Effect of nitrogen doping on medium-amplitude oscillatory shear (MAOS) response of nanotube/polyvinylidene fluoride nanocomposites: Molecular simulations, rheology, and broadband electrical conductivity

2020 ◽  
Vol 64 (6) ◽  
pp. 1343-1356
Author(s):  
Soheil Sadeghi ◽  
Mohammad Arjmand ◽  
Ivonne Otero Navas ◽  
Uttandaraman Sundararaj
Keyword(s):  
Electrical Conductivity ◽  
Polyvinylidene Fluoride ◽  
Nitrogen Doping ◽  
Molecular Simulations ◽  
Oscillatory Shear ◽  
Medium Amplitude Oscillatory Shear

scholarly journals Intra-Cycle Elastic Nonlinearity of Nitrogen-Doped Carbon Nanotube/Polymer Nanocomposites under Medium Amplitude Oscillatory Shear (MAOS) Flow

Nanomaterials ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1257 ◽  
Author(s):  
Milad Kamkar ◽  
Soheil Sadeghi ◽  
Mohammad Arjmand ◽  
Ehsan Aliabadian ◽  
Uttandaraman Sundararaj
Keyword(s):  
Rheological Properties ◽  
Polymer Nanocomposites ◽  
Polyvinylidene Fluoride ◽  
Viscoelastic Behavior ◽  
Oscillatory Shear ◽  
Dispersed Systems ◽  
Nitrogen Doped ◽  
Elastic Nonlinearity ◽  
Medium Amplitude Oscillatory Shear ◽  
Nitrogen Doped Carbon

This study seeks to unravel the effect of carbon nanotube’s physical and chemical features on the final electrical and rheological properties of polymer nanocomposites thereof. Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized over two different types of catalysts, i.e., Fe and Ni, employing chemical vapor deposition. Utilizing this technique, we were able to synthesize N-CNTs with significantly different structures. As a result, remarkable differences in the network structure of the nanotubes were observed upon mixing the N-CNTs in a polyvinylidene fluoride (PVDF) matrix, which, in turn, led to drastically different electrical and rheological properties. For instance, no enhancement in the electrical conductivity of poorly-dispersed (N-CNT)Ni/PVDF samples was observed even at high nanotube concentrations, whereas (N-CNT)Fe/PVDF nanocomposites exhibited an insulative behavior at 1.0 wt%, a semi-conductive behavior at 2.0 wt%, and a conductive behavior at 2.7 wt%. In terms of rheology, the most substantial differences in the viscoelastic behavior of the systems were distinguishable in the medium amplitude oscillatory shear (MAOS) region. The stress decomposition method combined with the evaluation of the elastic and viscous third-order Chebyshev coefficients revealed a strong intra-cycle elastic nonlinearity in the MAOS region for the poorly-dispersed systems in small frequencies; however, the well-dispersed systems showed no intra-cycle nonlinearity in the MAOS region. It was shown that the MAOS elastic nonlinearity of poorly-dispersed systems stems from the confinement of N-CNT domains between the rheometer’s plates for small gap sizes comparable with the size of the agglomerates. Moreover, the intra-cycle elastic nonlinearity of poorly-dispersed systems is frequency-dependent and vanished at higher frequencies. The correlation between the microstructure and viscoelastic properties under large shear deformations provides further guidance for the fabrication of high-performance 3D-printed electrically conductive nanocomposites with precisely controllable final properties for engineering applications.

scholarly journals Carbon Nanotube versus Graphene Nanoribbon: Impact of Nanofiller Geometry on Electromagnetic Interference Shielding of Polyvinylidene Fluoride Nanocomposites

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1064 ◽  
Author(s):  
Mohammad Arjmand ◽  
Soheil Sadeghi ◽  
Ivonne Otero Navas ◽  
Yalda Zamani Keteklahijani ◽  
Sara Dordanihaghighi ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Carbon Nanotube ◽  
Electromagnetic Interference ◽  
Polyvinylidene Fluoride ◽  
Network Formation ◽  
Molecular Simulations ◽  
Graphene Nanoribbon ◽  
Emi Shielding ◽  
Pvdf Matrix ◽  
The Impact

The similar molecular structure but different geometries of the carbon nanotube (CNT) and graphene nanoribbon (GNR) create a genuine opportunity to assess the impact of nanofiller geometry (tube vs. ribbon) on the electromagnetic interference (EMI) shielding of polymer nanocomposites. In this regard, GNR and its parent CNT were melt mixed with a polyvinylidene fluoride (PVDF) matrix using a miniature melt mixer at various nanofiller loadings, i.e., 0.3, 0.5, 1.0 and 2.0 wt%, and then compression molded. Molecular simulations showed that CNT would have a better interaction with the PVDF matrix in any configuration. Rheological results validated that CNTs feature a far stronger network (mechanical interlocking) than GNRs. Despite lower powder conductivity and a comparable dispersion state, it was interestingly observed that CNT nanocomposites indicated a highly superior electrical conductivity and EMI shielding at higher nanofiller loadings. For instance, at 2.0 wt%, CNT/PVDF nanocomposites showed an electrical conductivity of 0.77 S·m−1 and an EMI shielding effectiveness of 11.60 dB, which are eight orders of magnitude and twofold higher than their GNR counterparts, respectively. This observation was attributed to their superior conductive network formation and the interlocking ability of the tubular nanostructure to the ribbon-like nanostructure, verified by molecular simulations and rheological assays.

scholarly journals The Synthesis and Electrochemical Performance of Si Composite with Hollow Carbon Microtubes by the Carbonization of Milkweed from Nature as Anode Template for Lithium Ion Batteries

