US3567525A - Heat treated ferromagnetic particles - Google Patents

Heat treated ferromagnetic particles Download PDF

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US3567525A
US3567525A US739732A US3567525DA US3567525A US 3567525 A US3567525 A US 3567525A US 739732 A US739732 A US 739732A US 3567525D A US3567525D A US 3567525DA US 3567525 A US3567525 A US 3567525A
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powder
particles
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Arthur Hughes Graham
Ernest Lewis Little Jr
Jack D Wolf
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/09—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials mixtures of metallic and non-metallic particles; metallic particles having oxide skin
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/06—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder
    • H01F1/061—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys in the form of particles, e.g. powder with a protective layer

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  • Ferromagnetic alloy particles of iron, nickel or cobalt, and optionally chromium supersaturated with boron, nitrogen or phosphorus which are prepared by reduction of a solution containing salts of the appropriate metals, are converted to polyphase particles of substantially unchanged size having improved magnetic properties by heating below their sintering temperatures.
  • the ferromagnetic particles are useful for making magnets and for making magnetic recording members.
  • the above ferromagnetic particles consist of a supersaturated solid solution of the boron, nitrogen or phosphorus in an alloy of the metals, with a coating of metal oxide and/or adsorbed moisture on the surface of the particles. It has now been discovered that the chemical constitution of the particles can be modified and the magnetic properties improved by a heat treatment process, while maintaining the fine particle size.
  • a ferromagnetic composition comprising polyphase, non-pyrophoric particles generally having single domain behavior and having a maximum dimension of about 4 microns, said particles consisting of at least one metal consisting of iron, cobalt and nickel, and from to 20% chromium and at least one of B,N or P, in an amount less than the minimum amount required to form a compound with all of said metal, said particles having a polyphase microstructure with the metals as one phase and compounds of the constituent metals with said B, N or P as at least one additional phase, said polyphase particles being coated with a thin oxide film.
  • This invention also comprises a method of making the above particles by heating particles consisting essentially of a single-phase alloy of a metal selected from at least one of iron, nickel, cobalt and from 0 to 20% chromium, super-saturated with at least one of B, N or P in an 3,567,525 Patented lVlar.
  • the starting materials of the present invention containing boron are prepared by the borohydride reduction of the soluble metal salts of iron, nickel, or cobalt with alkali or alkaline earth borohydrides as taught by Miller and Oppegard.
  • the reduction is generally carried out in solution preferably approaching saturation, and at a temperature less than C.
  • the borohydride solution preferably is added to the solution of metal salts rather than vice versa with agitation kept to the minimum required to ensure thorough mixing of the ingredients.
  • the reduction is accomplished in the presence of a magnetic field of at least 100 Oe. and preferably at least 1000 0e.
  • Chromium salts can be added to the reaction mixture in which case metallic chromium is formed as a solid solution in the essential iron, nickel or cobalt. Chromium salts alone, however, are not reduced to the metal by wet reduction.
  • chromium is to be incorporated, the efiiciency of incorporation is greatest at 40 or greater.
  • the presence of chromium increases the oxidation stability of the particles. In general, from 0.4 to 20% of chromium should be present, and preferably from 8 to 20%.
  • the percentage of acicular particles increases with temperature of the reduction process.
  • a magnetic field of at least 100 0e. and preferably greater than 1000 oe. in order to promote the formation of acicular particles.
  • the heat treatment of the present invention modifies the metallurgical nature of the particles and greatly improves the saturation magnetization and certain other magnetic properties without substantially varying the particle dimensions.
  • sodium hypophosphite, NaH PO is used as the reducing agent in basic ammoniacal solution (pH 9 or greater) and with a catalytic amount of palladium chloride PdCl in place of sodium borohydride system described above.
  • nitrogen can be introduced by using hydrazine in ammonical aqueous solutions with catalytic amounts of palladous chloride.
  • the solution medium is an aqueous system, but when some, or all, of the reactants have sparing solubility in water miscible organic solvent may replace at least part of the water.
  • the above systems are compatible with each other and mixtures of the above reducing systems can be used to introduce mixtures of the above elements in supersaturated solution in the metal components of the precipitated particles.
  • Palladous compounds also catalyse the reduction of the metal salts with alkali or alkaline earth metal borohydrides.
  • palladous salts When palladous salts are employed as a catalyst, small quantities of palladium metal are introduced into the resultant composition.
  • the temperature and time at which the single phase particles formed in the above precipitation process are heated to achieve polyphase structure varies with the nature and properties of the ingredients and cannot be generically defined in a manner common to all systems except that in all cases the temperature and time must be less than those conditions under which substantial sintering (i.e., substantial changes in particle dimension) occur. Conditions close to the sintering conditions are preferred.
  • FIG. 3 is a plot of the saturation magnetization of the above composition after heat treatment plotted against time at the temperatures indicated.
  • FIG. 4 is a plot of o' /zr the remanence ratio, against time at the temperatures indicated.
  • the remanence ratio gives some indication of the domain structures. For a random assembly of isotropic single domain particles, the remanence ratio is theoretically 0.5.
  • FIG. 5 shows a plot of the intrinsic coercivity, H as a function of time at the various temperatures indicated.
  • a reaches a maximum value at about 68 hours, and continues substantially constant.
  • H reaches a maximum in about 1 /2 hours, and after 8 hours commences to degrade, indicating that sintering occurs.
  • Observation of the particles using an electron microscope can likewise be employed to determine the amount of sintering by observing the change in particle dimensions.
  • a reaches a maximum in under two hours; ,H however is degraded even at heating times of /2 hour, (T /0' is similarly degraded by sintering.
  • the heat treatment step can be performed in air but preferably an inert gas is employed, or hydrogen is used to provide a reducing atmosphere and prevent excessive oxidation of the particles.
  • the particles After heat treatment when a reducing atmosphere is employed, it is desirable to passivate the particles by exchanging the hydrogen for an inert gas, preferably a noble gas such as argon containing a small amount of oxygen, suitably from 0.01 to 10% by volume.
