Corrosion-resistant permanent magnet and intravascular blood pump comprising the magnet
This invention is directed to a corrosion-resistant permanent magnet, to a method for producing a corrosion-resistant permanent magnet, and to an intravascular blood pump comprising the magnet. The magnet is corrosion resistant due to a composite coating comprising a first layer structure and optionally a second layer structure on the first layer structure, each layer structure comprising an inorganic layer, a linker layer on the inorganic layer, and an organic layer formed from poly(2-chloro-p-xylylene) on the linker layer. The inorganic layers comprise aluminum and/or aluminum oxide.
1. A corrosion-resistant permanent magnet comprising:
a magnet body, and
a composite coating provided on and covering surfaces of the magnet body, the composite coating comprising a first layer structure on the magnet body and a second layer structure on the first layer structure, each layer structure comprising, in the order recited,
an inorganic layer,
a linker layer on the inorganic layer, and
an organic layer formed from poly(2-chloro-p-xylylene) on the linker layer,
wherein the inorganic layer of the first layer structure either comprises an aluminum layer on the magnet body, or comprises an aluminum layer on the magnet body and an aluminum oxide layer on the aluminum layer,
wherein the inorganic layer of the second layer structure comprises at least one of an aluminum layer or an aluminum oxide layer, and
wherein the composite coating has at least one aluminum oxide layer having a thickness of at least 50 nm.
2. The corrosion-resistant permanent magnet of claim 1 , wherein a linker layer is provided between the first layer structure and the second layer structure.
3. The corrosion-resistant permanent magnet of claim 2 , wherein at least one of the linker layers is a monolayer, or wherein the linker layer has a thickness in a range from 20 nm to 50 nm.
4. The corrosion-resistant permanent magnet of claim 2 , wherein the linker forming at least one of the linker layers is selected from silanes, and silanes having a thiol, phosphine or disulfide group.
5. The corrosion-resistant permanent magnet of claim 4 , wherein the linker is selected from 3-(2-pyridylethyl)thiopropyl trimethoxysilane, 3-(4-pyridylethyl)thiopropyl trimethoxysilane, and 2-(diphenylphosphino)ethyl triethoxysilane.
6. The corrosion-resistant permanent magnet of claim 1 , wherein the inorganic layer of the second layer structure is an aluminum oxide layer.
7. The corrosion-resistant permanent magnet of claim 1 , wherein the magnet body is a sintered magnet body.
8. The corrosion-resistant permanent magnet of claim 1 , wherein the magnet body is a rare-earth metal iron boron permanent magnet.
9. The corrosion-resistant permanent magnet of claim 1 , wherein the magnet body is rod-shaped with all edges being rounded.
10. The corrosion-resistant permanent magnet of claim 1 , wherein a thickness of the aluminum layer of the first layer structure and/or the second layer structure is from 0.5 μm to 15 μm, or from 1 μm to 10 μm, or from 1 μm to 5 μm.
11. The corrosion-resistant permanent magnet of claim 1 , wherein the thickness of the aluminum oxide layer of the first layer structure and/or the second layer structure is from 50 nm to 200 nm, or from 80 nm to 120 nm.
12. The corrosion-resistant permanent magnet of claim 1 , wherein a combined thickness of the aluminum layer and the aluminum oxide layer of the first layer structure and/or the second layer structure is in a range from 5 μm to 15 μm.
13. The corrosion-resistant permanent magnet of claim 1 , wherein the thickness of the layer formed from poly(2-chloro-p-xylylene) of the first layer structure and/or the second layer structure is in a range from 5 μm to 20 μm.
14. The corrosion-resistant permanent magnet of claim 1 , wherein the thickness of the composite coating is no more than 200 μm, preferably no more than 50 μm.
15. The corrosion-resistant permanent magnet of claim 1 , wherein all layers of the composite coating completely extend over all surfaces of the magnet body.
16. An intravascular blood pump comprising an electric motor, wherein the electric motor comprises a permanent magnet, the permanent magnet comprising:
a magnet body, and
a composite coating provided on and covering surfaces of the magnet body, the composite coating comprising a first layer structure on the magnet body and a second layer structure on the first layer structure, each layer structure comprising, in the order recited,
an inorganic layer,
a linker layer on the inorganic layer, and
an organic layer formed from poly(2-chloro-p-xylylene) on the linker layer,
wherein the inorganic layer of the first layer structure either comprises an aluminum layer on the magnet body, or comprises an aluminum layer on the magnet body and an aluminum oxide layer on the aluminum layer,
wherein the inorganic layer of the second layer structure comprises at least one of an aluminum layer or an aluminum oxide layer, and
wherein the composite coating has at least one aluminum oxide layer having a thickness of at least 50 nm.