Oriented strontium ferrites which yield superior ceramic permanent magnets are produced by the four-step process of A. preparing small particles of agglomerated less than 0.1 micron grains of ferric oxide and strontium oxide, B. maintaining the particles of agglomerated oxides at temperatures of from about 800.degree. C to 1100.degree. C for up to about 24 hours to cause the oxides to react (ferritize) and form less than 0.5 micron diameter crystallites of strontium ferrite, C. sintering the crystallites into a solid body either by maintaining them at from 1100.degree. C to 1300.degree. C for not more than two hours, or preferably by maintaining them at from 800.degree. C to 1300.degree. C while applying pressure, and D. hot forging the body by applying pressures of up to about 30,000 psi at temperatures of from 800.degree. C to 1300.degree. C.
This application is a continuation-in-part of application Ser. No. 390,624, filed Aug. 22, 1973, which was a continuation application of Ser. No. 183,838, filed Sept. 27, 1971, now abandoned.
An improved process for forming high quality ferrite magnets utilizes relatively coarsely ground magnetic materials. The process includes pre-milling a blended and calcined magnetic material to about 0.7-1.2 microns, pressing the blend into a preform shape in the presence of an orienting magnetic field, granulating the preformed material, pre-sintering the granules short of complete sintering, milling the granules to a coarse size of about 1-2 microns, forming the milled blend into desired forms in the presence of an orienting magnetic field, sintering the pressed material, and optionally machining the sintered material.
An iron ore or mill scale is crushed to form a powder having an average particle diameter not exceeding 12 microns. The powder is heated at a temperature of 600.degree. C. to 900.degree. C. in the presence of oxygen to form an iron oxide containing at least 98.0% of Fe.sub.2 O.sub.3. The iron oxide is mixed with strontium oxide or carbonate. The mixture is calcined to form strontium ferrite. The calcined product is pulverized, the crushed material is molded in a magnetic field, and the molded product is sintered to yield a magnet of strontium ferrite having a high level of performance.
A method is provided for the treatment of water so as to reduce or destroy micro-organisms therein as well as other causes of skin diseases or waterborne diseases in human beings and animals, wherein the water is passed through a magnetic field being presented by a permanent magnet showing an energy product (BH).sub.max of more than 20 kJ/m.sup.3 to which the water is exposed and a coercive force Hc of more than of about 200 kA/m at 25.degree. C.
A device is provided for the treatment of water so as to reduce or remove micro-organisms therein as well as possible other causes of skin diseases or waterborne diseases in human beings and animals. The device comprises at least one permanent magnet provided with an axially extending opening, said magnet subjecting passing water to a magnetic field and being made of a magnet material presenting an energy product of more than approximately 20 and preferably more than approximately 40 kJ/m.sup.3 and a coercive force of preferably more than approximately 200 kA/m at 25.degree. C., the north pole of said magnet being positioned at one axial end face and the south pole at the opposite axial end face, and where the water is passed through the axially extending opening in the magnet. Moreover, a method of treating the water is provided, whereby the water is allowed to pass said device immediately before or adjacent a tapping point.
A polycrystalline ferromagnetic metal oxide has a density of 97% or more to less than 100%; and a method of manufacturing a polycrystalline ferromagnetic metal comprises a step of treating a polycrystalline ferromagnetic metal oxide under a high pressure reducing gas for high densification.
