Category Archives: Materials Science

Liquid Metal? In A Watch?

Yes. In a watch. Not just any watch, but an Omega.

In any case, watch. I mean the video at that link, and you’ll love the slogan: “Sometimes, the most unlikely partnerships are the most enduring.” And I guess we could add, “the most expensive.”

Here’s the short description from that page on the bulk metallic glass that goes by its trade name “Liquidmetal®”:

Liquidmetal®: seamless bonding, remarkable hardness

The Liquidmetal® alloy is an amorphous metal – a metallic material with a disordered, non-crystalline atomic structure. Its fusion temperature is half that of conventional titanium alloys but when it is cooled, its hardness is three times as great as that of stainless steel. Its amorphous structure allows it to bond seamlessly with the ceramic bezel.

The Liquidmetal® is a bulk metallic glass alloy consisting of five elements: zirconium, titanium, copper, nickel and beryllium. A bulk metallic glass can, by virtue of its low critical cooling rate, be formed into a structure with a thickness of more than a tenth of a millimetre. Zirconium is an important constituent part both of the Liquidmetal® alloy and of the ceramic material which is made of zirconium dioxide (Zr02).

Thanks for the pointer to my friend and colleague Ram (Prof. U. Ramamurty), who is well known for his studies of mechanical behaviour of bulk metallic glasses.

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BTW, this blog has had a chance to post about Liquidmetal® sometime ago.

Golden Trivia

From Who’s Got All The Gold, And Who’s Mining It:

All Gold Ever Mined – The total amount of gold ever mined is estimated to be worth around US$5 trillion.

How Gold is Used – You might have though (like me) that most of the gold in the world stored in bank vaults and lock-boxes? Actually, 78 % of the worlds’ gold is made into jewelery. Other industries, mostly electronics, medical, and dental, require about 12%. The remaining 10% of the yearly gold supply is used in financial transactions.

Materialia Indica

Just a quick note — after a dormant period of over 16 months! — to tell you that I have started blogging at Materialia Indica, an India-centric group blog by and for materials science folks — academics, researchers, post-docs, grad and undergrad students. See the About page for details. [Update (1 June 2009): Materialia Indica now has a new, more spacious and more feature-rich home at Ning, which offers a complete suite of networking and community-building features that we have always wanted (and our blog lacked). In particular, becoming a member and starting a discussion is far easier for all the members of a community in a social network than in a blog. Hence the move to Ning.

If you are interested in materials science/engineering education and research in India, Materialia Indica is the place to be. Come on in and join us. You don’t need a special invitation from anyone; just click on the ‘sign-up’ link, fill in the details, and you are in!]

As of now, my co-bloggers are Guru (M.P. Gururajan, IIT-D) and Phani (G. Phanikumar, IIT-M).

We would like to expand our team. If you are interested — or, if you know someone who might be interested, let us know through the contact form on the Contributors page.

Now, this blog can go back to being silent …9

Some links …

Exon points us to this Science Roll post with a compilation of science-oriented video archives.

Philip Ball has a post recounting the history (and the key person) behind the development of goggles that filter out UV and IR radiation.

Guru points us to some of the classic papers from the previous centuries that Philosophical Magazine has published on its website along with some commentary.

This article in the Hindu is about a study on the saddle point configuration for nucleation of a bubble in superheated water. It claims that this study overturns a conventional view; I am yet to figure out how!

Liquid Metal

Check out this video that compares the elastic properties — in particular, the resilience or the amount of stored elastic energy — of three materials: an amorphous alloy, stainless steel and titanium. The video is from Liquidmetal Technologies, a California based company founded to commercialize the research on amorphous alloys (or metallic glasses) conducted at Caltech by Prof. William L. Johnson. Do check out the Liquidmetal website; there is a wealth of materials-oriented information (including applications of amorphous alloys) there.

iMechanica links

The iMechanica site is a treasure. The good folks there post not only their recent papers and preprints, but also stuff that’s of interest to a general audience as well. Let me just link to a bunch of these general purpose things that appeared there recently:

In addition, there are course notes on offer:

Here are some links that should interest materials people:

And finally, here are some tips for finding information on iMechanica:

MIT’s progress in making synthetic spider silk

From this report [via slashdot]:

“If you look closely at the structure of spider silk, it is filled with a lot of very small crystals,” said Gareth McKinley, a professor of mechanical engineering and part of the group that devised the new method of producing the material.

