US3535104A - Ferromagnetic particles containing chromium - Google Patents
Ferromagnetic particles containing chromium Download PDFInfo
- Publication number
- US3535104A US3535104A US827386A US3535104DA US3535104A US 3535104 A US3535104 A US 3535104A US 827386 A US827386 A US 827386A US 3535104D A US3535104D A US 3535104DA US 3535104 A US3535104 A US 3535104A
- Authority
- US
- United States
- Prior art keywords
- particles
- magnetic
- chromium
- solution
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000002245 particle Substances 0.000 title description 46
- 239000011651 chromium Substances 0.000 title description 45
- 229910052804 chromium Inorganic materials 0.000 title description 31
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title description 23
- 230000005294 ferromagnetic effect Effects 0.000 title description 9
- 230000005291 magnetic effect Effects 0.000 description 38
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 35
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 32
- 239000000243 solution Substances 0.000 description 30
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 27
- 239000000843 powder Substances 0.000 description 27
- 239000000047 product Substances 0.000 description 27
- 239000000203 mixture Substances 0.000 description 25
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 24
- 229910052742 iron Inorganic materials 0.000 description 21
- 229910052796 boron Inorganic materials 0.000 description 19
- 239000012153 distilled water Substances 0.000 description 17
- 229910052751 metal Inorganic materials 0.000 description 15
- 239000002184 metal Substances 0.000 description 15
- 238000000034 method Methods 0.000 description 15
- 229910052759 nickel Inorganic materials 0.000 description 15
- 229910001868 water Inorganic materials 0.000 description 15
- 229910017052 cobalt Inorganic materials 0.000 description 13
- 239000010941 cobalt Substances 0.000 description 13
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 13
- 150000003839 salts Chemical class 0.000 description 12
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 11
- 239000011230 binding agent Substances 0.000 description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 229910045601 alloy Inorganic materials 0.000 description 8
- 239000000956 alloy Substances 0.000 description 8
- 230000005415 magnetization Effects 0.000 description 8
- 238000001914 filtration Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 238000007605 air drying Methods 0.000 description 5
- 239000003153 chemical reaction reagent Substances 0.000 description 5
- -1 poly(ethylene terephthalate) Polymers 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 4
- 229910000640 Fe alloy Inorganic materials 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 238000011946 reduction process Methods 0.000 description 4
- 230000000284 resting effect Effects 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- 229910000521 B alloy Inorganic materials 0.000 description 3
- 241000080590 Niso Species 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 150000001844 chromium Chemical class 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000696 magnetic material Substances 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 229910017061 Fe Co Inorganic materials 0.000 description 2
- WNLRTRBMVRJNCN-UHFFFAOYSA-N adipic acid Chemical compound OC(=O)CCCCC(O)=O WNLRTRBMVRJNCN-UHFFFAOYSA-N 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000006247 magnetic powder Substances 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000005020 polyethylene terephthalate Substances 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 239000012265 solid product Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- OEPOKWHJYJXUGD-UHFFFAOYSA-N 2-(3-phenylmethoxyphenyl)-1,3-thiazole-4-carbaldehyde Chemical compound O=CC1=CSC(C=2C=C(OCC=3C=CC=CC=3)C=CC=2)=N1 OEPOKWHJYJXUGD-UHFFFAOYSA-N 0.000 description 1
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 239000012448 Lithium borohydride Substances 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- 235000021355 Stearic acid Nutrition 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- WWDCXOYZSDFMDE-UHFFFAOYSA-N [Fe].B#[Cr] Chemical compound [Fe].B#[Cr] WWDCXOYZSDFMDE-UHFFFAOYSA-N 0.000 description 1
- YWNBJZVPFAVYHC-UHFFFAOYSA-N [Fe].[Cr].[Ni].[B] Chemical compound [Fe].[Cr].[Ni].[B] YWNBJZVPFAVYHC-UHFFFAOYSA-N 0.000 description 1
- LNWBFIVSTXCJJG-UHFFFAOYSA-N [diisocyanato(phenyl)methyl]benzene Chemical compound C=1C=CC=CC=1C(N=C=O)(N=C=O)C1=CC=CC=C1 LNWBFIVSTXCJJG-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000001361 adipic acid Substances 0.000 description 1
- 235000011037 adipic acid Nutrition 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002056 binary alloy Inorganic materials 0.000 description 1
- 229910052810 boron oxide Inorganic materials 0.000 description 1
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 238000003490 calendering Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 229920002301 cellulose acetate Polymers 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- VRKNSQQFHRIXPD-UHFFFAOYSA-N chromium cobalt iron nickel Chemical compound [Fe][Ni][Cr][Co] VRKNSQQFHRIXPD-UHFFFAOYSA-N 0.000 description 1
- 229940044175 cobalt sulfate Drugs 0.000 description 1
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 1
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 238000007373 indentation Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000006249 magnetic particle Substances 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000013528 metallic particle Substances 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 1
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000011236 particulate material Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 230000011514 reflex Effects 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000008347 soybean phospholipid Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000008117 stearic acid Substances 0.000 description 1
- 238000012916 structural analysis Methods 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 229920002803 thermoplastic polyurethane Polymers 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Images
Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
- G11B5/70605—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys
- G11B5/70615—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material metals or alloys containing Fe metal or alloys
-
- 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
- H01F1/065—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 obtained by a reduction
-
- 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
Definitions
- Iron alloys with chromium and boron, optionally containing cobalt and/ or nickel can be made in the form of ferromagnetic particles by reduction of a solution of the appropriate metal salts with an alkali metal borohydride, preferably at an initial temperature between 40 and 100 C. If formed in a magnetic field, the particles chain up to acicular particles of higher coercivity.
- the particles can be compacted to form permanent magnets and are useful for making recording members such as magnetic tape.
- Preferred compositions include iron/chromium/boron a1- loys having a very small amount of nickel or cobalt or both which improves the magnetic properties.
- This invention relates to new ferromagnetic compositions and more particularly compositions comprising fine ferromagnetic particles of iron optionally alloyed with nickel and/or cobalt, and containing boron and chromium.
- novel ferromagnetic alloy particles of the present invention have cross-sectional dimensions of 0.01 to 0.3 microns, a length of 0.01 to 4 microns and preferably an axial ratio of at least 3 :1; consisting essentially by weight of up to 35% cobalt, up to 35% nickel, and from 0.4 to 20%, preferably from 8 to 20%, chromium, and 1.0 to 7.5% boron dissolved therein, and oxygen either as metal oxide, metal hydroxide or as moisture balance Fe in an amount of at least 30%.
- iron alloys containing from 8 to 12% by weight of chromium, from 1.0 to 7.5 by weight of boron, and from about 0.1 to by weight of at least one of cobalt and nickel.
- compositions are produced by the reduction, in solution, of a mixture of the appropriate metal salts with an alkali-metal borohydride or alkaline earth metal borohydride and, if elongated particles are desired, preferably in the presence of a magnetic field of at least oe. and more preferably at least 1000 oe.
