What is vacuum

What is vacuum, an understandable question for anyone who does not know this.
A hole group of people who work with vacuum on a daily basis to achieve certain results that cannot be achieved without vacuum.

You too, as reader of this article, are currently making use of these results, perhaps without being aware of it.
Do you realize that the many electronic components in your computer, as well as the flat screen on which the letters appear, were created using vacuum! 

We actually live at the bottom of a very deep ocean of air.
Now air is composed of a large amount of different gases, of which nitrogen (almost 80%) and oxygen (approx. 20%) are the most important.

At the bottom of this “ocean” the air pressure is one atmosphere and therefore higher than on top of a mountain, there the air is a lot thinner (the air pressure is lower there).
The higher we get, the thinner the air becomes and with that the oxygen content is also getting smaller.
We then have trouble breathing.
Climbers of high mountains often carry bottles of oxygen.
This “thin” air is the beginning of vacuum.
As soon as the air pressure falls below one atmosphere, we speak of a vacuum.

On Earth we can create the vacuum in a relatively simple way.
Vacuum technology uses pumps that can pump the air from so-called vacuum chambers.
Processes can take place in that vacuum that are completely unimaginable under atmospheric pressure.
Now ‘vacuum’ is a flexible term.
The number of air molecules in a cm3 is so great that the technique is unable to remove all molecules from a vacuum chamber.
Fortunately, that is not necessary either.
There are sufficient processes that already run smoothly at low pressure. 

The vacuum is classified as follows:

The free path length:

A second important aspect is the following, molecules move at high speed and constantly collide with each other, especially at a pressure of 1000 mBar (  atmosphereic pressure)
There, the road between two collisions is very small.
But if there are fewer molecules in a vacuum chamber, the distance that the molecules can travel between two collisions increases.
At a pressure of 10-3 mbar this distance is already 6.7 cm, at a pressure of 10-6 mbar this distance is 1000x as great ( 67 m !)
This is called the free path length and this aspect makes many processes possible. 

Solutions with Vacuum:

Preventing physical or chemical reactions:
Thanks to a good vacuum pump, Edison was able to make a light bulb in 1879.
By removing the air (and in particular the oxygen) from the glass bulb, the filament did not burn and the bulb stayed on for a long time.
Based on this invention, today we have the most diverse energy-efficient lamps that provide a lot of light.
But your vacuum-packed coffee also stays fresh longer if the air (read oxygen) is pumped out of the pack.
And that of course applies to all vacuum-packed food! In the art, more and more metals are brazed, melted, hardened and sintered under vacuum; making transistors and integrated circuits is also part of this.

Creating a differential pressure:

The pressure difference between vacuum and the air surrounding us provides us with unprecedented forces.
With the help of suction cups, we lift windows or plates or large rolls of paper without damaging them.
The clamping of material on milling machines is also done with vacuum.
Furthermore, filtration with vacuum is faster, brake lines can be quickly filled with brake fluid and all kinds of plastic containers can be formed for packaging purposes.

Reducing Energy Transfer:

A good example is the familiar thermos with coffee.
Because it is made up of an inner and an outer bottle with a vacuum insulation in between, the coffee stays hot for much longer.
This principle is also applied in district heating, hot water is transported to homes through a kilometer-long “thermos” flask without significant heat losses.
Liquid gases at very low temperatures are stored in large metal thermos flasks.

Removing gas from a material.

The so-called impregnating oil, which gives electrical components better insulation, must first be feed of water and air, which are dissolved in the oil.
This is done under vacuum.
The electrical components, such as transformers, motors, capacitors, high voltage cables, etc., are also evacuated, so that all air is out.

Subsequently, these components are immersed under vacuum in the degassed impregnation oil and then aerated to one atmosphere.

The oil will now reach everywhere where there used to be air, which has improved the insulation many times over.
In addition, liquid metals such as steel and aluminum are degassed under vacuum, so that no casting galls are formed and a much more homogeneous material is formed.

Vacuum freeze-dried products such as medicines and food have a much longer shelf life.
Without a vacuum, there would be no proper refrigeration systems, air conditioners, or freezers.

Increasing the free road length:

The number of applications by increasing the free path length is very large.
Mass spectrometers, electron microscopes and particle accelerators are used scientifically.
A much wider field of application is vapor deposition.
Your glasses have anti-reflective lenses, your camera and binoculars the same.

Thanks to the vacuum technique, several thin layers can be applied to these types of surfaces, which greatly improve the quality of the lens.
For example, special mirrors and also foil are evaporated, just look at the pack of coffee or the heating blanket for traffic victims!

Thin layers are also applied with the so-called sputter method, but these can be very hard, so that drills, milling, molds, but also spectacle frames and ballpoint pens not only have a beautiful golden shine, but are also scratch-resistant and wear-resistant.
And with the sputter method, the beautiful glass walls of modern buildings are provided with a transparent thin layer with a beautiful color, which also reflects heat.
Another example is the CD disk, each CD is provided in a vacuum with a reflective layer in 1.5 seconds, so that you can enjoy high-quality music.

Creating clean conditions:

The ultra high vacuum can no longer be ignored in scientific research of surfaces.
Whether it is research on catalysts, corrosion or semiconductors, without ultra high vacuum we would not have the knowledge needed to understand nature.
But the fabrication of the most complicated integrated circuits for computers also requires a clean room, as does the testing of the satellites for space travel.

Reducing Frictional Resistance:

It is not without reason that the planes fly at such a great height! At an altitude of 10 km, the pressure is only 260 mbar, which gives much less air resistance than at sea level.
On Earth, ultracentrifuges run under vacuum, soil samples are examined in a centrifuge that runs in vacuum.

For the storage of energy, gyroscopes and flywheels rotate in vacuum and it is being considered to have goods transported at great speed over long distances in vacuum tunnels.( Hyperloop systems)

The above is just a selection of the many, many applications of vacuum.
Without a vacuum, we would still be sitting by a candle and sending messages through a human messenger.

Now we grab our mobile phone and talk directly to the other end of the world or send an email from our computer.
Thanks to the vacuum technology,……………… this is all possible!

With many thanks to ing. Theo Mulder
Co Author:
Book vacuum science and Technology.