Group 18 elemnt Uses

  Figure 1.1 summarizes the main uses of helium. Both helium and argon are used to provide inert atmospheres, for example for arc-welding  and during the growth of single Si or Ge crystals for the semiconductor industry. Argon is also used in laboratory inert atmosphere (‘dry’or ^،glove^،) boxes for handling airsensitive compounds. Being very light and non-inflammable,  He is used to inflate the tyres of large aircraft, and in = balloons including weather balloons and NASAs unmanned suborbital research balloons. Liquid He is an important coolant and is used in highfield NMR spectrometers including those used in medical imaging. The superconductivity of metals cooled to the temperature of  liquid He suggests that the latter may become important in power transmission. An O₂/He mixture is used in place of O₂/N₂ for deep-sea divers; He is much less soluble in blood than N₂, and does not cause ‘the bends’ when the pressure is released on surfacing. Helium is also used as a heattransfer agent in gas-cooled nuclear reactors, for which it has the advantages of being non-corrosive and of not becoming radioactive under irradiation. Neon, krypton and xenon are used in electric discharge signs (e.g. for advertising) and Ar is contained in metal filament bulbs to reduce evaporation from the filament.

Fig. 1.1 Uses of helium in the US in 2001. The total consumption of ‘grade A’ helium in the US in 2001 was 83 × 10⁶ m³. [Data: US Geological Survey.]