Gas-Temperature Imaging in a Microwave-Plasma Nanoparticle-Synthesis Reactor Using Multi-Line NO-LIF Thermometry

Review of Optical Thermometry Techniques for Flows at the Microscale towards Their Applicability to Gas Microflows

Thermometry techniques have been widely developed during the last decades to analyze thermal properties of various fluid flows. Following the increasing interest for microfluidic applications, most of these techniques have been adapted to the microscale and some new experimental approaches have emerged. In the last years, the need for a detailed experimental analysis of gaseous microflows has drastically grown due to a variety of exciting new applications. Unfortunately, thermometry is not yet well developed for analyzing gas flows at the microscale. Thus, the present review aims at analyzing the main currently available thermometry techniques adapted to microflows. Following a rapid presentation and classification of these techniques, the review is focused on optical techniques, which are the most suited for application at microscale. Their presentation is followed by a discussion about their applicability to gas microflows, especially in confined conditions, and the current challenges to be overcome are presented. A special place is dedicated to Raman and molecular tagging thermometry techniques due to their high potential and low intrusiveness.

Laser-induced incandescence for non-soot nanoparticles: recent trends and current challenges

Laser-induced incandescence (LII) is a widely used combustion diagnostic for in situ measurements of soot primary particle sizes and volume fractions in flames, exhaust gases, and the atmosphere. Increasingly, however, it is applied to characterize engineered nanomaterials, driven by the increasing industrial relevance of these materials and the fundamental scientific insights that may be obtained from these measurements. This review describes the state of the art as well as open research challenges and new opportunities that arise from LII measurements on non-soot nanoparticles. An overview of the basic LII model, along with statistical techniques for inferring quantities-of-interest and associated uncertainties is provided, with a review of the application of LII to various classes of materials, including elemental particles, oxide and nitride materials, and non-soot carbonaceous materials, and core-shell particles. The paper concludes with a discussion of combined and complementary diagnostics, and an outlook of future research.

Synthesis of Small Carbon Nanoparticles in a Microwave Plasma Flow Reactor

Unusually small carbon nanoparticles were synthesized in a microwave plasma flow-reactor by pyrolysis of 0.3–1.2% CH4, C2H4, and C2H2 with 0.3–3.6% addition of molecular hydrogen in argon. Final particle sizes were analyzed by in-line particle-mass spectrometry (PMS) and by transmission electron microscopy (TEM). TEM measurements of primary particle sizes were found to be in a good agreement with PMS data. The carbon particles formed in the plasma generated by a 2.45 GHz magnetron with an applied power of 180 W and a total pressure of 13 mbar have diameters of 4–6 nm. The type of hydrocarbon precursor and 0.3–3.6% of hydrogen addition did not noticeably influence the final particle sizes. The formation of such small particles is attributed to the low pressure and the comparably low operation power. This method of small carbon nanoparticles synthesis could be useful for the production of carbon black material, where large surface area is important.