Photocatalytic Conversion of Organic Pollutants in Air: Quantum Yields Using a Silver/Nitrogen/TiO2 Mesoporous Semiconductor under Visible Light

This research studies the photocatalytic conversion of methanol (25–90 µmol/L range) as a volatile organic compound (VOC) surrogate into CO2, using a N/Ag/TiO2 photocatalyst under visible light irradiation in a Photo-CREC Air unit. The N/Ag/TiO2 mesh supported photocatalyst is prepared via the solvothermal method. While the bare-TiO2 is inactive under visible light, the N/Ag/TiO2 2 wt.% loaded stainless-steel woven mesh displays 35% quantum yields, with 80% absorbed photons and 60% methanol conversion in a 110 min irradiation period. Results obtained are assigned to silver surface plasmon resonance, silver and nitrogen species synergistic impacts on band gap, and their influence on particle agglomerate size and semiconductor acidity. The determined quantum yields under visible light in a Photo-CREC Air unit, are the highest reported in the technical literature, that these authors are aware of, with this opening unique opportunity for the use of visible light for the purification of air from VOC contaminants.

Silica-Polypropylene Nanocomposites for Film Capacitors: Structure–Property Studies and the Role of Biaxial Stretching Conditions

Biaxial-stretching-induced morphology development anddielectric properties of hydrophobic fumed silica-BOPPnanocomposite films were investigated. The precursor (cast)film morphology, pre-heating as well as biaxial stretchingtemperature and stretch ratio were found to profoundly affect thesilica-BOPP film bulk morphology, surface texture and theformation of particle/agglomerate-induced cavitation uponbiaxial stretching. Isothermal high-field conductivity andthermally stimulated depolarization current measurementsindicated decreasing high-field/high-temperature conductivityand modification of trap density of states upon incorporation ofnanosilica in comparison to neat BOPP. Large-area DCdielectric strength is, however, sensitive to thermal/mechanicalstresses upon biaxial stretching, hence necessitating carefuloptimization of the nanocomposite formulation and processing.

Effect of engine operating conditions on soot layer permeability and density in diesel particulate filters

Understanding the variation of soot deposit properties in diesel particulate filters is necessary for their real-life modeling and onboard control. In this study, the effect of exhaust mass flow rate and particle agglomerate size on the soot layer permeability and density was investigated experimentally and analyzed using a well-validated model. A bare and a coated diesel particulate filter were loaded at five different engine operating points, specially selected to explore these effects in a heavily used part of the diesel engine map. Particle emissions were characterized in terms of particle agglomerate size distribution and primary particle diameter, while soot layer permeability and density were estimated indirectly by fitting the model to the pressure drop recordings. To this end, an automatic calibration procedure was applied to obtain values in a consistent and repeatable manner. The results showed considerable variation in both permeability and density. Furthermore, some trends could be identified after depicting the particle characterization data and soot layer properties in contour plots. Increased permeability appeared at the engine operating point with high flow rate and large particle agglomerate size. Lower density was obtained at the operating points with large particle agglomerate diameter.