Tailored Rheological Behavior of Mullite and BSAS Suspensions Using a Cationic Polyelectrolyte

2005 ◽  
Author(s):  
Glen H. Kirby ◽  
Kevin M. Cooley ◽  
Beth L. Armstrong
Keyword(s):  
Yield Stress ◽  
Rheological Behavior ◽  
Elastic Moduli ◽  
Flow Behavior ◽  
Critical Concentration ◽  
Aqueous Suspension ◽  
Aqueous Media ◽  
Shear Thinning ◽  
Dip Coating ◽  
Cationic Polyelectrolyte

The effects of a cationic polyelectrolyte, polyethylenimine, on the rheological behavior of aqueous mullite and celsian phase, barium strontium aluminosilicate (BSAS) suspensions have been studied to optimize a dip-coating process. The surface of the ceramic particles was characterized in aqueous media using zeta potential measurements. The ionization behavior and hydrodynamic radius of polyethylenimine in aqueous media was characterized by potentiometric titration and dynamic light scattering measurements, respectively. The rheological behavior of concentrated ceramic suspensions containing polyethylenimine was characterized by stress viscometry and elastic modulus measurements. Polyethylenimine imparts repulsive, electrosteric interactions between mullite and BSAS particles in aqueous suspension, resulting in shear thinning flow behavior, linear elastic moduli, and yield stress values that are minimized for suspensions with a critical PEI concentration of 0.2 mg PEI per m2 of mullite and 0.4 mg PEI per m2 of BSAS, respectively. The elastic moduli and yield stress of mullite and BSAS suspensions were nearly identical at equivalent fractions of their critical PEI concentration. Uniform coatings were obtained upon dipping SiC, Si3N4, and Si-metal substrates into shear-thinning suspensions containing PEI at 81–88% of the critical concentration. Dense mullite coatings were demonstrated on SiC substrates after sintering at 1400°C.

Rheological Behavior of Seed Gum from Cassia fistula

2019 ◽  
Vol 818 ◽  
pp. 16-20
Author(s):  
Wancheng Sittikijyothin ◽  
Khanaphit Khumduang ◽  
Keonakhone Khounvilay ◽  
Rattanaphol Mongkholrattanasit
Keyword(s):  
Shear Rate ◽  
Flow Behavior ◽  
Critical Concentration ◽  
Shear Thinning ◽  
Zero Shear Viscosity ◽  
Specific Viscosity ◽  
Cross Model ◽  
Linear Slope ◽  
Mechanical Spectra ◽  
Seed Gum

The C. fistula gums in aqueous solutions clearly exhibited shear-thinning flow behavior at high shear rate, however, at higher concentrations, pronounced shear thinning was observed. The value of zero shear viscosity [h0] was predicted by fitting Cross model. A plotting of specific viscosity at zero shear rate (hsp0) against coil overlap parameter (C[h]) was shown the linear slope of dilute and simi-dilute as 1.43 and 4.10, respectively, which found the critical concentration (C*) about 7.08/[h]. While, the mechanical spectra in the linear viscoelastic region of gum solutions showed the typical shape for macromolecular solutions.

Computational Modeling of Enhanced Laminar Flow Heat Transfer in Viscoplastic Fluids in Corrugated-Plate Channels

2002 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Yield Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Bingham Plastic ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Colburn Factor ◽  
Power Law Index

The enhanced heat transfer in laminar viscoplastic, shear thinning, Herschel-Bulkley fluid flows in sinusoidal corrugated-plate channels is investigated. With uniform-temperature plate walls, periodically developed flows are considered for a wide range of flow rates (10 ≤ Reg ≤ 700) and pseudoplastic flow behavior indices (n = 0.54, 0.8, and 1.0; the latter representing a Bingham plastic). The effects of fluid yield stress are simulated for the case where τy = 1.59 N/m2, representing a 0.5% xantham gum aqueous solution. Typical velocity and temperature distributions, along with extended results for isothermal friction factor ƒ and Colburn factor j are presented. The effect of the yield stress is found to be most dominant at low Reg regardless of the power law index n, and the recirculation or swirl in the wall trough regions is weaker than in the cases of Newtonian and power-law liquids. At higher Reg, the performance of the Herschel-Bulkley fluid asymptotically approaches that of the non-yield-stress power-law fluid. At low Reg, the yield stress increases ƒ by an order of magnitude and j is enhanced because of the higher wall gradients imposed by the plug-like flow field. The relative heat transfer enhancement, represented by the ratio (j/ƒ), and the role of the fluid yield stress and shear-thinning (or pseudoplastic) behaviors are also discussed.