- the magnetic particles of the present invention can be made into magnetic objects. Thus, they can be compacted to form useful permanent magnets or other magnetic objects with or without a binding material.
- Any binding material used can be a thermosetting or thermoplastic organic polymeric binder or an air-drying, film-forming binder.
- the finely particulate material of the present invention can also be used in magnetic recording members such as magnetic recording tapes.
- metal salts can be used including the halides, sulfates and nitrates. Salts of organic acids, e.g., acetic acid or stearic acid, can also be used. It is preferred that the metals be in low valence state (compatible with the requirement of solubility) in order to reduce the amount of the borohydride compounds needed for the reduction.
- the preferred ionic borohydride compounds for use in the process of this invention are sodium and potassium borohydrides.
- Other alkali metal and alkaline earth metal borohydrides such as lithium borohydride, magnesium borohydride and calcium borohydride are operable, but are less readily available. While the proportion of metal borohydride and metal salts can be Varied considerably, the preferred proportion is about one mole of metal borohydride to two moles of metal salts.
- the pressure at which the reaction is carried out is normally atmospheric pressure, but higher or lower pressures can be employed if desired.
- Temperature has a pronounced effect on the process. Ambient temperature is operable, but it has been found that the efficiency with which chromium metal is incorporated into the composition of this invention increases with temperature up to about 40 C. Above 40 C. the efliciency is substantially constant with temperature. The proportion of boron incorporated decreases steadily with increasing temperature, but to less extent than the variation of chromium incorporation with increasing temperature. Heat is liberated in the reduction process, and it is therefore difficult to maintain the process temperature constant, particularly when large batches are to be processed. Accordingly, it is preferred to conduct the reduction process at a minimum initial temperature of about 40 C. Higher temperatures can be employed, but increasing temperature increases the loss of valuable borohydride reagent by the catalytic action of the fine metallic particles produced. Accordingly, it is preferred to operate at temperatures less than 100 C.
- the metal salts are dissolved in water or other solvent to form a strong solution, preferably saturated.
- the borohydride reagent is also dissolved to form a strong solution, which is then added to the solution of metal salts.
- the reagent solutions are mixed together in a relatively brief period which is suitably from 2 seconds to 30 min utes, the relatively longer times in this range being used for larger-scale preparations. Ten minutes is a generally useful time over which to add the borohydride reagent solution to the solution of metal salts.
- the reaction mixture should be stirred during the addition of the reagents to effect mixing, but excessive stirring hinders the formation of acicular particles, and if these are desired, excessive stirring should be avoided.
- a rotating magnet can be employed to assist mixing and to provide a'magnetic field.
- the reaction can be conducted in the presence of a magnetic field of at least 100 cc. and preferably of at least 1000 oe. in order to promote the formation of acicular particles.
- a suitable method of performing the reaction is to employ a non-magnetic reaction vessel, which can be glass, ceramic or stainless steel to contain the reactants, which is placed in the field of a permanent magnet or an electromagnet.
- the particles are washed immediately with water, acetone or the like and then dried.
- Elemental analysis indicates that the composition of the present invention contains a minor amount of oxygen, which in view of the above consideration and the very high surface/volume ratio of the particles is in part attributable to oxidation of the surface, and, in part, to absorption of water or other oxygenated solvent on the surface of the particles.
- the transverse dimensions of the particles vary from about 0.01 to 0.3 microns, and the lengths are about 0.01 to 4 microns.
- the axial ratio of the majority of the elongated particles is at least 3 to 1 and may be as much as 100:1 or higher.
- the products When produced in the absence of a magnetic field, the products contain a high percentage of equiaxed particles, the size of the particles being dependent on the particular composition.
- the particles With Fe/Cr/B compositions the particles are generally in the range of 0.05 to 0.08/L. Small amounts of cobalt and/or nickel decrease the particle size and increase the coercivity. The percentage of iron or nickel which provides a useful effect depends on the concentra tion of other materials present. With from 8 to 12% Cr and 1 to 7% B by weight, the compositions should contain from about 0.1 to about 5% and preferably from 0.5 to 2% by weight of at least one of nickel and cobalt to obtain enhanced magnetic properties.
- elongated particles which appear to be chains of the equiaxed particles.
- These elongated particles can be described as acicular, although when viewed using the electron microscope, the surface of these particles is undulating rather than smooth.
- the particles show substantially improved oxidation stability over iron or iron alloy particles which do not contain chromium.
- the chromium content should be at least 5% by weight.
- the preferred compositions of the present invention contain from about 8 to 20% by weight of chromium.
- 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, based on the total composition of binder, is employed. High percentages of binder can be used, but are not generally desirable, since the binder is generally inert magnetically.
- the particles can be mixed with a film-forming binder and coated as a suitable substrate to form a magnetic recording member.
- a common form of a magnetic recording 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 line AA.
- a substrate (1) is provided, which is generally a flexible polymeric film having suitable mechanical properties, i.e., it should be flexible as noted above, dimensionally stable with time, and under stress.
- Suitable polymeric film supports include films of poly(ethylene 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.
- the ferromagnetic particles of the present invention can be used to manufacture other recording members such as the patterned recording members employed for reflex thermomagnetic imaging as taught by Nacci, Belgian Pat. 627,017 in which the magnetic material in a film-forming binder is printed in the form of a halftone pattern on a substantially transparent substrate, or filled into indentations or grooves embossed in the surface of a transparent supporting member.
- EXAMPLE 1 A solution of 43.5 g. of FeSO '7H O and 20 g. of Cr (SO -xH O (3035% H O by weight) in 500 ml. of distilled water was prepared, and 7.6 g. of NaBH was dissolved in 250 ml. of distilled Water. The NaBH solution was slowly added to the metal salts solution. A vigorous, exothermic reaction took place and a black, magnetic solid separated. This solid was thoroughly washed with water and then with acetone. It was allowed to air dry. The product weighed 6 g. It contained 59.85% Fe, 16.95% Cr. 5.32% B, balance oxygen and water. The product had an intrinsic coercive force, ,H,,, of 253 oe., a saturation magnetization, 0' of 41.8 emu/g. and a remanence ratio (F /0' of 0.258.
- EXAMPLE 2 A solution of 27.8 g. of FeSO -7H O and 2.5 g. of K Cr (SO -24H O in 200 ml. of distilled water was put in a 2-liter beaker resting on the poles of a horseshoe magnet having a field of 1500 0e. A solution of 3.8 g. of NaBH in ml. of cold, distilled water was slowly added over a ten-minute period. The black precipitate was separated by filtration and washed with water and then acetone. It was suspended in ml. of acetone for 16 hours before filtering and air drying. The product weighed 4 g. It contained 66.86% Fe, 6.82% Cr, 3.06% B, balance oxygen and water.
- the product had an intrinsic coercive force, H of 417 oe., a saturation magnetization, a of 96 emu/g. and a remanence ratio (er 0) of 0.302, Particle size: Av. diam.: ca. 0.064 av. length: ca. 1
- Examples 3-6 illustrates the preparation of products containing various proportions of iron and chromium.
