Inert gas evaporation

Synthesis of nano-structured alloys by the inert gas evaporation technique A precursor material, either a single metal or a compound, is evaporated at low temperature, producing atom clusters through homogeneous condensation via collisions with gas atoms in the proximity of a cold collection surface. To avoid cluster coalescence, the clusters are removed from the deposition region by natural gas convection or forced gas flow. A similar technique is sputtering (ejection of atoms or clusters by an accelerated focused beam of an inert gas, see 6.9.3). 

Inert Gas Evaporation Technique. Inert gas evaporation technique is a familiar method in an aerosol production of ultrafine particles as already mentioned in Section... 

The various methods of preparation employed to prepare nanoscale clusters include evaporation in inert-gas atmosphere, laser pyrolysis, sputtering techniques, mechanical grinding, plasma techniques and chemical methods (Hadjipanyas Siegel, 1994). In Table 3.5, we list typical materials prepared by inert-gas evaporation, sputtering and chemical methods. Nanoparticles of oxide materials can be prepared by the oxidation of fine metal particles, by spray techniques, by precipitation methods (involving the adjustment of reaction conditions, pH etc) or by the sol-gel method. Nanomaterials based on carbon nanotubes (see Chapter 1) have been prepared. For example, nanorods of metal carbides can be made by the reaction of volatile oxides or halides with the nanotubes (Dai et al., 1995). 

Figure 6.36. Illustrations of apparati used in the gas-phase synthesis of 0-D nanoparticles. Shown are (a) plasma system (b) spark-facilitated growth (c) laser vaporization/pyrolysisf (d) laser evaporation (e) laser ablation (f) inert-gas evaporation " (g) electrospray system " (h) spray pyrolysis. " ...

Physical vapor deposition (PVD) techniques such as evaporation or sputtering may also be used to synthesize 0-D nanoparticles. One technique, known as inert gas evaporation (Figure 6.36f), consists of evaporation of a precursor material within a cooling inert gas at low pressures ca. 100 Pa). Vaporization may be accomplished via resistive heating, ion bombardment (sputtering), or laser irradiation. As one... 

Cross-section illustration of an inert-gas evaporation system. Shown are an inconel pipe (1), a crucible containing the precursor (2), tube furnace (3), evapmatitm zone (4), and cap-free (5) or gas-return cap (6) inert-gas diluter configurations to introduce cooling carrier gas to control the size of the nanoparticles. Reproduced with permission from Wegner, K. Walker, B. Tsantilis, S. Pratsinis, S. E. ChemEng Sci. 2002,57, 1753. Copyright 2002 Elsevier B.V. 

How would one utihze inert gas evaporation to pattern micron-sized arrays of 0-D nanoparticles ... 

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