Precious metal composite materials of two or more different types of compatible materials are synthesized by physical methods. Creed (K.G.Kreider) points out that its characteristics are:
(1) its composition is selected and designed by human beings.
(2) it is made artificially, not natural.
(3) there are at least two different phases of independence.
(4) its performance depends on the performance of each component.
(5) its components have a repeated geometry, so that the material can be considered macroscopically homogeneous.
(6) the excellent properties of a single component material.
Precious metal composites are metal matrix composites, which have similar properties to precious metals, such as good conductivity, thermal conductivity, oxidation resistance and corrosion resistance. According to the form and distribution of the non precious metal phase, it can be divided into four kinds: noble metal layered composite material, dispersion strengthening noble metal composite, particle reinforced metal compound material and precious metal fiber composite. It is mainly used in electronic and electrical industry as electrical contact materials, electrochemical industry as electrode materials, glass, glass fiber industry as crucibles, leaking materials, and experimental crucible materials. Noble metal composite has excellent comprehensive properties because of its characteristics of composition phase. Its use is not only of great technical significance, but also has great economic significance due to the obvious reduction of the amount of precious metals.
In the precious metal and its alloy matrix, the dispersed chemical and thermodynamic stable high melting or high hardness oxides, carbides, or particulates with special properties as the reinforced phase of the noble metal composite. In general, the particle size of the dispersion strengthened phase is 0. 01 to 0. 1um, the content is less than 1% (volume fraction). The dispersion and distribution of non deformable enhanced phase particles in the precious metal and its alloy matrix can prevent the dislocation movement of the matrix metal, restrict the movement of grain boundary and grain growth, so that the recrystallization temperature, the high temperature strength and the creep resistance of the matrix metal can be improved obviously. At the same time, the dispersion strengthening is limited because of the addition of the strengthening phase. The processability and corrosion resistance of precious metal composites are similar to those of matrix precious metals.