摘要
In-air epitaxy of nanostructures(Aerotaxy)has recently emerged as a viable route for fast,large-scale production.In this study,we use small-a ngle X-ray scatteri ng to perform direct in-flight characterizati ons of the first step of this process,i.e.,the en gineered formatio n of Au and Pt aerosol nan oparticles by spark gen erati on in a flow of N2 gas.This represe nts a particular challe nge for characterizati on because the particle density can be extremely low in con trolled production.The particles produced are exami ned duri ng producti on at operatio nal pressures close to atmospheric conditions and exhibit a log no rmal size distributi on ranging from 5-100nm.The Au and Pt particle productio n and detection are compared.We observe and characterize the nanoparticles at different stages of synthesis and extract the corresponding domi nant physical properties,in cludi ng the average particle diameter and sphericity,as in flue need by particle sintering and the prese nee of aggregates.We observe highly sorted and sin tered spherical Au nano particles at ultra-dilute concen tratio ns(<5×10^5 particles/cm^3)corresponding to a volume fraction below 3×10^-10,which is orders of magnitude below that of previously measured aerosols.We independently confirm an average particle radius of 25 nm via Guinier and Kratky plot analysis.Our study indicates that with high-intensity synchrotron beams and careful con sideratio n of backgro und removal,size and shape info rmati on can be obtai ned for extremely low particle concentrations with industrially relevant narrow size distributions.