  • an inert gas preferably a noble gas such as argon containing a small amount of oxygen, suitably from 0.01 to 10% by volume.
  • the passivation process is normally conducted at or close to ambient temperature and pressure, although this is not critical. Times for the process can range from 5 to about 4 hours, and depend on the oxygen content of the gas mixture.
  • both X-ray and electron diffraction show the diffraction pattern of the major metallic component, e.g., with iron alloys an X-ray diffraction pattern of u-iron is obtained.
  • the compositions are evidently single phase with the minor metallic components and the metalloid or non-metals in solution.
  • compositions are those containing a substantial amount, preferably 50% or more of iron or cobalt or mixtures thereof, and optionally with minor amounts of nickel or chromium, which contain boron, i.e., the starting materials are prepared by borohydride reduction.
  • compositions having improved magnetic properties can be obtained by the heat treatment process of this invention from the alloys described by Miller and Oppegard, however, chromium may also be incorporated in the alloys as indicated above.
  • chromium When iron is the major component of the alloys, chromium may be present in any proportion up to 20% by Weight and boron preferably from 1 to 5.5% by weight. The chromium is generally at least 0.4% by weight, when present and most preferably from 5 to 20% by weight.
  • the preferred range of chromium content is from 0 to 17% by Weight and boron from 1 to 5.6% by weight.
  • the preferred range of chromium content is 0 to 7% and the boron content is 1 to 5.6% by weight.
  • compositions containing iron as a major component are preferred.
  • Iron-cobalt-boron alloys in which the cobalt content is 30 to 35% are particularly useful for the manufacture of permanent magnets.
  • Minor amounts of cobalt have been found beneficial in improving particle morphology, particularly when chromium is included to improve the stability of the magnetic properties under humid or moist conditions.
  • iron compositions containing 0.1 to 5% by weight of cobalt and from 8% to 20% by weight of chromium with 1 to 5.5% by weight of boron also form a preferred class of compositions.
  • Oxygen is always present in the as precipitated starting materials and is believed to occur in the form of oxides and/or hydroxides or hydrous oxides on the surfaces of the particles together with oxygen in the form of 'Water which is occluded or adsorbed in the particles. Substantially, all the water is eliminated, however, by baking at 200 C. and in thecompositions of this invention, the oxygen is principally present in the form of metal oxides, which are believed to be formed as a protective coating particularly during the passivation step.
  • the particles can be compacted by the techniques known in the field of powder metallurgy to form useful permanent magnets.
  • small quantities of organic or inorganic binder can be present. Generally from about 2% to 30% by weight of binder based on the total composition is employed. Higher percentages of binder can be used, but are not generally desirable, since the binders are generally inert magnetically.
  • the particles can be mixed with a film-forming binder and coated on a suitable substrate to form a magnetic recording member.
  • a common form of a magnetic member, magnetic tape is shown in FIGS. 1 and 2 of the appended drawings.
  • FIG. 1 shows a plan view of a magnetic tape.
  • FIG. 2 shows a cross section of the tape along the lines A-A.
  • a substrate 1 is provided which is generally a flexible polymeric film having suitable mechanical properties, i.e., it should be flexible and dimensionally stable with time and under stress.
  • Suitable polymeric film supports include film of polyethylene terephthalate which has been oriented by stretching biaxially, cellulose acetate and like materials.
  • a coating of ferromagnetic particles in a binder 2 is coated onto the surface of the supporting film and calendered to a smooth, even layer.
  • EXAMPLE 1 A solution of 15.2 g. of NaBH dissolved in 250 ml. of distilled water was added dropwise to a solution containing 43.5 g. of FeSO -7H O and g. of Cr (SO -xH O dissolved in 500 ml. of distilled water in the absence of an external magnetic field. A vigorous exothermic reaction occurred forming 20 g. of a black magnetic powder. The powder was filtered, washed with 500 ml. of distilled water, washed with 500 ml. of acetone, and allowed to dry in air. The composition of the powder was 33.8% Fe, 14.1% Cr and 3.2% B, the balance consisting principally of oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of equiaxed particles about 0.1 in diameter.
  • the powder had a saturation megnetization (a of 10.6 emu/g, a remanent megnetization (0-,) of 1.8 emu/ g. and an intrinsic coercivity H,) of 86 0e.
  • This powder was heat treated in air at a temperature ranging from 275 to 300 C. for 1 hr. After heat treatment, the powder has a a of 71.1 emu/g, a a, of 13.5 emu/g., and an H of 333 oe.
  • EMMPLE 2 A solution of 7.6 g. of NaBH dissolved in 250 ml. of distilled water was added dropwise to a solution containing g. of and g. of CI2(SO4)3'XH2O dissolved in 500 ml. of distilled 'water in the absence of an external magnetic field. A black, magnetic powder was formed by an exothermic chemical reaction. The powder was filtered, washed, and dried in a manner similar to that described in Example 1. The chemical composition of the powder was 69.8% Fe, 12.7% Cr, and 2.2% B, the balance consisting principally of oxygen present as metallic oxides and adsorbed moisture, The powder consisted essentially of equiaxed particles about 0.05; in diameter.
  • Examples 3 through 7 illustrates the effect of heat treatment on increasing the a and a of iron-boron alloy powders containing 0 to 11.2 percent by weight chromium and also show the effect of chromium addition on preventing significant degradation of the a of the heat treated and passivated products when they are exposed to hot, humid atmospheres.
  • the iron-boron alloy powders containing 0 to 11.2% chromium were synthesized in the presence of a magnetic field of about 1500 cc.
  • a two-liter beaker resting on the poles of a horseshoe magnet was charged with a solution containing salts of the metallic components of the desired alloy dissolved in 200 ml. of distilled water.
  • a solution of 3.8 g. of NaBH in 100 ml. of distilled water was slowly added to the beaker in a period of time of about 10 min.
  • a vigorous exothermic reaction occurred forming a black, magnetic powder.
