Particle Characterization
What Is a Particle?
At the most basic level, we can define a particle as being a discrete sub-portion of a substance. For the purposes of this guide, we shall narrow the definition to include solid particles, liquid droplets or gas bubbles with physical dimensions ranging from sub-nanometer to several millimeters in size. The most common types of materials consisting of particles are:
- powders and granules, e.g. pigments, cement, pharmaceutical ingredients
- suspensions, emulsions and slurries, e.g. vaccines, milk, mining muds
- aerosols and sprays, e.g. asthma inhalers, crop protection sprays
There are two main reasons why many industries routinely employ particle characterization techniques:
Better Control of Product Quality
- ability to charge a higher premium for your product
- reduce customer rejection rates and lost orders
- demonstrate compliance in regulated markets
Better Understanding of Products, Ingredients and Processes
- improve product performance
- troubleshoot manufacturing and supply issues
- optimize the efficiency of manufacturing processes
- increase output or improve yield
- stay ahead of the competition
In addition to chemical composition, the behavior of particulate materials is often dominated by the physical properties of the constituent particles. These can influence a wide range of material properties including, for example, reaction and dissolution rates, how easily ingredients flow and mix, or compressibility and abrasivity. From a manufacturing and development perspective, some of the most important physical properties to measure are:
Particle size l Particle shape l Surface properties
Mechanical properties l Charge properties l Microstructure
Depending upon the material of interest, some or all of these could be important and they may even be interrelated: e.g. surface area and particle size. For the purposes of this guide, we will concentrate on two of the most significant and easily measured properties: particle size and particle shape.
There is a wide range of particle characterization techniques that can be used to measure particulate samples. Each has its relative strengths and limitations and there is no universally applicable technique for all samples and all situations.
Many particle characterization techniques require the sample to be analyzed in a dispersed form where the individual particles are spatially separated. In order to do this there are two basic approaches:
- wet dispersion – particles dispersed in a liquid
- dry dispersion – particles dispersed in a gas (usually air)
Key Analysis
Particle Size
By far the most important physical property of particulate samples is particle size. Analysis of particle size distributions from sub-nanometer to millimeters.
Particle Shape
This microscope allows for detailed work such as microsurgery, watch making and circuit board inspection and manufacturing
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