Saturday, September 24, 2005

Watch out, its coming.....

Costal areas all over the world are prone to attack. Most of the time the attack comes from the sea and in the form of storms. Whether it is India or America, they natural destruction stories remain the same. These monster attackers are named differently all over the world in America it is called Hurricane, in Japan and China it is called Typhoon, In south and south east Asia it is called cyclone. However, all of them form following a similar mechanism. Warm air flowing over the sea suck water as vapour, because the temperature of the air would be as high as 80 oC, these water vapour cools down at higher altitude and releases heat which results in more heated air which is light, this air gains a speed of 200 miles per hour and due to earth rotation the air starts whirling around an eye, this is how it looks.

Red part of the hurricane contains water. These tropical cyclones travels 300-500 km a day,
they loses strength but very slowly and before it tames it hits the costal life. This monster has three weapons. First is of course storm, which hits at a speed of 200 km/hr. it is followed by heavy downpour, much more than that of any low pressure cloud pouring. It has got a disguise also. Once the eye crosses the land the rain and storm stops, it is an warning which people often misses, the storm comes from the opposite direction. It is huge and deadly. The devastation has just started. Almost 90% of the casualties come from the surge of water, the third weapon of hurricane. The sea levels go up by 10 to 30 ft. and in extreme cases it reaches 40 ft.! The surge of water we saw in New Orleans is actually due to this. The storm carries through the coast and may travel till 1000 miles! Slowly loses its pace and die down. The devastation is always quite tragic. It affects the flora and fauna immensely. Moreover, geophysical changes are also come along with them. has posted some before and after Katrina photograph in their web page.
Typhoons and Hurricanes are normally named, although “Katrina” rocked USA, it is not the deadliest ones world has witnessed till now. In India in the year 1999 there was a cyclone hit. Actually there was couple of cyclones that hit costal Orissa. First one hit Andhra Pradesh, Orissa and West Bengal and the second one without warning hit Orissa and India saw the one of the worst cyclone hit. The Cyclone lasted for 2 days and whole state was out of the world. It was said the wind speed reached 310 km/hr with an water surge of 20-30 ft. It completely destroyed the state; there was no account of the death toll as well as the homeless. A huge part of the coast beacame a barren land, with all the trees uprooted. The economy and life was affected such a way that still people are recovering from it.
Science has progressed so much that following the Hurricane is possible from its birth hence it is possible to do the necessary evacuation. Computer simulations following the satellite imaging have done a real miracle, but researches are on in this topic. One big topic is the effect of pollution like global warming in the frequency of the storm. Recently there was an article on hurricane on a work by a group from university of Tennessee in Knoxville. They are studying the Pine trees in coastal US and it was claimed that these trees bear signs of Hurricane, so the frequency of it can be identified at least for last 100 years! We don’t know whether these are signals of destructions that are coming or passing by!

Orissa Cyclone
Hurricane mark in Pine trees.

Thursday, September 22, 2005


If you search segregation in google, first few hits will be about racial segregation; strictly speaking I am not going to talk about it. It’s the segregation in materials world is my cup of tea. While working with oxide ceramics defects are something that never left me and now I say I love defects! There are classic effects you get to see due to presence of point and line defects in the materials, whether its semiconductor or any structural applications. Segregation is a results caused by point defects. It has been exploited in many ways. Optoelectronic, Transistor, structural ceramics, there are numerous occasions when segregation is the key. In the ionic solids, the Schottky defects causes ions to go to the interfaces, primarily they require a lattice discontinuity, so this place may be a surface, a grain boundary or any interface. Thus there is a local charge builds up there and a potential difference between the bulk and the surface is generated. The magnitude depends on the defect concentration, temperature. Like colloids there exists an isoelectric point where surface charge becomes zero and then with an increase in temperature or defect concentration it reverses. Segregation is a subject of interest of the structural community as this process retards grain growth. The space charge which forms at the boundary actually pins the grain boundary mobility. Sounds interesting? It has more effects; when you reduce the grain size that is in the nanometer range lot of material properties in oxide ceramics is controlled by segregation, hope you didn’t believe it! Segregation captures a huge part in grain boundary engineering. Si3N4 brittle in nature but it is toughened by adding some dopants, but how it helps was not known till very recently. Last year a paper in nature showed experimentally evidences of La segregation in La doped Si3N4, La actually segregates to the boundary and helps in forming elongated grains which in turn toughens the material. Following figure is actually taken from the paper.

N. Shibata et al. Nature Vol. 428, pp730-33, 2004.

This is an STEM micrograph of a grain boundary in La doped Si3N4, bright fringe in the middle correspond to the amorphous film and the brighter spots in that are actually La. Segregation in YTZ is in discussion for a while and now it is said that nanocrystalline YTZ are more creep resistant that the submicron grain one because of Y+3 segregation. It is known that Y+3 play a role there but it is not understood which role it plays, so lots of questions. Sometimes segregation is detrimental, YTZ although has potential use as bone replacement, can not have an immediate use as Y segregation causes brittleness of the material. There are lots of interesting stuffs in this field and I am happy as I will have jobs in hand till the questions are answered. I really like defects.

