Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Breakthrough in materials science: Kiel research team can bond metals with nearly all surfaces

08.09.2016

How metals can be used depends particularly on the characteristics of their surfaces. A research team at Kiel University has discovered how they can change the surface properties without affecting the mechanical stability of the metals or changing the metal characteristics themselves. This fundamentally new method is based on using an electro-chemical etching process, in which the uppermost layer of a metal is roughened on a micrometer scale in a tightly-controlled manner. Through this “nanoscale-sculpturing” process, metals such as aluminium, titanium, or zinc can permanently be joined with nearly all other materials, become water-repellent, or improve their biocompatibility.

The potential spectrum of applications of these “super connections” is extremely broad, ranging from metalwork in industry right through to safer implants in medical technology. Their results have now been published in the prestigious journal “Nanoscale Horizon” of the Royal Society of Chemistry.


The targeted etching process of “nanoscale-sculpturing” roughens the upper layer of metal (here aluminium, 20 µm = 0.02 mm), thereby creating a 3D-structure with tiny hooks.

Melike Baytekin‐Gerngroß

“We have now applied a technology to metals that was previously only known from semiconductors. To use this process in such a way is completely new,” said Dr. Jürgen Carstensen, co-author of the publication. In the process, the surface of a metal is converted into a semiconductor, which can be chemically etched and thereby specifically modified as desired.

“As such, we have developed a process which – unlike other etching processes – does not damage the metals, and does not affect their stability,” emphasised Professor Rainer Adelung, head of the “Functional Nanomaterials” team at the Institute for Materials Science. Adelung stressed the importance of the discovery: “In this way, we can permanently connect metals which could previously not be directly joined, such as copper and aluminium.”

How does the “nanoscale-sculpturing” process work exactly?

The surfaces of metals consist of many different crystals and grains, some of which are less chemically stable than others. These unstable particles can be specifically removed from the surface of a metal by a targeted etching. The top surface layer is roughened by the etching process, creating a three-dimensional surface structure. This changes the properties of the surface, but not of the metal as a whole. This is because the etching is only 10 to 20 micrometers deep – a layer as thin as a quarter of the diameter of human hair. The research team has therefore named the process “nanoscale-sculpturing”.

The change due to etching is visible to the naked eye: the treated surface becomes matt. “If, for example, we treat a metal with sandpaper, we also achieve a noticeable change in appearance, but this is only two-dimensional, and does not change the characteristics of the surface,” explained Dr. Mark-Daniel Gerngroß of the research team on materials sciences from Kiel.

Through the etching process, a 3D-structure with tiny hooks is created. If a bonding polymer is then applied between two treated metals, the surfaces inter-lock with each other in all directions like a three-dimensional puzzle. “These 3-D puzzle connections are practically unbreakable. In our experiments, it was usually the metal or polymer that broke, but not the connection itself,” said Melike Baytekin-Gerngroß, lead author of the publication.

Surfaces with multifunctional properties

Even a thin layer of fat – such as that left by a fingerprint on a surface – does not affect the connection. “In our tests, we even smeared gearbox oil on metal surfaces. The connection still held,” explained Baytekin-Gerngroß. Laborious cleaning of surfaces, such as the pre-treatment of ships' hulls before they can be painted, could thus be rendered unnecessary.

In addition, the research team exposed the puzzle connections to extreme heat and moisture, to simulate weather conditions. This also did not affect their stability. Carstensen emphasised: “Our connections are extremely robust and weather-resistant.” A beneficial side-effect of the process is that the etching makes the surfaces of metal water-repellent. The resulting hook structure functions like a closely-interlocked 3D labyrinth, without holes which can be penetrated by water. The metals therefore possess a kind of built-in corrosion protection. “We actually don't know this kind of behaviour from metals like aluminium. A lotus effect with pure metals – i.e. without applying a water-repellent coating – that is new,” said Adelung.

Potentially limitless applications

“The range of potential applications is extremely broad, from metalworking industries such as ship-building or aviation, to printing technology and fire protection, right through to medical applications,” said Gerngroß. Because the “nanoscale-sculpturing” process not only creates a 3D surface structure, which can be purely physically bonded without chemicals – the targeted etching can also remove harmful particles from the surface, which is of particularly great interest in medical technology.