Rheological Behavior of Filled Polymeric Systems I. Yield Stress and Shear‐Thinning Effects

1988 ◽  
Vol 32 (7) ◽  
pp. 703-735 ◽  
Author(s):  
A. J. Poslinski ◽  
M. E. Ryan ◽  
R. K. Gupta ◽  
S. G. Seshadri ◽  
F. J. Frechette
Keyword(s):  
Yield Stress ◽  
Rheological Behavior ◽  
Shear Thinning ◽  
Polymeric Systems

Rheological Behavior of Silicon Nitride Whiskers

1992 ◽  
Vol 287 ◽  
Author(s):  
Patricio Toro ◽  
Oscar Wittke
Keyword(s):  
Rheological Behavior ◽  
Carbothermal Reduction ◽  
Ceramic Body ◽  
Flow Behavior ◽  
Aqueous Suspension ◽  
Slip Casting ◽  
Sem Analysis ◽  
Ftir Analysis ◽  
Rice Husks ◽  
X Ray

ABSTRACTSi3N4 whiskers are found through SEM analysis of powder obtained by carbothermal reduction of calcined Chilean rice husks. X-ray and FTIR analysis showed that the ceramic material was mainly α-Si3N4. A stable aqueous suspension with 30 or 40 wt% Si3N4 was obtained at pH = 8.5. A maximum viscosity at pH = 4.0 and low rpm was also observed and this rheological behavior is consistent with the zeta potential data. An irregular flow behavior near pH 4.0 shows a decrease in viscosity that is related to active impurities as detected by potentiometric titrations.These rheological studies conducted allowed production of a Si3N4 green ceramic body measuring 170 × 25 × 5 mm formed by slip casting. The optimal aqueous suspension of powder contained the following: 17.0 g Si3N4, 1.0 g Cu2O, 1.3 g bentonite, and 20.0 g water.

The Influence of Concentrations of Cement Particles on Rheological Behavior and Thixotropy of Portland Cement Paste

2018 ◽  
Vol 276 ◽  
pp. 27-34 ◽  
Author(s):  
Mindaugas Macijauskas ◽  
Gintautas Skripkiūnas
Keyword(s):  
Portland Cement ◽  
Yield Stress ◽  
Cement Paste ◽  
Rheological Behavior ◽  
Flow Behavior ◽  
Plastic Viscosity ◽  
Rotational Rheometer ◽  
Coaxial Cylinders ◽  
Dynamic Yield ◽  
Portland Cement Paste

The influence of concentration of cement particles φc on rheological behavior (flow behavior, dynamic yield stress, plastic viscosity) and thixotropy of the Portland cement CEM I 42.5 R paste was investigated in this research. Also, thixotropy was evaluated by index of reversible structure of Portland cement paste. Concentration of cement particles φc ranged from 0.434 to 0.518. Investigation was carried out using rotational rheometer Rheotest RN4.1 with coaxial cylinders. The tests revealed that as φc decreases from 0.518 to 0.434, rheological behavior of Portland cement paste is improved: yield stress decreases from 12.7 Pa to 7.1 Pa as well as plastic viscosity – from 4.3 Pa·s to 0.88 Pa·s. The exponential correlation between φc and index of reversible structure of Portland cement paste was found. As φc decreases from 0.518 to 0.434, index of reversible structure of Portland cement paste, which describes a thixotropy, decreases from 5291 Pa·min to 977 Pa·min.

Hemorheology and the Flow Behavior in a Separated Flow Region

2013 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Yield Stress ◽  
Heart Valves ◽  
Flow Behavior ◽  
Circulatory System ◽  
Separated Flow ◽  
Flow Region ◽  
Shear Thinning ◽  
Momentum Conservation ◽  
Artificial Organs ◽  
Rotary Blood Pumps

Separating flows can be encountered in the cardiovascular circulatory system and many biomedical applications such as artificial organs, rotary blood pumps, heart valves, stents, catheters, and probes. The current study investigates the influence of hemorheology on the flow behavior in a confined separated flow region. Recent hemorheological models and data are utilized to account for the yield stress and shear-thinning non-Newtonian characteristics of human blood. The flow field information is obtained by numerically solving the governing mass and momentum conservation equations along with the Herschel-Bulkley rheological model. The yield shear-thinning model always results in the smallest flow separation region. The yield stress and shear-thinning non-Newtonian models predict lower recirculation strength in comparison with the Newtonian model.

Rheology and Storage Tests of Dead Sea Shampoo

2004 ◽  
Vol 14 (2) ◽  
pp. 96-103 ◽  
Author(s):  
Basim Abu-Jdayil ◽  
Hazim Mohameed ◽  
Tamara Snobar ◽  
Maha Sa’id
Keyword(s):  
Rheological Properties ◽  
Salt Concentration ◽  
Rheological Behavior ◽  
Room Temperature ◽  
Storage Time ◽  
Flow Behavior ◽  
Salt Content ◽  
Shear Thinning ◽  
Dead Sea ◽  
Consistency Coefficient

Abstract Changes in the rheological properties of hair shampoo samples differing in the content of Dead Sea (DS) salt were studied. The rheological properties were tested during a 28-day storage period at three different storage temperatures (cold, room temperature and accelerated conditions). Steady rheological tests were performed and the conductivities of the shampoo samples were determined. The parameters of the power law model; the consistency coefficient and the flow behavior index were used to quantify the effect of storage time and temperature on the rheological behavior of hair shampoo in the presence of DS salt. The consistency coefficient of the salt free shampoo samples stored at 8°C and at room temperature decreased with storage time, and the rheological behavior changed from shear thinning to Newtonian. On the other hand, the samples stored at 45°C exhibited a shear thinning behavior, which did not change with storage time. Shampoo samples with 1.5 wt% DS salt content, showed the maximum viscosity and the rheological behavior of the samples did not change with the storage time. An exception were the samples stored at 45°C, which behaved like the salt free samples stored at room temperature. The conductivity of hair shampoo increased linearly with storage time and salt concentration. A discontinuity at a salt concentration of 1.5% was observed. However, the conductivity of hair shampoo increased with increasing the storage temperature.

