Matthew W. Liberatore

Colorado School of Mines, Golden, CO, United States

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Publications (34)56.04 Total impact

  • Eric B. Webb, Carolyn A. Koh, Matthew W. Liberatore
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    ABSTRACT: Structure I methane hydrates are formed in situ from water-in-mineral oil emulsions in a high pressure rheometer cell. Viscosity is measured as hydrates form, grow, change under flow, and dissociate. Experiments are performed at varying water volume fraction in the original emulsion (0–0.40), temperature (0–6 °C), and initial pressure of methane (750–1500 psig). Hydrate slurries exhibit a sharp increase in viscosity upon hydrate formation, followed by complex behavior dictated by factors including continued hydrate formation, shear alignment, methane depletion/dissolution, aggregate formation, and capillary bridging. Hydrate slurries possess a yield stress and are shear-thinning fluids, which are described by the Cross model. Hydrate slurry viscosity and yield stress increased with increasing water volume fraction. As driving force for hydrate formation decreases (increasing temperature, decreasing pressure), hydrate slurry viscosity increases, suggesting that slower hydrate formation leads to larger and more porous aggregates. In total, addition of water to a methane saturated oil can cause more than a fifty-fold increase in viscosity if hydrates form.
    Industrial & Engineering Chemistry Research. 04/2014; 53(17):6998–7007.
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    ABSTRACT: Block copolymers of polystyrene-b-poly(vinyl benzyl trimethylammonium tetrafluoroborate) (PS-b-[PVBTMA][BF4]) were synthesized by sequential monomer addition using atom transfer radical polymerization. Membranes of the block copolymers were prepared by drop casting from dimethylformamide. Initial evaluation of the microphase separation in these PS-b-[PVBTMA][BF4] materials via SAXS revealed the formation of spherical, cylindrical, and lamellar morphologies. Block copolymers of polystyrene-b-poly(vinyl benzyl trimethylammonium hydroxide) (PS-b-[PVBTMA][OH]) were prepared as polymeric alkaline anion exchange membranes materials by ion exchange from PS-b-[PVBTMA][BF4] with hydroxide in order to investigate the relationship between morphology and ionic conductivity. Studies of humidity [relative humidity (RH)]-dependent conductivity at 80 °C showed that the conductivity increases with increasing humidity. Moreover, the investigation of the temperature-dependent conductivity at RH = 50, 70, and 90% showed a significant effect of grain boundaries in the membranes against the formation of continuous conductive channels, which is an important requirement for achieving high ion conductivity. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1751–1760, 2013
    Journal of Polymer Science Part B Polymer Physics 12/2013; 51(24):1751-1760. · 2.22 Impact Factor
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    ABSTRACT: An alkaline exchange membrane (AEM) based on an aminated trimethyl poly(phenylene) is studied in detail. This article reports hydroxide ion conductivity through an in situ method that allows for a more accurate measurement. The ionic conductivities of the membrane in bromide and carbonate forms at 90 °C and 95% RH are found to be 13 and 17 mS cm−1 respectively. When exchanged with hydroxide, conductivity improved to 86 mS cm−1 under the same experimental conditions. The effect of relative humidity on water uptake and the SAXS patterns of the AEM membranes were investigated. SAXS analysis revealed a rigid aromatic structure of the AEM membrane with no microphase separation. The synthesized AEM is shown to be mechanically stable as seen from the water uptake and SAXS studies. Diffusion NMR studies demonstrated a steady state long-range diffusion constant, D∞ of 9.8 × 10−6 cm2 s−1 after 50–100 ms. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1743–1750, 2013
    Journal of Polymer Science Part B Polymer Physics 12/2013; 51(24):1743-1750. · 2.22 Impact Factor
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    ABSTRACT: In this study, new alkaline exchange membranes were prepared from the perfluorinated 3M ionomer with various quaternary ammonium cations attached with sulfonamide linkage. The degree of functionalization varied depending on the cation species, resulting in different ion exchange capacities (IECs), 0.33–0.72 meq g−1. There was evidence of polymer degradation when the films were exposed to hydroxide, and hence all membrane characterization was performed in the chloride form. Conductivity was dependent on cation species and IEC, Ea = 36–59 kJ mol−1. Diffusion of water through the membrane was relatively high 1.6 × 10−5 cm2 s−1 and indicated restriction over a range of diffusion times, 6–700 ms. Water uptake (WU) in the membranes was generally low and the hydration level varied based on cation species, λ = 6–11. Small-angle scattering experiments suggested ionic aggregation, 37–42 Å, independent of cation species but slight differences in long-range order with cation species. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1761–1769, 2013
