Hard‐sphere Colloidal Dispersions: The Scaling of Rheological Properties with Particle Size, Volume Fraction, and Shear Rate

In this study, waste polyethylene terephthalate (PET) polymer binder systems were used to prepare copper-graphite metal injection molding (MIM) feedstock. A mixer and screw extrusion were used to achieve optimized feedstock, and the rheological properties of the resulting fluids were evaluated using a capillary rheometry to simulate the injection molding process. The solid loadings in the copper-graphite mixes were investigated in the ranges of 51-53% using PET binder system. The effects of shear rate (γ), solid volume fraction (φ) and temperature (T) on the rheological behavior of the copper/graphite MIM feedstocks are discussed.High viscosity trend was notably recorded as shear rate increased relatively. The results indicated that this feedstock system shows dilatant characteristic and lots of further work shall be conducted in attempt to establish this as an ideal binder system.

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Rheological Behavior of Highly Filled EPDM Compounds with Calcium Carbonate, Carbon Black, Silica and Zinc Oxide

Rubber Chemistry and Technology ◽

10.5254/1.3538390 ◽

1996 ◽

Vol 69 (4) ◽

pp. 628-636 ◽

Cited By ~ 18

Author(s):

Li Li Li ◽

James L. White

Keyword(s):

Particle Size ◽

Zinc Oxide ◽

Calcium Carbonate ◽

Shear Rate ◽

Carbon Black ◽

Shear Viscosity ◽

Volume Fraction ◽

Carbonate Carbon ◽

Yield Value ◽

Yield Values

Abstract The shear viscosity, creep and constant shear rate transients have been measured for 0.20 volume fraction compounds of an EPDM with calcium carbonate, carbon black, silica and zinc oxide of similar particle size at 100°C. Measurements have been made in a creep sandwich instrument, pressurized rotational rheometer and a capillary rheometer and cover nine decades of shear rate. All of the compounds exhibit enhanced viscosities and yield values; i.e. there are stresses below which there is no flow. The greatest yield values and increased viscosities are with the compounds with calcium carbonate and zinc oxide. More extensive studies were made with the EPDM-calcium carbonate system, where it was shown that, increasing particle size reduces shear viscosity and yield values. Further, surface treating calcium carbonate with stearic acid signifcantly reduces the shear viscosity and yield value of the corresponding EPDM compound.

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An improved small-angle X-ray scattering analysis of δ′ precipitation in an Al–Li alloy for growth kinetic studies

Journal of Applied Crystallography ◽

10.1107/s0021889898017282 ◽

1999 ◽

Vol 32 (3) ◽

pp. 426-435 ◽

Cited By ~ 5

Author(s):

Cheng-Si Tsao ◽

Tsang-Lang Lin

Keyword(s):

Particle Size ◽

Size Distribution ◽

Hard Sphere ◽

Volume Fraction ◽

The Other ◽

Improved Method ◽

Saxs Data ◽

X Ray ◽

X Ray Scattering ◽

Two Parameters

An improved method for small-angle X-ray scattering (SAXS) data analysis is developed to reconstruct the free-form particle size distribution of δ′ precipitation in an Al–Li alloy. This improved method consists of four iterative steps; the interparticle interference is also included. The indirect transform method (ITM) plus a hard-sphere (HS) model which considers the depleted zones are used in the analysis of δ′ precipitation in an Al–Li alloy. Two parameters, namely the hard-sphere volume fraction, ηHS, and the ratio of hard-sphere radius to the particle radius,RHS/R, which determine the structure factor of the interparticle effect, are iteratively calculated using the monodisperse assumption and Gaussian size distribution. These two parameters are finally used in reconstructing the particle size distribution by the ITM + HS method. This method is tested by analysing simulated SAXS data and shows a better agreement than found in similar studies. This improved method is applied to analyse a set of experimental SAXS intensities from δ′ (Al3Li particles) precipitation in an Al–9.7 at.% Li alloy. The monodisperse results are compared with the polydisperse ITM + HS results. The current ITM + HS method fits the SAXS data better than the other methods. The variations of average radii with aging time were found to follow the kinetic power law. The SAXS results are used to investigate the theoretical kinetic model of the volume-fraction effect on late-stage coarsening (Ostwald ripening). By comparing both experimentally obtained asymptotic size distributions of δ′ particles as well as coarsening rate constants with those predicted by the various kinetic models, the modified Lifshitz–Slyozov–Wagner (MLSW) theory is found to be in better agreement with the experimental results than the other theories.

