2015) in press.

Determination of the liquid steel viscosity curves using a high temperature rheometer

Rheological measurements of high melting temperature materials require specialist equipment, which allow to obtain high temperature inside. This situation take place in case of iron alloys. In literature there is lack of information about rheological properties of liquid iron solutions. This paper is intended to supplement the data in this regard; included in the study of iron solutions rheological properties: five chemical composition with carbon amount in the range between 0.39 – 0.89%, while used shear rate in the range between 40-180 s-1. Obtained viscosity values are set in the range between 0.002-0.018 Pa·s. The obtained results could be used for verification of the model which calculate the parameters of liquid iron alloys during casting, in which the viscosity is one of the mane parameter.

Ultrasonic viscosity measurement using the shear-wave reflection coefficient with a novel signal processing technique

Real-time viscosity measurement remains a necessity for highly automated industry. To resolve this problem, many studies have been carried out using an ultrasonic shear wave reflectance method. This method is based on the determination of the complex reflection coefficient's magnitude and phase at the solid-liquid interface. Although magnitude is a stable quantity and its measurement is relatively simple and precise, phase measurement is a difficult task because of strong temperature dependence. A simplified method that uses only the magnitude of the reflection coefficient and that is valid under the Newtonian regimen has been proposed by some authors, but the obtained viscosity values do not match conventional viscometry measurements. In this work, a mode conversion measurement cell was used to measure glycerin viscosity as a function of temperature (15 to 25 degrees C) and corn syrup-water mixtures as a function of concentration (70 to 100 wt% of corn syrup). Tests were carried out at 1 MHz. A novel signal processing technique that calculates the reflection coefficient magnitude in a frequency band, instead of a single frequency, was studied. The effects of the bandwidth on magnitude and viscosity were analyzed and the results were compared with the values predicted by the Newtonian liquid model. The frequency band technique improved the magnitude results. The obtained viscosity values came close to those measured by the rotational viscometer with percentage errors up to 14%, whereas errors up to 96% were found for the single frequency method.

A New High-Temperature Oscillating Cup Viscometer

A new oscillating cup viscometer for temperatures up to 2,300°C has been constructed. A vacuum furnace with a graphite heater is used for heating the sample. The temperatures of the furnace and sample are measured by both a thermocouple and a pyrometer. The temperature is controlled with a stability better than 1 K. The oscillation of the cup is measured with a reflected laser beam using a position sensitive detector. The measured values of angle and time are then fitted to an analytical oscillation function. From the parameters of this function, the viscosity values are calculated using the Roscoe formalism. Measurements were carried out on pure metals at temperatures up to 1,700°C because of limitations of the thermocouple. The obtained viscosity values showed good agreement with literature data.

Metrological Assessment of the Coefficient of Friction of Various Types of Silica Using the Motor Current During ILD-CMP

AbstractIn the work presented the coefficient of friction (COF) was firstly determined metrologically by a systematic assessment of motor currents for different products of pressure and velocity (p v). With all seven test slurries it could be shown that the inserted energy ECMP is proportional to the product of pressure and velocity. The COF of the parameter domain considered here does not depend on the inserted energy or the product of p v in a first approximation. For all tested slurries it was demonstrated that, both the COF and the removal rate (RR) behave analogously (low COF→ low RR).Measurements of the viscosity η have shown that η is not a constant in the shear rate range relevant for CMP. Using the obtained viscosity values a mean slurry film thickness in the range of 2,5 -C 6 μm could be calculated.

Noncontact technique for determining viscosity from the shape relaxation of ultrasonically levitated and initially elongated drops

We present a technique that can determine the viscosity of highly viscous liquids, particularly, undercooled liquids that exist at temperatures below their freezing points. The technique involves levitation of a liquid drop using an ultrasonic standing wave, and elongation of the drop by rotating it beyond the point of bifurcation. The elongated drop is then allowed to be restored to its original shape by surface tension driven relaxation. The time-dependent shape parameters of the relaxing drop are related to the viscosity through a relaxation model. In addition, this technique can also determine the surface tension that has a known relationship with the angular velocity at the bifurcation point. The feasibility of the technique is demonstrated by performing the measurement using sucrose solutions as a model liquid drop. The obtained viscosity values show a good correlation with those determined by a falling ball method.

Experimental Study of Si3 N 4 Viscosity for Calibration of Stress‐Dependent Models of Silicon Oxidation

Basic parameters characterizing silicon nitride viscosity have been obtained from experiments on films. Changes in film thickness and intrinsic stress after various types of high‐temperature annealing have been studied. A considerable stress increase during a temperature ramp‐up is attributed to film structure densification. The contribution of the ramp‐up and ramp‐down stages of annealing to film shrinkage was excluded from the calculations of nitride viscosity. The resulting viscosity is higher than previously reported. Based on the experimentally obtained viscosity values, the process of local oxidation of silicon (LOCOS) was simulated. The viscosity of thermal oxide and stress‐dependent parameters of the viscoelastic oxidation model were extracted by comparing the simulated boundary geometry of LOCOS structures with cross‐sectional scanning electron microscopy images. It is found that the enhancement of oxidant diffusion in oxide regions subjected to tensile stress is a major cause for the increase in pad oxide thickness under a narrow nitride mask during field oxidation. © 1999 The Electrochemical Society. All rights reserved.

Liquid viscosities and densities of HFC-134a+glycol mixtures

Liquid viscosity and density of six binary mixtures of HFC-134a with glycols [ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol (400), and polypropylene glycol (2000)] have been measured in the temperature range from 273 to 333 K. The viscosity was measured by a rolling-ball viscometer calibrated with standard liquids of viscosities and densities (JS5, JS10, JS20, and JS50). The density was measured with a glass pycnometer. The uncertainties of the measurements were estimated to be less than 3.4 % for viscosity and 0.04 % for density, respectively. An equation is given to represent the obtained viscosity values as a function of weight fraction and temperature.

A new analysis method for the membrane viscosity from steady-state fluorescence depolarization.

The absolute value of the viscosity in membrane lipid bilayers, which is different from the microviscosity advocated by Shinitzky, could be calculated from steady-state fluorescence depolarization of a hydrocarbon fluorophore, 1,6-diphenyl-1,3,5-hexatriene (DPH). This method was based on the theory of time-resolved fluorescence anisotropy and empirical relationships between fluorescence life time and the anisotropy parameters such as half cone angle in wobbling motion and wobbling diffusion rate of the fluorescent probe. Obtained viscosity values of various membranes from this method were consistent with those from time resolved method within experimental error.

Investigation of the viscosity of dilute solutions of mixed polymers

A study was made of the viscosity of solutions of mixed polymer homologues and of incompatible mixtures of polymers in two groups. For the first group of polymers, as well as for the polymer homologues, there is fulfillment of the law of additivity, while for the second group it was found that there were positive and negative deviations of experimentally obtained viscosity values from the calculated values. The experimental results agree well with a theoretical analysis of the viscosity of the solutions of mixed polymer homologues and of the polymers in the first group. For solutions of mixed polymers in the second group anomalies in the relation of viscosity to the composition of the mixtures are due to the formation of supermolecular structures that have varying stability towards changes in temperature.