    Journal of Polymer Science Part B Polymer Physics 12/2013; 51(24):1761-1769. · 2.22 Impact Factor
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    ABSTRACT: Chemical mechanical polishing (CMP) is an essential technology used in the semiconductor industry to polish and planarize a variety of materials for the fabrication of microelectronic devices (e.g., computer chips). During the high shear (∼1,000,000 s-1) CMP process, it is hypothesized that individual slurry particles are driven together to form large agglomerates (≥0.5 μm), triggering a shear thickening effect. These shear-induced agglomerates are believed to cause defects during polishing. In this study, we examined the shear thickening of a 25 wt% fumed silica slurry with 0.17 M added KCl using in situ small-angle light scattering during rheological characterization (rheo-SALS). The salt-adjusted slurry displays ∼3-fold increase in viscosity at a critical shear rate of 20,000 s-1 during a stepped shear rate ramp from 100 to 25,000 s-1. As the shear rate is reduced back to 100 s-1, the slurry thickens irreversibly displaying a final viscosity that is 100-times greater than the initial viscosity. Corresponding rheo-SALS images indicate the formation of micrometer scale structures (2-3 μm) that directly correlate with the discontinuous and irreversible shear thickening behavior of the fumed silica slurry; these micron scale structures are 10-times the nominal particle diameter (∼0.2 μm). The scattering patterns from the 25 wt% slurry were corroborated through rheo-SALS examination of 27 and 29 wt% slurries (CKCl=0.1 M). All slurries, regardless of ionic strength and solids loading, display scattering patterns that are directly associated with the observed thickening behavior. Scattering was only observable during and after thickening (i.e., no scattering was detected in the absence of thickening). This work serves as the first in situ observation of micrometer scale structures within the fumed silica CMP slurry while under shear.
    Langmuir 09/2013; · 4.38 Impact Factor
  • Eric B Webb, Carolyn A Koh, Matthew W Liberatore
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    ABSTRACT: The in situ formation and flow properties of methane hydrates formed from water-in-oil microemulsions composed of water, dodecane, and aerosol OT surfactant (AOT) were studied using a unique high pressure rheometer. AOT microemulsions have high stability (order of months), well characterized composition, and yield reproducible results compared to hydrate studies in water-in-crude oil emulsions. Viscosity increases on the order of minutes upon hydrate formation, and then decreases on the order of hours. If significant unconverted water remained after the initial formation event, then viscosity increases for a time as methane slowly dissolves and converts additional water to hydrate. In addition to transient formation measurements, yield stresses and flow curves are measured for a set of experimental conditions. Hydrate slurry viscosity and yield stress increase with increasing water volume fraction, increasing initial pressure, decreasing temperature, and decreasing formation shear rate. Hydrate slurry viscosity and yield stress are most sensitive to temperature, followed by water volume fraction, initial pressure, and formation shear rate.
    Langmuir 08/2013; · 4.38 Impact Factor
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    ABSTRACT: Suspensions of corn starch and water are the most common example of a shear thickening system. Investigations into the non-Newtonian flow behavior of corn starch slurries have ranged from simplistic elementary school demonstrations to in-depth rheological examinations that use corn starch to further elucidate the mechanisms that drive shear thickening. Here, we determine how much corn starch is required for the average person to "walk on water" (or in this case, run across a pool filled with corn starch and water). Steady shear rate rheological measurements were employed to monitor the thickening of corn starch slurries at concentrations ranging from 0 to 55wt.% (0-44vol.%). The steady state shear rate ramp experiments revealed a transition from continuous to discontinuous thickening behavior that exists at 52.5wt.%. The rheological data was then compared to macro-scopic (∼5gallon) pool experiments, in which thickening behavior was tested by dropping a 2.1kg rock onto the suspension surface. Impact-induced thickening in the "rock drop" study was not observed until the corn starch concentration reached at least 50wt.%. At 52.5wt.%, the corn starch slurry displayed true solid-like behavior and the falling rock "bounced" as it impacted the surface. The corn starch pool studies were fortified by steady state stress ramps which were extrapolated out to a critical stress value of 67,000Pa (i.e., the force generated by an 80kg adult while running). Only the suspensions containing at least 52.5wt.% (42vol.%) thickened to high enough viscosities (50-250Pas) that could reasonably be believed to support the impact of a man's foot while running. Therefore, we conclude that at least 52.5wt.% corn starch is required to induce strong enough thickening behavior to safely allow the average person to "walk on water".