“It’s highly reinforced.”

The secret of spider silk’s combined strength and flexibility, according to scientists, has to do with the arrangement of the nano-crystalline reinforcement of the silk as it is being produced—in other words, the way these tiny crystals are oriented towards (and adhere to) the stretchy protein.

Emulating this process in a synthetic polymer, the MIT team focused on reinforcing solutions of commercial rubbery substance known as polyurethane elastomer with nano-sized clay platelets instead of simply heating the mixing the molten plastics with reinforcing agents.

Some materials links

Invisible electronics.

To create their thin-film transistors, [Tobin J. ] Marks’ group [at Northwestern] combined films of the inorganic semiconductor indium oxide with a multilayer of self-assembling organic molecules that provides superior insulating properties.

Synthetic Gecko materials that mimics “microscopic hairs on a gecko foot”. It is “made of layers covered with thousands of stalks with splayed tips made of a polyimide, a synthetic like Nylon.”

Metamaterials with negative refractive index:

[Gunnar] Dolling’s metamaterial is made by depositing a layer of silver on a glass sheet, covering this with a thin layer of nonconducting magnesium fluoride, followed by another silver layer, forming a sandwich 100 nm thick. Dolling then etched an array of square holes through the sandwich to create a grid, similar to a wire mesh.

A key advance in Flexible electronics:

The trick to being able to manufacture—rather than handcraft—large arrays of single-crystal transistors was to devise a method for printing patterns of transistors on surfaces such as silicon wafers and flexible plastic. The first step is to put electrodes on these surfaces wherever a transistor is desired. Then the researchers make a stamp with the desired pattern out of a polymer called polydimethylsiloxane. After coating the stamp with a crystal growth agent called octadecyltriethoxysilane (OTS) and pressing it onto the surface, the researchers can then introduce a vapor of the organic crystal material onto the OTS-patterned surfaces. The vapor will condense and grow semiconducting organic single crystals only where the agent lies. With the crystals bridging the electrodes, transistors are formed.

Finally, is open peer review experiment at Nature a failure?

Nano-knives and superplastic nanotubes

First, the nano-knife (via slashdot):

A prototype microtome knife for cutting ~100 nm thick slices of frozen-hydrated biological samples has been constructed using multiwalled carbon nanotubes (MWCNT). A piezoelectric-based 3-D manipulator was used inside a Scanning Electron Microscope (SEM) to select and position individual MWCNTs, which were subsequently welded in place using electron beam-induced deposition (EBID).

The device employs a pair of tungsten needles with provision to adjust the distance between the needle tips, accommodating various lengths of MWCNTs. We have performed experiments to test the breaking strength of the MWCNT in the completed device using an atomic force microscope (AFM) tip. An increasing force was applied at the midpoint of the nanotube till the point of failure, which was observed in-situ in the SEM.

Next, the superplastic nanotubes of carbon:

The theoretical maximum tensile strain — that is, elongation — of a single-walled carbon nanotube is almost 20%, but in practice only 6% is achieved. Here we show that, at high temperatures, individual single-walled carbon nanotubes can undergo superplastic deformation, becoming nearly 280% longer and 15 times narrower before breaking. This superplastic deformation is the result of the nucleation and motion of kinks in the structure, and could prove useful in helping to strengthen and toughen ceramics and other nanocomposites at high temperatures.

Mechanics of superheroes

The spider-‘silk’ produced by Spiderman about as thick as his arm — it’s more like ‘spider-rope’. But, does it really need to be that thick? No, says this SciAm article on the wonderful combination of mechanical properties of real spidersilk.

The different silks have unique physical properties such as strength, toughness and elasticity, but all are very strong compared to other natural and synthetic materials. … The movie Spider-Man drastically underestimates the strength of silk�real dragline silk would not need to be nearly as thick as the strands deployed by our web-swinging hero in the movie.

