Plasma: The fourth state of matter
For most people, matter surrounding us in everyday life is composed of solids, liquids, or gases. But there is a fourth state of matter: plasma.
Plasma may be less known, but you observe it on a regular basis without even realizing it. Every time you see lightning, electric sparks, fluorescent or Northern lights, or even when you gaze at the stars, you are experiencing illuminated matter in the plasma state. As much as 99.99 per cent of the visible universe is plasma.
“Plasma is an ionized gas, which means that sufficient energy is provided to free electrons from atoms or molecules and to allow both species – ions and free electrons – to coexist. This electron “sea” allows matter in the plasma state to conduct electricity, somewhat like a conductive metal. This is one of the properties that makes plasma so radically different from their gaseous counterpart,” explains Richard Dolbec, Program Director Emerging Technologies at Tekna.
Plasma can also be a chemically reactive environment. Take nitrogen, a gas considered as inert under normal conditions. Once ionized in a plasma, nitrogen ions become reactive species that can react and change the nature of elements, forming a metal nitride, for instance.
“Plasma can reach temperatures of about 10,000 degrees Celsius, equal to the temperature at the surface of the sun, and way beyond the hottest flame resulting from fuel combustion, which burns at approximately 3000 degrees Celsius,” says Dolbec.
Artificial plasma can be generated in several different ways, but based on a common principle: there must be energy input to produce and sustain it. In fluorescent light bulbs for example, the tube contains a small bit of mercury and an inert gas (typically argon) kept under very low pressure. Electricity flows through the tube when the light is turned on. The electricity acts as an energy source and charges up (or ionizes) the gas. This charging and exciting of the atoms creates glowing plasma inside the bulb, a cold plasma made to emit light we can see.
“This is clearly different from the proprietary plasma core technology developed by Tekna where the heat from the plasma is used for melting and even evaporating metals, aiming at producing advanced metallic powders. Tekna has developed a plasma torch technology that generates plasma by induction with power levels of 400 kW and capable of withstanding temperatures above 10,000 degrees Celsius. Next generation will be engineered to reach up to 2 MW – that is two millions of Watts,” says Nicolas Dignard, CTO Plasma Systems.
The Tekna torch consists of a coil wrapped around a confinement chamber through which a gas mixture continuously flows. The coil applies a strong radio-frequency electric fields inside the chamber and thanks to the conductive nature of the plasma, electric energy from the coil is converted into thermal energy in the gas.
“By mastering this very hot environment, Tekna has developed the best powders for additive manufacturing, can produce nanopowders used in microelectronic and energy storage, and can also be used for testing materials used in supersonic conditions,” says Richard Dolbec.