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Universitat Politècnica de Catalunya BarcelonaTech: Characterization of 3D Printing for Ceramic Fuel Cell Electrolytes

Albert Folch Alcaraz recently submitted a Master’s thesis to the Universitat Politècnica de Catalunya BarcelonaTech. In ‘Mechanical and Microstructural Characterization of 3D Printed Ceramic Fuel Cells Electrolytes,’ Alcaraz delves further into digital fabrication using ceramic as a versatile material for creating solid oxide fuel cells—electrochemical devices capable of transforming chemical energy to electrical energy.

Striving to ‘bring science and society closer together,’ Alcaraz aims to develop energy devices that offer better efficiency, as well as offering clean energy that can be generated with less effect on our environment. Fuel cells are categorized regarding the types of electrolytes contained within, from low temperature (the alkaline fuel cell (AFC), the proton exchange membrane fuel cell, and the phosphoric acid fuel cell (PAFC)) to high temperature (operating at 500 – 1000 oC as two different types, the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC)).

SOFCs are made from ceramic, comprised of an anode that oxidizes and then sends electrons to the external circuit—and the oxidant which feeds into the cathode, thus ‘accepting’ electrons and then undergoing a reduction reaction. Electricity is created via electron flow from the anode to the cathode.

Working schematisation of a SOFC

Solid ceramic electrolytes prevent corrosion, offer superior mechanical performance for smaller, lighter weight structures, but do still present some challenges in terms of processing and temperatures.

“In theory, any gases capable of being electrochemically oxidized and reduced can be used as fuel and oxidant in a fuel cell,” states Alcaraz.

Working scheme of a fuel cell

Physical and chemical characteristics of the four components of a SOFC

For suitable performance, fuel cells must contain the following

High conversion efficiency
Environmental compatibility
Modularity
Sitting flexibility
Multifuel capability

Different applications of fuel cells; a) Fuel cell in the Toyota Mirai model and, b) a fuel cell for ships as part of a maritime project for the U.S. Department of Energy

More traditional techniques for production with ceramic materials include uniaxial and isostatic pressing, tape casting, slip casting, extrusion, and ceramic injection molding. 3D printing has been used in connection with ceramics and a variety of different projects around the world, to include the use of ceramic brick structures in architecture, porous ceramics with bioinspired materials, and establishing parameters in quality assurance.

Techniques such as powder bed binder jet/inkjet 3D printing are popular with the use of ceramics.

“It must be mentioned that although printed material in plaster-based printers is a ceramic material, if impregnated with and adhesive, it will not be a pure ceramic but a polymer-ceramic composite. As no extreme heating is required during and after processing, colors can be added to the part,” stated Alcaraz.

Examples of powder bed binder jet/inkjet 3D printed parts

Other popular 3D printing methods include selective laser melting (SLM), stereolithography (SLA), and robocasting. Alcaraz noted, however, that 3D printed samples demonstrated 98 percent relative density in comparison to tradition methods—and especially when compared to cold isostatic pressing.

“It has been demonstrated that the 3D printing specimens present similar micro- and nano- mechanical properties with the sample fabricated by a conventional processing route. In terms of the Vickers Hardness, the 3D printed specimens presented higher values than the specimen produced by CIP,” concluded the researchers. “As far as for the nanoindentation hardness and elastic modulus, the 3DP parts presented similar values of hardness. Nevertheless, it has been found that the values found for the elastic modulus are sensitive to different aspects such as the porosity and the roughness of the parts, giving less concise values.

“Concerning the reduction of printing defects, it is recommended to treat the feedstock before printing in order to achieve an homogenous particle size of the powder and be able to use a nozzle with a smaller diameter in order to enhance the resolution of the final 3D printed part. Finally, it would be interesting to follow the investigation of microcompression of the printed samples in order to extract the compression elastic modulus value through a different experiment and compare it to the nanoindentation technique. Furthermore, in the compression stress-strain curve obtained for the 3D printed specimen it is clear to observe a densification process (serrated zone) due to the presence of internal porosity heterogeneously distributed along the entire specimen.”

