Biological materials are fascinating because they are very light but have the ability to withstand extreme forces. Nacre is amazingly tough thanks to a multi-layer arrangement of platelet-shaped calcium carbonate crystals (“bricks”) and proteins (“mortar”) in the form of a “brick wall”.
A Finnish and Swedish team headed by Andreas Walther and Olli Ikkala has now developed a nacre analogue with mechanical properties that outperform those of some high-performance polymers. It also acts as a heat shield, as the scientists report in the journal Angewandte Chemie.
There is much interest in the imitation of robust biomaterials and their use in construction and coatings. “It has previously been very difficult to even get samples of significant size” says Ikkala, “production scale was completely out of the question.” The team from the University of Aalto (Helsinki) and the Royal Institute of Technology in Stockholm has recently developed a simple and fast production method that resembles paper production, is environmentally friendly and economical, and can be used for the production of whisper-thin foils, laminates, and coatings of nacre analogues. The films can be made as large as desired and demonstrate outstanding mechanical properties.
Like true nacre, the analogues have a brick-wall structure of “hard” and “soft” materials: The “bricks” consist of hard clay platelets that are coated with a soft polymer. The hard component acts as a supporting and strengthening member, while the soft segments is an efficient binder and can dissipate energy. Now there is a further improvement: the researchers coated the silicate platelets with polymer molecules that have multiple positive charges (polycations), instead of neutral polymers. By selecting the negatively charged counterions with the right properties, the mechanical properties of the highly transparent, pliable films can easily be varied, and improved. Increasing the charge increases the elasticity and tensile strength, because the adhesion between the polycation-coated platelets is stronger.
One other property of the new synthetic nacre analogues is particularly intriguing: when the materials are exposed to flame, the embedded polymer burns up to form a material with an interior of porous foam and an armored skin on the outside. This construction provides protection against heat and flames as effectively as a heat shield. “Our new material has potential as a fire-proof coating or as a component of fire- or heat-shielding films” says Walther. “Their light weight makes them particularly interesting for aerospace and marine applications.”
Author: Andreas Walther, Aalto University, Helsinki (Finland), mailto:firstname.lastname@example.org
Title: Supramolecular Control of Stiffness and Strength in Lightweight High-Performance Nacre-Mimetic Paper with Fire-Shielding Properties
Angewandte Chemie International Edition 2010, 49, No. 36, 6448–6453, Permalink to the article: http://dx.doi.org/10.1002/anie.201001577
Cryo-electron microscopy achieves unprecedented resolution using new computational methods
24.03.2017 | DOE/Lawrence Berkeley National Laboratory
How cheetahs stay fit and healthy
24.03.2017 | Forschungsverbund Berlin e.V.
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
24.03.2017 | Materials Sciences
24.03.2017 | Physics and Astronomy
24.03.2017 | Physics and Astronomy