F A Q's on Particle Size Analyzing
- What is particle?
Particle is minute object with certain size and shape as well as basic elements making up powder. It is very small macroscopically, but microscopically contains numerous molecules and atoms.
- What is particle size?
Just as its name implies, size of the particle is particle size.
- What is particle size distribution?
The percent, particles with different diameter exist in total powder, is particle size distribution. It is represented in certain ways.
- How to express particle size distribution?
1)Table: Percents corresponding to some diameters of particles are given in table to represent particle size distribution; it includes differential distribution and cumulative distribution.
2)Figure: Represent particle distribution by histogram and curves, etc.
3)Function: Represent particle distribution functionally including R-R distribution and normal distribution.
- What is particle diameter?
It is the diameter of particle, normally expressed by micrometer.
- What is equivalent particle diameter?
When certain physical characteristic of a particle is the same as or approximately the same as a spherical particle of the same constitution, we represent diameter of this particle with diameter of the sphere. Equivalent diameter can be divided into following kinds in different ways of measurement:
1)Equivalent volumetric diameter: Diameter of spherical particle having the same constitution and volume as the particle to be tested. Particle diameter obtained by laser methods is generally recognized as equivalent volumetric diameter.
2)Equivalent sedimentation speed diameter: Diameter of spherical particle having the same constitution and sedimentation speed as the particles to be tested. Diameter obtained by gravity sedimentation or centrifugal sedimentation belongs under this, also known as Stokes diameter.
3)Equivalent resistance diameter: Diameter of spherical particle having the same constitution and resistance as the particle to be tested. Diameter obtained by Coulter methods belongs under this.
4)Equivalent projection area diameter: Diameter of spherical particle having the same constitution and projection area as the particle to be tested. Diameter obtained by image analysis belongs under this.
- Why introduce equivalent particle diameter?
Particles actually exist in the shape of non-sphere; it’s hard to describe how big it is by particle diameter alone. Furthermore, diameter is the simplest parameter describing size of a geometric object, so concept of equivalent particle diameter is introduced.
- What is D50?
Also known as Median diameter or Medium value of particle diameter, it is particle diameter value in case cumulative distribution percentage reaches 50%. It is one of the important parameters representing characteristics of particle of powder. For a sample, if D50=5μm, there are 50% particles larger than 5μm, 50% smaller than 5μm.
- What is average diameter?
It is used to represent averaged particle size of powder by weighted average on particle size distribution. It includes averaged weight diameter, volumetric diameter, area diameter and number diameter etc.
- What is D97?
What is the purpose of it?It is value of particle diameter when percentage of cumulative distribution reaching 97%. Normally it is used to represent larger particles, an important particle size index in production and application of powder.
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