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[Source / Images: ‘Mechanical and Microstructural Characterization of 3D Printed Ceramic Fuel Cells Electrolytes’]

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Olivier van Herpt: The 3D Printed Blue and White Collection in Porcelain

[Image: Koos Breukel]

One of the greatest things about reporting on the world of 3D printing is learning about its more unusual uses. It’s obvious that 3D printing is changing the way many larger (and smaller) companies create, prototype, and manufacture today as they embrace the benefits of greater speed in production, affordability (often producing parts at a fraction of the cost), and the ability to design and print onsite rather than going through a third party. We continually follow serious developments within the industrial world, to include automotive, medicine, medical devices, aerospace, construction, art—and so much more—but 3D design and 3D printing together allow for an infinite amount of innovation. Because of that, you never know what’s coming next!

Here’s a good example: blue and white 3D printed porcelain. Delving into the world of textiles and materials, we are able to learn more about the process Olivier van Herpt, a Dutch designer, went through in creating his 3D version of the blue and white delftware which is the Netherlands’ national product—and one with a rich history too.

Blue Delft originally came about as designers in the Netherlands wanted to make a local knockoff similar to porcelain being imported from China. Because they lacked kaolin, however, the Netherlands version came off with what may have originally been an unintended look of its own. The earthenware was exotic but still retained the oriental and decorative style.

Van Herpt began using a ceramic 3D printer as he worked to improve the creation of porcelain, eventually making 14 stackable pieces. His printer is capable of producing ceramic objects up to 90 cm high, with thin walls and a hard clay body. Van Herpt has always been on a mission to ‘push the limits of existing 3D printing technologies,’ and has created collections that are meant to soften up the hard edges of industrial design. While also enjoying working with larger pieces and alternative materials such as paraffin, clay, and more, the impactful designer enjoys bringing a human element into industry.

“The consistent flow of material is proven by the fine layers that manifest in the precision of the printing process. The unglazed surface underlines the character of the material and is shown in the structure as a result of the movement of the printer. The tiled surface indicates the digital provenance of the object applied in a precise, sinuous form,” states van Herpt in the case study regarding the project.

“The blue pattern is the translation of human interaction by the machine. Cobalt pigment is applied by hand on the clay body before being inserted in the extruder. The pattern is then reconstructed by the 3D printer, resulting in a radial gradient celebrating cooperation between man and machine.”

Find out more about the designer and his functional 3D printed ceramic objects here.

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[Source / Images: Olivier van Herpt]

Chinese scientists conduct ceramic 3D printing tests for off-world construction

Scientists at the Technology and Engineering Center for Space Utilization of the Chinese Academy of Sciences (CAS) have successfully completed an experiment to 3D print ceramic parts containing lunar dust under microgravity. Using Digital Light Processing (DLP) technology on board the Airbus ZERO-G parabolic flight aircraft run by Novespace of Switzerland. The 3D printing experiment further explores […]

Team Effort Uses 3D Printing to Restore Coral Reefs

[Image: SECORE: Paul Selvaggio]

Coral reefs are the most diverse ecosystems on Earth, with thousands of animal and plant species living in their colorful ocean-floor habitats. These reefs are in quite a bit of trouble currently, however. In the past 30 years, 50 percent of the world’s coral reefs have died and if changes aren’t made to slow the progression of climate change and curb other human-caused damage to the reefs, 90 percent of them may die in the next century. Coral reefs aren’t just vital to the plants and animals that call them home, but to humans as well – they provide a lot of income through tourism and fishing, as well as protecting coastlines during violent storms.

Saving them, therefore, is critical, and involves some human intervention at this point. Coral are sessile animals, meaning that they take root like plants but capture their food from the ocean water. Coral polyps root themselves in ocean rocks, gradually reproducing and growing until they form the lush, brightly colored reefs that people travel thousands of miles to see. It’s a slow process, though – coral reefs grow by centimeters each year, taking thousands of years to become large and thriving. Right now, coral reefs don’t have thousands of years, so they need our help.

Several organizations have been trying to help coral by 3D printing artificial reefs and sinking them in the ocean in hopes of attracting free-floating coral polyps to embed themselves and begin reproducing. An organization called SECORE International (Sexual Coral Reproduction) is also using 3D printing, but taking a more hands-on, aggressive approach. SECORE is a nonprofit global network of scientists, public aquarium professionals and local stakeholders working to protect and restore coral reefs. Along with its partners, which include the California Academy of Sciences (CAS) and the Nature Conservancy, SECORE is developing restoration processes that leverage the natural reproductive habits of coral.

