Graphene a miracle material?

So far, silicon has been the prime material when it comes to hardware for smartphones or processors. But how much longer will it enjoy that role? Because there’s a serious alternative called graphene. It’s much stiffer than steel but ­lighter than silicon. Graphene can conduct electricity and heat with similar effectiveness as silicon. But where does graphene come from?

Graphite, a modified carbon from which ­pencil leads are made, is the main component of graphene. It’s best to imagine this material of the future as an extremely thin layer of graphite atoms that are arranged in a hexagonal pattern. Under a microscope, a graphene layer like that resembles a honeycomb.

Professor Tim Hosenfeldt, PhD, Senior Vice President, Corporate Research and Innovation & Central Technology at motion technology company Schaeffler, sees graphene as having high potential for a wide variety of possible uses. “The electronic, optical, thermal, and mechanical properties of graphene have opened the door to many practical and commercial applications,” says Hosenfeldt. “As a transparent and flexible ­conductor, graphene can be used for producing solar cells, energy storage systems and converters, rollup monitors and touchscreens, and LED lamps. In addition, graphene clearly raises the frequency of electromagnetic signals. As a result, faster transistors are possible. Sensors made of graphene meet with great interest too because thanks to their exceptional sensitivity they can detect individual molecules of hazardous substances. Graphene oxide distributed in the air, for instance, can eliminate radioactive pollutants.”

The fields of possible uses in fact are equally extensive as complex. According to Hosenfeldt, graphene’s future potential is particularly great in battery storage systems where the material enables extremely short charging times (up to 60 times faster than with conventional ­lithium-ion cells). Hosenfeld sees promising development potential also as superconductors, as high-strength structural materials, or in energy production and storage.

In addition, graphene could lower the costs of hydrogen production because it’s particularly effective in transporting protons and so could replace expensive membranes.

However, there’s a downside: So far, producing graphene has been enormously complex and costly. But a solution seems to be emerging in that regard as well. With its 3DG (three-dimensional graphene) production technology, Chinese automaker GAC is aiming to reduce the production costs of originally ­several hundred euros per gram to a tenth of that price, according to information released by the company.

“Potentially, graphene and related materials could be used to produce lighter, more compact, and more powerful components for vehicles and for energy storage and conversion systems. The challenge lies in economical manufacturing, like we successfully did with three-dimensional carbon modifications.”

How cracks close themselves

Self-healing materials used to be part of the science fiction world, but today they’re a reality. Due to smart processes, they can repair themselves – regardless of the type of damage: cuts, cracks, or fractures. These materials contain living biological cells providing them with properties that just exist in nature. The human skin serves as a role model. Essentially, living materials like these consist of two components: of organisms such as yeasts or bacteria that are supposed to fulfill a specific function and have been programmed accordingly, and of a carrier material into which the living organisms are enclosed.

These organisms have specific metabolic properties and can produce a variety of substances, ranging from inorganic salts to metal oxides and bi-polymers to highly effective active ingredients in medical drugs. This ability can be used for producing technical and medical materials with novel functions that non-living materials don’t have. Besides self-regeneration of the ­material after having been damaged, that includes ­flexible adjustment to environmental stimuli or extremely long life.

The construction materials industry has been investigating self-repairing materials for a long time, and successfully so. There’s concrete that heals itself, enabled by bacteria that in the form of spores are cast into the concrete. Spores can survive for decades and centuries. When a crack emerges in the concrete water entering there revives the spores. They start producing ­calcium carbonate – lime. That lime seals the crack from the inside. Because the bacteria “heal” the cracks that have emerged the concrete lasts longer, a building doesn’t have to be torn down. That saves material resources and energy, and reduces greenhouse gases.

The University of Cambridge pursues the self-healing capacities of concrete as well. The researchers there have 3D-printed a supporting structure made of concrete. Not only is it less bulky than comparable cast parts and so saves more materials but it’s also equipped with sensors that can independently monitor the construction for decades and initiate auto-repairs. The self-healing effect works with paints and varnishes as well. Initially, they were intended for self-repairing car paints. However, what already works with microscopically small scratches that may, for instance, be caused by a carwash leaves a disturbing crater landscape in the case of paint scratches that are visible by the naked eye.

