Provided is a powder for annealing separator that is used for a grain-oriented electrical steel sheet and enables obtainment of a grain-oriented electrical steel sheet having excellent magnetic properties as a result of favorable purification of impurities in steel. The powder for annealing separator contains magnesium oxide as a main component, and has a nitrogen gas permeability of 0.020 cm/s or more and 0.50 cm/s or less in a state of being applied between coiled steel sheets before start of secondary recrystallization.

The invention provides a process for manufacturing ceramics and refractories comprising the steps of producing a porous powder comprising nanograin sized particles wherein the particles have a Young’s modulus value that is smaller in value compared to the same crystalline material; compacting and processing the powder such that the powder forms a stable homogeneous composite; and sintering the composite for a time and temperature to lead to uniform shrinkage of the composite to make a dense homogenous material.

A magnesium oxide powder, including a specific magnesium oxide particle, can suppress an increase in viscosity when a resin is filled therewith and can realize high thermal conduction of a resin composition including the resin, and a filler composition, a resin composition, and a heat dissipation part including the magnesium oxide powder. The magnesium oxide powder includes a magnesium oxide particle, wherein an oil absorption of the magnesium oxide particle in the case of linseed oil measured according to JIS K 5101-13-1 is 2.5 mL/10 g or less.

The purpose of the present invention is to provide: spherical magnesium oxide having high sphericity, exceptional moisture resistance, and exceptional fluidity in a resin composition when a resin is filled therewith. The present invention is a spherical magnesium oxide characterized by containing 300-2000 ppm of boron, by the content of lithium being less than 15 ppm, and by the sphericity read from an SEM photograph in a volume-based cumulative 50% particle diameter (D50) range of 3-200 μm by laser diffraction scattering particle size distribution measurement being 1.00-1.20.

The purpose of the present invention is to provide: spherical magnesium oxide having high sphericity, exceptional moisture resistance, and exceptional fluidity in a resin composition when a resin is filled therewith. The present invention is a spherical magnesium oxide characterized by containing 300-2000 ppm of boron, by the content of lithium being less than 15 ppm, and by the sphericity read from an SEM photograph in a volume-based cumulative 50% particle diameter (D50) range of 3-200 μm by laser diffraction scattering particle size distribution measurement being 1.00-1.20.

The objective of the present invention is to provide: a spherical magnesium oxide which has high sphericity and excellent moisture resistance, and has excellent fluidity by which a resin composition exhibits excellent fluidity when filled in a resin; and a method for producing the same. The present invention is a spherical magnesium oxide characterized in that: 10-2000 ppm of boron is contained; the total content of silicon and phosphorus is 300-4000 ppm; and the sphericity that can be read from the SEM photograph is 1.00-1.10, when the volume-based cumulative 50% particle diameter (D50) measured by means of a laser diffraction scattering particle size distribution measurement, is in the range of 3-200 μm.

The objective of the present invention is to provide: a spherical magnesium oxide which has high sphericity and excellent moisture resistance, and has excellent fluidity by which a resin composition exhibits excellent fluidity when filled in a resin; and a method for producing the same. The present invention is a spherical magnesium oxide characterized in that: 10-2000 ppm of boron is contained; the total content of silicon and phosphorus is 300-4000 ppm; and the sphericity that can be read from the SEM photograph is 1.00-1.10, when the volume-based cumulative 50% particle diameter (D50) measured by means of a laser diffraction scattering particle size distribution measurement, is in the range of 3-200 μm.

A process and apparatus for manufacture of biocide products are described. The biocide properties arise from the caustic calcined powder, from carbonates such as such as magnesite and dolomite, and from hydroxides such as brucite. The method of manufacture is based on the production of high surface area oxide particles using an indirectly heated counterflow reactors for specifically calcining the carbonates and the hydroxides without significant sintering. The biocide products may be a powder or a hydrated slurry. A hydrated slurry is preferred for agricultural applications as a spray. For aquaculture applications, the products have a preferred particle size distribution to impact the aquatic and benthic ecosystems, and a Ca/Mg ratio that promotes the growth of the cultivates species when applied as a powder or a slurry. For applications such as a marine paint, the powder product or the slurry product is mixed with various agents to form a setting coating, and is applied to the infrastructure that is otherwise subject to biofilm growth.

A process and apparatus for manufacture of biocide products are described. The biocide properties arise from the caustic calcined powder, from carbonates such as such as magnesite and dolomite, and from hydroxides such as brucite. The method of manufacture is based on the production of high surface area oxide particles using an indirectly heated counterflow reactors for specifically calcining the carbonates and the hydroxides without significant sintering. The biocide products may be a powder or a hydrated slurry. A hydrated slurry is preferred for agricultural applications as a spray. For aquaculture applications, the products have a preferred particle size distribution to impact the aquatic and benthic ecosystems, and a Ca/Mg ratio that promotes the growth of the cultivates species when applied as a powder or a slurry. For applications such as a marine paint, the powder product or the slurry product is mixed with various agents to form a setting coating, and is applied to the infrastructure that is otherwise subject to biofilm growth.

The invention is referred to chemical technology, namely to active high-purity magnesium oxide and its production method.

Active high-purity magnesium oxide, including the surface treated one, has BET specific surface area from 70 to 200 m.sup.2/g, average particle size (d50) determined by laser diffraction method not more than 10 microns, iodine activity in the range from 70 to 200 mg J/g MgO, citric activity not more than 40 s, pore volume in the range from 3.2×10.sup.−2 cm.sup.3/g to 10.2×10.sup.−2 cm.sup.3/g, diameter of 10% of the particles not more than 2 microns, diameter of 90% of the particles not more than 30 microns, mass fraction of residue on the 150 micron sieve not more than 1%, mass fraction of residue on the 45 micron sieve not more than 2%, mass fraction of chlorides not more than 0.1%, mass fraction of calcium not more than 0.1%, mass fraction of substances insoluble in hydrochloric acid not more than 0.05%, mass fraction of iron not more than 0.005%, mass fraction of impurities of each of Ti, Co, Mo, V, Sb, Ba cations not more than 1 ppm, Pb, Cd, As, Hg not more than 0.1 ppm.

Method for the production of active high-purity magnesium oxide including the surface treated one consists of calcination of magnesium hydroxide obtained by interaction of magnesium salt solution with alkaline agent. Magnesium hydroxide crystals are produced by continuous method in divided and isolated between each other zones in the presence of seed crystals of magnesium hydroxide and liquid oil products with mole ratio of ions of alkaline agent and magnesium chloride OH.sup.−/Mg.sup.++ within the range (1.9÷2.1):1, with the temperature in all zones not less than 40° C. and magnesium hydroxide crystals suspension residence time in each isolated zone not less than 20 minutes.

Active high-purity magnesium oxide produced by this method has high activity and high chemical purity that allows to use it as a filler for rubbers, adhesives, plastics, polymers, as stabilizers in production of chloroprene rubbers, refining additives of organic solvents, in production of catalysts, special ceramics, special glass, in pharmaceutical, pharmacopoeial and food industries, in production of magnesia cement and other magnesium-containing materials.