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

2 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.1 Basic components of the light-scattering optical particle counter.

3 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.2 Detector response when a single particle passes through the sample chamber of a light-scattering OPC.

4 Copyright © 2011, Elsevier Inc. All rights Reserved. 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).

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

6 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.5 An enlargement of the 0.2–0.3-μm size channel from Fig. 4.4, which more clearly shows the reversed saw tooth pattern. Instead of a sudden increase in particle count with the entry of each basket, we see a decrease in particle count. This is the result of exceeding the coincidence count 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 size channel.

7 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.6 Principle of operation for a single-stage impactor.

8 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.7 An Andersen single-stage impactor, designed to sample biological aerosols directly onto an agar-coated collector.

9 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.8 The quartz crystal microbalance impactor.

10 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.9 The virtual impactor.

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

12 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.11 Flow diagram of a differential electrical mobility analyzer.

13 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.12 A 10-stage diffusion battery. It contains 11 sample ports, one for the inlet and 10 for the separation stages.

14 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.13 Preflight photograph of the spacecraft materials to be flown in earth orbit to study their contamination behavior [14].

15 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.14 Principle of operation of the extinction-based liquid-borne particle counter.

16 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.15 A particle surface attracts a tightly bound inner layer of positive ions. This in turn attracts 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 polarized double layer. The repulsion of the outer layers prevents the particle from agglomerating onto the surface.

17 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.16 A typical low-power light microscope. These microscopes typically feature stereo vision, magnifications of up to 40× (80× with a 20× objective), and long working distances. The long working distance of 5–8 cm allows samples to be manipulated by hand while still maintaining focus.

18 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.17 A dark-field polarized light microscope suitable for analytical light microscopy.

19 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.18 Combination horizontal and vertical scale eyepiece reticule.

20 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.19 Patterson globe and circle eyepiece reticule.

21 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.20 The definitions for sizing particle diameters using a light microscope.

22 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.21 A typical fluorescence microscope.

23 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.22 Light path for a typical fluorescence microscope.

24 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.23 What is happening in a scanning electron microscope? The incident beam of electrons will be scattered back toward the detector. The primary scattered electrons will have brightness contrast to indicate high atomic number materials (brighter) versus low atomic number materials (darker). Secondary scattered electrons do not provide atomic number contrast. Auger electrons are emitted by atoms very near the surface, typically within 2 nm, and their energies are characteristic of the element from which they originate. X-rays have energies, which are characteristic of the element from which they are emitted. X-rays are produced from a volume within the sample, generally to a depth of about 1–5 μm.

25 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.24 What is happening in the atomic force microscope?

26 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.25 A typical atomic force microscope.

27 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.26 A typical FTIR microscope. The monochromator cabinet is on the left with an attenuated total reflectance accessory installed in the sample compartment. The IR microscope is on the right showing the clear plastic nitrogen shroud for the sample compartment.

28 Copyright © 2011, Elsevier Inc. All rights Reserved. FIGURE 4.27 A typical Raman microscope.