Cold plasma in the air: what is it and how it works?
Today, plasma technologies penetrate into various industries, from processing
textiles prior to air cleaning and decontamination and treatment of various diseases. But what is
plasma, how is it obtained and how does it find application in a variety of fields?
Plasma is called the fourth state of matter, but in fact it would be
it is more correct to call the first state of the substance. Historically, plasma was discovered in the XIX century
in the century, after it was long known about three other states of matter – solid,
liquid and gaseous. However, in reality, it was plasma that arose first.
The universe appeared as a result of the Big Bang, and in the first moments of its existence
the whole substance was concentrated in a very small area of space and had
unimaginable energy – this was the original plasma of very high density and
colossal temperature. The substance under these conditions exists in the form of ions (atoms
without one or two electrons that “fly” separately). Plasma is an energy gas.
consisting almost entirely of charged particles (ions and electrons), which are not only
collide with each other, but are also attracted and repelled by electric
forces. During the first second of the universe’s life, plasma expanded greatly and
cooled, although its temperature remained very high. This process continues and
today, and the universe is still 99.9% composed of plasma. All stars, starting with ours
The suns are huge masses of hot plasma. Temperature inside the Sun reaches
tens of millions of degrees, while on the surface – “only” hundreds of thousands of degrees.
However, there are areas of highly cooled matter in the universe, where electrons
“return” to atoms, which thus become neutral, their temperature
drops and the substance is a conventional (non-ionized) gas, or forms
denser states, – liquid and solid. Planets, in particular our Earth, as well as
asteroids and comets are an example of cooled matter, which in the universe is only less than 0.1
%! Our Earth also has an atmosphere that protects it from hot radiation
the universe and protects against the sharp radiation of the Sun. Living in our oasis of “tranquility,”
we are not used to seeing a substance in a plasma state. However, sometimes conditions for such
the energy state of the substance occurs on Earth. For example, we observe
lightning, in the cord of which air enters the state of hot plasma. Today
day four (or, more precisely, the first) state of matter can be created artificially.
For example, plasma is created and is a source of colossal energy in thermonuclear
reactor. Electric welding and electric arc between the electrodes of the battery – this is also
examples of hot plasma.
However, in addition to hot plasma, gas atoms can be ionized without heating. We see
examples of cold plasma on Earth in the form of polar lights, daylight lamps,
sometimes flashes of ionized air can be seen on high-voltage lines
power transmission. These are examples of how air ionizes and becomes plasma not in
the result of heating, and due to its permeating energy flows (space
radiation that “ignites” the northern lights), or due to the applied high
voltage (in daylight lamps or on high-voltage wires). Cold plasma
also consists of ions and electrons, although their concentration is much lower than in hot
plasma. But unlike hot plasma, cold plasma can be used in
processes without the risk of melting or damaging materials by heating.
What is the basis for the action of cold plasma lit in ordinary air?
Unlike from the case of discharged air (northern lights, advertising tubes), in air or, as
they say there are relatively few ions in atmospheric plasma, but many energetically
neutral excited particles, the so-called gas radicals. To them first of all
relates to atomic oxygen, as well as hydroxyl groups (OH), ozone, nitrogen oxides;
other excited atoms, and molecules. Radicals are chemically active particles. Time
arising in cold plasma, they immediately enter into reactions with those introduced into the plasma
materials, whether metals, polymers, textiles or even human bodies. Cold
plasma quickly and efficiently affects and changes properties of treated materials
due to its chemical action. For various treatments become
unnecessary solutions of chemicals (which also need to be neutralized
after use). After the action of the plasma, the remaining radicals disintegrate in the air,
returning to conventional air gases.
Application of cold atmospheric plasma is highly efficient and high
environmentally friendly technology that saves water and reduces
the necessary chemicals, as well as accelerated technological processes. No
also losses on unnecessary heating, which is an additional source
savings. Interest in innovative application-based technologies
atmospheric plasma for both material treatment and purification of water and air, and
also in medicine and agriculture continues to increase in accordance with
modern requirements for efficiency, environmental friendliness and low cost
technological processes.