Understanding Doped Conductive Coatings
There are both nonconductive and conductive coatings. To limit or promote the flow of electrical or heat current away from or into a coated object, fillers are used. A doped thin-film coating may be used or a conductive coating which, by CVD, is a thin film deposited on a substrate.
Many people may already have an understanding of what a conductive coating is. But what does the word “dope” refer to? Doping is a process by which the properties of an intrinsic semiconductor are altered by the addition of impurities. If a semiconductor has very little conductivity, in order to increase its conductivity, doping is done. As a result of doping, extrinsic semiconductors are formed.
We’re going to take a look at doped conductive coatings and how they’re used.
Electromagnetic Waves
Electromagnetic radiation is a funny thing. On the one hand, there are negative characteristics such as the possibility of electromagnetic information leakage, electromagnetic environmental pollution, and electromagnetic interference. On the plus side, however, are benefits such as long-distance and high-speed wireless information transmission. Why would the negative characteristics be a problem? Here’s a perfect example:
The capture of Saddam Hussein had everything to do with electromagnetic waves. His discovery was perpetuated by the detection of a phone call between his wife and him. United States intelligence surveillance picked up the electromagnetic information produced by electromagnetic leakage during the phone conversation. They locked in on his hiding place and the rest is history.
A Shield Is Needed
Preventing the leakage described above is just the beginning of the need for shielding. In the past, metal complex materials were used as the traditional method of electromagnetic shielding. They had their shortcomings, however, and have been replaced by new and improved coatings and coating applications.
Uses for Conductive Coatings
As suggested earlier, these conductive coatings are doped thin films or deposited by CVD. Uses include the following:
- In electrical conductive couplings
- On photocopy machine parts to aid thermal dissipation
- In printed circuits
- In aircraft paints for antistatic protection
- To shield from EMI (electromagnetic interface) and more
Depending on the application, the coating may come initially from a standard coating. Conductive material is added (the coating is filled) with materials that are conductive: i.e., gold, silver, copper, nickel, graphite. Recently, graphene and carbon nanotubes have been used for conductivity and coatings as fillers.
All conductive fillers have both disadvantages and advantages, depending on what they’re made from. To better understand doped conductive coatings, let’s take a look at a couple of fillers.
Carbon Conductive Filler
Thermal cracking carbon black, tank carbon black, oil furnace carbon black, and acetylene carbon black are all included as carbon black conductive fillers. They have poor dispersion but excellent electrical conductivity.
Having good conductivity, asphaltene and polyacrylonitrile have the downside of being difficult to process and having high production costs.
Metal Conductive Powder Filler
Nickel powder, silver, and copper are included in metal powder conductive fillers. Nickel has several advantages such as stable electrical conductivity, good oxidation resistance, and moderate to low price. With better low-frequency shielding than nickel, copper also has excellent conductivity. Silver has a slow oxidation speed and the best conductivity.
Metal oxides have good heat resistance but poor electrical conductivity. Included in metal oxide conductive fillers are zinc oxide, titanium dioxide, and tin oxide.
A&A Coatings has a complete understanding of any and all modern day coatings, regardless of what they are used for. We coat substrates of all types, sizes, and shapes. If you would like to find out what our thermal spray coatings can do for your business, contact one of our knowledgeable representatives today.