  • the product was filtered, washed with water, and washed with acetone. After washing, the product was suspended in acetone for about 16 hrs. before final filtering and air drying.
  • Table I The compositions of the metallic salt solutions for synthesis of the products and the composition of products produced are summarized in Table I.
  • Example 4 after heat treatment contained 79.4% Fe, 6.7% Cr and 3.4% B.
  • the passivation treatment rendered the powders nonpyrophoric and also imparted resistance to degradation of a by hot, humid atmospheres.
  • the effect of heat treatment and passivation on the magnetic properties of the powders is summarized in Table II.
  • the as-prepared powder had a a of 77.9 emu/g, a
  • the stability of a of the heat treated and passivated powders was tested by exposing them to air at 65 C. and 50% relative humidity for 20 hrs.
  • the results of the stability tests are reported in Table III, where the percent decrease in saturation magnetization is given under the 75 heading percent Aa TABLE III cobalt-boron powders and also illustrate the structural changes that occur during heat treatment.
  • the powder products were prepared in an external mag- E 1 C -+9 ieg s a e P t A netic field by the dropwise addition of a solution contain- X m Y es 1 Y es 5 ing 3.8 g. of NaBH dissolved in 100 ml.
  • An iron-chromium-boron powder was synthesized according te the procedure described for Example 7.
  • the powder consisted essentially of acicular particles with an average length of about 2 and an average width of about 006 Its chemical composition was 66.7% Fe, 10.3% Cr, and 1. 5% B, the balance being principally composed of oxygen present as metallic oxides, hydroxides or absorbed moisture.
  • Example 10 Analysis of electron diffraction patterns from the sample heat treated at 500 C. (Example 10) indicated that a metallic boride, M B, precipitated from the supersaturated solid solutions during heat treatment.
  • the boride precipitate had the body-centered-tetragonal structure of Fe B (ASTM diffraction data card No. 3-1053), which according to Bertaut and Blum is isomorphous with a Cr B chromium boride 0F. Bertaut and P. Blum, C. R. Acad. Sci. Paris, 236,105 (1953)).
  • Examples 1 l-l 3 indicate the effect of heat treatments in hydrogen on increasing the (T5 of irondried by the general procedure described in Example 1, they were heat treated in hydrogen at 400 C. for 4 hrs. The products were then cooled to ambient temperature and passivated in argon containing about 1% by volume of oxygen. Data on the effect of heat treatment on the magnetic properties of the products appear in Table VI.
  • the products were composed of acicular particles with widths ranging from about 003 to about 0.06;.
  • EXAMPLES 14-25 The tendency for a fine powder to sinter and agglomerate during heat treatment is a function of temperature, time at temperature, and powder composition. Examples 14 through 25 illustrate the effect of sintering and agglomeration on decreasing the coercivity and the remanence ratio of an iron-cobalt-boron alloy powder with a percent Fe to percent Co ratio of about 4 to 1 (59.6% Fe; 15.6% Co; 4.1% 3).
  • Samples of an iron-cobalt-boron powder prepared by the method described in Example 12 were subjected to heat treatments in hydrogen at temperatures ranging from 300 to 600 C. After heat treatment, the samples were cooled to ambient temperature and passivated in a gaseous mixture of argon plus about 1% oxygen. The coercivities, remanence ratio, and average particle dimensions of heat treated and passivated powders appear in Table VII.
  • the coercivities, remanence ratio, and average particle dimensions of heat treated and passivated powders appear in Table VII.
  • the powder had an H,, of 790 and a ar /0 ratio of 0.42. It was composed essentially of acicular particles with an average length of about 0.5 7 and an average width of about 0.05 14. There were no significant changes in the shape or size of the particles during four-hour heat treatments at temperatures up to 425 C. An increase in the temperature of a four-hour heat treatment from 425 C. to 500 C. increased the width of some particles by a factor of ten and decreased the coercivity of the product by a factor of four.
  • EXAMPLE 26 A metallic, magnetic powder was prepared by the addition of a solution of NaBH to a solution containing 33.4 g. of FeSO -7H O, 22.4 g. of CoSO -7H O and g. of K Cr (SO -24H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 37.6% Fe, 18.4% C0, 10.0% Cr. and 3.6% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of acicular particles with an average width of about 003 and an average length of about 0.3a.
  • the powder had a a of 60 emu/g, a a /a ratio of 0.38, and an H of 440 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing about 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 109.2 emu/g, a a /a ratio of 0.47, and an H of 949 oe.
  • the composition was 41.4% Fe, 34.9% C0, 13.5% Cr and 4.2% B.
  • EXAMPLE 27 A metallic, magnetic powder was prepared by the addition of a solution of 3.8 g. NaBH in 100 ml. of water to a solution containing 44.6 g. of FeSO '7H O and 10.5 g. of NiSO -6H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500-oe. by the same general procedure described in Examples 3 through 7. The composition of the product was 56.4% Fe, 19.3% Ni, and 3.1% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of acicular particles with an average width of about 0.02 and an average length of about 0.4,u.
  • the powder had a a of 97.3 emu/g. a a' /J ratio of 0.44, and an H. of 1020 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 139.5 emu/g, a a /a ratio of 0.39, and an H of 765 oe.
  • the composition was 61.1% Fe, 21.6% Ni, 3.6% B.
  • EXAMPLE 28 A metallic, magnetic powder was prepared by the addition of a solution of 3.8 g. of NaBH, in ml. of water to a solution containing 44.6 g. of FeS0 -7H O, 10.5 g. of and 1 0f K2CI'2(SO4)424H2O dis solved in 200 ml. of water.
  • the synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7.
  • the composition of the product was 48.6% Fe, 18.1% Ni, 1.75% Cr, and 3.5% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder consisted essentially of equiaxed particles about 0.04 7 in diameter.
  • the powder In the as-prepared condition, the powder has a a of 66 emu/g, a 0 /0 ratio of 0.43, and an H of 1040 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 109 emu/g, a a' /a ratio of 0.46, and an H of 1090 oe.
