The present application provides a 3D printing method. The present application can provide as a method for efficiently performing 3D printing, for example, a 3D printing method capable of more rapidly and efficiently producing a three-dimensional shape precisely realized up to a fine portion.

This silver paste includes a silver powder and a solvent, in which the silver powder includes first silver particles having a particle size of 100 nm or more and less than 500 nm, second silver particles having a particle size of 50 nm or more and less than 100 nm, and third silver particles having a particle size of 1000 nm or more and less than 10000 nm, and the content of the first silver particles is 12% by volume or more and 90% by volume or less, the content of the second silver particles is 1% by volume or more and 38% by volume or less, and the content of the third silver particles is 5% by volume or more and 80% by volume or less, regarding a total amount of the silver powder as 100% by volume.

A method for producing fine copper particles includes producing fine copper particles having a coating film containing cuprous oxide on a surface by heating copper or a copper compound in a reducing flame formed by a burner. The fine copper particles are produced by adjusting a mixing ratio between a combustible gas and a combustion supporting gas which form the reducing flame such that a volume ratio of CO/CO.sub.2 is in a range of 1.5 to 2.4.

There are provided a spherical silver powder which has the same diameter as that of a spherical silver powder produced by a conventional wet reduction method and which can sufficiently sinter the silver particles thereof to cause the silver particles to be adhered to each other at a relatively low temperature to form a conductive film having a low volume resistivity when it is used for a baked type conductive paste, and a method for producing the same. A spherical silver powder, which contains a neutral or basic amino acid having a carbon number of not less than 5 in each of particles thereof and which has an average particle diameter D.sub.50 of 0.2 to 5 μm based on a laser diffraction method, is produced by adding the neutral or basic amino acid having the carbon number of not less than 5 (such as proline, tyrosine, tryptophan, phenylalanine, arginine or histidine) to a water reaction system containing silver ions to mix a reducing agent therewith to deposit silver particles by reduction.

Provided is a method of producing spherical silver powder, which makes it possible to easily produce spherical silver powder having primary particle diameters with less variation than conventional powder and spherical silver powder obtained by the method. The method of producing spherical silver powder includes a reduction precipitation step of precipitating silver particles by reduction by adding a reductant including hydrazine carbonate to an aqueous reaction system containing silver ions.

A tungsten-carbide-based hard material includes the following components: tungsten carbide with an average particle size of 0.1-1.3 μm; 1.0-5.0 wt. % (Co+Ni), with a ratio of Co/(Co+Ni) in wt. % of 0.4≤Co/(Co+Ni)≤0.95; 0.1-1.0 wt. % Cr, with a ratio of Cr to (Co+Ni) in wt. % of 0.05 Cr/(Co+Ni) 0.20; 0.01-0.3 wt. % Mo; and 0.02-0.45 wt. % Me, where Me represents one or more elements from the group Ta, Nb, Hf and Ti, preferably Ta and/or Nb; and wherein 0.01≤Me/(Co+Ni)≤0.13.

A copper paste for joining contains metal particles and a dispersion medium, in which the copper paste for joining contains copper particles as the metal particles, and the copper paste for joining contains dihydroterpineol as the dispersion medium. A method for manufacturing a joined body is a method for manufacturing a joined body which includes a first member, a second member, and a joining portion that joins the first member and the second member, the method including: a first step of printing the above-described copper paste for joining to at least one joining surface of the first member and the second member to prepare a laminate having a laminate structure in which the first member, the copper paste for joining, and the second member are laminated in this order; and a second step of sintering the copper paste for joining of the laminate.

To provide novel low-temperature sinterable copper particles that can be sintered even at a low temperature of, for example, around 100° C. or less, and a method for producing a sintered body by using the same. The low-temperature sinterable copper particles according to the present invention are coated with a carboxylic acid, and a surface of the copper particle is oxidized so as to have a cuprous oxide fraction (Cu.sub.2O/(Cu+Cu.sub.2O)) in the copper particle of 4% by mass or less or so as to have an average coating thickness of cuprous oxide of 10 nm or less. The low-temperature sinterable copper particles are subjected to low-temperature firing in an atmosphere of 0.01 Pa or less.

A method for synthesis of nanoparticles are described. The method includes dispersing metal oxide powder in a mixture of a base liquid and a surfactant to form a primary mixture, grinding the primary mixture using a grinding media by periodically adding a surfactant solution to form a slurry, extracting a predetermined amount of sample from the slurry at periodic time intervals to obtain a testing solution to assess particle size of in the slurry using a particle size analyzer; and systematically adding the surfactant solution and the grinding media to the slurry based on the assessed particle size in the testing solution until a mean particle size of the nanoparticles is achieved.

Provided herein are methods of preparing three-dimensional photonic crystals having tunable optical properties and control over stopband location and width, the three-dimensional photonic crystals comprising nanoparticles and spacer groups.