New developments in spark production of nanoparticles

The paper selects a number of recent developments in spark production of nanoparticles that are important for production of nanopowders and nanoparticulate materials. It explains the method, including recent improvements, and refers to theoretical considerations as well as practical experience in controlling the main particle parameters determining the product properties, namely size and composition. The paper focusses on particles below 10 nm, where the spark method works best. Values for feasible production rates and energy efficiencies are estimated using published data. Spark mixing is identified as a feature that renders great potential to the method, especially for catalysis but also for other purposes, as it opens myriads of new possibilities in the form of material combinations. The most important condition for this potential to turn into industrial application is the capability of scaling up. The basic principles that allow mixing are treated, methods are reviewed and examples for applications are given. These include the creation of new phases that only exist in the nanoparticulate state. A new technique allowing an increase of the production rate of a single electrode pair by a factor of 10(2)-10(3) is introduced. It allows production nanoparticles typically 5 nm in size at a rate of 1 g/h, and this rate can arbitrarily be increased further by operating multiple sparks in parallel. The energy requirement is in the order of 3 kWh/g. The paper stems on adoption and interpretation of published articles as well as on new developments that are presented for the first time.