Graphene/polyvinylidene fluoride (PVDF) composites were prepared using in-situ solvothermal reduction of graphene oxide in the PVDF solution. The electrical conductivity of the composites was greatly improved by doping with graphene sheets. The percolation threshold of such composite was determined to be 0.31 vol.%, being much smaller than that of the composites prepared via blending reduced graphene sheets with polymer matrix. This is attributed to the large aspect ratio of the SRG sheets and their uniform dispersion in the polymer matrix. The dielectric constant of PVDF showed a marked increase from 7 to about 105 with only 0.5 vol.% loading of SRG content. Like the other conductor-insulator systems, the AC conductivity of the system also obeyed the universal dynamic response. In addition, the SRG/PVDF composite shows a much stronger nonlinear conduction behavior than carbon nanotube/nanofiber based polymer composite, owing to intense Zener tunneling between the SRG sheets. The strong electrical nonlinearity provides further support for a homogeneous dispersion of SRG sheets in the polymer matrix.
Aqueous graphene oxide-dispersed multi-walled carbon nanotubes were used as inks for the simple, fast, and industrially scalable fabrication of hybrid transparent conductive films by rod coating.
Facile synthesis of silver-decorated reduced graphene oxide as a hybrid filler material for electrically conductive polymer composites Linxiang He and Sie Chin Tjong * Nano silver-decorated reduced graphene oxide (Ag-RGO) sheets were synthesized by simply dissolving graphite oxide and silver nitrate in N,N-dimethylformamide and keeping the suspension at 90 C for 12 h. These highly stable hybrid sheets were then incorporated into a polar polymer, polyvinylidene fluoride (PVDF), to prepare the Ag-RGO/PVDF nanocomposites via solution mixing. The Ag-RGO hybrid sheets were dispersed homogeneously in the polymer matrix, resulting in a low percolation threshold of 0.17 vol%. Above the percolation threshold, electrical conductivity of the Ag-RGO/PVDF composite system was about one order of magnitude higher than that of thermally reduced graphene/PVDF composites. This was attributed to the high intrinsic electrical conductivity of silver. The improved electrical properties render this novel composite system an attractive material for antistatic, electrostatic dissipative and electromagnetic/radio frequency interference shielding applications.Furthermore, the resistivity of the composite system increased with increasing temperature, generating a pronounced positive temperature coefficient effect of resistivity. Fig. 8 Effect of temperature on resistivity of Ag-RGO/PVDF composites with 0.17 vol% and 0.24 vol% filler loadings.Fig. 9 (a) Stress-strain curves of Ag-RGO/PVDF nanocomposite sheets with different Ag-RGO contents. (b) Tensile strength (left) and tensile strain (right) versus Ag-RGO loading content.This journal is
Graphene‐based epidermal dry electrodes have generated wide interests in electrocardiography (ECG) monitoring to screen cardiovascular diseases in time. Nevertheless, the poor stability, mechanical strength, and integration are significant obstacles hindering further product marketing of graphene electrodes in health care. Herein, robust, reusable, and patterned graphene‐based wearable dry electrodes are fabricated based on laser writing technology and supported by polydimethylsiloxane (PDMS) layers. After bending tests over 10 000 cycles and high‐power ultrasonic treatments (5 h), graphene/PDMS electrodes are demonstrated to have excellent stability and reusability for ECG recording. Taking the advantages of the designable and efficient CO2 laser production technique, a “staff‐shape” graphene electrode consisting of six chest‐lead electrodes and corresponding lead lines can be facilely customized and fabricated according to users’ somatotype to greatly simplify the acquisition procedure of 12‐lead ECG, realizing the acquisition of V1–V6 ECGs for all‐round cardiac monitoring. After thorough analysis of ECG patterns, the integrated chest electrode exhibits desirable sensitivity and reliability comparable to wet Ag/AgCl electrodes. The reusable graphene/PDMS electrodes are suitable for long‐term ECG monitoring and the integrated electrode presents a novel strategy to wearable 12‐ECG recording.
A solid mixture of graphene oxide (GO) with polyvinylidene fluoride (PVDF) was investigated as the precursor material for fabricating graphene-PVDF nanocomposites. The mixture was prepared by solution mixing GO in PVDF solution followed by coagulation.Hot-pressing of the mixture led to the reduction of GO to graphene, and transformed the material to a graphene-PVDF nanocomposite.Consequently, the in situ thermally reduced graphene (TRG) sheets were found to be dispersed homogeneously in the polymer matrix. This resulted in a very low percolation threshold of 0.12 vol% TRG. In addition, hot-pressed GO-PVDF mixtures with higher filler loadings were employed as the master batches for forming conductive polymer composites by melt compounding. This processing route has great potential for scalable production of electrically conductive graphene-polymer nanocomposites.
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