Basic Research on Elemental and Size Analytical System for Nano-Sized Suspended Particulate Matter Using Contactless Optical Measurement Techniques

Basic Research on Elemental and Size Analytical System for Nano-Sized Suspended Particulate Matter Using Contactless Optical Measurement Techniques

S. Ikezawa, T. Ueda
Copyright: © 2013 |Pages: 12
DOI: 10.4018/ijmtie.2013010102
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Abstract

A contactless sensing system for nano-sized carbonaceous particulate matter using laser-induced incandescence (LII) and laser-induced breakdown spectroscopy (LIBS) is presented. The LIBS technique allows detecting elemental composition and density of the SPMs, and LII technique allows to measure particulate size. LII technique is temporal resolved method that enables measurement of soot particulate sizes in a combustion process. In the case of the measured material consisting of a carbonaceous element, it is easy to determine the particulate diameter distribution derived from the time-profile of emission attenuation signals during cooling process, because the cooling behaviour is characteristic of the particulate diameter in LII technique. However, in actuality, the SPMs consist of several different types of elements. By using LIBS technique, the elemental analysis is able to conduct easily.
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2. Experimental Setup

Figure 1 shows a schematic of the combined system that consists of LII and LIBS. The optical layout of the system consists of the following devices: a Nd:YAG laser, a spectrograph, a streak camera, and a delay pulse generator. The Nd:YAG laser was operated at 1064 nm to generate a 50 mJ Q-switched pulse with a width of 8 ns (full width at half maximum, FWHM). The emissions from the particulate target were guided into the spectrograph and dispersed by a grating with a groove density of 1200 lines/mm, photoemissive electrons were temporally resolved using a streak camera, and the data were stored in and processed by a computer. The LII technique is based on the analysis of the cooling behaviour of the particulates after irradiation by the laser pulse. By using the Stefan-Boltzmann law for a black body, the LII signal gives the profile of the intensity decay time depending on the particulate size.

Figure 1.

Schematic of the LII and LIBS combined system

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