Friday, September 16, 2005

A Night Club with difference!

Students from the Department of Metallurgy in IISc are extremely active, and those who work talk really little! It is reflected well for years through TMS night club talk series. Last Wednesday it was the 325th night club talk. In the campus, academic community knows about looking around, Sci forum and newly born CCS, which are perhaps much younger talk series compared to TMS night club talk series, its run by a TMS students’ chapter and apart from the invited talks, all night club talks are delivered by the students and believe me it is one of the longest running TMS Students Chapter in the whole world. We have our own world, we have our own prestigious talks, and we have our own discussions. In a faculty & staff driven institute it is really amazing that without any force (driving I meant) students volunteer to talk. The figure 325 is really huge; and it is an honour to speak in these occasions as they are the milestones for the series. Though I did no have the chance to speak in these occasions, but I have attended more that 150 talks! It covered all spectrums. From bacteria to self assembly, from ALE to casting, from NMR to DSC, from iron making to spintronix, from mobile phones to chips; we heard almost every field of material science. Technology changed, from OHP we shifted to digital projector and from the seminar hall we had shifted to Brahm Prakash Committee Room, but the character remained the same. A legacy we are carrying for a decade and it is like Prof. Ranganathan says(on some other context) “…it is in the memory of the department” . So join us at 9:30 p.m. in BPCR on Wednesday, we will share thoughts and “a cup of tea in the tea board”.

Tuesday, September 06, 2005

Materials, Mimicry and MEMS by Dr. Julia King

It’s all about fans! Prof. Julia King, from rolls royce today delivered really a fascinating talk on aero-engine in our prestigious faculty hall. When I first saw those real huge jet engines, I wondered how much science and technology must have been gone into it. She today talked about the physics, engineering and design of the fans and the engine as a whole!
Her talk started with the general concern on global warming and the contribution of aerospace industries to it. She showed a B-52 bombers emitting considerable amount of un-burnt hydrocarbon. According to her noise pollution due to high engine noise levels is also a cause of concern primarily in cities. So she addressed all the problems in sequence. Her presentation began with an animations on how an engine works. It was evident that materials design is the key for the turbines blades inside the engine! The material they use for the fans are Ni bases super alloys and there is a problem with the randomly oriented polycrystals. The grain boundaries parallel to the air flow is a bad news: they are the site where the fatigue crack initiates under cyclic loading so the blades were processed with oriented grains with boundaries perpendicular to the air flow. Final step towards this grain boundary engineering was to remove the grain boundaries, i.e. use of single crystals! No boundaries so no flaws. It is important to reduce the weight of the blades which is a new field of research and shape memory alloys and metallic foam appeared to be potential material for that. There was a job also for the combustion engineers but from the material scientist point of view it was necessary to talk about the chamber material. Composite materials were shown to have better run for that. When the discussion boiled down to noise she mentioned how the noise is generated from the engine, the solution for that was to have a turbulent mix of two kinds of air coming out of the jet, for that it was observed serrated outer wall of the jet instead of smooth wall is quite effective. The criteria was it should remain close while it is flying at low altitudes (high temp. region) and at high altitude they should open up . In a nice experiment she showed actually how shape memory alloys acts as an actuater under changing temperature; it was really a nice piece of experiment. There was an ineresting info: eagles can fly at a speed of 200 Mph and consume an energy equivalent to only 10% of its own weight. At the end of her talk she showed some video clippings of some testing on the fans. They were amazing! First one was under tremendous water flow, 2nd one was fans performance under cold condition (T= 233 K), 3rd one was what if a single blade breaks? And final one was what happens when birds hit the jet, I am not going to tell you what happens then, you have to listen to Dr. King. I could not put any of her slides which I would loved to post, may be some other day......

Game over!

Time to write some good things! It was really beautiful 4 seasons Yes! I am talking about cricket seasons. It was an opportunity I never thought I will get, but with my luck was shining at its best, I got the chance to play serious cricket after a gap of 4 years. People fall in love, so did I, with this great game called Cricket. I always felt happy when I stayed long in the crease. It won’t be wrong to say that destiny was grinning when I was batting last weekend. That was probably my last serious cricket match where I spend the longest time in the crease!
I met with cricket quite early age of my life. I had a friend called Santanu who had a proper kit; we used to play with cork balls which were extremely hard. We used to play wearing one pad, most of the players were Rightie so they used to tell me to tie the pad in the left leg, I was a natural leftie so it was the wrong leg for me so one ball one day came and straight away hit my front right leg’s sean bone, I was hurt on the my first cricket match and what a consequence, my last day was very similar, i had an injured hand; One day I had started playing it on the other day I left it. I had many friends into my life; some left me some I had left! But this is more than any pain I came accross. By this time if you are reading it you might have gave up on me but believe me its my soul speaking not me :D You had enough fun, leave me now the game is over!