Nanometer Particles: Modern Methods of Research

Speaker(s): 
Date: 
August 10, 1999 - 12:00pm
Location: 
Bldg. 90
Seminar Host/Point of Contact: 

"Nanometer particles" (with diameter below 50 - 100 nm) have attracted attention during recent years because of their increasing role in industries such as powder technology and semiconductors. They also play a critical role in atmospheric processes. At this size range the properties of particles are different from those of bulk materials and single molecules. This promises new technological innovations and potential scientific discoveries. At the same time it makes the detection and characterization of such particles imperative.  Optical methods, which allow for simultaneous measurement of size and concentration of particles in the micron size range, can not be applied for research of nanometer aerosol particles. Because of this the main approach is two step characterization: First, size classification-using diffusion of particles or mobility in electric field. Second, the detection of classified particles. Condensation Nuclei Counters (CNC) are widely used for the detection of nanometer particles in combination with different size classification methods. In CNC's the initial size of particles is increased significantly to allow the use of simple optical counters to measure the number concentration of initial particles. The results of development and evaluation of Turbulent Mixing CNC will be presented. The potential applications of this method resulting from combination of the extreme size sensitivity (d< 3 nm), the high flow rate and the possibility of controlling the sensitivity will be discussed.

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