Nanoparticle Formation by Laser Ablation and by Spark Discharges — Properties, Mechanisms, and Control Possibilities

Laser ablation (LA) and spark discharge (SD) techniques are commonly used for nanoparticle (NP) formation. The produced NPs have found numerous applications in such areas as electronics, biomedicine, textile production, etc. Previous studies provide us information about the amount of NPs, their size distribution, and possible applications. On one hand, the main advantage of the LA method is in the possibilities of changing laser parameters and background conditions and to ablate materials with complicated stoichiometry. On the other hand, the major advantage of the SD technique is in the possibility of using several facilities in parallel to increase the yield of nanoparticles. To optimize these processes, we consider different stages involved and analyze the resulting plasma and nanoparticle (NP) parameters. Based on the performed calculations, we analyze nanoparticle properties, such as mean size and mean density. The performed analysis (shows how the experimental conditions are connected with the resulted nanoparticle characteristics in agreement with several previous experiments. Cylindrical plasma column expansion and return are shown to govern primary nanoparticle formation in spark discharge, whereas hemispherical shock describes quite well this process for nanosecond laser ablation at atmospheric pressure. In addition, spark discharge leads to the oscillations in plasma properties, whereas monotonous behavior is characteristic for nanosecond laser ablation. Despite the difference in plasma density and time evolutions calculated for both phenomena, after well-defined delays, similar critical nuclei have been shown to be formed by both techniques. This result is attributed to the fact that whereas larger evaporation rate is typical for nanosecond laser ablation, a mixture of vapor and background gas determines the supersaturation in the case of spark

Formation de nanoparticules par décharge d’étincelle à pression atmosphérique

Au cours de la dernière décennie, les nanoparticules métalliques ont trouvé de nombreuses applications dans divers domaines tels que l'optique, la photonique, la catalyse, la fabrication de matériaux, les énergies renouvelables, l'électronique, la médecine et même les cosmétiques. Les nouveaux développements de ces applications nécessitent des méthodes de synthèse de nanoparticules fiables donnant une grande quantité de nanoparticules aux propriétés spécifiques. Les méthodes à base de plasma, tels que des décharges d'étincelles et d’arcs sont parmi les plus prometteuses car elles permettent une augmentation considérable de la vitesse de production et une diminution des coûts. Le contrôle de ces processus est cependant toujours difficile et nécessite de nombreuses études détaillées, à la fois expérimentales et théoriques. Dans cette thèse, les décharges d'étincelles sont étudiées numériquement. L'objectif principal est de mieux comprendre les principaux mécanismes impliqués dans la décharge d'étincelle avec un faible écartement d’électrodes et sous pression atmosphérique. Ensuite, sur la base de la modélisation détaillée proposée, la quantité de nanoparticules produites ainsi que leur distribution en taille est prédite et est comparée avec les résultats expérimentaux correspondants. Dans le modèle proposé, seules les conditions initiales, la géométrie du système et les propriétés du matériau sont utilisés comme paramètres d'entrée. Une décharge d’étincelle unique est divisée en plusieurs unités selon les échelles spatiales et temporelles des processus physiques comme suit: modèles de (i) flux plasma, (ii) décharge, (iii) hydrodynamique, (iv) couche cathodique, (v) érosion d’électrode et (vi) formation de nanoparticules. Les résultats du modèle combiné sont ensuite comparés à la fois avec d'autres résultats théoriques et à des résultats expérimentaux. Enfin, les possibilités d'optimisation de la production de nanoparticules par décharge d'étincelles sont proposées sur la base de la variation des paramètres expérimentaux et sur l'analyse de la quantité de particules produites et de leur taille moyenneDuring last decade, metal nanoparticles have found many applications in various areas, such as optics, photonics, catalysis, material manufacturing, renewable energy, electronics, medicine and even cosmetics. Further development of these applications requires reliable nanoparticle synthesis methods providing a large amount of nanoparticle with required properties. Plasma-based methods, such as spark and arc discharges are among the most promising since they allow a considerable increase in the production rate and a decrease in costs. The control over these processes is, however, still challenging and requires many detailed studies, both experimental and theoretical. In this thesis, spark discharge is investigated numerically. The main objective is to better understand main mechanisms involved in spark discharge with a short gap under atmospheric pressure. Then, based on the proposed detailed modeling, the amount of the produced nanoparticles, their size distribution should be predicted and compared with the corresponding experimental results. In the proposed model, only initial conditions, geometry of the system and material properties are used as input parameters. A single spark event is divided into several units according to localization and time scales of physical processes as follows: (i) streamer model, (ii) discharging model, (iii) hydrodynamic model, (iv) cathode layer model, (v) electrode erosion model and (vi) nanoparticle formation model. The results of the combined model are then compared both with other theoretical and experimental results. Finally, possibilities of optimization the nanoparticle production by spark discharge are proposed based on the variation of the experimental parameters and on the analysis of the resulted particle yield and mean siz