    Journal of Colloid and Interface Science 02/2013; · 3.17 Impact Factor
  • Ala Bazyleva, Babajide Akeredolu, Matthew W. Liberatore
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    ABSTRACT: Viscosity, μ, of Ugnu heavy oil (North Slope of Alaska, USA) saturated with methane was measured at temperatures from 0 to 60 °C, pressure from 15 to 1800 psi, and shear rate of 0.1–500 s–1 using a high-pressure rheology apparatus constructed for this work. Under all saturated conditions, the oil behaves as a Newtonian fluid. The influence of temperature, pressure, and methane concentration was analyzed, and important regularities in the viscosity were established. A two-variable Antoine-type correlation, μ = f(T, p), with 6 fitting parameters was developed using 48 points on a p,T,μ-diagram for Ugnu oil. Since produced oil is accompanied by sand and water, their influence on the viscosity of Ugnu oil saturated with methane at 1500 psi was also studied. The relative viscosity of the Ugnu oil + water emulsions at temperatures from 2 to 60 °C increased linearly with increasing water concentration from 0 to 20 wt % following the Einstein viscosity model for dilute suspensions. Although possible in the time scale of days, hydrate formation at temperatures below 13 °C (thermodynamic hydrate formation temperature at 1500 psi) did not interfere with the rheological measurements for the emulsions. Due to rapid sand particle sedimentation in methane-saturated Ugnu oil during experimental stages, the impact of sand concentration on the live oil viscosity could not be evaluated. Overall, the viscosity of Ugnu oil as a function of pressure and temperature can be used to simulate the oil’s behavior during production.
    Energy & Fuels. 01/2013; 27(2):743–751.
  • Chemical Engineering Education 01/2013; 47:122-132.
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    ABSTRACT: An extensive SAXS investigation of the 3M perfluorinated sulfonic acid ionomer was performed to investigate the morphological changes that occur during and after annealing at temperatures above the Tα. The effect of film thickness in the range studied, 11–45 μm, was found to be negligible. These properties were studied as a function of equivalent weight from 700 to 1100 and correlated with the water uptake as measured by dynamic vapor sorption. Isoscattering points were observed in dynamic annealing experiments of the unboiled annealed films at q = 0.023, 0.096 Å–1. On initial water uptake these films also showed isoscattering points at q = 0.024, 0.220 Å–1; q = 0.029, 0.223 Å–1; and q = 0.030, 0.211 Å–1 at 50, 80, or 95 °C, respectively, indicating a decrease in the symmetry of the scattering objects in these size regimes. Isoscattering points were absent in similar water uptake experiment for the films after boiling.
    Macromolecules 09/2012; 45(18):7495-7503. · 5.93 Impact Factor
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    ABSTRACT: The prediction of viscosity in the extraction of heavy and viscous oil resources is essential for the economically viable production of these resources. A rheological and chemical investigation of oils from the McMurray formation produced at different depths was undertaken. Chemical analysis using high-resolution time-of-flight mass spectrometry (TOF MS), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance spectroscopy (NMR) suggested specific compounds representative of the compound classes observed in these heavy oils: [1] water, [2] sec-hexadecyl naphthalene, [3] 2,2′,5,5′-tetramethyl-1,1′-biphenyl, [4] 1-methylanthracene, and [5] cyclopentylcyclopentane. All three analytical techniques detected the monoaromatic, diaromatic, and triaromatic ring hydrocarbons as being the most abundant species in this heavy oil. Specific molecules with intense FTIR modes near 1600 cm–1 and 1380 cm–1 were not identified, and these may account for unknown species in asphaltene fractions. Correlations between heavy-oil chemistry and its viscosity were built using a partial linear square fit (PLS) regression from vibrational modes in the FTIR spectra, predicting an inverse correlation between water and viscosity.