  • the composition was 53.1% Fe; 22.3% Ni; 4.6% B.
  • EXAMPLE 29 A metallic, magnetic powder was prepared by the addition of a solution of 3.8 g. of NaBH in 100 ml. of water to a solution containing 44.6 g. of FeSO -7H O, 5.3 g. of NiSO -6H O, and 5.7 g. of CoSO -7H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 54.1% Fe, 7.7% Ni, 7.0% Co, and 3.3% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of acicular particles wth an average width of about 0.03 and an average length of about 0.2
  • the powder had a a of 32.5 emu/g, a a,/a ratio of 0.35, and an H,, of 500 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 86 emu/g, a er /0' ratio of 0.35, and an H of 564 oe.
  • the composition was 56.4% Fe, 8.9% Ni, 12.1% Co, 5.2% B.
  • a metallic, magnetic powder was prepared by the addition of a solution of 3.8 g. of NaBH in 100 ml. of water to a solution containing 44.6 g. of FeSO -7H O, 5.3 g. of NiSO -6H O, 5 .7 g. of CoSO -7H O and 1 g. of K2CI2(SO4)4'24H2O dissolved in ml. of water.
  • the synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7.
  • the composition of the product was 50.1% Fe, 6.8% Ni, 6.5% Co, 1.9% Cr, and 3.1% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder consisted essentially of equiaxed particles about 0.02/1. in diameter.
  • the powder had a a of 68.3 emu/g, a 03/ a ratio of 0.40, and an ,H of 825 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 119.6 emu/g., a a /a of 0.41, and an H of 1020 oe.
  • the composition was 52.8% Fe, 9.3% Ni, 8.8% Co, 3.7% B.
  • EXAMPLE 31 A metallic powder was prepared by the addition of a solution of NaBH 1 g. in 100 ml. H O) to a solution containing 56.2 g. of CoSO -7H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 79.71% Co and 5.6% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 34 emu/g, a a /o' ratio of 0.235 and an H of 35 oe.
  • the powder was heat treated in hydrogen at 300 C. for 4 hrs., cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 65, a a /a ratio of 0.42, and an H,, of 275 oe.
  • EXAMPLE 32 A metallic powder was prepared by the addition of a solution of NaBH, (3.8 g. in 100 ml. H O) to a solution containing 28.1 g. of Co.SO -7H O and 26.3 g. of NiSO -6H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Example 3 through 7. The composition of the product was 48.6% C0, 30.3% Ni and 4.1% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 8 emu/g, a a /o' ratio of 0, and an H of 0.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume oxygen. After heat treatment and passivation, the powder had a a of 52 emu/g, a a /o' ratio of 0.423, and an H,, of 580 oe.
  • EXAMPLE 3 3 A metallic, magnetic powder was prepared by the addition of a solution of 3.8 g. of NaBH in 100 ml. of water to a solution containing 45 g. of CoSO '7H O, 0f NISO46HZO, and 1 of K Cr (SO -24H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 61.2% Co, 7.5% Ni, 0.4% Cr, and 7.4% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of equiaxed particles about 0.05 1 in diameter.
  • the powder had a a of 19 emu/g, a a /o' ratio of 0.16, and an H of 30 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 77 emu/g, a a' /a ratio of 0.40, and an ,H,, of 630 oe.
  • EXAMPLE 34 A metallic powder was prepared by the addition of a solution of 3.8 g. NaBH in 100 ml. of water to a solution containing 52.4 g. of NiSO -6H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 12 68.7% Ni, and 5.3% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of equiaxed particles about 0.02 in diameter.
  • the powder had a a of 2.1 emu/ g. and an H,, 20 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 30 emu/g. a a /a ratio of 0.27, and an H,, of 142 oe.
  • EXAMPLE 3 5 A metallic powder was prepared by the addition of a solution of 3.8 g. NaBH, in 100 ml. of water to a solution containing 57.4 g. of NiCl -6H O and 1 g. of CrCl -6H O dissolved in 200 m1. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 74.5% Ni, 3.5% Cr, and 5.4% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted of equiaxed particles about 0.02 1. in diameter.
  • the powder had a a of 1.5 emu/g, a a /o' ratio of 0.07, and an H 20 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 29.8 emu/g, a o' /o' ratio of 0.26, and an H of 112 oe.
  • EXAMPLE 36 This example illustrates the fabrication of heat treated, iron-chromium-boron alloy powder into a magnetic recording tape.
  • Example 7 Several duplicate batches of an iron-chromium-boron alloy powder were prepared by the technique described in Example 7 and blended in a rotating plastic canister containing poly(tetrafluoroethylene) balls.
  • the powder blend 'Was heat treated in hydrogen at 450 C. for 4 hrs. and then passivated in argon containing about 1% by volume oxygen.
  • the powder had a a of 128 emu/g, a a a ratio of 0.38, and an H,, of 560 oe.
  • the heat treated and passivated powder was ground with 20- to 30-mesh sand in a slurry of tetrahydrofuran plus soya lecithin for 2 hrs. and then mixed in the sand grinder with a binder consisting of 50%, by weight, of a soluble polyester-urethane resin made from diphenylmethane diisocyanate, adipic acid and 'butanediol, and 50% of a vinylidene chloride/acrylonitrile /20 copolymer.
  • the binder-powder system contained about 30 volume percent of powder. After mixing, the binderpowder slurry was filtered through a 2-;/. screen to remove the sand.
  • Coatings of the filtered slurry were then spread on a 1.5-mil thick film of poly(ethylene terephthalate).
  • the coated films which were about 3 inches wide and 30 inches long, were passed between the poles of two plate magnets that created a field of about 800 oe. parallel to the long direction of the tape before the coating dried.
  • the tape was then dried in air for about 24 hrs. and dried in a vacuum desiccator for about 16 hrs.
  • the magnetic tape fabricated from the iron-chromiumboron powder had a 5,. /2" of 1.49 maxwells, a B /B of 0.70, and an H,, of 465 oe.
  • EXAMPLE 37 This example illustrates the fabrication of a heattreated, iron-cobalt-boron alloy powder into a magnetic recording tape.
  • Example 12 Several duplicate batches of an iron-cobalt-boron powder were prepared by the technique described in Example 12 and blended and compacted in a rotating plastic canister containing poly(tetrafluoroethylene) balls.
  • the powder blend was heat treated in hydrogen at 400 C. for 4 hrs. and then passivated in argon containing about 1% by volume of oxygen. In the heat treated and passivated condition the powder had a a of 168, a a /o' ratio of 0.46, and an H of 840 oe.
  • the heat treated and passivated powder was ground in a sand shaker with 20- to 30-mesh sand in a slurry of tetrahydrofuran plus soya lecithin for 1 hr. and then mixed in the sand shaker with a binder consisting of 50%, by weight, of a soluble polyester-urethane resin made from diphenylmethane diisocyanate, adipic acid and butanediol, and 50% of a vinylidene chloride/acrylonitrile 80/20 copolymer.
  • the binder-powder system contained about 40 volume percent of powder. After mixing, the binder-powder slurry was filtered through a 10-,u screen to remove the sand.
  • Coatings of the filtered slurry were then spread on a 1.5 mil thick film of poly(ethylene terephthalate).
  • the coated films which were about 3 inches wide and 30 inches long, were passed between the poles of two plate magnets that created a field of about 800 Oe. parallel to the long direction of the tape.
  • the tape was then dried in air for about 24 hrs. and dried in a vacuum desiccator for about 16 hrs.
  • the magnetic tape fabricated from the Fe-Co-B powder had a 4),- /2" of 2.40 maxwells, a B of 2480 gauss, a B /B of 0.69 and an H of 720 oe.
  • EXAMPLE 38 An iron-cobalt-boron powder was prepared by the addition of a solution of NaBH to a solution containing 33.4 g. of FeSO -7H O and 22.4 g. of CoSO -7H O dissolved in 200 ml. of distilled water. The synthesis was performed in the presence of an external magnetic field of about 1500 oe. by the same general procedure described for Examples 3 through 7. The composition of the product was 50.6% Fe, 28.5% C0, and 3.5% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture. The powder consisted essentially of acicular particles with an average width of about 0.04;; and an average length of about 0.7
  • the powder had a a of 119 emu/g, a ar /0' ratio of 0.47 and an H of 1260 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment of passivation, the powder has a a of 186 emu/g., a a /a ratio of 0.49, and an H,, of 1150 oe.
  • EXAMPLE 39 Several synthesis runs of an iron-chromium-boron alloy powder were prepared by the dropwise addition of a 1 molar NaBH solution into a solution containing 1 I mol/l. of FeSO -7H O and 0.125 mol/l. of
  • the powder Before heat treatment, the powder had an H of 385 oe., a a of 84 and a a /o' ratio of 0.35. It was composed essentially of acicular particles with an average width of about 0.07 and an average length of about 0.5 Examination of the heat treated products in an electron microscope failed to reveal any changes in particle shape or size which would be indicative of sintering. The high H and a /a ratios of the heat treated products are also indicative of the fact that sintering has not occurred.
  • EXAMPLE 40 A 2-liter beaker resting on the poles of a permanent magnet (1500 oe.) was charged with a solution containing 56.2 g. of CoSO -7H O dissolved in 200 ml. of distilled water and 200 ml. of concentrated NH OH. A solution of 3.8 g. NaBH 21.2 g. NaH PO and 10 ml. NH NH -H O in 200 ml. of distilled water was added. The accelerator (10 ml. Pd'Cl 1%) was added and the reaction mixture was allowed to stand for 30 minutes. It was then filtered and the product Was washed with 500 ml. of distilled water and 500 ml. of acetone.
  • the composition of the product (6.2 g.) was 84.76% Co, 2.55% B, 5.12% P, and 0.66% N, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 50 emu/g, a a /a ratio of 0.129 and an H of 130.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder has a a of 86 emu/g, a a /o' ratio of 0.211 and an H of 145.
  • EXAMPLE 41 A two-liter beaker was charged with a solution containing 56.2 g. of CoSo -7H O, 1 g. K Cr (SO -24H O and 5 g. of the disodium salt of ethylenediamine tetracetic acid dissolved in 200 ml. of distilled water and 200 ml. of concentrated NH OH. A solution of 3.8 g. of NaBH in 100 ml. of distilled water was added slowly to the beaker in a period of time of about 10 minutes. The accelerator, 10 ml. PdCl (1% solution) was added and the reaction mixture was allowed to stand for two hours. The reaction mixture was filtered and the product was washed with ml. dilute NH OH and ml.
  • the composition of the product (4.0 g.) was 79.1% Co, 2.4% Cr, 1.8% Pd and 4.6% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 67 emu/g., a ar /0' ratio of 0.14 and an H of 65.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature and passivated in argon containing 1% by 'volume of oxygen. After heat treatment and passivation, the powder has a a of 106 emu/g, a a /a ratio of 0.26 and an H,. of 260.
  • the structure of the product as determined by X-ray powder patterns taken with C Kat-radiation was that of hexagonal-close-packed cobalt. No extra diffraction lines which could be attributed to a boron containing phase or a body centered-cubicchromi ium 'phase were detected in the pattern from the aschemically prepared powder.
  • the product consisted of a mixture of a hexagonal-closepacked cobalt phase, a face-centered cubic cobalt phase and a boride phase with the structure of Co B (ASTM X-ray data card No. 13-133 EXAMPLE 42 The procedure described below was used in the following two examples.
  • a two-liter beaker resting on the poles of a permanent magnet 1500 oe.) was charged with a solution containing 55.6 g. of FeSO -7H O dissolved 200 ml. of distilled water.
  • a solution of NaBH and NaH PO in 150 ml. of distilled water was added slowly to the beaker in a period of time of about 10: minutes.
