A team of researchers in the United States have defied what we have always believed to be true about the intimate relationship between electricity conduction and heat. Conductors are no longer behaving as some physical laws stated.
In school, we learn that good conductors of electricity are also good conductors of heat. Materials such as gold, silver, and copper have both abilities—heating up and conducting electricity in a fairly easy way. It’s like an implicit rule that we always have in the back of our heads, even if we may not think of ourselves as interested in physics and thermodynamics. For example, for survival purposes, we don’t touch wires that we know are conducting large amounts of electricity.
So, we can say we have a correlation of this kind: creation of energy = creation of heat. We even have laws supporting this, such as the Wiedemann-Franz Law, which in states, in short, what we just discussed—good electricity conductors are good conductors of heat. We can even make use of the Joule effect that approaches the way that some part of the energy traveling in a conductor will be lost in heat due to electrons crashing into atoms of the material.
The vanadium dioxide (VO2) provides a completely different perspective to electricity conduction and shakes the physics world by demonstrating that there is a different path, with some specific conditions, (this is how it always works, right?) to conducting energy without heat. So how does this work?
Vanadium dioxide (VO2) has the strange ability of switching from a transparent insulator to a conductive metal at the temperature of 67 degrees Celsius (152 degrees Fahrenheit).
This was completely unexpected, as explained by lead researcher Junqiao Wu:
“It shows a drastic breakdown of a textbook law that has been known to be robust for conventional conductors. This discovery is of fundamental importance for understanding the basic electronic behavior of novel conductors.”
This “drastic breakdown,” according to Wu, may imply making a better use of some materials that in another context wouldn’t be useful anymore, such as converting wasted heat from engines and appliances back into electricity.
“The electrons were moving in unison with each other, much like a fluid, instead of as individual particles like in normal metals,” Wu said.
Imagine a turbulent and laminar flow in a river or in a waterfall. Normal metals would behave as the Niagara Falls, with water particles colliding into each other in a violent way (creating heat), while vanadium dioxide behaves instead as a calm and peaceful lake, flowing in a way that you can hardly perceive (not creating heat).
Interestingly, vanadium dioxide, also possesses other properties such as being able to “tune it” in a way that, mixed with other materials, the heat and electricity conducted can be manipulated and having the ability of becoming “invisible” by not being detected at temperatures around 30 degrees celsius (86 degrees Fahrenheit), but then reflecting infrared light above 60 degrees Celsius (140 degrees Fahrenheit). That would still be invisible to us because it wouldn’t be inside of the Visible Spectrum.
As usual, there is still some more work to do before developing this into real-world applications, but this is an exciting advancement for the electricity field.
» Source » By Manuel García Aguilar