Vacuum technology

Vacuum technology refers to any type of technology in which various processes are carried out in conditions lower than the atmospheric pressure. A vacuum is defined as any space that is completely empty of physical matter. For instance, outer space (the zone between planets) consists of a partial vacuum. There is virtually no air or physical matter. In a true vacuum, not even sound can travel. For the purposes of manufacturing, however, a vacuum is used to describe differences in atmospheric pressure. Atmospheric pressure measures the weight of air and the resulting pressure exerted by it.

Earth has a layer of air that surrounds the planet. However, this layer has different amounts of air at various altitudes. Places located higher in the atmosphere have lower amounts of air than would be found at sea level. For instance, if someone were to fill a container with air on Mount Everest, it would contain a much lower percentage of air than if it had been filled at ground level. Therefore, there is low atmospheric pressure inside the container, which is to say that there is less air from above pushing down. If this container were not protected against changes in atmospheric pressure, when brought to ground level, it would be crushed by the changes in pressure. This is because air will naturally seek to fill the space where there is lower pressure. In the case of a sealed container such as a plastic bottle, the force from the higher air pressure outside will crush the bottle to fill the gap created by the lower air pressure inside the container.

Air particles create pressure on the walls of any space, such as a container. The fewer air particles in any given space, the less force that is exerted onto the walls of that container. Vacuum technology uses these principles to pump air from a chamber to create a lower atmospheric pressure. These principles have many real-world applications in industry, science, and technology.

Background

Vacuum technology seeks to replicate a perfect vacuum. A perfect vacuum is one in which there are no air particles present. However, it is virtually impossible to create a perfect vacuum. The closest naturally occurring state to a perfect vacuum is found in outer space, where there are only a few trace hydrogen atoms per cubic meter. To simulate vacuum conditions on Earth, scientists have developed various types of vacuum chambers that are able to create different vacuum levels. These range from an extremely high vacuum (XHV), in which even trace gases are removed, to a low vacuum, like that used in vacuum cleaners. In between these extremes are several other forms of vacuums. Only a small number of specialized facilities in the world are capable of replicating XHV conditions, while low vacuums are a common piece of technology. The only practical uses for XHV conditions are for accelerator and storage ring facilities, to stimulate conditions in outer space, and, in some cases, to produce specialized forms of semiconductors.

Ultra-high vacuums (UHVs), which are slightly less powerful than XHVs, are primarily used by chemists, engineers, and physicists for scientific research in such fields as X-ray photoelectron spectroscopy. To achieve this state, gases are forcibly pumped by such devices as UHV chambers, cryopumps, and helium compressors. These devices require special seals and gaskets that prevent even the slightest hint of air leakage. High vacuums (HVs) require less effort to create and are used for smelting and annealing processes that change the structure of metals to help make them stronger, harder, or more malleable.

Medium (or intermediate) vacuums have many applications. They are used in the production of steel, the manufacture of lightbulbs, the drying of plastics, and for freeze-drying food. Low (or rough) vacuums are used in the operation of vacuum cleaners and for industrial handling. Low vacuums are also created through some natural processes, such as human respiration.

An XHV is one in which a pump or chamber is able to replicate an environment that is 99.999 percent free of particles—only slightly less than a perfect vacuum and the closest rate achievable on Earth. UHVs and high vacuums are defined as those that establish environments between 99 and 99.999 percent of atmospheric pressure, while low and medium vacuums operate at levels at 99 percent or lower.

Overview

The applications of vacuum technology can be split into two categories: those that require vacuums to work, or alternately, those in which vacuums are used as part of the manufacturing process. In the first category are such devices as lamps, tubes, vacuums, pumps, accelerators, and actuators. Products that rely on vacuums during the manufacturing process include those in such industries as food packing, coating, degassing, packaging, and electronics. About 40 percent of the sales of vacuum technology are used for the manufacture of semiconductors.

One of the most important mechanisms that rely on vacuums to work is a vacuum actuator. This device uses vacuum pressure to create and convert energy that is used to allow motion. Such devices are found in many systems in vehicles, including headlights, transmission shift controls, ventilation systems, and windshield wipers.

Outgassing is another form of vacuum technology. This process releases traces of gases trapped inside materials such as metals. Using vacuum technology, all gas pockets are released by baking these materials under the pressure of a vacuum. This allows the vapor pressure of these materials to be boiled off and released. They are then cooled to reduce the potential for natural outgassing that can occur when they are put into regular use. Outgassing is particularly useful for increasing the structural integrity of materials. This process is also used to create molds and to establish and preserve UHVs.

One of the most common uses for vacuums is for pumping. For instance, this technology can be used to suction materials from deep wells. This works by expanding the volume of a container and then lowering the pressure inside, thereby creating a type of artificial vacuum. This vacuum then fills with air as a result of the reduced pressure. This enables the creation of a suction force that pulls the materials up.

Vacuum technology also has a breadth of other uses. These may include removing gases for drying, dehydrating, or freeze-drying food. Similarly, vacuum technology can be used to remove atmospheric constituent parts to create lighting tubes and bulbs, for leak detection, to melt materials, or for packaging. Vacuums also have applications for lifting or transporting materials by creating a pressure difference that functions as a type of suction.

Bibliography

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