    Energy & Fuels. 06/2012; 26(7):4445–4453.
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    ABSTRACT: A unique high-pressure rheology apparatus is used to study the in situ formation and flow properties of gas hydrates from a water-in-crude oil emulsion. Viscosity and pressure of the hydrate slurry are measured during hydrate formation, growth, aggregation, and dissociation. The rheology of the hydrate slurries varies with time, shear rate (1–500 s–1), water content (0–50%), and temperature (0–6 °C). Hydrate slurry viscosity increases rapidly with time when hydrates form and then decays after going through a maximum as hydrate aggregates breakup or rearrange. Yield stress increases with annealing time up to 8 h and then remains constant. Hydrate slurry viscosity decreases with an increasing shear rate (i.e., they are shear thinning). Viscosity and yield stress both increase with an increasing water content. During dissociation, the viscosity increases just before the hydrate equilibrium temperature. Finally, transient viscosity measurements at varying temperatures suggest that mechanisms, such as cohesion forces and shear forces, competitively affect hydrate slurry viscosity.
    Energy & Fuels. 05/2012; 26(6):3504–3509.
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    ABSTRACT: We present a novel setup for a high pressure rheometer operating with concentric cylinders geometry for in situ studies of hydrate formation and rheological characterization. The apparatus uses an external high pressure mixing cell to saturate water-in-oil emulsions with methane gas. The capability of mixing combined with a true rheometer design make this apparatus unique in terms of setup and sample formation. We have used the apparatus to form gas hydrates in situ from water-in-oil emulsions and characterize suspension rheological properties such as yield stress and shear-thinning behavior.
    The Review of scientific instruments 01/2012; 83(1):015106. · 1.52 Impact Factor
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    ABSTRACT: Chemical mechanical polishing (CMP) is a fundamental technology used in the semiconductor manufacturing industry to polish and planarize electronic materials. During the high shear (≥1,000,000 s − 1) polishing process, it is hypothesized that individual slurry particles begin to interact and collide with one another forming large agglomerates (≥0.5 μm). These agglomerates are suspected of causing defects such as scratches or gouges during polishing, which costs the semiconductor industry billions of dollars annually. We have developed a method for investigating the shear thickening behavior of fumed silica slurries (20–34 wt.%) under high shear using a parallel-plate geometry in a conventional rotating rheometer. The CMP slurries displayed irreversible thickening at shear rates exceeding 10,000 s − 1. Viscous heating and sample evaporation are shown to be inconsequential to the witnessed shear thickening behavior. Also, the observed thickening is not a result of a critical rheometer speed, as the thickening was independent of the experimental gap height. In agreement with previous work, the slurries thickened at lower shear rates as silica concentration was increased. The shear thickening of the fumed silica slurries is truly shear-induced, and therefore, the thickening of CMP slurries can be examined using a rotational rheometer at small gap heights (≤100 μm).
    Rheologica Acta 01/2012; 51(7):637. · 1.63 Impact Factor
  • Michael W. Nolte, Matthew W. Liberatore
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    ABSTRACT: An oak bio-oil was aged at 90 °C using various times and methods. A novel method for aging bio-oils under shear is introduced and compared to standard (quiescent) aging experiments. In a hermetically sealed concentric cylinder rheometer, aging with shear for 8, 16, and 24 h showed increases in viscosity of 57, 300, and 720%, respectively. A similar increase in viscosity was observed after quiescently aging of sealed samples in a forced air oven (100, 120, and 740% after 8, 16, and 24 h, respectively). Another aging experiment under shear consisted of three 8 h aging steps with intermediate viscosity measurements. Viscosity increases were comparable to the 8, 16, and 24 h tests. A control experiment in the rheometer without shear found the increase in viscosity to be 30–50% less than the sheared experiments. The number-average molecular weight increased as samples were heat-treated at 90 °C for longer times. The water content showed small increases and decreases with aging, which was attributed to the heterogeneity of the sample. Real-time viscosity measurements during the 90 °C aging step found that the rate of viscosity growth decreased over time. An exponential decay function estimated the viscosity to be 90% of the steady-state viscosity after 3 days at 90 °C.
