Elegant Surface of CoNi Alloys toward Efficient Magnetorheological Performances Realized with Carbon Quantum Dots

Designing and fabricating a rational surface architecture is one of the critical factors to achieve desirable physical and chemical properties and still remains an immense challenge. Herein, a series of CoNi‐based hierarchical microspheres with different surface morphologies, including litchi‐like, seed‐of‐plane‐tree‐like, and waxberry‐like shapes, are obtained via surface nucleation of carbon quantum dots (CQDs) with different concentrations in liquid polyol. Microstructure investigations suggest that all the CoNi microspheres are uniformly with enhanced surface roughness with the increasing concentration of CQDs. This study provides insight into the surface dominant magnetorheological (MR) behaviors of these CoNi‐based suspensions. Taking both the synergistic benefits of paramagnetic CoNi microspheres and surface architecture, the resulting CoNi microspheres exhibit enhanced interparticle friction for enhancing their MR effects compared with smooth surface microspheres, opening up the possible mechanism for revealing the MR effect. Moreover, this facile strategy can be extended as an effective path to achieve high‐performance MR behaviors for engineering applications. To design and fabricate rational architecture is a critical factor to achieve desirable properties. A series of CoNi microspheres with different surface morphologies, including smooth, litchi‐like and waxberry‐like, are obtained via adjusting the ratio of carbon quantum dots (CQDs). Taking the synergistic benefits of paramagnetic behavor and architecture, the resulting CoNi microspheres exhibit enhanced magnetorheological (MR) effect.