Particle Size Analysis

Question 1

What are the problems with particle size analysis?

Answer 1

Irregular particle shapes = unpredictable
Range of particle sizes
2-dimensional info = lose info on entire dimension

Question 2

What is the solution to particle size analysis?

Answer 2

Equivalent sphere
Statistics

Question 3

What is equivalent sphere diameter?

Answer 3

Hypothetical sphere that has an equivalent measurable property (eg. vol, SA) as particle

Question 4

What is the perimeter diameter?

Answer 4

Diameter of equivalent sphere with same perimeter (circumference)

Question 5

What is the projected area diameter?

Answer 5

Diameter of equivalent sphere with the same projected area

Question 6

What are the statistical diameters?

Answer 6

Feret’s diameter
Martin’s diameter

Question 7

What is Feret’s diameter?

Answer 7

Average length of line across the projected width of particle (dF)

Question 8

What is Martin’s diameter?

Answer 8

Average length of line bisecting particle into equal areas

Question 9

What is the hydrodynamic diameter?

Answer 9

Diameter of hypothetical equivalent sphere that diffuses in the same way as the particle under investigation

Question 10

What is the hydrodynamic diameter affected by?

Answer 10

Ionic strength
Surface structure
Shape

Question 11

What is convexity?

Answer 11

Convex hull perimeter divided by actual particle perimeter

Question 12

What is aspect ratio?

Answer 12

Width divided by length

Question 13

What is circularity?

Answer 13

Circumference of equivalent area circle divided by actual perimeter of particle

Question 14

What is solidity?

Answer 14

Actual particle area divided by convex hull area

Question 15

Describe normal particle size distribution on graph

Answer 15

Symmetrical
Mean = median = mode
Standard deviation

Question 16

Describe bimodal distribution

Answer 16

Suggest 2 distinct populations of different particle size
= 2 peaks = modes

Question 17

What does it mean when the graph is negatively skewed?
Shifts right

Answer 17

More larger particles than smaller ones
Mean < median < mode

Question 18

What does it mean when the graph is positively skewed?
Shifts left

Answer 18

More smaller particles than larger ones
Mean > median > mode

Question 19

What are D-values?

Answer 19

Equivalent sphere diameter at specified percentiles

Question 20

What is D10?

Answer 20

10% of particles are below this diameter

Question 21

What is D25?

Answer 21

25% of particles are below this diameter

Question 22

What is D50?

Answer 22

50% of particles are below this diameter (median)

Question 23

What is D75?

Answer 23

75% of particles are below this diameter

Question 24

What is D90?

Answer 24

90% of particles are below this diameter

Question 25

What does span indicate?

Answer 25

Width of particle size distribution

Question 26

How do you calculate span?

Answer 26

D90 - D10 --------------- D50

Question 27

What numbers is interquartile coefficient of skewness (IQCS)?

Answer 27

-1 to 1

Question 28

What is IQCS < 0?

Answer 28

Negative skew

Question 29

What is IQCS > 0?

Answer 29

Positive skew

Question 30

What is IQCS = 0?

Answer 30

Normal distribution

Question 31

What is the equation for polydispersity index?

Answer 31

σ ---- *2 μ Standard deviation Mean particle size

Question 32

What happens if polydispersity index is below 0.2?

Answer 32

Narrow particles approx. same size = monodispersed

Question 33

Describe laser diffraction

Answer 33

Wet or dry samples Scattered light detected by photodetectors Particle size determined from angular light intensity

Question 34

Describe dynamic light scattering

Answer 34

Laser light scattered by particles in Brownian motion Wet samples only

Question 35

What do smaller particles do?

Answer 35

Diffuse more rapidly

Question 36

What happens if the particles move faster?

Answer 36

Different scatter flucuation

Question 37

How is hydrodynamic diameter of particle determined in dynamic light scattering?

Answer 37

Stokes-Einstein equation