A Preparation Method for Ag-WC-C Contacts

Adopt solid phase sintering method to prepare Ag-WC-C contacts (Material: silver powder, plate-like grains of tungsten carbide and graphite powder), wherein milling method can be chemical coating powder method.
Preparation process:
1. According to percentage of their content to weigh silver powder, tungsten carbide powder, graphite powder and metal additive powder, such as cobalt (Co), nickel (Ni) or zirconium (Zr). Among which,
Silver accounts for 84-85%; tungsten carbide powder of 12%; graphite powder of 3%; metal additive powder accounting for 0-1%.
Use stainless steel wire mesh to sieve the above-mentioned materials, and then pour them into a blender after mixing.
2. The preparation of silver nitrate solution. Silver should be fully dissolved in concentrated nitric acid.
3. The prepared silver nitrate solution is poured into the reaction vessel, then, complex it with ammonia, until the PH value rise to 10. Then adding the mixing powder to reaction vessel and stirring.
4. Continue stirring, use atomization device to add the reducing agent hydrazine hydrate to the reaction vessel in liquid spray-way until the reaction is sufficient.
Hydrazine hydrate, a colorless transparent oily liquid owns strong basicity and strong reducibility, which can act as a reducing agent and an antioxidant.
5. Washing the mixing powder with distilled water after processing by the above steps until it is neutral, then dry it in a dryer, the temperature is controlled at 90 ℃, dry mixing powder of silver coating can be available.
6. Pressing the dry mixing powder of silver coating (cold pressing), to form its shape, then, sintering it in a sintering furnace, in hydrogen atmosphere, temperature of 750-890 ℃, sintering time of 3-5h, and then re-pressing at a pressure of 10-20T / Cm2 and, ultimately, Ag-WC12-C3 contacts is prepared.



 

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