Functionalization Of Large Scale Carbon Nanotube Film Toward Multifunctional Material

Carbon nanotubes（CNT）possess unique properties due to their structure.However,they are difficult to process due to their nanoscale size.In this research,large scale carbon nanotube films（CNTF）fabricated via floating catalyst chemical vapour deposition（FCCVD）exhibits excellent electro-mechanical-thermal behavior,easy processability and reusability.These properties are desirable in wearable electronics,multifunctional smart structures and soft robotics.The electro-heating（E-heating）behaviors of CNTF with various dimensions and deformations were studied by applying various voltages.The as-produced CNTF reached a steady-state temperature of 310℃（1×0.5 cm²）within 1 second under a low voltage of 2.5 V by the homogeneous temperature distribution.Moreover,E-heating performance of CNTF remained stable after twisting and bending deformations along with On/Off voltage switching cycles（～200 times）.As a potential application,the CNTF integrated 3D spacer woven composites de-iced the ice by 338 times weight ratio within few minutes,demonstrating promising performances as lightweight,high efficiency E-thermal material.However,the assembled CNTF possessed pores and loose structure,thus exhibited low performance properties.An innovative and effective strategy was proposed to densify the microstructure of CNT assembly by compression in acetone solvent（wet-compression）.During this process,the CNTF was displaced into acetone solvent and compressed（3 MPa）.Due to the good affinity and low surface tension,acetone easily penetrated into the CNTF and acted as a lubricant to decrease the interactions between the neighboring CNTs.Therefore,the CNTF was condensed in thickness from 11.3 to 8.4μm（34.5%decrease）with a CNT volume fraction increment（～11%to～14.7%）under wet-compression treatment.Consequently,the tensile strength,electrical conductivity and gauge factor were respectively enhanced by 97%,34%and 43%along the direction of CNT alignment and by 213%,42%and 101%towards the CNT transverse direction.As a potential application,modified CNTF/epoxy composites were fabricated as strong de-icing parts of an airplane.The tensile strength increased to 742 MPa（by 21%）and effectively melted ice by 250times weight ratio within 1 minute;performing as strengthened lightweight multifunctional materials.Tremendous efforts have been conducted to enhance CNTF electro-mechanical properties by doping,functionalization and resin impregnation.However,deep infiltration was hardly achieved due to the highly packed CNT.Herein,an easy,inexpensive and gentle method was introduced,to expand the ultra-packed CNT layers thus enhance CNTF permeability.The as-prepared CNTF was overnight immersed in an aqueous solution of hydrogen peroxide（H₂O₂,30%）and successfully expanded.The ecofriendly treatment purified the CNTF and significantly increased its thickness by～2000 times through H₂O₂degassing effect.To fully explore such an astonishing behavior,a novel bioinspired soft actuator based expanded CNT film and Polydimethylsiloxane（PDMS）which could expand,retract,lift weight and work in different environments was demonstrated.The multifunctional actuator was trigged by expanding the gas trapped through joule heating effect.Subjected to low voltage（3 V）the proposed actuator exhibits ultrafast response,lift～50 times its weight and could be actuated up to 100 times.Together,the newly functionalization and bioinspired design is believed to open new horizons in the development of intelligent actuators,multifunctional electronic textiles,smart robots,medical devices and environmental sorption devices.Finally,a highly stretchable and high effective CNTF/PDMS heater was developed for wearable and protective applications.The fabricated heater enabled superior stretchability,because of the unique design of micro-crimped structures that allow the CNTF to maintain heat at high strain of 105%.The CNTF/PDMS heater exhibited excellent thermal performance,with a high thermal response at low voltage,reached206℃ with limited applied voltage（2 V）and heating up time（～30 s）,exhibiting a superb electro-thermal conversion efficiency（h＿（r+c）～2.8 m W/℃）.We demonstrated a potential application of using CNTF/PDMS heater as an external heating source for batteries at low temperature（-20℃）.The result shows that,the discharge capacity of the heated LIB at-20℃ enhanced from 0.48 Ah to 0.7 Ah,which provides a rapid and energy-efficient heating strategy for batteries.Our work provides a universal approach towards the design of flexible and wearable heaters with high stretchability and good thermal response,which offers promising opportunity for thermal management in wearable applications and electro-devices.