Titanium is often used for medical implants. To mechanically fix the titanium in place, small quantities of aluminium are added. However, the aluminium can trigger undesirable side-effects in the body. “With our process, we can remove aluminium particles from the surface layer, and thereby obtain a significantly purer surface, which is much more tolerable for the human body. Because we only etch the uppermost layer on a micrometer scale, the stability of the whole implant remains unaffected,” explained Carstensen.

The researchers have so far applied for four patents for the process. Businesses have already shown substantial interest in the potential applications. “And our specialist colleagues in materials sciences have also reacted enthusiastically to our discoveries,” said a delighted Adelung.

Original publication:
M. Baytekin-Gerngross, M.D. Gerngross, J. Carstensen and R. Adelung: Making metal surfaces strong, resistant, and multifunctional by nanoscale‐sculpturing. Nanoscale Horizon. DOI: 10.1039/C6NH00140H
http://pubs.rsc.org/en/content/articlelanding/2016/nh/c6nh00140h#!divAbstract

Photos are available to download:
http://www.uni-kiel.de/download/pm/2016/2016-285-1.jpg
Caption: A strip of aluminium – the surface of which has been treated with an electro-chemical etching process – is permanently bonded with thermoplastic by heating.
Photo/Copyright: Julia Siekmann / Kiel University

http://www.uni-kiel.de/download/pm/2016/2016-285-2.jpg
Caption: Large metal surfaces can also be treated with nanoscale sculpturing. Although the etching is only applied to a thin layer on a micrometer scale, the resulting change is visible to the naked eye: the treated surface of the aluminium in the foreground has become matt.
Photo/Copyright: Julia Siekmann / Kiel University

http://www.uni-kiel.de/download/pm/2016/2016-285-3.jpg
Caption: The Kiel-based research team of Melike Baytekin-Gerngroß (on the left), Mark-Daniel Gerngroß, Jürgen Carstensen and Rainer Adelung compares test results in the laboratory.
Photo/Copyright: Julia Siekmann / Kiel University

http://www.uni-kiel.de/download/pm/2016/2016-285-4.jpg
Caption: Aluminium plates which have only been sandblasted (in the background of the picture) cannot be glued successfully. The two glued plates separate again at the interface between glue and metal – this can be seen by the fact that there is no white glue residue visible on one of the two plates.
The aluminium plates in the foreground of the picture were treated with the etching process “nanoscale-sculpturing” before being glued. These plates could also be separated. But the white glue particles left on both plates demonstrate that the bond between metal and glue is not broken, but rather the glue itself.
Photo/Copyright: Julia Siekmann / Kiel University

http://www.uni-kiel.de/download/pm/2016/2016-285-5.jpg
The targeted etching process of “nanoscale-sculpturing” roughens the upper layer of metal (here aluminium, 20 µm = 0.02 mm), thereby creating a 3D-structure with tiny hooks. A surface treated with this process can inter-lock like a three-dimensional puzzle with the surfaces of almost all other materials, forming unbreakable bonds. With this method, it is even possible to create bonds between aluminium and copper.
Photo/Copyright: Melike Baytekin‐Gerngroß

http://www.uni-kiel.de/download/pm/2016/2016-285-6.jpg
The roughened surface structure of zinc in 10,000x magnification (2 µm = 0.002 mm).
Photo/Copyright: Melike Baytekin‐Gerngroß

Contact:
Prof. Dr. Rainer Adelung
Functional Nanomaterials
Institute for Materials Science
Kiel University
Tel.: +49 (0)431/880-6116
E-mail: ra@tf.uni-kiel.de

Dr. Jürgen Carstensen
Functional Nanomaterials
Institute for Materials Science
Kiel University
Tel. +49 (0)431/880-6181
E-mail: jc@tf.uni-kiel.de

Dr. Boris Pawlowski | Christian-Albrechts-Universität zu Kiel

More articles from Materials Sciences:

nachricht New biomaterial could replace plastic laminates, greatly reduce pollution
21.09.2017 | Penn State

nachricht Stopping problem ice -- by cracking it
21.09.2017 | Norwegian University of Science and Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: The fastest light-driven current source

Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.

Graphene is up to the job

Im Focus: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Nerves control the body’s bacterial community

26.09.2017 | Life Sciences

Four elements make 2-D optical platform

26.09.2017 | Physics and Astronomy

Goodbye, login. Hello, heart scan

26.09.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>