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Plasma: the fourth state of matter

Like fish in the ocean, we humans too, live in a giant ocean. We spend all our lives in a gigantic ocean of plasma, but we're barely aware what it is! Physicist Max Babi explains all about plasma - the fourth state of matter.

Just what is plasma?

'Plasma' is a Greek word meaning 'that which is diffuse' i.e. unclear, or semi-transparent. It is also defined by physicists as 'ionized matter'. This is the plasma of physics. Don't confuse it with 'biological plasma' which is a colourless jellylike liquid in our blood.

All matter is composed of atoms which are 'neutral'. That means they do not carry any electrical charge. Sometimes a flash of high voltage, or heating to extreme temperature will cause the 'outermost' electrons to get knocked off. These electrons will then knock off electrons from neighbouring atoms. This creates a mass of ionized matter, which is called plasma. Plasma is considered the 4th state of matter.

The other three states of matter are solids, liquids and gases, all of which are neutral in normal conditions. The plasma state is similar to the gaseous state, and yet it is very different. How?

Gases are electrically neutral, but plasmas contain both positive and negative charges. Gases cannot conduct electricity, plasmas can. Gases are not influenced by electromagnetic fields; plasmas can be deflected, focused or diverged by such fields.

How does a gas become plasma?

Even solids and liquids can be ionized but they would most often become vaporized whilst becoming plasmas. This is because it requires extreme temperatures to create plasma. The figure below illustrates a few different kinds of plasmas:

different kinds of plasma

Plasmas are not always hot –they can be cold too, as long as matter is ionized. A tubelight, a CFL, are comparatively cool to touch, so is the plasma TV screen. The outer space beyond our solar system is all plasma! More than 99% of the universe exists in plasma state.

When a heat source is used to excite a gas into its plasma state, it is called a thermal plasma and it gives off more heat, light, radiation and noise or vibration. Many devices have been designed to make to use of these energies efficiently.

The uses of plasmas

Micro-plasma welding is a method used to join paper thin sheets of metals. The joint becomes invisible after polishing. Stainless steel water storage tanks and other kitchen implements are made this way.
Plasma spray process is a most magical use of thermal plasmas –it is the only coating process that can apply any material on to any material.

  1. Metal on to metal: Titanium on to mild steel, to prevent corrosion of steel.
  2. Non-metal on to metal: alumina on to stainless steel. Alumina reduces the wear and tear on the stainless steel vessel due to industrial processes.
  3. Metal on to non-metal: copper on to porcelain used in capacitors. Plasma-spraying copper onto the porcelain makes it 'solderable', so that electric wires can be attached to it.
  4. Non-metal on to non-metal: Teflon on to magnesia (ceramic). Some chemicals like hydrofluoric acid can corrode the ceramic vessels they are kept in; coating them with Teflon prevents corrosion.

This is a Plasma Torch in action:

different kinds of plasma

In addition, there are 'cold' plasmas generated in vacuum or in atmospheric conditions. These plasmas utilize the electronic properties of materials in plasma state, not heat nor light. Today, cold plasmas are used in hand-washers, sterilizers for biomedical tools, making plastics attract or repel liquids for ease in printing and further protection, and hundreds of more magical uses.

© Max Babi, 2010

Tags :     History and Future     plasma     states of matter     micro-plasma welding    


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