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
  • C04B35/2691—Other ferrites containing alkaline metals
• • 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

Definitions

• the core has an outer diameter not exceeding 0.9 mm. and inner diameter of half the outer diameter. The switching time of the core does not exceed 0.7 pLSCC.
• Our invention relates to an annular magnetic core suited for use as a magnetic memory element, and to a method of manufacturing such a magnetic core. More particularly, our invention relates to a magnetic core consisting essentially of a ferrite having a substantially rectangular hysteresis loop.
• magnetic memory elements are generally used at present in electronic computers. Their suitability for this use is determined by the pulse or dynamic characteristics of such memory elements. In this connection, it is important that there be a marked difference between the maximum value uVl of the undisturbed one-signal and the maximum value dVz of the disturbed zero-signal. (It is known that in a high-grade storage element, the value uVl and the value rVl, that is to say, the maximum value of the disturbed one-signal, differ only slightly.)
• the time interval between the beginning of the control current pulse and the instant at which the output voltage of the one-signal reaches its maximum value must have a substantially constant value within a wide temperature range.
• the starting time is not taken as the beginning of the control current pulse, but at the instant at which the control current reaches a strength of 10% of its maximum value.
• the term peak time (T of a magnetic core is, in this case, to be understood to mean the time interval between the instant at which the control current reaches a strength of 10% of its maximum value and the instant at which the output voltage of the one-signal produced by the particular control current pulse has become a maximum. Obviously this peak time depends upon the rise time (T,) of the control current pulse.
• a further object of our invention is to provide a magnetic memory element having a large difference between the maximum value uVl of the undisturbed one-signal and the maximum value dVz of the disturbed zero-signal.
• a still further object of our invention is to provide a magnetic memory element in which the rise time of a control current pulse is 0.1 microsecond.
• Another object of our invention is to provide a magnetic memory element in which the switching time for a control pulse is less than 0.7 microsecond.
• Still another object of our invention is to provide a magnetic memory element in which the output voltage and the peak time are substantially independent of temperature over a wide temperature range.
• Yet another object of our invention is to provide a method of manufacturing a magnetic memory element having improved pulse characteristics which are substantially constant over a wide temperature range.
• the magnetic memory cores consist essentially of materials having a spinel structure and a composition corresponding substantially to the formula Li Fe O in which x, y and z must satisfy the following conditions: 7.8g(x+3y) 58.0 0.19gx/y5022 3.9gy/zg4.0
• cores preferably should have an outer diameter not exceeding 0.9 mm. and an inner diameter of at least onehalf the outer diameter.
• the cores have to be made in accordance with the method described further on in this specification.
• Such cores exhibit at least the following properties.
• the switching time for such a core does not exceed 0.7 microsecond.
• the value of the quotient uVl/dVz is greater than 4.5 with a disturbance ratio of 0.61.
• the temperature coefiicient for uVl does not exceed 0.7% per C., and the temperature coefficient for T does not-exceed 0.03% per C., both being applicable between 0 and C.
• the temperature coefficient for dVz is negligibly small while that of T, (which is less critical) is about equal to that of T
• a magnetic core can be Li O.5Fe O allowance being made for'the fact that dur- L ing heating a slight amount of lithium may evaporate.
• the prefired initial mixture is finelydivided and pressed into rings of the specified dimensions.
• the resulting product is heated to a temperature between 1275 C. and 1330 C. in air or a mixture of air and oxygen on a supporting surface made of a refractory metal or a refractory metal alloy within a period of time of 90 seconds.
• the latter temperature is maintained for 4 to 12 minutes and subsequently the sintered product is cooled to a temperature between 875 C. and 1030 C. at a rate of most C. per minute.
• the sintered product is th n rapidly cooled by bringing it into contact with air or an air-oxygen mixture at room temperature.
