A new, bigger home for Materialia Indica

Update (31 August 2013): Things have changed since we mad this announcement back in 2009. Due primarily to lack of activity at our site at ning.com, we are saying good bye to it. Now, the Materialia Indica community  has a page on Facebook and Google +.

This blog will continue to exist. Some of the content from the ning.com site may get transplanted here, along with the original content that appeared here first.

[End Update; Original post appears below]

A quick announcement to tell you all that Materialia Indica now has a second home which is bigger, more open, and more feature-rich.

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Classics in Materials Science: Shockley and Read’s dislocation models of crystal grain boundaries

Any crystalline material contains many defects. Depending on the topology of the defects, they can be classified as point, line, surface and volume defects. Of these, only point defects are equilibrium defects — that is, at any temperature above absolute zero, it is energetically favourable for the system to create these defects — a specific number of them, which number, varies from system to system and within a system with temperature. An example of a line defect is the dislocations; an example of a surface defect is the grain boundary.

In some circumstances, the surface defect, namely, the grain boundary, can be considered to be made up of line defects, namely, the dislocations. Though such dislocation models of grain boundaries date back to early 1940s, Read and Shockley, in a classic paper in 1950 [1], used such a model to calculate the energy of a grain boundary — which continues to be a landmark study. In this post, I will discuss this paper of Read and Shockley.

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On computer simulations in materials science

The conventional analytical treatment of actual systems can in fact only be successfully performed in the simplest cases. It fails when a more or less realistic model of multiphase alloys in considered. As a matter of fact, computer simulation is a new approach to the probelm and is applicable to real alloys. The computer makes it possible to solve problems that have been considered unsolvable. The use of high-speed computers for modeling the processes occurring in alloys cannot be obviated, and I believe that computer-simulated research will form a new field in the material sciences.

Even the first attempts to simulate, with the help of computers, the martensitic transformation and the strain-induced coarsening in decomposed alloys using but idealized crude models gave an encouragingly good description of those processes, and the results obtained are sometimes in excellent agreement with electron microscopic observations. We may hope that the use of more realistic (and therefore more elaborate) models will make it possible to come close to theoretically predicting the structures of two-phasealloys applied in industry.

There is another problem that should be mentioned. The physical processes occurring in alloys are affected by varied factors that sometimes conceal the important characteristics of the phenomenon. Eliminating them may be a difficult problem which can hardly be solved in all cases. From this standpoint computer simulation serves as an “experiment” carried out under ideal conditions in the absence of any interfering factors.

— A G Khachaturyan, Theory of structural transformations in solids, 1983.

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Materializing Innovation at GE …

Hi Friends,
I am Suchismita, a new blogger to Materialia Indica. For the last 8 years, I have been with the Materials Research team at GE Global Research. I am also an alumnus of IISc, so when Abi mentioned about Materialia Indica, I was very excited to be part of this opportunity to touch base with my alma-mater, and the extended materials community at large. I will start with sharing the story of our materials team at GE, and what we do.
Materials Research Lab at GE Global Research, Bangalore, consists of about 35 scientists. In the true spirit of this unique engineering discipline, we have experts from all fields- metallurgists, chemists, physicists, materials scientists, mechanical engineers, all coming together to develop better materials for a variety of applications: ranging from superalloys & coatings for jet engines, to materials for sustainable energy sources, materials for lighting applications, scintillators for healthcare applications, and so on. We have a Metallurgy lab and a Ceramics lab, and I will talk about the Metallurgy lab to begin with.
The Metallurgy lab has aligned itself into 3 CoEs (Centers of Excellence) – Corrosion, Structure Properties and Modeling & Tribology. While each of these are individually anchored in metallurgy, they represent distinct technical skill sets by themselves.
Corrosion CoE is rooted in physical metallurgy and electrochemistry. Over the years the CoE has developed unique competencies to study localized corrosion under high pressure and temperature using autoclaves and potentiostats to arrive at materials or process environments that are not prone to localized corrosion or crevice corrosion. This CoE has now built unique capabilities to evaluate materials for sour gas environments.
Modeling CoE has its foundations based on multiscale modeling. Atomistics & first principles calculations provide critical inputs on thermodynamic parameters such as stacking fault energies, APB energies, etc. that feed into next scale Phase Field models. Ab initio modeling is also invaluable as a stand-alone tool when it comes to understanding surface reactions: extremely useful for designing next-generation coatings. Thermodynamic modeling follows next, to complement this information & feeding into microstructural models based on Phase Field or Cellular Automata, which track the microstructural evolution during solidification and as-solidified structures. The end aim of all of these is however, to tie up with higher scale mechanical behavior models, to fit the last piece of “structure-property” modeling. CDM(Continuum Damage Mechanics) based models or other strength models then provide with component strength information based on inputs from all the above length/time scales.
Tribology CoE has been at the forefront of developing relationships between thermal sprayed and PVD coating structures and wear properties – specializing in developing customized test methods to simulate different forms of wear, and through the understanding of the wear mechanisms derived places bets on new and existing coating structures to solve customer issues. These are evaluated through customized test set ups to demonstrate improved performance under close to field conditions.
Here’s just a flavor of the different teams we have in Metallurgy and our focus areas.
Sounds too serious? Well, I must admit, that our time at work is not consumed by only the above. To entertain our fatigued brains, we have regular screenings of Bollywood blockbusters & musical extravaganza at our amphitheatres, in addition to the gym facilities & entertainment center equipped with pool tables, TT, & other indoor games. National religions such as cricket & football tournaments are frequently celebrated! And I must say, that a lot of ideas buzz out of these informal meets under fun-fare alongside scheduled brainstorming meetings. Overall, the culture of open exchange of fundas between people of diverse disciplines make this place a great learning centre!

