Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.
Issue link: http://mp.epubxp.com/i/879896
6 OCTOBER 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 10 UP FRONT Acoustic Approach Targets Defects in Concrete Bridges The new detection system drags multiple strings of metallic balls along concrete. Photo courtesy of UNL. University of Nebraska (UNL) (Lincoln, Nebraska) researchers have designed an acoustic approach to detecting defects in concrete bridge decks. According to Jinying Zhu, a civil engineering professor, the sys- tem represents a faster, more accurate alter- native to conventional methods. "When we find delamination, we should fix it," Zhu says. Otherwise, she notes, the combination of road salt and precipitation in the winter could cause further corrosion. The system consists of a pushcart that drags multiple strings of balls made of brass. These balls produce different acoustic fre- quencies when striking delaminated vs. pris- tine concrete. Small attached microphones record sound and send it to a laptop that processes the signals. A specialized GPS unit tracks the cart's location. By correlating sig- nals with the position, the system's software generates a color-coded map that illustrates the location and dimensions of defects. Deep blue indicates pristine concrete, and dark red represents severe delaminations. Bridge inspectors have traditionally sought out delaminations by dragging chains and listening for hollow spots, and marking them with chalk or paint. "It's a very slow process, and it's subjective," Zhu says. As a result, her research team replaced chain links with metallic balls connected by nylon string. They found the ball-and-string combo enhanced the desired signals while reducing the noise. They also found that the balls produced more data points. Unlike chain links, which slide along the concrete while being dragged, the balls hop into the air when encountering even slight rough patches. Each time they land, they produce another signal—lessening the chances of missing a delamination. The researchers tested their system on multiple state bridges, adding that it takes about 20 minutes to assess bridge segments that would require roughly two hours with traditional chain-drag methods. For more information, visit news.unl.edu. Magnetic Nanoparticles Slow Corrosive Bacteria in Biofilms Bacteriophages combined with nanoparticle clusters are drawn into biofilms with a magnet. Photo courtesy of the Alvarez Group. Magnetic nanoparticle clusters are showing potential to punch through biofilms to reach and purge bacteria that can foul water treatment systems with problems such as corrosion, according to scientists at Rice University (Houston, Texas) and the Univer- sity of Science and Technology of China (Hefei, China). The nanoclusters developed through Rice's engineering research center carry bacteriophages—viruses that infect bacteria and propagate—and deliver them to targets that resist chemical disinfection. The phages were combined with nano- clusters of carbon, sulfur, and iron oxide that were further modified with amino groups. The amino coating prompted the phages to bond with the clusters head-first, which left their infectious tails exposed and able to infect bacteria. A weak magnetic field draws the clusters—and the phages— into biofilms to their targets. Without the pull of a magnetic host, these phages would disperse in solution, largely fail to penetrate biofilms, and allow bacteria to grow in solution and corrode metal—a costly problem for water distribu- tion systems. The researchers say biofilms can be ben- eficial in some wastewater treatment or industrial fermentation reactors because of their enhanced reaction rates and resis- tance to exogenous stresses. "However, bio- films can be very harmful in water distribu- tion and storage systems since they can shelter pathogenic microorganisms that pose significant public health concerns and may also contribute to corrosion and asso- ciated economic losses," says Rice student and study co-author Ping feng Yu. For more information, visit news.rice.edu. Researchers Create Digital 'Dictionary' of Metal Building Blocks Researchers at Brigham Young University (BYU) (Provo, Utah) developed a technique to produce a "dictionary" of the atomic building blocks found in metals, alloys, semiconductors, and other materials. Their approach analyzes data to provide insight into structures associated with specific mechanisms, processes, and properties. The goal of the project, which could be a 10- to 20-year process, is to more efficiently develop materials that help create strong, lightweight, and corrosion-free metals and alloys. "We're using machine learning, which means algorithms can see trends in data that a human can't see," says Engineering Professor Eric Homer. Researchers say their project, supported by the U.S. Department of Energy (Washington, DC), is the first attempt to combine the scientific knowl- edge of factors influencing grain boundaries with the computer algorithms of machine learning. These grain boundaries can influ- ence a metal's strength, corrosion resis- tance, and conductivity. "Siri works by taking sounds and turn- ing them into vowels and consonants and ultimately words by accessing a massive database," says BYU physicist Gus Hart, referring to the voice-controlled personal assistant on Apple devices. "We're using the same concept. We have a large database, and our algorithm is taking grain boundar- ies and comparing them against that data- base to connect them to certain properties." For more information, visit news.byu.edu. —Ben DuBose