Final Report: Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle Formation

EPA Grant Number: R826654
Title: Development of a Novel Condensation Nuclei Counter and Application to Ultrafine Particle Formation
Investigators: Hopke, Philip K. , Lee, Doh-Won , Mavliev, Rashid , Smoridin, Vladimir , Wang, Hwa-Chi
Institution: Clarkson College , Illinois Institute of Technology
EPA Project Officer: Shapiro, Paul
Project Period: October 1, 1998 through September 30, 2001
Project Amount: $393,657
RFA: Exploratory Research - Environmental Chemistry (1998) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Sustainability , Land and Waste Management , Air , Engineering and Environmental Chemistry

Objective:

The main objectives of this research project were to: (1) develop a novel condensation nuclei counter (CNC) that scans over a range of supersaturation via turbulent mixing and using different working fluids for investigating the vapor-to-particle conversion; and (2) investigate the factors affecting heterogeneous nucleation for different particle types and working fluids. Of particular interest are the chemical interactions of working fluid molecules with ions and nanometer size nuclei.

Summary/Accomplishments (Outputs/Outcomes):

A new turbulent mixing condensation nuclei counter (TMCNC) has been developed that provides flexibility in adjusting the degree of supersaturation in the system. The system has been characterized to permit identification of the onset of homogeneous nucleation, determine the efficiency of the system as a function of particle size and vapor concentration, and determine if there is an effect of nuclei composition on the lower size detection limit for the system.

Initial experiments were conducted using the original turbulent mixing CNC system (Mavliev, et al., 2000; Mavliev, et al., 2001). Supersaturation was controlled by means of changing the dibutylphthalate (DBP) vapor pressure in nozzle flow by saturating only a predetermined part of the flow while the total flow and temperature remain constant. This approach allows changing the initial DBP vapor pressure while keeping the flow structure and temperature field unchanged. The DBP concentration in the outlet of the vapor generator was measured experimentally for different ratios of saturated and bypass flows and found to be close to estimated values. Experimental results for transitions from heterogeneous nucleation to homogeneous nucleation are presented for NaCl and WOx particles at various DBP vapor pressures. With the increase in DBP vapor pressure, the concentration of enlarged particles increases until it reaches a plateau. At higher initial values of DBP pressure, homogeneous nucleation prevails and the number concentration of particles follows a curve typical for homogeneous nucleation recorded in the absence of nuclei. Nuclei with different mobility diameters were activated at different values of vapor pressure. There are significant differences in the slopes of particle activation curves for NaCl and WOx particles. The reasons for such differences are a subject for the continuing research of this project and studies continue at this time. This work largely completes the work on the nucleation of DBP on various substrates.

A new and improved turbulent mixing CNC has been designed, constructed, and studied. We conducted side-by-side tests of two identical units to ensure that the parallel measurements taken at the Illinois Institute of Technology (IIT) and Clarkson would be comparable. We took a series of measurements of nucleation of additional vapor compounds on a series of different composition nuclei at both schools. Nucleation for all of the vapors have been measured for NaCl, silver, and carbon particles. These results have prompted some limited additional studies on related solid substrates such as KCl and AgCl.

We have experimentally measured the contact angle for most of the combinations of the vapor compounds on the various substrates. These data were then used in interpreting the results of the nucleation measurements.

Table 1. Heterogeneous Nucleation of Working Fluids' Vapor on NaC1, Ag, KC1, and AgC1.

Vapor Substance Nuclei Substance
Dibutylphthalate NaCl
Octadecane Ag
Octadecanol C
Octadecanoic Acid KCl and AgCl


At IIT, heterogeneous nucleation of working fluids' vapor on NaCl, Ag, KCl, and AgCl was examined. Three different patterns of nucleation and growth were observed. In the case of octadecanoic acid, all of the nuclei were activated and could then grow as they accumulated vapor. The activation of these nuclei did not appear to be dependent on the composition of the nucleus. For octadecane, octadecanol, and DBP, a bimodal pattern was observed for all of the nuclei except in the case of octadecanol on NaCl. In this case, some nuclei activate and grow while the remaining particles keep their initial size distribution. In the case of octadecanol with NaCl, a second mode only slightly larger than the initial size distribution forms in the presence of even small amounts of vapor. When the partial pressure of octadecanol reaches a sufficiently high value, some of the nuclei activate into a grown mode. It appears that nucleation occurs on both of the smaller modes in equal proportion as the relative intensity of the two smaller modes remains unchanged as the vapor concentration is increased. To more fully interpret these results, a theoretical model was developed.