  • the reaction mixture was filtered and the product was washed with 500 ml. of distilled water and 500 ml. of acetonefAfter washing, the product was suspended in acetone for about 16 hrs. before 'final filtering and air-drying.
  • the amounts of reducing agent employed for preparations -A and B are shown in Table X.
  • the composition of the products is shown in Table XI.
  • Magnetic data for the materials. before and after heat treatment are given in Table XIIJI V
  • the powders were heat treated in diydrogen at 400 C. for 4 hrs., cooled to ambient temperatures and passivated in argon containing 1% by volume oxygen.
  • the powder had a a of 63 emu/g, a o' /o' ratio of 0.127 and an H of 38.5.
  • the powder was heat treated inhydrogerr at 400 C. for 4 hrs., cooled'to ambient temperature, and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder has a a of 112 emu/g, a a ia ratio of 0.250, and an H of 240 oe.
  • the composition of the product (2.7 g.) was 78.6% C0, 11.2% Ni, 2.0% P, 4.25% Pd and 0.84% N, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 97 emu/g, a a /a ratio of 0.35 and an H of 590.
  • the powder was heat treated in hydrogen at 400 C. for 4hrs., cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 106, a (T /0' ratio of 0.38 and an H of 499 oe.
  • EXAMPLE 45 A two-liter beaker resting on the poles of a horseshoe magnet (1500 oe.) was charged with a solution containing 28.1 g. of CoSO -7H O and 28.1 g. NiSO -6H O dissolved in 200 m1; of distilled water. A solution of 5.8 g; of NaBH and 10 ml. NH NH z-H o in 100 ml. of distilled water was slowly added 'to the beaker in a period of time of about 10 minutes. The reaction mixture was filtered and the product was washed with 500 mi; of distilled water and 500 ml. of acetone. After washing, the product was suspended in acetone for about 16 hrs. before final filtering and air drying. The composition of the product (13.1 g.) was 35 .10% C9, 21.27% Ni, 5.41% B and 1.05% N, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 2.2 emu/g, a a /a' ratio of 0 and an H of 0.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs., cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder had a a of 75 emu/g, a a a ratio of 0.32'0'and an H of 390 oe.
  • EXAMPLE 46 A two-liter beaker was charged with a solution containing 56.2 g. CoSO -7H O dissolved in 100 ml. of distilled water and 100 ml. of concentrated NH Q H. A solution of 21.2 g. of NaH PO in 50 ml. of distilled water was added to the Co++ solution. The accelerator 10 ml. E'dClz, 1%) was added and the reaction mixture was heated to 100 C. for liminutesi It was then allowed .to stand ,at room temperature for 16 hoursJIhe reaction mixture was filtered and the product was washed with 500 ml. of distilled water and 500 ml. of acetone. After washing, the product was suspendedin acetone for about 16 hrs.
  • the composition of .the product (19.1 g.) was 46.04% Co, 7.78%? and 40.2% 0. I if In the as-prepared condition, the powder had a a of 22.6 emu/g, a a Za ratio of 0.155, and an H of 375.
  • the powder was heat treated in hydrogen at 400 C. for 4 hours, cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen.
  • the powder After heat treatment and passivation, the powder has a a of 53, a (r /a ratio of 0.208 and an I-I of 394.
  • EXAMPLE 47 A two-liter beaker resting on the poles of a horseshoe magnet (1500 e.) was charged with a solution containing 33.4 g. FeSO '7H O, 22.4 g. CoSO -7H O and 2 g. (NH HPO dissolved in 200 ml. of distilled water. A solution of 3.8 g. of NaBH in 100 ml. of distilled water was slowly added to the beaker in a period of about 10 minutes. The reaction mixture was filtered and the product Was washed with 500 ml. of distilled water and 500 ml. of acetone. After washing, the product was suspended in acetone for about 16 hrs. before filtering and air-drying. The composition of the product (5.9 g.) was 42.82% Fe, 28.31% Co, 2.77% P and 4.52% B, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a 0' of 95 emu/g, a o' /a' ratio of 0.378, and an H of 630 oe.
  • the powder was heat treated in hydrogen at 400 C. for 4 hours, cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder has a a of 123 emu/g, a (T /0' ratio of 0.495 and an H of 1330.
  • EXAMPLE 48 A two-liter beaker was charged with a solution containing 11.2 g. CoSO -7H O and 47 g. NiSO -6H O dissolved in 200 ml. of distilled water and 200 ml. of concentrated NH OH. Hydrazine hydrate (10 ml.) and the accelerator (10 ml. PdCl 1%) were added and the reaction mixture allowed to stand for 2 hours. It was then filtered and the product was washed with 125 ml. dilute NH OH and 125 ml. of acetone. After washing, the product was suspended in acetone for about 16 hrs. before final filtering and air drying. The composition of the product (1.1 g.) was 73.75% Co, 12.88% Ni, 6.32% Pd and 1.44% N, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a 0' of 98 emu/g, a o' /a ratio of 0.224, and an ,H of 280 oe.
  • the powder was heat treated in hydrogen at 300 C. for 4 hours, cooled to ambient temperature and passivated in argon containing 1% by volume of oxygen. After heat treatment and passivation, the powder has a a of 115 emu/g, a o' /o' ratio of 0.243 and an H of 290.
  • EXAMPLE 49 A two-liter beaker was charged with a solution containing 47.6 g. of CoCl -6H O dissolved in 200 ml. of distilled water and 200 ml. of concentrated NH OH. A solution of 3.8 g. of NaBH in "100 ml. of distilled water and ml. of NH NH -H O was added to the beaker and the reaction mixture was allowed to stand for two hours. It was then filtered and the product was washed with 125 ml. of dilute NH OH and in acetone for about 16 hours before final filtering and air drying. The composition of the product (2.5 g.) was 85.02% Co, 1.80% B and 0.27% N, the balance being principally oxygen present as metallic oxides and adsorbed moisture.
  • the powder had a a of 109 emu/g, a o' /tr ratio of 0.23 and an H of 170 cc.
