Can a fish in the Amazon inspire ‘flexible’ ceramics?
An armorlike arapaima fish scale resists being fractured by a piranha tooth that is slowly pressed into it. In fact, it is the tooth that fails. Credit: Meyers Group: Credit: UCSD Jacobs Sch. of Eng.
If you ever watch cable TV’s River Monsters (and, honestly, who doesn’t!), you might be familiar with a large Amazonian “living fossil” fish that goes by the name arapaima.
The arapaima have a reputation for being one of the few animals in the Amazon that hungry piranha don’t bother. Why? Apparently it is because evolution has draped the arapaima in a flexible skin of “armor” that is effectively impenetrable to the piranhas’ teeth. The fish has “scales,” but there aren’t many other species among fish that come close to the defenses of the arapaima.
Researcher Marc Meyers, an expert on bio-inspirational design and a professor at the Jacobs School of Engineering at University of California, San Diego, knew of this reputation and speculated that if the arapaima are indeed protected from piranhas’ bites, maybe insights from the structure of the arapaima’s scales could provide ideas for engineering new materials, such as flexible ceramics.
(Meyers’ name may be familiar to some. He was one of the stars in one of the episodes of Nova’s “Making Stuff” TV series, in which he discussed the strength of mullosk shells.)
As can be seen in the above video, Meyers, along with his students and colleagues, set up a simple desktop test. They attach an arapaima scale to a soft rubber base (to simulate the fish’s soft muscle and tissue under the scale) and mounted a single piranha tooth in a press. The tooth is then pressed into the scale. In each case, the tooth can partially penetrate the scale, but the tooth cracks before the scale suffers a total fracture.
Credit: Meyers Group; UCSD.
Meyers says in a UC San Diego release that the structure of the scale is combination of a mineralized outer layer with a clever and tough internal design (see diagram from the press release). This tough inner layer has collagen fibers stacked in alternating directions “like a pile of plywood.” He says the mix of materials in the scale is similar to the hard enamel of a tooth deposited over softer dentin.
Implications? Meyers says that the arapaima’s design should serve as bioinspiration for lots of things that need to be both tough and flexible, for example body armor, fuel cells, insulation and aerospace designs.
Some lessons for engineers are from this work are:
- Combine hard and soft materials
- Stack the materials in the underlying layer with different orientations
- Texture is key, and a varying surface provides more capability.
On this last point, Meyers notes that each scale has an exterior that is “corrugated.” According to the story, “the corrugated surface keeps the scales’ thick mineralized surface intact while the fish flexes as it swims. Ceramic surfaces of constant thickness are strained when forced to follow a curved surface. The corrugations allow the scales to ‘be bent more easily without cracking,’ Meyers said.”
Meyers says he will also be studying the scales of another unusual fish, the alligator gar whose scales were reportedly used as arrow tips.
Corrugated texture of arapaima scales. Credit: Meyers Group; UCSD Jacobs Sch. of Eng.
Meyers et al. have written about their studies in the The Journal of the Mechanical Behavior of Biomedical Materials in the paper, “Biological materials: A materials science approach” (doi:10.1016/j.jmbbm.2010.08.005).
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‘Shaping the Future of Ceramics’ is theme of international congress in Chicago this July
Katherine Faber, president of the 4th International Congress on Ceramics, on “Shaping the Future of Ceramics.” Credit: ACerS.
I really enjoy going to meetings. The big, conference kind, that is — not so much the day-to-day inhouse kind!
Conferences give me the chance to follow the buzz: the who, what, where and how of ceramic technology. I get the technical details from the sessions, but I get the most out talking to meeting the attendees about their work, what trends they are seeing, who they are collaborating with, what problems they are encountering, etc.
There is just no substitute for the “live action” that happens at a meeting. So, I’m really looking forward to the 4th International Congress on Ceramics this July in Chicago.