3D printed seeding units. [Image: SECORE/Valérie Chamberland]

Certain coral species naturally broadcast egg and sperm cells, which are collected by SECORE, fertilized, and then raised in tanks until they become freely swimming larvae. Those larvae are then introduced to 3D printed “seeding units” that resemble places on natural reefs where coral would attach. Once the coral have embedded themselves, the seeding units are planted on reef areas in need of restoration.

It’s an effective approach, but a costly one, unfortunately.

“One of the ways SECORE is aiming to reduce these costs is by designing seeding units that do not need to be manually attached to the reef, but rather can be sown from a boat or other method, similar to how a farmer would sow seeds in a field,” said SECORE Project and Workshop Manager Aric Bickel.

3D printing is another way to keep costs down, as well as to rapidly produce the seeding units. SECORE aims to produce a million of the units by 2021, and hundreds of thousands of units annually by then. Phase One of the project is taking place in the Caribbean, with research and training hubs in Mexico, Curaçao and the Bahamas.

“3D printing allows us to do a bit of rapid prototyping. We were looking at several different materials, and 3D printing allows us to print a variety of materials,” Bickel said. “It also saves the cost of having to make molds or castings which, particularly for the initial prototypes, would be a significant amount of money invested.”

A diver with a tray of the seeding units [Image: SECORE/Benjamin Mueller]

CAS is one of SECORE’s primary funding providers, and because SECORE is a small team with limited engineering capabilities, CAS turned to the Autodesk Foundation, with which it looked into various design firms for help with the development of the seeding units.

“In collaboration with the Foundation, we reached out to several design firms,” Bickel said. “Emerging Objects seemed like they would be the best folks to help us out with this next design phase and hopefully with the iterative design phases as we go forward.”

One of the main challenges SECORE has been having is finding the best material and design combination for the seeding units. Not just any shape can be used – the units need to be able to wedge themselves into the reefs without manual assistance. The material is an issue, too. SECORE had been using rough cement for the seeding units, but that material worked a little too well – in addition to attracting corals, it also attracted quite a few competing organisms.

“One issue was with competition from other species on the units themselves,” said Bickel. “What the trials showed is that a slicker surface will cut down on that potential competition. The needle that you have to thread here is having a surface that’s rough enough for corals to settle on and to attach to but smooth enough that it’s not a good location for other organisms such as sponges and algae to attach to.”

Several years of trials and experiments revealed ceramic to be a good potential material for the seeding units. Emerging Objects has plenty of experience in the experimental use of 3D printed ceramic, but needed to be able to 3D print the material on a large scale, so the company reached out to Boston Ceramics for help.

“Boston Ceramics is one of the few companies we’re aware of in the world that can potentially meet some of the demands for the number of substrates we’ll be using,” said Bickel.

The team used Autodesk Netfabb to design the original shape, a tetrapod, for the seeding units, and has been experimenting with other designs that are better suited to landing and wedging themselves in the surfaces of the reefs and protecting the larvae. One of those designs looks like a ninja throwing star.

[Image: SECORE/Valérie Chamberland]

“The question we posed to our working group was, ‘Can you give us your best impression of what promotes coral larvae to grow, and what’s going to allow them to survive in the ocean as they grow up in these early life stages?’” said Bickel.

The SECORE project is not one of immediate gratification. The organization grows its corals from embryos in small conglomerations of cells, and depending on the species, it can take several years for the corals to become sexually mature. In earlier life stages, however, the coral can still provide habitats for fish and other species.

This elkhorn coral was outplanted by SECORE five years ago. Since then, it has grown into a mature colony, which now spawns with other elkhorn colonies in the waters of Curaçao. [Image: SECORE/Paul Selvaggio]

“It’s definitely an investment in the future,” Bickel said. “I think that with really complicated ecosystems, we’re talking many years before you start seeing comparable structure return to areas that are being restored. The main focus at the moment is, can we improve our methods and our technologies to upscale this type of restoration to the levels needed to counteract the decline?”

SECORE isn’t the only organization working to do so, and the hope is that with enough of them putting effort into restoring coral reefs, the damage can be mitigated and even reversed.

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[Source: Autodesk]