Hexbyte Glen Cove Exploding and weeping ceramics provide path to new shape-shifting material

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Creating shape-shifting materials is not an easy process. It involves a delicate tuning of the distances between atoms by compositional changes, so that the two phases fit together well. This diagram shows what happened when researchers implemented this recipe with one sample of ceramic material. Instead of improving the deformability of the ceramic, they observed that some specimens gradually fell apart into a pile of powder, a phenomenon they termed “weeping.” Credit: Gu, et al., University of Minnesota and Kiel University

An international team of researchers from the University of Minnesota Twin Cities and Kiel University in Germany have discovered a path that could lead to shape-shifting ceramic materials. This discovery could improve everything from medical devices to electronics.

The research is published in Nature.

Anyone who has ever dropped a coffee cup and watched it break into several pieces, knows that ceramics are brittle. Subject to the slightest deformation, they shatter. However, ceramics are used for more than just dishes and bathroom tiles, they are used in electronics because, depending on their composition, they may be semiconducting, superconducting, ferroelectric, or insulating. Ceramics are also non corrosive and used in making a wide variety of products, including , , , space shuttle tiles, chemical sensors, and skis.

On the other end of the materials spectrum are . They are some of the most deformable or reshapable materials known. Shape memory alloys rely on this tremendous deformability when functioning as medical stents, the backbone of a vibrant medical device industry both in the Twin Cities area and in Germany.

The origin of this shape-shifting behavior is a solid-to-solid phase transformation. Different from the process of crystallization–melting–recrystallization, crystalline solid–solid transitions take place solely in the solid state. By changing temperature (or pressure), a crystalline solid can be transformed into another crystalline solid without entering a .







This video shows a sample of ceramic material that has a composition tuned to have excellent compatibility between phases, but poor compatibility at grain boundaries. It explodes when passing through phase transformation. Credit: Jascha Rohmer, Kiel University

In this new research, the route to producing a reversible shape memory ceramic was anything but straightforward. The researchers first tried a recipe that has worked for the discovery of new metallic shape memory materials. That involves a delicate tuning of the distances between atoms by compositional changes, so that the two phases fit together well. They implemented this recipe, but, instead of improving the deformability of the ceramic, they observed that some specimens exploded when they passed through the phase transformation. Others gradually fell apart into a pile of powder, a phenomenon they termed “weeping.”

With yet another composition, they observed a reversible transformation, easily transforming back and forth between the phases, much like a shape memory material. The mathematical conditions under which reversible transformation occurs can be applied widely and provide a way forward toward the paradoxical shape-memory .

“We were quite amazed by our results. Shape-memory ceramics would be a completely new kind of functional material,” said Richard James, a co-author of the study and a Distinguished McKnight University Professor in the University of Minnesota’s Department of Aerospace Engineering Mechanics. “There is a great need for shape memory actuators that can function in high temperature or in corrosive environments. But what excites us most is the prospect of new ferroelectric ceramics. In these materials, the phase transformation can be used to generate electricity from small temperature differences.”







This video shows a sample that has a composition tuned to have excellent compatibility between phases, but poor compatibility at grain boundaries. It gradually falls apart at the grain boundaries on passing through phase transformation. A phenomenon the authors call “weeping.”. Credit: Jascha Rohmer, Kiel University

The team from Germany was responsible for the experimental part and the chemical and structural investigation at the nanoscale.

“For the explanation of our experimental discovery that, contrary to expectation, the ceramics are extremely incompatible and explode or decay, the collaboration with Richard James’ group at the University of Minnesota was very valuable,” says Eckhard Quandt, a co-author of the study and a professor in the Institute for Materials Science, at Kiel University. “The theory developed on this basis not only describes the behavior, but also shows the way to get to the desired compatible ceramics.”

James also highlighted the importance of the collaboration between the University of Minnesota and Kiel University.







