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Tech Front: Li-ion Battery Tech Leads to Hydrogen Production

 

Developers of electric cars that used lithium-ion batteries are racing the champions of hydrogen-fueled vehicles to see which will succeed the greenhouse gas-producing gasoline-powered internal combustion engine.

They’ve been racing in different directions—until now: Scientists at Stanford University have created a low-voltage, low-cost “water splitter” that uses a single catalyst to continuously produce both hydrogen and oxygen from water. That catalyst was created by a team co-led by Yi Cui, an associate professor of materials science and engineering at Stanford and of photon science at the SLAC National Accelerator Laboratory, using lithium-ion battery technology.

“Our group has pioneered the idea of using lithium-ion batteries to search for catalysts,” Cui said. “Our hope is that this technique will lead to the discovery of new catalysts for other reactions beyond water splitting.” Stanford University graduate student Haotian Wang examines the novel water splitter that produces hydrogen and oxygen gas 24 hours a day, seven days a week.

The water-splitting device is described in a study published on June 23 in the journal Nature Communications and was announced in a Stanford news release the same day.

Despite its sustainable reputation, most commercial-grade hydrogen is made from natural gas, a fossil fuel. As a greener alternative, researchers have sought to develop a cheap and efficient way to extract pure hydrogen from water. A conventional water-splitting device consists of two electrodes submerged in a water-based electrolyte.

“Our water splitter is unique because we only use one catalyst, nickel-iron oxide, for both electrodes,” said graduate student Haotian Wang, lead author of the study. “This bi-functional catalyst can split water continuously for more than a week with a steady input of just 1.5 volts of electricity. That’s an unprecedented water-splitting efficiency of 82% at room temperature.”

Wang and his colleagues discovered that nickel-iron oxide, which is cheap and easy to produce, is actually more stable than some commercial catalysts made of precious metals. The team built a conventional water splitter with one platinum and one iridium, Wang said. That device started off well, needing only 1.56 volts to split water initially, but within 30 hours the voltage needed to be increased nearly 40%, “a significant loss of efficiency,” according to Wang.

In conventional water splitters, the hydrogen and oxygen catalysts often require different electrolytes with different pH–one acidic, one alkaline–to remain stable and active. “For practical water splitting, an expensive barrier is needed to separate the two electrolytes, adding to the cost of the device,” Wang said.

To find catalytic material suitable for both electrodes, the Stanford team borrowed a technique used in battery research called lithium-induced electrochemical tuning. The idea is to use lithium ions to chemically break the metal oxide catalyst into smaller and smaller pieces. “This process creates tiny particles that are strongly connected, so the catalyst has very good electrical conductivity and stability,” Cui said.

 

Web Content: Polymer Fiber Mimics Spider Silk

Polytechnique Montréal researchers have produced a biomimetic polymer fiber directly inspired by the structure of spider silk. They say that composites made by weaving together tough fibers of this type could make possible safer and lighter casings for aircraft engines, as an example. Or at least that’s their spin.

The university announced that Professors Frédérick Gosselin and Daniel Therriault, along with their master’s student Renaud Passieux have recently published an article about the project in the journal Advanced Materials.

Spider silk is 3–8 µm in diameter but five to ten times tougher than steel or Kevlar.Only 3–8 µm in diameter but five to ten times tougher than steel or Kevlar, spider silk has remarkable elongation and stretch-resistance properties that humans have long sought to replicate. Spider silk owes its exceptional strength—its ability to absorb a large amount of energy before failing—to the particular molecular structure of the protein chain of which it’s composed. The mechanical origin of its strength drew the interest of researchers at the Laboratory for Multiscale Mechanics in Polytechnique Montréal’s Department of Mechanical Engineering.

“The silk protein coils upon itself like a spring. Each loop of the spring is attached to its neighbors with sacrificial bonds, chemical connections that break before the main molecular structural chain tears,” explained Gosselin, who, along with Therriault, is co-supervising Passieux’s master’s research work. He added: “To break the protein by stretching it, you need to uncoil the spring and break each of the sacrificial bonds one by one, which takes a lot of energy. This is the mechanism we’re seeking to reproduce in laboratory.”