I will be back to share specific materials stories with you soon, but, here’s some food for thought before I leave-
Did you know: The widely known beneficial effect of Boron in enhancing ductility in Ni-base alloys was actually a serendipitous discovery through contamination from crucibles containing B during melting of the alloy. Here’s a snapshot of the original 1958 article:

Boron_effect

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Cancer and Nanobombs

Recent issue of Materials Today reports:

In the realm of science fiction, the idea of tiny nanorobots that can enter the human body and seek out and destroy unwanted elements has been prevalent. This idea has been made a reality by a research team led by Bin Kang and Yaodong Dai at Nanjing University and the Georgia Institute of Technology. They have used what is called the photoacoustic effect of carbon nanotubes (CNTs) to make what are essentially nanogrenades that can target and destroy cancer cells.

[Original work: Kang et al., Small (2009), doi: 10.1002/smll.200801820]

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Classics in Materials Science: Potts model and its relevance to simulation of microstructures

A soap bubble is an extraordinarily beautiful thing and yet it requires virtually no skill to produce. This is because surface tension does all the work for you, making sure that a perfect spherical membrane is produced every time. In fact it is impossible to blow imperfect bubbles. Even if you try to blow the bubble through a noncircular orifice you may at first achieve a temporary nonequilibrium shape […] but the end result is always a perfect sphere.

In this chapter we will show how such beautiful but tyrannical surface tension effects can be investigated using the computational equivalent of soap bubble solution: the Potts model. Like soap bubble solution is is easy to use and provides fundamental insights into surface tension phenomena; but also like soap bubble solution, it can lead to a sticky mess.

— Mark Miodownik, Chapter 3. Monte Carlo Potts Model, in Computational Materials Engineering: An introduction to microstructure evolution, Edited by K G F Janssens, D Raabe, E Kozeschnik, M A Miodownik, and B Nestler, Academic Press, 2007.

Potts model is widely used in the materials science literature to simulate a wide variety of microstructural features and phenomena: be it grain growth — normal and abnormal, recrystallization or Zener pinning (and, the article by Miodownik, from which I quote above, discusses all these and much more). In fact, to quote Miodownik again,

At the moment for large 3D systems, with complicated textures and pinning phases, the model has no equal.

In this Classics in Materials Science post, I would like to talk about Potts model and the paper in which Potts outlined it [1].

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Clean water for everyone: How can nanotechnology help?

Overcoming the difficulties of nanotechnology water treatments means developing innovative solutions to engineer a usable product. One answer could be to develop methods where the nanoparticles need not be suspended in the water. For example, one can stick — or ‘immobilise’ — the nanoparticles onto suitable materials such as steel or polymer sheets,which in turn can be easily dipped in and out ofwater tanks to work as catalysts or adsorbents.

This needs care to retain nanoparticles’ size and integrity so as to keep the benefits of operating at the nanoscale. But if it can be done, immobilisation is a good technique since it would keep water free of nanoparticles during and after water treatment. We, here at the Indian Institute of Science, Bangalore, are developing such a technique for degrading organic molecules using nano titanium dioxide. The results have been very promising and we are working closely with the University of Johannesburg to scale up the process in the near future.