• EXAMPLE I A mixture of 16.7 mol. percent of finely-divided lithium carbonate, Li CO and 83.3 mol. percent of finelydivided iron oxide, Fe O was prefired at a temperature of 550 C. for two hours. After the prefired product had been cooled, it was finely-divided and compressed to form rings. These rings were heated to a temperature of 1300 C. in air on a supporting surface consisting of platinum or a platinum-rhodium alloy in an electric furnace in a period or" time of 60 seconds, held at that temperature for 10 minutes, and then cooled in and together with the furnace to 950 C. in a period of time of minutes. The cores were subsequently taken from the furnace and quenched in contact with air of room temperature.
• the outer diameter of the resulting sintered bodies was 0.820 mm. and their inner diameter 0.500 mm.
• the pulse characteristics are specified in the table following Example III.
• EXAMPLE II A mixture of 16.3 mol. percent of finely-divided lithium carbonate, Li CO and 83.7 mol. percent of finely-divided iron oxide, F6 0 was prefired at 750 C. for two hours. The prefired product was cooled, finely-divided and then compressed to form rings. These rings were heated to a temperature of 1282 C. in air on a supporting surface of platinum or a platinum-rhodium alloy in an electric furnace in a period of time of seconds, held at that temperature for 10 minutes, then cooled to 980 C. in and together with the furnace. Finally, the rings were quenched in contact with air of room temperature.
• the outer diameter and the inner diameter of the resulting sintered bodies were equal to those of the sintered bodies obtained according to Example I.
• the pulse characteristics are specified in the table following Example III.
• EXAMPLE III A mixture of 17.9 mol. percent of finely-divided lithium carbonate, Li CO and 82.1 mol. percent of finely-divided iron oxide, Fe O was prefired at 750 C. for two hours. The prefired product was cooled, finely-divided and then compressed to form rings. These rings were heated to a temperature of 1300 C. in air on a supporting surface of platinum or a platinum-rhodium alloy in an electric furnace of a peroid of time of 45 seconds, held at the said temperature for 10 minutes, then'cooled to 900 C. in and with the aid of the furnace in a period of minutes. Subsequently, the rings were taken from the furnace and quenched in contact with air of room temperature.
• the outer and inner diameters of the resulting sintered bodies were equal to those of the sintered bodies manu- 4 factured according to Example I.
• the pulse characteristics are specified in the following table.
• Example I Example II Example 111 Control current (ma) G50 650 650 T (micro seconds)" 0. 280 0. 310 0. 310 '1, (micro seconds) 0. 1 0. 1 O. 1 '1', (micro scconds) 0. (1'00 0 610 0. 610
• a method of manufacturing an annular magnetic core having an outer diameter not exceeding 0.9 mm., an inner diameter of at least one-half the outer diameter, a switching time not exceeding 0.7 microsecond, a value of the quotient uVl/dVz of 4.5 with a disturbance ratio of 0.61, a temperature coefficient for uVl not exceeding 0.7% per C. and a temperature coefficient for T not exceeding 0.03% per C., both of said temperature coefiicients.
• said core consisting essentially of a material having a composition corresponding to the formula Li Fe O where: (x-t-Sy) is greater than 7.8 and less than 8.0, x/y is greater than 0.19 and less than 0.22, and z is between 3.9 and 4.0 comprising the steps, mixing in finely-divided form about 16 to 18 mol percent of U 0 and about 82 to 84 mol percent of Fe O heating the mixture to a temperature of about 500 C. to 700 C. to prefire the same, finely-dividing the prefired mixture, compressing the finely-divided prefired mixture into annular rings having the specified dimensions, heating the rings to a temperature between about 1275 C. and 1330 C.
• refractory metal support is an alloy of platinum and rhodium.

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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)
• Magnetic Ceramics (AREA)
• Soft Magnetic Materials (AREA)
• Glass Compositions (AREA)
• Compounds Of Iron (AREA)

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Cited By (1)

Citations (3)

• 0
  • NL NL290005D patent/NL290005A/xx unknown
• 1964
  • 1964-03-04 US US349499A patent/US3413228A/en not_active Expired - Lifetime
  • 1964-03-04 DE DE19641471343 patent/DE1471343B2/de active Pending
  • 1964-03-05 DK DK111264AA patent/DK117086B/da unknown
  • 1964-03-05 CH CH287864A patent/CH462337A/de unknown
  • 1964-03-05 AT AT190164A patent/AT242405B/de active
  • 1964-03-06 ES ES0297293A patent/ES297293A1/es not_active Expired
  • 1964-03-09 BE BE644928A patent/BE644928A/xx unknown
  • 1964-12-12 OA OA50834A patent/OA00765A/xx unknown

Patent Citations (3)

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