Efficient Sonochemistry through Microbubbles Generated with Micromachined Surfaces

Sonochemical reactors are used in water treatment, the synthesis of fine chemicals, pharmaceutics and others. The low efficiency of sonoreactors have prevented its massive usage at industrial scales. Controlling the appearance of bubbles in place and time is the most limiting factor. A novel type of sonochemical reactor was designed making use of micro-fabrication techniques to control the nucleation sites of micro-bubbles. The efficiency was increased first by locating the nucleation sites in the most active region of a micro-chamber; additionally the desired chemical effect was significantly higher at the same powers than when not controlled. Silicon substrates were micromachined with "artificial nucleation sites" or pits, and placed at the bottom of the micro-chamber. The pits entrap gas which, upon ultrasonic excitation, sheds off a stream of microbubbles. The gas content of the pits is not depleted but is replenished by diffusion and the emission of microbubbles can continue for hours

A predictive model obtained by identification for the ultrasonic "equivalent" flow velocity at surface vicinity

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Electropolishing Behavior of Additive Layer Manufacturing 316L Stainless Steel in Deep Eutectic Solvents

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Electropolishing of CuZn brasses and 316L stainless steels: Influence of alloy composition or preparation process (ALM vs. standard method)

International audienceIn the present paper, electropolishing behavior of different brass alloys (CuZn39Pb2, CuZn42) in phosphoric acid is studied to observe the impact of alloying elements on polishing quality. In the same way, the influence of the manufacturing process is also evaluated through the comparison of a “standard” stainless steel and a stainless steel prepared by Additive Laser Manufacturing (ALM). An electrochemical study was first performed to determine the best treatment conditions for each material/electrolyte pair and to study the electropolishing mechanism and its kinetic dependence on diffusion. Metallic samples are fully characterized before and after electropolishing in their respective electrolytes so that a relationship to manufacturing variables, crystallographic properties and microstructure can be established. While the biphasic composition of brasses studied here leads to a preferential attack of the β phase, somewhat difficult to manage, the presence of lead in copper alloy does not really disturb the process, even if lead particles are not removed from the surface. Furthermore, the manufacturing mode seems to play an important role in stainless steel polishing. The metallographic studies highlight a difference in microstructure between the two kinds of samples and reveal that they do not have the same crystalline organization even after a mechanical pre-treatment. This had to be taken into account in the global process organization

Equivalent fluid velocity: a help for sonoreactor design

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