That’s from this article in SciDev.Net by my friend and colleague Prof. Ashok Raichur.

You may also be interested in other articles in the SciDev.Net series on how nanotechnology may be harnessed for making clean water available for all.

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Metals and Stars

This is the International Year of Astronomy. Some of the earliest discoveries of humankind revolve around metallurgy and astronomy. In fact the seven metals of antiquity are all closely identified with the heavenly bodies. Thus the sun is linked to gold and silver is associated with the moon. As the meteorites rained down from the sky, metallurgy was known as Siderurgy ( literally of the stars ) in many languages. It was a pleasure to read the review of as fascinating book by Richard Holmes. It expands our view of uses of metals in the distant past!

From Books and Arts
Nature 457, 31-32 (1 January 2009) | doi:10.1038/457031b; Published online 31 December 2008

Year of astronomy: Voyaging to discovery, alone
David Bodanis1

BOOK REVIEWED
-The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science
by Richard Holmes

HarperPress/Pantheon: 2008/2009. 380 pp/576 pp. £25/$40

Everyone knows how to be a great scientist. First, you have to be really smart. Having awed your school science teacher is good. Humbling all the others at university is even better. Then you need to find a place where you can let your solitary genius come out. You might escape to a coffee shop to think; or if your parents are really rich, to a trendy loft apartment or, better still, a remote and windswept cottage. There you will engage in the next and most crucial of stages: the creative torture.

There is an art to this. It is important your torment doesn’t end too quickly — otherwise you’d show you had been working on a problem that was too simple. Yet if the torment never ends, you’ll have nothing to tell anyone about and will remain unknown. After some time, ideally a few months, you get to have a ‘eureka moment’. At that point all you have to do is write up your discovery, accept the plaudits, be it from department colleagues or the Swedish Academy, and then if you can bear it, repeat from the start.

We smile at this recap but the basic vision — science as an endeavour of individual creative genius that explodes in an instant of discovery — is one we take for granted. Yet, as Richard Holmes describes in his new book The Age of Wonder, it was not always so. Most founders of modern science in the 1600s, such as Isaac Newton, rarely saw their work this way. For them the process was clinical, building on a slow accumulation of insight.

The big shift took place in the decades around 1800, a period called the Romantic era. The pursuit of progress by thinkers and artists became more a wait for a divine spark of inspiration than the steady toil of uncovering that had been accepted by their predecessors. And any means by which that spark could be nurtured was embraced.

To guide readers through the science and culture of this period, Holmes masterfully dips in and out of the life of Joseph Banks. He is an inspired choice. As a curly haired 26-year-old, Banks was aboard HM Bark Endeavour on the momentous day in April 1769 when it first glided into sight of Tahiti. Ostensibly Banks was just the expedition’s plant collector, but he soon became more fascinated by the island’s human inhabitants.

For most of the British crew — young men who had been away from female company for long months — the explorations in Tahiti were of one sort only, with the initial going rate being one ship’s nail for one sexual encounter. That rate soon changed — as Holmes describes with gentle skill, the Tahitians were quick to grasp the workings of the market economy, and had a keen eye for the other useful metal objects aboard the ship. Hyperinflation set in, and at one point “there was a crisis when one of the Endeavour’s crew stole a hundredweight bag of nails, and refused to reveal its whereabouts even after a flogging”.

Banks looked further. He took up Tahitian mistresses too, but systematically recorded the local language, studied their religious systems, and even hinted at the true functional significance of native actions that, at first, seemed to be merely bizarre. Within a few months he had helped set the stage for the modern science of anthropology.

Back in London, Banks’s insights, energy and inherited wealth eventually led to him becoming president of the Royal Society. From his headquarters, as Holmes gracefully phrases it, “his gaze swept steadily round the globe like some vast, enquiring lighthouse beam”. His own days of direct discovery were over, but couldn’t other like-minded individuals be encouraged to carry on such wondrous, intense investigations?

One of the young men Banks chose to support was Humphry Davy: friend of the Romantic poets, and — in his quick, intense creation of a safe coal-miner’s lamp in response to underground disasters — a man who made himself into a perfect exemplar of the new, Romantic style of discovery. Davy hurried to the mines, spent intense weeks with the miners and then took himself off to an isolated lab where, using his unique genius, he cracked the problem.

