Why is this technology stagnant for over half a century ?

[Externet]

What are the hurdles that prevent from coming up with at least a working gadget beyond keeping it just as a curiosity for scratching heads ?

 

How would you design a useful machine from this 'borrowed' technology nitinol (Nickel Titanium Naval Ordnance Laboratory) ?

 

Is there a way to formulate the alloy for smaller delta temperatures ?

 

Please ignore the "Free" word in the title below. Does not apply.

 

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You will read between the lines it is a 'Godsent' material... Yeah, call it 'God'

 

 

Edited February 14, 2013 by Externet

[Enthalpy]

Shape memory alloys are used the big way! They make surgical implants, superelastic frames for glasses, actuators to release satellites from launchers...

 

If you mean specifically the thermal engine: it's not used because of its horrible efficiency of ~1% at best. Gas or vapour engines achieve commonly 30-40% efficiency. This is essentially because E is a few times PV in a gas while it's many times PV in a solid. In other words, a gas expands a lot at heat, so mechanical work can be harvested, while you invest much heat for nothing in a solid.

 

A competitor to shape memory materials is the "wax thermostat" (search keywords), far cheaper and with similar (in)efficiency and force vs move, usable over a smaller temperature range.

 

Shape memory engines can be imagined where efficiency isn't essential but simplicity is. One attempt was to produce electricity from the residual heat of car exhausts - not to make substantial propulsion power, but to replace the alternator.

 

Smaller temperature difference: is there enough pressure from potential users on manufacturers? For electricity-driven actuators it's not so important. For surgery it could be, but bio-compatibility is the absolute criteria there.

[Przemyslaw.Gruchala]

In most of these devices on video metal is put to hot water, changing shape, then put to cold water and changing shape again.

 

But something has to heat water in the first place.

 

Hot water is cooling all the time, giving fraction of its energy to either piece of metal, and air.

 

And reverse process happens with cold water.

 

If we won't heat hot water and keep cool cold water, their temperature will suddenly will go to the same point. And device will stop moving.

Edited February 16, 2013 by Przemyslaw.Gruchala

[nukngnir]

This technology hasn't been stagnant at all! The main problem has been that it's such an unusual and incredibly complex material that it has taken fifty years of research just to get a good grasp on the material itself. It wasn't until the late 1990's when the atomic force microscope (AFM) became readily available that some real break-throughs started to occur. The National Science Foundation is still pouring millions of dollars each year into researching the material aspects of nitinol. While there is still a whole world of improvement to be made in understanding the material before mechanical engineers can begin doing a good job of building heat engines with it, we're a whole lot closer. If you read the literature published by the scientists interviewed in this video, you'll see that they really had more questions than answers. My guess is that you'll start seeing more and more companies build something useful out of it.

 

The most recent development that I'm aware of is an air temperature generator by Kellogg's Research Labs url removed by mod