A Surprise in Materials Chemistry: At Vienna University of Technology, materials for lightweight construction, protective clothing or sports equipment can be produced at high temperatures and high pressures. This process is faster, better and more eco-friendly than other techniques.
The earth’s crust works like a pressure cooker. Minerals typically do not form under standard conditions, but at high temperatures and pressures. However, an environment of extreme heat and pressure has been considered to be absolutely unsuitable for organic molecules.
„Microflowers" made of PPPI, the world's most mechanically stable organic polymer. The blossoms are approximately five microns wide.
Scientists at Vienna University of Technology found out that under such seemingly hostile conditions, organic materials with remarkable material properties can be synthesized – for instance Kevlar, an extremely versatile high-performance material.
Steam Instead of Toxins
It seems counterintuitive: one might expect large, complex organic molecules to be destroyed by heat and high pressure. But at 200 degrees Celsius and 17 bars, Miriam Unterlass and her team at TU Vienna have synthesized organic polymers, which are usually extremely hard to create and require highly toxic additives. Instead of hazardous solvents, the team at TU Vienna uses nothing but harmless water vapour, making the new method extremely eco-friendly.
The principle of so-called “hydrothermal synthesis” is well known from geology. Many gemstones only form deep down in the ground, in high-pressure water reservoirs. In contrast to these inorganic minerals, which are often mainly made up of silicon and metal ions, many high-performance materials are organic. They primarily consist of carbon and hydrogen.
Kevlar is an example of such a high-performance polymer. It is extraordinarily robust and it is used for protective clothing or for construction elements that are supposed to withstand extreme strain. Such materials also play an important role in aircraft construction, because they are much lighter than any metal parts with comparable properties. Organic high-performance polymers are huge organic molecules with a very stiff structure, kept in place by a multitude of bonds between the atoms.
Extremely Durable, but Hard to Synthesize
Such durable materials, however, are very hard to synthesize: “We have to deal with two contradictory requirements”, Miriam Unterlass explains. “On the one hand, we want to have rigid materials which do not dissolve and do not melt even at high temperatures. On the other hand, this means that we cannot just dissolve and then crystalize them, as we would if we were dealing with simple rock salt, for example.” The technique developed at TU Vienna works quite differently: the polymers are forming and are crystallizing simultaneously, uniquely supported by hydrothermal conditions.
There are many advantages to this procedure: no dangerous byproducts are created, the energy consumption is dramatically reduced, and the synthesis in the pressure reactor is much faster than it would be using any other techniques. Also, the final product is better: “Our method yields materials with higher crystallinity, which further improves the mechanical rigidity”, says Miriam Unterlass.
Looking Inside with Infrared Light
Fine-tuning of the process is complicated, however. Mass and energy transport inside the reactor have to be very well known to understand exactly what is taking place. Of course the pressured rector cannot just by opened during the reaction to see what is happening. Therefore, a special infrared probe is used, which can easily withstand the extreme conditions inside the reactor. “When we put the probe inside the reactor, we can follow in real-time what happens inside, without having to draw any samples”, Unterlass explains.
With the new high-temperature IR-probe – it is one of only two such devices worldwide – it will become easier to develop even more synthetic techniques. The team has plenty of ideas: “There is a plethora of organic molecules which promise great material properties if we manage to polymerize them”, says Miriam Unterlass.
Dr. Miriam Unterlass
Institut für Materialchemie
Technische Universität Wien
Getreidemarkt 9, 1060 Wien
Florian Aigner | Eurek Alert!
Less is more to produce top-notch 2D materials
20.11.2017 | The Agency for Science, Technology and Research (A*STAR)
The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
20.11.2017 | Earth Sciences
20.11.2017 | Earth Sciences
20.11.2017 | Life Sciences