Foaming‐Assisted Silicon Direct Nitridation for Mass Preparation of Si ₃ N ₄ Whiskers as Thermally Conductive Fillers

Direct nitridation is widely applied for industrial‐scale preparation of Si 3 N 4 , while facing a persistent challenge of incomplete nitridation due to melting and volatilization of Si powder. In this work, a foaming‐assisted route, in which the porous Si foams were used as the staring material, was developed to prepare the Si 3 N 4 whiskers from the perspective of mass production. A complete nitridation at 1300°C could be achieved, which is lower or comparable to those reported previously for preparation of whiskers. The interconnected “pores” of Si foam not only provided the N 2 pathways, which enabled it to enter the interior efficiently, thus promoting its reaction of Si nitridation regardless of foam sizes, but also provided enough surface for the growth of whiskers. The as‐prepared Si 3 N 4 whiskers could be potentially used as a thermally conductive filler in resin composites, which enhanced the heat transfer and robustness of the polymer matrix. By simply stacking these Si foams in an industrial nitriding furnace, a scale‐up preparation of Si 3 N 4 whiskers can be realized without complex operations, anticipating its applicability for industrial production.