A team led by the Pretzker Institute for Molecular Engineering at the University of Chicago discovered materials that violate the traditional rules of thermal and mechanical physics, as they shrink when heated and expanded under pressure, in what indicates an unconventional internal structure, which represents great progress in basic sciences.
According to the study Published in the journal Nature, researchers used accurate temperature and pressure control devices such as “diamond cells”, with accurate imaging techniques to observe the legendary and thermal changes together for this substance.
The team has found that the inner crystal core reacts in a way that makes the atoms move and rearrange them when changing the temperature or pressure, leading to this unexpected behavior.
Semi -stable materials
This newly discovered substance joins the semi -stable materials category, which are materials found in a temporary state of balance, that is, it is not in the lowest possible energy (stable condition), but in this case it remains for a long time without changing on its own, and it can return to its stable condition only if it is stimulated by an external factor (such as heat, pressure or radiation).
Diamonds are an example of these materials, as it is an unstable carbon form, while the stable shape of the carbon is graphite, but diamonds may remain thousands of years without automatically turning into a stable shape, and it needs high temperatures and pressure to turn.
To understand instability, imagine a ball on a hill, the ball is not stable at the top of the hill and is ready to fall immediately, and as soon as you leave it with your hands, you roll down to the bottom to settle and stand.
The case of “almost stability” falls between the two cases (the top of the hill and the bottom of the hill), in which case it represents a ball near the top of the hill, but it is hidden in a cavity.
Stretch
As for the new material, it has a very special feature of these substances, which is negative thermal expansion.
Thermal expansion is a well -known phenomenon. When the material heats it, its size is expanded and the size grows because the molecules move quickly and move away from each other, but in the negative thermal expansion the opposite occurs as the material shrinks when heating!
This seems intuitive but real, and it has many reasons, including the unconventional movement of the atoms. In some materials, the atoms not only move forward and backward, but rather move at an angle, or in a networking manner that presses the composition instead of expanding it.
The atoms can be shaken in a way that “pulls” the neighbors inward when heating, besides these materials possess an open and open billion (such as cages), so that they can be folded or closed when heated.
Wide applications
According to the study, these materials can revolutionize batteries technology by restoring old electric car batteries to a new similar performance. After years of driving, the electric car that is supposed to travel 600 km with one charge, will weaken and limit it between 300 and 450 km, but with pushing the materials to its stable condition, the maximum distance can be restored to the same situation when the cars were new.
These materials can also contribute to the development of new batteries with higher qualitative energy, and enable future applications such as structural batteries.
Structural batteries represent an innovative mixture of working as a chemical battery, and work as part of the construction structure in terms of geometric aspects, storing energy such as traditional batteries, but they carry structural loads such as solid structures (the outer structure of the plane, the body of the car … etc.).