Solid Characterisation

Question 1

What is Martin’s Diameter?

Answer 1

The length of the line which bisects the particle image

Question 2

What is Ferets Diameter?

Answer 2

The distance between two tangents on opposite sides of the particle

Question 3

What is the equivalent circle diameter?

Answer 3

The circle with area equal to projected particle area

Question 4

For which type of particle are Martin’s, Ferets and equivalent circle diameter used?

Answer 4

Irregular-shaped particles

Question 5

What is used describe a regular shaped particle?

Answer 5

The shape and dimensions

Question 6

What are the two methods to measure the particle dimensions?

Answer 6

(I) Using a sieve

(ii) Using sedimentation techniques

Question 7

What dimensions does a sieve obtain?

Answer 7

The equivalent sphere diameter. The diameter of a sphere passing through the same sieve aperture, volume based particle size.

Question 8

What dimensions does sedimentation techniques obtain?

Answer 8

The diameter of a sphere having the same sedimentation velocity as the particle under the same conditions. Hydrodynamic or aerodynamic particle size.

Question 9

What is plotted on the axes of particle size distribution? What is the shape of the curve?

Answer 9

x-axis = particle size
y-axis = f(x)
Inverse parabolic.

Question 10

What is plotted on the axis of cumulative distribution? What is the shape of the curve?

Answer 10

x-axis = particle size
y-axis = F
The curve is flat initially, steep incline and then plateaus

Question 11

Is it necessary for the particle population by number, surface and volume to be the same?

Answer 11

No

Question 12

What is fN(x)

Answer 12

fraction of particles in the size range x to x+dx

Question 13

What is fs(x)

Answer 13

fraction of total surface of particles in the size range of x to x+dx

Question 14

What is Nfn(x)

Answer 14

number of particles in x to x+dx

Question 15

Describe sieve analysis

Answer 15

Standard sieves are available in a variety of size ranges. They are arranged with decreasing size from top to bottom. The smallest of these is an impervious pan.

Question 16

Describe microscopy

Answer 16

Optical microscope for particle size measurement to 0.001 micrometres.
Electron microscope to 0.001 micrometres.

Question 17

Describe sedimentation

Answer 17

Same shaped particles of same density sink at different velocity in a fluid depending on their size. Sampling at a particular time and using Stokes law for particles travelling at their terminal velocity allows determination of particle size. Sampling a particle at a depth h at a time t gives us Ut = h/t and plugged into Stokes equation to get particle size x.

Question 18

Describe permeametry

Answer 18

Fluid flow through packed bed. Use Carman-Kozeny equation for laminar flow through randomly packed bed.

Question 19

Describe laser diffraction

Answer 19

Light passing through a suspension, the diffraction is inversely proportional to particle size. Measure the diffraction pattern of particles with a detector.