#phase change materials

[materialsscienceandengineering]

Making heat behave like data

A reconfigurable device breaks the usual link between heat absorption and emission, enabling direction-controlled thermal radiation for futu

(Nanowerk News) Normally, a material absorbs and emits heat in a linked way: a surface that absorbs heat well at a certain wavelength and direction will also emit heat in the same ways. This fundamental relationship, known as reciprocity, limits our ability to independently control heat absorption and heat emission. But if absorption and emission could be separated, engineers could design devices that absorb heat from one direction while emitting it in another. By ‘steering’ thermal energy, they could create more efficient thermal management, energy conversion, infrared sensing, and thermal communication technologies.

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[bumblebeeappletree]

The future of insulation and hot water? A water heater like you've never seen. When it comes to heating and cooling our homes, or producing hot water, a heat pump is one of the most energy efficient ways to go. However, there’s a category of material that can store heat for a water heater, or in insulation to reduce your heating and cooling needs. Phase change materials (PCM) have high energy storage properties, can be easy to install, and don’t take up a lot of space. We're essentially talking about a heat battery. Are phase change materials a good option for our homes? Let’s see if we can come to a decision on this.

Check out Belinda Carr’s excellent videos on building science: https://youtu.be/tZtfieRzdl4

And eFIXX Energy: https://www.youtube.com/watch?v=t1x4J...

Watch How the CO2 battery could be the future of energy storage? https://youtu.be/GSzh8D8Of0k?list=PLn...

Video script and citations:

https://undecidedmf.com/youve-never-s...

Follow-up podcast:

Video version - https://www.youtube.com/channel/UC4-a...

Audio version - http://bit.ly/stilltbdfm

[materialsscienceandengineering]

Antimony's bonding characteristics offer insights into phase change materials

A new study that provides unprecedented insights into the chemical bonding of antimony could have a profound impact on materials research. The collaboration between scientists from Leipzig University, RWTH Aachen University and the DESY synchrotron in Hamburg combined experimental measurements with theoretical calculations. The findings will help scientists to better understand phase change materials and, in particular, improve their application in data storage and thermoelectrics. The research has now been published in Advanced Materials. The study combined experimental measurements with theoretical calculations, with the aim of analyzing the nature and strength of the chemical bonding in antimony. "The strength of a bond depends directly on the distance between the atoms," says Professor Claudia S. Schnohr of the Felix Bloch Institute for Solid State Physics at Leipzig University, adding that comparisons with other materials such as metals and semiconductors show that this distance dependence is characteristic of the type of chemical bond.

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[materialsscienceandengineering]

Aerogel-based phase change materials improve thermal management, reduce microwave emissions in electronic devices

Electronic devices are getting more and more complex as they are built to carry out an ever-increasing number of functions. This can be seen in the increased functionality in our personal devices such as our phones, tablets and watches, let alone in industrial devices. However, their growing complexity can lead to performance and safety issues. These issues include device overheating or emitting microwaves that can result in health issues and that can reduce a device's performance and interfere with other devices. Chinese scientists from Beijing Normal University have been working on building shielding for electronic devices using multifunctional composite phase change materials (PCMs) to address these performance issues. PCMs are man-made materials built by combining different types of elements, allowing the creation of a new material with very specific purpose driven characteristics. In this case, the researchers are looking to improve thermal management, solar-thermal conversion and microwave absorption in the electronic devices.

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[materialsscienceandengineering]

New candidate for universal memory is fast, low-power, stable and long-lasting

We are tasking our computers with processing ever-increasing amounts of data to speed up drug discovery, improve weather and climate predictions, train artificial intelligence, and much more. To keep up with this demand, we need faster, more energy-efficient computer memory than ever before. Researchers at Stanford have demonstrated that a new material may make phase-change memory—which relies on switching between high and low resistance states to create the ones and zeroes of computer data—an improved option for future AI and data-centric systems. Their scalable technology, as detailed in Nature Communications, is fast, low-power, stable, long-lasting, and can be fabricated at temperatures compatible with commercial manufacturing. "We are not just improving on a single metric, such as endurance or speed; we are improving several metrics simultaneously," said Eric Pop, the Pease-Ye Professor of Electrical Engineering and professor, by courtesy, of materials science and engineering at Stanford. "This is the most realistic, industry-friendly thing we've built in this sphere. I'd like to think of it as a step towards a universal memory."

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[materialsscienceandengineering]

Engineers weave advanced fabric that can cool a wearer down and warm them up

Textile engineers have developed a fabric woven out of ultra-fine nano-threads made in part of phase-change materials and other advanced substances that combine to produce a fabric that can respond to changing temperatures to heat up and cool down its wearer depending on need.

Materials scientists have designed an advanced textile with nano-scale threads containing in their core a phase-change material that can store and release large amounts of heat when the material changes phase from liquid to solid. Combining the threads with electrothermal and photothermal coatings that enhance the effect, they have in essence developed a fabric that can both quickly cool the wearer down and warm them up as conditions change.

A paper describing the manufacturing technique appeared in ACS Nano on August 10.

Many occupations, from firefighters to farmworkers, involve harsh hot or cold environments. Cold storage, ice rinks, steel forges, bakeries, and many other job sites require workers to make frequent transitions between different and sometimes extreme temperatures. Such regular temperature changes are not only uncomfortable but can cause illness or even injury, and require a cumbersome constant change of clothing. A sweater will keep a worker warm in a cold meat locker, but could overheat the same worker when they leave that space.

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[materialsscienceandengineering]

A machine learning–based tool to model phase-change memory materials

Computer simulations can greatly contribute to the study of new promising materials for technological applications. These include so-called phase-change materials (PCMs), substances that release or absorb thermal energy while melting and solidifying, which are promising for the development of memory components. Researchers at University of Oxford and Xi'an Jiaotong University in China recently developed a machine learning model that could help to simulate these materials at an atomic scale, realistically replicating the conditions under which devices operate. Their model, presented in a paper published in Nature Electronics, can produce detailed simulations at a high speed, helping users to better understand the processes unfolding in devices based on PCMs. "Our paper describes a computer simulation approach for modeling PCMs, which are used in digital data storage and processing," Volker Deringer, one of the researchers who carried out the study, told Tech Xplore. "Simulations of this type, called 'molecular dynamics' (MD), have typically been used to describe a few hundred atoms or so, and those small-scale simulations have already been very useful in the PCM community.

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[materialsscienceandengineering]

Glasses: GeSbTe

Not necessarily a glass - or, at least, not always a glass - germanium-antimony-tellurium (GeSbTe or GST) is a phase-change material capable of reversibly switching between its amorphous and crystalline forms. Composed of germanium, antimony, and tellurium, it’s actual composition can vary between compositions such along the GeTe-Sb2Te3 line in the ternary phase diagram shown above (such as Ge2Sb2Te5, GeSb2Te4, and GeSb4Te7).

Certain properties of amorphous GST can very vastly from the same properties of crystalline GST, largely due to the change in the chemical bonds in the material after the phase transition. Its amorphous structure has high resistance while the crystalline phase has low resistance. Currently, GST has the fastest phase transition measured in memory devices thus far. As an amorphous material, it is classified as a chalcogenide glass with a glass transition temperature of around 100°C.

Current applications of GST mostly take advantage of its phase-change properties, such as data storage applications known as phase-change memory. Potential future applications of such phase change materials include flexible displays, logic devices, and plasmonic-based circuits, among others.

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