Development and implementation of advanced diagnostics for investigating carbons relevant in combustion, environment and material fields

Combustion technologies have been improved over time and the analysis of even lower pollutants emissions from exhausts requires the development of fast and high-sensitivity advanced diagnostics. At the same time, strategies for developing self-sustained and energetically economic processes for fuel/combustion-derived advanced materials are currently developed, aimed to make these products more economically desirable and of widespread use in everyday life. This PhD Thesis is focused on the testing and application of two advanced diagnostic techniques based on mass spectrometry (Molecular Beam Time of Flight Mass Spectrometry) and on a biosensor (based on a Quartz Crystal Microbalance) aimed to high sensitivity analysis of flame reactor and real engine exhausts, respectively. A comparison with a conventional technique typically employed in environmental analyses (GC-MS) is also provided. Measurements performed on the MB-TOFMS with two different ionization sources highlighted the enhancement in PAH detection performed by using photo-ionization at 266 nm. An innovative method for the “in-situ” calibration of the raw spectra obtained with the MB-TOFMS system in a wider range of masses is also presented, which is desirable for combustion-related studies. The QCM sensor has produced reliable results for Benzo[a]pyrene analysis even though miniaturization of this device is needed and still under design. In the second part of the present PhD work carbon materials generated from rich flames have been characterized and it has been highlighted that, by varying the flame experimental conditions, i.e. the residence time and the fuel/oxidant ratio, materials with different structural properties can be obtained. In particular, higher residence times result in increased structural order, thus making flame systems suitable for the one-pot synthesis of carbon materials. Moreover, these materials could also undergo thermal post-treatment to induce further modifications of their structure. In this view, due to the higher disposability with respect to flame-formed carbons, thermal annealing in mild conditions of a carbonaceous resin has been preliminarily investigated. Two different fractions have been collected from each annealing process at a fixed temperature: an upper fraction, i.e. light volatilized species, and a bottom fraction, i.e. the carbonized solid. These fractions have been deeply characterized by several techniques (UV-Visible absorption, fluorescence, SEC, XRD analysis, SEM, elemental analysis, Raman spectroscopy and TG) and it has been found that by increasing the thermal treatment temperature, an increase of the aromatic moieties occurs in the upper fraction, where the temperature is lower, while, for the bottom fraction, chemical and structural modifications are induced by carbonization, resulting in materials with increased order. On the basis of the present results, it is reasonable to hypothesize that in a next future the post-treatment processes based on the thermal annealing in mild conditions could be combined with a proper flame synthesis for obtaining carbon materials with the desired properties to be useful for energy, catalysis, biological and yet unimagined application fields