A Potential Soot Mass Determination Method from Resistivity Measurement of Thermophoretically Deposited Soot

Abstract

Miniaturized detection systems for nanometer-sized airborne particles are in demand, for example in applications for onboard diagnostics downstream particulate filters in modern diesel engines. A soot sensor based on resistivity measurements was developed and characterized. This involved generation of soot particles using a quenched co-flow diffusion flame; depositing the particles onto a sensor substrate using thermophoresis and particle detection using a finger electrode structure, patterned on thermally oxidized silicon substrate. The generated soot particles were characterized using techniques including Scanning Mobility Particle Sizer for mobility size distributions, Differential Mobility Analyzer-Aerosol Particle Mass analyzer for the mass-mobility relationship, and Transmission Electron Microscopy for morphology. The generated particles were similar to particles from diesel engines in concentration, mobility size distribution, and mass fractal dimension. The primary particle size, effective density and organic mass fraction were slightly lower than values reported for diesel engines. The response measured with the sensors was largely dependent on particle mass concentration, but increased with increasing soot aggregate mobility size. Detection down to cumulative mass as small as 20-30 µg has been demonstrated. The detection limit can be improved by using a more sensitive resistance meter, modified deposition cell, larger flow rates of soot aerosol and modifying the sensor surface.

Experimental determination of deposition of diesel exhaust particles in the human respiratory tract

“…(3)). This is similar to observations made previously in studies employing diesel exhaust, as well as for flame soot generators (Park et al, 2003;Maricq & Xu, 2004;Olfert et al, 2007;Malik et al, 2011a). The mass-mobility exponents reported by Park et al (2003) for a John Deere engine, at 10-75% load, measured using the DMA-APM technique were 2.33-2.41 with effective densities ranging from 1.20 g/cm 3 for 50 nm particles down to 0.30 for 300 nm particles.…”

“…For agglomerates formed in diffusion limited processes, the relation between m agg and d me has been shown in several previous studies (Park et al, 2003;Maricq & Xu, 2004;Olfert et al, 2007;Pagels et al, 2009;Malik et al, 2011a) The set-up is used for measuring particle effective density of agglomerates and volatile mass fraction on-line. Particles with a single d me are selected with the DMA and thereafter their mass is measured by the APM.…”

Design Considerations and Performance Evaluation of a Compact Aerosol Particle Mass Analyzer

“…The APM has been used, often in combination with a differential mobility analyzer (DMA), for evaluation of various particle properties such as "effective" density (McMurry et al 2002;Geller et al 2006;Malloy et al 2009;Liu et al 2012), morphology through estimation of the mass-mobility exponent (Park et al 2003a; Ku et al 2006;Kim et al 2009;Nakao et al 2011;Scheckman and McMurry 2011;Torvela et al 2011;Eggersdorfer et al 2012;Guha et al 2012;Ku and Evans 2012), the mixing ratio of internally-mixed particles (Sakurai et al 2003;Park et al 2008;Khalizov et al 2009;Ma and Zachariah 2009), material density (Park et al 2004;Kuwata et al 2012), particulate mass concentration (Park et al 2003b;Saito et al 2008), mass (Kuwata et al 2009;Lall et al 2009), volume (Lall et al 2008), and porosity (Lee et al 2011). The APM can also be used as a generator of particles having a specified mass (Malik et al 2011;Moteki et al 2011;Laborde et al 2012;Beranek et al 2012). A variant of the APM called the Couette Particle Mass Analyzer (CPMA) has been developed (Olfert and Collings 2005;Olfert et al 2006), and used for similar purposes (Olfert et al 2007;Cross et al 2010).…”

Thermal Management System for Particle Sensors Design, Performance and Verification

“…A new and innovative way of managing the temperature of a sensor device protruding into hot gas flows was proposed and patented in 2009 [6][7] [8]. The concept consists of a closed thermally conductive pipe, sealed at both ends.…”