Ferromagnetic powder composition
The present invention relates to an electrically insulated iron-based soft magnetic powder composition, a soft magnetic composite component obtainable from the powder composition and a process for producing the same. Specifically, the invention concerns a soft magnetic powder composition for the preparation of soft magnetic components working at high frequencies, the components being suitable for use e.g. as inductors or reactors for power electronics.
1. A composition comprising particles A and particles B, each of the particles A and B comprising a core, the core of the particles A being a soft magnetic iron based core, and the core of the particles B being formed from an Fe—Si alloy,
wherein an amount of a total of the particles A and B relative to a total weight of the composition is 85% by weight or more,
wherein the core of the particles B consists of Fe, Si, and less than 2% of other elements,
wherein the surface of each core of the particles A and B is coated with a phosphorus-containing insulating layer A1 and B1, respectively,
and wherein the particles A having the insulating coating layer A1 are provided with a further layer A2 on top of the layer A1, the layer A2 being formed from a compound of formula (I), or a reaction product of formula (I):
M(OR 1 ) x (R 2 ) y Formula (I)
wherein M is selected from Si, Ti, Al, or Zr;
R 1 is a straight or branched alkyl group having 4 or less carbon atoms;
R 2 is an organic group optionally containing a functional group, and
x+y are integers denoting the number of groups OR 1 and R 2 , respectively, and if M is Si, Zr or Ti, x is chosen from 1, 2 and 3, and y is chosen from 1, 2 and 3, with the proviso that (x+y)=4; and
if M is Al, then x is chosen from 1 and 2, and y is chosen from 1 and 2, with the proviso that (x+y)=3;
wherein the reaction product is a product obtained by a reaction of one molecule of a compound of formula (I) with one or more molecules of a compound of formula (I) and/or with the layer A1; and
wherein the particles A further comprise particles C that are adhered to the layer A2 or which are incorporated into the layer A2, the particles C being particles of a material having Mohs hardness of 3.5 or less.
2. The composition according to claim 1 , wherein the particles B are provided with a layer B2 on the layer B1, the layer B2 being formed from a compound of formula (I), or a reaction product of formula (I):
M(OR 1 ) x (R 2 ) y Formula (I)
wherein M is selected from Si, Ti, Al, or Zr;
R 1 is a straight or branched alkyl group having 4 or less carbon atoms;
R 2 is an organic group optionally containing a functional group, and
x+y are integers denoting the number of groups OR 1 and R 2 , respectively, and if M is Si, Zr or Ti, x is chosen from 1, 2 and 3, and y is chosen from 1, 2 and 3, with the proviso that (x+y)=4; and
if M is Al, then x is chosen from 1 and 2, and y is chosen from 1 and 2, with the proviso that (x+y)=3,
and wherein optionally the particles B contain particles C that are adhered to or incorporated into the layer B2.
3. The composition according to claim 1 , wherein said powder composition further comprises a lubricant.
4. The composition according to claim 1 , wherein the layer A2 and/or B2 is formed from a compound of formula (I), or wherein the layer A2 and/or B2 is formed from a reaction product of a compound of formula (I), wherein the number of metal atoms M in one molecule is from 2-20.
5. The composition according to claim 1 , wherein R 2 includes one or more of the following functional groups: amine, diamine, amide, imide, epoxy, mercapto, disulfido, chloroalkyl, hydroxyl, ethylene oxide, ureido, urethane, isocyanato, acrylate, glyceryl acrylate, carboxyl, carbonyl, and aldehyde.
6. The composition according to claim 1 , wherein the compound of formula (I) or a reaction product thereof is an oligomer of the compound of formula (I), and wherein the oligomer is selected from alkoxy-terminated amino-silsesquioxanes, amino-siloxanes, oligomeric 3-aminopropyl-alkoxy-silane, 3-aminopropyl/propyl-alkoxy-silane, N-aminoethyl-3-aminopropyl-alkoxy-silane, or N-aminoethyl-3-aminopropyl/methyl-alkoxy-silane, or mixtures thereof.
7. The composition according to claim 1 , wherein the particles C include bismuth or bismuth (III) oxide.
8. The composition according to claim 1 , wherein the weight ratio of particles A and B (A:B) is from 95:5 to 50:50.
9. The composition according to claim 1 , wherein the core particles of the particles A have an apparent density of 3.3-3.7 g/mL.
10. The composition according to claim 1 , wherein layer A2 comprises a compound of formula (I), a dimer, and/or an oligomer thereof.
11. The composition according to claim 1 , wherein the reaction product is a polycondensate of two or more compounds of Formula (I) wherein the compounds may be the same or different from each other.
12. A method for producing a compacted and heat-treated component, comprising the steps of
a) providing a composition as defined in claim 1 ,
b) compacting the composition, optionally mixed with a lubricant, in a uniaxial press movement in a die,
c) ejecting the compacted component from the die, and
d) optionally heat-treating the ejected component in a non-reducing atmosphere at a temperature of up to 800° C.
13. Component, obtainable by compacting a composition as defined in claim 1 .
14. Component according to claim 13 , which is an inductor core.
15. Inductor core according to claim 14 , having a resistivity ρ of 3,000 μΩm or higher; a saturation magnetic flux density Bs of 1.1 T or higher; a core loss of 21 W/kg or less at a frequency of 10 kHz and an induction of 0.1 T; a coercivity at 10 000 A/m of 240 A/m or less; and a DC-bias of not less than 50% at 4 000 A/m.