Copper sulfide CuS

Fe Content:20%
Cu Content:12–20%
MgO content:˃5%

Copper Sulfide, CuS is a black or dark gray inorganic compound. Its crystal structure is usually cubic and its chemical properties are relatively stable. Copper sulfide exists in the form of rare minerals in nature, such as Chalcocite.

Properties of copper sulfide:
Appearance: dark brown amorphous powder or granular solid.
Melting point: it decomposes at about 220℃.
Density: relatively large.
Solubility: Very difficult to dissolve in water, with very low water solubility product constant (Ksp).

Application:
Copper sulfide has its applications in many fields. Although its direct application in brake pads is not common, it is more prominent in the following fields:
1. Catalyst: Because of its special electronic structure, copper sulfide can be used in the catalytic process of some chemical reactions.
2. Photoelectric materials: Copper sulfide has semiconductor properties, which may be used in photoelectric devices, solar cells and other fields.
3. Metallurgical industry: In some copper ore refining processes, copper sulfide, as a component of copper ore, is extracted by hydrometallurgy or pyrometallurgy.

Speculation on its function in brake pads;
Although there are few reports on the direct application of copper sulfide in brake pads, if it is used as a reinforcement or friction modifier, it may theoretically have the following functions:
Wear resistance: The hardness of copper sulfide is relatively high. If it is added as a filler in brake pad material, it may help to improve the wear resistance of the material.
Friction performance adjustment: the friction coefficient of copper sulfide may have some influence on the friction performance of brake pads, but its stability at high temperature and whether it will lead to environmental protection problems of brake dust need to be considered in practical application.