Toda Kogyo Corporation

Nippon Electric Co., Ltd.

Masao Kiyama

Toshio Takada

Norimichi Nagai

Nanao Horiishi

Yasutaka Ota

Katsunori Fujimoto

Norio Sugita

Akihiko Hirayama

Tsutomu Katamoto

Keizo Iwase

Masatomo Yonezawa

Tomeji Ohno

Tokihiro Kurata

Nanao Hiriishi

Toshikazu Akita

Disclosed herein are plate-like hematite particles having an average particle diameter of 0.5 to 5.0 .mu.m, a lamellar thickness of 50 to 500.ANG. and a plate ratio (the ratio of the average particle diameter to the lamellar thickness) of 50:1 to 500:1, an iron oxide pigment showing a golden color and comprising the plate-like hematite particles, and a process for producing the plate-like hematite particles.

Plate-like hematite particles, a pigment comprising the same and showing

Disclosed herein are plate-like barium ferrite particles with a solid solution of zinc on the surface thereof, which have an average particle diameter of not less than 0.03 .mu.m and less than 0.1 .mu.m, a BET specific surface are of 55 to 80 m.sup.2 /g, a coercive force of 300 to 1,500 Oe and a magnetization of not less than 57 emu/g, preferably not less than 60 emu/g, in magnetic field of 10 KOe, and which are represented by the following formula (I):

Plate-like barium ferrite particles suitable for use in magnetic

Disclosed herein are plate-like barium ferrite particles with a solid solution of zinc on the surface thereof, which have an average particle diameter of 0.05 to 0.3 .mu.m, a coercive force of 300 to 1,500 Oe and a magnetization of not less than 55 emu/g in magnetic field of 10 KOe, and which are represented by the following formula (I):

Disclosed herein are Ba-containing plate-like magnetoplumbite type ferrite particles for magnetic recording containing ions of one metal (II) selected from Ni and Zn and ions of one metal (IV) selected from Ti, Sn and Zr, and having zinc incorporated as a solid solution close to the particle surface and the change of coercive force of said particles at a temperature of -20.degree. to 120.degree. C. in the range of -0.5 to +0.5 Oe/.degree.C., and a process for producing the same.

Plate-like magnetoplumbite ferrite particles for magnetic recording and

Disclosed herein are plate-like barium particles which are suitable for use in precursor of sintered magnets and magnetic recording media, which have an average particle diameter of not less than 0.03 .mu.m and less than 0.1 .mu.m, and which are represented by the following formula (I):

Process for producing plate-like barium ferrite particles

Disclosed herein are hexagonal plate-like barium ferrite particles for magnetic recording, represented by the formula: BaFe.sub.12-x-y M.sub.x Ti.sub.y O.sub.19 wherein x and y are independently 0.6 to 1.2 and M is Co(II) or Co(II) and a divalent metal other than Co, having the width of the particle of 0.1 to 0.4 micrometer and a BET specific surface area (S) of 20 to 50 m.sup.2 /g, and showing a magnetization (M) of larger than 40 emu/g in a magnetic field of 10 KOe and a coercive force (Hc) of 500 to 1000 Oe, and a process for producing the same.

Hexagonal plate-like barium ferrite particles for magnetic recording and

Disclosed herein are plate-like barium ferrite particles having BET specific surface area of 20 to 70 m.sup.2 /g and average particle diameter of 0.05 to 0.3 .mu.m, and showing a magnetization of higher than 30 emu/g in a field of 10 kOe and coercive force of 300 to 1,000 Oe, represented by the formula BaCo.sub.x Ti.sub.x Fe.sub.12-2x O.sub.19 wherein x is 0.1 to 0.5, and a process for producing the same.

Plate-like barium ferrite particles for magnetic recording and process

Disclosed herein are plate-like barium ferrite particles for magnetic recording, comprising plate-like particles represented by the formula:

Disclosed herein is a process for producing the plate-like barium ferrite particles represented by the formula (I):

Process for production of plate-like barium ferrite particles for

Disclosed herein are the plate-like barium ferrite particles for use in magnetic recording, showing a specific surface area of 11 to 50 m.sup.2 /g, a value of magnetization of higher than 25 emu/g in a magnetic field of 10 KOe and a coercive force of 600 to 1100 Oe, and a process for producing the same.

Plate-like barium ferrite particles for use in magnetic recording and

Barium ferrite particles of a coercive force of not more than 1,000 Oe suitable for use as a magnetic material for magnetic recording and a process for producing said particles are disclosed herein.

Barium ferrite particles and process for producing said particles

Disclosed herein is a process for producing plate-like barium ferrite particles for magnetic recording, represented by the formula:

Process for producing plate-like barium ferrite particles for magnetic

On disposing of an acidic aqueous waste including ferrous ions, the ferrous ions are oxidized to produce iron compound precipitate in a remaining waste liquid. With the temperature of the waste kept between 50.degree. C and 75.degree. C and with pH of the waste liquid adjusted between 3.5 and 5.2, fine particles of the iron compound otherwise produced agglomerate into large polycrystalline particles. The large particles are readily separated from the waste liquid, which is now substantially neutral and transparent.

Method of disposing of a ferrous-ion containing acidic aqueous waste by

Fine crystalline powder, from 0.02 to 0.2 micron in average particle size, of a composition Pb(Zr.Ti)O.sub.3. Parts of Zr and Ti of the composition may be substituted for with Mn and Sb, Nb, and/or Ta. The powder is produced by preparing an acidic aqueous solution of the constituent metallic ions, neutralizing the solution to provide a suspension of hydroxides of the metals, and subjecting the suspension to hydrothermal reaction at 150.degree.-300.degree.C. The powder provides piezoelectric ceramics of a high sintered density without resorting to hot pressing.

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Kyoto, Japan

Masao Kiyama