Imran Saleem Flashcards
Particle size influences?
Powder flow Powder mixing Solubility and stability Dissolution Aerosol deposition
Where do inhaled particles deposit?
Bigger than 5microns - mouth and trachea
1-5microns - sediment in the bronchi and bronchioles
Less than 1micron - diffuse into alveoli
What is convection when referring to powder mixing?
Transfer of large groups of powder from one part of the mixer to another
What is shear when referring to powder mixing?
Layer of material move or flow over one another
What is diffusive mixing when referring to powder mixing?
Particles fall under gravity through voids created
When does powder segregation or demixing take place?
When the particles are different size, shape or density
What is percolation segregation?
When smaller particles fall through voids between larger particles
What is trajectory segregation?
When larger particles have a greater kinetic energy and travel greater distances than smaller particles
How would you overcome segregation?
Sieving
Milling of components - size reduction
Produce an ordered mix
How do you decrease the size of a particle?
Ball milling - rotate particles around in a ball and will take parts off each other and get smaller
Fluid energy milling
What particle size is required when ball milling?
1-500 micrometers
What particle size is required when using the fluid energy mill?
1-50,000 micrometers
In what sort of way does particle size affect dissolution?
Small particles dissolve more rapidly than larger particles
What mechanism is used to evaluate the degree of mixing?
HPLC - high performance liquid chromatography
How high must the funnel be held when measuring the angle of repose?
10cm
How can you measure powder flow?
Measure the angle of repose
What technique can you use to work out the particle distribution?
Sieving
At what particle size is sieving viable?
45-1000 micrometers
What is the sieving equivalent diameter?
The size of a sphere that will just pass through the mesh of a particular sieve
When should you use the sieving method?
Materials analysed have good flowability
Range of different densities present
Material is robust
Material must me dry
When should using a sieve not be used?
When dealing with fine powders
Particles are fragile
The powder easily acquires an electrical charge
When material easily adheres to the sieve
List the features of a SEM?
3D image
Able to capture images
Can measure to nm range
Great depth of field
List the features of a TEM?
2D images
Able to capture images
Can measure to nm range
What are the range for the SEM, TEM and light microscope?
SEM - 0.05-1000 micrometers
TEM - 0.001-0.05 micrometers
Light microscope - 1-1000 micrometers
What is the range a coulter counter?
0.1-1000 micrometers
