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Projects / Programmes source: ARIS

Heterogeneous surface recombination of neutral reactive plasma species on nanostructured materials

Research activity

Code Science Field Subfield
2.09.02  Engineering sciences and technologies  Electronic components and technologies  Electronic components 

Code Science Field
P240  Natural sciences and mathematics  Gases, fluid dynamics, plasmas 

Code Science Field
2.05  Engineering and Technology  Materials engineering 
Keywords
nanostructure, catalytic material, recombination coefficient, plasma, atom loss, heterogenous surface recombination
Evaluation (rules)
source: COBISS
Researchers (1)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  33326  PhD Gregor Primc  Electronic components and technologies  Head  2016 - 2017  266 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,987 
Abstract
Heterogeneous surface recombination of neutral oxygen and hydrogen atoms on advanced nanostructured materials suitable for the catalyst tips of laser-driven catalytic sensors will be studied experimentally. The existing experimental reactor will be equipped with a couple of atom sources employing microwave discharges in the surfatron mode, a movable copper mesh for adjusting the atom density independently from discharge parameters and a system for measuring the recombination coefficients using the Smith’s configuration. Nanostructured materials whose recombination activities are supposed to be superior will be prepared either by anodic oxidation or by plasma synthesis of metal oxide nanostructures according to our original method. Apart from nanotubes and nanowires of high aspect ratio, two dimensional nanowalls of metal oxides will be synthesized as well and their stability upon treatment with neutral O- and H-atoms at elevated temperatures will be studied. The recombination coefficients for oxygen atoms for iron, copper, nickel, titanium and palladium oxides will be determined systematically at different temperatures from room temperature to about 1000 K at different fluxes of neutral atoms onto the nanostructured catalysts. The density of atoms in the vicinity of the catalyst will be adjusted by placing a copper mesh at different distances from the catalyst. Any pressure dependence of the recombination coefficient will be determined from measurements at different pressures from about 10 Pa to 1000 Pa and at constant atom density. The constant atom density will be adjusted independently from atom density in the microwave plasma using the movable mesh which will serve as a sink for atoms. Any reversible and irreversible change of the recombination coefficient versus the catalyst temperature will be elaborated. The oxide nanostructures will be reduced by exposure to as-synthesized nanostructured catalysts to hydrogen plasma. The reduction of the oxide versus catalysts temperature will be studied as well as the stability of the morphology upon reduction. The recombination coefficients for hydrogen atoms will be determined systematically on such structures, following the procedure adopted for oxygen atoms. The measurements will reveal materials of different catalytic activity for O and H atoms and thus selectivity in terms of atom detection. The results will represent a solid background for development of a multi-catalyst sensor for real-time monitoring of the density of said atoms in processing plasmas nowadays used on industrial scale. The novel sensor will be suitable for process control in advanced eco-friendly technologies of polymer activation, selective etching of organic compound from composite materials as well as discharge cleaning of components in electro and automotive industries.
Significance for science
The key contribution of the postdoctoral project "Heterogeneous surface recombination of neutral reactive plasma species on nanostructured materials" to the global knowledge is an explanation for the unusual behavior of the density of atoms in the non-thermal weakly ionized state of the gas together with nanostructured materials. A review of literature shows a paradox, since various authors have reported different values ??of this parameter for the same material. I explained the paradox by capturing atoms into slots of the nanostructured material. This can be explained by the fact that the average free path of the gas particles under low pressure is always significantly larger than the typical lateral nanostructure material slits' dimension. Atoms tha are captured inside the nanostructured material, eventually recombine with the surface. They typically do not leave the surface after a single collision, but experience several collisions within the slit before they actually leave the surface, so that in the approximation of an infinite number of collisions within the nanostructured material, the coefficient for all materials is equal to 1. In practice, of course, atoms do not experience as many collisions, which makes the recombination coefficient gradually increasing with increasing nanostructuredness and is asymptotically approaching to ??1 when the ratio between the lateral and vertical dimension of the slits of na nostructured material goes towards zero. This increase in the coefficient leads to interesting phenomena, which are described in an article published in the reputable magazine Composites Science and Technology (IF 4.9), which is labeled with exceptional achievemnts A'' (according to Slovenian standards).
Significance for the country
The project entitled "Heterogeneous surface recombination of neutral reactive plasma species on nanostructured materials" contributed to the reputation of Slovenia through global science in the specific field of interaction of strongly non-homogeneous gas states with the surfaces of solid materials. The focus of our research in this field is the consequence of the needs of the Slovenian industry in knowledge that is crucial for the optimisation of technological procedures for the plasma processing of products and semi-finished products for the electrical, automotive and chemical industries. Our industry uses plasma technologies to clean and activate polymeric semi-products, selective etching of composites and for deposition of thin protective films. Numerous problems emerged that could be better addressed by understanding the basic processes of interaction of reactive plasma particles with treated materials. Even though this project is based on a basic research, the results can be directly used for optimizing existing processes in terms of improving plasma treatment process uniformity, thereby improving the quality of products as well as in terms of reducing the production cycle time. Both improvements lead to increased competitiveness of Slovenian industry products on the global market and thus indirectly raising added value per employee.
Most important scientific results Interim report, final report
Most important socioeconomically and culturally relevant results Interim report, final report
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