Uses

Uses
vaccuum is useful in a variety of processes and devices. Its first common use was in incandescent light bulbs to protect the tungsten filament from chemical degradation. Its chemical inertness is also useful for electron beam welding, for chemical vapor deposition and dry etching in semiconductor fabrication and optical coating fabrication, for cold welding, for vaccuum packing and for vaccuum frying. The reduction of convection improves the thermal insulation of thermos bottles and double-paned windows. Deep vaccuum promotes outgassing which is used in freeze drying, adhesive preparation, distillation, metallurgy, and process purging. The electrical properties of vaccuum make electron microscopes and vaccuum tubes possible, including cathode ray tubes. The removal of air friction is useful for flywheel energy storage and ultracentrifuges.
High to ultra-high vaccuum is used in thin film deposition and surface science. The high vaccuum allows for contamination-free deposition of materials. Ultra-high vaccuum is used when atomically clean substrates are studied, as only a very good vaccuum preserves atomic-scale clean surfaces for a reasonably long time of the order of minutes to days.
Suction is used for a very wide variety of applications. The Newcomen steam engine used vaccuum instead of pressure to drive a piston. In the 19th century, vaccuum was used for traction on Isambard Kingdom Brunel's experimental atmospheric railway.