Other materials science stories that may be of interestPublished on July 16th, 2012 | Edited by: Peter Wray
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(Wall Street Journal) Employees at the General Electric Co. plant here are working on a tricky problem: how to mass produce parts from materials so new to jet engines, and so fragile to work with, that they must first learn by hand how to build them. GE is betting the future of its $18 billion jet-engine business on these composite materials-carbon fiber and ceramics that are more durable and weigh a third less than those made with the usual nickel and titanium alloys. The hope is to create engines that consume less fuel and cut maintenance costs for airlines. That’s if GE can build enough of the parts on time. Batesville plant manager Orianna Barrera and her team are still working out the best way to use carbon fiber to make parts like fan platforms-pieces that are installed between the front fan blades in GE’s GEnx engines, which power Boeing Co.’s new Dreamliner widebody jets.
Most people buy cornstarch to make custard or gravy, but Scott Waitukaitis and Heinrich Jaeger have used it to solve a longstanding physics problem with a substance known to generations of Dr. Seuss readers as “Oobleck,” and to scientists as a non-Newtonian liquid. The University of Chicago’s Waitukaitis and Jaeger suspect that many similarly constituted suspensions – liquids laden with micron-sized particles – will behave exactly the same way. Scientists and engineers have attempted to explain the underlying physics of this phenomenon since the 1930s, but with incomplete success. Now Waitukaitis and Jaeger report in the July 12 issue of the journal Nature how compressive forces can generate a rapidly growing, solid-like mass in the suspension. The study culminates a long struggle to understand a phenomenon that has elicited a wide range of explanations over the years.
By squeezing a porous solid, scientists surprisingly made its cavities open wider, letting in —and trapping—europium ions. Given the similarities between europium and uranium ions, the team, based at the University of South Carolina, Yonsei University (Korea), and Stanford University, thinks the innovation could represent a promising new avenue for nuclear waste processing. The focus of their work is natrolite, one of the many examples of aluminosilicate minerals called zeolites, which contain tiny, regularly spaced pores. Zeolites come in more than a hundred different forms, and the composition of each variant determines the size of the cavity and thus the kinds of molecules and ions that can be retained, or excluded, within. As a result, zeolites can separate and sort chemical species: Added to a solution containing a mixture of ions, they can selectively retain only those ions that can fit within the pores. The authors are building on a series of studies that demonstrate how to assert control over the kinds of guests that zeolites will hold within their cavities. The team uses a stimulus that is seldom used to control cavity size: pressure.
To the long list of exceptional physical properties of graphene, engineers have added yet another: piezoelectricity. Bend, squeeze, or twist it and it will produce an electric charge. Yet, while graphene is many things, it is not piezoelectric. Perhaps most valuably, piezoelectricity is reversible. When an electric field is applied, piezoelectric materials change shape, yielding a remarkable level of engineering control. Piezoelectrics have found application in countless devices from watches, radios and ultrasound to the push-button starters on propane grills, but these uses all require relatively large, three-dimensional quantities of piezoelectric materials. However, a Stanford University team’s engineered graphene has, for the first time, extended such fine physical control to the nanoscale.
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