- the general procedure was as described in Example 2. In all cases a solution of 3.8 g. of NaBH in 100 ml. of cold, distilled water was used. The amounts of iron and chromium salts and analytical data on products are summarized in Table I.
- Example 111., a. Ur r/ 's As indicated in the general definition of the products above, the oxygen present in the particles of this invention can be in the form of metal oxides and/ or hydroxides or as moisture.
- the amount of moisture in a product made by the method of Example 3 was found to be 3.02%. This moisture content was determined as follows: The Weight loss of a sample heated in a vacuum of 0.1 micron was measured on a Du Pont 950 Thermo-gravimetric Analyzer. The sample was heated from room temperature to 400 C. at a rate of l/minute. The sample lost 3.02% of its original weight between room temperature and 175 C., with no additional loss to 400 C.
- Examples 7-15 illustrate the eifect of temperature on the product using the same quantities of material and the same general procedure except that the reaction vessel was maintained in a constant temperature bath at the stated temperatures and in a field of 1700 oe.
- the results are given in Table III.
- Example 4H5 a. at 4/ 5 EXAMPLES 20-24 These examples illustrate the preparation of IFe-Cr-B products containing various proportions of cobalt.
- the general procedure was as described in Example 2. In all cases, a solution of 3.8 g. of NaBH in 100 ml. of cold, distilled water was used. The amounts of iron and chromium salts were 44. 6 g. of FeSO -7H O and 20 g. of K Cr (SO -24H O. The amount of cobalt sulfate used and analytical data for the products are summarized in Table VI.
- EXAMPLE 26 An iron-nickel-chromium-boron alloy powder was synthesized in the presence of a magnetic field of about 1700 oe.
- a 2-liter beaker resting on the poles of a horseshoe magnet was charged with a solution containing 52.8 g. of FeSO -7H O, 2.6 g. of NiSO -6H O, and 1 g. of K Cr (SO -24H O 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 l0-min. period.
- a vi orous exothermic reaction occurred forming a black magnetic powder.
- the powder product was filtered, washed with water, and washed with acetone. After washing, the product was suspended in acetone for about 16 hr. before final filtration and air drying.
- the chemical composition of the powder was 73.78% Fe, 1.27% Ni, 4.10% Cr and 2.14% B. It had a (T of 106 emu/g, an H of 1155 oe., and a a' /o' ratio of 0.47.
- the powder consisted essentially of acicular particles with an average width of about 0.04 1. and an average length of about 0.6 When a powder product is prepared by the same procedure as described for this example in the absence of an external magnetic field, equiaxed particles of about 0.03 in diameter are formed.
- a 2-liter beaker resting on the poles of a horseshoe magnet was charged with a solution containing 50.0 g. of FeSO -7H O, 2.8 g. of CoSO -7H O, 2.6 g. of NiSO -6H O, and 1 g. of K Cr (SO -24H O dissolved in 200 ml. of distilled water.
- a solution of 3.8 g. of NaBl-L; in 100 ml. of distilled water was slowly added to the beaker in a 10-min. period.
- the coated magnetic stirring bar was attached to the tip of the buret in such a way that the tip rotated in phase with the rotating horseshoe magnet.
- a black solid separated as the addition proceeded. Occasional external stirring was necessary to disperse the bulky solid product.
- the mixture was filtered, and the solid product was washed with two liters of distilled water and one liter of acetone and allowed to stand in acetone for 16 hours. It was separated by filtration and air dried. The yield was 13.0 g.
- the product contained 76.82% Fe, 0.15% Co, and 7.77% Cr, the balance being boron, oxygen and water.
- H 520 oe., a saturation magnetization, a of 109 emu/g., a remanence magnetization, 0 of 41 emu/g, and a remanence ratio, er /(r of 0.376. It consisted of about 75% acicular particles, with average diameter 0.05 and average length 072.
- Example 29 The general procedure of Example 28 was employed. A solution of 278 g. of FeSO -7H O, 50 g. of K2CI'2(SO4)424H2O and g. of in 1 litCr of distilled water was prepared and a solution of 19 g. of NaBH in 500 ml. of cold, distilled Water was slowly added. The precipitate formed was collected and washed as previously described. The product contained 71.0% Fe, 8.4% Cr, 3.1% Co, and 2.29% B, the balance being oxygen, hydrogen and water. The particles had an average width of 0.04 micron. The measured magnetic properties were H of 710 oe., a of 114 emu/g, a, of 43 emu/g. and o' /a' of 0.377. The results of this experiment in comparison with Example 5 show that a small amount of cobalt incorporated in an iron/chromium/boron alloy increases the coercivity of the particles.
- the chemical composition of the powder was 66.56% Fe, 3.47% Co, 1.22% Ni, 5.04% Cr, and 2.11% B. TABLEIX It had a a of 92 emu/g, an H of 1190 oe., and a Percent; (T /0' ratio of 0.48.
- the powder consisted essentially of E 1 F C C acicular particles with an average width of about 0.04/L xamve e r o 1 W1 and an average length of about 1,5.
- equiaxed particles of about 0.03 1. in diameter are 1219 0I5 0I5 0:03 formed.
- EXAMPLE 28 F 50 7H 0 (278 K Cr (SO 24H 0 (50 g) 6 TABLE X e 4' 2 2 2 4 4' 2 l and CoSO -7H O (2 g.) were dissolved in distilled water, emu/g emu/g and the solution was made up to a volume of one liter. gig g; 33 8.11 1; The solution was placed in a constant-temperature bath 765 88 37 0:420 set at C., and a 1700-0e. horseshoe magnet capable 23 g 8%; of being rotated was placed below the assembly. With 810 3 42 01480 the horseshoe magnet rotating at about 15 r.p.m., 500 ml.
- the chromium-containing alloys of the invention are more resistant to oxidation than similar alloys containing no chromium.
- the enhanced oxidation resistance is illustrated as follows:
- An Fe-B powder and Fe-Cr-B powders containing 2.3, 3.7, 5.7, 7.1 and 11.0% of Cr were prepared by the method of Example 2.
- a sample of each product was immersed in 30% by weight of nitric acid at 25 C. for 3 minutes, and another sample of each product was immersed for 10 minutes.
- Each mixture was filtered, and solid was washed with water and dried to a constant weight in a vacuum oven. The weight percentage of each powder that had dissolved was calculated.
- Table XI The results are summarized in Table XI and show clearly the beneficial effect of increasing chromium content.
- the Fe-B powders reacted violently and completely with the nitric acid, while the powder containing 11.0% Cr showed no visible reaction with the acid for 3 minutes.
- Percent Cr The stability towards oxidation by 30% nitric acid is related to the stability of metals in moist air (The Corrosion Handbook, Ed. Uhlig, John Wiley & Sons, New York, N.Y., 1948, p. 28).
- alloys of this invention are useful in magnetic applications, e.g., as magnets and in magnetic tapes. These utilities are illustrated in Examples A and B, which follow.
