Aim
Nanoparticles with specific properties are often synthesized in gas-phase processes. They have the advantage of providing material with high purity and high production rates can be achieved in continuous flow systems. The properties of the produced particles depend largely on the conditions during the synthesis. Non-intrusive laser-optical methods enable the observation of these conditions during the synthesis. Gas-phase temperature and species concentrations are of major interest. This information is used for the development and validation of simulation methods that describe the entire synthesis reaction. For these applications, however,  no established measurement approaches are available so far. The facility at IVG allows the development of diagnostics methods for nearly all operating conditions, which can then be transferred to synthesis plants on a larger scale.

Approach
Laser-Induced fluorescence spectroscopy enables the quantification of both temperature and species concentration from based on electronically excited molecular or atomic species with subsequent collection of fluorescence signals. On one hand techniques for the detection of important species are developed, such as atomic species or small molecules (mostly oxides or fragments of the metal organic precursors). On the other hand, the fluorescence spectra often strongly depend on temperature and thus provide an opportunity for measuring local gas-phase temperatures. For temperature measurements, typically small concentrations of nitric oxide (NO) are added to the fresh gases as a measurement target. Based on light sheet techniques, these quantities can be determined in two or even three spatial dimensions. The measured data support the modeling of the process and helps to validate numerical simulation methods.

References
Kronemayer H., Ifeacho P., Hecht C., Dreier T., Wiggers H., Schulz  C. Appl Phys B 88:373-377 (2007)
Hecht C., Kronemayer H., Dreier T., Wiggers H., Schulz C. Appl Phys B 94:119

Contact
apl. Prof. Dr. habil. Hartmut Wiggers, Hartmut Wiggers, Tel: +49 (0)203-379 8087, IVG