Abstract: Iron particles for purifying soil or ground water of the present invention comprise a mixed phase of ?-Fe phase and Fe3O4 phase, and having a BET specific surface area of 5 to 60 m2/g, an Fe content of not less than 75% by weight based on the weight of the iron particles and a sulfur content of not less than 1,000 ppm. The iron particles are capable of decomposing or insolubilizing harmful substances such as organohalogen compounds and/or heavy metals, cyanogen, etc. contained in the soil or ground water in efficient, continuous and economical manners.

Abstract: Iron composite particles for purifying soil or ground water, comprise ?-Fe and magnetite, and having a ratio of a diffraction intensity D110 of (110) plane of ?-Fe to a sum of a diffraction intensity D311 of (311) plane of magnetite and the diffraction intensity D110 (D110/(D311+D110)) of 0.30 to 0.95 as measured from X-ray diffraction spectrum of the iron composite particles, an Al content of 0.10 to 1.50% by weight and an S content of 3500 to 7000 ppm; a process for producing the iron composite particles; a purifying agent containing the iron composite particles; a process for producing the purifying agent; and a method for purifying soil or ground water.

Abstract: A purifying agent for purifying soil or ground water which comprises a water suspension containing iron composite particles comprising ?-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 ?m, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight, and polyaspartic acid or a salt thereof. The purifying agent is capable of decomposing aliphatic organohalogen compounds or aromatic organohalogen compounds contained in the soil or ground water in an efficient, continuous and economical manner.

Abstract: Iron composite particles for purifying soil or ground water, comprise an iron component, at least one noble metal selected from the group consisting of ruthenium, rhodium and palladium, and carbon or aluminum, and having a noble metal content of 0.01 to 5.00% by weight and a particle diameter of 0.01 to 1.0 ?m. The iron composite particles and the purifying agent according to the present invention are capable of decomposing aliphatic organohalogen compounds such as dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1-dichloroethylene, cis-1,2-dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, tetrachloroethylene, 1,3-dichloropropene or the like, and aromatic organohalogen compounds such as dioxins, PCB (polychlorinated biphenyl) or the like, which are contained in soil, ground water or waste water, at ordinary temperature in an efficient and economical manner.

Abstract: A purifying agent for purifying soil or ground water of the present invention comprises a water suspension containing iron composite particles comprising ?-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 ?m, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight, and at least one additive selected from the group consisting of polymaleic acid, salts of polymaleic acid, sodium hydrogencarbonate and sodium sulfate. The purifying agent of the present invention is capable of decomposing aliphatic organohalogen compounds or aromatic organohalogen compounds contained in soil or ground water in an efficient, continuous and economical manner.

Abstract: Iron particles for purifying soil or ground water of the present invention comprise a mixed phase of ?-Fe phase and Fe3O4 phase, and having a BET specific surface area of 5 to 60 m2/g, an Fe content of not less than 75% by weight based on the weight of the iron particles and a sulfur content of not less than 1,000 ppm. The iron particles are capable of decomposing or insolubilizing harmful substances such as organohalogen compounds and/or heavy metals, cyanogen, etc. contained in the soil or ground water in efficient, continuous and economical manners.

Abstract: The present invention relates to spindle-shaped goethite particles having an average major axial diameter of 0.05 to 0.18 &mgr;m, spindle-shaped hematite particles having an average major axial diameter of 0.05 to 0.17 &mgr;m, spindle-shaped magnetic metal particles containing iron as a main component, which exhibit an adequate coercive force, good dispersibility, good oxidation stability and excellent coercive force distribution notwithstanding the average major axial diameter thereof is as small as 0.05 to 0.15 &mgr;m, and processes for producing the respective particles. Especially, the spindle-shaped magnetic metal particles containing iron as a main component, have an average major axial diameter of 0.05 to 0.15 &mgr;m, an aspect ratio of from 5:1 to 9:1, a size distribution (standard deviation/average major axial diameter) of not more than 0.30, a crystallite size D110 of 130 to 160 Å, a Co content of from 0.

Abstract: Secondary agglomerates of magnetic metal particles for magnetic recording, have a sodium content of not more than 20 ppm and a calcium content of not more than 40 ppm, an average particle diameter of 300 to 800 &mgr;m and an upper limit of particle diameters of 2,000 &mgr;m, and comprise magnetic metal primary particles having an average major axis diameter of 0.05 to 0.25 &mgr;m.

Abstract: Secondary agglomerates of magnetic metal particles containing primary particles having an average major axial diameter of 0.05 to 0.25 &mgr;m, said secondary agglomerates having an average particle diameter of 300 to 800 &mgr;m, an upper limit of particle diameter of 2,000 &mgr;m and a repose angle of 38 to 45°. The secondary agglomerates exhibit not only excellent handing property due to high storage efficiency, high transport efficiency and good flowability thereof, but also excellent kneading property when kneaded with various binder resins and organic solvents in a kneader, and excellent dilution-dispersibility when diluted with an additional amount of the organic solvent, upon the production of coating-type magnetic recording media, so as to more improve a surface smoothness and squareness of a magnetic coating film obtained therefrom, and a process for producing such secondary agglomerates of magnetic metal particles for magnetic recording.

Abstract: Iron particles for purifying soil or ground water of the present invention comprise a mixed phase of &agr;-Fe phase and Fe3O4 phase, and having a BET specific surface area of 5 to 60 m2/g, an Fe content of not less than 75% by weight based on the weight of the iron particles and a sulfur content of not less than 1,000 ppm. The iron particles are capable of decomposing or insolubilizing harmful substances such as organohalogen compounds and/or heavy metals, cyanogen, etc. contained in the soil or ground water in efficient, continuous and economical manners.