    Energy & Fuels. 07/2011; 25(7):3314–3317.
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    ABSTRACT: Gadolinium metal-organic framework (Gd MOF) nanoparticles are an interesting and novel class of nanomaterials that are being studied as a potential replacement for small molecule positive contrast agents in magnetic resonance imaging (MRI). Despite the tremendous interest in these nanoscale imaging constructs, there are limitations, particularly with respect to controlling the particle size, which need to be overcome before these nanoparticles can be integrated into in vivo applications. In an effort to control the size, shape, and size distribution of Gd MOF nanoparticles, hydrotropes were incorporated into the reverse microemulsion synthesis used to produce these nanoparticles. A study of how hydrotropes influenced the mechanism of formation of reverse micelles offered a great deal of information with respect to the physical properties of the Gd MOF nanoparticles formed. Specifically, this study incorporated the hydrotropes, sodium salicylate (NaSal), 5-methyl salicylic acid, and salicylic acid into the reverse microemulsion. Results demonstrated that addition of each of the hydrotropes into the synthesis of Gd MOFs provided a simple route to control the nanoparticle size as a function of hydrotrope concentration. Specifically, Gd MOF nanoparticles synthesized with NaSal showed the best reduction in size distributions in both length and width with percent relative standard deviations being nearly 50% less than nanoparticles produced via the standard route from the literature. Finally, the effect of the size of the Gd MOF nanoparticles with respect to their MRI relaxation properties was evaluated. Initial results indicated a positive correlation between the surface areas of the Gd MOF nanoparticles with the longitudinal relaxivity in MRI. In particular, Gd MOF nanoparticles with an average size of 82 nm with the addition of NaSal, yielded a longitudinal relaxivity value of 83.9 mM⁻¹ [Gd³⁺] sec⁻¹, one of the highest reported values compared to other Gd-based nanoparticles in the literature to date.
    ACS Applied Materials & Interfaces 04/2011; 3(5):1502-10. · 5.01 Impact Factor
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    ABSTRACT: Pyrolysis oils were produced from hardwood or softwood feedstocks in a vacuum batch reactor and trapped at 0°C. The vacuum process was used to intentionally avoid the presence of entrained char particles. The hardwood feedstock was a pelletized mixture of various Eastern tree species. The softwood samples were de-barked Lodgepole pine (Pinus contorta) and Douglas Fir (Pseudotsuga menziesii) wood cut into the same dimensions as the pellets. The oils’ physical (viscosity) and chemical (speciation) properties were measured as-produced and after aging. The total liquid and char yields ranged from ∼50 to 55% and 25 to 27% respectively. Measured water contents were 30% or more, which are greater typically reported from fast pyrolysis oils produced in fluidized beds. Aging took place in covered glass containers at room temperature over a period of 5 months. Gas chromatography–mass spectrometry (GCMS) was used to characterize the oils’ volatile components. Since bio-oils are mixtures of hundreds of different compounds with wide-ranging molecular weights and polarities, the oils were extracted using benzene followed by methanol. Out of ca. 80 non-polar and 100+ polar compounds GCMS showed a few chemical species present in the freshly produced oils were absent in the aged oils. The oils’ viscosities at shear rates (measured between 1 and 1000s−1) increased by approximately a factor of 2.5 during aging. To determine if this was due to polymerization reactions during aging or simply water and other volatile material losses, freshly made oils were aged at an accelerated rate by using elevated temperatures (65°C and 85°C) in a water-saturated environment between 1 and 7 days. The oils are fairly stable with respect to aging both over long periods of time (months) at room temperature and at elevated temperatures, 65°C and 85°C for shorter time periods (days). It is concluded that high water content and char-free characteristics act to slow polymerization reactions.
    Journal of Analytical and Applied Pyrolysis - J ANAL APPL PYROL. 01/2011; 91(1):190-198.
