RPM
06-11-2008, 04:56 PM
Here is some info I found on the net about neo magnets.
What materials do magnets attract?
Ferromagnetic materials are strongly attracted by a magnetic force. The elements iron (Fe), nickel (Ni), and cobalt (Co) are the most commonly available elements. Steel is ferromagnetic because it is an alloy of iron and other metals.
What materials can I use to block/shield magnetic fields?
Magnetic fields cannot be blocked, only redirected. The only materials that will redirect magnetic fields are materials that are ferromagnetic (attracted to magnets), such as iron, steel (which contains iron), cobalt, and nickel. The degree of redirection is proportional to the permeability of the material. The most efficient shielding material is the 80 Nickel family, followed by the 50 Nickel family.
What are neodymium magnets? Are they the same as "rare earth"?
Neodymium magnets are a member of the rare earth magnet family. They are called "rare earth" because neodymium is a member of the "rare earth" elements on the periodic table. Neodymium magnets are the strongest of the rare earth magnets and are the strongest permanent magnets in the world.
What are neodymium magnets made from and how are they made?
Neodymium magnets are actually composed of neodymium, iron and boron (they are also referred to as NIB or NdFeB magnets). The powdered mixture is pressed under great pressure into molds. The material is then sintered (heated under a vacuum), cooled, and then ground or sliced into the desired shape. Coatings are then applied if required. Finally, the blank magnets are magnetized by exposing them to a very powerful magnetic field in excess of 30 KOe.
Do I have to worry about temperature with neodymium magnets?
Yes. Neodymium Iron Boron magnets are sensitive to heat. If a magnet heated above its maximum operating temperature (176°F (80°C) for standard N grades) the magnet will permanently lose a fraction of its magnetic strength. If they are heated above their Curie temperature (590°F (310°C) for standard N grades), they will lose all of their magnetic properties. Different grades of neodymium different maximum operating and Curie temperatures.
Do neodymium magnets require a keeper?
No, neodymium magnets do not require a keeper for storage like Alnico magnets.
Will neodymium magnets lose strength if they are held in repelling or attracting positions for a long time?
In most applications, the answer is simply "no". If the magnets will be exposed to higher temperatures while in repelling applications, the answer is "possibly". The exact answer is a bit too complicated.
Can I make a magnet that I already have any stronger?
No, once a magnet is fully magnetized (saturated), it cannot be made any stronger.
Why are most neodymium magnets plated or coated?
Neodymium magnets are composed mainly of Neodymium, Iron, and Boron. If neodymium magnets are not plated, the iron in the material will oxidize very easily if exposed to moisture. Even normal humidity will rust the iron over time. To protect the iron from exposure to moisture, most neodymium magnets are plated or coated.
What is the difference between the different platings and coatings?
The coatings do not affect the magnetic strength or performance of the magnet. The preferred coating is dictated by preference or by the magnets intended application. Nickel is the most common choice for plating neodymium magnets, and is actually a triple plating of nickel-copper-nickel. It has a shiny silver finish and has good resistance to corrosion. Black nickel has a shiny, black/charcoal appearance and is slightly more corrosion resistant than regular nickel. It is also a triple plating of nickel-copper-black nickel. Zinc has a dull gray/bluish finish, that is more susceptible to corrosion than nickel. Zinc can leave a black residue on hands and other items. Epoxy is basically a plastic coating that is virtually 100% corrosion resistant as long as the coating is intact. From our experience, it is the least durable of the common coatings. Gold plating is applied over the top of nickel plating, so gold plated magnets have the same characteristics as nickel plated ones, but with a gold finish.
I noticed that the plastic- and rubber-coated magnets have a lower pull force than nickel-plated magnets of the same size. Does the plastic/rubber weaken the magnet?
These materials don't "weaken" the magnet, but the volume of magnet material is reduced to allow room for the coatings, which reduces the pull force. The layer of plastic or rubber also creates distance between the magnet and metal surface which also reduces the pull force.