International Ceramic Federation convenes these international congresses biennially in cooperation with several international societies. ACerS is the host and organizing society of this fourth congress. ACerS had the privilege of hosting and organizing the first ICC in Toronto in 2006 and is very pleased to reprise the role.
The theme of this congress is “Shaping the Future of Ceramics,” and as you might expect, this refers not just to processing and properties, but also to the business of ceramic science, engineering, product development and manufacturing.
Katherine Faber, president of the ICC4 says the meeting is “designed to bring together international leaders in business and research to investigate new opportunities and emerging opportunities in terms of ceramic design and ceramic manufacturing.”
Indeed, the meeting is organized into themes that reflect this goal: Aerospace; Aerospace; Biology and Medicine; Electro-, Magnetic-, Optical-Ceramics and Devices; Environment, Energy and Transportation; Infrastructure; Nanostructured Ceramics; Security and Strategic Materials; and Workforce Development. Over 600 international attendees representing business, academia and government are expected.
The technical program, Faber says, “is geared toward emerging opportunities in energy, health, transportation and aerospace. We’ll also hear about nanotechnology and nanodevices, as well as other electrical, optical and magnetic materials.”
It seems natural, then, that this year ACerS’s Ceramic Leadership Summit be incorporated into ICC4. The CLS, now in its third year, is a forum for exploring and addressing the business issues and challenges facing the ceramics and glass industries, in both realms of established industries and emerging technologies.
Faber notes, that the combined meeting is an opportunity to bring together those “creating the knowledge and doing the innovating,” to the mutual benefit of all.
There is a lot more going on—an innovative poster session, a short course on sintering, keynote and plenary talks—all in the pleasant setting of downtown Chicago. Over the next few weeks, we’ll be sharing with you a sampling of the talks that are scheduled for ICC4 and CLS and other updates as we learn about them.
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VO2 foils eyed for mass production for thermochromic window applications
Photographs of sample films at room temperature. Credit, Gao et al.; RSC Energy Environ. Sci.
The notion of making functional and flexible ceramic foils is fascinating, but a little counterintuitive, isn’t it?
Thus, I am always intrigued when new techniques and applications are discovered. A while back I wrote about a group from ETH Zurich that mastered ultrathin, transparent and flexible foils using yttria stabilized polycrystalline tetragonal zirconia.
This weeks brings news of another transparent and flexible film based on vanadium dioxide developed by Chinese researchers at the Shanghai Institute of Ceramics, including ACerS member Yanfeng Gao. The new VO2 film is being eyed for use in thermochromic windows, which retain transparency in the visible range but dynamically regulate the passage of wavelengths that transfer solar heat and energy in the ultraviolet and infrared ranges.
Smart window researchers have had an interest in VO2 because they’d like to exploit a particular property: At 68°C (in the case of VO2 bulk single crystals), the material undergoes a reversible, thermally induced phase transition that shifts the optical properties in the near-infrared region from a low-temperature transparent state to a more reflective state.
In an email, Gao says materials based on VO2 nanoparticles, particularly VO2 foils that easily can be used with glass panels, are attractive for applications in construction and automotive industries. Heretofore, making such foils from solutions of nanoparticles has been tricky and unreliable because of the instability of the nanoparticles. But, Gao and his colleagues report in a paper in the Royal Society of Chemistry’s journal, Energy and Environmental Science, that they have figured out a new process that solves previous shortcomings and may be scalable to large-area mass production.
Gao, who works in SIC’s State Key Laboratory of High Performance Ceramics and Superfine Microstructure, says, “In this paper, we report a novel all-solution process that can be used to prepare transparent, stable and flexible VO2-based composite films. These films exhibit UV-shielding properties and an excellent temperature-responsive thermochromism in the near infrared region.”
The breakthrough? Gao says the answer came when the group coated the VO2 nanoparticles with a thin SiO2 shell. “The shell, Gao says, “significantly improved their anti-oxidation and anti-acid abilities.”