- EXAMPLE A An iron-chromium-boron powder prepared as described in Example 1 was formed into a permanent magnet as follows: A l-gram sample of the powder was pressed in a 1.5" x 0.1" mold at 80,000 p.s.i. and room temperature. The resulting bar was magnetized by placing it in a magnetic field. The bar had a coercive force, H of 335 oe., a saturation magnetization per gram, of 74.2 emu/g. and a remanence ratio of 0.414.
- EXAMPLE B A blend of several batches of Fe-Cr-B powder synthesized by the technique described in Example 2 above was fabricated into magnetic recording tapes.
- the powder blend was comminuted for 5 hours with poly(tetrafluoroethylene) balls in a rotating plastic canister to increase its apparent bulk density from about 0.1 to 1.0 g./cc.
- the powder blend had an H of 459 oe., a of 98 emu/g., and a o of 36 emu/ g.
- the average chemical composition of the powder was 71.6% Fe, 9.6% Cr, 1.5% B, and 14.2% 0.
- the powder was ground with 20- to 30-mesh sand in a slurry of tetrahydrofuran plus soya lecithin for 1 hour and then mixed in the sand grinder with a binder consisting of 50%, by weight, of a soluble polyester-urethane resin made from diisocyanatodiphenylmethane, adipic acid and butanediol, and 50% of vinylidene chloride/acrylonitrile /20 copolymer.
- the binderpowder system contained about 30 volume percent of powder. After mixing, the binder-powder slurry was pressure 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 long direction of the tape.
- the tape was then dried in air for about 24 hours and dried in a vacuum desiccator for about 16 hours.
- Measurements of properties of the Fe-Cr-B magnetic tape are summarized in Table XII.
- Ferromagnetic alloy particles having cross-sectional dimensions of 0.01 to 0.3 micron and a length of 0.01 to 4 microns consisting essentially of, by weight, up to 35% cobalt, up to 35% nickel, 0.4% to 20% chromium, 1.0 to 7.5% of boron dissolved therein, oxygen either as metal oxide, metal hydroxide or moisture, and the balance iron in an amount of at least 30%.
- composition of claim 1 in which the axial ratio of said particles is at least 3:1.
- a magnetic recording member containing, as the magnetic material, the particles of claim 3.
- Composition of claim 3 in which chromium is present in an amount of from 8 to 12% together with from 0.1 to 5% by Weight of at least one of nickel and cobalt.
- composition of claim 5 in which said nickel and cobalt are present in an amount of from 0.5 to 2% by weight.
Description
. FER-ROMAGNET PARTICLES CONTAINING CHROMIUM Filed May 23, 1969 IN VENTORS ERNEST LEWIS LITTLE, JR. JACK D. WOLF A ORNEY United States Patent US. Cl. 75.5 7 Claims ABSTRACT OF THE DISCLOSURE Iron alloys with chromium and boron, optionally containing cobalt and/ or nickel, can be made in the form of ferromagnetic particles by reduction of a solution of the appropriate metal salts with an alkali metal borohydride, preferably at an initial temperature between 40 and 100 C. If formed in a magnetic field, the particles chain up to acicular particles of higher coercivity. The particles can be compacted to form permanent magnets and are useful for making recording members such as magnetic tape. Preferred compositions include iron/chromium/boron a1- loys having a very small amount of nickel or cobalt or both which improves the magnetic properties.
FIELD OF THE INVENTION This invention relates to new ferromagnetic compositions and more particularly compositions comprising fine ferromagnetic particles of iron optionally alloyed with nickel and/or cobalt, and containing boron and chromium.
The Miller and Oppegard US. Pat. 3,206,338 describes and claims ferromagnetic alloys of iron with boron and optionally cobalt and/ or nickel in the form of fine acicular particles. Despite the fine particle size of these alloys, they are nonpyrophoric. In accordance with the present invention, it has been discovered that when chromium salts are included in certain reaction mixtures containing iron and reduction is carried out on them with a borohydride, alloys containing metallic chromium in substantial proportions are produced which have improved oxidation stability (compared with the alloys of Oppegard and Miller) and good magnetic properties. This discovery is particularly surprising, since chromium is classified as a reluctant metal which cannot be produced by wet chemical reduction of its salts.
SUMMARY OF THE INVENTION The novel ferromagnetic alloy particles of the present invention have cross-sectional dimensions of 0.01 to 0.3 microns, a length of 0.01 to 4 microns and preferably an axial ratio of at least 3 :1; consisting essentially by weight of up to 35% cobalt, up to 35% nickel, and from 0.4 to 20%, preferably from 8 to 20%, chromium, and 1.0 to 7.5% boron dissolved therein, and oxygen either as metal oxide, metal hydroxide or as moisture balance Fe in an amount of at least 30%.
Especially preferred are iron alloys containing from 8 to 12% by weight of chromium, from 1.0 to 7.5 by weight of boron, and from about 0.1 to by weight of at least one of cobalt and nickel.
The compositions are produced by the reduction, in solution, of a mixture of the appropriate metal salts with an alkali-metal borohydride or alkaline earth metal borohydride and, if elongated particles are desired, preferably in the presence of a magnetic field of at least oe. and more preferably at least 1000 oe.
The magnetic particles of the present invention, preferably in elongated or acicular form, can be made into magnetic objects. Thus, they can be compacted to form useful permanent magnets or other magnetic objects with or without a binding material. Any binding material used can be a thermosetting or thermoplastic organic polymeric binder or an air-drying, film-forming binder.
The finely particulate material of the present invention can also be used in magnetic recording members such as magnetic recording tapes.
DETAILED DESCRIPTION OF THE INVENTION The reduction process by which the novel magnetic materials of the present invention are made is generally conducted in aqueous solution, but alcohol, tetrahydrofuran, or like organic solvents can also be used as a reaction medium.
A wide variety of metal salts can be used including the halides, sulfates and nitrates. Salts of organic acids, e.g., acetic acid or stearic acid, can also be used. It is preferred that the metals be in low valence state (compatible with the requirement of solubility) in order to reduce the amount of the borohydride compounds needed for the reduction.
The preferred ionic borohydride compounds for use in the process of this invention are sodium and potassium borohydrides. Other alkali metal and alkaline earth metal borohydrides such as lithium borohydride, magnesium borohydride and calcium borohydride are operable, but are less readily available. While the proportion of metal borohydride and metal salts can be Varied considerably, the preferred proportion is about one mole of metal borohydride to two moles of metal salts.
The pressure at which the reaction is carried out is normally atmospheric pressure, but higher or lower pressures can be employed if desired.
Temperature has a pronounced effect on the process. Ambient temperature is operable, but it has been found that the efficiency with which chromium metal is incorporated into the composition of this invention increases with temperature up to about 40 C. Above 40 C. the efliciency is substantially constant with temperature. The proportion of boron incorporated decreases steadily with increasing temperature, but to less extent than the variation of chromium incorporation with increasing temperature. Heat is liberated in the reduction process, and it is therefore difficult to maintain the process temperature constant, particularly when large batches are to be processed. Accordingly, it is preferred to conduct the reduction process at a minimum initial temperature of about 40 C. Higher temperatures can be employed, but increasing temperature increases the loss of valuable borohydride reagent by the catalytic action of the fine metallic particles produced. Accordingly, it is preferred to operate at temperatures less than 100 C.
