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# What is the material with the largest thermal expansion? Answered

I've looked many places online, but none seem to give me the Solid with the largest thermal expansion. It shouldn't be too expensive or hard to come by and it would be great if it could be purchased pre-cut into a square or at least could be cut by hand. This is very important for my upcoming project that I would love to share with you! Thank you so very much!

PS: in the length of 6cm and a temperature difference of 41 degrees Celsius (or Kelvin) this material needs to expand by at least 2mm

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I believe it would depend on several factors

>Working tempreature

>weather its a wire or a sheet like material

>the strain the material is subjected to.

All said I think you should go with aluminum or zinc

Go to a library and get an engineering materials values book. It will list alpha (linear expansion coefficient) and beta (volumetric expansion coefficient ). Larget is better for you. Also kelvin is a starting point not a delta so it would be degrees c not k.

Side comment: The kelvin is the SI unit of temperature. It is a "delta," with the (arbitrary!) zero set to "absolute zero" (technically kelvins are referenced to the triple-point of water, assigned the value 273.16). Degrees celsius have the same magnitude as kelvins, but a different zero.

Resolution 3 would seem to favour me, wikipedia you. And btw you are off by .01 degrees

http://en.wikipedia.org/wiki/Triple_point_of_water#Triple_point_of_water

No, I'm not wrong.

Resolution three states, "that the unit of thermodynamic temperature and the unit of temperature interval are one and the same unit, which ought to be denoted by a single name and a single symbol." The kelvin is the unit of interval, according to Resolution 3 (1967/68).

The reference temperature for kelvins is the triple point, which is assigned the value of 273.16 K. That value is 0.01 kelvins above the freezing point of water at STP, which is 273.15 K.

Kelvins are never referred to as "degrees."

Always seemed dumb that they ARE the same unit, for different jobs.

Hmmm; I don't agree. Dimensionally, x and dx must have the same units, or you can't measure slopes sensibly.

Err, You're making my point, so we should have "degrees K" and "K"

Try reading my comment and resolution three again.

I did. You claimed that kelvins are "not a delta." I quoted Resolution 3 (1967/68), which is abundantly clear that kelvin revers to both the value and the interval. In fact, I quoted the exact text from the resolution above. So. Try reading my comment and resolution 3 (1967/68) again.

1) I never said you were wrong. So no, you did not reread my comment, at least not with any understanding.
2) pre 1967 °C was the delta K was the starting point. °C is still allowed accruing to the notes.
3) Plonk.

According to your postscript, the actual expansion you want is like:
2/60 = 0.0333 = 3.33%  at a ΔT of 41 C

which corresponds to a coeff of linear expansion of:
2/60/41 = 8.13e-4/degC = 813e-6 /degC

Then if you go look at this table:
http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

It looks like the biggest numbers there are only like 200e-6/degC, for materials like "polyethylene" and "extruded acrylic".  Also keep in mind the absolute temperatures involved are important too.  If the high temp in your ΔT is near 100 degC or so, these materials might be getting weak and squishy as they expand.

BTW, if you just want a displacement caused by temperature, there are other tricks more clever than just an expanding rod. Like this:
http://en.wikipedia.org/wiki/Bimetallic_strip
They used to put bimetallic strips in thermostats, in the days before temperature sensing electronics.

Water, if you put it in a narrow vessel will exhibit large movements on application of heat.

I thinks you will be pushing it to find something, fairly available, cheap and give the properties you need. Re design and use something simpler.

Water when solid (as stipulated by the question the material should be solid) does not show standard linear expansion depending on the range alpha and beta could be positive or negative.

Have you looked at shape-memory alloys or waxes ?