Surface organic modification method for nano silicon nitride powder

The invention discloses a surface organic modification method for nano silicon nitride powder. A coupling agent is used as a surface modifier. The method includes the specific steps: in the environment of a weakly acidic aqueous solution with the pH of 4-5 and the environment of a constant-temperature gas bath or water bath reactor at 3-5 DEG C, slowly adding nano silicon nitride and the surface modifier at the same time, wherein the addition of nano silicon nitride and the surface modifier are controlled to be started at the same time and the addition of the nano silicon nitride and the surface modifier is controlled to be stopped at the same time; increasing the temperature of the reactor to 20-30 DEG C, and slowly stirring for 10-15 min to complete physical coating and chemical grafting modification of nano silicon nitride; finally, obtaining the modified nano silicon nitride powder by filtering and vacuum drying. The method has an obvious modification effect, can reinforce and toughen a polymer matrix and can enhance the wear resistance and weather resistance of the polymer matrix at the same time; in addition, the method is simple in operation step, the operation temperature is in the normal temperature range, energy conservation and environment protection of the process are achieved, and the filtrate can be recycled.