[Image above] Pixabay
Looking back at my posts this year, I find that I focused on three themes: advanced energy, process and measurement improvements, and guidance for authors.
I suppose these topics should not surprise me. My passion for environmental issues such as advanced energy should be clear to those who read my posts. As an analytical engineer and problem solver by training, I seek out efficiencies and the benefits they bring.
Thus, I chose my five favorite CTTs of 2021 to tell a larger story of advanced energy and how ceramics can address these needs with an eye toward cost-effective manufacturing.
“Moving away from carbon-based energy and toward sustainable energy infrastructure is important for long-term world health. The latest Kavli Lecture hosted by The Royal Society looks at the possible role of fusion energy in our sustainable energy future.”
I was impressed with the Kavli lecture, which, like so many meetings these past two years, was delayed and eventually held virtually. As I was writing about the progress being made in the United Kingdom and European Union toward nuclear fusion scale-up, I also was fascinated to learn more about the fusion naysayers’ point of view.
Indeed, billions and perhaps trillions have been spent on this technology, yet “ignition” (net positive reaction energy) has yet to be achieved. Still the research is moving forward as the technology promises electricity generation with minimal greenhouse gas emissions and radioactive waste.
It will be interesting to see if fusion energy will provide electric baseloads in the future or if that global need will be met by energy storage methods, such as next-generation batteries or hydrogen.
“MAX phases are layered ceramic materials with both ceramic and metal-like properties, as well as good radiation tolerance, making them ideal candidates for use in next-generation nuclear power technologies. Two recent papers investigate the irradiation of Cr2AlC to determine its potential for this application.”
Ceramics will play a substantial role in fusion energy, from superconducting magnet wire to radiation and heat shielding within the reactor, and more. It’s important to note that the radiation in fusion reactors is mainly in the form of high-energy ions of hydrogen, helium, and other “fuel” or “product” elements of the reaction. The momentum transferred by these ions colliding with the shielding material moves atoms around, much like billiard balls. These motions can result in changes to the crystal structure or complete destruction (amorphitization), which in turn weakens the shielding.
MAX phases show promise for shielding applications and can be fabricated relatively inexpensively, two characteristics that dovetail directly with issues identified in the Kavli lecture. The two studies discussed in this CTT showed very different damage mitigation mechanisms, albeit for very different ions. In one, helium ion implantation took advantage of the layered structure of the MAX phases. The helium ions reorganized the elements in the “open” layers and created dimensionally compatible solid solutions. Annealing reverted the structure back to the MAX phase, albeit with some delamination due to helium migration. In the other study, xenon ions implanted in amorphous phase boundaries with minimal effect on the MAX phase.
“Many researchers are working to uncover alternatives to yttria stabilized zirconia for use as environmental barrier coatings. High-entropy oxides are among the classes of materials being explored, and two papers in Journal of the American Ceramic Society explore different high-entropy oxide systems.”
Complicated structures are also the driving force behind high-entropy materials. More than just alphabet soups of elements, high-entropy oxides are designed by taking a typical material such as yttrium tantalite (YTaO4) and partially substituting elements with the same valence but different sizes. For example, cerium (Ce3+) for the yttrium (Y3+) or niobium (Nb5+) for tantalum (Ta5+). The size differences lead to disorder, i.e., higher entropy.
Much like MAX phases, high-entropy oxides can resist damage via structural rearrangement. The structural rearrangement of high-entropy materials leads to higher toughness, a macroscopic property. Interestingly, the structure of high-entropy materials can absorb mechanical energy via ferroelastic twinning transformations. Basically, the absorbed energy shifts the crystal structure in space but doesn’t disrupt it. Imagine an umbrella turning inside out to absorb high winds. Yet the distortion creates structures so strong that when cracks do form, they cannot break bonds within the crystals. Instead, they deflect and run along the grain boundaries.
“Recent articles on carbon nanotube-containing ceramic composites showed improved properties compared to the original ceramic composite. Two recent articles in ACerS journals demonstrate these improvements.”
Crack deflection and reducing manufacturing costs are key design parameters for studies on incorporating carbon nanotubes into ceramics. Authors of two recent papers found that additions of small amounts of nanotubes (0.5–5% depending on the application) dramatically improved toughness through a mix of crack deflection, strength of the nanotubes, and fiber pull-out. Low cost-manufacturing was achieved via low-cost methods such as spray-coating of an enamel suspension or freeze-drying of an alumina suspension.
TOC alerts in CTT
My final favorite is not a singular post. Rather, we instituted posting snippets of the tables of content for the four ACerS Journals in the CTT e-newsletter as each issue is published. You can subscribe to the e-newsletter here.
I very much hope you found these posts to be useful and, even better, they inspired you to sign up to receive New Content Alerts so you can stay informed about the latest articles published by ACerS. If you have not yet signed up for New Content Alerts, follow the instructions here to get the TOC alerts along with the Accepted Article and Early View listings delivered to your email every month.