A thick-film copper paste is made. A displacement reaction with low cost is used to precipitate nano-silver (Ag) to be grown on copper particles. Thus, the thick-film copper paste is made of the copper powder coated with nano-Ag. The paste can be sintered in the air and is increased in overall electrical conductivity. The copper inside is not oxidized. Its resistance on electromigration is good. Furthermore, the paste can be added with frit as a sintering aid to assist sintering the nano-Ag-coated copper paste. Furthermore, even in a high-temperature heat treatment, the powder of nano-Ag-coated copper is still antioxidant and can replace the silver paste used in the current market.

Frangible firearm projectiles, firearm cartridges containing the same, and methods for forming the same. The firearm projectiles are formed from a compacted mixture of metal powders that includes zinc and iron powders and which may include an anti-sparking agent. The compacted mixture is heat treated for a time sufficient to form a plurality of discrete alloy domains within the compacted mixture. The frangible firearm projectile may be formed by a mechanism that includes vapor-phase diffusion bonding and oxidation of the metal powders and that does not include forming a liquid phase of any of the metal powders or utilizing a polymeric binder. A majority component of the frangible firearm projectile may be iron. One or more of zinc, bismuth, tin, copper, nickel, tungsten, boron, and/or alloys thereof may form a minority component of the frangible firearm projectile. The anti-sparking agent may include a borate, such as boric acid.

Frangible firearm projectiles, firearm cartridges containing the same, and methods for forming the same. The firearm projectiles are formed from a compacted mixture of metal powders that includes zinc and iron powders and which may include an anti-sparking agent. The compacted mixture is heat treated for a time sufficient to form a plurality of discrete alloy domains within the compacted mixture. The frangible firearm projectile may be formed by a mechanism that includes vapor-phase diffusion bonding and oxidation of the metal powders and that does not include forming a liquid phase of any of the metal powders or utilizing a polymeric binder. A majority component of the frangible firearm projectile may be iron. One or more of zinc, bismuth, tin, copper, nickel, tungsten, boron, and/or alloys thereof may form a minority component of the frangible firearm projectile. The anti-sparking agent may include a borate, such as boric acid.

A method of sintering electrically conducting powders in an air atmosphere for obtaining a sintered product includes the following step sequence: placing the powders in an electrically isolating mold, applying a pressure to the powders between 100 and 500 MPa, and applying to the powders a sintering current at a sintering voltage during a sintering time, for sintering the powders. Before applying the sintering current density to the powders, an activation current density is lower than the sintering current density at an activation voltage greater than the sintering voltage during an activation time lower than the sintering time, to reduce the electrical resistance of the powders.

A method of printing a three dimensional article (201) can include forming a bottom layer of the three dimensional article (201) by spraying a dry build material powder (210) onto a build platform (230) while heating the dry build material powder (210). The dry build material powder (210) can include metal or ceramic particles mixed with a polymeric binder having a softening point temperature. The dry build material powder (210) can be heated to a temperature above the softening point temperature such that the dry build material powder (210) adheres to the build platform (230). Subsequent layers can be formed by spraying dry build material powder (210) onto a lower layer while heating the dry build material powder (210) such that the dry build material powder (210) adheres to the lower layer.

Process for manufacturing a copper part comprising at least the following successive steps: shaping a part by stereolithography, the shaping being carried out by: forming a layer of paste comprising a powder of copper particles, one or more photopolymerizable precursors of a first resin, a photoinitiator and, optionally, an optical additive, photopolymerizing the photopolymerizable precursor(s) of the first resin, the steps and forming a cycle that can be repeated a plurality of times, carrying out a first heat treatment, under an oxidizing atmosphere containing at least 10 vol % of an oxidizer, such as dioxygen, at a first temperature Td so as to eliminate the first resin, and carrying out a second heat treatment, under a reducing atmosphere, at a second temperature Tf, above the first temperature Td, so as to sinter the copper particles to obtain a copper part.

Process for manufacturing a copper part comprising at least the following successive steps: shaping a part by stereolithography, the shaping being carried out by: forming a layer of paste comprising a powder of copper particles, one or more photopolymerizable precursors of a first resin, a photoinitiator and, optionally, an optical additive, photopolymerizing the photopolymerizable precursor(s) of the first resin, the steps and forming a cycle that can be repeated a plurality of times, carrying out a first heat treatment, under an oxidizing atmosphere containing at least 10 vol % of an oxidizer, such as dioxygen, at a first temperature Td so as to eliminate the first resin, and carrying out a second heat treatment, under a reducing atmosphere, at a second temperature Tf, above the first temperature Td, so as to sinter the copper particles to obtain a copper part.

Frangible firearm projectiles, firearm cartridges, and methods for forming the same. The projectiles are formed from metal powder and include an anti-sparking agent. One or more of iron, zinc, bismuth, tin, copper, nickel, tungsten, boron, and/or alloys thereof may form the metal powder. The projectiles may be formed from a compacted mixture of two or more different metal powders. The anti-sparking agent may include a borate, such as boric acid, zinc chloride, and/or petrolatum. The anti-sparking agent may be dispersed within, and/or applied as a coating on, the exterior of the projectile. The compacted mixture may be heat treated for a time sufficient to form a plurality of discrete alloy domains within the compacted mixture. Such domains may be formed by a mechanism that includes vapor-phase diffusion bonding and oxidation of the metal powders and that does form a liquid phase of the metal powder or utilize a polymeric binder.

Frangible firearm projectiles, firearm cartridges, and methods for forming the same. The projectiles are formed from metal powder and include an anti-sparking agent. One or more of iron, zinc, bismuth, tin, copper, nickel, tungsten, boron, and/or alloys thereof may form the metal powder. The projectiles may be formed from a compacted mixture of two or more different metal powders. The anti-sparking agent may include a borate, such as boric acid, zinc chloride, and/or petrolatum. The anti-sparking agent may be dispersed within, and/or applied as a coating on, the exterior of the projectile. The compacted mixture may be heat treated for a time sufficient to form a plurality of discrete alloy domains within the compacted mixture. Such domains may be formed by a mechanism that includes vapor-phase diffusion bonding and oxidation of the metal powders and that does form a liquid phase of the metal powder or utilize a polymeric binder.

A method is provided for printing a three-dimensional object. The method comprises, depositing a layer of metal powder onto a powder bed of a three-dimensional printer. A liquid is heated to generate a vapor. The liquid is removed from the vapor to dry the vapor by heating the vapor above a condensation temperature of the liquid. The dry vapor is deposited onto the powder bed of the three-dimensional printer.