Simple gravimetric (e.g. weighing) methods have long been used to assess the total mass of particulate material, and flow-counter instruments are widely used to obtain distributions of particles by number and average size.
But for truly accurate assessment of unknown or variable particle populations, only direct particle-by-particle imaging provides sufficiently detailed knowledge for meaningful characterization.
Direct Particle Imaging
Fortunately, such microscopic examination can today be conducted by automated microscopes from easily prepared filter samples. However, light-based (optical) microscopes are severely limited in their ability to characterize particle populations accurately. Fortunately, there is a superior alternative available; electron-beam imaging provides demonstrable advantages in the critical areas of:
• Contrast mechanisms
• Depth of focus
• Dynamic control
• Elemental composition
Superiority of Electron Beam Imaging
The first four factors alone have repeatedly proved to establish the superiority of electron-beam imaging for accurate and reliable quantification of the sizes and shapes of both fine and coarse particles. And, surprisingly to many, a well-engineered electron-beam tool is comparable in cost and ease of use with a similarly automated light-based system. But, for many applications, it is the unique capability of electron-beam technology to unambiguously characterize inorganic particles by their elemental composition that provides the definitive advantage over all other methods.
There are many useful techniques available for inferring selected parameters of particle distributions, but when reliable characterization of particle populations by either morphology or composition is essential, electron-beam imaging is the clear choice.