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 2 5 MATERIALS TESTING PRESERVES MARITIME GEM Engineers at the University of Southampton and the National Museum of the Royal Navy (NMRN), both in the U.K., are collaborating to find the best materials to ensure the 18th century warship HMS Victory is weatherproof for another 50 years. The University’s nC2 Engineering Consultancy carefully designed a series of tests to assess the long-term performance of a range of paints, caulking, glues, and metal fastenings. The team is conducting a variety of tests on specially prepared samples. Tests are repeated using different RESEARCH TRACKS combinations of products on samples that have been treated to simulate the effects of wear, rain, sunlight, and time. For example, paint is tested for adherence to wood along with flexibility and water resistance. The same tests are then conducted on samples that have been aged using UV and salt spray, and samples that have been cooled or heated to specific temperatures. The first phase of the project is now underway. Using hundreds of oak samples prepared by NMRN’s shipwrights, nC2 is assessing the performance of nine different types of caulking and glue and five paint systems. A future phase will examine metal plank fastenings to see how they interact with the wood, paint, and caulking and examine any corrosion. www.southampton.ac.uk. PERKING UP PEROVSKITES Researchers at the University of California, Los Angeles along with colleagues from five other universities discovered the key reason why perovskite solar cells degrade in sunlight. Metal halide perovskites are of particular interest due to their promising application in energy-efficient, thinfilm solar cells. Perovskite-based solar cells can be manufactured at much lower costs than their silicon-based counterparts, making solar energy more accessible if the widely known degradation from long exposure to illumination could be addressed. A common surface treatment used to remove solar cell defects involves depositing a layer of organic ions HMS Victory in Portsmouth with HMS Queen Elizabeth behind. Courtesy of NMRN. that makes the surface too negatively charged. The team found that while the treatment is intended to improve energy-conversion efficiency during the fabrication process of perovskite solar cells, it also unintentionally creates a more electron-rich surface—a potential trap for energy-carrying electrons. This condition destabilizes the orderly arrangement of atoms, causing perovskite solar cells to become increasingly less efficient over time and ultimately making them unattractive for commercialization. With the new discovery, the team found a way to address the cells’ longterm degradation by pairing the positively charged ions with negatively charged ones for surface treatments. The switch enables the surface to be more electron-neutral and stable, while preserving the integrity of the defect-prevention surface treatments. Researchers tested the endurance of their solar cells in a lab under accelerated aging conditions and 24/7 illumination: The cells retained 87% of their original sunlight-to-electricity conversion performance for more than 2000 hours. In the control group, solar cells manufactured without the fix dropped to 65% of their original performance over the same time and conditions. ucla.edu. Thin-film perovskite solar cell produced with a manufacturing process tweak. Courtesy of UCLA. Researcher Nicola Symonds performs a tensile test on a wood sample. Courtesy of NMRN.
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