Functional nanoparticles by controlled production and coating in aerosol processes
Final Report Abstract
The results obtained during the funding period comprise the following topics: 1. Theoretical considerations of future control requirements during the synthesis of tailor made nanocomposites which comprises process and reactor design. 2. An extensive literature review and new model calculations of nanoparticle transport mechanisms with special emphasis on their aggregates formed in aerosol processing were conducted. 3. For the experimental studies at UCLA the Flame Spray Pyrolysis (FSP) (aerosol process) was selected and successfully established at UCLA based on the following considerations: this method is directly related to dominant industrial processes and commodities; material characteristics that are reproducible; ability to collect the nanoparticles as a dry powder and in a new process designed at UCLA in any non-viscose liquid directly from the aerosol phase; design of crystalline materials in which the external surface area plays a dominant role without microporosity; primary particle and crystallite size control; control of hard agglomerate size; doping with transition metals. While other aerosol processes such as laser ablation are capable of delivering some of the characteristics they have been proven insufficient during the study in delivering sufficient production rates which are required to evaluate the coating process and to provide sufficient material quantities for the undertaken toxicological studies. I have worked with the laser ablation process for diagnostic studies of nanoparticles. 4. The main results of the conducted research regarding the novel insights of nanotoxicology are planned to be published within the next 6 month. 5. The established FSP process at UCLA was also used to manufacture and directly (in situ) deposit tin dioxide nanoparticles on sensor substrates. For the first time a combination of two porous layers for gas-sensor fabrication were achieved directly from the gas phase. Two different sensing layers were deposited on ceramic substrates, i.e., pure tin dioxide and palladium-doped tin dioxide. The top layer was a palladium-doped alumina as a filter. The fabricated sensors were tested with methane, CO, and ethanol. In the case of CH4, the pure tin dioxide sensor with the Pd/Al2O3 filter showed higher sensor signals and improved selectivity with respect to water vapor compared to single tin dioxide films. At temperatures up to 250 °C the Pd doping of the tin dioxide strongly increased the sensitivity to all gases. At higher temperatures the sensor signal significantly decreased for the Pd/SnO2 sensor with a Pd/Al2O3 filter, indicating high catalytic activity. Electrical conductivity and percolation behavior of such porous films composed of nanoparticle aggregates prepared by an aerosol deposition technique was theoretical evaluated with respect to aggregate structure and film packing density. 6. Further collaborative work on nanoparticle aerosol technology during the DFG funding period has been undertaken with the University of New South Wales, Australia and the ETH Zürich, Switzerland.
Publications
- Aerosol and Air Quality Research, 7(3) 304-342 (2007)
Mädler, L., Friedlander, S.K.
- Composites Part A: Applied Science and Manufacturing, in 38(12), 2451-2459 (2007)
Schulz, H., Burtscher, H., Mädler, L.
- J. Catal., 251(2) 271–280 (2007)
Teoh, W.Y., Mädler, L., Amal, R.
- J. Mater. Res., 22(4) 850-857 (2007)
Sahm, T., Rong, W., Barsan, N., Mädler, L., Friedlander, S.K., Weimar, U.
- Powder Technology 175 (1) 1-7 (2007)
Christofides, P.D., Li, M. and Mädler, L.
- Sens. Actuator B-Chem., 127(1), 63-68 (2007)
Sahm, T., Rong, W., Barsan, N., Mädler, L., Weimar, U.