Here’s a quick description of what makes up one of the several forms of spidersilk:

Dragline silk is a composite material comprised of two different proteins, each containing three types of regions with distinct properties. One of these forms an amorphous (noncrystalline) matrix that is stretchable, giving the silk elasticity. When an insect strikes the web, the stretching of the matrix enables the web to absorb the kinetic energy of the insect�s flight. Embedded in the amorphous portions of both proteins are two kinds of crystalline regions that toughen the silk. Although both kinds of crystalline regions are tightly pleated and resist stretching, one of them is rigid. It is thought that the pleats of the less rigid crystalline regions not only fit into the pleats in the rigid crystals but that they also interact with the amorphous areas in the proteins, thus anchoring the rigid crystals to the matrix. The resulting composite is strong, tough, and yet elastic.

BMQ

A quick note to tell you — particularly those of you in Bangalore — about the Bangalore Materials Quiz (BMQ), an annual event organized by us for the students of Classes XI and XII. As the name suggests, BMQ covers all aspects of materials: their physics, chemistry, production, processing, properties (mechanical, thermal, electrical, magnetic, optical, …), applications and use.

I have created the BMQ blog which will be used to both disseminate information and coordinate our team’s activities.

BMQ is organized almost entirely by the wonderful graduate students of our Department. They orchestrate all aspects of the event, with some minimal guidance (and cheering from the sidelines) from me. This is the tenth year since I took over the responsibility of running this show, and I have met some of the brightest students (one of them runs this blog) through it.

BMQ is not a mega event; we usually get about 25 teams (of two each) every year. This year, we hope to attract 50 teams. On the other hand, we aren’t set up to handle a large number of teams either; so 50 is the hard limit!

The Prize we offer is admittedly small — books worth about Rs. 500 for each student! But the top two teams from BMQ get to take part in a grander event with bigger prizes at stake (see the blog for details).

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Well, if you know anyone in Bangalore-based schools (higher secondary schools and pre-university colleges) who might be interested in BMQ, do please spread the word. Many thanks in advance.

Online books in materials science?

Note: Originally posted on 24 January 2005.

Towards the end of his Netspeak column in today’s Hindu, J. Murali points to the Internet Text Archive, “an excellent web location that hosts links to several free open source textbook digitizing [or] hosting projects that include Project Gutenberg, Children’s Library, Million Books Project and Open Source Books”. It is probably worth a look.

If you look around on the web, you will find quite a few books whose authors (and in some cases, publishers too) have chosen to offer them for free. Among the publishers, the following are noteworthy:

  • Open Book project of O’Reilly, a well known publisher in the fields of programming and software development
  • eScholarship program of the California Digital Library, one of the University of California libraries. Some of the books in CDL are open for public; check out this subject list to see if there is anything of interest to you.

Then there are books that live both in shelves and in hard disks. Sure, some of them are quite specialized (with a potential readership of, say, a few hundreds); but, there are a few others which are at the undergraduate or equivalent level in popular subjects (software development!); Examples of the latter include:

I am not sure about the others, but I do know that the first two are very popular: they are still in print, you can buy them in shops, and apparently, many people do! In fact, Eckel loves this publishing model, and says, “All of my future books will be electronically published on my site first, and will stay on the site”.

There are still a few other books which live almost entirely in the electronic world; for example, The Temple of Quantum Computing is an introductory book that its author has described as quantum computing for dummies.

Is there a good reason why there are not many online books (available either for free or for a reasonably small price) in materials science and engineering? I found two online texts in Chemistry: Dynamic Textbook of Physical Chemistry and Concepts in Chemistry. I listed them in my Thermodynamics course website.

It is entirely possible that there are more such books that are available online, and are useful for students of materials science and engineering. If you know of any, do please send me its URL, and let us start compiling a list here!

Update (25 Jan 2005): The process of building up this list begins here! Here we go:

If you know more such online texts, bring’em on!

Crystallization

Bento, a chemical physicist (or should it be a physical chemist?) has a two part   series on the liquid-to-solid transformation (aka solidification in metallurgy!). The treatment, which uses the concept of an order paramter, is quite common in physics and chemistry literature (actually, statistical mechanics literature). Those working with phase filed models should be quite comfortable with it.