Formation de nanoparticules par décharge d’étincelle à pression atmosphérique

During last decade, metal nanoparticles have found many applications in various areas, such as optics, photonics, catalysis, material manufacturing, renewable energy, electronics, medicine and even cosmetics. Further development of these applications requires reliable nanoparticle synthesis methods providing a large amount of nanoparticle with required properties. Plasma-based methods, such as spark and arc discharges are among the most promising since they allow a considerable increase in the production rate and a decrease in costs. The control over these processes is, however, still challenging and requires many detailed studies, both experimental and theoretical. In this thesis, spark discharge is investigated numerically. The main objective is to better understand main mechanisms involved in spark discharge with a short gap under atmospheric pressure. Then, based on the proposed detailed modeling, the amount of the produced nanoparticles, their size distribution should be predicted and compared with the corresponding experimental results. In the proposed model, only initial conditions, geometry of the system and material properties are used as input parameters. A single spark event is divided into several units according to localization and time scales of physical processes as follows: (i) streamer model, (ii) discharging model, (iii) hydrodynamic model, (iv) cathode layer model, (v) electrode erosion model and (vi) nanoparticle formation model. The results of the combined model are then compared both with other theoretical and experimental results. Finally, possibilities of optimization the nanoparticle production by spark discharge are proposed based on the variation of the experimental parameters and on the analysis of the resulted particle yield and mean sizeAu cours de la dernière décennie, les nanoparticules métalliques ont trouvé de nombreuses applications dans divers domaines tels que l'optique, la photonique, la catalyse, la fabrication de matériaux, les énergies renouvelables, l'électronique, la médecine et même les cosmétiques. Les nouveaux développements de ces applications nécessitent des méthodes de synthèse de nanoparticules fiables donnant une grande quantité de nanoparticules aux propriétés spécifiques. Les méthodes à base de plasma, tels que des décharges d'étincelles et d’arcs sont parmi les plus prometteuses car elles permettent une augmentation considérable de la vitesse de production et une diminution des coûts. Le contrôle de ces processus est cependant toujours difficile et nécessite de nombreuses études détaillées, à la fois expérimentales et théoriques. Dans cette thèse, les décharges d'étincelles sont étudiées numériquement. L'objectif principal est de mieux comprendre les principaux mécanismes impliqués dans la décharge d'étincelle avec un faible écartement d’électrodes et sous pression atmosphérique. Ensuite, sur la base de la modélisation détaillée proposée, la quantité de nanoparticules produites ainsi que leur distribution en taille est prédite et est comparée avec les résultats expérimentaux correspondants. Dans le modèle proposé, seules les conditions initiales, la géométrie du système et les propriétés du matériau sont utilisés comme paramètres d'entrée. Une décharge d’étincelle unique est divisée en plusieurs unités selon les échelles spatiales et temporelles des processus physiques comme suit: modèles de (i) flux plasma, (ii) décharge, (iii) hydrodynamique, (iv) couche cathodique, (v) érosion d’électrode et (vi) formation de nanoparticules. Les résultats du modèle combiné sont ensuite comparés à la fois avec d'autres résultats théoriques et à des résultats expérimentaux. Enfin, les possibilités d'optimisation de la production de nanoparticules par décharge d'étincelles sont proposées sur la base de la variation des paramètres expérimentaux et sur l'analyse de la quantité de particules produites et de leur taille moyenn

Numerical Analysis of Promising Techniques of Nanoparticle Generation: Laser Ablation vs Spark Discharge at Atmospheric Pressure

