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Intro to ASUs_Gas World Jan12.pdf
Despite their high price tags, demand for these rare gases is rising rapidly since numerous industries – ranging from electronics and glass fibre through lighting to automotive and aerospace – are increasingly harnessing the benefits of noble gases. Similar to oxygen and nitrogen, the rare gases xenon, neon and krypton are also obtained from air using cryogenic separation and purification. For several years now, Linde has been meeting rising demand for these gases by developing innovative plant concepts that boost the capture of rare gases from secondary streams in major air separation plants.
Best known for its fluorescent capabilities, the noble gas neon (Ne) also plays a key role in ophthalmology. A mixture of neon, fluorine and argon is used during operations on corneas, for example, to correct eyesight via a laser beam.
A mixture of neon, fluorine, argon and helium gases is used in today’s standard cold laser treatments such as excimer lasing. Many of the fluorine, argon and neon gas mixtures produced by Linde go to manufacturers of these kinds of eye laser devices. Excimer lasers, however, are not limited to medical applications. They are also deployed in the electronics industry, for example, in microlithography processes for electronic circuits. Excimer lasers are also used to manufacture mobile phone displays and drill microscopic holes in the nozzles of inkjet printers.
Krypton (Kr) is a key success factor in energy-saving windows. It is used as a filler gas between insulated glass panes as its low thermal conductivity increases the effectiveness of insulation. 40% or more of all krypton produced worldwide is used for this purpose.
As with xenon, krypton is also becoming an increasingly important gas in the lighting sector. The car industry, for example, now offers headlights that work with krypton. This rare gas is also used as a filler gas in halogen bulbs, energy-saving bulbs and gas discharge tubes in illuminated billboards. Replacing nitrogen/argon with krypton in halogen energy-saving lamps and fluorescent lamps increases bulb life and produces more effective lighting.
Krypton is also used as sputter gas (ionised form) in the physical vapour deposition (PVD) technique to create thin metallic surface film on materials. This sputter deposition application is used to coat various materials with a thin film on semiconductor devices, glass and food packing materials (eg aluminised PET film for snack bags). Inert argon or xenon can also be used as sputtering gases.
The extremely rare noble gas xenon (Xe) only accounts for 0.000009% of air. It is only used where lighter noble gases are not effective. This includes applications such as plasma screens and semiconductors as well as car headlights, camera flashes and anaesthetics.
The growing popularity of xenon headlights in cars coupled with regulations mandating energy-saving bulbs has sent demand for this gas skyrocketing. Brightness is not the only reason behind the automobile industry’s move to xenon lights. Lower energy and fuel consumption was an equally appealing factor. Xenon bulbs can also be used in cinema projectors, light projectors and camera flashes. Xenon accounts for at least 5% of the gas mixture in plasma screens. It is used with neon to fill the many small cells between two glass plates. Every pixel is made up of three of these cells. To create a colour image, each cell is individually charged using a transistor, causing the gas to temporarily ionise and form plasma.
Xenon is also used in the aerospace industry for ion thrust propulsion, a technology that utilises ion beams to propel space rockets. Put simply, an ion beam is generated by initially ionising xenon and then using an electrical or magnetic field to accelerate the ions.