Inert gas condensation technique

Inert gas condensation technique Separated nanometer-sized nanoparddes of Fe,... 

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). 

The bottom-up approach represents the concept of constructing a nanomaterial from basic building elements, that is, atoms or molecules. This approach illustrates the possibility of creating materials of SEs with exactly the properties desired. The second approach, the top-down method, involves restructuring a bulk material in order to create a nanostructure. Inert gas condensation, considered a bottom-up technique, was the first method used to intentionally construct a nanostructured material, and has become a widespread means of producing nanostructured metals, alloys, intermetallics, ceramic oxides, and composites... 

A number of processes are being used for producing nanomaterials for bulk production. The most common techniques used for synthesizing nanostructure materials include inert gas condensation, mechanical alloying, thermal spraying, electrodeposition, jet vapor deposition, vacuum thermal evaporation, and controlled chanical precipitation. 

Numerous methods, which include inert gas condensation, high energy ball-milling, flame pyrolysis, electron beam vapour deposition, rapid solidification, reactive sputtering, chemical vapor deposition, sol-gel technique, microemulsion, co-precipitation, hydrothermal method, spark erosion and electrodeposition, are available for the synthesis of nanocrystalline materials (Koch, 2003b ... 

Either UV-VIS or IR spectroscopy can be combined with the technique of matrix isolation to detect and identify highly unstable intermediates. In this method, the intomediate is trapped in a solid inert matrix, usually one of the inert gases, at very low temperatures. Because each molecule is surrounded by inert gas atoms, there is no possiblity for intermolecular reactions and the rates of intramolecular reactions are slowed by the low temperature. Matrix isolation is a very useful method for characterizing intermediates in photochemical reactions. The method can also be used for gas-phase reactions which can be conducted in such a way that the intermediates can be rapidly condensed into the matrix. 

Another thin film technology based nanoparticle preparation route is gas condensation, in which metal vapor is cooled to high levels of supersaturation in an inert gas ambient [126-128]. In these experiments particles necessarily nucleate in the gas phase. In a promising extension of this technique a pulsed laser beam replaces the conventionally used thermal metal vapor source [120,121,129-134]. 

Dynamic headspace GC-MS involves heating a small amount of the solid polymer sample contained in a fused silica tube in a stream of inert gas. The volatile components evolved on heating the sample are swept away from the sample bulk and condensed, or focused on a cryogenic trap before being introduced onto the chromatographic column via rapid heating of the trap. The technique can be used qualitatively or quantitatively DHS-GC-MS is considered to be well suited towards routine quantitative analysis. 

In the thermal desorption technique excavated soil is heated to around 200 to 1000°F (93 to 538°C). Volatile and some semivolatile contaminants are vaporized and carried off by air, combustion gas, or inert gas. Off-gas is typically processed to remove particulates. Volatiles in the off-gas may be burned in an afterburner, collected on activated carbon, or recovered in condensation equipment. Thermal desorption systems are physical separation processes that are not designed to provide high levels of organic destruction, although some systems will result in localized oxidation or pyrolysis. 

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