. 24/7 Space News .
TECH SPACE
Sugar-based carbon hollow spheres that mimic moth eyes
by Staff Writers
Washington DC (SPX) Jan 07, 2016


Sample of self-ordering of Christmas cake balls decoration in Petri dish. Image courtesy D. Bychanok/ Research Institute for Nuclear Problems BSU, Belarus. For a larger version of this image please go here.

Antireflective coatings are used to cut surface glare in everything from eyeglasses and camera lenses to solar cells, TV screens and LED devices. Now researchers from Research Institute for Nuclear Problems of Belarusian State University in Belarus and Institut Jean Lamour-Universite de Lorraine in France have developed a novel, low-cost, ultra-lightweight material that could be used as an effective anti-reflective surface for microwave radiation based on the eyes of moths.

The eyes of moths are covered with a periodic, hexagonal pattern of tiny bumps smaller than the wavelength of the incident light. They act as a continuous refractive index gradient, allowing the moths to see at night and avoid nocturnal predators, like the bat.

The physiology also makes the moth eye one of the most effective antireflective coatings in nature. It has already successfully been mimicked by scientists for developing high-performance antireflective coatings for visible lights - albeit coatings that are often expensive to fabricate and difficult to customize.

The new material cuts down reflections from microwaves rather than from visible light - invisible energy from a different part of the energy spectrum. Blocking microwave reflection is an important application for precise microwave measurements, and the coating may be used as a radar absorbing material in stealth technology, a technique that makes make an airplane invisible to radar, or police traffic radar that uses microwaves to measure car speed.

Described this week in the journal Applied Physics Letters from AIP Publishing, the new technology is based on a monolayer of hollow carbon spheres packed in two dimensions and has been demonstrated to be able to achieve almost perfect microwave absorption, i.e. near 100 percent absorption of microwaves in the Ka-band (26-37 gigahertz) frequency range, the first antireflective material to achieve this.

"Based on the experimental and modeling results, we found that using hollow carbon spheres with larger spherical diameters and optimal shell thickness it is possible to achieve almost perfect microwave absorption," said Dzmitry Bychanok, the primary author and a researcher at the Research Institute for Nuclear Problems of Belarusian State University in Belarus.

The novel coating material they produced can be completely derived from biological resources, he added, which may make it greener, lower-cost, easier to fabricate and ultra-lightweight compared to conventional antireflective coatings.

How they Made the Material
Hollow carbon spheres with uniform diameter can be used for producing ordered periodic structures. To mimick the structure of moth eyes, the researchers compactly packed hollow carbon spheres in two dimensions to form a hexagonal-patterned monolayer, which is a strong, electrically conductive coating material as well.

"You can picture the geometry of the hollow sphere monolayer as that of Christmas cake decoration balls compactly filled in a Petri dish - filling a flat surface with identical balls will lead to a spontaneous hexagonal self-ordering," Bychanok explained. "The spatial distribution of the hollow sphere monolayer is ideally hexagonal, but in practice it is more in-between cubic and hexagonal. The thickness of the monolayer is in the range of one to two millimeters."

In the experiment, carbon hollow spheres were fabricated by a template method based on fish eggs or sugar-based polymer beads with certain diameters. Specifically, the researchers coated the bio-based template spheres with sugar, then "pyrolysed" them - a chemical modification based on thermally decomposing the resultant spheres in inert atmosphere. During such heating, the sugar coating was converted into char at the surface of the spheres, while the inner template sphere was largely destroyed and decomposed into gas, leaving a hollow carbon sphere.

Using theoretical modeling based on long-wave approximation and experimental measurements, the team studied the electromagnetic properties of monolayers based on different-parameter hollow spheres in Ka-band (microwave) frequency. The result showed that, for electromagnetic applications requiring high absorption, the most preferable hollow spheres are those with larger radii or diameters. Additionally, each value of hollow sphere radius has an optimum shell thickness to achieve the highest absorption coefficient.

"Our study showed that the monolayer formed by spheres with a radius of six millimeters and a shell thickness of about five micrometers enables the highest microwave absorption coefficient, which is more than 95 percent at 30 gigahertz," said Bychanok.

Bychanok said the work pointed out that moth-eye-like two-dimensional ordered structures based on hollow conducting spheres are promising systems for microwave radiation absorption applications. The team's next step is to investigate and develop three-dimensional periodic structures for an effective manipulation of microwave radiations.

The article "Hollow carbon spheres in microwaves: bio inspired absorbing coating" is authored by D. Bychanok, S. Li,A. Sanchez-Sanchez, G. Gorokhov, P. Kuzhir, F.Y. Ogrin, A. Pasc,T. Ballweg, K.Mandel, A. Szczurek, V. Fierro and A. Celzard. It will be published in the journal Applied Physics Letters on Jan.5, 2015 (DOI: 10.1063/1.4938537).


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
American Institute of Physics
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TECH SPACE
Adjustable adhesion power
London, UK (SPX) Jan 05, 2016
Imagine a new type of tyres whose structure has been designed to have greater adhesion on the road. Quite a timely discussion during the long winter nights. French physicists have now developed a model to study the importance of adhesion in establishing contact between two patterned, yet elastic, surfaces. Nature is full of examples of amazing adjustable adhesion power, like the feet of ge ... read more


TECH SPACE
South Korea to launch lunar exploration in 2016, land by 2020

Death rumors of Russian lunar program 'greatly exaggerated' - Deputy PM

Russia Postpones Plans on Extensive Moon Exploration Until 2025

Rare full moon on Christmas Day

TECH SPACE
Boulders on a Martian Landslide

NASA suspends March launch of InSight mission to Mars

University researchers test prototype spacesuits at Kennedy

Marshall: Advancing the technology for NASA's Journey to Mars

TECH SPACE
Gadgets get smarter, friendlier at CES show

Congress to NASA: Hurry up on that 'habitation augmentation module'

NASA Reaches New Heights

Astronauts Tour Future White Room, Crew Access Tower

TECH SPACE
China launches HD earth observation satellite

Chinese rover analyzes moon rocks: First new 'ground truth' in 40 years

Agreement with Chinese Space Tech Lab Will Advance Exploration Goals

China launches new communication satellite

TECH SPACE
NASA Delivers New Video Experience On ISS

British astronaut dials wrong number on Xmas call from space

Space Station Receives New Space Tool to Help Locate Ammonia Leaks

Two whacks is all it takes for spacewalk repair

TECH SPACE
Russian Proton-M Carrier Rocket With Express-AMU1 Satellite Launched

45th Space Wing launches ORBCOMM; historically lands first stage booster

SpaceX rocket landing opens 'new door' to space travel

NASA orders second Boeing Crew Mission to ISS

TECH SPACE
Nearby star hosts closest alien planet in the 'habitable zone'

ALMA reveals planetary construction sites

Monster planet is 'dancing with the stars'

Exoplanets Water Mystery Solved

TECH SPACE
Chameleons deliver powerful tongue-lashing

Transition metal catalyst prompts 'conjunctive' cross-coupling reaction

Coulomb blockade in organic conductors found, a world first

Adjustable adhesion power









The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us.