  • the powder was heat treated in hydrogen at 400 C. for 4 hrs. cooled to ambient temperature and passivated in argon containing 3% by volume of oxygen. After heat treatment and passivation, the powder has a as of 128 emu/g, a (T /0' ratio of 0.22 and an H of 190 oe.
  • a ferromagnetic composition comprising polyphase particles having a maximum dimensions of about 4 microns, said particles consisting essentially of at least one metal consisting of iron, cobalt and nickel and up to 20% of chromium and at least one element selected from B, N or P in an amount less than the minimum amount required to form a compound with all of said metal, said particles having a polyphase microstrncture with the metals as one phase and compounds of the constituent metals with said B, N or P as at least one additional phase, said polyphase particles being coated with a thin oxide film.
  • composition of claim 2 wherein said particles are iron with from 0.4 to 20% chromium and 1 to 8% of boron.
  • composition of claim 2 wherein said particles are iron with from 0.1 to 5% by weight of cobalt, 8 to 20% of chromium and 1 to 5.5% of boron.
  • a permanent magnet composed of the particles of claim 1.
  • a permanent magnet composed of the particles of claim 2.

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Cited By (33)

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US3661556A (en) * 1969-03-03 1972-05-09 Du Pont Method of making ferromagnetic metal powders
US3663318A (en) * 1970-10-05 1972-05-16 Du Pont Process for making ferromagnetic metal powders
DE2225796A1 (de) * 1971-05-27 1972-12-14 Tdk Electronics Co Ltd Verfahren zur Herstellung von magnetischem Material in Pulverform
US3755008A (en) * 1971-03-24 1973-08-28 Graham Magnetics Inc Process for enhancing magnetic properties of metal powder by heat treating with salt
DE2326258A1 (de) 1972-05-22 1973-12-13 Minnesota Mining & Mfg Feine nadelfoermige teilchen auf eisenbasis enthaltendes magnetisches aufzeichnungsmaterial
JPS4941899A (enrdf_load_stackoverflow) * 1972-05-22 1974-04-19
US3855016A (en) * 1971-03-24 1974-12-17 Graham Magnetics Inc Acicular cobalt powders having high squarenesss ratios
US3859130A (en) * 1971-04-15 1975-01-07 Ibm Magnetic alloy particle compositions and method of manufacture
JPS5041097A (enrdf_load_stackoverflow) * 1973-08-15 1975-04-15
US3899369A (en) * 1974-03-11 1975-08-12 Ibm Process for the production of magnetic materials having selective coercivity by using selected D.C. magnetic fields
DE2434096A1 (de) * 1974-07-16 1976-02-05 Basf Ag Verfahren zur herstellung nadelfoermiger, eisenhaltiger ferromagnetischer metallpigmente
US3943012A (en) * 1973-08-18 1976-03-09 Fuji Photo Film Co., Ltd. Magnetic recording medium
US3954520A (en) * 1974-03-11 1976-05-04 International Business Machines Corporation Process for the production of magnetic materials
US3975217A (en) * 1974-03-29 1976-08-17 Sherritt Gordon Mines Limited Finely divided magnetic cobalt powder
US4054530A (en) * 1973-09-28 1977-10-18 Graham Magnetics, Inc. Iron-nickel-cobalt magnetic powder and tape prepared therefrom
US4063000A (en) * 1974-09-17 1977-12-13 Fuji Photo Film Co., Ltd. Process for production of ferromagnetic powder
DE2756275A1 (de) * 1976-12-20 1978-11-16 Hitachi Maxell Nadelfoermige ferromagnetische metallteilchen und verfahren zu ihrer herstellung
US4131495A (en) * 1975-12-02 1978-12-26 Bbc Brown, Boveri & Company, Limited Permanent-magnet alloy
US4246316A (en) * 1975-11-05 1981-01-20 Fuji Photo Film Co., Ltd. Magnetic recording medium
US4384892A (en) * 1978-03-16 1983-05-24 Kanto Denka Kogyo Co., Ltd. Production of magnetic powder
EP0075870B1 (en) 1981-09-24 1986-12-30 Hitachi Maxell Ltd. Magnetic recording medium
US4752344A (en) * 1986-12-22 1988-06-21 International Business Machines Corporation Magnetic layer and method of manufacture
US4836865A (en) * 1986-03-12 1989-06-06 Matsushita Electric Industrial Co., Ltd. Magnetic nitride film
US5156922A (en) * 1989-01-27 1992-10-20 Toda Kogyo Corporation Acicular magnetic iron based alloy particles for magnetic recording and method of producing the same
US5238483A (en) * 1989-01-27 1993-08-24 Toda Kogyo Corporation Acicular magnetic iron based alloy particles for magnetic recording and method of producing the same
US5585198A (en) * 1993-10-20 1996-12-17 Sanyo Electric Co., Ltd. Magnetorsistance effect element
US5620784A (en) * 1994-08-04 1997-04-15 Sanyo Electric Co., Ltd. Magnetoresistive film
US5656381A (en) * 1993-03-24 1997-08-12 Sanyo Electric Co., Ltd. Magnetoresistance-effect element
US5680091A (en) * 1994-09-09 1997-10-21 Sanyo Electric Co., Ltd. Magnetoresistive device and method of preparing the same
US5695858A (en) * 1994-03-23 1997-12-09 Sanyo Electric Co., Ltd. Magnetoresistive element
US5736921A (en) * 1994-03-23 1998-04-07 Sanyo Electric Co., Ltd. Magnetoresistive element
US20130194060A1 (en) * 2011-08-25 2013-08-01 Taiyo Yuden Co., Ltd. Wire-wound inductor
CN113774217A (zh) * 2021-08-19 2021-12-10 南方科技大学 电子产品浸出液中多种金属离子的同步回收方法

