Classifications

• • 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

Definitions

• Iron powders (which may contain, in addition, nickel and/or cobalt) to be used for magnetic recording are prepared according to the invention by reducing the metal oxidic or metal hydroxidic starting material in a finely divided state with a gaseous reduction agent (preferably hydrogen) at a pressure of at least 10 atm.
• a gaseous reduction agent preferably hydrogen
• the advantage hereof is that the reduction is effected at an acceptable rate at comparatively low temperatures at which sintering of the formed metal particles does not yet occur. Actually, such a sintering unfavorably affects the properties of the powders in question with a view to their usability for magnetic recording.
• the invention relates to a method of preparing a metal powder consisting at least substantially of iron, for magnetic recording.
• metal powders of the above mentioned type which may consist of an alloy of iron with nickel and/or cobalt by reduction of the metal oxides and/or metal hydroxides by means of hydrogen or another gaseous reduction agent at a pressure of 1 atm.
• the reduction then proceeds very slowly. in order to perform the reduction at a rate which is acceptable for practical purposes, it must be carried out at temperatures above 300 C.
• this exhibits the drawback that the formed metal particles sinter so that a product is formed which is not or at least less readily suitable as a material for magnetic recording.
• the invention removes the above-mentioned drawback in that the reduction is carried out at a temperature not exceeding 300 C. and at a pressure of the gaseous reduction agent of at least atm. As a result of this a reduction speed is obtained which is acceptable for practical purposes in every respect, while nevertheless the temperature at which the reduction is effected, remains below the level at which the above-mentioned sintering of the formed metal particles begins to occur.
• the reduction may be promoted by withdrawing water which is formed during the reaction from the gas atmosphere and the reaction space. Therefore the reduction is preferably carried out in the presence of a water-binding agent in the reaction space.
• a water-binding agent is, for example,
• EXAMPLE I Two porcelain crucibles were placed in an autoclave, capacity 500 ml. in the lowermost crucible 30 g. of CaO were provided while the uppermost crucible contains 'y-Fe O in the form of accicular particles the largest dimension of which was smaller than 1 micron and a ration (length/thickness) of approximately 5.
• the autoclave was rinsed three times with hydrogen, then filled with the desired quantity of hydrogen, followed by heating at a temperature of maximally 300 C. which temperature was maintained for 4 hours. After cooling, the autoclave was evacuated after which so much ethanol was provided in the crucible containing the formed iron that this iron was entirely immersed. Said crucible was then taken out of the autoclave. The ethanol was decanted from the crucible after which the iron was dried in air.
• the following table A provides a survey of the values measured in the resulting iron powder compositions of the saturation magnetization (o' s), which is to be understood to mean the magnetic moment per kilogram in a field of i0 amp./m. expressed in volt-sec. m./kg. and of the product (p xfli of thema etic permeabil ity, p.,, (i.e. the ratio B/H of the magnettc ux density in volt-seconds per square meter and the magnetic field strength in amp./m, everything in vacuo), and the magnetization coercive force, ,l-h.
• the quantities of iron oxide to be reduced are slightly adapted to the'hydrogen pressure used in that sense that said quantities are larger as the pressure of hydrogen is higher, this with the object of varying the ratio of the quantities of iron oxide and hydrogen not too much.
• EXAMPLE II The performance of the experiments differs from those described in example I only in that in these experiments an iron oxide composition consisting of a--Fe,0;,particles in the form of hexagonal dipyramids having a longitudinal axis of approximately 800 A were used.
• Table B gives a survey of the values measured in the resulting iron powder compositions of the saturation magnetization, 0,, and of the product ,H,.) of the magnetic permeability, n and the magnetiza tion coercive force ,l-l
• a method of preparing iron powder suitable for magnetic recording comprising the step of reducing powdered iron oxide the particles of which have a largest dimension not exceeding in at a temperature not exceeding at 300 C. in hydrogen at a pressure of at least 10 atm.

Landscapes

• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Power Engineering (AREA)
• Hard Magnetic Materials (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Soft Magnetic Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=19802944

Family Applications (1)

Country Status (7)

Cited By (6)

Families Citing this family (2)

Citations (2)

• 1968
  • 1968-03-05 NL NL6803123A patent/NL6803123A/xx unknown
• 1969
  • 1969-02-26 US US802679*A patent/US3607219A/en not_active Expired - Lifetime
  • 1969-02-28 GB GB00765/69A patent/GB1204991A/en not_active Expired
  • 1969-03-03 BE BE729304D patent/BE729304A/xx not_active Expired
  • 1969-03-03 CH CH318569A patent/CH515331A/de not_active IP Right Cessation
  • 1969-03-04 FR FR6905884A patent/FR2003248A1/fr not_active Withdrawn
  • 1969-03-04 AT AT211969A patent/AT306763B/de not_active IP Right Cessation

Patent Citations (2)

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