At Clarkson, experimental heterogeneous nucleation of the working fluids' vapor on carbon particles was measured. Experimental nucleation rates from these results were calculated and then compared to the estimated nucleation rates based on Fletcher's heterogeneous nucleation theory. This theory parallels the experiments with octadecanol and octadecanoic acid at high supersaturation ratio for DBP. However, the theory shows discrepancy with the observed phenomena at low supersaturation for dibutyl phthalate, especially for octadecane. Hydrophilicity of functional groups of working fluids was considered as an important factor. Several other possible hypotheses related to physicochemical properties of carbon particles and working fluids' vapor for the discrepancies in heterogeneous nucleation and observed particle growth also have been discussed in a paper submitted for publication by Dr. Lee. Further study of all of the observed phenomena and a more careful theoretical evaluation are required to understand the observations more accurately. However, the project has permitted the development of an improved condensation nuclei counter. It can activate particles smaller than 2 nm and can scan the supersaturation so that it provides a useful tool for studying heterogeneous nucleation. There has been sufficient interest in this system that it is currently being developed into a potential commercial product with the assistance of the New York State Energy Research and Development Authority, New York State Office of Science, Technology and Academic Research, and Rupprecht and Patashnick, Inc.

References:

Mavliev R, Wang HC. Design and performance characteristics of a turbulent mixing condensation nuclei counter. Journal of Aerosol Science 2000;31:933-944.

Mavliev R, Wang HC, Hopke PK, Lee DW. A transition from heterogeneous to homogeneous nucleation in the turbulent mixing CNC. Aerosol Science Technology 2001;35:586-595.


Journal Articles on this Report : 8 Displayed | Download in RIS Format

Other project views: All 20 publications 8 publications in selected types All 8 journal articles
Type Citation Project Document Sources
Journal Article Anisimov MP, Hopke PK, Terry J, Rasmussen DH, Shandakov SD, Pinaev VA. Surface topology of the ion-induced vapor nucleation rate. Aerosol Science and Technology 1998;29(6):547-556. R826654 (Final)
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  • Journal Article Anisimov MP, Hopke PK, Shandakov SD, Shvets II. n-Pentanol-helium homogeneous nucleation rates. The Journal of Chemical Physics 2000;113(5):1971-1975. R826654 (Final)
  • Abstract: AIP-Abstract
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  • Journal Article Lee D-W, Hopke PK, Rasumussen DH, Wang H-C, Mavliev R. Comparison of experimental and theoretical heterogeneous nucleation on ultrafine carbon particles. Physical Chemistry B 2003;107(50):13813-13822. R826654 (Final)
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  • Journal Article Mavliev R, Wang H-C. Design and performance characteristics of a turbulent mixing condensation nuclei counter. Journal of Aerosol Science 2000;31(8):933-944. R826654 (2000)
    R826654 (Final)
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  • Journal Article Mavliev R, Hopke PK, Wang H-C, Lee D-W. A transition from heterogeneous to homogeneous nucleation in the turbulent mixing CNC. Aerosol Science and Technology 2001,35(1):586-595. R826654 (1999)
    R826654 (2000)
    R826654 (Final)
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  • Journal Article Mavliev R, Hopke PK, Wang H-C, Lee D-W. Experimental studies of heterogeneous nucleation in the turbulent mixing condensation nuclei counter. The Journal of Physical Chemistry B 2004;108(14):4558-4564. R826654 (Final)
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  • Journal Article Smorodin VY, Hopke PK. Condensation activation and nucleation on heterogeneous aerosol nanoparticles. The Journal of Physical Chemistry B 2004;108(26):9147-9157. R826654 (Final)
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  • Journal Article Smorodin VY, Hopke PK. Relationship of heterogeneous nucleation and condensational growth on aerosol nanoparticles. Atmospheric Research 2006;82(3-4):591-604. R826654 (Final)
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  • Supplemental Keywords:

    particulate matter, condensation nuclei counter, heterogeneous nucleation, ultrafine particles, continuous monitoring, detection efficiency, homogenous nucleation, iron-induced nucleation, condensation nucleus counter, measurement methods, ambient air, indoor air, ultrafine particulate matter., RFA, Scientific Discipline, Air, particulate matter, Ecology, Environmental Chemistry, tropospheric ozone, Engineering, Chemistry, & Physics, ambient aerosol, homogenous nucleation, particulates, aerosol particles, particle chamber, cloud condensation, trace gases, ozone depletion, ambient air, ozone, chemical composition, cloud chamber, radiation balance, human exposure, ultrafine particulate matter, condensation nuclei counter, reactive gases, ultrafine particles

    Relevant Websites:

    http://www.clarkson.edu/chemistry/faculty/ph.html Exit

    Progress and Final Reports:

    Original Abstract
  • 1999 Progress Report
  • 2000 Progress Report