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5124
Author(s):  
Eun Hyuk Chung ◽  
Jong Pil Kim ◽  
Hyun Gyu Kim ◽  
Jae-Min Chung ◽  
Sei-Jin Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Electrochemical Performance ◽  
Pore Size ◽  
Lithium Ion Batteries ◽  
Polyvinylidene Fluoride ◽  
Lithium Ion ◽  
Size Analysis ◽  
Pore Size Analysis ◽  
Hollow Carbon

It has been reported that improving electrical conductivity and maintaining stable structure during discharge/charge process are challenge for Si to be used as an anode for lithium ion batteries (LIB). To address this problem, milkweed (MW) was carbonized to prepare hollow carbon microtubes (HCMT) derived from biomass as an anode template for LIB. In order to improve electrical conductivity, various materials such as chitosan (CTS), agarose, and polyvinylidene fluoride (PVDF) are used as carbon source (C1, C2, and C3) by carbonization. Carbon coated HCMT@Si composits, HCMT@Si@C1, HCMT@Si@C1@C2, and HCMT@Si@C1@C3, have been successfully synthesized. Changes in structure and crystallinity of HCMT@Si composites were characterized by using X-ray diffraction (XRD). Specific surface area for samples was calculated by using BET (Brunauer–Emmett–Teller). Also, pore size and particle size were obtained by particle and pore size analysis system. The surface morphology was evaluated using high resolution scanning electron microscopy (HR-SEM), Field Emission transmission electron microscopy (TEM). The thermal properties of HCMT@Si composites were analyzed by thermogravimetric analysis (TGA). Our research was performed to study the synthesis and electrochemical performance of Si composite with HCMT by the carbonization of natural micro hollow milkweed to form an inner space. After carbonization at 900 °C for 2 h in N2 flow, inner diameter of HCMT obtained was about 10 μm. The electrochemical tests indicate that HCMT@Si@C1@C3 exhibits discharge capacity of 932.18 mAh/g at 0.5 A/g after 100 cycles.

scholarly journals Time-strain separability in medium-amplitude oscillatory shear

2019 ◽  
Vol 31 (2) ◽  
pp. 021213 ◽  
Author(s):  
Luca Martinetti ◽  
Randy H. Ewoldt
Keyword(s):  
Oscillatory Shear ◽  
Medium Amplitude Oscillatory Shear

Fabrication of Infrared Detector Based on of Polyaniline/Polyvinylidene Fluoride Blend Films and their Pyroelectric Measurement

2014 ◽  
Vol 605 ◽  
pp. 103-106 ◽  
Author(s):  
A.M. El-Shaer ◽  
A.K. Aboulseoud ◽  
M. Soliman ◽  
Sh. Ebrahim
Keyword(s):  
Electrical Conductivity ◽  
Polyvinylidene Fluoride ◽  
Infrared Detector ◽  
Polymeric Materials ◽  
Electrical Signal ◽  
Pyroelectric Coefficient ◽  
Low Noise ◽  
Output Resistance ◽  
Blend Films ◽  
High Output Impedance

Infrared detection based on polymeric materials is continuously developed in order to be cheap and easy to processing and also having high pyroelectric coefficient to convert heat to electrical signal. PANI/DBSA was blended with polyvinylidene fluoride (PVDF) with different weight ratios to improve pyroelectric coefficient and electrical conductivity of PVDF. The temperature dependence of the electrical conductivity is measured in the range of 20-100 °C It was found that the pyroelectric coefficient increased from 1.5×10-8 C/m2 °C for pristine PVDF to 2.61×10-5 C/m2 °C at 25 wt.% PANI at 30 °C. The infrared detector circuit connected to the gate of a voltage follower JFET with high input impedance was designed to convert the high output impedance of the sensor into the output resistance. The output from the sensor and JFET is amplified in two stages of operational amplifier with high voltage gain with low noise.

scholarly journals Small and Medium Amplitude Oscillatory Shear Rheology of Model Branched Polystyrene (PS) Melts

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 365
Author(s):  
Hyeong Yong Song ◽  
Lorenz Faust ◽  
Jinha Son ◽  
Mingeun Kim ◽  
Seung Joon Park ◽  
...  
Keyword(s):  
Low Frequency ◽  
Oscillatory Shear ◽  
Zero Shear Viscosity ◽  
Plateau Modulus ◽  
Intrinsic Nonlinearity ◽  
Linear Viscoelastic ◽  
The Difference ◽  
Total Molecular Weight ◽  
Branched Polystyrene ◽  
Medium Amplitude Oscillatory Shear

Linear and nonlinear rheological properties of model comb polystyrenes (PS) with loosely to densely grafted architectures were measured under small and medium amplitude oscillatory shear (SAOS and MAOS) flow. This comb PS set had the same length of backbone and branches but varied in the number of branches from 3 to 120 branches. Linear viscoelastic properties of the comb PS were compared with the hierarchical model predictions. The model underpredicted zero-shear viscosity and backbone plateau modulus of densely branched comb with 60 or 120 branches because the model does not include the effect of side chain crowding. First- and third-harmonic nonlinearities reflected the hierarchy in the relaxation motion of comb structures. Notably, the low-frequency plateau values of first-harmonic MAOS moduli scaled with M w − 2 (total molecular weight), reflecting dynamic tube dilution (DTD) by relaxed branches. Relative intrinsic nonlinearity Q0 exhibited the difference between comb and bottlebrush via no low-frequency Q0 peak of bottlebrush corresponding to backbone relaxation, which is probably related to the stretched backbone conformation in bottlebrush.

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