[time-nuts] OCXO housings - Why copper and not iron/steel?

[Richard (Rick) Karlquist]

Yes, we want conductivity, and not heat capacity.

On 10/30/2020 3:06 PM, Luiz Alberto Saba wrote:
> If my memory serves me, copper has the better conductivity of all the periodic table...
> 

Actually, carbon is at the top of the list.
Then silver, then copper.

Rick N6RK


> Enviado do meu iPhone
> 
>> Em 30 de out. de 2020, à(s) 18:56, Attila Kinali <attila at kinali.ch> escreveu:
>>
>> Moin,
>>
>> I have been looking at heat capacities of different materials
>> lately. One thing that struk me odd is, that the volumetric
>> heat capacity of copper, which is the thing that most people
>> use when building something that needs to have high heat capacity
>> to get stable temperature, has only a volumetric heat capacity
>> of 3.45 J/(cm^3·K). Meanwhile, the much cheaper iron has
>> a volumetric heat capacity of 3.53 J/(cm^3·K) and steel
>> even 3.75 J/(cm^3·K).
>>
>> In an OCXO, which is generally size limited, getting the most
>> heat capacity in the limited volume would be the main goal,
>> wouldn't it? Also optimizing for price would be a major thing.
>> I can understand that iron is probably not the right choice
>> due to its tendency to oxidize. But using a soft (annealed) steel
>> would be easy to machine, cheaper per piece and give almost 10%
>> higher heat capacity in the same volume.
>>
>> So why do people choose copper instead of steel?
>>
>>
>>             Attila Kinali
>>
>> PS: Fun fact: Water has a volumetric heat capacity of 4.18 J/(cm^3·K)
>> at 25°C. We should fill OCXOs with water! :-D
>>
>> -- 
>> <JaberWorky>    The bad part of Zurich is where the degenerates
>>                 throw DARK chocolate at you.
>>
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