A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 1 8 METALS | POLYMERS | CERAMICS generators. But the researchers think the process could easily be scaled up to make superhard metal coatings or larger industrial components. The key to the process, scientists say, is the chemical treatment given to the nanoparticle building blocks. Metal nanoparticles are typically covered with ligands, which generally prevent the formation of metal-metal bonds between particles. The team found a way to strip those ligands away chemically, allowing the clusters to fuse together with just a bit of pressure. In theory, the technique could be used to make any kind of metal and even metallic glass. The team has patented the technique and foresees widespread potential in both industry and the scientific research community. brown.edu. Various types of plate-lattices were designed and built by engineers in Glasgow, in the pursuit of lightweight engineering. Courtesy of University of Glasgow. This gold “coin” was made from nanoparticle building blocks. Courtesy of Chen Lab/Brown University. TOUGHER THAN ALUMINUM METAMATERIAL A team led by University of Glasgow, U.K., engineers developed a new plate-lattice cellular metamaterial capable of impressive resistance to impacts. Scientists say their new 3D-printed material, made by combining commonly used plastics with carbon nanotubes, is tougher and lighter than similar forms of aluminum. The material could lead to the development of safer structures for use in the aerospace, automotive, renewables, and marine industries. The composite uses mixtures of polypropylene, polyethylene, and multiwall carbon nanotubes. The researchers used their nanoengineered filament composite as the feedstock in a 3D printer that fused the filaments together to build a series of plate-lattice designs. Those designs were then subjected to a series of impact tests. The hybrid design, which amalgamated elements of all three typical plate-lattice designs, proved to be the most effective in absorbing impacts, with the polypropylene version showing the greatest impact resistance. Using specific energy absorption as a measure, the team found that the polypropylene hybrid plate-lattice could withstand 19.9 joules per gram—a superior performance over similarly designed microarchitected metamaterials based on aluminum. www.gla.ac.uk. MAKING SUPERHARD METALS Researchers from Brown University, Providence, R.I., created a new method to customize metallic grain structures by smashing individual metal nanoclusters together to form solid macroscale hunks of solid metal. Mechanical testing of the metals manufactured using the technique showed that they were up to four times harder than naturally occurring metal structures. The researchers made centimeter-scale coins using nanoparticles of gold, silver, palladium, and other metals. Items of this size could be useful for making high-performance coating materials, electrodes, or thermoelectric Researchers from the University of California’s San Diego and Berkeley campuses, Carnegie Mellon University, and the University of Oxford produced islands of amorphous, noncrystalline material inside high-entropy alloys. Potential applications include landing gear, pipelines, and automobiles, with the new material able to make these structures lighter, safer, and more energy efficient, according to the team. ucsd.edu. BRIEF IMPROVING CERAMIC FUEL CELL PERFORMANCE Researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed a new technology
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