Deformation induced absorption band-tunable smart CNTs/Ti₃C₂Tx-WPU electromagnetic wave absorbing aerogel

Intelligent devices and multi-functional integrated electromagnetic functional materials have been widely concerned, and it's really matter to develop intelligently adjustable electromagnetic wave (EMW) absorbing materials. However, MXene Ti₃C₂Tx-based aerogel with adjustable strain and EMW absorption properties have rarely been reported. We use Water-borne polyurethane (WPU) as a binder to connect CNTs/Ti₃C₂Tx absorbent into CNTs/Ti₃C₂Tx-WPU aerogel with high resilience. The bidirectional freeze-drying method results in the periodic structure of the aerogel. Under external stress, when the critical buckling load is reached, the aerogel will buckle, resulting in the reduction of layer spacing and contact resistance. Due to the threshold effect caused by compression, the conductivity increases, which significantly affects the dielectric loss and EMW absorption properties. Meanwhile, when the applied stress is removed, the shape of aerogel can recover, indicating the aerogel has excellent elasticity. We selected the aerogel with a mass fraction of 0.2 wt% for compression to research its mechanical and dielectric properties. With 42% compression stain, the minimum reflection loss of the sample reached −68.2 dB. At 50% maximum compression stain, the CNTs/Ti₃C₂Tx-WPU aerogel can be cycled at least 100 times and keep structure stable. With the increase of stress, the EMW absorption band shifts to the high-frequency. When the stress is removed, absorption band returns to its original position. It provides an effective avenue to explore electromagnetic absorbers with intelligent response.