The metal salts are dissolved in water or other solvent to form a strong solution, preferably saturated. The borohydride reagent is also dissolved to form a strong solution, which is then added to the solution of metal salts.
The reagent solutions are mixed together in a relatively brief period which is suitably from 2 seconds to 30 min utes, the relatively longer times in this range being used for larger-scale preparations. Ten minutes is a generally useful time over which to add the borohydride reagent solution to the solution of metal salts. The reaction mixture should be stirred during the addition of the reagents to effect mixing, but excessive stirring hinders the formation of acicular particles, and if these are desired, excessive stirring should be avoided. A rotating magnet can be employed to assist mixing and to provide a'magnetic field.
As indicated above, the reaction can be conducted in the presence of a magnetic field of at least 100 cc. and preferably of at least 1000 oe. in order to promote the formation of acicular particles. A suitable method of performing the reaction is to employ a non-magnetic reaction vessel, which can be glass, ceramic or stainless steel to contain the reactants, which is placed in the field of a permanent magnet or an electromagnet.
After the reduction process, the particles are washed immediately with water, acetone or the like and then dried.
Structural analysis by X-ray diffraction and electron diffraction of the Fe-Cr-B powder shown in Examples 2, 4 and 5 indicates that the principal phase present is the body centered cubic structure of a-iron, the reflection being somewhat diffuse. No extra reflection that could be attributed to a boride or boron oxide is present. Since the solubility of boron in iron at room temperature is less than 0.01% by weight [M. Hansen, Constitution of Binary Alloys, McGraw-Hill, p. 251, 1958], the compositions of the present invention are solid solutions of metallic chromium in u-iron, supersaturated with boron.
Elemental analysis indicates that the composition of the present invention contains a minor amount of oxygen, which in view of the above consideration and the very high surface/volume ratio of the particles is in part attributable to oxidation of the surface, and, in part, to absorption of water or other oxygenated solvent on the surface of the particles.
The transverse dimensions of the particles vary from about 0.01 to 0.3 microns, and the lengths are about 0.01 to 4 microns. The axial ratio of the majority of the elongated particles is at least 3 to 1 and may be as much as 100:1 or higher.
When produced in the absence of a magnetic field, the products contain a high percentage of equiaxed particles, the size of the particles being dependent on the particular composition. With Fe/Cr/B compositions the particles are generally in the range of 0.05 to 0.08/L. Small amounts of cobalt and/or nickel decrease the particle size and increase the coercivity. The percentage of iron or nickel which provides a useful effect depends on the concentra tion of other materials present. With from 8 to 12% Cr and 1 to 7% B by weight, the compositions should contain from about 0.1 to about 5% and preferably from 0.5 to 2% by weight of at least one of nickel and cobalt to obtain enhanced magnetic properties.
In the presence of a magnetic field, elongated particles are obtained which appear to be chains of the equiaxed particles. These elongated particles can be described as acicular, although when viewed using the electron microscope, the surface of these particles is undulating rather than smooth.
The particles show substantially improved oxidation stability over iron or iron alloy particles which do not contain chromium. For optimum stability, the chromium content should be at least 5% by weight. The preferred compositions of the present invention contain from about 8 to 20% by weight of chromium.
The particles can be compacted by the techniques known in the field of powder metallurgy to form useful permanent magnets. Optionally, small quantities of organic or inorganic binder can be present, generally from about 2 to 30% by weight, based on the total composition of binder, is employed. High percentages of binder can be used, but are not generally desirable, since the binder is generally inert magnetically.
In the powder form the particles can be mixed with a film-forming binder and coated as a suitable substrate to form a magnetic recording member. A common form of a magnetic recording 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 line AA. In the figures, a substrate (1) is provided, which is generally a flexible polymeric film having suitable mechanical properties, i.e., it should be flexible as noted above, dimensionally stable with time, and under stress. Suitable polymeric film supports include films of poly(ethylene 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. In addition to conventional magnetic tapes employed for magnetic recording, the ferromagnetic particles of the present invention can be used to manufacture other recording members such as the patterned recording members employed for reflex thermomagnetic imaging as taught by Nacci, Belgian Pat. 627,017 in which the magnetic material in a film-forming binder is printed in the form of a halftone pattern on a substantially transparent substrate, or filled into indentations or grooves embossed in the surface of a transparent supporting member.
EMBODIMENTS OF THE INVENTION This invention is further illustrated by the following examples, which should not, however, be constnled as fully delineating the scope of this discovery. In these examples, parts and percentages are by Weight unless otherwise specified. The horseshoe magnets used in the examples had field strengths of 1500-1700 oe. Magnetic properties were determined by packing the powders in tubes and placing them in an extraction magnetometer with an applied field of about 4400 oe. Saturation magnetization values, a and remanent magnetization values, o' are given in the examples as emu/g.
EXAMPLE 1 A solution of 43.5 g. of FeSO '7H O and 20 g. of Cr (SO -xH O (3035% H O by weight) in 500 ml. of distilled water was prepared, and 7.6 g. of NaBH was dissolved in 250 ml. of distilled Water. The NaBH solution was slowly added to the metal salts solution. A vigorous, exothermic reaction took place and a black, magnetic solid separated. This solid was thoroughly washed with water and then with acetone. It was allowed to air dry. The product weighed 6 g. It contained 59.85% Fe, 16.95% Cr. 5.32% B, balance oxygen and water. The product had an intrinsic coercive force, ,H,,, of 253 oe., a saturation magnetization, 0' of 41.8 emu/g. and a remanence ratio (F /0' of 0.258.
EXAMPLE 2 A solution of 27.8 g. of FeSO -7H O and 2.5 g. of K Cr (SO -24H O in 200 ml. of distilled water was put in a 2-liter beaker resting on the poles of a horseshoe magnet having a field of 1500 0e. A solution of 3.8 g. of NaBH in ml. of cold, distilled water was slowly added over a ten-minute period. The black precipitate Was separated by filtration and washed with water and then acetone. It was suspended in ml. of acetone for 16 hours before filtering and air drying. The product weighed 4 g. It contained 66.86% Fe, 6.82% Cr, 3.06% B, balance oxygen and water. The product had an intrinsic coercive force, H of 417 oe., a saturation magnetization, a of 96 emu/g. and a remanence ratio (er 0) of 0.302, Particle size: Av. diam.: ca. 0.064 av. length: ca. 1
EXAMPLES 315 Examples 3-6 illustrates the preparation of products containing various proportions of iron and chromium. The general procedure was as described in Example 2. In all cases a solution of 3.8 g. of NaBH in 100 ml. of cold, distilled water was used. The amounts of iron and chromium salts and analytical data on products are summarized in Table I.
The magnetic properties of the above products are summarized in Table II.
