ADVANCED MATERIALS & PROCESSES | MAY/JUNE 2024 13 SURFACE ENGINEERING COLD SPRAY TANTALUM COATING Researchers at the University of Wisconsin-Madison are using a new coating technology to produce a hardworking material that can withstand the harsh conditions inside a fusion reactor. The team used a cold spray process to deposit a coating of tantalum on stainless steel, then tested it in extreme conditions. Notably, they found that the material is exceptionally good at trapping hydrogen particles, which is beneficial for compact fusion devices. “We discovered that the cold spray tantalum coating absorbs much more hydrogen than bulk tantalum because of the unique microstructure of the coating,” says Professor Kumar Sridharan, FASM. “The simplicity of the cold spray process makes it very practical for applications.” Over the past decade, Sridharan’s research group has introduced cold spray technology to the nuclear energy community by implementing it for multiple applications related to fission reactors. In fusion devices, plasma is heated to extremely high temperatures, and atomic nuclei in the plasma collide and fuse, producing energy. However, some hydrogen ions may get neutralized and escape from the plasma. To avoid this, the researchers aimed to create a new surface for plasma-facing reactor walls that could trap hydrogen particles as they collide with the walls. Tantalum is inherently good at absorbing hydrogen— and the team suspected that creating a tantalum coating using a cold spray process would boost its hydrogentrapping abilities even more. During testing, it was discovered that when heating the material to a higher temperature, it expelled the trapped hydrogen particles without modifying the coatings, a process that essentially regenerates the material so it can be used again. Another major benefit of the cold spray method is that it allows repair of reactor components on site by applying a new coating rather than requiring a completely new part. The team plans to use their new material in the Wisconsin HTS Axisymmetric Mirror, an experimental device under construction near Madison, which will serve as a prototype for a next-generation fusion power plant that UWMadison spinoff Realta Fusion plans to develop. wisc.edu. CHEMICAL FREE VIRUCIDAL SURFACE An international team of researchers from Australia’s RMIT University and the University of Rovira i Virgili (URV) in Spain created a surface that uses mechanical means to mitigate the infectious potential of viruses. Made of silicon, the artificial surface consists of a series of tiny spikes that damage the structure of viruses they encounter. The process of making the virucidal surfaces starts with a smooth metal plate, which is bombarded with ions to strategically remove material. The result is a surface full of needles that are 2 nm thick and 290 nm high. “In this case, we used silicon because it is less complicated technically speaking than other metals,” explains URV researcher Vladimir Baulin. The findings show that this method is extremely effective and incapacitates 96% of viruses that come into contact with the surface within a period of six hours. The study confirmed that the surfaces have a virucidal effect because of the ability of the needles to destroy or incapacitate viruses by damaging their external structure or piercing the membrane. Using this technology in high-risk environments such as laboratories or health centers in which there is potentially dangerous biological material would make it easier to contain infectious diseases and make these environments safer for researchers, health workers, and patients. www.urv. cat/en, www.rmit.edu.au. From le : Engineer Jeremiah Kirch, postdoctoral researcher Mykola Ialovega, and assistant scientist Marcos Xavier Navarro-Gonzalez work on the implementation of tantalum coatings as a plasma-facing material for the WHAM device, pictured in the background. Courtesy of Mykola Ialovega. Graphical depiction of artificial surface with spikes used to pierce and kill viruses. Courtesy of URV and RMIT University (Australia).
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