A metal particle aggregate includes metal particles and an organic substance. The metal particles include first particles that contain one or both of silver and copper in an amount of 70% by mass or more relative to 100% by mass of all metals and have a particle diameter of 100 nm or more and less than 500 nm at a ratio of 20 to 30% by number, and include second particles that have a particle diameter of 50 nm or more and less than 100 nm, and third particles that have a particle diameter of less than 50 nm at a ratio of 80 to 70% by number in total. Surfaces of the first to third particles are covered with the same protective film.

A new seedless synthesis of anisotropic nanoscale gold nanoflower (AuNF) particles uses bidentate thiolate ligands to protect the nanoparticle surface and a combination of reagents (for example, ligand, ascorbic acid, and hydroxide) to synthesis AuNF with controlled size and anisotropic properties. Compared to prior art gold nanospheres, AuNF produced approximately a 15-fold improvement in a drug delivery assay.

Nano-engineered materials for powder metallurgy and workpieces created using the materials. Workpieces include primary phase powders having nano-engineered partial or complete coatings and/or secondary phases adhered to interfaces of their constituent materials. Nano-engineered coatings are provided for metallic, polymeric and/or ceramic powder metallurgy feedstock powders to produce workpieces with superior performance and/or functional benefits, as are methods of manufacturing injection molding and additive manufacturing feedstock powders containing these coatings and additional respective functional benefits.

The method is: a preparation step in which a magnetic metal source, a nucleating agent, a complexing agent, a reducing agent, and a pH adjusting agent are prepared as starting materials; a crystallization step in which a reaction liquid that includes the starting materials and water is prepared, and a crystallized powder that includes the magnetic metals is made to crystallize in the reaction liquid by a reduction reaction; and a recovery step in which the crystallized powder is recovered from the reaction liquid. The magnetic metal source includes a water-soluble iron salt and a water-soluble nickel salt, the nucleating agent is a water-soluble salt of a metal that is more noble than nickel, and the complexing agent is at least one type of substance selected from the group consisting of a hydroxy carboxylic acid, a salt of a hydroxy carboxylic acid, and a derivative of a hydroxy carboxylic acid.

To provide a fine nickel powder for an internal electrode paste of an electronic component, the nickel powder obtained by a wet method and having high crystallinity, excellent sintering characteristics, and heat-shrinking characteristics. The nickel powder is obtained by precipitating nickel by a reduction reaction in a reaction solution including at least water-soluble nickel salt, salt of metal nobler than nickel, hydrazine as a reducing agent, and alkali metal hydroxide as a pH adjusting agent and water; the reaction solution is prepared by mixing a nickel salt solution including the water-soluble nickel salt and the salt of metal nobler than nickel with a mixed reducing agent solution including hydrazine and alkali metal hydroxide; and the hydrazine is additionally added to the reaction solution after a reduction reaction initiates in the reaction solution.

The present invention provides a method for the manufacture of transition metal oxide fine particles, the method comprising the steps of: heating a strong-alkaline aqueous solution while stirring same; adding to and dissolving in the heated strong-alkaline aqueous solution a transition metal oxide; adding a strong-acid aqueous solution to the strong alkaline aqueous solution in which the transition metal oxide is dissolved, while stirring same, thereby re-dissolving a solid generated at the interface between the strong-alkaline aqueous solution and the strong-acid aqueous solution; adjusting the pH of the mixed aqueous solution resulting from mixing the strong-alkaline aqueous solution and the strong acid aqueous solution, through adjustment of the adding rate and amount of the strong-acid aqueous solution, to precipitate transition metal oxide fine particles; and separating the transition metal oxide fine particles from the mixed aqueous solution and sequentially washing, drying, and thermally treating the separated transition metal oxide fine particles.

There are provided a silver powder, which is able to form an electrically conductive film having a low resistance value even if the period of time for firing an electrically conductive paste is shorter than that for firing conventional electrically conductive pastes when the silver powder is used as the material of the electrically conductive paste, and a method for producing the same. A large-diameter silver powder, which has a crystalline size of 50 nm or less and which has a particle diameter (D.sub.50) of 1 μm or more and 4 μm or less, the particle diameter (D.sub.50) of the large-diameter silver powder being a particle diameter corresponding to 50% of accumulation in a particle size distribution of the large-diameter silver powder, is mixed with a small-diameter silver powder, which has a crystalline size of 50 nm or less and which has a particle diameter (D.sub.50) of 0.3 μm or more and less than 1 μm, the particle diameter (D.sub.50) of the small-diameter silver powder being a particle diameter corresponding to 50% of accumulation in a particle size distribution of the small-diameter silver powder, to produce a silver powder, which has a crystalline size of 50 nm or less and which has a pressed density of 6.3 g/cm.sup.3 or more.

To provide a fine nickel powder for an internal electrode paste of an electronic component, the nickel powder obtained by a wet method and having high crystallinity, excellent sintering characteristics, and heat-shrinking characteristics. The nickel powder is obtained by precipitating nickel by a reduction reaction in a reaction solution including at least water-soluble nickel salt, salt of metal nobler than nickel, hydrazine as a reducing agent, and alkali metal hydroxide as a pH adjusting agent and water; the reaction solution is prepared by mixing a nickel salt solution including the water-soluble nickel salt and the salt of metal nobler than nickel with a mixed reducing agent solution including hydrazine and alkali metal hydroxide; and the hydrazine is additionally added to the reaction solution after a reduction reaction initiates in the reaction solution.

There is provided a spherical silver powder which is capable of being sintered at a lower temperature. The spherical silver powder of spherical silver particles has cavities, each of which is formed in a corresponding one of the spherical silver particles and each of which has a major axis of 100 to 1000 nm and a minor axis of 10 nm or more, the ratio of the major axis to the minor axis (major axis/minor axis) being 5 or more, the major axis being the length of the long side of a rectangle which has a minimum area and which circumscribes the outline of a cross-section of a corresponding one of the cavities on an image of the cross-section of the corresponding one of the silver particles exposed by polishing the surface of a resin after the silver powder is embedded in the resin, and the minor axis being the length of the narrow side of the rectangle.

A method loading powder into a mold can include immersing the mold comprising one or more microchannels into a suspension comprising the powder and a surfactant suspended in a dispersant, wherein the powder comprises particles having an average particle size of less than 100 μm, wherein the mold is substantially entirely covered by the suspension; heating the suspension having the mold immersed therein under a temperature condition suitable to lower the stability of the particles of the powder in the suspension such that the particles settle out of solution and into the one or more microchannels; and applying an ultrasonic wave to the heated suspension to further settle the particles of the powder into the one or more microchannels thereby filling the one or more microchannels of the mold with the powder.