1 Copyright © 2011, Elsevier Inc. All rights Reserved. Size Analysis and Identification of Particles Chapter 4 Roger W. Welker

Copyright © 2011, Elsevier Inc. All rights Reserved. 1

Size Analysis and Identification of Particles

Chapter 4

Roger W. Welker


FIGURE 4.1 Basic components of the light-scattering optical particle counter.


FIGURE 4.2 Detector response when a single particle passes through the sample chamber of a light-scattering OPC.


FIGURE 4.3 Two or more particles in the sample chamber simultaneously result in an error in both particle concentration (smaller than true concentration) and particle size (larger than true particle size).


FIGURE 4.4 Particle concentrations in a cleaning tank, as measured by an optical particle counter. The traces for each size range show a significant increase each time a basket enters the tank for the bottom three traces, forming a saw tooth pattern. Conversely, the smallest size range (0.2–0.3 μm) at the top of the chart shows a decrease: a reverse saw tooth pattern.


FIGURE 4.5 An enlargement of the 0.2–0.3-μm size channel from Fig. 4.4, which more clearlyshows the reversed saw tooth pattern. Instead of a sudden increase in particle count with the entryof each basket, we see a decrease in particle count. This is the result of exceeding the coincidencecount limit for the smallest size channel. The coincident counts are recorded as larger particles,subtracting the counts from the smallest size channel and transferring them to the next larger sizechannel.


FIGURE 4.6 Principle of operation for a single-stage impactor.


FIGURE 4.7 An Andersen single-stage impactor, designed to sample biological aerosols directly onto an agar-coated collector.


FIGURE 4.8 The quartz crystal microbalance impactor.


FIGURE 4.9 The virtual impactor.


FIGURE 4.10 Principal components of the condensation particle counter. A working fluid is condensed on particles too small to be detected and counted by a conventional particle counter. The particles grow to a size that can be detected by an optical particle counter.


FIGURE 4.11 Flow diagram of a differential electrical mobility analyzer.


FIGURE 4.12 A 10-stage diffusion battery. It contains 11 sample ports, one for the inlet and 10 for the separation stages.


FIGURE 4.13 Preflight photograph of the spacecraft materials to be flown in earth orbit to studytheir contamination behavior [14].


FIGURE 4.14 Principle of operation of the extinction-based liquid-borne particle counter.


FIGURE 4.15 A particle surface attracts a tightly bound inner layer of positive ions. This in turnattracts a second layer of more loosely bound negative ions. This forms the electrical double layer.The particle is shown next to a surface of a similar material forming another, similarly polarizeddouble layer. The repulsion of the outer layers prevents the particle from agglomerating onto thesurface.


FIGURE 4.16 A typical low-power light microscope. These microscopes typically feature stereovision, magnifications of up to 40× (80× with a 20× objective), and long working distances. Thelong working distance of 5–8 cm allows samples to be manipulated by hand while still maintainingfocus.


FIGURE 4.17 A dark-field polarized light microscope suitable for analytical light microscopy.


FIGURE 4.18 Combination horizontal and vertical scale eyepiece reticule.


FIGURE 4.19 Patterson globe and circle eyepiece reticule.


FIGURE 4.20 The definitions for sizing particle diameters using a light microscope.


FIGURE 4.21 A typical fluorescence microscope.


FIGURE 4.22 Light path for a typical fluorescence microscope.


FIGURE 4.23 What is happening in a scanning electron microscope? The incident beam ofelectrons will be scattered back toward the detector. The primary scattered electrons will havebrightness contrast to indicate high atomic number materials (brighter) versus low atomic numbermaterials (darker). Secondary scattered electrons do not provide atomic number contrast. Augerelectrons are emitted by atoms very near the surface, typically within 2 nm, and their energies arecharacteristic of the element from which they originate. X-rays have energies, which are characteristicof the element from which they are emitted. X-rays are produced from a volume withinthe sample, generally to a depth of about 1–5 μm.


FIGURE 4.24 What is happening in the atomic force microscope?


FIGURE 4.25 A typical atomic force microscope.


FIGURE 4.26 A typical FTIR microscope. The monochromator cabinet is on the left with anattenuated total reflectance accessory installed in the sample compartment. The IR microscope ison the right showing the clear plastic nitrogen shroud for the sample compartment.


FIGURE 4.27 A typical Raman microscope.

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1 Copyright © 2011, Elsevier Inc. All rights Reserved. Size Analysis and Identification of Particles Chapter 4 Roger W. Welker