Method for coating nano-silver on the surface of diamond micro-powder

A method for coating nano-silver on the surface of diamond micro-powder mainly uses silver ammonia solution as chemical plating solution and a mixed solution of glucose and polyvinylpyrrolidone as reducing agent to chemically plate silver nano-particles on the surface of ammoniated diamond micro-powder. The method has the advantages of simple operation, high utilization rate of the coated silver salt, uniform coating of the prepared silver-coated diamond micropowder, controllable weight gain, improved conductivity of the diamond micropowder, and improved sintering conditions of the diamond micropowder in the metal bond. The holding force of the diamond sintered body on the diamond fine powder is enhanced.

Requirement: 1. a method for coating nano-silver on the surface of diamond micropowder, is characterized in that: it comprises the following steps: (1) ammoniation treatment of diamond micropowder: adding the diamond micropowder with a particle size of 0.1 to 38 microns to a content of 25 ~28% analytically pure ammonia water, add 20 grams of diamond micropowder per liter of ammonia water, stir evenly, ultrasonically vibrate for 1 hour at a frequency of 40 kHz, power 180 W, rinse with absolute ethanol three times, and bake at 40 ~ 50 ℃ (2) Preparation of reaction solution ①Preparation of silver ammonia solution: Dissolve silver nitrate in deionized water, the concentration is 55-60 grams of silver nitrate per liter of solution, in deionized water Add analytically pure (25%) ammonia water to prepare a dilute ammonia solution. The concentration of the diluted ammonia solution is 0.188 mol/liter. According to the volume ratio of silver nitrate solution: dilute ammonia solution = 1: 3.5 to 3.8, the dilute ammonia solution is mixed. Slowly add it dropwise to the silver nitrate solution, stirring while adding dropwise, until a just clear and colorless solution is formed, then add 10 grams of sodium dodecyl sulfate per liter of solution, and add sodium dodecyl sulfate to the silver ammonia solution, let the solution stand for 0.5 hours to obtain silver ammonia solution; 2. Preparation of reducing agent solution: add 45 grams of glucose, 0.1 liter of anhydrous ethanol, and 1.5 grams of polyvinylpyrrolidone per liter of deionized water. ratio, add glucose, absolute ethanol and polyvinylpyrrolidone into deionized water, stir until completely dissolved, to obtain a reducing agent solution; (3) chemical plating: add the amount of ammoniated diamond micropowder per liter of silver ammonia solution The ratio of 10～50 grams, in above-mentioned silver ammonia solution, add the ammoniated diamond micropowder of above-mentioned step (1), carry out magnetic stirring, stirring speed is 20～30 rev/min; Then slowly drip above-mentioned reducing agent solution to containing diamond In the silver ammonia solution of micropowder, the dropping rate is 1-3 ml/min, and the added amount of reducing agent solution is equal to the volume of silver ammonia solution; stable magnetic stirring for 4-6 hours, after the silver is completely reduced, rinse with absolute ethanol for three times. The silver-coated diamond is filtered out and dried at 40-50°C; the weight gain of the diamond micropowder can reach 2-100%; the size of the silver particles plated on the surface of the diamond micropowder is between 1 and 50 nanometers.