Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A coating that protects against heat and oxidation

24.11.2014

Researchers have developed a coating technique that they plan to use to protect tur- bine engine and waste incinerator components against heat and oxidation. A topcoat from micro-scaled hollow aluminium oxide spheres provides heat insulation, in the lab, already proved more economical than conventional techniques.

Gases don’t conduct heat as well as solids do. Cellular or aerated concretes take advantage of this effect, which experts call “gas-phase insulation”.


Hollow balls of aluminum oxide are fi lled with gas. Scientists have developed an economical way of manufacturing these insulators.

© Fraunhofer ICT

The heat barrier is achieved by air encased in the cavities of the concrete. But gas-phase insulation has far greater potential than keeping our homes warm. It can also be used to protect turbine engine and waste incinerator components when subjected to intense heat. All you need to do is transfer this effect to a coating that is just a few hundred micrometers thick.

Temperature differences of over 400 degrees Celsius

Scientists at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal have not only done just that, they’ve also done it in a particularly economical way. They’ve designed a coating that consists of an outer topcoat from conjoined aluminium oxide spheres.

“These spheres are hollow and filled with gas,” explains coatings expert Dr. Vladislav Kolarik from the ICT’s Energetic Systems department. When the outer side of a part is exposed to temperatures of 1000 degrees Celsius, these gas-filled spheres reduce temperatures on the part’s inner side to under 600 degrees Celsius – as the ICT scientists have demonstrated in their laboratories.

Since gas and steam turbines used for energy generation, combustion chambers, waste incinerator generators and temperature sensors, and reactors in the chemical and petrochemical industries are all subjected to temperatures of up to 1000 degrees Celsius, there is considerable demand of thermal protection.

What’s most remarkable is that the heat insulating layer from hollow aluminium oxide spheres is obtained on the basis of a conventional, economic process. Operators only have to do some simple math to see the benefits: conventional thermal barrier techniques – most of which are based on ceramic materials – are expensive. The process the scientists adapted was originally designed to protect metallic components from oxidation.

“We’ve optimized the technique so that the coat not only retains its oxidation protection, but furthermore protects against heat,” says Dr. Kolarik. The basic coating layer forms by interaction of aluminum particles and the metallic component. This is done by depositing aluminum powder on the surface of the metal and heating it all up to a suitable temperature over several hours. The result is an aluminum-rich coating on the component’s surface that protects against oxidation at high temperature. With the new procedure the topcoat from the hollow aluminum oxide spheres is additionally formed. “Up to now, it never occurred to anyone to use these spheres to produce another coating layer – they were just a waste product,” says Dr. Kolarik.

Now the scientists have refined the process so they can produce both coating layers in the required thickness. The way it works is to take aluminum particles and mix them with a viscous liquid bonding agent. This produces a substance similar to a paint or slurry, which the scientists then manually paint, spray or brush onto the metallic component. “All that’s left is to add a fair bit of heat,” says Dr. Kolarik. But it’s all easier said than done: Dr. Kolarik and his team have had to precisely fine tune the size and size distribution of the aluminum particles, the temperature and duration of the heating stage and the viscosity of bonding agents. “Just like a master chef, the first job was to come up with a winning recipe.”

“We’re currently in the process of putting the findings from the EU-funded PARTICOAT project into practice. This involves coating bigger and bigger components without exceeding the temperature limits for each application area. At the same time we’re trying out techniques to automate the whole coating process. Our plan is to follow in the footsteps of the aerated concrete that helps insulate our homes – that’s been in series production for a long time now,” says Dr. Kolarik.

More information:
http://www.particoat.eu

Dr. Vladislav Kolarik | Fraunhofer-Institut
Further information:
http://www.fraunhofer.de/en/press/research-news/2014/november/a-coating-that-protects-against-heat-and-oxidation.html

More articles from Process Engineering:

nachricht New technology for ultra-smooth polymer films
28.06.2018 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

nachricht Diamond watch components
18.06.2018 | Schweizerischer Nationalfonds SNF

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Subaru Telescope helps pinpoint origin of ultra-high energy neutrino

16.07.2018 | Physics and Astronomy

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides

16.07.2018 | Life Sciences

New research calculates capacity of North American forests to sequester carbon

16.07.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>