DC Electrical conductivity and EMI shielding studies of Graphene/Acrylonitrile Butadiene Styrene Nanocomposites SK Sharma, VK Sachdev, RP Tandon* Mats Lab, Department of Physics and Astrophysics, University of Delhi, Delhi, India ram_tandon@hotmail.com
Abstract A low cost solvent free tumble mixing technique has been developed for preparation of graphene/ABS nanocomposite. Effects on electrical and EMI shielding properties of nanocomposites have been studied as a function of graphene loading. selective dispersion of graphene in ABS matrix resulted in a low percolation threshold
Dispersion Technique
Shielding Measurements
Graphene powder was dispersed in ABS by tumble mixing technique Mixture powder of graphene and ABS was rotated in the tumbler for 200 min Prolonged tumble mixing evenly disperse the graphene, and puts a coating of it on ABS particles A series of rectangular pellets of X-band waveguide size (22.86 X 10.16 mm2) with content 0.1–10 wt % of Graphene in ABS were prepared by hot compression. The pellets prepared were characterized for DC conductivity and EMI shielding in X band
Shielding mechanism
X band EMI Shielding measurements using two port vector network analyzer
Tumble Mixing Technique for selective dispersion of nanofiller
Results and Discussion DC electrical conductivity
EMI shielding characterization Shielding effectiveness of composites increases with increasing graphene content Composites with 10 wt % of graphene demonstrated a total shielding effectiveness (SETotal) of 24.32 dB at 9 GHz It is evident from SEref and Seabs that shielding mechanism is absorption dominated (SE_reflection)
(SE_absorption)
(SE_total)
(SE at 9 GHz)
• Conductivity increase abruptly by several orders of magnitude on initial addition of Graphene and saturates for higher concentration
Aeff = Pabs / (Pinc – Pref)
• percolation threshold at 0.5 wt % of graphene. • Conductivity of 10 wt% percolated sample is 8.04 × 10-2 S cm-1.
SEM micrograph of graphene stacks
Reflectance, Absorbance and Transmittance of composite pellets as a function of conductivity
SE at 9 GHz as a function of conductivity
Conclusions A low experimental percolation threshold for graphene/ABS nanocomposites is reported in this work. The low value of percolation threshold observed here is endorsed to selective localization of graphene and network formation in ABS matrix. Method of composite preparation do not involve any solvent, and hence can be considered as industrially viable technique. SE increases with increasing graphene content. The required EMI shielding for different electronic devices is about 15–20 dB. Thus, composite with 10 wt % graphene having 24.32 dB SE appears to be promising for its commercial use as shielding material. Study of R, A, T, Aeff, SEref, and SEabs suggests that the shielding is absorption dominated.