Essentially, the VO2 nanoparticles are given a SiO2 shell using tetraethyl orthosilicate (the thickness of the shell can be fine-tuned) and treated with a silane couple to increase dispersion. The last step is to cast the suspension on a PET substrate.
At 13.6% solar modulation efficiency, the researchers report in the paper that their VO2-based film is able to match the efficiency levels of other thermochromic films. This is also considerably higher than VO2 films produced by sputtering and other methods.
Gao says, “Traditional glass foils are usually based on thin notable metal layers for reflection of solar irradiation or organic dyes that can absorption solar heat. … The stability of these kinds of foils is still questionable. To our knowledge the current research reports on the first VO2 ceramic foils, and more importantly, the foils show excellent optical properties (visible transmittance and solar modulation ability, maybe the best in the world.).
As far as “smart” performance goes, Gao et al. report in the paper that they observed while testing a typical sample of the VO2 film, “… in a heating cycle from 35°C to 85°C, the transmittance at 1500 nm decreased from 57.7% (at 35°C) to 14.9% (at 81°C) gradually… In a cooling cycle, the transmittance of film increased from 14.9% (at 75°C) to 57.7% (at 35°C).”
The promise of increased energy efficiency via thermochromic windows has drawn worldwide attention. Gao says it is a big concern for developing countries, such as China, which already has buildings occupying 52 billion square meters “waiting new techniques to improve their energy efficiency and to reduce greenhouse gas emissions. We are aiming to develop a new material along with a novel process that can be finally commercialized and used to for building glasses.”
Gao says scaling the group’s technique to large-area production is the next challenge, and says that a collaborative effort is worthwhile. “This method should be considered as a basis for mass production,” he says, “The method should combine with some techniques to efficiently fabricate and to improve performance-cost ratios. … We hope that colleagues working in related fields can join to consider innovations based on the current technology. As an important part of an eco-home, we hope that such kind of smart windows can be applied practically in the near future.”
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News on glass & refractory world
• The owner of glass manufacturer Pilkington, Nippon Sheet Glass, has announced that it will close one of its three UK production lines in an effort to cut costs. The job cuts are the second major headcount reduction in two years: In March 2010, the firm cut 6,700 jobs in the wake of the global financial crisis.
• According to reports, approximately 500 tons of molten glass was spilled in an incident on 30th January 2012 at Guardian Industries’ glass manufacturing plant in De Witt, Iowa, US. The glass leak happened during routine maintenance and six fire departments spent approximately five hours pouring cold water on the spill.
• Zimbabwe’s sole glass manufacturer, Zimglass, is set to resume operations in April 2012 after the company secured funding to refurbish its furnaces.
• AGC Glass Company North America has announced that it plans to restart float G1, an idled production line at its Tennessee plant, USA and re-instate 100 jobs once the line becomes operational. The company shut down the production line in 2008 and laid-off approximately 250 people at the time.
• Seeing the promising prospects for container glass, Taiwan Glass Group, Taiwan’s largest glass maker, plans to expand production capacity at its plant in Hsinchu County, northern Taiwan by integrating two old production lines and adding a new one.
• Magnezit Group has acquired Panteleymonovka Refractory Plant (town Gorlovka), one of the biggest enterprises in Ukraine for production of magnesia refractories.
Editor’s note: We welcome Italy-based P. Carlo Ratto to our team of bloggers. Ratto is a former council member at GLG and consultant at RHI AG Glass Division - Monofrax & Refel plants and is business development manager, Fused Cast at Vesuvius Group (Monofrax). For more information, readers are urged to consider joining some of the ceramic-related Linked In groups, such as the Ceramic Engineers’ Group and the Friends of Refractories Group.
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Ceramics and glass business news of the week
Here is what we are hearing:
Integration of Hanse Chemie Inc. USA, into Evonik Goldschmidt Corp.
