Title: Particle%20characterization
1Particle characterization
2Why determinate particle size
- List three things that you know will be affected
by particle size
3My three things
- Delivery of particles to the lungs
- Solubility of active pharmaceutical compounds
- Bulk density
4What do you want to characterize
- Particle
- Size
- Morphology
- Material properties
- Porosity
- Density
- Hardness/elasticity(later)
- Surface properties
- Chemical composition
- Surface energy
- Roughness
- Powder
- Particle distribution
- Flowability/cohesion
- Specific surface
- Density
- Porosity
- Air content
- Water content (later)
5Size and Morphology Describe these two particle
collections
6Size and Morphology Different descriptive terms
for particles
- Particle form
- spherical, ellipsoid, granular, blocky, flaky,
platy,prismodal, rodlike, acicular, needle
shaped, fibrous irregular,dendrites, irregular,
agglomerates - But also particle surface
- Smooth, spotty, rough, porous, with cracks,
hairy
7Size and Morphology Measurement of particle size
- Reduce to known geometry
- Volume
- Cubes
- Spheres
- Ellipsoids
- Area
- Circles
- Squares
- Ellipses
- Lengths
- Characteristic lengths
- Feret and Martin diameters
- Relate to the geometry
- Fit into the geometry
- Have equal Volume or Area
- Have equal properties
A Projected a rea PPerimeter dequivalent
diameter Ssurface area Vvolume
8Size and Morphology Descriptors based on
diameters of circles
- dcircDiameter of circumscribed minimum circle
- dinscDiameter of inscribes maximum circle
- deqDiameter of the circle having same area as
projection area of particle - Shape descriptorCircularity
- deq/dcirc
9Size and Morphology More descriptors according
to the same principles
Namn Definition Formula
Volume diameter Diameter of a sphere having the same volume as the particle
Surface diameter Diameter of a sphere having the same surface as the particle
Surface volume diameter Diameter of a sphere having the same surface to volume ratio as the particle
Projected area diameter Diameter of the circle having the same area as the projection area of particle
Perimeter diameter Diameter of the circle having the same perimeter as the projection peramiter of particle
10Size and Morphology Feret and Martin diameter
Df0
- The Feret diameter the distance between two
tangents to the contour of the particle in a well
defined orientation. - The Martin diameter, is the length of a line that
divide the area of the particle into two equal
halves. - Normally measured
- Mean the mean over several orientations
- Ylargest
- Xsmallest
- Elongation Y/X
Dm0
11Size and Morphology Unrolled diameter
- The mean chord length through the center of
gravity of the particle
12Size and Morphology Diameter Defined from equal
properties
- Drag diameter
- Diameter of a sphere having the same resistance
to motion as the particle in a fluid of the same
viscosity and the same speed - Free-falling diameter
- Diameter of a sphere having the same density and
the same free-falling speed as the particle in a
fluid of the same density and viscosity - Stoke diameter
- The free falling diameter of a particle in the
laminar flow region - Aerodynamic diameter
- the diameter of a sphere of unit density (1g/cc)
that has the same gravitational settling velocity
as the particle in question.
13Size and Morphology Stoke diameter
- For small particles lt0.5?m Brownian motions
counteract gravitational forces and the system
will be stable - For larger particles
- Density matching will hinder sedimentation
msolventg
Brownian motion
a
mpartg
14Size and Morphology Diameter Defined from equal
properties contin..
- Equivalent light-scattering diameter
- Diameter of the sphere giving the same intensity
of light scattering as that of a particle,
obtained by the light-scattering method - Sieve diameter
- The diameter of the smallest grid in a sieve
that the particle will passe through
15Size and MorphologyFrom descriptors
- Elongation L/B or dferet(max)/dferet (min)
- Circularity for example dins/dcirc
- Sphericity (Wandells)
16Size and Morphology Form descriptors
- Form factors f/k will describe the form
- Space Filling Factor The ratio between the area
of a circumscribed rectangle or circumscribed
circle of the image and that of the particle eg
A/LB eller 4A/pr2
17Material propertiesDensity
- True particle density The density of the
material - Apparent particle density Density of the
particle when inner porosity is included - Effective or aerodynamic particle density
Density if outer porosity is included. Related to
the density that a air or gas stream will measure.