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The Effect of Nano SiO2 Particle Size Distribution on Rheological Behaviour of Shear Thickening Fluids

Archives of Metallurgy and Materials ◽

10.2478/amm-2013-0167 ◽

2013 ◽

Vol 58 (4) ◽

pp. 1323-1326 ◽

Cited By ~ 4

Author(s):

A. Idźkowska ◽

M. Szafran

Keyword(s):

Particle Size ◽

Shear Rate ◽

Particle Size Distribution ◽

Size Distribution ◽

Volume Fraction ◽

Ceramic Powder ◽

Shear Thickening ◽

Measuring System ◽

Maximum Volume ◽

Maximum Volume Fraction

Abstract In present work the influence of particle size distribution on the dilatant effect of shear thickening fluid was investigated. As a ceramic powder a mixture of silicas 200 and 7 nm in ratio 95:5, 90:10, 85:15, 80:20, 75:25, 50:50 was used. A dispersing agent was poly (propylene glycol) of a molecular weight of 425 g/mol. The as prepared slurries were examined on a rotational rheometer Kinexus Pro with a plate-plate measuring system at room temperature, where the viscosity as a function of shear rate was investigated. The measurement showed that by partially replacing greater particle size by smaller one, it is possible to shift the onset of shear thickening to the higher value of shear rate, however, the decreases of dilatant effect is observed. The influence of particle size distribution on a maximum volume fraction also was investigated. The maximum volume fraction which was passible to obtain was 35 vol%.

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The effects of interparticle interactions and particle size on reversible shear thickening: Hard-sphere colloidal dispersions

Journal of Rheology ◽

10.1122/1.1392295 ◽

2001 ◽

Vol 45 (5) ◽

pp. 1205-1222 ◽

Cited By ~ 195

Author(s):

Brent J. Maranzano ◽

Norman J. Wagner

Keyword(s):

Particle Size ◽

Hard Sphere ◽

Shear Thickening ◽

Colloidal Dispersions ◽

Interparticle Interactions

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Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids

Entropy ◽

10.3390/e23080979 ◽

2021 ◽

Vol 23 (8) ◽

pp. 979

Author(s):

Abderrahim Bakak ◽

Mohamed Lotfi ◽

Rodolphe Heyd ◽

Amine Ammar ◽

Abdelaziz Koumina

Keyword(s):

Shear Rate ◽

Rheological Properties ◽

Dynamic Viscosity ◽

Volume Fraction ◽

Solid Volume Fraction ◽

Heat Extraction ◽

Rheological Characterization ◽

Shear Rates ◽

Rheological Measurements

The dynamic viscosity and rheological properties of two different non-aqueous graphene nano-plates-based nanofluids are experimentally investigated in this paper, focusing on the effects of solid volume fraction and shear rate. For each nanofluid, four solid volume fractions have been considered ranging from 0.1% to 1%. The rheological characterization of the suspensions was performed at 20 ∘C, with shear rates ranging from 10−1s−1 to 103s−1, using a cone-plate rheometer. The Carreau–Yasuda model has been successfully applied to fit most of the rheological measurements. Although it is very common to observe an increase of the viscosity with the solid volume fraction, we still found here that the addition of nanoparticles produces lubrication effects in some cases. Such a result could be very helpful in the domain of heat extraction applications. The dependence of dynamic viscosity with graphene volume fraction was analyzed using the model of Vallejo et al.

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Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

Sustainability ◽

10.3390/su13095086 ◽

2021 ◽

Vol 13 (9) ◽

pp. 5086

Author(s):

Fatih Selimefendigil ◽

Hakan F. Oztop ◽

Ali J. Chamkha

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Particle Size ◽

Aspect Ratio ◽

Power Law ◽

Volume Fraction ◽

Inclined Magnetic Field ◽

Magnetic Field Effects ◽

Power Law Nanofluid ◽

Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

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A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽

10.3390/catal11040491 ◽

2021 ◽

Vol 11 (4) ◽

pp. 491

Author(s):

Alina E. Kozhukhova ◽

Stephanus P. du Preez ◽

Aleksander A. Malakhov ◽

Dmitri G. Bessarabov

Keyword(s):

Electron Microscopy ◽

Particle Size ◽

Combustion Temperature ◽

Volume Fraction ◽

Morphological Characteristics ◽

Al Alloy ◽

Impregnation Method ◽

Case Scenario ◽

Worst Case ◽

Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

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