Another of Banks’s protégés was William Herschel, the immigrant Hanoverian astronomer. Herschel is most famous now for having measured the orbit of Uranus and establishing this body as a planet, which almost became known as planet George to honour King George III. But Herschel also worked out the shape of the Milky Way and the Sun’s off-centre position in it, and he discovered infrared radiation.

Although his work relied on the dull accumulation of observational facts, it was the role of sudden insight and genius that Herschel and others emphasized in their written accounts. In Herschel’s case, it was true to his character: he had risen in society by transforming his own life and moving to England. Wouldn’t he imagine there were fresh realms — new planets, stars beyond our Solar System, light beyond the visible spectrum — to uncover in nature as well?

Our notion of earlier scientists, including Newton, was rewritten to fit this Romantic view. The young poet William Wordsworth, for example, had famously devalued science with his harsh line that when we probe the mechanism of a natural process, “we murder to dissect”. But decades later, as the work of Banks and his protégés became better known, Wordsworth shifted to admire science, seeing Newton as the archetypal Romantic hero: “Voyaging through strange seas of Thought, alone.”

Over time, the simplest Romantic imagery slid away. Few of the hundreds of physicists working today at CERN, the European particle-physics lab near Geneva, Switzerland, must view themselves as voyaging anywhere alone. But the Romantic era left great legacies. Newton’s static Universe was gone, and Herschel’s dynamic one — in which stars evolved and the heavens were ever-changing — was in its place. This mutable view was useful for the next notable young man, one Charles Darwin, when he was ready to embark on his own voyage of discovery on HMS Beagle in 1831. And even among today’s doctoral candidates at CERN, who doesn’t hope that maybe, with enough concentration, something very special and very unique could still burst out?

1.David Bodanis is a writer based in London, and author of Electric Universe. His forthcoming book is on the Ten Commandments.

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Bone

rob-ritchie

In her NYTimes article, Natalie Angier has several quotes from Rob Ritchie of UC-Berkeley on the mechanical behaviour of bones (check out his recent publications):

… [H]ealthy bone is disciplined bone, with a structure enviably organized at every scale yet probed, from the caliper calibrations of femurs and phalanges down to the nano dimensions of bone’s constituent atoms. “It’s all in the architecture,” said Robert O. Ritchie, a professor of materials science at the University of California, Berkeley, who studies bone.

Bone is built of two basic components: flexible fibers of collagen and brittle chains of the calcium-rich mineral hydroxyapatite. But those relatively simple ingredients, the springy and the salty, are woven together into such a complex cat’s cradle of interdigitating layers that the result is an engineering masterpiece of tensile, compressive and elastic strength. “We only wish we could mimic it,” Dr. Ritchie said.

[…]

Behind the dissolution of bone with age is a system designed for the itinerant years of youth. The skeleton is a multipurpose organ, offering a ready source of calcium for an array of biochemical tasks, and housing the marrow where blood cells are born. Yet above all the skeleton allows us to locomote, which means it gets banged up and kicked around. Paradoxically, it copes with the abuse and resists breaking apart in a major way by microcracking constantly. “Bone microcracks, that’s what it does,” Dr. Ritchie said. “That’s how stresses are relieved.”

* * *

Image courtesy: Prof. Ritchie’s home page.

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Nuclear tests without nukes

An interesting pieces of an article about fusion power that is about to be demonstrated at National ignition facility in the year 2010.  For full article go here

……Next year, researchers at the Lawrence Livermore National Laboratory (LLNL) in California hope to tick that box off Gould’s list. Despite his foresight, Gould could not have imagined the lengths to which scientists and engineers would have to go to bring his prediction to reality. LLNL’s National Ignition Facility (NIF), which was officially completed last month, is a laser on a truly epic scale. The building housing it is 10 stories high and covers an area the size of three football fields; for a very brief instant, its beams deliver a power of 500 terawatts, more than the power-generating capacity of the entire United States.

If all goes according to plan, some time in 2010 the power of those beams will be directed at a small beryllium sphere filled with hydrogen isotopes. The resulting implosion will crush the hydrogen to a temperature and pressure higher than in the core of the sun. If NIF’s scientists get everything right, the hydrogen isotopes will do what they do in the sun: fuse together into helium nuclei and release a huge store of energy. NIF’s principal aim is to reach “ignition”: a self-sustaining fusion burn that gives off more energy than was put in to make it happen–something that so far has occurred only in nuclear explosions and stars……

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