Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Materials for Future Green Tech Devices

17.07.2014

Comprehensive analysis in the journal "APL Materials" provides blueprint for making thermoelectric materials that convert heat and electricity with greater efficiency

From your hot car to your warm laptop, every machine and device in your life wastes a lot of energy through the loss of heat. But thermoelectric devices, which convert heat to electricity and vice versa, can harness that wasted heat, and possibly provide the green tech energy efficiency that's needed for a sustainable future.


APL Materials

Schematic illustration of the multilayer configuration with layers of different porosity (graded porous material). Each layer contains a concentration of periodically distributed pores of the same size (only one set of such particles is shown).

Now, a new study shows how porous substances can act as thermoelectric materials—pointing the way for engineering the use of such materials in thermoelectric devices of the future.

About 70 percent of all the energy generated in the world is wasted as heat, said Dimitris Niarchos of the National Center for Scientific Research Demokritos in Athens, Greece. He and Roland Tarkhanyan, also of NCSR Demokritos, have published their analysis in the journal APL Materials, from AIP Publishing.

To create the technology needed to capture this heat, researchers around the world have been trying to engineer more efficient thermoelectric materials. One promising material is one that's filled with tiny holes that range in size from about a micron (10-6 meters) to about a nanometer (10-9 meters). "Porous thermoelectrics can play a significant role in improving thermoelectrics as a viable alternative for harvesting wasted heat," Niarchos said.

Heat travels through a material via phonons, quantized units of vibration that act as heat-carrying particles. When a phonon runs into a hole, it scatters and loses energy. Phonons thus can't carry heat across a porous material as efficiently, giving the material a low thermal conductivity, which turns out to increase the efficiency of heat-to-electricity conversion. The more porous the material, the lower the thermal conductivity, and the better it is as a thermoelectric material.

So far, however, researchers have yet to systematically model how porous materials maintain low thermal conductivity, Niarchos said. So he and Tarkhanyan studied the thermal properties of four simple model structures of micro-nano porous materials. This analysis, Niarchos says, provides a rough blueprint for how to design such materials for thermoelectric devices.

Overall, the researchers found that the smaller the pores and the closer they're packed together, the lower the thermal conductivity. Their calculations match data from other experiments well, Niarchos said. They also show that, in principle, micro-nano porous materials can be several times better at converting heat to electricity than if the material had no pores.

The first model describes a material filled with holes of random sizes, ranging from microns to nanometers in diameter. The second is one with multiple layers in which each layer contains pores of different size scales, which gives it a different porosity. The third is a material that's composed of a three-dimensional cubic lattice of identical holes. The fourth is another multilayered system. But in this case, each layer contains a cubic lattice of identical holes. The size of the holes is different in each layer.

According to the analysis, the first and fourth models have lower thermal conductivities than the second. The third model seems to be the best one, as it also has a lower thermal conductivity than the fourth model.

Except for the first model, however, all the models aren't practical because they represent idealized situations with a perfect arrangement of pores, Niarchos said. It's also practically impossible to create precisely equal-sized pores. The first model is thus the most realistic.

Still, he said, all the distinct models demonstrate the importance of porosity in thermoelectric materials. Built upon simple and general analytical formulas, the models allow for a very fast and accurate computation of the effective lattice thermal conductivity of a porous material and the systematic analysis of such materials.

The article, "Reduction of thermal conductivity in porous ‘gray’ materials," is authored by Roland H. Tarkhanyan and Dimitris Niarchos. It appears in the journal APL Materials on July 15, 2014. After that date, it can be accessed at: http://scitation.aip.org/content/aip/journal/aplmater/2/7/10.1063/1.4886220

ABOUT THE JOURNAL
APL Materials is a new open access journal featuring original research on significant topical issues within the field of materials science. See: http://aplmaterials.aip.org

Jason Socrates Bardi | newswise

Further reports about: AIP APL Devices Physics conductivity electricity heat lattice materials models nanometers pores porous

More articles from Materials Sciences:

nachricht Diamonds get more beautiful with laser lamps
16.04.2015 | Heraeus Noblelight GmbH

nachricht X-ray study images structural damage in lithium-ion batteries
15.04.2015 | Deutsches Elektronen-Synchrotron DESY

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Astronomers reveal supermassive black hole's intense magnetic field

Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a supermassive black hole in a distant galaxy

Astronomers from Chalmers University of Technology have used the giant telescope Alma to reveal an extremely powerful magnetic field very close to a...

Im Focus: A “pin ball machine” for atoms and photons

A team of physicists from MPQ, Caltech, and ICFO proposes the combination of nano-photonics with ultracold atoms for simulating quantum many-body systems and creating new states of matter.

Ultracold atoms in the so-called optical lattices, that are generated by crosswise superposition of laser beams, have been proven to be one of the most...

Im Focus: UV light robot to clean hospital rooms could help stop spread of 'superbugs'

Can a robot clean a hospital room just as well as a person?

According to new research out of the Texas A&M Health Science Center College of Medicine, that is indeed the case. Chetan Jinadatha, M.D., M.P.H., assistant...

Im Focus: Graphene pushes the speed limit of light-to-electricity conversion

Researchers from ICFO, MIT and UC Riverside have been able to develop a graphene-based photodetector capable of converting absorbed light into an electrical voltage at ultrafast timescales

The efficient conversion of light into electricity plays a crucial role in many technologies, ranging from cameras to solar cells.

Im Focus: Study shows novel pattern of electrical charge movement through DNA

Electrical charges not only move through wires, they also travel along lengths of DNA, the molecule of life. The property is known as charge transport.

In a new study appearing in the journal Nature Chemistry, authors, Limin Xiang, Julio Palma, Christopher Bruot and others at Arizona State University's...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

HHL's Entrepreneurship Conference on FinTech

13.04.2015 | Event News

World Conference On Regenerative Medicine 2015: Registration And Abstract Submission Now Open

25.03.2015 | Event News

University presidents from all over the world meet in Hamburg

19.03.2015 | Event News

 
Latest News

Engineer Improves Rechargeable Batteries with MoS2 Nano 'Sandwich'

17.04.2015 | Power and Electrical Engineering

Comparing Climate Models to Real World Shows Differences in Precipitation Intensity

17.04.2015 | Earth Sciences

A blueprint for clearing the skies of space debris

17.04.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>