International audienceLaser ablation (LA) and spark discharge (SD) techniques are commonly used for nanoparticle formation. On one hand, the main advantage of the LA method is the high ablation rate and in the possibilities of changing laser parameters and background conditions. On the other hand, the major advantage of the SD technique is in the possibility of using several facilities in parallel to increase the yield of nanoparticles [1]. To optimize these processes, we consider different stages involved and analyze the resulting plasma and nanoparticle (NP) parameters. Thus, laser ablation includes [2](i)laser-induced material heating and laser plume formation;(ii)plasma plume formation and its expansion in a background gas;(iii)particle ejection, formation by expansion-driven nucleation and growth during diffusion.Then, spark discharge is numerically analyzed. The model consists of several parts as follows(i)streamer formation and its propagation at atmospheric pressure; (ii)gas breakdown, plasma column formation and its expansion;(i)electrode heating, evaporation and erosion; (ii)particle formation by collisional growth.Based on the performed calculations, we analyze nanoparticle parameters, such as mean size and mean density. The performed analysis shows how the experimental conditions are connected with the resulted nanoparticle characteristics in agreement with several previous experiments [3,4]. Support from the European Union Seventh Framework Program (FP7/2007-2013) under grant agreement n° 280765 (BUONAPART-E) is gratefully acknowledged.[1] T.E. Itina and A. Voloshko, Nanoparticle formation by laser ablation in air and by spark discharges at atmospheric pressure, Appl. Phys. A. vol. 113, no3, pp. 473-478,(2013) .[2] T.E. Itina, M.E. Povarnitsyn, A. Voloshko, Laser-based synthesis of nanoparticles: role of laser parameters and background conditions, SPIE Proc. Vol. 8969, Synthesis on Photonics of Nanoscale Materials XI, 896905 (2014)[3] A. Pereira, P. Delaporte, M. Sentis, W. Marine, A. L. Thomann, C. Boulmer-Leborgne, J. Appl. Phys. Vol. 98, pp. 064902 (2005).[4] N. S. Tabrizi, Q. Xu, N. M. van der Pers, A. Schmidt-Ott, J. Nanopart. Res. Vol. 12, pp. 247-259 (2010)

Nanoparticle formation by laser ablation and by spark discharges: properties, mechanisms and control possibilities

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Numerical investigation of nanoparticle formation by spark discharge

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Comparison of laser ablation with spark discharge techniques used for nanoparticle production

International audienceBased on numerical modeling, we compare laser ablation and spark discharge as promising methods of nanoparticle formation. First, we consider spark discharge between parallel plate metal electrodes. Second, we investigate nanosecond laser ablation of a metal target. For both phenomena copper is chosen to be nanoparticle material and argon at atmospheric pressure is used as an ambient gas. Despite different energy inputs, both differences and similarities are revealed in the corresponding plasma properties. The time-evolution of the critical particle sizes are, however, found to be similar in both cases

The influence of spark discharge parameters on nanoparticle formation and their sizes

International audienceRecently, it has been shown that a parallel system of metal electrodes in spark discharge is an efficient source of aerosols [Tabrizi et al, 2009; Meuller et al, 2012]. To better understand the mechanisms involved in this process, we present calculation results focused at the nanoparticle formation by a single spark event.To analyze the experimental results and to optimize the synthesis procedure, a numerical modelling of the main physical processes taking place during spark discharge is performed. Because of difference in time scales of the phenomena involved in spark discharge it is considered that general model consists of several stages: (i) streamer formation and propagation between electrodes; (ii) streamer-to-spark transition; (iii) gas heating and expansion, (iv) electrode evaporation and erosion; (v) nanoparticles formation due to both nucleation, coalescence and growth. It is shown that surface roughness is an important parameter that determines the major mechanism of electrode material injection in the gas. Gas between electrodes is heated to high temperature that leads to expansion so that electrode material vapour is injected into low-density hot gas area (Figure 1). The influence of plasma column parameters on nanoparticle size distribution and amount is studied. In particular, it is shown that for the well-defined conditions, the radius of critical nuclei can be of order of a single atom radius that causes direct collisional nanoparticle formation [Xiong and Pratsinis, 1991] without nucleation stage. A careful analysis based on the performed modelling allows us to determine the optimal set-up parameters for the production of nanoparticles with the required sizes.AcknowledgementsThe research leading to these results has received funding from the European Union’s Seventh Framework Programme under Grant Agreement n° 280765 (BUONAPART‐E).ReferencesN. S. Tabrizi, M. Ullmann, V. A. Vons, U. Lafont and A. Schmidt-Ott: J. Nanopart. Res. (2009) 11:315–332.Bengt O. Meuller, Maria E. Messing, David L. J. Engberg, Anna M. Jansson, Linda I.M. Johansson, Susanne M. Norlén, Nina Tureson and Knut Deppert: Aerosol Sci. and Tech. (2012) 46:1256–1270.Y. Xiong and S.E. Pratsinis, J. Aerosol Sci. (1991) 22: 637