Untitled Essay Research Paper Cryogenics and the

Untitled Essay, Research Paper

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 have Tc’s between 1 K and 15 K (or -457.68

(F and -432.67 (F) so they would not be very useful to us on a day to day basis[McClintock

208-226]. Then in 1986, J Gregore Bednorz and K. Alex Muller discovered that an

oxide of lanthanum, barium, and copper becomes superconductive at 30 K. This discovery

shocked the world and stimulated scientists to find even more "High-Temperature

Superconductors". After this discovery, in 1987, scientists at the University of

Houston and the University of Alabama discovered YBCO, a compound with a Tc of 95 K. This

discovery made superconductivity possible above the boiling point of liquid Nitrogen, so

now the relatively cheap, liquid nitrogen could replace the high priced liquid helium

required for cryogenic experiments. To date the highest reported Tc is 125 K, which

belongs to a compund made of Thallium, Barium, Calcium, Copper, and Oxygen. Now, with the

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