#elastocaloric

Developing a futuristic elastomer with ultrahigh strain-induced crystallization

Strain-induced crystallization can strengthen, toughen, and facilitate an elastocaloric effect in elastomers. The resulting crystallinity can be induced by mechanical stretching in common elastomers that are typically below 20%, with a stretchability plateau. In a new report now published in Science Advances, Chase M. Hartquist and a team of scientists in mechanical engineering and materials sciences at MIT and Duke University in the U.S. used a class of elastomers formed by end-linking to achieve a percentage of strain-induced crystallinity. The deswollen and end-linked star elastomer abbreviated as DELSE reached an ultrahigh stretchability to scale, beyond the saturated limit of common elastomers, to promote a high elastocaloric effect with an adiabatic temperature change.

Novel durable copper-aluminum-zinc shape memory alloys for energy-efficient refrigeration

The elastocaloric effect is a phenomenon where a material displays a temperature change when it is exposed to a mechanical stress. The change in temperature occurs due to an entropy difference resulting from a martensitic transformation accompanied by material's crystal structure change under stress.

An analogous effect is observed when the rubber band is stretched: its polymer chains line up in an ordered manner, causing its entropy to decrease. This leads to the rubber band discharging heat to its surroundings and becoming warmer. When the rubber band is released, the opposite occurs, and the rubber band cools down.

Like rubber bands, metallic superelastic shape memory alloys (SMAs) can also utilize the elastocaloric effect for cooling. Copper (Cu)-based SMAs consisting of Cu, aluminum (Al), and zinc (Zn) are particularly promising due to their low cost and modest stress demands for triggering the temperature lift. However, Cu-Al-Zn SMAs suffer from cyclical fatigue issues as their coarse crystal grains and numerous grain boundaries are susceptible to fracture from repeated expansion and contraction.

Squeezable Metal Offers a Greener Approach to Refrigeration

A system built around a metal that gains and loses heat when compressed could lead the way to the commercialization of chemical-free refrigeration technology. 

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Refrigeration systems that use materials that cool in response to an applied electric, magnetic, or mechanical force offer environmentally friendly alternatives to the greenhouse-gas-leaking ones found in most homes and factories (see Feature: In Hot Pursuit of 21st Century Cooling). Now researchers have demonstrated a cost-effective, scalable version of one of these so-called “caloric cooling” systems [1]. Their approach, which uses a material that responds to a mechanical force, exceeds performance records set by methods that rely on magnetic fields. The researchers say their technology is also much less expensive to make and to operate and could be ready for commercial use within a year. 

In Hot Pursuit of 21st Century Cooling

Caloric materials could potentially replace conventional cooling systems with planet-friendly technology, but making them cheap and practical is a major challenge.

It’s not exactly a looker, but a five-foot tall, A-shaped engineering rig at the University of Maryland’s College Park campus could potentially evolve into a partial solution for a warming planet. At the heart of this refrigeration prototype is a material that gets cold just by being squeezed and released. It’s one of many so-called caloric materials that could provide for the world’s rapidly expanding cooling needs without exacerbating climate change. These materials cool in response to pressure, electric fields, or magnetic fields. Completely absent from this solid-state cooling concept are the volatile liquid refrigerants that are the lifeblood for just about all current cooling technologies and that are important contributors to global warming.

As the world’s billions of air conditioners, refrigerators, chillers, and dehumidifiers age and become throwaways, their refrigerants mostly leak into the atmosphere, where they trap solar radiation far more powerfully than carbon dioxide. And every day, the increasingly sweaty citizens of the planet install about 260,000 new air-conditioning (AC) units. At that rate, the number of ACs will likely balloon from the current 1.2 billion or so to 4.5 billion by 2050 [1]. The vapor-compression systems inside cooling appliances already consume about 20% of global electricity, the generation of which is a top source of humanity’s carbon dioxide emissions. Without a planet-wide redo of cooling technology, the explosive growth expected in cooling demand and supply is destined to make global warming worse. And that, in turn, will increase demand for more cooling.

Experimental Methods For Investigation Of Shape Memory Based Elastocaloric Cooling Processes And Model Validation.

If you struggle to remember names, numbers, faces, important dates such as birthdays and anniversaries? At the end of the program, the participants performed slightly better than a control group on a memory test. Even take the concepts you’re learning and reason forward with them; apply them to imagined novel situations, which creates more neural connections to reinforce the memory. There are…

Experimental Methods For Investigation Of Shape Memory Based Elastocaloric Cooling Processes And Model Validation.

If you struggle to remember names, numbers, faces, important dates such as birthdays and anniversaries? At the end of the program, the participants performed slightly better than a control group on a memory test. Even take the concepts you’re learning and reason forward with them; apply them to imagined novel situations, which creates more neural connections to reinforce the memory. There are…