Method of preparing silver-based electrical contact materials with directionally arranged reinforcing particles

A method of preparing silver-based electrical contact materials with directionally arranged reinforcing particles comprising steps of:

• (A) dissolving reinforcing powders in hydrazine hydrate solution to form a mixed solution, adding the mixed solution into AgNO3 solution for stirring, simultaneously adding ammonia for adjusting a PH value of the AgNO3 solution which forms precipitates through a reaction, filtering out precipitation following the reaction, and washing and drying the filtered precipitation, thereby obtaining composite powders with Ag coating on the reinforcing phase, wherein a weight ratio of the reinforcing phase to AgNO3 is calculated according to a content of the material needed, and a weight ratio of the hydrazine hydrate to AgNO3 is calculated according to Ag on reduced by the hydrazine hydrate;
• (B) granulating the composite powders obtained from the step (A);
• (C) placing the composite powders obtained from the step (B) and silver powders into a powder mixer for mixing, wherein a weight ratio of the composite powders to the silver powders is calculated according to the content of the preparation material needed;
• (D) cold-isostatically pressing the composite and silver powders obtained from the step (C);
• (E) sintering the cold-isostatically pressed body to form a sintered body;
• (F) hot-pressing the sintered body to form a hot-pressed body;
• and
• (G) hot-extruding the hot-pressed body, wherein during the hot-extrusion process, the composite powders with Ag coating on the reinforcing phase flow with softened Ag in the silver powders, due to coating of Ag, the reinforcing powders are easily open, and directionally arranged along an extrusion direction for forming a fibrous structure, thereby obtaining the silver-based electrical contract material with directionally arranged reinforcing particles,
• wherein in the step (A), a weight ratio of the reinforcing powders to AgNO3 is 1/4-10/3;
• a weight ratio of the hydrazine hydrate to AgNO3 is 2/3-1/3;
• a stirring speed is 80rev/min-120rev/min;
• an adjusted PH value after adding the ammonia is 8-11;
• a reaction time is 3-10 hours;
• a drying temperature is 40-100° C.;
• and a drying time is 5-10 hours.