Saturday, October 29, 2005

Three scientific mini-revolutions in the eighties


This post is dedicated to Prof. Richard E. Smalley, a Nobel winner for the discovery of fullerenes, that marked the beginning of the most exciting of the three mini-revolutions in the 80s. He passed away yesterday.

In the eighties, three mini revolutions happened in the fields of physics and chemistry of materials, that expanded scientists' minds without the help of hallucinogens.

The first one happened in 1984 when a team of scientists led by Prof. Dan Schechtman reported a crystalline substance -- an alloy of aluminum and manganese -- that exhibited five-fold symmetry, which is impermissible in conventional crystallography, the science of ordered arrangement of atoms and molecules in a crystal. Such materials with five-fold symmetry are now called 'quasicrystals'.

A few quick examples of rotational symmetry are the four-fold (or, 360/4 = 90 degree) symmetry of a square, and the six-fold or 60-degree symmetry of a perfect hexagon. In contrast, a rectangle has only a two-fold symmetry. These symmetries are consistent with 'normal' crystals that have an ordered and repetitive (or, periodic) arrangement of atoms and molecules. Five-fold or 72-degree symmetry was thought to be impossible in materials, until the discovery of the quasicrystals.

Immediately after this epochal event, many groups swung into action and reported many other materials that had such unconventional symmetry. Several groups from India too participated in and contributed to this excitement; notable among them are a group in IISc led by my departmental colleagues Prof. S. Ranganathan (whose book on the legendary Wootz steel we had a chance to review a while ago) and Prof. Kamanio Chattopadhyay, and another group in IT-BHU led by Professors Ramachandra Rao, S. Lele and G.V.S.S. Sastry.

The second mini-revolution was unleashed in 1986 when some exotic ceramic materials (oxides of yttrium-barium-copper oxide) were shown to behave in a superconducting fashion below reasonably high temperatures of around 90 Kelvin (almost 180 degrees Celsius below the freezing temperature of water!). The existing superconducting materials showed this behaviour at unbelievably low, and very-difficult-to-achieve temperatures of around 5 Kelvin; I believe one of them could behave so at about 25 Kelvin. The newly discovered materials, christened high temperature superconductors, made superconductivity possible at temperatures above the key barrier of 77 Kelvin (-196 degrees Celsius), the boiling point of liquid nitrogen, which is eminently achievable on a routine basis.

Several groups in India were also early contributors to the fields of high temperature superconductors, buckyballs and carbon nanotubes). I would like to mention the group led by Prof. C.N.R. Rao, who won the first India National Science Prize just this year.

The third and the biggest of the three (at least in my opinion) is the discovery of a new form of carbon, in which each molecule has 60 carbon atoms arranged in the shape of a football. Since it resembled the famous geodesics designed by the architect Buckminster Fuller, these molecules of carbon were promptly named buckminsterfullerene; since that name was quite a mouthful, its popular name now is either fullerene, or a catchier 'buckyballs'.

By themselves, the buckyballs might not have had a transformational effect; their discovery was followed by the 1991 discovery of carbon nanotubes -- sheets of carbon (actually graphite, a form of carbon) neatly rolled to form a pipe or a tube, whose girth is a mere nanometer or so. The discovery of nanotubes (the first key papers came from a group led by Dr. Sumio Ijima at NEC labs in Japan; one of their authors is Prof. P.M. Ajayan, the topper of my class in IT-BHU!) opened up a new chapter in the emerging field of nanotechnology.

The scientists involved in the discovery of buckyballs have won a Nobel Prize; and so have the scientists who were involved in the discovery of materials that were the precursors of the high-Tc-superconductors. The Nobels for the discovery of quasicrystals and carbon nanotubes are yet to happen, but many -- including me! -- believe it is only a matter of time.

3 Comments:

  1. Abi said...

    Hmmm... What the hell is wrong with its permalink? Why doesn't it work?

  2. Aswin said...

    Ya..does not work.. a spurious underscore is sitting there(republish??). I am linking to ur archives page for the scian melt.

  3. Abi said...

    Hi Aswin,

    I don't know what magic (or was it voodoo?) your comment performed on my blog, but the permalink works now! Even the 'spurious underscore' that you referred to is still there, and yet ...

    Blogger is really mysterious!

    And, thanks for the link in SciAn Melt. You can use the permalink itself now. Thanks again for the magic!