TABLE 11 Example 111., a. Ur r/ 's As indicated in the general definition of the products above, the oxygen present in the particles of this invention can be in the form of metal oxides and/ or hydroxides or as moisture. The amount of moisture in a product made by the method of Example 3 was found to be 3.02%. This moisture content was determined as follows: The Weight loss of a sample heated in a vacuum of 0.1 micron was measured on a Du Pont 950 Thermo-gravimetric Analyzer. The sample was heated from room temperature to 400 C. at a rate of l/minute. The sample lost 3.02% of its original weight between room temperature and 175 C., with no additional loss to 400 C.
Examples 7-15 illustrate the eifect of temperature on the product using the same quantities of material and the same general procedure except that the reaction vessel was maintained in a constant temperature bath at the stated temperatures and in a field of 1700 oe. The results are given in Table III.
TABLE III p., Cr, 13, 0. percent percent 4151., a. o,- (Yr/0' The morphologies of the powders were determined by the use of an electron microscope at a magnification of 20,000X. The particles synthesized below 40 C. Were about 50% acicular with average dimensions of about 1.0 x 0.08 1. The particles synthesized at 40 C. or greater were about 8% acicular with typical dimensions of 1.6 x 0.054
EXAMPLES 16-19 The magnetic properties of these same materials are summarized in Table V.
1 5 TABLE V Example 4H5 a. at 4/ 5 EXAMPLES 20-24 These examples illustrate the preparation of IFe-Cr-B products containing various proportions of cobalt. The general procedure was as described in Example 2. In all cases, a solution of 3.8 g. of NaBH in 100 ml. of cold, distilled water was used. The amounts of iron and chromium salts were 44. 6 g. of FeSO -7H O and 20 g. of K Cr (SO -24H O. The amount of cobalt sulfate used and analytical data for the products are summarized in Table VI.
TABLE VI Approx. avg. dimensions, Percent microns Fe Co Cr B Diam. Length A solution of 44.6 g. of FeSO -7H O, 10.5 g. of NiSO -6H O and l g. of K Cr (SO' -24H O in 200 ml. of distilled water was put in a 2-liter beaker resting on the poles of a horseshoe magnet of field strength 1500 oe. A solution of 3.8 g. of NaBH in 100 ml. of cold, distilled water Was slowly added over a ten-minute period. The black precipitate was filtered and Washed with water and then acetone. It was suspended in 125 ml. of acetone for 16 hours before filtering and air drying. The product Weighed 4.1 g. It contained 48.57% Fe, 18.11% Ni, 1.75% Cr, 3.48% B, balance oxygen and water. The 65 product had an intrinsic coercive force, H of 1040 oe.,
TABLE IV Approx. avg. dimensions, Percent microns K2C12(SO4)4-24H2O Example (g.) Fe Co Cr B Diam. Length a saturation magnetization per gram, a of 66 emu/ g. and a remanence ratio, (T of 0.425.
EXAMPLE 26 An iron-nickel-chromium-boron alloy powder was synthesized in the presence of a magnetic field of about 1700 oe. A 2-liter beaker resting on the poles of a horseshoe magnet was charged with a solution containing 52.8 g. of FeSO -7H O, 2.6 g. of NiSO -6H O, and 1 g. of K Cr (SO -24H O 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 l0-min. period. During the addition of the NaBH solution, a vi orous exothermic reaction occurred forming a black magnetic powder. The powder product was filtered, washed with water, and washed with acetone. After washing, the product was suspended in acetone for about 16 hr. before final filtration and air drying.
The chemical composition of the powder was 73.78% Fe, 1.27% Ni, 4.10% Cr and 2.14% B. It had a (T of 106 emu/g, an H of 1155 oe., and a a' /o' ratio of 0.47. The powder consisted essentially of acicular particles with an average width of about 0.04 1. and an average length of about 0.6 When a powder product is prepared by the same procedure as described for this example in the absence of an external magnetic field, equiaxed particles of about 0.03 in diameter are formed.
EXAMPLE 27 An iron-cobalt-nickel-chromium=boron alloy powder was synthesized in the presence of a magnetic field of about 1700 oe. A 2-liter beaker resting on the poles of a horseshoe magnet was charged with a solution containing 50.0 g. of FeSO -7H O, 2.8 g. of CoSO -7H O, 2.6 g. of NiSO -6H O, and 1 g. of K Cr (SO -24H O dissolved in 200 ml. of distilled water. A solution of 3.8 g. of NaBl-L; in 100 ml. of distilled water was slowly added to the beaker in a 10-min. period. During the addition of the NaBH solution, 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 hr. before final filtration and air drying.
coated magnetic stirring bar was attached to the tip of the buret in such a way that the tip rotated in phase with the rotating horseshoe magnet. A black solid separated as the addition proceeded. Occasional external stirring was necessary to disperse the bulky solid product. After the addition was complete, the mixture was filtered, and the solid product was washed with two liters of distilled water and one liter of acetone and allowed to stand in acetone for 16 hours. It was separated by filtration and air dried. The yield was 13.0 g. The product contained 76.82% Fe, 0.15% Co, and 7.77% Cr, the balance being boron, oxygen and water. It had an intrinsic coercive force, H of 520 oe., a saturation magnetization, a of 109 emu/g., a remanence magnetization, 0 of 41 emu/g, and a remanence ratio, er /(r of 0.376. It consisted of about 75% acicular particles, with average diameter 0.05 and average length 072.
EXAMPLE 29 The general procedure of Example 28 was employed. A solution of 278 g. of FeSO -7H O, 50 g. of K2CI'2(SO4)424H2O and g. of in 1 litCr of distilled water was prepared and a solution of 19 g. of NaBH in 500 ml. of cold, distilled Water was slowly added. The precipitate formed was collected and washed as previously described. The product contained 71.0% Fe, 8.4% Cr, 3.1% Co, and 2.29% B, the balance being oxygen, hydrogen and water. The particles had an average width of 0.04 micron. The measured magnetic properties were H of 710 oe., a of 114 emu/g, a, of 43 emu/g. and o' /a' of 0.377. The results of this experiment in comparison with Example 5 show that a small amount of cobalt incorporated in an iron/chromium/boron alloy increases the coercivity of the particles.
EXAMPLES 30-35 The general procedure employed with these examples was as described for Example 2. In all cases a solution of 3.8 g. of NaBH in 100 ml. of cold water was employed. The amounts of the other reactants are summarized in Table VIII. The analytical data of the products is given in Table IX and the magnetic properties of the products are given in Table X.
TABLE VIII FGSO4- KzC1 (SO4)4- COSO4- N1304- Example 71320, 1;. 241120, g. 7H2O fiHzO Yield, g.
The chemical composition of the powder was 66.56% Fe, 3.47% Co, 1.22% Ni, 5.04% Cr, and 2.11% B. TABLEIX It had a a of 92 emu/g, an H of 1190 oe., and a Percent; (T /0' ratio of 0.48. The powder consisted essentially of E 1 F C C acicular particles with an average width of about 0.04/L xamve e r o 1 W1 and an average length of about 1,5. When a powder 8'8; product is prepared by the same procedure as described 8:6 217 1'5 0: 05 for this example in the absence of an external magnetic 8 38% field, equiaxed particles of about 0.03 1. in diameter are 1219 0I5 0I5 0:03 formed.