:thumbsup:
What materials do magnets attract?
Ferromagnetic materials are strongly attracted by a magnetic force. The elements iron (Fe), nickel (Ni), and cobalt (Co) are the most commonly available elements. Steel is ferromagnetic because it is an alloy of iron and other metals.
What materials can I use to block/shield magnetic fields?
Magnetic fields cannot be blocked, only redirected. The only materials that will redirect magnetic fields are materials that are ferromagnetic (attracted to magnets), such as iron, steel (which contains iron), cobalt, and nickel. The degree of redirection is proportional to the permeability of the material. The most efficient shielding material is the 80 Nickel family, followed by the 50 Nickel family.
What are neodymium magnets? Are they the same as "rare earth"?
Neodymium magnets are a member of the rare earth magnet family. They are called "rare earth" because neodymium is a member of the "rare earth" elements on the periodic table. Neodymium magnets are the strongest of the rare earth magnets and are the strongest permanent magnets in the world.
What are neodymium magnets made from and how are they made?
Neodymium magnets are actually composed of neodymium, iron and boron (they are also referred to as NIB or NdFeB magnets). The powdered mixture is pressed under great pressure into molds. The material is then sintered (heated under a vacuum), cooled, and then ground or sliced into the desired shape. Coatings are then applied if required. Finally, the blank magnets are magnetized by exposing them to a very powerful magnetic field in excess of 30 KOe.
Do I have to worry about temperature with neodymium magnets?
Yes. Neodymium Iron Boron magnets are sensitive to heat. If a magnet heated above its maximum operating temperature (176°F (80°C) for standard N grades) the magnet will permanently lose a fraction of its magnetic strength. If they are heated above their Curie temperature (590°F (310°C) for standard N grades), they will lose all of their magnetic properties. Different grades of neodymium different maximum operating and Curie temperatures.
Do neodymium magnets require a keeper?
No, neodymium magnets do not require a keeper for storage like Alnico magnets.
Will neodymium magnets lose strength if they are held in repelling or attracting positions for a long time?
In most applications, the answer is simply "no". If the magnets will be exposed to higher temperatures while in repelling applications, the answer is "possibly". The exact answer is a bit too complicated.
Can I make a magnet that I already have any stronger?
No, once a magnet is fully magnetized (saturated), it cannot be made any stronger.
Why are most neodymium magnets plated or coated?
Neodymium magnets are composed mainly of Neodymium, Iron, and Boron. If neodymium magnets are not plated, the iron in the material will oxidize very easily if exposed to moisture. Even normal humidity will rust the iron over time. To protect the iron from exposure to moisture, most neodymium magnets are plated or coated.
What is the difference between the different platings and coatings?
The coatings do not affect the magnetic strength or performance of the magnet. The preferred coating is dictated by preference or by the magnets intended application. Nickel is the most common choice for plating neodymium magnets, and is actually a triple plating of nickel-copper-nickel. It has a shiny silver finish and has good resistance to corrosion. Black nickel has a shiny, black/charcoal appearance and is slightly more corrosion resistant than regular nickel. It is also a triple plating of nickel-copper-black nickel. Zinc has a dull gray/bluish finish, that is more susceptible to corrosion than nickel. Zinc can leave a black residue on hands and other items. Epoxy is basically a plastic coating that is virtually 100% corrosion resistant as long as the coating is intact. From our experience, it is the least durable of the common coatings. Gold plating is applied over the top of nickel plating, so gold plated magnets have the same characteristics as nickel plated ones, but with a gold finish.
I noticed that the plastic- and rubber-coated magnets have a lower pull force than nickel-plated magnets of the same size. Does the plastic/rubber weaken the magnet?
These materials don't "weaken" the magnet, but the volume of magnet material is reduced to allow room for the coatings, which reduces the pull force. The layer of plastic or rubber also creates distance between the magnet and metal surface which also reduces the pull force.
:thumbsup: