Is neodymium powder as strong of a magnet as solid neodymium

[chemisthypnos]

In attempting to make magnetized neodymium powder, I grinded neodymium magnets into a powderusing a belt sander. However, I found that the magnetic properties of the neodymium had decreased substantially. It would appear that any attempt to grind the magnets into a powder using this method seems to cause the diminishing magnetic field observed https://en.wikipedia.org/wiki/Neodymium_magnet .

Is it possible for neodymium powder to be as magnetic as a solid neodymium magnet?

 

[Tom.G]

It seems not. There is too much air in the result. Since air is not a very good magnetic field conductor, the addition of the fields of individual particles can't occur without loss thru the air spaces.

Also using a grinder may have exceeded the Curie temperature of Neodymium, 310°C. If you were getting Red sparks from the grinding the temperature was around 700°C, Yellow sparks are 1000°C and up.

 

[Borek]

First thing that comes to mind: solid magnet is made so that domains are ordered as ↑↑↑↑↑↑, in powder they will automatically order as ↑↓↑↓↑↓, guess in which case the magnetic field looks stronger.

 

[CWatters]

+1

Most likely you will end up with some random orientation which is practically the definition of un-magnitised.

PS: Did the belt sander survive the experience or did the motor end up full of metal fragments?

 

[berkeman]

In attempting to make magnetized neodymium powder, I grinded neodymium magnets into a powderusing a belt sander.

Did you wear a well-fitting N95 mask and safety goggles while you were doing this grinding?

 

[jrmichler]

From the wiki: Sintered Nd2Fe14B tends to be vulnerable to corrosion. Small hot particles from grinding will corrode very fast, as in milliseconds. You may have neodymium oxide powder, unless you did the grinding in an inert atmosphere.

Neo magnets are made by sintering the non-magnetic powder. Magnetizing them is the last step. If your powder clumps tightly, it may still have some magnetism. If it flows easily, the magnetism is gone. If it has not been oxidized, you could remagnetize it if you have an electromagnet strong enough.

 

[trurle]

In attempting to make magnetized neodymium powder, I grinded neodymium magnets into a powderusing a belt sander. However, I found that the magnetic properties of the neodymium had decreased substantially. It would appear that any attempt to grind the magnets into a powder using this method seems to cause the diminishing magnetic field observed https://en.wikipedia.org/wiki/Neodymium_magnet .
Is it possible for neodymium powder to be as magnetic as a solid neodymium magnet?

Some nuances do exist.
1) Some non-magnetic materials (for example SUS304 steel) are actually become magnetic after grinding, because of mechanical stresses inducing changes in inter-atomic distance and crystal structure, enhancing magnetic properties
2) Air spaces between grains are detrimental to permeability of "soft" ferromagnetics, as Tom.G correctly noted, but this is not applicable for coercitive strength of permanent magnet, therefore attraction force of powdered permanent magnet to "soft" ferromagnetic is not much affected.
3) Very fine magnetic powders tends to be more magnetically "soft" - i.e. lower coercitive strength, although "small" is something in range of 0.01um, not attainable with regular grinder.
4) Chemical alteration (i.e. rusting) will happen for NeFeB magnets, as jrmichler correctly noted

Overall, i expect strength of NdFeB magnet to decrease after grinding, confirming your observation. For magnet strength increase, you may try to carefully grind only nickel-chrome coating of magnet, although it will negatively affect magnet longevity.

 

[DrClaude]

2) Air spaces between grains are detrimental to permeability of "soft" ferromagnetics, as Tom.G correctly noted, but this is not applicable for coercitive strength of permanent magnet, therefore attraction force of powdered permanent magnet to "soft" ferromagnetic is not much affected.
3) Very fine magnetic powders tends to be more magnetically "soft" - i.e. lower coercitive strength, although "small" is something in range of 0.01um, not attainable with regular grinder.
4) Chemical alteration (i.e. rusting) will happen for NeFeB magnets, as jrmichler correctly noted

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