Search results for "ozone"
showing 10 items of 300 documents
Abatement of 3-methylbutanal and trimethylamine with combined plasma and photocatalysis in a continuous planar reactor
2014
International audience; This paper deals with the 3-methylbutanal ((CH3)2CHCH2COH) removal with the help of a nonthermal surface plasma discharge coupled with photocatalysis. The capability of this process for gas treatment was studied. A planar reactor system was developed in order to perform the effect of adding photocatalytic material in plasma surface discharge barrier dielectric (SDBD) zone on (i) 3-methylbutanal removal, (ii) selectivity of CO2 and CO, (iii) byproducts formation such ozone formation. It was found that the influence of the UV light generated by SDBD reactor was very low. The activation of the photocatalyst media could be negligible. Whereas, the introduction of externa…
Oxidative degradation properties of Co-based catalysts in the presence of ozone
2007
Four series of cobalt-based catalysts, such as bare Co3O4 and CoO, CoOx-CeO2 mixed oxides, CoOx supported over alumina and alumina-baria and CoMgAl and CoNiAl hydrotalcites have been synthesized and investigated for the oxidative degradation of phenol in the presence of ozone. Characterizations were obtained by several techniques in order to investigate the nature of cobalt species and their morphological properties, depending on the system. Analyses by XRD, BET, TPR, UV-visible diffuse reflectance spectroscopy and TG/DT were performed. The CoNiAl hydrotalcite exhibits, after 4 h of reaction, the highest phenol ozonation activity followed by Co(3 wt%)/Al2O3-BaO and CoMgAl. The samples Co(1 …
Low temperature atomic layer deposition of noble metals using ozone and molecular hydrogen as reactants
2013
Abstract Atomic layer deposition (ALD) of noble metals by thermal processes has relied mostly on the use of molecular oxygen as a reactant at temperatures of 200 °C and above. In this study, the concept of using consecutive ozone and molecular hydrogen pulses with noble metal precursors in ALD is introduced for palladium, rhodium, and platinum metals. This approach facilitates the growth of noble metal thin films below 200 °C. Also the ALD of palladium oxide thin films is demonstrated by the ozone-based chemistry. The growth rates, resistivities, crystallinities, surface roughnesses, impurity contents, and adhesion of the films to the underlying Al 2 O 3 starting surface are reported and th…
Preparation methods to optimize the performance of sensor discs for fast chemiluminescence ozone analyzers.
2013
Fast ozone (O(3)) measurements (1-50 Hz) in the atmosphere are required for airborne studies and for the measurement of ground-based O(3) fluxes by the eddy covariance technique. Fast response analyzers, based on heterogeneous chemiluminescence, need dye coated sensor discs on which the chemiluminescence is generated. In this study, we present three new preparation methods for those sensor discs. Currently available sensor discs exhibit a fast temporal decay of sensitivity, resulting in short duty times which is troublesome for many field applications. To produce sensor discs that provide more stable signals over time, three dyes and nine energy transfer reagents were tested (as well as dif…
Control of Oxygen Nonstoichiometry and Magnetic Property of MnCo2O4 Thin Films Grown by Atomic Layer Deposition
2010
Spinel-structured (Mn,Co)3O4 thin films were reproducibly fabricated by atomic layer deposition (ALD) using Mn(thd)3, Co(thd)2, and ozone as precursors. A full control of the cation ratio was achieved in the temperature interval 140−160 °C within which also the growth rate remained constant. Precise control of the oxygen content of as-deposited MnCo2O4+δ films was achieved through postdeposition heat treatments at prefixed temperatures in air and N2 atmospheres, as evidenced from the monotonous increases of both the unit cell volume and the Curie temperature (TC) with increasing annealing temperature/decreasing oxygen partial pressure. The TC value varied from 92 K for the as-deposited MnCo…
Ozone-Based Atomic Layer Deposition of Al2O3 from Dimethylaluminum Chloride and Its Impact on Silicon Surface Passivation
2017
Dimethylaluminum chloride (DMACl) as an aluminum source has shown promising potential to replace more expensive and commonly used trimethylaluminum in the semiconductor industry for atomic layer deposited (ALD) thin films. Here, the Al2O3 DMACl-process is modified by replacing the common ALD oxidant, water, by ozone that offers several benefits including shorter purge time, layer-by-layer growth, and improved film adhesion. It is shown that the introduction of the ozone instead of water increases carbon and chlorine content in the Al2O3, while long ozone pulses increase the amount of interfacial hydrogen at silicon surface. These are found to be beneficial effects regarding the surface pass…
Selectivity improvement of semi-conducting gas sensors by selective filter for atmospheric pollutants detection
2006
International audience; The monitoring of atmospheric pollution using chemical gas sensors is a challenge due to the lack of selectivity of most existing devices. However, their performances can be improved using filtering films achieving the separation or the removal of some gases. This study is focused on the detection of carbon monoxide and of oxidant pollutants (nitrogen dioxide and ozone) by sensors constituted of SnO2, or phthalocyanine compounds. Two types of filters were investigated. Filters based on MnO2 powder are successful to remove ozone while preserving nitrogen dioxide in a large temperature range from ambient to 400 -C, but they partially convert carbon monoxide. The second…
Effect of ozone concentration on silicon surface passivation by atomic layer deposited Al2O3
2015
Abstract We study the impact of ozone-based Al2O3 Atomic Layer Deposition (ALD) on the surface passivation quality of crystalline silicon. We show that the passivation quality strongly depends on the ozone concentration: the higher ozone concentration results in lower interface defect density and thereby improved passivation. In contrast to previous studies, our results reveal that too high interface hydrogen content can be detrimental to the passivation. The interface hydrogen concentration can be optimized by the ozone-based process; however, the use of pure ozone increases the harmful carbon concentration in the film. Here we demonstrate that low carbon and optimal hydrogen concentration…
The potential of cirrus clouds for heterogeneous chlorine activation
1996
The ER-2 data from ascents and descents through layers of cirrus clouds are utilized to study the heterogeneous reactions of ClONO 2 with H 2 O, of HOCl and ClONO 2 with HCl, and their potential role for the activation of chlorine in the tropopause regions which could affect ozone there. Lacking measured data for the three chlorine containing molecules their abundances as a function of altitude have been calculated from a 2D model. The aerosol surface data measured by a Forward Scattering Spectrometer Probe (FSSP-300) on the ER-2 were corrected for the expected asphericity of cirrus cloud particles by means of a T-matrix method. The results indicate considerable potential of cirrus clouds f…
A composite study on the structure and formation of ozone miniholes and minihighs over central Europe
2005
[1] Two different mechanisms have been proposed to be important for the formation of extreme total ozone events in mid-latitudes, so-called miniholes: (A) far-range meridional transport of air masses from regions with different climatological ozone mixing ratios, and (B) (local) adiabatic vertical displacement of isentropes. Here, the relative importance of these two mechanisms is studied using two different ozone profile reconstruction techniques for all miniholes and minihighs (events with anomalously high ozone) during the time period 1980–1989 over Switzerland. Composites for the two types of events of their vertical potential vorticity (PV) reveal a vertical dipole structure of PV anom…