  • Nicholas B. Wyatt, Casey M. Gunther, Matthew W. Liberatore
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    ABSTRACT: The viscosity of several polyelectrolytes is measured in both salt free solutions and solutions in the high salt limit. At low polymer concentrations, the zero shear rate viscosity decreases as much as 100-fold upon addition of a monovalent salt, namely NaCl. However, as polymer concentration increases, the viscosity difference between polymer in salt free and in monovalent salt solution diminishes. Further, the zero shear rate viscosity becomes independent of added monovalent salt at the critical polyelectrolyte concentration cD. Above cD, the addition of monovalent salt increases the zero shear rate viscosity of the entangled polyelectrolyte solutions. The viscosity increase agrees with viscosity scaling theory for polyelectrolytes in the entangled regime. Polyelectrolytes exhibiting an increase in viscosity above cD in the presence of monovalent salt include three natural anionic polyelectrolytes (xanthan, carrageenan, welan), one synthetic anionic polyelectrolyte (hydrolyzed polyacrylamide), and one natural cationic polyelectrolyte (chitosan). Generally, these polyelectrolytes are relatively high molecular weight (>1 M Dalton), which makes cD experimentally accessible (e.g., cD = 0.2 wt% for xanthan). The magnitude of the viscosity increase is as high as 300% for xanthan and nearly independent of monovalent salt concentration in the high salt limit. The increase in viscosity in monovalent salt solution and magnitude of cD appear to be heavily influenced by the molecular characteristics of the polymers such as monomer weight, molecular structure, and chain conformation.Graphical abstract
    Polymer. 01/2011; 52(11):2437-2444.
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    ABSTRACT: Molecular inclusion compounds called clathrate hydrates are a common concern in oil and gas pipelines, as they cause disruption to production. These crystalline compounds are over 80mol% water and are often only stable at high pressures and low temperatures. As a means to understand the rheology of clathrate hydrates, we investigated ice slurries, in crude oil, as a simple analogy to clathrate hydrates. A series of water-in-oil emulsions were prepared at different volume fractions of water, ranging from 0.10 to 0.70. Water used in the samples was deionized watger or a 3.5 wt% NaCl brine solution. The emulsions were cooled to -10°C and the viscosity and yield stress were analyzed as a function of time after nucleation.No yield stresses were observed at volume fractions below 0.2 for fresh water and 0.3 for brine solution. In the fresh water system, the yield stress varied with increasing volume fraction. Between volume fractions of 0.25–0.55, yield stresses were on the order of 300Pa, and at larger volumer fractions (0.6–0.7) yield stress quickly increased to an unmeasurable value (greater than 3000Pa, the instrument’s limit). In the brine system, yield stress increased with volume fraction of water. After formation of ice, flow was stopped and the system was “annealed”. During the “annealing” period, the magnitude of complex viscosity of the fresh water system reached a peak value after two hours, decreased for approximately four hours, and then changed little for the next forty hours. The yield stress during “annealing” mimicked the trend of the magnitude of complex viscosity. In the brine system, the magnitude of complex viscosity increased over the first three hours, then changed little. However, the yield stress decreased as the “annealing” time increased. Following the measurements of yield stress, the slurry was conditioned at 500s-1 and the apparent viscosity was analyzed as a function of shear rate. At volume fractions greater than 0.10 the slurry was found to be shear thinning and exhibited a viscosity increase compared to the initial emulsion.
    Fuel and Energy Abstracts 01/2011; 166(14):859-866.
  • Nicholas B. Wyatt, Casey M. Gunther, Matthew W. Liberatore
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    ABSTRACT: AbstractThe ability to reduce the frictional drag in turbulent flow in pipes and channels by addition of a small amount of a high molecular weight polymer has application in myriad industries and processes. Here, the drag reduction properties of the polyelectrolyte xanthan are explored in differing solvent environments (salt free versus salt solution) and delivery configurations (homogeneous versus stock solution dilution). Drag reduction effectiveness increases when an entangled xanthan solution is diluted compared to solutions prepared in the dilute regime. Based on dynamic rheological measurements of the elastic modulus, residual entanglements and network structure are hypothesized to account for the observed change in drag reduction effectiveness. Drag reduction effectiveness is unchanged by the presence of salt when the stock solution concentration is sufficiently above the critical concentration cD. Finally, the drag reduction effectiveness decreases with time when diluted from an entangled stock solution but remains greater than the homogeneous case after more than 24 h.
    Journal of Non-Newtonian Fluid Mechanics. 01/2011;