18Surface properties Particle surface
- Properties
- Roughness of the surface
- Composition
- Surface energy
- Influences
- Stability
- Total area
- Particle size reduction
- Adsorption of other substances to the surface
- Aggregation
- Release of adsorbed material
19Surface properties To evaluate surfaces
properties
- ESCA, XPS - Composition
- FTIR - Composition
- AFM- Surface morphology and surface energy
- Raman microscopy- composition
- Electron microscopy -Surface morphology
20Surface properties To evaluate surface energy -
Contact angles
- Gives information on how easily a liquid wets a
surface. - Low contact angle with water for hydrophilic
surfaces. - Contact angle hysteresis
- Chemically heterogeneous surface.
- Surface roughness.
- Surface porosity
- Surface changes when wetted.
21Assignments particlesTask
- Test and compare two different techniques for
size determinations (half a day) - Microscopy
- Light scattering
- Answer the questions in the assignment
description on a seminar (Tue 28 Apr 13.15) - As usuell hand in a short technical note
22Assignments particlesPractical issues
- Do the assignment in groups of three
- Use our sample or your own
- Microscopy use the microscope to take picture but
do the major part of the analyses afterwards
Image J is a free program
23Size distribution Particle size distribution
- Why is the mean value not enough to describe
particle size distributions - How can we describe the distribution
- Based on what properties
- Based on what type of statistic distribution
24Size distribution Type of distributions
- Different type of diameters
- Different type of distribution
- Number (0)
- Length (1)
- Area (2)
- Volume (3)
- Weight (w) V?
- How will these differ from one another?
- How do you calculate the mean particle size
- Can you transfer mean particle size between the
different distributions?
25Size distributionAverage particle size
Number mean length diameter d(1,0) 2
Number mean surface diameter d(2,0) 2,16
Number mean volume diameter d(3,0) 2,29
Weighted mean length diameter d(3,0)
Length surface mean diameter d(2,1) 2,33
Length volume mean diameter d(3,1) 2,45
Surface Volume mean diameter d(3,2) 2,57
weight moment mean diameter d(4,3) 2,72
26Size distributionDifferent distributions
27Size distribution Type of statistic distribution
- Normal distribution
- Log Normal
- RosinRammler (Weibull) Distribution
28Size distribution Special properties of log
distributions
- If the number is log distributed so is the
length, surface, and volume - With the same geometric mean deviation
- Hatch-Choate relationships will transfer one type
of mean diameter into another
29Size distribution Description of particle size
distribution
- Mean diameter
- Standard mean,
- Geometric mean
- variability
- Standard deviation
- Geometric standard deviation
- Skewness
30PowderSpecific surface
- Surface per weight
- Factors that increase surface area
- Decrease in particle size
- Increase in surface roughness
- Inner porosity (if available)
- Method dependent parameter
- Permeatry
- Gas adsorption
- Gas diffusion
- Porosimetery
- Importance
- Dissolution
- Chemical reactions
- Adsorption of other molecules
- Flow though particle beds
31PowderDensity, air content and porosity
- Density (?b) weight of powder/Volume of powder
- Air content air in pores(entrapped air) and air
in between particles (void air) - Porosity
- In particle
- Between particles
32PowderFlow properties and powder density
- Angle of repose
- Bulk density
- Tapping density
- Carrs index
- Hausner ration
Flow character Angle Carrs index
Very good lt20 5-15
Good 20-30 12-16
Ok 18-21
Poor 30-34 25-35
Very poor 33-38
Extremely poor gt40 gt40