Confined Dispersion of Zinc Hydroxystannate Nanoparticles into Layered Bimetallic Hydroxide Nanocapsules and Its Application in Flame-Retardant Epoxy Nanocomposites

In many fields, nanoparticles are frequently dispersed onto kinds of nanocarriers integrated into hybrid nanocomposites to acquire advanced performance. However, the nanoparticles usually tend to agglomerate on the surface, according to traditional synthetic methods. Besides, the exposed state of loaded nanoparticles and the weak adhesion with the supporters make them fall off during practical application, leading to "second agglomeration" of the nanoparticles and attenuated synergistic effects. In this work, we engineered layered bimetallic (Ni-Co) hydroxides (NCHs) into enclosed nanocages derived from metal organic frameworks (MOFs). Zinc hydroxystannate (ZHS) nanoparticles were selected to be confined dispersed within the hollow cavity of the three-dimensional nanocages. ZHS nanoparticles were tightly immobilized, monodispersing to form a novel multiyolk@shell nanostructure with NCH nanocages. To prove the effectiveness of this structural design, the as-synthesized hybrids ZHS@NCH were introduced into the epoxy matrix to inquiry its performance. Compared to neat ZHS, neat NCH, and physical mixture of ZHS and NCH, ZHS@NCH conferred better flame retardancy, thermal stability, and mechanical properties upon the epoxy nanocomposites. With the adding amount of 6 wt % ZHS@NCH, the UL-94 rating of the nanocomposite was V-0, and the peak of heat release rate value was reduced by 69.1%, while the mechanical properties were slightly influenced. The ingenious synthetic strategy gives insights into uniform distribution of nanoparticles within nanocapsules and enlightens the facile fabrication of multiyolk@shell nanomaterials.