These researchers are developing a quadrupole mass spectrometer system to measure the composition of freshly nucleated nanoparticles in the atmosphere. Sampling a sufficient number of particles to ensure adequate signal-to-noise is a challenge with this work. The electrodynamic focusing device would enable preconcentration of particles before they enter the instrument, thereby enhancing signals.
Ying Dong, Graduate Student Researcher
Taesung Kim, Graduate Student Researcher
David B. Kittelson, Faculty Collaborator
Sandeep Nijhawan, Graduate Student Researcher
Seok Joo Park, Research Associate
Hiromu Sakurai, Research Associate
99/19 |
"The Effect of Substrate Temperature on the Properties of Nanostructured Silicon Carbide Films Deposited by Hypersonic Plasma Particle Deposition," J. Blum, N. Tymiak, A. Neuman, Z. Wong, N.P. Rao, S.L. Girshick, W.W. Gerberich, P.H. McMurry, and J. Heberlein, University of Minnesota Supercomputing Institute Research Report UMSI 99/19, February 1999. Publication in press. |
99/23 |
"Thermal Plasma Deposition of Nanostructured Films," A. Neuman, J. Blum, N. Tymiak, Z. Wong, N.P. Rao, W.W. Gerberich, P.H. McMurry, J. Heberlein, and S.L. Girshick, IEEE Transactions on Plasma Science, 27, p. 46 (1999). |
99/246 |
"Hypersonic Plasma Particle Deposition of Nanostructured Silicon Carbide Films," N. Tymiak, D.I. Iordanoglou, D. Neumann, A. Gidwani, F. Di Fonzo, M.H. Fan, N.P. Rao, W.W. Gerberich, P.H. McMurry, J. Heberlein, and S.L. Girshick, Proceedings of the 14th International Syumposium on Plasma Chemistry, 4, p. 1989 (1999). |
In this mass spectrometer system, nanoparticles are sampled at one atm and transported into a vacuum through a small orifice (nozzle). The large pressure drop across the orifice causes supersonic expansion, and the physical and chemical characteristics of the particles might be altered while they travel across the expansion. In addition, trajectories of the particles in the vacuum are determined by the interaction between the particles and the supersonic flow, which eventually affects the particle collection efficiency of the mass spectrometer. Therefore, knowledge about the behavior of nanoparticles in supersonic expansion is crucial in developing the new mass spectrometer system.
It is known that the nanoparticles are focused easily below 10-3 atm from the analytic computation. The pressure is changed from one atm to a low pressure in nozzle expansion flow so computation of the behavior of nanoparticles under the coupled condition of electrodynamic focusing field and nozzle expansion flow is necessary.
Numerical simulations of particle trajectories are being carried out (i) in an electrodynamic focusing device, (ii) in a supersonically expanding flow, and (iii) in the coupled condition of the electrodynamic focusing field and the supersonically expanding flow. Particle transport in an electrodynamic focusing device requires an unsteady, three-dimensional analysis. At first, the unsteady electric field and the gas flow field are computed for a given geometry. Using these electric and flow fields, particle trajectories are calculated. Simulations of nanoparticles in supersonic expansion requires computation of a compressible fluid, and these researchers are numerically studying various types of nozzles to find an appropriate one for their instrument. Particle behavior is then calculated in the electrodynamic focusing and supersonically expanding flow field.
|
|
URL: http://www.msi.umn.edu/about/publications/annualreport/ar2000/depts/IT/MechEng/mcmurry.html |
|
| This page last modified on Friday, 30-May-2008 16:14:05 CDT | ||
| Please direct questions or problems to help@msi.umn.edu | ||
|
Website related questions or problems should be directed to
webmaster@msi.umn.edu
The Supercomputing Institute does not collect personal information on visitors to our website. For the University of Minnesota policy, see www.privacy.umn.edu. © 2001 by the Regents of the University of Minnesota |
||