Description of an aerodynamic levitation apparatus with applications in Earth sciences

摘要

Background: In aerodynamic levitation, solids and liquids are floated in a vertical gas stream. In combination withCO2-laser heating, containerless melting at high temperature of oxides and silicates is possible. We applyaerodynamic levitation to bulk rocks in preparation for microchemical analyses, and for evaporation and reductionexperiments.Results: Liquid silicate droplets (~2 mm) were maintained stable in levitation using a nozzle with a 0.8 mm boreand an opening angle of 60°. The gas flow was ~250 ml min~(-1).Rock powders were melted and homogenized formicrochemcial analyses. Laser melting produced chemically homogeneous glass spheres. Only highly (e.g. H2O)and moderately volatile components (Na, K) were partially lost. The composition of evaporated materials wasdetermined by directly combining levitation and inductively coupled plasma mass spectrometry. It is shown thatthe evaporated material is composed of Na > K Si. Levitation of metal oxide-rich material in a mixture of H2and Ar resulted in the exsolution of liquid metal.Conclusions: Levitation melting is a rapid technique or for the preparation of bulk rock powders for major, minorand trace element analysis. With exception of moderately volatile elements Na and K, bulk rock analyses can beperformed with an uncertainty of ± 5% relative. The technique has great potential for the quantitative determinationof evaporated materials from silicate melts. Reduction of oxides to metal is a means for the extraction and analysis ofsiderophile elements from silicates and can be used to better understand the origin of chondritic metal.