EXAMPLE 28 F 50 7H 0 (278 K Cr (SO 24H 0 (50 g) 6 TABLE X e 4' 2 2 2 4 4' 2 l and CoSO -7H O (2 g.) were dissolved in distilled water, emu/g emu/g and the solution was made up to a volume of one liter. gig g; 33 8.11 1; The solution Was placed in a constant-temperature bath 765 88 37 0:420 set at C., and a 1700-0e. horseshoe magnet capable 23 g 8%; of being rotated was placed below the assembly. With 810 3 42 01480 the horseshoe magnet rotating at about 15 r.p.m., 500 ml. of a solution of 19 g. of NaBH in distilled water was added to the solution of metal salts at a rate of 25 ml. per minute from a buret with a flexible tip. A small plastic- As pointed out above, the chromium-containing alloys of the invention are more resistant to oxidation than similar alloys containing no chromium. The enhanced oxidation resistance is illustrated as follows:
An Fe-B powder and Fe-Cr-B powders containing 2.3, 3.7, 5.7, 7.1 and 11.0% of Cr were prepared by the method of Example 2. A sample of each product was immersed in 30% by weight of nitric acid at 25 C. for 3 minutes, and another sample of each product was immersed for 10 minutes. Each mixture was filtered, and solid was washed with water and dried to a constant weight in a vacuum oven. The weight percentage of each powder that had dissolved was calculated. The results are summarized in Table XI and show clearly the beneficial effect of increasing chromium content. The Fe-B powders reacted violently and completely with the nitric acid, while the powder containing 11.0% Cr showed no visible reaction with the acid for 3 minutes.
TABLE XI Exposure to 30 wt. percent HNO percent Fe+percent Cr 3 min. 10 min.
Percent Cr The stability towards oxidation by 30% nitric acid is related to the stability of metals in moist air (The Corrosion Handbook, Ed. Uhlig, John Wiley & Sons, New York, N.Y., 1948, p. 28).
As also pointed out above, the alloys of this invention are useful in magnetic applications, e.g., as magnets and in magnetic tapes. These utilities are illustrated in Examples A and B, which follow.
EXAMPLE A An iron-chromium-boron powder prepared as described in Example 1 was formed into a permanent magnet as follows: A l-gram sample of the powder was pressed in a 1.5" x 0.1" mold at 80,000 p.s.i. and room temperature. The resulting bar was magnetized by placing it in a magnetic field. The bar had a coercive force, H of 335 oe., a saturation magnetization per gram, of 74.2 emu/g. and a remanence ratio of 0.414.
EXAMPLE B A blend of several batches of Fe-Cr-B powder synthesized by the technique described in Example 2 above was fabricated into magnetic recording tapes. The powder blend was comminuted for 5 hours with poly(tetrafluoroethylene) balls in a rotating plastic canister to increase its apparent bulk density from about 0.1 to 1.0 g./cc. The powder blend had an H of 459 oe., a of 98 emu/g., and a o of 36 emu/ g. The average chemical composition of the powder was 71.6% Fe, 9.6% Cr, 1.5% B, and 14.2% 0.
After comminution, the powder was ground with 20- to 30-mesh sand in a slurry of tetrahydrofuran plus soya lecithin for 1 hour and then mixed in the sand grinder with a binder consisting of 50%, by weight, of a soluble polyester-urethane resin made from diisocyanatodiphenylmethane, adipic acid and butanediol, and 50% of vinylidene chloride/acrylonitrile /20 copolymer. The binderpowder system contained about 30 volume percent of powder. After mixing, the binder-powder slurry was pressure 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 long direction of the tape. The tape was then dried in air for about 24 hours and dried in a vacuum desiccator for about 16 hours. Measurements of properties of the Fe-Cr-B magnetic tape are summarized in Table XII.
TABLE XII.--PROPERTIES OF Fe-Cr-B MAGNETIC TAPE /2" max. 1.285 Coating thickness, mils a- 0.260 B,, g. 1,530 12,02 0.70 H.;, oe 440 The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. Ferromagnetic alloy particles having cross-sectional dimensions of 0.01 to 0.3 micron and a length of 0.01 to 4 microns consisting essentially of, by weight, up to 35% cobalt, up to 35% nickel, 0.4% to 20% chromium, 1.0 to 7.5% of boron dissolved therein, oxygen either as metal oxide, metal hydroxide or moisture, and the balance iron in an amount of at least 30%.
2. Composition of claim 1 in which the axial ratio of said particles is at least 3:1.
3. Composition of claim 2 in which chromium is present in an amount of from 8 to 20% by weight.
4. A magnetic recording member containing, as the magnetic material, the particles of claim 3.
5. A magnet formed from the particles of claim 3.
6. Composition of claim 3 in which chromium is present in an amount of from 8 to 12% together with from 0.1 to 5% by Weight of at least one of nickel and cobalt.