As of Jan. 1, 2012, the US Hanse Chemie business of Hanse Chemie AG and Nanoresins AG, has been merged into Evonik Goldschmidt Corp. At the same time, Hanse Chemie Inc. USA has been dissolved as a legal entity. The acquisition of the two firms by Evonik was finalized on May 12, 2011. Both companies are headquartered in Germany and produce raw materials and components for the manufacture of sealants, adhesives, molding and casting compounds, and other products. Most of the Hanse Chemie Inc. business is incorporated into the Interface & Performance business line whose activities surrounding the silicone specialties are directed at a variety of industrial markets. Activities in the paint and coatings industry, especially those concerning nanocomposites, extremely fine-particle silicas, are now part of the Coatings & Additives Business Unit of Evonik.
3M launches high density versions of its embedded capacitance material at DesignCon 2012
3M announced the initial availability of its high-capacitance Embedded Capacitance Material at DesignCon 2012, providing design engineers a new way to improve power integrity and reduce electromagnetic interference. Unlike previous 3M ECM versions, which have a maximum capacitance density of approximately 10 nF per square inch, and some existing commercial competitor offerings, which have a maximum capacitance density of approximately 6 nF per square inch, the 3M ECM high-capacitance density solutions offer a capacitance density range from 20 up to 40 nF per square inch, making it the one of the highest capacitance density, halogen-free ECM solutions on the market. This helps design engineers provide hi-fidelity signals, high-signal-to-noise ratio in radio frequencies and higher speed digital signals in a variety of high-performance applications such as small form factor computer hardware, high-performance RF boards, microphones, integrated circuit packaging and consumer electronics.
Mantec consolidates ceramic activities
Mantec, the British technology group with a portfolio of manufacturing businesses based in Stoke-on-Trent, has announced that with immediate effect the three companies previously operated as subsidiaries of the technical ceramic division have now merged into a single, business - Mantec Technical Ceramics Ltd (www.mantectechnicalceramics.com). The three companies involved are Taylor Tunnicliff, Ceramic Gas Products and Fairey Filtration Systems. They have in any case been operating under common management, from the same premises, for the past four years and so this a logical step to take. While the name of Mantec Technical Ceramics will now be the one associated with all administrative, legal, accounting and sales channels, leading brand names owned and manufactured by the group will naturally be retained.
Polycrystalline ceramics with cubic spinel structure transmit well in the visible and mid IR wavelengths of the electromagnetic spectrum. ALON and magnesia spinel are especially attractive, and are leading lightweight transparent armor candidates for future combat systems. These have enormous performance advantage over glass and justify their rapid development. Surmet achieves full density and transparency using the conventional sinter/hot isostatic Ppress process that includes green body formation and high-temperature sintering, followed by HIPping.
Molycorp Inc. announced that Molibdenos y Metales S.A. (Molymet), the world’s largest processor of the strategic metals molybdenum and rhenium, has agreed to invest approximately $390 million in the company in exchange for 12.5 million shares of Molycorp common stock. The price of the Molycorp shares to be purchased were valued based on the 20-day volume weighted average share price as of the close of trading on Jan. 30, 2012 plus a 10% premium. Molycorp has agreed to appoint to its board of directors upon the closing of the proposed investment a nominee to be designated by Molymet.
Thermablok aerogel insulation strips installed in new ‘green’ US Border Patrol station in Texas
Crews working construction on the environmentally sustainable Fabens US Border Patrol Station in Clint, Texas have just completed installing 21,000 linear feet of Thermablok aerogel insulating strips on studs throughout the 51,000 square foot facility. The strips reduce thermal bridging, the prime cause of energy loss in buildings. When RVK Architects of San Antonio collaborated with Jacobs Engineering Group of Houston to design the eco-friendly structure already years in the planning, they included Thermablok in the original design. The strips went up easily since they have peel and stick adhesive already attached to the back of the product. The facility also is fitted with solar heaters, sky lights, glazed windows and energy efficient equipment for a low-carbon footprint.
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