29 Questions
What are the key concepts discussed in Particulate Suspensions?
Hard, and Slightly Deformable, Spheres; Nonspherical Particles; Electrically Charged Particles; Particles in Viscoelastic Liquids
Differentiate between Suspensions, Colloids, and Solutions based on particle size.
Suspension: larger particle size > 10 µm; Colloids: particle size 1-1000 nm; Solutions: < 10 µm
What are the two types of heterogeneous systems in colloid dispersion?
Sol-gel (solid/polymeric particles in liquid) and emulsion (liquid droplets in liquid)
Why is it crucial to control the structure and flow properties of suspensions in industrial processing?
To transform a liquid, moldable suspension into a solid-like one that retains its shape and ensure commercial success
What are the types of products where suspensions and colloids are commonly used?
Suspensions: drilling muds, foodstuffs, pharmaceuticals; Colloids: paints, inks, blood, milk, mayo
Explain the significance of shear thinning vs. shear thickening in particulate suspensions.
Shear thinning and shear thickening influence the flow behavior of suspensions under different conditions.
What is the reduced shear stress for monosized spherical particles?
𝜎 𝑎3 𝑘𝐵 𝑇 𝝈𝒓
What does the empirical Krieger-Dougherty Equation describe?
Relationship between volume fraction and viscosity in shear thinning
At what volume fraction do hard spheres exhibit a specific behavior in shear thinning?
𝜙𝑚 ≈ 0.63 - 0.64
What are the two plateau values in the shear-thinning viscosity equation?
𝜂𝑟0 and 𝜂𝑟∞
What is the significance of the shear-thinning behavior observed in particles with grafted layers?
Sensitivity to the deformability of the stabilization layers
What is the universal function for monosized spherical particles?
𝜂𝑟 ≡ 𝜂Τ𝜂𝑠
What is the approximate range of 𝜙𝑚 for hard spheres?
0.63 - 0.64
What can small errors in the determination of 𝜙 lead to?
Large errors in the estimated value of 𝜂
How does 𝜂 behave at high 𝜙?
𝜂 becomes sensitive to small variations in particle properties
What is the equation used to adjust the 'hard sphere' radius and 𝜙 for particles with steric-stabilization?
𝜙 = 𝜙0 Δ 1+ 𝑎 3 𝝓𝟎
What is the 'Farris effect' related to in terms of particle-size distribution?
Viscosity minima at the fraction of large particles
What is a consequence of the packing of small particles into the interstices between large ones in the 'Farris effect'?
Viscosity minima
How can sedimentation be prevented in a suspension?
By matching the densities of particle & solvent or using a very viscous suspending medium
What promotes the suspension of small particles in a liquid?
Agitation, which leads to Brownian motion
What can particle collisions due to Brownian motion lead to?
Aggregation
When can particle inertia occur in a liquid medium?
For particles larger than 10 µm in a medium of low viscosity
How can wall slip be prevented in dense particle suspensions?
Matching dielectric properties of particle and fluid combinations
What is the recommended particle size to maintain stable suspensions?
Below ~1 µm
What type of particles might be the most shear thickening?
Particles with 'soft' or long-ranged repulsive interparticle potentials
What factor is associated with a factor-of-two increase in viscosity as the Peclet number is increased?
Formation of clusters containing particles driven by shear into close proximity
How do sterically- or electrostatically- stabilized particles contribute to shear thickening?
They contribute by forming layered structures under modest shear.
What is the range of Peclet number associated with the factor-of-two increase in viscosity?
From around 10 to 10^4
How do the details of cluster production vary in different samples?
They vary depending on the nature of the repulsive potential between particles.
Test your knowledge on particulate suspensions in chemical engineering with this quiz covering key concepts such as hard spheres, nonspherical particles, electrically charged particles, and particles in viscoelastic liquids.
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