Patent US4128235A successfully refreshed from Google Patents.
Patent EP0105122A2 successfully refreshed from Google Patents.
EP0105122A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Processes for making ferrite powder and ferrite blocks
Assignee: International Business Machines Corp
•
Filing: 1983-08-02
•
Granted: —
•
Expires: 2003-08-02
Abstract
Abstract Fine ferrite powder is produced by adding an ammonium oxalate solution to a solution containing ferrous ions and divalent metal ions to co-precipitate oxalates. After separating, washing and drying the co-precipitated particles, they are calcined for several hours at a relatively low temperature (eg 200°C) before completing the calcination at a higher temperature (eg 800°C). The particles are then vibro-energy or ball milled and dried. Dense ferrite blocks can be made from the ferrite powder. by pressing the powder into a mold, sintering the molded ferrite and then isostatically pressure compacting it at a temperature of 1200°C and at a pressure of 2.00 x 10 8 Pascals. Dense nickel-zinc ferrite blocks produced in this manner are particularly suitable for the manufacture of magnetic transducer heads.
Inventors
- 👤 Eugene Bertrand Rigby
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 15:31
CPC Classifications
C; C01; C01G; C01G49/00; C01G49/0018; C01G49/0072; C01G49/0036; C01G49/0063; C01G49/009; C01G53/00; C01G53/80; C01G53/82; C04; C04B; C04B35/00; C04B35/01; C04B35/26; C04B35/265; C01P; C01P2002/00; C01P2002/30; C01P2002/32
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
70 words
A process for making ferrite powder comprising adding a precipitating agent to an aqueous solution containing ferrous ions and divalent metal ions to form co-precipitated material, separating the co-precipitated material from the liquid, washing the co-precipitated material to remove contaminants, drying the co-precipitated material, calcining the co-precipitated material and milling the calcined material to form a ferrite powder characterised in that the precipitating agent is a solution of ammonium oxalate.
Claim 2
Dependent Claim
70 words
A process for making ferrite powder comprising adding a precipitating agent to an aqueous solution containing ferrous ions and divalent metal ions to form co-precipitated material, separating the co-precipitated material from the liquid, washing the co-precipitated material to remove contaminants, drying the co-precipitated material, calcining the co-precipitated material and milling the calcined material to form a ferrite powder characterised in that the precipitating agent is a solution of ammonium oxalate.
Claim 3
Dependent Claim
49 words
A process as claimed in claim 1, in which the ammonium oxalate solution is at a temperature of 95°C ± 5°C when it is added to the aqueous solution and the aqueous solution is at a temperature of 50°C 5°C when the ammonium oxalate solution is added to it.
Claim 4
Dependent Claim
51 words
A process as claimed in claim 1 or claim 2, in which the calcining is performed in two stages, the first stage comprising maintaining the co-precipitated material at a temperature of approximately 200°C for several hours and the second stage comprising maintaining the material at a temperature of approximately 800°C .
Claim 5
Dependent Claim
29 words
A process as claimed in any preceding claim, in which the milling of the calcined material is performed using a polyurethane lined vibro-energy mill containing dense zirconium dioxide pellets.
Claim 6
Dependent Claim
27 words
A process as claimed in any preceding claim, in which the aqueous solution contains ions of at least one of the metals Mn, Zn, Ni and Mg.
Claim 7
Dependent Claim
25 words
A process as claimed in claim 5, in which the aqueous solution contains nickel and zinc ions in order to produce a nickel-zinc ferrite powder.
Claim 8
Dependent Claim
22 words
A process as claimed in any preceding claim in which the aqueous solution is formed by dissolving pure metal sulfates in water.
Claim 9
Dependent Claim
29 words
A process as claimed in any preceding claim, in which the co-precipitated material is separated from the liquid by means of a centrifuge and decantation of the supernatant liquid.
Claim 10
Dependent Claim
41 words
A process of making a block of ferrite material comprising isostatically compacting ferrite powder formed by a method as claimed in any preceding claim into a mold at ambient temperature and then pressure compacting the ferrite material at an elevated temperature.
Claim 11
Dependent Claim
44 words
A process as claimed in claim 9, in which the pressure compacting consists of an isostatic process performed at a temperature of approximately 1200°C and at a pressure of 1.93 x 10 8 to 2.00 x 10 8 P ascals (28 to 29 Kpsi).
Claim 12
Dependent Claim
28 words
A process as claimed in claim 9, or claim 10, including sintering the molded ferrite material prior to the step of pressure compacting it at an elevated temperature.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.