Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
  • C04B35/265—Compositions containing one or more ferrites of the group comprising manganese or zinc and one or more ferrites of the group comprising nickel, copper or cobalt

Definitions

• the present invention therefore relates to annular magnetic cores having an external diameter less than 0.9 mm., an internal diameter of at least half the external diameter and a height of 0.2 mm. to 0.3 mm.
• the invention more particularly relates to preparing ferrite cores having properties which make them especially suitable for use in large memories.
• large memory is to be understood. herein to mean a memory including at least 1 million of cores, which operate in accordance with a so-called word-organized system in which the information can be Written in coincidence, but in which reading is effected with the aid of one pulse on a given line. Hitherto so-called drum memories have been used for this purpose, but these are roughly slower by a factor of 100 with respect to core memories.
• the memory cores In order to reduce the cost of the equipment as far as possible, it is necessary in order to control the memory to use switching cores which in turn are controlled by inexpensive transistors. As a result thereof, the control current for the present memory cores is in practice substantially limited to a maximum of approximately 200 mamps. In order that under these conditions, it is still possible to observe a distinct difference between the above-mentioned l-signal and the above-mentioned O-signal, without the use of very expensive reading amplifiers, the memory cores must satisfy the additional requirement that the output voltage of the l-signal is at least 18 mvolts.
• the present invention provides a method for making a new class of ferrite cores which are distinguished by very low costs of production and which also fulfills the following conditions:
• rise time T is to be understood herein to mean the time interval between the instants when the control current attains a value of 10% and 90% respectively of its maximum strength. During this time interval, the strength of the control current increases approximately in a linear relationship with time.
• the magnetic cores according to the invention may be manufactured as follows:
• An initial mixture consisting of finely divided oxides of iron, manganese, copper and zinc (which oxides may each be replaced wholly or partly by an equivalent amount of one or more compounds of the same metal which can change to the respective oxides upon heating and in which the relative amounts of iron (calculated as Fe O manganese (calculated as MnO), copper (calculated as CuO), and'zinc (calculated as ZnO) are:
• Mol. percent is presintered by heating to a temperature between 600 C. and 700 C.
• the presintered product is subsequently pulverized and then granulated with the aid of an or-' ganic binder. From the granulate a fraction of a grain size between 50 and 120 microns is then separated by sieving. This fraction is compacted to form rings which are heated to a temperature between 1350 C. and 1370 C. within a time period of 60 seconds either in air, or in a mixture of air and oxygen on a substrate of a refractory metal or a refractory metal alloy (for example platinum, rhodium, iridium or an alloy of at least two such metals). The rings thus heated are subsequently cooled down to a temperature between 930 C. and 975 C. at a rate of at most 30 C./min. and eventually quenched in contact with air at room temperature.
• a refractory metal or a refractory metal alloy for example platinum, rho
• Example A finely divided mixture consisting of 5 mol. percent of CuO, 5 mol. percent of ZnO, 55 mol. percent of MnO and 40 mol. percent of l e- 0 was presintered at a temperature of 625 C. for 2 hours and then cooled down and pulverized. 100 gms. of the powder were stirred in a mortar containing 55 cos. of 6% solution of polyvinyl alcohol in water to form a paste. This paste was dried at 80 C. up to a weight of 110 to 118 gms. The dry mass thus obtained was pulverized and sieved through various sieves having steadily decreasing sizes of mesh, namely, 600, 200, 100 and microns.
• the fraction 100 to 75 microns was dried at C. for 16 hours and subsequently sieved on two sieves having mesh sizes of microns and 75 microns respectively.
• the material passed through the final sieves was molded into rings at a molding density of about 2.7 gms./ccm.
• the rings had an external diameter of 0.97 mm. an internal diameter of 0.61 mm. and a height of 0.3 mm.
• the rings were heated in air and on a sintering substrate consisting of a platinum-rhodium alloy as follows: They were introduced into the oven at a rate such as to reach the hottest zone of the oven within 45 seconds. The temperature in this Zone was 1365 C.
• a control current of 190 mamps was used for measuring the pulse characteristics.
• the disturbance ratio was 0.55
• the measuring temperature was 40 C.
• the rise time T was 0.2 microsecond. The results measured were as follows:
• the measuring conditions were the same as those previously mentioned.
• the results measured were found to be:
• a method of manufacturing an annular magnetic core having an external diameter less than 0.9 mm., an internal diameter of at least half the external diameter, and a height of 0.2 to 0.3 mm., a value of uVl l8 rnv. and a value of the quotient uV1/dVz 5 at a disturbance ratio of 0.55 and a rise time (T) of 0.2 microsecond comprising the steps of forming a finely-divided mixture of about 39 to 41 mol. percent of Fe O about 49 to 51 mol. percent of MnO, about 4 to 6 mol. percent of CuO, and about 4 to 6 mol. percent of ZnO, heating said mixture to a temperature between about 600 C.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Soft Magnetic Materials (AREA)
• Magnetic Ceramics (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

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Family Applications (1)

Country Status (12)

Citations (3)

• 1964
  • 1964-03-28 NL NL6403377A patent/NL6403377A/xx unknown
• 1965
  • 1965-03-24 DE DE19651646767 patent/DE1646767A1/de active Pending
  • 1965-03-24 US US442536A patent/US3372216A/en not_active Expired - Lifetime
  • 1965-03-25 AT AT272665A patent/AT250071B/de active
  • 1965-03-25 GB GB12697/65A patent/GB1094527A/en not_active Expired
  • 1965-03-25 NO NO157393A patent/NO119648B/no unknown
  • 1965-03-25 SE SE3910/65A patent/SE304792B/xx unknown
  • 1965-03-25 CH CH416565A patent/CH465727A/de unknown
  • 1965-03-25 DK DK155365AA patent/DK116806B/da unknown
  • 1965-03-26 BE BE661714A patent/BE661714A/xx unknown
  • 1965-03-26 ES ES0311036A patent/ES311036A1/es not_active Expired
  • 1965-03-27 FR FR10979A patent/FR1432037A/fr not_active Expired

Patent Citations (3)

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