Their project involves making micron-sized microstructured fibers that have mechanical properties similar to those of spider silk. “The filament forms a series of loops or coils, kind of like when you pour a thread of honey onto a piece of toast,” said Passieux. “It forms regular periodic patterns, which we call instability patterns.”

The fiber then solidifies as the solvent evaporates. Some instability patterns feature the formation of sacrificial bonds when the filament makes a loop and bonds to itself. At that point, it takes a pull with a strong energy output on the resulting fiber to succeed in breaking the sacrificial bonds, as they behave like protein-based spider silk.

 

Biofuel Research Broke the Mold


Scientists at the Manchester Institute of Biotechnology (MIB) at UK’s University of Manchester have identified the exact mechanism and structure of two key enzymes isolated from yeast molds that together provide a new, cleaner route to the production of hydrocarbons. The university announced the discovery in a June news release, saying that the discovery will lead to the development of new applications in biofuels and sustainable chemical manufacturing.

Published in the science journal Nature, the research offers the possibility of replacing the need for oil in current industrial processes with a greener and more sustainable natural process.

Lead investigator Professor David Leys, noting the finite and dwindling level of oil reserves used for fuels, plastics and petrochemicals, said, “While the direct production of fuel compounds by living organisms is an attractive process, it is currently not one that is well understood, and although the potential for large-scale biological hydrocarbon production exists, in its current form it would not support industrial application, let alone provide a valid alternative to fossil fuels.”

Leys and his team investigated in detail the mechanism whereby common yeast mold can produce kerosene-like odors when grown on food containing the preservative sorbic acid. They found that these organisms use a previously unknown modified form of vitamin B2 (flavin) to support the production of volatile hydrocarbons that caused the kerosene smell. Their findings also revealed the same process is used to support synthesis of vitamin Q10 (ubiquinone).

Using the Diamond synchrotron source at Harwell in Britain, they analyzed this bio catalytic process at the atomic level and found it shares similarities with procedures commonly used in chemical synthesis but previously thought not to occur in nature.

Leys said: “Now that we understand how yeast and other microbes can produce very modest amounts of fuel-like compounds through this modified vitamin B2-dependent process, we are in a much better position to try to improve the yield and nature of the compounds produced.”

 

Friction Stir Lap Joining of Aluminum-Lithium Alloy for Aerospace 

 Friction Stir Welding, first invented by TWI in 1991, is becoming a joining method of importance in aerospace.Friction Stir Welding (FSW) is a relatively recent joining process that uses friction to heat adjoining metal structures enough to plasticize and ‘stir’—intermix—them without actually melting them as in traditional welding. First proven out by UK’s The Welding Institute (TWI) in 1991, it’s been beneficial to the production of metallic wings, fuselages and other aerostructures. At Vanderbilt University, four Dept. of Mechanical Engineering researchers—BT Gibson, MC Ballun, GE Cook and AM Strauss—took a look at the weld strengths of conventional FSW compared to weaved FSW and pulsed FSW. They shared their results in “Friction stir lap joining of 2198 aluminum–lithium alloy with weaving and pulsing variants,” published in the April 2015 edition of SME’s Journal of Manufacturing Processes.

Lap joints of 2198-T8 Al–Li alloy in 1.6-mm sheet thickness were friction stir welded to investigate the combination of this material and assembly method for the manufacturing of aerospace structures, they write. They also looked at tool geometry variables, comparing a more traditional flat shoulder tool geometry operated with a tilt angle to a tapered shoulder tool geometry operated at a 0° tilt angle, which offers the possibility of simplifying robotic welding operations. Another variable examined was the use of faying surface sealant, “the use of which is critical in aerospace applications, to determine its impact on weld strength and to characterize its interactions with welding parameters and process variants,” they wrote. Their conclusions—and a wealth of current process research and how to submit your own research—can be accessed via the journal’s Web site at http://www.journals.elsevier.com/journal-of-manufacturing-processes/.

Tech Front is edited by Senior Editor Michael C. Anderson 

 

This article was first published in the August 2015 edition of Manufacturing Engineering magazine. Click here for PDF.


Published Date : 8/1/2015

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