11-09 :: September 2011


nanotimes News in Brief


Nanometre-sized bubbles con- taining the gases hydrogen and oxygen can apparently combust spontaneously, although nothing happens in larger bubbles. For the first time, researchers at the University of Twente’s MESA+ Institute for Nanotechnology have demonstrated this sponta- neous combustion in a publica- tion in Physical Review E. They intend to use the phenomenon to construct a compact ultra- sonic loudspeaker.


The fact that a violent reaction takes place is already evident from the damage incurred by the electrodes with which the reaction is initiated. These elec- trodes are used to make hydro- gen and oxygen by electrolysis, in the usual manner, in an ultra-small reaction chamber. If the plus and minus poles are continu- ally alternated, tiny bubbles containing both gases arise.


The frequency with which the poles are alternated determines the size of the bubbles: the higher the frequency, the smaller the bubbles. Combustion only takes place in bubbles that are smaller than 150nm; nothing happens in larger bubbles. Early experiments in microreactors also showed that nothing happened in larger bubbles; the heat can dissipate to the larger internal surface. Researcher Vitaly Svetovoy was working on the construction of an actuator for rapidly building pressure when he


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Formation of bubbles at the electrodes during electrolysis (can be seen in a and b).


Situations c, d, and e show the formation of both hydrogen and oxygen on the left, hydrogen alone in the middle and oxygen alone on the right.


Situation e shows combustion taking place on the left. No bubbles can be seen on the electrodes. © Vitaly Svetovoy


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