| Graphene has a unique two-dimensional honeycomb lattice structure,which is the thinnest two-dimensional crystal material,with a thickness of only 0.335 nm.Graphene exhibits excellent electrical,mechanical and optical properties,with the electron transfer rate of 200000 cm~2/(V·s),the young's modulus of 1000 GPa,the fracture strength of 130 GPa and the transparence of97.7%.In this regards,graphene can be widely used in solar cells,supercapacitors,biological detection,display device,fuel cells and so on.Nanocrystalline Cellulose(NCC)is a kind of environmental friendly nanomaterial with abundant resources.NCC has excellent mechanical properties and physicochemical property,e.g.,high crystallinity(>70%)and large specific surface area(~70 m~2/g).In addition,NCC also has good biocompatibility,biodegradability and stable chemical properties.In this sense,NCC can be widely used in medicine,food and daily chemicals.In recent years,the application of NCC in flexible transparent films has attracted much attention.In the present work,the NCC/graphene flexible conductive film was designed and prepared using NCC as a substrate,which may endow NCC film with special conductivity,and enhance the mechanical properties,and the synergistic effect of NCC and graphene was fully exploited.It provides a new idea for the preparation of graphene conductive films,and has great significance for the research and development of high-performance flexible transparent conductive films.Based on this,in the present work,NCC was initially prepared via sulfuric acid hydrolysis using microcrystalline cellulose(MCC)as raw materials.The obtained NCC samples exhibited a rod like structure with length of 300-600 nm and diameter of 30-80 nm.Moreover,the as-prepared NCC was subsequently used as dispersant for the production of graphene/NCC composite dispersion solution with different formulation.In order to evaluate the dispersion of graphene/NCC composite dispersion solution,dynamic and steady state rheological properties,TEM,UV-vis and sedimentation experiments were carried out.The experimental results showed that with the increase of NCC content,the shear viscosity,shear stress,storage modulus and loss modulus of graphene/NCC dispersion solution decreased,and the sedimentation of composite dispersion solution reduced gradually,and the UV-Vis absorption peak increased significantly,which indicated that the addition of NCC contributed to the dispersion of graphene/NCC composite dispersion solution.Meanwhile,the TEM results further proved that the addition of NCC suspension promoted the dispersion of graphene/NCC composite dispersion solution.Afterwards,pure NCC thin films were prepared based on ultrasonic treatment and vacuum filtration.Based on NCC based films,various graphene/NCC dispersion solutions were evenly coated on the surface of NCC films via spin dispersion method,and NCC/graphene nanocomposite flexible conductive film was achieved.Furthermore,XRD,TG,mechanical properties,electrical conductivity,transmittance and SEM were measured and employed to evaluate the effect of NCC addition on the overall properties of nanocomposite conductive films.The results showed that the addition of NCC was effective in improving the dispersion of graphene,which facilitated the enhancement of the conductivity and mechanical properties of NCC/graphene composite films,and led to the decrease in the transmittance and thermal stability of the composite film.In comparison to the composite films without NCC addition,the maximum increase of tensile strength and elastic modulus of composite films can reach 96.8%and 71.3%,respectively,and the maximum reduction of elongation at break can reach 70%.The maximum conductivity of NCC/graphene conductive films can reach 2.25 S/cm. |
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