Role of reactive species in processing materials at laboratory temperature by spray plasma devices

Processing the aerosol of metal salts in non-equilibrium plasma represents a promising technique that combines the advantages of spray pyrolysis with the high reactivity of plasmas at nearlaboratory temperature in order to produce mixed-oxides and perovskite materials. The aim of this paper is to describe the principles of this new technique and to present the various applications and latest developments. This technique’s capacity to deposit various mixed metal oxides with precise stoichiometry is demonstrated. It is shown that oxidant plasma species play a key role in the chemical transformation of starting materials into oxides at laboratory temperature, while the configuration of the reactor determines the morphology and texture of the deposited layers. Two different reactor configurations are presented. The porous layers of La _x Sr_1−x MnO₃ as the cathode for fuel cells were synthesised in a wave shock reactor configuration, while nanostructured ZnO-Al layers to form a transparent conductive cathode for photovoltaic cells were deposited in the spray plasma reactor of the latest generation for this technique. The experimental results emphasise the role of plasma species in the rate of chemical reactions and in the chemical composition of the deposited layers.     

Spectroscopic Characterization of CH4 + CO2 Plasmas Excited by a Dielectric Barrier Discharge at Atmospheric Pressure

Plasma processing of a (CH ₄ +CO ₂ ) mixture can lead to the formation of synthesis gas (CO+H ₂ ). The use of a nonthermal plasma for this type of process seems very promising. We report here an electric and spectroscopic characteristic of plasma created in a (CH ₄ +CO ₂ ) mixture by a high-voltage, steep front-voltage (>10 ¹² V/s), very-short-pulse triggered dielectric barrier discharge in a tubular cell. Particular attention was payed to the determination of the rotational temperature for C ₂ . Time resolved investigation of the Swan band leads to an estimated value around 3000 K.