For long period storage of liquid nitrogen, usually stainless steel containers are preferred. What is the basic reason behind it?
Those containers are dewars, that means they are double-walled with a vacuum in the gap. Stainless steel is just a convenient material for it. Corrosion-resistant, reasonably strong and tough, weldable, bad thermal conductor, reasonably cheap, reflecting like a mirror. Aluminum alloys would perhaps be an alternative. But they couldn't be anodized to protect from wear and corrosion, because they would in that case absorb and emit far infrared radiation and increase the loss of nitrogen. Aluminum alloys are also better thermal conductors. And strong aluminum alloys are usually not weldable without a heat treatment afterwards. Easily weldable alloys are often too soft.
Glass dewars were used for smaller quantities in the past. They are better insulators, but they are also a real hazard in the lab because they tend to implode and send glass shrapnel all around. Stainless steel is really an ideal choice.
Update:
The material has to be tough and strong *at the temperature of liquid nitrogen*. That excludes a lot of steels, and you'l have to select your stainless steel carefully. It should have a lot of nickel to stabilize the austenitic phase, if I recall correctly.
Those containers are dewars, that means they are double-walled with a vacuum in the gap. Stainless steel is just a convenient material for it. Corrosion-resistant, reasonably strong and tough, weldable, bad thermal conductor, reasonably cheap, reflecting like a mirror. Aluminum alloys would perhaps be an alternative. But they couldn't be anodized to protect from wear and corrosion, because they would in that case absorb and emit far infrared radiation and increase the loss of nitrogen. Aluminum alloys are also better thermal conductors. And strong aluminum alloys are usually not weldable without a heat treatment afterwards. Easily weldable alloys are often too soft.
Glass dewars were used for smaller quantities in the past. They are better insulators, but they are also a real hazard in the lab because they tend to implode and send glass shrapnel all around. Stainless steel is really an ideal choice.
Update:
The material has to be tough and strong *at the temperature of liquid nitrogen*. That excludes a lot of steels, and you'l have to select your stainless steel carefully. It should have a lot of nickel to stabilize the austenitic phase, if I recall correctly.
Liquid nitrogen easily mixes with air and creates liquid oxygen, liquid O2 in contact with carbon steel or most metals would be a good source of instant corrosion.
I should add to the above mentioned advantages of SS its small coefficient of thermal expansion as well as permeability that allow the dewar to be cycled several times between "high" and low temperatures (life time..).
Prof. (Dr )S. Devanarayanan,
Stainless steel is suitable for manufacturing Dewars, since 1) it weldable, 2) it can give light weight Dewar, 3) it is unbreakable, 4) It can reflect heat radiation 5) it has good thermal conductivity 6) Thermal expansivity is very low with cryogenic temperatures, 7) it outperforms other metals for Dewar making and 8( it has good resistance to breaking
The materials used for cryostats should be robust and obey low thermal conductivity. The last requirement is valid only for material of neck. The stainless still is one of such material, but there are examples when the liquid nitrogen Dewars were made of aluminum alloy with the neck from the glass fiber.
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