This video shows a sample of ceramic material that transforms back and forth between the phases, much like a shape memory material. The mathematical conditions under which reversible transformation occurs can be applied widely and provide a way forward toward the paradoxical shape-memory ceramic. Credit: Jascha Rohmer, Kiel University

“Our collaboration with Eckhard Quandt’s group at Kiel University has been tremendously productive,” added James. “As in all such collaborations, there is sufficient overlap that we communicate well, but each group brings plenty of ideas and techniques that expand our collective ability to discover.”

In addition to James and Quandt, the research team included Lorenz Kienle from Kiel University Andriy Lotnyk from the Leibniz Institute of Surface Engineering, and graduate students Hanlin Gu, Jascha Romer, and Justin Jetter.



More information:
Hanlin Gu et al, Exploding and weeping ceramics, Nature (2021). DOI: 10.1038/s41586-021-03975-5

Citation:
Exploding and weeping ceramics provide path to new shape-shifting material (2021, November 17)
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from https://phys.org/news/2021-11-ceramics-path-shape-shifting-material.html

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Hexbyte Glen Cove Making the best decision: Math shows diverse thinkers equal better results thumbnail

Hexbyte Glen Cove Making the best decision: Math shows diverse thinkers equal better results

Hexbyte Glen Cove

Sketch of the collective decision-making process described by Karamched et al. In a population of undecided agents (blue), an early adopter (red) makes a poor decision. Seeing this decision, a set of early adopters follow suit, but a slightly larger set of early adopters (green) picks the most beneficial solution. After observing the decision-making dynamics of the early adopters, laggards make their decision, leading a large fraction of the population to correct the initial, poor decision. Credit: APS/Alan Stonebraker

Whether it is ants forming a trail or individuals crossing the street, the exchange of information is key in making everyday decisions. But new Florida State University research shows that the group decision-making process may work best when members process information a bit differently.

Bhargav Karamched, assistant professor of mathematics, and a team of researchers published a new study today that tackles how groups make decisions and the dynamics that make for fast and accurate decision making. He found that networks that consisted of both impulsive and deliberate individuals made, on average, quicker and better decisions than a group with homogenous thinkers.

“In groups with impulsive and deliberate individuals, the first decision is made quickly by an impulsive individual who needs little evidence to make a choice,” Karamched said. “But, even when wrong, this fast decision can reveal the correct options to everyone else. This is not the case in homogenous groups.”

The paper is published in Physical Review Letters.

Researchers noted in the paper that the exchange of is crucial in a variety of biological and social functions. But Karamched said although information sharing in networks has been studied quite a bit, very little work has been done on how individuals in a network should integrate information from their peers with their own private evidence accumulation. Most of the studies, both theoretical and experimental, have focused on how isolated individuals optimally gather evidence to make a choice.

“This work was motivated by that,” Karamched said. “How should individuals optimally accumulate evidence they see for themselves with evidence they obtain from their peers to make the best possible decisions?”

Krešimir Josić, Moores Professor of Mathematics, Biology and Biochemistry at the University of Houston and senior author of the study, noted that the process works best when individuals in a group make the most of their varied backgrounds to collect the necessary materials and knowledge to make a final decision.

“Collective social decision making is valuable if all individuals have access to different types of information,” Josić said.

Karamched used mathematical modeling to reach his conclusion but said there is plenty of room for follow-up research.

Karamched said that his model assumes that evidence accrued by one individual is independent of evidence collected by another member of the group. If a group of individuals is trying to make a decision based on information that is available to everyone, additional modeling would need to account for how correlations in the information affects collective -making.

“For example, to choose between voting Republican or Democrat in an election, the information available to everyone is common and not specifically made for one individual,” he said. “Including correlations will require developing novel techniques to analyze models we develop.”



More information:
Bhargav Karamched et al. Heterogeneity Improves Speed and Accuracy in Social Networks, Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.125.218302

Citation:
Making the best decision: Math shows diverse thinkers equal better results (2020, November 16)
retrieved 17 November 2020
from https://phys.org/news/2020-11-decision-math-diverse-thinkers-equal.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Read More Hexbyte Glen Cove Educational Blog Repost With Backlinks —