Abstract: Spindle-shaped magnetic metal particles containing iron as a main component of the present invention, have an average major axis diameter (L) of 0.05 to 0.15 &mgr;m; a coercive force of 111.4 to 143.2 kA/m; a Co content of from 0.5 to less than 5 atm % based on whole Fe; a crystallite size of from 150 to less than 170 Å; a ratio of Al to Co from 1.0:1 to less than 2.0:1; a specific surface area (S) represented by the formula: S≦−160×L+65; an oxidation stability (&Dgr;&sgr;s) of saturation magnetization of not more than 5.0%; and an ignition temperature of not less than 140° C. The spindle-shaped magnetic metal particles containing iron as a main component, exhibit an adequate coercive force, and are excellent in dispersibility, oxidation stability and coercive force distribution despite fine particles, especially notwithstanding the particles have an average major axis diameter as small as 0.05 to 0.15 &mgr;m.

Abstract: Spindle-shaped magnetic metal particles containing iron as a main component of the present invention, have an average major axis diameter (L) of 0.05 to 0.15 &mgr;m; a coercive force of 111.4 to 143.2 kA/m; a Co content of from 0.5 to less than 5 atm % based on whole Fe; a crystallite size of from 150 to less than 170 Å; a ratio of Al to Co from 1.0:1 to less than 2.

Abstract: Spindle-shaped magnetic metal particles containing iron as a main component, having an average major axis diameter (L) of 0.05 to 0.15 &mgr;m; a coercive force of 111.4 to 159.2 kA/m; a Co content of from 5 to less than 15 atm % based on whole Fe; a crystallite size of from 150 to less than 170 Å; a ratio of Al to Co from 0.3:1 to less than 2.0:1; a specific surface area (S) represented by the formula: S≦−160×L+65; an oxidation stability (&Dgr;&sgr;s) of saturation magnetization of not more than 4.5%; and an ignition temperature of not less than 145° C. The spindle-shaped magnetic metal particles containing iron as a main component, exhibit an adequate coercive force, and are excellent in dispersibility, oxidation stability and coercive force distribution despite fine particles, especially notwithstanding the particles have an average major axis diameter as small as 0.05 to 0.15 &mgr;m.

Abstract: Secondary agglomerates of magnetic metal particles for magnetic recording, have a sodium content of not more than 20 ppm and a calcium content of not more than 40 ppm, an average particle diameter of 300 to 800 &mgr;m and an upper limit of particle diameters of 2,000 &mgr;m, and comprise magnetic metal primary particles having an average major axis diameter of 0.05 to 0.25 &mgr;m.

Abstract: Spindle-shaped goethite particles are disclosed, which contain not less than 0.5 and less than 8 atom % of Co based on the total Fe and 5 to 10 atom % of Al based on the total Fe, and have an average major axis diameter of 0.18 to 0.30 &mgr;m, a size distribution (standard deviation/major axis diameter) of not more than 0.22, an average minor axis diameter of 0.025 to 0.045 &mgr;m and an average aspect ratio is 5 to 10. Spindle-shaped hematite particles and spindle-shaped magnetic iron-based alloy particles are also disclosed, which are produced from the above goethite particles. The spindle-shaped goethite particles of the present invention provide spindle-shaped magnetic iron-based alloy particles which are excellent in dispersibility (high squareness and high orientation), excellent both in weatherability and in coercive force distribution, and are useful as household DAT, 8 mm, Hi-8 tapes, VTR tapes for business purposes, computer tapes or floppy disks.

Abstract: The present invention relates to spindle-shaped goethite particles having an average major axial diameter of 0.05 to 0.18 &mgr;m, spindle-shaped hematite particles having an average major axial diameter of 0.05 to 0.17 &mgr;m, spindle-shaped magnetic metal particles containing iron as a main component, which exhibit an adequate coercive force, good dispersibility, good oxidation stability and excellent coercive force distribution notwithstanding the average major axial diameter thereof is as small as 0.05 to 0.15 &mgr;m, and processes for producing the respective particles. Especially, the spindle-shaped magnetic metal particles containing iron as a main component, have an average major axial diameter of 0.05 to 0.15 &mgr;m, an aspect ratio of from 5:1 to 9:1, a size distribution (standard deviation/average major axial diameter) of not more than 0.30, a crystallite size D110 of 130 to 160 Å, a Co content of from 0.

Abstract: Secondary agglomerates of magnetic metal particles containing primary particles having an average major axial diameter of 0.05 to 0.25 &mgr;m, said secondary agglomerates having an average particle diameter of 300 to 800 &mgr;m, an upper limit of particle diameter of 2,000 &mgr;m and a repose angle of 38 to 45°. The secondary agglomerates exhibit not only excellent handing property due to high storage efficiency, high transport efficiency and good flowability thereof, but also excellent kneading property when kneaded with various binder resins and organic solvents in a kneader, and excellent dilution-dispersibility when diluted with an additional amount of the organic solvent, upon the production of coating-type magnetic recording media, so as to more improve a surface smoothness and squareness of a magnetic coating film obtained therefrom, and a process for producing such secondary agglomerates of magnetic metal particles for magnetic recording.

Abstract: Disclosed herein are granulated particles for magnetic particles for magnetic recording, comprising: acicular ferric hydroxide oxide particles or acicular iron oxide particles; and at least one selected from the group consisting of semisynthetic starch and semisynthetic cellulose and having a bulk density of not less than 0.3 g/cm.sup.3 and a powdering ratio of not more than 40%, and a process for producing the granulated particles, and magnetic particles obtained from such granulated particles.