A composite member having an excellent heat resistance is provided. The composite member includes: a substrate composed of a composite material including a non-metal phase and a metal phase; and a metal layer that covers at least a portion of a surface of the substrate, wherein a metal included in each of the metal phase and the metal layer is mainly composed of Ag, and a ratio of a content of Cu to a total content of Ag and Cu in a boundary region of the metal layer with the substrate is less than or equal to 20 atomic %.

A method is described for protecting a silver surface against tarnishing. This involves depositing a layer of a silver-copper alloy on a substrate, which may be a silver substrate. The alloy comprises between 0.1 wt % and 10 wt % of copper relative to the total weight of the alloy. At least one layer of a metal oxide or a nitride having a thickness in a range of 1 nm to 200 nm is deposited on the alloy to protect against tarnishing. The presence of copper in the silver-copper alloy enhances the alloy's adhesion without altering the silver color.

A method is described for protecting a silver surface against tarnishing. This involves depositing a layer of a silver-copper alloy on a substrate, which may be a silver substrate. The alloy comprises between 0.1 wt % and 10 wt % of copper relative to the total weight of the alloy. At least one layer of a metal oxide or a nitride having a thickness in a range of 1 nm to 200 nm is deposited on the alloy to protect against tarnishing. The presence of copper in the silver-copper alloy enhances the alloy's adhesion without altering the silver color.

A reducing material including a two-dimensional hydrogen boride-containing sheet having a two-dimensional network composed of (BH).sub.n (n≥4).

A composite including a two-dimensional hydrogen boride-containing sheet having a two-dimensional network composed of (BH).sub.n (n≥4) and a metal nanoparticle.

A reduction method including: a step of dispersing the reducing material according to any one of Claims 1 to 5 in an organic solvent to prepare a dispersion liquid containing the reducing material; and a step of reducing a metal ion having a redox potential which is given as a standard electrode potential of −0.26 V/SHE or higher by mixing the dispersion liquid with the metal ion.

A method for synthesizing a copper-silver alloy includes an ink preparation step, a coating step, a crystal nucleus formation step and a crystal nucleus synthesis step. In the ink preparation step, a copper salt particle, an amine-based solvent, and a silver salt particle are mixed, thereby preparing a copper-silver ink. In the coating step, a member to be coated is coated with the copper-silver ink. In the crystal nucleus formation step, at least one of a crystal nucleus of copper having a crystal grain diameter of 0.2 μm or less and a crystal nucleus of silver having a crystal grain diameter of 0.2 μm or less is formed from the copper-silver ink. In the crystal nucleus synthesis step, the crystal nucleus of copper and the crystal nucleus of silver are synthesized.

A method for synthesizing a copper-silver alloy includes an ink preparation step, a coating step, a crystal nucleus formation step and a crystal nucleus synthesis step. In the ink preparation step, a copper salt particle, an amine-based solvent, and a silver salt particle are mixed, thereby preparing a copper-silver ink. In the coating step, a member to be coated is coated with the copper-silver ink. In the crystal nucleus formation step, at least one of a crystal nucleus of copper having a crystal grain diameter of 0.2 μm or less and a crystal nucleus of silver having a crystal grain diameter of 0.2 μm or less is formed from the copper-silver ink. In the crystal nucleus synthesis step, the crystal nucleus of copper and the crystal nucleus of silver are synthesized.

A substrate includes a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, the protective coat includes a first coat of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, and on the first coat of Al.sub.2O.sub.3, a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, the substrate including a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm. Embodiments also relate to a method for manufacturing such a substrate.

A substrate includes a final silver-plated surface protected against silver tarnishing by a protective coat having a thickness between 1 nm and 200 nm, the protective coat includes a first coat of Al.sub.2O.sub.3 deposited on said final silver-plated surface and having a thickness between 0.5 nm and 100 nm, and on the first coat of Al.sub.2O.sub.3, a second coat of TiO.sub.2 having a thickness between 0.5 nm and 100 nm, the substrate including a coat of a silver and copper alloy comprising between 0.1% and 10% by weight of copper with respect to the total weight of the alloy, forming said final silver-plated surface, said coat of a silver and copper alloy having a thickness between 1000 nm and 3000 nm. Embodiments also relate to a method for manufacturing such a substrate.

A method for synthesizing a copper-silver alloy includes an ink preparation step, a coating step, a crystal nucleus formation step and a crystal nucleus synthesis step. In the ink preparation step, a copper salt particle, an amine-based solvent, and a silver salt particle are mixed, thereby preparing a copper-silver ink. In the coating step, a member to be coated is coated with the copper-silver ink. In the crystal nucleus formation step, at least one of a crystal nucleus of copper having a crystal grain diameter of 0.2 μm or less and a crystal nucleus of silver having a crystal grain diameter of 0.2 μm or less is formed from the copper-silver ink. In the crystal nucleus synthesis step, the crystal nucleus of copper and the crystal nucleus of silver are synthesized.

A method for synthesizing a copper-silver alloy includes an ink preparation step, a coating step, a crystal nucleus formation step and a crystal nucleus synthesis step. In the ink preparation step, a copper salt particle, an amine-based solvent, and a silver salt particle are mixed, thereby preparing a copper-silver ink. In the coating step, a member to be coated is coated with the copper-silver ink. In the crystal nucleus formation step, at least one of a crystal nucleus of copper having a crystal grain diameter of 0.2 μm or less and a crystal nucleus of silver having a crystal grain diameter of 0.2 μm or less is formed from the copper-silver ink. In the crystal nucleus synthesis step, the crystal nucleus of copper and the crystal nucleus of silver are synthesized.