What’s so special about Gorilla Glass?

Many vendors are quick to trumpet the use of Corning's Gorilla Glass in their products. The glass is used as a protective outer layer for many devices, from smartphones to large flat panel televisions. But what makes Gorilla Glass different?

The answer lies in the composition of the glass itself. Most display glass is an alumina silicate formulation, which is made up of aluminum, silicon, and oxygen. The glass also contains sodium ions spread throughout the material. And this is where the difference starts.

The glass is put in a bath of molten potassium at about 400 degrees. The sodium ions are replaced by potassium ions in a process that's a bit like soaking a pickle in salty brine. It's a diminishing process: More of the sodium ions are replaced by potassium at the surface of the glass, and then fewer and fewer are exchanged as you go further into the glass.

Why change from sodium to potassium? Sodium (Na) has an atomic number of 11, while potassium (K) has an atomic number of 19. If you remember your high school chemistry, this indicates that the potassium atoms are significantly larger than the sodium atoms. (The atomic radius of a neutral sodium atom measures out as 180 pico-meters and potassium at 220 pico-meters, so potassium measures out as more than 20% larger.)

Imagine that you have a box packed tightly with tennis balls. What would happen if you took out the top layer of tennis balls and replaced them -- one for one -- with larger softballs? The softball layer would be squeezed together much more tightly and it would be harder to get one out.

That's what happens with glass when the potassium ions take the place of the sodium ions. The potassium ions take up more space and create compression in the glass. This makes it more difficult for a crack to start, and even if one does start, it is much less likely to grow through the glass.

The concept of strengthening glass through ion exchange is not new; it has been known since at least the 1960s. And other companies offer glass that has been strengthened by this type of process. Corning's Gorilla brand of strengthened glass has gained considerable market share, however, and has a very visible presence in the marketplace.

The company Corning working on this technology and come up with innovations like Gorilla Glass Windshield for Automobiles (Ford GT) and "A Day made up of Glass" Concept.

How Hydrogen Bomb Works?

On Wednesday, World leaders scrambled to investigate claims from North Korea that it had developed a hydrogen bomb in violation of United Nations Security Council resolutions. While the communist country has some level of nuclear capability, it wasn't immediately clear that they had successfully built a working atomic bomb. How it is going to work at International and political level of the World is out of scope of our blog, Let's discuss about How the hydrogen bomb work in the World of Nuclear Physics.

Atomic weapons are plutonium-based and involve a process called fission that splits plutonium into smaller atoms, releasing massive amounts of energy. Whereas, Hydrogen bombs are made with uranium. Instead of splitting big atoms, Hydrogen bomb combines small atoms to release a massive nuclear force hundreds of times more powerful than an atomic weapon.

Fusion Reaction

At extremely high temperatures, the nuclei of hydrogen isotopes deuterium and tritium can readily fuse, releasing enormous amounts of energy in the process. Weapons that take advantage of this process are known as fusion bombs, thermonuclear bombs or hydrogen bombs. Fusion bombs have higher kiloton yields and greater efficiencies than fission bombs, but Deuterium or tritium has to be highly compressed at high temperature to initiate the fusion reaction.

Fusion bomb uses lithium-deuteride, a solid compound that doesn't undergo radioactive decay at normal temperature, as the principal thermonuclear material. As Tritium has short half-life, bomb designers rely on a fission reaction to produce tritium from lithium. The majority of radiation given off in a fission reaction is X-rays, and these X-rays provide the high temperatures and pressures necessary to initiate fusion. So, a fusion bomb has a two-stage design -- a primary fission or boosted-fission component and a secondary fusion component.

Hydrogen Bomb Design

To understand this bomb design, imagine that within a bomb casing you have an implosion fission bomb and a cylinder casing of uranium-238 (tamper). Within the tamper is the lithium deuteride (fuel) and a hollow rod of plutonium-239 in the center of the cylinder. Separating the cylinder from the implosion bomb is a shield of uranium-238 and plastic foam that fills the remaining spaces in the bomb casing.

Detonation of the bomb causes the following sequence of events:

1. The fission bomb implodes, giving off X-rays, which heat the interior of the bomb and the tamper; shield used prevents premature detonation of the fuel. The heat causes the tamper to expand and burn away, exerting pressure against the lithium deuterate, which is placed inside it, lithium deuterate is squeezed by about 30-fold. 
2. The compression shock waves initiate fission in the plutonium rod. 
3. The fissioning rod gives off radiation, heat and neutrons. 
4. The neutrons go into the lithium deuterate, combine with the lithium and make tritium. 
5. The combination of high temperature and pressure are sufficient for tritium-deuterium and deuterium-deuterium fusion reactions to occur, producing more heat, radiation and neutrons. 
6. The neutrons from the fusion reactions induce fission in the uranium-238 pieces from the tamper and shield. 
7. Fission of the tamper and shield pieces produce even more radiation and heat. 
8. The bomb explodes.

The result is an immense explosion with a 10,000-kiloton yield -- 700 times more powerful than the Little Boy explosion.