Medical device technology is another field in which interesting applications could emerge, for instance in the area of implants or wearables for monitoring diseases, or regarding low-cost sensors for environmental monitoring. An application that’s already on the horizon today is actuators for soft robotics. That involves materials changing their shape or volume when exposed to light, external impulses, moisture, or specific substances. Another interesting product is coatings that renew themselves. In the case of its “Corrotect” specialty coating, a corrosion protection for rolling bearings and precision parts, Schaeffler works with ultra-thin layers of silicon oxide nanoparticles that can heal themselves due to contact with oxygen in the event of ­damage.

With her research, Professor Aránzazu del ­Campo, Scientific Director of the Leibnitz Institute for New Materials, wants to imbue materials with new ­vigor, but also names issues, particularly with a view toward recycling. “It’s important,” she says, “to clarify the question of how to ensure that the utilization of living materials does not pose any risks to the environment – i.e., biocontainment, in other words, the biosafety of laboratories. For instance, as early as in the material development stage you must include in your plans the possibility that the cells contained cannot survive under certain conditions.” Despite all the strides that have been made in bionics – not everything seems to have been decrypted yet.

As light as ceramics, but harder than steel

Ceramics are some of the oldest artificial materials in human history. Finds suggest that ceramics, i.e., inorganic non-metallic materials, were used as far back as 25,000 years ago. They include stoneware, terracotta, and porcelain, for example. But ceramics aren’t used only in households and museums but also increasingly in high-tech components as a more capable alternative to steel. The motion technology company Schaeffler, for instance, produces balls for high-precision rolling bearings from ceramics instead of steel for forward-thinking industries such as wind energy, aerospace, and nearly all electrified applications.

Technical ceramics like that are characterized by extreme hardness, minimal mass, resistance against high temperatures and chemicals, high wear resistance, low friction against steel, and excellent electrical properties in terms of insulation and dielectric strength. These characteristics make ceramics a material that’s favored by sectors such as wind and solar power, fuel cells, the chemical industry, electrical engineering, high-temperature engineering, aerospace, mechanical engineering, microsystem engineering, or medical device technology.

The material properties of ceramics are inseparably linked to the manufacturing steps they involve, which consist of preparing the powder, forming, and firing. Due to various firing processes and firing atmospheres as well as the grain size and firing temperatures, a wide variety of properties of the same substance mixture can be achieved.

The evolution of understanding the properties microstructure in the realm of ceramics keeps creating novel material concepts. In addition to fiber composite materials, hybrid composites based on ceramic-metal-polymer combinations are becoming more and more important. Schaeffler Special Machinery recently presented a novel system for multi-material 3D printing that can produce parts in a material combination of metals and ceramics. “The solution provides customers with innovative material combinations, new functional integration in components and tools, plus higher flexibility in the design of products and tools,” says Bernd Wollenick, Senior Vice President Schaeffler Special Machinery.

Indications are that ceramics will become a key element in the development of lighter, safer, and more powerful solid-state traction batteries and so might decisively influence the evolution of electric mobility. In a solid-state battery, a thin ceramic layer works simultaneously as a solid electrolyte and separator. However, up to now, the sintering process to produce the ceramic elements used to require temperatures above 1,000 °C (1,832 °F). That caused technical problems as well as driving up energy consumption and price. But a new synthesis process developed by researchers at the Massachusetts Institute of Technology (MIT) and TU Munich only requires 500 °C (932 °F) and so could become an important door opener for the market entry of ­ceramic solid-state batteries with ranges of more than 1,000 kilometers (621 miles).

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CO₂ can be a raw material too

Carbon dioxide is one of the main drivers of climate change – so CO₂ emissions must decrease in the future. Fraunhofer researchers are pointing out one possible pathway toward carbon reduction: They use the climate gas as a base material, for instance for plastics. “We use the ­climate-damaging waste product CO₂ as a raw material source,” says Dr. Jonathan Fabarius, Senior Scientist for Microbial Catalysis at the Fraunhofer Institute. “To do so, we’re pursuing two approaches: First, the heterogeneous chemical catalysis, in which we convert the CO₂ into methanol by means of a catalyst. Second, electrochemistry with which we produce formic acid from the CO₂.”

What makes this approach special is the combination with biotechnology or, more precisely, with fermentation by microorganisms. The researchers use methanol and formic acid as food for microorganisms that produce further products from it. An example of a product like that is organic acids that are used as building blocks for polymers – CO₂-based plastics could be produced in that way. Amino acids can be produced in that way as well, for instance as food supplements or animal feed.