Effects of Grain Boundary Disorder on Yield Strength

It was recently reported that segregation of Zr to grain boundaries (GB) in nanocrystalline Cu can lead to the formation of disordered intergranular films [1,2]. In this study we employ atomistic computer simulations to study how the formation of these films affects the dislocation nucleation from the GBs. We found that full disorder of the grain boundary structure leads to the suppression of dislocation emission and significant increase of the yield stress. Depending on the solute concentration and heat-treatment, however, a partial disorder may also occur and this aids dislocation nucleation rather than suppressing it, resulting in elimination of the strengthening effect

Posterminaries: Warming to the Fight

Multiscale effects are challenging issues in materials science, but ours is not the only domain in which they are of current interest. Global climate change obviously operates at the largest length-scales available on a planet the size of Earth (or even Saturn, where the famous red spot is shrinking) but it is a product of effects that operate on the scales of individual machines, buildings, cities, tidal systems, and the molecular reactions within each of these. Understanding all of these is a daunting task

Posterminaries: Signing Off

“Bright lights” are a universal metaphor for the generic big city, but there are a few cities that are iconically associated with specific and highly recognizable bright lights. Times Square is the world-known symbol for New York City, as are the lights in Piccadilly Circus for London, and The Strip for Las Vegas. For most of the second half of the 20th century the light for these displays was generated by neon glowing in intricately formed glass tubes, and their particular hues, jerky animation, and flickering unreliability symbolized all that was simultaneously glamorous and tawdry about night life in the city

Posterminaries: Business Lessens

Let there be no mistake about it: The news business is in trouble. Once it was powerful enough to have been identified as an unofficial branch of government in the United Kingdom (the “fourth estate”) and accorded its own mention in the First Amendment to the U.S. Constitution, but today the press is in a steep decline. Newspapers are failing across the world and those that survive are getting very lean

Posterminaries: No, No, Nano

Your siblings already know that you do stuff that they cannot, and probably don’t even want to, understand. But their husbands and wives are more insistent. “What’s all this nanotechnology stuff, anyway? Where can I buy some stock in it?” There are colleagues, too, who still ask after all this time, “Is this ‘nano’ thing real or just a bunch of hype? Isn’t it just the same stuff we were already doing with a new label?

Posterminaries: Learning about the Learning Curve

Among the pleasures of the “researcher lifestyle” is the joy of always learning something new. If the shock of the new is the jolt that gets you going, then you probably have the mindset of a researcher, or maybe an artist. Art and science share some aspects as lifestyles, but there are essential differences, too. Paul Gaugin commented that “art is either plagiarism or revolution,” but science certainly does not have to be plagiarism if it is not revolutionary: in fact, it had better not. Researchers almost always work in the context of what has been discovered before

Posterminaries; Contributions to a Conceit

Humankind has always thought that it is special. Even from an early age we humans are instinctively sure of our superiority. It was certainly inconceivable to me, at age four or so, that my six-year old sister could be right about anything, so when she casually informed me that I was “just an animal,” I confidently dismissed her pronouncement as mere rhetoric. Or I probably would have, if I had known what rhetoric was. Still, it was certainly a disquieting thought that there was no fundamental difference between humans and animals

Posterminaries: Preferred Futures—and How Do We Get There From Here?

The last several months have seen new attention being paid to alternative sources of energy, and to the area of energy efficiency in general. You can choose your own reason for taking an interest: reversing global warming, peak oil theory, escaping from OPEC’s control of prices, stopping the flow of oil revenues to terrorist organizations, creating new jobs, or more parochially just generating more funding for research. These are all good reasons, and while some of them appeal to certain people more than others, there are now few people living in developed countries who deny the need to move away from dependence on oil, if not all fossil fuels