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DE2743298A1 (de) * 1977-09-27 1979-04-05 Basf Ag Ferromagnetische, im wesentlichen aus eisen bestehende metallteilchen und verfahren zu deren herstellung
US4229234A (en) * 1978-12-29 1980-10-21 Exxon Research & Engineering Co. Passivated, particulate high Curie temperature magnetic alloys
JPS5999706A (ja) * 1982-11-29 1984-06-08 Kanto Denka Kogyo Kk 磁気記録用強磁性金属粉末の製造方法
DE19932473A1 (de) * 1999-07-12 2001-01-25 Vacuumschmelze Gmbh Korrosionsfreie Eisen-Nickel-Legierung für Fehlerstromschutzschalter

Cited By (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3661556A (en) * 1969-03-03 1972-05-09 Du Pont Method of making ferromagnetic metal powders
US3663318A (en) * 1970-10-05 1972-05-16 Du Pont Process for making ferromagnetic metal powders
US3755008A (en) * 1971-03-24 1973-08-28 Graham Magnetics Inc Process for enhancing magnetic properties of metal powder by heat treating with salt
US3855016A (en) * 1971-03-24 1974-12-17 Graham Magnetics Inc Acicular cobalt powders having high squarenesss ratios
US3859130A (en) * 1971-04-15 1975-01-07 Ibm Magnetic alloy particle compositions and method of manufacture
DE2225796A1 (de) * 1971-05-27 1972-12-14 Tdk Electronics Co Ltd Verfahren zur Herstellung von magnetischem Material in Pulverform
DE2326258A1 (de) 1972-05-22 1973-12-13 Minnesota Mining & Mfg Feine nadelfoermige teilchen auf eisenbasis enthaltendes magnetisches aufzeichnungsmaterial
JPS4941899A (enrdf_load_stackoverflow) * 1972-05-22 1974-04-19
JPS5041097A (enrdf_load_stackoverflow) * 1973-08-15 1975-04-15
US3966510A (en) * 1973-08-15 1976-06-29 Fuji Photo Film Co., Ltd. Ferromagnetic powder for magnetic recording medium and method for preparation thereof
US3943012A (en) * 1973-08-18 1976-03-09 Fuji Photo Film Co., Ltd. Magnetic recording medium
US4054530A (en) * 1973-09-28 1977-10-18 Graham Magnetics, Inc. Iron-nickel-cobalt magnetic powder and tape prepared therefrom
US3899369A (en) * 1974-03-11 1975-08-12 Ibm Process for the production of magnetic materials having selective coercivity by using selected D.C. magnetic fields
US3954520A (en) * 1974-03-11 1976-05-04 International Business Machines Corporation Process for the production of magnetic materials
US3975217A (en) * 1974-03-29 1976-08-17 Sherritt Gordon Mines Limited Finely divided magnetic cobalt powder
DE2434096A1 (de) * 1974-07-16 1976-02-05 Basf Ag Verfahren zur herstellung nadelfoermiger, eisenhaltiger ferromagnetischer metallpigmente
US4063000A (en) * 1974-09-17 1977-12-13 Fuji Photo Film Co., Ltd. Process for production of ferromagnetic powder
US4246316A (en) * 1975-11-05 1981-01-20 Fuji Photo Film Co., Ltd. Magnetic recording medium
US4131495A (en) * 1975-12-02 1978-12-26 Bbc Brown, Boveri & Company, Limited Permanent-magnet alloy
DE2756275A1 (de) * 1976-12-20 1978-11-16 Hitachi Maxell Nadelfoermige ferromagnetische metallteilchen und verfahren zu ihrer herstellung
US4384892A (en) * 1978-03-16 1983-05-24 Kanto Denka Kogyo Co., Ltd. Production of magnetic powder
EP0075870B1 (en) 1981-09-24 1986-12-30 Hitachi Maxell Ltd. Magnetic recording medium
US4836865A (en) * 1986-03-12 1989-06-06 Matsushita Electric Industrial Co., Ltd. Magnetic nitride film
US5049209A (en) * 1986-03-12 1991-09-17 Matsushita Electric Industrial Co., Ltd. Magnetic nitride film
US4752344A (en) * 1986-12-22 1988-06-21 International Business Machines Corporation Magnetic layer and method of manufacture
US5156922A (en) * 1989-01-27 1992-10-20 Toda Kogyo Corporation Acicular magnetic iron based alloy particles for magnetic recording and method of producing the same
US5238483A (en) * 1989-01-27 1993-08-24 Toda Kogyo Corporation Acicular magnetic iron based alloy particles for magnetic recording and method of producing the same
US5656381A (en) * 1993-03-24 1997-08-12 Sanyo Electric Co., Ltd. Magnetoresistance-effect element
US5585198A (en) * 1993-10-20 1996-12-17 Sanyo Electric Co., Ltd. Magnetorsistance effect element
US5738929A (en) * 1993-10-20 1998-04-14 Sanyo Electric Co., Ltd. Magnetoresistance effect element
US5695858A (en) * 1994-03-23 1997-12-09 Sanyo Electric Co., Ltd. Magnetoresistive element
US5736921A (en) * 1994-03-23 1998-04-07 Sanyo Electric Co., Ltd. Magnetoresistive element
US5620784A (en) * 1994-08-04 1997-04-15 Sanyo Electric Co., Ltd. Magnetoresistive film
US5680091A (en) * 1994-09-09 1997-10-21 Sanyo Electric Co., Ltd. Magnetoresistive device and method of preparing the same
US20130194060A1 (en) * 2011-08-25 2013-08-01 Taiyo Yuden Co., Ltd. Wire-wound inductor
US8629748B2 (en) * 2011-08-25 2014-01-14 Taiyo Yuden Co., Ltd. Wire-wound inductor
CN113774217A (zh) * 2021-08-19 2021-12-10 南方科技大学 电子产品浸出液中多种金属离子的同步回收方法

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FR2014221A1 (enrdf_load_stackoverflow) 1970-04-17
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GB1234378A (enrdf_load_stackoverflow) 1971-06-03
DE1931521A1 (de) 1971-04-22
SE344383B (enrdf_load_stackoverflow) 1972-04-10
DE1931521B2 (de) 1971-10-07

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