Microfluidic Channel Fabrication With Tailored Wall Roughness

2012 ◽  
Author(s):  
Jing Ren ◽  
Sriram Sundararajan
Keyword(s):  
Flow Behavior ◽  
Surface Texturing ◽  
Microfluidic Channel ◽  
Dip Coating ◽  
Etch Depth ◽  
Wall Roughness ◽  
Random Surface ◽  
Lab On Chip ◽  
On Chip ◽  
Autocorrelation Length

Realistic random roughness of channel surfaces is known to affect the fluid flow behavior in microscale fluidic devices. This has relevance particularly for applications involving non-Newtonian fluids, such as biomedical lab-on-chip devices. In this study, a surface texturing process was developed and integrated into microfluidic channel fabrication. The process combines colloidal masking and Reactive Ion Etching (RIE) for generating random surfaces with desired roughness parameters on the micro/nanoscale. The surface texturing process was shown to be able to tailor the random surface roughness on quartz. A Large range of particle coverage (around 6% to 67%) was achieved using dip coating and drop casting methods using a polystyrene colloidal solution. A relation between the amplitude roughness, autocorrelation length, etch depth and particle coverage of the processed surface was built. Experimental results agreed reasonably well with model predictions. The processed substrate was further incorporated into microchannel fabrication. Final device with designed wall roughness was tested and proved a satisfying sealing performance.

Investigation on the Rheological Behavior of Polyamide6/Montmorillonite Nanocomposites by Reactive Extrusion

2011 ◽  
Vol 233-235 ◽  
pp. 1998-2001 ◽  
Author(s):  
Ming Zhao ◽  
Xiao Zhong Lu ◽  
Kai Gu ◽  
Xiao Min Sun ◽  
Chang Qing Ji
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Reactive Extrusion ◽  
Shear Thinning ◽  
Experimental Results ◽  
Montmorillonite Nanocomposites

The rheological behavior of PA6/montmorillonite(MMT) by reactive extrusion was investigated using cone-and-plate rheometer. The experimental results indicated that PA6/MMT exhibited shear-thinning behavior. The shear stress of both neat PA6 and PA6/MMT increased with the increase in the shear rate. The reduction of the viscous activation energy with the increase of shear stress reflected PA6/MMT can be processed over a wider temperature.

The physicochemical and DNA binding studies of some medicinal compounds in solutions

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Abbas Khan ◽  
Naila ◽  
Muhammad Humayun ◽  
Muhammad Sufaid Khan ◽  
Luqman Ali Shah ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Aqueous Media ◽  
Research Work ◽  
Binding Constants ◽  
Physicochemical Study ◽  
Solution Temperature ◽  
Binding Studies ◽  
Experimental Conditions ◽  
Medicinal Compounds ◽  
Association Behavior

Abstract To understand the expected mode of action, the physicochemical study on the solution properties of medicinal compounds and their interaction with deoxyribonucleic acid (DNA), under varying experimental conditions, is of prime importance. The present research work illustrates the physicochemical study and interaction of certain medicinal compounds such as; Levofloxacin, Ciprofloxacin, and Ibuprofen with DNA. Density, viscosity and surface tension measurements have been performed in order to determine, in a systematic manner, the physicochemical, volumetric and thermodynamic properties of these compounds; and most of these parameters have shown different behavior with varying concentration of solution, temperature of the medium and chemical nature/structure of the compound. In addition, these drugs showed a spontaneous surface-active and association behavior in aqueous solutions. The flow behavior, surface properties, volumetric behavior and solute–solvent interaction of these drugs were prominently influenced by experimental variables and addition of DNA to their solutions. UV–Visible spectroscopy was also used to examine the interaction of these drugs with DNA in aqueous media in detail. Calculated values of binding constants (Kb) for all complexes of drug-DNA are positive, indicating a fruitful binding process. It is seen that a smaller Kb value reflects weaker binding of the drug with DNA and vise versa. Due to the difference in the chemical structure of drugs the values of binding constant are different for various drug-DNA complexes and follow the order Kb(Levofloxacin-DNA) > Kb(Ciprofloxacin-DNA) > Kb(Ibuprofen-DNA). On the basis of spectral changes and Kb it can be said that the binding of all these drugs with DNA may be of physicochemical nature and the dominating binding force be of hydrogen bonding between oxygen of drugs and hydrogen of DNA units and the drug having more oxygen atoms showed stronger binding ability. The data further suggest a limited possibility of chemical type attachment of these drugs with DNA.

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