Cryogenics and the Future

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  • Topic: Cryogenics, Superconductivity, Temperature
  • Pages : 5 (1495 words )
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  • Published : October 8, 1999
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Cryogenics and the Future

Cryogenics is a study that is of great importance to the human race and has been a major project for engineers for the last 100 years. Cryogenics, which is derived from the Greek word kryos meaning "Icy Cold," is the study of matter at low temperatures. However low is not even the right word for the temperatures involved in cryogenics, seeing as the highest temperature dealt with in cryogenics is 100 (C (-148 (F) and the lowest temperature used, is the unattainable temperature -273.15 (C (-459.67 (F). Also, when speaking of cryogenics, the terms Celsius and Fahrenheit are rarely used. Instead scientists use a different measurement called the Kelvin (K). The Kelvin scale for Cryogenics goes from 173 K to a fraction of a Kelvin above absolute zero. There are also two main sciences used in cryogenics, and they are Superconductivity and Superfluidity.

Cryogenics first came about in 1877, when a Swiss Physicist named Rasul Pictet and a French Engineer named Louis P. Cailletet liquefied oxygen for the first time. Cailletet created liquid oxygen in his lab using a process known as adiabatic expansion, which is a "thermodynamic process in which the temperature of a gas is expanded without adding or extracting heat from the gas or the surrounding system"(Vance 26). At the same time Pictet used the "Joule-Thompson Effect," a thermodynamic process that states that the "temperature of a fluid is reduced in a process involving expansion below a certain temperature and pressure"(McClintock 4). After Cailletet and Pictet, a third method, known as cascading, was developed by Karol S. Olszewski and Zygmut von Wroblewski in Poland. At this point in history Oxygen was now able to be liquefied at 90 K, then soon after liquid Nitrogen was obtained at 77 K, and because of these advancements scientist all over the world began competing in a race to lower the temperature of matter to Absolute Zero (0 K) [Vance, 1-10].

Then in 1898, James DeWar mad a major advance when he succeeded in liquifying hydrogen at 20 K. The reason this advance was so spectacular was that at 20 K hydrogen is also boiling, and this presented a very difficult handling and storage problem. DeWar solved this problem by inventing a double- walled storage container known as the DeWar flask, which could contain and hold the liquid hydrogen for a few days. However, at this time scientists realized that if they were going to make any more advances they would have to have better holding containers. So, scientists came up with insulation techniques that we still use today. These techniques include expanded foam materials and radiation shielding. [McClintock 43-55]

The last major advance in cryogenics finally came in 1908 when the Dutch physicist Heike Kamerling Onnes liquefied Helium at 4.2 and then 3.2 K. The rest of the advances in cryogenics have been extremely small since it is a fundamental Thermodynamic law that you can approach but never actually reach absolute zero. Since 1908 our technology has greatly increased and we can now freeze sodium gas to within 40 millionths of a Kelvin above absolute zero. However, in the back of every physicists head they want to break the Thermodynamic law and reach a temperature of absolute zero where every proton, electron, and neutron in an atom is absolutely frozen.

Also , their are two subjects that are also closely related to cryogenics called Superconductivity and Superfluidity. Superconductivity is a low-temperature phenomenon where a metal loses all electrical resistance below a certain temperature, called the Critical Temperature(Tc), and transfers to "...a state of zero resistance,..."(Tilley 11). This unusual behavior was also discovered by Heike Kamerlingh Onnes. It was discovered when Onnes and one of his graduate students realized that Mercury loses all of its electrical resistance when it reaches a temperature of 4.15 K. However, almost all elements and compounds...
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