7. Composition of claim 5 in which said nickel and cobalt are present in an amount of from 0.5 to 2% by weight.
References Cited UNITED STATES PATENTS 3,206,338 9/1965 Miller et a]. 75-.5
HYLAND BIZOT, Primary Examiner W. W. STALLARD, Assistant Examiner U.S. Cl. X.R. 148-3155,
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US82738669A | 1969-05-23 | 1969-05-23 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3535104A true US3535104A (en) | 1970-10-20 |
Family
ID=25249087
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US827386A Expired - Lifetime US3535104A (en) | 1969-05-23 | 1969-05-23 | Ferromagnetic particles containing chromium |
Country Status (1)
Country | Link |
---|---|
US (1) | US3535104A (en) |
Cited By (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3634063A (en) * | 1970-04-23 | 1972-01-11 | Ampex | Acicular, stable magnetic iron particles |
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 |
DE2326258A1 (en) * | 1972-05-22 | 1973-12-13 | Minnesota Mining & Mfg | FINE NEEDLE-SHAPED IRON-BASED PARTICLES CONTAINING MAGNETIC RECORDING MATERIAL |
US3855016A (en) * | 1971-03-24 | 1974-12-17 | Graham Magnetics Inc | Acicular cobalt powders having high squarenesss ratios |
US3902888A (en) * | 1971-08-19 | 1975-09-02 | Fuji Photo Film Co Ltd | Process for preparing ferromagnetic alloy powder |
US3943012A (en) * | 1973-08-18 | 1976-03-09 | Fuji Photo Film Co., Ltd. | Magnetic recording medium |
DE2738421A1 (en) * | 1976-08-27 | 1978-03-02 | Victor Company Of Japan | MAGNETIC METALLIC POWDER AND ITS USE |
US4217152A (en) * | 1973-11-16 | 1980-08-12 | Fuji Photo Film Co., Ltd. | Process for production of ferromagnetic powder |
US4221614A (en) * | 1978-03-14 | 1980-09-09 | Tdk Electronics Co., Ltd. | Method of manufacturing ferromagnetic magnetic metal powder |
US4222798A (en) * | 1978-03-14 | 1980-09-16 | Tdk Electronics Company Limited | Method of manufacturing ferromagnetic metal powder |
US4404024A (en) * | 1978-03-16 | 1983-09-13 | Kanto Denka Kogyo Co., Ltd. | Production of magnetic powder |
US4437881A (en) | 1982-07-31 | 1984-03-20 | Toda Kogyo Corp. | Acicular ferromagnetic alloy particles and process for producing said particles |
US4483724A (en) * | 1982-09-27 | 1984-11-20 | Allied Corporation | Iron-boron solid solution alloys having high saturation magnetization and low magnetostriction |
EP0207583A2 (en) * | 1985-07-03 | 1987-01-07 | The Standard Oil Company | Amorphous metal alloy compositions and synthesis of same by solid state incorporation/reduction reactions |
US20040211293A1 (en) * | 2003-04-25 | 2004-10-28 | Shamblen Clifford Earl | Method for fabricating a martensitic steel without any melting |
US20110163910A1 (en) * | 2006-02-22 | 2011-07-07 | Enraf B.V. | Radar liquid level detection using stepped frequency pulses |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3206338A (en) * | 1963-05-10 | 1965-09-14 | Du Pont | Non-pyrophoric, ferromagnetic acicular particles and their preparation |
-
1969
- 1969-05-23 US US827386A patent/US3535104A/en not_active Expired - Lifetime
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3206338A (en) * | 1963-05-10 | 1965-09-14 | Du Pont | Non-pyrophoric, ferromagnetic acicular particles and their preparation |
Cited By (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3634063A (en) * | 1970-04-23 | 1972-01-11 | Ampex | Acicular, stable magnetic iron particles |
US3663318A (en) * | 1970-10-05 | 1972-05-16 | Du Pont | Process for making ferromagnetic metal powders |
US3855016A (en) * | 1971-03-24 | 1974-12-17 | Graham Magnetics Inc | Acicular cobalt powders having high squarenesss ratios |
US3755008A (en) * | 1971-03-24 | 1973-08-28 | Graham Magnetics Inc | Process for enhancing magnetic properties of metal powder by heat treating with salt |
US3902888A (en) * | 1971-08-19 | 1975-09-02 | Fuji Photo Film Co Ltd | Process for preparing ferromagnetic alloy powder |
JPS5928964B2 (en) * | 1972-05-22 | 1984-07-17 | ミネソタ マイニング アンド マニュファクチュアリング コンパニ− | magnetic recording medium |
JPS4943604A (en) * | 1972-05-22 | 1974-04-24 | ||
DE2326258A1 (en) * | 1972-05-22 | 1973-12-13 | Minnesota Mining & Mfg | FINE NEEDLE-SHAPED IRON-BASED PARTICLES CONTAINING MAGNETIC RECORDING MATERIAL |
US3943012A (en) * | 1973-08-18 | 1976-03-09 | Fuji Photo Film Co., Ltd. | Magnetic recording medium |
US4217152A (en) * | 1973-11-16 | 1980-08-12 | Fuji Photo Film Co., Ltd. | Process for production of ferromagnetic powder |
DE2738421A1 (en) * | 1976-08-27 | 1978-03-02 | Victor Company Of Japan | MAGNETIC METALLIC POWDER AND ITS USE |
US4221614A (en) * | 1978-03-14 | 1980-09-09 | Tdk Electronics Co., Ltd. | Method of manufacturing ferromagnetic magnetic metal powder |
US4222798A (en) * | 1978-03-14 | 1980-09-16 | Tdk Electronics Company Limited | Method of manufacturing ferromagnetic metal powder |
US4447264A (en) * | 1978-03-16 | 1984-05-08 | Kanto Denka Kogyo Co., Ltd. | Production of magnetic powder |
US4404024A (en) * | 1978-03-16 | 1983-09-13 | Kanto Denka Kogyo Co., Ltd. | Production of magnetic powder |
US4437881A (en) | 1982-07-31 | 1984-03-20 | Toda Kogyo Corp. | Acicular ferromagnetic alloy particles and process for producing said particles |
US4483724A (en) * | 1982-09-27 | 1984-11-20 | Allied Corporation | Iron-boron solid solution alloys having high saturation magnetization and low magnetostriction |
EP0207583A2 (en) * | 1985-07-03 | 1987-01-07 | The Standard Oil Company | Amorphous metal alloy compositions and synthesis of same by solid state incorporation/reduction reactions |
EP0207583A3 (en) * | 1985-07-03 | 1988-08-31 | The Standard Oil Company | Amorphous metal alloy compositions and synthesis of same by solid state incorporation/reduction reactions |
US20040211293A1 (en) * | 2003-04-25 | 2004-10-28 | Shamblen Clifford Earl | Method for fabricating a martensitic steel without any melting |
US7553383B2 (en) * | 2003-04-25 | 2009-06-30 | General Electric Company | Method for fabricating a martensitic steel without any melting |
US20110163910A1 (en) * | 2006-02-22 | 2011-07-07 | Enraf B.V. | Radar liquid level detection using stepped frequency pulses |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3535104A (en) | Ferromagnetic particles containing chromium | |
US3206338A (en) | Non-pyrophoric, ferromagnetic acicular particles and their preparation | |
US3567525A (en) | Heat treated ferromagnetic particles | |
US4050962A (en) | Manufacture of ferromagnetic, acicular metallic iron particles by hydrogen reduction | |
US4384892A (en) | Production of magnetic powder | |
US4447264A (en) | Production of magnetic powder | |
US3770500A (en) | Magnetic materials and method of making same | |
US4305753A (en) | Process for producing ferromagnetic metallic particles | |
US3574685A (en) | Manufacture of magnetic particles by reacting iron,cobalt,or nickel salts with oxalic acid salts in dialkyl sulfoxide | |
US4167582A (en) | Magnetic metallic powder containing iron and magnetic recording medium using same powder | |
GB1597680A (en) | Manufacture of acicular ferromagnetic pigment particles | |
US3837912A (en) | Environmentally stable iron-based magnetic recording medium | |
US3726664A (en) | Magnetic alloy particle compositions and method of manufacture | |
US3977985A (en) | Magnetic recording medium comprising cobalt or cobalt alloy coated particles of spicular magnetite | |
US4273807A (en) | Acicular α-iron particles and recording media employing same | |
US6136061A (en) | Nanostructured metal compacts, and method of making same | |
DE1931664B2 (en) | FERROMAGNETIC PARTICLES | |
US3278440A (en) | Shaped fine particle ferrites and method for their preparation | |
US3859130A (en) | Magnetic alloy particle compositions and method of manufacture | |
US4059463A (en) | Process for producing ferromagnetic powder | |
CA1132008A (en) | Metallic iron particles for magnetic recording produced by reducing an iron oxide precursor coated with an antimony compound | |
US4305752A (en) | Metallic iron particles for magnetic recording | |
US4207092A (en) | Acicular α-iron particles, their preparation and recording media employing same | |
EP0075991A2 (en) | Magnetic recording medium and method for the production thereof | |
CA1043588A (en) | Powdery material for magnetic recording medium and process for production of same |