Optimal design of a reactor for gas-phase generation of metal microclusters
Abstract
A new aerosol reactor for generation of metal microclusters of controlled size and composition has been built and tested. This reactor is an improved version of the Multiple Expansion Cluster Source (MECS) developed by Andres and his students. The new reactor is shown to be capable of producing clusters having: (1) controlled size in the range of 1 nm-20 nm, (2) controlled composition involving more than a single metal species and (3) narrow size distribution approaching the theoretical minimum for a pure birth condensation process. A kinetic model for the reactor predicts cluster size very well. When helium is used as the cooling gas, the clusters stop growing at an ultimate size that is determined by the initial ratio of metal monomer to metal dimer entering the condensation region. When argon is used as the cooling gas, these so called "normal" clusters aggregate to form larger clusters of up to 20 nm diameter. This aggregation process occurs on nuclei formed early in the condensation region and appears to proceed via a pure birth mechanism similar to that controlling growth of normal clusters.
Degree
Ph.D.
Advisors
Andres, Purdue University.
Subject Area
Chemical engineering
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