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6 NOVEMBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 11 UP FRONT Corrosive Water Risk Rises in Bay Thomas Point Shoal Lighthouse. Photo by United States Coast Guard, PA1 Pete Milnes. Chesapeake Bay, the largest U.S. estuary, could have more corrosive water than expected in a layer 10 to 15 m beneath the surface, a new study finds. A decline in cal- cium carbonate (CaCO 3 )-shelled organ- isms—particularly oysters—may be ham- pering the bay's ability to deal with acidity. "Oysters and other bivalves provide a built-in Tums effect that naturally helps the bay deal with corrosive water," says George Waldbusser, a marine ecologist with Oregon State University (Corvallis, Oregon). "They generate large amounts of [CaCO 3 ] struc- tures, which may be able to buffer the increasing amounts of carbon dioxide [CO 2 ] entering the bay. Overharvesting and dis- ease have reduced the number of oysters, however." Their study found pH levels in this strat- ified layer to be ~7.4, nearly a unit lower than surface waters, where the pH is ~8.2. Several factors likely caused this corrosive zone, including hypoxia from agricultural nutrients entering the bay and depleting oxygen levels, as well as the generation of hydrogen sulfide (H 2 S) in bottom waters mixing with other layers. "This study shows for the first time that the oxidation of [H 2 S] and ammonia from the bottom waters could be a major contrib- utor to lower pH in coastal oceans and may lead to more rapid acidification in coastal waters compared to the open ocean," says lead author Wei-Jun Cai from the University of Delaware (Newark, Delaware). For more information, visit www. oregonstate.edu. Carbon Nanofiber Electrode Reduces Corrosive Fluids The carbon nanofiber electrode can replace corrosive electrolyte fluids. Photo courtesy of Drexel. Researchers with Drexel University (Phila- delphia, Pennsylvania) have created a sol- vent-free, fabric-like electrode material to make energy storage devices—batteries and supercapacitors—that are faster, more durable, and less susceptible to leaks. Traditional electrolyte fluids can be cor- rosive, toxic, and even flammable. To keep up with mobile technologies, devices are subject to material shrinking during design, leaving them vulnerable to short-circuiting. The Drexel electrode uses a thick, ion-rich gel electrolyte that is absorbed in a free- standing mat of carbon nanofibers to pro- duce a liquid-free device. "To allow industrially relevant electrode thickness and loading, we have developed a cloth-like electrode composed of nanofibers that provides a well-defined, three-dimen- sional open pore structure for easy infusion of the solid electrolyte precursor," says Vibha Kalra, a professor in Drexel's College of Engineering. "The open-pore electrode is also free of binding agents that act as insu- lators and diminish performance." The key is a fiber-like framework cre- ated through electrospinning, which extrudes the solution through a rotating electric field. The ionogel is absorbed to cre- ate an electrode-electrolyte network. The performance characteristics are tied to this combination, because contact is made over a larger surface area. This process also elim- inates the need for scaffolding materials used to form the physical electrode, thereby reducing costs. Their next step is applying this tech- nique to the production of solid-state batteries. For more information, visit www. drexel.edu. Electronic Water Sensor Detects Lead from Corrosion The electronic lead sensor features two pairs of electrodes. Photo courtesy of Wen-Chi Lin, Burns Lab, University of Michigan. A new electronic sensor could alert users to the presence of lead within days. The sensor was developed by University of Michigan (Ann Arbor, Michigan) researchers follow- ing the water crisis in Flint, Michigan, where corrosion of service pipes after a water source change caused lead to leach into the water supply. According to Mark Burns, T.C. Chang Professor of Chemical Engineering at the university, standard sample tests require running water for several minutes and could miss any lead leaching from the home's pipes. He says the sensor, costing ~$20, could be placed at key points in a city water system and at taps in homes. The trick is separating lead from other metals that may be present. In response, researchers designed the sensor to differentiate different metals by relying on two pairs of electrodes, each with a neutral neighbor. The positive electrode and its neutral neighbor set up an electron- poor environment, while the negative elec- trode and its neutral neighbor create an electron-rich environment. Lead is attracted to the positive side, as it is the only contaminant metal that readily loses more electrons and oxidizes further. As lead builds up on the positive electrode, it reaches the neutral electrode, closes the circuit, and generates voltage. Above a 1 V signal, the system registers a hit. "There could be an app that would mon- itor all the taps, and it could just send you a message when it detected an event," Burns says. Researchers are seeking partners to bring the technology to market. For more information, visit www.umich. edu. —Ben DuBose